Image forming apparatus

Abstract

An image forming apparatus is disclosed. The image forming apparatus includes a rotatable photosensitive member, a charging member, an exposure unit, a developing member, a transfer member, and a pre-exposure unit. The pre-exposure unit exposes the surface of the photosensitive member after a toner image is transferred to a recording material and before it is charged by the charging member. The pre-exposure unit includes a substrate disposed adjacent to one end of the photosensitive member in the longitudinal direction relative to the photosensitive member, and a first light-emitting element and a second light-emitting element having directional characteristics narrower than those of the first light-emitting element are mounted in the substrate.

Description

Technical Field

[0001] This invention relates to an image forming apparatus, such as a laser printer, that utilizes an electrophotographic method. Background Technology

[0002] Recently, light-emitting diodes (hereinafter referred to as LEDs) have become widely used as small and inexpensive light sources, and are used not only in display devices but also in lighting or functional components in many products. For example, LEDs are used in fluorescent lamps, backlights for liquid crystal displays, lamps that illuminate originals in image reading devices such as scanners, or discharge lamps (hereinafter referred to as pre-exposure units) in image forming apparatuses. A pre-exposure unit is a device in an image forming unit of an image forming apparatus such as a laser printer that reduces the surface potential of the photosensitive drum and emits light to perform pre-exposure to form a surface potential even after the toner image formed on the photosensitive drum has been transferred onto the recording material. For example, Japanese Patent Application Publication (JP-A) 2012-163601 discloses an example of a method of emitting light from a pre-exposure unit onto a photosensitive drum. In JP-A 2012-163601, a configuration is proposed in which light is projected from the end of a light guide positioned in the longitudinal direction together with the photosensitive drum by an LED, and the photosensitive drum is uniformly exposed in the longitudinal direction by reflecting the projected light at gaps in the light guide. Alternatively, for example, in Japanese Patent Application Publication (JP-A) 2010-160185, instead of providing a light guide, a configuration is disclosed in which LEDs are provided at each end of the photosensitive drum in the longitudinal direction and light is projected onto the photosensitive drum.

[0003] However, the light guide installed in the pre-exposure unit of JP-A 2012-163601 is expensive. Furthermore, the configuration in JP-A 2010-160185 requires LEDs to be installed at both ends of the photosensitive drum in the longitudinal direction. Therefore, it requires substrates with LEDs mounted on both sides, signals from / to the control unit configured to control the LEDs, and signal cables as power supply voltage harnesses. At least one of the two signal cables connecting to the control unit and the two substrates needs to be sufficiently long. Longer cables also increase the working time and cost during assembly processing.

[0004] Conventional pre-exposure units do not include diagnostic functions for the LED used as a light source and cannot detect LED malfunctions. Even when the LED malfunctions, printing can still be performed on the recording material without the LED emitting light on the photosensitive drum. Therefore, it is difficult for users of image forming apparatuses to notice any LED malfunctions. However, when the pre-exposure unit is not working and the charge on the photosensitive drum has not decreased, an "overlapping" phenomenon occurs: the image formed on the photosensitive drum in the previous exposure blurs and overlaps with the image formed in the next exposure. As a result, in printing where image quality is important, such as photographic printing, a noticeable degradation in image quality is observed. Summary of the Invention

[0005] In the above context, the object of the present invention is to configure reliable pre-exposure while reducing costs.

[0006] To address the aforementioned problems, this disclosure comprises the following components.

[0007] According to one aspect of the present invention, an image forming apparatus is provided, comprising: a rotatable photosensitive member; a charging member configured to charge the photosensitive member; an exposure unit configured to emit light to expose the photosensitive member charged by the charging member and form a latent image; a developing member configured to develop the latent image using a toner; a transfer member configured to transfer a toner image developed by the developing member to a recording material; and a pre-exposure unit configured to expose the surface of the photosensitive member after the toner image is transferred to the recording material and before it is charged by the charging member, wherein the pre-exposure unit includes a substrate disposed adjacent to one end of the photosensitive member in a longitudinal direction relative to the photosensitive member, and a first light-emitting element and a second light-emitting element are mounted in the substrate, the second light-emitting element having a directional characteristic narrower than that of the first light-emitting element.

