JP2008013289A - Detecting device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect the physical quantity on an object for detection with good accuracy by changing light receiving sensitivity by a simple constitution. <P>SOLUTION: In a detection device, detection resistors R1-R3 and switch elements SW1-SW3 provided corresponding to each of the detection resistors R1-R3 are provided on a control substrate 82, and each of the detection resistors R1-R3 and the switch elements SW1-SW3 is connected to an output terminal of a first light receiving element 90B in parallel. A switching signal for performing the switching so that an electric signal as a sensor output from the first light receiving element 90B runs in the corresponding detection resistors R1-R3 by switching ON/OFF of the switches is input in each input terminal of the switch elements SW1-SW3 from a CPU 84. The sensitivity of a first transmissive sensor 90 is switched by changing the synthesized resistance value of a circuit comprising the detection resistors R1-R3 with the electric signal running therein and a detection resistor R4 by the ON/OFF combination of the switch elements SW1-SW3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a detection apparatus and an image forming apparatus, and in particular, a detection apparatus that emits light to a detection object and detects a physical quantity related to the detection object by transmitted light or reflected light of the detection object, and the detection apparatus The present invention relates to an image forming apparatus including

  Conventionally, by using a transmissive sensor and detecting the amount of light transmitted through a sheet with a light receiving element, the sheet thickness, double feed, remaining sheet quantity, and the like are detected.

  At this time, in the transmissive sensor, the amount of received light is very weak when a thick sheet or a large number of sheets are double-fed, and the amount of received light is very strong when an OHP or ultra thin sheet is used. When trying to detect thick paper, the sensitivity on the thin paper side becomes dull, and when trying to detect plain paper, the sensitivity for the thick paper and the thin paper becomes dull and difficult to detect.

  As a countermeasure, there is known a double feed detection device that changes the amplification factor of a signal detected by a light receiving element in accordance with the amount of transmitted light (Patent Document 1). In order to change the amplification factor, the circuit of this double feed detection device is provided with one operational amplifier, two analog switches, and two resistors in accordance with a change in one stage.

In addition, a transmission type paper presence / absence detection sensor is known in which a detection resistor connected in series with a light receiving element is switched by a switch to prevent erroneous detection due to deterioration of the light emitting element or reduction in the amount of emitted light due to paper dust adhesion ( Patent Document 2).
JP 2004-256293 A Japanese Patent Laid-Open No. 7-172634

  However, the technique described in Patent Document 1 has a problem that the circuit configuration for changing the amplification factor becomes complicated and the cost increases.

  Further, in the technique described in Patent Document 2, the light reception sensitivity is switched as correction when the light emission amount of the paper presence / absence detection sensor is reduced, and switching of the light reception sensitivity according to the thickness and the number of sheets of light emission is disclosed. Absent.

  In view of the above facts, an object of the present invention is to provide a detection apparatus and an image forming apparatus that can detect a physical quantity related to a detection target with high accuracy by switching light reception sensitivity with a simple configuration.

  In order to achieve the above object, a detection apparatus of the present invention receives a light emitting element that emits light, transmitted light that has passed through a detection object, and reflected light that has been reflected from the detection object. A light receiving element that outputs an electrical signal corresponding to the amount of light received, a variable resistance circuit that is connected to the light receiving element so that the electrical signal output by the light receiving element flows, and that can change a resistance value, and the electrical signal When the voltage of the electric signal is higher than the upper limit value of the predetermined range, the resistance value of the variable resistance circuit is changed to be small, and when the voltage of the electric signal is lower than the lower limit value of the predetermined range The resistance value changing means for changing the resistance value of the variable resistance circuit to be increased, and the inspection based on the voltage of the electric signal when the resistance value of the variable resistance circuit is changed by the resistance value changing means. It is configured to include a detecting means for detecting a physical quantity relating to an object of an elephant.

  According to the detection apparatus of the present invention, the light emitting element emits light, the detection object is irradiated with light, and the light receiving element transmits either the transmitted light transmitted through the detection object or the reflected light reflected from the detection object. One of them is received, and an electrical signal corresponding to the amount of received light is output. Here, since the electric signal flows into the variable resistance circuit, and the voltage of the electric signal is determined by the resistance value of the variable resistance circuit, the voltage of the electric signal is changed by changing the resistance value of the variable resistance circuit. The light receiving sensitivity is changed.

  Then, when the voltage of the electric signal is higher than the upper limit value of the predetermined range by the resistance value changing means, the resistance value of the variable resistance circuit is changed so as to decrease, and the voltage of the electric signal output by the light receiving element Is within a predetermined range. On the other hand, when the voltage of the electric signal is lower than the lower limit value of the predetermined range, the resistance value changing means changes the resistance value of the variable resistance circuit so as to increase, and the voltage of the electric signal output by the light receiving element. Is within a predetermined range.

