JP2006138933A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct defective exposure caused by the contraction/expansion of an exposure body due to temperature change highly precisely without being affected by vibration and impact. <P>SOLUTION: A temperature sensor 43 is arranged near a 1st LPH 7a and a 2nd LPH 7b. Dot-shifting of a plurality of LED elements involved in the 1st LPH 7a and the 2nd LPH 7b and the light quantity of the LED element are controlled by a controller 41 in accordance with the temperature measured by the temperature sensor 43. The defective exposure is reduced, and black/white stripes formed in the outputted image become inconspicuous. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer to which an electrophotographic system is applied, and more particularly to an image forming apparatus capable of forming a large size image such as A0 size or A1 size.

  In recent years, as an image forming apparatus such as a copying machine or a printer to which an electrophotographic system is applied, a model capable of printing a large size image such as an A0 size or an A1 size has been manufactured. Each component of the large size image forming apparatus is larger than each component of a normal image forming apparatus capable of printing up to A3 size. For example, an LED print head that exposes a photosensitive drum (hereinafter simply referred to as LPH) needs to be about three times as long as an LPH provided in a normal apparatus. However, large LPHs are expensive parts due to yield and versatility problems. Therefore, in order to reduce the cost, a plurality of A3 size LPHs are connected to perform wide image exposure. The plurality of LPHs are performed by dividing the exposure in the width direction of the image. In this way, when an image is divided and exposed with a plurality of LPHs, image misalignment at the joint portion of the image becomes a problem.

  The plurality of LPHs are arranged on the housing in a staggered manner so as to be parallel to each other and shifted in the longitudinal direction. At the time of arrangement, each LPH is aligned, and at this stage, no image shift occurs. However, the environmental temperature may differ greatly between the manufacturing location and the usage location of the image forming apparatus. Further, when the image forming apparatus is used, the internal devices generate heat. For this reason, LPH may expand and contract under the influence of temperature change. Then, a relative positional shift between adjacent LPHs occurs, and an exposure failure occurs. When such an exposure failure occurs, black streaks and white streaks appear in the output image. The following Patent Document 1 is disclosed as a technique for solving the exposure failure.

In Patent Document 1, a sensor that detects a positional deviation of an LED and a shape memory alloy that contracts when energized are used. When the sensor detects a position error of the LED, the shape memory alloy is energized, and the LPH error is mechanically corrected.
JP 2002-52757 A

  However, the technique of Patent Document 1 has a problem in accuracy. According to the technique of Patent Document 1, the LPH is fixed on the housing with a certain degree of freedom in order to correct the positional deviation of the LPH due to a temperature change. In other words, the LPH is not firmly fixed on the housing. For this reason, the LPH itself may be displaced from the mounting position due to vibration or impact. Therefore, the accuracy at the time of attachment cannot be maintained. There is also a problem of increased costs.

  The present invention has been made in view of such a situation, and provides an image forming apparatus that accurately corrects an exposure failure caused by contraction / expansion of an exposed body due to a temperature change without being affected by vibration or impact. It is a problem to be solved.

  In order to achieve the above object, the invention described in claim 1 includes a photosensitive member having a photosensitive material on a peripheral surface of a cylindrical or columnar member and rotating about its own axis, and on the photosensitive member side. A plurality of exposure bodies that contain a plurality of image exposure elements facing each other in a state of being arranged in parallel to the longitudinal direction of the image exposure elements, and the axial center of the photoconductor and the longitudinal direction are substantially parallel and adjacent to each other. Image formation for forming a wide image in the longitudinal direction by rotating the photosensitive body while fixing the exposed bodies in a state shifted in the longitudinal direction, dividing the photosensitive material by each of the exposed bodies and exposing In the apparatus, a temperature measuring unit that measures an environmental temperature or a temperature in the vicinity of the plurality of exposed bodies, and an image exposure element that is assigned to a divided portion of the image according to the temperature measured by the temperature measuring unit is specified, and Light emission / non-light emission of image exposure element and Controls the amount, characterized by comprising an exposure correcting means for correcting the exposure defects caused by contraction and expansion of the respective exposure member due to temperature changes.

  According to a second aspect of the present invention, in the first aspect of the present invention, the image exposure elements assigned to the divided portions of the image have different control values.

