JP2015124046A - Image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation apparatus capable of discriminating the cause of a jam determined from a failure in detecting a recording material.SOLUTION: A conveyance path where a recording material P is conveyed is provided with a line sensor 25a and with a conveyance sensor 29a downstream from the line sensor 25a in the conveyance direction. The line sensor 25a detects an opaque recording material P conveyed along the conveyance path, and the conveyance sensor 29a detects a transparent recording material P conveyed along the conveyance path. A CPU 301 determines the type of the conveyed recording material and whether abnormality occurs to the conveyance of the recording material according to the detection result of the line sensor 25 and the detection result of the conveyance sensor 29.

Description

  The present invention relates to an image forming apparatus such as a printer, a scanner, a copying machine, or a multifunction machine in which these functions are integrated. More specifically, the present invention relates to a transport mechanism that is provided in an image forming apparatus and transports a recording material such as paper on which an image is formed.

  In the image forming apparatus, when the recording material is transported obliquely or the transport position is deviated when the recording material is transported, a shift occurs in the position or direction of the image formed on the recording material. For example, when the recording material is obliquely fed during conveyance, an image is formed obliquely with respect to the recording material. In order to align the position and direction of the image formed on the recording material, a skew correction mechanism for the recording material and a horizontal resist that corrects the position of the recording material in the direction perpendicular to the conveying direction (the width direction of the recording material) (Hereinafter referred to as “lateral registration”) There is a correction mechanism. Further, there is an image leading edge registration (hereinafter referred to as “leading registration”) correction mechanism that aligns the recording material and the position at which the image of the recording material is formed in the recording material conveyance direction.

  Patent Document 1 discloses an invention of an image forming apparatus provided with a skew feeding correction mechanism. In Patent Document 1, the skew of the recording material with respect to the conveyance direction is corrected by abutting the leading end of the recording material against a registration roller disposed on the upstream side in the conveyance direction of the recording material with respect to the image forming unit. Patent Document 2 discloses an invention of an image forming apparatus provided with a lateral registration correction mechanism. In Patent Document 2, the horizontal end position (horizontal registration) of the recording material is detected by a line sensor, and the roller itself for conveying the recording material is sandwiched so that the horizontal end position becomes a predetermined position. Together, they are shifted in a direction perpendicular to the transport direction. Thereby, the lateral registration correction of the recording material is performed.

  An image forming apparatus including both a skew feeding correction mechanism and a lateral registration correction mechanism performs skew feeding correction and lateral registration correction of a recording material using a registration roller. In addition, a line sensor for detecting the lateral end of the recording material is disposed upstream or downstream of the registration roller with respect to the recording material conveyance direction. On the upstream side of the registration roller and the line sensor, a conveying roller that rotates to abut the recording material against the registration roller is disposed. The skew correction of the recording material is performed by curving the front end side of the recording material with the front end of the recording material being abutted against the registration roller while the registration roller is stopped. Thereafter, the lateral edge position of the recording material is detected by the line sensor, and the registration roller is shifted according to the detected lateral edge position, thereby correcting the lateral registration of the recording material.

  Patent Document 3 discloses an invention of an image forming apparatus provided with a leading edge registration correction mechanism. In Patent Document 3, a sensor for detecting the presence or absence of a recording material is disposed upstream of a transfer portion that transfers an image onto the recording material in the conveyance direction of the recording material. By adjusting the conveying speed of the recording material based on the detection timing of the recording material by this sensor, the recording material and the position where the image is formed on the recording material are matched. The sensor can increase detection accuracy by using a prism reflection type sensor.

JP 2009-286547 A JP 2008-189395 A JP 2007-86726 A

  In the image forming apparatus, the type of recording material for image formation (hereinafter referred to as “paper type”) is set by the user before image forming processing is performed. In an image forming apparatus provided with a leading edge registration correction mechanism, when an OHT sheet is transported without setting an OHT (OverHead Transparency) sheet as a paper type, the prism reflection sensor may detect the transported OHT sheet. Can not. In addition, the prism reflection type sensor cannot detect the recording material even when troubles such as delay or stop of the conveyance of the recording material occur due to slippage of the conveying roller of the image forming apparatus or high load.

  As described above, when the prism reflection type sensor cannot detect the recording material, the image forming apparatus performs the same process as when the jam occurs and stops the operation. However, the cause of the failure to detect the recording material cannot be determined. In the above example, it cannot be determined whether the jam is caused by the conveyance of a recording material of a paper type different from the set paper type, or the jam occurs due to a conveyance trouble of the recording material. Therefore, for example, depending on the user, forgetting to set the paper type as the OHT sheet and continuing to flow the OHT sheet, jamming is repeated, which is a cause of lowering usability. Therefore, the improvement is desired.

  In order to solve such a conventional problem, an object of the present invention is to provide an image forming apparatus capable of determining the cause of a jam caused by a failure to detect a recording material.

  An image forming apparatus of the present invention that solves the above-described problem is provided in a conveyance path through which a recording material is conveyed, and includes a first detection unit that detects a recording material of a first paper type conveyed through the conveyance path; A second detection unit that is provided downstream of the first detection unit in the conveyance direction of the recording material and detects a recording material of a second paper type different from the first paper type; Determining means for determining whether there is an abnormality in the paper type of the recording material to be conveyed and the conveyance of the recording material according to the detection result by the first detection means and the detection result by the second detection means. It is characterized by that.

  According to the present invention, the first detection means detects the recording material of the first paper type, the second detection means detects the recording material of the second paper type, and conveys according to these detection results. It is determined whether there is an abnormality in the paper type of the recording material to be recorded and the conveyance of the recording material. This makes it possible to determine the cause of the jam due to the fact that the recording material cannot be detected by the second detection means.

1 is an overall configuration diagram of an image forming apparatus. (A)-(c) is explanatory drawing of the operation | movement which detects discrimination | determination of the kind of recording material, and the conveyance stop of a recording material. The figure showing the relationship between the kind and recording state of a recording material, and the output value of each sensor. The block diagram of a control part. (A)-(c) is a figure which shows the output value from a line sensor. 6 is a flowchart showing processing at the time of image formation. The flowchart of the process of OHT determination mode. The timing chart of the operation of the resist unit.

<Overall configuration>
FIG. 1 is an overall configuration diagram of an image forming apparatus according to the present exemplary embodiment.

  The image forming apparatus includes an image output unit 1P, a reader unit 4, and an operation unit 5. The reader unit 4 and the operation unit 5 are provided on the image output unit 1P. The operation unit 5 includes a display unit such as a display in addition to buttons and the like operated by the user, and also functions as a touch panel. The user can perform various settings for the image forming process, for example, the paper type of the recording material P used for image formation, by the operation unit 5. The reader unit 4 functions as a scanner that reads a document image. The reader unit 4 reads a document image in accordance with an instruction from the operation unit 5, generates image data of the read document image, and transmits the image data to the image output unit 1P. The image output unit 1 </ b> P performs image forming processing according to the instruction from the operation unit 5 and the image data transmitted from the reader unit 4.

  The image output unit 1P is broadly divided into an image forming unit 10, a paper feeding unit 20, an intermediate transfer unit 30, a fixing unit 40, a reverse double-side unit 50, a double-sided conveyance unit 60, a paper discharge unit 70, and a control unit 80. The image forming unit 10 includes four stations having the same configuration.

  The image forming unit 10 includes photosensitive drums 11a to 11d which are image carriers that are rotationally driven in the direction of the arrow in the drawing. Primary chargers 12a to 12d, optical systems 13a to 13d, and developing units 14a to 14d are arranged in a rotational direction of the photosensitive drums 11a to 11d at positions facing the outer peripheral surfaces of the photosensitive drums 11a to 11d. The Hereinafter, when the photosensitive drums 11a to 11d, the primary chargers 12a to 12d, the optical systems 13a to 13d, and the developing units 14a to 14d are not distinguished, the photosensitive drum 11, the primary charger 12, the optical system 13, and the developing unit are used. It is described as 14.

  The primary charger 12 uniformly charges the surface of the photosensitive drum 11. The optical system 13 forms an electrostatic latent image on the photosensitive drum 11 by irradiating the charged photosensitive drum 11 with a light beam such as a laser beam modulated according to image data. A yellow electrostatic latent image is formed on the photosensitive drum 11d in accordance with yellow image data. A cyan electrostatic latent image is formed on the photosensitive drum 11c in accordance with cyan image data. A magenta electrostatic latent image is formed on the photosensitive drum 11b according to the magenta image data. A black electrostatic latent image is formed on the photosensitive drum 11a in accordance with the black image data.

  The electrostatic latent image formed on the photosensitive drum 11 is developed with toner stored in the developing device 14. As a result, a toner image is formed on the photosensitive drum 11. The electrostatic latent image formed on the photosensitive drum 11d is supplied with yellow toner from the developing device 14d, and is visualized as a yellow toner image. The electrostatic latent image formed on the photosensitive drum 11c is supplied with cyan toner from the developing device 14c, and is visualized as a cyan toner image. The electrostatic latent image formed on the photosensitive drum 11b is visualized as a magenta toner image by supplying magenta toner from the developing device 14b. The electrostatic latent image formed on the photosensitive drum 11a is visualized as a black toner image by supplying black toner from the developing device 14a. A cleaner 15 for cleaning the surface of the photosensitive drum 11 is disposed on the downstream side in the rotation direction of the photosensitive drum 11.

  The paper supply unit 20 includes a cassette 21 that stores a recording material P such as paper on which an image is formed. As the recording material P, plain paper or an OHT sheet can be used. The recording material P stored in the cassette 21 is conveyed toward the intermediate transfer unit 30. For this purpose, the paper feeding unit 20 includes a pickup roller pair 22 that takes out the recording material P from the cassette 21 one by one, and a plurality of conveyance roller pairs 23 that convey the recording material P taken out by the pickup roller pair 22 to the registration roller pair 26. And a conveyance guide 24.

  In the conveyance path on the upstream side of the registration roller pair 26 in the conveyance direction of the recording material P, the recording material P in the direction orthogonal to the conveyance direction of the recording material P (the width direction of the recording material) and its end (lateral end). A line sensor 25a for detecting the position is provided. A black sheet 25b that absorbs irradiation light from the line sensor 25a is provided at a position facing the line sensor 25a. The registration roller pair 26 shifts the recording material P to a predetermined position in the width direction by shifting in the width direction of the recording material P detected by the line sensor 25a in a state where the recording material P is sandwiched. The registration roller pair 26 sends the recording material P to the intermediate transfer unit 30 in synchronization with the image formation timing in the image forming unit 10.

  A pre-registration roller pair 27 having a separation mechanism is disposed upstream of the registration roller pair 26 in the conveyance direction of the recording material P. A registration sensor 28 for determining the presence or absence of the recording material P on the conveyance guide 24 is disposed at a position facing the conveyance guide 24 across the line sensor 25a. A conveyance sensor 29 a that detects the recording material P on the conveyance guide 24 is provided in the conveyance path downstream of the registration roller pair 26 in the conveyance direction of the recording material P. A prism 29b for returning the irradiation light from the conveyance sensor 29a is provided at a position facing the conveyance sensor 29a with the conveyance guide 24 interposed therebetween. The registration sensor 28, the registration roller pair 26, the line sensor 25a, and the conveyance sensor 29a are collectively referred to as a “registration unit”.

