JP2023051297A - Brake device - Google Patents

Abstract

To obtain, as one example, a brake device which can suppress an increase of a friction force between screws which are screwed with each other, and the lowering of the mechanical rigidity and durability of a screw.SOLUTION: A brake device according to the present embodiment comprises a rotating member and a linear motion member at which male screws and female screws are arranged, and one of the rotating member and the linear motion member has a first region and a second region in which a first screw is arranged, and which are aligned in a direction along a rotating shaft. The first region has a first end and a second end which are connected to the second region, a first groove is formed at the first region, a range in which the first screw in the second region is arranged is larger than a range in which the first screw in the first region is arranged in a peripheral direction, the second screw is engaged with the first screw in the second region, the linear motion member moves in a first direction, and the second screw thereby approaches the second end.SELECTED DRAWING: Figure 2

Description

Embodiments of the present invention relate to braking devices.

2. Description of the Related Art Conventionally, there is known a braking device that converts rotation of a rotary member driven by a motor into linear motion of a linear motion member, and presses a brake pad against a brake rotor via a piston by the linear motion member. The threads of the rotating member are provided with grooves, for example. The grooves supply lubricating oil to the male and female threads that mesh with each other, and reduce friction between the male and female threads (Patent Document 1).

DE 102018005598 A1

However, in the conventional configuration, the contact area between the male thread and the female thread is reduced by the groove, which increases the normal force per contact area. An increase in normal force increases the frictional force between the male thread and the female thread, possibly accelerating wear of the threads. Dust generated by wear increases the coefficient of friction between the male thread and the female thread, which may cause abnormal noise. Regarding the groove, for example, if a large circumferential width is ensured over the entire length of the screw, it is advantageous from the viewpoint of ensuring the supply amount of lubricating oil. There is still room for improvement in terms of the increase in , and the impact on the mechanical strength and durability caused by the provision of the grooves on the screw.

Therefore, the present invention has been made in view of the above, and provides a braking device capable of suppressing an increase in the frictional force between screws that mesh with each other and a decrease in the mechanical strength and durability of the screws.

A braking device according to an embodiment of the present invention includes, as an example, a rotating member provided with one of a male screw and a female screw that meshes with the male screw, and rotatable around a rotation axis; The other of the female threads is provided, and when the rotating member rotates about the rotating shaft in the first rotating direction, it moves in the first direction along the rotating shaft, and the rotating member moves in the first direction along the rotating shaft. a linear motion member that moves in a second direction opposite to the first direction when rotated in a second rotational direction opposite to the rotational direction; a piston that is pushed in a first direction and moves in the first direction to press the braking member against the brake rotor; is provided with a first screw that is one of the male screw and the female screw provided in the member, and has a first region and a second region arranged in a direction along the rotation axis, The first region includes a first end connected to the second region, which is one end of the first region in the direction along the rotation axis, and the first end in the direction along the rotation axis. and a second end that is the other end of the region of and a first groove that divides the first screw in the circumferential direction around the rotation axis is provided in the first region, and In the circumferential direction, the range in which the first screw is provided in the second region is larger than the range in which the first screw is provided in the first region. At least a portion of the other second screw in the direction along the rotation axis meshes with the first screw in the second region, and the direct-acting member moves in the first direction. , said second screw approaches said second end. Therefore, as an example, when the braking member wears due to repeated braking, the position of the linear motion member moves in the first direction. By moving the position of the direct-acting member in the first direction, the portion of the second screw that has been located closer to the first end than the second end, for example, approaches the second end and moves toward the second end. For example, the portion of the screw that was located on the opposite side of the second end from the first end now engages with the first screw in the first region. In the first area, dust generated by abrasion can be discharged into the first groove. Furthermore, in the second region, the contact area between the first screw and the second screw (contact area per screw thread circumference) is the same as that of the first screw and the second screw in the first region. contact area (same as above). Therefore, when at least a portion of the second screw meshes with the first screw in the second region, the normal force per contact area between the first screw and the second screw is reduced, which in turn reduces the force of the first screw. Frictional forces between the screw and the second screw are reduced. Wear of the first screw and the second screw is reduced by reducing the frictional force between the first screw and the second screw. Thereby, the braking device of this embodiment can suppress an increase in the frictional force between the first screw and the second screw. Further, in the braking device according to the embodiment of the present invention, as an example, in the circumferential direction, the range in which the first screw is provided in the second region corresponds to the range in which the first screw is provided in the first region. Since the first groove is provided in the first screw to be larger than the first groove, for example, the first groove is provided over the entire first region and the second region, Compared to the aspect in which the range where the first screw is provided in the first region and the range where the first screw is provided in the second region are the same size, the first screw in the second region The strength and durability of the first screw can be improved by the extent that the area where the screw is provided is larger than that of the first region.

FIG. 1 is a cross-sectional view schematically showing the braking device according to the first embodiment. FIG. 2 is a cross-sectional view schematically showing the rotation/linear motion conversion mechanism of the first embodiment. FIG. 3 is a front view showing the rotary member of the first embodiment; FIG. FIG. 4 is a partial cross-sectional view showing the rotating member of the first embodiment. FIG. 5 is a cross-sectional view schematically showing male threads and female threads of the first embodiment. FIG. 6 is a cross-sectional view schematically showing the rotation-to-linear motion converting mechanism in the saturation state of the first embodiment. FIG. 7 is a graph schematically showing an example of changes in the coefficient of friction between the male thread and the female thread in the first embodiment. FIG. 8 is a cross-sectional view schematically showing a rotation/linear motion converting mechanism according to the second embodiment. FIG. 9 is a cross-sectional view schematically showing a rotation/linear motion converting mechanism according to the third embodiment.

(First embodiment)
A first embodiment will be described below with reference to FIGS. 1 to 7. FIG. Note that, in this specification, the constituent elements according to the embodiment and the description of the relevant elements may be described with a plurality of expressions. The components and their descriptions are examples and are not limited by the expressions herein. Components may also be identified by names different from those herein. Also, components may be described in terms that differ from the terms used herein.

FIG. 1 is a cross-sectional view schematically showing a braking device 10 according to the first embodiment. As shown in FIG. 1 , the braking device 10 has a caliper 11 , a brake rotor 12 , a rotation/linear motion conversion mechanism 13 , a rotation transmission mechanism 14 , a motor 15 and an ECU 16 . The rotation/linear motion conversion mechanism 13 and the rotation transmission mechanism 14 are built in the caliper 11 .

The braking device 10 can operate both as a hydraulic brake and as an electric brake. For example, the caliper 11 constitutes a hydraulic brake, and the caliper 11, the rotation/linear motion conversion mechanism 13, the rotation transmission mechanism 14, and the motor 15 constitute an electric brake. The braking device 10 may simply be an electric brake.

The electric brake is a so-called electric parking brake (EPB). That is, the braking device 10 is configured such that the braking state by the electric braking function is maintained during parking. Note that the electric brake may be operated during running or when the vehicle is stopped.

The caliper 11 has a body 21 , pistons 22 , two brake pads 23 and piston seals 24 . The brake pad 23 is an example of a braking member. A cylinder 25 is provided in the body 21 .

The cylinder 25 is a substantially cylindrical hole extending along the central axis Ax. The central axis Ax is an example of a rotation axis. The central axis Ax in this embodiment is the center of the cylinder 25 . Note that the rotation axis is not limited to the central axis Ax of the cylinder 25 .

