JP2007200506A - Electromagnetic linear actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively form an outer yoke and to increase the thrust of an electromagnetic linear actuator. <P>SOLUTION: In the electromagnetic linear actuator (50) comprising a fixed part and a movable part (60) linearly moving along the axial direction to the fixed part by an electromagnetic force, the fixed part includes a magnetic circuit (70) comprising yoke members (71, 74) and a magnet (72) and the movable part (60) includes a coil (61). The yoke member is constituted of the outer yoke (71) and an inner yoke (74). The outer yoke (71) has a rectangularly cylindrical shape having a bottom formed by assembling a flat plate formed by press punching. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a recording / reproducing apparatus represented by DLT (Digital Linear Tape) and LTO (Linear Tape Open), and more particularly, to an electromagnetic linear actuator that can be used as a head feed mechanism of a magnetic head actuator assembly used therefor. .

  This type of recording / reproducing apparatus has been developed for computer system backup, and various recording / reproducing apparatuses have been proposed. For example, a recording / reproducing apparatus that functions as a DLT is disclosed in Patent Document 1, for example.

  A recording / reproducing apparatus (hereinafter simply referred to as “drive device”, “tape drive”, or “drive”) receives a tape cartridge (hereinafter also simply referred to as “cartridge”) having a single reel (supply reel). It has a built-in take-up reel. When the tape cartridge is mounted on the drive device, the magnetic tape is pulled out of the tape cartridge and taken up by a take-up reel via a head guide assembly (HGA). The head guide assembly is for guiding a magnetic tape (hereinafter also simply referred to as “tape”) drawn from the tape cartridge to the magnetic head. The magnetic head exchanges information between the magnetic tape and the magnetic head. The head guide assembly is generally composed of an aluminum plate having a boomerang shape and six large guide rollers each using a bearing.

  The head guide assembly is also called a tape guide assembly, which is disclosed in, for example, Patent Document 2. An example of the guide roller is disclosed in Patent Document 3.

  In general, a magnetic tape drive includes a substantially rectangular parallelepiped housing having a common base, as described in, for example, Japanese Patent Application Laid-Open No. H10-228707. The base has first and second spindle motors (reel motors). The first spindle motor has a spool (take-up reel) permanently attached to the base, and the spool is sized to receive a magnetic tape flowing at a relatively high speed. The second spindle motor (reel motor) is adapted to receive a removable tape cartridge. The removable tape cartridge is manually or automatically inserted into the drive through a slot formed in the drive housing. When the tape cartridge is inserted into the slot, the cartridge is engaged with a second spindle motor (reel motor). Before rotating the first and second spindle motors (reel motors), the tape cartridge is connected to a permanently mounted spool (take-up reel) by a mechanical buckling mechanism. Many rollers (guide rollers) positioned between the tape cartridge and the permanent spool guide the magnetic tape as it moves back and forth at a relatively high speed between the tape cartridge and the permanently mounted spool. To do.

  The digital linear tape drive having such a configuration requires a device for the take-up reel to pull the tape from the supply reel. Such a pulling device is disclosed in Patent Document 5, for example. According to Patent Document 5, a take-up reel is connected to a take-up leader means (first tape leader), and a supply tape leader means (second tape leader) is fixed to a tape on the supply reel. The first tape leader has a mushroom-like tab at one end thereof. The second tape leader has a locking hole. The tab is engaged with the locking hole.

  Furthermore, a mechanism for joining the first tape leader to the second tape leader is also required. Such a joining mechanism is disclosed in Patent Document 6, for example.

  Further, in Patent Document 7, the end of the leader tape (second tape leader) is locked to the tape end hooking portion of the tape cartridge without requiring an ear piece protruding to the side of the leader tape. The structure of the locking portion of the leader tape that can be used is disclosed.

  Patent Document 8 discloses a lock system for preventing the take-up reel of the tape drive from rotating when the tape cartridge is not inserted into the drive.

  The magnetic tape drive further includes a magnetic head actuator assembly, which is positioned between the take-up spool and the tape cartridge on a tape path defined by a plurality of rollers. In operation, the magnetic tape flows back and forth between the take-up spool and the tape cartridge and closely approaches the magnetic head actuator assembly while flowing over a defined tape path. An example of such a magnetic head actuator assembly is disclosed in Patent Document 4 above.

  On the other hand, an example of a tape cartridge mounted on a digital linear tape drive is disclosed in Patent Document 9.

  Patent Document 10 discloses a “tape drive” in which a tape leader is pushed from a tape cartridge to a take-up reel without using a buckling mechanism or a winding leader.

  The magnetic head actuator assembly includes a tape head assembly (hereinafter also simply referred to as “head assembly”) and a head feed mechanism. The head assembly includes a pair of flexible printed circuits (a head) that extends in the vertical direction, a head holder that holds the magnetic head, and a magnetic head that is electrically connected to an external circuit. FPC).

  On the other hand, the head feed mechanism is for moving the head assembly up and down while holding the head assembly. As disclosed in Patent Document 4, the conventional head feed mechanism includes a threaded lead screw (threaded shaft) and mechanically moves the head assembly up and down by rotating the lead screw. (Linear motion). In other words, a “mechanical linear actuator” is employed as a conventional head feed mechanism.

