JPS5914767Y2 - Rotation speed detection device - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a rotation speed detection device that detects the rotation speed and temperature of a rotating device and generates a control signal.

FIG. 1 shows an example of a conventional rotation speed detection circuit proposed by the inventors.

In the figure, 1 is a search coil, 11 is its core, D is a diode, Trl is a transistor, Ql is a voltage comparator, Ro, R10, R12°RL are fixed resistors, voo is a power supply voltage, and E is a ground.

C11 is a smoothing capacitor. The search coil 1 induces pulses by moving a magnet 61 attached to a rotating device 6.

The number of pulses is proportional to the number of rotations, and the voltage is also proportional to the number of rotations.

The pulse train induced in the search coil 1 is rectified by the diode D and amplified by the transistor Tr1.

The amplified DC signal is supplied to the voltage comparator Q1.

Voltage comparator Q1 connects the above input and fixed resistors R1□, R12
Reference voltage Vref created by = Vcc - R1□/
(R1, +R1□), input ≧ reference voltage Vre
In the case of f, the output is in a zero volt state (hereinafter referred to as "°L").

).

Conversely, if input≦reference voltage Vref, the output is ■.

0 state (hereinafter referred to as "H").

). In the conventional rotation speed detection circuit described above, the reference voltage Vref=Vcc "R12/(Rh +R12)
is proportional to the power supply voltage Vcc, and the power supply voltage Vcc directly affects the detected rotation speed.

In addition, the core 11 for the search coil 1 in this type of conventional rotational speed detection circuit is made of a material with a high Curie point T (for example, 200°C or higher), and also serves as a temperature sensor. was previously unknown.

This invention aims to provide a rotation speed detection circuit with a temperature sensor that is not only stable with respect to power supply voltage fluctuations, but also capable of detecting the temperature T of rotating equipment and generating a control signal based on T. be.

FIG. 2 is a block diagram of the rotational speed detection circuit with a temperature sensor according to this invention.

In FIG. 2, 1 is a search coil, 11 is its core,
2 represents a gate, 3 represents a charging circuit, and 4 represents a gate.

6 indicates a rotating part of the rotating device.

As the rotating part 6 rotates, the magnet 61 attached to the rotating part 6 rotates, and a pulse train proportional to the rotation speed N is induced in the search coil 1.

The period of this pulse train is inversely proportional to the pulse frequency, that is, the number of revolutions N, and the height of the pulse train is proportional to the number of revolutions N.

The gate 2 determines whether or not to transmit the pulse train to the charging circuit 3 based on the height of the pulse train.

That is, voltage comparison is performed. The charging circuit 3 always becomes "H" unless the pulse train from the gate 2 is transmitted, and the output of the gate 4 also becomes "H".

On the other hand, when the pulse train from the gate 2 is transmitted, the charging circuit 3 becomes "L" and the output of the gate 4 becomes "L".

The charging circuit 3 is "L" only while the pulse height exceeds the voltage comparison level by the gate 2 (during the pulse width), and the voltage increases with time between pulses, and when the next pulse is transmitted, the pulse is turned on again. It becomes "L" only during the width (that is, it becomes a sawtooth wave).

Gate 4 is a voltage comparator circuit that sets the output to "H" or "L" depending on the height of this sawtooth wave.

The detection level of the rotation speed is defined by the height of the sawtooth wave, ie, N, and is independent of the height of the input pulse.

In order to ensure the above operation, gate 1
It is necessary to set the time constant of the charging circuit 3 to be sufficiently longer than the period of the pulse train that can pass through.

FIG. 3 shows an example of the temperature characteristics (hereinafter referred to as MT characteristics) of magnetic permeability of the material used as the core 11 of the search coil 1.

The core 11 is made of Mn-Zn ferrite, Ni-Zn
ferrite etc. can be used.

For example, the Curie point Tc of Mn-Zn ferrite can be arbitrarily changed as shown in the characteristic diagram shown in FIG. 3 by changing the comparison between Mn ferrite and Zn ferrite.

