JP2006335025A - Light quantity control device and image formation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light quantity control device capable of prolonging a life of a photosensor, and an image formation device. <P>SOLUTION: The light quantity control device comprises: the photosensor (end detection sensor 332) comprising a light emitting means (light emitting unit 332a) which emits using a driving current supplied from a power source and a photodetecting means (photodetector 332b) which detects the light emitted from the light emitting means; a judging means (driving current control circuit 416) which judges a color and/or density of the above irradiated medium based on the detection signal from the above photodetecting means; and a control means (driving current control circuit 416, driven current supply circuit 417) which controls the amount of the riving currents supplied to the above light emitting means from the power source. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light amount control device and an image forming apparatus including the light amount control device.

  Conventionally, an image forming apparatus such as a laser printer or a copying machine has been used. In this type of image forming apparatus, if all recording media such as paper on which image formation is performed are conveyed to the same position, an image can be formed at the same position on the recording medium. Misalignment may occur due to various slips that occur in the transport path or bending of the recording medium, and this misalignment causes a deviation in the image forming position.

  For this reason, in the transport direction (sub-scanning direction), alignment is usually performed by a registration roller immediately before image formation. In addition, with respect to a direction (main scanning direction) perpendicular to the transport direction, the end position detection sensor constituted by a contact type line sensor or the like detects the passage position in the main scanning direction and determines the image forming position according to the passage position. By doing so, a technique for performing alignment has been proposed. This close contact type line sensor includes an illumination LED that irradiates the recording medium, and a photosensor that detects the position of the recording medium by reflected light from the recording medium.

By the way, the light quantity of the LED for illumination mentioned above falls with time, and there exists a problem that the exact writing position cannot be determined by this light quantity fall. Therefore, conventionally, even if the detection function of the recording medium (recording paper) is reduced due to a decrease in the amount of light of the illumination LED over time, correction of the threshold value of the comparator or correction of the illumination LED of the edge detection sensor periodically or as necessary A technique for discriminating between a white background and a black background has been proposed (for example, see Patent Document 1).
JP 2002-248804 A

  However, in the technique of Patent Document 1, since the driving voltage of the illumination LED is set to be high, when using a recording medium such as white paper that is most commonly used, the illumination LED has an excessive amount of light. There is a problem that the life of the photosensor is shortened, and in particular, a contact type line sensor used for an end detection sensor or the like is expensive, so that there is a problem that the financial burden on the user required for replacement increases. .

  The subject of this invention is providing the light quantity control apparatus and image forming apparatus which can prolong the lifetime of a photosensor.

In order to solve the above-mentioned problem, the invention described in claim 1
A photosensor having a light emitting means for emitting light by a drive current supplied from a power source and a light detecting means for detecting reflected light from the irradiated medium of light emitted from the light emitting means;
Determination means for determining the color and / or density of the irradiated medium based on a detection signal from the light detection means;
Control means for controlling the amount of drive current supplied from the power source to the light emitting means based on the determination result of the determining means;
It is characterized by having.

Furthermore, the invention according to claim 2 is the invention according to claim 1,
The control means maximizes the supplied drive current amount during the determination of the color and / or density of the irradiated medium by the determination means.

Furthermore, the invention according to claim 3 is the invention according to claim 1 or 2,
The control means controls the amount of drive current supplied by an analog voltage control method.

Furthermore, the invention according to claim 4 is the invention according to any one of claims 1 to 3,
The control means controls the supplied drive current amount by a PWM method for modulating a pulse width of a signal related to lighting of the light emitting means.

Furthermore, the invention according to claim 5 is the invention according to any one of claims 1 to 4,
A lighting start signal output means for outputting a lighting start signal instructing the lighting start to the light emitting means;
A determination start signal output means for outputting a determination start signal for instructing the determination means to start the determination of the color and / or density of the irradiated medium;
The determination start signal output means outputs the determination start signal after the light emitting means is turned on by the lighting start signal.

Furthermore, the invention according to claim 6 is the invention according to any one of claims 1 to 5,
The light emitting means has a plurality of light emitting elements,
The control means turns on the plurality of light emitting elements alternately or at a predetermined timing so that the lighting times of the respective elements are equal.

Furthermore, the invention according to claim 7 is the invention according to claim 6,
The control means turns on the plurality of light emitting elements simultaneously when the amount of reflected light detected by the light detection means is lower than a predetermined value.

Furthermore, the invention according to claim 8 is the invention according to any one of claims 1 to 4,
The photosensor is a contact type line sensor,
The light emitting means is a light emitting element array in which a plurality of light emitting elements are arranged in a line,
The light detecting means is a light receiving element array in which a plurality of light receiving elements are arranged in a line.

