EP2143529B1 - Grinding method for simultaneous production of two functional surfaces on a workpiece - Google Patents

Description

State of the art

The present invention relates to a grinding method for simultaneously producing two functional surfaces on a workpiece.

In component manufacturing very often several functional surfaces are to be processed by grinding. If the contour allows it, several functional surfaces can be machined with just one tool - on rotationally symmetrical components, for example, the outer and end surfaces. This happens if possible in only one process step. For various products used in higher pressure systems - e.g. Diesel injection technology - are often used preferred forms on frontal surfaces, for example, to ensure sealing functions.

In the case of special functional requirements of the component, there is frequently the requirement that no burr is created at the transition between two adjoining functional surfaces. If a rounding is permissible, this requirement can be met by mapping the contour of the workpiece over the grinding tool. However, if in addition a sharp-edged transition between two functional surfaces is required (eg sealing edge) and thus no rounding by the tool radius is permissible, two tools are usually used, which process the functional surfaces simultaneously. However, for this purpose, a corresponding machine concept is to be provided which, for example via two cross slides, enables the simultaneous machining of two surfaces.

Depending on the component shape, another possibility is to simultaneously machine the surfaces with a tool. A typical application is an outer cone (seat), which merges into an end face, which also - for example, as a high-pressure sealing surface - must be convex or concave spherical. The transition between cone and end face can be designed as a sealing edge. With conventional methods, the grinding spindle is pivoted about 30-45 ° to the workpiece spindle, resulting in an increased need for space for the grinding machine, which u.a. restricts further processing possibility on the machine.

In the US 2836939 describes a grinding process with which only one surface can be ground simultaneously. There are described methods for different surface shapes, such as concave or convex. Simultaneous grinding of multiple surfaces is not disclosed there.

Advantages of the invention

In contrast, the method according to the invention has the advantage that, for example, sealing surfaces having a preferred shape can be produced in conjunction with a sharp-edged, burr-free sealing edge. Thanks to this burr-free and sharp-edged sealing edge, a high component quality and functionality is guaranteed. At the same time, a low-cost and simple machine technology with a small installation space and optimized cycle time can be used. The inventive simultaneous machining of two functional surfaces results in a high process reliability for the dimensional accuracy of the sealing edge diameter. Due to the fixed geometric setting of the tool, the dimensional stability is hardly influenced by the process. This results in a high process reliability for convex or concave preferred shapes. Consequently, therefore, a simple correction strategy for the process reliability or dimensional stability is given.

This is achieved according to the invention by using this rotationally symmetrical grinding tool for the simultaneous production of a first functional surface and a second functional surface on a workpiece. In this case, the tool comprises a main body with an annular tool end face, wherein the tool end face has a circular processing edge or cutting edge in order to produce the first functional surface. Furthermore, the tool used comprises a conical projection which is arranged on the tool end face in order to produce the second functional surface, in particular bevel on the workpiece. The geometry of the tool according to the invention can also be described by defining the base of the conical projection smaller than the tool end face. Furthermore For example, the lateral surface of the conical projection has the largest circumference on a side facing the base body.

The process according to the invention serves e.g. for producing a component having a front surface with a concave or convex preferential shape (for example with a sealing function) in conjunction with burr-free and sharp-edged sealing edge at the transition to another functional surface by grinding with only one tool in one processing step. In addition to the cycle time, this concept also reduces the number of machine components, in particular machine axes and grinding spindles. Since the grinding spindle according to the invention is pivoted only a small amount to the workpiece spindle, only little space is required. In addition, the tool according to the invention can also be used in conventional grinding machines.

The dependent claims show preferred developments of the invention.

In an advantageous embodiment, it is provided that the tool end face is incident to a tool rotation axis by a clearance angle γ and is thus funnel-shaped. This clearance angle or this funnel-shaped collapse is particularly important if, in addition to the second functional surface, a convex first functional surface is machined. It should be noted that in this case the tool end face can not only have flat but also a concave or convex surface. Furthermore, it is sufficient for concave first functional surfaces and advantageous to make the tool end face flat and thus perpendicular to the tool rotation axis.