  The intermediate transfer unit 30 includes an intermediate transfer belt 31 as an intermediate transfer member. The intermediate transfer belt 31 is wound around a drive roller 32, a tension roller 33 that is biased by an elastic member (not shown) and applies an appropriate tension to the intermediate transfer belt 31, and a secondary transfer roller 34. The drive roller 32 rotates the intermediate transfer belt 31.

  Primary transfer rollers 35a to 35d that form primary transfer regions Ta, Tb, Tc, and Td in pairs with the photoconductor drums 11a to 11d at positions facing the photoconductor drums 11a to 11d with the intermediate transfer belt 31 interposed therebetween. Be placed. A secondary transfer roller 36 that forms a secondary transfer region Te that forms a pair with the secondary transfer roller 34 is disposed at a position facing the secondary transfer roller 34 across the intermediate transfer belt 31. A cleaner 37 for cleaning the image forming surface of the intermediate transfer belt 31 is disposed downstream of the secondary transfer region Te in the rotation direction of the intermediate transfer belt 31.

  The fixing unit 40 guides the recording material P to a fixing roller 41a having a heat source such as a halogen heater therein, a pressure roller 41b pressed against the fixing roller 41a, and a nip portion between the fixing roller 41a and the pressure roller 41b. A pre-fixing roller pair 42 and a pre-fixing guide 43 are provided. The pressure roller 41b may be configured to include a heat source similar to that of the fixing roller 41a.

  The paper discharge unit 70 includes an inner discharge roller pair 71 that conveys the recording material P thermally fixed by the fixing unit 40, an outer discharge roller pair 72 that discharges the recording material P to the outside, and the reversing duplex unit 50 and the outer A flapper 73 that leads to one of the discharge roller pair 72 is provided. The reversing double-sided unit 50 includes a plurality of reversing double-sided roller pairs 51 and a reversing double-sided guide 52 that can rotate forward and reverse. The reversing duplex unit 50 also includes a sheet discharge flapper 53 that guides the recording material P reversed by the reversing duplex guide 52 to the outer discharge roller pair 72 at the time of reversed discharge, and a duplex surface that guides the recording material P to the duplex conveying unit 60 at the time of duplex printing. A flapper 54 is provided. The double-sided conveyance unit 60 includes a plurality of double-sided conveyance roller pairs 61 that convey the recording material P from the reverse double-sided unit 50 to the paper feeding unit 20 and a double-sided conveyance guide 62 that guides the recording material P. The control unit 80 includes a CPU (Central Processing Unit) for controlling the operation of each unit described above, a motor drive board, and the like.

<Operation of Image Forming Apparatus>
In the image forming apparatus having such a configuration, when an image forming instruction is input from the operation unit 5, the recording material P is taken out from the cassette 21 one by one by the pickup roller pair 22. The taken recording material P is conveyed by a plurality of conveyance roller pairs 23 to a registration roller pair 26 via a pre-registration roller pair 27 that is driven in a wearing state. At this time, the registration roller pair 26 is stopped. In this state, the recording material P is abutted against the registration roller pair 26 to form a loop of the recording material P, thereby correcting the skew of the recording material P. Thereafter, the registration roller pair 26 starts rotating in accordance with the image formation timing of the image forming unit 10.

  The image forming unit 10 forms a toner image on the photosensitive drum 11 d located on the most upstream side in the rotation direction of the intermediate transfer belt 31 by the process described above in accordance with an image forming instruction from the operation unit 5. The toner image formed on the photosensitive drum 11d is transferred to the intermediate transfer belt 31 in the primary transfer region Td by the primary transfer roller 35d to which a high voltage is applied. The toner image transferred onto the intermediate transfer belt 31 is conveyed to the next primary transfer region Tc. A toner image is formed on the photosensitive drum 11c in accordance with the timing at which the toner image transferred onto the intermediate transfer belt 31 is conveyed to the primary transfer region Tc. In the primary transfer region Tc, the toner image formed on the photosensitive drum 11c is transferred so as to be superimposed on the toner image transferred in the primary transfer region Td. Thereafter, similarly, transfer is performed in the primary transfer regions Tb and Ta, so that a full-color toner image is formed on the intermediate transfer belt 31.

  The recording material P conveyed by the rotation of the registration roller pair 26 passes over the conveyance sensor 29a. The conveyance sensor 29a detects the recording material P that passes therethrough. In accordance with this detection timing, the rotational speed of the registration roller pair 26 is adjusted so that the toner image transferred onto the intermediate transfer belt 31 and the image forming position on the recording material P coincide with each other in the secondary transfer region Te. The

  When a full-color toner image is formed on the intermediate transfer belt 31, the recording material P is conveyed to the secondary transfer region Te. When the recording material P enters the secondary transfer region T2 and contacts the intermediate transfer belt 31, a high voltage is applied to the secondary transfer roller 36 in accordance with the passing timing of the recording material P. As a result, the full-color toner image on the intermediate transfer belt 31 is transferred to the recording material P.

  The recording material P onto which the toner image has been transferred is guided to the nip portion between the fixing roller 41a and the pressure roller 41b of the fixing unit 40 by the pre-fixing guide 43. The toner image is fixed on the surface of the recording material P by the heat and nip pressure of the fixing roller 41 a and the pressure roller 41 b of the fixing unit 40. The recording material P on which the toner image is fixed is conveyed by the pair of inner discharge rollers 71 and is conveyed in the direction of the reverse double-sided portion 50 by the flapper 73 at the time of reverse paper discharge or reverse side printing at the time of double-sided printing. The recording material P on which the toner image has been fixed is conveyed in the direction of the outer discharge roller pair 72 by the flapper 73 after single-sided printing or after reverse-side printing during double-sided printing. The outer discharge roller pair 72 discharges the recording material P to the outside of the image output unit 1P.

