JP4974054B2 - Electric tool - Google Patents

Description

  The present invention relates to an electric tool using a brushless motor.

  Generally, in a power tool, a brushless motor that does not require electrical connection using a brush and a commutator to a rotor attached to a rotating shaft may be used as a means for realizing miniaturization of the power tool. However, when a brushless motor is driven, a relatively large power loss is generated as heat, which affects the operation of the motor and causes a reduction in efficiency and failure. Specifically, there are copper loss caused by current flowing through the stator coil and iron loss caused in the stator core material due to the change in magnetic flux density, and the loss of these stator portions becomes the main heat source. For this reason, cooling structures for various stators have been proposed in conventional brushless motors. For example, as a conventional stator cooling structure, as disclosed in Patent Document 1 below, an opening for sucking outside air into the motor housing, and an opening for discharging cooling air inside the housing to the outside of the housing, Are provided in the housing so as to be spaced apart from each other in the direction of the rotation axis across the stator, and air is introduced into the housing by a fan integrally attached to the rotor, and in particular, by flowing cooling air between the stator coils A structure for directly cooling the stator coil portion has been proposed.

Further, in the brushless motor, the output transistor that constitutes the switching element of the inverter circuit board (motor drive circuit board) supplies a large current drive signal to the stator coil, so the amount of heat generation increases and cooling measures are required. . As a cooling structure for an inverter circuit board, a structure in which an inverter circuit board is arranged together with a stator portion of a motor on a cooling gas flow path in a motor housing has been proposed as disclosed in Patent Document 2 below. .
JP 2004-274800 A JP 2005-102370 A

  However, in the above structure, air can be taken in from the outside to cool the stator and inverter circuit board of the brushless motor, while air is blown into the stator, so that dust in the air is clogged between the rotor and the stator. There is a problem. Therefore, a structure in which the stator and the rotor are hermetically sealed by wall surfaces surrounding the outer core portion of the stator from both sides in the axial direction, in particular, a structure using a circuit board as the wall surface is conceivable. In such a structure, the coil wound around the stator and the circuit board are connected by soldering, but if the stator and the circuit board vibrate when using the electric tool, stress is generated in the coil and the soldering part. There is a problem that the coil is disconnected or the soldered part is detached.

  In view of such circumstances, the present invention suppresses an increase in the number of parts and an increase in cost, and has a compact configuration, efficiently cools the stator and the circuit board, and improves the vibration resistance of the brushless motor and the dustproof function. It is intended to provide an electric tool that can realize the above.

  The present invention relates to an electric tool using a brushless motor.

In order to achieve the above object, an invention according to claim 1 is a power tool, a housing in which an air inflow hole and an air exhaust hole are formed, a brushless motor held in the housing, and the brushless A circuit board having a plurality of switching elements for driving and controlling the motor, and a fan accommodated in the housing and disposed in the vicinity of the air discharge hole. And a plurality of teeth projecting radially inward from the inner peripheral surface side of the cylindrical body portion and extending in the axial direction of the cylindrical body portion, and the inner surface of the housing on the outer peripheral surface side of the cylindrical body portion a stator supported by the, a coil wound along each of said teeth has an axis of rotation, is rotatably disposed in the stator substantially concentrically positioned on the inner peripheral surface side of the stator Rotor and axial direction of the stator An annular portion located at an end of the coil and a stator covering portion that covers the teeth to insulate the teeth and the coil, and the coil is wound around the teeth covered by the stator covering portion. And the circuit board extends in a direction substantially orthogonal to the rotation axis and is on the opposite side of the fan to the brushless motor. The coil is electrically connected, and is screwed to the insulating member located on the air inflow hole side .

According to the electric tool of the first aspect, since the circuit board is located on the air inflow hole side, compared with the case where the circuit board is arranged on the air exhaust hole side, the fresh air taken in from the air inflow hole is used. The circuit board can be efficiently cooled. Moreover, since the insulating member for insulating the teeth and the coil is also used as a member for fixing the circuit board, an increase in the number of components can be suppressed. Further, since the circuit board is fixed to the insulating member and the insulating member is held by winding the coil around the teeth, the circuit board, the teeth, the coil, and the insulating member vibrate together when the brushless motor is driven. In addition, the tensile stress generated in the coil can be kept small, and the coil can be prevented from breaking. In addition, since the circuit board is screwed to the insulating member, the circuit board is securely fixed to the insulating member as compared with the case where the circuit board is fixed using a claw or an adhesive.

