JPH04195171A - Copying machine - Google Patents

Abstract

PURPOSE:To always obtain an image with excellent image quality even when a copying machine is used by any magnification within the range of variable power by providing patterns for a potential sensor and for a toner sensor and specifying the positions of the potential sensor and the toner sensor and the positions of the respective patterns. CONSTITUTION:The potential sensor 20 which detects the surface potential of a photosensitive body, the toner sensor 17 which detects the density of a toner image formed on the photosensitive body and the respective patterns 21a and 21b for the potential sensor and the toner sensor which are arranged at a right angle to the carrying direction of a paper by being closely brought into contact with a specified corner on an original platen other than an original surface are provided. Then, the sensors 20 and 17 are disposed so that the components of a right angle direction to the carrying direction of the paper at the respective positions of the sensors 20 and 17 mutually become different. Besides, the pattern for a potential sensor 21a is arranged at such an area that it is projected on a position within the range of the variable power and corresponding to the sensor 20 and the pattern for a toner sensor 21b is arranged at an area other than it. Thus, the image with the excellent image quality is always obtained even when the copying machine is used by any magnification within the range of the variable power.

Description

DETAILED DESCRIPTION OF THE INVENTION E-INDUSTRIAL APPLICATION FIELD The present invention relates to a variable magnification copying machine based on document position corners using electrostatic latent image technology, and particularly to process control thereof.

[Prior Art] An electrostatic latent image is formed by exposing an image of a document to a photoconductor that has been uniformly charged in advance, and the electrostatic latent image is converted into a visible toner image through a development process in which toner is attached to the image. There are already many copying machines in use that use electrostatic latent image technology, which forms an image on plain paper by transferring and fixing the toner image onto the paper.

In general, images formed using this type of electrostatic latent image technology have a charging potential that changes depending on ambient conditions such as temperature and humidity, and the characteristics of charge dissipation due to exposure. However, the image quality obtained is often inconsistent, and especially due to humidity, the image quality deteriorates, such as fogging, in which white areas do not come out white and become smeared.

Therefore, when the photoreceptor is charged and a white or bright color pattern is exposed, the potential remaining on the photoreceptor is detected by a potential sensor, and the light intensity of the exposure lamp is adjusted according to the detected value so that good image quality can be obtained. Techniques for feedback control of voltages of chargers, developing biases, etc. are being developed.

Further, as the number of copies increases, the toner in the developing unit is consumed, resulting in problems such as insufficient density in black areas.

Therefore, a technique is also known in which, when a black or dark pattern is exposed and developed, the density of toner adhering to that area is detected by a toner sensor, and toner is replenished according to the detected value.

Furthermore, as shown in Japanese Patent Application Laid-Open No. 63-189874, in a slit exposure type copying machine that performs exposure by scanning the optical system, the above potential sensor pattern and toner sensor pattern are scanned by the optical system. There was also a proposal to install them in parallel in a direction perpendicular to the direction.

[Problems to be Solved by the Invention] As described above, the proposal for arranging both patterns side by side in a direction perpendicular to the scanning direction is suitable for copying machines with a fixed magnification such as a full-size copying machine,
Alternatively, even in a variable-magnification copying machine, the document is placed in contact with the document based on one side of the document table perpendicular to the paper transport direction (same as the optical system scanning direction), and the document position is such that the center of that side matches the center line of the document. There is no problem in the case of a center-based variable magnification copying machine.

However, although the internal mechanism is a little more complicated, setting the original is easier than using a center reference, so the original is placed in contact with two specific sides of the copy table that are perpendicular to each other, as is used in high-performance copying machines. A variable magnification copying machine based on a document position corner, particularly a variable magnification copying machine having a large variable magnification range, has the following problems.

In other words, when a corner-based variable-magnification copying machine is provided with orthogonal parallel patterns, the image position of the boundary line between the two parallel patterns changes in the orthogonal direction according to the magnification. If the positions of each sensor are not properly arranged in advance, there is a risk that the image position of the pattern may deviate from the sensor, or that the sensor may detect a different pattern.

In particular, in the case of a copying machine with a large variable magnification range, no matter how you set it up, it is inevitable that the sensor will detect different patterns, resulting in incorrect control and a significant loss of image quality. there were.

This invention has been made in view of the above points, and is a variable magnification type based on a corner that can always provide an image of excellent image quality without causing erroneous control, regardless of the magnification within the variable magnification range. The purpose is to provide copying machines.

