Caliper body of disc brake for vehicle

Abstract

To form a caliper body by selectively assembling either of a radial mount type anti-vehicle body side caliper half body and an axial mount type anti-vehicle body side caliper half body to a vehicle body side caliper half body.SOLUTION: Working fluid introduction holes for introducing working fluids into cylinder holes toward bottom part sides of the cylinder holes from joining faces are formed at a vehicle body side caliper half body 5, a radial mount type anti-vehicle body side caliper half body 6, and an axial mount type anti-vehicle body side caliper half body. The introduction hole which is formed at the radial mount type anti-vehicle body side caliper half body 6 and the introduction hole formed at the axial mount type anti-vehicle body side caliper half body communicate with the introduction holes which are formed at the vehicle body side caliper half body 5 at the joining faces. Either of the radial mount type anti-vehicle body side caliper half body 6 or the axial mount type anti-vehicle body side caliper half body is joined to the vehicle body side caliper half body 5 via the joining faces, and selectively assembled thereto.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a caliper body for a vehicle disc brake, and more particularly to a split caliper body formed by connecting a pair of caliper halves arranged on both sides of a disc rotor with a bridge portion. [Background technology]

[0002] Conventionally, split caliper bodies formed by connecting a pair of caliper halves arranged on both sides of a disc rotor with a bridge portion include a caliper body half arranged on the opposite vehicle body side of the disc rotor, which is provided with a radial mount type vehicle body mounting portion having an insertion hole for a vehicle body mounting bolt in the radial direction of the disc (see, for example, Patent Document 1), and an axial mount type vehicle body mounting portion having an insertion hole for a vehicle body mounting bolt in the axial direction of the disc (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-12149 [Patent Document 2] Patent No. 4212185 Summary of the Invention [Problem to be solved by the invention]

[0004] As shown in the above-mentioned Patent Documents 1 and 2, in caliper bodies having different mounting types to the vehicle body, even if the vehicle body side caliper halves have the same shape, each caliper body is designed and manufactured separately.

[0005] Therefore, the present invention aims to provide a caliper body for a vehicle disc brake in which either a radial mount type anti-vehicle side caliper half having a radial mount type vehicle body mounting portion, or an axial mount type anti-vehicle side caliper half having an axial mount type vehicle body mounting portion can be selectively assembled to the vehicle body side caliper half. [Means for solving the problem]

[0006] In order to achieve the above object, the caliper body of the vehicle disc brake of the present invention is a caliper body for a vehicle in which either a radial mount type opposite vehicle body caliper half having a radial mount type vehicle body attachment part or an axial mount type opposite vehicle body caliper half having an axial mount type vehicle body attachment part is joined to a vehicle body side caliper half disposed on the vehicle body side of a disc rotor via their respective joining surfaces and fastened together with a connecting bolt, so that the caliper body can be selectively assembled to the vehicle body side caliper half disposed on the vehicle body side of a disc rotor. The side caliper half, the radial mount type opposite vehicle body side caliper half, and the axial mount type opposite vehicle body side caliper half each have a working fluid inlet hole formed from the joint surface toward the bottom side of the cylinder bore, and the inlet hole formed in the radial mount type opposite vehicle body side caliper half and the inlet hole formed in the axial mount type opposite vehicle body side caliper half are each formed so as to communicate with the inlet hole formed in the vehicle body side caliper half at the joint surface.

[0007] In addition, it is preferable that the radial mount type opposite vehicle body caliper half and the axial mount type opposite vehicle body caliper half have a seal groove provided on the outer periphery of the opening of the inlet hole that opens into the joint surface, either a union hole for introducing hydraulic fluid into the inlet hole or a bleeder hole for discharging air in the hydraulic fluid, and a female threaded hole for fastening the connecting bolt. Effect of the Invention

[0008] According to the caliper body of the vehicle disc brake of the present invention, the vehicle body side caliper half, the radial mount type anti-vehicle body side caliper half, and the axial mount type anti-vehicle body side caliper half each have a hydraulic fluid inlet hole formed from the joint surface of the caliper halves toward the bottom of the cylinder bore, for introducing hydraulic fluid into the cylinder bore, and the inlet hole formed in the radial mount type anti-vehicle body side caliper half and the inlet hole formed in the axial mount type anti-vehicle body side caliper half are formed so as to communicate with the inlet hole formed in the vehicle body side caliper half at the joint surface, so that whether the radial mount type anti-vehicle body side caliper half or the axial mount type anti-vehicle body side caliper half is joined to the vehicle body side caliper half, the inlet holes are connected and hydraulic fluid can be supplied to each cylinder bore. This allows either a radial mount type anti-vehicle body side caliper half or an axial mount type anti-vehicle body side caliper half to be selectively assembled to the vehicle body side caliper half, so that the same vehicle body side caliper half can be used even for caliper bodies with different mounting types to the vehicle body, thereby reducing costs.

