WO2001094775A1

WO2001094775A1 - Fixing means for a fuel injection valve

Info

Publication number: WO2001094775A1
Application number: PCT/DE2001/002060
Authority: WO
Inventors: Uwe Liskow; Heinz Martin Krause; Albrecht Baessler; Stefan Lauter; Thomas Fuerst
Original assignee: Robert Bosch Gmbh
Priority date: 2000-06-03
Filing date: 2001-05-31
Publication date: 2001-12-13
Also published as: DE10027669A1

Abstract

The invention relates to fixing means (1) for a fuel injection valve (3) which can be inserted into a receiving bore (5) of a cylinder head (2) in an internal combustion engine, for directly injecting fuel into a combustion chamber (4) of said internal combustion engine. Said fixing means have a sleeve (12) comprising a step (13), said sleeve being at least partially located in the receiving bore (5). The sleeve (12) surrounds the fuel injection valve (3) peripherally and the cross-section of said sleeve (12) changes at the step (13). The fixing means (1) has at least one sealing element (11) which lies adjacent to the sleeve (12) in the vicinity of the step (13) and which is axially subjected to a pre-tensioning force when assembled.

Description

Fasteners for a fuel injector

State of the art

The invention relates to a fastening means for a fuel injector according to the preamble of claim 1.

From DE 197 43 103 AI a fastener according to the preamble of claim 1 is known, which is designed as a heat protection sleeve. The fastening means is inserted into a stepped receiving bore of a cylinder head of an internal combustion engine, and it surrounds a spray-side nozzle body of a fuel injector inserted into the receiving bore. The fastening means has a collar at one end, which bears against a step of the receiving bore. The tubular sleeve of the fastening means is bent over at the spray-side end in order to achieve a double position of the sleeve which is acted upon radially to seal an annular gap formed between the nozzle body and the receiving bore. In order to apply a radial prestress to the bent section of the sleeve, the nozzle body of the fuel injector has a conical section which is pushed into the sleeve and is clamped in the sleeve in the region of the bent section. From the conical section of the nozzle body there is therefore between the nozzle body and the sleeve against the direction of insertion of the nozzle body into the fastening means an annular gap is formed in order to enable the insertion of the conical section of the nozzle body up to the bent region of the sleeve.

A disadvantage of the fastening means known from DE 197 43 103 AI is that the fuel injector is jammed in the fastening means. Since the fuel injector also bears against an inclined step of the receiving bore, the axial position of the fuel injector is completely determined, which has disadvantages, which will be discussed below. In addition, the nozzle body jammed in the fastener is difficult to loosen, so that an expansion of the fuel injector, e.g. for maintenance or assembly work.

Another disadvantage is that the pretension with which the bent section of the sleeve is acted upon can only be predetermined approximately by design, so that the fastening means can be permeable to gases if the pretensioning is too low, or the nozzle body or the fastening means is damaged can become if the preload is too large.

From DE 197 35 665 AI a fuel injection system is known in which a fuel injection valve is connected to a fuel distributor line by means of an intermediate piece. The fuel injector is attached to a cylinder head by a hold-down device in the form of a clamping claw. A nozzle body of the fuel injector is inserted into a receiving bore in the cylinder head, whereby the position of the axis of the fuel injector is predetermined. Since several such fuel injection valves are arranged together on the fuel distributor line and the fuel distributor line is rigid, it is necessary to compensate for an axis offset and an axis inclination between the axis of the fuel injector and the axis of a connecting piece for each fuel injector. The compensation takes place via the intermediate piece, wherein the intermediate piece has sealing rings which enable the intermediate piece to be tilted without fuel escaping into undesired areas when fuel is introduced from the fuel distributor line into the fuel injection valve.

In the fuel injection valve of the fuel injection system, a groove is also provided on the nozzle body of the fuel injection valve, into which a sealing ring for sealing an annular gap between the nozzle body and the cylinder head is introduced.

The known from DE 197 35 665 AI solution to compensate for the position and angle deviation at the connection between the fuel rail and the fuel injector has the disadvantage that an additional intermediate piece is required, which requires additional space, whereby the fuel rail further from the cylinder head is spaced. In addition, the intermediate piece requires additional assembly effort.

