JPH09117181A - Dc brushless motor driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the variation of the rotation of a DC brushless motor caused by the chopping of the driving current by setting the chopping period of a chopping driving current so that a natural number of cycles of periods can be contained in one commutating period to the chopping driving current. SOLUTION: A chopping frequency computing section 70 makes computation by using the chopping frequency corresponding to the rotating speed command value Nt in accordance with a target speed signal TS. The section 70 sets a chopping driving current when a permanent-magnet rotor 14 is rotated at the command value Nt so that the chopping driving current can be contained by (n) (=1, 2,...) cycles in one commutating period to drive windings 11-13. For a three-layer four-pole DC brushless motor 10, therefore, the section 70 computes the value of the chopping period Tc of the motor 10 so that a relation Tc =Tr /(6×N) can be met (Tr : the specified period of rotation of the motor 10). As a result, the noise level of the motor 10 can be reduced and the efficiency of the motor 10 can be improved by effectively suppressing the variation of the rotation of the motor 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC brushless motor drive device capable of adjusting a rotation speed by chopping a drive current supplied to a drive winding and changing its duty ratio. Is.

[0002]

2. Description of the Related Art Generally, driving of a DC brushless motor is provided with a switching element group for switching a driving current supplied to a driving coil of each phase, and the switching element group of the switching element group is selected according to the position information of the magnet rotor. The drive current is commutated by controlling the on / off, and the rotating torque is given to the magnet rotor according to the change of the magnetic field generated thereby. When controlling the rotation speed of the magnet rotor, the control signal for turning the switching element on and off is chopped to make the drive current to the drive winding a pulse-shaped chopping drive current, and the duty cycle By changing the ratio, the effective power supplied to the drive winding is adjusted to change the rotation speed.

[0003]

By the way, the commutation of the drive current is carried out by applying the drive current to the drive windings of two adjacent phases, and then driving the drive winding of one of the phases. In this configuration, the drive current is supplied to the drive winding of the next phase adjacent to the above, which is sequentially and cyclically switched. Therefore, taking the case of a drive winding of three-phase Y connection as an example, when focusing on the drive current I _A flowing in the drive winding of the first phase, one commutation, which is the first half of the period in which the drive current I _A flows. Third in the cycle
The drive current I _C is flowing in the phase drive winding, and the drive current I _C
In one commutation cycle, which is the latter half of the period in which _A flows, the drive current I _C is flowing in the drive winding of the second phase. Therefore, depending on the chopping frequency when chopping the drive current, the effective supply current value in one commutation cycle, which is the first half of the drive current I _A , and the effective supply current value in one commutation cycle, which is the latter half, are different. Occurs. For example, a state occurs in which there are four chopping drive current peaks in one commutation cycle, but there are three chopping drive current peaks in the subsequent one commutation cycle. If such a state occurs, the effective supply current value will eventually increase or decrease every other commutation cycle, which has been a cause of fluctuations in the rotation of the motor.

As a countermeasure against this, it is conceivable to increase the chopping frequency so that the value of the effective supply current in each commutation period is substantially the same. However, when the chopping frequency is set high, it is necessary to make the rising and falling edges of the chopping drive current waveform steep in order to prevent the efficiency of the motor from decreasing. It causes another problem of disturbing the equipment. Also, in a device in which the motor is integrated with a compressor used for an air conditioner, a cooling or refrigerating device, the chopping frequency is increased because the drive winding of the motor is in the refrigerant atmosphere such as CFC. Then, leakage current increases and electric shock may occur. Therefore, there is a limit to increase the chopping frequency, and there is also a problem that the rotation fluctuation problem cannot be avoided by changing the chopping frequency.

The object of the present invention is therefore to solve the abovementioned problems in the prior art, to reduce the rotational fluctuations due to the chopping of the drive current without significantly increasing the chopping frequency, Another object of the present invention is to provide a DC brushless motor drive device capable of suppressing the generation of noise components due to chopping.

