JPH0560182B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a rotating head type magnetic recording/reproducing device, which controls the rotational speed of the head and the tape running speed when the tape is running at high speed, thereby adjusting the relative speed between the head and the tape. This invention relates to a relative speed control device for keeping the speed constant.

(2) Technical Background of the Invention In recent years, the recording density of tapes used in rotating head type magnetic recording and reproducing devices has improved, and many programs are often recorded on the same tape.
Therefore, it is necessary to search for programs. Rotating head VTRs have a dedicated track for searching recorded programs.
A method of recording address signals here to search and edit programs is widely used for business purposes. However, since the tape width of home-use VTRs is narrow, it is not desirable to provide a dedicated track for program retrieval from the standpoint of tape usage efficiency, and furthermore, a fixed head must be provided for this purpose, which increases costs. Therefore, the address signal is recorded on the video track together with the main signal without providing a dedicated track. In this case, a digitally encoded address signal is recorded at a predetermined position for each video track.

When reproducing a digital signal recorded at high density, the rising and falling edges of the reproduced waveform are generally inclined, and the peak position thereof is shifted due to intersymbol interference. Therefore, after waveform equalization is performed, a pit clock is generated by the PLL circuit.
The digital signal is reproduced and demodulated by this bit clock. In this case, if the relative speed between the tape and the head (hereinafter referred to as relative speed) changes, the frequency characteristics of the waveform equalization circuit and the capture range and lock range of the PLL circuit must be changed accordingly. For this reason, the relative speed needs to be approximately constant. Furthermore, in order to search for programs at high speed, it is necessary to read address signals recorded on the tape while running the tape at a higher speed than when recording. However, when the tape is run at a higher speed than during recording, if the rotational speed of the drum and the inclination angle of the drum relative to the tape are constant, the relative speed is different from that during recording and the address signal cannot be stably read. Therefore, it is necessary to keep the relative speed constant for reading the address signal. Program searches are performed by running the tape at high speed in either the forward or reverse direction, and the relative speed ratio in the forward and reverse directions is several times higher.

Furthermore, if there is no track dedicated to program search, there is a problem that the dedicated track cannot be used for speed detection necessary to keep the tape running speed constant. In other words, if there is a track dedicated to program search, it has a fixed head for that purpose, so a tape running speed signal can be obtained from this head, and the running speed can be controlled and kept constant using this signal. Without a dedicated search track, speed detection must be performed by other means.

(3) Purpose of the Invention The present invention provides a rotating head magnetic recording/reproducing device in which when a tape without a dedicated track such as an address signal is run at high speed during playback, the relative velocity can be easily adjusted by controlling the speeds of the head and tape. The purpose of the present invention is to provide a relative speed control device for keeping the speed constant.

(4) Summary of the invention A drum motor that, when a tape is run at n times the standard speed during playback, has a constant relative speed with respect to the tape running speed and direction setting signal, which is the same as at the standard speed. The rotational speed N _o is N _o = A・n+B (A, B are constants, n is the ratio of high speed running speed/standard running speed, and the polarity of n is positive when the tape running direction is forward, and reverse direction. The voltage proportional to this calculation result is used as a reference voltage to control the drum motor.Next, the rotation speed N _o of the drum motor is detected, and this rotation speed is
At N _o, calculate the formula M _o = -C/N _o + D (C and D are constants), and calculate the M _o that should be obtained when the tape running speed is necessary to maintain a constant relative speed (when the head moves once). Find the number of tracks crossed during tracing, and use the voltage proportional to this M _o as the reference voltage.
This is a relative speed control device for a magnetic recording/reproducing device that compares the voltage proportional to the number of tracks crossed by the head and detects it when the tape is actually running, and runs the tape at a constant speed based on the comparison result to maintain a constant relative speed.

