WO2001014735A1

WO2001014735A1 - Fuel injection valve for internal combustion engines

Info

Publication number: WO2001014735A1
Application number: PCT/DE2000/002672
Authority: WO
Inventors: Friedrich Boecking
Original assignee: Robert Bosch Gmbh
Priority date: 1999-08-20
Filing date: 2000-08-10
Publication date: 2001-03-01
Also published as: EP1125057A1; JP2003507655A; DE19939455A1; CZ20011386A3; KR20010080200A

Abstract

The invention relates to a fuel injection valve for internal combustion engines. The inventive fuel injection valve (10) has an adjustable stroke limit (32) for the valve needle (18). The stroke limit (32) has a limiting stop (34) which is displaceably guided in a guiding bore (36) of the fuel injection valve; and at least one actuator. Said limiting stop (34, 34a) has an axial gap (62, 62a) in which the actuator (64) is located. When the actuator (64) is actuated, it expands in such a way that the limited stop (34, 34a) is expanded and becomes jammed in its guiding bore (36). In this way, it is possible to adjust a stroke for the valve needle (18) throughout a very large range with a relatively small actuator (64).

Description

Fuel injection valve for internal combustion engines

State of the art

The invention is based on a fuel injection valve for internal combustion engines according to the preamble of claim 1. Such a fuel injection valve known from DE 43 32 124 AI has an adjustable stroke limitation for the valve needle. The stroke limiter has a limit stop, which is displaceably guided in a guide bore of the fuel injection valve, and an actuator. The limit stop and the actuator are arranged axially one behind the other and around the valve needle. By actuating the actuator, it changes its axial length, which limits the stroke limitation for the valve needle and thus its stroke. Through this

The stroke of the valve needle can be changed within a range of approx. 0.1 mm. If a larger change in the stroke is necessary, several actuators must be arranged one behind the other, which, however, makes the axial length of the fuel injection valve very large.

It is also known to directly control a valve needle so as to achieve a change in the stroke. However, this requires a great deal of effort. Advantages of the invention

The fuel injection valve for internal combustion engines according to the invention with the characterizing features of claim 1 has the advantage that the stroke of

Valve needle can change in a very large area. In addition, only a very small actuator is required. It is advantageous here to design the limit stop as a ring arranged around the valve needle with an axial gap.

If two brake shoes, which are fixed in the axial direction of the fuel injection valve and between which two actuators are arranged, are arranged in the gap, the actuators can be fixed, which is favorable for the electrical connections.

If a spring element is arranged in the guide bore of the limit stop axially to the limit stop and exerts a force acting on the limit stop against the opening direction of the fuel injection valve, the limit stop can be brought into an initial position. For this purpose, the spring element is supported on a shoulder surface of the fuel injection valve, which faces away from the opening direction of the fuel injection valve.

It is expedient that the limit stop during an injection process by a shoulder surface in the opening direction of the fuel injection valve

Valve needle is displaceable in the opening direction, since the limit stop can thereby be displaced without additional means. A simple construction and an easy assembly is given if the limit stop has a washer which is arranged between the limit stop and the shoulder surface of the valve needle.

If a shoulder surface which forms an end stop for the limiting stop and which points away from the opening direction is formed in the guide bore, there is a maximum stroke of the valve needle. The field element is also protected against damage.

Furthermore, it proves to be very favorable to use a piezoelectric element as the actuator.

Further advantages and advantageous developments of the object of the invention can be found in the description, the drawing and the claims.

drawing

An embodiment of the fuel injection valve for internal combustion engines according to the invention is shown in the drawing and explained in more detail in the following description. Show it:

1 shows a longitudinal section through a partially illustrated fuel injection valve, FIG. 2a shows a view of a first stroke limitation, FIG. 2b shows a plan view of the stroke limitation according to FIG. 2a,

3a shows a view of a second stroke limitation and FIG. 3b shows a plan view of the stroke limitation according to FIG. 3a. Description of the embodiment

A fuel injection valve 10 for internal combustion engines shown in FIG. 1 has a valve body 12 which is axially clamped to a valve holding body 14 by means of a union nut (not shown). The valve body 12 has an axial guide bore 16 in which a valve needle 18 is guided so as to be axially displaceable. At the end of the valve needle 18, which projects into a combustion chamber of the internal combustion engine to be supplied, there is an as

