Abstract:
A brake booster includes an atmosphere chamber, a working chamber, a valve assembly, and an air passageway. The atmosphere chamber includes an air inlet, and the working chamber is in fluid communication with the atmosphere chamber. The valve assembly is positioned between the atmosphere chamber and the working chamber, and the valve assembly includes a plunger configured to cooperate with a valve seat to selectively enable or prevent fluid flow from the atmosphere chamber to the working chamber. The air passageway is defined within the atmosphere chamber between the air inlet and the valve assembly. The air passageway is void of any springs.

Description:
FIELD OF THE INVENTION 
       [0001]    The present disclosure generally relates to braking systems, and in particular to a pneumatic brake booster for a braking system. 
       BACKGROUND OF RELATED ART 
       [0002]    Vehicles often include a hydraulic braking system for reducing the speed of the vehicle and/or maintaining the vehicle in a stopped position. Hydraulic braking systems include a master cylinder fluidly coupled to one or more hydraulic cylinders. The master cylinder includes an input shaft, which activates the hydraulic cylinders in response to the input shaft moving in a braking direction. Typically, a user moves the input shaft in the braking direction by depressing a foot pedal. Each activated hydraulic cylinder moves one or more brake pads against a drum, rotor, or other rotating element to brake the vehicle. Releasing pressure upon the foot pedal, such that the foot pedal moves in a release direction to a deactivated position, causes the input shaft to move in the release direction, which deactivates the hydraulic cylinders and permits the drum, rotor, and/or other rotating elements to rotate freely. 
         [0003]    To reduce the force applied to the foot pedal when braking the vehicle, most hydraulic braking systems include a pneumatic brake booster. Some users find that moving a master cylinder input shaft that is coupled directly to a foot pedal requires the user to impart a force upon the foot pedal in excess of that which may be comfortably and repetitively applied. To this end, the pneumatic brake booster amplifies the force exerted on the foot pedal such that the user may move the input shaft of the master cylinder with correspondingly less force being exerted on the foot pedal. 
         [0004]    In general, the pneumatic brake booster includes a housing, a valve shaft, a shell, a diaphragm, and a valve. The diaphragm is coupled to the input shaft of the master cylinder, the housing, and the shell. The diaphragm divides an internal cavity of the shell into a booster chamber and a vacuum chamber. The valve separates the booster chamber into an atmosphere chamber and a working chamber. Vacuum generated by a gasoline engine or a vacuum pump is coupled to the vacuum chamber, such that the vacuum chamber is maintained at a pressure less than the atmospheric pressure. The valve shaft, which is coupled to the valve and the brake pedal, is configured to open the valve in response to the brake pedal moving in the braking direction. Biasing members close the valve in response to the brake pedal moving in the release direction. 
         [0005]    When the valve is closed, vacuum is supplied to the working chamber, such that the working chamber and the vacuum chamber are maintained at the same pressure level. The approximately equal pressure on each side of the diaphragm causes the diaphragm to remain stationary. 
         [0006]    When a user exerts a force upon the brake pedal, the booster amplifies the force, such that the user may move the input shaft of the master cylinder more easily. As described above, exerting a force on the brake pedal causes the valve to open. As a result, air from the atmosphere is drawn through the atmosphere chamber and the valve, and then into the working chamber. The imbalance of pressure between the vacuum chamber and the working chamber tends to move the diaphragm, the valve shaft, the valve, and the input shaft of the master cylinder in the braking direction. Accordingly, the imbalance of pressure amplifies the force exerted on the brake pedal, thereby making the braking system easier to operate. 
         [0007]    As explained above, opening the valve results in airflow between the atmosphere chamber and the working chamber. However, the construction of typical brake boosters includes elements positioned within the atmosphere chamber that may impede the airflow. While such elements are often needed for proper operation of the brake booster, it would be advantageous to provide a brake booster that increases the airflow through the atmosphere chamber, thereby increasing the efficiency of the brake booster. 
       SUMMARY 
       [0008]    In accordance with one embodiment of the present disclosure, there is provided a brake booster comprising an atmosphere chamber, a working chamber, a valve assembly, and an air passageway. The atmosphere chamber includes an air inlet. The working chamber is in fluid communication with the atmosphere chamber. The valve assembly is positioned between the atmosphere chamber and the working chamber. The valve assembly includes a plunger configured to cooperate with a valve seat to selectively enable or prevent fluid flow from the atmosphere chamber to the working chamber. The air passageway is defined within the atmosphere chamber between the air inlet and the valve assembly, and the air passageway is void of any springs. 
