Abstract:
An electronic parking brake apparatus may include a driving member coupled to and actuating a parking cable, a case in which the driving member is housed, a cable ferrule disposed outside the case and coupled to a portion of the parking cable therethrough, wherein the cable ferrule is biased toward the case by the parking cable when the driving member actuates the parking cable, and a sensing member interposed between the case and the cable ferrule and measuring tension of the parking cable.

Description:
CLAIM OF PRIORITY 
     The present application claims the benefit of Korean Patent Application Number 10-2008-0095956 filed Sep. 30, 2008, the entire contents of which are incorporated herein for all purposes by this reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electronic parking brake apparatus, and more particularly, to an electronic parking brake apparatus, in which a sensor for measuring tension of a parking cable is implemented with a load cell based on a strain gauge, and is mounted on a cable ferrule, thereby reducing the length of the electronic parking brake apparatus. 
     2. Description of Related Art 
     In general, parking brakes for vehicles are used for stopping the vehicle or preventing movement of the vehicle during parking by a driver stepping on a parking brake pedal or pulling a parking brake lever. Recently an electronic parking brake (EPB) is used, which is operated by simple manipulation of a switch. 
     This EPB is configured so that, when a switch is pushed to drive a motor, a parking cable is pulled by rotation of the motor, and thereby generating a uniform braking force for each rear wheel. This EPB need measurement of the magnitude of tension of the parking cable pulled by the motor. To this end, the EPB measures force that is typically generated through variation in displacement of a spring, and precisely controls a locked state of the parking cable and a driving force of the motor on the basis of the measured force. 
     An EPB unit using a spring displacement sensor will be described below with reference to the accompanying drawings. 
       FIG. 1  illustrates the configuration of a conventional EPB unit on which a spring displacement sensor is mounted. 
     The EPB unit  100  includes an electronic control unit (ECU)  110  controlling a locking or unlocking force of a parking brake through power supplied by manipulation of a switch, a driving means  120  tightening or loosening the parking cable  140  manipulating a brake mechanism for rear wheels by means of driving of the EPB ECU  110 , and a sensing unit  160  measuring tension of the parking cable  140  tightened or loosened by the driving means  120  and then sending the measured signal to the EPB ECU  110 . 
     The EPB unit  100  also includes a motor  121  installed in a case  130  having a predetermined shape so as to run backwards or forwards according to the manipulation of the switch, a driving gear  122  rotatably engaged with a rotating shaft of the motor  121 , and a movable nut  124  engaged with a screw  123  and generating a linear moving force so as to pull or loosen the parking cable  140  by means of rotation of the driving gear  122 . 
     Here, the sensing unit  160  is configured so that an equalizer connecting shaft  162  thereof connected with the parking cable  140  cooperates with the movable nut  124 , thereby causing a movable pressure member  163  therein to compress a spring  161 . 
     At this time, a displacement sensor  164  such as a hall sensor located in the sensing unit  160  detects displacement of the movable pressure member  163  or the spring  161 , and sends the detected value to a sensor ECU  170 . Then, the sensor ECU  170  calculates a level of load, and then sends the calculated result to the EPB ECU  110 . In this process, the tension of the parking cable  140  is measured when the parking cable  140  is pulled. 
     In this manner, length of the case  130  is increased in a longitudinal direction of the parking cable  140  due to additional length of the sensing unit  160  located therein, which has an adverse influence on a layout of the vehicle. 
     Further, the sensor ECU  170  sending the measured value to the EPB ECU  110  is attached on one side of the sensing unit  160 , and thus moves together when the sensing unit  160  moves. Further, an interface  180  connected between the sensor ECU  170  and the EPB ECU  110  moves together when the sensing unit  160  moves. In this process, the interface  180  interferes with the interior of the case  130  to be shorted out or cut off. 
     The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art. 
     BRIEF SUMMARY OF THE INVENTION 
     Various aspects of the present invention are directed to provide an electronic parking brake (EPB) unit having a load cell, in which the load cell is mounted on a cable ferrule, thereby reducing the length of the electronic parking brake apparatus, and in which a sensor electronic control unit (ECU) is fixed to a case, thereby preventing an interface connecting the sensor ECU and an EPB ECU from being shorted out or cut out. 
     In an exemplary embodiment of the present invention, an electronic parking brake apparatus may include a driving member coupled to and actuating a parking cable, a case in which the driving member is housed, a cable ferrule disposed outside the case and coupled to a portion of the parking cable therethrough, wherein the cable ferrule is biased toward the case by the parking cable when the driving member actuates the parking cable, and/or a sensing member interposed between the case and the cable ferrule and measuring tension of the parking cable. 
     The sensing member may receive an external force when the parking cable is actuated to measure the tension of the parking cable. The external force may be a compression force. 
     The sensing member may be attached to a stationary member to fasten the sensing member between the case and the cable ferrule. 
     The sensing member maybe attached to the cable ferrule. 
     The sensing member may be attached to outer surface of the case. 
     The sensing member may include a weight sensor based on a strain gauge. 
     In another aspect of the present invention, the electronic parking brake apparatus may further include a parking brake electronic control unit installed in the case, and/or a sensor electronic control unit installed at a stationary member, and sending a value of the tension of the parking cable measured by the sensing member to the parking brake electronic control unit. 
     The stationary member is the case. The sensor electronic control unit may be attached to inner surface of the case. 
     The case may include a fastening nut, which allows the parking cable to pass through and move therethrough. 
     The sensing member may be interposed between the fastening nut and the cable ferrule. 
     The sensing member may be attached to the fastening nut. 
     The sensing member may be attached to a stationary member to fasten the sensing member between the fastening nut and the cable ferrule. 
     The sensing member may be attached to the cable ferrule. 
     The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description of the Invention, which together serve to explain certain principles of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates the configuration of a conventional electronic parking brake (EPB) unit on which a spring displacement sensor is mounted. 
         FIG. 2  illustrates the configuration of an exemplary EPB unit according to the present invention. 
         FIG. 3  is a cross-sectional view illustrating part A of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are 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. 
       FIG. 2  illustrates the configuration of an electronic parking brake (EPB) unit according to an exemplary embodiment of the present invention.  FIG. 3  is a cross-sectional view illustrating part A of  FIG. 2 . 
     According to an exemplary embodiment of the present invention, the EPB unit  200  includes an EPB electronic control unit (ECU)  210  controlled by manipulation of a driver, a driving member  220  driven by the EPB ECU  210  and pulling or loosening a parking cable  240 , and a sensor  260  measuring tension of the parking cable  240 . 
     The EPB ECU  210  and the driving member  220  are installed in a case  230  having a predetermined shape, and opposite ends of the case  230  are closed by fastening nuts  235 , in the center of each of which a hole into which the parking cable is inserted is formed. 
     The driving member  220  includes a driving motor  221  driven by the EPB ECU  210 , a driving gear  222  operated by the driving motor  221 , a screw  223  rotatably installed by the driving gear  222 , and a movable nut  224  linearly moving along the screw  223 . 
     The parking cable  240  is connected to one end of the movable nut  224  through the fastening nut  235 . The parking cable  240  is connected to the movable nut  224  at one end thereof, and braking member of wheels at the other end thereof. Thereby, the parking cable  240  is pulled or loosened when the movable nut  224  linearly moves, and thus operates the braking member. 
     A cable ferrule  250  is coupled to the parking cable  240 , wherein the cable ferrule  250  extends from the outside of the case  230 , and is fixed to a bracket. This bracket is no more than a means for positional restriction, and thus undergoes minute deformation, because the cable ferrule  250  moves together when the parking cable  240  is displaced by the driving member  220 . 
     The sensor  260  is a load cell based on a strain gauge, and is located between the fastening nut  235  and the cable ferrule  250 . 
     In an exemplary embodiment of the present invention, the sensor  260  may be attached to the fastening nut  235  or the cable ferrule  250 , and measures the tension of the parking cable  240 . In another exemplary embodiment of the present invention, the sensor  260  may be attached to a stationary member that may fasten the sensor  260  between the fastening nut  235  and the cable ferrule  250 . 
     In this manner, since the sensor  260  similar to the strain gauge is mounted on the cable ferrule  250  outside the case  230 , and measures the tension of the parking cable  240 . Thereby, a length of the case  230  can be reduced, which can be favorably applied to a layout of the vehicle. 
     In this state, when the EPB unit is operated, the parking cable  240  is pulled by the driving member  220 . Thereby, the tension is applied to the parking cable  240  in the direction of an arrow “a.” Due to this tension, the cable ferrule  250  attached to the parking cable  240  slightly moves in the direction of the arrow “a,” and thus the sensor  260  attached to the cable ferrule  250  is pressed and thus subjected to a change in resistance. This resistance change is allowed to measure the tension of the parking cable  240 . 
     Further, the measured value is sent to the EPB ECU  210  through a sensor ECU  270 . The EPB ECU  210  and the sensor ECU  210  are connected with an interface  280 . 
     Here, the sensor ECU  270  is fixed on one side of the interior of the case  230 . 
     In this manner, because the sensor ECU  270  is fixed in the case  230 , the interface  280  connected with the EPB ECU  210  does not move together with the sensor ECU  270  in the case  230 , so that the interface  280  can be prevented from being shorted out or cut off. 
     For convenience in explanation and accurate definition in the appended claims, the terms “rear”, “forward”, and “backward” are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures. 
     The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.