JPH04282654A - Image forming device - Google Patents

Abstract

PURPOSE:To offer an image forming device which starts an image forming action at fixed timing regardless of the emitted light quantity of a fluorescent lamp being a light source and which can quickly form an excellent image even at a first copying time. CONSTITUTION:By a control part 22, the fluorescent lamp 13 is made to emit light based on the detection signal of a transfer paper detection switch 23 through an emitted light quantity control circuit 24 and a developing bias control circuit 25 and the bias of a reference level V1 is impressed on a developing roller 43 at the same time. Besides, when the emitted light quantity of the lamp 13 just before the start of the image forming action detected by a light quantity detection sensor 6 does not arrive at a prescribed first reference level C1, it is changed to a second reference level C2 by the control part 22. Simultaneously, the bias value of the roller 43 is changed to the prescribed bias level V2 changed as much as the quantity corresponding to difference between the first reference level C1 and the detected emitted light quantity with respect to the reference level V1.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention involves irradiating a document with light and forming an electrostatic latent image on the surface of a photoreceptor drum by the reflected light.
The present invention relates to an image forming apparatus such as a copying machine that visualizes the electrostatic latent image using charged toner, and particularly relates to controlling the amount of light emitted from a light source and controlling the potential difference between a photoreceptor drum and a developing roller.

0002

Conventionally, in image forming apparatuses such as copying machines, light from a light source provided in an optical system is irradiated onto the surface of a document, and the reflected light is guided to a photoreceptor drum to form an electrostatic latent image on the drum surface. is starting to form. Furthermore, this electrostatic latent image is
Visualization is achieved by electrically adhering toner charged to a predetermined potential by a developing device to the drum surface.

Furthermore, since the predetermined amount of light is not reached immediately after the light source starts emitting light, in conventional image forming apparatuses, after the light source starts emitting light, the amount of light emitted rises to the reference level and the exposure of the document surface is performed at a stable timing. Scanning is now taking place.

0004

However, in the conventional image forming apparatus described above, since exposure scanning is not performed simultaneously with light emission from the light source, the copying operation is delayed accordingly. In particular, during the first copy after the power is turned on, the light source is at approximately the same temperature as room temperature, and it takes time for the amount of light emission to rise to the standard light emission level, so the start time of copying is delayed.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus that can perform image forming operations as quickly as normal copying from the first copy after power is turned on. do.

[0006]

[Means for Solving the Problems] In order to solve the above problems, the present invention irradiates light from a light source onto the surface of a document, and uses a developing roller to charge an electrostatic latent image formed on the surface of a photoreceptor by the reflected light. In the image forming apparatus, the image forming apparatus includes: a light amount detection means for detecting the light amount of the light source at the time of starting formation of the electrostatic latent image; and a comparison means for comparing the detected light amount with a first reference light emission amount. , a light emission control means for maintaining the light emission amount of the light source at a second reference light emission amount lower than the first reference light emission amount when the detected light amount is lower than the first reference light emission amount; When the amount of light is lower than the first reference amount of light emission, the potential difference between the photoreceptor and the developing roller is changed according to the difference between the detected amount of light and the first reference amount of light emission. and compensation control means for compensation.

Note that when the detected amount of light is lower than the first reference amount of light emission, the potential difference between the photoreceptor and the developing roller is equal to the difference between the detected amount of light and the first reference amount of light emission. It is advisable to set it to a higher or lower value depending on the situation.

[0008]

According to the first aspect of the invention, the light source emits light at the start of a copying operation, and the amount of light emitted from the light source is detected at the start timing of forming an electrostatic latent image on the photoreceptor. This detected amount of light is compared with a first reference amount of light emission, and it is determined from the comparison result whether the amount of light emission has reached the first reference amount of light emission. When the detected light amount has not reached the first reference emitted light amount, the emitted light amount of the light source is maintained at a second reference emitted light amount that is lower than the first reference emitted light amount, and the electrostatic potential builds up on the surface of the photoreceptor. An image is formed. On the other hand, at this time, the potential difference between the photoreceptor and the developing roller is changed from the reference potential during normal copying by an amount corresponding to the difference between the detected light amount and the first reference light emission amount, and the electrostatic potential is Visualization of the image is performed.