[0006]

A feature of the present invention for solving the above-mentioned problems is to provide a DC brushless motor driving device having a magnet rotor and a drive winding, in which a rotational position of the magnet rotor is provided. A commutator means for providing a drive current to the drive winding, which has a switching element, and a commutator means for commutating the chopping drive current to the drive winding according to the detection result of the position detection circuit. And a means for supplying a commutation control signal for ON / OFF controlling the switching means of the commutator means so that the chopping cycle of the chopping drive current is within one commutation cycle for the chopping drive current. The point is that each n (natural number) cycles is entered.

The position detection circuit for detecting the rotational position of the magnet rotor may be configured to detect the rotational position from the voltage induced in the drive winding, or the position of the magnet rotor may be detected magnetically or optically. A sensor for detection may be provided, and two rotational positions may be detected by the output from this sensor.

Since the chopping cycle of the pulse-shaped chopping drive current is set to be n (natural number) cycles in one commutation cycle of the chopping drive current,
The effective supply current values are equal in any commutation cycle, and the rotation of the magnet rotor does not fluctuate.

[0009]

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

In FIG. 1, 10 is a 3-phase Y-connected 3
A four-phase DC brushless motor having a phase A drive winding 11, a B phase drive winding 12, a C phase drive winding 13, and a permanent magnet rotor 14 magnetized to four poles. ing. The DC brushless motor 10 is a motor for driving a compressor of an air conditioner, and is integrally incorporated in a compressor (not shown). Therefore, the drive windings 11 to 13 of the DC brushless motor 10 are in the atmosphere of chlorofluorocarbon, which is the refrigerant filled in the compressor. Since the DC brushless motor 10 has a known configuration, a detailed description of its structure is omitted.

Reference numeral 20 is a drive device according to the present invention for driving the DC brushless motor 10 with a chopping drive current.
A commutator unit 2 for giving a required drive current to
1 is provided. The commutator section 21 has a known configuration in which switching transistors 22 to 27 and diodes 28 to 33 are connected as shown in the drawing.

Reference numeral 40 indicates that the permanent magnet rotor 14 is rotated to rotate the permanent magnet rotor 1 to 13 to induce a reverse induced voltage in each of the drive windings 11 to 13.
4 rotational position, i.e., a set of sensorless signal Z _A indicating the result to determine the magnetic pole position, Z _B, a position detection circuit of the known circuit arrangement for outputting a Z _C. In this embodiment, the terminals A, B of the drive windings 11 to 13,
The terminal voltages V _A , V _B , and V _{C of C} are input to the position detection circuit 40, and a set of sensorless signals Z indicating the rotational position of the permanent magnet rotor 14 based on these input terminal voltages.
_It has a known circuit configuration for outputting _A , Z _B , and Z _C. The position detection circuit 40 is not limited to this configuration,
It goes without saying that another known configuration may be adopted in which the rotational position information of the permanent magnet rotor 14 is detected by magnetic or optical sensor means.

Reference numeral 50 indicates that the commutation of the drive current from the DC power source 34 with respect to the drive windings 11 to 13 necessary for rotating the permanent magnet rotor 14 depends on the position detection result of the permanent magnet rotor 14. The switching transistors 22 to 27 of the commutator unit 21 are turned on so that
It is a control signal generation unit for outputting a set of commutation control signals U to Z for off control. This control signal generator 5
0 has a function of setting the drive current flowing through the drive windings 11 to 13 as the chopping drive current so that the rotation speed of the DC brushless motor 10 can be controlled. Therefore, in the embodiment shown in FIG. 1, when any one of the switching transistors 22, 23, 24 of the commutator unit 21 is in the ON control state, chopping control is performed on the switching transistor in the ON control state. It is configured to give.

For this reason, the control signal generator 50 has a first control terminal 50A for receiving a frequency setting signal for setting the chopping frequency from the outside, and a pulse shape obtained by pulsing the drive current by the chopping. And a second control terminal 50B for receiving a duty ratio setting signal for setting the duty ratio of the chopping drive current from the outside.