[0008] According to one aspect of the present invention, an image forming apparatus is provided, the image forming apparatus comprising: a rotatable photosensitive member; a charging member configured to charge the photosensitive member; an exposure unit configured to emit light to expose the photosensitive member charged by the charging member and form a latent image; a developing member configured to develop the latent image using a toner; a transfer member configured to transfer a toner image developed by the developing member to a recording material; a pre-exposure unit configured to expose the surface of the photosensitive member after the toner image is transferred to the recording material and before it is charged by the charging member; and a controller configured to control the pre-exposure unit, wherein the pre-exposure unit includes a first substrate and a second substrate, the first substrate being disposed adjacent to one end of the photosensitive member in a longitudinal direction relative to the photosensitive member, and a first emitting light is mounted in the first substrate. A light-emitting element comprises a first light-emitting element that emits light from one end of a photosensitive member toward the surface of the photosensitive member near its center relative to the longitudinal direction. A second substrate is disposed adjacent to the other end of the photosensitive member, and a second light-emitting element is mounted in the second substrate. The second light-emitting element emits light from the other end of the photosensitive member toward the surface of the photosensitive member near its center relative to the longitudinal direction. A controller controls the first and second light-emitting elements to emit light, detects the electromotive force voltage generated by the second light-emitting element when the second light-emitting element receives light emitted by the first light-emitting element, or the electromotive force voltage generated by the first light-emitting element when the first light-emitting element receives light emitted by the second light-emitting element, and determines the presence or absence of a fault in the first and second light-emitting elements based on the detected electromotive force voltage.

[0009] Other features of the invention will become clear from the following description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0010] Figure 1 This is a cross-sectional view of the configuration of the image forming apparatus according to Embodiments 1 and 2.

[0011] Figure 2 This is an explanatory diagram illustrating the configuration of the pre-exposure unit according to Embodiment 1.

[0012] Figure 3 Parts (a) and (b) are explanatory diagrams of the directional characteristics of the LED according to Example 1.

[0013] Figure 4 These are tables and graphs indicating the experimental results according to Example 1.

[0014] Figure 5 This is an explanatory diagram illustrating the configuration of the pre-exposure unit according to Embodiment 2.

[0015] Figure 6 This is an explanatory diagram of the connection between the pre-exposure unit and the control unit according to Embodiment 2.

[0016] Figure 7 Parts (a) and (b) are explanatory diagrams of the processing of the control unit according to Embodiment 2. Detailed Implementation

[0017] Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0018] [Composition of the image forming apparatus]

[0019] Figure 1 This is a cross-sectional view illustrating the configuration of a monochrome laser printer 100 (hereinafter referred to as printer 100), which is an image forming apparatus as described in Application Embodiment 1. Figure 1 In this image forming unit, which forms an image on the recording material, a photosensitive drum 105, serving as a photosensitive element, and a charged roller 107, serving as a charged element that uniformly charges the photosensitive drum 105, are also included. Additionally, the image forming unit includes a laser scanner 102, which serves as an exposure element for forming a latent image by emitting a laser 113 onto the surface of the photosensitive drum 105. Furthermore, the image forming unit includes a developing roller 104, which serves as a developing element for developing the latent image formed on the photosensitive drum 105 using magnetic toner stored in a toner cartridge 103 to form a toner image. In the rotational direction of the photosensitive drum 105, upstream of the charged roller 107, the surface of the photosensitive drum 105 is exposed (pre-exposed) by a pre-exposure unit 108 disposed downstream of a transfer roller 106 to uniformly disperse the potential. A control unit 120 controls the image forming unit (etc.) so that the printer 100 performs its movement to form an image.

