JP3333442B2 - Drive device for brushless motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor driving apparatus for controlling a commutation advance angle by an inverter circuit.

[0002]

2. Description of the Related Art When a brushless motor having a permanent magnet on a rotor and a winding on a stator is driven, a position sensor for detecting the rotational position of the rotor, and a sensor corresponding to the detected rotational position are sequentially arranged. An inverter circuit for commutating the current of the stator is required. This position sensor
For example, an electrical angle of 60 [deg] according to the rotational position of the rotor
It outputs a position detection signal for each.

[0003] When a microcomputer as control means performs a rectangular wave drive of an inverter circuit of 120 [deg], a microcomputer commutates with a PWM signal synchronized with the position detection signal, and performs a sine wave-triangle wave comparison. When sine wave driving is performed by the method, the angular resolution is sufficiently increased by calculation based on the position detection signal (for example, 1).
[Deg]) It is configured to commutate the inverter circuit in synchronization with the PWM signal.

Further, in the case of performing variable speed driving, a voltage command value is calculated based on a deviation between a rotation speed command value and a rotation speed detection value obtained from a position detection signal by using any of the above driving methods. The brushless motor is configured to be driven at a variable speed by applying a voltage based on a PWM signal proportional to the voltage command value to the brushless motor.

[0005]

However, since the stator winding of a brushless motor has an inductance,
The rise of the phase current after the commutation is delayed with respect to the voltage, and as a result, the current phase is delayed with respect to the rotor position (induced voltage). The amount of the current delay increases as the rotational speed increases, and also depends on the magnitude of the current. Therefore, in a conventional brushless motor driving device, for example, the commutation phase is set so that the power factor and the efficiency of the brushless motor become high under the conditions of the rated rotation speed and the rated load. However, if the relationship between the detected rotor position and the commutation phase is fixed by setting, the commutation phase advances under other driving conditions, for example, at a low rotation speed, and the power factor and efficiency deteriorate. There was a problem that it would.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to always maintain a high power factor of a brushless motor without depending on the number of revolutions and load, and to improve efficiency. An object of the present invention is to provide a brushless motor driving device.

[0007]

To achieve the above object, a brushless motor driving apparatus according to the present invention comprises: an inverter circuit for driving a brushless motor having a permanent magnet on a rotor; and a position detecting a rotational position of the rotor. Detection means; rotation number calculation means for calculating a rotation number based on a position detection signal output from the position detection means; and voltage command value calculation means for calculating a voltage command value to be applied to the brushless motor. In a drive device for a brushless motor, a lead angle calculation means for calculating a commutation lead angle of the inverter circuit based on a comparison result between a voltage command value calculated by the voltage command value calculation means and an induced voltage of the brushless motor. (Claim 1).

With this configuration, the commutation advance angle is calculated so that the voltage command value, that is, the applied voltage of the brushless motor, and the induced voltage of the brushless motor substantially match, and the commutation timing of the inverter circuit is determined. Is done. On the other hand, in the brushless motor, a large torque is obtained when the phase of the induced voltage of each phase matches the phase current, and the induced voltage and the applied voltage become substantially equal. Therefore, according to the above means, the generated torque of the brushless motor can be kept high, and the brushless motor can be rotationally driven with high power factor and high efficiency.

In this case, it is preferable to provide an induced voltage calculating means for obtaining an induced voltage by multiplying a preset induced voltage constant by the number of revolutions. With this configuration, the induced voltage of the brushless motor can be obtained with high accuracy only by the calculation without adding a sensor such as a voltage detector for detecting the phase voltage of the brushless motor. Further, since the commutation advance angle can be accurately calculated, the power factor and efficiency of the brushless motor can be further improved.

It is preferable that an induced voltage calculation means is provided for calculating an induced voltage constant based on the voltage command value and the rotation speed and for obtaining an induced voltage by multiplying the induced voltage constant by the rotation speed. ). With such a configuration, during driving of the brushless motor, the induced voltage constant is calculated based on the voltage command value and the rotation speed, so that it is not necessary to measure the induced voltage constant in advance, and furthermore, according to the rotation speed. A slightly changing induced voltage constant can always be obtained correctly. Therefore, the brushless motor can be driven with a simple method and with a high power factor and high efficiency over a wide speed range.

Further, an induced voltage detecting means for detecting an induced voltage from the phase voltage of the brushless motor may be provided. With this configuration, the induced voltage of the brushless motor is directly detected, so that it is not necessary to measure the induced voltage constant in advance, and even if the characteristics of the brushless motor change due to a temperature change or the like, no error occurs, The brushless motor can be driven with high efficiency and efficiency.

In the above means, the induced voltage used by the lead angle calculating means is a correction voltage proportional to the load of the brushless motor, the induced voltage calculated by the induced voltage calculating means or the induced voltage detected by the induced voltage detecting means. (Embodiment 5). With such a configuration, in the lead angle control, it is possible to compensate for the effect of the voltage drop due to the winding resistance of the brushless motor that increases as the load becomes higher, so that it is possible to prevent a decrease in torque, a decrease in power factor and efficiency. it can.

In this case, the induced voltage used in the lead angle calculating means may be the induced voltage calculated by the induced voltage calculating means or the induced voltage obtained by adding a fixed correction voltage to the induced voltage detected by the induced voltage detecting means. good. (Claim 6). With this configuration, it is possible to compensate for a calculation error or a detection error of the induced voltage by adding a constant correction voltage to the induced voltage used in the lead angle calculation means. Also, for example, if a correction voltage equal to the voltage drop due to the winding resistance of the brushless motor corresponding to the load current at a medium load is added, the torque can be easily reduced with an increase in the load current, and the power factor and the efficiency can be reduced. The drop can be compensated.

