JPH0750762Y2 - Color image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an image forming apparatus of a type in which a transfer drum for clamping a transfer sheet and a photosensitive drum are arranged adjacent to each other, and an image is transferred onto the transfer sheet. The present invention relates to a device for detecting an error in separating a transfer sheet from a transfer drum.

[Conventional technology]

A transfer paper clamp in this type of image forming apparatus will be described with reference to FIG.

FIG. 4 is a side view of the transfer drum. The transfer drum 3 has a clamper on the outer peripheral portion. The tip of the transfer paper P is gripped by this clamper 6, and the transfer paper P is attached to the outer peripheral portion of the transfer drum 3. Is electrostatically wrapped.

5 and 6 are enlarged views in the vicinity of the clamper 6 showing a normally clamped state and a separated state. The front end of the transfer paper P is gripped up to the recess abutting position of the clamper 6 and is in the separated position. When the clamper 6 swings counterclockwise, the leading edge of the transfer paper P is flipped up by its "waist" and separated from the transfer drum by the separation claw 1H.

However, if the gripper 6 is shallowly gripped as shown in FIG. 7, the clamper 6 cannot push up the transfer sheet P at the time of separation as shown in FIG. 8 and rides on the transfer sheet P. It will be.

[Problems to be solved by the device]

In the above-mentioned state, the transfer paper P remains wound and becomes a separation jam.

Usually, the image forming apparatus is provided with a sheet passing sensor in the sheet discharging portion, and if the transfer sheet is not discharged at a predetermined timing, the jam processing control is performed. However, in the time until the sensor of the paper discharge unit detects the clamper 6, the clamper 6 rides on the transfer paper P, that is, projects from the outer peripheral surface of the transfer drum 3, as shown in FIG. There is a problem that the photoconductor drum is damaged even if it reaches the contact position with 2. Further, if the sensor is soiled by the scattered toner inside the apparatus, it may be erroneously detected, and the state of the transfer sheet may not be reliably detected, and the photosensitive drum may be damaged.

The first object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, to detect an error in separating the transfer paper on the transfer drum at an early stage, and to prevent an accident. Furthermore, the second is to suppress the occurrence of erroneous detection because the sensor is soiled by the scattered toner of the device
The purpose of.

[Means for Solving the Problems]

In order to achieve these objects, the present invention is provided with a photoconductor and a transfer drum, and a photosensitive member is provided on a transfer paper wound around the transfer drum, the tip of which is held by a clamper which is swingably installed on the transfer drum. Color image formation provided with a conveying means for sequentially transferring a plurality of colors of developer formed on the body, and for conveying the transfer paper separated from the transfer drum at a predetermined position by releasing the grip of the clamper to a fixing device. In the apparatus, a transfer paper detection sensor for detecting a transfer paper conveyance state has a moving distance of 1 in the rotation direction from the transfer paper separation position from the transfer drum to the contact position between the transfer drum and the photoconductor, and the transfer paper from the separation position. when the moving distance to the position of the sensor 1 ₁ and 1 ₁ <a position such that one relationship, provided in the conveying surface upwardly facing the transfer-sheet conveying surface of the conveying means It is characterized by

[Action]

Thus, in the present invention, the transfer paper arrives immediately after the separation position,
Since the sensor for detecting the passage, that is, for detecting the separation error is provided, the separation error can be detected early.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 shows the overall structure of a color copying machine which can obtain a mono-color or full-color copy. In this color copying machine, a transfer drum is provided in the vicinity of the photoconductor drum and is carried by this transfer drum. Paper (transfer paper P)
On the other hand, the image on the photoconductor drum, which has been visualized using the complementary color developer corresponding to each color separated color, is superimposed and transferred.

That is, this color copying machine 1 has
The photoconductor drum 2 rotatable in the direction of the arrow shown in the figure and the transfer drum 3 which is close to the photoconductor drum 2 and can move in the same direction at the same position at the same speed as the drum 2 are exposed. A section A is located around the drum 2, and a pre-charging section B, a developing section C, an erasing section D, and a cleaning section E, which perform a copying process in accordance with the rotation of the drum 2, are located. A transfer portion F is provided inside the portion facing the photoconductor drum 2, a paper feeding portion G is provided in front of the transfer portion F in the rotation direction of the transfer drum 3, and a paper feeding portion G is provided behind the transfer portion F in the rotation direction of the transfer drum 3. The separation part H is located.

In the exposure unit A described above, an optical system including a light source and a plurality of reflecting mirrors reciprocates in the scanning direction with respect to the document mounting table 1A with respect to the document mounting table 1A made of a transparent body fixed to the upper surface of the main body 1a. The document on the document table 1A is exposed and scanned a plurality of times, and reflected light from the document is separated by the filter 2A at each scanning and guided onto the photoconductor drum 2. .

The pre-charging portion B is composed of a well-known charger 1B located in front of the exposure position in the rotation direction of the photoconductor drum 2, and is uniform in the photoconductive layer of the photoconductor drum 2 with a preset polarity. Charge.

On the other hand, the developing section C is located behind the exposure light irradiation position in the rotation direction of the photosensitive drum 2, and the filter in the exposure section A is located.
2A, three developing tanks containing the developer of the color corresponding to the complementary color of the color separated, in FIG. 2, the developer of each color of cyan, magenta and yellow which are the complementary colors of the three primary colors. 1C, 2C, 3C and a developing tank 4C containing a black developer are arranged near the outer periphery of the photosensitive drum 2.

