JPH11318096A - Driver of brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the wasteful power consumption and furthermore, shorten the starting time by enabling quick and accurate detection of a rotor position at the start, in the driver of a brushless motor. SOLUTION: This driver is made to perform a series of start preparations of first stage (101-106) for making the rotor static immediately after turning the power on of a circuit, and second stage (107-108) for switching a maximum drive current Imax into a minimum drive current Imin, immediately after the completion of making it static and keeps it until the input of a start signal, a third stage (109-112) for rotating the motor immediately if the input of a start signal is made and detects the position of the rotor, while making it perform free run after a preset time, and a fourth stage (113-115) of terminating the free run, when the detection of the rotor position is completed and switching it into a stationary drive current Inor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor widely used as a drive motor of a machine such as a turbo-molecular pump which extremely dislikes dust and oil, and a motor having a relative position between a stator coil and a permanent magnet type rotor. The present invention relates to a brushless motor driving device that detects a target position based on an induced voltage induced in a stator coil without using a position sensor such as a Hall element and obtains a position detection signal.

[0002]

2. Description of the Related Art A brushless motor driving apparatus for obtaining a position detection signal based on an induced voltage induced in a stator coil is disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 5-111286. In such a brushless motor driving device, a circuit diagram for explaining the operation from the stabilization of the rotor to the end of the start-up / acceleration is shown in, for example, FIG. 4 and a flowchart thereof is shown in FIG. That is, in FIG. 4, 10 is a brushless motor, 20 is a drive circuit, 30 is a control circuit, and 40 is a current / voltage detection circuit. The brushless motor 10 includes a rotor 11 and three-phase stator coils 12U, 12V and 12W. The rotor 11 is a permanent magnet rotor on which at least a pair of permanent magnets are symmetrically mounted. The drive circuit 20 includes a drive voltage 27, and semiconductor switches 21, 22, 23, 24,
25 and 26.

A control circuit 30 includes a CPU 31 for performing various operations and other processes, a ROM 32 for storing programs for performing various processes in accordance with predetermined procedures, a RAM 33 for storing various data used for various processes, and an input / output device. It comprises an output interface I / O 34 and a data bus 35 connecting these components. RAM3
Reference numeral 3 denotes a storage unit 33a for a static determination threshold voltage Es, a storage unit 33b for a static determination threshold time Ts, a storage unit 33c for a position detection success / failure determination reference value, a storage unit 33d for a rated rotation speed, Storage section 33e of maximum drive current Imax, storage section 33f of steady drive current Inor, and set rotation speed Vs
Storage section 33j. Input / output interface I / O
A start input signal 44 is applied to an input port of a start-up switch or the like from the start-up means.
From 0, the terminal voltage signal 45 and the stator coil current signal 4
6 is added. Output ports A, B, C, D, E, and F of the input / output interface I / O 34 are connected to corresponding control terminals of the semiconductor switches 21, 22, 23, 24, 25, and 26, respectively.

[0004] Preparation for starting the conventional brushless motor driving apparatus shown in FIG. 4 will be described with reference to a flowchart shown in FIG. When the circuit power is turned on (201), CP
U31 determines whether or not the start signal has been input (202).
If ES, the static determination threshold voltage Es is read from the RAM 33,
The reading (203) of the static determination threshold time Ts and the maximum drive current Imax is performed. The CPU 31 controls the drive circuit 20 via the input / output interface I / O 34,
An inter-terminal voltage UV is applied between the terminals of the stator coils 12U and 12V so that the current flowing through the stator coils 12U and 12V becomes the maximum drive current Imax (204).
The voltage UV between the applied terminals thus applied is as shown in FIG.
As shown in (a), let alone the motor start preparation period,
This value is retained after startup.

The magnetic field generated by the maximum drive current Imax flowing through the stator coils 12U and 12V attracts one magnetic pole (S pole or N pole) of the permanent magnet of the rotor 11 to an intermediate phase between the stator coils 12U and 12V. . Due to this suction, the rotor 11 is fixed to the stator coil 1.
It swings back and forth around the middle phase between 2U and 12V. This rotation swing reduces its size over time,
And it stops at the position where the magnetic pole attracted to the intermediate phase coincides. FIG. 6B shows the fluctuation of the rotation of the rotor 11 and the fluctuation of the rotor position. In FIG. 6B, Ps indicates an intermediate position between the stator coils 12U and 12V. Due to the interaction between the rotation fluctuation of the rotor 11 and the magnetic field generated by the maximum drive current Imax, an induced voltage is generated at the terminals of the stator coils 12U and 12V. This induced voltage is the terminal voltage U
V is added to the input terminal of the current / voltage detection circuit 40 via lines 41 and 42. The current / voltage detection circuit 40 performs a predetermined process to generate a detection voltage UVa indicating the rotor position. The detection voltage UVa indicating the rotor position fluctuates as shown in FIG.

The detection voltage UVa is supplied as a detection voltage signal 45 via the input / output interface I / O 34 to the CPU.
The CPU 31 determines whether the change in the detection voltage UVa is smaller than the static determination threshold voltage Es (205). If YES, the CPU 31 determines that the change in the detection voltage UVa is less than the static determination threshold time. It is determined whether it is larger than Ts (2
06), and if this is also YES, the stabilization is completed (207).

Immediately after the completion of the stabilization, the CPU 31 supplies a control signal to the drive circuit 20 via the input / output interface I / O 34. Then, the drive circuit 20 applies the maximum drive current Imax to all the stator coils 12U, 12V and 12W.
To generate a rotating magnetic field (208),
Start rotation. The CPU 31 of the control circuit 30
With the angular acceleration at which the rotor is attracted to the rotating magnetic field from rpm and can follow the rotating magnetic field without step-out, the rotor is accelerated without using the detection voltage signal 45 representing the rotor position input from the current / voltage detection circuit 40. , Stator coil 12U, 1
Maximum drive current Imax supplied to 2V and 12W
The rotation magnetic field is controlled so that the rotation magnetic field generated by the rotation does not deviate from the rotor position (209). The CPU 31 controls the rotor 1 based on the detected voltage signal 45 indicating the rotor position.
The rotation speed V 1 is monitored, and it is determined whether the rotation speed V has reached the set rotation speed Vs (210). If the result of the determination is YES, the CPU 31 supplies a control signal to the drive circuit 20, and the drive circuit 20 switches the maximum drive current Imax to the steady drive current Inor. And the CPU 31
Performs the rotating magnetic field control based on the detection voltage signal 45 indicating the rotor position input from the current / voltage detection circuit 40 (211). While continuing driving in this state, the CPU 31
Determines whether the rotation speed V of the rotor 11 has reached the rated rotation speed Vnor (212). If the result of the determination is YES, the activation / acceleration of the motor is thereby completed.

As described above, in the conventional brushless motor driving device, the driving circuit 20 receives the control signal from the control circuit 30 and turns the stator coil 12 of the motor.
While applying drive voltage and current to U, 12V and 12W,
The induced voltage generated by the rotational movement of the rotor 11 is detected by the current / voltage detection circuit 40. Therefore, the induced voltage is added to the drive voltage for the terminal voltage between the phases.
In this case, noise is generated in the motor induced voltage due to fluctuations in drive torque and the like. In addition, since the rotation speed is low, the motor induced voltage also decreases accordingly, and the influence of noise is large. As a result, a deviation occurs in the rotor phase detection, resulting in a decrease or fluctuation in instantaneously generated torque. If such a condition is significant, the motor cannot be accelerated, and a restart is required. In some cases, this process may be repeated many times, resulting in time loss.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a drive device for a brushless motor that obtains a position detection signal based on an induced voltage induced in a stator coil. An object of the present invention is to provide a drive device capable of detecting a rotor position, reducing wasteful power consumption, and further shortening a start-up time.

[0010]

In order to solve the above problems, the present invention provides a permanent magnet rotor, a stator having a plurality of phases of stator coils, a drive circuit for supplying a drive current to the stator coils in accordance with a predetermined energizing timing, A current detection circuit for the stator coil and a control circuit for obtaining a position detection signal using the detection voltage of the current voltage detection circuit, and determining the energization timing based on the position detection signal to control the drive circuit. In the brushless motor drive device, the maximum drive current is supplied to one phase of the stator coil immediately after the circuit power is turned on, and the stabilization is performed based on the fluctuation of the detection voltage of the current voltage detection circuit.
Further, after the rotor is settled, the maximum drive current is supplied to all the stator coils to rotate the rotor, and after a preset time, the supply of the drive current is stopped and the rotor position is detected while performing free-run. I made it.

