JP2002350455A - Rotating speed detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotating speed detecting device capable of generating a rotating speed signal of a prescribed level regardless of a degree of a rotating speed. SOLUTION: This rotating speed detecting device has a rotating speed detecting gear 1 installed on a rotary shaft of a rotary body composed of a magnetic substance, an electromagnetic pickup 2 for detecting the rotating speed of the rotary body by a magnetic flux change in a magnetic path formed via the gear, and an output stabilizing circuit 5 for outputting an output signal of the pickup by converting the output signal into a prescribed signal level. The output signal of the electromagnetic pickup is imparted to the output stabilizing circuit 5 after removing noise by a filter. The output stabilizing circuit 5 converts the output signal into the prescribed signal level regardless of the rotating speed by having low amplification gain or the signal damping function when the rotating speed is high and the output signal of the pickup is large, and having high amplification gain when the rotating speed is low and the output signal of the pickup is small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation speed detecting device for detecting and controlling the rotation speed of a steam turbine or the like.

[0002]

2. Description of the Related Art A rotation speed detecting device for detecting and controlling the rotation speed of a steam turbine or the like generally uses an electromagnetic pickup. FIG. 6 is a block diagram showing a configuration of a rotation speed detecting device using an electromagnetic pickup. In this figure, an electromagnetic pickup 2 is disposed on a rotation speed detecting gear 1 of a magnetic material attached to a shaft end of a rotating shaft of a steam turbine or the like (not shown) with a small gap g therebetween. The rotation speed is detected by detecting that the magnetic resistance of the magnetic path formed by the rotation speed detection gear 1 and the magnetic resistance formed by the rotation of the rotation speed detection gear 1 changes with the rotation of the rotation speed detection gear 1 and inputting the signal to the control device 3 for signal processing. Is detected.

In this method, when the magnetic path from the electromagnetic pickup 2 switches from the convex portion to the concave portion of the rotation speed detecting gear 1, the magnetic flux changes to generate a voltage. Is approximately proportional, as shown in FIG. In other words, when the rotation speed of the steam turbine or the like is low, the output signal level of the electromagnetic pickup 2 is low, and the output signal level increases as the rotation speed increases.

[0004]

However, the control device 3, which inputs the detection signal of the electromagnetic pickup 2 and calculates and controls the rotation speed, is difficult to cope with a wide range of detection signal levels. There is a problem that it is necessary to adjust the position to an optimum value by fine adjustment of the position, signal attenuation by a resistor, or the like.

The present invention has been made under such a background, and an object of the present invention is to provide a rotation speed detecting device capable of generating a rotation speed signal of a predetermined level regardless of the rotation speed. .

[0006]

According to a first aspect of the present invention, there is provided a gear for detecting a rotational speed which is made of a magnetic material and is attached to a rotating shaft of a rotating body, and according to the present invention, an output signal of an electromagnetic pickup. Can be converted into a signal of a predetermined level and input to the control device, so that the rotation speed of the rotating body is detected by a change in magnetic flux of a magnetic path formed through the minute rotation speed detection gear at the mounting position of the electromagnetic pickup. And a signal stabilizing circuit for converting an output signal of the electromagnetic pickup into a predetermined signal level and outputting the converted signal.

According to the present invention, since the output signal of the electromagnetic pickup can be converted into a signal of a predetermined level and input to the control device, fine adjustment of the mounting position of the electromagnetic pickup, adjustment of the signal level attenuation, etc. Becomes unnecessary.

According to a second aspect of the present invention, in the rotation speed detecting device according to the first aspect, the output signal of the electromagnetic pickup is provided to the signal stabilizing circuit after noise is absorbed by a filter. And

According to the present invention, it is possible to eliminate disturbance of waveform and induction noise due to reflection at the terminal due to impedance mismatch caused by transmitting signals of a wide range of frequencies, and to detect rotation speed. Can be done accurately.

According to a third aspect of the present invention, in the rotation speed detecting device according to the first or second aspect, the signal stabilizing circuit is provided when the rotation speed of the rotating body is high and the output signal of the electromagnetic pickup is large. It has a low amplification gain, or a signal attenuating function, and has a high amplification gain when the rotation speed of the rotating body is low and the output signal of the electromagnetic pickup is small, so that the signal is converted to a predetermined signal level regardless of the rotation speed. It is characterized by outputting.

According to the present invention, a signal stabilizing circuit having an automatic gain adjusting function can input a rotation speed signal of a predetermined level to the control device regardless of the rotation speed.
Stable rotation speed control can be performed.

