JP4367415B2 - Electric tool - Google Patents

Description

  The present invention relates to a power tool such as a rotary hammer drill using a DC motor as a drive source.

  Electric tools using a DC motor as a drive source are widely used in practice (for example, see Patent Document 1). A rotary hammer drill as an example of this type of electric tool incorporates a DC motor as a drive source in a housing, and a magnet set (stator) 130 of this DC motor is an iron as shown in detail in FIG. A substantially cylindrical yoke 131 made of a ferromagnetic material such as, and two arc-curved magnets 132 disposed inside the yoke 131. A direction gap is formed. 10A is a sectional side view of the magnet assembly 130 (a sectional view taken along the line H-H in FIG. 10B), and FIG. 10B is a front view of the magnet assembly 130 (in the direction of arrow J in FIG. 10A). Figure)

  Here, the two magnets 32 are fixed to the inner peripheral surface of the yoke 131 by adhesion or the like in order to prevent the axial displacement and the circumferential rotation. Further, by inserting and engaging a spring-like magnet holder 135 formed in a U shape with a wire or the like in the circumferential clearance between these magnets 132, a force that pushes the magnet 132 outward is applied to the magnet 132. 132 is attached to the inner peripheral surface of the yoke 131 so that the magnet 132 does not come off even when the adhesion is weakened.

Further, as shown in FIG. 10 (a), a ring-shaped dust guard 133 is fitted on the periphery of the opening at one end of the yoke 131 in the axial direction, and this dust guard 133 enters dust into the DC motor. In addition, the air flow is improved to improve the cooling efficiency of the DC motor.
JP 2002-254337 A

  Here, FIG. 11 and FIG. 12 show a comparison of the air passage area when the magnet holder 135 shown in FIG. 10A is used and when it is not used.

  FIG. 11 is a front view of the magnet assembly 130 when the magnet holder 135 is not provided. In this case, a space formed between the arm 141 and the armature 141 by the circumferential clearance between the yoke 131 and the magnet 132 (the hatched portion in FIG. 11). ) Is the cooling air path. On the other hand, FIG. 12 is a front view of the magnet assembly 130 when the magnet holder 135 is provided. In this case, the space formed between the arm 141 by the circumferential clearance between the yoke 131 and the magnet 132 is as follows. The cross-sectional area is reduced by the magnet holder 135, and the cross-sectional area of the cooling air passage (shown by hatching in FIG. 12) is reduced by the reduced amount, thereby reducing the cooling efficiency.

  Further, as shown in FIG. 10, the yoke 131 is usually provided with a notch 131a, and the yoke 131 is rotated in the circumferential direction by fitting a projection (not shown) of the housing into the notch 131a. To prevent.

  However, even if the rotation of the yoke 131 is prevented by the above-described structure, if the adhesive force of the magnet 132 to the yoke 131 becomes weak, the magnet 141 has the structure shown in FIG. 132 may deviate in the axial direction or rotate in the circumferential direction. Further, in the configuration provided with the magnet holder 135 shown in FIG. 12, the magnet 132 cannot be removed, but the magnet 132 may rotate in the circumferential direction along the inner peripheral surface of the yoke 131 together with the magnet holder 135.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an electric tool that can easily prevent the magnet from coming off and rotating.

  Another object of the present invention is to provide an electric tool capable of improving the cooling efficiency.

In order to achieve the above object, an invention according to claim 1 includes a housing having a cylindrical body, a substantially cylindrical yoke incorporated in the housing , and a circumferential clearance provided on the inner periphery of the yoke. DC with a plurality of fixed magnets, an armature rotatably disposed with a radial gap between the magnets and a dust guard fitted to one end of the yoke in the axial direction In the electric tool using a motor as a drive source, a plurality of engaging protrusions that engage with a circumferential clearance formed between the magnets in the yoke are integrally formed on the dust guard, and a part of the body portion A first engagement portion is formed on the dust guard, and a second engagement portion that engages with the first engagement portion in the rotation direction is formed on the dust guard .

  According to a second aspect of the present invention, in the first aspect of the invention, the dust guard has a ring-shaped main body portion that protrudes axially outward from the axial end surface of the yoke. It is characterized in that the mating protrusion is integrally projected.

