JPS6270765A - Apparatus for detecting low speed rotation of rotary body - Google Patents

Abstract

PURPOSE:To make it possible to detect the low speed rotation of a rotary body, by a simple apparatus constitution such that a frequency dividing circuit dividing the frequency of a reference signal or a count circuit is provided and reset on the basis of the signal corresponding to the rotational speed of the rotary body. CONSTITUTION:When a motor 12 steadily rotates at a prescribed rotational speed, the signal FG outputted from the output terminal 32 of a FG (frequency generator) synchronizing circuit 28 has the same frequency as the reference signal REF outputted from the output terminal 38 of a reference signal generator 34 and also coincides with said reference signal in a phase. Therefore, the initial stage FF1 of a low speed operation detecting circuit 40 is ready to count the signal REF but cleared each time. Hereupon, FF1-FF4 hold an initial state and a low speed rotation detecting signal is not outputted to the output terminal 44 of the low speed rotation detecting circuit 40. When the rotational speed of the motor 12 is lowered, the cycle of the frequency signal generated from FG24 becomes long and the cycle of the signal FG outputted by the circuit 28 also becomes long. Then, FF1-FF3 of the circuit 40 count the signal REF corresponding to the length of the cycle of the signal FG.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a low-speed rotation detection device for a rotating body such as a motor.

Background: Technology Electric motors are widely used in a variety of mechanical devices. For example, there are many devices, such as the magnetic disk device 4, in which a motor that rotates a magnetic disk must be constantly rotated at a constant speed. These include not only magnetic disk drives for data processing, but also motors used in electronic still camera systems, for example.

As is well known, an electronic still camera system uses an imaging device such as a solid-state imaging device or an imaging cap, and a recording device δ that uses a small-diameter magnetic disk that is inexpensive and has a relatively large storage capacity as a recording medium, that is, a video floppy. This method involves rectangular alignment, photographing the subject purely electronically, and recording the video signal on a magnetic disk. The recorded video is read out by a separate reproducing device and reproduced as a soft copy on a single resolution image monitor device, or reproduced as a hard copy on an image recording medium such as stamp paper by a hard copy forming device.

A motor used in a video recording device such as a camera in an electronic still camera system or a +Ir generation device rotates a magnetic disk at a predetermined speed, for example, at 3 eoo revolutions per minute. In order to accurately record and reproduce video signals, the magnetic disk drive motor must maintain this constant rotation speed, and such drive motors require a mechanism to detect when the motor has stopped. For example, when an electric brake means is applied to stop the motor F, the brake means must be released by detecting low speed rotation of the motor. In addition, it is necessary to transmit the stopping of the motor to the control circuit of the device to control the restarter of the device. Therefore, there is a need for a low-speed rotation detection device that detects a decrease in the rotational speed of the motor.

Conventionally, for example, in a motor system that has a frequency generator that generates a frequency signal corresponding to the rotational speed of the motor, that is, a tacho generator, there has been a device that measures the period of this frequency signal to detect low-speed rotation of the motor. . In this type of device, for example, the period of the frequency signal from the motor is measured using a reference tarok signal that occurs at a predetermined frequency higher than the frequency signal from the motor, and the period of the frequency signal from the motor is measured.
゛Low speed rotation was detected by comparing it with the limit value. Therefore, this method requires many circuits such as a counting circuit, a decoder, and a comparison circuit, which makes the device configuration complicated.

/' Purpose It is an object of the present invention to provide a low-speed rotation detection device that can eliminate the drawbacks of the prior art and can detect low-speed rotation of a rotating body with a simple device configuration.

DISCLOSURE OF THE INVENTION The low-speed rotation detection device for a rotating body according to the present invention includes a reference signal generating means for generating a reference signal of a predetermined frequency, and a frequency signal having a frequency corresponding to the rotational speed of the rotating body to detect an initial state. The 1 frequency divider circuit receives the reference signal and outputs the divided output without being reset, so that the divided output can be used to reduce the frequency of the rotating body at low speed. This is used as a rotation detection signal.

DESCRIPTION OF EMBODIMENTS Next, embodiments of a low-speed rotation detection device for a rotating body according to the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, there is shown an embodiment in which the present invention is applied to a motor control system that steadily rotates a magnetic disk such as a video floppy at a predetermined rotational speed. In this embodiment, the magnetic disk IO is connected to an electric motor (M) 1
It is detachably attached to the output shaft 14 of No. 2. A magnetic head 18 is in sliding contact with the recording surface 16 of the magnetic disk 10 . The magnetic disk IO is constantly rotated by a motor 12 at a predetermined speed. Signal line 2 connected to magnetic head 1
For example, a signal such as a video signal is supplied to the recording surface 1 of the magnetic disk 10 by the magnetic head 1 day.
It is predicted to be 6. Alternatively, the signal recorded on the recording surface 16 is read out to the signal line 20 through the magnetic head 18.

