JPH1026865A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color image forming device capable of forming a clear image regardless of using period and also making the exchange cycle of the transfer belt of the intermediate transfer body longer than heretofore by providing a resistance value measuring means measuring the specific surface resistance value or the specific volume resistance value of the belt of the intermediate transfer body so as to change the transfer condition of the intermediate transfer body in accordance with the measured value. SOLUTION: This image forming device is provided with an image carrier 1 forming a toner image, the intermediate transfer body 2 brought into contact with the carrier 1 and operating, an intermediate transfer means 3 transferring the toner image formed on the carrier 1 to the body 2, the resistance value measuring means 5 measuring the specific surface resistance value or the specified volume resistance value of the belt part 4 of the body 2, and a transfer condition changing means 6 changing the transfer condition of the means 3 in accordance with the measured value by the means 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic copying machine,
The present invention relates to a color image forming apparatus such as a laser printer, and more particularly to a color image forming apparatus that transfers a toner image on a photosensitive member onto a transfer material by using an intermediate transfer member including a transfer belt.

[0002]

2. Description of the Related Art When a toner image obtained by visualizing an electrostatic latent image formed on a photoreceptor is transferred onto a transfer material, the toner image is first transferred onto an intermediate transfer member such as a transfer belt. An image forming system in which the toner image is collectively transferred onto a transfer material is mainly used for a color image forming apparatus having a plurality of developing devices. In a color image forming apparatus equipped with a mechanism that transfers a toner image on a photoreceptor to a transfer material using an intermediate transfer body consisting of a transfer belt, the life of the transfer belt is difficult to determine based on its appearance and copy samples. Set the time to replace the transfer belt temporally from the evaluation of reliability and image formation at the time of design, or set the time to replace the transfer belt from the number of copies used for image formation, and maintain it as a regular replacement part We change at time.

[0003]

However, in the above-mentioned prior art, the transfer belt of the intermediate transfer body is replaced as a regular replacement part during maintenance, so the transfer belt is replaced long before the belt reaches its original durability limit. In many cases, the number of times of replacement increases, which causes an increase in industrial waste and an increase in downtime of the apparatus due to maintenance or the like. Therefore, the present invention provides a specific surface resistance value of the belt of the intermediate transfer body, or a resistance value measuring unit for measuring a specific volume resistance value, by changing the transfer conditions of the intermediate transfer unit according to the measured value, It is an object of the present invention to provide a color image forming apparatus in which the life of a transfer belt of an intermediate transfer member is extended, and an increase in industrial waste and an increase in apparatus downtime due to maintenance or the like are prevented.

[0004]

In order to achieve the above object,
According to the first aspect of the present invention, the toner image formed on the image carrier is transferred onto an intermediate transfer member, and then the toner image on the intermediate transfer member is transferred onto a transfer material. In a color image forming apparatus having a function of fixing to a transfer material, an image carrier for forming a toner image, an intermediate transfer body operating in contact with the image carrier, and a toner image formed on the image carrier Transfer means for transferring an image to the intermediate transfer body, a specific surface resistance value of a belt portion constituting the intermediate transfer body, or a resistance value measuring means for measuring a specific volume resistance value, and measurement by the resistance value measuring means. Transfer condition changing means for changing the transfer condition of the intermediate transfer means according to the set value. The invention of Claim 2 is Claim 1
In the color image forming apparatus described above, when the intermediate transfer body is removed from the main body of the color image forming apparatus, the resistance value measuring unit is fixed to a part of the intermediate transfer body so that the resistance value measuring unit is removed together. It is characterized by having. According to a third aspect of the present invention, in the color image forming apparatus according to the first aspect, when the intermediate transfer body is removed from the color image forming apparatus main body, the resistance value measuring unit remains on the color image forming apparatus main body. The resistance value measuring means is fixed to a part of the color image forming apparatus main body.

