JP4909544B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to a copying machine, a printer, and a facsimile apparatus having an image forming unit in which unnecessary charges on the surface of the photosensitive drum are removed by irradiating light on the surface of the photosensitive drum on which an electrostatic image is formed. The present invention also relates to an image forming apparatus such as a multifunction peripheral having both functions.

In recent years, image forming apparatuses such as copiers and printers having an image forming unit that forms a toner image on the surface of a photosensitive drum on which an electrostatic image is formed and transfers the toner image onto a recording sheet have been widely used. ing. In such an image forming apparatus, in order to remove unnecessary charges remaining on the surface of the photosensitive drum after the toner image is transferred to the recording paper, a certain amount of light output from a semiconductor light emitting element such as a light emitting diode. Is applied to the surface of the photosensitive drum (for example, Patent Document 1). In such an image forming apparatus, it is possible to effectively suppress the charge remaining on the surface of the photosensitive drum after the transfer of the toner image to the recording paper is completed.
JP 2004-302155 A

  In the conventional image forming apparatus, in order to suppress the deterioration of the semiconductor light emitting element in removing unnecessary charges on the surface of the photosensitive drum, a low amount of light within a range in which unnecessary charges can be removed The surface is irradiated. For this reason, for example, in the case of using an amorphous silicon photoconductor, if the photoconductor on the surface of the photoconductor drum becomes fatigued by forming an image on a recording paper exceeding a certain number of sheets, a low amount of light that has hitherto been used. In this case, unnecessary charge inside the photoconductor cannot be removed, and a slight electrostatic image remains, which causes a so-called memory effect, and a ghost image is formed. Image quality).

  The present invention has been made in view of such circumstances, and an image forming apparatus capable of effectively removing unnecessary charges inside a photoconductor even when the photoconductor drum is old and the photoconductor is fatigued. The purpose is to provide.

In order to achieve the above object, the invention according to claim 1 is directed to a photosensitive member by irradiating the surface of the photosensitive drum with light emitted from a semiconductor light emitting element disposed along the axial direction of the photosensitive drum. An image forming apparatus having a charge eliminating unit for removing unnecessary charges on a drum surface, which is disposed between a supply end of a driving voltage for driving the semiconductor light emitting element and a ground potential. resistive elements in the element, a series connection circuit inductance element and control switch elements are connected in series, respectively, a control switch element of said series connection circuit and a drive control unit for on-off control by a pulse signal, the inductance element of the series connection circuit A short-circuit switch element connected in parallel; a counter unit that continuously counts the number of recording sheets formed on the photosensitive drum; and the short circuit A control signal is supplied to the switch element to control the on / off of the short-circuit switch element. When the continuous count number of recording sheets by the counter section does not reach a predetermined number, the short-circuit switch element is turned on and the inductance element And a switch switching control unit that turns off the short-circuit switch element and opens a short circuit at both ends of the inductance element when the count of the continuous count of recording sheets by the counter unit reaches a predetermined number . It is characterized by that.

According to the first aspect of the present invention, when the continuous count number of the recording paper does not reach the predetermined number, both ends of the inductance element are short-circuited by the short-circuit switch element, and the inductance element is not inserted into the energization circuit, and the recording is performed. When the continuous count number of sheets reaches a predetermined number, the short circuit between both ends of the inductance element by the short circuit switch element is opened, and the inductance element is inserted into the energization circuit. When the inductance element is inserted in the energization circuit, the control switch element is ON / OFF controlled by the pulse signal, so that the pulse voltage is supplied to the semiconductor light emitting element for irradiating the surface of the photosensitive drum. As a result of the transient response of the RLC series circuit composed of a resistance element, an inductance element, and a semiconductor light emitting element when the pulse voltage rises, an inrush current larger than the steady current flows. As a result, the photoconductor drum becomes old and the photoconductor Even when the toner is fatigued, unnecessary charge inside the photosensitive member can be effectively removed by the inrush current at the rise of the pulse voltage. In addition, since the inrush current flows through the semiconductor light emitting element only at the rising edge of the pulse voltage, it is possible to effectively suppress the deterioration of the semiconductor light emitting element as compared with the case where a large current is always applied. Further, when the inductance element is not inserted in the energization circuit, even if a pulse voltage is supplied to the semiconductor light emitting element for irradiating the surface of the photosensitive drum by controlling the on / off of the control switch element by the pulse signal, A large inrush current does not flow through the semiconductor light emitting device at the rise of the pulse voltage. That is, while the photoconductor drum is new, the short-circuit switch element is turned on so that the inductance element is not inserted in the energization circuit so that no inrush current flows through the semiconductor light emitting element. It can be prevented from deteriorating as necessary.

