JP4478384B2 - Iron core manufacturing method and apparatus suitable for the method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a manufacturing apparatus and a manufacturing method for a laminated iron core such as a motor and a transformer.
[0002]
[Prior art]
As a method of manufacturing laminated iron cores such as motors and transformers using electromagnetic steel sheets, the steel sheets are punched into unit iron cores, and a predetermined number of unit iron cores are laminated, and then bolted, caulked, welded, or adhesives are used. Generally, it is fixed using means such as varnish. After being fixed, the laminated iron core is subjected to processing such as incorporation of a winding coil, and used as an iron core for a transformer or a motor.
[0003]
When the laminated iron core is weakly bonded, if the unit iron core is unwound or if a gap is opened, the efficiency of coil winding work will be reduced, and in the case of a motor, it will cause noise and vibration. Need to stick.
[0004]
However, when fixing by bolting, it is necessary to provide a through-hole through which the bolt passes in the laminated iron core, and if a through-hole is provided in the laminated iron core, the magnetic properties of the laminated iron core will deteriorate. Similarly, when the laminated iron core is fixed by welding, the welded portion is thermally strained, and by caulking, the magnetic properties of the laminated iron core may be deteriorated by being machined during dowel formation.
[0005]
When fixing laminated iron cores using adhesives, magnetic steel sheets are processed into iron core shapes, laminated and temporarily fixed with a clamp, etc. and then immersed in a bath containing adhesive or varnish, or liquid The adhesive or varnish is dripped from above and the adhesive or varnish is infiltrated into the gap between the steel sheets using capillary action, and then fixed by heating, etc., but the adhesive or varnish penetrates into the deep part of the gap. In particular, in the case of motor stators, only the outer peripheral edge of the iron core penetrated by the adhesive is fixed, the teeth on the inner peripheral side become free, and both ends of the laminate rise and are heated. In some cases, the viscosity of the adhesive or varnish is too low, and excess adhesive or varnish flows out, resulting in a decrease in fixing strength, or difficulty in processing the flowed-out adhesive.
In addition, since it takes time for the adhesive and varnish impregnation to be fixed after application, there is a problem that workability is low.
[0006]
In order to solve such problems, in Patent Document 1, when a laminated iron core is fully impregnated, an insulating curing agent or a curing agent and a curing accelerator are attached in advance to a steel sheet constituting the laminated iron core. A method of laminating and winding and then impregnating is disclosed. This is because when the laminated iron core is fixed by impregnation, the hardener is attached in advance to harden the impregnated resin, thereby preventing the adhesive from flowing out and firmly fixing the steel plates together. It also secures sex.
[0007]
[Patent Document 1]
JP-A-57-3560
[Problems to be solved by the invention]
However, even in this method, it is necessary to apply an adhesive to each steel sheet constituting the laminated iron core, and although the time until fixing can be shortened, the laminated iron core is processed after being processed into a unit iron core by punching or the like. It cannot be said that the problem that workability until fixing is low has been solved.
In general, devices that automatically supply adhesive are also commercially available, but the adhesive hardens at the supply port during a pause, so maintenance is complicated, and the amount of adhesive applied depends on the viscosity of the adhesive solution due to temperature. There was a problem that it fluctuated.
[0009]
The inventors of the present invention have found a method for obtaining a laminated iron core with good workability and an apparatus suitable for the method by solving the problems in the case of fixing the laminated iron core using such an adhesive. It has been reached.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the gist of the present invention comprises the following configurations.
(1) In a manufacturing method of a laminated iron core in which unit iron cores punched from a magnetic steel sheet into a predetermined shape are laminated and fixed to each other, a powder is formed during the iron core lamination after the unit iron core punching step. body exhaust port is provided on opposite sides of the adhesive supply unit, by contacting the powder adhesive supply the air flow containing the powder adhesive to the iron core surface, the surface of the unit iron core or the outer peripheral side and the inner, A method for producing a laminated iron core, wherein a powder adhesive is applied to both peripheral end faces.
(2) The method for producing a laminated iron core according to (1), wherein a powder adhesive having an average particle size of 5 to 100 μm is used in the particle size distribution of the powder.
