WO2015128127A1

WO2015128127A1 - Fuel injector

Info

Publication number: WO2015128127A1
Application number: PCT/EP2015/051247
Authority: WO
Inventors: Holger Rapp; Wolfgang Stoecklein; Bernd Berghaenel; Marco Beier; Stefan Stein
Original assignee: Robert Bosch Gmbh
Priority date: 2014-02-28
Filing date: 2015-01-22
Publication date: 2015-09-03
Also published as: KR20160124126A; EP3111079A1; CN106662060A; KR102225328B1; CN106662060B; EP3111079B1; DE102014203642A1

Abstract

The invention relates to a fuel injector (10), in particular a common-rail injector for self-igniting internal combustion engines, comprising an injector housing (11) in which a sensor element is arranged in a low-pressure region (45) for at least indirectly detecting a fuel pressure prevailing in a high-pressure region (20), the sensor element resting against an elastically deformable sealing element (69) on the side remote from the high-pressure region (20), said sealing element sealing a receiving space (66) for the sensor element. According to the invention, the sensor element is designed in the form of a force sensor (75) having at least one strain measuring element, the force sensor (75) being connected to the sealing element (69).

Description

Description title

Fuel injector prior art

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

Such a fuel injector is known from DE 10 2010 044 012 A1 of the Applicant. In the known fuel injector, a sensor element embodied in the form of a pressure sensor is arranged in a snap-hole-like recess of a sensor plate, wherein the pressure sensor is covered or protected on the side facing away from the sensor plate in the recess by means of a membrane, in particular made of metal, which forms a sealing element , The known sealing element is used in addition to the power transmission of a coupled with an anchor transmission element of the prevention of the entry of fuel into the recess. A disadvantage of the known fuel injector is that a relatively complex and thus cost-intensive production of the contact surface is required by the formation of a contact surface for the pressure sensor in the recess at the bottom of the sensor plate to ensure a required flatness or roughness of the contact surface for the pressure sensor because the contact surface for a tool is very difficult to access. In particular, it is mentioned here that the pressure sensors commonly used require a relatively high flatness or low roughness of the contact surface for proper functioning of the pressure sensor. From the post-published DE 10 2013 220 032 A1 of the applicant, a further, generic fuel injector is also known, in which the receiving space for receiving the also formed as a pressure sensor sensor element is formed by two, in the axial direction of subsequent components, wherein the contact surface for the Pressure sensor on the side facing away from the sealing element forming component on the front page relatively easily revised over the entire surface or produces with the appropriate roughness and flatness can be. However, the use of two separate components also requires a relatively complex production.

Disclosure of the invention

Based on the illustrated prior art, the invention is based on the object, a fuel! Develop njektor according to the preamble of claim 1 such that a comparison with the prior art simplified construction with relatively simple and cost-effective manufacturability is made possible. This object is achieved in a fuel injector with the features of claim 1, characterized in that the sensor element is designed in the form of a force sensor with at least one strain gauge, and that the force sensor is connected to the sealing element. The invention takes advantage of the idea that when using such a strain gauge the strain gauge on the sealing element (sealing membrane) opposite side does not have to abut against a contact surface of the receiving space or may. Rather, even an axial distance between the strain gauge in the receiving space on the side facing away from the sealing element is required for the proper functioning of the expansion.

This eliminates in particular a particularly complex processing of a corresponding contact surface or the need to use a multi-part housing construction to form the receiving space for the sensor element.

Advantageous developments of the fuel injector according to the invention are listed in the subclaims.

Of particular advantage for the proper functioning of the fuel injector or the force sensor is that the at least one strain gauge is arranged on the opposite side of the sealing element at a distance from the bottom of the blind hole-like receiving space. In this case, it is meant that with every deformation occurring during operation of the sealing element, ie even with the largest deformation to be assumed, the strain gauge in the receiving space on the side opposite the sealing element does not touch or contact the bottom of the receiving space. In a structurally preferred embodiment of the expansion measuring element, it is provided that the at least one strain gauge element is designed in the form of a strain gauge.

A more accurate result of the force measurement and a compensation of component tolerances is achieved if either two, arranged offset by 90 ° to each other strain gauges or a plurality of strain gauges existing strain gauge assembly is provided in rosette shape.

A particularly simple and effective sealing of the receiving space for the force sensor is achieved when the sealing element is designed in the form of a disc-shaped sealing membrane, which is connected to a radially surrounding edge region with a carrier space forming the receiving space (sensor plate).

In particular, a reliable and tight connection between the sealing element and the carrier element (sensor plate) is achieved by a welded connection. For this purpose, it is provided that the carrier element and the sealing membrane of the same type, mutually weldable materials, in particular of metal, exist.

An especially preferred connection between the carrier element and the sealing element or the sealing membrane provides that the carrier element has a radially encircling support shoulder formed on the side facing the sealing membrane, against which the sealing membrane lies axially, and that the connection between the Sealing membrane and the support element in the region of the support shoulder takes place, preferably by a laser beam weld.

The assembly process of such a sealing membrane on the support shoulder can be particularly simple and accurate perform when the outer diameter of the sealing membrane is adapted to the diameter of the support shoulder. What is meant here is that the outer diameter of the sealing membrane is dimensioned such that it can be used only with mounting clearance in the recess which forms the support shoulder. A further preferred embodiment of the invention provides that the sealing element consists of metal, and that the at least one strain gauge is vapor-deposited on the sealing element in thin-film technology. Such a design creates a particularly cost-effective production of the force sensor at high quantities and also has the particular advantage that the receiving space in its size or depth only relatively flat and substantially only the size of the deformation of the sealing element (sealing membrane) must be adjusted ,

Another structurally preferred embodiment of the invention provides that the receiving space is arranged in the region of a return pipe or formed in a return pipe.

In addition, it is provided that on the sealing element on the opposite side of the at least one Dehnmesselement a pin-shaped transmission element is applied, which is connected to a magnet armature. In other words, this means that a movement of the magnet armature, which is transmitted via the pin-shaped element on the sealing element (sealing membrane), a movement of the injection member (nozzle needle) is closed.

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

This shows in:

Fig. 1 shows a longitudinal section through a fuel according to the invention! njektor,

Fig. 2 shows a portion of the fuel injector according to the invention

1 in an assembled view, also in longitudinal section and

3 shows one of several possible arrangements of strain gauges in the region of a membrane element designed as a sealing membrane for sealing a receiving space for a pressure sensor in plan view. The same elements or elements with the same function are provided in the figures with the same reference numerals. The fuel injector 10 according to the invention shown in FIG. 1 is part of a common rail injection system for injecting fuel into the combustion chamber, in particular of a self-igniting internal combustion engine. The fuel injector 10 has an injector housing 1 1, which comprises a nozzle body 12 on the side facing the combustion chamber, not shown, of the internal combustion engine. The cylindrically shaped nozzle body 12 has a recess 13 in which a nozzle needle 15 along a longitudinal axis 16 of the injector 1 1 is arranged up and down movable to close or release at the bottom or in the wall of the nozzle body 12 formed injection openings 17 ,

The side facing away from the injection openings 17 of the recess 13 of the nozzle body 12 is closed by a valve member 18, so that the recess 13 forms a high-pressure chamber 20 or high-pressure region for the fuel. The high pressure chamber 20 is connected via a formed in the injector 1 1 supply channel 21 and a fuel supply line 22 in particular with a designed as a rail storage element 23 in which high-pressure fuel (meaning a fuel pressure of, for example, 2000 bar or more) is located , which serves to supply the high-pressure chamber 20.