  Then, based on the voltage of the electric signal when the resistance value of the variable resistance circuit is changed by the resistance value changing means as described above, the detection means detects a physical quantity related to the object to be inspected.

  Therefore, by changing the resistance value of the variable resistance circuit so that the voltage of the electrical signal output from the light receiving element is within a predetermined range, the physical quantity related to the detection target is accurately switched by switching the light receiving sensitivity with a simple configuration. Can be detected.

  A variable resistance circuit according to the present invention includes a plurality of resistance elements connected to a light receiving element, and a plurality of switches provided corresponding to each of the plurality of resistance elements and switched to allow an electric signal to flow through the corresponding resistance elements. The resistance value changing means can change the resistance value of the variable resistance circuit by switching on / off of the plurality of switch elements and changing the combined resistance value of the plurality of resistance elements. As a result, the resistance value of the variable resistance circuit can be changed by the plurality of resistance elements and the plurality of switch elements, so that the light receiving sensitivity can be switched with a simpler configuration.

  Moreover, each of the resistance values of the plurality of resistance elements can be made different. As a result, the resistance value of the variable resistance circuit can be changed to many resistance values, so that it is possible to switch to many light receiving sensitivities.

  The light receiving element receives the transmitted light that has passed through the detection target, and the detection device detects when the resistance value of the variable resistance circuit is changed to a predetermined value by the resistance value changing unit. The light emitting device may further include a light emission amount adjusting unit that causes the light emitting device to emit light in the absence of an object and adjusts the light emission amount of the light emitting device based on the voltage of the electrical signal output by the light receiving device. Thereby, since the emitted light quantity of a light emitting element can be adjusted to desired light quantity, the physical quantity regarding a detection target object can be detected further accurately.

  The light emission amount adjusting means can adjust the light emission amount by the light emitting element when the resistance value of the variable resistance circuit is changed to be the smallest.

  The object to be detected is a recording medium, and the detecting means can detect at least one of the thickness and the number of the recording medium. Thereby, the heat and number of storage media can be accurately detected as physical quantities related to the detection target.

  The light receiving element receives the transmitted light that has passed through the recording medium, and the detection means outputs the light even if the resistance value of the variable resistance circuit is maximized by the resistance value changing means. When the voltage of the electrical signal is higher than the upper limit value in the predetermined range, it can be detected that the recording medium is OHP.

  The light receiving element receives the transmitted light that has passed through the recording medium, and the detection means outputs the light even if the resistance value of the variable resistance circuit is changed to the smallest value by the resistance value changing means. When the voltage of the electrical signal is lower than the lower limit value of the predetermined range, it can be detected that the recording medium is ultra-thick paper.

  An image forming apparatus according to the present invention includes the detection device described above and an image forming unit that forms an image on a recording medium.

  According to the image forming apparatus of the present invention, the thickness and number of recording media can be detected by the detection device, and an image can be formed on the recording medium by the image forming means in consideration of the detected contents. As a result, an image can be formed on the recording medium by processing suitable for the thickness and number of recording media.

  As described above, according to the detection apparatus and the image forming apparatus of the present invention, the resistance value of the variable resistance circuit is changed so that the voltage of the electric signal output from the light receiving element is within a predetermined range. With this configuration, it is possible to obtain an effect that the physical quantity related to the detection target can be accurately detected by switching the light receiving sensitivity.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the image forming apparatus 10 according to the embodiment of the present invention includes an engine unit 12, and a paper feeding unit 14 is provided below the engine unit 12.

  The paper feed unit 14 includes a paper tray 22 on which paper is stacked, and a paper feed roll 24 that sends out the paper from the paper tray 22. , 28, passes the paper feed path 30, and is conveyed to the transfer roll 74.

  After the toner image is transferred onto the paper by the transfer roll 74 and fixed by the fixing roll 32A of the fixing unit 32, the toner image is provided on the upper portion of the engine unit 12 by the discharge roll 36 or the discharge roll 38 depending on the position of the switching claw 34. The discharged first discharge tray 16 or the second discharge tray 18 is discharged.

  Here, in the case of double-sided printing, after the printing of the front surface is completed in the order as described above, before the paper is completely discharged to the first discharge tray 16, the discharge roll 36 is reversed and the paper is reversed. Supplied to the line 40. The paper is then returned to the paper feed path 30 through the transport rolls 42, 44, 46, and 48, and the back side of the paper is printed. In the case of manual printing, by placing paper on the manual feed tray 20, the paper is transported from the manual feed roll 49 to the paper feed path 30 via the transport roll 48 and printed.

 In the fixing unit 32, the fixing roll 32A is heated to a predetermined temperature by lighting a lamp (for example, a halogen lamp), and the toner image is formed on the sheet by the heating and pressurization by the heated fixing roll 32A. It has become established.

