JPH04362663A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device whose inside is appropriately cooled by a heat exhaust means after finishing an image forming operation. CONSTITUTION:The image forming device, in which the rotating speed of the heat exhaust means 21 is successively made lower by the specified lowering amount of rotation speed at intervals of specified time after finishing the image forming operation, is provided with a 1st detecting means 15 for detecting the size or the thickness of a recording material, a 2nd detecting means 17 for detecting the number of consecutively passing recording materials, and a control means 30 for controlling the time interval or the lowering amount of the rotation speed in accordance with signals from the 1st and the detecting means 15 and 17. Therefore, the heat exhaust means is controlled in accordance with remaining heat quantity in the device based on the difference of the size and the thickness of the recording material and the number of consecutively passing recording materials, and heat exhaust inside the device is appropriately performed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to image forming apparatuses such as copying machines and laser beam printers.

0002

2. Description of the Related Art Many image forming apparatuses such as copying machines have a heat source such as a heat fixing device inside, and the temperature within the main body of the image forming apparatus tends to rise. Therefore, such image forming apparatuses are often provided with a heat exhaust fan that discharges heat generated inside the apparatus body to the outside of the apparatus body.

[0003] This heat exhaust fan operates at maximum air volume when the apparatus starts image forming work and the heat fixing device etc. is in a heating state, but when a series of image forming operations are completed and the heat fixing device etc. When the heating state is released, the air volume is gradually reduced.

In this case, the air volume of the heat exhaust fan is adjusted by the rotation speed of the heat exhaust fan. For example, as shown in FIG. 10, the exhaust fan is rotated at the maximum rotation speed N during image formation. However, when the image forming operation is completed, the rotational speed decreases by a predetermined amount Δt at predetermined time intervals Δt.
The rotational speed is controlled to be reduced by N.

[0005]

[Problems to be Solved by the Invention] However, in the conventional type of heat exhaust fan described above, when controlling the image forming operation after the image forming operation is completed, it is difficult to control the number of continuous sheets of recording paper (number of continuous printing sheets), the size of the recording paper, The thickness was not taken into account at all, and the time interval Δt and rotational speed drop amount ΔN were set to constant values. Therefore, if the number of continuous sheets of recording paper increases,
Since the amount of heat stored in the apparatus main body also increases, this heat exhaust fan has a problem in that it takes time to lower the temperature inside the apparatus main body after the image forming operation is completed.

[0006] Also, if the recording paper is large or thick,
Since more heat is removed from the heat fixing device than with ordinary recording paper, the amount of heat stored inside the device itself is not that large.If you use this heat exhaust fan, the amount of heat stored inside the device body will be removed in less time than necessary. This will cause the temperature to drop. That is, there is a problem in that the heat exhaust fan is operated at a rotation speed higher than necessary, which shortens the life of the heat exhaust fan. In contrast, if the recording paper is small or thin, it will take time for the temperature inside the apparatus body to drop.

The present invention has been made in view of the above-mentioned problems, and its object is to provide an image forming apparatus whose interior can be appropriately cooled by heat exhaust means after the image forming operation is completed.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a fixing means for performing heat fixing, and heat generated from the fixing means and its peripheral equipment, and the amount of air discharged from the fixing means is controlled by the rotation speed. In an image forming apparatus, the rotational speed of the heat exhausting means is sequentially lowered stepwise by a predetermined rotational speed reduction amount at predetermined time intervals after the image forming operation is completed. a first detection means for detecting the size or thickness of the recording material; a second detection means for detecting the number of continuous sheets of recording material; and a first detection means for detecting the size or thickness of the recording material; The present invention is characterized in that it is provided with a control means for the heat exhaust means that changes the rotational speed reduction amount.

[0009]

[Operation] When the image forming operation is started, a large amount of heat is released from the fixing means and the like, so the heat inside the apparatus is discharged to the outside by the heat exhaust means. Even after a series of image forming operations are completed, there is residual heat in the fixing device, etc., and heat is accumulated within the device, so the heat exhausting means is decelerated by a predetermined amount of rotational speed reduction at predetermined time intervals. However, the air volume is reduced.

