WO2016206850A1

WO2016206850A1 - Fuel injector with control valve

Info

Publication number: WO2016206850A1
Application number: PCT/EP2016/060289
Authority: WO
Inventors: Fabian FISCHER; Oezguer Tuerker
Original assignee: Robert Bosch Gmbh
Priority date: 2015-06-24
Filing date: 2016-05-09
Publication date: 2016-12-29
Also published as: DE102015211705A1

Abstract

The invention relates to a fuel injector (10) for injecting fuel into the combustion chamber of an internal combustion engine having a nozzle needle (2) which is arranged such that it can be displaced longitudinally, wherein the nozzle needle (2) opens and closes at least one spray hole (4) into the combustion chamber by way of the longitudinal movement thereof. The longitudinal movement of the nozzle needle (2) can be controlled by way of the pressure in a control chamber (60), wherein the control chamber (60) can be connected to a low pressure chamber (35) by means of a control valve (18) which can be actuated by an actuator (28). The control valve (18) comprises a valve element (20) which can be moved by the actuator (2), a valve seat (42) and a closing element (44). The closing element (44) interacts with the valve seat (42) in order to open and close a hydraulic connection from the control chamber (60) to the low pressure chamber (35). The valve seat (42) is configured on a valve piece (12), and the valve element (20) is guided in an end region (11) of the valve piece (12), with the result that a guide gap (9) is configured between the valve element (20) and the end region (11). According to the invention, at least one groove (8) is configured on the valve element (20) and/or on the end region (11) in the region of the guide gap (9).

Description

Description title

Fuel injector with control valve The invention relates to a fuel! injector with a control valve.

PRIOR ART A fuel injector with a control valve is known from EP 2855914 A1. The known fuel injector is for injecting fuel into the combustion chamber of a

Internal combustion engine provided. It comprises a longitudinally displaceable arranged

Nozzle needle, wherein the nozzle needle opens and closes by its longitudinal movement at least one injection hole in the combustion chamber. The longitudinal movement of the nozzle needle is controllable by the pressure in a control room. The control chamber is connectable by means of an actuatable by an actuator control valve with a low-pressure chamber. The control valve comprises a valve element movable by the actuator, a valve seat and a closing element, wherein the closing element cooperates with the valve seat for opening and closing a hydraulic connection from the control space to the low-pressure space. The valve seat is formed on a valve piece. The valve element is in an end region of the

Valve piece out, so that between the valve element and the end portion

Guide gap is formed.

The valve element of the known fuel injector is not completely static

determined, so that there is a misalignment of the valve element in the valve piece. Due to this inconsistency, the valve element must align when reaching the stroke stop within the guide through the valve piece, so as to release the full opening cross-section of the valve seat. This alignment work

counteracting dampening fluid forces. If the damping fluid forces are too great, then the valve element can not fully align, which effectively reduces the stroke of the Valve element corresponds. Furthermore, this also leads to increased wear, both between the valve element and the valve sleeve and between the closing element and the valve seat.

epiphany

In contrast, the valve element of the inventively proposed fuel injector is oriented in the valve sleeve. Thus, there is no skewing of the valve element in the valve sleeve. Thus, on the one hand the valve element stroke is not reduced and, on the other hand, the wear of the entire control valve is minimized.

For this purpose, the fuel injector comprises a longitudinally displaceable nozzle needle, wherein the nozzle needle opens by its longitudinal movement at least one injection hole in a combustion chamber of an internal combustion engine and closes. The longitudinal movement of the nozzle needle is controllable by the pressure in a control chamber, wherein the control chamber is connectable by means of an actuatable by an actuator control valve with a low-pressure chamber. The

Control valve comprises a valve element movable by the actuator, a valve seat and a closing element. The closure member cooperates with the valve seat to open and close a hydraulic connection from the control chamber to the low pressure space. The valve seat is formed on a valve piece, and the valve element is guided in an end region of the valve piece, so that between the valve element and the

End region is formed a guide gap. According to the invention is in the field of

Guide gap formed on the valve member and / or at the end region at least one groove.

