Disk device

Abstract

The embodiment provides a magnetic disk device capable of detecting contact between a slider and a magnetic disk. The magnetic disk device of the embodiment comprises: a plurality of magnetic disks; a plurality of sliders including resistance elements disposed so as to be exposed to the recording surfaces of the magnetic disks and disposed corresponding to the plurality of magnetic disks; and a control unit that detects changes in resistance values ​​of the resistance elements disposed on the plurality of sliders.

Description

[0001] This application claims priority based on Japanese Patent Application No. 2021-15846 (filing date: February 3, 2021), and the present application incorporates the entire contents of the basic application by reference. Technical Field

[0002] The embodiment relates to a magnetic disk device. Background Art

[0003] Generally speaking, the slider of the magnetic disk device is provided with a thermal resistance element for making its head face protrude toward the magnetic disk side, and the thermal resistance element is mounted near the read element and the write element. The ABS (Air Bearing Surface) of the slider equipped with the read element and the write element is designed so that the suspension variation of the element part including the read element and the write element is small. Therefore, even if the slider vibrates for some reason, the vibration near the read element and the write element is smaller than the surrounding, and the thermal variation is also small. In addition, the position where the thermal resistance element is arranged is far away from the guide side that is likely to damage the magnetic disk the most, and it is difficult to detect the contact between the head face and the magnetic disk.

[0004] As described above, since it is difficult to detect the contact between the slider and the disk, contact may occur sometimes. When such contact occurs, not only will contamination occur, but there is also a risk of damage to the disk and loss of data. In addition, when reading / writing is continued in such a state, the following situations may occur: dust and the like generated by contamination may adhere to the slider, causing damage to other areas of the disk. In addition, since the slider accesses the damage generated on the disk, it may cause damage to the read element, write element, etc. provided on the slider, resulting in degradation of the element. In order to minimize such failures, it is necessary to detect the contact between the slider and the disk as soon as possible. Summary of the invention

[0005] An embodiment of the present invention provides a magnetic disk device capable of detecting contact between a slider and a magnetic disk.

[0006] A magnetic disk device according to one embodiment includes: a plurality of magnetic disks; a plurality of sliders including resistor elements exposed to recording surfaces of the magnetic disks and arranged corresponding to the plurality of magnetic disks; and a control unit that detects changes in resistance values ​​of the resistor elements respectively arranged on the plurality of sliders. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 This is a block diagram showing an example of the configuration of a system including a magnetic disk device according to an embodiment.

[0008] Figure 2 It is a transverse cross-sectional view of a slider according to another embodiment.

[0009] Figure 3 It is a bottom view of a slider according to another embodiment.

[0010] Figure 4 It is a cross-sectional view showing the structure of a plurality of sliders according to another embodiment.

[0011] Figure 5 This is a diagram showing an example of connection between resistance elements provided in a plurality of sliders and a head amplifier IC according to another embodiment.

[0012] Figure 6 This is a diagram showing an example of connection between the resistance element of the slider and the head amplifier IC according to the first embodiment.

[0013] Figure 7 It is a transverse cross-sectional view of a slider according to a modified example.

[0014] Figure 8 It is a bottom view of the slider involved in the modification example.

[0015] Fig. 9 It is a longitudinal side view of a slider involved in a modification example.

[0016] Fig.10 It is a bottom view of the slider involved in the modification example.

[0017] Fig.11 It is a bottom view of the slider involved in the modification example.

[0018] Fig.12 This is a diagram showing an example of connection between resistance elements respectively provided on a plurality of sliders and three head amplifiers according to the second embodiment.

[0019] Fig.13 This is a diagram showing an example of connection between the resistance elements respectively provided in a plurality of sliders and the head amplifier IC according to the third embodiment. DETAILED DESCRIPTION

[0020] Hereinafter, the embodiments will be described with reference to the accompanying drawings. In addition, the disclosure is only an example, and the invention is not limited by the contents described in the following embodiments. Deformations that can be easily thought of by those skilled in the art are of course included in the scope of the disclosure. In order to make the description clearer, in the accompanying drawings, the size, shape, etc. of each part are sometimes changed relative to the actual implementation form to schematically represent. In multiple drawings, the same reference numerals are sometimes given to the corresponding elements, and detailed descriptions are omitted.

