JP4121277B2 - Brushless DC motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a brushless DC motor including a stator on which a plurality of phase windings are mounted, a rotor on which permanent magnets are mounted, and the like.
[0002]
[Prior art]
A stator having a plurality of phase windings, a rotor having permanent magnets, a detector for detecting the rotational position of the rotor, a switching circuit for sequentially energizing each phase winding by turning on and off the plurality of switching elements, and this There is a brushless DC motor in which a drive control circuit for driving and controlling a switching circuit is covered with a resin and integrated.
[0003]
The drive control circuit is configured to sequentially generate a drive signal having a predetermined period width for each phase winding at a predetermined phase angle based on detection by the detector, and each drive generated by the drive signal generation unit. A drive unit that drives the switching elements on and off in a predetermined period width of the signal is provided, and the on / off drive duty of the drive unit is controlled in accordance with an externally commanded rotation speed (command speed). By this duty control, the rotational speed of the rotor is set to the command rotational speed.
[0004]
[Problems to be solved by the invention]
The phase angle of the drive signal with respect to the phase winding (energization timing of the phase winding) is always fixed.
For this reason, when the load applied to the brushless DC motor fluctuates, or when the duty control value for the rotational speed control changes greatly, there may be a problem that the driving efficiency is deteriorated or noise is increased. .
[0005]
The present invention takes the above-mentioned circumstances into consideration, and the object of the present invention is excellent in reliability that can always be operated with good efficiency and low noise without being affected by load fluctuations and duty control. Another object is to provide a brushless DC motor.
[0006]
[Means for Solving the Problems]
A brushless DC motor according to a first aspect of the present invention includes a stator having a plurality of phase windings, a rotor having a permanent magnet, detection means for detecting the rotational position of the rotor, and on / off of a plurality of switching elements. A switching circuit for energizing each phase winding, generation means for sequentially generating a drive signal having a predetermined period width for each phase winding at a predetermined phase angle based on detection by the detection means, and generated by this generation means Driving means for turning on / off each switching element in a predetermined period width of each driving signal, first control means for controlling the duty of on / off driving of the driving means in accordance with an externally designated rotational speed, A current limiting resistor provided in the operation voltage supply path for the switching circuit, and the voltage generated in the resistor and the generation according to the command rotational speed And it includes a second control means for controlling the phase angle of the drive signals generated by the stage, a. In particular, the second control means includes an integrating circuit for integrating the voltage generated in the resistor, and level conversion of the output voltage of the integrating circuit based on a winding or a linear constant of each phase winding. Level conversion unit, a correction value calculation unit that divides the allowable maximum value of the command rotation number by the current command rotation number to obtain a correction value, and the output voltage level of the level conversion unit and the correction value are multiplied. A phase angle control unit that sets the phase angle of each of the drive signals according to the multiplication result.
[0007]
According to a second aspect of the present invention, a brushless DC motor includes a stator having a plurality of phase windings, a rotor having a permanent magnet, detection means for detecting the rotational position of the rotor, and on / off of a plurality of switching elements. A switching circuit that sequentially energizes each phase winding, a drive control circuit that drives and controls the switching circuit, and a current limiting resistor provided in an operation voltage supply path for the switching circuit are integrally configured. The drive control circuit is configured to generate a drive signal having a predetermined period width for each phase winding at a predetermined phase angle based on detection by the detection unit, and a generation unit that generates the drive signal. Driving means for turning on / off each switching element in a predetermined period width of each driving signal, and turning on / off the driving means in accordance with an externally commanded rotational speed First control means for controlling the duty of movement, and second control means for controlling the phase angle of each drive signal generated by the generating means in accordance with the voltage generated in the resistor and the command rotational speed. ing. In particular, the second control means includes an integrating circuit for integrating the voltage generated in the resistor, and level conversion of the output voltage of the integrating circuit based on a winding or a linear constant of each phase winding. And a phase angle control unit that divides the output voltage level of the level conversion unit by the duty control value of the first control means and sets the phase angle of each drive signal according to the division result. ing.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
[1] A first embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a brushless DC motor 1 includes a stator 2 having phase windings Lu, Lv, and Lw in a star connection, a rotor 3 having permanent magnets, and a detection for magnetically detecting the rotational position of the rotor 3. For example, Hall elements H1, H2, H3, a switching circuit 4 for sequentially energizing the phase windings Lu, Lv, Lw by turning on and off the plurality of switching elements, and a drive control circuit 10 for driving and controlling the switching circuit 4. The current limiting resistor 5 and the like are covered with a resin so as to be integrated.
