JP4799882B2 - Static eliminator and image forming apparatus - Google Patents

Description

  The present invention relates to a static eliminator and an image forming apparatus that discharge light by projecting light onto a surface of a photosensitive drum on which an electrostatic latent image is formed.

  In an image forming apparatus using an electrophotographic process such as a copying machine or a printer, an electrostatic latent image is formed on the surface of a photosensitive drum, and this image is developed and visualized. In this type of image formation, there is an image forming apparatus that includes a charge removing device that discharges light by projecting a light beam onto the surface of the photosensitive drum for the purpose of erasing unnecessary charging and latent images.

  In this static eliminator, as a light source, for example, a plurality of LEDs (Light Emitting Diodes) are arranged in a straight line at substantially equal intervals so as to face the surface of the photosensitive drum, and the static elimination light from the LEDs is applied to the surface of the photosensitive drum. By irradiating substantially uniformly, unnecessary charges, latent images, and the like are removed substantially uniformly.

  In such a static eliminator, if the light quantity of the LED becomes non-uniform, the effect of neutralizing the surface of the photosensitive drum becomes non-uniform, and as a result, the print quality may deteriorate. For example, when a failure such as disconnection occurs in some LEDs and light is not emitted, the surface of the photosensitive drum facing the failed LED is not neutralized, and print quality may be significantly deteriorated.

Therefore, various proposals have been disclosed so far to make the light quantity of the LED uniform. For example, Patent Document 1 below proposes a static eliminator having a failure detection circuit that detects a disconnection of an LED at low cost by using a transistor switching operation.
JP 2003-76234 A

  On the other hand, the forward voltage Vf of the LED has a variation of about ± 5%, and due to this variation, a variation in the forward current If that defines the amount of light emitted by the LED occurs, and the desired static elimination effect cannot be obtained. There is a case.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a static eliminating device and an image forming apparatus capable of making the light quantity distribution of static eliminating light substantially uniform.

The static eliminator according to claim 1 is a static eliminator that neutralizes static electricity by projecting a light beam onto the surface of a photosensitive drum on which an electrostatic latent image is formed, and a current corresponding to a voltage between terminals of the constant voltage element. a plurality of constant current generating circuit for generating a said respectively connected in series with a plurality of each of the constant current generating circuit, a plurality of light source units to emit light beams to be projected on the surface of the photosensitive drum, the terminal of the constant voltage element One disconnection determination unit that determines the presence or absence of disconnection in each of the light source units based on the magnitude of the inter-voltage value is provided.

According to this configuration, the constant current generation circuit generates a current corresponding to the voltage between the terminals of the constant voltage element, so that a substantially constant current is generated with a simple configuration. In addition, since the light source unit is connected in series to the constant current generation circuit, a substantially constant current generated by the constant current generation circuit is supplied to the light source unit, and the amount of light rays projected on the surface of the photosensitive drum is substantially reduced. It is assumed to be constant.

Accordingly, a substantially constant current is generated with a simple configuration, and the substantially constant current is supplied to the light source unit. Therefore, the amount of charge removal light emitted from the light source unit is substantially constant, and the light amount distribution of the charge removal light. Can be substantially uniform.

Furthermore, according to this configuration, the disconnection determination unit determines whether the light source unit is disconnected based on the voltage value between the terminals of the constant voltage element. On the other hand, when the disconnection of the light source unit occurs, the current flowing through the limiting resistor of the constant current generating circuit is greatly reduced, so that the voltage value between the terminals of the constant voltage element is greatly reduced.

  Therefore, since the presence / absence of disconnection of the light source unit is determined based on the voltage value between the terminals of the constant voltage element, the value of which varies greatly depending on whether the light source unit is disconnected, the presence / absence of disconnection of the light source unit is accurately determined with a simple configuration. Determined.

  According to a second aspect of the present invention, there is provided a static eliminator including a switching circuit that performs on / off control of a voltage between terminals of the constant voltage element.

