JPH0736237A - Color image forming device - Google Patents

Abstract

PURPOSE:To provide a color image forming device capable of detecting toner density and automatically discriminating the paper kinds of a transfer material without increasing cost. CONSTITUTION:In the color image forming device provided with an optical sensor 21 constituted of a light emitting element and a light receiving element, the optical sensor 21 measures plural objects. The detection of toner density and the automatic discrimination of the paper kinds of a transfer material can be performed by the single optical sensor 21 without increasing the cost of the device by rotating the optical sensor 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus.

[0002]

2. Description of the Related Art In a color image forming apparatus of this type, a process of transferring a recording image formed by charging, exposing, and developing on an image carrier onto a recording paper is repeated a plurality of times to form a plurality of colors on the recording paper. There is one in which a desired color image is obtained by forming a superimposed image of (for example, DAS-
No. 2607727, JP-A-50-50935).

An outline of a conventional color image forming apparatus will be described with reference to FIG.

That is, FIG. 13 is a vertical sectional view of a conventional color image forming apparatus. As shown in the figure, a photosensitive drum 1 and a roller charger 2 are installed in the main body of the apparatus, and the photosensitive drum 1 is provided on the left side thereof. Is provided with a plurality of developing devices 4a, 4b, 4c, 4d rotatably supported by a support 3.

Further, on the right side of the photosensitive drum 1 in the main body of the apparatus, there is arranged a transfer drum 5 which holds a transfer material (not shown) and has a function of transferring the recording image on the photosensitive drum 1 onto the transfer material. ing.

Next, above the photosensitive drum 1 in the main body of the apparatus, a laser diode 7, which constitutes an exposure apparatus, a polygon mirror 9 driven to rotate by a high speed motor 8, a lens 10 and a folding mirror 11 are arranged. .

When a signal according to a yellow (hereinafter abbreviated as Y) image pattern is input to the laser diode 7, a laser beam corresponding to the signal is passed through the optical path 12 to the photosensitive drum 1. The latent image is formed on the photosensitive drum 1 by being irradiated. This latent image is visualized as a toner image by the developing device 4a when the photosensitive drum 1 rotates in the arrow direction.

On the other hand, when the transfer material is supplied from the transfer material cassette 13 by the pickup roller 14 in synchronism with the toner image on the photosensitive drum 1, the transfer material is held by the gripper 15 and subsequently transferred to the suction roller 16 and the transfer roller 16. Drum 5
The transfer material is electrostatically adsorbed on the transfer drum 5 by applying a voltage between the two, and the toner image on the photosensitive drum 1 is transferred onto the transfer material.

The above steps are magenta (hereinafter abbreviated as M), cyan (hereinafter abbreviated as C), and black (hereinafter B).
By carrying out for each color (abbreviated as K), toner images of a plurality of colors are formed on the transfer material.

The transfer material, to which the toner images of a plurality of colors have been transferred, is peeled from the transfer drum 5 by the separating claw 17 and then sent to the fixing device 18, where the toner images are fixed by the fixing device 18. The desired color image is thus obtained.

The transfer residual toner on the photosensitive drum 1 is cleaned by a cleaning device 6 such as a fur brush or blade means. The toner on the transfer drum 5 is also cleaned by a transfer drum cleaning device 19 such as a fur brush or a web, if necessary.

Incidentally, as the transfer material used in such a color image forming apparatus, an OHP sheet such as an OHP sheet is used in addition to plain paper. When forming a color image on this OHP sheet, if fixing is performed under the same conditions as for plain paper,
The toner on the OHP sheet is not completely melted and fixed, unmelted toner remains, and the surface of the toner layer becomes uneven. When a projected image is obtained from the OHP sheet with transmitted light, the transmitted light is complicatedly refracted due to the unevenness of the toner layer surface,
The color reproducibility of the image that is scattered and projected is extremely poor.

Therefore, when the transfer material is plain paper,
It has been proposed that the speed of the fixing device be switched depending on whether the sheet is used or not, so that the optimum fixing speed can be obtained for each transfer material (for example, Japanese Patent Laid-Open No. 59-1886).
73, JP-A-4-303858).

By the way, in order to switch the fixing speed, it is necessary to judge whether the transfer material is plain paper or OHP sheet.

