Exposure apparatus and image forming apparatus

Abstract

The present invention provides an image forming apparatus that can prevent focusing problems caused by warping of the holding member. [Solution] The image forming apparatus comprises a panel member facing a photoreceptor drum and having a plurality of light-emitting elements, a lens 60 that focuses light emitted from the light-emitting elements onto the photoreceptor drum, and a holding member 50 that holds the lens 60. The holding member 50 and the lens 60 are bonded together by a first adhesive portion SE1 located in the center in the longitudinal direction (width direction W) and a second adhesive portion SE2 located at the end in the longitudinal direction. The first adhesive portion SE1 and the second adhesive portion SE2 have different shrinkage rates.

Description

Technical Field

[0001] The present disclosure relates to an exposure apparatus and an image forming apparatus having a lens that focuses light emitted from a light emitting element onto a photoreceptor.

Background Art

[0002] Conventionally, an electrophotographic image forming apparatus that forms an electrostatic latent image on a photoreceptor using laser light or the like and forms an image on paper through processes of developing, transferring, and fixing the electrostatic latent image has been widely used. In recent years, as a light source for exposing a photoreceptor, a linear light source (LED array) in which point light sources such as light emitting elements are linearly arranged may be used, and a lens for forming an image of the light emitted from the LED array on the surface of the photoreceptor is provided. The lens is held via a holder, but when the holder is twisted, bent, or deformed, focus shift may occur. Therefore, a method of attaching the lens so as not to cause focus shift has been proposed (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0003] [

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A conventional LED head includes a substrate on which an LED array is mounted, a lens array provided on the light emitting surface side of the LED array, a flat portion on which the substrate is placed, and both side portions that extend downward orthogonally to the flat portion from both sides of the flat portion, and a plurality of support members that are arranged at a plurality of locations in the longitudinal direction on one side of the substrate and support the lens array, and each of the plurality of support members has one side surface of the lens array adhered by an adhesive.

[0005] In conventional LED heads, the lens array is held by a holder that extends along the longitudinal direction, and if the holder warps, there is a risk that the lenses will become distorted.

[0006] This disclosure is made to solve the above-mentioned problems and aims to provide an exposure apparatus and an image forming apparatus that can reduce the warping of the lens holding member and prevent focusing problems caused thereby. [Means for solving the problem]

[0007] The exposure apparatus according to this disclosure comprises a panel member facing a photoreceptor and having a plurality of light-emitting elements, a lens that focuses light emitted from the light-emitting elements onto the photoreceptor, and a holding member that holds the lens, wherein the holding member and the lens are bonded together by a first adhesive portion located in the center in the longitudinal direction and a second adhesive portion located at the end in the longitudinal direction, and the first adhesive portion and the second adhesive portion have different shrinkage rates.

[0008] In the exposure apparatus according to this disclosure, the first adhesive portion and the second adhesive portion may be configured to use adhesives with different shrinkage rates.

[0009] In the exposure apparatus according to this disclosure, the shrinkage rates of the first adhesive portion and the second adhesive portion may be set based on the amount of warping of the holding member in the longitudinal direction.

[0010] In the exposure apparatus according to this disclosure, the holding member and the lens are bonded together by a third adhesive portion provided between the first adhesive portion and the second adhesive portion, and the shrinkage rate may be configured to change in steps in the order of the first adhesive portion, the third adhesive portion, and the second adhesive portion.

[0011] In the exposure apparatus according to this disclosure, the first adhesive portion and the second adhesive portion may have different adhesive areas.

[0012] In the exposure apparatus according to this disclosure, the first adhesive portion and the second adhesive portion may be configured to have different amounts of adhesive applied.

[0013] The image forming apparatus according to this disclosure is characterized by comprising an exposure apparatus according to this disclosure. [Effects of the Invention]

[0014] According to this disclosure, the curvature of a retaining member can be reduced by using different shrinkage rates during bonding for a retaining member with different curvature amounts in the central and end portions. As a result, focusing problems caused by the curvature of the retaining member can be prevented. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic cross-sectional view showing an image forming apparatus according to an embodiment of the present disclosure. [Figure 2] This is a perspective view showing the print head of an exposure apparatus. [Figure 3] Figure 2 is a top view of the print head. [Figure 4] Figure 2 is a schematic cross-sectional view of the print head. [Figure 5] This is an explanatory diagram showing the positional relationship of the upward-curving retaining member with respect to the reference line. [Figure 6] This is an explanatory diagram showing the positional relationship of the downward-curving retaining member with respect to the reference line. [Modes for carrying out the invention]

[0016] The image forming apparatus according to the embodiment of this disclosure will be described below with reference to the drawings.