  In such a mechanical linear actuator, the position control of the head assembly is generally performed by open loop control. In the DLT, the storage capacity is increased. In “DLT1” which is the first generation DLT, the normal storage capacity is 40 GB, and the storage capacity when compressed is 80 GB. In addition, in “DLT2” that is the second generation DLT, the normal storage capacity is 80 Gbytes, and the compressed storage capacity is 160 Gbytes. In addition, in “DLT3” which is the third generation DLT, the normal storage capacity is about 150 Gbytes, and the compressed storage capacity is about 300 Gbytes. With a DLT having such a storage capacity, a mechanical linear actuator can sufficiently cope.

  However, “DLT4”, which is the next generation (fourth generation) DLT, has a normal storage capacity of 300 Gbytes, a compressed storage capacity of 600 Gbytes, and a large capacity (high storage density). For this reason, when the above-described mechanical linear actuator is used as a linear actuator for DLT having a large storage density, it is difficult to accurately control the head assembly to a desired position.

  On the other hand, in order to solve such problems in the mechanical linear actuator, an “electromagnetic linear actuator” that moves the head assembly up and down (linearly) electromagnetically is adopted as the head feed mechanism to control the position of the head assembly. Has been proposed for performing closed loop (feedback) control (see, for example, Patent Document 11). Since the electromagnetic linear actuator employs a feedback control method as a control method, the head assembly can always be accurately controlled to a desired position even if the magnetic tape fluctuates up and down during traveling. .

  Such an electromagnetic linear actuator generally includes a fixed portion, a movable portion that holds a head assembly (an object to be lifted) up and down along the vertical direction with respect to the fixed portion, and a movable portion of the movable portion. It has a guide for restraining (regulating) movement other than the (lifting / lowering) direction, and a base for attaching this guide.

  Here, the electromagnetic linear actuator can be divided into two types. The first type is a “movable magnet type” electromagnetic linear actuator, which includes a magnet in the movable part and a coil in the fixed part. The second type is a “movable coil type” electromagnetic linear actuator, which includes a permanent magnet and a yoke member in a fixed portion, and a coil in a movable portion.

  As described above, the electromagnetic linear actuator is suitable as a DLT actuator having a large storage capacity. However, as described above, the control method (control system) is completely different between the mechanical linear actuator and the electromagnetic linear actuator. For this reason, when using this electromagnetic linear actuator as a DLT linear actuator of a lower model (namely, the first generation or the second generation), the control system for the mechanical linear actuator that has been incorporated up to that point is used at all. Therefore, a new control system suitable for the electromagnetic linear actuator must be incorporated. That is, it is necessary to change the design of the lower-level model DLT.

  In order to solve such problems, as a fourth generation (upper model) DLT linear actuator (head feed mechanism) compatible with lower model DLTs, not only mechanical linear actuators, but also electromagnetic A “composite linear actuator” that can also operate as a linear actuator has been proposed. That is, the composite linear actuator is a combination of a mechanical linear actuator and an electromagnetic linear actuator. In such a composite type linear actuator, a mechanical linear actuator is used for rough position control (open loop control) of the head assembly, and an electromagnetic linear actuator is used for precise position control (closed loop control). It can be carried out.

  More specifically, the composite linear actuator is a mechanical linear actuator including a lead screw having a rotation center shaft extending in the axial direction and a main movable portion that linearly moves in the axial direction by the rotation of the lead screw. Including. The main movable portion operates as an electromagnetic linear actuator including a sub-fixed portion and a sub-movable portion that linearly moves in the axial direction with respect to the sub-fixed portion by electromagnetic force. The electromagnetic linear actuator is constituted by a voice coil motor (VCM). Therefore, the sub-fixed part is called a VCM fixed part, and the sub-movable part is called a VCM movable part. The sub-fixed portion includes a magnetic circuit including a yoke member and a permanent magnet, and the sub-movable portion includes an air-core coil. The air-core coil is fixed to a head holder (attachment portion) that holds the magnetic head. Such a composite linear actuator is disclosed in, for example, Patent Document 12 and Patent Document 13.

  The present invention relates to a composite linear actuator, and more particularly to an electromagnetic linear actuator used in a composite linear actuator. In this electromagnetic linear actuator, as described above, the sub-fixed portion includes a magnetic circuit including a yoke member and a permanent magnet. The yoke member includes a yoke base, a center yoke provided at the center of the yoke base, and an upper yoke provided at the upper part of the yoke base. The permanent magnet is composed of a pair of plate magnets housed in a yoke base. The yoke base and the upper yoke are collectively called an outer yoke.

  The sub movable portion is supported by a sub fixing portion including a magnetic circuit through a support means so as to be movable. As such a support means, an upper leaf spring and a lower leaf spring are used which fix the sub movable portion to the sub fixed portion so as to be linearly movable.

  Note that a recording / reproducing apparatus serving as an LTO is disclosed in Patent Document 14. In LTO, a composite linear actuator having the same structure as that used in DLT is used. In LTO, a servo track is recorded in advance on the magnetic recording surface side of the magnetic tape in parallel with the data track, and the magnetic head reads the servo track to thereby position the magnetic head on the magnetic tape. Control to the correct position.

  In the composite linear actuator described above, the mechanical linear actuator may be referred to as a head feed mechanism, and the electromagnetic linear actuator may be referred to as a voice coil motor. That is, the head feed mechanism is for performing coarse adjustment of the position of the magnetic head by moving the head assembly up and down, and the voice coil motor is for performing fine adjustment of the position of the magnetic head.

