JPH0659550A - Image forming device - Google Patents

Abstract

PURPOSE:To efficiently attain dust collection and cooling, in an image forming device executing the dust collection and cooling. CONSTITUTION:The openings of covers 50a, 50b, 50c and 50d surrounding the whole of a developing unit are communicated with the exhaust port of a main body left side wall by a duct 52 and a fan 54 and a filter mechanism 41 are provided in the vicinity of the main body left side wall in the duct 52. The filter mechanism 51 is composed of a fixing first filter member 51a having low duct collecting efficiency and a low pressure loss, a second filter member 51b having high duct collecting efficiency and a high pressure loss. a movable supporting mechanism 51c movably supporting the second filter member 51b between an actuating position A and a nonactuating position B, and a driving means moving/driving the second filter member 51b. Only when a toner concentration is high while the developing unit having high dust collecting necessity is actuated, the second filter member 51b is moved to the actuating position A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile and a printer, and more specifically, a filter means for cooling a predetermined image forming unit and preventing toner from scattering outside the apparatus. The present invention relates to operation and non-operation of filter means and switching of dust collecting capability in an image forming apparatus provided with air flow generating means and the like.

[0002]

2. Description of the Related Art Conventionally, in this type of image forming apparatus, for various purposes, a filter means, an air flow path forming member for connecting the periphery of a predetermined image forming unit and a place where the filter means is installed, and the filter means are provided. There is provided an air flow generating means for generating an air flow to flow out of the device via the air flow generating means. For example, in an image forming apparatus using a dry developing device, scattered toner from the dry developing device contaminates the inside of the image forming device to cause a problem in image formation, or a dry developing device using toners of different colors. In order to prevent color mixture between the dry developing device and to prevent the toner from being melted by heat in the dry developing device, air around the dry developing device is filtered through a filter means. Was discharged outside the device.

Regardless of whether a wet developing device or a dry developing device is used, ozone generated in a charging or transferring discharge device is prevented from leaking out of the image forming apparatus, and an optical device and a developing device are used. In order to prevent an excessive temperature rise of the image forming unit such as the apparatus, the air around the charging discharger and the image forming unit which should prevent the excessive temperature rise is discharged to the outside of the apparatus through the filter means. .

[0004]

However, in such a structure, the air flow passage through which the cooling air flow passes and the air flow passage through which the air flow for collecting toner, ozone, etc. As a result, the cooling airflow can also leave the device only via the filter means. For this reason, there is a problem that the filter means causes a pressure loss, and the cooling efficiency is reduced correspondingly. In particular, in the case of actively collecting the scattered toner around the dry developing device, it is necessary to use a filter means having a filter member having a high dust collecting efficiency. Since such a filter member has a large pressure loss, The cooling efficiency will also decrease significantly.

The present invention has been made in view of the above problems, and an object of the present invention is to efficiently perform both dust collection and cooling in an image forming apparatus that collects and cools dust. Is to

[0006]

