Proportional solenoid valve

Abstract: An electromechanical valve apparatus has an electrical winding (54) and a magnetic flux circuit defining a flux path therefor which includes a plurality of adjacent magnetic segments. The segments include a generally cylindrical center segment (31-36) with a fluid passage (52), an end segment (31), an outer segment (44) and a magnetic armature member (82). At least one of the segments is physically translatable within the valve apparatus along the flux path to adjust a portion of one of the magnetic segments that is in the flux path and the extent of an air gap adjacent the translatable segment. The apparatus includes a non-magnetic seat member (44) which is located near or at the point of highest flux density along the longitudinal axis through the electrical winding (54). The armature (82) is preferably an elongated member with its closed end located within the electrical winding near the non-magnetic seat member (44). The seat member (44) and armature (82) are enclosed within a chamber defining body (58) such as the bobbin (56). In an alternative embodiment, a flat disc member (98) is located at the base of the armature (82). The flat disc is retained within the base (88a) of the armature (82a). When no current is flowing in the winding (54), the flat disc member (98) rests against an armature seat (96a) formed in the chamber defining body (58) and prevents leakage of air from the fluid chamber (94). A further alternative embodiment allows ready calibration of the valve apparatus via a calibration fixture adopted to translate one of the magnetic segments within the flux path.

Description: The present invention relates to electromechanical valve apparatus. A variety of electromechanical valve apparatus employing solenoid valves have been developed in which electromagnetics are utilized in an attempt to control either hydraulic or pneumatic flow. Typically, such valves attempt to regulate the flow of fluid in an on-off fashion. Where modulation is desired, two valves are frequently used in a timed, alternating operation to provide an output which is a function of the timing and the two inputs. This same type of modulation has also been accomplished with a single device where the armature of the valve actuates between two oppositely disposed seats to permit a mixture of fluid at atmospheric pressure and fluid at a higher or lower pressure. In such a valve, a large mass iron armature is spring-biased against a first seat and utilized to prevent fluid flow through the seat. When in this position, fluid at atmospheric pressure is allowed to enter the valve through a second seat. At appropriate times, current is supplied to an electromagnetic winding and the spring force against the armature is overcome by the magnetic flux and the armature traverses an air gap until it contacts the second seat, located on the opposite side of the valve. When the armature contacts the second seat, fluid at atmospheric pressure is prevented from entering the valve through the second seat. Fluid at either a high pressure (above atmospheric) or a vacuum (below atmospheric) source is permitted to enter the valve through the first seat. At a later time in the cycle, the current is reduced in the winding and the solenoid is de-energized, allowing the spring force to overcome any hysteresis effects on the armature and cause the armature to travel back across the air gap to the first seat. This prevents flow from the high pressure fluid source or the vacuum fluid source through the first seat and allows fluid at atmospheric pressure to enter the valve through the second seat. In this on-off fashion, the armature alternatively and periodically allows fluid to enter the valve through the first seat and the second seat. By applying a controlled duty cycle to alternately open and close the inlets through the first and second seats, the valve attempts to provide the approximation of a desired outlet pressure. Such valves, however, are not able to provide adequate speed or control of the output pressure through this on-off electronic adjustability and fail to provide a linear relationship between the current input to the winding and the differential pressure output from the valve. Such systems often require feed-back or closed loop operation. Some of these prior art valves utilize complex assemblies that operate in conjunction with ball valves. Other types of these prior art valves utilize flapper-type valves that attempt to balance the electromagnetics against fluid blast or fluid flow. Many of the disadvantages and complexities of these prior art solenoid valves were eliminated with the development of the proportional solenoid valves of US-A-4534375 and US-A-4715396. In the aforementioned US-A-4715396 there is generally disclosed an electromechanical valve apparatus comprising an electrical winding having an axial length; a magnetic flux circuit for the winding defining a flux path comprising a plurality of adjacent magnetic segments, including a generally cylindrical centre segment which defines a fluid passage, an outer segment and an end segment adjacent a first end of the fluid passage; annular non-magnetic seat means having a central opening aligned with and disposed near the other end of the fluid passage; at least one of the segments being physically translatable within the valve apparatus along the flux path to adjust a portion of one of the segments in the flux path and to adjust the extent of an air gap adjacent the translatable segment; magnetic closure means comprising one of the segments and positioned adjacent the non-magnetic seat means, the closure means completing the flux path such that fluid flow urged by a predetermined pressure difference through the fluid passage and the seat means central opening can be modulated by varying the energization level of the electrical winding; and means defining a chamber having a cylindrical portion adjacent the seat means to enclose the magnetic closure means and to constrain the motion of the magnetic closure means substantially parallel to said axial length, the magnetic closure means being movable between a position against the seat means and a position displaced therefrom. More particularly, the development of the aforementioned proportional solenoid valves provided a mechanism for modulating the differential pressure in a chamber by varying the energization level of the electrical winding in an electromagnetic assembly between a vacuum source and ambient. This valve included a restriction in the fluid conduit between the vacuum source and the differential pressure chamber. Such a restriction substantially reduced the fluid flow required for actuation. The large mass armature of the prior