JPH0580625A - Image forming device - Google Patents

Abstract

PURPOSE:To continuously obtain an excellent image which is not influenced by the material of a fed recording medium. CONSTITUTION:When the image of a specified density patch is formed on an image carrier or the recording medium P by an image forming means, the density state of the density patch is detected by a density detection means (patch density sensor 12), and a setting means (image forming control part CONT) automatically sets an image forming condition such as a transfer current and the contrast potential of a drum, etc., based on the density state and information on the material of the recording medium P detected by a recording material detection means 11 at the time of feeding the recording medium.

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 capable of automatically setting image forming conditions based on read image density.

[0002]

2. Description of the Related Art Conventionally, in this type of image forming apparatus, the density of a toner image formed on an image carrier (for example, a photosensitive drum) is read, and image forming conditions (developing bias, etc.) set in the image forming means. Is controlled so that a clear image can always be obtained with a stable image density. Further, there is a method of reading the toner density developed on a recording medium (for example, recording paper) after fixing and controlling the image forming means so that the image density becomes appropriate by the obtained signal.
No. 70 is disclosed.

[0003]

However, when the toner density of the image developed and fixed on the recording medium is detected, the recording medium is detected by detecting a subtle change in the transfer condition due to the material of the recording medium or the environmental change. Since the control is not performed to give the image forming condition adapted to the above, there is a serious problem that the fixed image varies depending on the material of the recording medium and the environmental change and the image cannot be used as the image density detection image. there were.

The present invention has been made in order to solve the above-mentioned problems, and recording is fed by setting the image forming conditions according to the material of the recording medium onto which the developed image is transferred. An object of the present invention is to obtain an image forming apparatus that can continuously obtain a good image that is not affected by the material of the medium.

[0005]

An image forming apparatus according to the present invention is fed with image forming means for forming a predetermined density patch for determining a desired image or development density on an image carrier. Recording material detecting means for detecting material information of the recording medium, density detecting means for detecting a density state of the density patch imaged on the image carrier or the recording medium, and a density state detected by the density detecting means, And a setting unit for automatically setting the image forming condition of the image forming unit based on the material information of the recording medium detected by the recording material detecting unit.

[0006]

In the present invention, when a predetermined density patch is imaged on the image carrier or the recording medium by the image forming means, the density state of the density patch is detected by the density detecting means. An image having the optimum density for the material of the recording medium to be fed is automatically set by the setting means based on the material information of the recording medium detected by the recording material detection means at the time of feeding, and the image forming condition of the image forming means is automatically set. Allows formation.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view showing the construction of an image forming apparatus according to an embodiment of the present invention, showing, for example, the case of a 4-drum laser beam type digital color image forming apparatus. The configuration and operation of each unit will be described below.

In this apparatus, four image forming stations are provided around the electrophotographic photosensitive member so as to have image forming means, each of which corresponds to an image forming color, and each image forming station is formed. The toner image on the photoconductor is transferred to a transfer material conveyed by a belt-shaped moving body that moves to face the photoconductor. Image forming stations P for magenta, cyan, yellow, and black
m, Pc, Py and Pk are respectively photosensitive drums 1M and 1
C, 1Y, 1K are arranged and rotated in the arrow direction (clockwise direction). In addition, each photosensitive drum 1M, 1C, 1Y, 1K
The primary chargers 2M, 2C, 2Y, 2K and a scanning optical device (laser scanner) 3 as an optical scanning unit are provided around the
M, 3C, 3Y, 3K and developing devices 4M, 4C, 4
Y, 4K, and further cleaning devices 5M, 5C, 5
Y and 5K are arranged.

A recording medium, for example, the transfer material P is fed from the paper feed cassette 7 to the transfer section 6 through the recording material detecting means 11. Further, a transfer section 6 which constitutes one of image forming means.
Has a transfer belt (conveyor belt) 6a commonly used in each image forming station and transfer chargers 6M, 6C, 6Y, 6K for each drum, and a full-color image is formed on the transfer belt 6a. On the designated transfer material P,
This is achieved by successively transferring the toner images of the respective colors formed on the photosensitive drums 1M, 1C, 1Y and 1K in an overlapping manner. The transfer material P is supplied from the paper feed cassette 7, and the transfer material P that has completed the transfer process is separated and discharged to the tray 9 via the fixing device 8. 12 is a patch density sensor,
For example, the patch image transferred onto the transfer belt 6a is optically read, and the density information is output to the controller 15 of the image formation control unit CONT. In this embodiment, an image forming means is composed of the photosensitive drum, the developing device, the scanning optical device, the primary charger and the like, and the density patch data stored in the internal memory of the controller 15 of the image forming control unit CONT is used. Based on this, density patches for determining the image density state are formed on the conveyor belt 6a or the recording medium. 1
0M, 10C, 10Y, and 10K are transfer chargers.