Hereinafter, the direction along the central axis Ax is called the axial direction, the direction perpendicular to the central axis Ax is called the radial direction, and the direction rotating around the central axis Ax is called the circumferential direction. Further, one of the axial directions of the central axis Ax (the left direction in FIG. 1) is called a lock direction D1, and the other axial direction of the central axis Ax (the right direction in FIG. 1) is called a release direction D2. The locking direction D1 is an example of a first direction. The release direction D2 is an example of a second direction. The release direction D2 is opposite to the locking direction D1.

The cylinder 25 is a bottomed cylindrical hole that opens in the locking direction D1. The piston 22 is accommodated in the cylinder 25 so as to be reciprocatable along the central axis Ax. A hydraulic pressure chamber R is provided in the cylinder 25 .

As the hydraulic pressure in the hydraulic chamber R rises, the piston 22 moves in the lock direction D1 and presses the back plate 27 of the brake pad 23 to press the lining 28 of the brake pad 23 against the brake rotor 12 . As a result, the wheel of the vehicle that rotates together with the brake rotor 12 is braked, and a braking state by the hydraulic brake is obtained.

Piston 22 has an outer peripheral surface 22a and an end surface 22b. The outer peripheral surface 22a is formed in a substantially cylindrical shape facing outward in the radial direction of the central axis Ax. The end face 22b is the end face of the piston 22 in the locking direction D1.

The piston 22 is provided with a recess 22c. The recess 22c is a bottomed cylindrical hole that opens in the release direction D2. That is, the recess 22c is provided on the opposite side of the outer peripheral surface 22a and the end surface 22b. The recess 22c forms part of the hydraulic chamber R.

An outer peripheral surface 22 a of the piston 22 faces an inner peripheral surface 25 a of the cylinder 25 . The inner peripheral surface 25a of the cylinder 25 is the inner peripheral surface of the body 21 formed in a substantially cylindrical shape facing inward in the radial direction of the central axis Ax.

A minute gap (clearance) is provided between the outer peripheral surface 22 a of the piston 22 and the inner peripheral surface 25 a of the cylinder 25 . The outer peripheral surface 22a slides on the inner peripheral surface 25a while being lubricated by the hydraulic fluid present in the gap.

The piston seal 24 is interposed between the outer peripheral surface 22a of the piston 22 and the inner peripheral surface 25a of the cylinder 25 to seal the gap between the outer peripheral surface 22a and the inner peripheral surface 25a. As a result, the piston seal 24 prevents hydraulic fluid from leaking from the fluid pressure chamber R through the gap.

Piston seal 24 is attached to inner peripheral surface 25 a of cylinder 25 and is restricted from moving relative to body 21 . In addition, the piston seal 24 may be attached to the outer peripheral surface 22 a of the piston 22 .

As the hydraulic pressure in the hydraulic pressure chamber R decreases, the piston seal 24 draws the piston 22 toward the hydraulic pressure chamber R in the release direction D2 by elastic force, and separates the end face 22b of the piston 22 from the brake pad 23. have a function. That is, when the pressure of the piston 22 against the back plate 27 is released as the hydraulic pressure in the hydraulic pressure chamber R decreases, the pressing of the lining 28 against the brake rotor 12 by the piston 22 is released. As a result, a brake release state by the hydraulic brake is obtained. Thus, the caliper 11 can act as a hydraulic brake.

The rotation/linear motion converting mechanism 13 is provided inside the caliper 11 . The rotation/linear motion converting mechanism 13 has a rotating member 31 and a linear motion member 32 . The rotating member 31 is an example of a rotating member and member.

The rotating member 31 is supported by the body 21 so as to be rotatable around the central axis Ax. The linear motion member 32 is attached to the rotary member 31 so as to be linearly movable in the axial direction according to the rotation of the rotary member 31 .

The rotation transmission mechanism 14 is, for example, a speed reducer having a plurality of rotating elements such as gears. The rotation transmission mechanism 14 transmits rotation of the output shaft of the motor 15 to the rotating member 31 . The rotating member 31 rotates around the central axis Ax by torque input from the rotation transmission mechanism 14 .

The rotating member 31 has a coupling portion 41 , a flange 42 and a shaft 43 . The coupling portion 41 rotates integrally with the output shaft of the rotation transmission mechanism 14 . The flange 42 is positioned between the coupling portion 41 and the shaft 43 and is formed in a substantially disc shape projecting from the coupling portion 41 and the shaft 43 in the radial direction of the central axis Ax.

The shaft 43 protrudes from the flange 42 in the locking direction D1. The shaft 43 is formed in a substantially columnar shape extending in the axial direction along the central axis Ax. In this embodiment, the central axis Ax is also the central axis of the flange 42 and the shaft 43 .

A thrust bearing 44 is provided between the flange 42 and the body 21 of the caliper 11 . The body 21 axially supports the rotating member 31 via a thrust bearing 44 .

FIG. 2 is a cross-sectional view schematically showing the rotation/linear motion conversion mechanism 13 of the first embodiment. As shown in FIG. 2, the shaft 43 has an outer peripheral surface 43a. The outer peripheral surface 43a is a substantially cylindrical curved surface that extends in the axial direction and faces radially outward. A male screw 45 is provided on the outer peripheral surface 43a. The male screw 45 is an example of a male screw and a first screw.

The linear motion member 32 has a tubular portion 51 and two protrusions 52 . The cylindrical portion 51 is formed in a substantially cylindrical shape that extends in the axial direction and surrounds the central axis Ax. The tubular portion 51 has an inner peripheral surface 51a.

The inner peripheral surface 51a is a substantially cylindrical curved surface that extends in the axial direction and faces radially inward. A female screw 53 is provided on the inner peripheral surface 51a. Female thread 53 is an example of a female thread and a second thread.

The female thread 53 meshes with the male thread 45 of the rotating member 31 . In this embodiment, the length of the female thread 53 is shorter than the length of the male thread 45 in the axial direction. The female thread 53 is closer to the end of the linear motion member 32 in the release direction D2 than to the end of the linear motion member 32 in the lock direction D1. Note that the position of the female screw 53 is not limited to this example.

The protrusion 52 protrudes radially outward from the tubular portion 51 . The two protrusions 52 protrude from the cylindrical portion 51 in mutually opposite directions (upward and downward directions in each drawing). Note that the number and direction of the protrusions 52 are not limited to this example.

As shown in FIG. 1 , part of the rotation-to-linear motion conversion mechanism 13 is accommodated within the recess 22 c of the piston 22 . A portion of the shaft 43 of the rotating member 31 is positioned within the recess 22c of the piston 22 . Further, the direct-acting member 32 is provided so as to be axially movable within the concave portion 22c.

The recess 22c of the piston 22 is provided with two guide grooves 22d. The two guide grooves 22d are radially outward and recessed in mutually opposite directions (upward and downward directions in each drawing) and extend in the axial direction.

The protrusion 52 of the linear motion member 32 is housed in the guide groove 22d so as to be movable along the guide groove 22d. For example, the side surface of the guide groove 22d facing the circumferential direction contacts the side surface of the projection 52 facing the circumferential direction, thereby restricting the rotation of the linear motion member 32 around the central axis Ax.

As described above, the male thread 45 of the rotating member 31 and the female thread 53 of the linear motion member 32 are engaged with each other, and the rotation of the protrusion 52 of the linear motion member 32 is restricted by the guide groove 22d of the piston 22. Thereby, the linear motion member 32 can linearly move in the axial direction according to the rotation of the rotating member 31 . In other words, the linear motion member 32 can move substantially parallel in the axial direction.

The motor 15 is driven by drive power based on the control signal. The motor 15 rotates the output shaft of the motor 15 to rotate the rotating member 31 about the central axis Ax via the rotation transmission mechanism 14 .