art valves was replaced by a low-mass armature which provided quick response and resulted in proportional control and a near linear relationship between current input to the electrical winding and output differential pressure. In the proportional solenoid valve development the adjustment of the centre segment in the magnetic flux circuit allowed a variation of the set point of the current versus differential pressure curve. The result was greatly improved control over the current versus differential pressure relationship. It also generally eliminated any requirement of feed-back or closed loop operation for calibration. It is an object of the present invention to provide an electromechanical valve apparatus which better utilizes the efficiencies associated with the region of highest flux density of the flux circuit and which can be readily calibrated after manufacture to supply a specific pressure output given a specific pressure input and control current. In accordance with the present invention as claimed this object is accomplished in that the aforementioned generally disclosed electromechanical valve apparatus is characterized in that the generally cylindrical centre segment extends only over a portion of the axial length of the electrical winding, the non-magnetic seat means has its central opening aligned with and disposed near the other end of the fluid passage within said axial length, and said one segment comprising the magnetic closure means is partially within and movable along said axial length, and in that the physically translatable segment is the outer segment which is physically translatable within the valve apparatus along the flux path to adjust said portion of that outer segment in the flux path and to adjust the extent of the air gap adjacent the outer segment. A valve apparatus constructed in accordance with the present invention provides a solenoid valve having quick response and repeatability by locating the non-magnetic seat means nearer to the point of highest flux density but between the point of highest flux density and the magnetic closure means. The term "physically translatable" as used herein means any adjustment, rotation, translation, motion or alteration of motion. The term "air gap" in this context may include any non-magnetic gap in the flux path comprising air, non-magnetic solids or a combination thereof. The non-magnetic seat means is preferably located substantially near the centre of the vertical or longitudinal axis through the center of a bobbin or other support for the electrical winding. The magnetic closure means which is positioned adjacent the non-magnetic seat means is effectively displaced from the location of maximum flux and from the centre segment. An opening is preferably provided by the seat means and closure means which communicates with a differential pressure chamber such that a predetermined pressure difference in the chamber can be modulated by varying the energization level of the electrical winding. Translation of the portion of the outer segment along the flux path is effective to vary the reluctance of the flux path and an auxiliary air gap distance, to correspondingly adjust the response of the valve apparatus for a given energization level of the electrical winding to provide a given pressure difference. This is an adjustment normally made at the time of manufacture, thus eliminating need for subsequent calibration or closed loop operation. The apparatus of this invention may also include a chamber which encloses or is partially defined by the non-magnetic seat means and at least a portion of the magnetic closure means, or armature. The chamber is preferably defined, at least in part, by a wall which is cylindrical and constrains the motion of the armature substantially parallel to the longitudinal axis of the flux source and preferably includes a bobbin which supports the electrical winding. The armature is preferably a low mass elongated member. The armature includes a flat end portion and an elongated wall portion which terminates in a base portion. Notches are formed in the wall member, near the base, to permit fluid flow through the base of the armature. Another embodiment of the valve apparatus includes a flat disc member at the base of the armature. The flat disc member is retained within the armature by a series of indentations. When no current is flowing in the winding, the flat disc member rests against an armature seat and prevents leakage of air into or out of the differential pressure chamber. In another embodiment, an orifice restriction is located within the armature seat. In another embodiment, the armature may be configured to have its end portion contact the armature seat and prevent flow between the vacuum source and the differential pressure chamber. The utilization of an elongated armature with a flat disc member at its base, or a flat portion, to contact the opening to the vacuum source, provides a more efficient valve with a zero bias, that is, the substantial elimination of leakage of fluid from the vacuum source when the valve is without current in the electric winding of the solenoid. Such a zero bias proportional solenoid valve provides a new approach to proportional solenoid valves. As the outer segment defines a portion of the magnetic flux circuit, translation of the movable-portion of the outer segment to vary the auxiliary air gap is effective to vary the permeability of the auxiliary air gap and so vary the magnetic flux circuit. Therefore, translation of the movable portion of the outer segment can be used to change the electromagnetic characteristics of the valve apparatus and allow ready adjustment of the response of the valve apparatus for a given energization level of the electrical winding to provide a given pressure difference. This embodiment is also readily coupled to a closed-loop calibration device to allow precise and automated adjustment of the valve apparatus set point via the mechanical translation of the movable portion of the outer segment. In order that the present invention may be well understood the various embodiments thereof, which are given by way of example, will now be described in more detail and with reference to the accompanying drawings, in which: Fig. 1 is a side elevation view of a proportional solenoid valve not embodying the present invention; Fig. 2 is a top plan view of the same proportional solenoid valve; Fig. 3 is a side sectional view taken along the line 3-3 of Fig. 2, which shows the magnetic flux circuit; Fig. 4 is an exploded perspective view of several elements of the same flux circuit; Fig. 5 is a sectional view taken along line 5-5 of Fig. 4; Fig. 6 is a side elevation view of the inner portions of the same solenoid valve; Fig. 7 is a top plan view of the valve portion shown in Fig. 6; Fig. 8 is a side elevation view of an alternative proportional solenoid valve also not embodying the present invention, having a flat disc member at the base of the armature; Fig. 9 is an exploded perspective view of several elements of the magnetic flux circuit of the embodiment of Fig. 8; Fig. 10 is a sectional view taken along line 10-10 of Fig. 9 with a portion broken away; Fig. 11 is a side elevation view of another alternative proportional solenoid valve also not embodying the present invention, having the end portion of the armature structured to contact the armature seat; Fig. 12 graphically illustrates a plot of empirical data for pressure differential as a function of current; Fig. 13 is a side elevation view of an embodiment of the proportional solenoid valve of the present invention provided with a translatable adjustment plate for precise calibration of the apparatus after assembly; Fig. 14 is a sectional view of the apparatus shown in Fig. 13 along the line 14-14 detailing the translatable adjustment plate for precise calibration; Fig. 15 is a sectional view of the apparatus shown in Fig. 14 along the line 15-15 showing the interior components thereof; Fig. 16 is a sectional view of the apparatus of Fig. 14 along the line 16-16 detailing the translatable adjustment plate for precise calibration; Fig. 17 is a perspective view of the translatable adjustment plate, the outer member or mounting bracket forming a segment of the magnetic flux circuit, and a portion of the calibration fixture for precise calibration; and, Fig. 18 is a simplified block diagram of the same calibration fixture. Referring first to Figures 1 and 2, an electromechanical valve apparatus 10 has a top port 12 for the inlet of fluid at atmospheric pressure to the valve, and a port 14 for the application of fluid from or to a vacuum (below atmospheric pressure) source. An Outlet port 16 provides a means for accessing the differential pressure inside the valve apparatus. The means for accessing pressure can be utilized to operate a vacuum motor or a diaphragm operated assembly or any other type of pressure responsive device. The electromechanical valve apparatus, as shown in more detail in Figure 3, includes a plurality of adjacent magnetic segments which act to define a magnetic flux circuit with a flux path. The segments include an iron outer member or mounting bracket 18, having two end sections which are preferably a top section 20 and a bottom section 22. Also in the flux circuit is a generally cylindrically centre member 24. The centre member has a hollow passageway to define a fluid passage 26 with an inlet port 28 and an output port 30. The centre member is of iron or other ferromagnetic material. The centre member is shown in more detail in Figure 4. The centre member is formed of a plurality of cylindrical portions or sections 31, 32, 33, 34, 35, 36. The inner portions 32, 33, 34, 35 are preferably connected in a stepped or tapered relationship. The first end portion or top portion 31 of the centre member is also cylindrical and includes a slot 38 running across its midsection. The slot 38 extends from the upper surface 40 of the top portion 31 to the upper surface 42 of the inner section 32. This slot serves to allow greater flow of fluid into the centre member of the valve. The second end portion or bottom portion 36 of the centre member is also of cylindrical construction and is preferably of a diameter sufficient to allow sliding along a vertical axis within the inside of a round non-magnetic seat member 44. The centre member contains ribs 47, 48 and the non-magnetic seat member contains ribs 49 to allow an interference fit within the valve assembly. The non-magnetic seat 44 includes a lower face 50 and an upper face 51. The seat 44 also includes a passageway or aperture 52 through its centre. The bottom portion 36 of the centre member slides along a vertical axis within this passageway 52 of the non-magnetic seat 44. An electrical winding 54, shown more clearly in Figure 6, is mounted about the centre member 24 and the non-magnetic seat 44. The seat is preferably located near the centre of the vertical axis of the winding. The winding 54 is encased on its upper, lower and inner diameter surfaces in a bobbin 56 which is generally of plastic, or non-magnetic material. The bobbin forms a cylindrical chamber 58 which is utilized to contain the centre member 24 and the non-magnetic seat 44. The centre member 24 is adjustable or translatable along the vertical axis of the winding to abut the upper face 51 of the non-magnetic seat or to move to a position above the non-magnetic seat. The electric winding is connected to a pair of terminals 60, 62, shown in Figure 7. The terminals are connected to a suitable power supply which can supply an electric current to the winding 54. The power supply can be a direct current source, a square wave generator, a variable resistor, a pulse width modulation circuit, or an automobile on-board computer functioning as a signal source. The terminals 60, 62 and bobbin 56 are maintained in operative relationship by a housing 64. The housing 64, preferably formed of plastic, provides a structural support for the bobbin and centre member above the bobbin. The housing has a lateral portion 66 which extends around the outer member 18 and forms a support and covering for the outer member. The housing also has a base portion 68 into which two conduits are formed. A first fluid conduit 70 ends in the port 16. The second fluid conduit 72 ends in the port 14. The two conduits 70, 72 intersect in a fluid chamber 74. A restriction or orifice 75 is provided in the second conduit 72. The restriction 75 is located near the port 14 and acts to limit the fluid flow within the valve assembly. The restriction is of a cross sectional area which is substantially smaller than the cross sectional area of the fluid passage 26 through the centre member 24. Above the centre member 24 is a filter 76 which fits around the top portion 31 of the centre member. The filter acts to prevent materials from improperly entering the valve apparatus. Above the filter is a cap 78 which is removable from the housing 64 to allow adjustment of the inside pieces of the valve. A clip 80 is also formed in the housing 64 to permit mounting or other retention of the valve apparatus. Beneath the non-magnetic seat is a magnetic closure member or armature member 82. As shown in Figures 4 and 5, the armature is preferably an elongated cup member having a flat top or end portion 84 and a wall member 86. The wall member depends from the end portion 84 to a base portion 88. Notches 90 are provided in the wall member