JP2014155357A - Brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase torque without increasing a magnet quantity by efficiently turning magnetic fluxes of magnets towards the outer circumference in a magnetic flux concentrated brushless motor.SOLUTION: In a rotor 3 of a brushless motor 1 which is a magnetic flux concentrated motor, magnet mount holes 33 in which magnets 36 are accommodated are formed radially. Between neighboring magnet mount holes 33, a pseudo magnetic pole 37 is formed. Between a radially inner end of the magnet mount hole 33 and a radially inner end of the magnet 36, a cavity 38 is formed as a magneto-resistant part. In the center of the pseudo magnetic pole 37 at an inner circumferential side, a cavity groove 39 is formed as a magneto-resistant part. The cavity groove 39 is provided closer to the inner circumference than a position which is separated from a radially inner end face 36a of the magnet 36 by L/8 (L: radial length of magnet).

Description

  The present invention relates to a magnetic flux concentration type brushless motor, and more particularly, to a spoke type brushless motor having magnets arranged radially.

  In recent years, as in Patent Document 1, various so-called spoke-type brushless motors having a rotor in which a plurality of magnets are arranged radially around a rotating shaft have been proposed. FIG. 8 is an explanatory view showing the rotor configuration of such a spoke-type brushless motor. As shown in FIG. 8, in the rotor 51, the magnets 52 and the core members 53 are alternately arranged in the circumferential direction, and adjacent magnets 52 have the same polarity on opposite surfaces. Magnetic fluxes from the magnets 52 repel each other in the core member 53 and concentrate in the outer peripheral direction (arrow P). As a result, a pseudo magnetic pole portion 54 is formed on the outer periphery of the rotor 51 along the circumferential direction, and becomes a magnetic pole on the rotor side.

JP-A-6-311679

  However, in such a spoke-type magnetic flux concentration type brushless motor, in the radially inner portion 52a of the magnet 52, the magnetic flux emitted from its own N pole passes through the core member 53 on the radially inner side of the magnet 52 to the S pole. Magnetic flux leakage (shortcut) occurred due to the magnetic path leading to (arrow Q), and the magnetic force of the magnet could not be used effectively. In this case, if the size of the magnet is increased, the magnetic flux toward the outer peripheral direction can be increased. However, the amount of the magnet is increased and the outer diameter of the rotor is increased accordingly, so there is a limit.

  SUMMARY OF THE INVENTION An object of the present invention is to increase the torque without increasing the amount of magnet by efficiently directing the magnetic flux of the magnet in the outer circumferential direction in the magnetic flux concentration type brushless motor.

  A brushless motor of the present invention includes a stator including a plurality of teeth projecting radially inward and a coil wound around the teeth through a slot formed between the teeth, and an inner side of the stator A brushless motor having a plurality of poles and magnets constituting a plurality of poles housed in a radially formed magnet housing portion, wherein the rotor is adjacent to the magnet housing portion. A plurality of pseudo magnetic pole portions formed therebetween, a first magnetoresistive portion formed between a radial inner end of the magnet housing portion and a radial inner end of the magnet, A second magnetoresistive portion formed at a central portion on the circumferential side, and the second magnetoresistive portion is a radially inner end of the magnet when the radial length of the magnet is L. And which are located respectively on the inner peripheral side of a position of L / 8 from.

  In the present invention, a first magnetoresistive portion is provided on the radially inner end side of the magnet housing portion, and a second magnetoresistive portion is provided between the magnet housing portions, and the second magnetoresistive portion is disposed in the radial direction of the magnet. By providing it on the inner circumference side from the position of L / 8 (L: length in the radial direction of the magnet) from the inner end face, the extended surface distance between the magnet poles becomes longer, and the magnetic path that shortcuts the N and S poles is longer. Become. For this reason, the magnetic resistance in the radially inner portion of the magnet is increased, and the leakage magnetic flux in the portion is reduced.

  In the brushless motor, the rotor is formed by stacking a plurality of core plates made of a magnetic material, and the first magnetoresistive portion is formed from a center hole formed in the center of the rotor. It may be provided more than the plate thickness. In addition, the second magnetoresistive portion may be provided away from the adjacent magnet housing portion by a thickness greater than the plate thickness of the core plate. Furthermore, the distance between the radially inner end of the second magnetoresistive portion and the center hole formed in the center of the rotor is set between the radially inner end of the first magnetoresistive portion and the center hole. It may be set equal to or less than the distance.

  On the other hand, you may provide the opening part which faces the outer peripheral surface of the said rotor at the radial direction outer end of the said magnet accommodating part. In this case, a flange that extends to the outer peripheral surface of the pseudo magnetic pole portion may be formed to extend from at least one of the adjacent pseudo magnetic pole portions in the opening. Further, the opening may be formed so that an opening ratio with respect to a width along the circumferential direction of the magnet housing portion is 75% or less.

  In addition, a nonmagnetic portion may be provided in each of the radially inner portion and the radially outer portion of the magnet in the magnet housing portion, and the nonmagnetic portion may be made of synthetic resin.

  According to the brushless motor of the present invention, in the so-called spoke-type magnetic flux concentration type brushless motor, the first magnetic resistance portion is provided on the radially inner end side of the magnet housing portion, and the second magnetic resistance portion is provided between the magnet housing portions, Since the second magnetoresistive portion is provided on the inner peripheral side from the position of L / 8 (L: length in the radial direction of the magnet) from the radially inner end surface of the magnet, the magnetic resistance at the radially inner portion of the magnet is increased. It is possible to reduce the magnetic flux leakage at the part. For this reason, compared with the conventional magnetic flux concentration type brushless motor, the magnetic flux of the magnet can be used efficiently, and the torque can be increased without increasing the magnet amount.

It is sectional drawing of the brushless motor which is Embodiment 1 of this invention. It is sectional drawing along the AA line of FIG. It is explanatory drawing which shows the structure of the magnet attachment hole vicinity in the brushless motor of FIG. (A) is explanatory drawing which shows the torque change at the time of providing a space | gap part (1st magnetoresistive part) in a magnet attachment hole, (b) provided the space | gap groove (2nd magnetoresistive part) between magnet attachment holes. It is explanatory drawing which shows the torque change in a case. It is explanatory drawing which shows the rotor structure of the brushless motor which is Embodiment 2 of this invention, and has shown the structure which open | released the radial direction outer end of the magnet attachment hole. It is explanatory drawing which shows the rotor structure of the brushless motor which is Embodiment 2 of this invention, and has shown the structure which provided the opening part and the collar part in the radial direction outer end of the magnet attachment hole. It is explanatory drawing which showed the relationship between the width | variety (opening ratio) of an opening part, a torque, and a ripple. It is explanatory drawing which shows the rotor structure of the conventional spoke type brushless motor.

(Embodiment 1)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 is a cross-sectional view of a brushless motor 1 (hereinafter abbreviated as “motor 1”) according to Embodiment 1 of the present invention, and FIG. 2 is a cross-sectional view taken along the line AA of FIG. The motor 1 is a so-called spoke-type magnetic flux concentrating motor in which rotor magnets are arranged radially, and is used, for example, as a drive source of an electric power steering apparatus. As shown in FIG. 1, the motor 1 is an inner rotor type brushless motor in which a stator (stator) 2 is arranged on the outside and a rotor (rotor) 3 is arranged on the inside.

  The stator 2 is fixed inside a bottomed cylindrical motor case 4 (hereinafter abbreviated as case 4) by a fixing means such as an adhesive. The stator 2 includes a stator core 5, a stator coil 6 (hereinafter abbreviated as a coil 6) wound around a tooth 9 of the stator core 5, and a bus bar unit (terminal unit) attached to the stator core 5 and electrically connected to the coil 6. 7). The case 4 is formed in a bottomed cylindrical shape with iron or the like, and a bracket 8 (for example, made of aluminum die cast) is attached to an opening of the case 4 by a fixing screw (not shown).

  The stator core 5 is formed by laminating steel plate materials (for example, electromagnetic steel plates), and a plurality (12 in the present embodiment) of teeth 9 are provided projecting radially inward. A slot 31 is formed between adjacent teeth 9, and a coil 6 is accommodated therein. An insulator 11 made of synthetic resin is attached to the stator core 5, and a coil 6 is wound around the outside of the insulator 11. Thus, the stator 2 has a 12-pole (12-slot) configuration.

