Method for joining two metal sheets with a variable total thickness

Abstract

The disclosure relates to a method for joining metal sheets resting on one another with a variable total thickness by a clinching device comprising at least one punch and a die arranged coaxially to the punch. The punch is controllable by an electronic control unit and movable in an axial direction relative to the die. The metal sheets are arranged in a plane between the punch and the die, and the penetration depth necessary for joining the metal sheets is adjustable. Before joining the metal sheets, the current total thickness is determined with the aid of the control unit and the penetration depth is set depending on the total thickness. The method includes: storing a number of different total thicknesses or total thickness ranges in the control unit, assigning a penetration depth to a total thickness or to a total thickness range, and calibrating the clinching device.

Claims

1. A method for joining at least two metal sheets resting on one another with a variable total thickness by a clinching device comprising at least one punch and a die arranged coaxially to said punch, and at least the punch is arranged so as to be controllable by an electronic control unit and movable in an axial direction relative to the die, the metal sheets are arranged in a plane between the punch and the die, and a penetration depth for joining the metal sheets is adjustable, and before joining the metal sheets, a current total thickness is determined with aid of the control unit and the penetration depth is set depending on the current total thickness, and comprising: storing a number of different total thicknesses or total thickness ranges in the control unit; assigning the penetration depth to the total thickness or to the total thickness range; and calibrating the clinching device.

2. The method according to claim 1, wherein to calibrate the clinching device, the punch is moved from a zero position in the axial direction until it comes into contact with the die and a path covered by the punch then defines the zero position of the die, which is stored in the control unit.

3. The method according to claim 1, further comprising: positioning the clinching device in relation to the metal sheets to be joined so that the die rests against a lower side of a second sheet of the metal sheets; axially moving the punch into a position in which the punch rests against an upper side of a first metal sheet of the metal sheets; detecting a path covered by the punch; determining the current total thickness from the path covered by the punch and a calibrated zero position of the die; comparing the determined current total thickness with the stored total thicknesses or the total thickness ranges; selecting a value assigned to the determined current total thickness for the penetration depth; adjusting the penetration depth depending on the comparing; and joining the metal sheets with the adjusted penetration depth.

4. The method according to claim 1, wherein the penetration depth is infinitely variable.

5. The method according to claim 1, wherein the penetration depth can be adjusted in at least two steps.

6. The method according to claim 1, wherein to adjust the penetration depth, an anvil is arranged concentrically in the die and can be displaced in the axial direction relative to the die.

7. The method according to claim 4, wherein an adjustment device is provided to displace the anvil, said device being formed by a wedge.

8. The method according to claim 5, wherein an adjustment device is provided to displace the anvil, said device being formed by an adjustment slide that in its longitudinal direction comprises at least one effective step in the axial direction.

9. A method for joining at least two metal sheets resting on one another with a variable total thickness by a clinching device comprising at least one punch and a die arranged coaxially to said punch, and at least the punch is arranged so as to be controllable by means of an electronic control unit and movable in an axial direction relative to the die, wherein the metal sheets are arranged in a plane between the punch and the die, and the penetration depth necessary for joining the metal sheets is adjustable, wherein before joining the metal sheets, a current total thickness is determined with the aid of the control unit and the penetration depth is set depending on the current total thickness, comprising: storing a number of different total thicknesses or total thickness ranges in the control unit; assigning a penetration depth to the total thickness or to the total thickness range; axially moving the punch out of a first zero position into a position in which the punch rests against an upper side of a first metal sheet of the metal sheets; detecting a path covered by the punch; axially moving the die out of a second zero position into a position in which the die rests against a lower side of a second metal sheet of the metal sheets; detecting the path covered by the die; detecting a total thickness from a distance between the first zero position and the second zero position and the paths covered by the punch and die; comparing the detected total thickness with the stored total thicknesses or the total thickness ranges; selecting a value assigned to the detected total thickness for the penetration depth; adjusting the penetration depth based on the comparing; and joining the metal sheets with the adjusted penetration depth.

