EP2084393A1

EP2084393A1 - Screw connection for fuel injector

Info

Publication number: EP2084393A1
Application number: EP07788488A
Authority: EP
Inventors: Dietmar Uhlmann
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2006-10-20
Filing date: 2007-08-20
Publication date: 2009-08-05
Anticipated expiration: 2027-08-20
Also published as: WO2008046680A1; EP2084393B1; DE502007002705D1; CN101529084B; CN101529084A; ATE455956T1; DE102006049532A1

Abstract

The invention relates to a fuel injector (10) for injecting fuel into the combustion chamber of an internal combustion engine, having a holding body (14) and at least one nozzle body (22), wherein the nozzle body (22) is fastened to the holding body (14) of the fuel injector (10) under preload by means of a nozzle clamping element (16), characterized in that the nozzle clamping element (16) is connected to the holding body (14) by means of a latching connection (46, 56).

Description

description

title

Screw connection for fuel injector

State of the art

DE 196 50 865 A1 relates to a solenoid valve for controlling the fuel pressure in a control chamber of an injection valve, such as a common rail high-pressure accumulator injection system. Via the fuel pressure in the control chamber, a stroke movement of a valve piston is controlled, with which an injection opening of the injection valve is opened or closed. The solenoid valve comprises an electromagnet, a movable armature and a valve member which is moved with the armature and acted upon by a valve closing spring in the closing direction and which cooperates with the valve seat of the solenoid valve and thus controls the fuel drain from the control chamber.

In previously used fuel injectors, a screw connection is realized by means of a union nut which connects a nozzle body, a throttle plate resting thereon and a valve plate of a fuel injector with the holding body of the fuel injector. It is initially of minor importance, whether the fuel injector is actuated by means of a piezoelectric actuator or by means of a solenoid valve. In general, a sealing ring, which is preferably made of PTFE, is used to achieve a seal of the low pressure area of the fuel injector to the outside. To connect the nozzle retaining nut, which usually receives a nozzle body, a throttle plate and a valve plate, and the holding body, a thread is formed on the inside of the nozzle retaining nut. About this thread, the biasing force is achieved in the composite of holding body and nozzle body and the components inserted therein. The production of the thread on the one hand on the inside of the nozzle retaining nut and on the other hand on the outer peripheral surface of the holding body is complex and expensive, it can also lead to undesirable leakage at the thread and to a non-uniformly distributed effect of introduced by the Gewindeanzugsmoment in the Schraubverband biasing force. Disclosure of the invention

According to the invention, it is proposed to provide a non-threaded sealing bandage made of holding body and nozzle retaining nut, by the geometric shape of the fixation a higher surface pressure can be realized and a sealing bandage is provided, in which unintentional opening is prevented by a radial locking of a sleeve-shaped sealing element.

The proposed connection between a holding body of a fuel injector and the components associated with a nozzle body of the fuel injector by means of a sleeve-shaped locking element has the advantage that higher surface pressures on the resulting sealing surfaces in the sealing compound are possible, such. B. between an inserted into the sleeve-shaped locking element nozzle body, a resting on this throttle plate and a resting on the throttle plate valve plate. When using the inventively proposed, sleeve-shaped locking element, the thread on the inside and the external thread on the holding body can be omitted. Instead, only a locking and mounting groove on the sleeve-shaped locking element and a corresponding locking groove on the holding body are provided. The locking between the sleeve-shaped locking element and the holding body takes place via a number of locking segments, which are formed tongue-shaped on one of the end regions of the sleeve-shaped locking element. By eliminating the thread plasticizing operations and setting operations can be excluded at high axial forces. Furthermore, a rapid closing of the connection between the holding body and the sleeve-shaped locking element can be done by a simple snap lock, which also makes a complex tightening torque determination, as has been customary, superfluous.

Due to the geometric shape of the locking segments, which is preferably shown as a separate, circumferentially divided formed locking tongue, a defined locking force can be generated. The height of the axial force introduced into the sealing dressing depends on a height difference between the bearing surface of the nozzle body and locking lugs in combination with the rigidity of the resilient region. Furthermore, can be omitted by the inventively proposed, sleeve-shaped locking element a circumferential position orientation of the previously used nozzle lock nut, which affects the assembly time low. The connection between a nozzle body and components associated therewith and the holding body of the fuel injector, as proposed by the invention, can also be opened again

Due to the avoidance of a relative movement in the circumferential direction by the elimination of the screw and the risk of shearing is omitted for fixing pins, which may be required for correct installation of the valve and the throttle plate. If, on the other hand, the valve plate and the throttle plate are oriented in the correct position relative to one another, the use of fixing pins can be completely dispensed with.

