Variable output fluid pump system

Abstract

A variable output pump system is provided, the pump system having a first positive displacement pump; a pump drive operably coupled to the first positive displacement pump, wherein the pump drive operates the first positive displacement pump to have a first output profile during a first operating range and a second output profile during a second operating range, the pump drive having a hydraulic release being configured to decrease the second output profile as a hydraulic pressure increases.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of the following U.S. Provisional Applications Ser. No. 61 / 057,801 filed May 30, 2008; Ser. No. 61,059,069 filed Jun. 5, 2008; and Ser. No. 61 / 150,225 filed Feb. 5, 2009, the contents each of which are incorporated herein by reference thereto.BACKGROUND[0002]Exemplary embodiments of the present invention relate to fluid pumps, in particular a variable output pump system comprising a positive displacement pump and a variable speed ratio drive system.[0003]Positive displacement pumps are generally used in automotive and industrial applications due to their comparatively low overall cost and the packaging space requirements for such pumps. One example is an internal tip sealing gear type pump commonly known as a gerotor pump. These pumps (positive displacement gerotors and equivalents thereof) are configured to maintain oil pressure under certain conditions (e.g., high oil temperatures and engine idle rpm)...

AI Technical Summary

Benefits of technology

[0009]In accordance with another exemplary embodiment of the invention, a variable output pump system is provided, the pump system having a pressure-regulated slip drive for varying the output of at least one positive displacement pump. The pressure-regulated slip drive has at least one biasing member for providing a biasing force that tends to cause frictional engagement of at least a pair of engagement surfaces, and the pressure-regulated slip drive also has a fluid cavity in fluid communication with a fluid being pumped by the pump. The pressure of the fluid in the fluid cavity opposes the biasing force of the biasing member tending to engage the pair of engagement surfaces, thereby affecting the magnitude of the torque transmitted from one of the engagement surfaces to the other, thereby affecting the speed ratio between the engagement surfaces, and thus the output of the pump. The torque transmitted between engagement surfaces is preferably due to Coulomb friction during startup phases only, i.e. before fluid pressure is developed, thereafter transitioning to viscous oil film shearing between physically separated engagement surfaces of sufficient area and radius in order to avoid the wear inherent to Coulomb friction. The engagement surfaces are preferably formed with interactive lubricant passages that enable continually repeated flushing of the entirety of the contact areas of both members, for improved cooling and power dissipation capacity.

[0012]In still another exemplary embodiment, a method for varying the output of a positive displacement pump is provided, the method comprising: biasing at least one frictional engagement surface of a pressure-regulated slip drive towards frictional engagement with another frictional engagement surface with a biasing force in order to drive the pump. The biasing force is applied to a sealingly mobile load control member. Opposing the biasing force applied to the sealingly mobile load control member by fluid pressure in a fluid cavity disposed between a surface of the sealingly mobile load control member and a pressure containment member causes a reduction in the amount of the biasing towards frictional engagement of the at least two frictional engagement surfaces and thereby affects the output of the pump.

Problems solved by technology

The pressure of the fluid in the fluid cavity opposes the biasing force of the biasing member tending to engage the pair of engagement surfaces, thereby affecting the magnitude of the torque transmitted from one of the engagement surfaces to the other, thereby affecting the speed ratio between the engagement surfaces, and thus the output of the pump.

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