Abstract:
A modulator valve for an ABS system for heavy duty vehicles is disclosed. It uses non flow-through solenoid valve assemblies that simplify the machining and manufacturing costs associated with the present arrangement. This eliminates complex pilot passages and also achieves a quicker acting release of the brakes during normal service braking.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to heavy vehicle ABS modulators that presently use flow-through solenoids with complex pilot passages. In the field relating to antilock braking systems “ABS,” a modulator valve is situated between a source of air pressure and the brake chamber or actuator. The modulator is typically a three-way valve that under normal service operation selectively receives pressurized air upon depression of a brake valve and conveys the pressurized air to the brake actuators. Likewise, release of the brake valve shuts off the supply of air pressure to the brake actuators. 
     If an antilock event is sensed, an electronic control unit sends suitable signals to a solenoid valve assembly (usually a pair of solenoid valves) associated with the modulator. The solenoid valves provide an electro-pneumatic interface between the electronic controller and the air brake system. If an impending wheel lockup is sensed, the antilock controller immediately begins to modify brake application using the modulator. The coils associated with the respective solenoid valves are energized or de-energized in a predetermined sequence by the controller. As is known in the art, when a solenoid coil is energized, a core or shuttle is moved to either open or close an associated air passage. This either opens or closes the exhaust passage or reapplies air pressure to the brake actuator. Each of the solenoid valves is independently controlled by the electronic control unit. By opening and closing the solenoid valves, the antilock controller simulates brake “pumping” but at a rate substantially faster than the driver of a vehicle could actually pump the brakes to avoid skidding. 
     Although systems of this general type have met with substantial commercial success, there is always a need for improved efficiency and reduced manufacturing complexity. Associated with known arrangements is a relatively complex series of flow passages that interconnect the supply solenoid valve, exhaust solenoid valve, supply diaphragm, exhaust diaphragm, the supply or inlet port, the exhaust port, and the delivery port. Included among these complex flow passages are a series of pilot passages that interconnect the various components of the valve, i.e., pilot passages lead from opposite ends of the pair of solenoids to one of the diaphragm valves or to an exhaust passage. 
     Selected ones of these passages are used for connecting the flow passages to the exhaust port. The longer these passages are, the slower the reacting time in releasing the brakes. For example, when the foot or brake valve is released, it is preferred that the modulator be quickly and effectively connected to exhaust so that the brake actuators are released. 
     Moreover, known designs use flow-through solenoid valves which, although effective, require seals at each end and O-rings along the length thereof. 
     Thus, it would be desirable to provide a non flow-through solenoid valve assembly for heavy vehicle ABS modulators that overcome the noted problems. 
     SUMMARY OF THE INVENTION 
     The present invention contemplates a new and improved modulator that uses many of the same components but in a less complex manner. 
     According to the present invention, there is provided a pneumatic valve for controlling air flow to a brake chamber including a supply port that receives air from a source. An exhaust port provides a communication path to atmosphere and a delivery port is in communication with the brake chamber. A supply diaphragm is normally biased toward a closed position to prevent communication between the supply port and the delivery port. Similarly, an exhaust diaphragm is normally biased toward a closed position to prevent communication between the delivery port and the exhaust port. In response to an antilock event, a first solenoid valve regulates air flow between the supply port and the exhaust diaphragm. A second solenoid valve regulates air flow between the supply port and the supply diaphragm during an antilock braking event. At least one of the solenoid valves is a non flow-through valve in which only one end thereof is in fluid communication with a flow circuit. 
     According to another aspect of the invention, an exhaust cover that houses the first and second solenoid valves is substantially simplified. 
     According to another aspect of the invention, the second solenoid valve is a non flow-through solenoid in which only one end is in fluid communication with the flow circuit. 
     A principal advantage of the invention resides in providing an ABS modulator for heavy vehicles that has substantially reduced manufacturing complexity by reducing the number of pilot passages. 
     Another advantage of the invention resides in the simplified component design that results in reduced manufacturing costs. 
     Still another advantage of the invention is found in the quick acting release during normal service braking. 
     Still other advantages and benefits of the invention will become apparent to those skilled in the art upon a reading and understanding of the following detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may take physical form in certain parts and arrangements of parts, a preferred embodiment of which is described in detail in the specification. The preferred embodiment is illustrated in the accompanying drawings which form a part of the specification. 
     FIG. 1 shows a modulator valve in a non-actuated position. 
     FIG. 2 illustrates the modulator valve during a service brake application. 
     FIG. 3 shows the modulator valve in an ABS actuated mode with a supply solenoid valve actuated. 
     FIG. 4 illustrates the modulator with both of the first an second solenoid valves actuated. 