On the other hand, the amount of residual heat in the fixing means and the like and the amount of heat stored in the apparatus vary depending on the size and thickness of the recording material and the number of continuous sheets.

[0011] Therefore, the first detection means detects the size and thickness of the recording material, and based on the signals from the first and second detection means, the control means determines the operation time interval or rotational speed of the heat exhaust means. By changing the amount of descent, the amount of exhaust heat is controlled by the heat exhausting means to match the amount of residual heat in the fixing means and the like and the amount of heat stored in the apparatus.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the accompanying drawings.

First, a first embodiment of the present invention will be explained with reference to FIGS. 1 to 6.
This is explained by:

FIG. 4 shows the overall configuration of an image forming apparatus, and FIG. 10 shows a photosensitive drum, which is an image carrier, disposed approximately in the middle between the upper and lower parts of the main body 1 of the apparatus. A charging roller 11, a developing device 12, and a transfer roller 13 are arranged on the lower side of the main body 1 of the apparatus below the photosensitive drum 10. A roller 18 is provided. Also, the apparatus main body 1 above the photosensitive drum 10
A fixing device 19 having a heat source for thermally fixing the toner image on the recording paper P, a paper discharge roller 20, and a heat exhaust fan 21 are disposed on the upper side of the recording paper P.

That is, when the photosensitive drum 10 uniformly charged by the charging roller 11 is exposed to image light from a scanner unit (not shown) and an electrostatic latent image is formed on the photosensitive drum 10, the electrostatic latent image is formed on the photosensitive drum 10. Toner is supplied to the image by a developing device 12 and the image is visualized as a toner image. This toner image is then transferred onto the recording paper P via the transfer roller 13. On the other hand, the recording sheets P taken out one by one from the paper feed cassette 14 are sent toward the registration rollers 18, and are conveyed toward the photosensitive drum 10 and the transfer roller 13 at the same timing by the registration rollers 18. . When the toner image on the photosensitive drum 10 is transferred onto the recording paper P, the recording paper P is sent to the fixing device 19, and after the toner image is thermally fixed by the fixing device 19, The paper is discharged to the outside of the apparatus main body 1 via the paper discharge roller 20.

[0016] Here, the heat exhaust fan is activated when the image forming operation is started and the fixing device 19 etc. are in a heated state, and the unnecessary heat inside the apparatus main body 1 is discharged to the outside, and the image forming operation is completed. Even after this, the residual heat inside the apparatus main body 1 generated during the image forming operation is discharged to the outside while reducing the air volume at predetermined time intervals Δt. In this case, since the air volume of the heat exhaust fan 21 is adjusted by controlling the rotation speed, the air volume adjustment after the image forming operation is performed by changing the rotation speed N of the heat exhaust fan 21 to a predetermined rotation at a predetermined time interval Δt. This is done while reducing the speed by the amount of speed reduction ΔN.

FIG. 1 shows a control device for controlling the air volume of the heat exhaust fan 21 after the image formation is completed. This is the control section 30 of. A signal from the cassette switch 15 is input to the control unit 30, and the A/D input terminal 3 of the control unit 30 is input to the control unit 30.
A signal from the optical sensor 17 is input to 0b. Also,
A drive transistor 31 that drives the heat exhaust fan 21 is connected to an output terminal of the control section 30 . Note that a counting means 32 is attached to one side of the control section 30.

As shown in FIG. 4, the cassette switch 15 is attached to the mounting portion of the paper feed cassette 14 of the apparatus main body 1, and detects the type of paper feed cassette 14 and controls the size of the recording paper P by controlling the controller 30. The optical sensor 1
Reference numeral 7 is attached to the paper feed side of the registration roller 18 in FIG. 4, and is used to transmit the amount of light transmitted through the recording paper P to the control unit 30. This allows the thickness of the recording paper P and the number of continuous sheets of recording paper P to be detected. Ru. That is, in the control section 30, based on the transmitted light amount signal from the optical sensor 17, if the transmitted light amount is large, the recording paper P
is determined to be thin, and if the amount of transmitted light is small, it is determined to be thick, and the counter 30b counts the number of successive sheets of recording paper P that has passed through the detection section of the optical sensor 17 based on the magnitude of the amount of transmitted light from the optical sensor 17. .

