CN105658946B

CN105658946B - Fuel injector

Info

Publication number: CN105658946B
Application number: CN201480058638.9A
Authority: CN
Inventors: H·克雷舍尔; S·豪格; A·苏斯维拉; A·马德莱纳; A·雷蒂希
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2013-10-23
Filing date: 2014-09-30
Publication date: 2020-01-21
Anticipated expiration: 2034-09-30
Also published as: DE102013221554A1; EP3060789A1; CN105658946A; EP3060789B1; WO2015058929A1

Abstract

The invention relates to a fuel injector (10) comprising: an injector housing (11), in which injector housing (11) an injection element (20) is arranged longitudinally displaceable along a longitudinal axis (22); a control chamber (35) which is hydraulically connected to the high-pressure chamber (25) of the injector housing (11) and which can be hydraulically relieved via a discharge opening (30) in the direction of the low-pressure chamber (42) of the injector housing (11), wherein the flow rate of the pressure medium through the discharge opening (30) can be controlled by means of a valve element (40), wherein the valve element (40) is arranged axially displaceably in a preferably rod-shaped guide element (65; 65 a); the guide element is inserted into a bore (60) of the valve element (40) and is supported on a stationary housing element (55) on the side facing away from the valve element (40); and the guide element (65; 65a) has a first weakened region (71) in the region between a guide portion (61) of the guide element (65) in the valve element (40) and the stationary housing element (55), in which weakened region the cross section of the guide element (65; 65a) decreases.

Description

Fuel injector

Technical Field

The invention relates to a fuel injector, comprising: an injector housing in which an injection element is arranged longitudinally displaceable along a longitudinal axis; a control chamber which is hydraulically connected to a high-pressure chamber of the injector housing and which can be hydraulically relieved via an outlet opening in the direction of a low-pressure chamber of the injector housing, wherein the flow rate of the pressure medium through the outlet opening can be controlled by means of a valve element, wherein the valve element is arranged axially displaceably on a preferably rod-shaped guide element which is sunk into the bore of the valve element and is supported on the side facing away from the valve element on a stationary housing element, wherein the guide element has a first weakening region in the region of the guide element between a guide section in the valve element and the stationary housing element, in which first weakening region the cross section of the guide element is reduced.

Background

Such a fuel injector is known from the applicant's application DE 102008003348 a 1. The fuel injector used as a component of a common rail injection system in a self-igniting internal combustion engine has a nozzle needle, the end of which facing away from the injection openings is recessed in a valve block in a valve housing. A control chamber is formed in the valve block, which can be relieved via an outlet opening into a low-pressure region of the fuel injector. The movement of the nozzle needle is controlled in a known manner by the pressure in the control chamber in order to open and close the injection orifice. For this purpose, a valve element is provided which is arranged on the low-pressure side of the fuel injector and closes the outlet opening in the lowered position or releases it in the raised position. In the known fuel injector, the valve element is integrally formed as a projection on a substantially disk-shaped or sleeve-shaped magnet armature, which interacts with an electromagnetic coil, which, when energized, causes the valve element to be lifted from its position closing off the outlet opening. The armature is force-loaded by a pressure spring in the direction of the closed position of the valve element, in order to ensure that, when the solenoid is not energized: the fuel cannot flow out of the control chamber or the nozzle needle is located in a position in which it closes the injection opening. The armature is guided in the axial direction in a pin-shaped guide element which partially penetrates a through-opening formed in the armature. It is essential here that a relatively tight fit is formed between the outer diameter of the guide element and the bore diameter of the through-bore, in order to prevent, on the one hand, an undesired outflow of fuel via the return channel and via the annular gap between the guide element and the armature in the direction of the low-pressure chamber, and, on the other hand, an undesired movement of the armature or the valve element in a plane perpendicular to the longitudinal axis of the guide element, since, in the event of said movement, an undesired increased wear occurs at the fit between the valve element and the valve block. In connection, it is mainly: due to the arrangement or design of the guide element, the pressure of the control chamber always acts on the guide element at the end face facing the return channel. The hydraulic pressure is transmitted from the guide element to the injector housing via an element fixed to the housing.

