Abstract:
A non-powered evacuation and fill valve assembly is provided that is suitable for use in connection with hydraulic brake system. The assembly utilizes a pressure differential and/or the properties of material expansion to provide a tight seal. During evacuation of air from the system, the assembly is in an “open” position to permit air to pass. After the air has been evacuated from the system and the system has been filled with fluid, the valve assembly will assume a “closed” position. Thereafter, a tight seal is provided as long as the system is filled with a requisite amount of fluid.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to hydraulic brake systems. More particularly the present invention relates to a non-powered evacuation and fill valve assembly and a method for using the same in connection with a hydraulic brake system. 
     BACKGROUND OF THE INVENTION 
     Air within a hydraulic brake system will be compressed as the pressure within the system increases. This action reduces the amount of force that can be transmitted by the fluid. Therefore, it is important to keep all air out of the hydraulic system. 
     In vehicles, when an anti-lock brake system(ABS) unit is installed, air is evacuated from the hydraulic circuit before the unit is pre-filled with brake fluid. During the evacuation and fill process, solenoid valves for each brake circuit must be actuated. To effectuate the activation of the solenoid valves, a number of conventional designs require the connection of an electrical supply to the unit. However, this connection results in increased cycle time and cost in the vehicle assembly line. 
     Other conventional designs incorporate a spring-biased, normally closed, rubber check valve in which a very low spring force is applied to allow the valve to open during evacuation. However, during normal braking operations involving a sudden pedal release, the spring force is often not sufficient to keep the valve in the closed position. This situation can permit air to enter through the accumulator seals and result in a “soft” pedal, which can lead to eventual brake failure. 
     SUMMARY OF THE INVENTION 
     The present invention recognizes the disadvantages and limitations commonly associated with conventional hydraulic brake systems. Moreover, the present invention essentially utilizes a pressure differential or plug expansion to provide a “latching” or “locking” effect in connection with a non-powered evacuation and fill valve assembly. In the context of the present invention, the term “non-powered” means without the use of an external electric connection. 
     In one embodiment of the present invention, the evacuation and fill valve assembly is comprised of a valve and valve plate that connects low pressure and high pressure lines in each brake circuit. The assembly evacuates the air out of every part of the hydraulic cylinder unit and is typically switched on only once during the evacuation and pre-filling process (to evacuate air). Thereafter, the assembly typically remains in the closed position. 
     During the evacuation of air from the system, the aforementioned assembly stays open to allow air to be evacuated from the low pressure line. During fill or during subsequent testing and thereafter, the assembly remains closed to break the connection between low pressure and high pressure lines. Because the present invention makes use of a hydraulic pressure differential, there is no need for an electrical connection to actuate the solenoid valves. Further, the present invention eliminates the problem of designs that use a spring-biased rubber check valve by keeping the valve closed and secured during normal braking operations. 
     In another embodiment of the present invention, the evacuation and fill valve assembly is comprised of a plug that is formed of a material that expands in communication with brake fluid. After the filling process, the plug takes in and/or “absorbs” brake fluid, and expands. The expanded plug establishes a permanent connection between a valve body and the valve plug. This “latched” or “locked” condition exists as long as there is a sufficient amount of brake fluid in the system to expand the plug. As in the case of the previously mentioned, embodiment, no electrical connection is required. 
     In accordance with an embodiment of the present invention, a non-powered evacuation and fill valve assembly is provided that is suitable for use in connection with hydraulic brake system having a low pressure circuit, a higher pressure circuit, and a master cylinder. The assembly is comprised of a molded rubber valve including a retaining seal and a sealing area; a steel insert; and a valve plate that may include a retaining portion. During evacuation of air from the system, said rubber valve is in an open position relative to the valve plate to permit air in the low pressure circuit to flow through the evacuation and fill valve to the master cylinder. After evacuation of air from the system, a pressure differential is created on both sides of the evacuation and fill valve and it will move to a closed position relative to the valve plate and thereafter provide a tight seal as long as the system is filled with fluid. 
     In accordance with another embodiment of the present invention, a non-powered evacuation and fill valve assembly is provided that is comprised of a plug and a valve body. The plug is formed from a material, such as a plastic or rubber, which expands in communication with brake fluid. Preferably, the plug includes a rubber seal that, when in position, prevents air from entering the system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be more readily understandable from consideration of the accompanying drawings, wherein: 
     FIG. 1 is a section view of an embodiment of a valve provided in accordance with an aspect of the present invention. 
     FIG. 1A is a bottom plan view of the valve shown in FIG.  1 . 
     FIG. 2 is a section view of an embodiment of a valve plate provided in accordance with an aspect of the present invention. 
     FIG. 2A is a bottom plan view of the valve plate shown in FIG.  2 . 
     FIG. 3 is a section view that illustrates an evacuation and fill valve assembly shown in FIG.  3 . 
     FIG. 4 is a section view showing a preferred evacuation and fill valve assembly in the open position. 
     FIG. 5 is a section view showing a preferred evacuation and fill valve assembly in the closed position. 
     FIG. 6 is a section view of another preferred embodiment of an evacuation and fill valve assembly. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present invention will be described in detail with reference to drawing FIGS. 1-6, which form a part of this disclosure. 
     Referring first to FIG. 1, a sectional view of an embodiment of a valve  10  provided in accordance with an aspect of the present invention is shown. The valve  10  includes a central axis A and is preferably comprised of an upper portion  12  and a lower insert  14 . 
