JP2008145514A

JP2008145514A - Image forming apparatus

Info

Publication number: JP2008145514A
Application number: JP2006329604A
Authority: JP
Inventors: Masaru Watanabe; 賢渡邊
Original assignee: Canon Inc; キヤノン株式会社
Priority date: 2006-12-06
Filing date: 2006-12-06
Publication date: 2008-06-26

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of detecting the amount of moisture of a recording material at the same time as detecting the type of the recording material by using a detecting means for detecting the type of the recording material and a fixing means. For the purpose.
A sheet feeding unit that feeds a recording material, a conveyance unit that conveys the fed recording material, a fixing unit that heats the recording material and fixes an image on the recording material, and both surfaces of the recording material Double-sided printing means for forming an image, detection means for detecting the type of conveyed recording material, and setting means for setting image forming conditions based on the type of recording material detected by the detection means for detecting the type of recording material And means for detecting the moisture absorption amount of the recording material.
[Selection] Figure 1

Description

The present invention relates to an image forming apparatus using a recording material type and means for detecting the moisture absorption amount of the recording material.

As image forming apparatuses such as electrophotographic systems and ink jet systems, image forming techniques have been developed, and those capable of forming full-color images have started to be widely used. In these image forming apparatuses, for example, in electrophotography, a high voltage is applied to the photosensitive drum and the recording material in the process of transferring the toner to the recording material. However, the amount of water contained in the recording material varies depending on the storage conditions of the recording material. The recording material has electrostatic characteristics that change depending on the amount of moisture absorbed and is liable to cause image transfer failure, so that a high-quality transfer image may not be obtained. Therefore, for example, in Japanese Patent Application Laid-Open No. 61-26060 and Japanese Patent Application Laid-Open No. 6-156778, a heating element for heating the moisture-absorbed paper prior to the image forming operation is used as a guide part serving as a paper conveyance path, The recording material provided on the lower surface and transporting the guide portion is heated and dried.

On the other hand, various types of recording materials have been developed in order to form a wider variety of images. However, in order to obtain a high-quality image corresponding to various types of recording materials, it is necessary to optimize various conditions during image formation.

For example, in a fixing process in which toner transferred onto a recording material in an electrophotographic system is heated and pressed to be fixed on the recording material, the amount of heat required differs depending on the type of recording material. Based on this, it is necessary to control the temperature during fixing. Therefore, for example, in Japanese Patent Laid-Open No. 7-134022, the thickness of the recording material is detected by measuring a change in the distance between any conveying rollers depending on the presence or absence of the recording material. In Japanese Patent Application Laid-Open No. 2003-294401, a recording material pushes up a lever member installed in a conveyance path, and the thickness of the recording material is detected based on a fluctuation amount of the lever member.
JP-A 61-26060 JP-A-6-156778 Japanese Patent Laid-Open No. 7-134022 JP 2003-294401 A

As described above, when the moisture absorption amount of the recording material increases, the electrostatic characteristics of the recording material change, which may cause image defects. In this case, image transfer failure can be prevented by changing the output range of the transfer voltage in the process of transferring the toner to the recording material.

Further, in order to optimize the image forming conditions, it is necessary to detect the type of recording material. However, if the moisture absorption amount of the recording material is different, the rigidity of the recording material changes, which may affect the detection of the type of the recording material. However, if the moisture absorption amount of the recording material is known, the type of the recording material can be detected by changing the threshold value used to determine the type of the recording material.

However, in order to reduce the size and cost of the image forming apparatus, it is difficult to install a new apparatus for heating and drying the recording material.

Therefore, in the present invention, the detection unit for detecting the type of the recording material and the fixing unit are used to detect the type of the recording material and simultaneously detect the moisture absorption amount of the recording material, and based on the detected moisture absorption amount of the recording material. An object of the present invention is to provide an image forming apparatus capable of optimizing image forming conditions.

