Grinder

Abstract

To reduce the thickness of a head part of a flat head grinder.SOLUTION: The grinder includes an electric motor having a motor shaft extending in a first direction, a final output shaft extending in a second direction orthogonal to the first direction and configured such that a tool accessory can be attached thereto, and a first bearing supporting the final output shaft. The electric power steering device includes a second bearing that supports the final output shaft, a gear housing having a first through-hole that penetrates the gear housing in the second direction on a side opposite to the electric motor with respect to the final output shaft in the first direction and has a female screw, a bearing box that supports the second bearing and has a second through-hole that penetrates in the second direction coaxially with the first through-hole, and a screw that is screwed into the first through-hole and fixes the gear housing and the bearing box to each other in a state of being inserted in a direction from the bearing box toward the gear housing.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a grinder. [Background technology]

[0002] Grinders are known as a type of portable power tool. A grinder is a tool capable of performing various machining operations by transmitting the rotational driving force of a motor shaft of a motor to a spindle, thereby rotating and driving a tool bit attached to the spindle. One such type of grinder is known to have a layout in which the motor shaft and the spindle are perpendicular to each other. Such grinders are also called angle grinders. Among angle grinders, grinders with a thin head (i.e., the portion surrounding the spindle) are also called flat head grinders (see, for example, Patent Document 1 listed below). Flat head grinders allow the head to be inserted into narrow spaces where there are restrictions on the height at which the head can be inserted (in other words, the width in the direction in which the spindle extends when the grinder is in use) and allow machining of the narrow spaces. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2012 / 282846 Summary of the Invention [Problem to be solved by the invention]

[0004] In such flat head grinders, it is expected that the thickness of the head portion will be further reduced in order to improve convenience. [Means for solving the problem]

[0005] This specification discloses a grinder, which includes an electric motor having a motor shaft extending in a first direction, a final output shaft extending in a second direction perpendicular to the first direction and to which a tool accessory can be attached, a first bearing rotatably supporting the final output shaft, a second bearing located closer to the tool accessory than the first bearing in the second direction and rotatably supporting the final output shaft, a gear configured to transmit a rotational driving force of the motor shaft to the final output shaft, and a gear housing at least partially accommodating the gear, the electric motor having a motor shaft extending in a first direction relative to the final output shaft in the first direction. a gear housing having a first through hole penetrating the gear housing in a second direction on the opposite side to the first through hole and having a female thread; a bearing box positioned closer to the bit in the second direction than the gear housing and supporting a second bearing, the bearing box having a second through hole penetrating the bearing box in the second direction coaxially with the first through hole; and a screw that threads into the first through hole and fixes the gear housing and the bearing box to each other when inserted in a direction from the bearing box toward the gear housing.

[0006] According to this grinder, the first through hole is in the form of a through hole that penetrates the gear housing in the second direction. Therefore, when the first through hole is formed in the gear housing using a tap drill during the manufacturing stage of the grinder, the first through hole can be formed without any incomplete thread portion. Therefore, compared to conventional grinders in which the screw hole corresponding to the first through hole is a bottomed screw hole, the thickness of the gear housing at the location where the first through hole is located (i.e., the thickness of the head portion that is inserted into a narrow space with height restrictions) can be reduced by the length of the incomplete thread portion and the thickness of the gear housing that closes the screw hole. As a result, the head portion can be inserted into a space with greater height restrictions to perform machining, improving user convenience.

[0007] This specification further discloses a grinder that may include an electric motor having a motor shaft extending in a first direction, a tool accessory, a final output shaft extending in a second direction perpendicular to the first direction and to which the tool accessory can be attached, a first bearing rotatably supporting the final output shaft, a second bearing rotatably supporting the final output shaft and located closer to the tool accessory than the first bearing in the second direction, a gear configured to transmit rotational driving force of the motor shaft to the final output shaft, and a gear housing at least partially accommodating the gear. When the side where the final output shaft is located and the side where the electric motor is located in the first direction are defined as the front side and the rear side, respectively, and the side where the first bearing is located and the side where the second bearing is located are defined as the upper side and the lower side, respectively, an access angle, which is the angle between a first line extending from the front and upper edge of the tool bit to the rear and upper side and tangent to the gear housing, and a second line extending from the front and lower edge of the tool bit to the rear and lower side and tangent to a component of the grinder, as viewed in a direction perpendicular to the front-to-back direction and the up-down direction, may be less than 42 degrees.

[0008] With this grinder, the access angle is less than 42 degrees, so the thickness of the head portion is smaller than that of a conventional flat head grinder having an access angle of 42 degrees or more. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view of a grinder according to a first embodiment. FIG. [Figure 2] FIG. [Figure 3] FIG. [Figure 4] FIG. 4 is a partially enlarged view of FIG. [Figure 5] FIG. 4 is a partially enlarged view of FIG. [Figure 6] FIG. 3 is a partial vertical cross-sectional view of the grinder taken along line AA in FIG. 2. [Figure 7] FIG. [Figure 8] FIG. [Figure 9] FIG. [Figure 10] FIG. [Figure 11] FIG. 9 is a partial vertical cross-sectional view of the grinder taken along line BB in FIG. 8. [Figure 12] FIG. 8 is a longitudinal cross-sectional view taken along line BB in FIG. 7. [Figure 13] FIG. 10 is a perspective view showing an example of a state in which the cover is attached. [Figure 14] FIG. 1 is a perspective view showing the underside of the grinder, with the cover and tool insert removed. [Figure 15] FIG. 15 is a perspective view of the grinder with the pressing member of FIG. 14 removed. [Figure 16] FIG. 16 is a perspective view of the grinder with the sealing member of FIG. 15 removed. [Figure 17] FIG. 2 is a side view of a lead washer. [Figure 18] FIG. 4 is a cross-sectional view of the spindle and the inner flange when the electric motor is driven. [Figure 19] FIG. 10 is a cross-sectional view of the spindle and inner flange showing the maximum range of relative rotation between the spindle and inner flange. [Figure 20] FIG. 10 is a cross-sectional view of the spindle and inner flange according to the second embodiment when the electric motor is driven. [Figure 21] FIG. 10 is a cross-sectional view of a spindle and an inner flange according to a second embodiment, showing the maximum range of relative rotation between the spindle and the inner flange. DETAILED DESCRIPTION OF THE INVENTION

[0010] Representative, non-limiting embodiments of the present invention will now be described in detail with reference to the accompanying drawings. This detailed description is intended simply to provide those skilled in the art with details for implementing preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Additionally, additional features and inventions disclosed below may be used separately or in conjunction with other features and inventions to provide further improved devices, methods of making and using the same.

[0011] Furthermore, the combinations of features and steps disclosed in the following detailed description are not essential to practicing the invention in its broadest sense, but are described solely to illustrate specific exemplary embodiments of the invention. Furthermore, the various features of the exemplary embodiments described above and below, and those described in the independent and dependent claims, do not necessarily have to be combined in the exact embodiments described herein, or in the exact order listed, to provide additional and useful embodiments of the invention.

[0012] All features described in this specification and / or claims are intended to be disclosed individually and independently of one another as limitations on the original disclosure and claimed particulars, apart from any configuration of the features described in the embodiments and / or claims. Furthermore, all numerical ranges and group or aggregation descriptions are intended to disclose intermediate configurations thereof as limitations on the original disclosure and claimed particulars.

[0013] In one or more embodiments, the screw may be disposed within the first through hole such that the tip of the screw is recessed from the edge of the first through hole opposite the tool bit in the second direction by a distance greater than 0 mm and less than 1 mm. This configuration prevents the tip of the screw (the end opposite the head of the screw) from protruding from the gear housing. This allows the thickness of the grinder head to be minimized while preventing the tip of the screw from getting caught on a user's fingers or the workpiece.

[0014] In one or more embodiments, the edge of the first through hole opposite the tool bit in the second direction may have a chamfered shape. During the manufacturing process of a grinder, the gear housing is typically painted, and then the first through hole is formed using a tap drill. According to the above configuration, a gear housing having a chamfered shape around the location where the first through hole will be formed is created using a mold, the gear housing is painted, and then the first through hole is formed using a tap drill. This makes it difficult for the paint on the edge of the first through hole opposite the tool bit to peel off when the first through hole is formed.

[0015] In one or more embodiments, the first through hole may include a first side through hole and a second side through hole spaced apart in a third direction perpendicular to the first and second directions. The screw may include a first side screw inserted into the first side through hole and a second side screw inserted into the second side through hole. In a cross section passing through the axis of the first side screw and the axis of the second side screw, the edge of each of the first side through hole and the second side through hole opposite the tool bit in the second direction may be located closer to the tool bit than the center of the outer surface of the gear housing between the first side through hole and the second side through hole in the second direction. With this configuration, the height of the gear housing at the head portion is lower at both ends than at the center in the third direction. Therefore, when using the grinder by inserting the head portion into a narrow space with height restrictions, even if machining work is performed while rotating the head portion in the third direction (in other words, around the axis of the final output shaft), the head portion can be prevented from getting caught in surrounding obstacles.

