Abstract:
An hydraulic brake system that rapidly and precisely slows or reduces speed by constraining or stopping the movement of a link mechanism connected between a piston and a rotational driving shaft of a power system with physical force generated due to the incompressible fluid characteristic by constraining or stopping the flow of oil filled in an hydraulic oil chamber. The hydraulic brake system includes a lubricating section for supplying the oil reserved in a protective casing to friction sliding parts of respective components through pumping movement by utilizing the reciprocal movement of a piston rod, and an oil supplement section for supplementing the hydraulic oil chamber with the oil. The hydraulic brake system has improved durability and anti-abrasion, and provides emergency braking in the event of oil leakage.

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. Pat. application Ser. No. 09/553,688, filed on Apr. 21, 2000, now U.S. Pat. No. 6,360,854 claiming the international filing priority of an International Application No. PCT/KR00/00081, filed on Feb. 02, 2000. 
    
    
     BACKGROUND OF INVENTION 
     1. Field of the Invention 
     The present invention relates to a brake system for slowing or stopping a rotational driving shaft of a power system, and more particularly to a hydraulic brake system for accurately slowing or stopping a rotational driving shaft of a power system with a physical force which is produced due to an incompressible fluid characteristic. 
     2. Description of the Prior Art 
     The patent application for a hydraulic brake system which is capable of solving general problems of a conventional friction brake device has been filed by the same applicant with the Korean Industrial Property Office on Oct. 7, 1996 (Application No. 96-0444192), and granted a patent on Nov. 25, 1998 (Patent No.: 178774) which will be described briefly below. 
     According to the Korean Patent No. 178774, the hydraulic brake system includes a casing having a hydraulic oil inlet which is opened/closed by a bolt type cover, a piston section which is a sliding member disposed in the casing and has a piston shaft whose both ends protrude outward, a hydraulic pressure controlling ball valve disposed in a hydraulic oil passage in the casing for controlling the flow rate of hydraulic oil, a controlling lever which is a pivot member mounted on the outer surface of the casing for controlling the hydraulic pressure controlling ball valve, a movement section for driving the controlling lever, a brake section connected to the rear end of the piston shaft of the piston device for stopping the rotational driving shaft, and a protective box for surrounding the casing and brake device. 
     The hydraulic brake system constructed as above normally permits the hydraulic oil reserved in the hydraulic oil chamber to flow without any disturbance. Then when the brake is operated, by disturbing or stopping the hydraulic oil flow by operating the hydraulic pressure controlling ball valve, the hydraulic brake system slows or stops the rotational driving shaft of the power system through the brake section with a physical force which is produced due to the resistance or stoppage of the hydraulic oil flow, and thereby performs an efficient brake operation. Accordingly, even after a long period of continuous using time, the brake system has no problems such as breakage or non-operation. Further, in this brake system which is constructed by a new concept quite different from the conventional friction brake system, since there is no need to employ brake pads, there is no inconvenience of replacing the brake pads. Also, without having to employ a servo assisted brake, the hydraulic brake system can precisely perform the brake operation by only one process. 
     The above hydraulic brake system, however, has a shortcoming of having abrasions between friction sliding sections and accordingly a low persistence, since it has no lubricating structure for the friction sliding sections of the piston and brake sections. 
     Further, since the above hydraulic brake system has no safety device employed for any abnormal events such as hydraulic oil leakage, etc., the brake operation can not be performed when an abnormality occurs, accordingly having the high possibility of allowing an accident. 
     Further, since a link of the brake section and the piston shaft of the piston section are connected with each other by a guiding member which is generally in the shape of a shaft, unnecessary rolling occurs in addition to the reciprocal linear movement of the piston shaft. Accordingly, the piston shaft is curved by excessive force exerted thereto, and brake force is inaccurately controlled. 
     SUMMARY OF THE INVENTION 
     The present invention has been developed to overcome the above-mentioned problems of the prior art, and accordingly it is an object of the present invention to provide a hydraulic brake system capable of controlling abrasions between friction sliding sections by lubricating means for supplying oil for lubrication to the respective friction sliding members. 
     Another object of the present invention is to provide a hydraulic brake system capable of not only controlling the flow rate of hydraulic oil in the reservoir, but also supplementing hydraulic oil for an emergency brake operation in the event of a hydraulic oil leakage. 
     Still another object of the present invention is to provide a hydraulic brake system capable of controlling the brake force more accurately by transmitting link movement into the accurate reciprocal linear movement of the piston section. 
