The compressor crankshaft, as a core component of reciprocating compressors, directly influences the energy efficiency, reliability, and lifespan of the compressor. Below is an analysis from four dimensions: structural design, material technology, application scenarios, and technological trends, combined with the latest industry practices and data to comprehensively explore the technical development of this critical component.
I. Structural Design and Working Principle
1. Typical Structural Features
Compressor crankshafts typically consist of main journals, connecting rod journals, crank arms, and balance weights, adopting a symmetrical balanced design (such as H-type compressors) to reduce vibration. For example, the sliding bearings of the H22(VI)-260/15 compressor crankshaft use centrifugal casting to embed tin-based bearing alloy, forming a thin and uniform lining that enhances wear resistance and load-bearing capacity. The diameter tolerance of the main journals and connecting rod journals is controlled within ±0.002mm, with cylindricity error less than 0.001mm, ensuring stability during high-speed rotation.
2. Motion Conversion Mechanism
The rotating motion of the motor is converted into the reciprocating motion of the piston through a crank-slider mechanism to achieve gas compression. For instance, the eccentric part of the scroll compressor crankshaft drives the orbiting scroll to perform translational motion, forming a continuous compression chamber. The design must meet the following requirements:
- Dynamic Balance: The mass distribution of balance weights offsets reciprocating inertia forces, reducing vibration and bearing load.
- Lubrication System: Spiral oil grooves are machined on the journal surface, with pressure lubrication to ensure an oil film thickness of 20-50μm.
II. Material Selection and Manufacturing Process
1. High-Performance Material System
- Alloy Steel: Medium-carbon alloy steels such as 40Cr and 35CrMo, after quenching and tempering, achieve a hardness of HRC 30-40 and tensile strength exceeding 800MPa, suitable for high-pressure compressors (e.g., reciprocating compressors).
- Ductile Iron: Materials like QT600-3, through isothermal quenching, enhance fatigue strength by 30% and reduce costs by 20%-30% compared to alloy steel, widely used in compressors.
- Composite Materials: In the new energy sector, carbon fiber-reinforced polymers (CFRP) are introduced to reduce weight by 40% while maintaining strength, adapting to the high-speed requirements of hybrid systems.
2. Advanced Manufacturing Technologies
- Precision Forging: Tianrun Industry's crankshaft production line uses hot die forging presses and roll forging blanking processes, increasing material utilization to 85% and reducing machining allowance by 50%.
- Surface Treatment:
- Nitriding: 38CrMoAlA steel, after ion nitriding, achieves a surface hardness of HV 900-1200, improving wear resistance by 5 times.
- Fillet Rolling: Through a rolling force of 0.1-0.15mm, a residual compressive stress layer is formed at the crankshaft fillet, extending fatigue life by 1.5-2 times.
- 3D Printing Technology: Beifeng Intelligent's large-scale metal 3D printing equipment can manufacture complex lattice-structured crankshafts, reducing weight by 30% while maintaining strength.
III. Application Scenarios and Market Landscape
1. Core Application Fields
- Industrial Compressors: Reciprocating compressor crankshafts must withstand gas pressures of 20-100MPa. For example, in the fertilizer industry's syngas compressors, the crankshaft lifespan requirement exceeds 100,000 hours.
- Refrigeration and Air Conditioning: The scroll compressor crankshaft market reached 16.8 million units in 2021, with an annual growth rate of 9.7%, mainly supporting household air conditioners and cold chain equipment.
- New Energy Vehicles: Electric compressor crankshafts need to adapt to high speeds of 15,000-30,000rpm, using ceramic coating technology to reduce the friction coefficient to below 0.015.
2. Global Competition Landscape
- Leading Enterprises:
- Tianrun Industry: The world's second-largest crankshaft manufacturer, with an annual production capacity of 5,000 marine crankshafts and a market share exceeding 30%.
- Meixin Yishen: Holding over 40% of China's scroll compressor crankshaft market, its revenue grew by 17.8% year-on-year in 2022.
- Technical Barriers: High-end crankshafts (e.g., for aero-engines) require machining accuracy of 0.001mm and surface roughness Ra ≤ 0.2μm. Domestic enterprises are gradually breaking through through 78 patents.
){kind=link}