Nabtesco RV series high-precision gearbox

RV series precision cycloidal reducer technology full solution: high stiffness, small backlash, high torque precision transmission core

Introduction: The cornerstone of transmission in precision motion control

In modern industrial robots, CNC machine tools, assembly and conveying equipment, and various precision positioning systems, reducers play a core role in reducing speed, amplifying torque, and improving control accuracy. Although traditional gear reducers have a simple structure, they often suffer from problems such as large backlash, insufficient stiffness, and weak impact resistance, making it difficult to meet the dual requirements of high-precision trajectory control and heavy-duty working conditions. The cycloidal pinwheel reduction technology, especially the two-stage composite transmission scheme of "planetary spur gear+cycloidal pinwheel" adopted by the RV series, achieves compactness, lightweight, high stiffness, low backlash, and excellent overload bearing capacity through the unique structure of multi tooth simultaneous meshing, becoming a benchmark solution in the field of precision transmission.

This article is based on complete technical data of the RV series products, providing a comprehensive and systematic technical analysis of the three sub series RV-E, RV-C, and RV from multiple dimensions such as structural principles, performance parameters, selection process, installation specifications, lubrication and maintenance. It provides a professional, detailed, and directly applicable technical guide for mechanical design engineers, system integrators, and equipment maintenance personnel in engineering practice.

Series Overview and Core Advantages

The RV series is a general term for the products of the cycloidal pinwheel reducer family. Its core design concept is to accommodate as many teeth as possible in a limited volume, thereby achieving high stiffness, small backlash, low vibration, and long service life. Compared with traditional planetary or harmonic reducers, the RV series has significant advantages in the following aspects:

High stiffness: Multiple teeth support the load simultaneously, with extremely high torsional stiffness, and can maintain precise angular displacement even under heavy loads.

Lost motion: Through precision machining and pre tightening design, the clearance angle is extremely small, suitable for position servo control.

Overload resistance: The instantaneous maximum allowable torque can reach 500% of the rated torque and can withstand impact loads.

Compact and lightweight: The two-stage deceleration structure is integrated into one housing, and the output end is equipped with angular contact ball bearings, which can directly withstand external bending moments and axial forces.

Multiple configurations: Supports multiple working modes such as shell fixed shaft output and shaft fixed shell output, with a wide range of speed ratios.

According to the application scenarios and structural characteristics, the RV series is divided into three sub series:

RV-E series: Basic type, input gear directly connected to motor shaft, suitable for most general industrial robot joints, machine tool turntables, and positioners.

RV-C series: equipped with a central gear for more flexible input configuration, suitable for situations where wiring (cables, hoses) needs to be threaded from the center of the gearbox, such as robot wrists and rotary axes.

RV series (universal type): Similar to the E series, but including some older models (such as RV-15, RV-30, etc.), attention should be paid to specification differences when selecting and replacing.

The following will provide detailed explanations for each series, but first start with their common working principles.

Working principle: Implementation of two-stage precision deceleration

2.1 First stage - planetary spur gear reduction

Taking the RV-E series as an example, its input end is the input gear. When the servo motor drives the input gear to rotate, the input gear meshes with the spur gear installed on the crankshaft. According to the different gear ratios, the first stage can provide multiple speed ratio options. The input gear is usually machined and installed on the motor shaft by the user themselves, or standard parts can be ordered from Nabtesco.

2.2 Second Stage - Cycloid Needle Wheel Reduction

In addition to spur gears, the crankshaft also has two eccentric parts that are offset by 180 ° phase angle from each other. Install a cycloidal gear (RV gear) on each eccentric section. When the crankshaft rotates, the cycloidal gear undergoes eccentric motion, and the cycloidal teeth on its outer contour mesh with the cylindrical pins fixed on the inner ring of the housing.

Due to the special geometric shape of the cycloid gear profile, the cycloid gear moves one gear position relative to the needle teeth for each rotation of the crankshaft, and the direction of motion is opposite to that of the crankshaft. Simultaneous meshing of multiple teeth - usually with nearly half of the teeth in contact at the same time - results in even load distribution, greatly improving load-bearing capacity and torsional stiffness.