  According to this configuration, the voltage between the terminals of the constant voltage element is on / off controlled by the switching circuit, so that the current supplied to the light source unit (that is, charge removal light) is on / off controlled.

The static elimination apparatus according to claim 3, wherein the constant current generating circuit includes a transistor having one terminal of the constant voltage element connected to a control electrode, and one end connected to a first main electrode of the transistor, A limiting resistor for regulating the value, and the other terminal of the constant voltage element and the other end of the limiting resistor are connected via a ground .

According to this configuration, one terminal of the constant voltage element is connected to the control electrode of the transistor, and the other terminal of the constant voltage element and the first main electrode of the transistor are connected via the ground and the limiting resistor. A substantially constant current corresponding to the voltage between the terminals of the constant voltage element flows through the limiting resistor, and the constant current generating circuit is realized with a simple configuration.

The static eliminator according to claim 4 is characterized in that the light source unit includes a plurality of light emitting elements connected in series .

According to this configuration, since the light source unit includes a plurality of light emitting elements connected in series, the same current is applied to the light emitting elements in the light source unit, and the light amount distribution of the static elimination light emitted from the light emitting elements is substantially reduced. It is assumed to be uniform.

The static eliminator according to claim 5 is characterized in that the light emitting element is an LED.

According to this configuration, since the light emitting element is made of an LED, a light source having desired characteristics can be manufactured at low cost.

According to a sixth aspect of the present invention, there is provided an image forming apparatus comprising: the static eliminator according to any one of the first to fifth aspects; and a photosensitive drum on which an electrostatic latent image is formed on the surface and is neutralized by light from the static eliminator. It is characterized by comprising.

According to this configuration, an image forming apparatus in which the light amount distribution of the charge removal light is substantially uniform is realized.

According to the first aspect of the present invention, since a current is generated corresponding to the voltage between the terminals of the constant voltage element, a substantially constant current can be generated with a simple configuration, and the substantially constant current is generated by the light source unit. Therefore, the amount of charge removal light emitted from the light source unit is substantially constant, and the light amount distribution of charge removal light can be made substantially uniform.

Furthermore, according to this configuration, the disconnection determination unit determines whether the light source unit is disconnected based on the voltage value between the terminals of the constant voltage element. On the other hand, when the disconnection of the light source unit occurs, the current flowing through the limiting resistor of the constant current generating circuit is greatly reduced, so that the voltage value between the terminals of the constant voltage element is greatly reduced.

  Therefore, since the presence / absence of disconnection of the light source unit is determined based on the voltage value between the terminals of the constant voltage element, the value of which varies greatly depending on whether the light source unit is disconnected, the presence / absence of disconnection of the light source unit is accurately determined with a simple configuration Determined.

  According to the second aspect of the present invention, since the voltage between the terminals of the constant voltage element is on / off controlled, it is possible to on / off control the current supplied to the light source unit (that is, static elimination light).

  According to the third aspect of the invention, since a substantially constant current corresponding to the voltage between the terminals of the constant voltage element flows through the limiting resistor, the constant current generating circuit can be realized with a simple configuration.

  According to the fourth aspect of the present invention, since the same current is applied to the light emitting elements in the light source unit, the light quantity distribution of the static elimination light emitted from the light emitting elements can be made substantially uniform.

According to the fifth aspect of the present invention, since the light emitting element is made of an LED, a light source having desired characteristics can be manufactured at low cost.

According to the sixth aspect of the present invention, it is possible to realize an image forming apparatus in which the light amount distribution of the charge removal light is substantially uniform.

  Hereinafter, an example of an image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a side view of a copying machine as an example of an image forming apparatus according to the present invention.

  Although the case where the image forming apparatus is a copying machine will be described here, other image forming apparatuses (for example, a facsimile, a printer, etc.) may be used.

  The copying machine 1 includes a main unit 200, a sheet post-processing unit 300 disposed on the left side of the main unit 200, an operation unit 400 for a user to input various operation commands and the like, and an upper part of the main unit 200. A document reading unit 500 disposed and a document feeding unit 600 disposed above the document reading unit 500 are provided.

