JP2010127083A - Reciprocating compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively provide a small reciprocating compressor of a small torque variation, by restraining a variation in mass of a working fluid sucked in respective cylinder bores. <P>SOLUTION: A cylinder block (20) of the reciprocating compressor includes a supply chamber (102) formed in a central part in the radial direction of itself and making the working fluid sucked in via a suction port flow in, and a plurality of communicating passages (104) radially extending from the supply chamber (102) for supplying the working fluid in the supply chamber (102) to a suction chamber. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a reciprocating compressor, and more particularly to a reciprocating compressor with a suction distributor.

  The reciprocating compressor is incorporated in a refrigeration cycle system of a vehicle air conditioning system, for example. Specifically, the refrigeration cycle system includes a circulation path through which the refrigerant circulates, and a compressor, a radiator, an expander, and an evaporator are sequentially inserted in the circulation path. The compressor executes a series of processes including refrigerant suction, compression, and discharge steps. For this purpose, the compressor is supplied with power from, for example, a pulley.

A suction chamber, a discharge chamber, and a cylinder bore are defined inside the housing of the reciprocating compressor. The suction chamber and the cylinder bore communicate with each other via a suction valve, and the discharge chamber and the cylinder bore communicate with each other via a discharge valve.
In the reciprocating compressor, the rotation of the drive shaft is converted into the reciprocating motion of the piston. In a variable capacity reciprocating compressor, the stroke length of the piston is changed using, for example, the pressure in the crank chamber, thereby adjusting the discharge capacity. In this case, for example, the pressure of the crank chamber is changed by the opening / closing operation of a capacity control valve controlled from the outside, and thereby the discharge capacity is adjusted.

When the stroke length changes, the inclination angle of the swash plate as the cam member with respect to the drive shaft changes. In the case of an oscillating plate compressor, the rotation of the swash plate is converted into a reciprocating motion of the piston through the oscillating plate. Further, in the case of a swash plate type compressor, it is converted into a reciprocating motion of a piston through a shoe that is in sliding contact with the swash plate.
External control methods include a suction pressure control method that maintains the low pressure of the refrigeration cycle system, that is, the suction chamber pressure (suction pressure) of the compressor at a target value, and the high pressure in the refrigeration cycle system, that is, the discharge of the compressor. There is a differential pressure control method in which the differential pressure between the chamber pressure (discharge pressure) and the suction pressure is maintained at a target value.

In a reciprocating compressor, although there is one intake port, since a plurality of cylinder bores are concentrically arranged, there is a possibility that the intake gas concentration varies among the cylinder bores.
In order to prevent such a variation in intake gas concentration, a reciprocating compressor disclosed in Patent Document 1 includes a first low-pressure gas chamber and a second low-pressure gas chamber that communicate with each other via a plurality of communication holes in a cylinder head. Of low pressure gas chambers. According to this compressor, the intake gas is distributed from the first low-pressure gas chamber to the second low-pressure gas chamber through the plurality of communication holes, and the variation in the intake gas concentration is suppressed. As a result, the torque fluctuation of the compressor is prevented.
JP 2000-104660 A

In the compressor disclosed in Patent Document 1, the cylinder head becomes large due to the provision of the first low-pressure gas chamber and the second low-pressure gas chamber, leading to an increase in the size of the compressor itself and an increase in material costs. .
The present invention has been made based on the above-described circumstances, and the object of the present invention is to reduce the variation in the mass of the working fluid sucked into each cylinder bore and to reduce the cost of a small reciprocating compressor with small torque fluctuation. To provide.

  In order to achieve the above object, according to one aspect of the present invention, a discharge chamber and a suction chamber are partitioned inside, and a discharge port and a suction port communicating the discharge chamber and the suction chamber with the outside are provided. A formed cylinder head; a cylinder block joined to the cylinder head and having a plurality of cylinder bores arranged concentrically; a crankcase coupled to the cylinder block and having a crank chamber defined therein; and the crank chamber A variable displacement reciprocating compressor including a power conversion mechanism that converts a rotation of a drive shaft extending in a cylinder stroke to a reciprocating motion of a piston disposed in the cylinder bore, wherein the cylinder block has its own radial center And a supply chamber into which the working fluid sucked through the suction port flows, and the working fluid in the supply chamber To be supplied to the suction chamber, a reciprocating compressor is provided, characterized in that it comprises a plurality of communication passages extending radially from said supply chamber (claim 1).