In the first invention according to the present application, at the time of double-sided printing, the means for detecting the type of recording material and the fixing means are used, and the above-mentioned detection means is used for the first side at the time of double-sided printing, that is, before heating and drying. By detecting the difference between the measurement result and the second measurement on the second side, that is, the measurement result by the above-mentioned detection means after heating and drying, and comparing the detection result with a threshold value, the moisture absorption amount of the recording material is detected. Do. Then, based on the detected moisture absorption amount of the recording material, the image forming conditions can be optimized and a high quality image can be obtained.

In the second invention, the threshold used for detecting the type of the recording material is selected based on the moisture absorption amount of the recording material detected by the first invention, so that the recording material can be recorded regardless of the moisture absorption amount of the recording material. Detect the type of material.

As described above, according to the present invention, the type and moisture absorption amount of the recording material can be detected without installing a new apparatus for heating and drying the recording material. As a result, appropriate image forming conditions can be set based on the type of recording material and the amount of moisture absorption, and a high-quality image can be obtained.

(Example 1)
FIG. 1 shows the configuration of an image forming apparatus used in Embodiment 1 of the present invention. The surface of the photosensitive drum 101 is uniformly charged to a certain polarity by the charging roller 102, and then only the area under the exposure of the photosensitive drum 101 is neutralized by an exposure unit 103 such as a laser to form a latent image. The toner 105 of the developing device 104 is frictionally charged with the same polarity as the charging surface of the photosensitive drum 101 between the developing blade 104a and the developing sleeve 104b. Then, by applying a DC and AC bias to the developing gap portion where the photosensitive drum 101 and the developing sleeve 104b face each other, the toner 105 is selectively applied to the latent image forming portion of the photosensitive drum 101 while floating and vibrating by the action of electrolysis. After adhering, it is conveyed by the rotation of the transfer roller 106 and the photosensitive drum 101.

On the other hand, the recording material is set in a paper feeding cassette 107, conveyed by a paper feeding roller 108, and a high voltage having a polarity opposite to that of the toner 105 is applied by a transfer roller 106 on the back surface of the recording material. The recording material to which the high voltage is applied electrostatically attracts the toner 105 to the recording material side to transfer the image. Further, the reverse surface of the recording material is applied with a polarity opposite to that of the toner 105, and a transfer charge is applied to keep the transferred toner 105 held. The recording material to which the image has been transferred is heated and pressed by the fixing device 109 to fix the image, and is discharged by the FD roller 110.

In the case of double-sided printing, the FD roller 110 rotates in the reverse direction after a certain period of time after the trailing edge of the recording material passes through the paper discharge sensor 111. By this operation, the recording material is conveyed to the double-sided conveyance path, is again fed by the refeed roller 112, and image formation is performed again.

FIG. 2 shows the recording material thickness detecting means 113 used in this embodiment. The lever 201 is fixed to the conveyance path by a rotating shaft 202 and a bearing 203. The lever 201 is pushed up by the thickness of the recording material when the recording material is conveyed. When the recording material passes, the pressure spring 204 returns to the state before the recording material passes. The relationship between the thickness of the recording material and the amount of fluctuation of the lever 201 is expressed by the following expression 114.

However,
y: Lever fluctuation amount detected by the displacement detector [mm]
s: Recording material thickness [mm]
l: Horizontal distance from the rotation axis to the detector [mm]
L: Length of lever from the rotation axis to the transport path [mm]
h: Thickness of transport path [mm]
And The image forming apparatus detects the fluctuation of the lever 201 by the displacement detection device 206. However, the recording material being conveyed is in a state of floating from the conveyance path, and the behavior of the lever changes depending on the rigidity of the recording material. Since the rigidity of the recording material changes depending on the amount of moisture absorption, even with the same recording material, the lever varies depending on the amount of moisture absorption.

The first invention according to the present application will be described using the image forming apparatus provided with the recording material thickness detecting means described above.

