Abstract:
A motor driven brake system including a parking brake, in particular, a motor driven parking brake system in which a parking brake is implemented using a compact motor and a plurality of disks and friction pads mutually fractionized or released by the compact motor, so that it is possible to reduce operating noise of a solenoid as compared with that of an existing solenoid and to prevent a phenomenon that although a power failure of the compact motor occurs during driving, the braking power of the motor driven brake system is not released.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims under 35 U.S.C. §119(a) the benefit of Korean Patent Application No. 10-2012-0156060 filed Dec. 28, 2012, the entire contents of which are incorporated herein by reference. 
       BACKGROUND 
       [0002]    (a) Technical Field 
         [0003]    The present invention relates to a motor driven brake system. More particularly, the present invention relates to a motor driven brake system including a parking brake. 
         [0004]    (b) Background Art 
         [0005]    A motor driven brake system refers to a next-generation brake system which is able to provide a faster and more precise braking response performance as compared with an existing hydraulic brake system, a more simplified package layout due to removal of hydraulic pipe lines, minimal environment pollution without using brake oil, simple development of efficient application logic, improved collision safety due to removal of a master cylinder and a vacuum booster, and the like. 
         [0006]    In a motor driven brake system a brake pad is pressed by converting rotary power transmitted from a motor and a decelerator into linear power using a screw like mechanism. As a result, the motor driven parking brake system obtains braking power. On the contrary, when power is off, the screw like mechanism is unscrewed in the reverse direction by the pressing force of the brake pad, so that the braking power is released. 
         [0007]    Because of these features of the motor driven brake system, a separate parking brake apparatus may be combined with the motor driven brake system so that parking braking power can be provided when the power is off. That is, since a separate parking brake in the existing hydraulic brake system more expensive and heavy, a separate parking brake apparatus configured to share motor power for braking with the motor driven brake system may be mounted to the motor driven brake system in an effort to solve these problems. 
         [0008]    Hereinafter, the configuration and operation of a conventional motor driven brake system having a parking brake will be described with reference to  FIGS. 1 and 2 . 
         [0009]    In  FIGS. 1 and 2 , reference numeral  100  represents a motor driven brake system, and reference numeral  200  represents a parking brake. The motor driven brake system  100  includes friction pads  104  attached in a caliper housing  102 , and a disk  106  disposed between the friction pads  104  so as to be pressed by the friction pads  104 . A cylinder  108  movable forward and backward is installed in a horizontal through aperture of a caliper housing  102 , and a pressure member  110  having a screw aperture is integrally installed inside the cylinder  108 . 
         [0010]    In this case, a decelerator and an electric motor  114  having both side shafts are mounted at an inner end portion of the caliper housing  102 . Here, an outside shaft of the electric motor  114  is employed as a screw-shaped push rod  116  inserted and fastened into the screw aperture  112  of the pressure member  110 , and an inside shaft is employed as a rotating shaft  120  having a locking pin  118  formed on the outer circumferential surface thereof. 
         [0011]    Meanwhile, as one configuration of the parking brake  200 , a parking brake housing  202  is integrally mounted to an inner surface of the electric motor  114 , and the rotating shaft  120  of the electric motor  114  is rotatably disposed at a central portion of the parking brake housing  202 . 
         [0012]    A solenoid  204  is mounted on the inner surface of the parking brake housing  202 , and a horizontal pipe  206  is disposed between the solenoid  204  and the rotating shaft  120 . A sliding disk  208  in the shape of a vertical plate is integrally formed with the inner end portion of the horizontal pipe  206 . In this case, as shown in the sectional view taken along line D-D of  FIG. 2 , a locking groove  212  into which the locking pin  118  of the rotating shaft  120  is inserted is formed in the inside diameter surface of the horizontal pipe  206 . 
         [0013]    A spring  210  is disposed between the solenoid  204  and the sliding disk  208  to be compressible and expendable. A friction plate  214  that the sliding disk  208  frictionally contacts to perform parking braking is attached to the inner wall surface of the parking brake housing  202 . 
         [0014]    A controller  220  for turning on/off the power supplied to the device is connected to the electric motor  114  and the solenoid  204 . Thus, during normal braking, the controller  220  turns on the electric motor  114  and simultaneously turns on the solenoid according to a degree to which a brake pedal is pushed. 
         [0015]    Subsequently, when the push rod  116  of the electric motor  114  performs a standing rotation, the pressure member  110  fastened to the push rod  116  performs a rectilinear motion toward a vehicle outer direction. This is because the push rod  116  is formed in a screw like shape. 
         [0016]    Continuously, the cylinder  108  integrally formed with the pressure member  110  presses the friction pads  104 , and simultaneously, the disk  106  interposed between the friction pads  104  is pressed, so that braking is performed during driving. In this case, as power is applied to the solenoid  204 , the parking brake is released. 
         [0017]    That is, when the solenoid  204  is turned on, the solenoid  204  pulls the sliding disk  208  by means of the force from an electromagnet. In this case, the sliding disk  208  is spaced apart from the friction plate  214 , so that the parking brake is released the rotating shaft  120  of the electric motor  114  becomes rotatable. Simultaneously, the spring  210  disposed between the solenoid  204  and the sliding disk  208  is compressed. 
         [0018]    Accordingly, the forward/reverse rotation of the push rod  116  on the same axle with the rotating shaft  120  of the electric motor  114  is restricted, so that the braking operation of the motor driven brake system during driving can be smoothly performed together with the releasing of the parking brake. 
         [0019]    On the other hand, when power to the solenoid  204  is turned off after the motor driven brake system is operated, the sliding disk  208  is adhered closely to the friction plate  214  while being slid by the resilience of the spring  210 , so that the rotation of the rotating shaft  120  of the electric motor  114  is restricted, thereby operating the parking brake. 
         [0020]    That is, the locking pin  118  formed on the rotating shaft  120  of the electric motor  114  is stuck in the locking groove  212  in the horizontal pipe  206  integrally formed with the sliding disk  208  in the state in which the sliding disk  208  is adhered closely to the friction plate  214 , so that the rotating shaft  120  of the electric motor  114  is not rotated, thereby operating the parking brake. Accordingly, the reverse rotation of the push rod  116  on the same axle with the rotating shaft  120  of the electric motor  114  is restricted, so that the braking power of the parking brake is maintained. 
         [0021]    However, in the conventional motor driven brake system having the parking brake, the operating noise of the solenoid is increased during operation and releasing of the parking brake. Although the braking power should be released for the purpose of safety when the supply of power to the solenoid is stopped while driving, the braking power cannot be released once a power failure occurs. Therefore, the vehicle may lose control, possibly causing a fatal accident. 
         [0022]    In other words, when power is not supplied to the solenoid due to an error or failure in the controller when the motor driven brake system is operated during driving of the vehicle when the parking brake is released, i.e., when the power is applied to the solenoid to be turned on, the parking brake is operated as described above, and therefore, the braking power of the motor driven brake system may not be released. Accordingly, the vehicle may lose control thereby causing an accident. 
       SUMMARY OF THE DISCLOSURE 
       [0023]    The present invention provides a motor driven brake system in which a parking brake is implemented using a compact motor and a plurality of disks and friction pads mutually fractionized or released by the compact motor, so that it is possible to reduce operating noise of a solenoid as compared with that of an existing solenoid and to prevent a phenomenon that although a power failure of the compact motor occurs during driving, the braking power of the motor driven brake system is not released. 
         [0024]    In one aspect, the present invention provides a motor driven brake system including an electric motor for providing braking power, a push rod that is a shaft in the outer direction of the electric motor, a rotating shaft that is a shaft in the inner direction of the electric motor, and a parking brake housing mounted within the housing where an electric motor or electric motor/reducer is mounted. More specifically, this system including: sliding disks and friction pads, alternately mounted between the outside diameter of the rotating shaft and the inside diameter of the parking brake housing to restrict or release the rotation of the rotating shaft; a pressure member disposed adjacent to the outermost sliding disk to press the sliding disks and the friction pads, and having a screw aperture formed in an outer surface thereof; a compact motor mounted to an outside inner wall surface of the parking brake housing so as to be operated by receiving power supplied only in the braking of a parking brake and the releasing of the braking of the parking brake; and a screw-shaped push rod, as a driving shaft of the compact motor, inserted into the screw aperture of the pressure member so as to perform a standing rotation for the purposed of the forward-and-backward movement of the pressure member. 
         [0025]    In an exemplary embodiment, a guide member guiding a rectilinear movement of the pressure member while surrounding the outside diameter surface of the pressure member may be mounted to the inside diameter surface of the parking brake housing. 
         [0026]    In another exemplary embodiment, a fixing disk providing bearing power when the sliding disks and the friction pads are pressed may be mounted between the inner surface of the electric motor and the innermost friction pad. 
         [0027]    In still another exemplary embodiment, a first projection may be formed on the inside diameter surface of the parking brake housing, and a first recessed groove having the first projection inserted and fastened thereinto may be formed in the outside diameter surface of the friction pad. 
         [0028]    In yet another exemplary embodiment, a second projection may be formed on the inside diameter surface of the sliding disk, and a second recessed groove having the second projection inserted and fastened thereinto may be formed in the outside diameter surface of the rotating shaft. 
         [0029]    In still yet another exemplary embodiment, a third projection may be formed on the inside diameter surface of the guide member, and a third recessed groove having the third projection inserted and fastened thereinto may be formed in the outside diameter surface of the pressure member. 
         [0030]    Advantageously, since power for the parking brake while driving is not required like in the existing solenoid-type parking brake, it is possible to reduce power consumption and to considerably decrease the operating noise of the solenoid. 
         [0031]    Second, the existing solenoid-type parking brake has a disadvantage in that when a power failure of the solenoid occurs when the braking of the motor driven brake system is performed while driving, the vehicle loses control due to the phenomenon that the operating of the parking brake and the braking of the motor driven brake system is not performed because the solenoid does not turn off. However, in the present invention, it is unnecessary to supply power to the parking brake while driving, so that it is possible to prevent the brake from not releasing and to prevent any loss of control of the vehicle. 
         [0032]    Third, a multi-stage disk and a friction pad, including a compact motor, are used to prevent the unlocking of a motor for operating the motor driven brake system when the parking brake is operated, so that it is possible to reduce the weight and cost of the entire brake system. 
         [0033]    Fourth, although a failure of the parking brake occurs, the braking of the motor driven brake system and the releasing of the braking of the motor driven brake system are possible, thereby improving safety. 
         [0034]    The above and other features of the invention are discussed infra. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0035]    The above and other features of the present invention will now be described in detail with reference to certain exemplary embodiments thereof illustrated the accompanying drawings which are given hereinbelow by way of illustration only, and thus are not limitative of the present invention, and wherein: 
           [0036]      FIGS. 1 and 2  are sectional views illustrating a conventional motor driven brake system, in which  FIG. 1  shows a braking state and  FIG. 2  shows a brake releasing state; 
           [0037]      FIGS. 3 and 4  are sectional views illustrating a motor driven brake system according to an embodiment of the present invention, in which  FIG. 3  shows a braking state and  FIG. 4  shows a brake released state; 
           [0038]      FIG. 5  is a sectional view taken along line A-A of  FIG. 3 ; 
           [0039]      FIG. 6  is a sectional view taken along line B-B of  FIG. 3 ; 
           [0040]      FIG. 7  is a sectional view taken along line C-C of  FIG. 3 ; and 
           [0041]      FIGS. 8 and 9  are flowcharts illustrating an operation of the motor driven brake system according to the embodiment of the present invention. 
       
    
    
       [0042]    It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various preferred features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment. 
         [0043]    In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing. 
       DETAILED DESCRIPTION 
       [0044]    Hereinafter reference will now be made in detail to various embodiments of the present invention, examples of which are illustrated in the accompanying drawings and described below. While the invention will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention to those exemplary embodiments. On the contrary, the invention is intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims. 
         [0045]    It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, combustion, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g. fuels derived from resources other than petroleum). 
         [0046]    Additionally, it is understood that the below methods are executed by at least one controller. The term controller refers to a hardware device that includes a memory and a processor. The memory is configured to store the instructions and the processor is specifically configured to execute said instructions to perform one or more processes which are described further below. 
         [0047]    Furthermore, the control logic of the present invention may be embodied as non-transitory computer readable media on a computer readable medium containing executable program instructions executed by a processor, controller or the like. Examples of the computer readable mediums include, but are not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetic tapes, floppy disks, flash drives, smart cards and optical data storage devices. The computer readable recording medium can also be distributed in network coupled computer systems so that the computer readable media is stored and executed in a distributed fashion, e.g., by a telematics server or a Controller Area Network (CAN). 
         [0048]      FIGS. 3 and 4  are sectional views illustrating a motor driven brake system including a parking brake according to an exemplary embodiment of the present invention. In  FIGS. 3 and 4 , reference numeral  100  represents a motor driven brake system, and reference numeral  200  represents a parking brake. 
         [0049]    The motor driven brake system  100  basically includes friction pads  104  attached in a caliper housing  102 , and a disk  106  disposed between the friction pads  104  so as to be pressed by the friction pads  104  when the brakes are applied. 
         [0050]    A cylinder  108  movable forward and backward is installed in a horizontal through aperture of a caliper housing  102 , and a pressure member  110  having a screw aperture is integrally installed inside the cylinder  108 . 
         [0051]    In this case, a decelerator and an electric motor  114  having both side shafts are mounted at an inner end portion of the caliper housing  102 . Here, an outside shaft of the electric motor  114  is employed as a screw-shaped push rod  116  inserted and fastened into the screw aperture  112  of the pressure member  110 , and an inside shaft on the same axle with the outside shaft is employed as a rotating shaft  120 . 
         [0052]    Meanwhile, as one configuration of the parking brake  200 , a parking brake housing  202  is integrally mounted to an inner surface of the electric motor  114 , and the rotating shaft  120  of the electric motor  114  is rotatably disposed at a central portion of the parking brake housing  202 . 
         [0053]    Here, a plurality of sliding disks  302  and a plurality of friction pads  304  are alternately stacked and arranged between the outside diameter of the rotating shaft  120  and the inside diameter of the parking brake housing  202 . Here, the sliding disks  302  and the friction pads  304  restrict the rotation of the rotating shaft  120  to perform the braking of the parking brake or release the restriction of the rotation of the rotating shaft to release the braking of the parking brake. In this case, a fixing disk  316  is mounted between the inner surface of the electric motor  114  and the innermost friction pad  304 . Here, the fixing disk  316  serves as a support plate when the sliding disks  302  and the friction pads  304  are pressed. 
         [0054]    A pressure member  308  moving forward and backward as a means for pressing the sliding disks  302  and friction pads  304  is disposed adjacent to the outermost sliding disk. Thus, a screw aperture  306  for connecting the pressure member  308  to a compact motor  310  is formed in the outer surface of the pressure member  308 . 
         [0055]    Particularly, the compact motor  310  as a driving source allowing the pressure member  308  to move forward and backward so as to press the sliding disks  302  and the friction pads  304  is mounted to the outside inner wall surface. Thus, the compact motor  310  is maintained in a power-off state at normal times, and is driven by receiving power supplied only in the braking and releasing of the parking brake. 
         [0056]    To this end, a screw-shaped push rod  312  that is a driving shaft of the compact motor  310  is inserted and fastened into the screw aperture  306  of the pressure member  308  so as to perform a standing rotation. The push rod  312  allows the pressure member  308  to move forward and backward. 
         [0057]    A guide member  314  is mounted to the inside diameter surface of the parking brake housing  202 . The guide member  314  guides the rectilinear movement of the pressure member  308  while surrounding the outside diameter surface of a horizontal pipe of the pressure member  308 . 
         [0058]    In order to restrict the rotation of the friction pad  304 , as shown in  FIG. 5 , a first projection  318  is formed on the inside diameter surface of the parking brake hosing  202 , and a first recessed groove  320  is formed in the outside diameter surface of the friction pad  304 . 
         [0059]    Thus, the first projection  318  is inserted and fastened into the first recessed groove  320 , so that the friction pad  304  is fixed to the inside diameter surface of the parking brake housing  202 , and simultaneously, the inside diameter surface of the friction pad  304  is spaced apart from the rotating shaft  120 . 
         [0060]    In order to rotate the sliding disk  302  together with the rotating shaft  120 , as shown in  FIG. 6 , a second projection  322  is formed on the inside diameter surface of the sliding disk  302 , and a second recessed groove  324  is formed in the outside diameter surface of the rotating shaft  120 . 
         [0061]    Thus, the second projection  322  is inserted and fastened into the second recessed groove  324 , so that the sliding disk  302  is fixed to the outside diameter surface of the rotating shaft  120 , and simultaneously, the outside diameter surface of the sliding disk  302  is spaced apart from the inside diameter surface of the parking brake housing  202 . 
         [0062]    In order to ensure the rectilinear movement of the pressure member  308 , as shown in  FIG. 7 , a third projection  326  is formed on the inside diameter surface of the guide member  314 , and a third recessed groove  328  having the third projection  326  inserted and fastened thereinto is formed in the outside diameter surface of the pressure member  308 . Thus, when the pressure member  308  performs a forward-and-backward rectilinear movement, the third projection  326  of the guide member  314  is inserted into the third recessed groove  328 , thereby guiding the rectilinear movement of the pressure member  308 . Accordingly, it is possible to ensure the forward-and-backward rectilinear movement of the pressure member  308 . 
