JP2006341974A - Sheet detector, sheet conveying device, and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the number of sensors for detecting a sheet size, and to correctly detect the sheet size. <P>SOLUTION: In a sheet detector 10, first actuators 40A-D are operated by sheets S of various kinds of sizes. The first actuators 40A-D each rotates a second actuator 46 by a different quantity. The optical axis L of a sensor 50 passes through a movable range of a detection part 54 provided on the second actuator 46. When the detection part 54 is turned, the optical axis L passes through slits 54A-D formed in the detection part. The sensor 50 outputs the pulses by the number of the slits 54A-D through which the optical axis L has passed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sheet detection apparatus that detects a sheet, a sheet conveyance apparatus that conveys a sheet, and an image forming apparatus that forms an image on the conveyed sheet.

  As a sheet size detection mechanism in an image forming apparatus such as a laser beam printer or an ink jet printer, a mechanism in which a plurality of sensors connected to a control unit are arranged in the sheet width direction is generally used. However, this mechanism requires a plurality of sensors and a plurality of circuits for connecting each sensor to the control unit, and there is a problem that the configuration becomes complicated. Therefore, the purpose of this mechanism is to reduce the number of sensors as much as possible. Has been devised (see, for example, Patent Document 1).

  In the mechanism disclosed in Patent Document 1, a flag is operated by a leading edge portion of a conveyed sheet, and the operation of the flag is detected by a sensor. The outputs of the first sheet detecting means constituted by the sensor and the flag and the second sheet detecting means arranged on the upstream side of the first sheet detecting means and detecting the sheet are connected to the calculating means. The calculating means calculates the sheet width based on the detection time difference between the first sheet detecting means and the second sheet detecting means. With this mechanism, it is possible to deal with sheets of various sizes to be detected by the two detection means of the first sheet detection means and the second sheet detection means.

Here, in the mechanism of Patent Document 1, it is essential that the flag is brought into contact with the leading end corner of the sheet, but the leading end corner of the sheet having low rigidity such as thin paper is curled after coming into contact with the flag. Therefore, the operation of the flag is not stable and the sheet size cannot be detected accurately. Further, the operation of the flag cannot be stabilized even for a sheet in which the tip corner is originally curled or bent, and the size of the sheet cannot be accurately detected.
Japanese Patent Laid-Open No. 11-227988

  The present invention has been made in consideration of the above-described facts. The number of sensors for detecting the sheet size is reduced as much as possible, and the sheet size is accurately detected.

  The sheet detection apparatus according to claim 1 is disposed in at least a direction crossing the sheet conveyance direction or a sheet conveyance direction, and is operated by a plurality of first actuators operated by sheets of various sizes. And a single sensor that outputs a signal corresponding to the number of actuators.

  In the sheet detection apparatus according to claim 1, the plurality of first actuators are arranged at least in a direction intersecting with the sheet conveyance direction or in the sheet conveyance direction, and are arranged within the width of the sheet. The actuator is actuated in contact with the seat, and one sensor outputs a signal corresponding to the number of actuated first actuators. Accordingly, a determination unit is connected to the output of the sensor, and the width of the sheet (the length in the direction orthogonal to the conveyance direction) and the length (in the conveyance direction) are connected to the determination unit according to the number of the first actuators that are operated. Length) can be determined.

  Here, since the sheet size can be detected by one sensor, the mechanism of the sheet detection apparatus can be simplified. In addition, the size of the sheet is detected by the number of actuated actuators, and the need for the actuator to contact the leading edge of the sheet is eliminated. The size of the bent sheet can be accurately detected.

  A sheet detection apparatus according to a second aspect is the sheet detection apparatus according to the first aspect, further including a second actuator that is displaced by a different amount by each first actuator, wherein the sensor includes the second actuator. A signal corresponding to the displacement amount of the actuator is output.

  In the sheet detection apparatus according to the second aspect, each first actuator disposed within the width of the sheet displaces the second actuator by a different amount. One sensor outputs a signal corresponding to the amount of displacement of the second actuator, that is, a signal corresponding to the number of actuated first actuators.

  As described above, the second actuator is provided separately from the first actuator operated by the seat, and the operation of the second actuator is detected by the sensor, so that the degree of freedom of arrangement of the first actuator is increased.

  Various actuators such as a rotary actuator and a linear actuator can be applied to the second actuator, and the above-described displacement amount is a rotation amount, a linear movement amount, or the like.

  A sheet detection apparatus according to a third aspect is the sheet detection apparatus according to the first aspect, further including a second actuator that is actuated at a different timing by each first actuator, and the sensor includes the second sensor. A signal corresponding to the number of times the operation of the actuator is detected is output.

  In the sheet detection apparatus according to the third aspect, the first actuators disposed within the width of the sheet operate the second actuators at different timings. One sensor outputs a signal corresponding to the number of times that the operation of the second actuator is detected, that is, a signal corresponding to the number of the first actuators operated.

  A sheet detection apparatus according to a fourth aspect of the present invention is the sheet detection apparatus according to the first aspect, further including a second actuator that is operated at a different timing by each first actuator, and the sensor includes the second sensor. A signal corresponding to the time during which the operation of the actuator is detected is output.

  In the sheet detection apparatus according to the fourth aspect, each first actuator disposed within the width of the sheet operates the second actuator at different timings. One sensor outputs a signal corresponding to the time during which the operation of the second actuator is detected, that is, a signal corresponding to the number of operated first actuators.