The invention according to claim 2 is characterized in that, in addition to the feature according to claim 1, the circuit board is screwed so as to face the end face of the insulating member located on the air inflow hole side. And

According to the electric tool of the second aspect, in addition to the effect of the electric tool of the first aspect, the brushless motor can be cooled and the circuit board can be efficiently cooled.

According to a third aspect of the invention, in addition to the feature of the first or second aspect, the plurality of switching elements are provided on a surface of the circuit board opposite to the insulating member. Features.

According to the power tool of claim 3, in addition to the effect of the power tool of claim 1 or 2, the plurality of switching elements are arranged on the side opposite to the insulating member of the circuit board (on the air inflow hole side). Therefore, compared with the case where the circuit board is arranged on the air discharge hole side, the switching element and the circuit board can be efficiently cooled by the fresh air taken in from the air inflow hole.

  According to a fourth aspect of the invention, in addition to the features of the first to third aspects, a detection element for detecting the position of the rotor is provided on the surface of the circuit board on the insulating member side. It is characterized by.

  According to the power tool of claim 4, in addition to the effect of the power tool of claims 1 to 3, the surface on the insulating member side of the circuit board has a detection element for detecting the position of the rotor. Therefore, there is no need to separately prepare a member for fixing the detection element, the increase in the number of parts can be suppressed, and the housing space for the parts in the housing can be reduced. Further, since the circuit board and the insulating member are fixed to each other and positioned with respect to each other, the positional accuracy of the detection element is improved.

According to a fifth aspect of the invention, in addition to the features of the first to fourth aspects, the air inflow hole is formed at a position facing the plurality of switching elements .

According to the power tool described in claim 5, in addition to the effects of the power tool described in claims 1 to 4 , the switching element and the circuit board are made efficient by the fresh air taken in from the air inflow hole. Can be cooled to.

According to the electric tool according to claims 1 to 5 of the present invention, the increase in the number of parts and the cost increase are suppressed, and the structure is compact, and the stator and the circuit board are efficiently cooled. It is possible to achieve an excellent effect of improving the property.

  Hereinafter, a power tool according to an embodiment of the present invention will be described with reference to FIGS. 1 to 9.

  FIG. 1 shows an impact driver 1 as an example of an electric power tool according to an embodiment of the present invention. First, a schematic configuration of the impact driver 1 will be described with reference to FIG.

  The impact driver 1 includes a housing 2 constituting an outer shell. The housing 2 includes a motor housing portion 21, a power transmission housing portion 22 formed continuously with the motor housing portion 21, the motor housing portion 21 and the power transmission. The handle housing portion 23 hangs down from the housing portion 22.

  The motor housing portion 21 has a cylindrical shape, and houses a motor 30 serving as a drive source, a circuit board 40 that controls the motor 30, and a fan 50. An air inflow hole 21a for injecting air from the outside of the housing 2 is formed at the rear of the motor housing portion 21, and an air exhaust hole 21b for discharging air to the outside is formed at the front of the motor housing portion 21. Has been. An air passage 21c is defined between the outer side of the motor 30 and the inner surface 21A of the motor housing 21, and the air passage 21c communicates between the air inflow hole 21a and the air discharge hole 21b.

  The power transmission housing part 22 accommodates the power transmission mechanism part 60. The power transmission mechanism section 60 includes a speed reduction mechanism section composed of a planetary gear 61 and a ring gear 62, and a spindle 63 and a hammer 65 that is disposed on the spindle 63 so as to be slidable back and forth and is given a striking force by a spring 64. This is a well-known configuration including an impact mechanism portion and an anvil 66 that can receive a rotary tool by a hammer 65 and can hold a tip tool (not shown). The power transmission mechanism transmits the rotational force of the motor 30 to the anvil 66 as a rotational striking force. The hammer 65 is provided with a protruding portion (not shown). Further, the anvil 66 is provided with a recess (not shown) corresponding to the protrusion of the hammer 65. When the motor 30 is driven, the rotational force transmitted from the rotating shaft 35 of the motor 30 is decelerated by the planetary gear 61 and the ring gear 62, and the rotational force is transmitted to the spindle 63 to start the screw tightening operation. When a load exceeding a predetermined level is not applied to the anvil 66, the hammer 65 and the anvil 66 rotate together to obtain a rotational force by fitting the convex portion of the hammer 65 and the concave portion of the anvil 66. On the other hand, when the anvil 66 is loaded with a predetermined load or more, the anvil 66 is locked and does not rotate, the convex portion of the hammer 65 and the concave portion of the anvil 66 are disengaged, and the hammer 65 moves forward and hits by the action of the spring 64. You will gain power.

