JPS608462B2 - Electric motor rotation speed detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a motor rotation speed detection device that detects the rotation speed from the period of an alternating current signal induced in the stator winding of a three-phase non-commutator type motor.

A conventional rotational speed detection device as described above will be explained with reference to the signal waveform diagram of FIG.

Due to the rotation of the rotor including the permanent magnets, an alternating current signal as shown in waveform a in FIG. 1A is induced in one phase of the three-phase stator winding, and period T is the period during which the driving current is conducted. In order to obtain period information from this waveform a, the waveform b shown in FIG. 1B is obtained by shaping the waveform using the voltage Vt as a threshold level. However, this waveform b contains unnecessary periodic components due to the influence of switching noise generated by the self-inductance of the stator winding at the time of switching the drive current. In order to eliminate this, the waveforms c and d shown in FIG. 1C obtained from the rotor position detection section are
, e are processed to obtain a gate signal having a waveform f as shown in FIG. 1D. These waveforms f and b are processed by a NOR circuit to obtain a speed signal of a non-commutator type motor that is not affected by the switching noise, such as waveform g in FIG. 1E. In the speed detection configuration described above, since the gate signal for noise removal as described above is obtained from the signal position, the mechanical assembly variation of the position detection section causes the waveform Ut2 to change at the falling edge of the waveform f. There is a possibility that the falling time of waveform b may be later than that of waveform g, and in that case, the periodic information of waveform g, which is a speed signal, will be obtained only from the position signal, and the accuracy will deteriorate.

This can be reduced by increasing the mechanical assembly precision of the position detection section, but as the commutatorless motor is made smaller, more precise assembly is required, which reduces productivity and increases costs. . The present invention provides a rotation speed detection device that can solve the problems of the conventional example by combining a differential circuit and a current inverting amplifier as means for obtaining a gate signal from a position signal. Hereinafter, the present invention will be explained based on illustrated embodiments. FIG. 2 is a diagram showing the main circuit configuration of an embodiment of the present invention, and FIG. 3 is a signal waveform diagram of each part in FIG. . In Figure 2, 1 is a position detection unit that outputs a 3-phase position signal according to the position of the rotor including permanent magnets, 2 is a 3-phase stator winding of a commutatorless motor, and one end is are connected in common and connected to a potential point Va. 3 is a drive unit that differentially amplifies a three-phase position signal that is an output signal of the position detection unit 1 and sequentially supplies power to each phase of the three-phase stator winding 2 to drive the rotor; 4 is a drive unit that drives the rotor; This is a waveform shaping section that shapes the waveform of an AC signal induced in one phase of the phase stator winding 2 at a threshold level Vt and obtains its period information.

In general, in order to increase the period detection accuracy, the threshold level is set at the detection time Ut4 in Fig. 3B to Fig. 3A.
It is set so that it is located before the port 5 when the power supply by the drive unit 3 starts. Reference numeral 5 designates three transistors 11, 12, and 13 whose emitters are connected in common, and a constant current source 16 for supplying emitter current to these transistors, each of which receives the three-phase position signals of the position detection section 1 as a base input. 6 is a current inversion circuit consisting of a transistor 4 whose collector and base are commonly connected, and a transistor 5 whose base is connected to the base of a transistor 14 and whose characteristics are the same as those of the transistor 14 but whose emitter areas are different. In the amplifier, the collector of the transistor 14, which is the input terminal, is connected to the collector of the transistor 12, and the collector of the transistor 15, which is the output terminal, is connected to the transistors 11 and 1.
3 is connected to the outside.

The interpolation circuit 5 and the current inverting amplifier 6 constitute a gate signal generating means, and a gate signal is output from the collector of the transistor 15. A logic gate section 7 logically processes the gate signal and the output signal of the waveform shaping section 4 to obtain a speed signal of the non-rectified Viscount motor.

Next, the operation of this embodiment will be explained. During steady rotation, three-phase sinusoidal position signals as shown at c, d, and e in FIG. 3C are generated at the output ends A, C, and C of the position detection section 1, respectively. The position signal is differentially amplified by the drive unit 3 and is fed to the three-phase stator winding 2, so that the one-phase stator winding terminal 2 receives an AC signal as shown by waveform a in FIG. 3A. occurs. Here, T indicates the power supply period. The periodic signal obtained from the AC signal by the waveform shaping section 4 has a waveform b in FIG. 3B.
becomes. From this waveform, in order to remove unnecessary periodic components due to switching noise explained in the above-mentioned conventional example at time Ut, the falling edge of the gate signal in the above-mentioned conventional example is The point where the phase is 8 m ahead of the current time is detected, and the waveform h is shown in Figure 3D.
The gate signal shown in is obtained. In other words, the operation of the differential circuit 5 around the time is that the transistors 11 and 12
is in an active differential state, and transistor 13 is almost in a cutoff state.

Here, when the potential difference between the base potential of the transistor 11 and the base potential of the transistor 12 is 10 Δe, the amplitude of the position signal is Vp, and the phase reference is 4, Δe can be expressed by the following equation. △e=Gei-Vp●{Sin (81210)
- Breasts n (8-30)} - Multi vp Tsuyoshi 8 -.・[1] Also, the collector currents of transistors 11 and 12 are set to 1, .
, 1.2, the relationship with △e is Ae=(k・T
/Q)ln(1,./1,2) ... ■However, k...
...Bormann constant, T ...absolute temperature, Q
・・・・・・It becomes an electronic charge.

Next, the emitter area of the transistors 14 and 15 of the current inverting amplifier 6 is determined by AE. 4, A8.5, and the ratio (^E1
5/A8, 4) is A, the collector current of the transistor 15 is A times the current flowing into the transistor 14, that is, the collector current 1, 2 of the transistor 12. Therefore, the voltage level change points to the output terminal are 1, . :AI. 2
... {It will be 31 years old.

From the above formulas '1', {21, {3}, the phase difference h of the output change point for the time ratio 2 (corresponding to 8 in formula [1')] is calculated as 8m=-sin-1{2・(k・T/Q). m
A/No.Vp}...(4} If the amplitude of the position signal is determined, a design of 8 m can be made by the amplification degree A of the current inverting amplifier 6.

The thus obtained gate signal shown in waveform h in FIG. 3D and the output signal of the waveform shaping section 4 shown in waveform b in FIG. A speed signal with a period corresponding to the rotational speed of the non-commutated Viscount motor as shown by waveform i is obtained. As is clear from the above description, the present invention uses a gate signal generating means configured to combine a differential circuit and a current inversion amplifier and change the phase of the gate signal detection point depending on the current amplification degree of the current inversion amplifier. As a result, even when the non-commutated motor is downsized, it is possible to obtain a highly accurate speed signal without having to extremely increase the mechanical assembly accuracy of the position detection unit, which has the excellent effect of improving productivity. can get. In the above-described embodiments of the present invention, the thin signal was described as a sine wave, but the same effect can be obtained if the signal has a slope, such as a triangular wave or a trapezoidal wave.

In addition, the amplification degree of the current inversion amplifier is changed to transistors 4 and 1.
Although the emitter area ratio was determined based on the emitter area ratio of 5, the same effect can be obtained by inserting an emitter resistor into each transistor and determining based on the resistance ratio, and it goes without saying that this is included in the present invention.

[Brief explanation of drawings]

Figures 1A, B, C, D, and E are signal waveform diagrams for explaining the conventional rotational speed detection configuration, Figure 2 is a circuit configuration diagram of the main part of the embodiment of the present invention, and Figures 3A and B. , C, D, E' are signal waveform diagrams of various parts in FIG. 2. 1...Position detection section, 2...Stator winding, 3
...Drive section, 4...Waveform shaping section, 5...
・Differential circuit, 6...Current inversion amplifier circuit, 7...
...Logic gate section, 11 to 16...transistor. 1st picture 2 3rd picture

Claims (1)

[Claims] 1. A commutatorless electric motor having a rotor including a permanent magnet and a three-phase stator winding, a position detection means for obtaining a three-phase position signal according to the position of the rotor, and the position signal. a driving means for rotating the rotor by sequentially supplying power to each phase of the stator winding in accordance with the stator winding; a waveform shaping means for obtaining period information from an alternating current signal induced in the stator winding; and a waveform shaping means for obtaining period information from an alternating current signal induced in the stator winding; a differential circuit comprising three transistors whose output terminals are connected to their respective bases and whose emitters are commonly connected; and a constant current source that supplies the emitter current of the transistors; gate signal generation means constituted by a current inverting amplifier whose input end is connected to the collector of one transistor and whose output end is connected to the collectors of the remaining two transistors; an output signal of the waveform shaping means; and the gate signal generation means. 1. A rotational speed detection device for an electric motor, comprising logic gate means for logically processing an output signal of the means.