JP6536790B2 - Ferrite core, electronic component, and power supply device - Google Patents

Description

The present invention relates to a ferrite core having a low saturation magnetostriction near 100 ° C., suppressing noise during driving, and having a high saturation magnetic flux density.

A ferrite sintered body is used as a core material for a power source transformer or the like. The ferrite sintered body which forms a core (magnetic core) is called a ferrite core, and MnZn ferrite containing Mn and Zn is widely used. Also, in recent years, high saturation magnetic flux density has been required at high temperature as the power supply is miniaturized.

For example, in the ferrite of Patent Document 1, the composition of 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 substantially MnO The outer frame amounts of SiO ₂ : 0.0050 to 0.0050 wt% and CaO: 0.0200 to 0.2000 wt% with respect to the basic components to be contained, and further Ta ₂ O ₅ , ZrO ₂ , Nb ₂ O ₅ , characterized in that it contains a predetermined amount of at least one additive component selected from V ₂ O ₅ , K ₂ O, TiO ₂ , SnO ₂ and HfO ₂ and has a high saturation magnetic flux density.

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

Patent No. 3968188 gazette JP, 2013-118308, A

It is generally known that the noise is caused by magnetostrictive vibration. Although the noise reduction is reduced in Patent Document 2, it does not reduce the magnetostriction which is the cause of the noise, and it can not be said to be a fundamental solution method. In addition, there is also a problem that the use of the damping material increases the cost and labor at the time of manufacture.

Therefore, 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, the object of the present invention is to provide a ferrite core exhibiting high saturation magnetic flux density by suppressing the generation of noise during driving by reducing the magnetostriction at 100 ° C.

For this purpose, the present inventors focused on the composition of iron oxide, manganese oxide and zinc oxide as main components contained in MnZn ferrite and nickel oxide, cobalt oxide and titanium oxide as auxiliary components and are keenly aware of their characteristics. I did research. As a result, it has been found that saturation magnetostriction is small at 100 ° C., noise at the time of driving can be suppressed, and high saturation magnetic flux density can be realized, and the present invention has been completed.

That is, the ferrite core according to the present invention is mainly composed of 51.5 to 54.5 mol% of iron oxide in terms of Fe ₂ O ₃ , 7.0 to 11.5 mol% of zinc oxide in terms of ZnO, and the balance being manganese oxide. Mn-Zn-based ferrite containing a component, containing 500 to 10000 ppm of Ni in terms of NiO, 100 to 6000 ppm of Ti in terms of TiO ₂ and 500 to 4000 ppm of Co based on CoO with respect to the main component It is a ferrite core characterized by including.

Further, in the ferrite core of the present invention, it is preferable that 50 to 300 ppm of Si in terms of SiO ₂ and 200 to 3000 ppm of Ca in terms of CaCO _{3 be} contained in the main component as minor components.

In addition the ferrite core of the present invention, as an accessory component, a Nb calculated as _Nb 2 _{O 5} with respect to the main component 50～750Ppm, the Ta in _Ta 2 _{O 5} in terms 50～1500Ppm, the V in terms _{of V} 2 _{O 5} 50 It is preferable to contain 1000 ppm, and one or two or more types of Sn in an amount of 500 to 8000 ppm in terms of SnO ₂ .

By reducing the saturation magnetostriction at 100 ° C., noise during driving can be suppressed, and a high saturation magnetic flux density can be realized.

First, the reasons for limitation of the components in the present invention will be described.
In the ferrite core of the present invention, the amount of Fe as the main component is 51.5 to 54.5 mol% in terms of Fe ₂ O ₃ . In the following, the expression of the amount of Fe in terms of Fe ₂ O ₃ is simply expressed as the amount of Fe ₂ O ₃ or the like. If 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. becomes large. Therefore, in the present invention, the amount of Fe ₂ O ₃ is set to 51.5 to 54.5 mol%. The 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%, 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 mainly composed of MnO except the above-described unavoidable impurities.

Next, the subcomponents in the present invention will be described.
The ferrite core of the present invention has an amount of Ni of 500 to 10,000 ppm in terms of NiO as a minor component. NiO is effective for suppressing the magnetostriction, and in order to obtain the effect, it is added in an amount of 500 ppm or more based on the main component. However, if the addition amount is too large, the saturation magnetic flux density is reduced. Therefore, the amount of NiO is made 10000 ppm or less in the present invention. The preferred amount is 2000-10000 ppm.

The ferrite core of the present invention has a Ti content of 100 to 6000 ppm in terms of TiO ₂ as an accessory component. TiO ₂ can be substituted for 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 decreases. Therefore, in the present invention, the amount of TiO ₂ is set to 6000 ppm or less. The preferred amount is 1000 to 3000 ppm.

