JP2007330065A - Dc brushless motor for power tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To raise durability of a sensor base plate without impairing its positioning accuracy. <P>SOLUTION: A DC brushless motor is constituted in such a manner that the sensor base plate 30 is indirectly positioned to a rotor 11 in a direction of a tool length, by fitting a projection/recess of a motor housing 25 to a recess/projection of an insulator 22 of a stator 20. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a DC brushless motor suitable as a drive source of an electric tool such as an impact driver.

FIG. 9 shows an impact driver 50 incorporating a DC brushless motor 51 as a drive source. This DC brushless motor 51 includes a rotor 52 in which a magnet (permanent magnet) is attached to a rotor core of a laminated steel plate structure, and a drive coil that is wound around each tooth portion of the stator core of the laminated steel plate structure. 52, a sensor 53 having a stator 53 positioned around the rotor 52, magnetic sensors (Hall elements) 54b to 54b for detecting magnetic pole positions of the rotor 52, and magnetic poles of the rotor 52 detected by the sensor board 54. , And an electric circuit board (not shown in FIG. 9) for rotating the rotor 52 by sequentially passing a current to each drive coil of the stator 53 based on this position. Therefore, the equipment can be made compact and maintenance-free.
The rotor 52 is supported by a main body housing 55 of an electric tool via bearings 56 and 57 so as to be rotatable about its axis. On the other hand, the stator 52 is held by a motor housing portion 58 provided in the main body housing 55. A circular sensor substrate 54 is attached to the front end surface (right end surface in FIG. 9) of the stator 53. A positioning projection 54 a is provided on a part of the sensor substrate 54 in the circumferential direction so as to project in the radial direction.
Conventionally, as shown in FIG. 10, for example, this positioning projection 54 a is inserted into a positioning groove 55 a provided in the motor housing 58, and the sensor housing 54 has a machine length direction (rotation) relative to the motor housing 58 and the main body housing 55. The positioning of the child 52 in the axial direction) was performed.
Thus, the rotor 52 is supported with respect to the main body housing 55, and the sensor substrate 54 is positioned in the machine length direction, whereby the relative position (clearance between the two) of the magnetic sensors 54b to 54b with respect to the rotor 52 is high. It was supposed to be held with accuracy.
JP-A-6-90553 JP-A-8-126287

However, the positioning structure of the sensor substrate 54 of the conventional DC brushless motor 51 has the following problems.
That is, conventionally, by inserting a positioning projection 54 a projecting radially from a part of the peripheral edge of the sensor board 54 into the positioning groove 55 a of the main body housing 55, the sensor board 54 is made longer than the main body housing 55. The sensor substrate 54 is positioned in the machine length direction with respect to the rotor 52. For this reason, bending stress or the like is concentrated and applied to the positioning projection 54a of the sensor substrate 54 due to vibration of the stator 53, and as a result, the positioning projection 54a of the sensor substrate 54 is mainly damaged and the sensor substrate 54 is damaged. The durability of 54 may be impaired.
An object of the present invention is to improve the durability of a sensor substrate without impairing the positioning accuracy in the machine length direction with respect to the main body housing and thus the rotor.

For this reason, this invention was set as the DC brushless motor of the structure described in each claim of a claim.
According to the DC brushless motor of the first aspect, the stator insulator is unevenly engaged with the motor housing portion and positioned in the machine length direction. As a result, the sensor substrate attached to the insulator is attached to the motor housing portion and thus the main body housing. On the other hand, it is positioned in the machine direction. As described above, the structure is such that the sensor substrate is indirectly positioned with respect to the main body housing by engaging the insulator with the concave and convex portions with respect to the motor housing portion and positioning in the machine length direction. Since the sensor substrate is not subjected to bending or other external force even if it vibrates, the durability of the sensor substrate can be increased. As a result, the sensor substrate can be thinned while maintaining the durability of the sensor substrate. it can.
According to the DC brushless motor of claim 2, since the insulator is positioned by engaging with the motor housing portion at the end on the sensor substrate side at both ends of the insulator, the laminated structure of the stator iron core is used. The sensor substrate can be positioned with respect to the main body housing with higher accuracy without being affected by the accumulated error in the machine length direction.