near the base 88 to form a plurality of legs 92. In the preferred embodiment, the armature has four legs. The wall member defines a hollow inner portion of the armature. This hollow inner portion provides a fluid chamber or differential pressure chamber 74, which is shown in Figure 8. The differential pressure chamber is operatively connected to the first and second fluid conduits 70, 72, to allow fluid flow. The armature rests or seats against an armature seat member 96. The armature seat member 96 is integrally formed in the base portion 68 of the housing. The use of an elongated armature member eliminates the need for a spring member to keep the armature in an operating position, as required in prior art solenoid valves. Generally, the seat 44 is of a soft material such as brass and the armature is of a harder material such as iron or steel such that the combination of a soft material touching a harder material produces a superior seal. The seat may also be of a hard material such as non-magnetic stainless steel or plastic. An alternative embodiment of the armature is shown in Figures 8, 9 and 10. In this embodiment, the armature member 82a includes a flat disc member 98. The flat disc member is retained within the base portion 88a of the armature 82a by a plurality of indentations 100, 102 along the base portion of the armature. The flat disc member is annular in shape and is retained within the indentations in a secure, but non-tight fit. In the alternative embodiment, the restriction or orifice 75a of the second conduit is placed immediately below the base portion of the armature 82a. In this location, the orifice 75a serves as an armature seat member 96a. The seal between the flat disc member 98 and the orifice 75a is sufficient to prevent leakage of fluid from the second conduit member into the fluid chamber 94 when the armature is in the rest position against the armature seat 96a. Another alternative embodiment of the valve is shown in Figure 11. In this embodiment, the armature member 82b is shortened in length. The armature preferably extends at least beyond the end of the outer member in order to complete the magnetic flux circuit. Notches in the base of the armature member are not necessary in this embodiment. In this embodiment, the flat disc member is eliminated. In its place, the restriction or orifice 75b is extended within the armature 82b. This places the armature seat member 96b within the inside of the armature member 82b. The seal between the end portion 84 of the armature 82b and the orifice 75b is sufficient to prevent leakage of fluid from the second conduit member into the fluid chamber when the armature is in the rest position against the armature seat 96b. The prevention of leakage provides the zero bias feature of the present invention. The extension of the armature seat into the armature need not include the orifice. That is, the armature seat can be extended while the orifice is maintained at a location near the port 14. In all three embodiments, the flat top portion 84 of the armature 82 acts against the opening in the lower face 50 of the non-magnetic seat member 44. The armature acts at various positions between and including a fully closed position, in which the armature is seated against the non-magnetic seat 44, and a fully open position, in which the armature 82 is at its lowest possible position in the cylindrical chamber 58 and resting against the armature seat 96. The opening of the armature by its movement in the vertically downward direction allows fluid flow through the fluid passage 26 and non-magnetic seat 44 and around the outside of the wall member 86 of the armature through cylindrical chamber 58 and into the fluid chamber 74. The downward movement of the armature thus creates a fluid opening defined between the lower face 50 of the non-magnetic seat and the flat top portion 84 of the armature. Fluid in the fluid chamber 74 is accessed by the first and second conduits 70, 72. The cross sectional diameter of the fluid passage 26 is preferably on the order of 0.254cm (0.100 inch). The cross sectional inner diameter of the non-magnetic seat member is preferably on the order of 0.508cm (0.200 inch). These diameters are substantially larger than the cross sectional diameter of the orifice 75 which is preferably on the order of 0.508cm (0.020 inch). As described above, the non-magnetic seat member 44 is preferably located near the centre of the vertical axis of the electric winding 54 which is near the point of highest flux density of the winding. The armature is therefore also located near this same point of high flux density. The wall portion of the armature preferably extends down from this centre point in order to complete the flux circuit. That length is at least to the point of the bottom 22 of the outer member 18. The centre member 24 is slidable within the cylindrical chamber 58. Translation of the centre member in the vertical direction is effective to alter the distance of an air gap between the underside of the bottom portion 36 of the centre member and the top flat portion 84 of the armature. Alteration of this air gap distance changes the reluctance of the magnetic flux circuit of the centre member, armature and outer member and is useful to accomplish the calibration of the apparatus. The centre member can be retained in its final translated position by the ribs 47 and 48 which are in an interference fit with the inside of the bobbin 56. Access to the centre member is possible through the removable cap 78. Once the proper location of the centre member is attained, the centre member may be secured in place by any means known in the art such as welding or the use of an encapsulate. In operation, the magnetic closure member or armature 82 is rapidly responsive to an induced magnetic flux from a current passed through the electrical winding. A magnetic flux is produced by the winding in the magnetic flux circuit of the centre member, armature, outer member, and the air gap between the armature and the centre member. When a current is passed through the winding, the armature 82 is drawn toward the seat 44. When the current is interrupted, the armature falls, by gravity and the force of the fluid through the centre member, towards the armature seat 96. When a pressure lower than atmosphere (i.e., a vacuum) is imposed at the port 14, the vacuum condition is communicated to the fluid chamber 74 through the orifice restriction 75 and the fluid conduit 72. A differential pressure is created in the fluid chamber 74 by the flow of fluid at atmospheric pressure in through the centre member inlet port 28, the fluid passage 26 and out through the centre member output port 30. The fluid continues through the passageway 52 in the non-magnetic seat 44, the fluid opening created between the seat 44 and the armature 82, and along the outside of the wall member of the armature in the cylindrical chamber 58 through the notches 90 of the armature and into the fluid chamber 74. The different pressure in the fluid chamber is accessed through the fluid conduit 70 and the port 16. The pressure differential in the fluid chamber 74 is altered by movement of the armature in response to varying the energization level of the current in the electrical winding. This armature movement changes the amount of communication of fluid at atmospheric pressure with the fluid chamber. Energization of the electrical winding attracts the armature toward the centre member, overcoming the forces of gravity and the fluid flow through the fluid opening in the seat. The upward movement of the armature is limited by the non-magnetic seat. An empirical illustration of the change of the pressure differential (vacuum in inches of mercury) as a function of the current in milliamperes is shown in Figure 12. This data is only representative of a sample plot with one embodiment of the solenoid valve and is not intended to demonstrate any particular results other than the generally expected behaviour of the valve. Translation of the centre member of the valve apparatus along the flux path alters the portion of the centre segment that is in the flux path. Such translation also varies the air gap distance between the armature and the centre member and therefore alters the reluctance of the flux circuit. The centre member is thus translated along the vertical axis to find the appropriate set point for operation of the valve. Once this set point is found, the centre member is fixed in that position and the valve is operated along the current versus pressure differential curve for that set point. In operation, the armature moves vertically within the chamber formed by the bobbin. The flow of fluid around the outside of the wall member of the armature serves as a sleeve for the travel of the armature. The utilization of the flow restriction or orifice 75 results in the low flow characteristics of the valve and a limitation of movement of the armature to provide changes in the differential pressure in the fluid chamber. Utilization of the flat disc member 98 at the base of the armature against an armature seat 96 prevents leakage of fluid from the vacuum source into the chamber when the armature is in the rest position against the armature seat and the current is removed. This provides the zero bias characteristics of the present valve, that is, the zero output pressure differential at a condition of zero current. This relationship is shown in the graph of Figure 11. Moreover, location of the orifice 75a at the point of the armature seat 96 below the flat disc member 98 reduces the hysteresis effects. This is a result of the smaller fluid conduit at that point. The location of the seat member 44 at or near the point of highest flux density within the electrical winding provides greater control and repeatability of the pressure differential versus current characteristics of the present valve. Providing the air gap between the armature and the centre member at or near this point of highest flux density provides a more efficient and responsive valve. This also allows the use of a lower mass armature. However, the wall portion of the armature must be of appropriate length so that the armature remains in the flux path for all operating positions of the armature; that is, the armature wall portion must extend at least to the bottom of the outer member for all operating positions of the armature. The valve is manufactured by assembling the magnetic segments to form a magnetic flux circuit. The armature is first inserted into the valve from the top and allowed to rest against the armature seat on the base of the housing. The non-magnetic seat 44 is then driven into the centre of the chamber defined by the bobbin. The non-magnetic seat is preferably located as near as possible to the midpoint of the longitudinal axis running through the centre of the electrical winding, i.e., the point of highest flux density. Ribs along the seat provide the interference fit necessary to hold the seat in position. The centre member is then driven into the centre of the valve and above the seat. A current is applied to the winding and a vacuum source is connected to the vacuum source port 14. The differential pressure in the fluid chamber is accessed and measured through the port 16. The centre member is driven further into the valve centre and measurements taken until the proper set point of output differential pressure for a given vacuum pressure is reached. At that point, the location of the centre member is further secured by welding or other appropriate means and the remainder of the valve is assembled with the filter and cap placed on the top of the centre member. Shown in Fig. 13 is an alternative electromechanical valve apparatus shown generally at 110 and which is constructed in accordance with the invention. The valve apparatus 110 has a top port 112, best viewed in Fig. 14, for the inlet of fluid at atmospheric pressure to the valve, and a port 114 for the application of fluid from or to a vacuum (below atmospheric pressure) source. An Outlet port 116 provides a means for accessing the differential pressure inside the valve apparatus 110. As noted above, the means for accessing pressure can be utilized to operate a vacuum motor or a diaphragm operated assembly or any other type of pressure responsive device. The electromechanical valve apparatus 110, as shown in more detail in Figures 14, 15, and 16, also includes a plurality of adjacent magnetic segments which act to define a magnetic flux circuit with a flux path. The segments include an iron outer member or mounting bracket 118, having a middle section 119 oriented substantially parallel to the axis of the valve apparatus and two end sections which include preferably a top section 120 and a bottom section 122. The outer member is further comprised of a translatable adjustment plate 123. Also in the flux circuit is a generally cylindrical centre member 124. The centre member 124 has a hollow passageway to define a fluid passage 126 with an inlet port 128 and an output port 130. The centre member 124 is constructed of iron or other ferromagnetic material and is provided with a notch 132 that receives an "O" ring 134 of well known construction to provide sealing. At the bottom of the centre member 124 is mounted a non-magnetic valve seat 136. An electrical winding 154 is mounted about the centre member 124. The non-magnetic valve seat 136 is preferably located near the centre of the vertical axis of the winding 154. The winding 154 is encased on its upper, lower and inner diameter surfaces in a bobbin 156, which is generally constructed of plastic or some other non-magnetic material. The bobbin 156 forms a cylindrical chamber 158 which is utilized to constrain the centre member 124. The centre member 124, in contrast to other embodiments, is not the sole adjustable segment within the magnetic flux circuit, although it may be translatable along the vertical axis of the winding 154 to allow modifications of the permeability of the primary air gap. The electric winding 154 is connected to a pair of terminals 160, 162, shown in Figures 13 and 15. The terminals 160, 162 are connected to a suitable power supply which can supply an electric current to the winding 154. As noted above, the power supply can be a direct current source, a square wave generator, a variable resistor, a pulse width modulation circuit, or an automobile on-board computer functioning as a signal source. The terminals 160, 162 and the bobbin 156 are maintained in operative relationship by a housing 164. The housing 164, preferably formed of plastic, provides a structural support for the bobbin 156 and the centre member 124 above the bobbin 156. The housing 164 has a lateral portion 166 which extends around the outer member 118 and forms a support and covering for the outer member 118. The housing 164 also has a base portion 168 into which two conduits are formed. A first fluid conduit 170 begins at an orifice 173 and ends in the port 114. The second fluid conduit 172 ends at the port 116. The two conduits 170, 172 intersect in a fluid chamber 174. The orifice 173 has an inner diameter of about 0.508cm (0.020 inch) so as to limit the fluid flow within the valve assembly 110. The restriction of the orifice 173 is of a cross sectional area which is substantially smaller than the cross sectional area of the fluid passage 126 through the centre member 124. Above the centre member 124 is a filter 176 which fits around the top portion of the centre member 124. The filter acts to prevent materials from improperly entering the valve apparatus 110. Above the filter 176 is a cap 178 which is removable from the housing 164. A clip 180 is also formed in the housing 164 to permit mounting or other retention of the valve apparatus 110. Located beneath the non-magnetic valve seat 136 is a magnetic closure member or armature member 182. The armature 182 can be of similar construction to the armature 82 shown in Figures 4 and 5, or the alternative armature embodiments 82a and 82b shown in the Figures 8, 9, 10, and 11. As can be seen in Figures 14 and 15, a flat top portion 184 of the armature 182 acts against an opening in the non-magnetic valve seat 136. The armature 182 acts at various positions between and including a fully closed position, in which the armature 182 is seated against the non-magnetic valve seat 136, and a fully open position, in which the armature 182 is at its lowest possible position in the cylindrical chamber 158 and resting against the armature seat 196. The opening of the armature 182 by its movement in the vertically downward direction allows fluid flow through the fluid passage 126 and non-magnetic valve seat 136 and around the outside of the wall member 186 of the armature 182 through the cylindrical chamber 158 and into the fluid chamber 174. The downward movement of the armature thus creates a fluid opening defined between the lower face of the non-magnetic valve seat 136 and the flat top portion 184 of the armature 182. Fluid in the fluid chamber 174 is accessed by the first and second conduits 170, 172. The cross sectional diameter of the fluid passage 126 is preferably on the order of 0.254cm (0.100 inch). The cross sectional inner diameter of the non-magnetic valve seat 136 is preferably on the order of 0.508cm (0.200 inch). These diameters are substantially larger than the cross sectional diameter of the orifice 173 which is preferably on the order of 0.508cm (0.020 inch). As described above, the non-magnetic valve seat 136 is preferably located near the centre of the vertical axis of the electric winding 154, which is at or near the point of the highest flux density of the winding 154. The armature 182 is therefore also located near this same point of high flux density. The wall portion 186 of the armature 182 preferably extends down from this centre point in order to complete the flux circuit. That length is preferably at least to the point of the bottom portion 122 of the outer member 118. The position of the bottom of the centre member 124, the non-magnetic valve seat 136, and upper position of the armature 182 define a primary air gap (or the substantial absence of a magnetically permeable material). Adjustment of this air gap alters, in part, the reluctance of the magnetic flux circuit of the centre member 124, the armature 182 and the outer member 118. The centre member 124, once placed in the determined position, is retained in position by an interference fit with the inside of the bobbin 156 and the outside of the centre member 124. An auxiliary gap is provided by the configuration of the outer member 118. The outer member 118 forms, in a plane parallel to the axis of the apparatus 110 and within the magnetic flux circuit, a generally rectangular segment 119, best viewed in Figure 17. Near the centre of the segment 119, ferromagnetic material is removed from the segment 119, forming a bar 121. The bar 121 provides structural support for the outer member 118 and maintains the top portion 120 and the bottom portion 122 in a fixed relation. The translatable adjustment plate 123, located adjacent the outer member 118, is provided with a rack of drive teeth 129 on at least one edge and is held in position within a cavity 131 moulded in the housing 164 by retainers 133, as best seen in Figure 16. The translatable adjustment plate 123 is initially pressed into the cavity 131 until it is positioned adjacent the segment 119 of the outer member 118. A generally cylindrical adjustment cavity 137 is located to the side of the cavity 131 and receives a non-magnetic adjustment drive gear 202. Although the translatable adjustment plate 123 is generally immobile, it can be translated in a path parallel to the axis of the valve apparatus 110 by an external force, such as a torque applied through the non-magnetic adjustment drive gear 202 engaging the rack of drive teeth 129 on the translatable adjustment plate 123, by shearing the softer material of the housing 164 in its path. The resulting adjustable air gap between the main portion of the segment 119 and the translatable adjustment plate 123 thus form an auxiliary air gap establishing, in remaining