  A third aspect of the invention is characterized in that, in the first or second aspect of the invention, the engaging projection is formed in an arcuate curved surface shape along the inner peripheral shape of the yoke.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, a slit extending in the axial direction is formed in the engagement protrusion.

According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the dust guard is disposed at a front end portion of the yoke in the direction of assembly into the housing.

According to the first aspect of the present invention, since the engagement protrusion formed integrally with the dust guard is engaged with the circumferential clearance formed between the magnets in the yoke, the axial displacement of the magnet can be reduced. Circumferential rotation can be suppressed. In addition, since the engagement projection for preventing the magnet from coming off in the axial direction and rotating in the circumferential direction is formed integrally with the dust guard, the number of parts can be reduced, and the assemblability can be improved and the cost can be reduced. Further, when the magnet assembly provided with the dust guard is incorporated into the barrel portion of the cylindrical housing, the magnet assembly is fitted to the housing barrel in a state in which the housing-side engagement protrusion is engaged with the engagement groove provided in the dust guard. When incorporated in the part, the magnet assembly is accurately positioned with respect to the housing, so that the assembly of the magnet assembly is enhanced. Further, rotation with respect to the housing can be suppressed via the dust guard and the magnet.

  According to the second aspect of the present invention, it is possible to improve the function of the dust guard ring-shaped main body portion protruding axially outward from the axial end surface of the yoke to prevent the intrusion of dust such as iron powder.

  According to the third aspect of the present invention, since the engagement protrusion formed on the dust guard has an arcuate curved shape along the inner peripheral shape of the yoke, it is formed between the yoke and the amateur by the circumferential clearance between the yoke and the magnet. The reduction of the cross-sectional area due to the engaging projections of the air passage is minimized, the restriction of the flow rate of the cooling air passing through the air passage is suppressed, and the cooling efficiency of the DC motor is increased.

  According to the fourth aspect of the present invention, since the slit extending in the axial direction is formed in the engaging protrusion, when the dust guard is fitted to the yoke while the engaging protrusion is inserted between the magnets, the assemblability of the dust guard is improved. Without hindering, the engaging protrusion can easily engage with the magnet and function to prevent the magnet from coming off. Moreover, the reaction force with which the engaging protrusions press the circumferential end surface of the magnet is increased, and the axial prevention of the magnet can be suppressed. Furthermore, since the cross-sectional area of the air passage formed between the armature and the yoke is increased by the slit, the flow rate of the cooling air passing through the air passage is increased and the cooling efficiency of the DC motor is increased. It is done.

According to the fifth aspect of the present invention, since the dust guard is disposed at the front end portion of the yoke in the housing direction, the engagement groove provided on the dust guard before the magnet assembly is assembled into the housing is engaged with the housing side. The mating protrusions can be engaged, and the magnet assembly can be easily incorporated into the housing with good workability while positioning and locking the magnet assembly from the beginning.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a longitudinal sectional view of a rotary hammer drill 1 as an embodiment of an electric tool according to the present invention. The illustrated rotary hammer drill 1 includes a DC motor 3 as a driving source in a resin housing 2 as an outer member. The rotating shaft (motor shaft) 4 of this DC motor 3 is supported rotatably by bearings 5 and 6 at both ends. A cooling fan 7 is attached to the rotating shaft 4, and a fan guide 8 is disposed around the cooling fan 7. Further, a pinion 9 is formed at the front end portion of the rotating shaft 4 protruding forward from the bearing 5.

  The housing 2 is constructed by joining and integrating divided pieces 2A and 2B which are divided into two parts in the front and rear directions. A power cord for supplying power to the DC motor 3 is supplied to the handle portion 2B-1 of the divided piece 2B. 10 is connected. The handle 2B-1 of the split piece 2B includes a circuit (AC / DC converter) 11 for converting the AC power source to DC, and a switch 12 for turning ON / OFF the power supply to the DC motor 3. Is provided.

  By the way, an intermediate shaft 13 is arranged in front of the DC motor 3 in the housing 2 in parallel with the rotating shaft 4, and both ends of the intermediate shaft 13 are rotatably supported by bearings 14. The intermediate shaft 13 is provided with a reciprocating bearing 15 and gears 16 and 17, and the gear 16 meshes with the pinion 9 formed at the front end of the rotating shaft 4. Note that the diameter of the gear 16 is larger than the diameter of the pinion 9, and the gear 16 constitutes a speed reduction mechanism.

  A cylinder 18 is disposed in the front end portion of the housing 2 so as to be parallel and rotatable with the rotary shaft 4 and the intermediate shaft 13, and a gear 19 is provided on the outer peripheral portion of the cylinder 18. 13 is engaged with the gear 17. The diameter of the gear 19 is larger than the diameter of the gear 17, and these gears 17 and 19 constitute a reduction mechanism.

  A bottomed cylindrical piston 20 having one end (front end) opened is fitted in the cylinder 18 so as to be slidable in the front-rear direction, and a pressure chamber 22 defined by an intermediate element 21 is formed in the piston 20. Has been. An arm 15 a of the reciprocating bearing 15 is connected to the rear end portion of the piston 20, and a tip tool (drill bit) 23 is detachably attached to the tip portion of the cylinder 18. The tip tool 23 is slidable in the front-rear direction with respect to the cylinder 18 and is mounted so as to rotate integrally with the cylinder 18. A striking element 24 is interposed between the tip tool 23 and the intermediate element 21. It is installed.

  Thus, when the DC motor 3 is driven by operating the switch 12 to turn on, the rotation of the rotary shaft 4 is decelerated via the pinion 9 and the gear 16 and transmitted to the intermediate shaft 13, and the intermediate shaft 13 It is rotationally driven at a speed of Then, the arm 15a of the reciprocating bearing 15 swings back and forth to reciprocate the piston 20 back and forth in the cylinder 18, so that the pressure in the pressure chamber 22 in the cylinder 18 fluctuates. It is transmitted to the tip tool 23 via the intermediate piece 21 and the striker 24, and an impact force is applied to the tip tool 23.

  Further, the rotation of the intermediate shaft 13 is decelerated via the gears 17 and 19 and transmitted to the cylinder 18, and the cylinder 18 and the tip tool 23 attached thereto are rotationally driven at a predetermined speed.

  As described above, rotation and striking force are applied to the tip tool 23, and a drilling operation of a workpiece (not shown) is performed by the tip tool 23. Although not shown, the rotary hammer drill 1 according to the present embodiment is provided with a mode switching mechanism, and a rotation mode that gives only rotation to the tip tool 23 and rotation / hitting that gives rotation and impact force as described above. A mode can be selected.

  By the way, the DC motor 3 as a drive source is configured such that an armature (rotor) 41 is rotatably accommodated in a substantially cylindrical magnet set (stator) 30. Here, the magnet set 30 includes a substantially cylindrical yoke 31 made of a ferromagnetic material such as iron, and two arc-shaped curved magnets 32 disposed inside the yoke 31. Between the magnets 32, circumferentially spaced gaps are formed as described later (see FIG. 2B).

  The outer periphery of the fan guide 8 is fitted to the inner periphery of the housing 2, and the rear end (the left side in FIG. 1 is the front) is the front end of the yoke 31 of the magnet assembly 30. It is in contact with the inner periphery. A ring-shaped dust guard 33 is fitted on the inner periphery of the rear end of the yoke 31. In FIG. 1, reference numeral 25 denotes a carbon brush.

  Next, the gist of the present invention will be described with reference to FIGS.

<Embodiment 1>
2A is a side sectional view of the magnet assembly (a sectional view taken along line AA in FIG. 2B), and FIG. 2B is a front view of the magnet assembly (a view in the direction of arrow B in FIG. 2A). FIG. 3C is a cross-sectional view taken along the line C-C of FIG. 3A, FIG. 3 is an exploded perspective view of the magnet assembly, and FIG.

  As shown in FIG. 2A, a resin dust guard 33 is fitted on the inner periphery of the rear end of the yoke 31 (the right end of FIG. 2A). The two engaging projections 33b projecting from the ring-shaped main body 33a are integrally formed. A rectangular notch 31a is formed at one location on the other end (front end) of the yoke 31, and this notch 31a is formed in the fan guide 8 (see FIG. 1) (not shown). The yoke 31 is prevented from rotating by the engagement of the protrusions.