  By the way, on the right side of FIG. 1 of the image forming apparatus 10, four toner cartridges 64 filled with a developer (consisting of toner and magnetic carrier) for each color are arranged. The toner cartridge 64 is connected to developing units 60Y, 60M, 60K, and 60C, which will be described later, arranged in order from the top of FIG. 1 by a developer supply path 65, and the developer in the toner cartridge 64 is connected to the developing unit. Supplied to 60Y, 60M, 60K, and 60C.

  An exposure unit 62 is disposed on the left side of the toner cartridge 64 in FIG. 1, and the four laser beams L (Y), L (M), and L (K) corresponding to the image signal are provided from the exposure unit 62. , L (C) are the photosensitive drums 52Y, 52M, 52K, and 52C constituting the photosensitive unit 50 arranged on the left side of the exposure unit 62 in FIG. ) To form a latent image on the photosensitive drum 52.

  The photosensitive drum 52 is for yellow (52Y), magenta (52M), black (52K), and cyan (52C) from the top of FIG.

  The exposure unit 62 outputs laser light L (Y), L (M), L (K), and L (C) (hereinafter collectively referred to as laser light L) of each color Y, M, K, and C. And a modulation processing unit that modulates and scans the laser light L, an fθ lens that corrects the scanning speed on the exposure surface, and a cylindrical lens for surface tilt correction that has lens power in the scanning direction. And an optical system.

  In the exposure unit 62, the laser light L of each color emitted from the light source unit enters the modulation processing unit, is modulated according to the image information for each color, and is scanned by the polygon mirror 67 rotated by the polygon motor 63. (Main scanning). The laser beams L of the respective colors scanned by the polygon mirror 67 are reflected by the mirror group 69 in the arrangement direction of the photosensitive drums 52 corresponding to the respective colors and formed on the respective photosensitive drums 52.

  The photoconductor unit 50 is provided with a charging roll 56 and a refresh roll 54 corresponding to each photoconductor drum 52 (in FIG. 1, only those corresponding to the photoconductor unit 50Y are indicated by symbols). It is provided to rotate in contact with the body drum 52. In the charging roll 56, the photosensitive drum 52 is uniformly charged, and the toner flying from the magnet roll 80 provided in the developing device 58 is attached to the surface of the photosensitive drum 52. On the other hand, the refresh roll 54 discharges the photosensitive drum 52 to remove residual toner adhering to the surface of the photosensitive drum 52, thereby preventing ghosts and the like caused by the toner remaining on the surface of the photosensitive drum 52.

 Here, the developing device 58 is disposed on the lower right side of FIG. 1 of each photoconductor unit 50, and corresponds to each photoconductor drum 52 (52Y, 52M, 52K, 52C). 60M, 60K, and 60C are arranged in the vertical direction.

  On the other hand, an intermediate transfer unit 66 is disposed on the left side of the photoconductor unit 50 in FIG. 1, and three drum-shaped intermediate transfer bodies 68, 70, and 72 are provided. The two first intermediate transfer members 68 and 70 are arranged vertically in the vertical direction, and the upper first intermediate transfer member 68 includes two photosensitive drums 52Y and 52Y arranged at the upper portion of the photosensitive drum 52. The lower first intermediate transfer member 70 rotates in contact with the two photosensitive drums 52K and 52C disposed in the lower portion. The second intermediate transfer drum 72 rotates in contact with both the first intermediate transfer bodies 68 and 70, and the transfer roll 74 described above rotates in contact with the second intermediate transfer drum 72.

  Accordingly, the toner images are transferred from the photosensitive drums 52Y and 52M to the first intermediate transfer member 68, and the toner images are transferred from the photosensitive drums 52K and 52C to the first intermediate transfer member 70, respectively. The two color toner images transferred to the first intermediate transfer bodies 68 and 70 are transferred to the second intermediate transfer drum 72 to become four colors, and the four color toner images are transferred to the sheet by the transfer roll 74. Will be.

  A cleaning roll 76 and a cleaning brush 78 are disposed in the vicinity of the intermediate transfer members 68, 70, and 72, respectively, and the residual toner on the surface of the intermediate transfer members 68, 70, and 72 is scraped off.

  Further, a position where the paper is transported and passed, upstream of the transfer roll 74, from a first light emitting element 90A that emits light to the paper and a first light receiving element 90B that receives light transmitted through the paper. A first transmission type sensor 90 is provided.

  The image forming apparatus 10 includes a second light emitting element 92 </ b> A that is provided on the top of the paper stacked on the paper tray 22, emits light to the paper, a bottom surface of the paper tray 22, and There is provided a second transmission type sensor 92 comprising a second light receiving element 92B for receiving the transmitted light of the paper.

  The first light receiving element 90B and the second light receiving element 92B output an electrical signal corresponding to the amount of transmitted light received.

