JP3308077B2 - Fan control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a fan mounted on an image forming apparatus such as a copying machine, a facsimile, a laser printer, etc., particularly a fan driven by a DC brushless motor.

[0002]

2. Description of the Related Art In recent years, as various OA devices are introduced into offices, noise generated by the devices has been regarded as a problem. For example, since OA equipment has a built-in drive motor and the like, considerable heat is generated inside the equipment, and a plurality of fans are provided on the equipment housing surface to take in outside air to cool it and exhaust heat. The noise generated by these fans and built-in motors is a problem.

Accordingly, various proposals have been made for fan control. For example, see JP-A-63-954.
No. 70 discloses a configuration including control means for turning on / off a motor for driving a cleaning fan according to a detected temperature inside a copying machine. With such a configuration, noise can be eliminated while the drive motor is off, but the noise problem cannot be solved when the drive motor is on.

For example, in Japanese Patent Application Laid-Open No. 3-81783, a cooling fan is moved at a constant speed while an image is formed on a material to be transferred, and the cooling fan is operated at a variable speed while the image forming operation is on standby. It is disclosed. Thus, it is intended to reduce noise without lowering the image forming ability.

[0005]

However, an office in which OA equipment is installed is usually supplied with a rated voltage, and the driving speed of a motor designed to meet this rated voltage is shown in FIG. Forcibly changing the voltage using a smoothing circuit or the like for voltage control as shown in the figure imposes an unexpected load on the motor and shortens the product life. This shortened service life is contrary to the demand for improving the durability of the product.

Further, even when a plurality of conventional fans are installed on the surface of the apparatus housing, they are commonly controlled to be turned on / off for cooling the entire inside of the apparatus housing, or at most, for example, for a cleaning apparatus. Common on / off control has been performed for each fan for cooling the same device member or for flowing air to the ozone decomposition filter.

In view of the above situation and problems, the present invention realizes low noise of OA equipment, especially during standby, and without applying an extra load to the drive motor.
It is an object to realize a fan control method that also contributes to the reliability of a machine.

[0008]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method for controlling a plurality of fans mounted for the same member / same purpose in an image forming apparatus. The problem is solved by operating each fan by the PWM control method, and setting the on / off timing of each fan to be opposite to each other.

[0009]

[0010] Some sounds emitted by the OA equipment have various wavelengths, and others have a unique cycle due to resonance or the like. Among them are sounds that do not appear as much in noise measurements and thus do not significantly affect the measurements, but are offensive to human hearing. This is referred to as “sensual noise”, and the sensual noise is also unpleasant for humans around the OA equipment.

In order to reduce the sensual noise, various tests were conducted.
It has been found that it is better to set the time to 50 ms or less.

[0012]

The ratio between the on time and the off time of the fan may be 1: n (n is an integer of 1 or more).

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to an embodiment based on the drawings.

FIG. 1 shows a partial plane of an image forming apparatus to which a control method according to an embodiment of the present invention is applied. The transfer material fed from the right side of the drawing is transferred with image information when passing through the photosensitive drum 1, is fixed with the image information when passing through the fixing unit 2, and is discharged outside the apparatus. Photoconductor 1 etc.
It is driven by a drive motor 3 arranged at the rear part of the apparatus main body, in the figure, on the upper side through a gear device (not shown). In addition, a power transformer 4, a control board, and the like are arranged in the rear part of the apparatus main body, and the temperature inside the apparatus is higher than that in the front part of the main body.

In the vicinity of the fixing unit 2, a first fan 5 and a second fan are arranged in a direction perpendicular to the sheet passing direction for cooling the unit. FIG. 2 shows a control state of the first fan 5 and the second fan. At the time of copying, both the first fan 5 and the second fan 6 are equally driven by the voltage a ₁ V and rotate by continuous driving.
6 is switched to PWM (Pulse Width Modulation) control, and on / off is repeated every several tens of milliseconds. At this time, the on / off timings of the fans 5 and 6 are opposite to each other.