According to the second aspect of the invention, when the detected amount of light is lower than the first reference amount of light emission, the potential difference between the photoreceptor and the developing roller is equal to the detected amount of light. The value is set to a higher value according to the difference from the first reference light emission amount.

According to the third aspect of the invention, when the detected light amount is lower than the first reference light emitting amount, the potential difference between the photoreceptor and the developing roller is equal to the detected light amount. The value is set to be lower according to the difference from the first reference light emission amount.

[0011]

Embodiment FIG. 3 is a schematic diagram showing an embodiment of an image forming apparatus according to the present invention. The image forming apparatus shown in the figure is a simple, small, low-cost type image forming apparatus, and is composed of a movable table 2 consisting of a contact glass 11 and a document holder 12, and an apparatus main body 1. It is composed of a separable upper body and a lower body.

An exposure slit 1a is formed in the upper body of the apparatus main body 1 at approximately the center of the upper surface, and an image reading section 3 consisting of a lamp 13, a condensing lens 14, etc. is provided below the slit 1a. ing. Note that the lamp 13 is a fluorescent lamp that is low cost and generates little heat. Also,
The photosensitive drum 15 is disposed below the image reading section 3, and a charging device 16, a developing device 4, and a cleaning device 18 are further disposed around the photosensitive drum 15 from the upstream side. Further, a storage section 18a for storing collected toner is formed on the left side of the cleaning device 18.

The developing device 4 includes a developing vat 41 and a hopper 42 for storing replenishing toner, and above the developing vat 41 and hopper 42, there are a developer cartridge CS for supplying a starter agent and a replenishing toner, respectively. A cartridge CT is attached to the cartridge CT. A developing roller 43 is provided in the developing vat 41 facing the photosensitive drum 15, and a stirring roller 44 is provided below the supply port 42a of the hopper 42 for stirring the developer consisting of toner and carrier. It is being Further, a toner replenishment roller 45 is provided in the hopper 42 above the replenishment port 42a so that the roller circumferential surface covers the replenishment port 42a.

On the other hand, the lower body of the apparatus main body 1 is provided with a transfer paper supply tray 20 on one side and a paper discharge tray 21 for discharging the transfer paper on which an image has been formed on the other side. Further, a paper feed roller 5, a transfer/separation device 17, and a fixing device 19 are provided from the transfer paper feed tray 20 side to the paper discharge tray 21 side.

The image forming apparatus main body 1 is completed by combining the upper main body and the lower main body.

To explain the copying operation, after placing an original at a predetermined position on the contact glass 11, when a transfer paper is inserted into the paper feed tray 20, the transfer paper is detected by a transfer paper detection sensor (not shown), and the transfer paper is detected by a transfer paper detection sensor (not shown). A copy operation is started by the detection signal.

First, the transfer paper is conveyed to point P by the paper feed roller 5 and is placed in a standby state. Further, the table 2, which is located at the center in the initial state, once moves to the left, and when its right end reaches above the document reading section 3, the direction of movement is reversed to the right and document scanning is performed. . The lamp 13
is normally turned on at the same time as the start of the copying operation, and is dimmed to a reference light amount level for several seconds, for example, until the table 2 moves to the exposure start position. However, fluorescent lamp 1
If the light emission of No. 3 does not reach the reference light amount level within the above period, the light is adjusted to a predetermined value according to the light emission amount at the exposure start timing. Control of this dimming level will be described later.

The light irradiated through the slit 1a is reflected on the document surface, and the reflected light is reflected by the condenser lens 14.
is projected onto the photoreceptor drum 15. The photosensitive drum 15 is rotated to an exposure position while the surface of the drum is charged to a predetermined potential by a charging device 16, and an electrostatic latent image of a document image is formed on the drum surface by projection of the reflected light.

This electrostatic latent image is made visible by toner charged by the developing device 4. That is, the toner and carrier in the developing vat 41 are stirred by a stirring roller 44 and conveyed to a developing roller 43 charged to a predetermined potential, and further conveyed by the developing roller 43 to the photosensitive drum 15 side. Then, the toner charged by the developing roller 43 is electrically attached to the surface of the photoreceptor drum 15, and the electrostatic latent image is visualized.

The bias value of the developing roller 43 is set to a predetermined value depending on the dimming level of the light source, and the details will be described later.

