JPH1020715A - Electrophotographic printer and seam position deciding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To track while detecting a seam, by receiving a signal from a sensor, and determining the seam position in a belt as the function thereof. SOLUTION: A toner area coverage sensor is installed in adjacent to a photoreceptor belt 12, and a controller receives a signal generated by the sensor as a function of the reflectance of the belt, to determine the seam position of the belt as the function thereof. Ordinarily the photoreceptor belt has a constant reflectance along the longitudinal direction thereof, but the reflectance of the seam area 15 of the belt 12, is varied because of a splash or the weld of the seam for bonding the end parts of the belt 12. In the case when the reflectance of the belt is measured by utilizing a black toner area coverage(BTAC) sensor, the voltage signal output is variable. The belt seam 15 is detected to be tracked by using the variation, so that the image formation and the development are not performed on the seam area 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to an apparatus for registering a plurality of images on a photoreceptive member, and more particularly to a sensor and a photoreceptor (e.g., a photoreceptor). ) Is the seam
Control is performed so that an image is not formed in the area, and distortion and deterioration of the image are prevented.

[0002]

BACKGROUND OF THE INVENTION Printing presses often use a belt-type photoreceptor on which a latent image is formed. The belt is typically a plurality of laminated materials in which a ground layer is coated with a photoconductive material, which is then coated on an anti-curl backing layer. This material is formed into a web by seaming the belts to form a closed loop. Seam areas are undesirable for forming images thereon due to defects due to the seam itself. Many belts use holes (holes) or other marks that are detected at a distance from the seam and have dedicated detectors that sense that holes or marks pass through a point, thereby timing the image. Is taken. Therefore, it would be desirable to be able to detect the seam position and time the image formation without the need for holes or other dedicated marks on the belt and associated sensors.

[0003] The following disclosure relates to various aspects of the present invention.

US Pat. No. 4,318,610 discloses an apparatus for controlling the concentration of toner particles in a developer mixture using a signal from an infrared densitometer that measures the concentration of toner particles in two test patch areas. explain.

US Pat. No. 4,553,033 discloses an infrared reflection densitometer that provides an electrical signal responsive to the amount of toner particles on a photosensitive surface.

US Pat. No. 4,950,905 discloses a non-black colored toner sensor arrangement for detecting diffusely reflected light indicative of the density of the toner coverage per unit area.

[0007] US Patent No. 4,989,985 discloses a densitometer that measures the decrease in specular reflectance due to the progressive deposition of marking particles on a moving photoconductive belt, and the reflected light beam. An electrical signal is generated that is proportional to the spectral component of the total flux of

[0008] US Patent No. 5,291,245 discloses a seam detection circuit that uses a sensor located on one side of a transmissive photoreceptor belt relative to a light source. Irradiation from the light source is detected by a sensor and a characteristic signal is determined when the seam of the photoreceptor passes between the sensor and the illumination source.

[0009]

According to one aspect of the present invention, there is provided an electrophotographic printing machine having a belt-type light-receiving member, the electrophotographic printing machine including a toner area cover adjacent to a photoreceptor belt. A controller that includes a storage sensor, the sensor generating a signal as a function of the reflectance of the belt, and receiving the signal generated by the sensor to determine a seam position of the belt as a function thereof.

Another aspect of the present invention is a method of determining the position of a belt seam in an electrophotographic printing machine having a belt-type light-receiving member, wherein the reflectance of the belt is determined using a toner area coverage sensor. Sensing along the length and generating a signal indicative thereof; and determining the position of the seam as a function of the signal generated by the sensor.

[0011]

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1 of the drawings, an original is located in a document handler 27 on a raster input scanner (RIS) (shown schematically at 28). The RIS includes a document irradiation lamp, an optical system, a mechanical scan driver, and a charge-coupled device (CCD) array. RIS captures the entire document and converts it to a series of raster scan lines. This information is transmitted to an electronic subsystem (ESS) that controls the raster output scanner (ROS) described below.

FIG. 1 schematically illustrates an electrophotographic printing machine that commonly uses a photoconductive belt 10. Preferably, photoconductive belt 10 is made from a photoconductive material coated on a ground layer, which is then coated on an anti-curl backing layer. The belt 10 has an arrow 13
, And advancing the continuous portion so as to sequentially pass through various processing stations disposed around the moving path (path). Belt 10 is stripping roller 1
4. Tension roller 16 and drive roller 2
It is wound around zero. The roller 20 rotates to advance the belt 10 in the direction of arrow 13.