  The recording material P conveyed to the reversing double-sided part 50 is pulled into the reverse reversing double-sided guide 52 and stopped by a plurality of reversing double-sided roller pairs 51. Thereafter, the plurality of reverse double-sided roller pairs 51 rotate reversely, and the recording material P is guided by the double-sided flapper 54 to the outer discharge roller pair 72 for reverse paper discharge and to the double-sided conveyance unit 60 for double-sided printing. In the case of reverse paper discharge, the recording material P passes through the double-sided flapper 54, is then guided to the outer discharge roller pair 72 by the paper discharge flapper 53, and is discharged to the outside of the image output unit 1P by the outer discharge roller pair 72. At the time of duplex printing, the recording material P is conveyed by a plurality of duplex conveyance rollers 61, guided to a duplex conveyance guide 62, and merges with the conveyance guide 24 of the paper feeding unit 20. Thereafter, the recording material P is discharged to the outside of the image output unit 1P by the outer discharge roller pair 72 through the same process as the front surface printing.

<Determination of paper type and transport status>
As described above, the recording material P can be plain paper or an OHT sheet (transparent sheet). The image forming apparatus determines the paper type of the recording material P to be conveyed based on the detection results of the line sensor 25a and the conveyance sensor 29a. FIG. 2 is an explanatory diagram of the operation of detecting the paper type of the recording material P and detecting the occurrence of a jam in the recording material P using the registration unit. Here, a case will be described in which the paper type of the recording material P is set to plain paper by the operation unit 5 in the image forming apparatus. The temperature condition of the fixing unit 40 is set so as to be optimal for plain paper.

  FIG. 2A is an explanatory diagram in the case where the recording material P to be conveyed is plain plain paper. The line sensor 25a is a reflective sensor. When the recording material P is conveyed, the light irradiated to the recording material P from the light emitting portion of the line sensor 25a is reflected by the recording material P and guided to the light receiving portion of the line sensor 25a. Therefore, the output value from the light receiving unit of the line sensor 25a becomes high (High).

  The conveyance sensor 29a is a prism regressive transmission type sensor. When the recording material P, which is plain paper, is conveyed by the registration roller pair 26, the light emitted from the light emitting portion of the conveyance sensor 29a is blocked by the recording material P, and the output value of the light receiving portion of the conveyance sensor 29a is low. (Low).

  From the output value (High) of the line sensor 25a and the output value (Low) of the transport sensor 29a, the image forming apparatus can determine that the transported recording material P is plain paper. The image forming apparatus detects the lateral end position of the recording material P by using the line sensor 25a, corrects the lateral end position, and continues the conveyance to form an image.

  FIG. 2B is an explanatory diagram when the recording material P to be conveyed is a transparent OHT sheet. When the recording material P is conveyed, the light irradiated to the recording material P from the light emitting portion of the line sensor 25a passes through the recording material P and is absorbed by the black sheet 25b because the recording material P is an OHT sheet. The Therefore, the output value from the light receiving unit of the line sensor 25a is low (Low).

  When the recording material P, which is an OHT sheet, is conveyed by the registration roller pair 26, the conveyance sensor 29a transmits the light emitted from the light emitting portion of the conveyance sensor 29a through the recording material P and is returned by the prism 29b. It is guided to the light receiving part of the sensor 29a. Therefore, the output value of the light receiving unit of the conveyance sensor 29a becomes high (High).

  From the output value (Low) of the line sensor 25a and the output value (High) of the transport sensor 29a, the image forming apparatus can determine that the transported recording material P is an OHT sheet. Since the image forming apparatus determines that the recording material P is a plain paper, if the recording material P is determined to be an OHT sheet, the image forming apparatus stops conveying the recording material P.

  FIG. 2C is an explanatory diagram when the recording material P to be transported is plain paper and the recording material P is not transported to the position of the transport sensor 29a for some reason. When the recording material P is conveyed, the light irradiated to the recording material P from the light emitting portion of the line sensor 25a is reflected and guided to the light receiving portion of the line sensor 25a because the recording material P is plain paper. Therefore, the output value from the light receiving unit of the line sensor 25a becomes high (High).

  The light emitted from the light emitting unit of the conveyance sensor 29a is returned by the prism 29b because the recording material P is not conveyed, and is guided to the light receiving unit of the conveyance sensor 29a. Therefore, the output value of the light receiving unit of the conveyance sensor 29a becomes high (High). Based on the output value (High) of the line sensor 25a and the output value (High) of the transport sensor 29a, the image forming apparatus determines that the transport of the recording material P has stopped, stops the image formation, and determines that a jam has occurred. To do.

  FIG. 3 is a diagram illustrating the relationship between the type and conveyance state of the recording material P and the output value of each sensor in the case of FIG.

  As described with reference to FIG. 2, the line sensor 25 a and the transport sensor 29 a each output a detection result corresponding to the paper type of the recording material P. The image forming apparatus grasps the paper type and transport state of the recording material P from these detection results. If the detection result of the line sensor 25a and the detection result of the conveyance sensor 29a represent the same paper type, the image forming apparatus determines that the recording material P is being conveyed normally. In the image forming apparatus, if the detection result of the line sensor 25a and the detection result of the conveyance sensor 29a represent different paper types, an abnormality such as a jam occurs in the conveyance of the recording material P, and normal conveyance cannot be performed. Judge that The image forming apparatus stops the conveyance of the recording material P when the recording material P cannot be normally conveyed.

