JPH11184179A - Image forming device - Google Patents

Abstract

(57) [Problem] To form an image capable of always obtaining a good image without fusing toner on the surface of a photoconductor by preventing the temperature in the apparatus from becoming excessive after the durability of the photoconductor is advanced. Provide equipment. SOLUTION: The thickness of the photosensitive layer of the photoreceptor is detected by using a contact-type charging means, the number of rotations of the photoreceptor, the number of transfer materials, and the like, and when the thickness is reduced to a predetermined value, exhaust is performed. Increase the rotation speed or rotation time of the fan.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming apparatus such as a copying machine and a laser beam printer.

[0002]

2. Description of the Related Art A conventional image forming apparatus of this type irradiates an image exposure corresponding to a document image or an input image signal onto a surface of an image carrier uniformly charged by a charging means, and irradiates the surface of the image carrier. Forming an electrostatic latent image, developing the electrostatic latent image into a toner image by a developing unit, transferring the toner image to a transfer material by a transfer unit,
There are electrophotographic copying machines and printers in which a toner image on a transfer material is fixed on the transfer material by a fixing unit and output.

[0003] In such an image forming apparatus, there are many elements for promoting the temperature rise in the apparatus, such as electric parts such as a driving motor, a lamp for illuminating a document, and a heater of a fixing apparatus. As a result, the temperature inside the apparatus rises abnormally, and it is inevitable that various parts of the apparatus are affected, such as blocking (solidification) of the toner in the developing apparatus or thermal damage to the photosensitive member and other members. Therefore, in order to avoid such a situation, an exhaust fan is generally provided in the image forming apparatus.

[0004]

In the above-mentioned conventional image forming apparatus, the resin which forms the base of the toner for forming a visualized image has a glass transition point at about 40.degree.

Therefore, if image formation is continued at a temperature around the photoconductor of 40 ° C. or higher, a phenomenon occurs in which the toner on the surface of the photoconductor is softened and fixed. This phenomenon is particularly likely to occur in a high-temperature environment (hereinafter, this phenomenon is referred to as a fusion phenomenon).

In general, after the transfer process of the toner image is completed, the transfer residual toner remaining on the surface of the photoreceptor is removed by a cleaning unit to prepare for the next image forming process.

In this case, as a cleaning means, a method of scraping off the untransferred toner by bringing a plate-like elastic material into contact with the surface of the photoreceptor has been widely used. In particular, when such a cleaning means is provided, fusion tends to occur when the temperature in the apparatus increases. That is, when the temperature in the apparatus rises, the heat generated by the friction between the tip of the cleaning member and the surface of the photoconductor increases, and the toner existing at the interface between the tip of the cleaning member and the surface of the photoconductor softens, and the softened toner Is rubbed on the surface of the photoreceptor and is fused.

The phenomenon that the toner, which is an insulating material, is fused to the surface of the photoreceptor is fatal to the function of the photoreceptor. Therefore, as means for preventing fusion, it is effective to suppress an increase in the temperature inside the apparatus by the above-described exhaust fan or the like.

However, as the image formation is repeated, if the surface of the photoreceptor is scraped by a toner or a cleaning member, the surface roughness of the photoreceptor increases, and the softened toner tends to adhere. That is, when the durability of the photoconductor is advanced, fusion may easily occur even if the temperature is slightly increased.

As a countermeasure, it is conceivable to increase the capacity of the exhaust fan from the beginning, but this method has a problem that the life of the exhaust fan itself is shortened.

In order to extend the life of the exhaust fan, the cost of the exhaust fan itself increases, which is not practical.

Accordingly, the present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to prevent the temperature inside the apparatus from becoming excessive after the durability of the photosensitive member has advanced. It is an object of the present invention to provide an image forming apparatus capable of always obtaining a good image without fusing toner to the surface of a photoreceptor.

[0013]

SUMMARY OF THE INVENTION The present invention is an image forming apparatus having the following configuration.