Furthermore, by eliminating the screw connection when using the inventively proposed, sleeve-shaped locking element no key surface more of this required, which greatly simplifies its production. Another advantageous, with the use of the proposed solution according to the invention achievable effect is that the previously used PTFE sealing ring for sealing the high-pressure region of the low-pressure region of the fuel injector can be omitted if a low-pressure seal on a slightly convex shape of the inside of the sleeve-shaped locking element at least two positions is performed.

Due to the geometric configuration of the locking segments, which are designed in particular as locking tongues, higher surface pressures, compared with a screw connection and thus higher biasing forces in the screw can be realized. Fine threads within the scope of the screw connection on the nozzle retaining nut as well as on the holding body as well as for the application of a hexagonal key required key surfaces can be omitted. The assembly process is simplified in the direction of a simple snap connection, so that it is possible to dispense with torque or angle-controlled tightening methods and their monitoring. Since no twisting or screwing takes place during the assembly of the fuel injector proposed according to the invention, a shearing off of fixing pins which position the valve plate and throttle plate relative to one another can be prevented. Are valve and throttle plate oriented in the correct position when mounting the fuel injector to each other, the fixing pins are otherwise superfluous. The assembled injector bandage can be easily unlocked with the aid of an auxiliary tool, with a circumferential position orientation of the nozzle retaining nut is no longer required. By a special design of the region E of the nozzle retaining nut as Dehnbereich (see possible embodiment of the expansion according to Figure 4) is a defined axial force as a biasing force for the sealing compound on the stiffness of this range and the geometry of the nozzle retaining nut adjustable. Due to the geometrical design of the nozzle retaining nut with at least two crowned formations NEN low-pressure seals are integrated into the nozzle retaining nut, so that previously used, preferably made of PTFE seals for low pressure sealing can be omitted.

drawing

With reference to the drawing, the invention will be described below in more detail.

It shows:

1 shows a schematic representation of essential elements of a fuel injector according to the prior art,

2 shows a sectional view through a previously used nozzle retaining nut,

FIG. 3 a representation of a nozzle tensioning element of the fuel injector proposed according to the invention,

Detail A locking elements shown in latched position,

Detail B shows a plan view of the locking elements arranged on the nozzle clamping element according to FIG. 3,

Detail C an execution detail between the locking segments,

Detail D a detail of a mounting groove of the nozzle clamping element with assembly tool,

FIG. 4 shows a development of an expansion region on the nozzle clamping element according to the illustration in FIG. 3,

FIG. 5 shows a side view of the expansion region of the nozzle tensioning element, shown in unwound form in FIG. 4, with recesses, FIG.

FIG. 6.1 a locking segment before snapping into a latching groove, FIG.

FIG. 6.2 shows a locking segment latched in a latching groove; Figure 6.3 shows a disassembly tool for mounting the nozzle clamping element from the holding body and

Figure 7 is a representation of a erfϊndungsgemäß proposed fuel injector with mounted on the holder body according to the invention nozzle tensioning element.

variants

The illustration according to FIG. 1 shows that the fuel injector 10 known from the prior art has an electrical contact 12 in the head region. In addition, as shown in FIG. 1, the fuel injector 10 comprises a holding body 14 and a nozzle retaining nut 16 provided with an internal thread. A valve plate 18 and a throttle plate 20 and a nozzle body 22 are sealingly clamped to one another in the context of a screw connection 24 the fuel injector 10 forms a compact unit. From the illustrated in Figure 1, enlarged detail of the fuel injector 10 shows that the nozzle retaining nut 16 includes a fine thread 40 on the inside, which cooperates with a corresponding formed on the outer peripheral surface of the holding body 14 thread and the screw 24 forms. In the lower region of the nozzle retaining nut 16, this comprises at least one key surface 26, which serves for the attachment of a torque applying tool.

Through the holding body 14 extends a high-pressure inlet 30, which extends through the valve plate 18 and through the throttle plate 20. By the nozzle lock nut 16, the front sides of the holding body 14, valve plate 18, throttle plate 20 are employed on the end face of the nozzle body 22 and form a screw connection.