In order to achieve the above-mentioned object, the invention of claim 1 provides an air flow path forming member for connecting a filter means, a predetermined image forming unit periphery and the filter means installation location. And an image forming apparatus including an air flow generating unit that generates an air flow to flow out of the apparatus through the filter unit, so that the filter unit can be selectively set between an operating state and a non-operating state. And a filter operation switching means for activating the filter means when the image forming unit is in the operating state and switching the filter means to the inactive state in response to the end of the operation of the image forming unit. It is characterized by that. According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the filter operation switching means is configured so as to switch the filter means to a non-operation state after a fixed time has passed since the operation of the image forming unit was completed. It is what According to a third aspect of the present invention, a filter means, an air flow path forming member that connects the periphery of a predetermined image forming unit and the installation location of the filter means, and an air flow that flows out of the apparatus via the filter means are generated. In an image forming apparatus provided with an air flow generating means, the filter means is configured so that the dust collecting ability can be switched in at least two stages, and when the image forming unit is in an operating state, the filter means is provided with a predetermined dust collecting ability. Put in a state of exerting your ability,
Further, filter dust collecting ability switching means is provided for switching the filter means to a state in which the dust collecting ability is smaller than the predetermined dust collecting ability in response to the end of the operation of the image forming unit. Is. According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the filter dust collecting ability is switched to a state in which the filter means exhibits the small dust collecting ability after a predetermined time has passed from the end of the operation of the image forming unit. It is characterized in that the switching means is configured. According to a fifth aspect of the present invention, a filter means, an air flow path forming member that connects the periphery of a predetermined image forming unit and the installation location of the filter means, and an air flow that flows out of the apparatus via the filter means are generated. Toner for detecting the toner concentration of the developer in the two-component developing device in an image forming apparatus provided with an air flow generating means, wherein the filter means is configured to selectively take an operating state and a non-operating state. Based on the output of the density detecting means and the toner density detecting means, the filter means is activated when the detected toner density is higher than the reference value, and the filter means is activated when the detected toner density is lower than the reference value. And a filter operation switching means for switching the operation of the filter means so as to make the means inoperative. According to a sixth aspect of the present invention, there is provided a filter means, an air flow path forming member that connects the periphery of a predetermined image forming unit and the installation location of the filter means, and an air flow that flows out of the apparatus through the filter means. In an image forming apparatus provided with an air flow generating means, the filter means is constituted so that the dust collecting ability can be switched in at least two stages, and a toner concentration detecting means for detecting the toner concentration of the developer in the two-component developing device. And based on the output of the toner concentration detecting means, when the detected toner concentration is higher than the reference value, the filter means is brought into a state of exhibiting a predetermined dust collecting ability, and the detected toner concentration is higher than the reference value. When it is low, the filter dust collecting ability is switched to change the dust collecting ability of the filter means so as to bring the filter means into a state of exhibiting a dust collecting ability smaller than the predetermined dust collecting ability. In which it characterized in that a switching means.

[0007]