[0020] The paper feed section 101 stores recording material and feeds it to the feed path 112, through which the recorded material is fed to the transfer roller 106. The transfer roller 106 serves as a transfer unit for transferring a toner image formed on the photosensitive drum 105 onto the recording material. The fixing unit 114 is a unit for fixing the toner image transferred onto the recording material. The fixing unit 114 includes a fixing roller 109 that heats the toner image and a pressure roller 110 that presses the passing recording material by contacting the fixing roller 109. In the discharge section 111, the recording material that has passed through the fixing unit is discharged and stacked.

[0021] [Image Formation Action]

[0022] Next, the image forming operation of printer 100 will be described. When the control unit receives a print job command from an external device such as a personal computer (not shown), the control unit 120 of printer 100 simultaneously starts driving each motor in the device and starts driving laser scanner 102. Charged roller 107 is applied with a high voltage having a negative potential, contacts photosensitive drum 105 rotating in the direction of the arrow (clockwise) in the figure, and uniformly charges the surface of photosensitive drum 105. Laser scanner 102 emits laser 113 according to the image data included in the print job. Laser 113 emitted from laser scanner 102 exposes photosensitive drum 105. The areas on photosensitive drum 105 exposed by laser 113 lose charge and then form a latent image. Developing roller 104 includes a magnet internally, and by applying a developing charge with a high negative polarity from a voltage source (not shown), the magnet attracts magnetic toner in toner cartridge 103. Therefore, the developing roller 104 uses electrostatic force to transfer the toner onto the latent image on the surface of the photosensitive drum 105, thus forming a toner image.

[0023] On the other hand, recording material fed from the paper feed unit 101 via commands from the control unit 120 passes through the feed path 112 and is fed to the clamping area formed by the contact between the transfer roller 106 and the photosensitive drum 105. When a high positive transfer voltage is applied to the transfer roller 106 from a voltage source (not shown), the transfer roller 106 transfers the toner image formed on the photosensitive drum 105 onto the recording material. The recording material with the toner image transferred is fed to the fixing unit 114, and then to the fixing / clamping section formed by the contact between the fixing roller 109 and the pressure roller 110. In the fixing / clamping section, where the fixing roller 109 heats the toner image to several hundred degrees and the pressure roller 110 simultaneously applies pressure to the toner image, the toner image is fixed onto the recording material. The recording material with the toner image fixed is discharged and stacked in the discharge unit 111. After the toner image is transferred onto the recording material, the potential on the surface of the photosensitive drum 105 is uneven due to image formation. Therefore, the pre-exposure unit 108 exposes the surface of the photosensitive drum 105 with light emitted from an LED (not shown), which serves as a light source, to uniformly reduce the charge and potential on the surface of the photosensitive drum 105 to almost 0V. Thus, the image previously formed on the photosensitive drum 105 and transferred onto the recording material does not affect the image formed in the next cycle. The printer 100 performs a printing job by repeating the above image formation operation.

[0024] [Composition of the pre-exposure unit]

[0025] Next, the pre-exposure unit 108 in this embodiment will be described. Figure 2 This is a schematic diagram illustrating the configuration of the pre-exposure unit 108 in this embodiment. Figure 2 As shown, in the pre-exposure unit 108 of this embodiment, two LEDs, serving as light-emitting elements, are mounted on only one substrate, which differs from the configuration of a conventional pre-exposure unit as described above. Furthermore, in the conventional example of the pre-exposure unit described above, light emitted from the LEDs in the pre-exposure unit is exposed on the photosensitive drum via a light guide. On the other hand, in the pre-exposure unit 108 of this embodiment, light emitted from the two LEDs is directly exposed on the photosensitive drum 105 without a light guide. Therefore, as... Figure 2 As shown, the pre-exposure unit 108 is positioned vertically above one end of the photosensitive drum 105 relative to the longitudinal direction, tilted towards the photosensitive drum 105, so that light emitted from the LEDs exposes the entire surface of the photosensitive drum 105 in the longitudinal direction. Of the LEDs 1 and 2 mounted on the substrate, LED 1 is located below and LED 2 is located above and aligned in the vertical direction (also the up-down direction in the figure). Furthermore, Figure 2 The dashed lines indicate the areas reached by the light emitted from LED 1 and LED 2, and the areas reached by the light emitted from each LED are different. Figure 2 As shown, light emitted from LED 1 (first light-emitting element) exposes the area from the end of the pre-exposure unit 108 located on the longitudinal side of the photosensitive drum 105 to the vicinity of the center. On the other hand, light emitted from LED 2 (second light-emitting element) exposes the area from the vicinity of the center of the photosensitive drum 105 to the opposite side where the pre-exposure unit 108 is located on the longitudinal side of the photosensitive drum 105.

[0026] [Directional Characteristics of LEDs]

[0027] As mentioned above, LED 1 and LED 2 each have different directional characteristics. Figure 3 This is a graph showing the directional characteristics of LED 1 and LED 2. Figure 3 (a) shows the directional characteristics of LED 1 and Figure 3 (b) shows the directional characteristics of LED 2. Figure 3 The graph in the diagram indicates the spread of light emitted from the LED by relative brightness (relative luminous intensity) at each angle, and the directional characteristics of each LED are plotted on a semi-circular graph. In the directional characteristic graph, the numbers 0, 10, ... 90 on the outer edge of the semi-circular graph indicate the angle (in degrees) of light emitted from the LED, and the numbers 0, 50, 100 on the straight line that serves as the diameter of the semi-circular graph indicate the relative luminous intensity (in %). The directional characteristic graph shows how much the brightness decreases relatively as the angle of light emitted from the LED increases, when the brightness of the brightest part (angle) is 100% of the relative luminous intensity. Figure 3 As shown, LED 1 has a wider direction (wide-angle direction), and LED 2 has a narrower (acute-angle) direction (narrow-angle direction). In other words, light emitted from LED 1 can illuminate a wider and closer area around the substrate on which LED 1 is mounted, but cannot illuminate a farther area. On the other hand, light emitted from LED 2 can illuminate a farther and narrower area around the substrate on which LED 2 is mounted, but cannot illuminate a wider and closer area. Therefore, by mounting LED 1 and LED 2, which have different directional characteristics, on the same substrate, LED 1 can illuminate the area from the end of the photosensitive drum 105 where the pre-exposure unit is located to the vicinity of the center of the photosensitive drum 105 in the longitudinal direction, and LED 2 can illuminate the area from the vicinity of the center of the photosensitive drum 105 in the longitudinal direction to the other end opposite the end where the pre-exposure unit 108 is located. As a result, by exposing light to the photosensitive drum 105 from LED 1 and LED 2, the photosensitive drum 105 can be discharged.

[0028] [Discharge of the photosensitive drum using a pre-exposure unit]

[0029] Figure 4 Including tables ( Figure 4 (the upper part) and a graph drawn based on the data shown in the table ( Figure 4 (The lower part of the table) This table obtains the actual application of the constituent elements. Figure 2 The result of detecting the power (emission intensity) of the light emitted from LED 1 and LED 2 by measuring the light intensity meter when the pre-exposure unit 108 described in the figure is constructed. Figure 4 The table shown at the top of the image indicates, from top to bottom, the distance from the LED (in mm), the detected power of LED 1 (in mW), the detected power of LED 2 (in mW), and the sum of the detected power of LED 1 and LED 2 (in mW). The table shows the results measured at 10mm distances between 10mm and 150mm from the LEDs for the detected power of LED 1, the detected power of LED 2, and the sum of the detected power of LED 1 and LED 2.

