JP2010002738A - Curl determination method and curl determination device for transfer paper, and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure a correct amount of curl, taking into account of various environmental conditions and moisture of various transfer sheets of paper. <P>SOLUTION: The transfer paper curl determination method is for determining a curl in transfer paper caused by expansion and contraction resulting from a change in moisture of transfer paper heated and compressed in order to melt and fix a toner image formed on an image carrier by the image forming operation of an image forming apparatus and transferred to the transfer paper. In the method, a curl in the transfer paper is estimated (S4) according to a difference between the measurement value (S1) of the atmospheric humidity of space where the transfer paper is placed and the measurement value (S2) of the humidity of the transfer paper surface detected by a humidity detection sensor installed close and opposite to the transfer paper surface. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention applies a curl determination method, a curl determination device, and a determination method or a determination device for determining a curl of a transfer paper from a change in humidity near the transfer paper to which a toner image is transferred and fixed by an image forming operation. The present invention relates to an image forming apparatus.

In an electrophotographic image forming apparatus such as a multifunction machine equipped with a copying machine, a printer, a facsimile, etc., a toner image formed on a photosensitive drum by an image forming operation is transferred to a transfer paper (recording medium) by a transfer device. Then, an unfixed toner image is melted by being heated by a fixing device, fixed on a transfer sheet, and output (discharged) to the outside.
Many of the transfer papers to which toner images are transferred and heat-fixed by image forming operations are entangled with fibers made of wood pulp, and each of these fibers absorbs or dehumidifies moisture. . At this time, the fiber has a property of expanding when moisture is absorbed and contracting when dehumidifying.

The curling of the transfer paper is a phenomenon in which the transfer paper expands and contracts due to a change in the moisture content of the transfer paper, and the end of the transfer paper is pulled to the center and warps. Therefore, it is affected by environmental changes (temperature, humidity) around the transfer paper, and particularly greatly affected by humidity changes.
For example, when a transfer paper with a high moisture content is exposed to a dry environment, that is, a low humidity environment, the transfer paper tries to balance the surrounding environment, so moisture is dehumidified toward the surrounding environment. To do. In this way, the shrinkage of the transfer paper begins in the process of balancing with the surrounding environment, and at that time, the shrinkage occurs so that the edge of the transfer paper is pulled to the center, so the edge gradually curves and warps. Curl up.
Therefore, the curling of the transfer paper occurs when there is a difference between the surrounding environment where the transfer paper is placed and the moisture content of the transfer paper itself, and the larger the difference, the larger the amount of curling.

Further, in the image forming apparatus, when fixing the toner image transferred onto the transfer paper, a method of fixing the toner image onto the transfer paper through a heating roller and a pressure roller or a belt (nip portion) is the most recent method. However, when the transfer paper after fixing is heated at a high temperature, it is rapidly dried, that is, dehumidified, and is bent so as to warp upward (front side) or downward (back side), so-called. Curling occurs.
Such curling of transfer paper is more likely to occur due to the increase in the amount of toner transferred to the transfer paper, diversification of the types of transfer paper (multi-product types), etc., using full-color, multi-function composite copiers, etc. It tends to occur remarkably. Further, the curling of the transfer paper also occurs due to an environmental change in the place where the transfer paper is stored.
In other words, the curl of the transfer paper is more likely to occur when the moisture content of the transfer paper is changed, particularly when the moisture state is lower than the original moisture state.

  In the image forming apparatus, due to such curling of the transfer paper, image quality due to paper jam (jamming), deterioration or disturbance of transfer paper storage capacity in the paper discharge unit, or transfer failure during double-sided image formation, etc. Therefore, it is important to prevent the transfer paper from curling, and by setting and controlling each process condition according to the amount of curl generated on the transfer paper Therefore, it is necessary to prevent image quality failure and conveyance failure.

In order to solve such problems, various curl correction devices have been proposed so far.
For example, a method of applying stress in the opposite direction only to a certain curl direction, or providing two types of conveyance paths, selecting the curl direction of the transfer paper, dividing the curl direction according to the curl direction, A correction method has been proposed.
However, the curl direction and curl amount differ depending on the type of sheet such as transfer paper and the moisture content, and all curls cannot be corrected by such a correction method. Has a drawback that a large amount of heat is required to apply a large stress, which is very expensive and complicated.

  In addition, the amount of curl generated on the transfer paper is measured, and the curling of the transfer paper is performed in order to control the correction device, automatically control the image forming conditions, and control the transfer paper according to the measurement result. Many image forming apparatuses equipped with a detecting means for detecting water have been proposed. The humidity of water vapor generated from the transfer paper is detected to detect curl, and the moisture content of the transfer paper is determined from the detection result. There is a proposal to calculate and grasp the state of the transfer paper.

In Japanese Patent Laid-Open No. 2007-86054 (“Non-contact dew condensation detection method, non-contact dew condensation detection device, sheet deformation suppression method and image forming apparatus using the same”, Patent Document 1), The temperature / humidity sensor (4a, 4b) that measures the temperature and humidity of the gas in the ambient atmosphere is placed in the middle position, and the temperature / humidity sensor (4c) is placed at a position remote from the surface of the object (1), A flow sensor (5) that measures the gas flow direction or flow velocity in the ambient atmosphere of the object surface is provided, and the distribution of the ambient atmosphere to the object surface is determined by the measurement results of the temperature and humidity sensors (4a, 4b, 4c) and the flow sensor (5). By using the method of determining the state and transport process and detecting the behavior of the ambient atmosphere gas adsorbing and aggregating on the object surface and the behavior of the agglomerated liquid evaporating on the object surface, Transfer paper transport path The first and second measuring means are installed at locations upstream and downstream of the transfer device, and a third measuring device is installed in the vicinity of the fixing device so that the transfer paper moves on the conveyance path. It has been proposed to calculate the transpiration rate of the generated water and to estimate the deformation of the transfer paper from the calculated result.
In addition, the code | symbol used in the said description is what is shown by FIG.1, FIG.3, FIG.4 etc. of patent document 1. FIG.

However, the invention of Patent Document 1 has the following problems (1) to (4).
(1) A plurality of temperature / humidity sensors and flow sensors are arranged in one measuring means, and three measuring means constituting them are required. However, since there are differences in the electrical characteristics of the sensors, A detection error may occur as a real problem in the detected value. Therefore, when the transpiration rate is calculated using these detected values, further errors occur with respect to the calculation result, so that the accuracy of the finally calculated value decreases.
(2) The second measuring means is installed on the downstream side of the transfer device, that is, near the fixing device. In this case, it is considered that the transpiration amount of water changes due to the influence of the temperature from the fixing device, so that the deviation amount on the downstream side and the upstream side becomes larger than the original transpiration amount, and an error occurs in the transpiration rate. .

(3) The position where the transpiration behavior of the transfer paper is detected is the leading end of the transferred transfer paper, but an air flow is generated on the moving transfer paper surface. Even if the end has good ventilation and the amount of transpiration is large, the moisture flows on the back of the transfer paper, so even if the transpiration behavior at the end is detected, the original transpiration amount is not obtained.
(4) Since a plurality of measuring means are required to estimate the deformation of the transfer paper, the configuration becomes complicated and it is difficult to say that the configuration is preferable from the viewpoint of cost.
Therefore, (i) the measuring means is composed of one type to suppress detection errors due to electrical characteristics, and (ii) it is hardly affected by the fixing device, and the upstream side of the transfer device, that is, the transfer paper is stored. It is necessary to install it at a position near the paper feed tray, and (iii) capture the transpiration behavior between both ends of the transfer paper surface from the end to the end.
As a result, (iv) the configuration is simplified and is preferable from the viewpoint of cost.

  In JP 2007-322558 A (“moisture estimation device, sheet material processing device, moisture content estimation method, and sheet material processing method”, Patent Document 2), the moisture content of the sheet material at a position in contact with or close to the sheet material. In the apparatus for estimating the amount of water having first detecting means for detecting the first information relating to the step, the step of detecting the first information relating to the moisture contained in the sheet material and the information relating to the moisture contained in the sheet material are affected. A process of detecting the second information related to the factor, a moisture amount of the sheet material is estimated and calculated based on the first information and the second information, and an image forming process is performed based on the estimated and calculated moisture amount. It has been proposed that a process for adjusting the conditions is provided, and that the first detection means is provided with a heat conduction type humidity sensor formed by MEMS (Micro Electro Mechanical System) technology.

  However, in the invention of Patent Document 2, the value detected by the first detection means for detecting the humidity at a position close to the sheet material and the second detection means installed around the conveyance path in the apparatus are detected. It is said that the moisture content of the sheet material on which image processing is performed is estimated based on the information that has been processed, but the second detection means measures the environment around the conveyance path, that is, the environment in the apparatus, and the environmental impact The amount of moisture in the transfer paper that will vary depending on The environment (temperature, humidity) in the apparatus or around the conveyance path always has a distribution. For example, if the detection means is installed around the conveyance path near the fixing device that performs heat fixing, the environment becomes relatively high temperature. Conversely, if it is installed near the conveyance path near the sheet feeding unit in which the sheet material is stored, It becomes. Further, it is conceivable that the environment of the transfer portion that transfers the toner material to the sheet material is different from the above-described location. Even in a case where a continuous printing operation is performed, the environment of each image forming process unit changes from moment to moment depending on the number and time of continuous printing.

  Accordingly, the estimated moisture value of the sheet material varies greatly depending on the location where the detection means is installed. Therefore, it is not preferable to perform each image process control based on the estimated moisture value. In order to solve these problems, it is necessary to provide third, fourth, and fifth detection means for each image process (development, transfer, fixing, etc.), but the number of parts is inevitably increased. Since the cost increases, it is considered unsuitable for practical use.

Further, in the second embodiment of the invention of Patent Document 2, the first detection means is moved and the first and second detection means are also used, but the following (1) to (5) There is a problem.
(1) Depending on the distance traveled, there may be no difference in the detected value from the vicinity of the sheet material.
(2) When the detection means moves, there is a possibility that the environment before the movement is moved to the position after the movement.
(3) The detection value can be expected to be disturbed by the air flow generated when the detection means is moved, and when it is attempted to move slowly to prevent this, an image that has been printed at high speed in recent years. In the forming apparatus, the detection cannot catch up with the transfer speed of the transfer paper.
(4) If the moving distance is increased in order to solve the problem (1), it takes time to move, so the problem (3) occurs.
(5) The above problems (1) to (4) are more prominent in a sensor having a higher detection response such as a heat conduction type humidity sensor formed by the MEMS technology specified by the applicant. Such usage is not appropriate, and it is desirable to detect with a configuration that does not need to be moved to another environment.

