Patent Publication Number: US-2023147075-A1

Title: Electric parking brake device for vehicle

Description:
TECHNICAL FIELD 
     The present invention relates to 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. 
     BACKGROUND ART 
     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 Patent Literature 1 and Patent Literature 2. 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1: JP 2020-8162 A 
         PTL 2: JP 2020-8165 A 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     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 Patent Literature 1, 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 Patent Literature 2, 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 Patent Literature 1 and Patent Literature 2, 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. 
     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 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. 
     Further, 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. 
     In addition to the configuration of the second feature, the present invention has a third feature that, the wall portion is formed into a shape that is increased in diameter with distance from the back plate. 
     In addition to the configuration of the second or third feature, the present invention has a fourth feature that, 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. 
     Still further, in addition to the configurations of the first to fourth features, the present invention has a fifth feature that, 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. 
     Advantageous Effects of Invention 
     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 third feature of the present invention, 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 fourth feature of the present invention, 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 fifth feature of the present invention, 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. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a front view of an electric parking brake device and is a view seen from the direction indicated by the arrow  1  of  FIG.  4    (first embodiment). 
         FIG.  2    is a view of a left rear wheel having the electric parking brake device mounted thereto when seen from an inner side in a vehicle-width direction (first embodiment). 
         FIG.  3    is a perspective view of the left rear wheel having the electric parking brake device mounted thereto when seen from a diagonally forward direction on the inner side in the vehicle-width direction (first embodiment). 
         FIG.  4    is a sectional view for illustrating a part of the electric parking brake device and a wheel taken along the line  4 - 4  of  FIG.  2    (first embodiment). 
     
    
    
     REFERENCE SIGNS LIST 
     
         
         
           
               13  back plate 
               15 , 16  brake shoe 
               17  wheel cylinder 
               21  anchor portion 
               40  wheel 
               40   b  rim portion 
               42  dust cover that is mounting member 
               44  electric actuator 
               54  snow accumulation suppressing member 
               54   a  wall portion 
               54   aa  outermost edge of wall portion 
               55  cutout 
             B drum brake 
             C rotation axis 
           
         
       
    
     DESCRIPTION OF EMBODIMENT 
     An embodiment of the present invention is described with reference to the accompanying  FIG.  1    to  FIG.  4   . 
     First Embodiment 
     First, in  FIG.  1   , 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  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  so as 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 an inner side of an upper portion of the back plate  13  so as 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  so as 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 portion  21  serving as a fulcrum at the time of expansion and contraction of the first and second brake shoes  15  and  16  is provided in a lower portion of the back plate  13 , and lower end portions of the first and second webs  15   a  and  16   a  are rotatably supported by the anchor portion  21 . In addition, the wheel cylinder  17  is fixed to an upper portion of the back plate  13  between upper end portions of the first and second brake shoes  15  and  16  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  15  and  16  to an expansion side through use of the anchor portion  21  as a fulcrum, and outer end portions of a pair of pistons  20  provided in the wheel cylinder  17  are arranged so as 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 lower end portions of the first and second webs  15   a  and  16   a  to the anchor portion  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 upper 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 upper 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 upper 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  so as 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  so as 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 upper 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 upper 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 so as 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  through, for example, caulking is engaged with a lower end portion of the parking brake lever  34 , and an upper end portion of the parking brake lever  34  is coupled to the upper 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 clockwise direction of  FIG.  1    through 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 clockwise direction of  FIG.  1   , the parking brake lever  34  rotates through 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 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 . 
     Also referring to  FIG.  2    to  FIG.  4   , the vehicle wheel, for example, the left rear wheel includes a wheel  40  having a rim portion  40   b  fixedly installed on an outer periphery of a disc portion  40   a  and a tire  41  mounted to the rim portion  40   b  of the wheel  40 , and the drum brake B is arranged on a radially inner side of the rim portion  40   b . The back plate  13  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  40   a  of the wheel  40 . In addition, the brake drum  14  of the drum brake B is fixed to the axle  11  together with the disc portion  40   a  of the wheel  40 . Further, a dust cover  42  including a cylindrical portion  42   a  that covers an end portion of the brake drum  14  on the inner side in the vehicle-width direction from a radially outward direction of the brake drum  14  is firmly attached to an outer surface of the back plate  13 , 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  44 , and the brake cable  37  is pulled by the power exerted by the electric actuator  44 . An actuator case  45  included in the electric actuator  44  is mounted, through intermediation of a mounting member  46 , to an upper portion of a side surface of the back plate  13  on an opposite side of the wheel cylinder  17  fixed to the inner side of the upper portion of the back plate  13  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  13  on the inner side in the vehicle-width direction. The mounting member  46  is firmly attached to the actuator case  45 , and the mounting member  46  is fastened to the back plate  13  with a plurality of bolts  47 . 
     A tubular portion  13   a  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  13 . The brake cable  37  is introduced into the back plate  13  from the tubular portion  13   a  and is routed so as to be located below the axle  11  in the back plate  13  under the state in which the drum brake B is mounted to the vehicle wheel. 
     The brake cable  37  is covered with an outer cable  48  between the actuator case  45  and the tubular portion  13   a . Both end portions of the outer cable  48  are mounted to the actuator case  45  and the tubular portion  13   a  through intermediation of guide tubes  49  and  50 , respectively. 
     Referring back to  FIG.  1   , in the anchor portion  21  that supports the lower end portions of the first and second webs  15   a  and  16   a  in the first and second brake shoes  15  and  16 , a plate  53  that is brought into abutment against the lower end portions of the first and second webs  15   a  and  16   a  and a holding member  51  that sandwiches the one end portions of the first and second webs  15   a  and  16   a  with the back plate  13  so as to prevent the first and second brake shoes  15  and  16  from coming off the back plate  13  are fixed to the back plate  13  with a pair of rivets  52  so that the plate  53  is sandwiched between the back plate  13  and the holding member  51 . 
     In addition, a guide portion  51   a  that guides the brake cable  37  is integrally provided to the holding member  51  so as to have a substantially U-shaped transverse sectional shape. 
     According to the present invention, an ice and snow accumulation suppressing member  54  including a wall portion  54   a , which extends from the back plate  13  to the inner side in the vehicle-width direction while facing an inner periphery of the rim portion  40   b  of the wheel  40  and which is arranged at least below the anchor portion  21 , is mounted to the outer peripheral edge portion of the back plate  13 . 
     Further, on a projected figure on a plane orthogonal to a rotation axis C of the vehicle wheel, as illustrated in  FIG.  2   , an outermost edge  54   aa  of the wall portion  54   a  along a radial direction of the back plate  13  is arranged outside of an imaginary circle IC which passes through an outermost end of the electric actuator  44  in the radial direction and which is centered on the rotation axis C. 
     In addition, the wall portion  54   a  is formed into an annular shape centered on the rotation axis C, and the ice and snow accumulation suppressing member  54  integrally includes the wall portion  54   a  and an inward flange portion  54   b  that protrudes in a radially inward direction from an end portion of the wall portion  54   a  on the back plate  13  side. Further, the wall portion  54   a  is formed into a shape that is increased in diameter with distance from the back plate  13 , and is formed into a tapered shape in this embodiment. 
     Incidentally, the wheel cylinder  17  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  13 , and a cutout  55  is formed in a peripheral edge portion of the wall portion  54   a  on an opposite side of the back plate  13  at least above the rotation axis C of the vehicle wheel. In this embodiment, the cutout  55  is formed in the peripheral edge portion of the wall portion  54   a  so as to be located above the wheel cylinder  17 . 
     In addition, the ice and snow accumulation suppressing member  54  is formed of an iron-based metal, and the ice and snow accumulation suppressing member  54  is welded directly to the back plate  13  or to the mounting member firmly attached to the back plate  13 . In this embodiment, the dust cover  42  that is the mounting member is firmly attached to the outer peripheral edge portion of the back plate  13 , and the inward flange portion  54   b  of the ice and snow accumulation suppressing member  54  is mounted to the back plate  13  so as to sandwich the dust cover  42  with the back plate  13 . The ice and snow accumulation suppressing member  54  may be welded to the dust cover  42 , or the ice and snow accumulation suppressing member  54  may be welded to the back plate  13  together with the dust cover  42 . 
     Next, the action of this embodiment is described. The ice and snow accumulation suppressing member  54  including the wall portion  54   a , which extends from the back plate  13  to the inner side in the vehicle-width direction while facing the inner periphery of the rim portion  40   b  of the wheel  40  and which is arranged at least below the anchor portion  21 , is mounted to the outer peripheral edge portion of the back plate  13  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  54   aa  of the wall portion  54   a  along the radial direction of the back plate  13  is arranged outside of the imaginary circle IC which passes through the outermost end of the electric actuator  44  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  40 , the refrozen ice and snow pass through the outer side of the electric actuator  44  when rotating together with the wheel  40 . Thus, the collision of the refrozen ice and snow with the electric actuator  44  can be prevented, and the influence caused by the collision of the ice and snow does not occur in the electric actuator  44 . That is, it is only required that the ice and snow accumulation suppressing member  54  have the function of defining the maximum size of the ice and snow refrozen in the lower portion of the wheel  40 , and it is not required that the ice and snow accumulation suppressing member  54  have high rigidity. 
     In addition, the wall portion  54   a  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  44 , and the refreezing of the ice and snow in the lower portion of the wheel  40  is suppressed. 
     In addition, the wall portion  54   a  is formed into a shape that is increased in diameter with distance from the back plate  13 . As a result, the intrusion of the snow into an area between the wheel  40  and the wall portion  54   a  can be more reliably suppressed by suppressing the gap between the outermost edge  54   aa  of the wall portion  54   a  and the rim portion  40   b  of the wheel  40  to be small while preventing the interference of the wall portion  54   a  with the electric actuator  44 . In addition, even when the snow adheres to the inner side of the wall portion  54   a , 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  54   a , and the refreezing in the lower portion of the wheel  40  can also be suppressed. 
     In addition, the wheel cylinder  17  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  13 , and the cutout  55  is formed in the peripheral edge portion of the wall portion  54   a  on the opposite side of the back plate  13  at least above the rotation axis C of the vehicle wheel. As a result, the maintenance related to the wheel cylinder  17  at the time of mounting of piping connected to the wheel cylinder  17  and the like is facilitated. 
     Further, the ice and snow accumulation suppressing member  54  formed of an iron-based metal is welded directly to the back plate  13  or to the dust cover  42  firmly attached to the back plate  13 . As a result, the mounting of the ice and snow accumulation suppressing member  54  to the back plate  13  is facilitated. 
     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.