JP5967425B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering apparatus.

The electric power steering device transmits the assist force generated by the electric motor to the steering mechanism via a reduction gear in the gear housing.
In this type of electric power steering device, since a relatively large current flows through the electric motor, a control unit for driving the electric motor is disposed between the electric motor and the speed reducer for the purpose of reducing power loss and noise. Thus, it has been proposed to integrate these with the control unit.

Typically, the control unit includes a control board on which a processing device for calculating a command value is mounted, and a power board on which a power element for an electric motor (which is a switching element and self-heats) is mounted. The control board is provided with heat generating electronic components such as an IC and an electrolytic capacitor for controlling the power element of the power board.
Patent Document 1 proposes a technique in which a power board is disposed on a pedestal provided in a motor housing in the vicinity of a fastening portion between the motor housing and the gear housing, and heat is radiated to the gear housing side through the fastening portion.

JP 2009-190478 A

In Patent Document 1, since the heat is radiated through the fastening portion, the heat radiation distance becomes long and the heat radiation property may be deteriorated. Further, since the power board and the control board are arranged in parallel, the space for accommodating the control unit becomes longer in the axial direction of the rotating shaft of the electric motor, and the electric power steering device is enlarged.
An object of the present invention is to provide an electric power steering apparatus that has good heat dissipation and can achieve downsizing.

In order to achieve the object, the invention of claim 1 includes an electric motor (18) including a motor housing (24) and a rotating shaft (27), a drive gear (20) coaxially connected to the rotating shaft, the combination comprised of said accommodating the driven gear (21) and the gears meshing with the drive gear the motor housing and butted gear housing (22) reduction gear including (19), and the motor housing and the gear housing In the housing (H) , an end wall (30) of the motor housing and an opposing portion of the gear housing facing the end wall of the motor housing in the axial direction (X1) of the rotating shaft . A partitioned storage chamber (35); and a control unit (12) stored in the storage chamber, the control unit having an axis (C1) of the rotating shaft A power module (44) having a plate shape extending in a direction parallel to the power module and mounting at least the power element (47), and electrically connected to the power module, mounting at least the control element (70), and rotating A control board (50) arranged orthogonal to the axis of the shaft, and the opposing portion of the gear housing has an insertion groove (48) into which the power module is inserted, and the power module Provides an electric power steering device (1) including a first surface (44a) and a second surface (44b) in contact with the corresponding inner wall surfaces (48a, 48b) of the insertion groove, respectively.

In addition, although the alphanumeric character in a parenthesis represents the corresponding component etc. in embodiment mentioned later, this does not mean that this invention should be limited to those embodiment as a matter of course. The same applies hereinafter.
Further, as in claim 2, the control module includes the control board and a resin mold part (51) obtained by molding the control board with resin, and is formed with an insertion hole (52) through which the rotation shaft is inserted. (45), and the power module may protrude orthogonally from the resin mold part in a state where the end part (441) of the power module is supported by the resin mold part.

  Further, as in claim 3, the motor module includes a power supply module (46) disposed between the end wall (30) of the motor housing that defines the housing chamber and the control module, and the power module includes the power module A plurality of terminals (54, 55) penetrating the resin mold portion and projecting toward the power supply module may be provided, and the plurality of terminals may include terminals connected to corresponding terminals of the power supply module.

According to a fourth aspect of the present invention, a flexible flat connection member (53) molded in the resin mold portion and electrically connecting the control board and the power module may be provided.
Moreover, you may provide the cyclic | annular elastic member (56) which seals between the outer periphery (51a) of the said resin mold part, and the inner periphery (31a) of the said combination housing like Claim 5.

  The control board may include a mounting surface exposed from the resin mold part, and an electrolytic capacitor as the control element may be mounted on the mounting surface.

According to the invention of claim 1, the speed reducer generates little heat when compared with the electric motor. Since both sides of the plate-like power module are in direct contact with the gear housing of such a reduction gear to dissipate heat, the heat dissipating effect can be greatly enhanced. Therefore, the reliability of the power module can be improved.
The plate-like power module is disposed orthogonal to the control board, extends in a direction parallel to the axis of the rotation shaft, and is inserted into the insertion groove of the gear housing. Therefore, the rotating shaft can be shortened in the axial direction, and the occurrence of vibration of the rotating shaft can be suppressed. Further, the storage chamber can be reduced in size with respect to the axial direction of the rotating shaft, and as a result, the electric power steering device can be reduced in size and weight.

