Patent Description:
Such electric parking brake device has been known from Patent Literature <NUM>.

PTL <NUM>: <CIT>. This document discloses features falling under the preamble of claim <NUM>.

In the electric parking brake device disclosed in Patent Literature <NUM> mentioned above, a parking brake lever is coupled to one of a pair of brake shoes, and another brake shoe operates to expand through braking gap automatic adjustment means in association with the operation of the parking brake lever, to thereby obtain a parking brake state. However, when there is abnormality in the braking gap automatic adjustment means, the gap between the brake shoes and the brake drum becomes excessively larger. As a result, even when the parking brake lever is driven to an operation position side by an electric actuator, a required parking brake force may not be obtained or it may take time to obtain the parking brake state. Accordingly, it is required to check whether or not the braking gap automatic adjustment means normally operates.

The present invention has been made in view of the above-mentioned circumstances, and has an object to provide an electric parking brake device capable of determining the presence or absence of abnormality in braking gap automatic adjustment means at the time of obtaining a parking brake state.

In order to achieve the object described above, the present invention has a first feature that there is provided an electric parking brake device, including: a drum brake including: braking gap automatic adjustment means for automatically adjusting a gap between a pair of brake shoes and a brake drum; and a parking brake lever configured to operate between an operation position for obtaining a parking brake state by bringing the pair of brake shoes into slide contact with the brake drum and a non-operation position for releasing the parking brake state; an electric actuator configured to exert power for driving the parking brake lever; and a control unit configured to control the operation of the electric actuator, wherein, when an application operation time of the electric actuator by a time when the parking brake state is obtained has exceeded a predetermined application operation end determination time, the control unit determines that the braking gap automatic adjustment means is abnormal.

Further, in addition to the configuration of the first feature, the present invention has a second feature of including current detection means for detecting an energization current to the electric actuator, wherein, when a detection value by the current detection means of an inrush current generated in response to the start of the operation of the electric actuator has exceeded a predetermined current threshold, the control unit performs abnormality determination of the braking gap automatic adjustment means.

Still further, in addition to the configuration of the second feature, the present invention has a third feature that, when the detection value by the current detection means of the inrush current is equal to or less than the current threshold, and the control unit determines that the application operation time from a start of an application operation of the electric actuator has exceeded a predetermined inrush current abnormality determination time, the control unit initializes the abnormality determination of the braking gap automatic adjustment means.

According to the first feature of the present invention, when the application operation elapsed time of the electric actuator by the time when the parking brake state is obtained at the time of the application operation of the electric actuator for obtaining the parking brake state has exceeded the application operation determination time, the control unit determines that the braking gap automatic adjustment means is abnormal. As a result, the presence or absence of abnormality in the braking gap automatic adjustment means can be determined at the time of obtaining the parking brake state, and the maintenance of the braking gap automatic adjustment means can be quickly performed.

In addition, according to the second feature of the present invention, when the inrush current generated in response to the start of the operation of the electric actuator has exceeded the current threshold, the abnormality determination of the braking gap automatic adjustment means is performed. As a result, it is possible to perform the abnormality determination of the braking gap automatic adjustment means under a state in which the inrush current is normally generated, and it is possible to differentiate the abnormality determination from the abnormality determination caused by the failure of the electric actuator or the like.

Further, according to the third feature of the present invention, when the inrush current is equal to or less than the current threshold, and it is determined that the inrush current elapsed time has exceeded the inrush current determination time, the abnormality determination of the braking gap automatic adjustment means is initialized. As a result, it is possible to avoid the abnormality determination of the braking gap automatic adjustment means under a state in which an abnormal inrush current is generated due to the failure of the electric actuator or the like.

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

First, in <FIG>, a drum brake B is provided on a vehicle wheel of a four-wheeled vehicle, for example, a left rear wheel, 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> 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 the back plate <NUM> 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 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 plate <NUM> serving as a fulcrum at the time of expansion and contraction of the first and second brake shoes <NUM> and <NUM> is fixedly installed on the back plate <NUM> to rotatably support one end portion (lower end portion in this embodiment) of each of the first and second webs 15a and 16a. In addition, the wheel cylinder <NUM> is fixed to the back plate <NUM> between the other end portions of the first and second brake shoes <NUM> and <NUM> 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 the use of the anchor plate <NUM> as a fulcrum, and outer end portions of a pair of pistons <NUM> provided in the wheel cylinder <NUM> are arranged 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 one end portions of the first and second webs 15a and 16a to the anchor plate <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 other 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 other 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 other 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> 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> 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 other 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 other 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 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> is engaged with one end portion (lower end portion in this embodiment) of the parking brake lever <NUM>, and the other end portion (upper end portion in this embodiment) of the parking brake lever <NUM> is coupled to the other 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 counterclockwise direction of <FIG> through the 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 counterclockwise direction of <FIG>, the parking brake lever <NUM> rotates through the 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 the 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>, and the parking brake lever <NUM> is urged toward the non-operation position side.

