Fixed/variable hybrid system

Abstract

A fixed / variable hybrid system has modified constant flow open center hydraulic valves (“fixed / variable valves”), including an open center core, spools, a power core, and a tank galley. A small fixed displacement pump provides fluid at a constant rate to the open center core. A variable displacement piston pump provides fluid directly to the power core as needed. Activation of spools partially restricts the open center core causing an increase in fluid pressure that is communicated to the variable displacement piston pump's load sense signal port, causing the pump to increase fluid flow and pressure to the power core. Activated spools direct pressurized fluid from the power core to the applications through selected hydraulic ports. Activated spools also direct fluid flow from selected hydraulic ports via the tank galley to a hydraulic tank. Pumping the majority of fluid only on an as-needed basis results in significant efficiencies.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority from and is related to the following prior application: Fixed Variable Hybrid System, U.S. Provisional Application No. 60 / 951,560, filed Jul. 24, 2007. The prior application, including the entire written description and drawings figures, is hereby incorporated by reference into the present application.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to hydraulic valve systems used, for example, in off-road earth moving, construction, and forestry equipment, such as backhoes, log loaders, feller bunchers, wheel loaders, and the like. Hydraulic valve systems are utilized, for example, to cause pistons to move a boom or bucket loader in a backhoe. The present invention relates to an improved design for such hydraulic valve systems.[0004]2. Brief Description of the Related Art[0005]Prior art hydraulic valve systems include the open center hydraulic valve system 110 ...

AI Technical Summary

Benefits of technology

[0032]It is another object of the embodiments of the fixed / variable hybrid system invention described herein to provide a hydraulic valve system capable of hydraulically operating the functions of heavy off-road equipment, such as earth moving, construction, and forestry equipment, while simultaneously significantly reducing unused hydraulic flow, and thereby significantly reducing the inefficient use of power associated with such unused flow.

[0042]As a result, significant fuel savings and power efficiencies are achieved by the present invention. Simply put, the fixed / variable hybrid system invention described herein utilizes a considerably smaller fixed displacement pump than prior art systems, resulting in less power being wasted pumping hydraulic fluid that is not operating any of the hydraulic functions (e.g., the boom) of the equipment (e.g., a backhoe), such as when the spools of the fixed / variable valves associated with the hydraulic functions are in a neutral position. Instead, the fixed / variable hybrid system utilizes only a small constant flow provided by a small fixed displacement pump, which in turn provides a signal in the form of a pressurized hydraulic fluid through a sense signal passage to a load sense signal port of a variable displacement piston pump to increase fluid flow to power core of the system only as needed upon demand when spool actuators (and their associated spools) are activated to operate an equipment function. Thus, the vast majority of operational power for the fixed / variable hybrid system is utilized only as needed, achieving significant fuel, power, and emission efficiencies. Moreover, the invention's fixed / variable hybrid system does not require any major design overhaul for the fixed / variable valves, or increase in size and weight of the fixed / variable valves, or significant increase in cost of the fixed / variable valves, as would be required if a variable displacement piston pump were to be merely substituted for the fixed displacement pump of the prior art open center hydraulic valve system.

Problems solved by technology

Hence, significant inefficiencies are inherent in the prior art open center hydraulic valve system 110.

Such a potential alternative therefore not only was largely rejected as being cost prohibitive, but the installation of such a large, heavy system was determined to be highly undesirable because, in many if not most applications, there is limited room available on equipment for the hydraulic system to be mounted.

Images