  Next, a circuit configuration for detecting the thickness and the number of sheets using the transmission sensors 90 and 92 will be described with reference to FIG. The circuit configuration of the first transmissive sensor 90 is the same as that of the first transmissive sensor 90, and therefore the circuit configuration of the first transmissive sensor 90 will be described below.

  The first transmission type sensor 90 is connected to a control board 82 on which a CPU 84 for controlling the entire image forming apparatus 10 is mounted.

  The control board 82 is provided with a light emission amount adjustment circuit 86 for adjusting the light emission amount of the first light emitting element 90 </ b> A. The light emission amount adjustment circuit 86 corresponds to the first adjustment control signal from the CPU 84. The amount of light emission is adjusted by controlling the voltage applied to the light emitting element 90A.

  Further, the control board 82 is provided with a plurality of (for example, three) detection resistors R1 to R3 and switch elements SW1 to SW3 provided corresponding to the detection resistors R1 to R3 as variable resistance circuits. Yes. Each of the detection resistors R1 to R3 is connected in series with one of the corresponding switch elements SW1 to SW3, and each of the switch elements SW1 to SW3 is connected to the output terminal of the first light receiving element 90B. The corresponding detection resistors R1 to R3 and switch elements SW1 to SW3 are connected in parallel to the output terminal of the first light receiving element 90B, and the switch elements SW1 to SW3 of the detection resistors R1 to R3. The terminal on the opposite side is grounded.

  Further, the first transmission sensor 90 is provided with a detection resistor R4, one end is connected to the output terminal of the first light receiving element 90B, and the other end is grounded.

  The output terminal of the first light receiving element 90 </ b> B is connected to the CPU 84, and an electrical signal as a sensor output of the first transmission sensor 90 is input to the CPU 84.

  Each of the input terminals of the switch elements SW1 to SW3 is connected to the CPU 84, and the switch is turned on and off so that any one of the corresponding detection resistors R1 to R3 has a sensor output from the first light receiving element 90B. A switching signal for switching so that an electric signal flows is input from the CPU 84 to each input terminal of the switch elements SW1 to SW3.

  Further, the first transmission sensor 90 is provided with a detection resistor R4, one end is connected to the output terminal of the first light receiving element 90B, and the other end is grounded.

  The resistance values of the detection resistors R1 to R4 are different, for example, 10 kΩ, 80 kΩ, 250 kΩ, and 700 kΩ, respectively.

  The sensitivity of the first transmissive sensor 90 can be switched by changing the combined resistance value of the circuit composed of the detection resistors R1 to R3 and the detection resistor R4 through which the electric signal flows, by a combination of on and off of the switch elements SW1 to SW3. it can. For example, as shown in FIG. 3, the sensitivity can be switched to eight types by combining on / off of the switch elements SW <b> 1 to SW <b> 3. In each of the eight types of sensitivity, as shown in FIG. 4, the sensor output of the first transmission sensor 90 is different for the same thickness of the paper, and the voltage level of the sensor output is the same for the same paper thickness. Is different. In the sensitivity 8, the sensitivity is improved in the region where the paper is thin, and the thickness of the thin paper can be accurately detected. However, in the region where the paper is thick, the sensitivity is low, The thickness of thick paper cannot be detected with high accuracy. On the other hand, with sensitivity 1, the sensitivity is improved in a region where the paper is thick, and the thickness of the thick paper can be accurately detected. However, in the region where the paper is thin, the voltage level of the sensor output is high. Therefore, the thickness of the thin paper cannot be detected.

  Next, the operation of the image forming apparatus 10 according to the first embodiment will be described. First, the flow of image forming processing will be described.

  Around each photosensitive drum 52, an image forming (printing) process for each color by a known electrophotographic method is performed as follows.

  First, each photosensitive drum 52 is rotationally driven at a predetermined rotational speed. As shown in FIG. 1, the surface of the photosensitive drum 52 is uniformly charged to a predetermined level by applying a DC voltage of a predetermined charging level (for example, about −800 V) to the charging roll 56. . In the present embodiment, only a DC voltage is applied to the charging roll 56, but an AC component may be superimposed on the DC component.

  Next, the surface of each photosensitive drum 52 having a uniform surface potential is irradiated with laser light L corresponding to each color by the exposure unit 62, and an electrostatic latent image corresponding to image information for each color is formed. The As a result, the surface potential of the exposed portion of the photosensitive drum 52 by the laser light L is neutralized to a predetermined level.

  The electrostatic latent image formed on the surface of each photoconductive drum 52 is developed by each corresponding developing device 58 and visualized on each photoconductive drum 52 as a toner image of each color.

