EP4197094A1

EP4197094A1 - Multiple temperature-control process for workpieces by means of a triplex furnace

Info

Publication number: EP4197094A1
Application number: EP21758702.1A
Authority: EP
Inventors: Karl Bauch; Gerhard Karl Mais; Wolfgang Weiss
Original assignee: Hedrich GmbH
Current assignee: Hedrich GmbH
Priority date: 2020-08-12
Filing date: 2021-08-12
Publication date: 2023-06-21
Also published as: JP2023539566A; MX2023001806A; US20230299652A1; KR20230061404A; DE102020004905A1; CN116348618A; BR112023002594A2; WO2022034164A1

Abstract

Multiple temperature-control process for stators (7) and rotors of electric motors and components consisting of materials with different magnetic properties by means of a triplex furnace (1) for the quick, efficient and uniform heating-up of preferably tubular components such as stators (7), wherein the magnetic parts of a component are primarily heated up by means of induction and at the same time non-magnetic parts of the same component are primarily heated up by means of infrared radiation, and at the same time and subsequently secondary heating takes place by means of convection, in particular by passive heating elements (10), which serves for finely adjusting the target temperature and for maintaining it.

Description

Designation: Multiple tempering process for workpieces using a triplex oven

description

The present invention relates to a method and an exemplary device in the form of a triplex furnace for quickly, efficiently and uniformly heating up preferably tubular components such as stators of electric motors made of different materials. The triplex oven enables the simultaneous use of three different heating processes, tailored to the different materials and parts of components such as electric motor motors.

In order to encapsulate and/or impregnate the current-carrying components of an electric motor, which are usually made of copper, it is necessary to heat the stators and rotors, which are made of sheet steel and copper rods, so-called hairpins, or copper wires, to temperatures between 80 and 180 °C. The impregnation and/or encapsulation of stators and rotors is carried out in particular to fix the components to one another, for better and defined heat dissipation and for additional electrical insulation.

The following invention is aimed in particular at stators of electric motors, which consist of a soft iron laminated core and a copper winding. In newer motors, the copper winding is often replaced by welded hairpins made of copper, which are embedded in the laminated core on the inner diameter and protrude axially on both sides as so-called winding heads. Efficient, fast and even temperature increase is both when preheating the stator for the impregnation and/or potting as well as for the subsequent temperature increases for gelling and curing.

In current systems for impregnating or encapsulating these components, circulating air ovens have usually been used to date, into which the stators are introduced for a minimum period of time or run through these ovens in order to reach the desired temperature. The heat is transferred by convection. These ovens are usually heated by gas or electricity. This type of heating is ineffective in a vacuum because there is no air as a heat transfer medium. This procedure is inexpensive, well tested, gentle and insensitive to long residence times, but it requires a considerable amount of time, space and energy.

For some years now, the stators have been individually tempered using infrared radiation, which is directed at the components from the outside. Here, the warming radiation hits the surface of the body to be heated directly. The heat transfer from the heat source to the air and from the air, or a gas, to the stator is thus eliminated. However, the surfaces of different materials are heated up considerably differently depending on the degree of reflection and thermal conductivity. Since the radiation affects the thin copper parts as well as the thick laminated core, an even temperature distribution in and on the stator can only be achieved by longer waiting times.

Induction furnaces are also known. In these furnaces or in this process for heating particularly magnetic materials such as iron, a high-frequency alternating magnetic field flows through the component. Since copper is not magnetic, essentially only the laminated core is heated with this process. The temperature must then be transferred from the laminated core to the copper parts. Hot spots, i.e Corners and edges where magnetic waves are concentrated must be taken into account. Overheating occurs very quickly here, leading to the destruction of the insulation or adjacent plastic parts.

DE 10 2017 005 532 A1 discloses a method and a heating device for inductively heating and keeping warm a stator or armature of an electric machine, the inductive heating taking place by means of electromagnetic fields of different frequencies, which are tuned to different materials. The laminated core and the protruding copper parts are heated by different inductors with different frequencies. Achieving a uniform temperature on the stator that is accurate to within a few degrees has proven to be very difficult in practice with direct heating methods such as induction and radiation and involves waiting times. The temperature measurement on the parts that are inevitably constantly rotating after impregnation is particularly problematic. In particular, with different starting temperatures or longer residence times, unacceptable deviations occur that impair the overall process.

