JP4575056B2 - Electric tool - Google Patents

Description

  The present invention relates to a power tool, and more particularly, to a brush wear detection technique for a motor provided for driving a tip tool.

  In an electric tool equipped with an electric motor, when the brush is worn and reaches a predetermined length, this is detected mechanically, and the technology for shutting off the current supply to the motor and stopping the motor is, for example, No. 6-36368 (Patent Document 1). In Patent Document 1, when the length of the brush reaches a predetermined length, this is mechanically detected and the brush is pulled away from the commutator surface, whereby the current flow between the brush and the commutator is reduced. It is configured to shut off.

According to the wear detection technique disclosed in Patent Document 1, the amount of wear is individually detected for each brush. For this reason, for example, in the case of a four-pole DC motor, of the four brushes, the brush connected to the same electrode (anode or cathode) as the first brush that has reached a predetermined length reaches a predetermined length. Until two brushes connected to different electrodes from the brush that has reached a predetermined length until the first reaches a predetermined length, other brushes that have reached the predetermined length are not paired. The motor is energized and driven by the pair of brushes. This phenomenon is not preferable because the motor performance is reduced and the commutation state becomes very bad, and the use of the electric tool in such a state places a burden on the motor.
Japanese Utility Model Publication No. 6-36368

  The present invention has been made in view of the above points, and in a power tool including a motor that supplies current to a commutator using at least two pairs of brushes, the length of one brush reaches a predetermined length. Then, it aims at providing an effective technique in reducing the energization drive time of the motor by energization of the brush which makes another pair as much as possible.

In order to achieve the above object, the invention described in each claim is configured.
According to the first aspect of the present invention, at least four brush holders arranged around the commutator, brushes accommodated in the brush holders, and a brush that urges each brush to pressurize the commutator. An electric tool is provided that includes a motor having an urging spring and drives the tip tool from the motor via a power transmission mechanism, thereby causing the tip tool to perform a predetermined machining operation. The “motor” in the present invention typically corresponds to a 4-pole DC motor or a 4-pole AC commutator motor, but a DC motor having more than 4 poles, an AC commutator motor, etc. Widely encompass. Further, both of a method of supplying current from a power source to a motor using a power cord and a rechargeable type of supplying current to a motor from a battery mounted on a tool body are included. In addition, the “electric tool” in the present invention is a so-called electric tool that uses a motor as a drive source, such as a work tool used for drilling work or tightening work, a work tool used for cutting work, cutting work, grinding work or polishing work, etc. Widely includes work tools.

  The motor of the electric tool according to the present invention includes a movable stopper member, an interlocking unit, a fixed stopper member, and a regulating unit. The movable stopper member is disposed so as to be movable relative to each brush in the major axis direction of the brush. When the length of the brush reaches a predetermined length, the movable stopper member is pushed by the brush biasing spring and approaches the commutator. It is allowed to move in the direction. Note that “the long axis direction of the brush” does not mean literally a perfect match, and it is sufficient if it has a long axis direction component. The interlocking means connects adjacent movable stoppers so as to interlock with each other. The fixed stopper member restrains the movable stopper member that moves toward the commutator at a position closest to the commutator. The restricting means restricts movement of the movable stopper member moved to the maximum approach position in a direction away from the commutator. Here, the “maximum approach position” is a position where the movable stopper member that is moved by being pushed by the brush biasing spring is closest to the commutator, and is appropriately designed at an appropriate position.

