Patent Description:
An electric parking brake device for a vehicle in which an electric actuator is mounted to an outer surface of a back plate of a drum brake, and a parking brake force is obtained by power exerted by the electric actuator has been known from <CIT> and <CIT>. Further prior art can be found in <CIT> and <CIT>.

Incidentally, when a vehicle equipped with an electric parking brake device travels during snowfall, the snow adhering to the inside of a wheel of a vehicle wheel may be melted at the time of stopping of the vehicle and then refrozen in a lower portion of the wheel. In this case, when the refrozen ice and snow rotate together with the wheel due to the start of movement of the vehicle, the ice and snow after being refrozen may collide with an electric actuator mounted to an outer surface of a back plate, which may influence the electric actuator.

Meanwhile, in <CIT>, before the accumulated matter formed of snow and mud adhering to an inner peripheral surface of a wheel interferes with the electric actuator at the time of traveling of the vehicle, the accumulated matter is scraped off with a protective member attached to a stationary member of a drum brake, to thereby prevent the electric actuator from being damaged. In addition, in <CIT>, the adhering matter adhering to an inner peripheral surface of a wheel is removed with a protector, such as a scraper or a barrier, which is arranged at a position displaced in a circumferential direction from a part of the electric actuator closest to the inner peripheral surface of the wheel, to thereby prevent the electric actuator from being damaged. According to the technologies disclosed in <CIT> and <CIT>, the ice and snow after being refrozen can be prevented from colliding with the electric actuator. However, the protective member and the protector need to destroy the ice and snow, and hence are required to have high rigidity.

The present invention has been made in view of the above-mentioned circumstances, and has an object to provide an electric parking brake device for a vehicle capable of preventing the collision of ice and snow refrozen in a wheel with an electric actuator through use of a member that is not required to have high rigidity.

In order to achieve the object described above, the present invention has a first feature that there is provided an electric parking brake device for a vehicle, including: a drum brake which includes a pair of brake shoes rotatably supported by an anchor portion provided in a lower portion of a back plate and which is arranged on a radially inner side of a rim portion of a wheel of a vehicle wheel; and an electric actuator which enables obtaining a parking brake state by driving the drum brake, the electric actuator being mounted to a side surface of the back plate on an inner side in a vehicle-width direction, wherein an ice and snow accumulation suppressing member including a wall portion, which extends from the back plate to the inner side in the vehicle-width direction while facing an inner peripheral surface of the rim portion and which is arranged at least below the anchor portion, is mounted to an outer peripheral edge portion of the back plate, and wherein, on a projected figure on a plane orthogonal to a rotation axis of the vehicle wheel, an outermost edge of the wall portion along a radial direction of the back plate is arranged outside of an imaginary circle which passes through an outermost end of the electric actuator in the radial direction and which is centered on the rotation axis.

In addition to the configuration of the first feature, the present invention has a second feature that, the wall portion is formed into an annular shape centered on the rotation axis.

According to an optional third feature, the wall portion is formed into a shape that is increased in diameter with distance from the back plate.

According to an optional fourth feature, a wheel cylinder configured to exert power for obtaining a service brake state in the drum brake is mounted to an upper portion of the back plate, and a cutout is formed in a peripheral edge portion of the wall portion on an opposite side of the back plate at least above the rotation axis of the vehicle wheel.

According to an optional fifth feature, the ice and snow accumulation suppressing member formed of an iron-based metal is welded directly to the back plate or to a mounting member firmly attached to the back plate.

According to the first feature of the present invention, the wall portion of the ice and snow accumulation suppressing member mounted to the outer peripheral edge portion of the back plate extends from the back plate to the inner side in the vehicle-width direction while facing the rim portion of the wheel and is arranged at least below the anchor portion, and on the projected figure on the plane orthogonal to the rotation axis of the vehicle wheel, the outermost edge of the wall portion along the radial direction of the back plate is arranged outside of the imaginary circle which passes through the outermost end of the electric actuator and which is centered on the rotation axis. As a result, even when ice and snow are refrozen in a lower portion of the wheel, the refrozen ice and snow pass through an outer side of the electric actuator when rotating together with the wheel. Thus, the collision of the refrozen ice and snow with the electric actuator can be prevented, and the influence caused by the collision of the ice and snow does not occur in the electric actuator. That is, it is only required that the ice and snow accumulation suppressing member have the function of defining the maximum size of the ice and snow refrozen in the lower portion of the wheel, and it is not required that the ice and snow accumulation suppressing member have high rigidity.

In addition, according to the second feature of the present invention, the wall portion of the ice and snow accumulation suppressing member is formed into an annular shape. As a result, the snow is less liable to enter the inside of the wheel, and the refreezing of the ice and snow in the lower portion of the wheel is suppressed.