[0021] (Configuration of Magnetic Disk Device)

[0022] Figure 1It is a block diagram showing an example of the structure of a system 150 having a magnetic disk device 10 involved in an embodiment. In the present embodiment, as the magnetic disk device 10, a hard disk drive (hereinafter also referred to as HDD) 10 is illustrated. The system 150 has a host 100 and an HDD 10. The host I / F 120 connects the host 100 with the HDD 10 and is used for the transmission and reception of commands, user data, command responses or status reports between the host 100 and the HDD 10. The host I / F 120, for example, follows the SATA (Serial Advanced Technology Attachment) standard and the SAS (Serial Attached SCSI) standard. The HDD 10 is connected to the host 100 via the host I / F 120 and functions as a data storage unit of the host 100. For example, the system 150 is a personal computer, a mobile device or a server device. For example, the host 100 is a chipset IC possessed by a personal computer or a mobile device or a server controller possessed by a server device.

[0023] The HDD 10 has a head-disk assembly (HDA) including a magnetic disk 1, a slider 2, an arm 3, a voice coil motor (VCM) 4, and a spindle motor (SPM) 5. The HDA is accommodated in a housing (not shown) of the HDD 10. The slider 2 has a head including a read head RH and a write head WH, a resistor element R, and a heater element HE.

[0024] In addition, the HDD 10 has a circuit block including a motor driver IC (hereinafter also referred to as a driver IC) 21, a head amplifier IC (hereinafter also referred to as a head IC) 22, a buffer memory 23, a nonvolatile memory 24, and a controller 60. The controller 60 includes a read / write channel (hereinafter also referred to as RWC) 61, a CPU 62, and a hard disk controller (hereinafter also referred to as HDC) 63. The head amplifier IC 22 includes at least a heater driver HD and a resistor element amplifier.

[0025] The HDD 10 according to the embodiment at least performs a process of recording data on the magnetic disk 1 (write process), a process of reading data recorded on the magnetic disk 1 (read process), a process of controlling the flying height of a part of the slider 2 (mainly the head) relative to the magnetic disk 1 (flying control process), and a process of detecting contact between the slider 2 and the magnetic disk 1. The flying control process is sometimes referred to as DFH (Dynamic Fly Height) control, and in the following description, the flying control process is also referred to as DFH control. Here, the flying height corresponds to, for example, the flying amount of the head from the surface of the magnetic disk 1. In the DFH control, by supplying a current (or voltage) to the heater element HE provided on the slider 2, a part of the slider 2 (the heater element HE and the peripheral part of the head) is heated and deformed by thermal expansion, and protrudes toward the magnetic disk 1. In addition, the current or voltage supplied to the heater element HE is described below as the power supplied to the heater element HE. The amount of protrusion of the part of the slider 2 can be controlled by information corresponding to the power supplied to the heater element HE.

[0026] The disk 1 is rotated by the SPM 5. The SPM 5 is rotationally controlled by a driving voltage or a driving current from the driver IC 21. The arm 3 and the VCM 4 constitute an actuator. The slider 2 is mounted on one end of the arm 3. The actuator moves the slider 2 to a target position on the disk 1. That is, the actuator moves the slider 2 mounted on the arm 3 in a radial direction on the disk 1 by the drive of the VCM 4. The VCM 4 is controlled by a driving voltage or a driving current from the driver IC 21.

[0027] The magnetic disk 1 has a recording surface, and a track (data track) is formed by recording data on the recording surface. That is, the magnetic disk 1 is configured as a recording medium having a recording surface for recording data. The recording surface of the magnetic disk 1 has at least a servo area, a user data area, and a system area. The servo area records servo data for controlling the position of the slider 2 on the recording surface, the user data area is used to record user data sent from the host 100, and the system area is used to record system data for managing the user data recorded in the user data area. The recording surface of the magnetic disk 1 may also have a cache area for temporarily recording user data to be recorded in the user data area.

