JP2009123290A - Navigation system and magnetic disk drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means by which a magnetic disk drive obtains altitude information from a navigation system without newly setting standards for requesting and transmitting information about altitude or atmospheric pressure between a navigation system and a magnetic disk drive. <P>SOLUTION: The controller of the navigation system records the altitude information in the magnetic disk drive, and the magnetic disk drive reads the altitude information recorded in the self device and adjusts floating height of a magnetic head slider. Timing at which the controller records the altitude information is once before stopping of the system, or once for each fixed time interval, or once when altitude is changed by a fixed threshold value or more, and timing at which the magnetic disk drive reads the altitude information and adjusts the floating height of the magnetic head slider is once at the start-up, once for each fixed time interval, or once when entering error recovery operation. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a navigation system equipped with a magnetic disk device, and more particularly to a technique for improving the reliability of a magnetic disk device that records and reproduces various information.

  In recent years, in a navigation system such as a vehicle, a magnetic disk device (HDD) is used as a storage device that records and reproduces various information such as map information, music, and video. The magnetic disk device includes a magnetic disk medium and a magnetic head. As the magnetic head is also called "magnetic head slider", the magnetic disk medium is magnetized and recorded information while floating on the magnetic disk by the action of the air bearing, and the magnetic state of the magnetic disk medium is read, Information is being reproduced. Here, for example, when writing information, the narrower the distance between the magnetic disk and the magnetic head, the smaller the spread of the magnetic field formed by the magnetic head, and the smaller the area magnetized on the magnetic disk medium. Get smaller. That is, in order to increase the recording density of the magnetic disk device, it is required to reduce the gap between the magnetic disk and the magnetic head, that is, the flying height of the magnetic head.

  On the other hand, if the flying height of the magnetic head becomes too small, the magnetic head and the magnetic disk come into contact intermittently or continuously. As a result, there is an increased risk of contact vibration causing information recording / reproducing errors, and wear and scratches damaging the magnetic head and magnetic disk medium. Therefore, it is desirable to keep the flying height of the magnetic head as small as possible without touching.

  However, the flying height varies and varies depending on the manufacturing / assembly tolerance of the magnetic head, the radial position on the magnetic disk, the operation mode (recording / reproducing), the environmental temperature difference, the environmental pressure difference, and the like. Therefore, conventionally, as a technique for removing variations and fluctuations in the flying height of the magnetic head, a heating element (heater) made of a thin film resistor or the like is attached in the vicinity of the recording / reproducing element, and a part of the magnetic head slider is heated and thermally expanded. Some have a recording / reproducing element close to the magnetic disk side. (For example, patent document 1). As an application form of this technology, the flying height of each magnetic head is inspected and stored at the time of inspection before shipment, and according to the proper energization amount unique to the magnetic head and the usage status of the magnetic disk device at the time of use. The amount of current supplied to the heating element is controlled.

  In Patent Document 2, in a mobile terminal device incorporating a magnetic disk, a position detection unit that detects a current position and an approximate altitude of a position detected by the position detection unit are determined, and the determined altitude is equal to or higher than a predetermined altitude. In some cases, a technique for restricting the use of a magnetic disk is disclosed. In Patent Document 3, the navigation device includes a magnetic disk device, density detection means for detecting the density of air, and information stored in the magnetic disk device when the density detected by the density detection means is greater than a predetermined value. A control unit that executes information processing for realizing a predetermined function based on the above, and stops the operation of the magnetic disk device when the value is lower than the predetermined value, and is damaged due to a decrease in the flying height of the magnetic head An invention for preventing the above is disclosed.

JP-A-2005-135501 JP 2006-351136 A JP 2007-026620 A

  Since the current magnetic disk device has a temperature sensor as information on the usage status, ambient temperature information can be obtained. It also has information on operation mode and radius position. However, information about atmospheric pressure cannot be obtained. The flying height of a magnetic head that is flying due to the action of an air bearing changes as the air pressure changes. If designed, sufficient recording density cannot be achieved. On the other hand, if the flying height is designed to be low without expecting a margin, the risk of contact between the magnetic head and the magnetic disk at a high altitude increases, and sufficient reliability cannot be achieved. Although a barometric pressure sensor manufactured by a micro electro mechanical system (MEMS) technology can be mounted on a magnetic disk device and barometric pressure information can be obtained from the sensor, it causes a significant cost increase.

  On the other hand, as a whole navigation system, information relating to altitude can be used from map information and position information obtained by a position detection device such as a global positioning system (GPS). If the altitude is known, the atmospheric pressure can also be calculated. Therefore, the control device of the navigation system only has to transmit information about altitude or atmospheric pressure to the magnetic disk device that is a storage device. However, there is no standard for requesting or transmitting information about altitude or atmospheric pressure between the current magnetic disk device and the control device of the navigation system that is the host.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide means for a magnetic disk device to use altitude information or atmospheric pressure information possessed by a navigation system without changing the current standard. . As a result, it is an object of the present invention to maintain the flying height of the magnetic head slider at an appropriate value regardless of the altitude of use and to improve the performance and reliability of the magnetic disk device.

