JPH0433589A - Motor speed control method - Google Patents

Abstract

PURPOSE:To vary the rotational speed of a motor, in multiple steps, from low speed to high speed by varying the ratio between an interval in which a high voltage is applied on the motor and an interval in which a low voltage is applied on the motor, in multiple steps, while repeatedly switching the applying voltage of the motor between the high and low voltages. CONSTITUTION:Waveform at the digital output terminal of a microcomputor(i.e. the waveform of a voltage switching signal), when the rotational speed of a DC fan is varied in 11 steps, is shown. The digital output terminal remains at '0' under low speed rotation. When the rotational speed is increased, the digital output terminal is pulled to '1' for an arbitrary time during single cycle TCY. The rotational speed increases as the duration T1 of '1' in one cycle increases whereas it decreases as the duration T1 decreases. The digital output terminal is kept at '1' during high speed rotation. Since too long cycle length TCY causes an unsmooth rotation, it must be set as short as possible.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for controlling the number of rotations (rotational speed) of a motor that drives, for example, a cooling fan of a computer device. Note that in the following figures, the same reference numerals indicate the same or corresponding parts.

[Conventional technology]

FIG. 1 is a block diagram showing a hardware configuration as an embodiment of the present invention, and the conventional technology will be explained using this diagram hereinafter. However, in the prior art, the repetitive opening/closing control means 2A in the microcomputer 2 is not provided. In FIG. 1, conventionally, a temperature sensor 1 detects the temperature inside the device, and a microcomputer (also abbreviated as microcomputer) 2 outputs the digital output. A voltage switching signal 6 as shown in FIG.
Alternatively, the controller switches to a low voltage DC power source EO and rotates the DC fan 5 at high or low speed. If the temperature is higher than the set temperature, a power source E1 of the rated voltage is applied to the DC fan 5 to rotate it at high speed, and if it is lower than the set temperature, a power source EO of a low voltage is applied to the DC fan 5 to rotate it at a low speed. There is a difference in the noise of the DC fan when rotating at low speed and when rotating at high speed, so when switching from low speed to high speed, the noise of the DC fan suddenly becomes louder, causing discomfort to the user of the device. may be given.

[Problem to be solved by the invention]

In the aforementioned speed switching method for DC fans, the rotation speed of the DC fan is in two stages: low speed rotation and high speed rotation, and regardless of the size of the temperature rise detected by the temperature sensor, if the temperature is higher than the set temperature, high speed rotation occurs. become. At this time, the noise of the DC fan suddenly becomes louder. Furthermore, when the temperature rises near the set temperature, low-speed rotation and high-speed rotation are frequently repeated, causing discomfort to the user due to the noise of the DC fan. Therefore, the problem of this invention is to reduce the rotational speed of the DC fan to the minimum necessary number of rotations based on the degree of temperature rise detected by the temperature sensor by improving only the software without modifying the hardware of the conventional device. To provide a motor speed control method capable of alleviating the discomfort given to a user by gradually increasing the rotation from low speed rotation, rather than suppressing the rotation speed to low speed or suddenly switching from low speed rotation to high speed rotation. There is a particular thing.

[Means to solve the problem]

In order to solve the above-mentioned problems, the method of the present invention is based on "a system in which the voltage supplied to the motor is switched to high voltage and low voltage, thereby switching the rotational speed of the motor to high and low speeds, respectively, and this switching is repeated. At the same time, the rotation speed of the motor can be reduced to a low speed by changing the ratio of the period during which the high voltage is applied to the motor (TI, etc.) and the period during which the low voltage is similarly applied (TO, etc.) in multiple stages. It is assumed that J is changed in multiple stages between .

[For use]

The voltage for high-speed rotation and the voltage for low-speed rotation are repeatedly switched and applied to the motor, and at this time, the ratio of the application period of the former voltage to the application period of the latter voltage is changed in multiple stages. The rotational speed of the rotor can be varied in multiple stages from low speed to high speed.

