JP2003223088A - Image forming apparatus and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus and its control method which can detect a dislocation of a recording medium and can compensate the writing starting position of an image with a simple and low-cost structure. <P>SOLUTION: The main body of the image forming apparatus having a printer controller 1 and an engine controller 2 is provided with a sheet detection sensor 3 that detects the dislocation of a sheet 4 and the sheet detection sensor 3 is constituted of a light emitting element 31 having an LED 32 and a light guide 33 and a light receiving element 34. In addition, a light intensity control means is provided on the light emitting element side of the sheet detection sensor 3 or a threshold setting control means according to a light reception level is provided on the side of the light receiving element. Then, the output voltage of the light receiving element 34 is fetched in a CPU 22 via a counter 24, the quantity of the dislocation of the sheet 4 is calculated by the CPU 22 and the kind of the sheet 4 is also discriminated. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic printer, an electrophotographic copying machine, or a FAX (facsimile) for forming an image on a recording medium, and more particularly to an image by detecting a misalignment of a recording medium conveyance position. The present invention relates to an image forming apparatus capable of correcting a forming position and a control method thereof.

[0002]

2. Description of the Related Art Conventionally, in this type of image forming apparatus, when a printing paper is fed from a cassette or a tray to a registration roller position by a paper feeding means, the paper is fed in a main scanning direction which is orthogonal to a conveying direction. If the paper is fed with misalignment, it does not have a function to correct the printed image in the process up to development, so an image with misalignment in the main scanning direction is formed. The Rukoto.

As an attempt to correct the above-mentioned misalignment of the paper, a reference guide plate is provided on one side of the paper to be conveyed,
A method has been proposed in which a sheet is forcibly conveyed along a reference guide plate by using skew rollers so that the sheet is conveyed along the reference guide plate.

FIG. 12 is a perspective view showing the structure of such a conventional example. In the configuration shown in the figure, the sheet is fed by the pickup roller 201 that picks up the sheet,
The sheet is conveyed along the reference guide plate 202 that is interlocked with the sheet. The lever of the reference guide plate 202 needs to be manually changed according to the sheet.

When the edge of the sheet is regulated by the reference guide plate 202, the picked-up sheet is conveyed and passes the skew roller 203. At this time, the skew roller 203, to which a predetermined tension is applied, is obliquely attached to the shaft so that the sheet follows the reference guide plate 202. Then, the sheet is conveyed obliquely by the skew rollers 203 and regulated along the reference guide plate 202.

Further, there has been proposed a method in which a motor is used and a drive flag is mechanically operated to detect the edge of the sheet.

[0007]

However, in the above-described method of conveying a sheet along the reference guide plate 202 at the time of sheet feeding, only the skew roller 203 is provided in order to deal with all of various sheet sizes. Correcting the position of the sheet with the guide sheet along the reference guide plate 202 by changing the sheet size from A3 sheet (312 mm) to postcard (100.5
All paper sizes up to (mm) will be supported,
It is necessary to provide the skew roller 203 for each sheet, which makes the mechanism complicated.

Further, it is necessary to set the reference guide plate 202 for each paper size, and the configuration is complicated even in the method of mechanically driving the flag using a motor. Therefore, it is disadvantageous in terms of installation space and cost.

Further, when the paper is conveyed in the so-called vertical type, it is necessary to suck the fed paper so that the paper does not fall under its own weight. In order to correct the position of the paper itself, it is necessary to provide a mechanism for separating the paper from the suction member in order to free the paper once, and then,
It is necessary to control the paper so that the paper is free and the position of the paper follows the reference guide.

Further, in an image forming apparatus having a double-sided mechanism, when the front and rear transport paths of the paper are different, the paper position during the front transport and the paper position during the back transport are different,
When the paper shift occurs in the main scanning direction, an image with a shift in the print image positions on the front surface and the back surface is formed.

The present invention has been made in view of the above problems, and is an image forming apparatus capable of detecting a positional deviation of a recording medium and correcting an image writing start position with a simple and low-cost configuration. An object is to provide an apparatus and a control method thereof.

[0012]

The image forming apparatus and the control method thereof according to the present invention are configured as follows.

(1) In an image forming apparatus for forming an image on a recording medium according to an image signal, a detecting means for detecting a positional deviation of the recording medium with respect to a direction orthogonal to the conveying direction of the recording medium is provided, and A calculation unit that calculates the amount of positional deviation of the recording medium in the main scanning direction based on the detection result of the detection unit, and a correction unit that corrects the writing position of the image on the recording medium according to the calculation result of the calculation unit are provided. .

(2) In the above (1), the detecting means is
It has a discrimination function of detecting the conveyed recording medium itself and discriminating the type of the recording medium.

(3) In the above (1) or (2),
The detection means is adapted to perform a plurality of detection operations by a plurality of detection locations provided in the main scanning direction of the recording medium and a plurality of detection locations provided in the sub scanning direction.

(4) In any one of the above (1) to (3), the detection means is a transmission type or reflection type detection system equipped with a light emitting element and a light receiving element, and the light from the light emitting element depends on the recording medium. The position of the recording medium is detected depending on whether or not the light is shielded.

(5) In the above (4), the light receiving element is
An array type non-contact type optical sensor is configured.