  Further, as a VCM type electromagnetic linear actuator, a fixed portion comprising a cylindrical outer yoke using a magnetic material, a magnet fixed to the inner peripheral surface of the outer yoke, and a cylindrical inner yoke using a magnetic material And a movable part having a coil serving as a thrust generating part is known (see, for example, Patent Document 15).

JP-A-9-198639 Japanese National Patent Publication No. 9-500753 JP 2000-100025 A JP 2000-501547 A Japanese Patent Publication No. 3-7595 Japanese Patent Publication No. 6-39027 JP 2000-100116 A Japanese Patent Laid-Open No. 11-86381 JP 2000-149491 A Japanese Patent Laid-Open No. 11-316991 JP 2002-233127 A JP 2004-86973 A JP 2004-87654 A JP-T-2002-530794 Japanese Examined Patent Publication No. 1-2668

  As described above, a recording / reproducing apparatus (tape drive) having a large storage capacity includes an electromagnetic linear actuator for fine adjustment using a VCM.

  In the conventional VCM type electromagnetic linear actuator as disclosed in Patent Document 15, the outer yoke of the fixed portion has a cylindrical shape. Such a cylindrical outer yoke is manufactured using machining such as cutting or deep drawing. As a result, the cost of the conventional outer yoke structure is higher than that of the sheet metal part of the press. Moreover, since the outer yoke has a cylindrical shape, a cylindrical or arc-shaped magnet must be used as a magnet fixed to the inner peripheral surface thereof. Such a cylindrical or arc-shaped magnet is more expensive than a flat magnet.

  Furthermore, when the outer yoke is manufactured by deep drawing, it is difficult to increase the plate thickness. And the thinner the plate thickness, the more easily the magnetic saturation. On the other hand, the thrust in the VCM electromagnetic linear actuator increases as the magnetic flux passing through the coil increases. Therefore, in the outer yoke with a thin plate thickness, the magnetic flux leaks from a magnetically saturated location. As a result, since the magnetic flux passing through the coil is reduced, the thrust of the VCM electromagnetic linear actuator is reduced. In addition, since the leakage magnetic flux increases, it causes deterioration of the characteristics of the VCM electromagnetic linear actuator.

  An object of the present invention is to provide an electromagnetic linear actuator having a magnetic circuit including an inexpensive outer yoke.

  Another object of the present invention is to provide an electromagnetic linear actuator that can increase thrust.

  Other objects of the invention will become apparent as the description proceeds.

  According to the present invention, an electromagnetic linear system comprising a fixed portion (172, 70; 70A; 70B) and a movable portion (60) that moves linearly along the axial direction (Z) with respect to the fixed portion by electromagnetic force. An actuator (50; 50A; 50B), wherein the fixed part has a magnetic circuit (70; 70A; 70B) comprising a yoke member (71; 71A; 71B, 74) and a magnet (72), and is movable. The part includes a coil (61), and the yoke member is composed of an outer yoke (71; 71A; 71B) and an inner yoke (74). In the electromagnetic linear actuator, the outer yoke (71; 71A; 71B) Has a bottomed N-square tube shape (N is an integer of 4 or more) constructed by assembling a press-punched flat plate. Near actuator can be obtained. The N may be 4, for example.

  According to the first aspect of the present invention, the axial direction is a vertical direction (Z) of the electromagnetic linear actuator, and the outer yoke (71) includes a square plate-shaped bottom yoke (711), The bottom yoke is composed of four side wall yokes (712) extending upward from the edges of the four sides, and the inner yoke is composed of a cylindrical inner yoke (74) standing from the center of the bottom base. The magnet (72) is composed of four plate-shaped magnet pieces (712) attached to the inner walls of the four side wall yokes, and the coil (61) is composed of the four plate-shaped magnets. An electromagnetic linear actuator (50) disposed in a gap between the piece and the cylindrical inner yoke is obtained.

  According to the second aspect of the present invention, the axial direction is the vertical direction (Z) of the electromagnetic linear actuator, and the outer yoke (71A) includes a square plate-shaped bottom yoke (711A), The bottom yoke is composed of two L-shaped side wall yokes (712A) bent in an L shape extending upward from the four edges of the bottom yoke, and the inner yoke is erected from the center of the bottom base. The magnet (72) is composed of four plate-shaped magnet pieces (721) attached to the inner walls of the two L-shaped side wall yokes, and is composed of a cylindrical inner yoke (74). (61) provides the electromagnetic linear actuator (50A) arranged in the gap between the four flat-plate-shaped magnet pieces and the cylindrical inner yoke.

  According to the third aspect of the present invention, the axial direction is the vertical direction (Z) of the electromagnetic linear actuator, and the outer yoke (71B) is formed into a box shape by bending one press plate. The outer yoke has a square plate-shaped bottom yoke portion (711B) and four rectangular plate-shaped side wall yoke portions (upwardly extending from the edges of the four sides of the bottom yoke portion). 712B), the inner yoke is composed of a cylindrical inner yoke (74) standing from the center of the bottom base, and the magnet (72) is attached to the inner walls of the four side wall yoke portions. The four plate-shaped magnet pieces (721) are arranged, and the coil (61) is disposed in a gap between the four plate-shaped magnet pieces and the cylindrical inner yoke. Is an electromagnetic linear actuator (50B) is obtained.

  The reference numerals in the parentheses are given for ease of understanding, and are merely examples, and of course are not limited thereto.