In Japanese Patent Laid-Open No. 9-204080 (“Recording Paper Water Content Detection Method and Image Forming Apparatus”, Patent Document 3), the transfer paper passes through the fixing section and the transfer paper transport section of the image forming apparatus that performs thermal fixing control. The transfer paper is heated using a heat roller that can heat the part, the generated water vapor is detected by a humidity sensor, and the control conditions for each process (transfer, fixing) in image formation are changed based on the detected information However, when the transfer paper is heated, the amount of water vapor generated varies depending on the amount of water the transfer paper has. For example, when a transfer paper containing a lot of moisture is heated, a large amount of water vapor is generated. In particular, in a fixing unit that performs heat fixing processing, when water vapor is generated, it is expected that the water droplets adhere to the periphery of the apparatus and become dewed.
The adhering water droplets remain in the apparatus and may cause image defects, conveyance defects, and apparatus defects. Therefore, an exhaust function for removing water drops is necessary. The transfer paper has an optimal moisture content (around 4 to 6%) during image formation. For this reason, if the transfer paper is heated in the transfer paper transport section before image formation, this moisture content will collapse and the moisture content of the transfer paper will be reduced, possibly degrading the image quality. There is.

Furthermore, the transfer paper is partially heated to capture the amount of water vapor generated. However, the amount of water vapor generated from the transfer paper may be very small depending on the amount of water the transfer paper has. In this case, the generated water vapor becomes easy to become familiar with the surrounding environment, and the difference from the surrounding environment cannot be determined, so that accurate control over the transfer paper becomes impossible.
Therefore, it is more accurate to measure the original moisture content of the transfer paper without externally applying the transfer paper to the transfer paper.

  In addition to the above-described conventional technology, when a plurality of transfer papers continuously pass through the transfer paper conveyance path, such as when continuous printing (continuous image formation) is performed by continuously feeding transfer paper, transfer is performed. The environment in the image forming apparatus changes depending on the moisture content of the paper. For example, when continuous printing is performed continuously on transfer paper with a high moisture content, the inside of the image forming apparatus is in a high humidity state, so condensation occurs in a fixing device that performs heat fixing, or in a developing device, A filming phenomenon may occur due to moisture adsorbed by the discharge product adhering to the surface of the photosensitive drum, which causes image quality defects.

Therefore, the present invention can measure the curling state of the transfer paper being conveyed accurately and stably at a high speed with a simple configuration even during continuous printing. It is an object of the present invention to provide a transfer paper curl determination method or an image forming apparatus using a determination device that can be applied to uses other than determination.
JP 2007-86054 A JP 2007-322558 A JP-A-9-204080

[Problem 1]
The curling of the transfer paper occurs when there is a difference between the surrounding environment where the transfer paper is placed and the moisture content of the transfer paper itself, and the larger the difference, the larger the curling amount. For example, in a high humidity environment where the transfer paper has a large amount of water and the humidity of the surrounding environment where the transfer paper is placed is high, the moisture state is already balanced and curling is unlikely to occur. On the other hand, even when the moisture content of the transfer paper is low and the environmental humidity is low, the moisture state is similarly balanced and curling is unlikely to occur.
Therefore, it is necessary to measure an accurate curl amount corresponding to various environmental conditions and various transfer paper moisture conditions.

[Problem 2]
Further, the transfer speed of transfer paper that moves in recent image forming apparatuses is 200 mm / sec or more.
Therefore, it is necessary to measure the moisture state of each transfer sheet conveyed at high speed with high speed and high sensitivity.

[Problem 3]
In addition, there is a method that uses a means to measure the moisture content of the transfer paper using a plurality of high-speed humidity sensors, etc., but with regard to measuring the curl amount by that method, there are differences in the electrical characteristics and detection location of the humidity sensor. Since a measurement error due to the above may occur greatly, it is difficult to configure with a plurality of detection means.
Therefore, a detection method using a single detection means that can easily suppress measurement errors is required.

In relation to the problems 1 to 3, the characteristics of the humidity detection sensor, the detection of the moisture state of the transfer paper by the humidity detection sensor, and the like will be described with reference to FIGS.
FIG. 26 shows a comparison between the detection result in the vicinity of the transfer paper surface by the heat conduction type humidity detection sensor Ha recommended in the present invention and the same detection result by the capacitance type humidity detection sensor Hb. The graph shows data when a transfer paper having a moisture content of about 9% is left in an environment having an air temperature of 23 ° C. and a humidity of 30% RH, and shows a humidity change tendency for several minutes immediately after being left. At this time, the measurement distance from the surface of the transfer paper is set to 1 mm or less.
As shown in FIG. 26, the capacitance-type humidity detection sensor Hb has a low detection sensitivity, so the amount of change in humidity is small, and the peak is captured at a point lower than the original moisture transpiration value. Also, since the response speed is slow, the peak detection time is also slow. On the other hand, in the heat-conducting humidity detection sensor Ha, the transfer paper is set immediately below the humidity detection sensor, and at the same time exhibits a high response and catches a peak at an early timing.

FIG. 27 is a graph showing a comparison of detection results when the transfer paper reciprocates under the humidity detection sensors Ha and Hb under the same conditions as in FIG.
As in the case of FIG. 26, it can be seen that the capacitance type humidity detection sensor Hb has a small amount of change in humidity when the transfer paper passes and the detection timing is also delayed. It is also clear that the amount of change in humidity during passage is smaller than when the transfer paper is stopped. As described above, when the detection sensitivity is low and the response speed performance is low, the humidity change of the transfer paper cannot be accurately captured, and the detection performance appears remarkably when the transfer paper is moved.
Therefore, by using the heat conduction type humidity detection sensor recommended in the present invention, high sensitivity and high speed detection are possible, and the humidity change of the place where the humidity detection sensor is installed when the transfer paper passes is detected. In addition, it is possible to detect in real time as the moisture transpiration state from the moment when the transfer paper starts to pass. In addition, it is possible to capture the humidity distribution from the end to the end of the surface of the transfer paper that passes at a moving speed of 200 mm / sec or more. It is necessary to estimate the curl amount by correlating these humidity changes with the curl amount of the transfer paper.

When moisture evaporates from the surface of a liquid or solid object into the air, the humidity in the space near the surface changes and distribution is created. The distribution varies depending on the surface shape, temperature, humidity, wind speed, etc., but the range in which the humidity varies greatly is generally a narrow space within 1 cm from the surface. It mixes with the surrounding air and has an almost uniform distribution.
The moisture contained in the transfer paper appropriately adjusted for moisture is 4 to 6%, and the amount of moisture is a few hundred milligrams. Therefore, the amount of water released from the surface of the transfer paper is also very small. To detect this small amount of water, the more the distance from the transfer paper is, the easier it is to become familiar with the environment of the place. Because the difference cannot be determined, the humidity detection sensor mounted at a position where the distance from the transfer paper, such as the periphery of the device or the vicinity of the transfer paper storage tray, is not clearly defined, is used for the transfer paper itself. Since it is difficult to determine the moisture generated from the ink, it is necessary to define the detection distance from the transfer paper and detect it.

As described above, the humidity detection sensor needs to specify and detect the detection distance from the transfer paper, but if the specified detection distance is not always kept constant during measurement, it has the same moisture content. When the transfer paper is detected, the same value cannot be acquired, so that it is necessary to devise so that the detection distance can be kept constant.
In addition, when a humidity detection sensor (sensor unit) and its constituent parts are arranged in a portion through which the transfer paper passes, the transfer paper contacts or collides with the humidity detection sensor and its constituent parts depending on the behavior of the transfer paper. May interfere with the movement of Therefore, the humidity detection sensor and its components need to be shaped and configured so as not to interfere with the moving transfer paper.

As described above, the humidity detection sensor needs to detect and detect the detection distance from the transfer sheet, but the transfer sheet that moves in the image forming apparatus does not always move with a certain behavior. Absent. In addition, there are a plurality of types of transfer papers, which are frequently used in image forming apparatuses and the like, and are named as A6 (105 mm × 148 mm) or B6 (128 mm × 182 mm) according to Japanese Industrial Standards (JIS). There is a transfer paper of a small size called, and there is also a transfer paper of a smaller size, so depending on the size of the transfer paper, the humidity detection sensor passes through the position facing the transfer paper surface. During this time, there is a possibility that the humidity of the transfer paper cannot be accurately detected.
Therefore, a humidity detection sensor (sensor unit) that detects the moisture content of the transfer paper always keeps the detection distance specified according to the behavior of the moving transfer paper constant and also matches the transfer speed of the transfer paper. It is necessary to devise so that it can measure while moving.

  Moisture movement that occurs on the transfer paper is a change in the direction and amount of water vapor, so the installation of a humidity detection sensor (sensor unit) changes the flow of water vapor and captures the original amount of water change. Therefore, the humidity detection sensor needs to have a shape and structure that does not hinder moisture movement.

Means taken to solve the above problems will be described together with the action.
[Solution 1] (corresponding to claim 1)
Solution 1 taken in order to solve the above problem is to transfer the toner image formed on the image carrier to the transfer paper by the image forming operation by the image forming apparatus, and to melt and fix the transferred toner image. Assuming a transfer paper curl determination method for determining the curl of the transfer paper caused by the expansion and contraction accompanying the moisture content change of the heat-pressed transfer paper,
Depending on the difference between the atmospheric humidity measurement value of the space where the transfer paper is placed and the transfer paper surface humidity measurement value obtained by the humidity detection sensor placed close to and opposite the transfer paper surface, the transfer paper Is to guess the curl.

[Work]
The effect | action of the said solution means 1 is demonstrated referring FIG.1, FIG.2, FIG.4 and FIGS. 6-9.
The moisture contained in a substance is largely related to the relative humidity of the surrounding air, although it depends on the type and temperature of the substance. (Masafumi Ueda, “Humidity and Evaporation”, published by Corona (February 2000), p. 31-32, 76-77, 83-84)
If the relationship between the moisture of a substance at a constant temperature and the relative humidity of air in equilibrium with the substance is examined in advance, the moisture of the substance can be obtained by measuring the relative humidity and temperature.
Further, if the humidity of the air in close contact with the object surface and the humidity (moisture) of the object surface are known, it is possible to estimate the dry state of the object and the evaporation state of the moisture from the object surface. If there is a difference in water vapor pressure between the object surface and the surrounding air, movement of water vapor occurs between the object surface and the air side.

If the water vapor pressure on the surface of the object is Es and the water vapor pressure of the air is E, when E <Es, so-called water evaporation occurs in which the water vapor moves from the object surface into the air. On the contrary, when Es <E, water vapor moves from the air side to the object surface, and the water vapor is condensed or absorbed on the object surface. This is a phenomenon that occurs when condensation occurs, but in the case of transfer paper, there is almost no condensation and it is absorbed inside the transfer paper.
That is, if the relative humidity around the transfer paper and the relative humidity in the vicinity of the surface of the transfer paper are clarified, the movement state of the water vapor can be understood, and the curl of the transfer paper can be determined by the difference between them. It becomes.