The drive transistor 31 rotates the heat exhaust fan 21 at a predetermined rotational speed based on a pulse signal output from the control section 30. This pulse signal is as shown in FIG. 2. To rotate the heat exhaust fan 21 at a low speed, a pulse signal with a long period as shown by A in the figure is used, and to rotate it at a high speed, a pulse signal with a long period as shown by B in the figure is used. A pulse signal with a short period as shown in is used. The counting means 32 stores a predetermined time interval Δt given by the reference value signal 32C from the control section 30, and also stores the predetermined time interval Δt given by the reference value signal 32C from the control section 30.
Counting of time is started based on a counting start signal 32a from 0, and when this reaches a predetermined time interval Δt, a count-up signal 32b to this effect is issued to the control section 30.

In response to input signals from the cassette switch 15 and the optical sensor 17, the control unit 30 determines the amount of rotational speed reduction ΔN of the heat exhaust fan 21. In this case, for example, 4
rotational speed reduction amount ΔN1, ΔN2, ΔN3, ΔN4 (
Note that ΔN1>ΔN2>ΔN3>ΔN4) is determined. ΔN1 is when the recording paper P is an envelope (when it is thick with a double or quadruple structure) and the amount of heat absorbed from the fixing device 19 is the largest, and ΔN2 is when the thickness of the recording paper P is This is a case where the thickness is more than a predetermined value, although it is not as thick as an envelope. ΔN3 This is the case where images are continuously formed on a predetermined number of sheets or less of recording paper P whose thickness is equal to or less than a predetermined value, and ΔN4 is a case where images are formed on more than a predetermined number of consecutive sheets of recording paper P whose thickness is equal to or less than a predetermined value. (continuous paper feeding), and the amount of heat absorbed from the fixing device 19 is the smallest.

Furthermore, the control unit 30 determines the rotational speed N of the heat exhaust fan 21 based on the rotational speed reduction amount ΔN,
Based on this rotational speed N, a pulse signal as shown in FIG. Rotate at speed.

Next, a method of controlling the rotational speed of the heat exhaust fan 21 will be explained with reference to FIG.

First, when the main switch of the image forming apparatus is turned on, a reference value (time interval Δt) is input from the control unit 30 to the counting means 32 (step 1), and a print command from the operator is waited for (step 2). Then, if there is a print designation, it will be YES and the cassette switch 15 will be pressed.
It is determined whether or not the recording paper P to be used is an envelope (detected through the size by the cassette switch 15) based on the signal from the cassette switch 15 (step 3). The rotational speed reduction amount ΔN is determined to be ΔN1 (step 4), and the process proceeds to step 10'. Also,
If NO and it is determined that it is not an envelope, optical sensor 1
Based on the signal from 7, it is determined whether the thickness of the recording paper P is equal to or greater than a predetermined value (the value recorded in the ROM 30C of the control unit 30) (step 5), and if the result is YES and it is thicker than the predetermined value, it is determined. If it is determined, the rotation speed reduction amount ΔN of the exhaust heat fan 21 is determined as ΔN2 (step 6), and step 10
'Proceed to '.

If the above answer is NO and it is determined that the recording paper P is thinner than a predetermined value, continuous feeding of the recording paper P is performed based on a signal from the counter 30a which is activated in response to a signal from the optical sensor 17. The number of sheets is a predetermined value (ROM 30 of the control unit 30
It is determined whether the rotational speed is greater than or equal to the value recorded in C) (step 7), and if the answer is YES and it is greater than or equal to the predetermined value, the amount of rotational speed reduction is determined to be ΔN4 (step 8), and step 1
Proceed to 0'. In step 10', it is determined whether the printing work has been completed. If the answer is YES and the printing work is completed, the process proceeds to step 11. Further, if the result in step 7 is NO and the number of continuous sheets of recording paper P is less than a predetermined value, the rotational speed reduction amount ΔN is determined to be ΔN3 (step 9), and it is determined whether the printing work is completed or not. (Step 10). If the printing operation continues, the answer is NO and the process proceeds to step 7, where it is determined whether the number of consecutively passed sheets is greater than or equal to a predetermined value (step 7). In this case, since the number of consecutively passed recording sheets P is added to the counter 30a, the number of consecutively passed sheets is sequentially changed, but if the number of consecutively passed sheets is finally less than a predetermined value, the rotation speed Amount of descent Δ
N is determined to be ΔN3, and the answer in step 10 is YES, and the process proceeds to step 11.