  In the present invention, since the outer yoke has a bottomed N-square cylindrical shape formed by assembling a press-punched flat plate, the outer yoke can be manufactured at low cost. Further, since the thickness of the outer yoke can be increased, the thrust of the electromagnetic linear actuator can be increased.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, a tape drive 10 as a recording / reproducing apparatus to which the present invention is applied will be described with reference to FIGS. FIG. 1 is a perspective view of the tape drive 10 with the upper lid removed as viewed from the upper surface side. FIG. 2 is a perspective view of the tape drive 10 shown in FIG.

  The tape drive 10 is for receiving the cartridge 20 and has a take-up reel 11 built therein. The take-up reel 11 is also called a spool. The tape drive 10 includes a substantially rectangular parallelepiped housing (chassis) 12 having a common base. The base has first and second spindle motors (reel motors). The first spindle motor has a spool (winding reel) 11 permanently attached to the base of the housing 12, and the spool 11 receives a magnetic tape (not shown) flowing at a relatively high speed. The size is fixed. A second spindle motor (reel motor) 13 is adapted to receive a removable cartridge 20. The removable cartridge 20 is inserted into the tape drive 10 through the cartridge holder 14 formed in the housing 12 of the tape drive 10 along the insertion direction indicated by the arrow A.

  When the cartridge 20 is inserted into the cartridge holder 14, the cartridge 20 is automatically loaded after being engaged with the cartridge holding mechanism 15, and the cartridge 20 is engaged with the second spindle motor (supply reel motor) 13. Before rotating the first and second spindle motors (reel motors), the cartridge 20 is permanently attached to the cartridge 20 by a grabber (not shown) and a leader pin (not shown). 11 is connected. Many rollers (guide rollers) 16 positioned between the cartridge 20 and the permanent spool 11 are used when the magnetic tape moves back and forth between the cartridge 20 and the permanently attached spool 11 at a relatively high speed. Guide it.

  The tape drive 10 further includes a head actuator 17 having a magnetic head (hereinafter also simply referred to as a head) 17a. The head actuator 17 is positioned between the take-up reel 11 and the cartridge 20 on a tape transfer path (not shown) defined by the plurality of rollers 16. During operation, the magnetic tape flows back and forth between the take-up reel 11 and the cartridge 20 and is in close proximity to the head actuator 17 while flowing on the defined tape transport path.

  The tape drive 10 has a first switch SW <b> 1 provided on the main surface of the chassis 12 on the front right side. The first switch SW1 is for detecting a position at which automatic loading is started after the cartridge 20 is inserted into the cartridge holder 14. The first switch SW1 is composed of a photo interrupter. The cartridge holder 14 has a first shielding plate (not shown) for shielding the first switch SW1.

  The tape drive 10 includes a mode motor 30 on the main surface of the chassis 12. The mode motor 30 is connected to a mode gear 32 on the back side of the chassis 12 through seven reduction gears 31 (only three reduction gears are shown in FIG. 1). A sensor substrate 34 is provided on the back side of the chassis 12 so as to face the mode gear 32. Anyway, the mode gear 32 is driven by the mode motor 30.

  As shown in FIG. 1, the tape drive 10 includes a second switch SW <b> 2 for detecting that the cartridge 20 is correctly received (inserted) in the cartridge holder 14. The second switch SW2 is also a photo interrupter. The tape drive 10 includes a cartridge holder locking mechanism 36 for locking the cartridge holder 14. The cartridge holder locking mechanism 36 is for preventing the cartridge holder 14 from moving in the insertion direction A unless the cartridge 20 is correctly inserted into the cartridge holder 14. Therefore, when the cartridge 20 is correctly inserted into the cartridge holder 14, the cartridge holder 14 is unlocked by the cartridge holder locking mechanism 36, and the cartridge holder 14 can move in the insertion direction A. The cartridge holder locking mechanism 36 includes a second shielding plate 361 for shielding the second switch SW2.

  As shown in FIG. 2, the tape drive 10 includes a gear cam 38 that meshes with the mode gear 32. The gear cam 38 is also called a cam gear. The gear cam 38 has a cam groove which will be described later.

  As shown in FIG. 1, the tape drive 10 includes an arm housing 40 that is rotatably provided around a rotation shaft 401 on the main surface of the chassis 12. The arm housing 40 has a horizontal arm 402 extending in the horizontal direction and a vertical arm 403 extending in the vertical direction. An engaging pin 402 a is provided at the tip of the horizontal arm 402, and an engaging pin 403 a is provided at the lower end of the vertical arm 403. The engagement pin 403a engages with the cam groove of the gear cam 38.

  The tape drive 10 also includes a cam slider 42 that is formed integrally with the cartridge holder 14. The cam slider 42 has a slider opening 421 extending in a direction orthogonal to the insertion direction A. The engagement pin 402 a of the horizontal arm 402 of the arm housing 40 described above is inserted into the slider opening 421.

  Therefore, the cartridge holder 14 that holds the cartridge 20 is connected to the mode gear 32 via the cam slider 42, the arm housing 40, and the gear cam 38. The combination of the mode motor 30, the mode gear 32, and the cartridge holder 14 serves as an ejection mechanism that abuts the cartridge 20 accommodated in the tape drive 10 against the cartridge 20 and ejects it out of the tape drive 10.

  When the cartridge 20 is inserted into the cartridge holder 14, the cartridge 20 is held by the cartridge holder 14 via the cartridge holding mechanism 15. When the cartridge 20 is completely inserted into the cartridge holder 14, the cartridge 20 is engaged by the cartridge holding mechanism 15.

  The cartridge holder 14 is movable only along the insertion direction A by guide means described later. The cartridge holding mechanism 15 is movable along the L-shaped path by the guide means.

  According to such a configuration, when the cartridge holder 14 is moved in the insertion direction A by manually inserting the cartridge 20 into the cartridge holder 14, the arm housing 40 rotates clockwise around the rotation shaft 401. Rotate. As a result, since the gear cam 38 rotates around its central axis, the mode gear 32 engaged with the gear cam 38 also rotates around its central axis. This is a manual loading operation.

  On the other hand, as described above, the mode gear 32 and the mode motor 30 are connected via the seven reduction gears 31. Therefore, when the mode motor 30 is rotated in a predetermined direction, the mode gear 32 rotates in a predetermined direction. As a result, the gear cam 38 meshed with the mode gear 32 also rotates in a predetermined direction. As a result, the arm housing 40 having the engagement pin 403a engaged with the cam groove of the gear cam 38 rotates around the rotation shaft 401 in the clockwise direction. Accordingly, when the cartridge holder 14 moves in the insertion direction A, the cartridge 20 engaged with the cartridge holding mechanism 15 also moves in the insertion direction A. This is an automatic loading operation.

  Switching between the manual loading operation and the automatic loading operation is performed by turning on / off the first switch SW1.

  Next, with reference to FIG. 1 and FIG. 2, the guide means for guiding the cartridge holder 14 and the cartridge holding mechanism 15 will be described.

  The tape drive 10 includes a first guide wall 46 and a second guide wall 47 extending in the insertion direction A as guide means. Since the first guide wall 46 is arranged on the right side in the insertion direction A, it is called a right guide wall. Since the second guide wall 47 is arranged on the left side in the insertion direction A, it is called a left guide wall.

  As shown in FIG. 1, the first guide wall (right side guide wall) 46 has a first guide groove hole 461 for guiding the cartridge holder 14 and a second guide wall for guiding the cartridge holding mechanism 15. And a guide groove 462. The first guide groove 461 extends along the insertion direction A. On the other hand, the second guide groove hole 462 has an L-shape that extends along the insertion direction A and extends in a direction perpendicular to the insertion direction A and toward the chassis 12. A first guide pin 141 protruding from the right side wall of the cartridge holder 14 to the side is engaged with the first guide groove hole 461. A second guide pin 152 protruding from the right side wall of the cartridge holding mechanism 15 to the side is engaged with the second guide groove hole 462.

  As shown in FIG. 2, the second guide wall (left guide wall) 47 includes a pair of third guide grooves 473 for guiding the cartridge holder 14 and a pair for guiding the cartridge holding mechanism 15. 4th guide groove hole 474. The pair of third guide groove holes 473 extend along the insertion direction A. On the other hand, the pair of fourth guide groove holes 474 has an L shape extending in the insertion direction A and extending in a direction perpendicular to the insertion direction A toward the chassis 12. A pair of third guide pins 143 projecting sideways from the left side wall of the cartridge holder 14 are engaged with the pair of third guide grooves 473, respectively. A pair of fourth guide pins 154 projecting sideways from the left side wall of the cartridge holding mechanism 15 are engaged with the pair of fourth guide groove holes 474, respectively.

  Next, the head actuator 17 provided with the electromagnetic linear actuator 50 according to the first embodiment of the present invention will be described with reference to FIGS. 3 and 4 in addition to FIG. The illustrated head actuator 17 is a composite linear actuator. As described above, the composite linear actuator 17 is a combination of the electromagnetic linear actuator 50 and the mechanical linear actuator.

  FIG. 3 is a perspective view showing the external appearance of the electromagnetic linear actuator 50 in the composite linear actuator, and FIG. 4 is an exploded perspective view of the electromagnetic linear actuator 50.

  As shown in FIG. 1, the head actuator 17 includes a threaded lead screw (threaded shaft) 171 having a rotation center axis extending in the vertical direction (axial direction) as a rotating part, and a lead as a linear moving part. A head lift body 172 that moves up and down along the rotation center axis as the screw 171 rotates is provided. The lead screw 171 has a lead screw gear (not shown) that rotates the lead screw 171 around the rotation center axis by another driving means (for example, a stepping motor) on the lower end side thereof. An electromagnetic linear actuator 50 described later is attached to the head lift body 172. The head lift body 172 and the magnetic circuit 70 constitute a sub-fixing portion of the electromagnetic linear actuator 50.

  The composite linear actuator 17 includes a mechanical linear actuator. The mechanical linear actuator includes a main movable part. The main movable portion includes the head lift body 172 and the electromagnetic linear actuator 50. Anyway, the combination of the lead screw 171 and the main movable part constitutes a mechanical linear actuator. Since the detailed structure of the main movable part of the mechanical linear actuator (sub-fixing part of the electromagnetic linear actuator) is not directly related to the gist of the present invention, illustration and description thereof are omitted.

  The illustrated electromagnetic linear actuator 50 is for moving the magnetic head 17a as the object to be lifted up and down along the vertical direction Z. The magnetic head 17a extends in the vertical direction (vertical direction) Z. The magnetic head 17a is held by a head holding plate (not shown). A head assembly is constituted by the magnetic head 17a and the head holding plate. The head holding plate is attached to a sub movable portion 60 described later.

