JPH05137657A - Rotation control method at starting of mill motor - Google Patents

Abstract

PURPOSE:To prevent poor rotation of a mill motor due to heavy load at the starting of a low speed operation of the mill motor so arranged to allow the selection of high and low speed operations. CONSTITUTION:A mill motor 1 is so arranged to allow the selection of a high speed operation by an applied voltage for high speed operation and a low speed operation by the applied voltage for low speed operation lower than the applied voltage for the high speed operation. At the start when the low speed operation is selected. the mill motor 1 is rotated at the number of rotations higher than that in the low speed operation by applying the voltage higher than that for the low speed operation only for a specified time. Then, the motor is rotated at the number of revolutions in the low speed operation by applying the voltage for the low speed operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation control method for starting a motor of a mill (mill motor) used for grinding coffee beans.

[0002]

2. Description of the Related Art Normally, a single-phase AC motor is used for this type of mill motor. In addition, some mills can select high speed operation for fine grinding (regular) and low speed operation for rough grinding (mild). In such a mill,
Switching between high-speed operation and low-speed operation is performed by changing the applied voltage of the mill motor, and the applied voltage of the mill motor is controlled as follows, for example. That is, a mill motor and a triac are connected in series to a 100V single-phase AC power source, and phase control is performed to control the on / off cycle of the gate voltage of the triac by a triac drive signal, whereby the applied voltage is high at high speed rotation,
The applied voltage of the mill motor is controlled so that the applied voltage becomes low at low speed rotation. For example, when driving at high speed,
The triac drive signal (gate voltage) is always on and static output is performed, and the applied voltage of the motor is 100
Set to V. During low speed operation, the AC power supply voltage is 1
Phase control is performed in which the triac drive signal (gate voltage) is turned on / off for a predetermined time every cycle, and the voltage applied to the motor is set to 60V.

[0003]

However, in the conventional rotation control method of the mill motor as described above, when the low speed operation for rough grinding is selected, the rotation speed of the motor is low from the start, Depending on the state of the beans placed in the mill due to insufficient driving torque, the load may increase, resulting in poor rotation. In extreme cases, the state may be locked and rotation may not be possible.

The object of the present invention is to solve the above problems,
It is an object of the present invention to provide a rotation control method at the time of starting a mill motor, which can prevent a motor rotation failure due to a high load at the time of starting at low speed operation.

[0005]

A rotation control method for starting a mill motor according to the present invention includes a high speed operation by an applied voltage for a high speed operation and a low speed operation by an applied voltage for a low speed operation which is lower than an applied voltage for a high speed operation. It is a rotation control method at the time of starting the mill motor that can be selected
When the low-speed operation is selected, the applied voltage higher than the applied voltage for low-speed operation is applied for a predetermined time to rotate the mill motor at a higher rotation speed than during low-speed operation, and then the applied voltage for low-speed operation is set. It is characterized in that the voltage is applied to rotate at a rotation speed during low speed operation.

[0006]

When the low speed operation is selected, the applied voltage higher than the applied voltage for the low speed operation is applied for a predetermined time to start the mill motor at a higher rotation speed than the low speed operation. , Rotation failure does not occur.

[0007]

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

FIG. 1 shows the electrical configuration of the mill motor (1) and its control device, and FIG. 2 shows the signal waveforms of the respective parts.

In FIG. 1, a 100V single-phase AC power source (2)
The mill motor (1) and the triac (3) are connected in series with the primary winding (4a) of the transformer (4). The secondary winding (4b) of the transformer (4) is connected to the input terminal of the stabilization circuit (6) through the bridge full-wave rectifier circuit (5), and the output terminal of the stabilization circuit (6) is connected to the control circuit ( It is connected to the power supply terminal of 7). The control circuit (7) includes a microprocessor and controls the motor (1) as described later. The control circuit (7) is connected to one terminal of the secondary winding (4b) of the transformer (4) and generates the power supply synchronization signal as shown in Fig. 2 (b) from the AC power supply voltage signal of Fig. 2 (a). To do. Control circuit (7)
Is connected to the gate of the triac (3) and outputs a gate drive signal to control the gate voltage to drive the triac (3) on / off. The TRIAC (3) is turned on and the motor (1) is powered (2) only while the TRIAC drive signal (gate voltage) is ON.
The AC power supply voltage from is applied. Also, the control circuit (7)
A switch for high speed rotation (high speed switch) (8) for fine grinding and a switch for low speed rotation (low speed switch) (9) for rough grinding are connected to the.