The scanning optical devices 3M, 3C, 3Y, 3K
Is a laser light source that is not shown, a rotating polygon mirror that scans the laser light from the laser light source, an fθ lens that focuses the scanning beam on the generatrix of the surface of the photosensitive drum, and a reflection mirror that deflects the light beam. , A beam detection device for detecting a specific position of the scanning beam. The image formation control unit CONT in the figure monitors various sensor outputs and sets and controls the image formation conditions so that optimum image formation can be performed.

In the image forming apparatus thus constructed, when a predetermined density patch is formed on the image carrier or the recording medium by the image forming means, the density detecting means (patch density sensor 12) detects the density patch. A density state is detected, and based on this density state and the material information of the recording medium detected by the recording material detecting means 11 at the time of feeding the recording medium, the setting means (image forming control unit CONT) sets the image forming condition of the image forming means. Is automatically set to enable image formation with optimum density for the material of the recording medium to be fed.

FIG. 2 shows the recording material detecting means 1 shown in FIG.
It is a schematic circuit diagram explaining the operating mechanism of 1.

In the figure, 11a and 11b are conductor rollers to which a constant voltage is applied from a power source 11c.

In the operation mechanism thus configured,
When a constant voltage is applied to the conductor rollers 11a and 11b, when the recording medium fed from the sheet feeding cassette 7 passes between the conductor rollers 11a and 11b, it may be changed depending on the material and the environmental condition of the recording medium. The resistance value changes and the conductor roller 11
The current I passing through a and 11b also changes. Therefore, the change in the current I is measured by an ammeter (not shown) to detect the material and environmental condition of the recording medium passed. The nip pressure between the conductor rollers 11a and 11b is always kept constant. As a measuring method, a change in voltage due to a constant current may be measured. Furthermore, the material of the recording medium may be determined from the unevenness information obtained by scanning the surface of the recording medium to be fed with, for example, a diamond stylus, without being limited to the electrical measurement processing as described above. Ultrasonic waves may be applied to the surface of the recording medium to be fed and the measurement may be carried out from the deviation of the amount of reflection, and if the material of the recording medium can be determined, it is not limited to an electrical measuring mechanism.

FIG. 3 shows the image forming control unit CON shown in FIG.
It is a control block diagram which shows the principal part structure of T.

In the figure, 12 is a patch density sensor,
The patch density transferred to the transfer belt 6a is detected, for example, on the downstream side of a black image forming station which is an image forming station on the downstream side, and the detection signal is detected by A / D.
The controller 15 is notified via the converter 14. Thirteen
Is an A / D converter for A / D converting the voltage value or the current value measured by the recording material detection means 11 and notifying the controller 15. 17 is a contrast potential setting circuit,
The controller 15 adjusts the surface potential according to the contrast potential determined from the difference between the developing bias potential and the bright portion potential. Reference numeral 18 is a back potential setting circuit, which is a controller 15
Adjusts the amount of laser light according to the back potential determined from the difference between the developing bias potential and the dark portion potential. A look-up table 19 adjusts the density level so that the gradation characteristic is linear. Reference numeral 20 denotes a transfer current circuit, which indicates the voltage value or current value measured by the recording material detection means 11 as A
Transfer chargers 6M, 6C, 6Y, so that the charging level becomes optimum according to the recording material information notified by D / D conversion.
The transfer current applied to 6K is determined.

FIG. 4 is a diagram showing the image density control configuration of the black station of the image forming apparatus shown in FIG.
The same parts as those in FIG. 1 are designated by the same reference numerals.

In the figure, reference numeral 51 denotes an electrometer, which outputs the surface potential (light portion potential, dark portion potential, residual potential, etc.) detected by the potential sensor 51K to the controller 15 as potential data. A density sensor 13K detects the toner density of the developing device 4K. Reference numeral 16 is a power source for the primary charger 2K.

In the controller 15, when the surface potential of the photosensitive drum 1K is detected by the potential sensor 51K and the potential data is output from the electrometer 51, a plurality of bright portions stored in advance are referred to while referring to the output potential data. The light portion potential of the photosensitive drum 1K is set so that the potential data is obtained, that is, the controller 15 adjusts and sets the light amount of the laser beam emitted from the laser scanner 3K, and the set plurality of light portion potentials are set to the photosensitive drum 1K. The latent image corresponding to the test patch 22 is sequentially formed on the photosensitive drum 1K from the laser scanner 3K for each of the plurality of set bright part potentials, and the latent image of each test patch 22 is developed by the developing device 4K. , And is transferred to the conveyor belt 6a. Then, the test patch image densities transferred to the conveyor belt 6 a are read by the light receiver 12 a and the light source 12 b of the patch density sensor 12, and the light quantity level signal is fed back to the controller 15. Hereinafter, the image forming condition setting control operation in the image forming apparatus according to the present invention will be described with reference to the flowchart shown in FIG.

FIG. 5 is a flow chart showing an example of an image forming condition setting control procedure in the image forming apparatus according to the present invention. Note that (1) to (9) indicate each step.

When the recording medium is fed from the paper feeding cassette 7, when the recording medium passes through the recording material detecting means 11, the conductor rollers 11a and 11b of the recording material detecting means 11 are shown in FIG. Since the current I passing through the recording medium changes, the controller 15 detects the recording material of the recording medium by measuring the amount of change (1). In parallel with this, a plurality of test patches 22 are transferred onto the transfer belt 6a (2), the patch density is detected by the patch density sensor 12 (3),
The patch density data is input to the controller 15 via the A / D converter 14. The test patch 22 constituting the density patch has 20H, 40H, 80H of FFH (hexa) gradation.
, A0H, and FFH, five tone patches are created under preset reference conditions. The material of the transfer means used in this embodiment is polyurethane, polycarbonate, PVdF (polyvinylidene fluoride).
Etc. are possible. The toner has an average particle size of 3 to 20 μm.
The color pigment is dispersed in a polyester resin at m and silica is applied as an external additive. Styrene-acrylic resin depending on the color of the toner, carbon black as the colorant, benzene yellow pigment, anthraquinone dye. A copper phthalocyanine pigment or the like may be used.

In this way, the contrast potential Vcont, which is the difference between the developing bias potential and the bright portion potential, is determined in order to suppress the maximum density Dmax from the patch density fetched by the controller 15 to a constant value (4), Controller 15
Sets the set value in the contrast potential setting circuit 17.

Next, in order to improve the reproducibility of the highlight portion, the back potential Vback which is the difference between the developing bias potential and the dark potential is determined (5), and the controller 15 causes the back circuit 1 to operate.
Set the set value to 8. Then, the lookup table 19 is determined in order to linearly correct the gradation characteristic.
(6). Next, the transfer current is determined from the result of the recording material detection means 11 so as to achieve proper transfer efficiency (7), and the controller 15 sets the transfer current value in the transfer current circuit 20. In this way, the image forming state is established based on the image forming conditions set by the steps (1) to (6), and the image is formed on the photosensitive drum 1K based on the input image data (8), and the recording is performed. The image developed on the photosensitive drum 1K is transferred to the recording medium fed to the medium (9), fixed and discharged.

As described above, a clear color image having an appropriate density can always be formed on any recording medium that can be fed based on the material and surface state information of the recording medium and the patch density.

In the above embodiment, the case where the plurality of test patches 22 are transferred to the transfer belt 6a and the predetermined image forming condition is set has been described. However, the formation of the test patch 22 and the image formation at each image forming station are described. May be processed in parallel as shown in FIGS. 6 and 7.

FIG. 6 is a plan view showing a transfer process of the test patch 22 showing another embodiment of the present invention.

The test patch 2 is provided on the image margin of the recording medium.
2 is transferred, the patch density is detected by the patch density sensor 12, the image forming conditions are determined, and then the test patch 22 is retransferred by the drum 21 shown in FIG. 7 before image fixing.

That is, the test patch 22 is transferred in order from the first image forming station in the thrust direction to the margin of the leading end in the paper feeding direction. After passing through the fourth image forming station and reading the density by the patch density sensor 12, a voltage is controlled to be applied to the fifth drum 21 as shown in FIG.
When the electric potential is such that 2 is retransferred and the image portion passes, the potential application is controlled so as not to retransfer. In this way, the maximum density Dmax from the read patch density,
Corrects highlight re-generation, gradation linearity, and transfer efficiency.

In the above embodiment, the case where the original image and the test patch are formed in parallel by one image forming process has been described, but only the test patch 22 is formed on the recording medium in the first image forming operation. Then, after the appropriate image forming conditions are determined, the recording medium is circulated around the transfer belt 6a while being adsorbed on the transfer belt 6a after the test patch cleaning, and enters the first image forming station.
A document image is formed as the image forming operation for the first time. This makes it possible to always obtain a stable image from the first sheet. Further, this operation may be performed at an arbitrary timing, and may be configured to be executed only at the first image formation immediately after the main body power is applied.

As shown in FIG. 8, a resistist sensor 62 (including a light receiver 62a and a light source 62b) and a resister sensor 63 (including a light receiver 63a and a light source 63b) provided in a 4-drum type image forming apparatus. ) May be configured to have the function of the patch density sensor 12 also.

Since the registrationist sensors 62 and 63 detect the registration deviation of the photosensitive drum 1K in the drum axial direction, the registrationist correction mark is formed at the end portion orthogonal to the conveyance direction of the conveyor belt 6a. Patch 2
2 is also transferred as test patches 22a and 22b to the ends of the conveyor belt 6a orthogonal to the conveying direction. At that time, there may be density shading due to uneven transportation of the developer. Therefore, the read image information of the test patches 22a and 22b may be subjected to a predetermined correction calculation and taken into the controller 15 as one density signal for control.

Further, as described in the above embodiment, when the test patch 22 is directly transferred to the transfer belt 6a, the read image information is affected by the surface condition of the transfer belt 6a, for example, the transfer belt 6a. If there are scratches on the surface, it will not be possible to read normally,
The transfer belt 6a is located at the position where the test patch 22 is directly transferred.
The adverse effect can be eliminated by controlling the transfer position so that the transfer is made to the same position above.

Further, when the density cannot be read depending on the type of toner used, if carbon black is contained in, for example, a black toner, the light reaching the near infrared is absorbed and the signal is not output. Occurs. Therefore, in such a case, in the test patch 22 forming area in the black image forming station, an image forming station upstream of that, that is, magenta,
The test patch 22 in the black image forming station can be detected by performing the background color transfer in advance in any of the cyan and yellow image forming stations.

In each of the above embodiments, the test patch 22
The description has been given of the case where the image is transferred to the transfer belt 6a or the recording medium and the transferred test patch 22 is read to adjust the density level. However, the photosensitive drums 1M, 1C of the image forming stations where the test patch 22 is developed are developed.
It may be configured to directly read on 1Y and 1K.

[0035]

As described above, according to the present invention, the image forming means for forming a predetermined density patch for determining a desired image or development density on the image carrier, and the material of the recording medium to be fed. Recording material detecting means for detecting information, density detecting means for detecting a density state of a density patch imaged on an image carrier or a recording medium, and density state and recording material detecting means detected by the density detecting means Since it has a setting means for automatically setting the image forming condition of the image forming means based on the material information of the recording medium detected by the above, it is possible to obtain an image of an optimum density that matches the material of the recording medium to be fed and environmental changes. Since the image forming conditions of the image forming unit can be set as described above, it is possible to always obtain a good image that is not affected by the material of the recording medium that can be fed.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram illustrating a configuration of an image forming apparatus according to an exemplary embodiment of the present invention.

FIG. 2 is a schematic circuit diagram illustrating an operating mechanism of the recording material detection unit shown in FIG.

FIG. 3 is a control block diagram showing a main configuration of an image formation control unit CONT shown in FIG.

4 is a diagram showing an image density control configuration of a black station of the image forming apparatus shown in FIG.

FIG. 5 is a flowchart showing an example of an image forming condition setting control procedure in the image forming apparatus according to the present invention.

FIG. 6 is a plan view showing a transfer process of a test patch according to another embodiment of the present invention.

7 is a cross-sectional view showing a retransfer process of the test patch shown in FIG.

FIG. 8 is a perspective view illustrating a configuration of main parts of an image forming apparatus according to another embodiment of the present invention.

[Explanation of symbols]

 11 recording material detection means 12 patch density sensor CONT image formation control unit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location G03G 15/04 120 9122-2H

Claims (1)

[Claims] 1. An image forming means for forming a predetermined density patch for determining a desired image or a development density on an image carrier, and a recording material detecting means for detecting material information of a fed recording medium. A density detecting means for detecting a density state of a density patch imaged on the image carrier or the recording medium, a density state detected by the density detecting means and the recording detected by the recording material detecting means An image forming apparatus comprising: a setting unit that automatically sets an image forming condition of the image forming unit based on material information of a medium.