[Means for Solving the Problems] In order to achieve the above object, the present invention uses a specific corner of the document table on which the document is placed as a reference for the document position, and uses electrostatic latent image technology to display a variable magnification on the paper. A copying machine that forms an image includes: a potential sensor that detects the surface potential of a photoconductor; a toner sensor that detects the density of a toner image formed on the photoconductor;
Each pattern for a potential sensor and a toner sensor are arranged close to a specific corner of the document table outside the original plane and perpendicular to the paper conveyance direction, and the patterns for the potential sensor and toner sensor are arranged in the paper conveyance direction at each position of the potential sensor and toner sensor. The pattern for the potential sensor is placed in the area projected at the position corresponding to the potential sensor within the variable magnification range, and the pattern for the toner sensor is placed in the other areas. This is what I did.

Furthermore, when the magnification is set so that the potential sensor pattern is projected at a position corresponding to the toner sensor, the lamp that illuminates the document is turned off when the toner sensor is activated.

Furthermore, it is preferable to form the potential sensor pattern in white or a light density color, and the toner sensor pattern in black or a color near black density.

[Function] With the above configuration, the potential sensor can detect the surface potential of the electrostatic latent image of the potential sensor pattern over the entire magnification range and perform correct feedback control.

Further, since the toner sensor pattern can be arbitrarily arranged in an area other than the area of the potential sensor pattern, the toner sensor can detect the toner image of the toner sensor pattern within the normal magnification range.

When the magnification range becomes larger and the toner sensor detects the toner image of the potential sensor pattern,
Since the lamp that illuminates the document is turned off when the toner sensor is activated, a potential sensor pattern formed in white or bright colors has the same effect on the photoreceptor as a toner sensor pattern formed in black or dark colors. , the toner sensor can accurately detect toner concentration.

[Example] Hereinafter, an example of the present invention will be specifically described with reference to the drawings.

FIG. 3 is an overall configuration diagram showing an example of a copying machine embodying the present invention.

The copying operation of this copying machine is started when an operator sets necessary copying conditions from an operation section (not shown) provided on the copying machine main body and presses a print button.

The original 1 placed on the contact glass 2 is
emits light, is reflected by the irradiation mirror 3a, and irradiates the entire surface with light for a predetermined period of time.

The reflected light from the original 1 is reflected by the first mirror 4a, the lens 4. An image is formed at a predetermined magnification through the second mirror 4b, and the photoreceptor belt 5 is exposed.

The photoreceptor belt 5 is uniformly charged in advance by a charger 6, and an electrostatic latent image is formed by exposure.

The electrostatic latent image on the photoreceptor belt 5 is charged in unnecessary portions by an eraser 7 and then developed by a developing unit 8 and converted into a visible toner image.

The toner image is transferred to a transfer paper by a transfer charger 9 in a transfer section.

The transfer paper is fed from either the paper feed trays 10a, 10b, 10c or the double-sided tray 10d, passes through the conveyance path 11, comes into contact with the registration rollers 12, stops once, and then moves to the transfer section in time with the toner image. sent to.

The transfer paper on which the toner image has been transferred is sent to a fixing unit I4 by a conveyor belt 13, where it is fixed, and then discharged to a paper discharge tray 15.

After the toner image is transferred to the transfer paper, the charges and toner remaining on the photoreceptor belt 5 are removed by the cleaning unit 16, and the photoreceptor belt 5 is again transferred to the charger 6.
is charged and enters the next exposure cycle.

A two-component developer consisting of toner and carrier (or one component consisting of toner) is contained in a container 8a of the developing unit 8, and is agitated and made uniform by an agitator 8b.

The developer is supplied to and carried by each developing roller 8c,
The toner is attracted to the electrostatic latent image on the photoreceptor belt 5 to form a toner image.

As copying is repeated, the toner in the container 8a is gradually consumed, and the ratio of toner to carrier in the developer, that is, the toner ratio, gradually decreases.

This decrease in the toner ratio is detected as a change in toner concentration by the toner sensor 17, and in response, the toner is replenished in the required amount by the replenishment roller 19 from the toner replenishment device 18 attached to the developing unit 8, and the capacity 8a The toner ratio within is maintained within a certain range.

On the other hand, the potential sensor 2o that detects the surface potential of the photoreceptor is
It is provided immediately downstream of the exposure position of the photoreceptor belt 5 so that it does not overlap with the toner sensor 17 in the moving direction of the photoreceptor belt 5 .