On the other hand, the transfer paper waiting at point P is conveyed at a predetermined timing, and the toner image on the photosensitive drum 15 is transferred onto this transfer paper by the transfer/separation device 17. and,
The transfer paper on which the toner image has been transferred is separated from the photoreceptor drum 15, fixed by a fixing device 19, and then discharged to a paper discharge tray 21. In addition, the photosensitive drum 15 after transfer
The toner remaining on the drum surface is removed by the cleaning section 18, and the drum is charged again by the charging device 16, and the same image forming operation as described above is repeated until the image forming of one document is completed. This is because the circumferential length of the photosensitive drum 15 is shorter than the original size, so the original image is divided and images are formed on the transfer paper.

During this image forming operation, the table 2, which has finished scanning the original, reverses its moving direction and returns to its initial position.

FIG. 1 is a block diagram of a control system for adjusting the light of the light source 13 and setting the bias of the developing roller 43 in an image forming apparatus according to the present invention.

In the figure, reference numeral 22 denotes a control section that centrally controls the image forming operation. Reference numeral 23 denotes a transfer paper detection switch that detects that transfer paper is inserted into the paper feed tray 20. 24 is a light emission control circuit that controls light emission, extinguishing, and dimming of the light source (fluorescent lamp) 13 based on a control signal from the control unit 22, and has a built-in PWM control circuit for driving the fluorescent lamp 13. . The light emission control circuit 24 adjusts the amount of light emission to a predetermined value by changing the duty ratio of the drive voltage supplied to the fluorescent lamp 13. A developing bias control circuit 25 controls the bias of the developing roller 43 based on a control signal from the control section 22.

FIG. 2 shows the control operation of the above control system.
Explain using. Figure 2 shows the fluorescent lamp 13 after copying has started.
4 is a waveform diagram of the amount of light emitted and the developing bias of the developing roller 43. FIG. When a transfer paper detection signal is input from the transfer paper detection switch 23 at point A, the control section 22 sends a light emission signal to the light emission amount control circuit 24 and also sends a bias setting signal to the developing bias circuit 25. The light emission amount control circuit 24 receives the light emission signal and turns on the fluorescent lamp 13. Further, the developing bias control circuit 25 receives the bias setting signal and applies a bias of a reference level V1 to the developing roller 43. This reference level V1 is a rated value and is a bias level set in normal operation.

After the lighting starts, the amount of light emitted from the fluorescent lamp 13 is detected by the light amount detection sensor 6, and this detection data is input to the control section 22. The control unit 22 controls the light emission data of the fluorescent lamp 13 and the first reference level C at a predetermined timing point B immediately before the start of exposure scanning (immediately before the start of image formation).
1 to determine whether the amount of light emission has reached the first reference level C1. This first reference level C1 is a rated value, and is a light emission amount set in normal operation.

If the detection level C has not reached the first reference level C1 as shown by the solid line in FIG. At the same time, the second reference level C
2 is sent as the control value. The light emission amount control circuit 24 changes the duty ratio of the drive voltage of the fluorescent lamp 13 based on the second reference level C2 inputted in response to this instruction signal, and adjusts the light emission amount of the fluorescent lamp 13 to the second reference level C2. Dimming to.

Further, the control section 22 sends an instruction signal to change the bias control value to the developing bias control circuit 25, and also calculates a predetermined bias level V2 that is higher than the reference level V1 and sends it as a control value. This bias level V2 is a bias level that increases the reference level V1 by that amount in accordance with the level difference when the dimming level of the fluorescent lamp 13 is changed from the first reference level C1 to the second reference level C2. This is a predetermined level that can compensate for the decrease in density of the electrostatic latent image on the surface of the photoreceptor drum 15 due to reducing the amount of light emitted from the lamp 13 from the first reference level C1 to the second reference level C2 during development.

Although this bias level V2 can be calculated using an arithmetic expression, it is preferable to directly calculate it using a pre-stored conversion table of the bias level V2 corresponding to the second reference level C2. The developing bias control circuit 25 is
Upon receiving the instruction signal, the bias level of the developing roller 43 is changed from the reference level V1 to the control level V2 (Fig. 2
(see solid line).

On the other hand, if the amount of light emission has already reached the first reference level C1 as shown by the dashed line in FIG.
2, a light emission amount control circuit 24 and a developing bias control circuit 2;
5, the above-mentioned level change instruction signal is not sent.