The arrangement according to the invention of the at least one groove in the guide gap reduces the damping forces and moments acting there between the valve element and the valve element, thereby enabling alignment of the valve element and thus avoiding an oblique position of the valve element and resulting lifting losses. The at least one groove ensures a pressure equalization over the circumference of the valve element. As a result, the hydraulic forces on the same

Valve element, especially in the radial direction. For this purpose, the at least one groove can be formed either on the valve element or on the valve piece, or several grooves can be formed on both parts. The prevention of misalignment of the valve element in the valve sleeve minimizes or additionally prevents the wear between the valve element and the valve sleeve, but also the wear between the closing element and the valve seat, since the valve element moves in the ideal case coaxially to the valve seat.

In an advantageous embodiment, the at least one groove is formed on the valve element. This is very easy to manufacture and reduces the moving mass of the valve element. This also improves the injection characteristics of

Fuel injector, since the valve element can be accelerated and decelerated faster.

In another advantageous embodiment, the at least one groove is formed on the end region, ie on the valve piece. This is the preferred because strength reasons, because the valve element is not weakened.

In developments of the invention, both parts, both the valve element and the valve seat, may have one or more grooves. The alignment of the valve element to the valve sleeve can be done even better because, for example, by crossing of axial and longitudinal grooves on the opposite component, a type of lubrication pockets can be generated.

In advantageous embodiments, the at least one groove in the axial direction, ie in

Opening direction or in the closing direction of the valve element is formed. Advantageously, in this embodiment, three or four grooves are distributed uniformly over the circumference. As a result, the valve element can align very well with the valve sleeve, since a comparatively constant hydrostatic pressure is built up in the grooves.

In advantageous developments, the at least one groove - or the three or four grooves - arranged in the axial direction at a distance a to the valve seat side beginning of the guide gap. As a result, the leakage flow cross-section - ie the

Flow cross section of the guide gap - not over the entire length of the

Leading gaps increased. This results in a type throttle of length a, which seals the seat well against the low pressure chamber. In another advantageous embodiment, the at least one groove is arranged in the axial direction at a distance b from the low-pressure space. This will be the

Leakage flow cross section is not increased over the entire length of the guide gap. This results in a kind of throttle of length b, which seals the seat space or the guide gap well against the low-pressure chamber.

In a combined embodiment, the at least one groove can be arranged both at a distance a from the seat space and at a distance b from the low-pressure space. This increases the sealing of the seat space with respect to the low-pressure space. This results in a first throttle of length a from the seat to the guide gap and a second throttle of length b from the guide gap to the low-pressure chamber.

Advantageously, the valve element is substantially cylindrical. Thereby, the essential valve function can be represented axially symmetrical, which is both a functional advantage and increases the strength.

In an advantageous development, the at least one groove is formed in a radially circumferential direction to the cylinder axis of the valve element. That is, the groove or grooves run tangentially to the opening or closing direction of the valve element. As a result, the amount of leakage through the guide gap does not increase. When training in radial

Direction should preferably be provided two to four grooves in order to achieve a favorable pressure distribution in the guide gap for the alignment of the valve element.

In advantageous embodiments, the valve element and the closing element are made in one piece. An end surface of the valve element thus cooperates with the valve seat. This is a component-saving and cheap version of the control valve.

Furthermore, thereby the closing element or the end face and the of the

Valve piece guided surface of the valve element can be made in one setting, so that very tight tolerances can be realized.