According to the invention of claim 2, of the control modular Interview Lumpur composed of a control board and the resin mold portion, since the power module to perpendicularly from the resin mold portion projects, insert the power module of the gear housing A layout to be inserted into the groove can be easily realized. Further, the power module and the control module can be handled as a single unit, and the assemblability is good.

According to the invention of claim 3, the terminal extending from the power module passes through the resin mold part of the control module and protrudes toward the power module, and is connected to the corresponding terminal of the power module. Therefore, the power module can be easily connected to the power supply module by inter-terminal connection.
According to the invention of claim 4, since the control board and the power module arranged orthogonally are resin-molded in a state of being electrically connected via the flexible flat connection member, the connection of the connection portion The reliability of can be increased.

According to the invention of claim 5, since the space between the outer periphery of the resin mold portion and the inner periphery of the combination housing is sealed with the annular elastic member, it is possible to reliably prevent the intrusion of grease or the like from the gear housing side. Can do.
According to the invention of claim 6, since the control board includes the mounting surface exposed from the resin mold portion, and the electrolytic capacitor as the control element is mounted on the exposed mounting surface, the heat dissipation is good. Therefore, the temperature rise of the electrolytic capacitor can be suppressed, and the durability time of the electrolytic capacitor can be extended.

1 is a schematic diagram of an electric power steering apparatus according to an embodiment of the present invention, and shows a schematic configuration of the electric power steering apparatus. It is sectional drawing of the principal part of an electric power steering device. It is an expanded sectional view of the important section of an electric power steering device. It is a typical exploded perspective view of a power module and a control module.

  Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a schematic diagram showing a schematic configuration of an electric power steering apparatus 1 according to an embodiment of the present invention. Referring to FIG. 1, an electric power steering apparatus 1 includes a steering member 2 such as a steering wheel, a steering mechanism 4 that steers a steered wheel 3 in conjunction with rotation of the steering member 2, and steering of a driver. And a steering assist mechanism 5 for assisting. The steering wheel 2 and the steering mechanism 4 are mechanically coupled via a steering shaft 6 and an intermediate shaft 7.

In this embodiment, the steering assist mechanism 5 will be described based on an example in which an assist force (steering assist force) is applied to the steering shaft 6. However, the present invention is applied to the pinion shaft described later. The present invention can be applied to a structure for giving or an assisting mechanism 5 for giving assist force to a rack shaft, which will be described later.
The steering shaft 6 extends linearly. Steering shaft 6 includes an input shaft 8 connected to steering wheel 2 and an output shaft 9 connected to intermediate shaft 7. The input shaft 8 and the output shaft 9 are connected via a torsion bar 10 so as to be relatively rotatable on the same axis. That is, when a steering torque greater than a certain value is input to the steering wheel 2, the input shaft 8 and the output shaft 9 rotate in the same direction while rotating relative to each other.

  A torque sensor 11 disposed around the steering shaft 6 detects the steering torque input to the steering wheel 2 based on the relative rotational displacement amounts of the input shaft 8 and the output shaft 9. The torque detection result of the torque sensor 11 is input to an ECU 12 (Electronic Control Unit) as a control device. Further, the vehicle speed detection result from the vehicle speed sensor 23 is input to the ECU 12. The intermediate shaft 7 connects the steering shaft 6 and the steering mechanism 4.

The steered mechanism 4 includes a rack and pinion mechanism including a pinion shaft 13 and a rack shaft 14 as a steered shaft. A steered wheel 3 is connected to each end of the rack shaft 14 via a tie rod 15 and a knuckle arm (not shown).
The pinion shaft 13 is connected to the intermediate shaft 7. The pinion shaft 13 rotates in conjunction with the steering of the steering wheel 2. A pinion 16 is connected to the tip of the pinion shaft 13 (the lower end in FIG. 1).

  The rack shaft 14 extends linearly along the left-right direction of the automobile. A rack 17 that meshes with the pinion 16 is formed in the middle of the rack shaft 14 in the axial direction. By the pinion 16 and the rack 17, the rotation of the pinion shaft 13 is converted into the axial movement of the rack shaft 14. The steered wheel 3 can be steered by moving the rack shaft 14 in the axial direction.

