Abstract:
An electromagnetically actuated hydraulic switch unit is provided by an armature plunger which reciprocally shuttles between partially overlapping magnetic paths and operating a hydraulic valve circuit through bistable snap blade means. Snap blades open and close entry ports, exit ports and vent ports to connect various passages in a housing and perform given hydraulic functions. The ratio of the permeances of the two magnetic paths, created by dedicated coaxial coils, is controlled such that one path always overpowers the other by an amount greater than the mechanical gradients of a pair of snap blades in hydraulic fluid filled cavities, to insure plunger movement in either direction.

Description:
This is a continuation of application Ser. No. 406,649, filed Aug. 9, 1982, now abandoned. 
    
    
     BACKGROUND AND SUMMARY 
     The invention relates to an electromagnetically actuated hydraulic valve switching unit. 
     An armature plunger reciprocally shuttles between two magnetic paths. A pair of coils are energizable to create magnetic fluxes having portions of their linkage paths in common, including through the plunger. When either coil is energized, a flux path is created around that coil through the plunger, and another flux path is created around both coils through the plunger. The ratio of the permeances of the two paths is controlled such that one path always overpowers the other, to insure plunger movement in either direction. 
     The armature plunger actuates bistable snap blade means in a hydraulic valve circuit. A housing includes a cavity into which a portion of the armature plunger extends an engages the snap blade. The housing has a hydraulic fluid entry port into the cavity, a hydraulic fluid exit port out of the cavity, and a hydraulic fluid vent port out of the cavity. A first position of the snap blade blocks the vent port and opens the entry port such that hydraulic fluid may flow from the entry port to the exit port. A second position of the snap blade blocks the entry port such that hydraulic fluid may flow from the exit port to the vent port. The preferred embodiment further includes a second vent port comprising an annulus around a shaft segment of the armature within a journaled portion of the housing for venting hydraulic fluid from the cavity along the shaft-journal interface. The preferred emobidment further includes dual snap blades and cavities at opposite ends of the armature plunger for tandem operation of a hydraulic circuit. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cutaway isometric view of an electromagnetically actuated hydraulic valve switching unit constructed in accordance with the invention. 
     FIG. 2 is an isolated cross sectional view of a portion of FIG. 1. 
    
    
     DETAILED DESCRIPTION 
     Switching unit 2 includes a housing 4 having hydraulic valve means 6, including bistable snap blade means 8 and 9 operable between different hydraulic circuit positions, and having electromagnetic actuator means 10 for operating the hydraulic valve snap blade. Electromagnetic actuator means 10 includes an armature plunger 12 axially reciprocal left and right according to energization of left or right coil 14 or 16. Armature plunger 12 includes left and right extension shafts 18 and 20 fixedly secured to plunger 12 in threaded relation. 
     Bistable snap blades 8 and 9 are actuated between their bistable positions by shafts 20 and 18. Snap blade 8 has a lower end 24 fixedly secured in housing 4, for example by rivet 26. Snap blade 8 has an upper end 28 which is free to move left and right. The top and bottom ends 28 and 24 of snap blade 8 are connected by outer side segments one of which 30 is seen in FIG. 1. Double Euler beams are formed by a pair of cantilever arms 32 and 34 extending from respective top and bottom ends of the snap blade to a gap therebetween. Shaft 20 extends into this gap and engages the opposing facing edges of cantilever arms 32 and 34 by a staked washer arrangement 36. 
     Snap blade 9 is comparable and includes a bottom end 38 fixed in housing 4 by rivet mount 40, and having an upper free end 42 for left-right movement. Top and bottom ends 42 and 40 are joined by outer side segments one of which 44 is seen in FIG. 1. Double Euler beams are formed by a pair of cantilever arms 46 and 48 and engaged in the gap therebetween by shaft 18 at staked washers 50. 
