JP5313180B2 - Laser fixing device - Google Patents

Description

  The present invention relates to a laser fixing apparatus that fixes a toner image on a recording paper by irradiating a laser beam, and more particularly to a configuration of a laser array in which laser light source elements are arranged.

  An electrophotographic image forming apparatus (for example, a printer) includes a fixing device that fixes an unfixed toner image formed on a sheet by heat melting the sheet. As an example of the fixing device, there is known an electrophotographic image forming apparatus that irradiates a toner image with light and fixes the toner image on a recording sheet in a non-contact manner. Since this fixing method is heated in a non-contact manner, it has a feature that warm-up is unnecessary as compared with a roller fixing method that is a conventional contact heating method.

  As an image forming apparatus for fixing in a non-contact manner with light as described above, a fixing apparatus for fixing toner using laser power as disclosed in Patent Document 1 has been proposed.

  According to Patent Document 1, a plurality of low-power semiconductor lasers are used, and a plurality of laser light sources and each laser light emitted from the light sources are focused on a toner image in the same region, thereby compensating for power shortage. It describes that the toner is melted and fixed. It is described that the whole apparatus can be simplified because it is possible to use an inexpensive semiconductor laser with a low output.

  Patent Document 2 proposes a method of driving a thermal head that is divided into blocks every 64 blocks as a multi-gradation data input method (64 gradations) to a line head, although it is not a laser fixing device. . Therefore, it is also conceivable to simplify the drive circuit by dividing the laser and driving it for each block.

JP-A-2005-55516 JP-A-8-300711

  In Patent Document 1, it is only necessary to drive individual laser elements, and it is necessary to prepare a drive circuit for each individual laser element in a parallel circuit, which is expensive and increases the capacity of the power source. In addition, since individual lasers have manufacturing variations, stable irradiation may not be possible due to this characteristic difference.

  Further, from the contents of Patent Document 2, it is conceivable that the laser element is driven by a block. However, if the block division is not performed in consideration of the paper size, the portion that cannot be fixed in the unit of the block eventually becomes the individual laser element. It has to be driven and has the same problem as that of Patent Document 1.

  The present invention has been made in view of the above problems, and even if the paper size changes, the laser element can be divided and controlled by driving, and the characteristic difference between the individual laser light source elements can be absorbed. An object of the present invention is to provide a laser fixing device capable of stable irradiation.

  The present invention provides a laser fixing apparatus for fixing an unfixed toner image on a conveyed recording paper by melting the toner by irradiation of a laser beam to form an array block by arranging a plurality of laser elements in series. It is characterized by comprising laser generating means in which a plurality of blocks are arranged in series in the conveyance width direction of the recording paper, and fixing control means for performing drive control of laser irradiation in units of the array blocks.

  As a result, it is not necessary to prepare a drive circuit for each laser element, and the capacity of the entire power supply can be reduced, so that the cost can be reduced.

  Further, the laser generating means in the present invention is characterized in that a plurality of blocks corresponding to the length in the transport width direction of each paper size to be used are provided and arranged in series.

  As a result, it is not necessary to prepare a drive circuit for each laser element according to the paper size, and the circuit can be simplified because the control is performed in units of blocks, and the cost can be reduced.

  In the present invention, the paper size is an A system, a B system, or an inch system, and the laser generator has the array block arranged corresponding to the width of the paper size of each system. .

  Thus, by standardizing the array in accordance with the paper size, mass production can be achieved, and cost reduction can be expected.

  The laser fixing device according to the present invention is provided in the vicinity of the array block, detecting means for detecting the intensity of the irradiated laser light, and storage means for storing variation data of output characteristics of individual laser elements in advance. And feedback means for performing feedback control by obtaining a laser output control value for correcting the variation based on the detection value by the detection unit and the variation value stored in the storage unit.

  As a result, stable laser irradiation can be obtained by absorbing the inherent laser output variation of each element, so that an optimum fixing characteristic and an image without deterioration can be obtained.

  The feedback control in the present invention is current value control.

  As a result, since the current value of the IV (current-voltage) characteristic of the laser element changes abruptly at a certain value when voltage control is performed, it is not preferable for control when the voltage value varies even slightly. By stably controlling the laser irradiation, it is possible to obtain an image having optimum fixing characteristics and no deterioration.

  In the present invention, the laser element is provided with a switching transistor, and the feedback means shifts the irradiation ON-OFF timing of each laser element by the switching transistor.

  As a result, it is possible to absorb variations in the characteristics of individual laser elements, and it is possible to obtain an image having optimum fixing characteristics and no deterioration by stably controlling laser irradiation.

  The laser elements in the present invention are all configured using the same output specifications.

  As a result, production can be facilitated by using the same standard, and cost reduction due to mass production can be expected. Also, manufacturing variations can be reduced.

