Patent Publication Number: US-2023150466-A1

Title: Electric parking brake device

Description:
TECHNICAL FIELD 
     The present invention relates to 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. 
     BACKGROUND ART 
     Such electric parking brake device has been known from Patent Literature 1 and Patent Literature 2. In the electric parking brake device disclosed in Patent Literature 1, 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 2, 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. 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1: JP 2006-298094 A 
         PTL 2: JP 2014-205391 A 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     Incidentally, in the electric parking brake device disclosed in each of Patent Literature 1 and Patent Literature 2, 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. 
     Solution to Problem 
     In order to achieve the object described above, 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 start 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. 
     Advantageous Effects of Invention 
     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. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a front view of a drum brake (first embodiment). 
         FIG.  2    is a rear view of the drum brake (first embodiment). 
         FIG.  3    is a block diagram for illustrating a configuration for controlling an electric actuator (first embodiment). 
         FIG.  4    is a flowchart for illustrating a control process at the time of the parking brake (first embodiment). 
         FIG.  5    is a timing chart for showing an example of an operation state of the electric actuator at the time of the parking brake, and changes in signals of a service brake, a timer, and an activation continuation request of a control unit (first embodiment). 
         FIG.  6    is a timing chart for showing another example of an operation state of the electric actuator at the time of the parking brake, and changes in signals of the service brake, the timer, and the activation continuation request of the control unit (first embodiment). 
     
    
    
     REFERENCE SIGNS LIST 
     
         
         
           
               17  wheel cylinder 
               34  parking brake lever 
               37  brake cable 
               38  electric actuator 
               66  hydraulic pressure sensor serving as service brake detection means 
             B drum brake 
             C control unit 
           
         
       