  In order to solve the above problems, in the navigation system according to the present invention, the control device of the navigation system records altitude information or atmospheric pressure information on the magnetic disk device, and the magnetic disk device records altitude information or atmospheric pressure information recorded on itself. To adjust the flying height of the magnetic head slider.

  More preferably, the timing at which the control device records altitude information or barometric pressure information is once before the system shuts down, once every fixed time interval, or once when the altitude or barometric pressure changes more than a certain threshold. The magnetic disk device reads the altitude information or barometric pressure information and adjusts the flying height of the magnetic head slider once at system startup, once at regular time intervals, or once at the start of error recovery operation. is there.

  More preferably, the control device issues a command to write altitude information or atmospheric pressure information to a logical address that is predetermined at the time of system development, and the magnetic disk device is a physical address corresponding to the logical address that is predetermined at the time of device development. To read altitude information or barometric pressure information and adjust the flying height of the magnetic head slider.

  More preferably, when the magnetic disk device reads altitude information or barometric pressure information recorded on the magnetic disk device, the magnetic disk device may have the magnetic altitude at a maximum altitude and a minimum barometric pressure with respect to the specifications of the navigation system. The flying height of the magnetic head slider is adjusted so that the head slider does not contact the magnetic disk medium.

  More preferably, when the magnetic disk device reads altitude information or atmospheric pressure information recorded on itself, the power applied to the heating element is made substantially zero.

  More preferably, when the magnetic disk device receives a command to record at a predetermined logical address during system development in order to record altitude information or atmospheric pressure information sent from the control device, normal data is received. Is recorded at a frequency lower than the recording frequency.

  Alternatively, since the magnetic disk device records altitude information or barometric pressure information sent from the control device, when it receives a command to record at a predetermined logical address during system development, it should have redundancy. And repeatedly record.

  Alternatively, the magnetic disk device is a hybrid type magnetic disk device having both a storage area for magnetic recording on the disk and a storage area for storage in an attached nonvolatile semiconductor memory, and a logical address determined in advance during system development. Is a part of a storage area arranged on the nonvolatile semiconductor memory.

  According to the present invention, it is possible to provide means for the magnetic disk device to use altitude information or atmospheric pressure information possessed by the navigation system without changing the current standard. As a result, the flying height of the magnetic head slider can be maintained at an appropriate value regardless of the usage altitude, and the performance and reliability of the magnetic disk device can be improved.

Embodiments of the present invention will be described below with reference to the drawings.
[overall structure]
FIG. 1 is a block diagram of a navigation system according to an embodiment of the present invention. This navigation system is used by being mounted on a vehicle, and includes a navigation system mounted on a portable terminal carried by a person, for example. Here, the following description will be given on the assumption that the navigation system is mounted on a vehicle. .

  A control device 31 plays a central role in the navigation system 30 shown in FIG. 1, and includes a CPU that performs arithmetic processing, a ROM that stores programs, a RAM that functions as a working memory, and the like. The control device 31 is connected to the following devices.

  Communication device 32: a function for communicating with the outside of the navigation system 30 using wireless communication. Use short-range communication such as Bluetooth to exchange information with other devices in the vehicle, wirelessly communicate traffic information, parking lot availability, etc. with communication terminals installed near the road, mobile phones Alternatively, it has a function of connecting to the Internet using the infrastructure of a simple mobile phone.

  Position detection device 33: detects the current position of the navigation system 30. At present, a position detection device that detects a current position by a global positioning system (GPS) method is generally used, but a device that detects a current position by another method may be used.

  Storage device 10: In general, there may be an optical disk device or the like, but in this embodiment, it is nothing but a magnetic disk device. Map information, input travel schedule information, destination information, etc. are recorded / reproduced. In recent years, navigation systems often have a function of providing entertainment for vehicle occupants, and a function of recording and reproducing video and music information is sometimes required.

  Display device 34: Specifically, it is a liquid crystal display or the like, and displays map information, route search results, destination arrival scheduled time, etc. in response to a request from the control device 31. In addition to visual display, guidance by hearing (voice guidance) is also included.

  Input device 35: used when a user inputs information to the navigation system 30. Specifically, a button, a touch panel, a keyboard, a voice recognition device, and the like are included.

  Although a typical configuration of the navigation system is shown here, for example, a navigation system that does not include the communication device 32 and a navigation system that does not include the display device 34 and is connected to a television are also included in the scope of the present invention. It is.

[Magnetic disk unit: HDD]
FIG. 2 is a block diagram of the entire magnetic disk device mounted on the navigation system 30, and FIG. 3 is a schematic cross-sectional view showing the configuration of the magnetic head slider mounted on the magnetic disk device and its peripheral portion.
The magnetic disk device 10 includes a spindle motor 2, a magnetic disk medium 3, a carriage assembly 4, a magnetic head slider 5, a preamplifier 7, a voice coil motor 8, a temperature sensor 9, a read / write channel 11, a motor driver 12, and a hard disk controller (HDC). 13, a microcomputer 14, and a memory 15. The read / write channel 11, motor driver 12, HDC 13, microcomputer 14, and memory 15, the above five components may be separated into separate chips on the signal processing board. You may live on one chip.
The spindle motor 2 rotationally drives one or a plurality of disk-shaped magnetic disk media 3. The carriage assembly 4 is rotationally driven by a voice coil motor 8 and relatively moves a magnetic head slider 5 attached to the tip of the carriage assembly 4 on the magnetic disk medium 3 in a substantially radial direction. The magnetic head slider 5 has an air bearing surface, and floats on the magnetic disk medium 3 with air pressure.

