Drum brake device

Abstract

A drum brake device (B) according to the present invention is configured in such a manner that, when a rotational force corresponding to movement transmitted from a sleeve (72) to a drive ring (11), which is generated by meshing of external helical teeth (72Ba) and internal helical teeth (11A) in accordance with the movement of the sleeve (72), is greater than a first rotational resistance applied to the drive ring (11) and is smaller than a second rotational resistance acting on a threaded portion of the sleeve (72) and a screw (73), the rotational force corresponding to the movement transmitted from the sleeve (72) to the drive ring (11) is smaller than a first rotational resistance applied to the drive ring (11). The drive ring (11) rotates to move the sleeve (72) without rotation, and when the rotational force corresponding to the movement is smaller than the first rotational resistance and larger than the second rotational resistance, the sleeve (72) moves while rotating with respect to the screw (73) via the engagement portion.

Description

Technical Field

[0001] The invention relates to a drum brake device. Background Art

[0002] The drum brake device comprises: a cylindrical brake drum which is arranged on the vehicle and installed so as to be rotatable together with the axle; and a pair of brake shoes which are swingably held on an anchor bracket and arranged along the inner circumference of the brake drum. The rotation of the brake drum (the wheel arranged on the axle) is braked by using the friction generated between the brake shoes by pressing the linings arranged on the brake shoes opposite to the brake drum against the inner circumference of the brake drum.

[0003] In such a drum brake device, there is a structure as follows: an expander is installed at the front end of the brake shoe, which is extended outward according to the braking operation, and the brake shoe is moved by the extension of the expander to press the brake shoe against the inner peripheral surface of the brake drum (for example, refer to Patent Document 1). The expander of the drum brake device has a sleeve member and a pressing member provided in a housing. The sleeve member is configured to be movable in the moving direction of the brake shoe and to rotate only in one direction around a rotation axis extending in the above-mentioned moving direction, and to move in the above-mentioned moving direction by a driving force from a driving mechanism. The pressing member is screwed and installed with the sleeve member, and moves in the above-mentioned moving direction integrally with the sleeve member, so that the brake shoe moves and is pressed against the brake drum.

[0004] The brake shoe (the lining of the brake shoe) wears due to friction with the brake drum, but if the gap between the brake shoe and the brake drum (hereinafter also referred to as the shoe gap) increases due to the wear, it also becomes a cause of deterioration of the braking effect. Therefore, the drum brake device is provided with a gap adjustment mechanism, which reduces the shoe gap according to the wear of the brake shoe and automatically adjusts the gap between the brake shoe and the brake drum to always keep a constant gap. The gap adjustment mechanism is configured so that when the braking action is released and the pressing member moves toward the housing side, the sleeve member is relatively rotated independently with respect to the pressing member (rotated in one direction mentioned above) so that the pressing member screwed with the sleeve member is extended toward the outside (increasing the amount of the pressing member sent out relative to the sleeve member toward the axial direction of the above-mentioned rotating shaft), thereby moving the brake shoe toward the brake drum side and reducing the shoe gap.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent No. 6382340 Summary of the invention

[0008] Problems to be solved by the invention

[0009] In a drum brake device, when the brake shoe is pressed against the inner peripheral surface of the brake drum, the brake shoe and the brake drum may be greatly elastically deformed. In the case of the above elastic deformation, in the conventional drum brake device, when the brake action is released and the brake shoe and the brake drum are elastically restored, the clearance adjustment may be performed when the pressing member moves toward the housing side. Therefore, even if the clearance adjustment is excessive and the braking action is released, there is a risk of brake drag in which the brake shoe contacts the inner peripheral surface of the brake drum, thereby causing the brake drum to heat up when the vehicle is running.

[0010] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a drum brake device capable of preventing the occurrence of brake drag and appropriately adjusting the clearance.

[0011] Means used to solve problems

[0012] In order to solve the above-mentioned problem, the drum brake device involved in the present invention comprises: a cylindrical brake drum, which is arranged on a rotating member and can rotate together with the rotating member; a brake shoe, which is movably arranged on a fixed member and arranged opposite to the inner peripheral surface of the brake drum; an expander, which moves the brake shoe according to a braking operation so that the brake shoe abuts against the inner peripheral surface of the brake drum; and a driving mechanism, which applies a driving force to the expander, and the expander comprises: a sleeve member, which can move freely along the moving direction and can move along the moving direction The extended rotating shaft is installed on the fixed member to rotate as the center, and is moved in the moving direction by the driving force from the driving mechanism; and a pressing member is installed on the sleeve member by screwing with a thread centered on the rotating shaft, and the front end presses the brake shoe to move the brake shoe, and external helical teeth are formed on the outer periphery of the sleeve member. The drum brake device has a driving ring member, which has internal helical teeth meshing with the external helical teeth on the inner peripheral side, and the internal helical teeth meshing with the external helical teeth are installed on the sleeve member. The outer periphery of the member, the drum brake device is configured to press the drive ring member against the fixed member toward the axial direction of the rotating shaft, and apply a first rotational resistance to the drive ring member. The drum brake device is configured such that, when the sleeve member is moved by the driving force from the driving mechanism, the brake shoe is brought into contact with the inner peripheral surface of the brake drum by the pressing member to apply braking action or release the driving force from the driving mechanism to release braking action, when the movement corresponding rotational force transmitted from the sleeve member to the drive ring member by the meshing of the external helical teeth and the internal helical teeth according to the movement of the sleeve member is larger than the first rotational resistance applied to the drive ring member and smaller than the second rotational resistance acting on the screw-engaged portion of the sleeve member and the pressing member, the drive ring member rotates and causes the sleeve member to move in the moving direction without rotating, and when the movement corresponding rotational force is smaller than the first rotational resistance and larger than the second rotational resistance, the sleeve member moves in the moving direction while rotating relative to the pressing member via the meshing portion.