FIG. 3 is a front view showing the rotating member 31 of the first embodiment. When the output shaft of the motor 15 rotates in one direction, the rotating member 31 rotates in the normal rotation direction Dn around the central axis Ax shown in FIG. The forward rotation direction Dn is an example of a first rotation direction. When the rotary member 31 rotates in the forward rotation direction Dn, the linear motion member 32 advances (moves) straight in the locking direction D1.

The linear motion member 32 moving in the locking direction D1 pushes the piston 22 in the locking direction D1. The piston 22 pushed by the direct-acting member 32 moves in the lock direction D<b>1 to press the lining 28 against the brake rotor 12 via the back plate 27 . As a result, a braking state is obtained by the electric braking function, in which the wheels of the vehicle rotating integrally with the brake rotor 12 are braked.

When the output shaft of the motor 15 rotates in the reverse direction, the rotating member 31 rotates in the reverse direction Dr around the central axis Ax shown in FIG. The reverse rotation direction Dr is the direction opposite to the forward rotation direction Dn. The forward rotation direction Dn and the reverse rotation direction Dr are included in the circumferential direction.

When the rotary member 31 rotates in the reverse direction Dr, the direct-acting member 32 moves straight (moves) in the release direction D<b>2 away from the piston 22 . Due to the movement of the linear motion member 32 in the release direction D2, the pressing force of the piston 22 against the back plate 27 is reduced, and the pressure of the lining 28 against the brake rotor 12 by the piston 22 is released. As a result, a state in which braking by the electric braking function is released (non-braking state) is obtained. Thus, the caliper 11, the rotation/linear motion conversion mechanism 13, the rotation transmission mechanism 14, and the motor 15 can operate as an electric brake.

In this embodiment, the ECU 16 of FIG. 1 controls the motor 15 of the braking device 10 . The ECU 16 may also be called an electronic control unit. The ECU 16 may be configured partially by hardware such as a CPU and a controller that execute software, or may be configured entirely by hardware. Note that the motor 15 may be controlled not only by the ECU 16 but also by a controller dedicated to the braking device 10, for example.

The ECU 16 controls the motor 15 so that the rotating member 31 rotates in the forward rotation direction Dn, for example, when receiving an instruction signal to shift to the braking state from the operation switch (SW) of the electric braking function. On the other hand, when the ECU 16 receives an instruction signal to release the braking state from the operation switch, the ECU 16 controls the motor 15 so that the rotating member 31 rotates in the reverse direction Dr.

FIG. 4 is a partial cross-sectional view showing the rotating member 31 of the first embodiment. FIG. 4 shows a cross section of part of the rotating member 31 along the line F4-F4 of FIG. As shown in FIG. 4 , shaft 43 of rotating member 31 has first region 61 and second region 62 .

Each of first region 61 and second region 62 is part of shaft 43 . The first region 61 and the second region 62 are arranged in the axial direction. A male thread 45 is provided in each of the first region 61 and the second region 62 .

A portion of the male screw 45 provided in the first region 61 is hereinafter referred to as a male screw 45A, and a portion of the male screw 45 provided in the second region 62 is hereinafter referred to as a male screw 45B. Sometimes. In this embodiment, the male threads 45A and 45B have substantially the same cross-sectional shape and are continuous with each other.

The cross-sectional shapes of the male screws 45A and 45B may be different from each other, or may be separated. However, the male threads 45A and 45B form one male thread 45 that can mesh with one female thread 53. As shown in FIG. That is, the female screw 53 can move between a position where it meshes with the male screw 45A and a position where it meshes with the male screw 45B beyond the boundary between the male screw 45A and the male screw 45B.

The first region 61 extends axially. The first region 61 has a first inner end 61a and a first outer end 61b. The first inner end 61a is an example of a first end. The first outer end 61b is an example of a second end.

The first inner end 61 a is one end of the first region 61 in the axial direction connected to the second region 62 . In this embodiment, the first inner end 61a is the end of the first region 61 in the release direction D2.

The first outer end 61b is the other end of the first region 61 in the axial direction. In this embodiment, the first outer end 61b is the end of the first region 61 in the locking direction D1 and the end of the shaft 43 in the locking direction D1.

The second region 62 is continuous with the first region 61 and extends in the axial direction. The second region 62 has a second inner edge 62a and a second outer edge 62b.

The second inner end 62 a is one end of the second region 62 in the axial direction connected to the first region 61 . In this embodiment, the second inner end 62a is the end of the second region 62 in the locking direction D1.

The first inner end 61a and the second inner end 62a are provided at the same position in the axial direction. A first inner edge 61 a and a second inner edge 62 a are boundaries between the first region 61 and the second region 62 .

The second outer end 62b is the other end of the second region 62 in the axial direction. In this embodiment, the second outer end 62b is the end of the second region 62 in the release direction D2 and the end of the shaft 43 in the release direction D2. A second outer end 62 b is connected to the flange 42 . Note that the second outer end 62b is not limited to this example.

Two first grooves 65 are provided in the first region 61 . Note that the number of first grooves 65 is not limited to this example. One first groove 65 may be provided in the first region 61, or three or more first grooves 65 may be provided.

The first groove 65 opens in the outer peripheral surface 43a of the shaft 43 and divides the male screw 45A in the circumferential direction. That is, the male screw 45A has a plurality of portions that are spaced apart from each other in the circumferential direction via the first grooves 65 . Note that when the number of the first grooves 65 is one, the plurality of portions are connected to each other at positions separated from the first grooves 65 . In other words, the first groove 65 extends across the threads of the male thread 45A.

The first groove 65 extends axially between the first inner end 61a and the first outer end 61b. Note that the first groove 65 may extend in other directions. For example, the first groove 65 may spirally extend around the central axis Ax. The two first grooves 65 are equally spaced apart in the circumferential direction.

The lengths of the two first grooves 65 in the axial direction are substantially equal. The widths of the two first grooves 65 in the circumferential direction are also substantially equal. The depths of the two first grooves 65 in the radial direction are also substantially equal. Note that the shapes of the two first grooves 65 may be different from each other.

The depth of the first groove 65 in the radial direction is the distance between the top of the male thread 45A and the bottom of the first groove 65 in the radial direction. In this embodiment, the depth of the first groove 65 is longer (deeper) than the height of the male screw 45A. The depth of the first groove 65 may be equal to or shorter (shallower) than the height of the male screw 45A.

The second region 62 is not provided with a groove that divides the male screw 45B in the circumferential direction. Therefore, in the axial direction, the positions where the ends of the first groove 65 are provided in the release direction D2 are the first inner end 61a of the first region 61 and the second inner end 62a of the second region 62. can be defined as

The male screw 45A is circumferentially divided by the first grooves 65 . In other words, the first groove 65 lacks the male thread 45A. On the other hand, the male screw 45B is not divided by the groove. Therefore, the male screw 45B is provided over the entire area (perimeter) of the second region 62 in the circumferential direction. Note that the male screw 45B may be missing.

In the circumferential direction, the range in which the male threads 45B are provided in the second area 62 is larger than the range in which the male threads 45A are provided in the first area 61 . The range in which the male screw 45 is provided is at least one of the length in the circumferential direction and the angle around the central axis Ax.

FIG. 5 is a cross-sectional view schematically showing the male thread 45 and the female thread 53 of the first embodiment. As shown in FIG. 5, the male thread 45 has a plurality of threads 71 . Each of the plurality of threads 71 has two side surfaces 71a and 71b. Also, the female screw 53 has a plurality of screw threads 72 . Each of the plurality of threads 72 has two sides 72a, 72b. One side surface 71b, 72b faces substantially the locking direction D1. The other side surfaces 71a and 72a face substantially the release direction D2.

