JPS5930064A - Speed detector - Google Patents

Abstract

PURPOSE:To enable a highly accurate detection of a transient speed change with a relatively low FG frequency by intermittent feeding of a tape in the reproduction of a VTR for a speed detector designed to enable the realization of a noiseless slow operation stably. CONSTITUTION:An output (a) of an FG amplifier 23 is applied to a Schmitt circuit 34 at a timing tc for starting a brake and positive and negative edges of the output (b) thereof 34 are synthesized via a differentiation circuit to obtain an output (d) through the base of a transistor Q1. When the positive edge of the output (d) is inputted into the output of a transistor Q2, the waveform at the point ''b'' is as shown by (e). On the other hand, when the negative edge of the waveform (d) is inputted into a base of a transistor Q3, the transistor Q3 is conducted at the moment of a load edge and a charge voltage of a capacitor C4 fills a capacitor C6 to be held until the subsequent pulse comes. When the potential of the capacitor C6 is taken out with a buffer transistor Q4, with a resistance R9 being infinite, the output is like a staircase as shown by the solid line in the drawing (f), resulting in a detection errors DELTAt. The detection errors DELTAt can be reduced drastically as shown by the broken line by setting the resistance R9 so as to generate a charge ripple almost equal to the detection ripple DELTAVF in the vicinity of the detection level.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a speed detection device, and more particularly to a speed detection device useful for stably realizing p-noiseless slow motion by intermittent tape feeding during VTR playback. be.

1123 and 2, (1) is the supply reel, (2) is the take-up reel, and (3) is the cassette. The case of (
41i key, (5) is the tension arm, ((1
) is the guide post of the rotating cylinder (8), (7) is the rotating magnetic head, (9) is the control head, QO is the capstan shaft, 00 is the pinch roller, (2) is the capstan DD motor (hereinafter referred to as the motor) ), the flywheel is also replaced with a part of the motor. 01 is directly connected to the motor a, which drives the intermediate roller OFj via the knocker and belt 0◆. , 01 is the guide post,
0η is an intermediate roller, which is located between the intermediate roller Orj and the take-up idler 01 in the case of normal running or fast forwarding. .

In the case of normal running and slow mode, the magnetic tape (4) is driven in the direction of the take-up reel (2) by the capstan shaft 0 (l) and the pinch roller aυ driven by the motor a group, and at the same time, The motor Q rotates the take-up idler 01 via the pulley θ4, the belt 0, the intermediate roller O[9, and the intermediate pulley (17). It is set so that a certain slip torque is generated between the take-up idler 01 and the take-up reel stand OFD, and this slip torque causes υ
, the T-magnetic tape (4) is driven by the cabstan shaft θ (■) and is wound by rotating the take-up reel stand 0 barrel.Next, during playback, the rJI14A tape (4) is intermittently fed. The circuit for performing noiseless throw will be explained. In Fig. 6, (d) is a divider, and the input to this divider is a rotating magnetic head (7) 1.
(Same) 411L head change switching pulse, N'I'' SC is an 80Hz rectangular wave, and if the frequency division ratio of the frequency divider (2) is set to 1/6, for example, it becomes 1/ The output of the divider (d) is delayed for a certain period of time by the mono multi-circuit 1l!8H for timing signal adjustment, and the flip-flop circuit (c) is set. The set output is input to the drive circuit (d) of motor 0'4, which causes the motor to rotate for 0 seconds.
The flow is accelerated.