     FIG. 5 is a schematic representation of the non-flow through solenoid arrangement of the present invention. 
     FIG. 6 is an illustration of the valve body and exhaust cover of the present invention with selected portions shown in cross-section for ease of illustration. 
     FIGS. 7A and 7B provide a comparison of the existing pilot passage complexity (FIG. 7A) relative to that achieved with the present invention (FIG.  7 B). 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings wherein the showings illustrate the preferred embodiment of the invention and are not intended to limit the invention, the Figures show a modulator valve A that employs non flow-through solenoids to decrease complexity and reduce manufacturing costs associated therewith. More particularly, and turning first to FIGS. 1-4, a brief review of an existing, prior art arrangement of an ABS modulator is shown and described below. The modulator is a three-way valve including a valve body B having a first or supply port  10  that communicates with a source of pressurized air through a brake valve BV. The modulator includes a second or delivery or brake port  12  that communicates with the brake chamber BC of the brake actuators. In addition, a third or exhaust port  14  is provided for exhausting pressurized air to atmosphere. 
     As shown in FIG. 1, the supply port communicates through passage  16  with a first or supply diaphragm  20 . The supply diaphragm is normally biased via a spring  22  toward a closed position with valve seat  24 . This prevents communication between the supply port  10  and the delivery port  12 . As shown in FIG. 2, when the brake valve is open and provides pressurized air to the supply port  10 , the closing bias of the spring  22  is overcome and the supply diaphragm is moved away from the valve seat  24  to provide pressurized air to the delivery port. This allows application of the brakes during what is referred to as normal service braking. 
     In addition, an exhaust diaphragm  30  is urged by spring  32  toward a closed position against valve seat  34 . This prevents communication of the pressurized air that enters the modulator past valve seat  24  to the delivery port with an exhaust passage  36  that leads to the exhaust port  14 . Thus as shown in FIGS. 1 and 2, the exhaust diaphragm is disposed in a closed position. As will also be recognized, when the supply diaphragm is moved away from the valve seat  24  during a service brake application, pressurized air is also provided through pilot passage  38  to a first or exhaust solenoid valve  40 . Particularly, the passage  38  communicates with a pusher member  42 , particularly a first end  44 , of the solenoid valve. As shown in FIGS. 1 and 2, the pusher member  42  is biased or urged by spring  46  toward a normally open position allowing communication between passage  38  and passage  50  that communicates with the exhaust diaphragm  30 . Alternatively, when coil  48  of the solenoid valve is energized, the pusher member is urged toward a closed position preventing communication between flow passages  38 ,  50 . When the brakes are applied during normal service application, pressurized air from pilot passage  38  communicates through the first solenoid  40 , through the passage  50  and, along with the spring  32 , urges the exhaust diaphragm toward a closed position. This provides a pressure assist to urge the diaphragm valve toward a closed position during normal service brake application. 
     As will be further recognized from FIGS. 1 and 2, passage  38  also communicates with a second or supply solenoid valve assembly  60  and supply passage  16 . A pusher member  62  of the second solenoid is urged by spring  64  toward a normally closed position against valve seat  66 . That is, the flow passage  38  and supply passage  16  cannot communicate with the opposite face of the diaphragm  20  unless the coil  68  moves the pusher member against the force imposed by the spring. Instead, a pilot passage  70  connects the supply diaphragm with the exhaust port through the second solenoid valve assembly  60 , and through passage  72 . 
     Although not particularly shown, it will be understood that a rapid exhaust is provided when the exhaust diaphragm  30  is urged away from its seat  34  and the brake port  12  is in communication with the exhaust port  14 . In that arrangement, the brake actuators are quickly released as the pressure exits the brake chamber through the exhaust passage  36  to port  14 . 
     FIGS. 3 and 4 represent the same modulator valve structure as referenced with respect FIGS. 1 and 2, and will be briefly described herein to provide an indication of the ADS operation. As indicated above, the first or exhaust solenoid valve  40  is urged toward a normally open position. The second or supply solenoid valve  60  is urged toward a normally closed position. In response to an antilock braking event, the coils  48 ,  68 , associated with the first and second solenoid valve assemblies  40 ,  60 , respectively, are selectively energized to urge the respective pusher members  42 ,  62  to overcome the bias of the springs. Thus as shown in FIG. 3, the second solenoid valve  60  is energized. This provides communication between pilot passage  38  and passage  16  and passage  72 , moving the diaphragm  20  to a closed position so that a constant air pressure is provided to the delivery port  12 . 
     FIG. 4 illustrates the energization of the first solenoid assembly (while the second solenoid valve assembly also remains energized) which closes off communication between passage  38  and passage  50 . In this manner, the exhaust diaphragm  30  is urged away from its valve seat  34  thus allowing the delivery port  12  to communicate with the exhaust port  14 . 
