Abstract:
An apparatus is described wherein for a device for controlling the flow of fluid. A housing having an inlet for receiving the fluid, an outlet for discharging the fluid, and a bore connecting the inlet to the outlet is provided. A piston is disposed in the bore and has a through bore for permitting the flow of the fluid through the piston. A valve member is disposed in the bore of the piston and adapted to engage an internal surface of the piston to block fluid flow through the piston and therefore through the housing, the piston responding to an increase in pressure at the outlet as a result of the fluid flow for moving in a direction toward the valve member until the valve member engages the piston surface to restrict fluid flow. A stop member is disposed in the housing and extends into the bore of the piston for stopping movement of the piston after it engages the valve member. Further, the embodiment includes means for normally positioning the valve member away from the surface so that fluid flows through the piston.

Description:
BACKGROUND 
     This disclosure relates generally to brake pressure proportioning in-line ball valves, and more particularly to an improved valve having relatively few components and a relatively short length. 
     Brake proportioning valves are used in automobiles and other vehicles. In these applications, it is often necessary to proportion brake fluid pressure between front and rear wheel brakes, or cylinders, as less braking power is needed in the rear wheel brakes. A brake pedal is operably attached to a master cylinder, which is connected to the wheel brakes via hydraulic lines. Depressing the brake pedal causes the master cylinder to increase hydraulic pressure at its outlet. The master cylinder outlet is connected to separate hydraulic lines for the front and rear wheel brakes, or for the right and left wheel brakes, to carry the increased hydraulic pressure through the lines to the respective wheel brakes. In either case, a brake proportioning valve, or a plurality of brake proportioning valves, is disposed between the master cylinder outlet and the rear wheel brakes to allow proportionately less hydraulic pressure from the master cylinder to reach the rear wheel brakes, thereby achieving the proper braking proportion. 
     The brake proportioning valve has an inlet connected to the master cylinder, and an outlet operably connected to the rear wheel brakes. At low inlet pressures, where the brake is not applied, brake fluid flows freely in both directions through the brake proportioning valve. However, as brake fluid pressure increases at the valve&#39;s inlet in response to application of the brake pedal, a predetermined level is reached where pressure at the valve&#39;s outlet forces a piston to engage a ball to restrict the flow of brake fluid to the rear wheel brakes. 
     This predetermined level is known as the knee point pressure, and is equivalent to the force holding the valve open divided by a differential relating to the area of the inlet pressure seal and the area of the outlet pressure seal. For the valve to perform, the outlet seal diameter must be greater than the inlet seal diameter. Thus, there is a benefit in making the inlet seal diameter as small as possible so that the outlet seal, and therefore the entire valve, does not take up a great deal of space. 
     A brake proportioning valve of the prior art is disclosed in U.S. Pat. No. 5,522,651, and provides proportioning of brake fluid pressure using a plunger of two diameters against which hydraulic pressure operates, and a check ball located in the plunger and held off its seat under low outlet pressure conditions by a rod and valve lifter. The ball is biased in place by a ball spring. At high outlet pressure, i.e., above the knee point pressure, the plunger contacts the ball and restricts fluid flow. A continuation-in-part of the above-referenced patent, U.S. Pat. No. 5,741,049, operates similarly. 
     However, several disadvantages are associated with this prior art. First, the rods do not directly engage their respective housings. Instead, each rod requires extra elements, such as a valve lifter assembly, to support the rod, thereby complicating manufacture. Second, the ball springs could become completely compressed by the balls, undesirably restricting fluid flow. Third, the outlet seal diameters are larger than their respective plunger springs&#39; diameter, thus limiting the variety of plunger spring strengths that can be used, and hence lowering the possible range of knee points. 
     Therefore, what is needed is an apparatus having less components and steps in assembly, as well as a shorter length when compared to the above system, without having the disadvantages associated with the systems. 
     SUMMARY 
     Accordingly, one embodiment disclosed herein is a device for controlling the flow of fluid, and therefore fluid pressure. A housing having an inlet for receiving the fluid, an outlet for discharging the fluid, and a bore connecting the inlet to the outlet is provided. A piston is disposed in the bore and has a through bore for permitting the flow of the fluid through the piston. A valve member is disposed in the bore of the piston and adapted to engage an internal surface of the piston to block fluid flow through the piston and therefore through the housing, the piston responding to an increase in pressure at the outlet as a result of the fluid flow for moving in a direction toward the valve member until the valve member engages the piston surface to restrict fluid flow. A stop member is disposed in the housing and extends into the bore of the piston for stopping movement of the piston after it engages the valve member. Further, the embodiment includes means for normally positioning the valve member away from the surface so that fluid flows through the piston. 
     One advantage of the embodiment described herein is that a piston spring surrounds the valve member and the greater part of the piston, resulting in a relatively shorter valve length. 