  FIG. 1 is an internal configuration diagram for explaining a schematic configuration of an image forming apparatus according to an embodiment of the present invention. In this figure, an image forming apparatus 10 constitutes a copying machine configured to form an image on a recording sheet based on an original image captured by an image sensor that converts light into an electrical signal. The image reading unit 12 to be read, the document placing unit 14 located above the image reading unit 12, the image forming unit 16 located below the image reading unit 12, and substantially the same height position as the document placing unit 14. The operation panel 18 is provided.

  The image reading unit 12 includes a first optical system 22, a second optical system 24, and an image capturing unit 26. The first optical system 22 is for irradiating a document surface with light to obtain a document image, and includes an exposure light source 28 such as a halogen lamp and a reflector 30 that irradiates the document surface with light from the exposure light source 28. A reflecting mirror 32 that guides the reflected light from the original surface obtained by irradiation with the exposure light source 28 to the second optical system 24 by directing the reflected light in the horizontal direction is provided integrally.

  The second optical system 24 is disposed on the left side of the first optical system 22 in the drawing, and guides the reflected light from the document surface obtained by the first optical system 22 to the image capturing unit 26. A first reflecting mirror 34 and a second reflecting mirror 36 that guide the reflected light from the document surface reflected by the reflecting mirror 32 of the optical system 22 to the image capturing unit 26 are provided. The first and second reflecting mirrors 34 and 36 receive the reflected light from the original surface reflected by the reflecting mirror 32 of the first optical system 22 by the first reflecting mirror 34 and guide it to the second reflecting mirror 36. The reflected light from the document surface reflected by the second reflecting mirror 36 is directed to the image capturing unit 26 by directing it in the horizontal direction.

The image capturing unit 26 is disposed on the right side of the second optical system 24 in the figure, and is disposed on the right side in the figure inside the case body 40 having a rectangular parallelepiped shape made of a metal plate or the like. CCD (Charge Coupled Device) that reads the original image consisting of reflected light by converting light into an electrical signal
The image sensor 42 as a line sensor composed of the above-mentioned line sensor and an external side surface of the case body 40 on the second optical system 24 side, and a document image made of reflected light guided by the second optical system 24 is applied to the image sensor 42. The lens 44 is formed with an image. The document image read by the image sensor 42 is subjected to predetermined signal processing, converted to a digital signal, and stored in a memory (not shown).

  A pair of guide rails 46 (in the drawing) guide the first optical system 22 and the second optical system 24 between the left end position in the drawing and the right end position in the drawing in the upper part of the image reading unit 12. Are shown at both ends in the width direction (depth direction in the figure), the first optical system 22 and the second optical system 24 are engaged with the guide rail 46, and are guided by a drive motor (not shown). It is configured to reciprocate along the rail 46.

  The document placing section 14 includes a contact glass 50 mounted on the upper portion of the image reading section 12, a document pressing section 52 that opens and closes on the upper surface of the contact glass 50, and an automatic document disposed above the document pressing section 52. And a feeding unit 54. Here, the contact glass 50 includes a first contact glass 56 through which a document conveyed by the automatic document feeder 54 passes and a second contact glass 58 on which a stationary document is placed. The document pressing unit 52 constitutes a document bundle discharge unit whose upper surface is placed on the automatic document feeding unit 54.

  The automatic document feeder 54 automatically feeds a bundle of documents placed at a predetermined position one by one on the first contact glass 56, while the document that has been read is sequentially ejected on the upper surface of the document retainer 52. It was made to return to.

  The image forming unit 16 includes an optical unit 60, an image forming unit 62, a fixing unit 64, and a paper conveying unit 66. The optical unit 60 is for exposing a document image read by the image sensor 42 read from the memory (not shown) to a later-described photosensitive drum 70, and based on the read image data. A light emitting unit 67 that converts the generated modulation signal into laser light and outputs the laser light, and a reflection mirror 68 that reflects the laser light from the light emitting unit 67 toward a photosensitive drum 70 described later.

