JPH0338674A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent transfer efficiency from changing and to stably obtain a high-quality image by detecting a charge quantity applied to a transfer material by a charge applying means by the use of a detecting means and correcting the change of the transfer efficiency caused by the kind of the transfer material, environmental variation or consecutive copying. CONSTITUTION:A transfer material attracting means 50 is provided with a corona charger 51 for attraction which is installed inside a transfer drum 30D and gives the charge having a polarity opposite to a toner image on a photosensitive drum 1 to the back surface of a transfer material carrier sheet 34 and a conductive roller 52 which is installed outside the transfer drum 30D. A DC constant-current source 85 is disposed between the conductive roller 52 of a transfer device 30 in an image forming device and an earth and a voltage detecting means 86 is provided. Based on the detected charge quantity, a transfer current value, etc., to a transfer means is changed so that the change of the transfer efficiency caused by the kind of the transfer material, the environmental variation or the consecutive copying may be corrected.

Description

[Detailed Description of the Invention] 1. The present invention relates to an image forming apparatus such as an electrophotographic copying machine,
In particular, the present invention relates to improvements in transfer devices in color image forming apparatuses.

Conventionally, when copying images of multiple colors, a multiple transfer method is used that uses a transfer drum in which a high-resistance film (transfer material carrying sheet) is wrapped around a drum-shaped frame. The fed transfer material is gripped by a gripper 151 disposed on a part of the surface of a transfer drum 15013, as shown in FIG. 14, for example. This hammer gripper type transfer drum is disclosed in, for example, Japanese Patent Application Laid-open No. 150354/1983. In addition, there is also a method of electrostatically adsorbing the transfer material to the transfer material carrying sheet and conveying it by providing a means for applying an electric charge to the transfer material carrying sheet and the transfer material without using a gripper. It is disclosed in Japanese Patent No.-32079. The transfer device in the image forming apparatus shown in FIG. 15 is an example of this. Of course, a gripper system may also be provided with electrostatic adsorption means.

In FIG. 15, reference numeral 51 denotes an adsorption charger of the transfer device 30. The adsorption charger 51 is used to apply charges to the transfer material carrying sheet 34 from the inside, and the adsorption charger 51 and the adsorption charger 51 are used on the opposite side of the transfer material carrying sheet 34. Using the four electric rollers 52 facing each other,
The transfer material P is charged with a polarity opposite to that of the adsorption charger 51. The conductive roller 52 is grounded, and the adsorption charger 51
It is also used as a counter electrode. The transfer material P is electrostatically attracted to the transfer material carrying sheet 34 and conveyed to the transfer area, after which the toner image on the photosensitive drum I is transferred.

In order to obtain a color image, so-called multiple transfer is performed in which the transfer process is repeated, and the transfer material P is transferred to the transfer material carrying sheet 3.
As a pre-treatment for separation from 4, AC charge removal is performed using a pair of opposing weight-removal corona dischargers (pair chargers) 16 to neutralize the charge and weaken the electrostatic adsorption force. A push-up member 53 for separating the leading edge of the transfer material disposed on a part of the transfer drum frame from the transfer material carrying sheet 34 operates, and the separating claw 42 is moved between the transfer material P and the transfer material carrying sheet 34. The separation is completed by adding the

The transfer material P is conveyed to the fixing device 18, and after being fixed, the transfer material P is transferred to paper, and copying is completed.

However, in the above conventional example, the image quality deteriorates due to changes in the transfer efficiency due to changes in the environment and the type of transfer material, charge-up of the transfer material carrying sheet, etc., and continuous sheet copying is difficult. There is a drawback that charge-up of the transfer material-bearing sheet on the opposite side leads to a decrease in transfer efficiency and deterioration of image quality.

Although it is possible to use means for detecting changes in the environment or the seed angle of the transfer material, such a method has the drawback of increasing costs.

