JPH0430543Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a highly accurate rotational speed detection device capable of detecting speed fluctuations even during one rotation.

A highly accurate rotational speed detection device is essential for precise speed control. A typical rotational speed detection device includes a slit disk in combination with a speed detection generator and a photoelectric element. However, speed detection generators have large voltage pulsations during one rotation due to slot ripples, brush noise, etc., and although the number of pulses per rotation of the slit disk is accurate, there are limitations in mechanical accuracy and assembly accuracy. Therefore, it is difficult to make the pulse interval constant with respect to the rotation angle during one rotation, and frequency pulsations occur depending on the rotation angle, making it impossible to accurately detect the instantaneous speed. Due to these causes, the pulsating component included in the rotational speed detection output becomes a major hindrance in precise speed control because it is amplified by an error amplifier.

In view of this, the present invention utilizes the principle of a magnetic recorder and applies it to a speed detection device in order to eliminate the above-mentioned obstacles, thereby reducing the influence of mechanical accuracy. be. The drawings illustrate embodiments of the invention. A magnetic disk 3 (a disk coated with a magnetic material for magnetic recording or made of a magnetic material) is attached to the shaft 2 of the electric motor 1,
A separately fixed magnetic head 4 for recording and reproducing is brought into contact with or close to the magnetic disk 3.

The electric motor 1 is rotated at a constant speed, and the magnetic head 4
Writing is performed on the magnetic disk 3 by supplying a signal of a constant frequency to the magnetic disk 3. In order to rotate the electric motor 1 at a constant speed, it is preferable to connect a large flywheel 5 directly to the shaft and use an auxiliary electric motor 6 to drive the belt 7. Depending on the application, the electric motor itself may rotate at a constant speed. When writing is completed, flywheel 5,
Auxiliary motor 6 and constant frequency oscillator 8 are not required.

In order to write a constant frequency signal to the magnetic disk 3 via the magnetic head 4, the oscillation output of the oscillator 8 is applied to the magnetic head 4 via the amplifier 10 and the write/read switch 11.

When detecting the rotational speed, the magnetic signal recorded on the magnetic disc 3 is read by the magnetic head 4 and the frequency of the obtained reproduction output signal is directly measured, or the frequency of the reproduced output signal obtained is directly measured, or
A DC rotation signal S ₁ is obtained through the converter 9.

If writing is performed on the magnetic disc 3 after the magnetic disc 3 is attached to the shaft, writing can be performed in the same state as reading, and mechanical accuracy such as the mounting accuracy of the magnetic disc 3 does not affect the accuracy of speed detection. There is no pulsation in the detection signal generated by the detection device regardless of this.
In addition, since the density of magnetic recording can easily be more than 100 cycles per 1 mm, the recording radius can be set to 50 mm.
If so, one rotation can be approximately 30,000 cycles, and the instantaneous speed of the motor can be easily detected.

In writing on a magnetic disk, the writing phase after one rotation is not necessarily the same phase as the signal that has already been written, but this does not become a problem because the number of signal cycles during one rotation is large.

If a small hole or slit is provided in the magnetic disk 3 and the index pulse _S2 is obtained by the photoelectric device 10, the frequency ratio of the reproduction signal and the index pulse will be constant in the reproduction state, so that the speed detection can be performed. Since the instrument can be calibrated with high precision and the rotation angle of the motor can be known, the speed pulsation of the motor can be analyzed. Note that 13 indicates a light source, and 14 indicates a hole on the magnetic disk.

As described above, according to the device of the present invention, instantaneous rotational speed detection can be performed with extremely high accuracy, and a speed detection signal without pulsation can be obtained.

[Brief explanation of the drawing]

The drawings are diagrams showing an embodiment of the speed detection device according to the present invention. 1...Electric motor, 3...Magnetic disc, 4...Magnetic head.

Claims (1)

[Claims for Utility Model Registration] 1. A magnetic disc attached to a rotating shaft, a magnetic head fixed at a predetermined position, and a magnetic disc with the magnetic head in a recording state while rotating the rotating shaft at a constant rotational speed. It is equipped with a writing means for writing a signal of a constant frequency on the disk, and a reading means for reading the signal recorded on the magnetic disk by putting the same magnetic head in a reproduction state, A rotational speed detection device characterized in that it detects the rotational speed of the rotating shaft. 2 A hole is provided in the magnetic disk attached to the rotating shaft,
The rotation speed detection device according to claim 1, characterized in that the device includes a device for detecting the angle of the rotation shaft by detecting the position of the hole. 3 The signal reproduced by the magnetic head is
The rotational speed detection device according to claim 1, characterized in that a DC voltage output is obtained through a converter.