Further, the first drive current Imax is supplied to one phase of the stator coil immediately after the power supply of the circuit is turned on, and the first voltage is set based on the fluctuation of the detection voltage of the current voltage detection circuit.
A second step in which the maximum drive current Imax supplied to one phase of the stator coil is switched to the minimum drive current Imin immediately after the completion of the stabilization, and held until a start signal is input;
As soon as the start signal is input, the maximum drive current Imax is supplied to all the stator coils, and after a preset time, the supply of the drive current is stopped and free-run is performed to compare the phase shift with the setting accuracy. When the phase and the phase shift reach within the set accuracy, the free-run is terminated, and a series of startup preparations for a fourth phase in which the maximum drive current Imax is switched to the steady drive current Inor is performed. .

[0012]

FIG. 1 is a circuit diagram showing an embodiment of a brushless motor driving apparatus according to the present invention. In FIG. 1, 10 is a brushless motor, 20 is a drive circuit, 30 is a control circuit, and 40 is a current / voltage detection circuit. The brushless motor 10 includes a permanent magnet rotor 11 and three-phase stator coils 12U, 12V and 12W. The drive circuit 20 includes a drive voltage 27, semiconductor switches 21 and 2,
2, 23, 24, 25 and 26.

The control circuit 30 includes a CPU 31, a ROM 32,
It comprises a RAM 33, an input / output interface I / O 34, and a data bus 35. The RAM 33 includes at least a storage unit 33 a for the static determination threshold voltage Es,
A storage unit 33b for a static determination threshold time Ts, a storage unit 33c for a position detection success / failure determination reference value, and a storage unit 33 for a rated rotation speed
d, a storage unit 33e for the maximum drive current Imax, a storage unit 33f for the steady drive current Inor, a storage unit 33g for the minimum drive current Imin, and a storage unit 33h for the free run set value. The input port of the input / output interface I / O 34 has a start input signal 44 from start means such as a start switch.
And a circuit power-on signal 48, and a terminal voltage signal 45 and a stator coil current signal 46 from the current / voltage detection circuit 40. Input / output interface I / O
The 34 output ports A, B, C, D, E and F are connected to corresponding control terminals of the semiconductor switches 21, 22, 23, 24, 25 and 26, respectively.

In short, the circuit of one embodiment of the present invention shown in FIG.
In the conventional circuit of FIG. 4, a storage unit 33g for the minimum drive current Imin and a storage unit 33h for the free-run set value are added to the RAM 33, and the input / output interface I / O is added.
The circuit power-on signal 48 is applied to the input port 34.

The preparation for starting the brushless motor driving apparatus according to the embodiment shown in FIG. 1 will be described with reference to the flowchart of FIG. When the circuit power is turned on (101), the CPU 31 reads from the RAM 33 the static determination threshold voltage Es, the static determination threshold time Ts, and the maximum drive current Im.
ax is read (102). The CPU 31 controls the drive circuit 20 via the input / output interface I / O 34, and applies an inter-terminal voltage UV between the terminals of the stator coils 12U and 12V so that the current flowing through the stator coils 12U and 12V becomes the maximum drive current Imax. Let it. The voltage UV between the applied terminals thus applied is as shown in FIG.
As shown in (a), it is held until a free-run start time described later.

Due to the magnetic field generated by the maximum drive current Imax flowing through the stator coils 12U and 12V, one magnetic pole (S-pole or N-pole) of the permanent magnet of the rotor 11 is attracted to an intermediate phase between the stator coils 12U and 12V. . Due to this suction, the rotor 11 is fixed to the stator coil 1.
It swings back and forth around the middle phase between 2U and 12V. This rotational wobble decreases in magnitude over time and comes to rest at locations where the poles attracted to the intermediate phase coincide. FIG. 3B shows the fluctuation of the rotation of the rotor 11 and the fluctuation of the rotor position. In FIG. 3B, Ps is the stator coil 1
Represents an intermediate position between 2U and 12V. Due to the interaction between the rotation fluctuation of the rotor 11 and the magnetic field generated by the maximum drive current Imax, an induced voltage is generated at the terminals of the stator coils 12U and 12V. This induced voltage is added to the inter-terminal voltage UV and applied to the input terminal of the current / voltage detection circuit 40 via lines 41 and 42. Current / voltage detection circuit 4
0 is a detection voltage UV representing a rotor position by performing a predetermined process.
a is generated. The detection voltage UVa representing this rotor position
Fluctuates as shown in FIG.