FIG. 1 shows a transfer in a stopped state when a transfer paper conditioned in a certain environment (having a moisture state higher than the ambient humidity) is left in an environment where the relative humidity is lower than the conditioned environment. It is the graph which caught the humidity change near the surface of paper.
A humidity detection sensor is installed so as to face the upper surface of the stopped transfer paper, and measurement is started. Immediately after the start of measurement, the detected value increases due to water evaporation. After that, the amount of evaporation from the transfer paper decreases due to the balance with the surrounding environment, so the detection value also decreases with the decrease, and the moisture state of the transfer paper tries to keep a balance with the surrounding environment. The amount of change gets smaller and gets closer to the surrounding environment.

On the contrary, as shown in FIG. 2, when the transfer paper contains less moisture than the surrounding environment (transfer paper having a moisture state lower than the ambient environment humidity), the surrounding paper absorbs the surrounding moisture. Therefore, the humidity decreases at the start of detection, and thereafter, the humidity change amount (moisture state) of the transfer paper changes so as to increase. Then, the moisture state of the transfer paper tends to maintain a balance with the surrounding environment, so that the amount of change in moisture gradually decreases and approaches the ambient environment.
In addition, when the difference between the ambient environment and the moisture state contained in the transfer paper is small, or when it is almost compatible with the ambient environment, the amount of change in humidity is also small.

FIG. 4 shows a change in humidity in the vicinity of the surface of the transfer paper when the humidity detection sensor is installed so as to face the upper surface of the transfer paper under the same measurement conditions as in FIG. The humidity change in the vicinity of the surface of the transfer paper when the same transfer paper is reciprocatingly moved directly under the humidity detection sensor under the same measurement conditions as in FIG. FIG. 5 is a graph showing a comparison (see a solid line in FIG. 4). At this time, the measurement distance between the humidity detection sensor and the transfer paper surface was set to 1 mm or less, and the transfer paper moving speed was set to 210 mm / s.
As shown in the graph of FIG. 4, as the time passes, the maximum value of the solid line graph indicating the detected humidity by the transfer paper during passage movement is the dotted line graph indicating the humidity change tendency by the transfer paper at the stop time You can see that they are almost identical.
Therefore, the humidity change due to the transfer paper at the time of stoppage and the humidity change due to the transfer paper at the time of movement are substantially the same, and it can be seen that detection is possible in either situation. The phenomenon described above indicates a state in which a transfer paper containing a large amount of moisture is exposed to a dry environment, that is, a low humidity environment, and vice versa. Needless to say, when exposed to a high-humidity environment, the reverse phenomenon occurs even during movement, as in the stopped state shown in FIG.

FIG. 6 is a graph showing a change tendency of the curl amount generated when the humidity changes near the surface of the transfer paper shown in FIG. The vertical axis in FIG. 6 represents the curl amount by the distance (mm) from the plate surface to the end of the transfer paper when the transfer paper is placed on the horizontal plate.
As shown in FIG. 1, the moisture state of the transfer paper tends to keep a balance with the surrounding environment, so that the amount of change in humidity gradually decreases and becomes a value approaching the surrounding environment. Simultaneously with this state change, the transfer paper curls. As shown in FIG. 6, the edge of the transfer paper gradually warps from the moment it is exposed to the surrounding environment. Thereafter, the warping amount, that is, the curl amount becomes maximum after a certain elapsed time, but it is known that the change tendency is different if the type of the transfer paper is the same but the type is different.

FIG. 7 is a graph showing the change in curl amount for different types of transfer paper having a thickness of about 68 μm, which is the most frequently used in the market, which is called “55k paper” in terms of the continuous quantity unit.
A is a transfer paper called high-quality paper manufactured from a new pulp fiber, and B is a transfer paper called so-called recycled paper manufactured by reusing old paper. When these transfer papers were conditioned in an environment with a humidity of 75% RH and then left to stand in an environment with a humidity of 20% RH, the amount of curl of each transfer paper was compared. It turns out that it becomes a change tendency.
Further, the difference between transfer papers having different thicknesses was confirmed under the same conditions as shown in FIG. As in FIG. 7, A is a transfer paper having a thickness of about 68 μm, C is a transfer paper having a thickness of about 126 μm called “90k paper”, and D is a transfer paper having a thickness of about 128 μm called “110k paper”. It is paper and all are high-quality paper.
From the above, as shown in FIG. 7 and FIG. 8, it can be seen that there is a difference in the amount of change that curls depending on the thickness and type.

The relationship shown in FIG. 9A is established when the results so far are viewed in terms of the relationship between the maximum amount of change when the transfer paper curls and the humidity near the surface of the transfer paper and the ambient environment humidity. In addition, it has been clarified that the difference between the ambient humidity and the humidity in the vicinity of the surface of the transfer paper is that the larger the difference is, the easier the curl is generated, which is a common relationship between the respective surveys.
Therefore, by referring to these relationships, it is possible to determine the occurrence of curling according to the amount of change in humidity.
However, the relationship between them is, for example, that the toner image formed on the image carrier by the image forming operation by the image forming apparatus is transferred, and passes through the fixing device that is heat-pressed to melt and fix the transferred toner image. After that, it appears remarkably, and the moisture of the transfer paper is rapidly evaporated by heating, and the evaporation amount increases. Therefore, the time when the curl occurs is earlier than the time shown in FIGS.

In the case of using such a case, the humidity change amount and curl corresponding to heating are added to the relationship shown in FIG. 9A by adding the conditions when those transfer papers are heated. The relationship with the amount of change is as shown in FIG. Therefore, curl determination at the time of heating can be easily performed based on these relationships.
Therefore, each process condition, for example, the conveyance control unit and the fixing control unit is controlled based on the transfer paper curl determination information, and the transfer paper conveyance speed, conveyance mechanism, and fixing temperature are appropriately set according to the transfer paper curl. By controlling, it is possible to prevent image quality failure and conveyance failure.

[Solution 2] (corresponding to claim 2)
The solution means 2 taken to solve the above problem is that the toner image formed on the image carrier by the image forming operation by the image forming apparatus is transferred to the transfer paper, and the transferred toner image is fused and fixed. Assuming a transfer paper curl determination method for determining the curl of the transfer paper caused by the expansion and contraction accompanying the moisture content change of the heat-pressed transfer paper,
Install a humidity detection sensor at a position facing the transfer paper surface close to the transfer paper transport path,
The humidity measured within the vicinity of the transfer paper transport path detected when there is no transfer paper passing on the transfer paper transport path, and the humidity within the time when the transfer paper passes the position facing the humidity detection sensor. The curling of the transfer paper is estimated according to the difference from the measured value of the transfer paper surface humidity detected by the detection sensor.

[Operation]
The operation of the solving means 2 will be described with reference to FIG. FIG. 3 is a graph showing a result of detecting humidity change in the vicinity of the surface of the moving transfer paper using a heat conduction type humidity detection sensor.
The transfer paper is conditioned to a moisture content of about 9%, and the measurement environment (ambient environment) is an air temperature of 23 ° C. and a humidity of 20% RH. At this time, the measurement distance between the surface of the transfer paper and the humidity detection sensor is set to 1 mm or less, and the transfer speed of the transfer paper is set to 210 mm / s.
When the transfer paper accompanies movement, the diffusion layer fluctuates and the air flow, that is, moisture movement changes depending on the position of the transfer paper surface, so that the humidity detection value also changes. The air flow is generated in a direction opposite to the direction in which the transfer paper moves, and at this time, water evaporated from the transfer paper rides on the flow and flows behind the transfer paper.
Therefore, the front end of the transfer paper with respect to the moving direction is detected with a small amount of water evaporation, and is detected more toward the center of the transfer paper. When the moving speed is constant, it becomes maximum at a certain point, and moisture evaporation from the transfer paper decreases due to the balance with the ambient environmental humidity, so the detection amount also decreases.

As shown in FIG. 3, when the transfer paper starts to pass through the sensor part of the humidity detection sensor, the amount of water evaporation detected is small, and the maximum amount is detected when it passes through the central part. Since the water content itself decreases due to the balance, the detection amount also decreases.
However, in order to grasp these phenomena, as shown in FIG. 3, it is necessary to capture these changes within the time during which the transfer paper passes through the sensor portion, that is, within one second.
This problem can be solved by increasing the detection sensitivity by disposing the sensor part of the humidity detection sensor as close as possible to the surface of the transfer paper (0.1 mm or more and 2 mm or less). It is possible to solve the problem by increasing the detection sensitivity and the response speed by adopting a heat-conducting humidity sensor to which the MEMS technology can be applied. The measurement method uses the fact that the thermal conductivity of the atmospheric gas changes according to the concentration (humidity) of water vapor, and is disclosed in, for example, Japanese Patent No. 2889909 (see paragraph [0081]). By using the existing humidity sensor, it is possible to capture moisture movement (humidity change) between the transfer paper and the surrounding environment with high accuracy and high speed, and the transfer paper passes through the sensor section. It becomes possible to capture the humidity change in the meantime, and the curl of the transfer paper can be determined from the obtained humidity change amount.

  Further, the humidity detection near the surface of the transfer paper also changes depending on the detection direction with respect to the surface of the transfer paper. For example, when the transfer paper is horizontal, it differs depending on whether the detection direction is upward or downward, and also when the transfer paper is vertical. However, these problems can be solved by limiting the above-described measurement distance.

[Embodiment 1] (corresponding to claim 3)
In Embodiment 1, in the transfer paper curl determination method of Solution 2 described above, while humidity detection is performed at a position where the humidity detection sensor is close to and opposed to the transfer paper surface, it is transported and moved with the humidity detection sensor. The distance from the transfer paper surface is kept constant.

[Work]
The movement of water vapor is also referred to as a surface layer because there is a diffusion layer in which water vapor moves by diffusion in a space close to the surface of the object, and this diffusion layer is in close contact with the surface. When moisture evaporates in the atmosphere, it hardly moves by diffusion only in the space other than the diffusion layer, and convection is applied after moving by diffusion. However, even if there is convection, if the water vapor pressure gradient in the diffusion layer can be known, the mass of water vapor evaporated from the surface can be obtained.
That is, by detecting the humidity at a distance close to the transfer paper, it is possible to grasp the moisture evaporation state of the transfer paper without being affected by the surrounding environment.
Therefore, in order to keep the distance between the surface of the transfer paper and the sensor part of the humidity detection sensor constant, by providing a member serving as a guide in the portion constituting the sensor part, the distance is kept constant with respect to the surface of the transfer paper. can do.

