Patent Description:
Such a vehicle drum brake is already known in PTL <NUM>.

<CIT> discloses a cable guide pipe support structure for a drum brake with a guide pipe portion detachably supported by a torroidal projection on a back plate of the brake drum.

In the vehicle drum brake disclosed in PTL <NUM>, a guide part integrally provided with a suppression member guides a brake cable with a cantilever structure floating from an anchor plate and an anchor attachment part, and thus a moment and a shear force due to an input from the brake cable act on the guide part, and it is necessary to increase a plate thickness of the suppression member having the guide portion in order to have a strength to withstand the moment and the shear force.

The invention has been made in view of such circumstances, and an object of the invention is to provide a vehicle drum brake capable of increasing a strength of a guide part with respect to a brake cable.

In order to achieve the above object, a first characteristic of the invention is a vehicle drum brake in which a pair of brake shoes configured to slidingly contact a brake drum, and a brake lever configured to rotate to cause the brake shoes to slidingly contact the brake drum so as to obtain a braking force are accommodated in a back plate, an anchor plate that abuts on one end of each of the pair of brake shoes to rotatably support the brake shoes is fixed on an anchor attachment part that is formed on the back plate in a manner rising inward of the back plate, a guide part that guides a brake cable coupled to the brake lever is fixedly provided inward of the anchor attachment part in a radial direction of the back plate, and at least one of the back plate and the anchor plate is integrally provided with a support part that abuts on the guide part to support the guide part.

In addition to a configuration of the first characteristic, a second characteristic of the invention is that the anchor plate and a suppression member that sandwiches the one end of each of the pair of brake shoes together with the anchor attachment part are fixed on the anchor attachment part, and the guide part is integrally provided with the suppression member in a manner projecting toward a center side of the back plate.

In addition to a configuration of the first or second characteristic, a third characteristic of the invention is that the support part abuts on the guide part in a direction parallel to a central axis of the back plate.

In addition to the configuration of the first characteristic, a fourth characteristic of the invention is that the support part abuts on the guide part in the radial direction of the back plate.

In addition to the configuration of the first or second characteristic, a fifth characteristic of the invention is that at least one of the back plate and the anchor plate is integrally provided with a first support part that abuts on the guide part in the radial direction of the back plate and a second support part that abuts on the guide part in a direction parallel to a central axis of the back plate.

According to the first characteristic of the invention, the support part integrally provided on at least one of the back plate and the anchor plate abuts on the guide part to support the guide part, and thus is capable of ensuring a strength of the guide part while avoiding an increase in the number of members.

According to the second characteristic of the invention, the guide part is integrally provided with the suppression member, and thus is capable of ensuring the strength of the guide part without increasing a plate thickness of the suppression member.

According to the third characteristic of the invention, the support part abuts on the guide part in the direction parallel to the central axis of the back plate, and thus is capable of increasing a strength against a shear force and a vertical component of forces acting on the guide part from the brake cable.

According to the fourth characteristic of the invention, the support part abuts on the guide part in the radial direction of the back plate, and thus is capable of increasing a strength against a moment due to an input acting on the guide part from the brake cable.

According to the fifth characteristic of the invention, the support part abuts on the guide part from both the radial direction of the back plate and the direction parallel to the central axis of the back plate, and thus is capable of increasing the strength against the moment, the shear force, and the vertical component of the forces acting from the brake cable.

Embodiments of the invention will be described with reference to the drawings.

A first embodiment of the invention will be described with reference to <FIG>. First, in <FIG>, a drum brake B is provided on a wheel of a four-wheeled vehicle, for example, a left rear wheel. The drum brake B includes: a fixed back plate <NUM> having a through hole <NUM> in a center for allowing an axle <NUM> of the left rear wheel to pass through; first and second brake shoes <NUM>, <NUM> arranged in the back plate <NUM> in a manner capable of slidingly contacting wifchan inner periphery of a brake drum <NUM> that rotates together with the left rear wheel; a wheel cylinder <NUM> fixed to the back plate <NUM> so as to exert a force for expanding the first and second brake shoes <NUM>, <NUM>; a braking gap automatic adjustment unit (so-called automatic adjuster) <NUM> that automatically adjusts a gap between the first and second brake shoes <NUM>, <NUM> and the brake drum <NUM>; and a return spring <NUM> provided between the first and second brake shoes <NUM>, <NUM>.