    
     DESCRIPTION OF EMBODIMENT 
     An embodiment of the present invention is described with reference to the accompanying  FIG.  1    to  FIG.  6   . 
     First Embodiment 
     First, in  FIG.  1   , 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  13  having, in a center portion, a through hole  12  for allowing an axle  11  of the left rear wheel to pass therethrough; first and second brake shoes  15  and  16  arranged in the back plate  13  to be brought into slide contact with an inner periphery of a brake drum  14  that rotates together with the left rear wheel; a wheel cylinder  17  fixed to the back plate  13  to exert a force for causing the first and second brake shoes  15  and  16  to operate to expand; braking gap automatic adjustment means (so-called auto adjuster)  18  for automatically adjusting the gap between the first and second brake shoes  15  and  16  and the brake drum  14 ; and return springs  19  provided between the first and second brake shoes  15  and  16 . 
     The first and second brake shoes  15  and  16  include: first and second webs  15   a  and  16   a  each formed in a bow-like flat plate shape along the inner periphery of the brake drum  14 ; first and second rims  15   b  and  16   b  formed continuously from the first and second webs  15   a  and  16   a  to be orthogonal to outer peripheries thereof, respectively; and first and second linings  15   c  and  16   c  bonded to outer peripheries of the first and second rims  15   b  and  16   b , respectively. 
     An anchor plate  21  serving as a fulcrum at the time of expansion and contraction of the first and second brake shoes  15  and  16  is fixedly installed on the back plate  13  to rotatably support one end portion (lower end portion in this embodiment) of each of the first and second webs  15   a  and  16   a . In addition, the wheel cylinder  17  is fixed to the back plate  13  between the other end portions of the first and second brake shoes  15  and  16  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  15  and  16  to an expansion side through the use of the anchor plate  21  as a fulcrum, and outer end portions of a pair of pistons  20  provided in the wheel cylinder  17  are arranged to be opposed to the other end portions (upper end portions in this embodiment) of the first and second webs  15   a  and  16   a.    
     A coil spring  22  that urges the one end portions of the first and second webs  15   a  and  16   a  to the anchor plate  21  side is provided between the one end portions of the first and second webs  15   a  and  16   a , and a pair of return springs  19  that urge the first and second brake shoes  15  and  16  in a contraction direction are provided between the other end portions of the first and second webs  15   a  and  16   a.    
     The braking gap automatic adjustment means  18  includes: a contraction position regulating strut  24  which is formed between the first and second webs  15   a  and  16   a  included in the first and second brake shoes  15  and  16  and which can be extended by rotation of an adjusting gear  23 ; an adjusting lever  25  which has a feed claw  25   a  that is engaged with the adjusting gear  23  and which is rotatably supported by the second web  16   a  of the second brake shoe  16  of the first and second brake shoes  15  and  16 ; and an adjusting spring  26  that urges the adjusting lever  25  to rotate to the side on which the adjusting gear  23  rotates in a direction of extending the contraction position regulating strut  24 . 
     The contraction position regulating strut  24  regulates the contraction positions of the first and second brake shoes  15  and  16 , and includes: a first rod  27  having a first engaging and coupling portion  27   a  that is engaged with a position closer to the other end portion of the first web  15   a  included in the first brake shoe  15  of the first and second brake shoes  15  and  16 ; a second rod  28  which has a second engaging and coupling portion  28   a  that is engaged with a position closer to the other end portion of the second web  16   a  included in the second brake shoe  16  and which is arranged coaxially with the first rod  27 ; and an adjusting bolt  29  having one end portion that is inserted into the first rod  27  to be relatively movable in an axis direction and having the other end portion that is threadedly engaged with the second rod  28  coaxially. The adjusting gear  23  is formed on an outer periphery of the adjusting bolt  29  to be arranged between the first and second rods  27  and  28 . 
     A first locking recess  30  for engaging the first engaging and coupling portion  27   a  is formed on a side edge facing the axle  11  side closer to the other end portion of the first web  15   a , and a second locking recess  31  for engaging the second engaging and coupling portion  28   a  is formed on a side edge facing the axle  11  side closer to the other end portion of the second web  16   a.    
     The adjusting lever  25  having the feed claw  25   a  that is engaged with the adjusting gear  23  is rotatably supported by the second web  16   a  through the intermediation of a support shaft  32 , and the adjusting spring  26  is provided between the second web  16   a  and the adjusting lever  25 . Further, the spring force of the adjusting spring  26  is set to be smaller than the spring force of the return springs  19 . 
     In the braking gap automatic adjustment means  18 , at the time of causing the first and second brake shoes  15  and  16  to operate to expand through the operation of the wheel cylinder  17 , when the first and second brake shoes  15  and  16  expand by a certain value or more due to the abrasion of the first and second linings  15   c  and  16   c , the adjusting lever  25  rotates about the axis of the support shaft  32  due to the spring force of the adjusting spring  26 . As a result, the effective length of the contraction position regulating strut  24  is corrected to be increased in accordance with the rotation of the adjusting gear  23 . 
     Incidentally, the drum brake B includes a parking brake lever  34  capable of generating a parking brake force in accordance with the operation, and the parking brake lever  34  is arranged to overlap with a part of the first web  15   a  in the first brake shoe  15  in front view (direction illustrated in  FIG.  1   ) in a direction along the rotation axis of the brake drum  14  and is extended long along a longitudinal direction of the first web  15   a.    
     An engaging piece  36  fixed to one end portion of a brake cable  37  is engaged with one end portion (lower end portion in this embodiment) of the parking brake lever  34 , and the other end portion (upper end portion in this embodiment) of the parking brake lever  34  is coupled to the other end portion of the first web  15   a  in the first brake shoe  15  through the intermediation of a pin  35 . 
     When the parking brake of a vehicle operates, the parking brake lever  34  is driven to rotate in a counterclockwise direction of  FIG.  1    through the use of the pin  35  as a fulcrum by the pulling force input from the brake cable  37 . Due to the rotation of the parking brake lever  34 , a force in a direction in which the second lining  16   c  included in the brake shoe  16  is brought into pressure contact with the inner periphery of the brake drum  14  acts on the second brake shoe  16  via the contraction position regulating strut  24 . Further, when the parking brake lever  34  is continuously driven to rotate in the counterclockwise direction of  FIG.  1   , the parking brake lever  34  rotates through the use of the engagement portion with the first engaging and coupling portion  27   a  of the contraction position regulating strut  24  as a fulcrum. Then, the first brake shoe  15  operates to expand through the intermediation of the pin  35 , and the first lining  15   c  of the first brake shoe  15  is brought into pressure contact with the inner periphery of the brake drum  14 . That is, the parking brake lever  34  operates to an operation position at which the first and second linings  15   c  and  16   c  of the first and second brake shoes  15  and  16  are brought into pressure contact with the inner periphery of the brake drum  14 , 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  34  is stopped by loosening the brake cable  37 , the parking brake lever  34  returns to a non-operation position together with the first and second brake shoes  15  and  16  that operate due to the spring force of the return springs  19  in a direction of separating from the inner periphery of the brake drum  14 , and the parking brake lever  34  is urged toward the non-operation position side. 