[0030] in addition, Figure 4 The graph shown on the lower side is based on Figure 4 The values ​​of detected power (emission intensity) and distance for LED 1 and LED 2 are plotted in the table above. Figure 4In the graph, the horizontal axis indicates the distance from the LED (in mm) and the vertical axis indicates the detected power (in mW). The dashed line in the graph indicates the detected power of LED 1, which has a wider directional angle, and the dotted / dashed line indicates the detected power of LED 2, which has a narrower directional angle. Additionally, the solid line in the graph indicates the sum of the detected power of LED 1 and LED 2 at each distance.

[0031] like Figure 4 As shown, the detected power of the light emitted from LED 1 reaches its maximum at a distance of 60 mm from the center of the photosensitive drum 105 in the longitudinal direction, and the detected power of the light emitted from LED 2 reaches its maximum at a distance of 120 mm in the longitudinal direction of the photosensitive drum 105. The solid line graph indicating the sum of the detected powers of LED 1 and LED 2 is wavy, but it shows that light with a detected power (emission intensity) always greater than 20 mW is exposed until a distance of 140 mm from the light source (LED) is reached. Because as long as the pre-exposure unit continues to emit light including a fixed emission intensity (e.g., 20 mW), the residual charge on the photosensitive drum 105 can be discharged, the wavy solid line graph is not a problem. Figure 4 As shown, in the case of only a single LED from LED 1 or LED 2, the detected power is less than 20mW at a certain distance. For example, the detected power of LED 1 is less than 20mW at distances between 10mm and 40mm and between 90mm and 150mm. Similarly, the detected power of LED 2 is less than 20mW at distances between 10mm and 100mm and between 140mm and 150mm.

[0032] However, by aligning LED 1 and LED 2 vertically (in the up-down direction), emitting light at different directional angles each time allows for a detectable power greater than 20mW, and exposes the photosensitive drum 105 longitudinally from one end to the other. As mentioned earlier, in this embodiment, reducing the substrate for mounting the LEDs to one and eliminating the use of light guides reduces costs. Furthermore, reducing to one substrate compared to using two substrates allows for shorter assembly time and reduced failure risk for greater reliability.

[0033] As described above, according to this embodiment, reliable pre-exposure can be performed at a lower cost.

[0034] In Example 2, a diagnostic method for inspecting LEDs disposed in the pre-exposure unit will be described.

[0035] [Composition of the pre-exposure unit]

[0036] Figure 5 This is a schematic diagram showing the positional relationship between the pre-exposure unit, the photosensitive drum 105, and the charged roller 107 in Embodiment 2. Note that... Figure 5 LED 1 and LED 2 are LEDs in a pre-exposure unit mounted on a substrate near each end of the photosensitive drum 105 in the longitudinal direction. The pre-exposure unit in this embodiment applies the method described in JP-A2010-160185 above: exposing light for pre-exposure from around the two ends of the photosensitive drum 105 in the longitudinal direction without a light guide. Specifically, the photosensitive drum 105 is discharged by exposing the left half of the photosensitive drum 105 in the longitudinal direction in the image with LED 1 and the right half of the photosensitive drum 105 in the longitudinal direction in the image with LED 2. Note that in this embodiment, the pre-exposure unit is described as having LEDs positioned near the two ends of the photosensitive drum 105 in the longitudinal direction.

[0037] An LED (Light Emitting Diode), serving as the light source in a pre-exposure unit, is a light-emitting element in which the PN junction of a semiconductor is exposed to the outside. By applying current between the cathode and anode terminals of the LED, the PN junction emits, and light is exposed to the outside. Solar cells are similar to LEDs in that the PN junction is exposed to the outside. When exposure occurs on the LED's emitting portion (PN junction), current is applied between the anode and cathode terminals, and a voltage is generated. Of course, because the LED's PN junction is configured to emit efficiently when current is applied, the electromotive force voltage of an LED is much lower than that of a solar cell. However, depending on the intensity of the light exposed on the LED's emitting portion and the output impedance, several voltages can be generated.