The nozzle needle 15 is guided within the high-pressure chamber 20 on the side facing away from the injection openings 17 with an axial end portion 25 radially in a recess of the valve member 18, wherein from the recess a volume variable control chamber 26 is formed. The control chamber 26 is connected via a Kraftstoffzuführbohrung with therein inlet throttle 27 with the

High-pressure chamber 20 connected. In the high pressure chamber 20, the nozzle needle 15 has a shoulder 28, against which a closing spring 30 is supported with an end face, while the shoulder 28 opposite the end face of the closing spring 30 abuts against the underside 31 of the valve piece 18. The nozzle body 12 is radially surrounded by a sleeve-shaped holding body 34 which is pressure-tight manner, not shown, in known manner, for example by means of a nozzle lock nut with the nozzle body 12. Within the holding body 34, a securing ring 36 is arranged, which braces the valve member 18 axially against the valve member 18 facing the end face of the nozzle body 12 via a formed on the holding body 34 threaded connection. The valve piece 18 has in the longitudinal axis 16 a Abiaufbohrung 38, in which an outlet throttle 39 is arranged. The drainage bore 38 opens on the side opposite the control chamber 26 in a conically formed seat surface 41. The seat surface 41 acts with a valve element in the form of a

Valve sleeve 42 together, which forms a sealing seat with the seat surface 41 in the lowered position shown in FIG. 1. The valve sleeve 42 is guided radially in a guide piece 43 and disposed in the direction of the longitudinal axis 16 up and down. The guide piece 43 surrounds the valve sleeve 42 on the side facing the valve piece 18 with a radial distance. The holding body 34 forms a low-pressure space 45, which is hydraulically connected to the control space 26 via a plurality of drainage bores 46 and the drainage bore 38 when the valve sleeve 42 is lifted off the seat 41. The valve piece 18 facing away from the end face of the valve sleeve 42 is provided with a

Anchor plate 48 of a magnet armature operatively connected, which cooperates with a magnetic core 49 arranged in a magnetic coil 50. The anchor plate 48 has a through hole 52 which is penetrated by a pin-shaped transmission element 55, which is guided in a through hole 56 of the valve sleeve 42 at least substantially free of leakage, and in

Direction of the longitudinal axis 16, depending on the pressure applied to the end face 57 of the fuel, is arranged movable up and down.

On the armature plate 48 opposite side of the magnetic core 49 of this example by the spring force of a plate spring 58 is subjected to force, which presses the magnetic core 49 axially against a radially circumferential shoulder 59 of the holding body 34. The magnetic core 49 has a through hole 61 in which a further closing spring 62 is arranged, which abuts with its one end face on the armature plate 48, and with its other end on a sensor plate 65, and the anchor plate 48 and the with Anchor plate 48 operatively connected

Valve sleeve 42 in the direction of the seat 41 force. The on the opposite side of the armature plate 48 of the magnetic core 49, consisting of metal sensor plate 65 forms a support member, which is also in the low pressure region or in the low pressure chamber 45. The sensor plate 65 has, concentric to the longitudinal axis 16, a blind-hole-shaped recess 66 which, on the side facing the armature plate 48, has a region with an enlarged diameter, which forms a radially encircling support shoulder 68. The recess 66 forming a receiving space is closed by means of a metallic sealing element in the form of a (elastically deformable) sealing membrane 69, as can be seen in particular with reference to FIG. 2. Here, the diameter of the circular sealing membrane 69 is adapted to the (inner) diameter of the recess 66 so that the sealing membrane 69 can be mounted in the recess 66 with only a small radial mounting clearance in the region of the larger diameter of the recess 66 and axially on the Support shoulder 68 rests, wherein the armature plate 48 facing outside 71 of the sealing membrane 69 is preferably flush with the bottom 72 of the sensor plate 65. To form a tight connection between the sealing membrane 69 and the sensor plate 65, the sealing membrane 69 in the region of the support shoulder 68 by means of a radially circumferential weld (not shown), in particular with a

Laser beam weld connected.