Another method for tempering electric motor motors and rotors is resistance heating. In this case, the winding is subjected to high, low-frequency currents at low voltage. Here, due to the electrical resistance, the heat is only generated in the current-carrying parts and must be transferred from there to the steel components such as the laminated core. This requires a considerable period of time if the same temperature is required on all components and is also not very efficient because of the high energy intensity. Long periods of time for tempering the components in series production with the specified short cycle times mean a large number of workpiece carriers and clamping devices, large furnaces with considerable space and energy requirements and with long start-up and throughput times. A large number of components in the system make it inflexible and expensive.

EP 2 905 346 A1 discloses a method for imprinting a temperature profile on a sheet steel component and a heat treatment device, comprising a production furnace for heating the sheet steel component to a temperature above the AC3 temperature and a thermal post-treatment station for impressing a temperature profile on the sheet steel component, wherein the one or more areas of the sheet steel component are cooled and heated in the thermal post-treatment station by means of convection and/or by means of radiation and/or by means of heat conduction.

A regulation for a method and a device for the heat treatment of parts made of aluminum or an aluminum alloy is known from DE 692 24 349 T2.

A regulation and control device for a device for induction heating of a workpiece with an induction device is known from DE 10 2012 007 959 A1.

DE 10 2018 101 226 A1 discloses a device for the inductive hardening of elongated workpieces, such as axle shafts, side shafts or drive shafts, having at least one hardening station and one tempering station, the at least one hardening station having an inductor device for heating and a quenching device for Quenching the workpieces, at least one multi-axis robot being provided in order to remove the workpieces to be hardened from a feed device into the hardening station and place them on a discharge device.

Finally, EP 2 640 546 B1 discloses a device for inductively heating metallic components during welding, comprising at least one flexible induction element and means for automatically controlling and regulating the power and, if necessary, the frequency of a medium-frequency generator connected to the induction element, the flexible Induction element and the coolant line can be repeatedly plastically or elastically deformed and manually or automatically adapted to the shape of components to be heated.

The task is therefore to generate a process and a system that allows fast, energy-efficient, uniform, space-saving and precise temperature control of components made of different materials such as e.g. B. stators made of steel and copper.

The object is achieved with a method as described in claim 1. The following claims show developments of the method and an exemplary device for implementing the method.

The new process also meets the requirement that impregnated stators and rotors, i.e. those which are dripped with resin that is still liquid, must rotate continuously in order to prevent the impregnation material from dripping off and imbalance.

The new process is characterized by the simultaneous heating of components made of different materials with different materials heating processes with different heat sources that are tailored to the material and the component. This process also enables stators, for example, to be heated from the inside and outside at the same time. With such a method and a device adapted to it, a very fast and thus energy- and space-saving heating and also a uniform heating of such components is possible for the first time. The new process is characterized by high energy efficiency because most of the heat is fed directly to the component or, in the case of induction, is even generated in the component.

In contrast to the conventional heat transfer ovens, referred to here as convection ovens, the thermal chamber can be made very small due to the direct introduction of a large part of the required amount of heat, because only little air circulation is necessary due to the rotating components. The small design results in little radiating surface and thus low heat loss. The heat-insulated housing of the solution we proposed therefore gives off only little heat to the environment. Due to the design feature that the heating elements for the direct component heating also serve to feed the convection heating is another helpful feature to keep the furnace space or the thermal space small. On the one hand, the IR emitters or reflectors can be moved in such a way that the air surrounding the components is heated. On the other hand, ferritic passive heating elements in particular, which the inductor acts on, serve as a heat source for the convective heating. The intensity with which the inductor acts on the passive heating elements is temperature-controlled. The inductor is preferably movably mounted and can be adapted to different component sizes and optionally to different component shapes by means of at least one actuator. Due to the mobility of the inductor, it can also be brought into the effective range of the passive heating elements. Som it can use the same inductor for both direct heating of the component as well as for temperature control of the passive heating elements for the convection heating. Ferritic finned tubes, molded components, plates, rods or grids are proposed as passive heating elements. The temperature on these stationary elements can be measured just as reliably as the air temperature in the heating station. The interaction of the inductor with the passive heating elements creates a convection oven together with the rotating component that ensures air flow. Optionally, the circulation of the air in the thermal room can be supported by a hot air fan. The convection heating process is used to slightly adjust the component temperature, to equalize the temperature in the component itself and to maintain a target temperature that has been reached during waiting times, e.g. e.g. when the following system parts are at a standstill. Indirect heating is activated in particular by reducing the distance between the passive heating element and the inductor, e.g. B. by pivoting, turning, moving, etc., as well as by the different levels of loading of the inductor.

A feature of the new procedure is the simultaneous effect of induction, IR radiation and convection. Optionally, the IR radiation is replaced or supplemented by resistance heating of the copper parts using high, low-voltage currents.

With the appropriate arrangement, the passive heating elements can also be heated by the infrared radiators.

The intensity and duration of the induction and/or the IR radiation from 0 to 100% is specified by the operator depending on the component. On the other hand, the heating output can be calculated based on the difference between the actual and target temperature, taking into account specified Regulate maximum temperatures. Since the temperature on these moving parts can only be measured with insufficient certainty and can only be measured on the surface, the temperature of the component is preferably controlled according to the following scheme. The starting temperature of a stator with a known mass of copper and sheet steel is measured. The target temperature is fixed. From the heating power introduced into the stator, the frequency converter for the induction heating can represent this, and the duration of the effect, the amount of heat introduced can be determined and compared with the required calculated amount of heat according to a predetermined degressive power curve. Alternatively, it is possible to program the amount of heat input into the component according to a table depending on the temperature rise and the component.

The well-known non-contact and contact measuring methods are used to measure the temperature.

For an even temperature distribution on and in the stator, it preferably rotates during the entire heating process and is also heated from the inside and outside. So that different components or stator sizes can be effectively heated with the same inductors and IR emitters, these are movably mounted. This is also necessary for heating elements arranged inside the stators, so that the stators can move on to the next station. A moving, short inductor also enables long stators to be evenly heated through alternating linear movement. The same goes for the IR heating elements. In addition, this mobility of the active heating elements also enables the targeted start-up and heating of the passive heating elements for temperature control by convection. Another feature of the new process is the simultaneous heating of the rotating component from the inside and outside with different heat sources. The heat sources are matched to the respective material and the shape of the component. The intensity with which the heat sources act on the corresponding section of the component over a specified period of time results in the heat output to be introduced or the desired temperature.

Convection supports direct component heating and is mainly important when it comes to temperature equalization in the component and maintaining the desired target temperature. Due to the rotation of the components, in particular the stators and rotors, there is a continuous flow around the components without the use of the otherwise usual circulating air fan. This saves installation space, energy and generates no noise. Due to the unnecessary integration of fans and baffles and the use of the existing heating elements, a very small boiler room is possible, which can be insulated inexpensively and heated quickly. With regard to high energy efficiency, the heated room is provided with reflective elements such as mirrors or corresponding foils or coatings as far as possible. A one-way mirror pane is installed inside the triplex oven room, which reflects 60 to 95% of the thermal radiation but still allows a view into the oven.

To drive through the triplex oven, it is equipped with flaps and/or brushes or temperature-resistant drop curtains on the component feed openings and/or the thermal room recesses.

A uniform defined rotation of the stators is in particular after the application or introduction of the liquid impregnating compound in the Usually a varnish or resin, necessary to maintain an even layer on the winding and an even filling of the slots. At standstill, the impregnating compound would drip off. In the case of rotating components such as rotors, the uneven distribution would also result in an impermissible imbalance.

For components that cannot be heated from the outside and inside at the same time due to a missing bore, the opposite or lined-up arrangement of the preferably movable heating elements is proposed.

An exemplary device for implementing the method in the form of a triplex furnace essentially consists of a thermal chamber and a component transport unit connected to it. The component transport unit transports the component carriers in steps or continuously through the thermal room. For this purpose, the component carriers are rotatably mounted and positioned on a transport element or between several transport elements such as chains. For the continuous rotation of the components, the component carriers are driven by means of a separate drive, which acts on a pinion seated on the component carriers.

Optionally, the rotational movement of the component carriers is generated with the same chains between which the component carriers equipped with sprockets are positioned.

The component carriers for rotating components are designed as internal clamps or as external clamps and create the connection between the moving components in the thermal chamber and the attached component transport unit.

The thermal room contains the heating elements for direct and indirect

Component heating such. B. inductors, IR emitters as well Passive heating elements and IR radiation absorbers or reflectors for convective heating. The triplex oven has a modular structure and has at least one heating station that has the heating elements described above. The number of heating stations lined up in a triplex oven depends on the technical specifications. The housing gives the largest component only little space in order to keep the volume of the thermal room as small as possible and to achieve a small temperature difference between floor and ceiling. Towards the component transport unit, the thermal room has a recess on one side over the entire length, in which the workpiece carrier moves. The recess is preferably covered with multiple rows of busts or other resilient covering elements. If subsequent or upstream system parts have a different temperature level than the thermal room, these are closed at the entrance and exit with slidably mounted closing elements such as flaps or gates that are equipped with actuators. These entrances, which are preferably designed as a sliding element, are only opened for the passage of the workpiece carrier, possibly with a component. Since the heating of the components and in particular the potting material or the impregnating resin causes evaporation during gelling and hardening, the thermal room has a preferably controllable suction system. The thermal room is equipped with a variety of sensors, especially contact and non-contact temperature sensors.

