{"id":8386,"date":"2025-01-30T16:56:02","date_gmt":"2025-01-30T07:56:02","guid":{"rendered":"https:\/\/www.nikkidenso.co.jp\/cms\/?page_id=8386"},"modified":"2025-02-03T09:25:54","modified_gmt":"2025-02-03T00:25:54","slug":"about","status":"publish","type":"page","link":"https:\/\/www.nikkidenso.co.jp\/en\/technology\/dd-knowledge\/about\/","title":{"rendered":"Basic knowledge of the direct drive motor"},"content":{"rendered":"\n
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What is a direct drive motor?<\/h2>\n\n\n\n

The conventional AC servo motor is generally a high-revolution, low-torque motor. In order for this motor to provide high torque, an intermediate mechanism consisting of such components as gears and belts is necessary. This makes the mechanism complex, leading to increased mechanical loss and lower accuracy due to backlash. As a result, the motor requires frequent maintenance.<\/p>\n\n\n\n

By contrast, the direct drive motor connects directly to the workpiece without the need for an intermediate mechanism consisting of speed reducers, belts, etc. This makes its power transmission system more rigid and enables backlash-less, high-speed accurate driving. What’s more, the motor saves space and generates quiet drive power.<\/p>\n\n\n\n

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Structure of the direct drive motor<\/h3>\n\n\n\n

The direct drive motor mainly consists of four units – stator, rotor, bearing, and rotation position detection sensor (encoder).<\/p>\n\n\n\n

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Cross roller bearings are often used. A single bearing can take radial loads, axial loads, and moment loads. These bearings make the motor thinner and much more rigid, compared to when double-row angular ball bearings are used. Moreover, since its structure allows the bearing space to be adjusted, precompression can also be applied, thus providing highly accurate rotation.<\/p>\n\n\n\n

In addition, when used with a high-resolution encoder, the motor enables high-accuracy control. When compared to the typical AC servo motor having 8 to 12 motor poles, the direct drive motor features a multi-pole structure with 20 motor poles or more. For larger direct drive motors, the number of motor poles is more than 100. They achieve low torque ripple and large torque.<\/p>\n\n\n\n

Features of the direct drive motor and benefits of its introduction<\/h3>\n\n\n\n

1 | Space-saving<\/h4>\n\n\n\n

The speed reducer that generates large motor is structurally large and requires a lot of space. With the direct drive motor that needs no speed reducer, by contrast, the entire drive system can be compact and space-saving.<\/p>\n\n\n\n

2 | Maintainability<\/h4>\n\n\n\n

In the case of the AC servo motor with a speed reducer, as the gear sliding part of the speed reducer wears out, the motor needs to be disassembled and cleaned to remove metal powder, degraded grease, and other foreign matter and then reassembled and adjusted. The direct drive motor in principle requires no maintenance because it has a simple structure with no gear sliding part. Moreover, since the motor has no speed reduction mechanism, quick acceleration or deceleration does not cause it to fail, break, or otherwise become damaged.<\/p>\n\n\n\n

3 | High response<\/h4>\n\n\n\n

Thanks to the low-inertia rotation part and the drive system with increased rigidity, the servo control characteristics are directly reflected, making it possible to improve the machine performance.<\/p>\n\n\n\n

Video of the high-speed, high-response operation (high-speed handler)<\/h5>\n\n\n\n
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