JP2007025114A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus equipped with a recording paper discrimination sensor having a highly precise discrimination performance. <P>SOLUTION: The image forming apparatus is equipped with the recording paper discrimination sensor including a first light emitting means for emitting light to be reflected by the surface of the recording paper, a second light emitting means for emitting light to be transmitted through the recording paper, a first light receiving means for receiving the regular-reflected light reflected by the surface of the recording paper, and a second light receiving means for receiving the irregular-reflected light reflected by the surface of the recording paper and the light transmitted through the recording paper, and for discriminating the recording paper based on the comparison of the output of the first light receiving means and the output of the second light receiving means with prescribed thresholds, and such a failure is prevented that light irregularly reflected by the recording paper of small basis weight is detected as darker one by simultaneously emitting light from the first light emitting means and the second light emitting means, consequently, highly precise discrimination can be attained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus related to a sensor for detecting the glossiness or light transmittance of a recording sheet to determine the type or basis weight of the recording sheet.

  An image forming apparatus such as a copying machine or a laser printer includes 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. A transfer unit that transfers the developer image by the developing device to a recording sheet conveyed in a predetermined direction; and the recording sheet that has received the transfer of the developer image by the transfer unit is heated under predetermined fixing processing conditions. A fixing device for fixing the developer image on the recording paper by applying pressure is provided.

  Conventionally, in such an image forming apparatus, for example, the size and type of recording paper (hereinafter also referred to as paper type) are set by a user on an operation panel or the like provided in the main body of the image forming apparatus. Then, control is performed so as to set the fixing processing conditions (for example, the fixing temperature and the conveyance speed of the recording paper passing through the fixing device).

  Alternatively, using a sensor for discriminating recording paper in the image forming apparatus, for example, as proposed in Patent Document 1, a surface image of the recording paper is picked up by a CMOS sensor, and the surface smoothness of the recording paper is detected. The type of recording paper is determined by the method, and development conditions, transfer conditions, or fixing conditions are variably controlled.

Further, there has been proposed an apparatus for determining the thickness of the recording paper by the transmitted light by providing a light source at a position facing the sensor for determining the recording paper and detecting the transmitted light (for example, Patent Document 2). reference).
JP 2002-182518 A JP 2001-139189 A

  However, the above-described conventional image forming apparatus has the following problems.

  Depending on the recording paper to be detected, there is a difference in the thickness of the recording paper. If the recording paper is thick, the light will not be transmitted through the recording paper, but irregularly reflected light will be detected correctly, but if the recording paper is thin, the light will be And diffusely reflected light is detected darkly. As a result, a phenomenon occurs in which the glossiness of the recording paper is detected at a high level and the glossiness of the recording paper is erroneously determined.

  Therefore, in the present invention, an image forming apparatus that prevents the irregularly reflected light of the recording paper from being detected in the dark by using the detection result of the transmitted light and simultaneously emitting the transmitted light when detecting the reflected light. The purpose is to provide.

  The present invention has been made for the purpose of solving the above-described problems, and includes the following configuration as one means for achieving the object.

  A first invention is a recording paper discrimination sensor for discriminating the type and thickness of a recording paper based on the amount of reflected light reflected on the surface of the recording paper and the amount of transmitted light transmitted through the recording paper, and reflects on the surface of the recording paper First light emitting means for emitting light for light, second light emitting means for emitting light for transmitting the recording paper, specularly reflected light reflected on the surface of the recording paper, and diffusely transmitted light transmitted through the recording paper A first light receiving means for receiving light at different times, and a second light receiving means for receiving irregularly reflected light reflected at the surface of the recording paper and regular transmitted light transmitted through the recording paper at different times, The first and second light emitting means can emit light at the same time.

  The second invention is characterized in that when the first and second light emitting means emit light simultaneously, the light emission amount of the second light emitting means is changed according to the detected paper thickness.

  In addition, there is provided means for variably controlling the conditions of the transfer unit and the fixing device of the image forming apparatus using the detection result.

  Further, the first invention of the present invention will be described as follows.

(1) A first light emitting means for irradiating light on the surface of the recording paper, a first light emitting means, a second light emitting means installed on the opposite side of the recording paper, and a positive light reflected on the surface of the recording paper A first light receiving means for receiving the reflected light; and a second light receiving means for receiving the diffusely reflected light reflected by the surface of the recording paper and the transmitted light that has passed through the recording paper. In an image forming apparatus provided with a recording paper discrimination sensor for discriminating the type of recording paper by comparing the output of the second light receiving means with a predetermined threshold value,
An image forming apparatus, wherein when the reflected light is detected using the first light emitting unit and the first and second light receiving units, the second light emitting unit emits light simultaneously.

  According to the present invention, even when the glossiness on the paper surface is the same but the detection result is different due to the difference in thickness, the present invention can accurately detect the glossiness without affecting the paper thickness. It becomes like this.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

  FIG. 1 shows the configuration of a recording paper discrimination sensor 100 according to the first embodiment of the present invention. As shown in FIG. 1, the recording sheet discrimination sensor 100 is an LED 101 that is a first light emitting unit, an LED 104 that is a second light emitting unit, a phototransistor 103 that is a first light receiving unit, and a second light receiving unit. A phototransistor 102 is included.

  When detecting the transmitted light of the recording paper, the LED 104 is caused to emit light, and the light emitted from the LED 104 is diffused by the diffusion plate through the light collecting guide 14 for condensing the light, and then recorded. The back surface of the paper P is irradiated.

  The transmitted light from the recording paper P is condensed through the slit 12 and received by the phototransistor 102. Thereby, the transmittance of the recording paper P is detected.

  When detecting the glossiness of the recording paper, the LEDs 101 and 102 are caused to emit light simultaneously. Light emitted from the LED 101 is applied to the surface of the recording paper P on the recording paper conveyance guide 105 through the slit 11, and the light emission guide emitted from the LED 104 is provided to collect the light. After being diffused by the diffusion plate, the back surface of the recording paper P is irradiated.

  The reflected light from the recording paper P is collected through the slits 12 and 13 and received by the phototransistors 102 and 103, and the transmitted light is collected through the slit 12 and received by the phototransistor 102. Thereby, the glossiness of the recording paper P is detected.

  In the present embodiment, the LED 101 is arranged so that the LED light irradiates the recording paper P with light at a predetermined angle from an oblique direction as shown in FIG.

  Next, a block diagram showing the internal configuration of the sensor control unit will be described with reference to FIG.

  Reference numerals 301 and 302 denote light emitting elements, and 303 and 304 denote light receiving elements. Reference numeral 305 denotes a light emitting element driving unit for driving the light emitting elements 301 and 302, and reference numeral 306 denotes a main control unit for controlling the light emitting element driving unit. A signal processing unit 307 performs A / D conversion on the output value from the light receiving element with a resolution of 10 bits and calculates the output value of the phototransistors 102 and 103. Reference numeral 308 denotes a comparison operation unit that performs a comparison operation with a set value stored in advance in the memory 309 based on the result of the signal processing unit. A memory 309 represents a nonvolatile memory such as an EEPROM, and stores setting values for recording sheet discrimination. The memory 309 stores at least one type of light emission amount value for the light emitting element 302. For example, the transmitted light amount of the reference paper is detected using the reference paper at the time of factory shipment, and the light emission amount value obtained by calculating the result and using the result is stored in the memory 308.

In the method of detecting the basis weight of the recording paper using the transmitted light amount, the transmitted light amount value of the recording paper when the set light amount of the LED 104 is set to a certain predetermined light amount is compared with a preset threshold value. The basis weight of the recording paper P can be determined. For example, a paper having a basis weight of 75 g / m ² or less is thin paper, a paper having a basis weight of more than 75 g / m ² and 105 g / m ² or less is plain paper, and a basis weight of more than 105 g / m ² and 120 g / m ² or less. If the paper is thick paper 1, and the paper having a basis weight larger than 120 g / m ² is thick paper 2, it can be discriminated into four types: thin paper, plain paper, thick paper 1 and thick paper 2 by the above detection method.