  Further, the laser element according to the present invention is configured by combining elements having different outputs.

  As a result, even if the laser elements have different output standards, the difference in characteristics can be absorbed by providing a feedback circuit, so that excess inventory can be amortized and manufacturing costs can be expected to be reduced.

  The array block according to the present invention is modularized for each block, and is configured to be replaceable from a base member on which the array block is mounted.

  As a result, it is not only easy to replace the module at the time of trouble by modularization, but it is economical because only the failed module needs to be replaced without replacing the entire laser unit.

  According to the present invention, it is not necessary to prepare a drive circuit for each laser element, and the capacity of the entire power supply can be reduced, so that the cost can be reduced. Moreover, it is easy to absorb the difference in characteristics due to manufacturing variations of individual laser elements.

1 is a schematic view showing an internal structure of a dry electrophotographic color image forming apparatus. It is the figure seen from the paper conveyance direction of the laser fixing device. It is a schematic diagram of a transmission type sensor. It is the figure seen from the perpendicular | vertical direction with respect to the paper conveyance direction of a laser fixing apparatus. 2 is a control block diagram of the image forming apparatus. FIG. It is a block diagram which shows a laser fixing apparatus. It is a block diagram which shows the other Example of a laser fixing apparatus. It is the figure which showed the electric current-voltage characteristic of a laser element. It is the figure which showed the output-current characteristic of a laser element. It is a block diagram which shows the further another Example of a laser fixing apparatus. It is the figure which showed the drive timing of the laser element.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

An embodiment of the present invention will be described with reference to FIG.
FIG. 1 is a schematic diagram showing the internal structure of a dry electrophotographic color image forming apparatus.
This image forming apparatus forms a multicolor or single color image on a predetermined recording member (recording paper) based on, for example, image data transmitted from each terminal device on the network.

The image forming apparatus 1 includes a visible image forming unit 50 (50Y, 50M, 50C, and 50B), a recording paper transport unit 30, a fixing device 40, and a supply tray 20.
The image forming apparatus 1 includes four visible image forming units 50Y, 50M, 50C, and 50B arranged in parallel corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (B). Has been. That is, the visible image forming unit 50Y forms an image using yellow (Y) toner, and the visible image forming unit 50M forms an image using magenta (M) toner to form a visible image. The unit 50C forms an image using cyan (C) toner, and the visible image forming unit 50B forms an image using black (B) toner. A specific arrangement is a so-called tandem type in which four sets of visible image forming units 50 are arranged along a recording paper conveyance path connecting the supply tray 20 of the recording paper P and the fixing device 40.

  The visible image forming units 50 have substantially the same configuration, that is, the photosensitive drum 51, the charger 52, the laser beam irradiation means 53, the developing device 54, the transfer roller 55, and the cleaner unit 56, respectively. Are provided, and each color toner is multiplex-transferred onto the conveyed recording paper P.

  Here, the photosensitive drum 51 carries the image to be formed by rotating in the F direction. The charger 52 charges the surface of the photosensitive drum 51 uniformly to a predetermined potential. The laser beam irradiation unit 53 exposes the surface of the photosensitive drum 51 charged by the charger 52 according to the image data input to the image forming apparatus 1, and forms an electrostatic latent image on the surface of the photosensitive drum 51. To do. The developing unit 54 visualizes the electrostatic latent image formed on the surface of the photosensitive drum 51 with toner of each color. The transfer roller 55 is applied with a bias voltage having a polarity opposite to that of the toner, and transfers the formed toner image onto the recording paper P conveyed by the recording paper conveying means 30 described later. The cleaner unit 56 removes and collects the toner remaining on the surface of the photosensitive drum 51 after the development processing in the developing unit 54 and the transfer of the image formed on the photosensitive drum 51. The transfer of the toner image onto the recording paper P as described above is repeated four times for four colors.

  The recording paper conveying means 30 includes a driving roller 31, an idling roller 32, and a conveying belt 33. The recording paper P is moved in the Z direction so that a visible image forming unit 50 forms a toner image on the recording paper P. It is to be transported. The drive roller 31 and the idling roller 32 stretch the endless transport belt 33. The drive roller 31 is rotated by being controlled at a predetermined peripheral speed, thereby rotating the endless transport belt 33. Yes. The transport belt 33 generates static electricity on the outer surface, and transports the recording paper P while electrostatically attracting the recording paper P.

  In this way, the recording paper P is transferred to the conveying belt 33 while the toner image is transferred thereto, and then peeled off from the conveying belt 33 by the curvature of the driving roller 31 and conveyed to the fixing device 40.

  The laser fixing device 40 applies a suitable heat to the recording paper P, dissolves the toner, and fixes it to the recording paper P, thereby forming a robust image.