  According to a third aspect of the present invention, in the first aspect of the present invention, a limit value is provided for the amount of light quantity change of the end element among the image exposure elements assigned to the divided portion of the image, and the control exceeds this limit value. Is required, the amount of light of other elements adjacent to the element at the end is also changed.

  According to a fourth aspect of the present invention, in the first aspect of the present invention, the exposure correction unit performs control based on a table in which the control method of the image exposure element is associated with the temperature in advance.

  The invention according to claim 5 is the invention according to claim 4, wherein the temperature of the table can be arbitrarily set.

  According to a sixth aspect of the present invention, there is provided a photosensitive member having a photosensitive material on a peripheral surface of a cylindrical or columnar member and rotating about its own axis, and a plurality of image exposure elements facing toward the photosensitive member. A plurality of exposure bodies included in a state of being arranged in parallel with the longitudinal direction of the photosensitive body, the axial center of the photoconductor and the longitudinal direction are substantially parallel, and adjacent exposure bodies are arranged in the longitudinal direction. In an image forming apparatus in which the photosensitive member is rotated while being fixed in a shifted state, the photosensitive material is divided and exposed by each of the exposure members, and a wide image is formed in the longitudinal direction. And a misregistration detecting unit that detects a relative misregistration amount in the longitudinal direction that occurs between the exposed bodies, and a position misalignment measured by the misregistration detection unit, and is assigned to a divided portion of the image. Identify the image exposure element and its image Controlling light emission and non-emission and the light quantity of the optical device, characterized by comprising an exposure correcting means for correcting the exposure defects caused by contraction and expansion of the respective exposure member due to temperature changes.

  The invention described in claim 7 is characterized in that, in the invention described in claim 6, the image exposure elements assigned to the divided portions of the image have different control values.

  According to an eighth aspect of the present invention, in the invention of the sixth aspect, a limit value is provided for an amount of change in light quantity of an end element among the image exposure elements assigned to the divided portion of the image, and the control exceeds the limit value. Is required, the amount of light of other elements adjacent to the element at the end is also changed.

  The invention according to claim 9 is the invention according to claim 6, wherein the exposure correction means performs control based on a table in which image exposure element control methods and displacement amounts are associated in advance. To do.

  According to a tenth aspect of the present invention, in the invention according to the ninth aspect, the positional deviation amount of the table can be arbitrarily set.

  According to the present invention, positional deviation correction of LPH is performed not by mechanical means, but only by light emission / non-light emission and light amount control of LED elements. Since no mechanical means is used, the LPH is firmly fixed to the housing. Therefore, it is possible to correct the exposure failure caused by the contraction / expansion of the exposed body due to the temperature change with high accuracy without being affected by vibration or impact. Moreover, since light emission / non-light emission and light amount control of the LED element can be freely set, wide and precise adjustment is possible, and long-term reliability is high.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In the first embodiment, the temperature inside the exposure device is measured, and the dot shift of the LED element and the light amount of the LED element are controlled in accordance with the result. It makes the white lines inconspicuous.

  FIG. 1 is a diagram illustrating an internal configuration of the image forming apparatus.

  In FIG. 1, the image forming apparatus 1 is mainly composed of an image forming unit 2, a paper feed unit 3, and a storage unit 4 that stores a control circuit, a spare paper feed roll, and the like. In the image forming unit 2, the charging roll 6, the exposure device 7, the developing device 8, the transfer roll 12, and the static eliminator 13 are arranged in this order along the peripheral surface of the photosensitive drum 5.

  The photosensitive drum 5 is rotationally driven at a predetermined rotational speed in the direction of arrow A about its own axis by a driving means (not shown). As the photosensitive drum 5, for example, a drum having a diameter of about 100 mm using a photosensitive member made of OPC or the like is used. The charging roll 6 uniformly charges the surface of the photosensitive drum 5 to a predetermined potential. The means for charging the surface of the photosensitive drum 5 is not limited to the charging roll 6 but may be a charger such as a scorotron. The exposure device 7 is provided with a plurality of exposure bodies. FIG. 1 shows a first LPH 7a, a second LPH 7b, and a third LPH 7c as exposure bodies. The first to third LPHs 7a, 7b, and 7c expose an image on the surface of the photosensitive drum 5 to form an electrostatic latent image corresponding to the image information. The developing device 8 develops the electrostatic latent image formed on the surface of the photosensitive drum 5 to form a toner image. As a developing method of the developing device 8, there are a one-component developing method, a two-component developing method including a toner and a carrier, and the like. The transfer roll 12 transfers the toner image formed on the surface of the photosensitive drum 5 onto the roll paper 11 fed from the paper feed unit 3. The static eliminator 13 separates the toner image from the surface of the photosensitive drum 5 by a static elimination action.