  Next, the toner images of the respective colors formed on the photosensitive drums 52 are electrostatically primarily transferred onto the corresponding primary intermediate transfer drums 68 and 70. Here, the Y and M toner images formed on the photosensitive drums 52Y and 52M are on the primary intermediate transfer drum 68, and the K and C toner images formed on the photosensitive drums 52K and 52C are the primary intermediate. Each image is transferred onto the transfer drum 70.

  Thereafter, the toner image formed on the primary intermediate transfer drums 68 and 70 is electrostatically secondary-transferred onto the secondary intermediate transfer drum 72. As a result, on the secondary intermediate transfer drum 72, toner images from a single color image to a quadruple color image of each of Y, M, K, and C are formed.

  Finally, the toner image formed on the secondary intermediate transfer drum 72 is tertiary-transferred onto the paper passing through the paper conveyance path by the transfer roll 74. After the paper is tertiary transferred, the toner image formed on the paper is heated and fixed by the fixing unit 32, and the image forming process is completed.

  Next, the flow of the light emission amount adjustment process will be described. As an initial operation, it is necessary to adjust the light emission amounts of the first light emitting element 90A and the second light emitting element 92A in order to detect the thickness and the number of sheets with high accuracy from the transmitted light amount. Since the adjustment of the light emission amount of the first light emitting element 90A and the adjustment of the light emission amount of the second light emitting element 92A are the same processing, the adjustment of the light emission amount of the first light emitting element 90A will be described below. explain.

  When the initialization process is performed in the image forming apparatus 10, a light emission amount adjustment process routine shown in FIG. 4 is executed.

  First, in step 100, it is determined whether or not there is no paper at the sensor detection position of the first transmission type sensor 90. If there is no paper, the process proceeds to step 104. If it is, in step 102, the paper is transported, the paper is not in the sensor detection position, and the process proceeds to step 104.

  In step 104, all of the switch elements SW1 to SW3 are turned on so as to obtain the lowest sensitivity (sensitivity 8 in the example of FIG. 4), and the combined resistance value of the circuit including the detection resistors R1 to R4 through which the electric signal flows is obtained. In step 106, the first light emitting element 90A is caused to emit light, the first light receiving element 90B receives light, and an electric signal as a sensor output is taken in according to the amount of received light.

  In step 108, it is determined whether or not the voltage level Vcal of the acquired sensor output is 2.48V or more and 2.52V or less, and is 2.48V or more and 2.52V or less. In some cases, it is determined that the light emission amount has been adjusted to an appropriate amount and the light emission amount adjustment processing routine is terminated. However, if the sensor output voltage level Vcal is less than 2.48 V, the light emission amount is determined. In step 110, it is determined whether the light amount is set to the maximum light amount. If it is set to the maximum light amount, it is impossible to adjust the light amount to be larger than this. Therefore, in step 112, a sensor cleaning message is displayed on the display panel (not shown) of the image forming apparatus 10. If the maximum light intensity is not set, the light emission amount adjustment circuit 86 sets the light emission amount larger by a predetermined amount in step 114, and the process returns to step 106 to output the sensor output. take in.

  In step 108, if the sensor output voltage level Vcal is higher than 2.52 V, it is determined that the light emission amount is large, and in step 116, it is determined whether the light amount is set to the minimum light amount. If it is set to the minimum light amount, it is impossible to adjust the light amount to be smaller than this. Therefore, in step 118, a sensor failure message is displayed on the display panel (not shown) of the image forming apparatus 10. If the minimum light intensity is not set, the light emission amount adjustment circuit 86 sets the light emission amount to be smaller by a predetermined amount in step 120, and the process returns to step 106 to output the sensor output. Capture.

  As described above, by executing the light emission amount adjustment processing routine, when the initialization process is performed in the image forming apparatus 10, the light emission amount of the light emitting element 90A of the first transmission type sensor 90 is an appropriate amount. Adjusted to Similarly, the light emission amount adjustment processing routine is executed for the second transmission type sensor 92.

  Next, the flow of the paper thickness detection process will be described.

  When the image forming process is performed in the image forming apparatus 10, a paper thickness detecting process routine shown in FIG. 6 is executed.

  First, in step 130, it is determined whether or not the sheet is conveyed to the detection position of the first transmission type sensor 90 and stopped, and the sheet is conveyed to the detection position of the first transmission type sensor 90 to detect the detection position. When the sheet is stopped, the process proceeds to step 132, and the switch element SW1 is set to set the predetermined combined resistance value so that the first transmission sensor 90 has a predetermined sensitivity (for example, sensitivity 4 in FIG. 4). In step 134, the first light emitting element 90A is caused to emit light and is received by the first light receiving element 90B. In accordance with the amount of received light, the electrical output as the sensor output is turned on. Capture the signal.

