JP2015231938A - Ferrite core, electronic component and electric power unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ferrite core having small saturation magnetostriction near to 100°C, suppressed sound squeak at drive and high saturation flux density.SOLUTION: There is provided a ferrite core 10 which is a MnZn-based ferrite containing iron oxide of 51.5 to 54.5 mol% in terms of FeO, zinc oxide of 7.0 to 11.5 mol% in terms of ZnO and the balance manganese oxide as a main component, and Ni of 500 to 10000 ppm in terms of NiO, Ti of 100 to 6000 ppm in term of TiOand Co of 500 to 4000 ppm in terms of CaO to the main component.

Description

The present invention relates to a ferrite core having a low saturation magnetostriction in the vicinity of 100 ° C., a noise reduction during driving, and a high saturation magnetic flux density.

Ferrite sintered bodies are used as magnetic core materials for power transformers and the like. The ferrite sintered body forming the core (magnetic core) is called a ferrite core, and MnZn-based ferrite containing Mn and Zn is widely used. In recent years, a high saturation magnetic flux density at a high temperature has been demanded with the miniaturization of a power source.

For example, in the ferrite of Patent Document 1, Fe ₂ O ₃ : 52 to 56 mol%, ZnO: 6 to 14 mol%, NiO: 4 mol% or less, CoO: 0.01 to 0.6 mol%, and the balance is substantially composed of MnO. The basic component contains SiO ₂ : 0.0050 to 0.0500 wt% and CaO: 0.0200 to 0.2000 wt% in the outer frame amount, and further Ta ₂ O ₅ , ZrO ₂ , Nb ₂ O. ₅ , V ₂ O ₅ , K ₂ O, TiO ₂ , SnO _2, and HfO ₂ are contained in a predetermined amount and have a high saturation magnetic flux density.

On the other hand, the noise generated when the power source is driven is also important. For example, in Patent Document 2, transformer noise is reduced or prevented by sandwiching a damping material between the legs of the core having a plurality of legs. It is characterized by providing a transformer.

Japanese Patent No. 3968188 JP 2013-118308 A

It is generally known that squeal is caused by magnetostrictive vibration. In Patent Document 2, although the noise is reduced, it does not reduce the magnetostriction that causes the noise and cannot be said to be a fundamental solution. In addition, there is a problem that the use of the vibration damping material increases the cost and labor during manufacturing.

Accordingly, an object of the present invention is to provide a ferrite core that can solve the above-described problems of the prior art. In particular, an object of the present invention is to provide a ferrite core that reduces noise during driving by reducing magnetostriction at 100 ° C. and exhibits a high saturation magnetic flux density.

Under such a purpose, the present inventors pay attention to the composition of iron oxide, manganese oxide, zinc oxide as main components contained in MnZn-based ferrite and nickel oxide, cobalt oxide and titanium oxide as subcomponents, and diligently their characteristics. I did research. As a result, it has been found that the saturation magnetostriction is small at 100 ° C., the noise during driving can be suppressed, and a high saturation magnetic flux density can be realized, and the present invention has been completed.

That is, the ferrite core of the present invention, 51.5～54.5Mol% iron oxide calculated as _Fe 2 _{O 3,} 7.0～11.5Mol% of zinc oxide calculated as ZnO, the main balance being manganese oxide It is MnZn type ferrite containing a component, Comprising: With respect to this main component, Ni contains 500 to 10000 ppm in terms of NiO, Ti contains 100 to 6000 ppm in terms of TiO ₂ , and Co contains 500 to 4000 ppm in terms of CoO It is a ferrite core characterized by including.

Moreover, in the ferrite core of the present invention, it is preferable that Si and Si are contained in an amount of 50 to 300 ppm in terms of SiO ₂ and Ca in an amount of 200 to 3000 ppm in terms of CaCO ₃ as subcomponents.

Furthermore, in the ferrite core of the present invention, as subcomponents, Nb is 50 to 750 ppm in terms of Nb ₂ O ₅ , Ta is 50 to 1500 ppm in terms of Ta ₂ O ₅ , and V is 50 in terms of V ₂ O ₅ as subcomponents. ～1000Ppm, it is preferable to include one or more 500~8000ppm the Sn in terms of SnO _2.