Within the recess 66 of the sensor plate 65, a force sensor 75 is arranged, which serves for at least indirect detection of the pressure of the fuel in the high-pressure chamber 20 or for detecting the movement of the nozzle needle 15, either directly with the sealing membrane 69 or as in the embodiment via the transmission element 55 is arranged in operative connection with the sealing membrane 69. Essential to the invention is the specific arrangement or design of the force sensor 75 in the recess 66 of the sensor plate 65. According to the invention, it is provided that the force sensor 75 consists of at least one strain gauge in the form of a strain gauge 77. The strain gauge 77 is preferably vapor-deposited on the facing side of the sealing membrane 69 on a contact surface of the sealing membrane 69 in thin-film technology. Alternatively, the at least one strain gauge 77 is connected to the sealing membrane 69 in any other suitable manner, depending on the design of the strain gauge 77. Preferably, however, the force sensor 75 is in the form of two, by 90 ° (with respect to

3, in the form of several, in the illustrated embodiment in the form of three, in their angular position about the common longitudinal axis 16 offset from each other strain gauges 77a to 77c in rosette shape. It is also essential that the recess 66 with its bottom 78 has such a depth that even with a maximum raised nozzle needle 15 and the maximum lifted transmission element 55, the ground 78 facing surfaces of the strain gauges or (s) 77, 77a to 77c preferably not yet in contact with the base 78 or only in such a contact, that the measurement result of the strain gauges 77, 77a to 77c, caused by the deformation of the sealing membrane 69, is not falsified.

On the magnetic core 49 opposite side of the sensor plate 65, this is connected to a return pipe 80. The return pipe 80 consists in the illustrated embodiment of two parts, a plate-shaped housing part 81 and a sleeve-shaped nozzle member 82, wherein the housing part 81 and the nozzle member 82 are connected by an annular circumferential weld 83, in particular a laser weld, pressure and media density. In the nozzle element 82 is concentric with the

Longitudinal axis 16, a return bore 84 is formed, which has a return line 85 connection with a return tank 86 (fuel tank). Slits or openings 87, 88 designed to carry electrical connection lines 91, 92 of the magnetic coil 50 or of the strain gauges 77, 77a to 77c are arranged, for example, in the sensor plate 65 and at least in the housing part 81 by machining processes. The connection lines 91, 92 are electrically connected to a connection plug, not shown in FIG. 1, which is designed, for example, as an injection molding of the return connection piece 80 made of plastic. The sensor plate 65 and the housing part 81 are penetrated by a common, with respect to the longitudinal axis 16 obliquely arranged return passage 93, on the one hand connection to the low pressure chamber 45 of the injector 1 1, and on the other hand with the return bore 84 in the nozzle element 82.

On the housing part 81, a radially encircling retaining shoulder 95 is formed on its outer circumference, which is arranged in operative connection with a union nut 96, which in turn cooperates via an internal thread 97 formed on the union nut 97 with a holding body 34 formed external thread 98. By means of the union nut 96, the component assembly consisting of the sensor plate 65 and the return connection 80 can be clamped axially in the direction of the magnet core 49.

The operation of the fuel injector 10 takes place in a known per se and therefore only briefly explained below way: When not energized

Magnetic coil 50, the nozzle needle 15 is pressed by the spring force of the closing spring 30 against a formed in the nozzle body 12 sealing seat, so that the injection openings 17 are closed. At the same time, the valve sleeve 42 is pressed by the spring force of the closing spring 62 against the seat surface 41. When the electromagnet 50 is energized, the armature plate 48 is moved in the direction of

Solenoid 50 pulled against the spring force of the closing spring 62. In this case, the valve sleeve 42 lifts off from the seat surface 41, so that fuel located in the control chamber 26 passes via the drainage bore 38 into the low-pressure space 45, from there via the drainage bores 46 into the return bore 84 and can then flow back into the return tank 86. By the reduced