Further, the induced voltage used in the lead angle calculating means is equal to the induced voltage calculated by the induced voltage calculating means or the induced voltage detected by the induced voltage detecting means and a correction voltage proportional to the load of the brushless motor. An induced voltage obtained by adding the correction voltage can be used (claim 7). With such a configuration, the voltage drop due to the winding resistance of the brushless motor can be compensated by the correction voltage proportional to the load, and the calculation error or the detection error of the induced voltage can be compensated by the constant correction voltage.

Further, the induced voltage used in the lead angle calculating means is an induced voltage calculated by the induced voltage calculating means, an induced voltage detected by the induced voltage detecting means, or an induced voltage obtained by adding a correction voltage to these induced voltages. Preferably, the induced voltage is obtained by multiplying a correction coefficient according to the winding temperature of the brushless motor or the load of the brushless motor. According to this configuration, the effect of the voltage drop caused by the change in the winding resistance depending on the winding temperature of the brushless motor can be compensated more accurately, and the brushless motor can be driven with high power factor and high efficiency.

On the other hand, an inverter circuit for driving a brushless motor having a permanent magnet in the rotor, position detecting means for detecting a rotational position of the rotor, and a rotational speed based on a position detection signal output from the position detecting means. A driving device for a brushless motor, comprising: a rotation speed calculation device for calculating a rotation speed command value; and a voltage command value calculation device for calculating a voltage command value to be applied to the brushless motor by multiplying the rotation speed command value by an induced voltage constant. A lead angle calculating means for calculating a commutation lead angle of the inverter circuit based on a comparison result between a number command value and the rotational speed may be provided (claim 9).

With this configuration, after applying a voltage equal to the induced voltage obtained by multiplying the rotational speed command value by the induced voltage constant to the brushless motor, the rotational speed substantially matches the rotational speed command value. The commutation advance angle is calculated to determine the commutation timing. On the other hand, in the brushless motor, when the applied voltage is substantially equal to the induced voltage, the phases of the induced voltage and the current match, and a large torque is obtained. Therefore, according to the above means, the generated torque of the brushless motor can be kept high, and the brushless motor can be rotationally driven with high power factor and high efficiency.

In the above, there is provided a limit processing operation means for setting a limit value to the commutation advance angle calculated by the advance angle operation means (claim 10). With such a configuration, step-out due to excessively advanced or delayed commutation timing can be prevented, so that the brushless motor can be driven stably.

Further, the limit processing calculating means may set a limit value of the commutation advance angle according to the rotation speed.
1). With such a configuration, the limit value of the advance angle can be narrowed according to the number of revolutions, so that the brushless motor can be driven more stably.

The difference between the voltage command value calculated by the voltage command value calculating means and the induced voltage of the brushless motor can be controlled within a range of ± 10% of the induced voltage of the brushless motor. Item 12). With this configuration, the difference between the voltage command value calculated by the voltage command value calculation means and the induced voltage of the brushless motor is controlled within a range of ± 10% of the induced voltage at which the efficiency of the brushless motor is small. Therefore, the calculation accuracy of the induced voltage calculation unit and the lead angle calculation unit can be reduced without significantly lowering the efficiency. Therefore, the configuration of these calculation means can be simplified, and the processing capacity can be reduced, so that the cost of adjustment and the like can be reduced.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIG. In FIG. 1 showing the electrical configuration of the driving device, a driving device 1 for a brushless motor includes an inverter circuit 2 and a control circuit as a control means for controlling the inverter circuit 2, for example, a microcomputer 3.

In the inverter circuit 2, the U-, V-, and W-phase buses of the three-phase AC power supply 4 are connected to respective phase input terminals 12 of a rectifier circuit 11 having three-phase bridge-connected diodes 5 to 10.
u, 12v, and 12w, respectively, and the rectifier circuit 11
Positive DC power supply line 13 and negative DC power supply line 1
4 and a switching element 16 to 21 such as an IGBT, for example, and return diodes 22 to 27 connected in parallel to the smoothing capacitor 15.
Are connected to each other by a three-phase bridge connection. U, V, W of this inverter main circuit 28
To the phase output terminals 29u, 29v, and 29w, a brushless motor 30 having a permanent magnet (not shown) on a rotor and a three-phase winding (not shown) wound on a stator is connected.

The brushless motor 30 is provided with a position sensor 31 as position detecting means. The position sensor 31 has the same number of poles as the number of poles of a rotor attached to the rotating shaft of the brushless motor 30. It comprises a body and a Hall IC for detecting its magnetic force. Then, as the rotor of the brushless motor 30 rotates, the position sensor 31 outputs three position detection signals having a duty of 50% corresponding to the rotor position θ to each other with an electrical angle of 120 °.
The signal is output as an H level or an L level with a phase difference of [deg].

On the other hand, in the microcomputer 3,
A rotation speed calculation circuit 32 as a rotation speed calculation means detects a level change (edge) of three position detection signals output from the position sensor 31, and detects a time between edges generated at an electrical angle of 60 [deg]. Is measured, the rotation speed f of the brushless motor 30 at that time is calculated. In this case, if the rotational speed f is calculated using the time average value of a plurality of edge intervals measured in advance,
It is possible to obtain a stable rotational speed f excluding an error due to fluctuation of the position detection signal.

The voltage command value calculation circuit 33 functions as a voltage command value calculation means, and inputs the rotation speed command value f * of the brushless motor 30 and the rotation speed f of the brushless motor 30 output from the rotation speed calculation circuit 32. And the deviation (f * −
f) an internal regulator, for example PID, after obtaining
Input to the adjuster. Then, a voltage command value V * (effective value) of the brushless motor 30, which is the calculation result, is output to a PWM control circuit 34 and a lead angle calculation circuit 37 described later.

