JPH07319233A - Toner mark detecting device in electrophotographic printer - Google Patents

Abstract

PURPOSE:To eliminate the need of precisely attaching mark sensors. CONSTITUTION:This toner mark detecting device is provided with a printing means 1 printing a toner mark 5, two mark sensors 10 and 101 detecting the density of the Loner mark 5, further, a mark signal discriminating means 3 discriminating the maximum or minimum values of the output signals of these mark sensors 10 and 101 and outputting the values and a toner concentration control circuit 6 controlling the concentration of toner with the output signal selected by the mark signal discriminating means 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner mark detecting device in an electrophotographic printer, and more particularly to a toner mark detecting device in an electrophotographic printer.

[0002]

2. Description of the Related Art Conventionally, in this type of electrophotographic printer, when the developer is a two-component system, it is necessary to supply the toner to the developing device as the toner is consumed. Since the toner is consumed by printing, the print density is reduced. That is, since the amount of toner per unit area is reduced, the print density is reduced. As a countermeasure, a method of controlling the print density by printing a toner mark and converting the density of the toner mark into a signal by an optical sensor has been conventionally used and is a known fact.

FIG. 4 is an overall configuration diagram showing an example of a conventional printer device 13. Referring to FIG. 4, the paper 11 is sent to the transfer unit 15 by the tractor unit 19. The transfer unit 15 is formed as an electrostatic latent image on the photosensitive drum 12 by the laser light 14 emitted from the optical unit 20, and the developing unit 2
The image visualized as a toner image is transferred onto the sheet 11. The paper 11 is sent to the fixing unit 16 again by the tractor unit 19. The fixing unit 16 includes a discharge tube 21 that fixes the toner on the paper 11 by the flash light energy. Further, the transport roller 17 is the fixing unit 1.
The sheet 11 is discharged from the sheet 6, and the sheet 11 that has been printed by the stacker 18 is folded.

In the meantime, in the electrostatic latent image forming process on the photosensitive drum 12, a latent image of a mark having a constant shape and size is formed at an appropriate position outside the printing area, and the mark is used as a toner mark by the developing device 2. It is visualized and transferred to a predetermined position on the paper 11. The toner mark transferred in this way moves together with the paper 11 and passes under the mark sensor 10, at which time the print density is detected. Mark sensor 10
Uses a reflective optical sensor that is a combination of a light emitting element and a light receiving element, and utilizes the fact that the resistance value of the light receiving element changes depending on the reflectance of an object that faces it. To detect the toner density, a circuit for converting the resistance value change of the light receiving element due to the difference in light reflectance between the paper surface of the non-printed portion and the toner mark portion into a voltage value gives a detection output as a change amount of the voltage level.

FIG. 5 schematically shows the density detection of the toner mark 5 by the mark sensor 10 and the print density control system. Referring to FIG. 5, the mark sensor 1
The output of 0 is input to the toner concentration control circuit 6, and the toner concentration control circuit 6 compares the output value of the mark sensor 10 with the reference voltage value. A supply command is output to the supply motor 9.
When the toner supply motor 9 operates, the screw 7 provided at the bottom of the toner hopper 8 rotates. The screw 7 conveys the toner and inputs it to the developing device 2. In this way, when the toner is supplied to the developing device 2, the print density increases, and the toner supply is continued until the output value of the mark sensor 10 exceeds the reference voltage value. When the output value of the mark sensor 10 eventually exceeds the reference voltage value, the toner supply is stopped.

As described above, an appropriate print density is maintained, but if the positional relationship between the print position of the toner mark 5 and the mark sensor 10 is not set with high accuracy, the sensor detection value The actual print density and the actual print density may not match the values considered in advance, and the target print density may not be maintained. As a measure for preventing the mark sensor 10 and the toner mark 5 from being misaligned, for example, there is JP-A-62-81648. According to the present invention, the mounting method of the mark sensor 10 is improved, and the mark moving unit 10 is held by the sensor moving device to secure the mounting position accuracy.

[0007]

In this conventional printer device, the tractor and the device body are composed of many parts, and it is inevitable that the finished product will be distorted. For this reason, although the mark sensor mounting position is made adjustable, the position of the mark sensor cannot be accurately aligned with the toner mark.

An object of the present invention is to provide a toner mark detecting device in an electrophotographic printer which solves the above problems and eliminates the need for accurately mounting a mark sensor.

[0009]

A toner mark detecting device in an electrophotographic printer according to the present invention comprises a printing means for printing a toner mark, a plurality of detecting means for detecting the density of the toner mark, and a plurality of these detecting means. And a control means for controlling the toner density according to the output signal selected by the determining means.

Further, the discriminating means of the toner mark detecting device in the electrophotographic printer of the present invention is means for discriminating the maximum value or the minimum value of the output signal of the detecting means and outputting the value.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of an embodiment of the present invention, and FIG. 2 is a detailed diagram showing a positional relationship between a toner mark and a toner sensor. Referring to FIGS. 1 and 2, the toner mark detecting device in the electrophotographic printer of this embodiment includes a printing unit 1 for printing a toner mark 5 and two mark sensors 10 and 101 for detecting the density of the toner mark 5. And these mark sensors 10 and 101
The mark signal discriminating means 3 for discriminating the maximum value of the output signal and outputting the value, and the toner concentration control circuit 6 for controlling the toner concentration by the output signal selected by the mark signal discriminating means 3. .