The first and second brake shoes <NUM>, <NUM> are constituted by first and second webs 15a, 16a formed in a bow-like flat plate shape along the inner periphery of the brake drum <NUM>, first and second rims 15b, 16b that are continuously provided in a manner orthogonal to respective outer peripheries of the first and second webs 15a, 16a, and first and second linings 15c, 16c attached to respective outer peripheries of the first and second rims 15b, 16b.

In the back plate <NUM>, an anchor plate <NUM> serving as a fulcrum during expansion and contraction of the first and second brake shoes <NUM>, <NUM> is fixed so as to rotatably support one end (lower end in this embodiment) of each of the first and second webs 15a, 16a. The wheel cylinder <NUM> is fixed on the back plate <NUM> between the other ends of the first and second brake shoes <NUM>, <NUM>, so as to be operated by an output hydraulic pressure of a master cylinder (not shown) operated by a brake pedal to exert a force for driving the first and second brake shoes <NUM>, <NUM> toward an expansion side with the anchor plate <NUM> as the fulcrum. The wheel cylinder <NUM> includes a pair of pistons <NUM> each having an outer end facing the other end (upper end in this embodiment) of each of the first and second webs 15a, 16a.

A coil spring <NUM> is provided between the one ends of the first and second webs 15a, 16a to bias the one ends of the first and second webs 15a, 16a toward the anchor plate <NUM>. The return spring <NUM> is provided between the other ends of the first and second webs 15a, 16a to bias the first and second brake shoes <NUM>, <NUM> in a contraction direction.

The braking gap automatic adjustment unit <NUM> includes: a contraction position control strut <NUM> that is provided between the first and second webs 15a, 16a of the first and second brake shoes <NUM>, <NUM> and can be extended by rotation of an adjust gear <NUM>; an adjust lever <NUM> that includes a feed claw 25a engaging with the adjust gear <NUM> and is rotatably supported by the second web 16a of the second brake shoe <NUM> among the first and second brake shoes <NUM>, <NUM>; and an adjust spring <NUM> that rotatably biases the adjust lever <NUM> to a side to rotate the adjust gear <NUM> in a direction to extend the contraction position control strut <NUM>.

The contraction position control strut <NUM> controls a contraction position of each of the first and second brake shoes <NUM>, <NUM>, and includes: a first rod <NUM> including a first engaging coupling part 27a, a second rod <NUM> including a second engaging coupling part 28a and arranged coaxially with the first rod <NUM>, and an adjust bolt <NUM> whose one end is inserted into the first rod <NUM> in a manner relatively movable in an axial direction and whose other end is coaxially screwed to the second rod <NUM>. The adjust gear <NUM> is arranged between the first and second rods <NUM>, <NUM> and formed on an outer periphery of the adjust bolt <NUM>.

The adjust lever <NUM> including the feed claw 25a engaged with the adjust gear <NUM> is rotatably supported by the second web 16a via a support shaft <NUM>. The adjust spring <NUM> is provided between the second web 16a and the adjust lever <NUM>. A spring force of the adjust spring <NUM> is set smaller than a spring force of the return spring <NUM>.

The drum brake B includes a parking brake lever <NUM> that can generate a parking brake force in response to rotation in one direction (counterclockwise direction in <FIG>). The parking brake lever <NUM> overlaps with a part of the first web 15a of the first brake shoe <NUM> in a front view in a direction along a rotation axis of the brake drum <NUM> (a direction shown in <FIG>), and extends long along a longitudinal direction of the first web 15a.

A cable end <NUM> fixed to one end of the brake cable <NUM> is engaged with a locking part 34a provided at one end (lower end in this embodiment) of the parking brake lever <NUM>. The other end (upper end in this embodiment) of the parking brake lever <NUM> is rotatably supported by the other end of the first web 15a of the first brake shoe <NUM> via a pin <NUM>.