[0009] In addition, the radial mount type caliper half opposite the vehicle body and the axial mount type caliper half opposite the vehicle body have a seal groove provided on the outer periphery of the opening of the inlet hole that opens into the joint surface, either a union hole for introducing hydraulic fluid into the inlet hole or a bleeder hole for discharging air in the hydraulic fluid, and a female threaded hole for fastening the connecting bolt, so that the shape of the vehicle body side caliper half can be made as simple as possible, thereby enabling further cost reduction. [Brief description of the drawings]

[0010] [Figure 1] 1 is a front view of a vehicle disc brake showing an example of an embodiment of the present invention in which a radial mount type caliper half body on the opposite side to the vehicle body is used for a caliper body. [Diagram 2] FIG. [Diagram 3] FIG. [Figure 4]FIG. [Diagram 5] FIG. 5 is a cross-sectional view of FIG. 4 . [Figure 6] 6 is a cross-sectional view taken along line VI-VI of FIG. [Figure 7] FIG. 7 is a cross-sectional view taken along line VII-VII of FIG. [Figure 8] FIG. 13 is a front view of the essential parts with a union bolt and a hose banjo attached to the union hole. [Figure 9] FIG. 11 is a side view showing a state in which a union bolt and a hose banjo are attached to a union hole. [Figure 10] XX cross-sectional view of FIG. 8. [Figure 11] 1 is a front view of a caliper body showing a first embodiment of the present invention. [Figure 12] FIG. 4 is a rear view of the caliper half on the opposite side to the vehicle body. [Figure 13] FIG. 13 is a cross-sectional view taken along line XIII-XIII of FIG. [Figure 14] FIG. [Figure 15] FIG. 4 is a rear view of the caliper half on the vehicle body side. [Figure 16] 16 is a cross-sectional view taken along line XVI-XVI of FIG. 15. [Figure 17] FIG. 1 is a front view of a vehicle disc brake using a caliper body in which a radial mount type caliper half opposite the vehicle body is replaced with an axial mount type caliper half opposite the vehicle body. [Figure 18] FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Figures 1 to 18 show an example of a vehicle disc brake of the present invention, in which Figures 1 to 16 show a vehicle disc brake using a radial mount type caliper half on the opposite side of the vehicle body in the caliper body, and Figures 17 and 18 show a vehicle disc brake using a caliper body in which the radial mount type caliper half on the opposite side of the vehicle body is replaced with an axial mount type caliper half on the opposite side of the vehicle body. Note that arrow A indicates the rotation direction of the disc rotor that rotates together with the wheel when the vehicle moves forward, and the disc rotation out side and disc rotation in side described below refer to the direction when the vehicle moves forward.

[0012] As shown in Figures 1 to 16, a vehicle disc brake 1 comprises a disc rotor 2 that rotates together with a wheel (not shown) in the direction of arrow A, a caliper body 3 that is attached to the vehicle body at one side of the disc rotor 2, and a pair of friction pads 4, 4 that are arranged opposite each other inside the caliper body 3, sandwiching the disc rotor 2.

[0013] The caliper body 3 is formed by integrally connecting a vehicle body side caliper half 5 and a radial mount type anti-vehicle body side caliper half 6 separated by a bridge portion 3a spanning the outer periphery of the disc rotor 2 with two connecting bolts 7, 7.