In advantageous developments, the valve element is designed sleeve-shaped with an inner surface. Preferably, the inner surface is arranged radially surrounding a valve pin. Thereby, the force acting on the valve element resulting hydraulic force in the axial direction, ie in the opening or closing direction of the control valve can be reduced. Further advantageously, the diameters of the inner surface of the valve element and the valve seat are the same size, wherein the inner surface is cylindrical and the valve seat are circular. This is a pressure or force balanced

Control valve realized. In the closed state, that is to say when the valve element designed as an anchor sleeve bears against the valve seat, these are on the valve element

acting hydraulic forces almost balanced, so in total about zero. Thus, the control of the control valve by the actuator can be done very quickly with already low power. The design of a pressure compensated control valve in the present invention requires a control valve with a valve pin.

In advantageous embodiments, the valve element is acted upon by a valve spring in the closing direction of the valve seat. As a result, the control valve is closed in a simple and fast manner when the actuator exerts no opening force on the valve element more. Especially with very fast closing and opening movements of the

Valve element is a possible coaxial alignment of the valve element to the valve sleeve advantageous because the alignment then acts very wear-reducing.

In advantageous embodiments, the end region is designed as a cylindrical extension with an inner guide surface. As a result, the guide can be made axially symmetrical, in the direction of the cylinder axis of the guide surface. This is particularly advantageous in tribology.

In advantageous embodiments, the actuator is an electromagnetic actuator and the valve element is accordingly designed as an armature. This is a simple form of direct control of the valve element.

BRIEF DESCRIPTION OF THE DRAWINGS With reference to the drawing, the invention will be described in more detail below.

Show it:

1 shows a section through a fuel injector proposed according to the invention for injecting fuel into the combustion chamber of an internal combustion engine, wherein only the essential regions are shown. 2 shows a further embodiment of the fuel injector, wherein only the essential areas, in particular a control valve, are shown. 3 shows a longitudinal section and a section AA through a valve element and a

Valve sleeve of the control valve.

4 shows a longitudinal section and a section B-B through the valve element and the

Valve sleeve in another embodiment of the control valve.

variants

1 shows a first embodiment variant of the fuel injector with control valve proposed according to the invention, only the essential areas being shown.

1 shows a fuel injector 10, which comprises a valve piece 12. The valve piece 12 is received in a holding body 14 via a valve clamping screw 16. The valve piece 12 defines a control chamber 60 which is formed via a valve piece 12 in the

Inlet throttle 61 from a high pressure source 84, for example a

Hochdrucksammeiraum (common rail) or a delivery unit is pressurized with system pressure. The control chamber 60 in the valve piece 12 is depressurized via an outlet throttle 62, wherein a flow channel formed by a spherical here

Closing element 44 is closed. A valve seat 42 formed on the valve seat 42 is closed by the ball-shaped closing element 44 in the position shown in FIG. As a result, the control space 60 of the fuel injector 10 is not

depressurized, but is below system pressure level. Optionally, the closing element 44, as shown in Figure 1, in a cap 46 on the

Bottom of a pressure surface 52 of the valve member 20 is added. The closure member 44 and the cap 46 are located within a seat 48 in which the valve seat 42 is located. In the seat 48 there is a seat pressure 50 or Niederraumdruck. In the valve piece 12, a nozzle needle 2 is longitudinally displaceable for opening and closing formed in the holding body 14 injection holes 4 in a combustion chamber a

Internal combustion engine arranged. An injection nozzle 4 opposite end face of the nozzle needle 2 limits the control chamber 60, whereby the end face is pressurized. The longitudinal movement of the nozzle needle 2 is thus controlled by the pressure in the control chamber 60, as is widely known from the prior art.

The fuel! The injector 10 of the embodiment of FIG. 1 has a control valve 18, which essentially comprises a valve element 20 and the closing element 44, the valve piece 12 and the valve seat 42. An upper stroke stop for limiting the Ventilelementhubs is identified by the reference numeral 26 and by a magnetic underside 30 of a magnet formed as an electric actuator 28 for actuating the fuel! Njektors 10 given. In this embodiment, accordingly, the valve element 20 is designed as an anchor. Alternatively, however, another actuator 28, for example a piezoelectric actuator 28, may also be used.