The operation unit 400 includes an operation panel 401, a start key 402, a numeric keypad 403, and the like. The operation panel 401 displays various operation screens and a liquid crystal display (LCD: Liquid) that displays various operation buttons and the like for the user to input various operation commands.
(Crystal Display) or the like.

  The start key 402 is used for the user to input a print execution command and the like, and the ten key 403 is used for inputting the number of copies to be printed.

  The document feeding unit 600 includes a document placement unit 601, a document discharge unit 602, a paper feed roller 603, a document transport path 604, a contact glass 605, and the like, and the document reading unit 500 includes a scanner 501 and the like.

  The paper feed roller 603 feeds out the original set on the original placement unit 601, and the original conveyance path 604 conveys the delivered original one by one on the scanner 501 one by one.

  The scanner 501 includes an imaging device (CCD; Charge Coupled Device), and sequentially reads the conveyed document. The read document is discharged to the document discharge unit 602.

  The scanner 501 reads a document while moving in the direction indicated by the arrow A (right direction in the drawing) along the contact glass 605 when reading the document placed on the contact glass 605.

  The main body 200 includes a plurality of (here, three) paper feed cassettes 201a to 201c, a plurality of (here, three) paper feed rollers 202a to 202c, a transfer roller 203, an intermediate transfer body roller 204, a photosensitive member. A drum 205, an exposure device 206, yellow, magenta, cyan, and black developing devices 207Y, 207M, 207C, and 207K, a fixing roller 208, a discharge port 209, a discharge tray 210, a recording paper conveyance path 211, and the like.

  The photosensitive drum 205 is uniformly charged by the charging device 205a while rotating in the direction of the arrow. The exposure device 206 converts a modulation signal generated based on the image data of the document read by the document reading unit 500 into a laser beam and outputs it, and forms an electrostatic latent image on the photosensitive drum 205 for each color. is there.

  The developing devices 207Y, 207M, 207C, and 207K supply each color developer to the photosensitive drum 205 to form a toner image for each color. The intermediate transfer body roller 204 is configured to transfer a toner image of each color from the photosensitive drum 205 and form a color toner image on the intermediate transfer body roller 204.

  In addition to the developing devices 207Y, 207M, 207C, and 207K and the intermediate transfer roller 204, there is an upstream side of the charging device 205a with respect to the rotation direction indicated by the arrow of the photosensitive drum 204 around the photosensitive drum 205. In addition, on the downstream side of the intermediate transfer roller 204, a cleaning blade 205b that removes toner adhering to the surface of the photosensitive drum 205 after transfer, and a static elimination according to the present invention that neutralizes the surface of the photosensitive drum 205 by exposure. A device 700 is provided.

  The neutralization device 700 removes charges such as an electrostatic latent image formed on the surface of the photosensitive drum 205 by the exposure device 206 by irradiating with a neutralization light emitted from a neutralization LED (701 to 718 shown in FIG. 2) described later. To do.

  On the other hand, the paper feeding rollers 202a to 202c pull out the recording paper from the paper feeding cassettes 201a to 201c in which the recording paper is stored, and the recording paper conveyance path 211 conveys the drawn recording paper to the transfer roller 203. is there. The transfer roller 203 transfers the toner image on the intermediate transfer body roller 204 to the conveyed recording paper. The recording paper onto which the toner image has been transferred is conveyed to the fixing roller 208 through the recording paper conveyance path 211, and the fixing roller 208 heats the transferred toner image to fix it on the recording paper. The recording sheet on which the toner image is fixed is conveyed to the discharge port 209 via the recording sheet conveyance path 211 and is carried into the sheet post-processing unit 300. The recording paper is also discharged to the discharge tray 210 as necessary.

  The paper post-processing unit 300 includes a carry-in port 301, a recording paper conveyance path 302, a carry-out port 303, a stack tray 304, and the like. The recording paper conveyance path 302 sequentially conveys the recording paper carried into the carry-in port 301 from the discharge port 209 and finally discharges the recording paper from the carry-out port 303 to the stack tray 304. The stack tray 304 is configured to move up and down in the direction of the arrow in accordance with the number of recording sheets stacked from the carry-out port 303.

