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Hydraulic control valve system with electronic load sense controlHydraulic control valve system with electronic load sense control description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060191262, Hydraulic control valve system with electronic load sense control. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] Not Applicable STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT [0002] Not Applicable BACKGROUND OF THE INVENTION [0003] 1. Field of the Invention [0004] The present invention relates to hydraulic circuits that operate machinery; and more particularly to controlling the pressure of hydraulic fluid supplied to power actuators of that machinery. [0005] 2. Description of the Related Art [0006] Construction machinery, such as backhoes, have working members which are driven by several hydraulic cylinder and piston assemblies. Each cylinder is divided into two internal chambers by the piston and selective application of hydraulic fluid under pressure to either of the chambers moves the piston in a corresponding direction. [0007] Application of hydraulic fluid to the cylinder often is controlled by a spool valve, such as the one described in U.S. Pat. No. 5,579,642. In this type of valve, a manual operator lever is mechanically connected to a control spool which slides within a bore in a valve body. The pump and tank of the system are connected to ports in the valve body and the cylinder chambers are coupled to workports. Movement of the spool into various positions directs pressurized hydraulic fluid from the pump to one of the cylinder chambers and drains hydraulic fluid from the other cylinder chamber to the tank. By varying the size of orifices through which the fluid flows in the spool valve, the rate of flow into the cylinder chambers can be varied, thereby moving the piston at proportionally different speeds. [0008] To facilitate control, pressure compensating systems have been designed to maintain an approximately constant pressure drop across the spool valve. Those previous systems included sense lines which transmitted the hydraulic pressure at the valve workports to a control input of a variable displacement hydraulic pump. Typically, the greatest of the workport pressures for several working members is selected by a chain of shuttle valves as the pressure to apply to the pump control input. The resulting self-adjustment of the pump output as the workport pressure fluctuates provides an approximately constant pressure drop across the valve orifices whose cross-sectional area is controlled by the machine operator. This facilitates control because, with the pressure drop held constant, the speed of movement of each working member is determined only by the cross-sectional area of the corresponding orifice. Hydraulic systems of this type are disclosed in U.S. Pat. Nos. 4,693,272 and 5,579,642. [0009] There is a trend with respect to construction and agricultural equipment away from manually operated hydraulic valves toward electrically controlled solenoid valves. This change in technology facilitates computerized regulation of various machine functions. Electrical control of system simplifies the hydraulic plumbing as the control valves can be located near the cylinder and not in the operator cab. Thus only a common pair of pump and tank lines needs to be run to the hydraulic actuators throughout the machine. However, for pressure compensation, the load sense pressure lines still must be run among the valve assemblies and the pump. Therefore, it is desirable to achieve pressure compensation without extending load sense pressure lines throughout the machinery. SUMMARY OF THE INVENTION [0010] The present invention controls the hydraulic output pressure of a pump in response to system pressures that are electrically sensed. [0011] A hydraulic system employs a control valve to regulate the flow of fluid from a source to a hydraulic actuator that is connected to a workport of the valve. An apparatus is provided for controlling the pressure of fluid supplied to the control valve. That apparatus comprises first and second pressure sensors which produce electric signals respectively indicating pressure at the workport and of the fluid supplied to the control valve. Several preferred embodiments of the apparatus includes a proportional control valve receives fluid from the source and controls the application of that fluid to a hydraulic circuit node in response to an electric signal applied to a control input. [0012] A controller has inputs to which the electric signals from the first and second sensors are applied and responds to those signals by producing a pressure command. The preferred embodiment of the controller includes a feed forward branch and a feedback circuit. The feed forward branch processes the pressure command to produce a first output signal, and the feedback circuit responds to the pressure command and the second electric signal by producing a second output signal. The feedback circuit preferably incorporates a PID controller. The first and second output signals are summed into a combined output signal that is applied to the proportional control valve to manipulate the pressure at the hydraulic circuit node. [0013] A mechanism responds to pressure at the hydraulic circuit node by varying the pressure of fluid supplied to the control valve. BRIEF DESCRIPTION OF THE DRAWINGS [0014] FIG. 1 is a schematic diagram of a hydraulic system according to the present invention which controls a variable displacement pump in response to sensed workport pressure; [0015] FIG. 2 is a schematic diagram of another embodiment of the present invention which includes a valve circuit that varies the supply pressure from a constant displacement pump in response to the sensed workport pressure; [0016] FIG. 3 is block diagram of an electronic circuit that controls a variable displacement pump by an electrical signal; and [0017] FIG. 4 depicts the control process employed to control the components in FIGS. 1-3. DETAILED DESCRIPTION OF THE INVENTION [0018] With initial reference to FIG. 1, a hydraulic circuit 10 has a variable displacement pump 12 which draws hydraulic fluid from a tank 14 and furnishes the fluid under pressure to a supply line 16. The pressure at which the fluid is furnished to the supply line 16 is determined based on pressure applied at a control input 18 of the pump 12. Specifically, the pump is designed to produce an output pressure that is a given amount, known as the margin, greater than the pressure at the control input 18. Continue reading about Hydraulic control valve system with electronic load sense control... Full patent description for Hydraulic control valve system with electronic load sense control Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Hydraulic control valve system with electronic load sense control patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Hydraulic control valve system with electronic load sense control or other areas of interest. ### Previous Patent Application: Gasoline to pneumatic engine conversion zero emission & fuel cost Next Patent Application: Hydrostatic transmission Industry Class: Power plants ### FreshPatents.com Support Thank you for viewing the Hydraulic control valve system with electronic load sense control patent info. 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