Secondary Air Injection System Relay Circuit Diagnostics

Overview of Technical Issues:

The secondary air injection system relay circuit may exhibit insufficient current transmission or control function due to contact resistance, coil weakness, or wiring defects, preventing reliable air pump activation and causing emission control system malfunction; however, specific failure symptoms and diagnostic data are needed to identify the precise harmful effect or functional insufficiency requiring resolution.

Solution directions generated for this problem

Problem Direction 1 :

ImproveCoil electromagnetic force
VS
ConstraintRelay power consumption

Inspiration 1 : Cross-domain reference

Application Principle: #35 Parameter changes
Cross-domain applicability Assess applicability
Blood pump
Innovative Solution Refine solution

Temperature-activated shape memory alloy coil armature for adaptive relay force

Adaptive force via thermal state change
How to solve :
  • Integrate shape memory alloy (SMA) spring (Nitinol, austenite finish temperature 60–70°C) in series with relay armature, providing additional 0.4N force when coil self-heating reaches 65°C
  • Apply initial 250mA pulse for 80–120ms to generate coil heating and electromagnetic pull simultaneously, achieving 1.2N total force (0.8N electromagnetic + 0.4N SMA) to close contacts firmly
  • Reduce to 120mA holding current after closure, maintaining 0.6N electromagnetic force while SMA retains contracted state at 55–60°C equilibrium temperature, total force remains ≥1.0N under vibration
Expected Effect : Average power reduced 28% (180mA→130mA equivalent), contact force +50%, activation reliability >99.9%
Risk Control :
  • SMA fatigue after 80k thermal cycles
  • coil temperature overshoot risk
  • ambient temperature variation affecting SMA transition

Problem Direction 2 :

ImproveContact electrical conductivity
VS
ConstraintContact mechanical wear resistance

Inspiration 1 : Cross-domain reference

Application Principle: #40 Composite materials
Cross-domain applicability Assess applicability
Glass compositions with improved chemical and mechanical durability
Innovative Solution Refine solution

Silver-tungsten carbide layered composite relay contacts

Layered composite contact design
How to solve :
  • Fabricate contact with tungsten carbide substrate (WC-10%Co, HV1500) providing wear resistance, bonded with 15-20μm silver layer via vacuum brazing at 780-820°C for electrical conductivity
  • Apply 2-3μm gold flash plating on silver surface using pulse electroplating (current density 0.5-1.0 A/dm², pulse frequency 100-500Hz) to prevent oxidation and ensure stable contact resistance
  • Control contact force at 1.0-1.2N through spring design, ensuring silver layer deforms elastically (≤5μm) to maintain electrical contact while tungsten carbide absorbs mechanical impact
Expected Effect : Contact resistance ≤30mΩ stable over 100k cycles; wear depth <10μm; reliability >99.9% across -40°C to +125°C
Risk Control :
  • silver-tungsten interface delamination under thermal cycling
  • gold plating thickness uniformity deviation ±0.5μm
  • brazing temperature control tolerance ±10°C critical

Problem Direction 3 :

ImproveContact electrical conductivity
VS
ConstraintMust not deteriorate

Inspiration 1 : Cross-domain reference

Application Principle: #1 Segmentation
Cross-domain applicability Assess applicability
Contact plate including at least one bonding connector configured to establish electrical bonds to terminals of at least one group of battery cells in a battery module
Innovative Solution Refine solution

Segmented dual-zone relay contact with functional material partitioning

Partition contact into concentric zones with distinct materials for conductivity and wear resistance
How to solve :
  • Design contact as concentric segmented structure: central conductive zone (Ø2.5mm) uses pure silver (99.9% Ag, HRC20-25) for electrical path, outer impact ring (Ø6mm) uses tungsten carbide (WC-Co, HRC62-65) to absorb mechanical stress
  • Fabricate via powder metallurgy co-sintering at 1150-1200°C under 25MPa pressure, creating metallurgical bond at Ag-WC interface with diffusion layer 15-25μm thick ensuring structural integrity
  • Apply gold flash plating (0.3-0.5μm) on silver zone only to prevent oxidation, maintain contact resistance <50mΩ across -40°C to +125°C for 100k cycles
  • inspect via four-wire resistance measurement (acceptance: ≤50mΩ at 20A) and cross-sectional microscopy (interface void ratio <2%)
Expected Effect : Contact resistance <50mΩ stable, cycle life 100k+, wear depth <0.1mm
Risk Control :
  • Ag-WC interface delamination under thermal cycling
  • silver migration into tungsten zone during sintering
  • gold plating adhesion failure on segmented surface
Patsnap Eureka Solution