|
(11) | EP 2 371 467 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
| published in accordance with Art. 153(4) EPC |
|
|
|
|
||||||||||||||||
| (54) | METHOD FOR MANUFACTURING INDUCTORS FOR INDUCTION HEATING USING MICROFUSION TECHNIQUES |
| (57) The method consists in the implementation of given steps for producing an inductor
for induction heating. Firstly the planes of the inductor are generated in two dimensions
and then planes are generated in three dimensions, these being suitable for use with
a wax deposition system This is followed by the creation, by means of wax deposition,
of a model of the inductor in two stages which will form the inside and the body of
the inductor, respectively. A mould with the external form of the inductor and with
dimensions larger than the inductor is formed. The inductor model is introduced Into
the mould. The mould is filled with a high-conductivity alloy and introduced into
a microfusion oven. Once dried in the oven, mould extraction is performed by means
of physical mechanisms and chemical pickling agents, thereby obtaining the inductor. |
OBJECT OF THE INVENTION
[0001] The present invention, as this specification states in its title, refers to a method for manufacturing inductors for induction heating using MICROFUSION techniques. By using this manufacturing system four major improvements over current manufacturing systems are achieved. The first of these improvements is the use of a data storage system for storing physical and mechanical characteristics of the inductor, thus allowing the exact reproduction of new inductors, which optimizes the processes of replacing inductors for processes wherein hundreds of thousands of pieces are manufactured. The second of the improvements is the use of a suitable highly conductive metal alloy, in order to minimize losses in the inductor and thereby increase the half-life thereof, being able to duplicate with respect to the inductors made with pure copper and silver solders. The third of the improvements is the use of planes in three dimensions for optimizing the inductors and lowering the points of higher current density by changing the geometric characteristics thereof, by means of minor modifications to the planes increasing the durability of the inductors is creased, by removing the hot spots thereof. The fourth of the improvements, is the internal design of the inductor, through which the cooling thereof flows, being able to increase the flow rate with respect to those made with copper tube, or increase the thickness of the inductor wall where appropriate.
BACKGROUND OF THE INVENTION
[0002] Since the use of induction heating for quenching the pieces in a large-number, for example for automotive pieces, a heating inductor has been required. This heating inductor needs to have a very long half-life in order to make the largest possible number of pieces. From the beginning, it has been desired that the inductor had an infinite life, since changing the inductor, meant having to check that the quenching profile was still the same. This check is necessary because there can not be certain that two inductors are equal. The difference between each inductor is because these are manually manufactured, and despite being manufactured with the same planes the physical manufacturing may be slightly different. The manual manufacturing of the inductors has generated other kind of problems, such as can be errors in the solders, slightly different dimensions, partial blockage inside the inductor, etc. All of these errors due to manual production have been attempted to be solved through automation in the procedure for manufacturing the inductors. All the automation attempts in the manufacturing of inductors have been made by means of machine tools developed for precisely machining the pieces. These machine tools are designed to basically work on hard materials such as carbon steel. The problem of automation in the manufacturing of inductors is basically the use of current technology for machining solid pieces of copper. The system used basically consisted of, from a large piece of copper, machining the exterior of the inductor removing all the excess of copper. With this system a large amount of copper chips are generated, many machine tools are broken, and the hollow interior of the inductor is not obtained. Therefore it is necessary to perform a subsequent machining wherein the gap of the inductor is unknown. Subsequently, there is known that the end through which the tool had been introduced should be capped, in this second process the inductor undergoes deformations with the possibility of water leaks. This method only applies to a very specific type of inductor for induction heating.
[0003] A MICROFUSION method for obtaining jewelry pieces has been used from some time. This method consists of filling a mould with a noble material for making these pieces of jewelry. For making the moulds, a wax original mold usually made by hand is usually used. The materials used in jewelry pieces usually are gold, silver, etc. The functionality of the pieces made by MICROFUSION is only ornamental, and should have no power requirement.
[0004] There is no background of the use of microfusion processes for obtaining inductors for induction heating, which require an electrical functionality.