[0014] The vehicle body side caliper half 5 has an action portion 5b with cylinder holes 5a, 5a arranged side by side in the disk circumferential direction, and a bridge portion half 5c constituting approximately half of the bridge portion 3a, and the radial mount type opposite vehicle body side caliper half 6 also has an action portion 6b with cylinder holes 6a, 6a arranged side by side in the disk circumferential direction, and a bridge portion half 6c constituting approximately half of the bridge portion 3a, similar to the vehicle body side caliper half 5. In addition, the length in the disk axial direction of the bridge portion half 6c of the radial mount type opposite vehicle body side caliper half 6 is formed longer than the length in the disk axial direction of the bridge portion half 5c of the vehicle body side caliper half 5, and is formed so that when the caliper body 3 formed by butting and joining the bridge portion halves 5c, 6c to each other is assembled to the vehicle body, the joining surface 8 is located closer to the vehicle body than the width direction center CL1 of the disc rotor 2.

[0015] In the vehicle body side caliper half 5, pistons 9, 9 are inserted into the cylinder holes 5a, 5a, and hydraulic chambers 10, 10 into which hydraulic fluid is introduced are defined between the bottom side of the cylinder holes 5a, 5a and the pistons 9, 9. A first hydraulic fluid introduction hole 11 (an introduction hole of the present invention) is drilled from the dividing surface which becomes the joint surface 8 on the disc rotation side of the bridge part half 5c toward the hydraulic chamber 10 of the cylinder hole 5a on the disc rotation side. The bottom of the cylinder hole 5a on the disc rotation side has a first contoured part 5d which connects the hydraulic chamber 10 on the disc rotation side with the first hydraulic fluid introduction hole 11 by contouring, and a second contoured part 5e which is contoured toward the hydraulic chamber 10 on the disc rotation side. Furthermore, a third contouring process portion 5f is formed at the bottom of the cylinder hole 5a on the disc rotation side, and is contoured toward the second contouring process portion 5e. By connecting the second contouring process portion 5e and the third contouring process portion 5f, the first hydraulic fluid introduction hole 11, the hydraulic pressure chamber 10 on the disc rotation side, and the hydraulic pressure chamber 10 on the disc rotation side are connected to each other.

[0016] Furthermore, a bleeder hole 12 is provided on the disc rotation side of the bridge half body 5c and at the disc radial outer end, which opens to the disc radial outer end face 5g and communicates with the first working fluid introduction hole 11. The bleeder hole 12 has a female thread portion 12a for screwing a bleeder screw 13 on the opening side, and a mounting seat surface 5h for the bleeder screw 13 is formed on the disc radial outer end face 5g on the outer periphery of the opening. The bleeder screw 13 has an air discharge hole on its inner periphery and a male thread portion 13a on its outer periphery that screws into the female thread portion 12a, and a rubber bleeder cap 13b is attached to the tip head.

[0017] In the radial mount type anti-vehicle body caliper half 6, similarly to the vehicle body side caliper half 5, pistons 14, 14 are inserted into cylinder holes 6a, 6a, and hydraulic chambers 15, 15 are defined between the bottom side of the cylinder holes 6a, 6a and the pistons 14, 14. A second hydraulic fluid introduction hole 16 (an introduction hole of the present invention) is drilled from the dividing surface which becomes the joint surface 8 of the disc rotation side of the bridge part half 6c toward the hydraulic chamber 15 of the disc rotation side, and the first hydraulic fluid introduction hole 11 and the second hydraulic fluid introduction hole 16 communicate with each other at the joint surface 8. A seal groove 17a is provided on the outer periphery of the opening where the second hydraulic fluid introduction hole 16 opens to the joint surface 8, and a seal member 17 is attached to the seal groove 17a. The bottom of the cylinder hole 6a on the disk rotation side has a fourth contoured portion 6d that connects the hydraulic chamber 15 on the disk rotation side and the second hydraulic fluid introduction hole 16 by contouring, and a fifth contoured portion 6e that is contoured toward the hydraulic chamber 15 on the disk rotation side. Furthermore, a sixth contoured portion 6f that is contoured toward the fifth contoured portion 6e is formed at the bottom of the cylinder hole 6a on the disk rotation side, and by connecting the fifth contoured portion 6e and the sixth contoured portion 6f, the second hydraulic fluid introduction hole 16, the hydraulic chamber 15 on the disk rotation side, and the hydraulic chamber 15 on the disk rotation side are connected.

