EP2287460B1 - Fuel injector for a combustion engine - Google Patents

Abstract

The fuel injector has a valve plate (1) which forms a valve seat (7) for a valve bolt (5), where the valve bolt is guided in a sealing sleeve (8) in a slidable manner. The valve bolt is movable with the actuation of an actuator unit enlarged by the valve seat in an opening position. A receiving plate (18) is provided between the valve plate and a chock plate (2).

Description

State of the art

The invention relates to a fuel injector for injecting fuel into a combustion chamber of an internal combustion engine, comprising a valve plate which forms a valve seat for a valve pin, which is displaceably guided in a sealing sleeve and separates a return space from a valve space when in contact with the valve seat via a bolt head. wherein the valve space communicates with a control space of a nozzle needle via a flow restrictor passing through a throttle plate and is connectable to a high pressure inlet via a bypass, and wherein the valve pin is movable from the valve seat to an open position upon actuation of an actuator unit to flow Allow fuel from the valve chamber in the return chamber and initiate this by a pressure drop in the control chamber, an opening movement of the nozzle needle.

In FIG. 1 is a fuel injector of the prior art in the area of a valve plate 1 'to see. This valve plate 1 is arranged together with a throttle plate 2 'within a housing 3', wherein the valve plate 1 and the throttle plate 2 'between them define a valve space 4'. In the valve chamber 4 ', a valve pin 5' is arranged, which via a bolt head 6 'with a, on the valve plate 1' formed valve seat 7 'is brought into contact and also in a sealing sleeve 8' slidably guided. Between the bolt head 6 'of the valve pin 5' and the sealing sleeve 8 'is further a spring element 9' placed on the one hand in the unactuated state of the fuel injector the bolt head 6 'to the valve seat 7' and on the other hand, the sealing sleeve 8 'against the throttle plate 2 'pretensions. When the bolt head 6 'comes into contact with the valve seat 7', the valve space 5 'is replaced by a valve chamber 5' by a return space 10 '. separated, which is in communication with a low pressure region of the fuel injector. Furthermore, the valve chamber 4 'is connected via a flow restrictor 11' extending through the throttle plate 2 'to a control chamber 12' of a nozzle needle 13 'which is connected to the inlet throttle 14' with a high-pressure inlet 15 'by means of an inlet throttle 14' also passing through the throttle plate 2 '. the fuel injector is in communication. Finally, in the throttle plate 2 'is still a relief hole 16' is provided which connects a, between the valve pin 5 ', sealing sleeve 8' and throttle plate 2 'defined space with the low pressure region of the fuel injector. By this connection is at the front ends of the valve pin 5 'in each case a nearly equal pressure, which means that the valve pin 5' with a reduced operating force and only almost against a force of the spring element 9 'in the sealing sleeve 8' moved can be.

If the valve pin 5 'is now displaced axially by the action of a coupler module 17' - not shown here - actuator, so filled with high pressure fuel valve space 4 'with the low pressure return chamber 10' by lifting the bolt head 6 ' from the valve seat 7 'connected. This causes a pressure drop in the valve chamber 4 'and on the outlet throttle 11' and in the control chamber 12 ', which in known manner causes an opening movement of the nozzle needle 13' and initiates an injection process. During the injection process, the valve pin 5 'remains in the open position, so that under high pressure fuel escapes steadily from the valve chamber 4' in the return chamber 10 '. Finally, an end of the injection process is initiated by a discharge of the respective actuator unit, wherein the coupler module 17 'moves back in the axial direction and the valve pin 5' is pressed via the spring element 9 'with the bolt head 6' in the valve seat 7 '. As a result, no further fuel can flow back out of the valve chamber 4 'into the return chamber 10' and the pressure in the control chamber 12 'is raised again via the inlet throttle 14'. From a defined pressure in the control chamber 12 ', this causes a closing movement of the nozzle needle 13' and thus an end of the injection process.

It is further generally known that the valve chamber 4 'of such a fuel injector via a bypass also with the high-pressure inlet 15' is directly in communication to the end of the injection process and from a Contact the bolt head 6 'with the valve seat 7' to fill the valve chamber 4 'and via the outlet throttle 11' and the control chamber 12 'with fuel under high pressure. This results in an additional filling of the control chamber 12 ', which in total results in a faster pressure increase in the control chamber 12' and thus also an earlier closing movement of the nozzle needle 13 '. Usually, the bypass also runs in the throttle plate 2 'and flows between the sealing sleeve 8' and the walls of the valve chamber 4 'in this one.

