LOWIFARベアリング
Deep groove ball bearings are among the most widely used rolling bearings due to their simple structure, high rotational speed, low friction, and versatile applications. While selecting the correct bearing size and material is important, bearing internal clearance is another critical factor that directly affects bearing performance, service life, operating temperature, and noise.
Choosing the appropriate clearance helps ensure stable operation and prevents premature bearing failure.
What Is Bearing Internal Clearance?
Bearing internal clearance refers to the total distance that one bearing ring can move relative to the other before installation.
There are two types of internal clearance:
- Radial Clearance – Movement perpendicular to the shaft axis.
- Axial Clearance – Movement parallel to the shaft axis.
For deep groove ball bearings, radial internal clearance is the parameter most commonly specified.
During operation, the actual operating clearance becomes smaller due to interference fits, thermal expansion, and operating loads. Therefore, selecting the correct initial clearance is essential.
Standard Bearing Clearance Classes
The most common clearance classes for deep groove ball bearings include:
| Clearance Class | Description | Relative Clearance |
|---|---|---|
| C2 | Smaller than normal | Small |
| CN (Normal) | Standard clearance | Medium |
| C3 | Greater than normal | Large |
| C4 | Greater than C3 | Larger |
| C5 | Largest standard clearance | Very Large |
Generally:
C2 < CN < C3 < C4 < C5
Each clearance class is designed for different operating conditions rather than representing better or worse quality.
Applications of Different Clearance Classes
C2 Clearance
C2ベアリングは内部すきまが小さく、軸のたわみが最小限で高い回転精度が求められる用途に適しています.
典型的な用途には:
- 精密機器
- 計測機器
- 軽負荷の電動機
- 家庭用電化製品
- 低温環境
利点:
- 振動が低い
- 運転音が低減される
- 位置決め精度が向上
CN (Normal) すきま
CNは一般的な産業用途で最もよく使用されるすきまである.
適用先:
- ポンプ
- ギアボックス
- 農業機械
- ファン
- コンベヤ
- 一般用途の電動機
運転温度と負荷が中程度の場合, CNすきまは剛性とベアリング寿命の優れたバランスを提供する.
C3すきま
C3ベアリングは標準ベアリングよりも大きな内部すきまを提供し、工業用機器で広く使用されている.
推奨用途:
- 高速電動機
- 自動車用オルタネータ
- コンプレッサー
- 産業用ファン
- 工作機械
- 繊維機械
利点には:
- 熱膨張へのより良い対応
- 運転中のプリロードのリスク低減
- 動作温度の低下
- より高速度下での軸受寿命の延長
C3 クリアランスは高速用途で最も一般的な選択肢の一つ.
C4 クリアランス
C4 軸受はより過酷な運転条件向けに設計されている.
典型的な用途には:
- 採掘機器
- 振動スクリーン
- 重負荷コンベヤ
- 破砕機
- 製鋼所
- 高温機械
これらの用途では通常、軸の大きな膨張や重荷重が発生し, より大きなクリアランスが必要となる.
C5 クリアランス
C5 軸受は最も大きな内部クリアランスを提供し、一般的には特殊な機器用に用いられる.
一般的な用途:
- 特殊振動機械
- 非常に高温の機器
- 重工業機械
- 特定のカスタム設計システム
過度なクリアランスは振動や騒音を増加させる可能性があるため, C5 should only be selected when specifically required by the application.
Factors Affecting Clearance Selection
Selecting the correct clearance depends on several operating conditions.
1. 使用温度
As temperature increases, the shaft generally expands more than the bearing housing, reducing internal clearance.
Higher operating temperatures usually require larger initial clearance, such as C3 or C4.
2. Shaft and Housing Fit
Interference fits compress the bearing rings and reduce internal clearance.
Typical examples:
- Tight shaft fit → Smaller operating clearance
- Heavy interference fit → Larger initial clearance recommended
3. Rotational Speed
High-speed applications generate more heat, reducing clearance during operation.
For this reason, many high-speed electric motors use C3 clearance.
4. Load Conditions
Heavy radial loads can cause elastic deformation of the bearing components.
Applications with heavy loads may benefit from larger clearance to maintain stable operation.
5. Precision Requirements
High-precision equipment often requires smaller clearance to improve shaft positioning accuracy and reduce vibration.
However, insufficient clearance may result in excessive heat generation if thermal expansion is not properly considered.
Common Industries and Recommended Clearance
| Industry | Recommended Clearance |
|---|---|
| 電動モーター | CN or C3 |
| ポンプ | CN or C3 |
| ファンおよびブロワー | C3 |
| コンプレッサー | C3 |
| 自動車用途 | C3 |
| 工作機械 | CN or C3 |
| 採掘機器 | C4 |
| Vibrating machinery | C4 or C5 |
| 食品加工機械 | CN or C3 |
| 農業機械 | CN |
Consequences of Incorrect Clearance Selection
Selecting inappropriate bearing clearance can lead to various problems.
If clearance is too small:
- Higher operating temperature
- Increased friction
- Bearing seizure
- Reduced bearing life
- Higher power consumption
If clearance is too large:
- Increased vibration
- Higher running noise
- Reduced rotational accuracy
- Uneven load distribution
- Shortened bearing life
Proper clearance selection helps achieve the optimal balance between rigidity, temperature control, and durability.
LOWIFAR Deep Groove Ball Bearings
LOWIFAR supplies a comprehensive range of deep groove ball bearings in various materials and clearance classes to meet different industrial requirements.
Available options include:
- Chrome Steel Bearings
- Stainless Steel Bearings (420, 440C, 304, 316)
- Hybrid Ceramic Bearings
- Full Ceramic Bearings
- オープン, ZZ, and 2RS designs
- Clearance options: C2, CN, C3, C4, and C5
- Precision grades: ABEC-1, ABEC-3, ABEC-5, and ABEC-7
Whether your application requires high speed, corrosion resistance, low noise, or elevated temperature performance, selecting the appropriate internal clearance is essential for maximizing bearing reliability and service life.
Conclusion
Bearing internal clearance is one of the most important parameters affecting the performance of deep groove ball bearings. There is no universally “best” clearance class—only the one that best matches the application’s operating conditions.
By considering operating temperature, shaft fit, speed, 荷重, and precision requirements, engineers can choose the most suitable clearance to improve efficiency, reduce maintenance costs, and extend bearing life.
If you are unsure which clearance is appropriate for your application, LOWIFAR’s engineering team can provide technical support and recommend the optimal bearing solution based on your operating conditions.