[0013] In the drum brake device involved in the present invention, preferably, the drum brake device comprises: a clutch ring member, which is fixed to the fixed member and has an abutment receiving surface facing one end face of the axial direction of the rotating shaft of the drive ring member and with which the one end face abuts; and a force applying member, which is arranged on the fixed member so that a force that presses the one end face against the abutment receiving surface acts on the drive ring member, a clutch ring side concave-convex portion continuous along the circumferential direction of the rotating shaft is formed on the abutment receiving surface, and a drive ring side concave-convex portion continuous along the circumferential direction of the rotating shaft that can abut and engage with the clutch ring side concave-convex portion is formed on the one end face, and the drive ring member is configured to rotate while the drive ring side concave-convex portion moves relative to the abutment position of the clutch ring side concave-convex portion in the circumferential direction of the rotating shaft in a state where the force acts, and during the rotation, the first rotation resistance acts on the drive ring member via the abutment portion between the clutch ring side concave-convex portion and the drive ring side concave-convex portion.

[0014] In the drum brake device according to the present invention, preferably, the clutch ring side concave-convex portion and the drive ring side concave-convex portion are composed of a plurality of triangular teeth arranged along the circumferential direction of the rotating shaft and having a triangular cross-sectional shape along the circumferential direction.

[0015] In the drum brake device according to the present invention, preferably, each of the triangular teeth has a pair of inclined surfaces, and the pair of inclined surfaces are configured to have different gradients from each other.

[0016] In addition, in the drum brake device involved in the present invention, preferably, the expander has a transmission member, which is freely movably arranged on the fixed member along the moving direction and transmits the driving force from the driving mechanism to the sleeve member, and the sleeve member is freely rotatably installed on the transmission member in one direction and the other direction around the rotation axis.

[0017] In the drum brake device according to the present invention, preferably, the sleeve member includes a sleeve base portion and a sleeve auxiliary portion formed separately from the sleeve and fixed to the sleeve base portion, and the external helical teeth are formed on an outer periphery of the sleeve auxiliary portion.

[0018] In addition, in the drum brake device involved in the present invention, it is preferred that the drum brake device is constructed to be able to increase or decrease the axial delivery amount of the pressing member relative to the sleeve member toward the rotating shaft by manually adjusting the rotation position of the sleeve member in one direction and another direction around the rotating shaft.

[0019] Effects of the Invention

[0020] According to the drum brake device involved in the present invention, when the movement corresponding rotational force transmitted from the sleeve member to the drive ring member by the meshing of the external helical teeth and the internal helical teeth according to the movement of the sleeve member is larger than the first rotational resistance applied to the drive ring member and smaller than the second rotational resistance acting on the threaded part of the sleeve member and the pressing member, the drive ring member rotates to move the sleeve member in the moving direction without rotating. At this time, the delivery amount of the pressing member relative to the sleeve member does not increase or decrease. Therefore, in the case where the second rotational resistance acting on the threaded part of the sleeve member and the pressing member increases as in the process of elastic recovery of the brake shoe and the brake drum, the sleeve member and the pressing member can be moved in the moving direction as a whole without adjusting the gap between the brake shoe and the brake drum, so that the drag of the brake can be prevented. In addition, when the movement corresponding rotational force is smaller than the first rotational resistance and larger than the second rotational resistance, the sleeve member moves in the moving direction while rotating relative to the pressing member via the meshing part. At this time, the amount of the pressing member extended relative to the sleeve member increases, thereby enabling appropriate adjustment of the gap between the brake shoe and the brake drum. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a front view showing the drum brake device according to the present embodiment.

[0022] Figure 2 It is along Figure 1 The cross-sectional view indicated by arrows II-II in FIG. 1 shows the drum brake device when it is not in operation.

[0023] Figure 3 It is along Figure 1 The cross-sectional view indicated by arrows II-II in FIG. 1 shows the operation of the drum brake device.

[0024] Figure 4 It is a partial cross-sectional view showing the structure of a drive clutch mechanism provided in the expander of the drum brake device.

[0025] Figure 5 It is a perspective view showing the sleeve in the above-mentioned dilator.

[0026] Figure 6 It is a perspective view showing a drive ring in the above-mentioned dilator.

[0027] Figure 7 It is a perspective view showing a clutch ring in the above-mentioned expander.

[0028] Figure 8 It is a side view showing the structure of the connection portion between the screw rod and the brake shoe in the above expander. DETAILED DESCRIPTION

[0029] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Figures 1 to 8 The overall structure of a drum brake device according to an embodiment of the present invention will be described.

