JPH0574201B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to a rotary transformer used in a VTR, and relates to suitable transformer core dimensions and structure that cause less interference between audio and video signals and less transmission loss. . [Background of the Invention] In a multi-channel rotary transformer, for example, the channels found in Japanese Patent Application Laid-Open No. 14615-1980, No. 166726-1983, No. 56918-1988, and Publication No. 31787-1987 In order to suppress crosstalk between coils that transmit signals, there is a method of placing a short-circuit conductor between the coils that transmit signals, or using a short-circuit coil only when in use. This is a case where the number of grooves is 2 to 3, and there is ample space between the grooves, and the distance between the grooves is not narrow, and the distance is not specified. [Object of the Invention] An object of the present invention is to provide a rotary transformer in which audio signals and video signals are less likely to be interfered with, and in which transmission loss is reduced. [Summary of the Invention] The present invention minimizes the rate at which the coupling coefficient of adjacent channels deteriorates due to the short ring when using the short ring effect to suppress crosstalk between channels in a multi-channel rotary transformer. . This takes into account the groove spacing, the arrangement of video channels and audio channels in the core groove, and the turn ratio. [Embodiment of the invention] Various standards for VTR (VHS, β, 8m/m, etc.)
The diameter of the helical scan cylinder used is also standardized, and even if an attempt is made to increase the outer diameter of the built-in rotary transformer, there is a certain limit value depending on the machining accuracy and strength of the cylinder. Furthermore, even if one attempts to reduce the inner diameter of the transformer core, since it is a rotating body, there is a shaft in the center, and a bearing or the like must be installed, and there is a certain limit value as with the outer circumference. As described above, there are various standards for VTRs, and there appears to be no uniformity in the dimensions of the rotating transformer core used.However, from the perspective of the inner diameter/outer diameter ratio, the current inner diameter/outer diameter ratio is A line from 0.25 to 0.3 can be drawn. If this ratio is to be increased and the number of grooves arranged concentrically on the core surface increases (multi-channel formation), the core groove interval will inevitably become smaller. As the core groove spacing becomes smaller, the amount of crosstalk between channels generally increases. Furthermore, when using short-circuited coils in unused channels to suppress crosstalk, adjacent grooves (channels)
The rate at which the coupling coefficient of is reduced increases. Therefore, the groove spacing is 1.2mm for transformer cores with an outer diameter of φ58mm to φ45mm, and the groove spacing is 0.9mm for transformer cores with an outer diameter of φ37mm or less.
It has been experimentally found that by setting the value above , it is possible to suppress the rate of coupling coefficient deterioration when the adjacent channels are shot. The cylinder used in VTRs is generally the first
As shown in FIG. 9, a rotating cylinder 1 integrated with a rotating shaft 4 is rotated by a bearing 5 provided at the center of a fixed cylinder 2. Fixed video and audio recording and reproducing heads 31 and 32 are attached to the outer periphery of the rotating cylinder and are arranged so as to be slightly exposed from the space between them and the fixed cylinder 2. In general, a plurality of magnetic heads used in a VTR are allocated to special heads depending on the intended use, such as video or audio, and are arranged around the outer periphery of the rotating cylinder 1. In the cross-sectional view of FIG. 19, two magnetic heads 3 among these plural heads are shown.
Only 1,32 are listed. The magnetic tape travels while being wound diagonally across a stationary and rotating cylinder, and as the rotating cylinder 1 rotates, the magnetic heads 31 and 32 come into contact across the tape diagonally, and the magnetic tape runs on the magnetic tape. Perform recording and playback. In order to receive and receive signals between the magnetic heads 31 and 32 attached to the outer circumference of the rotary cylinder 1 and the stationary side in this way, rotary transformers 81 and 82 are arranged through a slight gap Gl. There is. The outer diameter of the cylinder φ ₀ of a VHS system VTR is φ 62 mm, and the diameter of the bearing part located at the center is approximately φ 19 mm.