[0018] Furthermore, a union hole 18 is provided at the disc rotation side end of the bridge half 6c, which opens to the disc rotation side end face 6g and communicates with the second hydraulic fluid introduction hole 16. The union hole 18 has a female thread portion 18a for screwing a union bolt 19 on the opening side, and a mounting seat surface 6h for the union bolt 19 is formed on the disc rotation side end face 6g on the outer periphery of the opening. A hose banjo 21 fixed to the end of a brake hose 20 is attached to the union bolt 19, and a rotation stop portion 6i for the hose banjo 21 is formed on the outer periphery of the mounting seat surface 6h. The anti-rotation portion 6i includes a wall portion 6j that protrudes from the outer periphery of the mounting seat surface 6h and protects the connection between the union bolt 19 and the hose banjo 21, and an engagement portion 6k formed by cutting out a part of the wall portion 6j and preventing the hose banjo 21 from rotating. The hose banjo 21 is clamped by this engagement portion 6k to prevent the hose banjo 21 from rotating together when the union bolt 19 is screwed into the union hole 18. The union bolt 19 includes a male thread portion 19a that screws into the female thread portion 18a and a hexagonal head portion 19b. A fluid passage hole 19c is formed inside the male thread portion 19a, and the brake hose 20 communicates with the union hole 18 via the union bolt 19.

[0019] In addition, radial mount type vehicle body mounting portions 6n, 6n equipped with mounting bolt insertion holes 6m, 6m in the radial direction of the disk are formed on the disk rotation entry side and disk rotation exit side of the radial mount type anti-vehicle body caliper half 6, and the caliper body 3 is attached to the vehicle body by screwing mounting bolts inserted into the mounting bolt insertion holes 6m, 6m into the caliper mounting portions provided on the vehicle body side.

[0020] The caliper body 3 is formed by joining the vehicle body side caliper half 5 and the radial mount type anti-vehicle body side caliper half 6 formed in this manner at the bridge portion 3a, and by fastening the connecting bolts 7, 7 inserted into the bolt insertion holes 7a, 7a formed in the vehicle body side caliper half 5 to the female threaded holes 7b, 7b formed in the radial mount type anti-vehicle body side caliper half 6, the first working fluid inlet hole 11 and the second working fluid inlet hole 16 are connected to each other, and as a result, the first working fluid inlet hole 11 and the second working fluid inlet hole 16 are connected to the hydraulic chambers 10, 10 of the vehicle body side caliper half 5 and the hydraulic chambers 15, 15 of the radial mount type anti-vehicle body side caliper half 6. Furthermore, since the union hole 18 communicates with the second working fluid introduction hole 16, working fluid is supplied to the hydraulic chambers 10, 10, 15, 15 via the union bolt 19 and the first working fluid introduction hole 11 and the second working fluid introduction hole 16. Since the bleeder hole 12 communicates with the first working fluid introduction hole 11, air mixed in the working fluid introduced into the first working fluid introduction hole 11, the second working fluid introduction hole 16, and the hydraulic chambers 10, 10, 15, 15 is discharged to the outside via the bleeder screw 13.

[0021] Each friction pad 4 is composed of a lining 4a that slides against the side of the disc rotor 2 and a metal back plate 4b to which the lining 4a is attached. A hanging piece 4c is extended from the upper center of the back plate 4b, and a hanger pin 22 is inserted into the hanging piece 4c. The hanger pin 22 is installed in the axial direction of the disc on both of the action parts 5b, 6b through a ceiling opening 3b formed in the bridge part 3a of the caliper body 3, and can move in the axial direction of the disc between the torque receiving parts 5i, 5i, 6p, 6p provided on the disc rotation inlet side and the disc rotation outlet side of the vehicle body side caliper half 5 and the radial mount type anti-vehicle body side caliper half 6. A pad spring 23 is provided across the back plate 4b, the bridge part 3a, and the hanger pin 22, and presses the friction pads 4, 4 against the disc rotation outlet side and the radially inward direction of the disc.

[0022] A vehicle disc brake 31 shown in Figures 17 and 18 uses a caliper body 33 formed by replacing the radial mount type caliper half 6 opposite the vehicle body with an axial mount type caliper half 32 opposite the vehicle body.