In the nozzle body 22 of the fuel injector 10, a control chamber 32 is formed by a control space sleeve 34, which is employed by means of a spring 36 to the underside of the throttle plate 20. The spring 36 surrounds a, preferably needle-shaped injection valve member 38, wherein the spring 36 is supported on a received by the injection valve member 38 ring. The nozzle retaining nut 16 is screwed by means of the fine thread 40 with the holding body 14 of the fuel injector 10.

The illustration according to FIG. 2 shows a section through the nozzle retaining nut. FIG. 2 shows that the nozzle retaining nut 16 shown in a perspective section comprises the fine thread 40 on the inside in the head region and has at least one key recess 26 on the outer circumference for attachment of a tool applying a torque. The nozzle retaining nut 16 shown in FIG. 2 comprises a first diameter D _1J , a second inner diameter D ₁₂ and a third inner diameter D ₁₃ . Furthermore, it is apparent from the perspective sectional illustration according to FIG. 2 through the nozzle retaining nut 16 that the nozzle retaining nut 16 has different wall thicknesses Si, S ₂ and S3 in the region of the mentioned diameters, the wall thicknesses Sl, S2 and S3 pointing downwards in the direction of the at least one key area 26 increases.

The illustration according to FIG. 3 shows a longitudinal section through the nozzle clamping element proposed according to the invention. From the sectional view according to FIG. 3 and the associated details A, B, C and D, it can be seen that the nozzle tensioning element 16 contains a fixing region 42 indicated by reference number 42 in its head region. Seen in the vertical direction, a number of locking tongues 44 extend within the fixing region 42 along the circumference of the nozzle clamping element 16 proposed according to the invention. Each of the locking tongues 44 comprises on the inside, ie. H. on the outer circumference of the holding body 14 facing surface, a projection 46 which is preferably hook-shaped. The locking tabs are separated from each other by gaps 48 to provide radial plasticity. The gaps 48 between the individual locking tongues 44 in the fixing region 42 of the nozzle clamping element 16 are represented in detail "C" on an enlarged scale.

Below the fixing region identified by reference numeral 42, a first spherical shape 50 is formed on the inner peripheral surface of the nozzle chuck 16. This is within the range of the nozzle clamping element 16 (see illustration according to Figure 2), in which this the first inner diameter D _{1; 1} has. In the transition region of the wall of the nozzle clamping element 16 as shown in FIG. 3 from the first inner diameter D _1J to the second inner diameter D ₁₂ , a mounting groove 58 is formed on the outer circumference of the nozzle clamping element 16 and the second spherical shape 52 on the inner circumferential surface. Details of the mounting groove 58 are shown in detail Below the second spherical shape 52 of the nozzle clamping element 16 there is a zone in which recesses 66 are annularly mounted in a perforation pattern 62, which in the schematic embodiment variant of the nozzle clamping element shown in FIG Eight have. Below the region provided with the perforation pattern 62 extends a bearing surface 54 on which the shoulder of the nozzle body 22 is supported in the mounted state (compare illustration according to FIG. 7).

It can be seen from the detail "A" that the projection 46 of the locking tongue 44 is formed in a projection c with respect to the inner side of the locking tongue 44 and engages in a latching groove 46 formed on the outer circumference of the retaining body 14. The angle of inclination is designated α in that the projection 46 extends on the locking tongue 44. The strength of the resilient region of the locking tongue 44 is selected to an extent which exceeds the projection c.

The detailed representation "B" can be taken from the fact that a multiplicity of locking tongues 44 are arranged adjacent to one another in the circumferential direction along the circumference of the head region of the nozzle tensioning element 16 shown in Figure 3. Each of the locking tongues 44 is comparable to the respectively adjacent locking tongue 44 via a gap 48 Detail "C", separated. Preferably, on the inside of each of the locking tongues 44 formed in the fixing region 42 of the nozzle clamping element 16, a projection 46 is formed which engages in the locking groove 56 formed circumferentially on the holding body 14.

3, a mounting tool 60 can be latched into the mounting groove 58 shown in FIG. 3 on the outer peripheral surface of the nozzle clamping element 16. The mounting tool 60 is inserted from below into the mounting groove 58 on the outer circumference of the nozzle clamping element 16 and e designates the mounting groove depth, in which the base of the mounting groove 58 is formed in comparison to the outer circumferential surface of the nozzle tensioning element 16. In the region of the mounting groove 58, the inner peripheral surface of the nozzle tensioning element is opposite the second spherical shape.

