Proportional Variable Force Solenoid Control Valve

This invention relates to control valve for regulating fluid pressure and, more particularly, to a proportional variable force solenoid operated valve wherein the pressure is regulated by a variable force which is proportional to the magnitude of electrical current applied to the solenoid.

While proportional variable force solenoid control valves are employed in various fluid control applications, a typical application is to modulate main line fluid pressure in an electronic transmission to control the smoothness of shifting between gears of the electronic transmission.

Prior proportional variable force solenoids typically require very close tolerances and precise adjustment of the air gap between the armature and a pole piece in order to attempt to achieve proportional control characteristics.

Other such solenoids involve the use of a trunk pole piece in order that the magnetic field operating on the armature is a function solely of flux density rather than a combination of magnetic circuit permeance and flux density. The trunk pole piece is adjustable in order to change the core gap to achieve proportional control. In addition to the additional bulk, complexity and cost of employing a pole piece, such prior art devices are expensive to manufacture and require close manufacturing tolerances.

It is an object of the invention to eliminate the need to maintain the close manufacturing tolerances associated with the air gap in a solenoid while also eliminating the need for an adjustable air gap.

Another object of this invention is to significantly reduce the cost of manufacture of a proportional variable force solenoid operated valve while maintaining substantially linear proportional control.

It is a further object of this invention to simplify the design and assembly of such solenoid control valves.

It is also an object of this invention to improve the reliability of such solenoid operated valves.

It is yet a further object of this invention to reduce the size of a proportional variable force solenoid operated valve.

A proportional variable force solenoid operated valve employs a solenoid constructed with an armature suspended within the longitudinal bore of the solenoid bobbin with a permanent ring magnet disposed adjacent one end of the armature creating a magnetic field which biases the armature toward a position corresponding to an open valve position. A coil spring biases the armature toward a position corresponding to a closed valve position providing a balancing force against the magnetic field of the permanent ring magnet. The force of the magnetic field of the coreless solenoid varies in proportion to the magnitude of electrical current applied to the solenoid and in turn moves the armature between open and closed valve positions in proportion to the magnitude of such electrical current without the requirement of a separate pole piece. This provides a proportional variable force control valve which employs a coreless solenoid without an air gap thereby simplifying the design, lowering the cost of manufacture, while providing a more compact design and improving the reliability of such valves.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention as illustrated in the accompanying drawing.

FIG. 1 is an end elevational view of the proportional variable force solenoid valve of the present invention;

FIG. 2 is a view in longitudinal cross section, taken along the line 2--2 in FIG. 1 showing the valve in the closed position;

FIG. 3 is a partially fragmented view in longitudinal cross section, taken along the line 2-2 in FIG. 1 showing the valve in the open position;

FIG. 4 is a view in vertical cross section taken along the line 4--4 in FIG. 2; and

FIG. 5 is a view in vertical cross section taken along the line 5--5 in FIG. 2.

Referring to FIGS. 1 through 5, the proportional variable force solenoid control valve 10 includes valve member 12 and solenoid 14. The solenoid 14 includes an electromagnetic coil 16 wound with approximately 700 turns about a plastic bobbin 18 which has a cylindrically shaped bore hole 20 through the longitudinal axis thereof. An armature 22 formed of ferromagnetic material such as leaded steel is suspended within the bore hole 20 of the plastic bobbin 18 by a pair of plate springs 24, 26 mounted at opposite ends of the armature 22. The plate springs 24, 26 are formed from very thin stainless steel and have a configuration, best seen in FIG. 5, which provides a very low spring rate. These plate springs 24, 26 suspend the armature for free axial longitudinal movement within the bobbin 18 while at the same time isolating the armature 22 from noise, vibration and interference with the remaining structure of the solenoid 14. A substantially doughnut shaped, flat, steel flux washer 28 is disposed within a recess 30 formed in the front end of the bobbin 18. Flux washer 28 is formed from a pair of identical opposing C-shaped halves contacting each other with each half having a cut out at the top to accommodate a portion of the top of the bobbin. The flux washer 28 contacts the steel shell 32 which forms an outer housing for the solenoid 14 and thereby provides a concentration of flux of the electromagnetic field at the front end of the armature 22. An axially magnetized ring magnet 34 (FIGS. 2 and 3) is disposed in an annular recess 36 at the rear end of the bobbin 18 axially rearward from the coil 16. Ring magnet 34 is formed of rare earth samarium cobalt which has generally superior performance characteristics such as greater energy products permitting a reduced size magnet resulting in a compact solenoid in addition to enhanced stability, for example, minimum loss of magnetism due to elevated temperatures. The axially magnetized ring magnet 34 is significantly less expensive than a radially magnetized ring magnet which would necessarily require a plurality of radially magnetized pieces. Ring magnet 34 produces a magnetic field equivalent to approximately 1200 amp turns and thus substantially saturates the armature 22 even in the absence of current to the coil 16. Thus, a relatively smaller electromagnetic field is required to move the armature 22 between the positions shown in FIGS. 2 and 3.

The armature 22 is hollow with a steel seal plug 38 press fit into its front end. A cup shaped spring retainer 40 formed of half hardened brass is press fit into the opposite or rearward end of the armature 22. A coil spring 42 is trapped between the inside of the spring retainer 40 and a plastic cap screw 44 threadably received in a threaded central aperture of the plastic end cap 46. The outer end of the end cap 46 includes an hexagonal socket 48 providing means for adjusting, via a tool such as an allen wrench, the force exerted by the coil spring 42 on the armature 22. The plate spring 26 is trapped between a shoulder near the outer edge of the rear of the bobbin 18 and the inner edge of the end cap 46 which in turn is held in place by the rear flange 50 of the shell 32 which engages an annular shoulder on the end cap 46.

A plastic connector body 52 is mounted on top of bobbin 18 and extends under a raised area at the top front of shell 32. Electrical contacts 54 extend upward through the bobbin 18 and through apertures in the connector body 52. The lower ends of the electrical contacts 54 are connected to the wires of the electromagnetic coil 16 for receiving an electrical current input signal from a variable current source (not shown).

The valve member 12 includes an aluminum nozzle 56 having an end wall 58 which is secured to the solenoid 14 by a plurality of tabs 60 extending from the shell 32 and crimped over the front portion of the end wall 58 (FIG. 1). An elastomeric diaphragm 62 is sandwiched between the end wall 58 and the front of the bobbin 14. The diaphragm 62 includes a central opening which is received in an annular recess 64 on the central portion of the sealed plug 38. The diaphragm 62 seals and thereby protects the solenoid 14 from contaminants which might pass through the valve member 12 with the flow of pressurized fluid. This seal greatly enhances the reliability as well as the durability of the solenoid 14. The nozzle 56 includes a longitudinal passageway 66 having a cylindrical configuration which houses a cylindrical nozzle filter 68 having openings provided at its opposite ends. The nozzle filter 68 is formed of nylon mesh mounted about a plastic frame and filters particulate matter from the control ports 80. A supply plug 70 of half hardened brass is press fit into the open front end of the longitudinal passageway 66. The supply plug 70 includes an inlet 72 having a diameter of approximately .030 inches. Inlet 72 communicates with four exhaust ports 74 each having a diameter of approximately .125 inches via outlet 76 extending longitudinally from the inner end of the passageway 66 through a valve seat forming a sharp edge orifice 78 with a diameter of approximately .080 inches. The front face of the seal plug 38 disposed adjacent the sharp edge orifice 78 forms a poppet valve 84. Four control ports 80 each having a diameter of approximately .090 inches are disposed about the nozzle 56. Poppet valve 84 regulates the pressure of the fluid flowing out control ports 80 by opening to permit pressurized fluid to be exhausted out exhaust ports 74 thereby reducing the pressure of the fluid flowing through the control ports 80 in direct proportion to the opening of the poppet valve in accordance with the linear movement of the armature 22 which in turn is directly proportional to the amount of current supplied to the coil 16 of the solenoid 14. An 0-ring seal 82 is provided between the rear end of the nozzle filter 68 and the inner end wall of the passageway 66.