When the exposure scan is completed, the control section 2
2 sends a light-off signal to the light emission amount control circuit 24 to turn off the fluorescent lamp 1.
3 is turned off, and a bias stop signal is sent to the developing bias control circuit 25 to stop applying the bias voltage to the developing roller 43.

In the present invention, it is sufficient that the potential difference between the photosensitive drum 15 and the developing roller 43 changes depending on the light emission level of the fluorescent lamp 13, and the voltage difference between the photosensitive drum 15 and the developing roller 43 can be changed in accordance with the light emission level of the fluorescent lamp 13. The charging voltage on the surface may be changed according to the light emission level of the fluorescent lamp 13. Furthermore, the polarities of the developing roller 43 and the photosensitive drum 15 can be set as appropriate depending on the polarity of the toner.

As described above, the present invention prevents deterioration of image quality by changing the dimming level according to the light intensity of the lamp 13 immediately before the start of image formation, and adjusting the developing bias by the amount that the dimming level has been changed. This is particularly effective when a fluorescent lamp is used as a light source and the time it takes for the amount of light to stabilize varies depending on the temperature of the filament at the start of lighting, or when the light emission level decreases due to deterioration over time.

[0034]

As explained above, the present invention detects the amount of light emitted from a fluorescent lamp immediately before the start of image formation, and if the detected amount of light does not reach the first reference amount of light, the amount of light emitted from the fluorescent lamp is adjusted. Since the image formation is performed by changing the setting to the detected light intensity, the image formation start timing can be kept constant regardless of the luminescence intensity of the fluorescent lamp, and the image formation can be performed quickly from the first copy operation when the power is turned on. Image formation can be performed.

Furthermore, while changing the setting of the light emission amount of the fluorescent lamp to a detected light amount lower than the first reference light emission amount, the amount of light emitted between the photoreceptor and the developing roller is adjusted according to the difference between the reference light emission amount and the detected light amount. Since the potential difference is changed, the fogging density does not decrease due to insufficient amount of light, and images can be formed satisfactorily.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram showing the system configuration of an image forming apparatus according to the present invention.

FIG. 2 is a time chart of the amount of light emitted from a fluorescent lamp and the developing bias for explaining the operation of the image forming apparatus according to the present invention.

FIG. 3 is a schematic configuration diagram showing an example of an image forming apparatus according to the present invention.

[Explanation of symbols]

1 Image forming device 3 Image reading section 4 Developing device 5 Paper feed roller 6 Light amount detection sensor 13. Fluorescent light 14 Condensing lens 15 Photoreceptor drum 16　Charging device 17 Transfer/separation device 18 Cleaning device 19 Fixing device 22 Control section 23 Transfer paper detection switch 24 Light amount control circuit 25 Development bias control circuit 43 Developing roller 44 Stirring roller

Claims (3)

[Claims] 1. An image forming apparatus that irradiates light from a light source onto the surface of a document, and visualizes an electrostatic latent image formed on the surface of a photoreceptor by the reflected light using toner charged by a developing roller. a light amount detection means for detecting the light amount of the light source at the time of starting image formation; a comparison means for comparing the detected light amount with a first reference light emitting amount; and the detected light amount is lower than the first reference light emitting amount. When the detected light amount is lower than the first standard light emission amount, the light emission control means maintains the light emission amount of the light source at a second reference light emission amount that is lower than the first reference light emission amount; An image characterized by comprising: compensation control means for compensating by changing the potential difference between the photoreceptor and the developing roller by an amount corresponding to the difference between the detected light amount and the first reference light emission amount. Forming device. 2. When the detected amount of light is lower than the first reference amount of light emission, the compensation control means adjusts the potential difference between the photoreceptor and the developing roller to be equal to the difference between the detected amount of light and the first reference amount of light emitted. 2. The image forming apparatus according to claim 1, further comprising bias control means that sets the value to a higher value in accordance with a difference from a reference amount of light emission. 3. When the detected amount of light is lower than the first reference amount of light emission, the compensation control means adjusts the potential difference between the photoreceptor and the developing roller to a level between the detected amount of light and the first reference amount of light emitted. 2. The image forming apparatus according to claim 1, further comprising bias control means that sets the value to be lower according to a difference from a reference light emission amount.