When the steering wheel 2 is steered (rotated), this rotation is transmitted to the pinion shaft 13 via the steering shaft 6 and the intermediate shaft 7. The rotation of the pinion shaft 13 is converted into an axial movement of the rack shaft 14 by the pinion 16 and the rack 17. Thereby, the steered wheel 3 is steered.
The steering assist mechanism 5 includes an electric motor 18 for assisting steering and a speed reducer 19 for transmitting the output torque of the electric motor 18 to the steering mechanism 4. The speed reducer 19 includes a worm shaft 20 as a drive gear, a worm wheel 21 as a driven gear that meshes with the worm shaft 20, and a gear housing 22 that houses the worm shaft 20 and the worm wheel 21.

The worm shaft 20 is connected to a rotating shaft (not shown) of the electric motor 18 through a joint (not shown). The worm shaft 20 is rotationally driven by the electric motor 18. The worm wheel 21 is connected to the steering shaft 6 so as to be able to rotate together. The worm wheel 21 is rotationally driven by the worm shaft 20.
When the electric motor 18 rotationally drives the worm shaft 20, the worm wheel 21 is rotationally driven by the worm shaft 20, and the worm wheel 21 and the steering shaft 6 rotate together. The rotation of the steering shaft 6 is transmitted to the pinion shaft 13 via the intermediate shaft 7. The rotation of the pinion shaft 13 is converted into the axial movement of the rack shaft 14. Thereby, the steered wheel 3 is steered.

  The electric motor 18 is controlled by an ECU (Electronic Control Unit) 12 as a control unit. The ECU 12 controls the electric motor 18 based on the torque detection result from the torque sensor 11, the vehicle speed detection result from the vehicle speed sensor 23, and the like. Specifically, the ECU 12 determines a target assist amount using a map in which the relationship between the torque and the target assist amount is stored for each vehicle speed, and controls the assist force generated by the electric motor 18 to approach the target assist amount. To do.

FIG. 2 is a schematic perspective view of the steering assist mechanism 5. Referring to FIG. 2, the electric motor 18 includes a motor housing 24 and a rotating shaft 27 that is rotatably supported by the motor housing 24 via a pair of bearings 25 and 26.
The motor housing 24 includes a bottomed cylindrical motor housing main body 28 and an end member 29 that closes the open end of the motor housing main body 28. The end member 29 includes an end wall 30 fitted to the motor housing main body 28 and a cylindrical portion 31 protruding from the end wall 30 toward the gear housing 22.

On the other hand, the gear housing 22 of the speed reducer 19 includes a cylindrical drive gear housing housing 32 in which the worm shaft 20 is housed, a cylindrical driven gear housing housing 33 in which the worm wheel 21 is housed, and a drive gear housing housing 32. The cylindrical part 34 which protrudes from the end surface 32a of this is provided.
The cylindrical portion 31 of the motor housing 24 and the cylindrical portion 34 of the gear housing 22 are abutted with each other. Flange is formed at the ends of the cylindrical portions 31 and 34 that are abutted with each other, and both cylindrical portions 31 and 34 are inserted through fixing screws (not shown) that pass through both flanges, that is, The gear housing 22 and the motor housing 24 are fastened to each other.

  The cylindrical portion 31 of the motor housing 24 and the cylindrical portion 34 of the gear housing 22 serve as a control device between the end surface 32 a of the drive gear housing housing 32 and the end wall 30 of the end member 29 of the motor housing 24. A storage chamber 35 for storing the ECU 12 is defined. The end surface 32 a and the end wall 30 constitute an inner wall surface of the storage chamber 35 and face the axial direction X1 of the rotating shaft 27 of the electric motor 18. The gear housing 22 and the motor housing 24 combined with each other constitute a combined housing H that defines the accommodation chamber 35.

The rotating shaft 27 and the worm shaft 20 of the electric motor 18 are arranged side by side on the same axis, and both are connected via a joint 36 so as to be able to transmit power. The pair of end portions of the worm shaft 20 are rotatably supported by the drive gear housing 32 via a pair of bearings 37 and 38, respectively.
The electric motor 18 is configured as a three-phase brushless motor, and includes a rotor 39 connected to the outer periphery of the rotating shaft 27 so as to be integrally rotatable, and a stator 40 fixed to the inner periphery of the motor housing body 28. The stator 40 includes a stator core 41 fixed to the inner periphery of the motor housing main body 28 and a plurality of coils 42. Stator core 41 includes an annular yoke and teeth projecting radially inward from the inner periphery of the yoke. Each coil 42 is wound around a corresponding tooth.

The motor housing 24 accommodates a bus bar 43 having an annular shape or a C shape. The coil 42 wound around each tooth is connected to the bus bar 43. The bus bar 43 functions as a power distribution member for distributing power to each coil 42.
The ECU 12 as a control unit accommodated in the accommodation chamber 35 includes a power module 44, a control module 45, and a power supply module 46.

As shown in FIG. 3 which is an enlarged cross-sectional view, the power module 44 has a plate shape extending in a direction parallel to the axis C <b> 1 of the rotating shaft 27. The power module 44 has at least a power element 47 mounted thereon. The power element 47 is a switching element such as an FET (electrolytic effect transistor).
The drive gear housing 32 of the gear housing 22 is formed with an insertion groove 48 extending in a direction parallel to the axis C1 of the rotating shaft 27 (that is, the axis of the worm shaft 20). A plate-like power module 44 is inserted and fitted into the insertion groove 48. The insertion groove 48 has a first inner wall surface 48a and a second inner wall surface 48b that face each other.

On the other hand, the power module 44 has a first surface 44a and a second surface 44b. The first surface 44a of the power module 44 is in surface contact with the first inner wall surface 48a of the insertion groove 48 so that heat can be transferred. In addition, the second surface 44b of the power module 44 is in surface contact with the second inner wall surface 48b of the insertion groove 48 so that heat can be transferred.
A power element 47 is mounted on the first surface 44 a of the power module 44, and a metal heat radiating plate 49 is provided on the second surface 44 b of the power module 44. The surface of the first surface 44a and the surface of the second surface 44b are covered with an insulating protective film. The protective film may be a film having a thickness of 100 μm or less composed of a resin such as epoxy, polyimide, PEEK (polyetheretherketone), or an oxide such as AlO, AlN, SiN or the like. A film having a thickness of 100 μm or less made of nitride or the like may be used.

The first surface 44 a is a heat radiating surface for the power element 47. Further, since the source or drain of the power element 47 is connected to the heat radiating plate 49, the second surface 44b is also a heat radiating surface for the power element.
As shown in FIG. 3 and FIG. 4, which is a schematic exploded perspective view, the control module 45 includes a control board 50 arranged orthogonal to the axis C 1 of the rotation shaft 27, and at least a part of the control board 50. And a resin mold part 51 molded with resin. The control module 45 is formed with an insertion hole 52 through which the rotary shaft 27 is inserted. The insertion hole 52 is inserted through the control board 50 and the resin mold part 51.

  The control board 50 includes a mounting surface 50 a molded by the resin mold portion 51 and a mounting surface 50 b exposed from the resin mold portion 51. A microcomputer (not shown) as a control element for controlling the power element 47 is mounted on the molded mounting surface 50a. An electrolytic capacitor 70 as a control element for controlling the power element 47 is mounted on the exposed mounting surface 50b.

With the end 441 of the power module 44 supported by the resin mold part 51 of the control module 45, the power module 44 protrudes orthogonally from the resin mold part 51.
The end 441 of the power module 44 and the control board 50 are electrically connected by a flexible flat connection member 53 molded in the resin mold part 51. The flat connection member is, for example, an FPC (flexible printed circuit) or an FFC (flexible flat cable).

  A plurality of motor output terminals 54 and a plurality of power supply terminals 55 (see FIG. 4) are provided as a plurality of terminals protruding from the end 441 of the power module 44 through the resin mold portion 51 and projecting toward the electric module 46 side. Is provided. The motor output terminal 54 and the power supply terminal 55 are connected to a power circuit in the power module 44. Each end of the motor output terminal 54 and the power supply terminal 55 is connected to a corresponding terminal of a corresponding connector held by the power supply module 46.