In FIG. 2, (c) shows two switches.
(8) Shows the input signal from (9). (d) and (e) show the triac drive signal and the applied voltage of the motor (1) at high speed operation, and (f) and (g) show the triac drive signal and the applied voltage of motor (1) at the low speed operation, respectively. Shows.

FIG. 3 is a flow chart showing an example of the rotation control processing of the motor (1) by the control circuit (7).

Next, referring to FIGS. 2 and 3, the motor
An example of the rotation control method (1) will be described.

In the flow chart of FIG. 3, the switch
When any of (8) and (9) is operated and a switch input signal is input to the control circuit (7), in step 1, the type of operated switch (8) and (9) is checked. And fast switch
When (8) is operated, the process proceeds to step 2 and static output is performed in which the triac drive signal is always on. As a result, the applied voltage of the motor (1) becomes 100 V which is the applied voltage for high speed rotation, the motor (1) rotates at high speed, and high speed operation for fine grinding is performed. Step 1
When the low speed switch (9) is operated in step 3, the process proceeds to step 3 and static output is performed in which the triac drive signal is turned on only for a preset fixed time, for example, about 5 seconds. As a result, the applied voltage of the motor (1) becomes 100 V for about 5 seconds, and the motor (1) rotates at high speed.
When 5 seconds have elapsed, the process proceeds to step 4, where phase control is performed to turn on / off the triac drive signal for a predetermined time every cycle of the AC power supply voltage. This allows the motor (1) to operate only during a certain phase angle of one cycle of the AC power supply voltage.
AC power supply voltage is applied to the terminals of the motor, and the applied voltage of the motor (1) becomes 60V which is the applied voltage for low speed rotation.
(1) rotates at low speed, and low speed operation for rough grinding is performed.

In FIG. 2, at time t1, the high speed switch (8)
When the switch input signal is input by operating
As shown in (d), the time is synchronized with the next power supply synchronization signal.
At t2, the triac drive signal turns on and is held in the on state. As a result, as shown in FIG. 2 (e), the AC power supply voltage is directly applied to the motor (1), and the applied voltage of the motor (1) becomes 100V.

In FIG. 2, the low speed switch (9) is turned on at time t1.
When the switch input signal is input by operating
As shown in (f), the time is synchronized with the next power supply synchronization signal.
At t2, the triac drive signal turns on, and at time t3
Is kept on for about 5 seconds. As a result, the AC power supply voltage is directly applied to the motor (1) for about 5 seconds from time t2 to time t3, and the applied voltage of the motor (1) becomes 100V. After the time point t3, the triac drive signal is turned on for a fixed time (phase angle) T1 in one cycle T of the AC power supply voltage. This ensures that the motor (1) will only run while the TRIAC drive signal is on.
An AC power supply voltage is applied to the motor to perform phase control, and the voltage applied to the motor (1) becomes 60V.

The configuration of each part of the control unit of the mill motor (1) and the rotation control method are not limited to those in the above embodiment,
It can be changed appropriately within the scope of the present invention. For example, in the above-described embodiment, the applied voltage is set to 100 V, which is the same as that in the high speed operation, for about 5 seconds at the time of startup in the low speed operation.
The applied voltage at this time may be a value higher than the low speed operation and lower than the high speed operation, for example, 90V.

[0017]

According to the rotation control method for starting the mill motor according to the present invention, as described above, the rotation failure of the mill motor may occur even when the load is large at the time of start when the low speed operation is selected. It is also possible to prevent the mill motor from becoming locked and unable to rotate due to a high load.

[Brief description of drawings]

FIG. 1 is an electric block diagram of a rotation control device for a mill motor showing an embodiment of the present invention.

FIG. 2 is a time chart showing signal waveforms of respective parts of the rotation control device of FIG.

FIG. 3 is a flowchart showing an example of rotation control processing of the control circuit of FIG.

[Explanation of symbols]

 (1) Mill motor (2) 100V single phase AC power supply (3) Triac (7) Control circuit (8) High speed switch (9) Low speed switch

Claims (1)

[Claims] 1. A high-speed operation using an applied voltage for high-speed operation,
A rotation control method at the time of start of a mill motor that allows selection of low-speed operation with an applied voltage for low-speed operation that is lower than the applied voltage for high-speed operation. Apply the applied voltage higher than the applied voltage for low speed operation for a period of time to rotate the mill motor at a higher rotation speed than that during low speed operation, and then apply the applied voltage for low speed operation to rotate at the rotation speed during low speed operation. A rotation control method for starting a mill motor, which is characterized in that.