[0017] Figure 1 is a schematic cross-sectional view showing an image forming apparatus according to an embodiment of the present disclosure.

[0018] The image forming apparatus 100 is a multifunctional device having a copying function, a scanner function, a facsimile function, and a printer function, and transmits the image of the document read by the image reading device 130 to the outside, or forms the image of the document read by the image reading device 130 or the image received from the outside in color or monochrome on a recording medium such as paper.

[0019] Above the image reading device 130, a document conveying device 110 supported to be openable and closable is provided. The document conveying device 110 conveys one or a plurality of documents one by one in order. The image reading device 130 reads the document placed on the document placement table 130a by scanning the scanning optical system 130b, or reads the document conveyed by the document conveying device 110 to generate image data.

[0020] The image forming apparatus 100 is provided with a fixing device 1, a developing device 2, a photosensitive drum 3 (an example of a photoreceptor), a drum cleaning device 4, a charger 5, an intermediate transfer belt device 7, a secondary transfer device 11, an exposure device 12, a paper feeding unit 18, and the like.

[0021] In the image forming apparatus 100, image data corresponding to a color image using each color of black (K), cyan (C), magenta (M), and yellow (Y), or a monochrome image using a single color (for example, black) is handled. The image forming apparatus 100 is provided with four developing devices 2, photosensitive drums 3, drum cleaning devices 4, and chargers 5 for forming four types of toner images, each of which is associated with black, cyan, magenta, and yellow, and four image stations Pa, Pb, Pc, and Pd are configured.

[0022] The charger 5 uniformly charges the surface of the photoreceptor drum 3 to a predetermined potential. The exposure device 12 has a panel member 42 facing the surface of the photoreceptor drum 3 and exposes the surface of the photoreceptor drum 3 to form an electrostatic latent image. The developing device 2 develops the electrostatic latent image on the surface of the photoreceptor drum 3 to form a toner image on the surface of the photoreceptor drum 3. The drum cleaning device 4 removes and recovers residual toner from the surface of the photoreceptor drum 3. Through the above series of operations, toner images of each color are formed on the surface of each photoreceptor drum 3. The panel member 42 will be described in detail later with reference to Figures 2 to 4.

[0023] The intermediate transfer belt device 7 comprises intermediate transfer rollers 6, an endless intermediate transfer belt 71, an intermediate transfer drive roller 72, an intermediate transfer driven roller 73, and a cleaning device 9. Four intermediate transfer rollers 6 are provided inside the intermediate transfer belt 71 to form four different toner images corresponding to each color. The intermediate transfer rollers 6 transfer the toner images of each color formed on the surface of the photoreceptor drum 3 to the circulating intermediate transfer belt 71.

[0024] The intermediate transfer belt 71 is stretched over the intermediate transfer drive roller 72 and the intermediate transfer driven roller 73. In the image forming apparatus 100, the toner images of each color formed on the surface of each photoreceptor drum 3 are sequentially transferred and superimposed to form a color toner image on the surface of the intermediate transfer belt 71. The cleaning device 9 removes and collects waste toner that remains on the surface of the intermediate transfer belt 71 without being transferred to the paper.

[0025] The secondary transfer device 11 traps the paper that has been transported through the paper transport path 21 in the transfer nip section TN between the secondary transfer roller 11a and the intermediate transfer belt 71. As the paper passes through the transfer nip section TN, the toner image on the surface of the intermediate transfer belt 71 is transferred to the paper and it is then transported to the fuser device 1.

[0026] The fixing device 1 includes a fixing belt 31 and a pressure roller 32 that rotate around an axis. The fixing device 1 inserts the paper on which the toner image has been transferred into the nip portion N between the fixing belt 31 and the pressure roller 32, heats and pressurizes it, and fixes the toner image to the paper. Although not shown in Figure 1, the fixing device 1 may have components other than the fixing belt 31 and the pressure roller 32.