  3, between the outer periphery 51a of the resin mold part 51 of the power module 44 and the inner periphery of the combination housing H (corresponding to the inner periphery 34a of the cylindrical part 34 of the gear housing 22 in this embodiment). Is provided with an annular elastic member 56 that seals between the two. The annular elastic member 56 is held in a circumferential groove provided on the outer periphery 51a of the resin mold part 51, for example.

  The power supply module 46 is disposed between the control module 45 and the end wall 30 of the end member 29 of the motor housing 24. The power supply module 46 includes a resin frame 57 fixed to the end wall 30 of the motor housing 24 using a fixing screw (not shown), and a power supply component 58 (electrolytic capacitor, relay, coil, etc.) attached by the resin frame 57; The first connector 59, the second connector 60, the third connector 61, a power supply connector to which an external power supply connector (not shown) is connected, and at least a part of the resin frame 57 and the connectors 59 to 61 are molded. The resin mold part 62 is provided.

The first connector 59 includes a terminal 63 to which a motor output terminal 54 extending from the power module 44 is connected. The second connector 60 (see FIG. 4) includes a terminal (not shown) to which a power supply terminal 55 extending from the power module 44 is connected. For simplification, the resin mold portion 62 is not shown in the power supply module 46 shown in FIG.
The third connector 61 shown in FIG. 4 has a motor output terminal 65 (see FIG. 4) to which a lead terminal 64 (the lead terminal 64 extends from the bus bar 43) of the electric motor 18 that penetrates the end wall 30 of the motor housing 24 is connected. 3).

The motor output terminal 54 from the power module 44 is connected to the lead terminal 64 via an insert bus bar (not shown) in the power supply module 46 and the motor output terminal 65 of the third connector 61. The connector housings of the connectors 59 to 61 may be constituted by a part of the resin frame 57.
According to the present embodiment, the following operational effects are achieved. That is, the speed reducer 19 hardly generates heat when compared with the electric motor 18. Since both surfaces (the first surface 44a and the second surface 44b) of the plate-like power module 44 are in direct contact with the gear housing 22 of the speed reducer 19 to dissipate heat, the heat dissipation effect can be remarkably enhanced. . Therefore, the reliability of the power module 44 can be improved. In addition, the durability time can be extended.

  The plate-like power module 44 is arranged orthogonal to the control board 50, extends in a direction parallel to the axis C1 of the rotary shaft 27, and is inserted into the insertion groove 48 of the gear housing 22. Yes. Therefore, the rotating shaft 27 can be shortened in the axial direction X1, and the occurrence of vibration of the rotating shaft 27 can be suppressed. Further, with respect to the axial direction X1 of the rotating shaft 27, the storage chamber 35 can be reduced in size, and as a result, the electric power steering device 1 can be reduced in size and weight.

  Moreover, since the power module 44 protrudes orthogonally from the resin mold part 51 of the control module 45 comprised by the control board 50 and the resin mold part 51, the power module 44 is inserted in the insertion groove 48 of the gear housing 22. The layout can be easily realized. Further, the power module 44 and the control module 45 can be handled as a single unit, and the assemblability is good.

  Further, terminals (motor output terminal 54 and power supply terminal 55) extending from the power module 44 pass through the resin mold portion 51 of the control module 45 and protrude toward the power supply module 46, and these terminals (motor output terminal 54 and The power terminal 55) is connected to the corresponding terminal of the power module 46. Therefore, the power module 44 can be easily connected to the power supply module 46 by inter-terminal connection.

Further, since the control board 50 and the power module 44 arranged orthogonally are resin-molded in a state where they are electrically connected via the flexible flat connection member 53, the connection of the connection portion by the connection member 53 is performed. The reliability of can be increased.
Further, since the space between the outer periphery 51a of the resin mold portion 51 and the inner periphery of the combination housing H (the inner periphery 34a of the cylindrical portion 34 of the gear housing 22) is sealed by the annular elastic member 56, the gear housing 22 is sealed. Intrusion of grease or the like into the storage chamber 35 from the inside can be reliably prevented.

  In addition, the electrolytic capacitor 70 as a control element mounted on the mounting surface 50b of the control board 50 has a relatively low heat-resistant temperature, and tends to decrease the durability time when the temperature becomes high. Since the mounting surface 50b on which the electrolytic capacitor 70 is mounted is exposed from the resin mold portion 51 of the control module 45 and has good heat dissipation, the temperature rise of the electrolytic capacitor 70 as a control element is suppressed, and the electrolytic capacitor The durability time of 70 can be lengthened.

