JP2002187641A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately calculate thickness of a sheet member. SOLUTION: The thickness of the sheet member P is calculated based on data before putting sandwiching the sheet member between thickness detection rollers 56 and data of the sheet member P sandwiched between the stopped thickness detection rollers 56.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art As a sheet material used in an image forming apparatus such as a copying machine or a laser beam printer, a recommended sheet material is almost determined by each apparatus.
In a copier or the like, when an image is formed on a sheet material such as paper, the weight of the sheet material, that is, the thickness of the sheet material whose correlation with the weight is known determines the quality of the image. Is a very large factor. In particular,
In a color copying machine that forms one image by superimposing four color toners (developers) on one sheet material, the amount of toner placed on the sheet material is considerably larger than in a black and white copying machine. Therefore, the difference in the thickness of the sheet material greatly affects the image quality. That is, in a general heating type fixing device that fuses and fixes a toner, as the sheet material is thicker, the amount of heat taken away by the sheet material at the time of fixing is larger, and accordingly, the melting of the toner is The amount of heat provided is reduced. For this reason, in a color image having a large amount of toner, the toner is not sufficiently melted and a fixing failure tends to occur. In order to prevent such defective fixing, a color copying machine requires particularly severe temperature management as compared with a black and white copying machine.

In addition, changing the transfer conditions (for example, transfer bias) for transferring a toner image to a sheet material in accordance with the thickness (density of the material) of the sheet material is also necessary for performing good transfer. Is important.

In an image forming apparatus such as a color copying machine, a user himself or herself inputs information about the thickness of a sheet material from an operation unit on a main body of the apparatus in order to perform the above-described fixing and transfer satisfactorily. Based on the input information, the control device controls the fixing conditions such as the fixing temperature and the fixing speed,
Further, transfer conditions such as a transfer bias are controlled.

However, according to the above-mentioned conventional example, since the user himself / herself inputs the information on the thickness of the sheet material by hand, even if there is an erroneous input by the user, the control device performs the operation based on the erroneous input. The image forming conditions such as the fixing condition and the transfer condition are set, so that a problem may occur. For example, even if one fixing condition is taken,
There have been problems such as poor fixing due to input errors and deformation of the sheet material due to excessive application of heat.

In recent years, there are a great number of types of sheet materials used for image formation, and information on the sheet materials includes, in addition to the above-mentioned thickness, the size, plain paper or special paper, and the like. Further, there are various kinds such as paper and other resin films. It is almost difficult for the user to accurately recognize these and input them correctly to the apparatus main body, and it is also a complicated operation.

Therefore, according to the invention described in Japanese Patent Application Laid-Open No. 9-34311, the image forming apparatus automatically detects the thickness of the sheet material and sets suitable image forming conditions based on the detected thickness. Devices have been provided.

[0008] The thickness detecting means is arranged in the conveying path and detects the thickness of the sheet material, and the control means changes the image forming condition based on the data on the thickness outputted by the thickness detecting means. And a pair of thickness detecting rollers, wherein at least one roller is disposed so as to be displaceable with respect to the other roller and sandwiches the sheet material in the conveyance path from the front and back directions. And a displacement amount detecting means for detecting a relative position of the other roller with respect to the one roller, wherein the displacement amount detecting means is the other roller before the pair of thickness detecting rollers sandwich a sheet material. And the data about the relative position of the other roller with the sheet material sandwiched therebetween are collected as one set of data, The data about the thickness of the sheet material calculated from one data before the insertion of the minute and the data in the state where the same number of rotations are inserted is output to the control device. . Here, it is necessary to collect data in a state where the sheet material is sandwiched while the paper is being conveyed.

[0009]

However, at this time,
Due to the impact when the sheet material enters the thickness detection roller,
Temporary distortion of the unit including the thickness detection means and lifting of the thickness detection roller occur, and this causes the error to be superimposed on the thickness data of the sheet material, making it difficult to accurately calculate the thickness of the sheet material. It was very difficult.

In view of the above circumstances, the present invention provides an image forming apparatus capable of accurately calculating the thickness of a sheet material without being affected by an impact when the sheet material enters a thickness detecting roller. With the goal.

[0011]

According to a first aspect of the present invention, there is provided a transport path for transporting a sheet material, and image formation on the sheet material transported through the transport path. And a pair of rollers disposed in the conveyance path, and the pair of rollers relatively displaces the sheet material conveyed through the conveyance path. Thickness detecting means for detecting the relative position of the pair of rollers, displacement detecting means for detecting the relative position of the pair of rollers, position detecting means for detecting the position on the circumference of at least one of the pair of rollers, A data holding unit for holding data from the position detecting unit and the displacement amount detecting unit before the sheet detecting unit sandwiches the sheet material, and a state in which the thickness detecting unit sandwiches the sheet material. The thickness of the sheet material is calculated based on the data from the position detection means and the displacement amount detection means when the conveyance of the sheet material is stopped, and the data held in the data holding means. A thickness calculating means.

According to a second aspect of the present invention, one of the pair of rollers is fixedly arranged with respect to the transport path, and the other roller is displaceable with respect to the transport path. Characterized by being arranged in

According to a third aspect of the present invention, an image forming condition is changed according to the thickness from the thickness calculating means.