[0005]

According to the first aspect of the present invention, the specific surface resistance value of the belt constituting the intermediate transfer member by the resistance value measuring means, or
The specific volume resistance value is measured, and the transfer condition of the intermediate transfer unit is controlled to be changed to a predetermined appropriate condition value in accordance with the value measured by the transfer condition changing unit. The appropriate transfer condition value corrects the deterioration phenomenon of the belt portion of the intermediate transfer member, and is selected so as to be an optimum image forming condition value. A color image forming apparatus that forms a beautiful image for a long period can be provided. According to the invention of claim 2, in addition to the invention of the color image forming apparatus of claim 1, when the intermediate transfer body is removed from the color image forming apparatus main body, the resistance value measuring means can be removed together. During the maintenance of the intermediate transfer member, the performance of the resistance value measuring means can be confirmed together. According to a third aspect of the present invention, in addition to the color image forming apparatus of the first aspect, when the intermediate transfer body is detached from the color image forming apparatus main body, the resistance value measuring means remains in the color image forming apparatus main body. Therefore, there is no possibility that the resistance value measuring means is damaged or hit at some places.

[0006]

Next, an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of an image forming unit of a color electrophotographic copying machine (hereinafter, referred to as a copying machine). Since the detailed configuration and functions of the color copying machine are known, the description will focus on the portions relating to the present invention. Image carrier 1 on which an electrostatic latent image is formed by an exposure device (not shown)
Is contacted with the developing sleeve 7a of the developing device 7 which is timed when rotating in the direction of the arrow (A),
Form a visible image of a single color toner. A belt (transfer belt) 4 as the intermediate transfer body 2 includes various rollers (4a,
4b, 4c, 4d, 4e) and the like, and is rotated in the direction of the arrow (c) by the belt charging charger 3, which is the intermediate transfer means 3, at the same timing as the movement of the toner image on the image carrier 1. The surface is charged. Thereafter, the belt portion 4 to which the electric charge is added and the image carrier 1 with the visualization of the color come into contact with each other and rotate, so that a single-color toner image is transferred from the image carrier 1 onto the belt 4 of the intermediate transfer body 2. Transfer.

Next, a visible image of another color toner is formed on the image carrier 1 by the developing sleeve 7b of the developing device 7. Through the same process as above, the remaining developing sleeve (7
c, 7d) The visualization of the toner is transferred from the image carrier 1 onto the belt 4 of the intermediate transfer member 2. When the overlapping process of the toner images of the respective colors formed from the four color developing sleeves (7a, 7b, 7c, 7d) is completed,
A color image is formed on the belt 4 of the intermediate transfer body 2. On the other hand, the transfer paper P fed from the direction of the arrow (d) is
When the intermediate transfer member 2 comes into contact with the belt 4, a charge is applied by the charging charger 8, and the color toner image on the belt 4 is transferred to the transfer paper P. The color toner image transferred to the transfer paper P is fixed by a fixing device in a next step (not shown). Four color developing sleeves (7a, 7
b, 7c, 7d) generally include black (Blac).
k), cyan, magenta
a) and four colors of yellow toner are used.

The image forming section shown in FIG. 1 is provided with a resistance value measuring means 5 for measuring a specific surface resistance value or a specific volume resistance value of the belt 4 of the intermediate transfer member 2. 5 is passed to a CPU section 6b as a transfer condition changing means 6, and the belt charging charger 3
CPU is set so that the value becomes a predetermined value according to the measured value.
The unit 6b sends a command to the transfer condition setting unit 6a, and the transfer condition setting unit 6a outputs a command to the charger power supply 3A to operate the belt charging charger 3 under the changed transfer condition. In FIG. 1, the resistance value measuring means 5 mainly includes a value detector 5a and a detected value amplifying section 5c, but the detected value amplifying section 5c is included in the CPU section 6b of the transfer condition changing means 6. Is also possible. Further, a ROM and a RAM necessary for the operation of the microprocessor are provided in the CPU 6b.
A change value of a transfer condition according to a resistance value of the belt 4 of the intermediate transfer body 2 described later is previously stored in a part of the ROM.