(3) During lamination of unit iron cores, a thermosetting powder adhesive is applied from the surface of the laminated iron core or from both the outer peripheral side and inner peripheral side end surfaces, and the laminated iron core is heated to a predetermined temperature and pressurized. The method for producing a laminated iron core according to (1) or (2), wherein the laminated iron core is integrated.
(4) Immediately after the punching process, the thermosetting powder adhesive is applied to the surface of the unit iron core, the unit iron cores to which the thermosetting powder adhesive is adhered are laminated, and the laminated iron core is heated to a predetermined temperature. And the laminated iron core is integrated by pressurizing, The manufacturing method of the laminated iron core as described in said (1) or (2) characterized by the above-mentioned.
(5) The unit according to any one of (1) to (4), wherein the unit has two or more unit iron core laminated portions, and is continuously punched and fixed by replacing the laminated portions immediately after the predetermined number of layers are laminated. Manufacturing method of laminated iron core.
(6) The method for producing a laminated iron core according to any one of (1) to (5), wherein a side pressure is applied to the iron core from a direction perpendicular to the laminating direction when the unit iron cores are laminated.
[0011]
(7) A punching portion having a male punching die and a female punching die is provided, and a unit iron core laminated portion for laminating the punched unit iron cores is separately provided, and a powder adhesive is provided. Using a tribo-type electrostatic powder coating device, an exhaust port is provided on the opposite surface of the powder adhesive supply unit, and the air flow containing the powder adhesive from the powder adhesive supply unit contacts the iron core surface. An apparatus for producing a laminated iron core, comprising an adhesive supply unit that applies the steel sheet surface of the unit iron core, or both the outer peripheral side and the inner peripheral side end surface.
(8) The unit for manufacturing a laminated iron core according to (7), wherein the unit iron core laminated portion includes a pressurizing mechanism.
(9) The unit for producing a laminated iron core according to (7) or (8), wherein the unit iron core laminated part is provided with a pressurizing and heating mechanism.
(10) The apparatus comprises two or more unit iron core laminated portions, and is continuously punched and fixed by providing an exchange device that replaces the laminated portions immediately after a predetermined number of layers are laminated and a unit iron core discharging device. (7) The manufacturing apparatus of the laminated iron core in any one of (9).
(11) The laminated iron core manufacturing apparatus according to any one of (7) to (10), further including a damper mechanism that applies a lateral pressure to the iron core laminated on the unit iron core laminated portion.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, specific modes for carrying out the present invention will be described.
In the present invention, the electromagnetic steel sheet used for the laminated iron core may be a non-oriented electromagnetic steel sheet or a directional electromagnetic steel sheet, and a general steel sheet may be used as the electromagnetic steel sheet. Further, a high Si material, an amorphous alloy, or the like can be used, and is particularly suitable for use of a thin steel plate having a thickness of 0.10 to 0.35 mm. However, the material having a normal thickness is not limited.
[0013]
In the present invention, the processing of the unit iron core requires an apparatus for punching a steel sheet into a unit iron core shape by a punching die, and after processing into a unit iron core shape with a punching die of the punching part, When the unit iron cores are continuously laminated, the laminated iron core is fixed by applying a powder adhesive to the surface of the steel sheet or the laminated end face.
[0014]
The type of resin used in the present invention is not particularly limited, but acrylic resin adhesives, urethane resin adhesives, epoxy resin adhesives, phenol resin adhesives, nylon resin adhesives Various adhesives such as adhesives, polyester adhesives, polyurethane resin adhesives, modified olefin resin adhesives, synthetic rubber adhesives, vinyl chloride resin adhesives, and composite adhesives combining these adhesives can be used. . Further suitable are thermosetting organic resin-based adhesives that undergo a chemical reaction by heating, and specifically, one or more of epoxy resin, phenol resin, etc. as the main component. It is an adhesive. Further, a polyester resin, nylon resin, polyurethane resin, modified olefin resin, synthetic rubber, or the like added with a crosslinking agent to impart thermosetting property is also suitable. Moreover, you may use the inorganic adhesive which a dehydration condensation reaction advances by heating, and the normal temperature curing type inorganic adhesive which has calcium phosphate etc. as a main component. When heating is not preferred, it is possible to use a pressure curable adhesive encapsulated in a microcapsule or the like that breaks the curing agent under pressure.
