JP2003162198A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To optimally control a transfer material thickness detecting sensor constituted of a magnetic body and a magnetic field sensor and for detecting the thickness of a transfer material so that the sensor does not interrupt the transport of the transfer material. <P>SOLUTION: The sensor is provided with the movable magnetic body arranged in contact with the transfer material and freely shifted in accordance with the contact with the transfer material, and the magnetic field sensor fixed to the base part of the movable magnetic body and for detecting the magnitude of the magnetic field formed by the movable magnetic body as the thickness of the transfer material. The movement of the movable magnetic body is controlled so that the movable magnetic body does not come into contact with the transfer material and the body is retreated in the case the thickness detection is not performed on the basis of the selection result of the thickness detection selecting means for deciding whether the detection of the thickness of the transfer material should be performed. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a laser beam printer.

[0002]

2. Description of the Related Art As a transfer material used in an image forming apparatus such as a copying machine or a laser beam printer, a transfer material recommended by each apparatus is almost determined. This is because in a copying machine or the like, when an image is formed on a transfer material such as paper, the weight of the transfer material, that is, the thickness of the transfer material, which has a known correlation with the weight, determines the quality of the image. This is because it is a very large factor. In particular, in a color copying machine in which four color toners (developer) are superposed on one transfer material to form one image, the amount of toner placed on the transfer material is larger than that of a black-and-white copying machine. However, the difference in the thickness of the transfer material greatly affects the image quality.
That is, in a general heating-type fixing device that melts and fixes toner, the thicker the transfer material, the more heat that is taken by the transfer material during fixing, and the more that the toner melts. The amount of heat provided is reduced. For this reason, in a color image with a large amount of toner, the toner is not sufficiently melted, and fixing failure tends to occur. In order to prevent such a fixing failure, a color copying machine is required to have particularly severe temperature management as compared with a monochrome copying machine.

Further, in order to achieve good transfer, it is also possible to change the transfer condition (for example, transfer bias) for transferring the toner image onto the transfer material according to the thickness of the transfer material (material density). Is important in.

In order to favorably perform the above-mentioned fixing and transfer, in an image forming apparatus such as a color copying machine, conventionally, a user himself inputs information about the thickness of a transfer material from an operation section on the main body of the apparatus. , Based on this input information
The controller controls the fixing conditions such as the fixing temperature and the fixing speed, and the transfer conditions such as the transfer bias.

[0005]

However, according to the above-mentioned conventional example, since the user himself / herself inputs the information about the thickness of the transfer material, even if the user makes an erroneous input, the control device is Image forming conditions such as fixing conditions and transfer conditions are set on the basis of the erroneous input, which may cause a problem. For example, even if one fixing condition is taken, there are problems such as poor fixing due to an input error and deformation of the transfer material due to excessive heat.

Recently, there are many kinds of transfer materials used for image formation, and the information about the transfer materials is as follows.
In addition to the above thickness, its size, whether it is plain paper or special paper,
Furthermore, there are various things such as paper and other resin films. It is almost difficult for the user to accurately recognize these and input correctly in the apparatus main body, and it is also a complicated work.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an image forming apparatus in which the thickness of a transfer material is accurately detected and suitable image forming conditions are set based on the detected thickness. Further, depending on the configuration of the thickness detecting means, there is a possibility that a transfer material such as thin paper, glossy paper, or OHP paper may be scratched or minutely deformed on its surface to cause an image defect. At the same time, the purpose is to eliminate.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a toner image formed on an image carrier based on image data is transferred through a conveyance path. In an image forming apparatus for performing image formation by fixing on a transfer material after being transferred to a material, a thickness detecting unit disposed in the transport path for detecting the thickness of the transfer material, and a thickness detecting unit are provided. Control means for changing the image forming conditions based on the data about the thickness to be output, wherein the thickness detecting means is arranged at a position where it abuts on the transfer material, and is movably displaced by the abutment. A working magnetic body provided,
The magnetic field sensor is fixed around the operating magnetic body and detects the magnitude of the magnetic field generated by the movable magnetic body as the thickness of the transfer material, and the thickness detecting means selects whether or not to carry out the operation. When the thickness detection selecting means is selected not to perform the operation by the thickness detection selecting means,
The movement of the movable magnetic body is controlled so that the movable magnetic body is retracted so as not to contact the transfer material.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 shows a schematic configuration of a digital color image forming apparatus 1 as an example of the image forming apparatus according to the present invention.

First, the configuration and operation will be described with reference to FIG.

The image forming apparatus 1 shown in FIG. 1 has a reader section 10 on the upper part of the apparatus main body 2 and a print section 20 on the middle section.
Further, a feeding / conveying section 50 for the transfer material P is provided in the lower part.

The reader unit 10 includes a document table 11 on which a document is placed, and a document pressure plate 1 for pressing the placed document from above.
2, a light source 13 that illuminates the image surface of the original, a plurality of mirrors 14 and lenses 15 that guide the reflected light from the image surface, a CCD 16a that performs photoelectric conversion of the reflected light, and an image processing unit 16 that performs various image processing. It is configured as a constituent member. An operation unit 200, which is a user interface, is provided on the upper surface of the reader unit 10 to set the number of image formations and other settings. Further, as shown in FIG. 2, the image processing unit 16 includes a CCD 16a, an A / D & S / H unit 16b, a shading correction unit 16c, an input masking unit 16d,
Magnification processing unit 16e, LOG conversion unit 16f, companding unit 16
g, a masking / UCR unit 16h, a γ correction unit 16i, and an edge enhancement unit 16j.

The operation of the reader unit 10 having the above-described structure is as follows.

A document is placed on the document table 11 with its image surface facing downward, and is pressed by the document pressure 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 passes through a plurality of mirrors 14 and lenses 15, and is converted into RGB.
An image is formed on the CCD 16 to which the three color filters of
Here, the signals are photoelectrically converted into RGB signals. The image signal, which has become an electric signal, is transmitted to the image processing unit 16 in FIG.
Processing is performed as follows according to the flow shown in. CCD
The signal from 16a is converted into digital data in the A / D & S / H unit 16b, and the returned digital data is corrected by the shading correction unit 16c and the input masking unit 16d. Further, during the scaling operation, the scaling processing unit 16e receives the scaling processing. Next, the LOG conversion unit 16f converts the RGB data into CMY data, and the compression / expansion unit 16g that compresses, stores, and expands the image data.
Entered in. The stored image data is read in synchronism with each color of the printing unit 20 described later, masked by the masking / UCR unit 16h, and then γ
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 section 20 includes an image control section 21 for synchronizing each color, four laser elements,
That is, laser elements 22M, 22C, 22Y, and 22K for magenta, cyan, yellow, and black colors, a polygon scanner 23 that scans the surface of a photosensitive drum, which will be described later, with laser light, four image forming portions, that is, a transfer direction of the transfer material P. The image forming units 30M for magenta, cyan, yellow, and black, which are sequentially arranged from the upstream side to the downstream side (from the right side to the left side in the figure),
The fixing device 40 is provided as a main constituent member of the fixing device 40 disposed on the further downstream side of the image forming unit 30K on the most downstream side. In addition, the above-mentioned most upstream magenta image forming unit 30M includes a photosensitive drum 31 rotatably supported in the direction of the arrow, and a surface of the photosensitive drum 31 that is arranged around the photosensitive drum 31 substantially in that order. A primary charging device 32 for charging, a developing device 33 for developing an electrostatic latent image on the photosensitive drum 31, and a transfer material P for transferring a toner image on the photosensitive drum 31.
Transfer charger 34 for transferring to the left side, a cleaner 35 for removing transfer residual toner on the photosensitive drum 31, and an auxiliary charger 3 for removing charge.
6 and a pre-exposure lamp 37 for removing residual charges. Further, a developer concentration sensor S1 that detects the developer concentration by the amount of reflected light from the developer on the developing roller 33a of the developing device 33, and a development concentration that detects the amount of reflected light from the toner image formed on the photosensitive drum 31. The sensor S2 is arranged.

The image forming units 30C and 30 of other colors are used.
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 unit 20 having the above-described structure forms a toner image on the transfer material P in the following manner based on the output image data sent from the reader unit 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 synchronism with other colors based on the output image data to scan the surface of the photosensitive drum 31 described above. As a result, an electrostatic latent image corresponding to magenta in the original image is formed on the surface of the photosensitive drum 31.
The electrostatic latent image is formed on the developing roller 33 to which a developing bias is applied.
Magenta toner is attached by a and is developed as a toner image. This toner image is transferred onto the surface of the transfer material P conveyed by the transfer belt, which will be described later, by the discharge of 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, and the auxiliary charger 3
The pre-exposure lamp 37 removes the residual charge after receiving the charge removal by 6, and the charge is used for the next image formation starting from the charging of the primary charger 32.

Similar to the magenta image forming unit 30M, toner images of respective colors are formed on the surfaces of the photosensitive drums in the downstream cyan, yellow, and black image forming units 30C, 30Y, and 30K. To be done. The transfer material P having the magenta toner image transferred to the surface thereof is sequentially conveyed by the transfer belt to the cyan, yellow, and black image forming units 30C, 30Y, and 30K on the downstream side, and the toner images of respective colors are successively transferred. The toner images of four colors are transferred and superposed on the surface. The transfer material P on which the four-color toner images have been transferred in this way is conveyed to the fixing device 40 by a pre-fixing belt, which will be described later, and is subjected to heat and pressure by the fixing roller 40a and the pressure roller 40b, and the toner image on the surface thereof. Is fixed. The transfer material P after fixing is discharged to the outside of the apparatus main body 2 as it is when an image is not formed on the back surface. On the other hand, when an image is formed on the back surface, the transfer material 50 described below is used. The toner is again supplied to the image forming unit 30M and the like, a toner image is formed on the back surface, and then the toner image is discharged to the outside of the apparatus main body 2.

The feeding / conveying unit 50 for feeding and transferring the transfer material P is
A paper feeding device 54 that has a conveyance path for the transfer material P and that has paper feed cassettes 51a and 51b, paper feed rollers 52a and 52b, and conveyance rollers 53a and 53b on the most upstream side in the conveyance direction of the transfer material P. I have it. Further, below the paper feed cassettes 51a and 51b, a paper size detection unit S3 for detecting the size of the transfer material P stored in these paper feed cassettes 51a and 51b when these are mounted on the apparatus main body 2, S4 is attached. The paper size detection units S3 and S4 are provided with an engagement unit arranged on the paper feed cassettes 51a and 51b side and a size detection switch (neither shown) on the apparatus main body 2 side.
When 51b is mounted, the engaging portion actuates the size detection switch corresponding to the size of the transfer material P, thereby outputting the code signal corresponding to the size as size information to the apparatus main body 2. In addition to the paper feeding device 54, a multi-paper feeding device 55 is provided. From the multi-sheet feeding device 55, various transfer materials P having different properties such as material and size can be supplied to the image forming unit 30M and the like. The information about the transfer material P supplied from here, for example, the material, size, thickness, etc., is input by the user from the operation unit (not shown), or the thickness is set as described below. It is automatically detected by the thickness detector.

On the upstream side of the image forming section 30M, the transfer material P being conveyed is temporarily stopped, and the image forming section 3
A registration roller 56 that conveys in synchronization with 0M or the like is arranged. The registration roller 56 includes an upper and lower pair of upper rollers 56a (see FIG. 7) and a lower roller 56b, and conveys the transfer material P so as to sandwich the transfer material P from both front and back surfaces.

At this time, in order to detect the thickness of the transfer material P once stopped, a paper thickness detecting section (thickness detecting means) S5 is formed on the upstream side of the registration roller 56. 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, there is arranged a transfer belt 57 which circulates in the direction of arrow K57 so as to come into contact with the photosensitive drums of the image forming portions 30M, 30C, 30Y and 30K of the respective colors from below. ing. The transfer belt 57 is configured to carry a transfer material P on its surface and convey the transfer material P to the image forming units 30M, 30C, 30Y, and 30K.

On the downstream side of the transfer belt, a pre-fixing belt 58 which is rotatable in the direction of arrow K58 is provided between the transfer belt and the fixing device 40. In addition, immediately downstream of the fixing device 40,
A pressurizing mechanism section (curving pressurizing device) 59 (described in detail later) is provided which can perform pressurization for fixing the transfer material P after fixing with a plurality of switchable pressurizing forces. . A discharge flapper 60 and a discharge tray 61 for selecting discharge or re-feed of the transfer material P are disposed on the downstream side of the pressure mechanism 59.
In addition, below the discharge flapper 60, the reverse conveyance path 62,
A reversing flapper 63 is provided, and a sheet re-feeding conveyance path 64 and a sheet re-feeding device 65 are provided further downstream.

The feeding / conveying device 50 having the above-mentioned structure operates as follows. Paper feeding device 54 or multi-paper feeding device 5
The transfer material P fed from No. 5 is temporarily stopped by the registration rollers 56, and thereafter, the above-mentioned image forming unit 30M,
The registration roller 5 is synchronized with the toner images of the respective colors formed on the photosensitive drums of 30C, 30Y, and 30K.
It is nipped and conveyed by 6, and further carried and conveyed by the transfer belt 57. When passing through the magenta image forming unit 30M, the transfer charger 34 transfers the magenta toner image onto the surface. After that, the transfer material P is similarly subjected to the cyan, yellow, and black image forming units 30.
When passing through C, 30Y, and 30K, toner images of respective colors are sequentially transferred. The transfer material P on which the four color toner images have been transferred is fixed by the pre-fixing belt 58 to the fixing device 4.
The toner image on the surface is fixed by being heated and pressurized. The transfer material P on which the toner image has been fixed is attached by the pressure mechanism 59. At the time of single-sided image formation, the discharge flapper 60 is set on the discharge side, and the transfer material P is discharged onto the paper discharge tray 61. On the other hand, at the time of double-sided image formation, the discharge flapper 60 is set to the re-feeding side, whereby the transfer material P is guided to the reverse conveyance path 62 and conveyed downward until the rear end passes through the reverse flapper 63. To be done. After that, when the reverse flapper 63 is switched and the transfer material P is conveyed upward, the transfer material P is
The reversing flapper 63 guides the sheet to the sheet re-feeding conveyance path 64 and stores it in the sheet re-feeding device 65. As a result, the transfer material P is
It is turned inside out. The transfer material P is transferred from here to the image forming unit 30.
The sheet is re-fed to M or the like, and the image is formed on the back surface in the same manner as when the image is formed on the front surface, and then the sheet is discharged onto the sheet discharge tray 61.

This is the end of the description of the configuration and operation of the entire image forming apparatus.

Next, FIG. 3 shows a block diagram of the above-mentioned image forming apparatus. This block diagram is a block diagram for performing optimum image formation according to the transfer material P. The system controller 71 performs various controls of the image forming apparatus, and is totally controlled by an internal CPU. In the figure, 72 is an image input section which constitutes a part of the reader section, 16 is an image processing section, 21 is a laser drive circuit (image control section) for modulating and driving a semiconductor laser based on image data, and 22 is a laser. A semiconductor laser (laser element) driven by a drive circuit 21. Further, 31, 33 and 34 are members constituting the above-mentioned magenta image forming portion 30M, 31 is a photosensitive drum on which an electrostatic latent image is formed by the output light of the semiconductor laser 22, and 33 is a photosensitive drum 31. A developing device for developing according to the latent image above, and a transfer charger 34 for transferring the toner image on the photosensitive drum 31 onto the transfer material P. Further, 40 is a fixing device that heats and presses the toner image on the transfer material P to fix the toner image, and 59 is a pressurizing mechanism portion for allowing the transfer material P after fixing to sit down. Then, S6 is a density distribution estimation circuit (hereinafter appropriately referred to as “estimation circuit”, which will be described later in detail) that estimates the image density distribution based on the image data output from the image processing unit 16.

Next, with reference to the block diagram of FIG. 3, an operation for performing optimum image formation in the image forming apparatus having the above-described structure 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 to modulate and drive the semiconductor laser 22.
By scanning and exposing the output light of the semiconductor laser 22 onto the charged photosensitive drum 31, the photosensitive drum 31
A charge distribution corresponding to image data, that is, an electrostatic latent image is formed on the surface. The electrostatic latent image is developed as a magenta toner image with toner attached by the developing device 33.

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

The toner images of four colors are heated and pressed by the fixing device 40 to be fixed on the transfer material P. There is an optimum fixing temperature for heat fixing this toner, which is
The fixing conditions are changed based on the size of the transfer material P detected by the paper size detection units S3 and S4, the thickness of the transfer material P detected by the paper thickness detection unit S5, and the image density distribution estimated by the estimation circuit S6. By doing so, it is realized.

For example, when the transfer 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 transfer material P. The transfer speed (fixing speed) of the transfer material P is changed to realize the optimum fixing condition. That is, when the transfer material P is thick, the fixing speed is slowed, and when the transfer material P is thin, the fixing speed is increased to melt the toner image. I try to give enough heat.

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

Further, a pressurizing mechanism section 5 for supporting the transfer material P after heat fixing according to the size and thickness of the transfer material P.
By switching the pressurizing amount of 9, the optimum pressurizing control for curling can be performed.

That is, in the block diagram shown in FIG. 3, the transfer charger 34, the fixing device 40, and the pressurizing mechanism unit are based on the outputs of the paper size detecting units S3 and S4, the paper thickness detecting unit S5, and the estimating circuit S6. 59 and the like are appropriately controlled to perform optimum image formation.

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

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

In FIG. 4, Data is image data, which is an 8-bit signal in this embodiment. Vclk is a synchronizing signal of image data, and Vsync is a sub-scanning synchronizing signal indicating the start of one image section. Henable is a main scanning image effective section signal, and Venable is a sub scanning image effective section signal. Based on the size of the transfer material P detected by the paper size detection units S3 and S4, the system controller 71 derives the number of main scanning pixels N and the number of sub-scanning pixels M for image formation, and corresponds to one area of the density distribution. Calculation of M / 4 and N / 4 is performed. Reference numeral 81 is a counter for counting the main scanning area, 82 and 85 are OR gates, 83 is an up counter showing a numerical value for instructing the main scanning area, and 84.
Is a counter that counts the sub-scanning area, 86 is an up counter that indicates a numerical value that indicates the sub-scanning area, 87 is an encoder that encodes a numerical value that indicates the area of the up counters 83 and 86, and 88 is input image data. Flip-flop, 89 is an AND gate for generating an enable signal, 90 is an adder for adding the image data and the image data integrated value of the selected region, and 91, 93 and 95 are for storing the image data added value of each region. Flip-flop, 92,
Reference numerals 94 and 96 are AND gates for generating enables of the respective areas, and reference numerals 97, 98 and 99 are buffers with output enable for outputting the image data integrated value of the respective areas to the adder.

To count the main scanning area, the number of pixels N / 4 in the main scanning area is loaded into the counter by Vsync before image formation, Vclk is counted and down-counted, and when the count reaches N / 4, N / By reloading 4 and outputting a carry of n clocks to the up counter 83 and incrementing the output of the up counter 83 indicating the area, the output of the up counter 83 is increased every N / 4 pixels. To be realized. As for the sub-scanning area, as in the case of the main scanning, by counting M / 4 Hsyncs, an area signal for each M / 4 line is generated and output to the encoder 87. On the other hand, the image data is
AND gate 89 of Henable and Venable
Vc is applied to the flip-rop 88 during the enable period by
It is stored in lk synchronization. The output of the flip-rop 88 is input to one input of the adder 90. To the other input of the adder 90, the data output of a predetermined area from the buffers 97, 98, 99 whose output is controlled by the encode signal indicating each area is input. By adding the two data and storing the output in a flip-flop that is enable-controlled so as to correspond to a predetermined area, the integrated values C00 to C33 of the image data corresponding to the area indicated by the encoder 87 are calculated. The concentration distribution stored in the flip-flop and read by the system controller 71 is estimated. Further, in FIG. 6, each signal of the video system, that is, Vsyn
c, Venable, Hsync, Henable, D
The approximate timings of ata and C are shown.

The calculated image density data C00 to C33
The image density distribution is estimated from the system controller 71.
It is calculated by

Next, FIG. 7a shows the paper thickness detecting unit S5 used in this embodiment.

The paper thickness detecting section S5 is a displacement amount detecting means 100.
And the registration roller 56, the transfer material detection sensor 105, and the magnetic body 100a of the displacement amount detection means 100 (in this device, the
Detection lever 106 for moving up and down (using 304)
And its supporting member 103 and the detection lever are driven,
A solenoid 102 for moving the magnetic body 100a up and down and a drive unit 104 thereof, and a spring 10 for constantly positioning the magnetic body 100a on the magnetic field sensor 100b side.
3 and 3.

The magnetic body 100a is fixed to the magnetic field sensor 100b side by the spring 101 when the solenoid 102 is not driven, that is, in a normal state such as a standby state of the apparatus, and the magnetic field sensor 100b output. However, it is installed so as to output a signal when the transfer material is not sandwiched.

The control of the paper thickness detecting section S5 is performed by driving the solenoid 102 and the magnetic field sensor 1 based on the outputs of various sensors (not shown), particularly the transfer material detecting sensor 105 and the like.
The control signal S12 (A / D clock or the like) of the A / D converter for A / D converting the 00b signal and the thickness data S14 (8 bits in this apparatus) after A / D are all system controller 71. The above CPU performs overall control calculation.

First, the details of the displacement amount detecting means 100 will be described.

The magnetic field sensor 100b is magnetically coupled to each other, and the coil L1 is arranged so that the inductance changes according to the position change of the movable magnetic body 100a.
L2 and the capacitors C1 and C2 that output the output signal of the oscillator OSC of the predetermined frequency to the coil L1 and form a resonance circuit with the coil L2. The movable magnetic body 100a is composed of the coils L1 and L2. Reference position (there is no transfer material P, the lower surface of the movable magnetic body 100a is the magnetic field sensor 100b).
It is configured to tune to the oscillation frequency in the state of being in contact with. After that, the movable magnetic body 1 is passed through the detection circuit.
The magnitude of the magnetic field generated by 00a is output as a voltage, which is amplified by the amplifier AMP1 to a predetermined input voltage of the A / D converter AD1, and then by the A / D converter AD1.
Thickness data is output.

Here, the oscillation frequency is selected to be several MHz to several tens of MHz for economical reasons. This is because when the frequency is low, it is necessary to increase the capacity of L1, L2, C1, and C2, while when the frequency is high, it becomes difficult to handle on the circuit, and in any case, the cost is increased. is there. The detection circuit is composed of a coupling capacitor C3, diodes D1 and D2, a resistor R1, a capacitor C4, and an amplifier AMP1. Resistance R
1. It is desirable that the time constant of the capacitor C4 is set high enough to prevent the input level of the amplifier AMP1 from changing due to ripple. All of the above circuits are the magnetic field sensor 100.
It is stored in b.

The operation will be specifically described.

When there is no transfer material P and the movable magnetic body 100a is at the above-mentioned reference position, the resonance frequency of the resonance circuit becomes equal to the oscillation frequency by the OSC, the impedance of the resonance circuit becomes the minimum, and the resonance circuit outputs it. The signal level becomes maximum, and the level of the signal output from the amplifier AMP1 also becomes maximum.

On the other hand, when the transfer material P is conveyed and the position of the movable magnetic body 100a changes according to its thickness, the inductances of the coils L1 and L2 change, and the resonance frequency of the resonance circuit oscillates accordingly. The frequency deviates from the frequency and decreases, and the impedance of the resonance circuit also increases. As a result, the level output from the resonant circuit is reduced as compared with the above. That is, the change in the resonance frequency of the resonance circuit including the coil L2 is larger than the change in the resonance frequency of the resonance circuit including the coil L1, and this change in the resonance frequency is detected as a change in tuning.

Next, FIG. 8 shows a detailed view of the pressing mechanism 59. It is generally known that when the toner image transferred onto the transfer material P is heated and fixed, the transfer material P after fixing curls toward the toner image side. In such a state, the stackability on the paper discharge tray 61 is significantly impaired, and at the same time, the paper discharge property to a sorter (post-processing device) widely used in copiers, printers, etc. is deteriorated, and further, jams are generated. There is a possibility of development, and the control of the curl amount after fixing is a very important issue. In the present embodiment, a curl amount management method is realized by sandwiching the transfer material P after fixing with a pair of sponge rollers 59a and a metal roller 59b. Since the toner image is formed on the upper surface of the transfer material P, the sponge roller 59a is arranged on the upper side and the metal roller 59b is arranged on the lower side in order to add the curl in the opposite direction, and the metal roller 59b is the sponge roller 59a. Curling is suppressed by using the bite into. The amount of pressurization is adjusted by driving the cam 59c.
Metal roller movable plate 59e swingable around 9d
Is controlled up and down in the direction of the arrow in the figure. This amount of pressurization can be adjusted in a plurality of steps or steplessly according to the shape of the cam 59c. Further, 59f is a carrying roller provided to improve the carrying property of the transfer material P. For adjusting the amount of pressure applied by the cam 59c of the pressure mechanism 59 and the metal roller movable plate 59e, refer to the above-described data such as the thickness of the transfer material P by the paper thickness detector S5 and the image density distribution by the estimation circuit S6. Then, the CPU on the system controller 71
It is controlled by.

FIG. 9 shows details of the operation unit 200 which is the user interface of FIG.

Reference numeral 201 is a ten-key pad, which is used when setting the number of image forming sheets, and the set value can be cleared by the C key. A start key 203 is used to instruct the start of the image forming operation. A stop key 202 is used when interrupting image formation. Reference numeral 204 denotes a reset key, which is used to return settings such as the number of sheets setting and the density setting to the initial state. A liquid crystal touch panel 206 displays the set items and sets a mode described later. Reference numerals 207, 208, and 209 denote setting keys in the liquid crystal touch panel, which are used to set the magnification at the time of image formation.
%, That is, in the same size, 207 and 209 set reduction and enlargement magnification settings stepwise each time they are touched. Two
10 is used when setting the size of the transfer material, and is appropriately selected according to the size of the transfer material stored in the transfer material storing means 54, 55. Reference numerals 211, 212, and 213 are used when setting the density of image formation, and 212 is used when automatically setting the density adjustment of image formation according to the density of the original detected by the density detecting unit (not shown). 21
1 and 213 are used when the concentration is manually set. 21
4 is a key for selecting the type of transfer material, such as thin paper, plain paper,
Select either thick paper, glossy paper, or OHP paper.
Based on the selected result, the fixing condition of the fixing device 40 and the pressurizing condition of the pressurizing mechanism section (curving pressurizing device) 59 are calculated. 205 is used when selecting whether or not to automatically detect the thickness of the transfer material by using the displacement amount detecting means 100 of the paper thickness detecting unit S5. When the automatic detection of the paper thickness is selected, the type of the transfer material selected by the transfer material type selection key becomes invalid, and based on the detection result of the paper thickness detection unit S5, the above-described fixing device 40 is used. And the pressure conditions of the pressure mechanism unit (curving pressure device) 59 are calculated. Normally, the thickness of the transfer material is automatically detected, but the paper thickness detection unit S
In consideration of the configuration of the displacement amount detecting means 100 of No. 5, the thickness of the transfer material is detected by the contact method, and therefore, there is a possibility that fine scratches generated on the surface of the transfer material may affect the image. Then, a configuration capable of stopping the detection function is added. All of the above signals from the operation unit 200 are input to the system controller 71, and at the same time, the display is also changed by the system controller 71.

FIG. 10 shows a flowchart for calculating the thickness of the transfer material P according to this embodiment.

The calculation of the thickness of the transfer material P is also totally controlled by the CPU on the system controller 71.

The transfer material P fed from the paper feeding devices 54 and 55 (see FIG. 1) through the paper transport path reaches the paper thickness detecting section S5, and the paper thickness of the transfer material P is detected (S).
1). First, it is determined whether or not to detect the paper thickness (S
2). This is determined by operating the paper thickness detection key 205 provided on the operation unit 200 by the operator, and the determination is made based on the information. If the paper thickness detection has not been selected, the movable magnetic body 100a is retracted (S13),
The registration roller is turned on (S11), and the paper thickness detection is ended (S12). If execution of paper thickness detection is selected, first, offset data before the transfer material P reaches the registration roller 56 is collected (S3). At this time, since the movable magnetic body 100a is set to the reference position, the solenoid drive circuit 104 is not driven and the spring 10
The tension of 1 brings the movable magnetic body 100a and the magnetic field sensor 100b into contact with each other. Thereafter, the collected offset data is temporarily stored as Doff, and the movable magnetic body 10
In order to prevent the transfer material P from colliding with 0a, and the occurrence of jams due to scratches, breakage, and retention of the tip of the transfer material P generated at the time of collision, the movable magnetic body is retracted (S5). To retract the movable magnetic body, the solenoid drive circuit 104 is driven, and the axis of the solenoid 102 moves in the direction of the arrow in FIG. 7A, so that the transfer material P can be smoothly moved away from the magnetic field sensor 100b. To do so. Movable magnetic body 1
00a, and then start feeding the transfer material P (S
6) It is determined whether or not the transfer material P has reached the registration rollers 56a and 56b (S7). This detects whether or not the transfer material P has passed below the transfer material detection sensor 105, and then the sensor 105 and the registration rollers 56a, 5 and 5.
It is determined from the moving time of the transfer material P, which corresponds to the distance to the 6b. After confirming that the transfer material P has reached the registration rollers 56a and 56b, the movable magnetic body 100a is lowered, and the transfer material P is sandwiched between the movable magnetic body 100a and the magnetic field sensor 100b (S8). At this time, as in (S3), the solenoid drive circuit 104 is not driven, and the movable magnetic body 100a is moved by the tension of the spring 101. After that, the transfer material P is sandwiched between the movable magnetic body 100a and the magnetic field sensor 100b to collect the thickness data Don of the transfer material P (S4), and the thickness of the transfer material P is calculated (S10). The thickness of the transfer material P is (S9)
A value obtained by subtracting the offset data Doff obtained in (S3) from the thickness data Don obtained in step S is D.
After the thickness of the transfer material P is calculated, the above-mentioned fixing conditions are set, the setting of the transfer material P is set, and the like, the registration rollers 56a and 56b are driven (S11), and the transfer material P is subjected to an image forming process. Then, the paper thickness detection sequence is ended (S12).

(Second Embodiment) In the first embodiment, the retracting timing of the movable magnetic body 100a is set immediately before reaching the registration roller, but the transfer material P is fed by the sheet feeding cassettes 51a and 51b and the multi-sheet feeding device. It is also possible to set at the same time as the paper is fed from 55, and the same effect can be obtained.

(Third Embodiment) In the first embodiment, the retracting timing of the movable magnetic body 100a is set immediately before reaching the registration roller. However, the paper thickness detection execution key 205 of the operation unit 200 is used to set the paper thickness. It is also possible to set the detection to be unexecuted and set at the same time, and the same effect can be obtained.

At this time, in the default setting of the image forming apparatus, the movable magnetic body 100a is kept in the retracted state,
It is possible to set the contact / non-contact of the movable magnetic body 100a only when the mode is changed to the thickness detection mode, and the same effect can be obtained.

[0060]

EFFECT OF THE INVENTION An image forming apparatus for transferring a toner image formed on an image carrier based on image data to a transfer material supplied through a conveying path and then fixing the toner image on the transfer material to form an image. In the above, there are provided a thickness detecting means arranged in the conveying path for detecting the thickness of the transfer material, and a controlling means for changing the image forming condition based on the data about the thickness output by the thickness detecting means. The thickness detecting means is disposed at a position where it comes into contact with the transfer material, and is provided around the movable magnetic body so as to be movably displaced by the contact, and is fixed around the movable magnetic body. A magnetic field sensor for detecting the magnitude of the magnetic field created by the body as the thickness of the transfer material is provided, and the thickness detecting means has a thickness detecting and selecting means for selecting whether or not to carry out the operation. The detection and selection means will not do that. When selected, the movement of the movable magnetic body is controlled so that the movable magnetic body is retracted so that the movable magnetic body does not come into contact with the transfer material, so that thin paper, glossy paper, or OHP paper can be obtained. For transfer materials such as
The influence of the thickness detecting means can be eliminated.

[Brief description of drawings]

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

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

FIG. 3 is a diagram showing how image forming conditions are changed according to the properties of a transfer 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 region of an estimation circuit.

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

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

FIG. 8 is a diagram showing details of a configuration of a pressurizing mechanism section.

FIG. 9 is a diagram showing details of an operation unit 200 shown in FIG.

FIG. 10 is a flowchart for detecting the thickness of the transfer material according to the first embodiment.

Continued front page    F term (reference) 2H027 DC02 DC03 DC04 DC19 DE04                       DE09 DE10 EA03 EA12 ED24                       ED25 ED30                 2H072 AA08 AA16 CA01 HA07 HA08                 3F048 AA02 AA05 AB01 BA06 BB02                       CA02 DA06 DC19 EB37

Claims (5)

[Claims] 1. An image forming apparatus which transfers a toner image formed on an image carrier based on image data to a transfer material supplied through a conveying path and then fixes the image on the transfer material to form an image. In the above, a thickness detecting means arranged in the transport path for detecting the thickness of the transfer material, and a control means for changing the image forming condition based on the data about the thickness output by the thickness detecting means. The thickness detecting means is arranged at a position where it abuts on the transfer material, and is provided around the movable magnetic body so as to be movably displaced by the abutment, and is fixed around the movable magnetic body. A magnetic field sensor for detecting the magnitude of the magnetic field created by the body as the thickness of the transfer material is provided, and the thickness detecting means has a thickness detecting and selecting means for selecting whether or not to carry out the operation. The detection is not performed by the detection selection means. When the selection is made, the movement of the movable magnetic body is controlled so that the movable magnetic body is retracted so as not to contact the transfer material. . 2. The transfer material is set at a timing at which the movable magnetic body is retracted so as not to contact the transfer material.
The image forming apparatus according to claim 1, wherein the image forming apparatus is carried out before being fed from a transfer material storing means for storing the transfer material. 3. The timing for retracting the movable magnetic body so as not to contact the transfer material is until the leading end of the transfer material reaches a registration roller. Image forming device. 4. The timing at which the movable magnetic body is retracted so as not to contact the transfer material is when the thickness detection selecting unit selects that the thickness detection is not performed. The image forming apparatus according to claim 1. 5. The movable magnetic body is retracted so as not to always come into contact with the transfer material when the image forming apparatus is in an initial state, and the thickness is detected by the thickness detection selecting means. The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled so as to be brought into contact only when selected.