They can adjust your seat and headlights, power your windows and wing mirrors, and help you brake and steer. In fact, they are found in anything that has an electrical movement or solenoid function. With as many as 80 electric DC motors stuffed inside a luxury car, Matthew Beecham reports on some novel ways in which to package them.
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As electric motors proliferate around the car, manufacturers have developed lighter and more compact units. Nobuo Ishii, senior manager of development, Asmo Co Ltd, said: “Vehicles are required to be safer, less harmful to the environment, more comfortable and convenient. In every field, we expect that smaller, lighter, and more efficient motors will be required to introduce new technologies and improve current systems.”
Engineers at Johnson Electric are also working on ways to reduce the size of automotive electric motors while retaining or improving existing performance. One solution involves the asymmetric winding of wire on the armature, which spreads the wire over a larger surface and results in a shorter, lighter armature. This contributes to an 18% reduction in overall motor length. Bosch has also introduced a new generation of lightweight miniature motors for use in various systems. Its latest range of actuator motors has an installation depth of just 30mm with an armature shaft diameter of 4mm. Typical applications include power windows and seats.
The number of electric motors per car varies depending on the segment and class. For example, the Toyota Celsior is equipped with around 80 electric motors whereas the Toyota Corolla is has about 30 electric motors. These applications range from the engine cooling fan to wiper motor and from the sunroof to the headlight.
Although electric motors have long since been used to power certain vehicle componentry, such as wiper systems, these markets have matured. “We are expecting significant growth with gearbox actuators [double clutch automated transmissions, actuation for transfer cases, torque distribution differential gears], power steering motors and electric machines for hybrid vehicles,” said Michael Pesch, vice president, advanced engineering and product development of Bosch’s Energy & Body Systems division. “We are actively involved in all these areas.”
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By GlobalDataAs the number of electric motors in vehicles increases, the collective weight of these motors also increases. There are some moves by vehicle makers to reduce the number of electric motors in seats in a bid to save cost and weight. Holger Lueking, sales manager, Cooling Fans Business Unit, Conti Temic, told us: “We are seeing a reduction in the number of motors used in some upmarket car seats. For example, some producers used to fit a motor to position the length position of their front seats on certain models. Today, the motor has been replaced with a manual adjuster.”
The automotive interiors giant Johnson Controls uses electric motors produced by various international manufacturers. Hardy Wolff, lead engineer at Johnson Controls Inc explained that in the case of customer orders, the motor chosen depends on the actual specifications of the carmaker concerned. In the case of new product developments that are independent of any OEM, a decision is reached based on the required performance and cost effectiveness of the motor for the individual project.
He told us: “Our company uses electric motors for all our electric seat adjusters, electric windows built into door panels, air ventilation controls in the cockpit, and steering wheel adjusters. It is to be expected that more DC electric motors will be used in automotive interiors in the future, since there is a general trend towards more electrification. This means that many manual functions, even in the lower vehicle segments, will increasingly be electrically operated in the future. At the same time, the use of actuators is also on the rise. Particularly when it comes to convenience features, such as backrest adjusters, the new electric actuators are becoming increasingly prevalent. For instance, our so-called Mechatronics Release enables simple seat adjustment, thanks to the integration of springs and actuators in the seating mechanism. At the touch of a button, the mechanism of the seats can be individually released or unlocked, which simplifies the whole process of seat adjustment. The big advantage of this mechanism is its simple operation, as it eliminates the need to push or pull a lever. It is also a cost-effective alternative to fully powered electric seat adjusters. In the rear of the vehicle, our Mechatronics Release enables the seats to be folded flat without any effort. This product is ready for serial production and would be available two years after ordering.”
In the power window department, Asmo observes a growing need for smaller, lighter motors to fit in the increasingly slim doors of modern cars. Asmo’s Ishii said: “As users demand for more high-class products, high functional systems will be equipped to even lower grade vehicles. In this context, we expect that demands for smaller, lighter motors, including motors with built-in control circuits for anti-pinch operation, will increase.”
Manufacturers also report demand for so-called ‘smart motors’ is growing fast, ie motors with built-in control circuits for anti-pinch operation. “The main reasons are NAFTA-legislation and an increasing standardisation in European specifications,” added Pesch.
On the wiper motor front, manufacturers note that reductions in weight and size as well as the improvement of exterior appearance are priorities for windscreen washer systems. Another requirement is the improvement of cleaning efficiency to reduce the amount of fluid used by washer systems. The company says it is working to develop lighter, more compact systems. It has also improved the exterior appearance by developing systems with nozzles in concealed locations, such as beneath the bonnet.
Asmo’s Ishii said: “The windscreen washer and wiper systems including motors are required to be designed to look more sophisticated and to be smaller [and] thinner to increase the space in the engine room for the pedestrian protection in case of [an] accident.”
As far as engine cooling applications are concerned, Continental Temic has introduced an EC (electronically commutated) fan module for the vehicle’s cooling system. The electronic control unit initiates continuously variable control of the brushless electric motors. Electronically commutated drives in combination with low-noise fans allow for maximum air power at a minimum noise level. At the same time, EC fan modules feature an ingenious space-saving design form, allowing for flexible solutions even in the most difficult mounting situations, and are especially advantageous in the event of a crash.
Depending on the customer’s wishes, modules can be built with single or double fans in the performance range of 400W to a maximum 1,200W. The company claims that its EC fan modules combine a long operating life with additional power reserves, which have a particularly beneficial effect on extreme routes (such as mountain pass roads). Lueking added: “Our brushless DC motors are the perfect fit for engine cooling fans. In order to meet the higher emission standards, manufacturers must consider ways in which to optimise engine temperature. More powerful brushless DC motors can efficiently cool larger engines. It is definitely a growing market. As far as other applications for brushless DC motors are concerned, we are currently talking with tier-one HVAC manufacturers about how to integrate brushless DC motors into the HVAC system since such motors offer a more powerful alternative to brush motors. This will still be a niche market albeit for HVAC applications.”
It is clear that manufacturers of brushless DC motors are pushing to develop smaller motors yet maintain power and speed. Above all, the driving force behind market growth is motorists’ insatiable demand for safety, comfort, economy, a clean environment and overall quality of driving.
Matthew Beecham
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