According to the optional third feature, the wall portion of the ice and snow accumulation suppressing member is formed into a shape that is increased in diameter with distance from the back plate. As a result, the intrusion of the snow into an area between the wheel and the wall portion can be more reliably suppressed by suppressing the gap between the outermost edge of the wall portion and the rim portion of the wheel to be small while preventing the interference of the wall portion with the electric actuator. In addition, even when the snow adheres to the inner side of the wall portion, the melt snow is easily allowed to slide to be discharged to the outside. Thus, the snow is less liable to be accumulated in the wall portion, and the refreezing in the lower portion of the wheel can also be suppressed.

According to the optional fourth feature, the wheel cylinder is mounted to the upper portion of the back plate, and the cutout is formed in the peripheral edge portion of the wall portion on the opposite side of the back plate at least above the rotation axis of the vehicle wheel. As a result, the maintenance related to the wheel cylinder at the time of mounting of piping connected to the wheel cylinder and the like is facilitated.

Further, according to the optional fifth feature, the ice and snow accumulation suppressing member is formed of an iron-based metal, and the ice and snow accumulation suppressing member is welded directly to the back plate or to a mounting member firmly attached to the back plate. As a result, the mounting of the ice and snow accumulation suppressing member to the back plate is facilitated.

An embodiment of the present invention is described with reference to the accompanying <FIG>.

First, in <FIG>, a drum brake B is provided on, for example, a left rear wheel of a four-wheeled vehicle, and the drum brake B includes: a fixed back plate <NUM> having, in a center portion, a through hole <NUM> for allowing an axle <NUM> of the left rear wheel to pass therethrough; first and second brake shoes <NUM> and <NUM> arranged in the back plate <NUM> so as to be brought into slide contact with an inner periphery of a brake drum <NUM> that rotates together with the left rear wheel; a wheel cylinder <NUM> fixed to an inner side of an upper portion of the back plate <NUM> so as to exert a force for causing the first and second brake shoes <NUM> and <NUM> to operate to expand; braking gap automatic adjustment means (so-called auto adjuster) <NUM> for automatically adjusting the gap between the first and second brake shoes <NUM> and <NUM> and the brake drum <NUM>; and return springs <NUM> provided between the first and second brake shoes <NUM> and <NUM>.

The first and second brake shoes <NUM> and <NUM> include: first and second webs 15a and 16a each formed in a bow-like flat plate shape along the inner periphery of the brake drum <NUM>; first and second rims 15b and 16b formed continuously from the first and second webs 15a and 16a so as to be orthogonal to outer peripheries thereof, respectively; and first and second linings 15c and 16c bonded to outer peripheries of the first and second rims 15b and 16b, respectively.

An anchor portion <NUM> serving as a fulcrum at the time of expansion and contraction of the first and second brake shoes <NUM> and <NUM> is provided in a lower portion of the back plate <NUM>, and lower end portions of the first and second webs 15a and 16a are rotatably supported by the anchor portion <NUM>. In addition, the wheel cylinder <NUM> is fixed to an upper portion of the back plate <NUM> between upper end portions of the first and second brake shoes <NUM> and <NUM> so as to operate with the 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> and <NUM> to an expansion side through use of the anchor portion <NUM> as a fulcrum, and outer end portions of a pair of pistons <NUM> provided in the wheel cylinder <NUM> are arranged so as to be opposed to the other end portions (upper end portions in this embodiment) of the first and second webs 15a and 16a.

A coil spring <NUM> that urges the lower end portions of the first and second webs 15a and 16a to the anchor portion <NUM> side is provided between the one end portions of the first and second webs 15a and 16a, and a pair of return springs <NUM> that urge the first and second brake shoes <NUM> and <NUM> in a contraction direction are provided between the upper end portions of the first and second webs 15a and 16a.

The braking gap automatic adjustment means <NUM> includes: a contraction position regulating strut <NUM> which is formed between the first and second webs 15a and 16a included in the first and second brake shoes <NUM> and <NUM> and which can be extended by rotation of an adjusting gear <NUM>; an adjusting lever <NUM> which has a feed claw 25a that is engaged with the adjusting gear <NUM> and which is rotatably supported by the second web 16a of the second brake shoe <NUM> of the first and second brake shoes <NUM> and <NUM>; and an adjusting spring <NUM> that urges the adjusting lever <NUM> to rotate to the side on which the adjusting gear <NUM> rotates in a direction of extending the contraction position regulating strut <NUM>.