By reducing the saturation magnetostriction at 100 ° C., it is possible to suppress squeaking during driving and to realize a high saturation magnetic flux density.

First, the reasons for limiting the components in the present invention will be described.
In the ferrite core of the present invention, the amount of Fe as a main component is 51.5 to 54.5 mol% in terms of Fe ₂ O ₃ . Hereinafter, the notation of Fe amount in terms of Fe ₂ O ₃ is simply expressed as Fe ₂ O ₃ amount or the like. When the amount of Fe ₂ O ₃ is less than 51.5 mol%, the saturation magnetostriction at 100 ° C. is reduced, but the saturation magnetic flux density is reduced. On the other hand, when the amount of Fe ₂ O ₃ exceeds 54.5 mol%, saturation magnetostriction at 100 ° C. increases. Therefore, in the present invention, the amount of Fe ₂ O ₃ is 51.5 to 54.5 mol%. A preferred amount is 51.5 to 54 mol%.

The amount of ZnO also affects the saturation magnetic flux density and saturation magnetostriction. When the amount of ZnO is less than 7.0 mol%, the saturation magnetostriction becomes large. When ZnO exceeds 11.5 mol%, the saturation magnetic flux density at 100 ° C. becomes small. Therefore, in the present invention, the amount of ZnO is set to 7.0 to 11.5 mol%. The ferrite core of the present invention is composed of MnO as the main component except for the inevitable impurities other than the above.

Next, subcomponents in the present invention will be described.
In the ferrite core of the present invention, the amount of Ni is 500 to 10,000 ppm in terms of NiO as a subcomponent. NiO is effective in suppressing magnetostriction, and is added in an amount of 500 ppm or more with respect to the main component in order to obtain the effect. However, when there is too much addition amount, a saturation magnetic flux density will become small. Therefore, in the present invention, the amount of NiO is 10000 ppm or less. A preferred amount is 2000-10000 ppm.

In the ferrite core of the present invention, the Ti content is set to 100 to 6000 ppm as TiO _{2 in} terms of TiO ₂ . TiO ₂ can be replaced with Fe in the spinel lattice as tetravalent Ti ions to reduce magnetostriction. In order to obtain the effect, 100 ppm or more is added to the main component. However, when the addition amount is too large, the saturation magnetic flux density becomes small. Therefore, in the present invention, the amount of TiO ₂ is set to 6000 ppm or less. A preferred amount is 1000 to 3000 ppm.

In the ferrite core of the present invention, the Co amount is set to 500 to 4000 ppm in terms of CoO as a subcomponent. CoO is effective in suppressing magnetostriction, and in order to obtain the effect, 500 ppm or more is added to the main component. However, when the addition amount is too large, the saturation magnetic flux density is reduced. Therefore, in this invention, the amount of CoO shall be 4000 ppm or less. A preferable amount of CoO is 500 to 3000 ppm.

Moreover, the effect is further enhanced by adding Ni, Ti and Co simultaneously. Ni or Co is dissolved in the B site in the spinel crystal to obtain a magnetostriction suppressing effect. However, when these are added alone, they are dissolved not only in the B site but also in the A site, and a sufficient effect on the amount added cannot be obtained. However, it is considered that Ni and Co are easily dissolved in the B site by adding Ti at the same time, and a larger magnetostriction suppressing effect can be obtained than when adding alone.

In the ferrite core of the present invention, the saturation magnetic flux density at 100 ° C. is as high as 380 mT or more by appropriately selecting the above-described composition, and the saturation magnetostriction at 100 ° C. can be reduced to suppress noise during driving.

In the present invention, the core loss can be suppressed by limiting the subcomponents as follows.
The ferrite core of the present invention can contain 50 to 300 ppm of SiO ₂ and 200 to 3000 ppm of CaCO ₃ as subcomponents. Si and Ca are segregated at the grain boundaries to form a high resistance layer and contribute to low loss, and have the effect of improving the sintering density as a sintering aid. If Si is less than 50 ppm in terms of SiO ₂ or Ca is less than 200 ppm in terms of CaCO ₃ , the above effects cannot be obtained sufficiently. On the other hand, when Si exceeds 300 ppm in terms of SiO ₂ or Ca exceeds 3000 ppm in terms of CaCO ₃ , the core loss deteriorates due to abnormal grain growth. SiO ₂ is 50~150ppm and CaCO ₃ are preferably be 500～2000Ppm, further SiO ₂ is 75~125ppm and CaCO ₃ is preferably set to 800～1600Ppm.

