This section provides overview, applications, and principles of torque sensors. Also, please take a look at the list of 18 torque sensor manufacturers and their company rankings.
Table of Contents
A torque sensor is a device used to measure torque (the force that twists a shaft).
It is sometimes called a torque gauge, etc. Some manufacturers use different types of gauges and meters. As an example of how they are used differently depending on the application, a torque gauge is used to measure by operating it against the object to be measured. In contrast, a torque sensor is used to measure by setting the object to be measured against the torque sensor. There are mechanical and electrical types, and the principle of measurement differs.
Torque sensors are used for many applications but mainly for testing, research, and quality control. For testing and research purposes, for example, they are used to measure the strength of test materials and parts against torsion and to determine the degree of torsion that occurs. For quality control purposes, they are used for spot checks to determine the degree to which container caps are tightened during production and for pre-shift checks to ensure that tools such as electric screwdrivers used on production lines are operating within normal limits.
In mechanical torque sensors, the force applied to the input shaft drives the meter needle on display via a spring. It uses the property that the angle of rotation of the spring is proportional to the force applied to the spring. Since the spring must deform for measurement, the measured value is not displayed unless the object to be measured rotates to some extent in the measurement. Electric torque sensors are designed to measure torque by transmitting the force applied to the input shaft to the measuring shaft in the measuring instrument, thereby distorting the measuring shaft and measuring the distortion. The strain of the measuring shaft is measured by using the resistance value of the strain gauge attached to the surface of the measuring shaft, which changes as the gauge deforms. Unlike mechanical sensors, the amount of deformation caused by strain is insignificant. Since mechanical torque sensors have a large amount of deformation for measurement, destruction can be prevented by installing a stopper against input exceeding the necessary amount, etc. However, because the amount of deformation of electric sensors is so small, they can easily be subjected to more torque than necessary, resulting in damage and erroneous measurement values.
Non-contact torque sensors are sensors that can detect shaft torque in a rotating state. Optical and magnetostrictive torque sensors are the two main types. Both optical and magnetostrictive types have a sensor on the rotating shaft to detect the torsion of the shaft caused by torque and display the torque value on a display meter.
The optical type uses an optical sensor to detect signals that are delayed by the twisting of the shaft due to torque load in relation to the rotation speed. Since an optical sensor is used, there is no resistance to shaft rotation. Also, the sensor itself has the advantage of being compact.
The magnetostrictive type (rotary transformer type) converts the AC signal emitted by the coil attached to the rotating shaft into a torque value. This method is widely used, but the detection part is complicated and requires a lot of space, making it difficult to obtain stable data. As a new method, products are now available that acquire data by supplying power to the strain gauge attached to the rotating shaft and the detection circuit in a non-contact manner.
Rotational torque detection is usually performed by installing a torque sensor on the shaft rotated by the motor. The torque sensor is built into the motor unit itself, eliminating the need for a separate unit. The configuration of the device is compact, and there is no need for adjustments between the torque sensor and the motor during installation. There are several types of construction available, depending on the specifications, such as products with a torque sensor built into the motor package or products that detect the load using the motor's current and voltage.
In industrial multi-axis robots, torque sensors are mainly integrated into the motor shaft unit. These sensors detect the torque value applied to the motor and gearbox as each arm of the robot is driven. The robot arm part uses the detected torque values to determine its operating state and control the amount and speed of movement during operation.
In cooperative robots, these torque values are also used to detect contact with people or obstacles.
*Including some distributors, etc.
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