JP2011104671A - Power tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure a sufficient air quantity of a cooling fan used for cooling a control element of a motor in a power tool formed with a thin external shape in the vicinity of a connecting part of a gear cover and a housing. <P>SOLUTION: This power tool (1) includes a motor 6 having a rotary shaft 10, housings (2, 32) for storing the motor 6, and a power transmission mechanism for transmitting power from the rotary shaft 10 to a spindle 11 for rotating a tip tool. Each of the housings includes a motor housing 2 for storing the motor and a tail cover 32 connected to a rear side of the motor housing and formed to be thicker than that of the motor housing. The cooling fan 4 is located in the tail cover 32 and mounted to the rotary shaft 10 at an opposite side of the tip tool side of the motor 6. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a power tool, and more particularly to a power tool in which a motor housing portion of a housing is thinned so that the housing can be easily gripped.

  A disk grinder (angle grinder) is used as an electric tool for rotating a tip tool mounted on a spindle by a motor. FIG. 11 is a top view of a conventional disc grinder, which is disclosed in Patent Document 1, for example. The disc grinder 101 has a motor housing 102 that houses a motor as a drive source, and a tail cover 104 having a plurality of air intake ports 119 is provided behind the motor housing 102. The tail cover 104 is provided with a power cord 114 connected to the outside and a power switch 118 for turning on / off the power of the disc grinder 101. A gear cover 103 is provided in front of the motor housing 102. The gear cover 103 accommodates a pair of bevel gears that change the direction of power transmission by the rotation shaft of the motor by about 90 degrees. The gear cover 103 is fixed by four screws 132 extending coaxially with the rotation shaft of the motor, and a grindstone 105 is attached to a spindle (output shaft) (not shown) in the gear cover 103. The lock pin 111 restricts the rotation so that the spindle does not rotate when the grindstone 105 is attached or detached.

The grindstone 105 has a diameter of about 100 to 125 mm, for example. There are various types of motors used in the disc grinder 101 using such a grindstone 105, but in consideration of the output required for work, an AC motor having a diameter of 50 mm or more has been conventionally used. Therefore, the diameter _{d 0} of the motor housing 102 that houses the motor, the diameter at a minimum is in the order of 56 mm. Such a disc grinder 101 is not suitable for working by holding the motor housing 102 with one hand.

  Since it is difficult to work while holding the motor housing 102, a handle 108 is detachably attached to the side of the gear cover 103. Although FIG. 11 shows an example in which the handle 108 is attached to the right side of the gear cover 103, the handle 108 may be attached to the left side instead of the right side. By attaching the handle 108, the operator can perform the grinding operation by holding the handle 108 with the right hand and pressing the motor housing 102 or the tail cover 104 with the left hand. Thus, by providing the detachable handle 108 to the disc grinder 101, good workability can be realized. However, since the handle 108 protrudes greatly from the main body of the disc grinder 101, there is a drawback in that it hinders work in a narrow place.

Japanese Patent Laid-Open No. 7-299606

  When working in a narrow place, there is a case where it is desired to work while holding the motor housing 102 with one hand without attaching the handle 108 as shown in FIG. Therefore, it has been desired to form the motor housing 102 as thin as possible so that the operator can easily grasp it. However, if the diameter of the motor housing 102 is reduced, the size of the cooling fan accommodated in the motor housing 102 may be reduced and a sufficient air volume may not be ensured.

  The present invention has been made in view of the above background, and an object of the present invention is to make it possible to secure a sufficient air volume of a cooling fan used for cooling a motor in an electric tool having a thin outer shape in the vicinity of a motor housing portion of a housing. That is.

  Another object of the present invention is to ensure a sufficient air volume of a cooling fan used for cooling a motor control element in an electric tool having a thin outer shape in the vicinity of a motor housing portion of a housing.

  Still another object of the present invention is to effectively cool a motor and a control element in an electric tool that grips the vicinity of the center of a main body with improved cooling air suction and discharge positions and air passages. It is in.

  Of the inventions disclosed in the present application, typical features will be described as follows.

  According to one aspect of the present invention, in an electric tool having a motor having a rotating shaft, a housing that houses the motor, and a power transmission mechanism that transmits power from the rotating shaft to a spindle that rotates the tip tool, The cooling fan is attached to the rotating shaft inside and opposite to the end tool side of the motor. The housing includes a motor housing that houses a motor, and a tail cover that is connected to the rear of the motor housing and has an axial thickness larger than that of the motor housing. The cooling fan is housed in the tail cover. Thus, the diameter of the cooling fan was configured to be larger than the outer diameter of the motor.

