RV Reducer VS Harmonic Reducer

RV reducer is a high-precision control reducer with a cycloidal pin wheel reduction structure. Due to the large number of gears engaged at the same time, the reducer has the characteristics of small size, lightweight, high rigidity, and overload resistance. In addition, due to the small backlash, rotary vibration, and inertia, it has good acceleration performance and can achieve smooth operation and obtain the accuracy of the correct position.

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When the wave generator is installed into the inner circle of the flex spline, it forces the flex spline to produce elastic deformation and to become elliptical, so those flex spline teeth at the long axis are inserted into the gear groove of the circular spline, which becomes a full engagement state; while at the short axis, the gear teeth of both flex spline and circular spline are completely untouched and in a separation state. The process between engagement and separation is in the state of meshing in or meshing out. When the wave generator rotates continuously, it forces the flex spline to deform, which makes the teeth of the two splines change their working state during the process of meshing in, engagement, meshing out, and separation, resulting in the so-called staggering teeth movement, thus realizing the movement transmission between wave generator and flex spline.

With the unmanned operation becoming more and more mature in recent years, industrial robots have become machines that are often used in many industries. Compared with general reducers, precision reducers, the core components of industrial robots, need to be unique and have the characteristics of short transmission chain, small volume, high power, light weight and easy control. The reducers with these two characteristics mainly include RV reducers and harmonic reducers. Many friends don't know the advantages and disadvantages between them. Today, Fu Bao will explain the differences between these two types of reducers.

1. Principles of RV and harmonic reducer.

RV reducer:

It is used for the three joints of the leg, waist and elbow of the robot with high torque, and the industrial robot with high load uses RV for the first, second and third axes. Compared with harmonic reducer, the key of RV reducer lies in processing technology and assembly technology.

RV reducer has higher fatigue strength, rigidity and service life, unlike harmonic drive, the motion accuracy will be significantly reduced with the increase of service time, and its disadvantages are heavy weight and large overall size.

Harmonic reducer:

Used for the end shafts of industrial robots or large robots with small load, the harmonic reducer is a kind of harmonic transmission device, which includes harmonic accelerator and harmonic reducer. Harmonic reducer mainly includes rigid wheel, flexible wheel, bearing and wave generator, and all of them are indispensable.

Among them, the number of teeth of the rigid wheel is slightly larger than that of the flexible wheel. Harmonic reducer used in small robots is characterized by small size, light weight, large bearing capacity, high motion accuracy and large single-stage transmission ratio.

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Both of them are engaged with less tooth difference, but the difference is that a key gear in harmonic is flexible and needs repeated high-speed deformation, so it is fragile and has limited bearing capacity and life. RV usually uses cycloid pin wheel, and the harmonic wave used to use involute tooth profile. Now some manufacturers use double circular arc tooth profile, which is much more advanced than involute tooth profile.

Compared with the harmonic reducer, RV transmission is a new kind of transmission, which is developed on the basis of the traditional pin-pendulum planetary transmission. It not only overcomes the shortcomings of the general pin-pendulum transmission, but also has a series of advantages such as small size, light weight, large transmission ratio range, long service life, stable accuracy, high efficiency and smooth transmission.

RV reducer is composed of cycloidal pinwheel and planetary bracket, which is widely used in industrial robots, machine tools, medical testing equipment, satellite receiving systems and other fields because of its small size, strong impact resistance, large torque, high positioning accuracy, small vibration and large reduction ratio.
 

The shell of RV reducer and cycloidal pin wheel are driven by solid steel, so it has strong bearing capacity. However, the flexspline of harmonic reducer can constantly deform to transmit torque, which determines that the ability of harmonic reducer to bear large torque and impact load is limited, so it is generally used in the front end.

2. Advantages and disadvantages of RV and harmonic reducer.

The harmonic reducer has a simple and compact structure and is suitable for miniaturization, low and medium load applications.
RV reducer has good rigidity, strong impact resistance, stable transmission and high precision, and is suitable for medium and heavy loads.

However, RV reducer needs to transmit great torque and bear great overload impact to ensure the expected working life, so it uses a relatively complex over-positioning structure in design, and it is difficult to control the manufacturing process and cost. RV reducer has no elastically deformed stress element, so it can bear a certain torque.


The bearing of RV reducer is its weak link, and it is easy to break through the bearing limit of the shaft when stressed, resulting in abnormal wear or fracture of the bearing. This problem is more prominent when running at high speed, so the rated torque of RV reducer decreases obviously with the input speed.

In fact, all types of reducers have their own advantages and disadvantages. We can't simply say that a certain type is good and a certain type is not good. All these need to be selected according to the actual situation, which is what many friends don't understand. When choosing a reducer, we don't know how to choose a robot that is more suitable for our own. At this time, we can consult the technicians in Fu Bao to help our customers choose the type more accurately.

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