JP4993193B2 - Electric tool - Google Patents

Description

  The present invention relates to an electric tool equipped with 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.
JP 2004-274800 A

  However, in the above structure, air can be taken in from the outside to cool the stator of the brushless motor. On the other hand, since air is blown into the stator, dust in the air is clogged between the rotor and the stator. .

  In view of such circumstances, the present invention intends to provide an electric tool that cools a brushless motor and that can realize dust-proofing of the brushless motor.

In order to achieve the above object, the present invention provides an electric tool, a housing in which an air inflow hole and an air discharge hole are formed, a brushless motor held in the housing and having a rotating shaft, and the rotating shaft. A fan that is fixed and located on the side of the air discharge hole, and a cover that is dust-proof inside the brushless motor and that has an insertion hole through which the rotation shaft is inserted. The inner peripheral surface of the housing and the brushless A ventilation passage is formed between the outer peripheral surface of the motor and the air inflow hole and the air discharge hole. The cover covers the end surface of the brushless motor on the air discharge hole side. The brushless motor is located on the inner peripheral surface side of the stator, a cylindrical stator supported on the inner surface of the housing, a coil wound around the stator, and the fan. , Substantially concentric with the stator A rotor which is rotatably arranged and is substantially coaxial with the rotating shaft, and an insulating member which is held by the stator by winding the coil and insulates the stator from the coil, and the cover Is held by being sandwiched between the stator and the housing .

  The invention described in claim 2 is characterized in that, in addition to the feature described in claim 1, a second cover that covers an end surface of the brushless motor on the air inlet hole side is provided.

  According to a third aspect of the present invention, in addition to the feature of the second aspect, the second cover is a circuit board for driving and controlling the brushless motor.

  According to a fourth aspect of the present invention, in addition to the feature according to any one of the first to third aspects, the cover is fixed to the housing on one or both of the housing and the cover. The rib for this is located in this ventilation path, It is characterized by the above-mentioned.

  The invention described in claim 5 is characterized in that, in addition to the feature described in claim 4, the rib has a deforming portion that is deformed when the cover is fixed to the housing.

  The invention described in claim 6 is characterized in that, in addition to the feature described in claim 4 or 5, the rib has a tapered portion for guiding the cover to a predetermined position in the housing.

The invention described in claim 7, in addition to the features of the invention described in any one of claims 1 to 6, concave or convex portion is formed on the cover, the cover is in the insulating member A protrusion or a depression that engages with the concave portion or the convex portion is formed.

  According to the first aspect of the present invention, when the fan driven by the brushless motor and the fan fixed to the rotating shaft rotates, the outside air taken in from the air inflow hole passes through the ventilation path as cooling air. The brushless motor is cooled from the outer peripheral surface and discharged from the air discharge hole to the outside. Since the cover for dust-proofing the inside of the brushless motor is arranged between the end face and the fan so as to cover the end face on the air discharge hole side of the brushless motor, the air of the brushless motor is cooled when the brushless motor is cooled as described above. Cooling air can be prevented from entering the brushless motor from the end surface on the discharge hole side. Even when the end surface on the air inlet hole side of the brushless motor is not covered, the end surface on the air discharge hole side is covered with the cover, so the ventilation resistance in the brushless motor is increased. Without entering the motor, the air flows in the ventilation path formed between the inner peripheral surface of the housing and the outer peripheral surface of the brushless motor, and is discharged to the outside. Therefore, even if the electric tool is used in the open air mixed with wood powder and metal powder, dust in the cooling air can be prevented from entering the brushless motor. Even if some cooling air flowing outside the ventilation path is generated and enters the brushless motor, the air volume and speed of the cooling air in the brushless motor are small because the cover is provided, and the dust in the cooling air is brushless. Since the force colliding with the motor is also small, the brushless motor can be prevented from being damaged.

  According to the invention described in claim 2 of the present invention, in addition to the effect of the invention described in claim 1, the second cover that covers the end surface on the air inlet hole side of the brushless motor is provided to seal both end surfaces of the brushless motor. Therefore, cooling air does not enter the brushless motor. Therefore, the dustproof function can be realized more effectively.

  According to the invention described in claim 3 of the present invention, in addition to the effect of the invention described in claim 2, since the circuit board for driving and controlling the brushless motor is also used as the second cover, it is necessary to provide a second cover separately. Without increasing the number of parts. In addition, the wiring path required for electrical connection between the brushless motor and the circuit board can be minimized.