[Embodiment 2] (corresponding to claim 4)
Embodiment 2 is to move the humidity detection sensor in accordance with the transfer speed of the transfer paper to be transported in the transfer paper curl determination method of Embodiment 1 described above.
[Work]
In order to keep the distance between the surface of the transfer paper and the sensor part of the humidity detection sensor constant, the part constituting the sensor part moves according to the behavior of the moving transfer paper, and the detection position is set with respect to the surface of the transfer paper. Can change.

[Embodiment 3] (corresponding to claim 5)
Embodiment 3 is the transfer paper curl determination method according to any one of Solution 1, Solution 2, Embodiment 1 or Embodiment 2 described above, and humidity detection is performed at a position where the humidity detection sensor is close to and faces the transfer paper surface. During the process, the sensor part of the humidity detection sensor is projected to be brought close to the surface of the transfer paper.
[Work]
By arranging the sensor unit of the humidity detection sensor in parallel with the surface of the transfer paper and having the sensor unit mounted on the humidity detection sensor face and protrude from the surface of the transfer paper, It is possible to measure by detecting before the flow of water vapor caused by the water movement between the water and the surrounding environment is hindered.

[Embodiment 4] (corresponding to claim 6)
Embodiment 4 is to set the distance between the sensor portion of the humidity detection sensor and the surface of the transfer paper to 0.1 mm or more and 2 mm or less in the transfer paper curl determination method of Embodiment 3 described above.

[Work]
The operation of the fourth embodiment will be described with reference to FIG. FIG. 5 is a graph showing the difference in the amount of change in humidity due to the difference in the measurement distance from the surface of the transfer paper (the distance between the surface of the transfer paper and the sensor unit).
As shown in FIG. 5, when the measurement distance is 3 mm or 5 mm with respect to the surface of the transfer paper, there is almost no difference from the surrounding environment, and moisture movement (humidity change amount) from the transfer paper is captured. However, if it is 2 mm or less, the amount of change in humidity from the transfer paper can be captured. In addition, as described above, when moisture evaporates, the existence of a diffusion layer in which moisture (water vapor) movement is linearly performed from the position where the evaporation is started has already been explained (by Masafumi Ueda, “Measurement of water vapor gradient and diffusion coefficient”, Applied Physics, Vol.25, No.4, published by Japan Society of Applied Physics (1956), p.145, and Masafumi Ueda, “Water evaporation rate by forced convection”, Applied Physics , Vol. 29, No. 7, published by the Japan Society of Applied Physics (1960) p.443).
For example, in the case of a water surface filled with water, the water can constantly move in a certain amount of water vapor, so that when the thickness of the diffusion layer is not affected by wind or the like, it reaches a height region of about 10 mm vertically from the water surface. It can exist, and even if there is an influence of wind, it is said that there is no problem up to about 2-3 mm.

  However, in the case of transfer paper, the moisture content of the transfer paper changes depending on the surrounding environment, and also changes depending on the thickness of the transfer paper. Therefore, in the case of a very small amount of moisture, the thickness region of the diffusion layer becomes small. Depending on the balance between the moisture state of the transfer paper and the surrounding environment, reverse water movement that absorbs moisture in the surrounding environment to the transfer paper occurs. Also in this case, a diffusion layer exists, and the thickness of the region at this time is a region of 2 mm or less in the case of the transfer paper and the surrounding environment. Therefore, since it becomes easy to be influenced by the surrounding environment, it is considered that an accurate moisture state of the transfer paper cannot be grasped.

Therefore, it is most preferable to arrange the sensor unit in an area where the change in the state of moisture movement (humidity change amount) can be captured greatly even under the same conditions, that is, in a space of 2 mm or less from the surface of the transfer paper. Although detection is possible even in a state where it is in contact with the surface of the transfer paper, if it is brought into contact with the surface of the transfer paper that is conveyed at a high speed of 200 mm / sec or more in the image forming apparatus, the surface of the transfer paper In addition to damaging the sensor, the sensor unit may be damaged, and it is necessary to consider the flapping operation of the transfer paper during conveyance. In the image forming apparatus, an allowable range in which the flapping of the transfer paper in the transfer paper transport path is permitted is 0.1 mm or less from the transport path surface. Therefore, it is considered that the measurement distance needs to be 0.1 mm or more away from the surface of the transfer paper.
Therefore, the measurement distance range from the surface of the transfer paper is set to 0.1 mm or more and 2 mm or less.

[Solution 3] (Corresponding to Claim 7)
Solution means 3 devised to solve the above-mentioned problem is that the toner image formed on the image carrier by the image forming operation by the image forming apparatus is transferred to the transfer paper, and the transferred toner image is fused and fixed. Assuming a transfer paper curl determination device that determines curl of transfer paper caused by expansion and contraction due to moisture content change of the heat-bonded transfer paper,
Depending on the difference between the atmospheric humidity measurement value of the space where the transfer paper is placed and the transfer paper surface humidity measurement value obtained by the humidity detection sensor placed close to and opposite the transfer paper surface, the transfer paper Is provided with means for estimating the curl.
[Work]
Since the effect | action regarding the said solution means 3 is the same as the effect | action (refer paragraph [0029]-[0037]) of the said solution means 1, the description is abbreviate | omitted.

[Solution 4] (corresponding to claim 8)
Solution means 4 taken to solve the above-mentioned problem is that the toner image formed on the image carrier by the image forming operation by the image forming apparatus is transferred to the transfer paper, and the transferred toner image is fused and fixed. Assuming a transfer paper curl determination device that determines curl of transfer paper caused by expansion and contraction due to moisture content change of the heat-bonded transfer paper,
Install a humidity detection sensor at a position facing the transfer paper surface close to the transfer paper transport path,
The humidity measured within the vicinity of the transfer paper transport path detected when there is no transfer paper passing on the transfer paper transport path, and the humidity within the time when the transfer paper passes the position facing the humidity detection sensor. A means for estimating the curl of the transfer paper according to the difference from the measured value of the transfer paper surface humidity detected by the detection sensor is provided.
[Work]
Since the operation relating to the solving means 4 is the same as that of the solving means 2 (see paragraphs [0039] to [0041]), description thereof is omitted.

[Embodiment 5] (corresponding to claim 9)
In the fifth embodiment, in the transfer paper curl determination apparatus of the above solution 4, the transfer carried with the humidity detection sensor while the humidity detection sensor is detecting the humidity at a position close to and opposed to the transfer paper surface. It has a holding means for holding the distance from the paper surface constant.
[Work]
Since the effect | action regarding the said Embodiment 5 is the same as the effect | action (refer paragraph [0043]) of the said Embodiment 1, the description is abbreviate | omitted.

[Embodiment 6] (corresponding to claim 10)
Embodiment 6 is that the transfer paper curl determination apparatus according to Embodiment 5 includes a moving unit that integrally moves the humidity detection sensor and the holding unit in accordance with the transport speed of the transported transfer paper.
[Work]
Since the effect | action regarding the said Embodiment 6 is the same as the effect | action of the said Embodiment 2 (refer [action] of a paragraph [0044]), the description is abbreviate | omitted.

[Embodiment 7] (corresponding to claim 11)
In Embodiment 7, in the transfer paper curl determination device according to any one of Solution 3, Solution 4, Embodiment 5, and Embodiment 6, humidity detection is performed at a position where the humidity detection sensor is close to and faces the transfer paper surface. During the process, the sensor part of the humidity detection sensor is projected to be brought close to the surface of the transfer paper.
[Work]
Since the effect | action regarding the said Embodiment 7 is the same as the effect | action of the said Embodiment 3 (refer [action] of a paragraph [0045]), the description is abbreviate | omitted.

[Embodiment 8] (corresponding to claim 12)
Embodiment 8 is to set the distance between the sensor portion of the humidity detection sensor and the surface of the transfer paper to 0.1 mm or more and 2 mm or less in the transfer paper curl determination apparatus of Embodiment 7 described above.
[Work]
Since the effect | action regarding the said Embodiment 8 is the same as the effect | action (refer Paragraphs [0047]-[0049]) of the said Embodiment 4, the description is abbreviate | omitted.

[Solution 5] (Corresponding to Claim 13)
The solution means 5 taken to solve the above-mentioned problem is that a humidity detection sensor installed at a position facing the transfer paper surface in close proximity and the expansion and contraction of the transfer paper based on the humidity detection information output from the humidity detection sensor. And an image forming apparatus having a determination means for determining curl,
The determination means is a difference between an atmospheric humidity measurement value in the apparatus on which the transfer paper is placed and a transfer paper surface humidity measurement value obtained by a humidity detection sensor installed at a position facing the transfer paper surface in close proximity. Accordingly, it is a determination means for estimating the curl of the transfer paper.
[Work]
Since the effect | action regarding the said solution means 5 is the same as the effect | action (refer paragraph [0029]-[0037]) of the said solution means 1, the description is abbreviate | omitted.

[Solution 6] (Corresponding to Claim 14)
The solving means 6 taken to solve the above problems includes a humidity detection sensor installed at a position facing the surface of the transfer paper conveyed on the transfer paper conveyance path in close proximity to the humidity, and the humidity output from the humidity detection sensor. On the premise of an image forming apparatus having determination means for determining curl of transfer paper based on detection information,
The determination means measures the atmospheric humidity measured around the conveyance path when the transfer paper is not being conveyed, and the transfer paper surface humidity measurement obtained by a humidity detection sensor installed at a position facing the transfer paper in the vicinity. This is a determination means for estimating the curl of the transfer paper according to the difference from the value.
[Work]
Since the operation relating to the solving means 6 is the same as that of the solving means 2 (see paragraphs [0039] to [0041]), the description thereof is omitted.

[Embodiment 9] (corresponding to claim 15)
In the ninth embodiment, in the image forming apparatus of the solving means 6, while the humidity detection sensor is performing humidity detection at a position close to and opposed to the transfer paper surface, the transfer paper surface conveyed with the humidity detection sensor And holding means for holding the distance constant.
[Work]
Since the effect | action regarding the said Embodiment 9 is the same as the effect | action (refer paragraph [0043]) of the said Embodiment 1, the description is abbreviate | omitted.

[Embodiment 10] (corresponding to claim 16)
Embodiment 10 is that in the image forming apparatus of Embodiment 9 described above, the humidity detection sensor and the holding unit have a moving unit that integrally moves in accordance with the conveyance speed of the transfer paper to be conveyed.
[Work]
Since the effect | action regarding the said Embodiment 10 is the same as the effect | action of the said Embodiment 2 (refer [action] of a paragraph [0044]), the description is abbreviate | omitted.

[Embodiment 11] (Corresponding to Claim 17)
In Embodiment 11, in the image forming apparatus according to any one of Solution 5, Solution 6, Embodiment 9, and Embodiment 10, humidity detection is performed at a position where the humidity detection sensor is close to and faces the transfer paper surface. In the meantime, the sensor part of the humidity detection sensor is projected so as to be close to the surface of the transfer paper.
[Work]
Since the effect | action regarding the said Embodiment 11 is the same as the effect | action of the said Embodiment 3 (refer [action] of a paragraph [0045]), the description is abbreviate | omitted.

[Embodiment 12] (corresponding to claim 18)
Embodiment 12 is to set the distance between the sensor portion of the humidity detection sensor and the transfer paper surface to 0.1 mm or more and 2 mm or less in the image forming apparatus of Embodiment 11 described above.
[Work]
Since the effect | action regarding the said Embodiment 12 is the same as the effect | action (refer Paragraphs [0047]-[0049]) of the said Embodiment 4, the description is abbreviate | omitted.

[Embodiment 13] (corresponding to claim 19)
In Embodiment 13, in the image forming apparatus according to any one of Solution 5, Solution 6, and Embodiments 9 to 12, the control means for controlling the operation of the entire image forming apparatus is configured such that the transfer paper is a humidity detection sensor. When the position does not pass through the position, the environmental control condition in the image forming apparatus is determined according to the atmospheric humidity measurement value obtained by the humidity detection by the humidity detection sensor.
[Work]
When the transfer sheet does not pass through the position facing the humidity detection sensor, the control means for controlling the operation of the entire image forming apparatus uses the value obtained by the humidity detection by the humidity detection sensor as the environment in the image forming apparatus. It is possible to expand to control conditions.

The effects of the present invention are summarized according to the claims as follows.
(1) Inventions according to Claims 1, 7, and 13 According to the inventions according to Claims 1, 7, and 13, a determination criterion based on “a relationship between a humidity change amount and a curl amount of a transfer sheet”. (See FIG. 9), the curl amount of the transfer paper can be estimated. As a result, by setting and controlling each process condition of the image forming apparatus in accordance with the curl amount of the transfer paper, it is possible to prevent image quality defects and conveyance defects from occurring.

(2) Inventions according to Claims 2, 8 and 14 According to the inventions according to Claims 2, 8, and 14, the transfer paper is controlled by accurately determining the curl amount of the transfer paper in a short time. Transport control and image control corresponding to each sheet can be performed. As a result, in an image forming apparatus that is transported at a high speed, it is possible to prevent image quality defects and transport defects.

(3) Inventions according to Claims 3, 9 and 15 According to the inventions according to Claims 3, 9 and 15, detection is performed at a distance close to the surface of the transfer paper while following the behavior of the transfer paper. By detecting the moisture state of the transfer paper more accurately without being affected by the surrounding environment, it becomes possible to detect the humidity change due to moisture generated from the surface of the transfer paper with high accuracy. As a result, it is possible to prevent image quality defects and conveyance defects from occurring in an image forming apparatus that is conveyed at high speed regardless of the type of transfer paper and the passing position.

(4) Inventions according to Claims 4, 10 and 16 According to the inventions according to Claims 4, 10 and 16, by moving the humidity detection sensor in accordance with the transport speed of the transfer paper transported. Regardless of the type and size of the transfer paper, it is possible to more accurately detect the moisture state of the transfer paper. As a result, in an image forming apparatus that is transported at a high speed, it is possible to prevent image quality defects and transport defects.

(5) Inventions according to claims 5, 11 and 17 According to the inventions according to claims 5, 11 and 17, the sensor part of the humidity detection sensor is projected so as to be close to the surface of the transfer paper. As a result, an effective structure that does not hinder the flow of water vapor is provided, so that highly accurate detection is possible, and the moisture state of the transfer paper can be detected more accurately. As a result, it is possible to prevent image quality defects and conveyance defects from occurring in an image forming apparatus that is conveyed at high speed.

(6) Inventions according to claims 6, 12 and 18 According to the inventions according to claims 6, 12 and 18, the distance between the sensor portion of the humidity detection sensor and the transfer paper surface is defined. Thus, it is possible to more accurately detect the moisture state of the transfer paper without being affected by the surrounding environment. As a result, in an image forming apparatus that is transported at a high speed, it is possible to prevent image quality defects and transport defects.

(7) The invention according to claim 19 According to the invention according to claim 19, the transfer paper is inserted between the transfer paper and the transfer paper during continuous printing, or when the power of the image forming apparatus is turned on. It was obtained because the environment in the image forming apparatus can be grasped from the humidity value (atmosphere humidity value) obtained by the humidity detection by the humidity detection sensor when not passing through the position facing the humidity detection sensor. By controlling the environment in the image forming apparatus according to the humidity value, the inside of the image forming apparatus can be maintained in an optimal image forming control state. As a result, in the image forming apparatus, it is possible to prevent the occurrence of an image quality defect or a conveyance defect.

Hereinafter, each embodiment of the present invention will be described with reference to FIGS.
[Embodiment 1]
First, Embodiment 1 of the present invention will be described with reference to FIGS.
FIG. 10 is a schematic diagram of a transfer paper curl determination apparatus that determines the occurrence of curl of the transfer paper according to Embodiment 1 of the present invention.
The humidity detection sensor 11 of the transfer paper curl determination apparatus shown in FIG. 10 has a sensor unit 11a that detects the humidity (water evaporation) of the transfer paper P, and a substrate unit 11b that is electrically connected to the sensor unit 11a. The substrate unit 11b and the control unit 13 are electrically connected via the signal line 22. The sensor unit 11a of the humidity detection sensor 11 employs a heat conduction type humidity sensor using MEMS (Micro Electro Mechanical System) technology.
The measurement method utilizes the fact that the thermal conductivity of the atmospheric gas changes according to the concentration (humidity) of water vapor, and is disclosed in, for example, Japanese Patent No. 2889909 (see paragraph [0081]). It is possible to use a humidity sensor capable of detecting temperature with a single structure.

The substrate portion 11b may be anything as long as the sensor portion 11a can be fixed and an electric signal can be taken out from the sensor portion 11a. However, an electronic circuit substrate processed with a generally used glass epoxy material or the like Is preferably used. The sensor unit 11 a is bonded to the substrate unit 11 b, joined to the substrate unit 11 b by a fine metal wire (not shown) or welding, and is electrically connected to the control unit 13 through the signal line 22.
At this time, the sensor unit 11 a is mounted in a state of protruding so as to be closest to the surface of the transfer paper P among the constituent members of the humidity detection sensor 11. As a result, the flow of moisture movement from the transfer paper P reaches the sensor unit 11a earliest, so that the transfer is not hindered by the constituent members (for example, the substrate unit 11b) of the humidity detection sensor 11. Moisture movement occurring between the paper P and the surrounding environment can be detected well.
In addition, by using a heat-conducting humidity sensor that applies MEMS technology, the sensor unit 11a can be reduced in size to a size of several millimeters and thin, and humidity detection can be performed accordingly. Since the entire sensor 11 can be made small, it can be installed even in a narrow space, which is very preferable.

FIG. 11 is a block diagram of the control unit 13 in the transfer paper curl determination device according to the first embodiment of the present invention.
A detection signal detected by the humidity detection sensor 11 is received by the A / D conversion circuit 13a and converted into a digital signal, and then converted into a humidity value (humidity measurement value) by the humidity calculation circuit 13b.
The converted humidity value is switched by the measurement switching circuit 13c between the atmospheric humidity value of the space in which the transfer paper is placed or the transfer paper surface humidity value in a state close to the transfer paper, and in the space in which the transfer paper is placed. In the case of the atmospheric humidity value, it is stored in the first storage area 13d, and in the case of the transfer sheet surface humidity value in a state close to the transfer sheet, it is stored in the second storage area 13e, and the first and second storage areas 13d, After the respective data are stored in 13e, the difference calculation circuit 13f calculates the difference value (humidity change amount) of the humidity data.
The calculated difference value is checked against the “relation between the difference value of humidity data and the curl amount” stored in the determination parameter section 13g, and the occurrence of curl is determined.

FIG. 12 is a schematic diagram illustrating a state in which moisture movement from the transfer paper P is captured by the humidity detection sensor 11 installed so as to be close to the humidity-controlled transfer paper P. The sensor unit 11a of the humidity detection sensor 11 is set so that the distance (interval) between the surface of the transfer paper P is 0.1 mm or more and 2 mm or less.
FIG. 13 is a graph showing the relationship between the sensor output of the humidity detection sensor 11 (sensor unit 11a) and time shown in FIG. 12, and the humidity of the transfer paper conditioned in a high humidity environment is lower than that in the humidity control environment. The moisture behavior of the transfer paper that occurs when left in the surrounding environment is indicated by the amount of change in relative humidity detected in a predetermined space near the surface of the transfer paper.

14A and 14B are schematic views of a typical humidity detection sensor unit in the transfer paper curl determination apparatus according to the first embodiment of the present invention. FIG. 14A is a perspective view, FIG. 14B is a front view, and FIG. It is AA sectional drawing of).
The humidity detection sensor 11 is provided with a guide member 11c that defines a detection distance from the surface of the transfer paper P, thereby defining a measurement distance from the surface of the transfer paper to the sensor unit 11a. The measurement distance at this time is preferably set to 0.1 mm or more and 2 mm or less, but considering the case where the difference between the humidity near the surface of the transfer paper and the ambient environment humidity is small, the difference in humidity change is Most preferably, it should be 1 mm or less, which can be grasped the largest.
The guide member 11c has a leading end bent into an L-shape, thereby improving the adhesion with the surface of the transfer paper P and ensuring the stability at the time of adhesion. Further, the sensor unit 11a can directly contact the surface of the transfer paper P. It also has a role to protect from touching.

  The guide member 11c may be made of any material, but it is preferably not affected by the ambient temperature and does not adsorb moisture, such as fluorine-based resin (Teflon (registered trademark)) or polycarbonate. It is preferable to be composed of a plastic resin such as Still, if the guide member 11c is too close to the sensor portion 11a, the detected value may change due to the temperature of the guide member 11c or the evaporating moisture adhering to the surface of the guide member. It is preferable to attach away from the part 11a.

[Embodiment 2]
A second embodiment of the present invention will be described with reference to FIG. FIG. 15 is a humidity detection sensor unit in the transfer paper curl determination apparatus according to the second embodiment, and is a schematic diagram showing a representative one in consideration of detection of the moving transfer paper surface, (a) is a perspective view, (b) is a front view, (c) is a BB sectional view of (b).
The basic configuration of the humidity detection sensor unit according to the second embodiment is the same as that of the first embodiment shown in FIG.
The difference from the first embodiment is the shape of the guide member 11c ′. Since the guide member 11c ′ is brought into close contact with the surface of the moving transfer paper P, when the moving transfer paper P approaches the guide member 11c ′ in a shape having a corner as shown in FIG. The portion that contacts the member 11c ′ not only damages the transfer paper but also damages the humidity detection sensor unit. Therefore, as shown in FIG. When the transfer paper P approaches the guide member 11c ′ due to the movement by floating the end of the guide member 11c ′ (the front end or the rear end in the transfer paper movement direction). , Have a role to prevent collisions. Further, even when the humidity detection sensor unit is moved together with the transfer paper P, since the contact area is small, a smooth operation is possible.