At temperatures above the Curie point Tc, that is, at temperatures above Tc3 for material A, above Tc2 for material B, and above Tc1 for material C in FIG.

Therefore, for example, Mn- with material B and one Curie point Tc2
When Zn-based ferrite is used as the core 11 of the search coil 1, a pulse train is induced in the search coil 1 at a temperature below Tc2, but no pulse train is induced at a temperature above Tc2.

That is, when the temperature is less than Tc2, the pulse train passes through the gate 2 in FIG. 2, and the charging circuit 3 is set to L99.

As a result, the output of gate 4 becomes "L99".

On the other hand, T. In the case of a temperature of 2 or more, the pulse train is not induced in the search coil 1, and the charging circuit 3 becomes "H9? The output of the gate 4 is H", and outputs the same control signal as when the rotation speed N is below No. Occur.

Figure 4 is a characteristic diagram showing the relationship between the pulse train induced in the search coil 1 and the rotation speed, where the solid line shows the relationship between the rotation speed N and the height of the pulse train, and the broken line shows the relationship between the rotation speed N and the period. show.

However, the temperature is below the Curie point Tc.

In the figure, ``■'' indicates the voltage required for the pulse train to pass through the gate 2, and NO indicates the rotation speed of the rotating device 6 at that time.

FIG. 5 shows an example of a wiring diagram of the rotation speed detection circuit with a temperature sensor according to this invention.

1 is a search coil, Ql is a voltage comparator, and fixed resistor R1
□ and R1□ are bias voltage supply circuits for activating the voltage comparator Q1, and correspond to the gate 2.

Fixed resistor R20 and capacitor C2□ correspond to charging circuit 3.

Q2 is a voltage comparator and corresponds to gate 4.

COo, CO2, and CO3 are capacitors for preventing malfunction.

Every time the magnet 61 passes by the side of the search coil 1 due to the rotation of the rotating device 6, a pulse is induced in the search coil 1.

The induced pulse train is applied between the inverting and non-inverting inputs of voltage comparator Q1.

The voltage comparator Q1 includes a reference voltage of mV called an offset voltage, and when the pulse train is higher than this reference voltage, the capacitor C2□ is short-circuited by the pulse train.

When the pulse train is lower than the reference voltage, capacitor C2 is not short-circuited and is charged to the power supply voltage Vcc.

When short-circuited by a pulse train, the voltage waveform across the capacitor becomes a sawtooth wave, and the height of this sawtooth wave and the reference voltage built into the voltage comparator Q2 (normally
cc), the fixed resistor 21. If capacitor C2□ is selected, the output of voltage comparator Q2 will always be "L".

If not shorted by the pulse train, capacitor C2,
The voltage across it is charged and becomes equal to the power supply voltage Vcc.

The voltage across the capacitor C2□ is the reference voltage,
The output of gate 4 is always "H".

As mentioned above, if the pulse train induced in the search coil 1 exceeds the reference voltage of the voltage comparator Q1'',
It can be seen that the output is "L", and if it does not exceed, it is "H".

In other words, when the rotation speed N is greater than or equal to a specific value No, the output is “
If it is less than L'', No, it becomes “H”.

Even if the one-way rotation number N is No or higher, if the temperature of the search coil 1 is higher than the one point Tc of the curve, no pulse train is induced in the search coil 1 as described above, the output becomes "H", and the rotation speed This is equivalent to the case where N is less than or equal to No.

FIG. 6 shows a sectional view of an embodiment of the search coil 1 according to this invention.

In the figure, 11 is a core, 12 is a coil, and 13 is a bobbin.

The core 11 and bobbin 13 are threaded, and by rotating the core 11, the relative position with respect to the coil 12 can be changed.

That is, by rotating the core 11, the height of the pulse train induced in the search coil 1 can be continuously adjusted, so that NO can be arbitrarily selected.