When using the clearance angle, it is necessary when creating a convex first functional area that the clearance angle γ is greater than or equal to α. Thus, a convex first functional surface can be generated with an inner processing edge of the annular tool face.

Further advantageous is a circular rounded machining edge. To influence the roughness of the first functional surface, a radius of the machining edge on the tool according to the invention can be changed. The larger the radius is chosen, the larger the engagement width of the tool and the smaller the roughness on the workpiece. This rounding also improves the edge stability of the tool according to the invention. It is also advantageous to optimally adjust the roughness of the first and the second functional surfaces by the choice of grinding parameters and / or wheel specification of the tool and / or by the workpiece speed and / or the tool speed. However, the editing edge does not necessarily have to be defined. So it is also advantageous to edit the first functional area with an undefined processing edge.

It is also advantageous to form the conical extension as a truncated cone. The upper end of the conical extension is not needed for machining the second functional surface and thus it is sufficient to provide a frusto-conical extension.

In a further advantageous embodiment, a lateral surface of the conical projection is flat or concave or convex. As a result, the shape of the second functional surface or chamfer can be influenced.

The invention describes a grinding method according to claim 1. The simultaneous processing according to the invention of both surfaces in one clamping with only one tool, the number of processing stations is reduced, moreover, can be with the inventive method due to the simple structure - compact grinding spindle with low tilt angle compared to Workpiece spindle - use a simple, conventional machine concept and leave room for additional processing stations. If, as in the prior art, grinding is performed with two tools, there is also the risk that the sealing edge diameter deviates if one of the tools deviates from the nominal dimension. When machining with only one tool, even with an axial offset of the workpiece or tool, there is no negative influence on the sealing edge diameter. Highly accurate sealing surfaces and sealing edges with very high functionality can be manufactured reliably and inexpensively. The further advantages of the method according to the invention have already been discussed in detail in connection with the tool used. The method according to the invention comprises the steps according to claim 1.

It should be noted here that the term "movement of the workpiece and / or the tool" means "moving the workpiece and / or the tool" understand is. Furthermore, in the method according to the invention with a circular machining edge of an annular tool face of a base body of the tool, the first functional surface, in particular workpiece end face, of the workpiece is processed. Partly at the same time, the second functional surface, in particular a chamfer, of the workpiece is machined with a conical projection on the tool end face.

Advantageously, the workpiece and / or the tool is moved along the workpiece rotation axis or slightly obliquely thereto.

In an advantageous embodiment, for a spherically concave configuration of the first functional surface, the angle of attack α is selected such that the workpiece rotational axis and the tool rotational axis intersect on a side of the first functional surface facing the tool.

Alternatively, it is advantageously provided that, for a spherically convex design of the first functional surface, the angle of attack α is selected such that the workpiece rotation axis and the tool rotation axis intersect on a side of the first functional surface facing away from the tool. Thus, with the method according to the invention, preferred shapes can be achieved reliably even with very low values in the range of a few μm for spherical convexities or concaves.

It is also advantageous that, with the method according to the invention, a burr-free edge, in particular a sealing edge, is formed between the first functional surface and the second functional surface. Since in the method according to the invention, the two adjoining functional surfaces are produced in one processing step and thus at least partially simultaneously, it is possible to produce this burr-free or sharp edge.

It is also advantageous that a diameter of the edge, in particular sealing edge, can be adjusted by a radial offset between the tool and the workpiece. By radial offset is meant here the displacement of, for example, the workpiece parallel to the workpiece rotation axis. However, the tool according to the invention can also be offset in a corresponding manner. For continuous control and improvement of the dimensional accuracy or process reliability, the sealing edge diameter is not only due to the radial Set offset, but can be corrected by this radial offset also steadily.

Furthermore, it is advantageous that the shape, in particular the concavity or convexity, of the first functional surface is formed or produced as a function of the angle of attack and / or a diameter of the machining edge and / or of the radial offset. If, for example, the diameter of the processing edge is once dressed, only the front surface needs to be dressed at regular intervals. Since the first functional surface, i.e., the preferred shape, is determined essentially by the diameter of the machining edge and the angle of attack or the change in the angle of attack, the quality of the first functional surface remains constant.

