Fluid handling – Processes – Involving pressure control
Reexamination Certificate
1999-10-07
2001-08-07
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Processes
Involving pressure control
C137S625650, C251S129080
Reexamination Certificate
active
06269827
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
MICROFICHE APPENDIX
Not Applicable
BACKGROUND OF THE INVENTION
The present invention relates to an electrically operated variable force solenoid pressure control valve of the type which may be employed for use in automatic transmission controllers for controllably reducing a fluid inlet pressure to an outlet control pressure.
A known variable force solenoid pressure control valve has utilized a stepped diameter spool. The differential area between the stepped diameters is used to apply a known force proportional to the control or output pressure which known force can more readily be overcome by the solenoid to provide desired actuation of the spool.
Referring to
FIG. 4
, a known stepped diameter spool valve is shown with the solenoid omitted for the sake of brevity having an operating rod
1
connected to the solenoid armature which moves spool
2
having a large diameter valving land
3
movable in spool bore
4
with a reduced diameter valving land
5
movable in reduced diameter spool bore
6
. Land
3
valves flow to exhaust port
7
; whereas, land
5
valves flow from inlet port
8
to annular recess
9
which is continuously connected with the control pressure outlet port
13
.
However, the manufacture of a valve having a stepped bore and stepped spool requires that extremely fine control of the concentricity between the stepped diameters be maintained. This results in very tight tolerances on the machining of the spool and the bore and therefore increases the cost of the valve resulting in a prohibitively expensive valve construction for high volume mass production motor vehicle automatic transmission usage. Therefore, it has been desired to provide a way or means of utilizing the differential area technique to control the force required to actuate the valve spool against the pressure forces of the hydraulic fluid and yet provide such a valve which is relatively easy to manufacture and which eliminates the need for control of concentricity between different diameters and unusually tight machining tolerances.
Furthermore, it has been desired to reduce the effective pressure transients during the operation of the valve in a hydraulic control system such as the shift control circuit of an automatic transmission in a manner which is cost effective. Heretofore, variable force solenoid valves have employed annular grooves in the valve spool bore to provide flow of fluid for balancing the pressure forces on the spool. However, it has proven costly to machine such grooves in the spool bore; and, therefore it has been desired to eliminate the need for such costly manufacturing operations and yet provide a way to enable the flow of fluid for balancing pressure forces on the spool.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a variable force solenoid operated pressure control valve of the type wherein an electric signal to the solenoid is employed to provide a desired control pressure in a hydraulic control circuit to provide actuation of a hydraulically operated device such as, for example, a piston or diaphragm type actuator. The valve of the present invention is particularly suitable for use in electrically controlling the pressure in a shift control circuit for an automatic transmission of the type employed in passenger cars and light truck motor vehicles.
The valve of the present invention employs a straight valving bore with a valving spool slidably received therein for movement by a rod connected to a solenoid armature. The rod is rigidly attached to one end of the spool, preferably by press fit engagement, and extends outwardly of the spool bore in sealed arrangement for contacting the armature solenoid. The spool has fluid pressure chambers formed at opposite ends; and thus, the presence of the rod in the end of the spool creates a differential area for the spool ends resulting in a net force from the pressure forces acting on the spool ends.
The spool has a first land for valving flow from an inlet port to a recess or control pressure chamber and a second land disposed for valving flow to an exhaust port. The recess or control pressure chamber is continuously connected to a control pressure port disposed intermediate the supply and exhaust ports and is adapted for connection to the hydraulic control circuit of the device to be actuated. The control pressure chamber or recess is connected to the fluid chambers at the opposite ends of the spool by separate restrictive or metering passages formed in the spool. The restrictive passages provide attenuated flow to the pressure chambers on the ends of the spool to maintain the desired pressure force balance; however, the passages are effective to dampen transients and thus reduce oscillations of the spool.
The construction of the solenoid operated pressure control valve of the present invention employs a straight bore and spool construction which reduces manufacturing tolerances and cost and creates a differential pressure area on the spool ends by employing a rod press fitted into the end of the spool. The balance of pressure forces on the spool ends is controlled and attenuated by restrictive passages communicating with the chambers at the spool ends which passages are formed between the control pressure chamber and the spool end chambers exclusively by metering passages formed in the spool thereby eliminating the need for providing such passages in the spool bore.
The valve of the present invention thus provides improved valve performance by providing for attenuation of transients and maintaining pressure force balance on the spool yet provides a simplified construction and reduced manufacturing costs.
REFERENCES:
patent: 4678006 (1987-07-01), Northman et al.
patent: 4947893 (1990-08-01), Miller et al.
patent: 5261637 (1993-11-01), Curnow
patent: 5513673 (1996-05-01), Slavin et al.
patent: 5513832 (1996-05-01), Becker et al.
patent: 5577534 (1996-11-01), Ward
patent: 5853028 (1998-12-01), Ness et al.
patent: 5855229 (1999-01-01), Gluf
patent: 5894860 (1999-04-01), Baldauf et al.
Eaton Corporation
Johnston Roger A.
Michalsky Gerald A.
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