Precautions for roller chain transmission

Precautions for roller chain transmission

In the field of mechanical transmission, roller chain transmission is widely used due to its high efficiency and reliability. However, in order to ensure the efficient operation and extend the service life of the roller chain transmission system, the following key points must be noted.

1. Installation precautions
(I) Transmission ratio and wrap angle
The transmission ratio of roller chain transmission is usually 7:1, and can reach 10:1 at ultra-low speed. The wrap angle of the small sprocket and the chain should be kept above 120°, and the suspension transmission should reach above 90°. The appropriate transmission ratio and wrap angle can ensure the transmission efficiency and the service life of the chain.
(II) Distance between axes
The preferred value of the center distance between the two sprockets is 30-50 times the pitch of the roller chain. If the load changes greatly during transportation, the center distance can be set to less than 20 times. The appropriate distance between axes helps to reduce chain wear and vibration.
(III) Loose edge amount
Roller chain transmission does not require initial tensioning, but needs to be set to a certain degree of looseness. The setting of the slack amount should be adjusted according to the specific working conditions. In general, the slack amount is about 4% of the span. In the case of vertical transmission, large center distance, heavy load or reverse operation, the slack amount should be 2% of the span.
(IV) Parallelism and horizontality of the shaft
Whether the sprocket is installed correctly is crucial to the service life and normal operation of the roller chain. Use a spirit level to adjust the horizontality of the two shafts to ensure that it is within the range of ±1/300; use a caliper to adjust the parallelism of the two shafts to ensure that it is within the range of ±1/300. For different center distances, the alignment accuracy requirements of the sprocket are as follows:
Center distance to 1m: ±1mm
Center distance 1~10m: ±1mm
Center distance above 10m: ±10mm
(V) Installation configuration
The closer the center point connection line of the two sprockets is to the horizontal, the better the transmission effect of the roller chain. In vertical or quasi-vertical transmission, an idler wheel or tensioner should be used so that the sprocket can be removed smoothly when the chain is slightly extended. The following points should also be noted during installation:
When the center distance is short, the center distance can be lengthened by moving the shaft support to make the chain slightly tensioned.
When the center distance is long, an idler wheel can be added on the inner side of the loose side to support the roller chain.
For chains running at high speed and with varying loads, the use of chain guide rail stoppers can effectively reduce vibration.
When the transmission is vertical, the tensioner can be installed to adjust the chain tension in time to ensure the precise engagement of the sprocket and the chain.

2. Lubrication precautions
(I) The importance of lubrication
Lubrication plays a vital role in roller chain transmission. Good lubrication can reduce chain wear, reduce noise, and prevent corrosion, thereby extending the service life of the chain. Insufficient or improper lubrication can lead to problems such as premature wear and breakage of the chain.
(II) Lubrication methods
Depending on the use environment and working conditions, there are mainly the following ways to lubricate roller chains:
Manual refueling: suitable for low-speed, light-load transmission systems. Apply lubricating oil directly between the pin and sleeve of the chain.
Oil bath lubrication: The chain is immersed in the oil tank and the chain is lubricated by the circulation of oil. It is suitable for medium-speed and medium-load transmission systems.
Splash lubrication: An oil-slinging plate is installed in the housing, and the lubricating oil is splashed onto the chain through the oil-slinging plate. It is suitable for high-speed and medium-load transmission systems.
Forced lubrication: The lubricating oil is forced to be delivered to various parts of the chain using an oil pump. It is suitable for high-speed and heavy-load transmission systems.
(III) Selection of lubricating oil
The selection of lubricating oil should be determined according to the working environment and temperature of the chain. In general, the viscosity of the lubricating oil should be moderate, which can ensure good lubrication effect without blocking the lubrication channel due to excessive viscosity. For different temperature ranges, the recommended lubricating oil viscosity is as follows:
-10℃～0℃: SAE10W
0℃～40℃: SAE20
40℃～50℃: SAE30
50℃～60℃: SAE40

3. Maintenance precautions
(I) Regular inspection
Regular inspection is an important part of roller chain transmission maintenance. The inspection contents include:
Chain wear: measure the elongation of the chain. When the elongation reaches 1.5% of the chain length, consider replacing the chain.
Sprocket wear: check the wear of the sprocket teeth. If the wear is serious, replace the sprocket in time.
Lubrication: check the amount and quality of the lubricating oil to ensure that the lubricating oil is sufficient and clean.
Chain tightness: check whether the chain tightness is appropriate and adjust it if necessary.
(II) Cleaning and lubrication
Clean the chain and sprocket regularly to remove dust, debris and oil stains on the surface. After cleaning, apply lubricating oil in time to ensure that all parts of the chain are fully lubricated.
(III) Replace worn parts
When the chain or sprocket is severely worn, it should be replaced in time. When replacing, choose products of the same model and specification as the original chain or sprocket to ensure the normal operation of the transmission system.

4. Troubleshooting precautions
(I) Common faults and causes
Chain breakage: It may be caused by chain overload, fatigue wear or insufficient lubrication. The solution is to replace the chain and check the lubrication system.
Chain elongation: It is mainly caused by chain wear. When the chain elongation reaches a certain extent, the chain should be replaced.
Sprocket wear: It may be caused by insufficient lubrication or poor engagement between the chain and the sprocket. The solution is to replace the sprocket and check the lubrication system.
Chain shaking: It may be caused by improper chain tightness, insufficient lubrication or improper installation of the sprocket. The solution is to adjust the chain tightness, check the lubrication system and the installation status of the sprocket.
(II) Troubleshooting methods
Chain breakage: Replace the chain and check the lubrication system.
Chain elongation: Replace the chain.
Sprocket wear: Replace the sprocket and check the lubrication system.
Chain shaking: Adjust the chain tightness, check the lubrication system and the installation status of the sprocket.

5. Precautions for service life
(I) Judgment of service life
The service life of roller chains is usually judged by the elongation of the chain. When the elongation of the chain reaches 1.5% of its length, the chain should be replaced. In addition, the wear, lubrication and wear of the chain and sprocket should be checked regularly to ensure the normal operation of the transmission system.
(II) Methods to extend service life
Correct installation: Install in strict accordance with the installation requirements to ensure the correct engagement of the chain and sprocket.
Good lubrication: Check and replace the lubricating oil regularly to ensure that all parts of the chain are fully lubricated.
Regular inspection: Check the wear, tightness and lubrication of the chain regularly to find and solve problems in time.
Avoid overload: Avoid running the chain under overload to reduce chain wear and fatigue.

6. Precautions for selection
(I) Selection principles
When selecting a roller chain, the selection should be based on factors such as the load, speed, and working environment of the transmission system. The following points should be considered when selecting:
Strength of the chain: Select a chain of appropriate strength according to the load of the transmission system.
Speed of the chain: Select a chain of appropriate speed grade according to the speed of the transmission system.
Pitch of the chain: Select an appropriate chain pitch according to the number of teeth and center distance of the sprocket.
Number of chain rows: Select an appropriate number of chain rows according to the load and space requirements of the transmission system.
(II) Selection calculation
The selection calculation includes the following steps:
Calculate the tension of the chain: Calculate the tension of the chain according to the load and speed of the transmission system.
Calculate the corrected tension of the chain: Correct the tension of the chain according to the use factor and speed factor.
Calculate the acceleration and deceleration tension of the chain: Calculate the acceleration and deceleration tension of the chain according to the acceleration and deceleration requirements of the transmission system.
Calculate the inertia tension of the chain: Calculate the inertia tension of the chain according to the inertia requirements of the transmission system.
Select the appropriate chain model: Select the appropriate chain model according to the calculation results.