JPS5913264A - Picture forming device - Google Patents

Abstract

PURPOSE:To form a copy image with excellent color balance by measuring the amount of toner on an intermediate transfer body, and varying the efficiency of transfer from a photoreceptor to the intermediate transfer body or from the intermediate transfer body to transferring paper according to the measured value. CONSTITUTION:The photosensitive drum 1 is exposed to an original picture which is color-separated by a color separation filter 10 and its latent image is developed 18 with toner in corresponding colors. The developed images are positioned and transferred successively to a picture carrier sheet 222 supported on the surface of a transfer drum 22 by the 1st transfer corona electrifier 221 in the transfer drum 22, forming a multicolor picture. The densities of patch images in colors Y, M, and C formed outside of a copy picture area are detected and the high voltage power source 37 of the electrifier 221 and the grid bias power source 38 of a before-transfer electrifier 19 are controlled on the basis of the measured values. The multicolor picture on the transfer drum 22 is transferred 28 to the transferring paper 25 at a time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transfer device, and more specifically, the present invention relates to a transfer device that transfers an image on an image carrier carrying a developed image to an intermediate transfer member, and further transfers the image on the intermediate transfer member again to another transfer material. The present invention relates to a transfer device.

Conventionally, in image forming apparatuses such as transfer-type color electrophotographic apparatuses, which sequentially form color images using different toners on an image bearing member such as a photoreceptor drum, and multiple-transfer each color image onto a transfer material, various types of image forming apparatuses have been used. A method has been proposed.

If we divide these methods into two categories, one type is made of rubber, metal, plastic, film, etc.

The transfer material is wrapped around a transfer material support roller or a transfer material support belt, and a bias voltage is applied to four sides (roller or belt) to transfer the toner image on the image carrier onto the transfer material several times in sequence. A multicolor image is obtained by transferring the image.

In addition, similar to the above, an endlessly moving roller or belt is used as an intermediate transfer member, and the toner image on the image carrier is sequentially transferred multiple times onto this intermediate transfer member. The multicolor image is finally transferred all at once onto a transfer material.

The former method requires a means to wrap the transfer material around the transfer material support means and a means to prevent the transfer material from shifting during the multiple transfer steps, such as a gripper that grips the leading edge of the transfer material. , requires extremely complicated means such as a suction device that suction-holds the transfer material on the transfer material support means.

On the other hand, the latter method does not require the above-mentioned transfer material holding device and can prevent positional deviations during multiple transfers with high precision.

However, in any of the above transfer devices, it is difficult to transfer the developed images on the image carrier onto the transfer material at a constant transfer rate. Especially many color images.

The multiple transfer grade has the disadvantage that if the transfer rate of each color toner is different, the color balance of the copied image changes, making it impossible to obtain a good color image.

Factors that change this transfer rate include differences in toner particle size distribution and tribocharge amount, or changes in electrostatic attraction force due to repeated transfer steps of the intermediate transfer body. especially,
In a method in which an intermediate transfer body is constructed by wrapping an insulating film around a cylinder with an opening, and a toner image is transferred by applying a corona discharge from inside the transfer body, the potential on the back side of the film, which is the image carrier, tends to fluctuate. . Other factors include changes in the surface resistance of the intermediate transfer member, and charge accumulation with the same polarity as the toner polarity that occurs on the surface of the same intermediate transfer member.

As a solution to the above problem, US Patent Specification @ 3
．． No. 822.093, a transparent electrode to which a bias voltage of opposite polarity to the toner is applied is provided on a part of the photosensitive drum, the electrode portion is developed, and the developed images are transferred to the transfer drum. Detects changes in transmittance of residual toner,
A method is known in which the bias voltage of the transfer drum is controlled in accordance with the detection signal.

However, in this method, electrodes are provided on the photosensitive drum itself,
A mechanism for applying a bias voltage is required, which complicates the device configuration. Approximately 5% to 30% of the amount of toner during development
Since residual toner corresponding to ' This causes accuracy problems.

Furthermore, in a method in which a toner image on an image carrier is multicolored developed on an intermediate image carrier, and then the multicolor toner image is transferred all at once to a transfer material, the transfer efficiency changes depending on the thickness of each color toner. , a problem arises in that the color balance cannot be maintained well.

In view of the above problems, an object of the present invention is to detect the amount of toner transferred on an intermediate transfer material with a simple device configuration and with high accuracy,
The present invention provides a new transfer device that can control the transfer amount to be constant and obtain good images.

The present invention will be described in detail below using specific examples with reference to the drawings. FIG. 1 is an explanatory diagram of an example in which the transfer device of the present invention is applied to a color copying machine.

In FIG. 1, reference numeral 1 denotes an electrophotographic photosensitive drum having an insulating layer, a photoconductive layer, and a conductive substrate on its surface, and is rotatably supported by a shaft 2 and rotates in the direction of an arrow 3. An original placed on an original platen glass 4 in synchronization with the rotation of the drum 10 is illuminated by an illumination lamp 6 integrally formed with a first scanning mirror 5, and the reflected light is scanned by a second scanning mirror 7. The first scanning mirror 5 and the second scanning mirror 7 move at a speed ratio of l:%.

The reflected light image of the document passes through a lens 8 and a third mirror 9, is separated into colors by a color separation filter 10, and is imaged on the surface of the photosensitive drum 1 by an exposure section 11.

On the other hand, the photosensitive drum l is charged in advance by a lamp 13 and an alternating current band r in a device 14, and then charged by a primary charger 15, after which the original image is subjected to merit exposure in the exposure section 11. At the same time as this exposure, static electricity is removed or reversely charged by a secondary charger 16 that generates an alternating current or a corona of opposite polarity to the primary corona, and then the entire surface is further exposed using a full surface exposure lamp 17. As a result, an electrostatic latent image corresponding to the original image is formed on the drum 1.

The electrostatic latent image formed on the photosensitive drum 1 as described above is then visualized by a developing device 18 using toner having a polarity opposite to that of the primary charge. This developer 18 is yellow 187.
Magenta 187. Cyan 18. The developing device is composed of three developing devices, and each developing device designated in accordance with the color separation filter used for exposure works individually to obtain a toner image of the required color.

Next, the developed image formed on the photosensitive drum 1 is charged at the position of the pre-transfer charger 19 by a charge VL thread having a polarity opposite to that of AC or primary charging simultaneously with the uniform exposure of the lamp 20. The grid wire provided at the opening of this pre-transfer band m device 19 includes
A predetermined bias voltage is applied to each color, and the photosensitive drum 1
The upper side is charged to a predetermined voltage from approximately QV, for example.

The development on the photosensitive drum l is carried out at the transfer position by a first transfer corona charger 22 in a transfer drum 22 rotatably supported by a non-shaft 21, which will be described in detail later. As a result, the images are aligned and sequentially transferred onto the image supporting sheet 222 supported on the surface of the transfer drum 22, thereby forming a multicolor image.

After the transfer, the residual toner on the surface of the photosensitive drum 1 is cleaned by a cleaning device 12 comprising an elastic blade, and the photosensitive drum 1 proceeds to the next color-based toner image forming cycle.

On the other hand, @1 transfer belt weapon 22. The first color transferred by
The toner images of the second and third colors are placed on the image bearing sheet 22. At the same time, it is removed each time by AC chargers 22 and 224. The chargers 223 and 224 face each other, and the phases of the alternating current voltages applied to the respective discharge wires are different by 180° to enhance the static elimination effect.

In the above process, if the AC chargers 223 and 224 do not remove static electricity or if the static electricity removal is weak, charges with the opposite polarity to the transfer charge will accumulate on the toner image supporting surface of the image bearing sheet 22t, and as the number of transfers progresses, This will reduce the toner transfer rate.

FIG. 2 shows an image bearing sheet 22. a copy image area d (portion surrounded by a broken line) to be transferred to and a transmission density detection image area a, l) used for controlling the amount of toner transferred from the ζ photosensitive drum l to this image bearing sheet 222.

Detected image areas a, b, and c are each yellow.

It is configured to correspond to monochrome development of magenta and cyan.

The latent images on the photosensitive drum 1 corresponding to these detected image areas a, h, and C are banded at position i7 where the surface of the photosensitive drum 1 is uniform.
After being removed, the blank exposure lamps 16a provided in corresponding areas a, b, and c are blinked to form two zones in FIG. 1 at the positions of the vessels 16. That is, when forming a detection image area in the shape of FIG. 2, a light shielding plate is provided between the plurality of lamps 16a arranged in the direction of the axis of the photosensitive drum, and the number of lamps in the direction of the drum axis is adjusted according to the developing device to be used. Control blinking.

Latent image 1 on photosensitive drum l corresponding to each image area a, b, c
t-L 1t4 1st After development with yellow, magenta, and cyan color toners, the toner images are sequentially transferred to form toner images for each color. Here, the detected image area a.

b and c are drawn even if they are outside the copy image area d.

33 in Figure 1. ~33. l) Blooming image area a in Figure 2
.