         [0009]    In accordance with another embodiment of the present disclosure, there is provided a pneumatic brake booster for a brake system including a housing, a sleeve, a valve body, a valve plunger, a valve seat, a valve spring, and an atmosphere chamber. The sleeve is positioned within the housing. The valve body is at least partially positioned within the housing and configured to move in a linear direction. The valve plunger is positioned within the housing and configured to move in the linear direction. The valve seat is associated with the sleeve. The valve spring extends between the valve body and the valve plunger and is configured to bias the valve plunger toward the valve seat. The atmosphere chamber is within the housing, is void of springs, and is defined at least in part by the sleeve. 
         [0010]    In accordance with yet another embodiment of the present disclosure, there is provided a vacuum brake booster comprising a housing, a valve plunger, a valve rod, a valve body, a sleeve, and an air passage. The housing defines a housing end opening, and the valve plunger is movably located within the housing. The valve rod is coupled to the valve plunger and extends through the housing end opening. The valve body is located within the housing. The sleeve structure is interposed between the housing and the valve rod. The sleeve structure includes a valve seat, which defines a valve opening. The plunger is configured to cooperate with the valve seat to selectively enable or prevent fluid flow through the valve opening. The air passage is free of springs and is defined between the housing end opening and the valve opening. The air passage extends along an inner surface of the sleeve structure. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0011]    Features of the present disclosure will become apparent to those of ordinary skill in the art to which this device pertains from the following description with reference to the figures, in which: 
           [0012]      FIG. 1  depicts a cross sectional view of a portion of a brake booster having an atmosphere chamber void of any springs; and 
           [0013]      FIG. 2  depicts an end view of the brake booster of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    For the purpose of promoting an understanding of the principles of the device described herein, reference will now be made to the embodiment(s) illustrated in the figures and described in the following written specification. It is understood that no limitation to the scope of the device is thereby intended. It is further understood that the device includes any alterations and modifications to the illustrated embodiment(s) and includes further applications of the principles of the device as would normally occur to one of ordinary skill in the art to which this device pertains. 
         [0015]    As shown in  FIG. 1 , a pneumatic/vacuum brake booster assembly  100  includes an atmosphere chamber  104 , a working chamber  108 , a valve assembly  112 , and a control rod  136 , each of which are at least partially positioned with a housing  120 . The valve assembly  112  controls airflow from the atmosphere chamber  104  to the working chamber  108 .  FIG. 1  depicts the valve assembly  112  in a closed position in which the valve assembly  112  prevents airflow from the atmosphere chamber  104  to the working chamber  108 . Leftward movement of the rod  136  opens the valve assembly  112  and enables airflow from the atmosphere chamber  104  to the working chamber  108 . The atmosphere chamber  104  is void of springs and other obstructions that may impede the airflow. 
         [0016]    The atmosphere chamber  104  is a chamber exposed to the atmosphere surrounding the booster  100 . In the embodiment of  FIG. 1 , the atmosphere chamber  104  is defined at least in part by the housing  120 , a sleeve assembly  168 , a housing boot  126 , and the valve assembly  112 . The atmosphere chamber  104  extends from an input side of the housing  120  (opposite the valve assembly  112 ), through the sleeve  168 , and to the valve assembly  112 . The atmosphere chamber  104  fluidly communicates with the working chamber  108  in response to the valve assembly  112  being in the open position. While the atmosphere chamber  104  has been described in the embodiment of  FIG. 1  as being defined by the housing  120 , the sleeve assembly  168 , the housing boot  126 , and the valve assembly  112 , it should be recognized that in other embodiments the atmosphere chamber  104  may be defined by fewer or more components than those described above and those illustrated in  FIG. 1 . 
         [0017]    With reference still to  FIG. 1 , the housing  120  defines an internal cavity, which is divided into the working chamber  108  and the atmosphere chamber  104  by the valve assembly  112 . In some embodiments, the housing  120  moves in a linear direction  144  in response to movement of a diaphragm (not shown) of the booster  100 , as is known to those of ordinary skill in the art. The input side of the housing  120  defines a housing end opening  140  through which the negative pressure of the working chamber  108  draws air from the atmosphere surrounding the booster  100  in response to opening the valve assembly  112 . 
         [0018]    The housing boot  126  surrounds at least a portion of the housing  120 . As shown in  FIG. 2 , inlets  124  formed in the boot  126  couple the atmosphere chamber  104  to the atmosphere surrounding the booster  100 . With reference again to  FIG. 1 , the housing boot  126  includes a grommet  130  through which the rod  136  extends. The housing boot  126  may be formed from a flexible material, which enables the boot  126  to conform to the position of the housing  120  and the rod  136 . 
         [0019]    The sleeve assembly  168 , which surrounds a portion of the rod  136 , includes a tapered section  172 , a valve seat  132 , and a seat spring  176 . The tapered section  172  engages an inner wall of the housing  120  and remains stationary relative to the housing  120 . The valve seat  132  moves in the linear direction  144  relative to the housing  120  for the distance  180 . The seat spring  176 , which is a compression spring, biases the valve seat  132  toward a plunger  128  of the valve assembly  112 , as described below. 
         [0020]    The atmosphere chamber  104  defines an air passageway  116 , which extends between the housing end opening  140  and the valve assembly  112 . As shown in  FIG. 1 , the air passageway  116  may extend along an inner surface of the sleeve  168 . In particular, the tapered section  172  tapers the air passageway  116  from a wide region nearest the inlets  124  to a narrow region nearest the valve assembly  112 . Similar to the atmosphere chamber  104 , the air passageway  116  is void of any springs that impede the airflow through the air passageway  116 . 
         [0021]    With continued reference to  FIG. 1 , the working chamber  108  is a chamber separated from the atmosphere chamber  104  by the valve assembly  112 . In the embodiment of  FIG. 1 , the working chamber  108  is defined at least in part by the valve assembly  112 , the housing  120 , and the sleeve assembly  168 . The working chamber  108  extends leftward from the valve assembly  112 . When valve assembly  112  is closed, the working chamber  108  may be coupled to a vacuum source (not shown). When the valve assembly  112  is open, air from the atmosphere enters the working chamber  108  and acts upon the diaphragm (not shown) of the booster  100  in order to reduce a force required to activate a hydraulic braking system (not shown). While the working chamber  108  has been described in the embodiment of  FIG. 1  as being defined by the valve assembly  112 , the housing  120 , and the sleeve assembly  168  it should be recognized that in other embodiments the working chamber  108  may be defined by fewer or more components than those described above and those illustrated in  FIG. 1 . 
         [0022]    The valve assembly  112  is positioned between the atmosphere chamber  104  and the working chamber  108 , and controls airflow from the atmosphere chamber  104  to the working chamber  108 . The valve assembly  112  includes a valve body  152 , a plunger  128 , a valve seat  132 , and a return spring  156 . The valve body  152  is at least partially positioned in the working chamber  108  of the housing  120 . The valve body  152  moves in the linear direction  144  in response, to among other factors, movement of the rod  136  and the plunger  128 . The return spring  156  biases the plunger  128  toward the sleeve assembly  168 . The valve body  152  may contact the valve seat  132  in response to the valve assembly  112  being in the closed position. 
         [0023]    As shown in the embodiment of  FIG. 1 , the valve body  152  includes a spring channel  188 , a plunger slot  192 , and a plunger opening  164 . The spring channel  188  communicates fluidly with the plunger slot  192  and receives the return spring  156 . A width  196  of the spring channel  188  enables the return spring  156  to move in the linear direction  144 . The spring channel  188  surrounds the plunger opening  164 , which extends through the valve body  152 . The plunger slot  192  receives the plunger  128  and enables the plunger  128  to move in linear direction  144 . 
         [0024]    The plunger  128  cooperates with the valve seat  132  to enable or prevent airflow from the atmosphere chamber  104  to the working chamber  108 . In response to the valve assembly  112  being in the closed position, the plunger  128  contacts the valve seat  132  to prevent airflow into the working chamber  108  from the atmosphere chamber  104 . As shown in  FIG. 1 , the plunger  128  includes a protuberance  160 , a flange  200 , a cavity  204 , and a head  208 . The protuberance  160  extends through the plunger opening  164  in the valve body  152 . The protuberance  160  aligns the plunger  128  with the valve seat  132 , among other functions. The flange  200  is positioned between the protuberance  160  and the head  208  as measured in the linear direction  144 . The flange  200  may contact the plunger slot  192  as the plunger  128  slides within the valve body  152 . The head  208  contacts the valve seat  132  to decouple the working chamber  108  from the atmosphere chamber  104 . A width of the flange  200  and a width of the head  208  as measured in a direction  212  is approximately the same as a width of the plunger slot  192  as measured in the direction  212 . The head  208  includes a domed surface, which extends toward the sleeve assembly  168 . The domed surface may be received by a corresponding shaped depression in the valve seat  132 . The cavity  204  is formed in the center of the plunger  128  and extends from the head  208  to the protuberance  160  in the linear direction  144 . A width of the cavity  204  in the direction  212  exceeds a width of the rod in the direction  212 . Furthermore, it is noted that the plunger  128  defines a ring shaped void  220  between the flange  200  and the head  208 . 