  A lower end portion of the handle housing portion 23 is configured to be detachable from a battery pack case 71 that accommodates a battery pack 70 made of a lithium ion secondary battery, a nickel-cadmium secondary battery, or the like (not shown). The handle housing portion 23 is provided with a trigger switch 24, and houses a part of wiring for supplying electric power from the battery pack 70 to the motor 30 and a motor driving circuit. When the battery pack case 71 is attached to the handle housing portion 23, the battery pack 70 and the motor drive circuit device are electrically connected via the trigger switch 24. The housing 2 will be described below with the anvil 66 side as the front, the air inflow hole side 21a as the rear, the motor housing portion 21 and the power transmission housing portion 22 as the upper side, and the battery pack case 71 side as the lower side.

  According to the impact driver 1 configured as described above, when the operator pulls the trigger switch 24 while holding the handle housing portion 23, the trigger switch 24 is turned on, and the driving force from the motor 30 is transmitted. The screw 63 can be tightened by applying a rotational striking force to the tip tool mounted on the anvil 66.

  Next, the configuration around the motor 30 according to the present embodiment will be described with reference to FIGS. The motor 30 is a brushless motor including a stator 31 having a cylindrical outer shape, a coil 32, and a rotor 33 disposed in the inner peripheral portion of the stator 31.

  The stator 31 includes a cylindrical body portion 31A and a plurality of teeth 34 that project radially inward from the inner peripheral surface side of the cylindrical body portion 31A and extend in the axial direction of the cylindrical body portion 31A. Insulating members 81 and 82 that are electrically insulated are attached to the tooth 34 from both ends in the rotational axis direction. A part of the outer peripheral surface 31B of the stator 31 is supported by the motor housing portion 21, and an air passage 21c is defined between the remaining portion of the outer peripheral surface 31B and the inner peripheral surface of the motor housing 21.

  The insulating member 81 is attached to the rear end of the stator 31, and the insulating member 82 is attached to the front end of the stator 31. As shown in FIG. 8, the insulating member 81 has a stator covering portion 81A that covers the teeth 34 to insulate the teeth 34 and the coil 32, and an annular portion 81B in which a female screw hole 81a is formed. . Similarly to the insulating member 81, the insulating member 82 includes a stator covering portion 82 </ b> A that covers the teeth 34 and insulates the teeth 34 and the coil 32. As shown in FIGS. 3, 6, and 7, the insulating member 81 and the insulating member 82 are held by the stator 31 by winding the coil 32 around the teeth 34 covered with the stator covering portions 81 </ b> A and 82 </ b> A. The coil 32 includes an axial winding portion 32A wound along the axial surface of the tooth 34 and a shaft end surface winding portion 32B wound along the axial end surface of the tooth 34. The insulating members 81 and 82 are held by the teeth 34. The coil 32 is wound around a plurality of teeth 34 in sequence to form a star-connected three-phase coil.

  As shown in FIG. 6, among the terminals of the coil 32, the coil 32 that is wound around the teeth 34 is wound on the start end side by overlapping the coil 32 that is subsequently wound. It is pulled out from the inside of the winding part. The portion on the start end side is bent in a substantially crank shape.

  The rotor 33 includes a rotating shaft 35 rotatably supported at both ends by bearings supported by the motor housing portion 21, and a main body portion 36 that is press-fitted coaxially to the rotating shaft 35 and rotates integrally with the rotating shaft 35. Four permanent magnet members 37 are embedded in the main body portion 36 in the rotation axis direction. A fan 50 is fixed to the front side of the rotating shaft 35 and in the vicinity of the air discharge hole 21 b of the motor housing portion 21. When the motor 30 is driven, the fan 50 rotates integrally with the rotary shaft 35, sucks external air from the air inflow hole 21a, and discharges it to the outside through the air passage 21c and the air discharge hole 21b.

