JPS5831830B2 - Brushless DC motor drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a so-called permanent magnet type plasticsless DC motor in which a permanent magnet is used in the rotor and a plurality of excitation coils are arranged to sequentially supply excitation current to the stator. Two Hall power generation elements are arranged on the rotor, the rotational position of the rotor is detected by the voltage generated by the Hall power generation elements, and these two detection signals are used to select the coil to which the excitation current should be supplied and to determine the excitation current. This invention relates to a drive circuit for a plasticless DC motor that determines the polarity of the motor.

SUMMARY OF THE INVENTION An object of the present invention is to provide a drive circuit with a simple configuration that can drive a tessellationless DC motor with a single polarity-switchable amplifier.

A further object of the present invention is to provide a drive circuit that can reliably start rotating the rotor in a desired direction as soon as it receives the DC power output, no matter where the rotor is at rest. shall be.

The present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic configuration of a plasticsless DC motor in which the drive circuit of the present invention can be implemented.

In the figure, M is an explanatory diagram of the configuration of an electric motor.

1 is a rotor that can use a permanent magnet 2, and 0 is a rotating shaft.

Magnetic pole pieces N and S are fixed to the N and S magnetic poles of the permanent magnet 2, respectively, and at one end in the axial direction of the magnetic pole pieces N and S (front front in the figure), there is a rotor that acts on the Hall power generation element described later. Auxiliary magnetic poles n and s are bonded to create a leakage magnetic field of the permanent magnet 2.

The auxiliary magnetic pole nts is not shown in the explanatory diagram of M, and only n and s are shown separately in diagram C.

The auxiliary magnets n, 5 are a pair of semicircular soft iron plates, with the negative side facing N.
, are adhered to the side surfaces of the S magnetic pole, and face each other with narrow gaps q1 and q2 in between.

If the central magnetic axis of the permanent magnet 2 is pp, it passes through the center O (11 0 (plane 12 and the magnetic axis pp are orthogonal when viewed from the axial direction.

Coils A and B are two sets of excitation coils wound around the stator core placed around the rotor.
The central axis a-a of the coil B and the central axis b-b of the coil B are the center O
are perpendicular to each other.

A ring-shaped soft iron plate 4 shown in Fig. D is fixed to a motor frame (not shown), and as shown in Fig. 1B, one side thereof faces the surfaces of the auxiliary magnetic poles n and s and is placed close to n9s. .

Two Hall power generation elements xy are attached to the surface of the soft iron plate 4 facing the auxiliary magnetic pole.

As shown in Figure D, the Hall power generation elements x and y are located symmetrically with respect to a plane containing the central axis a-a of one excitation coil, e.g., A, and the rotation axis O, and the included angle X-0-y is approximately 90 They are arranged in a uniform manner.

A constant DC driving current is supplied from a constant voltage source EB to the current end of each Hall power generation element through a resistor block, and when the element approaches the auxiliary magnetic pole n or S of the rotor 1, the output end of the element Generates a DC voltage ■ whose polarity corresponds to the polarity of the adjacent auxiliary magnet.

This DC voltage above ■ is called the rotor rotational position detection signal,
The output (1) of X is called a first rotational position detection signal, and the output vy of y is called a second rotational position detection signal.

The first rotational position detection signal Vx is applied to a first polarity discrimination amplifier OPX, which will be described later.

The OPX amplifies the detection signal and produces an output that changes into two values depending on the polarity of the first detection signal.
“Generate signal X.

The second rotational position detection signal Vy generated in the second Hall power generation element y is similarly amplified by the second polarity discrimination amplifier OPy, and the output of OPy is given a binary value of 0 corresponding to the polarity of Vy.
1 Generate signal Y.

The output voltage of a DC power source (not shown) for driving the motor is applied to an input 5 of an amplifier SA whose polarity can be switched.

This polarity switching amplifier SA is the first polarity discrimination amplifier OP.
is controlled by the output signal X of
In response to the signal value, an inverted output -EX or a non-inverted output + is generated at the output 6.