[0028] Servo data is data that is recorded in the manufacturing process of the HDD 10 and is not recorded after the HDD 10 is shipped. System data includes data that should be managed in the write process and the read process performed in the HDD 10. In addition, the system data may be recorded in the nonvolatile memory 24 instead of the system area of ​​the magnetic disk 1. User data includes not only data that is sent from the host 100 and then recorded, but also data that has been recorded in the user data area or the cache area and data that is read from the user data area or the cache area.

[0029] The slider 2 has at least a head, a resistor element R, and a heater element HE, and the head includes a read head RH and a write head WH. The read head RH reads data recorded on the track on the disk 1. The read data includes servo data, user data, and system data. The write head WH writes user data and system data on the disk 1. The read head RH is configured as a read unit, and the write head WH is configured as a recording unit. In addition, in the following description, the slider 2 is sometimes referred to as a head or a head. The resistor element R is a thermal resistor element, and its resistance value changes when heat is supplied. The resistor element R is, for example, an HDI sensor, which is used to detect the distance between the head and the recording surface of the disk. The heater element HE generates heat according to the supplied power to heat a part of the slider 2. The heated part of the slider 2 thermally expands and protrudes toward the disk 1. A heater element HE is provided between the read head RH and the write head WH, or a heater element HE is provided near the read head RH and near the write head WH. The heater element HE is formed by a resistor or a coil as a circuit element. In Figure 1 Although a single magnetic disk 1 and a slider 2 are shown in the figure, the HDD 10 may be provided with a plurality of magnetic disks 1 and a plurality of sliders 2 corresponding to the recording surfaces of the plurality of magnetic disks 1 .

[0030] The head amplifier IC22 has a read amplifier, a write driver (none of which is shown in the figure), a resistor element amplifier, and a heater driver HD. The read amplifier amplifies the read signal read by the read head RH and outputs it to RWC61. The write driver outputs a write current corresponding to the write data provided from RWC61 to the write head WH. The resistor element amplifier is connected to the resistor element R provided on the slider 2, amplifies the signal read from the resistor element R, and outputs it to RWC61. The heater driver HD outputs a heater current (or heater voltage) corresponding to the heater data provided from the CPU62 or HDC63 to the heater element HE. The heater data is data indicating a value corresponding to the heater current (or heater voltage). In addition, hereinafter, the heater current or heater voltage will be described as heater power only.

[0031] The controller 60 is configured as a single-chip integrated circuit that at least integrally includes a RWC 61, a CPU 62, and a HDC 63. The controller 60 is configured as a semiconductor circuit such as a SoC, an FPGA, an ASIC, or an LSI. The buffer memory 23 is a volatile memory that can transfer data at a higher speed than the disk 1, and a DRAM (SDRAM) or an SRAM can be applied. The non-volatile memory 24 is a non-volatile recording unit, and a semiconductor memory such as a NOR type or a NAND type flash memory can be applied. The buffer memory 23 and the non-volatile memory 24 can also be arranged inside the controller 60 without being connected to the outside of the controller 60. The non-volatile memory 24 can also apply a part of the recording area of ​​the disk 1.

[0032] RWC61 includes a read channel and a write channel (neither of which is shown in the figure). The read channel processes the amplified read signal provided by the head amplifier IC22, and decodes the data including servo data, user data, and resistance value data read from the resistor element R1. RWC61 performs processing related to the detection and correction of errors in user data in the read channel, and generates information for evaluating the read user data. This information can be sent to CPU62 according to a request from CPU62. In addition, RWC62 sends the decoded resistance value data to CPU62. The read channel includes a Viterbi decoding circuit and an LDPC decoding circuit. The write channel outputs the write data obtained by encoding the data to be written provided by HDC63 to the head amplifier IC22.

