JP2017147306A - Non-contact power receiving coil device and non-contact power receiving core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-contact power receiving coil device which can reduce a leak magnetic flux which is produced in reception of a power.SOLUTION: A non-contact power receiving coil device comprises: a core made of a magnetic material, into which a magnetic flux formed on a power supply side flows; and a conducting wire in which an induced current is produced by the magnetic flux. The core has: an inner peripheral wall part extending around a center hole of the core along the conducting wire, and disposed on an inner peripheral side of the conducting wire; an outer peripheral wall part disposed on an outer peripheral side of the conducting wire; and a connection wall part connecting the inner peripheral wall part and the outer peripheral wall part. The conducting wire is disposed in a groove portion surrounded by the inner peripheral wall part, the outer peripheral wall part and the connection wall part.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a non-contact power receiving coil device that receives power from a power feeding side in a non-contact manner and a non-contact power receiving core used therefor.

  In recent years, there has been an increase in electronic devices that employ a charging method in which electric power is transmitted from a power feeding side to a power receiving side by a non-contact method such as electromagnetic induction. For example, by adopting a non-contact method as a charging method of an electronic device having a secondary battery, it is not necessary to provide a connection terminal as in the case of adopting a contact method for connecting terminals, for example, waterproofness etc. This is advantageous from the viewpoint.

  When non-contact type power transmission is performed like a non-contact electromagnetic induction charging mechanism, a technology that uses a core into which a magnetic flux formed on the power feeding side flows in a device on the power receiving side together with a coil that generates an induced current Has been proposed (see Patent Document 1). There has been proposed a technique for improving the power transmission efficiency by using such a non-contact power receiving coil device having a core and a coil.

JP 2009-123943 A

  However, in the conventional non-contact power receiving coil device, the spread of the magnetic flux formed between the power feeding side and the power receiving side core is wide. In particular, when the distance between the power feeding side and the power receiving side core is increased, the leakage magnetic flux increases. This may cause problems such as a decrease in transmission efficiency.

  This invention is made | formed in view of such a subject, The objective is to provide the coil apparatus for non-contact electric power reception which can suppress the leakage magnetic flux which arises at the time of electric power reception.

A non-contact power receiving coil device according to the present invention includes:
A non-contact power receiving coil device having a core made of a magnetic material into which a magnetic flux formed on a power feeding side flows, and a conductive wire that generates an induced current by the magnetic flux,
Each of the cores extends around the central hole of the core along the conductive wire, and an inner peripheral wall portion disposed on the inner peripheral side of the conductive wire and an outer peripheral wall portion disposed on the outer peripheral side of the conductive wire. And a connecting wall portion connecting the inner peripheral wall portion and the outer peripheral wall portion,
The conducting wire is arranged in a groove portion surrounded by the inner peripheral wall portion, the outer peripheral wall portion, and the connection wall portion.

  In the non-contact power receiving coil device according to the present invention, the core has an inner peripheral wall portion, an outer peripheral wall portion, and a connecting wall portion, and the conducting wire is disposed in a groove portion surrounded by these wall portions, And the spread of magnetic flux formed between the power receiving side and the leakage magnetic flux can be suppressed. That is, in such a non-contact power receiving coil device, the distance between the core on the power feeding side and the power receiving side is set such that the inflow portion of the magnetic flux from the power feeding side to the power receiving side, and the inflow portion of the magnetic flux from the power receiving side to the power feeding side. Therefore, it is possible to reduce the leakage magnetic flux. Further, by suppressing the spread of the magnetic flux, it is possible to keep the power transmission efficiency high even if the distance between the power feeding side and the power receiving side is widened.

  In addition, for example, the groove portion may be U-shaped in a cross section along the radial direction of the central hole, and the inner peripheral wall portion and the outer peripheral wall portion have the same length in the depth direction of the groove portion. May be.

  By making the core and the groove formed in the core U-shaped, it is possible to more suitably suppress the leakage magnetic flux.

  For example, the core may be configured by combining a plurality of divided cores that are separate from each other.

  Such a core is advantageous in terms of impact resistance compared to an integral continuous core.

  Further, the plurality of divided cores may include a first core and a second core having the same shape.

  By configuring the core by combining the first core and the second core having the same shape, the types of components included in the non-contact power receiving coil device can be reduced, and the manufacturing can be facilitated and the cost can be reduced.

  Further, for example, the core may house the conductive wire in the groove part in a range of 270 degrees or more and less than 350 degrees around the central hole.

  The core does not have to be an annular shape (circular ring, elliptical ring, or square ring shape) that completely surrounds the central hole, but has a shape that surrounds the central hole, such as an arc shape, a C ring shape, or an L shape. Any shape can be used. However, the induction current generated in the conducting wire can be increased by accommodating the conducting wire in the groove portion in the range of 270 degrees or more around the central hole. In addition, since the conductor is accommodated in the groove around the central hole in a range of less than 350 degrees, the core can be reduced in size and weight, and the conductor can be easily pulled out of the groove. Is possible.

  Further, for example, at least one of the outer peripheral wall portion and the inner peripheral wall portion may be formed with a notch for drawing the lead wire from the groove portion to the outside.

  By forming a notch in the core, it is not necessary to secure a space in the depth direction of the groove outside the core for the wiring of the conductor, so such a non-contact power receiving coil is a device to be mounted. Contributes to downsizing.

  Further, for example, the length of the connecting wall portion in the width direction of the groove portion may be longer than the length of the inner peripheral wall portion and the outer peripheral wall portion in the depth direction of the groove portion.

  Such a non-contact power receiving coil is thin, which contributes to thinning of a device to be mounted.

The core according to the present invention is a non-contact power receiving core into which a magnetic flux made of a magnetic material and formed on the power feeding side flows,
All extend around the central hole, and the inner peripheral wall portion disposed on the inner peripheral side, the outer peripheral wall portion disposed on the outer peripheral side, and the connection wall portion connecting the inner peripheral wall portion and the outer peripheral wall portion. And having
A ring-shaped or arc-shaped groove portion surrounded by the inner peripheral wall portion, the outer peripheral wall portion, and the connection wall portion is formed.

  Such a non-contact power receiving core is suitably used for the above-described non-contact power receiving coil device.

FIG. 1 is a cross-sectional view showing a non-contact power receiving coil device and a non-contact power feeding coil device corresponding to the non-contact power receiving coil device according to an embodiment of the present invention. FIG. 2 is a plan view of the non-contact power receiving coil device shown in FIG. FIG. 3 is a plan view of a core included in the non-contact power receiving coil device shown in FIG. FIG. 4 is a perspective view of a split core included in a non-contact power receiving coil according to a modification. FIG. 5 is a conceptual diagram showing a usage state of the split core shown in FIG. FIG. 6 is a cross-sectional view illustrating a modification of the non-contact power feeding coil device corresponding to the non-contact power receiving coil device.

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

  FIG. 1 shows a non-contact power receiving coil device 10 (hereinafter referred to as a coil device 10) and a non-contact power supply coil device 60 (hereinafter referred to as a power supply side coil device 60) corresponding to the coil device 10 according to an embodiment of the present invention. FIG. The coil device 10 is mounted on a power receiving side device 50 that operates using the power received via the coil device 10, and is housed in a housing 51 of the power receiving side device 50.

  Examples of the power receiving device 50 on which the coil device 10 is mounted include portable mobile terminals such as mobile phones, smartphones, and tablets, so-called wearable terminals such as electronic watches, and other electronic devices. In the present embodiment, the power receiving device 50 will be described using an electronic timepiece having a communication function called a so-called smart watch as an example. The casing 51 of the power receiving device 50 is provided with a secondary battery (not shown) for storing the power received via the coil device 10, a display device (not shown), and the like in addition to the coil device 10. .

  The coil device 10 includes a core 20 made of a magnetic material into which a magnetic flux formed on the power feeding side (power feeding side coil device 60) flows, and a conductive wire 30 that generates an induced current by the magnetic flux formed on the power feeding side. . FIG. 2 is a plan view of the coil device 10 shown in FIG. 1 as viewed from the power supply side (Z-axis negative direction side).

  As shown in FIG. 2, the core 20 has an annular outer shape surrounding the central hole 21 located in the center of the core 20 when viewed from the Z-axis direction. As shown in FIGS. 3 and 1, which are plan views of only the core 20, the core 20 includes an inner peripheral wall portion 22 disposed on the inner peripheral side of the conducting wire 30 and an outer peripheral wall portion disposed on the outer peripheral side of the conducting wire 30. 24, and a connecting wall portion 26 that connects the inner peripheral wall portion 22 and the outer peripheral wall portion 24.

  As shown in FIG. 3, the inner peripheral wall portion 22, the outer peripheral wall portion 24, and the connection wall portion 26 all extend around the central hole 21 of the core 20 along the conducting wire 30 and have an annular outer shape. doing. However, the outer peripheral wall portion 24 is formed with a notch 24c in which the height of the groove portion 28 in the depth direction (Z-axis direction) is lower than the other portions.

  As shown in FIGS. 1 to 3, the core 20 has three directions in the inner peripheral wall portion 22, the outer peripheral wall portion 24, and the connection wall portion 26 (the radially inner side of the central hole 21, the radially outer side, and the Z A groove 28 is formed so as to surround the axial positive direction. As shown in FIG. 3, the groove portion 28 has a ring shape when viewed from the Z-axis negative direction side, and the conductor 30 is disposed in the groove portion 28 as shown in FIG. 2.

  As shown in FIG. 1, the groove 28 is U-shaped in a cross section along the radial direction of the central hole 21. The core 20 is disposed near the surface of the casing 51 in such a posture that the opening of the groove portion 28 faces the surface side (Z-axis negative direction side). The inner peripheral wall portion 22 of the core 20 faces the outer peripheral wall portion 24 with the conducting wire 30 sandwiched in the radial direction of the central hole 21.

  As shown in FIG. 1, the length L1 in the depth direction (Z-axis direction) of the groove portion 28 in the inner peripheral wall portion 22 is equal to the length L2 in the depth direction (Z-axis direction) of the groove portion 28 in the outer peripheral wall portion 24. It has become. The length L3 in the width direction of the groove portion 28 in the connecting wall portion 26 that connects the Z-axis positive direction end portions of the inner peripheral wall portion 22 and the outer peripheral wall portion 24 is the width of the groove portion 28 in the inner peripheral wall portion 22 and the outer peripheral wall portion 24. It is longer than the lengths L1 and L2 in the depth direction.

  As shown in FIG. 2, the conducting wire 30 disposed in the groove portion 28 constitutes a ring-shaped coil (power-receiving side coil) that circulates around the central hole 21. The conducting wire 30 disposed in the groove portion 28 is drawn to the outside of the groove portion 28 through a notch 24 c formed in the outer peripheral wall portion 24. The number of turns of the conducting wire 30 is not particularly limited, and is appropriately determined according to the circuit of the power receiving side device 50 and the like.

  The core 20 is made of a magnetic material and is formed using a material such as ferrite or metal. The core 20 may include a material such as carbon or resin that binds magnetic powder such as ferrite or metal. Moreover, the core 20 may be comprised with the sintered compact, may be comprised with the magnetic sheet, and may be comprised by joining a sintered compact and a magnetic sheet.

  The conductive wire 30 may be a covered electric wire in which the outer periphery of a conductive core material containing Cu or the like is covered with an insulating coating such as a resin, but is not particularly limited as long as it is an electric wire that generates an induced current due to a change in magnetic flux. Moreover, the core material of the conducting wire 30 may be a single wire or a stranded wire.

  A power supply side coil device 60 shown in FIG. 1 is housed inside a housing 91 of a power supply side device 90. Examples of the power supply side device 90 include a charger for charging a secondary battery provided in the power reception side device 50, but are not particularly limited as long as power is supplied to the power reception side device 50.

  The power supply side coil device 60 includes a power supply side core 70 and a power supply side coil 80. The power supply side core 70 has an annular outer shape surrounding the power supply side central hole 71 located at the center of the power supply side core 70 when viewed from the positive Z-axis direction, like the power receiving side core 20. . The power supply side core 70 is formed with a power supply side core groove portion 78 that is ring-shaped when viewed from the Z-axis positive direction side so as to face the groove portion 28 of the core 20 on the power reception side. Is provided with a power supply side coil 80.

  The power supply side core 70 includes a power supply side inner peripheral wall portion 72 disposed on the inner peripheral side of the power supply side coil 80, a power supply side outer peripheral wall portion 74 disposed on the outer peripheral side of the power supply side coil 80, and a power supply side inner peripheral wall portion. 72 and a power supply side connection wall 76 connecting the power supply side outer peripheral wall 74. Power is supplied to the power supply side coil 80 from a secondary battery (not shown) provided in the power supply side device 90 or an AC power source connected via the power supply side device 90.

  The outer diameter of the power supply side core 70 and the diameter of the power supply side central hole 71 are substantially equal to the outer diameter of the core 20 on the power reception side and the diameter of the central hole 21. The power supply side core 70 is also made of a magnetic material like the core 20 of the coil device 10 and is formed using a material such as ferrite or metal. The power supply side coil 80 is also configured by a covered electric wire or the like wound around the power supply side central hole 71 in the same manner as the coil formed by the conducting wire 30.

  The power supply and power reception from the power supply side device 90 to the power reception side device 50 shown in FIG. 1 are performed in a state where the surface of the power supply side device 90 and the surface of the power reception side device 50 are in contact with or close to each other. That is, as shown in FIG. 1, power feeding and power reception are performed in a state where the groove portion 28 in which the conducting wire 30 is accommodated and the power feeding side core groove portion 78 in which the power feeding side coil 80 is accommodated are opposed to each other. Is called. At this time, the inner wall tip 22 a that is the tip of the inner peripheral wall portion 22 in the core 20 faces the power feeding side inner peripheral wall portion 72 of the power feeding side core 70, and the outer wall tip 24 a that is the tip of the outer peripheral wall portion 24 in the core 20. Faces the power supply side outer peripheral wall 74 of the power supply side core 70.

  In the state shown in FIG. 1, a magnetic flux is formed in the power supply side coil device 60 by passing an alternating current of a predetermined frequency through the power supply side coil 80. The magnetic flux formed by the power supply side coil device 60 flows into the core 20 disposed opposite to the power supply side core 70, and further flows from the core 20 into the power supply side core 70, whereby the core 20 and the power supply side core A flux loop through 70 is formed.

  The conducting wire 30 disposed in the groove portion 28 of the core 20 generates an induced current due to a change in magnetic flux in the core 20 and the like disposed around the conducting wire 30. The induced current generated in the conductive wire 30 is stored in a secondary battery or the like provided in the power receiving side device 50 and then used for the operation of the power receiving side device 50. In this manner, non-contact power feeding and non-contact power reception from the power feeding side coil device 60 to the power receiving side coil device 10 are performed.

  In the coil device 10 as described above, the conducting wire 30 that generates the induced current has three directions other than facing the feeding-side coil device 60, that is, the radially inner side, the radially outer side of the central hole 21, and the feeding-side coil device 60. Are arranged in the groove portion 28 surrounded by the inner peripheral wall portion 22, the outer peripheral wall portion 24 and the connection wall portion 26 in the opposite three directions. Therefore, the distances between the inner wall tip 22a and the outer wall tip 24a in the core 20 and the power supply side core 70 are all reduced. Thereby, the coil apparatus 10 can suppress the spread of the magnetic flux formed between the power feeding side and the power receiving side, and can suppress the leakage magnetic flux.

  Further, by arranging the conductive wire 30 in the groove portion 28 having a U-shaped cross section as shown in FIG. 1, the magnetic flux is prevented from spreading in the XY directions around the core 20, and the core 20 and the power supply side core 70. The magnetic flux can be concentrated at a position where and are opposed to each other. Therefore, the coil device 10 can suppress the leakage magnetic flux and increase the transmission efficiency, and can extend the transmission distance that can achieve the allowable transmission efficiency.

  In the coil device 10, the inner circumferential wall portion 22 located on the inner circumferential side with respect to the conducting wire 30 and the outer circumferential wall portion 24 located on the outer circumferential side have the same length in the depth direction of the groove portion 28. In such a coil device 10, by aligning the heights of the inner wall tip 22a and the outer wall tip 24a, both the inflow portion of the magnetic flux from the power feeding side to the power receiving side and the inflow portion of the magnetic flux from the power receiving side to the power feeding side. The distance between the cores 20 and 70 on the power feeding side and the power receiving side is reduced. Therefore, the coil device 10 can suppress the leakage magnetic flux and extend the transmission distance (the shortest distance between the power feeding side coil device 60 and the power receiving side coil device 10) that can achieve an acceptable transmission efficiency.