[0027] The paper feeding unit 18 is equipped with a paper feeding cassette for loading recording media (paper) used for image formation and is located below the exposure unit 12. The paper is pulled out of the paper feeding unit 18 by the pickup roller 16 and transported to the paper transport path 21. The paper transported to the paper transport path 21 passes through the secondary transfer unit 11 and the fixing unit 1, and is then discharged to the output tray 19 by the discharge roller 17.

[0028] The paper transport path 21 is equipped with a transport roller 13, a registration roller 14, and an ejection roller 17. The transport roller 13 facilitates the transport of the paper. The registration roller 14 transports the paper at a speed equal to the process speed at which the image is formed on the paper. This registration roller 14 is located between the paper feed unit 18 and the secondary transfer device 11 and adjusts the timing of the paper transport so that the toner image is transferred to the paper by the secondary transfer device 11. For example, the registration roller 14 holds the paper transported from the paper feed unit 18 and waits (stops temporarily), then starts transporting the paper at a constant speed in synchronization with the secondary transfer device 11.

[0029] When image formation is to be performed on the back side of the paper as well as the front side, the paper transport direction is changed by the discharge roller 17 and the paper is transported to the inversion transport path 22. In the inversion transport path 22, the paper is guided to the registration roller 14 with its front and back sides reversed by the inversion transport roller 15. The image forming apparatus 100 forms an image on the back side of the paper guided to the registration roller 14 in the same way as the front side and discharges it to the output tray 19.

[0030] Figure 2 is a perspective view showing the print head of the exposure apparatus, and Figure 3 is a top view of the print head shown in Figure 2. Note that in Figure 2, only a portion of the print head 12a is shown, and other components not shown in Figure 2 may be provided as appropriate.

[0031] In the exposure apparatus 12, a print head 12a is provided, each having four panel members 42 facing one of the four photoreceptor drums 3. The exposure apparatus 12 may be provided independently for each photoreceptor drum 3, as long as a panel member 42 is provided corresponding to each of the four photoreceptor drums 3. Since the four print heads 12a have substantially the same configuration, Figure 2 schematically shows one print head 12a extracted from the image.

[0032] In the image forming apparatus 100, the axial direction of the photoreceptor drum 3 along its rotation axis is parallel to the width direction of the paper on which the image is formed, and the photoreceptor drum 3 is configured to rotate around the axis of rotation. The print head 12a is a rectangular flat plate, with its longitudinal direction (width direction W) corresponding to the axial direction and its short direction corresponding to the rotation direction of the photoreceptor drum 3.

[0033] The print head 12a includes a base member 41, a holding member 50, and a lens 60 (lens array). As shown in Figure 4, which will be described later, a panel member 42 is attached to the upper surface of the base member 41.

[0034] The retaining member 50 is made of, for example, resin, and is a frame-shaped member that surrounds the side of the lens 60, with an opening in the center through which it passes in the height direction. The retaining member 50 is attached to the upper surface of the base member 41 so as to cover the upper part of the panel member 42. The lens 60 is attached to the retaining member 50 by inserting it into the opening provided in the retaining member 50.

[0035] The retaining member 50 and the lens 60 are bonded together at multiple points spaced apart in the width direction W. The bonding portion between the retaining member 50 and the lens 60 has a first bonding portion SE1 located in the center in the width direction W, second bonding portions SE2 located at both ends, and a third bonding portion SE3 located between the first bonding portion SE1 and the second bonding portion SE2.

[0036] Figure 4 is a schematic cross-sectional view of the print head shown in Figure 2. In Figure 4, to make the structure easier to understand, only the base member 41 and the retaining member 50 are hatched, while the hatching of the other members is omitted.

[0037] The panel member 42 has multiple light-emitting elements 42a. The light-emitting elements 42a are, for example, organic light-emitting diodes (OLEDs) or LEDs. In Figure 4, for clarity, the light-emitting elements 42a are depicted as protruding from the upper surface of the panel member 42, but in reality, they are formed inward so as not to protrude from the upper surface of the panel member 42.

