JP3298408B2 - Motor speed detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor speed detection circuit for detecting whether or not the speed of a motor exceeds a set value.

[0002]

2. Description of the Related Art When the rotation speed of an electric motor falls below a set value or rises above a set value, a rotation speed detection circuit is used to detect a decrease or a rise in the rotation speed. I have.

FIG. 4 shows a conventional rotation speed detecting circuit for a motor of this type. FIG. 5 shows the voltage waveform of each part of the circuit of FIG. 4. The left half of each of (A) to (E) shows the waveform in the case where the rotation speed of the motor is a low rotation speed which is equal to or lower than a set value. The right half shows the waveform when the rotation speed of the motor is higher than the set value.

[0004] The rotation speed detection circuit shown in FIG. 4 is driven at a high level (H level) as the rotation speed of a motor (not shown) increases.
An input is a rectangular wave-like rotation detection signal Vn (FIG. 5A) in which the period during which the state is kept short is inputted, and the period during which the high level state is maintained at the rising edge of the rotation detection signal is constant. (FIG. 5C), a pulse integration circuit 2 for integrating the edge detection pulse Vp, and an integrated voltage Vi (FIG. 5D) output from the pulse integration circuit 2 as a reference voltage Vr2 (see FIG. 5D). The detection signal V becomes high when the integrated voltage Vi is equal to or lower than the reference voltage Vr2, and becomes low (L level) when the integrated voltage Vi exceeds the reference voltage Vr2.
s (FIG. 5E).

[0005] The rotation detection signal Vn is, for example, a signal obtained by a rotary encoder attached to the rotating shaft of the electric motor.

The edge detection circuit 1 comprises an NPN transistor Q11, a diode D11, a capacitor C11 and a resistor R11.
R12 at the rising edge of the rotation detection signal Vn input from the input terminal 4 (FIG. 5).
B) and a trigger signal generating circuit 9 for outputting the trigger signal V
It comprises a monostable multivibrator integrated circuit IC3 triggered by t and a constant pulse generating circuit 10 which outputs an edge detection pulse Vp having a constant pulse width T 'and comprising a resistor R13 and a capacitor C12. The constant pulse width T 'is determined by the time constant of the resistor R13 and the capacitor C12.

The pulse integration circuit 2 is composed of a capacitor C13 and resistors R14 and R15.
p is smoothed and an integrated voltage Vi proportional to the rotation speed of the motor is output.

The comparison circuit 3 includes a voltage comparator IC2,
Voltage dividing resistors R6 and R7 for dividing a power supply voltage Eb obtained from a constant-voltage DC power supply (not shown) to generate a reference voltage Vr2 having a magnitude proportional to the set rotation speed of the motor. The comparison circuit 3 compares the integrated voltage Vi with the reference voltage Vr2, and outputs a detection signal Vs having a different level when the rotation speed of the motor is lower than the set rotation speed and when the rotation speed is higher than the set rotation speed.
Output from From the level of this detection signal, it is possible to detect whether or not the rotation speed of the electric motor exceeds the set rotation speed. In the illustrated example, since the integrated voltage Vi and the reference voltage Vr2 are input to the inverting input terminal and the non-inverting input terminal of the comparator IC2, respectively, the detection signal Vs is output when the rotational speed of the motor is lower than the set rotational speed. The state becomes a high level, and when the number of rotations of the motor exceeds the set number of rotations, the detection signal Vs becomes a low level state.

[0009]

In the rotation speed detection circuit as described above, the pulse width T 'of the edge detection pulse Vp generated by the edge detection circuit 1 is kept constant irrespective of the rotation speed of the motor. It is necessary. In the conventional motor speed detection circuit shown in FIG. 4, an expensive monostable multivibrator (in the example of FIG. 4) is used to maintain the pulse width T 'of the edge detection pulse Vp at a constant value. Since the integrated circuit IC3) is used, there is a problem that the manufacturing cost of the rotation speed detecting circuit is increased.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electric motor rotation speed detection circuit capable of realizing an edge detection circuit with a simple configuration without using an expensive monostable multivibrator and reducing the manufacturing cost. To provide.