[0038] [Diagnosis of the pre-exposure unit]

[0039] In this embodiment, the two LEDs of the pre-exposure unit are positioned facing each other at two ends on the longitudinal side of the photosensitive drum 105. When the LEDs are used as the pre-exposure unit, with both LEDs lit, light from the LEDs exposes the photosensitive drum 105, causing the photosensitive drum 105 to discharge. Furthermore, by utilizing the characteristic of generating voltage through light exposure of the LEDs, any LED malfunctions can be diagnosed based on whether an electromotive force voltage is generated when one LED is lit to illuminate the other. The function of diagnosing whether the LEDs have any malfunctions will be described below.

[0040] The LEDs in the pre-exposure unit are controlled by the CPU (Central Processing Unit) 121 (reference). Figure 6 ) control, the CPU 121 is Figure 1The control unit 120 shown in the figure has control components. The CPU 121 includes a pre-exposure mode for discharging the photosensitive drum 105 using the pre-exposure unit, and a diagnostic mode, as mentioned above, for diagnosing whether the LEDs in the pre-exposure unit have any faults. In the pre-exposure mode, the CPU 121 controls both LED 1 and LED 2 to be lit, and in the diagnostic mode, it controls LED 1 to be lit when LED 2 receives light as a light receiver, so as to measure the electromotive force voltage generated by LED 2. Since LED 1 and LED 2 are positioned facing each other, when LED 2 is working normally, LED 2 generates an electromotive force voltage due to receiving light from LED 1. For example, if LED 1 has any faults, light from LED 1 is not emitted, and LED 2 does not generate an electromotive force voltage. Therefore, if LED 2 is working normally, a fault in LED 1 can be detected. Similarly, LED 2 lights up LED 1, which receives light as a light receiver, and measures the electromotive force voltage generated by LED 1. When LED 1 is working normally, LED 1 generates an electromotive force voltage due to receiving light from LED 2. For example, if LED 2 has any fault, light from LED 2 will not be emitted, and LED 1 will not generate an electromotive force voltage. Therefore, if LED 1 is working normally, the fault in LED 2 can be detected.

[0041] [Composition of the control unit]

[0042] Figure 6The connection relationships of CPU 121, LED 1, and LED 2 described above are shown. LED 1 is connected to I / O port 1 of CPU 121 via a resistor through its anode terminal and to ground (ground) through its cathode terminal. Similarly, LED 2 is connected to I / O port 2 of CPU 121 via a resistor through its anode terminal and to ground (ground) through its cathode terminal. LED 1 and LED 2 are connected to different input / output ports (I / O port 1 and I / O port 2). Furthermore, as mentioned above, I / O port 1 connected to LED 1 and I / O port 2 connected to LED 2 need to detect the electromotive force voltage generated by LED 1 or LED 2 to diagnose whether the LED is faulty. Therefore, I / O port 1 connected to LED 1 and I / O port 2 connected to LED 2 need to include an A / D conversion function (analog-to-digital conversion) to convert the voltage signal, which is an analog input signal, into a digital value. Note that when LED 1 and LED 2 are used in the pre-exposure unit, I / O port 1 connected to LED 1 and I / O port 2 connected to LED 2 are switched to output ports by CPU 121. For example, when LED 1 and LED 2 are lit, I / O port 1 and I / O port 2 output high voltage signals, and when LED 1 and LED 2 are turned off, I / O port 1 and I / O port 2 output low voltage signals.