Furthermore, the invention according to claim 9 is the invention according to claim 8,
A lighting start signal output means for outputting a lighting start signal for instructing lighting start to the light emitting element array;
Transmission start signal output means for outputting a transmission start signal for instructing to start transmission of the detection signal after a predetermined time has elapsed from the output of the lighting start signal to the light receiving element array;
A determination start signal output means for outputting a determination start signal for instructing the determination means to start the determination of the color and / or density of the irradiated medium;
The determination start signal output means outputs the determination start signal after the transmission start signal is output.

Furthermore, the invention of claim 10 is the invention of claim 9,
When the amount of drive current supplied to the light emitting means is controlled by the PWM method, the frequency of the signal related to lighting of the light emitting element array is higher than the frequency of the transmission start signal.

Furthermore, the invention according to claim 11 is the invention according to claim 9 or 10,
The light emitting means is a light emitting element array group in which a plurality of the light emitting element arrays are arranged in parallel,
The control means is characterized in that the plurality of arranged light emitting element arrays are turned on alternately or at a predetermined timing so that the lighting times of the respective light emitting element arrays are equal.

Furthermore, the invention of claim 12 is the invention of claim 11,
The control means turns on the plurality of LED arrays simultaneously when the amount of reflected light detected by the light receiving element array is lower than a predetermined value.

Furthermore, the invention described in claim 13 is the invention described in any one of claims 1 to 12,
The light emission color of the light emitting means is white.

In order to solve the above problem, the invention according to claim 14 provides:
The light quantity control device according to any one of claims 1 to 13,
Image forming means for forming an image on a recording medium;
An image forming apparatus comprising:
The irradiated medium irradiated by the light emitting means of the light quantity control device is the recording medium.

  According to the first aspect of the present invention, by supplying a driving current amount corresponding to the color and / or density of the irradiated medium to the light emitting means, the driving current suitable for the color and / or density of the irradiated medium. Since the amount of light emitted from the light emitting means can be reduced, the life of the light emitting means and the light detecting means can be extended, and the life of the photosensor itself can be extended. be able to.

  According to the second aspect of the present invention, the amount of light from the light emitting means can be increased, and the reflected light detected by the light detecting means becomes clear, so that the color and / or density of the irradiated medium can be ensured. Can be determined.

  According to the third aspect of the present invention, the amount of drive current supplied to the light emitting means can be controlled by the analog voltage control method.

  According to the fourth aspect of the present invention, the amount of drive current supplied to the light emitting means can be controlled by the PWM method that modulates the pulse width of the signal related to the lighting of the light emitting means.

  According to the fifth aspect of the present invention, it is possible to determine the color and / or density of the irradiated medium in a state where the lighting of the light emitting means is stable.

  According to the sixth aspect of the present invention, the life of the photosensor can be extended by lighting a plurality of light emitting elements alternately or at predetermined timing so that the lighting times of the respective elements are equal.

  According to the seventh aspect of the present invention, when the amount of reflected light is lower than a predetermined value, the amount of light can be increased. Thereby, since the reflected light detected by the light detection detection means becomes clear, it is possible to reliably determine the color and / or density of the irradiated medium.

  According to the invention described in claim 8, a contact type line sensor can be used as the photosensor.

  According to the ninth aspect of the present invention, the color and / or density of the irradiated medium can be determined while the lighting of the light emitting element array is stable.

  According to the tenth aspect of the present invention, since the frequency of the signal related to lighting of the light emitting element array is higher than the frequency of the transmission start signal, the amount of drive current supplied to the light emitting means is determined from the transmission timing of the light detection signal. It can be precisely controlled.

  According to the eleventh aspect of the present invention, the life of the photosensor can be extended by lighting a plurality of light emitting element arrays alternately or at predetermined timing so that the lighting times of the respective light emitting element arrays are equal. .

  According to the twelfth aspect of the present invention, when the amount of reflected light is lower than a predetermined value, the amount of light can be increased. Thereby, since the reflected light detected by the photodetection detection array becomes clear, it is possible to reliably determine the color and / or density of the irradiated medium.

  According to the thirteenth aspect of the invention, since the emission color of the light emitting means is white, the color and density of the recording medium can be reliably determined.

  According to the fourteenth aspect of the present invention, the light quantity control device according to any one of the first to thirteenth aspects can be applied to an image forming apparatus.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples.

<First Embodiment>
FIG. 1 schematically shows a configuration of an image forming apparatus 100 according to the first embodiment. The image forming apparatus 100 is, for example, a copying machine, a printer, a facsimile machine, a multifunction machine having these functions, and the like, and forms an image on a recording medium P such as paper by an electrophotographic method.