Next, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows an electric tool 1 using a DC brushless motor 10 according to the present embodiment as a drive source. In this example, as an example of the electric tool 1, a so-called impact type screw tightening machine (impact driver) is shown. In the following description, the front-rear direction of the electric power tool 1 will be described with the right side in FIG.
The present embodiment is characterized by the DC brushless motor 10 as a drive source. The overall configuration of the electric power tool 1 is the same as that conventionally known, but will be briefly described below.
The electric tool 1 includes a tool body 2 and a grip portion 3 provided in a state of protruding from a side portion of the tool body 2.
The tool body 2 includes a substantially cylindrical body housing 4. The main body housing 4 has a two-divided structure that is divided into right and left by a dividing surface in the machine direction. FIG. 1 shows a state in which the main body housing 4 is opened. The rear portion of the main body housing 4 is closed by the rear housing 5.
The grip portion 3 is a portion that is gripped when the user uses the electric tool 1, and a trigger type switch lever 3 a that is pulled by the user with a fingertip is provided at the base portion (upper portion in FIG. 1). ing. When the switch lever 3a is pulled, the main switch 3b accommodated in the grip portion 3 is turned on to activate the DC brushless motor 10 as a drive source. Although not shown in FIG. 1, a battery attachment portion for attaching a battery pack as a power source of the electric tool 1 is provided at the lower portion of the grip portion 3.

In the main body housing 4, a DC brushless motor 10, a reduction gear train 6, a drive shaft 7, a rotary striking mechanism 8, and an anvil 9 are accommodated coaxially in order from the rear side. The rotational output of the DC brushless motor 10 is transmitted to the drive shaft 7 via the reduction gear train 6 and then transmitted to the anvil 9 via the rotary impact mechanism 8. A planetary gear mechanism is used for the reduction gear train 6. A drive shaft 7 is provided on the carrier side of the reduction gear train 6.
The rotary hitting mechanism 8 has a function of converting the rotation of the drive shaft 7 into a rotary hitting operation with respect to the anvil 9, and a hammer 8 a that is supported coaxially and rotatably with respect to the drive shaft 7; A compression spring 8b that urges the hammer 8a toward the tip side and steel balls 8c and 8c that restrict axial movement and rotation of the hammer 8a are provided.
The anvil 9 has a function of an output shaft of the electric tool 1 and is supported coaxially at the tip of the drive shaft 7 so as to be relatively rotatable. The anvil 9 is supported through a cylindrical bearing 4a attached to the tip of the main body housing 4 so as to be rotatable about its axis and not to be displaced in the axial direction. A tip tool such as a driver bit or a socket bit is attached to the tip of the anvil 9. In FIG. 1, the illustration of the tip tool is omitted.
At the stage where the screw tightening resistance is small after the start of screw tightening, the anvil 9 rotates in the screw tightening direction integrally with the drive shaft 7 via the rotary impact mechanism 8. When the screw tightening progresses and the screw tightening resistance is greater than the rotational force transmitted to the drive shaft 7, the hammer 8a moves back in the axial direction against the compression spring 8b, whereby the rotational power of the hammer 8a and the anvil 9 is increased. When the transmission of (screw tightening resistance) is interrupted, the hammer 8a rotates while moving forward by the compression spring 8b and strikes the anvil 9 in the screw tightening direction. When the anvil 9 is struck in the screw tightening direction, the screw is tightened further.

