JPH0752491B2 - Recording / playback device - Google Patents

Description

The present invention relates generally to magnetic recording and reproduction, and more particularly to converting areas for transfer of magnetically defined information between a signal-using device and a magnetic storage medium. It concerns a body of magnetic material for giving. The invention more particularly relates to the mechanical control of the position of the conversion zone on such an additional body of magnetic material. (As used herein, "transfer area" means an area for coupling magnetic flux in relation to the body having that area). The preferred embodiment of the invention described herein incorporates the physical gearing of the magnetic transducer core to set the conversion zone in a magnetically saturable body proximate to the physical path of the magnetic storage medium. It is associated with the use and movement of the conversion zone of the body by such movement of the core.

There are many situations in which it is desirable to transfer magnetically defined information between a magnetic storage medium and a signal-using device using an electromagnetic transducer that transforms the magnetic state of information into its electrical state. . Electromagnetic transducers typically have a physical gear (generally referred to as a transducing gear) between two magnetic poles.
And a body of a magnetic material having a high magnetic permeability. This gap interrupts the flux path within the transducer to allow coupling of the flux associated with the flux path. The magnetic flux is coupled from the magnetic flux path in the transducer to, for example, the magnetic recording medium by emanating from the body of magnetic material at the gear.
This gear also allows the head to pick up the magnetic flux emanating from a properly positioned magnetic storage medium. Signaling means are provided for sensing the detected magnetic flux flowing in the magnetic flux path and for transmitting the information defined by the magnetic flux to the desired signaling device. The signaling means are typically electrical coils positioned to detect changes in the magnetic flux traveling in the flux path and convert this magnetically defined information into corresponding electrical signals.
(While this detection is the transfer of information in one direction, ie from the magnetic medium to the magnetic transducer or head, the transfer of the other direction, ie from the magnetic head to the corresponding magnetic storage medium, is broadly quite similar. It should be understood that this information is converted from an electrical signal state to a magnetic signal state by passing the electrical signal through a coil that induces a magnetic flux corresponding to the flux path in the head). This technique is used in disk recorders with synthetic magnetic disk storage media. The electromagnetic converter having such a structure is made so as to be a "fly" (non-contact with the medium) during the recording / reproducing operation. This spacing between the head and the magnetic storage medium causes the well known wavelength dependent spacing loss. Furthermore, this spacing also compromises the efficiency of flux transfer.

In magnetic tapes or other data recorders, such as flexible (ie, floppy) disk recorders, that use this technique, the magnetic head is typically in contact with the media during signal transfer operations. Spacing losses are not such a significant issue in these recorders, but head and media wear becomes significant in relation to relative movement between media and contact heads. For example, in a wide band magnetic signal recording / reproducing apparatus, a high relative converter-to-storage medium speed is necessary for recording / reproducing a high frequency signal with a good quality resolution. In such devices, heads and storage media often must be replaced due to wear. In this connection, wear of the head surface is particularly harmful.

The development of rotary scanning magnetic tape recorders has led to an increase in relative head to tape speed. The transducer rotates at high speed in contact with the relatively slow moving magnetic tape. The transducer is typically mounted on a rotatable support element, such as a drum, for such rotation. Commonly used rotary scan recorders are of two basic types, commonly referred to as lateral scan and helical scan recorders, distinguished by the angle at which the transducer sweeps the tape. There are many problems associated with obtaining the desired accuracy and reproducibility of signals recorded by rotary scan recorders. For example, it is necessary to maintain very small mechanical tolerances at and between the rotary transducer support drum, the transducer structure and the location of the transducer on the drum. At the same time, it is necessary to keep the rotational speed of the converter, and thus the drum, accurate with respect to the speed at which the tape is passed through the rotary converter.

As will become clearer from the description below, the present invention is adaptable to various configurations for transferring information that can be defined by magnetic flux in magnetic heads and magnetic storage media. This utilization can provide transducer and media wear, wavelength reduction depending on spacing loss, and / or improved transducer efficiency.

The present invention is based on several findings. One finding is that the conversion zone can be made in the body of magnetic material without the need for physical gears. Furthermore, if this body of magnetic material is positioned in magnetic proximity to the magnetic storage medium, such a transducing zone may contribute to the coupling of magnetic flux between the body and the magnetic storage medium. It has also been found that it can be made in. It has also been found that the body part can be used to couple the magnetic flux in the flux path inside it to other magnetic body parts, such as the core of an electromagnetic transducer. Furthermore, it has been discovered that known magnetic head physical gears can be used to set the conversion zone of the body, as described below. (As used herein, the term "magnetically in close proximity", assuming saturation or some similar magnetic effect does not prevent coupling,
(This means that the body of magnetic material is positioned with respect to an adjacent object or magnetic field so that magnetic flux coupling occurs).

The body of soft magnetic material is usually located above the ends of the permanent magnet to trap and provide a path for the magnetic flux between the poles of the magnet. Such a body is called a keeper and is typically used to make a core for the transducer that acts to protect the permanent magnets from demagnetization. The magnetic material has properties similar to those of the keeper. The body of magnetic material used in connection with the present invention has basically the same properties as the keeper. In one embodiment of the invention, the body provides a conversion zone and performs a keeper function. For these reasons, the body of the magnetic material of the present invention is referred to herein as the "keeper". It is preferable that the material of the body has high absolute magnetic permeability, low coercivity and low magnetic saturation density. Such materials are commonly referred to as soft magnetic materials, as opposed to hard magnetic materials, i.e., materials having high coercivity and magnetic saturation density such as those that magnetically store information. The discovery of keeper efficiencies and the resulting magnetic recording / reproducing arrangements represents a major advance in the art. This is especially the case with regard to the ease of changing the position, i.e. in other words with respect to scanning the position of the conversion area within the keeper. It would be desirable to be able to use the techniques described above for scanning without the need for major reconstruction of many modern recording / reproducing devices. According to the invention, such a large reconstruction is such that if the scanning of the conversion zone of the keeper correspondingly moves the magnetic transducer or another body of magnetic material for setting the conversion zone on the body of the keeper. It has been found that in many situations it can be avoided if easily achieved by doing.

It should be noted that the presence of the conversion zone can be made transient. That is, it is only important that the conversion zone must be present when needed for the coupling of magnetic flux between the storage medium and the keeper. For example, if the conversion zone is provided by a magnetic flux induced by an AC current, the discontinuity in the magnetic flux density associated with the formation of the conversion zone will be essentially repetitive. If the transfer is from a magnetic storage medium, then it is practically only necessary that the conversion zone must be present when the recorded magnetic state to be detected has a coupling relationship to the conversion zone. Absent. When changes in magnetic state that are close to each other in time have to be detected and the conversion zone is given by the magnetic flux induced by the AC current, it can be obtained with a rectangular waveform different from the sine waveform. It is desired that the magnetic fluxes involved in the conversion zone be induced by a current that gives such a very fast transition. Furthermore,
In some situations it is desirable to control the coupling of the magnetic flux between the transducer and the storage medium by controlling the presence of the keeper in the transducing area.

Produce in the same one or more "meaningful" magnetic discontinuities or regions of substantially different permeability, as provided in electromagnetic transducers, typically by including physical conversion gears. As a result, the conversion area is formed in the keeper. The permeability gradient provides such discontinuities, and it is most preferred that there is a sharp permeability gradient between the regions of the body that provide the conversion zone and adjacent regions. The nature of such a gradient and the preferred manner of achieving this are described in detail below. Such discontinuities are most easily imparted to the body by having adjacent magnetically saturated and unsaturated regions. Furthermore, the transduction area can be easily generated and defined in the keeper by the cooperation of the physical gears of the known electromagnetic transducer and the source of the magnetic bias flux. This source or bias flux source may be associated with the transducer alone or with the keeper alone and in some cases both. Also, the bias flux source can be simply provided by the recording signal flux passing through the keeper. However, it is formed such that the position, size and shape of the conversion zone within the keeper are in magnetic proximity to the keeper and simultaneously maintain the body or source to mechanically move the magnetic material for the conversion zone with respect to the keeper. Can be changed by doing.

Keeper thickness is important in determining keeper performance. The choice of keeper thickness depends on its purpose and its location. For example, for reproduction operations, a well-defined conversion zone is preferred, and for reproduction of signals of short wavelength, short lengths are preferred. A relatively thin keeper is best for such operation. Thinners are preferred, for example, in applications where it is important to avoid head and media wear in contact recording and / or playback devices. The configuration of the converter / keeper / magnetic storage medium also affects the thickness of the keeper. In either case, the keeper thickness is selected in relation to the possible magnetic flux to create the transduction zone at the desired location. For example, in an arrangement in which the keeper engages the face of the magnetic core bearing the gear to physically bridge the gear and a predominant amount of bias flux flows through the head as well as the keeper, the keeper is The keeper / core cross-section perpendicular to the bias flux path close to the gearup is chosen to be large, so that the core close to the gearup is large, so that the part of the keeper bridging the physical gearup has a large flux density. , Preferably having a magnetic flux density that saturates the area with it. The saturated region has a low magnetic permeability, similar to a non-magnetic material, while the surrounding region has a high magnetic permeability. These regions cooperate to define a virtual transformation zone within the body.

In the preferred embodiment described herein, the bias flux that defines the transmutation zone at the keeper is the flux emanating from a known transducer configuration having a physical gap. The magnitude of this bias flux is selected to set adjacent regions of different permeability at selected portions of the keeper bridging the face of the transducer containing the physical gap. These areas serve to define areas for the keeper that are of "virtual gear" nature. This magnetically formed virtual gear or conversion area is used for signal recording and reproduction. This conversion zone extends in a direction through the keeper defined by a line extending in the physical gear between the magnetic transducer and the magnetic storage medium. Furthermore, the shape or size of the keeper's conversion zone can be controlled by appropriately controlling the shape and size of the boundaries between areas of greatly different permeability, that is, between the unsaturated and saturated parts of the keeper. Is.

Further, the method and apparatus of the present invention not only provide a moving magnetically formed transduction zone for a body part that does not have a physical gear, but also from a physical gear of a transducer or from recording on a magnetic storage medium. It is to be understood that it is possible to have the unique property of diverting the normally emitted unwanted flux, which adversely affects the desired magnetic state memory or flux transitions.

US Patent Application No. 06 / 808,921 describes a magnetic medium having a thin and soft magnetic keeper layer along with a hard magnetic layer for storing information signals. As described in this application, it is known to provide magnetic media for perpendicular magnetic storage with a layer of soft magnetic material in addition to a layer of hard magnetic material for storage. However, in the past, the primary purpose of providing such a layer of soft magnetic material was to include means for providing an unspecified, highly transparent flux path for the signal recording and reproducing flux. These layers do not provide a defined conversion zone for the signal transfer between the transducer and the medium, let alone move, and are necessary for the formation of such a moving conversion zone. I didn't provide a means to create the condition of different layers. Also, these layers were intentionally designed to be unsaturated due to being made thicker with respect to the expected magnetic flux density and without the effects of spacing and reproducing gear losses or wear of the magnetic transducer and magnetic recording media. . All of these are features that characterize the method and apparatus of the present invention.

More preferably, in a preferred embodiment of the invention, the keeper is essentially fixed or restrained with respect to a relatively loosely moving magnetic storage medium, such as a layer of a flexible substrate providing a magnetic tape. Maintained. The conversion area of the keeper is formed by the magnetic flux directed to the keeper by the magnetic core associated with the magnetic transducer. Such cores are moved at relatively high speed by mechanical means with respect to a fixed keeper so as to correspondingly move the conversion zone. The magnetic storage medium is maintained in contact with the keeper and can be flexibly moved with respect thereto. Thus, providing the keeper with a gearless conversion zone results in a high speed movement of the conversion zone without the need for the medium to make physical contact with the gearing surface of the high speed transducer core. As a result, wear that reduces the life of the magnetic core of the transducer is avoided. Also, the contact between the keeper and the magnetic storage medium acts to affect the effects of wavelength dependent spacing loss and to improve the efficiency of the recording / reproducing process. On the other hand, a small distance between the transducer core and the keeper is preferred. This spacing must be kept to a minimum to reduce reluctance loss in the signal path.

In the detailed description that follows, the method and apparatus of the present invention will be described with reference to specific embodiments thereof. However,
The keeper body can generally be used in combination with a signal-using device and a magnetic storage medium, and thus the invention is not limited to the embodiments described.

