All the disks in the hard disk are mounted on a rotating shaft, and each disk is parallel. There is a magnetic head on the storage surface of each disk, and the distance between the magnetic head and the disk is smaller than the diameter of the hair. All magnetic heads are connected to a head controller, which is responsible for the movement of each head. The magnetic head can move along the radial direction of the disk, and the disk rotates at a high speed of several thousand revolutions per minute, so the magnetic head can be positioned at the designated position of the disk to read and write data. Hard disk is a precision equipment, and dust is its enemy, so it must be completely sealed.
(a) the external structure of the hard disk.
At present, the common hard disks on the market are all 3.25-inch products, including half-height and full-height, except for the 5.25-inch structure of Bigfoot series of Quantum Company. The commonly used 3.5-inch hard disks are similar in appearance, and the product label is attached to the side without components, and the label is related to the hard disk. One end of the hard disk has a power socket, a jumper in the master-slave state of the hard disk, and a data cable connected to the socket.
The 1. interface includes a power socket and a data interface, wherein the power socket is connected with the host power supply to provide power guarantee for the hard disk. Data interface is the link between hard disk data and motherboard controller for transmission and exchange. According to different connection methods, it can be divided into EIDE interface and SCSI interface.
2. Most control circuit boards are welded with SMD components, including spindle speed regulating circuit, magnetic head drive and servo positioning circuit, read-write circuit, control and interface circuit, etc. There is also an efficient single ROM chip on the circuit board, and its solidified software can initialize the hard disk, power on and start the spindle motor, and initially seek, locate and detect faults after power on. Cache chips with different capacities are also installed on the circuit board.
3. The fixed cover is the panel of the hard disk, indicating the product model, origin, setting data, etc. Combined with the bottom plate into a sealed whole to ensure the stable operation of the hard disk and mechanism. The fixed cover plate and the side surface of the tray body are also provided with mounting holes, which is convenient for installation.
(B) the internal structure of the hard disk
The internal structure of hard disk consists of fixed panel, control circuit board, magnetic head assembly, interface and accessories. HardDiskAssembly (HDA) is the core of hard disk, which is encapsulated in the clean cavity of hard disk, including floating head assembly, head drive mechanism, disk and spindle drive mechanism, pre-read and write control circuit, etc.
1. The floating head assembly consists of a read-write head, a transmission arm and a transmission shaft. Magnetic head is the most important and critical part of hard disk technology. In fact, it is a combination of multiple magnetic heads made of integrated technology. Using non-contact head-disk structure, it flies on the surface of high-speed rotating disk after power-on, and the flight gap is only 0. 1 ~ 0.3 um, which can obtain extremely high data transmission rate. At present, the flying height of 5400 rpm hard disk is less than 0.3um, which is conducive to reading large high SNR signals and providing reliability of data transmission and storage.