Refrigerant Compressor Torque Control for Quiet Low-Speed Operation
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Solution Overview
Problem
Variable-speed reciprocating refrigerant compressors experience noise-related issues and vibration excitation at low rotational speeds due to varying load torque, leading to undesirable noise emissions and potential contact with the compressor housing during normal operation and shutdown processes.
Innovation Solution
An electronic control system that dynamically adjusts the operating torque of the compressor's drive unit to match the varying load torque over the crank angle, providing a positive operating torque during compression phases and reducing or eliminating it during suction phases, allowing for smoother operation and controlled shutdown without the need for braking torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the reciprocating refrigerant compressor is operated at low rotational speeds to reduce refrigeration requirements, then energy consumption is reduced, but noise emissions increase due to vibration excitation from varying load torque
Solution Approach 1:
The patent applies dynamics by making the operating torque dynamic rather than constant. The electronic control device continuously adjusts the operating torque of the drive unit based on the detected piston position and crank angle, enabling the compressor to operate smoothly at low rotational speeds without exciting vibrations, thus reducing noise emissions while maintaining low energy consumption
Solution Approach 2:
The patent changes the parameter of operating torque from a constant value to a variable value that depends on crank angle and piston position. By dynamically adjusting the torque parameter throughout the compression cycle, the system eliminates the load torque variations that cause vibrations and noise at low speeds
2Device complexity
If constant voltage is applied to the drive unit during compression, then control simplicity is maintained, but speed uniformity deteriorates due to varying load torque causing non-uniform rotational speed
Solution Approach 1:
The patent applies local quality by providing different operating torques at different crank angle positions. During the compression phase, a first operating torque is applied, while during the suction phase, a second operating torque is applied. This localized torque adjustment compensates for load variations at specific points in the cycle, maintaining uniform rotational speed without overly complicating the control system
Solution Approach 2:
The patent implements feedback by using a sensor to detect the piston position and crank angle, then using this information to dynamically adjust the operating torque. The electronic control device receives position feedback and automatically modulates the drive unit torque accordingly, achieving speed uniformity through closed-loop control
3Stability of the object's composition
If the compression mechanism is mounted via spring elements to compensate for vibrations, then vibration absorption is improved, but at low speeds the natural frequency excitation occurs causing increased deflection and potential contact with housing
Solution Approach 1:
The patent applies preliminary action by proactively adjusting the operating torque before vibration problems occur. By detecting the piston position and crank angle in advance, the control device preemptively modulates the torque to prevent load torque variations that would excite the spring elements' natural frequency, thus preventing vibrations and noise before they start
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
This approach enables quiet operation at low rotational speeds, prevents vibration-induced noise emissions, and ensures safe shutdown without piston reversal, maintaining the compressor's alignment with the housing and reducing energy consumption.
Implementation Method 1
It is possible to determine the relative position of the rotor of the DC motor and thus also the rotational speed of the motor or the compression mechanism on the basis of the counter-voltage (induction counter-voltage) induced in the motor winding.
Data Source
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AI summary
Electronic control device (13) for a refrigerant compressor, which comprises at least - a drive unit (18), - a compression mechanism (5) operatively connected to the drive unit (18), with at least one located in a cylinder of a cylinder block (8) between a lower and a top dead center reciprocating piston (9) driven via a crankshaft (6), wherein the electronic control device (13) is set up to - detect and control the rotational speed (ω) of the drive unit (18) and /or regulate, - to at least approximately detect the piston position, the electronic control device (13) being set up to drive the compression mechanism (5) via the drive unit (18) in such a way that, for the duration of a control time segment (Δt ), with several crankshaft revolutions, preferably with each crankshaft revolution of the control time section (Δt) at least one drive angle section (ΔΦ) and at least one running angle section (Φτ) is provided and wherein the compression mechanism during the at least one drive angle section (ΔΦ) has a positive operating torque (Bm) and during the at least one running angle section (Δτ) has a positive operating torque operating torque (Bm) is subject to reduced positive operating torque (Bmv) or no positive operating torque (Bm).