JPH0698588A - Method for starting sensorless polyphase direct current motor - Google Patents

Abstract

PURPOSE:To enable the reduction of power consumption during starting by, after the detection of motor start-up, ceasing the following stepping processes. CONSTITUTION:In a first stepping process, the output is produced by a stepping signal generator 3, and an energization switching circuit 4 is actuated, an output drive circuit 5 being turned on/off, according to control signals from a control circuit 2. Thus, stator coils u, v and w are sequentially excited. After the completion of the first stepping process, a first acceleration process is executed for a specified time with the final status of internal stepping maintained. If the control circuit 2 judges, during the process, that the motor has been completely started based on detect signals from a counter-electromotive force detecting circuit 7, connected to the stator coils u, v and w, the stepping process is ceased and the normal operation mode starts. If it is judged that the motor has not been sufficiently started, on the contrary, the counter-exciting current is sustained and a second stepping process starts. In the second stepping process, the direction of the current flow is reversed from negative to positive without quiescent times, and thus a large torque is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for starting a sensorless polyphase DC motor, and more particularly to a technique for reducing power consumption at the time of starting.

[0002]

2. Description of the Related Art Conventionally, a brushless polyphase DC motor has been used as a motor for rotating a magnetic disk drive. This type of motor is also called a spindle motor. For example, a stator that generates a magnetic field in an excited state, a rotor that includes a rotor magnet that obtains a rotational force by electromagnetic interaction with the magnetic field of the stator, and a rotational position of the rotor magnet. A structure having a sensor for detecting is well known, and in a spindle motor having such a structure, rotation control is often performed by an electronic circuit made into a semiconductor chip.

The magnetic field generation timing on the stator side in this case is controlled by detecting the rotational position of the rotor magnet by a sensor, and a Hall element has been conventionally used for this type of sensor. However, in recent years, in order to avoid downsizing of motors and deterioration of sensor characteristics, a so-called sensorless multi-phase sensor is used to detect the position of a rotor magnet by using an induced voltage generated in a coil that is not in use. DC motors are becoming popular.

At the time of starting the sensorless motor, when the motor is stopped, a counter electromotive voltage cannot be obtained, so that the rotor is first oscillated. For example, in a three-phase coil spindle motor, a stepwise process of sequentially supplying a drive current to the stator is repeated, and during this stepwise step, normally,
It includes a mode in which exciting currents in the forward, pause, and reverse directions are passed through each phase, and is driven by the attraction and repulsion between the magnetic field generated by passing the exciting current in such modes and the rotor magnet. Torque is generated and the motor is started.

However, such a sensorless polyphase DC motor has a technical problem to be described below, particularly in its starting method.

[0006]

That is, in the sensorless multi-phase DC motor, the position of the rotor magnet is detected by the induced voltage due to the magnetic flux interlinking with the coil, but there is no induced voltage when the motor is stopped. Also,
Since the polarity of the magnet is unknown, it is forced to start when starting. However, depending on the position of the rotor, a start failure may occur due to low torque, or a magnetic field due to energization may occur in the opposite direction, causing a reverse rotation of 60 degrees or more at the start-up.

Therefore, in order to avoid such an inconvenience and improve the starting reliability, conventionally, when the starting failure occurs even if a plurality of steps are repeated, the step is returned to the first step. A retry method in which the start is repeated, a part of the step is made into a double drive method, a reverse excitation period is provided between a plurality of steps, and a start method in which each method is used in combination is adopted. Here, the double drive method is a starting method developed by the present applicant, and includes a portion that reverses the energization direction from positive to negative or from negative to positive at the time of starting the motor without including a pause time. According to this starting method, a large variation range of the magnetic flux density is generated, the dead point of starting is eliminated, high torque is generated, and starting reliability is improved.

However, in such a start-up method in which retries are repeated, the next step is repeated even if the start-up is successful in the first step, resulting in extra power consumption and battery power consumption. It was regarded as a problem with the portable personal computers used. The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide a starting method of a sensorless polyphase DC motor capable of cutting extra power consumption at the time of starting. It is in.

[0009]

In order to achieve the above object, a stator having a stator for generating a current magnetic field in an excited state, and a rotor having a rotor magnet for obtaining a rotational force by electromagnetic interaction with the current magnetic field of the stator, A sensorless multi-phase DC circuit including a back electromotive voltage detection circuit for detecting an induced electromotive voltage of the stator, wherein a stepwise step of supplying a drive current for rotating the rotor in a predetermined direction to the stator is repeated at least twice or more. In the motor starting method, there is a reverse excitation step after a first step step in which a drive current is first supplied, and the back electromotive voltage detection is performed when the motor is started in the reverse excitation step or the first step step. When it is detected by the circuit, the stepping process after that is stopped.

As a result, the subsequent step step functions as a backup or a fail safe. Further, according to the present invention, during the first step process in which the drive current is first supplied, the double step operation in which the energization direction is reversed without including the pause period can be provided.

[0011]

According to the method of starting the sensorless multi-phase DC motor having the above-described structure, when the start of the motor is detected, the stepping process thereafter is stopped, so that the power consumption at the start is reduced. Further, according to the configuration of claim 2, since the double stepping operation in which the energization direction is reversed without including the pause time is performed during the first stepping step, the probability of starting the motor in the first stepping step is increased. It becomes extremely high, and it is possible to reduce the power consumption at the time of startup while ensuring the reliability of startup.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. 1 to 4 show a first embodiment of a method for starting a sensorless polyphase DC motor according to the present invention. The activation method shown in FIG.
It is applied to a single-phase sensorless DC motor.
Shows an entire configuration including a motor control system. In a DC motor, a stator (not shown) that generates a magnetic field in an excited state and a rotor (not shown) that obtains a rotational force by electromagnetic interaction with the magnetic field of the stator are shown. And a rotor.

The stator has three-phase stator coils u,
The back electromotive force which detects the back electromotive force induced in each stator coil u, v, w during the rest time when the exciting current is not supplied to each stator coil u, v, w. The detection circuit 1 is connected. The control system of this embodiment includes a control circuit 2 to which the detection signal of the counter electromotive voltage detection circuit 1 is input, a step signal generation circuit 3 that supplies a step signal to the control circuit 2, and an output side of the control circuit 2. And an energization switching circuit 4 and an output drive circuit 5 which are connected to each other.

The output drive circuit 5 receives an output signal from the energization switching circuit 4 which operates based on a command from the control circuit 2, and supplies an exciting current in a pattern set for each stator coil u, v, w. To do. The control circuit 2 controls the start-up of the motor and the steady operation after the start-up based on the signal from the back electromotive force detection circuit 1. FIG. 2 shows a control flow at the time of starting performed by the control circuit 2, and FIG. 3 shows a time chart of a step process at the time of starting.

In the stepwise step shown in FIG. 3, the first and second stepwise steps, the first acceleration step (reverse excitation step) and the second step.
The acceleration process is set, and the step process is repeated twice. Further, in the first and second step steps, nine internal steps 0 to 9 from the first to the ninth step are performed in a cycle synchronized with the inertia of the motor. In the control flow shown in FIG. 2, when the control circuit 2 receives the start signal and operates, first, in step s1, the first step process is executed.

In the first step step executed in step 1, the output drive circuit 5 is operated by operating the energization switching circuit 4 based on the output signal of the step signal generation circuit 3 based on the control signal of the control circuit 2. By turning on and off, for example,
In the first internal step 0, the stator coils u are energized to the same v, and in the second internal step 1, the stator coils w are energized to the same v, and each of these stator coils u, v, w is energized.
Are sequentially excited according to the set pattern.

Then, the first of 9 internal steps 0 to 9
When the step process is performed, the first acceleration process is performed for a predetermined time while keeping the state of the final internal step 9. At this time, in the present embodiment, by the detection signal of the counter electromotive voltage detection circuit 1 connected to each stator coil u, v, w,
The control circuit 2 determines whether or not the motor has been sufficiently activated (step s2).

To determine the start-up performed in step s2,
For example, the zero crossing of the back electromotive voltage in the first acceleration step, the magnitude of the rotor acceleration, the number of revolutions immediately after the end of the first acceleration step, etc. are larger than the empirically determined set values according to the shape of the motor. It is judged by whether or not step s
If 2 is determined to be sufficient, the stepping process thereafter is stopped, the control flow at the time of startup is terminated, and the normal operation mode is performed based on the detection signal of the back electromotive force detection circuit 1.

On the other hand, if it is determined in step s2 that the start-up has not been sufficiently started, the second step step is executed in step s4 while the reverse excitation current is held (step s3). As shown in FIG. 3, the second step process used in this embodiment has the same internal step 0 as the first step process.
~ 9 is set to repeat pattern, but the second
Each stator coil u, v, w before the step process is executed
The excitation state of is maintained in the state of the final internal step 9 in the first step, so that in the stator coil u, the double step operation in which the energization direction reverses from negative to positive without including the pause time is performed. It is provided and is a so-called double drive system.