[0030] like Figure 1 As shown, the drum brake device B is mainly composed of the following parts: a drum unit 3, which is arranged on the axle 1 and is provided with a brake drum 31 that can rotate together with the axle 1; a brake shoe unit 4, which is swingably arranged on an anchor bracket 2 fixed to the vehicle body and has a pair of brake shoes 40, 40 arranged along the inner circumferential surface of the brake drum 31; and an expander unit 5, which makes the brake shoes 40, 40 swing according to the braking operation and press against the inner circumferential surface of the brake drum 31.

[0031] The anchor bracket 2 has a circular hole-shaped opening 2a at the center, and is fixed to the axle housing (not shown) of the vehicle body via bolts (not shown) inserted into bolt holes 2b provided around the opening 2a. Figure 1 The supporting arm portion 2c is divided into two parts in a direction perpendicular to the paper surface), and the circular hole-shaped pin insertion openings 2d, 2d are arranged on the left and right when viewed from the front and are respectively opened on the front side and the inner side of the thickness direction of the supporting arm portion 2c.

[0032] A wheel rim (not shown) is mounted on a hub (not shown) rotatably mounted on the axle 1 protruding outward from the opening 2a of the anchor bracket 2 via a bearing, and is combined with a brake drum 31 to form a drum unit 3. In addition, a wheel is mounted on the wheel rim, and the brake drum 31 rotates integrally with the wheel via the wheel hub.

[0033] The brake shoe unit 4 is configured to include two brake shoes 40 disposed on the left and right sides in a front view, sandwiching the anchor bracket 2. The brake shoe 40 includes a web portion 41 extending in an arc shape, a rim portion 42 mounted on the outer peripheral end of the web portion 41, and a lining 43 fixedly mounted on the rim portion 42 by rivets or the like. The brake shoe 40 is disposed along the inner peripheral surface of the brake drum 31 so that the lining 43 faces the inner peripheral surface of the brake drum 31.

[0034] The base end of the brake shoe 40 is pivotally fixed to the anchor bracket 2 via an anchor pin 44 inserted into the pin insertion port 2d of the support arm portion 2c, and can be swung around the anchor pin 44. Figure 1 A return spring 45 is provided between the front ends of the pair of brake shoes 40, 40 to connect them. When the brake operation is not performed (when the brake is not in operation), the brake shoes 40, 40 are held in a position swung inward (i.e., a position separated from the brake drum 31) by the force of the return spring 45.

[0035] In addition, an expander unit 5 fixed to the anchor bracket 2 is disposed between the front ends of the brake shoes 40, 40. As will be described in detail later, when the brake operation (when the brake is actuated) is performed, the expander unit 5 extends the expanders 70, 70 to overcome the force of the return spring 45 and press the front ends of the brake shoes 40, 40 outward. The brake shoes 40, 40 are swung outward with the anchor pins 44, 44 as the center, and the linings 43, 43 are pressed against the inner peripheral surface of the opposing brake drum 31, and the rotation of the brake drum 31 is braked by the friction between the two. As a result, a predetermined braking action can be obtained with respect to the wheel that rotates integrally with the brake drum 31.

[0036] like Figure 2 as well as Figure 3 As shown, the expander unit 5 is constructed to include: a housing 50, which is formed by forming a wedge-shaped piece receiving portion 51 in the central space and forming a pair of cylinder portions 52, 52 connected to the wedge-shaped piece receiving portion 51 from both sides; a wedge-shaped piece unit 60, which, as a driving mechanism, has a wedge-shaped piece 61 pluggably installed in the wedge-shaped piece receiving portion 51; and expanders 70, 70, which are arranged in the cylinder portions 52, 52 and are constructed to be able to extend in the direction of the axis X (hereinafter also referred to as the "axis direction"). A shield 55 is installed at the open end of the cylinder portion 52 in the housing 50 via a retaining ring 56 (see Figure 4 ) In addition, the housing 50 is fixed to the anchor bracket 2, and together with the anchor bracket 2, constitutes a fixing member.

[0037] The expander unit 5 is constructed to be bilaterally symmetrical. Figure 2 as well as Figure 3 The configuration posture of the expander unit 5 shown in the figure is used as a reference, and the inner side of the housing 50 in the axial direction (the wedge-shaped member storage portion 51 side) is referred to as the "one end side", and the outer side of the housing 50 in the axial direction (the brake shoe 40 side) is referred to as the "other end side". In addition, Figure 2 The state of the expander unit 5 when the brake is not in operation is shown. Figure 3 The state of the expander unit 5 when the brake is in operation is shown.