  The image forming unit 62 includes a photosensitive drum 70 that is rotated at a constant speed. A charger 72, a developing unit 74, a cleaning unit 76, and a light irradiation unit 78 are provided along the peripheral surface of the photosensitive drum 70. In order. The photosensitive drum 70 is rotationally driven in a clockwise direction (in the direction of the arrow) by a driving motor (not shown). An electrostatic region is formed at a position facing the charger 72, and an optical region is formed in the electrostatic region. An electrostatic latent image is formed by irradiating laser light output from the unit 60 based on the original image, and the electrostatic latent image is developed into a toner image at a position facing the developing unit 74. A transfer roller 82 is disposed below the photoconductive drum 70, and the photoconductive drum 70 on which the toner image is formed transfers the toner image onto the recording paper at a position facing the transfer roller 82. After the toner image has been transferred onto the recording paper, the toner remaining on the surface of the photosensitive drum 70 is removed at a position facing the cleaning unit 76, and remains on the surface of the photosensitive drum 70 by the light irradiation unit 78. The charge is removed.

  The charger 72 includes, for example, a charging wire 84 having a length in the width direction of the photosensitive drum 70. A driving voltage is applied to the charging wire 84 from a driving power supply (not shown) to the photosensitive drum 70. An electrostatic region is formed on the surface of the photosensitive drum 70 by applying an electric charge. The developing unit 74 uses, for example, a two-component developer composed of a toner and a carrier. The developing unit 74 is developed in the state of being close to the developing body 86 having the developer loaded therein and the photosensitive drum 70. A developing roller 88 provided in the main body 86 and a toner cartridge 90 mounted on the upper portion of the developing main body 86 are provided.

  The developing body 86 includes a stirring roller (not shown) and the like, and the carrier and toner are rubbed by stirring the developer so that the toner is charged. The developing roller 88 has a surface charged by a driving voltage supplied from a driving power supply (not shown). The toner electrostatically attached to the surface of the developing roller 88 is charged with the photosensitive drum 70. It is made to adhere to the surface. The toner cartridge 90 is a cartridge filled with toner to be replenished in the development main body 86.

  The light irradiation unit 78 constitutes a static elimination unit, and includes a semiconductor light emitting element 94 such as a light emitting diode as shown in FIG. 2. For example, a plurality of chip type (in this embodiment, A first semiconductor light emitting element array 96 in which six semiconductor light emitting elements 94 are connected in series to each other, and a plurality of (six in the present embodiment) semiconductor light emitting elements 94 that are also chip-type connected in series with each other. Two semiconductor light emitting element arrays 98, and the semiconductor light emitting elements 94 of the first and second semiconductor light emitting element arrays 96, 98 are arranged in a row in the horizontal direction on the belt-like wiring substrate 100, and each light emitting element The surface is directed toward the surface of the photosensitive drum 70 and is disposed along the axial direction of the photosensitive drum 70.

  The fixing unit 64 performs a fixing process by heating the recording paper onto which the toner image has been transferred by the image forming unit 62. The fixing unit 64 is disposed in the upper part of the heat shielding box 104 and is heated by a built-in heater. A fixing roller 106, and a pressure roller 108 disposed in a lower part of the heat shielding box 104 and pressed against the fixing roller 106.

  The paper transport unit 66 transports the recording paper along the path indicated by the arrow A, and includes a cassette loading unit 112 for loading a paper feeding cassette PC that is stored in a state where recording papers of a predetermined size are stacked. The toner image is transferred by the photosensitive drum 70 and the upstream conveying path 114 that guides the recording paper drawn from the paper feeding cassette PC loaded in the cassette loading unit 112 to the photosensitive drum 70 by a paper feeding roller (not shown). A downstream conveyance path 118 is provided that guides the recording paper that has passed through the fixing roller 106 and the pressure roller 108 of the fixing unit 64 to a discharge tray 116 attached to the left side of the drawing.