     The above object is accomplished by a hydraulic brake system according to the present invention, including: a hydraulic oil reservoir having a hydraulic oil chamber filled with hydraulic oil; a piston device disposed in the hydraulic oil reservoir for being reciprocally and linearly moved; a link device disposed between the piston device and an eccentric cam formed on the rotational driving shaft of the power system, the link device moving in accordance with the rotation of the rotational driving shaft in a manner of tracing a circular arc path upward and downward and forward and backward; a connecting device for connecting the link device and the piston device in a manner that link device and the piston device are moved in relation to each other; a flow rate controlling section disposed in the hydraulic oil passage of the hydraulic oil reservoir for selectively stopping the piston device by controlling the flow rate of hydraulic oil; a protective casing for holding , thus supporting the above-mentioned respective components, the protective casing filled with hydraulic oil; and a lubricating section for pumping hydraulic oil of the protective casing to the friction sliding sections of the rotational driving shaft, the link device, and the connecting device, respectively. 
     Such a hydraulic brake system according to the present invention slows or stops the rotational driving shaft by disturbing or stopping the flow of the hydraulic oil of the hydraulic chamber by using a flow rate controlling section, and accordingly stopping the piston device and thus restricting the link device which is moved in relation to the piston device. 
     According to a preferred embodiment of the present invention, the link device includes a large-diameter section connected with the eccentric cam of the rotational driving shaft and a small-diameter section which is tapered. Further, the link device is bisected by the centerline of the eccentric cam of the rotational driving shaft into first and second link members, which are fastened by a pair of screws. Accordingly, the link device can be assembled more easily. 
     The connecting device includes a connecting member having a connecting hole though which the piston rod is connected, and a tapered connecting section connected with the small-diameter section of the link device for transmitting the movement of the link device into the reciprocal linear movement of the piston rod; a first guiding member fastened to the inner wall of the protective casing, having a guiding section accommodated in a sliding hole formed on the upper portion of the connecting member, the first guiding member for guiding the sliding movement of the connecting member from both sides of the connecting member; and a second guiding member having first and second guiding holes to which first and second guiding protrusions, respectively, protruding from the lower side of the connecting hole of the connecting member and form the middle portion of the connecting portion are accommodated, the second guiding member being fastened to the first guiding member by a plurality of screws. Accordingly, undesired force to other directions different from the linear direction of the piston rod is not applied, and bending of the piston rod is prevented, and the brake force is controlled more accurately. 
     The lubricating section includes: a second cylinder having a hydraulic oil suction hole and a discharge hole formed thereon vertically opposite to each other, the second cylinder extending from a side of the cylinder; a second piston extending from the piston to be inserted into and withdrawn out of the second cylinder according to the reciprocal linear movement of the piston for forming suction and discharging pressure in the second cylinder; a hydraulic oil suction pipe connected to the hydraulic oil suction hole of the second cylinder for conveying hydraulic oil of the protective casing to the interior of the second cylinder by the suctioning pressure of the second cylinder; a hydraulic oil feeding pipe disposed between the hydraulic oil discharge hole of the second cylinder and friction sliding sections of the above-mentioned respective components; and back flow preventing check valves respectively disposed in the hydraulic oil suction hole and the discharge hole of the second cylinder. Since hydraulic oil is supplied to the respective friction sliding sections for lubrication, possible abrasions of the friction sliding sections are prevented, and inner persistence of the system is improved. 
     According to another preferred embodiment of the present invention, the hydraulic brake system further includes a hydraulic oil supplementing section for supplementing hydraulic oil of the hydraulic oil reservoir in the event of a hydraulic oil leakage. 
     The hydraulic oil supplementing section includes: a secondary hydraulic oil reservoir disposed on the inner upper side of the protective casing for sucking in the hydraulic oil of the protective casing, and for reserving the sucked hydraulic oil therein; a hydraulic oil feeding pipe for connecting the secondary hydraulic oil reservoir and the hydraulic oil chamber of the hydraulic oil reservoir; and a valve disposed around the hydraulic oil feeding pipe for selectively blocking the hydraulic oil supply. 
     The valve includes: a valve body having upper and lower valve holes which have a plurality of slits radially formed thereon; and a ball positioned in the lower valve hole of the valve body at a predetermined distance from the upper valve hole for closing the valve hole by being elevated when the pressure of the hydraulic oil reservoir increases. Accordingly, consistent amount of hydraulic oil is maintained in the hydraulic oil reservoir, and hydraulic oil is automatically supplemented in the event of a hydraulic oil leakage for an emergency brake operation. 
     According to another preferred embodiment, brake forces are exerted to two portions of the rotational driving shaft of the power system. Accordingly, greater brake force is obtained, and more accurate and balanced brake operation is guaranteed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above objects and advantages will be more apparent by describing the present invention with reference to the accompanying reference drawings, in which: 
     FIG. 1 is a perspective view for schematically showing a hydraulic brake system according to a preferred embodiment of the present invention. 
     FIG. 2 is a side sectional view for explaining the structure and operation of the hydraulic brake system according to the present invention; 
     FIG. 3 is a side sectional view of FIG. 2; 
     FIG. 4 is a plain sectional view of FIG. 2; 
     FIG. 5 is a sectional view for showing one example of the connection section for connection a link section and a piston section of the hydraulic brake system according to the preferred embodiment of the present invention; 
     FIG. 6 is a perspective view of a hydraulic brake system according to another preferred embodiment of the present invention; 
     FIG. 7 is a sectional view corresponding to FIG. 3, for explaining the structure and operation of the hydraulic brake system according to another preferred embodiment of the present invention; and 
     FIG. 8 is a sectional view corresponding to FIG. 4, for explaining the structure and operation of the hydraulic brake system according to another preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     FIGS. 1 to  5  show a hydraulic brake system according to a preferred embodiment of the present invention. 
     In the drawings, a reference numeral  1  refers to a rotational driving shaft of a power system,  10  is a protective casing,  20  is a hydraulic oil reservoir,  30  is a piston device,  40  is a link device,  50  is a connecting device,  60  is flow rate controlling means (or referred to as a flow rate control valve),  70  is a lubricator (or referred to as lubricating means), and  80  is hydraulic oil supplementing means. 
     As shown in FIGS. 1 and 2, a rotational driving shaft  1  of the power system is integrally formed with a circular eccentric cam  5 . 
     As shown in FIGS. 3 and 4, the protective casing  10  is in the shape of cylinder at a predetermined width having closed ends, and surrounds, thus protects various components such as the hydraulic oil reservoir  20 , piston device  30 , link device  40 , connecting device  50 , flow rate controlling means  60 , a lubricator or lubricating means  70 , and hydraulic oil supplementing means (or referred to as a hydraulic oil supplement device)  80 , etc. 
     The protective casing  10  includes a shaft hole  11  formed in the center portion thereof, through which the rotational driving shaft  1  is passed. Further, about half of the protective casing  10  is filled with hydraulic oil. A sealing member  11   a  is disposed around the shaft hole  11  for preventing hydraulic oil leakage. 
     The hydraulic oil reservoir  20  includes a hydraulic oil chamber  21  filled with hydraulic oil, and a semi-circular bracket  2  fixed by a plurality of bolts  3  above the hydraulic oil reservoir  20  for rotatably supporting the rotational driving shaft  1 . 
     The piston device  30  includes a cylinder  31  formed across the hydraulic oil chamber  21  of the hydraulic oil reservoir  20 , a piston  32  slidably disposed within the cylinder  31 , and a piston rod  33  protruding from the piston  32  outside the cylinder  31 . 
     There are sealing members disposed around the front and rear sides of the cylinder  31  for preventing hydraulic oil leakage, and a compressing ring  32   a  disposed around the outer circumference of the piston  32  for preventing hydraulic oil flow to another direction. 
     The link device  40  is disposed between the eccentric cam  5  of the rotational driving shaft  1  and the piston rod  33  of the piston device  30 . When the rotational driving shaft  1  is rotated, the link device  40  is moved by the eccentric cam  5  tracing a circular arc path upward and downward, and forward and backward, and accordingly, the piston device  30  connected with the link device  40  is reciprocally and linearly moved. When the piston device  30  is stopped, the link device  40  which is connected with the piston device  30  is also stopped, and the rotational driving shaft  1  is slowed down, or stopped. 
     The link device  40  includes a large-diameter section  40   a  connected with the eccentric cam  5  of the rotational driving shaft  1 , and a small-diameter section  40   b  connected with the connecting section of a connecting device  50 , both of which will be described later. The small-diameter section  40   b  is tapered for load dispersion. Further, there are journal bearing made of special purpose metal disposed around the respective inner circumferences of the large and small-diameter sections  40   a  and  40   b  for an efficient rotation with the respective corresponding parts thereof. The link device  40  is bisected by the centerline of the eccentric cam  5  into two separate link members  41  and  42 , respectively, for an easier assembling of the rotational driving shaft  1  with respect to the eccentric cam  5 . These two link members  41  and  42  are fastened by a pair of screws, respectively. 
