JPS5842974A - Detector for direction of rotation - Google Patents

Abstract

PURPOSE:To prevent erroneous detection due to a noise signal and to allow a detection output to respond to a change in direction of rotation speedily, by detecting the direction of rotation on the basis of a rotational speed detection output and a rotational direction switching indication output. CONSTITUTION:An FF58 as a switching signal generating means generates a high-level output by the low-level output of an AND circuit 54 applied with a low-level output, etc., of normal rotation command from a control circuit 53 and a low-level output generated by a rotational speed detector 55 when a rotational speed is less than a specified value. This output of the FF58 never changes even when the output of the detector 55 is inverted to a high level as a result of an increase the rotational speed of a rotating body, thereby detecting normal rotation. Similarly, reverse rotation is detected by a low-level output from the FF58. Because of this constitution, the output of the FF never changes even if the output of the detector 55 oscillates owing to a noise, and the detection output of the FF is inverted at a rise of the detection output of the detector 55 which is nearly at the same timing with inversion in rotational direction to prevent erroneous detection due to a noise signal, thereby allowing the detection output to respond to a change in rotational direction speedily.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotational direction detection device, and more particularly to a device for detecting the rotational direction of, for example, a magnetic recording/reproducing section.

In various rotating mechanisms, it is often necessary to sequentially detect their rotational directions to instruct appropriate operations or to detect rotational direction costs in relation to other mechanisms.

FIG. 1 is a diagram showing an example of a direction detecting device conventionally provided in a capstan section of a magnetic recording/reproducing section. In the figure, the capstan motor is provided with a rotating shaft 3 molded integrally with a capstan 2. As shown in FIG.

A flywheel 4 is integrally attached to this rotating shaft a in order to detect the direction of rotation. Notches 5.5 are formed at a constant pitch on the circumference of the flywheel 4, and a light emitting diode/phototransistor pair 61 is placed facing each other with the flywheel 4 in between at the position where the notches 5.5 pass. Two sets of .71 and 62.72 are arranged. The first light emitting diode 6 phototransistor 71 pair and the second light emitting diode 62/phototransistor 72 pair are in a positional relationship that is shifted by 172e in the circumferential direction with respect to the circumferential angle e of the notch 5. is set up.

FIG. 2 is an electrical circuit diagram of the rotational direction detection device having the above structure, in which a constant voltage (□ power supply terminal 8 and ground − □゛・: via a resistor 9, the first and second light emitting diodes 61.
62 are connected in series. On the other hand, the phototransistors 71 and 72 are respectively pushed into the power supply terminal 8 and the ground part through the resistors 10 and 11, and the output of the first phototransistor 71 is the data terminal 1 of the D-type flip 70 knob 12.
3, the output of the second phototransistor 72 is input to the trigger terminal 14 of the flip 70 tube 1-2.

In the conventional detection device using the O-type flip-flop 12 as described above, when a positive pulse is input to the trigger element 14, if the input to the data terminal 13 is positive, the potential of the output terminal 15 changes. becomes positive, and if the input to the data terminal 13 is 0, the potential of the output terminal 15 becomes O. Furthermore, even if the input pulse to the trigger terminal 14 disappears, the output terminal 1
The potential of No. 5 retains its previous state.

The direction detection operation will be explained. In FIG. 1, when the motor 1 is rotated in a clockwise direction as viewed from the side of the motor 1, the notch 5 of the flywheel 4 passes through the position where the first photo and the lung staff 1 are installed. When the light from the first light emitting diode 61 is incident, the collector voltage of the phototransistor 71 decreases, while the collector voltage increases as the flywheel 4 passes through the flywheel 4 without the notch 5. FIG. 3(a) shows the change in collector voltage of the phototransistor as the phototransistor passes through the notch 5. The collector voltage of the second phototransistor 72 repeats decreases and increases in synchronization with passage of the notch 5 of the flywheel in the same WALL, but the positional relationship with the first phototransistor 71 is at the circumferential angle of the notch. Because it is installed at a position shifted by 1/2e from e, 1. The output waveform 1 of the collector voltage is the third
As shown in Fig. 2b,), the output waveform of the first phototransistor 71 is shifted by 1/4 in phase.

Assuming that the above-mentioned flip 70 knob 12 is designed to operate when the lock signal applied to the trigger terminal 14 changes from a low level to a high level, the clockwise rotation causes the first The phototransistor 7.1 outputs the collector voltage shown in 311I(a), and the second phototransistor 72. is the 311th.
(1)) Output the collector voltage shown in
It is input to input 5 terminals 13, 14 of type flip 4 flop 12, and a high level signal is derived at its output terminal 15, indicating clockwise rotation.