The male thread 45 and the female thread 53 of this embodiment are so-called sawtooth threads. The side surfaces 71b and 72a extend substantially radially. The side surfaces 71a and 72b are inclined with respect to the radial direction. It should be noted that the male threads 45 and female threads 53 may be other threads such as triangular threads, trapezoidal threads, and the like.

The angle θ1 of the thread 71 of the male screw 45 and the angle θ2 of the thread 72 of the female screw 53 are different from each other. Therefore, the male thread 45 and the female thread 53 can be in line contact with each other. The angle θ1 is the angle between the two side surfaces 71a, 71b of the screw thread 71. As shown in FIG. The angle θ2 is the angle between the two sides 72a, 72b of the thread 72. As shown in FIG.

In this embodiment, the angle θ1 is greater than the angle θ2. Therefore, the position P where the side surface 71b of the thread 71 and the side surface 72a of the thread 72 contact each other is closer to the valley 71d of the thread 71 than to the peak 71c of the thread 71 . In other words, position P is farther from trough 72d of thread 72 than from apex 72c of thread 72 . Therefore, the distance between the central axis Ax and the position P becomes relatively short, and the load of rotation of the rotary member 31 is reduced.

A gap G is formed between the male screw 45 and the female screw 53 . For example, a gap G is formed between the apex 71c of the thread 71 and the valley 72d of the thread 72 . A gap G is also formed between the valley 71 d of the screw thread 71 and the peak 72 c of the screw thread 72 .

The lining 28 of the brake pad 23 has a predetermined thickness when the brake device 10 is first manufactured or when the brake pad 23 is replaced with a new one. On the other hand, when the braking device 10 repeats braking, the thickness of the lining 28 decreases due to wear. Therefore, when the braking device 10 repeats braking, the position of the back plate 27 moves in the locking direction D1.

When the braking device 10 performs braking by the electric braking function, the linear motion member 32 moves to a position where the piston 22 contacts the back plate 27 and the lining 28 contacts the brake rotor 12 . Therefore, the position where the linear motion member 32 pushes the piston 22 also moves in the locking direction D1 as the lining 28 wears.

When the braking by the electric braking function is released, current is applied to the motor 15 and the rotating member 31 rotates in the reverse direction Dr. At this time, the ECU 16 measures the load acting on the motor 15 by measuring the current value flowing through the motor 15, for example. When the piston 22 is separated from the brake pad 23, the load and current value acting on the motor 15 are reduced. The ECU 16 stops the motor 15 when a predetermined time has passed since the current value fell below the threshold value. Therefore, the position of the direct-acting member 32 during non-braking also moves in the locking direction D1 as the lining 28 wears.

At least a portion of the female thread 53 is engaged with the male thread 45B in the second region 62 when the braking device 10 is first manufactured. In this embodiment, the entire area of the female thread 53 is engaged with the male thread 45B in the second region 62 when the braking device 10 is manufactured. At this time, the female thread 53 is separated from the male thread 45A in the first region 61 .

FIG. 2 shows the rotation-to-linear motion conversion mechanism 13 at the beginning when the braking device 10 of this embodiment was manufactured. In FIG. 2, the linear motion member 32 in the non-braking state is indicated by a solid line, and the linear motion member 32 in the braking state is indicated by a chain double-dashed line.

As shown by the two-dot chain line in FIG. 2, when the braking device 10 of the present embodiment was first manufactured, the direct-acting member 32 in the braking state pushing the piston 22 was separated from the male screw 45A in the first region 61. there is That is, when the braking device 10 is first manufactured, the entire area of the female thread 53 meshes with the male thread 45B regardless of whether the direct-acting member 32 is in the braking state or the non-braking state. A part of the female thread 53 in the direct-acting member 32 in the braking state may mesh with the male thread 45A. Also, a part of the female thread 53 in the linear motion member 32 in the non-braking state may mesh with the male thread 45A.

FIG. 6 is a cross-sectional view schematically showing the rotation/linear motion conversion mechanism 13 in a saturated state according to the first embodiment. The internal thread 53 approaches the first outer end 61 b of the first region 61 by moving the linear motion member 32 in the locking direction D<b>1 . For example, due to the movement of the direct-acting member 32 due to the wear of the lining 28 described above, the female screw 53 approaches the first outer end 61b. Further, at this time, at least in the direct-acting member 32 in the braking state, the entire area of the female thread 53 meshes with the male thread 45A. The female screw 53 also approaches the first outer end 61b by the movement of the direct-acting member 32 due to the rotation of the rotating member 31 in the forward rotation direction Dn.

When the braking device 10 repeats braking by the electric braking function, at least one of the male thread 45 and the female thread 53 wears out. The male thread 45 and the female thread 53 generate dust due to wear. The dust is part of the male thread 45 or the female thread 53 that has fallen off from the male thread 45 and the female thread 53 .

Dust, if present between male thread 45 and female thread 53, functions like an abrasive, for example. That is, the dust wears the thread 71 of the male screw 45 and the thread 72 of the female screw 53 as the rotating member 31 and the direct-acting member 32 rotate relative to each other. In addition, as this wear progresses, there is a risk that the angle θ1 of the screw thread 71 and the angle θ2 of the screw thread 72 will approach each other.

When the angle θ1 of the screw thread 71 and the angle θ2 of the screw thread 72 approach each other, the male screw 45 and the female screw 53 come into contact with each other through surface contact. Therefore, the coefficient of friction between the male thread 45 and the female thread 53 increases.

Dust can be discharged (accumulated) in the gap G between the male thread 45 and the female thread 53 . By forming a gap G between the male screw 45 and the female screw 53, it is possible to suppress an increase in the coefficient of friction between the male screw 45 and the female screw 53 due to wear.

FIG. 7 is a graph schematically showing an example of changes in friction coefficient of friction between the male thread 45 and the female thread 53 of the first embodiment. The solid line graph in FIG. 7 shows an example of changes in the friction coefficient in this embodiment.

The vertical axis in FIG. 7 indicates the friction coefficient of friction between the male thread 45 and the female thread 53 . The horizontal axis of FIG. 7 indicates the wear amount of the brake pad 23 . The amount of wear is the amount of thickness reduction from the initial thickness of the brake pad 23 .

The amount of wear of the brake pad 23 is roughly proportional to the number of times the braking device 10 brakes. Also, the amount of wear of the male thread 45 and the female thread 53 is roughly proportional to the number of times of braking in the braking device 10 . Therefore, the amount of wear of the male thread 45 and the female thread 53 is roughly proportional to the amount of wear of the brake pad 23 . Therefore, the horizontal axis of FIG. 7 indicates the amount of wear of the brake pad 23, the number of times of braking in the braking device 10, and the amount of wear of the male thread 45 and the female thread 53 at the same time.

As shown in FIG. 7, when the number of times of braking in the braking device 10 increases and the amount of wear of the brake pad 23, the male screw 45, and the female screw 53 increases, the generated dust causes the space between the male screw 45 and the female screw 53. The coefficient of friction of friction increases. At least one of the male thread 45 and the female thread 53 is worn out until the amount of wear of the brake pad 23 reaches the saturation point Ps in FIG. increase the coefficient of friction of the friction between

Hereinafter, a state in which at least one of the male thread 45 and the female thread 53 increases the coefficient of friction between the male thread 45 and the female thread 53 due to wear is referred to as a non-saturated state. A non-saturated state is an example of a first state. As shown in FIG. 2, at least a portion of the female threads 53 mesh with the male threads 45B of the second region 62 in the non-saturated state.

In the non-saturation state, the entire area of the female thread 53 meshes with the male thread 45B of the second region 62 from the beginning of manufacturing of the braking device 10 until the amount of wear of the brake pad 23 reaches the overriding point Pb in FIG. The amount of wear of the brake pad 23 and the coefficient of friction are roughly proportional from the time the braking device 10 is manufactured until the amount of wear of the brake pad 23 reaches the crossing point Pb.

When the wear amount of the brake pad 23 exceeds the crossing point Pb, part of the female thread 53 meshes with the male thread 45A of the first region 61 . Thus, in the first region 61 the first groove 65 faces the internal thread 53 . Dust generated by the male thread 45 and the female thread 53 can be discharged to the first groove 65 . Hydraulic fluid is also supplied between the male thread 45 and the female thread 53 through the first groove 65 . The hydraulic fluid can lubricate the male threads 45 and the female threads 53 .

Since dust is discharged into the first groove 65 and hydraulic fluid lubricates the male thread 45 and the female thread 53, the coefficient of friction increase (slope) of the friction between the male thread 45 and the female thread 53 is reduced. . However, in desaturated conditions, the coefficient of friction continues to increase.

By the time the amount of wear of the brake pad 23 reaches the saturation point Ps, the angle θ1 of the partial thread 71 of the male thread 45 and the angle θ2 of the partial thread 72 of the female thread 53 are approximately equal. Become. Therefore, the male thread 45 and the female thread 53 do not increase the coefficient of friction due to wear.

Hereinafter, a state in which the male thread 45 and the female thread 53 do not increase the coefficient of friction between the male thread 45 and the female thread 53 due to wear is referred to as a saturation state. A saturation state is an example of a second state. Note that the angle θ1 and the angle θ2 may remain different in the saturation state.

In the saturation state, the coefficient of friction between the male thread 45 and the female thread 53 may change temporarily. However, in saturation, the coefficient of friction remains substantially constant for at least a predetermined period of time.

As shown in FIG. 6, at least a portion of the female thread 53 meshes with the male thread 45A of the first region 61 in the saturation state. In the saturation state of this embodiment, the entire area of the female thread 53 meshes with the male thread 45A of the first region 61 . In the saturation state, for example, part of the female thread 53 of the linear motion member 32 in the non-braking state may mesh with the male thread 45B of the second region 62 .

As described above, at least a portion of the female thread 53 meshes with the male thread 45A of the first region 61 when the non-saturation state transitions to the saturation state. Further, in the present embodiment, when the non-saturation state transitions to the saturation state, the range of engagement between the female thread 53 and the male thread 45A increases.

A two-dot chain line graph in FIG. 7 shows changes in the friction coefficient in a comparative example in which the shaft 43 is not provided with the first groove 65 . Even when the first groove 65 is not provided on the shaft 43, when the wear amount of the brake pad 23 reaches the saturation point Ps, the male thread 45 and the female thread 53 do not increase the coefficient of friction due to wear. The saturation point Ps in this embodiment and the saturation point Ps in the comparative example are substantially equal.

The length of the first groove 65 is set so that the entire area of the female thread 53 meshes with the male thread 45A when the wear amount of the brake pad 23 reaches the saturation point Ps. Note that the length of the first groove 65 is not limited to this example.

The coefficient of friction in the saturated state of this embodiment is lower than the coefficient of friction in the saturated state of the comparative example in which the first grooves 65 are not provided. Furthermore, the coefficient of friction in the saturation state of this embodiment is lower than the coefficient of friction that may cause abnormal noise due to friction between the male thread 45 and the female thread 53 . Therefore, the braking device 10 of the present embodiment can suppress the generation of abnormal noise due to friction in the saturation state.

In the braking device 10 according to the first embodiment described above, the rotary member 31 has the first area 61 and the second area 62 arranged in the direction along the central axis Ax. A male screw 45 is provided in each of the first region 61 and the second region 62 . The first region 61 has a first inner end 61a and a first outer end 61b. The first inner end 61 a is one end of the first region 61 in the direction along the central axis Ax and is connected to the second region 62 . The first outer end 61b is the other end of the first region 61 in the direction along the central axis Ax. The first region 61 is provided with a first groove 65 that divides the male screw 45 in the circumferential direction around the central axis Ax. In the circumferential direction, the range in which the male threads 45B are provided in the second area 62 is larger than the range in which the male threads 45A are provided in the first area 61 . At least part of the female thread 53 meshes with the male thread 45B in the second region 62 at least at the beginning of manufacturing of the braking device 10 . By moving the linear motion member 32 in the lock direction D1, the female screw 53 approaches the first outer end 61b. For example, at least one of the male thread 45 and the female thread 53 wears due to repeated braking. Dust generated by the wear accumulates between the male thread 45 and the female thread 53 and increases the coefficient of friction between the male thread 45 and the female thread 53 . On the other hand, when the brake pad 23 wears due to repeated braking, the linear motion member 32 moves in the lock direction D1. By moving the position of the direct-acting member 32 in the locking direction D1, the female screw 53 (the portion located closer to the first inner end 61a than the first outer end 61b) is moved to the first outer end 61b. female screw 53 (the portion located on the opposite side of the first inner end 61a to the first outer end 61b; located between the first inner end 61a and the second outer end 62b); portion) engages with the male thread 45A in the first region 61. As shown in FIG. In the first area 61 , dust generated by abrasion can be discharged into the first grooves 65 . Furthermore, in the circumferential direction, the contact area between the male screw 45B of the second region 62 and the female screw 53 (the contact area per screw ridge) is larger than the contact area with (same as above). Therefore, when at least part of the female thread 53 meshes with the male thread 45B in the second region 62, the normal force per contact area between the male thread 45B and the female thread 53 is reduced, and the male thread 45B and the female thread 45B and the female thread 53 are thus reduced in normal force. Frictional force with the screw 53 is reduced. By reducing the frictional force between the male screw 45B and the female screw 53, wear of the male screw 45B and the female screw 53 is reduced. Since the wear of the male screw 45B and the female screw 53 has not progressed relatively when the braking device 10 is first manufactured, there is enough room for dust to accumulate between the male screw 45B and the female screw 53. An increase in the coefficient is particularly suppressed. As a result, the braking device 10 of the present embodiment can suppress an increase in the frictional force between the male screw 45 and the female screw 53, and the friction between the male screw 45 and the female screw 53 causes noise. can be suppressed. Further, in the present embodiment, in the circumferential direction, the first screw thread 45A is arranged such that the range in which the male screw 45B is provided in the second region 62 is larger than the range in which the male screw 45A is provided in the first region 61. Since the groove 65 is provided in the male thread 45, for example, the first groove is provided throughout the first region and the second region, and the male thread in the first region is provided in the circumferential direction. Compared to the aspect in which the range provided with the male screw 45B in the second region 62 is the same size as the range provided with the male screw 45B in the second region, the range provided with the male screw 45B in the second region 62 The strength and durability of the male screw 45 can be improved by the amount larger than that.

