CN113260469A

CN113260469A - Fine blanking process

Info

Publication number: CN113260469A
Application number: CN201980085891.6A
Authority: CN
Inventors: R·A·A·穆特塞尔斯; L·H·R·M·普林森; P-P·毛里茨
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2018-12-24
Filing date: 2019-12-23
Publication date: 2021-08-13
Also published as: WO2020135924A8; WO2020135924A1

Abstract

The invention relates to a fine blanking process for manufacturing transverse elements (51) of a push belt for a continuously variable transmission, wherein at least two transverse elements (51) are simultaneously blanked out of a strip (52) of base material at two blanking locations (1, 3; 2, 4) which are separated from each other in the length direction of the belt (52). According to the invention, slits (5; 5a, 5b, 5c) are provided on either side of at least one of the two punching positions (1, 3; 2, 4), said slits extending perpendicularly to the length direction of the strip (52).

Description

Fine blanking process

Technical Field

The present invention relates to a fine blanking process for blanking transverse elements of a metal drive belt (called pushbelt) of a continuously variable transmission. The transverse elements have at least two basic designs, each with a substantially trapezoidal base, which in the transmission is in frictional contact with the driving pulley. The first basic design of the transverse element also has a substantially triangular top portion which is connected in the middle of its base to the middle of the long side of the (trapezoidal) base portion. The second basic design of the transverse element also has two pillar portions, each of which is connected to a respective side edge of a long side of the basic portion.

Background

The push belt is further provided with at least one endless tensioning element, which typically comprises a set of nested flat metal rings, the transverse elements being slidably incorporated in the push belt along the outer edges of the tensioning elements in at least substantially continuous rows. Both the transverse elements and the annular tensioning elements are made of steel, although they are made of different alloys.

A push belt and said fine blanking process are generally known, for example from dutch patent publication NL-1019639 (C). It is described in this document that the transverse element needs to be manufactured with a very high dimensional accuracy to meet its application in pushbelts. By using a fine blanking process to cut out the transverse segments from the strip of base material, a high accuracy is indeed obtained, although at the expense of a reduced productivity, with respect to a standard blanking process. The fine blanking process is characterized in that, in the fine blanking apparatus, a relatively small clearance is used between the punch and the die, and a counter punch is used on the opposite side of the die.

Regarding such fine blanking process and apparatus, a specific arrangement of four blanking positions with respect to the length and width of the base material strip is described in dutch patent publication NL-1024957 (C). In this case, in each so-called blanking stroke of the fine blanking device, four transverse elements are simultaneously cut out of the base material strip, i.e. one element is cut out at each blanking position, leaving a correspondingly shaped hole in the strip. After each such blanking stroke the base material strip is advanced in its length direction in relation to the blanking position to present a new section thereof at each such blanking position for blanking out further transverse elements in the next blanking stroke.

The known arrangement of four blanking positions is designed to form the transverse segments optimally with the base material strip, i.e. to leave only a relatively small amount of scrap in the strip, i.e. the strip frame, after blanking. The four punching positions are located alternately diagonally to one another on opposite edges of the base material strip in relation to the width direction thereof. Furthermore, the two pairs of blanking positions located on opposite edges of the strip overlap each other in the width direction of the strip, which makes use of the fact that the top or pillar part of the transverse element is narrower than their respective base part.

A known limitation of this known fine blanking process is that the exact shape of the four simultaneously blanked transverse elements can be minimally different, so that at least in terms of the consistency of the four simultaneously cut elements, the dimensional accuracy thereof is still required. After all, any inaccuracies in the exact shape/size of the transverse element can disadvantageously accumulate in said rows of the pushbelt. These inaccuracies are due to the following: i.e. the clamping force and the cutting force applied during blanking of each individual transverse segment, typically vary slightly between the blanking positions, e.g. due to locally different material stiffness in the length direction of the base material strip. After all, before and after two of the four blanking positions, there are holes in the belt, which are left by the transverse elements which were blanked in the other two blanking positions in the previous two blanking strokes. However, such holes are not present at the other two blanking positions corresponding to the transverse elements blanked in the previous blanking stroke.