  The method for detecting the glossiness of the recording paper using the amount of reflected light is as follows.

  FIG. 3 schematically shows a measurement result in which the light emission amount is plotted on the horizontal axis and the ratio of the regular reflection light amount / the irregular reflection light amount is plotted on the vertical axis. A dotted line portion indicates a set light amount value when the light emission amount of the LED 101 is set to a predetermined light amount. From this figure, it is understood that the ratio of the regular reflection light quantity / the irregular reflection light quantity decreases in the order of OHT> Gloss film> Gloss paper> Plain paper. Ta, Tb, and Tc indicate threshold values for discriminating between OHT and gloss film, gloss film and gloss paper, and gloss paper and plain paper, respectively.

  Therefore, the type of the recording paper P can be determined by obtaining the ratio of the regular reflection light amount / the irregular reflection light amount when the LED 101 is illuminated with the set light amount value and comparing it with the preset threshold values Ta, Tb, Tc.

  FIG. 4 shows a control flowchart of the recording paper discrimination sensor.

  First, the LED 104 is caused to emit light with a light amount La adjusted in advance (S401). At that time, the LED 101 is turned off. The phototransistor 102 receives the normal transmitted light amount (S402), and the obtained output value is signal-processed (S403) to obtain a value Pb (normal transmitted light amount) indicating the glossiness of the recording paper. Then, a comparison operation is performed with the transparency determination threshold value Sa stored in advance in the memory (S404). If Sa ≦ Pb, it is determined as thin paper (S405). In the case of Pb <Sa, a comparison operation is performed with the transparency determination threshold value Sb stored in advance in the memory (S406). If Sb ≦ Pb, it is determined as plain paper (S407). In the case of Pb <Sb, a comparison operation is performed with the transparency determination threshold value Sc previously stored in the memory (S408). If Sc ≦ Pb, it is determined as thick paper 1 (S409). In the case of Pb <Sc, it is determined as thick paper 2.

  Next, the LEDs 101 and 104 are caused to emit light simultaneously with a light amount adjusted in advance (S410). The phototransistors 102 and 103 receive the irregularly reflected light amount and the regular reflected light amount (S411). The obtained output value is signal-processed (S412), and a value Pa (regularly reflected light amount / diffuse reflected light amount) indicating the glossiness of the recording paper is obtained. Ask. Then, it is compared with the glossiness determination threshold value Ta stored in advance in the memory (S413). If Ta ≦ Pa, it is determined as OHT (S414). If Ta> Pa, a comparison operation is performed with the glossiness determination threshold value Tb stored in advance in the memory (S415). If Tb <Pa, it is determined as a gloss film (S416). In the case of Pa ≦ Tb, the calculation is compared with the glossiness determination threshold value Tc stored in advance in the memory (S417). If Tc <Pa, it is determined as gloss paper (S418). If Pa ≦ Tc, it is determined as plain paper (S419).

  The operation for discriminating the recording paper in the present embodiment can be described in the same manner as the operation in the first embodiment.

  In the present embodiment, in addition to the control of the first embodiment, when the gloss level is detected, the amount of light emitted from the LED 104 is changed according to the basis weight of the recording paper.

  FIG. 5 shows a flowchart of the control.

  First, the LED 104 is caused to emit light with a light amount La adjusted in advance (S701). At that time, the LED 101 is turned off. The phototransistor 102 receives the normal transmitted light amount (S702), and the obtained output value is signal-processed (S703) to obtain a value Pb (normal transmitted light amount) indicating the glossiness of the recording paper. Then, a comparison operation is performed with the transparency determination threshold value Sa stored in advance in the memory (S704). If Sa ≦ Pb, it is determined as thin paper (S705). In the case of Pb <Sa, a comparison operation is performed with the transparency determination threshold value Sb stored in advance in the memory (S706). If Sb ≦ Pb, it is determined as plain paper (S707). In the case of Pb <Sb, a comparison operation is performed with the transparency determination threshold value Sc previously stored in the memory (S708). If Sc ≦ Pb, it is determined as thick paper 1 (S709). In the case of Pb <Sc, it is determined as thick paper 2.