10. The method according to claim 9, wherein the penetration depth is infinitely variable.

11. The method according to claim 9, wherein the penetration depth can be adjusted in at least two steps.

12. The method according to claim 9, wherein to adjust the penetration depth, an anvil is arranged concentrically in the die and can be displaced in the axial direction relative to the die.

13. The method according to claim 10, wherein an adjustment device is provided to displace the anvil, said device being formed by a wedge.

14. The method according to claim 11, wherein an adjustment device is provided to displace the anvil, said device being formed by an adjustment slide that in its longitudinal direction comprises at least one effective step in the axial direction.

Description

DETAILED DESCRIPTION OF THE DRAWINGS

(1) In the following, the invention will be explained in more detail with the aid of the following figures:

(2) FIG. 1 shows a partial representation of a clinching device in its starting position in a longitudinal cut;

(3) FIG. 2 shows an enlarged partial representation from FIG. 1;

(4) FIG. 3 shows a detail from FIG. 2;

(5) FIG. 4 shows a representation according to FIG. 1 in its measurement position;

(6) FIG. 5 shows an enlarged partial representation from FIG. 4;

(7) FIG. 6 shows a detail from FIG. 5;

(8) FIG. 7 shows a representation according to FIG. 1 after successful clinching;

(9) FIG. 8 shows an enlarged partial representation from FIG. 7;

(10) FIG. 9 shows a detail from FIG. 8;

(11) FIG. 10 shows a first embodiment of a die in a longitudinal cut;

(12) FIG. 11 shows an enlarged representation from FIG. 10;

(13) FIG. 12 shows a cut along the line XII-XII according to FIG. 10;

(14) FIG. 13 shows the cross section of a die with a punch arranged above it;

(15) FIG. 14a shows a representation according to FIG. 13 before a joining procedure with a first joining task;

(16) FIG. 14b shows a representation according to FIG. 14a after the joining procedure;

(17) FIG. 14c shows an enlarged detail according to FIG. 14a.

DETAILED DESCRIPTION

(18) The metal sheets B.sub.1, B.sub.2 to be joined are inserted lying on top of each other between the upper tool carrier 10.1 and the lower tool carrier 10.2 of a clinching tool 10 of the known type. A punch 11 is mounted in the upper tool carrier 10.1 such that it can be displaced in the axial direction A. The die 12 is provided in the lower tool carrier 10.2, wherein the anvil 12.1 arranged concentrically to said die. 20 indicates an electronic control unit, which is used to control the clinching device 10 and its individual components. The anvil 12.1 is driven by the adjusting element 13, which is arranged so that it can be moved in its longitudinal direction L and can feature a stepped cross-section, as indicated in 13.1, or a wedge-shaped cross-section.

(19) The initial position of the clinching device 10 is shown in FIGS. 1 to 3. The punch 11 and die 12 are in their respective zero positions A.sub.S0, A.sub.M0. Once the metal sheets B.sub.1, B.sub.2 have been brought into a plane between the upper tool carrier 10.1 and the lower tool carrier 10.2, the punch 11 and the die 12 are moved in the axial direction A until the punch 11 rests on the upper side B.sub.10 of the sheet B.sub.1 and the die 12 on the lower side B.sub.20 of the second sheet B.sub.2, and the punch 11 and die 12 are then in their measuring positions A.sub.S1, A.sub.M1. The total thickness D.sub.1 of the first metal sheet B.sub.1 and the second metal sheet B.sub.2 in this position corresponds to the distance between the punch 11 and die 12.

(20) The penetration depth DT.sub.i must always be less than the total thickness D.sub.i of the metal sheets B.sub.1, B.sub.2. It results from the path of the punch 11 into the die 12 and the volume within the die 12 formed by the cavity 12.3, which is variable due to the anvil 12.1 which can be displaced in the axial direction A.

(21) Different total thicknesses or total thickness ranges D.sub.i can be stored in the control unit 20 for different metal sheets B.sub.1, B.sub.2 to be joined together. Thickness ranges D.sub.i can include the sheet thickness±a given tolerance or different sheet thicknesses without tolerance.

(22) The total thickness D.sub.1 can be calculated from the fixed distance in the zero position of the punch 11 and die 12 and the path covered by the punch 11 from its zero position A.sub.S0 and its measuring position A.sub.S1 or the path covered by the die 12 from its zero position A.sub.M0 to its measuring position A.sub.M1.

