JP2019022343A - Electric tool - Google Patents

Abstract

To secure the air quantity of a fan without increasing an entire length of a rotor even if an integrally molded resin portion exists between a rotor core and the fan.SOLUTION: A hammer drill 1 includes a brushless motor 3 including a stator 10 and a rotor 11 which may rotate relative to the stator 10. The rotor 11 has a rotary shaft 12, a rotor core 18, and a centrifugal fan 30. The rotary shaft 12 and the rotor core 18 are integrated by a resin 35 supplied between the rotor core 18 and the centrifugal fan 30. A ventilation space A which allows communication between the radial outer side of the rotor core 18 and the centrifugal fan 30 side is formed at a resin portion 35a formed between the rotor core 18 and the centrifugal fan 30.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power tool such as a hammer drill.

  For example, as disclosed in Patent Document 1, a motor used as a drive source of an electric tool includes a stator and a rotor that can rotate with respect to the stator. It has a cylindrical rotor core that is arranged around the rotating shaft and is formed by laminating a plurality of electromagnetic steel plates, and a permanent magnet that is arranged inside the rotor core.

Japanese Patent Laying-Open No. 2015-56953

When manufacturing a rotor, if an adhesive is used to fix the permanent magnet to the rotor core, the adhesive may sag or the adhesive surface between the permanent magnet and the rotor core may vary due to shrinkage of the adhesive. is there. Due to this variation, the centrifugal force during rotation is concentrated on a part of the rotor core via the adhesive, and the rotor core may be damaged early.
Therefore, a method of integrating the rotating shaft, the rotor core, and the permanent magnet with resin instead of the adhesive is employed. In this case, since the resin is poured in while applying pressure, the adhesion surface between the permanent magnet and the rotor core can be made uniform, and the strength of the rotor can be secured. Moreover, double insulation is also possible by interposing a resin between the rotating shaft and the rotor core.
However, when the resin molding is performed by the runnerless method, it is necessary to arrange a gate in a direction orthogonal to the rotation axis to ensure a certain resin thickness in the axial direction. In this case, if the gate is disposed between the rotor core and the fan, the resin portion formed between the rotor core and the fan blocks the fan air path, and the air volume cannot be secured. If the fan is arranged away from the resin portion, the air volume can be secured, but the entire length of the rotor is increased accordingly, and the product dimension in the direction of the rotation axis is also increased.

  Therefore, the present invention has an object to provide an electric tool that can secure the air volume of a fan without increasing the overall length of the rotor even if a resin portion is integrally formed between the rotor core and the fan. is there.

In order to achieve the above object, an invention according to claim 1 includes a motor including a stator and a rotor rotatable with respect to the stator, and the rotor includes a rotating shaft, a rotor core, and a fan. The rotating shaft and the rotor core are integrated by a resin filled from between the rotor core and the fan,
The resin portion formed between the rotor core and the fan is characterized in that a ventilation space that communicates the outer side in the radial direction of the rotor core and the fan side is formed.
According to a second aspect of the present invention, in the configuration of the first aspect, the ventilation space is a surface on the fan side in the resin portion, and between a plurality of convex portions projecting at point-symmetrical positions around the rotation axis. It is formed.
According to a third aspect of the present invention, in the configuration of the second aspect, the convex portion is formed in the diameter direction of the rotor core.
According to a fourth aspect of the present invention, in the configuration of the third aspect, the convex portions are arranged in a cross shape when viewed from the axial direction of the rotating shaft.
According to a fifth aspect of the present invention, in the configuration according to any one of the first to fourth aspects, a recess for detecting a rotation angle is formed in a resin portion formed on the opposite side of the fan across the rotor core. It is characterized by.

  According to the present invention, since the ventilation space is formed in the resin portion formed between the rotor core and the fan, the entire length of the rotor is increased even if the resin portion formed by integral molding exists between the rotor core and the fan. The air volume of the fan can be ensured without doing so.