  In step 136, it is determined whether or not the voltage level V0 of the acquired sensor output is within a predetermined detectable range of 1.0 V or more and 2.7 V or less, and is 1.0 V or more, When the voltage is 2.7 V or less, it is determined that the combined resistance value of the detection resistors R1 to R4 is set so that the sensitivity of the first transmission sensor 90 becomes an appropriate sensitivity. Based on the set sensitivity and the voltage level V0 of the sensor output, the paper thickness is detected, and the paper thickness detection processing routine is terminated.

  If the voltage level V0 of the sensor output is less than 1.0 V in step 136, it is determined that the sensitivity is low and the combined resistance value is small. In step 140, the sensitivity having the highest sensitivity (in FIG. 4). It is determined whether or not the combined resistance value is set to the maximum so that the sensitivity becomes 1). If it is set to the highest sensitivity, the sensitivity cannot be increased any more. Therefore, in step 142, it is determined that the paper thickness is the maximum, and the paper is detected to be ultra-thick paper. When the thickness detection processing routine is finished, but the highest sensitivity is not set, in step 144, the switch elements SW1 to SW3 are switched on and off to increase the sensitivity by one step, and the combined resistance value is set to a large value. Then, the process returns to step 134 to capture the sensor output again.

  If the voltage level V0 of the sensor output is greater than 2.7 V in step 136, it is determined that the sensitivity is high and the combined resistance value is large. In step 146, the sensitivity having the lowest sensitivity (FIG. 4). Then, it is determined whether or not the combined resistance value is set to the minimum so that the sensitivity becomes 8). If the lowest sensitivity is set, the sensitivity cannot be lowered any more. Therefore, in step 148, it is determined that the paper thickness is the minimum, and the paper is detected to be OHP. When the detection processing routine is completed, but the lowest sensitivity is not set, in step 150, the switch elements SW1 to SW3 are switched on and off to set the combined resistance value small so that the sensitivity is lowered by one step. Returning to step 134, the sensor output is captured again.

  As described above, when the paper thickness detection processing routine is executed, the combined resistance value of the circuit through which the electrical signal flows is set so as to have an appropriate sensitivity according to the paper thickness of the paper, and the periphery of the paper thickness of the detection target paper In this range, the sheet thickness of the sheet is detected in such a manner that the voltage level of the sensor output varies greatly, so that the sheet thickness of the sheet can be detected with high accuracy.

  Then, image forming processing such as transfer processing and fixing processing is executed according to the detected paper thickness, and an image is formed on the paper.

  Next, the flow of the double feed detection process will be described.

  In the image forming apparatus 10, when an image forming process is continuously performed on a plurality of sheets conveyed from the same sheet tray 22, a double feed detection process routine shown in FIG. 7 is executed.

  First, in step 160, a variable n for identifying sheets on which images are continuously formed is set to an initial value of 1. In step 162, the above-described sheet thickness detection processing routine is performed for the nth sheet. Execute to detect the thickness (tn) of the nth sheet.

  In step 164, the paper thickness detection processing routine is similarly executed for the (n + 1) th sheet to detect the thickness (tn + 1) of the (n + 1) th sheet. In step 166, the detected value is detected in step 162. It is determined whether the thickness tn of the nth sheet and the thickness tn + 1 of the (n + 1) th sheet detected in step 164 have a relationship of tn + 1 ≧ 1.8 × tn, and n + 1 sheets If the paper thickness tn + 1 is not greater than 1.8 times the paper thickness tn of the nth sheet, in step 168, it is determined that the n + 1th sheet does not have a double feed and is normal, and n + 1 sheets An image forming process is performed on the eye sheet. In the next step 170, it is determined whether or not the image forming process is performed on the next sheet. When the image forming process is completed for all the sheets, the double feed detecting process routine is ended. If there is a next sheet, in step 172, n is incremented, and the process returns to step 164 to similarly detect the sheet thickness.

  If the n + 1th sheet thickness tn + 1 is equal to or greater than 1.8 times the nth sheet thickness tn in step 166, it is determined in step 174 that double feeding has occurred in the n + 1th sheet, The image forming process is stopped, and the double feed detection process routine is terminated.

  As described above, the double feed detection processing routine uses the paper thickness detected in the above-described paper thickness detection processing routine to compare the respective paper thicknesses of the continuously conveyed paper, and thus has a simple configuration. Thus, double feeding can be detected.

  Next, the flow of the remaining sheet detection process will be described.

  In the image forming apparatus 10, a remaining paper amount detection processing routine shown in FIG. 8 is executed at a predetermined timing or when a remaining paper amount detection instruction is input by the user.

