JP2007044845A - Electrical power tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrical power tool capable of inexpensively and rationally realizing low vibration and low noise. <P>SOLUTION: A structural body 20 having a parallel surface in the axial direction of a motor 2 is interposed between a stator 2b of the motor 2 and a housing 3 on a disc grinder (electrical tool) 1 with the motor 2 as a driving source built-in in the housing 3. Hereby, a passage of motor cooling air is formed of the parallel surface of the structural body 20, an outer surface of the stator 2b and an inner surface of the housing 3. Additionally, the structural body 20 is constituted of an elastic body or the whole or a part of the structural body 20 is constituted of a viscoelastic body. Furthermore, the structural body 20 is constituted of a member having higher heat conductivity than that of the housing 3. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power tool such as a disc grinder or a circular saw using a motor as a drive source.

  2. Description of the Related Art Electric tools that are driven by a motor and perform various operations such as cutting work materials such as concrete and wood and polishing metal welds and cut parts are widely known. As an example of this type of electric tool, the configuration of a disc grinder is shown in FIGS. 5 is a cutaway side view of the disc grinder, and FIG. 6 is a cross-sectional view taken along the line BB of FIG.

  A housing 3 having a substantially cylindrical shape of the illustrated disc grinder 1 incorporates a motor 2 as a drive source, and a rotor 2 a of the motor 2 is supported so as to be rotatable along the center of the housing 3. The both ends in the axial direction are rotatably supported by the front bearing 5 and the rear bearing 6.

  A pinion 7 is fixed to the tip of the rotor 2a, and the pinion 7 meshes with a gear 8 fixed to the spindle 9. The spindle 9 is rotatably supported by the gear cover 4 at two upper and lower positions via a bearing (not shown), and a tip tool 10 is fixed to the tip of the spindle 9.

  Therefore, when the rotor 2a of the motor 2 rotates, the rotation is transmitted to the tip tool 10 via the pinion 7, the gear 8 and the spindle 9, and the tip tool 10 is driven to rotate to cut a work material such as concrete (not shown). Required work such as cutting and grinding.

  By the way, the casing of the motor 2 includes a housing 3 that houses the motor 2, a handle 11, a gear cover 4, and a wheel guard 12.

  On the other hand, a cooling fan 13 for cooling the motor 2 is attached to the front side of the rotor 2a, and a centrifugal fan is used as the cooling fan 13. When the motor 2 is started and the cooling fan 13 is rotated by rotating the rotor 2a, the motor cooling air 15 is directed from the rear part (right side in FIG. 5) to the front part (left side in FIG. 5) by the fan guide 14. Flow occurs.

  The motor cooling air 15 is sucked into the housing 3 from the suction port 11a provided in the handle 11, and the motor cooling air 15 sucked into the housing 3 moves toward the front side of the housing 3 as indicated by an arrow in the figure. The motor 2 is cooled by passing through the gap between the rotor 2 a and the stator 2 b and the gap between the stator 2 b and the housing 3.

  In this type of disc grinder 1, the spindle 9 is subjected to loads such as the swinging of the rotor 2a, the collision force between the pinion 7 and the gear 8, the collision between the tip tool 10 and the work material (not shown), and the reaction force due to the machining. Then, the outer parts such as the housing 3 are transmitted to the outer parts such as the housing 3 through the support bearings 5 and 6 of the rotor 2a, so that the outer parts such as the housing 3 vibrate and noise generation is induced. Particularly, a loud sound is generated from the housing 3 having a large surface area, and this type of disc grinder 1 is often the largest noise source.

  As means for suppressing the generation of noise in the housing 3 as described above, the thickness of the outer parts such as the housing 3 is increased, or ribs are disposed to increase the rigidity thereof to suppress vibrations. A method is conceivable in which vibration transmission from a vibration source is interrupted by sandwiching an elastic body between a part such as 2a and the bearing holding part of the housing 3 and a coupling part of the part.

  Furthermore, it has been found that when the rib provided on the housing 3 is abutted against the stator 2b having a relatively small vibration amplitude, the vibration amplitude on the surface of the housing 3 becomes smaller and a higher noise reduction effect can be obtained.