     The connecting device  50  connects the link device  40  with the piston device  30 , for transmitting the movement of the link device  40  into the accurate reciprocal linear movement of the piston device  30 . As shown in FIG. 5, the connecting device  50  includes first and second guiding members  53  and  55 . The connecting member  51  includes a connecting hole  51   a  to which the piston rod  33  is connected, and a tapered connecting section  51   b  which is inserted into the small-diameter section  40   b  of the link device  40 . Further, a sliding hole  51   c  is formed in the upper portion of the connecting member  51 , and first and second guiding protrusions  51   d  and  51   e  protrude from the lower portion of the connection hole  51   a  and the middle portion of the connecting section  51   b , respectively. Meanwhile, the first and second guiding members  53  and  55  guide the sliding movement of the connecting member  51  from both sides of the connecting member  51 . Here, the first guiding member  53  is connected to the inner wall of the protective casing  10 , and the second guiding member  55  is fastened to the first guiding member  53  by a plurality of screw  57 . The first guiding member  53  includes a guiding section  53   c  accommodated in the sliding hole  51   c  of the connecting member  51 , and the second guiding member  55  includes first and second guiding hole  55   d  and  55   e  in which the first and second guiding protrusions  51   d  and  51   e  are slidably accommodated. 
     The flow rate controlling means  60  is disposed on the hydraulic oil passage formed in the hydraulic oil reservoir  20 , and selectively stops the piston rod  33  of the piston device  30  by disturbing or stopping the hydraulic oil flow. The flow rate controlling means  60  includes a valve  61  having a valve hole  61   a  which is aligned with the hydraulic oil passage of the hydraulic oil reservoir  20 , and a valve opening/closing means (or referred to hereafter as a valve open and close control)  62  for narrowing the opening degree of the valve hole  61   a  or blocking the valve hole  61   a  by rotating the valve  61 . 
     The lubricator (or lubricating means)  70  supplies hydraulic oil as a lubricating oil to the respective friction sliding sections of the respective components, such as to the contact areas between the rotational driving shaft  1  and the bracket  2 , large-diameter section  40   a  of the link device  40  and the eccentric cam  5 , small-diameter section  40   b  of the link device  40  and the connecting device  50 , and connecting device  50 , etc., by pumping the hydraulic oil of the protective casing  10  using reciprocal linear movement of the piston device  30 . by the lubricating means  70 , abrasions between the respective friction sliding sections are minimized, and accordingly, the persistence of the device is improved. 
     The lubricating means  70  includes a second cylinder  71 , a second piston  72 , a hydraulic oil suction pipe  73 , a hydraulic oil feeding pipe  74 , and two back flow preventing check valves  75  and  76 . The second cylinder  71  extends from the cylinder  31  of the piston device  30 , and has a hydraulic oil suction hole and a discharge hole formed therein vertically opposite to each other. The second piston  72  extends from the piston  32  of the piston device  30 . by the reciprocal linear movement of the piston  32 , the second piston  72  is inserted into and withdrawn out of the second cylinder  71 , forming suction and discharge pressure within the second cylinder  71 . Further, the hydraulic oil suction pipe  73  is connected with the hydraulic oil suction hole of the second cylinder  71  to permit hydraulic oil of the protective casing  10  to flow into the second cylinder  71  by the suction pressure of the second cylinder  71 . Further, the hydraulic oil feeding pipe  74  connects the discharge hole the second cylinder  71  with the respective friction sliding sections of the above-mentioned components, respectively. The two back flow preventing check valves  75  and  76  are disposed in the hydraulic oil suction hole and discharge hole of the second cylinder  71  for preventing both hydraulic oil discharge through the hydraulic oil suction hole, and hydraulic oil suction through the hydraulic oil discharge hole. 
     The hydraulic oil supplementing means  80  is a safety device which supplements hydraulic oil of the hydraulic oil reservoir  20  to the hydraulic oil chamber  21 , thereby enabling emergency brake operation in the event of a leakage of hydraulic oil of the hydraulic oil reservoir  20 . 