Valve closing member acting valve head 20 is formed. The valve head 20 has a conical sealing surface 22 facing the valve body 12, which cooperates with a corresponding valve seat surface 24 on the front side of the valve body 12 on the combustion chamber side. Radial injection bores 26 are formed at the end of the valve body 12 projecting into the combustion chamber, wherein an injection bore 26 would also be sufficient. The injection bores 26 are arranged such that when the valve needle 18 rests with its sealing surface 22 on the valve seat surface 24, the injection bores 26 are closed by the valve head 20. If the valve needle 18 moves during an opening movement in the opening direction indicated by an arrow 28, ie when the valve needle 18 moves into and out of the valve body 12, a connection is established between a pressure chamber 30 containing fuel and that in the valve body 12 the nozzle needle 18 is formed, and the injection bores 26 are created. Depending on how far the nozzle needle 18 moves out of the valve body 12, ie depending on how large the stroke of the valve needle 18, more or fewer injection bores 26 are released, whereby more or less fuel is injected. An adjustable stroke limiter 32 is provided to change the stroke of the valve needle 18. The stroke limiter 32 has a limit stop 34, which is displaceably guided in a guide bore 36 of the fuel injection valve 10. As can be seen from FIG. 1, the guide bore 36 is partly formed in the valve body 12 and partly in the valve holding body 14. However, it can be seen that the guide bore 36 can also be formed only in the valve body 12 or only in the valve holding body 14. In the present embodiment, the

Valve body 12 formed part 36 * of the guide bore 36 preferably a smaller diameter than the diameter of the part 36 "of the guide bore 36 formed in the valve holding body 14. Thus, the diameter of the part 36 'of the guide bore 36 is also smaller than that of the

Limiting stop 34. This results in a shoulder surface 37 at the transition from the valve body 12 to the valve holding body 14. The shoulder surface 37 on the valve body 12 faces away from the opening direction 28 and forms an end stop for the limiting stop 34.

A spring element 38 is arranged axially to the limit stop 34 in the guide bore 36 of the limit stop 34, which is preferably a helical spring. The spring element 38 exercises on the

Limiting stop 34 exerts a force acting against the opening direction 28 of the fuel injection valve 10. For this purpose, the spring element 38 is preferably supported on a shoulder surface 40 of the fuel injection valve 10, which is from the opening direction 28 of the fuel injection valve

10 points away, and is preferably formed on the valve body 12. A washer 44 is preferably provided on the end face 42 of the limit stop 34 facing away from the spring element 38. On the end face 46 of the end facing away from the end face 42 of the limit stop 34 U-washer 44, a shoulder surface 48 of the valve needle 18 can come to rest. The washer 44 of the limit stop 34 is thus arranged between the limit stop 34 and the shoulder surface 48 of the valve needle 18. As can be seen from FIG. 1, the washer 44 can also be formed in one piece with the limit stop 34. It is also possible that the shoulder surface 48 has a larger diameter, so that the washer 44 can be dispensed with entirely.

The valve needle 18 projects with a shaft part 50 into a spring chamber 52 provided in the valve holding body 14 and there has a spring plate 54 firmly connected to the valve needle 18. At this spring plate 54 engages a valve spring 56 which is located on one of the

End face 58 of the valve holding body 14 which points to the opening direction 28 and thus keeps the valve needle 18 prestressed via the sealing surface 22 in contact with the valve seat surface 24. A further shaft part 60 of the valve needle 18 adjoins the spring plate 54, via which the

Valve needle 18 can be operated in the usual way. That is, if a force is exerted on the shaft part 60 in the opening direction 28 that is greater than the spring force of the valve spring 56, the fuel injection valve 10 opens for an injection process.

Furthermore, a control device (not shown) for the fuel injection valve 10 is also provided.

It can be seen from FIGS. 2a and 2b that the

Limit stop 34 has an axial gap 62, in which an actuator 64, preferably a piezo element, is arranged. In the present exemplary embodiment, the limit stop 34 is a ring arranged around the valve needle 18 with an axial gap 62. The actuator 64 expands in the activated state, so that the gap 62 and thus also the limit stop 34 is widened, as a result of which the otherwise axially displaceable limit stop 34 clamps in its guide bore 36.

A modified limit stop 34a is shown in FIGS. 3a and 3b. Two brake shoes 66 are arranged in the gap 62a, between which at least one actuator 64, preferably two actuators 64, are arranged. The brake shoes 66 have approximately the length of the guide bore 36, so that they are preferably fixed in the axial direction. This has the advantage that the actuators 64 do not have to be moved. The limit stop 34a can slide along the brake shoes 66.

In operation, the valve body 12 of the

Fuel injection valve 10 is initially closed by valve needle 18, which is in the closed position. The limit stop 34, 34a is pressed with its washer 44 against the shoulder surface 48 of the valve needle 18 by the pressure force of the spring element 38. The actuator 64 is not activated by the control device. During an injection, the nozzle needle 18 is moved in the opening direction 28. The

Limit stop 34 and its washer 44 are thus also displaced in the opening direction 28 by the shoulder surface 48 of the valve needle 18. Once the required stroke has been reached, the actuator 64 is actuated by the control device in such a way that it expands in such a way that the limit stop 34, 34a clamps in the guide bore 36. The valve needle 18 cannot move any further in the opening direction 28 since its stroke is limited by the limit stop 34, 34a. This gives a certain opening cross-section for a certain amount of fuel is located on the one or more injection bores 26.

After the end of the injection process, the valve needle 18 returns to its closed position. Depending on the previous injection, the limit stop 34, 34a with its washer 44 can either be brought back into contact with the shoulder surface 48 of the valve needle 18 by the spring element 38 or can at least be shifted a little counter to the opening direction 28. As a result, the opening cross-section is the next injection process

Injection bore 26 or the injection bores 26 less, whereby less fuel is injected.

Alternatively, the limit stop 34 can remain in its position in that the actuator 64 is still controlled by the control unit. As a result, the valve needle 18 has the same stroke during the next injection process, as a result of which the same amount of fuel is injected.

If too little fuel has been injected, the valve needle 18 can move the limit stop 34, 34a further during the next injection, so that the stroke is increased. As a result, the opening cross section of the injection bore 26 or the injection bores 26 is enlarged, as a result of which more fuel is injected.

The limit stop 34, 34a can thus be moved again for each injection process or over several

Injections stay in the same position. The stroke of the valve needle 18 is thus very variable and adjustable in a large range by the limit stop 34, 34a. The actuator (s) 64 required are very small, since they are arranged in the gap 62, 62a of the annular limit stop 34, 34a.

Because of the shoulder surface 37 forming an end stop for the limit stop 34, the maximum stroke is

Given valve needle 12. In addition, it is ensured that the valve needle 18 is not moved too much during the opening process and the spring element 38 is thereby damaged, since the spring element 38 has sufficient space in the part 36 ^{λ of} the guide bore 36.

In the present exemplary embodiment, the stroke limitation 32 has been described with reference to a fuel injection valve 10 that opens to the outside. However, the stroke limiter 32 can also be used for fuel injection valves that open when the valve needle moves into the interior of the fuel injection valve. In this case, the spring element 38 is supported in the guide bore 36 on the shoulder surface opposite the shoulder surface 40. In this case, the spring element 38 is closed

Limit stop 34 with its washer 44. A shoulder surface 48 of the valve needle 18 is also supported on the washer 44. In the case of such a fuel injection valve, the opening direction points counter to the opening direction 28 shown in FIG. 1.

It is advantageous that the limit stop 34, 34a can be displaced in the opening direction 28 during an injection process by the shoulder surface 48 of the valve needle 18 pointing in the opening direction 28 of the fuel injection valve 10, as a result of which the limit stop 34, 34a can be displaced into the required position. Furthermore, the limit stop 34, 34a by the spring element 38 again brought into its starting position. This eliminates the need for an additional adjusting element for the limit stop 34

Claims

Expectations

1. Fuel injection valve (10) for internal combustion engines with an adjustable stroke limiter (32) for the valve needle (18), the stroke limiter (32) having a limit stop (34, 34a) which is displaceably guided in a guide bore (36) of the fuel injector (10) and has at least one actuator (64), characterized in that the limiting stop (34) has an axial gap (62, 62a) and that the at least one actuator (64) is arranged in the gap (62, 62a) in such a way that that the at least one actuator (64) widens the gap (62, 62a) in the activated state, so that the limit stop (34, 34a) clamps in its guide bore (66).

2. Fuel injection valve (10) according to claim 1, characterized in that the limiting stop (34, 34a) is a ring arranged around the valve needle (18) with an axial gap (62, 62a).

3. Fuel injection valve (10) according to claim 1 or 2, characterized in that in the gap (62a) two preferably in the axial direction of the

Fuel injection valve (10) stationary brake shoes (66) are arranged, between which at least one actuator (64), preferably two actuators (64), are arranged.

4. Fuel injection valve (10) according to one of claims 1 to 3, characterized in that in the guide bore (36) of the limit stop (34, 34a) axially to the limit stop (34, 34a), a spring element (38), preferably a coil spring, is arranged is, which exerts a force acting against the opening direction (28) of the fuel injection valve (10) on the limit stop (34).

5. Fuel injection valve (10) according to claim 4, characterized in that the spring element (38) is supported on a shoulder surface (40) of the fuel injection valve (10) which points away from the opening direction (28) of the fuel injection valve (10).

6. Fuel injection valve (10) according to one of claims 1 to 5, characterized in that the limit stop

(34, 34a) can be displaced in the opening direction (28) during an injection process by a shoulder surface (48) of the valve needle (18) pointing in the opening direction (28) of the fuel injection valve (10).

7. Fuel injection valve (10) according to claim 6, characterized in that the limit stop (34, 34a) a

Washer (44) which between the

Limit stop (34, 34a) and the shoulder surface (48) of the valve needle (18) is arranged.

8. Fuel injection valve (10) according to one of claims 4 to 7, characterized in that in the guide bore (36) an end stop for the limit stop (34, 34a) forming shoulder surface (37) is formed, which is from the opening direction (28) points away.

9. Fuel injection valve (10) according to one of claims 1 to 8, characterized in that the actuator (64) is a piezoelectric element.