Also in NL-1024957(C), a mirror-symmetrical arrangement of the blanking positions is described, which aims at improving the shape accuracy of the transverse element, but at the expense of a reduced utilization of the basic material.

Disclosure of Invention

The object of the invention is to improve the known fine blanking process, in particular with respect to the utilization of the applied basic material with respect to the shape/dimensional accuracy of the transverse element manufactured thereby.

According to the present disclosure, before blanking of the transverse element, the band of base material is provided with a slit, seen in the length direction of the band, both before and after the blanking position of the transverse element. By means of these slits, the local stiffness of the base material strip in its length direction is reduced and, in particular, can be advantageously equalized between the individual blanking positions. The slits extend at least mainly in the width direction of the strip of base material, preferably starting from the side edges of the strip of base material. Preferably, the slits extend from such side edges at least to a position corresponding to a long side of the basic portion of the transverse element (to be blanked). Preferably, the slot extends slightly beyond this position. Preferably, the slits are narrowed, seen in a direction from the respective side edge of the base material strip towards the middle of the strip. Preferably, the respective side of the slot is aligned at least substantially parallel to the respective side of the base of the transverse element closest thereto. Preferably, the slit ends in said width direction of the base material strip in an arcuate end surface between the slit sides. Preferably, the width of the arc defined by the arcuate end faces exceeds the width of the slit, defined by the distance between the said sides in the direction of the length of the strip of base material, or at least exceeds the minimum width of the narrow pinch slit.

Drawings

The invention will be explained in more detail hereinafter, by way of example, with reference to the accompanying drawings, in which:

fig. 1 schematically illustrates, in cross-section, a fine blanking process and a tool portion of a fine blanking apparatus to which the present invention relates;

FIG. 2 illustrates a known fine blanking process and apparatus based on a top view of the base material strip used therein;

FIG. 3 also illustrates, in a top view of the base material strip applied therein, a fine blanking process and apparatus according to the present disclosure; and

fig. 4 shows a preferred embodiment of a slit cut in a strip of base material according to the present disclosure.

Detailed Description

In order to illustrate the forming of a transverse element 51 for a push belt for a continuously variable transmission, fig. 1 schematically illustrates a so-called fine blanking process and an apparatus for cutting out the transverse element 51 from a strip-shaped basic material 52. The known fine blanking device comprises a die 45 and a guide plate 35 between which a strip 52 of base material is clamped. The device also comprises a punch 30 and a support member corresponding to the latter, called counter-punch 40. The outer contour of the punch 30 and the counter-punch 40 substantially corresponds to the outer contour of the transverse element 51 to be blanked. The movement of the punch 30 relative to the die 45, which results in the transverse element 51 being cut out of the strip 52 of base material, is indicated by the arrow P, the counter-punch 40 exerting a counter-force, but while still following the movement of the punch 30. A free space or gap is defined between the outer contour of the punch 30 and the inner contour of the die 45 and perpendicular to the outer contour of the punch 30 and the inner contour of the die 45, said inner contour of the die 45 also substantially corresponding to the outer contour of the transverse element 51. In fine blanking, a relatively small gap is applied, which gap amounts at least approximately to 1% to 5% of the thickness dimension of the base material strip 52 (i.e. the transverse element 51 to be blanked).

Fig. 2 shows a known arrangement for a fine blanking process and device for blanking transverse elements 51 on the basis of a base material strip 52. The dashed line 53 represents a step in the thickness direction of the strip 52 or a bend in this direction, which is usually, but not necessarily, applied in the manufacture of the transverse element 51. Also in fig. 2, the

dark spaces

1, 2, 3 and 4 represent four blanking positions 1-4 by the contour of four transverse elements 51 which are simultaneously cut out in a so-called blanking stroke of the fine blanking device, which is thus provided with four sets of the above-mentioned

blanking tools

30, 35, 40, 45.

This known arrangement of four blanking locations 1-4 is designed to make the actual forming of the transverse segments 51 optimally use the strip 52 of base material. The four blanking positions 1-4 are located diagonally to each other on alternating sides of the base material strip 52. Further, the two

pairs

1, 3 and 2, 4 of the blanking positions 1 to 4 located on opposite sides of the belt 52 overlap each other in the width direction of the belt 52, respectively. This is the case by virtue of the fact that the top portion 8 (or optionally the pillar portion thereof) of the transverse element 51 is narrower than its respective base portion 9.

Thus leaving a transverse element-shaped hole 10 in the strip 52 at each blanking position 1-4 after each blanking stroke. Furthermore, after each blanking stroke, i.e. between two subsequent blanking strokes, the strip 52 comprising the hole 10 is advanced with respect to the blanking positions 1-4 (i.e. in fig. 2 the strip 52 is fed to the right, as indicated by one of the respective arrows), thereby providing new, i.e. uncut, sections of the strip 52 to the four blanking positions 1-4 for the following blanking strokes. For example, after the transverse element 51 has been blanked out in a previous blanking stroke I at a blanking position 2, the strip 52 is fed to the right in fig. 2 (a distance slightly larger than twice the width of the basic portion 9 of the transverse element 51), so that a hole 10-2 remains in such a blanking position 2_IIs also conveyed to the right. At the same time, the hole 10-2 left by the earlier blanking strokes II, III_II、10-2_IIIIs (further) conveyed to the right. Of course, a similar procedure applies to the holes 10 formed at the other three

blanking positions

1, 3 and 4, as indicated by the dashed arrows in fig. 2.

As can be seen from fig. 2, the blanking locations 1-4 differ in the number of holes 10 adjacent to each respective blanking location 1-4. That is to say that the first and second electrodes,

the blanking position 1 has no hole 10 directly adjacent to it;

the blanking position 2 has a hole 10-1 in front of it_IThe hole diagonally crosses the belt 52;

the blanking position 3 has three holes 10 adjacent to it: in front of and diagonally across the first aperture 10-2 of the belt 52_ISecond hole 10-1 right in front thereof_IIAnd a third hole 10-1 right behind it_I(ii) a And

the blanking position 4 has four holes 10 adjacent to it: in front of and diagonally across the first aperture 10-3 of the belt 52_ISecond hole 10-2 right in front thereof_IIThe third hole 10-2 right behind it_IAnd a fourth aperture 10-1 behind and diagonally across the belt 52_II。

In this way, the local stiffness of the strip 52 is different for the four blanking locations 1-4, so that the precise shape of the four transverse elements 51 that are simultaneously blanked at such blanking locations 1-4 usually differs to a minimum, but disadvantageously. According to the present disclosure, the holes 10 directly in front of and behind the blanking

locations

3 and 4 have the greatest influence in this respect, so that the deviations of the transverse elements 51 occurring at these

locations

3 and 4 from the transverse elements occurring at the blanking

locations

1 and 2 are the greatest.

Fig. 3 illustrates an arrangement of a fine blanking process and apparatus according to the present disclosure. In this case, slits 5 are provided in the base material strip 52 in front of and behind each of the four blanking locations 1-4. As a result of this measure, the stiffness will advantageously be similar at each blanking position 1-4, at least in the length direction of the base material strip 52. Although in this respect an improvement can be obtained by providing a total of four slits 5, i.e. only with respect to the blanking positions 1 and 2 (since the blanking

positions

3 and 4 have holes 10 on both sides thereof), in the case of the presently considered mutual arrangement of the four blanking positions 1-4, these four slits 5 will also appear on both sides of the blanking

positions

3 and 4 after said advancement of the belt 52 between two blanking strokes.

In particular, according to the present disclosure, the slits 5 are punched, i.e. slits are cut from the strip 52, before the transverse element 51 is cut from the strip 52 between these slits 5. In other words, according to the present disclosure, the blanking process is performed in at least two stages, wherein a first stage comprises cutting at least two slits 5 in the side edges of the base material strip 52 and a second stage comprises cutting at least one transverse element 51 from the base material strip 52 between said two slits 5. Of course, in the presently considered mutual arrangement of the four blanking positions 1-4, in a first stage of the blanking process, the at least two slits 5 are cut out on both side edges of the strip 52 of base material, respectively, as is illustrated in fig. 3 by the four dark areas 5 representing the contour of the four simultaneously cut slits 5.

Preferably, the cutting of the slits 5 is synchronized with the cutting of the transverse segments 51, so that in each of said blanking strokes four slits 5 and four transverse elements 51 are simultaneously cut out of the strip 52 of base material. However, the slots 5 may be cut without the use of a counter punch, since they do not need to be shaped/dimensioned as precisely as the transverse elements 51.

In fig. 4, three possible embodiments of the slot 5 are shown. In its first embodiment 5a, the slot 5 is defined between two sides 6 and a smoothly curved end face 7 of the slot 5, wherein the two sides 6 extend from the respective side edges 54 of the strip 52 of base material and substantially perpendicularly to the side edges 54, the smoothly curved end face 7 of the slot 5 interconnecting the two sides 6.

In the second embodiment 5b, the width of the slot 5 defined by its end face 7 in the length direction of the strip 52 of base material preferably exceeds the distance between its side faces 6 in this direction. In this case, therefore, the curvature of the end face 7 extends over 180 degrees. This feature of the slot 5 advantageously allows a cylindrical pin to be inserted and retained therein to accurately position the strip of base material 52 relative to said blanking positions 1-4 in said second stage of the blanking process.

In the third embodiment 5c, said sides 6 of the slits 5 are inclined to each other from the respective side edges 54 of the strip of base material 52 towards an intermediate position of the strip of base material 52, preferably in alignment with a respective one of the two inclined sides of the (trapezoidal) base 9 of the transverse element 51.

Claims

1. A fine blanking process for blanking transverse elements (51) of a drive belt for a continuously variable transmission, wherein at least two transverse elements (51) are simultaneously blanked out of a strip of base material (52) at two blanking positions (1, 3; 2, 4) which are mutually separated along the length direction of the strip (52), the strip of base material (52) being held between a guide plate (35) and a die (45) of a fine blanking device, the transverse elements (51) being held between a punch (30) and a counter punch (40) of the fine blanking device, characterized in that the strip (52) is provided with slits (5; 5a, 5b, 5c) extending perpendicularly to the length direction of the strip (52) on both sides of at least one of the two blanking positions (1, 3; 2, 4).

2. The fine blanking process according to claim 1, characterised in that the slots (5; 5a, 5b, 5c) do not define any part of the contour of the transverse element (51).

3. The fine blanking process according to claim 1 or 2, characterised in that four transverse elements (51) are simultaneously blanked out of the strip (52) at four blanking positions (1-4) provided in two pairs, each pair of two blanking positions (1, 3; 2, 4), which are respectively arranged on mutually opposite sides of the strip (52) and are mutually offset in the length direction of the strip (52).

4. A fine blanking process according to claim 1, 2 or 3, characterised in that the fine blanking process is performed in at least two stages, wherein a first stage comprises cutting out slits (5; 5a, 5b, 5c) and a second stage comprises cutting out transverse elements (51) from the strip (52) of base material between the two slits (5).

5. The fine blanking process according to claim 4, characterised in that four slots (5; 5a, 5b, 5c) are cut simultaneously in the first stage and four transverse elements (51) are cut simultaneously in the second stage.

6. The fine blanking process of claim 4 or 5, wherein the first and second stages are performed simultaneously and separately from each other along the length of the strip (52).

7. The fine blanking process of any one of the preceding claims, wherein the slits (5; 5a, 5b, 5c) extend from respective side edges (54) of the strip (52).

8. The fine blanking process according to any one of the preceding claims, characterised in that the slits (5; 5a, 5b, 5c) extend to a position overlapping the long sides of the trapezoidal base (9) of the transverse element (51), seen in the length direction of the strip (52).

9. The fine blanking process as claimed in any one of the preceding claims, characterised in that the slits (5; 5a, 5b, 5c) are narrowed, seen in a direction from the respective side edge of the strip (52) towards the middle of the strip.

10. The fine blanking process according to any one of the preceding claims, characterised in that the slots (5; 5a, 5b, 5c) each end in a respective curved end surface (7).

11. Fine blanking process according to claim 10, wherein the arcuate end surfaces (7) enclose an angle larger than 180 degrees.