[0038] The wedge unit 60 is a member for applying driving force to the expander 70, and is mainly composed of a wedge 61 and a wedge spring 62. The wedge 61 is formed in an axial shape, and is installed in the housing 50 in a pluggable manner along the direction of the axis Y orthogonal to the axial direction (hereinafter also referred to as the "axis-orthogonal direction") by the action of the diaphragm of the chamber (not shown). Figure 2 As shown in FIG. 1 , when the brake is not in operation (when the brake is released), the wedge 61 is pulled outward relative to the wedge receiving portion 51 by the force of the wedge spring 62. Figure 3 As shown, when the brake is actuated, the wedge 61 overcomes the force of the wedge spring 62 and moves in the wedge receiving portion 51 in a direction perpendicular to the axis (in Figure 3 The wedge 61 is inserted into the wedge receiving portion 51 as the insertion end portion 61a, which is the end portion on one side of the wedge receiving portion 51 inserted into the wedge 61, and is formed into a wedge shape that tapers toward the front end, and has inclined surfaces 61b, 61b on both sides of the axial direction. In addition, the wedge 61 is provided with a roller retaining body 61d that supports a pair of rollers 61c, 61c. The pair of rollers 61c, 61c are arranged to be able to rotate freely relative to the roller retaining body 61d and to be able to move in directions (axial directions) approaching and separating from each other. In addition, the roller retaining body 61d is arranged to be able to reciprocate freely along the direction orthogonal to the axis, and is always pulled toward the outside side of the housing 50 (in the axial direction) together with the wedge 61 by the wedge spring 62. Figure 2 The roller holder 61d cooperates with the wedge 61 to convert the linear motion of the wedge 61 in the direction perpendicular to the axis into the linear motion of the expander 70 in the direction of the axis.

[0039] The expander 70 is constructed to include: a push rod 71, which is inserted into the cylinder portion 52 and is configured to be able to slide along the axial direction; a sleeve 72, which is arranged on one end side of the push rod 71 in the axial direction; and a screw 73, which serves as a pressing member and is threadedly engaged with the sleeve 72 in the axial direction and extends outwardly toward the side of the shell 51.

[0040] The tappet 71 is a member that functions as a transmission member that transmits the driving force from the wedge unit 60 to the sleeve 72, and has a main body 71a with an outer diameter slightly smaller than the inner diameter of the cylinder 52 at one end side in the axial direction, and a cylindrical portion 71b with an outer diameter smaller than the main body 71a at the other end side in the axial direction. The sleeve 72 has a cylindrical shape with an outer diameter equal to that of the main body 71a of the tappet 71, and the cylindrical portion covers the cylindrical portion 71b of the tappet 71 and is mounted on the tappet 71 so as to be rotatable about the axis X.

[0041] The push rod 71 is formed into a stepped cylindrical shape by a main body 71a and a cylindrical part 71b having different outer diameters. The main body 71a has an inclined surface 71c substantially parallel to the inclined surface 61b of the wedge 61. In addition, an O-ring 74 for ensuring the sealing between the push rod 71 and the sleeve 72 is installed on the outer periphery of the cylindrical part 71b of the push rod 71. The push rod 71 is inserted into the innermost part of the cylinder part 52 connected to the wedge storage part 51 so that the inclined surface 71c abuts against the peripheral surface of the roller 61c, and slides in the axial direction in the cylinder part 52 by the driving force from the wedge unit 60 acting through the roller 61c by utilizing the insertion and extraction action of the wedge 61.

[0042] The sleeve 72 is composed of a sleeve main portion 72A and a sleeve auxiliary portion 72B. The sleeve main portion 72A has a base portion 72Aa and an intermediate portion 72Ab, which have different outer diameters from each other. The outer diameter of the base portion 72Aa is formed to be equal to the outer diameter of the main body portion 71a of the push rod 71, and the outer diameter of the intermediate portion 72Ab is formed to be smaller than the outer diameter of the base portion 72Aa. In addition, the sleeve main portion 72A has a tool engaging portion 72Ac formed in an octagonal column shape on the other end side in the axial direction. A through hole 72Ad extending along the axial direction is formed in the sleeve main portion 72A (see Figure 5 ), an internal thread portion 72Ae for screwing the screw 73 is formed on the inner peripheral surface of the through hole 72Ad.

[0043] The sleeve auxiliary part 72B is formed into a cylindrical shape. The outer diameter of the sleeve auxiliary part 72B is formed to be equal to the outer diameter of the base part 72Aa of the sleeve main part 72A, and the inner diameter of the sleeve auxiliary part 72B is formed to be equal to the outer diameter of the middle part 72Ab of the sleeve main part 72A. The sleeve auxiliary part 72B is pressed into the middle part 72Ab of the sleeve main part 72A and integrated with the sleeve main part 72A. A plurality of concave external helical teeth 72Ba (see Figure 5 ). In addition, the sleeve 72 can also form the sleeve main part 72A and the sleeve auxiliary part 72B as a whole through one component. As in the present embodiment, by forming the sleeve main part 72A and the sleeve auxiliary part 72B separately and pressing the sleeve auxiliary part 72B into the sleeve main part 72A after forming the external helical teeth 72Ba in the sleeve auxiliary part 72B, there is an advantage of easily forming the external helical teeth 72Ba. In addition, the sleeve main part 72A and the sleeve auxiliary part 72B can also be formed of different materials. The sleeve 72 is inserted into the cylinder part 52 of the housing 50 in such a way that the axis X becomes the rotation axis and can rotate around the rotation axis in one direction (for example, left-handed when viewed from one end side in the axis direction) and around the rotation axis in another direction (for example, right-handed when viewed from one end side in the axis direction).