  According to another feature of the invention, the motor is a brushless DC motor and a circuit board on which a switching element for driving the motor is mounted is provided in the tail cover. The circuit board is preferably arranged behind the cooling fan so as to be perpendicular to the axial direction of the motor. The rotating shaft and the spindle are arranged in a substantially orthogonal direction, and the power transmission mechanism includes bevel gears fixed to the rotating shaft and the spindle, respectively, and the two bevel gears are arranged inside the gear case.

  According to still another aspect of the present invention, an air intake is formed in the vicinity of the rear end of the motor housing, and an air outlet is provided in the outer peripheral portion of the cooling fan of the tail cover, so that the air taken in from the air intake Flows through the space between the outer wall of the motor and the motor housing to near the front end of the motor, changes direction, flows between the stator and rotor of the motor, flows into the cooling fan, and is discharged to the outside through the discharge port. . In addition, an air intake port is formed at the rear of the tail cover discharge port. Air is sucked from the air intake port of the motor housing and the air intake port of the tail cover by the cooling fan, and the switching element is cooled by the sucked air. After that, it was configured to be discharged to the outside through the discharge port. Instead of providing an air intake near the rear end of the motor housing, an air intake may be formed near the front end of the motor housing (for example, a gear case) to introduce air.

  According to still another aspect of the present invention, a motor having a rotating shaft, a housing that houses the motor, a tip tool holding portion that is driven by one end of the rotating shaft and can hold the tip tool, and the other end of the rotating shaft The electric tool was configured to have a permanent magnet fixed to the magnet and a rotational position detecting element provided at a position facing the permanent magnet. This electric tool has a bearing for holding a rotating shaft, and the permanent magnet is provided on the side opposite to the motor with respect to the bearing.

  According to still another aspect of the present invention, a motor having a rotating shaft, a housing that houses the motor, a tip tool holding portion that is driven by the rotating shaft and can hold the tip tool, and a rear portion of the rotating shaft are held. In an electric tool having a bearing, an extending portion extending rearward from the bearing is provided on the rotating shaft, a permanent magnet is fixed to the extending portion, and a rotational position detecting element is provided at a position facing the permanent magnet. Moreover, the cooling fan which can cool a motor was fixed to the extending | stretching part.

  According to the first aspect of the present invention, since the cooling fan is attached to the rotating shaft inside the housing and opposite to the tip tool side of the motor, the size of the housing part that accommodates the motor is limited. Since a cooling fan having a large outer diameter can be attached, the inside of the housing can be effectively cooled.

  According to the invention of claim 2, the cooling fan is accommodated in the tail cover connected to the rear of the motor housing and formed thicker than the motor housing, so that the motor housing is not limited by the size of the cooling fan. Can be formed thinly. With this configuration, an electric tool that is easy for an operator to hold with one hand can be realized.

  According to the invention of claim 3, since the cooling fan is a fan having a diameter larger than the outer diameter of the motor, a sufficient air volume can be secured and the inside of the housing can be effectively cooled.

  According to the invention of claim 4, the motor is a brushless DC motor, and the circuit board on which the switching element for driving the brushless DC motor is mounted is provided in the tail cover. The diameter of the housing can be reduced.

  According to the invention of claim 5, since the circuit board is arranged behind the cooling fan so as to be perpendicular to the axial direction of the motor, it is possible to realize an arrangement structure that is easy to assemble and fix.

  According to the sixth aspect of the present invention, the rotating shaft and the spindle are arranged in a substantially orthogonal direction, and the power transmission mechanism includes the bevel gears fixed to the rotating shaft and the spindle, respectively. Can be realized. In addition, since the speed reduction mechanism can be realized by a combination of bevel gears, high torque can be generated using a small motor as a power source, and thus the weight of the electric tool can be reduced.

  According to the invention of claim 7, the air taken in from the air intake provided near the rear end of the motor housing flows through the space between the outer wall of the motor and the motor housing to the vicinity of the front end of the motor. Since the motor flows between the stator and the rotor of the motor and flows into the cooling fan and is discharged to the outside through the discharge port, the entire motor can be efficiently cooled from the front end to the rear end. Moreover, since the discharge port is on the rear side of the motor, the dust generated by the work due to the discharged air is reduced.

  According to the invention of claim 8, since the switching element is cooled by the air sucked from the air intake port of the tail cover and then discharged to the outside by the discharge port, the switching element can be directly cooled by the taken-in outside air, A high cooling effect can be realized.

  According to the ninth aspect of the present invention, the air taken in from the air intake port near the front end of the motor housing is caused to flow through the space between the outer wall of the motor and the motor housing and the space between the stator and the rotor of the motor. Therefore, there is no reversal of the air flow direction inside the motor housing, so that air can flow smoothly.