The basic operation of the printing means 1 is the same as that of the conventional example shown in FIG. 1 is different from the conventional example in that a plurality of mark sensors 10 are provided, the mark signal discriminating means 3 inputs the output signals of the plurality of mark sensors, and the output of the mark signal discriminating means 3 is the toner density. It is input to the control circuit 6, and the toner density control circuit 6 drives the toner motor 9 based on the output.

Toner mark printed by the printing means 1
5 moves with the paper 11 to move the mark sensors 10 and 1
The print density of the toner mark 5 is
To be detected. The mark sensors 10 and 101 are luminescent elements.
Using a reflective optical sensor that combines a child and a light receiving element,
The resistance value of the light receiving element changes depending on the reflectance of the facing object
You are taking advantage of what you do. No print part for toner concentration detection
Receiving light due to the difference in light reflectance between the paper surface and the toner mark area
The voltage is converted by the circuit that changes the resistance value of the element to the voltage value.
The detection output is obtained as the level change amount. Two marks
Sensors 10 and 101 are fixed with respect to the toner mark 5.
Fixed at a distance, each mark sensor 10 and
101 is fixed so as to be integrated. In addition,
The center of the ark 5 and the center of the two mark sensors match
Is installed. Each output signal is a mark signal
It is connected to another means 3. The mark signal discrimination means 3 is
The signals sent from the sensor 10 and 101
The peak voltage analysis circuit 4 is provided. Peak voltage
The analysis circuit 4 includes a mark sensor 10 and a mark sensor 101.
The output of is compared and the maximum value is output. For example, shown in Figure 3.
So that the sampling of the output voltage of the mark sensor 10
Voltage v₁, V₂And v₃Peak voltage v₂ Ask for.
At the same time, the peak voltage v of the mark sensor 101_FiveSeeking v₂
And v_FiveAnd v₂Is the solution. Peak voltage analysis circuit
The output of 4 is input to the toner density control circuit 6 and the toner density is controlled.
Of the peak voltage analysis circuit 4 and the reference voltage.
If it is excessive by comparing with the pressure value, stop the supply and
Output a supply command to the toner supply motor 9 to supply
It When the toner supply motor 9 operates, the toner hopper 8
The screw 7 provided at the bottom of is rotated. Screw 7
Conveys the toner to the developing device 2. Like this
When toner is supplied to the developing device 2, the print density increases,
Until the output value of the peak voltage analysis circuit 4 exceeds the reference voltage value.
Then the toner supply is continued. Output of peak voltage analysis circuit 4
When the force value exceeds the reference voltage value, the toner supply is stopped.

In the above description, the mark signal discriminating means 3 detects the maximum value of the output voltage of the mark sensors 10 and 101, but the mark sensors 10 and 101 are the same.
When the polarities of the output voltages of are opposite, the minimum value is detected.

As described above, by providing a plurality of mark sensors, there is no need to make adjustments based on the print position of the toner mark during assembly adjustment during production of the mark sensor, inspection during actual operation, and replacement work. Sensor mounting work is possible. Further, the printing position of the toner mark changes depending on the assembly position of the printing unit, and differs for each printer device. Therefore, it suffices to perform adjustment so that the toner mark is printed within a certain range. Installation adjustment is unnecessary.

The present invention can be used not only in a printer device that prints a toner mark on printing paper, but also in a printer device that prints a toner mark on a photosensitive drum.

[0017]

As described above, according to the present invention,
By providing a plurality of detection means for detecting the density of the toner mark, a determination means for determining the output signals of the plurality of detection means, and a control means for controlling the toner density by the output signal selected by the determination means, It is possible to carry out the work of transferring the mark sensor without adjusting the toner mark printing position as a reference.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is a detailed view showing a positional relationship between a toner mark and a toner sensor in this embodiment.

FIG. 3 is a diagram for explaining the operation of the mark signal discrimination means of this embodiment.

FIG. 4 is a diagram showing an overall configuration of a conventional electrophotographic printer.

FIG. 5 is a diagram showing a configuration of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 printing means 2 developing device 3 mark signal discrimination means 4 peak voltage analysis circuit 5 toner mark 6 toner concentration control circuit 7 screw 8 toner hopper 9 toner motor 10, 101 mark sensor 11 paper 12 photosensitive drum 13 printer device 14 laser light 15 transfer section 16 Fixing Section 17 Conveying Roller 18 Stacker 19 Tractor Unit 20 Optical Section 21 Discharge Tube

Claims (2)

[Claims] 1. A printing means for printing a toner mark, a plurality of detecting means for detecting the density of the toner mark, a discriminating means for discriminating output signals of the plural detecting means, and the discriminating means. A toner mark detection device in an electrophotographic printer, comprising: a control unit that controls the toner density according to the output signal. 2. The toner mark in an electrophotographic printer according to claim 1, wherein the discriminating means is means for discriminating a maximum value or a minimum value of an output signal of the detecting means and outputting the value. Detection device.