In an advantageous embodiment of the method, the clearance angle γ is greater than the angle of attack α selected for generating a convex first functional surface, so that even at γ <90 ° a convex first functional surface can be generated with sharp transition to the second functional surface.

The method according to the invention is used particularly advantageously in that the first functional surface and the second functional surface are produced on a part of a fuel injection system, in particular a coupler sleeve. The invention is thus used, for example, in the fine machining of various products from diesel injection technology, in which a plurality of functional surfaces on end faces have to be processed. Particular advantages result from the method according to the invention, as soon as a convex or concave preferred shape on a component end face for sealing function in combination with a sealing edge is required in the field of diesel injection technology, which must have no burr formation and be formed almost without rounding (sharp) got to. The concavity or convexity can be just a few microns here. Both requirements can only be fulfilled at the same time by either two tools being used at the same time (simultaneous grinding with two grinding spindles) or one tool processing both surfaces simultaneously. Even without the requirement for burr-free, sharp edges, there is an economic advantage through the grinding with reduced cycle time.

drawings

Figur 1

eine zum Teil aufgebrochene Darstellung des im erfindungsgemäßen Verfahren verwendeten Werkzeugs nach einem ersten Ausführungsbeispiel mit einem bearbeiteten Werkstück,

Figur 2

eine stirnseitige Draufsicht auf das Werkstück, bearbeitet durch das Werkzeug nach dem ersten Ausführungsbeispiel, mit Werkzeugeingriffsbahnen,

Figur 3

eine zum Teil aufgebrochene Darstellung des im erfindungsgemäßen Verfahren verwendeten Werkzeugs nach einem zweiten Ausführungsbeispiel mit einem bearbeiteten Werkstück, und

Figur 4

eine zum Teil aufgebrochene Darstellung des im erfindungsgemäßen Verfahren verwendeten Werkzeugs nach einem dritten Ausführungsbeispiel mit einem bearbeiteten Werkstück.

Hereinafter, three embodiments of the invention will be described with reference to the accompanying drawings. In the drawing is:

FIG. 1

a partially broken view of the tool used in the method according to the invention according to a first embodiment with a machined workpiece,

FIG. 2

a frontal plan view of the workpiece, machined by the tool according to the first embodiment, with tool engagement paths,

FIG. 3

a partially broken view of the tool used in the method according to the invention according to a second embodiment with a machined workpiece, and

FIG. 4

a partially broken view of the tool used in the method according to the invention according to a third embodiment with a machined workpiece.

Description of the embodiments

The following is with reference to FIG. 1 a tool 1 for the method according to a first embodiment of the present invention described.

FIG. 1 shows the rotating grinding tool, consisting of a base body 2, a conical extension 3 and a shaft 24. The main body 2 may also be referred to as a grinding wheel. Furthermore shows FIG. 1 an already machined workpiece 4.

The main body 2 is cylindrical and has on its side facing the workpiece 4 an annular end face 22 with a round processing edge 21, formed as an outer edge on. The annular end face 22 is formed as a ring around the conical projection 3. At his, one Machine-side facing, the base body 2 is in the likewise cylindrical, but narrower shaft 24 via. This shaft 24 is used for clamping the tool 1 in the machine tool. Furthermore, a tool rotation axis 23 is located. To this tool rotation axis 23, the tool 1 rotates rotationally symmetrical. Further, a clearance angle γ denotes a funnel-shaped collapse of the annular end surface 22.

The conical extension 3 has a lateral surface 31 and a frustoconical surface 32. The conical projection 3 is located centrally and thus rotationally symmetrical on the base body 2 of the tool 1. Around this conical projection 3 around the annular end face 22 is formed.