With reference to the accompanying drawings, FIGS. 1, 2A and 2B are schematic perspective views of an embodiment of the present invention in which the transducer core provides reciprocating motion in relation to a fixed keeper, and FIG. FIG. 4 is a schematic perspective view of another embodiment of the present invention in which the transducer core is rotated relative to a fixed keeper, and FIG. 4 is a cross sectional view of a track and / or track along a magnetic recording medium. Or FIG. 5 is a schematic perspective view of an apparatus using the transducer / keeper combination of the present invention for reproduction, and FIG. 5 shows recording and / or recording on a track set on a magnetic recording medium sent along a helical path. FIG. 6 is a schematic perspective view of an apparatus using the transducer / keeper combination of the present invention for reproduction, FIG. 6 is an example of magnetic flux density versus permeability characteristics of known magnetic materials, and FIG. 7 is a book. Conversion area set in a differentially permeable layer of an embodiment of the invention The magnetic flux density-permeability characteristic over the length of is shown.

In the following description and drawings, like elements are designated with like reference numbers to facilitate comparison between various embodiments.
Descriptions of similar elements and circuit parts shown in one or more of the figures in the drawings are not repeated with respect to each of these figures.

Embodiments in accordance with the present invention are described next in connection with FIGS. 1-7, which show magnetic fields with properties similar to those used to manufacture magnetic transducers, commonly referred to as cores. It has a body 20 of material which defines a pair of magnetic poles 22, 24 between which a physical gear 26 of the type used to effect magnetic signal transfer in accordance with the present invention.
To form. The body or core 20 is mounted for movement in relation to a fixed body 28 of magnetic material which preferably has the characteristics of a keeper without physical gear.
The keeper 28 is a core if the physical gear 26 defined by the core is for the formation of a conversion zone.
A conversion area 50 that follows the movement of 20 is defined inside. In FIG. 1 there is shown schematically a magnetic transducer 10 formed by a core 20 made of a preferred magnetic material such as ferrite. A non-magnetic material such as glass or silicon dioxide is provided between the poles 22, 24 to obtain a well-defined physical gear 26 of the type typically used as a transducing gear. The transducer core 20, the magnetic poles 22, 24 and the gear 26 can be constructed according to known magnetic head manufacturing methods, and thus a detailed description thereof will not be given. An elongated keeper 28 of thin "soft" magnetic material having the above-mentioned properties, such as permalloy.
Are arranged close to the magnetic poles 22 and 24 so as to bridge the gear 26. In this embodiment, the transducer core 20 and keeper 28 are maintained in a close positional relationship,
There is no physical contact between these two elements as shown by the spacing 29. As will be apparent from the description below, this spacing prevents detrimental wear of the transducer 10 when it is being moved with respect to the keeper 28. In the presently described embodiment, the width dimension of the gear 26, which corresponds to the width dimension W of the track 64 recorded along the magnetic storage medium 56, extends at a right angle to the lengthwise direction 62 of the keeper 28.

The keeper 28 is constructed as a rigid, continuous side or layer of magnetic material such that no physical gear is present in the transduction zone. The width of the keeper in the embodiment of FIG. 1 is equal to the width W of the gear 26, but the keeper may be made wider as in the embodiment of FIG. The keeper 28 preferably has a very small thickness t in the direction of the gear depth, for example between 0.00025 and 0.002 inches. It may be attached by vacuum sputtering or plating to a thin substrate such as Mylar or Kepton made by Dupont or made in the form of a thin film. For example, the substrate may have a thickness between 0.001 and 0.005 inches.

In the embodiment of FIG. 1, the body 30 of magnetic material forming the converted signal core 30 is attached in magnetic coupling relation to the keeper 28. The core 30 may be made of, for example, a magnetic material commonly used for the manufacture of magnetic transducer cores. The signal core 30 abuts the lateral surface of the keeper 28 at both ends 32, 34 to form a closed signal flux path 36.

The conversion signal winding 38 is wound around the signal core 30. Winding 38
Is used to convert electrical signals provided by an external signal source, shown generally at 40, into magnetic signals for recording by a transducer / keeper assembly on a recording medium such as magnetic tape 56. It In addition, winding 38 is used to convert the signal recorded on magnetic tape 56 and picked up by the transducer / keeper assembly into an electrical signal as described in more detail below. In order to more clearly distinguish between the signal core 30 and the converter core 20, the core 20 is hereinafter referred to as the back core and the core 30 is referred to as the front core. The front core 30 is preferably a front surface 41 of the keeper 28 that faces the recording medium 56 so as to avoid contact with the medium.
Are arranged at an angle of m. Bias control winding 42 is wound around back core 20 and control current Ic is provided to it by a variable current source. It includes a variable resistor 44 and a DC controlled voltage source 46. In another embodiment, an adjustable AC controlled current source may be used in this embodiment instead of a DC source.

When no control current is applied to the bias control winding 42,
The keeper 28 magnetically branches the gear 26 and the recording medium 56.
No signal transfer is performed. However, the control current
When Ic is applied to control winding 42 from source 46, that current causes control flux 48 in back core 20. This control flux 48 is coupled by the gear 26 to a closely spaced thin keeper 28 which magnetically bridges it. The keeper thus acts as a return path to the back core 20 for the bias control flux 48.

Since the keeper 28 has an extremely small cross section in the direction perpendicular to the control magnetic flux passage 48 bridging the gear cup 26,
The magnetic flux emitted from 26 locally saturates the keeper 28 in the region 50 bridging the gear 26, as indicated by the hatched portion. This sets a low magnetic permeability in the region 50 corresponding to that of a non-magnetic material such as air. A keeper 28 that surrounds the saturation region and extends closely across the magnetic core 20.
The magnetic flux densities in the other regions of the are much smaller than those in the region 50, so these regions do not saturate and remain highly transparent. Thus, the saturation region 50 is localized between the two abutting highly permeable portions 52, 54 of the keeper 28 to provide a "gearless" exchange area.

When the area 50 of the keeper 28 is saturated as described above,
A recording signal flux 36 extending through the signal core 30 and the transparent portions 52, 54 of the keeper 28 is coupled by the keeper to interrupt the magnetic storage medium or tape 56 when the keeper is in close contact. For example, in the embodiment of FIG. 1, tape
56 passes through keeper 28 and is in direct contact with it in the longitudinal direction
It progresses to 57 slowly. Recording current Is from signal source 40
Is applied to the signal winding 38, the recording magnetic flux
Induced by 36. It extends through the conversion signal core 30 and the keeper 28. Since the adjacent magnetically saturated and unsaturated regions define the conversion zone 50, the magnetic flux is thus low independently of the wavelength extending from the magnetically unsaturated regions 52 and 54 of the keeper 28 to the tape 56. Directed along the reluctance flux path. Alternatively, when the transducer / keeper assembly of FIG. 1 is used in a replay operation, the signal flux from tape 56 intercepts keeper 28 in conversion zone 50, which is the flux path for keeper 28 and signal core 30. The signal winding 38 is interrupted to follow 36 and produce an output voltage Vs on the output line 59.