     The hydraulic oil supplementing means  80  includes a secondary hydraulic oil reservoir  81  formed at the upper inner portion of the protective casing  10  which is connected to the hydraulic oil chamber  21  of the hydraulic oil reservoir  20  through the hydraulic feeding pipe  82  to supplement hydraulic oil to the hydraulic chamber  21 . The secondary hydraulic oil reservoir  81  is connected with a hydraulic oil suction pipe  83  which extends toward the lower portion of the protective casing  10 . The hydraulic oil of the protective casing  10  is sucked through the hydraulic oil suction pipe  83  by the pressure difference of the secondary hydraulic oil reservoir  81 , and is reserved in the second hydraulic oil reservoir  81  at a consistent amount. There is a valve  90  disposed around the hydraulic oil feeding pipe  82  for selectively blocking hydraulic oil fed into the hydraulic oil chamber  21  of the hydraulic oil reservoir  20  through the hydraulic oil feeding pipe  82 . The valve  90  includes a valve body  91  in the shape of hollow sphere  91 , and a ball  92 . Valve holes  91   a  and  91   b  are formed above and below the valve body  91 , respectively, and a plurality of slits are radially formed on the lower valve hole  91   b . Further, the ball  92  is positioned in the lower valve hole  91   b  having a predetermined gap fro the upper valve hole  91   a . In such a situation, the hydraulic oil is fed into the hydraulic oil chamber  21  through a plurality of open slits, and the amount of hydraulic oil can be maintained consistently in the hydraulic oil chamber  21 . When the brake pressure is applied to the hydraulic oil chamber  21 , the ball  92  is elevated by the pressure to close the upper valve hole  91   a . Accordingly, normal brake pressure is applied to the hydraulic oil chamber  21 , and the brake operation is performed. 
     Hereinafter, the operation of the hydraulic brake system constructed as above according to the present invention will be described. 
     During the normal operation of a power system, as the rotational driving shaft  1  is rotated, the link device  40  connected to the eccentric cam  5  of the rotational driving shaft  1  is moved, tracing a circular arc path upward and downward, and forward and backward. Such a movement of the link device  40  is transmitted to the piston device  30  through the connecting device  50 , and accordingly, the piston device  30  reciprocally and linearly moved. Here, since the hydraulic oil passage of the hydraulic oil chamber  21  is open, the reciprocal linear movement of the piston device  30  is smoothly performed with a smooth flow of hydraulic oil. 
     Then in order to slow or stop the rotational driving shaft  1 , by operation the valve  61  disposed on the hydraulic oil passage, the flow rate of hydraulic oil is reduced, and flow resistance occurs due to the incompressible fluid characteristic. Accordingly, the piston rod  33  is slowed down, and the movement of the link device  40  connected to the piston rod  33  is also restricted, and rotational speed of the rotational speed of the rotational driving shaft  1  is reduced. 
     Meanwhile, by operating the valve  61  to maximum extent, the hydraulic oil passage is closed, and hydraulic oil flow is stopped. Accordingly, the piston rod  33  is stopped, and the movement of the link device  40  is completely restricted, and the rotational driving shaft  1  is stopped. 
     During the above brake operation, there can be abrasions at the respective friction sliding sections of the respective components, such as at the friction sliding sections of the rotational driving shaft  1  and bracket  2 , link device  40  and eccentric cam  5 , and the connecting device, etc., since excessive weight is applied thereto. According to the present invention, however, since the hydraulic oil of the protective casing  10  is pumped to the respective friction sliding sections by the lubrication means  70 , such abrasions are minimized. 
     Further, in the event of hydraulic oil shortage, since hydraulic oil is supplemented from the hydraulic oil reservoir  20  to the secondary hydraulic oil reservoir  81 , a consistent amount of hydraulic oil can be maintained. Such an oil supplementation is also performed in the event of oil leakage for the emergency brake operation. 
     Meanwhile, as shown in FIGS. 6 to  8 , the hydraulic brake system according to the present invention has greater brake force by its structure for exerting brake force two portions of the rotational driving shaft  100 . Such will be described in greater detail with reference to the hydraulic brake system according to another preferred embodiment of the present invention. 
     As shown in FIGS. 6 to  8 , the rotational driving shaft  100  of the power system includes a pair of circular plate eccentric cams  105  and  105 ′ formed thereon at a predetermined distance from each other. The pair of eccentric cams  105  and  105 ′ are eccentrically formed around the rotational driving shaft  100  horizontally opposite to each other with respect to the rotational driving shaft  100 . 
     The protective casing  110  includes a shaft hole  111  through which the rotational driving shaft  100  is passed. Further, half of the protective casing  110  is filled with hydraulic oil, and a sealing member  111   a  is disposed around the shaft hole  111  for preventing hydraulic oil leakage. 
     The hydraulic oil reservoir  120  includes two hydraulic oil chambers  121  and  121 ′ filled with hydraulic oil. Above the hydraulic reservoir  120 , there is a bracket  200  fixed by a plurality of bolts  300  for rotatably supporting the rotational driving shaft  100 . 
     Further, the hydraulic oil reservoir  120  includes two piston devices  130  and  130 ′ corresponding to the hydraulic oil chambers  121  and  121 ′, to be reciprocally and linearly moved from opposite directions of the hydraulic oil reservoir  120 , respectively. 
     Further, between the eccentric cams  105  and  105 ′ of the rotational driving shaft  100  and the two piston devices  130  and  130 &#39;s, link devices  140  and  140  are disposed, respectively. The link devices  140  and  140  and the piston devices  130  and  130 &#39;s are connected with each other by connecting devices  150  and  150 ′ to be moved in relation to each other. Accordingly, when the rotational driving shaft  100  is rotated, the link devices  140  and  140 ′ whose one ends are connected to the eccentric cams  105  and  105 ′ are moved by tracing the circular arc path upward and downward, and forward and backward, and accordingly, the piston devices  130  and  130 , which are connected with the other ends of the link devices  140  and  140 ′ through the connecting devices  150  and  150 ′, are reciprocally and linearly moved. 
     The flow rate controlling means  160  is disposed on the hydraulic oil passage formed in the hydraulic oil reservoir  110 , for selectively stopping the piston devices  130  and  130 ′ by disturbing of stopping the flow of hydraulic oil. Accordingly, the movement of the link devices  140  and  140 ′ connected with the piston devices  130  and  130 , which are moved in relation to the link devices  140  and  140 ′, is restricted, and the rotational driving shaft  100  is slowed, or stopped. Here, the flow rate controlling means  160  simultaneously opens/closes the two hydraulic oil passages of the hydraulic oil chambers  121  and  121  in the hydraulic oil reservoir  110 . 
     Further, the hydraulic brake system according to another preferred embodiment of the present invention includes two lubricating means  170  and  170 ′ for pumping hydraulic oil of the protective casing  110  to the friction sliding sections of the respective components by using reciprocal linear movement of the piston devices  130  and  130 ′, and hydraulic oil supplementing means  180  for supplementing hydraulic oil from the hydraulic oil reservoir  120  in the event of a hydraulic oil leakage. Here the hydraulic oil supplementing means  180  supplies hydraulic oil to the two hydraulic oil chambers  121  and  121 ′ of the hydraulic oil reservoir  120 . 
     Description of other structures and components will be omitted since the same have been described above in the description of the preferred embodiment of the present invention. By the same reason, their respective brake operations will be also omitted. 
     The unique feature of another preferred embodiment of the present invention lies in the structure for exerting brake force to the two portions of the rotational driving shaft  100 , which has the effects of greater brake force, accuracy, and balance. 
     Although another preferred embodiment describes a structure for exerting brake force to two portions of the rotational driving shaft, it is not strictly limited thereto, but can have variations, such as exerting brake forces to three, four, or more portions of the rotational driving shaft. 
     As described above, according to the present invention, during the operation of the hydraulic brake system, since hydraulic oil of the protective casing is pumped by reciprocal linear movement of the piston device to the friction sliding sections of the respective components for lubrication thereof, abrasions of the respective components in contact with the friction sliding sections are controlled, and persistence of the brake system is improved. 
     Further, according to the present invention, since the link device and the piston device are connected with each other in a manner that the movement of the link device is transmitted to the piston device exclusive of other unnecessary forces to another direction, undesired results such as bending of piston rod of the piston device, etc., cam be prevented, and more accurate brake operation can be performed. 
     Further, according to the present invention, due to the means for supplementing the hydraulic oil of the hydraulic oil reservoir to the hydraulic oil chamber, a consistent amount of hydraulic oil can be maintained in the hydraulic oil chamber. Also, in the event of a hydraulic oil leakage, hydraulic oil can supplemented for emergency brake operation, so that risk of accident is prevented. 
     Meanwhile, in the hydraulic brake system according to another preferred embodiment of the present invention, since brake force is applied to two portions of the rotational driving shaft, greater brake force can be obtained, and more accurate and balanced brake operation is also guaranteed. 
     While the present invention has been particularly shown and described with reference to the preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be effected therein without departing from the spirit and scope of the invention as defined by the appended claims.