  The humidity detection sensor unit described above is merely representative, and any shape can be used as long as the measurement distance from the surface of the transfer paper P can be kept constant and the movement of the transfer paper P is not hindered. It may be. For example, a roller may be provided at both ends of the guide member so that the guide member can be easily moved on the surface of the transfer paper (see FIG. 21), a measurement distance adjustment mechanism for finely adjusting the measurement distance, and the like. May be given.

[Embodiment 3]
A third embodiment of the present invention will be described with reference to FIGS. 16 and 17.
First, the control unit and the display panel in the transfer paper curl determination apparatus of this embodiment will be described with reference to FIG. FIG. 16 is a block diagram of a control unit and a display panel of the transfer paper curl determination apparatus.
The third embodiment is characterized by the control unit and the display panel in the transfer paper curl determination device, and the other configurations are the same as those of the first embodiment shown in FIGS. 10 and 11. The overlapping description is omitted.
In FIG. 16, the same reference numerals are given to those having the same functions as those in the first embodiment shown in FIG. 11. In addition, description of structural blocks that are basically indispensable in terms of the device configuration such as a power source for driving the transfer paper curl determination device and a power switch associated therewith is omitted.

First, in order to measure the surrounding environment where the transfer paper P is placed, a signal is transmitted from the first switch 19d to measure the humidity of the surrounding environment. The measured humidity value (atmospheric humidity measurement value) is sent to the first storage area 13 d of the control unit 13. Subsequently, in order to measure the humidity on the surface of the transfer paper, a signal is transmitted from the second switch 19e to measure the humidity near the surface of the transfer paper. The measured humidity value (transfer paper surface humidity measurement value) is also sent to the second storage area 13e of the control unit 13.
The curl occurrence determination based on the difference value of the humidity data is performed in the same manner as in the first embodiment (FIG. 11). If the result suggests the occurrence of curl, the display panel 19 is curled. A process for transmitting the effect is performed. Any means may be used for transmission, and an LED light emitting element 19b may be provided on the display panel 19 to light up when curling occurs, or a liquid crystal panel 19a may be provided to display a message, and a buzzer 19c is provided. You may make a sound. Needless to say, the calculated result may be displayed on a liquid crystal panel or an LED segment as it is.

Next, a curl determination method common to the first to third embodiments of the present invention will be described with reference to FIG. FIG. 17 is a flowchart for explaining a curl determination method for transfer paper.
First, an ambient humidity value (atmosphere humidity measurement value) when there is no transfer paper at a position facing the humidity detection sensor 11 (sensor unit 11a) is acquired (measured) (step S1). Subsequently, when there is a transfer sheet at a position facing the humidity detection sensor 11 (sensor unit 11a), a transfer sheet surface humidity value (transfer sheet surface humidity measurement value) in the vicinity of the transfer sheet surface is acquired (measured). (Step S2).
Then, the controller 13 calculates the humidity change x by subtracting the ambient environment humidity value and the transfer paper surface humidity value (step S3), and stores them in the determination parameter section 13g of the controller 13 in the next step S4. The curl amount at the humidity change x is determined based on the relationship between the humidity change amount and the transfer sheet curl amount (see FIG. 9).

[Embodiment 4]
A fourth embodiment of the present invention will be described with reference to FIGS. FIG. 18 is a schematic diagram illustrating the image forming apparatus according to the present embodiment. FIG. 19 is a block diagram illustrating a control system of the image forming apparatus according to the present embodiment.
The image forming apparatus 1 according to the fourth embodiment shown in FIG. 18 includes a charging device 3, a writing device (exposure device) 4, a developing device 5, a primary transfer device 6, and a cleaning device around a photosensitive drum 2 as an image carrier. 7 is arranged for a plurality of colors (four colors in the figure), and an endless transfer belt 40 is arranged at a portion in contact with each photosensitive drum 2. A cleaning device 42 is disposed on the downstream side of the transfer belt 40, a secondary transfer device 41 is disposed on the upstream side, and the fixing device 8 is disposed on the upper side of the secondary transfer device 41.

During the image forming operation of the image forming apparatus 1, the surface of the photosensitive drum 2 that is rotationally driven at a predetermined process speed is uniformly charged by the charging device 3, and the image information of the document read by the reading device (not shown) Accordingly, the writing device 4 performs exposure to form an electrostatic latent image, and then the developing device 5 develops the toner (developer) to form a toner image on the photosensitive drum 2 for each color. Is done.
The toner images of a plurality of colors formed on the respective photosensitive drums 2 are sequentially superimposed and transferred by the primary transfer device 6 onto the transfer belt 40 that is rotationally driven at a predetermined process speed. Then, the toner image carried on the transfer belt 40 by the secondary transfer device 41 is transferred to the transfer paper P transported from the paper feed cassette 9 to the secondary transfer site through the transfer paper transport path 10 at a predetermined timing. Superimposed transfer.
The transfer paper P onto which the toner image has been transferred is conveyed to the fixing device 8 and heated and pressed between the fixing roller 8a and the pressure roller 8b, whereby the toner image is fixed on the transfer paper P. The transfer paper P on which the toner image is fixed is discharged to the outside by a paper discharge roller (not shown).

After the toner image on the photosensitive drum 2 is transferred to the transfer belt 40, the toner remaining on the surface of the photosensitive drum 2 is removed by the cleaning blade 7a of the cleaning device 7 and used for the next image formation. .
Further, after the toner image on the transfer belt 40 is transferred to the transfer paper P, the remaining toner is removed from the surface of the transfer belt 40 by the cleaning blade 42a of the cleaning device 42 and used for the next image formation.
In the image forming apparatus 1, a humidity detection sensor 11 is disposed near the upper portion of the paper feed cassette 9, and the periphery of the paper feed cassette 9 before the transfer paper P is fed from the paper feed cassette 9. The humidity in the environment is detected in advance, and the humidity (moisture evaporation) in the vicinity of the surface of the transfer paper P when printing is started and paper is fed from the paper feed cassette 9 is detected.
In FIG. 18, reference numeral 12 denotes a paper feed roller.

As shown in FIG. 19, the control unit (measuring unit) 13 performs “humidity change amount” stored in advance in the sensor output (humidity value) input from the humidity detection sensor 11 and the memory 14 according to the flowchart shown in FIG. 17. And the curl amount of the transfer paper ”(the relationship shown in FIG. 9), the curl amount of the transfer paper P fed from the paper feed cassette 9 is determined.
The CPU 15 as a control unit that controls the entire operation of the image forming apparatus 1 controls the conveyance control unit 16 and the fixing control unit 17 based on the curl determination information of the transfer paper P output from the control unit 13 to transfer the transfer paper. The conveyance speed and fixing temperature of P are controlled. In addition, the CPU 15 controls the environment control unit 18 according to the humidity value of the surrounding environment output from the control unit 13 and rotates a fan (not shown) provided in the image forming apparatus 1. (Shown in detail).

[Embodiment 5]
Embodiment 5 of the present invention will be described with reference to FIGS. FIG. 20 is a schematic diagram showing the image forming apparatus according to the present embodiment, and FIG. 21 is an installation structure when the humidity detection sensor (having rollers at both ends of the guide member) described in the second embodiment is applied. (A) is a front view, (b) is a CC cross-sectional view thereof.
In the fifth embodiment, as shown in FIG. 20, the humidity detection sensor 11 is disposed in the vicinity of the transfer paper transport path 10 between the paper feed cassette 9 and the secondary transfer device 41, and the paper feed cassette 9, the curl of the transfer paper P conveyed through the transfer paper conveyance path 10 is determined. Other configurations and operations are the same as those in the fourth embodiment shown in FIGS.

As shown in FIG. 21, the humidity detection sensor 11 has a predetermined distance from the transfer paper P at the intermediate portion of a rod-shaped shaft 21 that rotatably supports a pair of guide rollers 20a and 20b as holding means. It is installed near the transfer paper conveyance path 10 so as to face each other. Each of the guide rollers 20a and 20b is in contact with the surface of the transfer paper P being conveyed, and always maintains a constant distance between the humidity detection sensor 11 and the surface of the transfer paper P. The sensor unit 11a of the humidity detection sensor 11 is set such that the distance (interval) between the surface of the transfer paper is 0.1 mm or more and 2 mm or less.
In addition, by using a heat conduction type humidity sensor applying MEMS technology as the sensor unit 11a, the shape of the humidity sensor itself can be reduced to a size of several millimeters, and the humidity detection sensor 11 is accordingly adjusted. Since the whole can be made small, it can be installed even in a narrow space. Further, the guide rollers 20a and 20b are rotatably provided on the shaft 21 so as to be positioned on both sides of the sensor unit 11a, and the transfer paper P is partially pressed, so that the sensor unit 11a and the transfer paper P are separated. The distance is always kept constant, and the collision between the transfer paper P and the sensor unit 11a can be prevented.

If the distance between the pair of guide rollers 20a and 20b and the sensor portion 11a of the humidity detection sensor 11 is too short, there is a possibility that the moisture movement between the transfer paper P and the surrounding environment may be hindered. However, if it is separated too much, the transfer paper P may bend and the distance from the sensor unit 11a cannot be kept constant, and the transfer paper P may be caught by the sensor unit 11a and cause a conveyance failure. is there. Therefore, each guide roller 20a, 20b is preferably installed at a position about 30 to 50 mm away from the sensor portion 11a of the humidity detection sensor 11.
Further, in order to more accurately grasp the time during which the transfer paper P passes through the position facing the sensor unit 11a of the humidity detection sensor 11, when the transfer paper P passes in the vicinity of the sensor unit 11a. A reactive electrical switch (not shown) is provided to detect the humidity while the switch is on due to the passage of the transfer paper P, and transfer is performed from the change in humidity value acquired during the period when this switch is on. The curl amount of the paper P may be obtained. The switch to be used is most preferably a light-reflective photosensor switch that can detect the presence of transfer paper, a micro switch that can be turned on / off with a low load, or the like.

  In this way, the curl amount of the transfer sheet P to be conveyed can be determined. Therefore, in the image forming apparatus according to the fifth embodiment, the CPU 15 (see FIG. 19) of the image forming apparatus according to the fourth embodiment. Similarly to the case, the conveyance control unit 16 and the fixing control unit 17 are controlled based on the transfer sheet curl determination information output from the control unit 13, and the transfer sheet conveyance speed and fixing are controlled according to the curl amount of the transfer sheet. Each temperature can be appropriately controlled.

[Embodiment 6]
A sixth embodiment of the present invention will be described with reference to FIG. 22A and 22B are schematic views showing the installation structure of the humidity detection sensor in the image forming apparatus of the present embodiment, where FIG. 22A is a plan view and FIG. 22B is a side view thereof.
In the sixth embodiment, as shown in FIG. 22, the humidity detection sensor 11 is fixed to the back surface (transfer paper conveyance path side) on the front end side of a thin plate-like sensor mounting member 23 as a holding unit, and the transfer paper conveyance path. It is installed near (not shown), and the sensor mounting member 23 is rotatably inserted in the middle part of the rod-shaped shaft 21.
A bar-shaped guide member 23a is provided integrally on the side surface on the base end side of the sensor mounting member 23 so that the transfer paper moving on the transfer paper conveyance path can be brought into contact with the front end portion. The guide member 23 a is shorter than the sensor mounting member 23 and is disposed below the sensor mounting member 23 (on the transfer paper conveyance path side). 22A and 22B, the left side direction (arrow direction) is the transfer paper P conveyance direction. The configuration of the humidity detection sensor 11 is the same as that described in the first embodiment (see FIG. 10).

According to the installation structure of the humidity detection sensor 11 in the image forming apparatus according to the sixth embodiment, when the transfer paper P moves on the transfer paper conveyance path (not shown), the leading end of the guide member 23a is the surface of the transfer paper. , The tip end side of the sensor mounting member 23 that is rotatably inserted in the shaft 21 is rotated upward (on the opposite side to the transfer paper conveyance path), and the humidity detection sensor 11 is moved from the surface of the transfer paper. They are held apart by a predetermined distance (with a predetermined interval). In the present embodiment, the shape and angle of the guide member 23a and the sensor mounting member 23 are set so that the distance between the sensor unit 11a of the humidity detection sensor 11 and the surface of the transfer paper P is 1 mm or less.
Since the tip of the guide member 23a contacts the transfer paper P while being rubbed, it is desirable that the guide member 23a has a rounded shape so as not to damage the transfer paper. Further, it is preferable that the sensor attachment member 23 inserted rotatably in the shaft 21 is rotated with a light force by reducing the frictional force (friction coefficient). Further, by reducing the weight of the sensor mounting member 23, it is possible to operate with a lower load. Therefore, the sensor mounting member 23 is preferably formed using a plastic material.

  As a result, even if a change occurs in the behavior of the transfer sheet P being moved (during conveyance) at a position facing the humidity detection sensor 11, the sensor mounting member 23 and the guide member 23a are moved up and down in accordance with the movement of the transfer sheet. Therefore, the distance between the transfer paper surface and the sensor unit 11a is always kept constant, and the humidity detection sensor 11 does not collide with the transfer paper. Furthermore, since it is possible to measure the humidity change of the transfer paper surface without pressing down the transfer paper P, the transfer paper P cannot be pressed down, and even in a place where there is a certain change in the behavior of the transfer paper, The curl amount of the transfer paper can be determined.

[Embodiment 7]
A seventh embodiment of the present invention will be described with reference to FIG. FIG. 23 is a schematic diagram showing an installation structure of a humidity detection sensor in the image forming apparatus of the present embodiment, where (a) is a plan view and (b) is a side view thereof. In FIG. 23, members having the same functions as those of the sixth embodiment shown in FIG.
In the seventh embodiment, as shown in FIG. 23, a pair of slide guide members 24a and 24b are installed on the upper side (opposite side of the transfer paper transport path) on both sides of the transfer paper transport path (not shown). In order to move both ends of the shaft 21 movably in the groove 24c formed in the slide guide members 24a and 24b along the transfer paper conveyance direction, and to move the shaft 21 along the transfer paper conveyance direction. A driving belt 26 and a motor 25 for driving the driving belt 26 are installed. Thus, the slide guide members 24a and 24b having the groove 24c, the motor 25, and the drive belt 26 constitute a sensor attachment member 23 to which the humidity detection sensor 11 is fixed and a moving means for moving the guide member 23a. In FIGS. 23A and 23B, the left direction (arrow direction) in the figure is the transfer paper P conveyance direction.

Further, as shown in FIG. 23B, the passage of the transfer paper is detected on the side opposite to the slide guide members 24a and 24b with respect to the transfer paper P conveyed on the transfer paper conveyance path (not shown). When the photosensor 27 is provided and the transfer paper is conveyed to the vicinity of the slide guide members 24a and 24b and the photosensor 27 detects the transfer paper P, the motor 25 rotates in accordance with the transfer speed of the transfer paper. The shaft 21 to which the humidity detection sensor 11 is attached is moved in accordance with the conveyance speed of the transfer paper P along the groove portion 24c by the drive belt 26 that is rotated by a number and is rotated in response thereto.
The detection means for detecting the passage of the transfer paper P may be anything as long as it can detect the transfer paper in addition to the photo sensor 27, and may be a mechanically operated switch, for example.

  As a result, the sensor mounting member 23 to which the humidity detection sensor 11 is fixed moves up and down in accordance with the behavior of the transfer paper P, the distance between the transfer paper surface and the sensor portion 11a is always kept constant, and the transfer paper. Since the humidity detection sensor 11 can be moved in accordance with the moving speed of the transfer paper, even when a transfer paper of a small size (for example, A6 plate, B6 plate, etc.) is detected or the transfer paper is moved at a high speed. It is possible to secure a sufficient time for determining the curl amount of the transfer paper.

[Embodiment 8]
An eighth embodiment of the present invention will be described with reference to FIG. FIG. 24 is a schematic side view showing the installation structure of the humidity detection sensor in the image forming apparatus of this embodiment.
When almost no up and down behavior of the transfer paper P transported through the transfer paper transport path occurs, the transfer paper P is installed above the transfer paper transport path 10 so that the transfer paper P is transported as shown in FIG. The humidity detection sensor 11 may be fixed to the back side (transfer paper conveyance path side) of the thin plate-shaped sensor mounting member 28. In FIG. 24, the left direction (arrow direction) in the figure is the transfer paper P conveyance direction.
Also in this case, the distance between the sensor mounting member 28 and the transfer paper conveyance path 10 is set so that the distance between the sensor unit 11a of the humidity detection sensor 11 and the surface of the transfer paper P is 0.1 mm or more and 2 mm or less. Adjust the distance.

[Embodiment 9]
Embodiment 9 of the present invention will be described with reference to FIG. FIG. 25 is a flowchart for explaining the operation of the image forming apparatus according to the present embodiment.
When a plurality of transfer papers continuously pass through the transfer paper conveyance path as in the case of continuously feeding the transfer paper and performing continuous printing (continuous image formation), the image forming apparatus depends on the moisture content of the transfer paper. The environment inside changes. Therefore, in the ninth embodiment, the environmental control condition in the image forming apparatus is determined according to the value obtained by the humidity detection by the humidity detection sensor 11 when the transfer paper does not pass through the position facing the humidity detection sensor 11. I decided to decide.

The operation of the image forming apparatus according to the ninth embodiment will be described with reference to FIG.
First, in step S11, it is determined whether the image forming apparatus is turned on (when the power is turned on) or not. When the power is turned on (step S11: Yes), the environmental humidity value at that time is acquired, and environmental control is performed using the environmental humidity value (step S12).
Specifically, in the control system shown in FIG. 19, the control unit 13 acquires the environmental humidity value in the apparatus based on the sensor output from the humidity detection sensor 11. The CPU 15 controls the environmental control unit 18 based on the environmental humidity value output from the control unit 13 and controls a fan motor (not shown) that rotates a fan (not shown) provided in the apparatus. Thereby, the environment in the apparatus is controlled by the airflow generated by the fan that rotates at a predetermined rotational speed.

  If the power is not turned on in step S11 (step S11: No), it is determined whether the printing operation (image forming operation) is started or not (step S13). When the printing operation is started in step S13 (step S13: Yes), it is determined whether or not the transfer paper is passing the position facing the humidity detection sensor 11 (step S14). In step S14, when the transfer sheet is passing the position facing the humidity detection sensor 11 (step S14: Yes), the process (transfer sheet surface humidity value) of step S2 in the flowchart in the third embodiment shown in FIG. Thereafter, the process of the next step S3 of this flowchart is executed.

  In step S14, when the transfer sheet is not passing through the position facing the humidity detection sensor 11 (step S14: No), when the printing operation is not started in step S13 (step S13: No), and step S12. After the environmental control in the apparatus is performed, the process of step S1 (acquisition of the ambient environmental humidity value when there is no transfer paper) in the flowchart in the third embodiment shown in FIG. 17 is performed. The processing of the next step S2 of this flowchart is executed, and the curl amount at the humidity change amount x is determined from the parameter based on the “relation between the humidity change amount and the curl amount of the transfer paper” shown in FIG.

The determination as to whether or not the transfer paper is passing through the position facing the humidity detection sensor 11 is provided with, for example, an electrical switch that reacts when the transfer paper passes through the position facing the humidity detection sensor 11. Can be performed. In addition, it is not necessary to detect the ambient humidity value between the passages of the transfer paper every time. The number of continuous prints is defined, and between the passages of the transfer paper after the prescribed number of sheets is printed. The ambient humidity value may be detected.
In each of the above-described embodiments, the determination of the curl amount of the transfer paper onto which the toner image of the image forming apparatus is transferred has been described, but other than this, for example, the paper making process of paper, cardboard or edible dry seaweed The present invention can be similarly applied when determining the curl amount in a manufacturing process or the like.
Furthermore, the moisture content of the transfer paper and the thickness of the transfer paper can be obtained by using the present invention in combination with the invention according to Japanese Patent Application No. 2008-007819 or Japanese Patent Application No. 2007-205693, which corresponds to the prior application of the applicant. Can be detected at the same time, and control can be performed according to the detected values.