DESCRIPTION OF THE INVENTION
[0005] The present invention consists of implementing a number of steps result of which is obtaining a given inductor for induction heating.
[0006] The first step, element 1 in Figure 1, consists in generating one or more two-dimensional planes, with the external physical characteristics of the heating inductor. This step takes into account which will be the part that will be in the vicinity of the piece to be treated. This initial design will be determined by, previous experiences, simulations carried out with proper tools for such purpose, etc.
[0007] The second step, element 2 in Figure 1, consists in generating a plane in three dimensions, which meets the characteristics determined by the initial planes. This plane in three dimensions has both the face and the exterior of the inductor, and the inside thereof, through which the cooling water of inductor will flow. In this plane will be drawn, both the electrical connections (1) of the inductor, and the connections for the cooling water (2). The plane in three dimensions must contain all the information on inductor model, since over this plane both cooling and electrical improvements will be made, such as the possible future modifications to be carried out In new versions of the inductor. The generation of this plane has to be done on a data storage medium that stores information on the inductor for producing replicas besides having the ability to communicate with a printer for printing wax layers. In this plane in three dimensions three different spaces must be defined, the first space is determined by the internal parts (4) of the inductor (through which the cooling flows), the second of the spaces is formed by the body (5) of the inductor (the tube walls), the third space is formed by the external part of the inductor (corresponding to the areas wherein no operation has to be done). For the first of the spaces can be sustained it is necessary to use areas that communicate it to the third of the spaces. These communication areas have to be in places through which high current density does not flow, since they can produce unwanted interfaces. Sprues or stalks needs to be designed so as being used for filling of the alloys, as well as for coating the first of the spaces.
[0008] The third step, item 3 in Figure 1, consists of the deposition of thin layers of wax that are formed one above the other the three-dimensional model defined in the second step. For the formation of wax layers, two waxes with different melting temperature are used. The wax, melting temperature of which is the lowest (8) is used for forming the first of the spaces defined in the second step (the hollow interior of the inductor through which the cooling water flows). The wax, melting point of which is the highest (9) is used to form the body of the inductor. This third step has to be done with specific machines for the deposition of wax layers. The mechanical characteristics of the wax must be such as to allow a three-dimensional model completely rigid. In the case of small sized inductors it is necessary to define in the second step connection parts of the weakest areas. These connection areas will be eliminated in the final machining process of the inductor.
[0009] The fourth step, element 4 in Figure 1, aims to fill the body of the inductor with optimum alloy for use in induction heating. This step is divided into two main parts. The first part undergoes the model obtained in the third step to a temperature slightly above the melting temperature of the wax of the first of the spaces (the wax with the lowest melting temperature). Once the wax is liquid is evacuated by gravity and the space that contained thereof (first space) is filled with a high-flow ceramic coating, so that all voids of this space are filled. The piece is put in an oven at a controlled temperature and humidity in order to produce the drying of the ceramic coating. The second part of this fourth step is to introduce the three-dimensional model of the third step in a mould dimensions of which are between 0.1 mm and 500 mm, preferably between 1 mm and 50 mm and more preferably between 20 mm and 30 mm larger than the dimensions of the inductor. The mould containing the inductor and inside of which there is also a ceramic coating is filled with ceramic coating. It is important to make connections so-called blast nozzles (3) that allow the ceramic coating of the outer mould remains attached to the ceramic coating of the internal part (the first part of the fourth step). To properly forge this second coating is also necessary to control its temperature and humidity in the oven. After forging the ceramic coating the oven temperature is increased until exceeding the melting temperature of the wax with the highest melting point. The wax that occupied the second space in a liquid state is extracted in a vacuum oven, leaving hollow whole the body of the inductor. This final mould is introduced into a Microfusion oven with centrifugal motion and filled with the suitable alloy that enables a high conductivity and prevents the pores. The filler alloy consists of any highly conductive element or combination of elements result of which has high conductivity, preferably a combination of 75% silver and 25% copper, with a variation of these ratios to a maximum of 10% and preferably to a maximum of 5%.