The outer circumference of the motor's rotor is magnetized at regular intervals, and the rotational speed of the rotor D is detected by the FG detection head (d), and its output is sent to the quick-return yarn of the cab stan via the FG amplifier unit. It is input to the control circuit (goods). The motor (self) rotates due to the nut output of the flip-flop circuit (c). The motor is accelerated during 'r1 in Fig. 8 (a), and when the set speed Ft of the speed system control circuit (c) is reached, the speed control is operated for 1 hour, the rotational speed becomes constant, and the motor sleep current decreases. The magnetic tape (4) is driven by the rotation of the motor Q, which is recorded on the control head (9) and outputs one control signal. The circuit is inputted to trigger the brake monomulti circuit 0 shown in Figure 8, which has a time constant of %Tz after a time delay of I°3. The output of the monomulti circuit (to) is input to the cab stan reversing circuit (11), which generates a reversing torque in the υ drive circuit, and changes the rotational speed of the cab stan Qi 01 from F to F at time T2. Figure 8 (d)
Bring it to a stop state as shown in . On the other hand, by resetting the flip-flop circuit (a) with the delayed output of the mono-multi circuit, the output of the flip-flop circuit becomes zero and the motor drive circuit (d) stops.
@8 The braking period T in Fig. 8 (a) is a long time, and if it is too short as shown by the broken line, the motor 02 will not stop accurately and rotate forward as shown by the broken line in (2). If the motor 04 rotates sluggishly in the direction indicated by the dashed line and does not lengthen as shown by the dashed line, the motor 04 will reverse and stop smoothly.
．． In either case, the magnitude of the noise during the slot becomes unstable.

It is very important to accurately stop motor 4 using the reverse brake at T2, and an example of evaluating the margin of the brake will be explained using Figure 4. The optimum brake described above changes not only with changes in tape speed but also with motor load.

Figure 4 shows a summary of the load fluctuations of the motor 02, including the position of the magnetic tape (4), the take-up idler a1, and the take-up reel stand (
It shows the change in the optimal braking force when the renal slip torque is changed. Slow speed 1/t is 4!
! Set the speed to OB times the 1L normal speed in the slow mode of 4 semi-mode. Brake timing T! IJ-171,
The brake force is changed according to the brake flow III.

First, using a take-up reel stand with a slip torque of 1209 cm between the take-up reel stand 0 and the take-up idler (II), observe the changes in the F-G waveform at the end of winding the magnetic tape (4). The reversal phenomenon (088
(shown by the dashed-dotted line in Figure (d)) begins to occur. -j. r
, when IB is gradually decreased, forward rotation occurs at point (a). Similarly, at point (c) at the beginning of magnetic tape (4),
(d) Measure the point. Next, set the slip torque to 8 0-1
Similarly forward rotation within the range of 70 fOR. By plotting the inversion limit, Figure 4 is obtained. As shown in Fig. 4, the optimum braking force changes very critically depending on tape load and mechanical load fluctuations. Fig. 6 shows l/S at standard speed in 8x mode (long time mode). ) was evaluated in the same way, and the operation timing of the mono multi-circuit H (41θ) was changed as shown in DI8 diagram (e).The speed F2 at the time of slowing is naturally 1. According to IA of ?1, if the brake is applied in reverse mode from low speed, the phenomenon of forward rotation and reversal is unlikely to occur due to variations in mechanical load and tape load, and the brake will be applied stably as shown in Figure 5. I understand.The shaded area shows that whether the magnetic tape (4) is at the end of winding or at the beginning, even if the slip torque is changed from 8O to 150y, the flow of brake 1# is 320 to 500 nlA.
This is an area in which the brakes can be applied stably even when the speed is changed to .

In this way, even with the same mechanism and the same reversing brake, the stability varies greatly depending on the motor speed at which the brake starts to be applied.