[Magnetic head slider]
As shown in FIG. 3, the magnetic head slider 5 and the peripheral portion thereof, the magnetic head slider 5 includes therein a recording element 5 a for magnetically recording data on the magnetic disk medium 3 and reproducing the recorded data. And a reproducing element 5b. Further, the magnetic head slider 5 is provided with a heating element 5c in the vicinity of the recording / reproducing element, which adjusts the distance (flying height) between the recording / reproducing element and the magnetic disk medium by utilizing thermal expansion deformation.
The flying height adjustment using the heating element is merely an example, and the effect of the present invention can be equally obtained by another flying height adjustment method using a piezoelectric element or an electrostatic actuator.

[Preamplifier]
The preamplifier 7 receives a signal representing information to be recorded, amplifies the signal, and outputs the amplified signal to the recording element 5 a of the magnetic head 5. The preamplifier 7 amplifies and outputs the reproduction signal output from the reproduction element 5b. Further, the preamplifier 7 according to the present embodiment receives an instruction for the amount of power to be output to the heating element 5c, and supplies a current (or voltage) of the specified amount of power to the heating element 5c.
A flexible wiring “flexible printed cable” (FPC) 6 that deforms and absorbs the rotational motion of the voice coil motor 8 is provided in the middle of a path that electrically connects the magnetic head slider 5 and the read / write channel 11. 7 is mounted on the flexible printed cable 6 by soldering or the like.

[HDD overall configuration (continued)]
Returning to FIG. 2, the temperature sensor 9 detects the environmental temperature in the vicinity of the magnetic head slider 5 and outputs a signal representing the detected temperature. The temperature sensor 9 may be disposed on the flexible printed cable 6, for example. Alternatively, it may be arranged on a signal processing board (card) as in the HDC 13 and the microcomputer 14.

  The read / write channel 11 outputs a signal obtained by code-modulating data to be recorded to the preamplifier 7. The read / write channel 11 performs code demodulation on the reproduction signal output from the preamplifier 7 and outputs the data obtained by the demodulation to the HDC 13.

  The motor driver 12 outputs a drive current to the spindle motor 2 and the voice coil motor 8 in accordance with an instruction input from the microcomputer 14 to operate the spindle motor 2 and the voice coil motor 8.

  The HDC 13 receives data to be recorded and commands transferred from an external host, and transfers reproduction data output from the read / write channel 11 to the host. In the present embodiment, the external host is the control device 31 of the navigation system.

  The microcomputer 14 controls each part such as controlling the motor driver 12 in order to control the position of the magnetic head slider 5. The microcomputer 14 is a program control device and operates according to a built-in program and / or a program stored in the memory 15. In the magnetic disk device having the flying height adjustment function, the microcomputer 14 instructs the preamplifier 7 on the amount of current to be supplied to the heating element 5c.

  The memory 15 stores a program executed by the microcomputer 14 and data necessary for executing the program. Further, the memory 15 stores a value (control parameter corresponding to the energization amount to the heating element 5 c) that is referred to by the microcomputer 14 when controlling the heating element 5 c and is set in the heating element control register of the preamplifier 7. ing. An example (table) of this control parameter will be described later. The memory 15 includes a nonvolatile memory such as an EEPROM (electrically erasable ROM). Further, the memory 15 may include a partial area on the magnetic disk medium 3. In this case, the control parameters are stored on the magnetic disk medium 3 at the time of manufacture, and are first copied to a memory that can be accessed at high speed from the magnetic disk medium 3 after power-on at the time of use, and are referred to in the control of the heating element 5c. .

[How to make slider and heater]
A schematic method of forming the magnetic head slider 5 will be described with reference to FIG. First, on a wafer 5d of an alumina / titanium carbide sintered body (referred to as Altic), a large number of recording elements 5a, reproducing elements 5b, heating elements 5c, and wirings leading to them are laminated by a thin film process. Next, the wafer state is cut into a bar state, and further separated into individual sliders by dicing. Before and after that, the air bearing surface 5f is smoothly polished in a bar state or a slider state to form a carbon protective film. Further, a step bearing having a shape that effectively generates air pressure is formed on the air bearing surface 5f.

  4 is a cross-sectional view of the heating element 5c layer as viewed from the air outflow end face 5g side of FIG. The material of the heating element 5c is a conductive thin film having a relatively high resistance value, such as a nickel / chromium alloy. After a uniform film is formed by sputtering or the like, unnecessary portions are removed by milling or the like to form a contour as shown in FIG. The removed portion is filled with an insulating film 5e such as alumina. In the present embodiment shown in FIG. 3, the heating element 5c is disposed between the altic part 5d and the reproducing element 5b. However, if the flying height of the recording / reproducing element part can be effectively controlled by thermal expansion, another position is provided. But you can. For example, it may be between the recording element 5a and the reproducing element 5b. If the ratio between the thickness of the conductive film and the length and width of the meandering partial thin line is appropriately designed, a resistance value of, for example, 100 ohms can be realized.