  The conveyance belt 14 feeds the roll paper 11 from the upstream photosensitive drum 5 to the downstream fixing device 15. The fixing device 15 applies heat and pressure to the roll paper 11 to perform fixing processing of the toner image. The roll paper 11 on which the toner image is fixed is cut into a predetermined size such as A0 size, if necessary, and then discharged onto a discharge tray (not shown) disposed outside the image forming apparatus main body 1.

  FIG. 2 is a view showing the configuration of the exposure device, and is a view showing the exposure device 7 viewed from the photosensitive drum 5 side in FIG.

  The exposure unit 7 is mainly composed of an external casing 21 and first to third LPHs 7a to 7c. The first to third LPHs 7a to 7c are fixed to the housing 21 in a state facing the photosensitive drum 5 side. As the first to third LPHs 7a to 7c, for example, those corresponding to the A3 size of 12 inches in length are used. The first to third LPHs 7 a to 7 c are arranged so that their longitudinal directions are substantially parallel to the axis of the photosensitive drum 5 and are separated from the peripheral surface of the photosensitive drum 5 by the same distance. For this reason, the first to third LPHs 7 a to 7 c are parallel to each other in a state along the peripheral surface of the photosensitive drum 5. The first to third LPHs 7a to 7c are arranged in the order of the first LPH 7a, the second LPH 7b, and the third LPH 7c so as to be shifted from each other in the longitudinal direction, and the first LPH 7a and the third LPH 7c are arranged on the same straight line. That is, the arrangement of the first to third LPHs 7a to 7c is staggered, and the second LPH 7b is adjacent to the first LPH 7a and the third LPH 7c. The first to third LPHs 7a to 7c are arranged so that both ends of the second LPH 7b overlap with one end sides of the first LPH 7a and the third LPH 7c, respectively, when viewed from the downstream side in the rotation direction of the photosensitive drum 5 in the casing 21 portion. The Note that the number of LPHs may be two, or four or more.

  As described above, the image area in the axial direction of the photosensitive drum 5 is divided by the plurality of first to third LPHs 7a to 7c arranged without generating a gap over the entire image width in the axial direction of the photosensitive drum 5. ing. Then, the first to third LPHs 7a to 7c expose individual areas, whereby the entire image width of the photosensitive drum 5 is exposed. The first LPH 7a and the third LPH 7c are on the same straight line, but the second LPH 7b is positioned downstream of the first LPH 7a and the third LPH 7c. Therefore, by delaying the exposure start time of the second LPH 7b from the exposure start times of the first LPH 7a and the third LPH 7c in accordance with the rotational speed of the photosensitive drum 5, the same line in the axial direction of the circumferential surface of the photosensitive drum 5 is exposed. Is done. The first LPH 7a and the third LPH 7c are not necessarily on the same straight line. If the delay time at the start of exposure is appropriate, the same line can be exposed by the first to third LPHs 7a to 7c.

  FIG. 3 is a view showing a cross section of the LPH. Since the first to third LPHs 7a to 7c have the same structure, the first LPH 7a will be described as a representative here.

  The first LPH 7 a is mainly composed of an LPH housing 31, a plurality of condenser lenses 32, an insulating substrate 33, a plurality of LED elements 34, and a drive circuit 35. An insulating substrate 33 is installed inside the LPH casing 31. On the insulating substrate 33, a plurality of LED elements 34 are arranged at a predetermined arrangement density (for example, 600 dpi) in the longitudinal direction of the first LPH 7a, that is, the direction perpendicular to the paper surface of FIG. The insulating substrate 33 is provided with a drive circuit 35 that drives the LED element 34. In the light irradiation direction of each LED element 34, a condenser lens 32 is provided so as to penetrate the LPH housing 31. The condensing lens 32 condenses the light emitted from the opposing LED elements 34 and exposes the image forming position corresponding to the focal length in a dot shape. Normally, the position of the first LPH 7a is set so that the peripheral surface of the photosensitive drum 5 is located at this image forming position.

