GB2324059A

GB2324059A - Method for the purpose of producing a divided disc

Info

Publication number: GB2324059A
Application number: GB9806940A
Authority: GB
Inventors: Dieter Kienzler; Horst Harndorf
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1997-04-07
Filing date: 1998-03-31
Publication date: 1998-10-14
Anticipated expiration: 2018-03-31
Also published as: GB9806940D0; DE19714186A1; FR2761622B1; FR2761622A1; JPH10309633A; GB2324059B

Abstract

Method for the purpose of producing a disc (31) which is divided in an axial manner by means of a separating cut, wherein the separating cut surfaces are off-set from the overall cutting plane (43) by a value of a slit displacement (S) corresponding to the separating cut width, wherein during the cutting procedure the position of the separating tool is displaced at least once from a first side of the overall cutting plane (43) to a second side with respect to the overall cutting plane (43), so that the separating cut surfaces of the disc parts produced contact each other at least partially in the overall cutting plane (43) when the disc parts are mutually rotated 180‹ about a radial axis of the disc (31). The disc may be used in fuel injection valves for internal combustion engines.

Description

1 2324059

DESCRIPTION METHOD FOR THE PURPOSE OF PRODUCING A DIVIDED DISC

The present invention relates to a method for the purpose of producing a disc which is divided in an axial manner by means of a separating cut, wherein the separating cut surfaces are off-set from the overall cutting plane by a value of a slit displacement corresponding to the separating cut width.

A divided disc of this type, which is known for example from DE-OS 43 40 883, is used therein as a stroke stop disc of a fuel-injection valve for internal combustion engines. This fuel-injection valve comprises a pistonshaped valve member which opens outwards and comprises on its valve member shaft an annular shoulder, formed on a reduction in cross-section, and comprises an annular collar disposed on the reduction in crosssection, wherein these mutually facing stop surfaces on the valve member form in each case a stroke stop which defines the stroke movement of the valve member in the opening and closing direction. In so doing, a stroke stop disc is provided between the stop surfaces on the stop collar and on the annular shoulder and forms with its axial end faces in each case the fixed counter stops for the stroke stop surfaces on the valve member. This stroke stop disc is formed in two-parts in order to facilitate assembly thereof. This two-part disc has hitherto been divided into two disc halves by means of a separating cut, wherein in order to guarantee the dimensional accuracy the separating cut width must be compensated during the dividing process. For this purpose the cutting tool is displaced from the overall cutting plane by a known differential quantity (slit 2 displacement). In a further operation the dimensionally accurate disc halves are then assembled in pairs to form a stroke stop disc, wherein a dimensionally accurate circular cross-section is produced.

However, the known production method for the purpose of producing a divided disc has the disadvantage that it is only possible in each case to manufacture one complete stroke stop disc from two lots. This results in each case in the loss of the second disc half, so that the known production method requires large quantities of material and furthermore is twice as expensive to manufacture.

In accordance with the present invention, during the cutting procedure the position of the separating tool is displaced at least once from a first side with respect to the entire cutting plane to a second side with respect to the entire cutting plane, so that the separating cut surfaces of the disc parts produced contact each other at least partially in the entire cutting plane when the disc parts are rotated 1800 with respect to each other about a radial axis of the disc.

In contrast to the known arrangements described above, a method in accordance with the invention for the purpose of producing a divided disc, has the advantage that the quantity of materials used can be halved with respect to the known production methods, so that the manufacturing outlay can also be halved. This is achieved in an advantageous manner by virtue of the fact that the separating cut on the disc is performed in a stepped manner, wherein a slit displacement, which corresponds to the separating cut width, from the overall cutting plane is provided on the stepped cut surfaces. This slit displacement 3 on the respective mutually off-set stepped cut surfaces is displaced, in each case in a mutually opposed manner, from the overall cutting plane, wherein this slit displacement, starting from the middle axis, corresponds exactly to the separating cut width, e.g the overall dimension of the electrode width and burnup during electro-erosive separation. During the cutting procedure, the position of the separating tool is displaced at least once from a first side with respect to the overall cutting plane to a second side with respect to the overall cutting plane, so that the separating cut surfaces of the disc parts produced, contact each other at least partially in the overall cutting plane, after the parts are mutually rotated about 1800 and after said parts are joined together along the separating surfaces.

When assembling the divided disc at a later stage, one of the disc halves is rotated 1800 about a radial axis of the disc, so that the slit displacement can be fully compensated and a circular cross-section which is divided in two and is dimensionally accurate is produced in a proper manner. In so doing, the separating cut on the disc should comprise at least two stepped shoulders from a radially outer region to a radially inner region of the disc. The use of the method in accordance with the invention for the purpose of producing a divided disc for the production of the stroke stop disc of a fuelinjection valve is particularly advantageous, since the dimensional accuracy of the stroke stop disc is extremely significant with regard to the guidance of the valve member. For this purpose the divided disc comprises an axial throughgoing bore in which the piston-shaped valve member of the fuel-injection valve is guided in a sliding manner. The separating cut on this stroke stop disc 4 preferably comprises four stepped cut surfaces along the entire cutting plane, wherein a first cut surface, which extends from the peripheral surface in a radial manner inwards, is off-set by a value of the slit width in a first direction and a second cut surface, which adjoins the first cut surface and issues into the through-going bore, is off-set from the overall cutting plane in a second direction which is opposite to the first direction. A further third cut surface adjoins the through-going bore in a radial manner outwards along the overall cutting plane and is off-set from the overall cutting plane in the first direction once again and is adjoined in a radial manner outwards by a fourth cut surface which is off-set from the overall cutting plane in the second direction and issues once again at the peripheral surface of the disc. The overall cutting plane bisects the axis of the disc in an advantageous manner, however, it is alternatively possible to perform off-centre separating cuts. The separating cut can be performed by means of a mechanical metal removing process, however, owing to the higher degree of accuracy this separating cut should be performed by means of an electro-erosive separation method, e.g wire-EDM. The production method in accordance with the invention has the advantage that it is not necessary subsequently to process further the separating cut surface to achieve dimensional accuracy.

Further advantages and advantageous embodiments of the subject matter of the invention are evident in the description, the drawing and in the claims.

The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings, in which:- Figure 1 is a longitudinal sectional view of a fuel-injection valve; Figure 2 is an enlarged illustration of the disc divided in accordance with the invention in the final assembled position, and Figures 3 and 4 show, in two views, illustrations of the disc in accordance with the invention during the production method.

A fuel-injection valve for internal combustion engines of the outwardlyopening construction type is illustrated in Figure 1. This fuelinjection valve comprises a cylindrical valve body 1, which protrudes with its lower free end into a combustion chamber of the internal combustion engine to be supplied and which, with its upper end face remote from the combustion chamber, is clamped in an axial manner against a valve holding body by means of a tensioning nut 3. The valve body 1 comprises an axial guide bore 7 in which a piston-shaped valve body 8 is guided in an axial manner. This valve member 9 comprises on its combustion chamber-side end a closing head 11 which has an enlarged cross- section and forms with its annular end face facing the valve body 1 a valve sealing surface 13 with which, for the purpose of controlling an injection cross-section, the said closing head cooperates with a valve seat surface 15 formed on the combustion chamber-side end face of the valve body 1. Furthermore, the valve member 9 comprises a pressure shoulder 17 which points in the direction towards the valve seat 15 and which protrudes into a pressure chamber 19 which is formed by virtue of a widening in cross-section 6 of the guide bore 7 and which extends as far as into the region of the valve seat surface 15. In so doing, the pressure working surface on the closing head 11 is formed in the opening direction of the valve member 9 to be larger than the pressure shoulder 17. The valve member 9 comprises on its end, which is remote from the combustion chamber and protrudes out of the guide bore 7, a valve member shaft 21 which has a reduced cross- section and protrudes into a spring chamber 23 formed in the valve holding body 5. A valve spring 25 is clamped into this spring chamber 23 and is supported in a fixed manner on the end face 27, remote from the combustion chamber, of the valve body 1 and on the other side acts upon a spring plate 29 provided on one end, remote from the combustion chamber, of the valve member shaft 21, and in this manner holds the valve member 9 in position against the valve seat 15. A stroke stop disc 31 and a distance ring 33 are clamped between the valve spring 25 and the end face 27, remote from the combustion chamber, of the valve body 1. Moreover, the valve member 9 comprises on its valve member shaft 21 in the region of the distance ring 33 a stop collar 35 which is guided in a sliding manner in the bore of the ring 33 and which with its lower end face 37, facing the combustion chamber, cooperates with the upper end face 39 of the stroke stop disc 31, which on the other side is held in position against the end face 27, remote from the combustion chamber, of the valve body 1 by way of the valve spring 25. Furthermore, for a supply of high pressure fuel into the combustion chamber 19 an axial pressure duct is provided in the valve body 1 and valve holding body 5 which pressure duct, starting from an external fuelinjection line, issues into the pressure chamber 19. At the fuel-injection valve 7 the fuel is injected in a known manner by virtue of the supply of high pressure fuel into the pressure chamber 19 as far as onto the closing head 11 where the high pressure fuel acting in the opening direction raises the valve member 9 from the valve seat 15 against the restoring force of the valve spring 25 and thus opens the fuel-injection cross- section. In so doing, the stroke stop disc 31, in cooperation with the stop collar 35 on the valve member 9, defines the maximum opening stroke movement, so that considerable importance is attached to this stroke stop disc 31.

In order to render it possible to assemble the stroke stop disc 31 between the stop collar 35 and an annular shoulder formed on a reduction in cross-section of the valve member 9, the stroke stop disc 31 is formed in a divided manner.

To this end the stroke stop disc 31 in accordance with the invention comprises in an advantageous manner the cross-sectional shape illustrated in Figure 2, wherein the method for the purpose of producing the divided stroke stop disc 31 will now be explained with reference to Figures 3 and 4.