This output ±EX is guided to a switching circuit SW controlled by an output signal Z of an arithmetic circuit EL, which will be described later.

On the other hand, the output signal X of the first polarity discrimination amplifier OPX and the output signal Y of the second polarity discrimination amplifier OPy are applied to the exclusive OR circuit EL, where an exclusive OR operation of both signals is performed.

The output signal Z of EL controls the connection of the switching circuit SW.
Selectively connect cut point 7 to 8 or 9.

Hereinafter, the operation of the electric motor M by the above-mentioned drive circuit will be explained.

Now, when the n-pole of the auxiliary magnetic pole of the rotor approaches the Hall power generation element X, a signal
The value of the output signal X when the s pole approaches X is set to 0.

In addition, when the n-pole is brought close to the Hall power generation element y, OPy
The value of the output signal Y is 51", and the value of the signal Y when the 9s pole is close to y is 10".

Further, when the signal X power is φl", the output signal of the polarity switching amplifier SA is +EX1.0", and the output signal is -EX.

Now, as shown in FIG. 1C and D, the central magnetic axis P17P of the permanent magnets N and S of the rotor 1 is aligned with the central axis a of the exciting coil A
If the rotational position of the rotor 1 when parallel to -a is taken as the reference position, in this position, the n-pole of the rotor auxiliary magnetic pole faces the Hall power generating elements X and y.

If the rotor makes one rotation clockwise from this reference position, the opposing relationship between the x and y elements and fi and S will be as shown in Table 1.
column, changes as shown in the second column, and this X, y and n,
Corresponding to the combination of opposing relationships with s, X9Y and Z are the third, fourth, . and take the values shown in the fifth column.

In the switching circuit SW, when Z is 20'', contact 7 is connected to 9, and the output of SA +EX or - is supplied to coil B, and when Z is &S 1 //, it is supplied to coil A. As a result, no matter what rotational position the rotor is in with respect to the stator, torque acts on the rotor in a constant direction, causing it to rotate in a constant direction.

That is, in the case of FIG. 1, when the polarity of the shaft is positive, it rotates to the right, and when it is negative, it rotates in the opposite direction.

FIG. 2 shows a schematic configuration of a main part of a drive circuit according to another embodiment of the invention of the present application.

In the figure, shown in Figure 1! Elements corresponding to the constituent elements shown in FIG.

Fig. 2 (The difference between the drive circuit shown in Fig. 1 and the circuit shown in Fig. 1 is that the output signal Also, the switching circuit SW is directly switched and connected by the output signal Z of the second polarity discrimination amplifier OP, so that the logic operation circuit EL is not required.

The operation of this drive circuit will be explained as follows.

A linear integrated circuit is used in the first polarity discrimination amplifier OPX, and the levels of the output signal
It is.

Therefore, the polarity of the output signal vy of the Hall power generating element y is determined in relation to the polarity n of the auxiliary pole adjacent to y or both the polarities of S and X.

Table 2 shows the polarity of the output signal X of OPx and the polarity of the output signal Z of OPy for the combinations of Hall power generation elements X and y facing each other.

The amplifier used as OPy here is a linear IC like OPX.

1. If we consider the polarities n and s of the auxiliary magnetic poles to be + and -, respectively, then if the polarity of be.

If the polarity of the output signal ■ of the polarity switching amplifier SA is reversed by changing the polarity of the signal can do.

The drive circuit of FIG. 1 requires an exclusive OR circuit EL, but the drive circuit of FIG. 2 does not require a b-h-mEL.

Furthermore, in the circuit of FIG. In order to adapt the output signals X1 and Y of each of the second polarity discrimination amplifiers to the input of the IC circuit used in the arithmetic circuit EL, the levels of X and Y must be converted before being supplied to the EL.
In the circuit of FIG. 2, there is no need to perform level conversion of X and Z.

For example, as the arithmetic circuit EL in FIG.
-X when using an IC.

Y♂Q //, ”+ 1 //Level, i.e. ±E
8 must be converted to an input level o, 5V compatible with TTL.

Next, a means for ensuring rotor position discrimination using the Hall power generation element will be described.

Referring to Fig. 1, the rotation angle of the rotor in the clockwise direction from the reference position is expressed as θ, and when θ is close to approximately 45 degrees,
The auxiliary magnetic poles n and S of the rotor are both Hall power generation elements
be as close as possible.

Therefore, the rotational position detection signal ° generated at X gradually changes through zero as θ changes, as shown in FIG. In other words, R is applied to the operational amplifier OP using an IC circuit.
Connect the calculated resistors 1 to R4 and set the relationship between R1 and R4 as (1
) If it is assumed that the amplifier is amplified by a normal differential amplifier selected as shown in the equation, the amplifier output X takes an intermediate value between the positive and negative saturation voltages of OP ±Es near where θ crosses 45 degrees.

As a result, this signal X is sent to the polarity switching amplifier SA,
(2) When switching the polarity, the switching force is reliable.

Also, θ changes and becomes close to 135 degrees, n9S
When both are close to the Hall power generation element y to the same extent, if the output signal of y can be amplified by the differential amplifier shown in Fig. 4, the absolute value of the output Y (Z in the case of Fig. 2) will decrease, 1st
In the case shown in the figure, the arithmetic operation of the arithmetic circuit EL becomes uncertain, and even in the tilted drive circuits of FIGS. 1 and 2, the switching of the switching circuit SW by the signal Z becomes uncertain.

Therefore, if the rotor is stopped at such a rotational position, the rotor may not start even if the input DC voltage ■ is applied.

In the present invention, first. A differential amplifier having the configuration shown in FIG. 3 is applied to each of the second polarity discriminating amplifiers to eliminate the above-mentioned drawbacks.

In the circuit of FIG. 3, the values of the operational resistors R1 to R4 connected to the operational amplifier OP are selected so as to satisfy the following equation.

In other words, each resistor value is determined so that the value on the right side is slightly larger than the value on the left side, the amount of positive feedback is slightly larger than the amount of negative feedback of OP, and the entire circuit in Fig. 3 is made to have positive feedback slightly. The circuit operates as an amplifier circuit.

In this way, the output of this differential amplifier has hysteresis characteristics and dramatically changes from one saturation voltage to the other saturation voltage.

Therefore, even in the range where the rotational position detection signal (or) takes a value close to zero as shown in Figure 5a and gradually changes as the rotational angle θ changes, O
The value of the signal X or Y (Z in the circuit in Figure 2) generated at the output of PX or OP is ± as shown in Figure 5.
Es 4 Tracing the dramatic changes in Es.

19th each second polarity discrimination amplifier OP, OP.

If we use a differential amplifier with the characteristics shown in Figure 3 as
Two effects are brought about.

First, no matter what rotation angle position the rotor is stopped at,
When a direct current voltage of a predetermined polarity is applied to the input of the drive circuit, the motor rotor immediately responds to this and reliably starts rotating in a predetermined direction.

Second, even if the rotation of the rotor includes short-period minute vibrations and the rotational position detection signal (A) changes according to these minute vibrations, the output signals X, Y (or Z) of the polarity discriminator amplifier will change accordingly. There is no possibility of so-called chattering occurring near the polarity change point in response to this minute vibration.

Therefore, the phase delay of the excitation current caused by the coil inductance near the rotation angle at which the excitation coil is switched is amplified by this chattering, which prevents the system from oscillating when this motor is used as a drive motor for a servo system. be able to.

Figure 6 shows the waveform of θ when the rotation of the rotor includes short-period minute vibrations and the waveform of the signal Z that controls the switching circuit SW when the feedback amplifier in Figure 3 is used as OPy. show.

In the figure, θ and θ2 are the polarity change points of the signal Z, and indicate the values of θ such that -E8→+E8 and +Es→−E8, respectively.

[Brief explanation of drawings]

FIG. 1 shows a schematic configuration of a brushless DC motor that can implement the drive circuit of the present invention. FIG. 2 shows a schematic configuration of a main part of a drive circuit according to another embodiment of the invention of the present application. FIG. 3 shows the first drive circuit in the drive circuit shown in FIG. 1 or FIG. 1 shows a schematic connection diagram of a circuit suitable for a second polarity discriminating amplifier; FIG. FIG. 4 shows a connection diagram of a commonly known differential amplifier. Figures 5a and 5b are diagrams for explaining the operation of the embodiment of the present invention, where a shows the relationship between the rotor rotation angle and the output voltage of the Hall power generating element, and b shows the relationship between the rotation angle and the polarity discrimination amplifier output. shows the relationship between FIG. 6 is a waveform diagram for explaining the operation of the embodiment of the present invention, which shows the waveform of the rotation angle and the waveform of the signal driving the switching circuit when the rotation of the rotor includes a minute vibration component. Explain the relationship. M...Motor part, 1...Rotor, 2...Permanent magnet, n, s...Auxiliary magnetic pole, XeY...Hall power generation element, OP...First polarity discrimination amplifier, OPy...・・・
Second polarity discrimination amplifier, SA... polarity switching amplifier, SW
...Switching circuit, EL...Exclusive OR circuit, A, B
...Stator excitation coil.

Claims (1)

[Scope of Claims] 1. First and second Hall power generation elements each supplied with a DC drive current and arranged close to the rotor at a constant interval from each other; A 16th second polarity discrimination amplifier is connected to the output terminal of the Hall power generation element and generates a binary output signal corresponding to the polarity of the rotational position detection signal generated at the output terminal of each Hall power generation element, connected to the output of the DC power supply. and a polarity switching amplifier that generates an output with a polarity corresponding to the polarity of the power supply output or an output with a polarity opposite to the corresponding polarity by being controlled by the output signal of the first polarity discrimination amplifier; a logic operation circuit that receives the output of the second polarity discrimination amplifier and generates an output signal with a value corresponding to the exclusive OR of both output signal values; A drive circuit for a brushless DC motor, comprising a switching circuit that connects an output to a specific excitation coil among a plurality of excitation coils included in a motor stator. 2. Each of the first and second polarity discriminating amplifiers according to claim 1 comprises an operational amplifier and a feedback circuit that positively feeds back at least the output of the amplifier to the input side. Drive circuit for brushless DC motor. 3. A first Hall power generation element to which a constant DC drive current is supplied, which is disposed close to the rotor and generates a first rotational position detection signal related to the rotational position of the rotor; a first polarity discrimination amplifier that is connected to the rotor and amplifies the first rotational position detection signal and generates a first binary output signal corresponding to the polarity of the detection signal; a second rotational position detection device that is disposed at a predetermined distance and is supplied with a drive current from the output of the first polarity discrimination amplifier, and that is related to the first binary output signal and the rotational position of the rotor; a second Hall power generation element that generates a signal, a second polarity discrimination amplifier that amplifies the second rotational position detection signal and generates a second binary output signal corresponding to the polarity of the second position detection signal, and a DC power source. a polarity switching amplifier connected to the output and controlled by the first binary output signal to generate a DC output with a polarity corresponding to the polarity of the output of the DC power supply or a DC output with a polarity opposite to the polarity of the DC output; Controlled by the second binary output signal, the output of the polarity switching amplifier is directed to a specific excitation coil determined by the signal value of the second binary output signal among a plurality of excitation coils included in the motor stator. A drive circuit for a plasticless DC motor equipped with a connecting switching circuit. 4. Each of the first and second polarity discriminating amplifiers in claim 3 includes an operational amplifier and a feedback circuit that positively feeds back at least the output of the operational amplifier to the input side. Drive circuit for the described plasticless DC motor.