JPH0757654B2 - Recording device and image alignment method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for aligning an image formed on a sheet in a copying machine using a sheet, a laser beam printer or the like.

[0002]

2. Description of the Related Art A recording apparatus for recording an image by forming an image on a rotating body by slit exposure or beam scanning and transferring the image onto a paper sheet is widely known. However, in such a device,
A registration roller was used for image registration.

In the alignment using the registration rollers, there is no problem if the paper feed speed is about 200 mm / S, but if it exceeds about 500 mm / S, the positioning accuracy is lowered.

For example, when the paper is fed at 500 mm / S, the stop time at the registration roller is 30 mm / S.
It's just a degree. Considering the response speed of the clutch connecting the registration roller and the drive reduction, it is close to the response limit of a normal clutch unless it is a special clutch such as a powder clutch. For this reason, the time during which the clutch is turned on and off tends to vary, and the activation time of the registration roller also varies. In the case of the above-mentioned transport speed of 500 mm / S, a variation of 2 mm / S results in a positional error of 1 mm on the paper. As described above, the conventional method has a drawback that the recording position error on the paper increases as the paper transport speed increases. Further, the clutch and the like also need to be highly accurate.

The present invention has been made in view of the above-mentioned conventional drawbacks.
(EN) Provided is a recording device capable of image registration control, which is less dependent on the operating characteristics of a clutch or a sheet driving device.

In general, in order to align images with high accuracy, an optical system considering variations of individual devices,
It requires highly precise adjustment of the transport system. The present invention has been made in view of the above points, and an object thereof is to provide an image alignment method capable of performing highly accurate alignment while reducing troublesome adjustment. That is, according to the present invention, the detection value regarding the positional relationship between the paper sheet conveyed at a predetermined timing and the visible image on the photosensitive drum is measured before the recording operation on the paper sheet, and the paper sheet is detected according to the detection value. This is to change the image writing timing by the laser beam in the recording on the leaf body.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 schematically shows the basic structure of a laser beam recording apparatus to which the present invention is applied. The laser beam emitted from the laser oscillator 1 is a lens 2, an A / O modulator 3 utilizing a known acousto-optic effect,
The light enters the light modulation system formed by the lens 4. Here, the lens 2 functions to focus and project the laser beam on the black reflecting surface generated in the A / O modulator, and the lens 4 converts the laser beam diffracting and diverging from the black reflecting surface into a parallel light beam. It works to do.

The lens 2 and the lens 4 are not required when using a known E / O modulator utilizing the electro-optical effect, and the above-mentioned light is used when the laser oscillator is a gas laser or semiconductor laser capable of current modulation. It goes without saying that the modulation system can be omitted.

The laser beam emitted from the lens 4 becomes a parallel light beam, enters the beam expander 7, and the beam diameter is expanded as the parallel light beam.

The laser beam whose beam diameter is further expanded is incident on a polyhedral rotating mirror 8 having one or a plurality of mirror surfaces. The polyhedral rotating mirror 8 is attached to a shaft supported by a highly accurate bearing (for example, an air bearing), and is driven by a motor 9 for constant speed rotation (for example, a hysteresis synchronous motor or a DC servo motor). The laser beam swept horizontally by the polygon mirror 8 is imaged as a spot on the photosensitive drum 14 by the imaging lens 13 having the f-θ characteristic. In a general imaging lens, when the incident angle θ of the light beam is set, r = f for the position r where the image is formed on the image plane.
Tan θ- (1) (f: focal length of the imaging lens), which is reflected when the polyhedral rotating mirror 8 is rotated at a constant speed as in the present embodiment.
In FIG. 2, the incident angle to the imaging lens 13 changes linearly with time. Therefore, the photosensitive drum 14 which is the image surface
The moving speed of the imaged spot position above changes non-linearly and is not constant. That is, the moving speed increases at the point where the incident angle increases. Therefore, when the laser beam is turned on and a spot row is drawn on the photosensitive drum 14 at a constant time interval, the intervals are wider at both ends as compared with the central part. In order to avoid this phenomenon, the imaging lens 13 is designed so as to have a characteristic of r = f · θ ------ (2). Such an imaging lens 13 is called an f-θ lens. Furthermore, when parallel light is imaged in a spot shape by an imaging lens, the minimum spot diameter dmin is

[0012]

[Outer 1] λ: wavelength of light used A: given by the entrance aperture of the imaging lens, and when f and λ are constant, a smaller spot diameter dmin can be obtained by increasing A. The beam expander 7 described above is used to give this effect. Therefore, the required d
When min is obtained by the beam diameter of the laser oscillator, the beam expander 7 is omitted.

As described above, the deflected and modulated laser beam 52 is applied to the photosensitive drum 14 to be visualized by an electrophotographic process, and then transferred and fixed on plain paper to be output as a hard copy. As a d example of the electrophotographic process applied to this embodiment, as described in Japanese Patent Publication No. 42-23910 of the present applicant, a photosensitive drum having a conductive support, a photoconductive layer and an insulating layer as a basic constituent. 14
The surface of the insulating layer is charged positively or negatively in advance by the first corona charger 16 to charge the surface of the photoconductive layer and the insulating layer or the inside of the photoconductive layer with a charge having a polarity opposite to the charge polarity. And then the surface of the non-charged insulating layer is irradiated with the laser beam and, at the same time, the AC corona discharger 17
AC corona discharge is applied to form a pattern on the surface of the insulating layer due to the difference in surface potential generated according to the pattern of light and darkness of the laser beam, and the entire surface of the insulating layer is uniformly exposed by the exposure lamp 18 for contrast. A high electrostatic latent image is formed on the surface of the insulating layer, and the electrostatic latent image is developed by a developing device 19 with a developer containing charge colored particles as a main component to be visualized and thereafter exposed by means described below. The visible image is transferred onto a sheet (hereinafter referred to as paper) pressed against the drum 14 by the transfer charger 22, and then the transferred image is fixed by a fixing unit as described below to form an electrophotographic print image. On the other hand, after the transfer is performed, the surface of the insulating layer is cleaned by the cleaning device 23 to remove the remaining charged particles, and the photosensitive drum 14 is repeatedly used. That. As yet another example, an electrophotographic electrostatic imaging process such as that described in the applicant's Japanese Patent Publication No. Sho 42-19748 is applied. That is, a photosensitive plate having a conductive support, a photoconductive layer and an insulating layer as a basic constituent is used, and the surface of the insulating layer is uniformly positively or negatively charged in advance by the first corona discharge. And the surface of the insulating layer or the inside of the photoconductive layer to capture the charge having the opposite polarity to the charged polarity, and further apply the corona discharge to the surface to be charged to attenuate the charge on the surface of the insulating layer. After the process of irradiating the laser beam as a signal, forming an electrostatic latent image on the surface of the insulating layer according to the light and darkness of the laser beam, and thereafter developing the electrostatic image, it is the same as the first embodiment. .

Reference numeral 15 is a pre-charger 16a for pre-electrification, which is a pre-exposure lamp. The pre-electrification charger 15 makes the surface unit of the photosensitive drum 14 constant and uniform, and the pre-exposure lamp 16 'has a constant photosensitive layer characteristic. They serve to make uniform and have a function of erasing various prior records remaining on the photosensitive drum 14 that have passed through the cleaning device 23, for example, a residual potential, and help to always obtain a stable image. The present applicant has proposed an electrostatic latent image stabilizing method as a means for always obtaining a stable and good image in the electrophotographic process applied to this embodiment. Reference numeral 21 denotes an electrostatic potentiometer for realizing such means, which is provided with a bright portion of the photosensitive drum 14, that is, a portion exposed by scanning with a laser beam and a dark portion, to measure the electrostatic potential of each.

Reference numeral 20 is a carrier removing device for preventing carriers mixed in the developer in the developing device 19 from adhering to the photosensitive drum 14 and adhering to the paper or entering the cleaning device 23.

FIG. 2 shows the arrangement of the optical system in FIG. 1 in a three-dimensional manner. In the explanation of FIG. 1, parts having the same function are designated by the same reference numerals (the same applies hereinafter).

In FIG. 2, reference numeral 51 detects a scanning start position of the laser beam 52 swept by a beam detector composed of a small incident slit and a photoelectric conversion element (for example, PIN diode) having a fast response time. ,
As will be described later, the start timing of the modulation control signal for giving desired optical information on the photosensitive drum 14 is determined.

The laser beam from the laser oscillator 1 is an A / O modulation signal 3 according to the modulation signal formed by the modulation signal forming circuit 5 by the recording signal applied from the input terminal 6.
Then, the light is modulated by the light, and scanning is performed while forming an image on the surface of the photosensitive drum 14 by the deflecting action of the rotary polygon mirror 8.