[How to use heater (flying height design)]
The energization amount to the heating element 5c for adjusting the flying height is adjusted by the use head and zone, the use temperature, the use altitude (atmospheric pressure), and the use mode. Specifically, in consideration of the flying height variation of each magnetic head slider 5, even if other low flying conditions such as temperature and use mode overlap at the lowest atmospheric pressure corresponding to the highest altitude determined as a specification, the magnetic The step bearing is designed so that the head slider 5 does not contact the magnetic disk 3.

[How to use the heater (individual flying height difference)]
The compensation for the flying height difference of the individual head slider will be described. The flying height differs for each head slider. Using the contact detection method described later, in the pre-shipment test process, if contact detection is performed by gradually increasing the heating element energization amount in a certain zone or in each zone, the distance to contact for each head slider ( Clearance) can be obtained individually. In the product, a value obtained by subtracting a certain reliability margin from the heating element energization amount leading to contact is recorded in the memory 15 for each head. When a seek command before recording / reproduction comes from the host, the value of the heating element control register of the preamplifier 7 is appropriately updated based on the head number information to be recorded / reproduced.

  The head slider clearance is not determined by contact detection, and in the pre-shipment test process, the heating element energization amount is gradually increased in a certain zone or in each zone, and the recording / reproduction performance such as error rate. There is also a method of conducting a test and setting the energization amount when the desired value is reached as the specific energization amount of the head slider. In that case, a procedure called a clearance check is required in which a value obtained by adding the energization amount corresponding to the reliability margin to the determined energization amount is actually applied to confirm that no contact occurs.

[Contact detection method]
There are the following types of parameters for determining whether or not the magnetic head slider 5 and the magnetic disk 3 are in contact with each other by gradually increasing the energization amount to the heating element 5c in the pre-shipment test process.
First method: It is determined that the contact is based on a change in strength of the magnetic reproduction signal, that is, even if the energization amount is increased, the flying height does not decrease further by the contact. As an index representing the magnetic reproduction signal, for example, the gain (VGA: variable gain amplifier) of the gain adjustment parameter is used. There are two types of VGA: servo data VGA (servo VGA) and user data VGA (data VGA).
Second method: It is determined that the contact is caused by an increase in variation in the magnetic reproduction signal, that is, frictional vibration (flying direction) due to contact. The above-described servo VGA gain, data VGA gain, and other variations between sectors, or when measured multiple times in the same sector, are calculated and used for contact determination.
Third method: It is determined that contact is caused by an increase in variation in positioning error (PES: position error signal), that is, frictional vibration (in-plane direction) due to contact.
Fourth method: It is determined that the contact is caused by an increase in variation in the current value applied to the voice coil motor 8, that is, frictional vibration (in-plane direction) due to contact.

[How to use heater (zone)]
The compensation for the flying height difference due to the zone on the magnetic disk medium will be described. The flying height varies depending on the zone. The average profile can be known by the design value or the sample test in the laboratory. Further, in the pre-shipment test process, if contact detection is performed by gradually increasing the heating element energization amount in each zone, a profile can be individually obtained for each head slider. In the product, the appropriate heating element energization amount for each zone is recorded in the memory 15 as a table. When a seek command before recording / reproduction comes from the host, the value of the heating element control register of the preamplifier 7 is appropriately updated based on the zone information to be recorded / reproduced.

  Although the method of storing the control parameters by dividing the magnetic disk medium 3 into a large number of zones is the most accurate, a common control parameter is set over the entire magnetic disk medium 3 (that is, the number of zones is only one). The method is fine. Further, for example, a method may be used in which control parameters are stored in a small number of zones such as the outer peripheral part, the intermediate peripheral part, and the inner peripheral part, and control is performed by interpolating with a primary expression or a secondary expression in the meantime.

[How to use the heater (temperature)]
The compensation for the flying height difference due to the environmental temperature will be described. When the environmental temperature is high, the flying height decreases due to the influence of thermal protrusion due to the difference in linear expansion coefficient between the material of the recording / reproducing element and the surrounding material. Conversely, when the environmental temperature is high, the flying height increases. In the embodiment of the present invention, on the basis of the result obtained by examining the influence of the environmental temperature on the flying height in advance in the laboratory, the product has the memory 15 and the appropriate heating element energization amount for each temperature zone in a single numerical value (coefficient). Alternatively, they are recorded as a plurality of numerical values (tables). When a seek command before recording / reproduction comes from the host, the value of the heating element control register of the preamplifier 7 is appropriately updated based on information from the temperature sensor 9.

  Between the upper and lower limits of the operation compensation temperature, it may be divided into a number of temperature zones and all control parameters corresponding to each temperature zone may be stored. Only the control parameters of the specified number of temperature zones may be stored, and control may be performed by interpolating with a linear expression or a quadratic expression during that time.