  In the coil device 10, the length L3 in the width direction of the groove portion 28 in the connection wall portion 26 of the core 20 is longer than the lengths L1 and L2 in the depth direction of the groove portion 28 in the inner peripheral wall portion 22 and the outer peripheral wall portion 24. It has become. As a result, the coil device 10 can be thinned while securing the volume of the groove 28 that accommodates the conducting wire 30.

  In addition, although the thickness of the inner peripheral wall part 22, the outer peripheral wall part 24, and the connection wall part 26 in the core 20 is not specifically limited, For example, the inner peripheral wall part 22, the outer peripheral wall part 24, and the connection wall part 26 shall be the same thickness. Can do.

  Further, as shown in FIG. 2 or FIG. 3, the outer wall 24 of the coil device 10 is formed with a notch 24c for leading the lead wire 30 out of the groove 28 to the outside, so that the inner wall tip 22a shown in FIG. The outer wall tip 24a can be brought into contact with or close to the housing 51. Such a coil device 10 can shorten the distance between the core 20 and the power supply side core 70 at the time of power supply and power reception, and can suppress leakage magnetic flux. Further, the notch 24 c of the core 20 contributes to downsizing of the power receiving side device 50. In addition, the notch of the core 20 may be provided in the inner peripheral wall part 22, or may be provided in both the inner peripheral wall part 22 and the outer peripheral wall part 24.

  The coil device according to the present invention has been described with reference to the embodiment. However, the coil device according to the present invention is not limited to the embodiment, and it goes without saying that many other modifications are included in the technical scope of the present invention. . For example, in the coil device 10, the core 20 has an annular shape as viewed from the Z-axis direction, but the core may have another annular shape such as an elliptical ring shape or a square ring shape, A ring that is not partially connected may be used. Further, the core of the coil device 10 may have a shape surrounding only a part of the central hole, such as an arc shape or an L shape.

  FIG. 4 is a perspective view showing a split core 120a included in a coil device (a power receiving side coil device) according to a modification. The split core 120a has an arc shape, and a groove portion 128 extending in an arc shape is formed in the split core 120a in the same manner as the outer shape. In the groove portion 128, a conducting wire that generates an induced current is disposed.

  The split core 120a includes an inner peripheral wall portion 122 disposed on the inner peripheral side of the conductive wire, an outer peripheral wall portion 124 disposed on the outer peripheral side of the conductive wire, and a connection wall portion that connects the inner peripheral wall portion 122 and the outer peripheral wall portion 124. 126. The groove portion 128 is surrounded by the inner peripheral wall portion 122, the outer peripheral wall portion 124, and the connection wall portion 126. The groove part 128 is U-shaped in the cross section along the radial direction of the center hole 121 (in the split core 120a, a hole having a common center with the arc center), like the groove part 28 shown in FIG.

  FIG. 5 is a conceptual diagram illustrating a core of a coil device according to a modification. The core of the coil device according to the modification is formed by combining a plurality of (three in the example shown in FIG. 5) split cores 120a that are separate from each other. The three divided cores 120a have the same shape, and the core shown in FIG. 5 includes two or more (three in the example shown in FIG. 5) divided cores 120a having the same shape.

  The core shown in FIG. 5 has a C-ring-like outer shape, whereas the conducting wire arranged in the groove 128 is annular like the conducting wire 30 shown in FIG. Is disposed outside the groove 128. The core formed by combining the split cores 120a is sufficient if a part of the conducting wire is accommodated in the groove portion 128, but such a core does not conduct the conducting wire around the central hole 121 in a range of 270 degrees or more and less than 350 degrees. It is preferable to be accommodated in the groove 128. By setting the angle Θ indicating the range in which the conducting wire is accommodated in the groove 128 to 270 degrees or more, the induced current generated in the conducting wire can be effectively increased. In addition, by setting the angle Θ indicating the range in which the conducting wire is accommodated in the groove portion 128 to be less than 350 degrees, the core can be reduced in size and weight, and the conducting wire can be easily pulled out of the groove portion 128. Is possible.