The first engaging coupling part 27a of the first rod <NUM> in the braking gap automatic adjustment unit <NUM> is engaged with a first locking recess <NUM> provided in a side edge of the parking brake lever <NUM> that is near the other end of the parking brake lever <NUM> and faces the axle <NUM>. The second engaging coupling part 28a of the second rod <NUM> is engaged with a second locking recess <NUM> provided at a side edge of the second web 16a of the second brake shoe <NUM> that is near the other end of the second web 16a and faces the axle <NUM>.

According to the above braking gap automatic adjustment unit <NUM>, in a case where the first and second brake shoes <NUM>, <NUM> are expanded by a certain value or more due to friction of the first and second linings 15c, 16c when the first and second brake shoes <NUM>, <NUM> are expanded by an operation of the wheel cylinder <NUM>, the adjust lever <NUM> is rotated around the axis of the support shaft <NUM> by the spring force of the adjust spring <NUM>, and thus an effective length of the contraction position control strut <NUM> is increased and corrected in accordance with rotation of the adjust gear <NUM>.

During a parking brake operation of a vehicle, the parking brake lever <NUM> is driven to rotate in the counterclockwise direction in <FIG> by a traction force input from the brake cable <NUM> with the pin <NUM> serving as the fulcrum. By the rotation of the parking brake lever <NUM>, a force in a direction in which the second lining 16c of the brake shoe <NUM> is brought into pressure contact with the inner periphery of the brake drum <NUM> acts on the second brake shoe <NUM> via the contraction position control strut <NUM>. When the parking brake lever <NUM> is continuously driven to rotate in the counterclockwise direction of <FIG>, the parking brake lever <NUM> rotates with an engagement part thereof with the first engaging coupling part 27a of the contraction position control strut <NUM> serving as a fulcrum. At this time, the first brake shoe <NUM> expands through the pin <NUM> and the first lining 15c of the first brake shoe <NUM> is brought into pressure contact with the inner periphery of the brake drum <NUM>. That is, the parking brake lever <NUM> is operated to an operation position where the first and second linings 15c, 16c of the first and second brake shoes <NUM>, <NUM> are brought into pressure contact with the inner periphery of the brake drum <NUM>, and a parking brake state is obtained in this state.

When the brake cable <NUM> is loosened to stop applying a rotation driving force to the parking brake lever <NUM>, the parking brake lever <NUM> returns to a non-operation position together with the first and second brake shoes <NUM>, <NUM>, which are operated by the spring force of the return spring <NUM> in a direction away from the inner periphery of the brake drum <NUM>.

With reference to <FIG>, the brake cable <NUM> is pulled by a power exerted by an electric actuator <NUM>. The electric actuator <NUM> includes: a screw shaft <NUM> coupled to the brake cable <NUM>; an actuator case <NUM> that supports the screw shaft <NUM> in a manner capable of reciprocating in an axis direction while preventing rotation of the screw shaft <NUM>; an electric motor <NUM> supported by the actuator case <NUM> in a manner allowing rotation in forward and reverse directions; and a motion conversion mechanism (not shown) interposed between the electric motor <NUM> and the screw shaft <NUM> and housed in the actuator case <NUM> while being capable of converging a rotation motion generated by the electric motor <NUM> into a linear motion of the screw shaft <NUM>.

The actuator case <NUM> of the electric actuator <NUM> is attached to the back plate <NUM> via an attachment member <NUM> on a side opposite to the wheel cylinder <NUM>. The attachment member <NUM> is fixed to the actuator case <NUM>, and fastened to the back plate <NUM> by a plurality of, for example, three bolts <NUM>.

The brake cable <NUM> is, except for a part thereof, covered with an inner cable coat <NUM> made of resin, and one end of the brake cable <NUM> on the electric actuator <NUM> side is coupled to the screw shaft <NUM> of the electric actuator <NUM> via a cable joint <NUM>. A front part of a lower part of the back plate <NUM> along a vehicle longitudinal direction is integrally provided with a cylindrical part 13a protruding therefrom. The brake cable <NUM> is introduced into the back plate <NUM> from the cylindrical part 13a, and is routed so as to be located at a position lower than the axle <NUM> in the back plate <NUM> in a state where the drum brake B is mounted on the wheel.

A protection cylinder <NUM> that covers a coupling part of the screw shaft <NUM> and the brake cable <NUM> is attached to the actuator case <NUM>. Between the protection cylinder <NUM> and the cylindrical part 13a of the back plate <NUM>, the brake cable <NUM> is covered by an outer cable <NUM> together with the inner cable coat <NUM>. Both ends of the outer cable <NUM> are attached to the protection cylinder <NUM> and the cylindrical part 13a via guide tubes <NUM>, <NUM>.

The outer cable <NUM> is made by winding a wire made of, for example, iron into a coil shape, and receives a reaction force output by the electric actuator <NUM>. A metallic cylindrical member may be used instead of the outer cable <NUM>.

With reference to <FIG> and <FIG> as well, the anchor plate <NUM> abuts on one end (lower end) of each of the first and second webs 15a, 16a of the first and second brake shoes <NUM>, <NUM>. The anchor plate <NUM> and a suppression member <NUM> that sandwiches the one end of each of the first and second webs 15a, 16a together with the back plate <NUM> so as to prevent floating of the first and second brake shoes <NUM> and <NUM> from the back plate <NUM> are fixed to an anchor attachment part <NUM> formed on the back plate <NUM> in a manner rising inward of the back plate by a pair of rivets <NUM> in a state in which the anchor plate <NUM> is sandwiched between the anchor attachment part <NUM> and the suppression member <NUM>.

A guide part <NUM> that guides the brake cable <NUM> covered with the inner cable coat <NUM> is fixedly provided inward of the anchor attachment part <NUM> in a radial direction of the back plate <NUM>. In this embodiment, the guide part <NUM> is integrally provided with the suppression member <NUM> in a manner projecting from the suppression member <NUM> toward a center side of the back plate <NUM>.

The guide part <NUM> integrally includes: a flat plate part 48a which is flush with and continuous with the suppression member <NUM> and extends toward the center side of the back plate <NUM>, a first curved part 48b which is continuous with a distal end of the flat plate part 48a and is curved in a direction away from the back plate <NUM>, and a second curved part 48c which is continuous with the flat plate part 48a and the first curved part 48b at an end of the parking brake lever <NUM> side of the flat plate part 48a and forms a substantially U-shaped groove <NUM> in cooperation with the first curved part 48b.

According to the invention, at least one of the back plate <NUM> and the anchor plate <NUM>, in the first embodiment, the anchor plate <NUM>, is integrally provided with a support part <NUM> that abuts on the guide part <NUM> to support the guide part <NUM>. The support part <NUM> abuts on the guide part <NUM> in a direction parallel to a central axis of the back plate <NUM>, and extends from the anchor plate <NUM> toward the center side of the back plate <NUM> in a manner flush with and continuous with the anchor plate <NUM>, so as to abut on the flat plate part 48a of the guide part <NUM> from the back plate <NUM> side.

Next, an action of the first embodiment will be explained. The anchor attachment part <NUM> rising inward of the back plate <NUM> is formed on the back plate <NUM>, the guide part <NUM> that guides the brake cable <NUM> covered with the inner cable coat <NUM> is fixedly provided inward of the anchor attachment part <NUM> in the radial direction of the back plate <NUM>, and at least one of the back plate <NUM> and the anchor plate <NUM>, in the first embodiment, the anchor plate <NUM>, is integrally provided with the support part <NUM> that abuts on the guide part <NUM> to support the guide part <NUM>. Therefore, it is possible to ensure a strength of the guide part <NUM> while avoiding an increase in the number of members.

In addition, in the first embodiment, the guide part <NUM> is integrally provided on the suppression member <NUM>, which is fixed to the anchor attachment part <NUM> together with the anchor plate <NUM> so as to sandwich the anchor plate <NUM> together with the anchor attachment part <NUM>, in a manner projecting toward the center side of the back plate <NUM>. Therefore, it is possible to ensure the strength of the guide part <NUM> without increasing a plate thickness of the suppression member <NUM> including the guide part <NUM>.

The support part <NUM> abuts on the guide part <NUM> in the direction parallel to the central axis of the back plate <NUM>. Therefore, it is possible to increase a strength against a shear force and a vertical component of forces acting on the guide part <NUM> from the brake cable <NUM>.

A second embodiment of the invention will be explained with reference to <FIG>. An anchor attachment part <NUM> that rises inward of the back plate <NUM> is formed on the back plate <NUM>. The anchor plate <NUM> and the suppression member <NUM> which sandwiches the anchor plate <NUM> together with the anchor attachment part <NUM> are fixed to the anchor attachment part <NUM> by the rivets <NUM>. A guide part <NUM> that guides the brake cable <NUM> covered with the inner cable coat <NUM> is integrally provided on the suppression member <NUM> in a manner projecting from the suppression member <NUM> toward the center side of the back plate <NUM>.

The guide part <NUM> has a substantially J-shaped cross section, and integrally includes: a vertical wall part 52a that extends from an inner end of the suppression member <NUM> along the radial direction of the back plate <NUM> to a side that enters the back plate <NUM>, and a curved part 52b that is continuous with a distal end of the vertical wall part 52a and is curved in a semicircular shape. The brake cable <NUM> is guided by the curved part 52b.

At least one of the back plate <NUM> and the anchor plate <NUM>, in the second embodiment, the back plate <NUM>, is integrally provided with a support part <NUM> that abuts on the guide part <NUM> to support the guide part <NUM>.

The support part <NUM> is integrally included in the anchor attachment part <NUM> of the back plate <NUM>, and is integrally formed with the anchor attachment part <NUM> in a manner abutting on the vertical wall part 52a of the guide part <NUM>, so that the support part <NUM> abuts on the guide part <NUM> in the radial direction of the back plate <NUM>.

According to the second embodiment, similar to the first embodiment, it is possible to ensure a strength of the guide part <NUM> without increasing the plate thickness of the suppression member <NUM> including the guide part <NUM> while avoiding the increase of the number of members. In addition, the support part <NUM> abuts on the guide part <NUM> in the radial direction of the back plate <NUM>, and thus it is possible to increase a strength against a moment input from the brake cable <NUM> to the guide part <NUM>.

A third embodiment of the invention will be explained with reference to <FIG>. The anchor attachment part <NUM> rising inward of the back plate <NUM> is formed in the back plate <NUM>. The anchor plate <NUM> and the suppression member <NUM> sandwiching the anchor plate <NUM> together with the anchor attachment part <NUM> are fixed to the anchor attachment part <NUM> by the rivets <NUM>. A guide part <NUM> that guides the brake cable <NUM> covered with the inner cable coat <NUM> is integrally provided on the suppression member <NUM> in a manner projecting from the suppression member <NUM> toward the center side of the back plate <NUM>.

The guide part <NUM> has a substantially J-shaped cross section, and integrally includes: a vertical wall part 55a that extends from the inner end of the suppression member <NUM> along the radial direction of the back plate <NUM> to the side that enters the back plate <NUM>, and a curved part 55b that is continuous with a distal end of the vertical wall part 55a and is curved in a semicircular shape. The brake cable <NUM> is guided by the curved part 55b.

At least one of the back plate <NUM> and the anchor plate <NUM>, in the third embodiment, the back plate <NUM>, is integrally provided with first and second support parts <NUM>, <NUM> that abut on the guide part <NUM> to support the guide part <NUM>.

The first and second support parts <NUM>, <NUM> are integrally included in the anchor attachment part <NUM> of the back plate <NUM>. The first support part <NUM> abuts on the guide part <NUM> in the radial direction of the back plate <NUM>, and the second support part <NUM> abuts on the guide part <NUM> in a direction parallel to the central axis of the back plate <NUM>.

The first support part <NUM> is integrally formed with the anchor attachment part <NUM> in a manner abutting on the vertical wall part 55a of the guide part <NUM>, and the second support part <NUM> is integrally formed with the anchor attachment part <NUM> in a manner abutting on the curved part 55b of the guide part <NUM>.

According to the third embodiment, similar to the first embodiment and the second embodiment, it is possible to ensure a strength of the guide part <NUM> without increasing the plate thickness of the suppression member <NUM> including the guide part <NUM> while avoiding the increase of the number of members. In addition, the first support part <NUM> abuts on the guide part <NUM> in the radial direction of the back plate <NUM> and the second support part <NUM> abuts on the guide part <NUM> in the direction parallel to the central axis of the back plate <NUM>. Therefore, it is possible to increase a strength against a moment due to input from the brake cable <NUM> to the guide part <NUM> and a strength against a shear force and a vertical component of forces acting on the guide part <NUM> from the brake cable <NUM>.

A fourth embodiment of the invention will be explained with reference to <FIG>. An anchor attachment part <NUM> that rises inward of the back plate <NUM> is formed on the back plate <NUM>. The anchor plate <NUM>, a flat plate-shaped plate member <NUM> sandwiched between the anchor plate <NUM> and the anchor attachment part <NUM>, and a suppression member <NUM> that sandwiches the anchor plate <NUM> and the plate member <NUM> together with the anchor attachment part <NUM> are fixed to the anchor attachment part <NUM> by rivets <NUM>.

A guide part <NUM> that guides the brake cable <NUM> covered with the inner cable coat <NUM> is fixedly provided inward of the anchor attachment part <NUM> in the radial direction of the back plate <NUM>. In the fourth embodiment, the guide part <NUM> is integrally provided with the plate member <NUM> in a manner projecting from the plate member <NUM> toward the center side of the back plate <NUM>.

The guide part <NUM> is formed in a substantially J-shaped cross section, and integrally includes: a vertical wall part 68a that extends from an inner end of the plate member <NUM> along the radial direction of the back plate <NUM> to the side that enters the back plate <NUM>, and a curved part 68b that is continuous with a distal end of the vertical wall part 68a and is curved in a semicircular shape. The brake cable <NUM> is guided by the curved part 68b.

At least one of the back plate <NUM> and the anchor plate <NUM>, in the fourth embodiment, the back plate <NUM>, is integrally provided with a support part <NUM> that abuts on the guide part <NUM> to support the guide part <NUM>.

The support part <NUM> is integrally included in the anchor attachment part <NUM> of the back plate <NUM>, and is integrally formed with the anchor attachment part <NUM> in a manner abutting on the vertical wall part 68a of the guide part <NUM>, so that the support part <NUM> abuts on the guide part <NUM> in the radial direction of the back plate <NUM>.

According to the fourth embodiment, similar to each embodiment described above, it is possible to ensure a strength of the guide part <NUM> without increasing a plate thickness of the plate member <NUM> including the guide part <NUM> while avoiding the increase of the number of members. In addition, the support part <NUM> abuts on the guide part <NUM> in the radial direction of the back plate <NUM>, and thus it is possible to increase a strength against a moment input from the brake cable <NUM> to the guide part <NUM>.

Claim 1:
A vehicle drum brake, wherein
a pair of brake shoes (<NUM>, <NUM>) configured to slidingly contact a brake drum (<NUM>), and a brake lever (<NUM>) configured to rotate to cause the brake shoes (<NUM>, <NUM>) to slidingly contact the brake drum (<NUM>) so as to obtain a braking force are accommodated in a back plate (<NUM>),
an anchor plate (<NUM>) that abuts on one end of each of the pair of brake shoes (<NUM>, <NUM>) to rotatably support the brake shoes (<NUM>, <NUM>) is fixed on an anchor attachment part (<NUM>, <NUM>, <NUM>) that is formed on the back plate (<NUM>) in a manner rising inward of the back plate (<NUM>),
a guide part (<NUM>, <NUM>, <NUM>, <NUM>) that guides a brake cable (<NUM>) coupled to the brake lever (<NUM>) is fixedly provided inward of the anchor attachment part (<NUM>, <NUM>, <NUM>) in a radial direction of the back plate (<NUM>), and
at least one of the back plate (<NUM>) and the anchor plate (<NUM>) is integrally provided with a support part (<NUM>, <NUM>, <NUM>, <NUM>) that abuts on the guide part (<NUM>, <NUM>, <NUM>, <NUM>) to support the guide part (<NUM>, <NUM>, <NUM>, <NUM>).