According to a fourth aspect of the present invention, the pair of rollers are registration rollers.

According to a fifth aspect of the present invention, the displacement amount detecting means includes a light emitting diode for irradiating a measuring light to a peripheral surface of a roller disposed to be displaceable with respect to the conveyance path; A light receiving position sensor for receiving the measurement light reflected by the peripheral surface of the pair of rollers, and detecting a relative position of the pair of rollers based on a light receiving position of the measurement light received by the light receiving position sensor. I do.

According to a sixth aspect of the present invention, the position detecting means includes a disk formed with a slit and rotating in synchronization with the one roller, a photosensor for detecting the slit, and the one roller. And a counter that operates in accordance with the rotation of the roller, and detects a position on the circumference of the one roller based on the detection of the slit and the count by the counter.

According to a seventh aspect of the present invention, there is provided an image forming apparatus comprising: a conveying path for conveying a sheet material; and image forming means for forming an image on the sheet material conveyed through the conveying path. An apparatus having a pair of rollers disposed in the conveyance path, and a thickness detection unit that sandwiches the sheet material conveyed through the conveyance path by relatively displacing the pair of rollers; and Displacement amount detecting means for detecting the relative position of the pair of rollers, position detecting means for detecting the position on the circumference of at least one of the rollers in the pair of rollers, and before the thickness detecting means sandwiches the sheet material. Holding the data from the position detection means and the displacement amount detection means in the state, and detecting the position when the thickness detection means stops the conveyance of the sheet material with the sheet material sandwiched therebetween. And data from means and said displacement amount detecting means, based on the data held in the data holding means, characterized by calculating the thickness of the sheet material.

With the above arrangement, the thickness of the sheet material is calculated from the data in a state where the conveyance is stopped by stopping the pair of rollers of the thickness detecting means. Data obtained when the sheet material enters the pair of rollers of the thickness detecting means is not used for calculating the thickness.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of a digital color image forming apparatus 1 as an example of an image forming apparatus according to the present invention, and FIG. 2 is a block diagram showing details of an image processing section. First, the configuration and operation will be described with reference to FIGS.

The image forming apparatus 1 shown in FIG. 1 has a reader unit 10 in the upper part of the apparatus main body 2, a print unit 20 in the middle part,
Further, a feeding / conveying section 50 for the sheet material P is provided at a lower portion.
The reader unit 10 includes a document table 11 on which a document is placed, a document pressure plate 12 for pressing the placed document from above, a light source 13 for irradiating an image surface of the document, and a plurality of mirrors for guiding reflected light from the image surface. 14 and lens 15, C for performing photoelectric conversion of reflected light
CD 16a and image processing unit 1 for performing various image processing
6 as a main component. Further, as shown in FIG. 2, the image processing unit 16 includes a CCD 16a, an A / A
D & S / H section 16b, shading correction section 16c, input masking section 16d, scaling processing section 16e, LOG conversion section 16f, companding section 16g, masking / UCR section 16
h, a gamma correction unit 16i, and an edge enhancement unit 16j.

The operation of the reader unit 10 having the above configuration is as follows. An original is placed on an original platen 11 so that the image surface thereof faces downward, and is pressed by an original pressing plate 12 from above. The light source 13 moves in the direction of arrow K1 while irradiating light, and scans the image surface of the document. The reflected light image from the image plane is converted into RGB light via a plurality of mirrors 14 and lenses 15.
Is imaged on the CCD 16 to which the three color filters are applied,
Here, the signals are photoelectrically converted into RGB signals. The image signal converted into an electric signal is output to the image processing unit 16 as shown in FIG.
Is processed as follows in accordance with the flow shown in FIG. CCD
The signal from 16a is converted to digital data in A / D & S / H section 16b, and the converted digital data is corrected by shading correction section 16c and input masking section 16d. Further, at the time of the magnification operation, the image is subjected to magnification processing by the magnification processing section 16e. Next, the LOG converter 16f converts the RGB data into CMY data, and compresses, stores, and decompresses the image data.
Is input to The stored image data is read out in synchronization with each color of the printing unit 20 described later, and is subjected to a masking process by the masking / UCR unit 16h.
The output image data of YMCK is created by the correction unit 16i and the edge enhancement unit 16j, and sent to the next printing unit 20.

As shown in FIG. 1, the printing unit 20 includes an image control unit 21 for synchronizing each color, four laser elements,
That is, laser elements 22M, 22C, 22Y, and 22K for each of magenta, cyan, yellow, and black, a polygon scanner 23 that scans the surface of a photosensitive drum described below with laser light, and four image forming units (image forming units), that is, sheets. Image forming units 30M, 30C, 30Y, 30K for the respective colors of magenta, cyan, yellow, and black arranged in order from the upstream side to the downstream side in the transport direction of the material P (from right to left in the figure). The fixing device 40 disposed further downstream of the image forming section 30K on the most downstream side is configured as a main component. Also,
The uppermost magenta image forming section 30M charges the surface of the photosensitive drum 31 rotatably supported in the direction of the arrow and arranged around the photosensitive drum 31 substantially in the rotation direction. Primary charger 32, photosensitive drum 31
A developing unit 33 for developing the electrostatic latent image thereon, a transfer charger 34 for transferring the toner image on the photosensitive drum 31 to the sheet material P, a cleaner 35 for removing transfer residual toner on the photosensitive drum 31,
An auxiliary charger 36 for removing charges and a pre-exposure lamp 37 for removing residual charges are provided. Further, the developing device 33
A developer density sensor S1 for detecting the developer density based on the amount of reflected light from the developer on the developing roller 33a and a developing density sensor S2 for detecting the amount of reflected light from the toner image formed on the photosensitive drum 31 are arranged. Have been.