The workpiece 4 has a first functional surface 41, also called the workpiece end face or preferred form. Laterally on this first functional surface 41, a second functional surface 42 in the form of a conical chamfer is formed on the workpiece 4. This second functional surface 42 thus forms the transition from the first functional surface 41 to the lateral surface of the rotationally symmetrical workpiece 4. Between the first functional surface 41 and the second functional surface 42, a sealing edge 43 is formed. This sealing edge 43 is sharp and burr-free. The workpiece 4 rotates about a workpiece rotation axis 44.

Furthermore shows FIG. 1 Also geometric sizes of the tool 1 and the workpiece 4. The tool 1 has at its thickest point, the base body 2, the tool _diameter D _wz . The annular tool end face 22 has the ring width b _r . Furthermore, the truncated cone diameter D _{f is located} at the thinnest point of the conical projection 3. The angle between the tool rotation axis 23 and the workpiece rotation axis 44 is referred to as the angle of attack α. The lateral surface 31 of the conical projection 3 merges with the cone angle β.

Furthermore, a workpiece _diameter D _ws and a depth t of the concave first functional surface 41 are shown.

During execution of the method according to the invention, the workpiece 4 rotates in a workpiece spindle, while the rotating tool 1 is set at the angle of attack α to the workpiece 4 and along the workpiece rotation axis 44 on the workpiece Workpiece 4 is moved. Alternatively, of course, the workpiece 4 can be moved or moved into the tool 1. With the machining edge 21 at the transition between tool _diameter D _wz and annular end face 22 of the tool 1, the convex or concave spherical first functional surface 41 is generated.

If the employment of the tool 1 by the angle of attack α according to FIG. 1 Thus, the workpiece rotation axis 44 intersects the tool rotation axis 23 on a tool-facing side z of the first functional surface 41 and results in a concave spherical first functional surface 41. If the tool 1 is employed with a negative angle α alternatively, the workpiece rotation axis 44 cuts the tool rotation axis 23 on one side facing away from the tool a of the first functional surface 41 and it is a spherically convex first functional surface 41 is generated. This will be addressed to the Figures 3 and 4 demonstrate.

The lateral surface 31 on the tool 1 or on the conical projection 3 generates the second functional surface 42 on the workpiece 4. Alternatively, the lateral surface 31 may also be concave or convex to produce a second functional surface 42 with radius. In order to be able to introduce the particular contour into the tool 1 or into a grinding wheel by dressing, and also to enable the grinding of convex first functional surfaces 41, the clearance angle γ is introduced at the annular end face 22 of the base body 2.

By the grinding process, the degree of sharp-edged and free sealing edge 43 with the sealing edge diameter D _κ is formed on the workpiece 4 in addition to the first function spherical surface 41 at the transition between the first functional surface 41 and the second functional surface 42nd The convexity or concavity of the spherical first functional surface 41 arises as a function of the pivoting of the setting angle α, the workpiece diameter D _WZ and a radial offset e1, e2. This radial offset e1, e2 is set between the machining edge 21 and the workpiece rotation axis 44. Thus, the convexity or concavity of the spherical first functional surface 41 can be produced reliably even in the range of a few μm.

FIG. 2 shows the workpiece 4 in plan view of its end face. The workpiece 4 is in this case by the tool 1 according to the invention according to the first embodiment been edited. Shown is the sealing edge 43 with a sealing edge diameter D _κ and a Bearbeitungsantanteneingriffsbahn 5 and a continuation engagement track 6. The machining edge engaging track 5 is formed by the engagement of the machining edge 21 in the workpiece 4. The continuation engagement track 6 results from the engagement of the lateral surface 31 of the conical projection 3 in the Workpiece 4.

FIG. 3 shows the tool 1 for the method according to a second embodiment and a machined workpiece 4. In the second embodiment, the same or functionally identical parts are denoted by the same reference numerals as in the first embodiment.

The tool 1 in FIG. 3 has a significantly larger clearance angle γ than the tool 1 according to the first embodiment. Furthermore, the first functional surface 41 is convex.

The angle of attack α is selected such that the workpiece rotation axis 44 intersects the tool rotation axis 23 on a side of the first functional surface 41 facing away from the tool. Further, the processing edge 21 is offset by a distance f from the workpiece rotation axis 44.