The ferrite core of the present invention has a Co content of 500 to 4000 ppm in terms of CoO as an accessory component. CoO is effective in suppressing the magnetostriction, and in order to obtain the effect, it is added in an amount of 500 ppm or more to the main component. However, if the amount added is too large, the saturation magnetic flux density will be reduced. Therefore, in the present invention, the amount of CoO is set to 4000 ppm or less. The preferred amount of CoO is 500 to 3000 ppm.

Moreover, the effect is further enhanced by simultaneously adding Ni, Ti and Co. By dissolving Ni and Co in the B site in the spinel crystal, the magnetostriction suppressing effect can be obtained. However, when these are added alone, they are not only dissolved at the B site but also at the A site, and a sufficient effect can not be obtained with respect to the addition amount. However, by simultaneously adding Ti, it is considered that Ni and Co are easily dissolved in the B site, and it is possible to obtain a greater magnetostriction suppressing effect than adding it 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, and the saturation magnetostriction at 100 ° C. can be reduced to suppress the noise at the time of driving.

In the present invention, core loss can be suppressed by limiting 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 accessory components. Si and Ca are segregated at grain boundaries to form a high resistance layer to 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 can not be sufficiently obtained. Further, when Si exceeds 300 ppm in terms of SiO ₂ , or Ca exceeds 3000 ppm in terms of CaCO ₃ , deterioration of core loss due to abnormal grain growth becomes large. It is preferable to set 50 to 150 ppm of SiO ₂ and 500 to 2000 ppm of CaCO ₃ , and more preferably, 75 to 125 ppm of SiO ₂ and 800 to 1600 ppm of CaCO ₃ .

The ferrite core of the present invention can contain, as auxiliary components, 50 to 750 ppm of Nb ₂ O ₅ and 50 to 1500 ppm of Ta ₂ O ₅ . Nb and Ta are components having the function of increasing the grain boundary resistance. When 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 , no improvement effect is obtained. In addition, if Nb exceeds 750 ppm in terms of Nb ₂ O ₅ or Ta exceeds 1500 ppm in terms of Ta ₂ O ₅ , core loss is increased due to abnormal grain growth, so 50 to 750 ppm of Nb ₂ O ₅ and Ta ₂ O _{5 5} was limited to the range of 50 to 1500 ppm. When the content is increased, it is preferable to contain 100 to 300 ppm of Nb ₂ O ₅ and 100 to 600 ppm of Ta ₂ O ₅ in order to cause abnormal grain growth.

The ferrite core of the present invention can contain V ₂ O ₅ in the range of 50 to 1000 ppm as an accessory component. V is a component having a function to increase intergranular 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. It is preferable to contain V ₂ O ₅ in a range of 100 to 500 ppm because abnormal grain growth occurs when the content is increased.

The ferrite core of the present invention can contain 500 to 8000 ppm of SnO ₂ as an accessory component. SnO ₂ is a component that is partially present in grain boundaries and promotes grain boundary re-oxidation in the cooling process after sintering to reduce loss. SnO ₂ also acts as a tetravalent ion to replace atoms of the spinel lattice to lower the bottom temperature. However, if the addition amount is too large, abnormal grain growth is caused to increase loss, so 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 do not necessarily have to be added in the form of oxides, and may be mixed, for example, in the form of carbonates.

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

Next, a manufacturing method suitable for the ferrite core according to the present invention will be described.
As a raw material of the main component, a powder of an oxide or a compound which becomes an oxide upon heating is used. Specifically, Fe ₂ O ₃ powder, Mn ₃ O ₄ powder, ZnO powder or the like can be used. The average particle diameter of each raw material powder may be appropriately selected in the range of 0.1 to 3 μm. After wet mixing of the raw material powder of the main component, calcination is performed. The temperature of the pre-baking may be a predetermined temperature within the range of 800 to 1100 ° C. The stabilization time of calcination may be appropriately selected in the range of 0.5 to 5 hours. After calcination, the calcined material is crushed, for example, to an average particle diameter of about 0.5 to 3 μm. In the present invention, not only the raw material of the above-described main component, but also a powder of a composite oxide containing two or more metals may be used as the raw material of the main component. For example, oxidation and calcination of an aqueous solution containing iron chloride and manganese chloride gives a powder of a composite oxide containing Fe and Mn. The powder and the ZnO powder may be mixed to form the main component material. In such a case, preliminary baking is unnecessary.

The auxiliary components are added after calcination. For the addition after the calcination, the raw material of the auxiliary component may be added to the calcined material and the above-mentioned pulverization may be performed, or the raw material of the auxiliary component can be added and mixed after the calcination of the calcined material. However, NiO, TiO ₂ and CoO can also be subjected to calcination together with the main component material.
An oxide or a powder of a compound that becomes an oxide upon heating can also be used as a raw material of the accessory component. 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 consisting of the main component and the accessory components is granulated into granules in order to smoothly carry out 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, which is sprayed with a spray dryer and dried. The particle size of the obtained granules is preferably about 80 to 300 μm.