(6) In the above (5), the light emitting element is
The light from the point light source is converted into a linear light source by the light guide so that the light is evenly distributed on the light receiving surface of the light receiving element.

(7) In any one of the above (4) to (6), a control means for controlling the lighting time of the light emitting element to control the amount of emitted light is provided.

(8) In the above (7), the control means is
In the initialization operation until the image forming apparatus main body is powered on and ready for printing, a calibration function is provided, and the light emission amount of the light emitting element is controlled according to the analog output value obtained from the light receiving element.

(9) In the above (7) or (8),
The control means controls the amount of light emitted from the light emitting element at predetermined intervals.

(10) In any one of the above (7) to (9), the control means has a function of judging a failure by comparing the output value of the light receiving element with a preset reference value.

(11) In any one of the above (4) to (10), the light receiving element has a function of masking a portion other than a necessary detection area according to the size of the recording medium.

(12) In any one of the above (4) to (10), a comparator for comparing the analog output value from the light receiving element with a predetermined threshold value and binarizing it, and a predetermined value according to the output from this comparator. The counter has a counter for counting, and the position of the recording medium is detected by the count value.

(13) In the above (12), the process of performing a predetermined count operation according to the output from the comparator is repeated a plurality of times to detect the position of the end portion of the recording medium, and the count value should be equal to or more than the predetermined count number. In that case, it was judged as something abnormal and the correction control of the image writing position was not performed.

(14) In the above (12) or (13), the threshold value of the comparator is set to a predetermined value following the analog output value of the light receiving element.

(15) In the above (12) or (13), the threshold value of the comparator is automatically set based on the output value obtained from the comparator and a predetermined count number stored in advance. .

(16) In any one of the above (12) to (15), the dirt on the light receiving surface of the light receiving element is judged based on the difference between the output value obtained from the comparator and the predetermined count number stored in advance. I did it.

(17) In any one of the above (12) to (16), the writing position in the main scanning direction is controlled based on the result of performing a predetermined arithmetic processing on the output value obtained from the comparator. .

(18) In a method of controlling an image forming apparatus for forming an image on a recording medium according to an image signal, a positional deviation of the recording medium with respect to a direction orthogonal to the conveying direction of the recording medium is detected, and the detection result is detected. Based on the above, the position shift amount of the recording medium in the main scanning direction is calculated, and the writing position of the image on the recording medium is corrected according to the calculation result.

(19) In (18) above, the conveyed recording medium itself is detected and the type of the recording medium is discriminated.

(20) In any one of (18) and (19) above, a plurality of detection points provided in the main scanning direction of the recording medium and a plurality of detection points provided in the sub-scanning direction are used to perform detection operations a plurality of times. did.

(21) In any one of the above (18) to (20), whether the light emitting element and the light receiving element detect the transmission method or the reflection method and whether or not the light from the light emitting element is blocked by the recording medium. The position of the recording medium is detected by.

(22) In the above item (21), the amount of emitted light is controlled by controlling the lighting time of the light emitting element.

(23) In the above item (22), the amount of light emitted from the light emitting element is controlled in accordance with the analog output value obtained from the light receiving element in the initialization operation until the image forming apparatus main body is powered on and printing becomes possible. I did it.

(24) In the above item (22) or (23), the amount of light emitted from the light emitting element is controlled at predetermined intervals.

(25) In any one of the above (22) to (24), the failure judgment is made by comparing the output value of the light receiving element with a preset reference value.

(26) In any one of the above (21) to (25), the area other than the necessary detection area of the light receiving element is masked according to the size of the recording medium.

(27) In any one of (21) to (25) above, the analog output value from the light receiving element is compared with a predetermined threshold value to be binarized, and a predetermined count operation is performed according to the binary output, The position of the recording medium is detected by the count value.

(28) In the above (27), the process of performing a predetermined counting operation in accordance with the binary output is repeated a plurality of times to detect the position of the end portion of the recording medium. It is judged that something is wrong and the correction control of the image writing position is not performed.

(29) In (27) or (28) above, the threshold value to be compared with the analog output value from the light receiving element is set to a predetermined value following the analog output value of the light receiving element.

(30) In the above (27) or (28), the threshold value to be compared with the analog output value from the light receiving element is based on the output value obtained from the comparison result and a predetermined count number stored in advance. I set it automatically.

(31) In any one of the above (27) to (30), the light receiving surface of the light receiving element is contaminated due to the difference between the output value obtained from the result of comparison with the threshold value and the predetermined count number stored in advance. I decided to judge.

(32) In any one of (27) to (31) above, the writing position in the main scanning direction is controlled based on the result of performing a predetermined arithmetic processing on the output value obtained from the comparison result with the threshold value. I did it.

[0045]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

In the embodiment of the present invention, the main body of the image forming apparatus is provided with a sheet position deviation detecting sensor unit, and the detecting sensor unit is installed in the sheet conveying direction and the direction orthogonal to the conveyed sheet. Further, a means for detecting the feeding position state of the sheet fed to the predetermined position from the sheet feeding side, a calculating means for calculating the feeding position deviation amount of the sheet based on the detection result, and this calculating means. The writing start position of the image to be printed is changed based on the feeding position shift amount calculated by.

