JPH05142906A - Copying machine - Google Patents

Abstract

PURPOSE:To enhance the positional accuracy of a toner concn. sensor relative to a teansfer belt. CONSTITUTION:The transfer belt 65 is mounted on a front plate 90 and a rear plate 91. The rear plate 91 is fixed to a copying machine main body and the front plate 90 is fixed via a positioning plate 94 to the copying machine main body. A 2nd transfer device 72 is mounted on a supporting plate 100. The rear wall 101 thereof is supported by the rear plate 91 and the front wall 104 is supported by the front plate 90. The toner concn. sensor 81 is mounted on the front plate 90 and is positioned relative to the transfer belt 65.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mounting structure of a sensor for detecting a change in image density or a change in color balance due to deterioration of a developer on the surface of an intermediate transfer member in a color copying machine or the like.

[0002]

2. Description of the Related Art As shown in FIG. 5, a color copying machine includes a photoreceptor 4 as a belt-shaped primary side recording medium wound around a pair of driving rollers 2 and 3 inside a copying machine body 1. The photoconductor 4 is provided with a charge eliminating device 5, a charging device 6, a blank lamp 7, developing devices 8, 9, 10, 11 and a primary side cleaning device 12, and the developing devices 8, 9, 1 are provided.
0, 11 are yellow, magenta, cyan,
It is filled with black toner.

A document table 13 for placing a document is provided on the upper part of the copying machine main body 1. Below the document table 13, a light source 14, mirrors 15, 16, 17, 18, 19 and a color separation filter are provided. An optical system 22 including a lens 20 and a lens 21 is provided to scan a document placed on the document table 13, and reflected light is guided to the photoconductor 4 between the charging device 6 and the blank lamp 7. Form an electrostatic latent image. Further, the color separation filter 20 is switched so that only the respective colors of blue, green and red are transmitted.

Then, an intermediate transfer for overlapping the toner images of a plurality of colors by being wound around three rollers 23, 24 and 25 on the one driving roller 2 side of the photosensitive member 4 and contacting the photosensitive member 4. A transfer belt 26 as a body is arranged. Around the transfer belt 26, a transfer charging device 27, a transfer device 28, a secondary side cleaning device 29, and a secondary side static eliminator 30 are provided.

In the figure, 31 is a paper cassette, 32 is a paper feed roller, 33 is a suction belt, and 34 is a fixing device.

In the case of a color copying machine, deterioration of the yellow, magenta, and cyan developers due to life causes a change in copy density and a deterioration in color balance, which significantly impairs copy image quality.

Therefore, the toner density on the transfer belt is detected by a toner density sensor (gamma sensor) 35, and a feedback back is made so as to correct the surface potential of the photosensitive member according to a certain standard.

At present, the gamma sensor 35 is the transfer belt 2
It is attached near the surface so as to face 6. Also, as a sensor unit for the main body 1 of the copying machine,
It can be detached by sliding it to the front side.

This is to prevent the transfer belt 26 and the photosensitive member 4 from being detached and to clean the sensor.

Here, the sensor unit comprises a gamma sensor 35 and a support 36 for supporting the gamma sensor 35. The sensor unit is positioned by positioning holes in the rear frame 37 of the copying machine body on the rear side as shown in FIG. 37a, the front side is determined by the positioning hole 39a of the front plate 39 for positioning the front side of the process unit including the photoconductor 4 and the transfer belt 26 on the front frame 38 of the main body.

[0011]

In the above-mentioned conventional positioning structure, the positional relationship between the sensor 35 and the transfer belt 26, that is, the sensor unit and the process unit is such that the rear side is through the rear frame 37 and the front side is the front plate 39. Since the sensor 35 and the transfer belt 26 are positioned independently of each other, there is a drawback that accuracy is difficult to obtain.

The connector 40 of the sensor unit shown in FIG. 7 is connected to the main body of the copying machine through the connector 41 of the front plate 39, and the connector is pulled out each time the front plate 39 is removed, such as when the photoconductor or transfer belt is replaced. It is necessary, time-consuming, and troublesome.

Moreover, since the conductors and connectors pass through the front side of the main body, the appearance is impaired.

In view of the above, an object of the present invention is to provide a copying machine in which the position accuracy of the toner density sensor for automatic image density control and the intermediate transfer member is improved.