[0038] The retaining member 50 is fixed to the base member 41 at both ends in the width direction W, and is held at a distance from the base member 41 at the portion facing the panel member 42. The structure for creating a gap between the retaining member 50 and the base member 41 can be designed as appropriate. For example, a step may be provided on the upper surface of the base member 41 so that the ends supporting the retaining member 50 protrude, or a spacer may be inserted and fixed between the retaining member 50 and the base member 41.

[0039] In the holding member 50, a coating portion 51 is formed in the portion corresponding to the adhesive portion by cutting out the edge of the opening for attaching the lens 60. The coating portion 51 is a groove extending downward from the upper surface (holding upper surface 50a) of the holding member 50 and is a portion that receives the adhesive 80 dripped from above.

[0040] In this embodiment, a UV adhesive (ultraviolet-curing adhesive) is used as the adhesive 80 for bonding the lens 60 and the holding member 50. When bonding the lens 60 and the holding member 50, the adhesive 80 is dropped onto the application area 51 and cured by irradiating it with UV (ultraviolet) light. The adhesive 80 may be any of several types of adhesives with different shrinkage rates, such as epoxy adhesives, acrylic adhesives, or modified acrylic adhesives.

[0041] As shown in Figure 4, the light LB emitted from the light-emitting element 42a is focused onto the surface of the photoreceptor drum 3 through the upper surface of the lens 60 (upper lens surface 60a). Ideally, the gap between the light-emitting element 42a and the lens 60 should be 0.05 mm or less, and if this gap deviates significantly from the set value, there is a risk of focusing problems. Incidentally, the retaining member 50 is made of resin, and warping may occur during molding. In the assembly process, the lens 60 and the retaining member 50 are bonded together with the warping of the retaining member 50 corrected, but when the correction is released, distortion may occur in the lens 60 due to the force trying to return the warp to its original shape.

[0042] In contrast, this disclosure reduces the warping of the retaining member 50 by creating a difference in the shrinkage rate at each adhesive portion. Next, the warping of the retaining member 50 at each adhesive portion will be explained with reference to Figures 5 and 6.

[0043] Figure 5 is an explanatory diagram showing the positional relationship of the upward-curving retaining member with respect to the reference line, and Figure 6 is an explanatory diagram showing the positional relationship of the downward-curving retaining member with respect to the reference line.

[0044] Figures 5 and 6 show the change in the positional relationship of the upper surface (upper surface 50a) of the retaining member 50 with respect to the reference line KL. The upper surface curve HZ is the height of the upper surface 50a measured in advance, and shows the change along the width direction W, corresponding to the curvature of the retaining member 50 in the width direction W. The reference line KL is assumed to be a horizontal straight line representing the upper surface 60a of the lens. In Figures 5 and 6, the distance in the height direction between the upper surface curve HZ and the reference line KL is defined as the amount of curvature of the retaining member 50. The first amount of curvature GL1 indicates the amount of curvature in the part corresponding to the first adhesive part SE1, and the second amount of curvature GL2 indicates the amount of curvature in the part corresponding to the second adhesive part SE2.

[0045] The upper surface curve HZ shown in Figure 5 corresponds to the upward-curving retaining member 50. The retaining member 50 has a portion corresponding to the first adhesive portion SE1 that protrudes upward, and a portion corresponding to the second adhesive portion SE2 that slopes downward. Therefore, the upper surface curve HZ is a curve that protrudes upward in the center, so that it is convex upward, and the first curvature amount GL1 is smaller than the second curvature amount GL2.

[0046] When the lens 60 and the retaining member 50 are bonded together, increasing the shrinkage rate results in greater warp correction. In the case of Figure 5, the shrinkage rate due to bonding at the first bonding section SE1 is set to be smaller than the shrinkage rate due to bonding at the second bonding section SE2. Specifically, an adhesive with a low shrinkage rate is used at the first bonding section SE1, and an adhesive with a high shrinkage rate is used at the second bonding section SE2.

