Abstract:
A pneumatic pressure brake booster system includes an air pressure chamber; an ambient air chamber; a flexible diaphragm separating the air pressure chamber and the ambient air chamber; at least one air pressure source communicating with the air pressure chamber; a brake pedal shaft engaged by and movable with the diaphragm; and a brake master cylinder engaged by the brake pedal shaft.

Description:
FIELD 
     The disclosure generally relates to automotive brake boosters. More particularly, the disclosure relates to an automotive pressure brake booster system which imparts assist forces to a brake system using a pressure servo booster instead of a vacuum booster, and a pneumatic pressure brake booster method. 
     BACKGROUND 
     Vacuum boosters are commonly used to boost the brake pressure of automotive braking systems. However, vacuum boosters may not be suitable for some vehicles such as those with turbocharged or supercharged engines, engines with stop-start features, gas-electric hybrids and electric powertrains. Therefore, an external auxiliary vacuum pump may be required for these applications. The vacuum pump performance is limited to some fraction of the ambient air pressure and may be severely limited at high altitudes. Moreover, large vacuum boosters may be required to achieve high assist forces in an ever-decreasing package space for smaller vehicles. 
     Accordingly, an automotive pressure brake booster system and method in which assist forces are imparted to a brake system using a pressure servo booster instead of a vacuum booster may be desirable for some applications. 
     SUMMARY 
     The disclosure is generally directed to a pneumatic pressure brake booster system. An illustrative embodiment of the system includes an air pressure chamber; an ambient air chamber; a flexible diaphragm separating the air pressure chamber and the ambient air chamber; at least one air pressure source communicating with the air pressure chamber; a brake pedal shaft engaged by and movable with the diaphragm; and a brake master cylinder engaged by the brake pedal shaft. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will now be made, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is a schematic diagram illustrating an illustrative embodiment of the pneumatic pressure brake booster system connected to front and rear brakes of an automotive braking system; 
         FIG. 2  is a schematic block diagram of an illustrative embodiment of the pneumatic pressure brake booster system; and 
         FIG. 3  is a flow diagram of an illustrative embodiment of a pneumatic pressure brake booster method. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the described embodiments or the application and uses of the described embodiments. As used herein, the word “exemplary” or “illustrative” means “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” or “illustrative” is not necessarily to be construed as preferred or advantageous over other implementations. All of the implementations described below are exemplary implementations provided to enable persons skilled in the art to practice the disclosure and are not intended to limit the scope of the claims. Moreover, the illustrative embodiments described herein are not exhaustive and embodiments or implementations other than those which are described herein and which fall within the scope of the appended claims are possible. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. 
     Referring initially to  FIGS. 1 and 2  of the drawings, an illustrative embodiment of the pneumatic pressure brake booster system, hereinafter system, is generally indicated by reference numeral  100 . As shown in  FIG. 1 , the system  100  may be adapted for connection to a vehicle braking system  122  of a vehicle (not shown) having a pair of front brakes  124  and a pair of rear brakes  128  to operate the front and rear brakes  124 ,  128 . In some applications, the vehicle having the vehicle braking system  122  may have a turbocharged or supercharged engine, an engine with stop-start features or an electric powertrain, or may be a gas-electric hybrid. The system  100  may facilitate enhanced braking capability and higher assist forces generated by the vehicle braking system  122 . The system  100  may additionally facilitate enhanced space-efficient packaging of the braking system components in smaller vehicles. 
     The system  100  includes a pressure servo booster  101 . The pressure servo booster  101  may have a design which is similar to that of a standard or conventional vacuum booster which is known by those skilled in the art, with notable exceptions described below. As shown in  FIG. 2 , the pressure servo booster  101  has a booster shell  101   a  with a brake pedal side  101   b  and a brake master cylinder side  101   c . The booster shell  101   a  has an interior air pressure chamber  106  on the brake pedal side  101   b  and an interior ambient air chamber  102  on the brake master cylinder side  101   c . A flexible diaphragm  114  separates the ambient air chamber  102  and the air pressure chamber  106 . The diaphragm  114  can be deployed in a pre-deformed position indicated by the phantom lines and a deformed position indicated by the solid lines in  FIG. 2 . At least one ambient air vent  103  in the booster shell  101   a  communicates with the ambient air chamber  102 . Accordingly, as it is deployed from the pre-deformed position indicated by the phantom lines to the deformed position indicated by the solid lines in  FIG. 2 , the diaphragm  114  forces ambient air  104  from the ambient air chamber  102  through the ambient air vent or vents  103 . Conversely, as the diaphragm  114  returns from the deformed position back to the pre-deformed position, the resulting drop in air pressure draws ambient air  104  into the ambient air chamber  102  through the ambient air vent or vents  103 . 
     At least one source  108 ,  110  of pressurized air  111  communicates with the air pressure chamber  106 . In some embodiments, such as when a turbo-charged or super-charged engine is present, the source of pressurized air  111  may include engine intake air  108  from the engine air intake manifold (not shown) of the vehicle. In some embodiments, the source of pressurized air  111  may include an auxiliary pressure pump  110 . In some embodiments, the source of pressurized air  111  may include both engine intake air  108  and an auxiliary pressure pump  110 . A hose coupling  116  may detachably couple the auxiliary pressure pump  110  to the air pressure chamber  106 . 