  According to the tenth aspect of the present invention, the permanent magnet is fixed to the other end of the rotating shaft of the motor, and the rotational position detecting element provided at a position facing the permanent magnet is provided to detect the position of the motor. The degree of freedom of the arrangement position of the control board on which the rotational position detecting element is mounted is increased, and the control board can be arranged at a position slightly away from the motor. As a result, the cooling effect can be enhanced even when a semiconductor switching element is mounted on the control board.

  According to the eleventh aspect of the invention, since the bearing having the rotating shaft is provided and the permanent magnet is provided on the side opposite to the motor with respect to the bearing, the rotational position detection can be performed even if the control board is arranged away from the motor. Elements can be placed on the control board.

  According to the twelfth aspect of the present invention, the extending portion extending backward from the bearing is provided on the rotating shaft of the motor, the permanent magnet is fixed to the extending portion, and the rotational position detecting element is provided at a position facing the permanent magnet. The degree of freedom of the arrangement position of the control board on which the rotational position detecting element is mounted is increased, and the control board can be arranged at a position slightly away from the motor.

  According to the invention of claim 13, since the cooling fan is fixed to the extending portion, the cooling fan larger than the diameter of the motor can be provided without being limited by the size of the housing that houses the motor, and a high cooling effect. Can be realized.

  The above and other objects and novel features of the present invention will become apparent from the following description and drawings.

1 is a cross-sectional view showing an entire disc grinder 1 according to an embodiment of the present invention. 1 is a top view of a disk grinder 1 according to an embodiment of the present invention. It is a fragmentary sectional view for demonstrating the flow of the cooling wind of the disk grinder 1 which concerns on the Example of this invention. It is sectional drawing of the AA part of FIG. It is sectional drawing of the BB part of FIG. It is sectional drawing of the CC section of FIG. It is a perspective view which shows the shape of the cooling fan 4 of FIG. 1, and is the figure seen from diagonally forward. It is a figure which shows the shape of the stator press 31 of FIG. 1, (1) is a front view, (2) is a side view. It is sectional drawing which shows the whole disc grinder 51 which concerns on the 2nd Example of this invention. It is a top view of the disk grinder 51 which concerns on 2nd Example of this invention. 1 is a top view of a conventional disc grinder 101. FIG. It is a side view which shows the state which hold | gripped the conventional disc grinder 101. FIG.

  Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, a description will be given using a disc grinder as an example of an electric tool, parts having the same function are denoted by the same reference numerals, and repeated description will be omitted. Further, in this specification, description will be made assuming that the front-rear, left-right, and up-down directions are the directions shown in FIGS.

  FIG. 1 is a sectional view of a disc grinder 1 according to an embodiment of the present invention. The disc grinder 1 includes a motor housing 2 that houses a motor 6, a tail cover 32 that is attached to the rear of the motor housing 2, and a gear cover that is attached to the front of the motor housing 2 and accommodates a pair of bevel gears 38 and 39. 3 and a circular grindstone 5 attached to the spindle 11 and attached to the spindle 11 extending downward from the gear cover 3. In the present embodiment, the grindstone 5 is used as the tip tool (processed part) attached to the disc grinder 1, but it is not limited to the grindstone but may be other grinding parts, cutting parts, or polishing parts.

  The motor housing 2 accommodates a brushless DC type motor 6. The motor 6 is a so-called inner rotor type in which a rotor 7 having a permanent magnet is attached to a rotating shaft 10 and a stator having a coil 9 wound around a stator core 8 on the motor housing 2 side. In order to make the diameter of the motor 6 as small as possible, it is preferable to use a thin cylindrical magnet (permanent magnet) such as a tubular neodymium sintered magnet for the rotor 7. Further, in order to reduce the diameter of the motor 6, it is preferable that the stator core 8 is composed of, for example, divided cores divided into six for each tooth at equal intervals in the circumferential direction. The outer diameter (diameter) of the motor housing 2 of the present embodiment is preferably about 35 mm to 45 mm so that the operator can easily hold it with one hand. For this reason, the diameter of the stator core 8 is preferably 28 to 38 mm. .

  The rotating shaft 10 of the motor 6 is rotatably held by two bearings 13a and 13b. The bearing 13 a is held by the gear cover 3, and the bearing 13 b is held by the motor housing 2. An annular bearing stopper 30 is sandwiched between the front end portion of the motor housing 2 and the gear cover 3, and the bearing stopper 30 holds the rear of the bearing 13a. A stator press 31 for pressing the stator core 8 of the motor 6 is disposed behind the bearing stopper 30. The gear cover 3 is fixed to the motor housing 2 by four screws 37 (see FIG. 2, but only the upper two are shown in FIG. 2) which are arranged at substantially equal intervals in the circumferential direction and extend in the axial direction.