  In the case of an electric tool including a cylindrical housing 3 such as the disc grinder 1, the stator 2 b of the motor 2 is opened on the mating surface with the gear cover 4 (see FIG. 5) before the gear cover 4 is assembled to the housing 3. However, the cross-sectional outer shape of the stator 2b is not a complete circular shape, but as shown in FIG. Ends 2c1 and 2c2 of the coil 2c protrude from both sides.

  Therefore, if an attempt is made to place a rib corresponding to the recess 2e on the outer surface of the stator 2b on the inner peripheral surface of the housing 3, the rib and the coil end 2c1 interfere with each other when the stator 2b is inserted. Could not be established.

  The concave portion 2e of the stator 2b is provided for reducing the weight of the stator 2b and securing the air path of the motor cooling air 15 after cooling the ends 2c1 and 2c2 of the coil 2c. Disturbances occurred when passing through the upstream coil end 2c1, which caused noise and reduced cooling efficiency.

By the way, as a method for reducing the noise of the motor in the electric tool, the most general method is to arrange a plurality of ribs in the housing to achieve high rigidity, or to increase the impact force of the gear as shown in Patent Document 1. In order to reduce this, a method has been proposed in which a gap is provided between the bearing and the housing in the axial direction of the shaft.
JP 2002-262509 A

  The method of reinforcing the ribs of the housing, which is one of the methods for reducing the noise of the motor in an electric power tool, can change the natural frequency of the housing, and is therefore effective for an excitation force having a specific frequency. However, the effect is small for an excitation force having a broadband frequency component such as an impact force.

  Further, in the method of increasing the thickness of each member such as the housing to increase the rigidity thereof, there is a problem that not only the power tool is increased in weight but the cost is not increased, but the handling and operability are deteriorated.

  On the other hand, the method of providing a gap as disclosed in Patent Document 1 has no reduction effect on noise generated by the vibration of the housing due to the swing of the rotor.

  In fact, no measures have been taken against problems such as noise caused by the disturbance of cooling air after cooling the motor coil and a decrease in cooling efficiency due to the flow loss of the cooling air.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an electric tool capable of rationally realizing low vibration and low noise at low cost.

  In order to achieve the above object, according to a first aspect of the present invention, there is provided an electric tool comprising a motor as a drive source incorporated in a housing, and a plane parallel to the motor axial direction between the motor stator and the housing. It is characterized by interposing a structure having

  According to a second aspect of the present invention, in the first aspect of the present invention, a motor cooling air passage is formed by the parallel surface of the structure, the outer surface of the stator, and the inner surface of the housing.

  A third aspect of the invention is characterized in that, in the first or second aspect of the invention, the structure is formed of an elastic body.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, all or a part of the structure is formed of a viscoelastic body.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the structure is formed of a member having a thermal conductivity higher than that of the housing.

  According to the first aspect of the present invention, the structure is interposed between the housing and the stator, and since the vibration amplitude of the stator is small, the vibration of the housing is directly suppressed by the stator and the structure, As a result, low vibration and low noise of the electric tool can be realized at low cost and reasonably.

  According to the second aspect of the present invention, the motor cooling air passage is formed by the parallel surface of the structure, the outer surface of the stator, and the inner surface of the housing. It is suppressed and low noise is realized, and the flow loss of the motor cooling air is suppressed to be small, and the cooling efficiency of the motor is increased.

  According to the third aspect of the present invention, since the structure is made of an elastic body, the structure is easily deformed when the structure is press-fitted or disassembled, and the assemblability and the maintenance are improved.

  According to the invention described in claim 4, since the structure includes a viscoelastic body, a high vibration energy absorption effect by the viscoelastic body can be obtained, and the vibration propagation of the stator to the housing can be more effectively performed. It is possible to cut off and realize further low vibration and low noise of the electric power tool. In addition, since the structure is easily deformed by using a viscoelastic body, the stator can be easily press-fitted into the housing, and the ease of assembly and maintenance during disassembly can be improved.