     Also referring to  FIG.  2   , the brake cable  37  is pulled by the power exerted by an electric actuator  38 , and the electric actuator  38  includes: a screw shaft  39  coupled to the brake cable  37 ; an actuator case  40  that supports the screw shaft  39  so that the screw shaft  39  can reciprocate in the axis direction while blocking the rotation thereof; an electric motor  41  accommodated in the actuator case  40  to freely rotate in forward and backward directions; and a motion conversion mechanism (not shown) that is accommodated in the actuator case  40  to be provided between the electric motor  41  and the screw shaft  39  while enabling the rotary motion generated in the electric motor  41  to be converted into the linear motion of the screw shaft  39 . 
     The actuator case  40  of the electric actuator  38  is mounted to the back plate  13  on an opposite side of the wheel cylinder  17  through the intermediation of a mounting member  43 . The mounting member  43  is fixed to the actuator case  40 , and the mounting member  43  is fastened to the back plate  13  with a plurality of, for example, three bolts  44 . 
     The screw shaft  39  of the electric actuator  38  is coupled to the brake cable  37  through the intermediation of a cable joint  51 , and the coupling portion between the screw shaft  39  and the brake cable  37  is covered with a protective cylinder  50  connected to the actuator case  40 . 
     A tubular portion  13   a  is integrally provided to project from a front portion along a vehicle front-and-rear direction of a lower portion of the back plate  13 , and the brake cable  37  is introduced into the back plate  13  from the tubular portion  13   a . In addition, the brake cable  37  is covered with an outer cable  45  formed by winding an iron wire in a coil shape between the protective cylinder  50  and the tubular portion  13   a . An end portion of the outer cable  45  on the electric actuator  38  side is mounted to the protective cylinder  50  through the intermediation of a guide tube  52 , and an end portion of the outer cable  45  on the back plate  13  side is mounted to the tubular portion  13   a  through the intermediation of a guide tube  53 . 
     In addition, a holding plate  46  that sandwiches the anchor plate  21  with the back plate  13  is mounted to the lower portion of the back plate  13  with a pair of rivets  47  together with the anchor plate  21  between the one end portions of the first and second webs  15   a  and  16   a , and a guide portion  46   a  that guides the brake cable  37  is integrally formed on the holding plate  46  to have a substantially U-shaped transverse sectional shape. 
     In  FIG.  3   , the electric power of a battery  61  is supplied to the electric motor  41  in the electric actuator  38  through a drive circuit  62 , and the operation of the electric motor  41 , that is, the operation of the drive circuit  62  is controlled by a control unit C. Instruction means  63  for detecting that a vehicle user has performed an operation for obtaining the parking brake state by operation of the electric actuator  38  and outputting a signal for instructing the electric actuator  38  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  17  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  64 , the brake hydraulic pressure output from a master cylinder  65  acts on the wheel cylinder  17 . A hydraulic pressure sensor  66  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  67  connecting the master cylinder  65  and the master cylinder  65  to detect the brake hydraulic pressure, and the brake hydraulic pressure detected by the hydraulic pressure sensor  66  is input to the control unit C. 
     The control unit C performs the control in accordance with the process illustrated in  FIG.  4    at the time of the parking brake. In Step S 1 , a determination is made on whether or not the electric actuator  38  is in an operation state. When it is determined that the electric actuator  38  is in the operation state, an activation continuation request of the control unit C is turned on in Step S 2 , and it is checked in Step S 3  whether or not the application operation of the electric actuator  38  has been completed. When the completion of the application operation of the electric actuator  38  is confirmed, the flow proceeds to Step S 4 . In Step S 4 , a first predetermined time is set, and the brake hydraulic pressure detected by the hydraulic pressure sensor  66  is acquired in Step S 5 . After that, in Step S 6 , 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 S 6 , the flow returns from Step S 6  to Step S 4 . When it is determined that the vehicle is not in the service brake state, the flow proceeds from Step S 6  to Step S 7 , and time is counted. 
     When it is determined, in Step S 8  following the count in Step S 7 , that the first predetermined time has elapsed, the flow proceeds to Step S 9 , 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 S 8  that the first predetermined time has not elapsed, the flow proceeds from Step S 8  to Step S 10 , and the brake hydraulic pressure detected by the hydraulic pressure sensor  66  is acquired. In Step S 11  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 S 11  that the vehicle is not in the service brake state, the flow returns from Step S 11  to Step S 7 . When it is determined that the vehicle is in the service brake state, the flow proceeds from Step S 11  to Step S 12 , and the previous count value is reset. 
     In Step S 13  following Step S 12 , 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 S 13 , the flow proceeds to Step S 14 , and time is recounted to determine whether or not the second predetermined time has elapsed in Step S 15 . When the second predetermined time has not elapsed, the flow returns to Step S 14 . When it is confirmed that the second predetermined time has elapsed, the flow proceeds from Step S 15  to Step S 9 . 
     According to a such control process, after the completion of the application operation of the electric actuator  38 , the control unit C starts to count in response to the end of the detection of the service brake by the hydraulic pressure sensor  66  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.  5   , when the electric actuator  38  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 t 1 , the timer starts the count. At a time t 2  at which the first predetermined time has elapsed from the time t 1 , 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  66  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.  6   , when the service brake state is ended at a time t 3 , the timer starts to count, and a count value is reset when the service brake state is obtained at a time t 4  at which the time less than the first predetermined time has elapsed from the time t 3 . When the service brake state is ended at a time t 5  thereafter, the recount by the timer is performed. At a time  16  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  38 , the control unit C starts to count in response to the end of the detection of the service brake by the hydraulic pressure sensor  66  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  61  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  66  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  66  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  38  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  38  attached thereto. 
     The embodiment of the present invention has been described. However, the present invention is not limited to the above-mentioned embodiment. Various changes in design can be made without departing from the scope of the gist of the present invention.