WO2004079180A1

WO2004079180A1 - Valve comprising a spring element for a fuel injector

Info

Publication number: WO2004079180A1
Application number: PCT/EP2004/001880
Authority: WO
Inventors: Jürgen Dick; Heinz Lixl; Johann Massinger; Martin Simmet
Original assignee: Siemens Aktiengesellschaft
Priority date: 2003-03-04
Filing date: 2004-02-25
Publication date: 2004-09-16
Also published as: EP1601869B1; EP1601869A1; DE502004005498D1

Abstract

The invention relates to a valve for a fuel injector, which is composed of a valve housing, a valve body with a sealing seat for the valve body and of a spring element, which pretensions the valve body into a closing position on the sealing seat. To this end, the spring element is placed downstream from the sealing seat.

Description

description

Valve with spring element for a fuel injector

The invention relates to a valve of a fuel injector with a valve housing with a sealing seat for a valve body, with a spring element that prestresses the valve body in a closed position on the sealing seat.

DE 199 58 239 discloses an injection valve with a valve that limits an outflow from a control room. In the injection valve, fuel is led to a control chamber at a very high pressure from a high-pressure accumulator via a high-pressure bore through an inlet throttle. In the control room, the fuel pressure acts on a rear end of an axially movable nozzle needle. The movement of the nozzle needle opens and closes injection holes that lead to the combustion chamber of an internal combustion engine. When the injection valve is open, the injection holes are connected to a nozzle chamber which is formed at the front end of the nozzle needle and which in turn is connected to the high-pressure accumulator. If full fuel pressure is applied to the nozzle needle both in the control room and in the nozzle chamber, the nozzle needle is pressed down due to the larger effective area in the control room and closes the injection holes. If the valve is closed, essentially the full fuel pressure is present in the control chamber, so that the nozzle needle closes the injection holes that lead into the combustion chamber of the internal combustion engine.

If the valve is opened, the fuel pressure acting on the nozzle needle from the control chamber decreases, while the pressure in the nozzle chamber remains the same, so that the nozzle needle nem sealing seat and fuel is injected from the nozzle chamber through the injection holes into the combustion chamber of the internal combustion engine. The valve has a closing member which is biased by a spring against a sealing view. The spring is located in the control room, ie on the high pressure side.

The object of the invention is to create a simplified structural design of such a valve, in order thereby to simplify handling during assembly while at the same time reducing the size of the valve.

The object is achieved according to the features of claim 1.

The downstream side of the valve is far more accessible for the assembly of the spring element acting on the valve body than the high pressure side and, as a result, offers favorable prerequisites for efficient assembly. The design of the valve can be simplified as well as downsized. Through the direct attachment of the spring element on the valve plate, an improved reaction speed of the valve can be achieved. Likewise, the spring element can be installed in the relaxed state and adapted to the spatial conditions.

In a further embodiment of the invention, the spring element is clamped between the valve housing and the valve cone. With a conventional design, this side of the valve is easily accessible, which in turn favors assembly.

Due to a smaller number of individual parts, the valve according to the invention is cheaper to manufacture. This also enables the valve to respond more quickly, since no further lifting or pushing element is required, as in the prior art.

It is particularly expedient to provide a shoulder-like support surface on the valve body for bearing the spring element. For this purpose, the valve body can be provided with a groove, the inside diameter of which is smaller and the outside diameter of which is larger than the diameter of the bore of the spring element engaging in the groove. This generally circumferential groove serves as a support surface for the spring element, while a surface of the valve plate serves as an abutment. The valve body is thus to be manufactured from a single workpiece. The shoulder-like support surface and the groove can be attached using a single tool by turning and / or milling. The valve body, spring element and surface of the valve plate can be exactly matched to each other. Additional closure elements for the spring element are not required. It is also possible to punch the spring element from a single spring steel plate.

A simple insertion of the spring element is provided by an extended insertion opening arranged in it, which opens into the bore of the spring element. The insertion opening can also be an enlarged bore, by means of which the spring element is pushed onto the head of the valve body in order to be laterally displaced into the groove of the valve body. The spring tension can be adjusted to the high pressure of the flow medium. Due to its small design, the component can also be used in a spatially limited environment, since there are no spring elements that can be locked to rotate. The insertion opening can be arranged in the middle of the spring element or at the two outer ends.

Another embodiment of the invention has a latching surface on the side, expediently on both sides of the bore of the spring element engaging in the groove of the valve body, in order to give the spring element a reliable fit in the groove and to preclude lateral displacement of the plate spring out of the groove. The individual components of the plug valve do not need to be disassembled in order to install and tension the spring element. The insertion opening can be adapted to different valve body diameters. In addition, the spring element is unable to leave the engaged position horizontally or vertically in the upstream direction of the valve.

A modified embodiment for the support surface of the valve body consists in that the support surface is arranged on a ring fastened on the head of the valve body. The ring can be non-positively mounted on the valve body after the spring element has been pushed onto the head beforehand by the head being passed through the bore of the spring element. The flow opening for the fuel can now be closed by the valve body in a force-locking and positive-locking manner with respect to the valve plate, so that no additional sealing elements are required and a direct and direct opening or closing of the passage is possible with the aid of the valve body. Indirect sealing via a hydraulic system is not necessary. In the support surface of the valve housing for the spring element, a groove or groove is expediently arranged as a flow opening for the fuel.

In a preferred embodiment, the contact surface of the spring element, which rests on the valve housing, is not flat, but is designed to be curved or wavy. The wavy or curved shape serves as compensation and ensures a secure fit if the spring element is not designed to be rotationally symmetrical.

Further details, features and advantages of the invention will become apparent from the following description of some embodiments of the invention, ^'and with reference to the drawing. Here show:

1 shows a plan view of the head of the assembled cone valve body;

Fig. 2 shows a section along line A-A in Fig.l; Fig. 3 shows a section along line B-B in Fig. 1 in an enlarged view;

Figure 4 is a spring element in plan view.

5 shows the spring element according to FIG. 4 in a side view;

Figure 6 shows the assembly of the spring element in plan view. Fig. 7 is a section along line A-A in Fig. 6;

8 shows a further embodiment in plan view;

Fig. 9 is a section along line A-A in Fig. 8;

10 shows the detail X from FIG. 9 in an enlarged representation; 11 shows a further embodiment of the spring element in a perspective view,

12 shows a further embodiment of the spring element in side view and top view, 13 shows an injection valve with a servo valve into which a spring element according to FIGS. 1 to 12 can be inserted.

1 shows a top view of a valve plate 3 which has a recess 8. In a bottom surface of the recess 8, a recessed, second recess 26 is made, into which a spring element 12 is inserted. The spring element has an elongated rounded shape and is made of a thin sheet. The second recess 26 has a shape that essentially corresponds to the width of the spring element 12, but is longer than the spring element 12. The spring element 12 is shown in Fig. 1 in the assembled state. A valve body 5 is arranged in the middle of the spring element 12 and is positively connected to the spring element 12. A valve head 6 protrudes through a central bore 14 of the spring element 12. The valve head 6 has a circular cross section, the diameter of which in the end region is larger than the diameter of the central bore 14. The central bore 14 merges into two outer bores 13. The outer bores 13 have a partial circular shape, the diameter of which is greater than. the diameter of the valve head 6. A surface 9 of the valve plate 3 is designed as a flat surface. The recess 8 essentially has a circular cross section.

Fig. 2 shows the valve plate 3 in cross section AA of the figure. The valve plate 3 has a valve bore 4 which opens into the second recess 26. In the direction of the second recess 26, the valve bore 4 tapers via a conically tapering valve seat 7. A valve body 5 is introduced into the valve bore 4, which is designed to taper conically via a sealing surface 27 to a groove 10. The groove 10 delimits a cylindrical section of the valve body 5 which merges into the valve head 6 via the groove 10. The valve head 6 has a larger diameter than the valve body 5 in the region of the groove 10. The spring element 12 bears with circular segment-shaped edge regions of the central bore 14 on opposite sides of the groove 10. The spring element 12 is positively connected to the valve body 5 in the direction perpendicular to the longitudinal direction of the valve body 5 by the circular segment-shaped edge regions. In addition, a displacement of the spring element 12 in the longitudinal direction of the valve body 5 is not possible due to the wider valve head 6.

The cross-section of the spring element 12 has a shape that is curved in the center region, which, with two end regions, which are arranged in the region of the outer bores 13, rest on the valve plate 3 in the second recess 26. A central region of the spring element 12, in which the central bore 14 is arranged, is raised from a base area of the second recess 26 and bears against the valve head 6. As shown in FIG. 2, the valve body 5 is pressed against the valve seat 7 of the valve plate 3 by the deflection of the spring element 12 with the sealing surface 27. In this way, the valve bore 4 is sealed in a flow direction 2, which leads from the bottom to the top. The valve body 5 has a smaller cross section in the valve bore 4 than the valve bore 4, so that fuel can flow from below to the valve seat 7. To open the valve bore 4, it is necessary for the valve body 5 to be pressed against the biasing force of the spring element 12 from top to bottom, so that the sealing surface 27 of the valve body 5 lifts off the valve seat 7. This creates an opening in the Valve bore 4 is released so that fuel can flow upwards through the valve plate 3 from below.

FIG. 3 shows a cross section B-B through FIG. 1. It can clearly be seen that the spring element 12 lies directly against the valve head 6 in the region of the central bore 14. In the area of the groove 10, the valve body 5 has a smaller diameter than in the area of the valve head 6.

4 shows an enlarged illustration of the spring element 12. It can be clearly seen that the central bore 14 has identical, identical circular segments 28 as edge regions, the diameter of which essentially corresponds to the diameter of the valve body 5 in the region of the groove 10. The middle bore 14 is connected to the outer two bores 13 via intermediate regions 29. In the end regions, the spring element 12 has partial rings 30 with which the spring element 12 rests on the valve plate 3 in the installed state.

The diameter of the outer bores 13 is larger than the diameter of the central bore 14 and at the same time larger than. the diameter of the valve head 6. This allows the valve head 6 to be pushed through an outer bore 13 during assembly of the spring element 12 and then a positive connection of the spring element 12 to the valve body 5 can be achieved by laterally displacing the spring element 12 relative to the valve body 5. When moving laterally, the intermediate region 29 of the spring element 12 is temporarily widened by the valve body 5 in the region of the groove 10 until the valve body 5 reaches the central bore 14. The spring element 12 is made of an elastic material, preferably spring steel, so that the spring derelement 12 in the area of the intermediate areas 29 after the valve body 5 is pushed back to the original shape.

5 shows the spring element 12 in a side view, in which the curved shape of the spring element 12 with a central curvature 31 can be clearly seen. The central curvature 31 is essentially formed in the region of the central bore 14

6 shows the position of the spring element 12 during assembly and fastening with the valve body 5. The spring element 12 is arranged to the far right in the second recess 26. Subsequently, the valve body 5 with the valve head 6 is inserted from below through the valve bore 4 and the valve head 6 is pushed through the left, outer bore 13.

This position is shown in cross section in FIG. 7. The spring element 12 is then shifted to the left, so that the spring element 12 engages with the central bore 14 around the groove 10 on the valve body 5. On the one hand, the valve body 5 is prestressed with the sealing surface 27 against the valve seat 7 and thus the valve bore 4 is closed. In addition, the spring element 12 is detachably and positively attached to the valve body 5.

During assembly, the spring element 12 is moved in a first assembly direction 17. The middle curvature 31 of the spring element 12 is pressed in the direction of the valve plate 3. Since the spring element 12 rests with the right and left partial ring 30 on the valve plate 3, the valve body 5 is pulled into the valve seat 7 by this pretensioning. FIG. 10 shows an enlarged illustration of the second valve according to FIG. 9.

