Portable grinder

Abstract

A portable sander is provided. The portable sander has an electric motor having a motor shaft; an output shaft arranged in parallel with the motor shaft and configured to transmit rotation of the motor shaft; a sanding section connected to the output shaft and configured to perform a sanding motion by rotation of the output shaft; a first bearing rotatably supporting the output shaft; and a second bearing arranged at a position closer to the sanding section than the first bearing in a direction in which the output shaft extends, i.e., an axial direction, and rotatably supporting the output shaft. The first bearing and the second bearing are arranged so as to be located at positions not overlapping with a constituent member located at a radially outermost position among constituent members of the electric motor, when viewed in a direction in which the motor shaft and the output shaft are arranged in parallel, i.e., an axial arrangement direction. Accordingly, it is possible to improve the layout within the device of the portable sander having two or more shafts arranged in parallel.

Description

Technical Field

[0001] This invention relates to a portable grinder. Background Technology

[0002] In the prior art, a portable grinder is known, which has an electric motor, an output shaft, and a grinding section. The output shaft is arranged parallel to the motor shaft of the electric motor and transmits the rotation of the motor shaft; the grinding section is connected to the output shaft and performs grinding motion through the rotation of the output shaft. For example, Patent Documents 1 and 2 disclose a grinder with such two shafts. In this grinder, the rotation of the motor shaft can be slowed down and transmitted to the output shaft and then to the grinding section. Furthermore, in the grinder disclosed in Patent Document 2, that is, in a grinder that uses a battery as the power source for the electric motor and the battery is configured to protrude rearward from the housing, by configuring the electric motor relative to the output shaft on the side opposite to the battery, the center of gravity of the grinder can be prevented from being excessively biased towards the battery side. As a result, the distribution of pressure when the grinder presses against the workpiece is made more uniform, thereby enabling uniform grinding.

[0003] [Existing Technical Documents]

[0004] [Patent Literature]

[0005] Patent Document 1: International Publication No. 2018 / 168421

[0006] Patent Document 2: Japanese Invention Patent Publication No. 2013-129016 Summary of the Invention

[0007] [The technical problem that the invention aims to solve]

[0008] However, there is still room for improvement in the internal layout of the aforementioned grinders. For example, in grinders with two shafts arranged in parallel, the dimensions in the direction of the two shafts inevitably increase, thus reducing the grinder's operability. This problem is not limited to grinders with two shafts arranged in parallel; it is prevalent in various portable grinders with two or more shafts arranged in parallel.

[0009] [Technical solutions used to solve technical problems]

[0010] According to one aspect of the present invention, a portable grinder is provided. The portable grinder includes an electric motor, an output shaft, a grinding section, a first bearing, and a second bearing. The electric motor has a motor shaft; the output shaft is arranged parallel to the motor shaft and configured to transmit rotation of the motor shaft; the grinding section is connected to the output shaft and configured to perform grinding motion via rotation of the output shaft; the first bearing rotatably supports the output shaft; the second bearing is arranged closer to the grinding section than the first bearing in the axial direction of the output shaft and rotatably supports the output shaft. The first and second bearings are configured such that, when viewed along the direction in which the motor shaft and the output shaft are arranged parallel to each other (i.e., the axial alignment direction), they are located at a position that does not overlap with the outermost radially arranged component of the electric motor.

[0011] According to this portable grinder, the components of the electric motor do not interfere with the first and second bearings used to support the output shaft. Therefore, compared to the case where at least one of the first and second bearings overlaps with the outermost radial component of the electric motor (hereinafter also referred to as the outermost component) when viewed from the shaft arrangement direction, the distance between the motor shaft and the output shaft can be reduced. Therefore, the size of the portable grinder in the shaft arrangement direction can be reduced. For example, in the case where the first bearing overlaps with the outermost component of the electric motor when viewed from the shaft arrangement direction, the output shaft, the first bearing, the retainer for holding the first bearing, and the outermost component are arranged in the shaft arrangement direction. On the other hand, according to this method, within the range where there is no contact with the motor shaft and the outermost component, the distance between the motor shaft and the output shaft can be reduced by an amount corresponding to the arrangement space of the first bearing and the retainer.

[0012] According to one aspect of the invention, the first bearing may also be configured to partially overlap with the electric motor when viewed along the axial direction. This arrangement further reduces the distance between the motor shaft and the output shaft.

