Motors: expansible chamber type – With motive fluid valve – Inlet fluid supplemented by controlled fluid pressurized in...
Reexamination Certificate
1999-12-15
2001-07-31
Ryznic, John E. (Department: 3745)
Motors: expansible chamber type
With motive fluid valve
Inlet fluid supplemented by controlled fluid pressurized in...
C091S440000
Reexamination Certificate
active
06267041
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to hydraulic control systems used in work machines and, more particularly, to a hydraulic regeneration circuit for improving the response time and performance of a hydraulic system.
BACKGROUND ART
Construction and earthmoving equipment as well as a wide variety of other types of work machines are commonly used in a wide variety of different types of construction and earthmoving applications. These work machines typically include a wide variety of hydraulically actuated implements and/or work attachments such as buckets, front shovels, scrapers and the like which are utilized in different applications to accomplish different tasks. The control and operation of these various implements and/or work attachments preferably have a be timely response to the operator input commands controlling the operation thereof without sacrificing performance or power.
Sometimes a delay in implement or work attachment responsiveness may occur during a particular work application due to the fact that the hydraulic pump servicing the operation of the particular implement cannot provide the necessary amount of fluid flow to the implement actuator means as requested by the operator. For example, this may occur when an implement such as a blade on a track type tractor is rapidly lowered to the ground and the operator input is thereafter immediately actuated to lower the blade into the ground. For example, if the blade is raised above the ground line, then lowered, the blade will rapidly lower to the ground due to gravity. The rapid lowering movement will cause the cylinder to void. Further lowering of the blade is delayed until the pump fills the void in the cylinder. The delay typically occurs because during this rapid movement the hydraulic pump servicing the particular hydraulic circuit will be providing a large amount of fluid to the actuating means controlling the movement and operation of the implement or work attachment. Where the implement actuating means is a hydraulic cylinder, the hydraulic pump will provide fluid flow to either the head end portion or the rod end portion of the hydraulic cylinder to control the extension or retraction thereof. When fluid flow is provided to the rod end portion of the cylinder thereby retracting the same, fluid present in the head end portion is contracted and allowed to exit therefrom under pressure and escape to other portions of the circuit In the example where a blade associated with a track type tractor is rapidly lowered at low pressure, the hydraulic pump will be providing a large amount of fluid to the head end portion of the actuating cylinder. When the cylinder is then requested to move immediately in the same direction at high pressure, the hydraulic pump is unable to provide enough fluid flow to the head end portion of the cylinder in order to meet the responsiveness desired by the operator. In other words, the head end portion of the actuating cylinder is not refilled, or regenerated, fast enough to achieve the desired responsiveness.
Although some hydraulic control systems employ a regeneration circuit to fill the expanding side of a hydraulic cylinder or other actuator means with fluid exhausted from the contracting side, it would be desirable to provide a regeneration circuit which would be more responsive to certain parameters which are indicative of the operator requesting a rapid movement of the actuator means associated with a particular implement or work attachment. In this regard, it would also be desirable to provide a regeneration circuit which will increase the efficiency of filing the expanding side of a hydraulic actuating cylinder.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF THE INVENTION
In one aspect of the present invention, a fluid regeneration circuit is provided for a hydraulic system utilizing a hydraulic actuating cylinder for controlling the movement of an implement or other work attachment, the present regeneration circuit being specifically triggered for expanding the head end portion of the actuating cylinder based upon the velocity or rate of movement of the piston associated with the cylinder. More particularly, the present regeneration circuit includes an electrohydraulic regeneration or diverter valve positioned in fluid communication with the rod end portion of the actuating cylinder and actuatable so as to divert fluid flow from the rod end portion of the actuating cylinder to the head end portion thereof when so commanded. A position sensor is coupled to the actuating cylinder for monitoring the position of the piston within the actuating cylinder, the position sensor being coupled to an electronic controller which is operable to monitor the rate of movement or velocity of the piston within the actuating cylinder.
The electronic controller is likewise coupled to the diverter valve such that if the velocity of the cylinder piston exceeds a predetermined velocity, the controller will output an appropriate signal to the diverter valve actuating such valve so as to divert fluid from the rod end portion to the head end portion of the actuating cylinder thereby filling the head end portion of the cylinder faster so as to provide better responsiveness to the operator input commands controlling the operation of the implement. The diverter valve will continue to divert fluid to the head end portion of the actuating cylinder until the velocity of the cylinder piston drops to another predetermined velocity. At this point, the controller will output an appropriate signal to the diverter valve discontinuing regeneration of the actuating cylinder and returning the diverter valve to its normal position wherein fluid flow from the rod end portion of the cylinder is allowed to flow to other portions of the hydraulic system. Accordingly, the present regeneration or diverter valve functions to regenerate the head end portion of the actuating cylinder based solely upon the rate of movement or velocity of the cylinder piston.
The present diverter valve can be either a proportional valve or an on/off type valve, the proportional valve arrangement allowing proportional regeneration to the head end portion of the actuating cylinder based upon the velocity of the cylinder piston. A wide variety of different types of diverter valves as well as a wide variety of different types of position sensors can be utilized with the present invention. Also, velocity sensors specifically designed to output a signal indicative of the velocity of the cylinder piston can likewise be utilized in place of a position sensor.
The present fluid regeneration circuit is therefore specifically responsive to the rapid movement of the implement actuating cylinder based upon the cylinder piston velocity parameter and such regeneration circuit can be utilized in a wide variety of different types of work machines as well as a wide variety of different hydraulic circuit applications The present regeneration circuit provides a more responsive regeneration capability and increases the overall efficiency of filling the expanding side of a actuating hydraulic cylinder.
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Shah Vijay P.
Skiba Richard J.
Stratton Kenneth L.
Caterpillar Inc.
McPherson III W. Bryan
Ryznic John E.
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