The print position in the line direction on the paper is applied with a modulation control signal after a preset time has elapsed from the time when the signal was generated by the beam detector 51 provided corresponding to the scanning start position of the deflected laser beam. Adjusted accordingly. The scanning direction of the laser beam is shown by an arrow 53 in FIG.

Next, the conveyance of paper will be described. When the paper 31 stacked on the paper feeding stage 30 is sent to the conveyance path by the paper feeding roller 32, the pair of registration rollers 3
Correct the skew at the time of feeding by 3 and align the leading edge of the paper. The paper exiting the registration roller 33 comes into contact with the drum 14 through a transport guide 34 that forms a part of the transport path. A photo sensor 47 is arranged between them, and the output thereof detects the slow speed of the paper after passing through the registration rollers. The image on the drum 14 is transferred onto the paper 31 by the transfer charger 22. The paper after transfer is sent to the conveyor belt 39 when it is separated from the drum 14 by a separating means (not shown). A photo sensor 35 is arranged in the middle of the conveyance belt 39, and the output of the photo sensor 35 detects the presence or absence of a jam in the conveyance path from the paper feed roller 32 to the drum 14. Further, the paper 31 is sent to the conveyor belt 39 and enters the fixing device 40. Here, the toner on the paper 31 is fused under the heat and pressure of the fixing device 40 to form a permanent image. Paper 3 after fixing
1 is sent by the conveyor belt 41, and a jam between the photosensors 35 and 36 is detected by the photosensor 36 and the photosensor 35 arranged in front of the paper discharge roller 42. The normally conveyed paper exits the paper ejection roller 42,
The sheets are stacked on the first output tray 43.

As will be described later, the photo sensor 47 is used.
After the paper is detected by the paper, the paper is detected by the photo sensor 36 after a lapse of a predetermined time, the paper discharge switching plate 44 is switched to the position of the broken line, and the paper regarded as abnormal is discharged by the paper discharge roller 42. , 45 to the second output tray 46
Loaded on top. A photo sensor 37 is arranged immediately in front of the paper discharge roller 45, and detects that the non-sheet is surely conveyed to the second output tray 46.

FIG. 3 is a block diagram showing the control unit of the LBP. Reference numeral 100 denotes a CPU, 47, 37, 102 for controlling the operation of the LBP according to the program stored in the ROM.
Corresponds to the photosensors 47 and 37 of FIG. The signals from the photo sensors 47 and 37 are sent to the comparator 10.
3, 104 is compared with the reference value and input to the CPU 100. Further, the drive signal from the CPU 100 is fed through the switching circuits 105, 106 and 107 to the paper feed roller clutch 108, which is provided between the motor (not shown) that is constantly rotating and the paper feed roller 32. Is output to a registration clutch 109 provided between a motor (not shown) rotating in the direction not shown and a registration roller, and a paper discharge switching solenoid 110 that controls the paper discharge switching plate 44, and the paper feed roller 32, the registration roller 33, and paper discharge switching. The plate 44 is driven. or,
The image writing timing signal VTS is output from the CPU 100 to the page information output circuit 113.

The video signal VS from the page information output circuit 113 and the permission signal PS from the CPU 100 are input to the AND gate 114, and the output from the AND gate 114 is passed through the A / O driver 115 (corresponding to 5 in FIG. 1). A /
Input to the O modulator 116. As a result, the A / O modulator 1
16 (corresponding to 3 in FIG. 1) is turned on / off according to the video signal. A status code signal from the CPU 100 drives the display element 112 via the decoder 111.

Timing charts are shown in FIGS.
When the print start command is issued in FIG. 5, the delay time T
After _1, turns on the paper feed clutch at time T _1, and off after Tf ₁ hour hold, then holds the Tf ₂ hours off, the inner top surface of the paper housed in the paper feed cassette paper (N = 1) is fed, and then N = 2, 3 ... In order for the fed paper to be conveyed by forming a predetermined loop in the registration roller portion, the registration clutch is moved for ₁ hour after Tr ₁ from the time T ₁ .
The transfer is stopped by turning off for a time Tr ₂ , and then the registration clutch is turned on again to transfer. However, as the time Tr ₂ below, but those fixed, making it possible to present ± △ time of correction, whereas the same for the following time T _2, T ₃ ···, from time T ₁ After Tl time, the page information is output from the page information output circuit and n =
1, 2, ... Pages are written and the screen returns to FIG. When the clutch of the registration roller is turned on and the paper passes through the registration roller, the paper is conveyed by the photo sensor 47 and the time t when the output of the sensor becomes H is checked. If it is within the specified time Tc ± ΔT, it means that the paper has been conveyed at the proper timing, and the leading edge of the image does not deviate more than the allowable value when the image is transferred from the photoconductor. Means The fed N = 1st page of paper represents the timing of t ₁ = Tc.
Similarly, it means that the paper of the N = 2nd page has been conveyed at the timing of Tc-ΔT <t ₂ <Tc, and the paper of the N = 3rd page has the allowable timing at the timing of Tc + ΔT <t _3. It means that it has been transported over.
In this case, it means that the paper has come late, and the image transferred onto the paper has a small leading edge margin, or in an extreme case, the leading edge of the image is chipped. On the other hand, conversely Tc-ΔT
If the timing is> t _{3, the} paper is conveyed faster than the permissible time, and the trailing edge margin is small.
Alternatively, in an extreme case, the trailing edge of the image is missing.

