JP2002095280A - Dc brushless motor controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To deal with a load of a wide range when a DC brushless motor is controlled. SOLUTION: A DC brushless motor controller lengthens a sampling mask period of a position detection signal as the motor load increases and controls commutation timing to a leading phase.

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 control device using an inverter, and more particularly, to a relative rotation between a magnet rotor and an armature winding by a speed electromotive force induced in the armature winding. The present invention relates to a DC brushless motor control device that detects a position and performs rotation speed control.

[0002]

2. Description of the Related Art A DC brushless motor control device which controls a rotational speed by detecting a relative position between a magnet rotor and an armature winding by a speed electromotive force induced in an armature winding. One conventional example is disclosed in, for example, Patent No. 2642.
357. This is because the three-phase velocity electromotive force generated in the armature winding is compared with the neutral point voltage or 1/2 of the DC voltage of the star connection, and the commutation is performed by the pulse signal obtained as the output of the comparator. Is obtained.

In this embodiment, a pulse signal output from a comparator for a certain period of time immediately after commutation so that a spike voltage at a motor terminal generated immediately after commutation does not hinder position detection of a magnet rotor. Not to refer to.

[0004]

In the above embodiment, when the motor load is large, stable operation becomes difficult for the following two reasons.

First, the first reason will be described. The spike voltage at the motor terminal immediately after the commutation is generated by the return current flowing from the motor to the inverter. While the return current flows through the diode constituting the inverter bridge circuit, it becomes impossible to detect the position of the magnet rotor with reference to the motor terminal voltage. Therefore, in the above embodiment, the pulse signal output from the comparator is not referred to for a certain period of time immediately after commutation.

Incidentally, the motor current is almost proportional to the load of the motor, and the return current increases as the load increases. Therefore, as the motor load increases, the time during which the spike voltage appears at the motor terminal becomes longer, and the time during which the position of the magnet rotor can be detected becomes shorter. In the above-described embodiment, the time during which the return current is flowing is 5 times of one energizing period.
If it exceeds 0%, there will be no time to detect the position of the magnet rotor, and the motor will not be able to operate.

Further, a second reason will be described. At the start of the DC brushless motor, the induced voltage generated by the armature is small during low rotation, making it difficult to detect the position.
Perform synchronous operation to determine the commutation timing forcibly,
After the acceleration, the operation is switched to the normal operation based on the position detection with reference to the induced voltage. At this time, if the timing of the commutation by the synchronous operation and the timing of the commutation by the normal operation by the position detection with reference to the induced voltage are different, there is no time to detect the position of the magnet rotor immediately after the switching, and the motor Operation becomes impossible.

[0008] The reasons for these will be described in detail in the embodiments, but when the motor load is large, it is difficult to operate in a stable state.

It is an object of the present invention to provide a DC brushless motor control device which can solve such a problem and can operate in a stable state when the DC brushless motor is operated under a wide range of load conditions.

[0010]

In order to achieve the above object, the present invention provides a three-phase speed electromotive force generated in an armature winding and a voltage between the upper and lower arms of a semiconductor switching element constituting an inverter bridge circuit. The reference to the pulse signal obtained from the comparator for judging the magnitude of the / 2 value or the neutral point voltage of the armature winding is not performed for a predetermined time immediately after the commutation of the inverter. The predetermined period is lengthened as much as possible so that the commutation timing is obtained from the pulse signal obtained from the comparator.

Further, the present invention has a configuration in which, as the motor load increases, the predetermined period is lengthened, and the commutation timing is advanced to control the phase.

Further, according to the present invention, the pulse signal obtained from the comparator is referred to immediately after commutation of the inverter, and the commutation timing is advanced to control the phase as the load on the motor increases.

Further, according to the present invention, the state of the motor load is
The configuration is such that it is estimated from the value of the DC current flowing through the inverter.

Further, according to the present invention, the state of the motor load is
The configuration is such that it is estimated from the length of time during which a spike voltage appears immediately after commutation that appears in any of the three-phase motor terminal voltages.

Further, the present invention provides a method for switching from a synchronous operation in which a commutation timing is determined without referring to a pulse signal obtained from a comparator to a normal operation in which a commutation timing is determined from a pulse signal obtained from a comparator. The commutation timing of the normal operation is controlled so that the respective energization times before and after the switching have the same length.

[0016]

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

FIG. 1 is a circuit diagram showing an embodiment of a DC brushless motor driving device according to the present invention, wherein 1 is a DC brushless motor driving device such as a microcomputer,
Are the rotor magnetic pole position detection circuit of the DC brushless motor,
Is a DC brushless motor rotor, 4-a, b are DC voltage Vd detection resistors, 5-a, b, c, d, e, f are freewheeling diodes, and 6-a, b, c, d, e, f are Semiconductor switching elements, 7-a, b, c are stator windings, 8-a,
b and c are comparators, 9-a, b and c are pull-up resistors, 1
0-a, b, c, d, e, and f are motor terminal voltage detection resistors, and 11 is a DC current detection resistor.

The microcomputer 1 comprises semiconductor switching elements 6-a, 6b,
Drive signals U +, U-, V +, V-, W for c, d, e, f
Output +, W-.

The rotor magnetic pole position detecting circuit 2 includes a comparator 8-
a, b, c and pull-up resistors 9-a, b, c are composed of motor terminal voltage detection resistors 10-a, b, c, d, e, f, and the comparators 8-a, b, c are The motor terminal voltage of each phase obtained from the motor terminal voltage detection resistors 10-a, b, c, d, e, and f and the half of the DC voltage Vd obtained from the DC voltage Vd detection resistors 4-a, b. The values are compared and the position detection signals U, V, W are output to the microcomputer 1.

FIG. 2 shows the outline of the drive signals U +, U-, V +, V-, W +, W- of the semiconductor switching element, the motor terminal voltages Vu, Vv, Vw and the position detection signals U, V, W. T60 indicates one energized section of the DC brushless motor, and the energized phase of the brushless motor is switched for each energized section. For example, at time T0, the driving signals W +, V- of the semiconductor switching elements are output, and the energized phases of the brushless motor become V and W phases. At time T1, the driving signals U +, V- of the semiconductor switching elements are output, and the brushless motor is driven. The energized phases of the motor are the U phase and the V phase. Time T again from time T6
It returns to the energizing section of 0 and repeats this thereafter. Note that the motor terminal voltage in the figure has a more complicated waveform in the actual machine than in the figure, but is simplified as far as it does not interfere with the description.

When such drive signals U +, U-, V +, V-, W +, W- of the semiconductor switching elements are output, the terminal voltages of the respective phases of the motor are represented by Vu, Vv, Vw. The induced voltage generated by the rotation of the rotor appears at the motor terminal of the non-energized phase. By comparing the motor terminal voltage of the non-energized phase with a half value of the DC voltage Vd, the magnetic pole position of the rotor is detected. A signal can be obtained. For example, in the energizing section between times T0 and T1, the energizing phases of the motor are the V phase and the W phase, and the non-energizing phases are the U phase. Therefore, the U-phase motor terminal voltage and the DC voltage Vd are equal to one.
The value of / 2 is compared by the comparator 8-a, and the comparison result is used as the position detection signal U. Similarly, in the energized section between T1 and T2, the non-energized phase is the W phase, and the motor terminal voltage of the W phase is compared with a half value of the DC voltage Vd by the comparator 8-c. The position detection signal is assumed to be W.

The position detection signal U will be described by taking the period between T0 and T1 as an example. Immediately after the commutation at time T0, a spike voltage is generated in the motor terminal voltage Vu, which is due to the return current flowing through the motor. In order to perform accurate position detection, it is necessary to consider the effect of the return current flowing through the inverter bridge. During a certain period immediately after the switching of the current-carrying phase, a return current flows through one of the return diodes 5-a, b, c, d, e, and f constituting the inverter bridge, and the return diode is turned on. When a return current flows through the return diodes 5-a, b, and c of the upper arm, a voltage of approximately Vd appears in the motor terminal voltage on the path through which the return current flows.

On the other hand, the return diode 5-d,
When the return current flows through e and f, a voltage of approximately 0 appears in the motor terminal voltage on the path through which the return current flows. In the figure, the terminal voltages Vu, Vv, Vw of the respective phases of the motor become Vd or 0 immediately after the energized phase is switched, and appear as spike-shaped waveforms in the terminal voltages of the respective phases of the motor. The spike-shaped waveform causes the position detection signal U to be at the Hi level. When the return current disappears after a lapse of time from the commutation, the spike voltage also disappears. At this time, the voltage induced by the rotor appears in the motor terminal voltage,
If the induced voltage is smaller than 1/2 of Vd, the position detection signal U becomes Lo level. Ta in the figure corresponds to this timing. The level of the induced voltage rises with the rotation of the rotor, and if the induced voltage is larger than 1/2 of Vd, the position detection signal U becomes Hi level. Tb in the figure corresponds to this timing. Measure the time from commutation to time Tb,
The commutation is performed at the same time after the time Tb, that is, at the time T1, so that an energization pattern corresponding to the magnetic pole position of the rotor can be obtained.

FIG. 3 shows each signal when the motor load is larger than that in FIG. Each signal is shown when the motor load is larger than that in FIG. 2 as in FIG. explain.
Figure 2 shows the time during which the return current flows as the motor load increases.
Is longer than Therefore, the period of the Hi level of the position detection signal U generated immediately after the commutation becomes longer, and conversely, the period of the Lo level becomes shorter. This Lo level signal is necessary for detecting the time Tb. This is because the time Tb cannot be determined unless the Hi level generated by the spike voltage immediately after commutation and the Hi level generated by the magnitude of the induced voltage are distinguished.

Therefore, immediately after the commutation, the sampling mask period Tm is set so that the Hi level of the detection position detection signal U is not detected. After the lapse of Tm, sampling of the position detection signal U is started, and the timing at which the signal level changes from Lo to Hi is determined as time Tb. There is also a method of determining the time Tb without setting the sampling mask period. For example, sampling starts immediately after commutation, and H
The point in time when a continuous pattern of i, Lo, Hi is input is represented by Tb.
It may be. However, in either method, Lo
If the level cannot be detected, accurate position detection cannot be performed.

FIG. 4 shows each signal when the motor load is further increased than in FIG. This is a state in which the period during which the return current flows has reached 50% of one conduction section T60.
At this time, for example, the position detection signal U between time T0 and T1
Does not generate a signal at Lo level, and the time Tb cannot be determined no matter how the sampling mask period Tm is set. Therefore, accurate position detection cannot be performed, and it becomes difficult to control the rotation of the motor.

Therefore, a method of controlling the commutation phase and the sampling mask period so that the position can be detected even when the period in which the return current flows is 50% or more of the one energizing section T60 will be described.

FIG. 5 shows the U-phase terminal voltage and the position detection signal U.
And the commutation phase. The commutation phase is an advanced phase when the commutation timing is earlier than the magnetic pole position of the rotor, and a lag phase when the commutation timing is late. Respectively,
3A shows the case of a lag phase, FIG. 3B shows the case of no lead phase, and FIG. The induced voltage generated by the rotation of the rotor appears at a later timing when the commutation is performed in the advanced phase than in the case where the commutation is not performed. For example, in the case of the position detection signal U between T0 and T1, the Lo level period of (c) is longer than the Lo level period of (a), and the period during which the position can be detected is longer. In the case of the position detection signal U between T3 and T4, the Hi level period of (c) is longer than the Hi level period of (a), and the period during which the position can be detected is longer.

FIG. 6 shows a signal when the motor load is increased as compared with the case of FIG. This is a state in which the period during which the return current flows has reached 50% of one conduction section T60. At this time, in (a) and (b), the position detection signal U between the times T0 and T1 does not include a signal having a Lo level, and accurate position detection cannot be performed. On the other hand, in (c), the Lo level signal appears and the position can be detected. In addition, a high level signal is not generated in the position detection signal U between the time T3 and the time T4, and accurate position detection cannot be performed.
In this case, a Hi level signal appears and position detection is possible. In this way, by performing commutation in the advanced phase, position detection can be performed even when the motor load is large and the return current is flowing for a long time.

FIG. 9 shows an example of a method for controlling the sampling mask period and commutation phase of the position detection signal according to the motor load. Here, the evaluation function is Ta
X100 / T60 (Equation 1) is an index indicating the ratio of the time during which the return current flows to one conduction period.
Since the evaluation function and the load current Id are in a proportional relationship, the state of the motor load may be estimated from Id. The motor load is estimated from the evaluation function or the load current, and the commutation phase is controlled accordingly. When the evaluation function approaches 50%, the period during which the position can be detected is reduced. Therefore, when the evaluation function reaches a predetermined value a, the commutation phase is controlled to be advanced.
In addition, control is performed so as to increase the sampling mask period Tm of the position detection signal as the period in which the return current flows increases. Note that a leading phase may be set as an initial value of the commutation phase. In short, even if the motor load increases,
What is necessary is just to set the sampling mask period and the commutation phase so that the position can be detected. However, the shorter the masking period of sampling, the better the accuracy of position detection is, and if the commutation phase is advanced too much, there are disadvantages such as a decrease in motor efficiency. Therefore, it is necessary to appropriately adjust within the range where position detection is possible. It is.

The first reason why stable operation becomes difficult when the motor load is increased and the countermeasures have been described above.

Next, a second reason and countermeasures will be described. When starting the DC brushless motor, during low rotation, the induced voltage generated by the armature is small and it is difficult to detect the position.Therefore, synchronous operation is performed to forcibly determine the commutation timing. Switch to normal operation based on the referenced position detection. At this time, if the timing of the commutation by the synchronous operation is different from the timing of the commutation by the normal operation by the position detection with reference to the induced voltage, there is no time to detect the position of the magnet rotor immediately after the switching.
Operation of the motor becomes impossible.

FIG. 7 shows the driving signals U +, U of the semiconductor switching element when switching from synchronous operation to normal operation.
−, V +, V−, W +, W− and motor terminal voltages Vu, V
The outline of v, Vw and the position detection signals U, V, W will be described. T
Reference numerals 60, T60 ', T60 ", and T60""denote one energized section of the DC brushless motor, and the energized phase of the brushless motor is switched for each energized section. Before the time T2, the synchronous operation is performed, and after the time T2, the normal operation is performed.The figure shows a case where the commutation timing by the synchronous operation is delayed from the commutation timing by the actual position detection. At this time, for example, if commutation occurs after a lapse of half T60 '/ 2 of one energization period from time Tb, T60 "becomes shorter than T60' as shown in the figure, and the vehicle rapidly accelerates at the time of switching. As a result, for example, as shown in the terminal voltage waveform between time T3 and T4, position detection becomes impossible, and there is a possibility that rotation control of the motor may not be performed.

FIG. 8 shows an example in which control is performed so that one energization period does not suddenly change immediately after switching to prevent trouble in position detection. As in FIG. 7, time T2 is the timing of switching from the synchronous operation to the normal operation. The synchronous operation is performed before the time T2, and the normal operation is performed after the time T2. One energization period T60 'immediately before switching is measured, and one energization period T60 "immediately after switching is set equal to T60'. Specifically, the time from time T2 to time Tb at the time when time Tb is determined Is calculated, and the time difference from T60 'is set as Tc'. This makes it possible to make the energization periods before and after switching the same length, thereby preventing position detection failure at the time of switching. Is T
By appropriately adjusting the length of c ″, it is possible to control the leading phase of commutation.

With the above configuration and control method, it is possible to operate the DC brushless motor in a stable and efficient state even when operating under a wide range of load conditions.

[0036]

As described above, according to the DC brushless motor control according to the present invention, 3
A pulse signal obtained from a comparator which compares and determines the magnitude of the phase electromotive force and the half value of the voltage between the upper and lower arms of the semiconductor switching element constituting the inverter bridge circuit or the neutral point voltage of the armature winding. The reference is not performed for a predetermined time immediately after commutation of the inverter, and the predetermined period is lengthened as the load on the motor increases, so that the commutation timing is obtained from a pulse signal obtained from the comparator; and According to the present invention, as the motor load increases, the predetermined period is lengthened, and the commutation timing is advanced to control the phase.Further, the present invention refers to a pulse signal obtained from the comparator. The commutation timing is advanced immediately after the commutation of the inverter, and the commutation timing is advanced as the motor load increases. The state is configured to be estimated from the value of the DC current flowing through the inverter. Further, according to the present invention, the state of the motor load is the time during which the spike voltage appears immediately after the commutation that appears in any one of the three-phase motor terminal voltages. In addition, the present invention determines the commutation timing from the pulse signal obtained from the comparator from the synchronous operation that determines the commutation timing without referring to the pulse signal obtained from the comparator. When switching to normal operation, the commutation timing of normal operation is controlled so that each energization time before and after switching is the same length, so that even when the DC brushless motor is operated under a wide range of load conditions It is possible to operate in a stable and efficient state.

[Brief description of the drawings]

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

FIG. 2 is an operation explanatory diagram of the DC brushless motor control device according to the present invention.

FIG. 3 is an explanatory diagram of an operation of the DC brushless motor control device according to the present invention.

FIG. 4 is an operation explanatory diagram of the DC brushless motor control device according to the present invention.

FIG. 5 is an operation explanatory diagram of the DC brushless motor control device according to the present invention.

FIG. 6 is an operation explanatory diagram of the DC brushless motor control device according to the present invention.

FIG. 7 is a diagram illustrating the operation of the DC brushless motor control device according to the present invention.

FIG. 8 is an operation explanatory diagram of the DC brushless motor control device according to the present invention.

FIG. 9 is an operation explanatory diagram of the DC brushless motor control device according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... DC brushless motor control device, such as microcomputer, 2 ... DC brushless motor rotor magnetic pole position detection circuit, 3 ... DC brushless motor rotor, 4-a,
4-b: DC voltage detection resistor, 5-a, 5-b, 5-c,
5-d, 5-e, 5-f ... reflux diode, 6-a, 6
-B, 6-c, 6-d, 6-e, 6-f ... semiconductor switching elements, 7-a, 7-b, 7-c ... stator windings, 8-a, 8-b, 8-c ... Comparator, 9-a, 9-
b, 9-c ... pull-up resistance, 10-a, 10-b, 1
0-c, 10-d, 10-e, 10-f: motor terminal voltage detection resistance, 11: DC current detection resistance, Vd: DC voltage between the upper and lower arms of the inverter bridge, Id: DC (load) current, U + ... U + phase semiconductor switching element drive signal, V + ... V + phase semiconductor switching element drive signal, W + ... W + phase semiconductor switching element drive signal,
U-: U-phase semiconductor switching element drive signal, V-
... V-phase semiconductor switching element drive signal, W -... W
-Phase semiconductor switching element drive signal, U ... U phase position detection signal, V ... V phase position detection signal, W ... W phase position detection signal, Vu ... U phase motor terminal voltage, Vv ... V phase motor terminal voltage, Vw ... W phase motor terminal voltage, T0, T1, T2
T3, T4, T5, T6 ... commutation time, Tm ... sampling mask period of position detection signal, Ta, Tb ... change timing of position detection signal, Tc, Tc '... time from time Tb to commutation, T60, T60 ', T60 ", T6
0 '''... 1 energization period, ph ... commutation phase.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Koji Murayama, 800, Tomita, Ohira-machi, Shimotsuga-gun, Tochigi Prefecture Inside the Cooling and Refrigerating Dept., Hitachi, Ltd. Within Hitachi, Ltd.Cooling Division (72) Inventor Junichi Takagi 800, Tomita, Ohira-machi, Shimotsuga-gun, Tochigi Prefecture Inside (72) Inventor Shigeru Kishi 800, Tomita, Ohira-cho, Shimotsuga-gun, Tochigi Hitachi, Ltd. F-term (Ref.) 5H560 BB04 BB07 BB12 DA13 DC13 EB01 SS01 TT07 UA02 XA12 XA15

Claims (6)

[Claims] 1. An inverter device formed by connecting a three-phase bridge connection of a star-connected armature winding having a neutral point and not being grounded, and six semiconductor switching elements with control electrodes, A DC brushless motor having a freewheeling diode connected in parallel, a magnet rotor, a half-value of a three-phase speed electromotive force generated in the armature winding and a voltage between upper and lower arms of the bridge-connected semiconductor switching element or In a DC brushless motor driving device including a comparator for comparing and judging magnitude of a neutral point voltage of an armature winding, a pulse signal obtained from the comparator is referred to for a predetermined time immediately after commutation of an inverter. The commutation timing is obtained from the pulse signal obtained from the comparator by extending the predetermined period as the motor load increases. DC brushless motor control apparatus according to claim. 2. The DC brushless motor driving apparatus according to claim 1, wherein the predetermined period is extended and the commutation timing is advanced to control the phase as the motor load increases. Motor control device. 3. The DC brushless motor driving device according to claim 1, wherein the pulse signal obtained from the comparator is referred to immediately after commutation of the inverter, and the commutation timing advances as the load on the motor increases. A DC brushless motor control device characterized in that the phase is controlled. 4. A brushless DC motor according to claim 1, wherein the state of the motor load is estimated from a value of a DC current flowing through an inverter. Control device. 5. The direct current brushless motor driving device according to claim 1, wherein the state of the motor load is such that a spike voltage immediately after commutation appears in any one of three-phase motor terminal voltages. A DC brushless motor control device, characterized in that it is estimated from the length of time during which it is performed. 6. The DC brushless motor driving device according to claim 1, wherein the synchronous operation for determining the commutation timing without referring to the pulse signal obtained from the comparator is performed, and the pulse signal obtained from the comparator is used. A DC brushless motor control device characterized in that when switching to normal operation for determining commutation timing, the commutation timing of normal operation is controlled so that the respective energization times before and after the switching have the same length.