The PWM control circuit 34 includes a position calculation unit and a PWM calculation unit (not shown). The position calculation unit detects level changes (edges) of the three position detection signals output from the position sensor 31 and obtains position signals at electrical angle intervals of 60 [deg].
The angular resolution of the position signal is increased by further finely calculating the rotor position during 0 [deg].

More specifically, the time interval between the preceding position signals is measured, and the angle (electrical angle 60 [deg]) is divided by the measured time to determine the amount of change in the rotor position per unit time. By multiplying the elapsed time after the generation of the position signal by the amount of change in the rotor position per unit time, the rotation angle of the rotor can be estimated and calculated. Also, when a new position signal is generated, if the rotation angle estimated and calculated is reset to the true rotation angle corresponding to the position signal, no calculation error is accumulated.

The PWM operation section includes a voltage command value operation circuit 33
A commutation phase angle obtained by adding a commutation advance angle θL from a later-described advance angle calculation circuit 37 to the rotation angle of the rotor obtained from the position calculator, as an effective value. , A three-phase sine wave modulated wave having a certain phase relationship is generated. Then, by comparing the modulated wave with a triangular wave as a carrier wave, a pulse width modulated U, V, W phase PWM signal is obtained and output to the gate drive circuit 35. The above-described determined phase relationship is determined so that a voltage that can provide a high power factor and high efficiency at a rated speed and a rated load is output, for example.

The gate drive circuit 35 includes a PWM control circuit 3
4 is insulated, level-converted to an appropriate voltage, and output to each gate of the switching elements 16 to 21 of the inverter main circuit 28. Note that the gate drive circuit 35 may be provided independently outside the microcomputer 3.

An induced voltage calculating circuit 36 as an induced voltage calculating means multiplies the induced voltage E of the brushless motor 30 by multiplying a previously measured induced voltage constant KE by the rotation speed f calculated by the rotation speed calculation circuit 32. It is configured to calculate. The induced voltage constant KE can be obtained from theoretical calculations based on the structure of the rotor and the stator of the brushless motor 30, the characteristics of the permanent magnet of the rotor, and the like. Brushless motor 30 at that time
Can be determined by measuring the line voltage and the number of rotations. Further, when the lead angle control portion of the present driving device 1 is dissociated and the gate signals of the switching elements 16 to 21 of the inverter main circuit 28 are simultaneously turned off from the state where the brushless motor 30 is driven, the brushless motor 30 is turned off. The same applies when the line voltage and the rotation speed f are measured.

Lead angle calculation circuit 3 as lead angle calculation means
7 calculates the deviation (V * −E) between the voltage command value V * calculated by the voltage command value calculation circuit 33 and the induced voltage E of the brushless motor 30 calculated by the induced voltage calculation unit 36, and A commutation advance angle .theta.L is calculated by inputting to a provided regulator, for example, a PID regulator.

Next, the operation of this embodiment will be described. First, when the rotation speed command value f * is given, the voltage command value calculation circuit 33 inputs a rotation speed deviation (f * -f) which is a difference between the rotation speed command value f * and the rotation speed f to the PID adjuster. Then, the voltage command value V *, which is the effective value of the voltage applied to the brushless motor 30, is calculated. And the inverter main circuit 28
A commutation phase having an effective value equal to the voltage command value V * and obtained by adding the commutation advance angle θL from the advance angle calculation circuit 37 to the rotor position of the brushless motor 30 detected by the position sensor 31. A three-phase sinusoidal voltage having a fixed phase relationship with the angle is output.

That is, the position sensor 31, the rotation speed calculation circuit 32, the voltage command value calculation circuit 33, the PWM control circuit 34,
According to the speed control feedback loop including the gate drive circuit 35, the inverter main circuit 28, and the brushless motor 30 to be controlled, when the rotation speed command value f * is higher than the rotation speed f of the brushless motor 30,
Acceleration is performed by increasing the voltage applied to the brushless motor 30 according to the voltage command value V *. Conversely, when the rotation speed command value f * is lower than the rotation speed f of the brushless motor 30, the voltage applied to the brushless motor 30 is reduced. As a result, the deceleration is performed, and the follow-up control of the rotational speed f to the rotational speed command value f * is performed.

The brushless motor 30 can be driven only by the speed control loop (ie, the commutation phase angle θL = 0). In this case, however, the brushless motor 30 is driven in accordance with the speed or the load as described above. Since the power factor and efficiency of the motor 30 greatly change, the efficiency of the brushless motor 30 is reduced except for a part of the operating range that is optimally adjusted.

When the phase of the induced voltage matches the phase of the current, the motor power factor and the efficiency of the brushless motor 30 increase. Particularly, at a light load, the induced voltage E of the brushless motor 30 and the applied voltage (equal to the voltage command value V *). ) Are substantially equal in size. On the other hand, if the phase of the voltage applied to the brushless motor 30, that is, the timing of commutation is delayed and the phase of the current with respect to the induced voltage is delayed, the brushless motor 3
The applied voltage tends to increase as the 0 phase current decreases. Conversely, when the phase of the current with respect to the induced voltage advances, the phase current increases and the applied voltage tends to decrease.

Therefore, in the induced voltage calculation circuit 36,
The induced voltage E of the brushless motor 30 is calculated by multiplying the induced voltage constant KE by the rotational speed f, and the lead angle calculating circuit 37 adjusts the deviation (V * -E) between the voltage command value V * and the induced voltage E by PID adjustment. Commutation advance angle θL
Is calculated. The PWM control circuit 34 determines the phase of the applied voltage by using the commutation phase angle obtained by adding the commutation advance angle θL to the detected rotor position.

