What are the Designs of Parts Related to the Air Distribution Mechanism?
What is the Air Distribution Structure?
Engine valve train parts (internal combustion engine gas distribution mechanism) is in accordance with the engine in each cylinder work cycle and ignition sequence requirements, timing open and close the cylinder intake and exhaust valves, so that the fresh combustible mixture (gasoline engine) or air (diesel engine) to enter the cylinder in time, the exhaust gas from the cylinder in time to discharge. In the compression and work stroke, close the valve to ensure the sealing of the combustion chamber.
Valve Locking Block Design
- Multi-slotted counter top structure lock block
The structure of the lock block installation, two lock block against the top, the valve and the lock block radial clearance, the valve can be free to rotate with the engine vibration. To improve valve wear, especially to improve the working condition of the exhaust valve is more favorable.
The structure of the lock block is usually made of low carbon steel cold heading, and then nitriding treatment, the lock block structure is complex and difficult to process.
2 single slot locking block structure
The lock block structure is simple, the selection of material processing as above. When installed, the locking block tightly hooped valve, the valve can not rotate.
Valve Stem Oil Seal Design
In order to reduce oil consumption, reduce the harmful components and particles in the exhaust gas. In the valve stem and valve guide with valve oil seal, to prevent excessive oil absorption combustion chamber burned. The right amount of lubricant can lubricate the valve seat. As the emission regulations become stricter and stricter, the requirements for the valve stem oil seal also become stricter and stricter, and the oil seal rubber material, lip geometry spring, etc. should be more carefully determined. Make sure it plays the function of oil seal and at the same time, make it have the ability of wear resistance, fatigue resistance, aging resistance, etc.
1.Single groove oil seal
The structure of single groove oil seal is simple, but the oil sealing effect is poor, which is suitable for the engine with high requirements on exhaust and oil consumption.
The influence of main structure parameters on oil sealing capacity and reliability are as follows.
α angle: the larger the α angle, the worse the oil sealing capacity, generally α: 30°～60°
β angle: the larger the β angle, the worse the oil sealing capacity, generally β: 15°～30°
h value: the larger the h value, the better the oil sealing capacity, generally h: 0.2～0.8
Unit radial force Fc: the larger the Fc, the better the oil sealing capacity, generally Fc: 4-10 (N/mm)
Lip fillet radius: the larger the R, the worse the oil sealing capacity, generally R: 0～0.3, the smaller the R, the greater the wear.
Valve stem roughness; the greater the roughness, the worse the oil sealing capacity, generally Ra: 0.2～0.8
Vacuum degree: related to the operating conditions of the engine. The greater the vacuum degree, the greater the amount of oil leaking into the combustion chamber through the duct.
Lip natural state diameter d: should be smaller than the valve stem diameter of about 0.8 ~ 1.3mm, the diameter d should be consistent with the unit radial force
Fc is consistent.
- Multi-groove oil seal
Multi-groove oil seal adopts labyrinth type seal, with complex structure and high precision requirement for mold, which is more suitable for engines with high emission requirement or supercharger.
Generally, it adopts three-slot or four-slot structure, the radius of the slot is 0.3~0.6mm and the depth is 0.3~0.6. The inner diameter in the natural state is smaller than the valve stem by 0.8mm~12mm.
The main parameters of the above two oil seal structures are recommended values, and the reasonable size should be selected according to different models and different emission regulation requirements through oil seal test bench sealing test.
Common materials of valve stem oil seal: mainly propylene glycol, silicone rubber and fluorine rubber.
The first two materials have poor anti-aging performance, but low price; while fluorine rubber has good anti-aging performance. Strong corrosion resistance, good oil sealing effect, but the cost is higher, most tend to use fluorine rubber as valve oil seal material.