It is a longitudinal cross-sectional view of a hammer drill. (A) is the plane of the resin part between a centrifugal fan and a rotor core, (B) shows the side surface of a rotor, (C) shows the back surface of a rotor, respectively. (A) is a longitudinal section of the rotor, and (B) is a transverse section of the rotor core.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a longitudinal sectional view of a hammer drill as an example of an electric tool. The hammer drill 1 includes an output housing 4 that accommodates an output portion 5 and extends forward above a motor housing 2 in a vertical direction that accommodates a brushless motor 3. Below the motor housing 2, there is provided a battery mounting portion 6 in which the controller 7 is accommodated and two battery packs 8 and 8 can be mounted below the controller 7. A handle 9 is provided in the vertical direction across the battery mounting portion 6 from the rear of the output housing 4.

The brushless motor 3 is an inner rotor type having a stator 10 and a rotor 11 inside the stator 10, and is housed in the motor housing 2 in a posture in which the rotating shaft 12 of the rotor 11 is directed upward.
The stator 10 includes a stator core 13, an upper insulator 14 and a lower insulator 15 provided above and below the stator core 13, and a plurality of coils 16, 16,... Wound around the stator core 13 via the upper and lower insulators 14, 15. have. Fixed to the lower end of the lower insulator 15 is a sensor circuit board 17 mounted with a rotation detection element (not shown) that detects the position of a permanent magnet 21 of the rotor core 18 described later and outputs a rotation detection signal.

As shown in FIGS. 2 and 3, the rotor 11 is a cylindrical rotor core formed by laminating a rotating shaft 12 positioned at the axial center and a plurality of electromagnetic steel plates 19, 19,. 18 and permanent magnets 21, 21... Inserted into a plurality of through holes 20, 20... Concentrically formed inside the rotor core 18. At both ends in the circumferential direction of each through-hole 20, projecting spaces 20 a and 20 a that project beyond the both ends of the permanent magnet 21 and project outward in the circumferential direction are formed. .. Are caulked portions of the electromagnetic steel sheet 19 and are concentrically arranged between the through holes 20, 20 adjacent in the circumferential direction inside the through holes 20, 20.
The rotary shaft 12 is supported by a bearing 23 having a lower end provided at the bottom of the motor housing 2, an upper end supported by a bearing 24 provided at the output housing 4 and protruding into the output housing 4, and a pinion 25 formed at the upper end. The gears 28 and 29 provided on the front and rear intermediate shafts 26 and the crankshaft 27 are engaged with each other. A centrifugal fan 30 is provided on the rotating shaft 12 below the bearing 24, and a baffle plate 31 is provided in the motor housing 2 below the rotary fan 12.

A disc-shaped upper sleeve 32 having the same diameter as the rotor core 18 is disposed between the rotor core 18 and the centrifugal fan 30 on the upper side. A short cylindrical portion 33 that is longer in the axial direction than the intermediate portion is provided around the outer peripheral edge of the upper sleeve 32, and the lower end is brought into contact with the upper end surface of the rotor core 18. The resin can be injected before and after the upper sleeve 32. Since the short cylinder portion 33 has the same length of protrusion in the vertical direction from the intermediate portion, it can be assembled to the rotary shaft 12 without taking the vertical direction into consideration. The inner diameter of the center hole of the upper sleeve 32 is substantially the same as the center hole 18 a of the rotor core 18. However, the shape of the center hole 18a of the rotor core 18 is not circular, but has an octagonal cross section as shown in FIG.
On the other hand, a lower sleeve 34 having a smaller diameter than the rotor core 18 and having an outer periphery positioned on the inner side of the permanent magnet 21 is disposed between the lower side of the rotor core 18 and the bearing 23, and contacts the lower end surface of the rotor core 18. ing. The upper and lower sleeves 32 and 34 are made of brass, the upper sleeve 32 is used for preventing the permanent magnet 21 from coming off, and the lower sleeve 34 is used for balance adjustment by cutting the outer surface.