It is a rung for a light source that irradiates images b and c, and is a rung for a light source that irradiates images b and c.
Three rollers are arranged in a row in the axial direction according to the color of the developing device. Opposing the lamp 33 of the cutter: 34. ~34M is the detection part rt area 2. b. C that detects the transmitted light that has passed through C (with a light receiving member such as Is or 813 C,
3. ~33. Three lamps are also arranged in the axial direction of the transfer drum 22 corresponding to each lamp. lamp 3
31 to 33, and a light receiver 34. ~34, when using a reflective type, a filter with a complementary color relationship to the toner color transferred to the detection image area j t beC is provided between the d1 light source and the light receiver, and the S/N at the time of detection is Easy to compare.

However, when the transmission method is used and the toner used is powder, as in the embodiment shown in Figure 1, the transmitted light is easily scattered, so it is difficult to obtain a sufficient S/N ratio even without using a complementary color filter. can. The light receiving member 34. - 343, in order to detect the amount of toner after transfer, when any of the image areas a, b, and c to be detected each time each color toner is transferred passes, a light source and a light receiving area corresponding to a predetermined detection image area are used. The amount of light transmitted through the toner is detected by operating the device.

The transfer amount detection signals of each color toner detected by the light source and light receiver are sequentially transmitted to the detection circuits 351 to 351 of FIG. 1. and control circuit 36. , through the first transfer charger 22. high-voltage power supply 37 and grid bias power supply 38 of the pre-transfer charger 19
control. Then, the amount of toner transferred to the document image following the toner transfer in the detected image area is controlled to an appropriate value pressure.

The light source 33I, the light receiving member 341. Detection circuit 35° and control circuit 36. One set is used to control the transfer amount of one color toner.

In carrying out the present invention, effects can be obtained by controlling at least any L power supplies without controlling all of the power supplies 37 and 38 mentioned above at the same time.

Control circuits 361 to 361 of the embodiment of FIG. has a built-in standard voltage generation circuit and comparison circuit, and a detection circuit 357. The output signal of the standard voltage generating circuit is compared with the output signal of the standard voltage generating circuit.

Then, the control circuit 36. ~8
For example, the first transfer charger 22 . High voltage power supply 3
7 to set an appropriate amount of toner transfer.

Note that the amount of toner transferred is limited within a certain range by the first transfer charger 22. The amount increases when the voltage applied to the grid or the voltage applied to the grid of the pre-transfer charger 19 is increased. In the first illustrated device, when the toner has negative polarity, the transfer charger 2
2. The applied voltage to +5.0KV to +8.0KV (7
) The voltage applied to the grid of the pre-transfer charger 19 (the voltage applied to the discharge charger 1 is -6.0 KV) is controlled in the range of 0 to -500V.

The above-mentioned transfer amount detection of each color toner is performed by blank exposure control to detect image areas a, b, and C on the photosensitive drum when copying is performed again after a certain period of rest. Corresponding latent images are formed, developed, and transferred, and sequence control is performed to form transferred images of three color toners in detection image areas a, b, and C of the transfer drum. Alternatively, the copying interval may be controlled at an arbitrary copy interval by the operator selecting a transfer amount detection switch.

As an example of forming the detection image area, as shown in FIGS. 3a and 3b, it is possible to form it outside the copy image area d, or even in the direction of the rotation axis of the image bearing sheet as shown in FIG. It may also be set in the circumferential direction of the sheet as shown in Figure 3.

On the other hand, the transfer paper 25 in the cassette 24 is fed into the machine by the paper feed roller 26, and the timing is taken by the register roller 27. At the transfer position, the transfer paper 25 is transferred onto the image bearing sheet 222 by the corona discharge action of the second transfer charger 28. The multicolor images formed are transferred onto the transfer paper 25 all at once. At this time, from the inside of the transfer drum 22, the toner image has the same polarity (i.e., II
2 transfer charger 28) or an AC charger 22. By performing corona discharge, even a thick layer of two or three colors of toner can be transferred to transfer paper extremely efficiently.

The reason for this is that the charger 22. The sheet 22. of the transfer drum 22 due to the corona discharge of the sheet 22. The electric charge on the back side of the sheet 22. is eliminated, and the binding force of the toner on the surface of the transfer drum is favorably reduced, or the same sheet 22. The purpose is to charge the back side of the sheet 226 with a charge having the same polarity as the toner image and repel the toner on the surface of the sheet 226, thereby assisting the efficiency of retransfer by the second transfer belt 28. It also serves as a counter electrode for drawing out the corona of the charger 2211IIi (transfer charger 28r), and increases the shadow emission tt of the charger 28 toward the toe image, thereby increasing the retransfer efficiency. Contributing.