  According to the invention described in claim 4 of the present invention, in addition to the effect of the invention described in any one of claims 1 to 3, the cover is attached to either one or both of the housing and the cover. Since the rib for fixing to the housing is provided in the ventilation path, the cover vibrates integrally with the housing even if vibration is generated during use of the power tool, and rattling of the cover can be prevented. Needless to say, the ribs have dimensions and shapes that do not completely block the ventilation path and do not hinder the flow of cooling air.

  According to the invention described in claim 5 of the present invention, in addition to the effect of the invention described in claim 4, since the rib has a deforming portion that deforms when the cover is fixed to the housing, manufacture of the cover and the housing is possible. Errors and assembly errors can be absorbed by the deforming portion, and the cover can be more securely fixed to the housing.

  According to the invention described in claim 6 of the present invention, in addition to the effects of the invention described in claim 4 or 5, the rib has a tapered portion for guiding the cover to a predetermined position in the housing. Can be easily assembled in the housing, and the assemblability is improved.

  According to invention of Claim 7 of this invention, in addition to the effect of the invention as described in any one of Claims 1 thru | or 6, it is formed in the recessed part or convex part formed in the cover, and an insulating member. By engaging the protrusions or depressions, the cover and the insulating member can be fixed and positioned with respect to each other. In addition, since the insulating member is held by the cylindrical stator supported on the inner surface of the housing by winding the coil, the cover and the stator are fixed via the insulating member without providing a separate member. Rotation of the cover together with the rotor and the rotating shaft can be prevented.

  Hereinafter, an electric power tool according to an embodiment of the present invention will be described with reference to FIGS. 1 to 11. 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 includes a brushless motor 30 serving as a driving source, a circuit board 40 that controls the brushless motor 30, a fan 50, and a cover 60 for protecting the brushless motor 30 from dust. Accommodate. 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 exhausting air to the outside is formed at the front of the motor housing portion 21 (see FIG. 10) is formed. Further, a ventilation path 21c is defined between the outer peripheral surface of the brushless motor 30 and the inner peripheral surface 21A of the motor housing portion 21, and the ventilation path 21c is formed between an air inflow hole 21a and an air discharge hole 21b (FIG. 10). They communicate with each other.

  The power transmission housing part 22 accommodates the power transmission mechanism part 70. The power transmission mechanism 70 includes a speed reduction mechanism composed of a planetary gear 71 and a ring gear 72, a spindle 73, and a hammer 75 that is slidable back and forth on the spindle 73 and is given a striking force by a spring 74. This is a well-known configuration composed of an impact mechanism portion and an anvil 76 that is provided with a rotating impact force by a hammer 75 and can hold a tip tool (not shown). The power transmission mechanism transmits the rotational force of the brushless motor 30 to the anvil 76 as a rotational impact force. The hammer 75 is provided with a protruding portion (not shown). The anvil 76 has a recess (not shown) corresponding to the protrusion of the hammer 75. When the brushless motor 30 is driven, the rotational force transmitted from the rotating shaft 35 of the brushless motor 30 is decelerated by the planetary gear 71 and the ring gear 72, and the rotational force is transmitted to the spindle 73 to start the screw tightening operation. When a load exceeding a predetermined value is not applied to the anvil 76, the hammer 75 and the anvil 76 rotate together to obtain a rotational force by fitting the convex portion of the hammer 75 and the concave portion of the anvil 76. On the other hand, when the anvil 76 is loaded with a predetermined load or more, the anvil 76 is locked and does not rotate, the convex portion of the hammer 75 and the concave portion of the anvil 76 are disengaged, and the hammer 75 moves forward and hits by the action of the spring 74. You will gain power.

  A lower end portion of the handle housing portion 23 is configured to be detachable from a battery pack case 81 that houses a battery pack 80 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 also accommodates a part of wiring for supplying electric power from the battery pack 80 to the brushless motor 30 and a motor driving circuit. When the battery pack case 81 is attached to the handle housing portion 23, the battery pack 80 and the motor drive circuit device are electrically connected via the trigger switch 24. The housing 2 will be described below with the anvil 76 side as the front, the air inflow hole 21a side as the rear, the motor housing portion 21 and the power transmission housing portion 22 side as the upper side, and the battery pack case 81 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 75 can be tightened by applying a rotational striking force to the tip tool mounted on the anvil 76.

