Method and apparatus for the simultaneous production of several different sheet metal stacks from several stacked electrical steel sheets

Abstract

Method (10) for the simultaneous production of several different lamination stacks (2) produced from several stacked electrical steel sheets (12), wherein in a device (1) an adhesive (24) of a coating (16) of the electrical steel sheet (12) is activated and the electrical steel sheet (12) is bonded (19) to the lamination stack (2) under the influence of pressure, the electrical steel sheet (12) is punched (14) from a strip of sheet metal (15) immediately before or during stacking, wherein the coating (16) of the strip of sheet metal (15) is applied during the production or finishing of the strip of sheet metal (15) and the strip of sheet metal (15) which is coated (16) on at least one side is fed to the device (1), the adhesive (24) is activated in the device (1) before joining (19) already during the punching (14) and hardens in the device (1), and the punching (14)Stacking and joining (19) of the electrical steel sheets (12) is carried out by means of a multi-function tool (3) designed as a progressive die with several jointly actuated tool segments (27, 28, 29), and the adhesive (24) is activated by the action of temperature, wherein the adhesive (24) becomes active by heating to or above a certain temperature, the reaction temperature, and / or electromagnetic radiation, including ultraviolet radiation and / or infrared radiation.

Description

The invention relates to a method for the simultaneous production of several different sheet metal stacks from several stacked electrical steel sheets, wherein in a device the adhesive of a coating applied to one side of the electrical steel sheet is activated under the influence of heat and the electrical steel sheet is joined to the sheet metal stack under the influence of heat and pressure. Furthermore, the invention relates to a device for the simultaneous production of several different sheet metal packages, wherein the device comprises a punch, a depositing station, a printing die and an activation device provided in the printing die. A process of the aforementioned type is known from German patent application DE 38 29 068 C1. This describes a process in which individual stamped parts are placed on a stack and then baked together with the stack by the influence of heat. For this purpose, a coating applied to the underside of the stamped part, so-called baking varnish, is heated by contact between the top side of the stamped part and a heated press die, at least until the required reaction temperature is reached. A device of the aforementioned type is known from German patent application DE 203 18 993 U1. This document shows a stamping and packaging device for producing sheet metal packages from a multitude of stamped parts, comprising a stamping tool for producing the stamped parts, a feeding device by means of which raw material is supplied to the stamping tool, and an adhesive application device. The efficiency of an electric motor is influenced by several of its components, which together enable the conversion of electrical into kinetic energy. These components include laminated cores, through which power transmission occurs. Laminated cores are used, for example, as parts of the stators and / or rotors of electric motors. Laminated cores are made of many very thin electrical steel sheets. Electrical steel sheets exhibit excellent properties in conducting and amplifying magnetic fields. The individual steel laminations are insulated from each other and significantly influence the efficiency of the electric motor. The composition and stress-free state of the laminations, their electrical resistance, and the integrity of the insulation are all important factors in this regard.These influencing factors are largely determined by the process, in particular the planar or point bonding of the sheets to each other, and the processing quality, for example the punching burr. The publication DE 35 35 573 A1 discloses a device and a method in which the adhesive for joining a die-cut part to the stack is first applied to the stack and then another die-cut part is placed on the stack. The application of adhesive to a raw material prior to the die-cutting of the individual lamellae of the lamella pack is known from publication EP 1 833 145 A2. It is further shown how the raw material is unwound from a coil. DE 203 18 993 U1 also describes the application of adhesive to the sheet metal strip used to manufacture the stack, the subsequent punching of stamped parts from this sheet metal strip and the joining of the stamped parts to form the stack. A punching device with a heated punching blade is known from the publication DE 20 2008 015 770 U1. It is also known from DE 102 17 173 A1 to produce stamped parts from a sheet metal strip using one device and to assemble