The detection voltage UVa is supplied as a detection voltage signal 45 to the CPU via the input / output interface I / O 34.
The CPU 31 determines whether the change in the detection voltage UVa is smaller than the static determination threshold voltage Es (104). If YES, the CPU 31 determines that the change in the detection voltage UVa is less than the static determination threshold time. It is determined whether or not Ts is larger than Ts (105), and if this is also YES, settling is completed (106).
Becomes

Immediately after the completion of the stabilization, the CPU 31 supplies a control signal to the drive circuit 20 via the input / output interface I / O 34, and the drive circuit 20 transmits the control signals to the stator coils 12U and 1U.
The minimum drive current Imin is supplied to 2 V (107), and in this state, it is determined whether the start signal 44 is input to the control circuit 30 (108). If the determination is YES, CPU 31 provides a control signal to drive circuit 20. Then, the drive circuit 20 includes all the stator coils 12U, 1U,
The maximum drive current Imax is supplied to 2V and 12W to generate a rotating magnetic field (109), and the rotation of the rotor 11 is started. The rotation speed of the rotor 11 increases with time. C
The PU 31 determines whether or not a preset free-run start time has been reached (110). If the result of the determination is YES, the CPU 31 provides a control signal to the drive circuit 20. Then, the drive circuit 20 includes all the stator coils 12U, 1U,
Turning off the applied voltage to 2V and 12W, the rotor 11
Is free-run (111).

With the rotor 11 free-running, the drive device of the present invention detects the rotor position. That is, in this state, the brushless motor 10 functions as a generator, and the stator coils 12U, 12V, and 12
Induced voltages UV, UW, and WU corresponding to the rotational movement of the rotor 11 due to free running are generated between the W terminals.
These induced voltages are applied to the input terminal of the current / voltage detection circuit 40 via lines 41 and 42, and the current / voltage detection circuit 40 performs a predetermined process to generate a detection voltage representing the rotor position.

These detected voltages are supplied as a detected voltage signal 45 via the input / output interface I / O 34 to the CPU 31.
The CPU 31 detects a phase shift from a change in the detected voltage by a predetermined calculation, and continues to monitor the phase shift to determine whether or not the detected phase shift is within the target set accuracy. (11)
2). If the result of the determination is YES, CPU 31 provides a control signal to drive circuit 20. Then, the drive circuit 20 supplies the steady drive current Inor to all the stator coils 12U, 12V and 12W to generate a rotating magnetic field (11
3) The rotation of the rotor 11 is started. The free run ends at this point. The CPU 31 includes the current / voltage detection circuit 4
Rotation magnetic field control is performed based on the detected voltage signal 45 indicating the rotor position input from 0, and it is determined whether or not the rotation speed V of the rotor 11 has reached the rated rotation speed Vnor (11).
4). If the result of the determination is YES, the activation / acceleration of the motor is completed (115).

A driving device for a brushless motor according to the present invention is characterized in that a circuit power-on signal 48 is applied to the control circuit 30. As a result, as shown in the flowchart of FIG. 2, the rotor is positioned immediately after the circuit power is turned on. Further, after the rotor positioning is completed, the maximum drive current Imax is continuously supplied to the stator coil until the start signal 44 is input, so that the maximum drive current Imax is not consumed so that wasteful power is not consumed or heat is generated. From the minimum drive current Imin. The minimum drive current Imin may be determined experimentally and given, or feedback control may be performed so that the detection voltage UVa indicating the rotor position does not vibrate.
When the deviation is zero due to feedback control, Imin
Becomes zero.

In the brushless motor driving device according to the present invention, the start signal is confirmed after the completion of the stabilization, and a rotating magnetic field is first generated by the maximum driving current Imax to give a rotating motion to the motor, and the set value (start time And the end time), the free run is performed, and the rotor position is detected efficiently during the free run period. That is, since the brushless motor 10 functions as a generator during the free-run period, the voltage between the terminals of the stator coil detected by the current / voltage detection circuit 40 is only the induced voltage. Therefore, noise due to uneven driving torque fluctuation, which is a problem in the conventional example, does not occur in the driving device according to the present invention.