[0013] According to one aspect of the present invention, the portable grinder may also have a controller configured to control the operation of an electric motor.

[0014] According to one aspect of the invention, the controller may also be configured on the side opposite to the motor shaft in the shaft arrangement direction relative to the output shaft. According to this method, since the distance between the controller and the electric motor becomes greater, the controller is less susceptible to the heat generated at the electric motor.

[0015] According to one aspect of the invention, the controller may also be configured in the axial direction at a position that at least partially overlaps with the output shaft. According to this method, compared to the case where the controller is configured in the axial direction at a position farther from the grinding section than the output shaft, the size of the portable grinder in the axial direction can be reduced.

[0016] According to one aspect of the present invention, the portable grinder may also include a battery mounting section. The battery mounting section may be configured in the axial direction relative to the output shaft on the side opposite to the motor shaft, and may also be usable for attaching and detaching the battery, which serves as the power source for the electric motor. The battery mounting section may be configured to hold the battery in a tilted position, moving further away from the output shaft as it moves towards the first bearing from the second bearing side. The controller may also be configured in the axial direction between the output shaft and the battery mounting section, tilted further away from the output shaft as it moves towards the first bearing side. According to this configuration, because the battery and controller are tilted, the axial dimension of the portable grinder can be reduced compared to a configuration where the battery and controller are parallel in the axial direction.

[0017] According to one aspect of the present invention, the portable grinder may have a battery.

[0018] According to one aspect of the present invention, in the aforementioned configuration where the battery mounting portion is tilted, the portable grinder has a housing for housing an electric motor, an output shaft, a first bearing, a second bearing, and a controller. The housing may also have a shape and size that allows the user to grip it, on the side opposite to the second bearing in the axial direction relative to the first bearing. The battery mounting portion may also be located at the end of the housing on the side opposite to the motor shaft in the axial alignment direction relative to the output shaft. According to this configuration, since the battery mounting portion is tilted, the battery mounted in the battery mounting portion can be prevented from protruding outwards in the axial direction beyond the grippable portion of the housing. Therefore, when the user grips the housing for grinding operations, interference between the battery and the user's arm can be suppressed. Furthermore, it can be ensured that the user-gripable portion of the housing is larger along the axial alignment direction. Therefore, the user can easily grip the housing. Also, when the battery is tilted as described above, the center of gravity of the portable grinder tends to shift towards the battery side relative to the output shaft, but when the grippable portion extends towards the battery side, the user can grip the portion closer to the center of gravity. Therefore, users can hold the portable grinder stably with less force.

[0019] According to one aspect of the present invention, the housing may also have a size and shape that does not protrude outward beyond the grinding section in the direction from the output shaft to the motor shaft. According to this approach, the housing can be prevented from obstructing the grinding operation. For example, if the housing protrudes outward beyond the grinding section, it may come into contact with protruding parts of the workpiece being ground or surrounding objects during the grinding operation, potentially resulting in the grinding section being unable to reach the corners of the area requiring grinding. According to this approach, such an undesirable situation will not occur. Portable grinders according to the above-described approaches can easily implement this approach even when manufacturing small portable grinders (i.e., portable grinders with a small grinding section area when viewed from the axial direction) because the distance between the motor shaft and the output shaft can be reduced.

[0020] According to one aspect of the invention, the portable grinder may also have a housing that at least houses the electric motor, output shaft, first bearing, and second bearing. The housing may have a size and shape that does not protrude outwards beyond the grinding section in the direction from the output shaft to the motor shaft. The aforementioned adverse conditions will not occur according to this approach.

[0021] According to one aspect of the present invention, the first bearing and the second bearing may each be a ball bearing. According to this method, a larger load can be borne by the first bearing and the second bearing. Attached Figure Description

[0022] Figure 1 This is a left view of a grinding machine according to an embodiment of the present invention.

[0023] Figure 2 This is a right view of the grinder.

[0024] Figure 3 This is the front view of the grinder.

[0025] Figure 4 It is a partial sectional view showing a portion of the grinding machine.

[0026] Figure 5 The section representing a part of the grinder is shown in cross-section. Figure 3 A partial sectional view of AA.

[0027] Figure 6 It is along Figure 2 A cross-sectional view of BB's grinder.

[0028] Figure 7 This is a right-hand view of the interior of the grinder, showing the state after the right housing has been removed.