The control signal generator 50 is constructed as described above, and in response to the sensorless signals Z _A , Z _B and Z _C supplied from the position detector 40, the first and second control terminals 5 are provided.
A switching transistor of the commutator unit 21 so that a chopping drive current having a frequency and a duty ratio according to each setting signal externally applied to 0A and 50B is applied to a required drive winding according to the rotational position of the permanent magnet rotor 14 at that time. It outputs a set of commutation control signals U to Z for controlling ON and OFF of 22 to 27. The commutation control signals U to Z are respectively applied to the bases of the corresponding switching transistors. Since the configuration itself of the control signal generator 50 that performs the above-described functions is known,
Here, detailed description of the configuration of the control signal generator 50 is omitted.

In order to operate the DC brushless motor 10 at a desired rotation speed, the drive device 20 is provided with a rotation speed command input section 60 from which the desired rotation speed value can be obtained. Can be input as a command value. The target speed signal TS indicating the input rotation speed command value N _t is output from the rotation speed command input unit 60, and is input to the chopping frequency calculation unit 70 and the duty ratio calculation unit 80, respectively.

The chopping frequency calculator 70 calculates a chopping frequency corresponding to the rotational speed command value N _t at that time according to the target speed signal TS. The frequency is determined here at, for example, about 3 KHz, and the chopping drive current is n (= 1, 1, within one commutation cycle for the drive windings 11 to 13 when the permanent magnet rotor 14 rotates at N _t) .
2, ...) It is decided to enter for one cycle. Therefore, in the case of the DC brushless motor 10 having three phases and four poles, the value of the chopping cycle T _c is T _c = T _r / (6 when the specified rotation cycle of the DC brushless motor 10 is T _r. × n) (1) is calculated. The frequency setting signal FS indicating the calculation result in the chopping frequency calculation unit 70 is input to the first control terminal unit 50A of the control signal generation unit 50.

In addition to the target speed signal TS, a set of sensorless signals Z _A , Z _B , Z _C
Actual rotation signal AS indicating the times of the actual rotational speed value N _a of the computed DC brushless motor 10 in the rotational speed calculating section 90 based on is input. In the duty ratio calculation unit 80, the difference between the rotational speed command value N _t and the actual rotational speed value N _a of the target velocity signal TS and the actual rotation signal AS is calculated, required to the rotational speed difference ΔN to zero The value of the duty ratio of the chopping drive current is calculated.
The duty ratio setting signal DS indicating the calculated duty ratio value is the second control terminal 50B of the control signal generating section 50.
Is input to

Next, the operation of the drive device 20 shown in FIG. 1 will be described with reference to FIG.

FIG. 2 shows a commutation control signal provided from the control signal generator 50 to the bases of the switching transistors 22 to 27 of the commutator unit 21 in order to commutate the chopping drive current to the drive windings 11 to 13. U-Z
It is a figure which shows each waveform of. In FIG. 2, reference numeral T _r is one rotation cycle of the DC brushless motor 10 according to the rotation speed command value N _t indicated by the target speed signal TS. A commutation cycle indicated by reference symbol T _t is one cycle of commutation with respect to the drive windings 11 to 13, which is performed by the switching operation of the switching transistors 22 to 27 of the commutator 21. In this embodiment, since the DC brushless motor 10 has three phases and four poles, the commutation period _Tt is ⅙ of the rotation period _Tr . That is,
Drive windings 11 to 11 at times T1, T2, T3, ...
The drive current to 13 is commutated by the commutator 21 based on the sensorless signals Z _A , Z _B , and Z _C.

In the example shown in FIG. 2, at time T1, the level of the commutation control signal U is "0" or "1" due to chopping.
The mode is repeated in a cycle according to the frequency setting signal FS, and the level of the commutation control signal Y is already in the state of "1" at this point. Therefore, the chopping drive current according to the chopping of the commutation control signal U is flowing through the drive windings 11 and 12, and this state continues until time T2 when this one commutation cycle T _t ends. here,
As described above, the chopping cycle of the commutation control signal U is set according to the calculation result of the chopping frequency calculation unit 70. In this example, the chopping cycle is 1/1 of the rotation cycle T _r , where the value of n in the equation (1) is 3.
It is specified in 8. Therefore, within the commutation period T _t between times T1 and T2, the chopping drive current for exactly 3 cycles flows through the drive windings 11 and 12. The duty ratio of the chopping drive current in this case is determined by the duty ratio setting signal DS, and the effective supply current value of the chopping drive current is controlled so that the rotation speed command value N _t indicated by the target speed signal TS is obtained. ing.

At time T2, the level of the commutation control signal Y becomes "0" and the level of the commutation control signal Z becomes "1". As a result, the switching transistor 27 is turned on instead of the switching transistor 26, and the chopping drive current is passed through the drive windings 11 and 13 within one commutation period from time T2 to T3. Again, as in the case of previous, just chopping current of three cycles in one commutation period T _t of the time T2~T3 flows through the drive windings 11 and 13. The same applies to the subsequent commutation cycles.

As described above, although the driving current is chopped, the frequency (cycle) is determined according to the equation (1), that is, the cycle of the chopping drive current included in each commutation cycle. Since the numbers are all set to be equal, the effective supply current values of the chopping drive current in each commutation period are all equal. Therefore, even if the chopping drive current is supplied, there is no variation in the effective supply current value of the chopping drive current within each commutation cycle, so that rotation fluctuation does not occur as in the conventional case. Therefore, there is the advantage that the noise level is reduced and the motor efficiency is also improved. Also, since it is not necessary to significantly increase the chopping frequency,
Since there is no leakage current from the drive winding in the Freon, there is no risk of electric shock.

In the waveform diagram shown in FIG. 2, the chopping drive current in one commutation cycle starts from its rising and ends at the fourth rising timing, but this is an example. For example, as shown in FIG. 3, even in a mode in which one commutation cycle includes three arbitrary cycles, there is no problem because it is suitable for the purpose of making the effective supply current values the same.
Further, the chopping of the switching transistor in the commutator 21 is performed by the switching transistor 2
In addition to 2, 23, 24, switching transistor 2
Of course, steps 5, 26 and 27 may be performed.

FIG. 4 shows another embodiment of the present invention. The drive device 100 shown in FIG. 4 is an example of a mode in which the rotation speed of the DC brushless motor 10 is not set, and the duty ratio command input unit 110 sets the duty ratio of the chopping drive current so that the DC brushless motor 10 can be driven. In order to change the rotation speed and to maintain the relationship between the chopping cycle and the one commutation cycle at a required relationship even if the DC brushless motor 10 has a rotation fluctuation, the rotation speed calculation unit 90
1 is different from the drive device 20 shown in FIG. 1 in that the chopping frequency of the chopping drive current is calculated in the chopping frequency calculation unit 70 according to the actual rotation signal AS from. Since other configurations of the drive device 100 are the same as those of the drive device 20, the same parts as those of the drive device 20 in the drive device 100 are designated by the same reference numerals, and the description thereof will be omitted.

According to the driving device 100, the duty ratio setting signal DS from the duty ratio command input unit 110 is input to the second control terminal 50B of the control signal generating unit 50, whereby the duty ratio of the chopping drive current is determined. The permanent magnet rotor 14 of the DC brushless motor 10 rotates at a rotation speed according to this duty ratio. Moreover, the chopping frequency is determined at the chopping frequency calculation unit 70 in the same manner as the drive unit 20 shown in FIG. 1 in accordance with the actual rotational speed value N _a at that time. In the chopping frequency calculation unit 70 shown in FIG. 4, the target speed signal TS
Instead, the only difference is that the required chopping frequency is calculated according to the actual rotation signal AS.

According to the configuration of the drive device 100, the rotation speed of the DC brushless motor 10 changes according to the duty ratio command value input from the duty ratio command input section 110, but the cycle T _{c of the} chopping frequency is the same. sometimes from rotation period T _a of the actual rotational speed value n _a, the following equation _{T c = T a / (6} × n). . . (2) Here, n is calculated according to a natural number. Therefore, also in this case, the effective supply current values of the chopping drive current in each commutation cycle are equal to each other, and it is possible to effectively prevent the rotation fluctuation.

FIG. 5 shows another example of the embodiment of the present invention. In the drive device 200 shown in FIG. 5, chopping frequencies that meet a predetermined condition are preliminarily stored in the chopping frequency storage unit 210,
This is different from the drive device 20 shown in FIG. 1 in that a rotation speed command value that matches these matching frequencies can be commanded discretely by the rotation speed command input unit 60. Since other configurations of the drive device 200 are the same as those of the drive device 20, the same parts as those of the drive device 20 in the drive device 200 are designated by the same reference numerals, and the description thereof will be omitted.

According to the configuration of the driving device 200, the chopping frequency storage unit 210 stores a plurality of predetermined fixed frequency values, and the rotation speed command input unit 60 stores the rotation speed corresponding to the fixed frequency values. Select values one after another and command. The target speed signal TS indicating the rotation speed command value selected by the rotation speed command input unit 60 is given to the chopping frequency storage unit 210, and the target speed signal TS is supplied.
The fixed frequency value corresponding to the content of is selected as the chopping frequency, and the frequency setting signal FF indicating the selected frequency value is the first control terminal 50A of the control signal generator 50.
Is input to

In the case of the drive unit 200 as well as in the case of the drive unit 20, the target speed signal TS is calculated by the duty ratio calculation unit 8
0 is also input, and since the feedback control of the rotation speed of the DC brushless motor 10 is performed in the duty ratio calculation unit 80 so that the rotation speed value according to the target speed signal TS is maintained, the frequency setting is discrete. However, the effective supply current values of the chopping drive current in one commutation cycle can all be made equal. As described above, according to the configuration in which the chopping frequency is fixed and the command value of the rotation speed is selectively commanded, the configuration can be simpler than that of the drive device 20 shown in FIG.

[0031]

As described above, according to the present invention, the number of chopping drive currents included in each commutation cycle is set to be equal, so that the chopping drive current in each commutation cycle is determined. The effective supply current values of all are the same, and even if the chopping drive current is supplied, there is no variation in the effective supply current value of the chopping drive current within each commutation cycle, so without increasing the chopping frequency. It is possible to effectively suppress the rotation fluctuation of the DC brushless motor. Therefore, there is the advantage that the noise level is reduced and the motor efficiency is also improved. Moreover, since it is not necessary to significantly increase the chopping frequency, it is possible to expect an effect of reducing the leakage current from the drive winding.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a DC brushless motor drive device according to the present invention.

FIG. 2 is a waveform diagram of signals of various parts for explaining the operation of the DC brushless motor drive device of FIG.

FIG. 3 is a waveform diagram for explaining the relationship between the waveform of the chopping drive current and the commutation period.

FIG. 4 is a block diagram showing another embodiment of the DC brushless motor drive device according to the present invention.

FIG. 5 is a block diagram showing still another embodiment of a DC brushless motor drive device according to the present invention.

[Explanation of symbols]

 10 DC brushless motor 11, 12, 13 Drive winding 14 Permanent magnet rotor 21 Commutator part 20, 100, 200 Drive device 22-27 Switching transistor 40 Position detection circuit 50 Control signal generation part Tr Rotation cycle Tt Commutation cycle Tc Chopping cycle U to Z commutation control signal

Claims (1)

[Claims] 1. A drive device for a DC brushless motor comprising a magnet rotor and a drive winding, wherein the drive winding has a position detection circuit for detecting a rotational position of the magnet rotor and a switching element. A commutator means for applying a drive current to the drive coil, and a commutator means for controlling the on / off control of the switching means of the commutator means so as to commutate the chopping drive current for the drive winding according to the detection result of the position detection circuit. A means for supplying a flow control signal, wherein the chopping cycle of the chopping drive current is n (=) within one commutation cycle for the chopping drive current.
A DC brushless motor drive device characterized in that it is defined so as to include 1, 2, ... Cycles.