Accordingly, the position sensor 31, the rotation speed calculation circuit 32, the induced voltage calculation unit 36, the lead angle calculation circuit 37, the PW
According to the lead angle control feedback loop including the M control circuit 34, the gate drive circuit 35, the inverter main circuit 28, and the brushless motor 30 to be controlled,
If the voltage command value V * is higher than the induced voltage E of the brushless motor 30, the delay is compensated by advancing the phase of the voltage applied to the brushless motor 30 by the commutation advance angle θL (> 0). When the value V * is lower than the induced voltage E of the brushless motor 30, the phase of the voltage applied to the brushless motor 30 is changed to the commutation advance angle θL (<
The lead is compensated by delaying by the absolute value of 0), so that the induced voltage E and the voltage command value V * match, and control is performed so that the induced voltage and the current have the same phase.

The advance angle control feedback loop has a smaller loop gain and a slower calculation cycle than the speed control feedback loop, so that both controls do not interfere with each other.

As described above, according to the first embodiment, the commutation advance angle θL is calculated so that the voltage command value V * substantially matches the induced voltage E of the brushless motor 30, and the commutation of the inverter circuit is performed. Since the timing is determined, the phases of the induced voltage and the phase current substantially match, the generated torque can be increased, and the brushless motor 30 can be rotationally driven with a high power factor and high efficiency. Further, the induced voltage E is calculated as the product of the induced voltage constant and the rotational speed f which can be measured accurately in advance.
Can be accurately obtained, so that the advance angle control can be performed with high accuracy.

Next, a second embodiment of the present invention will be described with reference to FIG. In addition,
The same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. Only different components will be described.

In FIG. 2, the induced voltage calculation circuit 38
The induced voltage constant KE is calculated by dividing the voltage command value V * output from the voltage command value calculation circuit 33 at a predetermined timing by the rotation speed f at that time. And
During normal operation, the induced voltage E of the brushless motor 30 is calculated by multiplying the induced voltage constant KE by the rotation speed f.

In the configuration in which the microcomputer 3 uses the above-described induced voltage calculation circuit 38, the function of the lead angle calculation circuit 37 is stopped (θL) until the brushless motor 30 reaches a certain frequency after being driven from the stopped state. = 0)
Let it be. This is to prevent a meaningless voltage from being input to the lead angle calculation circuit 37 while the induced voltage constant KE is not identified, thereby preventing the lead angle control from being disrupted.

After reaching a certain frequency, the induced voltage constant KE is determined by dividing the voltage command value V * by the rotational speed f at the determined timing. The reason why the calculation is performed at a certain frequency or more is that the voltage command value V * is small and the calculation error increases in the low rotation speed region. Further, as the load increases, the influence of the voltage drop due to the winding resistance of the brushless motor 30 increases. Therefore, it is preferable to perform the above identification under a relatively light load state. The identification timing of the induced voltage constant KE may be determined as needed, for example, at regular time intervals, when the rotational speed changes, or when an external command is input.

After the induced voltage constant KE has been identified, as described in the first embodiment, the induced voltage E of the brushless motor 30 is calculated by multiplying the induced voltage constant KE by the rotation speed f, and the voltage command value V * And its induced voltage E are input to the advance angle calculation circuit 37 to obtain a commutation advance angle θ.
Lead angle control is performed using L.

As described above, according to the second embodiment,
In addition to the effects of the first embodiment, the induced voltage calculation circuit 38 of the driving device 1 has a function of identifying the induced voltage constant KE, so that the measurement of the induced voltage constant of the brushless motor 30 becomes unnecessary. When the induced voltage constant KE is always identified or when the rotational speed changes, an induced voltage constant that slightly changes according to the rotational speed can always be obtained correctly.
Therefore, the brushless motor 30 can be driven with a high power factor and high efficiency over a wide speed range by a simple method that does not require measurement of the induced voltage constant.

Next, a third embodiment of the present invention will be described with reference to FIG. In addition,
The same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. Only different components will be described.

In FIG. 3, a current detector 39 is formed using, for example, a Hall element so as to detect a DC component, and a positive DC power supply line between the rectifier circuit 11 and the smoothing capacitor 15 in the inverter circuit 2. Current I flowing through 13
(Hereinafter, referred to as load current I).

The induced voltage calculation circuit 40 adds a correction voltage proportional to the load current I detected by the current detector 39 to the induced voltage E calculated by the above-described induced voltage calculation circuit 36, and induces it again. It is configured to output the voltage E to the lead angle calculation circuit 37.

In the case of the above configuration, the calculated induced voltage E is obtained by adding the correction voltage proportional to the load to the product of the rotational speed f and the induced voltage constant KE. The reason for adding such a correction voltage is that when the load of the brushless motor 30 increases and the phase current increases, the voltage drop due to the winding resistance of the brushless motor 30 increases, and as a result, the applied voltage (voltage command value V * ) Is greater than the induced voltage E (the product of the rotational speed f and the induced voltage constant KE) of the brushless motor 30 by the voltage due to the voltage drop, so that the increase is compensated for. Therefore, a voltage corresponding to this voltage drop is set as the correction voltage.

The load current I detected by the current detector 39 is substantially proportional to the load of the brushless motor 30. The load current I is supplied from the rectifier circuit 11 to the smoothing capacitor 15.
Since the current flows into the circuit, it includes a ripple component, but the ripple component can be removed by passing through a filter (not shown).

As described above, according to the third embodiment,
By adding a correction voltage proportional to the load to the induced voltage E, which is the product of the rotational speed f and the induced voltage constant KE, the voltage drop due to the winding resistance of the brushless motor 30 is compensated. Also, no error occurs in the advance angle control, and the brushless motor 30 can be driven with a high power factor and high efficiency at all times.