  The rotor 11 is integrated with resin. In the molding die, as shown in FIG. 3A, a cylindrical space S1 is formed between the rotor core 18 and the upper and lower sleeves 32 and 34 around the largest diameter intermediate portion 12a of the rotary shaft 12. Between the upper sleeve 32 and the rotor core 18, a disk-shaped space S2 that communicates with the cylindrical space S1 is formed. In addition, a disk-shaped space S3 communicating with the cylindrical space S1 is formed on the upper side of the upper sleeve 32 and the centrifugal fan 30. A gap S4 communicating with the space S2 is formed. Further, a disk-shaped space S5 communicating with the cylindrical space S1 is formed around the lower end portion 12b having the smallest diameter on the lower side of the lower sleeve 34.

  Among these, the disk-shaped space S3 formed at the uppermost part is not equal in diameter in the axial direction of the rotary shaft 12, but is formed in a cylindrical shape between the centrifugal fan 30 and the upper sleeve 32, A cylindrical central portion S3a that is continuous with the cylindrical space S1, and is thinner in the axial direction than the central portion S3a and has the same diameter as the inside of the short cylindrical portion 33 above the upper sleeve 32, and is continuous with the central portion S3a. The disc-shaped thin portion S3b, the upper surface from the central portion S3a at the same height and continuously in the circumferential direction radially, the lower surface continues to the thin portion S3b, and the radially outer end is the same position as the thin portion S3b. The four convex portions S3c, S3c,. The resin-molded gate is disposed at the outer end of one convex portion S3c.

  Resin 35 is filled in these spaces S1 to S5 in the molding die in the order of S3, S3 to S1, S1 to S2 and S5, S2 to S4 from the outer end of the convex portion S3c where the gate is disposed, The rotating shaft 12, the rotor core 18, the permanent magnet 21, and the upper and lower sleeves 32 and 34 are integrated. Even when the cylindrical space S1 is filled with the resin 35, the center hole 18a of the rotor core 18 is octagonal so that the rotating shaft 12 is integrated with the rotor core 18 without slipping. In particular, ring-shaped upper grooves 12c and lower grooves 12d, and spiral grooves 12e communicating with both grooves between the upper grooves 12c and the lower grooves 12d are recessed in the outer peripheral surface of the intermediate portion 12a where the resin 35 is molded. The integration between the resin 35 and the rotary shaft 12 is strengthened.

  And, as shown in FIG. 2 (A), the cylindrical portion 36 formed by the central portion S3a is formed between the centrifugal fan 30 and the upper sleeve 32 by the resin 35 formed by the disk-shaped space S3. A disc portion 37 that is continuous with the cylindrical portion 36 and is formed by the thin portion S3b, and a cylindrical portion 36 and the disc portion 37 that are continuous with the cylindrical portion 36 and the convex portion S3c are formed in the diameter direction of the rotor core 18 and are orthogonal to each other. A resin portion 35a composed of four ridges 38, 38,. Due to the resin portion 35a, a fan-shaped ventilation space A in a plan view is formed between the centrifugal fan 30 and the upper sleeve 32 and communicates with the radially outer side of the rotor core 18 and the centrifugal fan 30 between the ridges 38,. , A... Are formed.

  In FIGS. 2 and 3, reference numeral 39 denotes a recess formed in the lower surface of the resin portion 35b formed around the lower end 12b of the rotating shaft 12, and the rotation detection when the balance correction is performed by the lower sleeve 34 ( This is used for detecting a recess 39 by irradiating a laser. The lower end portion 12b of the rotating shaft 12 has a smaller diameter than the intermediate portion 12a, but the lower end side resin portion 35b where the recessed portion 39 is formed overlaps the rotor core 18 and the lower sleeve 34 in the vertical direction. Therefore, even if an upward tensile force is applied to the rotating shaft 12, the resin portion 35b on the lower end side prevents the removal.