Therefore, an object of the present invention is to reduce the transfer efficiency by changing the transfer efficiency due to changes in the environment, the type of transfer material, or due to continuous copying.
An object of the present invention is to provide an image form IO&*i that can prevent deterioration of 1j quality and stably obtain high lI Sakiga images.

Therefore, the above object is achieved by an image forming apparatus according to the present invention. To summarize, the present invention provides an image forming apparatus that includes a transfer device that conveys a transfer material and brings it into contact with an image carrier carrying a toner image, and transfers the toner image on the image carrier to the transfer material. In the apparatus, a transfer material adsorption means for electrostatically adsorbing the transfer material to the transfer material carrier is provided at a contact position where the image carrier and the transfer material contact, and acts from the transfer material carrier side. a transfer means for transferring the toner image on the fi carrier onto the transfer material; and a transfer means provided on the downstream side of the transfer means with respect to the moving direction of the transfer material carrier, and separating the transfer material from the transfer material carrier. The transfer material adsorption means has a charge applying means that applies an electric charge to the transfer material carrier from inside the transfer material carrier, and the transfer material adsorbing member faces the transfer material carrier with the transfer material carrier therebetween. The charge applying means applies an electric charge to the transfer material at a position, and the detection means detects the amount of electric charge applied to the transfer material, and the amount of electric charge applied to the transfer material detected by the detection means is The image forming apparatus is characterized in that the transfer means is controlled by V+ based on a detection signal.

According to one aspect of the present invention, the transfer means includes a charge applying means for applying a charge to the transfer material carrier or a voltage applying means for applying a voltage, and the transfer means includes a charge applying means for applying a voltage to the transfer material carrier, and the transfer means is provided with a charge applying means for applying a voltage to the transfer material detected by the detecting means. The transfer device is configured to control the amount of charge applied to the transfer means or the amount of voltage applied to the transfer means based on a detection signal of the amount of charge.

According to another uninvented aspect, it has a continuous copy mode;
The ¥L load applied to the transfer material in the first row when the first sheet of the transfer material is adsorbed, and the amount of the ¥L load applied to the transfer material in the first row when the n-th sheet of the transfer material is adsorbed. by detecting the difference in the electric charge applied to the transfer material.

The transfer device is configured to be controlled based on the detected difference in the amount of charge.

According to the present invention, the transfer means detects the amount of charge applied by the charge application means to the transfer material by the detection means, and corrects for changes in the transfer efficiency due to the type of transfer material, environmental changes, or continuous copying. Since the flow rate etc. of the transfer '1 are changed, changes in transfer efficiency can be prevented and high-quality images can be stably produced.

1 Next, let's talk about the image forming apparatus according to the present invention in accordance with the drawings. will be explained in detail.

Embodiment 1 FIG. 1 shows an embodiment in which an image forming r& device according to the present invention is implemented in a color electrophotographic device.

In this embodiment, an image bearing member, that is, an electrophotographic photosensitive drum 1 that is pivoted by a white flower and rotates in the direction of the arrow, is rotated once. Ti
A light image 3 is formed in accordance with the image information by an exposure means such as a laser beam exposure device, etc.
, and a static ffi latent image is formed on the photosensitive drum l. The electrostatic latent image is visualized as a toner image on a photosensitive drum 1 by, for example, a mobile developing device 4.

The mobile developing device 214 includes four developing units 4M and 4C14 that specifically accommodate four color developers: magenta developer, cyan developer, yellow developer, and black developer.
Y, 4B, and a guide (not shown) that holds these four developing devices and is movable in the horizontal direction. The mobile developing device 4 transports a desired developing device to a developing position facing the outer peripheral surface of the photosensitive drum 1, and develops the electrostatic latent image on the photosensitive drum 1.

