Fluid handling – Systems – Multi-way valve unit
Reexamination Certificate
1999-12-09
2001-03-27
Walberg, Teresa (Department: 3742)
Fluid handling
Systems
Multi-way valve unit
C417S053000
Reexamination Certificate
active
06206044
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a by-pass solenoid for a variable bleed flow system and method, and more particularly to a by-pass solenoid with an integral check valve for a hydraulic system and method for by-passing or bleeding excess flow of hydraulic fluid while maintaining a constant pressure.
2. Description of the Related Art
Solenoid actuated hydraulic valves are used in many types of machines and applications to control the flow of fluid (hydraulic or pneumatic) to and from fluid pressure devices, for example, hydraulic cylinders, hydraulic motors, pumps, etc. The valves are controlled by circuits which selectively energize the various solenoids in accordance with an intended operating sequence. Solenoid valves may be of the ON/OFF variety operating as either normally open or normally closed, or the solenoid valve may be a variable (proportional) force solenoid valve. A variable force solenoid valve is controlled by an electrical signal providing variable voltage or controlled current to provide an increasing or decreasing magnetic force on an armature for effecting movement of a spool valve. Movement of the spool valve results in an increase or decrease in fluid flow.
Solenoid valves have found recent application in automatic transmissions and power steering systems on some vehicles. The fluid pressure and/or flow is controlled to provide smooth gear shifting in the transmission, or to provide good steering wheel “feel” in power assist steering.
In electronic control applications for automatic transmissions, variable force solenoid valve assemblies are used to provide control over fluid pressures which are provided in response to electrical input signals supplied to the variable force solenoid assemblies by an engine control unit (ECU). The variable force solenoid valve assemblies are employed to regulate fluid control devices which cause the “shift-feel” of an automatic transmission.
Once such type of variable force solenoid valve is disclosed in U.S. Pat. No. 5,853,028 assigned to the Assignee of the present invention and incorporated herein by reference. U.S. Pat. No. 5,853,028 describes an improved variable force solenoid valve with a spool valve that experiences a minimum of oscillations and instability.
In an electronically controlled automatic transmission or a continuously variable transmission (CVT), it has become desirable to move the pump out from inside the transmission to a location where it may be operated directly from the engine of the vehicle. Since the engine speed will directly effect pump flow, a by-pass system is required to divert excess flow during high engine speed while maintaining a desired pressure. While a continuously variable pump may be employed for this type of application, a continuously variable pump is more expensive than a fixed displacement pump. So, it would be preferred to use the fixed displacement pump for cost reasons.
Consequently, there is a need for a simple, reliable hydraulic system and method to by-pass excess hydraulic fluid flow in a hydraulic circuit which can maintain a fairly constant fluid flow pressure. There exists a need for a fluid flow control device employed in the hydraulic system which allows return of excess fluid flow to the system reservoir, or allows re-circulation of excess fluid back to the pump inlet. The fluid flow control device would ideally offer a smaller size advantage along with being an integral flow control device.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a by-pass solenoid with integral check valve for use in a hydraulic system to bleed excess flow of hydraulic fluid in the hydraulic circuit while still maintaining a fairly constant system pressure. The by-pass solenoid in accordance with the present invention offers a compact, integral design.
Another object of the present invention is to provide a hydraulic system for by-passing excess pump flow in a hydraulic circuit that utilizes a by-pass solenoid with integral check valve to divert excess fluid flow and to maintain system pressure.
Still another object of the present invention is to provide a method for by-passing excess fluid flow in a hydraulic circuit at times when flow demand is low and pump flow is high while maintaining system pressure.
The above and other objects are accomplished with the employment of a by-pass solenoid with an integral check valve to divert excess fluid flow. The by-pass solenoid according to the present invention comprises a solenoid sub-assembly with a moveable armature constructed to translate with respect to an electrical coil in response to a change in an electrical signal. A valve sub-assembly having a valve body coupled to the solenoid sub-assembly receives a poppet valve member translatable with the armature. The valve sub-assembly includes a valve body with at least an inlet, an outlet, and a by-pass port for directing fluid flow. The valve body has a stepped bore extending therethrough and fluidly connects the inlet, outlet, and by-pass ports. The stepped bore includes at least a first chamber with a check valve assembly disposed therein. The check valve assembly is constructed to fluidly communicate with the inlet, outlet and by-pass ports and to selectively discharge fluid from the desired port.
The hydraulic system in accordance with the present invention includes pump means with at least first and second pumping elements. Each pumping element includes an inlet and an outlet. The first and second inlets receive hydraulic fluid from a system reservoir. The first pumping element of the pump means directs the hydraulic fluid to the first outlet. Likewise, the second pumping element directs the hydraulic fluid to the second outlet. A by-pass solenoid with integral check valve assembly includes an inlet port fluidly connected to the first outlet of the pump means. The by-pass solenoid with integral check valve assembly receives hydraulic fluid therefrom and discharges the fluid through an outlet port fluidly connected to the second outlet of the pump means when the solenoid is in a de-energized position (normal mode of operation). The check valve assembly is constructed to allow hydraulic fluid flow through the check valve assembly to a by-pass port upon actuation of the by-pass solenoid. A controller in electrical communication with the by-pass solenoid actuates the by-pass solenoid from the de-energized position to the energized position (which changes the normal mode of operation to the by-pass mode of operation) to re-direct the flow of hydraulic fluid from the solenoid outlet port to the by-pass port within the solenoid for re-circulating the hydraulic fluid.
The present invention is also directed to a method for regulating excess flow of hydraulic fluid in a hydraulic system comprising the steps of: supplying hydraulic fluid to a first and second pumping element of pump means, each pumping element having an inlet and an outlet; pumping the hydraulic fluid from the first and second pumping elements through first and second outlets of the pump means, connecting an inlet port of a by-pass solenoid to the first outlet of the pump means for receiving hydraulic fluid therefrom; connecting an outlet port of the by-pass solenoid to the second outlet of the pump means for discharging hydraulic fluid therethrough; providing a check valve assembly within a first chamber of the by-pass solenoid, the check valve assembly being fluidly connected to the inlet port and outlet port of the by-pass solenoid; providing a by-pass port in the by-pass solenoid valve capable of being fluidly connected to the inlet port through the check valve assembly upon actuation of the by-pass solenoid; directing the hydraulic fluid from the first outlet into the inlet port of the by-pass solenoid through the check valve assembly and out through the outlet port; and actuating the by-pass solenoid to re-direct hydraulic fluid through the by-pass port of the by-pass solenoid to a selected location.
The various features of novelty
Eaton Corporation
Johnston Roger A.
Kalka Daniel S.
Pwu Jeffrey
Walberg Teresa
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