The length l and width W of the saturated region 50 correspond to the equivalent dimensions of the physical gear 26 of the back core 20. The magnetic characteristics of the keeper are such that the bias control flux necessary for saturating the region 50 bridging the conversion gap 26 is less than a detrimental level of the control flux emitted from the keeper to cause the magnetic state of the medium. Well chosen to be much lower. The level of the bias control flux is primarily a function of the magnetic material of the keeper 28 as well as the cross section in the direction perpendicular to the bias control flux path 48. On the other hand, its cross section is defined by the width W and the thickness t of the keeper. For a selected width W, a thinner keeper will need more flux due to saturation of region 50. For many reasons mentioned above, the thickness t of the keeper 28
Is desired to be small. However, an important reason for keeping the dimension t small in the embodiment of FIG. 1 is the small effective transduction zone depth in the direction of t, which reduces the reluctance through the saturated transduction zone 50. Large, thus keeping branch losses through the conversion zone 50 low. However, in a broadband high-density recording and reproducing device in which the keeper 28 is in contact with the recording medium 56,
It is also desirable to avoid or minimize wear that reduces life. For this reason, the choice of the keeper thickness t usually involves a compromise between minimizing branch loss and maximizing keeper life.

The above-described mechanical movement of the back converter core 20 relative to the fixed keeper 28 is obtained as follows in the embodiment of FIG. The back core 20 is rigidly attached to one end of a shaft 58, the other end of which is attached to the device 60 to provide a reciprocating movement in the direction of arrow 62. For example, device 60 may be configured as an electromagnetic actuator or other well known reciprocating device. It is important to obtain a linear velocity movement of the gear 26 with respect to the keeper 28 in order to avoid time-varying or non-linear signal transfer during recording and playback operations. Area of keeper 28 during operation
A control current Ic of sufficient magnitude to saturate 50 is provided to control winding 42 by voltage source 46. The tape 56 contacts the keeper 28 and is advanced in the direction of arrow 57, as described above. The back core 20 is moved in the direction of arrow 62 by a reciprocating device 60, thereby mechanically advancing the physical conversion gear 26 along the keeper 28. As mentioned above,
The position of saturation region 50 along keeper 28 in direction 62 follows the movement of physical gear 26 along the keeper.

The recording current signal Is applied to the signal winding 38 during the recording operation
Causes the corresponding signal flux 36 to flow through the passage 36. It is joined by the conversion zone 50 to make a recording along the transverse tracks 63, 64 on the tape 56. 63
A set of parallel tracks, such as, is recorded during movement of the front core 20 in one direction, and a second set of parallel tracks, such as 64, is recorded during movement of the front core in the opposite direction. It
Either set of tracks 63 or 64 in one direction core 20
Can be omitted by turning off either the recording current Is or the bias control current Ic during the movement of the.

The reproduction of the recorded signal along the parallel traversing tracks of the tape recording medium 56 is similar to the recording of the signal, i.e., while the conversion zone 50 is moving on the recording track on the medium 56. By reciprocating the front core 20 to 62,
It is obtained with the transducer / keeper assembly of the embodiment of FIG.
However, instead of applying the recording current to the signal winding 38,
The transducer / keeper assembly serves to detect the reproduced signal flux emanating from the medium 56, which enters the keeper 28 via the unsaturated regions 52, 54 adjacent the saturated region 50. The reproduction signal flux 36 interrupts the signal winding 38, which then provides the reproduction voltage Vs on the output line 59 for further processing in a known manner.

As is apparent from the above description, the transducer / keeper assembly of the embodiment of FIG. 1 moves relatively slowly by rapidly scanning the transducer aft core along a fixed keeper 28. A recording track pattern in the lateral direction can be given to the tape 56. The tape 56 is in direct contact with the fixed keeper 28, which has no physical gear. As discussed above, this contact results in a wavelength independent flux path between tape 56 and signal winding 38 that reduces the effects of spacing losses. Furthermore, in this embodiment of the invention, the need for a rotatable member to direct the transducer, as is common in video recorders, is avoided, while a relatively high transducer-to-medium scan speed is achieved. can get. Furthermore, there is no need for rotary transformers or slip rings to transfer signals between the transducer and the storage medium.

As briefly mentioned above, the control current source 46 is omitted for recording operation if sufficient recording signal current Is is provided by the source 40 to saturate the area 50 of the keeper 28. You can However, for regenerative operation, saturation of region 50 requires a bias flux, which is provided in the embodiment of FIG. 1 by applying a current Ic to control winding 42.

FIG. 2A shows one embodiment of the present invention, which is similar to that of FIG. 1, but similar in that the embodiment of FIG. 2A does not have a front core. In this example,
The signal and control windings 38, 42 are coupled to a single winding 39 located around the back core 20. This single winding 39 is connected to the bias control current source 46 mentioned above via a resistor 44 so as to receive the control current Ic mentioned above. In addition, this single winding 39 is also connected via line 64 to a record or playback amplifier (not shown in FIG. 2A). Series capacitor 66 is connected to line 64 to insulate bias controlled current source 46 and the signal intensifier coupled to line 64. Therefore, both the recording signal magnetic flux 36 and the control magnetic flux 48 extend in parallel through the core 20 and the keeper 28. In the recording mode of operation, when a recording current Is of sufficient magnitude to saturate the conversion area 50 of the keeper 28 is provided via the line 64, the control current source 46 and the resistor 44 cause this current to flow in the winding 39. As represented by the dotted line connecting the source and the resistance,
It may be omitted. However, during regeneration operation, the saturation of the conversion zone 50 causes the control current Ic to flow from the source 46 to a single winding.
It requires a bias magnetic flux as obtained by applying to 39. In the embodiment of FIG. 2A, the AC controlled current source is
It may be used instead of the DC source 46. In that case, instead of the capacitor 66, connect a filter (not shown) on the line 64 for isolating the AC control signal from the information signal being recorded or reproduced in relation to the magnetic recording medium. is necessary.