[0044] The screw rod 73 is formed into a rod shape extending in the axial direction and has an external thread portion 73a on the outer peripheral surface. The external thread portion 73a is configured to be threadedly engaged with the internal thread portion 72Ae of the sleeve 72 and extend outwardly from the side of the housing 50. A brake shoe connecting portion 73b having a pair of connecting surfaces 73c, 73c facing each other with the axis X sandwiched therebetween is formed on the other end side of the screw rod 73 in the axial direction. Figure 8As shown, the brake shoe connection portion 73b is connected to the brake shoe 40 via a connection member 80 fixed to the front end of the brake shoe 40. The connection member 80 has a connection portion 81 protruding toward the brake shoe connection portion 73b and is connected to the brake shoe connection portion 73b by inserting the connection portion 81 between the pair of connection surfaces 73c, 73c. ​​The screw 73 is connected to the brake shoe 40 via the connection member 80 through the brake shoe connection portion 73b and is in a state where rotation about the axis X is restricted (a state where rotation is not allowed).

[0045] The expander unit 5 (expander 70) constructed as described above has a gap adjustment function that automatically reduces the gap (shoe gap) between the lining 43 and the brake drum 31 to a predetermined gap when the lining 43 of the brake shoe 40 is worn. This gap adjustment function is achieved by having a drive clutch mechanism 10 in addition to the push rod 71, the sleeve 72, and the screw 73. In addition, the gap adjustment is performed by rotating the sleeve 72 screwed with the screw 73 in the other direction (the above-mentioned right rotation) around the rotation axis, thereby increasing the amount of the screw 73 sent out relative to the sleeve 72 in the other end side of the axial direction. Figure 5 As shown, the driving clutch mechanism 10 is mainly composed of a driving ring 11 , a clutch ring 12 and a wave spring 13 .

[0046] The drive ring 11 is formed in a circular ring shape, and a plurality of convex internal helical teeth 11A are formed on its inner circumferential surface. In addition, a drive ring side concave-convex portion 11B is formed on the end surface of one end side of the drive ring 11 in the axial direction, which is continuous in the circumferential direction of the axis X. The drive ring side concave-convex portion 11B is composed of a plurality of triangular teeth 11Ba of the same shape arranged in the circumferential direction of the axis X. Each triangular tooth 11Ba is formed so that the cross-sectional shape along the circumferential direction of the axis X is triangular and has a pair of inclined surfaces 11Bb and 11Bc. The pair of inclined surfaces 11Bb and 11Bc are configured so that their respective slopes (inclination angles relative to a plane perpendicular to the axis X) are different from each other (in the case of this example, the inclined surface 11Bb is steeper than the inclined surface 11Bc). The drive ring 11 configured as above is arranged in the housing 50 in a state where each internal helical tooth 11A is meshed with each external helical tooth 72Ba of the sleeve 72 (sleeve auxiliary portion 72B). The drive ring 11 is rotatable about the axis X in one direction (eg, left-handed when viewed from one end in the axial direction) and in the other direction (eg, right-handed when viewed from one end in the axial direction) about the axis X.

[0047] The clutch ring 12 is formed into a circular ring shape in the same manner as the drive ring 11. A clutch ring side concave-convex portion 12A is formed on the end face of the other end side of the axial direction of the clutch ring 12, which is continuous along the circumferential direction of the axis X. The clutch ring side concave-convex portion 12A is composed of a plurality of triangular teeth 12Aa of the same shape arranged along the circumferential direction of the axis X. In each triangular tooth 12Aa, the cross-sectional shape along the circumferential direction of the axis X is formed into a triangular shape and has a pair of inclined surfaces 12Ab and 12Ac. The pair of inclined surfaces 12Ab and 12Ac are configured so that their respective slopes (angles of inclination relative to a plane perpendicular to the axis X) are different from each other (in the case of this example, the inclined surface 12Ab is steeper than the inclined surface 12Ac). In addition, the clutch ring side concave-convex portion 12A has a shape equal to the drive ring side concave-convex portion 11B when the drive ring 11 is reversed with the axis perpendicular to the X axis as the center. Therefore, when the clutch ring side concavoconvex part 12A and the drive ring side concavoconvex part 11B are butted against each other, the two can mesh with each other. The clutch ring 12 having the above-mentioned structure is fixed in the housing 50 in a state where the clutch ring side concavoconvex part 12A and the drive ring side concavoconvex part 11B face and abut against each other.

[0048] The wave spring 13 is a biasing member that applies a biasing force (referred to as a drive ring biasing force) to the drive ring 11 to press the clutch ring side concave-convex part 12A against the drive ring side concave-convex part 11B. The wave spring 13 is held by a shield 55 attached to the open end of the cylinder part 52 via a snap ring 56 and is disposed in the housing 50.