Therefore, as shown in FIG. 7, the applicant of the present invention has proposed a brake control circuit that can provide braking stability equivalent to that at 8x speed at the same time when slowing at standard speed. This operation will be explained with reference to FIG. After driving the motor 0 and obtaining the control signal Q → in Figure 8, set the flip-flop circuit (9) with the delayed output of the monomulti (A number) for slow noise Di 14%.
This set output is multiplied by the number of inversion circuits and inputted to the frequency m pressure converter (2), and the motor speed is set to F2 (1/1 of Fl).
8) Set the output Vy of the frequency m pressure converter < it to the operating voltage of the Schmitt circuit (to), and trigger the monomulti circuit (b) with the time constant on the right with the output of the Schmitt circuit example. , the output shown in FIG. 8 (1) is obtained. By resetting the delayed output of the mono multi-circuit (b) and the edge of the flip-flop circuit, the output waveform of the flip-flop circuit 0 becomes the waveform for the period shown in Figure 8C), and thereby Inverting circuits 0:9 operate. According to the above 1III work, when the mechanical load force is added, (T, -L, ) decreases, and when it decreases by 1, (Tz-h) increases, and %T becomes the mechanical load. Due to this correction, the brake operation is greatly improved from the state shown in FIG. 4 to the state shown in FIG. 6, despite the target flK speed. In the above explanation, the detection speed is set to 1 of the standard speed for ease of explanation.
If it is possible to lower the detection speed to 1/8, it is natural that the brake stability region shown by diagonal lines in FIG. 5 will increase.

By the way, in order to stabilize the above-mentioned operation, it is essential to accurately detect the transient changing speed of approximately 8 Figure 6 Iζ), and to facilitate this, F
It is necessary to set the G frequency sufficiently high. That is,
Figure 9 0) shows an enlarged view of the rotational change of the motor CL path at the time of slotting in the standard mode shown in Figure 8 ←).
tn-tc is at a constant speed.If the diameter of the capstan shaft OQ is 11, the standard speed of VHS is 8 B, Fnit/sec.

At normal speed, the rotation speed of the capstan shaft OQ is 8 rp.
If s is υ, the speed setting (F,) at the time of slotting is 0.8 times the normal speed, and the number of FG magnetizations on the outer circumference of the rotor 3D is 86 minus 1z/time, then the FG of 1n-t, The frequency is 860 x 8 x OE ~860Hz, and the brake stability is 1ull f'F-Ill? a>Brake interval T3 is about 2Qnl@, tc, ~[
The change in FG during the period d is shown in Figure 9←).゛.

In this case, if the frequency detector (to) shown in Fig. 7 is used, the output of the frequency-voltage converter () can only be obtained in a stepped manner, and based on the set m pressure of the Schmitt circuit (), the output of (c)
It causes a detection error of it = However, FG
In order to make the frequency sufficiently high, it is necessary to increase the number of magnetized rotors Q9, which is technically difficult and causes a problem of increased costs.

OBJECTS OF THE INVENTION In view of the above points, it is an object of the present invention to provide a speed detection device that can accurately detect transient speed changes at a relatively low FG frequency.

Structure of the Invention To achieve the above object, the speed detecting device of the present invention comprises a converting means for converting the output of a frequency detector into a frequency m pressure, a charging/discharging means for smoothing the output of the φ converting means, The configuration includes a detection means for detecting when the output of the charging/discharging means reaches a predetermined pressure m.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In the first @, C'l is a Schmitt circuit, and this Schmitt circuit example shapes the signal from the FG amplifier (2) into the rectangular wave shown in FIG. 11(b). Note that the first
Figure 1 (a) shows the timing t for starting the brake.
It shows the output waveform of FG amplifier 1+ from c.