  Here, a pair of conveyance rollers (not shown) is disposed at appropriate positions on the upstream conveyance path 114 and the downstream conveyance path 118, and a pair of registration rollers (not illustrated) is disposed in the vicinity of the photosensitive drum 70. . In addition, a sheet number sensor 120 for counting the number of image formations (number of copies) by detecting the passage of the recording sheet on which the image is formed is disposed on the exit side of the fixing unit 64 in the downstream conveyance path 118. Yes. This number sensor 120 is constituted by a photo interrupter or the like, and counts the number of image formations (number of copies) of the recording paper by detecting the start and end of the recording paper passing between the light emitting element and the light receiving element. It is.

  The operation panel 18 includes a numeric keypad 122, a liquid crystal display unit 124, a start button 126, and the like. The numeric keypad 122 is for setting the number of image forming copies (the number of copies), and the liquid crystal display portion 124 is for setting the number display portion for displaying the set number of image forming copies and the image forming density (copy density). For example, a density setting unit for setting an image forming magnification (copying magnification) and the like, and a start button 126 is turned on when an image forming operation (copying operation) is started. belongs to.

  The image forming apparatus 10 configured as described above operates as follows. That is, the document bundle is placed on the automatic document feeder 54, the number of image forming units is set with the numeric keypad 122 of the operation panel 18, and the image forming density, the image forming magnification, etc. are set with the liquid crystal display unit 124. When the button 126 is turned on, the document is sequentially conveyed onto the first contact glass 56 and passes over the first contact glass 56. At this time, the reflected light from the document surface obtained by irradiating the document surface with light from the exposure light source 28 stopped at the position corresponding to the first contact glass 56 is the first optical system 22 and the second optical system. A document image is read by being guided to the image sensor 42 via the system 24 and stored in a memory (not shown). The document that has passed over the first contact glass 56 is discharged to the discharge portion on the upper surface of the document pressing portion 52.

  When the original is bound like a book or the like, the original pressing portion 52 is opened and the original is placed on the second contact glass 58, and the number of image forming copies is set with the numeric keypad 122 of the operation panel 18. When the start button 126 is turned on after setting the image formation density, the image formation magnification, and the like on the liquid crystal display unit 124, the exposure light source 28 scans the document surface, and the document surface is irradiated with light. The reflected light from the original surface obtained in (1) is guided to the image sensor 42 via the first optical system 22 and the second optical system 24, read, and stored in a memory (not shown).

  On the other hand, the surface of the photosensitive drum 70 is charged by the charger 72, and a laser beam corresponding to a document image stored in a memory (not shown) is emitted to expose the surface of the photosensitive drum 70, thereby electrostatic latent. An image is formed. Next, the toner supplied from the developing unit 74 to the photosensitive drum 70 adheres to the electrostatic latent image, whereby a toner image is formed on the surface of the photosensitive drum 70.

  Then, the recording paper stored in the paper feed cassette PC is fed to the opposite side of the registration roller via the upstream conveyance path 114 by a paper feed roller (not shown) and is synchronized with the formation of the electrostatic latent image. The pair of registration rollers is conveyed between the photosensitive drum 70 and the transfer roller 82. On the recording paper conveyed between the photosensitive drum 70 and the transfer roller 82, the toner image on the photosensitive drum 70 is transferred by the transfer roller 82 to which a voltage opposite in polarity to the polarity of the electrostatic latent image is applied. Thereafter, it is separated from the photosensitive drum 70 and conveyed to the fixing unit 64 via the downstream conveyance path 118, and is discharged to the discharge tray 116 after performing the fixing process. Note that the number of recording sheets that have completed image formation is counted when the recording sheet that has passed through the fixing unit 64 passes through the number sensor 120.

  After the toner image has been transferred, the toner remaining on the surface of the photosensitive drum 70 is removed by the cleaning unit 76, while the electric charge remaining on the surface of the photosensitive drum 70 is removed by the light irradiation unit 78. The These operations are sequentially repeated to form an image on a predetermined number of recording sheets.

  FIG. 3 is a diagram showing a circuit configuration for controlling the light emitting operation of each semiconductor light emitting element 94 of the first and second semiconductor light emitting element arrays 96 and 98 constituting the light irradiation unit 78. That is, a series circuit of the first resistance element R1 and the first inductance element L1 is connected between the first semiconductor light emitting element array 96 and the drive voltage Vcc, and the first semiconductor light emitting element array 96 and the ground potential are connected. An NPN-type first transistor Tr1 that functions as a switch element that is controlled to be turned on and off by a drive signal supplied from the outside is connected therebetween. The first transistor Tr1 is ON / OFF controlled by a pulse signal which is a drive signal supplied from a drive circuit 130 formed of a pulse generation circuit.