Also referring to <FIG>, the brake cable <NUM> is pulled by the power exerted by an electric actuator <NUM>, and 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> so that the screw shaft <NUM> can reciprocate in the axis direction while blocking the rotation thereof; an electric motor <NUM> accommodated in the actuator case <NUM> to freely rotate in forward and backward directions; and a motion conversion mechanism (not shown) that is accommodated in the actuator case <NUM> to be provided between the electric motor <NUM> and the screw shaft <NUM> while enabling the rotary motion generated in the electric motor <NUM> to be converted into the linear motion of the screw shaft <NUM>.

The actuator case <NUM> of the electric actuator <NUM> is mounted to the back plate <NUM> on an opposite side of the wheel cylinder <NUM> through the intermediation of a mounting member <NUM>. The mounting member <NUM> is fixed to the actuator case <NUM>, and the mounting member <NUM> is fastened to the back plate <NUM> with a plurality of, for example, three bolts <NUM>.

The screw shaft <NUM> of the electric actuator <NUM> is coupled to the brake cable <NUM> through the intermediation of a cable joint <NUM>, and the coupling portion between the screw shaft <NUM> and the brake cable <NUM> is covered with a protective cylinder <NUM> connected to the actuator case <NUM>.

A tubular portion 13a is integrally provided to project from a front portion along a vehicle front-and-rear direction of a lower portion of the back plate <NUM>, and the brake cable <NUM> is introduced into the back plate <NUM> from the tubular portion 13a. In addition, the brake cable <NUM> is covered with an outer cable <NUM> formed by winding an iron wire in a coil shape between the protective cylinder <NUM> and the tubular portion 13a. An end portion of the outer cable <NUM> on the electric actuator <NUM> side is mounted to the protective cylinder <NUM> through the intermediation of a guide tube <NUM>, and an end portion of the outer cable <NUM> on the back plate <NUM> side is mounted to the tubular portion 13a through the intermediation of a guide tube <NUM>.

In addition, a holding plate <NUM> that sandwiches the anchor plate <NUM> with the back plate <NUM> is mounted to the lower portion of the back plate <NUM> with a pair of rivets <NUM> together with the anchor plate <NUM> between the one end portions of the first and second webs 15a and 16a, and a guide portion 46a that guides the brake cable <NUM> together with the outer cable <NUM> is integrally formed on the holding plate <NUM> to have a substantially U-shaped transverse sectional shape.

In <FIG>, the electric power of a power source <NUM> is supplied to the electric motor <NUM> in the electric actuator <NUM> through a drive circuit <NUM>, and the operation of the electric motor <NUM>, that is, the operation of the drive circuit <NUM> is controlled by a control unit C. Instruction means <NUM> for detecting that a vehicle user has performed operation for obtaining the parking brake state by operation of the electric actuator <NUM> and outputting a signal for obtaining the parking brake state, current detection means <NUM> for detecting an energization current to the electric motor <NUM>, and notification means <NUM> for notifying the vehicle user of the results of the abnormality determination of the braking gap automatic adjustment means <NUM> and the abnormality determination of an inrush current by the control unit C are connected to the control unit C.

At the time of obtaining the parking brake state, the control unit C performs the abnormality determination of the braking gap automatic adjustment means <NUM> and the abnormality determination of an inrush current in accordance with the process illustrated in <FIG>. In Step S2 after it is determined in Step S1 that the electric actuator <NUM> is in an application operation state in which the parking brake state is obtained, a current value A(n) detected by the current detection means <NUM> is acquired, and the flow proceeds to Step S4 after timer count is performed in Step S3. In Step S4, a determination is made on whether or not a flag F is "<NUM>", and the flag F is used for determining whether or not the inrush current generated in response to the start of the operation of the electric actuator <NUM> is normal. When it is determined that the flag F is "<NUM>", the flow proceeds from Step S4 to Step S5, and determination is made on whether or not the detection value by the current detection means <NUM>, that is, the current value A(n) acquired in Step S2 exceeds a predetermined current threshold A0.

More specifically, as shown in <FIG>, a determination is made on whether or not the inrush current has been normally generated based on whether or not the inrush current generated from an energization start time t1 exceeds the predetermined current threshold A0. When it is confirmed in Step S5 that A(n)>A0 is satisfied, the flow proceeds from Step S5 to Step S6. The flag F is set to "<NUM>" assuming that the inrush current has been normally generated, and then the flow returns to Step S2. In addition, it is determined in Step S5 that A(n)≤A0 is satisfied, the flow proceeds from Step S5 to Step S7, and the flag F is set to "<NUM>". In the next Step S8, a determination is made on whether or not the application operation time, that is, the elapsed time from the time t1 of <FIG> exceeds a predetermined inrush current abnormality determination time T1. When it is determined that the elapsed time is equal to or less than the inrush current abnormality determination time T1, the flow returns to Step S2.