On the other hand, when the flywheel 4 rotates counterclockwise, the collector voltage of the second phototransistor 72 becomes the third
In contrast to the output waveform shown in figure (b),
Derive the output waveforms of ototran and distaff 1 & that are traced back by 1/4 phase as shown in No. 311 (0), and convert the respective output waveforms to DI! It is applied to input terminal 14 and input terminal 13 of flip-flop 12 . As a result, a low level signal is derived from the output terminal 15, and in response to the high level signal indicating the clock and direction, an output indicating the counterclockwise force and direction is generated, and the direction of rotation is detected.

By the way, in the front/rotation direction detection operation, the input signal to the D-type flip-flop 12 is not necessarily applied in a stable waveform as shown in 11% 311, but may be affected by vibrations due to external noise, etc. It is often accompanied by 2-. - Now, while the flywheel 4 is rotating once clockwise, the force signal applied to the trigger terminals 14 of the type 0 flip-flops 1 and 2 is accompanied by noise as shown in No. 411 (a). Assuming that it is applied as a clock signal, the input signal to the data terminal 13 shows the change in bl in FIG. In response to noise in the clock signal that occurs when the data terminal 13 is at a low level, a period in which the output signal is at a low level occurs, resulting in incorrect detection of the rotation direction. To address this drawback, the effects of vibration can be reduced by inserting a capacitor between the trigger terminal 14 and the ground to make the input signal to the trigger terminal 14 have a smooth waveform as shown in Figure 4(d). This is possible, but in such a circuit, the time required to change from low level to high level is longer, and the potential of the output terminal 15 remains at its previous state, just as in the case where there is no input pulse, and the output signal does not change. In particular, the OW flip 70 knob 12 is designed to operate when the signal applied to the trigger hand 14 changes from low level to high level, so if the direction of rotation changes, However, it will not change until the next positive pulse is input to the trigger terminal 14, and it will not be possible to appropriately represent the rotation direction.

” Therefore, the main object of the present invention is to provide a rotational direction detection device that reduces errors in the rotational direction detection operation caused by noise and rise speed associated with input pulse signals, and that increases the rotational direction detection speed. It is to be.

In summary, the present invention provides a rotational speed detection means output for detecting that the rotational speed of a rotating body has become below a certain level, and a rotational direction instruction for generating a signal instructing switching of the rotational direction of the rotating body. The direction of rotation of the rotating body is detected based on the output of the signal generating means.

The above objects and other objects and features of the invention will become more apparent from the following detailed description with reference to the drawings.

FIG. 5 is a schematic block diagram showing one embodiment of the present invention, and particularly shows an embodiment applied to a magnetic recording/reproducing device. In the configuration, the capstan motor 1 is provided with a rotation signal generator 51.

Although not shown, the rotation signal generator 51 includes, for example, a permanent magnet provided on the rotating shaft of the capstan motor 1, a Hall element for detecting the rotation of this permanent magnet, and the like. A rotation signal whose amplitude or period changes accordingly is derived. In addition, this rotation signal is generated! The rotation signal 151 may be configured using a flywheel, a photocoupler, etc., and the rotation signal is given to the servo circuit 52. The servo circuit 52 is
The capstan motor 1 is controlled to rotate at a constant speed by detecting variations in the amplitude or period of the rotation signal. The control 1 port 53 is
Although not shown, it includes, for example, a microcomputer, etc., and switches the mode of the magnetic recording/reproducing device according to signals from a keyboard (!lI not shown), etc., and the I/O of various drive devices.
Perform IJll. The servo circuit 52 is given a command signal a for forward and reverse rotation of the capstan motor 1 from the control circuit 53.

This rotational direction detection signal 8 becomes low level when instructing forward rotation of the capstan motor 1, becomes high level when instructing reverse rotation, and is also applied to one input of AND gate 54.

The rotation signal output from the rotation signal generator 51 is given to a rotation speed detection circuit 55. The rotational speed detection circuit 55 includes, for example, a Schmitt circuit, and detects a decrease in the rotational speed of the capstan motor IQ11 based on the applied rotational signal.

That is, the rotation speed detection path 55 detects when the rotation rate of the capstan motor 1 becomes less than a predetermined value (ideally, 0).
) Outputs a high level signal. The output of the rotation speed output circuit 1155 is the NOR gate 56 and 57.
The signal is applied to one input of a flip-flop 58 formed by the above-mentioned AND gate 54, and the other input of the AND gate 54.

Further, the output 0 of this AND gate 54 is applied to the other input of a 7-lip flop 58. flip flop 58
The output d is taken out from the output terminal 59 as a rotation direction detection signal.

Here, the level relationship between the signals a and b and the signal @d will be explained. When both signals a and b are at high level, signal d is at low level. Furthermore, when the signal a is at a high level and the signal a is at a low level, the flip-flop 58
's output letter remains unchanged.

Believe J! d retains its previous state. Further, when the signal a is at a low level and the signal is at a high level, the signal d is at a high level. When both a and b are at low level, the output state of the flip-flop 58 is not displayed.
Trust@6 maintains its previous state.

FIG. 6 is a time chart for explaining the operation of the embodiment shown in FIG. The operation shown in FIG. 5 will be described below with reference to FIG. 6.