The ferrite core of the present invention can contain 50 to 750 ppm of Nb ₂ O ₅ and 50 to 1500 ppm of Ta ₂ O ₅ as subcomponents. Nb and Ta are components that have a function of increasing the grain boundary resistance. If Nb is less than 50 ppm in terms of Nb ₂ O ₅ , or Ta is less than 50 ppm in terms of Ta ₂ O ₅ , there is no improvement effect. Further, when Nb exceeds 750 ppm in terms of Nb ₂ O ₅ or Ta exceeds 1500 ppm in terms of Ta ₂ O ₅ , the core loss increases due to abnormal grain growth. Therefore, Nb ₂ O ₅ is increased to 50 to 750 ppm and Ta ₂ O ₅ was limited to the range of 50 to 1500 ppm. When the content is increased, abnormal grain growth occurs, so that it is preferable to contain Nb ₂ O ₅ in the range of 100 to 300 ppm and Ta ₂ O ₅ in the range of 100 to 600 ppm.

The ferrite core of the present invention can contain V ₂ O ₅ in the range of 50 to 1000 ppm as a subcomponent. V is a component having a function of increasing the grain boundary resistance. When V is less than 50 ppm in terms of V ₂ O ₅ , there is no improvement effect. Also, V is because the core loss increases due to abnormal grain growth exceeds 1000ppm in terms _{of V} 2 _{O 5,} with limited V 2 _{O 5} in the range of 50 to 1000 ppm. When the content increases, abnormal grain growth occurs, so that V ₂ O ₅ is preferably contained in the range of 100 to 500 ppm.

The ferrite core of the present invention may contain 500 to 8000 ppm of SnO ₂ as a subcomponent. SnO ₂ is a component that partially exists at the grain boundary and promotes grain boundary reoxidation in the cooling process after sintering to reduce loss. SnO ₂ also serves to lower the bottom temperature by substituting with atoms of the spinel lattice as tetravalent ions. However, if the added amount is too large, abnormal grain growth is caused and the loss becomes high. Therefore, SnO ₂ is contained in the range of 500 to 8000 ppm. Preferably, SnO ₂ is contained in the range of 1000 to 3000 ppm. These components are not necessarily added in the form of an oxide, and may be mixed in the form of a carbonate, for example.

The ferrite core of the present invention can suppress loss at 100 ° C. by appropriately selecting the above-described composition.

Next, a manufacturing method suitable for the ferrite core according to the present invention will be described.
As the raw material of the main component, an oxide or a powder of a compound that becomes an oxide by heating is used. Specifically, Fe ₂ O ₃ powder, Mn ₃ O ₄ powder, ZnO powder, or the like can be used. What is necessary is just to select suitably the average particle diameter of each raw material powder in the range of 0.1-3 micrometers. The raw material powder of the main component is wet mixed and then calcined. The calcining temperature may be a predetermined temperature within the range of 800 to 1100 ° C. What is necessary is just to select the stable time of calcination suitably in the range of 0.5 to 5 hours. After the calcination, the calcined material is pulverized, for example, to an average particle size of about 0.5 to 3 μm. In the present invention, not only the above-mentioned main component materials, but also a composite oxide powder containing two or more metals may be used as the main component materials. For example, a complex oxide powder containing Fe and Mn can be obtained by oxidizing and baking an aqueous solution containing iron chloride and manganese chloride. This powder and ZnO powder may be mixed and used as a main component material. In such a case, calcining is unnecessary.

Add subcomponents after calcination. For the addition after calcining, the above-mentioned pulverization may be performed by adding the raw material of the subcomponent to the calcined material, or the subcomponent raw material can be added and mixed after the calcination of the calcined material. However, NiO, TiO ₂ , and CoO can be calcined together with the main component raw materials.
As a subcomponent material, an oxide or a powder of a compound that becomes an oxide by heating can also be used. Specifically, NiO powder, Co ₃ O ₄ powder, TiO ₂ powder, SiO ₂ powder, CaCO ₃ powder, Nb ₂ O ₅ powder, Ta ₂ O ₅ powder, SnO ₂ powder, or the like can be used.

The mixed powder composed of the main component and the subcomponent is granulated into a granule in order to smoothly execute the subsequent molding process. Granulation can be performed using, for example, a spray dryer. A small amount of a suitable binder such as polyvinyl alcohol (PVA) is added to the mixed powder, and this is sprayed and dried with a spray dryer. The particle size of the obtained granules is preferably about 80 to 300 μm.

The obtained granules are molded into a desired shape using, for example, a press having a mold having a predetermined shape, and this molded body is subjected to a firing step.
In the firing step, it is necessary to control the firing temperature and firing atmosphere. The firing temperature can be appropriately selected from the range of 1250 to 1500 ° C., but it is preferably fired in the range of 1300 to 1400 ° C. in order to sufficiently bring out the effect of the ferrite core of the present invention. As the firing atmosphere, the oxygen partial pressure may be appropriately adjusted in a mixed atmosphere of nitrogen and oxygen.

The sintered ferrite core according to the present invention can obtain a relative density of 93% or more, more preferably 95% or more.
The ferrite core obtained by the present invention can be used for a transformer, and the transformer obtained by the present invention can be used for a switching power supply device.

FIG. 1A is a perspective view showing an E-shaped ferrite core (magnetic core) according to this embodiment. As shown in FIG. 1A, an E-shaped ferrite core 10 is called an E-type core and is used for a transformer or the like. As a transformer in which an E-type core such as the ferrite core 10 is employed, a transformer in which two E-type cores are arranged to face each other as shown in FIG. 1B is known.

FIG. 2 is a block diagram illustrating a configuration of the switching power supply apparatus.

Switching power supply device 200 shown in FIG. 2 is a device for converting a DC input voltage _{V in} to a DC output voltage _{V out} (DC / DC converter), input for removing a noise component included in the DC output voltage _{V in} Filter 201, switching circuit 202 that converts the output of input filter 201 into alternating current, transformer 203 that transforms the output of switching circuit 202, rectifier circuit 204 that converts the output of transformer 203 into direct current, and the output of the rectifier circuit And a smoothing circuit 205 for smoothing. In the switching power supply device 200 having such a configuration, if the core according to the present invention is used as the core of the transformer 203, the noise generated in the transformer 203 can be suppressed, so that the noise problem of the switching power supply device 200 can be solved. it can.

The switching power supply device 200 shown in FIG. 2 is particularly suitable for use as a switching power supply device for automobiles.

FIG. 3 is a block diagram schematically showing the main part of the automobile provided with the switching power supply device 200.

As shown in FIG. 3, when the switching power supply device 200 is used for an automobile, the switching power supply device 200 is provided between the high voltage battery 210, the electric device 220, and the low voltage battery 230, and is supplied from the high voltage battery 210. The high voltage of about 144V or about 288V is stepped down to about 14V and supplied to the electric device 220, and the low voltage battery 230 is charged. Examples of the electric device 220 include an air conditioner and an audio device provided in an automobile.

Charging the high-voltage battery 210 is performed by electric power supplied from the power generation device 240. The output of the high voltage battery 210 is also supplied to the motor 250, and the motor 250 drives the drive system 260 based on the high voltage (about 144V or about 288V) supplied from the high voltage battery 210. In the fuel cell vehicle, the fuel cell main body serves as the power generator 240, and in the hybrid vehicle, the motor 250 also serves as the power generator 240.

The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. Needless to say, it is included in the range.

Hereinafter, the present invention will be described based on specific examples.
Fe ₂ O ₃ powder, Mn ₃ O ₄ powder and ZnO powder as main component raw materials, NiO powder, TiO ₂ powder, Co ₃ O ₄ powder, SiO ₂ powder, CaCO ₃ powder, Nb ₂ O ₅ as auxiliary component raw materials Powder, V ₂ O ₅ powder, Ta ₂ O ₅ powder and SnO ₂ powder were used. Tables 1 to 3 show the composition of the main component and the composition of the subcomponents. In Tables 1 and 2, in addition to the materials shown in the table, 100 ppm of SiO ₂ , 1000 ppm of CaCO ₃ and 200 ppm of Nb ₂ O ₅ were added. After these powders were wet mixed, they were calcined in the atmosphere at 900 ° C. for 3 hours.
A binder was added to the obtained mixture, granulated, and then molded to obtain a toroidal shaped body, an I-shaped shaped body, and an E-shaped shaped body. The obtained molded body was fired at a temperature of 1300 ° C. (stable part 5 hours, stable part oxygen partial pressure 2%) under oxygen partial pressure control, toroidal ferrite core (outer diameter 20 mm, inner diameter 10 mm, thickness 5 mm), an I-shaped ferrite core (length 70 mm, width 8 mm, thickness 8 mm) and an E-shaped ferrite core (length 40 mm, height 15 mm, width 5 mm).