  A sheet detection apparatus according to a fifth aspect is the sheet detection apparatus according to the third or fourth aspect, wherein the plurality of first actuators are arranged in a direction inclined with respect to a sheet conveyance direction. And

  In the sheet detection device according to claim 5, the plurality of first actuators are disposed in a direction inclined with respect to the sheet conveyance direction, and each first actuator disposed within the sheet width is formed by the sheet. Actuated at different timings, the second actuators are actuated at different timings by each first actuator.

  A sheet detection apparatus according to a sixth aspect is the sheet detection apparatus according to any one of the first to fifth aspects, wherein the sheet detection apparatus is operated by a sheet having a minimum size on the downstream side in the sheet conveyance direction from the first actuator. The sensor further includes a third actuator that operates the second actuator, and the sensor outputs a signal at a timing when the third actuator operates the second actuator.

  In the sheet detection apparatus according to the sixth aspect, the third actuator is actuated by the smallest size sheet on the downstream side in the sheet conveying direction from the first actuator to actuate the second actuator. One sensor outputs a signal at the timing when the third actuator operates the second actuator. As a result, a control unit can be connected to the output of the sensor, and the registration position of the sheet can be controlled by this control unit.

  As described above, the sensor for detecting the size of the sheet and the sensor for detecting the registration position of the sheet are combined to achieve further cost reduction.

  The sheet detection apparatus according to claim 7 is the sheet detection apparatus according to any one of claims 1 to 6, wherein the sensor has a pulse number of pulses corresponding to the number of the first actuators operated. A signal is output.

  In the sheet detection apparatus according to the seventh aspect, one sensor outputs a pulse signal having a pulse number corresponding to the number of actuated first actuators. Accordingly, it is possible to connect a determination unit to the output of the sensor and cause the determination unit to determine the sheet size according to the number of pulses of the pulse signal output from the sensor.

  Here, the sensor in this configuration may be an inexpensive sensor that outputs a digital signal such as a photoelectric sensor, so that the cost can be reduced.

  The sheet detection device according to claim 8 is the sheet detection device according to any one of claims 1 to 6, wherein the sensor has a pulse having a length corresponding to the number of the first actuators that are operated. A signal is output.

  In the sheet detection apparatus according to the eighth aspect, one sensor outputs a pulse signal having a length corresponding to the number of first actuators that have been activated. Accordingly, it is possible to connect a determination unit to the output of the sensor and cause the determination unit to determine the sheet size according to the length of the pulse signal output from the sensor.

  A sheet conveying apparatus according to a ninth aspect includes a conveying unit that conveys a sheet, and the sheet detecting apparatus according to any one of the first to eighth aspects.

  In the sheet conveying apparatus according to the ninth aspect, the sheet is conveyed by the conveying means, and the first actuator disposed within the width of the sheet is operated. One sensor outputs a signal corresponding to the number of first actuators that have been activated.

  According to a tenth aspect of the present invention, there is provided an image forming apparatus according to the ninth aspect, an image forming unit that forms an image on a sheet conveyed by the sheet conveying apparatus, and a signal output from the sensor. And determining means for determining the size of the sheet.

  In the image forming apparatus according to the tenth aspect, the image forming unit forms an image on the sheet conveyed by the sheet conveying apparatus. The determination unit determines the size of the sheet according to the signal output from the sensor. As a result, it is possible to form an image corresponding to the size of the sheet.

  An image forming apparatus according to an eleventh aspect is the image forming apparatus according to the tenth aspect, and further includes an image forming area control unit that controls the image forming area according to the size of the sheet determined by the determination unit. It is characterized by that.

  In the image forming apparatus according to the eleventh aspect, the image forming area control unit controls the image forming area in accordance with the size of the sheet determined by the determining unit. Thereby, an image can be formed in a desired area on the sheet.

  An image forming apparatus according to a twelfth aspect is the image forming apparatus according to the eleventh aspect, wherein the image forming unit exposes the image carrier and the image carrier to electrostatically attach the image carrier. An exposure unit that forms a latent image; a developing unit that develops the electrostatic latent image on the image carrier with toner; and a transfer unit that transfers a toner image from the image carrier to a sheet. The formation area control means controls the area where the exposure means exposes the image carrier according to the size of the sheet determined by the determination means.

  In the image forming apparatus according to claim 12, the image carrier is exposed by the exposure unit to form an electrostatic latent image on the image carrier, and the electrostatic latent image on the image carrier is developed with toner by the developing unit. The Then, the toner image is transferred from the image carrier to the sheet by the transfer means.

  Here, the area where the exposure means exposes the image carrier is controlled by the image forming area control means in accordance with the sheet size determined by the determination means. As a result, it is possible to prevent the outside of the image area of the image carrier from being exposed, and thus effects such as suppression of wear of the image carrier can be obtained.

  An image forming apparatus according to a thirteenth aspect is the image forming apparatus according to the twelfth aspect, according to a fixing unit that fixes a toner image on a sheet, and a width or length of the sheet determined by the determination unit. And fixing temperature control means for controlling temperature control of the fixing means.

  In the image forming apparatus according to the thirteenth aspect, the toner image transferred to the sheet is fixed by the fixing unit. Here, the temperature control of the fixing unit is controlled by the fixing temperature control control unit according to the sheet size determined by the determination unit. As a result, the temperature outside the sheet width of the fixing unit can be kept low, and troubles such as melting of parts around the fixing unit can be prevented.

  Since the present invention is configured as described above, the number of sensors for detecting the size of the sheet can be reduced as much as possible, and the size of the sheet can be detected accurately.

  Next, a first embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the image forming apparatus 12 includes a paper feed tray 14 that stores a sheet S such as plain paper. The sheet feed tray 14 is provided with a side regulating plate (not shown) that abuts against an end portion of the sheet S to be accommodated in the width direction (a direction orthogonal to the conveyance direction) to regulate the position of the sheet S in the width direction, A rear end regulating plate (not shown) is provided that contacts the rear end portion of S and regulates the position of the sheet S in the length direction (conveyance direction). The side regulating plate is slidable in the width direction of the sheet S, the trailing edge regulating plate is slidable in the length direction of the sheet S, and the sheet feeding tray 14 accommodates sheets S of a plurality of types. It is possible.

  Further, the image forming apparatus 12 includes a sheet conveying apparatus 18 that conveys the sheet S from the paper feed tray 14 to the image forming unit 16. The sheet conveying device 18 includes a sheet feeding roll 20 disposed at the downstream end of the sheet feeding tray 14 in the conveying direction. The paper feed roll 20 rotates in contact with the sheet S set at the top of the paper feed tray 14 and sends the top sheet S from the paper feed tray 14 to the image forming unit 16.

  Further, the image forming apparatus 12 includes a sheet detection apparatus 10. The sheet detection apparatus 10 is disposed in the conveyance path of the sheet S between the paper feed tray 14 and the image forming unit 16. The sheet detection apparatus 10 will be described later in detail.

  The image forming unit 16 includes a photosensitive drum 22 that rotates counterclockwise in the drawing, a charging roll 24 that is arranged around the photosensitive drum 22 in the counterclockwise direction in the drawing, an exposure device 26, and a developing device. 28, a transfer roll 30 and a cleaning device 32 are provided. The charging roll 24 rotates in contact with the photosensitive drum 22 to uniformly charge the photosensitive drum 22.

  The exposure device 26 uses a known exposure method such as an optical scanning method for scanning light in the axial direction of the photosensitive drum 22 or a line exposure method for exposing the photosensitive drum 22 in a line shape. An electrostatic latent image is formed on the image 22 based on the image data.

  Further, the developing device 28 rotatably supports the developing roll 28A that rotates opposite to the photosensitive drum 22 and the developing roll 28A, and the two-component developer composed of toner and carrier or the one-component developer composed only of toner. Is provided with a developing housing 28 </ b> B that accommodates a stirring mechanism (not shown). In the developing device 28, the toner accommodated in the developing housing 28B is agitated by the agitating mechanism and adsorbed and held on the developing roll 28A. Then, a developing bias is applied to the developing roll 28A, and the toner moves from the developing roll 28A onto the electrostatic latent image on the photosensitive drum 28. Thereby, the electrostatic latent image on the photosensitive drum 22 is visualized (developed).

  Further, the transfer roll 30 is in contact with the photosensitive drum 22 across the conveyance path of the sheet S, and a bias having a polarity opposite to that of the toner is applied to the transfer roll 30, whereby the sheet S is transferred from the photosensitive drum 22. The toner image is transferred to the surface. Further, the cleaning device 32 brings a blade or roll into contact with the photosensitive drum 22 to remove residual toner on the photosensitive member 22.

  A fixing device 34 is disposed on the downstream side in the transport direction of the image forming unit 16. The fixing device 34 includes a heating roll 34A that is in contact with the transfer surface of the sheet S, and a pressure roll 34B that is in pressure contact with the heating roll 34A across the conveyance path of the sheet S. The toner sheet is fixed to the sheet S by being pressed and heated by the heated roll 34A and the pressure roll 34B.

  Here, the sheet detection apparatus 10 will be described.

  As shown in FIGS. 2 to 4, the sheet detection device 10 is disposed in the width direction of the sheet S, and the leading ends of the sheets S of various sizes (for example, A5, B5, A4, and B4 as illustrated). The first actuators 40A, 40B, 40C, and 40D that operate by contacting the part are provided.

  The first actuators 40 </ b> A to 40 </ b> D have a rod shape and are swingably suspended from a support member (not shown) provided above the sheet S conveyance path to the sheet S conveyance path. A rotation shaft 42 formed on the upper support end of the first actuators 40A to 40D extends in the width direction of the sheet S, and the first actuators 40A to 40D swing along the conveyance direction of the sheet S. . Engagement beams 44A, 44B, 44C, and 44D extending in a direction substantially perpendicular to the first actuator 40 are formed at the support end portions of the first actuators 40A to 40D.

  The first actuators 40 </ b> A to 40 </ b> D are disposed away from the leading end corner of the sheet S so that the lower swing end does not lift up the leading end corner of the sheet S.

  Further, on the downstream side in the transport direction from the first actuators 40A to 40D, a second actuator 46 operated by the first actuators 40A to 40D and a sensor 50 for detecting that the second actuator 46 is operated are disposed. Has been. The second actuator 46 is rotatably supported by a support member (not shown) above the conveyance path of the sheet S and extends along the width direction of the sheet S, and the first actuator 46 extends from the circumferential surface of the rotation shaft 48. A plurality of (for example, four as shown) engagement beams 52A, 52B, 52C, and 52D extending upward from the engagement beams 44A to D of the actuators 40A to 40D, and the engagement beams from the peripheral surface of the rotating shaft 48. And a detected portion 54 extending to the opposite side of 52A-D.