The above-mentioned detecting means can also serve as the medium detecting means for the paper, and can detect the positional deviation of the paper in the direction orthogonal to the paper conveying direction. Further, the sheet position can be detected by including a light emitting element and a light receiving element, and whether or not to block light. The detection means constitutes an array-type non-contact type optical sensor in which a plurality of element chips that receive the amount of light uniformly emitted are connected.

The means for calculating the deviation amount of the paper by the output from the detecting means is an arithmetic unit (CPU), and the paper position deviation amount is calculated by a counter process in the arithmetic unit. Further, it has means for changing the writing start printing position of the image from the calculation result. Also, depending on the output voltage from the light receiving element and the output result from the comparator, dirt,
It also has a self-diagnosis function such as disconnection and failure.

[Embodiment 1] FIG. 1 is a block diagram showing a circuit configuration of an image forming apparatus according to the present invention, and shows an overall control configuration. This image forming apparatus includes a printer controller 1, an engine controller 2, and a unitized sheet detection sensor (detection means) 3. Reference numeral 4 denotes a sheet which is a recording medium.

The printer controller 1 is a CPU 1
1, writing start position control section (correction means) 12, and FiF
It has a memory 13. The engine controller 2 has a signal processing unit 21, and this signal processing unit 21
CPU (control means, calculation means) 22, counters 23, 2
4, a transistor 25, a comparator (comparator) 26,
And an inverter (inverter) 27. The paper detection sensor 3 includes a light emitting element 31 and a light receiving element 34, and the light emitting element 31 includes an LED 32 and a light guide (light guide body) 33.

FIG. 2 is a block diagram showing the system configuration of this embodiment. The image forming apparatus of this embodiment receives and expands image information in a predetermined description language sent from the host computer 5, and each color component has 8 bits (D0 to D0).
D (7) Y (yellow), M (magenta),
The printer controller 1 includes a signal processing unit 14 that outputs C (cyan) and K (black) image signals, and an engine controller 2 that mainly performs mechanical control.

Various control signals other than image signals are transmitted and received between the printer controller 1 and the engine controller 2 in the form of serial communication. These signals include
A synchronization signal (TOPS) indicating the sub-scanning direction of the page sent from the engine controller 2 to the printer controller 1
YNC), a synchronization signal (LSYNC) in the main scanning direction, and the like.

The printer controller 1 applies well-known masking (undercolor removal method) to the input R, G, B image signals to convert them into Y, M, C, K image signals, and then the image. As an 8-bit signal for each color component,
In the FiFo (FastInFastOut) memory 13, the printer controller 1 and the engine controller 2 are connected.
Of the data transfer clock (VCL
K) and output sequentially.

On the other hand, when the print start command is sent from the printer controller 1, the engine controller 2 starts driving the scanner motor 57. At this time, the reference clock from the reference oscillator built in the exposure apparatus (not shown) is divided by the frequency divider, and the phase difference between this divided clock and the feedback signal from the scanner motor 57 becomes a predetermined phase difference. As described above, the scanner motor 57 is rotated at a constant speed by the phase control circuit 28.

The rotation of the scanner motor 57 is transmitted to the polygon mirror 53 to rotate the polygon mirror 53 at a constant speed. When the polygon mirror 53 reaches steady rotation, the image signal is transferred from the printer controller 1 described above. Based on this image signal, the engine controller 2 causes the modulation amplifier 51 to convert the electric signal (image signal) into a laser signal. As a result, the semiconductor laser 52 is turned on toward the polygon mirror 53 that is steadily rotating, and the photosensitive drum 56 is irradiated with laser light via the polygon mirror 53, the imaging lens 54, and the reflection mirror 55.

When the laser light is emitted, the BD detection sensor 58 arranged on the main scanning axis detects the laser light and outputs a BD signal as a horizontal synchronizing signal. As a result, the photosensitive drum 56 is scanned and exposed by the laser light in synchronization with the BD signal, and an electrostatic latent image is formed. This electrostatic latent image is developed by a developing device (not shown).

On the other hand, although not shown, when the conveyor belt is rotated by a drive motor to reach a predetermined position, a vertical synchronization signal (TOPSYNC) is generated from the detection sensor. Then, after the vertical synchronization signal (TOPSYNC) is output, the BD signal generated by the detection sensor 58 in the exposure apparatus is used as a horizontal synchronization signal (LSYNC), and an image signal (in sync with the horizontal synchronization signal (LSYNC) ( VD
O) are sequentially sent to the semiconductor laser 52.

Further, the CPU in the engine controller 2
22 and the CPU 11 incorporated in the signal processing unit 14 in the printer controller 1 perform serial communication via the CMD / STS communication line to exchange control signals and synchronize the operations of the printer controller 1 and the engine controller 2.

FIG. 3 is a sectional view showing the construction of the paper transport system of this embodiment. By arranging the sheet detection sensor 3 for detecting the deviation of the sheet in the main scanning direction on the predetermined conveyance path before the pre-registration detection sensor 64 for detecting the registration roller 65, the deviation amount of the sheet can be reduced. The case of detection is shown as an example.

The paper fed from the multi-tray 61 or the paper set in the paper feed tray 62 and guided to the conveying path 66 by the pickup roller 63 has the leading edge detected by the pre-registration detection sensor 64. The surface of the detected sheet is printed according to the conveyance path 66, passes through the fixing roller 67, and the trailing edge is detected by the sheet discharge sensor 507.
Then, the paper is discharged to the outside by the paper discharge roller 69.

When the back side of the printed paper is also printed, the above-mentioned paper having an image fixed on the front surface is switched back and forth by driving the paper discharge roller 69 in a double-sided conveyance path. The sheet is again guided to the conveyance path passing through 70 and overlapping with the conveyance path from the sheet feeding tray 62 side, and is conveyed. Then, by supplying again from the double-sided conveyance path 70, it becomes possible to print on the back surface of the paper.

Here, the above-mentioned sheet edge detecting mechanism will be described with reference to FIG. The light emitting element 31 and the light receiving element 34 of the paper detection sensor 3 are attached to one end position of the paper 4 in the paper transport path. That is, the light emitting element 31 serving as a light emitting portion is arranged above the portion corresponding to the paper end of the paper conveying path, and the light receiving element 34 serving as a light receiving portion is arranged below. Then, the sheet edge exists between the light emitting element 31 and the light receiving element 34.

In the example shown in FIG. 4, the sensor 3 is arranged at the right end of the sheet 4, but the same applies when it is arranged at the left end on the opposite side. Further, it may be arranged on both sides of the edge of the sheet 4. The light emitting element 31 and the light receiving element 34 may be arranged upside down.

FIG. 5 is a diagram showing the paper detection system of this embodiment, showing the details of the paper detection sensor 3. The light emitting element 31 is composed of an LED 32 which is a point light source and a light guide 33 which uniformly converts the point light emission into a linear light source and irradiates it. The light receiving element 34 is generally composed of a photodiode.

FIG. 6 is a flow chart showing the control operation of the present embodiment based on the above-mentioned structure, (a) shows the control routine of the electric firmware after the power is turned on,
FIG. 7B shows a control routine for detecting a paper position deviation. The control process shown in this flowchart is performed by the CPU 11 and the engine controller 2 of the printer controller 1.
The CPU 22 executes the program according to a program stored in advance.

When the initial adjustment shown in FIG. 6A is started, first the loop setting of the light receiving area is performed (S1), and the sensor failure detection operation is performed (S2). If there is no sensor failure (S3), then the light quantity of the LED 32 is adjusted (S4),
If the sheet 4 is not an OHT sheet (S5), then the threshold value is adjusted (S6). Then, if the threshold value is not an error (S7), this control loop is ended (S8). If the sensor is faulty (S3), as with the threshold error (S7), the sensor dirt is warned (S10), the default setting is performed (S11), the paper position misalignment adjustment is prohibited (S12), and the control loop ends. Yes (S8). If an OHT sheet of paper is detected when the sensor fails (S9), OH
A T determination warning is given (S13).

Further, when the paper position detection of FIG. 6B starts, if there is no sensor stain warning described above (S2).
1) Detect a paper position deviation (S22). If the paper positional deviation is not guaranteed (S23), the positional deviation is corrected (S24), and if it is not guaranteed (S23), the positional deviation is not guaranteed (S25).

Next, the above-mentioned control operation will be described in detail with reference to FIGS. FIG. 7 shows a light receiving sensor (light receiving element 3
4) showing the detection area, FIG. 8 is a correlation diagram showing the relationship between the lighting time of the LED 32 and the output level (output voltage V) of the light receiving element 34, and FIG. 9 is an explanatory diagram showing the light amount control by time axis control. 10 is a diagram showing the timing of counting the amount of misregistration of the sheet, FIG. 11 is a diagram showing the method of detecting the misregistration of the sheet of this embodiment, and FIG. The relationship is shown, and FIG. 3B shows the output level (output voltage V) of the light receiving element 34 of the transmission type detection method.

When the image forming apparatus is powered on, the light receiving element 34 receives the predetermined CLK signal and RST signal. Then, in the initialization period before the paper 4 is conveyed, first, as shown in FIG. 7, the light receiving area of the light receiving element 34 for detecting the positional deviation of the paper 4 is reduced in influence of disturbance noise and dirt on the light receiving surface. To achieve this, for example, the first area is A3 to EXE horizontal size, the second area is B4 / B5 horizontal to LGL / LTR vertical size, and the third area is EXE vertical to B5 vertical size according to the media size to be used. It is divided into three areas. Further, the first and second detection positions for detecting the medium are also set in the longitudinal direction (main scanning direction) of the light receiving element 34.

Next, the LED 32 is fully turned on once, and the analog output from the light receiving element 34 is converted into digital data by the A / D converter inside the CPU (arithmetic processing unit) 22 and stored in the register inside the same. This digital data is represented by 8 bits (00 to FF (HEX)), and its output graph is shown in FIG. At this time, L
Since the ED 32 is fully lit, the analog output from the light receiving element 34 is a saturated voltage output.
Therefore, the voltage value stored in the internal register of the CPU 22 indicates FF (HEX).

Here, if the voltage level taken in the internal register of the CPU 22 is 40 (HEX) even though the light emitting element 31 is turned on at maximum,
In the actual failure detection, if the voltage level is lower than the maximum voltage level, it is determined that the output voltage cannot be obtained due to the wire breakage or the failure of the light emitting element 31 or the light receiving element 34. At this time, the determined flag (Flag) signal is used to notify the user of the failure on the operation panel via the controller 1.