(1) Charging means for uniformly charging the surface of the image carrier, and irradiating the uniformly charged surface of the image carrier with an image exposure corresponding to a document image or an input image signal, and Image exposure means for forming a latent image, visible image means for forming a toner image corresponding to the electrostatic latent image, transfer means for transferring the toner image to a transfer material, and thickness of a photosensitive layer of the image carrier In the image forming apparatus, the temperature control around the image carrier is performed in accordance with the detection result by the detecting means.

(2) The charging means is a contact-type charging device for charging a surface of the photoconductor by bringing a charging member, to which a charging bias is applied, into contact with the photoconductor. A means for applying a predetermined detection voltage to the charging member when corresponding to the non-image area of the body and measuring the amount of current flowing from the charging member to the image carrier at this time.

(3) The detecting means is means for counting the number of rotations of the image carrier.

(4) The detecting means is means for counting the number of passing transfer materials.

(5) A cooling fan for cooling the inside of the apparatus, wherein the rotation speed of the exhaust fan is changed in accordance with the result of detection by the detecting means.

(6) There is provided a cooling fan for cooling the inside of the apparatus, and the rotation time of the exhaust fan is changed according to the detection result by the detection means.

(7) A plurality of the cooling fans are provided, and the number of the cooling fans to be operated is changed according to a detection result by the detecting means.

(8) According to the detection result of the detection means, when the temperature in the apparatus becomes larger than a certain value, the image forming operation is stopped for a predetermined time.

According to the above-described image forming apparatus, the thickness of the photosensitive layer of the image bearing member is detected, and the temperature around the photosensitive member is controlled according to the detection result.

For example, by increasing the rotation speed or the rotation time of the exhaust fan from the point in time when the thickness of the photosensitive layer of the image carrier has decreased to a predetermined value, the temperature rise in the apparatus is suppressed, and the toner Can be prevented from fusing.

Further, by increasing the number of exhaust fans to be operated from the time when the thickness of the photosensitive layer has decreased to a predetermined value, it is possible to suppress the temperature rise in the apparatus and to fuse the toner to the surface of the image carrier. Can be prevented.

Further, by stopping the image forming operation for a predetermined time from the point in time when the thickness of the photosensitive layer of the image carrier has decreased to a predetermined value, the temperature rise in the apparatus is suppressed, and toner is deposited on the surface of the image carrier. Fusing can be prevented.

[0026]

[First Embodiment] FIG. 1 is a schematic view of an image forming apparatus according to first to sixth embodiments of the present invention.
This image forming apparatus is a transfer type laser beam printer or copying machine utilizing an electrophotographic process.

In FIG. 1, reference numeral 1 denotes a drum type electrophotographic photosensitive member (hereinafter, referred to as a photosensitive member) as an image bearing member.
It is rotationally driven at a predetermined process speed in the clockwise direction indicated by the arrow. The photosensitive member 1 rotates in the primary charging device 2 during the rotation process.
It is more uniformly charged to a predetermined polarity and potential. In the present embodiment, the photosensitive member is subjected to a negative charging process.

The primary charging device 2 of the present embodiment is a contact charging roller, and is driven to rotate as the photosensitive member rotates. Then, by applying a predetermined bias voltage from the power supply 3, the periphery of the rotary photoconductor 1 is charged to a predetermined polarity and potential by a contact charging method.

Next, the charged surface is subjected to image exposure processing of target image information by image exposure means 10 such as a laser scanner, and an electrostatic latent image of the target image information is formed on the surface of the photoconductor 1. You.

The electrostatic latent image is developed with a thin layer of toner carried on the developing sleeve 6a of the developing device 6 to become a visible image (toner image). The developing sleeve 6a is controlled by a clutch (not shown) and rotates in an image area. Then, a predetermined bias voltage (DC voltage, oscillation voltage; hereinafter, referred to as a developing bias) is applied from the power supply 7 to supply toner to the photoconductor. In this embodiment, reversal development is performed using negatively charged toner (negative toner).

Then, the toner image is fed to the transfer unit at a predetermined timing from the paper feeding unit side in a transfer portion which is a contact nip portion between the photosensitive member 1 and the transfer member 12 brought into contact with the photosensitive member 1. The image is sequentially transferred to the transfer material 14. The transfer member 12 of the present embodiment is a contact charging transfer roller, which is pressed against the photoconductor,
It rotates following the rotation of.