  The main body 33a of the dust guard 33 protrudes from the one end of the yoke 31 in the axial direction to the rear (to the right in FIG. 2A) by a predetermined amount, and suppresses intrusion of dust such as iron powder into the yoke 31. Fulfills the function of Further, the two engaging projections 33b protruding integrally from the main body 33a are formed opposite to each other at a position 180 ° apart in the circumferential direction, and as shown in FIG. The surface is formed into an arcuate curved surface so as to be in close contact with the inner peripheral surface of the yoke 31. A slit 33b-1 that is long in the axial direction is formed at the center in the width direction of each engagement protrusion 33b.

  Thus, the dust guard 33 is positioned so that each engaging projection 33b engages with the circumferential gap between the magnets 32 and pushed forward in the yoke 31, and the outer periphery of the main body 33a is moved to the yoke 31. It is attached to the yoke 31 by being fitted to the inner periphery of the rear end. Then, as shown in FIGS. 2A and 2B, the two engaging protrusions 33 b of the dust guard 33 engage with the circumferential gap between the two magnets 32 formed in the yoke 31, and each magnet. 32 is positioned in the circumferential direction, and rotation of the magnet 32 along the inner peripheral surface of the yoke 31 is prevented.

  The width dimension of each engagement protrusion 33b of the dust guard 33 is set to be slightly larger than the circumferential length of the circumferential gap between the magnets 32 (so as to ensure a predetermined press-fitting allowance). When the mating protrusions 33b are engaged with the circumferential gaps between the magnets 32, the respective engaging protrusions 33b are compressed and deformed in the width direction, and the reaction force (elastic force) acts on the circumferential end surfaces of the respective magnets 32. . As a result, the two magnets 32 are urged outward in the radial direction and are brought into close contact with the inner peripheral surface of the yoke 31, so that the adhesion force of each magnet 32 to the inner peripheral surface of the yoke 31 is weakened. Even if it exists, the magnet 32 does not come out from the yoke 31 in the axial direction, and these pieces are prevented from coming off effectively. Further, since the outer peripheral surfaces of the magnet 32 and the engaging protrusion 33b are formed in an arcuate curved surface along the inner peripheral surface of the yoke 31, and are in close contact with the inner peripheral surface of the yoke 31, the yoke 31 of the magnet 32 is Even when the adhesive force to the inner peripheral surface becomes weak, the magnet 32 is prevented from coming off in the radial direction.

  In this embodiment, since the slits 33b-1 extending in the axial direction are formed in the respective engaging projections 33b of the dust guard 33, the dust guard 33 is fitted to the yoke 31 while the engaging projections 33b are inserted between the magnets 32. At the time of wearing, the engaging protrusion 33b can easily engage with the magnet 32 without hindering the assembling of the dust guard 33, and the retaining of the magnet 32 can be functioned. Moreover, the reaction force that the engaging protrusion 33b presses the circumferential end surface of the magnet 32 becomes large, and the axial prevention of the magnet 32 can be suppressed. Furthermore, since the cross-sectional area of the air passage formed between the yoke 31 and the magnet 32 and the armature 41 is increased by the slit 33b-1, the flow rate of the cooling air passing through the air passage is increased and the direct current is increased. The cooling efficiency of the motor 3 is increased.

  By the way, when the DC motor 3 shown in FIG. 1 is driven, the cooling fan 7 also rotates together with the rotating shaft 4, and the cooling air induced by the cooling fan 7 is introduced into the DC motor 3 along the fan guide 8. Then, when the cooling air passes through the DC motor 3 in the axial direction, the DC motor 3 is cooled.

  Thus, in the present embodiment, the engagement protrusion 33b of the dust guard 33 is formed into an arc curved surface so as to be in close contact with the inner peripheral surface of the yoke 31, and the slit 33b-1 is formed at the center in the width direction. The cross-sectional area (shaded area in FIG. 4) of the air passage formed between the yoke 31 and the magnet 32 shown in FIG. 4 between the armature 41 and the armature 41 is obtained when the magnet holder 135 shown in FIG. 10 is used. It becomes larger than the cross-sectional area of the air passage shown in FIG. As a result, in the present embodiment, the flow rate of the cooling air passing through the air passage is increased and the cooling efficiency of the DC motor 3 is increased.