(5) Embodiments of the Invention A case will be described in which the present invention is applied to a rotating two-head type magnetic recording/reproducing device. FIG. 2 shows a rotating drum section used in the magnetic recording/reproducing apparatus of this embodiment, where 1 is a rotating drum, and 2A and 2B are rotating drums 1 and 2.
The heads 3A and 3B, each having a different azimuth angle, are attached to the drum 1 at an angular interval of 180° using magnets having mutually different polarities. 4 is a drum PU head (drum pick up head) which alternately outputs positive and negative drum pulses every half rotation of the drum 1 when the magnet 3A or 3B approaches. 5 is drum 1 with tape
It is wrapped around the circumference over an angular range slightly more than 90°. Therefore, the main signal to be recorded during one rotation of the drum 1 is time-compressed and recorded on two tracks. As described above, as shown in FIG. 3, the length L ₁ , width T _w ,
Tracks with an inclination θ ₁ are recorded side by side in the track width direction.

FIG. 1 shows a block diagram of an embodiment of the control device of the present invention. In the figure, 10 is an input terminal for a tape running speed setting signal, 11 is an input terminal for a tape running direction setting signal, and 12 is a predetermined calculation based on the tape running speed and direction setting signal to determine the number of rotations of the drum 1. a first arithmetic circuit that determines the rotation speed and generates a reference voltage corresponding to the rotation speed; 13 is a drum rotation control circuit; 14 is a drum motor drive circuit;
5 is a drum motor; 16 is a drum FG (drum frequency generator) for detecting the rotation speed of the rotating drum 1; 17 is a drum FF (drum flip-flop) that is set and reset by drum pulses; 18 is a drum motor; is a switch that is switched by the output of the drum FF 17 and selects and derives the playback output of the head 2A or 2B, 19 is a playback amplifier, 20 is a waveform shaping circuit that shapes the waveform of the output of the playback amplifier 19, and 21 is a waveform shaping circuit. A counting circuit 22 counts the output pulses of the circuit 20 in units of output periods of the drum FF 17 and outputs a voltage corresponding to the counted value, and 22 performs a predetermined calculation based on the output of the drum FG 16, that is, the rotation speed of the drum motor. 23 is a tape running control circuit, 24 is a reel motor drive circuit, and 25 is a reel motor.

With the above configuration, when the tape running speed and direction are arbitrarily set and respective setting signals are applied to the input terminals 10 and 11, the head is set at a constant relative speed with respect to the set tape running speed and direction signal. The drum motor 15 rotates so that. (The constant relative speed is the relative speed during recording.) On the other hand, the tape is run by detecting the actual rotational speed of the drum motor 15 and using a voltage based on this detected voltage as a reference voltage. A detailed explanation will be given below with reference to FIG.

A tape running speed setting signal and a direction setting signal are input to input terminals 10 and 11, respectively. n of the running speed of the tape during recording (hereinafter referred to as standard speed)
When running at double speed, the tape running speed setting signal is a signal corresponding to the absolute value of n, and the tape running direction setting signal is a signal corresponding to the polarity of n. These setting signals are input to the first arithmetic circuit 12, and the first arithmetic circuit 12 uses the following formula _No = A・n+B (1) (Here, _No is the number of rotations of the drum motor and the subscript is (n indicates the tape speed n times. A and B are constants.) The number of rotations of the drum motor 15 is calculated from the equation (n indicates the tape speed n times), and a voltage proportional to this number of rotations is generated as a reference voltage. The reference voltage is applied to the drum rotation control circuit 1.
3 and the drum motor drive circuit 14 to rotate the drum motor 15. The rotation direction of the drum motor 15 is set so that it rotates in the same direction regardless of whether the tape is running in the forward or reverse direction.
If the running direction of the tape is the same as during recording and the polarity of n is positive, the rotational speed N _o of the drum motor 15 increases,
In the opposite direction, if the polarity of n is negative, it decreases.

The drum FG 16 detects the rotation speed of the drum motor 15 and generates a voltage proportional to the rotation speed. The drum rotation control circuit 13 receives the reference voltage that is the output of the first arithmetic circuit 12 and the output of the drum FG16, and converts the output of the drum FG16 into a frequency -
After the voltages are exchanged, the difference voltage is compared with the reference voltage and is outputted and applied to the drum motor drive circuit 14, so that the drum motor 15 stably rotates at the rotational speed N _o . The output of the drum FG 16, that is, the rotation speed N _o of the drum motor 15 is determined by the second calculation circuit 22.
is input, and one head traces the tape once according to the following formula M _o = -C (1/N _o ) + D ... (2) (where C and D are constants). Calculate the number of tracks M _o that crosses between them.