[0010] The fifth step, element 5 in Figure 1 is to break the ceramic mould and extracting the inductor from inside. To eliminate the mould of third space mechanical methods, by breaking the ceramic coating, are used. To eliminate the mould of the first space (inside the inductor) pickling chemical agents that remove the coating are used. Once the inductor is obtained, it proceeds to eliminate the remaining parts of the mould that were used to connect the different spaces and plug the gaps leaved in the mould for filling the different spaces. In this process, machine tools for a final finishing of the inductor (7) are used.
[0011] The method for manufacturing inductors of the present invention, which comprises the previous steps, allows the repetition of steps for obtaining copies of the same inductor, element 6 in Figure 1, or introducing improvements in the inductor, element 7 in Figure 1,
BRIEF DESCRIPTION OF THE FIGURES
[0012]
Figure 1. - Shows the diagram of the different steps of the method used in manufacturing the heating inductor using MICROFUSION techniques, as well as the optimization, copying or improvement steps of such inductors.
Figure 2. - Represents an example of the two-dimensional plane defined in the first step of the present invention.
Figure 3. - Represents the plane in three dimensions defined in the second step of the present invention.
Figure 4. - Shows the inductor made by deposition techniques of thin layers of wax, as defined herein.
Figure 5. - Shows the mould before being introduced into the centrifugal MICROFUSION oven.
Figure 6. - Shows the inductor for heating induction when fully completed.
DESCRIPTION OF AN EMBODIMENT EXAMPLE OF THE INVENTION
[0013] The description of an example for manufacturing an inductor by the method described by the invention will be made below.
[0014] Through the plane of Figure 2 the physical characteristics of the inductor to be manufactured are represented. These physical characteristics are the dimensions of the inductor, electrical connections (1) and cooling connections (2). In said plane all views that define the inductor are represented, so that the inductor is perfectly defined. Thus all the necessary data to generate the three-dimensional representation of the inductor are provided, Figure 3. In this three-dimensional representation the electrical connections (1), Cooling connections (2), the blast nozzles (3), the internal parts (4), body (5) and external parts (6) of the inductor are also represented, as well as the inductor dimensions.
[0015] After generating the plane in three dimensions, the layer printer reproduces the model layers in three dimensions by depositing thin layers of wax with at least two types of waxes with different melting temperatures, Figure 4. These layers define the first, second and third spaces that corresponds to the internal (4), body (5) and external (6) spaces of the inductor, respectively.
[0016] To perform the first space of the inductor the wax (8) with the lowest melting point is used, whereas for performing the second space of the inductor the wax (9) with the highest melting temperature is used.
[0017] Then, the first space of the inductor is emptied by subjecting the inductor to a temperature above the melting temperature of the wax with the lowest melting temperature (8) and below the melting temperature of the wax with the highest melting temperature (9), after which the wax with the lowest temperature is evacuated by gravity.
[0018] Subsequently, the first space of inductor is filled with a high-flow ceramic coating, wherein the drying process is carried out by introducing thereof in an oven under controlled temperature and humidity.
[0019] Then the inductor is introduced in a mould composed of two parts (11, 12), Figure 5, in order to facilitate the introduction of the inductor in the mould, and an upper hole (10) to facilitate the entry of both the coatings and alloy. Said mould having dimensions 25 mm higher than the external dimensions of the inductor. The mould containing the inductor with a high flow coating is filled, after which it is introduced in an oven under controlled temperature and humidity for drying the ceramic coating.
[0020] Some connections are made between the coating of the first space of the inductor and the coating of the external mould containing the inductor, and then the coating is dried.
[0021] The oven temperature is Increased to above the melting point of the wax with the highest (9) melting temperature and making up the body of the inductor, and then the wax is extracted in a vacuum oven, such that the second space of the inductor is emptied.