In connection with the above description, it should be understood that FIGS. 1 and 2A schematically represent an arrangement according to the invention.
There are various ways in which the basic configuration can be incorporated. For example, the keeper 28 may have a width greater than the width W of the back core 20 as shown in FIG. 2A. By extending the width of the keeper 28 beyond one or both sides of the back core 20, the length l and width W of the saturation region 50 are substantially unchanged as described above and correspond to those of the gear 26. 1
As another example, the shaft 58 may be secured to a rigid indicator bracket and the back core 20 may be movably attached to it by various known suspension systems (not shown). The keeper 28 and the conversion signal core 30 may be fixedly instructed in such a bracket. The control winding 42 may be wound around the back core 20 and moved therewith as in the embodiment of FIGS. 1 and 2A. Alternatively, the control winding 42 may be fixed and mounted in a bracket, while the back core 20 is mounted along its winding for vertical movement without contact with it. Separate signal windings may be arranged in this manner. If desired, multiple back cores 20 may be mounted in a common shaft and driven by a common transfer device 60. In such a configuration, each core 20
May be associated with separate fixed keeper and signal windings, while a common fixed control winding may be provided associated with all cores. The transducer thus obtained may be used for synchronous recording and / or reproduction (sequential or simultaneous) associated with a number of parallel tracks along the recording medium.

FIG. 2B shows another embodiment of the converter / keeper assembly of the present invention. In this embodiment, instead of forming the magnetic circuit with the back core 20 closed through the physical gear 26 as in the embodiment of FIGS. 1 and 2A, the gear 26 produces a known magnetic head. Is formed between two spaced apart magnetic core members 20a, 20b made of a magnetic material of low coercivity and high permeability, as is commonly used for this purpose. Each core 20a, 20
b has a length approximately equal to the length of the fixed keeper 28 in the direction of the reciprocating movement of the core indicated by the arrow 62. Member 20
The a and 20b are held together by a non-magnetic member 13 such as aluminum which acts as a bracket. Bracket
13 is attached to a rod 58, which is driven by the transfer device 60 described above. The device 60 drives the cores 20a, 20b in a reciprocating motion in the direction of arrow 62 in the same manner as described above in connection with the embodiment of FIG. A combined control and signal winding 39 is wound around the front core 30. Thus, the bias control signal path 48 extends through the front core 30, the transparent portions 52, 54 of the keeper 28 and the magnetic back cores 20a, 20b. The signal flux path 36 is substantially the same as described above in connection with the embodiment of FIG. 1, but instead of extending through the length of the keeper 28, the back flux core 20a together with the bias flux is shown in FIG. 2B. , 20b through. In operation, area 5
Zero is saturated by the control flux 48 set by the control voltage Ic from either the DC or AC control source as described above. Due to the respective lengths of the back cores 20a, 20b, the bias flux set by the control current is the same regardless of the position of the physical gears 26 along the length of the keeper 28 except for the position of the physical gears. Held in. In this embodiment, the desired saturation conversion zone 50 is the physical gear 26.
The keeper 28 is set on the opposite side of the
When it is reciprocally moved by, it follows such a gear tape.

Another embodiment of the present invention will now be described in connection with Figures 3-5. In these embodiments, the back core 20 is rotated in close contact with a fixed keeper. One or more such back cores are disposed around the perimeter of the rotating head wheel and those portions that define the physical gear protrude from the wheel. The keeper is formed as a thin cylindrical segment and is arranged in an elastic relationship with the periphery of the rotating wheel. The keeper is maintained fixedly and in a closely spaced relationship with respect to the rotating core to bridge the rotating gear defined by the back core, which causes the rotating gear to sequentially sweep across the keeper.
The tape is fed longitudinally through and preferably in contact with a fixed keeper. In the embodiment of FIGS. 3 and 4, the physical gap formed on each back core scans across the tape, while in the embodiment of FIG. 5, the tape is fixed as described below. To the helical path while being scanned by the moving conversion zone set by the transducer which is rotated with respect to the keeper.

Referring to FIG. 3, there is shown a substrate 70 of non-magnetic material, such as aluminum, on which is mounted a rotating transducer / stationary keeper assembly 72. Head wheel 74 carries one or more back cores 20, which are similar to those described and illustrated above in connection with FIG. The control winding 42 is wound around each back core 20. If more than one core 20 is used, they are preferably equally spaced around the circumference of the wheel. The wheel 74 is made of a non-magnetic material such as aluminum, and is fixed to the motor shaft 75. The shaft 75 and the wheel 74 are driven by a motor 76. The motor 76 is held on the base 70 by a non-magnetic bracket 77 of, for example, aluminum. The keeper 78 is made of the keeper material described above, such as Permalloy or other thin magnetic material, and is rigidly attached to the substrate 70 by a non-magnetic bracket 79 of, for example, aluminum. The thickness of the keeper 78 is preferably
It is within the range described above in connection with FIG.

In the embodiment of FIG. 3, the keeper 78 has a uniform spacing between the rotating physical gear 26 and the keeper 78.
A cylindrical segment coaxially mounted relative to a rotationally mounted head wheel 74 and spaced from its periphery. Tape 80 is fed through keeper 78 and in physical contact with its outer surface 85 in the length direction indicated by arrow 82. The front core 86 having the signal winding 87 is rigidly attached to the keeper 78 in a manner similar to that of the embodiment of FIG. The front core 86 is U-shaped with its ends open in physical contact with the lateral surface of the keeper 78 so as to form a substantially closed magnetic circuit in the manner described above with respect to the embodiment of FIG. It preferably has a configuration.

A slip ring assembly 88 and a brush or wiper assembly 89 are also provided in the embodiment of FIG. The slip ring assembly comprises a rod 93 of insulating material, such as plastic, and a plurality of slip rings 90 located along the rod, the assembly including a motor shaft.
It is firmly attached to the 75 and rotates with it. Each slip ring 90 has a specific back core due to the conductor 91.
It is connected to a specific control winding 42 located at 20. For example, the slip ring 90 may be a metal plated on the surface of the insulating rod 93.

The brush or wiper assembly has an adjustable DC controlled voltage source 46.
It consists of a number of individual brushes 95 that are normally joined together. An individual adjustable series resistor 44 is provided for each brush to allow adjustment of the control current provided to the individual control winding 42.
Combined with 95. The assembly 89 is rigidly attached to the base 70 by an insulating bracket 94, such as aluminum. Known and readily available brush and slip ring assemblies 89, 90 may be used to connect the control current provided by the source 46 to the respective rotation control windings 42. For example, the brush block (part no. 3751-001) and the slip ring assembly (part no. And 90 are preferably used. The signal winding 87 is coupled to the recording signal circuit or connected to the reproduction signal circuit in the manner described below.

