Refrigerant Compressor Delivery Volume Control to Prevent Overheating

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Solution Overview

Problem

Refrigerant compressors face overheating issues during partial performance states, especially at low delivery volumes, due to insufficient cooling, which can lead to damage.

Innovation Solution

The delivery volume control system detects a compressor reference temperature and determines an operating state value group, using predetermined reference values to differentiate between critical and non-critical states, adjusting the delivery volume to prevent overheating by averaging values over defined periods to account for temperature inertia and fluctuations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the delivery volume of the refrigerant compressor is reduced to operate in partial capacity range, then energy efficiency is improved, but the cooling effect becomes insufficient leading to overheating

Engineering Contradiction:
Improvedelivery volumeVSAvoidcompressor temperature
Core Design Contradiction:
ProductivityVSTemperature

Solution Approach 1:

The control unit continuously monitors the compressor reference temperature and adjusts the delivery volume accordingly. When the temperature exceeds a threshold, the control unit increases the delivery volume to enhance cooling effect, and when temperature is acceptable, it reduces delivery volume to improve energy efficiency. This closed-loop feedback mechanism resolves the contradiction by dynamically balancing productivity and temperature control.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The system dynamically adjusts the delivery volume based on real-time temperature conditions rather than operating at a fixed setting. The delivery volume control adapts its operation to match the thermal state of the compressor, enabling the system to transition between partial capacity range (for efficiency) and higher capacity range (for cooling) as needed, thus resolving the static contradiction between productivity and temperature management.

Inventive Principle:
Principle #15Dynamics

2Reliability

If the delivery volume is continuously monitored and adjusted to prevent overheating, then reliability is improved, but the control system complexity increases

Engineering Contradiction:
Improvecompressor reliabilityVSAvoidcontrol system complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The control unit automatically monitors compressor reference temperature and adjusts delivery volume without requiring external intervention or complex external control systems. The system serves itself by using its own control capabilities to prevent overheating, thereby improving reliability while minimizing the addition of external complex control mechanisms.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The control unit performs multiple functions: it manages the primary compression control based on delivery volume setpoints and simultaneously monitors temperature and adjusts delivery volume to prevent overheating. By making the control unit multi-functional, the patent improves reliability without requiring a separate dedicated temperature control system, thus limiting the increase in overall system complexity.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Data Source

PatentEP3940231B1Refrigerant compressor
Publication Date: 2024.04.17 BITZER KUEHLMASCHINENBAU GMBH
  • EP3940231B1 patent drawingFigure 1
  • EP3940231B1 patent drawingFigure 2
  • EP3940231B1 patent drawingFigure 3~4

AI summary

In order to avoid critical operating conditions in a refrigerant compressor (10) for refrigeration systems, comprising a compressor unit (40) driven by a drive unit (60), wherein at least one of these units (60, 40) is equipped with a control unit (140, 70) which can be controlled by a delivery volume control (130) to control the refrigerant compressor (10) at different delivery volumes (FV), wherein an external delivery volume setpoint (EFVS) is transmitted to the delivery volume control (130), it is proposed that the delivery volume control (130) detects a compressor reference temperature (RT) of the compressor unit (40) by means of a sensor (152), that the delivery volume control (130) determines an operating state value group (BZW) for detecting an operating state of the refrigerant compressor (10) and then, taking into account predefined reference values ​​(GF),if the value of the determined operating condition value group (BZW) based on the compressor reference temperature (RT) allows a critical operating condition of the refrigerant compressor (10), specifies a delivery volume (FV) that results in the operation of the refrigerant compressor (10) outside the critical operating conditions (KB).