  Here, how the radial gap between the dust guard 33 and the armature 41 changes when the length of the slit 33b-1 formed in each engagement protrusion 33b of the dust guard 33 is changed is shown. 5 and FIG. 6 are used for verification. 5 (a) and 6 (a) are side sectional views of the magnet assembly, FIG. 5 (b) is a sectional view taken along the line DD of FIG. 5 (a), and FIG. 6 (b) is the same drawing (a). It is the EE sectional view taken on the line of).

  As shown in FIG. 5A, a short slit 33b-2 is formed in each engagement protrusion 33b of the dust guard 33, and the semicircular end position a ′ is shown in FIG. 5B. When the amateur 41 is positioned in front of the core end surface position f (in the direction of the arrow in the figure), the radial gap L1 between the dust guard 33 and the armature 41 is reduced, and the cooling air flowing through the gap L1 is throttled, and the flow rate is reduced. Since it is restricted, the cooling efficiency is lowered.

  In contrast, in the present embodiment, each engagement protrusion 33b of the dust guard 33 is formed with a slit 33b-1 longer than the slit 33b-2 shown in FIG. 5, and the slit 33b-1 has a semicircular shape. As shown in FIG. 2C, the end position a is positioned rearward (in the direction of the arrow in the figure) from the core end surface position f of the armature 41, so that the gap between the dust guard 33 and the armature 41 is shown in FIG. A radial gap L2 (> L1) larger than the radial gap L1 is formed, the flow rate of cooling air passing through the gap L2 is increased, and the cooling efficiency is improved.

  Further, a long slit 33b-3 as shown in FIG. 6A is formed in each engagement protrusion 33b of the dust guard 33, and the semicircular end position a ″ is further rearward than the present embodiment. When positioned, a radial gap L3 (> L0) larger than the radial gap L0 between the yoke 31 and the armature 41 is formed between the dust guard 33 and the armature 41 as shown in FIG. 6 (b). Therefore, the flow rate of the cooling air flowing between the yoke 31 and the armature 41 is further increased, and the cooling efficiency is further improved.

  In the present embodiment, the slit 33b-1 is formed in each engagement protrusion 33b of the dust guard 33. However, the slit 33b-1 is not always necessary, and as shown in FIG. It is not necessary to form a slit. 7A is a side sectional view of the magnet assembly showing another configuration of the present embodiment (a sectional view taken along line FF in FIG. 7B), and FIG. FIG.

<Embodiment 2>
Next, an embodiment of the present invention will be described with reference to FIGS.

  FIG. 8 is an exploded perspective view of a magnet set of a DC motor that is a drive source of the electric tool (rotary hammer drill) according to the present embodiment, and FIG. 10 is a front view of the rear half of the housing in which the magnet set is incorporated.

  Also in this embodiment, a resin dust guard 33 is fitted to one end of the yoke 31 of the magnet assembly 30 in the axial direction, and the dust guard 33 is incorporated in the yoke 31 as in the first embodiment. Two engaging projections 33b for integrally engaging the circumferential gap between the two magnets 32 to prevent the magnet 32 from rotating and coming off are integrally formed.

  Thus, in the present embodiment, the convex portion 33c is integrally protruded radially outward from a part of the ring-shaped main body portion 33a of the dust guard 33, and is formed on the outer surface of the convex portion 33c. An engaging groove 33d extending in the axial direction is provided through the shaft.

  By the way, the housing 2 of the electric power tool according to the present embodiment is configured by joining and integrating divided pieces divided into two parts in the front and rear, but as shown in FIG. 9, the latter half (rear divided piece 2B). Is formed integrally with a rectangular tube-shaped body portion 2B-2, and a rib-like oblique engagement protrusion extending in the axial direction (perpendicular to the plane of FIG. 9) is formed in the lower corner portion of the body portion 2B-2. 2a is integrally formed.

  Thus, the magnet assembly 30 in which the dust guard 33 is fitted to the axial end of the yoke 31 is placed on the front side of FIG. 9 on the body 2B-2 of the split piece 2B of the housing 2 with the dust guard 33 in front. In this state, the engaging protrusion 2a on the housing 2 side is engaged with the engaging groove 33d provided on the convex portion 33c formed integrally with the dust guard 33. The magnet set 30 is assembled into the body 2B-2 of the split piece 2B. Then, since the magnet assembly 30 is accurately positioned with respect to the housing 2, the assembly of the magnet assembly 30 is enhanced and its rotation is suppressed. Notches that have been conventionally machined can be omitted.

