JP2007223740A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of applying appropriate fixing conditions, transfer conditions and carrying conditions to various types of recording materials by performing optimal correction and of obtaining excellent images even when output of a recording material determination sensor is fluctuated in accordance with the ambient temperature and endurance deterioration. <P>SOLUTION: In the sensor for determining types of recording materials based on the surface reflection ratio of the recording materials inside a paper feeding cassette, when the paper feeding cassette has no recording materials, output of the sensor is corrected. In this configuration, when the ambient temperature is lower than normal operating temperature, for example immediately after power supply is turned on, the relative output of the sensor is reduced, and thereby, correcting operation of the sensor is not performed. Due to the correcting operation, detection errors of the sensor are reduced and accuracy of determination of the recording materials is improved. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as an ink jet printer, a copying machine, or a laser printer that has a detection device that detects the surface smoothness of a recording material and controls image forming conditions from the detection result of the surface smoothness of the recording material. .

  Image forming apparatuses such as copying machines and laser printers include a latent image carrier that carries a latent image and a developing device that visualizes the latent image as a developer image by applying a developer to the latent image carrier. . Further, the image forming apparatus includes a transfer unit that transfers the developer image by the developing device onto a recording material conveyed in a predetermined direction. Further, the image forming apparatus fixes the developer image on the recording material by heating and pressurizing the recording material, which has received the transfer of the developer image by the transfer unit, under predetermined fixing processing conditions. It has.

  Conventionally, in such an image forming apparatus, for example, the size and type (hereinafter also referred to as paper type) of a recording material as a recording material is set by a user on an operation panel or the like provided in the main body of the image forming apparatus. Then, the image forming apparatus performs control to change development conditions, transfer conditions or fixing processing conditions (for example, fixing temperature and conveyance speed of the recording material passing through the fixing apparatus) or image processing according to the setting. Alternatively, when the user sets the paper type at the time of printing from the host computer, the image forming apparatus performs control to change the development condition, the transfer condition, the fixing processing condition, or the image processing according to the designated paper type. Alternatively, a sensor for discriminating the type of recording material is built in the image forming apparatus, and the type of the recording material is discriminated from the detection result of the sensor. As an example of this configuration, for example, a surface image of a recording material is picked up by a CMOS sensor, the type of the recording material is determined by a method of detecting the surface smoothness of the recording material, and development conditions, transfer conditions or fixing conditions are variable. The structure to control is proposed (refer patent document 1). Further, there has been proposed an apparatus for discriminating a recording material by transmitted light by providing a light source at a position facing a sensor for discriminating the recording material and detecting transmitted light. Further, the recording material is irradiated with light from a light emitting source, and the light reflected from the recording material is received by light receiving elements at two positions, and the surface smoothness of the recording material is obtained by the ratio to determine the type of the recording material. A configuration has been proposed (see Patent Document 2).

JP 2002-182518 A Japanese Patent Laid-Open No. 2-138805

  However, in the conventional surface smoothness detection method, the output of the light receiving element fluctuates due to variations in the light emitting element and the light receiving element, changes with time, contamination of the element, ambient temperature, and the like. It is necessary to periodically calibrate the light emitting element and light receiving element outputs. In order to perform calibration, a calibration plate that guarantees the specified reflectance is installed at the detection position of the reflected light receiving element, and the amount of light that the light emitted from the light emitting element is reflected by the calibration plate and incident on the light receiving element is measured. To detect. Then, the amount of emitted light is adjusted so as to be a predetermined amount of light, or the paper type discrimination threshold held by the paper type discrimination means is corrected. At this time, the light emitting element and the light receiving element are installed on the upper surface of the stacking portion in the cassette on which the recording material is stacked, and the calibration plate is installed on the member pushing up the recording material on the lower side of the recording material stacking portion. . For this reason, the calibration plate does not appear at the detection position of the light receiving element unless all the recording material in the cassette is discharged by the printing operation. That is, the calibration operation can be performed only when there is no recording material.

  Here, when the power of the image forming apparatus is turned on, such as first in the morning, when there is no recording material, the temperature of the light emitting element and the light receiving element is low. For this reason, if calibration is performed at that time, there is a problem to be solved in that the type of recording material cannot be correctly determined when the internal temperature rises for a while after the power is turned on. It was.

  The present invention has been made in view of such problems, and an object thereof is to provide an image forming apparatus capable of stably printing a high-quality image.

  In order to achieve such an object, an image forming apparatus according to the present invention includes a recording material stacking unit that stacks a recording material, and a light irradiation unit that irradiates light onto the recording material stacked on the recording material stacking unit. The reflected light amount detecting means for obtaining the reflected light amount on the surface of the recording material by detecting the reflected light irradiated from the light irradiating means and reflected from the surface of the recording material, and the output of the recording material from the output of the reflected light amount detecting means An image forming apparatus that changes an image forming condition based on the attribute, a temperature detecting unit that detects an ambient temperature in the image forming apparatus, and a reflected light amount detection. A reflected light amount calibration plate having a predetermined reflectance with respect to the irradiation light amount of the means, and irradiating light from the light irradiation means to detect the reflected light amount from the reflected light amount calibration plate, thereby generating the light irradiation means. The reflected light amount calibration plate corrects the light quantity or the detection sensitivity of the reflected light quantity detection means or the discrimination criterion of the recording material discrimination means and moves the recording material in the recording material stacking means to a paper feed position. When the recording material is not stacked on the recording material stacking means, the reflected light amount calibration plate is moved by moving the recording material lifting and lowering means to the detection position of the reflected light amount detection means, If the recording material is not in the detection position and the reflected light amount calibration plate is raised, and the output result of the temperature detection means is within a predetermined range, the discrimination reference calibration operation of the recording material discrimination means is performed. It is characterized by.

  In order to achieve the above object, an image forming apparatus according to the present invention includes a recording material stacking unit that stacks a recording material, and a light irradiation unit that irradiates light onto the recording material stacked inside the recording material stacking unit. A reflected light amount detecting means for obtaining a reflected light amount on the surface of the recording material by detecting reflected light irradiated from the light irradiating means and reflected from the surface of the recording material, and the recording material from the output of the reflected light amount detecting means An image forming apparatus that changes an image forming condition based on the attribute, a temperature detecting unit that detects an ambient temperature in the image forming apparatus, and the amount of reflected light A light intensity calibration plate having a predetermined reflectance with respect to the light intensity of the detection means; and irradiating the light from the light irradiation means to detect the light intensity reflected from the reflected light intensity calibration plate. The reflected light amount calibration is performed on the recording material lifting / lowering means that corrects the light emission quantity or the detection sensitivity of the reflected light quantity detection means or the discrimination criterion of the recording material discrimination means and moves the recording material in the recording material stacking means to the paper feed position. A plate is provided, and when the recording material is not stacked on the recording material stacking means, the reflected light amount calibration plate is moved by raising the recording material lifting means to the detection position of the reflected light amount detection means, If the recording material is not in the detection position and the reflected light amount calibration plate is raised and the output result of the temperature detection means is within a predetermined range, the light emission means calibration operation is performed. It is characterized by that.

  In order to achieve the above object, an image forming apparatus according to the present invention includes a recording material stacking unit that stacks a recording material, and a light irradiation unit that irradiates light onto the recording material stacked inside the recording material stacking unit. A reflected light amount detecting means for obtaining a reflected light amount on the surface of the recording material by detecting reflected light irradiated from the light irradiating means and reflected from the surface of the recording material, and the recording material from the output of the reflected light amount detecting means An image forming apparatus that changes an image forming condition based on the attribute, a temperature detecting unit that detects an ambient temperature in the image forming apparatus, and the amount of reflected light A light intensity calibration plate having a predetermined reflectance with respect to the light intensity of the detection means; and irradiating the light from the light irradiation means to detect the light intensity reflected from the reflected light intensity calibration plate. The reflected light amount calibration is performed on the recording material lifting / lowering means that corrects the light emission quantity or the detection sensitivity of the reflected light quantity detection means or the discrimination criterion of the recording material discrimination means and moves the recording material in the recording material stacking means to the paper feed position. A plate is provided, and when the recording material is not stacked on the recording material stacking means, the reflected light amount calibration plate is moved by raising the recording material lifting means to the detection position of the reflected light amount detection means, If the recording material is not in the detection position and the reflected light amount calibration plate is raised and the output result of the temperature detecting means is within a predetermined range, the detection sensitivity calibration operation of the reflected light amount detecting means is performed. It is characterized by performing.

  With the above configuration, the image forming apparatus can correct a decrease in output due to durability and correctly determine the type of the recording material regardless of the ambient temperature change.

  ADVANTAGE OF THE INVENTION According to this invention, the image forming apparatus which can print a high quality image stably until the product lifetime can be provided.

  Embodiments to which the present invention can be applied will be described below in detail with reference to the drawings. In the drawings referred to in this specification, portions having the same function are denoted by the same reference numerals.

[Embodiment 1]
(Device configuration)
The image forming apparatus shown in FIG. 1 shows an application example to a tandem type full color image forming apparatus using an electrophotographic system. FIG. 1 is a longitudinal front view schematically showing the overall configuration of the full-color image forming apparatus. An image forming unit is disposed in the apparatus main body 100, and a recording material 201 before image formation is stored immediately below the image forming unit. A paper feeding unit (paper feeding cassette) 101 serving as a paper feeding device is provided. The paper feed cassette 101 is provided so as to be able to be pulled out and stored with respect to the apparatus main body 100 in the front-rear direction (left and right direction in the drawing). Further, a paper discharge tray (not shown) for discharging the recording material on which the image has been formed is provided above the image forming unit 100.

