EP2496822B1 - Injection nozzle for a leakless fuel injector - Google Patents

Description

Technical area

The invention relates to a method for producing a valve needle of a fuel injector according to the preamble of claim 1.

State of the art

Such a fuel injector is from the DE 10 2007 032 741 A1 known. The fuel injector described in this document is leak-free designed for high injection pressures by dispensing with a low-pressure stage. However, only small forces are available for closing the valve needle, which reduces the ability to inject small quantities of fuel. This disadvantage is difficult to compensate, for example, by the use of correspondingly fast switching control valves, which is expensive and expensive. Therefore, in the subject of this document, a permanent and constant closing force is generated on the valve needle by a sharp-edged gap choke is formed between the valve needle and the valve body in the pressure chamber. The gap choke is formed by a separately incorporated into the valve needle collar having a sharp edge at its outer edge, so that between the edge of the collar and the valve body the sharp-edged circumferential and thus an annular gap forming gap choke is formed. In addition, the federal government may also have lateral poles.

As an alternative to the embodiment described above, a relief bore in the form of a closing throttle may also be provided, such a bore being incorporated in a separate component in the form of a throttle plate. Such a throttle plate is due to the separate component an increased construction cost.

Another fuel injector with a throttle channel formed on a collar of the valve needle is off WO 02/48536 A known.

The invention is based on the object to provide a fuel injector in which one of the closing operation of the valve needle is optimized by an improved over the prior art closing throttle.

Disclosure of the invention

This object is achieved by the claimed manufacturing method. As a result, first of all the production is simplified, since the closing throttle is no longer incorporated into a separately produced federal government. The collar is guided as a part of the valve guide portion sealing in the valve body and only through the recess flows a well-defined amount of fuel. The flow rate and thus the closing behavior is improved or specified by this embodiment over the prior art.

Advantages of the invention

In development of the invention, the recess has a longitudinal extent, which has at least the simple maximum recess depth based on the number of all recesses. In a particularly advantageous embodiment, the longitudinal extension of the recess has twice the maximum recess depth based on the number of all recesses. The longitudinal extent refers to the axial length of the recess along the valve needle, while the recess depth refers to the (changing) distance of the recess to the valve body. These geometric design defines the pressure drop of the fuel along the closing throttle and thus influences the closing behavior of the valve needle. It has proven to be advantageous to arrange a total of three recesses distributed on the circumference of the valve needle.

In a further development of the invention, the at least one recess is circular arc-shaped. This embodiment offers advantages in the case of recess grinding.

According to the invention, an upper bevel, the recess and the flow recess in the flow direction of the fuel are arranged in alignment with each other in the valve needle guide region. By this configuration, turbulence in the flow of the fuel can be avoided. In this case, an annular gap can connect to the recess or else the flow recess directly follows the recess in the collar. The rotationally symmetrical intermediate region is basically without a hydraulic or mechanical function, but possibly offers advantages in the machining of the nozzle needle.

This advantage can be achieved in a further embodiment of the invention without the rotationally symmetrical intermediate region when a transition region is arranged between the recess and the flow gap recess, wherein the transition region has the same contour as the recess. This is advantageously achieved in that the recess and a gap area in front of the recess and the Strömungsspaltausnehmung are made in a grinding operation. In this case, then, the transition region can be made in a second grinding cycle by a simple reaction of the grinding tool. A particular advantage is that the valve needle does not have to be re-clamped for this second sanding cycle.

Fig.1

eine Schnittdarstellung einer in einem Ventilkörper längs verschiebbar angeordneten Ventilnadel mit einer segmentförmigen Aussparung an einem umlaufenden dichtenden Kragen,

Fig.2

eine Ansicht der Ventilnadel gemäß Fig.1,

Fig.3

eine Detailansicht einer Ventilnadel, bei der die segmentförmige Aussparung in einem Winkel zur Längsachse der Ventilnadel angeordnet ist,

Fig.4

eine Detailansicht einer Ventilnadel, bei der die segmentförmige Aussparung in einen Flächenanschliff integriert ist,

Fig.5

eine Ansicht einer Ventilnadel mit einer Aussparung in dem Kragen, die fluchtend zu einer dem Kragen unter Einschluss eines rotationssymetrischen Bereichs nachfolgenden Strömungsaussparung in der Nadelführung der Ventilnadel angeordnet ist,

Fig.6

eine Schnittdarstellung durch die Ventilnadel und den Ventilkörper gemäß Fig.5,

Fig.7

eine Detailansicht einer Ventilnadel mit einer Aussparung in dem Kragen, die fluchtend zu einer nachfolgenden Strömungsaussparung in der Nadelführung der Ventilnadel angeordnet ist,

Fig.8

eine Schnittdarstellung durch die Ventilnadel und den Ventilkörper gemäß Fig.5,

Fig.9

Position eines Schleifwerkzeugs bei einem ersten Schleifschritt zur Herstellung einer Ventilnadel gemäß Fig.7 und

Fig.10

Position eines Schleifwerkzeugs bei einem zweiten Schleifschritt zur Herstellung einer Ventilnadel gemäß Fig.7.

Show it:

Fig.1

a sectional view of a longitudinally displaceably arranged in a valve body valve needle with a segment-shaped recess on a circumferential sealing collar,

Fig.2

a view of the valve needle according to Fig.1 .

Figure 3

a detailed view of a valve needle, wherein the segment-shaped recess is arranged at an angle to the longitudinal axis of the valve needle,

Figure 4

a detailed view of a valve needle, in which the segment-shaped recess is integrated in a Flächenanschliff,

Figure 5

a view of a valve needle with a recess in the collar, which is arranged in alignment with a collar following the inclusion of a rotationally symmetric region flow recess in the needle guide of the valve needle,

Figure 6

a sectional view through the valve needle and the valve body according to Figure 5 .

Figure 7

a detailed view of a valve needle with a recess in the collar, which is arranged in alignment with a subsequent flow recess in the needle guide of the valve needle,

Figure 8

a sectional view through the valve needle and the valve body according to Figure 5 .

Figure 9

Position of a grinding tool in a first grinding step for producing a valve needle according to Figure 7 and

Figure 10

Position of a grinding tool in a second grinding step for producing a valve needle according to Figure 7 ,

Embodiment of the invention

The valve needles 1 and valve body 2 of a fuel injector shown in detail in the figures are designed in particular for use in self-igniting internal combustion engines with a common rail injection system. In this case, the fuel injector is suitable for precisely controlling even small fuel injection quantities which have to be metered as part of a pilot injection in order to achieve low emission values. The various embodiments all relate to a closing throttle, which is intended to ensure a stable closing of the valve needle 1 in fuel injectors without pressure stage. Through the closing throttle, a higher hydraulic pressure is built up than the closing throttle during the closing process of the valve needle 1 above the closing throttle, which supports and accelerates the closing process.

Fig.1 shows a valve needle 1, which is guided in a valve body 2 longitudinally displaceable. The valve body 2 has one with a valve needle tip 3 ( FIG. 2 ) cooperating with the needle seat, which cooperates with at least one injection opening, can be introduced through the fuel in a combustion chamber of an associated cylinder-piston unit of the internal combustion engine. The fuel taken from the rail of the common-rail injection system under high pressure (up to 3,000 bar) is supplied to the at least one injection opening controlled by a pressure space in the form of a gap formation between the nozzle needle 1 and the valve body 2.

The control normally takes an unillustrated and acting on a valve ball actuator module, wherein the valve ball with a in a Holding body of the actuator module incorporated valve seat cooperates. The valve seat is connected via a connecting line to a control chamber, which in turn is flow-connected to the rail via an inlet throttle. The control chamber is arranged opposite to the valve needle tip 3 at the end of the valve needle 1 in the valve body 2 cooperating with the holding body. In a switching position of the actuator module, the valve ball lifts from the valve seat and acting on the control room side end face of the valve needle 1 hydraulic pressure in the control chamber is lowered by discharge of fuel through the connecting line and further via a subsequent to the valve seat discharge line in the holding body. In this switching state, the valve needle 1 is moved from the approximately approaching under rail pressure at a pressure shoulder 14 of the valve needle 1 fuel against the force of a valve needle spring 4 in the direction of the holding body and the valve needle tip 3 lifts from the needle seat. The fuel is then injected into the combustion chamber, the at least one injection port. If the actuator module is moved into its second switching position, the valve ball is moved onto the valve seat and fuel flowing into the control chamber through the inlet throttle from the rail increases the hydraulic pressure in the control chamber. The valve needle tip 3 is pressed back onto the needle seat. The injection process is thus terminated.

Between the valve body 2 and the valve needle 1, an annular gap 5 is formed in an upper valve needle side region as part of the gap formation or the pressure chamber, in which - as stated - the standing under rail pressure fuel flows. Subsequent to the annular gap 5, the valve body 2 is formed so that it forms a guide 6, in which the valve needle 1 with an upper valve needle guide portion 11 is guided exactly. At the level of the transition region between the annular gap 5 and the guide 6, an upper bevel 7 is incorporated in the valve needle 1 and the upper valve needle guide portion 11, which extends to a circumferential sealing collar 8 of the valve needle 1. The collar 8 is part of the upper (or below explained below) Ventilnadetführungsbereichs 11 and acts at all positions that can take the longitudinally displaceable valve needle 1, always together with the guide 6, while the upper section 7 always protrudes into the annular gap 5. In the collar 8 a segment-shaped recess 9 is ground in extension to the upper section 7. On the circumference of the valve needle 1 can more, for example three, upper sections 7 and recessed in the collar 8 recesses 9 may be arranged distributed. Subsequent to the at least one recess 9, a rotationally symmetrical region 10 incorporated in the valve needle 11 follows in the form of a recess. At this rotationally symmetrical region 10 includes another cooperating with the guide 6 lower valve needle guide portion 11, in which at least one flow recess 12 is incorporated. The flow recess 12 is designed such that the fuel passes along the flow recess 12 without throttling losses in an annular space 13, which in turn is connected to the needle seat. The annular space 13 is created by a production of the valve needle 1 with a relation to the valve needle guide portion 11 of reduced diameter. As a result, the pressure shoulder 14 is formed.

FIG. 2 shows the according to FIG. 1 designed nozzle needle 1 in a perspective view, the control room end, however, is not shown.

FIG. 3 shows a variant of the valve needle 1, wherein the recess 9a is aligned at an angle to the longitudinal axis of the valve needle 1 in the valve guide portion 11. The recess 9a extends up to the rotationally symmetrical region 10 and can be configured such that the recess 9a itself forms the closing throttle. Alternatively, as in FIG. 3 illustrated, the closing throttle may be formed by a throttle point 17 in the collar 8a of the recess 9a.

In the variant according to FIG. 4 is in the existing flow recess 12 in the valve guide portion 11 of the valve needle 1, the closing throttle in the form of a throttle point 17a similar to FIG. 3 embedded or incorporated.

In the configuration according to the FIGS. 5 and 6 are the upper section 7, the recessed into the collar 8 recess 9 and the flow recess 12 in the flow direction of the fuel arranged in alignment with each other. Between the recess 9 and the flow recess 12, in turn, a rotationally symmetrical region 10 is incorporated into the valve needle 1. This arrangement is advantageous in terms of a turbulence-free flow of the fuel.

This differs from the embodiment according to the FIGS. 7 and 8 in that here no rotationally symmetrical region 10 is provided between the recessed recess 8 in the collar 8 and the flow recess 12. Instead, here is a transition region 15 between the recess 9 and the flow recess 12 is arranged. The particular advantage of this transition region 15 is that this as in the FIGS. 9 and 10 shown, easily in two consecutive grinding operations, without re-tightening the valve needle 1 can be made.

A grinding tool 16 has in the FIGS. 9 and 10 shown contour on and in a first grinding cycle according to FIG. 9 the upper bevel 7 is ground above or in the drawing to the left of the recess 9, the recess 9 itself and the flow recess 12 in the valve needle guide region 11 into the valve needle 1. Of particular importance here is that the upper section 7 is ground deeper than the flow recess 12 in the valve needle 1. Furthermore, the transition region 15 is shown in a raw state. However, it is also provided within the scope of the invention to loop the transition region 15 completely into the valve needle 1 during the second grinding cycle.

In a second grinding cycle according to FIG. 10 is traversed by a displacement of the grinding tool 16 to the right of the transition region 15 in the valve needle 1. In this case, only the part of the grinding tool 16 touches the Ventihnadel 1, which grinds this transition region 15.

Claims (4)

1. Method for producing a valve needle (1) which has a valve needle tip for interacting with a valve seat of a valve body (2) and, by means of the interaction of the valve needle (1) with the valve seat, permits or shuts off a flow of fuel to at least one injection opening, wherein, on the valve needle (1), there is formed an encircling, sealing collar (8, 8a) with at least one segment-shaped cutout (9, 9a) on the encircling sealing collar (8, 8a) for forming a closing throttle, and wherein the collar (8, 8a) is a constituent part of a valve-guiding region (11), and wherein an upper ground portion (7), the cutout (9, 9a) and a flow cutout (12) are arranged, in the flow direction of the fuel, in alignment in the valve needle guiding region (11), and a transition region (15) is arranged between the cutout (9, 9a) and the flow cutout (12), and the transition region (15) has the same contour as the cutout (9, 9a), characterized by the following method steps:

   - grinding the cutout (9, 9a), the upper ground portion (7) in front of the cutout (9, 9a) and the flow cutout (12) in one grinding process by means of a grinding tool (16),

   - grinding the transition region (15) by relocating the grinding tool (16).
2. Method according to Claim 1, characterized in that the cutout (9, 9a) has a longitudinal extent which amounts to at least one times the maximum cutout depth as viewed across the number of all cutouts (9, 9a).
3. Method according to one of the preceding claims, characterized in that the cutout (9, 9a) is formed in the shape of an arc of a circle.
4. Method according to one of Claims 1 to 3, characterized in that the upper ground portion (7) is ground into the valve needle (1) to a greater depth than the flow cutout (12).

Images