  Further, it can be determined from the detection result of the line sensor 25a whether or not the recording material P of the same paper type as the recording material P used for the image formation set in advance is being conveyed. When the line sensor 25a detects the recording material P of a paper type different from the set paper type, the image forming apparatus determines that an abnormality has occurred in the conveyance and stops the conveyance of the recording material P.

  FIG. 3 shows a case where the set paper type is plain paper. The image forming apparatus determines that the recording material P is normally conveyed when the output (detection result) of the line sensor 25a is “High” and the output of the conveyance sensor 29a is “Low”. When the output of the line sensor 25a is “Low”, the image forming apparatus determines that the paper type of the conveyed recording material P is different from the set paper type, and stops the conveyance of the recording material P. . In the image forming apparatus, when the output of the line sensor 25a is “High” and the output of the conveyance sensor 29a is “High”, an abnormality such as a jam occurs in the conveyance of the recording material P, and the normal conveyance cannot be performed. Judge.

  In the present embodiment, the line sensor 25a detects plain paper and the transport sensor 29a detects an OHT sheet, but this may be reversed. For example, the line sensor 25a may detect an OHT sheet, and the conveyance sensor 29a may detect plain paper. That is, the paper type of the recording material P detected by the line sensor 25a is either a transparent recording material or an opaque recording material, while the paper type of the recording material P detected by the transport sensor 29a is a transparent recording material or an opaque recording material. The other may be used.

<Control unit>
FIG. 4 is a configuration diagram of the control unit 80. The control unit 80 controls the operation of the entire image forming apparatus. FIG. 4 shows only the configuration according to the present embodiment. In FIG. 4, a configuration will be described in which the control unit 80 controls the registration drive motor 305 and the registration shift motor 306 with the registration sensor 28, the line sensor 25 a, and the transport sensor 29 a as inputs.

  The control unit 80 includes a CPU 301 having a threshold setting unit 313 and a recording material determination unit 314. The detection result of the registration sensor 28 is directly input to the CPU 301. The control unit 80 includes an analog processor 303a, a peak level detection unit 307, a low level detection unit 308, and a line sensor control unit 302 between the CPU 301 and the line sensor 25a. The control unit 80 includes an analog processor 303b and a conveyance sensor control unit 315 between the CPU 301 and the conveyance sensor 29a. The control unit 80 includes a motor control unit 304 between the CPU 301 and the registration drive motor 305 and the registration shift motor 306. In addition, the control unit 80 includes a D / A converter 309, a comparator 310, and a counter 311 in order to detect the lateral end position of the recording material P. Moreover, the function with which the control part 80 is provided is implement | achieved, for example, when CPU301 reads a predetermined computer program from the memory | storage device which is not shown in figure and executes it.

  The registration drive motor 305 and the registration shift motor 306 are motors connected to the registration roller pair 26. The registration drive motor 305 rotationally drives the registration roller pair 26. The registration shift motor 306 shifts the registration roller pair 26 in the direction perpendicular to the conveyance direction of the recording material P (lateral registration shift).

  The line sensor 25a operates with the detection of the recording material P by the registration sensor 28 as a trigger. In order to reliably detect the presence or absence of the recording material P, the registration sensor 28 preferably has a flag detection type configuration that detects the movement of a physical flag provided on the conveyance guide 24 of the recording material P, for example.

  When the detection result indicating that the recording material P is detected is input from the registration sensor 28, the CPU 301 instructs the line sensor control unit 302 to activate the line sensor 25a. In response to this instruction, the line sensor control unit 302 transmits a control signal necessary for the operation of the line sensor 25a to the line sensor 25a. The control signal includes, for example, a clock (CLK), a start pulse (SP), an LED on (LED_ON) signal for turning on a light source such as an LED (Light Emitting Diode) attached to the line sensor 25a, and the like.

  When the line sensor 25a receives the control signal and starts operating, the line sensor 25a outputs the amount of reflected light of the light irradiated on the recording material P that has been conveyed as an analog signal (OUT1). The analog signal output from the line sensor 25a is input to the analog processor 303a and converted into a digital signal. This digital signal is input to the peak level detection unit 307 and the low level detection unit 308. The peak level detection unit 307 and the low level detection unit 308 detect the peak level and low level of the digital signal and input them to the CPU 301.

  Further, when a detection result indicating that the recording material P has been detected is input from the registration sensor 28, the CPU 301 instructs the conveyance sensor control unit 315 to activate the conveyance sensor 29a. In response to this instruction, the conveyance sensor control unit 315 activates the conveyance sensor 29a. When the conveyance sensor 29a starts its operation, the detection result is input to the analog processor 303b as an analog signal. The analog processor 303b converts the input analog signal into a digital signal and inputs the digital signal to the CPU 301.

  In accordance with the detection result of the line sensor 25a and the detection result of the transport sensor 29a acquired in this way, the CPU 301 uses the recording material determination unit 314 to determine the paper type of the recording material P as described in FIG. The conveyance state is determined.

  Further, the CPU 301 calculates a threshold value by the threshold setting unit 313 according to the acquired detection result by the line sensor 25a and the detection result by the conveyance sensor 29a. The “threshold value” is a value for binarizing the detection result of the line sensor 25a. The threshold calculated by the threshold setting unit 313 is a digital signal. The threshold calculated by the threshold setting unit 313 is converted into an analog signal by the D / A converter 309 and set in the comparator 310. The comparator 310 compares the detection result of the line sensor 25a with a threshold value and binarizes it. The counter 311 counts the “High” time of the binarized detection result based on the clock signal output from the line sensor control unit 302. The count result is input to the CPU 301. The CPU 301 calculates the lateral edge position of the recording material P based on the count result, and calculates the deviation amount and deviation direction from the target lateral edge position. The CPU 301 converts the calculated deviation amount into the number of pulses of the motor, and outputs a direction for driving the registration shift motor 306 and a motor drive pulse to the motor control unit 304.

<Operation mode of control unit>
The control unit 80 operates in two operation modes: a lateral end detection mode for detecting the lateral end position of the recording material P and an OHT determination mode for determining whether or not the recording material P is an OHT sheet. FIG. 5 is a diagram illustrating a waveform according to an output value from the line sensor 25a in the horizontal end detection mode and the OHT determination mode. 5A shows the output waveform of the line sensor 25a in the horizontal end detection mode, and FIGS. 5B and 5C show the output waveform of the line sensor 25a in the OHT determination mode. The line sensor 25a irradiates light in a direction perpendicular to the conveyance direction of the recording material P.

  In FIG. 5A, in order to obtain the light emission amount B (S508 in FIG. 6) of the line sensor 25a in the horizontal end detection mode, a current of 5 [mA] is passed through the light emitting element of the line sensor 25a. The solid line in the graph represents the output waveform when the recording material P is plain paper.

  The controller 80 operates in the lateral edge detection mode at the timing when the recording material P is nipped between the registration roller pair 26 and conveyed. In the lateral end detection mode, the distance z between the line sensor 25a and the recording material P is about 0.3 [mm] due to the configuration. The focal length of the line sensor 25a used in this embodiment is 0.3 [mm]. Therefore, the light emitted from the line sensor 25a is efficiently reflected by the recording material P to the line sensor 25a.

  In the present embodiment, when the recording material P is plain paper, the output value from the line sensor 25a is about 2.9 [V] when the reflected light from the recording material P is received, depending on the peripheral portion of the recording material P. When the reflected light is received, it is about 0.1 [V], and there is a sufficient difference. In order for the line sensor 25a to irradiate light in a direction perpendicular to the conveyance direction of the recording material P, the output value changes at the lateral edge of the recording material P. Therefore, the CPU 301 can easily determine the horizontal end position of the recording material P.

  In FIG. 5B, in order to obtain the light emission amount A (S505 in FIG. 6) of the line sensor 25a in the OHT determination mode, a current of 5 [mA] is passed through the light emitting element of the line sensor 25a. The solid line in the graph represents the output waveform when the recording material P is plain paper, and the dotted line represents the output waveform when the recording material is an OHT sheet.

  The control unit 80 operates in the OHT determination mode at a timing when the recording material P is on the upstream side in the transport direction from the registration roller pair 26. In the OHT determination mode, the distance z between the line sensor 25a and the recording material P is about 2.4 [mm], which is longer than that in the horizontal end detection mode. Since the focal length of the line sensor 25a is 0.3 [mm], the reflection efficiency of the light from the line sensor 25a by the recording material P decreases as the distance z increases.

  Therefore, when the recording material P is plain paper, the difference between the peak level (Vp_B1) of the output value from the line sensor 25a and the low level (Vl_B1), that is, the reflected light from the plain paper and the reflected light from the outside of the plain paper. Is about 0.3 [V]. In consideration of electrical noise and flapping during conveyance of the recording material P, the OHT threshold (OHT_th) for determining whether or not the sheet is an OHT sheet is preferably about 1.0 [V]. Therefore, in this case, although the recording material P is plain paper, it is erroneously determined as an OHT sheet.

  In FIG. 5C, in order to obtain the light emission amount A (S505 in FIG. 6) of the line sensor 25a in the OHT determination mode, a current of 16 [mA] is supplied to the light emitting element of the line sensor 25a. The solid line in the graph represents the output waveform when the recording material P is plain paper, and the dotted line represents the output waveform when the recording material is an OHT sheet.

  Compared with the state of FIG. 5B, the light emission amount of the line sensor 25a increases. Therefore, when the recording material P is plain paper, the difference between the peak level (Vp_B1) of the output value from the line sensor 25a and the low level (Vl_B1), that is, the reflected light from the plain paper and the reflected light from the outside of the plain paper. Is about 2.8 [V]. As described above, when the difference between the output values is equal to or larger than the predetermined value, it is determined that the recording material P is plain paper. When the recording material P is an OHT sheet, the difference between the peak level (Vp_B2) and the low level (Vl_B2) of the output value from the line sensor 25a is 0.0 [V]. This is because when the light emitted from the line sensor 25a is not reflected by the recording material P, it is absorbed by the black sheet 25b and there is no reflected light, so that the reflected light received by the line sensor 25a does not depend on the light emission amount. is there. As described above, when the difference between the output values is less than the predetermined value, it is determined that the recording material P is an OHP sheet.

  As described above, in FIG. 5C, the difference in peak level between the plain paper and the OHT sheet is as large as about 2.8 [V], so that the paper type of the recording material P can be accurately determined.

  As described above, it is desirable that the light emission amount (light emission amount A) by the line sensor 25a in the OHT determination mode is larger than the light emission amount (light emission amount B) in the horizontal end detection mode. The specific numerical values described above are data in this configuration, and the numerical values are not limited.

<Operational form>
FIG. 6 is a flowchart showing processing at the time of image formation by the control unit 80. At the time of image formation, the user performs various settings for image formation through the operation unit 5. For example, the paper type of the recording material P is set.