  The image forming apparatus 100 includes yellow (Y), magenta (M), cyan (C), and black (Bk) image forming units 114, 115, 116, and 117 as four-color image forming units. Each image forming unit includes a drum-type electrophotographic photosensitive member, that is, photosensitive drums 106, 107, 108, and 109 as an image carrier. Around these photosensitive drums, there are provided charging rollers (not shown) as charging means for uniformly charging the photosensitive drums 106 to 109. Also, laser scanners 118, 119, 120, 121 as exposure means (latent image forming means) for exposing each photosensitive drum 106-109 to form an electrostatic latent image on the photosensitive drum 106-109 according to the image signal. Is provided. Further, developing devices 122, 123, 124, and 125 are provided as developing means for supplying the toner provided in the developer to the electrostatic latent images formed on the respective photosensitive drums 106 to 109 and visualizing them as toner images. Further, cleaning devices 126, 127, 128, and 129 are provided for removing and cleaning the toner adhering to the photosensitive drums 106 to 109.

  Further, an endless conveyance belt 103 as a conveyance unit that sequentially conveys the recording material 201 to the image forming units 114 to 117 of the respective colors is provided to face the photosensitive drums 106 to 109. The conveyor belt 103 is stretched around the driving roller 104 and the driven roller 105, and moves (rotates) in the direction of the arrow in the figure. The driving roller 104 is connected to a driving unit (not shown) including a motor, a gear, and the like, and drives the conveyance belt 103. The driven roller 105 rotates according to the movement of the conveyor belt 103 and applies a certain tension to the conveyor belt 103. Inside the conveyance belt 103, transfer members 110, 111, 112, and 113 are disposed in contact with the conveyance belt 103 so as to face the respective photosensitive drums 106 to 109. A transfer bias voltage is applied to the transfer member at the time of transfer, and a transfer bias having a polarity opposite to that of the toner is applied to the recording material P carried on the conveyor belt 103 via the conveyor belt 103. Thus, the conveyance belt 103 also functions as a transfer belt as a transfer unit.

  Further, the image forming apparatus 100 includes a paper feeding device including a paper feeding cassette 101 that accommodates the recording material P, a recording material supply roller 102, a conveyance roller 130, a guide (not shown), a registration roller 131, and the like. A fixing device 110 that fixes an unfixed toner image transferred to the recording material P in each of the image forming units 114 to 117 to the recording material P is provided on the downstream side of the conveying belt 103 in the recording material conveyance direction. .

  Data to be image-formed is sent from an external device such as a personal computer to the image forming apparatus 110 having such a configuration, and the image information processing according to the printer engine method well known to those skilled in the art is completed and the image-formable state is obtained. Become. Then, the recording material P is supplied from the paper feed cassette by the recording material supply roller 130 and the like, and reaches the conveying belt 103. Then, the recording material P is sequentially conveyed by the conveyance belt 103 to the image forming units 114 to 117 of the respective colors. In synchronization with the conveyance of the recording material P by the conveyance belt 103, the image signals of the respective colors are sent to the laser scanners 118 to 121, and electrostatic latent images are formed on the photosensitive drums 106 to 109. The electrostatic latent image is developed by each developing device and then transferred onto the recording material P by the transfer members 110 to 113.

  Thereafter, the recording material P is separated from the conveying belt 103, and the toner image is fixed on the recording material P by heat in the fixing device 110, and is discharged to the outside of the device.

  Since the operations of the image forming units 114 to 117 are the same, the yellow image forming unit 114 will be described as an example. The surface of the photosensitive drum 106 that is rotationally driven in the direction of the arrow in the figure is uniformly charged by the charging roller. The The laser scanner 118 scans and exposes the surface according to yellow image information that is color-separated into image information, and an electrostatic latent image is formed on the photosensitive drum 106. Next, the electrostatic latent image formed on the photosensitive drum 106 is visualized as a toner image by being supplied with toner by the developing device 122. The developing device 122 includes, for example, mainly resin toner particles (toner) as a developer, and carries and conveys the developer by a developer carrier to a development area facing the photosensitive drum 106. Further, the electrostatic latent image on the photosensitive drum 106 is usually developed by applying a developing bias in which an AC voltage and a DC voltage are superimposed on the developer carrying member.

  On the other hand, the recording material P supplied from the paper feed cassette 101 by the supply roller 102 and the like and electrostatically attracted to the conveyance belt 103 is conveyed so as to synchronize with the formation of the toner image in each of the image forming units 114 to 117. The toner image is transferred from the photosensitive drum 103 to the recording material P by a transfer bias applied to the transfer member 110 in a transfer region where the photosensitive drum 106 and the transfer member 110 face each other via the conveyance belt 103. Similarly, in the image forming units 115, 116, and 117, the toner images on the photosensitive drums 107, 108, and 109 are transferred to the recording material P by the transfer bias of the transfer members 111, 112, and 113, respectively.