[0009]
The switching circuit 4 is provided with a series circuit of upstream switching elements and downstream switching elements corresponding to three phases. As an upstream switching element and a downstream switching element for the U phase, the transistor Tu +, the transistor Tu−, and the V phase are used. Transistor Tv + and transistor Tv− as upstream switching elements and downstream switching elements, and transistor Tw + and transistor Tw− as upstream switching elements and downstream switching elements for the W phase, and a damper diode D in parallel with each of these transistors. Connected.
[0010]
An operating voltage (DC voltage) Vm is applied to the switching circuit 4 from the outside. The current limiting resistor 5 is inserted into the supply path of the operating voltage Vm. The resistor 5 functions to prevent an excessive current from flowing through the switching circuit 4 during an overload.
[0011]
A non-connected end of the phase winding Lu is connected to an interconnection point between the transistor Tu + and the transistor Tu− in the switching circuit 4. The non-connection end of the phase winding Lv is connected to an interconnection point between the transistor Tv + and the transistor Tv−. The non-connection end of the phase winding Lw is connected to the interconnection point between the transistor Tw + and the transistor Tw−.
[0012]
An operating voltage (DC 5V voltage) Vcc is applied to the drive control circuit 10 from the outside, and a rotational speed command signal (also referred to as a speed command signal) Vsp for commanding the rotational speed of the rotor 3 at a voltage level and the above-mentioned Output signals (rotational position detection signals) of the hall elements H1, H2, and H3 are input. The rotation speed command signal Vsp is input from a control unit or the like of a device on which the brushless DC motor 1 is mounted.
[0013]
This drive control circuit 10 is made into an IC logic, and its main part is shown in FIG.
In FIG. 2, reference numeral 11 denotes a drive signal generator, which sequentially applies drive signals having a predetermined period width (high level period) to the phase windings Lu, Lv, Lw at a predetermined phase angle based on detection of the Hall elements H1, H2, H3. To generate. These drive signals are supplied to the drive unit 12.
[0014]
The driving unit 12 drives each switching element of the switching circuit 4 on and off in accordance with a pulse signal supplied from a pulse width modulation unit 13 described later in a high level period of each driving signal.
[0015]
Reference numeral 13 denotes a pulse width modulation unit (PMW), to which the rotational speed command signal Vsp is input. The pulse width modulation unit 13 uses the voltage of the rotation speed command signal Vsp as a reference voltage, and chops the voltage of the triangular wave signal with the reference voltage, so that the width of the ON period (ON, OFF duty Du) according to the level of the reference voltage. %) Is output. This pulse signal is supplied to the driving unit 12.
[0016]
The pulse width modulator 13 constitutes first control means for controlling the duty Du of the on / off drive of the drive unit 12 according to the command rotational speed.
[0017]
An integrating circuit 14 integrates the voltage V0 generated in the resistor 5. The output voltage V1 of the integration circuit 14 is supplied to the level conversion unit 15. The level converter 15 converts the level of the output voltage V1 of the integrating circuit 14 based on a specific constant corresponding to, for example, the number of turns and the wire diameter of the phase windings Lu, Lv, and Lw. Specifically, the level of the output voltage V1 is multiplied by a constant, and a voltage V2 of a level corresponding to the multiplication result (= V1 × constant) is output. This output voltage V2 is supplied to the phase angle controller 16.
[0018]
Reference numeral 17 denotes a correction value calculation unit, which divides the allowable maximum value (Vspmax) of the command rotational speed by the current command rotational speed (Vsp), and thereby with respect to the phase angle of each drive signal generated by the drive signal generation unit 11. A correction value X (= Vspmax / Vsp) is obtained. The correction value X is supplied to the phase angle control unit 16.
[0019]
The phase angle control unit 16 multiplies the level of the output voltage V2 of the level conversion unit 15 by the correction value X, and is generated by the drive signal generation unit 11 to a magnitude corresponding to the multiplication result (= V2 × X). The phase angle of each drive signal is set.
[0020]
The integration circuit 14, the level conversion unit 15, the phase angle control unit 16, and the correction value calculation unit 17 control the phase angle of each drive signal according to the voltage V0 generated in the resistor 5 and the command rotational speed Vsp. Control means is configured.
[0021]
Next, the operation of the above configuration will be described.
When the operating voltages Vm and Vcc are applied to the switching circuit 4 and the drive control circuit 10, respectively, the transistors of the switching circuit 4 are turned on and off, and currents flow sequentially through the phase windings Lu, Lv, and Lw. This energization generates a magnetic field from the phase windings Lu, Lv, and Lw, and the rotor 3 rotates due to the interaction between the magnetic field and the permanent magnet of the rotor 3.
[0022]
At this time, the rotational position of the rotor 3 is detected by the Hall elements H1, H2, and H3, and drive signals for the phase windings Lu, Lv, and Lw are sequentially generated at a predetermined phase angle based on the detection. Each transistor is driven on and off during the high level period of these drive signals. The on / off driving duty Du is controlled in accordance with the rotational speed command signal Vsp. Thereby, the rotation speed of the rotor 3 is set to the command rotation speed according to the rotation speed command signal Vsp.
[0023]
On the other hand, the current Im flows through the resistor 5 with the operation of the switching circuit 4. This current Im varies depending on the magnitude of the load applied to the brushless DC motor 1 and the rotational speed of the rotor 3.
[0024]
The change in the current Im is detected by the drive control circuit 10, and the phase angle of each of the drive signals, that is, the phase winding, is determined according to the detection result and according to the command rotational speed which is the determining factor of the duty control value Du. The energization timing of the lines Lu, Lv, Lw is controlled.
[0025]
In this way, the load fluctuation is detected from the voltage V0 generated in the resistor 5, and the command rotational speed which is a determining factor of the duty control value Du is monitored, and the phase of each drive signal is determined according to these detection results and monitoring results. By variably setting the angle (set to an optimum value), it is possible to always operate with good efficiency and low noise without being affected by load fluctuations and duty control.
[0026]
In addition, since these control functions are incorporated into the brushless DC motor 1 as IC logic, there is no need to add a control circuit to the outside. The versatility is possible.
[0027]
In general, most of the current detection resistors (resistors 5) of the brushless DC motor are attached to the motor drive power supply line. In the case of PWM control, a regenerative current at the time of switching off flows in the current flowing through the resistor. It has no structure. Therefore, when the voltage detected by the current detection resistor is integrated and used as a phase adjustment signal, when the duty control value Du of the PWM control changes greatly, the phase adjustment signal is “winding current × Du”. This causes a problem of voltage information. In order to cope with this problem, it is necessary to adjust the signal for phase adjustment according to the change of the duty control value Du.
[0028]
In the present invention, even when the duty control value Du of PWM control changes greatly, the rotational speed command signal Vsp (determining factor of the duty control value Du) is used for the purpose of completely creating an optimum phase angle adjustment signal. (Command rotation speed) is monitored, and a configuration is applied in which a phase adjustment signal created from the voltage of the current detection resistor is corrected according to the monitoring result.
[0029]
[2] A second embodiment will be described.
In the second embodiment, as shown in FIG. 3, the correction value calculation unit 17 is removed from the drive control circuit 10, and the rotation speed command signal Vsp is supplied to the phase angle control unit 16.
[0030]
The phase angle control unit 16 grasps the duty control value Du determined by the pulse width modulation unit 13 from the rotational speed command signal Vsp, and divides the level of the output voltage V2 of the level conversion unit 15 by the grasped duty control value Du. Then, the phase angle of each drive signal generated by the drive signal generation unit 11 is set to a magnitude according to the division result (= V2 / Du).
Other configurations are the same as those of the first embodiment.
[0031]
As described above, the load variation is detected from the voltage V0 generated in the resistor 5, and the duty control value Du is determined from the rotation speed command signal Vsp. The phase angle of each drive signal is determined according to the detection result and the determination result. By making the variable setting (set to the optimum value), it is possible to always operate with good efficiency and low noise without being affected by load fluctuations and duty control.
[0032]
In addition, since these control functions are incorporated into the brushless DC motor 1 as IC logic, there is no need to add a control circuit to the outside. The versatility is possible.
In addition, this invention is not limited to said each embodiment, A various deformation | transformation implementation is possible in the range which does not change a summary.
[0033]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a brushless DC motor excellent in reliability capable of always operating with good efficiency and low noise without being affected by load fluctuations and duty control.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of each embodiment.
FIG. 2 is a block diagram showing a configuration of a main part of the drive control circuit in the first embodiment.
FIG. 3 is a block diagram illustrating a configuration of a main part of a drive control circuit according to a second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Brushless DC motor, 2 ... Stator, Lu, Lv, Lw ... Phase winding, 3 ... Rotor, H1, H2, H3 ... Hall element (detection means), 4 ... Switching circuit, 5 ... Resistor for current limitation DESCRIPTION OF SYMBOLS 10 ... Drive control circuit, 11 ... Drive signal generation part, 12 ... Drive part, 13 ... Pulse width modulation part, 14 ... Integration circuit, 15 ... Level conversion part, 16 ... Phase angle control part, 17 ... Correction value calculation part

Claims (2)

A stator having a plurality of phase windings;
A rotor having permanent magnets;
Detecting means for detecting the rotational position of the rotor;
A switching circuit for energizing each phase winding by turning on and off a plurality of switching elements;
Generating means for sequentially generating a driving signal having a predetermined period width for each phase winding at a predetermined phase angle based on detection by the detecting means;
Driving means for driving each switching element on and off in a predetermined period width of each driving signal generated by the generating means;
First control means for controlling the on / off drive duty of the drive means in accordance with an externally commanded rotational speed;
A current limiting resistor provided in an operating voltage supply path for the switching circuit;
Second control means for controlling the phase angle of each drive signal generated by the generating means according to the voltage generated in the resistor and the command rotational speed;
Equipped with,
The second control means includes an integration circuit that integrates the voltage generated in the resistor, and a level that converts the level of the output voltage of the integration circuit based on a winding of each phase winding or a specific constant corresponding to the linearity. A conversion unit, a correction value calculation unit that obtains a correction value by dividing the allowable maximum value of the command rotation number by a current command rotation number, and the output voltage level of the level conversion unit multiplied by the correction value. A phase angle control unit that sets the phase angle of each drive signal according to the result,
A brushless DC motor characterized by that. A stator having a plurality of phase windings;
A rotor having permanent magnets;
Detecting means for detecting the rotational position of the rotor;
A switching circuit for energizing each phase winding by turning on and off a plurality of switching elements;
Generating means for sequentially generating a driving signal having a predetermined period width for each phase winding at a predetermined phase angle based on detection by the detecting means;
Driving means for driving each switching element on and off in a predetermined period width of each driving signal generated by the generating means;
First control means for controlling the on / off drive duty of the drive means in accordance with an externally commanded rotational speed;
A current limiting resistor provided in an operating voltage supply path for the switching circuit;
Second control means for controlling the phase angle of each drive signal generated by the generating means according to the voltage generated in the resistor and the command rotational speed;
Equipped with,
The second control means includes an integration circuit that integrates the voltage generated in the resistor, and a level that converts the level of the output voltage of the integration circuit based on a winding of each phase winding or a specific constant corresponding to the linearity. A conversion unit; and a phase angle control unit that divides the output voltage level of the level conversion unit by the duty control value of the first control unit and sets the phase angle of each drive signal according to the division result. ,
A brushless DC motor characterized by that.

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