Therefore, the toner in the lowest layer of the transfer drum 22 can be sufficiently transferred, and an image with good color clarity can be obtained.

Furthermore, the improved transfer rate facilitates cleaning of the surface of the image bearing sheet 227, which is a later step. Transfer paper 2
5, immediately after being transferred and charged by the transfer charger 28, the reverse side of the transfer paper 25 is separated and neutralized by the AC charger 29, and the transfer paper is separated from the transfer drum 22. The sheet is then transferred to a conveyor belt 30, guided to a heat roller fixing device 31 coated with silicone oil, pressurized and heated, and then discharged onto a tray 32.

On the other hand, a cleaning device 23 using a fur brush that can come in contact with and separate from the surface of the image bearing sheet 229 of the transfer drum contacts the surface of the image bearing sheet 229 of the sheet 229. The remaining toner is cleaned. A sheet 22. facing the cleaning device 23. A cleaning brush 226 is provided which comes into pressure contact with the back surface of the cleaning brush 226.

Kome brush 22. When the cleaning device 23 operates, it not only performs mechanical backup but also cleans the back surface of the image bearing sheet 2.

As mentioned above, the color electrophotographic apparatus shown in Figure ya1 is
The developed images carried on the surface of the photosensitive drum 1 are sequentially transferred onto the transfer drum 22, and the obtained multicolor images are transferred all at once onto the transfer paper 25.

In the illustrated embodiment, the transfer drum 22 of the transfer device has an image bearing sheet 22, such as an insulating resin film, as shown in a perspective view in FIG. and a support member 22 that supports the film at its edges. And this film 2
2. and the supporting member 22. It consists of an elastic member 22s (the dotted part in FIGS. 4 and 5) interposed between.

FIG. 5 shows an axial cross-sectional view of the transfer drum 22. As shown in FIG. The above-mentioned support member 22. Fi has both cylindrical frame parts on both sides and a connecting part 22a that connects and integrates these two frame parts. Note that image-bearing sheets) 22. If it is sufficiently thick and maintains a mechanically cylindrical shape, the above-mentioned connecting portion is unnecessary.

Plastic films such as polyester, polypropylene, and triacetate are used as the insulating film for the above-mentioned image-bearing sheet. Thickness is 25μ~300
μ, preferably around 100μ.

In addition, in order to prevent as much as possible transfer unevenness, toner scattering, and charge-up phenomena on the image bearing surface due to the effects of peeling discharge that tend to occur immediately after separation from the photosensitive drum during transfer, the surface resistance is from 1 x 1 O 8 Ω] A high resistance film 22. is made of a relatively low resistance resin of 1012Ω or a photoconductive resin such as PVK or ZnO. A better transferred image can be obtained by coating the image-bearing surface of Film 22. and support member 22. The elastic member 228 interposed between is made of, for example, a low hardness rubber with a JIS hardness of 40 or less (low hardness such as urethane rubber, ethylene/propylene rubber, chloroprene rubber, NBR, natural rubber, silicone rubber, etc.). Or rubber and plastic foams (foamed butyl rubber, foamed polyurethane, foamed polyethylene, foamed polystyrene).

Foamed vinyl chloride, etc.) are used. The thickness of the elastic member 228 is preferably in the range of 0.5 fins to 5 fins.

FIG. 6 shows a sectional view of a color copying machine which is a modification of the apparatus shown in FIG. In the illustrated apparatus, as shown in FIG. 7, yellow and magenta are detected in the detection image area e provided on the image bearing sheet 222.

Develop the toner and toner of each cyan color one on top of the other. Then, the amount of toner in this image area e is detected by the light source 4.3, which is a detection means, and the receiving member 44, and the amount of toner transferred onto the transfer material 25 is controlled.

The formation of the toner image on the detection image area e is substantially the same as in the case of FIG. By turning on the lamp 16a at a predetermined timing each time each color is developed, a latent image is formed on the photosensitive drum l, and each color toner that has developed this latent image is added to the detected image area e as three color toners. form an image.

In the apparatus shown in FIG. 6, the light receiving member 44 detects the amount of transmitted light when passing through the detection image area e, and detects the amount of toner after the three color toners have been transferred. The detection signal is sequentially transmitted to the detection circuit 45 in the figure. Through the control circuit 46, the second transfer sleeper 28 and the charger 22. High voltage power supplies 47 and 48. Charger activated before turning 22. . 49, which is the grid bias power supply of the circuit. Note that in carrying out the present invention, effects can be obtained even if at least one power source is controlled without controlling all of the power sources 47, 48, and 49 described above.

