JP6787468B2 - Rotor core and its manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a rotor core constituting a motor and a method for manufacturing a motor core including a rotor core and a stator core constituting the motor.

In the automobile industry, development of higher output, lighter weight, and smaller drive motors is being promoted every day with the aim of further improving the running performance of hybrid vehicles and electric vehicles. In addition, home appliance manufacturers are also eager to develop motors built into various home appliances to further reduce their size and performance.

In order to improve the performance of the motor, how to reduce various losses generated inside the motor is an issue. For example, after electrical input, copper loss due to conductor resistance loss occurs in the coils that make up the motor, and iron loss (or high-frequency iron loss) occurs in the rotor and stator due to eddy current loss and hysteresis loss. The motor efficiency and torque performance will decrease according to these losses.

In manufacturing the stator core and the rotor core, the rotor core plate material and the stator core plate material are punched from the electromagnetic steel sheet, a plurality of rotor core plate materials are laminated, and the rotor core is manufactured by crimping or welding, and the plurality of stator core plate materials are laminated. However, the stator core is manufactured by crimping and welding.

In order to reduce the iron loss from the stator core and rotor core and improve the magnetic characteristics, both the stator core and rotor core are annealed at a predetermined temperature to remove machining strains such as presses, and annealing of semi-process materials is premised. A method of growing crystals that form both cores can be applied, as in the case of the material.

However, it is known that there is a trade-off that the magnetic properties are improved by growing the crystals of both the stator core and the rotor core by annealing, while the strength (tensile strength) of the core is lowered by the grain growth of the crystals. Has been done.

Since the iron loss of the stator core is low, the motor can be downsized and energy can be saved. On the other hand, since the rotor core is a member that rotates at high speed and exerts a strong centrifugal force during rotation, high strength that can withstand this strong external force is required. Therefore, it is difficult to say that annealing the rotor core is a preferable measure because it causes a decrease in strength. Therefore, a manufacturing method in which only the stator core is annealed and the rotor core is not annealed may be applied. However, the rotor core manufactured by this manufacturing method cannot be expected to improve the magnetic characteristics described above.

Here, in Patent Document 1, high magnetic flux density and high strength are achieved in the rotor material, and high magnetic flux density and low iron loss are achieved in the stator material while simultaneously collecting the rotor material and the stator material from the same steel sheet. A method for manufacturing a non-oriented electrical steel sheet having a high magnetic flux density to be obtained is disclosed. Specifically, it is a method of performing hot-rolled sheet annealing so that the crystal grain size is 50 μm or more and 500 μm or less in the production of a high magnetic flux density non-oriented electrical steel sheet whose steel sheet composition is defined by a predetermined mass ratio. ..

Japanese Unexamined Patent Publication No. 2004-27011

In the manufacturing method disclosed in Patent Document 1, since the hot-rolled sheet is annealed on the high magnetic flux density non-oriented electrical steel sheet, both the steel sheet for the stator core and the steel sheet for the rotor core are annealed. Therefore, in the steel sheet for the rotor core, the improvement of the magnetic characteristics can be expected as described above, but there is a concern that the strength is lowered.

The present invention has been made in view of the above problems, and a method for manufacturing a rotor core capable of manufacturing a rotor core having excellent magnetic characteristics and high strength, and a stator core having excellent magnetic characteristics in addition to the rotor core An object of the present invention is to provide a method for manufacturing a motor core that can be manufactured.

In order to achieve the above object, the method for manufacturing a rotor core according to the present invention is a method for manufacturing a rotor core that constitutes a rotor of a motor, in which a plate material for the rotor core is punched from an electromagnetic steel sheet, and a plurality of the plate materials for the rotor core are laminated. In the first step of manufacturing the rotor core precursor, a temperature difference at the time of annealing is provided between the outer peripheral side region and the inner peripheral side region of the rotor core precursor, and the outer peripheral side region is annealed at the temperature at which the crystal of the electromagnetic steel sheet grows. However, the inner peripheral side region comprises a second step of manufacturing a rotor core by annealing at a temperature at which the crystals of the electrical steel sheet do not grow.

In the method for manufacturing a rotor core of the present invention, an annealing is performed by providing a temperature difference at the time of annealing between the outer peripheral side region and the inner peripheral side region of the rotor core precursor with respect to the rotor core precursor in which a plurality of rotor core plate materials made of electromagnetic steel plates are laminated. It is characterized by manufacturing a rotor core. Specifically, the outer peripheral region is annealed at a temperature at which the crystals of the electrical steel sheet grow, and the inner peripheral region is annealed at a temperature at which the crystals of the electrical steel sheet do not grow.