Next, the measurement method of the present invention will be described.
The magnetostriction at 100 ° C. was measured using a strain gauge (KFG: general-purpose foil strain gauge) manufactured by Kyowa Denki. A strain gauge was attached to the side surface of the central portion of the I-type ferrite core. The absolute value of the rate of change in strain when the I core was excited and the strain no longer changed was defined as the saturation magnetostriction λs. In the following, the absolute value of the rate of change in the amount of distortion when the I core is excited and the amount of distortion does not change is simply expressed as saturated magnetostriction λs, or simply as saturated magnetostriction or λs.

The squealing at 100 ° C. was performed by placing each E-type core composition in a simple anechoic box. The measurement was performed by installing the core and the tip of the microphone of the sound level meter at a position 30 mm away. The sound pressure level was measured using a sound level meter (LA-5570) manufactured by Ono Sokki. The data shows the overall value (OA value) after A characteristic conversion. The A characteristic is a value weighted with a frequency as an amount representing a sound pressure level based on human hearing. The OA value is the sum of each sound pressure level subjected to frequency analysis.

The saturation magnetic flux density Bs at 100 ° C. was measured on a toroidal core under the condition of an excitation magnetic field of 1194 A / m using a Metron Giken DC magnetization characteristic tester (SK-110).

The core loss Pcv at 100 ° C. is obtained by using a toroidal ferrite core, winding 5 turns on the primary side and 5 turns on the secondary side, and a BH analyzer manufactured by IWASUSU under the condition of a maximum magnetic flux density of 200 mT at a frequency of 100 kHz. SY-8217).

From the above measurement results, the following can be understood.
“-” In the table indicates that the material is not added.

(Table 1)
If the amount of Fe ₂ O ₃ is less than 51.5 mol% (see Comparative Examples 1 and 2), the saturation magnetic flux density Bs at 100 ° C. (hereinafter omitted at 100 ° C.) will be smaller than 380 mT. Further, when the amount of Fe ₂ O ₃ exceeds 54.5 mol% (see Comparative Examples 7 and 8), the saturation magnetostriction becomes larger than 1.5 × 10 ⁻⁶ and the OA value becomes larger than 45 dB.
If the ZnO amount is less than 7.0 mol% (see Comparative Examples 3 and 5), the saturation magnetostriction becomes larger than 1.5 × 10 ⁻⁶ and the OA value becomes larger than 45 dB. Further, when the ZnO amount exceeds 11.5 mol% (see Comparative Examples 4 and 6), the saturation magnetostriction becomes small, but the saturation magnetic flux density Bs becomes smaller than 380 mT.

(Table 2)
If the amount of NiO as a subcomponent is less than 500 ppm (see Comparative Example 9), the saturation magnetostriction becomes large and the OA value becomes larger than 45 dB. Further, when the amount of NiO exceeds 10,000 ppm (see Comparative Example 10), the saturation magnetostriction becomes small, but the saturation magnetic flux density Bs becomes smaller than 380 mT.
When the amount of TiO _{2 as} a subcomponent is less than 100 ppm (see Comparative Example 11), the saturation magnetostriction becomes larger than 1.5 × 10 ⁻⁶ and the OA value becomes larger than 45 dB. Further, when the amount of TiO ₂ exceeds 6000 ppm (see Comparative Example 12), the magnetostriction becomes small, but the saturation magnetic flux density Bs becomes smaller than 380 mT.
If the amount of CoO as a subcomponent is less than 500 ppm (see Comparative Example 13), the saturation magnetostriction becomes larger than 1.5 × 10 ⁻⁶ and the OA value becomes larger than 45 dB. Further, when the amount of CoO exceeds 4000 ppm (see Comparative Example 14), the saturation magnetic flux density Bs becomes smaller than 380 mT.