  As shown in FIGS. 4 and 5, when the first actuators 40 </ b> A to 40 </ b> D are lowered by their own weight (shown by chain lines), there is a slight gap between the engaging beams 44 </ b> A to 44 </ b> D and the engaging beams 52 </ b> A to 52 </ b> D. Although there is a gap, when the first actuators 40A to D are rotated counterclockwise by the sheet S, the engaging beams 44A to D are engaged with the engaging beams 52A to D, respectively. The rotating shaft 48 is rotated in the clockwise direction.

  2, 4, and 5, the detected portion 54 is a fan-shaped plate, and four slits 54 </ b> A, 54 </ b> B, 54 </ b> C, 54 </ b> D extending in the radial direction are formed at predetermined intervals. . The slits 54A to 54D are arranged in the order of A, B, C, and D in the counterclockwise direction in the drawing.

  The sensor 50 is a transmissive photosensor that allows the optical axis L to pass through the movable range of the detected portion 54, and the optical axis L has slits 54 </ b> A to 54 </ b> D of the detected portion 54 as shown in FIGS. 4 and 5. A pulse is output each time the signal passes.

  Here, as shown in FIGS. 2 to 5, the lengths of the engaging beams 44A to 44D and the engaging beams 52A to 52D are not uniform, and gradually increase in the order of A, B, C, and D. It has become. For this reason, when the first actuator 40A is actuated by the A5 size sheet S, the first actuator is driven by the B5 size sheet S rather than the rotation amount (displacement amount) of the second actuator 46 (see FIG. 4A). The amount of rotation of the second actuator 46 when the actuator 40B is actuated becomes larger. That is, as the width of the sheet S increases, the amount of rotation of the second actuator 46 increases.

  On the other hand, in the state where the second actuator 46 is not operated (shown by a chain line in FIGS. 4 and 5), the detected portion 54 blocks the optical axis L at a position where the slit 54A is above the optical axis L. When the second actuator 46 is actuated by the actuator 40A, the slit 54A rotates to a position below the optical axis L (shown by a solid line in FIG. 4A). At this time, the optical axis L passes through the slit 54A and one pulse is output from the sensor 50 (see FIG. 4B). When the second actuator 46 is actuated by the first actuator 40B, the detected portion 54 rotates to a position where the slit 54B is below the optical axis L (see FIG. 4C). At this time, the optical axis L passes through the slits 54A and 54B, and two pulses are output from the sensor 50 (see FIG. 4D).

  Similarly, as shown in FIG. 5 (A), when the second actuator 46 is actuated by the first actuator 40C, the optical axis L passes through the slits 54A, 54B, 54C, and three pulses are output from the sensor 50 ( As shown in FIG. 5 (B) and FIG. 5 (C), when the second actuator 46 is actuated by the first actuator 40D, the optical axis L passes through the slits 54A, 54B, 54C, 54D and the sensor. 50 to 4 pulses are output (see FIG. 5D).

  A determination unit 56 (see FIG. 1) is connected to the output of the sensor 50. The determination unit 56 determines the size of the sheet S based on the output of the sensor 50 and outputs a determination result. Further, an image formation control unit 58 (see FIG. 1) is connected to the output of the determination unit 56. The image forming control unit 58 controls image forming conditions such as an exposure area by the exposure device 26 and a developing bias of the developing device 28 based on the determination result of the determining unit 56. Further, a fixing temperature adjustment control unit 60 (see FIG. 1) is connected to the output of the determination unit 56. The fixing temperature adjustment control unit 60 controls the temperature adjustment of the fixing device 34 based on the determination result of the determination unit 56.

  Specifically, when one pulse is output from the sensor 50, the determination unit 56 determines the size of the sheet S as A5 size, and when two pulses are output from the sensor 50, the determination unit 56 determines the size of the sheet S as B5 size. . The determination unit 56 determines the size of the sheet S as A4 size when three pulses are output from the sensor 50, and determines the size of the sheet S as B4 size when four pulses are output from the sensor 50.

  Then, the image formation control unit 58 controls the area where the exposure device 26 exposes the photosensitive drum 22 within the width of the sheet S having the size determined by the determination unit 56. As a result, it is possible to prevent the outside of the image area of the photosensitive drum 22 from being exposed, so that an effect such as suppression of wear of the photosensitive drum 22 can be obtained.

  Further, the fixing temperature adjustment control unit 60 increases the temperature of the heating roll 34 </ b> A if the width of the sheet S determined by the determination unit 56 is wide, and decreases it if it is narrow. As a result, the temperature outside the width of the sheet S in the fixing device 34 can be kept low, and troubles such as melting of parts in the fixing device 34 can be prevented.

  As described above, in the image forming apparatus 12 according to the present embodiment, the size of the sheet S can be detected by the single sensor 50, so that the mechanism of the sheet detection apparatus 10 can be simplified. In addition, since the size of the sheet S is detected by the number of the first actuators 40A to 40D that have been activated, the need to make the actuator contact the corner of the tip of the sheet S is eliminated. The size of a low sheet or a sheet with a bent corner can be accurately detected.

  Further, the second actuator 46 is provided separately from the first actuators 40 </ b> A to 40 </ b> D operated by the seat S, and the operation of the second actuator 46 is detected by the sensor 50. The degree of freedom increases.