The seal provided on the injection-side end of the fuel injector on the nozzle body, which consists of a groove in the nozzle body into which a sealing ring is inserted, for protecting the nozzle body from the temperature of the combustion gases has the disadvantage that the prestressing of the sealing ring is due to the cross section of the sealing ring is determined and cannot be set. When the elasticity of the sealing ring diminishes over the operating time of the fuel injector, the tightness of the seal diminishes, so that combustion gases can enter the annular gap formed between the nozzle body and the cylinder head. In addition, materials with an elasticity which enables the sealing ring to be introduced between the cylinder head and the pressure nozzle and which generates a suitable preload are generally not sufficiently heat-resistant, so that there are further problems with such a seal. From DE 198 08 068 AI a fuel injector with a nozzle body is known, which has a circumferential groove at its spray-side end, in which a sealing element is inserted. The sealing element consists of a bimetal or of a material with shape memory, the sealing element bending when heated, so that an outer diameter of the sealing element is larger than the diameter of the nozzle body. In the assembled state of the fuel injector, the sealing element bears against the inner wall of the receiving bore when the heating is sufficient, ie when the outer diameter of the sealing element reaches the diameter of the receiving bore due to the heating. If the sealing element heats up to a greater extent, the sealing element is also subjected to a radial prestress.

A disadvantage of the fuel injector known from DE 198 08 068 AI is that the bending of the sealing element is temperature-dependent, so that combustion gases can flow past the sealing element, in particular at low operating temperatures or immediately after the engine is started. This can also take place if the prestressing of the sealing element is not sufficient to provide the combustion gases with the required resistance. Therefore, malfunctions of the fuel injector can occur, particularly in the lower speed range and in the upper speed range.

Another disadvantage is that the pretensioning of the sealing element is determined by the geometric shape and the material composition of the sealing element and cannot be adjusted, so that at least the sealing element must be replaced in the event of changed operating conditions or if the material properties of the sealing element deteriorate. This also worsens the ease of maintenance of the fuel injector. Advantages of the invention

The fastener according to the invention with the features of the main claim has the advantage that a change in the position and inclination of the axis of the fuel injector is possible. The misalignment of the axis of the fuel injector is forced by the axis offset between a connecting piece of the cylinder head, which is due to the manufacturing tolerances and the temperature expansion. In addition, the sealing element is subjected to an axial pretensioning force that can be introduced via the housing of the fuel injector. If necessary, the sealing element can therefore be preloaded in an adjustable manner by means of a tightening force acting on the fuel injector from a holding device. In addition, the fastener according to the invention is simple to manufacture and can replace an existing intermediate piece, which is designed as described above, so that there is an inexpensive and space-saving fastening of the fuel injector in the receiving bore.

The measures listed in the subclaims permit advantageous developments of the fastening means for a fuel injector specified in the main claim.

The sealing element advantageously bears on a contact surface which is formed on a step of the receiving bore. As a result, the sealing element can be pretensioned against the contact surface of the cylinder head, whereby an advantageous absorption of the compressive force by the cylinder head is achieved and displacement of the sealing element due to the pretensioning force is prevented.

It is advantageous that the contact surface of the step is at least approximately perpendicular to the longitudinal axis of the receiving bore is oriented. As a result, the sealing element is subjected to a purely axial prestressing force, so that the prestressing force can advantageously be set. In addition, jamming of the fuel injector in the fastening means is prevented, so that the fuel injector can be removed more easily in the event of maintenance. Another advantage is that the radial position of the fuel injector can be predetermined from the outside without the fuel injector being self-centered as a result of the biasing force.

The step is advantageously designed in the form of a collar at one end of the sleeve. This makes the sleeve particularly easy to manufacture and universally applicable.

It is advantageous that the sleeve has two tubular sections, each with constant, different diameters, which are connected to one another at the step. This allows the fastener to be advantageously applied to the fuel injector. Pre-assembly is also made easier.

An inner surface of the sleeve advantageously interacts with a further sealing element which is connected to the fuel injection valve. This allows the gap between the fuel injector and the sleeve to be sealed.

It is advantageous that the sealing element consists of a soft metal or an at least partially elastically deformable metal alloy. As a result, the sealing element is designed to be heat and aging resistant. In addition, such a sealing element advantageously adapts to the sleeve and the fuel injector or the receiving bore, so that a reliable seal is provided. Furthermore, the axis inclination of the axis of the fuel injector can be easily enforced as adapts a sealing element made of soft metal or an elastically deformable metal alloy to the axis inclination.

It is advantageous that the sealing element is annular or that the sealing element is a plate spring. This allows the fastener to be manufactured inexpensively and simply.

The sealing element advantageously has an at least approximately rectangular cross section, as a result of which the pretensioning force acts on it at least approximately uniformly. As a result, the pretensioning force is evenly distributed over the width of the sealing element, so that an at least approximately constant pretension is generated in the sealing element.

It is advantageous that the sleeve is designed as a deep-drawn sheet metal part. This allows the fastener to be manufactured inexpensively.

drawing

Embodiments of the invention are shown in simplified form in the drawing and explained in more detail in the following description. Show it

1 shows a fuel injector which is used with a fastening means according to the invention in a receiving bore of a cylinder head and is connected to a fuel distributor line; and

Fig. 2 shows the section designated by II in Fig. 1 according to another embodiment of a fastener according to the invention. Description of the embodiments

1 shows a fuel injector 3 fastened with a fastening means 1 according to the invention in a cylinder head 2. The fuel injector 3 is used for injecting fuel directly into a combustion chamber 4 of the cylinder head 2 as a so-called direct petrol injection valve. However, the fastener according to the invention is also suitable for other applications.

The fuel injection valve 3 is inserted into a receiving bore 5. In this exemplary embodiment, the receiving bore 5 has a step 6, at which a first section 7 of larger diameter merges into a second section 8 of smaller diameter. The step 6 has a contact surface 9, which is oriented perpendicular to the longitudinal axis 10 of the receiving bore 5. The receiving bore 5 can have 1 further stages in accordance with the configuration of the fuel injection valve. In addition, the contact surface 9 of the stage 6 of the Au bore 5 with the longitudinal axis 10 include an angle that is not perpendicular.

The fastening means 1 comprises a sealing element 11, which rests on the contact surface 9 of the step 6, and a sleeve 12, the sealing element 11 resting on a step 13 of the sleeve 12. In this exemplary embodiment, the sealing element 11 consists of a soft metal with an at least approximately rectangular cross section, wherein it almost completely fills the space that is formed between the step 13 of the sleeve 12 and the contact surface 9 of the step 6 of the receiving bore 5. The sleeve 12 has a first tubular section 14 and a second tubular section 15, which are connected by means of the step 13. In accordance with the geometric shape of the fuel injection valve 3 and the geometric shape of the receiving bore 5, the tubular sections 14, 15 each have constant, different diameters on. The second tubular section 15 surrounds a nozzle body 16 of the fuel injector 3 circumferentially, and the first tubular section 14 circumferentially surrounds a lower middle part 17 of the fuel injector 3, the middle part 17 having an inclined step 18 at which the first tubular section 14 ends. The outer diameter of the first tubular section 14 enclosing the middle part 17 corresponds at least approximately to the diameter of an upper middle part 19 of the fuel injector 3, whereby the inclined step 18 creates a substantially stepless transition, so that the fuel injector 3 and the sleeve 12 fit into the Insert the first section 7 of the mounting hole 5. Correspondingly, the fuel injector 3 with the sleeve 12 fits into the second section 8 of the receiving bore 5.

A holding device 20 is provided for fastening the fuel injection valve 3 in the receiving bore 5. The holding device 20 has a screw 21 designed as an Allen screw, which is screwed into a threaded bore 22 of the cylinder head 2, and a hold-down device 23, which partially engages around the fuel injection valve 3 in a region 24. By tightening the screw 21, the fuel injection valve 3 can be subjected to an adjustable pretensioning force which can be introduced via the hold-down device 23 and which acts on the sealing element 11 via the step 13 of the sleeve 12.

In the exemplary embodiment, the screw 21 is screwed so far into the threaded bore 22 that the hold-down device 23 lies flat on the flat upper side 25 of the cylinder head 2. The sealing element 11 is therefore subjected to a maximum prestress. However, this also limits the maximum preload, which simplifies assembly. The holding device 20 and in particular the hold-down device 23 can also be designed differently, a lever support on the hold-down device 23 being conceivable. In the circumferential area 26 opposite the area 24, a connector plug 27 is provided on the fuel injection valve 3 for connecting an electrical supply line. The hold-down device 23 is interrupted in the illustrated embodiment in the area of the connector 27 so that it only partially surrounds the fuel injection valve 3. However, other configurations are also conceivable.

A fuel inlet port 28 of the

Fuel injection valve 3, via which fuel flows into fuel injection valve 3, is inserted into a connecting piece 29 of a fuel distributor line 30. The fuel distributor line 30 has a plurality of connecting pieces 29, into each of which a fuel injection valve 3 is inserted.

Since the plurality of connecting pieces 29 are rigidly connected to one another via the fuel distributor line 30, the axis of the connecting piece 29 does not generally exactly match the longitudinal axis 10 of the receiving bore 5, into which the fuel injection valve 3 is inserted, in all fuel injection valves due to production-related fluctuations. The receiving bore 5 is designed such that before the fuel injection valve 3 is fastened by means of the holding device 20 in the receiving bore 5, the fuel injection valve 3 can be axially displaced with respect to the longitudinal axis 10 of the receiving bore 5 and tilted somewhat, as a result of which the insertion of the plurality of fuel injection valves 3 in the several connecting pieces 29 of the fuel distributor line 30 are possible together.

After inserting the plurality of fuel injection valves 3 into the plurality of connecting pieces 29 of the fuel supply line 30, the screw 21 of the holding device 20 is tightened for each fuel injection valve 3. Through the generated A biasing force is applied to the sealing element 11 with a bias. If the fuel injection valve is only offset by an offset with respect to the longitudinal axis 10 of the receiving bore 5, the sealing element 11 is acted on uniformly, the fuel injector 3 not being displaced and none being moved due to the perpendicular orientation of the contact surface 9 to the longitudinal axis 10 of the receiving bore 5 Bracing of the housing of the fuel injector 3 takes place. The prestressed sealing element 11 seals the gap between the sleeve 12 and the cylinder head 2 in the area of the step 6. For sealing, the nozzle body 16 has a circumferential groove 31 in which a sealing ring 32 is arranged, so that the gap between the nozzle body 16 and the sleeve 12 below the area of the step 6 of the receiving bore 5 up to the combustion chamber 4 against the penetration is sealed by combustion gases.

If the axis position of the fuel injection valve 3 is inclined with respect to the longitudinal axis 10 of the receiving bore 5, then the prestressing force in the sealing element 11 made of soft metal produces a circumferentially different prestress, the soft metal partly adapting plastically and partly elastically to the inclined axis position of the fuel Injector 3 adjusts so that a seal in the area of step 6 of the receiving bore 5 is achieved by means of the sealing element 11. Since the force is introduced axially into the sealing element 11, an essentially likewise axially oriented pretension is generated in the sealing element 11, so that radial stresses are avoided which cause the housing of the fuel injector 3 to be braced and, under certain circumstances, a reduction in the sealing capacity of the sealing element 11 in the area of level 6 can result.

The fuel injector 3 is connected via a sealing ring 34 to the connecting piece 29, so that there is also scope for tilting the fuel injector 3 on the side of the fuel distributor line 30. The Sealing ring 34 is arranged between a collar 35 and a shoulder 36 of the fuel inlet connector 28.

The fuel is conducted from a main channel 37 of the fuel distributor line 30 via a connecting channel 38 into the interior 39 of the connecting piece 29. The fuel is introduced from the interior 39 into the fuel injection valve 3 via the fuel inlet connection 28.

