JPH11109798A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of executing optimum printing control for a different printing sheet of paper such as plain paper, glossy paper and an OHT. SOLUTION: An LED 120 and a photodiode 121 are arranged on the printing surface side of a printing sheet of paper 31, to measure the reflection characteristic of the printing surface side, a threshold for discriminating plain paper and glossy paper and a threshold for discriminating the front and rear surfaces of the glossy paper are set in advance, to discriminate the kind of the printing sheet of paper and the surface and backside of the glossy paper, based on the set values. Thus, printing control is executed on the basis of the result of the discrimination. In other words, the quantity of heat applied to a toner in a fixing device is controlled.

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 laser printer, a copying machine, a facsimile, etc. to which an electrophotographic system is applied.

[0002]

2. Description of the Related Art In recent years, an image forming apparatus using an electrophotographic system, for example, a laser printer using a laser scanning technique, has attracted attention in terms of its high quality, multiple gradations, and high-speed printing.

[0003] Printing paper, which is a printing medium used in such an electrophotographic image forming apparatus, has a variety of types at present and exists as various media having different sizes, transmittances, and glosses. I have. Against this background, there is a need for performing optimal image formation on various media in order to obtain high quality.

[0004] At present, there is a technology for detecting a transparent printing paper (hereinafter abbreviated as "OHT") for an overhead projector and printing the fixing property of a developer (toner) in a sequence different from that of plain paper. . In general, there is a method in which the fixing performance is optimized by increasing the temperature of the fixing device or decreasing the speed of the fixing device, for example.

[0005] In addition to plain paper, there is glossy paper, so-called glossy paper. In printing on such glossy paper, there is a device having a function of performing similar image printing control and producing gloss.

[0006]

However, as described above, in an apparatus for performing image printing control by detecting plain paper, OHT, and glossy paper, an impermeable printing paper such as glossy paper is used. There is a method of determining the printing paper by a method of detecting the surface reflectance, but glossy paper has different reflectances on the front and back, and it is expected when the user sets the front and back wrongly in the image forming apparatus. There was a problem that an optimal output could not be obtained.

When a gloss sensor is arranged on the back side of the image printing when discriminating the printing paper, an erroneous detection may occur when the printing paper has different gloss on the front and back sides.

Accordingly, a main object of the present invention is to provide an image forming apparatus capable of performing optimal print control on different print-receiving media.

Another object of the present invention is to provide an image forming apparatus capable of performing optimal printing control without erroneously detecting a printing medium.

[0010]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
Image formation that irradiates the medium to be printed with light from the light emitting element, receives the reflected light from the light receiving element and measures the light to determine the characteristics of the medium to be printed, and performs different printing control in accordance with the characteristics of the medium to be printed. The image forming apparatus is characterized in that the light-emitting element and the light-receiving element are arranged on a printing surface side of a print-receiving medium and a reflection characteristic on the printing surface side is measured.

It is preferable that the front and back sides of the printing medium are discriminated from the measured reflection characteristics on the printing surface side, and this is reported. It is preferable that the front and back sides of the printing medium are discriminated from the measured reflection characteristics on the printing surface side, and different printing controls are performed for the front side and the back side.

When the printing surface of the print-receiving medium is turned back from the measured reflection characteristic on the printing surface side, it is preferable to notify this and stop printing.

Preferably, the printing control is control of the amount of heat applied to the toner in the fixing device. Preferably, the type of the printing medium is plain paper, glossy paper, or overhead projector paper. Preferably, the distinction between plain paper and glossy paper is performed based on a preset threshold. Preferably, the distinction between the front and back of the glossy paper is performed based on a preset threshold.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

First, an embodiment of a color image forming apparatus will be described with reference to FIG.

As shown in FIG. 2, a photosensitive drum 1 and a roller charger 3 are disposed substantially at the center of the apparatus main body. The photosensitive drum 1 is driven at a speed of 100 mm / s by a driving unit (not shown).
It is driven in the direction indicated by the arrow in the figure at the peripheral speed of ec.

On the right side of the photosensitive drum 1 in the figure, developing cartridges 4a, 4a are formed by integrally forming a toner accommodating portion for accommodating toner and developing means for developing.
A support 9 rotatably supporting b, 4c and 4d is provided. Each developing cartridge 4a, 4b, 4c, 4d
Are arranged on the same circumference around the support rotating shaft 9a. The developing cartridges 4a, 4b, 4c, and 4d contain yellow toner, magenta toner, cyan toner, and black toner, respectively.

On the left side of the photosensitive drum 1 in the figure, a transfer drum 10 having a function of holding a printing paper as a printing medium and transferring an image on the photosensitive drum 1 to the printing paper is arranged.

A laser diode 11, a polygon mirror 13, a lens 14, and a folding mirror 15, which are driven by a high-speed motor 12, are disposed above the apparatus main body.