  Further, since one sensor 50 outputs a pulse signal having a pulse number corresponding to the number of actuated first actuators 40A to 40D, the determination unit 56 connected to the output of the sensor 50 causes the sensor to The size of the sheet S can be determined according to the number of pulses output from 50. Here, the sensor 50 in this configuration may be an inexpensive device that outputs a digital signal such as a photoelectric sensor, and thus the cost can be reduced.

  In the present embodiment, the sensor 50 outputs a pulse signal corresponding to the rotation amount of the second actuator 46 rotated by the first actuator, but the second actuator is configured to be linearly moved by the first actuator. The sensor may output a pulse signal corresponding to the displacement amount of the second actuator.

  Next, a second embodiment will be described. In addition, the same code | symbol is attached | subjected to the structure similar to 1st Embodiment, and description is abbreviate | omitted.

  As shown in FIGS. 6 and 7, the sheet detection device 70 is arranged in a direction inclined with respect to the width direction of the sheet S, and has various sizes (for example, A5, B5, A4, and B4 as shown in the figure). ), The first actuators 72A, 72B, 72C, and 72D that operate in contact with the leading end of the sheet S are provided.

  The first actuators 72 </ b> A to 72 </ b> D have a rod shape, and are swingably suspended from a support member (not shown) provided above the sheet S conveyance path to the sheet S conveyance path. The rotation shaft 42 formed at the upper support end of the first actuators 72A to 72D extends in the width direction of the sheet S, and the first actuators 72A to 72D swing along the conveyance direction of the sheet S. . In addition, engagement beams 76A to 76D extending in a direction substantially perpendicular to the first actuator 40 are formed at the support end portions of the first actuators 72A to 72D.

  The first actuators 72A to 72D have the same shape. In addition, the first actuators 72A to 72D are arranged so that the lower swing end does not lift the leading end corner of the sheet S, like the first actuators 40A to 40D of the first embodiment. It is arranged away from the tip corner.

  A second actuator 78 that is actuated by the first actuators 72A to 72D is disposed downstream of the first actuators 72A to 72D in the transport direction. The second actuator 78 is rotatably supported by a support member (not shown) above the conveyance path of the sheet S and extends along the width direction of the sheet S, and the first actuator 78 extends from the circumferential surface of the rotation shaft 82. A plurality of (for example, four as shown) engagement beams 52A, 52B, 52C, and 52D that extend upward from the engagement beams 76A to D of the actuators 72A to 72D and the peripheral surface of the rotary shaft 82 are engaged. The detected portion 84 extends to the opposite side of the joint beams 52A to 52D, and a weight 85 that hangs down from the peripheral surface of the rotating shaft 82.

  As shown in FIG. 7A, when the first actuators 72A to 72D are lowered by their own weight, a slight gap is left between the engaging beams 76A to D and the engaging beams 52A to 52D. However, when the first actuators 72A-D abut against the leading end of the sheet S and rotate counterclockwise in the figure, the engaging beams 76A-D engage with the engaging beams 52A-D, and the rotation shaft 82 rotates clockwise.

  Moreover, as shown in FIG. 7, the to-be-detected part 84 is a beam material. Further, the optical axis L of the sensor 50 is blocked by the detected portion 84 in a state where the first actuators 72A to D are lowered by its own weight, and passes from the light projecting side to the light receiving side when the detected portion 84 moves. The sensor 50 outputs a pulse each time the detected portion 84 moves and the optical axis L passes from the light projecting side to the light receiving side.

  As shown in FIG. 7A, the detected portion 84 and the engaging beams 52A-D are maintained in a horizontal state by the weight 85 in a state where the first actuators 72A-D are lowered by their own weight. In this state, as described above, the optical axis L of the sensor 50 is blocked by the detected portion 84. 7B, when the first actuators 72A to 72D are rotated counterclockwise by the sheet S, the engaging beams 76A to 76D are engaged with the engaging beams 52A to 52D. Then, the second actuator 78 rotates in the clockwise direction in the drawing. As a result, the detected portion 84 is lowered, the optical axis L passes from the light projecting side to the light receiving side, and the same number of pulse signals as the number of times the optical axis L passes from the light projecting side to the light receiving side are output from the sensor 50. (See FIG. 7F).

  As shown in FIG. 7C, when the first actuator 72A is further rotated counterclockwise in the drawing by the sheet S, the engagement beams 76A to D and the engagement beams 52A to 52D are engaged. Is coming off. Then, as shown in FIG. 7D, the weight 85 returns the detected portion 84 and the engaging beams 52A to 52D to the horizontal state. As a result, the optical axis L is blocked by the detected portion 84.

  Then, as shown in FIG. 7E, when the rear end portion of the sheet S passes through the first actuators 72A to 72D, the first actuators 72A to 72D rotate in the clockwise direction in the drawing by their own weight, and the engagement beam 76A-D engage with the engaging beams 52A-D, and the second actuator 78 rotates counterclockwise in the figure. Then, as shown in FIG. 7A, the second actuator 78 returns to the standby state by the action of the weight 85.

  Further, as shown in FIG. 6, the first actuators 72 </ b> A to 72 </ b> D are disposed to be inclined with respect to the width direction of the sheet S. The first actuators 72A to 72D are arranged in the order of A, B, C, D on the downstream side in the transport direction and the outside in the width direction.