  Next, the configuration of the brushless motor 30 according to the present embodiment will be described with reference to FIGS. The brushless motor 30 includes a stator 31 having a cylindrical outer shape, a coil 32, a rotor 33 disposed in the inner peripheral portion of the stator 31, and a rotating shaft 35 that penetrates the rotor 33 concentrically and rotates integrally with the rotor 33. And mainly consists of

  The stator 31 includes a cylindrical portion and a plurality of teeth that protrude radially inward from the inner peripheral surface side of the cylindrical portion and extend in the axial direction of the cylindrical portion. An insulating member 91 and an insulating member 92 are attached to both ends of the stator 31 so as to cover the teeth. Specifically, an insulating member 91 is mounted on the rear end of the stator 31 and on the air inflow hole 21a side, and an insulating member 92 is mounted on the front end of the stator 31 and on the air discharge hole 21b (FIG. 10) side. Has been. The insulating member 91 and the insulating member 92 are held by the stator 31 by winding the coil 32 around the teeth covered by the insulating member 91 and the insulating member 92. As shown in FIG. 6, the insulating member 92 is provided with positioning protrusions 92A. The coil 32 is sequentially wound around a plurality of teeth and connected to a motor drive circuit, thereby forming a star-connected three-phase coil.

  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. The terminal of the coil 32 is electrically connected to the circuit board 40. The motor drive circuit includes an inverter circuit composed of a well-known bridge circuit for supplying a drive current to the coil 32 of the brushless motor 30, a control circuit composed of 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 with screws so that the front surface 40 </ b> A that is the surface of the circuit board 40 on the insulating member 91 side is in close contact with the insulating member 91. The front surface 40 </ b> A of the circuit board 40 includes a Hall element 41 for detecting the rotational position of the rotor 33, and a lead wire 43 that energizes the circuit board 40 is electrically connected. The rear surface 40B, which is the surface on the side of the anti-insulating member 91 of the circuit board 40, includes six FETs 42 that are the above-described switching elements for turning on and off the current flowing through the coil 32. The FET 42 is provided on the circuit board 40. The coil 32 is electrically connected via a wiring pattern. 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.

  The rotor 33 is embedded in the main body 36 and a main body 36 that is press-fitted coaxially with the rotary shaft 35 that is rotatably supported by bearings supported by the motor housing portion 21 and rotates integrally with the rotary shaft 35. The four permanent magnet members 37 are arranged in the inner peripheral portion of the stator 31.

  A fan 50 is fixed on the front side of the rotating shaft 35 and in the vicinity of the air discharge hole 21 b (FIG. 10) of the motor housing portion 21. When the brushless motor 30 is driven, the fan 50 rotates integrally with the rotary shaft 35, sucks external air from the air inflow hole 21a, and draws air to the outside through the ventilation path 21c and the air discharge hole 21b (FIG. 10). Discharge. As shown in FIG. 8, the fan 50 includes a shaft portion 51 concentric with the rotation shaft 35 and having an end surface fixed to the end surface of the rotor 33, and a blade portion 52 including a plurality of blades extending from the shaft portion 51. ing.

  As shown in FIG. 8, the cover 60 includes a cover surface 60 </ b> A in which an insertion hole 60 a having a diameter slightly larger than the insertion shaft portion 51 is formed through the rotation shaft 35 and the shaft portion 51 of the fan 50. 6, the peripheral portion 60 </ b> B is formed with a recess 60 b that engages with a positioning protrusion 92 </ b> A provided on the insulating member 92. First, as shown in FIGS. 8 and 9, the cover 60 is disposed between the rotor 33 and the fan 50 when the rotor 33 and the fan 50 are press-fitted into the rotating shaft 35. Next, the cover 60 (FIG. 9) integrated with the rotating shaft 35 is inserted into the stator 31 (FIG. 7), and as shown in FIG. 7, the positioning projection 92 </ b> A of the insulating member 92 held by the stator 31. And the recess 60b of the cover 60 are engaged and positioned and fixed so as to cover the end surface of the stator 31 via the insulating member 92. In FIG. 7, the rotor 33 and the rotating shaft 35 are omitted.

  According to such a configuration, the cover 60 for dust-proofing the inside of the brushless motor 30 is disposed between the end surface and the fan 50 so as to cover the end surface of the brushless motor 30 on the air discharge hole 21b (FIG. 10) side. When the brushless motor 30 is cooled, the cooling air can be prevented from entering the brushless motor 30 from the end surface of the brushless motor 30 on the air discharge hole 21b (FIG. 10) side. Therefore, even if the impact driver 1 is used in the outside air in which wood powder or metal powder is mixed, it is possible to reduce dust in the cooling air from entering the brushless motor 30.

  Further, the circuit board 40 is closely fixed to the insulating member 91, covers the end face of the brushless motor 30 on the air inflow hole 21a side, and both end faces of the brushless motor 30 are sealed, so that cooling air enters the brushless motor 30. There is nothing. Therefore, the dustproof function can be realized more effectively. In addition, since the circuit board 40 is also used as a cover for protecting the brushless motor 30 from dust, it is not necessary to separately provide a cover, and an increase in the number of components can be suppressed. In addition, the wiring path required for electrical connection between the coil 32 wound around the stator 31 and the circuit board 40 can be minimized.

  Further, by engaging the recess 60b formed in the cover 60 with the positioning projection 92A formed on the insulating member 92, the cover 60 and the insulating member 92 can be fixed to each other and positioned relative to each other. Further, since the insulating member 92 is held by the cylindrical stator 31 supported by the inner peripheral surface 21A of the motor housing portion 21 by winding the coil 32, the cover 60 and the stator 31 are not insulated from each other. The cover 60 can be prevented from rotating together with the rotor 33 and the rotation shaft 35 without providing a separate member.

  As shown in FIGS. 10 and 11, the motor housing portion 21 is provided with ribs 21 </ b> B for fixing the cover 60. The ribs 21B have dimensions and shapes that do not completely block the ventilation path 21c and do not hinder the flow of cooling air. The rib 21 </ b> B is provided with a deformed portion 21 </ b> C that is deformed when the cover 60 is fixed, and a tapered portion 21 </ b> D that guides the cover 60 to an arrangement location in the motor housing 21. The deformed portion 21C protrudes rearward from the rib 21B by more than the assembly tolerance between the cover 60 and the housing 2, and has a substantially triangular cross section.

  When the cover 60 is assembled into the motor housing portion 21 integrally with the stator 31, the cover 60 is guided by the taper portion 21D, pressed by the rib 21B, and positioned and fixed to the motor housing portion 21. Specifically, the top of the deformed portion 21 </ b> C provided on the rib 21 </ b> B is crushed by the cover 60 and deformed so as to correspond to the cover 60, and the cover 60 is fixed to the motor housing portion 21. Therefore, the brushless motor 30 is positioned and fixed to the motor housing portion 21 via the cover 60, and the cover 60 is fixed between the end surface and the fan 50 so as to cover the end surface of the brushless motor 30 on the air discharge hole 21b side. The

  According to such a configuration, the rib 21B for fixing the cover 60 to the motor housing portion 21 is provided in the motor housing portion 21 so as to be positioned in the ventilation path 21c. Even if vibration occurs, the cover 60 vibrates integrally with the motor housing portion 21 and can prevent the cover 60 from rattling.

  In addition, since the deformed portion 21C that is deformed when the cover 60 is fixed to the motor housing portion 21 is provided on the rib 21B, manufacturing errors and assembly errors of the cover 60 and the motor housing portion 21 are absorbed by the deformable portion 21C, and more reliably. The cover 60 can be fixed to the motor housing portion 21.

  Further, since the rib 21B has a tapered portion 21D for guiding the cover 60 to a predetermined position in the motor housing portion 21, it is easy to incorporate the cover 60 into the motor housing portion 21 and improve assemblability.

  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.

  For example, in the above embodiment, the circuit board 40 is fixed so as to be in close contact with the insulating member 91 in order to cover the end surface of the stator 31 on the air inflow hole 21a side. You may provide the cover which covers an end surface separately.

