JPH04345447A - Image forming device - Google Patents

Abstract

PURPOSE:To carry out a stable conveyance as well as to obtain a stable image even when a reclaimed paper liable to generate a curl is used. CONSTITUTION:When the kind of a paper is discriminated by a paper kind detecting sensor 25, a heating means 41 composed of heater (1), heater (2), or heater (n) or a humidification regulating means composed of the heating device 41 and a humidifying device 45 are controlled by a control means 40, to maintain the relative humidity in a paper feeding means 6 at a specific value, and the curl generating amount of the paper is suppressed to less than a specific value.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to image forming apparatuses such as copying machines, printers, and facsimile machines, and particularly to image forming apparatuses characterized by humidity control in paper feeding apparatuses having paper feeding trays, paper feeding cassettes, etc. Regarding.

0002

2. Description of the Related Art In recent years, recycled paper has come to be used even in copying machines in order to reuse resources. However, this recycled paper has the disadvantage that it is inherently weak and tends to curl, and is also susceptible to the effects of the environment, especially humidity, and tends to curl when the humidity changes. Further, when such curling occurs, there are problems in that it causes abnormal images due to poor adhesion at the transfer section, and conveyance abnormalities due to edge folds (corners of the paper are folded) and jams.

[0003] Therefore, many techniques related to curl removal and curl countermeasures have been proposed. For example, Japanese Utility Model Application Publication No. 59-30156 proposes a technique for removing curls by applying stress in the opposite direction only to curls in a certain direction. Also, Utsukai Showa 63-65
Japanese Patent No. 661 proposes a technique for correcting curls by providing two types of conveyance paths, sorting out curls in paper, and dividing the conveyance paths according to the direction of the curl. Furthermore, Japanese Utility Model Application Publication No. 195335/1983 proposes a technique for detecting the amount and direction of curl and controlling the humidity adjusting means in the paper storage section.

0004

[Problem to be solved by the invention] Here, the types of paper,
Although the curl direction and curl amount differ depending on the moisture content,
The technique disclosed in Japanese Patent Publication No. 65661 does not clear everything, and requires a large amount of stress or heat to clear everything, making it very expensive and complicated. In addition, the above-mentioned Utility Model No. 63-19
The technique disclosed in Japanese Patent No. 5335 also has the drawback that the curl amount measuring device requires a large space and is expensive.

The present invention solves the above-mentioned drawbacks of the prior art and provides an image forming apparatus that can produce stable images and perform stable conveyance even when recycled paper that is prone to curling is used. The purpose is to

[0006]

[Means for Solving the Problems] The above object is to provide a paper feeding device that stores paper and feeds the paper one by one, a paper conveyance path that guides and conveys the paper fed from this paper feeding device, and a paper conveyance path that guides and conveys the paper fed from this paper feeding device. A paper type detection means disposed on the transport path or near the paper feeder, a humidity adjustment means disposed within the paper feeder, and the humidity adjustment means is controlled according to the detection output of the paper type detection means. This is achieved by comprising a control means.

[0007] In this case, the paper type detection means is composed of, for example, a reflective photo sensor that detects the light reflectance of paper, or a micro switch that is turned on and off by a switch piece of a paper feed cassette for a specific paper. be done. Further, the humidity adjusting means is constituted by a heating device or a combination of a heating device and a humidifying device.

[0008]

[Operation] When the type of paper (for example, plain paper or recycled paper) is determined by the paper type detection means consisting of a reflective photo sensor or micro switch, the humidity level is determined by a heating device or a combination of a heating device and a humidifying device. The adjusting means is controlled by the control means to maintain the relative humidity within the paper feeding device at a predetermined value and to suppress the amount of curl to a predetermined value or less.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings. FIG. 1 is a block diagram of a copying machine according to an embodiment of the present invention. The copying machine main body 1 includes a document table 2 and an automatic document feeder 3.
, an optical device 4 that illuminates and exposes a document, an image forming device 5 that forms a latent image of the document image exposed by the optical device 4 and further visualizes it, a plurality of paper feed devices 6, and a paper feed device. 6, a transfer section 8, a fixing section 9, a curl detection section 10, and a paper conveyance path 7 that guides and conveys the paper fed from the paper conveyance path 7; and a paper discharge tray 11 for discharging the paper.

