EP2592260B1 - Fuel injector, method for the assembly of a fuel injector and tensioning device for mounting of a fuel injector - Google Patents

Description

State of the art

The invention relates to a fuel injector according to the preamble of claim 1. Furthermore, the invention relates to a method for mounting a fuel injector according to the invention and a clamping device for use in the assembly of a fuel injector according to the invention.

A fuel injector according to the preamble of claim 1 is already known from practice. It is used to inject fuel into the combustion chamber of a particular self-igniting internal combustion engine. The injector housing used in the known fuel injector consists of a nozzle body in which a nozzle needle is guided up and down movable. The nozzle body is clamped axially with the interposition of a throttle plate and a valve plate against a holding body of the fuel injector. For this purpose, a nozzle retaining nut, which is designed in the form of a union nut, and which abuts with a radially inwardly extending collar which acts as an axial stop against a formed on the nozzle body stage. Furthermore, the nozzle retaining nut at its end facing away from the nozzle body on an internal thread which cooperates with a formed on the holding body external thread to secure the nozzle retaining nut on the holding body or can tense.

During operation of the fuel injector, it is imperative that the tightness of the injector is guaranteed. In the case of the component assembly consisting of the nozzle body, the throttle plate and the valve plate and the holding body, this results in the fact that, due in particular to the steadily increasing operating pressures within the fuel injector, relatively high axial clamping forces must be applied by the nozzle clamping nut. This is only possible by increasing the torque or torque of the nozzle lock nut. As a result, however, torques are transmitted to the throttle plate and the valve plate, which can lead to a rotation of the addressed components with respect to the longitudinal axis of the fuel injector. Since the rotational angle position of the components but especially due to arranged in the throttle plate and in the valve plate through holes that must be aligned, it is known from the prior art beyond the nozzle body, the throttle plate, the valve plate and the holding body, for example to connect with each other by means of axially arranged pins. As a result, although a rotation of the components is prevented from each other, but the provision of the pins means a weakening of the components or the need to increase the cross-section of the components, if necessary. In addition, the torque to be transmitted (at a certain diameter of the components or the pins) is limited, so that the mentioned ever-increasing torques on the nozzle lock nut without the risk of damage to the components can no longer be transferred.

From the WO 2005/066487 A1 is a method and apparatus for stretching the clamping nut of an injector known, wherein the clamping nut is stretched and is supported at the other end of the thread. From the EP 2 187 042 A1 In addition, an injector with a plurality of superimposed elements is provided, which are pressed together by the clamping nut.

Disclosure of the invention

Based on the illustrated prior art, the invention has the object, a fuel injector according to the preamble of claim 1 such that even at relatively high operating pressures, meant here operating pressures that are more than 1500 bar, always a dense component network or a dense Kraftstoffinjektor is achieved, wherein during the manufacture of the fuel injector damage to the components or a rotation of the components to each other to be prevented. This object is achieved according to the invention in a fuel injector with the features of claim 1 achieved in that the nozzle retaining nut holding means for a clamping device for elastically extending the nozzle retaining nut in the longitudinal direction thereof at least in a partial region between the collar (the nozzle retaining nut) and the threaded bore. In other words, this means that in a fuel injector according to the invention, a nozzle retaining nut is used in which by clamping in a clamping device, an elastic extension in the longitudinal direction is made possible, so that within the nozzle retaining nut arranged components can then be connected to the holding body largely free of torque by the force applied to the nozzle retaining nut by the tensioning device is lifted after arranging the components in the nozzle retaining nut and the manufacture of the threaded connection between the nozzle retaining nut and the holding body. As a result, the nozzle lock nut shortens after installation in their length, so that the mentioned dense bond between the components is achieved.

There are first and second holding elements are provided, wherein the two holding elements axially spaced from each other are arranged on the outside of the nozzle retaining nut. As a result, the holding means can be particularly easy to bring into operative connection with a clamping device.

In order to maximize the extension of the nozzle retaining nut or to reduce the tensile stresses introduced into the nozzle retaining nut via the clamping device, the at least one first retaining element in an end region of the nozzle retaining nut facing away from the threaded bore and the at least one second retaining element are at a short distance at an end region of the nozzle retaining nut facing the threaded bore arranged for threaded bore Advantageous developments of the inventive fuel injector are listed in the dependent claims.

In a preferred embodiment of the holding elements is proposed that these are designed as radially encircling retaining grooves. Such retaining grooves are particularly easy to produce or produce on the nozzle retaining nut, in particular by grinding or embossing.