(23) If the total thickness D.sub.i of the metal sheets B.sub.1, B.sub.2 has been determined as above, this value is compared with the values D.sub.i stored in the control unit 20 and the penetration depth DT.sub.i, which is assigned to the corresponding value in the control unit 20, is adjusted by moving the anvil 12.1 in the axial direction A from the lower side B.sub.20 of the second sheet 2 into the interior of the die 12. If this penetration depth DT.sub.i is adjusted, the punch 11 is moved towards the die 12 and the two metal sheets B.sub.1, B.sub.2 are inserted into each other and thus joined.

(24) The total thickness D.sub.i is determined before each joining process of the newly inserted sheets B.sub.1, B.sub.2 and is used for process monitoring. As long as the total thickness D.sub.i lies within a tolerable range, there is no adjustment of the penetration depth DT.sub.i. If the penetration depth DT is infinitely variable, it can be provided for that the control unit 20 individually adjusts the penetration depth DT.sub.i for each joining process by moving the anvil 12.1 in the axial direction A.

(25) An alternative way to determine the total thickness D.sub.i of the two metal sheets B.sub.1, B.sub.2 is as follows:

(26) Before the two metal sheets B.sub.1, B.sub.2 are inserted, the punch 11 is moved in the axial direction A on the die 12 until it is in direct contact with the anvil 12.1. The path covered by the punch 11 then defines the zero position A.sub.M0 (FIG. 1) of the die 12, which is stored in the control unit 20. The metal sheets B.sub.1, B.sub.2 are placed in a plane between the die 12 and the punch 11. The clinching device is then positioned in relation to the metal sheets B.sub.1, B.sub.2 to be joined so that the die 12 rests against the lower side B.sub.20 of the second sheet B.sub.2. The punch 11 is moved in the axial direction A until it rests on the upper side B.sub.10 of the first sheet B.sub.1. The path covered by the punch 11 is then determined and the total thickness D.sub.i of the two metal sheets B.sub.1, B.sub.2 is calculated from the path covered by the punch 11 and the calibrated zero position A.sub.MO of the die 12. In this case too, a number of penetration depths DT.sub.i have been previously stored in the control unit 20. The determined total thickness D.sub.1 is then compared with the stored total thicknesses or total thickness ranges D.sub.i and the value for the penetration depth DT.sub.1 assigned to the determined total thickness D.sub.1 is selected and the clinching process then started.

First Example of an Embodiment

(27) In the first example of an embodiment, which is shown more schematically in FIGS. 10 and 14, the die 12 consists mainly of the main body 12.2 and the anvil 12.1, which is mounted within said main body such that it can be displaced and fixed in at least two positions, and which together form a cavity 12.3 into which is inserted. The main body 12.2 of the die 12 is fixed in the lower tool carrier 10.2. Transversely to the joining direction (=axial direction A) an adjusting element 13 is provided, which is formed by a stepped adjustment slide 13.1, which is guided in a sliding manner in the longitudinal direction L in a recess 10.3 provided in the lower tool carrier 10.2. In the simplest case, the recess 10.3 is designed as a through-flow bore. In the case of a two-part tool carrier 10.2, it is formed by two grooves that lie opposite one another. The adjustment slide 13.1 is driven by electric motor, hydraulically or pneumatically. The adjustment slide 13.1 is provided with a slot 13.1.1 in the centre, through which the anvil 12.1 passes with its lower end 12.1.1 and is positioned in a bore provided in the lower tool holder 10.2 that extends in the joining direction. For better guidance in the slot 13.1.1 the lower end 12.1.1 of the anvil 12.1 is diametrically flattened, as shown in FIG. 11. The adjustment slide 13.1 is designed with a step 13.1.1, which is realized by a chamfer 13.1.2 and thus a first area that is thinner in the joining direction, with which a first, larger penetration depth DT of the die 12 is adjusted, and a second area that is thicker in the joining direction, with which a second, smaller penetration depth is set. The cavity 12.3 is therefore enlarged or reduced. By displacing the adjustment slide 13.1 in the longitudinal direction L, the annular bead 12.1.2 of the anvil 12.1 rests either on the first area 13.3, resulting in a larger penetration depth DT, or on the second area 13.4, resulting in a smaller penetration depth DT, and is supported in the tool carrier 10.2 by the adjustment slide 13.1. To be able to set more than two penetration depths DT, further steps can be provided in the adjustment slide 13.1. The angle of the chamfer 13.1.2 is selected in such a way that the bead 12.1.2 can easily slide up or down over the step 13.1.1. It is not absolutely necessary to slit the adjustment slide 13.1. The lower end of the anvil 12.1 could also be formed by the annular bead 12.1.2, which then forms a flange resting on the adjustment slide 13.1, if the guidance of the anvil 12.1 in the upper part of the tool carrier 10.2 is sufficient and an additional support in the lower part does not seem necessary. In this case, the adjustment slide 13.1 can be designed without a slot.

(28) The die 12 can consist of several die segments 12a, 12b as described in the second example of an embodiment. The other components there can also be used in the die according to this first example of an embodiment. Only the adjustment device 13 is replaced.

Second Example of an Embodiment

(29) The die 12 consists of the main body 12.2, the anvil 12.1, which is mounted in said main body such that it can be displaced and fixed in different positions, the opposite die segments 12a, 12b, which are mounted in a casing sleeve 14 which is essentially rectangular in cross section, open at the top and fixed to the main body 12.2, and the tool carrier 10.2 in which the main body 12.2 is fixed by means of screws 16. The die segments 12a, 12b are mounted in the main body 12.2 such that they can be displaced transversely to the joining direction against the force of leaf springs 15.

(30) The die segments 12a, 12b together with the upper end of the anvil 12.1 form a cavity 12.3 into which is inserted. To change the depth of the cavity 12.3, the position of the anvil 12.1 in the main body 12.2 can be infinitely varied and fixed in place in each case. To this end, a wedge 13.2, which is activated by an external force, is provided, which is also arranged such that it can be displaced transversely to the vertical axis H (=joining direction). In addition to the positioning movement, the wedge 13.2 also exerts a bearing force on the anvil 12.1, which determines the holding force required for joining.

(31) The wedge 13.2 is preferably designed to be self-locking in order to absorb the necessary holding forces. Its drive is arbitrary. It is preferably hydraulic or pneumatic. A drive via a stepper motor or a lever mechanism is also conceivable.

(32) In the position shown in FIGS. 14a to 14c, the anvil 12.1 is moved far upwards, so that a small cavity 12.3 is formed for joining thin metal sheets B.sub.1, B.sub.2. More specifically, FIG. 14a shows a representation according to FIG. 13 before a joining procedure with a first joining task. FIG. 14b shows a representation according to FIG. 14a after the joining procedure. FIG. 14c shows an enlarged detail according to FIG. 14a.

(33) To join them, the metal sheets B.sub.1, B.sub.2 are placed on the die 12 and the punch 11 is moved towards the die 12. The material of the metal sheets B.sub.1, B.sub.2 is deformed into the cavity 12.3, wherein the die segments 12a, 12b are displaced transversely to the vertical axis (H) against the force of the leaf springs 15, thereby increasing the cavity 12.3 in the radial direction. Of course, the die 12 may also comprise only a single die element or several die segments that cannot be displaced.

(34) In the joining task shown in FIG. 13, thicker metal sheets B.sub.1, B.sub.2 are to be joined together. For this purpose, the wedge 13.2 is displaced to the right (in the figure), thereby shifting the anvil 12.1 downwards and forming a larger cavity 12.3. Joining is conducted as described above. Instead of joining the overlapped metal sheets B.sub.1, B.sub.2 together by clinching them, they can also be joined suing semi-hollow self-piercing rivets. A rivet, not shown here, is then pressed into the cavity 12.3.

(35) The explanations provided for this example of an embodiment can also apply in the same way to the first example of an embodiment if the wedge 13.2 is replaced by the adjustment slide 13.1 (and vice versa).

(36) It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to an exemplary embodiment, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular means, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.