Linear Motor Forcer Cooling: Liquid vs Air Methods

Overview of Technical Issues:

The forcer in the linear motor generates harmful waste heat during electromagnetic energy conversion, and if the cooling medium cannot absorb and remove this heat sufficiently, the forcer temperature rises excessively, degrading magnetic performance and force output while risking thermal damage to insulation and permanent magnets; the goal is to select and optimize a cooling method that adequately removes this harmful heat to maintain stable motor performance.

Solution directions generated for this problem

Problem Direction 1 :

ImproveHeat removal capacity
VS
ConstraintCooling system energy consumption

Inspiration 1 : Cross-domain reference

Application Principle: #2 Taking out (Extraction)
Cross-domain applicability Assess applicability
Laser package having multiple emitters configured on a support member
Innovative Solution Refine solution

Embedded heat pipe array with passive thermal extraction for linear motor forcer

Extract waste heat passively via embedded heat pipes
How to solve :
  • Embed axial heat pipe array (6–8 units, OD 6mm, copper-water) directly into forcer coil slots at 15mm spacing, vapor chamber at 60–80°C evaporates and transports heat to external finned condenser without pumping power
  • Route heat pipe condensers to aluminum fin stack (fin thickness 0.8mm, pitch 3mm, total area 0.4m²) mounted on motor housing exterior, rejecting 800–1200W via natural convection at ΔT=40K
  • Use sintered copper wick (porosity 55–65%, pore size 10–50μm) inside heat pipes for capillary return, ensuring continuous operation without gravity dependence or auxiliary power
Expected Effect : Heat removal 1000W, zero pump power, forcer temp ≤85°C
Risk Control :
  • heat pipe vapor pressure deviation
  • wick dry-out under peak load
  • thermal contact resistance at embedment interface

Problem Direction 2 :

ImproveHeat removal capacity
VS
ConstraintSystem design complexity

Inspiration 1 : Cross-domain reference

Application Principle: #1 Segmentation
Cross-domain applicability Assess applicability
Multi-layer contact plate configured to establish electrical bonds to battery cells in a battery module
Innovative Solution Refine solution

Modular plug-in heat pipe cooling units for linear motor forcer

Divide cooling into independent modules
How to solve :
  • Design self-contained heat pipe modules with sintered copper wick (porosity 60–70%) and water working fluid, each unit 50×20×5mm targeting specific forcer coil hot spots
  • Each module operates independently via passive phase-change heat transfer — evaporation at forcer surface (≥150°C), condensation at external fins (≤60°C), gravity return, achieving 80–120 W thermal transport per unit without pumps or external power
  • Implement plug-and-play mechanical interface with spring-loaded thermal pads (0.6mm thickness, ≥3 W/m·K conductivity) ensuring 0.05–0.15 K·cm²/W contact resistance, allowing field installation in under 5 minutes per module and individual replacement without system disassembly
Expected Effect : Heat removal +65%, zero auxiliary power, module replacement <5min, system component count −40%
Risk Control :
  • heat pipe wick sintering quality variation
  • thermal contact resistance exceeding 0.2 K·cm²/W
  • working fluid charge amount deviation ±5%

Problem Direction 3 :

ImproveHeat transfer efficiency
VS
ConstraintCooling system energy consumption

Inspiration 1 : Cross-domain reference

Application Principle: #3 Local quality
Cross-domain applicability Assess applicability
High brightness laser-sustained plasma broadband source
Innovative Solution Refine solution

Spatially-graded thermal conductivity forcer structure for targeted heat extraction

Zone-specific thermal design for forcer
How to solve :
  • Embed high-conductivity copper inserts (≥380 W/m·K) only at coil hot spots where heat flux exceeds 50 W/cm², use standard aluminum (≥200 W/m·K) elsewhere to create thermal gradient paths directing heat to housing surfaces
  • Design anisotropic heat spreaders with 0.6mm copper layers bonded to 3mm aluminum backing at coil regions, achieving 3–5× faster lateral heat spreading to low-temperature zones without increasing coolant flow
  • Integrate passive thermal shunts connecting hot spots directly to motor housing outer surfaces via copper straps (15mm × 2mm cross-section), bypassing coolant loop for 25–35% of peak heat load
Expected Effect : Pumping power reduced 40–50%; hot spot temperature reduced 15–20°C; overall heat transfer efficiency improved 35%
Risk Control :
  • copper-aluminum interface thermal resistance exceeding 0.02 K·cm²/W
  • thermal expansion mismatch causing delamination after 500 thermal cycles
  • manufacturing tolerance of ±0.1mm affecting thermal contact quality

Problem Direction 4 :

ImproveHeat transfer efficiency
VS
ConstraintSystem design complexity

Inspiration 1 : Cross-domain reference

Application Principle: #3 Local quality
Cross-domain applicability Assess applicability
Circuits and methods for wearable device charging and wired control
Innovative Solution Refine solution

Zoned thermal conductivity forcer structure with gradient material distribution

Apply gradient thermal conductivity only where needed
How to solve :
  • Map forcer heat flux distribution via thermal imaging
  • embed high-conductivity copper inserts (≥380 W/m·K) only in coil regions exceeding 50 W/cm² heat flux, use standard aluminum (≥200 W/m·K) elsewhere to reduce material cost and machining complexity
  • Design press-fit copper insert pockets with 0.05mm interference fit in forcer housing at identified hot spots
  • inserts are 15–25mm diameter, 8–12mm depth, positioned within 2mm of coil windings for direct conduction path
  • Maintain single-piece housing design with no additional cooling channels or interfaces
  • copper inserts conduct heat to aluminum housing perimeter where natural convection and radiation reject heat to ambient, eliminating pumps and plumbing
Expected Effect : Heat transfer efficiency +40–55% vs uniform aluminum; component count unchanged; no added auxiliary power
Risk Control :
  • thermal contact resistance at insert-housing interface exceeding 0.5 K·cm²/W
  • copper insert positioning tolerance deviation beyond ±1mm reducing effectiveness
  • long-term thermal cycling causing insert loosening after 5000+ cycles

Problem Direction 5 :

ImproveThermal stability duration
VS
ConstraintCooling system energy consumption

Inspiration 1 : Cross-domain reference

Application Principle: #3 Local quality
Cross-domain applicability Assess applicability
Cooling arrangement for engine components
Innovative Solution Refine solution

Zoned thermal mass buffer with gradient cooling intensity

Deploy zoned thermal mass to extend stable operation without continuous high-power cooling
How to solve :
  • Embed phase-change material (PCM) packs with melting point 65–75°C directly around forcer coil hot spots (heat flux >50 W/cm²) to absorb transient thermal spikes
  • use paraffin-based PCM with latent heat ≥200 kJ/kg, encapsulated in 0.6mm aluminum pouches for rapid heat absorption during first 3 hours
  • Increase motor housing wall thickness from 5mm to 12mm using aluminum alloy 6061 (thermal diffusivity 6.5×10⁻⁵ m²/s) to create distributed thermal mass that buffers heat in moderate-flux zones (20–50 W/cm²), extending stable duration to 6+ hours
  • Add passive thermosiphon loop with sintered copper wick connecting housing to external finned radiator
  • natural convection driven by 15–25°C temperature differential continuously rejects accumulated heat at 50–80W without pump power, preventing thermal saturation beyond 8 hours
Expected Effect : Stable operation 8+ hours; auxiliary power <60W; thermal saturation eliminated
Risk Control :
  • PCM encapsulation leak risk
  • housing thickness increases mass by 15%
  • thermosiphon vapor pressure control

Problem Direction 6 :

ImproveThermal stability duration
VS
ConstraintSystem design complexity

Inspiration 1 : Cross-domain reference

Application Principle: #1 Segmentation
Cross-domain applicability Assess applicability
Semiconductor device
Innovative Solution Refine solution

Modular thermal buffer housing for extended stable operation

Redesign motor housing as thermal buffer
How to solve :
  • Segment the motor housing into independent thermal zones — forcer zone with 12–18mm thick aluminum walls (Al6061-T6, ≥167 W/(m·K)), stator zone with standard 5mm walls, mechanically joined by bolted flanges
  • Each zone functions as plug-and-play thermal module — forcer housing absorbs 1.2–1.8 MJ heat capacity (specific heat 0.9 kJ/kg·K, mass 8–12 kg), extending stable operation from 2–3 hours to 6–8 hours without additional components
  • Add passive thermosiphon channels cast into thickened housing walls (10mm diameter vertical passages spaced 40mm apart) — natural convection transfers accumulated heat to external finned surfaces (fin height 25mm, spacing 8mm), rejecting 150–250W continuously to ambient air without pumps or fans
Expected Effect : Thermal stability duration +150–200%; zero added auxiliary power; component count unchanged
Risk Control :
  • housing casting defect rate
  • thermal contact resistance at bolted interfaces
  • ambient temperature exceeds 35°C baseline
Patsnap Eureka Solution