A DC brushless motor 10 as a drive source is a motor having a four-pole structure, and is a rotor (rotor) 11 having a magnet (permanent magnet) and a rotor 11 fixed to the inner side of the main body housing 4 and on the inner peripheral side thereof. And a sensor substrate 30 having Hall elements 31 to 31 for detecting the positions of the magnetic poles of the rotor 11, and an electric control substrate having a drive circuit. The electric control board is disposed on the front end side of the grip portion 3, and the illustration thereof is omitted.
The rotor 11 includes a rotor core 12 in which a large number of circular thin steel plates are stacked. Around the rotor core 12, four-pole ring magnets 13 to 13 are fixed. A rotating shaft 14 is fixed to the center of the rotor core 12.
The rotating shaft 14 protrudes from both sides of the rotor core 12. As shown in FIG. 1, the front side (reduction gear train 6 side) of the rotary shaft 14 is rotatable and axially (machine length) via a front bearing 15 and the rear side via a rear bearing 16 held in the rear housing 5. (Direction) is supported in a state of not moving. The front bearing 15 is held by an intermediate partition wall 4b that partitions the body housing 4 forward and backward. The inside of the main body housing 4 is partitioned into a DC brushless motor 10 side (rear side) and a rotary impact mechanism 8 side (front side) by the intermediate partition wall 4b.
A cooling fan 17 is attached to the rear side of the rotating shaft 14 and between the rotor core 12 and the rear bearing 16. The cooling fan 17 rotates integrally with the rotor 11.

The stator 20 has a substantially cylindrical shape, and a stator core 21 having a laminated steel plate structure in which a large number of thin steel plates are laminated, and an electrically insulating member 22 called an insulator that electrically insulates the stator core. It has. FIG. 4 shows the fixed iron core 21 alone, and FIG. 5 shows the stator 20 covered with the electrical insulating member 22. Six tooth portions 21 a to 21 a are provided on the inner peripheral side of the stator core 21. A range excluding the outer peripheral surface of the stator core 21 and the front end surface of each tooth portion 21 a is covered with an electrical insulating member 22. A drive coil 23 is wound around a portion of each tooth portion 21 a covered with the electrical insulating member 22. The distal end surface of each tooth portion 21 a that is not covered by the electrical insulating member 22 is located in a state where a certain gap is provided between the distal end surface and the peripheral surface of the rotor 11.
As shown in FIG. 1, the stator 20 is held on the inner peripheral side of a motor housing portion 25 that is integrally provided inside the main body housing 4. The motor housing portion 25 also has a bifurcated structure that is divided into left and right, like the main body housing 4. The motor housing portion 25 includes a side wall portion 25a, a rear wall portion 25b, and an engaging protrusion 25c.
The side wall portion 25 a is provided along the entire circumference of the stator 20. The side wall portion 25a positions the stator 20 in a state in which displacement in the radial direction is restricted.
A rear wall 25b is provided behind the side wall 25a so as to protrude toward the inner periphery. The rotating shaft 14 and the cooling fan 17 of the rotor 12 are located on the inner peripheral side of the rear wall portion 25b. The stator 20 is held in a state in which the rear surface (the rear surface of the electrical insulating member 22) is in contact with the rear wall portion 25b, so that the stator 20 is positioned in a state in which rearward displacement is restricted. Yes.
The engaging protrusion 25c is provided in a state of projecting to the inner peripheral side in front of the side wall 25a. The engagement protrusion 25 c is provided along the entire circumference of the stator 20. The function of this engagement protrusion 25c will be described later.

A sensor substrate 30 is attached to the front surface of the electrical insulating member 22. On the front side of the electrical insulating member 22, a substantially circular step portion 22a is provided over the entire circumference. The sensor substrate 30 is mounted in the stepped portion 22a. FIG. 6 shows the sensor substrate 30 alone. The sensor substrate 30 has a substantially disk shape, and a relief hole 30a for positioning the front bearing 15 is provided at the center thereof.
As shown in FIG. 6, a terminal connection plate 30 b for wiring connection is provided at a lower part of the sensor substrate 30 so as to protrude in the radial direction. As shown in FIG. 7, the terminal connection plate portion 30b is projected to the outer peripheral side of the electrical insulating member 22 (downward in FIGS. 2 and 7) through the cutout portion 22b in which a part of the stepped portion 22a is cut out. ing.
The three magnetic sensors 31 to 31 attached to the sensor substrate 30 are sensors for detecting which position of the magnetic pole of the rotor 11 is opposed to which tooth portion 21a of the stator 20, and this example In, Hall elements are used. As shown in FIG. 7, the sensor substrate 30 is screwed into the stepped portion 22a of the electrical insulating member 22 with three screws 32 to 32, so that the three magnetic sensors 31 to 31 are adjacent to each other in the circumferential direction. It arrange | positions in the state which mutually matched the phase with respect to the three tooth parts 21a-21a which fit. While detecting the position of the magnetic pole of the rotor 11 by the three magnetic sensors 31 to 31, the rotor 11 is rotated by causing current to flow sequentially from the electric control board to the drive coils 23 to 23. The basic configuration of the DC brushless motor 10 is a conventionally known technique, and no particular change is required in the present embodiment.