Near the surface of the stopped transfer paper when the humidity-controlled transfer paper (transfer paper having a moisture state higher than the ambient humidity) is left in an environment having a relative humidity lower than the humidity-controlled environment. It is a graph which shows the humidity change. Near the surface of the stopped transfer paper when the humidity-controlled transfer paper (transfer paper having a moisture state lower than the ambient humidity) is left in an environment having a relative humidity higher than the humidity-controlled environment. It is a graph which shows the humidity change. These are graphs showing the humidity change in the vicinity of the surface of the transfer paper when the conditioned transfer paper (transfer paper having a moisture state higher than the ambient environmental humidity) moves and passes. Compare the humidity change near the surface of the transfer paper when the transfer paper is reciprocally moving under the humidity detection sensor and the humidity change near the surface of the transfer paper when it is stopped. It is the shown graph. These are graphs showing the amount of change in humidity that can be detected when the measurement distance between the humidity detection sensor (sensor unit) and the surface of the transfer paper is changed. These are graphs showing a change tendency of the curl amount generated when the moisture state of the transfer paper changes. Is a graph showing the change tendency of the amount of curl generated when the moisture state changes between transfer paper (A) manufactured from new pulp fibers and recycled transfer paper (B) manufactured by recycling used paper. is there. These are graphs showing the change tendency of the curl amount generated when the moisture state changes for transfer papers having different thicknesses. These are graphs showing the relationship between the humidity change amount and the curl change amount in the transfer paper, where (a) shows the case of non-heating, and (b) shows the case of heating. FIG. 3 is a schematic diagram of a transfer paper curl determination apparatus that determines occurrence of curl of a transfer paper according to Embodiment 1 of the present invention. These are the block diagrams of the control part in the transfer paper curl determination apparatus of Embodiment 1 of this invention. These are the schematic diagrams which show a mode that the humidity detection sensor installed adjacent to the transfer paper is catching the moisture movement from a transfer paper. Shows the moisture behavior of the transfer paper that occurs when the transfer paper conditioned in a high humidity environment is left in an ambient environment with a lower humidity than the humidity control environment, and shows the amount of relative humidity change detected near the surface of the transfer paper. It is a graph. FIG. 4 is a schematic diagram of a typical humidity detection sensor unit in the transfer paper curl determination device according to the first embodiment of the present invention, where (a) is a perspective view, (b) is a front view, and (c) is a view in (b). It is AA sectional drawing. These are the typical diagrams of the typical humidity detection sensor unit in the transfer paper curl determination apparatus of Embodiment 2 of this invention, (a) is a perspective view, (b) is a front view, (c) is (b). It is BB sectional drawing. These are the block diagrams of the control part and display panel in the transfer paper curl determination apparatus of Embodiment 3 of this invention. These are the flowcharts which show the curl determination method of the transfer paper common to Embodiments 1-3 of this invention. These are the schematic diagrams which show the image forming apparatus by Embodiment 4 of this invention. These are the block diagrams explaining the control system of the image forming apparatus by Embodiment 4 of this invention. These are the schematic diagrams which show the image forming apparatus by Embodiment 5 of this invention. These are the schematic diagrams which show the installation structure at the time of applying the humidity detection sensor (what provided the roller at the both ends of the guide member) by Embodiment 2 of this invention, (a) is a front view, (b) is ( It is CC sectional drawing of a). These are the schematic diagrams which show the installation structure of the humidity detection sensor in the image forming apparatus of Embodiment 6 of this invention, (a) is a top view, (b) is the side view. These are the schematic diagrams which show the installation structure of the humidity detection sensor in the image forming apparatus of Embodiment 7 of this invention, (a) is a top view, (b) is the side view. These are typical side views which show the installation structure of the humidity detection sensor in the image forming apparatus of Embodiment 8 of this invention. These are flowcharts for explaining the operation of the image forming apparatus according to the ninth embodiment of the present invention. These are graphs showing the results of detecting the humidity change in the vicinity of the surface of the transfer paper by the heat detection type (Ha) and capacitance type (Hb) humidity detection sensors. These are graphs showing the results of detecting changes in humidity during the reciprocating movement of the transfer paper by means of the heat conduction type (Ha) and capacitance type (Hb) humidity detection sensors.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 2 ... Photosensitive drum 3 ... Charging apparatus 4 ... Writing apparatus (exposure apparatus)
DESCRIPTION OF SYMBOLS 5 ... Developing device 6 ... Primary transfer device 7 ... Cleaning device 8 ... Fixing device 9 ... Paper feed cassette 10 ... Transfer paper conveyance path 11 ... Humidity detection sensor 11a ... Sensor part 11b ... Substrate part 11c, 11c '... Guide member 12 ... Paper feed roller 13 ... Control unit 14 ... Memory 15 ... CPU
DESCRIPTION OF SYMBOLS 16 ... Conveyance control part 17 ... Fixing control part 18 ... Environmental control part 19 ... Display panel 20a, 20b ... Guide roller 21 ... Shaft 22 ... Signal line 23, 28 ... Sensor mounting member 23a ... Guide member 24a, 24b ... Slide guide member 24c ... groove 25 ... motor 26 ... drive belt 27 ... photo sensor 40 ... transfer belt 41 ... secondary transfer device 42 ... cleaning device P ... transfer paper

Claims (19)

The toner image formed on the image carrier by the image forming operation by the image forming apparatus is transferred to the transfer paper, and is expanded or contracted due to the moisture content change of the transfer paper that is heat-pressed to melt and fix the transferred toner image. In the transfer paper curl determination method for determining the curl of the generated transfer paper,
Depending on the difference between the atmospheric humidity measurement value of the space where the transfer paper is placed and the transfer paper surface humidity measurement value obtained by the humidity detection sensor placed close to and opposite the transfer paper surface, the transfer paper A curling judgment method for transfer paper, wherein the curling of the transfer paper is estimated. The toner image formed on the image carrier by the image forming operation by the image forming apparatus is transferred to the transfer paper, and is expanded or contracted due to the moisture content change of the transfer paper that is heat-pressed to melt and fix the transferred toner image. In the transfer paper curl determination method for determining the curl of the generated transfer paper,
Install a humidity detection sensor at a position facing the transfer paper surface close to the transfer paper transport path,
The humidity measured within the vicinity of the transfer paper transport path detected when there is no transfer paper passing on the transfer paper transport path, and the humidity within the time when the transfer paper passes the position facing the humidity detection sensor. A transfer paper curl determination method which estimates curl of a transfer paper according to a difference from a measured value of surface humidity of the transfer paper detected by a detection sensor. While the humidity detection sensor is performing humidity detection at a position facing the transfer paper surface in close proximity,
3. The transfer paper curl determination method according to claim 2, wherein a distance between the humidity detection sensor and the transfer paper surface to be transported is kept constant.   4. The transfer paper curl determination method according to claim 3, wherein the humidity detection sensor is moved in accordance with a transfer speed of the transfer paper being transferred. While the humidity detection sensor is performing humidity detection at a position facing the transfer paper surface in close proximity,
5. The transfer paper curl determination method according to claim 1, wherein a sensor portion of the humidity detection sensor is protruded to be close to the transfer paper surface.   6. The transfer paper curl determination method according to claim 5, wherein a distance between the sensor portion of the humidity detection sensor and the transfer paper surface is set to 0.1 mm or more and 2 mm or less. The toner image formed on the image carrier by the image forming operation by the image forming apparatus is transferred to the transfer paper, and is expanded or contracted due to the moisture content change of the transfer paper that is heat-pressed to melt and fix the transferred toner image. In the transfer paper curl judgment device for judging the curl of the transfer paper that occurs,
Depending on the difference between the atmospheric humidity measurement value of the space where the transfer paper is placed and the transfer paper surface humidity measurement value obtained by the humidity detection sensor placed close to and opposite the transfer paper surface, the transfer paper A transfer paper curl judging device comprising means for estimating the curl of the transfer paper. The toner image formed on the image carrier by the image forming operation by the image forming apparatus is transferred to the transfer paper, and is expanded or contracted due to the moisture content change of the transfer paper that is heat-pressed to melt and fix the transferred toner image. In the transfer paper curl judgment device for judging the curl of the transfer paper that occurs,
Install a humidity detection sensor at a position facing the transfer paper surface close to the transfer paper transport path,
The humidity measured within the vicinity of the transfer paper transport path detected when there is no transfer paper passing on the transfer paper transport path, and the humidity within the time when the transfer paper passes the position facing the humidity detection sensor. A transfer paper curl judging device comprising means for estimating the curl of the transfer paper according to a difference from the measured value of the transfer paper surface humidity detected by the detection sensor. While the humidity detection sensor is performing humidity detection at a position facing the transfer paper surface in close proximity,
9. The transfer paper curl determination apparatus according to claim 8, further comprising a holding unit that holds a constant distance between the humidity detection sensor and a transfer paper surface to be conveyed.   The transfer paper curl determination apparatus according to claim 9, further comprising a moving unit that integrally moves the humidity detection sensor and the holding unit in accordance with a transport speed of the transported transfer paper. While the humidity detection sensor is performing humidity detection at a position facing the transfer paper surface in close proximity,
11. The transfer paper curl determination device according to claim 7, wherein the humidity detection sensor is brought close to the transfer paper surface so as to protrude.   12. The transfer paper curl determination apparatus according to claim 11, wherein a distance between a sensor portion of the humidity detection sensor and a transfer paper surface is set to 0.1 mm or more and 2 mm or less. An image forming apparatus having a humidity detection sensor installed at a position facing and in close proximity to the transfer paper surface, and a determination means for determining expansion and contraction and curl of the transfer paper based on humidity detection information output from the humidity detection sensor In
The determination means is a difference between an atmospheric humidity measurement value in the apparatus on which the transfer paper is placed and a transfer paper surface humidity measurement value obtained by a humidity detection sensor installed at a position facing the transfer paper surface in close proximity. An image forming apparatus, comprising: a determination unit that estimates transfer sheet curl according to the above. A humidity detection sensor installed at a position facing the surface of the transfer paper that is conveyed on the transfer paper conveyance path in close proximity to the transfer paper, and a determination unit that determines the curl of the transfer paper based on the humidity detection information output from the humidity detection sensor In an image forming apparatus having
The determination means measures the atmospheric humidity measured around the conveyance path when the transfer paper is not being conveyed, and the transfer paper surface humidity measurement obtained by a humidity detection sensor installed at a position facing the transfer paper in the vicinity. An image forming apparatus, comprising: a determination unit that estimates curl of a transfer sheet according to a difference from a value. While the humidity detection sensor is performing humidity detection at a position facing the transfer paper surface in close proximity,
The image forming apparatus according to claim 14, further comprising a holding unit that holds a constant distance between the humidity detection sensor and the surface of the transfer paper to be conveyed.   The image forming apparatus according to claim 15, further comprising a moving unit that moves the humidity detection sensor and the holding unit integrally in accordance with a conveyance speed of a transfer sheet to be conveyed. While the humidity detection sensor is performing humidity detection at a position facing the transfer paper surface in close proximity,
The image forming apparatus according to any one of claims 13 to 16, wherein a sensor unit of the humidity detection sensor is protruded to be close to a transfer paper surface.   18. The image forming apparatus according to claim 17, wherein a distance between a sensor portion of the humidity detection sensor and a transfer paper surface is set to 0.1 mm or more and 2 mm or less.   When the transfer sheet does not pass through the position facing the humidity detection sensor, the control unit that controls the operation of the entire image forming apparatus is configured to display the image according to the atmospheric humidity measurement value obtained by the humidity detection by the humidity detection sensor. The image forming apparatus according to claim 13, wherein an environmental control condition in the forming apparatus is determined.

Images