     Another advantage of the embodiment described herein is that the stop member has an extension which protrudes through a valve member spring, thus preventing complete compression of the spring and consequent restriction of flow. Also, the stop member&#39;s extension has a cross slot to prevent the valve member from blocking the extension bore and restricting flow during inlet pressure release. 
     Yet another advantage of the embodiment described herein is that the positioning means directly engages the housing instead of being supported by additional components, thus simplifying manufacture. Furthermore, the housing edge is staked over the stop member, which is more reliable than a pressed-in retainer. 
     Another advantage of the embodiment described herein is that an inlet pressure seal is disposed inside the piston, which results in a more favorable variation between the inlet seal area and the outlet seal area. Also, no bored venting passage is required, thus facilitating manufacture. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a longitudinal sectional view of an embodiment of the present invention in a first orientation. 
     FIG. 2 is a transverse sectional view of the embodiment of FIG. 1, taken along a line  2 — 2  of FIG. 1 
     FIG. 3 is a longitudinal sectional view of an embodiment of the present invention in a second orientation. 
     FIG. 4 is a longitudinal sectional view of an alternative embodiment of the present invention. 
     FIG. 5 is a longitudinal sectional view of yet another alternative embodiment of the present invention. 
     FIG. 6 is a longitudinal sectional view of yet another alternative embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1 and 2 of the drawings, the reference numeral  20  refers to a brake proportioning in-line valve of one embodiment of the present invention. The valve  20  has a generally hexagonal housing  21  which may be made of metal or other durable material. The housing  21  has an inlet end portion, depicted on the right as viewed in FIG. 1, and an outlet end portion, depicted on the left as viewed in FIG.  1 . It is understood that the valve  20  is connected in a vehicle fluid braking system, with the inlet end portion connected to the outlet of a master cylinder, and the outlet end portion connected to at least one rear wheel brake cylinder, or caliper, as will be explained. As these features are all conventional, they will not be described further. An external threaded portion  21   a  of the housing  21 , and a staked edge  21   b  of the housing  21 , are located at the inlet end portion. 
     The housing  21  has an axial through bore  22  which is stepped along its length to form a series of sections  22   a - 22   e  extending from the inlet end portion to the outlet end portion. The corresponding diameters of the sections  22   a - 22   d  range from the largest to the smallest, respectively. The bore sections  22   a - 22   e  may be produced by any conventional means, and define a series of shoulders or steps,  22   f ,  22   g , and  22   h , at the junction of the sections  22   a  and  22   b , sections  22   b  and  22   c , and sections  22   c  and  22   d , respectively. The section  22   e  is internally threaded and adapted to mate with a hydraulic line (not shown), which operably connects to the rear wheel brakes. 
     A cap, generally referred to by reference numeral  28 , is disposed in the housing  21 . The cap  28  is substantially T-shaped in cross section, and is held in a relatively tight fit between the housing step  22   f  and the staked edge  21   b . The cap  28  includes a rounded edge  28   a  adjacent to the staked edge  21   b  to facilitate attachment. It is understood that any other conventional means may be used for retaining the cap  28 , such as a pressed in retainer. For reasons to be described, it is desirable that the attaching means allow air to pass between the cap  28  and the housing  21 . 
     An inlet seat  28   b  is formed in the cap  28 , and is inwardly tapered to register with an axial through bore  28   c . The exterior of the cap  28  further includes a flat surface  28   d  oriented opposite the inlet seat  28   b  for reasons to be described. A portion of the flat surface  28   d  engages the step  22   f  of the housing  21 , and the flat surface  28   d  is located at an end of the area defined by the section  22   b  of the housing  21 . 
     The cap  28  includes an extension  28   e  that extends into the bore section  22   b  for reasons to be described. The extension  28   e  is cylindrical in shape, with the cap bore  28   c  extending axially throughout its length. An end  28   f  of the extension includes a transverse slot  28   g . A radial stepped down portion  28   h  of the extension is disposed approximately midway down the extension  28   e . An annular flange  28   i  is formed on extension  28   e , and a seal  30  is disposed between the flange  28   i  and the stepped down portion  28   h , for reasons to be described. 
     A piston  32  is slidably mounted within the areas defined by the sections  22   b  and  22   c  of the housing  21 , and slidably extends over the cap extension  28   e . The piston  32  is cylindrical, and substantially Y-shaped in cross section, as will be explained. 
     An annular flange  32   a  is formed on the outer surface of the piston  32 . The outer surface of the piston  32  also has a radial groove  32   b  which receives an outlet pressure elastomeric seal  34 , forming a seal between the piston  32  and the wall of the housing  21  defining the section  22   c . The seal  34  isolates the outlet brake fluid pressure in section  22   c  to the left of the seal  34 , as viewed in FIG. 1, and therefore in sections  22   d  and  22   e . The pressure outside the piston  32  to the right of the seal  34 , as viewed in FIG. 1, is kept at atmospheric pressure because venting occurs at the joint between the cap  28  and the housing  21 . 
     A relatively large bore  32   d  is formed in the piston  32  and is connected, through a tapered bore, or seat,  32   e  to a relatively small bore  32   f . The large bore  32   d  extends over a portion of the cap extension  28   e . The inlet seal  30  engages the surface of the piston  32  defining the bore  32   d  to isolate the brake fluid inlet pressure in the cap bore  28   c  and the piston bore  32   d . The bore  32   f  is subjected to the above described outlet pressure. 
     A spring  36  extends between the flat surface  28   d  of the cap  28  and the annular flange  32   a  to bias the flange against the housing step  22   g . The diameter of the piston spring  36  is greater than the diameter of the bore section  22   c , for reasons to be described. 
     The piston  32  moves between the position shown in FIG. 1 to an intermediate position between the position of FIG. 1 and a position in which an end  32   c  of the piston  32  engages the flat surface  28   d  of the cap  28 . An example of this intermediate position is shown in FIG. 3, it being understood that the term intermediate position defined herein means any position between the position of FIG.  1  and the position in which the end  32   c  of the piston  32  engages the flat surface  28   d . The piston also has another end  32   g , disposed in bore section  22   c , as will be explained. 
     A ball  38  is disposed in the large bore  32   d  of the piston  32 . When the piston  32  is in the intermediate position of FIG. 3, the ball  38  engages the seat  32   e , forming a seal. A spring  39  extends between the ball  38  and the annular flange  28   i  of the cap  28  and over a portion of the cap extension  28   e . The spring  39  thus urges the ball  38  in a direction indicated by arrow B. 
     Referring to FIGS. 1-3, a rod  40  in the form of a flat, rectangular piece of metal is disposed inside the small bore  32   f  of the piston  32 . A first end  40   a  of the rod  40  engages the ball  38 , and a second end  40   b  of the rod  40  engages the housing step  22   h.    
     It is understood that the valve  20  is connected in a hydraulic braking system for a vehicle that includes a brake pedal operably attached to a master cylinder, which is connected to rear wheel brakes via hydraulic lines. Since all of the components, with the exception of the valve  20 , are conventional, they are not shown. 
     In operation, depressing the brake pedal causes the master cylinder to produce increased hydraulic pressure. The brake proportioning valve  20  is disposed between the master cylinder and the rear wheel brakes to allow proportionately less hydraulic pressure from the master cylinder to reach the rear wheel brakes. An inlet pressure is developed in the inlet end portion as a result of increasing hydraulic pressure from the master cylinder when the brake pedal is applied. Similarly, an outlet pressure is developed in the outlet end portion. Outlet pressure depends on the hydraulic equilibrium of the piston, the force associated with the piston spring, and increases or decreases in the inlet pressure. 
     At low inlet end portion pressures, where the brake is not applied, the valve  20  is in the position of FIG.  1 . In this position, brake fluid flows freely through the brake proportioning valve in directions indicated by arrows A and B, and therefore some brake fluid is present in the valve. 
     The valve has a normal or passive first position, as illustrated in FIG.  1 . When the vehicle brake pedal is applied, additional brake fluid enters the cap seat  28   b , and passes through the cap bore  28   c  and into the large bore  32   d  raising the inlet pressure, which, as noted above, is isolated by the seal  30 . As long as the piston  32  is in this position, fluid flows around the ball  38 , past the seat  32   e , past the rod  40  and through the bore  32   f , and through the sections  22   d  and  22   e , and on to the rear wheel brakes. In this position, the inlet pressure is essentially equal to the outlet pressure. 
     As inlet pressure increases with continued application of the brake pedal, the outlet pressure correspondingly increases until the outlet pressure eventually reaches the above-defined knee point pressure, and creates a force acting on the end  32   g  of the piston  32  that is sufficient to force the piston  32  in a direction, indicated by arrow A (to the right, as viewed in FIG.  1 ), overcoming the force of the spring  36 . The piston  32  moves to the intermediate position, as shown in FIG. 3, and thus the piston seat  32   e  engages the ball  38 , stopping fluid flow. 
     As inlet pressure increases, it momentarily overcomes the force created by the outlet pressure, causing the piston  32  rapidly to shift in the direction of arrow B, allowing some fluid to escape around the ball  38  before the resulting increase in outlet pressure quickly moves the piston  32  back again to the position of FIG. 3, resealing the valve. Thus, further increases in the inlet pressure above the knee point pressure results in increases in outlet pressure at a reduced rate. The piston  32  remains in the position illustrated in FIG.  3 . 
     As inlet pressure decreases, on brake pedal release for example, the piston  32  moves in the direction indicated by arrow A until the end  32   c  of the piston engages the flat surface  28   d  of the cap  28  to stop further movement of the piston  32 . This occurs before the ball spring  39  is completely compressed, preventing an undesirable restriction in flow. When the inlet pressure equals the outlet pressure, the ball  38  disengages from the seat  32   e . When the pressures decrease below the knee point pressure, the piston  32  returns to the passive first position, as depicted in FIG.  1 . 
     Thus, the valve  20  allows fluid to flow freely to the rear wheel brakes at low master cylinder outlet hydraulic pressures and restricts the flow of brake fluid to the rear wheel brakes at predetermined higher master cylinder outlet hydraulic pressures, thereby achieving the proper braking proportion between the front and rear wheel brakes. 
     Several advantages result from the foregoing assembly. For example, the spring  36  surrounds the greater part of the piston  32  and, therefore, the inlet seal  30  and the ball  38 . When compared with a spring which is oriented at the end of a piston  32 , the present invention results in a shorter valve length. Also, as noted above, the diameter of the piston spring  36  is greater than the diameter of the outlet seal  34 , resulting in more design options, including the ability to use stronger springs for producing higher knee points. 
     Further, this embodiment uses only two elastomeric seals, and thus reduces breakable components. Also, because the inlet seal  30  is disposed inside the piston  32 , whereas the outlet seal  34  is disposed outside the piston  32 , a more favorable differential is created between the area subjected to the inlet pressure and the area subjected to the outlet pressure, allowing a smaller valve to produce the same knee points as prior art methods. 
     It is understood that variations can be made within the scope of the invention. For example, the housing  21  could be produced in a variety of shapes, and the transition from section to section of the bore  22  may be gradual instead of stepped. A one piece element could replace the ball  38  and rod  40 , having a first portion including a sealing surface shape, such as a ball or cone, and a second portion which is long and narrow. Also, the ball spring  39  is depicted as a straight spring, however, a conical spring, or some other means of exerting force could be used. During flow from the outlet end portion to the inlet end portion, as occurs during brake release, the ball  38  could be pushed far enough to engage the cap extension  28   e . If the ball  38  were pushed all the way to the end  28   f  of the cap extension  28   e , the spring  39  would still not be fully compressed and the cross slot  28   g  would allow fluid flow around the ball  38  as a second means to prevent undesirable flow restriction. 
     Furthermore, it is understood that all spatial references are for the purpose of example only and are not meant to limit the invention. 
     Referring to FIG. 4 of the drawings, the reference numeral  42  refers to a brake proportioning in-line valve of another embodiment of the present invention. This embodiment incorporates several components of the previous embodiment which are given the same reference numbers. According to FIG. 4, the ball  38  is held in place by gravity and a cap  46  replaces the cap  28  of the previous embodiment. An extension  46   a  of the cap  46  has an end  46   b  which extends across the large bore  32   d . The valve must be oriented in a direction indicated by arrow C, so that gravity keeps the ball  38  engaged with the rod  40 . This embodiment has several advantages, including making the cap extension  46   a  easier to machine because it has no annular flange, and minimizing flow restrictions because the brake fluid does not have to flow through a ball spring. By reducing flow restrictions, and eliminating the force associated with the ball spring, this embodiment further reduces hysteresis, the lag found when a fluid force changes direction. 
     Referring to FIG. 5 of the drawings, the reference numeral  48  refers to a brake proportioning in-line valve of another embodiment of the present invention. This embodiment incorporates several components of the first embodiment which are given the same reference numbers. According to FIG. 5 a cap  50  is provided in place of the cap  28  of the embodiment of FIGS. 1-3. The cap  50  has a flat surface  50   a  for mating with a fluid inlet. This embodiment could mate with a variety of fluid delivery systems, however, a passage in the system may be required for venting, and another sealing element (not shown) required on the valve  48  to prevent leakage. 
     Referring to FIG. 6 of the drawings, the reference numeral  52  refers to a brake proportioning in-line valve of another embodiment of the present invention. This embodiment incorporates several components of the first embodiment which are given the same reference numbers. According to FIG. 6, the ball  38  and spring  39  of the embodiment of FIGS. 1-3 are replaced by a relatively large ball  54  and a spring  56 , respectively. As a result, the embodiment has a different pressure proportioning ratio than an embodiment using a smaller ball. 
     This disclosure shows and describes several illustrative embodiments, however, the disclosure contemplates a wide range of modifications, changes and substitutions. Such variations may employ only some features of the embodiments without departing from the scope of the underlying embodiment. Accordingly, any appropriate construction of the appended claims will reflect the broad scope of the underlying embodiment.