An outlet nozzle 34 with a low-pressure connection and the electric actuator 28 in the form of a magnet are enclosed by a magnetic sleeve 32 and screwed to the holding body 14 by a magnetic clamping nut. Within the holding body 14 and

inside the magnetic sleeve 32, a low pressure space 35 is formed. The low-pressure space 35 is hydraulically formed with the seat space 48 through in the valve piece 12

Abiaufbohrungen 22 connected. The Abiaufbohrungen 22 may optionally be designed as throttle bores. The low-pressure space 35 in turn is connected to the

Low pressure connection of the drain nozzle 34 hydraulically connected, wherein the

Low pressure connection in a return system of the fuel! Njektors 10 leads.

1 shows that the valve element 20 of the control valve 18 is acted upon by a valve spring 36, which exerts a valve spring force 38 in the direction of the valve seat 42. The valve spring 36 is supported on a bearing surface 40 on the inside of the drain nozzle 34.

The valve piece 12 has a sleeve-shaped end piece 1 1, on which an inner

Guide surface 13 is formed. By the guide surface 13, the valve member 20 is longitudinally movably guided with an outer cylindrical surface 21, so that the valve element 20 is moved almost coaxially with the valve seat 42. Between the guide surface 13 of Valve piece 12 and the cylindrical surface 21 of the valve element 20, a guide gap 9 is formed, which is preferably only a few microns wide.

According to the invention in the end piece 1 1 of the valve piece 12 on the guide surface 13 radially encircling grooves 8 are formed, which thus locally enlarge the guide gap 9. In alternative embodiments, the grooves 8 may also be formed in the valve element 20 on the cylindrical surface 21. The grooves 8 serve to minimize acting on the valve element 20 radial damping forces, which counteract a coaxial alignment of the valve element 20 to the valve piece 12.

2 shows a further embodiment of the fuel injector 10, wherein only the essential areas, in particular the control valve 18, are shown. The areas of the fuel injector 10 which are not explained in detail below are analogous to the embodiment of FIG.

In the embodiment of Figure 2, the valve element 20 is designed as an anchor sleeve and at the same time forms the closing element 44, so it is made in one piece with this. On a cylindrical inner surface 19 of the valve element 20 and the valve element sleeve, a valve pin 15 is arranged, which is supported on the discharge nozzle 34. The valve pin 15, the valve element 20 and the valve piece 12 define a valve space 3, which, viewed hydraulically, extends from the outlet throttle 62 to the at least one drainage bore 22. Between the valve pin 15 and the inner surface 19, a sealing gap is formed, which has only a very small leakage. In the position of the control valve 18 shown in FIG. 2, the valve element 20 cooperates with the valve seat 42, so that the pressure in the control chamber 60 is maintained at high pressure level. To relieve the pressure of the control chamber 60, the valve member 20 lifts off from the valve seat 42 and thus opens a hydraulic connection from the valve chamber 3 to the seat 48, which in turn via the at least one Abiaufbohrung 22 with the

Low pressure space 35 and further connected to the low pressure port.

In this embodiment, the control valve 18 can also be designed as a pressure-balanced or force-balanced control valve 18, namely, when the two diameters of valve seat 42 and inner surface 19 are equal. Then, in the closed state of the control valve 18, ie upon contact of the valve element 20 to the valve seat 42, the hydraulically resulting force, in particular in the axial direction, to the closing element or the valve element 20 zero.

In the embodiment of FIG. 2, the grooves 8 are formed on the cylindrical surface 21 of the valve element 20. In this case, three radially circumferential grooves 8 are formed. Again, the grooves 8 may be formed on the guide surface 13 of the valve member 12 in alternative embodiments. In this case, any number of grooves 8 can be arranged in any direction. The preferred directions are radially circumferential, axial and thread-shaped. In the following, further embodiments of the grooves 8 will be described; For example, while the control valve 18 of Figure 2 with inner surface 19 of the valve member 20 and valve pin 15 was selected as the basis. However, the embodiments described below are also applicable to the control valve 18 of Figure 1. 3 shows in longitudinal section and in section A-A three grooves 8, which are arranged in the axial direction on the cylindrical surface 21 of the valve element 20. In this case, the grooves 8 are preferably arranged at an axial distance a from the beginning of the guide gap 9 or the seat space 48, in order not to obtain any additional leakage cross section over the entire guide gap 9. As seen in section A-A, the grooves 8 have a rectangular contour in cross-section. Alternatively, however, they may also be trapezoidal, semicircular or otherwise concave. In general, any number of grooves 8 - preferably uniformly distributed over the circumference - be formed on the cylindrical surface 21; However, it is advantageously three or four grooves 8. FIG. 4 shows in longitudinal section and in section B-B four grooves 8 which are arranged in the axial direction on the guide face 13 of the valve piece 12 and the end piece 11, respectively. The grooves 8 are preferably arranged with an axial distance a to the valve seat side beginning of the guide gap 9 or at a distance a to the seat 48, in order to obtain no additional leakage cross section over the entire guide gap 9. Optionally or alternatively, the grooves 8 can also be at an axial distance b from the end of the

Guide gap 9 have. As seen in section BB, the grooves 8 have a semicircular contour in cross-section. Alternatively, however, they may also be trapezoidal, rectangular or otherwise concave. In general, any number of grooves 8 - preferably distributed uniformly over the circumference - be formed on the guide surface 13; however, advantageously, there are three or four grooves 8. The operation of the fuel injector 10 is as follows:

The nozzle needle 2 is arranged in a pressure chamber, which is hydraulically in constant communication with the high-pressure source 84 via a high-pressure inlet, for example a common rail or a high-pressure pump. For injecting fuel into the combustion chamber of the internal combustion engine, the nozzle needle 2 is lifted off a nozzle needle seat. The movement of the nozzle needle 2 is controlled by the control valve 18. The control valve 18 is actuated by the actuator 28 and controls the pressure in

Control chamber 60. If high pressure prevails in the control chamber 60, it presses the nozzle needle 2 against the force of a nozzle spring and counteracts a resulting hydraulic force acting on the nozzle needle 2 in the pressure chamber against the nozzle needle seat. If an injection of the fuel into the combustion chamber of the internal combustion engine, the control valve 18 is controlled by the actuator 28 so that the valve element 20 and the closing element 44 lifts from the valve seat 42. As a result, the pressure in the control chamber 60 is relieved by the outlet throttle 62 into the seat space 48 and further into the low-pressure space 35. With the reduced pressure in the control chamber 60, the nozzle needle 2 is lifted against the nozzle spring by the resulting hydraulic force in the nozzle chamber from the nozzle needle seat and thereby releases the spray holes 4. Thus, the injection of high-pressure fuel from the pressure chamber through the injection holes 4 takes place in the combustion chamber of the internal combustion engine. To terminate the injection process, the activation of the actuator 28

terminated, so that the valve element 20 and the closing element 44 of the

Valve element spring 36 again pressed against the valve seat 42 and thus the

Outflow throttle 62 is closed. As a result, the pressure in the control chamber 60 is again increased by the inflow via the inlet throttle 61 so that this causes a closing of the nozzle needle 2 together with the force of the nozzle spring.

Due to inconsistencies, the valve element 20 must be on reaching the

Hubanschlags on the actuator 28 and at a residual air gap within the

Align guide through the valve piece 12 or through the end piece 11, so as to release the full opening cross section on the valve seat 42. In this case, the alignment of the valve element 20 damping fluid forces (or -momente), similar to at a squish gap in the guide gap 9 between the valve element 20 and valve piece 12 arise, contrary. If the damping forces (moments) are too large, the valve element 20 can not fully align, which effectively reduces the stroke of the

Valve element 20 corresponds.