[0023]

According to the brushless motor driving device of the present invention, a storage unit for a minimum drive current and a storage unit for a free-run set value are added to the RAM of the control circuit in the conventional circuit.
In addition, since the circuit power-on signal is applied to the input port of the input / output interface I / O of the control circuit, neither the complexity of the configuration nor the cost increase due to the addition is caused. Above all, it is a unique start-up preparation that includes the stage of detecting the rotor position while free-running after the rotor has been settled. Therefore, it is possible to quickly and accurately detect the rotor position at start-up, and during the start-up preparation period. In addition, unnecessary power consumption was reduced, heat generation was suppressed, and the startup time was further reduced. Having such excellent effects, the present invention is extremely useful as a drive device for a brushless motor for a turbo-molecular pump having a magnetic bearing and extremely small motor damping.

[Brief description of the drawings]

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

FIG. 2 is a flowchart of startup preparation up to motor startup in the brushless motor driving device according to the present invention.

FIG. 3 is a diagram showing a temporal change of an applied terminal voltage, a rotor position, and a detected voltage in a brushless motor driving device according to the present invention, and a relationship between them;

FIG. 4 is a circuit diagram of one embodiment of a conventional motor drive device.

FIG. 5 is a flowchart of startup preparation up to motor startup in a conventional motor drive device.

FIG. 6 shows an applied terminal voltage in a conventional motor driving device,
FIG. 4 is a diagram illustrating a temporal change of a rotor position and a detection voltage, and a correlation between them.

[Explanation of symbols]

Reference Signs List 10 brushless motor 11 rotor 12U, 12V, 12W stator coil 20 drive circuit 21, 22, 23, 24, 25, 26 semiconductor switch 27 drive voltage 30 control circuit 31 CPU 32 ROM 33 RAM 33a of static determination threshold voltage Es Storage section 33b Storage section for static determination threshold time Ts 33c Storage section for position detection success / failure judgment reference value 33d Storage section for rated rotation speed 33e Storage section for maximum drive current Imax 33f Storage section for steady drive current Inor 33g Minimum drive Current Imin storage unit 33h Free-run set value storage unit 33j Set rotation speed Vs storage unit 34 Input / output interface I / O 35 Data bus 40 Current / voltage detection circuit 41, 42, 43 line 44 Start signal 45 Terminal voltage signal 46 Stator coil current signal 47 Control signal line 4 Circuit power-on signal

Claims (3)

[Claims] 1. A rotor to which a permanent magnet is attached, a stator having a plurality of stator coils, a drive circuit for supplying a drive current to the stator coil in accordance with a predetermined energizing timing, a current voltage detection circuit for the stator coil, and a current voltage detection for the stator coil A brushless motor driving device comprising: a control circuit that obtains a rotor position detection signal using a detection voltage of the circuit, determines an energization timing based on the position detection signal, and controls the driving circuit. A brushless motor drive device, wherein a maximum drive current is immediately supplied to one phase of a stator coil, and a stabilization is performed based on a fluctuation of a detection voltage of the current voltage detection circuit. 2. After the rotor is settled, the maximum drive current is supplied to all the stator coils to rotate the rotor, and after a preset time, the supply of the drive current is stopped to detect the rotor position while performing free-run. 2. The brushless motor driving device according to claim 1, wherein the driving is performed. 3. A permanent magnet rotor, a stator having a plurality of phases of stator coils, a drive circuit for supplying a drive current to the stator coils in accordance with predetermined energization timing, a current voltage detection circuit for the stator coils, and detection of the current voltage detection circuit. A drive circuit for controlling the drive circuit by obtaining a rotor position detection signal using a voltage and determining an energization timing based on the position detection signal. A first stage in which a maximum drive current is supplied to one phase of the above and a stabilization is performed based on the fluctuation of the detection voltage of the current / voltage detection circuit. Is switched to the minimum drive current and is held until the start signal is input. The third step of supplying the maximum drive current to the data coil, stopping the supply of the drive current after a preset time, causing free-run, and comparing the phase shift with the set accuracy, and when the phase shift is within the set accuracy. Then, a free running is terminated, and a series of startup preparations including a fourth step of switching the maximum drive current to the steady-state drive current is performed.