[0015]
The adhesive used in the present invention must be a powder, and more preferably has a relatively small particle size with an average particle size of 5 to 100 μm in the particle size distribution of the powder. If the average particle size is less than 5 μm, the risk of clogging during powder feeding increases, and the cost during pulverization increases. If it exceeds 100 μm, the adhesion deteriorates when applied to a steel sheet.
[0016]
In the case of heating in the present invention, as heating means to be used, electric heating, induction heating, dielectric heating, electromagnetic wave irradiation, direct contact heating, etc. can be used, and although not particularly limited, direct contact heating by an electric heater has a structure. Simple and suitable. In the present invention, it is possible to quickly melt and heat cure the powder adhesive applied to the laminated iron core by installing the heating device in the laminated part and heating.
[0017]
Next, as a method of applying pressure to fix the iron core, a pressure punch is used in the present invention, but the pressure punch can be used also as a male die of a punching die. In this case, when the predetermined number of punches is reached, it is possible to apply a large pressure to the laminated iron core by making the male stroke larger than the normal punch stroke, thereby further increasing the fixing strength. it can. Moreover, in order to make the fixed laminated iron core stronger, after this step, it may be heated under pressure again.
[0018]
In the present invention, as a method of applying the powder adhesive, a method of applying the powder adhesive to the surface of the steel sheet one by one before lamination may be used, or a method of applying from the end face during the lamination may be used.
When applying the powder adhesive to each sheet on the surface of the steel sheet, by providing the male or female powder pneumatically device inside punching mold or inside the pressing punch, without reducing the workability It is possible to apply a powder adhesive.
[0019]
Furthermore, it is possible to make the powder adhere extremely thinly on the iron core surface by providing an exhaust port on the opposing surface of the powder adhesive supply section. That is, when airflow containing powder is blown onto the iron core surface, the airflow is smoothly rectified and contacted with the iron core surface by ensuring the escape path of the airflow, so that the powder adheres uniformly. Can do.
[0020]
In addition, when applying the powder adhesive from the end face, an extremely large effect can be obtained by providing an exhaust port on the opposite face. Conventionally, when the powder adhesive is applied from the laminated end face of the iron core, the ratio of the powder entering the gap between the iron cores is small and adhering to the laminated end face unnecessarily, but as disclosed in the present invention Moreover, it is possible to smoothly introduce the adhesive into the gap between the laminated iron cores by providing an exhaust port on the opposing surface of the powder supply unit.
[0021]
The shape of the exhaust port is not particularly limited, but if the spraying position changes as it is laminated, a slit-shaped exhaust port is preferable. It is preferable to provide the above exhaust ports.
It is also effective to generate a negative pressure at the site where the powder adhesive is applied to the laminated iron core by providing a sirocco fan or the like downstream of the exhaust port in order to smoothly guide the air flow containing powder to the exhaust port. This is particularly effective when the powder adhesive is applied from the laminated end face.
[0022]
As a conventional iron core fixing technique using an adhesive, it is common to use a liquid adhesive, but the laminated iron core of the present invention uses a powder adhesive to adhere to the steel sheet surface of the iron core. The laminated iron core is characterized by being heated and pressed.
[0023]
The apparatus for feeding the powder adhesive is not particularly limited, and a commercially available apparatus may be used. As a commercially available powder feeding apparatus, an electrostatic powder coating apparatus for powder coating is also suitable for the present invention. The corona method and the tribo method are known as electrostatic powder coating apparatuses, and either one may be used in the present invention, but the tribo method is simpler and more suitable.
In the present invention, it can be used in combination with other fixing methods. In the case of a motor stator, it is possible to fix the outer peripheral portion by caulking and fix each tooth on the inner periphery using an adhesive.
[0024]
In the present invention, when heating, a heat insulating member can be installed between the punching die and the heating device. The temperature required for curing the organic resin thermosetting powder adhesive is generally between 80 ° C. and 200 ° C., and in the case of inorganic adhesive, it is 100 ° C. to 700 ° C. Since very high accuracy is required, it is necessary to prevent heat from being transmitted to the heated portion by a heat insulating member so that the mold does not expand. The heat insulating member used here is desirably a material having high heat resistance such as ceramics, but is not particularly limited.