Next, a fourth embodiment of the present invention will be described with reference to FIG. In addition,
The same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. Only different components will be described.

In FIG. 4, the induced voltage calculation circuit 41 includes:
The induced voltage E calculated by the above-described induced voltage calculation circuit 36
Further, a constant correction voltage δh is added thereto, and the added correction voltage δh is output as an induced voltage E to the advance angle calculation circuit 37 again.

In the above configuration, the calculated induced voltage E
Is obtained by further adding a constant correction voltage δh to the product of the rotational speed f and the induced voltage constant KE. The correction voltage δh is determined by the measurement error of the induced voltage constant KE and the brushless motor 3
This is for compensating for the deviation between the applied voltage (equal to the voltage command value V *) and the induced voltage E both due to the voltage drop due to the winding resistance of 0. The amount of this deviation increases in proportion to the rotation speed or the current. For example, if a correction voltage δh that can be compensated for just about at a moderate load and around a moderate rotation speed is selected, compared to the case where no compensation is made, In addition, the error of the induced voltage E can be reduced by at least approximately half or more.

As described above, according to the fourth embodiment,
By adding a constant correction voltage δh to the calculation of the induced voltage E, the measurement error of the induced voltage constant KE and the voltage drop due to the winding resistance of the brushless motor 30 are simultaneously compensated, so that the error of the lead angle control is reduced. The brushless motor 30 can be maintained at a high power factor and a high efficiency by a simple method without adding a current detector or the like.

Next, a fifth embodiment of the present invention will be described with reference to FIG. In addition,
The same components as those in FIG. 3 are denoted by the same reference numerals, and the description thereof will be omitted. Only different components will be described.

In FIG. 5, the induced voltage calculation circuit 42
The induced voltage E calculated by the above-described induced voltage calculation circuit 36
Further, a correction voltage proportional to the load current I detected by the current detector 39 and a fixed correction voltage δh ′ are added, and the result is output to the lead angle calculation circuit 37 as an induced voltage E again. ing. That is, the induced voltage calculating circuit 40 shown in FIG. 3 and the induced voltage calculating circuit 41 shown in FIG. 4 both have a function of compensating for a deviation between the applied voltage (equal to the voltage command value V *) and the induced voltage E. ing.

In this case, the correction voltage proportional to the load current I compensates for the voltage drop due to the winding resistance of the brushless motor 30, and the constant correction voltage δh 'compensates for the deviation due to the measurement error of the induced voltage constant KE. Is set. Therefore,
According to the fifth embodiment, the voltage drop due to the winding resistance and the measurement error of the induced voltage constant KE can be independently compensated, and the brushless motor 30 can be driven with high power factor and high efficiency. .

Next, a sixth embodiment of the present invention will be described with reference to FIG. 6, which shows an electric configuration of a driving device. In addition,
The same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. Only different components will be described.

In FIG. 6, the temperature detector 43 is constituted by, for example, a thermistor, etc.
The winding temperature T of the stator is measured.
The correction coefficient calculation circuit 44 is calculated by an induced voltage calculation circuit 45, which will be described later, according to the load current I detected by the current detector 39 and the winding temperature T of the stator of the brushless motor 30 detected by the temperature detector 43. A correction coefficient ε for correcting the induced voltage E is output.

The induced voltage calculation circuit 45 multiplies the induced voltage E calculated by the above-described induced voltage calculation circuit 36 by the correction coefficient ε obtained by the correction coefficient calculation circuit 44, and again multiplies it as the induced voltage E by the lead angle. It is configured to output to the arithmetic circuit 37.

In the above configuration, the correction of the induced voltage E by obtaining the correction coefficient ε in accordance with the load current I and the winding temperature T is performed by increasing the voltage drop due to the winding resistance of the brushless motor 30 with an increase in the load. , And the effect of an increase in the winding resistance itself accompanying an increase in the winding temperature T.
That is, when the load current I or the winding temperature T increases,
The state in which the applied voltage (equal to the voltage command value V *) is higher than the induced voltage E (the product of the rotational speed f and the induced voltage constant KE) of the brushless motor 30, and a deviation between the applied voltage and the induced voltage E exists. When the advance angle control is performed in the step (b), the commutation advance angle is advanced compared to the optimum angle, and the brushless motor 3
This is because the phase of the induced voltage of 0 (true) and the current phase are shifted, and the efficiency is deteriorated. Therefore, the correction coefficient ε is set to a value that can compensate for the voltage drop due to the winding resistance and the increase in the winding resistance by multiplying the induced voltage E (the product of the rotational speed f and the induced voltage constant KE). You.

As described above, according to the sixth embodiment,
Since the voltage drop due to the winding resistance of the brushless motor 30 due to the increase in the load and the influence of the change in the winding resistance itself due to the rise in the winding temperature T in the lead angle control are compensated, the motor load and the motor temperature change. However, no error occurs in the advance angle control, and the brushless motor 30 can always be driven with a high power factor and high efficiency.

Next, a seventh embodiment of the present invention will be described with reference to FIG. 7 showing an electric configuration of a driving device. In addition,
The same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. Only different components will be described.

In FIG. 7, a lead angle calculation circuit 46 as a lead angle calculation means receives the rotation speed command value f * of the brushless motor 30 and the rotation speed f of the brushless motor 30 output from the rotation speed calculation circuit 32. And the deviation (f * −
f) an internal regulator, for example PID, after obtaining
Input to the adjuster. The commutation advance angle .theta.L, which is the result of the calculation, is output to the PWM control circuit 34.