  Next, the recording material P is separated from the conveyance belt 103 and conveyed to the fixing device 110. Here, the toner image is fixed on the recording material P and becomes a permanent image. Thereafter, the recording material P is discharged from a recording material discharge portion (not shown) provided outside the apparatus to a discharge tray (not shown). In addition, the photosensitive drums 106 to 109 after the transfer of the toner image are prepared for subsequent image formation by removing the transfer residual toner adhering to the surfaces thereof by the cleaning devices 126 to 129.

  The recording material discrimination sensor 200 is disposed in the paper feeding unit 101, irradiates light on the surface of the recording material P stacked on the paper feeding unit 101, detects the reflected light, and performs a predetermined calculation. The type of the recording material P is determined. FIG. 5 shows a circuit example of the recording material discrimination sensor. The control CPU 300 outputs an analog voltage to the operational amplifier 301 via the control ASIC 323. The operational amplifier 301 controls the Tr1 so that a current corresponding to the input voltage flows through the LED1, thereby keeping the light emission amount of the LED1 constant. As shown in FIG. 3A, the LED 1 irradiates light on the surface of the recording medium 201 in the paper feed cassette 101 and reflects the light reflected by the phototransistor Ptr. In FIG. 5, Ptr1 flows out a current corresponding to the amount of light received. The current is converted into a voltage by the combined resistance value of the resistors R5, R6, and R7. At this time, the combined resistance value is switched depending on whether SW1 and SW2 are ON or OFF, thereby changing the conversion rate (light receiving sensitivity) for converting current into voltage. The control CPU can set which switch is turned on via the control ASIC 323. The operational amplifier 302 outputs the voltage-converted light amount value multiplied by a predetermined value [(R6 + R7) / R6 times]. The output value is input to the A / D conversion port of the control ASIC 323.

(Description of operation)
Next, the operation of the control CPU in one embodiment of the recording material discrimination apparatus and the image forming apparatus using the method of the present invention will be described with reference to FIG. FIG. 6 is a diagram illustrating a configuration of each unit controlled by the control CPU 300. In FIG. 6, a CPU 300 is connected to a recording material discrimination sensor 200 and polygon mirrors, motors, and lasers included in optical units 312 to 315 for each color via an ASIC 323. The CPU 300 controls the optical unit for scanning a laser on the photosensitive drum surface and drawing a desired latent image. Similarly, the CPU 300 has a paper feed motor 316 for conveying the recording material, a paper feed solenoid 317 used to start driving the paper feed roller for feeding the recording material, and whether the recording material is set at a predetermined position. The paper cassette cassette presence / absence sensor 203 for detecting whether or not is controlled. Similarly, the CPU 300 controls a high-voltage power source 319 that controls primary charging, development, and transfer bias necessary for the electrophotographic process, and a drum drive motor 320 that drives the photosensitive drum and the transfer roller. Similarly, the CPU 300 controls the belt driving motor 321, the fixing unit 110, and the low voltage power supply unit 320 for driving the transfer belt 103 and the rollers of the fixing unit 110. Further, the control CPU 300 monitors the temperature with a thermistor (not shown) and controls to keep the fixing temperature constant.

  The control CPU 300 is connected to the memory 324 via the control ASIC 323, and the memory 324 performs all or part of the above control and processing performed by the control CPU 300 in each embodiment described in this specification. A program and data to be executed are stored. That is, the control CPU 300 executes the operations of the embodiments of the present invention using the program and data stored in the memory 324.

  The ASIC 323 performs motor speed control inside the recording material determination sensor 200 and the optical units 312 to 315 and speed control of the paper feed motor based on an instruction from the control CPU 300. The speed control of the motor is performed by detecting a tack signal from a motor (not shown) and outputting an acceleration or deceleration signal to the motor so that the interval between the tack signals becomes a predetermined time. For this reason, it is more advantageous that the control circuit is composed of a circuit based on the hardware of the ASIC 323 so that the control load on the CPU 300 can be reduced.

  When the control CPU 300 receives an instruction print command from a host computer (not shown), the control CPU 300 determines the presence / absence of a recording material by a paper cassette cassette presence / absence sensor 203. Then, when there is paper, the control CPU 300 causes the LED of the recording material discrimination sensor 200 to emit light with a predetermined amount of light via the ASIC 323 to irradiate the recording material, and the reflected light from the recording material is received by the phototransistor. At this time, the ASIC 323 causes the LED to emit light at a predetermined timing and a predetermined pulse, and takes in a voltage corresponding to the output voltage obtained by performing I / V conversion of the photocurrent flowing through the phototransistor from the A / D conversion input port.

  The result of A / D conversion by the ASIC 323 is stored in a register inside the ASIC 323. Then, the CPU 300 reads the register in the ASIC 323, and determines the type of the recording material fed based on the read result. FIG. 8 shows a discrimination example. FIG. 8 shows an example in which the amount of incident light on Ptr is divided into rough paper, plain paper, gloss paper / gross film, and OHT. Control is performed to change the developing bias condition of the high-voltage power supply 319 according to the determination result.

  For example, in the case of so-called rough paper where the surface fibers of the recording material are rough, control is performed to prevent toner scattering by lowering the developing bias than plain paper and suppressing the amount of toner adhering to the surface of the recording material. This is because the amount of toner adhering to the surface of the recording material is large especially in the case of rough paper, so that the problem that the image quality deteriorates due to the scattering of the toner due to the paper fibers is solved.

  Further, the CPU 300 determines the type of the fed recording material, and controls to change the temperature condition of the fixing unit 110 according to the result. For example, in the case of the rough paper, since the surface fibers are rough, the toner is poorly fused, and optimization is performed by changing the fixing temperature. Further, in the case of OHT, there is an effect on the problem that the permeability of OHT deteriorates if the fixing property of the toner adhering to the surface of the recording material is poor.

  Further, the CPU 300 determines the type of the fed recording material, and controls to change the recording material conveyance speed in accordance with the result. Control of the conveyance speed is realized by resetting the speed control register value of the ASIC 323 that actually controls the speed by the CPU 300. The fixing temperature conditions vary depending on the type of recording material.For example, gloss paper and gloss film with a relatively large heat capacity are controlled at a high fixing temperature, while plain paper with a relatively small heat capacity is fixed at a lower fixing temperature. To do. Alternatively, the recording material conveyance speed can be changed and controlled depending on the type of the recording material.

  Further, in the case of OHT or glossy paper, it is possible to improve the image quality by increasing the gloss by further improving the fixability of the toner adhering to the surface of the recording material.

  Further, as shown in FIG. 4, the recording material discrimination sensor reduces the amount of received light depending on the durability time due to the contamination of the sensor and the deterioration of the light emitting element. In order to prevent erroneous determination of the recording material at this time, as shown in FIG. 2, when there is no recording material, the bottom plate 150 of the sheet feeding cassette is lifted by the spring 151, and the calibration plate 202 attached to the bottom plate records the recording plate. Move to the front of the material discrimination sensor. When the paper feed cassette paper presence / absence sensor 203 detects that there is no recording material in the paper feed cassette 101, the amount of light reflected from the recording material discrimination sensor calibration plate 202 as shown in FIG. By detecting it, the amount of light quantity deterioration of the recording material discrimination sensor can be detected. In order to correct the detected light amount deterioration amount, the control CPU 300 increases the light emission amount of the recording material discrimination sensor, increases the light reception sensitivity of the phototransistor, or changes the threshold value of the recording material discrimination.

  However, the phototransistor used as the reflected light receiving element of the recording material discrimination sensor is greatly different in relative output depending on the ambient temperature as shown in FIG. For this reason, the relative output is low when the sensor is cold, for example, immediately after the power is turned on. At this time, when the correction of the light amount deterioration of the recording material discrimination sensor 200 is executed, the recording material is replenished to the paper feed cassette 101, and the temperature in the image forming apparatus rises by performing the printing operation. The relative output of the phototransistor increases. When the relative output increases, the recording material discrimination sensor outputs a higher detection result to the control CPU 300, and the risk that the control CPU 300 erroneously discriminates that the recording material has a high reflected light amount increases.

  Therefore, in order to prevent this erroneous determination, even if the paper cassette cassette presence / absence sensor 203 of the paper cassette 101 detects that there is no recording material, the output of the temperature / humidity sensor 325 shown in FIG. For example, the control CPU 300 determines that the temperature is low. Then, the control CPU 300 does not perform the light quantity calibration operation of the recording material discrimination sensor, and discriminates the paper type using the previous LED irradiation light quantity and the discrimination threshold.

  The operation at this time will be described with reference to the flowchart of FIG. The control CPU 300 confirms the output of the sheet cassette cassette presence / absence sensor 203 in step S11. In step S12, the control CPU 300 determines whether there is a recording material in the cassette. If there is no recording material, the control CPU 300 detects the in-machine temperature from the temperature / humidity sensor output in step S13. The control CPU 300 determines whether or not the in-machine temperature detected in step S14 is, for example, 15 ° C. or higher. If the temperature is lower than 15 ° C., the control CPU 300 performs the normal initial operation step S17 and does not perform the calibration operation. If it is 15 ° C. or higher, the control CPU 300 executes the calibration operation of the recording material discrimination means (step S15). Based on the result of the calibration operation, the control CPU 300 corrects the light emission quantity, the light reception quantity, and the discrimination threshold of the discrimination unit (step S16), performs the initial operation (step S17), and enters standby. Here, it is set as 15 degreeC or more as an example of a temperature range. However, this changes depending on the mounting position of the temperature sensor, the temperature characteristics of the recording material discrimination sensor, and the like, and is not specified in the range of 15 ° C. or higher.

  As described above, calibration of the recording material discriminating means when the in-machine temperature is low is prohibited. For this reason, when the temperature in the image forming apparatus rises as during printing and the relative output of the phototransistor of the recording material discrimination sensor rises, it is possible to take an appropriate amount of emitted light, sensitivity or a recording material discrimination threshold. Further, it is possible to reduce erroneous discrimination of the recording material, and furthermore, it is possible to print a high-quality image by applying an optimum image forming condition according to the recording material.

[Embodiment 2]
(Device configuration)
Since the configuration of the apparatus is the same as that of the first embodiment, description thereof is omitted.

(Description of operation)
Since the basic configuration and determination method are the same as those in the first embodiment, detailed description thereof is omitted.

  As shown in FIG. 7, the relative output of the phototransistor used as the reflected light receiving element of the recording material discrimination sensor is greatly different depending on the ambient temperature. For this reason, the relative output is low when the sensor is cold, for example, immediately after the power is turned on. At this time, when the correction of the light amount deterioration of the recording material discrimination sensor 200 is executed, the recording material is replenished to the paper feed cassette 101, and the temperature in the image forming apparatus rises by performing the printing operation. The relative output of the phototransistor increases. When the relative output increases, the recording material discrimination sensor outputs a higher detection result to the control CPU 300, and the risk that the control CPU 300 erroneously discriminates that the recording material has a high reflected light amount increases.

  In the present embodiment, the control CPU 300 stores the change curve of the amount of received light with respect to the durable sheet number shown in FIG. 4, counts the number of printed sheets since the previous calibration, and detects the sheet cassette sheet presence / absence sensor of the sheet cassette 101. 203 detects that there is no recording material. Even in this case, the control CPU 300 determines that the control CPU 300 is in a low temperature state if the output of the temperature / humidity sensor 325 shown in FIG. Then, the control CPU 300 does not perform the light quantity calibration operation of the recording material discrimination sensor, predicts the attenuation amount of the light quantity from the printed sheet count, increases the LED irradiation light quantity of the recording material discrimination sensor 200, increases the light receiving sensitivity, or discriminates. Lower the threshold.

  FIG. 10 shows a flowchart at this time. When the control CPU 300 determines to calibrate the recording material discrimination sensor, the control CPU 300 checks the output of the paper cassette cassette presence / absence sensor 203 (step S21). If there is no recording material in the paper feed cassette in step S22, the control CPU 300 detects the internal temperature from the output of the temperature / humidity sensor in step S23. In step S24, the control CPU 300 determines whether the detected temperature is, for example, 15 ° C. or more and 35 ° C. or less. As a result of the determination, if the temperature is not in the range of 15 ° C. to 35 ° C., the control CPU 300 does not perform the calibration operation of the recording material determination unit, The amount of attenuation is predicted based on FIG. 4 (step S27). The control CPU 300 corrects the light emission quantity, light reception sensitivity, and discrimination threshold of the recording material discrimination sensor from the predicted attenuation amount of the received light quantity (step S28). Further, when the detected temperature is in the range of 15 ° C. to 35 ° C. in step S24 and does not affect the detection performance of the recording material discrimination sensor, the control CPU 300 executes the calibration operation of the recording material discrimination means shown in step S25. I do. Then, the control CPU 300 corrects the light emission amount, the light receiving sensitivity, and the determination threshold value of the recording material determination unit from the detection result. Here, the temperature range is 15 ° C. or more and 35 ° C. or less. However, this changes depending on the mounting position of the temperature sensor, the temperature characteristics of the recording material discrimination sensor, and the like, and is not specified only in the range of 15 ° C to 35 ° C.

  As described above, even when a certain amount of time has passed since the power was turned on and the temperature in the image forming apparatus rises, the relative output of the phototransistor of the recording material discrimination sensor rises, and the predicted amount of attenuation is shown. to correct. As a result, it is possible to obtain an appropriate amount of light emission, light receiving sensitivity, or recording material discrimination threshold, to reduce misidentification of the recording material, and to apply high image forming conditions suitable for the recording material. It is possible to print high quality images.

[Embodiment 3]
(Device configuration)
Since the configuration of the apparatus is the same as that of the first embodiment, description thereof is omitted.

(Description of operation)
Since the basic configuration and determination method are the same as those in the first embodiment, detailed description thereof is omitted.

  As shown in FIG. 7, the relative output of the phototransistor used as the reflected light receiving element of the recording material discrimination sensor is greatly different depending on the ambient temperature. For this reason, the relative output is low when the sensor is cold, for example, immediately after the power is turned on. At this time, when the correction of the light amount deterioration of the recording material discrimination sensor 200 is executed, the recording material is replenished to the paper feed cassette 101, and the temperature in the image forming apparatus rises by performing the printing operation. The relative output of the phototransistor increases. When the relative output increases, the recording material discrimination sensor outputs a higher detection result to the control CPU 300, and the risk that the control CPU 300 erroneously discriminates that the recording material has a high reflected light amount increases.

  In this embodiment, at the time of shipment from the factory, individual characteristics of the relative output with respect to the ambient temperature as shown in FIG. 7 of the phototransistor Ptr mounted on the recording material discrimination sensor 200 are stored in the storage means 324 shown in FIG. Keep it.

  When the sheet cassette cassette presence / absence sensor 203 of the sheet cassette 101 detects that there is no recording material, the control CPU performs a light quantity calibration operation of the recording material discrimination sensor. At this time, the ambient temperature of the phototransistor is predicted from the output value of the temperature / humidity sensor 325 shown in FIG. 6, and the relative output reduction rate is obtained from the value stored in the recording means 324 based on the value. In consideration of the output reduction rate, the increase / decrease of the LED irradiation light amount of the recording material discrimination sensor 200 or the increase / decrease of the discrimination threshold is determined.

  Furthermore, when the temperature in the image forming apparatus rises for a while after the power is turned on, the relative output of the phototransistor of the recording material discrimination sensor increases accordingly. If the control CPU 300 detects that the output of the temperature / humidity sensor 325 has changed, the control CPU 300 considers the relative output reduction rate of the phototransistor stored in the storage means 324 and increases or decreases the LED irradiation light amount of the recording material discrimination sensor 200, or The increase / decrease of the discrimination threshold is determined.

  FIG. 11 shows a flowchart at this time. When the control CPU 300 determines to calibrate the recording material discrimination sensor, the control CPU 300 checks the output of the paper cassette cassette presence / absence sensor 203 (step S31). If there is no recording material in the paper feed cassette in step S32, the control CPU 300 executes the calibration operation of the recording material discrimination sensor in step S33. The control CPU 300 continues to detect the in-machine temperature from the output of the temperature / humidity sensor (step S34). The control CPU 300 reads out the relative output characteristic data of the phototransistor corresponding to the detected in-machine temperature from the memory 324 (step S35). The control CPU 300 corrects the light emission quantity, light reception sensitivity, and discrimination threshold of the recording material discrimination sensor from the detected light quantity in the calibration operation in step S33 and the relative characteristic data of the phototransistor in step S35. The control CPU 300 also detects the temperature inside the apparatus at the time of recording material discrimination, reads the relative output characteristic data of the recording material discrimination sensor at that time from the memory 324, and corrects the amount of emitted light, the light sensitivity, and the discrimination threshold corresponding to the data. (Step S36).

  As described above, regardless of the temperature of the phototransistor, it is possible to obtain an appropriate light emission amount, light receiving sensitivity setting, and recording material determination threshold value, and to reduce erroneous determination of the recording material. Furthermore, a high-quality image can be printed by applying an optimum image forming condition according to the recording material.

[Other Embodiments]
In addition to the embodiments described above, the following embodiments can be implemented.
(1) The above-described embodiment can also be realized by software that sequentially executes each data processing. That is, a storage medium (or recording medium) in which a program code of software that realizes the functions of the above-described embodiments is recorded is supplied to the system or apparatus. Needless to say, an embodiment to which the present invention can be applied is also achieved by the computer (or CPU or MPU) of the system or apparatus reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment, and is a CD (compact disc), MD (magnetic disk), memory card, MO (magneto-optic disc). ) And the like.

  The functions of the above-described embodiments are not only realized by executing the program code read by the computer. For example, an operating system (OS) running on the computer performs part or all of the actual processing based on the instruction of the program code. Further, it goes without saying that the case where the functions of the above-described embodiment are realized by the processing is also included in the embodiment to which the present invention can be applied.

  Further, consider a case where the program code read from the storage medium is written in a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer. In this case, based on the instruction of the program code, the CPU or the like provided in the function expansion card or function expansion unit performs part or all of the actual processing. It goes without saying that the case where the functions of the above-described embodiment are realized by the processing is also included in the embodiment to which the present invention can be applied.

(2) In the above-described embodiment, an image forming apparatus that is a color laser printer has been described. However, not only a printer, but also an image forming apparatus that is a multifunction peripheral, an image forming apparatus that is a copier having a copy function, and an image scanner. The present invention can be applied to an image reading apparatus having only a function.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment to which the present invention can be applied. It is a schematic block diagram of the paper feed cassette of embodiment which can apply this invention. 1A and 1B are diagrams illustrating a schematic configuration of a recording material discrimination sensor according to an embodiment to which the present invention can be applied, in which FIG. 1A illustrates light reception from a recording medium, and FIG. 2B illustrates light amount detection from a calibration plate. It is a figure showing the graph which shows the example of the output fall with respect to the durable number of sheets of the recording material discrimination | determination sensor of embodiment which can apply this invention. It is a figure which shows the example of the control circuit of the recording material discrimination | determination sensor of embodiment which can apply this invention. 1 is a schematic block diagram of an image forming apparatus according to an embodiment to which the present invention can be applied. It is a figure showing the graph which shows the temperature characteristic of the phototransistor used with the recording material discrimination | determination sensor of embodiment which can apply this invention. It is a figure which shows the example of the threshold value of recording material discrimination | determination of embodiment which can apply this invention. It is a flowchart of Embodiment 1 which can apply this invention. It is a flowchart of Embodiment 2 which can apply this invention. It is a flowchart of Embodiment 3 which can apply this invention.