[How to use the heater (operation mode)]
The compensation for the flying height difference according to the operation mode such as recording / reproducing will be described. During recording, the recording current acts in the same way as the heating element current to cause thermal expansion deformation, so that the flying height is lower than during reproduction. An average value can be obtained from the design value or the sample test in the laboratory for the degree of decrease (the amount of change in flying height due to light protrusion). Also, in the pre-shipment test process, by comparing the reproduced signal waveform amplitude immediately after continuous writing with the reproduced signal waveform amplitude without writing, the amount of flying change due to light protrusion can be individually determined for each head slider. . In the product, the heating element energization amount for correcting the light protolusion is recorded in the memory 15. When a seek command before recording / reproduction comes from the host, the value of the heating element control register of the preamplifier 7 is appropriately updated based on the operation mode information.

[Power table]
To summarize the above heating element energization amount setting method, an energization amount table as shown in FIG. 5 is created before shipment and recorded in the memory 15. When a seek command before recording / reproduction is received from the host, based on the head number information and zone information to be recorded / reproduced, the temperature zone output from the temperature sensor 9 and the operation mode information, the heating element control register of the preamplifier 7 The value is updated appropriately.

[Addition is power]
There are three types of heating element control of the preamplifier 7: power control, voltage control, and current control. The flying height change by the heating element is roughly proportional to the power and proportional to the square of the voltage or current. Therefore, the degree of heating to the heating element is first calculated by electric power. In the case of power control, simple addition is sufficient. That is, the total power is calculated by adding the power corresponding to the flying height difference due to the individual head slider zone, the flying height difference due to the environmental temperature, and the flying height difference depending on the operation mode. On the other hand, when calculating using the voltage or current value, it is necessary to calculate the sum of the squares of the voltage or current for compensating for the difference in individual flying height, and to obtain the total voltage or current.

[Operation example of magnetic disk unit]
Next, an operation example of the magnetic disk device 10 will be described. In the following description, the memory 15 of the magnetic disk device 10 is set with a value (control parameter) for controlling the energization amount to the heating element 5c during recording and reproduction for each head, zone, and temperature zone. It shall be.
When receiving a command for recording data and data to be recorded from the control device 31 of the navigation system 30, the HDC 13 outputs the data to be recorded to the read / write channel 11 and the microcomputer 14 sends the data to the motor driver 12. An instruction to move the magnetic head slider 5 to the recording position corresponding to the command is output. At this time, the microcomputer 14 acquires information on the environmental temperature based on a signal output from the temperature sensor 9. And the microcomputer 14 acquires the control parameter (control parameter at the time of recording) stored in the memory 15 corresponding to the temperature zone of the environmental temperature represented by this acquired information. The microcomputer 14 outputs an instruction to the preamplifier 7 that the energization amount to the heating element 5c should be the predetermined value. Therefore, the preamplifier 7 supplies a predetermined amount of current to the heating element 5c. The heating element 5 c heats the vicinity of the recording / reproducing element of the magnetic head slider 5.

  On the other hand, the read / write channel 11 outputs a signal obtained by modulating the data to be recorded to the preamplifier 7, and the preamplifier 7 amplifies this signal and outputs it to the recording element 5 a of the magnetic head slider 5. As a result, the data to be recorded is recorded on the magnetic disk medium 3.

  Similarly, when receiving a command for reproducing data from the control device 31, the HDC 13 outputs a reproduction instruction based on the reproduction command to the read / write channel 11, and the microcomputer 14 reproduces the motor driver 12 according to the command. An instruction to move the magnetic head slider 5 to the position is output. At this time, the microcomputer 14 acquires information on the environmental temperature based on a signal output from the temperature sensor 9. And the microcomputer 14 acquires the control parameter (control parameter at the time of reproduction | regeneration) stored in the memory 15 corresponding to the temperature zone of the environmental temperature represented by this acquired information. The microcomputer 14 outputs an instruction to the preamplifier 7 that the energization amount to the heating element 5c should be the predetermined value. Accordingly, the preamplifier 7 supplies a predetermined amount of current to the heating element 5c. The heating element 5 c heats the vicinity of the recording / reproducing element of the magnetic head slider 5.

  On the other hand, the preamplifier 7 amplifies the reproduction signal output from the reproducing element 5b of the magnetic head slider 5 and outputs the amplified signal to the read / write channel 11. The read / write channel 11 demodulates the signal amplified by the preamplifier 7. The reproduction data is generated and output to the HDC 13. The HDC 13 outputs this reproduction data to the control device 31.

[Barometric pressure compensation method]
Up to this point, the method of compensating for the flying height variation and fluctuation due to the individual flying height difference, zone, temperature, and operation mode has been described. Hereafter, in the embodiment of the present invention, a method for compensating for flying height variation due to atmospheric pressure change will be described.
The flying height of the magnetic head slider flying by the action of the air bearing changes as the atmospheric pressure changes. Since the current magnetic disk device is equipped with a temperature sensor, temperature information can be obtained. It also has information on operation mode and radial position. It also has information on the difference in individual flying height by detecting the individual flying height (contact detection) in the pre-shipment test process. However, information about the atmospheric pressure cannot be obtained by a single magnetic disk device. If the atmospheric pressure sensor is mounted on the magnetic disk device, it causes a significant cost increase.