According to the first aspect of the present invention, when one movable stopper member is pushed by the brush biasing spring and moved in the direction approaching the commutator, the movable stopper member is adjacent to the movable stopper member via the interlocking means. When the stopper member is moved away from the commutator and one movable stopper is moved further toward the commutator to reach the maximum approach position, the fixed stopper member restrains the movable stopper at the maximum approach position. In addition, the movement of the movable stopper member moved to the maximum approach position in a direction away from the commutator is restricted. Therefore, according to the first aspect of the present invention, based on the fact that one movable stopper member is moved by the brush biasing spring after the length of one brush reaches a predetermined length, the movable stopper member The two movable stopper members adjacent to each other are moved in a direction away from the commutator via the interlocking means, and approach the brush biasing spring by the amount of movement (the amount away from the commutator). As a result, the time when the brush urging spring comes into contact with the adjacent movable stopper member is earlier than before (before movement). After that, when one movable stopper member moves to the maximum approach position, the movable stopper member is fixed to the maximum approach position (a state in which the movable stopper member cannot move in either the direction toward or away from the commutator). Thus, the movement of all the movable stopper members connected via the interlocking means is fixed. As a result, first, the urging force of the brush urging spring does not reach the first brush that reaches the predetermined length, and thereafter the urging force by the brush urging spring in the order in which the brush urging spring contacts the movable stopper member. Does not reach the brush, and the motor (between the brush and commutator) is cut off and the motor is stopped.
That is, according to the present invention, after the length of one brush reaches a predetermined length, this is detected, and the brush biasing spring that pressurizes the other brush is applied to the movable stopper member at an early stage. By adjusting so as to be in contact with each other, it becomes possible to reduce the energization drive time of the motor by another pair of brushes after one brush reaches a predetermined length.

(Invention of Claim 2 )
According to the invention described in claim 2 , the movable stopper member in the electric tool according to claim 1 is provided in each brush holder so as to be movable in the same direction as the major axis direction of the brush, and the interlocking means are adjacent to each other. The movable stopper members are arranged in a spanning manner, one end of which is connected to one movable stopper member, and the other end is connected to the other movable stopper member so as to be relatively rotatable. Yes. According to such a configuration, a system for interlocking the movable stopper members adjacent to each other so as to move in mutually opposite directions can be configured with a simple structure and at a low cost.

(Invention of Claim 3 )
According to the invention described in claim 3 , the movable stopper member in the electric tool according to claim 1 is arranged in a spanning manner between the movable stopper members adjacent to each other, and the central portion in the spanning direction is provided. Each of the swinging members is configured to be pivotally supported as a rotation center, and each of the swinging members is overlapped with the adjacent swinging member at the end portion in the spanning direction, so that the adjacent movable stopper members are adjacent to each other. It is the structure which interlock | cooperates so that it may move to the direction opposite to each other. According to such a configuration, a system that interlocks movable stopper members adjacent to each other so as to move in mutually opposite directions can be configured with a small number of components.

  According to the present invention, in a power tool including a motor that supplies current to a commutator using at least two pairs of brushes, after one brush reaches a predetermined length, another pair is formed. A technique effective in reducing the energization drive time of the motor by energizing the brush as much as possible has been provided.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. This embodiment will be described using an electric (rechargeable) impact driver as an example of an electric tool. FIG. 1 is a partially cutaway side view schematically showing the overall configuration of an impact driver 100 according to the first embodiment. As shown in FIG. 1, the impact driver 100 according to the present embodiment is generally attached to a main body 101 that forms an outline of the impact driver 100 and a distal end region of the main body 101 so as to be detachable. A driver bit 109 for performing a screw fastening operation of various screws is mainly configured. The driver bit 109 corresponds to the “tip tool” in the present invention.

  The main body 101 includes a motor housing 103, a gear housing 105, and a hand grip 107. A drive motor 121 is accommodated in the motor housing 103. The drive motor 121 corresponds to the “motor” in the present invention. The hand grip 107 is provided with a trigger 125 for turning on a power switch (not shown) of the drive motor 121. In the gear housing 103, a speed reduction mechanism 111 configured by a planetary gear device for appropriately reducing the rotation of the output shaft 122 of the drive motor 121, a spindle 112 driven to rotate by the speed reduction mechanism 111, and the spindle 112 to the ball 113. A hammer 114 that is rotationally driven with the transmission member as a transmission member, and an anvil 115 that is rotationally driven by the hammer 114 are disposed. The hammer 114 is relatively movable in the longitudinal direction of the spindle 112 and is urged toward the anvil 115 side by a compression coil spring 116. The tip of the anvil 115 protrudes from the tip of the gear housing 105, and the driver bit 109 is detachably attached to the protruding tip.