  Next, the LEDs 101 are caused to emit light simultaneously with a light amount adjusted in advance (S710). Then, it is determined whether or not the result of the transmitted light detection is thin paper (S711), and if it is thin paper, the LED 104 is illuminated with αLa (S712). It is determined whether or not the result of transmitted light detection is plain paper (S713). If the result is plain paper, the LED 104 is illuminated with βLa (α> β) (S714). The phototransistors 102 and 103 receive the irregularly reflected light amount and the regular reflected light amount (S715). The obtained output value is signal-processed (S716), and a value Pa (regularly reflected light amount / diffuse reflected light amount) indicating the glossiness of the recording paper is obtained. Ask. Then, it is compared with the glossiness determination threshold value Ta stored in advance in the memory (S717). If Ta ≦ Pa, it is determined as OHT (S718). If Ta> Pa, a comparison operation is performed with the glossiness determination threshold value Tb stored in advance in the memory (S719). If Tb <Pa, it is determined as a gloss film (S720). In the case of Pa ≦ Tb, the calculation is compared with the glossiness determination threshold value Tc + stored in the memory in advance (S721). If Tc <Pa, it is determined as gloss paper (S722). If Pa ≦ Tc, it is determined as plain paper (S723).

  FIG. 6 is a view showing an image forming apparatus according to the second embodiment of the present invention.

  In the figure, 1001 is an image forming apparatus, 1002 is a paper cassette, 1003 is a paper feed roller, 1004 is a transfer belt driving roller, 1005 is a transfer belt, 1006 to 1009 are photosensitive drums of yellow, magenta, cyan and black, 1010 to 1013 Transfer rollers, 1014 to 1017 are yellow, magenta, cyan, and black cartridges, 1018 to 1021 are yellow, magenta, cyan, and black optical units, and 1022 is a fixing unit.

  The image forming apparatus transfers an image of yellow, magenta, cyan, and black on a recording sheet by using an electrophotographic process, and heat-fixes the toner image by a fixing roller based on temperature control.

  Each color optical unit is configured to form a latent image by exposing and scanning the surface of each photosensitive drum with a laser beam, and a series of these image forming operations is performed from a predetermined position on the conveyed recording paper. Scan control is performed in synchronization with the transfer.

  Further, the image forming apparatus feeds and conveys recording paper, which is recording paper, a transfer belt drive motor that drives a transfer belt drive roller, each color photosensitive drum, and a photosensitive drum drive motor that drives the transfer roller. A fixing drive motor for driving the fixing roller is provided.

  Reference numeral 1023 denotes a recording paper discrimination sensor, which irradiates light on the surface of the recording paper fed and conveyed, collects the reflected light to form an image, and detects an image of a specific area on the recording paper.

  A control CPU (not shown) included in the image forming apparatus applies a desired amount of heat to the recording paper by the fixing unit 1022 to fuse and fix the toner image on the recording paper.

  Next, the operation of the control CPU will be described with reference to FIG.

  FIG. 7 is a diagram illustrating the configuration of each unit controlled by the control CPU.

  In the figure, 20 is a CPU, 21 is a recording paper discrimination sensor, 22 to 25 are provided with polygon mirrors, motors and lasers, and an optical unit for scanning a laser on the photosensitive drum surface to draw a desired latent image, 26 A paper feed motor for transporting recording paper, 27 is a paper feed solenoid used to start driving a paper feed roller for feeding recording paper, and 28 is used to detect whether the recording paper is set at a predetermined position. A paper presence sensor 29, a primary charging necessary for the electrophotographic process, development, primary transfer, a high voltage power source for controlling the secondary transfer bias, 30 a drum driving motor for driving the photosensitive drum and the transfer roller, and 31 a transfer A belt drive motor for driving the belt and the rollers of the fixing unit, 32 is a fixing unit and a low-voltage power supply unit, and the thermis (not shown) is controlled by the control CPU. Monitoring the temperature, the control is performed to keep the fusing temperature constant.