In addition to the paper output tray 11 for double-sided copying, an intermediate tray 12 is provided to temporarily store the paper transported by the paper transport path 7, and a switching claw 13 is used to switch between the paper output tray 11 and the paper output tray 11.
and the intermediate tray 12 can be switched and connected to the paper transport path 7. From the intermediate tray 12, the paper is sent to the paper transport path 7 with the paper turned upside down by the feeding means 14 and the connection path 15, and the back side of the paper is transferred with a toner image by the image forming device 5 in the transfer section 8, as well as the front side. The image is then fixed by the fixing unit 9 and discharged onto the paper discharge tray 11.

As the image forming device 5, a known means is used. In FIG. 1, an OPC belt is used as the photoreceptor 16, and the charging section 17,
Exposure section 18, development section 19, transfer section 8, cleaning section 2
0 is placed. A large-capacity paper feeder 21 and known post-processing devices such as a sorter 22 and a finisher 23 can be additionally assembled into the copying machine main body 1. The paper fed from the paper feeding device 6 is transferred to the image forming device 5 in the transfer section 8.
The toner image is then transferred and fixed in the fixing section 9. When the paper is heated in the fixing section 9, curling occurs in the paper due to the heating effect of the heat and fluctuations in moisture content (evaporation).

[0012] As shown in FIG. 2, the amount of curl is expressed by the amount a of the leading edge of the paper when ten sheets are stacked one on top of the other. Figure 3 shows the difference between the moisture content at the time of paper feeding and the amount of curl after fixing.
The relationship shown in is obtained. The horizontal axis in the figure is the water content (%
), the vertical axis represents the curl amount a, and curves A and B each represent the characteristics of different types of paper. In this case, the amount of curl toward the opposite side of the image (back curl) is shown as a negative value, and the amount of curl toward the side of the image (face curl) is shown as a positive value. From the characteristic curve in FIG. 3, it can be seen that it is desirable that the moisture content of the paper is approximately 7% or less.

Furthermore, when the state in which the moisture content of paper changes depending on the atmosphere (relative humidity) was measured, a relationship as shown in FIG. 4, for example, was obtained. The horizontal axis in the figure is relative humidity (%),
The vertical axis indicates water content (%). Curve A is on paper G, curve B is on paper G.
is the characteristic curve of H paper. From FIG. 4, it can be seen that even for the same paper, the amount of curl and the direction of curl change depending on the relative humidity of the atmosphere.

[0014] Generally, the moisture content of paper for copying machines is controlled at around 6% at the time of manufacture, and the packaging is devised to block moisture so as to prevent excess moisture from being absorbed. In addition, some copying machines maintain the sealability of the paper feed tray or provide a heater in the tray to control relative humidity. Based on the above, the type of paper (for example, plain paper or recycled paper) is first detected, and then the relative humidity in the paper feeder is adjusted to approximately 60% according to the type in order to keep the moisture content below 7%, as shown in Figure 4. % or less.

[0015] First, the paper type detection mechanism will be described. In FIG. 1, each paper feed device 6 arranged in three stages
A paper type detection sensor 25 consisting of a reflective photo sensor is installed at a certain distance from the top surface of the set paper.
are provided for each. If the color or reflectance of the paper set in each paper feed device 6 differs, the output of the paper type detection sensor 11 will differ. Figure 5 shows the output characteristics of plain paper and recycled paper.
The sensor output PA of plain paper with a width of 5 is P1 ~
It is higher than the sensor output PB which has a width of P2. Therefore, humidity adjustment control, which will be described later, is performed based on the difference in the output P of the paper type detection sensor 11 when detecting plain paper and when detecting recycled paper.

FIG. 6 is a configuration diagram of the paper type detection sensor 25, which is composed of a reflective photo sensor. Paper type detection sensor 2
Reference numeral 5 includes a light emitting element 25a, a light receiving element 25b that receives reflected light from the sheet of paper irradiated by the light emitting element 25a, and further an operational amplifier 25c. The output from this operational amplifier 25c is input to a CPU, which will be described later, through an A/D converter.

FIGS. 7 and 8 are enlarged configuration diagrams of a paper feeding device section according to another embodiment, and the paper feeding device 6 includes a paper feeding cassette 30 that is detachable from the main body of the device, and a friction separation pad. It is composed of a paper feed roller 31 having a pressure-bonded paper. There are two types of paper cassettes 30, one for recycled paper and one for plain paper (even within plain paper, there are dedicated cassettes for each size). A switch piece 32 is attached to the top surface of the paper feed cassette 30 for recycled paper shown, and this switch piece 32 faces a paper type detection sensor 25 composed of a micro switch.

When the paper feed cassette 30 for recycled paper is set in the main body of the apparatus, the micro switch is pressed by the switch piece 32 and turned on, while the paper feed cassette 30 for plain paper shown in FIG. is set in the main body of the apparatus, there is no switch piece 32 and the micro switch remains off, so the CPU 40 determines the type of paper feed cassette 30, that is, the paper type (recycled paper or plain paper). can be judged. As a result, control described below is executed.

Next, the humidity adjusting means for adjusting the humidity inside the paper feeding device 6 will be described. FIG. 9 is a configuration diagram of a paper feeding section showing an example of a humidity adjusting means. In this example,
As a humidity adjustment means, a heater (heating device) 41 is provided at the bottom of each paper feed device 6a, 6b, 6c.

FIG. 10 is a control block diagram according to the first embodiment. In FIG. 10, 25 is a paper type detection sensor;
40 is a CPU, 41 is a heater [heaters (1) to (n)]
, 42 is a heater control device, 43 is a curl permissible level setting device [curl permissible level setting device (1) to (n)], 4
4 is a storage section. Note that when there are n paper feed devices,
There are also n curl tolerance level setting devices 43. As mentioned above, the relative humidity, moisture content, moisture content, amount of curl, and direction of curl differ depending on the type of paper. These data are input into the storage section 44 in advance.

FIG. 11 is a flowchart showing the control contents of the first embodiment. First, the paper type detection sensor 25 reads the type of transfer paper (plain paper or recycled paper), and if it is recycled paper (Y in S1 and S2), the temperature and humidity at that time are shown in the figure. The data is read as data for recycled paper from a thermohygrometer (S3). If plain paper is used (N in S1 and S2), data for plain paper is read in the same way (S4). Then, for each transfer paper, the read data is compared with the data previously stored in the storage section 44 (S5, S6), and the curl amount tolerance level is extracted from the curl tolerance level setting device 43. Based on this input information, the curl amount excess signal and curl direction signal are sent to the CPU 4.
0 to the heater control device 42, whereby each heater 41 is independently controlled on and off (S7
, S8).

FIG. 12 is a configuration diagram of a paper feeding section showing another example of the humidity adjusting means. In this example, in addition to the heater 41,
An ultrasonic humidifier (humidifier) 45 is provided. If there are multiple paper feed devices 6, the duct 46 connects each paper feed device 6.
It is designed to humidify the air. 47 is a valve that opens and closes each duct 46.

FIG. 13 is a control block diagram according to the second embodiment. In FIG. 13, only the parts that are different from the control block shown in FIG. 10 are shown: 48 is a humidifier control device, and 49 is a humidifier activation device.

FIG. 14 is a flowchart showing the control contents of the second embodiment. In steps S11 and S12,
The same processing and determination as steps S1 and S2 shown in FIG. 11 are performed, and then the curl estimation data for recycled paper and the curl estimation data for plain paper are read (S13).
, S14). The estimated curl is a back curl (S
15, Y in S16), if the curl amount exceeds the predetermined amount (N in S17, N in S18), the heater 41 serving as a dehumidifier is set so that the estimated curl amount is less than the predetermined amount as the relative humidity decreases. It is turned on until it becomes (S19, S20). On the other hand, the estimated curl is a face curl (N in S15, S16
If the curl amount exceeds the predetermined amount (N in S21, N in S22), the ultrasonic humidifier 45 is operated until the relative humidity increases and the estimated curl amount becomes less than the predetermined amount ( S23, S24).

[0025]

As described above, according to the invention set forth in claim 1, when the paper type detection means determines the paper type (for example, plain paper or recycled paper), the humidity adjustment means is controlled. Since the relative humidity inside the paper feeding device is kept at a predetermined value by controlling the paper feeder and the amount of curl is kept below a predetermined value,
You can always obtain stable image quality and transport performance. According to the invention set forth in claim 2, in addition to the effect of the invention set forth in claim 1, cost reduction and device simplification can be achieved by using a general-purpose photo sensor as the paper type detection means. . According to the invention recited in claim 3, in addition to the effect of the invention recited in claim 1, means for detecting the type of paper feed cassette is provided as the paper type detection means, so that a dedicated cassette is used for each paper type. This makes it suitable for devices of this type. According to the invention set forth in claim 4, in addition to the effect of the invention set forth in claim 3, cost reduction and device simplification can be achieved by using a general-purpose micro switch as the paper type detection means. can. According to the invention set forth in claim 5, in addition to the effect of the invention set forth in claim 1, the humidity adjusting means
By configuring only the heating device, cost reduction and device simplification can be achieved. According to the invention set forth in claim 6, in addition to the effect of the invention set forth in claim 1, the humidity adjusting means
By including a humidifying device in addition to the heating device, more efficient humidity adjustment can be achieved.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the amount of curl.

FIG. 3 is a characteristic diagram showing the relationship between the water content at the time of paper feeding and the amount of curl after fixing.

FIG. 4 is a characteristic diagram showing the relationship between paper moisture content and relative humidity.

FIG. 5 is an output characteristic diagram of a paper type detection sensor.

FIG. 6 is a configuration diagram of a reflective photo sensor as a paper type detection sensor.

FIG. 7 is a configuration diagram of main parts when a micro switch is used as a paper type detection sensor.

FIG. 8 is a configuration diagram of main parts when a micro switch is used as a paper type detection sensor.

FIG. 9 is a configuration diagram of a paper feeding section showing an example of a humidity adjusting means.

FIG. 10 is a control block diagram according to the first embodiment.

FIG. 11 is a flowchart showing the control contents of the control block diagram in FIG. 10;

FIG. 12 is a configuration diagram of a paper feeding section showing another example of humidity adjusting means.

FIG. 13 is a control block diagram according to a second embodiment.

FIG. 14 is a flowchart showing the control contents of the control block diagram in FIG. 13;

[Explanation of symbols]

6 Paper feeding device 7 Paper conveyance path 25 Paper type detection sensor 40 CPU 41 Heater 45 Ultrasonic humidifier

Claims (6)

[Claims] Claim 1: A paper feeding device that stores sheets of paper and feeds them one by one, a paper conveyance path that guides and conveys the sheets fed from this paper feeding device, and this paper conveyance path or the above-mentioned sheet feeding device. a paper type detection means arranged somewhere in the vicinity to detect the paper type; a humidity adjustment means arranged within the paper feeding device to adjust the humidity of the atmosphere inside the paper feeding device; and a paper type detection means arranged within the paper feeding device. an image forming apparatus comprising: a control means for controlling the humidity adjusting means according to a detection output of the humidity adjusting means; 2. The image forming apparatus according to claim 1, wherein the paper type detection means is comprised of a reflective photo sensor that measures the light reflectance of the transfer paper. 3. The apparatus according to claim 1, wherein the paper type detection means includes means for detecting the type of a dedicated paper feed cassette for each paper type that is attached to and detached from the main body of the apparatus. image forming device. 4. The paper type detecting means according to claim 3, wherein the paper type detection means is constituted by a micro switch that detects the presence or absence of a switch operating piece installed in advance according to the type of paper feed cassette. image forming apparatus. 5. The image forming apparatus according to claim 1, wherein the humidity adjusting means is constituted by a heating device that heats the atmosphere within the paper feeding device. 6. The image forming apparatus according to claim 1, wherein the humidity adjusting means includes, in addition to the heating device, a humidifying device that humidifies the atmosphere inside the paper feeding device.