The operation of the conversion assembly 72 of FIG. 3 will now be described. The principle of the recording and reproducing operation uses the fixed keeper and the rotating back core of FIG. 3 and is in the same manner as described above in connection with the embodiment of FIG. However, instead of the reciprocating motion described above, the back core is rotated into a circular path in one direction with respect to the keeper and tape. A more uniform and linear scan of the recording medium is thereby obtained. The synchronization of the rotational speed with respect to the tape movement in the longitudinal direction is likewise achieved by such movement of the back core.

When the rotary transducer / fixed keeper assembly described above is used to perform signal recording along the longitudinally moving tape 80, the recording current is transferred from a known recording circuit (not shown) to the conversion winding. Given to 87. At the same time, the control current Ic
Are provided to the rotation control windings via brush and slip ring assemblies 88,89. Each physical gear 26
The magnetic flux generated from it as it sequentially rotates through the keeper 78 saturates the area of the keeper bridging the gap. This saturated region is, in effect, an extension of the gear 26, as described above in connection with various transducer / keeper assembly embodiments. The keeper surrounding this saturated region
The magnetic flux from the permeable portion of 78 enters the adjacent medium. Thus, as the tape 80 contacts its outer surface 85 and passes through the keeper 78, the signal flux from the keeper stores the signal along the parallel tracks 97 of the tape.

As is apparent from the embodiment of FIG. 3, the mechanically rotating physical gear 26 neither contacts the keeper 78 nor the medium 80. Gear wear due to transducer-to-medium contact is avoided. Furthermore, keeper wear is minimized. This is because only the relatively loosely moving medium comes into contact with the smooth gearless surface of the fixed keeper. Due to the lower keeper-to-tape speed, the tape repellency of recorders with high relative transducer-to-tape speed is also reduced.

Signal transfer occurs on each track as it passes through the transducer core 20 by the keeper 78. Preferably, the back core 20 is transferred between the tape 80 and the conversion winding 87 by an adjacent back core in which a continuous information signal, i.e., an uninterrupted signal in time, continuously rotates past a fixed keeper 78. Separated around wheel 74 to obtain. However, signal transfer may occur selectively by switching the bias control currents on and off as the keeper is scanned in a number of revolutions in close proximity to the back core, for example in bursts separated in time. (For recording modes of operation, the recording current signal can be controlled for this purpose.) Related to the above description of the transducer / keeper assembly embodiment of FIG. 2B. Then, it is the rear cores 20a, 20 of the embodiment of FIG.
It should be understood that by attaching b to the rotating wheel 74, it may be used in the device of FIG.

FIG. 4 shows a schematic diagram of a broadband high density recording and reproducing apparatus using a rotary transducer / fixed keeper assembly 107, similar to the assembly 72 of the embodiment of FIG. Here, the keeper 78 is attached to the non-magnetic support bracket 79 by, for example, epoxy. Slot 81 is a bracket that allows head wheel 74 to rotate closely with keeper 78.
It is provided at 79. The transducer / keeper assembly of this embodiment differs from that of FIG. 3 in that a single winding 39 has a back core 20.
They are different in that they are wrapped around and are coupled to receive both the signal current and the bias control current. Accordingly, the back core 20 serves to provide control and signal flux paths as described above with respect to the embodiment of FIG. 2A,
And the front core is not required in the embodiment of FIG. In the apparatus of FIG. 4, the control current Ic as well as the recording current Is or the reproduction voltage Vs is provided by rotary coupling elements such as the slip ring and brush assemblies 88, 89 described above in connection with the embodiment of FIG. Is applied to the winding 39 of the rotating back core 20.
The recording current signal or reproducing voltage is coupled to winding 39 through a rotary transformer assembly having a primary portion 110 and a secondary portion 112. The primary portion 110 is rigidly attached to and rotates with the head wheel 74 on the rotary motor shaft 75. One rotating primary transformer section 110 is provided for each back core 20. Each primary transformer section 110 has a primary winding 114 attached to one winding 39. Capacitor 66 is coupled between winding 39 and primary winding 114 to isolate the signal processing circuitry from the DC bias control circuitry.

The apparatus shown in FIG. 4 includes a recording signal processor 116 and a reproduction signal processor 118.
And process the signals prior to transfer between them and the tape 80. The apparatus of FIG. 4 can be used for high density recording and reproduction of television signals or other high frequency broadband signals along a track 97 extending across a lengthwise moving tape. Switch 124 is shown to select a recording or playback or play mode of operation. In the recording operation mode, the recording current Is is applied to the secondary winding 128 of the transformer through the switch 124 and the line 126 to the recording amplifier.
Combined from 120. Line 126 when in playback mode
A switch 124 connects the reproduction voltage Vs from the secondary winding 128 to the reproduction amplifier 122. Recording and playback signal processors 116 and 118 and amplifiers 120 and 122 used in the field of recording and playback of wideband signals such as television signals may be used in the apparatus of FIG. Therefore, its detailed description is not given.

Further, for the apparatus of FIG. 4, a tape feed mechanism (not shown) of the type used in known rotary head cross-scan tape recording and reproducing apparatus for television signals is provided on the outer surface 85 of the keeper 78. It can be used to contact and feed the tape 80 in the longitudinal direction 82. Also, the uncomplicated tape feeding mechanism used in known audio tape recording and reproducing devices may be used as well.

A servo system 130 is provided to adjust the rotation of the head wheel drive motor 76 with the longitudinal feed of the tape 80.
In the recording mode of operation, the servo system 130 rotates the head wheel 74 and thus the keeper 78 so that the recorded tracks 97 are evenly distributed across the tape at an accurate angle with respect to the length of the tape. It serves to adjust the scanning speed of the conversion area and the feeding speed of the tape 80. In addition, the track 184 of the control signal is recorded by the fixed transducer 182 along the length 82 of the tape 80 to facilitate scanning of the conversion area 29b and adjustment of the tape 80 feed during playback. During playback, the transducer 182 is used to replay the recorded control signal from the track 184 in a manner well known in the art, and the tape 18
It is used to synchronize the zero feed with the rotation of the head wheel 74 and thus the scanning of the conversion area of the keeper 78. The multi-pole switch 186 connects the winding 183 of the transformer 182 and the servo circuit 91 to the input line 187 when in the position indicated in the recording mode of operation. In the other position shown, switch 186 connects winding 183 with servo circuit 191 and inputs line 187, and thus the control signal, to servo circuit and transducer 182.
Disconnect from. Instead of a control signal, switch 186 uses servo circuit 191 to use the playback or play reference signal received on line 196 in the manner described in more detail below.
Give to.