  According to the fifth aspect of the present invention, since the structure is composed of a member having a thermal conductivity higher than that of the housing, the heat of the stator can be efficiently transferred to the structure. Therefore, it is possible to efficiently dissipate heat, and the cooling efficiency of the motor can be further increased. Further, by improving the cooling efficiency of the motor, the cooling fan can be reduced in size, and the noise generated from the cooling fan can be kept low.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a cutaway side view of a disc grinder as an embodiment of an electric power tool according to the present invention, FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, and FIGS. 3 (a) to 3 (g) and FIGS. (C) is a perspective view which shows the various forms of a structure.

  Since the basic configuration of the disc grinder 1 shown in FIGS. 1 and 2 is the same as that of the conventional one shown in FIGS. 5 and 6, the description thereof will be omitted, and the characteristic configuration of the present invention will be described below. Only will be described. In FIG. 1 and FIG. 2, the same elements as those shown in FIG. 5 and FIG.

  As shown in FIGS. 1 and 2, also in the disc grinder 1 according to the present invention, a housing 2 accommodates a stator 2b combined with a coil 2c. In addition, as shown in FIG. 2, recesses 2e that are recessed toward the inner diameter side are formed at two locations on the outer periphery of the stator 2b, and between the recess 2e and the inner periphery of the housing 3, the motor 2 A long space S is formed in the axial direction (in the direction perpendicular to the paper surface of FIG. 2 and hereinafter simply referred to as “axial direction”).

  Further, end portions 2c1 and 2c2 of the coil 2c protrude from both sides in the axial direction of the stator 2b, and are between the end portions 2c1 and 2c2 of the coil 2c in the axial direction, and the recesses 2e of the stator 2b and In the two spaces S formed between the housing 3, a triangular cylindrical structure 20 having a parallel surface 24 in the axial direction is interposed as shown in FIG.

  Here, the height of the structure 20 is slightly larger than the height (diameter in the radial direction) of the space S between the housing 3 and the recess 2e of the stator 2b. Is accommodated in a compressed and deformed state, and the parallel surface 24, the outer surface of the recess 2e of the stator 2b, and the inner surface of the housing 3 form a long passage for motor cooling air in the axial direction. The structure 20 can be composed of an elastic body such as plastic, a metal material such as aluminum die casting, or a viscoelastic body such as rubber, but is composed of an elastic body such as plastic or a viscoelastic body such as rubber. This is more convenient because the elastic body 20 is easily deformed during press-fitting and disassembly, and the assemblability and maintainability are improved.

  Thus, in the actual working state of the disc grinder 1, the rotor 2a is swung around, the collision force between the pinion 7 and the gear 8, and further, the collision between the tip tool 10 and the work material (not shown) or machining. A load such as a reaction force is transmitted to outer parts such as the gear cover 4 and the housing 3 through the spindle 9 and the support bearings 5 and 6 of the rotor 2a.

  However, in the disc grinder 1 according to the present embodiment, since the structure 20 is interposed in the two spaces S formed between the recess 2e of the stator 2b and the housing 3, The housing 3 is always coupled to the stator 2b having a small vibration amplitude through the structure 20. Here, since the vibration amplitude of the stator 2 b is small, the vibration of the housing 3 is directly suppressed by the stator 2 b and the structure 20. As a result, low vibration and low noise of the disc grinder 1 can be realized at a low cost and with a simple structure in which the structure 20 is provided.

  The space S between the housing 3 and the stator 2b is a passage for motor cooling air after passing through the end 2c1 of the coil 2c protruding from the stator 2b, and the end 2c-1 of the coil 2c. After cooling, the structure of the motor cooling air flow is likely to be disturbed.

  However, in this embodiment, as described above, the motor cooling air after cooling the end 2c-1 of the coil 2c by the parallel surface 24 of the structure 20, the outer surface of the stator 2b, and the inner surface of the housing 3 is used. Since the passage is formed, the rectifying effect by the passage suppresses the disturbance of the motor cooling air inside the housing 3 (in the space S), thereby realizing low noise and reducing the flow loss of the motor cooling air to reduce the motor 2. The cooling efficiency is increased.