Here, the "outer peripheral region" means, for example, an annular region on the outer circumference in a range from the circular outer peripheral contour line to the inside of a predetermined length in a circular rotor core in a plan view, and is referred to as an "inner peripheral region". Means a region on the center side of the rotor core other than the outer peripheral side region and the like.

The outer peripheral side region can define a range from the circular outer peripheral contour line of the stator core to about 5 mm, for example, where the iron loss is relatively large. Therefore, the iron loss of the rotor core can be effectively reduced by growing the crystals in the outer peripheral region to improve the magnetic characteristics.

On the other hand, the inner peripheral side region of the rotor core is a region having high strength (tensile strength) because the crystals are not grown, and the provision of this inner peripheral side region guarantees the high strength of the rotor core. it can.

Further, in another embodiment of the method for manufacturing a rotor core according to the present invention, in the second step, the temperature is such that the crystals of the electromagnetic steel sheet do not grow in the inner peripheral region, and the processing during the punching process is performed. Anneal at a temperature that removes strain.

Since the machining strain is introduced into the rotor core plate material to be machined during the punching process of the electrical steel sheet, the machining strain during the punching process is maintained at a temperature at which the crystals of the electrical steel sheet do not grow in the inner peripheral region. By annealing at the temperature at which it is removed, it is possible to eliminate the deterioration of the magnetic characteristics of the inner peripheral region due to the punching process.

Further, in another embodiment of the method for manufacturing a rotor core according to the present invention, in the second step, heat insulating materials are arranged at least on the upper surface and the lower surface of the rotor core precursor in the circumferential direction of the rotor core precursor. The rotor core precursor is placed in an annealing furnace with the extending side surface exposed to perform annealing.

In a state where heat insulating materials are arranged on the upper surface and the lower surface of the rotor core precursor and the side surfaces extending in the circumferential direction of the rotor core precursor are exposed, for example, only the side surface of the rotor core is exposed to the outside. When annealing is performed in this state, since the upper and lower surfaces of the rotor core are protected by a heat insulating material, only the side surface of the rotor core is directly heated to raise the temperature, and heat is gradually transferred from the side surface to the inside of the rotor core.

By terminating the annealing at the stage where the outer peripheral region of the rotor core precursor is heated to a predetermined temperature and annealed, the crystals of the electrical steel sheet in the outer peripheral region can be grown as desired, and the rotor core precursor can be grown. It is possible to suppress the grain growth of crystals of the electromagnetic steel sheet in the inner peripheral region.

The upper and lower surfaces of the rotor core precursor are covered by the heat insulating material only on the upper and lower surfaces corresponding to the inner peripheral side region of the rotor core precursor, in addition to covering the entire upper and lower surfaces of the rotor core precursor with the heat insulating material. May be covered with a heat insulating material.

Further, in another embodiment of the method for manufacturing a rotor core according to the present invention, in the second step, a moving space in which the rotor core precursor rolls and moves is provided, and a heating device is arranged around the moving space. An internal mobile annealing furnace is used, and heating is executed from the side surface of the rotor core precursor in a process in which the rotor core precursor rolls and moves in the moving space under the operation of the heating device to perform annealing.

Using an internally mobile annealing furnace equipped with a moving space in which the columnar rotor core precursor rolls and moves, the rotor core precursor is annealed by heating it from the side with a heating device while rolling and moving the rotor core precursor. Annealing of the outer peripheral region can be performed efficiently. As a method of rolling and moving the rotor core precursor, for example, an annular gear is attached to the rotor core precursor, and a long gear extending in the longitudinal direction of the moving space and sliding in the moving space is attached to the rotor core precursor. The rotor core precursor can be rolled and moved into the moving space by engaging the annular gear attached to the body and sliding the long gear.

A preheating zone and a high temperature heating zone are continuously provided in the internal mobile annealing furnace, and the entire rotor core precursor reaches a predetermined temperature in the process of rolling and moving the rotor core precursor in the preheating zone maintained at a relatively low temperature. A production method may be used in which preheating is performed, and then annealing is actively performed from the side surface of the rotor core precursor in the process of rolling and moving the rotor core precursor through the high temperature heating zone to promote the grain growth of crystals in the outer peripheral region.

The present invention also extends to a method of manufacturing a motor core composed of a rotor core constituting a rotor of a motor and a stator core constituting a stator, and this manufacturing method punches a plate material for a rotor core and a plate material for a stator core from an electromagnetic steel sheet. First step of laminating a plurality of the rotor core plate materials to produce a rotor core precursor, and laminating a plurality of the stator core plate materials to produce a stator core precursor, the outer peripheral side region and the inner circumference of the rotor core precursor. A temperature difference at the time of annealing is provided in the side region, the outer peripheral region is annealed at the temperature at which the grain of the electromagnetic steel sheet grows, and the inner peripheral region is annealed at the temperature at which the crystal of the electrical steel sheet does not grow to form the rotor core. It comprises the second step of manufacturing and annealing the precursor for the stator core to manufacture the stator core.

The method for manufacturing a motor core of the present invention is a method for manufacturing both a rotor core and a stator core (both are collectively referred to as a motor core) constituting a motor, and the rotor core is manufactured by a method common to the above-mentioned method for manufacturing a rotor core. It is characterized by points.

By punching the rotor core plate material and the stator core plate material from the common electromagnetic steel plate, the waste portion of the electromagnetic steel plate can be reduced as much as possible, and the material yield can be improved.

In the second step, the entire stator core precursor is annealed at a temperature at which crystals grow to improve the magnetic properties.

Since the rotor core manufactured by the manufacturing method of the present invention has excellent magnetic characteristics and high strength, and the manufactured stator core also has excellent magnetic characteristics, these motor cores are excellent in performance. Used for manufacturing.

Further, also in the method for manufacturing a motor core according to the present invention, as another embodiment of the manufacturing method, in the second step, at a temperature at which crystals of the electromagnetic steel plate do not grow in the inner peripheral region of the rotor core precursor. There is also a form of annealing at a temperature at which processing strain during the punching process is removed.

Further, in another embodiment of the method for manufacturing a motor core according to the present invention, in the second step, heat insulating materials are arranged at least on the upper surface and the lower surface of the rotor core precursor, and in the circumferential direction of the rotor core precursor. The rotor core precursor is placed in an annealing furnace with the extending side surface exposed, and the stator core precursor is also placed in the annealing furnace to annealing both precursors.

For example, by arranging the rotor core precursor inside the stator core precursor, placing both core precursors in a common annealing furnace, and annealing both core precursors at the same time, annealing is as small as possible. Annealing can be performed efficiently while using the furnace.

Further, in another embodiment of the method for manufacturing a motor core according to the present invention, in the second step, a moving space in which the rotor core precursor rolls and moves is provided, and a heating device is arranged around the moving space. Using an internally mobile annealing furnace, heating is executed from the side surface of the rotor core precursor in the process of rolling and moving the rotor core precursor in the moving space under the operation of the heating device to perform annealing, and the stator core precursor is subjected to the annealing. The body is annealed by placing it in a separate annealing furnace.

By rolling and moving the rotor core precursor into the moving space of the internal mobile annealing furnace and continuously directly heating the side surface of the rotor core precursor with a heating device around the moving space, the side surface (outer peripheral side) of the rotor core precursor is heated. Annealing from the area) can be performed efficiently. On the other hand, the stator core precursor is placed in a separate annealing furnace and annealed so that crystals grow as a whole, whereby a stator core having excellent magnetic characteristics is produced.

As can be understood from the above description, according to the rotor core manufacturing method and the motor core manufacturing method of the present invention, a temperature difference during annealing is provided between the outer peripheral side region and the inner peripheral side region of the rotor core precursor, and the outer peripheral side region is defined as the outer peripheral side region. By annealing at the temperature at which the grains of the electrical steel sheet grow and the inner peripheral region is annealed at the temperature at which the crystal of the electrical steel sheet does not grow, it is possible to manufacture a rotor core with excellent magnetic characteristics and high strength. Furthermore, a motor core provided with such a rotor core can be manufactured.

It is a schematic diagram explaining the first step of the manufacturing method of the rotor core of this invention. It is a schematic diagram explaining the first step of the manufacturing method following FIG. It is a schematic diagram explaining Embodiment 1 of the 2nd step of the manufacturing method of a rotor core. It is a figure explaining the heating control flow of the outer peripheral side region and the inner peripheral side region of a rotor core precursor at the time of annealing. It is a schematic diagram explaining Embodiment 2 of the 2nd step of the manufacturing method of a rotor core. It is a perspective view of the manufactured rotor core. It is a schematic diagram explaining the first step of the manufacturing method of the motor core of this invention. FIG. 7 is a schematic view illustrating the first step of the manufacturing method following FIG. 7. It is a schematic diagram explaining the second step of the manufacturing method of a motor core. It is a figure explaining the heating control flow of the stator core precursor, the outer peripheral side region and the inner peripheral side region of a rotor core precursor at the time of annealing. It is a perspective view of the manufactured motor core. It is a figure which showed the experimental result which specifies the relationship between the annealing temperature and the strength of a rotor core after annealing. It is a figure which showed the experimental result which identifies the relationship between the annealing temperature and the iron loss of a rotor core after annealing. It is a figure which showed the experimental result about iron loss and strength of an Example and a comparative example.

Hereinafter, embodiments of the rotor core manufacturing method and the motor core manufacturing method of the present invention will be described with reference to the drawings.

(Embodiment of a method for manufacturing a rotor core)
1 and 2 are schematic views illustrating the first step of the rotor core manufacturing method of the present invention in order, and FIG. 3 is a schematic diagram illustrating the first embodiment of the second step of the rotor core manufacturing method. FIG. 4 is a diagram illustrating a heating control flow of the outer peripheral side region and the inner peripheral side region of the rotor core precursor at the time of annealing. Further, FIG. 5 is a schematic view illustrating the second embodiment of the second step of the rotor core manufacturing method.

First, as shown in FIG. 1, a plurality of plate materials 1 for rotor cores are manufactured by punching a wide range of electromagnetic steel plates S into a disk shape having a predetermined diameter with a press machine (not shown) or the like. The electromagnetic steel sheet S includes an electromagnetic steel sheet in which the average particle size of the crystals forming the electromagnetic steel sheet is in the range of about 20 to 30 μm, which is a so-called fine grain material, and the average particle size of the crystals is 50 μm. The above-mentioned so-called normal particle size material can be applied.

Next, as shown in FIG. 2, the manufactured plurality of rotor core plate members 1 are laminated, and the rotor core precursor 10'is manufactured by caulking, welding, or the like.

Here, the rotor core precursor 10'has a columnar shape, and has a side surface 10'd, an upper surface 10'e, and a lower surface 10'f extending in the circumferential direction. Further, it is provided with a magnet slot according to the number of magnetic poles, and the illustrated example is a form in which one magnetic pole is formed by three permanent magnets (not shown), and two magnet slots in the shape of a C in a plan view. 10'a and one magnet slot 10'b in which the longitudinal direction is arranged in the circumferential direction are opened between them. However, there are various forms of magnet slots, such as a form in which one magnetic pole is composed of permanent magnets arranged in one magnet slot 10'b, or two magnets in which one magnetic pole is in the shape of a C. It may be in the form of a permanent magnet arranged in the slot 10'a. Further, a shaft slot 10'c is provided at the center position of the rotor core precursor 10'. The magnet slots 10'a and 10'b and the shaft slot 10'c may be provided for each rotor core plate material 1 before laminating, or each rotor core plate material 1 may be laminated. Later, it may be opened from the upper surface 10'e to the lower surface 10'f (the above is the first step).

In contrast to the rotor core precursor 10'manufactured in the first step, in the second step, the rotor core is annealed by providing a temperature difference at the time of annealing between the outer peripheral side region and the inner peripheral side region of the rotor core precursor 10'. To do. This second step will be described with reference to FIGS. 3, 4, and 5.

First, the first embodiment of the second step will be described with reference to FIGS. 3 and 4. As shown in FIG. 3, the heat insulating material I is arranged on the upper surface 10'e and the lower surface 10'f of the rotor core precursor 10', and the side surface 10'd extending in the circumferential direction of the rotor core precursor 10'is exposed to the outside. This is placed in the annealing furnace K1 in which the heating device H is built.

By operating the heating device H, heating is performed from the side surface 10'd of the rotor core precursor 10'in the annealing furnace K1 (X direction).

That is, in the annealing furnace K1, the heat input from the upper surface 10'e and the lower surface 10'f of the rotor core precursor 10'is suppressed by the heat insulating material I, while the heat input from the side surface 10'd exposed to the outside is suppressed. Is actively performed. Therefore, in the rotor core precursor 10', annealing from the side surface 10'd proceeds.

In this annealing process, the heating control flow of the outer peripheral side region and the inner peripheral side region of the rotor core precursor shown in FIG. 4 is executed.

In FIG. 4, the temperature T1 indicates the upper limit of the temperature range in which the crystals forming the electromagnetic steel plate grow, the temperature T2 indicates the upper limit of the temperature range in which the crystals do not grow, and the temperature T3 indicates the electromagnetic steel plate. The lower limit value of the temperature range which can remove the machining strain introduced into the rotor core plate material 1 at the time of punching from S is shown.

In the annealing process, the outer peripheral region of the rotor core precursor 10'is heated to a temperature T1 at time t1 and annealed at a temperature T1 for a predetermined time until time t2. On the other hand, the inner peripheral region of the rotor core precursor 10'is annealed while gradually increasing the temperature so as to reach the temperature T2 at time t2. Then, the heating is finished at the stage of time t2, and the control for cooling the annealing furnace K1 is executed (the above is the first embodiment of the second step).

Here, the outer peripheral side region of the rotor core precursor 10'is a range in which the magnetic characteristics of the finally manufactured rotor core are significantly reduced due to iron loss, for example, an annular range 5 mm inward from the side surface 10'd. Can be defined as the outer peripheral region. On the other hand, the inner peripheral side region of the rotor core precursor 10'is an inner region excluding the outer peripheral side region of the rotor core precursor 10'.

Next, the second embodiment of the second step will be described with reference to FIG. In this embodiment, as shown in FIG. 5, an internal mobile annealing furnace K2 is used, which includes a moving space MS in which the rotor core precursor 10'rolls and moves, and heating devices H are arranged on the left and right sides of the moving space MS. To do.

In the internally movable annealing furnace K2, a preheating zone YZ, a high temperature heating zone HZ, and a cooling zone CZ are continuously provided, and a long gear G2 that slides in the moving space MS is further arranged. A heat insulating material I is attached to the upper and lower surfaces of the rotor core precursor 10', and an annular gear G1 is attached to one of the heat insulating materials I, and the gears G1 and G2 are meshed with each other. By sliding the long gear G2 with a drive unit (not shown) (Z direction), the rotor core precursor 10'rotates through the gear G1 (Y1 direction) and moves in the moving space MS at a high temperature from the preheating zone YZ. It can advance to the heating zone HZ and further to the cooling zone CZ (Y2 direction). First, the entire rotor core precursor 10'is preheated to a predetermined temperature in the process of moving the rotor core precursor 10'while rolling (Y1 direction) (Y2 direction) in the preheating zone YZ held at a relatively low temperature. Since the rotor core precursor 10'has a columnar shape and only the side surface 10'd is exposed to the heating device H, the side surface 10'd of the rotor core precursor 10'is directly heated (in the X direction). ) Therefore, heat input proceeds from the side surface 10'd of the rotor core precursor 10'.

Next, the preheated rotor core precursor 10'enters the high temperature heating zone HZ. For example, a halogen heater can be applied to the heating device H in the high temperature heating zone HZ, and heating at a higher temperature than the preheating zone YZ is executed. In the high temperature heating zone HZ, annealing of the outer peripheral side region of the rotor core precursor 10'progresses by receiving heat from the side surface 10'd of the rotor core precursor 10'where heat higher than that of the preheating zone YZ rotates. After the rotor core precursor 10'is annealed in the high temperature heating zone HZ, the rotor core precursor 10'moves to the cooling zone CZ, where cooling takes place. The heating control shown in FIG. 4 is also executed in the second step shown in FIG. 5 (the above is the second embodiment of the second step).

As described above, the rotor core 10 shown in FIG. 6 is manufactured by the manufacturing method according to the first embodiment and the second embodiment of the first step and the second step. Here, the rotor core 10 includes slots 10a and 10b for magnets and slots 10c for shafts, and crystals grow in the outer peripheral side region 10A where crystals grow in a predetermined width w range from the side surface 10d and inside the outer peripheral region 10A. It is provided with a non-inner peripheral region 10B.

In the outer peripheral side region 10A, the magnetic characteristics are high due to the grain growth of the crystals, and it is possible to effectively reduce the iron loss. Further, in the inner peripheral side region 10B, since the crystals are not grown, the strength (tensile strength) is high. Therefore, the rotor core 10 is a core having excellent magnetic characteristics and high strength.

(Embodiment of Manufacturing Method of Motor Core)
7 and 8 are schematic views illustrating the first step of the motor core manufacturing method of the present invention in order, FIG. 9 is a schematic diagram illustrating the second step of the motor core manufacturing method, and FIG. 10 is annealing. It is a figure explaining the heating control flow of the stator core precursor, the outer peripheral side region and the inner peripheral side region of a rotor core precursor at time.