[0029] [Explanation of reference numerals in the attached figures]

[0030] 10: Grinding machine; 20: Housing; 20a: Right housing; 20b: Left housing; 21: Bolt; 22: Upper part; 23: Switch; 30: Grinding part; 31: Grinding pad; 32: Base; 33a, 33b: Clamper; 34a, 34b: Operating handle; 35: Boss; 40: Battery; 45: Battery mounting part; 50: Electric motor; 51: Motor housing; 52: Motor shaft; 61: Output shaft; 62: First bearing; 63: Second bearing; 64, 65: Bearing retainer; 66, 67: Pulley; 68: Belt; 69: Bearing; 71: Balancer; 72: Bolt; 73: Leg; 74, 75: O-ring; 76: Sleeve; 80: Controller; 91: Fan; 92: Dust collection nozzle. Detailed Implementation

[0031] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Furthermore, in the following embodiments, an orbital sander (hereinafter simply referred to as a sander) 10 is illustrated as a portable grinder. The sander 10 illustrated in this embodiment is a small sander, that is, a type of sander with a small grinding area, also referred to as a miniature sander.

[0032] like Figure 1 and Figure 2 As shown, the grinder 10 includes a grinding section 30, an electric motor 50, and an output shaft 61. The motor shaft 52 of the electric motor 50 is arranged parallel to the output shaft 61. One end of the output shaft 61 is connected to the grinding section 30. The grinder 10 is configured such that the rotational driving force of the electric motor 50 is transmitted to the output shaft 61, and the grinding section 30 performs grinding motion through the rotation of the output shaft 61. Details will be described later.

[0033] In the following description, the direction in which the motor shaft 52 and the output shaft 61 are arranged parallel to each other is defined as the front-rear direction of the grinder 10. In the front-rear direction, the side where the motor shaft 52 is located is defined as the front side, and the side where the output shaft 61 is located is defined as the rear side. Furthermore, the direction in which the motor shaft 52 and the output shaft 61 extend is defined as the vertical direction of the grinder 10. In the vertical direction, the side where the grinding section 30 is located is defined as the lower side, and the opposite side is defined as the upper side. Furthermore, the direction orthogonal to the front-rear direction and the vertical direction is defined as the left-right direction of the grinder 10. In the left-right direction, the right side when viewing the front from the rear is defined as the right side of the grinder 10, and the opposite side is defined as the left side of the grinder 10.

[0034] like Figures 1-3As shown, the sander 10 has a housing 20. The housing 20 is a bottomed cylindrical shape with a closed upper end. The sander 10 is a so-called palm sander, and the upper part 22 of the housing 20 has a shape and size that allows a user to hold it. That is, the upper part 22 also functions as a handle for the user to hold with one hand when using the sander 10. Figure 3 As shown, the upper part 22 is shaped to gradually narrow in width towards the lower part, making it easy for the user to grip. The housing 20 is secured by multiple bolts 21 (see reference). Figure 2 The right shell 20a and left shell 20b will serve as the split shells (see reference). Figure 3 They are formed by combining with each other.

[0035] like Figure 4 As shown, the electric motor 50 is housed in the housing 20. The electric motor 50 is positioned approximately at the center of the housing 20 in the vertical direction and near the front end of the housing 20 in the front-rear direction (see reference). Figure 4 ), and is positioned approximately at the center of the housing 20 in the left-right direction (see reference). Figure 6 The electric motor 50, referred to as a can motor, has a motor housing 51 made of thin-walled sheet metal. The motor housing 51 houses the rotor, stator, and other components (not shown) that are constituent parts of the electric motor 50. In this embodiment, the electric motor 50 is a brushed motor. By using a can motor as the electric motor 50, it is not necessary to assemble the associated components one by one into the housing, thus improving assemblability. However, the electric motor 50 can also be a brushless motor. A motor shaft 52 extends from the lower end of the motor housing 51. A pulley 67 is fixed around the extending motor shaft 52.

[0036] like Figure 4 As shown, the output shaft 61 is rotatably supported within the housing 20 by a first bearing 62 and a second bearing 63. In this embodiment, the first bearing 62 and the second bearing 63 are ball bearings. As described above, the output shaft 61 extends vertically parallel to the motor shaft 52. The output shaft 61 is configured to be located at the center of the grinding section 30 (described later) when viewed vertically. The first bearing 62 supports the upper end of the output shaft 61. The first bearing 62 is fixed to the housing 20 by a bearing retainer 64. The second bearing 63 is located vertically below the first bearing 62 (in other words, closer to the grinding section 30 than the first bearing 62) and supports the output shaft 61 near its center. The second bearing 63 is fixed to the housing 20 by a bearing retainer 65. The bearing retainer 65 also supports the motor housing 51.