         [0063]    Hereinafter, the operation of the motor driven brake system configured as described above will be described as follows. 
         [0064]    Operation (Braking) of Parking Brake 
         [0065]      FIG. 3  is a section view illustrating an operating state of the parking brake of the motor driven brake system according to the embodiment of the present invention.  FIG. 8  is a flowchart illustrating an operation of the motor driven brake system. 
         [0066]    When the push rod  116  of the electric motor  114  performs a standing rotation in the forward direction by applying power from the controller  220  to the electric motor  114  of the motor driven brake system  100 , the pressure member  110  fastened to the push rod  116  performs a rectilinear movement toward a vehicle outer direction. This is because the push rod  116  is formed in a screw shape. 
         [0067]    Continuously, the cylinder  108  integrally formed with the pressure member  110  presses the friction pads  104 , and simultaneously, the disk  106  interposed between the friction pads  104  is pressed, so that braking of the vehicle is performed. 
         [0068]    When the clamping force of the friction pad  104  with respect to the disk  106  is greater than a reference value A or when the rotational angle of the electric motor  114  is greater than a reference value B, the controller  220  applies power to the compact motor  310 . Accordingly, when the push rod  312  of the compact motor  310  performs a standing rotation in the forward direction, the pressure member  308  fastened to the push rod  312  moves forward. This is because the push rod  312  is also formed in the screw shape. 
         [0069]    Continuously, as the pressure member  308  moves forward, the sliding disk  302  and the friction pad  304  are adhered closely to each other, so that the rotating shaft  120  of the electric motor  114  is restricted so as not to be rotated any more. 
         [0070]    When the current applied from the controller  220  to the compact motor  310  is greater than a reference value C or when the rotational angle of the compact motor  310  is greater than a reference value D, the supply of power to the electric motor  114  and the compact motor  310  is stopped. Thus, the rotating shaft  120  of the electric motor  114  is restricted, and simultaneously, the reverse rotation of the push rod  116  on the same axle with the rotating shaft  120  is restricted, thereby performing the operation (braking) of the parking brake. 
         [0071]    Releasing of Operation (Braking) of Parking Brake 
         [0072]      FIG. 4  is a sectional view illustrating a released state of the parking brake of the motor driven brake system according to the embodiment of the present invention.  FIG. 9  is a flowchart illustrating an operation of the motor driven brake system. First, when the push rod  116  of the electric motor  114  performs a standing rotation in the reverse direction by applying power from the controller  220  to the electric motor  114  of the motor driven brake system, the pressure member  110  fastened to the push rod  114  performs a rectilinear movement toward a vehicle inner direction. This is because the push rod  116  is formed in the screw shape. 
         [0073]    Simultaneously, when the push rod  312  of the compact motor  310  performs a standing rotation in the reverse direction by applying power from the controller  220  to the compact motor  310 , the pressure member  308  fastened to the push rod  312  moves backward. This is because the push rod  312  is also formed in the screw shape. 
         [0074]    Continuously, as the pressure member  308  moves backward, the state in which the sliding disk  302  and the friction pad  304  are adhered closely to each other is released, so that the rotating shaft  120  of the electric motor  114  becomes a rotatable state. Thus, the cylinder  108  integrally formed with the pressure member  110  of the motor driven brake system  100  moves backward, and the clamping force of the disk  106  due to the friction pad  104  is released, so that the braking of the parking brake is released. 
         [0075]    Finally, when the current applied from the controller  220  to the compact motor  310  is greater than a reference value E or when the rotational angle of the compact motor  310  is less than a reference value F, the supply of power to the compact motor  310  is stopped. 
         [0076]    Meanwhile, since the restriction of the rotating shaft  120  of the electric motor  114  is released during driving of the vehicle, the controller  220  controls the driving of the electric motor  114  according to the input of a brake pedal, so that the braking of the motor driven brake system can be smoothly performed. Further, since it is unnecessary to supply power to the compact motor of the parking brake while driving, the braking of the motor driven brake system is not released, so that it is possible to easily prevent the occurrence of a spin of the vehicle. 
         [0077]    The invention has been described in detail with reference to exemplary embodiments thereof. However, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.