  When the user gives an instruction to start printing from the operation unit 5 (S501: Y), the CPU 301 acquires the paper type setting of the recording material P (S502). Here, the CPU 301 acquires which of the plain paper and the OHT sheet is set for the recording material P.

  When the CPU 301 acquires the paper type of the recording material P, the CPU 301 determines whether the registration sensor 28 has detected the conveyed recording material P (S503). When the registration sensor 28 detects the recording material P (S503: Y), the CPU 301 starts the operation of the line sensor 25a (S504). The CPU 301 sets the light emission amount of the line sensor 25a to the light emission amount A by the line sensor control unit 302 (S505), and performs processing in the OHT determination mode (S506). In the OHT determination mode, the CPU 301 determines whether the conveyed recording material P is an OHT sheet. If it is an OHT sheet, the CPU 301 sets the OHT flag to “1”. The processing in the OHT determination mode will be described later.

  When the processing in the OHT determination mode is completed, the CPU 301 drives the registration drive motor 305 by the motor control unit 304 to start the rotation of the registration roller pair 26 (S507: Y). When the registration roller pair 26 starts rotating, the CPU 301 shifts the processing mode to the lateral end detection mode. In the horizontal end detection mode, the CPU 301 sets the light emission amount of the line sensor 25a to a light emission amount B smaller than the light emission amount A (S508), and detects the horizontal end position of the recording material P (S509).

  When the horizontal end position of the recording material P is detected, the CPU 301 causes the line sensor control unit 302 to end the operation of the line sensor 25a (S510). The CPU 301 derives the operation amount of the registration shift motor 306 according to the lateral edge detection result of the recording material P (S511). Thereafter, the CPU 301 drives the registration shift motor 306 by the operation amount derived by the motor control unit 304, thereby performing the lateral registration shift of the registration roller pair 26 (S512). Thereby, the lateral registration correction is performed.

  After the lateral registration shift, the CPU 301 determines whether or not the set paper type of the recording material P is an OHT sheet (S513). If the paper type of the set recording material P is an OHT sheet (S513: Y), and the OHT flag is “1” as a result of the OHT determination mode (S514: Y), the CPU 301 displays an image on the recording material P. Formation is performed (S522). In this case, since the set paper type matches the paper type of the recording material P actually conveyed, the normal image forming process is performed.

  If the paper type of the set recording material P is an OHT sheet (S513: Y) and the OHT flag is not “1” as a result of the OHT determination mode (S514: N), the CPU 301 displays the display unit of the operation unit 5 Is displayed, and the process is terminated (S515). In this case, the set paper type does not match the paper type of the recording material P actually conveyed. Specifically, the set paper type is an OHT sheet, and the actually transported recording material P is not an OHT sheet. The CPU 301 determines that a jam has occurred because the actually conveyed recording material P is not an OHT sheet, and displays the occurrence of the jam on the display unit.

  When the set paper type of the recording material P is not an OHT sheet (S513: N), the CPU 301 waits until a predetermined time elapses after the registration roller pair 26 starts rotating in S507 (S516). In this embodiment, when the paper type of the recording material P is not an OHT sheet, the setting is plain paper. When the predetermined time has elapsed (S516: Y), the CPU 301 determines whether the conveyance sensor 29a recognizes the recording material P (whether the output of the conveyance sensor 29a is “Low”) (S517). When the conveyance sensor 29a recognizes the recording material P (S517: Y), the paper type of the recording material is plain paper. In this case, the set paper type matches the paper type of the recording material P actually conveyed. For this purpose, the CPU 301 performs normal image formation on the recording material P (S522).

  When the output of the conveyance sensor 29a is “High” and the conveyance sensor 29a does not recognize the recording material P (S517: N), the CPU 301 stops the conveyance of the recording material P (S518). The CPU 301 that stopped conveying the recording material P determines the value of the OHT flag (S519).

  When the OHT flag is “1” (S519: Y), the set paper type is not an OHT sheet, and the recording material P actually conveyed is an OHT sheet. Therefore, the CPU 301 displays that the jam has occurred on the display unit of the operation unit 5 and ends the process (S520). The CPU 301 notifies the user by displaying on the display section that a jam has occurred because the set paper type and the actually transported recording material P are different.

  When the OHT flag is not “1” (S519: N), the set paper type is not an OHT sheet, and the recording material P actually conveyed is not an OHT sheet. In this case, the CPU 301 displays on the display unit of the operation unit 5 that the recording material P has not reached the conveyance sensor 29a, and ends the process (S521). The CPU 301 notifies the user by displaying on the display section that a normal jam of the recording material P has occurred.

  When normal image forming processing is performed (S522), the CPU 301 determines whether there is a next job (S523). For example, when there is a next job such as continuous printing (S523: N), the CPU 301 repeats a series of processes from S502. When there is no next job (S523: Y), the CPU 301 ends the process.

<OHT determination mode>
The processing in the OHT determination mode in S506 of FIG. 6 will be described with reference to the flowchart of FIG.

  When the OHT determination mode is started, the CPU 301 first clears the OHT flag and sets “0” (S601). After clearing the OHT flag, the CPU 301 acquires the peak level “Vp” of the output value of the line sensor 25a from the peak level detection unit 307, and acquires the low level “Vl” from the low level detection unit 308 (S602, S603).

  When the difference between the acquired peak level “Vp” and low level “Vl” is smaller than the OHT threshold value (OHT_th) (S604: Y), the CPU 301 determines that the recording material P is an OHT sheet. As a result, the CPU 301 sets the OHT flag to “1” and ends the processing in the OHT determination mode (S605). When the difference between the acquired peak level “Vp” and low level “Vl” is equal to or greater than the OHT threshold (OHT_th) (S604: N), the CPU 301 determines that the recording material P is other than an OHT sheet. As a result, the CPU 301 ends the processing in the OHT determination mode while leaving the OHT flag as it is.