The visible image, that is, the toner image, on the photosensitive drum 1 is carried by a transfer device 130, which will be explained in detail later, and is conveyed in the direction of the arrow in the figure by the transfer device 2130, and then transferred to a transfer material P that is brought into contact with the photosensitive drum 1. transcribed into. Transfer material P
is transferred to the transfer device 21 in synchronization with the image by the registration roller 6a.
30.

After the residual toner on the surface of the photosensitive drum 1 is cleaned by a cleaning device 20, the photosensitive drum 1 is subjected to a color image process again.

An embodiment of the transfer device 30 used in the color electrophotographic apparatus of the present invention will be explained with reference to FIGS. 2 and 3. In this embodiment, the transfer device 30 is provided at both ends. The cylindrical rings 31, 32 and the connecting portion 33 connecting the rings 31, 32 are shown on the right. These cylindrical rings 31.3
2 and the connection 19833 constitute a transfer material carrier made of a dielectric film, that is, a drum frame on which the transfer material carrier sheet 34 is wound. The transfer device 1130 further includes a separating means 40. #The separating means 40 includes a separating claw supporter 41 provided along the axial direction of the transfer drum 30D, a plurality of peeling members fixed to the supporter 41, and three separating claws 42 in this embodiment. An outer pressing roller 42a for separation is integrally provided at the tip of the separation claw 42 for the purpose to be explained later. Moreover, at both ends of the support body 41,
As can be seen from FIGS. 2 and 4, abutment rollers 45.46 are provided via suitable support plates 43.44. The abutting rollers 45, 46 abut against the cylindrical ring 31, 32 of the copying drum 30D when a separation pawl operation clutch (not shown) operates, and the guide mechanism 35 formed on the ring 31, 32 .36, the tip of the one-separation claw 42 is rotated downward, that is, in the normal direction of the transfer drum 30D.

A notch 37 is formed in the connecting portion 33 so that the separating claw 42 can be easily inserted between the transfer material carrying sheet 34 and the transfer material P adsorbed and carried by the transfer material carrying sheet 34. As shown in FIGS. 1 and 5, the tip of the transfer material carrying sheet 34 has a cut 34a extending to the transfer material non-image area along the notch 37 of the connecting portion 33. 34 (shaded portion in FIG. 5) is fixed to the connecting portion 33 in such a manner that the curvature of the portion is locally increased.

Furthermore, to explain the transfer device 30, in this embodiment, the transfer device 30 transfers the transfer material P fed to the transfer device 30.
It has a transfer material adsorption means 50 for adsorbing and holding the transfer material on the transfer material carrying sheet 34.

The transfer material adsorption means 50, as shown in FIG.
Provided inside the transfer drum 30D and the photosensitive drum l
Transfer material carrying sheet 3 is charged with a polarity opposite to that of the toner image above.
4, and a conductive roller 52 provided on the outside of the transfer drum 30D. This conductive roller 52 is
By being grounded, it becomes a counter electrode of the adsorption corona charger 51 and gives the transfer material an electric charge of opposite polarity to the charge applied to the adsorption corona charger.
4 has the effect of statically adsorbing the transfer material P.

The transfer material P attracted by the transfer device 30 is transferred; 7'f
The back surface of the transfer material carrying sheet 34 is transported to the transfer area where the electric appliance 15 is arranged, and in order to transfer the first color toner image, for example, magenta toner image on the photosensitive drum 1, to the first transfer material P. A transfer corona charger 15 is used to apply a charge having a polarity opposite to that of the toner. Subsequently, the same latent image is created again on the photosensitive drum l and developed with the first color toner, and the toner image of the m1 color is similarly transferred to the second transfer material.

By the time the first transfer material comes to the position of the conductive roller 52 for the second time, the conductive roller 52 is released and moved to a position that does not disturb the toner image transferred onto the transfer material P, for example, from the transfer material carrying sheet 34. It is separated outward by more than 2 mm.

Next, a second image is formed on the photosensitive drum 1 in synchronization with the first transfer material to which the first color toner image is transferred.
The toner image of the color is transferred onto the first transfer material P using the transfer corona charger 15, and the toner image of the second color is also transferred to the second transfer material to which the toner image of the first color has been transferred. is transcribed. Thereafter, toner images of four colors are transferred to each of the two transfer materials P in the same manner.

According to the present invention, the transfer current value is determined as follows,
The size transfer frt and Mt are transferred (tF and supplied to the electric appliance 15).

An example of determining the transfer current value is shown below.

Fig. 6 shows the cases of plain paper and OHP, which are passed through the adsorption corona charger 51? The relationship between the lt current value (adsorption charging current value) and the current value flowing into the transfer material P from the conductive roller 52 (adsorption inflow current value) is shown. Solid line is plain paper, broken line is OH
This is the case of P. This shows that when the attraction charging current value is constant, the attraction inflow current value changes depending on the type of transfer material.

FIG. 7 is a graph showing an example of the relationship between the transfer current value and the density (reflection density) of the toner image transferred onto the transfer material P when a toner image of constant rotation is formed on the photosensitive drum L. be. From this, depending on the type of transfer material, the area with high density, that is, the area with an appropriate transfer current value where transfer efficiency is high (the area indicated by the arrow in Figure 7).When the solid line is plain paper, the broken line is O
It can be seen that in the case of HP) is different.

Therefore, for example, the adsorption charging current value is 200. In case A, the current detecting means 80 detects the adsorption inflow 'lrL flow f', the detected value is taken into the CPU 100, and the CPU
U100 causes the transfer current value to be switched via the constant current source 90 for transfer at a point where the suction R inflow 711 current value is 6.5 A as shown in Table 1, for example.

Referring to Table 1 and FIG. 1, the transfer device 30 includes a pair of sheets facing each other with a transfer material carrying sheet 34 in between, in order to weaken the adsorption force of the transfer material to the transfer material carrying sheet after the transfer process is completed. A of
A C corona discharger 16 is provided to eliminate static electricity from the transfer material P and the transfer material carrying sheet 34.

When the transfer is completed as described above, the first transfer material P
As can be seen from FIGS. 1 and 4, the abutting rollers 45 and 46 of the separating means 40 are actuated by a separation pawl operation clutch (not shown) to separate the transfer material from the transfer material carrying sheet 34. Cylindrical ring 31.32 of drum 30D
and is guided by a guide groove 35.36 formed in said ring 31.32. As a result, the separation claw 42
The tip is rotated downward, that is, in the normal direction of the transfer drum 300 and toward the transfer material carrying sheet 34, and the one-separation claw 42
A separating outer pressing roller 42 a that is driven integrally with the transfer material carrying sheet 34 is pressed against the transfer material carrying sheet 34 . IJ! The outer separation pressing roller 42a is a notch in the connecting portion 33! ! 37, and at a place where the curvature of the transfer material carrying sheet 34 is locally changed, the tip of the transfer material and the transfer material carrying sheet 34
A separation claw 42 is inserted between the two and the transfer material P is separated from the transfer material carrying sheet 34.

Incidentally, when the transfer material P is separated, it is preferable to perform AC corona discharge using the corona discharger 54 in order to prevent image disturbance due to peeling discharge that occurs when the transfer material P and the transfer material carrying sheet 34 are separated.

After the transfer and separation steps are completed, the transfer material P is conveyed to the fixing device 18, where heat is applied to mix and fix the toner colors, and the sheet is ejected to complete image formation.

Example 2 FIG. 8 shows an example of the configuration of the image forming apparatus in this embodiment.

As shown in FIG. 8, in this embodiment, a DC constant-11 current 1t85 is disposed between the conductive roller 52 of the transfer device 30 in the image forming apparatus and the ground, and a voltage detection means 86 is provided. In FIG. 8, the same reference numerals as in FIG. 1 indicate the same members.

Current flowing through the adsorption corona charger (ti (adsorption charge t
i, value) is 200 A, and the environmental change when the current value flowing into the transfer material P from the conductive roller 52 is 10←A,
In particular, the relationship between the voltage detected by the voltage detection means 86 and the change in relative humidity is shown in FIG. It can be seen that as the relative humidity becomes lower than this, it becomes difficult for the adsorption-It inflow current to flow.

Further, FIG. 10 shows the transfer current value when a certain amount of toner image is formed on the photosensitive drum 1 and the density (reflection density) of the toner image transferred onto the transfer material P at a relative humidity of 15% and 50%. %
, 80% (dashed line is 80%, solid line is 50%)
, - dotted chain line indicates the case of 15%), it can be seen from this that the appropriate range of the transfer current value changes depending on the relative humidity. The appropriate ranges for relative humidity of 80%, 50%, and 15% are indicated by dashed lines, solid lines, and dashed-dotted arrows.

Therefore, depending on the value detected by the voltage detection means 86, for example, as shown in Table 2, less than 1.4 KV (area A), 1.4 kV or more2, less than OKV (area B), 2.
In each case of OKV or more (region C), the CPU 100 switches the transfer current value to the transfer charger 15 via the transfer constant current power source 90.

Table 2 Example 3 In this embodiment, a case of continuous copying will be explained.

Although the configuration of Example 2 is also possible in this embodiment/example, the configuration is the same as that of Example 1, that is, the current detection means 80 is provided between the conductive roller 52 and the ground.

A pair of static elimination corona dischargers 1 shown in Fig. 1 during continuous copying
If the static elimination ability of the transfer material 6 is low, the transfer material carrying sheet 34 (see FIG. 2) will be charged up. This tendency is remarkable in low humidity environments.

This tendency is noticeable in low humidity environments.

In FIG. 11, for example, at a relative humidity of 15%, a discharger (internal static elimination W) 16 placed inside the transfer material carrying sheet 34 has a
AC? A DC differential current is superimposed on the tt pressure Vp p = 12.0 KV so that the DC differential current becomes -100, A, and the discharger (external negative electric device) 16 disposed outside the transfer material carrying sheet 34 is The phase of the AC voltage applied to Nairiku Electric Appliance 16 is shifted by π to set Vpp=10. The relationship between the number of continuous copies and the adsorption inflow type fi and clay measured by the 1rL flow detection means 80 when OKV is applied is shown.

Further, FIG. 12 shows the change in density when a certain amount of toner image is formed on the photoreceptor and the transfer current value is fixed at, for example, 150 gA.

From this, depending on the number of copies during continuous copying,
The It flow value changes and the concentration decreases.

Therefore, during continuous copying, for example, as shown in FIG. 13, the transfer current is changed depending on the difference between the value of the suction inflow current flowing through the transfer material and the value of the suction inflow current for the first sheet. Here, the solid line is the transfer current for the first color, the broken line is the transfer current for the second color,
- The dashed-dot line shows the transfer current of the third color, and the dashed-two dotted line shows the transfer current of the fourth color.

After the separation and fixing steps are completed, the paper is ejected, the input number of copies are repeated, and then the copying ends.

As described above, in the image forming apparatus of the present invention, the developing device is provided with a detection means for detecting the amount of electric charge applied by the electric charge applying means to the transfer material, and the detected electric charge is Depending on the amount
In order to compensate for changes in transfer efficiency due to changes in the type of transfer material, environmental changes, or continuous copying, the amount of transfer to the transfer means is changed, preventing changes in transfer efficiency and achieving high image quality. Images can be stably obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an image forming apparatus of the present invention. FIG. 2 is a perspective view showing essential parts of a transfer device included in the image forming apparatus of FIG. 1. FIG. 3 is a perspective view showing a guide frame in the transfer device of FIG. 2. FIG. FIG. 4 is a side view of the transfer device of FIG. 2. FIG. 5 is a perspective view showing a sheet portion of the transfer material supporting sheet of the transfer device shown in FIG. 2 at the connecting portion of the guide frame. FIG. 6 is a graph showing an example of the relationship between the attraction charging current value and the attraction inflow current value in the transfer device of FIG. FIG. 7 is a graph showing the relationship between the transfer current value and the density of the transferred toner image in the transfer device of FIG. FIG. 8 is a schematic diagram showing another embodiment of the image forming apparatus of the present invention. FIG. 9 is a graph showing the relationship between the relative humidity and the voltage applied to the adsorption conductive roller when the adsorption current value is constant in the transfer device included in the image forming apparatus shown in FIG. FIG. 10 is a graph showing the relationship between the transfer current value and the density of the transferred toner image in the same transfer device. FIG. 11 is a graph showing the relationship between the number of copies and the suction inflow current value during continuous copying in a transfer device provided in still another embodiment of the image forming apparatus of the present invention. Figure 12 shows iJ! in the same transfer device. , is a graph showing the relationship between the number of copies and the density of a transferred toner image during continuous copying. FIG. 13 is a graph showing the relationship between the suction inflow current value and the transfer current value during continuous copying in the same transfer device. FIG. 14 is a perspective view showing a transfer drum in a transfer device included in a conventional image forming apparatus. FIG. 15 is a schematic configuration diagram showing another conventional image forming apparatus. l: Photosensitive drum 4: Developing device 15: Transfer charger 16 + static elimination discharger 30: Transfer device 51: Adsorption? rF'e device 52: Conductive port for attraction 80: Current detection means 90: Constant current power source for transfer 00: CPU Two Figure 4 Figure 5 Figure 6 Adsorption charging current value Figure 7 (μA) Transfer current value (1st color) Fig. 8 50 Relative humidity 00 (%) L+-, -@Sick body (approximately exceeding the candle) 0 Fig. 11 Continuous" [-7 niku○ Fig. 12 0 Number of continuous copies 00 (sheets) ) Fig. 13 Adsorption inflow current difference value Fig. 14 Fig. 15

Claims (1)

[Scope of Claims] 1) An image comprising a transfer device that conveys a transfer material and brings it into contact with an image carrier carrying a toner image, and transfers the toner image on the image carrier to the transfer material. In the forming apparatus, a transfer material adsorption means for electrostatically adsorbing the transfer material to the transfer material carrier, and a transfer material adsorption means provided at a contact position where the image carrier and the transfer material contact each other, and actuated from the transfer material carrier side. a transfer means for transferring the toner image on the image carrier to the transfer material; and a transfer means provided on the downstream side of the transfer means with respect to the moving direction of the transfer material carrier, for transferring the transfer material from the transfer material carrier. and a transfer material separating means for separating the transfer material, the transfer material adsorption means having a charge applying means for applying an electric charge to the transfer material carrier from inside the transfer material carrier, and an opposing member with the transfer material carrier sandwiched therebetween. an electric charge applying means for applying an electric charge to the transfer material at a position where the transfer material is applied, and a detection means for detecting an amount of electric charge applied to the transfer material, the amount of electric charge applied to the transfer material detected by the detection means; An image forming apparatus characterized in that the image forming apparatus is configured to control the transfer means based on a detection signal. 2) The transfer means has a charge applying means for applying an electric charge to the transfer material carrier or a voltage applying means for applying a voltage, and based on a detection signal of the amount of charge applied to the transfer material detected by the detecting means. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is configured to control an amount of charge applied to the transfer means or an amount of voltage applied to the transfer means. 3) It has a continuous copying mode, and the amount of charge applied to the first transfer material when adsorbing the first transfer material, and the amount of charge applied to the n-th transfer material of the transfer material. During adsorption, the nth
2. The image forming apparatus according to claim 1, wherein the image forming apparatus is configured to detect a difference in the amount of charge applied to the second transfer material, and to control the transfer means based on the detected difference in the amount of charge.