  Further, in the above embodiment, the circuit board 40 is fixed so as to be in close contact with the insulating member 91 in order to cover the end surface of the stator 31 on the air inflow hole 21 a side, but the circuit board 40 is separated from the brushless motor 30. It may be arranged at the position. With such a configuration, even if the end surface on the air inflow hole 21 a side of the brushless motor 30 is not covered, the end surface on the air discharge hole 21 b side is covered with the cover 60, so the ventilation in the brushless motor 30 is performed. Since the resistance increases, the penetration of the cooling air into the brushless motor 30 is reduced, and the air passage 21c formed between the inner peripheral surface 21A of the motor housing portion 21 and the outer peripheral surface of the brushless motor 30 is reduced. Cooling air can be discharged to the outside. Even if a part of the cooling air flowing outside the ventilation path 21c is generated and enters the brushless motor 30, the amount and speed of the cooling air in the brushless motor 30 are reduced by providing the cover 60. Since the force with which the dust inside collides with the brushless motor 30 is also small, the brushless motor 30 can be prevented from being damaged.

  In the above embodiment, the rib 21 </ b> B is provided in the motor housing portion 21, but a rib for fixing the cover 60 to the housing 2 may be provided in the cover 60.

  Moreover, in the said embodiment, although the cross section of the deformation | transformation part 21C provided in the rib 21B provided in the motor housing part 21 was made into the substantially triangular shape, the shape of the deformation | transformation part 21C is not limited to this, The cover 60 is attached. What is necessary is just a shape which deform | transforms so that a dimensional tolerance may be absorbed, when fixing to the motor housing part 21. FIG.

  In the above embodiment, the concave portion 60b formed in the cover 60 and the positioning projection 92A that engages the concave portion are provided in the insulating member 92. However, the convex portion is provided in the cover 60, and the convex portion is provided in the insulating member 92. An engaging recess may be provided.

  The electric power tool of the present invention can be suitably used for a tool having a cooling fan 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 an assembly drawing of a cover and an insulating member. In embodiment of this invention, it is a perspective view of the brushless motor with which the circuit board and the cover were fixed. In embodiment of this invention, it is an assembly drawing of a rotating shaft, a cover, and a fan. In embodiment of this invention, it is a perspective view of the rotating shaft to which the rotor, the cover, and the fan were fixed. It is a principal part enlarged view of the housing in embodiment of this invention. It is a perspective view of a housing in an embodiment of the invention.

Explanation of symbols

1: Impact driver 2: Housing 21: Motor housing
21A: Inner peripheral surface 21B: Rib 21C: Deformed portion 21D: Tapered portion
21a: Air inlet hole 21b: Air outlet hole 21c: Ventilation path
30: Brushless motor 31: Stator 32: Coil 33: Rotor
35: Rotating shaft 40: Circuit board 50: Fan 60: Cover
60A: Cover surface 60B: Peripheral part 60a: Insertion hole 60b: Concave part
91, 92: Insulating member 92A: Positioning protrusion

Claims (7)

A housing having an air inlet hole and an air outlet hole;
A brushless motor held in the housing and having a rotating shaft;
A fan fixed to the rotating shaft and located on the air discharge hole side;
A dust-proof inside the brushless motor, and a cover formed with an insertion hole through which the rotating shaft is inserted,
Between the inner peripheral surface of the housing and the outer peripheral surface of the brushless motor, a ventilation path is formed to communicate the air inflow hole and the air discharge hole.
The cover is disposed between the end surface and the fan so as to cover the end surface on the air discharge hole side of the brushless motor.
The brushless motor
A cylindrical stator supported on the inner surface of the housing;
A coil wound around the stator;
A rotor positioned on the inner peripheral surface side of the stator, substantially concentric with the stator and rotatably arranged, and substantially coaxial with the rotation shaft;
An insulating member that is held by the stator by winding the coil and that insulates the stator from the coil;
The electric tool characterized in that the cover is held by being sandwiched between the stator and the housing .   The power tool according to claim 1, further comprising a second cover that covers an end surface of the brushless motor on the air inlet hole side.   The electric power tool according to claim 2, wherein the second cover is a circuit board that drives and controls the brushless motor.   4. The rib according to claim 1, wherein a rib for fixing the cover to the housing is provided in either or both of the housing and the cover. The power tool according to any one of the above.   The electric tool according to claim 4, wherein the rib has a deforming portion that deforms when the cover is fixed to the housing.   6. The electric tool according to claim 4, wherein the rib has a tapered portion for guiding the cover to a predetermined position in the housing. The recess or projection is formed in the cover, and the projection or recess that engages with the recess or projection of the cover is formed in the insulating member. The electric tool according to any one

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