First, as shown in FIG. 7, a predetermined set of the stator core plate 2 and the rotor core plate are formed by punching a plurality of sets of the stator core plate 2 and the rotor core plate 1 from the inner region of the electromagnetic steel plate S as a set. 1 is manufactured. By punching the rotor core plate 1 from the stator core plate 2 and the region inside the stator core 2 in this way, the discarded portion of the electromagnetic steel plate S can be reduced as much as possible, and the material yield can be increased.

Next, as shown in FIG. 8, a plurality of manufactured rotor core plate materials 1 are laminated to produce a rotor core precursor 10'by crimping, welding, or the like, and similarly, a plurality of produced stator core plate materials 2 are produced. The stator core precursor 20'is manufactured by laminating and crimping, welding, or the like (the above is the first step).

Next, as shown in FIG. 9, regarding the rotor core precursor 10', the heat insulating material I is arranged on the upper surface 10'e and the lower surface 10'f of the rotor core precursor 10', as in FIG. It is placed in the annealing furnace K1 in which the heating device H is built in the state of being arranged inside the stator core precursor 20'. In this way, since the rotor core precursor 10'is arranged inside the stator core precursor 20'and both are annealed at the same time, the annealing furnace K1 can be made as small as possible and annealed efficiently. Can be done.

Here, the stator core precursor 20'is not provided with a heat insulating material in order to promote annealing as a whole. The stator core precursor 20'is placed on the pedestal D in order to adjust the heights of the rotor core precursor 10'and the stator core precursor 20'.

By operating the heating device H, the stator core precursor 20'is heated from the upper surface and the side surface thereof (in the X direction) in the annealing furnace K1, and the rotor core precursor 10'creates a space between the stator core precursor 20' and the stator core precursor 20'. It is heated from the side surface 10'd through (X direction).

Therefore, in the annealing furnace K1, the heat input from the upper surface 10'e and the lower surface 10'f of the rotor core precursor 10'is suppressed by the heat insulating material I, while the heat input from the side surface 10'd exposed to the outside is suppressed. The stator core precursor 20'is actively subjected to heat input from the side surface and the upper surface exposed to the outside, and annealing proceeds respectively.

In this annealing process, the heating control flow of the stator core precursor, the rotor core precursor's outer peripheral region and the inner peripheral region shown in FIG. 10 is executed.

In FIG. 10, the temperature T1 indicates the upper limit of the temperature range in which the crystals forming the electromagnetic steel plate grow, the temperature T2 indicates the upper limit of the temperature range in which the crystals do not grow, and the temperature T3 indicates the electromagnetic steel plate. The lower limit value of the temperature range which can remove the machining strain introduced into the rotor core plate material 1 at the time of punching from S is shown.

In the annealing process, the outer peripheral region of the rotor core precursor 10'is heated to a temperature T1 at time t1 and annealed at a temperature T1 for a predetermined time until time t2, and the inner circumference of the rotor core precursor 10'is executed. The side region is annealed while gradually increasing the temperature so that the temperature reaches T2 at time t2. Further, the stator core precursor 20'executes heating control in which the temperature rises to the temperature T1 at a time t3 earlier than the time t1 and annealing is performed at the temperature T1 for a predetermined time until the time t2. Then, the heating is finished at the stage of time t2, and the control for cooling the annealing furnace K1 is executed (the above is the second step).

As described above, as shown in FIG. 11, the motor core 30 including the rotor core 10 and the stator core 20 is manufactured by the manufacturing method according to the first step and the second step.

Here, as shown in FIG. 6, the rotor core 10 includes slots 10a and 10b for magnets and slots 10c for shafts, and in the outer peripheral side region 10A and the inside thereof where crystals are grown in a predetermined width w range from the side surface 10d. It has an inner peripheral region 10B in which crystals are not grown. The outer peripheral side region 10A imparts high magnetic properties, and the inner peripheral side region 10B guarantees high strength.

On the other hand, the stator core 20 has high magnetic characteristics due to the grain growth of the entire crystal, and is a core with reduced iron loss.

Therefore, the rotor core 10 having excellent magnetic characteristics and high strength can be manufactured, and further, the stator core 20 having excellent magnetic characteristics can be manufactured.