The method and an exemplary device in the form of a triplex oven are explained in more detail on the basis of the figures shown in the drawing. Show it:

1 shows a possible arrangement of the primary heating elements for the simultaneous heating of a stator (7) from the inside and outside with different heat sources

2 shows the section of an exemplary embodiment of a triplex oven (1)

3 shows a component carrier (6) as an internal clamp with the stator (7) placed on it

FIG 1 shows in section a simplified possible arrangement of the active and passive heating elements in the thermal chamber (2) using the example of a component in the form of a stator (7) for electric motors, which essentially consists of a laminated core (7.1) made of soft iron sheets and a copper winding (7.2 ) consists. The ends of the copper rods that protrude beyond the laminated core on both sides are referred to as the end winding. On its inner circumference, the laminated core has longitudinal grooves in which the copper rods are embedded. The stator (7) is supported, transported and set in rotation by a component carrier (6), which is shown here in simplified form as an external clamp. The thermal space (2) is defined by a heat-insulating thermal space housing (2.1). The thermal room housing (2.1) has at least one slot-shaped recess (2.2) towards the component transport unit (5). The component carrier (6) and with it the stator (7) are moved along this recess (2.2) in order to rotate from one heating station to the other or from one part of the system to the next. For the primary heating of the stator (7), both an externally arranged inductor (8) for the inductive heating of the laminated core in particular and at least one infrared radiator (9) positioned in the central bore of the stator (7) for heating the copper rods can be seen. Combined with an actuator and due to the displaceable mounting of the primary heating elements, these can be adapted to different component sizes, in particular to different stator dimensions, or can be inserted into the stators (7). It is also possible to move the primary heating elements and in particular the inductor (8) into the active area of the passive heating elements (10) in the case of displaceable mounting in order to temper them for the convective heating of the thermal chamber (2) and thus the component. In the case shown, the IR heating tubes are also movably mounted so that they can move axially into and out of the central bore of the stator (7).

The inductor (8) and/or the IR heating tubes are preferably movably mounted and connected to actuators for automatic positioning. Thus, the primary heating elements can be programmatically adapted to different component dimensions or stator dimensions and at the same time use as an energy source for the passive heating elements (10) for convective heating of the thermal chamber (2) and the stator (7), by z. B. the inductor (8) is activated and moved into the interaction area of ferritic passive heating elements (10). The inductor (8) thus heats either the component or the passive heating element (10). The IR tubes can be used in the same way. The rotational movement of the stator (7) and/or a hot-air fan (11) ensures that the air is circulated in the thermal chamber (2).

With this arrangement of the heating elements, the stator (7) is heated simultaneously from the outside and inside by direct heat input by means of induction into the laminated core and IR radiation into the copper rods and/or additionally and subsequently on all sides by the temperature-controlled surrounding air, i.e. by convection Temperature maintained or matched to target temperature. The thermal room (2) is preferably already when retracting the stator (7) brought to the target temperature by means of the infrared radiator (9) and the passive heating elements (10).

2 shows a cross section through a simplified triplex furnace (1) consisting of a component transport unit (5) and a thermal chamber (2). The component carrier (6), shown as an internal clamp with a clamped stator (7), is mounted with its sprockets between chains in the component transport unit (5) and extends through a recess (2.2) that runs along the transport route between the component transport unit (5) and the thermal chamber (2). is introduced into the thermal chamber (2). So that the axis of the component carrier (6) can move through the sealed recess (2.2), the recess (2.2) is covered with flexible covers, e.g. B by means of brushes, curtains, resilient fins and resilient heat-resistant seals such as inflated silicone hoses. In this representation, the inductor (8) is arranged on the outside above the laminated core and the infrared radiators (9) are directed from the outside onto the copper rods of the end windings. The temperature-controlled air surrounding the stator (7) for convective heating is not shown. The thermal chamber (2) consists of a housing lined with a thermal insulation layer and at least one component feed opening (3), which is also used for component removal.

