Variable-Speed Speed-Up Mechanism with Overspeed Brake

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Solution Overview

Problem

In variable-speed speed-up mechanisms, the rotational speed of the variable-speed rotor can exceed the rated speed due to power shutdown or other abnormalities, leading to potential damage or inefficiency.

Innovation Solution

A mechanism incorporating a planetary gear transmission system with a brake mechanism that detects abnormal states, such as excessive rotational speed, temperature, or vibration, and stops the variable-speed input shaft or rotor to prevent overspeed without affecting the constant-speed rotor, using a detection unit, brake unit, and brake control unit to manage the rotation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a variable-speed electric motor is used to control the rotational speed of the rotary machine, then the rotational speed can be adjusted according to load conditions, but the rotational speed may exceed the rated speed during abnormalities such as power shutdown

Engineering Contradiction:

Improverotational speed adjustment capabilityVSAvoidrotational speed control under abnormal conditions

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The electric device is segmented into two independent motors: a constant-speed electric motor and a variable-speed electric motor. This segmentation allows independent control of each motor's speed, enabling the constant-speed motor to provide a baseline rotational speed while the variable-speed motor adjusts speed according to load conditions. During abnormalities, the constant-speed motor ensures the rotary machine does not stop completely, preventing the variable-speed rotor from exceeding rated speed.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A planetary gear transmission device is introduced as an intermediary mechanism between the two electric motors and the rotary machine. The planetary gear system combines the rotational forces from both motors and transmits them to the rotary machine, enabling precise control of the output speed while isolating the variable-speed motor's speed variations from directly affecting the rotary machine's minimum operational speed.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If the rotational speed of the variable-speed electric motor is determined by the inertia of the rotary machine during power shutdown, then the motor can coast down naturally, but the rotational speed may become greater than the rated rotational speed

Engineering Contradiction:

Improvenatural coast-down behaviorVSAvoidoverspeed damage risk

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The constant-speed electric motor provides preliminary counter-action by maintaining a baseline rotational speed that opposes the uncontrolled coast-down of the variable-speed motor. This preliminary action prevents the variable-speed rotor from accelerating beyond rated speed during power shutdown by ensuring the planetary gear system receives continuous controlled input from the constant-speed motor.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The system implements feedback control by monitoring the rotational speeds of both electric motors and the planetary gear transmission device. The control mechanism adjusts the variable-speed motor's operation based on feedback signals, preventing overspeed conditions during abnormal situations while maintaining ease of operation during normal conditions.

Inventive Principle:

Principle #23Feedback

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 prevents the rotational speed of the variable-speed rotor from exceeding the rated speed, ensuring safe and efficient operation by monitoring and controlling abnormal conditions, thereby protecting the system from damage and maintaining performance.

Implementation Method 1

a planetary gear transmission device which changes the rotational driving force generated by the electric device and transmits the rotational driving force to the rotary machine

Methodology Applied

Scientific EffectPlanetary gear mechanism: Gear

Implementation Method 2

a brake mechanism which is configured to detect an abnormal state of the variable-speed electric motor, stops rotation of at least one of the variable-speed input shaft and the variable-speed rotor

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS11060587B1Variable-speed speed-up mechanism

Publication Date: 2021.07.13 MITSUBISHI HEAVY INDUSTIES COMPRESSOR CORP

AI summary

A variable-speed speed-up mechanism (1) includes an electric device (50) and a transmission device (10). In the transmission (10), an internal gear carrier shaft (37) forms a constant-speed input shaft (Ac), and a planetary gear carrier shaft (27) forms a variable-speed input shaft (Av). The electric device (50) includes a constant-speed electric motor (51) having a constant-speed rotor (52) which is configured to rotate the constant-speed input shaft (Ac), and a variable-speed electric motor (71) having a variable-speed rotor (72) which is connected to the variable-speed input shaft (Ac). The variable-speed speed-up mechanism (1) further includes a brake mechanism (200) which is configured to detect an abnormal state of the variable-speed electric motor (71), stop the rotation of at least one of the variable-speed input shaft (Ac) and the variable-speed rotor (72), and continue the rotation of the constant-speed rotor (52).