When it is confirmed in Step S4 that the flag F is "<NUM>", the flow proceeds from Step S4 to Step S9. Then, a determination is made on whether or not the application operation of the electric actuator <NUM> has been ended, and the parking brake state has been obtained. The end of the application operation is determined, for example, based on the detection of a current value by the current detection means <NUM> at a time when the linings 15c and 16c of the pair of brake shoes <NUM> and <NUM> are brought into pressure contact with the brake drum <NUM> due to the forward rotation operation of the electric motor <NUM>, with the result that the rotational load of the electric motor <NUM> becomes a set value.

When it is determined in Step S9 that the application operation of the electric actuator <NUM> has not been ended, and the parking brake state has not been obtained, the flow returns to Step S2. When it is determined that the application operation of the electric actuator <NUM> has been ended, the flow proceeds from Step S9 to Step S10. In Step S10, a determination is made on whether or not the application operation elapsed time of the electric actuator <NUM> by the time when the parking brake state is obtained has become equal to or more than a predetermined application operation end determination time T2. In Step S10, when it is determined that the application operation elapsed time has become equal to or more than the application operation end determination time T2 from the time t1 to time t2, and the application operation of the electric actuator <NUM> has been ended, for example, as indicated by the chain line in <FIG>, it is determined in Step S11 that the braking gap automatic adjustment means <NUM> is abnormal, and the vehicle user is notified of the determination by the notification means <NUM> in Step S12.

In addition, when it is determined in Step S10 that the application operation of the electric actuator <NUM> has been ended with the elapsed time less than the application operation end determination time T2 from the time t1 to the time t2 as indicated by the solid line in <FIG>, it is determined in Step S13 that the braking gap automatic adjustment means <NUM> is normal, and the vehicle user is notified of the determination by the notification means <NUM> in Step S14. Further, in Step S15, a timer count value is set to "<NUM>" to initialize the abnormality determination of the braking gap automatic adjustment means <NUM>.

In addition, when it is determined in Step S8 that the state in which the current value A(n) acquired in Step S2 is equal to or less than the current threshold A0 has continued even after the inrush current abnormality determination time T1 under a state in which the inrush current is generated, it is determined in Step S16 that the inrush current is abnormal. Then, the flow proceeds from Step S16 to Step S15, and the timer count value is set to "<NUM>" to initialize the abnormality determination of the braking gap automatic adjustment means <NUM>.

Next, the action of this embodiment is described. When the application operation elapsed time of the electric actuator <NUM> by the time when the parking brake state is obtained has exceeded the predetermined application operation end determination time T2, the control unit C configured to control the operation of the electric actuator <NUM> capable of exerting power for driving the parking brake lever <NUM> determines that the braking gap automatic adjustment means <NUM> is abnormal. As a result, the presence or absence of abnormality in the braking gap automatic adjustment means <NUM> can be determined at the time of obtaining the parking brake state, and the maintenance of the braking gap automatic adjustment means <NUM> can be quickly performed.

In addition, the control unit C performs the abnormality determination of the braking gap automatic adjustment means <NUM> when the detection value A(n) by the current detection means <NUM> of the inrush current generated in response to the start of the operation of the electric actuator <NUM> has exceeded the predetermined current threshold A0. As a result, it is possible to perform the abnormality determination of the braking gap automatic adjustment means <NUM> under a state in which the inrush current is normally generated, and it is possible to differentiate the abnormality determination from the abnormality determination caused by the failure of the electric actuator <NUM> or the like.

Further, when the detection value by the current detection means <NUM> of the inrush current is equal to or less than the current threshold A0, and the control unit C determines that the application operation time from the start of the application operation of the electric actuator <NUM> has exceeded the predetermined inrush current abnormality determination time T1, the control unit C initializes the abnormality determination of the braking gap automatic adjustment means. As a result, it is possible to avoid the abnormality determination of the braking gap automatic adjustment means <NUM> under a state in which an abnormal inrush current is generated due to the failure of the electric actuator <NUM> or the like.

Claim 1:
An electric parking brake device, comprising:
a drum brake (B) including:
braking gap automatic adjustment means (<NUM>) for automatically adjusting a gap between a pair of brake shoes (<NUM>, <NUM>) and a brake drum (<NUM>); and
a parking brake lever (<NUM>) configured to operate between an operation position for obtaining a parking brake state by bringing the pair of brake shoes (<NUM>, <NUM>) into slide contact with the brake drum (<NUM>) and a non-operation position for releasing the parking brake state;
an electric actuator (<NUM>) configured to exert power for driving the parking brake lever (<NUM>); and
a control unit (C) configured to control the operation of the electric actuator (<NUM>),
characterized in that the control unit (C) determines whether or not the braking gap automatic adjustment means (<NUM>) operates normally based on an application operation time of the electric actuator (<NUM>) by a time when the parking brake state is obtained, and determines that the braking gap automatic adjustment means (<NUM>) does not operate normally when the application operation time has exceeded a predetermined application operation end determination time (T2).