In the exemplary embodiment shown, the sleeve 12 has two tubular sections 14, 15 which are connected to one another by means of the step 13. The sleeve 12 can also be designed differently. For example, the step 13 of the sleeve 12 can be formed in the form of a collar at one end of the sleeve 12. Either the first section 7 or the second section 8 can be omitted. The first section 7 or the second section 8 can also be formed only partially. In addition, a plurality of steps, which are similar to step 13, can also be provided in the sleeve 12. In the exemplary embodiment shown, an end face 40 of the step 13 is oriented essentially perpendicular to the axis of the sleeve 12, the axis of the sleeve 12 essentially coinciding with the longitudinal axis 10 of the receiving bore 5. The end face 40 can also enclose a non-perpendicular angle with the axis of the sleeve 12.

FIG. 2 shows the section designated II in FIG. 1 in accordance with a further exemplary embodiment of the fastening means 1 according to the invention. Elements which have already been described are provided with the same reference numerals, as a result of which a repeated description is unnecessary.

In this embodiment, the sealing element 11 is designed as a plate spring. Therefore, the space 45 between the step 13 of the sleeve 12 and the contact surface 9 of the step 6 of the receiving bore 5 is only partially with the sealing element 11 filled. An axial inclination between the axis of the connecting piece 29 (FIG. 1) and the longitudinal axis 10 of the receiving bore 5 compensates the sealing element 11 in this exemplary embodiment when subjected to the prestressing force by means of an elastic deformation.

Both in the first exemplary embodiment according to FIG. 1 and in the second exemplary embodiment according to FIG. 2, an annular gap 46 is formed between the central part 17 of the fuel injection valve 3 and the first tubular section 14 of the sleeve 12, between the central part 19 of the fuel injection valve 3 and an annular gap 47 is formed in the receiving bore 5 and an annular gap 48 is formed between the nozzle body 16 of the fuel injection valve 3 and the second tubular section 15 of the sleeve 12 in order to offset the axis of the connecting piece 29 (FIG. 1) and the longitudinal axis 10 to enable the receiving bore 5 by moving the fuel injection valve 3 in the radial direction.

The invention is not restricted to the exemplary embodiments described. In particular, other configurations of the sealing element 11 are also possible.

Claims

Expectations

1. Fastening means (1) for a fuel injection valve (3) that can be used in a receiving bore (5) of a cylinder head (2) of an internal combustion engine for direct injection of fuel into a combustion chamber (4) of the internal combustion engine with an at least partially in the receiving bore (5) Sleeve (12) which surrounds the fuel injection valve (3) and has a step (13) at which the cross section of the sleeve (12) changes, characterized in that the fastening means (1) has at least one sealing element (11), wherein the sealing element (11) abuts the sleeve (12) in the area of the step (13) and is axially loaded with a prestressing force in the assembled state.

2. Fastening device according to claim 1, characterized in that the sealing element (11) bears on a contact surface (9) which is formed on a step (6) of the receiving bore (5).

3. Fastening device according to claim 2, characterized in that the contact surface (9) of the step (6) is at least approximately perpendicular to the longitudinal axis (10) of the receiving bore (5).

4. Fastening device according to one of claims 1 to 3, characterized in that the step (13) at one end of the sleeve (12) is designed in the form of a collar.

5. Fastening device according to one of claims 1 to 3, characterized in that the sleeve (12) has two tubular sections (14, 15) each with constant, different diameters, which are connected to each other at the step (13).

6. Fastening device according to one of claims 1 to 5, characterized in that an inner surface of the sleeve (12) cooperates with a further sealing element (32) which is connected to the fuel injection valve (3).

7. Fastening device according to one of claims 1 to 6, characterized in that the sealing element (11) consists of a heat-resistant material.

8. Fastening device according to claim 7, characterized in that the sealing element (11) consists of a soft metal or of an at least partially elastically deformable metal alloy.

9. Fastening device according to one of claims 1 to 8, characterized in that the sealing element (11) is annular.

10. Fastening device according to one of claims 1 to 9, characterized in that the sealing element (11) is a plate spring.

11. Fastening device according to one of claims 1 to 8, characterized in that the sealing element (11) has an at least approximately rectangular cross-section, as a result of which the prestressing force acts on it at least approximately uniformly.

12. Fastening device according to one of claims 1 to 11, characterized in that the sleeve (12) is designed as a deep-drawn sheet metal part.