On the other hand, in FIG. 1, the output unit 5 has a cylindrical tool holder 40 that extends in the front-rear direction and is rotatable, and a bevel gear 41 that is externally mounted on the rear end of the tool holder 40 is provided at the upper end of the intermediate shaft 26. The bevel gear 42 is meshed. A cylinder 43 is inserted and mounted in the tool holder 40, and a piston 44 provided in the cylinder 43 is connected to a crank pin 46 provided in an eccentric position at the upper end of the crankshaft 27 via a connecting rod 45. Yes.
A striker 48 is accommodated in the cylinder 43 in front of the piston 44 via an air chamber 47 so as to be movable back and forth, and an impact bolt 49 is accommodated in the tool holder 40 in front of the piston 44 so as to be movable back and forth. ing. Here, when a tip tool such as a drill bit is inserted from the tip of the tool holder 40, the rear end of the tip tool retracts the impact bolt 49 to a position where it abuts the receiving ring 50 in front of the cylinder 43, and the rear end is lowered. Project into the cylinder 43. Reference numeral 51 denotes an operation sleeve that is externally attached to the front end of the tool holder 40 and performs an attaching / detaching operation of the tip tool.

In the battery mounting portion 6, two terminal blocks 52, 52 capable of slidingly mounting the battery packs 8, 8 from the left and right directions are arranged in the front-rear direction, and the controller 7 is accommodated above them. The controller 7 includes a control circuit board on which a microcomputer and a switching element (not shown) are mounted, and is supported in the front-rear direction by inverted U-shaped ribs 53, 53 erected on the inner surface of the battery mounting portion 6. A light 54 for illuminating the front of the output unit 5 using LEDs is provided in front of the controller 7, and guard plates 55 covering the front and rear of the mounted battery packs 8, 8 are provided before and after the battery mounting unit 6. 55 is formed to project downward.
A switch 56 and a capacitor 57 that are electrically connected to the controller 7 are provided in the handle 9, and a switch lever 58 is provided on a plunger that protrudes forward from the switch 56.

  Therefore, in this hammer drill 1, when the switch lever 58 is pushed in with a hand holding the handle 9 and the switch 56 is turned on, the battery pack 8 supplies power to the brushless motor 3 and the rotating shaft 12 rotates. That is, the microcomputer of the controller 7 obtains the rotation detection signal indicating the position of the permanent magnet 21 of the rotor 11 output from the rotation detection element of the sensor circuit board 17 to acquire the rotation state of the rotor 11, and obtains the acquired rotation state. Accordingly, the ON / OFF of each switching element is controlled, and the rotor 11 is rotated by causing a current to flow sequentially to each coil 16 of the stator 10.

  When the rotary shaft 12 rotates in this way, the intermediate shaft 26 rotates at a reduced speed through the gear 28, and the tool holder 40 is rotated together with the tip tool through the bevel gears 42 and 41. At the same time, the crankshaft 27 is decelerated and rotated through the gear 29, the piston 44 reciprocates in the cylinder 43 through the connecting rod 45, and the striker 48 is moved back and forth through the air chamber 47. Therefore, the striker 48 strikes the tip tool via the impact bolt 49.

In addition, air inlets (not shown) are formed on the left and right side surfaces of the battery mounting portion 6 that are the left and right sides of the controller 7, and the air outlets that are not shown are formed on the left and right side surfaces of the motor housing 2 that are the left and right sides of the centrifugal fan 30. Is formed, and the controller 7 is disposed between the air inlet and the brushless motor 3. Therefore, the air sucked from the intake port by the rotation of the centrifugal fan 30 accompanying the rotation of the rotating shaft 12 first contacts the controller 7 to cool the controller 7, and then passes through the motor housing 2 to move the brushless motor 3. Cooling. Then, it passes through the central hole of the baffle plate 31 and is discharged from the outside of the centrifugal fan 30 through the exhaust port.
At this time, in the resin portion 35a formed between the centrifugal fan 30 and the rotor core 18, fan-shaped ventilation spaces A, A,... That connect the outer peripheral side of the rotor core 18 and the centrifugal fan 30 side are formed. Therefore, the air that has cooled the brushless motor 3 can flow from the radially outer side to the center side through each ventilation space A and pass through the center hole of the baffle plate 31. Therefore, the necessary air volume by the centrifugal fan 30 can be secured, and the cooling performance of the brushless motor 3 and the controller 7 can be maintained.