Also in the second step of this motor core manufacturing method, the internally mobile annealing furnace K2 shown in FIG. 5 is used for annealing the rotor core precursor 10', and FIG. 9 is used for annealing the stator core precursor 20'. There is also a method of using the annealing furnace K1 shown.

(Experiments and results that verified the strength and iron loss of the rotor core)
The present inventors have manufactured a rotor core by the production method of the present invention (Example), an unannealed rotor core test specimen (Comparative Example 1), and an entire rotor core annealed at 750 ° C. (Comparative Example). In order to estimate the characteristics of the test piece (Comparative Example 3) in which the entire 2) and the rotor core were annealed at 850 ° C., a test piece was cut out from the steel plate of the material and subjected to the same heat treatment as the rotor core for the test. In the test piece of the example, in a rotor core having a diameter of 150 mm in a plan view, an annular range of 5 mm from the outer circumference thereof was set as an outer peripheral side region, the inner side thereof was set as an inner peripheral side region, and the outer peripheral side region was annealed at 800 to 850 ° C. The inner peripheral region was annealed at 650 to 750 ° C. and simulated. All of the test pieces are rotor core plate materials obtained by punching out electromagnetic steel plates, and use fine-grained materials having an average particle size of less than 50 μm. Here, it is known that the grain growth of the crystal of the electrical steel sheet is not performed in the temperature range of 750 ° C. or lower, and the machining strain during punching is removed in the temperature range of 650 ° C. or higher. In this experiment, regarding the strength of the test piece, a tensile test piece was prepared from fine-grained materials having different annealing temperatures, and the yield strength when a tensile test was performed by a tensile tester was measured. Further, the iron loss test is similarly measured with a measuring test piece cut out from fine-grained materials having different annealing temperatures.

In this experiment, the strength and iron loss of the above Examples and Comparative Examples 1 to 3 were verified, and when a rotor core precursor was produced and the rotor core precursor was annealed, the annealing temperature was variously changed and each annealing was performed. Experiments were conducted to measure the yield strength and iron loss of the material after annealing at temperature. The experimental results on the annealing temperature and the yield strength (Yp) of the material are shown in FIG. 12, and the experimental results on the annealing temperature and the iron loss of the rotor core are shown in FIG. The numerical values on the vertical axis of FIG. 12 indicate the amount of decrease in the yield strength after annealing from the yield strength of the rotor core before annealing with the fine-grained material. The strength shown by the dotted line in FIG. 12 indicates the yield strength of the normal particle size material. Further, the numerical values on the vertical axis of FIG. 13 indicate the result of iron loss before annealing of the rotor core by the fine-grained material as 100, and the iron loss after annealing of the rotor core by the fine-grained material as a ratio to this 100.

From FIG. 12, it has been demonstrated that the strength after annealing changes significantly with the annealing temperature of 750 ° C. as a boundary, and more specifically, the strength of the rotor core significantly decreases in the range of annealing temperature of 750 ° C. or higher. Therefore, when focusing only on the strength of the rotor core, it is preferable to adjust the annealing temperature to a temperature lower than 750 ° C.

Here, the applicable range of the examples is shown in the figure. In the rotor core according to the embodiment, the outer peripheral side region is annealed at 800 to 850 ° C., and the inner peripheral side region is annealed at 650 to 750 ° C. In the rotor core according to the embodiment, a high strength of the rotor core can be guaranteed by providing a temperature difference between the outer peripheral side region and the inner peripheral side region and annealing the inner peripheral side region at a temperature lower than 750 ° C.

Further, as shown in FIG. 13, as for the iron loss after annealing, the iron loss after annealing changes significantly with the annealing temperature of 750 ° C as a boundary, and more specifically, the iron loss of the rotor core changes in the range of the annealing temperature of 750 ° C or higher. It has been proven to be significantly reduced. Therefore, when focusing only on the iron loss of the rotor core, it is preferable to adjust the annealing temperature to a temperature higher than 750 ° C.

In the rotor core according to the embodiment, a temperature difference is provided between the outer peripheral side region and the inner peripheral side region, and the outer peripheral side region is annealed at a temperature higher than 750 ° C., thereby guaranteeing excellent magnetic characteristics with a high iron loss reduction effect. can do.

FIG. 14 is a diagram showing experimental results regarding rotor iron loss and strength of Examples and Comparative Examples 1 to 3. In the figure, strength ⊚ indicates that the amount of decrease in yield strength from before annealing in FIG. 12 is about 0 MPa to 20 MPa, strength ◯ indicates about 20 MPa to 40 MPa, and strength Δ indicates yield exceeding 40 MPa. It shows the amount of decrease in strength.

From FIG. 14, it is demonstrated that when Comparative Example 1 is set to 100, the iron loss is remarkably reduced to the same level (about 87) in Comparative Example 3 and Example in which the whole is annealed at 850 ° C. Further, regarding the strength, it can be seen that the examples have the same strength as that of Comparative Example 1 without annealing. That is, it has been demonstrated that a rotor core having excellent magnetic characteristics and high strength can be obtained by the manufacturing method of the present invention in which annealing is performed by providing a temperature difference between the outer peripheral side region and the inner peripheral side region.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and there are design changes and the like within a range not departing from the gist of the present invention. Also, they are included in the present invention.

1 ... Rotor core plate material, 2 ... Stator core plate material, 10 ... Rotor core, 10'... Rotor core precursor, 10A ... Outer peripheral side region, 10B ... Inner peripheral side region, 10a, 10'a, 10b, 10'b ... For magnets Slots, 10c, 10'c ... shaft slots, 10'd ... side surfaces, 10'e ... top surface, 10'f ... bottom surface, 20 ... stator cores, 20'... stator core precursors, 30 ... motor cores, S ... electrical steel sheets, K1 ... Annealing furnace, K2 ... Internally mobile annealing furnace, MS ... Moving space, H ... Heating device, I ... Insulation material, G1, G2 ... Gear

Claims (10)

A rotor core having a laminate of a plurality of rotor core plates.
The rotor core has an outer peripheral side region located on the outer peripheral side of the rotor core and an inner peripheral side region located on the inner peripheral side of the rotor core, and a magnet slot is provided on the outer peripheral side.
The outer peripheral side region is an annular range extending radially from the outer peripheral contour line of the rotor core to an arbitrary position between the outer peripheral contour line and the radial center portion of the magnet slot.
A rotor core in which the average particle size of the crystals in the outer peripheral region is larger than the average particle size of the crystals in the inner peripheral region. The rotor core according to claim 1, wherein the average particle size of the crystals in the outer peripheral region is 50 μm or more, and the average particle size of the crystals in the inner peripheral region is less than 50 μm. The rotor core according to claim 1 or 2, wherein the outer peripheral region is a surface layer of the rotor core. The rotor core according to any one of claims 1 to 3, wherein the yield strength of the inner peripheral region is 70 MPa or more and 120 MPa or less larger than the yield strength of the outer peripheral region. It is a method of manufacturing the rotor core that constitutes the rotor of the motor.
A plate material for a rotor core is punched from an electromagnetic steel plate, and a plurality of the plate materials for the rotor core are laminated to form an outer peripheral side region located on the outer peripheral side of the rotor core and an inner peripheral side region located on the inner peripheral side of the rotor core. The first step of manufacturing a rotor core precursor having a rotor core precursor provided with a magnet slot on the outer peripheral side.
A temperature difference during annealing is provided between the outer peripheral side region and the inner peripheral side region of the rotor core precursor, the outer peripheral side region is annealed at the temperature at which crystals of the electromagnetic steel sheet grow, and the inner peripheral side region is the electromagnetic steel plate. Consists of a second step in the production of the rotor core by annealing at a temperature at which the crystals do not grow.
A method for manufacturing a rotor core, wherein the outer peripheral side region is an annular range extending in the radial direction from the outer peripheral contour line of the rotor core to an arbitrary position between the outer peripheral contour line and the radial center portion of the magnet slot. .. The fifth step is to manufacture the rotor core in which the average particle size of the crystals in the outer peripheral region is 50 μm or more and the average particle size of the crystals in the inner peripheral region is less than 50 μm. How to make a rotor core. The method for manufacturing a rotor core according to claim 5 or 6, wherein the outer peripheral region is a surface layer of the rotor core. The method for producing a rotor core according to any one of claims 5 to 7, wherein in the second step, the rotor core precursor is annealed in an annealing furnace to produce the rotor core. The method for manufacturing a rotor core according to any one of claims 5 to 8, wherein in the second step, the outer peripheral region is annealed at a predetermined constant temperature for a predetermined constant time to produce the rotor core. In the second step, by annealing the rotor core precursor, the yield strength of the outer peripheral region is reduced by 110 MPa or more and 130 MPa or less from before annealing, and the yield strength of the inner peripheral region is reduced by 40 MPa or less from before annealing. The method for manufacturing a rotor core according to any one of claims 5 to 9.

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