[0033] HDC63 is connected to the buffer memory 23 and the non-volatile memory 24, and controls the sending and receiving of data transmitted between them. The data transmitted between HDC63 and the buffer memory 23 includes read data and write data transmitted between the host 100 and data related to the suspension control process. The read data is user data read from the disk 1, and the write data is user data written to the disk 1. The data related to the suspension control process includes data for setting the power supplied to the heater element HE. The data transmitted between HDC63 and the non-volatile memory 24 includes the program executed by the CPU 62, the system data and / or the suspension control process. In addition, HDC63 is connected to RWC61, and performs processing on data input from RWC61 or data output to RWC61. Further, HDC63 is connected to the host 100, and performs processing on commands and user data sent from the host 100, or command responses, status reports and user data output to the host 100. The processing of user data includes processing related to write gate in write processing, processing related to read gate in read processing, and processing related to servo gate required in servo control. HDC63 notifies CPU62 of an execution request for suspension control processing corresponding to a command input from host 100. HDC63 is composed of an interface circuit for controlling the transmission and reception of data between buffer memory 23, non-volatile memory 24, RWC61 and host 100. HDC63 can output heater data to heater driver HD. In this case, HDC63 can generate heater data based on instructions from CPU62 and output the generated heater data, or can be provided with heater data from CPU62 and output the supplied heater data.

[0034] CPU62 is an IC also called a microprocessor or a microcontroller. CPU62 controls VCM4 via driver IC21 and performs positioning control (servo control) of the head (read head RH and write head WH). Servo control includes at least control of positioning the head at a certain position in the radial direction of disk 1 and control of moving the head from the current position to the target position on disk 1. In addition, CPU62 controls the writing process and reading process of disk 1 at least via RWC61. CPU62 controls the suspension control process in parallel with the writing process and the reading process. In addition, the servo process can be executed as a part of the writing process and the reading process. CPU62 outputs heater data to the heater driver HD in the suspension control process. Further, CPU62 detects the contact between slider 2 and disk 1 based on the resistance value data sent from RWC62. In addition, the resistance value data is, for example, a current value or a voltage value. When the contact is detected, CPU62 stores data indicating that the contact is detected in non-volatile memory 24. The CPU 62 uses the HDA and circuit blocks described above in accordance with the program in controlling the plurality of processes. The CPU 62 is configured as a control unit or a control circuit that controls the plurality of processes.

[0035] (Other embodiments)

[0036] Next, refer to Figure 2 to Figure 5 An example of connection between the resistance element of the slider and the head amplifier IC in another embodiment different from the present embodiment will be described. Figure 2 is a cross-sectional view of the slider, Figure 3 is the bottom view of the slider. Figure 4 It is a cross-sectional view of the structure of multiple sliders. Figure 5 This is a diagram showing the connection between the resistance elements provided in the plurality of sliders and the head amplifier IC.

[0037] like Figure 2 and Figure 3 As shown, the resistor element (thermal resistor element) R1 is provided on the trailing side of the slider 2 and approximately in the center of the side pad 2A. A read head RH and a write head WH (not shown) are provided in the vicinity thereof. As already described, generally, the ABS of the slider 2 provided with the read head RH and the write head WH is designed so that the suspension fluctuation of the read head RH and the write head WH becomes small. Therefore, even if the slider 2 vibrates for some reason, the vibration of the read head RH and the write head WH is smaller than that of the surroundings, and the thermal fluctuation is also small. Therefore, the change in the resistance value of the resistor element R1 is also small, which makes it difficult to detect the contact between the slider 2 and the magnetic disk 1. In addition, the resistor element R1 is provided on the trailing side and is arranged at a position away from the leading side that may damage the magnetic disk 1. Due to this, it is also difficult to detect the contact between the slider 2 and the magnetic disk 1.