In the impact driver 100 configured as described above, when the drive motor 121 is energized for the screw tightening operation, the spindle 112 and the hammer 114 rotate together when the tightening torque by the driver bit 109 is light. To do. In this light load state, the hammer 114 is kept engaged with the anvil 115 by the urging force of the compression coil spring 116. For this reason, the anvil 115 also rotates integrally with the hammer 114, and the screw tightening operation by the driver bit 109 is performed.
On the other hand, when the tightening torque increases and a predetermined high load state is reached, the hammer 114 moves backward in the direction away from the anvil 115 against the compression coil spring 116, and then the biasing force of the compression coil spring 116 is increased. Is engaged with the anvil 115 with shocking rotational torque, and a large tightening torque is generated in the driver bit 109 through the anvil 115. Since the operating principle of the impact driver 100 itself belongs to a well-known technical matter, a detailed description of the configuration and operation is omitted for convenience.

  Next, the drive motor 121 will be described. The drive motor 121 in the present embodiment is a four-pole DC motor using the battery 127 as a drive power source. The schematic configuration of the drive motor 121 will be described below with reference to FIG. The drive motor 121 includes an output shaft 122, a cooling fan 151 that rotates integrally with the output shaft 122, an armature 133 that rotates integrally with the output shaft 122, a stator 135 that is fixed to the motor housing 103, and one end side of the output shaft 122. A commutator 137 provided on the opposite side of the speed reduction mechanism 111, four brushes 145 that slide in contact with the outer peripheral surface of the commutator 137 and supply current, four brush holders 143 that house each brush 145, and brush holders The brush holder base 141 having a substantially disk shape for fixing 143 is mainly used. One end (rear end) of the output shaft 122 is rotatably supported by the motor housing 103 via a bearing 123, and the other end (deceleration mechanism side) is rotatably supported by the gear housing 105 via a bearing 124. . The cooling fan 151 is a centrifugal fan, and is disposed between the armature 133 and the commutator 137. The air is introduced from the armature 133 side and the commutator 137 side, and the air flows out radially to thereby rectify the cooling fan 151. The child 137, the brush 145, the armature 133, and their peripheral parts are cooled. Then, the cooled wind is discharged to the outside from a wind window (not shown) provided in the motor housing 103. The armature 133 is provided with a coil. The output shaft 122, the armature 133, and the commutator 137 constitute a rotor.

  When power is supplied to the drive motor 121 configured as described above, a current flows through a coil disposed in the armature 133, and the armature 133 and the output shaft 122 are integrally rotated. At this time, the commutator 137 and the brush 145 appropriately switch the direction of the current flowing through the coil of the armature 133 so that the armature 133 and the output shaft 122 continuously rotate in a predetermined direction. Since the operating principle of the DC motor itself belongs to a well-known technical matter, a detailed description of its operation is omitted for convenience.