The outer diameters of the flat rotary transformers 81 and 82 for receiving and receiving signals from the channel have the transformer core shape shown in FIG. 6 and the dimensions shown in the tables shown in FIGS. 7 to 9. Another standard VTR for 8m/m tape
The outer diameter of the cylinder φ ₀ is 40 mm, and the dimensions of its bearing part are approximately φ 10 mm. The rotary transformers 81 and 82 used in this are shown in FIG. , and have the dimensions shown in the table of FIG. Comparing the 8mm standard and the VHS standard, in the 8mm standard, the audio signal and video signal are superimposed and the signal system is processed by separating the frequency bands used, whereas in the VHS standard, the audio signal and the video signal are The difference is that the video signals are differentiated and are transmitted by separate channels in the rotating transformer. Therefore, in the VHS standard, it is necessary to provide a dedicated channel for audio signals in addition to the video signal system, so the rotary transformer will have multiple channels. First, an example for an 8mm VTR will be shown. Since the signals transmitted in the rotary transformer include audio signals with low frequency components, it is necessary to suppress the crosstalk between channels to about 40 dB or less. For this purpose, a short ring (short-circuit conductor) is installed in the rotary transformer. It may be necessary to short-circuit the secondary side (fixed side) of the transformer. However, it is well known that there is a phenomenon in which the coupling coefficient of other channels deteriorates due to the short circuit effect. In view of the above, the present invention prototyped rotary transformers of various shapes and found design conditions for rotary transformers in which coupling coefficient deterioration due to short circuit effects is minimized. This will be explained below. A 4-channel type (turns ratio 2:6) rotating transformer with the dimensions shown in the tables of Figs. 10 to 13 is constructed under the same turns ratio, same frequency, and same air gap length Gl, and the combined inductance of each channel is
The Ls coupling coefficient K was compared. However, the state of the secondary side of channels other than the measurement channel is open when a shot ring is present, and short-circuited when there is no shot ring. The result is the first
As shown in Figure 7. In the figure, the horizontal axis is the area S of the concentric annular band, which is the opposing surface between the transformer cores, on both side walls of the coil groove in the ferrite core, which is the main magnetic circuit of each channel. In the case of the table in Figure 10 (Δ symbol), the distance between the grooves is 1.0 even though other channels are short-circuited.
Since the length is more than mm, L and K between the channels are also uniform. Regarding K, generally speaking, the larger the groove diameter is, the closer the groove is located to the outer diameter of the transformer core, the lower the K value tends to be compared to the inner groove channel. In the case of the table in Figure 11 (○ symbol), the shot ring is arranged on TR3, and the track TR2
Since the distance between the grooves of TR3 and TR3 is 0.9mm, the deterioration of K of TR2 is smaller. Furthermore, the track TR4 located on the outer diameter also has a relatively large distance of 1.0mm from the shot ring, so K deterioration is kept low. In the case of the table in Figure 12 (× symbol), TR3 and TR
The distance between the grooves of channel 4 is as small as 0.8 mm, and K is significantly degraded compared to other channels due to the short circuit effect. In the case of the table in Figure 13 (□ symbol), track TR
This is an example of installing a short ring on TR3 and TR5, and TR2, TR3 and TR5.
Since the distance between the grooves between TR3 and TR4, and between TR4 and TR5 is 0.8mm, which is small as in the case of Fig. 12, K of tracks TR4 and TR5 has greatly deteriorated. From the above, when arranging four or more structures in a small-diameter transformer with an outer diameter of 37 mm or less, it is essential that the distance between the grooves be 0.9 mm or more in order to keep the variation in the coupling coefficient between channels small. becomes. An example regarding the VHS standard is shown below. Figure 2,
The size examples shown in the tables of FIGS. 4 and 5 are of a 4 to 5 channel type and do not have a shot ring. A comparison of the combined inductance Ls and the coupling coefficient K of these devices is shown in FIGS. 14 to 16. The conditions were that the measurement frequency (0.5 MHz) was fixed, channels other than the measurement channel were short-circuited on the secondary side of the transformer, and the inter-transformer gap Gl (75 μm) and turns ratio (1:4) were kept constant. Also, the horizontal axis is the area S of both side walls of the coil groove as described above.
And so. In the case of Fig. 2 (Fig. 14), the number of channels is small and the distance between the grooves can be made sufficiently large at 1.4 mm.
The influence of the short circuit effect is hard to appear, and there is no significant deterioration of the coupling coefficient K, but it is located at the outermost diameter.