FIG. 2 shows that the resistance detector 5a is
2 shows an arrangement state when the resistance value of the belt 4 is measured. On the image forming surface 11 side with the belt 4 interposed therebetween, a resistance value detector 5 is provided.
a, a metal plate 5b (fixed) such as a stainless steel plate is sandwiched from the opposite side. Further, the resistance value detector 5a is fixed to the support bracket 13, and one end of the support bracket 13 is connected to the eccentric cam 1 as shown in the figure.
It touches 2. The eccentric cam 12 is a stepping motor 1
5 is connected to the shaft 14. Further, a pressing force is applied to the support bracket 13 by a force of a spring or the like (not shown) so as to contact the lower belt 4. Accordingly, the rotation of the stepping motor 15 causes the eccentric cam 12 to move the support bracket 13 up and down, and further moves the resistance value detector 5 a away from and away from the belt 4. During image formation, the resistance detector 5a is separated from the belt 4 so as not to be a load of rotation of the belt 4, and the resistance detector 5 is attached to the surface of the belt 4 only during resistance measurement.
a is pressed with a predetermined pressure. In addition, the resistance value detector 5a
Can measure an arbitrary position of the belt 4 during non-image formation. For example, the belt 4 is repeatedly stopped and stopped by a predetermined amount, and a resistance value and a life of the belt 4 are determined from measured values at a plurality of points. Has become.

FIG. 3 is a diagram showing a change state of the resistance value of the belt 4 of the intermediate transfer body 2 with respect to the number of sheets of the transfer paper. Thus, the color image forming apparatus of the intermediate transfer system is
The material of the belt 4 of the intermediate transfer body 2 is a medium resistance (1 × 10 ⁷ to
In the case of a 1 × 10 ¹¹ ) material, its resistance decreases as the image forming operation is performed, due to wear due to friction and deterioration with time due to high pressure. When the resistance value of the belt 4 decreases, the potential of the transfer charge decreases, and the transfer of the toner image from the image carrier 1 onto the belt 4 of the intermediate transfer member 2 is not sufficiently performed. Greatly affects image quality. As a method of compensating for the above-described deterioration in image quality, there is a method of changing the set value of the belt charging charger 3 to change the potential of the transfer charge.
In general, it is common to change the power of the laser of the exposure apparatus during a maintenance cycle, since the state of the decrease in the resistance value cannot be easily grasped from the appearance. Therefore, in the present invention, the resistance value of the belt 4 is directly measured to give the optimum potential of the transfer charge, and the conditions for always forming the optimum image are provided. As a detector for measuring the resistance value of the belt 4, there is, for example, High Leicester manufactured by Mitsubishi Chemical Corporation.

FIG. 4 shows an embodiment of the present invention shown in FIG.
FIG. 9 is a diagram illustrating a relationship between an appropriate transfer current and the number of transfer sheets passed. As can be seen from FIG. 4, during the initial period of paper passing (approximately 10,000 sheets in the figure), the appropriate transfer current value largely changes, and then passes through a slowly changing area (about 10,000 to 30,000 sheets) and almost changes. It moves to the area without (about 30,000 sheets or more). Therefore, since the appropriate transfer current value is not linear with respect to the number of sheets passed, the correction amount is greatly different between the first stage correspondence at the initial stage of sheet passing and the second stage at the advanced sheet passing. If the transfer current value is corrected according to the above determination, the state where the correction is excessive or the correction is too small is likely to occur. Therefore, belt 4
It is desirable that the transfer current value be corrected in real time by directly measuring the resistance value. FIG. 5 and FIG. 6 show a case where the resistance value detector 5a is fixed to a part of the intermediate transfer member 2 and the intermediate transfer member 2 is removed from the color image forming apparatus main body. An example is shown in which the resistance value detector 5a is also removed when removing. FIG. 5 shows a state in which the belt 4 is attached to the framework 16 of the intermediate transfer body 2, and the resistance value detector 5 a is fixed to the framework 16 of the intermediate transfer body 2. FIG. 6 is a diagram showing a state in which the belt 4 and the resistance value detector 5a are attached to the framework 16 of the intermediate transfer body 2. According to this embodiment, the state of the resistance value measuring means can be checked when the belt of the intermediate transfer member is replaced, and if necessary, the resistance value measuring means can be easily cleaned, adjusted, or replaced. Further, although not shown, the invention of claim 3 has the resistance value detector 5a attached to the color image forming apparatus main body,
When removing the intermediate transfer body from the color image forming apparatus main body, it is also possible to cause only the resistance value detector 5a to remain in the color image forming apparatus main body. According to this embodiment, it is possible to prevent the resistance value measuring means from being hindered from being damaged at the time of belt replacement, or being prevented from being hit at some places.