  On the other hand, the navigation system 30 as a whole can use altitude information from the map information read from the magnetic disk device and the position information obtained by the position detection device 33. More specifically, the first method for obtaining altitude information directly from the global positioning system (GPS) of the position detection device 33 and the map read from the magnetic disk device by obtaining only the horizontal position information from the GPS. There is a second method for obtaining the altitude at the current position from the contained contour line information, and the effect of the present invention can be effectively obtained by either method.

  If the altitude is known, the atmospheric pressure can also be calculated. When the control device 31 of the navigation system transmits information relating to “altitude or atmospheric pressure” (hereinafter simply referred to as “altitude”) to the magnetic disk device 10 that is a storage device, the magnetic disk device 10 obtains information relating to atmospheric pressure. be able to. However, there is no standard for requesting or transmitting altitude information between the current magnetic disk device and the control device of the navigation system that is the host. Therefore, in this embodiment, the control device 31 only issues a command to record altitude information at a specific logical address of the magnetic disk device 10 at a specific timing. The magnetic disk device 10 reads altitude information recorded on itself at a predetermined timing and adjusts the flying height of the magnetic head slider 5 by adjusting the energization amount to the heating device 5c. The “specific logical address” is determined in advance between the navigation system 30 and the magnetic disk device 10 during development. The magnetic disk device 10 accesses a physical address (cylinder number, head number, sector number) corresponding to a predetermined logical address, reads altitude information or atmospheric pressure information, and adjusts the flying height of the magnetic head slider 5.

  The “specific logical address” is described as it is necessary to be an address that can be referred to by both the control device 31 of the navigation system as a host and the magnetic disk device 10. In FIG. 6, the storage area recognized by the control device 31 where the logical address assigned to the altitude information exists and the logical address received by the magnetic disk device 10 are converted into physical addresses existing in the user area for the magnetic disk device 10. A state to do is shown typically. The altitude information is assigned to a logical address and is recorded in an area that can be accessed from the control device 31 of the navigation system (for a magnetic disk device, not a reserved area but a user area).

[Recording timing]
The timing at which the control device 31 records altitude information on the magnetic disk device 10 is important. This is because vehicles, people, etc. may change altitude from moment to moment. If the timing is too open, the altitude is actually increased and the atmospheric pressure is lowered, and the flying height of the magnetic head slider 5 is reduced, but the flying height may not be adjusted in time. Therefore, the control device 31 records the altitude information on the magnetic disk device 10 once every fixed time interval such as 1 minute. A typical rate at which the flying height of the current magnetic head 5 decreases with an increase in altitude (atmospheric pressure decrease) is 1.5 nanometers per an altitude of 3000 meters. The flying height difference of 05 nanometers is not a problem. A one minute time interval is sufficient, as it will generally take more than one minute for the vehicle to move up and down 100 meters. On the other hand, if recording is performed once per minute in a short time of several milliseconds, the influence on other operation performance such as map search and video / music playback is extremely limited.

More preferably, the altitude is constantly monitored. For example, when there is an altitude change that exceeds a certain threshold, such as 100 meters or more compared to when the system is started, altitude information can be obtained even if a certain time interval has not elapsed. Is recorded on the magnetic disk device 10.
Further, it is desirable to record the latest altitude information on the magnetic disk device 10 even if a certain time interval has not elapsed once before the system is stopped.

[Reading timing]
The timing at which the magnetic disk device 10 reads the altitude information is once when the system is started, once every certain time interval, or once when an error recovery operation is started. If the fixed time interval is, for example, 1 minute, the frequency is sufficient as described above.

  FIG. 7 shows a flowchart of altitude information recording timing and reading timing after the navigation system 30 and the magnetic disk device 10 described above are activated.

[Set to the safe side when reading altitude information]
Here, since there is no atmospheric pressure information when the system is started, that is, when the magnetic disk device 10 is also started, there arises a problem of how to use the flying height. When the magnetic disk device 10 reads various programs and data from the reserved area at the start-up, and also when reading altitude information recorded in itself, the magnetic disk device 10 has a maximum altitude with respect to the specifications of the navigation system 30. Even so, it is necessary to adjust the flying height of the magnetic head slider 5 higher so that the magnetic head slider 5 does not contact the magnetic disk 3. Desirably, the power applied to the heating element 5c is zero or substantially zero.

[How to record advanced information data]
When the magnetic disk device 10 receives a command to record at a predetermined logical address at the time of system development in order to record altitude information sent from the control device 31, the frequency of recording normal data is used. It is better to record at a lower frequency. This is because, as described above, when the data is read, if the flying height of the magnetic head slider 5 is adjusted to be high (such as zero applied power to the heating element), it may not be read well at the normal data recording frequency. However, the read error rate can be reduced at low frequencies.

  Alternatively, since the magnetic disk device 10 records the altitude information sent from the control device 31, when it receives a command to record at a predetermined logical address at the time of development of the system, it is given redundancy. It is good to record repeatedly. This is because, if there is redundancy, even if there is a reading error alone, an error in the final information read repeatedly can be prevented.

  It is assumed that the above-mentioned altitude information is overwritten and recorded only for the latest information. However, if some of the latest information, for example, about 100 times of information is recorded as a set, it may be useful for failure diagnosis.