  FIG. 4 is a functional block diagram showing a control system of the exposure device according to the first embodiment.

  The temperature sensor 43 measures the temperature in or near the exposure device 7. If the image shift amount is mainly governed by the environmental temperature, the temperature sensor 43 may be placed in a place that is not easily affected by the heat generated in the apparatus, such as the paper feed unit 3. A thermistor is used as the temperature sensor 43. The measurement data of the temperature sensor 43 is output to the controller 41 as analog data. The controller 41 A / D converts the measurement data, and as a result, the temperature in the exposure unit 7 is recognized as digital data. The controller 41 divides the image data for one line output from an image data output device (not shown) into data for the first LPH 7a, data for the second LPH 7b, and data for the third LPH 7c, and further considers the temperature data. Thus, the command signal instructing the light emission / non-light emission and the light quantity of each of the LED elements 34 of the first to third LPHs 7 a to 7 c is output to the interface 42. The interface 42 outputs a command signal to the first to third LPHs 7a to 7c. The drive circuits 35 of the first to third LPHs 7a to 7c adjust the light emission / non-light emission and the light amount of the LED element 34 according to the command signal.

  Control in line units is difficult in terms of processing speed and the temperature change is minute, so in practice it is usually controlled for each sheet or each output operation.

  Next, description will be made regarding light emission / non-light emission and light amount control of the LED elements corresponding to the divided portions of the image.

  FIG. 5 is a diagram schematically showing the LED elements of the first LPH 7a and the second LPH 7b assigned in the vicinity of the divided portion of the image.

  In the state shown in FIG. 5, the LED elements 34 before the 1008th are used in the first LPH 7a, and the LED elements 34 after the 210th are used in the second LPH 7b. Therefore, the 1008th LED element 34a of the first LPH 7a and the 210th LED element 34b of the second LPH 7b are allocated to the joint of the image, that is, the divided portion. In addition, the number of each LED element 34 shown in this specification is used for convenience of explanation, and does not necessarily match the number of LED elements actually provided in the first LPH 7a and the second LPH 7b.

  As shown in FIG. 5, both the first LPH 7a and the second LPH 7b are fixed to the casing at the ends in the right direction of the drawing. On the other hand, it is fixed so that it cannot be moved in the vertical direction of the drawing and in the front-rear direction of the drawing by means (not shown) and can be moved in the left direction. Therefore, the first LPH 7a and the second LPH 7b contract and expand in the main scanning direction, that is, the longitudinal direction (left and right direction in the drawing) with the right end of the drawing fixed, due to the temperature change. Since the LED element 34a of the first LPH 7a is close to the fixed position of the first LPH 7a, it hardly displaces even if expansion / contraction occurs. On the other hand, since the LED element 34b of the second LPH 7b is far from the fixed position of the second LPH 7b, the LED element 34b is displaced when expansion / contraction occurs. Therefore, according to the fixing method as shown in FIG. 5, the relative positional relationship between the LED element 34a and the LED element 34b changes, and the dot interval of the image division portion changes. Then, an image defect occurs in the output image.

  In the present embodiment, light emission / non-light emission and light amount control of the LED element 34 are performed in order to reduce image defects due to a change in dot interval. The controller 41 is preset with a method for controlling the LED elements according to the measured temperature. For example, a table as shown in Table 1 below is set.

  In Table 1, the temperature measured by the temperature sensor 43 is associated with the dot shift of the LED element 34a in the first LPH 7a and the light quantity of the LED element 34a in the first LPH 7a and the LED element 34b in the second LPH 7b. Based on Table 1, the controller 41 controls light emission / non-light emission and light quantity of the LED elements 34 corresponding to the divided portions of the image. Specific examples will be described in order with reference to FIGS.

  6 to 11 are diagrams schematically showing LED elements of the first LPH 7a and the second LPH 7b allocated near the divided portion of the image, as in FIG.

  FIG. 5 shows an initial state (state at normal temperature) of the positional relationship between the first LPH 7a and the second LPH 7b. In the table, a certain temperature range centered on a predetermined temperature is set as normal temperature (reference). In Table 1, 25 ° C. or more and less than 30 ° C. is set as normal temperature.