[0023] In the axial mount type caliper half 32 opposite the vehicle body, pistons 34 are inserted into cylinder holes 32a, and a hydraulic chamber (not shown) is defined between the bottom side of the cylinder holes 32a and the pistons 34. A second hydraulic fluid introduction hole 36 (an introduction hole according to the present invention) is drilled from a dividing surface that becomes a joint surface 35 on the disk rotation side of the bridge half 32b toward the hydraulic chamber on the disk rotation side, and the first hydraulic fluid introduction hole 11 and the second hydraulic fluid introduction hole 36 formed in the vehicle body side caliper half 5 communicate with each other at the joint surface 35. A seal groove (not shown) is provided on the outer periphery of the opening where the second hydraulic fluid introduction hole 36 opens to the joint surface 35, and a seal member (not shown) is fitted in the seal groove.

[0024] The bottom of the cylinder hole 32a on the disk rotation side has a seventh contouring part 32c that connects the hydraulic chamber on the disk rotation side to the second hydraulic fluid introduction hole 36 by contouring, and an eighth contouring part 32d that is contoured toward the hydraulic chamber on the disk rotation side. Furthermore, a ninth contouring part 32e that is contoured toward the eighth contouring part 32d is formed at the bottom of the cylinder hole on the disk rotation side, and by connecting the eighth contouring part 32d and the ninth contouring part 32e, the second hydraulic fluid introduction hole 36, the hydraulic chamber on the disk rotation side, and the hydraulic chamber on the disk rotation side are connected. Furthermore, a union hole 37 that opens to the disk rotation side end face 32f and communicates with the second hydraulic fluid introduction hole 36 is provided at the disk rotation side end of the bridge half body 32b. The union hole 37 opens to the disk rotation side end face 32f and communicates with the second hydraulic fluid introduction hole 36. The union hole 37 has a female thread portion 37a and a mounting seat surface 37b provided on the disk outlet end face 32f on the outer periphery of the opening, and a rotation stopper portion 37c for the hose banjo is formed on the outer periphery of the mounting seat surface 37b.

[0025] In addition, vehicle body mounting arms 32h, 32h (vehicle body mounting portion of the present invention) having mounting bolt insertion holes 32g, 32g in the disk axial direction are extended on the disk rotation side and radially inward of the axially mounted caliper half 32 opposite the vehicle body, and the caliper body 33 is attached to the vehicle body by screwing mounting bolts inserted into the mounting bolt insertion holes 32g, 32g into the caliper mounting portion provided on the vehicle body side.

[0026] The caliper body 33 is formed by joining the vehicle body side caliper half 5 and the axial mount type anti-vehicle body side caliper half 32 at a bridge portion 33a, and by fastening the connecting bolts 7, 7 inserted into the bolt insertion holes 7a, 7a formed in the vehicle body side caliper half 5 to female threaded holes (not shown) formed in the axial mount type anti-vehicle body side caliper half 32, the first working fluid inlet hole 11 and the second working fluid inlet hole 36 are connected to each other, and as a result, the first working fluid inlet hole 11 and the second working fluid inlet hole 36 are connected to each hydraulic chamber. Furthermore, since the union hole 37 is connected to the second working fluid introduction hole 36, working fluid is supplied to each hydraulic chamber via the union bolt, the first working fluid introduction hole 11, and the second working fluid introduction hole 36, and since the bleeder hole 12 is connected to the first working fluid introduction hole 11, the first working fluid introduction hole 11, the second working fluid introduction hole 36, and the air mixed in the working fluid introduced into the each hydraulic chamber is discharged to the outside via the bleeder screw 13.

[0027] As described above, in this embodiment, regardless of whether the radial mount type anti-vehicle body side caliper half 6 or the axial mount type anti-vehicle body side caliper half 32 is joined to the vehicle body side caliper half 5, the first hydraulic fluid introduction hole 11 communicates with the second hydraulic fluid introduction hole 16 or the second hydraulic fluid introduction hole 36, and hydraulic fluid can be supplied to the cylinder holes 5a, 32a. As a result, even if the caliper bodies have different types of mounting to the vehicle body, they can be manufactured using the same vehicle body side caliper half 5, thereby reducing costs.

[0028] Furthermore, since the radial mount type opposite vehicle body side caliper half 6 and the axial mount type opposite vehicle body side caliper half 32 have the seal groove 17a, the union holes 18, 37, and the female threaded holes 7b, 7b for fastening the connecting bolt 7, the shape of the vehicle body side caliper half 5 can be made as simple as possible, thereby enabling further cost reduction.