As shown in FIGS. 3 and 4, the brush holder base 141 is formed of a circular plate having a circular through hole 142 through which a commutator 137 (see FIG. 2) can penetrate at the center, and is formed on the inner wall surface of the motor housing 103. It is fixed by fixing means such as screws. On the rear surface of the brush holder base 141 (the surface opposite to the cooling fan 151), four brush holders 143 are arranged at intervals of 90 degrees so as to surround the through holes 142. Each has a brush 145 (see FIG. 5 or 7) slidably accommodated. The brush 145 is urged by the torsion spring 147 so as to be pressed to the outer peripheral surface of the commutator 137 from the radial direction at a substantially right angle. The torsion spring 147 corresponds to the “brush biasing spring” in the present invention.
The torsion spring 147 has one arm portion 147a fixed to the brush holder 143 and the other arm portion 147b fixed to the brush 145 in a state where the winding portion is supported by a spring support member 144 fixed to the brush holder base 141. The brush is engaged (contacted) with the back surface, and is constantly biased so as to press the tip surface of the brush 145 against the outer peripheral surface of the commutator 137. That is, an arm portion 147b (hereinafter referred to as a brush pressure arm portion) that engages with the back surface of the brush 145 is configured to exert a resilient force to pressurize the brush 145 toward the commutator 137, The brush holder 143 is inserted into the brush holder 143 through a slit 143a provided in the brush holder 143, and moves toward the commutator 137 along the slit 143a as the brush 145 is worn.

  The four brushes 145 are connected to the plus side (anode) and minus (cathode) side of the battery 127 so as to form a pair. Further, between the brush holders 143, an air guide wall 149 having an arc-shaped cross section facing the outer peripheral surface of the commutator 137 with a predetermined gap is provided. The air guide wall 149 opens the rear portion of the motor housing 103. Air taken in (not shown) is guided along the outer peripheral surface of the commutator 137 to the cooling fan 151 side.

  Next, when the brush 145 of the drive motor 121 is worn, the brush wear detection mechanism 161 that cancels the pressurizing action of the brush 145 against the commutator 137 by the torsion spring 147 and stops the drive motor 121 will be described with reference to FIGS. The description will be given with reference. As shown in FIGS. 3 and 4, the brush wear detection mechanism 161 includes four movable stoppers 163 attached to each brush holder 143 so as to be movable in the same direction as the movement direction of the brush 145, and adjacent movable stoppers 163. The four links 165 connected to each other and a fixed stopper 167 that defines the moving end of each movable stopper 163 are mainly configured. The movable stopper 163 corresponds to the “movable stopper member” in the present invention, the fixed stopper 167 corresponds to the “fixed stopper member” in the present invention, and the link 165 corresponds to the “interlocking means” in the present invention.

  Each movable stopper 163 is arranged to be positioned in front of the brush pressure arm 147b that moves along the slit 143a of the brush holder 143, and when the length of the brush 145 reaches a predetermined length, the brush pressure arm The portion 147 b is set so as to contact the back surface of the movable stopper 163. The movable stopper 163 is configured to be moved toward the commutator 137 together with the brush 145 by the brush pressure arm portion 147b after the brush pressure arm portion 147b comes into contact. Each movable stopper 163 has a groove 163a extending in the same direction as the direction in which the movable stopper 163 moves. A fixed stopper 167 is fitted in the groove 163a so as to be relatively movable. The fixed stopper 167 is fixedly provided on the brush holder 143 and, as shown in FIG. 6, abuts against the end of the groove 163a of the movable stopper 163 which is pushed and moved together with the brush 145 by the brush pressure arm portion 147b. Thus, the movement of the movable stopper 163 is restricted. That is, the fixed stopper 167 defines a position where the movable stopper 163 is closest to the commutator 137, and this position corresponds to the “maximum approach position” in the present invention.

  The link 165 that connects the adjacent movable stoppers 163 to each other has one end rotatably attached to one movable stopper 163 and the other end rotatably attached to the other movable stopper 163. The stoppers 163 are interlocked so as to move in directions opposite to each other. That is, when one movable stopper 163 moves in a direction approaching the commutator 137, a force is applied so that the other movable stopper 163 moves in a direction away from the commutator 137.

  Further, the brush holder 143 is provided with a notch 143b (see FIG. 6) continuous with the slit 143a. The notch 143b is set as a recess extending in a direction crossing the extending direction of the slit 143a. When the movable stopper 163 is moved to a position defined by the fixed stopper 167, the brush pressurization of the torsion spring 147 is performed. The arm portion 147b is engaged, and the movable stopper 163 is restricted from moving away from the commutator 137. Said notch part 143b respond | corresponds to the "regulation means" in this invention. The brush pressure arm portion 147b is given an elastic force so as to move in a direction to engage with the notch 143b when facing the notch 143b.

