Fixing parts and cutting tools

Abstract

Provided are a fixing component and a cutting tool, which can be miniaturized while ensuring sufficient strength, and can fix a cutting blade with high strength. A fixing component, which presses and fixes a cutting blade set on a blade mounting portion of a tool body, comprises: a fixing component body having a pressing portion for pressing the cutting blade; an engaging protrusion protruding from the bottom of the fixing component body and engaging in an engaging hole formed on the tool body; and an engaging recess formed on the circumferential surface of the engaging protrusion, wherein the front end of a fixing screw is engaged, and the front end of the fixing screw is screwed into an internal thread connected to the engaging hole of the tool body; the engaging protrusion is pulled into the engaging hole by the fixing screw engaged in the engaging recess, so that the pressing portion presses and fixes the cutting blade.

Description

Technical Field

[0001] The invention relates to a fixing component and a cutting tool. Background Art

[0002] A cutting tool for cutting a workpiece includes: a tool body; a cutting insert provided on a mounting portion of the tool body; and a fixing member for fixing the cutting insert to the tool body (for example, see Patent Document 1). In the cutting tool, a screw is inserted into a through hole formed on the fixing member, and the screw is screwed and tightened to a threaded hole of the tool body, thereby pressing and fixing the cutting insert to the tool body through the fixing member.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2018 / 034339 Summary of the invention

[0006] Technical issues to be solved

[0007] However, in the above-mentioned cutting tool, since the fixing part is formed with a through hole for the screw to pass through, sufficient wall thickness must be provided around the through hole to ensure strength, and a sufficient surface area for the screw head to engage must also be ensured. Therefore, it is inevitable to enlarge the fixing part.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fixing member and a cutting tool which can be downsized while ensuring sufficient strength and can fix a cutting insert with high strength.

[0009] Technical solutions to solve problems

[0010] A fixing component in one aspect of the present invention is a fixing component for pressing and fixing a cutting blade on a blade mounting portion of a tool body, comprising: a fixing component body having a pressing portion for pressing the cutting blade; an engaging protrusion protruding from the bottom of the fixing component body and engaged in an engaging hole formed on the tool body; and an engaging recess formed on the circumferential surface of the engaging protrusion, in which the front end of the pressing component is engaged, and the front end of the pressing component is inserted into a hole portion connected to the engaging hole of the tool body, wherein the fixing component is configured so that the engaging protrusion is pulled into the engaging hole by the pressing component engaged in the engaging recess, thereby causing the pressing portion to press and fix the cutting blade.

[0011] In the fixing part of the above structure, there is no need for a through hole for the screw to pass through or a large surface for engaging with the head of the screw, which can achieve miniaturization. In this way, for example, when cutting such as inner diameter processing, the interference factor with the workpiece can be reduced, and the application range can be expanded. It is also possible to expand the space for chip discharge and suppress the frequency of sudden defects caused by chip blockage.

[0012] The engaging recessed portion may have a spherical convex contact convex portion formed at a bottom portion with which the front end surface of the pressing member abuts.

[0013] The fitting protrusion may form the engagement recessed portions at a plurality of positions in the circumferential direction.

[0014] The hole portion is an internal thread, and the fixing screw can be screwed into the internal thread as a pressing member.

[0015] The cutting tool in one aspect of the present invention includes: the above-mentioned fixing component; a tool body, having a blade mounting portion provided with a cutting blade, and a fixing component mounting portion equipped with a fixing component; and a cutting blade, which is arranged on the blade mounting portion and is pressed and fixed by the fixing component, wherein the fixing component mounting portion has: an engaging hole, in which an engaging protrusion of the fixing component is engaged; a hole portion, which is connected to the inner circumferential surface of the engaging hole; and a pressing component, which is inserted into the hole portion and the front end is engaged in the engaging recess of the fixing component.