However, a fuel injector of the prior art has the considerable disadvantage that in the opening position of the valve pin constantly fuel flows from the bypass into the return space. As a result, the return amount of the fuel injector increases significantly, resulting in an increase in the operating temperature of the fuel injector and a reduction in the injection pressure. In addition, the time interval between the movement of the valve pin in the open position and the opening movement of the nozzle needle is increased, since the reduction of the pressure in the control chamber is slower due to the fuel flowing continuously into the valve chamber.

It is therefore an object of the present invention to provide a fuel injector for injecting fuel into a combustion chamber of an internal combustion engine, in which in an open position of the valve pin, a flow of fuel from the bypass is effectively prevented in the valve chamber, while at the end of Injection a rapid filling of the control chamber via the bypass is possible.

Disclosure of the invention

This object is achieved on the basis of the preamble of claim 1 in conjunction with its characterizing features. The following, dependent claims give each advantageous embodiments of the invention.

The invention comprises the technical teaching that a receiving plate is provided between the valve plate and the throttle plate, which defines the valve space together with the valve plate and has a bore. The valve pin runs in this bore and is in the open position via a, the valve seat facing away sealing surface of the bolt head with the receiving plate in contact, whereby the bypass is separated from the valve chamber.

Advantages of the invention

By switching off the bypass in the open position of the valve pin escaping via the return space return quantity can be significantly reduced and thus a reduction in the operating temperature and an increase in the number of injections can be achieved at high speeds. Furthermore, it is possible by the interposition of the receiving plate to reduce the valve space to a minimum necessary for the flow and at the same time to simplify the manufacture of the valve seat on the valve plate considerably. By switching off the bypass can also faster pressure drop in the valve chamber and thus also in the control room can be achieved, which allows a previous injection. In addition, however, a faster return movement of the valve pin in a discharge of the actuator unit due to the voltage applied in the region of the bolt head high pressure can be achieved. As a result, the smallest quantity capability of the fuel injector is improved and scatters considerably reduced. Finally, the drop in injection pressure associated with a non-switchable bypass can be avoided.

According to one embodiment of the invention is in the open position of the valve pin, the sealing surface of the bolt head with a peripheral sealing edge on the receiving plate in contact, wherein the sealing surface and the receiving plate form an angle. By thus formed between the bolt head and receiving plate a part of the kinetic energy is absorbed by squeezing the fuel at an approach of the bolt head to the sealing edge of the receiving plate, whereby the delay is steadier and reduces the impact occurring when hitting the bolt head on the sealing edge of the receiving plate becomes.

In a further development of the invention, the sealing edge is formed at the transition of the bore in the, the valve chamber facing side of the receiving plate. Advantageously, the sealing edge is thereby placed concentrically and with a small difference in diameter for guiding the valve pin, which reduces the holding force necessary for the bypass shutdown.

According to an advantageous embodiment of the invention, the sealing sleeve is placed in a radial expansion of the bore and biased by a, between the receiving plate and sealing sleeve arranged spring element against the throttle plate. In this case, the spring element is advantageously designed as a plate spring. In this way, the sealing sleeve can be arranged to save space in the receiving plate and at the same time a sufficient bias against the throttle plate can be guaranteed.

It is a further embodiment of the invention that the sealing sleeve is in communication with the throttle plate via a circumferential biting edge. By this measure, a reliable sealing of the formed between the sealing sleeve, valve pin and throttle plate space is achieved.

In a further development of the invention, the bypass opens into the bore of the receiving plate. This has the advantage that a connection between the valve chamber and the high-pressure inlet can take place via a short bypass, while the high-pressure fuel passes from the opening into the bore over, between the sealing sleeve and receiving plate or receiving plate and valve pin existing gap to the valve chamber. In this way, a reduction of the production costs can be achieved.

It is a further, advantageous embodiment of the invention that the bypass is formed by a, in the receiving plate in the radial direction extending groove. By means of the provision of a groove on the receiving plate, for example in the form of a laser groove, the outlay for producing the bypass can be considerably reduced. Because due to the shutdown of the bypass requirements for the flow tolerances of the bypass throttle fall coarser, which allows the use of simpler manufacturing processes.

In a further development of the invention, the valve pin is movable against a return spring in the open position, which is placed in a, formed between the sealing sleeve and throttle plate space and communicates via a disc with a shaft of the valve pin. Advantageously, thereby a space-saving arrangement of a return spring of the valve pin can be realized.

Further, measures improving the invention will be described in more detail below together with the description of preferred embodiments of the invention with reference to FIGS.