[Details of flying height adjustment: power table correction]
After reading the altitude information, the magnetic disk device 10 corrects the power table shown in FIG. 5 if necessary. However, if there is no need for correction, for example, it does not need to be corrected, for example, it does not differ by more than a certain threshold compared to the previous altitude. Specifically, it is assumed that it is a step bearing (air bearing) of a magnetic head slider designed so as not to contact even at an altitude of, for example, 3000 meters defined as a specification. Further, it is assumed that the step bearing causes a decrease in flying height of 1.5 nanometers per an altitude of 3000 meters in the zone (radial position). If the altitude information obtained here is 0 meters above sea level, the energization amount to the heating device 5c is increased by 1.5 nanometers corresponding to an altitude difference of 3000 meters. If the obtained altitude information is 1500 meters above sea level, the energization amount to the heating device 5c is increased by an amount corresponding to half of 0.75 nanometers. If the obtained altitude information is 3000 meters, the energization amount does not increase. If the obtained altitude information exceeds the specification limit of 3000 meters and there is still room for reducing the energization amount, the energization amount should be further reduced.

  In addition to the method of correcting the power table on the memory 15 of the magnetic disk device 10, the microcomputer 14 appropriately determines the amount of current supplied to the heating device 5c when receiving an actual recording / reproducing command while keeping the power table as it is. The effect of the present invention can be obtained in the same way even when the correction is made according to the atmospheric pressure.

[Use storage area in non-volatile memory]
Next, another configuration example of the magnetic disk device will be described with reference to FIG. This magnetic disk device is a hybrid magnetic disk device 10 ′ that has both a storage area for magnetic recording on a magnetic disk and a storage area for storage in an attached nonvolatile semiconductor memory 16.

  The logical address at which altitude information is stored, which is predetermined when the system is developed, is a part of a storage area arranged on the nonvolatile semiconductor memory 16. In the magnetic disk device 10 described above, there is no information on the atmospheric pressure at the time of start-up, so there has been a problem that the flying height must be set to a safe side. However, in this hybrid type magnetic disk device 10 ', at the time of start-up, there is a problem. First, since altitude information is read from the nonvolatile semiconductor memory 16, it is not necessary to set the flying height of the magnetic head slider 5 to the safe side.

  The memory 15 existing from the conventional non-hybrid type magnetic disk device is also equipped with a nonvolatile semiconductor memory called EEPROM, and the basic part of the program (firmware) executed by the microcomputer 14 and the execution of the program The data required for is stored. However, data cannot be written by designating the EEPROM from the control device 31 of the navigation system as a host.

[Host with barometric pressure sensor]
The navigation system has been described above. However, the magnetic disk device is not limited to the navigation system, and other electronic devices in the vehicle such as a fuel injection control device or a portable electronic device such as a personal computer includes a pressure sensor. It is assumed that 10 or 10 'wants to obtain atmospheric pressure information from the host side without mounting an atmospheric pressure sensor inside itself. In that case, the host system records the atmospheric pressure information from the atmospheric pressure sensor at a specific logical address of the magnetic disk, once before the system stops, once every fixed time interval, or once when the atmospheric pressure changes by more than a certain threshold. To do. On the other hand, the magnetic disk device 10 or 10 'accesses the physical address corresponding to the logical address once at the time of start-up, once every fixed time interval, or once when entering the error recovery operation, and obtains altitude information or atmospheric pressure information. And adjust the flying height of the magnetic head slider. The information transferred from the host side to the magnetic disk device in this way may be atmospheric pressure information alone or a set with altitude information obtained from GPS or map information.

It is a block diagram showing the structural example of the navigation system which concerns on this invention. 1 is a block diagram illustrating a configuration example of a magnetic disk device according to the present invention. FIG. 2 is a partial configuration diagram of a magnetic disk device according to the present invention and a cross-sectional view of a magnetic head slider. It is sectional drawing which looked at the heating element part which is a part of FIG. 2 from the right side of FIG. It is a figure showing the electric power table which controls the heating element energization amount of the magnetic disc unit concerning the present invention. It is a figure which shows typically a mode that the logical address allocated to altitude information is converted into the physical address which exists in the user area of a magnetic disc unit. 7 is a flowchart showing altitude information recording timing and reading timing after the navigation system and the magnetic disk device are activated. It is a block diagram showing the other structural example of a magnetic disc apparatus.

Explanation of symbols

2 ... Spindle motor, 3 ... Magnetic disk medium, 4 ... Carriage assembly, 5 ... Magnetic head slider, 5a ... Recording element, 5b ... Reproducing element, 5c ... Heating element, 5d ... Substrate, 5e ... Insulating film, 5f ... Air Bearing surface, 5 g ... Air outflow end surface, 6 ... Flexible printed cable, 7 ... Preamplifier, 8 ... Voice coil motor, 9 ... Temperature sensor, 10 ... Magnetic disk device, 11 ... Read / write channel, 12 ... Motor driver, 13 ... Hard disk controller, 14 ... microcomputer, 15 ... memory, 16 ... nonvolatile semiconductor memory, 30 ... navigation system, 31 ... control device, 32 ... communication device, 33 ... position detection device, 34 ... display device, 35 ... input device.