  First, in step 180, the above-described paper thickness detection processing routine is executed using the second transmission sensor 92 to detect the paper thickness Ta1 of the paper stacked on the paper tray 22, and in step 182, In step 180, it is determined whether or not the paper is detected to be ultra-thick paper or OHP. If it is determined that the paper is OHP, it is determined in step 184 that there is no paper in the paper tray 22, and the image is displayed. The display panel of the forming apparatus 10 displays that there is no paper, and the paper remaining amount detection processing routine ends. On the other hand, if it is determined that the paper is ultra-thick paper, it is determined in step 186 that the remaining amount of paper is large, the display panel of the image forming apparatus 10 displays that the remaining amount of paper is large, and the remaining paper is displayed. The amount detection processing routine is terminated.

  If it is detected in step 182 that the paper is neither ultra-thick paper nor OHP, it is determined in step 188 that the remaining amount of paper is low, and it is determined that there is little paper on the display panel of the image forming apparatus 10. indicate. In step 190, it is determined whether or not image forming processing has been performed on one sheet. When one sheet is image-formed and one sheet is reduced from the sheet tray 22, the process proceeds to step 192. The paper thickness detection processing routine described above is executed again using the second transmission type sensor 92 to detect the paper thickness Ta2 of the paper loaded on the paper tray 22.

  In step 194, Ta2 is subtracted from Ta1 to calculate the paper thickness t per sheet in the paper tray 22, and in step 196, Ta2 / t is calculated as the remaining amount of paper. In step 198, The calculated remaining paper amount is displayed on the display panel, and the remaining paper amount detection processing routine is terminated.

  As described above, according to the image forming apparatus of the first embodiment, the electrical resistance output from the light receiving element is changed by changing the combined resistance value of the circuit including the detection resistor through which the electrical signal from the light receiving element flows. Since the signal voltage is within the detectable range, it is possible to detect the paper thickness and the number of sheets with high accuracy by switching the light receiving sensitivity with a simple configuration.

  In addition, since the combined resistance value of the circuit including the detection resistor through which the electric signal flows can be changed by the plurality of detection resistors and the plurality of switch elements, the light receiving sensitivity can be switched with a simple configuration.

  Further, by making each of the resistance values of the plurality of detection resistors different, the combined resistance value of the detection resistors can be changed to many resistance values, so that it is possible to switch to many light receiving sensitivities.

  In addition, since the light emission amount of the light emitting element can be adjusted to a desired light amount, the thickness and number of sheets of paper can be detected with higher accuracy.

  Further, it is possible to detect the paper thickness and the number of sheets with high accuracy and form an image on the paper by a process suitable for the thickness and the number of sheets.

  Further, by detecting the thickness of each of the continuously conveyed sheets and comparing the detected sheet thickness to detect double feed, it is possible to detect double feed with a simple configuration.

  Further, it is possible to detect the paper thickness of the paper stacked on the paper tray, and to detect the remaining amount of paper from the detected paper thickness. Further, by detecting the paper thickness with high accuracy, the remaining amount of paper can be detected with high accuracy.

  In the above-described embodiment, the case where the transmission sensor is provided with one detection resistor connected to the light receiving element has been described as an example. However, this detection resistor may be provided on the control board. In that case, a plurality of detection resistors are connected in parallel to the output terminal of the light receiving element, and no switch element is provided for one detection resistor so that an electrical signal from the light receiving element always flows. What is necessary is just to comprise.

  Further, although the case where the sheet thickness is detected by receiving the transmitted light of the sheet has been described as an example, the glossiness may be detected by receiving the reflected light of the sheet. In this case, when the detection target paper is glossy paper or OHP, the amount of reflected light is increased, so the combined resistance value is set to be small so that the sensitivity is low, and the detection target paper is normal. In the case of paper, since the amount of reflected light received is small, the combined resistance value may be set large so that the sensitivity is high.

  Next, an image forming apparatus according to a second embodiment of the present invention will be described. In addition, about the structure and operation | movement fundamentally the same as 1st Embodiment, the same code | symbol as 1st Embodiment is attached | subjected and the description is abbreviate | omitted.

  The image forming apparatus according to the second embodiment is different from the first embodiment in that a plurality of detection resistors are provided in series on the control board.

  As shown in FIG. 9, the control board 282 of the image forming apparatus according to the second embodiment is provided with a plurality of (for example, three) detection resistors R11 to R13, and the detection resistors R11 to R11. Corresponding to each of R13, switch elements SW11 to SW13 are provided. Each of the detection resistors R11 to R13 is connected in parallel with the corresponding switch element SW11 to SW13, and one end of the detection resistor R11 is connected to the output terminal of the first light receiving element 90B, and the detection resistor R11. To R13 are connected in series to the output terminal of the first light receiving element 90B.

  A detection resistor R14 having one end connected in series to the detection resistor R13 is provided, and the other end of the detection resistor R14 is grounded.

  The resistance values of the detection resistors R11 to R14 are different, for example, 470 kΩ, 180 kΩ, 56 kΩ, and 10 kΩ, respectively.

  In addition, each of the input terminals of the switch elements SW11 to SW13 is connected to the CPU 84, and the switch is turned on and off, and the corresponding detection resistors R11 to R13 are supplied with electric as sensor output from the first light receiving element 90B. A switching signal for switching so that a signal flows is input from the CPU 84 to each input terminal of the switch elements SW11 to SW13.

  The combined resistance value of the detection resistors R11 to R14 can be changed by switching on and off the switch elements SW11 to SW13, and the sensitivity of the first transmission sensor 290 can be switched.

  Note that the operation of the image forming apparatus according to the second embodiment is the same as that of the first embodiment, and a description thereof will be omitted.

1 is a schematic diagram illustrating a configuration of an image forming apparatus according to a first embodiment of the present invention. It is a circuit diagram which shows the structure of the transmission type sensor and control board which concern on the 1st Embodiment of this invention. It is a table | surface which shows the relationship between on-off of a switch element, and the sensitivity of a transmissive sensor. It is a graph which shows the relationship between the sensor output and paper thickness in each sensitivity. 3 is a flowchart showing the contents of a light emission amount adjustment processing routine in the image forming apparatus according to the first embodiment of the present invention. 3 is a flowchart showing the contents of a paper thickness detection processing routine in the image forming apparatus according to the first embodiment of the present invention. 3 is a flowchart showing the contents of a double feed detection processing routine in the image forming apparatus according to the first embodiment of the present invention. 5 is a flowchart showing the content of a remaining paper amount detection processing routine in the image forming apparatus according to the first embodiment of the present invention. It is a circuit diagram which shows the structure of the transmission type sensor and control board which concern on the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Engine part 22 Paper tray 82 Control board 84 CPU
86 Light emission amount adjustment circuit 90, 92, 290 Transmission type sensor 90A, 92A Light emission element 90B, 92B Light receiving element 282 Control board 290 Transmission type sensor R1, R2, R3, R4, R11, R12, R13, R14 Detection resistance SW1, SW2 , SW3, SW11, SW12, SW13 switch elements

Claims (9)

A light emitting element that emits light;
A light receiving element that receives one of transmitted light transmitted through the detection object and reflected light reflected from the detection object, and outputs an electrical signal corresponding to the received light quantity;
A variable resistance circuit that is connected to the light receiving element so that an electric signal output by the light receiving element flows and can change a resistance value;
When the voltage of the electric signal is higher than the upper limit value of the predetermined range, the resistance value of the variable resistance circuit is changed so that the voltage of the electric signal is lower than the lower limit value of the predetermined range. In the case, resistance value changing means for changing the resistance value of the variable resistance circuit to be large,
Detecting means for detecting a physical quantity related to the object to be inspected based on the voltage of the electric signal when the resistance value of the variable resistance circuit is changed by the resistance value changing means;
A detection device comprising: The variable resistance circuit includes a plurality of resistance elements connected to the light receiving element, and a plurality of switches provided corresponding to each of the plurality of resistance elements and switched to allow the electric signal to flow through the corresponding resistance elements. With elements,
2. The detection device according to claim 1, wherein the resistance value changing unit changes the resistance value of the variable resistance circuit by switching on and off of the plurality of switching elements to change a combined resistance value of the plurality of resistance elements. .   The detection device according to claim 2, wherein each of the resistance values of the plurality of resistance elements is different. The light receiving element receives the transmitted light that has passed through the detection object;
When the resistance value changing means changes the resistance value of the variable resistance circuit to a predetermined value, the light emitting element is caused to emit light in the absence of the detection object, and is output by the light receiving element. The detection device according to any one of claims 1 to 3, further comprising a light emission amount adjusting unit that adjusts a light emission amount of the light emitting element based on a voltage of an electric signal.   The detection device according to claim 4, wherein the light emission amount adjusting unit adjusts the light emission amount by the light emitting element when the resistance value of the variable resistance circuit is changed to be the smallest. The detection object is a recording medium,
The detection device according to claim 1, wherein the detection unit detects at least one of a thickness and a number of the recording media. The light receiving element receives transmitted light transmitted through the recording medium,
Even if the detection means is changed so that the resistance value of the variable resistance circuit is maximized by the resistance value changing means, the voltage of the electric signal output by the light receiving element is higher than the upper limit value in a predetermined range. The detection apparatus according to claim 6, wherein when the recording medium is high, the recording medium is detected to be OHP. The light receiving element receives transmitted light transmitted through the recording medium,
Even if the detection means is changed so that the resistance value of the variable resistance circuit is minimized by the resistance value changing means, the voltage of the electrical signal output by the light receiving element is lower than the lower limit value of a predetermined range. The detection device according to claim 6 or 7, wherein when the recording medium is low, the recording medium is detected to be ultra-thick paper. The detection device according to any one of claims 6 to 8,
Image forming means for forming an image on the recording medium;
An image forming apparatus.

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