[0016] A flat head grinder 10 (hereinafter simply referred to as the grinder 10) according to a first exemplary and non-limiting embodiment of the present disclosure will be described in more detail below with reference to the drawings. As shown in FIGS. 3 and 4 , the grinder 10 according to the first embodiment is configured to rotate a substantially disk-shaped tool bit 53 attached to a spindle 49. The spindle 49 is rotated by a rotational driving force provided by an electric motor 40. Grindstones, rubber pads, brushes, blades, and the like are available as tool bits 53 that can be attached to the grinder 10. A user selects an appropriate tool bit 53 depending on the desired processing operation and attaches it to the grinder 10. The grinder 10 can perform machining operations such as grinding, polishing, and cutting on a workpiece depending on the type of tool bit 53.

[0017] In the following description, the direction in which the motor shaft 41 of the electric motor 40 (in other words, the rotation axis AX1 of the electric motor 40) extends is defined as the front-rear direction of the grinder 10. In the front-rear direction, the side where the tool bit 53 is located is defined as the front side, and the opposite side is defined as the rear side. In addition, the direction in which the rotation axis AX2 of the spindle 49 (in other words, the rotation axis of the tool bit 53) extends is defined as the up-down direction of the grinder 10. In the up-down direction, the side where the tool bit 53 is located is defined as the bottom side, and the opposite side is defined as the top side. In addition, the direction perpendicular to the up-down direction and the front-rear direction is defined as the left-right direction of the grinder 10. In the left-right direction, the right side when viewed from the back side to the front side is defined as the right side of the grinder 10, and the opposite side is defined as the left side of the grinder 10.

[0018] 1 and 2, the grinder 10 includes a gear housing 20, a motor housing 30, a handle housing 31, and a rear housing 32. The gear housing 20, the motor housing 30, the handle housing 31, and the rear housing 32 are arranged in this order when viewed from the front.

[0019] The gear housing 20 accommodates a mechanical mechanism for transmitting the rotational driving force of the electric motor 40 to the tool bit 53 (details will be described later). The motor housing 30 accommodates the electric motor 40. In this embodiment, the electric motor 40 is a brushless motor. An operating member 36 for starting and stopping the electric motor 40 is disposed at the top of the motor housing 30. The electric motor 40 has an electric brake function. Specifically, when a user stops the electric motor 40 using the operating member 36 while the electric motor 40 is running, a current of the opposite phase flows through the electric motor 40, braking the electric motor 40. Then, after a predetermined time has elapsed or after the electric motor has rotated a predetermined angle, the power supply to the electric motor 40 is stopped. This allows the electric motor 40, and therefore the tool bit 53, to stop rotation early.

[0020] The handle housing 31 is intended to be gripped by the user's hand and has a generally cylindrical, elongated shape extending in the front-to-rear direction. A battery attachment section 33 to which a battery 34 can be attached and detached is located at the rear edge of the rear housing 32. The battery attachment section 33 is configured to be mechanically and electrically connectable to the battery 34. The electric motor 40 is configured to be driven by power from the battery 34. Alternating current power supplied from a commercial power source may be used instead of the battery 34.

[0021] As shown in FIG. 4 , the motor shaft 41 is rotatably supported by two bearings 44, 45 spaced apart in the front-rear direction. The bearing 44 is supported by the gear housing cover 35, which is disposed between the gear housing 20 and the motor housing 30, and supports the front end of the motor shaft 41. The bearing 45 is supported by the rear edge of the motor housing 30, and supports the rear end of the motor shaft 41. In this embodiment, the bearings 44, 45 are ball bearings, but they may also be needle bearings. In this embodiment, the bearings 44, 45 have different sizes (i.e., outer diameters). Specifically, the bearing 44 is larger than the bearing 45. However, the bearing 44 may be smaller than the bearing 45, or the bearings 44, 45 may have the same size.

[0022] As shown in FIG. 4 , a gear shaft 42 is coaxially connected to the motor shaft 41. The gear shaft 42 is accommodated in a gear shaft accommodating portion 22, which is the rear portion of the gear housing 20. The gear shaft accommodating portion 22 has a cylindrical shape that is closed in the circumferential direction of the rotation axis AX1, except for an opening 23 (described later). The gear shaft 42 is located in front of the motor shaft 41. A small bevel gear 43 is formed at the front end of the gear shaft 42. The gear shaft 42 is rotatably supported by two bearings 46 and 47 spaced apart in the front-rear direction. The bearing 46 supports the front end of the gear shaft 42, and the bearing 47 supports the rear end of the gear shaft 42. In this embodiment, the bearings 46 and 47 are ball bearings, but they may also be needle bearings. In this embodiment, the size of the bearing 46 is smaller than the size of the bearing 45. The bearing 47 has the same size as the bearing 44. That is, the bearing 46 located furthest forward is the smallest in size among the bearings 44 to 47. However, the bearings 46 and 47 may have the same size, in which case the bearings 46 and 47 may be smaller in size than the bearings 44 and 45.

[0023] As shown in FIG. 4 , the bearings 46 and 47 are supported on the cylindrical inner surface 24 of the gear shaft accommodating portion 22. Specifically, the bearing 46 is supported by a front support region 25 of the inner surface 24, and the bearing 47 is supported by a rear support region 26 of the inner surface 24. Due to the difference in size between the bearings 46 and 47, the inner diameter of the rear support region 26 is larger than the inner diameter of the front support region 25. With this configuration, the bearings 46 and 47 have different sizes (in other words, during the manufacture of the flat head grinder 10, the bearing 46, which is inserted first into the inner surface 24, is smaller in size than the bearing 47, which is inserted later), so that the bearings 46 and 47 can be well supported by molding only the front support region 25 and the rear support region 26, which support the bearings 46 and 47, respectively, with high precision. In other words, in contrast to when the bearings 46 and 47 have the same size, there is no need to precisely mold the entire area of ​​the inner surface 24, from the front support area 25 to the rear support area 26, with the same inner diameter. This makes it easier to manufacture the grinder 10.

[0024] As shown in FIG. 5 , the spindle accommodating portion 21 accommodates a large bevel gear 48, a first bearing 50, a second bearing 51, and an upper portion of a spindle 49. The rotational driving force of the motor shaft 41 is transmitted to the spindle 49 via the gear shaft 42 and the large bevel gear 48. Specifically, the large bevel gear 48 meshes with and is operably connected to the small bevel gear 43. The large bevel gear 48 is press-fitted around the periphery of the spindle 49 at the upper portion of the spindle 49, thereby firmly fixed to the spindle 49. The spindle 49 is rotatably supported about the rotation axis AX2 by a first bearing 50 and a second bearing 51 arranged spaced apart in the vertical direction. Specifically, the first bearing 50 directly supports the upper end of the spindle 49. The second bearing 51 is located below the first bearing 50. The second bearing 51 supports the radial outer edge of the large bevel gear 48 to be rotatable about the rotation axis AX2, and supports the spindle 49 via the large bevel gear 48. The rotation axis AX2 is perpendicular to the rotation axis AX1. A lower portion of the spindle 49 extends from the spindle accommodating portion 21.

[0025] As shown in Fig. 5, the lower edge of the spindle accommodating portion 21 is open. A bearing box 60 is attached to the lower edge of the spindle accommodating portion 21. As shown in Fig. 9, the bearing box 60 has a through-hole 69 in its center for inserting the spindle 49. The through-hole 69 extends in the vertical direction. As shown in Fig. 4, the thickness of the upper portion of the spindle accommodating portion 21 is smaller than the thickness of the upper portion of the gear shaft accommodating portion 22.

[0026] As shown in FIGS. 5 and 9 , the bearing box 60 includes a base 61 and a cover mounting portion 64. The base 61 includes a flat portion and a cylindrical portion that protrudes upward from the flat portion. The base 61 has a cylindrical inner surface 62. As shown in FIG. 5 , a step 63 that protrudes radially inward from the inner surface 62 is formed at the bottom of the base 61. The step 63 extends annularly in the circumferential direction. As shown in FIG. 5 , the second bearing 51 is disposed to fit into the inner surface 62 of the base 61. This restricts horizontal movement of the second bearing 51. The second bearing 51 is disposed such that its outer ring is sandwiched in the vertical direction between the inner surface of the spindle accommodating portion 21 and the step 63 of the base 61. This restricts vertical movement of the second bearing 51. The structure and function of the cover mounting portion 64 will be described later.