  The magnetic head 17a is electrically connected to an external circuit (not shown) through a flexible printed circuit (FPC) (not shown). An MR (magnetro-resistive) head is used as the magnetic head 17a. The MR head is a device that is very sensitive to static electricity and weak in static electricity resistance. Therefore, care must be taken when handling the MR head.

  The electromagnetic linear actuator 50 will be described with reference to FIGS. 3 and 4. As shown in FIGS. 3 and 4, coordinate axes orthogonal to each other are represented by an X axis, a Y axis, and a Z axis. Here, the X-axis direction is the left-right direction, the Y-axis direction is the front-rear direction, and the Z-axis direction is the up-down direction (axial direction, vertical direction).

  The electromagnetic linear actuator 50 includes a sub-fixed portion (172, 70), a sub-movable portion 60 that holds the head assembly up and down along the vertical direction Z with respect to the sub-fixed portion (172, 70), A shaft support mechanism (not shown) that supports the sub movable part 60 so as to be linearly movable with respect to the fixed part 70 is provided. The sub-fixing part (172, 70) is composed of the head lift body 172 and the magnetic circuit 70 as described above.

  The magnetic circuit 70 includes a bottomed rectangular cylindrical outer yoke 71, a magnet 72 fixed to the inner peripheral surface of the outer yoke 71, and a cylindrical inner yoke (center yoke) 74.

  The illustrated outer yoke 71 has a bottomed rectangular tube shape formed by press punching. More specifically, the outer yoke 71 includes a square plate-shaped bottom yoke 711 and four rectangular plate-shaped side wall yokes 712 extending upward from the edges of the four sides of the bottom yoke 711. On the other hand, the magnet 72 includes four flat magnet pieces 721 attached to the inner walls of the four side wall yokes 712 respectively. The inner surface of each magnet piece 721 has the same polarity. That is, for example, if the outer surface of each magnet piece 721 is an N pole, the inner surface is an S pole. Concentric with the outer yoke 71, a cylindrical inner yoke (center yoke) 74 is erected from the center of the bottom yoke 711.

  In the illustrated outer yoke 71, the bottom yoke 711 is made of a stamped steel plate, and each of the four side wall yokes 712 is also made of a stamped steel plate. The bottom yoke 711 and the four side wall yokes 712 are bonded to each other in a box shape using an adhesive such as a UV adhesive to form an outer yoke 71 as shown in FIG. The four magnet pieces 721 are fixed to the inner walls of the corresponding four side wall yokes 712 by bonding.

  On the other hand, the sub movable portion 60 includes a coil 61 wound around the axial direction Z, and a coil support portion 62 (FIG. 1) that supports the coil 61 at its upper end. The coil 61 is disposed in the gap between the magnet 72 and the cylindrical inner yoke 74. Thrust force acts on the coil 61 in the longitudinal direction (axial direction) Z according to Fleming's left-hand rule by passing an electric current therethrough.

  In the electromagnetic linear actuator 50 having the above-described structure, the outer yoke 71 can be configured to be inexpensive. The reason is that the conventional outer yoke is manufactured by high-cost processing such as cutting and deep drawing, but the outer yoke 71 according to the present embodiment is manufactured by inexpensive press punching processing, thereby reducing processing costs. Because it can be done. In the present embodiment, since the four flat magnet pieces 721 are used as the magnet 72, the magnet 72 can also be manufactured at low cost.

  Further, since the outer yoke 71 is manufactured by press punching, the thickness of the outer yoke 71 can be increased as compared with the case of manufacturing by deep drawing like a conventional outer yoke. Thus, since the magnetic saturation can be suppressed by increasing the thickness of the outer yoke 71, the leakage magnetic flux can be suppressed and the magnetic flux passing through the coil 61 can be increased. As a result, the thrust of the electromagnetic linear actuator 50 can be increased.

  The bottom yoke 711 has a yoke through hole 711a through which a shaft (not shown) of a shaft support mechanism (not shown) passes. The inner yoke 74 has an insertion hole 74a for inserting the shaft of the shaft support mechanism. Although not shown, the shaft support mechanism is for supporting the sub movable portion 60 so as to be linearly movable along the vertical direction Z with respect to the sub fixed portion. The shaft support mechanism extends in the axial direction Z, passes through the insertion hole 74a of the cylindrical inner yoke 74 and the yoke through hole of the bottom yoke 711, and the bottom yoke of the outer yoke 71 fitted to this shaft. 711 and a bearing fixed by caulking.

  On the other hand, the sub movable portion 60 includes a coil 61, a coil support portion 62 (FIG. 1) that supports the coil 61 at its upper end, and a head holding that holds the head 17a via a head holding plate (not shown). Part 63 (FIG. 1). The head holding plate is joined to the head holding portion 63. The head holding part 63 is provided in front of the outer yoke 71.

  Although not shown in the drawings, the coil support portion 62 is an annular coil holding portion for holding the coil 61, a bridge portion extending in the front-rear direction Y inside the coil holding portion, and a front portion extending from the coil holding portion. And a first arm portion coupled to the upper end of the head holding portion 63. The bridge portion has a first through hole for allowing the upper end portion of the shaft to pass through at the center thereof. The head holding portion 63 has a second arm portion extending rearward from the lower end thereof. A second through hole for allowing the lower end portion of the shaft to pass through is formed at the distal end portion of the second arm portion.