[0016] Effects of the Invention

[0017] According to the present invention, there is provided a fixing member and a cutting tool which can be reduced in size while ensuring sufficient strength and which can fix a cutting insert with high strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a side view of the cutting tool in this embodiment;

[0019] Figure 2 is a perspective view of the front end of the cutting tool in this embodiment;

[0020] Figure 3 is a schematic side view of a clamping portion of a cutting insert;

[0021] Figure 4 A schematic perspective view of a clamping portion of a cutting insert as seen from the rear;

[0022] Figure 5 A perspective view of the front end of the tool body with the cutting blade installed on the blade mounting portion;

[0023] Figure 6 A top view of the front end of the tool body with the cutting blade installed on the blade mounting portion;

[0024] Figure 7 is a side view of a fixed component;

[0025] Figure 8 A three-dimensional diagram of a fixed component;

[0026] Fig. 9 It is the front view of the fixed part;

[0027] Fig.10 A perspective view of the fixed component as seen from the lower rear;

[0028] Fig.11 A perspective view of a fixing member with a coil spring mounted on the front end of the fitting protrusion as seen from the back side;

[0029] Fig.12 A top view of a fixing member for explaining the shape of a fitting protrusion of the fixing member;

[0030] Fig.13 A perspective view of a fixing member showing an engagement state of a fixing screw with respect to an engagement recess formed on an engagement protrusion of the fixing member;

[0031] Fig.14 It is a side view of a part of a fixing member having a guide protrusion at the front part of a fitting protrusion.

[0032] Description of Reference Numerals

[0033] 10: Tool body;

[0034] 12: Blade mounting portion;

[0035] 21: Chimeric hole;

[0036] 22: internal thread (hole);

[0037] 23: fixing screw (pressing part);

[0038] 40: cutting blade;

[0039] 50: fixed parts;

[0040] 51: fixing component body;

[0041] 52: chimeric protrusion;

[0042] 55: pressing part;

[0043] 61: Engagement recess;

[0044] 62: Contact convex part;

[0045] 100: Cutting tools. DETAILED DESCRIPTION

[0046] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0047] (Cutting Tools)

[0048] like Figure 1 to Figure 4 As shown, the cutting tool 100 in this embodiment has: a tool body 10 and a cutting insert 40, and the tool body 10 includes: a fixing component 50 and a fixing screw 23. The cutting tool 100 is equipped with a cutting insert 40 at the front end of the tool body 10, and is a turning tool that performs outer diameter cutting or inner diameter cutting on a rotating workpiece by the cutting insert 40 at the front end of the tool body 10. The cutting insert 40 is pressed and fixed by the fixing component 50 of the tool body 10.

[0049] (Tool body)

[0050] The tool body 10 is formed in a prism shape, and a cutting blade 40 is installed at the front end. The tool body 10 has a blade mounting portion 12 at its front end, and the cutting blade 40 is mounted on the blade mounting portion 12. The tool body 10 is formed of a metal material such as steel. The material of the tool body 10 is preferably, for example, an alloy tool steel (SKS5) that is elastic and not prone to plastic deformation, a die steel (SKD61), a maraging steel, etc. It should be noted that the shape of the tool body 10 is not limited to a prism shape.

[0051] The insert mounting portion 12 has a mounting surface 13 and a side wall surface 14 erected substantially perpendicularly to the rear side of the mounting surface 13. On the insert mounting portion 12, the cutting insert 40 is arranged on the mounting surface 13 via a gasket 15. It should be noted that the cutting insert 40 may be directly arranged on the mounting surface 13 without the gasket 15.

[0052] The rear side of the blade mounting portion 12 of the tool body 10 is the fixed component mounting portion 16, and the fixed component 50 is mounted on the fixed component mounting portion 16. The fixed component mounting portion 16 has a mounting surface 17, and the mounting surface 17 is composed of a flat surface connected to the side wall surface 14 of the blade mounting portion 12. In addition, the fixed component mounting portion 16 also has a sliding surface 18 on the rear side of the mounting surface 17. The sliding surface 18 is an inclined surface that gradually slopes downward from the mounting surface 17 side to the rear.

[0053] like Figure 5 and Figure 6As shown, the fixing component mounting portion 16 has a fitting hole 21 and an internal thread (hole portion) 22. The fitting hole 21 is formed perpendicular to the mounting surface 17. The internal thread 22 opens on the side of the fitting hole 21 and is formed obliquely toward the fitting hole 21. In addition, the internal thread 22 is connected to the fitting hole 21 on the inner circumferential surface. A fixing screw (pressing component) 23 is screwed into the internal thread 22 from the upper side of the fixing component mounting portion 16, and the front end of the fixing screw 23 protrudes into the fitting hole 21. As the fixing screw 23, a hexagon socket set screw is used. It should be noted that in this example, a structure in which the fixing screw 23 is screwed into the internal thread 22 is illustrated, and a hole portion connected to the fitting hole 21 may be formed instead of the internal thread 22, and a pressing component such as a pin is inserted into the hole portion by operating a cam or an operating lever.