First, a portion of the photoconductive surface passes through charging station A. At charging station A, a corona generator (shown schematically at 22) charges photoconductive belt 10 to a relatively high, substantially uniform potential.

At exposure station B, when a controller or an electronic subsystem (ESS) (shown schematically at 29) receives image signals representing the desired output image, it processes these signals to convert the signals to an image. The image is converted to a continuous tone or gray scale drawing, and the converted image is output to, for example, a raster output scanner (ROS) (reference numeral 3).
0) is transmitted to a conversion (modulated) output generator. ESS 29 is preferably a stand-alone dedicated minicomputer. The image signal transmitted to the ESS 29 is generated from a RIS or computer as described above, which allows the electrophotographic printer to act as a remotely located printer for one or more computers. Alternatively, the printer may be a dedicated printer for a high-speed computer. ESS, corresponding to the continuous tone image that is desired to be reproduced on a printing press
The signal from 29 is transmitted to ROS 30. ROS3
0 includes a laser with a rotating polygon mirror block. The ROS illuminates the charged portion of photoconductive belt 10 with a resolution of about 300 pixels per inch or more. ROS exposes the photoconductive belt to E
An electrostatic latent image corresponding to the continuous tone image received from SS29 is recorded on the belt. As an alternative, ROS30
Illuminates the charged portion of photoconductive belt 10 on a raster-by-raster basis using a linear array of light emitting diodes (LEDs) arranged.

After the electrostatic latent image has been recorded on photoconductive surface 12, belt 10 advances the latent image to development station C. Here, the toner in the form of liquid or dry particles is electrostatically attracted to the latent image using a generally known technique. The latent image attracts the toner particles from the carrier particles to form a toner powder image thereon. As successive electrostatic latent images are developed, toner particles are depleted from the developer material. A toner particle dispenser (shown schematically at 39) signals the controller 29 to transfer toner particles to a developer housing 40 of a developer unit 38 based on a signal from a toner maintenance sensor (not shown).
Distribute into.

Still referring to FIG. 1, after developing the electrostatic latent image, the toner powder image on belt 10 advances to transfer station D. The printing sheet 48 is advanced to the transfer station D by the sheet feeding device 50. Preferably, the sheet feeding device 50 comprises a stack 54
And a feed roll 52 that comes into contact with the uppermost sheet. The feed roll 52 rotates so as to advance the uppermost sheet from the stack 54 to the vertical transport unit 56.
The vertical transport section 56 is provided with the advancing sheet 48 as a supporting material.
To the register transport section 57 passing through the image transfer station D, and from the photoreceptor belt 10 in a timing sequence such that the toner powder image formed on the photoreceptor belt 10 contacts the advancing sheet 48 at the transfer station D. Receive an image. The transfer station D transfers the ions to the sheet 48
And a corona generator 58 for spraying the back side of the corona. This causes the toner powder image to move from photoconductive surface 12 to sheet 4
Attracted to 8. After the transfer, the sheet 48 becomes the sheet 4
8 continues to move in the direction of the arrow 60 by the belt transporting unit 62 that advances the fusing station 8 to the fusing station F.

The fusing station F includes a fuser assembly (shown schematically at 70) for permanently fusing the transferred toner powder image to a copy sheet. Preferably, fuser assembly 70 includes a heated fuser roller 72 and a pressure roller 74 such that the powder image on the copy sheet contacts fuser roller 72.

The sheet then passes through a fuser 70 where the image is permanently fixed or fused to the sheet. After passing through the fuser 70, the gate 80 allows the sheet to move directly to the finisher or stacker via the output 84, or to pass the sheet through a duplex (double-sided printing) path 100, specifically, here a single sheet inverter. Bend into 82. That is, when the sheet is either a simplex (single-sided printing) sheet or a completed duplex sheet on which both front and back images are formed, the sheet is directly conveyed to the output unit 84 via the gate 80. . On the other hand, if the sheet is to be duplexed and only a one-sided image is
0 is positioned to deflect the sheet into the inverter 82 and into the duplex loop path 100.
Here, the sheet is inverted and then the promotion nip 10
2 and re-circulated to the belt transport 110 and returned back through the transfer station D and fuser 70 to receive and permanently fix the second side of the image on the back side of the duplex sheet. Exit via exit path 84.

The printed sheet is the photoconductive surface 1 of the belt 10
After being separated from 2, the residual toner / developer and paper fiber particles adhering to photoconductive surface 12 are removed at cleaning station E. The cleaning station E includes a rotatably mounted fiber brush that contacts the photoconductive surface 12 to disturb and remove the paper fibers, and a cleaning blade to remove untransferred toner particles. The blade is configured with either a wiper or doctor position depending on the application. Following cleaning, a discharge lamp (not shown) illuminates the photoconductive surface 12 to dissipate any remaining static charge before charging the belt for the next successive imaging cycle.

Various machine functions are coordinated by controller 29. The controller is preferably a programmable microprocessor that controls all of the machine functions described above, including toner distribution. The controller calculates the copy sheet comparison count, the number of circulating documents,
It provides the number of copy sheets, time delay, jam correction, etc. selected by the operator. Control of all of the exemplary systems described so far may be provided by a conventional control switch input from a printing machine console selected by an operator. Conventional sheet path sensors or switches may be used to keep track of document and copy sheet locations.

Referring to FIG. 2, a plan view of a typical photoreceptor belt configuration is shown. Holes 17 or marks (not shown) on the belt 12 are generally located at a position relative to the seam 15 of the belt. Next, the passage of a known mark is detected using the dedicated sensor 18, and the timing of the image is adjusted from this mark. This configuration is reliable,
Requires the addition of holes or other marks to the belt and dedicated sensors and associated controls for it.

Many printing presses in use today include a black toner area coverage sensor (Black
Toner Area Coverage sensors), a sensor known as a BTAC sensor, is used. These sensors emit an optical signal and measure the reflected signal to produce an analog voltage output as a function of the reflected optical signal. The photoreceptor belt typically has a constant reflectivity along its length, but at the seam portion 15 of the belt 12, the seam splash used to join the belt ends together (splash). ) Or a change (variation) in the reflectance due to welding. When measuring the reflectance of a belt using a BTAC sensor, there is a change in the voltage signal output as shown in the graph of FIG. This change can be used to detect and track the belt seam 15 and prevent image formation and development in the seam area 21 (FIG. 2). This seam tracking can be performed without additional hardware and the controller can be programmed to filter out spurious signals that may be caused by scratches or other marks that may be applied to the photoreceptor belt. You can call

A typical way to distinguish seams from BTAC recording noise is to perform a fast Fourier transform [Fft R (x) = R (f), I (f)] on the suspect seam area,
The power spectrum (Power Spectrums) is generated. This produces a unique frequency feature for each region. The actual seam is detected by comparison with the actual seam features programmed into the controller. Once properly identified, the center of moment of the curve of FIG. 3 is calculated. This point representing the centerline of the seam is then used as a registration point where the image pitch reset signal is generated, and the image frame for registration is properly detected and transferred to the substrate.

[0024]

In summary, the present invention provides an apparatus and method for detecting and tracking seams on a photosensitive belt of a printing press. The profile of the belt is created along its entire length using a standard BTAC sensor. The resulting signal varies as a function of belt reflectivity and is substantially constant outside of the belt seam area. An algorithm is used to filter out noise caused by scratches or dirt on the belt and detect and track the centerline of the seam. Since the image pitch reset signal is generated based on these records, no latent image is generated in the non-image forming area adjacent to the belt area.

[Brief description of the drawings]

FIG. 1 is a schematic front view of a typical electrophotographic printing machine using a toner maintenance system.

FIG. 2 is a schematic plan view of a photoreceptor belt showing known holes or marks on a belt type detector for detecting seams and non-image forming areas of the belt.

FIG. 3 is a graph showing voltage recording of a toner area coverage sensor when used to detect a seam area of a photoreceptor belt.

[Explanation of symbols]

 10 Photoconductive belt 29 Controller

Claims (3)

[Claims] 1. An electrophotographic printing machine having a belt-type light-receiving member, comprising: a toner area coverage sensor adjacent to a photoreceptor belt, said sensor generating a signal as a function of belt reflectivity; An electrophotographic printing machine, comprising a controller adapted to receive a signal generated by the sensor and determine a position of a seam in a belt as a function thereof. 2. A method for determining the position of a seam in a belt of an electrophotographic printing machine having a belt-type light-receiving member, the method comprising: using a toner area coverage sensor to determine the reflectance of the belt along its length. Sensing and generating a signal indicative thereof; and determining the position of the seam as a function of the signal generated by the sensor. 3. The seam position determining method according to claim 2, further comprising forming a latent image on a light receiving member in an area other than the seam.