First, assuming that the capstan motor 1 rotates in the normal rotation direction, the signal @a is at a low level, and the signal S is at a high level at the beginning of one rotation.

Therefore, the signal d becomes high level. g of capstan motor 1! @When speed 7 becomes active, the signal becomes 0-
However, the flip-flop 58 does not change the output signal, and the signal d remains at a high level.

Next, as shown in No. 8 al (a), the case where the signal - changes from low level to high level and reverse rotation of the capstan motors 1 and -1 is commanded will be explained.

In this case, the rotational speed of the capstan motor 1 decreases to a predetermined value or less after a short period of time has elapsed since the command for reverse rotation.
1 (b), the signal becomes high level.

At this time, since the signal d is at high level, the signal b&tAN
After passing through the D gate 54, the signal 0 becomes high level as shown in FIG. 6(C).

In this way, since both of the flip 70 knobs 58 are at a high level, the output d is inverted to a low level as shown in FIG. 6(d'). When the rotational speed of the capstan motor 1 in the reverse direction increases and the signal S becomes low level as shown in FIG. ,...force d maintains its previous state, ie, low level.

Next, as shown in FIG. 6(a), the case where the signal @a changes from the high level to the a-level and normal rotation of the capstan motor 1 is commanded will be described.

In this case, as shown in FIG. 6 ('b), the signal also becomes high level from the command for normal rotation. However, since the signal a is at a low level at this time, the signal @C remains at a low level. Therefore, the output d of the flip-flop 58 is inverted to a high level as shown in 6th al(d). Thereafter, the above-described operation is repeated.

Here, assume that the signal is vibrating.

If the signal a is at a low level and the capstan motor 1 is commanded to rotate forward, then the AND gate 54
The output O remains at a low level regardless of the signal level. Therefore, the signal d is kept at high level. Conversely, if signal a is at a high level and the capstan motor 1 is commanded to reverse, the output O of the AND')-t 54 will pass the noise pulses of the signal A. Therefore, the signal 4b and the signal C become high level at the same time, but under this input condition, the output d of the flip-flop 58 maintains the O- level. In this way, the 51st! In the embodiment 1, even if signal bk:wt movement occurs, false detection will not occur as in the conventional case.

Further, in the 511th embodiment, the polarity of the rotation direction detection signal 6 is reversed at the rising edge of the signal @b. The output timing of this signal @b is almost equal to the reversal timing of the rotational direction of the capstan motor 1 (to be exact, the rotational direction of the capstan motor 1 is reversed in the middle of the high level period of the signal), so the capstan motor Reversal of the rotational direction of the motor 1 can be quickly detected.

As described above, according to the present invention, the rotation direction of the n-roller is detected based on the output of the four-roll speed detection means and the output of the switching signal generation means. There is no possibility of false detection due to insufficient amount of food. Further, even when the rotational direction of the rotating body changes, a corresponding detection output can be quickly derived.

[Brief explanation of the drawing]

1al is a diagram showing the external appearance of the rotational direction detection device. No. 2m is a circuit diagram of a conventional rotational direction detection device. FIG. 3 is a waveform diagram of each part of the 2mth circuit. Figure 4 is the 21st
FIG. 1 is a waveform diagram for explaining the operation of am of No. 1; FIG. 5 is a schematic block diagram showing one embodiment of the present invention. FIG. 6 is a waveform diagram for explaining the operation of the embodiment shown in FIG. In the figure, 1 is a capstan motor, 51 is a rotation signal generator, 53 is a control path, 54 is an AND gate, 55 is a rotation speed detector, and 58 is a flip-flop. Agent Shin Kuzuno - (1 other person) 1 20 13 Figure 40 'i45 Tsubo 6

Claims (3)

[Claims] (1) A rotational direction detection device for detecting the rotational direction of a rotating body, comprising: a drive means for rotationally driving the rotating body; and detecting when the rotational speed of the one rolling body becomes below a certain level. a rotational speed estimation means for generating a rotational speed detection means, a rotational direction instruction signal generation means for generating a signal instructing the drive means to switch the rotational direction, and an output of the first rotation detection means and an output of the rotational direction instruction signal generation means. A rotational direction detection device comprising a rotational direction detection means for detecting the first rotation direction of the rotating body based on the above. (2) The rotational direction detection means detects the output of the rotational speed detection means and the first one from the one rotation direction instruction signal generation means.
A first level signal is output in response to an output instructing a rotation direction, and in response to an output from the first rotation speed detecting means and an output instructing a second rotation direction from the rotation direction instruction signal generating means. The rotational direction detection device according to claim 111I, further comprising signal output means for outputting a second level signal. (3) The signal output means includes storage means for storing and retaining its own output state until the output level of the signal output means is reversed and the output of the rotation direction instruction signal generation means is reversed and the output of the rotation detection means is output. , the rotational direction detection device according to claim 2 of the EIS.