According to the present invention, the air flow is generated in the air flow path forming member that connects the periphery of the predetermined image forming unit and the installation location of the filter means by the air flow generating means. Cools the image forming unit and collects dust from around the image forming unit. Further, in the inventions of claims 1 and 2, when the image forming unit is in an operating state and there is a large demand for dust collection from the periphery of the image forming unit, the filter means is brought into an operating state to exert a dust collecting action and to cool. When the image forming unit is in operation and the demand for dust collecting operation from the periphery of the image forming unit is relatively small, the filter means is deactivated to reduce pressure loss in the filter means. By reducing the loss of wind speed and air volume, the cooling efficiency is increased as compared with that during the operation of the image forming unit. Particularly, in the invention of claim 2, there is still a possibility that dust collecting objects such as toner and ozone are floating around the image forming unit. The filter means is operated for a certain period of time from the end of the operation of the image forming unit. Is kept in the operating state, and the filter means is switched to the non-operating state after the elapse of this fixed time. Further, in the inventions of claims 3 and 4, when the image forming unit is in an operating state and there is a large demand for dust collection from the periphery of the image forming unit, the filter means is brought into a state of exhibiting a predetermined dust collecting capability and compared. When the image forming unit is in the operating state and the dust collecting action from the periphery of the image forming unit is relatively small, the filter means is provided with the predetermined dust collecting action. By reducing the pressure loss in the filter means by making the dust collection capacity smaller than the dust capacity, thereby reducing the loss of wind speed and air volume, the cooling efficiency is higher than that during operation of the image forming unit. Try to increase.
Particularly, in the invention of claim 4, there is still a possibility that dust collecting objects such as toner and ozone are floating around the image forming unit. The filter means is operated for a certain period of time from the end of the operation of the image forming unit. Is kept in a state of exhibiting a predetermined dust collecting ability, and the filter means is switched to a state of exhibiting the small dust collecting ability after a lapse of this fixed time. Further, in the invention of claim 5, the detected toner concentration of the developer in the two-component developing device is higher than the reference value, and there is a high possibility that the amount of toner scattering around the image forming unit is high. When there is a large demand for dust collection from the area around the forming unit, the filter means is activated to exert the dust collection function and the cooling function, and the detected toner concentration of the developer in the two-component developing device is used as a reference. When the demand for dust collection from the periphery of the image forming unit is relatively small because the possibility that the amount of toner scattered around the image forming unit is low is lower than the value, the filter means is deactivated, By reducing or preventing the pressure loss in the filter means, thereby reducing the loss of the wind speed and the air volume, the toner of the developer in the detected two-component developing device is reduced. Degree the cooling efficiency is so enhanced as compared with when higher than the reference value. Further, in the invention of claim 6, the detected toner concentration of the developer in the two-component developing device is higher than the reference value, and there is a high possibility that the amount of toner scattering around the image forming unit is high. When there is a large demand for dust collection from the periphery of the forming unit, the filter means is brought into a state of exhibiting a predetermined dust collection ability to exhibit a relatively large dust collection effect and also a cooling effect, and the detected two-component development When the toner concentration of the developer in the device is lower than the reference value and the amount of toner scattering around the image forming unit is unlikely to be high, so when there is relatively little demand for dust collection from the image forming unit. , The filter means is brought into a state of exhibiting a dust collecting ability smaller than the predetermined dust collecting ability to reduce the pressure loss in the filter means, thereby reducing the wind speed and the air volume. By reducing the loss, the toner concentration of the developer in the detected two-component developing apparatus cooling efficiency is so enhanced as compared with when higher than the reference value.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an electrophotographic copying machine (hereinafter referred to as a copying machine) which is an image forming apparatus will be described below. FIG. 2 is a schematic configuration diagram of the entire copying machine according to the present embodiment. A color image reading device (hereinafter, referred to as a color scanner) 1 forms an image of a document 3 on a color sensor 7 via an illumination lamp 4, a mirror group 5, and a lens 6 to obtain color image information of the document, for example, Blue (Blue, hereinafter B), Green (Green, hereinafter G)
), Red (Red, hereinafter referred to as R) color-separated light is read and converted into an electrical image signal. Then, based on the B, G, and R color-separated image signal intensity levels obtained by the color scanner 1, color conversion processing is performed by an image processing unit (not shown), and black (hereinafter referred to as Bk),
Cyan (hereinafter C), Magenta (Magent)
a, hereinafter referred to as M), and yellow (Yellow, hereinafter referred to as Y) color image data. This is referred to as a color image recording device (hereinafter referred to as a color printer) 2
Bk, C, M, and Y are visualized, and the toner images thus obtained are superimposed to form a four-color full-color image.

The writing optical unit 8 of the color printer 2 converts the color image data from the color scanner 1 into an optical signal, performs optical writing corresponding to the original image, and forms an electrostatic latent image on the photosensitive drum 9. To do. The photoconductor drum 9 rotates counterclockwise as indicated by an arrow, and around the photoconductor drum 9, a photoconductor cleaning unit (including a pre-cleaning static eliminator) 10, a static eliminator 11, a charger 12, a potential sensor 13, and a Bk developing device. 14, a C developing device 15, an M developing device 16, a Y developing device 17, an optical sensor 18 for detecting a development density pattern, an intermediate transfer belt 19, a paper transfer unit 23 and the like are arranged.

Here, each of the developing devices in the illustrated example has developing sleeves (14a, 15a, 1) which rotate by bringing the brush of the developer into contact with the surface of the photoconductor 9 in order to develop the electrostatic latent image.
6a, 17a) and the developing paddles (14b, 15b, 16b, 17) that rotate to scoop and agitate the developer.
b), and a toner concentration sensor (14c, 15) for the developer.
c, 16c, 17c) and the like (see FIG. 1).

The intermediate transfer belt 19 is stretched around a drive roller 21, transfer bias rollers 20a and 20b, and a group of driven rollers, and is driven by a drive motor (not shown). A belt cleaning unit 22 is also provided so as to face the surface of the intermediate transfer belt 19. The belt cleaning unit 22 is composed of a brush roller, a rubber blade, and a contact / separation mechanism from the belt. After the Bk image of the first color is transferred to the belt, the second, third, and fourth colors are transferred to the belt. The contacting / separating mechanism 22c separates the belt surface from the belt surface during the period.

The paper transfer unit 23 is composed of a paper transfer bias roller, a roller cleaning blade, and a contact / separation mechanism from the belt. This bias roller is usually separated from the surface of the belt 19, but the four-color superimposed image formed on the surface of the intermediate transfer belt 19 is pressed by the contacting / separating mechanism at a timing when collectively transferring to the transfer paper. Then, a predetermined bias voltage is applied to the roller to transfer it to the paper.

Hereinafter, an outline of the copying operation will be described by taking an example in which the order of the developing operation (color image forming order) is Bk, C, M, and Y (however, the image forming order is not limited to this). . When the copy operation is started, the color scanner 1 starts reading Bk image data at a predetermined timing, and optical writing by a laser beam and latent image formation start based on the image data (hereinafter, electrostatic image based on Bk image data). The latent image is referred to as a Bk latent image. C, M, and Y are referred to as a C latent image, an M latent image, and a Y latent image, respectively). This B
Before the latent image front end reaches the developing position of the Bk developing device 14 so that development can be performed from the front end of the k latent image, the developing sleeve 1
4a is started to rotate and the Bk latent image is developed with Bk toner. After that, the developing operation of the Bk latent image area is continued, and when the trailing edge of the latent image passes the Bk developing position, the developing operation is disabled. This is completed at least before the leading edge of the C latent image by the next C image data arrives.

The Bk toner image formed on the photosensitive member 9 is transferred onto the surface of the intermediate transfer belt 19 which is driven at the same speed as the photosensitive member (hereinafter, the toner image transfer from the photosensitive member to the intermediate transfer belt is referred to as belt transfer). ). The belt transfer is performed by applying a predetermined bias voltage to the transfer bias rollers 20a and 20b while the photoconductor 9 and the intermediate transfer belt 19 are in contact with each other.

On the side of the photosensitive member 9, the Bk process is followed by the C process, but the C image data reading by the color scanner 1 is started at a predetermined timing, and the C latent image is formed by the laser light writing by the image data. C developing device 1
5 starts rotation of the developing sleeve 15a with respect to the developing position after the trailing edge of the previous Bk latent image has passed and before the leading edge of the C latent image has reached, so that the C latent image is converted into C toner. develop. After that, the development of the C latent image area is continued, and when the trailing edge of the latent image passes, the development is inoperative as in the case of the previous Bk developing device. This is also completed before the leading edge of the next M latent image arrives. In addition, regarding each process of M and Y,
The respective image data reading, latent image formation and development operations are carried out in the same manner as the steps Bk and C described above.

During this time, the Bk, C, M, and Y toner images sequentially formed on the photoconductor 9 are transferred to the intermediate transfer belt 19 by sequentially aligning them on the same surface, and a four-color superposed belt transfer image is transferred. Is formed. Then, the transfer paper 24 is fed by the paper feed roller 25 and the registration roller 26 at the timing when the leading edge of the four-color superimposed image on the intermediate transfer belt 19 reaches the paper transfer position.
The upper four-color superimposed toner image is transferred at once. As described above, the transfer paper 24 on which the four-color superimposed toner images are collectively transferred from the surface of the intermediate transfer belt is fixed to the fixing device 2 by the paper transport unit 27.
The toner image is conveyed to the No. 8 and is fixed at a predetermined temperature by the fixing roller 28a and the pressure roller 28b, and the toner image is fused and fixed, and is carried out to the copy tray 29 to obtain a full-color copy.

The photoreceptor 9 after the belt transfer is processed by the photoreceptor cleaning unit 10 (pre-cleaning static eliminator 10).
The surface is cleaned with a, the brush roller 10b, the rubber blade 10c), and the charge is removed uniformly by the charge removing lamp 11. Further, the surface of the intermediate transfer belt 19 after the toner image is transferred onto the transfer paper 24 is cleaned by pressing the cleaning unit 22 again by the contact / separation mechanism.

