Patent Description:
Such electric parking brake device has been known from Patent Literature <NUM> and Patent Literature <NUM>. In the electric parking brake device disclosed in Patent Literature <NUM>, when the rotation of a vehicle wheel is detected by a rotation sensor in a parked state of a vehicle, it is determined that the vehicle has started to move unintentionally, and the parking brake force is increased by operation of an electric actuator. In addition, in the electric parking brake device disclosed in Patent Literature <NUM>, the start of movement of a vehicle is accurately determined without sensitively sensing the shaking of the vehicle in a parked state thereof, and thus, a needless increase in parking brake force in cases other than the start of the movement is avoided.

Incidentally, in the electric parking brake device disclosed in each of Patent Literature <NUM> and Patent Literature <NUM>, to perform increase control of a parking brake force after parking, it is required to keep a control unit to be activated even after the ignition of an engine is turned off. However, when the control unit is carelessly kept activated for a long period of time, there is a risk in that a battery may run out.

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 reducing the load on a battery by preventing a control unit from being kept activated for a period of time that is longer than necessary.

The technical problem is solved by means of an electric parking brake according to claim <NUM>. The present invention has a first feature that there is provided an electric parking brake device which enables a service brake that generates a brake force in accordance with an operation input of a vehicle user and a parking brake that generates a brake force with the function of an electric actuator having operation controlled by a control unit, including service brake detection means connected to the control unit to detect whether or not the service brake has been applied after completion of application operation of the electric actuator, wherein the control unit starts to count in response to an end of detection of the service brake by the service brake detection means and stops operation of the control unit after an elapse of a first predetermined time from the start of the count.

Further, in addition to the configuration of the first feature, the present invention has a second feature that, the control unit resets the count in response to the detection of application of the service brake by the service brake detection means in the middle of time passage by the count and starts recount, and stops the operation of the control unit after an elapse of a second predetermined time from the start of the recount.

In addition to the configuration of the second feature, the present invention has a third feature that, the first predetermined time and the second predetermined time are set to be the same.

In addition to any one of the configurations of the first to third features, the present invention has a fourth feature that, the service brake detection means is a hydraulic pressure sensor configured to detect a brake hydraulic pressure for obtaining a brake force by the service brake.

Further, in addition to any one of the configurations of the first to fourth features, the present invention has a fifth feature that, the electric actuator coupled to a brake cable to drive a parking brake lever is attached to a drum brake including a wheel cylinder configured to generate the brake force by the service brake, the parking brake lever configured to operate to obtain the brake force by the parking brake, and the brake cable coupled to the parking brake lever.

According to the first feature of the present invention, the operation of the control unit is stopped when the first set time has elapsed after the end of the service brake. As a result, the load on a battery can be reduced by preventing the control unit from being kept activated for a period of time that is longer than necessary.

In addition, according to the second feature of the present invention, when the service brake has been applied in the middle by the time when the first set time elapses, the recount is started to stop the operation of the control unit after an elapse of the second predetermined time. As a result, when there is an additional operation input of the vehicle user after the end of the service brake, the increase control of the parking brake force can be performed.

According to the third feature of the present invention, the first predetermined time and the second predetermined time are the same. As a result, the increase control of the parking brake force can be reliably performed additionally.

According to the fourth feature of the present invention, the service brake detection means is a hydraulic pressure sensor configured to detect a brake hydraulic pressure. As a result, through the use of a hydraulic pressure sensor used in ordinary brake hydraulic pressure control, the use of a special sensor is made unnecessary to suppress an increase in the number of parts.

Further, according to the fifth feature of the present invention, the present invention can be suitably applied to the drum brake having the electric actuator attached thereto.

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> is integrally formed on the holding plate <NUM> to have a substantially U-shaped transverse sectional shape.

In <FIG>, the electric power of a battery <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 an operation for obtaining the parking brake state by operation of the electric actuator <NUM> and outputting a signal for instructing the electric actuator <NUM> on the start of the operation is connected to the control unit C.

In addition, the drum brake B generates a brake force when the wheel cylinder <NUM> operates in response to the operation input of the vehicle user at the time of the service brake. When the vehicle user steps on a brake pedal <NUM>, the brake hydraulic pressure output from a master cylinder <NUM> acts on the wheel cylinder <NUM>. A hydraulic pressure sensor <NUM> serving as a service brake detection means for detecting whether or not the service brake has been applied is inserted in a hydraulic pressure path <NUM> connecting the master cylinder <NUM> and the master cylinder <NUM> to detect the brake hydraulic pressure, and the brake hydraulic pressure detected by the hydraulic pressure sensor <NUM> is input to the control unit C.

The control unit C performs the control in accordance with the process illustrated in <FIG> at the time of the parking brake. In Step S1, a determination is made on whether or not the electric actuator <NUM> is in an operation state. When it is determined that the electric actuator <NUM> is in the operation state, an activation continuation request of the control unit C is turned on in Step S2, and it is checked in Step S3 whether or not the application operation of the electric actuator <NUM> has been completed. When the completion of the application operation of the electric actuator <NUM> is confirmed, the flow proceeds to Step S4. In Step S4, a first predetermined time is set, and the brake hydraulic pressure detected by the hydraulic pressure sensor <NUM> is acquired in Step S5. After that, in Step S6, determination is made on, based on the brake hydraulic pressure, whether or not the vehicle is in a service brake state.