[0037] like Figure 4As shown, the first bearing 62 and the second bearing 63 are configured such that, when viewed from the front-to-back direction (in other words, the direction in which the motor shaft 52 is arranged parallel to the output shaft 61), they do not overlap with the outermost radially positioned component (also called the outermost component) of the electric motor 50. In other words, the first bearing 62 is positioned above the upper end of the outermost component in the vertical direction, and the second bearing 63 is positioned below the lower end of the outermost component in the vertical direction. Here, "radial" refers to a direction orthogonal to the direction in which the motor shaft 52 extends, i.e., the axial direction. In this embodiment, by... Figure 4 It can be seen that the outermost component is the motor housing 51. In the case that the electric motor 50 does not have a motor housing 51, generally speaking, if the electric motor 50 is an internal rotor type motor, the outermost component is the stator; if the electric motor 50 is an external rotor type motor, the outermost component is the rotor.

[0038] Furthermore, in this embodiment, as Figure 4 As shown, the first bearing 62 and the second bearing 63 are configured to partially overlap with the electric motor 50 when viewed from the top and bottom. Figure 4 In the example shown, the outermost component of the electric motor 50, namely the motor housing 51, overlaps with the outer rings of the first bearing 62 and the second bearing 63, as well as the bearing balls. However, it is also possible to overlap only with the outer rings. Alternatively, if the electric motor 50 does not have a motor housing 51, the first bearing 62 and the second bearing 63 may partially overlap with the outermost component as defined by the structure of the electric motor 50.

[0039] like Figure 4 As shown, a pulley 66 is fixed around the output shaft 61. The pulley 66 is adjacent to the second bearing 63 on its lower side. The pulley 66 is positioned to overlap with pulley 67 when viewed from the front-rear direction. An annular belt 68 (see reference) is wound between pulley 66 and pulley 67. Figure 4 , Figure 5 and Figure 7 In this embodiment, the diameter of pulley 66 is larger than the diameter of pulley 67. Therefore, the rotation of motor shaft 52 is slowed down and transmitted to output shaft 61. However, it is also possible that the rotation of motor shaft 52 is not slowed down and transmitted to output shaft 61.

[0040] like Figure 4As shown, a fan 91 is mounted around the output shaft 61, and further, on the underside of the pulley 66. The housing of the fan 91 communicates with the dust collection nozzle 92. The dust collection nozzle 92 extends rearward at its lower and rearward ends on the housing 20. A cloth dust collection bag, a synthetic resin dust collection box, or a flexible hose connected to the dust collector (none shown) can be mounted on the dust collection nozzle 92.

[0041] The grinding section 30 is located at the bottom of the grinder 10 and includes a grinding pad 31, a base 32, and clamps 33a and 33b. When viewed from above, the grinding pad 31 and the base 32 have a generally rectangular shape. The base 32 is disposed on the grinding pad 31, and the two are joined together by bolts (not shown) extending in the vertical direction.

[0042] Sandpaper (not shown) is mounted on the abrasive pad 31 using clamps 33a and 33b. Specifically, clamp 33a extends above the base 32 along the right and rear edges of the base 32, and an operating handle 34a is mounted at its front end. Clamp 33b extends above the base 32 along the left and front edges of the base 32, and an operating handle 34b is mounted at its rear end. With the sandpaper positioned on the bottom surface of the abrasive pad 31, operating handle 34a is operated to clamp the rear end of the sandpaper between the portion of clamp 33a extending along the rear edge and the base 32, and operating handle 34b is operated to clamp the front end of the sandpaper between the portion of clamp 33b extending along the front edge and the base 32. Thus, the sandpaper is fixed relative to the abrasive pad 31. The bottom surface of the abrasive pad 31 functions as a polishing surface when using the grinder 10.

[0043] like Figure 1 and Figure 2 As shown, the grinding part 30 protrudes forward from the housing 20 in the front-rear direction. In other words, the housing 20 has a size and shape that does not exceed the forward protrusion of the grinding part 30. Therefore, when performing grinding operations using the grinder 10, the housing 20 will not come into contact with the protruding parts of the workpiece or surrounding objects, thus preventing the grinding part 30 from reaching the corners of the area to be ground.