For the transmission of particularly high clamping forces or to make the geometry or the size of the retaining grooves as small as possible, it is also proposed that the first and / or second holding elements more Have retaining grooves. As a result, the tensile forces transmitted by the tensioning device to the nozzle retaining nut are introduced into the nozzle retaining nut via a plurality of retaining grooves and thus minimized.

In order to be able to make the clamping device provided for use with the retaining grooves as simple as possible, it is also advantageous if the retaining grooves each have an axial stop surface.

Especially preferred is an embodiment of the fuel injector, in which the nozzle body and the holding body are axially braced against each other under the axial interposition of a throttle plate and a valve plate. In particular, it can be provided that the nozzle retaining nut, the holding body and possibly the throttle plate and the valve plate are connected to each other in the axial direction without these in their angular position to each other positioning, in particular pin-shaped holding means. This makes it possible to minimize the size of the fuel injector in terms of its cross-sectional area. Also, by eliminating the additional components, the manufacturing costs of the fuel injector are reduced and possible errors in the assembly of the fuel injector by the additional components excluded.

The invention also includes a method for assembling a fuel injector according to the invention. It is provided that initially takes place a clamping a union nut in a clamping device in the region of the holding means. Subsequently, an axial expansion force is applied to the nozzle retaining nut for elastic extension of the nozzle retaining nut. Thereafter (or before the application of the stretching force), a nozzle body and possibly a throttle plate and a valve plate are introduced into the nozzle retaining nut. Subsequently, a screwing of a holding body with the nozzle retaining nut and finally a loosening of the connection between the clamping device and the nozzle lock nut in the region of the holding means.

Particularly advantageous is a mounting method in which the screwing of the holding body with the nozzle retaining nut takes place substantially free of torque. This will affect the angular position of the components within the Nozzle locknut reliably prevented even without additional fasteners.

Furthermore, the invention comprises a clamping device for use in a fuel injector according to the invention. In this case, it is provided that at least two clamping elements which can be connected to the retaining means of the nozzle retaining nut are provided, wherein the axial spacing of the retaining means is mutually variable.

In a preferred embodiment of the tensioning device, it is proposed that the tensioning device has at least two tensioning elements which can be connected at least indirectly to the retaining means of the nozzle tensioning nut, wherein the axial spacing of the retaining means can be changed relative to one another. As a result, the distance of the clamping sections in the longitudinal direction by a rotation of the clamping means to each other in a particularly simple manner increase in order to introduce the required tensile stresses in the nozzle retaining nut.

A particularly simple installation of the clamping means on the nozzle lock nut is made possible when each of the clamping means consists of two cooperating half-shell elements which surround the nozzle lock nut at its periphery.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawing.

Fig. 1

einen Längsschnitt durch den unteren, rechten Bereich eines erfindungsgemäßen Kraftstoffinjektors,

Fig. 2

die bei dem Kraftstoffinjektor gemäß Fig. 1 verwendete Düsenspannmutter im Längsschnitt,

Fig. 3

ein Detail der Düsenspannmutter gemäß der Fig. 2 im Bereich einer oberen Haltegeometrie,

Fig. 4

ein Detail der Düsenspannmutter gemäß der Fig. 2 im Bereich einer unteren Haltegeometrie,

Fig. 5 bis 8

jeweils Teillängsschnitte durch gegenüber den Fig. 3 und 4 modifizierten Haltegeometrien,

Fig. 9

in perspektivischer Darstellung eine Spanneinrichtung für eine Düsenspannmutter gemäß der Fig. 2,

Fig. 10

die Spanneinrichtung gemäß Fig. 9 in teilweise geschnittener Längsansicht und

Fig. 11

in teilweise geschnittener Längsansicht eine gegenüber der Fig. 10 modifizierte Spanneinrichtung.

This shows in:

Fig. 1

a longitudinal section through the lower, right portion of a fuel injector according to the invention,

Fig. 2

in the fuel injector according to Fig. 1 used nozzle retaining nut in longitudinal section,

Fig. 3

a detail of the nozzle retaining nut according to the Fig. 2 in the area of an upper holding geometry,

Fig. 4

a detail of the nozzle retaining nut according to the Fig. 2 in the range of a lower holding geometry,

Fig. 5 to 8

each partial longitudinal sections through the opposite 3 and 4 modified holding geometries,

Fig. 9

in a perspective view a clamping device for a nozzle lock nut according to the Fig. 2 .