Pattern 2 for potential sensor 20 and toner sensor 17
1 is provided on the back' surface (lower surface) of a document guide 22 that regulates the document position in the left and right direction when viewing the contact glass 2 from above.

FIG. 4 is a block diagram showing an example of a control system of this copying machine, particularly a control system mainly including a feedback system that influences image quality.

C is the main controller that performs sequence control of the entire copying machine and process control of each part through feedback.
The PU 30 includes a ROM 31 that stores its programs, constant data, etc., and a RAM that temporarily stores variable data, etc.
32 and an input/output 1/F (interface) 33 are connected to each other by a pass line, and together constitute a microcomputer, and the toner sensor 17 . Data from various sensors such as the potential sensor 20 are input, and the bias power supply 34 . A clutch 35 that turns on and off the toner supply roller 19. It controls the regulator 36 and the like that change the voltage applied to the lamp 3 that irradiates the original.

That is, after the exposed portion of the toner sensor pattern on the photoreceptor belt 5 is developed, if the toner density detected by the toner sensor 17 is lower than a preset reference value, the CPU 30 Since the clutch 35 is actuated via F33, the replenishment roller 19 rotates and replenishes a certain amount of toner from the toner replenishing device 18 (FIG. 3) into the container 8a of the developing unit 8.

Further, the exposed portion of the potential sensor pattern on the photoreceptor belt 5 is detected by the potential sensor 20, and the CPU 30 outputs a value corresponding to the detected value (and ambient temperature and humidity) to the bias power source 34. Since the regulator 36 is commanded to control the bias voltage of the developing roller 8C and the light intensity of the lamp 3 to optimal values, high-quality images can always be obtained.

Feedback control by the potential sensor 20 is performed for each copy because it changes each time (especially for a while after the power is turned on) depending on the ever-changing ambient temperature, humidity, copying magnification, etc.

Therefore, the pattern 21 is always exposed on the head part of the original 1, regardless of the original size and copying magnification.
When the photoreceptor belt 5 begins to move, the head portion is erased by the eraser 7 after the detection by the potential sensor 20 is completed, and the image on the paper is not affected.

Feedback control by the toner sensor 17 is first performed at the initial setting when the power is turned on, and thereafter is repeatedly performed every 5 to 20 copies, although it varies depending on the copy size.

Since this step is performed after the development process and cannot be erased by the eraser 7, it is performed independently from the copying operation without transporting the paper or transferring.

FIG. 5 is a schematic side view showing an example of the relationship between the reference positions of the original 1 on the contact glass 2 and the electrostatic latent image on the photoreceptor belt 5, and the position of the lens 4 according to the copying magnification.
This is a view of FIG. 3 from the left side.

When looking at the contact glass 2 (Fig. 3) from above, the left and right positions of development are based on the right side, where the original l is brought into contact with the original guide 22, and the upper and lower positions are on the lower side, which is closer to the front (lower) side. Since the reference is the lower right corner reference, in Fig. 5, the document l
The reference side is the right side, and the left side on the photoreceptor belt 5 is the reference side.

The change in object-image distance due to copying magnification is the
The mirror 4a and the second mirror 4b each move to cover the document 1 on the contact glass 2, but the document 1 on the contact glass 2 does not move.
In the figure, the image side on the photoreceptor belt 5 is fixed, and the document 1 and the lens 4 side are shown moving relative to each other.

That is, the copy magnification is 2. (If the states of 2, 1, 1/(2° 1/2) are represented by ■ to ■, respectively, the positions of the original l are the same size ■ and the maximum ■ as shown by solid lines, respectively.

the minimum ■, and the magnification of their geometric middle term shown by the dashed line ■,
■, and the lens 4 is at a position ■~■ where the predetermined magnification is achieved on the line connecting each document reference side and the photoconductor reference side,
At intermediate magnifications, the original l and the lens 4 are at intermediate positions.

For example, the lens 4 moves on the curve shown by the two-dot chain line connecting ■ to ■, but both reference sides are always at the same position.

1 and 2 are schematic side views showing an example of the relative positions of the potential sensor 20 and the toner sensor 17, respectively, and the pattern 21. Among the positions shown in FIG. 2 times ■ 1 equal times ■ and the minimum magnification 1/2 times ■ are shown.

