Basic Selection of Gearbox Reducer

Basic Selection of Gearbox Reducer

Gearbox reducer selection can be quite difficult. Customers have a variety of gearbox reducers to choose from that are capable of fulfilling diverse requirements. A wrong decision could result in the purchase of a more expensive gearbox. The power transmission industry may need a gearbox that will support overhung loads while the motion control or servo industry may need a gearbox that will handle dynamic motion.

サイズ設定に関する最初の問題領域の 1 つは、モーターのサイズ設定と負荷のサイズ設定から発生します。モーターに合わせたサイズ調整が簡単になり、機能するギアボックスが得られる可能性がありますが、必要以上に大きなギアボックスを購入することになります。このギアボックスもアプリケーションには十分に適しています。ただし、負荷に応じたサイズにすることで、ギアボックスが用途に適合し、コスト効率が向上し、設置面積も小さくなる可能性があります。

Common Aspects of Sizing Applications

ギアボックスのサイジングには、あらゆる状況に当てはまるいくつかの側面があります。このセクションでは、これらの基準について詳しく説明し、洞察を提供します。

1. サービスファクター

Before sizing an application, the customer should determine the service factor.
Service factor can be generally defined as an application’s required value over the rated value of the unit. Service factor should be determined for conditions such as non-uniform load, hours of service, and elevated ambient temperature.

How would one interpret a service factor? A service factor of 1.0 means a unit has just enough capacity to handle the application. There is no tolerance for additional requirements, which could cause the gearbox to overheat or fail. For most industrial applications, a service factor of 1.4 is adequate. This service factor signifies that the gearbox can handle 1.4 times the application requirement. If the application requires 1,000 inch-pounds, the gearbox would be sized to handle 1,400 inch-pounds. Different factors will affect how much service factor should be used in a given application.

2. 周囲温度と環境

Higher ambient temperatures increase internal pressure, which will require an increase to the service factor used. High or low temperatures can require different seal materials and lubrication viscosities. The environment the gearbox will operate in is also an important consideration for sizing. Harsh environments can increase wear on the unit. Dusty or dirty environments often require special material to prevent corrosion or bacteria growth. Food or beverage plants require specific FDA compliant coatings and oil. Vacuum environments will require special grease and heat dissipation considerations, since there will be no air for cooling. Failure to account for these environmental features can result in a gearbox that cannot support the application properly. All of these aspects must be considered when sizing a gearbox.

3. 衝撃荷重または荷重の種類

衝撃や衝撃荷重が大きいと、ギアの歯やシャフト ベアリングの摩耗が増加する可能性があります。この摩耗は、サイズ設定時に考慮されていない場合、早期の故障を引き起こす可能性があります。これらの負荷にはサービスファクターを増やす必要があります。均一荷重は適用中に一定に保たれる荷重ですが、不均一荷重は適用中に変化します。不均一な荷重は、たとえ小さくても、均一な荷重よりも高いサービスファクタを必要とします。均一な荷重の例としては、一定の量の製品が載っているコンベアが挙げられます。不均一な負荷は、あらゆる種類の断続的な切断用途に当てはまります。この断続的な切削力により、ギアボックスのトルクが周期的に増加し、不均一な負荷が生じます。

4. 出力形式またはメカニズム

出力機構には、スプロケット、プーリー、歯付きピニオンなどがあります。ダブル出力シャフトやシャフトに取り付けられたブッシングなどのさまざまな出力構成により、ユニットの定格オーバーハング荷重が減少します。出力機構が異なると、考慮する必要がある異なるシャフト負荷が追加されます。ほとんどの機構では大きなラジアル荷重が発生しますが、ヘリカル ギアなどではアキシアル荷重も発生する可能性があります。これらの出力では、ラジアル荷重またはアキシアル荷重の増加に対応するために、異なるベアリングが必要になる場合があります。

5. 出力軸または中空穴のサイズ

When sizing an application, the output shaft and bore size must meet customer requirements. These could include a stainless output on the unit, and whether it has a keyed or keyless shaft, a keyed or keyless hollow bore, or a flanged output combined with any of the previous. Getting the correct bore size on a unit may force the customer to purchase a larger gearbox or a different style of gearbox to fit their current shaft. In some instances, the customer can modify their shaft to use the most cost-effective unit while providing an optimal solution.

6. ハウジングのスタイル

It is also important when selecting a gearbox to consider how it will mount. A unit could have mounting feet, a flange on the output, or just basic tapped holes on one or more sides. These housing styles could limit how a unit is mounted so having a variety of options could prevent custom frames or brackets from being needed. For example, having tapped holes on the bottom face of the unit would prevent the need for a special L-bracket to mount around the output.

Power Transmission

Some elements that affect the sizing process are industry specific. For the power transmission industry, output RPM, motor horsepower and frame size, and overhung load all impact the application calculations.

• 出力回転数 The customer must determine the ratio needed for the gearbox reducer to operate, or provide input/output speed and operating hertz (Hz) for calculations. The standard is a 1750 input RPM at 60 Hz. Any changes will need to be specified when sizing as it will change the ratio calculation. Failure to account for changes will result in a gearbox that does not match the customer’s requirement.

• Motor HP and Frame Size The gearbox reducer size and input option must be determined before calculating the service factor. Once the gearbox is sized, use the required HP to compute the actual service factor. Large HP motors generate heat that can adversely affect the reducer’s mechanical ratings. This reduced rating, based on the increased heat, is known as the Thermal Capacity of a reducer, and must be considered when using large motors.

• General Shaft Load サイズ設定では、負荷がギアボックスを損傷しないことを確認する必要があります。出力シャフトが耐えることができる力 (ポンド単位で測定) は、オーバーハング荷重定格として知られています。定格を下回ると減速機が破損する恐れがあります。

Motion Control

サーボ業界では、入力速度、慣性、動的トルク動作、特定のシャフト負荷、およびモーターシャフト直径がサイジングプロセスに影響します。

• Input Speed Input speed should not exceed the gearbox ratings or premature seal wear will occur due to increased pressure. Input speed can be accidently increased if there is an output mechanism with a ratio that is not considered when sizing, which is another reason why specifying any output mechanisms is so important.

• Inertia An inertia mismatch of less than 10:1 is desired for fine controlling of the output. This is important to obtain the high accuracy needed for some applications. Reducer size and ratio are main influences from the gearbox on inertia. Control engineers may request smaller mismatches or even specific amounts. Often a motor is chosen for its dynamic capabilities, not for its torque. It is common to use a motor with much more torque than needed for the application due to its increased rotor inertia. Some motor manufacturers even make motors specifically for high or low inertia ratings. This allows for better tuning of the application because of a lower inertia mismatch. When doing this, it is important to limit the output torque in the motor to prevent breaking the gearbox

• Dynamic Motion Cyclic motion may require using a higher service factor than continuous motion. This is because constant starts and stops cause additional wear on the gear teeth and seals. Cyclic reversing, which is constant back and forth motion between two points, requires an even higher service factor than cyclic or continuous

• Specific Shaft Loads ラジアル、アキシアル、およびモーメントのシャフト荷重をユニットの定格と照合する必要があります。これを怠ると、シャフトが破損したり、ベアリングやギアの歯が損傷したりする可能性があります。一般に、適切な強度のギアボックスを決定するために、同じサービス係数がこれらの定格に適用されます。アプリケーションで必要な場合は、軸受タイプを追加すると、これらの定格を高めることができます。

• Motor Shaft Diameter or Length モーターのシャフトはユニットに適合する必要があり、シャフトはカップリングと完全にかみ合うのに十分な長さでなければなりません。完全にかみ合わないと、入力の滑りが発生する可能性があります。これは必要なサービスファクターには影響しませんが、モーターの取り付けに関する問題を回避するために考慮することが重要です。一部のメーカーは、ユニットのサイズを大きくすることなく、減速機がより大きなモーターに対応できるようにする大入力設計を採用しています。

Conclusion

To achieve the best gearbox reducer solution, customers should size from the load. This will ensure they receive cost effective solution that fits the application. The service factor, environment, ambient temperatures, shock load, output style, and hours of service are all important aspects for sizing. The more information the customer provides, the more accurate the sizing process. This will ultimately yield a solution that matches the customer’s requirements! There are numerous sizing programs available that can help determine what gearbox is most appropriate for your application.