In the case of TR4, the K value is larger than the others because it is located outside the shorted coil, but it is an example of a relatively small difference in channel spacing. In the case of Fig. 4 (Fig. 15), the number of channels has increased for almost the same external dimensions as Fig. 2, and the distance between the grooves is significantly smaller at 1.125 mm, due to the short circuit effect. , is an example in which the deviation of the coupling coefficient K between channels is increasing. In the case of FIG. 5 (FIG. 16), this is an improved example in which the distance between the grooves is increased to 1.2 mm in order to reduce the deviation of the coupling coefficient K in FIG. 4. The above examples of rotary transformers used in the VHS standard transmit only video signals, but below we will show a type that has audio signal transmission channels on the same magnetic core (further multi-channeled). . In the previous explanation, the relationship between the connected head (a dedicated head is used depending on the usage mode) and the transformer core groove was not fixed, but due to reasons such as multi-channels and large diameter, the usage Since the coupling coefficient changes slightly depending on (such as a secondary side short-circuit state), the following explanation will be made with the type of magnetic head connected to the rotary transformer groove fixed.

〔Effect of the invention〕

(1) As described above, according to the present invention, when the short-circuit conductor and the transformer secondary side are short-circuited and used, the distance between the groove in which the short-circuit coil, etc. is disposed and the adjacent groove is set under the following conditions. By doing so, it is possible to suppress a significant deterioration of the coupling coefficient due to the short circuit effect and to make the coupling coefficient between channels of a multi-channel rotary transformer uniform. (a) When 5 or more grooves are provided on a product with a core outer diameter of 45 mm to 58 mm and a core inner diameter/outer diameter ratio of 0.3 or more, the distance between the grooves is 1.2 or more. (b) When the core outside diameter is φ37mm or less, the core inside diameter/outside diameter ratio is
When installing 4 or more grooves on a product with a diameter of 0.28 or more, the distance between the grooves is 0.9 mm or more. (c) The above-mentioned distance between grooves shall be the distance between the short-circuit conductor and the groove in which the coil or the coil used with the end of the secondary coil short-circuited is placed. (2) In a rotating transformer in which the audio channel and the video channel are arranged on the same core, the transmission loss of the video signal is minimized by arranging the audio channel on the outer diameter and the video channel on the inner diameter.
It becomes possible to obtain high-quality images. Furthermore, the resonance frequency can be set outside the video signal band, and the transmission characteristics between each channel can be made uniform. (3) The channel arranged on the outer diameter side short-circuits the end of the secondary transformer when in use or is adjacent to the groove in which the short-circuit coil and conductor are placed, etc. (1) above.
By taking the distance between the grooves according to , the resonant frequency can be suppressed outside the video band due to the influence of inductance suppression due to the short circuit effect, and the deterioration of the coupling coefficient can be minimized. (4) By making the turns ratio of the audio channel larger than that of the video channel, the combined inductance increases (proportional to the square of the turns ratio), but the transmission band of the audio channel is generally in a lower frequency range than that of the video channel. Therefore, the coupling coefficient can be increased without affecting the transmission characteristics of the audio channel. In terms of crosstalk, there are many factors that deteriorate the coupling coefficient of audio channels due to the need to place short-circuit conductors between audio channels and video channels, but for the reasons mentioned above, increasing the turns ratio can reduce the coupling coefficient. It becomes possible to compensate for the deterioration of

[Brief explanation of drawings]

Figures 1, 3, 6, and 20 are sectional views of main parts of the flat rotary transformer core of the present invention, Figure 2,
Figures 4, 5, 7 to 13 show the core outline,
A table showing groove dimensions, FIGS. 14 to 18 are characteristic diagrams for explaining the present invention, FIG. 19 is a main sectional view of a rotating cylinder, and FIGS. 21 to 23 are a rotating transformer having an audio signal channel. Connection form diagrams with magnetic heads, Figures 24 to 33, Gl = 50 μm,
It is a characteristic diagram showing Ls, LsH, and K in the case of 75 μm turns ratio 1:4 (audio channel 1:6), core outer diameter φ58, and 9 groove arrangement. Gl...Gap length between transformer cores, Ls...Transformer 2
Combined inductance when the magnetic head is not connected as seen from the next side, LsH... Inductance when the magnetic head is connected as seen from the secondary side of the transformer (total inductance), TR... Track (TR1 → Groove No.
Represents 1. ), φin...Core inner diameter dimension, φout...Core outer diameter dimension.

Claims (1)

[Scope of Claims] 1. A primary side transformer connected to a magnetic head and serving as a rotating side, and a secondary side transformer connected to an electric circuit and serving as a stationary side are arranged opposite to each other with a slight gap therebetween, A rotary transformer in which the side and secondary transformers have transformer cores having a plurality of concentric annular grooves, wherein the outer diameters of the transformer cores of the primary transformer and the secondary transformer are in the range of 45 mm to 58 mm, and The transformer core has an inner diameter/outer diameter ratio of 0.3 or more, and has at least one short-circuited conductor short-circuited in the groove of the transformer core, and is adjacent to the groove in which the short-circuit ring is buried. A rotating transformer characterized by having a distance of 1.2 mm or more between the groove and the groove. 2. A primary transformer that is connected to the magnetic head and serves as a rotating side, and a secondary transformer that is connected to an electric circuit and serves as a stationary side are arranged opposite to each other with a slight gap between them, and the primary and secondary transformers However, in a rotating transformer having a transformer core with a plurality of concentric annular grooves, the outer diameters of the transformer cores of the primary transformer and the secondary transformer are in the range of φ45 mm to φ58 mm, and the inner diameter/outer diameter of the transformer core is in the range of φ45 mm to φ58 mm. The transformer has a diameter ratio of 0.3 or more, a coil embedded in the transformer core groove of the secondary transformer is connected to an electric circuit, and has at least one short-circuit coil whose ends are short-circuited on the electric circuit side. , A rotary transformer characterized in that the distance between the groove in which the short circuit coil is buried and an adjacent groove is 1.2 mm or more. 3. Two audio signal coils for transmitting audio signals and a plurality of video signal coils for transmitting video signals are embedded in a groove on the same transformer core, and between the two audio signal coils and between the audio signal coil and the video signal. 3. The rotary transformer according to claim 1, wherein the short circuit ring or the short circuit coil is arranged in a groove between the signal coils. 4. A primary side transformer connected to the magnetic head and serving as a rotating side, and a secondary side transformer connected to an electric circuit and serving as a stationary side, are arranged opposite to each other with a slight gap between them, and the primary side transformer and the secondary side transformer However, in a rotating transformer having a transformer core with a plurality of concentric annular grooves, the outer diameters of the transformer cores of the primary transformer and the secondary transformer are in the range of φ45 mm to φ58 mm, and the inner diameter/outer diameter of the transformer core is in the range of φ45 mm to φ58 mm. The transformer has a diameter ratio of 0.3 or more, a coil embedded in the transformer core groove of the secondary transformer is connected to an electric circuit, and has at least one short-circuit coil whose ends are short-circuited on the electric circuit side. , A rotary transformer characterized in that the short circuit coil is arranged in the outermost groove. 5. A primary transformer that is connected to the magnetic head and serves as a rotating side, and a secondary transformer that is connected to an electric circuit and serves as a stationary side are arranged opposite to each other with a slight gap between them, and the primary and secondary transformers However, in a rotating transformer having a transformer core with a plurality of concentric annular grooves, the outer diameters of the transformer cores of the primary transformer and the secondary transformer are in the range of φ45 mm to φ58 mm, and the inner diameter/outer diameter of the transformer core is in the range of φ45 mm to φ58 mm. a diameter ratio of 0.3 or more, the audio signal coil transmitting the audio signal and the video signal coil transmitting the video signal; A rotary transformer characterized in that (secondary side/primary side) the audio signal coil is larger than the video signal coil. 6. A primary side transformer connected to the magnetic head and serving as a rotating side, and a secondary side transformer connected to an electric circuit and serving as a stationary side, are arranged opposite to each other with a slight gap between them, and the primary side and secondary side transformers However, in a rotating transformer having a transformer core with a plurality of concentric annular grooves, the outer diameters of the transformer cores of the primary transformer and the secondary transformer are in the range of φ45 mm to φ58 mm, and the inner diameter/outer diameter of the transformer core is in the range of φ45 mm to φ58 mm. A rotary transformer having a diameter ratio of 0.3 or more, comprising the audio signal coil and the video signal coil, which are disposed in a groove on the outer periphery of the audio signal coil and the video signal coil. 7. A primary transformer that is connected to the magnetic head and serves as a rotating side, and a secondary transformer that is connected to an electric circuit and serves as a stationary side are arranged opposite to each other with a slight gap between them, and the primary and secondary transformers However, in a rotary transformer having a transformer core with a plurality of concentric annular grooves, the outer diameter of the transformer cores of the primary transformer and the secondary transformer is φ37 mm or less, and the inner diameter/outer diameter ratio of the transformer core is 0.28 or more, and has at least one shot ring that is a conductor that is buried in the groove of the transformer core and short-circuited in advance, and the distance between the groove in which the short ring is buried and an adjacent groove is 0.9 mm or more. A rotating transformer characterized by having.