What is outer gear ring?

What is outer gear ring?

The outer ring gear is a common annular part in a mechanical transmission system, with teeth evenly distributed on the outer circumferential surface, usually used in conjunction with the internal ring gear, pinion or rack, to transmit rotational motion and torque through inter-tooth meshing. The tooth shape design of the Outer gear ring is diverse (such as straight teeth, helical teeth, herringbone teeth, etc.), which can realize different transmission ratios, steering and load requirements, and is widely used in reducers, gearboxes, construction machinery, automobile differentials and other fields. Most of its materials are made of high-strength alloy steel, and have undergone heat treatment processes such as quenching and carburizing to improve wear resistance and fatigue resistance, and ensure stable operation under high-speed and heavy-load conditions.

Outer gear ring features

Various tooth shapes: spur teeth, helical teeth, herringbone teeth and other designs adapt to different transmission needs.

Efficient transmission: Torque transmission and speed adjustment through inter-tooth meshing, supporting large gear ratios or steering functions.

High strength and wear resistance: alloy steel is made of quenching and carburizing to adapt to high-speed and heavy-duty conditions.

Modular design: easy to install and maintain, ensure accurate alignment with other components.

Wide range of applications: used in construction machinery, vehicle transmission, industrial equipment and other fields, with both reliability and adaptability.

How the Outer gear ring works

1. Basic meshing mechanism

Tooth design: Involute tooth profile (pressure angle 20°±2°) forms a conjugate meshing with the pinion or inner ring gear, and the contact point moves along the normal direction of the tooth surface to ensure smooth force transmission.

Modulus-to-digital matching: The tooth pitch (p=πm) is consistent with the modulus of the paired gear, so as to achieve no backlash or controllable backlash (0.05-0.2mm) and reduce shock vibration.

Contact Stress Distribution: The contact stress of the tooth surface is calculated by the Hertz formula (σ_H=0.418√(F/(bρ))) to optimize the tooth surface hardness (e.g., HRC58-62) for longer life.

2. Transmission mode analysis

Fixed shaft transmission: when the outer ring gear is fixed, the driving gear drives the planetary wheel to rotate to achieve deceleration and torque increase (transmission ratio i=z_ outer / (z_active ±z_planet)).

Differential transmission: In a differential, the Outer gear ring distributes power to the wheels through a half-shaft, allowing the speed difference between the left and right wheels (Δn = 2n_ outer ×sinθ) to accommodate steering.

Composite transmission: Multiple sets of Outer gear rings (e.g. dual-clutch gearbox) for fast gear changes with a response time of < 0.3 seconds.

3. Impact of key parameters

Gear ratio: The difference in the number of teeth determines the transmission ratio (i=z_ outer/z_ active), e.g. z_ outer=72, z_ active = 24, i=3.

Helix angle: β=8°-15° helical tooth design improves coincidence to 1.5-2.0 and reduces noise by 3-5dB.

Displacement coefficient: positive displacement (x=+0.5) enhances tooth root strength, and negative displacement (x=-0.3) improves meshing performance.

4. Dynamic response characteristics

Inertia matching: The moment of inertia (J=0.5mR²) needs to be matched with the drive system to avoid resonance frequency offset.

Lubrication and heat dissipation: The coefficient of friction is reduced to less than 0.08 thanks to oil mist lubrication (flow rate 5-15 L/min) or solid lubricating coating (MoS₂ thickness 3-5 μm).

Temperature compensation: The coefficient of thermal expansion (α=11.5×10⁻⁶/°C) is compensated by preload to ensure the meshing stability at high temperatures.

Precautions for outer gear ring applications

Installation alignment: The coaxiality of the paired gear should be strictly calibrated to avoid abnormal wear or vibration of the tooth surface due to eccentricity.

Lubrication management: select gear oil that meets the working conditions, clean the oil circuit regularly and replace the lubricant to prevent the failure of tooth surface gluing.

Load control: avoid long-term over-rated torque or speed operation, and prevent tooth root fatigue fracture or tooth surface plastic deformation.

Material adaptability: Select the corresponding material (such as stainless steel or superalloy) according to the environment (such as corrosion, high temperature) to ensure weather resistance.

Seal protection: Strengthen the sealing design in dusty or humid environments to prevent impurities from entering and aggravating wear or corrosion.

Dynamic balance: Dynamic balance verification is required during high-speed transmission to reduce the additional stress of vibration on the bearing and tooth surface.

Maintenance inspection: Regularly check the root crack through flaw detection (such as ultrasonic), measure the wear of the tooth surface, and replace the out-of-gauge parts in time.

Fastening reliability: anti-loosening measures (such as lock nuts, anti-loosening glue) are used to ensure the pre-tension of the connecting bolts to avoid impact load caused by loosening.

The price of the outer ring gear

The price of external gear rings varies significantly due to different materials, processes, specifications and application scenarios, and the unit price of low-end products (such as cast iron or nylon materials) is usually 50-500 yuan, which is suitable for small equipment or toys; The price of mid-end products (such as 45# steel or alloy steel ring gear) is 500-20,000 yuan, which is widely used in reducer and vehicle transmission; High-end precision external gear rings (such as carburizing and quenching alloy steel or powder metallurgy gear rings) are suitable for wind power, aviation and other fields, and the unit price can reach more than 50,000 to 200,000 yuan. In terms of materials, the price of alloy steel ring gear is 3-5 times that of ordinary cast iron, and the cost of stainless steel ring gear is higher; In terms of processing technology, the cost of high-precision grinding gear is increased by 40%-60% compared with ordinary gear hobbing, and the price of large-module gear rings has increased exponentially due to customized demand. The external gear ring of the automobile differential is about 800-2000 yuan, and the external gear ring of the wind power gearbox (diameter of more than 2 meters) often exceeds 150,000 yuan due to the complex process. When purchasing, it is recommended to give priority to manufacturers with heat treatment capabilities, bulk purchases can reduce costs by 15%-20% through platform price comparison, and high-end applications need to pay attention to ISO 1328 accuracy certification.

Supplier of outer gear rings

LTZC BEARING's main products are slewing rings, non-standard precision bearings, rolling mill bearings, bearing-related unit assembly, and oversized precision guide rails. The product processing range is outer diameter: 200 mm - medium 10000 mm.

LTZC offers external gear rings. If you are looking for a supplier of external gear rings, please contact us for the latest quotation.