The inventive arrangement of the at least one groove 8 in the guide gap 9, the damping forces and damping moments acting there between valve element 20 and valve piece 12 are reduced, whereby a lighter orientation of the valve element 20 is made possible and thus lifting losses can be avoided.

The at least one groove 8 provides a pressure equalization over the circumference of the valve element 20 and the cylinder surface 21. The at least one groove 8 may be formed either on the cylindrical surface 21 of the valve element 20 or on the guide surface 13 of the valve member 12. If the at least one groove 8 is designed to be radially encircling, then the amount of leakage in the guide gap 9 does not increase. When forming in the axial direction, preferably three or four grooves 8 should be provided. As a result, a very good alignment of the valve element 20 is achieved, however, the amount of leakage can also increase. Therefore, the axial grooves 8 are advantageously arranged at a distance a or b to the beginning or to the end of the guide gap 9.

Claims

Claims 1. Fuel injector (10) for injecting fuel into a combustion chamber of a

Internal combustion engine with a longitudinally displaceable nozzle needle (2), the nozzle needle (2) by its longitudinal movement at least one injection hole (4) opens and closes in the combustion chamber, the longitudinal movement of the nozzle needle (2) by the pressure in a control chamber (60) controllable is, wherein the control chamber (60) by means of an actuatable by an actuator (28) control valve (18) with a

Low pressure chamber (35) is connectable, wherein the control valve (18) comprises a of the actuator (2) movable valve element (20), a valve seat (42) and a closing element (44), wherein the closing element (44) with the valve seat (42 ) for opening and closing a hydraulic connection from the control chamber (60) to the

Low pressure chamber (35) cooperates, wherein the valve seat (42) on a valve piece

(12) is formed, wherein the valve element (20) in an end region (1 1) of the

Valve piece (12) is guided so that between the valve element (20) and the

End region (1 1) is formed a guide gap (9),

characterized in that

in the region of the guide gap (9) on the valve element (20) and / or on the

End region (1 1) at least one groove (8) is formed.

2. Fuel injector (10) according to claim 1, characterized in that the at least one groove (8) is formed in the opening direction of the valve element (20).

3. Fuel injector (10) according to claim 2, characterized in that the at least one groove (8) in the opening direction of the valve element (20) is arranged at a distance a to the valve seat side beginning of the guide gap (9).

4. Fuel injector (10) according to claim 2 or 3, characterized in that the

at least one groove (8) is arranged in the opening direction of the valve element (20) at a distance b from the low-pressure space (35).

5. fuel injector (10) according to claim 1, characterized in that the

Valve element (20) is substantially cylindrical.

6. fuel injector (10) according to claim 5, characterized in that the at least one groove (8) is formed in a radially circumferential direction to a cylinder axis of the valve element (20).

7. Fuel injector (10) according to any one of claims 1 to 6, characterized in that the valve element (20) and the closing element (44) are made in one piece.

8. fuel injector (10) according to claim 7, characterized in that the

Valve element (20) is designed sleeve-shaped with an inner surface (19).

9. fuel injector (10) according to claim 8, characterized in that the inner surface (19) radially surrounding a valve pin (15).

10. fuel injector (10) according to claim 9, characterized in that the inner surface

(19) is cylindrical, the valve seat (42) is circular and that the inner surface (19) and the valve seat (42) have the same diameter.

1 1. Fuel injector (10) according to one of claims 1 to 10, characterized in that the valve element (20) by a valve spring (36) in the closing direction of the

Valve seat (42) is acted upon.

12. Fuel injector (10) according to one of claims 1 to 1 1, characterized in that the end region (1 1) is designed as a cylindrical extension with an inner guide surface (13).

13. Fuel injector (10) according to one of claims 1 to 12, characterized in that the actuator (28) is an electromagnetic actuator and that the valve element

(20) is designed as an anchor.