Therefore, a very large torque is generated in the initial stage of the second step process. Even if the rotor is near the dead center with respect to the stator, the magnetic flux densities differ in the second step, so that the rotor can be started with a high probability. Then, when the second step process is executed,
In the acceleration process, the back electromotive voltage generation circuit 1 is again activated at this time.
It is determined in step s5 whether the motor has started based on the detection signal of.

When it is determined in step s5 that the motor has been sufficiently started, the stepping process thereafter is stopped, the control flow at the time of start is terminated, and the motor is operated in the normal operation mode as described above. It If it is determined in step s5 that the engine has not been fully activated, the process returns to step s1.
The operation similar to the above is repeated until the start of the motor is confirmed within the set time. However, in many cases, the final step s5 can be omitted.

FIG. 4 shows three cases that occur when the motor is started by the above control flow. The first case shown by in the figure is step s.
In FIG. 2, it is determined that the first step step has been sufficiently activated and the subsequent second step step is stopped, and the state indicated by the dotted line in FIG. Also, the first
In the case, what is indicated by a solid line is the one in which the second step process is further performed when the first step step has been sufficiently activated.

FIG. 4 shows a second case, and it is determined that the second case is not sufficiently activated in step s2, but the second step process is executed in step s4. Thus, it is the case where it is determined in step s5 that the motor has sufficiently started. In addition, in FIG.
In the third case, it is determined in step s2 that it has not been activated at all, but in step s4
By executing the second step process at step s5
This is the case when it is determined that the motor has started sufficiently.

As is apparent from the observation of the three cases in FIG. 4, particularly, if the motor is sufficiently started in the first step and the subsequent step is stopped, the rotation speed of the motor is lowered. It turns out that there is no smooth start. By the way, according to the sensorless multi-phase DC motor starting method as described above, when the back electromotive force detection circuit 1 detects that the motor has started in the first step step, the second step step thereafter. The power consumption at the time of starting is reduced because it is stopped.

FIG. 5 shows a second embodiment of the method for starting a sensorless polyphase DC motor according to the present invention. This figure shows another example of the internal stepping adopted in the first stepping step in the stepping step at startup shown in FIG. In the internal stepping shown in the figure, patterns 0 to 9 are set as in the case of FIG. 3, and in particular, the stator coils u, v, w
In each of the above, a double stepping operation is provided in which the energization direction reverses from negative to positive without including rest time.

That is, in the stator coil u, the internal step 6 is the double drive method, in the step v, the internal step 2 and 7 is the double step. If the step process having such a configuration is adopted as the first step process, the first step
The probability that the motor will be started in the stepping process becomes very high, and it is possible to reduce the power consumption at the time of starting while ensuring the reliability of starting.

[0027]

As described above in detail in the embodiments,
According to the starting method of the sensorless multi-phase DC motor of the present invention, the power consumption at the time of starting is reduced, which can contribute to the reduction of the current of the power source battery for driving the motor.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram including a control system of a multi-phase DC motor to which a starting method according to the present invention is applied.

FIG. 2 is a flowchart showing an example of a starting method according to the present invention.

FIG. 3 is an explanatory diagram of a stepping process performed by the flowchart shown in FIG.

FIG. 4 is an explanatory diagram of a starting state of the motor performed by the starting method shown in FIG.

FIG. 5 is an explanatory view showing another example of a step process adopted in the starting method of the present invention.

[Explanation of symbols]

 1 Back Electromotive Voltage Detection Circuit 2 Control Circuit 3 Stepping Signal Generation Circuit 4 Energization Switching Circuit 5 Output Drive Circuit u, v, w Stator Coil

Claims (2)

[Claims] 1. A stator including a stator that generates a current magnetic field in an excited state, a rotor including a rotor magnet that obtains a rotational force by electromagnetic interaction with the current magnetic field of the stator, and a back electromotive force that detects an induced electromotive voltage of the stator. In a method of starting a sensorless multi-phase DC motor, which comprises a voltage detection circuit, wherein a stepwise step of supplying a driving current for rotating the rotor in a predetermined direction to the stator is repeated at least twice, A reverse excitation step is provided after the supplied first step step, and when the back electromotive voltage detection circuit detects that the motor has started in the reverse step or the first step step, the subsequent steps are performed. A method for starting a sensorless multi-phase DC motor, characterized by stopping the advance process. 2. A double stepping operation in which the energizing direction is reversed without including a pause during the first stepping step in which the drive current is first supplied is provided.
A method for starting a sensorless polyphase DC motor as described.