The image forming units 30C and 30 of other colors
For Y and 30K, the above-described magenta image forming unit 3
Since the configuration is the same as that of 0M, its description is omitted.

The printing section 20 having the above-described configuration forms a toner image on the sheet material P in the following manner based on the output image data sent from the reader section 10 described above.

In the magenta image forming section 30M, the surface of the photosensitive drum 31 is uniformly charged to a predetermined potential by the primary charger 32. The image controller 21 drives the magenta laser element 22M in synchronization with other colors based on the output image data, and scans the surface of the photosensitive drum 31 described above. As a result, an electrostatic latent image corresponding to magenta in the document image is formed on the surface of the photosensitive drum 31.
The electrostatic latent image is formed on the developing roller 33 to which the developing bias is applied.
The magenta toner is attached by a to be developed as a toner image. This toner image is transferred to the surface of a sheet material P conveyed by a transfer belt, which will be described later, by discharging the transfer charger 34 from the inside of the transfer belt. After the transfer of the toner image, the transfer residual toner on the surface of the photosensitive drum 31 is removed by the cleaner 35, further, the charge is removed by the auxiliary charger 36, and the residual charge is removed by the pre-exposure lamp 37. It is used for the next image formation starting from charging.

Similarly to the magenta image forming section 30M, the toner image of each color is formed on the surface of each photosensitive drum also in the image forming sections 30C, 30Y and 30K of each color of cyan, yellow and black on the downstream side. Is done. The sheet material P on which the magenta toner image has been transferred is sequentially conveyed to the cyan, yellow, and black image forming units 30C, 30Y, and 30K on the downstream side by the transfer belt.
The toner images of the respective colors are sequentially transferred, and the toner images of the four colors are superimposed on the surface. The sheet material P to which the four color toner images are transferred is conveyed to the fixing device 40 by a pre-fixing belt described later, where the sheet material P is heated and pressed by the fixing roller 40a and the pressure roller 40b to form a toner image on the surface. Is established. The sheet material P after fixing is discharged to the outside of the apparatus main body 2 as it is when the image is not formed on the back surface, while, when the image is formed on the back surface, Again, the image forming unit 30M
After the toner image is formed on the rear surface, the toner image is discharged to the outside of the apparatus main body 2.

Feeding / conveying section 50 for feeding / conveying sheet material P
Has a conveying path for the sheet material P, and is provided at the most upstream side in the conveying direction of the sheet material P,
b, feed rollers 52a, 52b, transport rollers 53a, 5
3b is provided. Further, below these sheet cassettes 51a, 51b, when these are mounted on the apparatus main body 2, these sheet cassettes 51a,
Paper size detectors S3 and S4 for detecting the size of the sheet material P stored in the sheet 51b are additionally provided. The sheet size detection units S3 and S4 are provided in the sheet cassettes 51a and 51.
b, and a size detection switch (both not shown) on the apparatus main body 2 side. When the sheet feeding cassettes 51a and 51b are mounted, the engaging section Activate the size detection switch corresponding to the size of
As a result, a code signal corresponding to the size is output to the apparatus main body 2 as size information. In addition to the sheet feeder 54, a multi-sheet feeder 55 is provided. From the multi-sheet feeder 55, the image forming unit 30
Various sheet materials P having different properties such as material and size can be supplied to M and the like. The information about the sheet material P supplied from here, for example, the material, size, thickness, etc., can be input by a user from an operation unit (not shown), or the thickness can be obtained by using paper as described later. The thickness is automatically detected by the thickness detector.

A registration roller 56 is provided slightly upstream of the image forming unit 30M to temporarily stop the conveyed sheet material P and to convey the sheet material P in synchronization with the image forming unit 30M and the like. The registration roller 56 includes a pair of upper and lower upper rollers 56a (see FIG. 7) and a lower roller 56b, and conveys the sheet material P by sandwiching the sheet material P from both front and back surfaces by these rollers 56a and 56b. At this time,
The upper roller 56a moves according to the thickness of the sheet material P,
By utilizing the fact that the position of the upper roller 56a with respect to the lower roller 56b changes, this registration roller 56 is also used as a thickness detection roller. This registration roller 56
And a sensor or the like to be described later constitute a paper thickness detecting unit (thickness detecting means) S5. The detailed configuration and operation of the paper thickness detection unit S5 will be described later.

On the downstream side of the registration roller 56, a transfer belt 57 that rotates in the direction of arrow K57 so as to contact the photosensitive drums of the image forming units 30M, 30C, 30Y, and 30K of the respective colors from below is disposed. ing. The transfer belt 57 is configured to carry a sheet material P on its surface and to convey the sheet material P to each of the image forming units 30M, 30C, 30Y, and 30K.