On the other hand, the amount of Fe ₂ O ₃ is 51.5 to 54.5 mol%, the amount of ZnO is 7.0 to 11.5 mol%, and the amount of NiO is 500 to 10,000 ppm as a subcomponent with respect to the main component of the remaining MnO. When the content of TiO ₂ is 100 to 6000 ppm and the content of CoO is 500 to 4000 ppm, the saturation magnetostriction at 100 ° C. is 1.5 × 10 ⁻⁶ or less, the OA value is 45 dB or less, and the saturation magnetic flux density Bs is 380 mT or more. Can be obtained.

(Table 3)
Other subcomponents are as follows.
As described above, SiO ₂ and CaCO ₃ are segregated at the grain boundaries to form a high resistance layer and contribute to low loss and have the effect of improving the sintering density as a sintering aid. As shown, it affects the core loss Pcv. That is, by adding SiO ₂ and CaCO ₃ , the core loss Pcv can be reduced, but as shown in Table 3, the core loss becomes worse when added too much (see Examples 20 to 27). Therefore, when adding SiO ₂ and CaCO ₃ , SiO ₂ is set to 50 to 300 ppm and CaCO ₃ is set to 200 to 3000 ppm.
Further, by adding _Nb 2 _{O 5} and _Ta 2 _{O 5,} it is possible to reduce the core loss Pcv (see Example 28-34). However, since the core loss is deteriorated when adding too much in the same manner as in the case of SiO ₂ and CaCO ₃ , the optimum addition amount ranges from 50 to 750 ppm or less for Nb ₂ O ₅ and 50 to 1500 ppm or less for Ta ₂ O _5. To do.
_Further, by adding V 2 _{O 5,} it is possible to reduce the core loss Pcv (see Example 35-37). However, if too much is added as in the case of SiO ₂ and CaCO _3, the core loss becomes worse. Therefore, the optimum range of addition amount is 50 to 1000 ppm or less for V ₂ O ₅ .
Moreover, the core loss Pcv can be reduced by adding SnO ₂ (see Examples 38 to 40). However, if SiO ₂ is added too much as in the case of CaCO _3, the core loss becomes worse, so the optimum range of addition is SnO ₂ of 500 to 8000 ppm or less.

As described above, the ferrite core according to the present invention can sufficiently suppress the squeal of the core during driving by reducing the saturation magnetostriction near 100 ° C., and can increase the saturation magnetic flux density.

(A) It is a perspective view which shows the E-shaped ferrite core (magnetic core) which concerns on this embodiment. (B) It is a perspective view which shows the trans | transformer by which two E type | mold cores are opposingly arranged by the inside which concerns on this embodiment. It is a block diagram of a switching power supply device. It is a block diagram which shows the principal part of the motor vehicle provided with the switching power supply device.

10 ferrite core (magnetic core)
11 (middle leg)
12 (coil)
200 switching power supplies

Claims (5)

51.5～54.5Mol% iron oxide calculated as _Fe 2 _{O 3,} 7.0～11.5Mol% of zinc oxide calculated as ZnO, a MnZn ferrite containing main component balance being manganese oxide, A ferrite core comprising: Ni containing 500 to 10,000 ppm in terms of NiO, Ti containing 100 to 6000 ppm in terms of TiO ₂ , and Co containing 500 to 4000 ppm in terms of CoO. _2. The ferrite core according to claim 1, wherein Si is contained in an amount of 50 to 300 ppm in terms of SiO ₂ and Ca is contained in an amount of 200 to 3000 ppm in terms of CaCO ₃ with respect to the main component. Furthermore, Nb is 50 to 750 ppm in terms of Nb ₂ O ₅ , Ta is 50 to 1500 ppm in terms of Ta ₂ O ₅ , V is 50 to 1000 ppm in terms of V ₂ O ₅ , and Sn is 500 in terms of SnO ₂ with respect to the main component. The ferrite core according to claim 1, wherein the ferrite core contains 1 type or 2 types or more of ˜8000 ppm. The electronic component comprised using the ferrite core of any one of Claims 1-3 A power supply device comprising the electronic component according to claim 4.

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