Method for producing an electromagnetically actuated suction valve for a high-pressure pump

Abstract

Method for producing an electromagnetically actuated suction valve (1) for a high-pressure pump (2) of a fuel injection system, comprising the steps: - Inserting an armature (3) including a helical compression spring (4) partially accommodated in the armature (3) into a central recess (5) of a valve body (6), - placing a sleeve (7) for connecting the valve body (6) with a pole core (8) on the valve body (6), - Welding the sleeve (7) to the valve body (6), - Inserting the pole core (8) into the sleeve (7) so that the helical compression spring (4) is axially preloaded, and - Welding the sleeve (7) to the pole core (8), wherein the axial preload force of the helical compression spring (4) is adjusted indirectly via the depth (T) of a blind hole (9) formed in the pole core (8), wherein a pole core (8) classified according to the depth (T) of its blind hole (9) is used, characterized in that for selecting the pole core (8) the required depth (T) of the blind hole (9) is determined before mounting the pole core (8).

Description

[0001] The invention relates to a method for producing an electromagnetically actuated suction valve for a high-pressure pump of a fuel injection system, in particular a common rail injection system, having the features of the preamble of claim 1. The suction valve serves to fill an element chamber of a high-pressure pump with fuel, wherein it is preferably controllable in such a way that a defined amount of fuel can be metered. State of the art

[0002] An electromagnetically actuated suction valve of the type mentioned above is disclosed, for example, in published patent application DE 10 2014 220 757 A1. It comprises a magnetic coil for acting on a liftable armature, which can be directly or indirectly coupled to a liftable valve piston, which is acted upon in the closing direction by the spring force of a valve piston spring. To hold the valve piston in an open position when the magnetic coil is de-energized, a further spring is provided, the spring force of which is greater than that of the valve piston spring and acts upon the valve piston indirectly via the armature in the opening direction. When the magnetic coil is energized, a magnetic field builds up, which moves the armature against the spring force of the further spring toward a pole core in order to close a working air gap formed between the pole core and the armature.The armature loses contact with the valve piston, and the valve piston spring pulls the valve piston into a valve seat. The suction valve closes. When the solenoid coil is deenergized, the additional spring returns the armature to its original position, where it comes into contact with the valve piston again and lifts it from the valve seat against the spring force of the valve piston spring.

[0003] The spring force of the additional spring acting in the opening direction of the suction valve represents a value relevant to the function of the suction valve, which must be adjusted. The suction valve of DE 10 2014 220 757 A1 has a sleeve-shaped adjustment element that is inserted, in particular pressed, into a central bore of the pole core to support the spring. The axial preload of the spring, and thus the desired spring force, can then be adjusted via the offset of the adjustment element and the position of the pole core relative to the armature. However, this process is generally subject to tolerances.

[0004] The generic publication DE 10 2015 212 387 A1 shows an electromagnetically actuated suction valve for a high-pressure pump of a fuel injection system, in particular a common rail injection system, comprising an annular magnetic coil for acting on an armature which is accommodated in a recess of a valve body in a manner that can be moved by lifting and is acted upon by the spring force of an armature spring in the direction of a valve closing element that can be moved by lifting and interacting with a valve seat, wherein a pole core which is firmly connected to the valve body is located opposite the armature at a working air gap.

[0005] DE 10 2012 107 764 A1 discloses a common rail system (CRS) for an internal combustion engine of a vehicle having a high-pressure pump, wherein the common rail system comprises a flow control valve as an electromagnetic switching valve, which is arranged in the delivery line for controlling the amount of fuel supplied by the high-pressure pump to a high-pressure accumulator.

[0006] DE 10 2014 200 339 A1 discloses an electromagnetically controllable suction valve for a high-pressure pump of a fuel injection system, in particular a common rail injection system, comprising a magnetic actuator with an annular magnetic coil for acting on a stroke-movable armature and a pole core which, together with the armature, defines a working air gap.

[0007] The present invention is based on the object of optimizing the adjustment process, in particular the process is to be simplified so that the result is less subject to tolerances.

[0008] To achieve this objective, the method with the features of claim 1 is proposed, which relates to the production of an electromagnetically actuated suction valve. Advantageous developments of the invention are set forth in the subclaims. Disclosure of the invention

[0009] The method proposed for manufacturing an electromagnetically actuated suction valve comprises the following steps: - Inserting an armature including a helical compression spring partially accommodated in the armature into a central recess of a valve body, - Placing a sleeve to connect the valve body with a pole core on the valve body, - Welding the sleeve to the valve body, - Inserting the pole core into the sleeve so that the helical compression spring is axially preloaded, and - Welding of the sleeve to the pole core, whereby the axial preload force of the helical compression spring is adjusted indirectly via the depth of a blind hole formed in the pole core.

[0010] Indirect adjustment via the depth of the pole core's blind bore simplifies the adjustment process. In particular, the need to press an adjustment element into a central bore in the pole core is eliminated. This also reduces the risk of particles being generated during the pressing process, which could later impair the function of the suction valve. This simultaneously increases robustness. The direct support of the helical compression spring on the pole core also increases robustness.