The voltage command value V * is equal to the rotational speed command value f.
* Is calculated by multiplying * by the previously measured induced voltage constant KE.
The signal is input to the M control circuit 34. Note that the microcomputer 3 of the driving device 1 does not include the induced voltage calculation circuit.

In the above configuration, the voltage command value V * obtained by multiplying the rotation speed command value f * by the induced voltage constant KE is equal to the induced voltage E of the brushless motor 30, and the induced voltage E is always applied to the brushless motor 30. Is applied. On the other hand, as described above, when the phase of the induced voltage coincides with the phase of the current, the motor power factor and the efficiency are increased, and especially under a light load, the magnitude of the induced voltage E of the brushless motor 30 becomes substantially equal to the applied voltage. Therefore, the applied voltage is always the induced voltage E
In this embodiment, as long as the commutation phase is set optimally, the rotation speed is substantially equal to the rotation speed command value f * (even without the lead angle calculation circuit 46), and the high power factor and the high efficiency It becomes possible to drive with.

However, in practice, the optimum commutation phase changes according to the rotational speed f, the applied voltage becomes excessive or insufficient due to the setting error of the induced voltage constant KE, or the voltage due to the winding resistance of the brushless motor 30 The presence of the drop causes a shift in the rotational speed f, a lack of torque, and the like. Therefore, a lead angle calculation circuit 46 is added to form a speed control loop using the commutation lead angle θL as an operation amount, thereby causing the rotation speed f to follow the rotation speed command value f *, thereby stabilizing operation. Is being planned.

As described above, according to the seventh embodiment,
The microcomputer 3 outputs the induced voltage E of the brushless motor 30 calculated by the microcomputer 3, and controls the commutation advance angle θL in order to suppress various errors or rotation speed fluctuations caused by a transient state.
Is configured to perform the rotation speed control with the operation amount as
The motor power factor and efficiency can be increased, and variable speed driving can be performed stably.

Next, an eighth embodiment of the present invention will be described with reference to FIG. 8, which shows an electrical configuration of a driving device. In addition,
The same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. Only different components will be described.

In FIG. 8, a limit processing operation circuit 47 as a limit processing operation means includes a lead angle operation circuit 37.
For example, the upper limit of the electrical angle 60 [deg] and the electrical angle -60 [de]
g], and performs a limit process, and outputs the commutation advance angle θL ′ subjected to the limit process to the PWM calculation circuit 34. This limit value is set to a commutation advance angle θ L necessary and sufficient to compensate for a current delay due to the inductance of the winding of the brushless motor 30.

According to the eighth embodiment to which such a limit processing operation circuit 47 is added, the commutation advance angle θL becomes an excessive value during transition such as rapid acceleration / deceleration, and the brushless motor 30 Since the torque is prevented from being reduced and the step-out is prevented, stable driving can be performed.

Next, a ninth embodiment of the present invention will be described with reference to FIG. 9 showing an electric configuration of a driving device. In addition,
The same components as those in FIG. 8 are denoted by the same reference numerals, and description thereof will be omitted. Only different components will be described.

In FIG. 9, the limit processing operation circuit 48
The upper limit value and the lower limit value are set for the commutation advance angle θL in the same manner as in the limit processing operation circuit 47, and the upper limit value is set in accordance with the rotation speed f. It is configured.

According to the ninth embodiment to which the limit processing arithmetic circuit 48 is added, the upper and lower limit values are set small at a low commutation angle θL or at a low rotation speed where the change amount is small, and the commutation advance angle is set. The upper and lower limits can be set to be large at the angle θL or at a high rotational speed where the change amount is large. That is, the commutation advance angle θL is limited to the minimum necessary range for each rotation speed, so that more stable driving is possible.

Next, FIGS. 10 and 11 show the relationship between the motor applied voltage and the motor efficiency in the tenth embodiment of the present invention.
This will be described with reference to FIG.

In this embodiment, in the first to ninth embodiments, the lead angle control is performed so that the voltage applied to the brushless motor 30 is within ± 10% of the induced voltage E (in the seventh embodiment). Sets the induced voltage constant KE). Hereinafter, the reason will be described with reference to FIGS.

FIGS. 10 and 11 show the electrical configuration shown in FIG. 1 at 3600 [rpm] or 7200 [rpm].
m], the function of the lead angle calculation circuit 37 is stopped, and the commutation lead angle θL is given from the outside to the PWM calculation circuit 34, thereby obtaining the voltage command value V *. It shows the efficiency when (equal to the applied voltage) is increased or decreased. In the curves shown in the figures, the solid line is a load factor of 100% (rated load), the broken line is a load factor of 75%, the dashed line is a load factor of 50%, and the two-dot chain line is a load factor of 2
The case of 5% is shown.

In each of the figures, the brushless motor 3
When the applied voltage of 0 is substantially equal to the induced voltage E of the brushless motor 30 at each rotation speed, the efficiency becomes maximum,
Although the efficiency decreases as the two shift, the efficiency decreases in a region sandwiched by broken lines extending in the vertical direction in the figure around the induced voltage, that is, in an applied voltage range within ± 10% of the induced voltage E. Is relatively small and is considered to be practically acceptable.

Therefore, according to the tenth embodiment, even if the applied voltage does not completely match the induced voltage E, if the lead angle control is performed so as to be within ± 10% of the induced voltage E. , The efficiency can be kept relatively high. further,
Since the control accuracy can be reduced, a simple method can be used for calculating the induced voltage E, and the cost of the driving device 1 can be reduced.

Next, an eleventh embodiment of the present invention will be described with reference to FIG. The same components as those in FIG. 1 are denoted by the same reference numerals, description thereof will be omitted, and only different components will be described.