At the time of repeat copying, the color scanner 1
The operation and the image formation on the photosensitive member 9 proceed to the second Bk (first color) image process at a predetermined timing after the first Y (fourth color) image process. Further, in the intermediate transfer belt 19, the second Bk toner image is formed in the area where the surface is cleaned by the cleaning unit 22, following the batch transfer process of the first four-color superimposed image onto the transfer paper. Allow the belt to be transferred. After that, the same operation as the first sheet is performed. The transfer paper cassettes 30, 31, 32,
The reference numeral 33 stores transfer sheets of various sizes, which are fed and conveyed in the direction of the registration rollers 26 at a timing from a storage cassette of size sheets designated by an operation panel (not shown). Reference numeral 34 is a manual paper feed tray for OHP paper or thick paper.

The above is the description of the copy mode for obtaining four full colors, but in the case of the three-color copy mode and the two-color copy mode, the same operation as the above is performed for the designated color and the number of times. It will be. In the single-color copy mode, until the predetermined number of sheets are finished, only the developing device of that color is in a developing operation (agent standing) state, and the intermediate transfer belt 19 remains in contact with the surface of the photoreceptor 9. The belt cleaner 22 is driven at a constant speed in the forward direction, and the belt cleaner 22
The copy operation is performed in the state where the contact is kept.

Next, the dust collecting and cooling device in the copying machine of this embodiment will be described. The dust collecting and cooling device of the present embodiment includes a Bk developing device 14, a C developing device 15, and an M developing device 1.
6 and the Y developing device 17 collect and cool the scattered toner from the surroundings. FIG. 1 is a front view showing the schematic configuration thereof. Each developing device is independently provided with a casing, and a space exists between the casings. The entire four developing units are the photosensitive drum 9
Except for an opening facing the cover 50 and a connection port with a duct 52 connected to a filter mechanism 51 described later.
It is surrounded by b, 50c and 50d to be separated from the outside. The other opening of the duct 52 is connected to an exhaust port (not shown) formed in the left side wall 53 (see FIG. 2) of the main body of the color printer 2. This cover 50a, 50
b, 50c and the duct 52 constitute an air flow path forming member.

The left side wall 5 of the main body in the duct 52
A fan 54 as an air flow generating means is disposed in the vicinity of 3. The fan 54 sucks the air on the developing device side and discharges it from the exhaust port of the left side wall 53 of the main body.

Further, the filter mechanism 51 is arranged on the developing device side of the fan 54 in the duct 52. The filter mechanism 51 of this example is fixed to the inside of the duct 52 as shown in the drawing, and has a relatively low dust collection efficiency and a small pressure loss.
The filter member 51a, a second filter member 51b having a higher dust collection efficiency and a larger pressure loss than the first filter member 51a, and the second filter member 51b on the developing unit side of the first filter member 51a. An operating position A that can exhibit a filter function for the airflow in the duct 52 and a non-operating position B that cannot exhibit such a filter function are selected so as to be lined up so as to cover the entire surface of the first filter member 51a. Support mechanism 51 for movably supporting the movable support mechanism 51
c and a driving means (not shown) (for example, a solenoid or the like) that drives the movable support mechanism 51c to move the second filter member 51b between the operating position A and the inoperative position B. There is.

Here, in the illustrated example, the first filter member 51a and the second filter member 51b are made of the same material, and the thickness of the second filter member 51b is set larger. Not due to such a difference in thickness, but due to the difference in the material of the filter member (for example, the difference in the number of cells), the second filter member 51a is more likely to be second than the first filter member 51a.
The filter member 51b may have a higher dust collection efficiency and a larger pressure loss. Furthermore, both filter members 51a,
51b may be composed of exactly the same filter member.