[0044] like Figure 4As shown, the grinding section 30 is connected to the output shaft 61 via a bearing 69. Specifically, the bearing 69 is clamped between the fan 91 and the base 32, surrounding the lower end of the output shaft 61. The bearing 69 is configured eccentrically relative to the output shaft 61. The inner ring of the bearing 69 is supported by a balancer 71 located below it. The balancer 71 is fixed to the output shaft 61 by bolts 72 that engage with threaded holes formed at the lower end of the output shaft 61. The balancer 71 has a shape in which its center of gravity is offset in the opposite direction to the eccentricity of the bearing 69 relative to the output shaft 61. Accordingly, the generation of vibration caused by the eccentricity of the bearing 69 relative to the output shaft 61 can be suppressed.

[0045] like Figure 5 and Figure 6 As shown, the grinding part 30 is also connected to the housing 20 via four legs 73. The legs 73 are respectively disposed near the four corners of the rectangular base 32. Each leg 73 has a generally cylindrical shape extending vertically. The upper and lower ends of the legs 73 are formed as tapered portions with relatively small diameters. An O-ring 74 is disposed around the upper tapered portion, which engages with the housing 20 via the O-ring 74. An O-ring 75 is disposed around the lower tapered portion, which engages with the inner surface of the boss 35 of the base 32 via the O-ring 75. The legs 73 can be tilted vertically while crushing the O-rings 74 and 75. A sleeve 76 is disposed around the legs 73 to prevent dust from entering. The sleeve 76 is made of sponge and is elastic, and is installed in a slightly crushed state in the vertical direction. This maintains a high degree of dust resistance for the legs.

[0046] like Figure 1 , Figure 2 and Figure 4 As shown, a battery mounting portion 45 is provided in the front-rear direction on the rear side relative to the output shaft 61 (in other words, on the side opposite to the motor shaft 52). More specifically, the battery mounting portion 45 is located at the rear end of the housing 20. The battery mounting portion 45 is configured to house the battery 40, which serves as the power source for the electric motor 50, in a sliding manner from top to bottom. In this embodiment, the battery 40 has a rated voltage of 18V. However, the battery 40 may also have a rated voltage greater than 18V.

[0047] The battery mounting portion 45 is inclined so that it is further upward (in other words, further upward from the side of the second bearing 63 towards the side of the first bearing 62) and further away from the output shaft 61. Specifically, the battery mounting portion 45 has a guide rail and a terminal holder, wherein the guide rail is housed within a guide groove formed on the battery 40; the terminal holder holds terminals for electrical connection with the battery 40, and the guide rail and terminal holder are inclined so that they are further upward and further away from the output shaft 61. Accordingly, when the battery 40 is mounted in the battery mounting portion 45, the battery 40 is held in an inclined state, further upward and further away from the output shaft 61.

[0048] With the battery 40 installed in the battery mounting portion 45, the battery 40 is held at its maximum lower position in the vertical direction, within a range that does not interfere with the dust collection nozzle 92. At this time, the upper end of the battery 40 is located at approximately the same position as the upper end of the housing 20 in the vertical direction. That is, by holding the battery 40 at an angle as described above, it is possible to prevent the upper end of the battery 40 from protruding excessively upwards beyond the housing 20. Therefore, when the user holds the housing 20 from the rear, the battery 40 does not interfere with the user's arm. Moreover, since the battery mounting portion 45 is configured at an angle as described above, it is possible to ensure that the upper part 22 of the housing 20 for the user to hold is positioned relatively far back. Therefore, it is easy for the user to hold the housing 20. Furthermore, when the battery 40 is configured at an angle as described above, the center of gravity of the grinder 10 tends to be biased towards the battery 40 side relative to the output shaft 61 located at the center of the grinding portion 30, but when the upper part 22 extends rearward, the user can hold the part close to the center of gravity. Therefore, users can hold the grinder 10 stably with less force.

[0049] like Figure 4 and Figure 5 As shown, a controller 80 is housed within the housing 20. The controller 80 is electrically connected to the terminals of the battery mounting section 45 and the electric motor 50, and controls the operation of the electric motor 50 by controlling the power supplied from the battery 40 to the electric motor 50. In this embodiment, the controller 80 has a high-temperature protection circuit, an overcurrent protection circuit, and an over-discharge protection circuit. However, one or both of these protection circuits may be omitted.

