JPS61278877A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain a proper image always on the basis of a reference density adjusting value by forming density adjusting means to be worked in respective developing units to adjust image density in accordance with respective developers. CONSTITUTION:A halogen lamp rated by 80V and 250W is used for an original illuminating lamp 2, Vd dark part potential =400V is applied by a primary electric charger 7 and the lighting voltage of an original illuminating lamp 2 is adjusted so that Vl bright part potential =100V is obtained when the user sets up the scale of a density adjusting member to a reference density adjusting value F5 by the exposure of the white original. The image forming device executes a control process for determining the lighting voltage of the original illuminating lamp 2 prior to a copying process. To execute the control process, a white reference member W is arranged on the lower surface of an original board 3. When the control process is started, the reference latent image of the reference member W is formed on a photosensitive body 6, the potential of the reference latent image is measured and a proper lamp lighting voltage of each developing unit is determined.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus, and particularly relates to an image forming apparatus including a plurality of developing devices, each of which has a different color of developer. can be suitably applied not only to image forming apparatuses for two or three or more monochromatic colors, so-called multi-color image forming apparatuses, but also to full-color image forming apparatuses. In this specification, an image forming apparatus refers to a color copying apparatus , color printers that constitute the output units of computers and facsimile machines, and various other color printing devices.

Conventionally, in an image forming apparatus equipped with one developing device, when the image forming conditions change or when a special original is received, the exposure is adjusted to obtain an image with the appropriate density. Appropriate image density adjusting means is provided for adjusting one or more of the image density determining factors such as the amount of charge, the amount of charge, or the developing bias.

Recently, by arranging a plurality of developing devices along an electrostatic latent image carrier, such as an electrophotographic photoreceptor, and selecting an arbitrary developing device, it has become possible to copy colors other than black, such as red and green, using OT operation. 2. Description of the Related Art Image forming apparatuses such as color copying apparatuses or printing apparatuses that are capable of producing multiple color copies on a single sheet in combination with multiple modes have become widely used.

For example, in a commercially available copying machine having the above-mentioned functions, a developing bias is adopted as a proper image density adjustment means, and the developing bias of the developing device is adjusted so that a standard document is reproduced as an appropriate image using a different developer for each developing device. Optimal conditions have been set to allow this.

Further, the appropriate image density adjustment means includes an exposure amount adjustment means, that is,
It has a variable aperture diaphragm means or a lamp output changing means, and has the added function of adjusting the exposure amount to obtain an appropriate image when the image forming conditions change or when a special original is received. . The exposure amount can be set using the standard image density adjustment value based on the scale attached to the density adjustment operation member such as the density adjustment lever, dial, switch, etc. that is set by the operator. is the exposure v value, and under these conditions] the optimum developing bias conditions for each of the two developing devices are set.

Furthermore, the characteristics of the developer change over time depending on the environment, durability, etc. To deal with this, an appropriate image can be obtained by operating the density adjustment operation member mentioned above to increase or decrease the density, but if the variation from the standard image density adjustment value (scale) of the operation member is large. In this case, the user or service person may adjust the exposure setting so that a proper image is obtained when the operating member is aligned with the image density adjustment value (scale) and a black developing device is selected. The appropriate image density adjustment means is further provided with such a function. For this reason, when a developer other than black is selected, a problem arises in that an appropriate image cannot be obtained with the standard image density adjustment value.

The present invention provides, in an image forming apparatus having a plurality of developing devices, a density setting means that can be operated by the user to the same standard density adjustment value (scale) regardless of which developing device is selected. It is an object of the present invention to provide an image forming apparatus capable of obtaining a proper image in a state where the images are aligned.

(74) The above object is achieved by the present invention. To summarize, the present invention provides an image forming apparatus equipped with a plurality of developing units,
Regardless of which developer is selected, the exposure amount, charge amount, or development value is adjusted so that an appropriate image can be obtained with the same standard image density adjustment value set with the density adjustment operation member that can be operated by the user. The image forming apparatus is characterized in that it has an image density adjusting means for adjusting one or more of image forming factors such as bias in accordance with each developing device.