The impact driver 100 according to the present invention is configured as described above. When the power switch is turned on by pulling the trigger 125, the drive motor 121 is energized, and as described above, the speed reduction mechanism 111, the spindle The driver bit 109 is rotationally driven through 112, the hammer 114, and the anvil 115, and the screw tightening operation is performed.
The brush 145 that supplies the current of the battery 127 to the commutator 137 wears on the sliding surface due to relative sliding with the commutator 137, but the brush wear that stops the drive motor 121 based on the wear of the brush 145 hereinafter. The operation of the detection mechanism 161 will be described. First, the case where there is a difference in wear state between the brushes 145 will be described mainly with reference to FIGS. When the brush 145 is worn, the brush 145 is pushed by the brush pressing arm portion 147b of the torsion spring 147 along with the wear and is moved toward the commutator 137 (see the solid lines in FIGS. 5 and 7). The brush pressure arm portion 147b moves along the slit 143a of the brush holder 143. Of the four brushes 145, the brush pressing arm portion 147b that presses the brush 145 with the fastest wear first comes into contact with the movable stopper 163 (see the two-dot chain line in FIG. 7). Thereafter, the brush pressing arm portion 147b moves the movable stopper 163 together with the brush 145 in a direction approaching the commutator 137 as the wear of the brush 145 progresses.

  When the movable stopper 163 moves toward the commutator 137, the fixed stopper 167 fitted in the groove 163a of the movable stopper 163 is relatively moved, and the end of the groove 163a comes into contact with the fixed stopper 167. Thus, the movement of the movable stopper 163 is restricted. That is, the movable stopper 163 is stopped at a position close to the commutator 137. Therefore, the pressurization of the brush 145 by the brush pressurizing arm portion 147b is canceled, and it is considered that the brush 145 has reached so-called limit wear. At this time, the brush pressurizing arm portion 147b engages with the cutout portion 143b connected to the slit 143a (see FIG. 6). For this reason, the movable stopper 163 cannot move in a direction away from the commutator 137. In other words, the movable stopper 163 is locked in both the direction approaching the commutator 137 and the direction away from it, and as a result, all four movable stoppers 163 joined by the link 165 are locked.

  When the movable stopper 163 is moved to the commutator 137 side by the brush pressure arm portion 147 b of the torsion spring 147, the movable stopper 163 adjacent to the movable stopper 163 and the link 165 is separated from the commutator 137. Moved to. By this movement, the movable stoppers 163 on both sides approach the brush pressing arm portions 147b of the corresponding torsion springs 147, respectively. As a result, the contact timing of the brush pressing arm portions 147b of the adjacent torsion springs 147 with respect to the movable stopper 163 is advanced by the amount of movement of the movable stopper 163. Then, when the wear of the adjacent brushes 145 further progresses and the brush pressing arm part 147b pressing the brush 145 contacts the movable stopper 163, the brush pressing arm part 147b is in the contacted position. Retained. For this reason, the pressurization of the brush 145 (the pressing of the brush 145 against the commutator 137) by the brush pressurizing arm portion 147b is eliminated, and the energization to the drive motor 121 is interrupted. That is, the drive motor 121 can be stopped.

  As described above, according to the present embodiment, when there is a difference in wear state between the brushes 145, the movement of the movable stopper 163 corresponding to one brush 145 having the earliest wear is changed to the fixed stopper 167 and the notch. Energization by the brush 145 that is initially worn by regulating the engagement of the portion 143b and the brush pressure arm portion 147b and adjusting the contact timing of the brush pressure arm portion 147b to the adjacent movable stopper 163 to be advanced. The energization drive time of the drive motor 121 due to energization of the other pair of brushes 145 after being interrupted can be reduced.