         [0025]    The return spring  156  biases the plunger  128  in a direction that closes the valve assembly  112 , e.g. rightward as shown in  FIG. 1 . The return spring  156  extends between the valve body  152  and the plunger  128  and is positioned within the working chamber  108 . In particular, the return spring  156  is positioned in the spring channel  188  of the valve body  152 . Depending on the position of the plunger  128 , the return spring  156  may be located entirely within the spring channel  188 ; alternatively, a portion of the return spring  156  may be located within the plunger slot  192 . The return spring  156  biases the plunger  128  toward the valve seat  132  and away from the valve body  152  to close the valve assembly  112 . The valve spring  156  is a compression spring. 
         [0026]    The valve seat  132 , which may be described as being a portion of the sleeve assembly  168  or a portion of the valve assembly  112 , cooperates with the plunger  128  and/or the valve body  152  to fluidly decouple the working chamber  108  from the atmosphere chamber  104 . Accordingly, the valve seat  132  may include an elastomer gasket (not shown) or other member, which forms an airtight junction when in contact with the plunger  128  and/or the valve body  152 . The valve seat  132  defines an opening  184  through which the airflow passes when the valve assembly  112  is in the open position. The seat spring  176  biases the valve seat  132  toward the plunger  128  and the valve body  152 . 
         [0027]    The rod  136  transfers the braking force to the valve assembly  112 . The rod  136  extends through the grommet  130 , the housing end opening  140 , the atmosphere chamber  104 , and the opening  184 , and into the working chamber  108 . The plunger  128  receives a ball end  146  of the rod  136  within the cavity  204 , and a pedal end  148  of the rod  136  is coupled to a brake pedal of a vehicle (not shown) to receive the braking force. In response to receiving the braking force, the rod  136  moves leftward in the linear direction  144 . 
         [0028]    In operation, the booster  100  enables an unobstructed airflow to pass through the atmosphere chamber  104  and the valve opening  184 . In particular, due to the placement of the return spring  156 , airflow through the atmosphere chamber  104  is unimpeded by springs and/or other elements, except for the rod  136 . In comparison, some known boosters, include a return spring extending between the housing and the rod within the atmosphere chamber. In response to receiving the braking force, the return spring compresses, thereby causing the coils of the return spring to become positioned nearer to each other. The compacted arrangement of coils may, in some circumstances, restrict airflow through the atmosphere chamber. The booster of  FIG. 1 , however, includes the return spring  156  positioned behind the plunger  128  in the working chamber  108 , such that the airflow through the atmosphere chamber  104  remains unrestricted, even when the return spring  156  is under compression. The unobstructed airflow through the atmosphere chamber  104  may increase the response time of the booster  100 , e.g. the unobstructed airflow may cause the hydraulic brakes (not shown) associated with the booster  100  to become activated more quickly than compared to a booster having an airflow obstructed by a return spring positioned in the atmosphere chamber. 
         [0029]    In response to receiving the braking force, the rod  136  moves the plunger  128  leftward in the linear direction  144 , thereby separating the plunger  128  from the valve seat  132  and opening the valve assembly  112 . The open valve assembly  112  enables air to enter the working chamber  108  from the atmosphere chamber  104 . The pressure of the airflow within the working chamber  108  acts upon the diaphragm (not shown), as is known to those of ordinary skill in the art, and causes the valve body  152  to move leftward in the linear direction  144 . In some embodiments, as the valve body  152  moves leftward, the seat spring  176  moves the valve seat  132  leftward for a short distance, thereby temporarily maintaining the valve seat  132  against the valve body  152 . Continued movement of the valve body  152 , however, separates the valve body  152  from the valve seat  132  and enables additional airflow through the opening  184 . 
         [0030]    The valve assembly  112  closes in response to the elimination of the braking force. After the braking force upon the rod  136  subsides, the return spring  156  biases the plunger  128  and the rod  136  rightward in the linear direction  144 . Similarly, a valve body spring (not shown) biases the valve body  152  toward the valve seat  132 . The valve body  152 , under the biasing force of the valve body spring, may contact and move the valve seat  132  rightward relative to the tapered section  172  against the biasing force of the seat spring  176 . The return spring  156  biases the plunger  128  against the valve seat  132 . Once the plunger  128  and the valve body  152  are biased against the valve seat  132 , the airflow through the opening  184  ceases. 
         [0031]    The device described herein has been illustrated and described in detail in the figures and foregoing description, the same should be considered as illustrative and unrestrictive in character. It is understood that only the preferred embodiments have been presented and that all changes, modifications, and further applications that come within the spirit of the device described herein are desired to be protected.