Fig. 10

the tensioning device according to Fig. 9 in a partially sectioned longitudinal view and

Fig. 11

in partially sectioned longitudinal view one opposite the Fig. 10 modified clamping device.

The same components or components with the same function are provided in the figures with the same reference numerals.

In the Fig. 1 is the a combustion chamber of an internal combustion engine, not shown, in particular a self-igniting internal combustion engine, facing end portion of a fuel injector 10 according to the invention or its injector 11 is shown. The injector housing 11 comprises a nozzle body 12, in which a (not shown) nozzle needle is guided up and down movable. In the axial direction is followed by the nozzle body 12, a throttle plate 13 and a valve plate 14, to which in turn in the axial direction, a holding body 15 connects. The respective mutually facing end faces or end faces of the nozzle body 12, the throttle plate 13, the valve plate 14 and the holding body 15 are axially braced against each other to produce a sealed injector housing 11. Serves for this purpose in a known manner, a nozzle retaining nut 20, which has a radially inwardly projecting, circumferential collar 21 at its end portion associated with the nozzle body 12, which at one Paragraph 22 of the nozzle body 12 is applied, which thus forms an axial stop for the nozzle retaining nut 20 in the direction of the holding body 15.

The nozzle clamping nut 20 has at least on its inner side different diameter ranges, which are adapted to the respective outer diameter of the nozzle body 12, the throttle plate 13, the valve plate 14 and the holding body 15, such that the addressed components radially with minimal radial clearance of the nozzle lock nut 20 are.

On the holding body 15 facing end portion, the nozzle lock nut 20 on its inner wall a threaded bore 23 which cooperates with a corresponding external thread 24 which is formed on the valve plate 14 facing the end region of the holding body 15. About trained by the threaded bore 23 and the external thread 24 threaded connection 25 which is required to maintain the dense component network axial clamping force is transmitted to the components.

A fuel injector 10 described so far as well as the components described are already well known. It is essential to the invention that the nozzle retaining nut 20 holding means 30 for a particular in the FIGS. 9 and 10 recognizable clamping device 100 has. The holding means 30 comprise first holding elements 31 and axially spaced second holding elements 32. The first holding elements 31 are formed on the outer wall or on the outer circumference of the nozzle retaining nut 20 on the holding body 15 facing away from the end region. As in particular on the basis of Fig. 2 and 4 can be seen, the first holding member 31 is formed as a radially encircling holding groove 33. The retaining groove 33 has a (horizontal) abutment surface 35 which is arranged perpendicular to the longitudinal axis 34 of the nozzle retaining nut 20 and which merges via a short intermediate region 36 extending parallel to the longitudinal axis 34 into an obliquely or conically running transition surface 37.

The angle α of the transition surface 37 with respect to the longitudinal axis 34 is an example of about 20 ° at a radial width of the stop surface 35 of about 1 mm. Of course, it is also within the scope of the invention, a plurality of spaced apart in the longitudinal direction of the nozzle retaining nut 20 first holding elements 31 and holding grooves 33, which then together form the first holding elements 31.

The second holding elements 32 include, in particular with reference to the Fig. 2 and 3 It can be seen, two spaced apart in the longitudinal direction of the nozzle retaining nut 20, in the exemplary embodiment identically formed retaining grooves 38. The second holding elements 32 and the retaining grooves 38 are arranged in the longitudinal direction just below the height of the threaded bore 23 on the outer circumference of the nozzle retaining nut 20. The retaining grooves 38 are in principle formed like the retaining groove 33. This means that each of the retaining grooves 38 has an abutment surface 39 extending perpendicularly to the longitudinal axis 34, an intermediate region 40 and an obliquely or conically arranged transition surface 41, wherein the angle β of the transition surface 41, relative to the longitudinal axis 34, is identical to the angle α is formed, that is also about 20 °. It is essential that the inclination of the transition surfaces 37, 41 is aligned in different directions, so that the abutment surface 35 and the two abutment surfaces 39 can serve to secure the region of the nozzle retaining nut 20 arranged between the retaining elements 31, 32 in the direction of the double arrow 42 (FIG. Fig. 2 ) to act with a compressive force, which causes an elastic elongation of the nozzle lock nut 20 in the region between the holding elements 31 and 32.

