Viscous Clutch Fluid Capture System with Arcuate Reservoir
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Solution Overview
Problem
Viscous clutches suffer from 'morning sickness' due to shear fluid drain-back into the working chamber when unused, causing unwanted engagement and noise upon vehicle start-up, with existing solutions complicating manufacturing and increasing clutch size.
Innovation Solution
A viscous clutch design featuring a reservoir with an accumulator and arcuate or tortuous paths to retain shear fluid, preventing drain-back by isolating portions of the reservoir and using an accumulator in series with the reservoir to manage fluid flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a reservoir with openings or bores fluidically connected to the working chamber is used to store shear fluid, then the clutch can maintain low output speed and have kinetic energy available for rapid engagement, but shear fluid drain-back occurs into the working chamber when the clutch is idle, causing morning sickness
Solution Approach 1:
The reservoir is divided into multiple compartments by partition walls, creating separate storage areas for shear fluid. This segmentation prevents gravity-induced drain-back to the working chamber while maintaining fluid availability for engagement, resolving the contradiction between low idle speed capability and engagement control reliability.
Solution Approach 2:
An accumulator chamber is introduced as an intermediary component between the reservoir and the working chamber. The accumulator receives shear fluid from the reservoir through a restricted passage and can supply it to the working chamber when needed, acting as a buffer that prevents direct drain-back while maintaining operational fluid supply.
2Reliability
If complex structures are used to prevent morning sickness, then shear fluid drain-back can be reduced, but manufacturing and assembly become more difficult
Solution Approach 1:
The partition walls and accumulator chamber are integrated into the clutch housing as a unified structure rather than separate components. This merging of functions into a single molded housing simplifies manufacturing while maintaining the morning sickness prevention functionality, avoiding the need for complex assembly of multiple separate parts.
3Reliability
If morning sickness prevention mechanisms are added to the clutch, then shear fluid drain-back is reduced, but the size of the clutch increases in radial and/or axial direction
Solution Approach 1:
The accumulator chamber is positioned within or adjacent to the reservoir in a nested arrangement, with the partition walls utilizing the existing radial and axial space of the clutch housing. This nesting approach prevents fluid drain-back while minimizing the overall clutch size increase, as the prevention mechanism is embedded within the existing structure rather than adding external volume.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively reduces shear fluid drain-back, minimizing unwanted clutch engagement and noise, while maintaining a compact clutch design without increasing manufacturing complexity or size.
Implementation Method 1
an accumulator to accept the shear fluid from the return bore
Implementation Method 2
The drain-back problem is often dependent upon the rotational (or angular) orientation of the clutch when the clutch comes to rest, with gravity tending to induce relatively large volumes of drain back fluid into the working chamber
Implementation Method 3
These clutches employ a relatively thick shear fluid or viscous fluid
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A viscous clutch (20; 120; 220) includes an input member (24; 126; 224), an output member (26; 124; 226), a working chamber (38; 138; 238), a reservoir (36; 136; 236; 504; 604; 704; 804; 904; 1004; 1104) to hold a supply of a shear fluid, an outlet (36-2; 182; 236-2; 512; 612; 712; 812; 912; 1012; 1112), a return bore (26-2; 124B; 226-2), an accumulator (72; 502; 602; 702; 802; 902; 1002; 1102), and a first wall (70-1; 170; 270; 506; 606; 706; 806; 906; 1006; 1106) having an arcuate segment (70-1A; 506B; 606B; 706B; 806B; 906B; 1006B; 1106B). The reservoir is connected to the working chamber by a fluid circuit, along which the outlet passes the shear fluid from the reservoir to the working chamber and the return bore returns the shear fluid pumped out of the working chamber to the accumulator. The accumulator is arranged in series with the reservoir in the fluid circuit. The first wall is positioned within the reservoir to separate a first portion from a second portion.