As shown in FIG. 5, the three screw holes 22 c to 22 c into which the three screws 32 to 32 are tightened are the three-way positions in the circumferential direction of the stepped portion 22 a of the electrical insulating member 22, and the stator core It arrange | positions between 21 adjacent tooth parts 21a and 21a. Since each screw hole 22a is positioned between the adjacent tooth portions 21a, 21a, the cylindrical boss portion having the screw hole 22a does not get in the way and the winding of a sufficient length over the entire length of the tooth portion 21a. A wire can be applied, thereby providing a compact and efficient drive coil 23.
An engaging groove portion 22d is formed on the entire periphery of the front-side peripheral edge of the electrical insulating member 22. The engagement protrusion 25c is inserted (engaged with unevenness) over the entire circumference in the engagement groove 22d. Thereby, the position of the stator 20 with respect to the motor housing portion 25 in the machine length direction (front-rear direction, left-right direction in FIG. 1) is positioned. The width of the engaging protrusion 25c is set to a width that allows the engaging protrusion 25c to be inserted without rattling. For this reason, by inserting the engaging protrusion 25c into the engaging groove 22d, the stator 20 is positioned without rattling in the machine direction.
As a result of the stator 20 being positioned with high accuracy in the machine length direction relative to the motor housing portion 25, the position in the machine length direction of the sensor substrate 30 attached to the front surface of the stator 20 with respect to the motor housing portion 25 is accurately positioned. . As a result of the position of the sensor board 30 in the machine length direction being positioned with high accuracy, the position of the magnetic sensors 31 to 31 in the machine length direction with respect to the rotor 11 is positioned with high accuracy.

Next, in the DC brushless motor 10 according to the present embodiment, the sensor substrate 30 can be accurately attached to the front surface (stepped portion 22a) of the stator 20 in the rotation direction (rotation direction of the rotor 11). It has become.
As shown in FIG. 4, a positioning groove 21 b is formed on the circumferential surface of the stator core 21 along the axial direction over the entire length thereof. As shown in the figure, the positioning groove 21b is provided on the outer side (outer peripheral side) of one tooth portion 21a and hardly affects the magnetic field with respect to the circumferential position of the stator core 21.
Corresponding to the positioning groove 21b, escape grooves 22e and 22e are formed on the front and rear surfaces of the electrical insulating member 22. As shown in FIG. 5, the width dimension and the depth dimension of both escape groove portions 22e, 22e are set larger than the positioning groove portion 21b.
As shown in FIG. 6, a positioning groove 30 c is provided on the upper portion of the sensor substrate 30. The width dimension and the depth dimension of the positioning groove portion 30c exactly coincide with the positioning groove portion 21b of the stator core 21.
When the sensor substrate 30 is assembled to the front surface of the stator core 21 (the stepped portion 22a of the electrical insulating member 22), an assembly jig 35 is used. As shown in FIGS. 7 and 8, the assembling jig 35 includes a substrate portion 35a curved in an arc shape along the outer peripheral surface of the stator core 21, and a positioning protrusion integrally formed on the curved inner side of the substrate portion 35a. A portion 35b is provided. The board portion 35a is in close contact with the outer peripheral surface of the stator core 21 without a gap. Further, as shown in FIG. 8, the board portion 35 a has a length in the machine length direction that is longer than the stator 20.