Below, control of the controller 41 based on Table 1 is demonstrated. The term “expansion / contraction” used in the description means expansion / contraction based on the second LPH 7b at room temperature. Further, “the distance between the LED element 34a and the LED element 34b” means the first straight line that is in contact with the right end of the LED element 34a and orthogonal to the LPHs 7a and 7b, and the first line that is in contact with the left end of the LED element 34b and orthogonal to the LPHs 7a and 7b. Means a distance between two straight lines [1. Room temperature range (No. 5 in Table 1)]
As shown in FIG. 5, in the normal temperature range, the second LPH 7b hardly contracts or expands, and the distance between the 1008th LED element 34a and the 210th LED element 34b hardly changes. Therefore, as shown in Table 1, a good image can be obtained without performing dot shift or light amount adjustment of the LED element 34. Under normal temperature, the 1008th LED element 34a in the first LPH 7a and the 210th LED element 34b in the second LPH 7b are allocated to the divided portion of the image.

[2. In the case of the first low temperature range (No. 4 in Table 1)]
FIG. 6 shows light emission / non-light emission of the LED elements 34 of the first LPH 7a and the second LPH 7b in the first low temperature range (in the case of 20 ° C. or more and less than 25 ° C. in Table 1) lower than the lower limit temperature of the normal temperature range by t ° C. or less. The amount of light is shown.

  As shown in FIG. 6, under the first low temperature range, the second LPH 7b contracts slightly (moves in the right direction in the drawing), and the 1008th LED element 34a and the 210th LED element 34b Spacing is slightly smaller. In this state, when each LED element 34 emits light as in the initial setting, white streaks appear in the divided portion of the output image. Therefore, the 1008th LED element 34a in the first LPH 7a and the 210th LED element 34b in the second LPH 7b are assigned to the divided portions of the image, and as shown in Table 1, the LED elements 34a and 34b emit light brightly. The amount of light is adjusted as described above. Such control makes the white streaks appearing in the output image inconspicuous. As a result, a good image is obtained.

[3. In the case of the second low temperature range (No. 3 in Table 1)]
FIG. 7 shows the light emission of the LED elements 34 of the first LPH 7a and the second LPH 7b under a second low temperature range (in the case of 15 ° C. or more and less than 20 ° C. in Table 1) lower than the lower limit temperature of the first low temperature range by t ° C. or less. -Non-light emission and light intensity are shown.

  As shown in FIG. 7, under the second low temperature range, the second LPH 7b undergoes moderate contraction (movement to the right in the drawing), and the 1008th LED element 34a and the 210th LED element 34b Spacing increases. In this state, when each LED element 34 emits light as in the initial setting, white streaks appear in the divided portion of the output image. Therefore, as shown in Table 1, a dot shift on the + side is performed on the first LPH 7a side. Then, the 1009th LED element 34a in the first LPH 7a and the 210th LED element 34b in the second LPH 7b are allocated to the divided portion of the image. However, the distance between the 1009th LED element 34a and the 210th LED element 34b is narrow. Therefore, when each LED element 34 emits light in this state, black streaks appear in the divided portion of the output image. Therefore, as shown in Table 1, the light amount adjustment is performed so that the LED elements 34a and 34b emit dark light. By such control, white lines and black lines appearing in the output image become inconspicuous. As a result, a good image is obtained.

[4. In the case of the third low temperature range (No. 2 in Table 1)]
FIG. 8 shows the light emission of the LED elements 34 of the first LPH 7a and the second LPH 7b under the third low temperature range (in the case of 10 ° C. or more and less than 15 ° C. in Table 1) lower than the lower limit temperature of the second low temperature range by t ° C. or less. -Non-light emission and light intensity are shown.

  As shown in FIG. 8, under the third low temperature range, the second LPH 7b undergoes a large contraction (movement to the right in the drawing), and the 1008th LED element 34a and the 210th LED element 34b Spacing increases greatly. In this state, when each LED element 34 emits light as in the initial setting, white streaks appear in the divided portion of the output image. Therefore, as shown in Table 1, a dot shift on the + side is performed on the first LPH 7a side. Then, the 1009th LED element 34a in the first LPH 7a and the 210th LED element 34b in the second LPH 7b are allocated to the divided portion of the image. The interval between the 1009th LED element 34a and the 210th LED element 34b is substantially the same as the interval between the LED elements 34 provided in the first LPH 7a and the second LPH 7b. Such control makes the white streaks appearing in the output image inconspicuous. As a result, a good image is obtained.

[5. In the case of the fourth low temperature range (No. 1 in Table 1)]
Under the fourth low temperature range, control that combines control performed under the first low temperature range (light intensity increase) and control performed under the third low temperature range (dot shift) is performed. Therefore, the description is omitted here.

[6. In the case of the first high temperature range (No. 6 in Table 1)]
FIG. 9 shows light emission / non-light emission of the LED elements 34 of the first LPH 7a and the second LPH 7b in the first high temperature range (in the case of 30 ° C. or more and less than 35 ° C. in Table 1) higher than the upper limit temperature of the normal temperature range by t ° C. or less. And the amount of light is shown.

  As shown in FIG. 9, under the first high temperature range, the second LPH 7b is slightly expanded (moved leftward in the drawing), and the 1008th LED element 34a and the 210th LED element 34b The interval is slightly smaller and narrower. In this state, when each LED element 34 emits light in the same manner as in the initial setting, black streaks appear in the divided portion of the output image. Therefore, the 1008th LED element 34a in the first LPH 7a and the 210th LED element 34b in the second LPH 7b are assigned to the divided portions of the image, and as shown in Table 1, the LED elements 34a and 34b emit dark light. The amount of light is adjusted as described above. Such control makes black streaks appearing in the output image inconspicuous. As a result, a good image is obtained.

[7. In the case of the second high temperature range (No. 7 in Table 1)]
FIG. 10 shows the light emission of the LED elements 34 of the first LPH 7a and the second LPH 7b in the second high temperature range (in the case of 35 ° C. or more and less than 40 ° C. in Table 1) higher than the upper limit temperature of the first high temperature range by t ° C. or less. -Non-light emission and light intensity are shown.

  As shown in FIG. 10, under the second high temperature range, the second LPH 7b undergoes moderate expansion (moving leftward in the drawing), and the 1008th LED element 34a and the 210th LED element 34b The interval is narrowed. In this state, when each LED element 34 emits light in the same manner as in the initial setting, black streaks appear in the divided portion of the output image. Therefore, as shown in Table 1, a negative dot shift is performed on the first LPH 7a side. Then, the 1007th LED element 34a in the first LPH 7a and the 210th LED element 34b in the second LPH 7b are allocated to the divided portion of the image. However, the distance between the 1007th LED element 34a and the 210th LED element 34b is wide. Therefore, when each LED element 34 emits light in this state, white streaks appear in the divided portion of the output image. Therefore, as shown in Table 1, light amount adjustment is performed so that the LED elements 34a and 34b emit light brightly. By such control, white lines and black lines appearing in the output image become inconspicuous. As a result, a good image is obtained.

[8. In the case of the third high temperature range (No. 8 in Table 1)]
FIG. 11 shows the light emission of the LED elements 34 of the first LPH 7a and the second LPH 7b under a third high temperature range that is higher than the upper limit temperature of the second high temperature range by t ° C. or less (in the case of 40 ° C. or more and less than 45 ° C. in Table 1).・ No light emission and light intensity are shown.

  As shown in FIG. 11, under the third high temperature range, the second LPH 7b undergoes a large expansion (movement in the left direction in the drawing), and the 1008th LED element 34a and the 210th LED element 34b Spacing increases greatly. In this state, when each LED element 34 emits light in the same manner as in the initial setting, black streaks appear in the divided portion of the output image. Therefore, as shown in Table 1, a negative dot shift is performed on the first LPH 7a side. Then, the 1007th LED element 34a in the first LPH 7a and the 210th LED element 34b in the second LPH 7b are allocated to the divided portion of the image. The distance between the 1007th LED element 34a and the 210th LED element 34b is substantially the same as the distance between the LED elements 34 provided in the first LPH 7a and the second LPH 7b. Such control makes black streaks appearing in the output image inconspicuous. As a result, a good image is obtained.

[9. In the case of the fourth high temperature range (No. 9 in Table 1)]
Under the fourth high temperature range, control that combines control performed under the first high temperature range (dark light amount) and control performed under the third high temperature range (dot shift) is performed. Therefore, the description is omitted here.

  The control of the controller 41 using Table 1 has been described above.

  The temperature range in Table 1 can be set freely. Further, the dot shift and the light amount in Table 1 can be freely set. In Table 1, three levels of light quantity such as “dark, normal, and bright” are set, but two levels or four or more levels may be used. Further, for example, when the LED element 34a assigned to the divided portion of the image is to be brightened, but the light emission amount of the LED element 34a has reached a limit value, the other LED element 34b is brightened to The LED element 34b may compensate for the insufficient light quantity of 34a. Further, when the LED element 34b cannot compensate for the insufficient light quantity of the LED element 34a, dot shift may be performed. In short, it is only necessary that the white lines and black lines in the divided portions of the image become inconspicuous, and the combination of dot shift and light amount adjustment may be determined as appropriate.

  The control example in Table 1 corrects the joint portion of the image formed by the first LPH 7a and the image formed by the second LPH 7b, but corrects the joint portion of the image formed by another LPH. It is also applicable. It can also be applied to correct a plurality of joint portions. In this case, the temperature setting can be changed for each joint portion.

  Since the temperature in the exposure device 7 is not uniform, it is preferable to select the temperature of the portion where the temperature sensor 43 is most correlated with the image shift amount. If the deviation due to heat generation of the LED element 34 is dominant, the vicinity of the LED elements 34a and 34b is preferable. If the deviation due to the temperature rise in the apparatus is dominant, the vicinity of the exposure unit 7 is preferable. If the shift due to the environmental temperature change is dominant, a portion that is not affected by heat generation such as the fixing device 15 is preferable.

  Further, instead of performing the dot shift at the first LPH 7a, the second LPH 7b dot shift may be performed.

  Further, the present invention can be applied to the case where the first LPH 7a and the second LPH 7b are fixed at the left end instead of the right end as shown in FIGS. Is the right end, and the fixing position of the other LPH is the left end, the present invention can be applied.

  The second embodiment relates to a joint correction technique of an image forming apparatus configured to divide and expose the entire image width of a wide photosensitive body by connecting a plurality of LPHs. The amount of deviation of the LED element generated by the temperature change inside the device is measured, and by controlling the dot shift of the image data and the light amount correction of the LED based on the result, the black and white lines generated in the output image are not noticeable. To do.

  The first embodiment measures the temperature inside the exposure unit and discriminates the expansion / contraction state of LPH, whereas the second embodiment directly measures the expansion / contraction amount of LPH. Is.

  FIG. 4 is a functional block diagram showing a control system of the exposure device according to the second embodiment.

  The difference from the first embodiment is that a position sensor 53 is provided instead of the temperature sensor. As the position sensor 53, a photodiode is used. The photodiode 53 faces an LED element that is not used for exposure among the plurality of LED elements 34 provided in the second LPH 7b. The LED element not used for exposure here needs to be an LED element located in a direction opposite to the fixed position of the second LPH 7b. In FIG. 12, the LED element is in the vicinity of the left end of the second LPH 7b. In this embodiment, LED elements that are not used for exposure emit light for position measurement, not for exposure. The position sensor 53 detects the light of the LED element at all times or when necessary, and measures the amount of positional deviation from the initial state.

  In the case of the present embodiment, if the “temperature range” shown in Table 1 is replaced with the “positional deviation amount range”, the control contents of the first embodiment can be used as they are.

  According to the first and second embodiments, LPH positional deviation correction is performed not by mechanical means, but only by light emission / non-light emission and light amount control of LED elements. Since no mechanical means are used, the LPH is firmly fixed to the substrate. Therefore, it is possible to correct the exposure failure caused by the contraction / expansion of the exposed body due to the temperature change with high accuracy without being affected by vibration or impact. Moreover, since light emission / non-light emission and light amount control of the LED element can be freely set, wide and precise adjustment is possible, and long-term reliability is high.

  In the present invention, as long as the image forming apparatus uses a rotary photoreceptor and an exposure device, various other devices such as a general printer, a plotter, and an apparatus for forming an image on paper such as banknotes and securities are formed. It can be effectively used for an image forming apparatus.