[0011]

SUMMARY OF THE INVENTION According to the present invention, a rising edge of a rotation detection signal is input by inputting a rectangular wave rotation detection signal in which a period during which a high level state is maintained as the rotation speed of the motor increases becomes short. An edge detection circuit that generates an edge detection pulse, a pulse integration circuit that integrates the edge detection pulse, and an integrated voltage that is output by the pulse integration circuit is compared with a reference voltage, and when the integrated voltage exceeds the reference voltage And a voltage comparator that outputs a detection signal, and detects whether the rotation speed of the motor exceeds a set value.

In the rotation speed detection circuit for a motor according to the present invention, the edge detection circuit includes a rotation detection integration circuit for integrating a rotation detection signal, and an output when the output voltage of the rotation detection integration circuit is less than a threshold value. Is at a high level, and when the output voltage of the rotation detecting integration circuit becomes higher than the threshold value, the output becomes a low level state, and both the rotation detection signal and the output of the level discrimination circuit. And an AND circuit that outputs, as an edge detection pulse, a pulse signal that maintains a high level state only during a period when the signal is at a high level state.

The rotation detecting integration circuit includes a resistor having one end connected to a non-ground side input terminal to which a rotation detection signal is input, and a resistor connected between the other end of the resistor and ground and receiving the rotation detection signal. And a circuit that generates an integrated voltage for rotation detection at both ends of the capacitor.

The level discriminating circuit includes a threshold voltage generating voltage dividing circuit for dividing a constant power supply voltage to generate a threshold voltage having a level lower than the peak value of the rotation detecting integrated voltage; The rotation detection integrated voltage is compared with a threshold voltage to maintain a high level state when the level of the rotation detection integrated voltage is lower than the threshold voltage level. And a voltage comparator that generates an output signal that substantially drops to the ground potential when the voltage exceeds the voltage.

In the AND circuit, a resistor having one end connected to a terminal to which a rotation speed detection signal is input, an anode connected to the other end of the resistor, and a cathode connected to an output terminal of the voltage comparator. A pulse signal that holds a high-level state only while both the rotation detection signal and the output signal of the voltage comparator are at a high-level state as an edge detection pulse between the cathode of the diode and the ground potential section. It can be configured by a circuit generated between them.

The level discriminating circuit has a ground terminal connected to the ground potential section, a non-ground terminal, and a control terminal to which a rotation detecting integrated voltage is input. Is less than the threshold level, the connection between the ground side terminal and the non-ground side terminal is turned off, and when the rotation detection integrated voltage exceeds the threshold level, the ground side terminal and the non-ground side terminal are connected to each other. It can also be configured by a semiconductor switch that turns on between them. In this case, the cathode of the diode of the AND circuit is connected to the non-ground side terminal of the semiconductor switch.

When the edge detection circuit is constructed as described above, the rotation detection signal (FIG. 2A) is converted into a signal having a waveform whose rising and falling edges are gradual as shown in FIG. Is converted to Therefore, the output voltage of the level discriminating circuit which becomes a high level state when the output voltage of the rotation detecting integration circuit is less than the threshold value is as shown in FIG.
As shown in (C), the falling time is a rectangular wave voltage delayed by a certain time from the rising time of the edge of the rotation detection signal. Therefore, as shown in FIG. 2D, the edge detection pulse obtained from the AND circuit is a rectangular wave-like pulse that maintains a high level state for a certain period of time.

The rotation detecting integration circuit may be constituted by a resistor and a capacitor. The level discriminating circuit may be constituted by a voltage dividing circuit and a voltage comparator or when the input voltage exceeds a predetermined threshold level. The edge detection circuit can be configured with a small number of components without using an expensive monostable multivibrator, and the cost can be reduced.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of the configuration of a motor speed detection circuit according to the present invention, and FIG. 2 shows voltage waveforms at various points in FIG. 1 with respect to time t. The left half of each of FIGS. 2A to 2F shows a waveform when the rotation speed of the motor is equal to or less than the set value, and the right half shows a waveform when the rotation speed of the motor exceeds the set value. ing.

In FIG. 1, reference numeral 1 designates a rectangular wave-shaped rotation detection signal Vn (FIG. 2A) in which a period during which a high-level state is maintained with an increase in the rotation speed of a motor (not shown) is input and the rotation detection signal Vn is input. Is an edge detection circuit that generates an edge detection pulse Vp (FIG. 2D) at the rising edge of. 2 is a pulse integration circuit for integrating the edge detection pulse Vp, and 3 is an integration voltage Vi output from the pulse integration circuit 2.
(FIG. 2E) is compared with a reference voltage Vr2 (see FIG. 2E).
A comparison circuit that outputs a detection signal Vs (FIG. 2F) that becomes a high level state when the integrated voltage Vi is equal to or lower than the reference voltage Vr2 and becomes a low level state when the integrated voltage Vi exceeds the reference voltage Vr2. is there.