  As shown in FIG. 1, the image forming apparatus 100 includes a document feeding unit 1, a scanner unit 2, a printer unit 3, a supply unit 5, a conveying unit 6, and the like.

  The document feeder 1 includes a document feeder 11 and a document transport mechanism (not shown). The document O placed on the document feeder 11 is transported to the scanner unit 2 one by one by the document transport mechanism. To do.

  The scanner unit 2 includes a CCD (Charge Coupled Device) 22 and a light source 23 below a transparent contact glass 21, and the CCD 22 and the like are driven and controlled by a scanner control unit (not shown), and the document placed on the contact glass 21. O image data is read. Specifically, the original O is scanned by illumination from the light source 23, and the reflected light is imaged by the CCD 22 and subjected to photoelectric conversion to generate image data, which is output to the overall control unit 43 described later.

  Here, the image read by the scanner unit 2 includes not only image data such as graphics and photographs but also text data such as characters and symbols. The user can directly place the document O on the contact glass 21 in addition to feeding the document O from the document feeder 1.

  The printer unit 3 includes a registration roller 32, a position detection unit 33, a charging unit 34, an LD unit 35, a developing unit 36, a transfer unit 37, a fixing unit 38, and a cleaning unit 39 around a photosensitive drum 31 that is rotatably provided. Etc.

  The registration roller 32 is rotationally controlled by a driving unit (not shown) and transports the recording medium P transported by the transport unit 6 to the photosensitive drum 31 and corrects slip and paper bending in the sub-scanning direction.

  The position detection unit 33 is provided on the upstream side in the rotation direction of the photosensitive drum 31, detects a shift of the recording medium P in the main scanning direction, and outputs this shift detection signal to a printer control unit 42 described later.

  The charging unit 34 performs corona discharge on the surface of the photosensitive drum 31 to uniformly charge the surface of the photosensitive drum 31.

  An LD unit 35 having an LD (Laser Diode) light source in the main scanning direction of the photosensitive drum 31 is provided downstream of the charging unit 34 in the rotation direction of the photosensitive drum 31. By performing image exposure on the surface of the drum 31 based on the image signal, the charge on the surface of the exposed photosensitive drum 31 is attenuated and extinguished to form an electrostatic latent image. The LD unit 35 has a drive circuit (not shown), and the drive circuit is turned on / off by being driven and controlled by an overall control unit 43 described later.

  The developing unit 36 is provided on the downstream side of the LD unit 35 in the rotation direction of the photosensitive drum 31. By the developing unit 36, toner charged to the same polarity as the photosensitive drum 31 is converted into an electrostatic latent image on the surface of the photosensitive drum 31. To be attached.

  The transfer unit 37 is provided downstream of the developing unit 36 in the rotation direction of the photosensitive drum 31, and a conveyance path 60 c through which the recording medium P is conveyed is provided between the transfer unit 37 and the photosensitive drum 31. ing. The transfer unit 37 charges the recording medium P in a state of being pressed against the photosensitive drum 31, thereby attracting the toner to the recording medium P to transfer the toner image and discharging the charged recording medium P. The recording medium P is separated from the photosensitive drum 31.

  The fixing unit 38 is provided on the downstream side of the conveyance path of the recording medium P of the transfer unit 37, and the toner melted by heat is fixed to the recording medium P by the fixing unit 38, and the toner image is applied to the recording medium P. It is fixed.

  The cleaning unit 39 is provided downstream of the transfer unit 37 in the rotation direction of the photosensitive drum 31, and is pressed against the surface of the photosensitive drum 31 to remove and clean residual toner.

  The supply unit 5 includes a plurality of paper feed trays 51 and manual feed trays 52 in which the recording medium P is accommodated or placed. The recording media P accommodated or placed in the paper feed tray 51 and the manual feed tray 52 are respectively supplied to the printer unit 3 through the transport path 60a. Although FIG. 1 shows two paper feed trays 51 arranged one above the other below the printer unit 3, the number and arrangement of the paper feed trays 51 are not limited to this. The manual feed tray 52 is provided on the other side of the image forming apparatus 100. Similarly, a large capacity paper feed tray can be provided on the other side.

  The transport means 6 includes transport paths 60a, 60b, 60c, 60d, transport rollers (not shown), and the like. The recording medium P is transported from the supply unit 5 to each part in the printer unit 3 along the transport paths 60a, 60b, and 60c, and the recording medium P on which an image is formed from the printer unit 3 along the transport path 60d is discharged. It is discharged to the tray 53.

Next, the position detection unit 33 of the printer unit 3 will be described.
FIG. 2 is a perspective view illustrating a schematic configuration of the photosensitive drum 31, the registration roller 32, and the position detection unit 33 described above.