[0015]

As shown in FIG. 1, an intermediate transfer member 65 to which a toner image on a photoconductor 50 is transferred is attached to a copying machine main body 50, and an intermediate transfer member 65 is mounted. Transfer device 7 for transferring the toner image from the toner onto the sheet
2 is positioned with respect to the intermediate transfer body 65 and is detachably attached to the copying machine main body 50, and toner for detecting a change in image density from the toner density on the intermediate transfer body 65 for automatically controlling the image density. The density sensor 81 is attached to the second transfer device 72 and positioned with respect to the intermediate transfer body 65.

Then, the connector 10 of the second transfer device 72
The toner concentration sensor 81 is connected to the conductor 8, and the connector 108 is detachably attached to the connector 110 of the copying machine main body 50.

[0017]

In the means for solving the above problems, the second transfer device 72
Is positioned with respect to the intermediate transfer member 65.
On the other hand, it is necessary to stabilize the transfer efficiency by keeping the pressure of the transfer roller constant, and by using this, when the toner density sensor 81 is attached to the second transfer device 72, the intermediate toner density sensor 81 The positioning with respect to the transfer body 65 is performed.

Further, the toner concentration sensor 81 can be attached to and detached from the copying machine main body 50 at the same time as the attachment and detachment of the second transfer device 72, which simplifies the attachment and detachment work, and the toner concentration sensor 81 and the second transfer device 72 are separated from each other. , The connector can be shared, and the handling of the conductor becomes easy.

[0019]

1 is an exploded perspective view of an intermediate transfer member of a color copying machine and a mounting portion of a second transfer device according to an embodiment of the present invention.
FIG. 2 is an overall configuration diagram of the color copying machine.

In the color copying machine of this embodiment, as shown in FIG. 2, an original placing table 51 made of hard transparent glass is arranged at the upper end of the copying machine main body 50. A document (not shown) placed on the document table 51 is illuminated by a lamp unit 52, and reflected light from the document is reflected by the mirrors 53, 54, 55, the lens unit 56 and the mirror 5.
The photosensitive drum 59, which is rotatable in the direction of arrow B, is exposed through 7, 58. The lamp unit 52,
Sukiyana is composed of a mirror and the like.

In the rotation area of the photosensitive drum 59, a charging charger 60 for uniformly charging the surface of the photosensitive drum 59 prior to exposure is provided, and an electrostatic latent image is formed on the exposed portion.

Further, on the downstream side of the charging charger 60, a developing device having an inter-image eraser, a black developing tank 61, a yellow developing tank 62, a magenta developing tank 63 and a cyan developing tank 64 (not shown), a transfer belt 65, and a cleaning device. The portion 66 and the static elimination lamp 67 are arranged in this order. Toners of a corresponding color are stored in the developing tanks 61 to 64 of the developing device.

A transfer process unit T for transferring and superimposing the toner images on the photoconductor drum 59 is arranged below the photoconductor drum 59. The transfer process unit T is provided on the surface of the photoconductor drum 59. A drive roller 6 around which a transfer belt 65 as an intermediate transfer body is pressed and wound.
8, a driven roller 69, a pair of first transfer rollers 70, and a second transfer auxiliary roller 71.

A second transfer device 72 for transferring the toner image on the transfer belt 65 onto the sheet is arranged opposite to the second transfer auxiliary roller 71 with the transfer belt 65 interposed therebetween. The second transfer device 72 uses the second transfer roller 7
3 and a cleaning unit 74 for removing the toner remaining on the second transfer roller 73.

In the figure, reference numeral 75 is a paper feed cassette, 76 is a paper feed roller, 77 is a suction belt, 78 is a fixing device, and 79 is a paper discharge roller.

Color copying is performed by the following operation procedure. When the charging charger 60 uniformly charges the surface of the photoconductor drum 59, the first scanning is performed by the scanner, and the reflected light from the document passes through the color separation filter (not shown) and the image charger (not shown). ) Is subjected to slit exposure on the surface of the photosensitive drum, and a blue electrostatic latent image is formed on the exposed portion.

Then, an inter-image eraser (not shown) erases the portion corresponding to the non-image area of the electrostatic latent image, and the yellow toner is supplied from the yellow developing tank 62 to the electrostatic latent image of the image area which is not erased. , Toner images of the same color are formed.

The toner image circulates in the direction of arrow C and is partially transferred by the first transfer roller 70 onto the transfer belt 65 which is pressed against the surface of the photosensitive drum 59. At this time, a part of the toner that does not contribute to the transfer remains on the surface of the photosensitive drum 59, and the residual toner is removed by the cleaning unit 66.
Scrapes off. Then, the static elimination lamp 67 eliminates the residual charges on the surface of the photosensitive drum.