Claims (19)

A navigation system comprising a control device, a position detection device, and a magnetic disk device,
The magnetic disk device includes a magnetic disk for holding map information, and a magnetic head slider having a flying height adjustment mechanism,
The control device acquires altitude information or atmospheric pressure information from position information obtained by the position detection device, and records it on the magnetic disk device,
A navigation system, wherein the magnetic disk device reads altitude information or atmospheric pressure information recorded on the magnetic disk device and controls a flying height adjustment mechanism of the magnetic head slider to adjust the flying height of the magnetic head slider. The navigation system according to claim 1,
The timing at which the control device records altitude information or atmospheric pressure information acquired from the position information on the magnetic disk device is once before the system is stopped, once every fixed time interval, or at a constant altitude or atmospheric pressure. Once when it changes more than the threshold,
The timing at which the magnetic disk device reads the altitude information or atmospheric pressure information recorded on itself and adjusts the flying height of the magnetic head slider is once at system startup, once every fixed time interval, or error A navigation system characterized by being once at the time of entering the recovery operation. The navigation system according to claim 1,
The control device issues a command to write altitude information or atmospheric pressure information acquired from the position detection device to a predetermined logical address at the time of system development, and the magnetic disk device corresponds to the predetermined logical address. The navigation system is characterized in that a physical address is accessed and the altitude information or barometric pressure information is written. The navigation system according to claim 1,
The navigation system characterized in that the position detection device includes a global positioning system (GPS), and the control device acquires altitude information from the global positioning system. The navigation system according to claim 1,
The position detection device includes a global positioning system (GPS), and the control device is configured to obtain current position information from horizontal position information acquired from the global positioning system and contour information included in map information read from the magnetic disk device. A navigation system characterized by determining the altitude of a position. The navigation system according to claim 1,
When the magnetic disk device reads altitude information or atmospheric pressure information recorded on the magnetic disk device, the magnetic head slider does not move even at the maximum altitude and the minimum atmospheric pressure with respect to the specifications of the navigation system. A navigation system, wherein a flying height of the magnetic head slider is adjusted so as not to contact the magnetic disk. The navigation system according to claim 3,
When the magnetic disk device receives a command to record at a predetermined logical address at the time of system development in order to record altitude information or atmospheric pressure information sent from the control device, normal data is stored. A navigation system characterized by recording at a frequency lower than the recording frequency. The navigation system according to claim 3,
When the magnetic disk device receives a command to record at a predetermined logical address at the time of system development in order to record altitude information or atmospheric pressure information sent from the control device, it has redundancy. A navigation system characterized by recording repeatedly. The navigation system according to claim 3,
The magnetic disk device is a hybrid magnetic disk device having both a storage area for magnetic recording on the magnetic disk and a storage area for storage in an attached nonvolatile semiconductor memory,
A navigation system characterized in that a logical address predetermined at the time of system development is a part of a storage area arranged on the nonvolatile semiconductor memory. The navigation system according to claim 1,
The navigation system according to claim 1, wherein the flying height adjustment mechanism is a heating element installed in the vicinity of the recording / reproducing element of the magnetic head. The navigation system according to claim 10, wherein
A navigation system characterized in that when the magnetic disk device reads altitude information or atmospheric pressure information recorded on itself, the power applied to the heating element is substantially zero. A magnetic disk and a magnetic head slider having a flying height adjustment mechanism;
Record altitude information or barometric pressure information received from the host device on the magnetic disk,
A magnetic disk device, comprising: reading altitude information or atmospheric pressure information recorded on the magnetic disk; and controlling a flying height adjustment mechanism of the magnetic head slider to adjust the flying height of the magnetic head slider.   13. The magnetic disk apparatus according to claim 12, wherein the altitude information or the atmospheric pressure information recorded on the magnetic disk is read to adjust the flying height of the magnetic head slider once at startup or at regular time intervals. A magnetic disk device characterized in that it is once or at the time of entering an error recovery operation. The magnetic disk device according to claim 12, wherein
When receiving a command for writing altitude information or barometric pressure information to a logical address designated by a host device, a magnetic address corresponding to the logical address is accessed and the altitude information or barometric pressure information is written. Disk unit. The magnetic disk device according to claim 12, wherein
When reading altitude information or barometric pressure information recorded on the magnetic disk, the magnetic head slider can move the magnetic disk even if the altitude is the maximum altitude and the minimum barometric pressure with respect to the specifications of the magnetic disk device. The magnetic disk apparatus is characterized in that the flying height of the magnetic head slider is adjusted so as not to come into contact with the magnetic head. 15. The magnetic disk device according to claim 14, wherein
A magnetic disk device, wherein a command for writing altitude information or barometric pressure information to a logical address designated by a host device is received at a frequency lower than a frequency for recording normal data. 15. The magnetic disk device according to claim 14, wherein
A magnetic disk device characterized in that when a command for writing altitude information or barometric pressure information to a logical address designated by a host device is received, recording is repeated with redundancy. 15. The magnetic disk device according to claim 14, wherein
The magnetic disk device further comprising a non-volatile semiconductor memory, wherein the logical address is a part of a storage area arranged on the non-volatile semiconductor memory. The magnetic disk device according to claim 12, wherein
The magnetic disk apparatus, wherein the flying height adjustment mechanism is a heating element installed in the vicinity of a recording / reproducing element of the magnetic head.

Images