[0038] like Figure 4 As shown, sliders 2 are provided on both sides of a plurality of magnetic disks 1, and each slider 2 is provided with a Figure 2 and Figure 3 The resistor element R1 described in the above. Figure 5 As shown in FIG. 1 , the resistance element R1 of each slider 2 is connected in parallel to the head amplifier IC 22. Therefore, when detecting whether the slider 2 is in contact with the magnetic disk 1, the detection is performed by sequentially switching the slider 2 to be measured by the head amplifier IC 22. Therefore, even if it is possible to detect whether the measured slider 2 is in contact with the magnetic disk 1, it is impossible to detect whether the other sliders 2 are in contact with the magnetic disk. Therefore, in order to detect the contact of all the sliders 2 with the magnetic disk 1, it takes processing time.

[0039] (First embodiment)

[0040] Next, refer to Figure 6 An example of connection between the resistor element R1 of the slider 2 and the head amplifier IC 22 in the first embodiment will be described. The resistor element R1 in the slider 2 is arranged similarly to the resistor element R1 in the first embodiment. Figure 2 , Figure 3 The same position as described in .

[0041] In the first embodiment, instead of Figure 5 As shown in FIG. 1 , a plurality of resistor elements R1 and the head amplifier IC22 are connected in parallel, but Figure 6 As shown in FIG. 1 , a plurality of resistor elements R1 and the head amplifier IC 22 are connected in series. Therefore, the CPU 62 can obtain a change in the resistance value of the resistor element R1 connected in series by monitoring the resistance value outputted via the head amplifier IC 22 and the RWC 61. Therefore, the CPU 62 can detect an abnormality based on the change in the monitored resistance value, in other words, detect whether a slider 2 among the plurality of sliders 2 has come into contact with the magnetic disk 1.

[0042] In the absence of Figure 6 In the case of the structure shown, for example, when a certain impact is applied from the outside while the magnetic disk device 10 is operating, the presence or absence of the impact can be detected by a shock sensor provided at a predetermined position, but the presence or absence of contact between the slider 2 and the magnetic disk 1 cannot be detected. Figure 4In the structure shown, only the contact between the slider 2 of the head to be measured and the magnetic disk 1 can be detected. In contrast, in the magnetic disk device 10 of this embodiment, when an impact is given, the CPU 62 can monitor the resistance value outputted via the head amplifier IC 22 and the RWC 61, and based on the change in the resistance value, detect whether the slider 2 included in a certain head is in contact with the magnetic disk 1 for all the heads. In this case, when the position of the slider 2 when the impact occurs can be confirmed, the CPU 62 can also re-check whether there is such contact around the position. This inspection can be performed using the single parallel connection mode described later.

[0043] In addition, during so-called load / unload (LUL), there is a high risk that the slider 2 contacts the disk 1. Therefore, the CPU 62 can detect whether the LUL is performed safely by monitoring the change in the resistance value of the plurality of resistor elements R1 connected in series during the LUL. In this case, when contact is detected, the CPU 62 may also be concerned about contact in the outer area, and therefore recheck whether there is any abnormality around the LUL area. This inspection may be performed using the single parallel connection mode described later.

[0044] Furthermore, when the slider 2 moves from a predetermined position on the disk 1 to another predetermined position during a seek operation, the CPU 62 monitors the change in the resistance value of the plurality of resistor elements R1 connected in series, thereby being able to detect whether there is an abnormal seek operation. Here, the abnormal seek operation refers to the operation of performing LUL and contacting the inner stopper during the seek operation. In this case, when contact is detected, if the contact position can be confirmed, the CPU 62 may also re-check whether there is such contact around the position. This inspection may be performed using the single parallel connection mode described later.

[0045] Furthermore, the slider 2 is provided with a resistor element R1, so that by performing a seek from the outside to the inside (or from the inside to the outside), the CPU 62 can confirm the state of the disk 1 (whether there is an abnormality) based on the change in the resistance value of the plurality of resistor elements R1 connected in series. By adding such processing to the patrol action (an action performed when no command is received within a certain period of time), the CPU 62 can shorten the time for performing the state diagnosis of the disk 1 (for example, the detection of the presence or absence of the protrusion).