     A brake pedal shaft  119  slidably extends through sealed shaft openings (not shown) in the booster shell  101   a . The brake pedal shaft  119  traverses the ambient air chamber  102  and the air pressure chamber  106  of the booster shell  101   a . A brake pedal  118  engages a first end of a brake pedal shaft  119 . A second end of the brake pedal shaft  119  operably engages a brake master cylinder  120 . Responsive to depression of the brake pedal  118 , the brake pedal shaft  119  shifts from a pre-actuating position to an actuating position in which the brake pedal shaft  119  actuates the brake master cylinder  120 . The diaphragm  114  is attached to the brake pedal shaft  119  such that deformation of the diaphragm  114  into the ambient air chamber  102  augments movement of the brake pedal shaft  119  from the pre-actuating position to the actuating position in actuation of the brake master cylinder  120 . 
     A pedal return spring  112  may be fitted on the brake pedal shaft  119  in the ambient air chamber  102 . The pedal return spring  112  may be interposed between the diaphragm  114  and the booster shell  101   a . The pedal return spring  112  normally maintains the brake pedal shaft  119  in the pre-actuating position. Upon depression of the brake pedal  118 , the pedal return spring  112  is compressed as the brake pedal shaft  119  actuates the brake master cylinder  120 . Upon subsequent release of the brake pedal  118 , the pedal return spring  112  expands and returns the brake pedal shaft  119  to the pre-actuating position. Simultaneously, the brake pedal shaft  119  returns the diaphragm  114  to the pre-deformed position indicated by the phantom lines in  FIG. 2 . 
     In exemplary application of the system  100 , the engine intake air  108  and/or the auxiliary pressure pump  110  supplies air pressure  111  to the air pressure chamber  106 . The air pressure  111  in the air pressure chamber  106  applies force against the diaphragm  114  and biases the diaphragm  114  toward the ambient air chamber  102 . Consequently, upon subsequent depression of the brake pedal  118 , the brake pedal shaft  119  is pushed further into the brake master cylinder  120  and actuates the brake master cylinder  120 . Hydraulic fluid (not shown) flows from the brake master cylinder  120  to the front brakes  124  and the rear brakes  128  to actuate the brakes  124 ,  128  in the conventional manner. 
     As the brake pedal shaft  119  is pushed further into the brake master cylinder  120  upon depression of the brake pedal  118 , the air pressure  111  in the air pressure chamber  106  deforms the diaphragm  114  into the ambient air chamber  102 , causing ambient air  104  to exit the ambient air chamber  102  through the ambient air vent or vents  103 . Consequently, as it is deformed, the diaphragm  114  augments movement of the brake pedal shaft  119  further into the brake master cylinder  120 , reducing the magnitude of foot pressure which is required for application to the brake pedal  118  to facilitate actuation of the vehicle braking system  122 . This expedient may be particularly advantageous at high altitudes in which the pressure of the ambient air  104  is reduced. 
     Upon subsequent release of foot pressure from the brake pedal  118 , the pedal return spring  112  expands and returns the brake pedal shaft  119  and the brake pedal  118  to the pre-actuating position. The diaphragm  114  returns with the brake pedal shaft  119  to the pre-deformed position indicated by the phantom lines in  FIG. 2 . Simultaneously, ambient air  104  is drawn back into the ambient air chamber  102  through the ambient air vent or vents  103 . 
     It will be appreciated by those skilled in the art that compared with conventional vacuum boosters, the system  100  facilitates achievement of higher assist forces in smaller package space with brake pedal pressures several times the pressure of the ambient air  104 . Air pressure  111  can be supplied from the engine intake air  108  from the engine intake if pressurized, and/or from the auxiliary pressure pump  110 . The auxiliary pressure pump  110  can be used to pressurize the chassis suspension, air springs, dampers, etc. In some embodiments, the hose coupling  116  ( FIG. 2 ) can detachably couple the auxiliary pressure pump  110  to the air pressure chamber  106 . The auxiliary pressure pump  110  can be selectively uncoupled from the air pressure chamber  106  to enable a customer to inflate tires, toys, etc. 
     Referring next to  FIG. 3  of the drawings, a flow diagram  300  of an illustrative embodiment of a pneumatic pressure brake booster method is shown. In block  302 , air pressure is applied against a diaphragm. In some embodiments, the air pressure applied against the diaphragm may be from engine intake air. In some embodiments, the air pressure applied against the diaphragm may be from an auxiliary pressure pump. In block  304 , the diaphragm is deformed. In block  306 , a brake pedal is depressed. In some embodiments, ambient air may be expelled from an ambient air chamber while the diaphragm is deformed. In block  308 , actuation of the brake master cylinder is augmented by applying the force of the deforming diaphragm to the brake pedal shaft. 
     Although the embodiments of this disclosure have been described with respect to certain exemplary embodiments, it is to be understood that the specific embodiments are for purposes of illustration and not limitation, as other variations will occur to those of skill in the art.