[0027] As shown in FIG. 5 , the second bearing 51 is further held by a bearing retainer 55. Specifically, the bearing retainer 55 includes a cylindrical portion 56 and a flange 57. The cylindrical portion 56 is a cylindrical portion extending in the up-down direction. The flange 57 extends annularly from the lower edge of the cylindrical portion 56 radially outward. The large bevel gear 48 has an annular recess 48a on its lower edge. The annular recess 48a extends in the circumferential direction about the rotation axis AX2. The bearing retainer 55 is fixed to the large bevel gear 48 with the cylindrical portion 56 housed in the annular recess 48a. Specifically, the bearing retainer 55 is firmly fixed to the large bevel gear 48 by press-fitting the cylindrical portion 56 into the side surface of the annular recess 48a. The inner ring of the second bearing 51 is sandwiched in the vertical direction between a step 48b formed on the upper portion of the large bevel gear 48 and a flange 57. The flange 57 extends radially outward beyond the inner ring of the second bearing 51, thereby preventing dust from entering the interior through the gap between the inner ring of the second bearing 51 and the flange 57.

[0028] As described above, the spindle 49 and the large bevel gear 48 are firmly fixed by press fitting, and the large bevel gear 48 and the bearing retainer 55 are also firmly fixed by press fitting. The second bearing 51 is fixed in the vertical direction by being sandwiched between the large bevel gear 48 and the bearing retainer 55, so the vertical positional relationship between the spindle 49, the second bearing 51, and the large bevel gear 48 is also firmly fixed. Furthermore, the outer ring of the second bearing 51 is sandwiched in the vertical direction between the inner surface of the spindle accommodating portion 21 and the step portion 63 of the bearing box 60. This restricts vertical movement of the second bearing 51. Therefore, even if the inner flange 54 (described later) receives an upward force from the bit 53 when the grinder 10 is in use, the large bevel gear 48 receives the upward force from the inner flange 54, and the large bevel gear 48 is prevented from moving upward relative to the second bearing 51. As a result, it is possible to prevent the meshing between the small bevel gear 43 and the large bevel gear 48 from deteriorating due to the large bevel gear 48 moving upward.

[0029] The bit 53 is attached to the spindle 49 by an inner flange 54 and a lock nut 59. Specifically, as shown in FIG. 5 , the inner flange 54 is disposed below the bearing retainer 55. The inner flange 54 has a first through-hole 54a through which the spindle 49 passes. An O-ring 54b is attached to the periphery of the spindle 49 below the inner flange 54. The O-ring 54b engages with the inner flange 54, thereby preventing the inner flange 54 from falling off the spindle 49.

[0030] As shown in FIG. 5 , a lock nut 59 is disposed below the inner flange 54. Specifically, the lock nut 59 has a second through hole 59a through which the spindle 49 passes. A male thread 49a is formed at the lower end of the spindle 49. Furthermore, a female thread that threadably engages with the male thread 49a is formed on the inner surface of the lock nut 59, which defines the second through hole 59a. By disposing the tool bit 53 between the inner flange 54 and the lock nut 59 and tightening the lock nut 59, the tool bit 53 is clamped in the vertical direction between the inner flange 54 and the lock nut 59, and the position of the tool bit 53 relative to the spindle 49 is fixed.

[0031] In the grinder 10 described above, when the user turns on the operating member 36 to drive the electric motor 40, the rotation of the motor shaft 41 is transmitted to the spindle 49 via the gear shaft 42 and the large bevel gear 48 while being decelerated. At this time, the direction of the rotational motion is also converted from the direction about the rotation axis AX1 to the direction about the rotation axis AX2. With this mechanism, the spindle 49 rotates about the rotation axis AX2 in conjunction with the rotation of the motor shaft 41, and as a result, the bit 53 fixed by the inner flange 54 and the lock nut 59 rotates together with the spindle 49.

[0032] 1, a cover 70 is removably attached to the bearing box 60 (the attachment method will be described later). The cover 70 partially covers the bit 53 in an arc shape along the circumferential direction about the rotation axis AX2.

[0033] The above-described bearing box 60 is fixed to the spindle accommodating portion 21 as follows. As shown in FIG. 6 , the spindle accommodating portion 21 has two first through holes 27 that penetrate the spindle accommodating portion 21 in the up-down direction, forward of the spindle 49. A female thread is formed on the inner surface of the spindle accommodating portion 21 that defines the first through holes 27. The two first through holes 27 are located near both ends of the spindle accommodating portion 21 in the left-right direction. The two first through holes 27 are also located near the front edge of the spindle accommodating portion 21. Although not shown, the spindle accommodating portion 21 also has two other through holes similar to the first through holes 27, rearward of the spindle 49.

[0034] As shown in Figures 6 and 9, the bearing box 60 has four second through holes 68 that penetrate the base 61 of the bearing box 60 in the up-down direction (only two second through holes 68 are shown in Figure 9). As shown in Figure 6, the four second through holes 68 are located at the four corners of the base 61, i.e., front, rear, left, and right. No internal threads are formed on the inner surface of the base 61 that defines the second through holes 68, and the second through holes 68 have a shape that fits the heads of screws 15, which will be described later. The four second through holes 68 are coaxial with the two first through holes 27 of the spindle accommodating portion 21 and the two through holes described above.

[0035] 1 and 6, the bearing box 60 is fixed to the spindle housing 21 by inserting and tightening a screw 15 from bottom to top, which screws into the female thread on the inner surface that defines the first through-hole 27. As shown in Fig. 14, screws 15 are similarly inserted and tightened into the two through-holes of the spindle housing 21 that are located behind the spindle 49.

[0036] According to the above-described configuration, the first through hole 27 is in the form of a through hole that penetrates the spindle accommodating portion 21 in the vertical direction. Therefore, when forming the first through hole 27 in the spindle accommodating portion 21 using a tap drill during the manufacturing process of the grinder 10, the first through hole 27 can be formed so that no incomplete thread portion exists at the upper end of the first through hole 27. Therefore, compared to conventional grinders in which the screw hole corresponding to the first through hole 27 is a bottomed screw hole (i.e., a screw hole closed at the top), the thickness of the spindle accommodating portion 21 at the location where the first through hole 27 is located can be reduced by the length of the incomplete thread portion and the thickness of the spindle accommodating portion that closes the screw hole. As a result, when machining a narrow space with height restrictions, it becomes easier to insert a head portion into the space, improving user convenience. The head portion is the front end portion of the spindle accommodating portion 21 and is the portion that needs to be inserted into the space when machining a narrow space with height restrictions.

[0037] Typically, when the screw hole corresponding to first through hole 27 is a bottomed screw hole, the length of the incomplete thread is about 4 mm, and the thickness of the spindle accommodating portion that closes the screw hole is about 2 mm. Therefore, with the above configuration having first through hole 27, the thickness of the head portion can be reduced by about 6 mm compared to conventional grinders.

[0038] The ease of inserting the head into a narrow space with height restrictions can also be evaluated by the access angle θ. As shown in FIG. 7, the access angle θ is the angle formed by the first line L1 and the second line L2. When viewed in the left-right direction, the first line L1 extends from the front and upper edge of the tool bit 53 to the rear and upper side and is tangent to the spindle housing 21. When viewed in the left-right direction, the second line L2 extends from the front and lower edge of the tool bit 53 to the rear and lower side and is tangent to a component of the grinder 10. In this embodiment, as shown in FIG. 7, the component that defines the second line L2 is the cover 70. However, the component that defines the second line L2 may vary depending on the configuration of the grinder 10.

[0039] When there are multiple lines that respectively contact the spindle housing 21 at multiple locations, the term "straight line tangent to the spindle housing 21" refers to the line that first contacts the spindle housing 21 when a line extending in the vertical direction from the front and upper edge of the tool bit 53 toward the upper side is gradually tilted rearward with the front and upper edge of the tool bit 53 as a fulcrum. Similarly, when there are multiple lines that respectively contact the component parts of the grinder 10, the term "straight line tangent to the component parts of the grinder 10" refers to the line that first contacts the component parts of the grinder 10 when a line extending in the vertical direction from the front and lower edge of the tool bit 53 toward the lower side is gradually tilted rearward with the front and lower edge of the tool bit 53 as a fulcrum.

[0040] The configuration with the first through hole 27 described above allows the access angle θ to be less than 42 degrees, in contrast to conventional grinders where the access angle θ is 42 degrees or greater. The access angle θ may be 40 degrees or less. In this embodiment, the access angle θ is 39 degrees.

[0041] As shown in FIG. 6 , in this embodiment, the screw 15 is disposed in the first through-hole 27 so that its tip 15 a is recessed from the upper edge 27 a of the first through-hole 27 by a distance D1. This configuration prevents the tip 15 a of the screw 15 from protruding upward from the spindle accommodating portion 21. This prevents the tip 15 a of the screw 15 from getting caught on a user's finger or a workpiece. Setting the distance D1 to a value greater than 0 mm and less than 1 mm can achieve this effect while minimizing the thickness of the head. The distance D1 may be determined taking into account dimensional tolerances so that the tip 15 a of the screw 15 does not protrude upward from the upper edge 27 a of the first through-hole 27.