Brief description of the drawings

Figur 1

eine Schnittansicht eines Kraftstoffinjektors gemäß des Standes der Technik im Bereich eines Ventilbolzens,

Figur 2

eine Schnittansicht des erfindungsgemäßen Kraftstoffinjektors gemäß einer ersten Ausführungsform, im Bereich eines Ventilbolzens,

Figur 3

einen Detailansicht eines Kontaktbereichs zwischen dem Ventilbolzen und einer Aufnahmeplatte, und

Figur 4

eine Schnittansicht des erfindungsgemäßen Kraftstoffinjektors gemäß einer zweiten Ausführungsform.

Show it:

FIG. 1

3 a sectional view of a fuel injector according to the prior art in the region of a valve pin,

FIG. 2

3 a sectional view of the fuel injector according to the invention according to a first embodiment, in the region of a valve pin,

FIG. 3

a detailed view of a contact area between the valve pin and a receiving plate, and

FIG. 4

a sectional view of the fuel injector according to the invention according to a second embodiment.

Embodiments of the invention

In FIG. 2 is a sectional view of the fuel injector according to the invention according to a first embodiment in the region of a valve pin 5 can be seen. In this area, a receiving plate 18 is placed between a valve plate 1, which forms a valve seat 7 for a bolt head 6 of the valve pin 5, and a throttle plate 2. This receiving plate 18 defines together with the valve plate 1 a valve chamber 4 and has a bore 19 through which a shaft 20 of the valve pin 5 is passed. In a widening of the bore 19, a sealing sleeve 8 is furthermore placed, in which the valve pin 5 is guided displaceably via its shaft 20 and which is biased against the throttle plate 2 via a disc spring 21 placed between itself and the receiving plate 18. At its, the bolt head 6 facing away from the valve pin 5 is provided on its shaft 20 with a disc 22, via which it is in contact with a return spring 23. This return spring 23 is in a, between Throttle plate 2 and sealing sleeve 8 defined space placed and pushes the valve pin 5 with the bolt head 6 in the valve seat 7. As a result, the valve chamber 4 is separated by a lying above the valve pin 5 return chamber 10. Finally, the valve pin 5 is at the front end of the bolt head 6 with a - not shown here - Actuator in operative connection, in the actuation of the valve pin 5 is moved in the direction throttle plate 2.

While the return chamber 10 fuel at a low pressure level, in the range of atmospheric pressure leads, the valve chamber 4 via a bypass 24 with high-pressure fuel can be supplied. This bypass 24 communicates with a - not visible in this view - high-pressure inlet and opens radially into the bore 19 of the receiving plate 18 in the region of the sealing sleeve 8 a. Starting from this junction, the fuel can reach the valve chamber 4 in the further course via the gap formed between the receiving plate 18 and the sealing sleeve 8 and between the receiving plate 18 and the shaft 20 of the valve pin 5. In addition, the valve chamber 4 is connected via an outlet throttle 11 with a control chamber 12 of a nozzle needle 13 in connection, which passes through the throttle plate 2 and the receiving plate 18 and opens in the outer radial region of the valve chamber 4 in this.

As further from the detailed view in FIG. 3 shows, the receiving plate 18 has at the transition of the bore 19 in the, the valve chamber 4 facing side of the receiving plate 18 via a sealing edge 25 which occurs in a displacement of the valve pin 5 in the direction of the receiving plate 18 with a sealing surface 26 on the bolt head 6 in contact and thus preventing the flow of fuel from the gap between bore 19 and valve pin 5 in the valve chamber 4. In this case, the sealing surface 26 extends at the bolt head 6 with respect to its side facing the receiving plate 18 beveled so that both components enclose an angle α.

If current is applied to the actuator unit of the fuel injector, then the valve pin 5 is displaced counter to the return spring 23, overcoming a certain force limit in the direction of the receiving plate 18 and thus the bolt head 6 is moved out of the valve seat 7. Due to the differential pressure between the valve chamber 4 and the return chamber 10 then fuel flows from the valve chamber 4 in the return chamber 10 and causes a pressure drop In this case, fuel flows via the outlet throttle 11 and initially also via the bypass 24 and the gaps between the receiving plate 18 and the sealing sleeve 8 or the shaft 20 of the valve pin 5 in the valve chamber 4. However, as soon as the valve pin 5 has arrived in its open position and while the sealing surface 26 of the bolt head 6 has come into contact with the sealing edge 25, the subsequent flow through the bypass 24 is suppressed. From this point on, the total feed rate decreases because the volume flow of fuel flowing through the outlet throttle 11 remains constant due to the cavitating design of the outlet throttle 11, which leads to a faster decrease of the pressure in the control chamber 12. From a certain pressure level in the control chamber 12, this causes the manner known in the art to initiate an opening movement of the nozzle needle 13 and the start of an injection process.

If the actuator unit is subsequently discharged again at the end of the injection process, the valve pin 5 is pushed back again in the direction of the valve plate 1 via the return spring 23. This closing movement is supported by the high pressure between the sealing edge 25 and the sealing surface 26 flowing fuel. As soon as the bolt head 6 has again come into contact with the valve seat 7 on the valve plate 1, the pressure in the valve chamber 4 increases very rapidly owing to the fuel flowing in via the bypass 24, the control chamber 12 also being filled via the outlet throttle 11. In combination with the in the FIGS. 2 and 3 Not to be seen inlet channel of the control chamber 12 is thereby causes a rapid increase in pressure in the control chamber 12, thus achieving the initiation of a rapid closing movement of the nozzle needle 13.

In FIG. 4 is a sectional view of the fuel injector according to the invention according to a second embodiment in the region of the valve pin 5 can be seen. In contrast to the variant described above, a fuel supply of the valve chamber 4 is accomplished in this case via a bypass 24 in the form of a groove on the receiving plate 18. In this case, the bypass 24 is a very short connecting line between a high pressure inlet 15 and the gaps between the receiving plate 18 and the sealing sleeve 8 and the shaft 20 of the valve pin 5.

By means of the variants of the fuel injector according to the invention, it is thus possible to reduce the return amount considerably and thus to lower the operating temperature. The switchable bypass 24 in conjunction with a reduced valve chamber volume can be realized shorter switching cycles, whereby the smallest quantity capability is improved and the spray gaps can be reduced. In addition, a drop in the injection pressure can be avoided and the duration of an injection can be reduced. Finally, there are manufacturing advantages.

Claims (10)

1. Fuel injector for the injection of fuel into a combustion space of an internal combustion engine, comprising a valve plate (1) which forms a valve seat (7) for a valve pin (5) which is guided displaceably in a sealing sleeve (8) and, upon contact with the valve seat (7), separates a return space (10) from a valve space (4) via a pin head (6), the valve space (4) being connected to a control space (12) of a nozzle needle (13) via an outflow throttle (11) running through a throttle plate (2), and being connectable to a highpressure inflow (15) via a bypass (24), and, upon actuation of an actuator unit, the valve pin (5) being moveable from the valve seat (7) into an opening position in order to enable fuel to flow out of the valve space (4) into the return space (10) and thereby to initiate an opening movement of the nozzle needle (13) as a result of a pressure drop in the control space (12), characterized in that, between the valve plate (1) and the throttle plate (2), a reception plate (18) is provided, which together with the valve plate (1) defines the valve space (4) and which has a bore (19) in which the valve pin (5) runs, the valve pin (5), in the opening position, being in contact with the reception plate (18) via a sealing face (26), facing away from the valve seat (7), of the pin head (6), and at the same time separating the bypass (24) from the valve space (4).
2. Fuel injector according to Claim 1, characterized in that, in the opening position of the valve pin (5), the sealing face (26) of the pin head (6) is in contact with a peripheral sealing edge (25) on the reception plate (18), the sealing face (26) and the reception plate (18) forming an angle (α).
3. Fuel injector according to Claim 2, characterized in that the sealing edge (25) is formed at the transition of the bore (19) into that side of the reception plate (18) which faces the valve space (4).
4. Fuel injector according to one of Claims 1 to 3, characterized in that the sealing sleeve (8) is placed in a radial widening of the bore (19) and is prestressed against the throttle plate (2) via a spring element arranged between the reception plate (18) and sealing sleeve (8).
5. Fuel injector according to Claim 4, characterized in that the spring element is designed as a cup spring (21).
6. Fuel injector according to one of the preceding claims, characterized in that the sealing sleeve (8) is connected to the throttle plate (2) via a peripheral biting edge.
7. Fuel injector according to one of the preceding claims, characterized in that the bypass (24) issues into the bore (19) of the reception plate (18).
8. Fuel injector according to Claim 7, characterized in that the bypass (24) is formed by a groove extending in the radial direction in the reception plate (18).
9. Fuel injector according to one of the preceding claims, characterized in that the valve pin (5) is moveable into the opening position counter to a restoring spring (23) which is placed in a space formed between the sealing sleeve (8) and throttle plate (2) and which is connected via a washer (22) to a shank (20) of the valve pin (5).
10. Fuel injection system of an auto-ignition internal combustion engine, comprising at least one fuel injector according to one of Claims 1 to 9.

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