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

The fired 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 in a transformer, and the transformer obtained by the present invention can be used in a switching power supply device.

FIG. 1A is a perspective view showing an E-shaped ferrite core (magnetic core) according to the present embodiment. As shown in FIG. 1A, the E-shaped ferrite core 10 is called an E-shaped core or the like, and is used for a transformer or the like. As a transformer in which an E-shaped core such as the ferrite core 10 is adopted, one in which two E-shaped cores are disposed opposite to each other as shown in FIG. 1 (b) is known.

FIG. 2 is a block diagram showing the configuration of the switching power supply device.

Switching power supply apparatus 200 shown in FIG. 2 is an apparatus (DC / DC converter) for converting DC input voltage V _in into DC output voltage V _out , and an input for removing noise components included _in DC output voltage V _in. A filter 201, a switching circuit 202 for converting the output of the input filter 201 into alternating current, a transformer 203 for transforming the output of the switching circuit 202, a rectifier circuit 204 for converting the output of the transformer 203 into DC, and an output of the rectifier circuit And a smoothing circuit 205 for smoothing. In the switching power supply device 200 having such a configuration, when the core according to the present invention is used as the core of the transformer 203, the noise of the switching power supply device 200 can be solved because the noise generated by the transformer 203 can be suppressed. it can.

The switching power supply 200 shown in FIG. 2 is preferably used particularly as a switching power supply for a car.

FIG. 3 is a block diagram schematically showing a main part of a vehicle provided with switching power supply apparatus 200.

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

The high voltage battery 210 is charged by the 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 144 V or about 288 V) supplied from the high voltage battery 210. In the fuel cell vehicle, the fuel cell main body is the power generation device 240, and in the hybrid vehicle, the motor 250 doubles as the power generation device 240.

Although the preferred embodiments of the present invention have been described above, 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. It is needless to say that they are included in the scope.

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 raw materials for main component, NiO powder, TiO ₂ powder, Co ₃ O ₄ powder, SiO ₂ powder, CaCO ₃ powder, Nb ₂ O ₅ as raw materials for auxiliary components Powder, V ₂ O ₅ powder, Ta ₂ O ₅ powder and SnO ₂ powder were used. The composition of the main component and the composition of the subcomponents are shown in Tables 1 to 3. Further, Tables 1 and 2 and the SiO ₂ was added 100 ppm, the CaCO ₃ 1000 ppm, the 200ppm the _Nb 2 _{O 5} in addition to the materials shown in Table. After wet-mixing these powders, they were calcined at 900 ° C. for 3 hours in the atmosphere.
The obtained mixture was added with a binder, granulated, and then molded to obtain a toroidal-shaped molded body, an I-shaped molded body, and an E-shaped molded body. The resulting molded body is sintered at a temperature of 1300 ° C. (5 hours for stable part, 2% for oxygen partial pressure for stable part) under oxygen partial pressure control to obtain a toroidal shaped ferrite core (outer diameter 20 mm, inner diameter 10 mm, thickness) 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) were obtained.

Next, the measuring method of the present invention will be described.
The measurement of magnetostriction at 100 ° C. was performed using a strain gauge (KFG: general-purpose foil strain gauge) manufactured by Kyowa Denki. A strain gauge was attached to the side of the center of the I-type ferrite core. The absolute value of the rate of change of strain amount when the I core was excited and the strain amount did not change was taken as the saturation magnetostriction λs. In the following description, the absolute value of the rate of change in strain amount when the I core is excited and the strain amount does not change is simply expressed as saturation magnetostriction λs as saturation magnetostriction or λs.

The sounding at 100 ° C. was performed by setting each composition of E-shaped core in a simple anechoic box. The measurement was performed with the core and the tip of the microphone of the sound level meter placed 30 mm apart. The sound pressure level was measured using an Ono Sokki noise meter (LA-5570). The data indicates the overall value (OA value) after the A characteristic conversion. The A characteristic is a value obtained by weighting the frequency as an amount representing a sound pressure level based on human hearing. The OA value is the sum of each sound pressure level analyzed.

The saturation magnetic flux density Bs at 100 ° C. was measured under a condition of an excitation magnetic field of 1194 A / m by using a toroidal-shaped core with a direct current magnetization characteristic test device (SK-110) manufactured by Metron Giken.

The core loss Pcv at 100 ° C is obtained by using a toroidal shaped ferrite core and winding 5 primary and 5 secondary windings, and using IWATSU BH analyzer under a condition of maximum magnetic flux density 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 Fe ₂ O ₃ content 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.) becomes smaller than 380 mT. In addition, when the Fe ₂ O ₃ content 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.
In addition, when the amount of ZnO 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 amount of ZnO exceeds 11.5 mol% (see Comparative Examples 4 and 6), the saturation magnetostriction decreases but the saturation magnetic flux density Bs becomes smaller than 380 mT.