In the Fig. 5 to 8 By way of example, different geometric configurations of the second holding elements 32 are shown, which, of course, can also be transferred to the first holding elements 31 in a similar manner. In the Fig. 5 the case is shown in which in the longitudinal direction of the nozzle lock nut 20, three axially spaced-apart retaining grooves 38 are provided. In particular, it can be seen that the retaining grooves 38 extend radially inwardly from the outside of the nozzle retaining nut 20. In the in the Fig. 6 illustrated embodiment, the retaining grooves 38 are replaced by rectangular in cross-section retaining grooves 38a. In the in the Fig. 7 illustrated embodiment find retaining grooves 38b use whose geometry corresponds to the geometry of the retaining grooves 38, but the retaining grooves 38b extend radially outward from the outer side 43 of the nozzle lock nut 20. Extend in a similar way also the rectangular in cross-section retaining grooves 38c according to the Fig. 8 radially outward.

The in a synopsis of FIGS. 9 and 10 recognizable, the assembly of the fuel injector 10 serving clamping device 100 comprises two cooperating clamping elements 101, 102 for clamping the nozzle lock nut 20. Each of the two clamping elements 101, 102 each have two interconnected in the longitudinal direction, semicircular clamping shells 103 to 106. How best by the Fig. 10 can be seen, are formed on the inner circumference or on the inner surface of the clamping shells 103 to 106 clamping portions 107, 108, the shape of the shape of the holding elements 31 and 32 is adapted so that the clamping portions 107, 108 cooperate positively with the holding elements 31, 32. Furthermore, it can be seen that the longitudinally adjoining clamping elements 101, 102 are formed on the mutually facing end faces 109, 110 such that the end faces 109, 110 extend obliquely to the longitudinal axis of the clamping device 100. As a result, with a radial rotation of the clamping elements 101, 102, a change in the distance between the clamping sections 107, 108 is effected relative to each other.

In order to connect or secure the clamping elements 101, 102, which comprise the nozzle retaining nut 20 radially, with the nozzle retaining nut 20, a lower clamping ring 112 and an upper clamping ring 113 are furthermore provided which engage the clamping device 100 or the two clamping elements 101, 102 The two opposite end portions comprise radially from the outside.

The assembly of the nozzle body 12, the throttle plate 13, the valve plate 14 and the holding body 15 with the nozzle lock nut 20 is done as follows: First, in the clamping device 100, the nozzle lock nut 20 is clamped, as shown in the FIGS. 9 and 10 is shown. Subsequently, by means of a radial rotation of the two clamping elements 101, 102 in the areas between the holding elements 31 and 32 on the nozzle retaining nut 20, a compressive force acting in the longitudinal direction of the nozzle clamping nut 20 is produced, which causes a (elastic) elongation of the nozzle retaining nut 20. As soon as this is done, alternatively already before the clamping of the nozzle retaining nut 20 in the clamping device 100, the nozzle body 12, the throttle plate 13 and the valve plate 14 in the nozzle retaining nut 20 are introduced in their correct position. It is essential that when screwing the nozzle retaining nut 20 with the holding body 15, the nozzle lock nut 20 is still in the clamping device 100 and is subjected to the force of the clamping device 100 , When screwing or connecting the nozzle lock nut 20 with the holder body 15, it is sufficient to carry out the screwing with a relatively low torque, that is, as soon as the components are at an axial stop, the Verschraubprozess can be stopped. Subsequently, the two clamping elements 101, 102 of the clamping device 100 are rotated back into its original angular position, so that the clamping device 100 no longer transfers force to the nozzle retaining nut 20. This now tries to retake its original (shortened) length, wherein in the desired manner between the components desired sealing or the axial tension occurs.

In the Fig. 11 a modified tensioner 100a is shown. In the clamping device 100a find a preferably in the longitudinal direction in two parts, lower clamping ring 112a and an upper clamping ring 113a use, wherein the upper clamping ring 113a has a thread 117 on its outer side. While the upper clamping ring 113a bears directly against the second holding element 32 in a form-fitting manner, the lower clamping ring 112a is surrounded radially by a transition sleeve 119 which has a thread turn 118 on its outer side. It is essential that the two threads 117, 118 are oriented differently, that is, for example, the upper thread 117 is formed as a left-hand thread, while the lower thread 118 is formed as a right-hand thread (alternatively, it is conceivable, the two threads 117, 118 at the same orientation with different degrees of slope form). The clamping elements 101 a and 102 a have on their inner surface with the threads 117, 118 cooperating threaded portions 121, 122. Now, if the two clamping elements 101 a, 102 a to the nozzle clamping nut 20 is rotated in the same direction, so takes place due to the different direction of the threads 117, 118, an elongation of the nozzle retaining nut 20 in the longitudinal direction.