The positive edge of the output waveform of the Schmitt circuit O1e shown in FIG.
, a resistor (R1) and a diode (DI), and a capacitor (Cz), a resistor (R8) and a diode (to make a differential luJ path)
By outputting the combined output shown in Figure 11, the combined output shown in Figure 11 is connected to the transistor (Ql) via the resistor (R3).
) and obtain the waveform shown in Figure 11 as the director output (a) of the transistor (0+).The positive edge of this output waveform is connected to the capacitor (C,) and the resistor (Rs) (R6). The transistor (C2) is inputted to the transistor (C2) through the differentiating circuit.
It turns on at the positive edge of the waveform shown in the figure), discharges about m of the capacitor (C4), and is charged with a time constant determined by the capacitor (C4) and resistor (R7) until the next pulse arrives. The waveform at point +)) becomes the waveform shown in FIG. 11 (G). On the other hand, the negative electrode edge of the waveform shown in Figure 11) is
It is input to the pace of the transistor (C3) through the capacitor (C6) and the resistor (Rat) (R@), and at the moment of the negative electrode edge, the transistor (C3) becomes conductive and the capacitor (C4) is charged M. It is charged to (C6) (however, C4>C6) and held until the next pulse comes. By extracting m of the capacitor (C6) with a buffer transistor (C4) with sufficiently large input impedance, the resistance (Re) becomes infinite (oven).
The output waveform at this time has a step-like shape υ shown by the solid line in FIG. If the outputs at point (a) of the first throat are at constant intervals as shown in point 18 ((), and if the resistance (R,) is infinite, the waveform at point (C) will be as shown in Fig. The waveform becomes as shown in c), and the high resistance (R,) is connected between the capacitor (C6) and the electric line [
When inserted into the river, there is a resistance (R9) between the pulses.
and the time constant determined by the capacitor (C1), as shown in Figure 12 ←), and the output of the transistor (C4) has a full ripple waveform as shown in the first step), and the high resistance ( When Ro) is connected between the capacitor (C6) and the ground, a ripple waveform due to discharge as shown in Fig. By setting the resistance (Ro) so that a charge ripple approximately equal to the detection ripple Δyr near the detection level as shown in Fig.
As shown by the broken line in Figure 1), the detection error Δ[ can be significantly reduced. In the above explanation, we will explain the case where the speed decreases, but if the speed increases, we will refer to the discharge direction (Fig. 12 (E)).
It is natural that it will become. A quick look: [The charging and discharging directions are reversed depending on the polarity of the detector. Note that the resistance (R9) is
/ There is a tB east which is set taking into consideration the input impedance of the muffler transistor (C4) and the fI8 current when the transistor (C3) is off.

Advantages of the Invention As described in Section 2, according to the present invention, transiently changing speeds can be detected with high accuracy at a relatively low FG frequency, and its industrial utility value is extremely large.

[Brief explanation of drawings]

Figure 1 is a track plan view of a VTR, Figure 2 is a schematic side view of a VTR, Figure 3 is a waveform diagram of each part of the circuit in the constant time/constant braking system, and Figure 4 is a diagram of the circuit in the constant time/constant braking system. Fig. 5 is an explanatory diagram of the motor stopping accuracy during slow playback in the standard mode of the method, u) Fig. 5 is an explanatory diagram of the motor stopping accuracy during slow playback in the 8x mode of the constant time/constant braking method, and Fig. 6 is an explanatory diagram of the motor stopping accuracy during slow playback in the constant time/constant braking method. Figure 7 is a circuit block diagram of the main parts of the constant braking system. Figure 7 is a circuit block diagram of the improved T-brake control 611 circuit. Figure 8 is a waveform diagram of each part of the circuit shown in Figure 7. Figure 9 is a speed detection circuit. An illustration of the. The first part is a circuit diagram of a speed detection circuit according to an embodiment of the present invention, and FIGS. 11 and 12 are waveform diagrams of various parts of the circuit shown in FIG. 1θ. ■... Schmitt circuit, ←)... Inverting amplifier, (Q
,)~(Q,)...-transistor, (Dl)(crow)-
・・Diode-11 (R1) ~ (Rlt) ・=Resistance,
(C,) ~ (Cs ) -:) :/ Densa agent Yoshihiro Morimoto Figure 1 I Figure 2 Figure 3 (Hef, 2
Fig. 4 → Le (, A1 -I'e (41LA) Fig. 2 Fig. 7 Fig. 1 Fig. 7

Claims (1)

[Claims] 1. F/V converting the output of a frequency detector into frequency and voltage
a conversion means and a charging r for smoothing the output of this FA conversion means.
q means; and a detection means for detecting that the output of the charging/discharging means has reached a predetermined pressure. 2. The charging/discharging means sets its time constant to F at the detection level.
2. The speed detection device according to claim 1, wherein the speed detection device is set to a value that cancels a troublesome value by sampling the −V conversion.