Preferably, the suction chamber is located outside the discharge chamber as viewed in the radial direction of the cylinder head.
Preferably, the power conversion mechanism is connected to an outer peripheral portion of a rotor fitted to the drive shaft via a hinge and penetrated by the drive shaft, and is in an axial direction of the drive shaft with respect to the drive shaft. An annular cam member that can be tilted while moving, a swing plate that is connected to the piston via a connecting rod and is swung by the cam member, and is fitted to the drive shaft via a bearing, A joint shaft formed in the cylinder bore and supported by an inner peripheral surface of a support hole connected to the supply chamber so as not to rotate relative to the inner peripheral surface and to be slidable, and to swing integrally with the swing plate A joint case, a JS-side protruding portion provided integrally with the joint shaft, and a JC-side protruding portion provided integrally with the joint case so as to be able to roll. And a plurality of balls (claim 3).

In the reciprocating compressor according to the first aspect of the present invention, since the supply chamber is provided in the cylinder block and distributed to the suction chamber through the communication passage extending radially from the supply chamber, the distribution of the working fluid in the suction chamber becomes uniform. As a result, the mass of the working fluid sucked into each cylinder bore becomes uniform, and the torque fluctuation of the compressor is prevented.
In the reciprocating compressor according to the second aspect, even if the suction chamber is outside the discharge chamber and has a ring shape, the working fluid is uniformly and reliably distributed to each part of the suction chamber.

  The reciprocating compressor according to claim 3 is a variable capacity compressor, and the working fluid is uniformly and reliably distributed to each part of the suction chamber regardless of the change in the discharge capacity.

FIG. 1 shows a variable capacity reciprocating compressor according to a first embodiment applied to a refrigeration cycle system.
The refrigeration cycle system 10 includes a circulation path 12 through which a refrigerant as a working fluid circulates. A compressor, a radiator (condenser) 14, an expander (expansion valve) 16, and an evaporator 18 are sequentially inserted in the circulation path 12 in the flow direction of the refrigerant. The refrigerant circulates. That is, the compressor performs a series of processes including a refrigerant suction process, a suction refrigerant compression process, and a compressed refrigerant discharge process.

The compressor is a rocking plate type compressor and includes a cylinder block 20. A peripheral wall 24 of a front housing (crankcase) 22 is airtightly joined to one end side of the cylinder block 20. One end surface of the cylinder block 20, the peripheral wall 24 of the front housing 22, and the end wall 25 of the front housing 22 define a crank chamber 26.
A drive shaft 30 is disposed in the center of the crank chamber 26, and the drive shaft 30 passes through a substantially cylindrical bearing support portion 31 formed integrally with the outer surface of the end wall 25 of the front housing 22. Although not shown, for example, a pulley is connected to the outer end of the drive shaft 30 protruding from the bearing support portion 31. The pulley is rotatably supported by the bearing support portion 31 via a bearing (not shown). Engine power (not shown) is transmitted to the drive shaft 30 through the pulley.

A plurality of cylinder bores 32, for example, seven cylinder bores 32 are formed concentrically on the outer periphery of the cylinder block 20. Each cylinder bore 32 extends parallel to the drive shaft 30 and penetrates the cylinder block 20. These cylinder bores 32 are arranged at equal intervals in the circumferential direction of the cylinder block 20.
A piston 34 is slidably disposed in each cylinder bore 32, and the rotational movement of the drive shaft 30 is converted into a reciprocating movement of the piston 34 by a power conversion mechanism.

Specifically, a connecting rod 36 is connected to each piston 34 via a ball joint. The connecting rod 36 projects into the crank chamber 26, and the end of the connecting rod 36 is connected to a substantially ring-shaped swing plate 38 via a ball joint.
In order to reciprocate the piston 34, in other words, to swing the swing plate 38, a substantially disk-shaped rotor 40 is coaxially fixed to the drive shaft 30 so as not to be relatively rotatable. A thrust bearing 42 is disposed between the rotor 40 and the end wall 25 of the front housing 22, and a swash plate 46 as a cam member is connected to the rotor 40 via a hinge 44.