[0011] The method further comprises using a pole core classified according to the depth of its blind bore. This means that to adjust the axial preload force of the helical compression spring, a pole core of a specific pole core class is selected, which has a blind bore with a predetermined depth. Therefore, pole cores of different classes are preferably kept in stock in order to achieve the desired spring force adjustment by pairing a suitable pole core.

[0012] According to the invention, the required depth of the blind hole is determined before the pole core is installed to select the pole core. This means that the adjustment is preceded by a classification of at least one pole core. Preferably, several pole cores with blind holes of different depths are classified and kept in stock to enable a selection to be made from them.

[0013] To determine the required depth of the blind hole, a force corresponding to the desired axial preload is preferably applied to the helical compression spring inserted into the armature. The length of the helical compression spring projecting beyond the armature is then measured, from which the armature's stroke is subtracted. The remaining length corresponds to the required depth of the blind hole.

[0014] Since the armature stroke corresponds to the working air gap between the pole core and the armature, the armature stroke is adjusted by the position of the pole core relative to the armature or the valve body into which the armature is inserted. The position of the pole core relative to the valve body is then fixed by welding to the sleeve that surrounds at least part of the pole core and the valve body.

[0015] Advantageously, the sleeve is pressed onto the valve body when it is placed on it. This press fit facilitates the subsequent welding of the sleeve to the valve body.

[0016] Alternatively or additionally, it is suggested that the pole core be pressed into the sleeve during insertion. The interference fit achieved in this way facilitates the subsequent welding of the sleeve to the pole core. At the same time, the offset determines the axial distance between the pole core and the valve body, or adjusts the armature stroke. The subsequent welding then fixes the adjustment.

[0017] Before welding the sleeve to the pole core, the armature stroke and / or the axial preload of the helical compression spring should preferably be checked and readjusted if necessary. To check, the armature can be pressed against the pole core. If readjustment is required, the position of the pole core relative to the valve body can be varied by adjusting the offset of the pole core in the sleeve.

[0018] Alternatively or additionally, a pole core of a different pole core class can be used.

[0019] To optimize the adjustment of the armature stroke, it is recommended that an annular stop body be inserted into the central recess of the valve body before inserting the armature. The stop body then forms the lower end stop for the armature, while the upper end stop is formed by the pole core. The armature stroke is then determined by selecting a suitable, preferably graded, stop body.

[0020] The stop body is preferably supported on an annular shoulder of the valve body. Furthermore, the shoulder preferably surrounds a central opening through which the armature inserted into the valve body remains accessible. The armature stroke and / or the spring force of the armature spring can then be tested or measured via the opening.

[0021] When welding the sleeve to the valve body and / or the pole core, a circumferential weld is preferably applied. This circumferential weld results in a particularly robust and therefore permanent connection. At the same time, the circumferential weld seals the space accommodating the armature from the outside.

[0022] A preferred embodiment of the invention is explained in more detail below with reference to the accompanying drawings. These show: Fig. 1 a schematic longitudinal section through an electromagnetically actuated suction valve according to the invention, which is integrated into a high-pressure pump, Fig. 2 an exploded view of the components of the suction valve required to adjust the spring force of the helical compression spring of the Fig. 1 and Fig. 3 the components of the Fig. 2 after joining. Detailed description of the drawings

[0023] The Fig. The suction valve 1 shown in Figure 1 is integrated into a housing part 12 of a high-pressure pump 2. This means that the housing part 12 forms a valve seat 13 for a valve tappet 14, which is also guided for lifting movement via the housing part 12. The spring force of a spring 15 acts on the valve tappet 14 in the direction of the valve seat 13, so that the spring exerts a closing force on the valve tappet 14. The spring force of the spring 15 is counteracted by the spring force of a helical compression spring 4, which is supported on an armature 3 that can be coupled to the valve tappet 14.

[0024] To act on the armature 3, a magnet assembly 16 is provided with an annular magnet coil 17 that surrounds the armature 3. The armature 3 is accommodated in a recess 5 of a valve body 6, via which the magnet assembly 16 is connected to the housing part 12 of the high-pressure pump 2. A magnet sleeve 18 with an annular collar 19 sits on the valve body 6, which serves to support a union nut 20 screwed to the housing part 12. To adjust the stroke of the valve tappet 14, an adjusting ring 21 is inserted between the valve body 6 and the housing part 12.

[0025] The stroke of the armature 3 is adjusted, on the one hand, by an annular stop body 10, which is inserted into the recess 5 between the armature 3 and the valve body 6. On the other hand, the stroke of the armature 3 is predetermined by a working air gap 22, which remains between the armature 3 and a pole core 8 of the magnet assembly 16. To fix the position of the pole core 8 with respect to the armature 3, the pole core 8 is pressed into a sleeve 7 and welded to it. The sleeve 7 is also pressed onto the valve body 6 and likewise welded to it.