  Next, the case where the four brushes 145 are worn almost uniformly will be described with reference to FIGS. For convenience of explanation, in FIGS. 8 to 11, the brush 145, the brush holder 143, the torsion spring 147, the movable stopper 163, the fixed stopper 167, and the like located on the left side with respect to the commutator 137 are defined as a first group. Similarly, each member positioned on the lower side will be described as a second group, each member positioned on the upper side will be described as a third group, and each member positioned on the right side will be described as a fourth group.

As shown in FIG. 8, when the first group of brushes 145 reaches a predetermined length, the brush pressing arm portion 147b of the first group of torsion springs 147 hits the corresponding first group of movable stoppers 163, Thereafter, as the wear of the brush 145 proceeds, the movable stopper 163 of the first group is moved toward the commutator 137 together with the brush 145 of the first group. With the movement of the movable stopper 163 of the first group, the movable stopper 163 of the second group and the third group adjacent to the movable stopper 163 is moved in the opposite direction, that is, the direction away from the commutator 137 via the link 165. The movable stoppers 163 of the second group and the third group are moved closer to the brush pressing arm portions 147b of the second group and the third group by the amount of movement (the distance away from the commutator 137).
On the other hand, the movable stopper 163 of the fourth group facing the movable stopper 163 of the first group is moved in a direction approaching the commutator 137, and the movable stopper 163 of the fourth group is moved by the amount of the movement. It leaves | separates from the brush pressurization arm part 147b (refer FIG. 9).

  Subsequently, the brush pressing arm portion 147b with the larger wear amount of the brush 145 hits the movable stopper 163 of the second group or the third group first, and the brush pressing arm portion 147b with the smaller wear amount continues. (See FIG. 10). For this reason, the urging force of the second group and the third group of brush pressing arm portions 147b overcomes the urging force of the first group of brush pressing arm portions 147b that pressurizes the movable stopper 163 of the first group. The movable stopper 163 of the group is pushed back (see FIG. 11). Therefore, the movable stoppers 163 of the first group and the fourth group are moved away from the commutator 137, and as a result, the movable stopper 163 of the fourth group is moved to the brush pressure arm part 147b of the fourth group. Hit. Thus, finally, all the movable stoppers 163 come into contact with the brush pressurizing arm portion 147b, and all the four movable stoppers 163 are locked in movement (see FIG. 11). As a result, the brush pressure arm portions 147b of all the torsion springs 147 cannot press the brush 145, and the pressing of the brush 145 against the commutator 137 is eliminated. Thereby, the power supply to the drive motor 121 is cut off, and the drive motor 121 stops.

  For example, if the first group of brushes 145 and the second group of brushes 145 form a pair, and the third group of brushes 145 and the fourth group of brushes 145 form a pair, then the first group of movable stoppers 163 is provided. When the pressing of the first group of brushes 145 against the commutator 137 is canceled, the supply of current by the first group of brushes 145 and the second group of brushes 145 is cut off, and all four movable stoppers are removed. When the movement of 163 is locked, the supply of current by the third group of brushes 145 and the fourth group of brushes 145 is cut off.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS. This embodiment is a modification of the brush wear detection mechanism 161, and the drive motor 121 in which four brushes 145 are arranged around the commutator 137 is arranged to detect wear of each brush 145. The movable stopper 163 in the first embodiment is configured by a swing arm 171. Except for this point, the configuration is the same as that of the first embodiment described above. Therefore, the same reference numerals are given to the configuration, and description thereof is omitted or simplified.