The contraction position regulating strut <NUM> regulates the contraction positions of the first and second brake shoes <NUM> and <NUM>, and includes: a first rod <NUM> having a first engaging and coupling portion 27a that is engaged with a position closer to the upper end portion of the first web 15a included in the first brake shoe <NUM> of the first and second brake shoes <NUM> and <NUM>; a second rod <NUM> which has a second engaging and coupling portion 28a that is engaged with a position closer to the upper end portion of the second web 16a included in the second brake shoe <NUM> and which is arranged coaxially with the first rod <NUM>; and an adjusting bolt <NUM> having one end portion that is inserted into the first rod <NUM> so as to be relatively movable in an axis direction and having the other end portion that is threadedly engaged with the second rod <NUM> coaxially. The adjusting gear <NUM> is formed on an outer periphery of the adjusting bolt <NUM> so as to be arranged between the first and second rods <NUM> and <NUM>.

A first locking recess <NUM> for engaging the first engaging and coupling portion 27a is formed on a side edge facing the axle <NUM> side closer to the upper end portion of the first web 15a, and a second locking recess <NUM> for engaging the second engaging and coupling portion 28a is formed on a side edge facing the axle <NUM> side closer to the upper end portion of the second web 16a.

The adjusting lever <NUM> having the feed claw 25a that is engaged with the adjusting gear <NUM> is rotatably supported by the second web 16a through the intermediation of a support shaft <NUM>, and the adjusting spring <NUM> is provided between the second web 16a and the adjusting lever <NUM>. Further, the spring force of the adjusting spring <NUM> is set to be smaller than the spring force of the return springs <NUM>.

In the braking gap automatic adjustment means <NUM>, at the time of causing the first and second brake shoes <NUM> and <NUM> to operate to expand through the operation of the wheel cylinder <NUM>, when the first and second brake shoes <NUM> and <NUM> expand by a certain value or more due to the abrasion of the first and second linings 15c and 16c, the adjusting lever <NUM> rotates about the axis of the support shaft <NUM> due to the spring force of the adjusting spring <NUM>. As a result, the effective length of the contraction position regulating strut <NUM> is corrected to be increased in accordance with the rotation of the adjusting gear <NUM>.

Incidentally, the drum brake B includes a parking brake lever <NUM> capable of generating a parking brake force in accordance with the operation, and the parking brake lever <NUM> is arranged so as to overlap with a part of the first web 15a in the first brake shoe <NUM> in front view (direction illustrated in <FIG>) in a direction along the rotation axis of the brake drum <NUM> and is extended long along a longitudinal direction of the first web 15a.

An engaging piece <NUM> fixed to one end portion of a brake cable <NUM> through, for example, caulking is engaged with a lower end portion of the parking brake lever <NUM>, and an upper end portion of the parking brake lever <NUM> is coupled to the upper end portion of the first web 15a in the first brake shoe <NUM> through the intermediation of a pin <NUM>.

When the parking brake of a vehicle operates, the parking brake lever <NUM> is driven to rotate in a clockwise direction of <FIG> through use of the pin <NUM> as a fulcrum by the pulling force input from the brake cable <NUM>. Due to the rotation of the parking brake lever <NUM>, a force in a direction in which the second lining 16c included in 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 regulating strut <NUM>. Further, when the parking brake lever <NUM> is continuously driven to rotate in the clockwise direction of <FIG>, the parking brake lever <NUM> rotates through use of the engagement portion with the first engaging and coupling portion 27a of the contraction position regulating strut <NUM> as a fulcrum. Then, the first brake shoe <NUM> operates to expand through intermediation of 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> operates to an operation position at which the first and second linings 15c and 16c of the first and second brake shoes <NUM> and <NUM> are brought into pressure contact with the inner periphery of the brake drum <NUM>, and under this state, a parking brake state is obtained.

In addition, when the application of the rotational drive force to the parking brake lever <NUM> is stopped by loosening the brake cable <NUM>, the parking brake lever <NUM> returns to a non-operation position together with the first and second brake shoes <NUM> and <NUM> that operate due to the spring force of the return springs <NUM> in a direction of separating from the inner periphery of the brake drum <NUM>.

Also referring to <FIG>, the vehicle wheel, for example, the left rear wheel includes a wheel <NUM> having a rim portion 40b fixedly installed on an outer periphery of a disc portion 40a and a tire <NUM> mounted to the rim portion 40b of the wheel <NUM>, and the drum brake B is arranged on a radially inner side of the rim portion 40b. The back plate <NUM> of the drum brake B is fixed to, for example, a knuckle (not shown) forming a part of a suspension so as to be arranged on an inner side in a vehicle-width direction from the disc portion 40a of the wheel <NUM>. In addition, the brake drum <NUM> of the drum brake B is fixed to the axle <NUM> together with the disc portion 40a of the wheel <NUM>. Further, a dust cover <NUM> including a cylindrical portion 42a that covers an end portion of the brake drum <NUM> on the inner side in the vehicle-width direction from a radially outward direction of the brake drum <NUM> is firmly attached to an outer surface of the back plate <NUM>, that is, an outer peripheral edge portion of a side surface facing the inner side in the vehicle-width direction by, for example, welding.