[0042] 6, in this embodiment, the upper edge 27a of the first through hole 27 is chamfered to increase the diameter, forming a chamfered portion 28. During the manufacturing process of the grinder 10, the gear housing 20 is usually painted, and then the first through hole 27 is formed using a tap drill. In the configuration having the chamfered portion 28, the gear housing 20 having the chamfered portion 28 around the area where the first through hole 27 is to be formed is produced using a mold, the gear housing 20 is then painted, and then the first through hole 27 is formed using a tap drill. This makes it possible to prevent the paint on the upper edge 27a from peeling off when the first through hole 27 is formed.

[0043] As shown in FIG. 6, in this embodiment, in a cross section passing through the two axes of the two screws 15 located forward of the spindle 49 (i.e., the cross section shown in FIG. 6), the two upper edge portions 27a are located below the central portion 29 of the outer surface of the spindle accommodating portion 21 between the two first through holes 27 in the up-down direction. With this configuration, the height of the spindle accommodating portion 21 in the head portion is lower at both ends in the left-right direction than at the central portion 29. Therefore, when using the grinder 10 by inserting the head portion into a narrow space with height restrictions, even if machining work is performed while rotating the head portion left and right (in other words, around the axis of rotation AX2), it is possible to prevent the head portion from being caught by surrounding obstacles.

[0044] Furthermore, since grinder 10 includes gear shaft 42, the number of bearings, which are heat sources, is greater than that of a grinder that does not include gear shaft 42, resulting in a higher shell temperature. In particular, bearing 46 is located on the power transmission path closest to spindle 49 among bearings 44 to 47, and is therefore most susceptible to the effects of spindle vibration, which results in a higher shell temperature around bearing 46. However, in this embodiment, bearing 46 is the smallest among bearings 44 to 47, and therefore generates less heat, thereby reducing the shell temperature.

[0045] Furthermore, according to the grinder 10, the size of the bearing 46 is the smallest among the bearings 44 to 47, so as shown in Fig. 5, a space for forming a circumferential groove 25a for disposing the O-ring 25b can be secured in the front support region 25 on the inner surface of the gear shaft accommodating portion 22. As a result, the bearing 46 is supported by the gear shaft accommodating portion 22 via the O-ring 25b. With this configuration, the O-ring 25b can prevent leakage of grease for the bearing.

[0046] In an alternative embodiment, the number of bearings supporting the motor shaft 41 may be three or more. Alternatively, or in addition, the number of bearings supporting the gear shaft 42 may be one, or three or more. In this alternative embodiment, as long as the frontmost bearing among the bearings supporting the motor shaft 41 and the bearings supporting the gear shaft 42 has a size equal to or smaller than the smallest bearing among the remaining bearings, the shell temperature can be reduced and space for forming the circumferential groove 25a can be secured, just as in the present embodiment.

[0047] 8, the grinder 10 further includes a shaft lock mechanism 80. The shaft lock mechanism 80 is a mechanism for restricting rotation of the spindle 49 by restricting rotation of the gear shaft 42 when attaching or detaching the tool bit 53. By restricting rotation of the gear shaft 42, it is possible to prevent the spindle 49 from rotating together with the lock nut 59 when it is rotated.

[0048] As shown in FIG. 8, the shaft lock mechanism 80 includes a pin 81, an operating member 82, a biasing spring 83, and a stop ring 84. The pin 81 extends in the left-right direction so as to penetrate the right side surface of the gear shaft accommodating portion 22. A stop ring 84 is attached near the tip (left end) of the pin 81. When the stop ring 84 abuts against the inner surface of the gear shaft accommodating portion 22, the pin 81 is accommodated in the gear shaft accommodating portion 22 in a locked state so as to be movable in the left-right direction. An operating member 82 is connected to the base end (right end) of the pin 81. As shown in FIGS. 2 and 14, the operating member 82 is exposed to the outside of the gear shaft accommodating portion 22.

[0049] The biasing spring 83 is arranged in a compressed state between the operating member 82 and the outer surface of the gear shaft accommodating portion 22. The biasing spring 83 constantly biases the operating member 82 toward the right. Therefore, under normal circumstances, the pin 81 connected to the operating member 82 is also biased toward the right together with the operating member 82, and the pin 81 is maintained in a position where the stop ring 84 abuts against the inner surface of the gear shaft accommodating portion 22 (the position shown in FIG. 8 ).

[0050] As shown in FIG. 8 , the gear shaft 42 has an insertion opening 42a. The insertion opening 42a has a bottom and is located at a position corresponding to the pin 81 in the front-rear direction. The insertion opening 42a has a shape and size that fit the tip (left end) of the pin 81. When the user presses the operating member 82 leftward, the operating member 82 and the pin 81 move leftward against the biasing force of the biasing spring 83 and come into contact with the gear shaft 42. In this state, the user manually turns the spindle 49 until the insertion opening 42a faces the pin 81 (the position shown in FIG. 8 ). The tip of the pin 81 enters the insertion opening 42a of the gear shaft 42. This restricts the rotation of the gear shaft 42, and ultimately restricts the rotation of the spindle 49. In this state, the user can attach or detach the tool bit 53 by turning the lock nut 59 while pressing the operating member 82. When the user releases the pressure on the operating member 82, the pin 81 and the operating member 82 return to the position shown in FIG.

[0051] Next, a configuration for attaching and detaching the cover 70 will be described. As shown in Fig. 9, the bearing box 60 has a cover mounting portion 64 on the underside of the base 61. The cover mounting portion 64 protrudes downward in an annular shape from the lower surface of the base 61. The cover mounting portion 64 has a plurality of (five in the illustrated example) first protrusions 65 that protrude radially outward from the lower edge of the cover mounting portion 64. The multiple first protrusions 65 are spaced apart in the circumferential direction. Furthermore, the cover mounting portion 64 has a plurality of (five in the illustrated example) first recesses 66 between the multiple first protrusions 65 in the circumferential direction.

[0052] The multiple first protrusions 65 and the multiple first recesses 66 are spaced apart from the base 61 in the vertical direction, and as shown in Figures 5 and 9, a groove 67 is partially formed between the multiple first protrusions 65 and the base 61 along the circumferential direction.

[0053] As shown in FIGS. 1 and 10 , the cover 70 includes an upper cover 71 and a side cover 72. The upper cover 71 is a fan-shaped flat plate extending in a direction perpendicular to the up-down direction. The radial center of the upper cover 71 is cut out in a substantially arc-shaped manner. The radial inner edge of the upper cover 71 is partially cut out in the circumferential direction to form an open shape. This circumferentially cut-out portion is referred to as a cutout portion 79. As shown in FIG. 1 , the upper cover 71 partially covers approximately the rear half of the tool bit 53 above the tool bit 53. As shown in FIGS. 1 and 10 , the side cover portions 72 extend downward from the radial outer edge of the upper cover 71. As shown in FIG. 1 , the side cover portions 72 partially cover approximately the rear half of the tool bit 53 in a circular arc-shaped manner on the sides of the tool bit 53.

[0054] 10, the cover upper part 71 has a plurality of second protrusions 77 protruding radially inward on its radially inner edge. The plurality of second protrusions 77 (five in the illustrated example) are spaced apart in the circumferential direction. The cover upper part 71 also has a plurality of second recesses 78 (four in the illustrated example) between the plurality of second protrusions 77 in the circumferential direction.

[0055] When the rotational angle position of the cover 70 relative to the bearing box 60 is at a predetermined insertion position where the multiple first protrusions 65 and the multiple second recesses 78 are located at corresponding rotational angle positions and the multiple second protrusions 77 and the multiple first recesses 66 are located at corresponding angular positions, the multiple second protrusions 77 can pass through the multiple first recesses 66 of the bearing box 60 in the vertical direction. The multiple first protrusions 65 can also pass through the multiple second recesses 78 in the vertical direction. In this embodiment, the multiple first protrusions 65 and the multiple second protrusions 77 are configured so that the insertion position is uniquely determined (so that a unique relative rotational angle position is determined). Such a configuration can be achieved, for example, when at least one of the position, size, and shape of each of the multiple second protrusions 77 is asymmetric in the circumferential direction and at least one of the position, size, and shape of each of the multiple first recesses 66 exactly corresponds to each of the multiple second protrusions 77.

[0056] Such a cover 70 can be attached as follows. First, the user places the cover 70 in the insertion position relative to the bearing box 60, and then brings the cover 70 closer to the bearing box 60, fitting the cover 70 from below around the cover mounting portion 64 of the bearing box 60 until the top surface of the cover upper portion 71 abuts against the base 61. At this time, the multiple second protrusions 77 are positioned higher than the multiple first protrusions 65, and the cover 70 surrounds the bearing box 60 in the circumferential direction (more specifically, the cover upper portion 71 surrounds the portions of the bearing box 60 between the base 61 and the multiple first protrusions 65 and multiple first recesses 66). This relative position of the cover 70 with respect to the bearing box 60 is called the insertion position.