[0049] In the driving clutch mechanism 10 constructed in this way, a rotational resistance (referred to as the driving ring rotational resistance) is applied to the driving ring 11 to overcome the rotation of the driving ring 11 around the rotation axis. The driving ring rotational resistance can be adjusted by changing the slope of the inclined surface of each triangular tooth of the clutch ring side concave-convex part 12A and the driving ring side concave-convex part 11B. That is, the driving ring 11 rotates while moving the driving ring side concave-convex part 11B relative to the contact position of the clutch ring side concave-convex part 12A along the circumferential direction of the rotation axis under the state of receiving the driving ring force from the wave spring 13. During this rotation, the driving ring rotational resistance acts on the driving ring 11 via the contact portion between the clutch ring side concave-convex part 12A and the driving ring side concave-convex part 11B. The greater the slope of the inclined surface of each triangular tooth 12Aa of the clutch ring side concave-convex part 12A and the inclined surface of each triangular tooth 11Ba of the driving ring side concave-convex part 11B, the greater the driving ring rotational resistance. In the present embodiment, when the drive ring 11 rotates in one direction (the aforementioned left-hand rotation) around the rotation axis, the relatively gentle inclined surface 11Bc of the pair of inclined surfaces 11Bb and 11Bc of each triangular tooth 11Ba of the drive ring side concave-convex portion 11B passes over the relatively gentle inclined surface 12Ac of the pair of inclined surfaces 12Ab and 12Ac of each triangular tooth 12Aa of the clutch ring side concave-convex portion 12A. On the other hand, when the drive ring 11 rotates in the other direction (the aforementioned right-hand rotation) around the rotation axis, the relatively steep inclined surface 11Bb of each triangular tooth 11Ba of the drive ring side concave-convex portion 11B passes over the relatively steep inclined surface 12Ab of each triangular tooth 12Aa of the clutch ring side concave-convex portion 12A. Therefore, the drive ring rotation resistance acting on the drive ring 11 when the drive ring rotates in another direction (the above-mentioned right rotation) around the rotation axis (hereinafter also referred to as "drive ring right-hand rotation resistance") is greater than the drive ring rotation resistance acting on the drive ring 11 when the drive ring 11 rotates in one direction (the above-mentioned left rotation) around the rotation axis (hereinafter also referred to as "drive ring left-hand rotation resistance").

[0050] Next, the operation of the drum brake B when the brake is in operation and when it is not in operation and the clearance adjustment by the driving clutch mechanism 10 will be described. Next, a case where the brake drum 31 and the brake shoe 40 (lining 43) are elastically deformed to a large extent by the braking operation will be described.

[0051] First, when the brake operation is performed, the wedge 61 overcomes the force of the wedge spring 62 by the action of the diaphragm (maintenance chamber) not shown in the figure and moves in the insertion direction ( Figure 2 as well as Figure 3The pressing force is converted into a pressing force in the axial direction through rollers 61c, 61c by the wedge action of the inclined surfaces 61b, 61b of the wedge member 61 and the inclined surfaces 71c, 71c of the tappet 71, and is transmitted to the sleeve 72 through the tappet 71. Under the pressure, the sleeve 72 moves from one end side to the other end side in the axial direction in the cylinder portion 52 together with the tappet 71.

[0052] The sleeve 72 meshes with the drive ring 11 via the meshing portion between the external helical teeth 72Ba of the sleeve 72 and the internal helical teeth 11A of the drive ring 11. When the sleeve 72 moves to the other end side in the axial direction, a rotational force (hereinafter also referred to as "the corresponding rotational force of movement during braking") acts from the sleeve 72 to the drive ring 11 via these meshing portions to rotate the drive ring 11 in one direction (the above-mentioned left-hand rotation) around the rotation axis. On the other hand, the above-mentioned left-hand rotation resistance of the drive ring acts on the drive ring 11 by the action of the drive clutch mechanism 10. In addition, the sleeve 72 is screwed with the screw 73 via the screwing portion between the internal threaded portion 72Ae of the sleeve 72 and the external threaded portion 73a of the screw 73. When the sleeve 72 moves to the other end side in the axial direction, at the screwing portion between the sleeve 72 and the screw 73, a rotational resistance (hereinafter also referred to as "the sleeve rotational resistance during braking") that overcomes the rotation of the sleeve 72 around the rotation axis acts on the screw 73.

[0053] In this embodiment, the slope of the inclined surface 11Bc in each triangular tooth 11Ba of the clutch ring side concave-convex part 12A and the slope of the inclined surface 12Ac in each triangular tooth 12Aa of the clutch ring side concave-convex part 12A are set so that the above-mentioned braking movement corresponding rotational force is larger than the above-mentioned drive ring left-hand rotation resistance and smaller than the above-mentioned braking sleeve rotation resistance. Therefore, the drive ring 11 rotates in one direction around the rotation axis, while the sleeve 72 moves in the cylinder part 52 toward the other end side in the axial direction without rotating.

[0054] In addition, the screw rod 73 screwed with the sleeve 72 moves integrally with the sleeve 72 toward the other end side in the axial direction. Then, as the screw rods 73, 73 extend in the axial direction, the pair of brake shoes 40, 40 swing outward around the anchor pins 44, 44, and the lining 43 is pressed against the inner peripheral surface of the brake drum 31. The rotation of the brake drum 31 is braked by the friction between the two. If the brake drum 31 and the brake shoe 40 (lining 43) are elastically deformed by the lining 43 being pressed against the inner peripheral surface of the brake drum 31, the screw rod 73 also moves integrally with the sleeve 72 toward the other end side in the axial direction within the range of the elastic deformation.