3 shows a component carrier (6), which is equipped as an internal clamp for components with central bores and carries a stator (7). In the embodiment shown, the component carrier (6) has two sprockets, which are both the bearing points and drive elements for the rotation and transport of the stator (7). The sprockets are mounted between chains, as shown in DE 10 2019 004 954.3. Reference list:

1 = triplex oven

2 = thermal room

2.1 = thermal room enclosure

2.2 = thermal room recess

3 = component feed opening

4 = suction opening

5 = component transport unit

6 = component carrier

7 = stator

7.1 = laminated core

7.2 = copper winding

8 = inductor

9 = infrared heater

10 = passive heating element

1 1 = hot air fan

Claims

patent claims

1. Multiple temperature control process for stators (7) and rotors of electric motors consisting of soft iron sheets and copper rods and generally for components consisting of different materials with different magnetic and thermal properties, characterized in that the magnetic parts of a component are primarily heated by induction and at the same time the non-magnetic parts of the same component are heated primarily by means of infrared radiation and secondarily the heating takes place simultaneously and for the subsequent fine adjustment of the target temperature and its maintenance by convection.

2. Multiple temperature control method according to claim 1, characterized in that tubular components, in particular stators (7), are heated simultaneously with different heating methods, in particular by means of induction and infrared radiation, in the primary heating for rapid and uniform heating from the inside and outside.

3. Multiple temperature control method according to claim 1 and 2, characterized in that the intensity of the inner and outer heat source and thus the induction heater (8) and the Infrared heating can be regulated and controlled independently of one another according to the energy requirement and the target temperature of the material part assigned to or in the component. Multiple temperature control method according to at least one of Claims 1 to 3, characterized in that the component is set in motion and in particular in rotation by the surrounding air during the heating for uniform temperature distribution and for better heat transfer with convective heating and/or the inductor (8 ) and move the infrared radiators (9) either linearly. Multiple temperature control method according to at least one of Claims 1 to 4, characterized in that the heating energy for the convective heating of the components comes partly from the infrared source reflected from the component or from the infrared source radiated past and/or is introduced by at least one ferritic passive heating element (10) which is tempered by the inductor (8). Multiple temperature control method according to claim 1, characterized in that the non-magnetic but electrically conductive parts of the component to be heated in addition to or as an alternative to infrared radiation by means of resistance heating due to high 18

Conduction to be heated. Multiple temperature control method according to at least one of Claims 1 to 6, characterized in that a component is heated in accordance with the amount of heat required by the component and in particular its individual material parts for the required temperature increase on the basis of the masses of the various materials and their heat capacity in such a way that the thermal energy acting on the individual material part of a component is supplied according to program specifications until the desired amount of heat is introduced and the target temperature is reached. Triplex oven (1) as a device for quickly and efficiently heating stators (7) and rotors of electric motors for implementing the method according to at least one of claims 1 to 7, characterized in that the triplex oven (1) consists of at least one heating station consisting of a primary heater of at least one preferably movably mounted inductor (8) and at least one preferably movably mounted infrared radiator (9), a secondary convection heater and at least one located outside the thermal chamber (2). 19

Component transport unit (5) with component rotary drive. Triplex oven (1) according to claim 8, characterized in that the heat source of the secondary convection heating are passive heating elements (10), the ferritic passive heating elements (10) being connected to at least one inductor (8) and/or infrared light absorbers representing the passive heating elements for the infrared light radiators. Triplex oven (1) according to at least one of claims 8 to 9, characterized in that optionally both primary heating elements and secondary heating elements are mounted in variable positions and are connected to actuators. Triplex oven (1) according to at least one of Claims 8 to 10, characterized in that the triplex oven (1) consists on the one hand of a heat-insulated thermal chamber (2) with active and preferably additional passive heating elements, at least one closable component feed opening (3) and one along the Component movement direction extending thermal space recess (2.2) and optionally has suction openings (4), temperature sensors, lighting and at least one one-way mirrored glass pane, and to 20 others from a component transport device connected to the thermal chamber (2), the component carriers (6) of which project into the thermal chamber (2) and are moved and rotated by actuators using machine elements. Triplex oven (1) according to at least one of claims 8 to 11, characterized in that the inductor (8) is designed as a flexible hollow body that can optionally be deformed by actuators, preferably in the form of a flexible copper tube or a corrugated copper tube. Triplex oven (1) according to at least one of claims 8 to 12, characterized in that the triplex oven (1) has a temperature control for each of the three heating methods and for the component transport unit (5). Triplex oven (1) according to at least one of Claims 8 to 13, characterized in that a number of heating stations with primary and secondary heating elements are arranged in series in a thermal chamber (2).