The rotation detection signal Vn input to the edge detection circuit 1 is, for example, an output signal of a rotary encoder mounted on the rotor side of a motor whose rotation speed is to be detected. As a rotary encoder, for example, a magnetic flux generated by a permanent magnet is detected by a Hall element provided on the stator side of the electric motor, and a rectangular wave signal is obtained using the output of the Hall element, There is a type in which a voltage induced in a signal coil provided on the stator side of an electric motor is shaped into a waveform by a change in magnetic flux generated by the permanent magnet to obtain a rectangular wave rectangular signal. Further, a code disk having a number of slits at equal angular intervals and attached to the rotating shaft of the electric motor, and a light emitting element and a light receiving element arranged opposite to each other with the disk therebetween, and the slit of the code disk is In some cases, a rotary encoder that generates a pulse signal from the light receiving element every time the light passes through the position of the light emitting element and the light receiving element is used.

The edge detection circuit 1 includes a rotation detection integration circuit 5, a level discrimination circuit 6, and an AND circuit 7.

The rotation detecting integration circuit 5 outputs a rotation detection signal V
A resistor R1 has one end connected to the non-ground side input terminal 4 to which n is input, and a capacitor C1 connected between the other end of the resistor R1 and the ground.

The level discriminating circuit 6 comprises a resistor R2 and a resistor R3.
And a voltage divider IC1 for dividing the power supply voltage Eb to generate a threshold voltage Vr1, and a voltage comparator IC1. The inverting input terminal is connected to the non-ground terminal of the capacitor C1 of the rotation detecting integration circuit, and the non-inverting input terminal is connected to the voltage dividing point of the threshold voltage generating voltage dividing circuit.

The AND circuit 7 includes a series circuit of a resistor R4 having one end connected to the non-ground side input terminal 4 and a diode D1 having an anode connected to the other end of the resistor R4 and an output terminal of the voltage comparator IC1. And a wiring connected to the cathode of the diode D1.

One end of the pulse integration circuit 2 is an AND circuit 7.
And a capacitor C2 connected between the other end of the resistor R5 and the ground. The comparison circuit 3 comprises a voltage comparator IC2 and a series circuit of resistors 6 and R7. And a voltage dividing circuit. The non-inverting input terminal of the voltage comparator IC2 is connected to the connection point between the resistors R6 and R7, and the inverting input terminal is connected to the non-ground terminal of the capacitor C2. The output terminal of the voltage comparator IC2 is connected to the output terminal 8 of the rotation speed detection circuit.

In the above circuit, the rotation detection signal Vn (FIG. 2A) in the form of a rectangular wave input from the non-ground side input terminal 4 of the rotation speed detection circuit is input to the rotation detection integration circuit 5 and integrated. As a result, as shown in FIG. 2B, the signal is converted into a delayed signal Vd having a waveform whose rising and falling edges are gentle. This delay signal Vd is compared with the threshold voltage Vr1 by the voltage comparator IC1 of the level discrimination circuit 6 (see FIG. 2B). The voltage comparator IC1 keeps a high level state when the delay signal Vd is lower than the threshold voltage Vr1, and keeps a low level (almost ground potential) when the delay signal Vd is higher than the threshold voltage Vr1. ) To output the level discrimination signal Vb (FIG. 2C). The level discrimination signal Vb is a rectangular wave voltage signal whose rising edge and falling edge are delayed by a predetermined time from the falling edge and rising edge of the rotation detection signal Vn, respectively.

The AND circuit 7 has a high level only during a period T during which both the rotation detection signal Vn passed through the resistor R4 and the diode D1 and the level discrimination signal Vb output from the level discrimination circuit 6 are at a high level. Is output as an edge detection signal Vp (FIG. 2D). The period T during which the edge detection signal Vp is at a high level
Are the time constant of the rotation detecting integration circuit 5 and the level discrimination circuit 6
It can be adjusted appropriately by selecting the resistance values of the voltage dividing resistors R2 and R3.

The edge detection pulse Vp is applied to the pulse integration circuit 2
And is integrated. As shown in FIG. 2E, the integrating circuit 2 outputs an integrated voltage Vi having a magnitude proportional to the number of revolutions of the electric motor.

The comparison circuit 3 generates a reference voltage Vr2 (FIG. 2E) having a magnitude proportional to the set number of revolutions of the motor by dividing the power supply voltage Eb by a voltage dividing circuit composed of resistors R6 and R7. The reference voltage Vr2 is compared with the integral voltage Vi by the comparator IC2. The comparator IC2 holds the high level state when the integrated voltage Vi is equal to or lower than the reference voltage Vr2, and the detection signal Vs (FIG. 2F) holds the low level state when the integrated voltage Vi exceeds the reference voltage Vr2. ) Is output from the output terminal 8. Therefore, it is possible to detect whether the rotation speed of the electric motor is over the set value or below the set value, depending on whether the detection signal Vs is at the low level or the high level.

In the above example, the voltage dividing circuit for threshold voltage generation, which is composed of a series circuit of resistors R2 and R3, and the voltage comparator I
The level discriminating circuit 6 is constituted by C1 and the level discriminating circuit. The level discriminating circuit 6 has a predetermined threshold in which the level of the integrated voltage obtained across the capacitor C1 is set lower than the peak value (maximum value) of the integrated voltage. Any circuit can be used as long as it can discriminate whether it is higher or lower than the value, and is not limited to the above example. For example, when a ground terminal, a non-ground terminal connected to the ground potential portion, and a control terminal to which the rotation detection integrated voltage is input are provided, and the level of the rotation detection integrated voltage is lower than the threshold level, To turn off the ground-side terminal and the non-ground-side terminal, and turn on the ground-side terminal and the non-ground-side terminal when the rotation detection integrated voltage exceeds a threshold level. The above-mentioned level discrimination circuit can be constituted by a semiconductor switch.

FIG. 3 shows an example in which the level discriminating circuit 6 is constituted by a semiconductor switch. In this example, an NPN transistor Q1 is used as a semiconductor switch, and the transistor Q1 constitutes a level discriminating circuit. . The emitter of the transistor Q1 is grounded as the ground terminal of the semiconductor switch, and the collector is connected to the cathode of the diode D1 forming the AND circuit 7 as the non-ground terminal. The base of the transistor Q1 is connected as a control terminal to the output terminal of the rotation detecting integration circuit 5 (the non-ground side terminal of the capacitor C1).

In the level discriminating circuit 6 shown in FIG. 3, the voltage required to be applied between the emitter and the base of the transistor Q1 to make it conductive is the threshold voltage Vr1.

In the edge detection circuit 1 shown in FIG. 3, the rotation detection signal Vn is at a high level, and the magnitude of the delay signal Vl output from the rotation detection integration circuit 5 is smaller than the threshold value Vr1. Accordingly, a pulse which is at a high level only while the transistor Q1 is in the cut-off state is output as the edge detection pulse Vp.

When the level discriminating circuit 6 is constituted by semiconductor switches as in the example shown in FIG. 3, the rotational speed detection accuracy is slightly inferior to that of the circuit shown in FIG. Can be simplified as compared with the example of FIG. 1, so that the cost can be further reduced as compared with the example of FIG.

[0036]

As described above, according to the present invention, the edge detection circuit can be configured with a simple circuit configuration without using expensive parts such as a monostable multivibrator. There is an advantage that the cost of the number detection circuit can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration example of a detection circuit according to the present invention.

FIG. 2 is a waveform diagram showing voltage waveforms at various parts of the circuit of FIG.

FIG. 3 is a circuit diagram showing another configuration example of the detection circuit according to the present invention.

FIG. 4 is a circuit diagram showing a conventional example.