  As shown in the figure, the position detection unit 33 is provided between the photosensitive drum 31 and the registration roller 32 on the conveyance path of the recording medium P. The position detection unit 33 includes a tip detection sensor 331, an end detection sensor 332, and the like. The leading edge detection sensor 331 and the edge detection sensor 332 may be provided on the same side of the recording medium P, or may be provided on both sides so as to sandwich the recording medium P. The tip detection sensor 331 is more preferably provided upstream of the position detection unit 33.

  The leading edge detection sensor 331 is a reflection type photosensor or the like, and detects the leading edge and the trailing edge of the recording medium P conveyed on the conveyance path by driving the registration roller 32, and sends the detection signal to a driving unit 41 described later. Output.

  The end detection sensor 332 includes a light emitting unit 332a configured by an LED array group in which a plurality of LEDs (Light Emitting Diodes) arranged in a line are arranged in parallel in the sub-scanning direction; A contact type line sensor including a light receiving unit 332b in which a plurality of light receiving elements such as phototransistors are arranged in a line. The light receiving unit 332b detects reflected light from the recording medium P of the light emitted from the light emitting unit 332a, and outputs this detection signal to the drive unit 41 described later. Note that the number of LED arrays included in the light emitting unit 332a may be one, and the light emission color of the light emitting unit 332a is preferably white. In addition, the number of LED arrays included in the LED array group or the number of LEDs included in the LED array is arbitrary.

  FIG. 3 is a diagram illustrating a control system (hereinafter referred to as a position control system 40) according to the position detection unit 33. The position control system 40 includes a drive unit 41, a printer control unit 42, an overall control unit 43, and the like.

  The drive unit 41 supplies a drive current supplied from a power source (not shown) to the end detection sensor 332 to control ON / OFF of the light emitting unit 332a and to control driving of the end detection sensor 332 By generating various control signals (CLK, SI, LED_CONT1, LED_CONT2) and outputting them to the end detection sensor 332, the operation of the end detection sensor 332 is controlled.

  Of the control signals input from the drive unit 41 to the end detection sensor 332, the CLK signal is a sensor drive clock (for example, about 500 kHz to 1000 kHz) for driving the light receiving unit 332b of the end detection sensor 332. The edge detection sensor 332 is driven and the passing position of the recording medium P is measured based on the CLK signal. The SI signal is a signal for instructing the output timing of the VIDEO signal, and is output at predetermined time (clock) intervals in synchronization with the CLK signal. The light receiving unit 332b detects the end of the recording medium P with reference to the rising edge of the SI signal, and outputs a VIDEO signal as the detection signal.

  The LED_CONT1 signal and the LED_CONT2 signal are signals for individually ON / OFF control of each LED array included in the light emitting unit 332a, and the LED_CONTn corresponding to the number n (n ≧ 1) of the LED arrays one to one. A signal (n is the number of LED arrays) is generated and input to each LED array. That is, in the example of FIG. 3, it means that two LED arrays are arranged. In addition, when a plurality of LED arrays are arranged in the light emitting unit 332a, each LED array is turned on as a standard lighting state so that the LED arrays are alternately or at the same timing with the lighting times of the LED arrays being equal. / OFF control shall be performed. In addition, the drive unit 41 maximizes the amount of drive current supplied to the light emitting unit 332a during determination of the color and / or density of the recording medium P in a light amount control process (see FIG. 5) described later.

FIG. 4 is a block diagram showing the configuration of the drive unit 41.
The sample and hold circuit 411 samples and holds the VIDEO signal input from the light receiving unit 332 b in synchronization with the CLK signal, and outputs the sampled and held signal to the amplifier circuit 412. The amplifier circuit 412 amplifies the hold result input from the sample hold circuit 411 and outputs it to the comparator 413. The comparator 413 compares the value of the signal amplified by the amplifier circuit 412 with a predetermined value, counts the number of clocks of the CLK signal when the result is in a predetermined state, and uses the counted result as a deviation detection signal. The data is output to the printer control unit 42. The signal amplified by the amplifier circuit 412 is input to the A / D conversion circuit 414. The A / D conversion circuit 414 A / D converts the signal amplified by the amplification circuit 412 a predetermined number of times, and then outputs the signal after the A / D conversion to the averaging circuit 415. The averaging circuit 415 averages the signals after A / D conversion, and outputs the result (hereinafter referred to as an optical level signal) to the drive current control circuit 416.

  The drive current control circuit 416 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The drive current control circuit 416 controls the operation of the drive unit 41 in an integrated manner, and also detects an end detection sensor 332. Various control signals for controlling the driving of the sensor are generated and output to the end detection sensor 332. Specifically, the various control signals (CLK, SI, LED_CONT1, LED_CONT2) described above are output to the end detection sensor 332.