Due to the asymmetrical force effects, for example, due to the active pressure spring (which loads the armature or the valve element force into its closed position) or due to the asymmetrical flow behavior during fuel outflow, transverse forces can act on the armature, which in particular in the case of relatively high system pressures result: the guide element cannot be moved (laterally) due to the relatively high axial pressure in the region of the point at which it bears against the element fixed to the housing, so that increased wear or increased friction results due to the relatively tight fit between the outer diameter of the guide element and the through-opening in the armature.

In the fuel injector shown in DE 102008003348 a1, a first weakened region is provided approximately in the axial middle region of the guide element, in the region of which the cross section of the guide element decreases. Thereby, the bending stiffness of the guide element along its longitudinal axis is reduced.

Disclosure of Invention

Starting from this prior art, the object of the invention is to develop the fuel injector such that, in the event of transverse forces, increased wear on the guide element or on components which interact with the guide element is avoided, while no friction or only a relatively slight increased friction between these components should occur in order to ensure an easy axial movement of the valve element. According to the invention, this object is achieved in the case of the fuel injector according to the invention in the following manner: at least one second weakening region is arranged on the guide region of the guide element at a distance from the first weakening region in the axial direction, in which the cross section of the guide element decreases. This configuration with at least two weakened regions arranged at a distance from one another in the axial direction makes it possible to: in the event of transverse forces, the guide element is deformed in an "S" shape, so that in particular the section of the guide element guided in the valve element interacts with the valve element without increased friction or wear.

The invention also provides an advantageous development of the fuel injector.

In order to achieve an S-shaped configuration of the guide element in the event of transverse forces, it is particularly advantageous: the axial distance between the two weakened regions is between 50% and 80% of the length of the guide element, with the exception of the guide section in the valve element. It is thus possible, even when the deflection of the middle section of the guide element is relatively small or the angle of inclination thereof is relatively small: relatively large lateral movements of the valve element can be achieved; or due to this relatively large transverse movement, the friction in the guide portion of the valve element is relatively small.

In order to make it possible not to impede the movement or deformation of the guide element, provision is made, in particular, for: at least the intermediate section of the guide element between the two weakened regions is not guided in the radial direction. This is understood to be: independently of the deflection of the guide element, the deflected intermediate section does not come into contact with the component, so that in particular no undefined forces act on the guide element.

In order to reduce the surface pressure on the stationary housing element, it is advantageous: the guide element has a flat end face on the side facing the housing element.

A particularly simple and precise production of the guide element is possible if the guide element is of cylindrical design and has a constant cross section, except for the at least two weakening regions.

Furthermore, the same properties can be achieved in the area of the at least two weakened areas when the dimensions of the cross-section in the area of the at least two weakened areas are at least substantially equal in size.

The at least two weakening regions can be formed in the guide element particularly simply if the weakening regions are formed in the form of radially encircling annular grooves. Furthermore, this has the advantage that: regardless of the angular position of the guide element, a movement or tilting of the guide element can be achieved in all directions.

However, alternatively, it is also possible to provide: the weakened area is configured in the form of a cut or notch. In the case of such a configuration, for example, an asymmetrical behavior can be achieved with regard to the bending characteristic of the guide element, i.e., the guide element can be deflected particularly easily in one direction, while deflection in the other direction is more difficult. In this case, it is possible to provide: the guide element is arranged in a fixed rotational angle.

In order to reduce the notch effect, it is advantageous: the weakened region is rounded or provided with a radius.

The invention is preferably applied in fuel injectors where the pressure in the control chamber is at least 2000 bar. With such high control or system pressures, such high axial pressures occur on the guide element: without the configuration according to the invention, the effects produced in terms of increased friction or wear need to be taken into account or are particularly pronounced.

Drawings

Further advantages, features and details of the invention are explained in the following description of preferred embodiments and with reference to the drawings. Shown in the drawings are:

FIG. 1 is a longitudinal cross-sectional view of a portion of a fuel injector according to the present disclosure;

FIG. 2 is a detail view of FIG. 1 in the case of a modified guide element; and

fig. 3 is a schematic diagram for explaining the different functional sections of the guide element.

In the figures, identical elements or elements having the same function are provided with the same reference numerals.

Detailed Description

The fuel injector 10 according to the invention, which is shown in section in fig. 1, is part of a common rail injection system for injecting fuel into a combustion chamber, not shown, of a self-igniting internal combustion engine. The fuel pressure provided by the fuel injection system is preferably greater than 2000 bar. The fuel injector 10 has an injector housing 11, through which injector housing 11 a longitudinal bore 12 extends, wherein the longitudinal bore 12 has bore sections of different diameters. A valve block 15 with a shoulder 16 is axially supported on the step 13 of the longitudinal bore 12. In order to press the valve piece 15 axially against the step 13, the valve piece 15 is arranged on the side opposite the step 13 in operative connection with a press bolt 17, the external thread of the press bolt 17 interacting with a corresponding internal thread in the longitudinal bore 12.

On the side facing away from the pressure bolt 17, the valve block 15 has a blind hole 18, into which blind hole 18 an axial end region 19 of the injection element, which is in the form of a nozzle needle 20, is sunk. The blind bore 18 guides the end region 19 in the radial direction and furthermore allows an axial movement of the nozzle needle 20 in the direction of the longitudinal axis 22 of the nozzle needle 20. In the lowered position of the nozzle needle 15 shown in fig. 1, the nozzle needle closes at least one injection opening (not shown) in the injector housing 11, but in practice there may be a plurality of injection openings in order to prevent fuel from being ejected from a high-pressure chamber 25 formed in the injector housing 11 in the region of the nozzle needle 20. In contrast, in the raised position of the nozzle needle 20, which is not shown in the drawing, the at least one injection hole in the injector housing 11 is released, so that fuel is discharged or injected from the high-pressure chamber 25 into the combustion chamber of the internal combustion engine. The high-pressure chamber 25 is hydraulically connected to a fuel accumulator (common rail) 28 via a connection 26, which is indicated only by symbols in the injector housing 11, and via a fuel supply line 27, the fuel accumulator 28 supplying fuel at system pressure to the high-pressure chamber 25.

Starting from the bottom of the blind hole 18, a through-hole extends along the longitudinal axis 22, which forms the outlet opening 30, in which outlet opening 30 the outflow throttle 31 is formed as a cross-sectional narrowing. Inside the blind hole 18, which forms a variable-volume control chamber 35 in the region that is not penetrated by the end region 19 of the nozzle needle 20, the control chamber 35 is hydraulically connected to the high-pressure chamber 25 via a connecting bore 36 formed near the bottom of the blind hole 18 with an inlet throttle 37, so that fuel can flow from the high-pressure chamber 25 into the control chamber 35. As is known (and therefore not explained in detail here), the control chamber 35 serves to control the movement of the nozzle needle 20 by adjusting the fuel pressure in the control chamber 35 in order to release or close the at least one injection hole in the injector housing 11. For this purpose, the outlet opening 30 can be closed at least indirectly by means of a valve element 40, in order to prevent fuel from flowing out of the control chamber 35 via the outlet opening 30 into a low-pressure chamber 42 of the injector housing 11. The low-pressure chamber 42 is connected via a further connection 43 in the injector housing 11 and via a return line 44, for example, to a return reservoir (fuel tank) 45.