FIG. 5 is a waveform chart showing voltage waveforms at various parts of the circuit of FIG. 4;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 edge detection circuit 2 pulse integration circuit 3 comparison circuit 5 rotation detection integration circuit 6 level discrimination circuit 7 AND circuit IC1 voltage comparator IC2 voltage comparator Q1 NPN transistors R1 to R7 resistors C1 and C2 capacitors D1 diodes

Continuation of the front page (56) References JP-A-7-181193 (JP, A) JP-A 5-28927 (JP, U) JP-A 6-10869 (JP, U) JP-A 62-77923 (JP) , U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) G01P 3/42-3/489 G01D 5/245

Claims (3)

(57) [Claims] 1. An edge for generating an edge detection pulse at a rising edge of a rotation detection signal by inputting a rectangular wave rotation detection signal in which a period during which a high level state is maintained with an increase in the rotation speed of the electric motor is input. A detection circuit, a pulse integration circuit for integrating the edge detection pulse, and a voltage for comparing an integrated voltage output by the pulse integration circuit with a reference voltage and outputting a detection signal when the integrated voltage exceeds the reference voltage A comparator, and a motor rotation speed detection circuit that detects whether the rotation speed of the motor exceeds a set value.The edge detection circuit includes a rotation detection integration circuit that integrates the rotation detection signal. When the output voltage of the rotation detecting integration circuit is lower than the threshold value, the output is at a high level, and when the output voltage of the rotation detection integration circuit is higher than the threshold value, the output is high. A level discriminating circuit that is in a low level state, and a pulse signal that outputs a pulse signal that maintains a high level state only while both the rotation detection signal and the output of the level discriminating circuit are in a high level state as the edge detection pulse Circuit for detecting the number of revolutions of a motor. 2. An edge generating an edge detection pulse at a rising edge of the rotation detection signal by inputting a rectangular wave rotation detection signal in which a period during which a high-level state is maintained as the rotation speed of the motor increases becomes short. A detection circuit, a pulse integration circuit for integrating the edge detection pulse, and a voltage for comparing an integrated voltage output by the pulse integration circuit with a reference voltage and outputting a detection signal when the integrated voltage exceeds the reference voltage And a comparator for detecting whether or not the rotation speed of the motor exceeds a set value, wherein the edge detection circuit includes a non-ground side input terminal to which the rotation detection signal is input. And a capacitor connected between the other end of the resistor and the ground and charged through the resistor according to the rotation speed detection signal. A rotation detection integration circuit for generating a rotation detection integration voltage; and a threshold voltage generation circuit for dividing a constant power supply voltage to generate a threshold voltage having a level lower than a peak value of the rotation detection integration voltage. The voltage dividing circuit compares the rotation detection integrated voltage with the threshold voltage and holds a high level state when the rotation detection integrated voltage is lower than the threshold voltage. A level discriminator circuit comprising a voltage comparator that generates an output signal that becomes substantially ground potential when the voltage exceeds a threshold voltage; a resistor having one end connected to the non-ground side input terminal; An anode is connected and a cathode is composed of a diode connected to the output terminal of the voltage comparator. The high level is set only during a period when both the rotation detection signal and the output signal of the voltage comparator are at a high level. Lebe And an AND circuit for generating a pulse signal for maintaining the state of the pulse as the edge detection pulse between the cathode of the diode and a ground potential section. 3. An edge for generating an edge detection pulse at a rising edge of the rotation detection signal by inputting a rectangular wave rotation detection signal in which a period during which a high level state is maintained as the rotation speed of the motor increases becomes short. A detection circuit, a pulse integration circuit for integrating the edge detection pulse, and a voltage for comparing an integrated voltage output by the pulse integration circuit with a reference voltage and outputting a detection signal when the integrated voltage exceeds the reference voltage And a comparator for detecting whether or not the rotation speed of the motor exceeds a set value, wherein the edge detection circuit includes a non-ground side input terminal to which the rotation detection signal is input. And a capacitor connected between the other end of the resistor and the ground and charged through the resistor in response to a rotation speed detection signal. A rotation-detecting integration circuit for generating a detection-integrated voltage, a ground-side terminal connected to a ground potential section, a non-ground-side terminal, and a control terminal to which the rotation-detection integrated voltage is input; When the level of the integrated voltage for detection is lower than the threshold level, the state between the ground side terminal and the non-ground side terminal is turned off, and when the integrated voltage for rotation detection becomes higher than the threshold level, the grounding is performed. A level discriminating circuit for discriminating a level of the rotation detection integrated voltage by turning on and off the semiconductor switch; and A resistor having one end connected to an input terminal and a diode having an anode connected to the other end of the resistor and a cathode connected to a non-ground side terminal of the semiconductor switch, A pulse signal that holds a high-level state only while both the rotation detection signal and the potential of the non-ground side terminal of the semiconductor switch are at a high level state is used as the edge detection pulse. A circuit for detecting the number of revolutions of the electric motor, comprising: an AND circuit generated between them.