[0050] like Figure 4 and Figure 5 As shown, the controller 80 is positioned on the opposite side of the electric motor 50 in the front-to-back direction relative to the output shaft 61. In other words, the controller 80 is positioned between the output shaft 61 and the battery mounting portion 45 in the front-to-back direction. With this configuration, the distance between the controller 80 and the electric motor 50 is greater. As a result, the controller 80 is less susceptible to the heat generated at the electric motor 50.

[0051] And, as Figure 4 and Figure 5 As shown, the controller 80 is positioned in the vertical direction to partially overlap with the output shaft 61. That is, the controller 80 is positioned in the vertical direction such that, when viewed from a direction orthogonal to the vertical direction, the controller 80 partially overlaps with the output shaft 61. In this embodiment, the controller 80 partially overlaps with the output shaft 61 when viewed from the front-back direction. However, it is also possible for the controller 80 to partially overlap with the output shaft 61 when viewed from other directions orthogonal to the vertical direction (i.e., directions other than the front-back direction). Alternatively, the controller 80 may completely overlap with the output shaft 61. With this configuration, compared to positioning the controller 80 higher than the output shaft 61, the vertical dimensions of the grinder 10 can be reduced.

[0052] And, as Figure 4 and Figure 5 As shown, the controller 80 is tilted so that it is further upward (in other words, further upward from the side of the second bearing 63 towards the side of the first bearing 62) and further away from the output shaft 61. By tilting the controller 80 in the same orientation as the battery 40, the vertical dimensions of the grinder 10 can be reduced. In this embodiment, the tilt angle of the controller 80 is the same as the tilt angle of the battery mounting portion 45. Furthermore, one of the largest surfaces of the controller 80 faces upward and forward, while the largest surface on the opposite side faces downward and rearward. This configuration further reduces the vertical dimensions of the grinder 10.

[0053] like Figure 3 As shown, a switch 23 is provided on the upper part of the front surface of the housing 20. The switch 23 is electrically connected to the controller 80. The switch 23 is configured to start and stop the electric motor 50. The switch 23 has two buttons. One button is used to stop the electric motor 50. The other button is used to start the electric motor 50; each time the other button is pressed, the speed of the electric motor 50 changes sequentially in a preset number of increments.

[0054] The aforementioned grinder 10 operates as follows. First, when the user operates switch 23 to drive the electric motor 50, the motor shaft 52 begins to rotate. The rotation of the motor shaft 52 is transmitted to the output shaft 61 via pulleys 66 and 67 and belt 68. Since the bearing 69 connecting the output shaft 61 and the grinding unit 30 is eccentric relative to the output shaft 61, as the output shaft 61 rotates (rotates), the grinding unit 30 performs an eccentric circular motion (orbital motion) centered on the output shaft 61 while crushing the O-rings 74 and 75 arranged around the legs 73, causing the legs 73 to tilt. That is, the grinding unit 30 itself does not rotate, but moves in a circular motion along the horizontal plane while maintaining its posture. In this state, when the bottom surface of the grinding unit 30 is pressed against the workpiece, the eccentric circular motion of the grinding unit 30 functions as the grinding motion, and the sandpaper mounted on the bottom surface of the grinding unit 30 performs grinding.

[0055] According to the grinder 10, the first bearing 62 and the second bearing 63 are configured such that, when viewed from the front-rear direction, they do not overlap with the outermost component (i.e., the radially outermost component) of the electric motor 50. Therefore, the components of the electric motor 50 do not interfere with the first bearing 62 and the second bearing 63 used to support the output shaft 61. Therefore, compared to grinders in the prior art, the motor shaft 52 and the output shaft 61 can be brought closer together in the front-rear direction. Therefore, the size of the grinder 10 in the front-rear direction can be reduced. In particular, in the above embodiment, the first bearing 62 and the second bearing 63 are configured to partially overlap with the electric motor 50 when viewed from the vertical direction. Therefore, the size of the grinder 10 in the front-rear direction can be further reduced. As in the above embodiment, if the outer rings and bearing balls of the first bearing 62 and the second bearing 63 overlap with the electric motor 50, the gap between the motor shaft 52 and the output shaft 61 can be minimized.

[0056] Thus, by reducing the gap between the motor shaft 52 and the output shaft 61, even in a small grinder 10, the above-mentioned structure, which has the size and shape of the housing 20 not protruding forward beyond the grinding section 30, can be easily achieved.

[0057] The embodiments of the present invention have been described above, but these embodiments are for ease of understanding and are not intended to limit the invention. The present invention can be modified and improved without departing from its spirit, and its equivalents are included. Furthermore, within the scope of solving at least a portion of the above-mentioned technical problems or achieving at least a portion of the effects, any combination or omission of the structural elements described in the technical solution and specification is possible.

[0058] For example, if the diameter of the first bearing 62 is larger than the diameter of the second bearing 63, a configuration can be adopted such that, when viewed from the top and bottom, only the first bearing 62 partially overlaps with the outermost component, while the second bearing 63 does not partially overlap with the outermost component when viewed from the top and bottom. In this case, the gap between the motor shaft 52 and the output shaft 61 can sometimes be minimized. Furthermore, the first bearing 62 and the second bearing 63 can be positioned arbitrarily, as long as they are positioned so as not to overlap with the outermost component of the electric motor 50 when viewed from the front and back direction. This reduces the size of the device in the front and back direction compared to existing grinding machines.

[0059] Alternatively, the grinder 10 may have a power cord for connecting to an AC power source instead of the battery 40 and the battery mounting part 45.

[0060] Alternatively, one or more additional shafts may be installed between the motor shaft 52 and the output shaft 61. That is, the rotation of the motor shaft 52 may be transmitted to the output shaft 61 through one or more additional shafts.

[0061] Furthermore, the above embodiments are not limited to small orbital grinders, but can also be applied to any portable grinder in which the motor shaft and output shaft are arranged parallel. For example, the above embodiments can also be applied to large orbital grinders (also known as finishing grinders), random orbital grinders, and polishing machines.

Claims

1. A portable grinder, characterized in that, It includes an electric motor, an output shaft, a grinding section, a first bearing, and a second bearing, wherein... The electric motor has a motor shaft; The output shaft is arranged parallel to the motor shaft and configured to transmit the rotation of the motor shaft; The grinding section is connected to the output shaft and is configured to perform grinding motion by rotating the output shaft; The first bearing rotatably supports the output shaft; The second bearing is positioned closer to the grinding section than the first bearing in the axial direction of the output shaft, and rotatably supports the output shaft. The first bearing and the second bearing are configured such that, when viewed along the direction in which the motor shaft and the output shaft are arranged parallel to each other (i.e., the shaft alignment direction), they are located at positions that do not overlap with the outermost radially arranged component of the electric motor. The portable grinder also includes a controller configured to control the operation of the electric motor. The controller is configured on the opposite side of the motor shaft relative to the output shaft in the shaft arrangement direction. The controller is configured in the axial direction at a position that at least partially overlaps with the output shaft.

2. The portable grinder according to claim 1, characterized in that, The first bearing is configured to partially overlap with the electric motor when viewed along the axial direction.

3. The portable grinder according to claim 1, characterized in that, It has a battery mounting section, which is configured on the side opposite to the motor shaft in the shaft arrangement direction relative to the output shaft, and can be used to install and remove the battery that serves as the power source for the electric motor. The battery mounting section is configured to hold the battery in a tilted manner, such that the closer it moves from the second bearing side to the first bearing side, the further away it is from the output shaft. The controller is positioned between the output shaft and the battery mounting portion in the shaft alignment direction with an inclined orientation that moves further away from the output shaft as it moves from the second bearing side toward the first bearing side.

4. The portable grinder according to claim 3, characterized in that, It has the battery.

5. The portable grinder according to claim 3 or 4, characterized in that, It has a housing for housing the electric motor, the output shaft, the first bearing, the second bearing, and the controller. The housing has a shape and size that is user-friendly to hold on the side opposite to the second bearing in the axial direction relative to the first bearing. The battery mounting portion is located at the end of the housing on the side opposite to the motor shaft in the direction of the shaft arrangement.

6. The portable grinder according to claim 5, characterized in that, The housing has a size and shape that protrudes outward from the grinding section in the direction from the output shaft to the motor shaft.

7. The portable grinder according to any one of claims 1 to 4, characterized in that, It has a housing that at least accommodates the electric motor, the output shaft, the first bearing, and the second bearing. The housing has a size and shape that protrudes outward from the grinding section in the direction from the output shaft to the motor shaft.

8. The portable grinder according to any one of claims 1 to 4, characterized in that, The first bearing and the second bearing are both ball bearings.

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