  Further, a series circuit of the second resistance element R2 and the second inductance element L2 is connected between the second semiconductor light emitting element array 98 and the drive voltage Vcc, and the second semiconductor light emitting element array 98 and the ground potential are connected. An NPN-type second transistor Tr2 that functions as a switch element that is on / off controlled by a drive signal supplied from the outside is connected between the second transistors Tr2. The second transistor Tr2 is ON / OFF controlled by a pulse signal that is a drive signal supplied from the drive circuit 130 formed of a pulse generation circuit.

  Here, the first switch element SW1 that is on / off controlled by a drive signal supplied from the outside is connected in parallel to both ends of the first inductance element L1, and the drive signal supplied from the outside to both ends of the second inductance element L2. Are connected in parallel to each other. These first and second switch elements SW1 and SW2 are constituted by switch elements with control terminals such as MOSFETs, for example, and the first and second inductance elements are turned on while the photosensitive drum 70 is turned on. Both ends of L1 and L2 are short-circuited. When the number of recording sheets passing through the number sensor 120 exceeds a predetermined number or the like, the first photosensitive drum 70 is turned off when it becomes old and fatigued. The second inductance elements L1 and L2 are inserted into the energization circuit.

  FIG. 4 shows the first and second switching elements SW1 and SW2 in the circuit configuration shown in FIG. 3, and the first and second inductance elements L1 and L2 are inserted in the energization circuit, respectively. 2 is a time chart for explaining a light emitting operation of each semiconductor light emitting element 94 in two semiconductor light emitting element rows 96 and 98;

  That is, a pulse signal having a predetermined period is supplied from the driving circuit 130 to the bases of the first and second transistors Tr1 and Tr2, respectively, so that the first and second resistance elements R1 and R2, the first and second inductance elements L1. , L2, and the series circuits of the first and second semiconductor light emitting element arrays 96 and 98, a pulse voltage having a predetermined cycle of the drive voltage Vcc is necessary for static elimination of the photosensitive drum 70, as shown in FIG. It is repeatedly supplied for a predetermined period. As a result, a predetermined set current (steady current) Is flows through the first and second semiconductor light emitting element arrays 96 and 98 in the steady state as shown in FIG. When the voltage rises, an inrush current Ir larger than the steady current flows instantaneously.

  This inrush current Ir flows for the following reason. That is, since the depletion layer at the PN junction in the semiconductor light emitting element 94 has a predetermined capacitance and is equivalent to a capacitor, the first and second resistance elements R1, R2, first, and second inductance elements Each series circuit of L1, L2 and the semiconductor light emitting element 94 is an RLC series circuit, and an inrush current Ir flows due to a transient response of the RLC series circuit when a pulse voltage is applied. That is, an RLC series circuit including a capacitance provided in the semiconductor light emitting element 94, resistance elements R1 and R2 connected in series to the semiconductor light emitting element 94, and inductance elements L1 and L2 connected in series to the semiconductor light emitting element 94. An inrush current generator is configured.

  Incidentally, the capacitance value of the depletion layer at the PN junction in the semiconductor light emitting device 94 is 100 pF, the resistance values of the resistance elements R1 and R2 are 580Ω, and the inductance values of the first and second inductance elements L1 and L2 are 10 mH. 5 is configured, and a current waveform flowing in the RLC series circuit when a pulse voltage having an amplitude of 24 V, a rise / fall time of 50 μsec, and a pulse width of 1 msec (Duty 50%) is supplied to the RLC series circuit as shown in FIG. As shown in FIG. As is clear from FIG. 6, in the circuit including the inductance element, a large inrush current flows when the pulse voltage rises. In the RLC series circuit shown in FIG. 5, a large current in the reverse direction flows instantaneously even when the pulse voltage falls, but in the RLC circuit including the semiconductor light emitting element 94, a large current in the reverse direction is generated. There is no flow.

  On the other hand, the inductance element is removed from the RLC series circuit shown in FIG. 5, and the constants of the other elements are set to the same values as those in FIG. 5 to form an RC series circuit as shown in FIG. FIG. 8 shows a waveform of a current flowing in the RC series circuit when the same pulse voltage as that in the case is supplied. As is clear from FIG. 8, in a circuit that does not include an inductance element, a large inrush current does not flow when the pulse voltage rises.

  Thus, in the RLC series circuit including the first and second inductance elements L1 and L2, the inrush current Ir flows when the pulse voltage rises, so that the output light emitted from the semiconductor light emitting element 94 is instantaneously increased. The increased output light is repeatedly irradiated to remove the charge inside the photoconductor of the photoconductor drum 70, and the output light of the inrush current Ir and the steady current Is causes the surface of the photoconductor drum 70 to be exposed. The charge is removed.

  As described above, the increased output light radiated from the semiconductor light emitting element 94 is output only intermittently corresponding to the inrush current Ir, so that the deterioration of the semiconductor light emitting element 94 is effectively prevented. In the present embodiment, in order to prevent the semiconductor light emitting element 94 from deteriorating by flowing the inrush current Ir, the first and second switch elements SW1 and SW2 are closed while the photosensitive drum 70 is new. The first and second inductance elements L1 and L2 are not inserted in the energization circuit.

FIG. 9 is a block diagram for explaining the control operation of the image forming unit 16 in the image forming apparatus 10 configured as described above. That is, the image forming apparatus 10 includes a control unit 140 for controlling the entire operation at an appropriate position. The control unit 140 includes a CPU (Central Processing Unit) that executes arithmetic processing, a ROM (Read-Only Memory) that stores control processing programs and data, and a RAM (Random Access Memory) that temporarily stores data. However, here, the elements necessary for the control operation of the image forming unit 16 will be mainly described.

  That is, the control unit 140 includes an image reading unit 12, an image forming unit 16, an operation panel 18, a number sensor 120, a drive circuit 130, and an electrically rewritable EEPROM (Electrically Erasable and A storage unit 132 made up of Programmable ROM or the like is connected via a predetermined interface circuit. The control unit 140 includes a start button determination unit 142, a count execution unit 144, a number determination unit 146, a switch switching control unit 148, and function implementation units as the drive circuit control unit 150.

  Here, the start button determination unit 142 determines whether or not the start button 126 of the operation panel 18 is turned on. In the present embodiment, for example, a high signal is output when the start button 126 is turned on, and it is determined that the start button 126 is turned on by receiving this high signal.

  The count execution unit 144 counts the number of recording sheets on which an image is formed based on the detection signal output from the number sensor 120. The counted number of continuously formed images is stored in the storage unit 132 in an update manner. The count execution unit 144 forms a counter unit with the number sensor 120. The number discriminating unit 146 discriminates whether or not the continuous image forming number of recording sheets stored in the storage unit 132 exceeds the reference number by comparing with the reference number stored in the ROM or the like.

  The switch switching control unit 148 supplies control signals to the control terminals of the first and second switch elements SW1 and SW2 connected in parallel to both ends of the first and second inductance elements L1 and L2, thereby supplying the first and second switch elements. The elements SW1 and SW2 are on / off controlled. In this embodiment, the first and second switch elements SW1 and SW2 are turned on until the continuous image forming number of recording sheets exceeds the reference number starting from when the photosensitive drum 70 is replaced with a new one. 1 and the second inductance elements L1 and L2 are not inserted into the energization circuit of the semiconductor light emitting element 94, while the first and second switch elements SW1 and SW1 when the continuous image forming number of recording sheets exceeds the reference number. By turning off SW2, the RLC series circuit is configured such that the first and second inductance elements L1 and L2 are inserted in the energization circuit of the semiconductor light emitting element 94, whereby the photosensitive drum 70 is new. In the meantime, the semiconductor light emitting element 94 is prevented from being unnecessarily deteriorated.

  The drive circuit control unit 150 drives and controls the drive circuit 130 by supplying a control signal to the drive circuit 130. When performing neutralization of the photosensitive drum 70, for example, a high signal is supplied to drive the drive circuit 130. When the neutralization of the photosensitive drum 70 is completed by driving 130, a low signal is supplied so that the drive of the drive circuit 130 is stopped. During driving of the drive circuit 130, the first and second transistors Tr1 and Tr2 are on / off controlled by outputting a pulse signal of a predetermined cycle from the drive circuit 130.