On the other hand, when the voltage level is higher than the set predetermined voltage level, it is judged that the light amount from the light emitting element 31 is being received by the light receiving element 34, and the process shifts to the light amount adjusting routine shown in FIG. .

Controlling the switching time of the transistor 25 to control the light amount of the LED 32 will be described with reference to FIG.

The processing time (t) for one line of the light receiving element 34 is controlled with a resolution of 8 bits. That is, FF
It has a variable switching step width from (HEX) to 00 (HEX). The CPU 22 uses the FF (HE
By sequentially decrementing from X), the ON time of the transistor 25 is gradually shortened to attenuate the emitted light amount, and the value converted by the internal A / D converter and stored in the register is also gradually decreased. descend. Here, provisionally, the on-time of the transistor 25 is calibrated by feedback control so that the saturation level becomes −Nv. By such control, the light amount level can be set to a predetermined voltage.

Then, the arithmetic expression in the firmware for adjusting the LED light quantity shown in FIG. 6 is as follows: LED light quantity correction value = number of steps at target light quantity * Nv value / (AD value at maximum light quantity-A when light is off)
D value).

On the other hand, an algorithm for gradually increasing the amount of emitted light by operating the switching time control in increments from 00 (HEX) to FF (HEX) so as to achieve the set predetermined voltage level is also easy.

As the timing for controlling the light amount, the above-described calibration operation is executed during the initialization period after the power supply to the image forming apparatus is turned on, and the light amount control is performed for each predetermined number of printed sheets (cycle). Furthermore,
By monitoring the analog output voltage by the CPU 22 in real time, it is possible to control the light amount when the voltage becomes lower than the set voltage.

Next, the threshold adjustment will be described. In order to set a predetermined threshold value, a threshold value adjustment routine operates after the above-described light amount adjustment. Here, too, according to the paper size of the medium, an area other than the necessary detection area of the light receiving sensor is electrically masked so that the influence of disturbance noise and dirt can be reduced.

Therefore, in this embodiment, the threshold value can be set in each sheet position deviation detection area according to the medium size. The specific threshold value is set by comparing the count number in the preset mask area with the count number obtained by counting “Hi” which is the binary information output from the comparator 26, and when a difference of a predetermined value or more occurs. Judges that the sensor surface is dirty and cannot count a predetermined number of counts, lowers the threshold coefficient once set, and repeats the above operation until the number of counts is set again.

The calculation formula for the threshold voltage adjustment in the firmware is: threshold adjustment level = (set light amount voltage level−light shielding voltage level) * threshold coefficient + light shielding voltage level.

Even if the threshold coefficient is lowered, if there is a difference more than the number of counts provided internally, it is determined that the light receiving surface of the sensor is dirty with paper dust or the like, and a dirt flag signal is output. , A warning is given to the user on the operation panel via the controller 1. The user can clean the sensor surface with a brush or the like according to the notified warning signal. Then, the threshold setting is completed in the above sequence.

The output from the light receiving element 34 is turned off (OFF) when the light from the light emitting side is blocked by the paper 4, so that it is "Hi" depending on the position of the paper edge.
The position where "Lo" is switched is variable. By counting the output from the light receiving sensor by the counter 24 via the comparator 26, the edge of the paper can be detected.

The calculation logic waveform of the sheet edge is shown in FIG. 10, and the operation of the counter 24 shown in FIG. 1 will be described.

The signal processing section 21 of the engine controller 2
A counter 23 therein divides the frequency of the oscillator to generate a predetermined CLK signal and a reset signal. The light receiving element 3 receives the CLK signal and the reset signal from the counter 23.
When it is sent to 4, it is possible to obtain a predetermined analog signal whose output level varies depending on whether or not the light is blocked by the paper 4. This analog signal is input to the comparator 26 at the subsequent stage and compared with a predetermined threshold value that has been set, whereby binarization processing is performed.

Here, since the signal logic "Lo" from the comparator 26 is input to the inverter 27, the enable terminal of the counter 24 becomes "Hi", and the counting operation is performed in synchronization with the reference CLK. on the other hand,
When the signal logic from the comparator 26 becomes “Hi”,
The enable terminal of the counter 24 is inverted to “Lo”, and its count value (n) is held in synchronization with the reference CLK. Here, the count-up operation is performed from (0) to (n) for convenience.

The above count-up operation is performed n times to average the count values, and the "Hi" count number obtained as a result is compared with a predetermined count number stored in advance in an internal register. As a result, if the number of counts stored in the register is greater than or equal to the predetermined count, it is determined that the amount of misalignment is significantly different (erroneous detection) due to bending of the leading edge of the paper (media), and the correction of the image writing position is not performed. Not performed. Therefore, the image writing position is printed with the default printing accuracy.

On the other hand, if it is within the predetermined count number, the count value (n) calculated by the counter 24 is calculated by the CPU 22.
Then, the calculation processing is performed to calculate the deviation amount of the sheet 4.
The calculation result is transmitted to the CPU (arithmetic processing unit) 11 on the printer controller 1 side by a CMD / STS signal. The printer controller 1 receives the calculated value, and controls the writing start position 12 of the image to control the FiFo (FastInFastOut) memory 13 for developing the image. By adding or subtracting the position shift amount to the writing and reading control of the FiFo memory 13, the writing position of the image is controlled and the image signal is sent to the engine controller 2.

Since the image is printed from the corrected image writing position, the image can be drawn from the predetermined writing position set from the edge of the paper (media).

Next, it will be described that the sheet detection sensor 3 also has a function of discriminating the type of the sheet (media) itself. Here, in addition to the fed plain paper, for example, OH
It is also possible to double as a sheet discrimination such as a T sheet.

FIG. 11 shows a method of detecting the positional deviation of the sheet. The transmissive sheet detection sensor 3 has an O
Since the HT sheet has a property of transmitting light, the output value is larger than that of plain paper. Here, a case of using a transmission type will be described with reference to FIG.

The calibration operation is performed during the initialization period before the sheet 4 is conveyed onto the sheet detection sensor 3. First, the LED 32 is caused to emit light to receive the light receiving element 3
The analog output level obtained from 4 is sent to the CPU 22. In the CPU 22, the input analog value is converted into digital data by the internal A / D converter and stored in the internal register. The value stored in this register is used as a reference voltage, and a voltage that is, for example, 1/2 of the reference voltage is used as a threshold voltage.

Thus, in the case of plain paper or the like, the light is shielded by the amount of light received by the light receiving surface of the light receiving element 34, so that the analog output level becomes lower than the threshold voltage. Meanwhile O
In the case of an HT sheet or the like, light is transmitted, so that the analog output level increases above the threshold voltage.

Here, in order to avoid the influence of dirt on the light-receiving surface of the light-receiving element 34, two detection positions, a first and a second position, are provided in the main scanning direction, but these detection positions are set arbitrarily. be able to. Further, by performing the detection operation N times in the sub-scanning direction as well, it is possible to reduce erroneous detection due to dust or the like adhering to the medium (paper), and to perform the detection operation with higher accuracy. With this configuration,
It is also possible to determine the type of the sheet 4 conveyed on the sheet detection sensor 3.

Further, according to the above media discrimination, the OHT
When the sheet is determined, the image writing start position is not corrected as described above, and printing is performed with the default printing accuracy.

In the present embodiment, the analog voltage output from the light receiving element 34 is A / D converted and held in the register to determine the paper (media). However, for example, the comparator 26 provided in the latter stage of the analog output may perform binarization by a threshold voltage set in the same manner to make a digital determination, and input to the I / O port of the CPU 22. By such means, it is easy to have the function of discriminating the paper (media).

As described above, according to this embodiment, the image forming apparatus main body is provided with the sheet misalignment detecting means, and the light emitting element side of the detecting means is provided with the light quantity control means, or the light receiving side is provided with the light receiving level according to the light receiving level. A threshold setting control means is provided. Therefore, with a simple and low-cost configuration, it is possible to detect the positional deviation of the recording medium and correct the image writing start position.

In other words, the non-contact sensor that detects the amount of deviation of the sheet 4 and also determines the sheet is used, and even if there is a variation in the detection sensor or a light amount deterioration due to dirt durability, the print image is not lost and an appropriate print position is obtained. The image can be printed on the sheet, and the sheet can be reliably determined. Further, it has a self-diagnosis function and a protection function such as a failure of the detection unit and an erroneous detection, so that the detection for practical use becomes possible.

Although the color image forming apparatus has been described in the above embodiment, it is needless to say that it can be applied to a so-called monochrome printer.

[Embodiment 2] In Embodiment 2 and each of the embodiments described below, the operation of the sheet detection sensor 3 itself is the same as that of Embodiment 1 described above, and therefore the description thereof is omitted. Further, the other configurations are similar to those in FIGS.

In the circuit configuration shown in FIG. 1, in the first embodiment, the light emission amount of the LED 32 of the light emitting element 31 can be controlled and the threshold value setting of the comparator 26 can also be controlled to a predetermined value, but either one can be changed. It may be controlled. In other words, if the amount of emitted light is set to a fixed value,
It is conceivable that the analog output level converted according to the amount of received light may be deteriorated or lowered due to the influence of individual variations, dirt in the main body of the apparatus, and the like.

Therefore, the function similar to that of the first embodiment may be provided only by controlling the threshold voltage of the comparator 26 according to the analog output voltage level. On the contrary, a predetermined analog output can be obtained by setting the threshold voltage to a fixed value and controlling the amount of light emitted from the LED 32 in the same manner as the light amount control described in the first embodiment.

[Third Embodiment] In the third embodiment, regarding the positional deviation of the sheet 4 described in the first embodiment, the positional deviation amount is calculated based on the binarized signal through the comparator 26. is there. Then, in the first embodiment, when the paper (media) is discriminated, the analog output A of the light receiving element 34 is output.
Although the means for discriminating based on the A / D value has been described, the positional deviation detecting means for the sheet 4 also uses the CP value according to the A / D value.
It is also possible to serve as the comparator 26 by comparing with the value stored in the register inside the U, and the comparator 2 for detecting the positional deviation of the sheet 4 described in the first embodiment.
It is also possible to reduce 6.

[Fourth Embodiment] In the fourth embodiment, as described in the first embodiment, the value obtained by detecting the misalignment of the sheet is set to CP.
A calculation process is performed in U22 to calculate the deviation amount of the sheet 4. Then, the result is transmitted to the CPU 11 on the printer controller 1 side by the CMD / STS signal, and the printer controller 1 side receives the calculated value and controls the Fifo memory 13 which develops the image by the image writing position control unit 12. However, the LSYN generated from the BD signal inside the engine controller 2 has been described.
The C signal is changed according to the calculated value of the deviation amount of the sheet 4, the changed LSYNC signal is sent to the printer controller 1, and the LSYNC signal received by the printer controller 1 is received.
The image may be transmitted according to the C signal.

[0104]

As described above, according to the present invention,
With a simple and low-cost configuration, it is possible to detect the positional deviation of the recording medium and correct the image writing start position.

Further, it is possible to reliably detect the edge of the sheet by absorbing the variations in the light emitting element and the light receiving element and without being affected by dirt deterioration due to durability, noise in the apparatus, etc. It is possible to determine. Furthermore, even if erroneous detection due to failure or dirt is detected and notified, or there is no control function, it can be applied practically, greatly simplifying the installation space and reducing cost significantly. It is possible to contribute to.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of an image forming apparatus according to the present invention.

FIG. 2 is a block diagram showing a system configuration of an embodiment of the present invention.

FIG. 3 is a cross-sectional view showing the configuration of the paper transport system of the embodiment.

FIG. 4 is an explanatory view showing a paper edge detection mechanism of the embodiment.

FIG. 5 is an explanatory diagram showing a paper detection method of the embodiment.

FIG. 6 is a flowchart showing the control operation of the embodiment.

FIG. 7 is an explanatory diagram showing a detection area of a light receiving sensor.

FIG. 8 is a correlation diagram showing a relationship between an LED lighting time and an output level.

FIG. 9 is an explanatory diagram showing light amount control according to the embodiment.

FIG. 10 is a diagram showing the timing of counting the amount of misalignment of paper.

FIG. 11 is an explanatory diagram showing a sheet misalignment detection method according to the embodiment.

FIG. 12 is a perspective view showing a configuration of a conventional example.

[Explanation of symbols]

1 Printer controller 2 engine controller 3 Paper detection sensor 4 sheets (recording medium) 5 Host computer 11 CPU 12 Writing position control section (correction means) 14 Signal processing unit 21 Signal processing unit 22 CPU (control means, calculation means) 23 counter 24 counter 25 transistors 26 Comparator 27 inverter 28 Phase control circuit 31 light emitting device 32 LEDs (point light source) 33 Light guide (light guide) 34 Light receiving element 51 Modulation amplifier 52 Semiconductor laser 53 polygon mirror 54 Imaging lens 55 Reflective mirror 56 photoconductor drum 57 Scanner Motor 58 BD detection sensor 61 multi tray 62 paper tray 63 Pickup roller 64 Pre-registration detection sensor 65 Registration roller 66 transport path 67 fixing roller 68 Paper ejection sensor 69 paper ejection roller 70 double-sided transport path

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 21/00 510 B41J 3/00 M 5C074 H04N 1/036 G03G 15/04 120 1/113 H04N 1/04 104A 1/29 F term (reference) 2C362 BB28 BB40 CB49 CB53 CB57 2H027 DA01 DA07 DA32 DA41 DC04 DC10 DE02 DE07 DE09 EC02 EC06 EC07 EC09 EC10 EC12 EC18 EC20 ED04 ED06 ED17 EE01 EA01 HA04 HA04 OH01 HA04 OH01 KA04 HA04 HB09 HB20 ZA07 2H076 AB05 AB12 AB22 AB67 AB68 AB73 AB76 CA01 CA16 CA17 DA41 5C051 AA02 CA07 DB02 DB22 DB24 DB30 DC03 DE02 FA01 5C072 AA03 BA02 HA02 HA09 HA13 HB11 HB13 XA01 5C074 AA08 AA10 DD0816 A02

Claims (32)