[0012] The invention according to claim 4 is the invention according to claims 1 to 3.
The rotation speed detection device according to any one of the above, the electromagnetic pickup has a detection unit having a predetermined length in the rotation axis direction of the rotating body, the rotation speed detection gear is in the rotation axis direction of the rotating body. It is characterized in that it has a size corresponding to the detection unit of the electromagnetic pickup.

According to the present invention, a high-level signal can be output even at a low rotation speed by increasing the axial size of the electromagnetic pickup and the corresponding rotation speed detecting gear.

[0014] The invention according to claim 5 provides the invention according to claims 1 to 4.
The rotation speed detection device according to any one of the above, further comprising a light detection pickup that detects the rotation speed at the time of ultra low speed rotation, switching between the output signal of the light detection pickup and the output signal of the electromagnetic pickup according to the rotation speed Speed detection.

According to the present invention, the provision of the light detection pickup in addition to the electromagnetic pickup makes it possible to detect an extremely low speed rotation (for example, 4 to 6 rpm) such as turning, and corresponds to the entire rotation speed range of a steam turbine or the like. Thus, the rotation speed can be detected.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a rotation speed detecting device according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a rotation speed detection gear, which is formed by laminating disk-shaped magnetic steel plates having irregularities on the periphery thereof, and is attached to a rotation shaft of a steam turbine or the like (not shown). Rotates with.

The electromagnetic pickup 2 detects a change in magnetic flux due to a change in magnetic resistance when the convex portion of the rotational speed detecting gear 1 is a magnetic path and when the concave portion is a magnetic path, and detects a frequency proportional to the rotational speed. Is generated.

The filter 4 has a function of removing signal reflection and induced noise due to impedance mismatch of a transmission line for transmitting a detection signal of the electromagnetic pickup 2 which changes over a wide range in proportion to the rotation speed.

The output stabilizing circuit 5 includes the electromagnetic pickup 2
When the level of the generated signal is low, it has a high amplification factor, and when the signal level is high, it has a low amplification factor, or has a signal attenuation function, regardless of the signal level,
This is an amplifier with a variable amplification factor that outputs a predetermined value.

The control device 3 is a device that receives the output signal of the output stabilizing circuit 5, calculates the rotation speed of the steam turbine or the like, and controls the rotation speed.

FIG. 2 is a diagram showing the structure of the electromagnetic pickup 2. When the rotation speed detecting gear 1 and the electromagnetic pickup 2 are at the positions shown in FIG. 2, the magnetic flux emitted from the N pole of the permanent magnet 21 of the electromagnetic pickup 2 is projected through the gap g. A magnetic path returning to the S pole of the permanent magnet 21 through the portion 1a and the magnetic material 2 is formed. Gap g
Is extremely small, the magnetic resistance of this magnetic path is small, and the magnetic flux passing through the magnetic path increases. When the rotation detecting gear 1 rotates a little and the electromagnetic pickup 2 and the concave portion 1b are located at positions facing each other, no magnetic path is formed by the magnetic material, and a large magnetic resistance is exhibited. Less.

A voltage is generated in the detection winding 23 wound around the permanent magnet 21 by the above-described change in magnetic flux. Since the generated voltage has a frequency proportional to the unevenness of the rotation speed detecting gear 1, the rotation speed can be detected.

FIG. 3 is a diagram showing an example of the input / output voltage of the filter 4. FIG. 3A shows the filter input voltage, and it is difficult to match the impedance of the transmission line for all the signals of the electromagnetic pickup 2 that fluctuate widely with the change in the rotation speed. Occurs, the voltage at which the zero point is crossed becomes unstable, and the detection of the rotational speed becomes unstable. Further, the voltage shown in FIG. 3B is output after removing the influence of the induction noise of the transmission line.

FIG. 4 is a diagram showing characteristics of the output stabilizing circuit 5. The output of the electromagnetic pickup 2 becomes a voltage proportional to the rotation speed as shown by a dotted line. This is because the value of dφ / dt, which is a change in magnetic flux of the electromagnetic pickup 2, increases as the rotation speed increases. Therefore, the output stabilization circuit 5
Is configured to decrease as the rotational speed increases as shown in the figure. Therefore, the output of the output stabilizing circuit 5 has a substantially constant predetermined value regardless of the rotation speed, and the operation of the control device 3 can be stabilized.

The control device 3 calculates the rotation speed by half-wave rectifying the signal given from the output stabilizing circuit and detecting the rise of the signal.

Next, the shape of the electromagnetic pickup 2 will be described with reference to FIG. This figure is a view of the electromagnetic pickup 2 as viewed from the rotation speed detecting gear side. In this figure, the axial length l of the rotating shaft is increased, and at the same time, the dimension of the rotating speed detecting gear 2 in the rotating shaft direction is also equal to the length l of the electromagnetic pickup 2 (not shown). With such a shape, the signal level at the time of low-speed rotation can be increased without lowering the resolution of the signal at the time of high-speed rotation. The signal level during high-speed rotation also increases,
Since it can be attenuated by the output stabilizing circuit 5, there is no problem.

Further, in the case of a steam turbine, an extremely low speed (for example, 4 to 6 rpm) called turning, which is much lower than the rotational speed range usually used for cooling the turbine.
In some cases, it is necessary to detect the rotation speed even when rotating at.
In this case, since the signal detection by the electromagnetic pickup is impossible, the rotation speed is detected by the light detection pickup, and the detection means is switched to the electromagnetic pickup when the rotation speed is within the rotation speed range that can be detected by the electromagnetic pickup.

The operation of one embodiment of the present invention has been described above in detail with reference to the drawings. However, the present invention is not limited to this embodiment, and a design change or the like may be made without departing from the gist of the present invention. The present invention is also included in the present invention. For example, the rotating body is not limited to a steam turbine, but may be any kind of rotating body such as a motor.

[0029]

As described above, according to the present invention, the following effects can be obtained.

According to the first aspect of the present invention, since the output signal of the electromagnetic pickup can be converted into a signal of a predetermined level and input to the control device, fine adjustment of the mounting position of the electromagnetic pickup and attenuation of the signal level can be performed. It is not necessary to adjust or the like.

According to the second aspect of the present invention, it is possible to eliminate disturbance of waveform, induction noise, and the like due to reflection at the end due to impedance mismatch caused by transmission of a signal of a wide range of frequencies, and to reduce rotational speed. Can be detected accurately.

According to the third aspect of the present invention, a signal stabilizing circuit having an automatic gain adjustment function can input a rotation speed signal of a predetermined level to the control device regardless of the rotation speed, so that stable rotation speed control can be performed. It can be performed.

According to the fourth aspect of the present invention, it is possible to output a high-level signal even at a low rotational speed by increasing the axial dimension of the electromagnetic pickup and the corresponding rotational speed detecting gear.

According to the fifth aspect of the present invention, the provision of the light detection pickup in addition to the electromagnetic pickup makes it possible to detect an extremely low speed rotation (for example, 4 to 6 rpm) such as turning, and the total rotation speed of a steam turbine or the like. The rotation speed can be detected according to the range.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a rotation speed detection device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a structure of an electromagnetic pickup 2;

FIG. 3 is a diagram showing an example of input / output voltages of a filter 4;

FIG. 4 is a diagram showing characteristics of an output stabilization circuit 5;

FIG. 5 is a view showing the shape of an electromagnetic pickup 2;

FIG. 6 is a block diagram showing a configuration of a rotation speed detecting device using an electromagnetic pickup according to a conventional technique.

FIG. 7 is a diagram showing the relationship between the rotation speed and the output of the electromagnetic pickup 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Rotation speed detection gear 1a ... Protrusion of rotation speed detection gear 1b ... Recession of rotation speed detection gear 2 ... Electromagnetic pickup 21 ... Permanent magnet 22 ... Magnetic material 23 ... Detection winding 3 ... Control device 4 ... Filter 5. Output stabilization circuit

Claims (5)

[Claims] 1. A rotation speed detecting gear made of a magnetic material and attached to a rotating shaft of a rotating body, and a rotation speed of the rotating body is detected by a change in magnetic flux of a magnetic path formed through the rotating speed detecting gear. And a signal stabilizing circuit for converting an output signal of the electromagnetic pickup into a predetermined signal level and outputting the signal. 2. The rotation speed detecting device according to claim 1, wherein an output signal of said electromagnetic pickup is supplied to said signal stabilizing circuit after noise is absorbed by a filter. 3. The signal stabilizing circuit has a low amplification gain or a signal attenuating function when the rotation speed of the rotator is high and the output signal of the electromagnetic pickup is large, and the rotation speed of the rotator is low. 3. The rotation speed detecting device according to claim 1, wherein when the output signal of the electromagnetic pickup is small, the signal has a high amplification gain to convert the signal to a predetermined signal level and output the signal regardless of the rotation speed. 4. The electromagnetic pickup has a detection unit having a predetermined length in a rotation axis direction of a rotating body, and the rotation speed detecting gear is provided on a detection unit of the electromagnetic pickup in a rotation axis direction of the rotation body. The rotation speed detecting device according to any one of claims 1 to 3, wherein the rotation speed detecting device has a corresponding size. 5. A light detection pickup for detecting a rotation speed at a very low speed rotation, wherein a rotation speed is detected by switching between an output signal of the light detection pickup and an output signal of the electromagnetic pickup according to the rotation speed. The rotation speed detecting device according to claim 1, wherein: