JPH04347871A - Image forming device - Google Patents

Abstract

PURPOSE:To eliminate the need for manually adjusting the output signal level of a light quantity detector and to prevent the occurrence of the partial fatigue of a photosensitive body by automatically adjusting the output signal level of the light quantity detector to a prescribed level. CONSTITUTION:An automatic level adjusting means 1 automatically adjusting the output signal level of the light quantity detector to the prescribed level, and a motor control means 2 revolving a motor at the time of operating the automatic level adjusting means 1, are provided and the motor control means 2 rotates the motor to rotate the photosensitive body. On the other hand, a density detector output level adjusting means 3 automatically adjusting the output level of a density detector, and a motor control means 4 rotating the motor at the time of operating the density detector output level adjusting means 3, are provided. Therefore, it is unnecessary that the output level of the light quantity detector is manually adjusted, and the load of an operator can be reduced. Further, since the photosensitive body is rotated at the time of adjusting the output signal level of the light quantity detector, the photosensitive body hardly has the partial fatigue.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to image forming apparatuses such as copying machines and facsimile machines.

0002

2. Description of the Related Art In image forming apparatuses such as copying machines having a photoreceptor, a density detector is used to measure the density of an image formed on the photoreceptor, and this density detector is connected to a toner density controller. It is used for such things. The toner density controller forms an electrostatic latent image of a reference pattern on the photoreceptor, develops this electrostatic latent image into a visible image using a developer, and detects the density of this visible image using a density detector. The output signal of the density detector is compared with a reference value, and the toner density of the developer is controlled to be constant by controlling the supply of toner from the toner supply device to the developing device based on the comparison result. . As described above, an image forming apparatus using a density detector is known from, for example, Japanese Patent Laid-Open No. 136064/1983.

[0003] The above-mentioned concentration detector usually uses a reflection type photosensor consisting of a light emitting diode and a phototransistor. In general, this reflective photosensor has differences in output signals due to variations in the elements, and even if the amount of input light is the same, the output signal level fluctuates due to changes in characteristics or changes over time. Therefore, it is necessary to adjust the output signal level of each reflective photosensor to make it constant. Therefore, conventionally, the output signal level of the reflective photosensor is manually adjusted using a variable resistor so that it is constant with respect to the background portion of the photoreceptor. for example,
Japanese Unexamined Patent Publication No. 151667/1983 discloses that in an image forming apparatus, the amount of light from a light source for illuminating an original is detected by a light amount detector, and the output signal level of this light amount detector is manually adjusted using a variable resistor. What was done is described.

0004

In the image forming apparatus described above, the output signal level of the reflective photosensor is manually adjusted, which is troublesome for the operator. In particular, when adjusting the output signal level of a reflective photosensor, the light emitting diode of the reflective photosensor is turned on to irradiate the photoconductor while it is stopped. Partial fatigue due to exposure to light.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus which eliminates the need to manually adjust the output signal level of a light quantity detector and does not cause partial fatigue of the photoreceptor.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the invention of claim 1 provides a motor for rotating a recording material;
a light source for illuminating a document, an image forming process means for forming an image on the recording material based on exposure of a document image by illuminating the document from the light source when the recording material is rotated, and detecting the amount of light from the light source. As shown in FIG. 1, in an image forming apparatus that has a light amount detector that controls the light amount, and a light amount control means that controls the light amount of the light source according to the output signal of the light amount detector, the output signal level of the light amount detector is controlled. The invention comprises an automatic level adjusting means 1 that automatically adjusts to a predetermined level, and a motor control means 2 that rotates the motor when the automatic level adjusting means 1 is activated. A motor rotates the body, and an electrostatic latent image of a reference pattern is formed on the photoreceptor, this electrostatic latent image is developed by a developer into a visible image, and the density of this visible image is measured by a density detector. In the image forming apparatus, the image forming apparatus includes a toner density control means for detecting the density and comparing the output signal of the density detector with a reference value, and controlling the replenishment of toner from the toner replenishing device to the developing device based on the comparison result. 2, a concentration detector output level adjusting means 3 for automatically adjusting the output level of the concentration detector, and a motor control means 4 for rotating the motor when the concentration detector output level adjusting means 3 is activated. It is equipped with the following.

[0007]

[Operation] In the invention of claim 1, the output signal level of the light amount detector is automatically adjusted to a predetermined level by the automatic level adjusting means 1, and when the automatic level adjusting means 1 is activated, the motor controlling means 2 controls the motor. Rotate to rotate the photoreceptor.

In the invention of claim 2, the output level of the concentration detector is automatically adjusted by the concentration detector output level adjustment means 3, and when the concentration detector output level adjustment means 3 is operated, the motor control means 4 controls the motor. Rotate the photoreceptor.

[0009]

Embodiment FIG. 3 shows a part of a first embodiment of the present invention. This embodiment is an example of a copying machine, and the illumination device 11 is constituted by a light source consisting of an illumination lamp, for example, a fluorescent lamp 12 and a reflector 13. The light incident end of the optical fiber 14 for light amount detection is inserted and fixed into the hole of the reflector 13, and the illumination lamp 1
The light from 2 is introduced from the light incidence end. A slit exposure device including illumination device 11 exposes an image of a document placed on document table 15 . That is, the original placed on the original platen 15 is illuminated by the illumination device 11, and the reflected light image is transmitted through the first mirror 16, the second mirror 17, the third mirror 18, the lens 19, and the fourth mirror 20. Light scanning was performed by irradiating a recording material 21 made of a photoreceptor drum and by moving a scanner equipped with an illumination device 11 and a first mirror 16 to a third mirror 18 forward from its home position by a scanner motor. It then returns to its home position.

During a copying operation, the photosensitive drum 21 is rotationally driven by a motor, is uniformly charged by a charging charger 22, and then unnecessary portions are removed by an eraser 23.The photosensitive drum 21 is then subjected to image exposure of the document by the slit exposure device to remove static electricity. A latent image is formed. This electrostatic latent image is developed by the developing device 24 to become a visible image, which is transferred to the transfer paper fed from the paper feeder by the transfer device 25, and the transfer paper is separated by the separating corona discharger 26 and the separating claw 27. It is separated from the photosensitive drum 21. The transfer paper separated from the photosensitive drum 21 has a developed image fixed thereon by a fixing device (not shown), becomes a copy, and is discharged to the outside. Further, after the transfer paper is separated from the photosensitive drum 21, residual toner is removed by a cleaning device 28, and residual charges are removed by a static eliminator 10, making the next copy possible.

[0011] Such a copying operation is started by a copying operation start command from the print switch on the operation display section, and is continuously repeated for the number of copies set using the numeric keypad on the operation display section. Here, the charger 22, the eraser 23, the slit exposure device, the developing device 24, the paper feeding device, the transfer device 25, the separating corona discharger 26, the fixing device, the cleaning device 28, the static eliminator 10, etc. are connected to the photosensitive drum 21. It constitutes an image forming process means for forming an image on the transfer paper, transferring it to the transfer paper, and then fixing it. Further, a developing bias voltage is applied to the developing device 24 from a developing bias power source.

FIG. 4 shows the circuit configuration of this embodiment. The light from the illumination lamp 12 passes through the light intensity detection optical fiber 14 and is irradiated onto a light intensity detector 29 consisting of a photodiode. The signal is invertedly amplified by an inverting amplifier 32 including a resistor 30 and a resistor 31, and non-invertingly amplified by a non-inverting amplifier 33. In this non-inverting amplifier 33, the output terminal of the inverting amplifier 32 is connected to the + input terminal of the operational amplifier 34, and a resistor 35 is connected between the output terminal and the - input terminal of the operational amplifier 34, so that the - An input terminal is grounded via an electronic volume 36. The output signal of the non-inverting amplifier 33 is A/D converted by the A/D converter 37 to become a digital signal, which is input to the microcomputer 38. The microcomputer 38 judges the digital signal from the A/D converter 37, controls the electronic volume 36 so that the digital signal reaches a predetermined value, and adjusts its resistance value, thereby adjusting the gain of the non-inverting amplifier 33. . Therefore, even if the output signal level of the photodiode 29 fluctuates due to variations in the photodiode 29, changes in characteristics, or changes over time, the electronic volume 36 is adjusted so that the digital signal from the A/D converter 37 to the microcomputer 38 remains the same. is controlled by a microcomputer 38.

The microcomputer 38 also outputs a pulse width modulation (PWM) signal for controlling the illumination lamp 12 to a lamp control circuit 39, and the lamp control circuit 39 controls the illumination lamp 12 using the PWM signal from the microcomputer 38. drive Here, the light amount of the illumination lamp 12 is controlled by a PWM signal from the microcomputer 38, and for example, the duty ratio of the PWM signal is 100%.
When the PWM signal is at a high level, the maximum amount of light is output, and when the duty ratio of the PWM signal is 0% (when the PWM signal is at a low level), it is turned off. The microcomputer 38 normally controls the duty ratio of the PWM signal to the lamp control circuit 39 using a digital signal from the A/D converter 37 so that the light intensity of the illumination lamp 12 becomes a predetermined light intensity. Furthermore, the microcomputer 38 controls a motor 40 for rotating the photosensitive drum 21.

FIG. 5 shows a light source light amount adjustment program of the microcomputer 38. microcomputer 3
8 first rotates the motor 40 to rotate the photosensitive drum 21.
is rotated, and a PWM signal with a duty ratio of 100% is output to the lamp control circuit 39 to turn on the illumination lamp 12 with the maximum light intensity. Next, the microcomputer 38 reads the output signal (A/D input value) of the A/D converter 37 for the background portion of the photoreceptor drum 21, compares this A/D input value with the set value Va, and If /D input value<setting value Va, the electronic volume 36 is controlled so that the A/D input value increases by a predetermined value, and then the process returns to the step of comparing the A/D input value and Va.

If the A/D input value is less than Va, the microcomputer 38 outputs the A/D input value from the A/D converter 37.
Compare the input value with another set value Vb. Here, as shown in FIG. 6, Vb>Va. microcomputer 38
If the A/D input value>Vb, the electronic volume 36 is controlled so that the A/D input value decreases by a predetermined value, and then the process returns to the step of comparing the A/D input value and the set value Vb.

[0016]Then, the microcomputer 38
If /D input value>Vb, the illumination lamp 12 is turned off via the lamp control circuit 39, the motor 40 is stopped, and the light intensity adjustment of the illumination lamp 12 is completed. Here, the electronic volume 36 is of a type that retains the value adjusted by the microcomputer 38 even when the power is turned off.

According to this first embodiment, the microcomputer 38 determines the output signal level (
The output signal level of the photodiode 29) is automatically set to V.
Since it is adjusted to a predetermined level such that a<A/D input value<Vb, even if the output signal level of the photodiode 29 fluctuates due to variations in the photodiode 29, changes in characteristics, or changes over time, the output signal level of the illumination lamp 12 remains unchanged. The output signal level can be automatically adjusted to a predetermined level, and there is no need to manually adjust fluctuations in the output signal level of the photodiode 29. Moreover, since the photoreceptor drum 21 is rotated when adjusting the output signal level of the photodiode 29, even if the light from the illumination lamp 12 is irradiated onto the photoreceptor drum 21 via the optical systems 16 to 20, the photoreceptor drum is partially exposed. No fatigue occurs.

FIGS. 7 and 8 show various parts of a second embodiment of the present invention. This second embodiment is an example of a copying machine, in which a photosensitive drum 41 is rotationally driven by a motor during a copying operation and uniformly charged with positive charges by a charger 42. Next, the photoreceptor drum 41 is irradiated with light by an eraser 43 to remove charges in unnecessary areas, and a slit exposure device exposes the original image to form an electrostatic latent image.

The electrostatic latent image on the photoreceptor drum 41 is developed with a two-component developer by a developing device 44, and negatively charged toner is attached thereto to form a developed image. The developing device 44 is a developing roller 44
A magnetic brush developing device having a magnetic brush is used, and a developing bias voltage is applied to the developing roller 44a from a developing bias power source. Next, the photosensitive drum 41 is removed by a pre-transfer static eliminator 45.
The surface potential is uniformly lowered by corona discharge and light irradiation, and the transfer paper is fed from a selected one of the paper feeding devices 46 to 48 to the registration roller 51 via the conveyance paths 49 and 50. This transfer paper is sent out by the registration roller 51 with its leading edge aligned with the visible image on the photoreceptor drum 41, and the visible image on the photoreceptor drum 41 is transferred to the surface by positive corona discharge by the transfer charger 52, and separated. The photosensitive drum 41 is separated by the charger 53 and the separating claw 54.
It is separated from the paper and transported by a transport belt 55. Furthermore, the visible image is fixed on the transfer paper by a fixing device 56, resulting in a one-sided copy.

When making a one-sided copy, the sheet is delivered to the copy tray 61 by the paper discharge roller 60 via the reversing rollers 57 to 59.
is discharged to. In addition, during double-sided copying, the single-sided copy from the fixing device 56 is conveyed along the reversing guide plate 64 by the reversing rollers 57 to 59, the tapping rollers 62, and the reversing return rollers 63, and is then reversely conveyed by the branching claw 65 to the paper ejection path. The paper is then branched off and discharged onto a double-sided tray 66. Thereafter, the single-sided copy in the double-sided tray 66 is fed with the front and back sides reversed by the calling roller 67 and conveyed to the registration rollers 51 via the conveyance path 49, and a developing image is printed on the back side in the same way as when copying the front side. Transfer and fixing are performed to create a double-sided copy. This double-sided copy is discharged to a copy receiver 61 by a paper discharge roller 60 via reversing rollers 57 to 59.

After separation of the transfer paper, the photosensitive drum 41 is charged with AC corona discharge by a pre-cleaning static eliminator 68, and is then cleaned by a cleaning device 69 with fur brushes 69a,
The residual toner is removed by the cleaning blade 69b, and the static electricity is removed to zero by the static eliminator 70 in preparation for the next copying operation.

Such a copying operation is started by turning on the print switch on the operation display section, and is continuously repeated for the number of copies set by the ten keys on the operation display section.

Further, as shown in FIG. 9, in the slit exposure device, the original 72 on the original platen 71 is exposed to the light source 73.
At the same time, the movable optical system consisting of the light source 73 and the mirrors 74 to 76 moves forward from the home position. By performing optical scanning, an electrostatic latent image corresponding to the image density of the original is formed on the photoreceptor drum 41, and then the movable optical systems 73, 7
4 to 76 return to the home position. A side scale 79 for aligning the sides of the document 72 is installed on the side of the document table 71, and a reference pattern 80 having a constant density is provided below the side scale 79.
4 is a concentration detector 8 consisting of a reflective photosensor.
1 is placed.

During the copying operation, the movable optical systems 73 to 7
When the light source 73 is turned on when 6 is at the home position, the reference pattern 80 is illuminated by the light source 73, and the reflected light is irradiated onto the photoreceptor drum 41 via the optical systems 74 to 78. Upper charger 4
An electrostatic latent image of the reference pattern 80 is formed on the portion charged by 2. This electrostatic latent image is developed by a developing device 44 to become a visible image, which passes through a pre-transfer static eliminator 45, a transfer charger 52, a separation charger 53, and a separation claw 54, and is not transferred to a transfer paper, but is sent to a reflective photo sensor. After the density is optically detected by the pre-cleaning static eliminator 68 and removed by the cleaning device 69, the photosensitive drum 41 is neutralized to zero by the static eliminator 70. A toner density control section (not shown) is a reflection type photosensor 8 for developing the reference pattern 80.
The output signal No. 1 is compared with a reference value for toner replenishment, and depending on the result, the toner replenishment clutch is turned on for a predetermined period of time to replenish toner from the toner replenishment device to the developing device 44. By controlling toner replenishment in this way, the developing device 44
The toner density of the two-component developer in the image forming apparatus is controlled to be constant, and the image density of the copy is controlled to be constant. Note that the visible image of the reference pattern 80 is displayed multiple times, for example, once every five copying operations.
At other times, the electrostatic latent image of the reference pattern 80 is erased by the eraser 43.

FIG. 10 shows the circuit configuration of this copying machine. The reflective photosensor 81 includes a light emitting diode 81a and a phototransistor 81b, and a constant current circuit 82.
A current determined by the resistance value of the electronic volume 83 is passed through the light emitting diode 81a, and the light emitting diode 81a emits light with an amount of light proportional to the current from the constant current circuit 82. The light from the light emitting diode 81a is irradiated onto the photosensitive drum 41, and the reflected light is received by the phototransistor 81b. The phototransistor 81b has a collector connected to a power supply and an emitter grounded via a resistor 84.
An output signal is generated that is proportional to the amount of reflected light from the photoreceptor drum 41, that is, the density of the background portion of the photoreceptor drum 41. The output signal of this phototransistor 81b is converted into a digital signal by an A/D converter 85 and input to a microcomputer 86. The microcomputer 86 also operates a motor 87 for rotating the photoreceptor drum 11.
and controls on/off the transistor 88 connected in parallel with the light emitting diode 51a.

FIG. 11 shows the concentration detector adjustment program of the microcomputer 86. The microcomputer 86 first turns on the motor 87 to rotate the photosensitive drum 41 and turns on the light emitting diode 81a. Next, the microcomputer 86 controls the photosensitive drum 41
The output signal of the A/D converter 85 (A/D
This A/D input value is compared with the set value Va, and if the A/D input value < the set value Va, the electronic volume 83 is varied so that the A/D input value increases by a predetermined value. After that, the process returns to the step of comparing the A/D input value and Va. When the electronic volume 83 is varied, the current from the constant current circuit 82 to the light emitting diode 81a is varied, the amount of light emitted from the light emitting diode 81a is changed, the output signal of the phototransistor 81b is changed, and the A/D input value is changed. Change.

If the A/D input value is not <Va, the microcomputer 86 compares the A/D input value from the A/D converter 85 with another set value Vb. Here, as shown in FIG. 6, Vb>Va. If the A/D input value>Vb, the microcomputer 86 controls the electronic volume 83 so that the A/D input value decreases by a predetermined value, and then performs a step of comparing the A/D input value and the set value Vb. Return to

[0028] Then, the microcomputer 86
If /D input value>Vb, the transistor 88 is turned on, the light emitting diode 81a is turned off, and the adjustment of the concentration detector 81 is completed. Here, the electronic volume 83 is of a type that retains the value adjusted by the microcomputer 86 even when the power is turned off.

According to this second embodiment, the output signal level of the concentration detector 81 is automatically adjusted by the microcomputer 86 to a predetermined level such that Va<A/D input value<Vb. The output signal level of the concentration detector 81 can be automatically adjusted to a predetermined level.
There is no need to manually adjust the output signal level. Furthermore, since the photoreceptor drum 11 is rotated when adjusting the density detector 51, even if the photoreceptor drum 11 is irradiated with light from the density detector 81, the photoreceptor drum 11 will not be partially fatigued.

[0030]

[Effects of the Invention] As described above, according to the present invention, the output signal level of the light amount detector is automatically adjusted to a predetermined level, so there is no need to manually adjust the output signal level of the light amount detector. The burden on the operator is reduced. Moreover, since the photoreceptor is rotated when adjusting the output signal level of the light amount detector, partial fatigue of the photoreceptor can be eliminated.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the invention of claim 1.

FIG. 2 is a block diagram showing the invention of claim 2.

FIG. 3 is a sectional view showing a part of the first embodiment of the present invention.

FIG. 4 is a block diagram showing the circuit configuration of the same embodiment.

FIG. 5 is a flowchart showing a light source light amount adjustment program of the microcomputer in the same embodiment.

FIG. 6 is a diagram for explaining the same embodiment.

FIG. 7 is a sectional view showing a part of a second embodiment of the present invention.

FIG. 8 is a sectional view showing another part of the same embodiment.

FIG. 9 is a sectional view showing another part of the same embodiment.

FIG. 10 is a block diagram showing the circuit configuration of the same embodiment.

FIG. 11 is a flowchart showing a light source light amount adjustment program of the microcomputer in the same embodiment.

[Explanation of symbols]

1 Automatic level adjustment means 2 Motor control means 3 Concentration detector output level adjustment means 4
motor control means

Claims (2)

[Claims] 1. A motor for rotating a recording material, a light source for illuminating a document, and an image on the recording material based on exposure of a document image by illumination of the document by the light source when the recording material is rotated. An image forming apparatus comprising an image forming process means for forming an image, a light amount detector for detecting the amount of light from the light source, and a light amount control means for controlling the amount of light from the light source according to an output signal of the light amount detector. An image forming apparatus comprising: automatic level adjustment means for automatically adjusting the output signal level of a detector to a predetermined level; and motor control means for rotating the motor when the automatic level adjustment means is activated. . 2. A motor for rotating a photoreceptor, forming an electrostatic latent image of a reference pattern on the photoreceptor, and developing this electrostatic latent image into a visible image using a developing device. and toner density control means for detecting the density with a density detector, comparing the output signal of the density detector with a reference value, and controlling toner replenishment from the toner replenishing device to the developing device based on the comparison result. The image forming apparatus includes a density detector output level adjusting means for automatically adjusting the output level of the density detector, and a motor control means for rotating the motor when the density detector output level adjusting means is activated. An image forming apparatus characterized by: