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What is The Difference Between a Torque Motor And a Geared Motor?

Both torque motors and geared motors are widely used transmission equipment, and they are different in structure, principle, specification, performance characteristics, usage, and technical parameters.

What is a torque motor?

A torque motor is a special motor with soft mechanical characteristics and a wide speed range.
The shaft of this motor does not output power with constant power but with constant torque. Torque motors include DC torque motors, AC torque motors, and brushless DC torque motors. It is widely used in industrial fields such as textile, wire and cable, metal processing, paper making, rubber, plastic, and printing machinery.

What is The Difference Between a Torque Motor And a Geared Motor?插图

Features of torque motors:

It has soft mechanical properties and can stall. When the load torque increases, the speed can be automatically reduced, and the output torque can be increased at the same time. When the load torque is a certain value, the speed can be adjusted by changing the motor terminal voltage, but the adjustment rate of the speed is not good!

Therefore, a speed-measuring device is added to the motor shaft, and a controller is equipped. The voltage output by the speed measuring device is compared with the voltage given by the controller to automatically adjust the terminal voltage of the motor to stabilize the motor.

It has the characteristics of low speed, high torque, strong overload capacity, fast response, good characteristic linearity, and small torque fluctuation. It can directly drive the load without reducing the transmission gear, thereby improving the operating accuracy of the system.

In order to obtain different performance indicators, the motor has three different structural forms: small air gap, medium air gap, and large air gap. The small air gap structure can meet the general use accuracy requirements, and the advantage is that the cost is low; eliminates the cogging effect, reduces the torque fluctuation, basically eliminates the nonlinear change of the reluctance, the motor linearity is better, the electromagnetic air gap is enlarged, the armature inductance is small, the electrical time constant is small, but the manufacturing cost is high; The performance index of the medium air gap structure is slightly lower than that of the large air gap structure motor but much higher than that of the small air gap structure motor, and the volume is smaller than the large air gap structure motor, and the manufacturing cost is lower than the large air gap structure motor.

Direct drive DC torque motors are small in size and are especially suitable for servo applications that require maximum efficiency and best positioning accuracy with minimum size, weight, power, and response time. The DC torque motor is a servo actuator that can be directly connected to the load being driven. A DC torque motor has a permanent magnetic field and a wound armature that together convert power into torque. In textile, paper, rubber, plastic, metal wire, and wire and cable industries, torque motors need to wind products on rolls (discs).

The winding diameter of the torque motor is bigger and bigger from the beginning to the end. In order to keep the tension of the rolled object uniform (that is, the line speed remains constant), the reel speed is required to be smaller and the winding force is larger. The torque motor is a special motor with many stages, which can continue to run when the motor is at low speed or even stalled (that is, the rotor cannot rotate), without causing damage to the motor.

In this working mode, the motor can provide a stable torque to the load (hence the name torque motor). Torque motors can also provide torque in the opposite direction of rotation (braking torque). The shaft of the torque motor does not output power with constant power but with constant torque.

The structure of the torque motor:

Torque motors can be considered torque-optimized motors. The difference between a torque motor and a general motor is that it allows a high torque, and its heat dissipation performance is also very good, so it can also work normally under the condition of the motor stall and high current output. Torque motors are generally designed with DC brushless motors, but sometimes switched reluctance motors and induction motors are also used. Because there is no conceptual standard for torque motors, they are sometimes referred to as low-speed motors or high-torque motors.

The structure of the torque motor is donut-shaped, and it is divided into an outer rotor motor with the rotor on the outer ring and a stator on the inner ring, and an inner rotor motor with the stator on the outer ring and the rotor on the inner ring. Because the outer rotor can generate a larger torque under the same size, the outer rotor motor is more commonly used.

Some torque motors can only work within a specific angle range and cannot rotate a circle. This kind of torque motor is called a limited angle torque motor (limited angle torque motor) or a swing motor (swing motor). There are also linear motors that consider introducing characteristics similar to torque motors into linear motors.

Torque motor classification:

Torque motors include DC torque motors, AC torque motors, and brushless DC torque motors. It is widely used in machinery manufacturing, textile, paper, rubber, plastic, metal wire, and wire and cable industries.

Principle of torque motor:

The constant torque characteristic torque motor can keep the torque basically constant in a generally wide speed range and is suitable for transmission occasions that require constant torque when the speed changes. For example, in printing and dyeing machinery, when several rollers are used to convey the fabric since the fabric is not wound on the rollers, but only attached to the surface of the rollers and driven by them, the diameter of the rollers does not change. The motor with constant torque characteristic is used to ensure that the torque is constant and the tension of the fabric is constant at any speed.

Geared motor

The geared motor refers to the integration of the reducer and the motor (motor). This integrated body is also commonly referred to as a gear motor or geared motor. Usually a professional reducer manufacturer, after integrated assembly, is supplied with the motor as a whole.

What is The Difference Between a Torque Motor And a Geared Motor?插图1

The role of the geared motor:

Reduce the speed and increase the output torque at the same time. The torque output ratio is multiplied by the motor output and the reduction ratio, but attention should be paid not to exceed the rated torque of the reducer.

The speed reduction reduces the inertia of the load at the same time, and the reduction of the inertia is the square of the reduction ratio. You can look at the general motor has an inertia value.

Geared motor principle:

The gear reduction motor generally drives the large gear through the small gear on the input shaft of the electric motor, internal combustion engine, or other high-speed running power through the gear reducer (or reduction box) to achieve a certain purpose of deceleration, and then adopts a multi-stage structure. The speed is greatly reduced to increase the output torque of the geared motor. Its core function of “increasing power and deceleration” is to use gear transmission at all levels to achieve the purpose of deceleration, and the reducer is composed of gear pairs at all levels.

Classification of geared motors:

According to the transmission type, it can be divided into gear reduction motor, worm reduction motor, and planetary gear reduction motor; according to the number of transmission stages, it can be divided into single-stage and multi-stage reduction motor; according to the gear shape, it can be divided into cylindrical gear reduction motor and bevel gear reduction motor and conical-cylindrical gear motors; according to the layout of the transmission, it can be divided into expansion gear motors, shunt gear motors, and coaxial gear motors. According to the driving motor, it can be divided into a DC reducer, stepping reducer, coreless reducer, servo reducer, and so on.

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