The positioning protrusion 35b is provided over the entire length from the front end to the rear end of the substrate portion 35a. The width of the positioning protrusion 35b is set to a width that allows the positioning protrusion 35b to be inserted into the positioning groove 21b of the stator 20 and the positioning groove 30c of the sensor substrate 30 without rattling. The positioning protrusion 35b is provided in a state of being accurately parallel to the center axis of the stator 20 (the axis of the rotor shaft 14) in a state where the substrate portion 35a is in close contact with the outer peripheral surface of the stator core 21. ing.
In order to assemble the sensor substrate 30 to the front surface of the stator 20 (within the step portion 22a of the electrical insulating member 22) using the positioning jig 35, the sensor substrate 30 is attached to the step portion 22a as shown in FIGS. Next, the positioning projection 35b is inserted across the positioning groove 21b of the stator core 21 and the positioning groove 30c of the sensor substrate 30, and the substrate 35a is brought into close contact with the outer peripheral surface of the stator core 21. In this state, the positioning jig 35 is mounted.
In this way, the positioning jig 35 is set, and while holding this state, the three screws 32 to 32 are tightened in the screw holes 22c, respectively, so that the sensor substrate 30 is firmly held in the stepped portion 22a of the stator 20. Secure to. Thereby, the sensor substrate 30 is fixed in a state in which the sensor substrate 30 is accurately positioned with respect to the stator 20 in the circumferential direction (rotation direction of the rotor 11), and as a result, each magnetic sensor 31 is fixed to the stator core 21. Positioning with respect to each drive coil 23 in the rotational direction can be performed with high accuracy.

According to the DC brushless motor 10 configured as described above, with respect to the positioning of the stator 20 with respect to the motor housing portion 25 in the machine length direction, the engaging protrusion 25c provided on the motor housing portion 25 is replaced with the engaging groove portion 22d of the stator 20. The stator 20 is positioned in the motor housing portion 25 by being inserted into the motor housing portion 25. On the other hand, the terminal connection portion 30b, which is a part of the periphery of the sensor substrate 30 attached to the front surface of the stator 20, is not engaged with the motor housing portion 25 as in the prior art and protrudes in a free state. .
From this, when the stator 20 vibrates or the like, the external force generated by this is received by the engaging projection 25c on the motor housing portion 25 side, and the bending force is applied to the terminal connection portion 30b of the sensor substrate 30 as in the conventional case. Is not added, damage to the sensor substrate 30 can be avoided and its durability can be improved.

In the case of this embodiment, the engaging groove 22 d on the stator 22 side is provided on the front side of the electrical insulating member 22 and on the side very close to the sensor substrate 30. For this reason, the sensor substrate 30 can be accurately positioned in the machine length direction with respect to the motor housing portion 25 and the rotor 11 without being affected by the accumulated error due to the thickness of the laminated steel plates constituting the stator core 21. it can.
In this regard, for example, a similar engagement groove portion is provided in a portion of the electrical insulating member that covers the rear side of the stator core, and the motor housing portion 25 is provided in the vicinity of the rear wall portion 25b corresponding to the engagement groove portion. In the case where the protrusions are provided so as to engage with each other in a concave-convex manner, the addition of an external force to the sensor substrate can be eliminated to increase the durability, but the engagement groove portion of the stator and the sensor substrate can be improved. Since the stator core is located between them, errors in the plate thickness of each steel plate constituting the stator core may be accumulated, resulting in variations in the position of the sensor board in the machine length direction.
However, according to the illustrated configuration, the engagement groove portion 22d that engages with the motor housing portion 25 is provided close to the sensor substrate 30 (on the front side of the electrical insulating member 22). Regardless of the accumulated error of 21, the position of the sensor substrate 30 in the machine length direction with respect to the rotor 11 can be accurately positioned, thereby improving the detection accuracy of each magnetic sensor 31 and improving the control characteristics of the rotor 11. be able to.