During the recording mode of operation, typically a control signal on line 187 at half the vertical television field speed is received. This signal on line 187 is provided to the winding 183 of converter 182 via switch 186 and line 188. For this reason, the transducer 182 is recorded on the track 80 of the tape 80 at the same time that the information signal is recorded along the track 97, which extends in an intersecting manner.
Record the signal along 4. The control signal on line 187 is then provided to servo circuit 191 via switch 186 and line 189 which controls the operation of head wheel motor 76 in synchronism with the signal on line 187. This synchronization condition is a signal representing the rotational speed and position of the head wheel 74, and thus the conversion zone of the keeper 78 (received from a tachometer mechanism operatively coupled to the head wheel motor 76 via line 190) and control signals. Is obtained by comparing In response, the servo circuit 191 produces a correction signal which corrects the deviation of the head wheel 74, and thus the actual position of the conversion zone, from the desired position represented by the control signal on line 187. Generate a correction signal.

During playback, the servo circuit 191 receives via line 190 information related to the rotational speed and position of the head wheel 74, and thus the conversion zone of the keeper 78, received from the tachometer mechanism associated with the head wheel motor 76. Servo circuit 191 compares the information received via line 190 with the control signal information reproduced by converter 182 and received via line 189. In response to this comparison, a correction signal is generated on lines 192 and 199. Line 192 applies this received signal to head wheel motor 76 to cause rotation of head wheel 74, and thus acceleration or deceleration of the scan of the conversion zone along the width W of keeper 28. Line 199 provides this received correction signal to motor 194, which controls capstan 193 to correspondingly adjust the feed of tape 80. This control of the capstan 193 and head wheel 74 results in tape 8
It will maintain the alignment of the scanning conversion area at track 97, which extends crossing along 0. Such transducer-to-track control is enhanced by the use of a high resolution tachometer operatively linked to the capstan 193, which provides a high speed signal representative of the tape 143 feed rate. This tachometer signal is provided to servo circuit 191 for comparison with the play reference signal provided on line 196. As a result, a correction signal is generated and provided to motor 194 via line 199 for corresponding control of capstan 193. As is apparent from the above description, the device of FIG. 4 records and reproduces signals along tracks that extend transversely along a longitudinally moving medium in contact with the outer surface of the keeper. Is preferred. The rotating physical gears which effect the formation and movement of the gearless conversion zone do not come into contact with the keeper or the medium, so that such gears are not subject to wear. The wear of the transducer / keeper assembly is reduced to the extent that it is caused by the relatively swaying medium in contact with the smooth outer surface of the fixed gearless keeper.

FIG. 5 shows an embodiment of another wide band high density signal and reproducing apparatus of the present invention. The head wheel of FIG. 4 rotates in a plane substantially perpendicular to the length of the tape motion, while in the embodiment of FIG. 5, the head wheel rotates in a plane substantially parallel to the direction of tape motion. To do. This arrangement is particularly useful when it is desired to record substantially longer tracks on the tape, such as those produced by rotating helical scanning and longitudinal tape recording and reproducing devices.
In the known rotary helical scanning device, the tape is introduced from one side of the drum guide into a helical passage around a cylindrical tape guide drum for scanning by a rotary transducer, which is wound around the drum and the tape is drumed with respect to the exit position. Exit from other locations around the perimeter of the drum at different locations that are axially offset along the surface.

The information signal is recorded on separate parallel tracks that extend along the tape at an angle to the length of the tape.
As a result, a track length that greatly exceeds the width of the tape can be achieved. For a given helical scanning device configuration, the angular orientation of the recorded track is a function of both the tape feed rate around the tape guide drum and the rotational speed of the rotary transducer. Therefore, the resulting angle changes depending on the relative speed of both the rotary transducer and the tape feed. In most helical scanning devices, the transducer is supported by a tape guide drum which is formed by two angularly spaced cylindrical sections, one of which (usually the uppermost one) is rotatable. , Other parts are fixed.

However, the device of FIG. 5 differs significantly from known rotary helical scanning devices in that the physical gears on the transducer core do not contact the tape. Fifth
In the illustrated apparatus, the tape is in contact with a fixed keeper, which in this embodiment is a part of the rotating headwheel so as not to contact the rotating physical gear of the transducer core mounted on the wheel. Located circumferentially about the section and spaced from it.

In FIG. 5, a rotating head wheel 162 is coaxially arranged with a fixed upper drum 160, both of which are made of aluminum or other suitable non-magnetic material. Head wheel 162 has one or more back cores 20 rigidly attached to it and is mounted in a shaft that is rotated by drive motor 99. A portion of this shaft is shown at 161 in FIG. In the apparatus of FIG. 5, core 20 is attached to the lower surface of head wheel 162, for example by epoxy. However, they may be attached to it in any other preferred manner, for example by being inserted into a slot provided on the head wheel and held there by screws or mounting devices. A fixed or stationary lower drum 164 of a non-magnetic material such as aluminum is positioned coaxially with the upper drum 160 and has the same dimensions as the upper drum. The two drums are axially offset from each other so as to define a spacing or slot 166 for the rotating back core 20 between the drums. A keeper 187 of magnetic material, for example Permalloy, Sendust or Amorphous metal, is circumferentially arranged around a portion of the circumference of the drum 160,164 and is rigidly attached thereto, for example by screws. The keeper thickness is preferably selected within the ranges described above for the embodiment of FIG. The keeper 167 is separated from the rotating core 20 in such a way that the rotating core 20 rotates in close contact with (without contacting) the keeper. The core 20 shown in FIG. 5 has a common conversion signal and control winding 168 similar to winding 39 described above in FIG.

Magnetic tape 176 is fed longitudinally 177 around fixed drums 160, 164 and along a helical path extending in physical contact with keeper 167. To ensure intimate contact with the keeper, the tape is guided under tension around the drum by rotating tape guides 190,191.