[0046] In addition, as described above, when the CPU 62 detects that a slider 2 has come into contact with the disk 1 during a predetermined action, the information indicating that the contact has been detected may be stored in the nonvolatile memory 24. When configured in this way, the number of times the slider 2 has come into contact with the disk 1 can be counted in association with the predetermined action. At this time, the position where the contact was detected and the detection time may also be stored. When configured in this way, the CPU 62 can diagnose the state of the disk device by comparing with the threshold value pre-stored in the nonvolatile memory 24, and can output an attribute value based on the diagnosis result to the outside. Thus, the user can understand the state of the disk device 10. Therefore, the user can replace the disk device 10 before a fatal failure occurs in the disk device 10. In addition, in the above description, the case where the slider 2 and the disk 1 are detected during a predetermined action (impact, LUL, seek action, patrol action) is described, but the slider 2 and the disk 1 may be detected during idle time or read / write time in addition to or in addition to these actions.

[0047] In addition, the diagnosis of the magnetic disk device 10 thus performed by the CPU 62 can be utilized not only when the user uses it after it leaves the factory and enters the market, but also when it is inspected before leaving the factory. During the inspection, an abnormality inspection (e.g., a protrusion inspection) of the magnetic disk 1 is sometimes performed. During this inspection, in other technologies different from the present embodiment, one head and one magnetic disk are inspected. However, according to the present embodiment, the contact between the slider 2 and the magnetic disk 1 is roughly confirmed by a seek action. In the case where there is a suspected contact position based on the change in the resistance value, the inspection is performed so that only the suspected position is confirmed again, and the inspection time is shortened, thereby shortening the manufacturing time of the magnetic disk device 10. In addition, it is sufficient to use the separate parallel connection mode described later for reconfirmation.

[0048] (Variation Example)

[0049] Next, a modification of the arrangement of the resistor element R1 will be described with reference to the drawings. Although not shown in the drawings, all of the following modifications are configured such that each resistor element R1 and the head amplifier IC 22 are connected in series.

[0050] First, use Figure 7 to Figure 9 A first modification example will be described. Figure 7 is a cross-sectional view of the slider 2, Figure 8 is a bottom view of slider 2, Fig. 9 2 is a longitudinal side view of the slider 2. In addition, regarding the composition of the cross section of the plurality of sliders 2, the same as that already described Figure 4 are the same. In addition, Figure 7 As shown, the slider 2 performs pitch vibration, such as Fig. 9 As shown, rolling vibration is performed.

[0051] like Figure 7 to Figure 9 As shown, on the side block 2A of the slider 2, in addition to the resistor element R1 already described (see: Figure 4 ), a resistor element R2 is also provided. By adding the resistor element R2, a function of detecting whether the slider 2 and the magnetic disk 1 are in contact with each other can be realized in addition to the function of detecting the distance between the slider 2 and the magnetic disk.

[0052] Next, refer to Fig.10 A second modification example will be described. Fig.10 is a bottom view of slider 2. Fig.10 As shown, resistor elements R11, R12, R13, and R14 are provided at four corners of the slider 2. That is, resistor element R11 is provided on the leading side and inside, resistor element R12 is provided on the leading side and outside, resistor element R13 is provided on the trailing side and inside, and resistor element R14 is provided on the trailing side and outside. By configuring resistor elements R11, R12, R13, and R14 in this way, the CPU 62 can detect the contact between the slider 2 and the disk 1 regardless of how the slider 2 is tilted relative to the disk 1. In addition, by providing at least one of the four resistor elements R11, R12, R13, and R14, the contact between the slider 2 and the disk 1 can be detected. However, when only one resistor element is provided, the resistor element R11 is preferably provided, that is, the corner on the leading side and inside. This is because the corner on the leading side and inside of the slider 2 is most likely to contact the disk 1 and will be damaged with a high probability. In addition, when it is difficult to configure resistor elements both inside and outside, when the slider 2 contacts the magnetic disk 1 in LUL, the contacting portion is preferably the inside of the data area of ​​the magnetic disk 1, that is, configured like the resistor elements R11 and R13.