[0026] When the solenoid coil 17 is de-energized, the helical compression spring 4 keeps the suction valve 1 open. When the solenoid coil 17 is energized, the armature 3 moves against the spring force of the helical compression spring 4 in the direction of the pole core 8 to close the working air gap 22. In doing so, it detaches from the valve tappet 14, so that the spring 15 can pull the valve tappet 14 into the valve seat 13. The suction valve 1 closes. When the energization of the solenoid coil 17 is discontinued, the helical compression spring 4 returns the armature 3 to its original position, where it comes into contact with the valve tappet 14 and lifts it - against the spring force of the spring 15 - out of the valve seat 13. The suction valve 1 opens.

[0027] When the suction valve 1 is open, fuel flows through the valve seat 13 into an element chamber 23 of the high-pressure pump 2. The fuel present in the element chamber 23 is then compressed by a stroke of a pump piston 24 and fed to a high-pressure accumulator (not shown) via a high-pressure outlet 25. In order to meter a defined amount of fuel, the suction valve 1 can be controlled such that it initially remains open during the delivery stroke of the pump piston 24. An excess amount of fuel is then expelled from the element chamber 23. This requires the helical compression spring 4 to keep the suction valve 1 open against the pressure building up in the element chamber 23. The spring force of the helical compression spring 4 thus represents a functionally relevant variable that must be adjusted. In the suction valve 1 shown, the adjustment takes place during production of the suction valve 1, in particular during the assembly of the magnet assembly 16.The individual assembly steps are explained below using the . Fig. 2 and Fig. 3 explained.

[0028] As in particular the Fig. 2, the annular stop body 10 is first inserted into the recess 5 of the valve body 6. Then the armature 3 including the helical compression spring 4 is inserted into the recess 5. After that, the sleeve 7 is pressed onto the valve body 6 and welded to the valve body 6 by means of a circumferential weld seam 11. A force F is then introduced into the helical compression spring 4 which corresponds to the required spring force. The length L of the helical compression spring 4 which projects beyond the armature 3 can now be determined by measuring. If the stroke H of the armature 3 is subtracted from the length L, the required depth T of a blind hole 9 formed in the pole core 8 for receiving and supporting the helical compression spring 4 is obtained. If the depth T is known, a pole core 8 can be paired with a correspondingly deep blind hole 9.

[0029] To optimize the process, a pole core 8 is paired that is classified according to the depth T of its blind hole 9. This means that several pole cores 8 with blind holes 9 of different depths are kept in stock, so that only the correct pole core 8 needs to be selected.

[0030] To complete the assembly of the magnet assembly 16, only the pole core 8 must be connected to the valve body 6 via the sleeve 7. For this purpose, the pole core 8 is pressed into the sleeve 7. The sleeve 7 is then welded to the pole core 8 via a circumferential weld seam 11 (see Fig. 3).

[0031] To check the adjustment made, the armature 3 can be pressed in using a force F'. When pressed in, not only the spring force of the helical compression spring 4 but also the stroke H of the armature 3 can be measured.

Claims

[1] Method for producing an electromagnetically actuated suction valve (1) for a high-pressure pump (2) of a fuel injection system, comprising the steps: - Inserting an armature (3) including a helical compression spring (4) partially accommodated in the armature (3) into a central recess (5) of a valve body (6), - placing a sleeve (7) for connecting the valve body (6) with a pole core (8) on the valve body (6), - Welding the sleeve (7) to the valve body (6), - Inserting the pole core (8) into the sleeve (7) so that the helical compression spring (4) is axially preloaded, and - welding the sleeve (7) to the pole core (8), wherein the axial preload force of the helical compression spring (4) is adjusted indirectly via the depth (T) of a blind hole (9) formed in the pole core (8), wherein a pole core (8) classified according to the depth (T) of its blind hole (9) is used, characterized bythat in order to select the pole core (8) the required depth (T) of the blind hole (9) is determined before mounting the pole core (8). [2] Method according to claim 1, characterized by in that, in order to determine the required depth (T) of the blind hole (9), a force (F) is introduced into the helical compression spring (4) inserted into the armature (3), which force corresponds to the desired axial preload force, then the length (L) of the helical compression spring (4) projecting beyond the armature (3) is measured, from which the stroke (H) of the armature (3) is then deducted. [3] Method according to claim 1 or 2, characterized by that the sleeve (7) is pressed onto the valve body (6) when it is placed on it. [4] Method according to one of the preceding claims, characterized by that the pole core (8) is pressed into the sleeve (7) when inserted into it. [5] Method according to one of the preceding claims, characterized bythat before inserting the armature (3) an annular stop body (10) is inserted into the central recess (5) of the valve body (6). [6] Method according to one of the preceding claims, characterized by that when welding the sleeve (7) to the valve body (6) and / or the pole core (8), a circumferential weld seam (11) is set.

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