Patent Publication Number: US-2011072812-A1

Title: Brake for vehicle

Description:
This application claims the benefit of Korean Patent Application No. 10-2009-0091178 filed on Sep. 25, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the invention 
     The present invention relates to a brake for a vehicle. More particularly, the present invention relates to a brake for a vehicle, capable of preventing a vacuum connection pipe connected to a brake booster from being rotated. 
     2. Description of the Related Art 
     In general, a brake for a vehicle includes a brake booster generating boosting force and a master cylinder generating liquid pressure. 
     The brake booster generates great braking force based on small force by using pressure difference between vacuum pressure and atmospheric pressure and transfers the braking force to the master cylinder to generate braking hydraulic pressure. 
     The brake booster having the above function includes a casing having a front shell and a rear shell, an input shaft interworking with a brake pedal, and an output shaft receiving power that may vary depending on the operation of the input shaft. 
     The casing is divided into a static pressure chamber and a variable pressure chamber by a diaphragm and a power piston. A vacuum connection pipe is coupled to one side of an outer wall of the static pressure chamber to allow the static pressure chamber to communicate with an engine suction part. 
     In addition, a valve body is coupled to the casing to control the amount of air introduced into the brake booster. One end of the valve body is fixed to the diaphragm and the power piston and the other end of the valve body is formed with an air suction hole and protrudes outward from a rear end of the casing to communicate with the outside while interworking with the reciprocating movement of the input shaft. 
     In the initial state of the brake booster for the vehicle having the above structure, the static pressure chamber and the variable pressure chamber are maintained in the vacuum state by the engine suction part. When a driver steps on a brake pedal, the input shaft moves forward so that external air is introduced into the variable pressure chamber through the valve body. At this time, the external air is instantly introduced into the variable pressure chamber due to differential pressure, so the diaphragm and the power piston are pushed toward the static pressure chamber. Thus, amplified output force is transferred to the master cylinder assembly through the output shaft, thereby generating the braking hydraulic force. 
     If the driver puts the foot off the brake pedal, the input shaft returns to its initial position by a return spring and elastic restoring force of the power piston. In addition, air in the variable pressure chamber is introduced into the static pressure chamber under the vacuum state through a static pressure path, and air in the static pressure chamber is discharged through the vacuum connection pipe and a vacuum hose, so that the static pressure chamber is maintained in the vacuum state. Thus, the brake booster returns to the initial state. 
     The static pressure chamber must be constantly maintained under the vacuum state to allow the brake booster to perform its function. In this regard, the vacuum connection pipe connected to the vacuum hose is provide in the casing in such a manner that air contained in the static pressure chamber can be discharged by suction force of an engine. 
     In detail, one end of the vacuum connection pipe is connected to the casing of the brake booster and the other end of the vacuum connection pipe is connected to an end of the vacuum hose so that the static pressure chamber is communicated with the vacuum hose. 
     The vacuum connection pipe connected to the casing of the brake booster is made from metallic material or plastic material. If the vacuum connection pipe is made from the metallic material, the vacuum connection pipe is coupled to the casing through welding. In addition, if the vacuum connection pipe is made from the plastic material, the vacuum connection pipe is assembled with the casing. 
     However, in the case that the vacuum connection pipe made from the plastic material is assembled with the casing, the vacuum connection pipe may be tilted from the precise position due to the weight of the vacuum hose and vibration of the vehicle, so that the vacuum connection pipe may interfere with other components. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, there is provided a brake for a vehicle, capable of improving reliability by preventing a vacuum connection pipe connected to a brake booster from being rotated. 
     Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the invention. 
     The foregoing and/or other aspects of the present invention are achieved by providing a brake for a vehicle, the brake comprising: a brake booster generating boosting force and including a casing; a vacuum connection pipe coupled with the casing; a master cylinder body connected to the brake booster; and an oil tank communicated with the master cylinder body, wherein the oil tank includes an anti-rotation member extending from one side of the oil tank toward the vacuum connection pipe to prevent the vacuum connection pipe from being rotated. 
     The anti-rotation member is integrally formed with the oil tank. 
     The anti-rotation member is provided at an end thereof with a ring member surrounding an outer peripheral surface of the vacuum connection pipe. 
     The ring member is fitted around the outer peripheral surface of the vacuum connection pipe. 
     As described above, according to the brake for the vehicle of the present invention, an anti-rotation member is installed to the oil tank, so that the vacuum pipe can is be fixedly maintained in the precise position even if external force or vibration derived from the operation of the engine is applied to the vacuum connection pipe after the vacuum connection pipe has been assembled, thereby preventing the vacuum connection pipe from interfering with other components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a perspective view showing the schematic structure of a brake for a vehicle according to one embodiment of the present invention; and 
         FIG. 2  is a side sectional view of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements. The embodiments are described below to explain the present invention by referring to the figures. 
       FIG. 1  is a perspective view showing the schematic structure of a brake for a vehicle according to one embodiment of the present invention, and  FIG. 2  is a side sectional view of  FIG. 1 . 
     As shown in  FIGS. 1 and 2 , the brake for the vehicle according to one embodiment of the present invention includes a brake booster  5  generating boosting force and a master cylinder  600  generating liquid pressure. 
     The brake booster  5  includes a casing  10  having a front shell  11  and a rear shell  12  closely coupled with each other, a diaphragm  20  dividing the interior of the casing  10  into a static pressure chamber  15  and a variable pressure chamber  16 , a power piston  21  adjacent to the diaphragm  20  to receive power generated due to pressure difference between the static pressure chamber  15  and the variable pressure chamber  16 , a valve body  30  having one end slidably passing through the center of the diaphragm  20  and the other end protruding to the outside through the center opening of the rear shell  12  to control air introduced into the brake booster  5 , an input shaft  40  interworking with a brake pedal (not shown), and an output shaft  50  receiving power that may vary depending on the operation of the input shaft  40 . 