[0055] When the braking operation is released, the wedge 61 moves in the removal direction (ie, the direction in which the wedge 61 is removed from the wedge storage portion 51) due to the urging force of the wedge spring 62. Figure 3 as well as Figure 4The wedge 61 moves upwards (in the upward direction). The pressing force from the wedge 61 to the other end side of the expander 70 in the axial direction is reduced according to the movement of the wedge 61. As a result, the screw 73 and the sleeve 72 are allowed to move to one end side in the axial direction and the brake drum 31 and the brake shoe 40 are allowed to elastically recover. When the screw 73 moves to one end side in the axial direction, a rotation resistance (hereinafter also referred to as "sleeve rotation resistance during brake release") that overcomes the rotation of the sleeve 72 around the rotation axis acts on the screw 73 at the threaded portion between the screw 73 and the sleeve 72. In addition, when the sleeve 72 moves to one end side in the axial direction together with the screw 73, a rotation force (hereinafter also referred to as "rotation force corresponding to movement during brake release") that rotates the drive ring 11 in the other direction (the above-mentioned right-hand rotation) around the rotation axis acts from the sleeve 72 to the drive ring 11 through their meshing portions. On the other hand, the above-mentioned right-hand rotation resistance of the drive ring acts on the drive ring 11 due to the action of the drive clutch mechanism 10.

[0056] In the present embodiment, during the elastic restoration of the brake drum 31 and the brake shoe 40, the slope of the inclined surface 11Bb in each triangular tooth 11Ba of the clutch ring side concave-convex part 12A and the slope of the inclined surface 12Ab in each triangular tooth 12Aa of the clutch ring side concave-convex part 12A are set so that the above-mentioned brake release movement corresponding rotational force is smaller than the above-mentioned brake release sleeve rotation resistance and larger than the above-mentioned drive ring left rotation resistance. Therefore, the drive ring 11 rotates in the other direction around the rotation axis, while the sleeve 72 moves in the cylinder part 52 toward one end side in the axial direction without rotating.

[0057] The screw 73 screwed with the sleeve 72 moves toward one end in the axial direction together with the sleeve 72. At this time, since the sleeve 72 does not rotate, the amount of the screw 73 delivered relative to the sleeve 72 does not increase, and therefore, no clearance adjustment is performed.

[0058] If the elastic recovery of the brake drum 31 and the brake shoe 40 is performed by moving the screw rod 73 and the sleeve 72 toward one end side in the axial direction, the sleeve rotation resistance and the corresponding rotation force when the brake is released will be reduced accordingly. In addition, even if the elastic recovery of the brake drum 31 and the brake shoe 40 is completed, the screw rod 73 and the sleeve 72 are moved toward one end side in the axial direction by the action of the return spring 45 straddling the two brake shoes 40, 40 until they are stored in the predetermined position in the cylinder portion 52.

[0059] In this embodiment, when the elastic restoration of the brake drum 31 and the brake shoe 40 is completed, the slope of the inclined surface 11Bb in each triangular tooth 11Ba of the clutch ring side concave-convex part 12A and the slope of the inclined surface 12Ab in each triangular tooth 12Aa of the clutch ring side concave-convex part 12A are set so that the above-mentioned brake release movement corresponding rotational force is larger than the above-mentioned brake release sleeve rotation resistance and smaller than the above-mentioned drive ring counterclockwise rotation resistance. Therefore, the drive ring 11 does not rotate, while the sleeve 72 rotates in the other direction (the above-mentioned clockwise rotation) around the rotation axis while moving toward one end side in the axial direction in the cylinder part 52.

[0060] The screw 73 screwed with the sleeve 72 is rotated in the other direction (right-handed) about the rotation axis by the sleeve 72, and is fed toward the other end side in the axial direction by a feeding amount corresponding to the rotation angle of the sleeve 72. Thus, the gap is adjusted.

[0061] Thus, in the drum brake device B having the driving clutch mechanism 10, during the elastic recovery of the brake drum 31 and the brake shoe 40, the sleeve 72 does not rotate and the clearance adjustment is not performed when the screw rod 73 moves toward one end side in the axial direction, thereby preventing the occurrence of brake drag. In addition, after the elastic recovery of the brake drum 31 and the brake shoe 40 is completed, the sleeve 72 rotates and the clearance adjustment is performed when the screw rod 73 moves toward one end side in the axial direction, thereby appropriately and automatically adjusting the clearance between the inner peripheral surface of the brake drum 31 and the brake shoe 40.

[0062] Next, the case of manually adjusting the gap will be described. In the drum brake device B, a tool such as a wrench is engaged with the tool engaging portion 72Ac of the sleeve 72, and the sleeve 72 is manually rotated around the rotation axis, so that the amount of the screw 73 sent out relative to the sleeve 72 can be increased or decreased. Specifically, by rotating the sleeve 72 in one direction (the above-mentioned left-hand rotation) around the rotation axis, the amount of the screw 73 sent out relative to the sleeve 72 can be reduced. As a result, the gap between the inner circumferential surface of the brake drum 31 and the brake shoe 40 can be enlarged. In addition, by rotating the sleeve 72 in the other direction (the above-mentioned right-hand rotation) around the rotation axis, the amount of the screw 73 sent out relative to the sleeve 72 can be increased. As a result, the gap between the inner circumferential surface of the brake drum 31 and the brake shoe 40 can be reduced. In addition, when the sleeve 72 is rotated, the drive ring 11 rotates together with the sleeve 72.

[0063] In the conventional drum brake device, the amount of the screw delivered relative to the sleeve is increased or decreased by manually rotating the screw. The screw is connected to the brake shoe via a clamping member that restricts the rotation of the screw except during manual adjustment and allows the rotation of the screw during manual adjustment. The clamping member has the risk of being damaged by vibration during driving, but in the drum brake device B, since the clamping member described above is not used, there is no such concern.