A wave washer 61 helps to hold the nozzle 56 firmly in place when mounted in the fluid system such as a vehicle transmission housing (not shown). Notches 63 may be formed in the outer surface of nozzle 56 to receive a fastener clip (not shown) for securing the nozzle 56 to the transmission housing.

Referring to FIGS. 2 and 3, the operation of the proportional variable force solenoid control valve of the present invention will now be described. The inlet 72, exhaust ports 74 and control ports 80 of the nozzle 56 are connected to the pressurized fluid system in which pressurized fluid is supplied to the inlet 72 and flows out the control ports 80. Valve 84 is opened by the solenoid 14 as described previously to regulate the pressure of the fluid flowing out the control ports 80 by diverting fluid to the exhaust ports 84. The opening of the valve 84 in turn is controlled by linear displacement of the armature 22 in proportion to the amount of electrical current supplied to the solenoid 14 via electrical contacts 54. In the normally closed position as shown in FIG. 2 with no current flowing, there is no electromagnetic field and the coil spring 42 biases the armature 22 toward the position shown in FIG. 2 wherein the valve 84 is in the closed position with the face of the seal plug 38 sealed against the sharp edge orifice 78 thereby preventing the flow of pressurized fluid from the outlet 76 to the exhaust ports 74. The force of the coil spring 42 is sufficient to overcome the magnetic field created by the radially magnetized ring magnet 34 in addition to the force of the pressurized fluid against the face of the seal plug 38. With the valve 84 in this position, pressurized fluid entering the nozzle 56 through inlet 72 passes through the open front end of filter 66, through the nylon mesh of filter 66, and out the control ports 80. In this position, the fluid flowing out of the control ports 80 is at maximum pressure which can be reduced in a regulated fashion by applying electrical current to the coil 16 via contacts 54 creating an electromagnetic field which in addition to the magnetic field created by ring magnet 34 together with the force caused by the pressurized fluid through sharp edge orifice 76 against the face of the seal plug 38 overcomes the opposing spring force of the coil spring 42 and the relatively slight force of the plate springs 24, 26 thereby moving the armature 22 to the position shown in FIG. 3 corresponding to a maximum opening of the valve 84. This position permits maximum fluid flow out the exhaust ports 74 resulting in minimum pressure of the fluid flowing out of the control ports 80. The pressure of the fluid may be varied between the maximum and minimum valves directly proportional to the amount of current applied to the coil 16.

For example, in a typical application of the proportional variable force solenoid control valve of the present invention, the nozzle 56 is inserted into an automobile transmission housing to modulate the main line pressure to control several spool valves disposed in an electronic transmission control system thereby controlling the smoothness of shifting between gears of the electronic transmission. In such an application, fluid pressurized at approximately 200 psi is provided to the inlet 72. The spring force of the coil spring 42 is adjusted via the cap screw 44 to slightly open the valve 84 with no current supplied to the coil 16, thereby creating a slight bleed of fluid between the sharp edge orifice 76 and the face of the seal plug 38 and out the exhaust ports 74. The pressure of the fluid then flowing out of control ports 80 may be linearly controlled in proportion to the amount of current subsequently provided to the coil 16 via contacts 54 in the manner previously described. The elastomeric diaphragm 62 which is sealed about the central portion of the seal plug 38 within the annular recess or groove 64 flexes with the movement of the seal plug thereby protecting the solenoid 14 from contaminants which could be carried by the pressurized fluid in the chamber which communicates between the sharp edge orifice 76 and the exhaust ports 74 during operation of the valve 84.

Thus, a proportional variable force solenoid operated valve is provided utilizing a solenoid operator which does not require a trunk pole piece or any other such core device. The result is significantly more liberal manufacturing tolerances which otherwise would need to be close tolerances to maintain the required precise air gap associated with a core device. This coreless construction further eliminates the need to adjust such an air gap to maintain linear control for various input pressures. Manufacturing costs are reduced and reliability is improved in a more compact design of the proportional variable force solenoid operated valve of the present invention.

Although a preferred embodiment of the proportional variable force solenoid control valve of the present invention has been shown and described in detail, it should be noted that variations or modifications may be made without departing from the spirit or scope of the present invention.