  Next, the motor drive circuit will be described. The motor drive circuit includes a circuit board 40, is electrically connected to the coil 32, and has a function of driving the rotor 33 to rotate. It comprises an inverter circuit comprising a known bridge circuit for energizing a drive current to the coil 32 of the motor 30, a control circuit comprising a CPU for controlling the inverter circuit, and the like. The circuit board 40 is formed with an inverter circuit provided with a switching element, and control circuits other than the inverter circuit are appropriately arranged on several boards (not shown).

  The circuit board 40 is fixed to the insulating member 81 so as to cover the entire annular opening defined by the end surface of the annular portion 81B of the insulating member 81 located on the air inflow hole 21a side. Specifically, four through holes are formed at positions corresponding to the above-described female screw holes 81 a of the insulating member 81, and the front surface 40 A of the circuit board 40 is fixed with the male screws 90 so as to be in close contact with the insulating member 81. Has been. Specifically, the circuit board 40 is fixed to the insulating member 81 by screwing the male screw 90 into the female screw hole 81a of the annular portion 81B of the insulating member 81. The front surface 40 </ b> A on the insulating member 81 side of the circuit board 40 includes a hall element 41 for detecting the rotational position of the rotor 33. The rear surface 40B, which is the surface on the anti-insulating member 81 side of the circuit board 40, includes six FETs 42, which are the above-described switching elements for turning on and off the current flowing through the coil 32, and a wiring pattern provided on the circuit board 40. And is electrically connected to the coil 32. Further, the coil 32 terminal for the neutral point of each of the three-phase coils 32 of the stator 31 is electrically connected via the wiring pattern of the drive control circuit board so that the coil 32 is star-connected. It is made. An adhesive for preventing disconnection due to vibration during use of the tool is applied to the foot of the FET 42 and the base of the power supply line 43 wired from the circuit board 40.

  The terminal of the coil 32 is electrically connected to the circuit board 40 by being soldered in a wiring hole 40 a formed in the circuit board 40. The circuit board 40 has six wiring holes 40a. A crank-shaped bent portion, which is a terminal on the start end side of the winding of the drawn coil 32, is connected to the circuit board 40.

  According to such a configuration, the portion of the winding end of the coil 32 that is connected to the circuit board 40 has a bent shape that does not interfere with the winding portion of the coil 32 that follows the starting end portion. Therefore, even if the circuit board 40 and the coil 32 vibrate, the vibration is absorbed by the bent shape, the tensile stress generated in the coil 32 can be kept small, and the coil 32 can be prevented from being broken. On the other hand, as shown in FIG. 7, the winding end portion of the coil 32 is a portion following the winding portion and is not restrained, so that even if the motor 30 and the circuit board 40 vibrate, tensile stress is not generated. There is no problem.

  In the above configuration, when the motor 30 is driven, the fan 50 fixed to the rotating shaft 35 rotates, air is taken into the motor housing 21 from the air inflow hole 21a, and the taken-in air cools the circuit board 40. The motor 30 is cooled from the outside through an air passage 21c defined between the outside of the motor 30 and the inner surface of the motor housing 21, and is exhausted to the outside through the air discharge hole 21b. When fresh air is passed through the air passage 21c between the motor housing portion 21 and the motor 30, the motor 30 can be cooled from the outer surface side.

  Further, since the FET 42 is provided on the rear surface 40B of the circuit board 40 and the circuit board 40 is arranged on the air inflow hole 21a side, the circuit board 40 is taken in from the air inflow hole 21a as compared with the case where the circuit board 40 is arranged on the air exhaust hole 21b side. The fresh air can efficiently cool the FET 42 and the circuit board 40.

  Further, since the FET 42 is provided on the rear surface 40B of the circuit board 40, the electrical connection is facilitated as compared with the case where the FET 42 is not disposed on the circuit board 40. In addition, since it is not necessary to separately prepare a member for fixing the FET 42, the number of parts can be reduced, and the space for housing the parts in the housing 2 can be reduced.

  Further, since the circuit board 40 is held by the insulating member 81 so as to cover the entire annular opening defined by the end surface of the annular portion located on the air inflow hole side 21a of the annular portion 81B of the insulating member 81, Air taken in from the air inflow hole 21 a does not enter the motor 30. Therefore, even if the impact driver 1 is used in the air in which wood powder or metal powder is mixed, dust in the air does not enter the motor 30 and dust is clogged between the stator 31 and the rotor 33. Does not cause the locking phenomenon.