In step 11, the reference value (time interval Δt) is input to the counting means 32 for confirmation again. and,
Next, the rotational speed N of the heat exhaust fan 21 is determined to be N-ΔN, and the counting means 32 starts counting (step 12).
At the same time, the rotation speed N is set to N-ΔN. Then, it is determined whether the count value by the counting means 32 is the reference value or not (step 13), and if it is the reference value (that is, if the time Δt has elapsed), YES is determined.
Furthermore, after the rotational speed N of the heat exhaust fan 21 is lowered by ΔN (step 14), it is determined whether the rotational speed N is 0 (step 15). Rotational speed N is 0
If not, the answer is NO and returns to step 12, counting by the counting means 32 is started again, and the heat exhaust fan 21 is rotated for a period of Δt at the reduced rotational speed N. . When the rotational speed N finally reaches 0, the answer is YES in step 15, the operation of the heat exhaust fan 21 is stopped, and the cooling operation inside the image forming apparatus is completed.

The operation status of the exhaust heat fan 21 at each time interval Δt is shown in FIGS. 5 and 6, and when the rotational speed decrease amount ΔN is ΔN1, as shown in FIG. 5(a), for example, The rotational speed of the heat exhaust fan 21 is reduced by only one step during the time period Δt, and the cooling work inside the device main body 1 is completed within a short time.
As shown in (b), the rotational speed of the heat exhaust fan 21 is reduced in two steps during a time period of 2×Δt. In addition, when the amount of rotational speed decrease ΔN is ΔN3, as shown in FIG. Amount Δ
When N is ΔN4, as shown in FIG. 6(b), the rotational speed of the heat exhaust fan 21 is slowly reduced in four steps during a time period of 4×Δt.

As explained above, since the amount of heat discharged from the apparatus main body 1 by the heat exhaust fan 21 is controlled depending on the size, thickness, and number of sheets of recording paper P, the amount of heat discharged from the apparatus body 1 by the heat exhaust fan 21 is The heat inside the device main body 1 is properly discharged, and the heat exhaust fan 21 is operated unnecessarily.
Problems such as shortening the life of the device 1 or not being able to sufficiently exhaust heat from the inside of the device body 1 do not occur.

Next, a second embodiment of the present invention is shown in FIGS. 7 and 8.
This is explained by: Components having the same functions as those in the first embodiment are designated by the same reference numerals, and their explanations will be omitted.

In this embodiment, the rotational speed reduction amount ΔN of the heat exhaust fan 21 is assumed to be constant, and the time intervals Δt are set to Δt1, Δt2, Δt3, Δt4 (in addition,
Δt1<Δt2<Δt3<Δt4). That is, when the recording paper P is an envelope, the time interval Δt is Δt
1 and the smallest, as shown in FIG. 7(a), the device main body 1
The heat exhausting work inside the main body 1 is performed for only the shortest time, and if the thickness of the recording paper P is thicker than a predetermined value, the time interval Δt becomes Δt2, and as shown in FIG. The work will be done for a slightly longer time than above.

Further, when the thickness of the recording paper P is less than a predetermined value and the number of continuous sheets of recording paper P is less than a predetermined value, the time interval Δt becomes Δt3, as shown in FIG. 8(a). , the heat removal work inside the main body 1 of the apparatus is carried out for a relatively long time, and if the number of continuous sheets passed is larger than a predetermined value, the time interval Δt becomes Δ
At t4, the heat exhausting operation within the apparatus main body 1 is carried out for the longest time, as shown in FIG. 8(b).