A pre-fixing belt 58 that can rotate in the direction of arrow K58 is disposed downstream of the transfer belt and the fixing device 40. Further, immediately downstream of the fixing device 40,
A pressing mechanism (curved pressing device) 59 (to be described in detail later), which can perform pressing for fixing the sheet material P after fixing with a plurality of switchable pressing forces, is provided. . A discharge flapper 60 and a paper discharge tray 61 for selecting whether to discharge the sheet material P or to re-feed the sheet material P are provided downstream of the pressurizing mechanism 59. 6
2. A reversing flapper 63 is provided, and further downstream,
A paper re-feeding conveyance path 64 and a paper re-feeding device 65 are provided.

The feeding / conveying device 50 having the above-described structure operates as follows. Sheet feeder 54 or multi-sheet feeder 5
5 is temporarily stopped by the registration roller 56, and thereafter, the image forming unit 30
In synchronization with the toner images of the respective colors formed on the photosensitive drums M, 30C, 30Y, and 30K, the sheets are nipped and conveyed by registration rollers 56 and further conveyed by a transfer belt 57. At this time, the registration rollers 56
The paper thickness is detected by the paper thickness detection unit S5 having When the sheet material P carried on the transfer belt 57 passes through the magenta image forming unit 30M, the transfer charger 34 transfers a magenta toner image to the surface. Similarly, when the sheet material P passes through the image forming units 30C, 30Y, and 30K for cyan, yellow, and black, toner images of the respective colors are sequentially transferred. The sheet material P on which the transfer of the four color toner images has been completed is conveyed to the fixing device 40 by the pre-fixing belt 58, where it is heated and pressed to fix the toner image on the surface. The sheet material P after the toner image is fixed is crimped by the pressing mechanism 59. Here, at the time of one-sided image formation, the discharge flapper 60 is used.
Is set on the discharge side, and the sheet material P is discharged onto the discharge tray 61. On the other hand, at the time of double-sided image formation, the discharge flapper 60 is set on the re-feeding side, whereby the sheet material P is guided to the reversing conveyance path 62 and conveyed downward until the rear end passes the reversing flapper 63. Is done. Thereafter, when the reversing flapper 63 is switched and the sheet material P is conveyed upward, the sheet material P is guided to the re-feeding conveyance path 64 by the reversing flapper 63 and stored in the re-feeding device 65. Thus, the sheet material P is turned upside down.
The sheet material P is re-fed from here to the image forming unit 30M and the like, the image is formed on the back surface in the same manner as when the image is formed on the front surface, and then discharged onto the discharge tray 61. . This concludes the description of the configuration and operation of the entire image forming apparatus.

FIG. 3 is a block diagram of the above-described image forming apparatus. This block diagram is a block diagram for performing optimal image formation according to the sheet material P.
The system controller 71 performs various controls of the image forming apparatus, and performs overall control by an internal CPU. In the figure, reference numeral 72 denotes an image input unit constituting a part of the reader unit 10, reference numeral 16 denotes an image processing unit, reference numeral 21 denotes a laser driving circuit (image control unit) for modulating and driving a semiconductor laser based on image data, and reference numeral 22 denotes a laser. This is a semiconductor laser (laser element) driven by the drive circuit 21. Reference numerals 31, 33, and 34 denote members constituting the above-described magenta image forming unit 30M. Reference numeral 31 denotes a photosensitive drum on which an electrostatic latent image is formed by the output light of the semiconductor laser 22, and reference numeral 33 denotes a photosensitive drum 31. A developing device for performing development in accordance with the upper latent image, and a transfer charger 34 for transferring the toner image on the photosensitive drum 31 to the sheet material P. Further, reference numeral 40 denotes a fixing unit for fixing the toner image on the sheet material P by heating and pressing, and reference numeral 59 denotes a pressing mechanism for making the sheet material P after fixing fixed. And S6 is the image processing unit 1
6 is a density distribution estimating circuit for estimating the image density distribution based on the image data output from 6 (hereinafter referred to as an “estimating circuit” as appropriate, described in detail later).

Next, with reference to the block diagram of FIG. 3, an operation for performing an optimum image formation in the image forming apparatus having the above-described configuration will be described. The image information of the document is input as an electric signal through the image input unit 72, and the image processing unit 16 performs A / D conversion, shading correction,
Image processing necessary for image formation, such as LOG conversion, UCR processing, and γ correction, is added and output as output image data. The laser drive circuit 21 is driven based on the output image data, and the semiconductor laser 22 is modulated and driven.
The output light of the semiconductor laser 22 is scanned and exposed on the charged photosensitive drum 31, so that the photosensitive drum 31 is exposed.
On the surface, a charge distribution corresponding to image data, that is, an electrostatic latent image is formed. The electrostatic latent image is developed as a magenta toner image by attaching toner to the developing device 33.

This magenta toner image is transferred onto the surface of the sheet material P conveyed by the above-mentioned feeding / conveying section 50. Before the transfer of the toner image, the size of the sheet material P is detected in advance by the paper size detection unit S3 (S4), and the thickness is detected by the paper thickness detection unit S5. The transfer of the toner image causes the developing device 33
Is transferred onto the sheet material P. In the sheet material P, the toner image is recognized as a toner distribution. The estimation circuit S6 estimates the distribution of the toner on the sheet material P, that is, the image density distribution, based on the same image data as those used for image formation. Further, the toner images of the respective colors are sequentially transferred onto the sheet material P by the image forming units 30C, 30Y, and 30K of cyan, yellow, and black on the downstream side. At the time of these transfers, the image density distribution of each color is similarly estimated by the above-described estimation circuit S6.

The toner images for the four colors are fixed on the sheet P by heating and pressing by the fixing device 40. In order to heat and fix the toner, there is an optimum fixing temperature, which is determined by the sheet material P detected by the sheet size detecting units S3 and S4.
This is realized by changing the fixing conditions based on the size of the sheet material P, the thickness of the sheet material P detected by the paper thickness detection unit S5, and the image density distribution estimated by the estimation circuit S6.

For example, when the sheet material P is heated while being nipped and conveyed by the fixing roller 40a and the pressure roller 40b of the fixing device 40, the rotation speed of the fixing roller 40a is controlled according to the thickness of the sheet material P. Thus, the conveying speed (fixing speed) of the sheet material P is changed, thereby realizing optimum fixing conditions. That is, when the thickness of the sheet material P is large, the fixing speed is reduced. Conversely, when the thickness of the sheet material P is small, the fixing speed is increased to melt the toner image. Sufficient heat is provided.

Further, the transfer bias applied to the transfer charger 34 when the toner image is transferred from the photosensitive drum 31 onto the sheet material P is determined based on information on the size and thickness of the sheet material P. I have to.

Further, by switching the amount of pressurization of the pressurizing mechanism 59 for stiffening the sheet material P after heating and fixing according to the size and thickness of the sheet material P, the optimal curl removal pressure Control becomes possible.

That is, in the block diagram shown in FIG. 3, the transfer charger 34, the fixing device 40, and the pressing mechanism based on the outputs of the sheet size detectors S3 and S4, the sheet thickness detector S5, and the estimation circuit S6. 59 and the like are appropriately controlled to perform optimal image formation.

Next, since the paper size detection units S3 and S4 have been described above, the estimation circuit S6, the paper thickness detection unit S5, and the pressure mechanism 59 will be described in detail.

FIG. 4 shows a detailed circuit diagram of the estimation circuit S6. Here, since the amount of the developer (toner) used is considered to be roughly proportional to the integrated value of the image data, the estimating circuit S6 divides one image into a plurality of regions, and calculates the image data value in each region. Considering a circuit for performing integration, this embodiment will exemplify an example in which an image is divided into 16 4 × 4 regions and C00 to C33 shown in FIG. 5 are calculated. Here, Cmn is an image density value of each area.

In FIG. 4, Data is image data, and is an 8-bit signal in the present embodiment. Vclk is a synchronization signal for image data, and Vsync is a sub-scanning synchronization signal indicating the start of one image section. Enable is a main scanning image effective section signal, and Venable is a sub-scanning image effective section signal. Based on the size of the sheet material P detected by the sheet size detection units S3 and S4, the system controller 71 determines the number N of pixels in the main scan for forming an image,
The number M of pixels in the sub-scan is derived, and M / 4 and N / 4 corresponding to one area of the density distribution are calculated. 81 is a counter for counting the main scanning area, 82 and 85 are OR gates, 83 is an up counter indicating a numerical value indicating the main scanning area, 8
4 is a counter for counting the sub-scanning area, 86 is an up-counter indicating a numerical value indicating the sub-scanning area, 87 is an encoder that encodes a numerical value indicating the area of the up-counters 83 and 86, and 88 is input image data. A flip-flop 89; an AND gate 89 for generating an enable signal; 90 an adder for adding the image data and the integrated value of the image data of the selected area; 91, 93 and 95 storing the added value of the image data of each area Flip-flop, 92,
Reference numerals 94 and 96 denote AND gates for generating enable of each area, and reference numerals 97, 98 and 99 denote buffers with output enable for outputting an integrated value of image data of each area to an adder.

The number of pixels in the main scanning area is counted by counting the number of pixels N / 4 in the main scanning area into the counter by Vsync before image formation, counting Vclk and counting down. 4 is reloaded, a carry of n clocks is output to the up counter 83, and the output of the up counter 83 indicating the area is incremented, thereby increasing the output of the up counter 83 for every N / 4 pixels. Realize. In the sub-scanning region, as in the case of the main scanning, by counting Hsyncs M / 4 by one, a region signal for each M / 4 line is generated and output to the encoder 87. On the other hand, image data is
AND gate 89 between Henable and Venable
During the enable period by Vc
It is stored in sync with lk. The output of the flip-flop 88 is input to one input of an adder 90. To the other input of the adder 90, a data output of a predetermined area from the buffers 97, 98, and 99 whose output is controlled by an encode signal indicating each area is input. By adding these two data and storing the output in a flip-flop that is enabled and controlled to correspond to a predetermined area, the integrated values C00 to C33 of the image data corresponding to the area specified by the encoder 87 are obtained. The density distribution stored in the flip-flop and read by the system controller 71 is estimated. FIG. 6 shows video signals, that is, Vsyn.
c, Venable, Hsync, Henable, D
The schematic timings of data and C are shown.

The calculated image density data C00 to C33
Of the image density distribution from the system controller 71
It is performed by the calculation in.

Next, FIG. 7 shows a paper thickness detecting section S5 used in the present embodiment. The paper thickness detection unit S5 includes a displacement amount detection unit 100, a thickness detection roller 56 that is a thickness detection unit,
There is provided a position detecting unit 110 for detecting which point on the circumference of the thickness detecting roller 56 the displacement amount detecting unit 100 faces. The position detecting means 110 will be described later in detail. Note that the thickness detection roller 56 is also used as the above-described registration roller. Displacement detection means 100
Light Li (measurement light) from the light emitting diode 101 of FIG.
Is reflected by a reflection surface 56r which is a measurement surface of an upper roller 56a of a registration roller (thickness detection roller) 56, and the reflected light Lr is received by a light receiving position sensor 102. The lower roller 56b of the registration roller 56 is fixed in the thrust direction, and the upper roller 56a is installed in a free state. Therefore, when the sheet material P is sandwiched between the upper and lower rollers 56a and 56b, the sheet material P The configuration is such that the upper roller 56a moves according to the thickness. Therefore, the reflecting surface 56r moves according to the thickness of the sheet material P. When the sheet material P is thick, the reflecting surface 56r moves upward to approach the light emitting diode 101, and when the sheet material P is thin, moves downward to separate from the light emitting diode 101. As a result, the position of the measurement light received by the light receiving position sensor 102 changes according to the thickness of the sheet material P, and the sheet material P
Is input to the A / D converter 103 as an analog signal S11 which is a thickness signal of

Here, the blinking and light quantity control of the light emitting diode 101 are controlled by a control signal S from the system controller 71.
12 is controlled via a signal S13 output from the sensor LED control unit 104. Also, the control signal S
Reference numeral 12 also controls the A / D conversion timing of the A / D converter 103. A signal S14 corresponding to the digitized thickness of the sheet material P from the A / D converter 103 is sent to the system controller 71. Here, the thickness of the sheet material P is calculated by the CPU.

Here, the center position of the mounting shaft of the thickness detecting roller 56 is shifted due to a shift occurring during manufacturing, a variation at the time of mounting, or the like. For that reason,
As shown in FIG. 10, the distance between the thickness detection sensor and the thickness detection roller changes in a cycle corresponding to one rotation of the thickness detection roller. Since this change in distance directly appears as a change in thickness data, to cancel this, the data for the thickness has been data before the paper is inserted, and the data for the whole number of rotations regardless of the data in the sandwiched state. Was taking. In this case, data in a state where the transfer paper is sandwiched must be collected while the transfer paper is being conveyed.

However, in this case, as shown in FIG. 11, at the moment when the thickness detecting roller sandwiches the transfer paper, that is, at the moment when the transfer paper enters, the data of the thickness of the transfer paper becomes theoretical value due to the impact. Has a tendency to come out of the way. For this reason, when obtaining regular data, it is necessary to correct the offset by measuring and verifying the offset and subtracting the offset from the actual data. Since the offset varies depending on the type of the transfer paper and the unit including the thickness detecting means, it is difficult to improve the accuracy by the correction.

Therefore, the data with the transfer paper sandwiched is
It is the gist of the present invention that a method of collecting paper when the transfer paper is stopped and stabilized is adopted. What is needed at this time is data indicating a position on the circumference of the thickness detecting roller at which the transfer sheet is stopped with the transfer sheet interposed therebetween, and data at that position in a state where the transfer sheet is not pinched. . FIG. 9 is a diagram showing the configuration of the position detecting means 110.

The disk 111, which rotates in synchronization with the thickness detecting roller 56a, is provided with a slit 112, and the LED light receiving section 113b of the photo sensor 113
The slit is detected by detecting the infrared light from 13a. This slit position is set as a reference position. A counter in the system controller (not shown) is started according to the rotation of the thickness detecting roller. This counter counts from 1 to n, and when it counts to n, it starts counting from 1 again.
In synchronization with the rotation cycle of the first slit, the position is set to 1 at the position of the slit and to reach the n-th count immediately before the next slit. The thickness data is detected in synchronization with the count. In this way, the position of one circumference on the circumference of the thickness detection roller can be divided into 1 to n places where the reference position of the slit is 1 and n is immediately before the next slit.

FIG. 12 shows the relationship among the rotation signal of the thickness detection roller, the slit detection signal, the count signal, and the first data which is data when the transfer paper is not sandwiched, as described above. Things. Here, the first data is
It is desirable to collect data of an integral number of revolutions as much as possible in order to improve accuracy not only for one round. In this case, the data is obtained by averaging the values at each of 1 to n places,
It is stored in a RAM (data holding means) in a system controller (not shown) as first data of each location. FIG.
FIG. 7 illustrates the collection of second data, which is data in a state where a transfer sheet is sandwiched. When the sheet material reaches the thickness detecting roller, the thickness calculating means (not shown) turns off the rotation of the thickness detecting roller to collect the second data, and at the same time, turns off the count signal and outputs the second data and The thickness of the sheet material is calculated from the first data corresponding to the hour count value.

Next, FIG. 8 shows a detailed view of the pressing mechanism 59. In general, it is known that when a toner image transferred onto a sheet material P is fixed by heating, the sheet material P after fixing is curled toward the toner image. In such a state, the stackability on the paper output tray 61 is significantly impaired,
There is a possibility that the paper ejectability to a sorter (post-processing device) widely used in copiers, printers, etc. may deteriorate, and furthermore, the paper may develop into jams, etc., and it is very important to control the curl amount after fixing. It is a problem. In the present embodiment, as a method of managing the curl amount, a pair of the sponge roller 59a and the metal roller 59
This is realized by sandwiching the sheet material P after fixing with b. Since the curl has a toner image formed on the upper surface of the sheet material P, the sponge roller 59a is provided on the upper side and the metal roller 5 is provided on the lower side to apply the curl in the opposite direction.
9b, and the metal roller 59b is
Curling is suppressed by utilizing the bite into a. The amount of pressurization is controlled by driving the cam 59c to move the metal roller movable plate 59e swingable about the shaft 59d up and down in the direction of the arrow in FIG. The amount of pressurization can be adjusted in multiple steps or steplessly according to the shape of the cam 59c. 59f is the sheet material P
This is a transport roller provided to improve the transportability of the sheet. The adjustment of the amount of pressurization by the cam 59c of the pressurization mechanism 59 and the metal roller movable plate 59e is performed by the above-described paper thickness detection unit S5.
The system controller 7 refers to the data such as the thickness of the sheet material P according to
1 is collectively controlled by the CPU above.

FIG. 14 is a flowchart for calculating the thickness of the sheet material P when feeding paper according to the present embodiment. The calculation of the thickness of the sheet material P is also totally controlled and calculated by the CPU on the system controller 71. The sheet material P fed from the sheet feeding devices 54 and 55 (see FIG. 1) through the sheet conveyance path reaches the sheet thickness detecting unit S5, and the sheet thickness of the sheet material P is detected (S1). The registration roller is turned ON in order to collect data before the sheet material P reaches the registration roller 56 (S2). The registration roller 56 also serves as a thickness detection roller as described above. Here, since the thickness of the sheet material P is determined by measuring the amount of displacement of the upper roller 56a of the registration roller 56 as described above, the thickness of the sheet material P in a state where the registration roller 56 does not sandwich the sheet material P is determined. It is necessary to collect the first data. The thickness of the sheet material P is the registration roller 5
6 is derived from the difference between the first data when the sheet material P is not sandwiched and the second data when the sheet material P is sandwiched,
The first data when the sheet material P is not sandwiched therebetween is a reference value for calculating the thickness of the sheet material P. The registration roller 56 is the first data (Dr1, Dr2,..., Drn) at each of the positions 1 to n before the sheet material P is sandwiched.
Is started (S3). At a point in time where there is a relatively long time before the sheet feeding according to the present embodiment is started, a large amount of data is collected here, and from the viewpoint of improving the reliability of the data, the registration roller 56 has five rotations. Data is collected (S4). When the registration roller 56 makes five rotations, the collection of the first data before the sheet material P is sandwiched is stopped, and paper feeding is started to the registration roller 56 (S5). An average value of the data is calculated (S6). These data are held in data holding means (not shown).

When the sheet material P reaches the registration roller 56 (S7), the registration roller 56 is stopped and
Data collection of the second data (Dp1) sandwiching the sheet material P (S8), detecting at which position from 1 to n positions the registration roller has stopped (S9), the registration roller 56 The data before the registration roller 56 sandwiches the sheet material P according to the detected registration roller stop positions 1 to n are completed after the data collection and the detection of the registration roller stop position are completed. And the registration roller 56 collected in S8 is the sheet material P
The sheet thickness value representing the thickness of the first sheet material P is calculated based on the difference K with one piece of second data in a state sandwiching.
0). After the sheet material P passes through the registration roller 56,
The registration roller 56 is turned off (S11), and the paper thickness detection ends (S12).

In the above-described embodiment, the rotation of the registration roller 56 for collecting the first data is set to 5 in both cases. However, the present invention is not limited to this. Any number of times, such as two, three, six, or seven, may be used.

In the above-described embodiment, the case where the image forming apparatus is a color copying machine has been described. However, the present invention can of course be applied to an image forming apparatus such as a monochrome copying machine. . Even in a monochrome machine, the control and selection of transfer conditions or fixing conditions depending on the type of the sheet material P, particularly the difference in thickness, is a large factor in forming a high-definition image (especially a digital copying machine). This is an indispensable technique when higher definition image quality is required.

In the above embodiment, the thickness detecting roller 56 has the lower roller 56b fixed and the upper roller 5b fixed.
6a is displaceably arranged, but both rollers 56a, 5a
The thickness of the sheet material P may be detected by displacing the 6b and detecting the distance between them. However, in this case, the displacement detecting means 100
Also needs to be changed.

Further, the thickness detecting roller 56 can be provided independently without also serving as a registration roller.
In this case, the degree of freedom with respect to the arrangement position of the thickness detection roller 56 increases.