When the tip detection signal is input from the tip detection sensor 331, the drive current control circuit 416 turns on the light emitting unit 332a by outputting an LED_CONT signal based on this signal. The drive current control circuit 416 outputs an SI signal, which will be described later, to instruct the start of transmission of the VIDEO signal detected by the light receiving unit 332b to the light receiving unit 332b after a predetermined time has elapsed from the output of the LED_CONT signal. Determination of the color and / or density of the recording medium P is started based on the VIDEO signal transmitted from the light receiving unit 332b by the SI signal. In particular,
Based on the value of the light level signal averaged by the averaging circuit 415, the color and / or density of the recording medium P is determined.

  Further, the drive current control circuit 416 reads the drive current value corresponding to the determination result of the color and / or density of the recording medium P from the light amount control table stored in the ROM or other storage means, and this read drive Based on the current value, the drive current amount supplied to the light emitting unit 332a is specified. Then, by outputting a signal instructing the supply of the drive current amount to the drive current supply circuit 417, the drive current amount supplied to the light emitting unit 332a is controlled. Here, it is assumed that the light amount control table stores the color and / or density of the recording medium P in association with the drive current value corresponding to the color and / or density.

  The drive current supply circuit 417 supplies the drive power amount corresponding to the instruction signal input from the drive current control circuit 416 from the power source (not shown) to the light emitting unit 332a. Thereby, the light quantity of the light emission part 332a is controlled.

  The drive current control method is not particularly limited, and a known technique can be applied. For example, an analog voltage control method for controlling the amount of drive current supplied by an external analog voltage signal may be used. In this case, a digital signal indicating the amount of drive current output from the drive current control circuit 416 is converted into an analog voltage signal. It is assumed that a D / A conversion circuit or the like is provided. Further, a PWM (Pulse Width Modulation) method for controlling the lighting time by modulating the pulse width related to lighting of the light emitting unit 332a may be used. In this case, the pulse width (frequency) related to lighting of the light emitting unit 332a is set to SI. It is preferably larger than the signal output interval (frequency).

  Returning to FIG. 3, the printer control unit 42 includes a CPU, a ROM, a RAM, and the like, reads various setting values and system programs stored in a storage unit such as a ROM, and executes various processes. Specifically, based on the deviation detection signal input from the drive unit 41, the deviation in the main scanning direction of the recording medium P on the conveyance path is determined, and a signal indicating the determination result is sent to the overall control unit 43. Output.

  The overall control unit 43 includes a CPU, a ROM, a RAM, and the like, and comprehensively controls the entire image forming apparatus 100 by reading and executing various setting values and system programs stored in a storage unit such as a ROM. To do. Further, the overall control unit 43 corrects the position where the LD unit 35 forms an electrostatic latent image, based on a signal indicating the result of displacement in the main scanning direction of the recording medium P input from the printer control unit 42.

Hereinafter, the light amount control process in the first embodiment will be described with reference to FIGS. 5 and 6.
FIG. 5 is a flowchart showing the flow of the light amount control process. Each process in FIG. 5 indicates a process executed by the drive current control circuit 416.

  First, when a tip detection signal detected by the tip detection sensor 331 is input (step S11), the amount of drive current supplied to the light emitting unit 332a is maximized (step S12), and then detected by the light receiving unit 332b. The detected signal (VIDEO signal) is input (step S13).

  Next, an optical level signal is generated by the A / D conversion circuit 414, the averaging circuit 415, and the like based on the detection signal input in step S13 (step S14). Here, it is determined whether or not the value of the light level signal is equal to or greater than a predetermined value. If it is determined that the value is less than the predetermined value (step S15; No), a plurality of LEDs included in the light emitting unit 332a. The array is turned on at the same time (step S16), and the process returns to step S13 again. Note that the number of LED arrays that are simultaneously turned on is not particularly limited, but the number of LED arrays that are turned on each time the process returns to step S13 may be gradually increased.

  On the other hand, if it is determined in step S15 that the value of the light level signal is greater than or equal to a predetermined value (step S15; Yes), the color and / or density of the recording medium P based on the value of the light level signal. Is determined (step S17), and a drive current value corresponding to the determination result is specified from the light amount control table (step S18). Then, the amount of drive current supplied to the light emitting unit 332a is controlled based on the specified drive current value (step S19).

  Subsequently, a deviation detection signal is output to the printer control unit 42 (step S20). As a result, the printer control unit 42 determines the deviation of the recording medium P in the main scanning direction on the conveyance path, and the overall control unit 43 determines whether the LD unit 35 performs electrostatic charging based on the determination result from the printer control unit 42. The position where the latent image is formed is corrected.

  Next, based on the detection signal input from the leading end detection sensor 331, it is determined whether or not the trailing end of the recording medium P has been detected. If it is determined that the recording medium P has been detected (step S21; Yes), the light emitting unit 332a is turned off (step S22), and this process ends.

FIG. 6 is a time chart illustrating an example of a signal waveform pattern input / output to / from the drive unit 41 during the operation of the end detection sensor 332.
As shown in the figure, when the leading edge of the recording medium P is detected by the leading edge detection sensor 331 and this leading edge detection signal is input (rise of A in the figure), the supply of drive current to the light emitting unit 332a is maximized. (Timing B in the figure). After the tip detection signal is input, the optical level is detected by the A / D conversion circuit 414, the averaging circuit 415, and the like based on the VIDEO signal input from the light receiving unit 332b with the first SI signal as a reference (rising edge of C in the figure). A signal is generated.

  Next, the color and / or density of the recording medium P is determined based on the value of the light level signal, and the corresponding drive current value is read from the light amount control table, thereby controlling the supply amount of the drive current of the light emitting unit 332a. (Timing D in the figure), and in the state of this drive current supply amount, it is counted by the comparator 413 based on the VIDEO signal input from the light receiving unit 332b with the next SI signal as a reference (rise of E in the figure). The number of clocks of the CLK signal is output to the printer control unit 42 as a shift detection signal.

  As described above, according to the first embodiment, the driving current amount corresponding to the color and / or density of the recording medium P is supplied to the light emitting unit 332a, whereby the color and / or density of the recording medium P is supplied. In addition to being able to supply a drive current amount suitable for the light emitting portion 332a, it is possible to reduce the amount of light emitted from the light emitting portion 332a, so that the lifetime of the light emitting portion 332a and the light receiving portion 332b can be extended. The lifetime of the sensor itself can be extended. In particular, in the case of a contact type line sensor having a high unit price, the time required for replacement can be extended, and thus the cost of the contact type line sensor can be suppressed.

  In the first embodiment, the light emitting unit 332a is composed of a plurality of LED array groups arranged in parallel in the sub-scanning direction. However, other light emitting means (for example, a linear shape such as a xenon lamp) A plurality of light sources) may be arranged in parallel in the sub-scanning direction.

<Second Embodiment>
Next, a second embodiment of the image forming apparatus 100 will be described. In the second embodiment, a case where the light amount control device of the present invention is applied to the tip detection sensor 331 will be described. For simplification of description, the same elements as those in the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted as appropriate.

First, the tip detection sensor 331 of the second embodiment will be described with reference to FIGS. 2 and 7.
The tip detection sensor 331 includes a reflective photosensor including a plurality of light emitting units 331a configured by light emitting elements such as LEDs and one light receiving unit 331b configured by a light receiving element such as a CCD. The light receiving unit 331b detects reflected light from the recording medium P of the light emitted from the light emitting unit 331a, and outputs this detection signal to the driving unit 41. The light emission color of the light emitting portion 331a is preferably white. In addition, in FIG. 7, although the case where the four light emission parts 331a are provided is illustrated, the number shall not be restricted to this. Moreover, although the case where the one light-receiving part 331b is provided is illustrated, the number shall not be restricted to this.

  FIG. 7 is a diagram illustrating the position control system 40 of the position detection unit 33. The position control system 40 includes a drive unit 41, a printer control unit 42, an overall control unit 43, and the like.

  The drive unit 41 controls the ON / OFF of the light emitting unit 331a by supplying a drive current supplied from a power source (not shown) to the end detection sensor 332. When a plurality of light emitting units 331a are provided, the light emitting units 331a are turned on / off so that the lighting times of the light emitting units 331a are equal to each other or at predetermined timings as a standard lighting state. It is assumed that OFF control is performed. Further, the drive unit 41 maximizes the amount of drive current supplied to the light emitting unit 331a during determination of the color and / or density of the recording medium P in a light amount control process (see FIG. 8) described later.

  As shown in the figure, the drive unit 41 includes an amplifier circuit 412, an A / D conversion circuit 414, an averaging circuit 415, a drive current control circuit 416, and the like.

  The amplifier circuit 412 amplifies the detection signal input from the light receiving unit 331b and outputs the amplified detection signal to the A / D conversion circuit 414. The A / D conversion circuit 414 A / D converts the signal amplified by the amplification circuit 412 a predetermined number of times, and then outputs the signal after the A / D conversion to the averaging circuit 415. Then, the averaging circuit 415 averages the signals after A / D conversion, and outputs the resulting optical level signal to the drive current control circuit 416.

  The drive current control circuit 416 turns on each light emitting unit 331a by outputting a signal for ON / OFF control of the light emitting unit 331a. The drive current control circuit 416 determines the color and / or density of the recording medium P based on the value of the light level signal averaged by the averaging circuit 415. Further, the drive current control circuit 416 reads the drive current value corresponding to the determination result of the color and / or density of the recording medium P from the light amount control table stored in the ROM or other storage means, and this read drive Based on the current value, the drive current amount supplied to the light emitting unit 332a is specified. Then, by outputting a signal instructing the supply of the drive current amount to the drive current supply circuit 417, the drive current amount supplied to the light emitting unit 332a is controlled. Here, it is assumed that the light amount control table stores the color and / or density of the recording medium P in association with the drive current value corresponding to the color and / or density.

  The drive current supply circuit 417 supplies the drive power amount corresponding to the instruction signal input from the drive current control circuit 416 from the power source (not shown) to the light emitting unit 332a. Thereby, the light quantity of the light emission part 332a is controlled.

  The drive current control method is not particularly limited, and a known technique can be applied. For example, an analog voltage control method for controlling the amount of drive current supplied by an external analog voltage signal may be used. In this case, a digital signal indicating the amount of drive current output from the drive current control circuit 416 is converted into an analog voltage signal. It is assumed that a D / A conversion circuit or the like is provided. Moreover, it is good also as a PWM system which controls lighting time by modulating the pulse width concerning lighting of the light emission part 331a.

  Next, the flow of light amount control processing in the second embodiment will be described with reference to the flowchart of FIG. Each process in FIG. 8 shows a process executed by the drive current control circuit 416. As a premise of this process, it is assumed that the amount of drive current supplied to the light emitting unit 331a at the start of the process is the maximum.

  First, when a tip detection signal detected by the light receiving unit 331b of the tip detection sensor 331 is input (step S31), the optical level is detected by the A / D conversion circuit 414, the averaging circuit 415, and the like based on the tip detection signal. A signal is generated (step S32). Here, it is determined whether or not the value of the light level signal is equal to or greater than a predetermined value. If it is determined that the value is less than the predetermined value (step S33; No), the plurality of light emitting units 331a are simultaneously turned on. (Step S34), the process returns to step S31 again. Although the number of light emitting units 331a that are simultaneously turned on is not particularly limited, the number of light emitting units 331a that are turned on every time the process returns to step S31 may be gradually increased.

    On the other hand, if it is determined in step S33 that the value of the light level signal is greater than or equal to a predetermined value (step S33; Yes), the color and / or density of the recording medium P based on the value of the light level signal. Is determined (step S35), and a drive current value corresponding to the determination result is specified from the light amount control table (step S36). Then, the amount of drive current supplied to the light emitting unit 331a is controlled based on the identified drive current value (step S37).

  Subsequently, based on the detection signal input from the leading edge detection sensor 331, it is determined whether or not the trailing edge of the recording medium P has been detected. If it is determined that it has been detected (step S38; Yes), the light emission is performed. After the drive current supply amount to the unit 331a is set to the maximum value (step S39), this process ends. When another sensor capable of detecting the recording medium P is provided upstream of the leading edge detection sensor 331, the light emitting unit 331a is detected after the trailing edge of the recording medium P is detected by the leading edge detection sensor 331. The drive current supply amount to the light emitting unit 331a may be set to the maximum value at a timing calculated from the leading edge detection signal of the recording medium P output from another sensor.

  As described above, according to the second embodiment, the driving current amount corresponding to the color and / or density of the recording medium P is supplied to the light emitting unit 331a, whereby the color and / or density of the recording medium P is supplied. In addition to being able to supply a drive current amount suitable for the light emitting portion 331a and suppressing the amount of light emitted from the light emitting portion 331a, the lifetime of the light emitting portion 331a and the light receiving portion 331b can be extended. The lifetime of the sensor itself can be extended.

  The detailed configuration and detailed operation of the image forming apparatus 100 in the above embodiment can be changed as appropriate without departing from the spirit of the present invention.

  For example, in the present embodiment, the drive unit 41 includes the drive current control circuit 416 related to the light amount control of the light emitting unit 331a or the light emitting unit 332a. It is good also as an aspect with which the site | part was equipped.

  In the present embodiment, the light amount control device of the present invention is applied to the position detection unit 33 (edge detection sensor 332) that detects the deviation of the recording medium P in the main scanning direction. It is good also as applying not only to the site | part provided for another use.