  Each of the four swing arms 171 in the present embodiment is formed in a substantially ¼ arc shape, and is arranged so as to form a circular ring shape as a whole between adjacent brush holders 143. . Each swing arm 171 is arranged so that each end portion 171a is positioned on the front side (the side facing the commutator 137) of the brush arm portion 147b so that the end portion 171a is pushed by the brush pressure arm portion 147b of the torsion spring 147. In addition, at a central portion in the arc direction (a central portion between adjacent brush holders 143), it is rotatably supported by a rotating shaft 173 standing on the brush base holder 141. Therefore, when the brush pressing arm portion 147b moves in a direction approaching the commutator 137, the two swinging arms 171 are pushed by the brush pressing arm portion 147b on one end 171a and rotate in opposite directions. Moved. Further, the end portions 171a of the swing arm 171 are configured such that adjacent ones overlap (engage) with each other in the rotation direction so that the adjacent swing members 171 rotate in directions opposite to each other. It is configured to work with. The configuration in which the end portions 171a of the swinging member 171 overlap with each other corresponds to the “interlocking means” in the present invention.

  Further, the brush holder 143 is provided with a fixed stopper 167, and the rotation of the swing arm 171 is restricted by coming into contact with the swing arm 171 pushed and moved by the brush pressure arm portion 147b. That is, the fixed stopper 167 defines a position where the end 171a of the swing arm 171 is closest to the commutator 137, and this position corresponds to the “maximum approach position” in the present invention. Each brush holder 171 is provided with a notch continuous to the slit 143a, as in the first embodiment described above. The notch 143b is set as a recess extending in a direction intersecting with the extending direction of the slit 143a. When the swing arm 171 is rotated to a position defined by the fixed stopper 167, the brush pressurizing arm portion is formed. 147b is configured to be engaged. That is, the swing arm 171 moved to the position closest to the commutator 137 is locked at the moving position and cannot move in the direction away from the commutator 137.

  The brush wear detection mechanism 161 according to the present embodiment is configured as described above. Among the four brushes 145, when one brush 145, for example, the upper right brush 145 in the drawing reaches a predetermined length, as shown in FIG. 14, the brush pressure arm portion 147b of the torsion spring 147 that pressurizes the brush 145. Comes into contact with the end 171a of the swing arm 171. Then, one end 171a of the two swinging arms 171 is pushed, and both the swinging arms 171 are rotated in opposite directions as indicated by the arrows in the drawing with the rotation shaft 173 as the center. Further, the other end 171 a of the pivoting swing arm 171 contacts the movable stopper 163 on both sides, and moves the movable stopper 163 in a direction away from the commutator 137. The pivoting motion of the swing arm 171 is restricted by the swing arm 171 coming into contact with a fixed stopper 167 provided on the brush holder 145.

  As described above, the swing arm 171 in the present embodiment is configured to have the functions of the movable stopper 163 and the link 165 in the first embodiment described above. Therefore, according to the second embodiment, a mechanism similar to that of the first embodiment can be obtained. That is, there is a difference in the wear state of the four brushes 145, and one brush 145 is in a stage before the brush pressure arm portion 147b of the torsion spring 147 contacts the swing arm 171 for each of the three brushes 145. The first wear occurs when the swing arm 171 corresponding to the brush 145 is locked at a position closest to the commutator 137 and when the four brushes 145 are worn substantially evenly. It functions in the same way as the embodiment.

Although the present embodiment has been described with respect to the impact driver 100 used for screw tightening work as an example of an electric tool, the present invention is not limited to this, and cutting work, cutting work, grinding / polishing work, or drilling work is not limited thereto. It can be applied to various electric tools used in the above. In short, any work tool provided with the drive motor 121 can be applied.
In the present embodiment, a four-pole DC motor is described as an example of the drive motor 121. However, a four-pole AC commutator motor, a DC motor having more than four poles, an AC commutator motor, or the like. It is possible to apply to.