[0060]

As described above, according to the present invention, the thickness of the sheet material is calculated from the data when the conveyance is stopped by stopping the pair of rollers of the thickness detecting means. Therefore, data when the sheet material enters the pair of rollers is not used for the thickness calculation, and thus does not include an error when the sheet material enters. Thereby, the thickness of the sheet material can be accurately obtained.

Needless to say, since the thickness information of the sheet material is not manually input by the user, there is no possibility that improper image forming conditions are set due to an erroneous input or the like.

Further, according to the thickness from the thickness calculating means, fixing conditions (fixing temperature, fixing speed, etc.), transfer conditions (transfer bias, etc.), or a curving device for correcting the curl of the sheet material after fixing. When the image forming conditions such as the amount of pressurization are changed, these image forming conditions become optimal for the sheet material used for the image forming, and a good image can be formed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus according to the present invention.

FIG. 2 is a block diagram illustrating details of an image processing unit.

FIG. 3 is a diagram illustrating a state in which image forming conditions are changed depending on the properties of a sheet material used for image formation.

FIG. 4 is a block diagram showing details of an estimation circuit.

FIG. 5 is a diagram showing a calculation area of an estimation circuit.

FIG. 6 is a timing chart of each control signal for driving the estimation circuit.

FIG. 7 is a diagram illustrating details of a configuration of a paper thickness detection unit.

FIG. 8 is a diagram showing details of a configuration of a pressing mechanism.

FIG. 9 is a diagram illustrating details of a position detecting unit of a thickness detecting roller.

FIG. 10 is a diagram illustrating eccentricity of a thickness detection roller shaft.

FIG. 11 is a diagram illustrating a state in which data in a state where a transfer sheet is interposed is collected during conveyance.

FIG. 12 is a diagram illustrating a timing of collecting data in a state where a transfer sheet is not sandwiched.

FIG. 13 is a diagram illustrating a timing of collecting data in a state where a transfer sheet is sandwiched.

FIG. 14 is a flowchart for detecting the thickness of a sheet material during continuous paper feeding.

[Explanation of symbols]

 30 image forming means (image forming part) 56 thickness detecting means (registration roller)

Continued on the front page F term (reference) 2F065 AA06 AA30 BB13 BB15 CC02 DD03 FF09 FF17 GG07 HH13 JJ08 JJ16 MM04 UU03 UU05 2H027 DC02 DC10 DE02 DE07 DE10 EA03 EA12 EA18 EB04 EC06 EF09 ZA07 AH2A01 AA23A01 A23A01 BA06 BB02 BB05 CA02 CC02 DA06 DC08 DC14 EB37

Claims (7)

[Claims] 1. An image forming apparatus comprising: a conveying path for conveying a sheet material; and an image forming unit for forming an image on the sheet material conveyed through the conveying path. A thickness detection unit having a pair of rollers disposed, and sandwiching the sheet material conveyed through the conveyance path by the relative displacement of the pair of rollers; and a displacement detecting a relative position of the pair of rollers. Amount detecting means, Position detecting means for detecting a position on the circumference of at least one of the pair of rollers, and in a state before the thickness detecting means sandwiches a sheet material,
Data holding means for holding data from the position detecting means and the displacement amount detecting means; and the position detecting means when the thickness detecting means stops conveying the sheet material with the sheet material sandwiched therebetween. Image forming means for calculating a thickness of a sheet material based on data from the displacement amount detecting means and data held in the data holding means. apparatus. 2. The method according to claim 1, wherein one of the pair of rollers is fixedly disposed with respect to the transport path, and the other roller is disposed so as to be displaceable with respect to the transport path. The image forming apparatus according to claim 1. 3. The image forming apparatus according to claim 1, wherein an image forming condition is changed according to the thickness from the thickness calculating unit. 4. The image forming apparatus according to claim 1, wherein the pair of rollers are registration rollers. 5. A light emitting diode for irradiating a measuring light to a peripheral surface of a roller disposed so as to be displaceable with respect to the transport path, and a measuring light reflected by the peripheral surface of the roller. 3. The image forming apparatus according to claim 2, further comprising a light receiving position sensor for receiving light, and detecting a relative position of the pair of rollers based on a light receiving position of the measurement light received by the light receiving position sensor. . 6. The position detecting means includes: a disk having a slit formed therein and rotating in synchronization with the one roller; a photo sensor detecting the slit; and a counter operating in accordance with the rotation of the one roller. The image forming apparatus according to claim 1, further comprising: detecting a position on the circumference of the one roller based on the detection of the slit and the count by the counter. . 7. An image forming apparatus comprising: a conveying path for conveying a sheet material; and image forming means for forming an image on the sheet material conveyed through the conveying path. A thickness detection unit having a pair of rollers disposed, and sandwiching the sheet material conveyed through the conveyance path by the relative displacement of the pair of rollers; and a displacement detecting a relative position of the pair of rollers. Amount detecting means, Position detecting means for detecting a position on the circumference of at least one of the pair of rollers, and in a state before the thickness detecting means sandwiches a sheet material,
The position detection means and the displacement amount when holding the data from the position detection means and the displacement amount detection means, and stopping the conveyance of the sheet material with the thickness detection means sandwiching the sheet material. An image forming apparatus comprising: calculating a thickness of a sheet material based on data from a detection unit and data stored in the data storage unit.