these sheet metal parts into a stack using another device. Such subsequent hardening by means of a heating device arranged outside the actual device is also shown in DE 31 10 339 A1 and WO 2012 / 059 588 A1, whereby in WO 2012 / 059 588 A1 only the edge area of ​​the sheet metal package is subject to hardening heating by means of the heating device. JP 2003-133 152 A and WO 2012 / 027 855 A2 disclose an activation or curing of the adhesive within the device, which occurs in the brake of the die-cutting device after die-cutting has been completed. WO 2012 / 027 855 A2 also shows a thermal separation between the die-cutting die and the brake of the device, which is located in the oven section of the device and surrounded by the heating device. WO 2013 / 106 881 A1 also describes a device and a method for joining stamped parts into a stack, wherein the stamped parts are cut from an adhesive-coated metal strip using a stamping device and joined to form the stack. For this purpose, the stamping device includes an activation device in the form of a microwave radiation source, which activates the adhesive applied to the metal strip. Each stamped part is then pressed onto the stack, which is being assembled in a brake, by means of the stamping device, which also serves as a pressure die. The adhesive is activated by heating the adhesive, which contains carbon nanotubes or magnetite, through microwave irradiation, thereby exciting the carbon nanotubes or magnetite. Furthermore, a method and an apparatus of the aforementioned type are known from the generic patent US 2006 / 0 082 241 A1, which describes the production of teeth for a stator of an electric machine by punching extremely thin electrical steel sheets made of an amorphous magnetic material from a strip using a die and stacking them. The stacked electrical steel sheets are then bonded together in a die using a heating device to form a lamination stack or tooth. The adhesive necessary for bonding the electrical steel sheets is applied to the strip immediately before the punching process within the apparatus. Wuppermann, Dieter and Schoppa, Andreas: Information Sheet 401 - Electrical Strip and Sheet. Düsseldorf: Steel Information Center, 2005, pp. 1-23 also describes the production of electrical sheets with pre-applied insulating material for insulating and bonding sheet lamellae. In electrical machine construction, the term "lamination" refers to the joining of individual metal sheets, known as laminations or simply laminations, into a stack. A stack is an ordered arrangement of many sheets that are fixed together. Such a laminated core replaces the solid iron core. The sheets are joined to form the stack, for example, by screws or by clamps attached to the outside of the stack. While such connections allow for disassembly, the performance of the electrical machine is generally negatively affected by these fasteners, for example, through an electrical short circuit in the area of ​​the fasteners or a disrupted magnetic field. Another well-known joining method is welding. In this process, the sheets are thermally and materially bonded. The stamped and stacked lamellae are clamped in a fixture and joined at the outer radius by several welds oriented orthogonally to the plane of the lamellae. However, welding damages the lamellae and their insulating layer and can lead to increased eddy current losses or affect the magnetic field. While the weld seam hardly restricts design freedom, a package manufactured in this way cannot be disassembled non-destructively. A single-stage process known as stamping and stacking is used. In this process, the electrical steel sheet is stamped from the raw material in a single machine stroke, placed on the stack, and connected to the stack. During stamping and / or placement or joining, mechanical connections are created in the electrical steel sheet that interact with the connections of the adjacent sheets. These connections are raised areas, also called studs or bumps, which are embossed into the electrical steel sheet. Since the insulating coating can be damaged in the forming area, short circuits cannot be ruled out. Furthermore, the connection is structurally limiting and, due to the local connecting element, affects the magnetic field. The use of adhesives as bonding agents is also well-known. One form of bonding involves the use of so-called baking lacquers. The raw material, typically a virtually endless strip of sheet metal, is coated with a baking lacquer. After the individual lamellae are cut from the lacquer-coated strip, they are aligned, stacked on top of each other, and thus form a stack. This stack of unbonded sheets is then heated to the reaction temperature of the baking lacquer for a specific period, usually 30 to 150 minutes. The reaction temperature is generally between 150 and 250 degrees Celsius. During the heating process, the stack is subjected to a pressure of 2 to 6 Newtons per square millimeter by a clamping device. This is followed by a cooling phase lasting up to 60 minutes. Although the use of baking lacquer achieves a full-surface and durable bond between the individual lamellae without damaging the metal structure or the insulation layer, the baking and cooling process is very time-consuming and therefore difficult to integrate into continuous mass production. As an alternative to baking lacquer, reactive adhesives are used. These are added to the manufacturing process in liquid or low-viscosity form and applied to the raw material, unstacked stamped parts, or the stack using complex equipment. This can lead to contamination of the production equipment with the adhesive. To prevent adhesive from oozing out laterally from the stack, the adhesive is not applied across the entire surface, especially at the edges, which means that a complete bond between all layers cannot be guaranteed. A disadvantage of all known adhesives is that each electrical sheet must also have an insulating coating on at least one side. Against this background, the invention is based on the objective of implementing a method and a device of the type mentioned at the outset in such a way that mass production of sheet metal packages in high quantities with short cycle times becomes possible. This problem is solved by a method according to the features of claim 1. The dependent claims relate to particularly advantageous further developments of the invention. The invention provides a method for manufacturing a sheet metal stack consisting of several stacked electrical steel sheets, in which the electrical steel sheets are punched out immediately before or during stacking. By using a raw material that is coated on at least one side with a full-surface coating containing an adhesive, and by punching, stacking, and joining the sheets in a single operation, it is possible to mass-produce sheet metal stacks with short cycle times and in high volumes. Preferably, an adhesive is used for the coating that allows for high continuous operating temperatures, cures in less than ten seconds, and is stable over time. This can be achieved, for example, using anaerobic adhesives and latently reactive dispersions. Coatings made of epoxy / polyurethane hybrids have also proven suitable, particularly with regard to their tolerance to impurities.These coatings also result in minimal tool contamination, and the coatings are either not damaged or only minimally damaged during stamping. The raw material is a virtually endless strip of sheet metal, which is fed to the device, for example, from a roll, also called a coil. In a further advantageous development of the process, the punching, stacking, and joining of each electrical steel sheet on the lamination stack are carried out using a multi-functional tool. This enables the essential manufacturing steps to be performed in a single mechanical movement. This reduces the equipment requirements and cycle time. Furthermore, it has proven advantageous to activate the electrical steel sheet during the punching and / or stacking process before bonding it to the stack or package. For example, when using an adhesive that becomes active upon heating to or above a specific temperature, the reaction temperature, it is possible to shorten the time required to reach that temperature. If the adhesive is activated when the electrical steel sheet impacts the stack or package, the time required for the punch to press the sheet onto the stack or package is reduced. To bond the electrical steel to the stack, pressure is applied in addition to heating. The electrical steel is preferably pressed onto the stack using a multi-functional tool and / or at least for a contact time. The contact time is the period required for the adhesive to achieve a permanent and temperature-resistant bond between the electrical steel and the stack or bundle. The contact time, particularly when using an anaerobic adhesive, a latent reactive dispersion, and / or an epoxy / polyurethane hybrid coating, is less than 100 seconds, preferably less than 10 seconds. This results in a short cycle time combined with high production volume flexibility. Furthermore, by bonding the individual electrical steel sheets layer by layer to the existing stack, it is possible to eliminate cooling time. In addition, after the application of the last electrical steel sheet, a finished stack requiring no further processing leaves the device. The presented method increases both the energy efficiency of production and that of the product, for example, an electric drive for a motor vehicle. Furthermore, the features according to the invention have a positive effect on the reliability and service life of the product, as well as on production and product costs. The sheet metal strip is coated on at least one side. The coating consists of an adhesive and an insulating