Pressure in the control chamber 26 decreases acting on the nozzle needle 15 closing force, so that it lifts off from its sealing seat on the nozzle body 12 and the injection openings 17 releases for injecting fuel into the combustion chamber of the internal combustion engine. It is essential that the prevailing in the control chamber 26 pressure of the fuel via the Abiaufbohrung 38 always on the

Transmission element 55 is applied, which in turn is at least indirectly arranged operatively connected to the force sensor 75 and the strain gauges 77, 77a to 77c. As a result, the force sensor 75 (via a corresponding evaluation circuit) always detects the pressure of the fuel prevailing in the control chamber 26, as a result of which the pressure in the high-pressure chamber 20 or at least indirectly to the position of the nozzle needle 15 can be closed.

The fuel injector 10 described so far can be modified or modified in many ways, without departing from the spirit of the invention. For example, it is also conceivable to use the force sensor 75 in directly controlled fuel injectors 10, in which the actuation of the nozzle needle 15 takes place directly via an armature of an electromagnet connected to the nozzle needle 15. Furthermore, it is conceivable to form the sensor plate 65 as a disk-shaped insert part, which can be inserted into a return pipe 80. In this case, the housing part 81 is formed with a corresponding recess for the sensor plate 65.

Claims

Expectations

1 . Fuel injector (10), in particular common rail injector for self-igniting internal combustion engines, with an injector housing (1 1), in which a sensor element is arranged in a low-pressure area (45) for at least indirectly detecting a fuel pressure prevailing in a high-pressure area (20), wherein the sensor element is arranged on the side of an elastically deformable sealing element (69) facing away from the high pressure region (20) in operative connection with the sealing element (69) and wherein the sealing element (69) seals a receiving space (66) for the sensor element, characterized in that Sensor element is designed in the form of a force sensor (75) with at least one strain measuring element, and that the force sensor (75) is connected to the sealing element (69).

2. Fuel injector according to claim 1,

characterized,

that the at least one strain measuring element is arranged on the side opposite the sealing element (69) at a distance from the base (78) of the blind hole-like receiving space (66).

3. Fuel injector according to claim 1 or 2,

characterized,

that the at least one strain measuring element is designed in the form of a strain gauge (77; 77a to 77c).

4. Fuel injector according to claim 3,

characterized,

that two strain gauges (77) arranged offset by 90° to one another or several strain gauges (77a to 77c) are provided in rosette form.

Fuel injector according to one of claims 1 to 4,

characterized,

in that the sealing element (69) is designed in the form of a disk-shaped sealing membrane which is connected at a radially circumferential edge region to a carrier element (65) forming the receiving space (66).

Fuel injector according to claim 5,

characterized,

that the carrier element (65) and the sealing element (69) consist of identical materials that can be welded together, in particular metal.

Fuel injector according to claim 5 or 6,

characterized,

that the carrier element (65) has on the side facing the sealing element (69) a radially circumferential support shoulder (68) designed as a recess, against which the sealing element (69) rests axially, and that the connection between the sealing element (69) and the Carrier element (65) in the area of the support shoulder (68), preferably by a laser beam weld.

Fuel injector according to claim 7,

characterized,

that the outer diameter of the sealing element (69) is adapted to the diameter of the support shoulder (68).

Fuel injector according to one of claims 1 to 8,

characterized,

that the sealing element (69) is made of metal and that the at least one strain measuring element is vapor-deposited onto the sealing element (69) using thin-film technology.

10. Fuel injector according to one of claims 1 to 9,

characterized,

that the receiving space (66) is arranged in the area of a return connection (80) or is formed in a return connection (80).

1 1 . Fuel injector according to one of claims 1 to 10,

characterized,

in that a pin-shaped transmission element (55), which is connected to a magnetic armature (48), rests on the sealing element (69) on the side opposite the at least one strain measuring element.