The embodiment described above can be implemented with various modifications. For example, with respect to positioning of the stator 20 with respect to the motor housing portion 25 in the machine length direction, an engagement protrusion 25 c is provided on the motor housing portion 25, and the engagement protrusion 25 c is provided on the electrical insulating member 22 of the stator 20. Although the configuration in which the groove 22d is inserted into the groove 22d is illustrated as an example, the engagement groove 25d is provided at the front end of the motor housing 25 over the entire circumference as shown in FIG. It is good also as a structure which provides the engagement protrusion 22f over the perimeter on the electrical insulation member 22 side. By inserting the engaging protrusion 22f on the stator 20 side into the engaging groove 25d on the motor housing 25 side, the stator 20 can be positioned in the machine length direction with respect to the motor housing 25. Even with this configuration, the external force generated by the vibration of the stator 20 or the like is received by the motor housing portion 25 through the engaging protrusion 22f of the electrical insulating member 22 and is not added to the sensor substrate 30. Durability can be increased.
Further, the configuration in which the stator 20 is engaged with the motor housing portion 25 over the entire circumference is illustrated, but the engagement protrusion 25c (22f) and / or the engagement groove portion 22d (25d) or both of them are partly in the circumferential direction It is good also as a structure which provides about and sets the uneven | corrugated engagement part for positioning in a machine length direction to a part of circumferential direction.
Furthermore, although an impact-type screw tightening machine has been illustrated as an example of the electric tool, the present invention can be widely applied to other electric tools incorporating a DC brushless motor as a drive source.

It is a longitudinal cross-sectional view of the impact type screwing machine which uses the DC brushless motor which concerns on embodiment of this invention as a drive source. It is the (2) part enlarged view of FIG. This figure is a longitudinal sectional view showing a positioning structure of the stator with respect to the motor housing portion. It is a longitudinal cross-sectional view which shows the positioning structure of another form with respect to the motor housing part of a stator. FIG. 2 is a front view of a stator core alone (a diagram viewed from the right side in FIG. 1, the same applies hereinafter). It is a front view of a stator simple substance. It is a front view of a sensor substrate alone. It is a front view of a stator in a state where a sensor substrate is positioned on the front surface using a positioning jig. It is a longitudinal cross-sectional view of the stator in a state where the sensor substrate is positioned on the front surface using the positioning jig. It is a longitudinal cross-sectional view of the impact type screwing machine provided with the conventional positioning structure of the sensor substrate. It is the (10) part enlarged view of FIG. This figure is a longitudinal sectional view showing a positioning structure of the sensor substrate with respect to the motor housing.

Explanation of symbols

1 ... Electric tool (impact screw tightening machine)
2 ... Tool body 4 ... Main body housing 8 ... Rotary impact mechanism 10 ... DC brushless motor 11 ... Rotor (rotor)
12 ... Rotor core 13 ... Magnet 14 ... Rotating shaft 17 ... Cooling fan 20 ... Stator 21 ... Stator core (Steta core)
22 ... Electric insulation member (insulator)
22d ... engagement groove, 22f ... positioning projection 23 ... drive coil 25 ... motor housing 25a ... side wall, 25c ... engagement projection, 25d ... engagement groove 30 ... sensor substrate 30a ... relief hole, 30b ... terminal connection Part 31 ... Magnetic sensor (Hall element)
35 ... Positioning jig 54a ... Positioning projection 55a of sensor substrate 54 ... Positioning groove

Claims (2)

A DC brushless motor built in the body housing of the electric tool,
A DC brushless motor having a structure in which an insulator of a stator is unevenly engaged with a motor housing portion provided in the main body housing, and a sensor substrate attached to the stator is positioned in the longitudinal direction with respect to the rotor. 2. The DC brushless motor according to claim 1, wherein both front and rear end faces in the machine length direction of the stator core are covered with an insulator, and the concave and convex engaging portion is attached to the sensor substrate among both end portions of the insulator. DC brushless motor set on the side.

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