  For this reason, when the A5 size sheet S is conveyed to the image forming unit 16, only the first actuator 72 </ b> A is operated to output one pulse from the sensor 50, and the B5 size sheet S is conveyed to the image forming unit 16. In this case, the first actuator 72B is activated after the first actuator 72A is activated. Further, when the A4 size sheet S is conveyed to the image forming unit 16, the first actuator 72A is activated after the first actuator 72A is activated, and then the first actuator 72C is activated. Further, when the B4 size sheet S is conveyed to the image forming unit 16, the first actuator 72A is activated, the first actuator 72B is activated, the first actuator 72C is activated, and then the first actuator 72C is activated. The first actuator 72D is activated.

  Here, as shown in FIG. 8, the distance in the transport direction between the adjacent first actuators 72 is the first actuator 72 adjacent to the first actuator 72 on the upstream side in the transport direction after the first actuator 72 on the upstream side in the transport direction is operated. The length of the second actuator 78 is long enough to return to the standby state before the operation of.

  For this reason, after the pulse is output from the sensor 50 by the operation of the first actuator 72 on the upstream side in the transport direction, the second pulse is output from the sensor 50 when the adjacent first actuator 72 is operated. Specifically, the number of actuated first actuators 72A to 72D is equal to the number of pulses of the pulse signal output from the sensor 50.

  As described above, the first actuators 72A to 72D operated by the sheet S operate the second actuator 78 at different timings so that the sensor 50 outputs a pulse signal having the same number of pulses as the number of times the second actuator 78 is operated. By doing so, as in the first embodiment, the determination unit 56 (see FIG. 1) can determine the size of the sheet S based on the number of pulses of the pulse signal output from the sensor 50.

  In the present embodiment, a plurality of first actuators 72A to 72D are arranged to be inclined with respect to the transport direction, and the second actuator 78 is different by shifting the timing at which each first actuator 72A to D is operated. Although actuated at the timing, the plurality of first actuators 72A to 72A-D are arranged in the width direction, and the engagement beams 76A are made different in shape and angle from the engagement beams 76A-D and the engagement beams 52A-D. The second actuator 78 may be operated at different timings by shifting the timing at which -D and the engaging beams 52A-D are engaged.

  Next, a third embodiment will be described. In addition, the same code | symbol is attached | subjected to the structure similar to 1st, 2nd embodiment, and description is abbreviate | omitted.

  As shown in FIGS. 9 and 10, in the sheet detection device 90, the third actuator is located downstream in the conveyance direction from the first actuator 72 </ b> D and closer to the inner side in the width direction of the sheet S having the minimum size (A5 size) than the first actuator 72 </ b> A. 92 is disposed. The third actuator 92 is suspended from the same height as the first actuators 72A to 72D. The third actuator 92 has the same shape as the first actuators 72A to 72D, and an engagement beam 94 is formed at the support end. Further, the second actuator 96 includes an engaging beam 94 in addition to the rotation shaft 82, the engaging beams 52A to 52D, the detected portion 84, and the weight 85 (not shown) similar to the second actuator 78 of the second embodiment. An engaging beam 98 is provided to engage with. The engagement beam 98 extends above the engagement beam 94 from the peripheral surface of the rotation shaft 82. The sensor 100 passes the optical axis L at the same position as in the second embodiment.

  For this reason, as shown in FIG. 10A, when the sheet S is conveyed to the image forming unit 16, first, the first actuators 72 </ b> A to 72 </ b> D are activated and the second actuator 96 is activated. Then, the optical axis L passes from the light projecting side to the light receiving side, and 1 to 4 pulses are output from the sensor 100 (see FIG. 10F). Then, as shown in FIG. 10B, when the first actuators 72A to 72D are further rotated, the engagement beams 76A to D and the engagement beams 52A to 52D are disengaged, and the second actuator 96 is moved. The standby state is restored by the action of the weight 85.

  Then, as shown in FIG. 10C, the third actuator 92 is operated by the sheet S, the engaging beam 94 is engaged with the engaging beam 98, and the second actuator 96 is operated. Here, while the third actuator 92 is operated by the sheet S, the engagement between the engagement beam 94 and the engagement beam 98 is not released, and the optical axis L is blocked by the detected portion 84. There is no such thing.

  As shown in FIG. 10D, when the sheet S passes through the first actuators 72A to 72D, the first actuators 72A to 72D return to the standby position by their own weights, but the second actuator 96 includes the third actuator 92. To remain activated. Note that the amount of rotation of the second actuator 96 by the third actuator 92 is larger than the amount of rotation of the second actuator 96 by the first actuators 72A to 72D, and the first actuators 72A to 72D return to the standby position. Further, the engaging beams 76A to 76D and the engaging beams 52A to 52D are not caught.

  Then, as shown in FIG. 10E, when the rear end of the sheet S passes through the third actuator 92, the third actuator 92 and the second actuator 96 both return to the standby position under their own weight, and the optical axis L is covered. It is blocked by the detection unit 84.

  That is, as shown in FIG. 10F, the optical axis L is projected between the time when the leading edge of the sheet S reaches the third actuator 92 and the time when the trailing edge of the sheet S passes through the third actuator 92. The sensor 100 continues to output a pulse signal while passing from the light side to the light receiving side.

  When the image forming control unit 58 (see FIG. 1) connected to the output of the sensor 100 outputs a pulse signal for a long time (time during which the sheet S passes through one point) from the sensor 100, Then, image writing on the sheet S by the image forming unit 16 is started a predetermined time after the output of the pulse signal is started.