  Reference numeral 33 denotes an ASIC which performs motor speed control inside the recording paper discrimination sensor 11 and the optical units 22 to 25 and speed control of the paper feed motor based on an instruction from the control CPU 20.

  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 hardware circuit of the ASIC 33 to reduce the control load on the CPU 20.

  When receiving a print command according to an instruction from a host computer (not shown), the control CPU 20 determines the presence / absence of recording paper by the paper presence / absence sensor 28. If there is paper, the control CPU 20 drives the paper feed motor 26, drum drive motor 30, belt drive. The motor 31 is driven and the paper feed solenoid 27 is driven to convey the recording paper to a predetermined position.

  When the recording paper is conveyed to the position of the recording paper discrimination sensor 21, the control CPU instructs the recording paper discrimination sensor 21 to discriminate the recording paper to the ASIC 33, and the recording paper discrimination sensor 21 discriminates the type of the recording paper. To do.

  The temperature condition of the fixing unit 32 is variably controlled according to the result of the paper type determined by the recording paper sensor 21.

  This is particularly effective in the case of OHT, when the fixing property of the toner adhering to the surface of the recording paper is poor, the OHT permeability is deteriorated. Further, when the fixing temperature is high in the case of thin paper, there is a problem that the paper curls when being discharged.

  Further, the recording paper conveyance speed is variably controlled. The variable control of the conveyance speed is realized by the CPU 20 setting the speed control register value of the ASIC 33 that controls the speed control.

  In particular, in the case of OHT or glossy paper, it is possible to improve the fixability of the toner adhering to the surface of the recording paper and improve the gloss to improve the image quality.

  As described above, the present embodiment is characterized in that the type of the recording sheet is determined by the recording sheet determination sensor, and the CPU variably controls the control temperature condition of the fixing unit or the conveyance speed of the recording sheet based on the result. .

Diagram showing the configuration of the recording paper discrimination sensor Block diagram showing the internal configuration of the sensor controller Diagram for explaining the method of recording sheet discrimination Flow chart for explaining the first embodiment Flow chart for explaining the second embodiment The figure which shows the image forming apparatus in 3rd Example Control block diagram of image forming apparatus in third embodiment

Explanation of symbols

11, 12, 13 Slit 100 Recording paper discrimination sensor 101, 104 LED
102,103 phototransistor

Claims (5)

The first light emitting means for irradiating the surface of the recording paper, the first light emitting means is a second light emitting means installed on the opposite side of the recording paper, and the specularly reflected light reflected by the surface of the recording paper A first light receiving means for receiving light, and a second light receiving means for receiving the diffusely reflected light reflected by the surface of the recording paper and the transmitted light transmitted through the recording paper, the output of the first light receiving means and the second light receiving means In an image forming apparatus provided with a recording paper discrimination sensor for discriminating the type of recording paper by comparing the output of the light receiving means with a predetermined threshold value,
An image forming apparatus, wherein when the reflected light is detected using the first light emitting unit and the first and second light receiving units, the second light emitting unit emits light simultaneously.   When the reflected light is detected using the first light emitting means and the first and second light receiving means, the light quantity of the second light emitting means that emits light simultaneously is detected by the second light receiving means. The image forming apparatus according to claim 1, further comprising a control unit that controls the amount of light to an appropriate amount according to the amount of transmitted light.   The image forming apparatus according to claim 1, wherein a fixing condition of the fixing device can be set according to a result of the recording paper discrimination sensor.   The image forming apparatus according to claim 3, wherein a fixing condition of the fixing device controls a temperature of the fixing device.   The image forming apparatus according to claim 3, wherein a fixing condition of the fixing device controls a speed at which the recording paper passes through the fixing device.

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