[0012]

As described above, according to the first aspect of the present invention,
By selecting a change value of the transfer condition (optimum value according to the resistance value) according to the resistance value of the intermediate transfer body measured by the resistance value measuring means, and performing the transfer under the transfer condition changed by the transfer condition changing means, Since the deterioration phenomenon of the belt portion of the intermediate transfer body has been corrected and the replacement time of the transfer belt has been extended,
It has become possible to provide a color image forming apparatus capable of always forming a beautiful image by preventing an increase in industrial waste and an increase in apparatus downtime due to maintenance and the like. According to the invention of claim 2, in addition to the invention of the color image forming apparatus of claim 1, the intermediate transfer body and the resistance value measuring means can be detached together from the color image forming apparatus main body. Therefore, the state of the resistance value measuring means can be checked when the belt of the intermediate transfer member is replaced, and if necessary, cleaning, adjustment, or replacement of the resistance value measuring means can be easily performed. According to the third aspect of the present invention, in addition to the color image forming apparatus of the first aspect, even if the intermediate transfer member is detached from the color image forming apparatus main body, the resistance value measuring means is provided in the color image forming apparatus main body. As a result, it is possible to prevent the resistance value measuring means from getting in the way when the belt is replaced, and to prevent the resistance value measuring means from being damaged or hitting at some place.

[Brief description of the drawings]

FIG. 1 is a side view of a main part of a color image forming apparatus showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating a state in which a resistance value detector is attached to a belt of an intermediate transfer member.

FIG. 3 is an explanatory diagram illustrating a change in a resistance value of a belt of an intermediate transfer member with respect to the number of passed sheets.

FIG. 4 is an explanatory diagram showing a change in an appropriate transfer current with respect to the number of passed sheets.

FIG. 5 is an explanatory diagram illustrating a state before the belt of the intermediate transfer member and the resistance value detector are attached.

FIG. 6 is an explanatory diagram illustrating a state where a belt of an intermediate transfer member and a resistance value detector are attached.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Image carrier, 2 intermediate transfer body, 3 intermediate transfer means, or belt charger, 4 belts, 5 resistance value measurement means, 5a resistance value detector, 5b metal plate, 5c detection value amplification part, 6 transfer conditions Change means, 6a
Transfer condition setting unit, 6b CPU, 7 developing unit, 7a
Developing sleeve, 8 charger

Claims (3)

[Claims] 1. A method according to claim 1, wherein the toner image formed on the image carrier is transferred onto an intermediate transfer member, and then the toner image on the intermediate transfer member is transferred onto a transfer material. A color image forming apparatus having a function of fixing the toner image onto the image carrier, an intermediate transfer member operating in contact with the image carrier, and a toner image formed on the image carrier. An intermediate transfer unit for transferring to the intermediate transfer body, a specific surface resistance value of a belt part constituting the intermediate transfer body, or a resistance value measuring unit for measuring a specific volume resistance value; and A transfer condition changing means for changing a transfer condition of the intermediate transfer means in accordance with a resistance value. 2. The color image forming apparatus according to claim 1, wherein when the intermediate transfer body is removed from the main body of the color image forming apparatus, the resistance value measuring means is detached together with the intermediate value transfer means. A color image forming apparatus fixed to a part of a transfer body. 3. The color image forming apparatus according to claim 1, wherein when the intermediate transfer body is removed from the color image forming apparatus main body, the resistance value measuring unit remains on the color image forming apparatus main body side. A color image forming apparatus, wherein the value measuring means is fixed to a part of the color image forming apparatus main body.