[0057] Next, the user rotates the cover 70 around the rotation axis AX2 relative to the bearing box 60 from the insertion position to a rotation angle position where the multiple first protrusions 65 and the multiple second protrusions 77 correspond to each other. An example of such a rotation angle position is shown in FIG. 13 . At this rotation angle position, the notch 79 faces forward, and the circumferential center of the cover side portion 72 coincides with the left-right center of the grinder 10. The rotation angle position shown in FIG. 13 is a rotation angle position in a typical use state of the grinder 10. At this time, as shown in FIG. 13 , the multiple second protrusions 77 of the cover 70 are received in the grooves 67 of the bearing box 60, and the multiple first protrusions 65 and the multiple second protrusions 77 are engaged in the vertical direction. This allows the cover 70 to be fixed to the bearing box 60 without being dislodged in the vertical direction.

[0058] As described above, the first protrusions 65 and the second protrusions 77 are configured to have uniquely determined insertion positions, so when the user rotates the cover 70 from the insertion position to a rotation angle position where the first protrusions 65 and the second protrusions 77 correspond to each other, the cover 70 will not come off the bearing box 60 in the vertical direction against the user's intention.

[0059] As shown in FIG. 7, when the cover 70 is attached, the cover 70 is positioned forward of the front edge of the gear housing cover 35 and the front edge of the motor housing 30, and at least partially overlaps with the lower portion of the gear housing cover 35 and the lower portion of the motor housing 30 when viewed in the front-to-rear direction.

[0060] In this embodiment, the first protrusions 65 and the second protrusions 77 are engaged in the vertical direction at five locations along the circumferential direction, thereby achieving stable (i.e., minimal rattle) vertical retention. However, the number of first protrusions 65 may be any number at least two or more. The same applies to the second protrusions 77.

[0061] Furthermore, in this embodiment, as shown in Fig. 10 , the two second protrusions 77 that are furthest apart in the circumferential direction among the multiple second protrusions 77 are circumferentially spaced apart by an angle greater than 180 degrees along the radially inner edge of the cover 70. In Fig. 10 , this separation angle is indicated as θ2. With this configuration, even if an attempt is made to displace the cover 70 from the side where the notch 79 of the cover 70 is located toward the side where the notch 79 is not located (i.e., toward the rear from the mounting position in Fig. 13 ), the side surfaces of the two second protrusions 77 that are furthest apart in the circumferential direction engage with the bearing box 60 (more specifically, the side surfaces that define the groove 67). This prevents the cover 70 from coming off the bearing box 60 in the horizontal direction and restricts horizontal movement of the cover 70.

[0062] Furthermore, the grinder 10 includes a structure for fixing the rotational angular position of the cover 70 relative to the bearing box 60 at an appropriate position. This structure will be described below. As shown in FIG. 10 , the cover 70 includes a lock plate 73 on the upper surface of the cover upper part 71. When viewed from above, the lock plate 73 has an arc shape that follows the arc shape of the cover side part 72. The lock plate 73 is located in the radially outer half of the cover upper part 71. The lock plate 73 includes an attachment part 74 and multiple engagement parts 75. The attachment part 74 is a part that is parallel to the cover upper part 71 and is fixed to the upper surface of the cover upper part 71 by any means (e.g., welding). The multiple engagement parts 75 extend upward from the radially inner edge of the attachment part 74 and are arranged along the arc shape of the lock plate 73. Multiple engagement grooves 76 are formed between the multiple engagement parts 75 in the circumferential direction.

[0063] As shown in FIG. 11 , the grinder 10 further includes a rotation-stop mechanism 90. The rotation-stop mechanism 90 includes an operating member 91 and a regulating plate 92. As shown in FIGS. 2 and 11 , the operating member 91 is disposed in a recess 22b formed on the left and upper edge of the gear shaft accommodating portion 22 so as to be exposed from the gear shaft accommodating portion 22. As shown in FIG. 11 , a pin 94 is inserted through a connecting portion 93, which is a substantially rectangular portion on the front and upper side of the regulating plate 92, and the operating member 91 in the left-right direction. The pin 94 is a C-shaped elastic pin and connects the regulating plate 92 and the operating member 91 so as to prevent relative movement. An opening 22a is formed in the bottom surface of the recess 22b of the gear shaft accommodating portion 22, penetrating the bottom surface in the up-down direction. The connecting portion 93 is disposed so as to penetrate the opening 22a. The regulating plate 92 is housed in the gear shaft accommodating portion 22 except for the portion above the connecting portion 93. The operating member 91 has a size that prevents it from passing through the opening 22a.

[0064] As shown in FIG. 11 , the regulating plate 92 extends rearward from the connecting portion 93 inside the gear shaft accommodating portion 22. The regulating plate 92 has a support shaft portion 95 at its rear edge. The support shaft portion 95 is an annular portion having a through hole extending in the left-right direction. The support shaft portion 95 is located rearward of the rear edge of the opening 22a. A pin 96 is inserted into the through hole. The pin 96 is a C-shaped elastic pin and is immovable relative to the support shaft portion 95. The left and right ends of the pin 96 are rotatably supported in bosses formed inside the gear shaft accommodating portion 22. With this configuration, the operating member 91 and the regulating plate 92 can pivot about the pin 96.

[0065] As shown in Fig. 11 , a biasing member 97 is arranged in a compressed state between the upper inner surface of the gear shaft accommodating portion 22 and the regulating plate 92, between the operating member 91 and the support shaft portion 95 in the left-right direction. The biasing member 97 constantly biases the regulating plate 92 downward. Therefore, the regulating plate 92 is held in a position (see Fig. 11 ) where the bottom surface of the connecting portion 93 abuts against a pressing member 110 (details will be described later) whose position relative to the gear shaft accommodating portion 22 is fixed. The position (initial position) of the operating member 91 and the regulating plate 92 at this time is also referred to as a regulating position.

[0066] 11 and 14, the pressing member 110 has a through-hole 111 extending in the up-down direction. The regulating plate 92 has an engaging portion 98 that protrudes downward from its lower edge. The engaging portion 98 is a generally rectangular portion whose longitudinal direction is the front-to-rear direction. The engaging portion 98 passes through the through-hole 111 of the pressing member 110 and extends below the pressing member 110.

[0067] In this anti-rotation mechanism 90, when a user places a finger on the lower portion of the left side of the operating member 91 and pulls it rearward, the operating member 91 and the regulating plate 92 pivot upward about the pin 96. As shown in FIG. 7, the operating member 91 is marked with an arrow indicating the operating direction. This operation also causes the engaging portion 98 to pivot upward. The operating member 91 and the regulating plate 92 can pivot up to a position where an upper surface 99 of the middle portion of the operating member 91 in the front-to-rear direction abuts against the bottom of the recess 22b. The position of the operating member 91 and the regulating plate 92 at this time (operation limit position) is also referred to as the allowable position.

[0068] 11 , when the operating member 91 and the regulating plate 92 are in the regulating position, the engaging portion 98 is in a vertical position where its tip (lower edge) can fit into the engaging groove 76 of the cover 70. On the other hand, when the operating member 91 and the regulating plate 92 are in the allowing position, the engaging portion 98 is in a vertical position where its tip (lower edge) cannot fit into the engaging groove 76 of the cover 70 (not shown). In other words, the tip of the engaging portion 98 is in a position above the engaging portion 75 of the cover 70.

[0069] Therefore, the user can attach the cover 70 by following the procedure below. First, the user places the cover 70 in the insertion position and rotates the cover 70 to a predetermined position while pulling the operating member 91 rearward. Next, the user releases the pulling operation of the operating member 91. As a result, the engaging portion 98 attempts to return to the engaging position due to the biasing force of the biasing member 97. At this time, if the engaging groove 76 of the cover 70 is directly below the engaging portion 98, the engaging portion 98 fits into the engaging groove 76. In this state, even if the user attempts to rotate the cover 70 further, the engaging portion 98 abuts (engages) with the side surfaces of the engaging portions 75 located on both sides of the engaging portion 98, thereby restricting the rotation of the cover 70. On the other hand, if the engaging groove 76 of the cover 70 is not directly below the engaging portion 98, the engaging portion 98 abuts against the upper surface of the engaging portion 75. When the user further rotates the cover 70 from this state, the engagement groove 76 is positioned directly below the engagement portion 98, and the engagement portion 98 fits into the engagement groove 76 due to the biasing force of the biasing member 97. In this way, the user can position the cover 70 at a predetermined rotational position in the circumferential direction (a rotational position where the circumferential position of any one of the multiple engagement grooves 76 and the engagement portion 98 coincides).

[0070] When removing cover 70, the user pulls operating member 91 rearward to displace engagement portion 98 to the permitted position. In this state, the lower edge of engagement portion 98 is positioned above the upper surface of engagement portion 75, disengaging engagement portion 98 from engagement portion 75 and permitting rotation of cover 70. Therefore, the user can remove cover 70 by rotating cover 70 to the insertion position and then pulling out cover 70.

