Variable Displacement Linkage Mechanism With Adjustable Spherical Joints

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Solution Overview

Problem

Variable displacement hydraulic pumps and motors experience efficiency decreases at low displacement, particularly in applications operating at partial load, due to high mechanical friction and leakage in existing planar joints used in hydrodynamic bearings.

Innovation Solution

The development of variable displacement linkage mechanisms incorporating adjustable revolute joints, cam followers, connecting links, rocker links, and coupler links, which allow for adjustable positioning of revolute joints to minimize un-swept volume and enhance mechanical efficiency across the full displacement range.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If planar joints with hydrodynamic bearings are used in variable displacement machines, then smooth operation is achieved, but mechanical friction and leakage increase significantly

Engineering Contradiction:

Improvesmooth operationVSAvoidmechanical friction and leakage

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The patent replaces traditional planar hydrodynamic bearing joints with a spherical joint mechanism. This substitution eliminates the need for hydrodynamic lubrication while achieving smooth operation through the spherical geometry that allows for self-alignment and reduced friction. The spherical joint maintains contact through point or line contact rather than surface contact, significantly reducing mechanical friction and leakage losses.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent employs spherical joints instead of planar joints. The spherical geometry provides curved surfaces that enable smooth rotational movement while maintaining point contact, which reduces the area of contact and consequently reduces friction and leakage. The spherical shape allows for automatic alignment and distributes loads more effectively, achieving smooth operation without the energy losses associated with planar hydrodynamic bearings.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Use of energy by moving object

If variable displacement is implemented, then energy savings potential is achieved, but efficiency decreases significantly at low displacement

Engineering Contradiction:

Improveenergy savings potentialVSAvoidefficiency at low displacement

Core Design Contradiction:

Use of energy by moving objectVSLoss of energy

Solution Approach 1:

The patent implements a variable displacement mechanism where the spherical joint's position can be dynamically adjusted to change the displacement volume. The mechanism uses a piston-cylinder arrangement combined with spherical joints that allow for continuous adjustment of the displacement parameter. This dynamic adjustment capability enables the system to maintain high efficiency across the full displacement range, including low displacement conditions, by optimizing the mechanical efficiency at each operating point.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the displacement parameter dynamically through mechanical adjustment of the spherical joint position. By varying the geometric parameters of the linkage mechanism, the system can achieve different displacement volumes while maintaining high mechanical efficiency. The parameter change is achieved through the coordinated movement of the piston, connecting rod, and spherical joints, allowing efficient operation from full to partial load conditions.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If traditional variable displacement mechanisms are used, then displacement control is achieved, but mechanical friction and leakage increase

Engineering Contradiction:

Improvedisplacement controlVSAvoidmechanical friction and leakage

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The patent replaces traditional planar joint mechanisms with spherical joints for displacement control. The spherical joint mechanism provides the necessary degrees of freedom for displacement control while eliminating the friction and leakage problems associated with planar hydrodynamic bearings. The spherical geometry enables smooth motion control through point contact, maintaining adaptability for variable displacement application.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent segments the displacement control function into separate spherical joint components rather than using a single planar joint. The mechanism divides the motion control into rotational and translational components handled by different spherical joints, allowing independent optimization of each joint for minimal friction and leakage while maintaining overall displacement control capability.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS10408318B2Variable displacement linkage mechanism

Publication Date: 2019.09.10 REGENTS OF THE UNIVERSITY OF MINNESOTA

AI summary

A variable displacement linkage mechanism includes a slider mechanism, a cam, a connecting link, a rocker link, and a cam follower. The connecting link is coupled to the slider through a first revolute joint. The rocker link includes a rocker end and a ground end. The rocker end is coupled to the connection link through a second revolute joint, and the ground end is coupled to ground through a third revolute joint. The cam follower is coupled to the connecting link and engages the cam. A location of the third revolute joint is adjustable relative to the first revolute joint.