FIG. 4 shows the tool 1 for the method according to a third embodiment and a machined workpiece 4. In the third embodiment, the same or functionally identical parts with the same reference numerals as in the first or second embodiment are designated.

The tool 1 in FIG. 4 has a clearance angle γ of 90 °. Furthermore, the first functional surface 41 is convex. The angle of attack α corresponds to the angle of attack α from the second embodiment.

Due to the clearance angle γ of 90 °, the end face 22 is divided into an annular first plane 22a and an annular second plane 22b closer to the shaft 24. The processing edge 21 for processing the first functional surface 41 is seated on an inner side of the first plane 22a.

The use of the tool 1 or of the method according to the invention takes place, for example, in the machining of components for commercial vehicle injectors. An end face (first functional surface 41) with a concavity of 5 microns (on a measuring section of 0.45 mm) and a sealing edge with a diameter D _κ of 5.8 mm produced in the components, which (at the transition of the concave surface first Function surface 41) to an outer chamfer (second functional surface 42) is formed at an angle of 20 °. First scanning electronic investigations have already confirmed the sharp-edgedness and burr-freedom of the component, the process-reliable production of the concavity was verified by means of white-light interferometers. The components are manufactured using this process for prototyping and also for series production, which means that cycle time and cost reduction can be achieved.

Claims (11)

1. Grinding method for the simultaneous production of a workpiece end face, as a first functional surface (41), and of a chamfer, as a second functional surface (42) contiguous to the first functional surface (41), on a workpiece (4) by means of a rotationally symmetrical grinding tool (1), comprising the steps:

   - rotation of the workpiece (4) about a workpiece rotation axis (44) and rotation of the tool (1) about a tool rotation axis (23),

   - setting of the tool rotation axis (23) and/or of the workpiece rotation axis (44) in relation to one another at a set angle (α), and

   - movement of the workpiece (4) and/or of the tool (1) towards one another,

   - the first functional surface (41) of the workpiece (4) being machined by means of a circular machining edge (21) or an annular tool end face (22) of a basic body (2) of the tool (1), and

   - the second functional surface (42) of the workpiece (4) being machined by means of a conical extension (3) on the tool end face (22).
2. Grinding method according to Claim 1, characterized in that, for a concave form of the first functional surface (41), the set angle (α) is selected such that the workpiece rotation axis (44) and the tool rotation axis (23) intersect on a tool-facing side of the first functional surface (41).
3. Grinding method according to Claim 1, characterized in that, for a convex form of the first functional surface (41), the set angle (α) is selected such that the workpiece rotation axis (44) and the tool rotation axis (23) intersect on a tool-remote side of the first functional surface (41).
4. Grinding method according to one of Claims 1 to 3, characterized in that a burr-free edge (43), in particular sealing edge, is formed between the first functional surface (41) and the second functional surface (42).
5. Grinding method according to Claim 4, characterized in that a diameter (D_κ) of the edge (43) is set by means of a radial offset (e1, e2) between the tool (1) and the workpiece (4).
6. Grinding method according to one of Claims 1 to 5, characterized in that the shape of the first functional surface (41) is formed as a function of the set angle (α) and/or of an outside diameter (D_WZ) of the machining edge (21) and/or of the radial offset (e1, e2).
7. Grinding method according to one of Claims 1 to 6, characterized in that, by means of the method, the first functional surface (41) and the second functional surface (42) are produced on a part of a fuel injection system, in particular a coupler sleeve.
8. Grinding method according to one of the preceding claims, characterized in that the tool end face (22) is incident to a tool rotation axis (23) at a clearance angle (γ) or the tool end face (22) is perpendicular to the tool rotation axis (23).
9. Grinding method according to one of the preceding claims, characterized in that the circular machining edge (21) is rounded.
10. Grinding method according to one of the preceding claims, characterized in that the conical extension (3) is formed as a truncated cone.
11. Grinding method according to one of the preceding claims, characterized in that a surface area (31) of the conical extension (3) is of planar or concave or convex form.

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