Bearing limiting speed, running accuracy, and fits+
Koyo Bearingscontinues the bearing selection series with part 4. Be sure to catch up on parts 1 – 3 of selecting the right bearing below:
How to Select the Right Bearing Part 3: Bearing Dimensions and Service Life
在第4部分中，我們將解釋軸承限製速度，運行精度和適合，作為您選擇的軸承類型是否合適的措施。
When selecting a bearing, we need one that rotates stably and with the required accuracy, in a manner appropriate to the operating speed of the machine. What kind of things do we need to pay attention to when selecting bearings?
In Part 4, we will elaborate on the following two points you need to be aware of when selecting your bearing.
- 軸承應穩定旋轉，並且在機器的運行速度下具有所需的精度。
- The bearing should have the fits and internal clearance necessary to satisfy its service life.
1 – Limiting speed and running accuracy
Limiting speed
When a bearing rotates, its internal temperature rises due to friction resistance.
一旦軸承達到等於或大於一定量的轉速，它的溫度會巨大地增加，損害機器平穩地運行的能力。這一定的量稱為“限製速度”。我們的軸承目錄中的規格表顯示了每個軸承類型和一組尺寸的限製速度（見表2）。您應該根據機器的運行速度選擇具有限製速度的軸承，該軸承高於旋轉速度。
如果一台機器保持在軸承的限製速度高於，軸承的溫度會顯著增加，並且可能導致損壞（癲癇發作）。（見圖1.）
請注意，軸承的限製速度不僅受軸承的類型和尺寸而影響，而且還受到其耐受性，籠式和材料，潤滑劑，潤滑方法等的這種因素的大大影響。出於這個原因，如果您打算以高轉速使用軸承，請在做出決定之前谘詢JTEKT。
Tolerance
指定了軸承邊界尺寸精度和運行精度的軸承公差（參見表3），以及每個單獨軸承類型的幾種類型的公差類（參見表4）。
0級軸承為一般應用提供了足夠的性能。
Bearings of class 5 or higher are required for a precise running accuracy and a higher rotational speed, described in Table 5.
2. Bearing fits and bearing internal clearance
Bearing fits
“軸承符合”是我們所謂的軸承內環的孔徑與軸直徑之間的關係，或者軸承外圈的外徑與殼體的孔徑之間的關係。以下是對擬合類型的說明，以軸承內圈和軸之間的關係為例（參見圖2）。
Clearance fit
軸直徑小於內圈的孔徑，甚至在軸上安裝內圈之後，它們之間存在間隙。軸承安裝很簡單。
Interference fit
The shaft diameter is larger than the bore diameter of the inner ring, and the bearing is firmly locked in place on the shaft. This, however, can make it difficult to mount the bearing on the shaft, so consideration needs to be given to the mounting method.
過渡契合
This is somewhere between the clearance fit and the interference fit.
Based on the load direction and conditions, a suitable “fit” should be selected (see Table 6).
Load Characteristics and Fits – Koyo Ball & Roller Bearings Catalog
How to Select Fits – Koyo Ball & Roller Bearings Catalog
Making the wrong decision regarding clearance fit can result in circumferential relative sliipping (see Figure 3) on the fitting surface (the mounting surface between the bearing and the shaft or housing) and damage the bearing. For this reason, it is important to take care when deciding on the fits.
內部清關
“Bearing internal clearance” is defined as the total distance either inner or outer ring can be moved when the other ring is fixed. Internal clearance can be either radial or axial (see Figure 4).
軸承內部間隙對其性能具有顯著影響，因此選擇具有右內部間隙的軸承對於機器使用條件非常重要。
采用徑向軸承的例子，我們將解釋內部間隙對滾動元件負荷和疲勞壽命的影響。
- a) If there is an internal clearance, several rolling elements located near the direction of the load will come in contact with the inner and outer rings, causing a load to be placed. However, there is a clearance at the rolling elements on the opposite side of the load direction, and no load is applied [see Figure 5a) ].
- b）如果存在略有陰性的內部間隙，則更大數量的滾動元件與內圈和外圈接觸（參見圖5B），將放置在更多滾動元件上的負載分散。這會產生最長的疲勞壽命。但是，如果內部間隙跌幅遠低於0，則軋製元件上的負荷將變得過高，導致疲勞壽命顯著縮短（見圖6）。
如何選擇內部間隙
The bearing internal clearance should be selected in consideration of the “amount of reduction in clearance” from the clearance when rotating under a load while mounted in the machine (called the “operating clearance”) due to such factors as “fit” and “the bearing internal temperature difference.” Check the following about the internal clearance standard values broken down by bearing type and specifications as well as how to determine operating clearance, and…
如何確定操作間隙 - Koyo Ball＆Roller軸承目錄
Conclusion
在第4部分中，我們解釋了軸承限製速度，運行精度和適合，作為您選擇的軸承類型是否合適的措施。
- 您應該根據機器的運行速度選擇具有限製速度的軸承，該軸承高於旋轉速度。
- Bearings of class 5 or higher are required for a precise running accuracy and a higher rotational speed.
- 根據負載方向和條件選擇最佳軸承“擬合”。
- 根據操作間隙選擇軸承內部間隙。
探索koyo軸承的選擇，請訪問我們的專用頁麵here。
Works Cited
Koyo Bearings. (2020, April 06).Bearing Trivia。Retrieved from Koyo Bearings: https://koyo.jtekt.co.jp/en/2020/04/column02-04.html