On the other hand, the transfer material 14 is fed to the transfer section. When the leading end of the transfer material 14 enters the transfer portion, a predetermined transfer bias is applied to the transfer roller 12 from a power source, and the back surface of the transfer material with which the transfer roller 12 is in contact is contact-charged with a polarity opposite to that of the toner. The toner image on the photoconductor 1 is charged and transferred to the surface of the transfer material.

The transfer material 14 having received the transfer of the toner image through the transfer section is separated from the surface of the photoreceptor 1 and sent to the image fixing means 16, and the transferred toner image is transferred onto the transfer material 14 as a permanently fixed image. The image is fixed and discharged outside the machine as a print or a copy.

On the other hand, the surface of the photoreceptor 1 after passing through the transfer section is cleaned by removing the residual developer and other deposits by the cleaner section 13, and is further discharged and initialized by the discharger (discharge lamp) 15. , And are repeatedly provided for image formation.

The contact-type charging roller and the transfer roller may be provided with gears or the like, and may be forcibly driven by a driving means such as a motor.

The photoconductor shaving amount detecting means will be described below.

In the present embodiment, as a detecting means for detecting the amount of scraping of the photoconductor 1 between the conductive base 1b of the photoconductor 1 and the ground, the current flowing through the photoconductor 1 is measured. A detection circuit 16 having a resistance R is provided. When a predetermined AC or DC detection voltage is applied to the charging roller 2, the thickness of the photosensitive layer of the photosensitive member 1 is detected by measuring the voltage between the terminals of the resistor R.

FIG. 2 shows the amount of DC current measured when an AC voltage of 1.5 kVpp is superimposed on a DC voltage of 750 V and applied to the charging roller 2.

As can be seen, the amount of current flowing through the photosensitive member 1 increases as the thickness of the photosensitive layer decreases.

In general, the surface roughness increases from the point when the photosensitive layer is shaved by 10 μm from the initial stage, and fusion is likely to occur. For example, in the present embodiment, since the initial thickness of the photosensitive layer is 30 μm, the durability is advanced and the thickness is 20 μm.
, Ie, when the detected current exceeds 28 μA, it can be determined that fusion is likely to occur.

In the present embodiment, the case where the detection circuit 16 is provided between the conductive base 1b of the photoreceptor 1 and the ground has been described. However, the present invention is not limited to this. The above-described detection circuit 16 may be provided between the high-voltage power supply 3 and the ground.

Next, the temperature control will be described.

In FIG. 1, the exhaust device includes an exhaust fan 1
7 and an exhaust fan control device 18 for controlling the drive of the exhaust fan 17. As shown in FIG. 3, the exhaust fan starts rotating at a predetermined speed (this speed is called full speed) at the same time as the start of image formation, and continues to rotate until the end of image formation.

When image formation is not being performed (this is called a standby state), the exhaust fan is stopped or constantly rotating at a low speed (this speed is called a half speed).

In this embodiment, the rotation speed of the exhaust fan is controlled in accordance with the result of detecting the thickness of the photosensitive member.

That is, a low voltage is applied to the exhaust fan in the early stage of the endurance to perform the exhaust. On the other hand, if it is detected that the durability of the photoconductor has advanced and the film thickness of the photoconductor has become smaller than a predetermined value, a high voltage is applied to the exhaust fan to increase the rotation speed from the initial stage to exhaust the exhaust gas. Do.

With such a configuration, the load on the exhaust fan 17 is minimized, and after the durability of the photosensitive member is advanced, the temperature inside the apparatus is prevented from becoming excessive, and the photosensitive member is prevented from becoming excessive. It has become possible to always obtain a good image without fusing the toner to the surface.

The control for increasing the rotation speed of the exhaust fan 17 can be performed during image formation, during standby, or both.

[Embodiment 2] The basic configuration of this embodiment is the same as that of Embodiment 1 described above, and is different from Embodiment 1 in that in this embodiment, the above-described photosensitive film is used. The point is that the rotation time of the exhaust fan is switched according to the thickness detection result.

As shown in FIG. 3, in the early stage of durability, the exhaust fan starts rotating at full speed at the start of image formation, and at the end of image formation, the speed is reduced to half speed or stopped.
Thereafter, when it is detected that the film thickness of the photoreceptor has become smaller than a predetermined value, the rotation time during which the exhaust fan rotates at full speed after the completion of image formation is extended. Or,
The exhaust fan may be constantly rotated at full speed when it is detected that the thickness of the photoconductor has become smaller than a predetermined value.

With this configuration, it is possible to minimize the load on the exhaust fan and prevent the temperature inside the apparatus from becoming excessive after the durability of the photosensitive member has advanced,
It has become possible to always obtain a good image without fusing the toner to the photoreceptor surface. [Embodiment 3] The basic configuration of this embodiment is the same as that of Embodiment 1, and is different from Embodiment 1 in that in this embodiment, two exhaust fans are provided in the device. The number of exhaust fans to be operated is counted in accordance with the result of the photoconductor film thickness detection described above.

That is, in the initial stage of the endurance, one exhaust fan is operated to exhaust air. After that, the durability of the photoconductor progressed,
When it is detected that the thickness of the photoconductor has become smaller than a predetermined value, the two exhaust fans are operated to exhaust air.

With this configuration, it is possible to minimize the load on the exhaust fan and prevent the temperature inside the apparatus from becoming excessive after the durability of the photosensitive member has been advanced,
It has become possible to always obtain a good image without fusing the toner to the photoreceptor surface. The number of exhaust fans is 2
The number of fans is not limited to one, and a plurality of fans may be provided according to the configuration of the apparatus.

[Fourth Embodiment] The basic configuration of this embodiment is the same as that of the first embodiment.

As shown in FIG. 4, if the temperature inside the apparatus rises due to image formation and then is left for a while, the temperature inside the apparatus gradually decreases.

In this embodiment, a temperature sensor 19 is provided near the photosensitive member. When the temperature near the photoconductor reaches a certain value after detecting that the thickness of the photoconductor has become smaller than a predetermined value by the above-described detection means, the copying or printing operation is forcibly performed for a predetermined time. Stop.

With this configuration, it is possible to prevent the temperature in the apparatus from becoming excessive after the durability of the photosensitive member has advanced, and to always obtain a good image without fusing the toner to the surface of the photosensitive member. It became possible to obtain.

[Fifth Embodiment] When a plurality of exhaust fans are provided, it is not necessary to perform the same control on those exhaust fans, and only a part of the exhaust fans needs to be controlled by the number of rotations and the rotation time. May be controlled. That is, if the respective controls are performed separately for each exhaust fan, the object of the present application can be achieved more effectively.

That is, Embodiments 1, 2, 3 and 4
By using in combination, more efficient implementation of the present invention can be performed.

[Embodiment 6] In the first embodiment, the method of detecting the thickness of the photoconductor in the case of contact charging has been described. However, the present invention can be applied to the case of non-contact charging.

In this case, a method of counting the number of rotations of the photoconductor is used as a means for detecting the thickness of the photoconductor. That is, the number of rotations of the photoreceptor is counted, and when the predetermined number of rotations is reached, the temperature around the photoreceptor is controlled by the exhaust fan.

As shown in FIG. 5, a means for detecting the number of rotations of the photo sensor 20 and the like is provided near the photosensitive member.

FIG. 6 shows the amount of scraping of the photosensitive member with respect to the number of rotations of the photosensitive member. As described above, the surface roughness increases from the time when the photosensitive layer is shaved by 10 μm from the initial stage, and fusion is likely to occur. Therefore, in the present embodiment, it can be determined that fusion is likely to occur when the number of rotations reaches about 400,000.

Instead of counting the number of rotations of the photosensitive member, a method of counting the number of passing transfer materials, that is, the number of durable sheets themselves may be used.

In this case, as shown in FIG.
From the time when the number of sheets reaches 10,000, it can be determined that fusion is likely to occur.

[0066]

As described above, according to the present invention,
The thickness of the photosensitive layer of the image carrier is detected, and the temperature around the photoconductor is controlled according to the detection result.

That is, since the rotation speed or the rotation time of the cooling fan such as the exhaust fan is increased from the point in time when the film thickness of the photosensitive layer has decreased to a predetermined value, the temperature inside the apparatus is maintained even after the durability of the image carrier is advanced. By suppressing the rise, it is possible to always obtain a good image without fusing the toner to the surface of the image carrier.

Since the number of cooling fans to be operated is increased from the point in time when the film thickness of the photosensitive layer has decreased to a predetermined value, even after the durability of the image carrier has progressed, the temperature rise in the apparatus is suppressed, and A good image can always be obtained without the toner being fused to the surface of the carrier.

Further, since the image forming operation is forcibly stopped for a predetermined time from the point in time when the thickness of the photosensitive layer has decreased to a predetermined value, the temperature inside the apparatus can be increased even after the durability of the image carrier has advanced. , And a good image can always be obtained without fusing the toner to the surface of the image carrier.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to embodiments (1 to 6) of the present invention.

FIG. 2 is a diagram illustrating a detection current with respect to a film thickness of a photoconductor.

FIG. 3 is a diagram showing a rotation sequence of an exhaust fan according to Embodiments 2 and 3 of the present invention.

FIG. 4 is a diagram showing a temperature change in an apparatus main body according to a fourth embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of an image forming apparatus according to a sixth embodiment of the present invention.

FIG. 6 is a diagram illustrating a relationship between a photoconductor shaving amount and a rotation speed of a photoconductor according to a sixth embodiment.

FIG. 7 is a diagram illustrating the relationship between the photoconductor shaving amount and the number of copies / prints according to the sixth embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photoreceptor drum 2 ... Charging roller as a contact charging member 3 ... Charging bias application power supply 6 ... Developing means 10 ... Image exposure means 12 ... Transfer means (transfer roller) 14 ... Transfer material 17 ... Exhaust fan (cooling fan) 18 ... Exhaust fan control device 19 ... Temperature sensor 20 ... Photosensor for detecting the number of rotations of the photoconductor

Claims (8)

[Claims] A charging means for uniformly charging the surface of the image carrier; and an electrostatic latent image by irradiating the uniformly charged surface of the image carrier with image exposure corresponding to a document image or an input image signal. Image exposure means for forming an image, visible image means for forming a toner image corresponding to the electrostatic latent image, transfer means for transferring the toner image to a transfer material, and a thickness of a photosensitive layer of the image carrier. An image forming apparatus comprising: a detection unit configured to detect a temperature of the image carrier in accordance with a detection result of the detection unit. 2. The image forming apparatus according to claim 1, wherein the charging unit is a contact charging device that charges a surface of the photoconductor by bringing a charging member to which a charging bias is applied into contact with the photoconductor. Means for applying a predetermined detection voltage to the charging member and measuring the amount of current flowing from the charging member to the image carrier at this time. The image forming apparatus according to claim 1. 3. The image forming apparatus according to claim 1, wherein the detection unit is a unit that counts the number of rotations of the image carrier. 4. An image forming apparatus according to claim 1, wherein said detecting means is means for counting the number of passing transfer materials. 5. The apparatus according to claim 1, further comprising a cooling fan for cooling the inside of the apparatus, wherein a rotation speed of the exhaust fan is changed in accordance with a detection result by the detection means. 5. The image forming apparatus according to 4. 6. The apparatus according to claim 1, further comprising a cooling fan for cooling the inside of the apparatus, wherein a rotation time of the exhaust fan is changed according to a detection result of the detection unit.
5. The image forming apparatus according to 2, 3, or 4. 7. The image forming apparatus according to claim 5, wherein a plurality of the cooling fans are provided, and the number of the cooling fans to be operated is changed according to a detection result by the detection unit. 8. According to a detection result by the detection means,
2. The image forming apparatus according to claim 1, wherein the image forming operation is stopped for a predetermined time when the temperature in the apparatus becomes higher than a certain value.
5. The image forming apparatus according to 2, 3, or 4.