[Claims] 1. An image forming apparatus for forming an image on a recording medium according to an image signal, further comprising a detecting means for detecting a positional deviation of the recording medium in a direction orthogonal to a conveying direction of the recording medium, and the detecting means. A calculation unit that calculates the amount of positional deviation of the recording medium in the main scanning direction based on the detection result of the recording unit; and a correction unit that corrects the write start position of the image on the recording medium according to the calculation result of the calculation unit. An image forming apparatus characterized by. 2. The image forming apparatus according to claim 1, wherein the detection unit has a discrimination function of detecting the conveyed recording medium itself and discriminating the type of the recording medium. 3. The detection means performs a detection operation a plurality of times by a plurality of detection points provided in the main scanning direction and a plurality of detection points provided in the sub-scanning direction of the recording medium. Image forming device. 4. The detection means is a transmissive or reflective detection method including a light emitting element and a light receiving element, and determines the position of the recording medium depending on whether or not the light from the light emitting element is blocked by the recording medium. The image forming apparatus according to claim 1, wherein the image forming apparatus detects the image. 5. The image forming apparatus according to claim 4, wherein the light receiving element constitutes an array type non-contact type optical sensor. 6. The image forming apparatus according to claim 5, wherein the light emitting element converts the light from the point light source into a linear light source by the light guide and distributes the light uniformly to the light receiving surface of the light receiving element. apparatus. 7. The image forming apparatus according to claim 4, further comprising control means for controlling a lighting time of the light emitting element to control an amount of emitted light. 8. The control means has a calibration function in an initialization operation until the image forming apparatus main body is powered on and ready for printing, and the light emitting element emits light according to an analog output value obtained from the light receiving element. The image forming apparatus according to claim 7, wherein the light amount is controlled. 9. The control means controls the amount of light emitted from the light emitting element for each predetermined cycle.
The image forming apparatus described. 10. The image according to claim 7, wherein the control means has a function of judging a failure by comparing the output value of the light receiving element with a preset reference value. Forming equipment. 11. The image forming apparatus according to claim 4, wherein the light receiving element has a function of masking a portion other than a necessary detection area according to the size of the recording medium. 12. A comparator for comparing an analog output value from a light receiving element with a predetermined threshold value to binarize it, and a counter for performing a predetermined counting operation according to the output from the comparator, and the count value thereof. The image forming apparatus according to claim 4, wherein the position of the recording medium is detected by. 13. A process of performing a predetermined counting operation in accordance with an output from a comparator is repeated a plurality of times to detect the position of an end portion of a recording medium, and if it is equal to or more than a predetermined count number, it is judged as something abnormal. 13. The image forming apparatus according to claim 12, wherein the correction control of the image writing start position is not performed. 14. The image forming apparatus according to claim 12, wherein the threshold value of the comparator is set to a predetermined value following the analog output value of the light receiving element. 15. The threshold value of the comparator is automatically set based on an output value obtained from the comparator and a predetermined count number stored in advance.
3. The image forming apparatus according to item 3. 16. A function for judging dirt on a light-receiving surface of a light-receiving element based on a difference between an output value obtained from a comparator and a predetermined count number stored in advance. The image forming apparatus according to any one of 12 to 15. 17. The image forming method according to claim 12, wherein the write start position in the main scanning direction is controlled based on a result of performing a predetermined calculation process on the output value obtained from the comparator. apparatus. 18. A method of controlling an image forming apparatus for forming an image on a recording medium according to an image signal, wherein a positional deviation of the recording medium with respect to a direction orthogonal to a conveying direction of the recording medium is detected, and the detection result is used. A method of controlling an image forming apparatus, wherein a position shift amount of the recording medium in the main scanning direction is calculated based on the calculation result, and a writing position of an image on the recording medium is corrected according to the calculation result. 19. The recording medium itself conveyed is detected,
19. The method of controlling an image forming apparatus according to claim 18, wherein the type of the recording medium is determined. 20. The detection operation according to claim 18 or 19, wherein a plurality of detection locations provided in the main scanning direction and a plurality of detection locations provided in the sub-scanning direction of the recording medium are used to perform a plurality of detection operations. A method for controlling an image forming apparatus. 21. A light-emitting element and a light-receiving element perform a transmissive or reflective detection operation, and the position of the recording medium is detected depending on whether or not the light from the light-emitting element is blocked by the recording medium. 19. The method according to claim 18,
21. A method for controlling an image forming apparatus according to any one of 20 to 20. 22. The method of controlling an image forming apparatus according to claim 21, wherein the lighting time of the light emitting element is controlled to control the amount of emitted light. 23. The amount of light emitted from the light emitting element is controlled according to the analog output value obtained from the light receiving element in the initialization operation until the main body of the image forming apparatus is turned on and printing becomes possible. 23. The method of controlling an image forming apparatus according to claim 22. 24. The method of controlling an image forming apparatus according to claim 22, wherein the amount of light emitted from the light emitting element is controlled at predetermined intervals. 25. The method of controlling an image forming apparatus according to claim 22, wherein the failure is judged by comparing the output value of the light receiving element with a preset reference value. 26. A method of controlling an image forming apparatus according to claim 21, wherein a portion other than a necessary detection area of the light receiving element is masked according to the size of the recording medium. 27. An analog output value from the light receiving element is compared with a predetermined threshold value to be binarized, a predetermined counting operation is performed according to the binary output, and the position of the recording medium is detected by the count value. 2. The method according to claim 2, wherein
26. A method for controlling an image forming apparatus according to any one of 1 to 25. 28. A process of performing a predetermined count operation in accordance with binary output is repeated a plurality of times to detect the position of the end portion of the recording medium, and if it is equal to or more than a predetermined count number, it is judged as some abnormality and the image is detected. 28. The control method for an image forming apparatus according to claim 27, wherein correction control of the writing start position is not performed. 29. The image forming method according to claim 27, wherein the threshold value to be compared with the analog output value from the light receiving element is set to a predetermined value following the analog output value of the light receiving element. Device control method. 30. The threshold value to be compared with the analog output value from the light receiving element is automatically set based on the output value obtained from the comparison result and a predetermined count number stored in advance. 29. The method of controlling an image forming apparatus according to claim 27. 31. The contamination of the light-receiving surface of the light-receiving element is judged based on the difference between the output value obtained from the result of comparison with the threshold value and the predetermined count number stored in advance. 31. A method for controlling an image forming apparatus according to any one of 27 to 30. 32. The writing position in the main scanning direction is controlled based on the result of performing a predetermined arithmetic processing on the output value obtained from the comparison result with the threshold value. 7. A method for controlling an image forming apparatus according to any one of claims.