The operation of the image forming apparatus in this embodiment will be described with reference to FIG. In S301, the amount of change of the lever that has fluctuated depending on the recording material being conveyed is measured, and the paper type is detected. In S302, it is determined whether it is the first sheet or the second sheet. In the case of the second sheet or later, in S303, based on the moisture absorption amount of the recording material detected in S307, a high voltage output range such as a transfer voltage or a charging voltage is obtained. The output level is optimized, and image formation is performed in S304. In step S305, the first side or the second side is determined. In the case of the first side of both sides, the reverse operation is performed in S306, and the paper type is detected again in S301. In the case of the second side of both sides, the moisture absorption amount is detected in S307. The detection of the amount of moisture absorption calculates the difference d between the measurement results y1 and y2 of the lever fluctuation amount performed in the first and second paper type detection, and if the difference d is greater than the threshold dth, In other cases, it is determined as open paper. In S308, it is determined whether or not image formation is to be performed on the next recording material. If image formation is to be continued, the processing in S301 is performed again.

In this embodiment, one threshold is used when detecting the amount of moisture absorption, but a plurality of thresholds are used to detect the degree of moisture absorption in more detail, and the high-pressure output range in image formation is the amount of moisture absorption of the recording material. It is also possible to switch in more detail depending on the stage.

(Example 2)
A second invention according to the present application will be described with reference to FIG. The apparatus configuration described in the first embodiment is used. In S301, the amount of change of the lever that has fluctuated depending on the recording material being conveyed is measured, and the paper type is detected. In S302, it is determined whether it is the first sheet or the second sheet. In the case of the second sheet or later, in S401, the target temperature adjustment temperature is optimized according to the type of the detected recording material, and image formation is performed in S304. Do. In step S305, the first side or the second side is determined. In the case of the first side of both sides, the reverse operation is performed in S306, and the paper type is detected again in S301. In the case of the second side of both sides, the moisture absorption amount is detected in S307. The detection of the amount of moisture absorption calculates the difference d between the measurement results y1 and y2 of the lever fluctuation amount performed in the first and second paper type detection, and if the difference d is greater than the threshold dth, In other cases, it is determined as open paper. In S402, based on the detected moisture absorption amount of the recording material, the threshold value table Pth used for detecting the recording material type is switched to improve the recording material type detection accuracy. In S308, it is determined whether or not image formation is to be performed on the next recording material. If image formation is to be continued, the processing in S301 is performed again.

In this embodiment, the threshold used for detecting the amount of moisture absorption is one, but the threshold is used in a plurality to detect the degree of moisture absorption in more detail, and the threshold used to detect the type of recording material, It is also possible to switch in more detail according to the level of moisture absorption of the recording material.

1 is a configuration diagram of an image forming apparatus used in Embodiment 1. FIG. 3 is a side view of recording material thickness detection means used in Embodiment 1. FIG. 3 is a flowchart illustrating control according to the first embodiment. 10 is a flowchart illustrating control according to the second embodiment.

Explanation of symbols

102 Charging roller 104b Developing roller 106 Transfer roller 113 Means for detecting type of recording material

Claims

An image is formed on both sides of the recording material, a paper feeding device that feeds the recording material, a conveying device that transports the fed recording material, a fixing device that heats the recording material and fixes the image to the recording material In the image forming apparatus that sets the image forming condition based on the type of recording material detected by the double-sided printing unit, the detecting unit that detects the type of the conveyed recording material, and the detecting unit that detects the type of the recording material, The detection means for detecting the type of recording material is used to detect the type of recording material at the time of image formation on the first and second surfaces, and from the difference in measurement results, the amount of moisture absorbed by the recording material And an image forming condition is set based on the moisture absorption amount of the recording material.
2. The image forming apparatus according to claim 1, wherein a threshold used for determining the type of the recording material is switched based on the type of the recording material and the moisture absorption amount.