Given their capability to improve car safety, convenience and fuel efficiency, silicon magnetic sensors used in automotive motors will enjoy fast market growth with revenue expanding by nearly 40 percent in 2012, according to an IHS iSuppli special report on magnetic sensors from information and analysis provider IHS.
Revenue derived from the use of magnetic sensors in automotive motors will reach $160.3 million in 2012, up a solid 38.2 percent from $116.0 million this year, extending the steady rise of the market over the last three years. And although revenue growth after 2012 will moderate to the single digits, the five-year compound annual growth rate from 2010 to 2015 still will equate to a robust 16 percent. By 2015, magnetic sensor revenue in automotive motors will amount to $193.6 million.
While magnetic sensors are employed in a variety of motors used in industrial automated processes, their use is extensive in the automotive industry, which accounts for 50 percent of their market value. For instance, low-end to midrange cars have more than 10 electric motors such as for fan cooling, the alternator, and both front and rear wipers. Luxury cars have even more at almost 100 motors—a long list including sensors for HVAC blowers, electronic steering and throttle control, and transmission sensors for automatics and new double-clutch systems; as well as those for seat positioning, sunroof, tachometer, headlight positioning, headrests, and even control of air input flaps based on air quality information.
An important driver for efficient motors is energy consumption, where fractions of a liter in fuel savings can be critical and each gram of carbon dioxide produced as emissions is counted. Here, the trend is toward the electrification of pulley-driven motors and replacement by brushless DC motors. These efficient motors allow on-demand operation of the main powertrain components, such as water-cooling pumps, oil pumps and other auxiliary pumps, and to reduce overall energy needs.
Another application of magnetic sensors to motors is in shaft position encoding—found, for instance, in power windows for cars, in which the sensors determine how many complete turns a shaft has made in order to control the length of travel of the window lifter. Unusual loading conditions due to the presence of a hand also can be detected by the sensor to provide a so-called “anti-pinch” functionality, which results in the motor turning backward if an object is encountered.
Electronic power steering is likewise a fast-growing direct motor application, replacing electro-hydraulic alternatives that use a pump to build pressure in order to provide for greater fuel efficiency. The sensor requirement is in commutation of the motor and also in sensors that detect current.
In hybrid electric vehicles, magnetic sensors come into play in the monitoring of auxiliary motor inverters, where the battery DC needs to be changed to the motor AC current. Such a conversion requires the use of three current sensors—one for each phase of the motor.
Use of Hall IC and AMR Sensors Needed for Advanced Auto Applications
In general, automotive motors use Hall integrated circuits (IC) in a three-phase motor for commutation. A three-phase motor typically has six states, measured by three digital Hall ICs for closed-loop regulation. In some cases, magnetic sensors may not be required, and Hall ICs may be replaced by simple current measurement in the circuit. For example, DC motors that operate in an environment with constant speed and no load changes—such as a fan that constantly rotates—can infer the required knowledge of speed without the need for sensors.
However, in advanced motors where load changes and knowledge of torque is needed, the use of Hall ICs and some anisotropic magnetoresistive (AMR) sensors is required in order to measure the motor position of the shaft.
In particular, the use of AMR will increase in the next five years, with the biggest applications occurring in tachometer motors for speed and RPM instruments, for reasons of motor quietness.
NXP Semiconductors of the Netherlands is a major provider of AMR sensors, while Hall sensor IC alternatives are supplied by Micronas of Switzerland, Infineon Technologies of Germany, U.S.-based Allegro Microsystems, Melexis N.V. of Belgium, and Japan’s Asahi Kasei Microsystems.
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