At the time of PWM control, consider the control timing of two fans. As shown in FIG. 3, each of the on-timing or off-timing of the fans called phase the same thing, the on / off timing is referred to as the reverse and reverse phase (on-time in phase t ₁ and off-time t ₂ are equal in the example of FIG. 3, but t ₂ = 2t _{1 and the} like are also conceivable). Taking into account the noise generated when the fan is repeatedly turned on and off and the wind noise that fluctuates with changes in the rotation speed, the reverse phase control is more suitable for the purpose of the present invention. At that time, these t ₁ ,
It is preferable that each of t ₂ is 150 ms or less.

FIG. 4 shows that when t ₁ and t ₂ are made equal,
The result of noise measurement during standby in a certain copying machine when the off-timing is changed is shown as an average value (dB) at a power level of 12 seconds.

Similarly, FIG. 5 shows that when the on / off timing is changed at various time lengths of t ₁ and t ₂ , the monitor of 20 persons is asked whether the standby sound is quiet or unpleasant. The results of the questionnaire are shown below.

[0020]

In the fan control method according to the first aspect of the present invention, when the image forming operation is on standby, each fan is operated by the PWM control method, and the on / off timing of each fan is set to be opposite to each other. In addition, the wind noise that fluctuates in accordance with the change of the fan that rotates during standby is no longer annoying, does not cause discomfort to people around the machine, and can reduce noise during standby. This eliminates the need for a smoothing circuit for voltage control, which eliminates the need for an extra load on the drive motor, ensures the expected product life of the equipment, and reduces the failure rate of the fan and, consequently, the failure rate of the entire machine. Can be lowered.

[0021]

In the fan control method according to the second aspect, the on-time and the off-time of the fan driven at the time of standby are each extremely short, that is, 150 msec or less. The user does not feel the sound of the noise, which can reduce the harshness of the fans.

[0023]

In the fan control method according to the third aspect, the ratio between the on time and the off time of the fan is set to 1: n (n
Is an integer of 1 or more), the off-time of the fan in the machine operating time can be adjusted as needed, and the failure rate of the fan can be reduced.

[Brief description of the drawings]

FIG. 1 is a partial plan view of an image forming apparatus to which a control method according to an embodiment of the present invention is applied.

FIG. 2 is a diagram illustrating voltages and timings applied to a first fan and a second fan during standby and during copying.

FIG. 3 is a diagram illustrating control timings of a first fan and a second fan in the same phase and the opposite phase.

FIG. 4 is a diagram showing a noise measurement result in a certain copying machine provided with the control method of the present invention.

FIG. 5 is a diagram showing noise questionnaire results at various control timings by 20 monitors.

FIG. 6 shows an example of a smoothing circuit necessary for voltage control.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor drum 2 fixing unit 3 drive motor 4 power transformer 5 first fan 6 second fan

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-251873 (JP, A) JP-A-63-55568 (JP, A) JP-A-4-356063 (JP, A) JP-A-4- 215000 (JP, A) JP-A-2-119612 (JP, A) JP-A-2-110998 (JP, A) JP-A-63-173072 (JP, A) JP-A-2-76734 (JP, U) Shokai 61-17896 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/00 G03G 21/00 G03G 21/14 G03G 21/20 B41J 29/377 F04D 27 / 00-29/70 F25D 1/00 H05K 7/20

Claims (3)

(57) [Claims] 1. A fan control method for controlling a plurality of fans installed for the same member / the same purpose in an image forming apparatus, wherein each fan is operated by a PWM control method during a standby time of an image forming operation. A fan control method, wherein the on / off timing of each fan is set to be opposite to each other. 2. The method according to claim 1, wherein the on-time and the off-time are each set to 150 ms or less in the PWM control. 3. The fan control method according to claim 1, wherein the ratio between the on-time and the off-time of the fan is set to 1: n (n is an integer of 1 or more).