[0071] The anti-rotation mechanism 90 allows the user to use the grinder 10 with the rotation angle position of the cover 70 fixed. In this embodiment, the operating member 91 is made of resin, and the regulating plate 92 is made of metal. This improves the usability of the operating member 91 and increases the durability of the regulating plate 92.

[0072] Furthermore, in this embodiment, because the cover 70 has the cutout 79, when performing cutting operations using the grinder 10 (for example, when a cutting wheel is used as the tool insert 53), the grinder 10 can be used with the opening of the cutout 79 facing the workpiece. This method of use allows for a greater cutting depth than when the radially inner edge of the cover 70 has a closed shape. Furthermore, in this embodiment, because the lock plate 73 has multiple engagement grooves 76, the cover 70 can be attached in various orientations. This allows the user to hold the grinder 10 in a desired position to perform cutting operations. For example, the user can perform cutting operations while holding the grinder 10 with the right side facing vertically downward.

[0073] The anti-rotation mechanism 90 having the above-described configuration may require replacement of the operating member 91 and / or the regulating plate 92 for repair. During such replacement, the pin 94 must be removed to release the connection between the operating member 91 and the regulating plate 92. However, when the operating member 91 is displaced to the permissible position, the pin 94 is positioned so as to overlap the gear shaft accommodating portion 22 in the left-right direction. Therefore, even if the pin 94 is pressed from the left to the right using a thin rod, the pin 94 abuts against the gear shaft accommodating portion 22 (more specifically, the left surface that defines the recess 22b), preventing the pin 94 from being removed from the operating member 91 and the regulating plate 92. Therefore, the present embodiment includes a configuration for removing the pin 94 from the operating member 91 and the regulating plate 92.

[0074] Specifically, as shown in FIG. 12 , a pin relief hole 22c is formed in the left side surface of the gear shaft accommodating portion 22 (more specifically, the left side surface that defines the recess 22b). The pin relief hole 22c is a bottomed hole that extends in the left-right direction and has a larger diameter than the pin 94. The pin relief hole 22c is located adjacent to the operating member 91. In this embodiment, the pin relief hole 22c is located coaxially with the pin 94 when the operating member 91 is in the initial position, i.e., the engaged position. A user can easily release the connection between the operating member 91 and the regulating plate 92 by pressing the pin 94 toward the right with a rod from the left side and inserting the pin 94 into the pin relief hole 22c.

[0075] The grinder 10 further includes a structure for suppressing rattle of the cover 70 in the up-down direction. This structure will be described below. As shown in FIGS. 4 and 16, the bottom 22d of the gear shaft accommodating portion 22 has an opening 23. The interior and exterior of the gear shaft accommodating portion 22 are in communication with each other through the opening 23. The opening 23 is formed for attaching a stop ring 84 (see FIG. 8) to the pin 81 during the manufacturing process of the grinder 10. The opening 23 is located rearward of the bearing box 60 in the front-rear direction. The opening 23 is also located between the bearing 46 and the bearing 47 in the front-rear direction. As shown in FIG. 16, four screw bosses 22e extending in the up-down direction are formed in the gear shaft accommodating portion 22 around the opening 23.

[0076] As shown in FIGS. 4 and 15, the opening 23 is closed by a seal member 100. As shown in FIG. 15, the seal member 100 includes a flat base 101, a front portion 102 located in front of the base 101, and a rear portion 103 located in rear of the base 101. The front portion 102 and the rear portion 103 respectively constitute the front edge and the rear edge of the seal member 100. The front portion 102 and the rear portion 103 each have a shape that fits the arc shape of the bottom portion 22d of the gear shaft accommodating portion 22. The rear edge of the front portion 102 and the front edge of the rear portion 103 are each closed. The seal member 100 is arranged so that the right and left edges of the base 101 are located on the flat surfaces 22f, 22g (see FIG. 16) of the gear shaft accommodating portion 22 and the front portion 102 and the rear portion 103 fit the arc-shaped portion of the bottom portion 22d. As a result, the opening 23 is completely blocked by the seal member 100. Furthermore, the seal member 100 is disposed at a position where it does not overlap with the screw boss 22e when viewed in the up-down direction.

[0077] As shown in FIG. 15 , the underside of the rear portion 103 has a flat portion, and a plurality of protrusions 104 (three in the illustrated example) are formed on this flat portion. Each of the plurality of protrusions 104 protrudes downward from the flat portion in a dome shape. The plurality of protrusions 104 are also arranged in the left-right direction. The number of protrusions 104 is not particularly limited and may be any number equal to or greater than one. No protrusion equivalent to the protrusion 104 is formed on the front portion 102. Therefore, the top of the protrusion 104 is located lower than the top of the front portion 102.

[0078] As shown in FIG. 15, a plurality of protrusions 105 (five on the right side and three on the left side in the illustrated example) are formed on each of the left and right edges of the base 101. The plurality of protrusions 105 are arranged adjacent to the opening 23 and at positions overlapping with the flat surfaces 22f, 22g (see FIG. 16) of the gear shaft accommodating portion 22 when viewed in the up-down direction. Each of the plurality of protrusions 105 protrudes downward from the base 101 in a dome shape. The plurality of protrusions 105 are arranged in the front-rear direction. The number of protrusions 105 is not particularly limited and may be any number equal to or greater than one.

[0079] As shown in FIG. 14, the grinder 10 includes a pressing member 110. The pressing member 110 is in the form of a plate and includes a central portion 112, a right side portion 113, and a left side portion 114. The central portion 112 has a shape that generally matches the shape of the base 101 of the seal member 100. The right side portion 113 and the left side portion 114 extend in the front-rear direction from the right edge and the left edge of the central portion 112, respectively. The right side portion 113 and the left side portion 114 are positioned so as to overlap the right protrusion 105 and the left protrusion 105 of the seal member 100 when viewed in the up-down direction. Each of the right side portion 113 and the left side portion 114 has two through holes spaced apart in the front-rear direction. The horizontal positions of these through holes coincide with the horizontal positions of the four screw bosses 22e (see FIG. 15).

[0080] 14, the pressing member 110 is placed on the sealing member 100 and fixed to the gear shaft accommodating portion 22 by four screws 17 inserted into the four through holes and the four screw bosses 22e of the pressing member 110. In this way, the pressing member 110 presses the sealing member 100 upward via the protrusions 105.

[0081] According to the above-described configuration, the opening 23 of the gear shaft accommodating portion 22 is closed by the seal member 100, thereby preventing dust from entering the interior of the gear shaft accommodating portion 22 through the opening 23. Furthermore, as shown in FIGS. 4 and 7 , when the cover 70 is attached so that the rear portion 103 of the seal member 100 is positioned directly above the cover upper portion 71, the cover 70 (more specifically, a portion of the cover 70 near the rear edge) comes into contact with the protrusion 104 in the vertical direction. This prevents the cover 70 from rattling in the vertical direction. Furthermore, the seal member 100, which is required for closing the opening 23 of the gear shaft accommodating portion 22 for dust prevention purposes during the manufacture of the grinder 10, can also be used to prevent rattling of the cover 70. Therefore, there is no need to provide a dedicated part for rattling prevention.

[0082] Furthermore, since the protrusion 104 that abuts against the cover 70 to prevent rattle is formed on the rear portion 103 of the seal member 100, the distance between the rotation axis AX2 and the point where the cover 70 abuts against the seal member 100 is greater than when the protrusion 104 is formed at a position radially inward from the rear portion 103. Since vertical rattle of the cover 70 increases toward the radially outer side, this configuration can effectively suppress vertical rattle of the cover 70.

[0083] Furthermore, since no protrusions are formed on the front portion 102 of the cover 70, the cover 70 and the front portion 102 do not come into contact with each other in the vertical direction, as shown in Fig. 4. Therefore, when the cover 70 is rotated to attach or detach it, the cover 70 does not get caught on the front portion 102 and receive a rearward force, causing the front portion 102 to not flip over (that is, the sealing performance for the opening 23 is not impaired). Even if the rear portion 103 receives a rearward force from the cover 70, in this case the rear portion 103 is not displaced in a direction that opens the opening 23, and therefore the sealing performance is not impaired.

[0084] Furthermore, both left and right edge portions of the seal member 100 are pressed toward the gear shaft accommodating portion 22 by the right side portion 113 and the left side portion 114 of the pressing member 110, thereby improving the sealing performance of the opening 23 by the seal member 100. Moreover, since the protrusion 105 of the seal member 100 abuts against the pressing member 110, the pressing force of the pressing member 110 is concentrated on the protrusion 105, thereby further improving the sealing performance.

[0085] In this type of grinder, it is common to provide a retaining mechanism (or horizontal movement restricting mechanism) at a position corresponding to the diameter of the cover (in other words, the diameter of the tool bit) for each grinder model (more specifically, models with different tool bit diameters). On the other hand, the grinder 10 described above can selectively attach multiple covers 70 of different diameters, as long as the cover 70 is sized to be adjacent to the gear housing cover 35 in the left-right direction (i.e., the cover 70 does not interfere with the gear housing cover 35). In Figure 7, the cover 70 when a tool bit 53 with a diameter of 125 mm is used is shown by a solid line, and the cover 70 when a tool bit 53 with a diameter of 150 mm is used is shown by a dotted line.

[0086] Specifically, multiple covers 70 with different diameters but with the same shape and size of the second protrusion 77 and the second recess 78 can be attached to the bearing box 60 without changing the design of the bearing box 60. In this case, the function of restricting the vertical and horizontal movement of the cover 70 can be achieved regardless of the diameter of the cover 70. Furthermore, by maintaining the same radial distance between the rotation axis AX2 and the lock plate 73 among multiple covers 70 with different diameters, the anti-rattle function can also be achieved regardless of the diameter of the cover 70. In other words, there is no need to change the design depending on the diameter of the cover 70 (the diameter of the tool bit 53). Therefore, during the manufacturing process of the grinder 10, multiple models of grinders 10 equipped with multiple covers 70 with different diameters can share the same body. As a result, the manufacturing cost of multiple types of grinders 10 can be reduced.

[0087] The grinder 10 further includes a mechanism for preventing the lock nut 59 from loosening. Such a mechanism will be described below. In this embodiment, as described above, the electric motor 40 has an electric brake function. Therefore, when a user operates the operation member 36 to stop the electric motor 40, the electric motor 40, and therefore the spindle 49, quickly stops. At this time, the inertia of the tool bit 53 may loosen the lock nut 59 threadedly attached to the spindle 49 (the lock nut 59 may rotate in a direction that causes it to fall off the spindle 49). The mechanism for preventing the lock nut 59 from loosening is provided to prevent such loosening of the lock nut 59.

[0088] As shown in FIG. 5 , a lead washer 58 is disposed between the inner flange 54 and the large bevel gear 48 in the vertical direction. The lead washer 58 has a self-locking function that prevents the lock nut 59 from loosening. The lead washer 58 is an annular member that surrounds the spindle 49, and a clearance is ensured between the lead washer 58 and the spindle 49 that allows the lead washer 58 to rotate relative to the spindle 49. The lead washer 58 is located radially inward of the bearing retainer 55. The lead washer 58 includes an upper lead washer 58a and a lower lead washer 58b.

[0089] As shown in FIG. 17, the upper lead washer 58a has an upper surface 152a, which is its upper end surface, and an upper cam surface 151a opposite the upper surface 152a. The lower lead washer 58b has a lower surface 152b, which is its lower end surface, and a lower cam surface 151b opposite the lower surface 152b. As shown in FIG. 5, the upper surface 152a of the upper lead washer 58a and the large bevel gear 48 abut against each other in the vertical direction. Furthermore, the lower surface 152b of the lower lead washer 58b and the inner flange 54 abut against each other in the vertical direction.

[0090] As shown in FIG. 17, upper cam surface 151a and lower cam surface 151b form a wedge structure that meshes with each other and faces each other. Specifically, upper cam surface 151a has a shape in which a lead surface with a constant gradient and a step are repeated along the circumferential direction. Lower cam surface 151b has a shape in which a lead surface with a constant gradient identical to that of upper cam surface 151a and a step are repeated along the circumferential direction. The gradient of the lead surfaces of upper cam surface 151a and lower cam surface 151b is greater than the lead angle of male thread portion 49a of spindle 49. The lowest point of the wedge shape of upper cam surface 151a is also referred to as apex 153a. The highest point of the wedge shape of lower cam surface 151b is also referred to as apex 153b.

[0091] With this lead washer 58, when the rotation of the spindle 49 is suddenly stopped by the electric brake function of the electric motor 40, the large bevel gear 48, which is press-fitted onto the spindle 49, also stops suddenly, but the inner flange 54, which is not press-fitted onto the spindle 49, continues to rotate due to inertia. At this time, frictional forces act between the large bevel gear 48 and the upper lead washer 58a and between the inner flange 54 and the lower lead washer 58b. As a result, relative rotation occurs between the upper lead washer 58a and the lower lead washer 58b from the state in which the upper lead washer 58a and the lower lead washer 58b are engaged as shown in FIG. 17. Specifically, the upper lead washer 58a and the lower lead washer 58b rotate relative to each other such that the apex 153a of the upper lead washer 58a climbs up the lower cam surface 151b of the lower lead washer 58b. This causes the gap between upper cam surface 151a and lower cam surface 151b to gradually increase, resulting in lower lead washer 58b being pressed downward by upper lead washer 58a.

[0092] As described above, the gradient of the lead surfaces of upper cam surface 151a and lower cam surface 151b is greater than the lead angle of male thread portion 49a of spindle 49. For this reason, when relative rotation occurs between upper lead washer 58a and lower lead washer 58b, the female thread formed on the inner surface that defines second through hole 59a of lock nut 59 cannot climb the threads of male thread portion 49a of spindle 49. As a result, lock nut 59 is prevented from rotating in the loosening direction.

[0093] The spindle 49 and the inner flange 54 have a structure for effectively achieving a self-locking function due to the relative rotation between the upper lead washer 58a and the lower lead washer 58b. Specifically, the spindle 49 and the inner flange 54 have a size and shape such that when the inner flange 54 rotates a predetermined angle relative to the spindle 49, the radially inner edge that defines the first through-hole 54a of the inner flange 54 comes into contact with the spindle 49, restricting further rotation.

[0094] More specifically, as shown in Fig. 18, the spindle 49 has two opposing flat surfaces 49b, 49c in a cross section perpendicular to the up-down direction. Furthermore, in this cross section, the spindle 49 has a partially circular outer shape between the flat surfaces 49b and 49c in the circumferential direction. Furthermore, the radially inner edge portion of the inner flange 54 that defines the first through-hole 54a has two opposing flat surfaces 54c, 54d in a cross section perpendicular to the up-down direction. In this cross section, the radially inner edge portion of the inner flange 54 has a partially circular outer shape that matches the outer shape of the partially circular portion of the spindle 49 between the flat surfaces 54c, 54d in the circumferential direction. The flat surfaces 54c, 54d are located at rotational angle positions that generally correspond to the flat surfaces 49b, 49c of the spindle 49, respectively.

[0095] When the electric motor 40 is running, one circumferential edge of each of the flat surfaces 49b and 49c of the spindle 49 abuts against the flat surfaces 54c and 54d of the inner flange 54, as shown in Fig. 18, and the rotational force of the spindle 49 is transmitted to the inner flange 54. On the other hand, when the rotation of the spindle is suddenly stopped by the electric brake function of the electric motor 40, the inner flange 54 rotates relative to the spindle 49 due to inertia. At this time, when only the clearance between the spindle 49 and the inner flange 54 is taken into consideration, the rotation is possible up to a maximum of the other circumferential edge of each of the flat surfaces 49b and 49c of the spindle 49 abutting against the flat surfaces 54c and 54d of the inner flange 54, as shown in Fig. 19. In this embodiment, the maximum relative rotation angle between the spindle 49 and the inner flange 54, considering only the clearance between them (i.e., the relative rotation angle between the spindle 49 and the inner flange 54 from the state in Figure 18 to the state in Figure 19), is 26 degrees.

[0096] In this embodiment, the maximum relative rotation angle is set to a rotation angle equal to or greater than the distance (shown as D2 in FIG. 17 ) required for the apex 153a of the upper lead washer 58a to climb one of the lower cam surfaces 151b of the lower lead washer 58b. In this embodiment, the rotation angle corresponding to the distance D2 is 22.5 degrees. This setting ensures a satisfactory self-locking function of the lead washer 58. Specifically, this prevents a situation in which the spindle 49 and the inner flange 54 come into contact with each other before the self-locking function of the lead washer 58 is fully exerted, preventing further relative rotation between the spindle 49 and the inner flange 54 and thus preventing relative rotation between the upper lead washer 58a and the lower lead washer 58b. In an alternative embodiment, the maximum relative rotation angle may be 10 degrees or greater and 35 degrees or less, or 10 degrees or greater and 30 degrees or less. In further alternative embodiments, the maximum relative rotation angle may be a rotation angle corresponding to a distance greater than or equal to 1 / 2 of the distance D2 and less than or equal to twice the distance D2, or may be a rotation angle corresponding to a distance greater than or equal to the distance D2 and less than or equal to 1.5 times the distance D2.

[0097] In this embodiment, both the spindle 49 and the inner flange 54 are made of iron. The inner flange 54 may be plated with unichromate. This prevents the circumferential edges of the flat surfaces 49b and 49c of the spindle 49 from biting into the flat surfaces 54c and 54d, respectively, and prevents the circumferential edges of the flat surfaces 49b and 49c from being damaged when the circumferential edges of the flat surfaces 49b and 49c of the spindle 49 abut against the flat surfaces 54c and 54d of the inner flange 54, as shown in FIG.

[0098] The second embodiment will be described below. The grinder 10 according to the second embodiment differs from the first embodiment only in that it includes an inner flange 254 instead of the inner flange 54. The second embodiment will be described below, focusing only on the differences from the first embodiment. As shown in FIG. 20 , the radially inner edge of the inner flange 254 includes two opposing first cutouts 254b, 254c and two opposing second cutouts 254d, 254e in a cross section perpendicular to the up-down direction. Each of the first cutouts 254b, 254c and the second cutouts 254d, 254e has a shape in which the radially inner edge of the inner flange 254 is partially cut out radially outward. In this cross section, the radially inner edge of the inner flange 54 has a partially circular outline that matches the partially circular outline of the spindle 49 between the first notches 254b, 254c and the second notches 254d, 254e in the circumferential direction.

[0099] 20 , when the electric motor 40 is driven and the spindle 49 is rotating, the second abutment portion 254h of the second cutout portion 254d comes into surface contact with the flat surface 49b of the spindle 49. Similarly, the second abutment portion 254i of the second cutout portion 254e comes into surface contact with the flat surface 49c of the spindle 49. This allows the inner flange 254 to rotate together with the spindle 49.

[0100] When the rotation of the spindle 49 is suddenly stopped by the electric brake function of the electric motor 40, the inner flange 54 rotates relative to the spindle 49 due to inertia. At this time, considering only the clearance between the spindle 49 and the inner flange 254, as shown in FIG. 21 , the rotation is possible up to the point where the first abutment portion 254f of the first cutout portion 254b comes into surface contact with the flat surface 49b of the spindle 49. At this time, the first abutment portion 254g of the first cutout portion 254c also comes into surface contact with the flat surface 49c of the spindle 49. The maximum relative rotation angle between the spindle 49 and the inner flange 254, considering only the clearance between them, is 26 degrees, as in the first embodiment. Therefore, as in the first embodiment, sufficient relative rotation between the upper lead washer 58a and the lower lead washer 58b is permitted, allowing the lead washer 58 to effectively exhibit its self-locking function.

[0101] According to this configuration, the spindle 49 and the inner flange 254 come into surface contact with each other, which can prevent deformation of the spindle 49 and / or the inner flange 254 when they come into contact, and can prevent the spindle 49 from biting into the inner flange 254. Because such an effect can be obtained, the inner flange 254 does not need to be unichromate plated.

[0102] Although the embodiments have been described above, the above-described embodiments are intended to facilitate understanding of the present teachings and are not intended to limit the present invention. The present invention may be modified or improved without departing from the spirit thereof, and the present invention includes equivalents thereof. Furthermore, any combination or omission of each component described in the claims and specification is possible within the scope of solving at least part of the above-described problems or achieving at least part of the effects.

[0103] For example, the shapes and configurations of the components of the grinder 10 described above are merely examples, and any changes are possible as long as the functions of the components are ensured.

[0104] The correspondence between each component of the above embodiment and each component of the claims is shown below. However, each component of the embodiment is merely an example and does not limit the components of the present invention. The grinder 10 is an example of a "grinder." The front-to-rear direction is an example of a "first direction." The up-to-down direction is an example of a "second direction." The electric motor 40 is an example of an electric motor. The motor shaft 41 is an example of a "motor shaft." The spindle 49 is an example of a "final output shaft." The tool bit 53 is an example of a "tool bit." The first bearing 50 is an example of a "first bearing." The second bearing 51 is an example of a "second bearing." The large bevel gear 48 is an example of a "gear." The gear housing 20 is an example of a "gear housing." The first through hole 27 is an example of a "first through hole." The bearing box 60 is an example of a "bearing box." The second through hole 68 is an example of a "second through hole." The screw 15 is an example of a "screw." The upper edge 27a is an example of an "edge" of the first through hole. The first straight line L1 is an example of a "first straight line." The second straight line L2 is an example of a "second straight line." [Explanation of symbols]

[0105] 10...Grinder 15...Screw 15a...tip 17...Screw 20...Gear housing 21...Spindle housing 22...Gear shaft housing 22a...Aperture 22b...recess 22c...hole 22d...bottom 22e...Screw boss 22f...Flat surface 23...Aperture 24...Inside 25...Anterior support area 25a...Circumferential groove 25b...O-ring 26... Posterior support area 27...First through hole 27a...upper edge 28...Chamfer 29...Central part 30...Motor housing 31...Handle housing 32...Rear housing 33...Battery compartment 34...Battery 35...Gear housing cover 36...Operating member 40...Electric motor 41...Motor shaft 42...Gear shaft 42a...insertion port 43...Small bevel gear 44, 45, 46, 47...Bearings 48...Large bevel gear 48a...Annular recess 48b...Double section 49...Spindle 49a...male thread 49b,49c...plane 50...First bearing 51...Second bearing 53... Tip tool 54...Inner flange 54a...first through hole 54b...O-ring 54c,54d...plane 55...Bearing retainer 56...Cylindrical part 57...Flange 58...Lead washer 58a...Upper lead washer 58b...Lower lead washer 59...Lock nut 59a...Second through hole 60...Bearing box 61...Bass 62...Inside 63...Double section 64...Cover mounting part 65...First protrusion 66...First recess 67...Groove 68...Second through hole 69...Through hole 70...Cover 71...Top of cover 72...Cover side 73...Lock plate 74...Mounting part 75...Engagement part 76...Engagement groove 77...Second protrusion 78...Second recess 79...Notch 80...Shaft lock mechanism 81...pin 82...Operating member 83... bias spring 84...Stop ring 90...Anti-rotation mechanism 91...Operating member 92...Regulatory plate 93...Connection part 94...pin 95...Spindle part 96...pin 97... Urging member 98...Engagement part 99...Top surface 100...Sealing material 101...Bass 102...Front 103...rear 104,105...protrusion 110...Pressing member 111...Through hole 112...Central part 113...Right side 114...left side 151a...Upper cam surface 151b...lower cam surface 152a...Top surface 152b...bottom surface 153a, 153b...vertex 254...Inner flange 254b, 254c...First notch 254d, 254e...Second notch 254f, 254g...First contact part 254h, 254i...Second contact part L1...first line L2...Second line AX1...rotation axis AX2...rotation axis

Claims

1. a grinder, an electric motor having a motor shaft extending in a first direction; a final output shaft extending in a second direction perpendicular to the first direction and capable of mounting a tool bit; a first bearing that rotatably supports the final output shaft; a second bearing located closer to the tool bit than the first bearing in the second direction and rotatably supporting the final output shaft; a gear configured to transmit rotational drive force of the motor shaft to the final output shaft; a gear housing that at least partially accommodates the gear, the gear housing having a first through-hole that penetrates the gear housing in the second direction on a side opposite to the electric motor with respect to the final output shaft in the first direction and has an internal thread; a bearing box that is located closer to the tool bit than the gear housing in the second direction and supports the second bearing, the bearing box having a second through hole that penetrates the bearing box in the second direction coaxially with the first through hole; a screw that is threaded into the first through hole, the screw being inserted in a direction from the bearing box toward the gear housing to fix the gear housing and the bearing box to each other; A grinder comprising:

2. 2. The grinder of claim 1, The screw is disposed in the first through hole such that a tip of the screw is recessed by a distance greater than 0 mm and less than 1 mm from an edge of the first through hole on the opposite side to the tool bit in the second direction. Grinder.

3. 3. The grinder according to claim 1 or 2, The edge of the first through hole on the opposite side to the tool bit in the second direction has a chamfered shape. Grinder.

4. 4. The grinder according to claim 1, wherein: the first through hole includes a first side through hole and a second side through hole that are spaced apart in a third direction that is orthogonal to the first direction and the second direction, the screws include first side screws inserted into the first side through holes and second side screws inserted into the second side through holes, In a cross section passing through an axis of the first-side screw and an axis of the second-side screw, the edge portion of each of the first-side through hole and the second-side through hole on the opposite side to the bit in the second direction is located closer to the bit in the second direction than a center portion of an outer surface of the gear housing between the first-side through hole and the second-side through hole. Grinder.

5. a grinder, an electric motor having a motor shaft extending in a first direction; Tip tool and a final output shaft extending in a second direction perpendicular to the first direction and to which the tool bit can be attached; a first bearing that rotatably supports the final output shaft; a second bearing located closer to the tool bit than the first bearing in the second direction and rotatably supporting the final output shaft; a gear configured to transmit rotational drive force of the motor shaft to the final output shaft; a gear housing that at least partially accommodates the gear; Equipped with When the side where the final output shaft is located and the side where the electric motor is located in the first direction are defined as the front side and the rear side, respectively, and the side where the first bearing is located and the side where the second bearing is located are defined as the upper side and the lower side, respectively, an access angle, which is an angle formed by a first line extending from the front and upper edge of the tool bit to the rear and upper side and tangent to the gear housing, and a second line extending from the front and lower edge of the tool bit to the rear and lower side and tangent to a component of the grinder, when viewed in a direction perpendicular to the front-to-rear direction and the up-down direction, is less than 42 degrees. Grinder.

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