Linear Compressor Piston Collision Prevention via Motor Current Feedback
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Solution Overview
Problem
Linear compressors face noise generation due to collisions between the piston and the discharge valve, which is unavoidable in existing control methods that rely on detecting the top dead center, leading to inefficiencies and increased costs.
Innovation Solution
A compressor system with a pressure changing unit that alters the pressure variation rate before the piston reaches a virtual discharge surface, using a controller to detect changes in motor voltage or current to prevent collisions, thereby avoiding the discharge valve without the need for additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If feedback control is executed by detecting voltage and current applied to the compressor motor, then the control device can estimate piston stroke in a sensor-less manner, but the piston collides with the discharge valve because TDC detection is only possible after collision occurs
Solution Approach 1:
The invention applies preliminary action by detecting changes in voltage or current applied to the linear motor before the piston reaches TDC and collides with the discharge valve. The controller uses these detected changes as advance signals to adjust the driving force, preventing the collision before it occurs. This transforms the post-collision TDC detection method into a pre-collision prevention method, eliminating noise while maintaining sensor-less operation.
Solution Approach 2:
The invention implements feedback control by continuously monitoring voltage or current applied to the linear motor and using this information to adjust the driving force in real-time. When a change in voltage or current is detected that indicates the piston is approaching TDC, the controller reduces the driving force to prevent collision. This closed-loop feedback mechanism enables noiseless operation without requiring additional sensors.
2Device complexity
If the piston is reciprocated without mechanical locking, then the linear motor can directly generate linear driving force without mechanical conversion devices, but the piston may collide with the cylinder wall when excessive voltage is applied suddenly
Solution Approach 1:
The invention uses feedback control by detecting changes in voltage or current applied to the linear motor and using this information to adjust the driving force in real-time. This feedback mechanism prevents excessive voltage application that could cause the piston to collide with the cylinder wall, while maintaining the simplicity of direct linear motor-driven piston reciprocation without mechanical conversion devices.
Solution Approach 2:
The invention applies dynamics by making the driving force of the linear motor adjustable and controllable in real-time based on operating conditions. The controller dynamically adjusts the voltage or current applied to the linear motor, enabling the system to adapt to varying loads and prevent both collision with the cylinder wall and the discharge valve, while maintaining the structural simplicity of direct linear motor coupling.
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 effectively reduces noise and abrasion, lowers manufacturing costs, and enables high-efficiency operation by preventing piston-discharge valve collisions, extending component lifespan and improving operational stability.
Implementation Method 1
a linear motor to supply a driving force for the motion of the piston
Implementation Method 2
a pressure changing unit to change a variation rate of pressure applied to the piston before the piston reaches a virtual discharge surface (VDS) during the reciprocating motion
Data Source
Figure 1A~1B
Figure 2A
Figure 2B
AI summary
The present invention provides a linear compressor including a piston reciprocating within a cylinder, a linear motor to supply a driving force for the reciprocating motion, a discharge unit to discharge a refrigerant compressed in the cylinder therethrough, in response to the motion of the piston, a pressure changing unit to change a variation rate of pressure applied to the piston before the piston reaches a virtual discharge surface (VDS) during the reciprocating motion, to prevent collision between the piston and the discharge unit, wherein the virtual discharge surface is formed on at least part of the discharge unit facing a compression space within the cylinder.