  FIG. 2 is an explanatory view showing a method of connecting a static elimination LED disposed in the static elimination device 700. In the static eliminator 700, here, 18 static elimination LEDs 701 to 718 (corresponding to light emitting elements) are arranged linearly at equal intervals so as to face the surface of the photosensitive drum 205. And every six static elimination LED701-718 is connected in series, and three light source units are formed. In the example shown to (a), static elimination LED is connected in series for every six in order from one end (left end in a figure), and the light source units U11-U13 are formed. In the example shown in (b), the neutralizing LEDs are connected in series every two in order from one end (the left end in the figure) to form the light source units U21 to U23. Here, the case where it connects by the method shown to (a) is demonstrated.

  FIG. 3 is a configuration diagram illustrating an example of a control circuit of the static eliminator 700. One end of each of the light source units U11 to U13 is connected to a DC voltage source Vcc (here, 24V), and the other end is connected to a collector (corresponding to a second main electrode) of the transistors Q1 to Q3. The emitters (corresponding to the first main electrode) of the transistors Q1 to Q3 are grounded via limiting resistors R1 to R3 (here, the resistance values of R1 to R3 are set to 300Ω), respectively.

  One end of a Zener diode ZD1 (corresponding to a constant voltage element: Zener voltage Vz is 6.8 ± 0.15 V) is connected to the base (corresponding to the control electrode) of each transistor Q1 to Q3, and Zener diode ZD1 The other end of is grounded. Then, one end of the Zener diode ZD1 has a current adjustment resistor R4 (in this case, the resistance value of the current adjustment resistor R4 is 15 kΩ) for making the magnitude of the current flowing through the Zener diode ZD1 (that is, the voltage between the terminals) appropriate. Is connected to a DC voltage source Vcc (here, 24V).

  Furthermore, one end of the Zener diode ZD1 is connected to the negative input terminal of the comparator AMP (part of the disconnection determination unit, corresponding to the comparison operation circuit), and the on / off control transistor Q4 (corresponding to the switching circuit). ) Is connected to the collector. Voltage reference value information S2 from a CPU (Central Processing Unit) (corresponding to a part of the disconnection determination unit) that controls the entire copying machine 1 is input to the plus side input terminal of the comparator AMP, in the interface unit (D / A reference voltage signal VCZ (here, 4V) converted into an analog signal is input via the A converter.

  The comparator AMP is the difference between the reference voltage signal VCZ that is input to the plus side input terminal and the terminal voltage VZ of the zener diode ZD1 that is input to the minus side input terminal (here, the potential at one end of the zener diode ZD1). When the signal is positive, an ON signal is output, and when it is negative, an OFF signal is output. The output from the comparator AMP is converted into digital information S3 via the interface unit (A / D conversion unit) and input to the CPU. However, when the CPU has an analog input port, the output from the comparator AMP may be directly input to the analog input port.

  The emitter of the transistor Q4 is grounded, and an on / off signal V4 obtained by converting the on / off information S1 from the CPU into an analog signal via the interface unit (D / A conversion unit) is input to the base. The constant current generating circuit of the present invention corresponds to the circuit CI in the figure.

  The on / off control operation of the static elimination LEDs 701 to 718 of the control circuit of the static elimination device 700 configured as described above will be described. When the on / off information S1 from the CPU is on information (information for turning off the transistor Q4), the transistor Q4 is turned off, and the voltage across the Zener diode ZD1 becomes the Zener voltage Vz (= 6.8 ± 0.15V). Thus, the transistors Q1 to Q3 are all turned on.