When the above steps are completed, the charging charger 60 charges the surface of the photosensitive drum again uniformly, and the reflected light from the original obtained by the second scanning is slit-exposed to give a green electrostatic latent image. Is formed. Similarly, the non-image area is erased by the inter-image eraser,
Magenta toner is supplied from the magenta developing tank 63 to the electrostatic latent image to form a toner image of the same color. Then, this toner image is transferred to the transfer belt 65, and the images are superimposed. After that, when the same processing as described above is performed, the charging charger 60 is supplied to the photosensitive drum 59 again, and a toner image of the same color is formed. Then, this toner image is transferred to the transfer belt 65, and final image superposition is performed. Thereafter, the toner image on the transfer belt 65 on which the images are superimposed is transferred onto the copy sheet by the second transfer roller 73, and the fixing device
After 8 times, the sheet is discharged outside the machine by the discharge roller 79.

On the other hand, black and white copying is performed by supplying black toner to the charged image on the photosensitive drum 59 from the black developing tank 61 and transferring the toner image onto the copy paper via the transfer belt 65.

Around the transfer belt 65, there is a cleaning unit 80 for removing the toner remaining on the transfer belt 65, and a toner concentration sensor 81 consisting of an infrared sensor for detecting the amount of toner adhering to the transfer belt 65. It is distributed.

The toner density sensor 81 detects the image density for automatic image density control for keeping the image density constant when the density balance of yellow, magenta, and cyan is destroyed due to something in a color copying machine. To do.

Here, the automatic image density control will be described. The following items can be cited as causes of the density imbalance.

(1) Deterioration of developer with the number of copies (2) Reduction of transfer efficiency due to environmental change (3) Reduction of surface potential of photoconductor due to environmental change (4) Characteristic change of developer due to environmental change It is natural that the balance is designed to be prevented as much as possible, but the photoconductor potential and the developer characteristics are changed due to environmental changes, so it is necessary to correct the changes.

The toner density sensor 81 is provided on the transfer belt 65.
It is installed at a position where the toner adhesion amount above can be read. As shown in FIG. 3, a toner patch (a 2 × 3 cm pattern of yellow, magenta, and cyan) is created on the transfer belt 65 at a constant surface potential A at the initial installation of the main body, and the sensor output B value at that time is stored in the CPU. Remember.

The main body of the copying machine has a fixing temperature of 10 when the power is turned on.
This function works automatically when the temperature is below 0 ℃. First, an image patch of the surface potential A is created, its density is measured, and it is compared with the initially stored value B. When the value is different from this value, the grid potential of the charging charger 60 is changed, the transfer belt 65 is rotated until it becomes the same as the initial image density, and the surface potential of the photosensitive drum 59 is determined.

A reference sensor is provided for each of the change due to the life of the measuring unit and the temperature characteristic, and the white patch is read at all times, and the current of the light emitting element is determined by the value.

Further, when the surface potential is changed by this mechanism, if only the potential is simply changed, the color balance of yellow, magenta and cyan will be greatly lost. As shown in FIG. 4, when the surface potential is changed by a γ curve (a copy density curve with respect to the original density is called a γ curve), it shifts from the initial γ curve as shown by A. The ideal γ curve is best when the curves for each color are the same. On the other hand, when the amount of light is changed, the γ curve moves as shown by B in the figure. A relational expression between the surface potential, the amount of light and the C point is found so as to eliminate the change at the C point at the rising portion of the γ curve, and the C point does not change even if the surface potential is changed.

That is, even if the density correction mechanism works due to this equation, the point C of each color does not move and only the density is corrected.

This operation is performed for each of yellow, magenta, and cyan to determine the conditions for the next copy.

As described above, if the toner density sensor 81 is not accurately positioned with respect to the transfer belt 65, the image density is distorted and the image quality is deteriorated.

In order to improve the positional accuracy of the toner concentration sensor 81 with respect to the transfer belt 65, the transfer belt 65 is mounted on the copying machine main body 50 and the second transfer device 72 is mounted on the transfer belt 65 as shown in FIG. The toner density sensor 81 is mounted on the second transfer device 72 and positioned with respect to the transfer belt 65.

That is, the drive roller 68, the driven roller 69, and the second transfer auxiliary roller 71 of the transfer process unit T.
Each of the roller shafts is supported by a front plate 90 having a substantially triangular shape at one end on the front side of the main body, and is supported by a rear plate 91 at the other rear end, and the rear plate 91 is screwed to the main body rear frame 92. It has been stopped.

A pair of pins 93 are provided on the front plate 90 so as to project, and the pins 93 are engaged with the holes of the positioning plate 94.