     The upper portion  12  preferably has a generally cylindrical shape and is formed of rubber. However, other materials that serve a resilient sealing function in an automotive fluid environment may also be used to construct the upper portion  12 . In a preferred embodiment of the present invention, the valve  10  includes: (a) an retaining seal  16  that extends radially outward from central axis A; (b) a lower rim  18  positioned below the retaining seal  16  that extends radially outward from the central axis A; and (c) a lower annular protrusion  20  that extends in a generally upward direction from the lower rim  18 . 
     The lower insert  14  preferably is formed from a metal, such as steel, however other conventional materials may be used. In a preferred embodiment, the insert  14  includes at least one notch  22 , and preferably two generally, rectangular-shaped notches  22  positioned at opposed edges of the lower surface  24  of the insert  14 . FIG. 1A is a bottom view of the preferred embodiment of the valve  10  illustrated in FIG.  1 . As better illustrated in FIG. 1A, the lower insert  14  is generally circular and preferably also includes one or more flattened edge portions  26 . 
     FIG. 2 depicts a preferred embodiment of a valve plate  30  constructed in accordance with the present invention. The valve plate  30  has a generally annular shape and includes a retaining portion  31 . The retaining portion  31  preferably is an annular stepped portion. The plate  30  is preferably comprised of a metal, such as steel. It is important to note that the plate  30  can also be formed from other conventional materials provided that such materials are suited for the intended environment, i.e., a hydraulic brake fluid environment. 
     A preferred embodiment of the valve plate  30  includes first annular recess  32  and a second annular recess  34 . When the valve  10  and plate  30  are brought into sealing communication, the first annular recess  32  is designed to communicate with the retaining seal  14 , and the second annular recess  34  is designed to communicate with the second annular recess  34 . FIG. 2A generally depicts a bottom plan view of the plate  30  shown in FIG.  2 . 
     FIG. 3 is a section view that illustrates a valve  10  and plate  30  assembly shown in the context of a larger assembly that includes an outlet valve  36  and an ABS housing  38 . FIG. 3A is an enlarged view of the evacuation and fill assembly shown in FIG.  3 . 
     As shown in FIG. 4, a valve  10  and valve plate  30  are provided in connection with a normally closed (NC) valve bore  40  of each brake circuit. The master cylinder connection is identified generally by the number  42 . Preferably, the upper portion  12  is a rubber part that is molded onto a stamped steel insert  14  with two notches  22  and flats  26 . The valve plate  30  is secured in the ABS/TCS unit housing  38 . 
     During evacuation, vacuum is applied at the master cylinder and is effectuated through the master cylinder connection  42 . During this action, valve  10  is moved into an open position as shown in FIG.  4 . Air in the low pressure circuit above the valve  10  and valve plate  30  assembly is permitted to flow through the valve  10  to the master cylinder connection  42 . This creates a vacuum in the low pressure circuit without actuating the outlet valve  36  which is normally closed. During fill, hydraulic pressure is applied at the master cylinder and communicated through the master cylinder connection  42 . The valve  10  may or may not move upwardly to a closed position depending on the fill pressure applied. During subsequent ABS tests (e.g., roll tests), the pressure differential created on the two sides of the valve will move it upward to the closed position to seal the valve  10  against the valve plate  30  as shown in FIG.  5 . In the closed position, the retaining seal  16  rests above the retaining portion  31  of the valve plate  30 , thereby retaining or “locking” the valve  10  in the closed position. 
     Once such a “closed” position is established, the valve  10  will normally remain in that position. For instance, during normal braking operation, a small vacuum is created in the master cylinder and may be communicated through the master cylinder connection  42  if the pedal is released very quickly. However, the valve  10  typically will not move from a “closed” to an open position by such a vacuum since the retaining seal  16  will be secured and retained above the retaining portion  31  of the valve plate  30 , thereby prohibiting the undesired passage of air past the valve  10  to the master cylinder connection  42 . 
     In another preferred embodiment of the present invention, rather than utilizing a pressure differential on different sides of a valve, as disclosed above, the non-powered evacuation, filling and sealing of the assembly is accomplished utilizing the expansive properties associated with a brake fluid-absorbing material. FIG. 6 illustrates a cross sectional view of a preferred example of such an embodiment. As shown therein, the evacuation and fill assembly  50  may be comprised of valve body  52 , valve plug  54 , plug  56 , plug receiving portion  58 , a rubber sealing  60 , a first passage  62 , and a second passage  64 . The assembly  50  may optionally include one or more springs  66 , if desired. The rubber sealing is somewhat optional, but is used to ensure a good seal of valve body  52 . A bore  68  is shown positioned above the valve plug  54 . The plug  54  can be used to seal the bore  68 . 
     Preferably, plug  56  is comprised of a material that expands in or when exposed to brake fluid (BF), such as a rubber or a plastic. First passage  62  permits air to enter into the plug receiving portion  58 . Second passage  64  permits brake fluid (BF) to enter the receiving portion  58  and air to evacuate the receiving portion  58 . 
     After the receiving portion is filled with brake fluid, the plug  56  absorbs such fluid and expands. The expansion of the plug  56  establishes a generally permanent connection between the valve body  52  and the valve plug  54  as long as there is a sufficient volume of brake fluid in the system. Because the valve does not open or close thereafter, it cannot leak due to contamination of the brake fluid. 
     Although certain preferred embodiments of the present invention have been described, the invention is not limited to the illustrations described and shown herein, which are deemed to be merely illustrative of the best modes of carrying out the invention. A person of ordinary skill in the art will realize that certain modifications will come within the teachings of this invention and that such modifications are within its spirit and the scope as defined by the claims.