The parking brake state is obtained by driving the drum brake B through use of the electric actuator <NUM>, and the brake cable <NUM> is pulled by the power exerted by the electric actuator <NUM>. An actuator case <NUM> included in the electric actuator <NUM> is mounted, through intermediation of a mounting member <NUM>, to an upper portion of a side surface of the back plate <NUM> on an opposite side of the wheel cylinder <NUM> fixed to the inner side of the upper portion of the back plate <NUM> so as to exert power for obtaining a service brake state in the drum brake B, that is, the upper portion of the side surface of the back plate <NUM> on the inner side in the vehicle-width direction. The mounting member <NUM> is firmly attached to the actuator case <NUM>, and the mounting member <NUM> is fastened to the back plate <NUM> with a plurality of bolts <NUM>.

A tubular portion 13a is integrally provided so as to project from a front portion along a vehicle front-and-rear direction of the lower portion of the back plate <NUM>. The brake cable <NUM> is introduced into the back plate <NUM> from the tubular portion 13a and is routed so as to be located below the axle <NUM> in the back plate <NUM> under the state in which the drum brake B is mounted to the vehicle wheel.

The brake cable <NUM> is covered with an outer cable <NUM> between the actuator case <NUM> and the tubular portion 13a. Both end portions of the outer cable <NUM> are mounted to the actuator case <NUM> and the tubular portion 13a through intermediation of guide tubes <NUM> and <NUM>, respectively.

Referring back to <FIG>, in the anchor portion <NUM> that supports the lower end portions of the first and second webs 15a and 16a in the first and second brake shoes <NUM> and <NUM>, a plate <NUM> that is brought into abutment against the lower end portions of the first and second webs 15a and 16a and a holding member <NUM> that sandwiches the one end portions of the first and second webs 15a and 16a with the back plate <NUM> so as to prevent the first and second brake shoes <NUM> and <NUM> from coming off the back plate <NUM> are fixed to the back plate <NUM> with a pair of rivets <NUM> so that the plate <NUM> is sandwiched between the back plate <NUM> and the holding member <NUM>.

In addition, a guide portion 51a that guides the brake cable <NUM> is integrally provided to the holding member <NUM> so as to have a substantially U-shaped transverse sectional shape.

According to the present invention, an ice and snow accumulation suppressing member <NUM> including a wall portion 54a, which extends from the back plate <NUM> to the inner side in the vehicle-width direction while facing an inner periphery of the rim portion 40b of the wheel <NUM> and which is arranged at least below the anchor portion <NUM>, is mounted to the outer peripheral edge portion of the back plate <NUM>.

Further, on a projected figure on a plane orthogonal to a rotation axis C of the vehicle wheel, as illustrated in <FIG>, an outermost edge 54aa of the wall portion 54a along a radial direction of the back plate <NUM> is arranged outside of an imaginary circle IC which passes through an outermost end of the electric actuator <NUM> in the radial direction and which is centered on the rotation axis C.

In addition, the wall portion 54a is formed into an annular shape centered on the rotation axis C, and the ice and snow accumulation suppressing member <NUM> integrally includes the wall portion 54a and an inward flange portion 54b that protrudes in a radially inward direction from an end portion of the wall portion 54a on the back plate <NUM> side. Further, the wall portion 54a is formed into a shape that is increased in diameter with distance from the back plate <NUM>, and is formed into a tapered shape in this embodiment.

Incidentally, the wheel cylinder <NUM> that exerts the power for obtaining the service brake state in the drum brake B is mounted to the upper portion of the back plate <NUM>, and a cutout <NUM> is formed in a peripheral edge portion of the wall portion 54a on an opposite side of the back plate <NUM> at least above the rotation axis C of the vehicle wheel. In this embodiment, the cutout <NUM> is formed in the peripheral edge portion of the wall portion 54a so as to be located above the wheel cylinder <NUM>.

In addition, the ice and snow accumulation suppressing member <NUM> is formed of an iron-based metal, and the ice and snow accumulation suppressing member <NUM> is welded directly to the back plate <NUM> or to the mounting member firmly attached to the back plate <NUM>. In this embodiment, the dust cover <NUM> that is the mounting member is firmly attached to the outer peripheral edge portion of the back plate <NUM>, and the inward flange portion 54b of the ice and snow accumulation suppressing member <NUM> is mounted to the back plate <NUM> so as to sandwich the dust cover <NUM> with the back plate <NUM>. The ice and snow accumulation suppressing member <NUM> may be welded to the dust cover <NUM>, or the ice and snow accumulation suppressing member <NUM> may be welded to the back plate <NUM> together with the dust cover <NUM>.

Next, the action of this embodiment is described. The ice and snow accumulation suppressing member <NUM> including the wall portion 54a, which extends from the back plate <NUM> to the inner side in the vehicle-width direction while facing the inner periphery of the rim portion 40b of the wheel <NUM> and which is arranged at least below the anchor portion <NUM>, is mounted to the outer peripheral edge portion of the back plate <NUM> in the drum brake B, and on the projected figure on the plane orthogonal to the rotation axis C of the vehicle wheel, the outermost edge 54aa of the wall portion 54a along the radial direction of the back plate <NUM> is arranged outside of the imaginary circle IC which passes through the outermost end of the electric actuator <NUM> in the radial direction and which is centered on the rotation axis C. As a result, even when ice and snow are refrozen in the lower portion of the wheel <NUM>, the refrozen ice and snow pass through the outer side of the electric actuator <NUM> when rotating together with the wheel <NUM>. Thus, the collision of the refrozen ice and snow with the electric actuator <NUM> can be prevented, and the influence caused by the collision of the ice and snow does not occur in the electric actuator <NUM>. That is, it is only required that the ice and snow accumulation suppressing member <NUM> has the function of defining the maximum size of the ice and snow refrozen in the lower portion of the wheel <NUM>, and it is not required that the ice and snow accumulation suppressing member <NUM> have high rigidity.

In addition, the wall portion 54a is formed into an annular shape centered on the rotation axis C. As a result, the snow is less liable to enter the inside of the wheel <NUM>, and the refreezing of the ice and snow in the lower portion of the wheel <NUM> is suppressed.

In addition, the wall portion 54a is formed into a shape that is increased in diameter with distance from the back plate <NUM>. As a result, the intrusion of the snow into an area between the wheel <NUM> and the wall portion 54a can be more reliably suppressed by suppressing the gap between the outermost edge 54aa of the wall portion 54a and the rim portion 40b of the wheel <NUM> to be small while preventing the interference of the wall portion 54a with the electric actuator <NUM>. In addition, even when the snow adheres to the inner side of the wall portion 54a, the melt snow is easily allowed to slide to be discharged to the outside. Thus, the snow is less liable to be accumulated in the wall portion 54a, and the refreezing in the lower portion of the wheel <NUM> can also be suppressed.

In addition, the wheel cylinder <NUM> that exerts the power for obtaining the service brake state in the drum brake B is mounted to the upper portion of the back plate <NUM>, and the cutout <NUM> is formed in the peripheral edge portion of the wall portion 54a on the opposite side of the back plate <NUM> at least above the rotation axis C of the vehicle wheel. As a result, the maintenance related to the wheel cylinder <NUM> at the time of mounting of piping connected to the wheel cylinder <NUM> and the like is facilitated.

Claim 1:
An electric parking brake device for a vehicle, comprising:
a drum brake (B) which includes a pair of brake shoes (<NUM>, <NUM>) rotatably supported by an anchor portion (<NUM>) provided in a lower portion of a back plate (<NUM>) and which is arranged on a radially inner side of a rim portion (40b) of a wheel (<NUM>) of a vehicle wheel; and
an electric actuator (<NUM>) which enables obtaining a parking brake state by driving the drum brake (B), the electric actuator (<NUM>) being mounted to a side surface of the back plate (<NUM>) on an inner side in a vehicle-width direction,
wherein an ice and snow accumulation suppressing member (<NUM>) including a wall portion (54a), which extends from the back plate (<NUM>) to the inner side in the vehicle-width direction while facing an inner peripheral surface of the rim portion (40b) and which is arranged at least below the anchor portion (<NUM>), is mounted to an outer peripheral edge portion of the back plate (<NUM>), and
wherein, on a projected figure on a plane orthogonal to a rotation axis (C) of the vehicle wheel, an outermost edge (54aa) of the wall portion (54a) along a radial direction of the back plate (<NUM>) is arranged outside of an imaginary circle (IC) which passes through an outermost end of the electric actuator (<NUM>) in the radial direction and which is centered on the rotation axis (C), characterised in that the wall portion (54a) is formed into an annular shape centered on the rotation axis (C).