Flow Control Valve Backlash Elimination
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Solution Overview
Problem
Existing flow control valves experience backlash and hysteresis due to the interaction between male and female threaded portions, leading to overscrewing issues and the need for expensive rotary encoders for accurate position determination.
Innovation Solution
A flow control valve design incorporating a screw member connected to a valving element with an urging member that constantly biases the threaded portions, combined with packing to prevent vaporized chemicals from reaching the motor and a control device for precise torque and position control, eliminating backlash and hysteresis without a rotary encoder.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a screw member connects the rotary shaft and valving element, then the valving element can be moved within the movable range, but backlash and hysteresis occur in the flow control
Solution Approach 1:
The spring member applies a preliminary urging force to the valving element in the direction opposite to the motor's rotation direction. This pre-applied force eliminates backlash between the screw member and nut by maintaining constant contact pressure, preventing the looseness that would otherwise occur during bidirectional rotation of the rotary shaft.
Solution Approach 2:
The spring member is pre-compressed or pre-tensioned during assembly to establish an initial urging force on the valving element. This preliminary action ensures that the threaded connection remains tight and eliminates hysteresis effects before the motor begins operation, improving flow control precision from the start.
2Adaptability or versatility
If the motor rotates beyond the movable range of the valving element, then the motor can operate freely, but the screw member may be overscrewed causing motor failure
Solution Approach 1:
The spring member acts as a cushioning element that can be compressed to absorb excess rotational movement. When the motor attempts to rotate beyond the movable range, the spring compresses further, providing a mechanical buffer that prevents the screw member from being overscrewed and protects the motor from damage.
Solution Approach 2:
The spring member serves as an intermediary between the motor and the valving element's mechanical stop. Instead of the motor directly encountering the hard stop, the spring provides a gradual, compliant transition that mediates the energy transfer and prevents sudden impacts or overscrewing.
3Device complexity
If no position detection device is used, then the flow control valve remains simple and low-cost, but the control device cannot accurately determine the valving element position
Solution Approach 1:
The control device uses feedback from the motor's rotation angle (measured by the encoder on the motor shaft) and the known mechanical relationship between the screw member and valving element to calculate the valving element's position. This indirect feedback method achieves accurate position determination without adding complex position detection hardware to the valving element itself.
Solution Approach 2:
The patent replaces a direct mechanical position detection system (which would require additional sensors or encoders on the valving element) with an electrical/electronic calculation approach. The control device uses the motor's rotation data and screw pitch information to computationally determine position, substituting mechanical measurement with electronic calculation.
4Reliability
If the threaded portions are constantly biased, then backlash is reduced, but the friction force increases
Solution Approach 1:
The spring member's urging force is designed to be optimized for the specific application, balancing the need to eliminate backlash with the need to minimize excessive friction. By adjusting the spring constant and pre-compression force, the system finds an optimal parameter set that provides sufficient bias to eliminate backlash while keeping friction within acceptable limits for the motor's torque capacity.
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
The solution reduces or eliminates backlash and hysteresis, prevents overscrewing, and accurately determines the valving element's position without the need for a rotary encoder, enhancing the flow control valve's performance and reducing costs.
Implementation Method 1
an urging member that urges the valving element toward the motor side or toward the side opposite to the motor
Implementation Method 2
a valving element connected to a rotary shaft of the motor with a screw member
Data Source
AI summary
An object is to provide a flow control valve that is capable of reducing or eliminating backlash generated between a male threaded portion and a female threaded portion engaged with the male threaded portion and preventing or eliminating hysteresis in the flow level. The flow control valve includes a body having a fluid inlet and a fluid outlet, a cover attachable to the body, a motor disposed in a space defined by the body and the cover, a valving element connected to a rotary shaft of the motor with a screw member, and an urging member that urges the valving element toward the motor side or toward the side opposite to the motor.