part, the reluctance of the magnetic flux circuit of the centre member 124, the armature 182 and the outer member 118. In operation, the magnetic closure member or armature 182 is rapidly responsive to an induced magnetic flux from a current passed through the electrical winding 154. A magnetic flux is produced by the winding 154 via the magnetic flux circuit defined by the centre member 124, the armature 182 the outer member 118, and the air gap between the armature 182 and the centre member 124. When a current is passed through the winding 154, the armature 182 is drawn toward the non-magnetic valve seat 136. When the current is interrupted, the armature 182 falls, by gravity and the force of the fluid through the centre member 124, toward the armature seat 96. Optionally, a resilient member such as a spring can be positioned between the centre member 124 and the armature 182 to bias the armature 182 away from the non-magnetic valve seat 136. When a pressure lower than atmosphere (i.e., a vacuum) is imposed at the port 114, the vacuum condition is communicated to the fluid chamber 174 through the fluid conduit 170 and the orifice 173. A differential pressure is created in the fluid chamber 174 by the flow of fluid at atmospheric pressure in through the centre member inlet port 128, the fluid passage 126 and out through the centre member output port 130. The fluid continues through the fluid opening created within the non-magnetic valve seat 136, along the outside of the wall member 186 of the armature 182 in the cylindrical chamber 158 and into the fluid chamber 174. The different pressure in the fluid chamber is accessed through the fluid conduit 172 and the port 116. The pressure differential in the fluid chamber 174 is altered by movement of the armature 182 in response to varying the energization level of the current in the electrical winding 154. This armature 182 movement changes the amount of communication of fluid at atmospheric pressure with the fluid chamber 174. Energization of the electrical winding 154 attracts the armature 182 toward the centre member 124, overcoming the forces of gravity and the fluid flow through the fluid opening in the non-magnetic valve seat 136. The upward movement of the armature 182 is thus limited by the non-magnetic valve seat 136. After the centre member 124 of the valve apparatus is fixed following installation, the translation of the translatable adjustment member 123 along the flux path alters the outer segment 118 to alter the permeability of the flux path. As translation of the translatable adjustment member 123 also varies the auxiliary air gap distance between the outer member segment 119 and the plate 123, the reluctance of the flux circuit can be altered. The plate 123 is thus translated along the vertical axis to find the appropriate set point for operation of the valve apparatus 110. Once this set point is found, the plate is fixed in that position by any means known in the art, such as welding or the use of an encapsulate. A dust cover 141 is then placed over the plate 123 and the cavities 131 and 137 to protect the calibration and is pressed into a circular collar 143. Thus, the valve apparatus 110 may be continuously operated along the current versus pressure differential curve for that set point. The location of the non-magnetic valve seat 136 at or near the point of highest flux density within the electrical winding 154 provides greater control and repeatability of the pressure differential versus current characteristics of the present valve. Providing the primary air gap between the armature 182 and the centre member 124 at or near this point of highest flux density provides a more efficient and responsive valve apparatus 110. This also allows the use of a lower mass armature 182, permitting the use of the valve apparatus 110 with high frequency input currents. However, the wall portion of the armature 182 must be of appropriate length so that the armature 182 remains in the flux path for all operating positions of the armature 182; that is, the armature wall portion 186 must extend at least to the bottom portion 122 of the outer member 118 for all operating positions of the armature 182. The valve apparatus 110 is manufactured by assembling the magnetic segments to form a magnetic flux circuit. First, the non-magnetic bobbin 156 is moulded with the appropriate cavities, conduits and orifices. The electrodes 160, 162 are moulded into the bobbin 156 at this time. The winding 154 is then spun about the bobbin 156 until the preferred number of the turns are obtained, where the loose ends of the winding 154 are then soldered to the electrodes 160, 162. The armature is then inserted into the bobbin 156 from the top and allowed to rest against the armature seat 198 on the base of the bobbin 156. The outer member 118, without the plate 123, is then positioned about the bobbin 156. The flat top portion 120 is provided with an aperture 125 and slides over the upper surface of the bobbin 156 and the bottom portion 122 is provided with a yolk 127 that surrounds an appropriate molded notch in the base of the bobbin 156. The centre member 124 is then driven into the bobbin 156 though the aperture 125 into the centre of the valve apparatus 110 and above the armature 182. The housing 164 is then moulded about the assembly to form the remaining aspects of the valve apparatus 110. The translatable adjustment plate 123 is then pressed in the cavity 131, as seen in Figure 18. An electromechanical valve apparatus calibration mechanism 222, including a calibration fixture 220 and the valve apparatus 110 is then employed to finally position the translatable adjustment plate 123. The non-magnetic drive gear 202, attached to a non-magnetic drive shaft 204 of a fixture stepper motor 206, is either manually or automatically inserted into the generally cylindrical cavity 137. The non-magnetic drive gear 202 thus is caused to engage the rack of drive teeth 129 on one edge of the translatable adjustment plate 123. A control current is applied to the winding under the control of a microprocessor 208 and a fixed vacuum source is connected to the vacuum source port 114. The differential pressure in the fluid chamber 174 is accessed and measured by a sensor 210 through the port 116. The plate 123 is then translated via rotation of the non-magnetic drive gear 202 to modify the auxiliary air gap based on measurements taken of the differential pressure via the sensor 210 until the proper set point of the output differential pressure for the fixed vacuum pressure is obtained. At that point, the location of the plate 123 is secured by welding or other appropriate means and the remainder of the valve apparatus 110 is assembled.