[0054] In addition, in the fitting hole 21, a guide recess 25 is formed on its inner circumference. The guide recess 25 is located on the side opposite to the blade mounting portion 12 and is formed in a spherical concave shape. Further, in the fitting hole 21, a flow outlet 26 is also formed on its inner circumference. The flow outlet 26 is also located on the side opposite to the blade mounting portion 12 and is arranged lower than the guide recess 25.

[0055] like Figure 1 As shown, the tool body 10 having the insert mounting portion 12 and the fixing member mounting portion 16 at the front end has: a coolant main flow channel 31; coolant branch flow channels 32 and 33; and a plurality of coolant discharge flow channels 34 therein.

[0056] The coolant main flow channel 31 is formed along the long side direction of the tool body 10. The coolant main flow channel 31 has a plurality of inlets 35, 36, and 37. The inlet 35 is formed on the rear end face of the tool body 10, the inlet 36 is formed on the bottom face in the middle of the long side direction of the tool body 10, and the inlet 37 is formed on the bottom face on the front end side of the tool body 10. In addition, any one of these inlets 35, 36, and 37 supplies coolant to the coolant main flow channel 31, and the positions of the inlets 35, 36, and 37 that are not used for supplying coolant are sealed by hexagon socket set screws or the like.

[0057] The coolant branch flow channel 32 is formed at the upper part of the front end side of the tool body 10, and one end is connected to the coolant main flow channel 31. The other end of the coolant branch flow channel 32 is connected to the fitting hole 21, and its opening portion is the outflow port 26. The coolant supplied to the coolant main flow channel 31 is sent to the coolant branch flow channel 32. It should be noted that the fluid supplied to the coolant main flow channel 31 is not limited to the coolant, and various lubricants or coolants can also be used, and spray or air can also be supplied.

[0058] The coolant branch channel 33 is formed at the lower part of the front end side of the tool body 10, and one end is connected to the coolant main channel 31. In the coolant branch channel 33, its other end is connected to one end of a plurality of coolant discharge channels 34. The other end of the coolant discharge channel 34 opens near the front end of the tool body 10, and the opening portion is the discharge port 34a. The coolant supplied to the coolant main channel 31 is sent to the coolant branch channel 33. Then, the coolant sent to the coolant branch channel 33 passes through the coolant discharge channel 34 and is discharged from the discharge port 34a to cool and lubricate the vicinity of the back face of the cutting blade 40.

[0059] (Cutting inserts)

[0060] like Figure 5 and Figure 6 As shown, the cutting insert 40 mounted on the insert mounting portion 12 of the tool body 10 is formed into a flat, substantially triangular three-dimensional shape, for example. The cutting insert 40 has end faces 43 on both sides, and each end face 43 has three corners 41. In addition, the cutting insert 40 also has a fixing hole 42 at its center.

[0061] The cutting insert 40 has substantially triangular end faces 43 facing each other and three peripheral side faces 44 connecting the end faces 43. In the cutting insert 40, the cutting edges 46 are formed near the corners 41 on the ridge lines 45 between the end faces 43 and the peripheral side faces 44.

[0062] The cutting insert 40 is placed and fixed on the insert mounting portion 12 of the tool body 10, with any end face 43 facing upward and any one of the three corners 41 facing the front end. In this way, the cutting insert 40 can be used at a total of six locations on each end face 43 by using any one of the three corners 41 having the cutting edge 46 facing the front end.

[0063] (Fixed parts)

[0064] like Figure 7 to Figure 11 As shown in FIG. 1 , the fixing member 50 includes a fixing member body 51 and an engaging protrusion 52 . The engaging protrusion 52 extends downward from the bottom of the fixing member body 51 .

[0065] The fixing member body 51 is provided with a pressing portion 55 on the front end side of the fitting protrusion 52, and a pressing protrusion 56 protruding downward is formed on the pressing portion 55. The pressing protrusion 56 is a protrusion for fixing the cutting blade 40, and its shape can be any shape as long as it can press the inner peripheral surface of the fixing hole 42 of the cutting blade. In addition, the fixing member body 51 also has a sliding surface 58 that is gradually inclined backward downward on the side of the rear end portion 57 that is closer to the fitting protrusion 52.

[0066] The engaging protrusion 52 is formed in a cylindrical shape. The engaging protrusion 52 has engaging recesses 61 on both sides thereof. The engaging recesses 61 are formed in a concave shape that is gradually inclined toward the center side in the protruding direction of the engaging protrusion 52. A contact protrusion 62 that protrudes in a spherical convex shape is formed at the bottom of the engaging recess 61. In addition, a guide protrusion 63 in a spherical convex shape is formed near the root on the rear side of the engaging protrusion 52. Furthermore, the engaging protrusion 52 has an annular recess 65 at its front end, and a coil spring 66 is fitted and installed in the annular recess 65. In addition, an annular O-ring 67 is mounted at the root portion of the engaging protrusion 52.

[0067] like Fig.12 As shown, the front end 52a of the fitting protrusion 52 is formed into a circle with an outer diameter of D1. In contrast, the base end 52b side of the fitting protrusion 52 is formed into an elliptical shape with a major diameter D1 and a minor diameter D2, and the front-to-back direction of the fixing member 50 is the minor diameter direction. Therefore, the dimension of the fitting protrusion 52 in the front-to-back direction gradually decreases from the front end 52a to the base end 52b.

[0068] The fixing member 50 has a coolant inlet flow channel 71, a coolant discharge flow channel 72, and a coolant reservoir 73. One end of the coolant inlet flow channel 71 opens at the front end side of the guide protrusion 63 on the rear side of the fitting protrusion 52, and the opening portion is the inlet 74. The coolant inlet flow channel 71 is formed by bending the fitting protrusion 52 upward from the inlet 74 toward the fixing member body 51. In this example, two coolant discharge flow channels 72 are formed. On the front end side of the fixing member body 51, these coolant discharge flow channels 72 are arranged in parallel and formed in the front-to-back direction, and open at the front end of the fixing member body 51. Moreover, the opening portion of these coolant discharge flow channels 72 is the discharge port 72a. The coolant reservoir 73 is formed at an upper position of the fitting protrusion 52 on the fixing member body 51. The coolant inlet flow channel 71 and the coolant discharge flow channel 72 are connected to the coolant reservoir 73, respectively. The coolant reservoir 73 has a larger flow channel cross section than the coolant introduction flow channel 71 and the coolant discharge flow channel 72. It should be noted that the two coolant discharge flow channels 72 are not limited to being arranged in parallel.

[0069] (Fixing of cutting blades)

[0070] Next, a description will be given of a case where the cutting insert 40 provided on the insert mounting portion 12 of the tool body 10 is fixed by the fixing member 50 .

[0071] First, for the tool body 10 with the cutting insert 40 disposed on the insert mounting portion 12, the engaging protrusion 52 of the fixing member 50 is inserted into the engaging hole 21 of the fixing member mounting portion 16, so that the fixing member body 51 is disposed on the upper portion of the fixing member mounting portion 16. Then, the pressing protrusion 56 formed on the pressing portion 55 of the fixing member body 51 is inserted into the fixing hole portion 42 of the cutting insert 40. At this time, the coil spring 66 at the front end of the engaging protrusion 52 abuts against the bottom 21a of the engaging hole 21.

[0072] In this state, the fixing screw 23 is screwed into the internal thread 22 of the fixing member mounting portion 16 of the tool body 10. Fig.13 As shown in the figure, the front end of the fixing screw 23 protrudes into the fitting hole 21 and is inserted into one of the engaging recesses 61 formed on the fitting protrusion 52, and abuts against the contact protrusion 62 formed on the bottom of the engaging recess 61. Then, by further screwing the fixing screw 23, the fitting protrusion 52 is pulled into the fitting hole 21 by the tightening force of the fixing screw 23 to overcome the force of the coil spring 66. As a result, the fixing member 50 is pressed against the fixing member mounting portion 16 of the tool body 10. In this way, the pressing portion 55 of the fixing member 50 presses the cutting insert 40 onto the gasket 15 of the insert mounting portion 12 of the tool body 10 by the pressing force F1.

[0073] Furthermore, by pressing the fixing member 50 against the fixing member mounting portion 16, the sliding surface 58 of the fixing member body 51 contacts and slides with the sliding surface 18 of the tool body 10. Thus, the fixing member 50 is pulled toward the rear of the tool body 10 by the component force F3 of the reaction force F2 from the sliding surface 18 of the tool body 10. As a result, the pressing protrusion 56 embedded in the fixing hole portion 42 of the cutting insert 40 moves backward while abutting against the inner peripheral surface of the fixing hole portion 42. Thus, the cutting insert 40 is pulled toward the rear side of the insert mounting portion 12 of the tool body 10 by the pressing protrusion 56 of the fixing member 50 and is pressed against the side wall surface 14. In this way, the cutting tool 100 has a double clamping fixing method in which the fixing member 50 presses the upper end surface 43 of the cutting insert 40 and the inner peripheral surface of the fixing hole portion 42.

[0074] Here, the base end 52b of the elliptical shape of the fitting protrusion 52 of the fixing member 50 is smaller than the front end 52a in the front-to-back direction. Therefore, in the front-to-back direction of the fixing member 50, a gap is formed between the fitting protrusion 52 and the fitting hole 21, which gradually increases toward the base end 52b side of the fitting protrusion 52. Therefore, when the fitting protrusion 52 is pulled into the fitting hole 21 by the fixing screw 23, the fixing member 50 can be smoothly displaced to the rear of the tool body 10. It should be noted that the fitting protrusion 52 can also be an elliptical shape with the front-to-back direction of the fixing member 50 being the short diameter direction over the entire length. In this case, by making the short diameter on the base end 52b side smaller than the short diameter on the front end 52a side, a gap that gradually increases toward the base end 52b side of the engaging protrusion 52 and the engaging hole 21 in the front-to-back direction of the fixing part 50 can be formed, so that the fixing part 50 engaged in the engaging hole 21 can be smoothly displaced toward the rear of the tool body 10.

[0075] In addition, in the clamped state where the cutting insert 40 is fixed to the insert mounting portion 12, the guide protrusion 63 formed on the fitting protrusion 52 of the fixing member 50 is fitted into the guide recess 25 formed on the fitting hole 21 of the tool body 10. Thus, the fixing member 50 is prevented from rotating around the axis of the fitting protrusion 52 by the mutually fitting guide protrusion 63 and the guide recess 25. Therefore, it is possible to suppress the fixing member 50 from being moved when the cutting insert 40 of the cutting tool 100 is used for cutting processing, so that good cutting processing can be performed using the cutting insert 40.

[0076] It should be noted that if Fig.14 As shown in the figure, a guide protrusion 63 may be provided on the front side of the fitting protrusion 52 of the fixing member 50. In this case, the guide recess 25 into which the guide protrusion 63 provided on the front side of the fitting protrusion 52 can fit is provided on the blade mounting portion 12 side of the fitting hole 21. Thus, the anti-rotation effect of the fixing member 50 around the axis of the fitting protrusion 52 can be further improved.

[0077] In addition, in the clamped state where the cutting insert 40 is fixed to the insert mounting portion 12, the O-ring 67 mounted on the root of the fitting protrusion 52 of the fixing member 50 is in close contact with the mounting surface 17 of the fixing member mounting portion 16 of the tool body 10. This allows the bottom of the fixing member 50 and the mounting surface 17 of the fixing member mounting portion 16 to be sealed.

[0078] Furthermore, in the clamped state where the cutting insert 40 is fixed to the insert mounting portion 12, the inlet 74 of the coolant introduction channel 71 formed on the fitting protrusion 52 of the fixing member 50 is connected to the outlet 26 of the coolant branch channel 32 formed on the fitting hole 21 of the tool body 10. This allows the coolant fed from the coolant main channel 31 into the coolant branch channel 33 to be fed into the coolant introduction channel 71 of the fixing member 51. Moreover, the coolant fed into the coolant introduction channel 71 is fed into the coolant discharge channel 72 via the coolant reservoir 73 and discharged from the discharge port 72a at the front end of the fixing member 50. In this way, the coolant discharged from the discharge port 72a at the front end of the fixing member 50 is sprayed to the position where the cutting insert 40 performs cutting together with the coolant discharged from the discharge port 34a at the front end of the tool body 10. As a result, the position where the cutting insert 40 performs cutting is well cooled and lubricated. Here, a coolant reservoir 73 having a large flow channel cross section is provided between the coolant inlet flow channel 71 and the coolant discharge flow channel 72. Therefore, the pressure loss of the coolant generated when it is fed from the coolant inlet flow channel 71 to the coolant discharge flow channel 72 having a smaller inner diameter can be suppressed, so that the coolant can be discharged well from the discharge port 72a.

[0079] (Removal of cutting blade)

[0080] Next, a description will be given of a case where the cutting insert 40 fixed to the insert mounting portion 12 of the tool body 10 is removed by the fixing member 50 .

[0081] To remove the cutting insert 40, first, loosen the fixing screw 23 that fixes the fixing member 50. In this way, the fixing screw 23 will be pulled out from the engaging recess 61 of the fixing member 50. In this way, the elastic force of the coil spring 66 at the front end of the engaging protrusion 52 will push the fixing member 50 in the direction away from the fixing member mounting portion 16 of the tool body 10. Thereby, the fixing of the cutting insert 40 by the fixing member 50 is released. In this way, when the coil spring 66 pushes up the fixing member 50, the guide protrusion 63 of the engaging protrusion 52 engaged in the guide recess 25 of the engaging hole 21 will slide together with the guide recess 25. As a result, the rear side of the fixing member 50 is guided along the contact surface between the guide protrusion 63 and the guide recess 25, and the rear part of the fixing member 50 is smoothly pushed up. Therefore, it is easy to hold and remove the fixing member 50 after the rear part is pushed up from the fixing member mounting portion 16 of the tool body 10.

[0082] As described above, according to the fixing member 50 in this embodiment, a through hole for the screw to pass through or a large surface for engaging with the head of the screw is not required, and miniaturization can be achieved. In this way, for example, in cutting processing such as inner diameter processing, the interference factor with the workpiece can be reduced, and the application range can be expanded. It is also possible to expand the chip discharge space, and the frequency of sudden defects caused by chip clogging can be suppressed.

[0083] Furthermore, since the front end surface of the fixing screw 23 abuts against the spherical convex contact convex portion 62 , the tightening force of the fixing screw 23 can be impartially transmitted to the fitting protrusion 52 and pulled into the fitting hole 21 .

[0084] Furthermore, since the engaging recesses 61 are formed at a plurality of positions in the circumferential direction of the fitting protrusion 52 (two positions on both sides in this example), any of the engaging recesses 61 can be used according to the situation, and the left and right sides can be handled freely.

Claims

1. A fixing member for pressing and fixing a cutting insert disposed on a insert mounting portion of a tool body, wherein the fixing member is characterized in that: A fixing member body having a pressing portion for pressing the cutting blade; an engaging protrusion protruding from the bottom of the fixing member body and engaging with the engaging hole formed on the tool body; and An engaging recess is formed on the peripheral surface of the engaging protrusion, in which the front end of the pressing member is engaged, and the front end of the pressing member is inserted into a hole portion connected to the engaging hole of the tool body, in, The engaging protrusion is pulled into the engaging hole by the pressing member engaged with the engaging recess, so that the pressing portion presses and fixes the cutting insert.

2. The fixing component according to claim 1, characterized in that: The engaging recess has a spherical convex contact convex portion formed at a bottom portion with which the front end surface of the pressing member abuts.

3. The fixing member according to claim 1, characterized in that: The engaging protrusion has the engaging recesses formed at a plurality of positions in the circumferential direction.

4. The fixing member according to claim 1, characterized in that: The hole portion is an internal thread, and a fixing screw as the pressing member is screwed into the internal thread.

5. A cutting tool, characterized in that: include: The fixing member according to any one of claims 1 to 4; a tool body having an insert mounting portion on which the cutting insert is provided, and a fixing member mounting portion on which the fixing member is mounted; and The cutting blade is arranged on the blade mounting portion and is pressed and fixed by the fixing member. Wherein, the fixing component mounting portion has: an engaging hole into which the engaging protrusion of the fixing member is engaged; a hole portion communicating with the inner peripheral surface of the fitting hole; and The pressing member is inserted into the hole and a front end thereof is engaged with the engaging recess of the fixing member.

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