【Example】

The present invention will be described in detail below with reference to FIGS. 1 to 8. In the present invention, a repetitive opening/closing control means 28 is provided in the microcomputer 2 shown in FIG. 1 as a partial functional section that is assumed to share the function. In the present invention, the voltage switching signal 6 output from the digital output terminal DO of the microcomputer 2 is repeatedly changed in a waveform as shown in FIG. 3 by a program (software). That is, in FIG. 3, the voltage switching signal 6 (digital output Do) becomes "1" (high level) during period T1 during one cycle period TCY, and becomes "'0" (low level) during period TO. Here, the voltage switching device 4 is
It is assumed that the switch is switched to the power supply El (high speed, rated voltage) side, and the switch is also switched to the power supply EO (low speed, low voltage) side by the voltage switching signal 6 of "P0°". The switching cycle is repeated at a rate of several tens to hundreds of times per second.
By controlling the average voltage applied to the fan 5, the rotation speed of the DC fan 5 can be varied between low speed rotation and high speed rotation. Note that as a practical hardware configuration of the voltage switching device 4, a switching transistor or the like can be used to make it contactless. FIG. 4 shows the output waveform of the digital output terminal DO of the microcomputer 2 (that is, the waveform of the voltage switching signal 6) for each one cycle when the rotational speed of the DC fan 5 is changed in 11 steps. That is, in a low-speed circuit, DO remains at "0" and does not change. When increasing the rotation speed from low speed rotation, use 1 cycle TC
At any time during YO, the output of digital output terminal DO is “1”.
Make it ゛. The longer the "1" time T1 in one cycle, the closer to high-speed rotation, and the shorter it is, the closer to low-speed rotation. When high-speed rotation is desired, the output of the digital output terminal DO remains at "1". The length of one cycle TCY is
If it is too long, smooth rotation will not be obtained, so it is necessary to make it as short as possible considering the performance of the microcomputer 2, the response of the power supply, and the characteristics of the DC fan. FIG. 5 shows a flowchart of a program for changing the rotation speed of the DC fan 5 as shown in FIG. This program is executed by periodic interruption by a 1 ms timer, the length of one cycle TCY is 10 m5, and is an example intended to change the rotation speed from low speed to high speed in 11 steps. Here, W represents the parameter (specified value for how many milliseconds out of 1 cycle 10m5 to switch to high speed rotation) representing the time T1 for setting the digital output Do to "1" (high speed rotation), and the temperature rise detection program It is passed to the program shown in Figure 5 as a parameter to control the rotation speed. n is a time count value, which is incremented by 1 every time the program shown in FIG. 5 is executed, cleared at 10 m5 (when n=9), and becomes 0 again. When W=0, this program continues to set DO to "0" regardless of the value of n, so the DC fan 5 rotates at a low speed. Also, in the case of W-10, there is no relation to the value of n<Do
Since ``1'' continues to be set, the DC fan 5 rotates at high speed. When W is 1 to 9, when n=0, DO is set to "1'", and when n=W, DO is set to "0".In other words, according to the time chart in Figure 6. As shown, n=
During the time from 0 to n = W, DO becomes “1” and n =
From W to the next n=o, DO becomes "0". By repeating the above process, the rotation speed of the DC fan 5 is changed. Also, Fig. 7 is different from Fig. 5. Fig. 7 is basically the same as Fig. 5, but D
By checking the state of O, the number of times the digital output DO is set to 1- is made smaller than in FIG. In addition to the above method in which the cycle period TCY is constant and the duty ratio between high-speed rotation and low-speed rotation is changed, as shown in the time chart of Fig. 8, there is a method in which both the cycle period and the duty ratio are changed. There is also a method of changing the value, which can be executed by the program of the microcomputer 2 as in the above embodiment. The operations shown in FIGS. 4 to 8 correspond to the functions of the repetitive opening/closing control means 2 in the microcomputer 2. Next, FIG. 2 shows an embodiment with a different hardware configuration from that in FIG. 1, and the switching operation of the voltage switching device W4 is the same as that in FIG. 1. However, in FIG. 2, when the switch of the voltage switching device 4 is on the high speed side as shown by the solid line, the DC fan 5 is supplied with the power source EO, ! :
The sum voltage of E2 is added, and this sum voltage becomes the rated voltage. On the other hand, when the switch is on the low speed side as indicated by the broken line, a low voltage from the power source EO is applied to the DC fan 5 via the diode D1. In the above explanation, the motor that drives the fan is a DC motor, but an AC motor may be used as long as the motor can change its speed depending on the applied voltage, such as a high-slip induction motor. , power supplies EO, El,
E2 is replaced with an AC power supply.

【Effect of the invention】

According to the present invention, in a system in which the voltage supplied to a motor for driving a DC fan or the like is switched between a high voltage and a low voltage, the rotational speed of the motor is switched to high and low speeds, respectively. A period T1 during which the high voltage is applied to the motor, and a period TO during which the low voltage is similarly applied.
The rotational speed of the motor is changed in multiple stages from low speed rotation to high speed rotation by changing the ratio of 1 to 2 in multiple steps, so that the following effects can be obtained. ■It is possible to change the rotation speed of the DC fan in multiple stages using hardware that has a two-stage switching function of high-speed rotation and low-speed rotation. ■Even when switching from low speed rotation to high speed rotation, it is possible to change the rotation little by little, so it is possible to reduce the discomfort caused to the user compared to when the rotation speed suddenly changes. ■It becomes possible to control the rotation speed of the DC fan according to the degree of temperature rise, eliminating the need for unnecessarily high speed rotation, thereby reducing noise and power consumption.

[Brief explanation of drawings]

1 and 2 are block diagrams showing different embodiments of the hardware configuration of the present invention, FIG. 3 is a time chart for detailed explanation of the present invention, and FIG. 4 is a block diagram showing a first embodiment of the present invention. Fig. 5 is a flowchart corresponding to the operation in Fig. 4, Fig. 6 is a time chart for supplementary explanation of Fig. 5, and Fig. 7 is a time chart for explaining the specific operation.
FIG. 8 is a flowchart as a modification of the figure, and a time chart for explaining specific operation as a second embodiment of the present invention. 1: Temperature sensor, 2: Microcomputer, 2A: Repeated opening/closing control means, DO: Digital output (terminal), 6: Voltage switching signal, 4: Voltage switching device, EO, El E 2-0-040
, -0-0

Claims (1)

[Claims] 1) In a system in which the rotational speed of the motor is switched to high and low speeds by switching the voltage supplied to the motor to high voltage and low voltage, respectively, while repeating this switching, the rotational speed of the motor is The rotational speed of the motor is changed in multiple stages from low-speed rotation to high-speed rotation by changing the ratio between the period of voltage application and the period of applying the low voltage in multiple stages. A motor speed control method characterized by: