JPH0477649A - Paper discriminator - Google Patents

Abstract

PURPOSE:To achieve the detection of the type of papers and sheets by a relatively simple method detecting reflected scattered light to be reflected from a paper to discriminate the paper based on an output level thereof. CONSTITUTION:A paper detection sensor 10 is disposed near a resist detection sensor 8 to detect the type of a transfer paper P. The sensor 10 employs a light reflection type photosensor having a light emitting section 11 and a photo detecting section 12 and an output vlue is read out with the transfer paper P stopped at a position of a resist roller 9. At this point, utilizing a difference of a reflection scattering rate of light irradiating the transfer paper P, a paper is discriminated based on the level of a detection signal of the sensor 10. This enables detection of the type of paper simply thereby optimizing process conditions for automatic formation of an image on the transfer paper P through a controller.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a paper detection device suitable for use as paper type detection means for transfer paper in image forming apparatuses such as copying machines, facsimiles, and printers.

[Conventional technology]

Conventionally, efforts have been made to optimize various conditions such as development, transfer, and fixing in image forming devices that apply electrophotography, such as copying machines, laser printers, and facsimiles, in order to obtain good images on various types of transfer paper. is being done. In addition, in image forming apparatuses that use liquid ink, such as ink-shared recording apparatuses and simple printing machines, the conditions for forming images on recording paper are optimized in order to obtain good images on recording paper. There is.

Furthermore, with recycled paper or the like having poor smoothness, toner is not transferred to the fine concave portions of the paper, so the resulting transferred image has poor solid uniformity. Therefore,
Before being used as transfer paper, it is subjected to pressure processing in advance to obtain surface smoothness, and images are formed in the same way as ordinary (PPC) paper.

[Problem to be solved by the invention]

Among the various image forming apparatuses mentioned above, electrophotographic wet image forming apparatuses are particularly suitable for obtaining high-resolution images because the toner particle size of the developer is usually less than 1 μm, which is less than 1710 μm for dry toner. In such an image forming apparatus, which has been expected recently, since the electrophotographic process is based on a process in which toner moves electrophoretically in a dispersion medium, a dispersion medium is also required during transfer.

When using paper with poor surface smoothness as transfer paper, it is necessary to control the dispersion medium to a large extent in order to improve image precision. If pressure is applied from a pressure mechanism such as a fixing roller to the transfer paper being conveyed before the image is fixed, abnormal images such as flow detection are likely to occur. This is because transfer paper with excellent hygroscopicity absorbs the dispersion medium, so the toner image remains on the transfer paper even if pressure is applied, whereas with transfer paper with low hygroscopicity, the toner image remains on the transfer paper in the same state as transferred. It is thought that the abnormal image is caused because the dispersion medium is washed away when pressure is applied, and the toner image is also washed away accordingly.

Furthermore, since the toner image is fixed by drying the developer solvent, when a transfer paper with low hygroscopicity is used, the paper may be discharged with the formed image incompletely fixed. In that case, the image on the cover of the ejected and stacked transfer paper may be touched by the operator, or the image on the stacked transfer paper may be offset from the adjacent transfer paper, causing the image on the surface of the transfer paper or the superimposed transfer paper to be removed. Problems such as the back side of the paper being stained or the toner adhering to the transfer papers and the formed image being damaged when they are peeled off may occur.

FIG. 6 is an enlarged explanatory diagram showing a state in which such a problem occurs when transfer paper is piled up, and the figure shows a case where transfer paper with poor moisture absorption, such as a plastic sheet, is used. This is what is shown.

FIG. 7 is a diagram schematically showing the paper feeding, image forming, and paper ejecting operations of the image forming apparatus. In the figure, an image is formed on the transfer paper P stored in the first cassette (CO) of the paper cassette 3 in the image forming section 2 including the photoreceptor 13 of the image forming apparatus 1, and the paper is transferred to the paper output tray 5 outside the machine. Deposited. When the ejection of the transfer paper P is completed, the next transfer paper P on which an image will be formed is fed from the paper cassette CO. For example, transfer papers of different paper sizes are stored in the paper cassette C1.

As shown in Fig. 6, the image surface of the uppermost sheet of transfer paper formed and stacked in this manner is exposed in A, so there is a possibility that the operator's fingers etc. may directly touch the formed image. , image blurring and image peeling occur due to contact. In B, the image on the front surface of the transfer paper P stacked one on top of the other with incomplete fixation is offset from the back surface of the upper transfer paper P.

As described above, when different types of transfer paper are used under the same image forming conditions, various inconveniences occur. Generally P
Since the materials and surface conditions differ depending on the type of transfer paper, such as PC paper, art paper, OHP sheets, second original drawing paper, and recycled paper, which has recently been attracting attention, these papers cannot be used as recording paper or printing paper. When images are formed using paper, the fixability of ink and toner varies depending on the type of paper. Therefore, the optimum process conditions for obtaining the best image differ depending on the type of transfer paper, and in order to always obtain a good image, it is necessary to set the optimum conditions for image formation for each type of transfer paper and form the image. It is necessary to control it as follows.

In particular, efforts have been made to improve OHP sheets, but the conditions for forming images on OHP sheets are significantly different from those for general PPC paper.

Therefore, we detected differences in the surface properties of sheets and obtained information on light scattering caused by surface roughness using a simple method.
One possibility is to detect the type of paper. For example, conventional methods for measuring surface roughness include a contact method that measures metals, ceramics, etc. with high accuracy, but this method has many limitations in terms of equipment installation and measurement methods. It is not suitable for application to popular image forming devices such as copiers and office printers.

Further, transfer papers made of widely different materials, such as OHP sheets, have other unique characteristics such as excellent transparency to irradiated light. Therefore, a method of detecting the type of paper by combining it with information on the light transmittance and reflectivity caused by these materials was investigated.

The present invention was made under the above circumstances, and can be applied to the image forming method of an image forming apparatus, and can be applied to paper and paper in a relatively simple manner.
The purpose is to provide a means for detecting the paper type of sheets. In addition, it is an object of the present invention to provide a means that can more accurately discriminate paper types.

[Means to solve the problem]

In order to solve the above-mentioned object, the present invention provides a paper detection sensor including a light emitting section that emits irradiation light to be irradiated onto paper, a light receiving section that detects reflected and scattered light reflected from the paper, and the paper detection sensor. The paper is discriminated by a discriminating means that discriminates the paper based on the output level from the paper.

In addition to the above-mentioned means, a light emitting unit that emits irradiation light to be irradiated onto the paper, specularly reflected light and reflected scattered light reflected from the paper, specularly transmitted light and transmitted scattered light that transmits the paper, at least The paper may be discriminated by a paper detection sensor having a light receiving section that detects each of the two, and a discriminating means that discriminates the paper based on the output level from the paper detection sensor.

[Effect]

Upon receiving the output from the paper detection sensor, the discriminating means compares the output level of one or more output signals with, for example, a preset reference value to discriminate the paper.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a configuration diagram showing the main parts of a wet type copying machine to which this embodiment is applied. The general configuration of the copying machine will be explained according to the drawings.

In the figure, reference numeral 13 denotes a photosensitive drum, which is rotated in the direction of the arrow at a constant speed during copying. The rotating photosensitive drum 13 is uniformly charged by a charger 14 in the dark, and then irradiated with light by an exposure device (not shown) that forms an optical image of the original, thereby forming an electrostatic latent image on its surface. Non-image forming areas on both sides of the photosensitive drum 13 in the axial direction are neutralized by the eraser 15 . As the photosensitive drum 13 rotates, the electrostatic latent image on the surface reaches the position of the developing device 16, and becomes a developed image by the action of the developing device 16.

On the other hand, as shown by the broken line path from a paper feeder (not shown) located on the right side of the drawing, transfer paper P is conveyed to the upper part of the transfer device 18 via the conveyance roller 17, and the transfer paper P is conveyed to the upper part of the transfer device 18 by the action of the transfer device 18. The image (toner image) is transferred onto the transfer paper P. After the transfer, the transfer paper P is sent to the fixing device W4 by the conveyor belt 19, where it receives heat from the heater H of the heating roller 20, the toner image on the transfer paper P is fixed, and the transfer paper P is discharged. The paper rollers 21 eject the paper toward a paper ejection tray outside the machine.

As the photosensitive drum 13 rotates after the image has been transferred, residual toner is removed by a cleaner 22, and residual charge is removed by a static eliminator 23 consisting of a static eliminator lamp or a static eliminator charger to prepare for the next copying operation.

In the developing device 16, first and second developing rollers 25, 26 and a squeeze roller 27 are disposed in a developing container 24 in close opposition to the surface of the photosensitive drum 13 with a minute interval (approximately 0.1 mm) therebetween. ing. As shown by the arrows, the first and second developing rollers 25 and 26 have the same peripheral surface movement direction as the photoreceptor drum 13 and are driven to rotate at a faster speed, while the squeeze roller 27 and the developing rollers 25 and 26 It is rotated in the opposite direction.

The developer is supplied downstream from a developer supply nozzle 28 that is open above the first developing roller 25, and is supplied to the first and second developing rollers.
The developing rollers 25 and 26 uniformly wet the surface of the photosensitive drum 13. The remaining developer on the photosensitive drum 13 is wiped off by the squeeze roller 27. The developer used for development is collected into the developer tank 30 through a collection hole 29 provided at the bottom of the developer container 24.

In the above copying machine, under normal conditions, the transfer paper P is rpc
In the case of paper, the image forming conditions of the control unit, which will be described later, are set to be the optimal conditions, and the reflected and scattered light intensity measured by the paper sensor provided in the paper feed unit of the transfer paper and a certain reference value are set. Control is performed so that the image forming conditions at the image forming section are changed based on the comparison.

As the image forming conditions to be changed, for example, the number of rotations of the squeeze roller 27 may be changed to increase or decrease the amount of toner solvent attached to the transfer paper P, but in this embodiment, the photoreceptor drum 13 is exposed to light. Lamp regulator voltage VL that provides the exposure intensity of the exposure device, charging charger 1
5, the charging charger applied voltage VE when charging the photosensitive drum 13 and the transfer charger voltage ■A when applying a transfer charge to the transfer paper P of the transfer device 18 according to the determined paper type of the transfer paper P. It's changing.

Next, a schematic configuration of a paper feed section of a copying machine equipped with a paper detection sensor will be described.

FIG. 3 is a partially enlarged view of the paper feed section of the copying machine shown in FIG. 2. This figure shows a state in which only one sheet of the uppermost transfer paper P loaded in the paper feed cassette 3 has been transferred by the pickup roller 5, the feed roller 6, and the reverse roller 7, and has reached the registration roller 9. The transfer paper P that has reached the registration roller 9 is further conveyed to the transfer section, and the transfer paper P
A transferred image is formed thereon.

In this embodiment, an OHP detection sensor (paper detection sensor) 10 that detects the type of transfer paper P is installed near the registration detection sensor 8 disposed close to the registration roller 9, and the output value of the sensor is read. Transfer paper P is OHP
Determine whether the sheet is for use.

The OHP detection sensor 10 uses a light reflection type optical sensor having a light emitting part and a light receiving part, which will be described in detail later.In order to improve detection accuracy, the output value is determined when the transfer paper P is stopped at the registration roller 9 position. is read. At this time, by utilizing the difference in the reflection and scattering rate of the light irradiated onto the transfer paper P, the detection signal of the OHP detection sensor 10 becomes "ON" when the value is less than a certain predetermined value. The control device described below is
Process conditions (for example, charging potential) to automatically form an image on the transfer paper P when this detection signal "ON" state is detected.
Change the conditions so that they are optimal for OHP sheets.

In addition, manual OHP process settings are provided on the operation unit (not shown) so that the operator can perform image formation using OHP sheet process conditions at his/her own discretion, or in case the OHP detection sensor 10 fails. A switch is attached. General-purpose (for PPC paper) process conditions and O
The process conditions for HP sheets are set in advance and can be switched by the control device.

Here, a paper detection method using the OHP detection sensor 10 will be explained.

FIG. 1 is an explanatory diagram illustrating the paper detection method of the OHP detection sensor 10 when viewed from the side of the light-receiving surface of the transfer paper P. In the figure, 11 and 12 are respectively θ relative to the direction perpendicular to the light-receiving surface of the transfer paper P. a light emitting part of the OHP detection sensor 10 that emits irradiation light L0 that irradiates the transfer paper P with an inclination of;
and a light-receiving section that receives reflected and scattered light LEII+ that is also reflected with an inclination of θ1 (θ1 > θ.).

Assuming that the surface of the transfer paper P is a mirror surface, the irradiation light L0 irradiated onto the transfer paper P from the light emitting unit 11 is totally reflected on the surface of the transfer paper P and becomes specularly reflected light L□, resulting in scattered light and transmitted light. No light can be seen. However, the surface of filter paper/sheets that are generally used as transfer paper has minute irregularities and is often light-transparent, and furthermore, the composition of the substrate may be uneven or different from the substrate. Sometimes the surface is coated with a substance.

When these transfer papers P are irradiated with light at an angle with respect to the direction perpendicular to the paper surface, the irradiated irradiation light L0 has a characteristic ratio depending on the type of paper, and is divided into regular reflected light Lll, I, and specular transmitted light L.
□, and is generally divided into two types of scattered light, although weak, namely reflected scattered light LDll and transmitted scattered light LKIF.

When using a conventional reflective optical sensor, the light receiving part is placed in a position directly facing the irradiated light, and the reflected light is detected. However, in the present invention, instead of the specular reflected light LIIR, which is usually reflected with the maximum intensity, the diffused reflected light is detected. The feature is that it detects light LDl.

The intensity of the above-mentioned weak scattered light varies depending on the type of transfer paper being detected, depending on its surface condition and light transmittance. Table 1 shows the LDR of reflected and scattered light on various types of paper.
An example of relative values of intensities obtained by measuring and transmitted scattered light LDP is shown.

Table 1 As is clear from Table 1, the scattering tendency differs depending on the paper, so the type of transfer paper can be determined by comparing the intensity of the scattered light detected by the OHP detection sensor 10 with a value measured in advance. It becomes possible to do so.

Therefore, in the above-mentioned wet copying machine, by using the characteristics of reflected and scattered light shown in Table 1 as a paper discrimination means to determine the type of transfer paper, and by adjusting the image forming conditions to the type of transfer paper, it is possible to always obtain a good quality image. image formation. To do this, it is necessary to automatically detect the type of transfer paper fed and change process conditions accordingly.

Therefore, a control mechanism that controls the copying machine including the setting of process conditions of the copying machine will be described in detail based on the configuration diagram of the control section of the wet type copying machine shown in FIG.

Output signals from the key operation switch group 38 of the copying machine, the machine white state detection sensors (including the OHP detection sensor) 39, the pulse generator 40 that generates pulses synchronized with the rotation of the photoreceptor drum motor, etc. are sent to the CPU 31 by human input. be done.

The CPU 31 is connected to a ROM 33, a RAM 32, and input/output ports 34 and 35 via an address bus, a control bus, a data bus, and the like. The input/output coupler sofa 34,35 connects the display element 3 via the driver 36.
It is connected to a load such as 7. Therefore, the operations of the exposure, charging, and development systems, which are image forming systems, are controlled via the input/output port buffer 35 and driver 36.

FIG. 5 schematically shows a flowchart of the control program for the copying machine.

(a) is a main control routine, in which after turning on the main switch, initial settings for the entire copying machine (S-1) are performed, and then various copy mode settings made by the operator (S-2) are performed. Furthermore, the copy conditions are checked (S-3)L, and if the conditions are met, the process waits for the print key to be pressed. Copy start processing (S-4) follows print key 0N (S-4).
-5), perform copy operation processing (S-6).

Next, the copy operation processing subroutine of step S-6 will be explained according to (b). First, a pulse control process (S-9) for operating the copying machine is executed, and then a process condition setting process (S-10) and a process control process (111) are executed.
The copying operation continues until the number of copies preset by the operator is reached (S-12), and when the copying operation is completed, an end flag is set (S-13).

As shown in FIG. 5(C), the subroutine of the process condition setting process in step 5-10 is in the state fi (S-14) where the registration detection sensor is ON and the flag (general purpose) is ON.
(S-15) and the flag (OHP) is also ON (
S-16), but the OHP sheet SW (automatic) is ON.
(S-17), and the OHP detection sensor is ON (S-17).
-18), the flag (general purpose) is 0N (S-19)
be done.

Also, in step 5-17, switch for OHP sheet (automatic)
is OFF, and the OHP sheet SW (manual) is ON.
(S-23) and OH in step 5-18
When the P detection sensor is ON, the flag (OHP) is ON (
S-24). In step 5-14, the resist detection sensor is OFF, and the separation detection sensor after transfer is OFF.
(No in S-20), both the flag (general purpose) and the flag (OHP) are OFF (S-21), (
S-22). Steps 5-15 and Step 5
If any flag is turned ON at -16, the process returns to the copy operation processing subroutine.

In the process control processing subroutine of step 5-11 shown in (d), if the flag (general purpose) is 0N (S-25), the general purpose process control 11 (S-27) is activated, and the two blowfish (OHP) is ON (S-25). -26), then the OHP process (S-28) is executed.

In addition, step 5- shown in (e) and (f), respectively.
27. In the general-purpose process control and OHP process control processing subroutines of 3-28, the charger applied voltages VEP and V, respectively.

Set the lamp regulator voltage ■1 to VLP and VtO (S-30).
, (S-33), and further sets the transfer charger voltage (2) to vyr and VTO (S-31).

(S-34,).

Table 2 shows the magnitude relationship between the values of the charger applied voltage (4), the lamp regulator voltage (2), and the transfer charger voltage (2).

Table 2 *The copying machine uses an analog image exposure method Next, the second implementation is capable of distinguishing not only PPC paper and OHP sheets, but also a wider variety of transfer papers, based on the magnitude of the output value of the paper detection sensor. Explain an example. In this case, the flowchart of the control program is the same as that of the first embodiment (FIGS. 5(a) and 5(b)) regarding the main routine and subroutines for copy operation processing, and the process condition setting processing and process The control processing subroutine is
The routines are changed to those shown in FIGS. 5(C') and (d'). In this case, the control method expands the two-way paper detection method of the first embodiment, and uses four paper detection methods according to the output value of the paper detection sensor.
This makes it possible to detect the paper type and control the processing conditions to suit each paper type.

The flowcharts in FIGS. 5(c') and (d') will be explained below. In the process condition setting process in (C'),
First, the registration detection sensor 8 is ON (S-35), and all of the processing 1 flag to processing 4 flag are OFF (S-36).
-39 are all No), check the output level of the paper detection sensor 10, and if it is less than 25% of the maximum value (S
-40), and sets the processing 1 flag (14.1). Also,
50% when the output level of paper detection sensor 10 is 25% or higher
If it is less than (S-4, 2) processing 2 flag (S-43),
If it is 50% or more and less than 75% (S-44), set the processing 3 flag (S-4, 5), and if it is 75% or more of the maximum value (NO in S-44), set the processing 4 flag ( S-
46). Further, if the registration detection sensor 8 is in the OFF state, the output of the post-transfer separation detection sensor (not shown) is checked, and if it is in the OFF state (No in S-47), the processing 1 flag to the processing 4 flag is checked. Turn off all flags (S-48~S
-51).

Next, to explain the flowchart of the process control process in (d'), the process 1 flag to process 4 flag are checked sequentially (S-52 to S-55), and the control process 1 flag is checked according to the ON state of each flag. -Execute the routine of control processing 4 (S-56 to S-59).

The subroutine of control process 1 in step 5-56 is (e'
), set the charger applied voltage VE to VEI (S-60), set the lamp regulator voltage V to ■- (S61), and further set the transfer charger voltage ■1 to VTI (S-62). . Also,
In the subroutines of control processing 2 to control processing 4, although not shown, processing is performed according to a flowchart similar to the flowchart of control processing 1, and the voltages applied to the charger at that time are vEt*, E3+VEa, and the lamp regulator voltage. ■, are respectively V L Z +
In addition to V L 'IVL4, transfer charger voltage■
7 are set to ■1□, VT:ll and Vy4, respectively.

In this embodiment, four types of paper are detected depending on the level of the output value of the paper detection sensor, but as described above, a plurality of light receiving sections of the paper detection sensor are arranged at different positions.
Based on the information obtained from the information on the different light transmission or light reflection of the transfer paper, the paper type of the transfer paper can be determined. Next, a third embodiment of the present invention employing such a method will be described.

Table 3 shows not only the relative intensities of the reflected scattered light LDI and transmitted scattered light LDF shown in Table 1, but also the regular reflected light Lllll, positive 1
This shows the results of measuring the relative intensity of the 311M light LIF, and by using more Yari Chijoori to distinguish paper, it is more accurate than when discriminating only by scattered light. It becomes possible to identify the transfer paper.

According to Table 3, for example, the reflected and scattered light La1l of the coated paper and the second original paper have substantially similar intensities. However, since the intensity of the specularly transmitted light +-11P of the two is greatly different, the specularly transmitted light LI[F
By detecting the intensity of the two, accurate discrimination between the two becomes possible.

Similarly, by measuring reflected scattered light LI1m, transmitted scattered light transmitted ゎ1, specular reflected light 1-Rll, and specular transmitted light LIIF, and by combining the intensity information and using it as a means for paper discrimination, it is possible to detect many types of paper.・Discrimination is performed for sheets. The flowchart for paper type discrimination is based on the first and second embodiments.

The embodiments in which the present invention is applied to a copying machine have been described above, but it can also be easily applied to blinkers, facsimile machines, etc. in which image formation is performed using a similar method.

Furthermore, in an image forming apparatus equipped with a calendar processing device, the present invention detects whether recording paper has a rough surface, such as rag paper or recycled paper, and performs compression processing according to the detected information to create a smooth transfer paper. Recording may be performed under similar conditions.

As is clear from the above description, in this specification, the term "paper J" includes not only general paper making, but also flexible sheets, thick plate-like members, and the like.

〔Effect of the invention〕

As explained above, according to the present invention, a device that detects reflected and scattered light to discriminate paper can perform discrimination that reflects the roughness of the paper surface, compared to a discrimination device that uses a conventional reflective sensor. Therefore, effective discrimination can be made especially for paper/sheets of transfer paper used in image forming apparatuses.

In addition, devices that detect different types of reflected light and transmitted light and combine them to distinguish between paper types are used in cases where paper discrimination must be performed particularly strictly.
Accurate discrimination becomes possible.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram illustrating the paper detection method of an OHP detection sensor according to an embodiment of the present invention, FIG. 2 is a partially enlarged view of the paper feed section of a wet copying machine to which this embodiment is applied, and FIG. 3 4 is a configuration diagram showing the main parts of the copying machine, FIG. 4 is a configuration diagram of the control section of the copying machine, FIG. 5 is a flowchart of the control program for the copying machine, and FIG. FIG. 7 is an explanatory diagram showing the state in which this occurs. FIG. 7 is an explanatory diagram showing an outline of paper feeding, image forming, and paper ejecting operations of the image forming apparatus. ■...Image forming device, 3...Paper feeding power, 8...
・Registration detection sensor, 10...OHP detection sensor (
paper detection sensor), 11... light emitting section, 12... light receiving section. Figure S - Figure C σ (b) Figure and d' Figure Procedure Amendment (Method) % Formula % Display of Cases Case of Person Who Amends Name Sheet Discrimination Device of Patent Application Plain Invention Relationship with No. 2-1.90823

Claims (2)

[Claims] (1) A paper detection sensor equipped with a light emitting section that emits irradiation light to be irradiated onto the paper and a light receiving section that detects reflected and scattered light reflected from the paper; A paper discriminating device having discriminating means for discriminating. (2) A light emitting unit that emits the irradiation light that irradiates the paper, and detects at least two of the specularly reflected light and reflected scattered light that are reflected from the paper, and the specularly transmitted light and transmitted scattered light that pass through the paper. A paper discriminating device includes a paper detection sensor having a light receiving section, and a discriminating means for discriminating paper based on an output level from the paper detection sensor.