  Since the motor housing 2 requires a certain degree of strength, the motor housing 2 is preferably formed into a substantially cylindrical shape and manufactured by integral molding of a metal such as an aluminum alloy or a synthetic resin such as plastic. A tail cover 32 is attached to the rear side of the motor housing 2. The tail cover 32 is configured such that it can be divided into right and left on a vertical plane passing through an extension line of the rotating shaft 10 of the motor 6. Screw bosses 35a and 35b are formed on the right tail cover, and are fixed to the left tail cover 32 with screws 42 (see FIG. 2). Since the tail cover 32 is divided into left and right parts in this way, circuit components, boards, etc., which will be described later, are placed on one tail cover, and then the other tail cover is put on and screwed to facilitate assembly. As a result, assemblability is improved. Further, since there are few restrictions on assembly regarding parts and board arrangement, the tail cover 32 can be reduced in size. As a result, the outer shape, in particular, the diameter of the disc grinder 1 can be reduced while configuring the motor housing 2 as an integrated structure to increase the strength, and a compact electric tool can be realized.

  The gear cover 3 houses a bearing 13a that rotatably holds the front side of the rotary shaft 10, and a bevel gear 38 (first bevel gear) that is attached to the front end of the bearing 13a. The outer ring of the bearing 13 a is held by the gear cover 3. The bevel gear 38 is fixed to the tip of the rotating shaft 10 by a bolt 41 and meshes with a bevel gear 39 (second bevel gear) attached to the spindle 11. The rotation of the motor 6 is decelerated by these bevel gears 38 and 39, and the rotation direction is converted by 90 degrees. The spindle 11 is rotatably held by a bearing 40 of the gear cover 3 and a bearing (not shown) held in the spindle case 15, and a grindstone 5 is attached to the tip (lower end) thereof. The grindstone 5 has a diameter of 100 to 125 mm, for example, and rotates at a rotational speed reduced by the gear ratio of the bevel gears 38 and 39 with respect to the rotational speed of the motor 6. Almost half of the rotating grindstone 5 is covered with a foil guard 12. The wheel guard 12 is for protecting an operator from scattering of a ground member or damaged abrasive grains. By moving the fixing position of the wheel guard 12 in the circumferential direction, it is possible to change whether the wheel guard 12 covers the rear side of the grindstone 5, or covers the right half or the left half. In order to attach and detach the grindstone 5 to / from the spindle 11, a lock pin 36 (see FIG. 2) for restricting the rotation of the grindstone 5 is provided, but is not shown in FIG.

  A power cord 19 for supplying commercial power is connected to the tail cover 32, and AC, for example, 50 Hz and 100 V is supplied from the outside. A power switch 18 is provided at the rear end of the tail cover 32. Inside the tail cover 32, the power supply circuit 17 mounted on the power supply board 27 and the smoothing capacitor 20 are provided, and the supplied AC power is converted into predetermined DC power. The rectified DC power is sequentially supplied to each phase of the coil 9 from the inverter circuit constituted by the FET (field effect transistor) 24 and the like via the wiring 29 at predetermined intervals. The configuration of the inverter circuit and other circuits can use a known circuit for controlling a brushless DC motor, and therefore the description thereof is omitted here.

  A plurality of discharge ports 34 and air intake ports 33 that allow the inside and the outside of the tail cover 32 to communicate with each other are formed on the top, bottom, and left and right surfaces of the tail cover 32. The discharge port 34 has an opening larger than the air intake port 33 and is disposed on the outer peripheral side of the cooling fan 4. The position at which the air intake 33 is provided is relatively arbitrary, but in order to cool the FET 24 with the cooling air taken from the air intake 33, the air intake 33 is formed at a position where the air intake 33 is on the windward side with respect to the cooling fan 4. It is important to. Further, in addition to the air intake port 33, an air intake port 21 is provided in the vicinity of the rear end of the motor housing 2, and an extending portion 2b extending obliquely outward in the radial direction is provided in the vicinity of the rear end of the motor housing 2. It is formed continuously in the direction. By providing the extending portion 2b, the tendency of the operator to grip the front side of the extending portion 2b of the motor housing 2 becomes remarkable, and it is effective that the portion of the air intake 21 is gripped and covered. Can be blocked. Further, even if the vicinity of the extending portion 2b is gripped, it is possible to prevent the air flow to the air intake port 21 from being hindered.

  In the present embodiment, the rotating shaft 10 of the motor 6 extends rearward beyond the bearing 13b, and the cooling fan 4 is attached to the extended portion. Behind the cooling fan 4, a position detecting magnet 23 for detecting the rotational position of the rotor 7 is fixed to the rotating shaft 10 by a bolt 28. The position detecting magnet 23 is a magnet having a circular outer shape. By providing the position detecting magnet 23 at a position facing the control board 26, the rotational position detecting element 43 (see FIG. 3) such as a Hall IC is replaced with the motor 6. It can be provided on the control board 26 disposed at a position away from the control board 26.

  In the portion of the rotating shaft 10 that holds the cooling fan 4, a groove extending in the axial direction is formed at one place in the circumferential direction, and a metal key 22 is provided in the groove. On the other hand, a groove extending in the axial direction for fitting the key 22 is also formed on the inner peripheral surface of the cooling fan 4. By inserting the key 22, it is possible to prevent the cooling fan 4 from idling with respect to the rotary shaft 10, and the key 22 functions as a so-called detent. The cooling fan 4 is fixed by a bolt 28 together with the position detection magnet 23.

  FIG. 2 is a top view of the disc grinder 1 according to the embodiment of the present invention. The motor housing 2 has a cylindrical shape for an operator to grip, and this portion serves as a grip portion. In the vicinity of the rear end of the motor housing 2, an extending portion 2 b that protrudes outward like a ridge is formed. The extending portion 2b is ahead of the front end portion of the tail cover 32 by a predetermined distance. As a result, the motor housing 2 is formed with a small diameter portion 2c. And the air intake 21 is arrange | positioned in the recessed part so that it may hide in the extension part 2b seeing from the top. By forming the small-diameter portion 2c in this manner, even if the operator grasps the vicinity of the extending portion 2b, there is almost no possibility of sealing the air intake port 21, and stable air can be taken in. Furthermore, since the extension part 2b protrudes diagonally to the rear side, dust such as cutting powder generated by the grindstone 5 can be effectively prevented from being sucked from the air intake port 21.

  The tail cover 32 is divided into right and left parts by a right tail cover 32a and a left tail cover 32b, and is fixed by screws 42. The cross section of the tail cover 32 in the axial direction (front-rear direction) and the vertical plane is substantially square, and the control board 26 and the power supply board 27 are fixed to the tail cover 32 by ribs formed inside. The tail cover 32 is provided with a plurality of discharge ports 34 and a plurality of air intake ports 33. The discharge ports 34 are arranged so as to be arranged on the outer peripheral side of the cooling fan 4, and the air intake ports 33 are arranged so as to be arranged near the outer periphery of the control board 26 and the power supply board 27. In this embodiment, four outlets 34 are formed on each of the upper and lower sides of the tail cover 32, and eight air intake ports 33 are formed on each of the upper and lower sides of the tail cover 32. However, the number of outlets 34 may be increased without being limited to this number. Further, the air intake 33 may be provided on the side or rear of the tail cover 32. Note that the structure of the housing including the motor housing 2 and the tail cover 32 is not limited to the present embodiment, and the motor housing 2 and the tail cover 32a are manufactured in an integrated configuration, and only the tail cover 32b can be separated. Alternatively, other configurations may be used.

  FIG. 3 is a view for explaining the flow of cooling air of the disc grinder 1 according to the embodiment of the present invention. There are mainly two air streams flowing into the housing (2, 32). One is sucked in the direction of arrow a from the air inlet 21 for cooling the motor, flows between the outer peripheral portion of the stator core 8 and the inner wall of the motor housing 2, the direction of flow in the vicinity of the stator holder 31 is reversed, and the motor 6 , The air flows between the coils of the stator core 8 or between the stator core 8 and the rotor 7, and then flows into the cooling fan 4 and is discharged from the discharge port 34 as indicated by an arrow c. The other is sucked in the direction of the arrow b from the air intake port 33, flows around the power supply circuit 17 and the FET 24 on the rear side, then flows to the cooling fan 4, and is discharged from the discharge port 34 as indicated by the arrow c. It is. The flow of these air is indicated by the arrows in FIG. 3, from which the cooling fan 4 sucks air from the front and rear sides in the axial direction and flows the air outward in the radial direction, that is, a centrifugal fan. You will understand that.

  The air taken in from the air inlet 21 flows forward through a slight gap existing between the stator core 8 and the inner wall of the motor housing 2 and reaches the vicinity of the stator holder 31. Since there are notched portions on the upper and lower sides of the stator retainer 31, the air flow direction is reversed through the notched portions. The air passing through the upper part of the stator core 8 and the lower part of the inner wall of the motor housing 2 changes its direction downward, and the air passing through the lower part of the stator core 8 and the upper part of the inner wall of the motor housing 2 changes its direction downward. Change. Thereafter, the air flows to the rear of the motor 6 through an air gap between the rotor 7 and the stator core 8. A rear wall for holding the bearing 13b is formed on the rear side of the motor housing 2, and a plurality of holes 2a are formed in the rear wall for passing the wiring 29 and flowing the air backward. Passes through the hole 2a and flows into the cooling fan 4.

  The air flow taken in from the air inlet 33 passes between the power supply board 27 and the control board 26, passes through a through hole provided near the center of the control board 26, and follows the rear surface of the position detection magnet 23. It flows to the outer peripheral side, flows along the FET 24, and flows into the cooling fan 4. The inflowing air is discharged from the discharge port 34 in the direction of the arrow c by the cooling fan 4 together with the air that has passed through the motor 6 part. A part of the air is sucked by the cooling fan 4 from the air outlet 34 through the air outlet 34 and is directly discharged from the air inlet 33 along the inner wall of the tail cover 32 to the air outlet 34. Since the air flow can cool the outer peripheral surface of the FET 24, the cooling effect can be further improved.

  In this embodiment, the FET 24 generating a large amount of heat is mounted on the control board 26, but four (or two) of the six FETs are arranged to face the cooling fan 4, and two (or four) are arranged. ) Is arranged on the side opposite to the cooling fan 4. By arranging in this way, the wind sucked from the air intake 33 flows around the FET 24 and then flows into the cooling fan 4, so that the FET 24 can be effectively cooled.

  Next, the cross-sectional structure of each part of the motor housing 2 will be described with reference to FIGS. FIG. 4 is a cross-sectional view taken along a line AA in FIG. In the present embodiment, the stator core 8 is composed of six divided cores 8a to 8f in order to realize the motor 6 having a small diameter. The divided cores 8a to 8f are divided into six in the circumferential direction for each tooth. A copper wire is wound around each tooth portion of the divided cores 8a to 8f to form a coil 9. In the present embodiment, the coil 9 is preferably a star connection having three phases of U, V, and W phases. The coil 9 (U, V, W) is supplied via the FET 24 with a current controlled in the energization section having an electrical angle of 120 ° based on the position detection signal of the rotational position detection element 43.

  Concave portions 81 that are continuous in the direction parallel to the rotation axis are formed on the outer peripheral sides of the divided cores 8a to 8f. After the stator core 8 is assembled by combining six divided cores 8a to 8f, the shaft formed in the motor housing 2 is formed. The stator core 8 is inserted from the opening on the front side of the motor housing 2 while guiding the recess 81 with the rib 2d extending in the direction, and the abutting portion formed on the motor housing 2 (on the inner wall side near the air inlet 21) Push it to the position where it comes into contact with the part where the inner diameter is smaller. The ribs 2d are four protrusions that are provided in the inner wall of the motor housing 2 and that are continuous in the axial direction in order to hold the stator core 8 around which the coil 9 is wound. 4 shows a state in which the concave portions 81 of the split cores 8b, 8c, 8e, and 8f are in contact with the rib 2d, but the concave portions 81 of the split cores 8a and 8d are not in contact with the ribs.

  FIG. 5 is a cross-sectional view taken along the line BB in FIG. It will be understood from this figure that air can flow through the gap 14 between the stator core 8 and the inner wall of the motor housing 2. Further, on the inner peripheral side of the stator core 8, a rotor 7 including a rotor core 7b and a cylindrical magnet 7a is rotatably held. Although it is difficult to understand from the drawing, there is a space that is continuous in the axial direction between each coil 9 and between the magnet 7a and the stator core 8, and air can flow through this space.

  6 is a cross-sectional view taken along the line CC in FIG. It will be understood that, in the CC section, the diameter of the motor housing 2 is increased, and five air intake ports 21 are formed on the upper and lower sides. The air intake 21 communicates with the gap 14 shown in FIG. Although there is a space between the inner wall on the left and right sides of the motor housing 2 and the stator core 8 and between the two ribs 2d, in this embodiment, the air intake port 21 communicating with this space is not provided. However, the air intake 21 may be provided on the side of the motor housing 2 so as to communicate with this space.

  The stator core 8 is incorporated into the motor housing 2 so as to be inserted rearward from the front opening of the motor housing 2. After the stator core 8 abuts against the rear end of the inner wall of the motor housing 2, the stator press 31 is inserted from the opening on the front side, and the gear cover 3 is screwed to the motor housing 2 so as to sandwich the bearing stopper 30. Note that this assembling involves operations such as assembling the rotor portion of the motor 6 and drawing the wiring 29 from the coil 9 into the tail cover 32, but the assembling procedure is almost the same as the conventional one. The description here is omitted.

  By configuring as described above, the stator core 8 can be easily assembled and fixed to the motor housing 2. In addition, since a small gap is formed between the outer periphery of the stator core 8 and the inner periphery (inner wall) of the motor housing 2 by this configuration, the cooling air can flow through this space, and the stator core 8 and the coil 9 can be improved. Can be cooled.

  FIG. 7 is a perspective view showing the shape of the cooling fan 4, as viewed obliquely from the front. The cooling fan 4 is a centrifugal fan configured by an integrated structure such as plastic or light metal, and has eight fins 4b extending in the circumferential direction from the cylindrical body portion 4a. A through hole 4c is formed inside the body portion 4a to allow the extended portion of the rotary shaft 10 to pass therethrough. The through hole 4c is formed with a notch 4d extending in the axial direction for accommodating the key 22 (see FIG. 1) which is a detent member.

  FIG. 8 is a view showing the shape of the stator retainer 31, wherein (1) is a front view and (2) is a side view. The stator press 31 is a holding member for fixing the stator core 8 inserted in the motor housing 2. In addition, it plays a role as a guide member for guiding the airflow flowing through the outer periphery and the inside of the motor 6. The basic shape of the stator retainer 31 is a cylindrical shape, and a cutout portion 31a is formed that is cut out over a range of about 80 ° on the upper and lower sides on the rear side. The remaining portion, that is, the side portion where the cutout portion 31a is formed becomes a pressing portion 31b protruding rearward. The pressing portion 31b can hold the stator core 8 so as not to move in the front-rear direction.

  As described above, according to the present embodiment, since the cooling fan is attached to the extending portion on the side opposite to the tip tool side, which is the rotating shaft of the motor, it is large without being limited by the size of the housing portion that accommodates the motor. A cooling fan having an outer diameter can be attached, and the inside of the housing can be effectively cooled. In addition, the air taken in from the air intake port provided near the rear end of the motor housing flows through the space between the outer wall of the motor and the motor housing to the vicinity of the front end of the motor and changes its direction. Since it flows between the rotors, flows into the cooling fan, and is discharged to the outside through the discharge port, the entire motor can be efficiently cooled from the front end to the rear end. Furthermore, since the switching element is cooled with air sucked from the air intake of the tail cover and then discharged to the outside through the discharge port, the switching element can be directly cooled with the outside air taken in, and a high cooling effect can be realized. Can do.

  Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 9 is a sectional view showing the entire disc grinder 51 according to the second embodiment. Parts having the same configurations as those of the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and repeated description is omitted. In the second embodiment, the difference from the first embodiment is the flow of air for cooling the motor 6. In the disc grinder 51, an air intake port 59 is provided above the gear cover 53 so as to take in air from the direction indicated by the arrow d. The air taken in from the air intake port 59 passes through a hole formed in the bearing stopper 60 and flows into the motor housing 62. Then, it flows through the space inside the stator core 8 of the motor 6, flows into the tail cover 32, and reaches the cooling fan 4. On the other hand, the air flow flowing in the direction of the arrow b from the air intake port 33 is the same as in the first embodiment, and is discharged by the cooling fan 4 in the direction of the arrow c.

  As described above, according to the second embodiment, the air taken in from the air intake near the front end of the motor housing 62 is converted into the space between the outer wall of the motor and the motor housing, and the space between the stator and the rotor of the motor. Since there is no reversal of the air flow direction inside the motor housing 2, the air can flow smoothly. Further, since the motor housing 62 has a simple shape, an increase in manufacturing cost can be suppressed as compared with the first embodiment. In the second embodiment, air is not passed between the outer side of the stator core 8 and the inner wall of the motor housing 62. However, if the air is passed through this space, the cooling effect can be further enhanced. It is possible to effectively prevent heat from being transferred to the operator's hand. Moreover, you may arrange | position the dust prevention means which prevents that dust penetrate | invades into an air intake. For example, it is possible to provide a configuration in which a breathable filter or a metal mesh is provided at the air intake, or a plurality of small holes are provided in the air intake.

  As mentioned above, although this invention was demonstrated based on the Example, this invention is not limited to the above-mentioned Example, A various change is possible within the range which does not deviate from the meaning. For example, in the above-described embodiment, the description has been given based on the disc grinder having an angle angle of 90 degrees. However, the present invention can be similarly applied not only to this configuration but also to an angle grinder having an arbitrary angle other than 90 degrees and other electric tools. .

1 Disc grinder 2 Motor housing
2a (Motor Housing) Hole 2b (Motor Housing) Extension 2c (Motor Housing) Small Diameter 2d (Motor Housing) Rib 3 Gear Cover 3a, 3b (Gear Cover) Opening
3c (gear cover) discharge port 3d (gear cover) male screw 3e (gear cover) female screw 3f (gear cover) cylindrical part 3g (gear cover) rib
4 Cooling Fan 4a (Cooling Fan) Body 4b (Cooling Fan) Fin 4c (Cooling Fan) Through Hole 4d (Cooling Fan) Notch 5 Grinding Wheel 6 Motor 7 (Motor) Rotor 8 (Motor) Stator core 9 Coil 10 (motor) Rotating shaft 11 Spindle 12 Wheel guard 13a, 13b Bearing 14 Clearance 15 Spindle case 15a Flange 15b (spindle case) Male screw 15c Screw hole 16 Control circuit 17 Power supply circuit 18 Power switch 19 Power cord 20 Capacitor 21 Air intake 22 Key 23 Position detection magnet 24 FET 25 Cover 26 Control board 27 Power supply board 28 Bolt 29 Wiring 30 Bearing stopper 31 Stator retainer 31a Notches 31b (stator pressing) pressing portion 32 tail cover
33 Air intake port 33 Discharge port 35a, 35b Screw boss 36 Lock pin 37 Screw 38 Bevel gear (first bevel gear)
39 Bevel gear (second bevel gear) 40 Bearing 41 Bolt 42 Screw 43 Rotation position detecting element 51 Disc grinder 53 Gear cover 59 Air intake 60 Bearing stopper 61 Stator retainer
62 Motor housing 81 Recessed portion 101 (divided core) 101 Disc grinder 102 Motor housing
103 Gear Cover 104 Tail Cover 105 Grinding Wheel 108 Handle 111 Lock Pin 114 Power Cord 118 Power Switch 119 Air Intake 132 Screw

Claims (13)

A motor having a rotating shaft;
A housing for housing the motor;
In the electric tool having a power transmission mechanism for transmitting the power from the rotating shaft to the spindle for rotating the tip tool,
An electric tool characterized in that a cooling fan is attached to a rotation shaft inside the housing and opposite to the tip tool side of the motor. The housing includes a motor housing that houses the motor, and a tail cover that is connected to the rear of the motor housing and formed thicker than the motor housing.
The power tool according to claim 1, wherein the cooling fan is accommodated in the tail cover.   The electric power tool according to claim 2, wherein the cooling fan is a fan having a diameter larger than an outer diameter of the motor. The motor is a brushless DC motor;
The electric tool according to claim 3, wherein a circuit board on which a switching element for driving the brushless DC motor is mounted is provided in the tail cover.   The power tool according to claim 4, wherein the circuit board is disposed behind the cooling fan so as to be perpendicular to an axial direction of the motor.   6. The rotating shaft and the spindle are arranged in a substantially orthogonal direction, and the power transmission mechanism includes bevel gears fixed to the rotating shaft and the spindle, respectively. The electric tool according to one item. An air intake is formed near the rear end of the motor housing,
The tail cover is provided with a discharge port,
The air taken in from the air intake port flows through the space between the outer wall of the motor and the motor housing to the vicinity of the front end of the motor and changes its direction, and flows between the stator and the rotor of the motor. Into the cooling fan,
The power tool according to claim 6, wherein the power tool is discharged to the outside through the discharge port. An air inlet is further formed behind the outlet of the tail cover,
Air is sucked from the air intake port of the motor housing and the air intake port of the tail cover by the cooling fan,
The power tool according to claim 7, wherein the motor and the switching element are cooled by the sucked air and then discharged to the outside through the discharge port. An air intake is formed near the front end of the motor housing,
The tail cover is provided with a discharge port,
The air taken in from the air intake port flows between the outer wall of the motor and the motor housing and between the stator and rotor of the motor and flows into the cooling fan.
The power tool according to claim 6, wherein the power tool is discharged to the outside through the discharge port. A motor having a rotating shaft;
A housing for housing the motor;
A tip tool holding portion that is driven by one end of the rotating shaft and can hold the tip tool;
A permanent magnet fixed to the other end of the rotating shaft;
A power tool comprising: a rotational position detecting element provided at a position facing the permanent magnet. A bearing for holding the rotating shaft;
The electric tool according to claim 10, wherein the permanent magnet is provided on a side opposite to the motor with respect to the bearing. A motor having a rotating shaft;
A housing for housing the motor;
A tip tool holding portion that is driven by the rotating shaft and can hold the tip tool;
A bearing for holding a rear portion of the rotating shaft,
An extending portion extending rearward of the bearing is provided on the rotating shaft,
A permanent magnet is fixed to the extending portion,
A power tool characterized in that a rotational position detecting element is provided at a position facing the permanent magnet.   The power tool according to claim 12, wherein a cooling fan capable of cooling the motor is fixed to the extending portion.

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