JP4816146B2 - Sheet-like rare earth bonded magnet, method of manufacturing the same, and motor using the same - Google Patents

Description

  The present invention relates to a sheet-like rare earth bonded magnet having a thin wall and polar orientation, a method for producing the same, and a motor using the magnet.

  Rare earth bonded magnets are produced using magnet powders typified by NdFeB-based alloys or SmFeN-based alloys. Unlike a sintered magnet produced by a sintering method, this bonded magnet includes a binder component such as a thermoplastic resin or a thermosetting resin. For this reason, although the magnetic properties of the magnet are lowered, there is almost no shrinkage seen in sintered magnets, and a specially shaped magnet such as an annular shape, arc shape or thin wall shape can be produced with high dimensional accuracy without cracking. Is a feature. For this reason, among the bonded magnets, a hollow cylindrical magnet has been widely used in home appliances, electrical equipment, and information motors.

  The production of bonded magnets is represented by methods such as injection molding, extrusion molding, and compression molding. Among them, compression molding is greatly different from injection molding and extrusion molding. One of the differences is the composition ratio of the resin composition for bonded magnets (consisting of magnet powder and binder component). The resin composition for bonded magnets used for compression molding does not require fluidity at the molding temperature at the time of molding unlike injection molding or extrusion molding. Therefore, the ratio of the magnet powder to the binder component can be increased. That is, it can be said that a compression-bonded bonded magnet generally has higher magnetic properties than a bonded magnet formed by injection molding or extrusion molding.

  In order to realize higher performance of equipment equipped with motors, motors are required to be smaller, lighter, higher output, and more efficient, and with this, bond magnets are required to further improve magnetic properties. Yes. As described above, as a means for improving the magnetic characteristics, a rare earth magnet is used as the magnet powder, and a compression molding is performed to form a bonded magnet. Among them, various studies have been made since a magnetic material having an anisotropic rare earth magnet powder in which the crystal orientation is oriented in one direction can obtain higher magnetic characteristics.

  Magnet powder in which the crystal orientation is oriented in one direction is obtained by the following process. First, what is formed by hot upsetting is formed by pulverizing a bulk body obtained by mechanical orientation. In the case of HDDR treatment (hydrogen decomposition / recombination), Nd—Fe (Co) —B alloy ingot added with elements such as Ga, Zr, Hf, etc. is heat-treated in hydrogen and phase decomposed at 650-1000 ° C. This is obtained by dehydrogenation and recombination. The meaning of the HDDR treatment is that Nd-0 (Fe, Co) -B phase is hydrogenated (Hydrogenation), phase decomposition (Decomposition) at 650 to 1000 ° C., dehydrogenation (Desorption), and recombination (Recombination). is there.

The case where a bonded magnet is formed using the anisotropic magnet powder produced by HDDR process is demonstrated. The magnet powder is mixed with a thermosetting resin such as an epoxy resin, and then filled into a cavity of a mold to perform compression molding. When the magnet powder is cracked or broken during densification by compression molding, the NdFeB crystals are newly exposed, and their structure changes and the permanent demagnetization increases during high temperature exposure. Has problems with thermal stability. For this reason, the anisotropic Nd—Fe—B magnet powder produced by HDDR treatment is mixed with an anisotropic Sm—Fe—N magnet powder having an average particle diameter of 1 to 5 μm, and bonded. It is known that thermal durability is improved by using a magnet resin composition. This is because the anisotropic Sm-Fe-N magnet powder having an average particle diameter of 1 to 5 μm is dispersed during compression molding, and the pressure applied to the anisotropic magnet powder produced by HDDR treatment is dispersed.
It is considered to suppress the occurrence of breakage of the anisotropic magnet powder produced by the treatment.

  An anisotropic bonded magnet has a feature that the orientation direction of the magnet can be controlled by a magnetic field applied during molding. Among them, in the pole-oriented magnet, NS poles appear on one surface of the magnet, and NS poles hardly appear on the opposite surface (back surface). On the other hand, NS poles appear so that the radially oriented magnets are paired on both sides of the magnet. It is known that a pole-oriented magnet has higher magnetic characteristics than a radially oriented magnet having the same shape.