  When the base-emitter voltage of the transistors Q1 to Q3 is 0.60 to 0.65V, the voltages VR1 to VR3 between both ends of the limiting resistors R1 to R3 are 6.00 to 6.35V. The currents I1 to I3 (= 20 to 21.2 mA) flow through the light source units U11 to U13, and the charge eliminating LEDs 701 to 718 are turned on. In this way, since a substantially constant current flows through the neutralization LEDs 701 to 718, a substantially uniform neutralization light is irradiated on the surface of the photosensitive drum 205. In this state, since the Zener voltage Vz (= 6.8 ± 0.15 V) is input to the negative input terminal of the comparator AMP, the difference between the reference voltage signal VCZ and the inter-terminal voltage VZ is − (2.8). ± 0.15) V (that is, a negative value), and the output of the comparator AMP becomes an OFF signal.

Conversely, on-off information S1 from the CPU, if there off information (information to turn on the transistor Q4), the transistor Q4 is turned on, the voltage between the terminals substantially zero next to the Zener diode ZD1, all transistors Q1~Q3 is Turned off.

  Then, the collector currents I1 to I3 of the transistors Q1 to Q3 are turned off (= 0) (that is, the currents of the light source units U11 to U13 are stopped), and the static elimination LEDs 701 to 718 are turned off. In this way, the transistor Q4 functions as a switching circuit based on the on / off information S1 from the CPU, and the on / off control of the neutralization LEDs 701 to 718 is performed.

  Next, the disconnection detection operation of the static elimination LEDs 701 to 718 in the control circuit of the static elimination device 700 will be described. Here, for example, a case where the static elimination LED 718 is disconnected will be described. When the on / off information S1 from the CPU is on information (information for turning off the transistor Q4), the transistor Q4 is turned off, and the voltage across the Zener diode ZD1 becomes the Zener voltage Vz (= 6.8 ± 0.15V). Transistors Q1-Q3 are all turned on.

  Here, since the static elimination LED 718 is disconnected, the current I1 becomes zero, so the base current IR1 of the transistor Q1 limited by the current adjustment resistor R4 also becomes substantially zero. That is, the current adjustment resistor R4 and the limiting resistor R1 are connected through a PN junction between the base and emitter of the transistor Q1 that substantially functions as a diode.

  Accordingly, if the base-emitter voltage of the transistor Q1 is 0.625V, the voltage between the terminals of the Zener diode ZD1 is 1.08V (= (24−0.625) × 300 / (15000 + 300) +0.625). Become. Therefore, since 1.08V is input to the negative input terminal of the comparator AMP, the difference between the reference voltage signal VCZ and the inter-terminal voltage VZ becomes 2.92V (that is, a positive value), and the output of the comparator AMP. Becomes an ON signal.

  On the other hand, as described above, in a normal state where there is no disconnection, the output of the comparator AMP is an off signal, so the presence or absence of the disconnection is accurately detected by the output of the comparator AMP. That is, when the on / off information S1 from the CPU is the on information and the output information S3 of the comparator AMP is off, it is determined that no disconnection has occurred, and the on / off information S1 from the CPU is the on information. If the output information S3 of the comparator AMP is ON, it is determined that a disconnection has occurred.

  Thus, since the currents I1 to I3 are generated corresponding to the inter-terminal voltage VZ of the Zener diode ZD1, substantially constant currents I1 to I3 are generated with a simple configuration, and the substantially constant current I1. Since .about.I3 is supplied to the light source units U11 to U13, the light quantity of the static elimination light emitted from the light source units U11 to U13 can be made substantially constant, and the light quantity distribution of the static elimination light can be made substantially uniform.

  In addition, since the voltage between the terminals of the Zener diode ZD1 is on / off controlled by the transistor Q4, the currents I1 to I3 (that is, static elimination light) supplied to the light source units U11 to U13 are on / off controlled.

Further, the high potential side terminal of the Zener diode ZD1 is connected to the bases of the transistors Q1 to Q3, the low potential side terminal of the Zener diode ZD1 is grounded, and the emitters of the transistors Q1 to Q3 are connected via the limiting resistors R1 to R3. Grounded . The low potential side terminal of the Zener diode ZD1 and the ground side terminals of the limiting resistors R1 to R3 are connected to each other through the ground. Therefore , substantially constant currents IR1 to IR3 corresponding to the inter-terminal voltage VZ of the Zener diode ZD1 flow in the limiting resistors R1 to R3, and the constant current generating circuit CI is realized with a simple configuration.