Claims: An electromechanical valve apparatus comprising an electrical winding (154) having an axial length; a magnetic flux circuit for the winding (154) defining a flux path comprising a plurality of adjacent magnetic segments, including a generally cylindrical centre segment (124) which defines a fluid passage (126), an outer segment (118) and an end segment adjacent a first end (128) of the fluid passage (126); annular non-magnetic seat means (136) having a central opening aligned with and disposed near the other end (130) of the fluid passage (126); at least one (118) of the segments being physically translatable within the valve apparatus (110) along the flux path to adjust a portion (123) of one (118) of the segments in the flux path and to adjust the extent of an air gap adjacent the translatable segment (118); magnetic closure means (82; 82a; 82b; 182) comprising one of the segments and positioned adjacent the non-magnetic seat means (136), the closure means (82; 82a; 82b; 182) completing the flux path such that fluid flow urged by a predetermined pressure difference through the fluid passage (126) and the seat means central opening can be modulated by varying the energization level of the electrical winding (154); and means (156) defining a chamber (158) having a cylindrical portion adjacent the seat means (136) to enclose the magnetic closure means (82; 82a; 82b; 182) and to constrain the motion of the magnetic closure means (82; 82a; 82b; 182) substantially parallel to said axial length, the magnetic closure means (82; 82a; 82b; 182) being movable between a position against the seat means and a position displaced therefrom; characterized in that the generally cylindrical centre segment (124) extends only over a portion of the axial length of the electrical winding (154), the non-magnetic seat means (136) has its central opening aligned with and disposed near the other end (130) of the fluid passage (126) within said axial length, and said one segment comprising the magnetic closure means (82; 82a; 82b; 182) is partially within and movable along said axial length, and in that the physically translatable segment (118) is the outer segment (118) which is physically translatable within the valve apparatus (110) along the flux path to adjust said portion (123) of that outer segment (118) in the flux path and to adjust the extent of the air gap adjacent the outer segment (118). An electromechanical valve apparatus as claimed in claim 1, wherein the translation of the outer segment (118) along the flux path is effective to vary said portion (123) of the segment (118) in the flux path and the air gap distance and thus vary the reluctance of the flux circuit so as to correspondingly adjust the response of the valve apparatus (110) for a given energization level of the electrical winding (154) to provide a given pressure difference. An electromechanical valve apparatus as claimed in claim 1 or claim 2, wherein said portion (123) of the outer segment (118) is relatively movable in the valve apparatus (110) to adjust said air gap which is between said portion (123) of the outer segment (118) and the outer segment (118). An electromechanical valve apparatus as claimed in claim 3, wherein the outer segment (118) comprises a plurality of sections, one (119, 121) of the sections being oriented substantially along the flux path, the oriented section (119, 121) having two spaced end portions (119), and the movable portion (123) of the outer segment (118) being positioned substantially parallel to the oriented section (119, 121) and between the spaced end portions (119) so as substantially to span a distance between the spaced end portions (119) and to create an air gap distance between the movable portion (123) and one of the end portions (119). An electromechanical valve apparatus as claimed in claim 4, wherein the outer section (119, 121) includes a centre portion (121) between the spaced end portions (119), the movable portion (123) being positioned adjacent the centre portion (121). An electromechanical valve apparatus as claimed in any of the preceding claims, further comprising drive engaging means (129) for translation of the movable portion (123) of the outer segment (118) along the magnetic flux circuit, by which the valve apparatus (110) may be calibrated by applying a force to the drive engaging means (129) of the movable portion (123) so as to translate the movable portion (123) within the valve apparatus (110) and to vary the air gap distance and thus vary the reluctance of the magnetic flux circuit to obtain a predetermined response of the valve apparatus (110) for a given energization level of the electrical winding (154) so as to provide a given pressure difference. An electromechanical valve apparatus as claimed in claim 6, wherein the drive engaging means (129) comprises gear teeth (129)located along at least one edge of the movable portion (123). An electromechanical valve apparatus as claimed in claim 6 or claim 7, wherein said force applied to the gear teeth (129) located on the movable portion (123) is generated by a non-magnetic gear drive means (202). An electromechanical valve apparatus as claimed in any of the preceding claims, wherein the centre segment (124) is also physically translatable along the flux path to adjust the extent of an air gap between the end segment and the magnetic closure means (82; 82a; 82b; 182) thus to vary the reluctance of the flux circuit. An electromechanical valve apparatus calibration mechanism, comprising a valve apparatus (110) as claimed in any of claims 1 to 5 in combination with a calibration fixture, wherein the movable portion (123) of the outer segment (118) of the valve apparatus (110) is further provided with drive engaging means (129), and wherein the calibration fixture (220) comprises a non-magnetic drive means (202) for engaging the drive engaging means (129), and control means (208) to control translation of the movable portion (123) of the outer segment (118) to vary the air gap distance and thus vary the reluctance of the magnetic flux circuit to obtain a predetermined response of the valve apparatus (110) for a given energization level of the electrical winding (154) so as to provide a given pressure difference. An electromechanical valve apparatus calibration mechanism as claimed in claim 10, wherein the calibration fixture (220) further comprises sensing means (210) to measure the pressure difference of the valve apparatus (110), the sensing means (210) providing an output to the control means (208) proportional to the pressure difference, and wherein the control means (208) compares the output of the sensing means (210) to measure the pressure difference of the valve apparatus (110) and to cause the drive means (202) to adjust the position of the movable portion (123) of the outer segment (118) within the valve apparatus (110) to vary the air gap distance and thus vary the reluctance of the magnetic flux circuit to obtain a predetermined response of the valve apparatus (110) for a given energization level of the electrical winding (154) so as to provide a given pressure difference. An electromechanical valve apparatus calibration mechanism as claimed in claim 11, wherein the control means (208) is a microprocessor controlled device (208) which compares the output of the sensing means (210) to measure the pressure difference of the valve apparatus (110) and causes the drive means (202) to adjust the position of the movable portion (123) of the outer segment (118) within the valve apparatus (110) to vary the air gap distance and thus vary the reluctance of the magnetic flux circuit to obtain a predetermined response of the valve apparatus (110) for a given energization level of the electrical winding (154) so as to provide a given pressure difference.

Inventors: BARON TIBOR, BARON, TIBOR
Applicants: BORG WARNER AUTOMOTIVE ELECTRO, BORG-WARNER AUTOMOTIVE ELECTRONIC & MECHANICAL SYSTEMS CORPORATION
Application year: 1991
Main classification: F16K31
IPC codes: F16K31