In the above construction, when the fan 54 is driven, the casing of each developing device and the covers 50a, 50 are formed.
Air in the space surrounded by b, 50c, and 50d is sucked, passes through the duct 52, and is discharged to the outside of the machine. At this time, the scattered toner generated around each developing device also travels in the duct 52 along with the air flow and is collected by the filter mechanism 51. This prevents the toner from leaking out of the machine.
Further, the heat of the developing device is radiated to the outside of the machine along with the air flow, whereby the developing device is cooled. Here, when the second filter member 51b of the filter mechanism 51 is in the inoperative position B, the air flow in the duct 52 is the same as that of the first filter member 5
After passing only 1a, it is discharged out of the machine. For this reason,
Since the pressure loss in the filter mechanism 51 is only due to the first filter member 51a, the loss of the air volume and the wind speed is small and the cooling efficiency is high. On the other hand, since only the filter function of the first filter member 51a can be exhibited, the dust collection efficiency is lower than that when both filter members 51a and 51b exhibit the filter function. On the contrary, when the second filter member 51b of the filter mechanism 51 is in the operating position A, the airflow in the duct 52 is in addition to the first filter member 51a, and the second filter member 51b in the juxtaposed state. Since it is discharged to the outside of the machine after passing through,
The dust collection efficiency is improved as compared with the case where only the filter member 51a exerts the filter function. On the other hand, both filter members 5
Since the pressure loss occurs due to 1, 51b, the loss of the air volume and the wind speed is large and the cooling efficiency is low as compared with the case where only the first filter member 51a exerts the filter function.

Therefore, in the present embodiment, both filter members 51a and 51b are made to exert a filter function when the necessity of collecting dust is relatively large, and the first filter member is made when the necessity of collecting dust is relatively small. Only 51a is made to exhibit a filter function. Specifically, it is during the operation of the developing device that the need for collecting dust is relatively large.
The need for this is high when the toner concentration in each developing device is high, which causes a large amount of toner scattering from the developing device. Therefore, the second filter member 51b is moved to the operating position A to cause the filter members 51a and 51b to perform the filter function only when the developing device is in operation and the toner concentration in the developing device is high. During the period of, basically, the second filter member 51b is moved to the inoperative position. For this purpose, the outputs of the toner concentration sensors 14C, 15C, 16C and 17C for detecting the toner concentration in each developing device are used to compare the detected toner concentration with a predetermined reference value to drive the second filter member 51b. The movement is controlled by means.

FIG. 3 shows an example of a timing chart of control when the color printer 2 is in the monochrome copy mode. In FIG. 3, the fan is always driven, and for example, before the developing sleeve starts operating and the developing sleeve starts rotating, the output of the toner concentration sensor (S ₁ ,
S ₂ ) is read. Only when this output is larger than the value corresponding to the reference value (output S ₂ ), the second filter member 51 b is positioned at the operating position A during the operation of the developing device (rotating the developing sleeve) subsequent to this detection. Control movement.
When the second filter member 51b is once moved to the operating position A, the second filter member 51b is kept in the operating position A for a fixed time (T ₀ ) even after the operation of the developing device is completed. This is to reliably prevent toner leakage to the outside of the machine. The timing chart shown is for the single-color copy mode, but also in the full-color mode or the like, similarly, the second filter member 51b is set to the operating position A in accordance with the toner density of the developing device to be operated. Decide whether to move. When the toner concentration of any one of the four developing devices is higher than the reference value, the second filter member 51b is moved to the operating position A during a series of operating periods of the four developing devices. May be.

In the above embodiment, by moving the position of the second filter member 51b, both the filter members 51a and 51b exhibit a relatively high dust collecting efficiency, and the first filter member 51b. Only the relatively low dust collection efficiency state in which only the filter function is switched, but instead of this, the relatively high dust collection efficiency state and the relatively low dust collection efficiency state are set as follows. May be switched. FIG. 5 is a schematic configuration diagram of a filter mechanism therefor. In FIG. 5, the fan 5 in the duct 52
A filter mechanism is disposed closer to the developing device than 4 is. In the filter mechanism of this example, a first filter member 55a having a relatively low dust collection efficiency and a small pressure loss is fixed to the upper half of the duct 52 as shown in the drawing.
A second filter member 55b having a high dust collection efficiency and a large pressure loss is fixed to the lower half of the duct 52 below a.
Here, in the illustrated example, the first filter member 51a and the second filter member 51b are made of the same material, and the thickness of the second filter member 51b is set larger. Not due to such a difference in thickness,
Depending on the material of the filter member (for example, the number of cells), the second filter member 51b may have higher dust collection efficiency and larger pressure loss than the first filter member 51a.

Then, a position A where the air flow from the developing device side is passed to the developing device side with respect to both the filter members 55a and 55b, and only to the lower half of the duct 52 in which the second filter member 55b is provided, A drift plate 55c that can selectively take a position B that passes only through the upper half of the duct 52 in which the first filter member 52a is provided is movably attached. The drift plate 55c is driven and moved by a driving unit (not shown) (for example, a solenoid). By moving the drift plate 55c to the position A by the movement control of the drift plate 55c by this driving means,
The air flow from the developing device side can be made to pass through the second filter member 55b to have a relatively high dust collection efficiency, and the deflector plate 55c is moved to the position B, so that the air flow from the developing device side can be obtained. Can be made to pass through the first filter member 55a to have a relatively low dust collection efficiency. The switching between the relatively high dust collection efficiency state and the relatively low dust collection efficiency state can be performed using the same conditions as those in the above-described embodiment.

In each of the above embodiments, even when the developing device is in operation, when the toner concentration in the developing device is lower than a predetermined reference value, the dust collection efficiency is relatively low. Alternatively, the cooling efficiency may be improved by uniformly setting the relatively high dust collection efficiency during the operation of the developing device and by setting the relatively low dust collection efficiency only during the non-operation of the developing device. Also in this case, it is desirable to keep the relatively high dust collection efficiency for a certain period after the operation of the developing device. Further, in each of the above-described embodiments, even when the need for dust collection is relatively small, the air flow from the developing device side is passed through the first filter member 51a having relatively low dust collection efficiency and small pressure loss, and then out of the machine. However, instead of this, when the need for collecting dust is relatively small, the air flow from the developing device side is discharged to the outside of the machine without passing through the filter member. You may make it maximize. For this purpose, the first filter members 51a and 52a of each embodiment may be removed.

[0030]

According to the invention of claims 1 to 6, when there is a great demand for dust collection from the periphery of the image forming unit, the filter means is brought into an operating state or a state where a predetermined dust collection capability is exerted. In addition to exhibiting the cooling effect, and when there is relatively little demand for dust collection from the periphery of the image forming unit, the filter means is in the inactive state or exhibits a dust collection capacity smaller than a predetermined dust collection capacity. In this state, the pressure loss in the filter means is reduced or prevented, and the loss of the wind speed and the air volume is reduced, so that both dust collection and cooling can be efficiently performed.
In particular, according to the inventions of claims 1 to 4, the switching of the operation / non-operation of the filter means or the switching of the dust collecting ability of the filter means is performed according to the switching of the operation / non-operation of the image forming unit. Since it is performed, the operation / non-operation of the filter unit can be switched at an appropriate timing by a simple method such as using a signal for switching the operation / non-operation of the image forming unit. Further, according to the inventions of claims 2 and 4, there is a possibility that a dust collecting object such as toner or ozone is floating around the image forming unit. Since the filter means is kept in the operating state or the state where the predetermined dust collecting ability is exhibited, it is possible to more reliably prevent the leakage of the toner and the like to the outside of the image forming apparatus. According to the fifth and sixth aspects of the invention, the toner concentration of the developer in the two-component developing device is detected by detecting whether the filter means is operated or not operated or the dust collecting ability of the filter means is switched. Therefore, for example, even when the image forming unit is in operation, the toner density in the two-component developing device is low and the amount of toner scattering around the image forming unit is small. When the demand for collecting dust from the filter means is relatively small, the filter means is made inactive and the pressure loss in the filter means is reduced or prevented. Therefore, the cooling efficiency can be further improved without substantially reducing the dust collection efficiency.

