JPS583097Y2 - Rotation speed detection device - Google Patents

Description

[Detailed explanation of the invention] This invention consists of a DC generator and a field effect transistor (hereinafter referred to as F).
This invention relates to a rotational speed detection device that can detect the rotational speed and rotational direction of a rotating body that rotates a DC generator by using a combination of ET (abbreviated as ET).

In general, means for detecting tape running speed and tape running stop in a tape recorder includes, for example, a combination of a slit plate connected to a reel stand, a phototransistor, and a lamp.

However, this structure was expensive and had a complicated mechanism.

Furthermore, since detection of the running direction of the tape requires at least two sets of detection units, it is impossible to use a simple structure.

Also, if you use a DC generator that rotates with the rotating body,
In principle, in the output of a DC generator itself, the voltage indicates the number of revolutions, and the polarity of the voltage indicates the direction of rotation of the rotating body.

However, in order to process the output of the DC generator with both positive and negative polarities, the amplifier following the DC generator must be operated by a power source with both positive and negative polarities, which is extremely inconvenient.

The present invention solves these conventional problems.

That is, an object of the present invention is to enable detection of the rotational direction and rotational speed of a rotating body with a simple configuration using a single polarity amplifier.

One embodiment will be described below with reference to the drawings.

In Figure 1 a, l), 1 is a rotating body such as a reel shaft, 2
is a DC generator that is connected to this rotary body 1 via a bell (B) and rotates integrally with it, and in this embodiment, a magnet type DC motor is used.

3 is a generator output voltage setting resistor inserted between the positive side of the DC generator 2 and the gate part 4a of the FET 4;
5 is a FET load resistor inserted between the drain section 4b of the FET 4 and the power source B; 6 is a bias resistor inserted between the gate section 4a and the ground G; 7 is taken out from the drain section 4b. It is an output terminal.

Further, the negative side of the generator 2 and the source section 4C of the FET 4 are connected to the ground G.

In FIG. 1a, H indicates a bed portion, C indicates a capstan roller, and P indicates a pinch roller.

The operation of the above circuit configuration will be explained.

Figure 2 is a graph showing the characteristics of the output voltage with respect to the rotational speed of the generator 2 driven by the rotating body 1. The characteristic line 8 in this figure is positive or negative depending on the rotational direction and rotational speed of the generator. changes linearly in the direction.

In FIG. 3, 8' is the voltage VGS (horizontal axis) between the gate (4a) and ground G (horizontal axis) shown in FIG. 1, which corresponds to the output voltage 8 of the DC generator shown in FIG. 9 shows the relationship with the current ID (vertical axis) flowing through the drain 4b of the FET 4 shown in FIG. It shows the characteristics of the current ID flowing through the drain 4b when the power supply voltage element B is changed.

10 is the current ID flowing through the drain 4b and the output terminal 7.
It shows the relationship with the voltage of drain current ID
It is shown that as the voltage drop increases, the voltage drop across the resistor 5 also increases.

11 indicates the output voltage appearing at the output terminal 7.

In this case, the load line 10 and the characteristic curve 9 of Vcs = OV (
10) is moved to the horizontal axis, and this point indicates the stopped state of the generator 2.

That is, approximately the midpoint 12 of the power supply voltage terminal Bv from OV corresponds to the above-mentioned stopped state.

If the section from the midpoint 12 to 10B is an output of forward rotation, the section from the midpoint 12 to 0■ is an output of reverse rotation.

In other words, the output voltage of the DC generator 2 causes the drain voltage of the FET 4 to vary linearly depending on the rotation direction and rotation speed of the generator 2.

That is, in Figures 1 and 3, the voltage appearing at the output terminal 7 is at the voltage indicated by 12 in Figure 3 when the DC generator 2 is stopped, and when the DC generator rotates in the forward direction. When it is rotating in the forward direction of the power supply voltage +B, it moves according to its rotation speed, and when it is rotating in the reverse direction, it moves to the side lower than the voltage indicated by 12 according to its rotation speed.

Therefore, in order to detect the rotational direction and rotation stop of the rotary body 1, it is sufficient to connect a comparator circuit or the like to the output terminal 7 to determine the direction and the presence or absence of rotation.

Alternatively, the rotational speed of the rotating body can also be easily detected by connecting a conversion circuit.

Since the present invention has such a configuration, it is possible to detect the rotational speed and direction of the rotating body very easily using an amplifier operated by a unipolar power source, and its industrial efficiency is excellent. .

[Brief explanation of drawings]

Figures 1a and 1) are component countries and circuit diagrams showing one embodiment of the present invention, Figure 2 is a characteristic diagram of the output voltage of the DC generator shown in Figure 1, and Figure 3 is the same as Figure 1. FIG. 3 is a characteristic diagram of drain voltage, etc. of the FET shown in FIG. 2...DC generator, 4...FET, 5...
...Load resistance for FET, 6 ...Bias resistance, 7 ...Output terminal, 1 ...Rotating body.

Claims (1)

[Scope of utility model registration request] The positive side of a DC generator that rotates together with the rotating body is connected to the gate of a field effect transistor, the drain of the transistor is connected to a power source via a load resistor, and the negative side of the DC generator and the The other end of the bias resistor connected to the gate part and the source part of the transistor are connected to ground, and the rotation direction and rotation speed of the rotating body can be detected by the output voltage from the drain part. Speed detection device.