  The pole-oriented magnet is formed by using a mold in which a magnet having a high energy product such as a sintered magnet is previously incorporated in the mold for generating an orientation magnetic field. The magnet to be incorporated is placed in either direction on the side of the mold cavity. Using the mold having such a configuration, molding is performed by filling the mold cavity with a resin composition for a bond magnet mainly composed of magnetic powder and a binder. In the obtained bonded magnet, the NS pole appears on the surface on the side of the orientation magnet arranged in the mold and becomes a pole orientation magnet.

  Conventionally, most of such pole-oriented magnets are formed of injection-molded bonded magnets or sintered magnets using ferrite magnetic powder. Recently, a method of forming a polar orientation magnet by injection molding even with rare earth magnet powder has been disclosed (for example, see Patent Document 1).

  Also, a sheet-like polar orientation magnet is disclosed in which the orientation of the magnet powder is controlled in the in-plane direction of the sheet, and a polar orientation magnet is formed after post-magnetization (see, for example, Patent Document 2).

Further, as a method for producing a sheet-like magnet, a method for producing a sheet-like rare earth bonded magnet in which a green sheet containing soft magnetic powder and a green sheet containing rare earth magnet powder are integrally formed is disclosed.
JP 2000-195714 A JP 2004-55992 A Japanese Patent Laid-Open No. 2003-318052

  In order to form a sheet-shaped magnet having good bendability, it is effective to increase the resin ratio of a binder or the like contained in the magnet component. However, as described in Patent Document 1, a resin composition at an injection molding level using a resin composition with high fluidity has a problem that the magnetic properties that can be obtained as a result of a high resin ratio are lowered.

  When a resin composition having a low resin amount, which is a feature of compression molding, is used, the flexibility component such as a thermoplastic resin is relatively lowered and the bendability is lowered. Further, for example, when a mixture of a magnetic powder having a large particle diameter of about 100 μm and a magnetic powder having a small particle diameter of about 1 μm is used, the problem is that the bendability is significantly reduced.

  The sheet-like rare earth bonded magnet of the present invention is characterized by having a pseudo two-layer structure by changing the resin amount and the magnetic powder mixing ratio in the thickness direction. As the amount of resin increases, the flexibility increases, but the magnetic characteristics deteriorate. Therefore, when the ring shape is formed later, it is desirable to arrange the side having a low resin amount and high magnetic characteristics on the stator core side.

The flexibility also changes by changing the mixing ratio of the magnetic powder. When magnetic powders having different particle diameters are mixed, flexibility decreases due to an increase in powders having a fine particle diameter. A relatively large amount of fine powder is effective because it has a higher apparent density and improved magnetic properties.

  When molding, it is desirable to first fill the one with higher density, and then fill the other resin composition and then perform compression molding, but this does not affect the effect.

  The flexibility also changes depending on the plate thickness of the sheet magnet, and the flexibility increases as the plate thickness decreases. For this reason, it became possible to make a part of the magnet thin and to improve flexibility without substantially reducing the apparent effective magnet volume. When the strength is reduced with respect to thinning a part, the strength is improved by integrating the resin sheet with the magnet.

  The pole-oriented sheet-like bonded magnet of the present invention can be obtained with high magnetic properties, flexibility and strength even in a thin state of 1 mm or less. By using this magnet, the motor can be reduced in size, weight, output, and efficiency.

  Hereinafter, embodiments of the invention will be described with reference to the drawings.

  As shown in FIG. 1A, the present invention provides a pole-oriented sheet magnet having a pseudo two-layer structure by changing the amount of resin and the mixing ratio of magnetic powder in the thickness direction.

  As rare earth magnet powder, magnetically anisotropic Nd—Fe—B alloy powder prepared by HDDR treatment (hydrogen decomposition / recombination), that is, hydrogenation of Nd—Fe (Co) —B alloy, 650 Use of those prepared by HDDR treatment that undergoes phase decomposition, dehydrogenation, and recombination at ˜1000 ° C., or Nd—Fe—B alloy powder prepared by hot upsetting (Die-Up-Setting) it can.

  On the other hand, anisotropic SmFeN-based fine powder formed by RD (oxidation reduction) treatment or magnet powder obtained by previously inactivating the surface of the powder can be used.

  The solid epoxy oligomer used for coating the rare earth magnet powder is dissolved in a solvent or the like, and is adjusted so that the coating thickness is 0.1 μm or less calculated from the specific surface area of the magnet powder.

  In addition, the rare earth magnet powder can be used alone, but two mixed systems are desirable from the viewpoint of thermal stability, and also have high flexibility by changing the mixing composition ratio in the thickness direction. .

  The binder used in the present invention contains at least a powdered resin component having a thermocompression bonding function and a thermosetting functional group, and the rare earth magnet powder is compressed before the compression molding by the adhesive force of the binder component as a resin composition for a bond magnet. It has a role to prevent mechanical separation from the binder, and the binder is at least an epoxy oligomer that is solid at room temperature, a thermocompression-bonding polyamide that is sticky at room temperature, and a powdery latent epoxy that is added as needed. It is desirable to comprise a curing agent.

  The process for forming the resin composition used in the present invention will be described.

  The rare earth magnet powder prepared by dissolving an epoxy oligomer in an organic solvent is wet mixed. Acetone was used as the organic solvent. Wet mixing was performed using a kneader. Thereafter, the wet mixture is heated at 60-80 ° C. to remove the solvent and dry. And the dry blocky mixture was crushed. For the NdFeB-based alloy powder subjected to HDDR, the powder particle size distribution before and after the epoxy coating is almost the same.

  Next, the rare earth magnet powder whose surface is coated with the epoxy oligomer, the polyamide resin, and the lubricant are dry mixed. When producing resin compositions for bonded magnets having different resin amounts, the amount of polyamide resin can be increased or decreased here for adjustment. When increasing the amount of resin, it is also possible to increase the amount of epoxy oligomer described above. Moreover, when using multiple types of rare earth magnet powders of different alloy systems, mixing at this point is desirable. Then, the mixture is kneaded by heating and kneaded to be further pulverized into granules. The granule is separated into particles having a large particle size in a classification step, and the separated large particle is further pulverized and classified repeatedly to finally obtain a powder having a uniform particle size. The particle size of the obtained granules is preferably 500 μm or less, and more preferably 250 μm or less. A latent epoxy curing agent is dry-mixed with the granules to obtain a resin composition for bonded magnets.

  The sheet-like rare earth bonded magnet of the present invention is formed by compression molding, and is particularly preferably formed in a parallel magnetic field. The upper and lower punches and the cavity periphery of the mold are heated, and in this state, the resin composition for bonded magnets is filled. The filling is basically performed in two steps. If there is a method of filling two layers simultaneously in the future, that method is also possible. Each layer is a thing comprised by the resin composition from which the resin amount in a resin composition or the mixing ratio of magnetic powder differs. After the filling is completed, compression molding is performed using a mold (upper punch) in which an orientation magnet is embedded.

  The sheet-like rare earth bonded magnet taken out after the forming is typically thermally cured by heating at 160 ° C. for 20 minutes, and further rolled with a rolling roll at a rolling rate of 2 to 5%. A rare earth bonded magnet is obtained.

  When producing a rotor using a cylindrical rotor core using the above-mentioned sheet-like rare earth bonded magnet, as shown in FIG. 1 (b), on the inner peripheral side of the core, the surface side with a large amount of resin or the amount of fine powder is small and the magnetic properties The lower surface side is bonded to form a rotor core, which is used to constitute a motor. When a rotor is manufactured using a cylindrical rotor core, a surface side with a large amount of resin or a surface side with a small amount of fine powder and a low magnetic property is adhered to the inner peripheral side of the core.

  Next, a sheet magnet that is partially thinned will be described below. The molded body is formed of a mold composed of orientation magnets corresponding to the number of poles, and a mold having a surface such that the inter-electrode portion of the mold has a concave shape. By filling the resin composition for bonded magnets on the mold in which the magnet for orientation is embedded, the magnetic field for orientation is affected, and the surface of the packed layer has a convex shape on the arc.

  After that, a mold is arranged so that the above-described inter-electrode portion is an arc-shaped concave mold, and compression molding is performed. After the molding, only the thermosetting process is performed, and the rolling process is not performed. Regarding the step of integrating the sheet magnet with the resin layer, a method of compressing the sheet magnet and the resin film again after placing the resin film on the surface side having the arc-shaped convex portion of the sheet magnet or a thermoplastic resin Can be embedded in the recess of the magnet.

  When a rotor is manufactured using a cylindrical rotor core using the sheet-like rare earth bonded magnet as described above, as shown in FIG. 2 (c), the surface of the core having an irregular shape of the magnet surface or the magnet recess is thermoplastic. A rotor core is formed by adhering the resin-embedded surface side, and a motor is configured using the rotor core. When a rotor is manufactured using a cylindrical rotor core, a rotor core is formed by similarly bonding the surface having an irregular shape of the magnet surface on the inner peripheral side of the core or the surface side in which the thermoplastic resin is embedded in the magnet recess, The motor is configured using the above.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the examples.

  In this embodiment, an example using NdFeB powder (denoted as HDDR) having magnetic anisotropy processed by HDDR will be described.

  The resin composition for bonded magnets contains the rare earth magnetic powder and a binder as main components. As a constituent component of the binder, a constituent composed of a novolak type epoxy oligomer, a powdery latent epoxy curing agent, a polyamide powder and a lubricant which are solid at room temperature was used.

  Formation of the resin composition for bond magnets was performed in the following procedure.

  First, the above-mentioned novolac type epoxy oligomer dissolved in acetone is prepared. The epoxy concentration is adjusted to a thickness of 0.1 μm or less with respect to the magnet powder to be coated. In order to coat HDDR, a solution in which 0.5 wt% of an epoxy oligomer was dissolved was used. The mixture was dried and coarsely pulverized, mixed with polyamide resin and a lubricant. The amount of polyamide resin added to form resin compositions having different resin amounts was changed and prepared individually. In this example, an example in which the amount of polyamide is 1.5 to 4 wt% is shown. Each of these mixtures is kneaded using a hot roll or the like, and the kneaded product is pulverized and classified to adjust the particle size to 350 μm or less. After adjustment, a latent epoxy curing agent was added to this powder and dry mixed to obtain a resin composition for each bond magnet.

  The forming process of the sheet magnet was performed as follows. After keeping the inside of the mold cavity at 150 ° C. or higher, the prepared resin composition for bonded magnet is filled into the cavity. The filling was performed in order for each resin composition having a different amount of polyamide. After the completion of filling, a mold embedded with an orientation magnet is pushed in and molding is performed at 0.6 GPa. After cooling to 100 ° C. at the position of the mold, the mold embedded with the orientation magnet is removed. Thereafter, sheet magnets having different amounts of polyamide resin in the sheet thickness direction are taken out. This sheet-shaped magnet was heat-cured at 160 ° C. for 20 minutes in a nitrogen atmosphere, and after the curing was completed, it was rolled with a rolling roll at a rolling rate of 2 to 5%.

  In order to evaluate the flexibility of the obtained sheet magnet, a limit winding diameter test was conducted. A sheet magnet was wound in steps of φ5 from φ10 to φ60, and one large diameter that caused an abnormality on the surface was compared as a limit winding diameter. Table 1 shows the limit winding diameter test results with different amounts of resin. As a comparative example, a polyamide resin amount of 3 wt% was used. When the average is 3 wt% in the first layer 2.0 wt% and the second layer 4.0 wt%, the limit winding diameter φ10 and the bendability is improved. When the first layer is 1.5 wt% and the second layer is 3.0 wt%, the limit winding diameter is φ20, which is the same as that of a single layer product, but since the amount of polyamide resin is reduced, the bendability is improved. As a result of measuring the magnetic flux density on the surface of the sheet magnet, it was found that there was a peak between the poles as seen in the waveform of the surface magnetic flux density at the time of polar orientation, and it was confirmed that the magnetic orientation was polar. .

  A motor equipped with the polar orientation sheet magnet produced by the above production method has improved magnetic characteristics and high output. If the following permanent magnet-mounted motor is used, the performance of the motor can be improved. Table 1 below shows the results of the limit winding diameter test (resin amount difference).

  In the present embodiment, an example using two types of rare earth magnet powder will be described. Specifically, this was carried out using HDDr-treated magnetically anisotropic NdFeB powder (denoted as HDDR) and RD-treated SmFeN fine powder.

  The resin composition for bonded magnets contains the rare earth magnetic powder and a binder as main components. As a constituent component of the binder, a constituent composed of a novolak type epoxy oligomer, a powdery latent epoxy curing agent, a polyamide powder and a lubricant which are solid at room temperature was used.

  Formation of the resin composition for bond magnets was performed in the following procedure.

  First, the above-mentioned novolac type epoxy oligomer dissolved in acetone is prepared. The epoxy concentration is adjusted to a thickness of 0.1 μm or less with respect to the magnetic powder to be coated. In order to coat HDDR, a solution in which 0.5 wt% of an epoxy oligomer was dissolved was used. Since SmFeN has a smaller average particle size than HDDR, more epoxy oligomers are required. In the present invention, SmFeN adjusted to 2.0 wt. Prepare a mixture of HDDR and SmFeN coated with an epoxy oligomer in a weight ratio of 6: 4, and the amount of polyamide resin is the same as in Example 1 for evaluating the dependency on the amount of polyamide resin. 2 wt% to 5.0 wt% were prepared individually. Further, for the evaluation of the dependency on the mixing ratio, a mixture prepared by adding 3.0 wt% of polyamide resin to the mixture having a mixing ratio of 6: 4 to 9: 1 was separately prepared. These mixtures are individually kneaded using a hot roll or the like, and the kneaded product is pulverized and classified to adjust the particle size to 350 μm or less. After adjustment, a latent epoxy curing agent was added to this powder and dry mixed to obtain a resin composition for bonded magnets.

The molding process of the sheet magnet was performed in the same manner as in Example 1. After keeping the inside of the mold cavity at 150 ° C. or higher, the prepared resin composition for bonded magnet is filled into the cavity. The filling was performed in the order of individual resin compositions having different resin amounts or individual resin compositions having different mixing ratios. After the completion of filling, a mold embedded with an orientation magnet is pushed in and molding is performed at 0.6 GPa. After cooling to 100 ° C. at the position of the mold, the mold embedded with the orientation magnet is removed. Then, the sheet-like magnet from which the composition ratio of the magnet powder differs in the sheet thickness direction is taken out. This sheet magnet was thermally cured at 160 ° C. for 20 minutes in a nitrogen atmosphere, and rolled with a roll after curing was completed. The rolling rate is in the range of 2 to 5%. In order to evaluate the flexibility of the obtained sheet magnet, a limit winding diameter test was conducted. Table 2 shows the limit winding diameter test results with different resin amounts. As a comparative example, a polyamide resin having a weight of 3.5 wt% was used. When the average of the first layer is 2.0 wt% and the second layer is 5.0 wt% and the average is 3.5 wt%, the limit winding diameter is φ30 and the bendability is improved. When the first layer is 3.0 wt% and the second layer is 4.0 wt%, the limit winding diameter is φ25 and the bendability is improved. Table 3 shows the limit winding diameter test results with different composition ratios. The limit winding diameter is 40 by mixing two kinds of magnetic powders, and the bendability is worse than that of Example 1. However, in the combinations of Table 3 having different composition ratios, the limit winding diameter was φ25 to φ35, and the bendability was improved. As a result of measuring the magnetic flux density on the surface of the sheet magnet, every sample has a peak between the poles as seen in the waveform of the surface magnetic flux density at the time of polar orientation. It was confirmed that the magnet of the shape was polar-oriented.

  A motor equipped with the polar orientation sheet magnet produced by the above production method has improved magnetic characteristics and high output. If the following permanent magnet-mounted motor is used, the performance of the motor can be improved. Table 2 shows the results of the limit winding diameter test (resin amount difference).

Table 3 shows the results of the limit winding diameter test (composition ratio difference).

In this embodiment, HDDR and SmFeN two kinds of rare earth magnet powders will be described. As in Example 2, the bonded magnet resin composition was composed mainly of the rare earth magnetic powder and a binder, and the binder was a novolak epoxy oligomer that was solid at room temperature, a powdery latent epoxy curing agent, a polyamide powder, and A composition composed of a lubricant was used.

  The bond magnet resin composition was also formed in the same manner as in Example 2.

  Each of HDDR and SmFeN coated with an epoxy oligomer was mixed at a weight ratio of 6: 4, and the amount of polyamide resin was mixed at 3.0 wt%. These mixtures are kneaded, pulverized, and classified to adjust the particle size to 350 μm or less. After adjustment, a latent epoxy curing agent was added to this powder and dry mixed to obtain a resin composition for bonded magnets.

  The forming process of the sheet magnet was performed as follows. A die die 22 is combined with a lower die 21 with an orientation magnet embedded with an orientation magnet, and the inside of the cavity is kept at 150 ° C. or higher, and the prepared resin composition 23 for bonded magnet is filled into the cavity. The filling is in a non-uniform state due to the influence of the magnet for orientation. After completion of filling, the upper mold 24 having a concave surface with an arc shape is pushed in and molding is performed at 0.6 GPa. After cooling to 100 ° C. at the position of the mold, the mold whose surface has an arcuate concave shape is removed. Thereafter, a sheet-like magnet body 25 having a thickness different in the sheet longitudinal direction and having a convex surface having an arc shape and a flat bottom surface is taken out. This sheet magnet was thermoset at 160 ° C. for 20 minutes in a nitrogen atmosphere. The rolling process performed after completion of hardening is not implemented. The result of a limit winding diameter test for evaluating the flexibility of the obtained sheet magnet is φ30. As a result of measuring the magnetic flux density on the surface of the sheet magnet, as shown in the waveform of the surface magnetic flux density during polar orientation It has become a thing with a peak between poles, and it has confirmed that the magnet of this sheet | seat shape integrally molded was pole-oriented. In order to dispose and integrate the resin on the convex surface side, it was possible to dispose and compress the resin sheet on the magnet in the cavity after molding. When the resin was powdered and the upper mold was flat, an integrated product with the resin filled in the concave portion of the sheet magnet was obtained.

  A motor equipped with the polar orientation sheet magnet produced by the above production method has improved magnetic characteristics and high output. If the following permanent magnet-mounted motor is used, the performance of the motor can be improved.

  By using the polar-oriented sheet-like rare earth bonded magnet of the present invention, it is possible to produce a rotor magnet with improved thermal durability. A motor equipped with the magnet is reduced in size and weight, increased in output, and increased in power. Efficiency can be improved.

The figure which shows the structure of the sheet-like rare earth bond magnet of this invention The figure which shows an example of the shaping | molding process of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Magnet part 1st layer 12 Magnet part 2nd layer Soft magnetic metal body 13 Cylindrical rotor core 21 Mold die 22 Mold with magnet for orientation 23 Resin composition 24 Upper mold 25 Magnet body

Claims (8)

A resin composition for bonded magnets , comprising one or more anisotropic rare earth magnet powders and a thermosetting epoxy resin composition comprising an epoxy oligomer, a polyamide resin and an epoxy curing agent that coat the rare earth magnet powders A sheet-like rare earth bonded magnet compression-molded by
The bonded magnet is oriented so that the orientation direction of the anisotropic magnet powder becomes polar orientation, and the thermosetting epoxy resin composition for the one or more anisotropic rare earth magnet powders A pole-oriented sheet-like rare earth bonded magnet characterized in that a plurality of magnet bodies having different resin amounts are laminated. 2. The sheet-like rare earth bonded magnet according to claim 1, wherein the magnet powder is composed of at least one of an NdFeB alloy, an SmFeN alloy, and an SmCo alloy. 2. The sheet-like rare earth bonded magnet according to claim 1, wherein two layers of magnet bodies having different resin amounts are laminated . A mixture of two kinds of magnetic powders having different rare earth magnet powder average particle diameters, each magnet body of laminated sheet according to claim 1, wherein the mixing ratio of the two kinds of magnetic powder is different Rare earth bonded magnet. 5. The sheet-like rare earth bonded magnet according to claim 4, wherein the two kinds of magnet powder are composed of at least two of an NdFeB alloy, an SmFeN alloy, and an SmCo alloy. 6. The sheet-like rare earth bonded magnet according to claim 5, wherein the NdFeB alloy has an average particle diameter of 100 μm and the SmFeN alloy has an average particle diameter of 2 μm. 2. The sheet-like rare earth bonded magnet according to claim 1, wherein two layers of magnet bodies different in at least one of the coating amount by the epoxy oligomer and the content of the polyamide resin are laminated. Motor with a rotor which is formed by bonding the surface of the busy resin amount side in sheet form rare earth bonded magnet of claim 3, wherein the inner peripheral surface side of the cylindrical frame of the outer peripheral surface side or core of the cylindrical frame of the core.