  A bus bar unit 7 is attached to one end of the stator core 5 on the opening side of the case 4. The bus bar unit 7 has a structure in which a copper bus bar is insert-molded in a synthetic resin main body. Around the bus bar unit 7, a plurality of power supply terminals 12 project in the radial direction. When the bus bar unit 7 is attached, the end 6 a of the coil 6 drawn out from the stator core 5 is welded to the power feeding terminal 12. In the bus bar unit 7, the number of bus bars corresponding to the number of phases of the motor 1 (here, three for the U phase, V phase, W phase and one for connecting each phase) is provided. Yes. Each coil 6 is electrically connected to a power supply terminal 12 corresponding to the phase. The stator core 5 is press-fitted and fixed in the case 4 after the bus bar unit 7 is attached.

  A rotor 3 is inserted inside the stator 2. The rotor 3 has a rotor shaft 13, and the rotor shaft 13 is rotatably supported by bearings 14a and 14b. The bearing 14 a is fixed to the center of the bottom of the case 4, and the bearing 14 b is fixed to the center of the bracket 8. A cylindrical rotor core 15 and a rotor (resolver rotor) 22 of a resolver 21 serving as a rotation angle detection unit are attached to the rotor shaft 13. A stator (resolver stator) 23 of the resolver 21 is accommodated in a resolver bracket 24 made of synthetic resin, and is fixed to the inside of the bracket 8 by an attachment screw 25.

  The rotor core 15 has a configuration in which a plurality of thin core plates (steel plate materials) formed of a magnetic material are stacked, and the outer shape thereof is not a perfect circle but an eccentric shape. The rotor core 15 is provided with a shaft hole (center hole) 32 and a plurality of magnet mounting holes (magnet housing portions) 33. The shaft hole 32 is formed at the center of the rotor core 15, and the rotor shaft 13 is press-fitted and fixed therein. The magnet mounting holes 33 are rectangular holes extending along the radial direction, and 10 holes are radially arranged at equal intervals in the circumferential direction (10-pole configuration). Both the radially inner side and the outer side of the magnet mounting hole 33 are closed, and a bridge portion 35 is formed on the radially outer side. A rectangular parallelepiped magnet 36 is accommodated in each magnet mounting hole 33 and fixed by a fixing means such as an adhesive. Adjacent magnets 36 have the same polarity on opposite surfaces. A plurality of boss holes 34 for laminating the core plates at predetermined positions are provided in the axial direction on the inner side in the radial direction from the magnet mounting holes 33 by press stamping in the axial direction. Each boss hole 34 is formed in a round shape having a diameter n3 in a plan view, and an interval n4 that is equal to or greater than the thickness of the laminated core plate is provided between the shaft hole 32 and the magnet mounting hole 33. Is set. By setting each boss hole 34 in this way, inadvertent deformation of the core plate can be suppressed during press working.

FIG. 3 is an explanatory diagram showing a configuration in the vicinity of the magnet mounting hole 33. In the rotor core 15, the outer periphery between adjacent magnet mounting holes 33 is formed in an outer shape with a radius R. The center O _{1 of the} radius R is eccentrically arranged at a position shifted to the outer diameter side from the center O of the rotor 3. A portion having a radius R, that is, a portion between adjacent magnet attachment holes 33 is a pseudo magnetic pole portion 37 in which magnetic fluxes from the opposing magnets 36 repel each other and flow radially outward. Since the pseudo magnetic pole portion 37 is eccentrically formed with the radius R as described above, the outer periphery of the rotor core 15 has an uneven shape with the magnet mounting hole 33 portion as a trough and the pseudo magnetic pole portion 37 portion as a crest. The pseudo magnetic pole portion 37 is formed on the rotor core 15 in a salient pole shape. A gap portion (first magnetic resistance portion) 38 in which the magnet 36 does not exist is formed in a radially inner portion in the magnet attachment hole 33.

  Providing such a gap portion 38 on the inner side in the radial direction of the magnet 36 increases the magnetic resistance between different poles (between the N and S poles on the opposite surface) in the same magnet 36. In other words, due to the presence of the gap portion 38, in the magnet 36, the extended distance between different poles on the radially inner side (broken line T in FIG. 3) is increased, and the magnetic path for shortcutting the N and S poles is correspondingly increased. . For this reason, the magnetic resistance at the radially inner portion of the magnet 36 is increased, and the leakage magnetic flux at the portion is reduced.

  Further, the gap 38 has a longer surface distance as the radial length VL is larger, and the leakage flux reducing effect is increased. For this reason, it is desirable that the length VL of the gap 38 is as large as possible. As shown in FIG. 4 (a), in the experiments conducted by the inventors, when the width of the magnet 36 is 2 mm, the gap is large (VL: 1.7 mm) and the extra large (VL: 1.7 mm) compared to the conventional structure. (VL: 3.2 mm), a torque increase of 13% was achieved. Therefore, in the motor 1, the gap portion 38 is formed as large as possible within a range where it does not interfere with the boss hole 34, or within a range where the thickness of the core plate or more can be secured as a press-fitting allowance for the rotor shaft 13. Accordingly, the gap 38 is provided at a position separated from the shaft hole 32 of the rotor 3 by a thickness equal to or greater than the thickness of the core plate via the boss hole 34 and at a position separated from the boss hole 34 by a thickness equal to or greater than the thickness of the core plate. In addition, the space | gap part 38 does not need to be a simple square, and the inner end 38a of the space | gap part 38 can also be formed in polygonal shape or curved hole shape so that the boss hole 34 may be avoided.

  On the other hand, in the motor 1 according to the present invention, a gap groove (second magnetic resistance portion) 39 is further provided at an intermediate position between adjacent magnet mounting holes 33. As shown in FIGS. 2 and 3, the gap groove 39 is a rectangular through hole, and is formed at a position away from the magnet mounting hole 33 in the circumferential direction by a thickness equal to or greater than the thickness of the core plate. Further, the following upper limit position Y1 and lower limit position Y2 are set at the outer end 39a and the inner end 39b of the gap groove 39, respectively.

(A) Upper limit position Y1
A position 1/8 of the radial length L of the magnet 36 is shown from the radially inner end surface 36a of the magnet 36. The gap groove 39 is provided on the inner peripheral side from the upper limit position Y1. According to the experiments by the inventors, the same value can be applied to the upper limit value of 1/8 even when the magnet length L is different. Further, when the outer end 39a of the gap groove 39 is arranged on the outer peripheral side with respect to the L / 8 position, the flow of magnetic flux toward the radially outer side is hindered, and the torque is reduced. That is, the upper limit position Y1 is set as a position where the magnetic flux flow from the magnet 36 toward the radially outer side is not hindered by the gap groove 39.

(B) Lower limit position Y2
The range which can ensure the press-fitting allowance of the rotor shaft 13 is shown. The gap groove 39 is provided on the outer peripheral side from the lower limit position Y2. Here, since the rotor core 15 of this embodiment has a 10-pole configuration, the angle from the center of the rotor core 15 between the magnet mounting holes 33 is 36 °. However, the diameter of the rotor core 15 and the size of the magnet 36 are taken into consideration. Then, by setting the width b of the gap groove 39 to be smaller than the width of the magnet attachment hole 33, the lower limit position Y2 can be set closer to the shaft hole 32 side than the inner end 38a of the gap portion 38. On the other hand, the lower limit position Y2 is set so as to have a dimension larger than the thickness of the core plate, and thereby, inadvertent deformation of the core plate can be suppressed during press working. Further, when the dimension between the end surface 38a on the shaft hole 32 side of the magnet mounting hole 33 and the shaft hole 32 is n2, n2 is set to have the following relationship.
n2 = n3 + n4 × 2
The dimension n1 between the lower limit position Y2 and the shaft hole 32 is set to have the following relationship with the dimension n2 between the gap portion inner end 38a and the shaft hole 32.
n1 ≦ n2

  By providing such a gap groove 39, the area between the magnet mounting holes 33 (arrow W portion) is reduced, and the magnetic resistance at the radially inner portion of the magnet 36 is further increased. For this reason, the magnetic flux density at this portion is increased and magnetic saturation is more likely to occur, and the leakage magnetic flux of the magnet 36 is also reduced. As shown in FIG. 4 (b), in the experiments conducted by the inventors, a torque increase of 15% was achieved when the gap groove 39 was provided at the full upper and lower limit positions as compared with the case without the gap groove 39. . Further, although the torque increase effect is greater when the gap groove 39 is provided than when only the gap portion 38 is provided, it is more desirable to provide both. However, the gap groove 39 is easier to provide in terms of layout, and the rotor strength is easier to maintain. The gap 38 and the gap groove 39 can be formed regardless of the presence or absence of the boss hole 34.