  As described above, according to the output value of the line sensor 25a, it is determined whether or not the recording material P is an OHT sheet, and the result is represented by the OHT flag.

<Registration section operation>
FIG. 8 is a timing chart of the operation of the registration unit. As described with reference to the flowchart of FIG. 6, after the registration sensor 28 detects the conveyed recording material P, the line sensor 25a operates in the OHT determination mode (point a). When the processing in the OHT determination mode is completed, the registration roller pair 26 is driven (point b). The recording material P is transported by driving the registration roller pair 26.

  When the recording material P is conveyed, the operation mode of the line sensor 25a shifts to the horizontal end detection mode (point c). The line sensor 25a that has shifted to the lateral end detection mode detects the lateral end position of the recording material P. Based on the detection result of the lateral end position, the registration roller pair 26 moves in the direction perpendicular to the conveyance direction of the recording material P while holding the recording material P, and performs lateral registration correction (point d). After the lateral registration correction, the transport sensor 29a determines whether to detect the recording material P that has been transported (point e).

  Thus, by determining the output values of the line sensor 25a and the conveyance sensor 29a in accordance with the conveyance of the recording material P, the paper type and conveyance state of the recording material P can be determined. When the conveyance sensor 29a cannot detect the recording material P within a predetermined time, it can be determined whether the recording material P is an OHT sheet or a conveyance failure has occurred.

  25a ... line sensor, 26b ... black sheet, 26 ... registration roller pair, 28 ... registration sensor, 29a ... conveyance sensor, 29b ... prism, 301 ... CPU, 302 ... line sensor control unit, 303 ... analog processor, 304 ... motor control unit 305: Registration drive motor, 306: Registration shift motor 309, D / A converter, 310 ... Comparator, 311 ... Counter, 313 ... Threshold setting unit, 314 ... Recording material determination unit

Claims (12)

A first detection unit that is provided in a conveyance path in which the recording material is conveyed and detects a recording material of a first paper type conveyed in the conveyance path;
A second detection unit that is provided downstream of the first detection unit in the conveyance direction of the recording material and detects a recording material of a second paper type different from the first paper type;
A determination unit that determines whether an abnormality has occurred in the paper type of the recording material to be conveyed and the conveyance of the recording material in accordance with the detection result by the first detection unit and the detection result by the second detection unit; Characterized by comprising,
Image forming apparatus. The determination means determines that the recording material is the recording material of the first paper type when the first detection means detects the recording material and the second detection means does not detect the recording material,
When the first detection unit does not detect the recording material and the second detection unit detects the recording material, it is determined that the recording material is the recording material of the second paper type,
When both the first detection means and the second detection means detect a recording material, or when both the first detection means and the second detection means do not detect a recording material, the recording It is determined that an abnormality has occurred in material conveyance,
The image forming apparatus according to claim 1. The determination unit is configured to transfer the recording material when the paper type of the recording material to be conveyed is different from a preset paper type used for image formation as a result of detection by the first detection unit. It is determined that an abnormality has occurred,
The image forming apparatus according to claim 1. When the determination unit determines that an abnormality has occurred in the conveyance of the recording material, the determination unit further includes a control unit that stops the conveyance of the recording material.
The image forming apparatus according to claim 1. The recording material of the first paper type is one of a transparent recording material and an opaque recording material, and the recording material of the second paper type is the other of a transparent recording material and an opaque recording material. And
The image forming apparatus according to claim 1. The recording material of the first paper type is an opaque recording material,
The first detection unit irradiates light in a direction perpendicular to the conveyance direction of the recording material, and outputs an output value corresponding to reflected light from the recording material and a peripheral portion of the recording material as a detection result,
The determination unit determines that the recording material is the opaque recording material if the difference between the output values corresponding to the recording material and the peripheral portion of the recording material is equal to or greater than a predetermined value, and is less than the predetermined value. If it is, it is determined that the recording material is a transparent recording material,
The image forming apparatus according to claim 5. When the determination unit determines that the recording material is the opaque recording material, the recording device further includes a lateral end detection unit that detects a position where the output value changes as a lateral end of the recording material.
The image forming apparatus according to claim 6. A pair of registration rollers provided between the first detection means and the second detection means for conveying the recording material;
And a shift means for shifting the registration roller pair in a direction orthogonal to the conveyance direction of the recording material in accordance with the position of the lateral edge of the recording material detected by the lateral edge detection means. To
The image forming apparatus according to claim 7. The first detection means reduces the light emission amount when obtaining the output value output to the lateral edge detection means to be smaller than the light emission amount when obtaining the output value output to the determination means. Features
The image forming apparatus according to claim 7 or 8. A third detection means for detecting the presence or absence of the recording material by a physical flag provided in the transport path;
The first detection means is activated in response to the third detection means detecting the presence of the recording material,
The image forming apparatus according to claim 1. When the determination unit determines that an abnormality has occurred in the conveyance of the recording material, the determination unit further includes a notification unit that notifies the user of the abnormality.
The image forming apparatus according to claim 1. A first detection unit that detects a recording material of a first paper type that is provided in a conveyance path through which the recording material is conveyed, and that conveys the recording material relative to the first detection unit. A computer provided with second detection means provided on the downstream side for detecting a recording material of a second paper type different from the first paper type,
A determination unit that determines whether an abnormality has occurred in the type of the recording material to be conveyed and the conveyance of the recording material, according to the detection result by the first detection unit and the detection result by the second detection unit;
A computer program that functions as a computer program.