1 is a partially cut side view showing an overall configuration of an impact driver according to a first embodiment of the present invention. It is sectional drawing which shows the drive motor which concerns on 1st Embodiment. It is a perspective view which shows the brush wear detection mechanism which concerns on 1st Embodiment. It is a top view which similarly shows a brush wear detection mechanism. It is a side view of the brush wear detection mechanism regarding one brush. It is also a perspective view It is a schematic diagram explaining the operation | movement aspect of one movable stopper accompanying abrasion of a brush. It is a figure explaining a brush abrasion detection aspect. It is a figure explaining a brush abrasion detection aspect. It is a figure explaining a brush abrasion detection aspect. It is a figure explaining a brush abrasion detection aspect. It is a perspective view which shows the brush wear detection mechanism which concerns on the 2nd Embodiment of this invention. It is a top view which shows the brush wear detection mechanism which concerns on 2nd Embodiment. It is a schematic diagram which shows the operation | movement aspect of the brush wear detection mechanism which concerns on 2nd Embodiment.

100 Impact driver (electric tool)
101 Body 103 Motor housing 105 Gear housing 107 Hand grip 109 Driver bit (tip tool)
111 Deceleration mechanism (transmission mechanism)
112 Spindle (Transmission mechanism)
113 ball (transmission mechanism)
114 Hammer (Transmission mechanism)
115 Anvil (Transmission mechanism)
116 Compression coil spring 121 Drive motor (motor)
122 Output shaft 123 Bearing 124 Bearing 125 Trigger 127 Battery 133 Armature 135 Stator 137 Commutator 141 Brush holder base 142 Through-hole 143 Brush holder 143a Slit 143b Notch (regulator)
144 Spring support member 145 Brush 147 Torsion spring 147a One arm portion 147b The other arm portion (brush pressure arm portion)
149 Air guide wall 151 Cooling fan 161 Brush wear detection mechanism 163 Movable stopper (movable stopper member)
163a Groove 165 Link (interlocking means)
167 Fixed stopper (fixed stopper member)
171 Swing arm (movable stopper)
171a end (interlocking means)
173 Rotating shaft

Claims (3)

At least four brush holders arranged around the commutator;
A brush housed in each brush holder;
A brush energizing spring that energizes each brush to pressurize it toward the commutator;
The power tool drives the tip tool through a power transmission mechanism by energization driving of the motor, thereby causing the tip tool to perform a predetermined machining operation,
The motor is
The brush is disposed so as to be relatively movable in the major axis direction of the brush, and when the length of the brush reaches a predetermined length, the brush is pressed by the brush biasing spring to approach the commutator. A movable stopper member allowed to move; and
Interlocking means for connecting adjacent movable stopper members so as to interlock with each other;
A fixed stopper member that restrains the movable stopper member that moves toward the commutator at a position closest to the commutator;
Restricting means for restricting movement of the movable stopper member moved to the maximum approach position in a direction away from the commutator;
When one movable stopper member is pushed by the brush biasing spring and moved in a direction approaching the commutator, the movable stopper member adjacent to the movable stopper member is moved from the commutator via the interlocking means. The fixed stopper member stops the movable stopper at the maximum approach position when the one movable stopper is further moved toward the commutator and reaches the maximum approach position. An electric tool characterized by restricting movement of the movable stopper member moved to the maximum approach position in a direction away from the commutator. The electric tool according to claim 1 ,
The movable stopper member is provided in each brush holder so as to be movable in the same direction as the long axis direction of the brush, and the interlocking means is arranged in a spanning manner between the movable stopper members adjacent to each other, and has one end An electric tool characterized by comprising a rod-like member connected to one movable stopper member and the other end rotatably connected to the other movable stopper member. The electric tool according to claim 1 ,
Each of the movable stoppers is arranged in a spanning manner between the brush holders adjacent to each other, and is configured by a swinging member that is supported so as to be rotatable about a central portion in the spanning direction. The members are configured to interlock with each other so that the adjacent movable stopper members move in directions opposite to each other by overlapping each other with adjacent swinging members at the end portions in the spanning direction. Electric tool to do.

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