A rotary transducer is disposed coaxially with the drum assembly and has a rotating upper portion 169 attached to the motor shaft 161 and a stationary upper portion 170. Each rotating back core 20
Winding 168 is attached to a primary winding (not shown) provided on the rotating portion 169 of the rotary transformer. Capacitor 166 is coupled to isolate the signal processing circuitry from the DC bias control circuitry as described above in connection with the embodiment of Figures 2A and 4. During the regenerative mode of operation, the induced signal from the rotating primary winding to a stationary secondary winding (not shown) provided on the stationary or stationary portion 170 of the transformer is the line 126, switch 124 and amplifier. It is given to the reproduction signal processor 118 via 122.
In the recording operation mode, the signal to be recorded is transmitted from the recording signal processor 116 to the amplifier 120, the switch 124 and the line 126.
To the winding 168 via. The slip ring and brush assemblies 88 and 89 are similar to those described above with respect to FIG. 4, and thus their respective descriptions are not repeated with respect to FIG. The slip ring assembly 88 is rotatably coupled with the motor shaft 161 by a shaft extension 174.

As is apparent from the above description of the embodiment of FIG. 2B, when the device of FIG.
The separate flux biasing control current Ic can be omitted as long as sufficient recording current is coupled to the signal windings to saturate the lower gears or transducing zones in the keeper 167.

The apparatus of FIG. 5 is identical to the embodiment described above in connection with FIG. 4, but with the difference that tape 176 is fed in direction 177 through rotating head wheel 162. Fourth
In the illustrated embodiment, the gap 26 defined by the rotating back core 20 scans the tape at an angle substantially perpendicular to the length of the tape 80 and the feed direction. However, the fifth
In the illustrated embodiment, the gear 26 scans the tape 176 at a selected angle as indicated by n with respect to the length of the tape 176 and the feed direction 177, which angle is the recording track 175.
Selected according to the desired length for. As can be seen in FIG. 5, the illustrated embodiment of the invention is a tape 17
This produces a long track 175 of recorded information that extends at a very small angle for a length of 6.

As will be apparent from the above description, like the apparatus of FIG. 4, the embodiment of FIG. 5 is in contact with the outer surface of the keeper without the physical gears to provide approximately the length of the moving tape. It is preferred for recording and reproducing signals along tracks that extend along it. As mentioned above, this contact will set up a persistent path between the tape 176 and the winding 118 for wavelength independent signal information which reduces the effects of spacing losses. Furthermore, the rotating physical gears which form and move the gearless conversion zone do not come into contact with both the keeper and the medium, so that such gears are not subject to wear. The wear of the transducer / keeper assembly is reduced to the extent that it is caused by the relatively dull and progressive medium in contact with the smooth outer surface of the fixed gearless keeper. As mentioned above, one or more large magnetic discontinuities, i.e., portions of substantially different permeability, which are typically imparted to an electromagnetic transducer by including a physical transducing gear. Forming the keeper-less transducing zone in the keeper by making it offers some advantages that cannot be realized with conventional magnetic transducers associated with physical gears for signal transfer on magnetic recording media. The permeability gradient imparts such a discontinuity, and it is most preferred that there is a sharp permeability gradient between the region of the body providing the conversion zone and the adjacent region. The nature of such a gradient and the preferred embodiments for achieving this have been described in more detail above. Such discontinuities are most preferably imparted to the body by having adjacent regions that are magnetically saturated and unsaturated. In addition, the conversion zone can be easily generated and defined in the keeper by the cooperation of the physical gap of the known electromagnetic converter and the bias flux source.

FIG. 6 shows the magnetic permeability m versus magnetic flux density B of the preferred magnetic material for the manufacture of the keeper. As is clear from this property, this material has a large difference in magnetic permeability over a narrow range of magnetic flux density. FIG. 7 shows the effect of saturating the keeper in localized areas. As is apparent from FIGS. 6 and 7, the overall permeability versus magnetic flux density gradient is well known between the saturated region and the adjacent unsaturated region where the signal flux is coupled between the magnetic recording medium and the signal-using device. It is desirable to be as sharp as possible to obtain the defined boundaries.

The reluctance imparted by the keeper to the path of the magnetic flux along the path branching the transducer plays an important role in providing signal control between the magnetic recording medium and the signal-using device. This reluctance is selected in relation to the reluctance of such magnetic flux along the path extending through the operably associated transducer so as to ensure the transmission of the desired information. Relative reluctance refers to material, material thickness, transducer pole face portion size, saturated keeper area portion size in a plane perpendicular to the transducer face, keeper thickness, transducer and recording medium keeper. Is achieved by the selection of an appropriate combination of various characteristics, such as the distance separating the components (if any) and the length, width and depth of the transducer air gear.

While this invention has been shown and described with particular reference to its various embodiments, it will be understood that changes and modifications in form and detail may be made without departing from the spirit and scope of the claims. Should.

Claims (7)

[Claims] 1. A recording / reproducing apparatus for recording / reproducing a signal on / from a magnetic medium, comprising: a magnetic converter having a magnetic core forming a conversion gap; and a magnetic converter placed between the magnetic converter and the magnetic medium and facing the magnetic core. A keeper bridging the conversion gap during recording and reproduction, and means for moving the magnetic converter with respect to the keeper, wherein the magnetic converter supplies magnetic flux to the conversion gap and is located in the keeper. Means for saturating a portion, thereby forming a conversion region in the keeper, further for moving the magnetic transducer with respect to the keeper, and for moving the conversion region in the keeper during recording and reproduction; A signal recording / reproducing apparatus having. 2. The recording / reproducing apparatus according to claim 1, wherein the keeper is stationary. 3. The recording / reproducing apparatus according to claim 1, wherein the magnetic converter rotates with respect to the keeper. 4. A recording / reproducing apparatus according to claim 3, wherein the keeper is formed of a strip of magnetic material having a width equal to or larger than the width of the conversion gap, and the magnetic converter is A recording / reproducing apparatus which rotates without contacting the keeper. 5. The recording / reproducing apparatus according to claim 4, further comprising means for bringing the medium into contact with the keeper and passing the keeper. 6. A recording / reproducing apparatus for recording / reproducing a signal on / from a magnetic medium, comprising: a magnetic converter having a magnetic core forming a conversion gap;
The conversion gap protrudes from the periphery of the rotating member, and is placed at least near a part of the periphery of the rotating member so as to bridge the conversion gap when the magnetic transducer rotates with the rotating member. The magnetic converter supplies a magnetic flux to the conversion gap to saturate a portion of the keeper bridging the conversion gap,
Thereby, a signal recording / reproducing apparatus is formed, which forms a conversion region that moves in the keeper while the converter rotates. 7. The recording / reproducing apparatus according to claim 6, further comprising means for bringing the medium into contact with the keeper and passing the keeper.