Next, an image forming apparatus according to the present invention will be explained with reference to the drawings.

As described above, the image forming apparatus according to the present invention can be suitably embodied in a multi-color or full-color electrophotographic copying apparatus, a color printing apparatus, etc., but in this embodiment, for example, black and red color The description will be made in connection with a color electrophotographic copying apparatus for obtaining a two-color image.

Referring to FIG.
is illuminated by a document illumination lamp 2. The mirror 4A scans the document 1 at the same speed as the document illumination lamp 2, and the mirror 4B scans the document 1 at the same speed as the document illumination lamp 2.
, 4C similarly scan at half the speed of mirror 4A, and document illumination lamp 4A, mirrors 4A, 4B, and 4C are reversed at the scanning completion position (dotted line position). The slit light image of the original is irradiated by the imaging lens 5 and mirror 4D onto the electrophotographic photoreceptor 6 rotating in the direction of arrow a.

After the photoreceptor 6 is uniformly charged by the primary charger 7, it is made into a latent image by the image exposure, and then the photoreceptor 6 is turned into a latent image by the imagewise exposure.
B makes the latent image visible.

Next, the transfer paper 10 that has passed through the transfer guide 9 is charged by a transfer charger 11 so that the developed image (toner image) on the photoreceptor 6 is transferred to the transfer paper 1.
Transferred to 0. The transfer paper 10 is separated from the photoreceptor 6 by a separation roller rotating in direction b, and is transported to a fixing device (not shown). On the other hand, the toner image remaining on the photoreceptor 6 after transfer is removed from the photoreceptor surface by the cleaner device 13, and preparations for the next copying operation are made.

In this example, an OPC drum with a diameter of 108 mm was used as the photoreceptor 6, and the process speed was 200 mm/sec. Also, the original illumination lamp 2 has a rating of 80V and 250W.
A halogen lamp is used, and Vd is
(Dark potential) = 400V is given, and the scale of the concentration tlI adjustment operation member operated by the user is set to the standard concentration adjustment value (
The lighting voltage of the original illumination lamp 2 was adjusted so that vi (bright area potential) = ioov could be obtained by exposing a white original when adjusted to F5).

The developing device 8A contains a chromatic developer (toner) that does not contain magnetite, and the developing sleeve 14A that carries the developer and supplies it to the photoreceptor is configured to rotate in the C direction. The developing bias of the developing sleeve 14A is
Vpp (amplitude voltage) = 1300V, Vf so that appropriate image density can be obtained when Vd = 400V, Vtext = 100V.
(frequency)=1000Hz, Vd
A superimposed DC voltage with c(voltage)=+200V was used.

Further, the developing device 8B contains a black developer containing magnetite, and similarly, Vd=400V, vfL=too
The developing bias applied to the developing sleeve 14B rotating in the C direction so that a proper image is obtained when V is Vp.
An alternating voltage with p=1500V and Vf=1300Hz was used superimposed on a direct voltage with Vdc='+100V.

The developing bias of each of the developing devices 14A and 14B is controlled by a DC controller 16 so as to be applied to a selected developing device sleeve via a high voltage transformer 15A or 15B.

In addition, the characteristics of the developer vary greatly depending on durability and environment, so if the standard image density adjustment value (F5) does not produce a proper image, the system is configured to compensate by adjusting the image exposure amount. be done.

Conventionally, in an image forming apparatus having only one developing unit, if an appropriate image cannot be obtained with the standard density adjustment value (scale), the density adjustment operation member is slightly moved, or the density adjustment operation member is adjusted to the standard density. The lamp lighting voltage was reset so that the appropriate image density was reproduced when the value (scale) was adjusted.

However, in an image forming apparatus configured with a plurality of developing devices, as described above, the development characteristics vary greatly depending on the developing device, so the appropriate image density is determined depending on the condition of each developing device. In order to reproduce this, a correction function is required that independently corrects the image density determining factors.

An embodiment of the image density control means of the image forming apparatus according to the present invention will be described in more detail with reference to FIGS. 1, 2, and 3.