According to another explanation, at least a portion of the female thread 53 is such that at least one of the male thread 45 and the female thread 53 wears to reduce the coefficient of friction between the male thread 45 and the female thread 53. In the increased desaturation state, it engages external threads 45B in second region 62 . At least part of the female thread 53 meshes with the male thread 45A in the first region 61 when transitioning from the non-saturated state to the saturated state in which the friction coefficient of the male thread 45 and the female thread 53 does not increase due to wear. In particular, in this embodiment, the brake pad 23 is pressed against the brake rotor 12 when the female thread 53 transitions from the non-saturated state to the saturated state where the friction coefficient of the male thread 45 and the female thread 53 does not increase due to wear. The entire area of the female thread 53 in the braking state meshes with the male thread 45A in the first region 61 . In the non-saturated state, at least one of the male thread 45 and the female thread 53 wears due to, for example, repeated braking. Dust generated by the wear increases the coefficient of friction between the male thread 45 and the female thread 53 . On the other hand, when the brake pad 23 wears due to repeated braking, the linear motion member 32 moves in the locking direction D1. By moving the position of the direct-acting member 32 in the locking direction D1, the female thread 53 (the portion located on the side opposite to the first outer end 61b with respect to the first inner end 61a) moves to the first region 61. It comes to mesh with the male screw 45A in. That is, the engagement length between the female thread 53 and the male thread 45A in the first region 61 increases. In the first area 61 , dust generated by abrasion can be discharged into the first grooves 65 . Therefore, when at least part of the female thread 53 meshes with the male thread 45A in the first region 61, the increase (slope) of the coefficient of friction due to wear is reduced, and finally the increase in the coefficient of friction is reduced to a relatively low value. stop at . That is, at least a portion of the female thread 53 meshes with the male thread 45A in the first region 61, thereby reducing the coefficient of friction when transitioning from the non-saturated state to the saturated state. As a result, the braking device 10 of the present embodiment can suppress an increase in the frictional force between the male screw 45 and the female screw 53, and the friction between the male screw 45 and the female screw 53 can prevent noise from being generated. can be suppressed.

The angle θ1 of the thread 71 of the male screw 45 and the angle θ2 of the thread 72 of the female screw 53 are different from each other. Thereby, the contact area between the male screw 45 and the female screw 53 is reduced, and the frictional force between the male screw 45 and the female screw 53 is reduced. Also, a gap G is formed between the male screw 45 and the female screw 53 . Dust generated by abrasion between the male screw 45 and the female screw 53 can be discharged into the gap G. Therefore, the braking device 10 of the present embodiment can suppress an increase in the frictional force between the male screw 45 and the female screw 53, and prevent noise from occurring due to the friction between the male screw 45 and the female screw 53. can be suppressed.

A groove that divides the male screw 45 in the circumferential direction is not provided in the second region 62 . As a result, when at least a portion of the female thread 53 meshes with the male thread 45B in the second region 62, the normal force per contact area between the male thread 45B and the female thread 53 is reduced, and thus the male thread 45B and the female thread 53 is reduced. As a result, the braking device 10 of the present embodiment can suppress an increase in the frictional force between the male screw 45 and the female screw 53, and the friction between the male screw 45 and the female screw 53 causes noise. can be suppressed. Furthermore, the second region 62 can be held by, for example, a chuck when the rotary member 31 is provided with the first groove 65 by machining. Therefore, in the braking device 10 of this embodiment, the first groove 65 can be easily provided in the rotating member 31 .

(Second embodiment)
A second embodiment will be described below with reference to FIG. In the following description of the multiple embodiments, constituent elements having functions similar to those already explained are given the same reference numerals as the constituent elements already explained, and further explanation may be omitted. . In addition, a plurality of components with the same reference numerals may not all have common functions and properties, and may have different functions and properties according to each embodiment.

FIG. 8 is a cross-sectional view schematically showing the rotation/linear motion conversion mechanism 13 according to the second embodiment. In a second embodiment, two second grooves 81 are provided in the second region 62 . FIG. 8 shows one of the two second grooves 81 .

The second groove 81 opens in the outer peripheral surface 43a of the shaft 43 and divides the male screw 45B in the circumferential direction. Note that when one second groove 81 is provided in the second region 62 , the plurality of portions are connected to each other at positions separated from the second groove 81 . In other words, the second groove 81 extends across the threads 72 of the male thread 45B.

The second groove 81 extends axially between the second inner end 62a and the second outer end 62b. Note that the second groove 81 may extend in other directions. For example, the second groove 81 may extend spirally. The two second grooves 81 are equally spaced apart in the circumferential direction.

The lengths of the two second grooves 81 in the axial direction are substantially equal. The widths of the two second grooves 81 in the circumferential direction are also substantially equal. The depths of the two second grooves 81 in the radial direction are also substantially equal. Note that the shapes of the two second grooves 81 may be different from each other.

In this embodiment, the depth of the second groove 81 is longer (deeper) than the height of the male screw 45B. The depth of the second groove 81 may be equal to or shorter (shallower) than the height of the male screw 45B.

The width of the second groove 81 in the circumferential direction is shorter than the width of the first groove 65 in the circumferential direction. Therefore, in the circumferential direction, the range in which the male threads 45A are provided in the first area 61 is larger than the range in which the male threads 45B are provided in the second area 62 .

The second grooves 81 are connected to the ends of the corresponding first grooves 65 in the release direction D2. A position where the first groove 65 and the second groove 81 are connected in the axial direction is defined as a first inner end 61a of the first region 61 and a second inner end 62a of the second region 62. can be

A groove that tapers in the release direction D2 may be provided in the first region 61 and the second region 62 . In this case, a portion of the groove in the axial direction is the first groove 65 and another portion of the groove in the axial direction is the second groove 81 .

The width of the first groove 65 in the circumferential direction and the width of the second groove 81 in the circumferential direction may be the same. In this case, the number of first grooves 65 provided in the first region 61 is greater than the number of second grooves 81 provided in the second region 62 . Therefore, in the circumferential direction, the range in which the male threads 45A are provided in the first area 61 is larger than the range in which the male threads 45B are provided in the second area 62 .

In the braking device 10 of the second embodiment described above, the second region 62 is provided with the second groove 81 that divides the male screw 45 in the circumferential direction around the central axis Ax. As a result, when at least part of the female thread 53 meshes with the male thread 45B in the second region 62, dust generated by wear between the male thread 45 and the female thread 53 is discharged into the second groove 81. can be done. Further, the first groove 65 and the second groove 81 can supply hydraulic fluid to the male threads 45 and the female threads 53 . Therefore, the braking device 10 of the present embodiment can suppress an increase in the frictional force between the male screw 45 and the female screw 53, and prevent noise from occurring due to the friction between the male screw 45 and the female screw 53. can be suppressed.

Further, in the present embodiment, in the circumferential direction, the first screw thread 45A is arranged such that the range in which the male screw 45B is provided in the second region 62 is larger than the range in which the male screw 45A is provided in the first region 61. Since the groove 65 and the second groove 81 are provided in the male screw 45, for example, the first groove is provided over the entire first region and the second region, and in the circumferential direction, the first region Compared to the aspect in which the range where the male screw is provided and the range where the male screw is provided in the second region are of the same size, the range where the male screw 45B is provided in the second region 62 is The strength and durability of the male screw 45 can be improved by the amount larger than that of the first region 61 .

(Third embodiment)
A third embodiment will be described below with reference to FIG. FIG. 9 is a cross-sectional view schematically showing a rotation/linear motion conversion mechanism 13 according to the third embodiment. FIG. 9 shows the linear motion member 32 when the braking device 10 was first manufactured by a two-dot chain line, and shows the linear motion member 32 in the saturation state by a solid line.

As shown in FIG. 9, the rotating member 31 of the third embodiment is provided with a male screw 145 instead of the male screw 45. As shown in FIG. The male screw 145 is an example of a male screw and a second screw. External threads 145 are identical to external threads 45 of the first embodiment, except as noted below.

The male screw 145 is provided on the outer peripheral surface 43a of the shaft 43 at a position spaced apart from the flange 42 in the locking direction D1. The male thread 145 is not divided in the circumferential direction by grooves. In addition, the male thread 145 may be divided in the circumferential direction by grooves.

A female screw 153 is provided in place of the female screw 53 in the linear motion member 32 of the third embodiment. Female thread 153 is an example of a female thread and a first thread. Female thread 153 is identical to female thread 53 of the first embodiment, except as described below.

In the axial direction, the length of female thread 153 is greater than the length of male thread 145 . The female thread 153 is closer to the end of the linear motion member 32 in the lock direction D1 than to the end of the linear motion member 32 in the release direction D2. Note that the position of the female screw 153 is not limited to this example.

A linear motion member 32 of the third embodiment has a first region 161 and a second region 162 . The first region 161 and the second region 162 are arranged in the axial direction. A female screw 153 is provided in each of the first region 161 and the second region 162 .

A portion of the female thread 153 provided in the first region 161 is hereinafter referred to as a female thread 153A, and a portion of the female thread 153 provided in the second region 162 is hereinafter referred to as a female thread 153B. Sometimes.

The first region 161 extends axially and has a first inner end 161a and a first outer end 161b. The first inner end 161a is an example of a first end. The first outer end 161b is an example of a second end.

The first inner end 161 a is one end of the first region 161 in the axial direction connected to the second region 162 . In this embodiment, the first inner end 161a is the end of the first region 161 in the locking direction D1. The first outer end 161b is the other end of the first region 161 in the axial direction.

The second region 162 is continuous with the first region 161 and extends axially. The second region 162 has a second inner edge 162a and a second outer edge 162b. The second inner end 162 a is one end of the second region 162 in the axial direction connected to the first region 161 . The first inner end 161a and the second inner end 162a are provided at the same position in the axial direction. The second outer end 162b is the other end of the second region 162 in the axial direction.

Two first grooves 165 are provided in the first region 161 . The first groove 165 opens in the inner peripheral surface 51a of the tubular portion 51 and divides the female screw 153A in the circumferential direction. The first groove 165 extends axially between the first inner end 161a and the first outer end 161b. Note that the first groove 165 may extend in other directions.

The second region 162 is not provided with a groove that divides the female screw 153B in the circumferential direction. Therefore, in the circumferential direction, the range where the female thread 153B is provided in the second region 162 is larger than the range where the female thread 153A is provided in the first region 161 . Note that a groove may be provided in the second region 162 .

As indicated by the two-dot chain line in FIG. 9, at least a portion of the male thread 145 meshes with the female thread 153B in the second region 162 in a non-saturated state including the initial stage when the braking device 10 is manufactured. In the non-saturated state, at least one of the male threads 145 and the female threads 153 increases the friction coefficient of friction between the male threads 145 and the female threads 153 due to wear.

By moving the direct-acting member 32 in the locking direction D1, the male thread 145 (the portion located closer to the first inner end 161 a than the first outer end 161 b ) moves from the first region 161 to the first region 161 . approaches the outer end 161b of the . When the male screw 145 (the portion located on the opposite side of the first outer end 161b from the first inner end 161a) meshes with the female screw 153A of the first region 161, the male screw 145 and the female screw 153 are engaged. can be discharged to the first groove 165 . Also, hydraulic fluid is supplied between the male thread 145 and the female thread 153 through the first groove 165 .

At least a portion of the male thread 145 meshes with the female thread 153 A of the first region 161 when transitioning from the non-saturated state to the saturated state. In the saturated state, male threads 145 and female threads 153 do not increase the coefficient of friction due to wear.

As in the first and third embodiments described above, the first grooves 65 and 165 may be provided on the rotating member 31 or may be provided on the direct-acting member 32 . In addition, the rotating member 31 may be provided with a female screw, and the direct-acting member 32 may be provided with a male screw.

A braking device according to at least one embodiment described above includes, as an example, a rotating member provided with one of a male thread and a female thread that meshes with the male thread, and rotatable around a rotation axis; The other of the male thread and the female thread is provided, and when the rotating member rotates about the rotating shaft in the first rotating direction, the rotating member moves in the first direction along the rotating shaft. a linear motion member that moves in a second direction opposite to the first direction when rotated in a second direction opposite to the first direction; and the linear motion member that moves in the first direction. a piston that is pushed in the first direction by the moving member and moves in the first direction to press the braking member against the brake rotor; Each member is provided with a first screw that is one of the male screw and the female screw provided in the member, and has first and second regions aligned in a direction along the rotation axis. and the first region includes a first end connected to the second region, which is one end of the first region in the direction along the rotation axis, and a direction along the rotation axis and a second end that is the other end of the first region in the first region, and a first groove that divides the first screw in the circumferential direction around the rotation axis in the first region In the circumferential direction, the range in which the first screw is provided in the second region is larger than the range in which the first screw is provided in the first region, and the male screw and At least a part of the second thread, which is the other of the female threads, in the direction along the rotation axis meshes with the first thread in the second region, and the direct-acting member moves in the first direction. Movement brings the second screw closer to the second end. Therefore, as an example, when the braking member wears due to repeated braking, the position of the linear motion member moves in the first direction. By moving the position of the direct-acting member in the first direction, the portion of the second screw that has been located closer to the first end than the second end, for example, approaches the second end and moves toward the second end. For example, the portion of the screw that was located on the opposite side of the second end from the first end now engages with the first screw in the first region. In the first area, dust generated by abrasion can be discharged into the first groove. Furthermore, in the second region, the contact area between the first screw and the second screw (contact area per screw thread circumference) is the same as that of the first screw and the second screw in the first region. contact area (same as above). Therefore, when at least a portion of the second screw meshes with the first screw in the second region, the normal force per contact area between the first screw and the second screw is reduced, which in turn reduces the force of the first screw. Frictional forces between the screw and the second screw are reduced. Wear of the first screw and the second screw is reduced by reducing the frictional force between the first screw and the second screw. As a result, the braking device of the present embodiment can suppress an increase in the frictional force between the first screw and the second screw, and the friction between the first screw and the second screw can reduce the friction between the first screw and the second screw. It can suppress the occurrence of sound. Further, as an example, the braking device is configured such that, in the circumferential direction, the range in which the first screw is provided in the second region is larger than the range in which the first screw is provided in the first region. Since the first groove is provided in the first screw, for example, the first groove is provided throughout the first region and the second region, and in the circumferential direction, the first groove in the first region The range of the first screw provided in the second region is compared with the aspect in which the range of the screw provided in the second region and the range of the first screw provided in the second region are of the same size. is greater than that of the first region, the strength and durability of the first screw can be improved.