(Table 2)
When the amount of NiO as the accessory component is less than 500 ppm (see Comparative Example 9), the saturation magnetostriction becomes large and the OA value becomes larger than 45 dB. When the amount of NiO exceeds 10000 ppm (see Comparative Example 10), the saturation magnetostriction decreases but the saturation magnetic flux density Bs becomes smaller than 380 mT.
When the amount of TiO _{2 as} the accessory component 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. When the amount of TiO ₂ exceeds 6000 ppm (see Comparative Example 12), the magnetostriction decreases but the saturation magnetic flux density Bs becomes smaller than 380 mT.
When the amount of CoO which is an accessory component 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. In addition, when the amount of CoO exceeds 4000 ppm (see Comparative Example 14), the saturation magnetic flux density Bs becomes smaller than 380 mT.

With respect to the above, 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 balance of the main component of MnO is 500 to 10000 ppm of NiO as an accessory component. When the content of TiO ₂ is 100 to 6000 ppm and 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. You can get it.

(Table 3)
The other subcomponents are as follows.
As described above, SiO ₂ and CaCO ₃ segregate at grain boundaries to form a high resistance layer to contribute to low loss and have the effect of improving the sintering density as a sintering aid, as shown in Table 3. As shown, it affects the core loss Pcv. That is, by adding SiO ₂ and CaCO ₃ , core loss Pcv can be reduced, but as shown in Table 3, core loss becomes worse if it is added too much (see Examples 20 to 27). Therefore, when SiO ₂ and CaCO ₃ are added, 50 to 300 ppm of SiO ₂ and 200 to 3000 ppm of CaCO ₃ are added.
Moreover, the core loss Pcv can be reduced by adding Nb ₂ O ₅ and Ta ₂ O ₅ (see Examples 28 to 34). However, similar to the case of SiO ₂ and CaCO ₃ , too much addition leads to poor core loss, so the range of optimum addition amount is 50 to 750 ppm or less for Nb ₂ O ₅ and 50 to 1500 ppm or less for Ta ₂ O ₅ Do.
Moreover, the core loss Pcv can be reduced by adding V ₂ O ₅ (see Examples 35 to 37). However, if it is added too much in the same manner as in the case of SiO ₂ and CaCO _3, the core loss becomes worse, so the optimum addition amount range is 50 to 1000 ppm or less of 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 addition amount range is 500 to 8000 ppm or less of SnO ₂ .

As described above, the ferrite core according to the present invention can sufficiently suppress the ringing of the core during driving by reducing the saturation magnetostriction at around 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 transformer by which two E-type cores were opposingly arranged by the inside which concerns on this embodiment. It is a block diagram of a switching power supply device. FIG. 1 is a block diagram showing a main part of a motor vehicle provided with a switching power supply device.

10 Ferrite core (magnetic core)
11 (middle leg)
12 (coil)
200 switching power supply

Claims (5)

MnZn ferrite containing a main component in which iron oxide is 51.5 to 54.5 mol% in terms of Fe ₂ O ₃ , zinc oxide is 7.0 to 11.5 mol% in terms of ZnO, and the balance is manganese oxide, In this main component, Ni is contained 500 to 10000 ppm in NiO conversion, Ti is contained 100 to 6000 ppm in TiO ₂ conversion, Co is contained 500 to 4000 ppm in CoO conversion, and V is converted to V ₂ O ₅ in 50~1000ppm seen including,
1. A ferrite core having a saturated magnetostriction λs at 100 ° C. of 1.5 × 10 ⁻⁶ or less and an overall value after A characteristic conversion at 100 ° C. of 45 dB or less . MnZn ferrite containing a main component in which iron oxide is 51.5 to 54.5 mol% in terms of Fe ₂ O ₃ , zinc oxide is 7.0 to 11.5 mol% in terms of ZnO, and the balance is manganese oxide, In this main component, Ni is contained 500 to 10000 ppm in NiO conversion, Ti is contained 100 to 6000 ppm in TiO ₂ conversion, Co is contained 500 to 4000 ppm in CoO conversion, and Sn is 500 for SnO ₂ conversion. ~8000ppm seen including,
1. A ferrite core having a saturated magnetostriction λs at 100 ° C. of 1.5 × 10 ⁻⁶ or less and an overall value after A characteristic conversion at 100 ° C. of 45 dB or less . The ferrite core according to claim 1 or 2, wherein 50 to 300 ppm of Si in terms of SiO ₂ and 200 to 3000 ppm of Ca in terms of CaCO ₃ are contained with respect to the main component. 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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