Thus, according to the hammer drill 1 of the said form, the ventilation space A which connects the radial direction outer side of the rotor core 18 and the centrifugal fan 30 side to the resin part 35a formed between the rotor core 18 and the centrifugal fan 30 is provided. By forming, even if the resin part 35a by integral molding exists between the rotor core 18 and the centrifugal fan 30, the air volume of the centrifugal fan 30 can be secured without increasing the overall length of the rotor 11.
In particular, here, the ventilation space A is formed between a plurality of convex portions (ridges 38) projecting at point-symmetrical positions around the rotation shaft 12 on the surface of the resin portion 35a on the centrifugal fan 30 side. Therefore, the ventilation space A can be easily obtained using the shape of the resin portion 35a.

Further, since the ridges 38 are formed in the diameter direction of the rotor core 18, the ridges 38 have a shape along the flow of air to the centrifugal fan 30, and a rectifying action is obtained.
Furthermore, since the ridges 38 are arranged in a cross shape when viewed from the axial direction of the rotary shaft 12, a straightening action can be obtained uniformly over the entire circumference of the resin portion 35a.
Since the resin portion 35b formed on the opposite side of the centrifugal fan 30 with the rotor core 18 in between is formed with a recess 39 for detecting the rotation angle, the rotation angle can be easily detected using the resin portion 35b. Can be done.

In addition, the number and shape of the ridges are not limited to the above form, and the number is increased, the width is increased, the phase is aligned with the blades of the centrifugal fan, the shape is the same as the fan blades, etc. These can be changed as appropriate.
In addition, the protrusions are not limited to protrusions, but may be a fan in plan view that forms a radial ventilation space between them, or a plurality of protrusions that are circular or rectangular in plan view are intermittently arranged in the radial direction. By doing so, there is no problem even if a ventilation space is formed.

In addition, the arrangement and direction of the brushless motor are not limited to the above-described form, and may be forward, oblique, and left-right directions, and may be other motors without being limited to the brushless motor. The number and arrangement of the permanent magnets can be changed as appropriate, and one or both of the upper and lower sleeves can be omitted as well as the shape. The fan is not limited to a centrifugal fan, and may be an axial fan.
Further, the power tool is not limited to the hammer drill, and it is possible to secure the air volume of the fan according to the present invention even if it is another type such as an impact driver or a marnoco.

  1 .... hammer drill, 2 .... motor housing, 3 .... brushless motor, 4 .... output housing, 5 .... output part, 6 .... battery mounting part, 7 .... controller, 8 .... battery pack, 10 .... Stator, 11 ... rotor, 12 ... rotating shaft, 13 ... stator core, 14 ... upper insulator, 15 ... lower insulator, 16 ... coil, 17 ... sensor circuit board, 18 ... rotor core, 19 ... Magnetic steel sheet, 20 ... through holes, 21 ... permanent magnets, 23, 24 ... bearings, 32 ... upper sleeve, 34 ... lower sleeve, 35 ... resin, 35a, 35b ... resin part, 36 ... Cylindrical part, 37 ... Disk part, 38 ... Projection, 39 ... Recess part, 40 ... Tool holder, S1 ... Cylindrical space, S2, S3, S5 ... Disc-like space, S4 ... Clearance , S3a Central portion, S3b · · thinned portion, S3c · · convex portion, A · · ventilation space.

Claims (5)

A stator,
A motor including a rotor rotatable with respect to the stator,
The rotor is a power tool having a rotating shaft, a rotor core, and a fan, and the rotating shaft and the rotor core are integrated with a resin filled from between the rotor core and the fan. ,
An electric tool characterized in that a ventilation space is formed in a resin portion formed between the rotor core and the fan to allow communication between the radially outer side of the rotor core and the fan side.
Power tool.   2. The ventilation space is formed between a plurality of convex portions projecting at a point-symmetrical position around the rotation axis on the fan side surface of the resin portion. The electric tool as described in.   The electric tool according to claim 2, wherein the convex portion is formed in a diameter direction of the rotor core.   The electric tool according to claim 3, wherein the convex portions are arranged in a cross shape when viewed from the axial direction of the rotating shaft.   5. The electric power tool according to claim 1, wherein a recess portion for detecting a rotation angle is formed in a resin portion formed on the opposite side of the fan across the rotor core.

Images