[0025]
In the present invention, when heating is required, the laminated iron core is heated to a predetermined temperature by a heating device installed adjacent to the laminated portion after or after the predetermined number of unit iron cores are laminated. At this time, it is possible to align the end surfaces of the laminated iron cores using a side pressure device provided with a damper mechanism from the side surfaces of the laminated unit iron cores in the middle of the lamination.
[0026]
Further, in the present invention, it is possible to further increase efficiency by providing two or more stacked portions and installing the stacked portion movable device so that these can be alternately disposed immediately after the punched portions. After lamination is completed or whenever a unit iron core is supplied, pressurization is performed with a pressure device, the powder adhesive is melted and cured, and the laminated unit iron cores are bonded in whole or in part to secure the iron core. It is something to be made. The arrangement of the laminated parts is not limited to a method of moving in the direction perpendicular to the steel sheet supply direction, but may be a rotating method in which a large number of laminated parts are arranged in a circle, or other methods may be used.
[0027]
Further, after laminating the unit iron cores, it is possible to move from a position immediately after the punched portion and then pressurize again with a pressurizing device to firmly fix the unit cores.
[0028]
In the present invention, the following configuration can be considered as an apparatus suitable for the iron core manufacturing method described above.
That is, a punching section having a male punching die and a female punching die is provided, and a unit iron core laminated portion for laminating the punched unit iron cores is provided separately, and the powder adhesive is punched as described above. By providing a powder supply unit that is applied to the surface or end face of the extracted unit iron core, the unit iron cores stacked can be integrated. Regarding the powder supply unit, a powder supply unit is provided in the unit iron core lamination part when applied to the end surface of the unit iron core lamination part, and in a punching part when partially applied to the surface of the unit iron core. It is possible.
[0029]
Further, when the unit iron core is firmly fixed, it is possible to provide a pressurizing mechanism in the unit iron core laminated portion. As a pressurizing mechanism, a press punch or a press punch can be used as a male die of a punching die. Furthermore, in the case of using a thermosetting powder adhesive, it is possible to provide a heating mechanism in the unit core laminated portion in addition to the above pressurization. As the heating mechanism, energization heating, induction heating, dielectric heating, electromagnetic wave irradiation, direct contact heating and the like can be considered.
[0030]
Furthermore, it is also possible to use a side pressure device equipped with a damper mechanism so that the end surfaces of the laminated iron cores can be aligned from the side surfaces of the laminated unit iron cores in the unit iron core laminated portion. It is. Moreover, in this invention, it is also possible to install a laminated part movable apparatus so that two or more laminated parts may be provided and these can be alternately arranged immediately after the punched part. As a result, the efficiency can be further increased.
[0031]
【Example】
Example 1
FIG. 1 shows an embodiment of the present invention. When unit iron cores punched in advance from a magnetic steel sheet hoop into a predetermined motor core shape are laminated one by one, a thermosetting powder is formed on the iron core surface. After apply | coating an adhesive agent, it laminates | stacks and the cross-sectional explanatory drawing of the state currently adhere | attached by heating-pressing is shown.
[0032]
In the figure, 1 is a unit iron core that has been punched from a magnetic steel sheet in advance, 2 is a guide that holds the unit iron core in a laminated state, and 3 is a moving claw that is hooked on the iron core when only one unit iron core is taken out from the lower part of the guide. 4 is a slide rail for moving the unit iron core, 5 is a pressure cylinder, 6 is an exhaust pipe, 7 is a sirocco fan, 8 is a unit iron core in the stack, 9 is a heat insulating member, 10 is a heating device, 11 Is a laminated iron core holder, 12 is a powder adhesive supply pipe, 13 is a powder electrostatic gun, 14 is a powder adhesive supply tank, 15 is a mounting base, and 16 is a motor for driving the moving claw 3.
[0033]
The unit core 1 is arranged for each direction in which the unit cores 1 are stacked when the unit core 1 is placed in the guide 2. The moving claw 3 takes out the unit cores 1 one by one from the lower part of the guide 2, moves on the slide rail 4, and sends the unit cores to the laminated core holder 11. The powder adhesive fed from the adhesive supply tank 14 is charged by the powder electrostatic gun 13 while the moving claw 3 is retracted to the initial position, and then is supplied from the supply pipe 12 onto the laminated iron core 8. Applied. At this time, the airflow when blown onto the laminated iron core 8 is exhausted from the exhaust pipe 6 to the outside of the apparatus by the sirocco fan 7. The laminated iron core to be fixed is separated by intermittently stopping the air feeding of the powder adhesive when the predetermined number of unit iron cores are laminated. As the layers are stacked, the cradle 11 is lowered, and the laminated iron core 8 is heated to a predetermined temperature by the heating device 10. At this time, the laminated iron core is fixed by being pressurized by the pressure cylinder 5.