[0029] The present invention is not limited to the above-mentioned embodiment, and the communication between the cylinder bores and the hydraulic fluid introduction holes, and between adjacent cylinder bores, is not limited to that achieved by contouring, but may be achieved by plunging or by casting. Furthermore, a union hole may be provided in the vehicle body side caliper half, and bleeder holes may be provided in the radial mount type caliper half opposite the vehicle body and the axial mount type caliper half opposite the vehicle body. The number of cylinder bores formed in each caliper half is arbitrary. [Explanation of symbols]

[0030] Reference Signs List 1...vehicle disc brake, 2...disc rotor, 3...caliper body, 3a...bridge portion, 3b...ceiling opening, 4...friction pad, 4a...lining, 4b...back plate, 4c...hanging piece, 5...vehicle body side caliper half, 5a...cylinder hole, 5b...action portion, 5c...bridge half, 5d...first contoured portion, 5e...second contoured portion, 5f...third contoured portion, 5g...disc radial outer end surface, 5h...mounting seat surface, 5i...torque receiving portion, 6...radial mount type counter wheel Body side caliper half, 6a...cylinder hole, 6b...action portion, 6c...bridge half, 6d...fourth contouring portion, 6e...fifth contouring portion, 6f...sixth contouring portion, 6g...disk rotation side end surface, 6h...mounting seat surface, 6i...rotation stop portion, 6j...wall portion, 6k...engagement portion, 6m...mounting bolt insertion hole, 6n...vehicle body mounting portion, 6p...torque receiving portion, 7...connecting bolt, 7a...bolt insertion hole, 7b...female thread hole, 8...joint surface, 9...piston, 10...hydraulic chamber, 11...first hydraulic fluid introduction hole, 1 2...bleeder hole, 12a...female thread portion, 13...bleeder screw, 13a...male thread portion, 13b...bleeder cap, 14...piston, 15...hydraulic pressure chamber, 16...second hydraulic fluid introduction hole, 17...sealing member, 17a...sealing groove, 18...union hole, 18a...female thread portion, 19...union bolt, 19a...male thread portion, 19b...hexagonal head, 19c...fluid passage hole, 20...brake hose, 21...hose banjo, 22...hanger pin, 23...pad spring, 31...vehicle disc brake, 32 ...Axial mount type caliper half body on opposite side of vehicle body, 32a...cylinder hole, 32b...bridge half body, 32c...seventh contouring processed portion, 32d...eighth contouring processed portion, 32e...ninth contouring processed portion, 32f...disc rotation side end surface, 32g...mounting bolt insertion hole, 32h...vehicle body mounting arm, 33...caliper body, 33a...bridge portion, 34...piston, 35...joint surface, 36...second hydraulic fluid introduction hole, 37...union hole, 37a...female thread portion, 37b...mounting seat surface, 37c...rotation stop portion

Claims

1. A caliper body for a vehicle disc brake in which either a radial mount type anti-vehicle-side caliper half having a radial mount type vehicle body attachment portion or an axial mount type anti-vehicle-side caliper half having an axial mount type vehicle body attachment portion is joined to a vehicle body side caliper half disposed on the vehicle body side of a disc rotor via their respective joining surfaces and fastened with connecting bolts, thereby allowing selective assembly, the vehicle body side caliper half, the radial mount type opposite vehicle body side caliper half, and the axial mount type opposite vehicle body side caliper half are each formed with a hydraulic fluid inlet hole extending from the joint surface toward a bottom side of a cylinder bore, through which a hydraulic fluid is introduced into the cylinder bore; A caliper body for a vehicle disc brake, characterized in that the introduction hole formed in the radial mount type caliper half opposite the vehicle body and the introduction hole formed in the axial mount type caliper half opposite the vehicle body are formed so as to communicate with the introduction hole formed in the vehicle body caliper half at the joint surface.

2. 2. The caliper body of a vehicle disc brake according to claim 1, characterized in that the radial mount type caliper half and the axial mount type caliper half have a seal groove provided on an outer periphery of an opening of the inlet hole that opens to the joint surface, either a union hole for introducing hydraulic fluid into the inlet hole or a bleeder hole for discharging air contained in the hydraulic fluid, and a female threaded hole for fastening the connecting bolt.

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