The valve element 40 is a component of a solenoid armature and has a sleeve-shaped first region 46, on which first region 46 a disk-shaped or ring-shaped armature region 48 is connected on the side facing away from the valve block 15. The armature region 48 or the valve element 40 interacts with an electromagnetic coil 50 embedded in an annular magnetic core 49, the electromagnetic coil 50 attracting the valve element 40 in the direction of the magnetic core 49 when energized, the magnetic core 49 bearing axially against a closure plate 51 of the injector housing 11 on the side facing away from the valve element 40. The magnetic core 49 has a through-opening 53, in the region of which through-opening 53 a disk-shaped support plate 55 bears in a positionally fixed manner in the axial direction against the closure plate 51. A pressure spring 56, which is likewise arranged in the through-opening 53, is supported axially on one side against the support plate 55 and on the other side against the end face of the armature region 48 of the valve element 40 facing the pressure spring 56, so that the pressure spring 56 acts upon the valve element 40 with force into the lowered position shown in fig. 1, in which the sealing edge 57 of the sleeve-shaped region 46 of the valve element 40, forming a sealing seat, bears against a conical counter-surface 58 of the valve block 15, in order to prevent fuel from flowing out of the outlet opening 30 into the low-pressure chamber 42. The pressure spring 56 surrounds the guide element 65 with a radial distance.

The valve element 40 is penetrated by a through hole 60 of constant diameter. The guide section 61 of the pin-shaped guide element 65 is recessed into the through-opening 60 on the side of the through-opening 60 facing away from the valve block 15. On the side facing away from the guide element 65, the journal-shaped projection 63 of the valve block 15 is preferably recessed with a radial gap, in which a flattened area 64 is formed for the fuel to flow out in the direction of the sealing edge 57. The outer diameter of the guide element 65 is matched to the hole diameter of the through-hole 60 in such a way that: on the one hand, an at least virtually leak-free radial guidance of the valve element 40 on the guide section 61 is enabled; while on the other hand an axial movability of the valve element 40 in the direction of the double arrow 66 (parallel to the longitudinal axis 22) with relatively little friction is ensured.

The hydraulic pressure acting on the end face 67 via the control chamber 35 and the return line 30 always acts on the end face 67 of the guide element 65 facing the valve block 15. This axial force acting in the direction of the support plate 55 acts via the flat second end face 68 of the guide element 65, which is shown in fig. 1, on the support plate 55 and thus on the closing plate 51 of the injector housing 11. It is essential to the invention that the guide element 65 has two weakened

regions

71, 72 spaced apart from one another in the axial direction. The first weakened area 71 engages directly on the guide section 61 of the guide element 65, but is still located axially within the valve element 40. The second weakened area 72 is located adjacent the support plate 55. By means of these two weakened

regions

71, 72, the guide element 65 is divided into a total of three sections: one is a guide section 61 which is guided with a relatively tight fit in the through-hole 60 of the valve element 40; the other is an intermediate section 73, which is located between the two weakened

areas

71, 72; and finally a support section 74, which is designed to support the guide element 65 in the axial direction against the support plate 55. Preferably, the average spacing a between the two weakened

areas

71, 72 is between 50% and 80% of the length a of the guide element 65, excluding its guide section 61.

In the exemplary embodiment shown, the two

weakening areas

71, 72 are each formed by a radially encircling annular groove 75, the annular groove 75 preferably being provided with a rounding or radius 76. However, it is also possible to reduce or form the cross-section in the region of the weakened regions 71, 72 (which are preferably each configured to the same extent) by a linearly formed milled-in, milled-in or the like.

Fig. 2 shows a modified guide element 65a in relation to fig. 1, wherein the support section 74a is spherically formed or is formed with a radius 77 on the side facing the support plate 55, so that the guide element 65a bears in a punctiform manner against the support plate 55.

The function of the two weakened

areas

71, 72 is best explained with reference to fig. 3: when the valve element 40 is moved between its lowered position, which is shown in fig. 1, and a raised position, which is not shown in the drawings, in which fuel can flow from the control chamber 35 into the low-pressure chamber 42, a transverse force F can occur, which acts from left to right in the illustration of fig. 3 in the plane of the drawing. This transverse force F on the one hand causes the guide section 61 to continue to be guided in the through-opening 53 of the valve element 40 at least with almost no additional transverse force; on the other hand, the support section 74 rests against the support plate 55 in a full or vertical orientation on the basis of the hydraulic pressure prevailing in the control chamber 35. The two weakened

regions

71, 72 allow a parallel displacement (shown exaggerated in fig. 3) of the valve element 40, in which case the central section 73 is inclined relative to its original direction aligned with the longitudinal axis 22. Thus, the transverse force F acts as a deformation force on the guide element 65, 65a and in particular causes: no increased wear or increased friction occurs between the through-hole 60 and the guide section 61 compared to the case in which no transverse force F is present.