As described above, in this embodiment as well, the recording paper P
The heat exhaust fan 21
Since the amount of heat discharged from within the apparatus main body 1 by the image forming operation is controlled, the heat within the apparatus main body 1 is appropriately discharged after the image forming operation is completed, and the same effects as in the first embodiment can be obtained. Can be done.

Next, a third embodiment of the present invention will be explained with reference to FIG. Components having the same functions as those in the first embodiment are designated by the same reference numerals, and their explanations will be omitted.

This embodiment differs from the first embodiment only in that the rotational speed of the heat exhaust fan 21 is controlled by switching the drive transistor 31, and the rest is completely the same as the first embodiment. That is, a plurality of drive transistors 31A, 31B, 31C are provided between the control unit 30 and the heat exhaust fan 21.
are arranged in parallel, and this drive transistor 31A
, 31B, 31C and the heat exhaust fan 21 are provided with predetermined resistances R1, R2, R3 (the magnitude of the resistance value is R1>R2>
R3) are arranged, and the control unit 30 connects the drive transistors 31A to 31.
As C is selected, the heat exhaust fan 21 is sequentially rotated at a higher speed.

The drive transistor 31 is selected by the control unit 30 so that the heat exhaust fan 21 can be rotated at a predetermined rotational speed for a predetermined time interval Δt, and the size, thickness, and continuity of the recording paper P are By controlling the amount of heat discharged from the apparatus main body 1 by the heat exhaust fan 21 depending on the number of sheets passed, the same effects as in the first embodiment can be obtained in this embodiment.

In the first to third embodiments, the heat exhaust fan 21 was controlled depending on the size, thickness, and number of continuous sheets of recording paper, but the heat exhaust fan 21 was controlled depending on the size, thickness, and number of continuous sheets of recording paper. Of course, the heat fan 21 may also be controlled.

[0036]

Effects of the Invention As is clear from the above explanation, according to the present invention, the control means controls the exhaust heat according to the size, thickness, and number of continuous sheets of recording material through the first and second detection means. Since the operating time interval or rotational speed reduction amount of the means is changed, heat can be exhausted by the heat exhausting means in accordance with the amount of residual heat in the fixing means, etc. and the amount of heat stored in the apparatus, and the inside of the apparatus can be appropriately cooled. becomes.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a device that controls a heat exhaust fan of an image forming apparatus according to a first embodiment.

FIG. 2 is an explanatory diagram of pulses for rotationally driving a heat exhaust fan of the image forming apparatus.

FIG. 3 is a flowchart for explaining control of a heat exhaust fan of the image forming apparatus.

FIG. 4 is a sectional view of the image forming apparatus.

FIG. 5 is an explanatory diagram of the operating state of a heat exhaust fan of the image forming apparatus.

FIG. 6 is an explanatory diagram of another operating state of the heat exhaust fan of the image forming apparatus.

FIG. 7 is an explanatory diagram of the operating state of the heat exhaust fan of the image forming apparatus according to the second embodiment.

FIG. 8 is an explanatory diagram of another operating state of the heat exhaust fan of the image forming apparatus.

FIG. 9 is an explanatory diagram of the operating state of the heat exhaust fan of the image forming apparatus according to the third embodiment.

FIG. 10 is a diagram for explaining a conventional technique.

[Explanation of symbols]

15 Cassette switch (first detection means) 17
Optical sensor (first and second detection means) 19
Fixing device (fixing means) 21 Heat exhaust fan (heat exhaust means) 30 Control means N Rotation speed ΔN Rotation speed drop amount

Claims (1)

[Claims] 1. A fixing device that performs heat fixing, and a heat exhaust device that discharges heat generated from the fixing device and its peripheral equipment, and whose exhaust air volume is controlled by the number of revolutions,
In an image forming apparatus in which the rotational speed of a heat exhausting means is gradually lowered by a predetermined rotational speed reduction amount at predetermined time intervals after the image forming operation is completed, the size or thickness of the recording material is detected. a first detection means, a second detection means for detecting the number of continuously passed sheets of recording material, and an exhaust heat for changing the time interval or rotational speed reduction amount according to signals from the first and second detection means. An image forming apparatus comprising a control means for controlling the means.