  In addition, the same effects as those of the first embodiment can be obtained in the present embodiment.

  In the first and second embodiments, the configuration in which the two magnets 32 are disposed opposite to each other in the yoke 31 has been described. However, the number of the magnets 32 is arbitrary as long as it is two or more. The same number of engaging projections 33b as the magnets 32 are integrally formed.

  The present invention is also applicable to any electric tool other than a rotary hammer drill using a DC motor as a drive source, for example, a driver drill, a saver saw, an impact tool, and the like.

It is a sectional side view of the electric tool (rotary hammer drill) which concerns on this invention. (A) is a side sectional view of the magnet set of the electric power tool according to the present invention (cross-sectional view taken along line AA in (b)), and (b) is a front view of the magnet set (in the direction of arrow B in (a)). (FIG.), (C) is CC sectional view taken on the line of (a). It is a disassembled perspective view of the magnet assembly of the electric tool which concerns on this invention. It is a front view which shows the air path cross section formed in the magnet assembly of the electric tool which concerns on this invention. (A) is a sectional side view of a magnet assembly, (b) is a sectional view taken along line DD of (a). (A) is a sectional side view of the magnet assembly, (b) is a sectional view taken along line EE of (a). (A) is a side sectional view of the magnet set showing another embodiment of the present invention (cross-sectional view taken along line FF in (b)), and (b) is a front view of the magnet set (in the direction of arrow G in (a)). Figure) It is a disassembled perspective view of the magnet assembly of the electric tool which concerns on Embodiment 2 of this invention. It is a front view of the second half part of the housing of the electric tool which concerns on Embodiment 2 of this invention. (A) is a side sectional view of a magnet set of a conventional electric power tool (cross-sectional view taken along the line H-H in (b)), and (b) is a front view of the magnet set (a view in the direction of arrow J in (a)). It is. It is a front view which shows the air path cross section formed in the magnet assembly of the conventional electric tool. It is a front view which shows the air path cross section formed in the magnet assembly of the conventional electric tool.

Explanation of symbols

1 Rotary hammer drill (power tool)
2 Housing 2A, 2B Split piece 2B-1 Handle portion 2B-2 Body portion 2a Engagement protrusion (first engagement portion)
3 DC motor 4 Rotating shaft (motor shaft)
5,6 Bearing 7 Cooling fan 8 Fan guide 9 Pinion 10 Power cord 11 Circuit (AC / DC converter)
12 switch 13 intermediate shaft 14 bearing 15 reciprocating bearing 16, 17 gear 18 cylinder 19 gear 20 piston 21 intermediate element 22 pressure chamber 23 tip tool 24 striker 25 carbon brush 30 magnet assembly 31 yoke 32 magnet 33 dust guard 33a dust guard main body 33b Joint protrusion 33b-1 Slit 33c Protruding portion 33d Engaging groove (second engaging portion)

Claims (5)

A housing having a cylindrical body, a substantially cylindrical yoke incorporated in the housing, a plurality of magnets fixed with a circumferential clearance on the inner periphery of the yoke, and a magnet inside the magnet In an electric tool using a DC motor provided with a DC motor having a dust guard fitted to one end in the axial direction of the yoke as a rotationally arranged armature with a radial gap therebetween,
The dust guard is integrally formed with a plurality of engaging protrusions that engage with a circumferential gap formed between the magnets in the yoke, and a first engaging portion is formed in a part of the body portion. A power tool characterized in that a second engagement portion that engages with the first engagement portion in the rotational direction is formed on the dust guard .   2. The dust guard has a ring-shaped main body portion that protrudes outward in the axial direction from an axial end surface of the yoke, and the engaging protrusion is integrally projected on the main body portion. The electric tool described.   The electric tool according to claim 1, wherein the engagement protrusion has an arcuate curved surface shape along an inner peripheral shape of the yoke.   The electric tool according to claim 1, wherein a slit extending in the axial direction is formed in the engagement protrusion. The dust guard is disposed at the front end of the yoke in the direction of assembly into the housing.
The electric tool according to any one of claims 1 to 4, wherein

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