Further, the braking device according to at least one embodiment described above includes, as an example, a rotating member provided with one of a male thread and a female thread that meshes with the male thread and rotatable around a rotation axis. , the other of the male screw and the female screw is provided, and when the rotating member rotates in the first rotating direction about the rotating shaft, the rotating member moves in the first direction along the rotating shaft and rotates. a linear motion member that moves in a second direction opposite the first direction when the member rotates in a second direction opposite the first direction; and a linear motion member that moves in the first direction. a piston that is pushed in the first direction by the linear motion member and moves in the first direction to press the braking member against the brake rotor; One of the members is provided with a first screw that is one of the male screw and the female screw provided on the member, and has a first region and a second screw that are aligned in a direction along the rotation axis. A first groove is provided in the first region for dividing the first screw in the circumferential direction around the rotation axis, and the first groove in the second region in the circumferential direction is provided in the first region. The range in which one screw is provided is larger than the range in which the first screw is provided in the first region, and the second screw, which is the other of the male screw and the female screw, At least partially in the axial direction, at least one of the first thread and the second thread increases the coefficient of friction of friction between the first thread and the second thread due to wear. In a first state, the first thread engages in the second region, and from the first state, the first thread and the second thread do not increase the friction coefficient due to wear. When the braking member is pressed against the brake rotor, all of the second screw in the direction along the rotation axis meshes with the first screw in the first region. Therefore, as an example, when the braking member wears due to repeated braking, the position of the linear motion member moves in the first direction. By moving the position of the direct-acting member in the first direction, the portion of the second screw located on the opposite side of the second end than the first end, for example, moves to the first position in the first region. It comes to mesh with the screw. That is, the engagement length between the second screw and the first screw in the first region is increased. In the first area, dust generated by abrasion can be discharged into the first groove. Thus, when at least a portion of the second thread meshes with the first thread in the first region, the increase (slope) in the coefficient of friction due to wear is reduced, and ultimately the increase in the coefficient of friction is relatively low. stop at the value. That is, at least a portion of the second thread meshes with the first thread in the first region, thereby reducing the coefficient of friction when transitioning from the first state to the second state. Furthermore, the contact area between the first screw and the second screw in the second region (the contact area per screw thread circumference) is the contact area between the first screw and the second screw in the first region. It becomes larger than the contact area (same as above). Therefore, in the first state, the normal force per contact area between the first screw and the second screw is reduced, which in turn reduces the frictional force between the first screw and the second screw. . Reducing the frictional force between the first screw and the second screw reduces wear on the first screw and the second screw. As a result, the braking device of the present embodiment can suppress an increase in the frictional force between the first screw and the second screw, and the friction between the first screw and the second screw can reduce the friction between the first screw and the second screw. It can suppress the occurrence of sound.

In the braking device described above, for example, the thread angle of the male screw and the thread angle of the female screw are different from each other. Therefore, as an example, the contact area between the male thread and the female thread is reduced, and the frictional force between the male thread and the female thread is reduced. Also, a gap is formed between the male thread and the female thread. Dust generated by abrasion between the first screw and the second screw can be discharged into the gap. Therefore, the braking device of the present embodiment can suppress an increase in the frictional force between the first screw and the second screw, and noise is generated by the friction between the first screw and the second screw. can be suppressed.

In the braking device described above, as an example, the second region is not provided with a groove that divides the first screw in the circumferential direction. Therefore, as an example, when at least a portion of the second screw meshes with the first screw in the second region, the normal force per contact area between the first screw and the second screw is reduced, and thus A frictional force between the first screw and the second screw is reduced. As a result, the braking device of the present embodiment can suppress an increase in the frictional force between the first screw and the second screw, and noise caused by the friction between the first screw and the second screw can be suppressed. You can prevent it from happening. Furthermore, the second region can be held, for example by a chuck, when the member is provided with the first groove. Therefore, in the braking device of this embodiment, the member can be easily provided with the first groove.

In the braking device described above, as an example, the second region is provided with a second groove that divides the first screw in a circumferential direction around the rotation axis. Therefore, as an example, when at least a portion of the second thread is meshed with the first thread in the second region, dust generated by wear between the first thread and the second thread is deposited in the second groove. can be discharged to Further, the first groove and the second groove can supply lubricating oil to the first thread and the second thread. Therefore, the braking device of the present embodiment can suppress an increase in the frictional force between the first screw and the second screw, and noise is generated by the friction between the first screw and the second screw. can be suppressed.

In the above description, inhibition is defined as, for example, preventing an event, action or effect from occurring or reducing the degree of an event, action or effect. Also, in the above description, the restriction is defined as, for example, preventing movement or rotation, or allowing movement or rotation within a predetermined range and preventing movement or rotation beyond the predetermined range. .

Although the embodiments of the present invention have been exemplified above, the above embodiments and modifications are merely examples, and are not intended to limit the scope of the invention. The above embodiments and modifications can be implemented in various other forms, and various omissions, replacements, combinations, and modifications can be made without departing from the scope of the invention. Also, the configuration and shape of each embodiment and each modification can be partially exchanged.

DESCRIPTION OF SYMBOLS 10... Braking device 12... Brake rotor 22... Piston 23... Brake pad (braking member) 31... Rotary member 32... Direct-acting member 45, 45A, 45B... Male screw (first screw), 53 ... Female screw (second screw) 61, 161 ... First region 61a ... First inner end (first end) 61b ... First outer end (second end) 62, 162 ... second region 65, 165 ... first groove 71, 72 ... screw thread 81 ... second groove 145 ... male screw (second screw) 153, 153A, 153B ... female screw (second screw) 1 screw), Ax... Central axis (rotating axis), D1... Lock direction (first direction), D2... Release direction (second direction), Dn... Forward direction (first direction of rotation), Dr . . . reverse rotation direction (second rotation direction), .theta.1, .theta.2 .

Claims (5)

a rotating member provided with one of a male screw and a female screw that meshes with the male screw and rotatable around a rotation axis;
The other of the male thread and the female thread is provided, and when the rotating member rotates about the rotating shaft in a first rotating direction, the rotating member moves in a first direction along the rotating shaft. a linear motion member that moves in a second direction opposite the first direction when rotated in a second direction opposite the first direction;
a piston pushed in the first direction by the linear motion member moving in the first direction and moving in the first direction to press the braking member against the brake rotor;
and
One member of the rotating member and the linear motion member is provided with a first screw which is one of the male screw and the female screw, respectively, and extends along the rotation axis. having a first region and a second region aligned in a direction;
The first region includes a first end connected to the second region, which is one end of the first region in the direction along the rotation axis, and the first end in the direction along the rotation axis. and a second end that is the other end of the region of
A first groove is provided in the first region for dividing the first screw in a circumferential direction around the rotation axis,
In the circumferential direction, the range in which the first screw is provided in the second region is larger than the range in which the first screw is provided in the first region,
at least a portion of a second screw, which is the other of the male screw and the female screw, in a direction along the rotation axis meshes with the first screw in the second region;
movement of the linear motion member in the first direction causes the second screw to approach the second end;
braking device. a rotating member provided with one of a male screw and a female screw that meshes with the male screw and rotatable around a rotation axis;
The other of the male thread and the female thread is provided, and when the rotating member rotates about the rotating shaft in a first rotating direction, the rotating member moves in a first direction along the rotating shaft. a linear motion member that moves in a second direction opposite the first direction when rotated in a second direction opposite the first direction;
a piston pushed in the first direction by the linear motion member moving in the first direction and moving in the first direction to press the braking member against the brake rotor;
and
One member of the rotating member and the linear motion member is provided with a first screw which is one of the male screw and the female screw, respectively, and extends along the rotation axis. having a first region and a second region aligned in a direction;
A first groove is provided in the first region for dividing the first screw in a circumferential direction around the rotation axis,
In the circumferential direction, the range in which the first screw is provided in the second region is larger than the range in which the first screw is provided in the first region,
At least a part of the second screw, which is the other of the male screw and the female screw, in the direction along the rotation axis is worn out, so that at least one of the first screw and the second screw is worn. meshing with the first thread in the second region in a first state that increases the coefficient of friction between the first thread and the second thread;
When transitioning from the first state to the second state in which the friction coefficient is not increased due to wear of the first screw and the second screw, the braking member is pressed against the brake rotor. all of the second screw in the direction along the rotation axis meshes with the first screw in the first region;
braking device. 3. A braking device according to claim 1 or 2, wherein the thread angle of said male thread and the thread angle of said female thread are different from each other. 4. The braking device according to any one of claims 1 to 3, wherein the second region is not provided with grooves dividing the first screw in the circumferential direction. 4. The braking device according to any one of claims 1 to 3, wherein the second region is provided with a second groove that divides the first screw in the circumferential direction around the rotation axis.

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