  The coil device having the split core 120a according to the modification shown in FIGS. 4 and 5 also has the same effect as the coil device 10. In addition, a core formed by combining a plurality of split cores 120a is advantageous in terms of impact resistance because it hardly generates cracks or chips even when subjected to external impacts. Moreover, the characteristic of a coil apparatus can be easily adjusted by increasing / decreasing the number of the division | segmentation cores 120a combined.

  The shape of the power feeding side core 70 used corresponding to the power receiving side core 20 described above is not limited to the ring shape as shown in FIG. 1. For example, the power feeding side core 170 as shown in FIG. Good. As shown in FIG. 6, the power feeding side core 170 has a disk-like outer shape having an outer diameter substantially equal to the outer diameter of the power receiving side core 20, and has a cylindrical central protrusion formed in the central portion. Part 172 and a ring-shaped outer peripheral convex part 174 constituting the outer peripheral part of the power feeding side core 170.

  The power feeding side core 170 is formed between the central convex portion 172 and the outer peripheral convex portion 174, and is formed with a ring-shaped power feeding side core groove portion 178 that opens toward the positive direction of the Z axis. A power supply side coil 80 is disposed in the power supply side core groove 178. At the time of power supply / reception, the inner wall tip 22 a is disposed to face the central convex portion 172 of the power feeding side core 170, and the outer wall tip 24 a is disposed to face the outer peripheral convex portion 174 of the power feeding side core 170. Even when the coil device 10 is a combination with a power feeding device coil device having a power feeding side core 170 as shown in FIG.

DESCRIPTION OF SYMBOLS 10 ... Coil apparatus 20 ... Core 21, 121 ... Center hole 22, 122 ... Inner peripheral wall part 22a ... Inner wall front end 24, 124 ... Outer peripheral wall part 24a ... Outer wall front end 24c ... Notch 26, 126 ... Connection wall part 28, 128 ... Groove 30 ... Conductor 120a ... Divided core 50 ... Power receiving side device 80 ... Power feeding side coil 60 ... Power feeding side coil device

Claims (9)

A non-contact power receiving coil device having a core made of a magnetic material into which a magnetic flux formed on a power feeding side flows, and a conductive wire that generates an induced current by the magnetic flux,
Each of the cores extends around the central hole of the core along the conductive wire, and an inner peripheral wall portion disposed on the inner peripheral side of the conductive wire and an outer peripheral wall portion disposed on the outer peripheral side of the conductive wire. And a connecting wall portion connecting the inner peripheral wall portion and the outer peripheral wall portion,
The said conducting wire is arrange | positioned at the groove part enclosed by the said inner peripheral wall part, the said outer peripheral wall part, and the said connection wall part, The coil apparatus for non-contact electric power receptions characterized by the above-mentioned.   The non-contact power receiving coil device according to claim 1, wherein the groove is U-shaped in a cross section along the radial direction of the central hole.   The non-contact power receiving coil device according to claim 1 or 2, wherein the inner peripheral wall portion and the outer peripheral wall portion have the same length in the depth direction of the groove portion.   The non-contact power receiving coil device according to any one of claims 1 to 3, wherein the core is formed by combining a plurality of divided cores that are separate from each other.   The non-contact power receiving coil device according to claim 4, wherein the plurality of split cores include two or more split cores having the same shape.   The non-core according to any one of claims 1 to 5, wherein the core accommodates the conductive wire in the groove portion within a range of 270 degrees or more and less than 350 degrees around the central hole. Coil device for contact power reception.   The notch which pulls out the said conducting wire from the said groove part to the exterior is formed in at least one among the said outer peripheral wall part and the said inner peripheral wall part, The Claim 1 characterized by the above-mentioned. Non-contact power receiving coil device.   The length in the width direction of the groove portion of the connecting wall portion is longer than the length in the depth direction of the groove portion of the inner peripheral wall portion and the outer peripheral wall portion. A non-contact power receiving coil device according to claim 1. A non-contact power receiving core made of a magnetic material into which a magnetic flux formed on the power feeding side flows,
All extend around the central hole, and the inner peripheral wall portion disposed on the inner peripheral side, the outer peripheral wall portion disposed on the outer peripheral side, and the connection wall portion connecting the inner peripheral wall portion and the outer peripheral wall portion. And having
A ring-shaped or arc-shaped groove portion surrounded by the inner peripheral wall portion, the outer peripheral wall portion and the connection wall portion is formed.

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