1 is a diagram schematically illustrating a configuration of an image forming apparatus. It is a perspective view which shows schematic structure of a photosensitive drum, a registration roller, and a position detection part. It is a block diagram which shows the structure of the position control system which controls a position detection part. It is a block diagram which shows the structure of the drive part in 1st Embodiment. It is a flowchart which shows the flow of the light quantity control process in 1st Embodiment. It is a time chart which shows an example of the signal waveform pattern input-output to a drive part at the time of operation | movement of an edge part detection sensor. It is a block diagram which shows the structure of the drive part in 2nd Embodiment. It is a flowchart which shows the flow of the light quantity control process in 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 1 Document feed part 11 Document feed stand 2 Scanner part 21 Contact glass 3 Printer part 31 Photosensitive drum 32 Registration roller 33 Position detection part 331 Tip detection sensor 331a Light emission part 331b Light reception part 332 Edge detection sensor 332a Light emission Unit 332b light receiving unit 34 charging unit 35 LD unit 36 developing unit 37 transfer unit 38 fixing unit 39 cleaning unit 40 position control system 41 drive unit 411 sample hold circuit 412 amplification circuit 413 comparator 414 A / D conversion circuit 415 averaging circuit 416 drive Current control circuit 417 Drive current supply circuit 42 Printer control unit 43 Overall control unit 5 Supply unit 51 Paper feed tray 52 Tray 53 Paper discharge tray 6 Transport means 60a Transport path 60b Transport path 60c Transport path 60d Transport path

Claims (14)

A photosensor having a light emitting means for emitting light by a drive current supplied from a power source and a light detecting means for detecting reflected light from the irradiated medium of light emitted from the light emitting means;
Determination means for determining the color and / or density of the irradiated medium based on a detection signal from the light detection means;
Control means for controlling the amount of drive current supplied from the power source to the light emitting means based on the determination result of the determining means;
A light quantity control device comprising:   2. The light quantity control device according to claim 1, wherein the control unit maximizes the supplied drive current amount during determination of the color and / or density of the irradiated medium by the determination unit.   The light quantity control device according to claim 1, wherein the control unit controls the supplied drive current amount by an analog voltage control method.   The said control means controls the said drive current amount supplied by the PWM system which modulates the pulse width of the signal concerning lighting of the said light emission means, The Claim 1 characterized by the above-mentioned. Light quantity control device. A lighting start signal output means for outputting a lighting start signal instructing the lighting start to the light emitting means;
A determination start signal output means for outputting a determination start signal for instructing the determination means to start the determination of the color and / or density of the irradiated medium;
The light quantity control device according to any one of claims 1 to 4, wherein the determination start signal output means outputs the determination start signal after the light emitting means is turned on by the lighting start signal. . The light emitting means has a plurality of light emitting elements,
The light control device according to any one of claims 1 to 5, wherein the control means turns on the plurality of light emitting elements alternately or at a predetermined timing so that lighting times of the respective elements are equal. .   The light quantity control device according to claim 6, wherein the control means turns on the plurality of light emitting elements simultaneously when the light quantity of the reflected light detected by the light detection means is lower than a predetermined value. The photosensor is a contact type line sensor,
The light emitting means is a light emitting element array in which a plurality of light emitting elements are arranged in a line,
5. The light quantity control device according to claim 1, wherein the light detection unit is a light receiving element array in which a plurality of light receiving elements are arranged in a line. A lighting start signal output means for outputting a lighting start signal for instructing lighting start to the light emitting element array;
Transmission start signal output means for outputting a transmission start signal for instructing to start transmission of the detection signal after a predetermined time has elapsed from the output of the lighting start signal to the light receiving element array;
A determination start signal output means for outputting a determination start signal for instructing the determination means to start the determination of the color and / or density of the irradiated medium;
9. The light quantity control device according to claim 8, wherein the determination start signal output unit outputs the determination start signal after the transmission start signal is output.   The frequency of a signal related to lighting of the light emitting element array is higher than the frequency of the transmission start signal when the amount of drive current supplied to the light emitting means is controlled by the PWM method. 9. The light quantity control device according to 9. The light emitting means is a light emitting element array group in which a plurality of the light emitting element arrays are arranged in parallel,
The light quantity according to claim 9 or 10, wherein the control means turns on the plurality of arranged light emitting element arrays alternately or at a predetermined timing so that the lighting times of the respective light emitting element arrays are equal. Control device.   12. The light quantity control device according to claim 11, wherein the control means turns on the plurality of LED arrays simultaneously when the quantity of reflected light detected by the light receiving element array is lower than a predetermined value.   The light emission control device according to any one of claims 1 to 12, wherein a light emission color of the light emitting means is white. The light quantity control device according to any one of claims 1 to 13,
Image forming means for forming an image on a recording medium;
An image forming apparatus comprising:
An image forming apparatus, wherein the irradiated medium irradiated by the light emitting means of the light quantity control device is the recording medium.

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