Therefore, conventionally, an OHP mode switch is provided on the operation panel of the image forming apparatus for the above determination, and when an OHP sheet is used as the transfer material, the user turns the switch ON. A method of providing a paper type sensor including a light emitting element and a light receiving element in the middle of the transfer material conveying path and determining whether the transfer material is a plain paper or an OHP sheet based on a signal from the sensor is adopted. Came.

[0016]

By the way, requesting the user to operate the operation panel when using the OHP sheet not only annoys the user's hand, but also causes misprinting due to an operation error. Therefore, it is desirable to automatically determine the paper type of the transfer material.

On the other hand, in the color image forming apparatus, in order to stabilize the image density, a toner image for density detection of each color is experimentally formed on the photosensitive drum or the transfer drum prior to the normal printing operation. , The density of those toner images is detected by an optical sensor consisting of a light emitting element and a light receiving element,
This detection result is fed back to the image forming conditions such as the exposure amount and the developing bias.

Therefore, in the case where a paper type sensor is provided in the middle of the transfer material conveying path for automatically determining the paper type, a plurality of optical sensors having the same structure are present in the image forming apparatus. Therefore, the cost of the device is increased.

The present invention has been made in view of the above problems, and a purpose thereof is to form a color image capable of detecting the toner density and automatically determining the paper type of the transfer material without increasing the cost. To provide a device.

[0020]

In order to achieve the above object, the present invention provides a color image forming apparatus including an optical sensor including a light emitting member and a light receiving member, wherein a plurality of measurement targets of the optical sensor are provided. It is characterized by

[0021]

According to the present invention, the toner concentration can be detected and the paper type of the transfer material can be automatically determined by a single optical sensor without increasing the cost of the apparatus.

[0022]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

<First Embodiment> FIGS. 1 to 3 are diagrams for explaining the operation of the main part of a color image forming apparatus according to the first embodiment of the present invention, and FIG. 4 is a block diagram of an optical sensor. 1 to 3, the same elements as those shown in FIG. 13 are designated by the same reference numerals, and the description thereof will be omitted below.

In FIG. 1, reference numeral 21 is an optical sensor, and the optical sensor 21 is, as shown in FIG.
And a light receiving element 212 such as CdS and a holder 213, and is rotatably attached to the main body by a support member 214.

By the way, in the image density control in this embodiment, a toner image for density detection is formed on the photosensitive drum 1. Therefore, when the image density control is performed, the optical sensor 21 is driven by a driving means (not shown) in FIG. The measurement surface 215 is rotated in the direction of arrow a, and its measurement surface 215 is at the home position A (see FIG.
(State shown by a broken line in FIG. 1) to a position B (state shown by a solid line in FIG. 1) facing the photosensitive drum 1. The output from the optical sensor 21 at this time is sent to the density control circuit 23 by the changeover switch 22, and the density control for changing the exposure amount, the developing bias and the like is performed.

Next, when the normal printing operation is started, the optical sensor 21 is rotated in the direction of the arrow b in FIG. 2 by the driving means (not shown), and the measurement surface 215 of the optical sensor 21 faces the transfer drum 5 at the position C (FIG. 2). In the state indicated by the solid line). Then, when the transfer material held on the transfer drum 5 passes the measurement surface 215 of the optical sensor 21, the paper type of the transfer material is measured. Optical sensor 21 at this time
The output from is sent to the fixing device control circuit 24 by the changeover switch 22, and the fixing device control circuit 24 determines whether the transfer material is plain paper or OHP sheet based on the sent signal, and the fixing device 18 The fixing speed of is controlled to an optimum value for each.

After that, the Y, M, C, and BK toner images are transferred onto the transfer material, and the transfer material receiving the transfer of the toner image is
The toner image is fixed by the fixing device 18 whose fixing speed is optimally controlled as described above according to the paper type of the transfer material.
In this way, the desired color image is finally obtained.

When the paper type determination of the transfer material is completed,
The optical sensor 21 is rotated in the direction of arrow c in FIG. 3 by a driving unit (not shown), and returns to the home position A (state shown by the solid line in FIG. 3).

The home position A is located below the photosensitive drum 1 and the transfer drum 5, and the measuring surface 215 of the optical sensor 21 may be contaminated by scattered toner or the like. Optical sensor 2
The measurement surface 215 of No. 1 is prevented from becoming dirty.

Depending on the OHP sheet used, it is needless to say that in addition to the fixing speed, it is necessary to control other image forming conditions such as transfer bias in accordance with the paper type determination result.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIGS. Incidentally, FIG. 5 is a block diagram of the essential parts of the color image forming apparatus according to the second embodiment of the present invention.
FIG. 6 is a configuration diagram of the optical sensor, and FIGS. 7 and 8 are perspective views of the optical sensor.

In FIG. 5, reference numeral 21 is an optical sensor, and the optical sensor 21 is an LED as shown in FIG.
And a light receiving element 212 such as a photodiode and CdS, and a holder 213, and a measurement surface 215 thereof is opened and closed by a shutter 216. That is, the shutter 216 is opened as shown in FIG. 7 during the density measurement and the paper type measurement, and otherwise, the shutter 216 is opened.
The shutter 216 closes and the optical sensor 2
The measurement surface 215 of No. 1 is prevented from being soiled with toner.

Thus, in the image density control of this embodiment, a toner image for density detection is formed on the transfer drum 5. Then, this toner image is measured by the optical sensor 21, and the output from the optical sensor 21 at this time is sent to the density control circuit 23 by the changeover switch 22 to perform density control.

Next, in a normal printing operation, measurement is performed when the transfer material held on the transfer drum 5 passes the measurement surface 215 of the optical sensor 21, and its output is fixed by the changeover switch 22. To the container control circuit 24. Then, the fixing device control circuit 24 determines whether the transfer material is plain paper or an OHP sheet based on the sent signal, and controls the fixing speed of the fixing device 18 to an optimum value for each.

After that, the Y, M, C, and BK toner images are transferred onto the transfer material, and the transfer material which has received the transfer of the toner image is
The toner image is fixed by the fixing device 18 whose fixing speed is optimally controlled as described above according to the paper type of the transfer material.
Finally, the desired color image is obtained.

When the paper type determination of the transfer material is completed,
The shutter 214 of the optical sensor 21 is closed to prevent the measurement surface 215 of the optical sensor 21 from being soiled with toner.

Depending on the OHP sheet used, in addition to the fixing speed, it is necessary to control other image forming conditions such as transfer bias in accordance with the above-mentioned paper type determination result. In such a case, the optical sensor is used. Reference numeral 21 must be installed between the transfer material suction position and the transfer position as in this embodiment.

However, when changing only the fixing speed, the optical sensor 21 can be installed at an arbitrary position on the transfer drum 5.

Thus, according to the present embodiment, since the moving mechanism of the optical sensor 21 is unnecessary, the cost can be reduced and the measurement position is not displaced due to the movement of the optical sensor 21. Highly accurate measurement is always possible.

<Third Embodiment> Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 9 is a diagram showing changes in sensor output when the plain paper and the OHP sheet held on the transfer drum pass through the respective optical sensors, and FIG. 10 is a configuration diagram of the OHP sheet according to the third embodiment. 11 is a diagram showing a change in sensor output when the OHP sheet according to the third embodiment held on the transfer drum passes through the optical sensor, and FIG. 12 is the OH according to the third embodiment.
It is a figure which shows another structure of a P sheet.

When the OHP sheet and the plain paper held on the transfer drum respectively pass the measurement surface of the optical sensor, the output of the optical sensor becomes as shown in FIG. still,
The horizontal axis of FIG. 9 is the elapsed time from the start of the paper feeding operation, and the vertical axis is the output of the optical sensor.

As can be seen from FIG. 9, when the plain paper passes the measurement surface of the optical sensor, the output of the sensor changes greatly.

On the other hand, since the OHP sheet is transparent,
Even if the P-sheet passes through the measurement surface of the optical sensor, the output of the sensor hardly changes.

Therefore, if the output of the optical sensor largely changes after a predetermined time from the start of the paper feeding operation, it is determined that the plain paper is fed, and if there is almost no change, the OHP sheet is fed. is doing.

However, if the transfer material is not held on the transfer drum due to some reason such as a gripper grip error on the transfer drum, the optical sensor is used even if a predetermined time has elapsed after the paper feeding operation was started. Since there is no change in the output of, the OHP sheet is determined to have been fed, and an image is directly formed on the transfer drum.

Therefore, in this embodiment, in order to reliably judge that the OHP sheet is held on the transfer drum, the non-image portion at the front end of the OHP sheet is colored and the marker M is attached as shown in FIG. I attached it.

FIG. 11 shows the change in the sensor output when the OHP sheet with the marker M attached thereto is held on the transfer drum and has passed the measurement surface of the optical sensor.

Thus, according to the OHP sheet with the marker M attached, a change in sensor output as shown in FIG. 11 can be obtained, so that it can be seen that the OHP sheet has been fed.

If there is no change in the sensor output after a lapse of a predetermined time from the start of the paper feeding operation, it is judged that the transfer material is jammed on the way, and the optical sensor detects the paper jam sensor. You can also combine.

By the way, depending on the type of OHP sheet, there are cases where the optimum fixing conditions differ, and in addition, other image forming conditions such as transfer bias must be controlled. Therefore, if the density of the marker is changed according to the type of the OHP sheet, and the fixing condition is controlled according to the density of the marker read by the sensor, or if other image forming conditions are controlled, the OHP sheet is not affected by the type. It is possible to always obtain stable high-quality images.

As shown in FIG. 12, the OHP sheet 4
If the marker M is attached to the side, the type of the OHP sheet can always be correctly determined regardless of the orientation of the OHP sheet fed.

[0052]

As is apparent from the above description, according to the present invention, in the color image forming apparatus provided with the optical sensor including the light emitting member and the light receiving member, the measurement targets of the optical sensor are plural. The effect that the toner concentration can be detected and the paper type of the transfer material can be automatically determined by a single optical sensor can be obtained without increasing the cost of the apparatus.

[Brief description of drawings]

FIG. 1 is an operation explanatory view of a main part of a color image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is an operation explanatory view of a main part of the color image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is an operation explanatory view of a main part of the color image forming apparatus according to the first embodiment of the present invention.

FIG. 4 is a configuration diagram of an optical sensor according to a first embodiment of the present invention.

FIG. 5 is a configuration diagram of a main part of a color image forming apparatus according to a second embodiment of the present invention.

FIG. 6 is a configuration diagram of an optical sensor according to a second embodiment of the present invention.

FIG. 7 is a perspective view of an optical sensor according to a second exemplary embodiment of the present invention.

FIG. 8 is a perspective view of an optical sensor according to a second exemplary embodiment of the present invention.

FIG. 9 is a diagram showing a change in sensor output when a plain paper and an OHP sheet held on a transfer drum respectively pass an optical sensor.

FIG. 10 is a configuration diagram of an OHP sheet according to a third embodiment of the present invention.

FIG. 11 is a diagram showing a change in sensor output when an OHP sheet according to the third embodiment held on a transfer drum passes an optical sensor.

FIG. 12 is a diagram showing another structure of the OHP sheet according to the third embodiment of the present invention.

FIG. 13 is a sectional view showing a schematic configuration of a conventional color image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum (image bearing member) 21 Optical sensor 25 Eaves (protective member) 211 Light emitting element (light emitting member) 212 Light receiving element (light receiving member) 216 Shutter (measurement surface protecting member) M Marker (identifying part)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naoki Enomoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Mashiro Saito 3-30-2 Shimomaruko, Ota-ku, Tokyo Kyano (72) Inventor Yoichiro Maebashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Tatsuhiko Hayakawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroshi Sasame 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Haruo Fujii 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (9)

[Claims] 1. A color image forming apparatus comprising an optical sensor including a light emitting member and a light receiving member, wherein a plurality of measurement targets of the optical sensor are provided. 2. The color image forming apparatus according to claim 1, wherein the measurement target of the optical sensor is a developer carried on an image carrier. 3. The color image forming apparatus according to claim 1, wherein the measurement target of the optical sensor is a transfer material. 4. The color image forming apparatus according to claim 3, wherein the transfer material has an identification portion. 5. The optical sensor is movable between at least a first position for measuring a first measurement target and a second position for measuring a second measurement target. The color image forming apparatus according to claim 1. 6. The optical sensor comprises a first position for measuring at least a first measurement target, a second position for measuring a second measurement target, and a third position which is a home position when not measuring. The color image forming apparatus according to claim 1, wherein the color image forming apparatus is movable between the positions, and a protection member for protecting the measurement surface of the optical sensor is disposed at the third position. 7. The color image forming apparatus according to claim 1, wherein the optical sensor measures a plurality of measurement targets at the same position. 8. The image carrier is a transfer material carrier,
3. The color image forming apparatus according to claim 2, wherein the reflectance of the surface is different from the reflectance of the transfer material. 9. The color image forming apparatus according to claim 7, wherein the optical sensor has a measurement surface protection member that can be opened and closed.