However, the potential sensor 20. The toner sensor 17 is not in an actual position but in a relative position with respect to the photoreceptor belt 5,
The pattern (21) shown in parentheses is the pattern 21 that moves from ■ to ■ to ■, and the potential sensor pattern 21a and toner sensor pattern 21b on the lower surface thereof.
This is what is shown.

FIG. 1 shows the relationship between the potential sensor 20 and its pattern 21a. Since the surface potential due to the pattern 21a is always detected by the potential sensor 20 in the entire magnification range ■ to ■, the pattern 21a is (including margins on both sides), and the toner sensor pattern 21b is located in region B located on the right outer side of region A (actually, it is removed by the margin of A).
It is set in. Region C is a portion unrelated to detection.

The patterns 21a and 21b set in this manner have a relationship as shown in FIG. 2 with respect to the toner sensor 17.

In other words, at the maximum magnification ■, toner sensor pattern 2
The toner image 1b is detected by the toner sensor 17, and correct control is performed.

However, at the same magnification (2) and the minimum magnification (2), the toner image of the potential sensor pattern 21a is detected, resulting in erroneous control.

If the toner sensor 17 is positioned to the left and placed near the reference side, the toner image of the toner sensor pattern 21b can be always detected within the entire magnification range, as shown in FIG. Correct control can be performed without any problems by simply setting the pattern area.

However, if the toner sensor 17 is provided at the position shown in FIG. 2 due to mechanical constraints or the like, a problem of erroneous control may occur depending on the magnification.

In such a case, when the toner sensor 17 is set to a magnification that may cause the toner image of the potential sensor pattern 21a to be detected, the toner sensor pattern 21b
The lamp 3 for irradiating the pattern 21 may be turned off (or not turned on) during the exposure timing.

The potential sensor pattern 21a is formed in white or bright color, and the toner sensor pattern 21b is formed in black or dark color.

The potential sensor 20 mainly detects fog in bright areas of the document.

Since the pattern 21a is provided to prevent stains, the pattern 21a may be formed in white or bright color.On the other hand, the toner sensor 17 is provided to maintain the density of the dark part of the formed image, so the pattern 21a may be formed in white or bright color. 21b is preferably formed in black or dark color.

Therefore, if the lamp 3 is turned off during exposure, the bright potential sensor pattern 21a becomes black as well as the dark toner sensor pattern 21b, so even if the toner sensor 17 detects the toner image of the potential sensor pattern 21a. Correct control can be performed without causing erroneous control.

[Effects of the Invention] As explained above, according to the present invention, the magnification is adjusted based on the corner reference so that an image of excellent image quality can always be obtained without causing erroneous control no matter what magnification is used within the variable magnification range. 8. Providing variable copying machines.

[Brief explanation of the drawing]

1 and 2 are schematic side views showing an example of the relative positions of a potential sensor and a toner sensor and their respective patterns in a copying machine which is an embodiment of the present invention, and FIG. 3 is a copy thereof. Figure 4 is a block diagram showing an example of the control system, and Figure 5 is an example of the relative positional relationship between the document, lens, and photoreceptor depending on the copying magnification. It is a schematic side view. 1... Original 2... Contact glass (original table) 3... Lamp 4... Lens 5...
・Photoconductor belt 17... Toner sensor 20
...Potential sensor 21...Pattern 21a
...Potential sensor pattern 21b...Toner sensor pattern Fig. 4

Claims (1)

[Scope of Claims] 1. In a copying machine that forms an image with variable magnification on paper using electrostatic latent image technology, using a specific corner of the document table on which the document is placed as a reference for document position, the surface potential of the photoreceptor a toner sensor that detects the density of the toner image formed on the photosensitive member; Each pattern for the potential sensor and the toner sensor is provided, and the potential sensor and the toner sensor are arranged so that components in a direction perpendicular to the paper conveyance direction at each position are different from each other, and the potential sensor A copying machine characterized in that the toner sensor pattern is arranged in an area projected at a position corresponding to the potential sensor within a variable magnification range, and the toner sensor pattern is arranged in other areas. 2. In the copying machine according to claim 1, when the magnification is set such that the potential sensor pattern is projected at a position corresponding to the toner sensor, a lamp that illuminates the document is turned off when the toner sensor is activated. A copying machine characterized by: 3. The copying machine according to claim 1, wherein the potential sensor pattern is formed in white or a color with a light density. 4. The copying machine according to claim 1, wherein the toner sensor pattern is formed of black or a color with a density close to black.