[0034]
(Example 2)
FIG. 2 shows an embodiment of the present invention. When a magnetic steel sheet 21 is punched into a unit core shape of a motor core and the punched steel sheets are laminated to form a laminated core, a thermosetting powder is formed on the surface of the iron core. After apply | coating an adhesive agent, the cross-sectional explanatory drawing of the state fixed by heating and pressurizing, sticking the next iron core is shown.
[0035]
In the figure, 21 is a magnetic steel sheet (supply member), 22 is a male die for punching a guide hole when a unit iron core is punched from the supply member 21, 23 is a male die of an inner peripheral punching die, and 24 is a first stage outer periphery. A male die for punching die 25 is a female die for punching guide holes provided opposite to the die 22, 26 is a female die for inner peripheral punching corresponding to the die 23, and 27 is a die 24. A first-stage outer peripheral punching die female die 28 provided oppositely is a die base. Reference numeral 29 denotes a male die for punching the outer periphery of the unit iron core, which also serves as a pressure punch. Reference numeral 30 denotes a spring for adjusting the reduction force of the pressure punch. 31 shows a state immediately before the punched unit iron cores are stacked. Reference numeral 32 denotes an exhaust pipe provided for passing an air flow from the exhaust port to the outside of the mold, and reference numeral 33 denotes an outer peripheral punching female mold provided to face the male mold / pressure punch 29.
[0036]
A heating device 34 heats the laminated iron core 37 from the side surface, and is separated from the mold base 28 by a heat insulating member 35. Together with these and the male die combined pressure punch, a laminated portion is formed.
The adhesive supply device includes an adhesive supply tank 39, a powder adhesive supply pipe 37, and a powder electrostatic gun 38. With these, the powder adhesive is applied to the iron core surface.
[0037]
The electromagnetic steel sheet 21 in a coiled state is continuously fed into the apparatus of the present invention by a feeding device as a supply member. After the guide holes are provided by the guide hole punching dies 22 and 25, the inner peripheral side is punched by the male dies 23 and the female dies 26 of the punching dies. Next, the outer peripheral portion of a predetermined portion is punched out by the male die 24 and the female die 27 of the first stage outer peripheral punching die. Next, the steel plate 21 is punched into a unit iron core by the male die 29 and the female die 33 which are the second-stage outer peripheral punching die that also serves as a pressure punch, and the iron core is pushed into the female die 33 and laminated.
[0038]
After the male die 29 of the second-stage outer peripheral punching die also serving as a pressure punch rises, after the thermosetting powder adhesive fed from the adhesive supply tank is charged by the powder electrostatic gun 38 , And sprayed on the upper surface of the laminated iron core 36 through the supply pipe 37. Excess powder adhesive is discharged out of the mold from the exhaust pipe 32 together with the airflow. The laminated iron core 36 is heated from the side by the heating device 34 and is heated to a temperature of 160 ° C. at which the thermosetting powder adhesive is cured, and the laminated iron core is fixed.
[0039]
【The invention's effect】
According to the present invention, it is possible to continuously fix the iron core in the punching process of the laminated iron core using an adhesive and not the fixing using the conventional impregnation equipment. The core can be fixed, and the workability of the fixing process of the laminated iron core is greatly improved. Further, since a powder adhesive is used, handling is simple and maintenance is easy. Further, by providing an exhaust port, a thin and uniform coating is possible, so that a strong iron core can be produced with little uneven adhesion.
[Brief description of the drawings]
FIG. 1 shows a state in which unit iron cores obtained by punching electromagnetic steel sheets in a predetermined shape are coated and laminated on a steel sheet surface and laminated by heating and pressurizing each unit iron core.
[Fig. 2] A hoop-shaped non-oriented electrical steel sheet is punched into a unit iron core shape, and a powder adhesive is applied to the steel sheet surface for each unit iron core, and it is fixed by heating under pressure at the laminated part. Indicates the state.