If the tape is at standard speed, the heads will trace on the same track and will not cross other tracks. FIG. 4 shows the trajectory traced by the head when the tape runs at high speed in the forward and reverse directions. In the figure, a shows a case in which the tape runs at high speed in the forward direction, and b shows a case in which the tape runs at high speed in the reverse direction, both of which traverse a plurality of tracks. As is clear from this, if the number of tracks traversed by the head during one trace of the tape is always constant, then the tape is running at a constant speed.

Equations (1) and (2) will be described in detail later, but the number of tracks M _o that the head traverses and the drum motor 15
When the rotational speed N _o of is related by equation (2), the relative speed between the head and the tape is equal to the relative speed at the standard tape speed.

The second arithmetic circuit 22 receives the actual rotational speed of the drum motor 15 and calculates the number of tracks M _o by calculating equation (2).
Then, a reference voltage proportional to this number of tracks is generated. The polarity of this voltage is positive if the tape running direction is forward, that is, the drum motor 15 rotates faster than during recording, and negative if the tape runs in the reverse direction, that is, the drum motor 15 rotates slower than during recording.

On the other hand, a drum pulse synchronized with the rotation of the drum as shown in FIG. 5a is detected from the drum PU head. One period of this drum pulse is equal to one revolution of the drum, and also equal to one revolution of the drum motor 15. The drum pulse is input to drum FF17,
The drum FF17 outputs the pulse shown in b in the figure. The output of the drum FF 17 acts on the switch 18, and when the output is at a high level, the playback output of the head 2A that is tracing the tape at that time is derived and input to the playback amplifier 19, which outputs the output from the drum FF17.
When the output of the FF 17 is at a low level, the playback output of the head 2B that is tracing the tape at that time is derived and input to the playback amplifier. Figure c shows the output of the playback amplifier 19 while the drum makes one-half rotation, but since the tape is wrapped around the drum over an angular range of about 90 degrees, the output of the playback amplifier is the same as the drum's output. It outputs a voltage with the waveform shown in the figure only during a quarter rotation period. This output results from the head traversing the track. The tracks are recorded alternately by heads 2A and 2B with different azimuth angles, so when head 2A (or head 2B) crosses a track, every other track has the same azimuth angle as head 2A (or head 2B). It is in. The peak portions of the output waveform of the reproducing amplifier in the figure are outputs from tracks with matching azimuth angles, and the valley portions are outputs from tracks with mismatched azimuth angles. Therefore, the number of mountains is half the number of tracks traversed.

The playback output from the head 2A or head 2B amplified by the playback amplifier 19 is sent to the waveform shaping circuit 2.
It is input to 0. The waveform shaping circuit 20 slices the waveform shown in FIG. 5c at an appropriate level, shapes it into a rectangular wave, and outputs the pulse shown in FIG. 5d. The counting circuit 21 receives the output of the drum FF shown in FIG. 5b and the output of the waveform shaping circuit shown in FIG. 5d. The coefficient circuit 21 counts the output pulses of the waveform shaping circuit 20 in units of 1/2 rotation period of the drum, which is the output of the drum FF 17, and after counting is completed, holds and outputs a voltage proportional to the counted value, and performs counting. The result will be reset. During the next 1/2 rotation period of the drum, the counting circuit newly counts the output pulses of the waveform shaping circuit 20 and holds a voltage proportional to the counted value, but immediately before that, the output voltage held in the previous period is The hold is released.
As described above, the output voltage of the counting circuit 21 is a voltage proportional to the number of peaks of the head reproduction output that occur during one-quarter rotation of the drum, and as the number of peaks increases,
That is, when the tape runs at high speed (forward or reverse), the output voltage of the counting circuit 21 increases.