When it is determined that the vehicle is in the service brake state based on the determination in Step S6, the flow returns from Step S6 to Step S4. When it is determined that the vehicle is not in the service brake state, the flow proceeds from Step S6 to Step S7, and time is counted.

When it is determined, in Step S8 following the count in Step S7, that the first predetermined time has elapsed, the flow proceeds to Step S9, and the activation continuation request of the control unit C is turned off to stop the operation of the control unit C.

In addition, when it is determined in Step S8 that the first predetermined time has not elapsed, the flow proceeds from Step S8 to Step S <NUM>, and the brake hydraulic pressure detected by the hydraulic pressure sensor <NUM> is acquired. In Step S11 thereafter, a determination is made on, based on the brake hydraulic pressure, whether or not the vehicle is in the service brake state. When it is determined in Step S11 that the vehicle is not in the service brake state, the flow returns from Step S11 to Step S7. When it is determined that the vehicle is in the service brake state, the flow proceeds from Step S11 to Step S12, and the previous count value is reset.

In Step S13 following Step S12, a second predetermined time is set. The second predetermined time is the same as the first predetermined time in this embodiment. After the second predetermined time is set in Step S13, the flow proceeds to Step S14, and time is recounted to determine whether or not the second predetermined time has elapsed in Step S15. When the second predetermined time has not elapsed, the flow returns to Step S14. When it is confirmed that the second predetermined time has elapsed, the flow proceeds from Step S15 to Step S9.

According to a such control process, after the completion of the application operation of the electric actuator <NUM>, the control unit C starts to count in response to the end of the detection of the service brake by the hydraulic pressure sensor <NUM> and stops the operation of the control unit C after an elapse of the first predetermined time from the start of the count. That is, as shown in <FIG>, when the electric actuator <NUM> is changed from the non-operation state to the operation completion state through the operation state to obtain the parking brake state in the service brake state, the activation continuation request of the control unit C is in an ON state. When the service brake state is ended at a time t1, the timer starts the count. At a time t2 at which the first predetermined time has elapsed from the time t1, the activation continuation request of the control unit C is turned off, and the control unit C stops the operation thereof.

In addition, the control unit C resets the count in response to the detection of application of the service brake by the hydraulic pressure sensor <NUM> in the middle of time passage by the count started in response to the end of the detection of the service brake and starts recount. After an elapse of the second predetermined time from the start of the recount, the control unit C stops the operation thereof. That is, as shown in <FIG>, when the service brake state is ended at a time t3, the timer starts to count, and a count value is reset when the service brake state is obtained at a time t4 at which the time less than the first predetermined time has elapsed from the time t3. When the service brake state is ended at a time t5 thereafter, the recount by the timer is performed. At a time t6 at which the second predetermined time has elapsed, the activation continuation request of the control unit C is turned off, and the control unit C stops the operation thereof.

Next, the action of this embodiment is described. After the completion of the application operation of the electric actuator <NUM>, the control unit C starts to count in response to the end of the detection of the service brake by the hydraulic pressure sensor <NUM> serving as the service brake detection means for detecting whether or not the service brake has been applied and stops the operation of the control unit C after an elapse of the first predetermined time from the start of the count. As a result, the load on the battery <NUM> can be reduced by preventing the control unit C from being kept activated for a period of time that is longer than necessary.

In addition, the control unit C resets the count in response to the detection of application of the service brake by the hydraulic pressure sensor <NUM> in the middle of time passage by the count and starts recount. After an elapse of the second predetermined time from the start of the recount, the control unit C stops the operation thereof. As a result, when there is an additional operation input of the vehicle user after the end of the service brake, the increase control of the parking brake force can be performed.

Further, the first predetermined time and the second predetermined time are set to be the same. As a result, the increase control of the parking brake force can be reliably performed additionally.

In addition, as the service brake detection means, the hydraulic pressure sensor <NUM> used in ordinary brake hydraulic pressure control is used. As a result, the use of a special sensor is made unnecessary to suppress an increase in the number of parts.

Further, the electric actuator <NUM> for obtaining the parking brake is attached to the drum brake B. As a result, the present invention can be suitably applied to the drum brake B having the electric actuator <NUM> attached thereto.

Claim 1:
An electric parking brake device which enables a service brake and a parking brake wherein the service brake generates a brake force in accordance with an operation input of a vehicle user, and wherein the parking brake generates a brake force with the function of an electric actuator (<NUM>) having operation controlled by a control unit (C), comprising service brake detection means (<NUM>) connected to the control unit (C) to detect whether or not the service brake has been applied after completion of application operation of the electric actuator (<NUM>),
characterised in that
the control unit (C) starts to count in response to an end of detection of the service brake by the service brake detection means (<NUM>) and stops the control of the parking brake by the control unit (C) after an elapse of a first predetermined time from the start of the count.