JPH06189586A - Control method for cooling fan and circuit used for it - Google Patents

Abstract

PURPOSE:To obtain a control method and a control circuit for cooling fans which makes high-speed operation of the cooling fans possible at the time of device operation, and low-speed operation possible at the time of idling. CONSTITUTION:A transistor 1 and a zener diode 6 are provided in a power path of a cooling fan 5. At the time of device operation, the cooling fan 5 is operated at a high speed by supplying power without a voltage drop through a path formed by the transistor 1. And at the time of nonoperation, the cooling fan is operated at a low speed by dropping the voltage through a path formed by a zener diode 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling fan control method for various devices.

[0002]

2. Description of the Related Art With the improvement of office environment, there has been an increasing demand in recent years for low noise devices. For example, conventionally
In the printer device, the cooling fan is rotated during operation, but in the idle state, control is performed to stop the fan because the wind noise of the cooling fan is noisy.

[0003]

However, in the recent apparatus, it is not always preferable to stop the cooling fan at the time of idling because of the situation as described below.

First, in a device, such as a wire dot printer, which is relatively noisy in principle when the device is in operation, since the enclosure has a high sealing rate,
When the cooling fan is stopped, the air inside the enclosure does not get replaced.

Secondly, similarly, in the case of a wire dot printer as an example, the heat generation of the wire dot print head is reduced at the time of idling, but the energy consumption of the power supply unit or the control circuit is not reduced so much that the heat is generated even at the idling state. It doesn't go away. That is, in this way, although the degree of airtightness of the housing is increased, the heat generation inside the device is not lost, so in some cases, the cooling fan is stopped in an idle state more than when operating while rotating the cooling fan. In this case, the temperature inside the device may increase more greatly.

In order to avoid such a failure due to an increase in the internal temperature of the apparatus, an electronic component which is weak against high temperature, for example, a component having a high heat resistant temperature is adopted by changing the heat resistant temperature of the electrolytic capacitor from 85 ° C to 105 ° C. However, this will increase the cost of parts.

[0007]

In order to solve the above problems, the present invention provides a relatively large electric power energy to the cooling fan during operation of the device having the cooling fan to perform high-speed operation. After the operation is suspended and the engine is idled, relatively low electric power energy is applied to the cooling fan to operate at low speed.

The present invention also provides, as a circuit for implementing the above method, a control terminal to which a control signal is input, a first terminal connected to a power supply, and a second terminal connected to a cooling fan as an output.
And a constant voltage element provided between the first terminal and the second terminal of the transistor.

[0009]

Since the present invention is constructed as described above,
When the device having the cooling fan is in the idle state, the rotation speed of the cooling fan can be reduced to low speed rotation, and the wind noise of the cooling fan in the device can be prevented from being noticed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIG. In the cooling fan control circuit, the emitter is the power supply + V
A PNP transistor 1 connected to, a resistor 2 having one end connected to the emitter of the transistor 1 and the other end connected to the base of the transistor 1, a base resistor 3 having one end connected to the base of the transistor 1, and an output. Is connected to the other end of the base resistor 3, the input of which is the control signal input IN, and the Zener diode 6 whose cathode is connected to the emitter of the transistor 1 and whose anode is connected to the collector. . Incidentally, D
The cooling fan 5 having a C motor is connected between the collector of the transistor 1 serving as an output terminal and the ground power supply.

Here, the resistor 2 is mounted for the purpose of allowing the transistor 1 to perform a stable on / off operation, and for forming a discharge route of the electric charge remaining between the base and the emitter when the transistor 1 is turned off. Is something
The operation itself is possible without it. Further, a DC motor having a drive rating of 7 to 15 V is used as a drive source of the fan 5,
When it is desired to increase the driving force, a DC motor with a drive rating of 15 to 30 V may be used.

The operation of this control circuit will be described below. When an “H” level signal is input to the control signal input IN,
The output of the inverter 4 becomes "L" level, the emitter-base current flows through the transistor 1, and the transistor 1 is turned on. As a result, a voltage of (+ V-vON) is applied to the fan 5 when vON is the ON voltage of the transistor 1. Here, D used by the fan 5
When the C motor has a drive rating of 7 to 15 V, the power supply voltage + V is set to 15 V. Further, the on-voltage vON of the transistor 1 is set to about 0.7V. "H" to control signal input IN
When a level signal is input, a voltage close to the rated maximum of 14.3 V is applied to the fan 5 to operate at high speed.

When an "L" level signal is input to the control signal input IN, the output of the inverter 4 becomes "H" level. As a result, the flow of the emitter-base current of the transistor 1 is blocked and the transistor 1 is turned off. At this time, a current flows between the cathode and the anode of the Zener diode 6, and assuming that this Zener voltage is vZD, a voltage of (+ V-vZD) is applied to the fan 5.
Since the power supply voltage + V is also 15V, if the Zener diode 6 having a Zener voltage of 7V is selected, the voltage of 8V is applied to the fan 5 when the "L" level signal is input to the inverter 4. , Drive at low speed.

That is, when the DC motor of the cooling fan 5 is rotated at a low speed, the voltage applied to the cooling fan 5 can be adjusted by appropriately selecting the Zener voltage vZD of the Zener diode in advance, so that the voltage can be freely determined. It is possible to operate by low speed rotation.

When it is desired to adjust the low speed rotation, it is preferable to connect a plurality of Zener diodes having different Zener voltages in parallel and select the switching elements such as transistors.

Next, a second embodiment of the present invention will be described with reference to FIG. Although the fan 5 is connected to the ground side in the first embodiment, the fan is connected to the power supply + V side in this embodiment. In response to this, the transistor 1 is changed from a PNP transistor to an NPN transistor. The other structure is similar to that of the first embodiment. Even with such a configuration, the first
The same effect as that of the embodiment can be obtained.

Next, a third embodiment of the present invention will be described with reference to FIG. In the first and second embodiments, the fan control circuit that lowers the voltage applied to the fan 5 is used to perform the low-speed rotation operation, but in this embodiment, the fan 5 is intermittently supplied with electric power. The electric energy supplied to the fan 5 is reduced to operate at low speed.

In FIG. 3, the fan control circuit includes a PNP transistor 1, an open collector buffer 31 whose output is connected to the base of the transistor 1 and whose input is a control signal input IN, and a puller connected to the output of this buffer 31. And an up resistor 32. The cooling fan 5 is connected between the collector of the transistor 1 and the ground, and the diode 33 is connected in parallel with the cooling fan 5 in the reverse direction.

The operation of this circuit will be described below. When a "H" level signal is input to the control signal input IN, the output of the open collector buffer 31 becomes open state +5
The base current is supplied to the base of the transistor 1 through the pull-up resistor pulled up to V, and the transistor 1 is turned on. As a result, a voltage near + V is applied to the fan 5 and the fan 5 operates at high speed.

When a signal of "L" level is input to the control signal input IN, the output of the open collector buffer 31 becomes "L" level and the base current is not supplied to the base of the transistor 1 so that the transistor 1 is turned off. . As a result, the voltage application to the fan 5 is cut off and the operation is stopped. The diode 33 is provided in order to prevent the back electromotive force from being generated by the inductance component of the DC motor of the fan 1 and damaging the transistor 1 when the fan 5 is switched from the on state to the off state. This absorbs the back electromotive force and protects the transistor 1.

In order to operate the cooling fan 5 at a low speed by using this circuit, the intermittent control signal A shown in FIG. 4 is input to the control signal input IN. In the control signal A, for example, the on-time TcON is set to 0.1 second and the off-time TcOFF is set to 0.3 second. As a result, the electric power is intermittently supplied to the fan 5, but the motor of the cooling fan 5 continues to rotate due to inertia even when the electric power is not supplied, but the motor is lower than the rotational speed rating as shown in B but does not stop. Rotate at a moderate speed.

The intermittent frequency and the ratio of the ON time to the OFF time are not limited to the above ratios, and can be freely set within the range where the fan does not stop. That is, the intermittent frequency may be set to be relatively short when the rotation of the DC motor to be used is heavy and is to be stopped immediately by cutting off the power source, and may be set to be relatively long when it is not. However, it is preferably 1 second or less in order to reduce the speed vibration of the motor during the intermittent operation. Further, the ratio of the on-time to the off-time is increased if the temperature inside the device tends to be relatively high due to the elements mounted on the device.

In the circuit according to the third embodiment, the fan 5 can be connected to the power supply voltage + V side if the same modification as that of the first embodiment is changed to the second embodiment.

An example in which the cooling fan control in this embodiment is implemented in a printer will be described with reference to FIG.
When the printing operation is started in the printer device (step 52), a control signal for turning on the cooling fan is applied to the control signal input IN to operate the cooling fan at high speed (step 53). When the printing operation stops (Step 5
4) As shown in FIG. 6, after the hold time TH has elapsed (step 55), the control signal is turned off (step 5).
1). The hold time TH is set because each element generates heat immediately after the printing operation is stopped, and it is preferable to operate the cooling fan at a high speed for a predetermined time even after the printing is stopped. Therefore, if the heat generation after the printing operation is stopped is small, it may be set to 0. After this, the cooling fan 5
The operation including the routine 59 for intermittently supplying electric power for low speed operation is performed.

To supply power intermittently, the control signal is turned off (step 51) as described above, and after the off time TcOFF has elapsed (step 56), the control signal is turned on (step 57) and the on time is increased. After TcON has passed (Step 5
8) If the printing operation has not started yet (step 52), the process returns to step 51 to turn off the control signal. This is repeated until the printing operation starts or the power of the apparatus is turned off. As a result, control signal OFF (step 51) -TcOFF progress (step 56) -control signal ON (step 57) -TcON.
Power can be intermittently supplied in a cycle of progress (step 58) -confirmation of no print data (step 51) -control signal off (step 51).

The cooling fan control according to the present embodiment can be implemented at a lower cost than that of the cooling fan control according to the first or second embodiment because the circuit is simpler without using the Zener diode. Further, since the rotation speed of the fan 5 can be changed only by changing the ratio of the ON time of the control signal, the fan speed can be easily adjusted. On the other hand, in the cooling fan control according to the first and second embodiments, the rotation speed is always constant even at the low speed rotation, so that the speed vibration in the present embodiment is eliminated and the noise becomes less noticeable.

The cooling fan control circuit described above is shown in FIG.
By connecting the control signal input IN of the cooling fan control circuit 71 to the CPU 73 via the I / O port 72, the CPU 73 can be controlled.

In the printer device, the CPU 73 manages the printing operation as shown in FIG. 6A, and outputs a control signal to the control signal input IN to apply the control signal to the motor in the first and second embodiments. The voltage applied is set to a low voltage as shown by B, and in the third embodiment, the voltage applied to the motor is controlled to be applied intermittently. This control is performed such that the cooling fan operates at high speed during the printing operation in which the printer device generates a relatively large amount of heat, and operates at a low speed with the hold time TH when the printing operation ends and the amount of heat generated decreases. By controlling in this way, it is possible to switch between high-speed operation and low-speed operation without using any additional device such as a temperature sensor.

However, depending on the print data, the temperature inside the device becomes too high during the printing operation, and the hold time TH
There is a case where the inside of the device cannot be sufficiently cooled only by itself.
In addition, some devices have strict specifications and are required to have a long life. In such a case, a temperature sensor such as a thermistor may be provided via the I / O port and control by this may be performed.

[0030]

As described above, according to the present invention, since the operating noise of the device having the cooling fan is relatively high while the device having the cooling fan is operating, a large amount of electric power energy is applied and the noise of the cooling fan is also relatively high. The noise of the cooling fan is not annoying even during operation, and the device becomes quiet when the device is in the idle state.Therefore, a relatively small amount of electric energy is applied to the device so that the cooling fan rotates at a speed that does not stop it. Since the noise of the fan is reduced and the noise is controlled so that the noise is less noticeable, the operation of the device can be continued without stopping the cooling of the device.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a cooling fan control circuit for explaining a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a cooling fan control circuit for explaining a second embodiment of the present invention.

FIG. 3 is a circuit diagram of a cooling fan control circuit for explaining a third embodiment of the present invention.

FIG. 4 is a time chart for explaining the relationship between the control signal and the rotation speed of the cooling fan in the third embodiment of the present invention.

FIG. 5 is a flowchart for explaining a cooling fan control method according to the third embodiment of the present invention.

FIG. 6 is a flowchart for explaining a state in which the cooling fan control method according to the third embodiment of the present invention is applied to a printer device.

FIG. 7 is a block diagram for explaining a state in which a cooling fan control circuit according to the present invention is connected to a CPU.

[Explanation of symbols]

 1 Transistor 2 Resistor 3 Resistor 4 Inverter 5 Fan 6 Zener Diode 31 Buffer 32 Resistor 33 Diode

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masao Yaji 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd.

Claims (8)

[Claims] 1. When a device having a cooling fan is in operation, relatively high electric power energy is applied to the cooling fan to perform high-speed operation, and after the operation is interrupted and becomes idle,
A cooling fan control method for supplying a relatively small amount of electric power energy to the cooling fan for low-speed operation. 2. The cooling fan control method according to claim 1, wherein the low speed operation of the cooling fan is performed by intermittently applying a voltage in the vicinity of the rating of the cooling fan to the cooling fan. 3. The cooling fan control method according to claim 2, wherein the switching of the cooling fan from high speed operation to low speed operation is performed after a hold time has elapsed. 4. The cooling fan control method according to claim 2, wherein the intermittent voltage lengthens the ON time when the temperature inside the device is high, and shortens the ON time when the temperature inside the device is low. 5. The cooling fan control method according to claim 1, wherein the low speed operation of the cooling fan is performed by continuously applying a voltage lower than the rating of the cooling fan to the cooling fan. 6. The cooling fan control method according to claim 5, wherein the switching of the cooling fan from high speed operation to low speed operation is performed after a hold time has elapsed. 7. A switching element having a control terminal to which a control signal is inputted, a first terminal connected to a power supply, and a second terminal connected to a cooling fan as an output, and a first element of the transistor. A cooling fan control circuit composed of a terminal and a constant voltage element provided between the second terminal. 8. The cooling fan control circuit according to claim 7, wherein the switching element is a diode and the constant voltage element is a Zener diode connected in a reverse direction.