Therefore, in order to discharge the output paper of N = 3rd page to the second output tray which is different from the first output tray which stores the normal print paper, the N = third page is conveyed and the photosensor The output of 37 changes to H and after a certain delay time T, the discharge switching solenoid (not shown) is excited. On the other hand, by ejecting N = 3 pages, the information of n = 3 pages will be lost in the first output tray.
= 3 pages of information are controlled to be transferred onto N = 4 pages of paper.

Next, FIG. 6 shows details of the flow.

Here, n is the number of pages of output information, N is the number of pages to be fed, Tc, k ₁ , k ₂ , k ₃ and ΔT are constants, i, J and l are counter variables, AT, Tc ', t △
Is a variable.

At step 201, necessary constants are set. In step 202, print end (data end,
If it is not checked whether or not there is no remaining paper, etc., the process proceeds to step 203. In step 203, n pages (initially n = 1 page) are output, and in steps 204 to 207, N pages (first N). = 1 page). Step two
In Steps 209 and 210 for inputting the output time t of the photosensor at 08, the output time t is Tc = ΔT ≦ t ≦ Tc
It is checked whether or not it is + ΔT. If it is within those times, the process proceeds to step 211, and if not, the process proceeds to step 221. Step 221 is a process in the case where the deviation is more than the allowable time, and the paper discharge switching solenoid is controlled so as to discharge the paper of N pages to the second output tray, and the counter variables i and l are incremented by 1 in step 222. . Then, in step 223, the value of i is compared with the constant k ₁ , and i>
When the relationship k ₁ is established, a status code is output to a display device (not shown) in step 224, and the printer device is stopped. If i ≦ k _{1, the} output information page remains as it is, and the process proceeds to step 220, where the number of fed pages N
Is increased by 1. That is, n pages are output on N + 1 page paper. That is, in steps 222 and 223, when the situation in which the paper does not reach the photosensor 47 within the specified time and the paper is discharged to the second output tray occurs k ₁ times in succession, the apparatus is notified of the abnormal situation. To do. Abnormality in this case means a phenomenon such as slippage due to wear of the roller at the paper feed roller portion or defective registration at the registration roller portion. If i ≦ k ₁ in step 223,
Compare the value of l with the value of k ₃ . The variable counter 1 counts the cumulative number of processes branched to the step 221, and when the number exceeds the constant k ₃ , the process proceeds to step 224, and otherwise the process proceeds to step 220.

On the other hand, when the timing relationship works normally, the routine proceeds to step 211, where the variable counter i is set to zero. As a result, the timing deviation is cleared even if it continues up to k ₁ times, and the apparatus does not stop. In step 212, the page of output information is advanced by one page. At step 213, the result obtained by integrating the time t is AT
In step 214, the value of the variable counter j is checked. That is, for each numerical value of j = k ₂ , step 2
Proceed to 15. If j is not 0, the process proceeds to step 219,
Decrement the value of j by one and proceed to step 220.

In step 215, the value of j is initialized. In step 216, the integrated value obtained in step 213 is divided by j times to obtain an average value. The deviation Δ between the value Tc ′ obtained here and the initial setting value Tc is calculated in step 217.
Then, in step 218, this Δ is set as Tr ₂ + Δ as a new constant Tr ₂ with respect to the off time Tr _{2 of the} registration clutch shown in FIG. By this operation, it became clear that the operation off time of the registration clutch is controlled so as to correct the average timing deviation Δ. That is, △
If Δ is a positive value, the paper conveyance timing is too early and the leading edge of the image becomes large, so that the waiting time due to registration is increased. On the other hand, △
If is negative, the paper is conveyed too late and the leading edge of the image becomes small, so that the waiting time due to the registration is reduced. If step 218 is completed, the process proceeds to step 220.

Here, if the value of k ₂ is 1, it is obvious that the operation-off time of the registration clutch is corrected every time one sheet is fed. Generally, k ₂ is 100 to 500, k ₁
4th to 8th would be appropriate.

With respect to the processing flow described above, the following measures may be taken. For example, in a device body having only one output tray, when a time lag is detected to be out of an allowable value, it is treated as a jam. Is to stop the operation of the device.

In this embodiment, the example in which the off time of the registration roller, that is, the stationary time of the paper is controlled has been described. However, this method is an example in which the timing of the paper to be conveyed is controlled. This case, which is to make the writing timing variable, will be described with reference to FIG.

After Tl time from the start of paper feeding, laser writing on the drum was performed, and the time when the leading edge of the paper was detected by the photosensor after passing through the registration roller was deviated from the reference set time Tc by Δ. At this time, the deviation amount Δ is calculated as T1−Δ with respect to Tl in the next writing. In this case as well, Δ is added with a sign, and if Δ is a positive value, the timing at which the paper is conveyed is too early, and if Tl is left as it is, the leading edge of the image becomes large. If Δ is a negative value, the timing at which the paper is conveyed is too late, and if Tl remains as it is, the leading edge of the image becomes small. Therefore, it is necessary to delay laser writing.

As described above, it has been clarified that the deviation of the image transferred on the paper is reduced by making the image writing timing variable by the delay of the paper transportation even if the paper transportation timing is left unchanged.

As described above, it is possible to determine whether or not the deviation of the image transferred on the paper is out of the standard by checking the delay of the paper conveyance, and even if it is within the standard, it can be determined according to the deviation amount. By changing the resist or the image writing timing, it is possible to further reduce the variation in the leading edge of the image. Further, in the apparatus having the second output tray, the reliability of the output paper of the first output tray which stores normal output paper by discharging the paper whose deviation exceeds the standard to the tray. It becomes possible to raise. Further, by checking the frequency of discharge to the second output tray, it is possible to know the abnormality of the conveying system by checking the cumulative output number or the constant continuous discharge number.

[0037]

As described above, according to the present invention, the amount of deviation between the visible image on the drum and the conveying timing of the paper sheet is measured in advance by the detecting means and the time measuring means, and thereafter, based on this, the amount of deviation is conveyed. Since the timing to start the transportation of the sheet to be transported or the timing to start writing with the laser beam is controlled,
It is possible to prevent the positional deviation due to the increase in the transfer speed and reduce the troublesome adjustment work.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an LBP to which an embodiment of the present invention is applied.

FIG. 2 is a partially enlarged perspective view of the LBP shown in FIG.

FIG. 3 is a block diagram of a control system of an LBP to which an embodiment of the present invention is applied.

FIG. 4 is an operation timing chart in the embodiment of the invention.

FIG. 5 is an operation timing chart in the embodiment of the invention.

FIG. 6 is a flow chart for explaining the operation of the embodiment of the present invention.

FIG. 7 is an operation timing chart of another embodiment of the present invention.

[Explanation of symbols]

 1 Laser Oscillator 14 Photosensitive Drum 47 Photo Sensor 100 CPU 108 Paper Feed Roller Clutch 109 Registration Clutch

Claims (3)

[Claims] 1. A recording device for transferring a visible image formed on a drum onto a paper sheet for recording, and a conveying means for conveying the paper sheet to a transfer position, and a conveying means for conveying the paper sheet. Detecting means for detecting the paper sheet at a predetermined position, and having a timing means for timing the detection timing of the paper sheet by the detecting means, based on the detection timing timed by the timing means, by the transport means A recording apparatus characterized by controlling a conveyance start timing. 2. The recording apparatus according to claim 1, wherein the timing means measures the detection timing of a predetermined number of sheets, and based on those detection timings, the sheets conveyed thereafter are detected. A recording apparatus characterized by controlling a conveyance start timing. 3. The visible image and the paper sheet in an apparatus for forming a latent image on a photosensitive drum by using a laser beam, and transferring the visible image obtained by developing the latent image onto a paper sheet. A method of aligning with a body, in which a detected value relating to a positional relationship between a sheet conveyed at a predetermined timing and a visible image on a photosensitive drum is measured before a recording operation on the sheet, and the detection is performed. An image alignment method characterized in that an image writing timing by a laser beam in recording on the paper sheet is changed according to a value.