In FIG. 12, a voltage detector 49 is for detecting each phase voltage E0 of the brushless motor 30. Specifically, a high resistance and a low resistance connected in series, not shown, are provided for each phase. One end (high resistance side) of each phase detection resistor is connected to each phase terminal of the brushless motor 30, and the other end (low resistance side).
Are all connected in common to form a virtual neutral point. Then, the phase voltage E0 of the brushless motor 30 is obtained from both ends of the low-resistance of the phase detection resistors.

The induced voltage detection circuit 50 includes a voltage detector 49
The induced voltage E of the brushless motor 30 is detected from the phase voltage E0 of the brushless motor 30 detected by the above. Specifically, for example, the P of the PWM control circuit 34
The upper arm group (switching element 1) of switching elements 16 to 21 constituting inverter main circuit 28 is added to the WM signal.
6 to 18) or a lower arm group (switching elements 19 to 18)
21), a section is provided in which any one of the brushless motors 30 is simultaneously turned off.
Is configured to detect the induced voltage E. In this section, braking acts on the brushless motor 30, but if this section is set short, the influence of torque fluctuations and the like can be suppressed.

The speed control and the lead angle control after obtaining the above induced voltage E are as described in the first embodiment. Therefore, according to the present embodiment in which the induced voltage E of the brushless motor 30 is directly detected by the voltage detector 49 and the induced voltage detection circuit 50, the induced voltage constant K
The induced voltage E can be accurately detected without measuring E, and the brushless motor 30 can be driven with high power factor and high efficiency.

The present invention is not limited to the embodiment described above and shown in the drawings, but can be extended or modified as follows. The PWM control circuit 34 outputs 120 [d
eg] A rectangular wave drive of an energization type may be performed. The position sensor 31 may use a rotary encoder. In this case, the position calculation unit in the PWM control circuit 34 can be omitted or simplified.

In the third, fifth and sixth embodiments, the current flowing through the negative DC power supply line 14 between the rectifier circuit 11 and the smoothing capacitor 15 and the smoothing capacitor 15 A current flowing through the positive DC power supply line 13 or the negative DC power supply line 14 between the inverter and the inverter main circuit 28, or a phase current of the brushless motor 30 may be used.

In the seventh embodiment or the eleventh embodiment,
When calculating the voltage command value V *, if the load current I is detected by the above-described method and a correction voltage proportional to the load is added, or if a constant correction voltage is simply added, the load may change. However, high efficiency can always be maintained.

[0088]

Since the present invention is as described above,
The following effects are obtained. According to the driving device of the first aspect, the lead angle control is performed based on the comparison result between the voltage command value calculated by the voltage command value calculation means and the induced voltage of the brushless motor. The induced voltage substantially matches, and as a result, the phase of the induced voltage and the phase current becomes the optimal phase for generating torque. Therefore, the brushless motor can be rotationally driven with high power factor and high efficiency.

According to the second aspect of the present invention, in the induced voltage calculating means, the induced voltage can be accurately obtained by multiplying the preset induced voltage constant by the number of revolutions. Can be performed, and the power factor and efficiency of the brushless motor can be further improved.

According to the driving device of the third aspect, the induced voltage calculating means calculates the induced voltage constant based on the voltage command value and the rotation speed, and multiplies the induced voltage constant by the rotation speed to calculate the induced voltage. Therefore, it is not necessary to measure the induced voltage constant in advance, and the induced voltage constant can always be obtained correctly during driving. Therefore, it is possible to drive with a high power factor and a high efficiency over a wide speed range by a simple method.

According to the fourth aspect of the present invention, since the induced voltage is directly detected by the induced voltage detecting means from the phase voltage of the brushless motor, the induced voltage constant does not need to be measured in advance, and the temperature can be reduced. And the induced voltage constant that changes with the rotation speed can always be obtained accurately, so that the lead angle control with high accuracy can be performed, and the power factor,
And the efficiency can be further improved.

According to the driving device of the present invention, the correction voltage proportional to the load of the brushless motor is added to the induced voltage calculated by the induced voltage calculating means or the induced voltage detected by the induced voltage detecting means. , Or the induced voltage obtained by adding a fixed correction voltage, and furthermore, the lead angle control is performed using the induced voltage corrected by the winding temperature of the stator, so that the voltage drop due to the winding resistance of the brushless motor and the calculation error of the induced voltage Alternatively, the detection error can be compensated. Therefore, the brushless motor can always be driven with a high power factor and high efficiency irrespective of the load and the number of rotations.

According to the ninth aspect of the present invention, the voltage command value to be applied to the brushless motor is calculated by multiplying the rotation speed command value by the induced voltage constant, and the result of comparison between the rotation speed command value and the rotation speed is obtained. , The speed control using the commutation advance angle as the operation amount is performed, so that the brushless motor can be driven at a high power factor and with high efficiency at a variable speed.

According to the tenth and eleventh aspects of the present invention, a limit value is provided for the commutation advance angle calculated by the advance angle calculation means by the limit processing calculation means, so that the commutation timing is too advanced or too late. Can be prevented, and the brushless motor can be driven stably. In addition, since the limit value is set according to the rotation speed (claim 11), more stable driving can be performed.

According to the twelfth aspect of the present invention, the difference between the voltage command value calculated by the voltage command value calculation means and the induced voltage of the brushless motor is determined by the difference of the induced voltage of the brushless motor with a small decrease in efficiency. Since control is performed within the range of 10%, control accuracy can be reduced while maintaining high efficiency, and the configuration can be simplified.

[Brief description of the drawings]

FIG. 1 is an electrical configuration diagram of a brushless motor driving device according to a first embodiment of the present invention.

FIG. 2 is a view corresponding to FIG. 1 showing a second embodiment of the present invention.