In this embodiment, the density adjustment operation member is set to the standard density adjustment value (F
5), the lighting voltage of the original lamp 2 and the developing bias are independently controlled so that an appropriate image density is obtained in each developing device.

First, the image forming apparatus according to the present invention performs a control process for determining the lighting voltage of the original lamp 2 before performing the copying process.In order to carry out the control process, a white reference is provided on the lower surface of the original table 3. When a part W is placed (FIG. 1) and the control process is started, a latent image of the reference part W (
A reference latent image) is formed on the photoconductor 6, the potential of the reference latent image is measured, and the appropriate lamp lighting voltage for each developing device is determined.

FIG. 3 shows a flowchart for controlling the appropriate lamp lighting voltage. Referring also to FIG. 2, the scale of the density adjustment operation member is set to the standard density adjustment value (F5), and the developer selection button 17 Press to select the developer (step 1), the initial value lamp dimming signal (LINT) is transmitted from the DC controller 16 to the CVR 19, and the initial value lighting voltage V r m s is output from the CVR 19 (step 2) 0 Next, the reference white member W is illuminated with a light amount according to the voltage.
is illuminated, and the potential Vf of the latent image on the photoreceptor at that time
L is measured by the potential sensor 20 (FIG. 1) (step 3), and steps 2 and 3 are continued until Vi=100 (step 4). Since IjQ=100, the lighting voltage Vrm at the aS concentration adjustment value (F5)
s is determined (step 5).

Once the lighting voltage V r m s at the standard density adjustment value is determined, correction is performed for one selected developer. First, determine the type of the selected developer (Step 6) 1
The lighting voltage V rms is controlled via the lighting voltage variable means 18.
(step 7), and the output value of C R19, that is, the lighting voltage V r is corrected by the correction step 7.
ms is determined (step 8).

When the lighting voltage suitable for each developing device is determined as described above, at the same time, the high voltage transformer circuit 1 illustrated in FIG.
An AC bias drive signal and a DC bias control signal are transmitted from the DC controller 16 to the developing devices 5A and 15B, and bias conditions suitable for each developing device are determined.

1: After the control process is completed in the manner described above, the copying process is subsequently started, and the original is illuminated and developed using the lighting voltage and developing bias described above (step 9).

In the above explanation, first, the lighting voltage corresponding to the standard density adjustment value of the density adjustment operation member is determined, and then the lighting voltage variable means 18A, 18B corresponding to each developing device adjusts the lighting voltage corresponding to each developing device. Although the dimming signal is output from the DC controller 16, first the developing bias control signal corresponding to the standard density adjustment value of the density adjustment operation member is determined, and then the lighting voltage variable corresponding to each developer is determined. The corrected developing bias control signal corresponding to each developing device is sent to the DC controller 16 by means 18A and 18B.
It is also possible to have a configuration in which the output is output from.

As explained in Section 11, the image forming apparatus according to the present invention has a density adjusting means that operates for each developing device and can adjust the image density corresponding to each developing device, and always maintains the standard density. It is possible to obtain an appropriate image by adjusting the adjustment values.

[Brief explanation of the drawing]

Figure wIJ1 is a schematic diagram of an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a schematic circuit diagram showing one embodiment of the density adjusting means according to the present invention. FIG. 3 is a flowchart showing the control operation mode of the concentration adjusting means of FIG. 2. 6: NI image carrier 8A, 8B: Developing device 14A, 14B: Developing sleeve 16: DC controller 17: Developing device selection button 18A, 18B = Lighting voltage variable means 19: CVR FIG.

Claims (1)

[Claims] 1) In an image forming apparatus equipped with a plurality of developing devices, the same standard image density adjustment is set by a density adjustment operation member that can be operated by the user regardless of which developing device is selected. Image density adjustment means is provided for adjusting one or more of image forming factors such as exposure amount, charge amount, or development bias in accordance with each developing device with respect to the adjustment value so that an appropriate image can be obtained with the adjusted value. An image forming apparatus comprising: 2) The image density adjusting means first measures a reference potential of the latent image using a reference member, and adjusts image forming factors corresponding to each developing device based on the reference potential. The device according to item 1.