The swash plate 46 has a substantially ring shape and is penetrated by the drive shaft 30. The swash plate 46 can be tilted with respect to the drive shaft 30 while moving in the axial direction of the drive shaft 30 by the hinge 44.
A boss portion 48 is integrally formed on the inner peripheral edge of the swing plate 38, and the boss portion 48 projects from the swing plate 38 toward the rotor 40 or the swash plate 46. The boss portion 48 is surrounded by a swash plate 46, and a ball bearing as a radial bearing 50 is disposed between the boss portion 48 and the swash plate 46.

  The inner ring of the ball bearing is fixed to the boss portion 48, and the outer ring is fixed to the swash plate 46. An annular slide bearing is disposed as a thrust bearing 52 between the swing plate 38 and the swash plate 46. Therefore, the swash plate 46 and the oscillating plate 38 are connected so as to be relatively rotatable, and the oscillating plate 38 can also tilt with respect to the drive shaft 30 while moving in the axial direction of the drive shaft 30.

Since the compressor is of a swing plate type, the power conversion mechanism includes a swing plate rotation prevention unit for preventing the swing plate 38 from rotating along with the rotation of the drive shaft 30. The swing plate rotation preventing unit connects the swing plate 38 and the cylinder block 20 to prevent the swing plate 38 from rotating.
More specifically, the rocking plate rotation prevention unit has a substantially hollow cylindrical joint shaft 54, and the joint shaft 54 is fitted to the inner end side of the drive shaft 30 with a minute gap. A cylindrical slide bearing 56 is disposed between the inner peripheral surface of the joint shaft 54 and the outer peripheral surface of the drive shaft 30. The joint shaft 54 is slidable with respect to the drive shaft 30 through the sliding bearing 56.

Here, the inner end of the drive shaft 30 is located inside a cylindrical shaft hole (support hole) 58 formed in the center of the cylinder block 20. The shaft hole 58 opens into the crank chamber 26, and a plurality of grooves extending in the axial direction of the drive shaft 30 are formed on the inner peripheral surface of the shaft hole 58.
2, a plurality of keys 60 extending in the axial direction of the drive shaft 30 are formed on the outer peripheral surface of the central portion of the joint shaft 54 so as to be slidably engaged with these grooves. Has been. That is, the joint shaft 54 is spline-coupled to the inner peripheral surface of the shaft hole 58 so as to be slidable in the axial direction of the shaft hole 58. The spline coupling prevents the joint shaft 54 from rotating as the drive shaft 30 rotates.

If the rotation of the joint shaft 54 accompanying the rotation of the drive shaft 30 can be prevented and the joint shaft 54 can slide along the drive shaft 30, the number of grooves and keys may be one each. .
At one end of the joint shaft 54 on the crank chamber 26 side, for example, three projecting portions (hereinafter referred to as a JS side projecting portion or a JS side projecting portion) 62 projecting in the axial direction of the joint shaft 54 are integrally formed. Each JS side protrusion 62 has a substantially fan shape when viewed in the axial direction of the joint shaft 54.

These JS side protrusions 62 are arranged at equal intervals in the circumferential direction of the JS side protrusions 62, and each JS side protrusion 62 has grooves (JS side ball grooves) 64 on both side surfaces along its radial direction. The JS-side ball groove 64 is inclined with respect to the axial direction of the joint shaft 54 so as to approach the drive shaft 30 as the distance from the joint shaft 54 increases.
Further, the swing plate rotation prevention unit has a joint case 66 as shown in FIG. The joint case 66 is disposed coaxially with the joint shaft 54. The joint case 66 has a ring portion 68, and the ring portion 68 is fixed to the inner side in the radial direction of the swing plate 38 so as to be integrally rotatable. On the inner peripheral surface of the ring portion 68, three projecting portions (hereinafter referred to as joint case side projecting portions or JC side projecting portions) 70 projecting inward in the radial direction are integrally formed.

  These JC side protrusions 70 have a substantially fan shape when viewed in the axial direction of the ring portion 68. These JC side protrusions 70 are arranged at equal intervals in the circumferential direction of each of the JC side protrusions 70, and each JC side protrusion 70 has grooves (JC side ball grooves) 72 on both side surfaces along its own radial direction. . The JC-side ball groove 72 is inclined with respect to the axial direction of the ring portion 68 so as to move away from the drive shaft 30 as the distance from the joint shaft 54 increases.

FIG. 3 shows the joint case 66, the JS side protrusion 62, and the ball 74 in an assembled state when viewed along the axial direction of the joint case 66 from the joint shaft 54 toward the joint case 66. Yes. In FIG. 3, the joint shaft 54 is omitted, and the fracture surface of the JS side protrusion 62 is hatched.
The joint case 66 is disposed concentrically with the JS-side protrusion 62, and the JS-side protrusion 62 is positioned between the JC-side protrusions 70, respectively. Between the JS-side ball groove 64 and the JC-side ball groove 72 facing each other with a gap, one ball 74 is arranged to be able to roll one by one.

Referring again to FIG. 2, the JC side protruding portion 72 has an end surface on the innermost side in the radial direction of the ring portion 68, and this end surface is constituted by a curved surface 76. The curved surface 76 has an arc shape with a predetermined curvature as viewed in the longitudinal section of the JC side protruding portion 72.
Further, the swing plate rotation preventing unit has a sleeve 80 fitted to the drive shaft 30 via a cylindrical slide bearing 78. The sleeve 80 is also slidable in the axial direction of the drive shaft 30 together with the sliding bearing 78. The sleeve 80 has a barrel-shaped outer shape, and when viewed in the longitudinal section of the sleeve 80, the outer peripheral surface of the sleeve 80 has an arc shape having substantially the same curvature as the curved surface 76 of the JC-side protruding portion 72.

The curved surface of the JC-side protruding portion 72 is in sliding contact with the outer peripheral surface of the sleeve 80, and thus the joint case 66 is supported by the sleeve 80 so as to be swingable. The rotation of the joint case 66 accompanying the rotation of the drive shaft 30, that is, the rotation of the swing plate 38 is regulated by the joint shaft 54 via the balls 74.
Referring to FIG. 1 again, the cylinder block 20 supports the inner end side of the drive shaft 30 via a joint shaft 54 and a sliding bearing 56 so as to be relatively rotatable. The front housing 22 supports the outer end side of the drive shaft 30 via a radial bearing 82 so as to be relatively rotatable. A shaft seal 84 is disposed in the bearing support portion 31 of the front housing 22.

A cylinder head 88 is joined to the other end side of the cylinder block 20 by a plurality of connecting bolts 90 via a gasket (not shown) and a valve plate 86. Accordingly, the outer edge portion of the cylinder block 20, the front housing 22, and the cylinder head 88 constitute a compressor housing.
A discharge port (not shown) is formed in the cylinder head 88. The discharge port communicates with the radiator 14 through the circulation path 12 and communicates with a discharge chamber 92 defined in the cylinder head 88.

  The discharge chamber 92 can communicate with the cylinder bore 32 through a discharge hole 94 penetrating the valve plate 86, and the discharge hole 94 is opened and closed by a discharge valve (not shown). Further, the discharge chamber 92 can communicate with the crank chamber 26 through an external pipe 95, for example. A capacity control valve 96 capable of opening and closing the pipe 95 is inserted in the middle of the pipe 95, and the capacity control valve 96 can be controlled from the outside.

Instead of the pipe 95, an internal flow path extending from the cylinder head 88 to the crank chamber 26 through the valve plate 86 and the cylinder block 20 may be provided. A capacity control valve 96 may be inserted in the internal flow path.
A suction chamber 97 is defined in the cylinder head 88. The suction chamber 97 is partitioned outside the cylinder head 88 in the radial direction, and the suction chamber 97 is partitioned around the discharge chamber 92 when viewed in the radial direction of the cylinder head 88. That is, the discharge chamber 92 and the suction chamber 97 are separated from each other by the partition wall 98 that forms part of the cylinder head 88. The suction chamber 97 can communicate with the cylinder bore 32 through a suction hole 99 penetrating the valve plate 86, and the suction hole 99 is opened and closed by a reed valve (not shown) as a suction valve.

A suction port 100 is formed integrally with the cylinder head 88. The suction port 100 communicates with the evaporator 18 through the circulation path 12. The suction port 100 communicates with a suction chamber 97 defined in the cylinder head 88 via a suction working fluid distribution mechanism.
As shown in FIG. 4, the suction working fluid distribution mechanism has a cylindrical supply chamber 102 formed at the center in the radial direction of the cylinder block 20, and the supply chamber 102 is located on the valve plate 86 side of the shaft hole 58. It is connected to the same axis.

The suction working fluid distribution mechanism has seven grooves (communication passages) 104 formed at the end of the cylinder block 20 on the valve plate 86 side. The number of grooves 104 corresponds to the number of cylinder bores 32. The grooves 104 extend radially from the supply chamber 102, and one groove 104 is positioned between the cylinder bores 32 when viewed in the circumferential direction of the cylinder block 20.
Further, the suction working fluid distribution mechanism has a communication hole 106 formed in the valve plate 86 as shown in FIG. The position of the communication hole 106 matches the position of the tip of the groove 104, and the contour is located outside the flower-shaped partition wall 98. Therefore, the supply chamber 102 and the suction chamber 97 communicate with each other through the plurality of grooves 104 and the communication holes 106.

  An inlet hole 108 is formed in the valve plate 86, and the inlet hole 108 communicates with the suction port 100 through the inside of a substantially cylindrical introduction wall portion 110 formed integrally with the cylinder head 88. The introduction wall portion 110 penetrates the central portion of the discharge chamber 92, and the leading end of the introduction wall portion 110 is airtight with respect to the peripheral edge of the inlet hole 108 in the valve plate 86 via a gasket (not shown). It is in contact.

The crank chamber 26 communicates with the supply chamber 102 through the shaft hole 58. The minute gap in the spline connection between the joint shaft 54 and the shaft hole 58 functions as a throttle in the communication path that connects the crank chamber 26 and the supply chamber 102.
Hereinafter, the operation of the above-described compressor will be described.
When power is transmitted from the engine to the drive shaft 30, the drive shaft 30 rotates. As the drive shaft 30 rotates, the rotor 40, the hinge 44, and the swash plate 46 also rotate, and the swing plate 38 supported by the swash plate 46 so as to be relatively rotatable swings. The swing of the swing plate 38 is converted into a reciprocating motion of the piston 34 via the ball joint and the connecting rod 36.

While the swing plate 38 is swinging, rotation of the swing plate 38 accompanying rotation of the drive shaft 30 is prevented by the joint case 66, the ball 74, and the joint shaft 54.
By the reciprocating motion of the piston 34, a refrigerant suction process from the suction chamber 97 to the cylinder bore 32, a refrigerant compression process in the cylinder bore 32, and a refrigerant discharge process from the cylinder bore 32 to the discharge chamber 92 are executed. That is, due to the reciprocating motion of the piston 34, the refrigerant vaporized by the evaporator 18 is sucked into the compressor through the circulation path 12 and the suction port 100, and the refrigerant discharged from the discharge port of the compressor passes through the circulation path 12 to the radiator 14. Supplied.

  The discharge amount of the refrigerant, that is, the discharge capacity of the compressor is controlled by, for example, a suction pressure control method or a differential pressure control method. In the suction pressure control method, the discharge capacity is controlled so that the pressure in the suction chamber 97 (suction pressure) approaches the target value. In the differential pressure control method, the discharge capacity is controlled so that the difference between the pressure (discharge pressure) in the discharge chamber 92 and the suction pressure approaches the target value. In either case, the amount of current supplied to the solenoid of the capacity control valve 96 or the duty ratio of the current is adjusted as the operation amount.

When the discharge capacity of the compressor is maximum, the swing plate 38 is most inclined with respect to the plane orthogonal to the drive shaft 30 as shown in FIG. At this time, the radial center of the swing plate 38 is closest to the rotor 40.
On the other hand, when the discharge capacity of the compressor is minimum, the swing plate 38 is substantially parallel to the plane orthogonal to the drive shaft 30. At this time, the center of the swing plate 38 in the radial direction is furthest away from the rotor 40. That is, when the discharge capacity of the compressor is minimum, the radial center of the swing plate 38 moves toward the cylinder block 20 as compared to when the discharge capacity is maximum.

In this compressor, when viewed in the axial direction of the drive shaft 30, the radial center position of the swing plate 38 and the radial center position of the joint case 66 are interlocked, and the positions of the sleeve 80 and the joint shaft 54 are further linked. Is also linked.
Thus, in the compressor described above, the supply chamber 102 is provided in the cylinder block 20 and is distributed to the suction chamber 97 through the communication passage 104 extending radially from the supply chamber 102, so that the distribution of the working fluid in the suction chamber 97 becomes uniform. As a result, the mass of the working fluid sucked into each cylinder bore 32 becomes uniform, and the torque fluctuation of the compressor is prevented.

In the above-described compressor, even if the suction chamber 97 is outside the discharge chamber 92 and has an annular shape, the working fluid can be uniformly and reliably ensured in each part of the suction chamber 97 by the suction working fluid distribution mechanism. Distributed to.
Further, although the above-described compressor is a variable capacity compressor, the working fluid is uniformly distributed to each part of the suction chamber 97 by the suction working fluid distribution mechanism regardless of the change in the discharge capacity. The present invention is not limited to the first embodiment, and various modifications can be made.

Although the above-described compressor is a swing plate compressor, it may be a swash plate compressor. In the case of a swash plate type compressor, a tail portion is formed integrally with the piston 34, and the tail portion projects into the crank chamber 26. Each tail portion is formed with a spherical seat, and a pair of hemispherical shoes arranged on the spherical seat are in sliding contact with the outer peripheral portion of a swash plate as a cam member.
In the compressor described above, the number of cylinder bores 32 is not limited to seven.

In the compressor described above, the suction chamber 97 may be located on the radially inner side of the discharge chamber 92.
In the above-described compressor, the pressure in the crank chamber 26 is controlled on the inlet side (inlet control), but the present invention can also be applied to a compressor that controls (outlet control) the pressure in the crank chamber 26 on the outlet side. It is.

  Finally, the variable capacity reciprocating compressor of the present invention can be applied to various systems other than the vehicle air conditioning system, and the working fluid is not limited to the refrigerant.

It is the figure which showed the variable capacity reciprocating compressor of 1st Embodiment with the refrigerating cycle system of the vehicle air conditioning system. FIG. 2 is a schematic exploded view of a rocking plate rotation prevention unit applied to the compressor of FIG. 1. FIG. 3 is a diagram for explaining a mutual engagement state of a joint case, a ball, and a JS side protrusion in the swing plate rotation prevention unit of FIG. 2. It is a top view which shows the cylinder block applied to the compressor of FIG. FIG. 5 is a cross-sectional view taken along line VV in FIG. 1.

Explanation of symbols

20 Cylinder block 102 Supply chamber 104 Groove (communication path)

Claims (3)

A cylinder head in which a discharge port and a suction port are formed, and a discharge port and a suction port communicating with each of the discharge chamber and the suction chamber and the outside;
A cylinder block joined to the cylinder head and having a plurality of cylinder bores arranged concentrically;
A crankcase coupled to the cylinder block and having a crank chamber defined therein;
In a variable capacity reciprocating compressor comprising a power conversion mechanism that converts the rotation of a drive shaft extending in the crank chamber into a reciprocating motion of a piston disposed in the cylinder bore with a variable stroke length,
The cylinder block is formed at a central portion in a radial direction of the cylinder block, and a supply chamber into which a working fluid sucked through the suction port flows, and a supply chamber for supplying the working fluid in the supply chamber to the suction chamber. A reciprocating compressor comprising a plurality of radially extending communication passages.   2. The reciprocating compressor according to claim 1, wherein the suction chamber is positioned outside the discharge chamber as viewed in a radial direction of the cylinder head. The power conversion mechanism is
An annular cam that is connected to an outer peripheral portion of a rotor fitted to the drive shaft via a hinge, is penetrated by the drive shaft, and can tilt with respect to the drive shaft while moving in the axial direction of the drive shaft Members,
A rocking plate coupled to the piston via a coupling rod and rocked by the cam member;
A joint shaft that is fitted to the drive shaft via a bearing and is supported by an inner peripheral surface of a support hole formed in the cylinder bore and connected to the supply chamber so as not to rotate relative to the inner peripheral surface and to be slidable. When,
A joint case provided so as to be swingable integrally with the swing plate;
And a plurality of balls sandwiched between the JS-side protruding portion provided integrally with the joint shaft and the JC-side protruding portion provided integrally with the joint case. Item 3. The reciprocating compressor according to Item 1 or 2.

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