Although not described in detail, for example, each of the above-mentioned developing tanks is provided with a developing sleeve, a doctor, and a stirring blade having a built-in magnet for performing well-known magnetic brush development.

The erase section D is composed of, for example, light emitting diodes arranged in the axial direction of the photoconductor drum 2, and in order to remove the developer adhering to the non-image portion on the photoconductor drum 2 after development. The light is emitted with an amount of light capable of removing the electric charge remaining on the background portion of the photosensitive drum 2.

The cleaning unit E is located behind the position facing the transfer drum 3 in the rotation direction of the photosensitive drum 2,
Along with the rotation direction of the drum 2, it is composed of a charge eliminating charger 1E, a cleaning roller 2E, and a quenching lamp 3E which are sequentially arranged from the front side. The residual developer on the photoconductor drum 2 set to the electrically neutralized state is removed by the cleaning roller 2E having the same structure as the sleeve described above, and the residual charge on the photoconductor drum 2 is quenched. Remove with lamp 3E.

On the other hand, the transfer portion F of the transfer drum 3 is a charger 1F facing the photoconductor drum 2 with the peripheral wall of the transfer drum 3 sandwiched inside the transfer drum 3 which is provided so as to be able to come into contact with and separate from the photoconductor drum 2. When the transfer drum 3 approaches the photosensitive drum 2, the developer is charged with a reverse polarity.

The sheet feeding section G is located in front of the transfer section F in the rotation direction of the transfer drum 3 described above. This is composed of a two-stage sheet feeding cassette 1G, a pickup cup roller 2G, a feeding roller 3G, a merging portion feeding roller 4G, conveyance guide portions 5G1 and 5G2, and the like.

The separating section H includes a swingable separation claw 1H located behind the transfer section F in the rotation direction of the transfer drum 3, and a separation in the moving direction of the sheet separated from the transfer drum 3 by the separation claw 1H. Conveyor belt 2H located behind claw 1H
And the separation charger 3H, and conveys the paper separated from the transfer drum 3 to the fixing device I.

The fixing device I is a well-known roller fixing device composed of a heating roller 1I and a pressure roller 2I which comes into contact with the heating roller 1I and is driven to rotate. Eject the paper.

FIG. 3 is an external view of the transfer drum 3 on which the transfer paper P is wound. The transfer paper P is clamped by the clamper 6, while the clamper shaft 7 is lifted by the movement of the cam by the action of a solenoid or the like. The transfer paper P is separated from the transfer drum 3 by opening the clamper 6.

Next, a separation error detecting device according to an embodiment of the present invention will be described with reference to FIG.

A conveyor belt 2H is provided adjacent to the separation claw 1H,
A sensor 8 for detecting a separation error, which is a reflection type photo sensor, is arranged on the upper part of the above. This sensor 8 detects immediately after a separation error.

When the distance from the separation position to the sensor 8 is l ₁ , and the distance from the separation position to the contact point with the photosensitive drum 2 in the rotation direction of the transfer drum 3 is l, the sensor 8 is arranged at the position of l ₁ <l. To be done. Further, in order to further increase the margin, the sensor 8 is arranged so that l ₁ + α <l in consideration of the variation α. Incidentally, 9 is a fixing inlet guide plate.

With such a mounting position of the sensor 8, even if there is some variation in conveyance of the transfer paper P, the clamper 6 reaches the contact position with the photosensitive drum 2 due to a separation error. This separation error can be reliably detected before proceeding.

[Effect of device]

As described above, according to the present invention, since the transfer paper detection sensor is arranged at the position where the contamination from the scattered toner is suppressed, the transfer paper conveyance state can be ensured without causing the detection error of the sensor. Can be detected. In addition, since the separation error of the transfer paper can be reliably detected before reaching the contact position with the photoconductor in the state where the clamper protrudes due to the separation error, the damage of the photoconductor due to the projection clamper due to the separation error can be prevented. can do. further,
By considering the range of variation distance of the leading edge of the transfer paper, the above effect can be more reliably achieved.

[Brief description of drawings]

FIG. 1 is a schematic view of a main part of an image forming apparatus according to an embodiment of the present invention, FIG. 2 is the same overall configuration view, FIG. 3 is a perspective view of a transfer drum, and FIG. FIGS. 5, 5 and 6 are explanatory diagrams of a normal clamp state, FIGS. 7 and 8 are explanatory diagrams of a clamp failure state, and FIG. 9 is an explanatory diagram showing a state where the photosensitive drum is damaged by the clamper. is there. 2 ... Photosensitive drum, 3 ... Transfer drum, 6 ... Clamper, 8 ... Sensor.

Claims (1)

[Scope of utility model registration request] 1. A plurality of colors formed on a transfer paper, which is provided with a photosensitive member and a transfer drum, and whose tip is gripped by a clamper swingably installed on the transfer drum and wound on the transfer drum. In the color image forming apparatus, the developer is sequentially transferred, and the transfer paper that is released from the transfer drum at a predetermined position by releasing the grip of the clamper is transferred to the fixing device. The transfer paper detection sensor for detecting the state detects that the moving distance in the rotation direction from the transfer paper separation position from the transfer drum to the contact position between the transfer drum and the photoconductor is 1, and the separation position to the transfer paper detection sensor arrangement position. when the movement distance 1 ₁ and 1 ₁ <a position such that one relationship, mosquitoes, characterized in that provided on the conveying surface upwardly facing the transfer-sheet conveying surface of the conveying means Image forming apparatus.