The motor 12 is connected to a motor control circuit 22 through a drive line 21, and the motor control circuit 22 drives the motor 12 and controls it to rotate steadily at a predetermined rotation speed. Output of motor 12! 14, a frequency generator (FC) that generates a frequency signal whose frequency corresponds to its rotation speed;
24 are connected. The frequency signal output 26 is FG
It is connected to the synchronization circuit 28.

The FG synchronization circuit 26 is a circuit that shapes the waveform of the frequency signal received from the input 26 and outputs a rectangular wave having a predetermined pulse width and a phase synchronized with the reference signal received from the clock input 30 to the output 32 as a signal FC. be. Therefore, the signal F
The period of G depends on that of the frequency signal generated by the frequency generator 24, and its phase depends on the input 3 from the reference signal generator 34.
It is synchronized with that of the reference signal that is set to 0.

This device includes a reference signal generator 34, which includes an oscillation circuit, such as a crystal oscillator, that generates a relatively stable frequency signal, and a crystallization of this frequency signal to create a reference signal necessary for the device. It has a frequency dividing circuit. These reference signals are passed from output 30 to FC synchronization circuit 28 and from output 36 to FC synchronization circuit 28.
The signal is supplied from the output 38 to the motor control circuit 22, and from the output 38 to the toggle input CK of the first-stage clip-flop FFI of the low-speed rotation detection circuit 40. As shown in Figure 2,
The reference signal REF supplied by the reference signal generator 34 to the toggle input 38 of the flip-flop FFI has the same repetition frequency as the signal FC, and the signal FC has the same repetition frequency as the reference value q RE
F so that it is synchronized with F, i.e. occurs in the same phase.
The phase is adjusted by the C synchronization circuit 28.

In this embodiment, the low-speed rotation detection circuit 40 has the following functions as shown in the figure.
4 so that when the rotation speed of the motor 12 becomes low F below the specified 178, a low speed rotation detection signal is output to the output 44.
four cascaded toggle (T) type flip-flops F
It is composed of Fl-FF4. clip flop FF
The Q output 41 of I is connected to the toggle input GK of FF2.
The Q output 42 of FF2 is connected to the toggle input GK of FF3.
The Q outputs 43 of FF 3 are connected to the toggle input GK of FF 4, respectively. Q output 4 of flip-flop FF4
1 is connected to the input of the motor control circuit 22. Further, the clear terminals CLR of each stage of the flip-flops FFI to FF4 are commonly connected to the FC signal output 32 of the FG synchronization circuit 28. In this embodiment, the low-speed rotation detection circuit 40 is configured as a frequency dividing circuit that divides the frequency of the raw signal REF or a counting circuit that counts the frequency.

Therefore, when no signal is supplied to the clear terminal CLR of each stage, the frequency of the reference signal generated by the reference signal generator 34 at the output 38 is
i1′i, and the output 44 of the final stage FF4 has l/
A signal frequency-divided by 16 is output. F to clear input 32
When a signal ) is received from the G synchronization circuit 28, each stage F
Fl-FF4 are restored to the initial state all at once.

Motor control circuit 22 from control input 46! The motor 12 is started or stopped in response to the start or stop control signal F that is received, and the motor 12 is rotated steadily at a predetermined rotational speed based on the basic signal supplied from the reference signal generator 34. This is a circuit that controls this. In this embodiment, when a low speed rotation detection signal is received from the output 44 of the low speed rotation detection circuit 40, necessary actions such as starting the motor 12 (+1) or canceling the brake when the motor 12 is braked are performed. It is configured to take.

When the motor 12 is rotating steadily at a specified rotational speed, as shown in FIG. The output of 34 is output on the 3rd day (quasi signal REF
The frequencies are substantially the same, and the phases are also substantially the same. Therefore, the first stage F of the low speed rotation detection circuit 40
The FI attempts to count the J5 quasi-trust QREF at input 38, but is cleared each time. Therefore, in this state, each stage FFl-FF4 maintains its initial state, and therefore, no low-speed rotation detection signal is output to the output 44 of the circuit 40.

However, for example, when the rotational speed of the motor 12 decreases, the period of the frequency signal generated by the frequency generator 24 becomes longer, and the period of the signal FG output from the FG synchronization circuit 28 also becomes longer. Therefore, as shown in Fig. 753, the low speed rotation detection circuit 4
Each stage FFI to FF3 of 0 counts the reference signal REF.

More specifically, if the signal FC is not input to the clear input CLR, the state of the first stage FFI is changed in response to the reference signal REF;
is inverted, and its output 41 activates the toggle input CK of the second stage FF2. Therefore, when the signal FG is not input to the clear input CLR, the state 7rfI of the second stage FF2 is inverted, and the toggle input GK of the third stage FF3 is turned on by its output 42.In this way, each stage FFI ~
Until the signal FC arrives at the clear input 32 of FF3, they are normal! ;Continues stepping operation in response to REF.

As you will see, the final stage FF4 is configured to divide the reference signal REF of the input 38 by 1/18, so unless the rotational speed of the motor 12 falls below the specified 178, the final stage FF4 Before FF4 reaches set state 7g, signal FC arrives from output 32 of FC synchronization circuit 28, and all stages FFI to FF4 are reset. Therefore, as long as the rotational speed of the motor 12 is equal to or higher than the specified 178, no low-speed rotation detection signal is output from the output 44 of the final stage FF4.

However, when the rotational speed of the motor 12 drops below 1/8 of the specified value, as shown at time t1 in FIG.
The toggle input GK of is replaced with the output 43 of the previous stage FF3, and since the signal FG is not output from the FC synchronization circuit 28 by then, the final stage FF4 is not reset. Therefore, a low speed rotation detection signal is output to the output 44 of the final stage FF4.

The low speed rotation detection signal of the output 44 is input to the motor control circuit 22, and the circuit 22 responds to this by controlling the motor 12 to +.
If the motor 12 is activated or the motor 12 is braked, take necessary measures such as releasing the brake.

The embodiments described here are merely for explaining the present invention, and the present invention is not necessarily limited thereto, and modifications and variations that can be made by those skilled in the art without departing from the spirit of the present invention. Modifications are within the scope of this invention.

For example, the number of flip-flop stages included in the low-speed rotation detection circuit 40 depends on the lower limit of the low-speed rotation of the motor 12 to be detected. For example, when detecting at 1/2 of the specified rotation speed, use 2 stages, and when detecting at l/16, use 5 stages.
All you have to do is remove the flip-flops in the stage.

Also, the toggle input GK of the first stage flip-flop FFI
Basically, the frequency of the signal REF applied to T can be higher or lower than that of the signal 5; FG. For example, if the number of stages of flip-flops included in the constant speed rotation detection circuit 40 is the same, the frequency of the reference signal REF is the same as that of the signal F.
If it is set higher than C, the low-speed rotation detection limit value will be high, and if it is set lower than C, the single-speed rotation limit value will also be low. Therefore, the number of stages of print flops included in the constant speed rotation detection circuit 40 and the frequency of the reference signal REF should be determined in consideration of the frequency of the frequency signal generated by the frequency generator 24 to detect constant speed rotation of the motor 12. Designed according to the lower limit of rotation speed.

The principle of unreleased data is also applicable only when detecting a decrease in the rotational speed of a rotating body such as a motor, when the period of a periodic signal that should normally arrive at a predetermined period has fallen below the lower limit value. It can also be effectively applied to circuits that detect

Effects The low-speed rotation detection device for a rotating body according to the present invention has the following effects as described above.
! , (has a frequency dividing circuit or a counting circuit that divides the frequency of the quasi-signal, and is configured to reset it at No. 45 depending on the rotational speed of the rotating body. can detect low-speed rotation.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram showing an embodiment in which a low-speed rotation detection device for a rotating body according to the present invention is applied to a motor control system that steadily rotates a magnetic disk at a predetermined rotation speed. 2 is a waveform chart showing an example of a signal waveform appearing in each part of the device shown in FIG. 1, FIG. 2 shows the case of a specified rotation speed, and FIG. 3 shows the case of a low speed rotation detection operation. Description of symbols of main parts 12 Motor 22 Motor control circuit 24 Frequency generator 28 FG synchronization circuit 34 Reference signal generator 40 , low-speed rotation detection circuits FFl-FF4. T-type flip-flop tail 2 times FFIQ - FF2Q - F8ζ - FF4Q Time - 1 - - for 3 @ l target 19 - -

Claims (1)

[Claims] 1. A reference signal generating means for generating a reference signal of a predetermined frequency; and a means for generating a reference signal that is reset to an initial state upon receiving a frequency signal having a frequency corresponding to the rotational speed of a rotating body and that separates the reference signal. and a frequency dividing circuit that receives the reference signal and outputs a frequency divided output without being reset, thereby using the frequency divided output as a low speed rotation detection signal of the rotating body. A low-speed rotation detection device for a rotating body, characterized in that: 2. The device according to claim 1, wherein the rotating body normally rotates at a predetermined rotational speed, and the frequency of the reference signal is set to a frequency when the rotating body is rotating at the predetermined speed. substantially the same as the frequency of the frequency signal, the apparatus having synchronization means for receiving the frequency signal and a reference signal, synchronizing the former with the latter, and providing the synchronized frequency signal to the frequency divider circuit. A low-speed rotation detection device characterized by: 3. The device according to claim 2, wherein the frequency dividing circuit includes a plurality of stages of flip-flops connected in a subordinate manner, and the reference signal is input to the clock input of the first stage of the plurality of flip-flops. is input, the output of the synchronizing means is connected to a clear terminal of the plurality of flip-flops, and the low-speed rotation detection signal is output from the last stage of the plurality of flip-flops. Low speed rotation detection device.