Explanation of symbols

100 Image forming apparatus body 101 Paper cassette 102 Paper feed rollers 106, 107, 108, 109 Each color photosensitive drum 110 Fixing unit 200 Recording material discrimination sensor 201 Recording material 202 Recording material discrimination sensor calibration plate 203 Paper feed cassette paper presence sensor 300 Control CPU
323 Control ASIC
324 Storage means 325 Temperature / humidity sensor

Claims (4)

Recording material stacking means for loading a recording material, light irradiation means for irradiating the recording material loaded on the recording material stacking means, and reflected light irradiated from the light irradiation means and reflected from the surface of the recording material A reflected light amount detecting means for obtaining a reflected light amount on the surface of the recording material by detecting the recording material, and a recording material determining means for determining an attribute of the recording material from an output of the reflected light amount detecting means, and an image based on the attribute An image forming apparatus for changing a forming condition,
A temperature detection unit that detects an ambient temperature in the image forming apparatus; and a reflected light amount calibration plate that has a predetermined reflectance with respect to an irradiation light amount of the reflected light amount detection unit,
By irradiating light from the light irradiation means and detecting the reflected light quantity from the reflected light quantity calibration plate, the light emission quantity of the light irradiation means, the detection sensitivity of the reflected light quantity detection means, or the discrimination criterion of the recording material discrimination means is corrected. And
The reflected light amount calibration plate is provided in a recording material lifting / lowering means for moving the recording material in the recording material stacking means to a paper feeding position, and when the recording material is not stacked on the recording material stacking means, When the recording material lifting / lowering means is moved up to the detection position of the reflected light quantity detecting means, the reflected light quantity calibration plate is moved,
If the recording material is not in the detection position and the reflected light amount calibration plate is raised, and the output result of the temperature detection means is within a predetermined range, the discrimination reference calibration operation of the recording material discrimination means is performed. An image forming apparatus. Recording material stacking means for loading the recording material, light irradiation means for irradiating the recording material loaded inside the recording material stacking means, light irradiated by the light irradiation means and reflected from the surface of the recording material A reflected light amount detecting unit that obtains a reflected light amount on the surface of the recording material by detecting reflected light; and a recording material determining unit that determines an attribute of the recording material from an output of the reflected light amount detecting unit. An image forming apparatus for changing image forming conditions,
A temperature detection unit that detects an ambient temperature in the image forming apparatus; and a reflected light amount calibration plate that has a predetermined reflectance with respect to an irradiation light amount of the reflected light amount detection unit,
By irradiating light from the light irradiation means and detecting the reflected light quantity from the reflected light quantity calibration plate, the light emission quantity of the light irradiation means, the detection sensitivity of the reflected light quantity detection means, or the discrimination criterion of the recording material discrimination means is corrected. And
The reflected light amount calibration plate is provided in a recording material lifting / lowering means for moving the recording material in the recording material stacking means to a paper feeding position, and when the recording material is not stacked on the recording material stacking means, When the recording material lifting / lowering means is moved up to the detection position of the reflected light quantity detecting means, the reflected light quantity calibration plate is moved,
If the recording material is not in the detection position and the reflected light amount calibration plate is raised and the output result of the temperature detection means is within a predetermined range, the light emission means calibration operation is performed. An image forming apparatus. Recording material stacking means for loading the recording material, light irradiation means for irradiating the recording material loaded inside the recording material stacking means, light irradiated by the light irradiation means and reflected from the surface of the recording material A reflected light amount detecting unit that obtains a reflected light amount on the surface of the recording material by detecting reflected light; and a recording material determining unit that determines an attribute of the recording material from an output of the reflected light amount detecting unit. An image forming apparatus for changing image forming conditions,
A temperature detection unit that detects an ambient temperature in the image forming apparatus; and a reflected light amount calibration plate that has a predetermined reflectance with respect to an irradiation light amount of the reflected light amount detection unit,
By irradiating light from the light irradiation means and detecting the reflected light quantity from the reflected light quantity calibration plate, the light emission quantity of the light irradiation means, the detection sensitivity of the reflected light quantity detection means, or the discrimination criterion of the recording material discrimination means is corrected. And
The reflected light amount calibration plate is provided in a recording material lifting / lowering means for moving the recording material in the recording material stacking means to a paper feeding position, and when the recording material is not stacked on the recording material stacking means, When the recording material lifting / lowering means is moved up to the detection position of the reflected light quantity detecting means, the reflected light quantity calibration plate is moved,
If the recording material is not in the detection position and the reflected light amount calibration plate is raised and the output result of the temperature detecting means is within a predetermined range, the detection sensitivity calibration operation of the reflected light amount detecting means is performed. An image forming apparatus. A means for counting the number of images formed on the recording material, and an increase in the correction amount of the discrimination criterion of the recording material discrimination means or the light emission of the light irradiation means in response to an increase in the count value by the counting means; The image forming apparatus according to claim 1, wherein the correction amount of the light amount is increased or the correction amount of the detection sensitivity of the reflected light amount detection unit is increased.

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