In the detailed representations A, B, C and D belonging to FIG. 3, the nozzle clamping element 16 is locked at the upper end within the fixing region 42 by the locking tongues 44 with respect to the holding body 14. For this purpose, the nozzle tensioning element 16 is pushed from below over the correctly positioned to each other injector components, nozzle body 22, throttle plate 20, valve plate 18 and holding body 14 during assembly of the injector composite. The geometric coordination of the individual components relative to one another ensures that in the latched state of the locking tongues 44 within the fixing region 42 and the latching groove 56 on the holding body 14 a bias builds up. The amount of this preload force can be determined by the geometry of the components over the slope. Fϊgkeit the nozzle clamping element 16 within the Lochungsmusterbereiches 62 (Dehnbereich) are set with high process reliability.

It can be seen from the illustration according to FIG. 4 how the stiffness can be reduced to a desired degree by targeted perforation of the nozzle tensioning element.

The illustration according to FIG. 4 shows that the region illustrated in FIG. 3, in which the perforation pattern 62 is formed there, is shown unwound in the circumferential direction from 0 ° to 360 ° corresponding to the unwinding 64. Within the perforation pattern region 62 in the unwound representation according to FIG. 4, individual recesses 66 are offset relative to one another in the circumferential direction. Each of the recesses 66 is arranged at a distance 68 to a preceding recess 66. The length of each recess 68 is indicated by reference numeral 70. Size, shape, position and number of recesses 66 are based on the respectively required stiffness reduction within the provided with the Lochungsmuster 62 peripheral region of the nozzle clamping element 16. From the illustration in Figure 5 shows that the illustrated in Figure 4 in settlement 64 range of wall thickness of the nozzle clamping element 16 can be formed in a reduced material thickness 72. If an area with reduced material thickness 72 is formed on the nozzle clamping element 16, as shown in FIG. 5, the recesses 68 shown in FIG. 4 and FIG. 3 can be dispensed with, since the cross section reduction 72 alone in the nozzle clamping element 16, similar to the principle of a stretching - Screw, the desired stiffness reduction can be achieved.

The figure sequence of Figures 6.1, 6.2 and 6.3 are shown assembly and disassembly of the nozzle tensioning element on the holding body.

It can be seen from the illustration according to FIG. 6.1 that, when the nozzle clamping element 16 is mounted, it is slid upwards onto the holding body 14. Due to the elastic properties of the locking tongues 44 arranged in the fixing region 42 of the nozzle clamping element 16, they spread open slightly, so that the projection 46, as shown in FIG. 6.1, is pressed slightly outward.

If the nozzle clamping element 16 has reached its mounting, ie locking position, as shown in FIG. 6.2, then the respective projections 46, which are formed on the inner side of the locking tongues 44 of the nozzle clamping element 16, snap into the locking groove 46. Furthermore, the first spherical shape 50 shown in FIG. 3 formed on the inside of the nozzle tensioning element 16 extends over the circumference of the holding body 14. The diameter of the first spherical shape 50 and that of the holding body 14 are oversized with each other so that they form a first pressure seal of the injector, so that can be dispensed with additional sealing rings.

Shortly before the locking of the locking tongues 44 with their projections 46 in the locking groove 56, the expansion element 16 comes to rest on the nozzle body 22, since the support surface 54 contacts the end face of the nozzle body 22. Upon further advancement of the nozzle clamping element 16 in the direction of the latching groove 56 until latching of the locking tongues 44, the biasing force for elastic stretching of the expansion region 62 (hole pattern, cf. FIGS. 3 and 4) is applied via the assembly tool 60 to the mounting groove 58. After reaching the locking groove 56, the locking tongues 44 elastically spring back into their starting position (see illustration according to FIG. 6.2), latch into the locking groove 56 and lock the injector assembly. Thereafter, the mounting tool 60 can be removed. The elastic restoring force of the expansion region 62, 72 of the nozzle tensioning element 16 permanently brings the desired biasing force of the injector components in relation to each other.

Since no rotation of the components of the fuel injector 10 takes place relative to one another during the assembly process, fixing pins for rotationally fixing the components relative to one another can be dispensed with. Also on the key surfaces 26 (see illustration according to Figure 2) on the outer circumference of the nozzle clamping element 16 may be omitted.