Of the electric circuits described above, the control circuit 46 includes a standard voltage generation circuit and a comparison circuit, and compares the output signal of the detection circuit 45 with the output signal of the standard voltage generation circuit. and,
Depending on the compared level difference, the arithmetic control circuit and memory circuit built in the control circuit 46 control the high voltage flow of the high voltage power supply 47 of the second transfer charger 28 at a predetermined timing, thereby achieving an appropriate amount of toner transfer. is adjusted so that it is transferred to the transfer material.

In addition, in the retransfer of toner, within a certain range of tFi, the second
Transfer charger 28. Charger 22. voltage applied to or charger 22. , increases as the voltage applied to the grid increases. In the second illustrated device, when the toner has negative polarity, the voltage applied to the second transfer charger 28 is +5.0 I
(V ~ +8. OKV) range, and the charger 22
．． The voltage applied to the grid is in the range of -5, OKV to -7,0 KV, and the voltage applied to the grid of the charger 22+o (the voltage applied to the discharge wire is -6, OKV) is Ov to -5.
Controlled within the range of 00v.

The above-mentioned toner transfer amount detection is performed by blank exposure control prior to exposure of the original image when a copy operation is performed after a pause for a certain period of time, and a latent image corresponding to the detected image area e is formed on the photosensitive drum and then developed.

Sequence control is performed to form a transferred image of three toner colors on the detected image area e of the transfer drum. Alternatively, the operator can control the copying interval at any desired copying interval by selecting the retransfer amount detection switch.

Further, the above retransfer amount detection and control may be performed in combination with the control of the first transfer charger 228 and the like shown in the first figure. In this case, in addition to the detected image area shown in FIG. 2, an image area corresponding to the detected image area e shown in FIG. 7 may be provided.

FIG. 8 is a sectional view of an apparatus in which the present invention is applied to a digital color image forming apparatus, in which an insulating drum 40 having an insulating layer and a conductive substrate on its surface is used instead of the photosensitive drum 1 in FIG.
is used. On this insulating drum 40, an electrostatic image corresponding to the above color separation is formed by a multi-stylus head 41. The residual toner on this insulated drum is cleaned by a cleaning device 12, and the residual charge is removed by a current discharger 42, and the drum is prepared for the next process.

As an example of the use of the device shown in FIG.
is driven by a control circuit (not shown) to drive the insulating drum 40.
form a latent image on the surface. In this figure, the same members as those shown in FIG. 1 have the same functions as in the apparatus shown in FIG. 1. □ According to the present invention, the transfer amount of each color toner formed on an image bearing member such as a photosensitive drum or an insulating drum to an intermediate transfer member such as an image bearing sheet is corrected, and this corrected toner image is used as the final image. Since the toner is transferred to the transfer material immediately, a square image with good color balance can be obtained even if the transfer efficiency fluctuates due to toner deterioration or environmental changes.

Of course, it can also be applied to an image forming apparatus using monochromatic toner, and in such a case, it is possible to always obtain an image with a stable density of 1 to 1. □

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a copying apparatus to which a transfer device according to the present invention is applied, FIGS. 2 and 3 a, and FIG. 3 are explanatory diagrams showing a detection image area, and FIG. 4 is a perspective view of a transfer drum. , FIG. 5 is a partial cross-sectional view of the transfer drum, FIG. 6 is a cross-sectional view showing another embodiment of the present invention, FIG. 7 is an explanatory view showing the detected image area of the device, and FIG. 1 is a sectional view showing an embodiment of the pond of the present invention; 0 is a drum and an insulating drum; 18 is a developing device; 22. 22. is a first transfer corona discharger; 33. is a painter carrier sheet which is an intermediate carrier; ~33. I′i light source, 341 to 343 indicates a light receiving portion +4.

Claims (1)

[Scope of Claims] (1) means for forming a latent image on an image carrier; means for transferring a latent image on the image carrier; and a means for forming a latent image on the image carrier; a means for detecting the amount of developer on the intermediate carrier; a means for transferring the developer on the intermediate carrier to another transfer material; and a detection result by the developer amount detection means. An image forming apparatus comprising: means for changing transfer efficiency based on; (2J) The image forming apparatus according to claim (1), wherein the means for changing the transfer efficiency changes the discharge amount of a corona discharger which is the transfer means. (3) The above-mentioned Claim (1) characterized in that the means for "changing the transfer efficiency" changes the amount of discharge of a corona discharger performed before transferring the developer from the image carrier to the intermediate image carrier. (4) The means for changing the transfer efficiency is a corona discharger that is opposed to a transfer corona discharger used when transferring the developer from the intermediate image carrier to the transfer material. An image forming apparatus according to claim 0).