  Further, if the structure 20 is made of a high thermal conductivity material such as aluminum having a thermal conductivity higher than that of the housing 3, the heat of the stator 2b can be efficiently transmitted to the structure 20. Heat can be efficiently radiated from the structure 20. As a result, the cooling efficiency of the motor 2 can be further increased. Thus, by improving the cooling efficiency of the motor 2, it is possible to reduce the size of the cooling fan 13, and as a result, the noise generated from the cooling fan 13 can be kept low. When an aluminum material is used as the high thermal conductivity material constituting the structure 20, the thermal conductivity is 220 (W / m · K), and this value is the value of the stator 2b made of a silicon steel plate. The thermal conductivity is about 9 times larger than 25 (W / m · K), and the cooling effect by the structure 20 is increased.

  By the way, as the structure 20, a member having a T-shaped cross section shown in FIG. 3B, a member having a Y-shaped cross section shown in FIG. 3C, a member having a cross-sectional WH shape shown in FIG. A member having an H-shaped cross section shown in FIG. 3 (e), a round bar-like member shown in FIG. 3 (f), a cylindrical member shown in FIG. 3 (g), and the like can be employed. It has a parallel surface 24 and is made of an elastic body such as plastic, a metal material such as aluminum die casting, or a viscoelastic body such as rubber.

  Also, as shown in FIGS. 4A to 4C, a space S between the stator 2 b and the housing 3 is formed by using a composite part including a member 22 made of an elastic body or a metal material and a viscoelastic body 23 as a structure 21. The same effect as described above can be obtained even if it is interposed. In this case, since each structure 21 shown in FIGS. 4A to 4C is provided with the viscoelastic body 23, a high vibration energy absorption effect by the viscoelastic body 23 can be obtained, and the housing 3 Thus, vibration propagation of the stator 2b can be more effectively blocked, and further low vibration and low noise of the disc grinder 1 can be realized.

  Further, the structure 21 shown in FIGS. 4A to 4C has a parallel surface 24 parallel to the axial direction, and includes the parallel surface 24, the outer surface of the stator 2b, and the inner periphery of the housing 3. In order to form a passage for the motor cooling air after cooling the end 2c-1 of the coil 2c, the rectifying effect by this passage suppresses the disturbance of the motor cooling air inside the housing 3 (in the space S), thereby reducing low noise. As well as being realized, the flow loss of the motor cooling air is kept small, and the cooling efficiency of the motor 2 is increased.

  Moreover, since the structure 21 is easily deformed by using the viscoelastic body 23 for the structure 21, the stator 2b can be easily press-fitted into the housing 3, and the assemblability and the maintenance at the time of disassembly are improved.

  The present invention can be similarly applied to other arbitrary power tools using a motor as a drive source in addition to a disk grinder.

It is a fracture side view of a disc grinder as one form of electric tools concerning the present invention. It is the sectional view on the AA line of FIG. (A)-(g) is a perspective view which shows the various forms of a structure. (A)-(c) is a perspective view which shows the various forms of a structure. It is a fracture side view of a disc grinder as one form of the conventional electric tool. FIG. 6 is a sectional view taken along line B-B in FIG. 5.

Explanation of symbols

1 Disc grinder (electric tool)
2 motor 2a rotor 2b stator 2c coil 2c1 upstream coil end 2c2 downstream coil end 2e stator recess 3 housing 4 gear cover 5 front bearing 6 rear bearing 7 pinion 8 gear 9 spindle 10 tip tool 11 handle 12 Wheel guard 13 Cooling fan 14 Fan guide 15 Cooling air 20 Structure 21 Structure (composite part)
22 member 23 viscoelastic body 24 parallel plane S space

Claims (5)

In a power tool that has a motor built in a housing as a drive source,
A power tool characterized in that a structure having a plane parallel to the axial direction of the motor is interposed between the stator of the motor and the housing.   The electric tool according to claim 1, wherein a passage for motor cooling air is formed by the parallel surface of the structure, the outer surface of the stator, and the inner surface of the housing.   The electric tool according to claim 1, wherein the structure is made of an elastic body.   The electric tool according to any one of claims 1 to 3, wherein all or part of the structural body is formed of a viscoelastic body.   The power tool according to any one of claims 1 to 4, wherein the structural body is formed of a member having a thermal conductivity higher than that of the housing.

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