[0047] The upper surface curve HZ shown in Figure 6 corresponds to the downward-curving retaining member 50. The retaining member 50 has a portion corresponding to the first adhesive portion SE1 that protrudes downward, and a portion corresponding to the second adhesive portion SE2 that rises upward. Therefore, the upper surface curve HZ is a curve that protrudes downward in the center, so that it is convex downward, and the first curvature GL1 is greater than the second curvature GL2. In the case of Figure 6, an adhesive with a high shrinkage rate is used for the first adhesive portion SE1, and an adhesive with a low shrinkage rate is used for the second adhesive portion SE2.

[0048] As described above, the curvature of the retaining member 50 can be reduced by using different shrinkage rates during bonding, given that the amount of curvature differs between the central and end portions of the retaining member 50. As a result, focusing problems caused by the curvature of the retaining member 50 can be prevented. Furthermore, by using adhesives 80 with different shrinkage rates, it is easy to create a difference in shrinkage rates. In addition, by considering the amount of curvature of the retaining member 50 measured in advance, an appropriate shrinkage rate can be set.

[0049] The adhesive 80 needs to be applied to at least the first adhesive portion SE1 and the second adhesive portion SE2, but if the lens 60 and the holding member 50 are to be bonded more firmly, the adhesive 80 may also be applied to the third adhesive portion SE3. In this case, the type of adhesive 80 should be appropriately selected so that the shrinkage rate changes in stages in the order of the first adhesive portion SE1, the third adhesive portion SE3, and the second adhesive portion SE2. In other words, by gradually changing the shrinkage rate from the center to the edges in the width direction W, the warping of the holding member 50 can be gradually reduced.

[0050] In this embodiment, a configuration using adhesives 80 with different shrinkage rates has been described, but the invention is not limited to this, and a difference in shrinkage rate may be created using other methods. Alternatively, the bonding area may be different for the first bonding area SE1 and the second bonding area SE2. For example, the bonding area can be changed by changing the range in which the application area 51 is provided. In addition, the amount of adhesive 80 applied may be different for the first bonding area SE1 and the second bonding area SE2. In this way, the shrinkage rate can be easily changed by creating a difference in the bonding area or the amount of adhesive 80 applied.

[0051] Furthermore, the embodiments disclosed herein are illustrative in all respects and do not constitute a limiting interpretation. Accordingly, the technical scope of this disclosure is not to be interpreted solely by the embodiments described above, but is defined based on the claims. This includes all modifications within the meaning and scope of equivalents to the claims. [Explanation of Symbols]

[0052] 12. Exposure apparatus 12a printhead 41 Base member 42 Panel members 42a Light-emitting element 50 Retaining member 51 Coating area 60 lenses 80 Adhesives 100 Image forming apparatus SE1 1st adhesive part SE2 2nd adhesive part SE3 3rd adhesive part W (width direction, corresponding to the length direction)

Claims

1. A panel member having multiple light-emitting elements facing the photoreceptor, A lens that focuses the light emitted from the light-emitting element onto the photoreceptor, An exposure apparatus comprising a holding member for holding the lens, The holding member and the lens are bonded together by a first bonding portion located in the center in the longitudinal direction and a second bonding portion located at the end in the longitudinal direction. The first adhesive portion and the second adhesive portion have different shrinkage rates. An exposure apparatus characterized by the following.

2. An exposure apparatus according to claim 1, The first and second adhesive portions are made of adhesives with different shrinkage rates. An exposure apparatus characterized by the following.

3. An exposure apparatus according to claim 1, The shrinkage rates of the first and second adhesive portions are set based on the amount of curvature of the holding member in the longitudinal direction. An exposure apparatus characterized by the following.

4. An exposure apparatus according to claim 1, The holding member and the lens are bonded together by a third adhesive portion provided between the first adhesive portion and the second adhesive portion. The shrinkage rate changes in a stepwise manner in the order of the first adhesive portion, the third adhesive portion, and the second adhesive portion. An exposure apparatus characterized by the following.

5. An exposure apparatus according to claim 1, The first adhesive portion and the second adhesive portion have different areas to be bonded. An exposure apparatus characterized by the following.

6. An exposure apparatus according to claim 1, The amount of adhesive applied to the first adhesive portion and the second adhesive portion is different. An exposure apparatus characterized by the following.

7. An image forming apparatus comprising the exposure apparatus described in claim 1.

Images