8 shows a further embodiment of a valve in a plan view from the side of the recess 8. In the embodiment of the second valve, the recess 8 has a third recess 20 instead of the second recess 26, which is essentially cylindrical with two part-circular extension sections 32 is trained. The third recess 20 is arranged under a further spring element 19. The further spring element 19 is designed in the form of a circular disk with a central bore. When the second valve is open, the fuel flows through the valve bore 4 from below via the third recess 20 and the further widening sections 32. An unimpeded flow is possible with the valve bore 4 open.

Fig. 9 shows the second valve of Figure 8 in section A-A. The further spring element 19 is fastened to the valve head 6 of the valve body 5 via a clamping ring 21. In this embodiment, the clamping ring 21 replaces the groove 10 and the widened version of the valve head according to the previous figures. The further spring element 19 essentially has a circular disk shape with a central bore. The valve head 6 is guided through the central bore. The further spring element 19 also has a curved shape, the further spring element 19 having an arc shape in cross section. During assembly, the valve body 5 is first inserted into the valve plate 3 from below until the valve head 6 projects into the recess 8. The sits

Valve body 5 with its sealing surface 27 on the valve seat 7 of the valve plate 3. In this position, the further spring element 19 is pushed onto the valve head 6 until the further spring element 19 rests in the edge area on the valve plate 3. Then the further spring element 19 is pressed via a clamping ring 21 in the direction of the valve plate 3. Subsequently, the clamping ring 21 is poisoned with the valve head 6, so that the further spring element 19 is positively connected to the valve body 5. By depressing the further spring element 19, the further spring element is prestressed against the valve plate 3, so that the valve body 5 is pulled against the valve seat 7 of the valve plate 3 by the pretensioning of the further spring element 19.

FIG. 11 shows a third spring element 33, which is designed in the form of a circular disk in the base area, but which has a central, circular curvature 34. The cross-section of the curvature 34 along a cross-sectional line 37 is symmetrical to a central axis M and essentially corresponds to the cross-section of the spring element 12, as shown in FIG. 5. The third spring element 33 is curved upward in the edge region. The third spring element 33 has a central bore 14 which is connected to outer bores 13 via intermediate regions 29 according to the spring element 12 ^' . The third spring element 33 shows a combination of the circular disk shape with the central bore 14 and the outer bores 13.

12 shows a schematic illustration of a fourth spring element 35, which essentially has an elongated shape. In cross section, the fourth spring member 35 is formed with a central bulge, said Endbe ^¬ rich are bent upward. The fourth spring element 35 has a central, circular opening 36 which merges into lateral slots 38. The side slots 38 are formed in the longitudinal direction of the fourth spring element 35. The fourth spring element 35 is pushed for mounting with the bore 36 over a valve head 6 of a valve body 5 inserted into the valve plate 3. The diameter of the bore 36 is somewhat smaller than the diameter of the valve head 6, which merges into a circumferential groove 10 according to FIG. 2 via a step. The hole widens when pushed on

36 of the fourth spring element due to the slots 38 and takes on the original shape again after reaching the groove 10. The fourth spring element 35 is thus also positively connected to the valve body 5.

13 schematically shows an injection valve with a 2/2-way valve which is used as a servo valve and is designed in accordance with the shapes described in FIGS. 1 to 12. In the injection valve, fuel at a high pressure is fed from a high-pressure accumulator, which is not shown, via a high-pressure bore 41 and an inlet bore 42 with an inlet throttle 43 to a control chamber 44 in an injection valve body 45. In the control chamber 44, the fuel pressure then acts on a rear end of an axially movable nozzle needle 46. A movement of the nozzle needle 46 opens and closes injection holes 47 which are formed in the injection valve body 45 and which lead to a combustion chamber of an internal combustion engine. The injection holes 47 are connected to a nozzle chamber 48 when the injection valve is open. The nozzle chamber 48 is at the front end of the nozzle needle

46 formed in the injector body 45 and connected to the high pressure bore 41. If the full fuel pressure is present at the nozzle needle 46 both in the control chamber 44 and in the nozzle chamber 48, the nozzle needle 46 is pressed downward due to the larger effective area in the control chamber 44 and thereby closes the injection holes 47. From the control chamber 44 leads a connecting bore 51 in the injection valve body 45 with an outlet throttle 60 to a servo valve 49 integrated in the injection valve body 45, which in turn is connected to a fuel tank via an unpressurized fuel return 59. The servo valve is actuated and actuated by an electromagnetic or piezoelectric actuator 68 via a valve tappet 56. The servo valve 49 has the task of controlling the pressure that is exerted on the movable nozzle needle 46 in the control chamber 44 for closing and opening the injection valve. If the servo valve 49 is closed, the full fuel pressure is essentially present in the control chamber 44, so that the nozzle needle 46 closes the injection holes 47 which lead into the combustion chamber of the internal combustion engine. If the actuator 58 is controlled electrically, the valve tappet 56 exerts a force on the servo valve 49 pressurized with a spring element 12, 19, 33, 35. As a result, the servo valve 49 opens, so that a connection is established between the high pressure accumulator, the control chamber 44, the servo valve 49 and the fuel return 64. The resulting fuel flow via the servo valve 49 leads to a defined pressure drop in the inlet throttle 43 and the outlet throttle 60. Control chamber 44. As a result, the fuel pressure acting on the nozzle needle 46 in the control chamber 44 decreases, while the pressure in the nozzle chamber 48 remains the same, so that the nozzle needle 46 rises and fuel from the nozzle chamber 48 via the injection holes 47 into the combustion chamber Injecting internal combustion engine.

Claims

claims

1. Valve for a fuel injector with a valve housing with an outlet with a sealing seat _^ with a valve body, with a spring element, which prestresses the valve body into a closed position on the sealing seat, the spring element (12, 19; 33, 34) downstream after the sealing seat (7) is arranged.

2. Valve according to claim 1, characterized in that the spring element (12, 19, 33; 34) is clamped between the valve housing (1) and the valve body (5).

3. Valve according to claim 1 or 2, characterized in that the valve body (5) has a shoulder-like support surface on which the spring element (12, 19) bears.

4. Valve according to one of claims 1 to 3, characterized in that the valve body (5) has a groove (10) and that the spring element (12, 33, 34) is held in the groove (10).

5. Valve according to one of claims 1 to 4, characterized in that the central bore (14) opens into a bore (13) which has a larger diameter than the central bore (14), and that the spring element (12) with the central bore (14) is held on the valve body (5).

6. Valve according to claim 5, characterized in that a constriction is formed between the bore (13) and the central bore (14), which has a smaller diameter than the central bore (14).

7. Valve according to claim 5 or 6, characterized in that the bore (13) has a larger diameter than a head (6) of the valve body (5).

8. Valve according to claim 3, characterized in that as

Support surface a clamping ring (21) is arranged, which is attached to the head (6) of the valve body (5).

9. Valve according to one or more of claims 1 to 8, characterized in that the spring element (12, 19; 33, 34) has a centrally arranged deflection which is directed away from the valve housing (1).

10. Valve according to claim 9, characterized in that the deflection (31, 34) is arranged in the region in which the spring element (12, 19; 33, 34) is fastened to the valve body (5).

11. Valve according to one of claims 1 to 10, characterized in that the valve housing (1) has a recess with a flat surface which serves to receive the spring element (12, 19).

12. Valve according to one of claims 1 to 11, characterized in that the spring element (12, 19; 33, 34) has support areas (30) and that the support areas (30) have a curved shape.

13. Valve according to one of claims 1 to 12, characterized in that the spring element (12,19,33,34) is arranged on the low pressure side.