  Male screws (not shown) are cut at the upper and lower ends of the shaft. The upper end portion of the shaft passes through the first through hole of the bridge portion of the coil support portion 62 and is screwed with the first nut 83 (FIG. 1), whereby the upper end portion of the shaft is fixed to the coil support portion 62. Is done. On the other hand, the lower end portion of the shaft passes through the second through hole of the second arm portion of the head holding portion 63 and the second nut is screwed, whereby the lower end portion of the shaft is attached to the head holding portion 73. It is done.

  Thus, the sub movable part 60 is pivotally supported by the bearing through the shaft fixed to the sub movable part 60.

  An electromagnetic linear actuator 50A according to a second embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a perspective view showing the external appearance of the electromagnetic linear actuator 50A, and FIG. 6 is an exploded perspective view of the electromagnetic linear actuator 50A. The illustrated electromagnetic linear actuator 50A has the same configuration as that of the electromagnetic linear actuator 50 illustrated in FIGS. 3 and 4 except that the configuration of the magnetic circuit is changed as will be described later, and operates. To do. Therefore, the reference numeral 70A is attached to the magnetic circuit. Components having the same functions as those shown in FIGS. 3 and 4 are denoted by the same reference numerals, and only different points will be described below.

  The magnetic circuit 70A has the same configuration as that of the magnetic circuit 70 shown in FIGS. 3 and 4 except that the configuration of the outer yoke is changed as will be described later. Accordingly, reference numeral 71A is attached to the outer yoke.

  The illustrated outer yoke 71A is composed of a square plate-shaped bottom yoke 711A and two L-shaped side wall yokes 712A bent into an L shape.

  That is, in the outer yoke 71 shown in FIGS. 3 and 4, only the parts 711 and 712 made of press-punched flat plates are used, but in the outer yoke 71A shown in FIGS. In addition to the press part 711A, a press sheet metal part 712A including bending is also used.

  Even in the electromagnetic linear actuator 50A having such a configuration, the outer yoke 71A can be configured to be inexpensive. The reason is that the conventional outer yoke is manufactured by high-cost processing such as cutting and deep drawing, but the outer yoke 71A according to the present embodiment is manufactured by inexpensive press punching or bending processing. This is because costs can be reduced. Also in the present embodiment, since the four flat magnet pieces 721 are used as the magnet 72, the magnet 72 can also be manufactured at low cost.

  Further, since the outer yoke 71A is manufactured by press punching and bending, the thickness of the outer yoke 71A can be made thicker than when manufactured by deep drawing like a conventional outer yoke. Thus, since the magnetic saturation can be suppressed by increasing the thickness of the outer yoke 71A, the leakage magnetic flux can be suppressed and the magnetic flux passing through the coil 61 can be increased. As a result, the thrust of the electromagnetic linear actuator 50A can be increased.

  Furthermore, in the electromagnetic linear actuator 50A according to the second embodiment of the present invention, the outer yoke 71A uses the press sheet metal parts 711A and 712A including the press punching and / or bending process. Compared with the electromagnetic linear actuator 50 according to the first embodiment, there are also advantages that the number of parts can be reduced and the number of bonding steps can be reduced.

  With reference to FIG.7 and FIG.8, the electromagnetic linear actuator 50B which concerns on the 3rd Embodiment of this invention is demonstrated. FIG. 7 is a perspective view of the electromagnetic senior actuator 50B, and FIG. 8 is an exploded perspective view of the electromagnetic linear actuator 50B. The illustrated electromagnetic linear actuator 50B has the same configuration as that of the electromagnetic linear actuator 50 shown in FIGS. 3 and 4 except that the configuration of the magnetic circuit is changed as will be described later. To do. Therefore, the reference numeral 70B is attached to the magnetic circuit. Components having the same functions as those shown in FIGS. 3 and 4 are denoted by the same reference numerals, and only different points will be described below.

  The magnetic circuit 70B has the same configuration as the magnetic circuit 70 shown in FIGS. 3 and 4 except that the configuration of the outer yoke is changed as will be described later. Accordingly, reference numeral 71B is attached to the outer yoke.

  FIG. 9 shows the outer yoke 71B. 9A is a perspective view of the outer yoke 71A, FIG. 9B is a development view of the outer yoke 71B, FIG. 9C is a plan view of the outer yoke 71B, and FIG. 9D is an outer yoke 71B. (E) is a side view of the outer yoke 71B.

  The illustrated outer yoke 71B has a structure in which a single press plate is formed into a box shape by bending. That is, the outer yoke 71B includes a square plate-shaped bottom yoke portion 711B and four rectangular plate-shaped side wall yoke portions 712B extending upward from the four edges of the bottom yoke portion 711B.

  Note that the four flat-plate-shaped magnet pieces 721 of the magnets 72 are respectively attached to the inner walls of the corresponding four side wall yoke portions 712B.

  Also in the electromagnetic linear actuator 50B having such a configuration, the outer yoke 71B can be made inexpensive. The reason is that the conventional outer yoke was manufactured by high-cost processing such as cutting and deep drawing, whereas the outer yoke 71B according to the present embodiment is manufactured by inexpensive press punching and bending processing. This is because costs can be reduced. Also in the present embodiment, since the four flat magnet pieces 721 are used as the magnet 72, the magnet 72 can also be manufactured at low cost.

  Further, since the outer yoke 71B is manufactured by press punching and bending, the thickness of the outer yoke 71B can be increased compared to the case of manufacturing by deep drawing like a conventional outer yoke. Thus, since the magnetic saturation can be suppressed by increasing the thickness of the outer yoke 71B, the leakage magnetic flux can be suppressed and the magnetic flux passing through the coil 61 can be increased. As a result, the thrust of the electromagnetic linear actuator 50B can be increased.

  Furthermore, in the electromagnetic linear actuator 50B according to the third embodiment of the present invention, the outer yoke 71B is composed of a single sheet metal part including press punching and bending, so that the first embodiment of the present invention is implemented. Compared with the electromagnetic linear actuator 50 according to the embodiment, there are also advantages that the number of parts can be reduced and the number of bonding steps can be reduced.

  Although the present invention has been described with reference to preferred embodiments, it is obvious that various modifications can be made by those skilled in the art without departing from the spirit of the present invention. For example, in the embodiment described above, only the example of the bottomed rectangular tube shape has been described as the shape of the outer yoke, but the shape of the outer yoke is generally an N-shaped tube shape with a bottom (N is An integer of 4 or more).

It is a perspective view which shows the tape drive which is a recording / reproducing apparatus with which this invention is applied in the state which removed the upper cover. It is the perspective view which looked at the tape drive shown in FIG. 1 from the lower surface side. It is a perspective view which shows the external appearance of the electromagnetic linear actuator which concerns on the 1st Embodiment of this invention used for the tape drive of FIG. FIG. 4 is an exploded perspective view of the electromagnetic linear actuator shown in FIG. 3. It is a perspective view which shows the external appearance of the electromagnetic linear actuator which concerns on the 2nd Embodiment of this invention. FIG. 6 is an exploded perspective view of the electromagnetic linear actuator shown in FIG. 5. It is a perspective view which shows the external appearance of the electromagnetic linear actuator which concerns on the 3rd Embodiment of this invention. FIG. 8 is an exploded perspective view of the electromagnetic linear actuator shown in FIG. 7. FIG. 8A is a perspective view of the outer yoke used in the electromagnetic linear actuator of FIG. 7, FIG. 9B is a development view of the outer yoke, and FIG. 8C is a plan view of the outer yoke. It is a figure, (D) is a front view of an outer yoke, (E) is a side view of an outer yoke.

Explanation of symbols

10 Recording / playback device (tape drive)
17 Head actuator 17a Magnetic head 171 Lead screw 172 Head lift body 50, 50A, 50B Electromagnetic linear actuator 60 Sub movable part 61 Coil 62 Coil support part 70, 70A, 70B Magnetic circuit 71, 71A, 71B Outer yoke 711, 711A Bottom Yoke 711B Bottom yoke part 711a Yoke through hole 712 Side wall yoke 712A L-shaped side wall yoke 712B Side wall yoke part 72 Magnet 721 Flat magnet piece 74 Cylindrical inner yoke 74a Insertion hole

Claims (5)

An electromagnetic linear actuator comprising a fixed portion and a movable portion that moves linearly along the axial direction by electromagnetic force with respect to the fixed portion, wherein the fixed portion has a magnetic circuit comprising a yoke member and a magnet. In the electromagnetic linear actuator, the movable part includes a coil, and the yoke member includes an outer yoke and an inner yoke.
An electromagnetic linear actuator characterized in that the outer yoke has a bottomed N-square cylindrical shape (N is an integer of 4 or more) constructed by assembling press-punched flat plates.   The electromagnetic linear actuator according to claim 1, wherein N is four. The axial direction is the vertical direction of the electromagnetic linear actuator,
The outer yoke is composed of a square plate-shaped bottom yoke and four side wall yokes extending upward from the edges of the four sides of the bottom yoke,
The inner yoke is composed of a cylindrical inner yoke standing from the center of the bottom base,
The magnet is composed of four plate-shaped magnet pieces attached to the inner walls of the four side wall yokes,
The electromagnetic linear actuator according to claim 2, wherein the coil is disposed in a gap between the four flat magnet pieces and the cylindrical inner yoke. The axial direction is the vertical direction of the electromagnetic linear actuator,
The outer yoke is composed of a square plate-shaped bottom yoke and two L-shaped side wall yokes bent in an L shape extending upward from the edges of the four sides of the bottom yoke,
The inner yoke is composed of a cylindrical inner yoke standing from the center of the bottom base,
The magnet is composed of four plate-shaped magnet pieces attached to the inner walls of the two L-shaped side wall yokes,
The electromagnetic linear actuator according to claim 2, wherein the coil is disposed in a gap between the four flat magnet pieces and the cylindrical inner yoke. The axial direction is the vertical direction of the electromagnetic linear actuator,
The outer yoke has a structure in which a single press plate is formed into a box shape by bending, and the outer yoke has a square plate-shaped bottom yoke portion and upward from the four side edges of the bottom yoke portion. It is composed of four rectangular plate-shaped side wall yoke portions extending,
The inner yoke is composed of a cylindrical inner yoke standing from the center of the bottom base,
The magnet is composed of four flat plate-shaped magnet pieces attached to the inner walls of the two wall yoke portions,
The electromagnetic linear actuator according to claim 2, wherein the coil is disposed in a gap between the four flat magnet pieces and the cylindrical inner yoke.

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