FIG. 7 illustrates the relationship between the power supply voltage Vcc and No in an embodiment of the rotation speed detection circuit with a sensitivity sensor according to this invention.

As shown in the figure, NO is not affected by the power supply voltage Vcc at all.

FIG. 8 shows an example of the temperature characteristics of the rotational speed detection track with a temperature sensor which is provided with a temperature sensing function in the above embodiment.

If the rated rotational speed of the rotating equipment is 300 rpm, the shaded area surrounded by this straight line and the NO temperature curve (solid line) which is the detected rotational speed is the detection area, and the rest is the undetected area.

The temperature curve for No is at a certain temperature (34°C1 for the solid line)
In the case of the broken line, it increases rapidly at 69° C.), indicating that the single Curie point Tc of the Mn-Zn ferrite used as the core 11 of the search coil 1 contributes.

The control signal is "L" in the detection area and "H" in the undetected area.

Fig. 9 is a block diagram of another embodiment in which a voltage dividing circuit 5 is inserted between the search coil 1 and the gate 2 for the purpose of adjusting the detected rotation speed number, and Fig. 10 a and l) are the voltage dividing circuits. In this example, a shows an example in which a variable resistor R5□ and a constant resistor R5□ are used, and b shows an example in which an autotransformer 53 is used as a voltage dividing circuit.

As described above, according to this invention, the level of the detected rotational speed can be held constant even if the power supply voltage Vcc fluctuates.

Further, by changing the positional relationship between the core and the coil in the search coil, the predetermined rotation speed No. can be easily changed.

Furthermore, when a temperature-sensitive ferrite is used in the core of the search coil, it becomes possible to detect not only the number of rotations but also the temperature of the rotating equipment at the same time.

[Brief explanation of drawings]

Fig. 1 is an example of a conventional rotation speed detection circuit diagram, Fig. 2 is a block diagram of the rotation speed detection device according to this invention, Fig. 3 is a temperature characteristic diagram of magnetic permeability of temperature-sensitive ferrite, and Fig. 4 is A diagram showing the relationship between the pulse train and the rotational speed N, FIG. 5 is an example of a rotational speed detection circuit according to this invention, and FIG. 6 is a cross-sectional view of the search coil.
FIG. 7 is a relationship diagram between power supply voltage and detected rotation speed NO, FIG. 8 is a temperature-sensitive characteristic diagram, FIG. 9 is a block diagram of a rotation speed detection device according to another embodiment of this invention, and FIG. FIG. 2 is a circuit diagram showing a specific example of the voltage dividing circuit. In the figure, 1 is a search coil, 11 is a core, 12 is a coil, 13 is a bobbin, 2 is a gate, 3 is a charging circuit, 4 is a gate, 5 is a voltage dividing circuit, 6 is a rotating part of rotating equipment, 61 is a magnet It is. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (5)

[Scope of utility model registration request] (1) A magnet is provided on the rotating part of the rotating equipment, a search coil is arranged in correspondence with this magnet, and the rotational speed N of the rotating equipment is determined.
It is equipped with an electronic circuit that detects a signal pulse train proportional to and generates a control signal at a predetermined rotation speed No. This electronic circuit connects a search coil, a gate, a charging circuit, and a gate sequentially from the signal input side, and also connects a search coil, a gate, a charging circuit, and a gate. A rotation speed detection device characterized in that a coil is formed by winding a coil around a core, and the positional relationship between the core and the coil can be adjusted. (2) The rotational speed detection device according to claim 1, characterized in that a voltage comparator is used for the gate. (3) The rotational speed detection device according to claim 2, wherein the coil end of the search coil is connected between an inverting input terminal and a non-inverting input terminal of a voltage comparator. (4) The rotational speed detection device according to any one of claims 1 to 3, characterized in that a temperature-sensitive ferrite is used as the core. (5) The rotation detecting device according to any one of claims 1 to 4, wherein a voltage dividing circuit for a signal pulse train is inserted and connected between the search coil and the gate.