In the roller charger 3, an AC voltage of Vp-p (peak-to-peak) of -1500V at an AC frequency of 700 Hz is superimposed on a DC voltage of -700V to uniformly charge the surface of the photosensitive drum 1 to -700V. Is done.

When a signal according to, for example, magenta image information is input to the laser diode 11, a laser beam is irradiated on the photosensitive drum 1 through an optical path 16.
The portion of the photosensitive drum 1 irradiated with the laser beam is approximately −100.
V. When the photosensitive drum 1 advances in the direction of the arrow, the portions irradiated with the laser beam are the developing cartridges 4a, 4b, 4c,
It is visualized as a toner image by 4d (4b in this case) toner.

On the other hand, the printing paper 31 is fed by the pickup roller 18 from the inside of the printing paper cassette 17 in synchronization with the image on the photosensitive drum 1, and is printed on the peripheral surface of the transfer drum 10 by the gripper 22 and the suction roller 23.
Is held, and the toner image on the photosensitive drum 1 is transferred onto the printing paper 31 by the voltage between the photosensitive drum 1 and the transfer drum 10 applied from a high-voltage power supply (not shown).

The above steps are similarly performed for the cyan, yellow, and black colors, so that the printing paper 3
A plurality of toner images can be formed on one.

The printing paper 31 on which the color image is formed is
The toner image is separated from the transfer drum 10 by the separation charger 2 and the separation claw 24, and is fused and fixed by a known heating / pressure fixing device 25 to obtain a color image.

When the image density is controlled, the toner on the transfer drum 10 and the toner remaining without being transferred to the printing paper on the photosensitive drum 1 or the toner attached to the photosensitive drum 1 and the transfer drum 10 due to a jam are driven to rotate. The cleaning is performed by a fur brush 27 or a cleaning device 26 such as a blade unit. Further, the transfer drum 10 is electrically initialized by the charge removing roller 28 after its peripheral surface is cleaned.

Next, gloss / OH which is a characteristic part of the present invention is described.
The T detecting means will be described. Note that OHT is an abbreviation for overhead projector transparent printing paper, as described above.

As shown in FIG. 3, the gloss / OHT detecting means 100 includes a guide 30 disposed between the pickup roller 18 and the transfer drum 10.
, The light-emitting element L
ED 120 and photodiode 121 as light receiving element
And a gloss / OHT detection unit 123.
The guide 30 is provided with an opening 30 a through which light emitted from the photodiode 121 and light reflected by the printing surface 31 a of the printing paper 31 pass.

In the gloss / OHT detecting section 123, LE
The light emitted from D120 is applied to printing surface 3 of printing paper 31.
The amount of light reflected by 1a and incident on the photodiode 121 is detected.

As shown in FIG. 4, the gloss / OHT detecting section 123 outputs the output of the photodiode 121 to an amplifier 123.
This is a general configuration that performs amplification and detection at a. In this embodiment, detection is performed at the analog level.

In FIG. 1, the gloss / OHT detecting unit 123
The detected information is sent to the CPU 60, and the type of the print medium (print paper) is determined by the print medium determination unit 125.

A print sequence control mode setting section 126 connected to the print medium determining section 125 controls the fixing device 25 to perform an optimum print sequence according to the determined print medium.

Next, details of the sensor portion will be described. FIG.
, The LED 120 and the photodiode 121 are arranged on the printing surface 31 a side of the printing paper 31,
0 is irradiated on the printing paper 31 at the incident angle θ1, and the reflected light is incident on the photodiode 121 at the reflection angle θ2. It is desirable that the incident angle θ1 and each reflection θ2 be equal, but the light of the LED 120 is not necessarily equal because the light is wide-angle.

Printing paper 31 in printing paper cassette 17
Is picked up by the pickup roller 18 and advances. At this time, the printing paper 31 is the LED 1 described above.
20 and the photodiode 121. L according to the timing of this paper feeding
The ED 120 is turned on.

Since the surface reflectance of the printing paper 31 varies depending on the gloss, the input of the photodiode 121 varies depending on the printing paper, and the output of the gloss / OHT detecting unit 123 naturally varies depending on the gloss of the printing paper 31. Can be detected.

Next, a method of determining a medium (print paper), that is, a method of determining a print medium in the print medium determination unit 126 will be described. FIG. 5 is a diagram showing a change in the received light output as the printing paper advances.

In this embodiment, the type of the printing paper and the front and back of the glossy paper are determined by setting a threshold value in advance according to the degree of gloss of the printing paper. In the present embodiment, the CPU 60 determines the progress of the printing paper based on the driving time of the pickup roller 18 and a paper feeding roller (not shown), and detects output data from the gloss / OHT detecting unit 123.

The gloss varies depending on the type of printing paper, and plain paper, glossy paper, and OHT are used in ascending order of gloss. Also,
For glossy paper, there is a difference between the front side and the back side, and generally the front side has higher gloss. In this embodiment, the difference between the front and back characteristics is used for the front and back discrimination, and a threshold value is provided at an output value substantially intermediate between the front and back surfaces to discriminate this. Further, the distinction between glossy paper and plain paper is similarly made by setting a threshold value.

As for the OHT, the threshold value may be set at approximately the middle between the output values of the glossy paper and the OHT. However, since the OHT has a glossiness of 2 to 10 times that of the glossy paper, the upper limit of the output of the sensor is almost zero. Since there is an equal output, in this embodiment, 5 V
Is determined as OHT when 4.2 V or more is set as the upper limit.

Next, the control of the printing sequence will be described with reference to FIG. The print sequence control mode setting section 126 shown in FIG. 1 changes the print sequence according to the determined print medium so that an optimal image output for the print medium can be obtained.

In the present embodiment, when the determined print-receiving medium is glossy paper, control is performed to sufficiently melt the toner in order to achieve a smoother gloss. At this time, in the fixing device 25, the roller rotation speed of the fixing device 25 is controlled to half the rotation speed of plain paper in the case of glossy paper in order to sufficiently apply heat to the toner on the printing paper. In addition to this method, the same effect can be obtained by a method in which the roller temperature of the fixing device is increased.

When the determined printing paper is OHT, since the specific heat of OHT is larger than that of plain paper, the roller rotation speed of the fixing device 25 is controlled to be slow to sufficiently fix the toner. I have. In the image forming apparatus of this embodiment, the rotation speed of the fixing device 25 is controlled to half the rotation speed of plain paper in the case of OHT. In addition to this method, the effect is the same in a method such as raising the roller temperature of the fixing device.

As described above, in this embodiment, LEDs and photodiodes are arranged on the printing surface side of printing paper, and OHT, glossy paper, plain paper,
Further, it is possible to determine the front and back sides of the glossy paper, and to output under optimum printing conditions according to the result.

[0043]

As is apparent from the above description, according to the present invention, a light emitting element and a light receiving element are arranged on the printing surface side of a printing medium, and the reflection characteristics on the printing surface side are measured. Since it is possible to discriminate this on different print receiving media and print in a print sequence, it is possible to realize an image forming apparatus capable of outputting on different print receiving media under optimum printing conditions.

Further, by performing the front / back discrimination, if the user sets the image forming apparatus in the wrong orientation, the user can be warned of this and the user will not be mistaken in the front / back. be able to.

Further, when a gloss sensor is disposed on the back side of the image printing when the conventional printing paper is discriminated, erroneous detection may occur when the printing paper has different gloss on the front and back sides. Providing this makes it possible to more reliably detect the reflection characteristics of the printing paper.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for explaining a characteristic portion of the present invention.

FIG. 2 is a configuration diagram illustrating an embodiment of an image forming apparatus according to the present invention.

FIG. 3 is a configuration diagram illustrating a sensor unit of a gloss / OHT detection unit.

FIG. 4 is an explanatory diagram showing a gloss / OHT detection unit.

FIG. 5 is an explanatory diagram of print medium determination.

[Explanation of symbols]

 31 printing paper (printing medium) 31a printing surface 120 LED (light emitting element) 121 photodiode (light receiving element) 123 gloss / OHT detecting section 125 printing medium discriminating section 126 print sequence control mode setting section

Claims (8)

[Claims] 1. A print medium is irradiated with light from a light emitting element, and the reflected light is received and measured by a light receiving element to determine characteristics of the print medium, and different printing is performed according to the characteristics of the print medium. An image forming apparatus for controlling, wherein the light emitting element and the light receiving element are arranged on a printing surface side of a printing medium, and a reflection characteristic of the printing surface side of the printing medium is measured. 2. The image forming apparatus according to claim 1, wherein the front and back sides of the printing medium are discriminated from the measured reflection characteristics of the printing surface, and this is reported. 3. The image forming apparatus according to claim 1, wherein the front and back sides of the printing medium are determined based on the measured reflection characteristics on the printing surface side, and different printing controls are performed between the front side and the back side. . 4. When the print surface of the print-receiving medium is determined to be back from the measured reflection characteristics on the print surface side, this is reported and printing is stopped.
Image forming apparatus. 5. The image forming apparatus according to claim 1, wherein the print control is control of an amount of heat applied to toner in a fixing device. 6. The type of the medium to be printed is plain paper, glossy paper,
2. The image forming apparatus according to claim 1, wherein the image forming apparatus is an overhead projector sheet. 7. The image forming apparatus according to claim 6, wherein discrimination between plain paper and glossy paper is performed based on a preset threshold. 8. The image forming apparatus according to claim 6, wherein the front and back sides of the glossy paper are determined based on a preset threshold value.