  In addition, since each of the light source units U11 to U13 has six LEDs connected in series, the same currents I1 to I3 are applied to the LEDs in the light source units U11 to U13, respectively. The light quantity distribution of the discharged static electricity is made substantially uniform.

  In addition, since the constant current generation circuit CI is provided for each of the light source units U11 to U13 in which six LEDs are connected in series, currents I1 to I3 having an appropriate magnitude for each of the light source units U11 to U13. Can be applied, and the light quantity distribution of the static elimination light is made more uniform.

  Furthermore, since the presence / absence of disconnection of the light source units U11 to U13 is determined based on the voltage value VZ between the terminals of the Zener diode ZD1 whose value varies greatly depending on whether the light source units U11 to U13 are disconnected or not, the light source units U11 to U13 are determined. The presence or absence of disconnection is accurately determined with a simple configuration.

  In addition, since the comparator AMP compares the voltage value VZ between the terminals of the Zener diode ZD1 and the preset voltage value VCZ, the presence or absence of disconnection of the light source units U11 to U13 is accurately determined with a simple configuration. .

  In addition, this invention can take the following aspects.

  (A) In the present embodiment, the case where the image forming apparatus is the copying machine 1 has been described. However, another type of image forming apparatus (for example, a facsimile, a printer, or the like) may be used.

  (B) In this embodiment, although the case where the light source of the static elimination apparatus 700 is static elimination LED 701-718 as a point light source was demonstrated, the form which is another kind of light source may be sufficient. For example, a linear light source composed of an LED, a slit, a lens, and the like may be used.

  (C) In the present embodiment, the case where the constant current generating circuit CI generates a current corresponding to the voltage between the terminals of the Zener diode ZD1 (constant voltage element) has been described. However, the constant current generating circuit CI is connected in series. Alternatively, a current may be generated corresponding to a voltage (divided voltage) generated by being divided by a plurality of resistors. In this case, a constant voltage element such as the Zener diode ZD1 becomes unnecessary, and the static eliminator 700 is simplified.

  (D) In the present embodiment, the case where the constant voltage element is the Zener diode ZD1 has been described. However, other types of elements (or circuits) may be used. For example, a form that is a varistor may be used, or a form that uses a forward voltage of a diode (for example, when 10 diodes are connected in series, the voltage between terminals can be used as an alternative to a constant voltage element of about 6V).

  (E) In the present embodiment, the case where the transistors Q1 to Q3 and Q4 are bipolar PNP transistors has been described. However, other types of transistors may be used. For example, it may be a bipolar NPN transistor or a field effect transistor.

  (F) In the present embodiment, the case where the presence or absence of disconnection is determined by the comparator AMP has been described. However, instead of the comparator AMP, the base is connected to the other end (the side that is not one end) of the Zener diode ZD1. Alternatively, the presence or absence of disconnection may be determined by turning on or off a transistor whose emitter is grounded.

  FIG. 4 is a configuration diagram illustrating another example of the control circuit of the static eliminator 700. Differences from the control circuit of the static eliminator 700 shown in FIG. 3 will be described. In this control circuit, instead of the comparator AMP, a transistor Q5 having a base connected to the other end (the side other than the one end) of the Zener diode ZD1 is disposed.

  The emitter of the transistor Q5 is grounded, the collector of the transistor Q5 is connected to the DC voltage source Vcc via the resistor R5, and the collector current of the transistor Q5 is converted to digital information S5 via the interface unit (A / D conversion unit). And is input to the CPU.