The fuel injector 10 described so far as well as the tensioning device 100, 100a can be modified or modified in many ways without deviating from the idea of the invention. This consists in elastically lengthening or prestressing the nozzle retaining nut 20 axially in its longitudinal direction during assembly of components in the nozzle retaining nut 20 or before connecting the nozzle retaining nut 20 to a retaining body 15, thereby producing a biasing force in the nozzle retaining nut 20. which, after a largely torque-free assembly with the holding body 15 generates an axial clamping force on the components located within the nozzle clamping nut 20 in order to form a dense fuel injector 10 even at relatively high operating pressures.

Claims (11)

1. Fuel injector (10), in particular common-rail injector, having an injector housing (11) which comprises a nozzle body (12) which is braced axially at least indirectly against a holding body (15) by way of a nozzle clamping nut (20), wherein the nozzle clamping nut (20) has, in the manner of a sleeve nut, a collar (21) which bears axially against the nozzle body (12), and wherein the sleeve nut (20), on the side facing toward the holding body (15), interacts by way of a threaded bore (23) with an external thread (24) formed on the holding body (15),
   characterized in that the nozzle clamping nut (20) has holding means (30) for a clamping device (100; 100a) for elastically lengthening the nozzle clamping nut (20) in the longitudinal direction thereof between the collar (21) and the threaded bore (23), wherein the holding means (30) comprise a first holding element (31) and a second holding element (32) which are arranged axially spaced apart from one another on the outer side of the nozzle clamping nut (20), wherein the first holding element (31) is arranged in an end region of the nozzle clamping nut (20) averted from the threaded bore (23), and the second holding element (32) is arranged, at a smaller distance from the threaded bore (23), in an end region of the nozzle clamping nut facing toward the threaded bore.
2. Fuel injector according to Claim 1,
   characterized
   in that the holding elements (31, 32) are in the form of radially encircling holding grooves (33, 38; 38a to 38c).
3. Fuel injector according to Claim 2,
   characterized
   in that the first and/or the second holding elements (31, 32) each have multiple holding grooves (33, 38; 38a to 38c).
4. Fuel injector according to Claim 2 or 3,
   characterized
   in that the holding grooves (33, 38; 38a to 38c) each have an axial abutment surface (35, 39).
5. Fuel injector according to one of Claims 1 to 4, characterized
   in that the nozzle body (12) and the holding body (15) are braced axially against one another with the axial interposition of a throttle plate (13) and a valve plate (14).
6. Fuel injector according to Claim 5,
   characterized
   in that the nozzle clamping nut (12), the holding body (15) and possibly the throttle plate (13) and the valve plate (14) are connected to one another without in particular pin-shaped holding means which position these in their angular position relative to one another.
7. Method for assembling a fuel injector (10) according to one of Claims 1 to 6, having the following steps:

   - clamping a sleeve nut (20) into a clamping device (100; 100a) in the region of the holding means (30),

   - applying an axial stretching force to the nozzle clamping nut (20) in order to elastically lengthen the nozzle clamping nut (20),

   - inserting a nozzle body (12) and possibly a throttle plate (13) and a valve plate (14) into the nozzle clamping nut (20) before or after the axial stretching force is applied to the nozzle clamping nut (20),

   - screwing a holding body (15) to the nozzle clamping nut (20),

   - releasing the connection between the clamping device (100; 100a) and the nozzle clamping nut (20) in the region of the holding means (30).
8. Method according to Claim 7,
   characterized
   in that the screwing of the holding body (15) to the nozzle clamping nut (20) is performed substantially without a torque.
9. Clamping device (100; 100a) for use with a fuel injector (10) according to one of Claims 1 to 6, for the purposes of carrying out a method according to Claim 7 or according to Claim 8, characterized
   in that the clamping device (100; 100a) has at least two clamping elements (101; 101a, 102; 102a) which are at least indirectly connectable to the holding means (30) of the nozzle clamping nut (20), wherein the axial spacing of the holding means (30) to one another is variable.
10. Clamping device according to Claim 9,
    characterized
    in that the clamping elements (101, 102) have, on their face sides which face toward one another and which bear against one another, contact surfaces (109, 110) which run obliquely with respect to the longitudinal axis (34) of the nozzle clamping nut (20).
11. Clamping device according to Claim 9 or 10,
    characterized
    in that each of the clamping elements (101; 101a, 102; 102a) is composed of two half-shell-shaped clamping shells (103 to 106) which interact with one another and which surround the nozzle clamping nut (20) at the circumference thereof.

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