     Although the prior flow-through solenoid arrangement has met with substantial commercial success, the arrangement has complex passages formed in the modulator valve body. The present invention, schematically represented in FIG.  5  and structurally illustrated in FIG. 6, still achieves all of the benefits of the ABS brake operation while using non flow-through solenoids with simplified passages and a shortened exhaust cover arrangement. 
     Turning first to FIG. 5, the modified modulator valve employing non flow-through valve assemblies will be described in greater detail. For purposes of comparison and brevity, like numerals with a prefix of  100  added thereto will be used to identify like elements (e.g., service port  10  will be identified as service port  110  in the modified modulator). Again, the supply or a service port  110  selectively communicates with the delivery port  112  and an exhaust port  114 . More particularly, the service port  110  communicates through passage  116  with the supply diaphragm  120  that is normally biased toward a valve seat  124 . Upon supply of pressurized air through the passage  116 , the diaphragm is moved away from its seat to establish communication between the service port  110  and the delivery port  112 . In addition, the second or exhaust diaphragm  130  is normally urged toward its associated seat  134 . Pressurized air from port  110  flows through passage  138  to a first or brake solenoid valve assembly  140 . It includes a coil  148  that controls movement of a pusher member  142 . In the arrangement shown, a ball or check member  180  is associated with the solenoid assembly and urged toward a closed position by spring  146 . This provides a normally open communication between passage  138  and  150  that extends to one side of the exhaust diaphragm  130 . When energized, the coil  148  urges the pusher member  142  toward a second position (downwardly as shown in FIG. 5) pushing the ball member  180  against the bias of the spring  146  to engage seat  182 . This prevents fluid communication between passages  138  and  150 . As detailed above, this occurs in response to an antilock braking event where a pulsing operation is provided to the brakes. 
     The second or supply solenoid valve assembly  160  is in constant and direct communication with the service port  110 . A ball member  184  is urged by spring  166  toward a normally closed position to prevent fluid communication between passage  138  and the supply diaphragm  120 . Once the coil  168  is energized, however, the pusher member  162  urges the ball member  184 , overcoming the bias of the spring, to allow pressurized air from passage  138  therepast and urge the supply diaphragm toward a closed position. At the same time, the supply diaphragm is then shut off from the exhaust passage  136  and exhaust port  114  via passage  170  when the ball  184  engages the valve seat  186 . 
     As is evident from FIG. 5, and additionally illustrated in FIG. 6, the solenoid assemblies  140 ,  160  are non-flow through solenoids. That is, only one end of the solenoid valve assemblies are in communication with the fluid circuit or flow passages. This eliminates complex pilot passages associated with the second ends of the solenoid valve assemblies (compare FIGS.  1 - 4 ). As more particularly illustrated in FIG. 6, the valve body  190  is machined to accommodate the various flow passages, diaphragms, and pilot passages formed therein. The cover  192 , which now houses the solenoid valve assemblies  140 ,  160 , is greatly simplified and secured to the valve body with a bracket (not shown). Since only one end of each solenoid valve is in communication with the flow circuit, the cover  192  is machined with blind ends or closed end passages to receive the solenoid valve assemblies therein. The open ends of the respective passages that receive the non-flow through solenoid valves are then sealed to an external surface of the valve body. 
     Pressurized air does not pass through the solenoids as in the prior arrangement of FIGS. 1-4. Nevertheless, the service braking in antilock brake operations as described above remains unaffected. In fact, as graphically represented in FIGS. 7A and 7B, the pilot passages associated with the prior arrangement and the modified modulator valve assembly are drastically different. In FIG. 7A, four enlarged passages are required in the modulator valve. Three are provided in the body, namely, passages  194 , and a fourth passage  196  is provided in the exhaust cover. In the modified arrangement of FIG. 7B, only two pilot passages  198  are required. No pilot passages are required in the cover. Thus, substantially smaller diameter passages, and a reduced number of passages are achieved in the modified modulator of the present invention. 
     Moreover, the prior electromagnetic actuation of the solenoid valves is modified to a reliable electromagnetic actuation with a mechanical linkage  200 ,  202  which is an extension of the pusher members  142 ,  162  beyond the armature of the solenoid valves. The linkages engage the ball members  180 ,  184 , as described above. 
     In addition, the new arrangement eliminates the valve seat being formed on the pusher member of the solenoids. As is apparent, separate valve seats  182 ,  186  are provided in the non flow-through arrangement described above. 
     The invention has been described with reference to the preferred embodiment. Obviously, modifications and alterations will occur to others upon a reading and understanding of this specification. It is intended to include all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.