[Brief description of drawings]

FIG. 1 is a front view showing a schematic configuration of a main part of a color printer according to an embodiment.

FIG. 2 is a front view showing a schematic configuration of the entire image forming apparatus including the color printer.

FIG. 3 is a timing chart of control in the color printer.

FIG. 4 is a front view showing a schematic configuration of a filter mechanism according to a modification.

[Explanation of symbols]

 1 Color Image Reading Device 2 Color Image Recording Device 9 Photosensitive Drum 14 Black Developing Device 15 Cyan Developing Device 16 Magenta Developing Device 17 Yellow Developing Device 50a, 50b, 50c, 50d Cover 51 Filter Mechanism 51a First Filter Member 51b Second Filter Member 51c Movable support mechanism 52 Duct 53 Main body left side wall 54 Fan 55a First filter member 55b Second filter member 55c Drift plate

Claims (6)

[Claims] 1. A filter means, an air flow path forming member for connecting the periphery of a predetermined image forming unit and a location where the filter means is installed, and an air flow for generating an air flow to flow out of the apparatus through the filter means. In the image forming apparatus including the generating means, the filter means is configured to selectively take an operating state and a non-operating state, and when the image forming unit is in the operating state, the filter means is in the operating state. Further, the image forming apparatus is provided with a filter operation switching means for switching the filter means to a non-operational state in response to the end of operation of the image forming unit. 2. The image forming apparatus according to claim 1, wherein the filter operation switching means is configured so as to switch the filter means to a non-operational state after a lapse of a predetermined time from the end of the operation of the image forming unit. 3. A filter means, an air flow path forming member for connecting a periphery of a predetermined image forming unit and a place where the filter means is installed, and an air flow for generating an air flow to flow out of the apparatus through the filter means. In the image forming apparatus provided with the generating means, the filter means is configured so that the dust collecting ability can be switched in at least two stages, and when the image forming unit is in the operating state, the filter means is provided with a predetermined dust collecting ability. And a filter dust collection capacity switching means for switching the filter means to a state in which the filter means is brought into a state of exhibiting a dust collection ability smaller than the predetermined dust collection ability in response to the end of the operation of the image forming unit. An image forming apparatus characterized by. 4. The filter dust collecting capacity switching means is configured so as to switch the filter means to a state in which the small dust collecting capacity is exhibited after a lapse of a predetermined time from the end of the operation of the image forming unit. The image forming apparatus according to item 3. 5. A filter means, an air flow path forming member that connects a periphery of a predetermined image forming unit and a location where the filter means is installed, and an air flow for generating an air flow to flow out of the apparatus through the filter means. In the image forming apparatus including the generating unit, the filter unit is configured to selectively take an operating state and a non-operating state, and a toner concentration detecting unit for detecting the toner concentration of the developer in the two-component developing apparatus is provided. And the filter means based on the output of the toner concentration detecting means when the detected toner concentration is higher than the reference value, and the filter means is activated when the detected toner concentration is lower than the reference value. An image forming apparatus, comprising: a filter operation switching means for switching the operation of the filter means so as to be in an inoperative state. 6. A filter means, an air flow path forming member that connects a periphery of a predetermined image forming unit and a location where the filter means is installed, and an air flow for generating an air flow to flow out of the apparatus through the filter means. In the image forming apparatus including the generating means, the filter means is configured so that the dust collecting ability can be switched in at least two stages, and a toner concentration detecting means for detecting the toner concentration of the developer in the two-component developing device, Based on the output of the toner concentration detecting means, when the detected toner concentration is higher than the reference value, the filter means is brought into a state of exhibiting a predetermined dust collecting ability, and when the detected toner concentration is lower than the reference value. A filter dust collecting capacity switch for switching the dust collecting ability of the filter means so as to bring the filter means into a state of exhibiting a dust collecting ability smaller than the predetermined dust collecting ability. An image forming apparatus characterized in that a means instead.