     In FIG. 1, plunger 12 and shafts 18 and 20 are in their leftward position. Top free ends 42 and 28 of snap blades 9 and 8 are in their rightward position, and cantilever arms 46 and 48, and 32 and 34, are bowed leftwardly. When plunger 12 and shafts 18 and 20 are moved rightwardly, to be described, cantilever arms 46 and 48, and 32 and 34, are deflected, which flexure stores potential energy therein. When the cantilever arms are moved through center by travel of the shafts, the stored energy is released and top free ends 42 and 28 of the blades snap leftwardly to their leftward stable position. Plunger 12 and shafts 18 and 20 are then in their rightward position, and cantilever arms 46 and 48 and 32 and 34, are bowed rightwardly. Return travel of the plunger and shafts moves the cantilever arms back through center and the top free ends of the blades snap back rightwardly to their right stable position as shown in FIG. 1. 
     Housing 4 includes cavities 52 and 54 into which the shaft portions 18 and 20 of the armature plunger 12 extend and engage their respective snap blades 8 and 9. A hydraulic fluid entry port into cavities 52 and 54 is provided by port 56 and channels 58 and 60. Hydraulic fluid exit ports out of cavities 52 and 54 are provided by exit passages 62 and 64. Hydraulic fluid vent ports out of cavities 52 and 54 are provided by passages 66 and 68. Snap blades 8 and 9 have respective hydraulic valve seating pads 70 and 72 at their top free ends for engaging in sealing relation raised frustoconical seats, such as 74, FIG. 2 on entry port passages 58 and 60 and vent port passages 66 and 68. 
     When the top free ends 28 and 42 of the snap blades are in their rightward position as shown in FIG. 1, vent port 66 is blocked and entry port passage 58 is open such that hydraulic fluid may flow from entry port passage 56 into cavity 52 and out through exit port 62. This hydraulic fluid flow may perform a designated function, for example actuating a clutch by introducing hydraulic fluid into an actuation chamber 76 of a clutch housing 78 having a central fixed dividing wall 80. The hydraulic fluid pressure in chamber 76 drives piston 82 rightwardly. Also, when top free end 42 of snap blade 9 is in its rightward position as shown in FIG. 1, entry port passage 60 is blocked and vent port 68 is open. Hydraulic fluid may flow from port 64 into cavity 54 and out through passage 68. This in turn enables hydraulic fluid in chamber 84 of the clutch housing to be expelled and thus permit rightward movement of piston 86 which is rigidly secured to piston 82 by means of connecting shaft 88 extending through center dividing wall 80. The noted clutch application is of course only exemplary. 
     Housing 4 further includes second vent ports comprising annulus 90 and annulus 92 around respective shafts 20 and 18. Housing 4 includes a yoke segment 94 through which the shafts extend in journaled relation. Annuli 90 and 92 are formed in this housing yoke segment Vent passages 96 and 98 communicate with respective annuli 90 and 92 for venting hydraulic fluid from respective cavities 52 and 54 along the shaft-journal interface through respective annuli 90 and 92 and out vent passages 96 and 98. These second vent ports 90 and 92 are preferred where it is desired to avoid a tight seal at the shaft-journal interface. This in turn enhances speed of operation. Also, the cantilever arms and outer side segments of the snap blades are formed by wire-like members to effectively slice through the hydraulic fluid with minimal resistance, to further enhance speed of operation. 
     When plunger 12 and shafts 20 and 18 are actuated to their rightward position, upper free ends 28 and 42 of the snap blades snap to their leftward stable position. In this state of switching unit 2, hydraulic contact 70 blocks entry port passage 58 such that hydraulic fluid may flow from port 62 into cavity 52 and out passage 66. Hydraulic contact 72 blocks vent port 68, such that hydraulic fluid may flow from entry port 56 into cavity 54 and out through exit port 64 into chamber 84 to thus drive piston 86 leftwardly. 
     Electromagnetic actuator means 10 in housing 4 includes the noted left and right coaxial coils 14 and 16 energizable to create magnetic flux. These coils are wound on an insulating bobbin 102 which includes axial passage 104 therethrough for guiding reciprocal axial movement of armature plunger 12. Magnetically permeable yoke 94 directs the flux paths of the coils. The yoke comprises an E-shaped member having right and left outer legs 106 and 108 and a center leg 110 between the coils. The outer legs 106 and 108 extend back inwardly axially at 112 and 114 and have axial bores therethrough for guiding axial reciprocal movement of shafts 20 and 18 and form the journaled interface therewith through housing 4. Yoke segment 114 has an inner edge 116 forming a shoulder stop limiting leftward axial movement of plunger 12, and further includes a nonmagnetic spacer washer 118 between plunger 12 and yoke segment 114 abutting stop shoulder 116. Yoke segment 112 includes an inner edge 120 providing a stop shoulder for limiting rightward axial movement of plunger 12, and further including a nonmagnetic spacer washer 122 abutting stop shoulder 120. Wire pair 124 is provided for energizing coil 14 and wire pair 126 is provided for energizing coil 16. 
     If armature plunger 12 is in its leftward position as shown in FIG. 1, and if right coil 16 is energized, a primary flux path is created around energized coil 16 and a secondary flux path is created around both coils 14 and 16. The primary flux path around the energized coil 16 extends through right outer yoke leg 106, through axial yoke segment 112, through axial magnetic air gap 128 between plunger 12 and spacer 122 against shoulder stop 120, through plunger 12, through radial gap 130 across bobbin 102 between plunger 12 and center yoke leg 110, through center yoke leg 110, and back along the top of the yoke to right outer yoke leg 106 to complete the primary loop. The secondary flux path extends through right outer yoke leg 106, through axial yoke segment 112, through axial magnetic air gap 128, through plunger 12 through spacer 118 and shoulder stop 116, through axial yoke segment 114, through left outer yoke leg 108, and back through the top yoke segment to the right outer yoke leg 106 to complete the secondary loop. The primary path flux force pulls armature plunger 12 rightwardly to close axial magnetic air gap 128 and open a second gap between the left edge of plunger 12 and spacer 118 against stop shoulder 116. The secondary path flux force tends to hold the plunger in place in its leftward position with the left gap closed and the right gap 128 open. 
     The ratio of the permeances of the two paths is controlled such that one path always overpowers the other, to insure plunger movement in either direction for actuating the snap blades. The ratio of the radial width of gap 130 to the axial width of spacer 118 sets the ratio of the primary and secondary flux forces, whereby to control the net magnitude and direction of force on the plunger upon energization of right coil 16. The primary force is made to be always stronger than the secondary force. The structure is symmetric, and the same considerations apply for leftward movement of the plunger from its rightward position. The ratio of the noted widths may be determined empirically, or mathematically from simultaneous solution of Gaussian equations. In one implenentation, the width of radial gap 130 is 0.012 inch and the axial width of each of spacers 118 and 122 is 0.010 inch. It is to be noted that the width of axial magnetic air gap 128 is set by the axial width of spacer 118. Likewise, the axial width of the left gap when the plunger is in the rightward position is set by the axial width of spacer 122. 
     As noted, the structure is symmetric, and thus the above description applies equally for the reverse direction leftward movement of armature plunger 12 in response to energization of left coil 14. The noted ratio of the widths is set such that the primary flux force is greater than the secondary flux force, and such that the difference therebetween is greater than the mechanical gradient of the snap blades whereby to insure actuation of the latter. 
     It is to be noted that movement of the plunger induces a voltage signal in the nonenergized coil. This voltage signal may be used to afford feedback verification of actuation of the plunger to its alternate position. This feedback verification is afforded using existing flux linkages, with additional sensing circuitry. 
     Armature shuttle plunger 12 is thus reciprocal in housing 4 between left and right positions respectively closing and opening first and second gaps between plunger 12 and yoke 94 at shoulder stops 116 and 120. Plunger 12 is in overlapping flux paths in each of its left and right positions. Energization of the right coil 16 creates a primary flux around the latter attracting the plunger to its rightward position to close right gap 128 and open a left gap between the left edge of plunger 12 and washer 118 against left shoulder stop 116. Energization of right coil 16 also creates a secondary flux around both coils attracting plunger 12 to remain in its leftward position with the left gap closed and the right gap 128 open. Energization of left coil 14 creates a primary flux around the latter attracting plunger 12 to its leftward position to close the left gap and open the right gap 128, and creates a secondary flux around both coils attracting plunger 12 to remain in its rightward position with right gap 128 closed and the left gap open. The force on plunger 12 from the primary flux path around either coil is always stronger than the force on the plunger from the secondary path. 
     It is recognized that various modifications are possible within the scope of the appended claims.