  As described above, in the motor 1, the gap 38 and the gap groove 39 are provided between the magnet attachment holes 33 on the radially inner end side of the magnet attachment hole 33, and the gap groove 39 is formed on the radially inner end face 36 a of the magnet 36. By providing it on the inner peripheral side from the position of L / 8, the magnetic resistance in the radially inner portion of the magnet 36 can be increased without hindering the flow of magnetic flux toward the radially outer side. Further, by providing the boss hole 34 on the radially inner side of the magnet mounting hole 33, the magnetic path of this portion can be reduced, and the magnetic resistance at the radially inner portion of the magnet 36 can be increased. As a result, the leakage magnetic flux in the part is reduced, and the magnetic flux of the magnet can be used more efficiently than in the conventional magnetic flux concentration type brushless motor, and the torque can be increased without increasing the magnet amount. Become.

(Embodiment 2)
Next, Embodiment 2 of the present invention will be described. 5 and 6 are explanatory views showing the rotor structure of the brushless motor according to the second embodiment. In the following embodiments, the same members and portions as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the first embodiment, the configuration in which the inner and outer ends of the magnet mounting hole 33 are both closed is shown. However, in the rotor 3 having such a configuration, the magnetic flux may be short-cut through the bridge portion 35. There is sex. In this case, as shown in FIG. 5, if the outer peripheral side of the magnet mounting hole 33 is opened, a magnetic flux shortcut can be prevented. However, if the outer peripheral side of the magnet mounting hole 33 is completely opened, cogging may increase. Therefore, as shown in FIG. 6, the opening 42 is provided by partially cutting the radial outer end of the magnet mounting hole 33, and the flange 43 is provided on the outer periphery of the rotor 41, thereby suppressing a magnetic flux shortcut. The increase in cogging may be prevented. The rotor 41 in FIGS. 5 and 6 has a 14-pole configuration, and a boss hole 34 is disposed on the inner peripheral side of the gap groove 39.

  The flange 43 extends from at least one of the adjacent pseudo magnetic pole portions 37 so as to be continuous with the outer peripheral surface 37 a of the pseudo magnetic pole portion 37. In this case, it is determined which side is extended from the direction of rotation of the motor (extends toward the opposite side of the rotation direction), and the flange 43 is extended from both sides of the motor that rotates forward and backward. When the flange portion 43 is provided, the opening 42 of the magnet mounting hole 33 is set to be approximately the thickness of the core plate or smaller. FIG. 7 is an explanatory diagram showing the relationship between the width Z of the opening 42 and the torque and ripple. As shown in FIG. 7, the torque increases as the width Z of the opening 42 is increased, but the ripple increases rapidly when the width Z of the opening 42 is increased too much. Therefore, from the result of FIG. 7, the width Z of the opening 42 is 75% or less with respect to the width of the magnet 36 (= the width of the magnet mounting hole 33), that is, the opening 42 has an opening ratio of 75% (of the magnet 36). When the width is 2 mm, 1.5 mm or less is desirable.

  In the rotor 41, a spacer (nonmagnetic part) 44 made of a nonmagnetic material (for example, synthetic resin) is attached to the magnet attachment hole 33. The spacer 44 is attached to both the inner space 38 and the outer space 45 of the magnet mounting hole 33. The spacer 44 is formed in a rod shape, and is inserted into the magnet attachment hole 33 along the axial direction from the end face of the rotor 3. By attaching such a spacer 44 to the magnet attachment hole 33, the magnet 36 does not move due to centrifugal force. Further, in the configuration of FIG. 6, since the collar portion 43 also functions as a stopper, it is possible to prevent the magnet 36 from scattering.