Next, the disconnection detection operation of the static elimination LEDs 701 to 718 in the control circuit shown in FIG. 4 will be described. First, a case where there is no disconnection will be described. When the on / off information S1 from the CPU is on information (information for turning off the transistor Q4), all the transistors Q1 to Q3 are turned on, and the charge eliminating LEDs 701 to 718 are turned on. In this state, since the Zener voltage Vz (= 6.8 ± 0.15 V) is input as the base voltage V6 of the transistor Q5, the transistor Q5 is turned on, and the digital information S5 to the CPU is turned off (= Low level). It becomes.

  Next, the case where the static elimination LED 718 is disconnected will be described. When the on / off information S1 from the CPU is on information (information for turning off the transistor Q4), the transistor Q4 is turned off, and the voltage across the Zener diode ZD1 becomes the Zener voltage Vz (= 6.8 ± 0.15V). Transistors Q1-Q3 are all turned on.

  Here, since the static elimination LED 718 is disconnected, the current I1 becomes zero. Therefore, the base current IR1 of the transistor Q1 limited by the current adjustment resistor R4 also becomes substantially zero, and the base-emitter voltage of the transistor Q1 becomes zero. Assuming that the voltage is 625V, the voltage across the Zener diode ZD1 is 1.08V. Therefore, the transistor Q5 is turned off, and the digital information S5 to the CPU is turned on (= High level).

  In this way, when the on / off information S1 from the CPU is on information and the digital information S5 from the transistor Q5 is off, it is determined that no disconnection has occurred, and the on / off information S1 from the CPU. Is ON information and the digital information S5 from the transistor Q5 is ON, it is determined that a disconnection has occurred.

  (G) In the present embodiment, the case where the light source units U11 to U13 are composed of the same number of LEDs has been described, but a form composed of different numbers of LEDs may be used. For example, a configuration in which three, three, and six LEDs are respectively connected in series may be used.

  (H) In the present embodiment, the case where the three light source units U11 to U13 are provided has been described, but the number of the light source units may be any number.

1 is a side view of a copying machine as an example of an image forming apparatus according to the present invention. It is explanatory drawing which shows the connection method of static elimination LED arrange | positioned at a static elimination apparatus. It is a block diagram which shows an example of the control circuit of a static elimination apparatus. It is a block diagram which shows another example of the control circuit of a static elimination apparatus.

1 Copier 700 Static eliminator 701-718 LED
Q1-Q3 transistors (part of constant current generation circuit)
Q4 transistor (switching circuit)
R1 to R3 Limiting resistor (part of constant current generation circuit)
R4 Current adjustment resistor U11 to U13 Light source unit Vcc DC voltage source ZD1 Zener diode (constant voltage element)
AMP comparator (part of disconnection determination unit, comparison operation circuit)
CPU (part of disconnection determination unit)

Claims (6)

A static eliminator that discharges light by projecting light onto the surface of a photosensitive drum on which an electrostatic latent image is formed,
A plurality of constant current generating circuits for generating a current corresponding to the voltage between the terminals of the constant voltage element;
Are connected in series to each of said plurality of constant current generating circuit, a plurality of light source units to emit light beams to be projected on the surface of the photosensitive drum,
One static disconnection determination part which determines the presence or absence of the disconnection in each said light source unit based on the magnitude | size of the voltage value between the terminals of the said constant voltage element. The static elimination apparatus characterized by the above-mentioned.   The static eliminator according to claim 1, further comprising a switching circuit that performs on / off control of a voltage between terminals of the constant voltage element. The constant current generating circuit includes a transistor in which one terminal of the constant voltage element is connected to a control electrode;
One end of which is connected to the first main electrode of the transistor and has a limiting resistor for regulating a current value;
3. The static eliminator according to claim 1, wherein the other terminal of the constant voltage element and the other end of the limiting resistor are connected via a ground. The static eliminator according to claim 3, wherein the light source unit includes a plurality of light emitting elements connected in series . The static eliminator according to claim 4, wherein the light emitting element is an LED. The static eliminator according to any one of claims 1 to 5,
  An image forming apparatus comprising: a photosensitive drum on which an electrostatic latent image is formed on a surface and wherein the photosensitive drum is neutralized by light from the neutralizing device.

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