[0053] Next, a third modification example will be described. Fig.11 is a bottom view of slider 2. Fig.11 As shown in FIG. 1 , a resistor element R21 is provided near the heater element HE. As described above, the heater element HE is applied with a voltage, so that the head surface of the slider 2 protrudes toward the magnetic disk 1. Therefore, by providing the resistor element R21 near the heater element HE, the CPU 62 can detect whether the slider 2 is in contact with the magnetic disk 1 at a position where the slider 2 is closest to the magnetic disk 1. In addition, since the contact can be detected at a distance close to the magnetic disk 1, the S / N ratio can be improved.

[0054] (Second embodiment)

[0055] The second embodiment will describe a case where a plurality of head amplifier ICs 22 are provided in the magnetic disk device 10. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description of these components will be omitted.

[0056] Fig.12 2 is a diagram showing an example of connection between the resistor elements R1 provided in the plurality of sliders 2 and the head amplifier ICs 22A, 22B, and 22C. Fig.12 As shown, a plurality of resistance elements R1 are connected in series to the head amplifier ICs 22A, 22B, and 22C, respectively. In this way, when the magnetic disk device 10 is provided with a plurality of head amplifier ICs 22, the CPU 62 can detect the contact between the slider 2 and the magnetic disk 1 for each of the head amplifier ICs 22A, 22B, and 22C by monitoring the change in the resistance value of the plurality of resistance elements R1 connected in series to each of the head amplifier ICs 22A, 22B, and 22C. In addition, in the present embodiment, the case where there are three head amplifier ICs 22 is described, but the CPU 62 can detect the contact between the slider 2 and the magnetic disk 1 according to the number of head amplifier ICs provided in the magnetic disk device 10.

[0057] (Third embodiment)

[0058] The third embodiment describes a case where the configuration of connecting a plurality of resistor elements R1 in series and the configuration of connecting a plurality of resistor elements in parallel are switched in the head amplifier IC 22. The same reference numerals are used for the same configurations as those in the first embodiment, and detailed descriptions of these configurations are omitted.

[0059] Fig.13 1 is a diagram showing an example of connection between the resistor elements R1 respectively provided on the plurality of sliders 2 and the head amplifier IC. The head amplifier IC 22 and the plurality of resistor elements R1 are connected via connection lines L1 and L2. Switches S21 and S22 are provided between the connection lines L1 and L2. When the switches S21 and S22 are in a closed state, the plurality of resistor elements R1 and the head amplifier IC 22 are connected, and when the switches S21 and S22 are in an open state, the plurality of resistor elements R1 and the head amplifier IC 22 are disconnected. In addition, each resistor element R1 is provided one at each slider 2 (refer to Figure 4 ).

[0060] Furthermore, one of the plurality of resistor elements R1 is connected to another adjacent resistor element R1 via a switch S11. When the switch S11 is closed, the adjacent resistor elements R1 are connected, and when the switch S11 is open, the adjacent resistor elements R1 are disconnected.

[0061] The switches S11, S21, and S22 are opened and closed based on, for example, the instruction of the CPU 62. When the switch S11 is in the connected state, the switch S21 at the end (the uppermost switch S21 in the figure) and the switch S22 at the other end (the lowermost switch S22 in the figure) are in the connected state, and the other switches S21 and S22 are in the disconnected state, the plurality of resistor elements R1 are connected in series with the head amplifier IC 22. On the other hand, when the switch S11 is in the disconnected state and the switches S21 and S22 are in the connected state, the plurality of resistor elements R1 are connected in parallel with the head amplifier IC 22. Furthermore, by connecting the groups of switches S21 and S22 one by one with the switch S11 in the disconnected state, the plurality of resistor elements R1 can be connected in parallel with the head amplifier IC 22 one by one. In this way, the plurality of resistor elements R1 and the head amplifier IC 22 are configured to be connected in series or in parallel based on the instruction of the CPU 62, and the resistor element R1 can be connected to the head amplifier IC individually. That is, the CPU 62 can make the head amplifier IC 22 operate in three modes: the series connection mode, the parallel connection mode, and the single parallel connection mode. In addition, in this embodiment, the case where it operates in the three modes of the series connection mode, the parallel connection mode, and the single parallel connection mode is described, but it can be configured to include the series connection mode and the parallel connection mode.