FIG. 3 is a view corresponding to FIG. 1, showing a third embodiment of the present invention;

FIG. 4 is a view corresponding to FIG. 1, showing a fourth embodiment of the present invention;

FIG. 5 is a view corresponding to FIG. 1, showing a fifth embodiment of the present invention.

FIG. 6 is a view corresponding to FIG. 1, showing a sixth embodiment of the present invention;

FIG. 7 is a view corresponding to FIG. 1, showing a seventh embodiment of the present invention.

FIG. 8 is a view corresponding to FIG. 1, showing an eighth embodiment of the present invention;

FIG. 9 is a view corresponding to FIG. 1, showing a ninth embodiment of the present invention;

FIG. 10 shows 3600 [rp] showing a tenth embodiment of the present invention.
[m] is the relationship between the motor applied voltage and the efficiency at the number of rotations

FIG. 11 is a diagram showing the rotational speed of 7200 rpm.
Equivalent figure

FIG. 12 is a view corresponding to FIG. 1, showing an eleventh embodiment of the present invention.

[Explanation of symbols]

1 is a drive device, 2 is an inverter circuit, 3 is a microcomputer (control means), 28 is an inverter main circuit, 30
Is a brushless motor, 31 is a position sensor (position detection means), 32 is a rotation speed calculation circuit (rotation speed calculation means), 33
Is a voltage command value calculation circuit (voltage command value calculation means), 34 is a PWM control circuit, 35 is a gate drive circuit, 36, 38,
40 to 42 and 45 are induced voltage calculation circuits (induced voltage calculation means); 37 and 46 are lead angle calculation circuits (lead angle calculation means); 39 is a current detector; 43 is a temperature detector; , 47 and 48 are limit processing calculation circuits (limit processing calculation means), 49 is a voltage detector, and 50 is an induced voltage detection circuit (induced voltage detection means).

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-211796 (JP, A) JP-A-8-237987 (JP, A) JP-A 8-256496 (JP, A) JP-A-6-256496 189584 (JP, A)

Claims (12)

(57) [Claims] An inverter circuit for driving a brushless motor having a permanent magnet in a rotor; a position detecting means for detecting a rotational position of the rotor; and a rotational speed based on a position detection signal output from the position detecting means. A brushless motor driving device comprising: a rotation speed calculating means for calculating; and a voltage command value calculating means for calculating a voltage command value to be applied to the brushless motor, wherein a voltage command value calculated by the voltage command value calculating means A brushless motor driving device, comprising: a lead angle calculation means for calculating a commutation lead angle of the inverter circuit based on a result of comparison between the inverter circuit and an induced voltage of the brushless motor. 2. The brushless motor driving device according to claim 1, wherein an induced voltage calculating means for obtaining an induced voltage by multiplying a preset induced voltage constant by a rotation speed is provided. 3. An induced voltage calculating means for calculating an induced voltage constant based on a voltage command value and a rotational speed and obtaining an induced voltage by multiplying the induced voltage constant by the rotational speed. The driving device for a brushless motor according to claim 1. 4. The brushless motor driving device according to claim 1, further comprising an induced voltage detecting means for detecting an induced voltage from a phase voltage of the brushless motor. 5. The induced voltage used in the lead angle calculating means is obtained by adding a correction voltage proportional to the load of the brushless motor to the induced voltage calculated by the induced voltage calculating means or the induced voltage detected by the induced voltage detecting means. 5. The brushless motor driving device according to claim 2, wherein the driving voltage is an induced voltage. 6. The induced voltage used in the lead angle calculating means is an induced voltage calculated by the induced voltage calculating means or an induced voltage obtained by adding a fixed correction voltage to the induced voltage detected by the induced voltage detecting means. The drive device for a brushless motor according to any one of claims 2 to 4, wherein: 7. The induced voltage used in the lead angle calculating means is equal to the induced voltage calculated by the induced voltage calculating means or the induced voltage detected by the induced voltage detecting means, and a correction voltage proportional to the load of the brushless motor. The driving device for a brushless motor according to claim 2, wherein the induced voltage is an induced voltage obtained by adding a correction voltage. 8. The induced voltage used in the lead angle calculating means is an induced voltage calculated by the induced voltage calculating means, an induced voltage detected by the induced voltage detecting means, or an induced voltage obtained by adding a correction voltage to these induced voltages. 8. The brushless motor driving device according to claim 2, wherein the induced voltage is an induced voltage multiplied by a correction coefficient corresponding to a winding temperature of the brushless motor or a load of the brushless motor. 9. An inverter circuit for driving a brushless motor having a permanent magnet on a rotor, position detecting means for detecting a rotational position of the rotor, and a rotational speed based on a position detection signal output from the position detecting means. A driving device for a brushless motor, comprising: a rotation speed calculation device for calculating a rotation speed command value; and a voltage command value calculation device for calculating a voltage command value to be applied to the brushless motor by multiplying the rotation speed command value by an induced voltage constant. A brushless motor drive device comprising: a lead angle calculating means for calculating a commutation lead angle of the inverter circuit based on a comparison result between a number command value and the rotation speed. 10. The brushless motor according to claim 1, further comprising limit processing calculating means for setting a limit value to the commutation advance angle calculated by the lead angle calculating means. Drive. 11. The brushless motor driving device according to claim 10, wherein the limit processing calculating means sets a limit value of a commutation advance angle according to the number of rotations. 12. The brushless motor according to claim 1, wherein a difference between the voltage command value calculated by the voltage command value calculating means and the induced voltage of the brushless motor is controlled within a range of ± 10% of the induced voltage of the brushless motor. A drive device for a brushless motor according to any one of claims 1 to 11.