FIG. 1 is a diagram illustrating an internal configuration of the image forming apparatus. FIG. 2 is a diagram showing the configuration of the exposure unit. FIG. 3 is a view showing a cross section of the LPH. FIG. 4 is a functional block diagram showing a control system of the exposure device according to the first embodiment. FIG. 5 is a diagram schematically showing the LED elements of the first LPH 7a and the second LPH 7b assigned in the vicinity of the divided portion of the image. FIG. 6 is a diagram schematically showing LED elements of the first LPH 7a and the second LPH 7b assigned in the vicinity of the divided portion of the image. FIG. 7 is a diagram simply showing the LED elements of the first LPH 7a and the second LPH 7b assigned in the vicinity of the divided portion of the image. FIG. 8 is a diagram simply showing the LED elements of the first LPH 7a and the second LPH 7b assigned in the vicinity of the divided portion of the image. FIG. 9 is a diagram schematically showing the LED elements of the first LPH 7a and the second LPH 7b assigned in the vicinity of the divided portion of the image. FIG. 10 is a diagram simply showing the LED elements of the first LPH 7a and the second LPH 7b assigned in the vicinity of the divided portion of the image. FIG. 11 is a diagram simply showing the LED elements of the first LPH 7a and the second LPH 7b assigned in the vicinity of the divided portion of the image. FIG. 12 is a functional block diagram showing a control system of the exposure device according to the second embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 7 ... Exposure device, 7a ... 1st LPH, 7b ... 2nd LPH, 7c ... 3rd LPH, 41 ... Controller, 42 ... Interface, 43 ... Temperature sensor

Claims (10)

A photosensitive member having a photosensitive material on the peripheral surface of a cylindrical or columnar member and rotating about its own axis;
A plurality of exposure bodies containing a plurality of image exposure elements facing the photoreceptor side in a state of being arranged in parallel with the longitudinal direction of the photosensitive body;
The photosensitive member is rotated while fixing the adjacent exposure bodies in a state of being shifted in the longitudinal direction, the axial center of the photosensitive body being substantially parallel to the longitudinal direction. In the image forming apparatus that divides and exposes each of the exposure bodies to form a wide image in the longitudinal direction,
Temperature measuring means for measuring an ambient temperature or a temperature in the vicinity of the plurality of exposed bodies;
According to the temperature measured by the temperature measuring means, the image exposure element assigned to the divided portion of the image is specified, the light emission / non-light emission and the light quantity of the image exposure element are controlled, and each exposure body according to the temperature change An image forming apparatus comprising: an exposure correction unit that corrects an exposure failure caused by shrinkage / expansion. The image forming apparatus according to claim 1, wherein each image exposure element assigned to a divided portion of an image has a different control value. Of the image exposure elements assigned to the divided portion of the image, a limit value is provided for the amount of light change of the end element, and when control exceeding this limit value is required, another element adjacent to the end element The image forming apparatus according to claim 1, wherein the amount of light is also changed. The image forming apparatus according to claim 1, wherein the exposure correction unit performs control based on a table in which a control method of an image exposure element and a temperature are associated in advance. The image forming apparatus according to claim 4, wherein the temperature of the table can be arbitrarily set. A photosensitive member having a photosensitive material on the peripheral surface of a cylindrical or columnar member and rotating about its own axis;
A plurality of exposure bodies containing a plurality of image exposure elements facing the photoreceptor side in a state of being arranged in parallel with the longitudinal direction of the photosensitive body;
The photosensitive member is rotated while fixing the adjacent exposure bodies in a state of being shifted in the longitudinal direction, the axial center of the photosensitive body being substantially parallel to the longitudinal direction. In the image forming apparatus that divides and exposes each of the exposure bodies to form a wide image in the longitudinal direction,
A positional deviation detecting means for detecting a relative positional deviation amount in the longitudinal direction generated between adjacent exposed bodies in accordance with a temperature change;
According to the positional deviation amount measured by the positional deviation detection means, the image exposure element assigned to the divided portion of the image is specified, the light emission / non-emission and the light quantity of the image exposure element are controlled, and the temperature change An image forming apparatus comprising: an exposure correction unit that corrects an exposure failure caused by contraction / expansion of each exposure body. The image forming apparatus according to claim 6, wherein each image exposure element assigned to a divided portion of an image has a different control value. Of the image exposure elements assigned to the divided portion of the image, a limit value is provided for the amount of light change of the end element, and when control exceeding this limit value is required, another element adjacent to the end element The image forming apparatus according to claim 6, wherein the amount of light is also changed. The image forming apparatus according to claim 6, wherein the exposure correction unit performs control based on a table in which an image exposure element control method and a positional deviation amount are associated in advance. The image forming apparatus according to claim 9, wherein the amount of positional deviation of the table can be arbitrarily set.

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