     The valve body  30  has a cylindrical shape with multi-step configuration. The diaphragm  20  and the power piston  21  are coupled to an outer peripheral portion of one end of the valve body  30 , and the outer end of the valve body  30  is formed with an air suction part  31  and extends to the outside through the center of the rear shell to communicate with the atmosphere. 
     The valve body  30  is formed therein with a static pressure path  32  extending through the static pressure chamber  15  and the variable pressure chamber  16 , and a variable pressure path  33  through which the variable pressure chamber  16  is communicated with the atmosphere. In addition, a plunger  60  is provided in the valve body  30 . The plunger  60  is coupled with the end of the input shaft  40  to slidably move in the axial direction. A reaction disc  70  is provided between the output shaft  50  and the front end of the plunger  60  in order to transfer force to the output shaft  50  by boosting the force based on the difference in sectional area. In addition, a poppet valve  80  made from elastic material is provided in the valve body  30 . The poppet valve  80  selectively open/close the static pressure path  32  and the variable pressure path  33  in order to control air introduced into the valve body  30  according to the operation of the input shaft  40 . 
     A vacuum connection pipe  100  is coupled to an outer wall of the front shell  11  to allow the static pressure chamber  15  to communicate with an engine suction part (not shown), and a return spring  80  is installed in the static pressure chamber  15  to return the diaphragm  20 , the power piston  21  and the valve body  30  to their initial positions. 
     The vacuum connection pipe  100  is made from plastic material and has the right-angled elbow structure. One end  101  of the vacuum connection pipe  100  is communicated with the static pressure chamber  15  and the other end  102  of the vacuum connection pipe  100  is coupled with an end of the vacuum hose  120  connected to the engine suction part. 
     A coupling hole  14  is formed in the front shell  11  of the casing  10  that constitutes the static pressure chamber  15 , and a sealing member  110  made from elastic material is coupled into the coupling hole  14 . 
     One end  101  of the vacuum connection pipe  100  is press-fitted into a hollow part of the sealing member  110  and communicated with the static pressure chamber  15 , and the vacuum hose  120  is connected to the other end  102  of the vacuum connection pipe  100 . Anti-separation protrusions  103  are formed at both ends  101  and  102  the vacuum connection pipe  100 , so the vacuum connection pipe  100  is not separated from the sealing member  110  and the vacuum hose  120 . 
     A master cylinder  600 , which is connected to the output shaft  50 , is coupled with the front shell  11 . The master cylinder  600  includes a body  610  coupled with the front shell  11 , a first piston  620  accommodated in the body  610  and connected to the output shaft  50 , and a second piston  630  interworking with the first piston  620 . In detail, as the output shaft  50  moves forward, the first and second pistons  620  and  630  move forward so that oil supplied from an oil tank  700  communicated with the body  610  is transferred to front and rear wheels. A first spring  640  is elastically installed between the first and second pistons  620  and  630 , and a second spring  650  is elastically installed between the body  610  and the second piston  630 . The first and second springs  640  and  650  return the first and second pistons  620  and  630  to their initial positions when external force applied to the brake pedal has been removed. 
     The oil tank  700  is provided at one side thereof with an anti-rotation member  300  for preventing the vacuum connection pipe  100  from being rotated. 
     The anti-rotation member  300  extends to the vacuum connection pipe  100  from one side of the oil tank  700  and is integrally formed with the oil tank  700  when the oil tank  700  is manufactured. 
     The anti-rotation member  300  is provided at an end thereof with a ring member  350  made from elastic material such that the vacuum connection pipe  100  can be inserted into the ring member  350 . In addition, when the brake for the vehicle is assembled, the vacuum connection pipe  100  is inserted into the ring member  350  of the anti-rotation member  300 , so that the vacuum connection pipe  100  can be precisely fixed. 
     Hereinafter, the operation and effect of the brake for the vehicle according to the present invention will be described. 
     If the driver steps on the brake pedal while driving the vehicle, the input shaft  40  moves forward so that external air is introduced into the variable pressure chamber  16  under the vacuum state through the variable pressure path  33 . At this time, the diaphragm  20  and the power piston  21  are pushed toward the static pressure chamber  15  due to the differential pressure and the output shaft  50  moves the first and second pistons  620  and  630  of the master cylinder  600  in the forward direction by applying amplified force to the first and second pistons  620  and  630  of the master cylinder  600 , thereby generating the braking hydraulic pressure. 
     In addition, if the driver puts the foot off the brake pedal, air in the variable pressure chamber  16  is discharged to the static pressure chamber  15  under the vacuum state through the static pressure path  32 . Since the engine suction part is always driven, the air in the static pressure chamber  15  is discharged through the vacuum connection pipe  100  and the vacuum hose  120  so that the static pressure chamber  15  is maintained in the vacuum state. Thus, the brake booster  5  returns to the initial state. 
     In this case, the vacuum connection pipe  100  is subject to the rotation due to the weight of the vacuum hose  120  and vibration generated during the operation of the engine. However, since the vacuum connection pipe  100  is fitted into the ring member  350  of the anti-rotation member  300 , the vacuum connection pipe  100  can be fixedly secured without rotating. 
     Therefore, the vacuum connection pipe  100  can be prevented from interfering with other components. 
     Although few embodiments of the present invention have been shown and described, it would 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 claims and their equivalents.