The fuel injector 10 described so far can be modified or adapted in a number of ways and methods without departing from the inventive idea. It is therefore particularly conceivable to provide more than two weakened

areas

71, 72 on the guide elements 65, 65 a. The bending stiffness of the guide element 65, 65a can thereby be reduced again to a greater extent, wherein, for example, the respective reduction in the cross section in the region of the weakened

regions

71, 72 is weaker than in the case of the use of only two weakened

regions

71, 72.

Claims

1. A fuel injector (10) has: an injector housing (11) in which an injection element (20) is arranged longitudinally displaceable along a longitudinal axis (22); a control chamber (35) which is hydraulically connected to a high-pressure chamber (25) of the injector housing (11) and which can be hydraulically relieved via a discharge opening (30) in the direction of a low-pressure chamber (42) of the injector housing (11), wherein the flow rate of the pressure medium through the discharge opening (30) can be controlled by means of a valve element (40), wherein the valve element (40) is arranged axially displaceably on a guide element (65; 65a), which guide element (65; 65a) is immersed in a bore (60) of the valve element (40) and is supported on a stationary housing element (55) on the side facing away from the valve element (40), wherein the guide element (65; 65a) has a first weakening region (71) in the region of the guide element between a guide section (61) in the valve element (40) and the stationary housing element (55), in which the cross-section of the guide element (65; 65a) is reduced,

it is characterized in that the preparation method is characterized in that,

at least one second weakened region (72) is formed on the guide element (65; 65a) at an axial distance (a) from the first weakened region (71), wherein the cross section of the guide element (65; 65a) is reduced, the first and second weakened regions being configured such that the guide element can be deformed in an "S" shape in the presence of a transverse force.

2. A fuel injector according to claim 1, characterized in that the axial distance (a) between the first and second weakened areas (71, 72) is between 50% and 80% of the length (A) of the guide element (65; 65a) with the exception of the guide section (61).

3. A fuel injector according to claim 1 or 2, characterized in that at least one intermediate portion (73) arranged between the first weakened area (71) and the second weakened area (72) is not radially directed.

4. A fuel injector according to claim 1 or 2, characterized in that the guide element (65) has a flat end face (68) on the side facing the housing element (55).

5. A fuel injector according to claim 1 or 2, characterized in that the guide element (65; 65a) is cylindrically configured and has a constant cross section except for a first weakened area (71) and a second weakened area (72).

6. A fuel injector according to claim 1 or 2, characterized in that the cross-sectional dimensions in the area of the first and second weakened areas (71, 72) are substantially equal in size.

7. A fuel injector according to claim 1 or 2, characterized in that the first (71) and second (72) weakened areas are configured in the form of radially surrounding annular grooves (75).

8. A fuel injector according to claim 1 or 2, characterized in that the first weakened area (71) and the second weakened area (72) are configured in the form of a cut or a notch.

9. The fuel injector as claimed in claim 1 or 2, characterized in that the first and second weakened regions (71, 72) are configured rounded or have a radius (76).

10. A fuel injector according to claim 1 or 2, characterized in that the valve element (40) is designed as an armature (48) which can be actuated by a magnetic coil (50), and in that the guide element (65; 65a) is surrounded in the passage opening (53) of the magnet core (49) at a radial distance by a pressure spring (56) which is supported in the axial direction between the armature (48) and the stationary housing element (55).

11. A fuel injector according to claim 1 or 2, characterized in that the hole (60) in the valve element (40) is configured as a through hole in such a way that: the hydraulic pressure in the outlet opening (30) acts essentially on the end face (67) of the guide element (65; 65a) that is immersed in the opening (60).

12. A fuel injector according to claim 1 or 2, characterized in that the pressure in the control chamber (35) is greater than 2000 bar.

13. A fuel injector according to claim 1 or 2, characterized in that the guide element is rod-shaped.