  Here, the drive circuit 130 and the drive circuit control unit 150 that drives and controls the drive circuit 130 constitute a drive control unit that controls on and off of the first and second transistors Tr1 and Tr2, and is connected in series to the semiconductor light emitting element 94. The first and second transistors Tr1 and Tr2 that control the supply of the driving voltage Vcc to the semiconductor light emitting element 94, and the control signals are supplied to the control terminals of the first and second transistors Tr1 and Tr2, thereby A pulse voltage supply unit is composed of a drive control unit that controls on and off of the first and second transistors Tr1 and Tr2.

  FIG. 10 is a flowchart for explaining an example of the control operation of the image forming unit 16 in the image forming apparatus 10 configured as described above. Here, a case will be described as an example where the photosensitive drum 70 in a state where the continuous image forming number of recording sheets does not exceed a predetermined reference number is still in a new state. First, when the initial setting is executed by turning on a power switch (not shown) and the image forming preparation operation is completed, the start button determining unit 142 determines whether the start button 126 is turned on. (Step S1). During the image formation preparation operation when the power switch is turned on, the first and second switch elements SW1 and SW2 are turned on by the switch switching control unit 148, and the inductance elements L1 and L2 are inserted in the circuit. It is not in the state.

  If the determination in step S1 is affirmative, based on the original image read by the image reading unit 12, the image forming unit 16 applies the recording paper to the recording paper with the first and second switch elements SW1 and SW2 turned on. On the other hand, image formation is executed (step S3). If the determination in step S1 is negative, the process waits until the determination is affirmed.

  When image formation is performed on the recording paper by the image forming unit 16, the recording sheet passes the number sensor 120, and the count execution unit 144 counts the number of image formations (step S5). Whether or not the number has reached a predetermined reference number is determined by the number determination unit 146 (step S7).

  If the determination in step S7 is affirmative, the first and second switch elements SW1 and SW2 are switched off by the switch switching control unit 148 (step S9). As a result, the first and second switch elements SW1 and SW2 are turned on by the switch switching control unit 148 so that the inductance elements L1 and L2 are inserted into the circuit. Static elimination is performed. If the determination in step S7 is negative, the process proceeds to step S1 and the subsequent steps are repeatedly executed.

  As described above, the image forming apparatus 10 of the present invention includes the light irradiation unit 78 including the semiconductor light emitting element 94 for irradiating the surface of the photosensitive drum 70 along the axial direction of the photosensitive drum 70. The pulse voltage is continuously supplied to the semiconductor light emitting element 94 constituting the light irradiation unit 78 for a predetermined period so that an inrush current flows through the semiconductor light emitting element 94 at the rising of each pulse voltage. Even when the photoconductor drum 70 becomes old and the photoconductor becomes fatigued, unnecessary charges inside the photoconductor can be effectively removed, and a ghost image can be prevented from being formed on the next recording paper. In addition, since the inrush current flows through the semiconductor light emitting element 94 at the rise of each pulse voltage, the deterioration of the semiconductor light emitting element 94 can be effectively suppressed as compared with the case where a large current is always applied.

  Note that the image forming apparatus 10 according to the present invention is not limited to the above-described embodiment, and various modifications as described below can be adopted as necessary.

  (1) In the above-described embodiment, the semiconductor light emitting element 94 has an inrush current generating unit that allows an inrush current to flow through the semiconductor light emitting element 94, and the resistance elements R1 and R2 connected in series to the semiconductor light emitting element 94. And an RLC series circuit including inductance elements L1 and L2 connected in series to the semiconductor light emitting element 94, but is not limited thereto. For example, instead of a passive element circuit such as an RLC series circuit, it may be composed of an active element circuit configured such that a current larger than a steady current flows when the pulse voltage rises.

  (2) In the above-described embodiment, the light irradiation unit 78 is composed of two semiconductor light emitting element arrays, the first semiconductor light emitting element array 96 and the second semiconductor light emitting element array 98. However, the present invention is not limited to this. . For example, it can be composed of one semiconductor light emitting element array, or can be composed of three or more semiconductor light emitting element arrays.

  (3) In the above embodiment, the first switch element SW1 is connected in parallel to both ends of the first inductance element L1 connected in series to the first semiconductor light emitting element array 96 constituting the light irradiation unit 78, and the second semiconductor light emission. Although the second switch element SW2 is connected in parallel to both ends of the second inductance element L2 connected in series to the element row 98, the present invention is not limited to this. For example, the first switch element SW1 and the second switch element SW2 are not used, and the first inductance element L1 and the second inductance element L2 are always inserted even when the photosensitive drum 70 is new. You can also.

  (4) In the above embodiment, the pulse voltage is repeatedly supplied to the semiconductor light emitting element 94 for a predetermined period. However, the present invention is not limited to this. For example, when the photoconductor of the photoconductor drum 70 is not very fatigued, only one pulse may be supplied, and the number of pulses may be increased as the photoconductor becomes more fatigued.

  (5) In the above embodiment, an inductance element as a discrete component is used for the semiconductor light emitting element array constituting the light irradiation unit 78, but the present invention is not limited to this. For example, it is also possible to integrally form the inside of the semiconductor light emitting element.

  (6) In the above embodiment, the image forming apparatus 10 constitutes a copying machine, but is not limited thereto. For example, as long as it has a photosensitive drum for forming an image on recording paper, it may be a printer, a facsimile machine, a copier having a function of a printer, a facsimile machine, or the like.

FIG. 2 is a cutaway side view of a main part for explaining an internal configuration of the image forming apparatus according to the embodiment of the present invention. It is a figure which shows the structure of the static elimination part used for the image forming apparatus shown in FIG. FIG. 2 is a diagram showing a circuit configuration for controlling the light emitting operation of the semiconductor light emitting elements in the first and second semiconductor element rows constituting the static eliminating section used in the image forming apparatus shown in FIG. 4 is a time chart for explaining the light emitting operation of the semiconductor light emitting element in the circuit configuration shown in FIG. 3, and FIG. 4A is a diagram showing pulse voltages supplied to the first and second semiconductor element rows, FIG. (B) is a figure which shows the current waveform which flows into a 1st, 2nd semiconductor element row | line | column. It is a figure which shows a RLC series circuit. It is a figure which shows the electric current waveform which flows into an RLC series circuit at the time of supplying a pulse voltage to an RLC series circuit. It is a figure which shows RC series circuit. It is a figure which shows the current waveform which flows into RC series circuit at the time of supplying a pulse voltage to RC series circuit. FIG. 2 is a block diagram for explaining a control operation of an image forming unit in the image forming apparatus shown in FIG. 1. 4 is a flowchart for explaining an example of a control operation of an image forming unit in the image forming apparatus shown in FIG. 1.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 16 Image forming part 70 Photosensitive drum 78 Light irradiation part 94 Semiconductor light emitting element 130 Drive circuit 148 Switch switching control part 150 Drive circuit control part R1 Resistance element R2 Resistance element L1 First inductance element L2 Second inductance element Tr1 First transistor Tr2 Second transistor SW1 First switch element SW2 Second switch element Vcc Drive voltage

Claims (1)

The surface of the photosensitive drum has a charge eliminating unit that removes unnecessary charges on the surface of the photosensitive drum by irradiating light emitted from a semiconductor light emitting element disposed along the axial direction of the photosensitive drum. An image forming apparatus,
A series connection circuit which is disposed between a supply terminal of a driving voltage for driving the semiconductor light emitting element and a ground potential, wherein a resistance element, an inductance element and a control switch element are connected in series to the semiconductor light emitting element; ,
A drive control unit that turns on and off controlled by pulse signal control switching elements of the series circuit,
A short-circuit switch element connected in parallel to the inductance element of the series connection circuit;
A counter unit that continuously counts the number of recording sheets on which images are formed on the photosensitive drum;
Supplying a control signal to the short-circuit switch element to control the on-off of the short-circuit switch element, and when the continuous count number of recording sheets by the counter unit does not reach a predetermined number, A switch switching control unit that short-circuits both ends of the inductance element, and turns off the short-circuit switch element and opens a short circuit at both ends of the inductance element when the continuous count number of recording sheets by the counter unit reaches a predetermined number ; An image forming apparatus comprising the image forming apparatus.

Images