[0043] [Control of diagnostic functions]

[0044] Next, the control processing of CPU 121 when performing diagnostic functions will be described. Figure 7(a) describes the control process for diagnosing whether LED1 has any faults. In diagnosing whether LED1 has any faults, CPU 121 switches I / O port 1 connected to LED1 to an output port and I / O port 2 connected to LED2 to an input port including A / D conversion functionality. CPU 121 outputs a high-voltage signal from the I / O port connected to LED1 to light LED1. LED1 is turned on and lit by the high-voltage signal input to the anode terminal of LED1. On the other hand, light emitted from LED1 enters LED2, and LED2 is turned on. Therefore, current flows into the resistor connected to the anode terminal of LED2, and a voltage signal is input to I / O port 2 connected to LED2. Then, CPU 121 determines whether the electromotive force voltage generated by LED2 is greater than a fixed value based on the digital value of the input voltage signal converted by the A / D converter. When the electromotive force voltage is greater than the fixed value, CPU 121 determines that LED1 is lit and operating normally. Meanwhile, when LED 1 is not lit due to any fault, no light is emitted from LED 1, no light enters LED 2, and LED 2 does not generate an electromotive force voltage. Therefore, because the electromotive force voltage is less than a fixed value, CPU 121 determines that LED 1 is not lit and is not working properly. Note that the fixed value mentioned above can be determined from the results of actual experiments.

[0045] Additionally, for example, if the output voltage from LED 2 is sufficiently high (e.g., a few volts), an A / D conversion function is not required in the I / O port. Therefore, an I / O port without A / D conversion can be used. The reason for using an I / O port with A / D conversion in this embodiment will be described below. The output voltage from the LED may initially be too low to be recognized as sufficiently higher than the threshold level of the input signal at the I / O port—that is, the threshold level of the input signal from TTL or CMOS. On the other hand, because an I / O port with A / D conversion can adjustably fix the threshold level, it can fix the threshold level according to the configuration requirements of the pre-exposure unit.

[0046] Figure 7 (b) describes the control process for diagnosing whether LED 2 has any faults. In diagnosing whether LED 2 has any faults, CPU 121 switches I / O port 2 connected to LED 2 to an output port and switches I / O port 1 connected to LED 1 to an input port including A / D conversion functionality. The control process of CPU 121 for diagnosing whether LED 2 has any faults is the same as described above. Figure 7The same as (a) is omitted here. CPU 121 is able to perform printing without printing by using a method based on... Figure 7 (a) and Figure 7 The process described in (b) diagnoses LEDs 1 and 2 to confirm the presence or absence of a fault in the LEDs in the pre-exposure unit. As a result, the pre-exposure unit becomes more reliable.

[0047] As described above, according to this embodiment, pre-exposure can be more reliable and costs can be reduced.

[0048] While the invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the appended claims should be given the broadest interpretation to include all such modifications, equivalent structures, and functions.

Claims

1. An image forming apparatus comprising: a rotatable photosensitive member; a charging member configured to charge the photosensitive member; an exposure unit configured to emit light to expose the photosensitive member charged by the charging member and form a latent image; a developing member configured to develop the latent image with toner; a transfer member configured to transfer a toner image developed and formed by the developing member to a recording material; and a pre-exposure unit configured to expose a surface of the photosensitive member after the toner image is transferred to the recording material and before being charged by the charging member, wherein the pre-exposure unit includes a substrate disposed adjacent to one end portion of the photosensitive member with respect to a longitudinal direction of the photosensitive member, and a first light emitting element and a second light emitting element are installed in the substrate, the second light emitting element having a directional characteristic narrower than that of the first light emitting element. the first light emitting element emits light to expose the surface of the photosensitive member from the one end portion side of the photosensitive member where the substrate is disposed toward a vicinity of a center of the photosensitive member with respect to the longitudinal direction, and 2. The image forming apparatus according to claim 1, wherein wherein the second light emitting element emits light to expose the surface of the photosensitive member from the vicinity of the center of the photosensitive member with respect to the longitudinal direction toward the other end portion of the photosensitive member.

3. The image forming apparatus according to claim 2, further comprising a controller configured to control the pre-exposure unit, the controller controls the first light emitting element and the second light emitting element to emit light and expose the surface of the photosensitive member. wherein the first light emitting element and the second light emitting element include light emitting diodes.

4. The image forming apparatus according to claim 1, wherein ​

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