  Furthermore, since the Hall element 41 for detecting the position of the rotor 33 is provided on the front surface 40A of the circuit board 40, there is no need to separately prepare a member for fixing the Hall element 41, and the number of components can be reduced. The space for housing components in the housing 2 can be reduced. Further, since the circuit board 40 and the insulating member 81 are fixed to each other and positioned with respect to each other, the positional accuracy of the Hall element 41 is improved.

  Moreover, since the insulating member 81 for insulating the teeth 34 and the coil 32 is also used as a member for fixing the circuit board 40, the above-described effects can be obtained without increasing the number of components.

  In addition, since the circuit board 40 is fixed to the insulating member 81 with the male screw 90, the insulating member 81 that insulates the circuit board 40, the teeth 34, and the coil 32 is vibrated integrally when the impact driver 1 is used. As a result, the circuit board 40 and the coil 32 vibrate together, the tensile stress generated in the coil 32 can be suppressed, and the coil 32 can be prevented from being broken. In addition, the circuit board 40 can be reliably fixed to the insulating member 81 as compared with the case where the circuit board 40 is fixed using a claw or an adhesive.

  The electric power tool of the present invention is not limited to the above-described embodiment, and various changes can be made without departing from the scope of the present invention.

  The power tool of the present invention can be suitably used for a tool with impact such as an impact driver.

1 is an overall cross-sectional view of a power tool according to an embodiment of the present invention. It is a principal part enlarged view of FIG. It is sectional drawing along the III-III line in FIG. It is sectional drawing along the IV-IV line in FIG. It is sectional drawing along the VV line in FIG. In embodiment of this invention, it is explanatory drawing about the part by the side of the starting end of a coil. In embodiment of this invention, it is explanatory drawing about the part by the side of the terminal of a coil. In embodiment of this invention, it is a perspective view of the insulating member of the back side. In embodiment of this invention, it is a perspective view of the insulating member of the front side.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Impact driver 2 Housing 21 Motor housing part 21a Air inflow hole 21b Air discharge hole 21c Air passage 30 Motor 31 Stator 31A Cylindrical part 31B Outer peripheral surface 32 Coil 33 Rotor 34 Teeth 35 Rotating shaft 37 Permanent magnet member 40 Circuit board 40A Front surface 40B Rear surface 40a Wiring hole 41 Hall element 42 FET
50 Fan 81 Insulating member 81A Stator covering portion 81B Annular portion 81a Female screw hole 90 Male screw

Claims (5)

A housing having an air inlet hole and an air outlet hole;
A brushless motor held in the housing;
A circuit board including a plurality of switching elements for driving and controlling the brushless motor;
A fan housed in the housing and disposed in the vicinity of the air discharge hole ,
The brushless motor has a cylindrical body portion and a plurality of teeth protruding radially inward from the inner peripheral surface side of the cylindrical body portion and extending in the axial direction of the cylindrical body portion. A stator supported on the inner surface of the housing on the outer peripheral surface side;
A coil wound along each of the teeth;
Has an axis of rotation, a rotor rotatably disposed substantially coaxially with the stator is located on the inner peripheral surface of the stator,
An annular portion located at an axial end of the stator, and a stator covering portion that covers the teeth to insulate the teeth and the coil, and the coils covered by the stator covering portion An insulating member held by the stator by winding
The circuit board extends in a direction substantially orthogonal to the rotation axis, and is disposed on the air inflow hole side opposite to the fan with respect to the brushless motor to electrically connect the coil. A power tool characterized by being screwed to the insulating member located on the air inflow hole side . The electric power tool according to claim 1, wherein the circuit board is fixed by screws so as to face an end face of the insulating member located on the air inflow hole side. The power tool according to claim 1, wherein the plurality of switching elements are provided on a surface of the circuit board opposite to the insulating member. 4. The electric power tool according to claim 1, wherein a detection element for detecting a position of the rotor is provided on a surface of the circuit board on the insulating member side. 5. . The power tool according to any one of claims 1 to 4, wherein the air inflow hole is formed at a position facing the plurality of switching elements.

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