It goes without saying that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.
For example, in the above-described embodiment, an example in which the present invention is applied to a 10 pole 12 slot brushless motor has been described. Is widely applicable regardless. In the above embodiment, the rotor core 15 has an eccentric outer shape. However, the present invention can also be applied to a brushless motor having a rotor core with a circular outer shape without eccentricity. Furthermore, the brushless motor according to the present invention can be applied to other electric machines and devices such as hybrid vehicles and electric vehicles in addition to the electric power steering device.

DESCRIPTION OF SYMBOLS 1 Brushless motor 2 Stator 3 Rotor 4 Motor case 5 Stator core 6 Stator coil 6a End part 7 Bus bar unit 8 Bracket 9 Teeth 11 Insulator 12 Feeding terminal 13 Rotor shaft 14a, 14b Bearing 15 Rotor core 21 Resolver 22 Resolver rotor 23 Resolver stator 24 Resolver Bracket 25 Mounting screw 31 Slot 32 Shaft hole (center hole)
33 Magnet mounting hole (magnet housing)
34 Boss hole 35 Bridge portion 36 Magnet 36a Radial inner end surface 37 Pseudo magnetic pole portion 37a Outer peripheral surface 38 Air gap portion (first magnetic resistance portion)
38a Inner end 39 Gap groove (second magnetoresistive portion)
39a outer end 39b inner end 41 rotor 42 opening 43 flange 44 spacer (non-magnetic part)
45 void 51 rotor 52 magnet 52a radially inner portion 53 the core member 54 pseudo magnetic pole portion L magnet radial length O rotor center O ₁ pseudo magnetic pole portion radius center R pseudo pole radii Y1 gap groove upper position Y2 gap groove lower limit position n1 void Dimension n2 between groove lower limit position and shaft hole n2 Dimension between gap inner end and shaft hole n3 Boss hole diameter n4 Dimension between boss hole and shaft hole, boss hole and magnet mounting hole b Width of gap groove Z Width of opening

Claims (9)

A stator comprising a plurality of teeth projecting radially inward, and a coil wound around the teeth via a slot formed between the teeth;
A brushless motor having a rotor that is rotatably arranged inside the stator and that has a plurality of poles and is housed in a radially formed magnet housing portion,
The rotor includes a plurality of pseudo magnetic pole portions formed between adjacent magnet housing portions, and a first magnet formed between a radially inner end of the magnet housing portion and a radially inner end of the magnet. A resistance portion, and a second magnetic resistance portion formed at the inner peripheral side central portion of the pseudo magnetic pole portion,
The brushless, wherein the second magnetoresistive portion is provided on the inner peripheral side of the L / 8 position from the radially inner end face of the magnet when the radial length of the magnet is L. motor. The brushless motor according to claim 1,
The rotor is formed by laminating a plurality of core plates made of a magnetic material,
The brushless motor according to claim 1, wherein the first magnetoresistive portion is provided away from a center hole formed at a center of the rotor by a thickness equal to or greater than a thickness of the core plate. The brushless motor according to claim 1 or 2,
The rotor is formed by laminating a plurality of core plates made of a magnetic material,
The brushless motor according to claim 1, wherein the second magnetoresistive part is provided away from the adjacent magnet housing part by a thickness equal to or greater than the thickness of the core plate. The brushless motor according to any one of claims 1 to 3,
The distance between the radially inner end of the second magnetoresistive portion and the center hole formed in the center of the rotor is the distance between the radially inner end of the first magnetoresistive portion and the center hole. Brushless motor characterized by being the same or less. In the brushless motor according to any one of claims 1 to 4,
A brushless motor, wherein an opening that opens toward the outer peripheral surface of the rotor is provided at a radially outer end of the magnet housing portion. The brushless motor according to claim 5, wherein
A brushless motor, wherein a flange that extends from an outer peripheral surface of the pseudo magnetic pole portion is formed to extend from at least one of the adjacent pseudo magnetic pole portions in the opening. The brushless motor according to claim 5 or 6,
The brushless motor, wherein the opening has an opening ratio of 75% or less with respect to a width along the circumferential direction of the magnet housing portion. In the brushless motor according to any one of claims 1 to 7,
A brushless motor, wherein a nonmagnetic portion is provided in each of a radially inner portion and a radially outer portion of the magnet in the magnet housing portion. The brushless motor according to claim 8,
The brushless motor, wherein the nonmagnetic part is made of a synthetic resin.

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