[0062] In addition, the head amplifier IC 22 has a constant voltage control unit 221A and a constant current control unit 222B. By applying a specified voltage to the constant voltage control unit 221A based on the instruction of the CPU 62, a specified current can be passed through the resistor element R1 by the constant current control unit 222B, and the resistance value in three modes of the series connection mode, the parallel connection mode and the single parallel connection mode can be measured.

[0063] In the series connection mode, the CPU 62 detects whether all the sliders 2 are in contact with the magnetic disk 1 based on the change in the resistance value of all the sliders 2. When it is determined that there is contact based on the change, the CPU 62 switches the connection targets one by one in the single parallel connection mode to detect which slider 2 is in contact. In addition, detection can also be performed in the parallel connection mode, but the detection requires power, and the reduction in the S / N ratio becomes greater. On the other hand, by using the single parallel connection mode, detection can be performed with low power, and the S / N ratio can be improved.

[0064] In addition, several embodiments of the present invention are described, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the scope of the purpose of the invention. These embodiments and their variations are included in the scope and purpose of the invention, and are included in the invention described in the claims and their equivalents.

Claims

1. A magnetic disk device comprising: Multiple disks; a plurality of sliders including a resistor element disposed so as to be exposed toward a recording surface of the magnetic disk, and disposed corresponding to the plurality of magnetic disks; and a control unit that detects a change in resistance value of the resistance elements provided respectively on the plurality of sliders, The control unit switches the plurality of resistor elements provided on each of the sliders to be connected in series or in parallel. The control unit includes: a plurality of first switches for connecting adjacent resistance elements in series or disconnecting adjacent resistance elements among the plurality of resistance elements; and a plurality of second switches for connecting or disconnecting the plurality of resistor elements and the control unit in parallel, The control unit has a single parallel connection mode and a series connection mode, the single parallel connection mode is a mode in which the plurality of first switches are in a disconnected state and the plurality of second switches are sequentially connected, and the series connection mode is a mode in which the first switch is in a connected state, one of the second switches located at an end and one of the second switches located at the other end are in a connected state, and the other second switches are in a disconnected state. When a change in the resistance value of the plurality of resistor elements is detected through the series connection mode, the states of the plurality of first switches and the states of the plurality of second switches are switched to set to the separate parallel connection mode, and the change in the resistance value of the plurality of resistor elements is detected in sequence through the separate parallel connection mode obtained by the switching.

2. The magnetic disk device according to claim 1, The sliders include a heater for causing the head surface of each slider to protrude toward the recording surface of the magnetic disk. The control unit, The heaters are configured to apply voltages to each of the plurality of heaters. The resistance values ​​of the plurality of resistance elements of the slider including the heater to which the voltage is applied are detected in the parallel mode or the series mode.

3. The magnetic disk device according to claim 1 or 2, The magnetic disk device includes a plurality of control units. The plurality of resistor elements are divided into units of the control unit, and the control unit detects a change in resistance value of the plurality of resistor elements included in the divided units.

4. The magnetic disk device according to claim 1 or 2, The head surface of the slider is rectangular, and the resistor element is provided at a central position of the rectangular shape, at least any one of four corners of the rectangular shape, and any one of an end portion on a trailing side.

5. The magnetic disk device according to claim 1 or 2, The control unit detects whether the slider is in contact with the magnetic disk based on changes in resistance values ​​of the plurality of resistor elements.

6. The magnetic disk device according to claim 5, The control unit detects a change in the resistance value of the plurality of resistor elements during a patrol seek operation, and detects whether the slider is in contact with the magnetic disk based on the change in the resistance value.

7. The magnetic disk device according to claim 5, A memory device for storing data, The control unit stores the detection result of whether the slider is in contact with the magnetic disk in the memory, and when the number of results indicating the contact stored in the memory reaches a predetermined number, outputs information indicating the contact to the host.

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