  As described above, the sensor for detecting the size of the sheet S and the sensor for detecting the registration position of the sheet S are combined to achieve further cost reduction.

  Next, a fourth embodiment will be described. In addition, the same code | symbol is attached | subjected to the structure similar to 1st thru | or 3rd embodiment, and description is abbreviate | omitted.

  As shown in FIG. 11, in the sheet detection device 110, the distance in the conveyance direction between the adjacent first actuators 72 </ b> A to 72 </ b> D is shorter than that in the second and third embodiments, and is provided in the second actuator 112. The difference in length between the adjacent engagement beams 114A to 114D is smaller than the difference in length between the adjacent engagement beams 52A to 52D in the second and third embodiments. The first actuators 72A and 72B and the engaging beams 114A and 114B will be described as an example. As shown in FIGS. 11A and 11B, the engaging beams 52B and the second actuator 112 of the first actuator 72B are shown. The engagement between the engagement beam 52A of the first actuator 72A and the engagement beam 114A of the second actuator 112 is not released until the engagement beam 114B is engaged. Then, as shown in FIG. 11C, after the first actuators 72A and 72B disposed within the width of the sheet S are rotated by the maximum range, the second actuator 112 returns to the standby position. Therefore, as shown in FIG. 11 (F), the sensor 50 continues to output a pulse signal from when the first actuator 72A is actuated until the first actuator 72B returns to the standby position.

  Thereafter, as in the third embodiment, as shown in FIG. 11D, the second actuator 112 is actuated by the third actuator 92, and as shown in FIG. When the third actuator 92 is passed, the second actuator 112 returns to the standby position.

  The determination unit 56 (see FIG. 1) connected to the sensor 50 measures the time during which the pulse is output from the sensor 50, and determines the size of the sheet S according to the length of the measured pulse time. .

  Next, a fifth embodiment will be described. In addition, the same code | symbol is attached | subjected to the structure similar to 1st thru | or 4th embodiment, and description is abbreviate | omitted.

  As shown in FIG. 12, the image forming apparatus 120 is provided with a manual feed tray 122 for feeding the sheet S from the outside of the apparatus to the image forming unit 16. A sheet detection device 130 is disposed on the manual feed tray 122. As illustrated in FIG. 14, the sheet detection device 130 includes a plurality of (for example, four as illustrated) first actuators disposed along the conveyance direction on the set surface 122A on which the sheet S of the manual feed tray 122 is set. 124A to D, a second actuator 132 provided on the back surface side of the set surface 122A and operated by the first actuators 124A to 124D, and a sensor 50 for detecting the operation of the second actuator 132 are provided.

  The first actuators 124A to 124D are swingably supported on the set surface 122A, are urged by urging means (not shown), and protrude upward. Further, the engaging beams 126A to 126D formed at the support end portions of the first actuators 124A to 124D protrude to the back surface side. The second actuator 132 includes a rotating shaft 134 extending along the transport direction, engaging beams 136A to D extending from the peripheral surface of the rotating shaft 134 to the lower side of the engaging beams 126A to D, and a peripheral surface of the rotating shaft 134. And the detected portion 54 extending to the opposite side of the engaging beams 136A to 136D.

  The first actuator 124A is disposed in the vicinity of the rear end portion of the minimum size (A5 size) sheet S set on the manual feed tray 122, and the first actuator 124B is a B5 size sheet S set on the manual feed tray 122. It is arrange | positioned in the rear-end part vicinity. The first actuator 124C is disposed in the vicinity of the rear end portion of the A4 size sheet S set on the manual feed tray 122, and the first actuator 124D is disposed on the rear side of the B4 size sheet S set on the manual feed tray 122. It is disposed near the end.

  Here, the lengths of the engagement beams 126A to 126D are not uniform, and are gradually increased in the order of A, B, C, and D. Therefore, when the first actuator 124A is operated by the B5 size sheet S, the rotation amount (displacement amount) of the second actuator 132 when the first actuator 124A is operated by the A5 size sheet S is larger. The rotation amount of the second actuator 132 is larger. That is, as the width of the sheet S increases, the rotation amount of the second actuator 132 increases.

  On the other hand, when the second actuator 132 is not operated, the detected portion 54 blocks the optical axis L at a position where the slit 54A is below the optical axis of the sensor 50, and the A5 size sheet S is placed on the manual feed tray 122. When the first actuator 124A is set and the second actuator 132 is operated, the slit 54A rotates to a position above the optical axis L. At this time, the optical axis of the sensor 50 passes through the slit 54A, and a pulse signal of one pulse is output from the sensor 50. When the B5 size sheet S is set on the manual feed tray 122 and the second actuator 132 is operated by the first actuator 124B, the detected portion 54 rotates to a position where the slit 54B is above the optical axis L. . At this time, the optical axis of the sensor 50 passes through the slits 54A and 54B, and a two-pulse pulse signal is output from the sensor 50.

  Similarly, when the A4 size sheet S is set on the manual feed tray 122 and the second actuator 132 is actuated by the first actuator 124C, the optical axis of the sensor 50 passes through the slits 54A, 54B, 54C and the sensor 50 When a pulse signal of 3 pulses is output, the B4 size sheet S is set on the manual feed tray 122, and the second actuator 132 is operated by the first actuator 124D, the optical axis of the sensor 50 is slit 54A, 54B, 54C, A pulse signal of 4 pulses is output from the sensor 50 through 54D.

  A determination unit 56 (see FIG. 1) connected to the sensor 50 determines the size of the sheet S set on the manual feed tray 122 according to the number of pulses of the pulse signal output from the sensor 50.

  As described above, in the first to fifth embodiments, the sheet detection apparatus and the sheet conveyance apparatus according to the present invention have been described by taking the image forming apparatus using the electrophotographic method as an example. The present invention can also be applied to apparatuses other than apparatuses and image forming apparatuses that use sheets of various sizes.

1 is a side view schematically showing an image forming apparatus according to a first embodiment of the present invention. It is a perspective view which shows the sheet | seat detection apparatus of 1st Embodiment of this invention. It is a top view which shows the sheet | seat detection apparatus of 1st Embodiment of this invention. (A), (C) is a side view which shows the sheet | seat detection apparatus of 1st Embodiment of this invention, (B), (D) is a chart which shows the output waveform of a sensor. (A), (C) is a side view which shows the sheet | seat detection apparatus of 1st Embodiment of this invention, (B), (D) is a chart which shows the output waveform of a sensor. It is a top view which shows the sheet | seat detection apparatus of 2nd Embodiment of this invention. (A)-(E) are the side views which show the sheet | seat detection apparatus of 2nd Embodiment of this invention, (F) is a chart which shows the output waveform of a sensor. It is a perspective view which shows the sheet | seat detection apparatus of 2nd Embodiment of this invention. It is a top view which shows the sheet | seat detection apparatus of 3rd Embodiment of this invention. (A)-(E) are the side views which show the sheet | seat detection apparatus of 3rd Embodiment of this invention, (F) is a chart which shows the output waveform of a sensor. (A)-(E) are the side views which show the sheet | seat detection apparatus of 4th Embodiment of this invention, (F) is a chart which shows the output waveform of a sensor. It is a side view which shows the outline of the image forming apparatus of 5th Embodiment of this invention. It is a perspective view which shows the sheet | seat detection apparatus of 5th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Sheet detection apparatus 12 Image forming apparatus 16 Image forming part (image forming means)
18 Sheet conveying device 20 Paper feed roll (conveying means)
22 Photosensitive drum (image carrier)
26 Exposure apparatus (exposure means)
28 Developing device (developing means)
30 Transfer roll (transfer means)
34 Fixing device (fixing means)
40A to D First actuator 46 Second actuator 50 Sensor 56 Determination unit (determination means)
58 Image formation control unit (image formation area control means)
60 Fixing temperature control section (fixing temperature control means)
70 Sheet Detection Device 72A to D First Actuator 78 Second Actuator 80 Sensor 90 Sheet Detection Device 92 Third Actuator 100 Sensor 110 Sheet Detection Device 112 Second Actuator 120 Image Forming Device 124A to D First Actuator 130 Sheet Detection Device 132 Second 2 Actuator S Sheet

Claims (13)

A plurality of first actuators arranged in at least a direction crossing the sheet conveyance direction or a sheet conveyance direction and operated in contact with sheets of various sizes;
One sensor that outputs a signal according to the number of the first actuators that have been activated;
A sheet detection apparatus comprising: A second actuator displaced by a different amount by each first actuator;
The sheet detection apparatus according to claim 1, wherein the sensor outputs a signal corresponding to a displacement amount of the second actuator. A second actuator that is actuated at a different timing by each first actuator;
The sheet detection apparatus according to claim 1, wherein the sensor outputs a signal corresponding to the number of times the operation of the second actuator is detected. A second actuator that is actuated at a different timing by each first actuator;
The sheet detection apparatus according to claim 1, wherein the sensor outputs a signal corresponding to a time during which the operation of the second actuator is detected.   5. The sheet detection apparatus according to claim 3, wherein the plurality of first actuators are arranged in a direction inclined with respect to a sheet conveyance direction. A third actuator that is actuated by a sheet of a minimum size downstream of the first actuator in the sheet conveying direction to actuate the second actuator;
6. The sheet detection apparatus according to claim 1, wherein the sensor outputs a signal at a timing when the third actuator operates the second actuator. 6.   7. The sheet detection apparatus according to claim 1, wherein the sensor outputs a pulse signal having a number of pulses corresponding to the number of the first actuators that have been actuated.   The sheet detection apparatus according to claim 1, wherein the sensor outputs a pulse signal having a length corresponding to the number of the first actuators that are actuated. Conveying means for conveying the sheet;
The sheet detection apparatus according to any one of claims 1 to 8,
A sheet conveying apparatus comprising: A sheet conveying device according to claim 9,
Image forming means for forming an image on a sheet conveyed by the sheet conveying apparatus;
Determining means for determining the size of the sheet in accordance with a signal output from the sensor;
An image forming apparatus comprising:   The image forming apparatus according to claim 10, further comprising an image forming area control unit that controls the image forming area in accordance with a sheet size determined by the determining unit. The image forming means is
An image carrier;
Exposure means for exposing the image carrier to form an electrostatic latent image on the image carrier;
Developing means for developing the electrostatic latent image on the image carrier with toner;
Transfer means for transferring a toner image from the image carrier to a sheet,
12. The image forming apparatus according to claim 11, wherein the image forming area control unit controls an area where the exposure unit exposes the image carrier in accordance with a sheet size determined by the determination unit. . Fixing means for fixing the toner image on the sheet;
13. The image forming apparatus according to claim 12, further comprising a fixing temperature control unit that controls the temperature control of the fixing unit in accordance with the sheet size determined by the determination unit.

Images