1. Method for manufacturing inductors for induction heating using microfusion techniques,
characterized in that it comprises the following steps:
(1) generating at least one plane in two dimensions with the physical characteristics that make up the heating inductor to be manufactured,
(2) generating at least one plane in three dimensions with the physical characteristics of the inductor and wherein, in addition to electrical (1) and cooling (2) connections, three areas are defined:
- first space: internal parts (4) of the inductor, second space: body (5) of the inductor,
- third space: external parts (6) of the inductor,
(3) performing a three-dimensional model of the inductor by means of deposition of thin wax layers (8.9) that make up the physical characteristics of the inductor generated by the plane in three dimensions
(4) emptying the first space of the Inductor, then fill it with a specific coating, and then drying the coating,
(4.1) introducing the model in three dimensions in a mould with larger dimensions than the exterior dimensions of the Inductor, and filling the mould containing the inductor with a defined coating,
(4.2) performing some connections between the coating of the first space of the inductor and the coating of the outer mould containing the inductor, and then drying the coating,
(4.3) emptying the second space of the inductor,
(4.4) filling said second space of the inductor with a particular alloy, and drying said alloy, and
(5) removing the mould.
2. Method for manufacturing inductors for induction heating using microfusion techniques,
according to claim 1, characterized in that in order to make the internal part of the inductor and the body of the inductor,
at least two waxes (8, 9) with different melting temperatures are used.
3. Method for manufacturing inductors for induction heating using microfusion techniques,
according to claim 2, characterized in that, for making the first space of the inductor, the wax (8) with the lowest melting
temperature is used.
4. Method for manufacturing inductors for Induction heating using microfusion techniques,
according to claim 3, characterized in that, for making the second space of inductor, the wax (9) with highest melting temperature
is used.
5. Method for manufacturing inductors for induction heating using microfusion techniques,
according to claim 4, characterized in that the emptying of the first space is carried out by subjecting the inductor to a temperature
above the melting temperature of the wax with the lowest melting temperature (8) and
below the melting temperature of the wax with the highest melting temperature (9),
after which the wax with lowest temperature is evacuated by gravity.
6. Method for manufacturing inductors for Induction heating using microfusion techniques,
according to claim 5, characterized in that the first space of the inductor is filled by a high-flow ceramic coating, wherein
the drying process is carried out by introducing thereof in an oven under controlled
temperature and humidity.
7. Method for manufacturing inductors for induction heating using microfusion techniques,
according to claim 6, characterized in that the mould containing the inductor is filled by a high-flow ceramic coating, and then
placed in an oven under controlled temperature and humidity for drying the ceramic
coating.
8. Method for manufacturing inductors for induction heating using microfusion techniques,
according to claim 7, characterized in that the oven temperature is increased to above the melting point of the wax with the
highest (9) melting temperature and which makes up the body of the inductor, and then
the wax is extracted in a vacuum oven.
9. Method for manufacturing inductors for induction heating using microfusion techniques,
according to claim 8, characterized in that the mould is filled by a high-conductivity alloy by means of its introduction into
a microfusion oven with centrifugal motion.
10. Method for manufacturing inductors for induction heating using microfusion techniques,
according to claim 9, characterized in that the high-conductivity alloy preferably consists of 75% silver and 25% copper with
a maximum variation of these proportions preferably of 10% and more preferably of
5%.
11. Method for manufacturing inductors for induction heating using microfusion techniques,
according to claim 10, characterized in that in order to remove the ceramic part from the mould and extracting the inductor mechanical
and chemical methods are used.
12. Method for manufacturing inductors for induction heating using microfusion techniques,
according to claim 11, characterized in that in the chemical methods, pickling chemical agents are used.
13. Method for manufacturing inductors for induction heating using microfusion techniques,
according to claim 1, characterized in that the separation between the inductor and the mould from the exterior of the inductor
is between 0.1 mm and 500 mm, preferably between 1 mm and 50 mm and more preferably
between 20 mm and 30 mm.
14. Method for manufacturing inductors for induction heating using microfusion techniques,
according to claim 12, characterized in that the remaining parts defined in the ceramic mould are removed by a final machining
of the inductor, without interfering with the dimensions designed in the 3-dimensional
plane.