material. Preferably, the adhesive and the insulating material are a single material. It has also proven advantageous for the adhesive and the insulating material to be two different materials, applied as separate layers of the coating to one and / or both sides of the electrical steel strip. In a preferred embodiment, the electrical steel strip has a coating on both sides, with the coating on one side being an adhesive and the coating on the other side being an insulating material. In another exemplary embodiment, the sheet metal strip is coated on only one side, combining the two functions of bonding and electrical insulation. The problem is further solved with a device according to the features of claim 3. The dependent claims relate to particularly advantageous further developments of the invention. According to the invention, a device for producing a sheet metal stack is provided, in which a multi-functional tool is designed as a progressive die with several jointly actuated tool segments. The tool segments comprise a punch and a die. This allows the essential manufacturing steps to be carried out in a single mechanical movement. This reduces the plant engineering effort and the cycle time. According to the invention, the multi-functional tool also includes an activation device. This activation device makes it possible to activate the electrical steel sheet during punching and / or stacking. The activation device can be designed and / or connected to a corresponding control system such that the electrical steel sheet achieves the full reactivity of the adhesive used before or precisely upon contact with the stack or bundle. This contributes to a reduction in cycle time and thus to an increase in production output. The full-surface coating of the sheet metal strip enables a complete adhesive bond. According to the invention, the coating of the sheet metal strip takes place during its production or finishing. For the production of the sheet metal bundles, the coated sheet metal strip is taken from a coil as a semi-finished product. A further advantageous embodiment of the device according to the invention is that the depositing station includes an activation device. This makes it possible to set a specific temperature or temperature profile in the stack or package over the contact time with the pressure stamp. With respect to the geometry of the stack or package, the temperature profile is spatial; with respect to the dwell time of the stack or package during production in the device, the temperature profile is temporal. According to the invention, the activation device comprises a radiation source and / or a heating device for activating and / or curing the adhesive. A cooling device for activating and / or curing the adhesive would not be according to the invention. An activation device designed as a heating device is, according to the invention, encompassed by the tool segments. Furthermore, according to the invention, activation devices designed as radiation sources for emitting ultraviolet radiation and / or infrared radiation are arranged in the device. The heating device is, for example, designed as at least one heatable contact plate for conductive heating and / or as an inductor for inductive heating and / or the radiation source for emitting, for example, ultraviolet radiation, infrared radiation, or thermal radiation. The adhesive is activated and / or cured by exposure to temperature and / or electromagnetic radiation, specifically ultraviolet and / or infrared radiation. The adhesive may also be an anaerobic substance, a latently reactive dispersion, or an epoxy / polyurethane hybrid coating. The raw material, a virtually endless electrical steel strip, is coated with at least one such adhesive during its production. The adhesive is dry and stable at room temperature. Only during the manufacturing of the laminated cores is the adhesive activated by exposure to temperature and / or electromagnetic radiation, at which point it preferably cures extremely rapidly.Curing occurs, for example, through the application of temperature and / or electromagnetic radiation. Alternatively, self-curing is possible due to the chemical reaction initiated upon activation. This enables efficient production with short cycle times and high flexibility in production volumes. A preferred embodiment of the invention is that the adhesive exhibits electrically insulating properties. The invention allows for numerous embodiments. To further illustrate its basic principle, one of these is shown in the drawing and described below. Figure 1 shows a schematic representation of a first embodiment of a device with a multi-function tool, not according to the invention; Figure 2 shows a schematic representation of a section of the multi-function tool, not according to the invention; Figure 3 shows a schematic representation of a sheet metal stack during manufacturing; Figure 4 shows a schematic representation of a sheet metal stack during manufacturing; Figure 5 shows a schematic representation of a method, not according to the invention; Figure 6 shows a schematic representation of an embodiment of the device with several multi-function tools, according to the invention. Fig. 1 shows a device 1 for manufacturing a sheet metal stack 2, not according to the invention. The device 1 comprises a multi-function tool 3 and a discharge station 4. The multi-function tool 3 is designed as a machine tool with a tool segment 26 for performing several manufacturing functions in a single operation. The tool segment 26 comprises a punch 7 and a die 8, both of which are moved by an actuating device 21. The multi-function tool 3 also has an activation device 5. Each sheet metal stack 2 consists of several stacked electrical steel sheets 12, which are punched from a virtually endless strip of sheet metal 15 by means of the multi-function tool 3 and stacked to form a sheet metal stack 2. Fig. 2 shows a section of the multi-functional tool 3 not according to the invention. A cutting tool, the punch 7, and the pressure die 8 can be seen. In addition, a cooling device 6 and a heating device 9 are indicated as an activation device 5. Fig. 3 shows a laminated core 2 consisting of several stacked electrical steel sheets 12. The electrical steel sheets 12 are each punched out from a strip of sheet metal 15, placed on a stack in the same operation, and joined to form a laminated core 2. The electrical steel sheets 12 and the strip of sheet metal 15 are coated on one side with a coating 16. This coating 16 has the properties of both an adhesive 24 and an insulating material 25. The strip of sheet metal 15 is oriented such that the side with the coating 16 faces the laminated core 2. Fig. 4 shows a laminated core 2 consisting of several stacked electrical steel sheets 12. The electrical steel sheets 12 are each punched out from a strip of sheet metal 15, placed on a stack in the same operation, and joined to form a laminated core 2. The electrical steel sheets 12 and the strip of sheet metal 15 are provided on both sides with a coating 16. On one side, the coating 16 is an insulating material 25, and on the other side, an adhesive 24. Preferably, the strip of sheet metal 15 is oriented such that the side with the adhesive 24 faces the laminated core 2. Fig. 5 shows in a schematic representation the process of the non-inventive method 10 for producing a sheet metal stack 2. The sheet metal strip 15, unwound from a coil 13, was already coated on one side with an adhesive 24 during manufacturing. This sheet metal strip 15 is fed to the device 1 17 and guided through the device 1 in the feed direction 23. In the device 1, electrical steel sheets 12 for stator and / or rotor structures are punched out from the sheet metal strip 15 using a multi-function tool 3 14. During or immediately after punching 14, the electrical steel sheet 12 is placed onto a stack consisting of several identical electrical steel sheets 12 18. The stack is held in a depositing station 4 of the device 1. The multi-function tool 3 has an activation device 5 by means of which the adhesive 24 is activated. The multi-function tool 3 presses the electrical steel sheet 12 onto the stack and bonds it 19 to form a laminated core 2. The multi-function tool 3 is moved in the working cycle by means of an actuating device 21.The actuating device 21 comprises at least one hydraulic cylinder (not shown). After an electrical steel sheet 12 is joined to the lamination stack 2, the achieved height and number of layers of the lamination stack 2 are compared with a target value 20. If the target value is not reached, the lamination stack 2 is extended by adding another electrical steel sheet 12. Once the production of a lamination stack 2 held in the depositing station 4 is complete, it is removed from the device 1. This is done by means of a transport device 22. Fig. 6 shows an embodiment of a device 1 according to the invention with a multi-function tool 3, which, according to the invention, is designed as a progressive die tool with several jointly actuated tool segments 27, 28, 29. Embodiments are also possible in which the tool segments 27, 28, 29 can be actuated independently of one another. In the embodiment shown, all tool segments 27, 28, 29 are moved by means of an actuating device 21. The actuating device 21 comprises at least one hydraulic cylinder (not shown) for moving the tool segments 27, 28, 29 during the working cycle. Using this embodiment of the device 1, sheet metal stacks 2 are produced analogously to Figures 1, 2, 3, 4 to 5. The sheet metal strip 15, unwound from a coil 13, is guided through the device 1 according to the work cycle. The sheet metal strip 15 is processed by the individual tool segments 27, 28, 29 at each work cycle. For example, different shapes are punched out of the sheet metal strip 15 14. After each work cycle, the sheet metal strip 15 is advanced one position in the feed direction 23. The tool segments 27, 28, 29 each have at least one forming tool, for example, a punch 7, by means of which the sheet metal strip 15 is processed. In addition to the punch 7, which separates the electrical steel sheet from the sheet metal strip 15, the tool segments 27, 28, 29 also include a die 8 of the tool segments 28, with which the punched-out electrical steel sheets are guided into the depositing stations 4, where they are stacked and joined 19 to the lamination stacks 2 held in the depositing stations 4. In the first depositing station 4 in the feed direction 23, lamination stacks 2 with smaller dimensions, for example, for the rotors located inside an electric motor, are produced. In the second depositing station 4 in the feed direction 23, lamination stacks 2 with larger dimensions are produced, for example, for the stators located outside an electric motor. For joining 19, the adhesive 24 in the coating 16 of the sheet metal strip 15 is activated.To activate the adhesive 24, the tool segments 28 and 29 have an activation device 5. The activation devices 5 in the tool segments 28 and 29 are heating devices 9. The activation devices 5 of the tool segments 29 serve to preheat the sheet metal strip 15, while the activation devices 5 of the tool elements 28 heat the sheet metal strip 15, in particular the punched electrical steel sheets, or maintain a desired temperature level. Also shown are radiation sources 30 as activation devices 5, which are arranged in the device 1. To activate the adhesive 24, the radiation sources 30 and / or the activation devices 5 in the tool segments 28 and / or the activation devices 5 in the tool segments 29 can be used. Once the production of a sheet metal stack 2 held in the depositing stations 4 is complete, it is removed from the device 1. This is done by means of a transport device 22. Reference symbol list 1 Device 2 Sheet metal stack 3 Multi-function tool 4 Deposit station 5 Activation device 6 Cooling device 7 Punch 8 Die 9 Heating device 10 Process 12 Electrical sheet 13 Coil 14 Punching 15 Sheet metal strip 16 Coating 17 Feeding 18 Depositing 19 Joining 20 Comparison 21 Actuating device 22 Transport device 23 Feed direction 24 Adhesive 25 Insulating material 26 Tool segment 27 Tool segment 28 Tool segment 29 Tool segment 30 Radiation source

Claims

Method (10) for the simultaneous production of several different lamination stacks (2) produced from several stacked electrical steel sheets (12), wherein in a device (1) an adhesive (24) of a coating (16) of the electrical steel sheet (12) is activated and the electrical steel sheet (12) is bonded (19) to the lamination stack (2) under the influence of pressure, the electrical steel sheet (12) is punched (14) from a strip of sheet metal (15) immediately before or during stacking, wherein the coating (16) of the strip of sheet metal (15) is applied during the production or finishing of the strip of sheet metal (15) and the strip of sheet metal (15) which is coated (16) on at least one side is fed to the device (1), the adhesive (24) is activated in the device (1) before joining (19) already during the punching (14) and hardens in the device (1), and the punching (14)Stacking and joining (19) of the electrical steel sheets (12) is carried out by means of a multi-function tool (3) designed as a progressive die with several jointly actuated tool segments (27, 28, 29), and the adhesive (24) is activated by the action of temperature, wherein the adhesive (24) becomes active by heating to or above a certain temperature, the reaction temperature, and / or electromagnetic radiation, including ultraviolet radiation and / or infrared radiation. Method (10) according to claim 1, characterized in that the electrical sheet (12) is pressed onto the sheet stack (2) by the multi-function tool (3) for at least the duration of a contact time to connect (19) to the sheet stack (2). Device (1) for the simultaneous production of several different sheet metal stacks (2), wherein the device (1) comprises a depositing station (4) and a multi-function tool (3) designed as a progressive die with several jointly actuated tool segments (27, 28, 29), wherein the tool segments (27, 28, 29) comprise a punch (7), a pressure die (8) and an activation device (5) designed as a heating device (9), and in addition, activation devices (5) designed as radiation sources (30) for emitting ultraviolet radiation and / or infrared radiation are arranged in the device (1). Device (1) according to claim 3, characterized in that the depositing station (4) comprises an activation device (5). Device (1) according to claim 3 or 4, characterized in that the activation device (5) comprises a cooling device (6).

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