FIG. 6.3 shows how the locking tongues 44 are lifted out of the latching groove 56 on the holding body 14 with the aid of a dismantling tool 74 if the injector dressing is dismantled if necessary. After a pointing out in the radial direction of the projections 46 from the locking groove 56 on the circumference of the holding body 14, the Dü- can be peeled tension member 16 in the withdrawal direction 76 downward from the holding body 14 of the fuel injector 10, as shown in Figure 6.3.

Finally, it can be seen from the illustration according to FIG. 7 how the nozzle clamping element proposed according to the invention is arranged in the assembled state of the injector.

In the mounted state 80 of the nozzle clamping element 16 on the holding body 14 shown in FIG. 7, the locking tongues 44 formed inside the fixing area 42 are spaced apart by gaps with their respective projections 46 in the locking groove 56. The locking groove 56 extends on the outer circumference of the holding body 14 the lower end of the vertically extending locking tongues 44 is the first spherical shape 50, which causes a low pressure seal and which rests on the circumference of the holding body 14. The nozzle clamping element 16 also encloses the valve plate 18 and the throttle plate 20 and the nozzle body 22. According to FIG. 7, it can be seen that the nozzle body 22 is fixed by the nozzle tensioning element 16 to its bearing surface 54 and is pressed against the underside of the throttle plate 20 with its end face facing away from the combustion chamber end. As shown in FIG. 7, a circumferential surface 78 of the nozzle body 22 is set up with the second spherical formation 52, which is formed opposite the wall of the nozzle clamping element 16. Below the mounting groove 58 or the second spherical shape 52 formed on the inside of the nozzle tensioning element 16 extends an area with reduced material thickness 72 or a region in which a perforation pattern 62 extends from the recesses 66 shown in connection with FIGS. 3 and 4.

In the mounted state 80 of the nozzle clamping element 16 shown in FIG. 7, the latter has an expansion region 72 or 62, which is shown only schematically, which can be formed either in a reduced material thickness or in which the perforation pattern 62 extends from recesses 66.

Claims

claims

A fuel injector (10) for injecting fuel into the combustion chamber of an internal combustion engine, comprising a holding body (14) and at least one nozzle body (22), wherein the nozzle body (22) by means of a nozzle clamping element (16) under

Preload on the holding body (14) of the fuel injector (10) is fixed, characterized in that the nozzle clamping element (16) with the holding body (14) by a latching connection (46, 56) is connected.

2. Fuel injector according to the illustration according to claim 1, characterized in that the nozzle clamping element (16) has a fixing region (42) in which a number of locking tongues (44) are formed, which are separated from each other by gaps (48).

3. fuel injector (10) according to claim 2, characterized in that within the fixing region (42) of the nozzle clamping element (16) on locking tongues (44) projections (46) are formed.

4. fuel injector (10) according to claim 2, characterized in that the nozzle tensioning element (16) below the fixing region (42) on an inner circumferential surface at least one spherical shape (50, 52).

5. fuel injector (10) according to claim 1, characterized in that the nozzle clamping element (16) on its inner peripheral surface preferably has two spherical formations (50, 52) in the mounted state (80) of the nozzle clamping element (16) on

Holding body (14) form at least one sealing surface.

6. Fuel injector (10) according to claim 5, characterized in that the first spherical shape (50) and the second spherical shape (52) with respect to the outer circumferential surface of the holding body (14) for generating radial biases with

Oversize are made.

7. fuel injector (10) according to claim 1, characterized in that the nozzle clamping element (16) has a peripheral portion (62, 72) with defined adjustable axial stiffness.

8. Kraftstoffϊnjektor (10) according to claim 7, characterized in that within the range with defined adjustable axial stiffness, a perforation pattern (62) of annularly distributed arranged recesses (66) is formed.

9. fuel injector (10) according to claim 7, characterized in that within the range defined with adjustable axial stiffness of the nozzle clamping element (16), the nozzle clamping element (16) with reduced material thickness (72) is executed.

10. Fuel injector (10) according to claim 1, characterized in that the nozzle tensioning element (16) in the mounted state (80) on the holding body (14) with locking tongues

(44) is latched in the latching groove (56) and the nozzle tensioning element (16) with a bearing surface (54) biases the nozzle body (22) against the holding body (14) and the first spherical shape (50) forms a first seal to the holding body (14 ) and the second spherical shape (52) forms a second sealing surface on the circumference (78) of the nozzle body (22).