The positioning plate 94 is engaged with a pair of pins 96 protruding from the front frame 95 of the main body, whereby the transfer process unit T is positioned in the main body 50 of the copying machine.

The second transfer device 72 is mounted on a support plate 100 whose front and rear ends are bent.
A pair of pins 102 projecting from the rear wall 101 are attached to the rear plate 91.
The hole 103 formed in the front plate 90 and the pair of holes 105 formed in the front wall 104 of the support plate 100 into which the pin 106 protruding from the roller shaft 70a of the second transfer auxiliary roller 70 and the front plate 90 is inserted. The copying machine main body 50 is detachable. Thereby, the second transfer device 72 is positioned with respect to the transfer process unit T.

The toner concentration sensor 81 is formed by bending a protrusion 107 on the front wall 104 of the support plate 100.
And the positional relationship with the transfer belt 65 is
It is determined by the positional relationship between the second transfer device 72 and the transfer process unit T.

Further, on the rear wall 101 of the support plate 100,
The connector 108 is attached, and the conductor 108 from the second transfer device 72 and the toner concentration sensor 81 is connected to the connector 108. And the connector 108 is
The connector 110 attached to the rear plate 91 is detachable, and when the second transfer device 72 is pulled out to the front side and removed, the connector is pulled out accordingly.

Therefore, the positioning of the second transfer device 72 with respect to the transfer process unit T is necessary to stabilize the transfer efficiency by keeping the pressure of the second transfer roller 73 against the transfer belt 65 constant. By using this, the toner concentration sensor 81 is positioned, and the positional accuracy of the toner concentration sensor 81 with respect to the transfer belt 65 can be improved.

Further, the toner concentration sensor 81 can be attached to and detached from the copying machine main body 50 at the same time as the attachment and detachment of the second transfer device 72, which simplifies the attachment and detachment work, and the conductor of the toner concentration sensor 81 is connected to the second transfer device 72. Since it is housed inside, the connector can be shared and its handling is easy, and the conductor is not exposed to the outside and the aesthetics are not spoiled.

The present invention is not limited to the above embodiments, and it goes without saying that many modifications and changes can be made to the above embodiments within the scope of the present invention.

[0052]

As is apparent from the above description, according to the present invention, the intermediate transfer member is mounted on the main body of the copying machine, and the second transfer device is positioned with respect to the intermediate transfer member so that the intermediate transfer member can be detachably attached to the main body of the copying machine. Since the toner density sensor is mounted and mounted on the second transfer device and positioned with respect to the intermediate transfer member, the positioning of the second transfer device with respect to the intermediate transfer member is performed.
The toner density sensor is positioned as it is, and the positional accuracy of the toner density sensor with respect to the intermediate transfer member can be improved.

Further, since the conducting wire of the toner concentration sensor is housed in the second transfer device, the connector can be shared and the handling thereof is easy, and the conducting wire is not exposed to the outside and the appearance is not spoiled.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of an intermediate transfer member of a color copying machine and a mounting portion of a second transfer device according to an embodiment of the present invention.

[Figure 2] Overall configuration of color copier

FIG. 3 is an operation flow chart of automatic image density control.

FIG. 4 is a diagram of a γ curve showing the relationship between document density and copy density.

FIG. 5 is an overall configuration diagram of a conventional color copying machine.

FIG. 6 is an exploded perspective view showing a positioning structure of a photoconductor belt and a transfer belt with respect to a copying machine main body.

FIG. 7 is a perspective view of a mounting portion of the toner concentration sensor.

[Explanation of symbols]

 50 Copy Machine Main Body 65 Intermediate Transfer Body 72 Second Transfer Device 81 Toner Density Sensor 108 Connector 110 Connector

Front Page Continuation (72) Inventor Yoshiaki Masuda 22-22 Nagaike-cho, Abeno-ku, Osaka City, Osaka Prefecture

Claims (2)

[Claims] 1. An image for automatically controlling an image density, comprising an intermediate transfer member to which a toner image on a photosensitive member is transferred, and a second transfer device for transferring the toner image from the intermediate transfer member to a sheet. In a copying machine having a toner density sensor for detecting a change in density from the toner density on the intermediate transfer body, the intermediate transfer body is mounted on the copying machine body, and the second transfer device is positioned with respect to the intermediate transfer body. And a toner concentration sensor mounted on a second transfer device and positioned with respect to the intermediate transfer member. 2. The copying machine according to claim 1, wherein a conductor of a toner concentration sensor is connected to a connector of the second transfer device, and the connector is detachably attached to the connector of the copying machine main body. Copier.