  The present invention is not limited to the above embodiment. For example, in the above embodiment, the exposed mounting surface 50b on which the electrolytic capacitor 70 is mounted is the surface of the control board 50 on the electric motor 18 side. However, instead of this, the electrolytic capacitor 70 may be mounted on the mounting surface of the control board 50 where the surface on the speed reducer 19 side is exposed. Further, both mounting surfaces 50 a and 50 b may be molded by the resin mold part 51. In addition, various modifications can be made within the scope of the claims of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering device, 2 ... Steering member, 4 ... Steering mechanism, 5 ... Steering assist mechanism, 6 ... Steering shaft, 12 ... ECU (control unit), 18 ... Electric motor, 19 ... Reduction gear, 20 ... Warm Shaft (drive gear), 21 ... worm wheel (driven gear), 22 ... gear housing, 24 ... motor housing, 28 ... motor housing body, 29 ... end member, 30 ... end wall, 31 ... cylindrical portion, 32 ... drive Gear housing, 34 ... cylindrical part, 34a ... inner circumference, 35 ... accommodating chamber, 43 ... bus bar, 44 ... power module, 44a ... first surface, 44b ... second surface, 441 ... end, 45 ... control module 46 ... Power supply module, 47 ... Power element, 48 ... Insertion groove, 48a ... First inner wall surface, 48b ... Second inner wall surface, 49 ... Heat sink, 50 ... Control board, 50b ... (Exposed) ) Mounting surface 51... Resin mold part 51 a. Periphery 53. Connection member 54. Motor output terminal 55. Power terminal 56. Elastic member 57 Resin frame 58 Power component 59 First connector , 60 ... second connector, 61 ... third connector, 62 ... resin mold part, 63 ... terminal, 64 ... lead terminal, 65 ... motor output terminal, 70 ... electrolytic capacitor (control element), C1 ... (of rotating shaft) Axis, H ... Combination housing, X1 ... Axial direction

Claims (6)

An electric motor including a motor housing and a rotating shaft;
A reduction gear including a drive gear coaxially connected to the rotating shaft, a driven gear meshing with the drive gear, and a gear housing that accommodates both gears and abuts the motor housing ;
In the combination housing constituted by the motor housing and the gear housing , the end wall of the motor housing and the end wall of the motor housing are opposed to the end wall in the axial direction of the rotation shaft. A storage room partitioned by an opposing portion ;
A control unit housed in the housing chamber,
The control unit has a plate shape extending in a direction parallel to the axis of the rotating shaft, and is at least electrically connected to the power module mounted with the power element, and mounted with at least the control element, A control board arranged orthogonal to the axis of the rotation axis,
The facing portion of the gear housing has an insertion groove into which the power module is inserted,
The electric power steering apparatus, wherein the power module includes a first surface and a second surface that are in contact with the corresponding inner wall surface of the insertion groove so that heat can be transferred. The control module according to claim 1, comprising a control module including the control board and a resin mold part in which at least a part of the control board is molded with resin, and having an insertion hole through which the rotation shaft is inserted,
An electric power steering apparatus in which the power module protrudes orthogonally from the resin mold portion in a state where an end portion of the power module is supported by the resin mold portion. The power supply module according to claim 2, further comprising a power supply module disposed between an end wall of the motor housing that defines the storage chamber and the control module.
The power module includes a plurality of terminals protruding through the resin mold portion and projecting toward the power supply module.
The electric power steering apparatus, wherein the plurality of terminals include terminals connected to corresponding terminals of the power supply module.   4. The electric power steering apparatus according to claim 2, further comprising a flexible flat connecting member molded in the resin mold portion and electrically connecting the control board and the power module.   5. The electric power steering apparatus according to claim 2, further comprising an annular elastic member that seals between an outer periphery of the resin mold portion and an inner periphery of the combination housing. 6.   6. The electric power steering apparatus according to claim 2, wherein the control board includes a mounting surface exposed from the resin mold portion, and an electrolytic capacitor as the control element is mounted on the mounting surface. .

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