The tape running control circuit 23 receives the output of the counting circuit 21, the output of the second arithmetic circuit 22, and a tape running direction setting signal. Second arithmetic circuit 22
The output of is calculated by formula (2) as the number of tracks M _o that the head crosses while tracing the tape once when the tape is running at high speed while keeping the relative speed constant. The output is approximately one-half the number of tracks actually traversed by the head, and the tape running direction setting signal indicates the direction in which the tape should run. Tape running control circuit 23
halves the output of the second arithmetic circuit 22 and uses this as the reference voltage for the tape running speed. If the tape running direction is the opposite direction, the result of equation (2) is negative, so the polarity is reversed by the tape running direction setting signal and used as the reference voltage. The output of the counting circuit 21 is compared with the reference voltage, and the difference voltage is output from the tape running control circuit 22. This output passes through the reel motor drive circuit 24 and controls the reel motor 25. The tape is therefore run at a constant speed. The tape running direction setting direction is input to the reel motor drive circuit 24, and the rotation direction of the reel motor 25 is inputted to the reel motor drive circuit 24.
In other words, the tape running direction is controlled.

When running the tape at n times the standard speed as described above, set the rotation speed N o of the drum motor such that the relative speed becomes the same constant relative speed as at the standard speed with respect to the set tape speed and _direction . (1)
Calculate using the formula, control the drum motor to achieve this rotation speed, and use the actually detected drum motor rotation speed N _o to calculate equation (2), and when the drum motor rotation speed N _o , calculate M _o (the number of tracks the head crosses during one trace) obtained when the tape running speed should be a constant relative velocity, and calculate the calculated M _o and the number of tracks actually detected by tape running. This comparison results in a constant tape running speed and a constant relative speed. The basic equations (1) and (2) will be explained below. The following symbols are used in this explanation:

D: Diameter of the drum φ: Wrapping angle of the tape θ _o : Angle of the trace trajectory of the head relative to the tape V _o : Tape running speed N _o : Number of rotations of the drum V _o : Relative speed W: Tape effective width Note that the subscript n is a multiple of standard speed. That is, n=1 is when the vehicle is at standard speed, and n=0 is when the vehicle is stopped. The polarity of n is positive when the tape is running in the forward direction, and negative when it is running in the reverse direction.

Figure 6 shows the tape, H ₀ and H _o are the trajectories traced by the head, H ₀ is when the tape is stopped,
H _o is the case when the tape runs at n times the speed. H ₀
The length L ₀ is L ₀ =φ/2ππD=φD/2π (3). When the tape is running at n times the speed, the _{distance lo} that the tape travels while the drum rotates φ/2π is _lo = φ/2π・V _o /N _o (4), and H _o The length L _o is L _o =√( _{0 0} − _o ) ² + ² …(5). The head traces the length L _o of equation (5) at a rotational speed of N _o , but the time required for tracing is φ/2πN _o , so the relative speed v _o is v _o = L _o 2πN _o /φ... (6), and as is clear from the figure, W=L ₀ cosθ ₀ …(7). The rotation speed N _o of the drum is determined from the above equations (3) to (7) as follows: N _o =V _o cosθ ₀ +√v _o ² −(V _o sinθ ₀ ) ² /πD (8). Here, if the relative velocity v _o is the same as the relative velocity v ₁ at standard speed, then with v _o = v ₁ , N _o = V _o cosθ ₀ +√v ₁ ² − (V _o sinθ ₀ ) ² /πD... (9) becomes. V _o is n times the standard speed, and even when the tape is running at high speed, the relative velocity v ₁ is large compared to the tape running speed, and θ ₀ is usually about 6. Therefore, equation (9) is N It can be approximated by _o ≒V ₁ cosθ ₀ /πDn+v ₁ /πD (10).

On the other hand, when k heads are attached to the drum at equal intervals, each track records one track per V ₁ /kN ₁ in the length direction of the tape, so when the tape runs at high speed, it rotates at N _o . The number of tracks M _o that the drum crosses while rotating φ/2π is M _o = (l _o −l ₁ )kN ₁ /V ₁ = kφ(nN ₁ −N _o )/2πN _o …(1
1), so by substituting n obtained from equation (10) into equation (11), we get M _o = −kφN ₁ v ₁ /2πV ₁ cosθ ₀・1/N _o +kφ(πDN ₁ −
V ₁ cosθ ₀ )/2πV ₁ cosθ ₀ (12).

In equations (10) and (12), everything other than n and _No are constants, so equations (10) and (12) are N _o =A・n+B...(13) M _o = -C (1/N _o ) +D...(14) These are the equations (1) and (2) above.

As mentioned above, equation (13) can be used to
When traveling at high speed in the opposite direction, keep the relative speed constant.
The number of rotations of the drum motor required to make v ₁ is N _o , and equation (14) is the number of tracks crossed by the head corresponding to the speed at which the tape should run when the number of drum rotations is N _o . , (13) and (14), if the drum motor and tape running speed are controlled,
The tape can run at high speed at a constant speed, and the relative speed can be constant for each value of n.

Note that since the running speed of the tape is detected as a digital value called the number of tracks crossed by the head, (14)
Although there is an error in comparison with the calculation result obtained by the formula, in general, program search is performed at high speed, and the number of tracks traversed by the head is large, so the above-mentioned error does not pose a problem in practice.

Note that in this embodiment, the relative speed is set to be the relative speed v ₁ at the standard speed, but the relative speed may be determined arbitrarily.

In the embodiment shown in FIG. 1, the tape running speed setting signal and the tape running direction setting signal are input to the input terminals 10 and 11, respectively, and are input to the first arithmetic circuit 12. The setting signal may be input only to the input terminal 10 with the polarity of the running direction attached. In this case, if the tape running direction setting signal is separated and extracted from the input terminal 10 and applied to the tape running control circuit 23 and the reel motor drive circuit 24, the input terminal 11 can be omitted.

Further, the second arithmetic circuit 22 outputs positive and negative voltages according to equation (2), but if the absolute value of this voltage is output from the second arithmetic circuit 22, tape running control can be performed. The tape running direction setting signal applied to circuit 23 can be omitted.

(6) Effects of the Invention According to the present invention, when the tape is run at high speed during playback, the drum motor is controlled using the calculation result based on the tape running speed and the direction setting signal as a reference voltage, and the drum motor is controlled at a speed corresponding to the rotational speed of the drum motor. The reel motor is controlled using the calculation result based on the detected voltage as a reference voltage, and the tape running speed is detected based on the number of tracks crossed by the head, so the relative speed can be kept constant with a simple method, and a special speed detection method can be used. The tape can be made to run at a constant speed without providing any means.

[Brief explanation of the drawing]

FIG. 1 is an embodiment of the present invention, FIG. 2 is a rotating drum section used to explain this embodiment, FIG. 3 is a recording track diagram used to explain this embodiment, and FIG. 4 is a diagram of this embodiment. FIG. 5 is a waveform diagram of each part used to explain this embodiment, and FIG. 6 is an explanatory diagram of the principle of the present invention. 12: First arithmetic circuit, 13: Drum rotation control section, 14: Drum motor drive circuit, 15: Drum motor, 16: Drum FG, 17: Drum FF, 1
8: switch, 19: playback amplifier, 20: waveform shaping circuit, 21: counting circuit, 22: second arithmetic circuit, 23: tape running control circuit, 24: reel motor drive circuit, 25: reel motor.

Claims (1)

[Claims] 1. Input means for inputting a tape running speed setting signal and a tape running direction setting signal, and based on the signals obtained from this input means, N _o = A · n + B (A and B are constants, n is a high speed The ratio of running speed/standard running speed, and the polarity of n is positive when the tape is running in the forward direction and negative when it is in the reverse direction), and the drum motor rotation speed N based on this calculation result. means for generating a first reference voltage proportional to _o ;
A driving means for driving the drum motor by the output of the reference voltage generating means, a detecting means for detecting the rotational speed N _o of the drum motor, and a rotational speed N _o of the drum motor obtained from this detecting means, M _o = −
A means for generating _a second reference voltage proportional to the number of tracks M _o that the head crosses based on the result of this calculation, and counting the number of tracks that the head actually crosses. a generating means for generating a voltage proportional to the counted value; a comparing means for comparing the output voltage of the generating means with the absolute value of the output voltage of the second reference voltage generating means; A drive means for driving the reel motor by the output and the tape running direction setting signal,
A relative speed control device for a magnetic recording/reproducing device, characterized in that a tape is run at a constant speed to always obtain a constant relative speed. 2. The comparison means determines that when the output of the second reference voltage generation means is a voltage proportional to the absolute value of the calculation result of the formula M _o =-C/N _o +D, the head actually crosses this voltage. 2. A relative speed control device for a magnetic recording/reproducing device according to claim 1, characterized in that it is a comparison means for comparing a voltage proportional to a count value of the number of tracks.