[Explanation of symbols]
1: Unit iron core 2: Guide 3: Moving claw 4: Slide rail 5: Pressurizing cylinder 6: Exhaust pipe 7: Sirocco fan 8: Laminated iron core 9: Thermal insulation member 10: Heating device 11: Laminated iron core holder 12 : Powder adhesive supply pipe 13: Electrostatic gun 14: Powder adhesive supply tank 15: Mounting stand 16: Moving claw drive motor 21: Hoop-shaped electromagnetic steel plate 22: Male die 23 of guide hole punching die 23: Inside Male of peripheral punching die 24: Male die of first stage outer peripheral punching die 25: Female die of punching die for guide hole 26: Female die of inner peripheral punching die 27: Female of first peripheral punching die Mold 28: Mold base 29: Second-stage outer peripheral punching die combined pressure punch 30: Pressure punch spring 31: Unit iron core 32: Exhaust pipe 33: Second-stage outer peripheral punching die female die 34: Heating device 35: heat insulating member 36: laminated iron core 3 : Adhesive supply pipe 38: electrostatic powder gun 39: adhesive supply device

Claims (11)

  In a method for manufacturing a laminated iron core that is united by laminating and fixing unit iron cores punched into a predetermined shape from an electrical steel sheet, powder bonding is performed during the iron core lamination after the unit iron core punching process. By providing an exhaust port on the opposite surface of the agent supply unit and bringing the air flow containing the powder adhesive from the powder adhesive supply unit into contact with the iron core surface, the surface of the unit iron core, or the outer peripheral side and the inner peripheral side A method for producing a laminated iron core, wherein a powder adhesive is applied to both end faces.   The method for producing a laminated iron core according to claim 1, wherein a powder adhesive having an average particle size of 5 to 100 µm is used in the particle size distribution of the powder.   During the lamination of unit iron cores, a thermosetting powder adhesive is applied from the surface of the laminated iron core or from both the outer peripheral side and inner peripheral side end faces, and the laminated iron core is heated to a predetermined temperature and laminated by pressing. The method for producing a laminated iron core according to claim 1 or 2, wherein the iron core is integrated.   Immediately after the punching process, a thermosetting powder adhesive is applied to the surface of the unit iron core, the unit iron cores to which the thermosetting powder adhesive is adhered are laminated, and the laminated iron core is heated to a predetermined temperature to be applied. The method for producing a laminated iron core according to claim 1 or 2, wherein the laminated iron core is integrated by pressing.   5. The production of a laminated iron core according to claim 1, wherein the laminated iron core has two or more unit iron core laminated portions, and is continuously punched and fixed by replacing the laminated portions immediately after a predetermined number of layers are laminated. Method.   The method for producing a laminated iron core according to any one of claims 1 to 5, wherein a side pressure is applied to the iron core from a direction perpendicular to the laminating direction when the unit iron cores are laminated. A punching portion having a male punching die and a female punching die is provided, and a unit iron core laminated portion for laminating the punched unit iron cores is separately provided, and a powder adhesive is provided in a tribo type. Using an electrostatic powder coating device, and providing an exhaust port on the opposing surface of the powder adhesive supply unit, contacting the air flow containing the powder adhesive from the powder adhesive supply unit with the iron core surface, An apparatus for producing a laminated iron core, comprising an adhesive supply unit that applies to a steel sheet surface of a unit iron core, or both of an outer peripheral side and an inner peripheral side end face.   The apparatus for producing a laminated iron core according to claim 7, wherein the unit iron core laminated portion is provided with a pressurizing mechanism.   The apparatus for producing a laminated iron core according to claim 7 or 8, wherein the unit iron core laminated portion is provided with a pressurizing and heating mechanism.   8. The unit iron core laminating unit is provided with two or more, and a punching unit is continuously punched and fixed by including a replacement device that replaces the laminating unit immediately after a predetermined number of layers are stacked and a unit iron core discharging device. The manufacturing apparatus of the laminated iron core in any one of 9.   The apparatus for producing a laminated iron core according to any one of claims 7 to 10, further comprising a damper mechanism that applies a side pressure to the iron core laminated on the unit iron core laminated portion.

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