The stroke stop disc 31 is initially manufactured to its outer dimension. In a further operational step a centred through-going bore 41, which corresponds to the diameter of the valve member 9, is inserted into the stroke stop disc 31. In a further processing step the separating cut is performed in a stepped manner along the overall cutting plane 43, wherein a slit displacement "S", corresponding to the separating cut width, from the overall cutting plane 43 is provided on the stepped cut surfaces. The cut surface in the exemplified embodiment is subdivided into four stepped cut surfaces along the entire 8 cutting plane 43, wherein a first cut surface 45, which extends in a radial manner inwards from the peripheral surface, is off-set from the overall cutting plane 43 by a value of the slit width "S" in a first direction 47, and a second cut surface 49, which adjoins the first cut surface 45 and issues into the throughgoing bore 41, is off-set from the overall cutting plane 43 in a second direction 51 opposite to the first direction 47. A third cut surface 53 adjoins the opposite-lying end of the through-going bore 41 along the overall cutting plane 43 and is once again off-set from the overall cutting plane 43 in the first direction 47 and is adjoined directed in a radial manner outwards by a fourth cut surface 55 which is off-set from the overall cutting plane 43 in the second direction 51 and issues at the peripheral wall of the stroke stop disc 31. In so doing, the individual cut surfaces 45, 49, 53, 5,5 are preferably off-set in stepped manner with respect to each other. The stepped separating cuts are preferably performed by means of an electro- erosive separation method, e.g wire-EDM, in such a manner that the slit displacement "S", starting from the middle axis, corresponds exactly to the separating cut width (overall dimension of electrode width and burn- up). In a further operational step one of the disc halves is rotated 1800 about a radial axis of the stroke stop disc 31 and is assembled once again with the cut surfaces, so that the slit displacement can be fully compensated in the regions 57 and a bi-partite, dimensionally accurate circular-cross-section is produced as shown in Figure 2. This stroke stop surface 31 which is assembled in this manner can now be inserted into the bore of the spring chamber in such a manner so as to surround the valve member 9 in a radial manner, wherein a reliable guidance is guaranteed on the 9 wall of the spring chamber 23' and on the through-going bore 41.

Claims

1. A method for the purpose of producing a disc which is divided in an axial manner by means of a separating cut, wherein the separating cut surfaces are off-set from the overall cutting plane by a value of a slit displacement corresponding to the separating cut width, wherein during the cutting procedure the position of the separating tool is displaced at least once from a first side with respect to the overall cutting plane to a second side with respect to the overall cutting plane, so that the separating cut surfaces of the disc parts produced contact each other at least partially in the overall cutting plane when the disc parts are rotated 1801 with respect to each other about a radial axis of the disc.

2. A method according to claim 1, wherein by virtue of the fact that the separating tool is guided along the overall cutting plane in an alternately off-set manner, at least two stepped shoulders are worked-in on the overall cutting plane, of which a first step is provided in the radially outer region of the disc and a second step is provided in the radially inner region of the disc.

3. A method according to claim 2, wherein an axial through-going bore is provided in the disc.

4. A method according to claim 3, wherein four stepped cut surfaces are worked-in along the overall cutting plane, wherein a first cut surface, which extends from the peripheral surface of the disc in a radial manner inwards, is off-set from the overall cutting plane by a value of the slit width in a first direction and a second cut surface, which adjoins the first cut surface and issues into the through-going bore, is off-set from the overall cutting plane in a second direction opposite to the first direction and comprising a third cut surface, which adjoins the through-going bore in a radial manner along the overall cutting plane and is off-set from the entire cutting plane in the first direction once again and which is adjoined radially outwards by a fourth cut surface which is off-set from the overall cutting plane in the second direction.

5. A method according to any of claims 1 to 4, wherein the overall cutting plane bisects the axis of the disc.

6. A method according to any of claims 1 to 5, wherein the separating cut is performed by means of a mechanical metal removing process.

7. A method according to any of claims 1 to 5, wherein the separating cut is performed by means of an electro-erosive separation method.

8. A divided disc produced by means of a method according to claim 1, wherein the separating cut is formed on the disc parts in such a manner that, when the disc parts are joined together on the separating cut surfaces along the overall cutting plane in a first position of the disc parts with respect to each other, a complete circular cross-section is produced on the peripheral surface of the disc, and that in a second position of the disc parts, in which the disc parts are mutually rotated about 1800 with respect to the first position, a disc cross-section, which is reduced by the value of the separating cut width, is produced when the disc parts are joined together on the separating cut surfaces.

9. A divided disc according to claim 8, wherein the divided disc is formed as a stroke stop disc of a fuel-injection valve for internal combustion engines.

1 - 12

10. A method for the purpose of producing a disc which is divided in an axial manner by means of a separating cut, substantially as hereinbefore described with reference to Figs. 2 to 4 of the accompanying drawings.

11. A divided disc produced by the method of claim 10, substantially as hereinbefore described with reference to and as illustrated in Figs. 2, 3 and 4 of the accompanying drawings.