[0064] In addition, the present invention is not limited to the above-mentioned embodiment, and can be appropriately modified within the scope not departing from the gist of the present invention.

[0065] In the above embodiment, the drum brake device B is exemplified as a leader-follower type drum brake, but may be configured as a one-way servo type, a two-way servo type, or a double-leader type drum brake.

[0066] Description of reference numerals:

[0067] B: drum brake device; 1: axle (rotating component); 2: anchor bracket; 3: drum unit; 4: brake shoe unit; 5: expander unit; 10: drive clutch mechanism; 11: drive ring; 11B: drive ring side concave-convex portion; 11A: internal helical teeth; 12: clutch ring; 12A: clutch ring side concave-convex portion; 13: wave spring; 31: brake drum; 40: brake shoe; 50: housing; 60: wedge unit; 70: expander; 71: push rod; 72: sleeve; 72Ba: external helical teeth; 72Ae: internal threaded portion; 73: screw; 73a: external threaded portion.

Claims

1. A drum brake device, characterized in that: The drum brake device includes: a cylindrical brake drum which is provided on a rotating member and can rotate together with the rotating member; a brake shoe which is movably provided on a fixed member and is disposed opposite to the inner peripheral surface of the brake drum; an expander that moves the brake shoe according to a braking operation so that the brake shoe comes into contact with the inner peripheral surface of the brake drum; and a driving mechanism that applies a driving force to the expander, The expander comprises: a sleeve member, which is movably mounted on the fixed member and rotatably centered on a rotation axis extending in the moving direction, and is moved in the moving direction by a driving force from the driving mechanism; and a pressing member, which is screwed to the sleeve member by a thread centered on the rotation axis, and has a front end portion pressing the brake shoe to move the brake shoe. External helical teeth are formed on the outer periphery of the sleeve member, The drum brake device includes a drive ring member having internal helical teeth meshing with the external helical teeth formed on the inner circumference thereof, the internal helical teeth meshing with the external helical teeth and mounted on the outer circumference of the sleeve member. The drum brake device is configured to press the drive ring member against the fixed member in the axial direction of the rotating shaft to apply a first rotation resistance to the drive ring member. The drum brake device is configured such that when the sleeve member is moved by the driving force from the driving mechanism, the brake shoe is brought into contact with the inner peripheral surface of the brake drum by the pressing member to apply the brake or when the driving force from the driving mechanism is released to release the brake, When the movement corresponding rotational force transmitted from the sleeve member to the drive ring member by the meshing of the external helical teeth and the internal helical teeth according to the movement of the sleeve member is greater than the first rotational resistance applied to the drive ring member and smaller than the second rotational resistance acting on the threaded engagement portion of the sleeve member and the pressing member, the drive ring member rotates and causes the sleeve member to move in the movement direction without rotating, When the movement corresponding rotational force is smaller than the first rotational resistance and larger than the second rotational resistance, the sleeve member moves in the movement direction while rotating relative to the pressing member via the meshing portion.

2. The drum brake device according to claim 1, characterized in that: The drum brake device comprises: a clutch ring member fixed to the fixed member and having a contact receiving surface facing one end surface of the driving ring member in the axial direction of the rotating shaft and for contact with the one end surface; as well as a biasing member provided on the fixing member so that a force pressing the one end surface against the abutting receiving surface acts on the driving ring member, A clutch ring side concave-convex portion is formed on the abutting receiving surface and is continuous along the circumferential direction of the rotating shaft. The one end surface is provided with a driving ring side concave-convex portion which is capable of abutting and engaging with the clutch ring side concave-convex portion and is continuous along the circumferential direction of the rotating shaft. The drive ring component is configured to rotate while moving the abutment position of the drive ring side convex and concave portion relative to the clutch ring side convex and concave portion along the circumferential direction of the rotating shaft when the force is applied. During the rotation, the first rotational resistance acts on the drive ring component via the abutment portion between the clutch ring side convex and concave portion and the drive ring side convex and concave portion.

3. The drum brake device according to claim 2, characterized in that: The clutch ring side concavo-convex portion and the drive ring side concavo-convex portion are composed of a plurality of triangular teeth arranged along the circumferential direction of the rotating shaft and having a triangular cross-sectional shape along the circumferential direction.

4. The drum brake device according to claim 3, characterized in that: Each of the triangular teeth has a pair of inclined surfaces, and the pair of inclined surfaces are configured so that their slopes are different from each other.

5. The drum brake device according to any one of claims 1 to 4, characterized in that: The dilator includes a transmission member that is movably provided on the fixed member in the moving direction and transmits the driving force from the driving mechanism to the sleeve member. The sleeve member is mounted on the transmission member so as to be rotatable in one direction and the other direction around the rotation axis.

6. The drum brake device according to any one of claims 1 to 5, characterized in that: The sleeve member includes a sleeve base portion and a sleeve auxiliary portion which is formed separately from the sleeve and fixed to the sleeve base portion, and the external helical teeth are formed on the outer periphery of the sleeve auxiliary portion.

7. The drum brake device according to any one of claims 1 to 6, characterized in that: The drum brake device is configured to increase or decrease the amount of the pressing member sent out relative to the sleeve member in the axial direction of the rotating shaft by manually adjusting the rotation position of the sleeve member in one direction and the other direction around the rotating shaft.

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