  Here, the fixing device 40 will be described in detail with reference to FIG. FIG. 2 is a view of the laser fixing device as viewed from the paper conveyance direction.

  The fixing device 40 includes a laser irradiation unit 100 that emits laser light and a recording paper transport device 110 that transports the recording paper P.

  The laser irradiation unit 100 includes a laser generation unit 101, a collimator lens 102, a condenser lens 103, and a transmission sensor 104. The laser light emitted from the laser generating means 101 is converted into parallel light by the collimating lens 102 and is condensed by the condensing lens 112 so as to be focused at the paper surface position. The optical path is indicated by a broken line.

  The recording paper conveyance device 110 includes two tension rollers 111 and 112 and a heat-resistant endless belt 113, and the recording paper P is conveyed on the belt 113. The two tension rollers 111 and 112 have shaft cores (not shown) connected to bearings (not shown), and the tension rollers 111 are connected to a drive unit (not shown) via gears (not shown).

  The recording paper conveyance belt 113 is made of a material in which a conductive member such as carbon is dispersed in a resin such as polycarbonate, vinylidene fluoride, polyamideimide, or polyimide (PI), and is connected to the inner surface of the recording paper conveyance belt 113. The surface (outer peripheral surface) of the recording paper conveying belt 113 is configured to electrostatically attract the recording paper P by applying a bias voltage by the power source 114. By electrostatically attracting the recording paper P to the recording paper transport belt 113, the recording paper transport belt 113 and the recording paper P are brought into close contact with each other, and the paper can be prevented from floating. By preventing the paper from floating, the transmissive sensor 104 can be brought close to the vicinity of the paper surface, thereby enabling faster detection.

  The transmission sensor 104 has a light emitting unit 105 on the front side and a light receiving unit 106 on the back side. At this time, the transmissive sensor 104 is disposed in a direction perpendicular to the paper conveyance direction, parallel to the paper surface, and outside the both ends of the paper. Light is emitted so that light passes through the vicinity of the paper surface outside the condensing region in the vicinity of the condensing region, and the light receiving unit 106 is disposed so as to receive the corresponding region.

  By disposing the transmissive sensor 104 so that the vicinity on the paper surface can be detected, if the paper burns and smoke is generated, the transmissive sensor 104 can instantaneously detect it and prevent spread of the flame. In addition, by installing in the vicinity of the paper, it is possible to instantaneously detect a jam when the paper is jammed.

  As the transmissive sensor, for example, LV-H300 manufactured by Keyence is known. This is a laser diode having a light emitting portion of 660 nm. The light receiving portion detects only this wavelength (660 nm), converts the detected light amount into a voltage, and outputs a signal. At this time, it is possible to read the change in transmittance on the sensor by reading the amount of change in voltage.

  FIG. 3 shows a schematic diagram of the transmissive sensor, (a) is a side view of the transmissive sensor, and (b) is a front view of the light receiving unit.

  The light-receiving surface of the light-receiving unit 106 is a surface perpendicular to the optical axis of the light emitted from the light-emitting unit 105, and the light-receiving surface 121 is provided with shielding members 122 on the side surfaces (four surfaces, top, bottom, left, and right). It arranges so that it may not detect except the light of. The shielding member 122 only needs to be configured to prevent light from entering from other than the optical axis direction. The shielding member 122 is coated on a metal member such as aluminum with a light absorption film or an antireflection film (for example, black body coating) that can absorb a wavelength (for example, 660 nm) detected by the light receiving unit 106. It is desirable to be attached.

  FIG. 4 shows a view of the laser fixing device 40 in FIG. 2 as viewed from the direction perpendicular to the paper conveyance direction. The laser generating means 101 includes n laser elements LD1 to LDn in the paper conveyance direction. A plurality of laser arrays are arranged in the direction perpendicular to the width of the recording paper conveyance belt 113 (laser array).

  For example, when the entire surface of the recording paper is irradiated with a single laser element, it is necessary to scan the laser light in a direction perpendicular to the recording paper transport direction (width direction of the recording paper transport belt 113) in addition to the recording paper P transport direction. In addition, since the fixing process takes time, a fixing failure may occur when the fixing speed of a high-speed machine or the like is high. In addition, scanning with laser light increases the complexity and cost of the fixing device.

  On the other hand, by arranging the laser elements in a line as described above in the direction perpendicular to the paper conveyance direction (width direction of the recording paper conveyance belt 113), it is not necessary to scan the laser in the direction perpendicular to the paper conveyance direction. The fixing device can be configured in a limited space, and can be fixed at high speed.

  The transmissive sensor 104 is disposed so that the light emitting unit 105 and the light receiving unit 106 coincide with the direction in which the lasers are arranged, and is disposed outside the arranged laser elements LD1 to LDn.

  FIG. 5 is a control block diagram of the image forming apparatus according to the present embodiment.

  The image forming apparatus 1 is, for example, a multifunction device including a scanner 201, a printer 202, and a peripheral device 203. The scanner 201 includes a reading unit 211 that reads a document image. The printer 202 converts the read document image into an appropriate electrical signal and generates image data, an image forming unit 213 that prints out the generated image data, and a laser beam irradiation of a fixing unit (not shown). A fixing control unit 214 that controls driving of the fixing unit and a control unit 215 that controls the entire printer 202 are provided. In addition, an input unit 216 and a display unit 217 which are operation units are provided across both the scanner 201 and the printer 202. The peripheral device 203 includes a peripheral device control unit 218 that controls a finisher, a sorter, and the like, which are post-processing devices.

  The control unit 215 transmits the print position information of the image information received from the image processing unit 212 (refers to a signal indicating which print position is to be printed for each page with respect to the print job) to the fixing control unit 214 to fix the image. The control unit 214 performs control to drive each laser fixing device 40 based on the print position information received from the control unit 215 to irradiate laser light. The control unit 215 determines that printing is started based on the print information, and controls the rotation of the belt by a second driving unit (not shown) of the paper transport device 110.

  FIG. 6 shows a block diagram of the laser fixing device.

  The laser generation means 101 includes a plurality of semiconductor lasers (laser elements) LD1, LD2, LD3,. The semiconductor lasers are arranged as described with reference to FIG. For example, LD1 to LD3 are blocked (laser array block BK1), and a switch 108 is provided so that "ON-OFF" irradiation drive can be performed for each block. N laser array blocks as a whole are prepared up to BKN blocks. In the figure, LD1 to LD3 are described as blocks. However, the present invention is not limited to this, and there is no problem even if the number is other than three according to the performance of the element to be used.

Further, the length of each block corresponds to the width of each used paper size in accordance with the irradiation capacity. For example, a postcard size when ON driving to BK1 and the other is OFF driving, a B5R size when ON driving to BK1 + BK2 and the other are OFF driving, and an ON driving to BK1 + BK2 + BK3 and the other are OFF driving. For example, A4R size.
Although not shown in the drawing, the same method is used even when inch-type paper is used.

  In this way, the fixing control unit 214 can control “ON-OFF” of laser irradiation in units of blocks by controlling the switch 108. Accordingly, since it is not necessary to prepare a drive circuit for each laser element in the parallel circuit, a simple drive circuit is sufficient and the capacity of the power source can be reduced. Also, by standardizing according to the paper size, there is an advantage that mass production can be achieved and cost reduction can be expected.

  FIG. 7 shows a block diagram of another embodiment of the laser fixing apparatus.

  Laser light 221 is emitted from the laser irradiation block BK1. A photodiode (detection means) 222 is provided in the vicinity of the laser generation means 101 and has a function of monitoring the intensity of the laser light 221. A feedback circuit 223 and a memory circuit 224 are connected to the photodiode 222, and further connected to the fixing control unit 214.

  There are manufacturing variations in individual laser elements, and strictly speaking, the characteristics of each laser element usually change slightly. The memory circuit 224 stores output variation values with respect to standard inputs of individual elements in advance. When a laser is irradiated on each block according to a control signal from the fixing control unit 214, the output of each laser element varies depending on the characteristics. Since the output variation value of each laser element is stored in the memory circuit 224, a control value for eliminating the variation of each laser element is obtained from the monitor value of the laser light from the block BK1, as shown in FIG. The current value is controlled by the feedback circuit 223.

The reason why the current value is controlled is shown in FIG. 8, and the IV (current-voltage) characteristics of the laser element are generally as shown in the graph. For example, voltage control is performed to obtain an output of 1 mW. Since the current value changes abruptly depending on the value, it is not preferable in controlling. Therefore, control is performed using the current value.
The relationship between the current value and the laser output is proportional as shown in FIG. 9, and current control is performed so as to keep the laser output constant based on this relationship.

  In FIG. 7, a photodiode 222 is arranged in the vicinity of BK1, and the laser output from this block is detected to perform feedback control. However, the present invention is not limited to this example, and may be provided near another block, may be located at another laser element, or may be provided in plural.

  FIG. 10 is a block diagram showing still another embodiment of the laser fixing device.

  Each of the laser elements LD1, LD2, LD3,..., LDn of the laser generating means 101a is provided with switching transistors Ch1, Ch2,. Of course, the laser elements LD1, LD2, LD3,..., LDn are divided into blocks (BK1 to BKN), respectively. As described above, there are manufacturing variations in individual laser elements, and strictly speaking, the characteristics are usually slightly changed. In order to absorb these characteristics, as shown in FIG. 11, the switching transistors Ch1, Ch2,..., Chn are configured to shift the ON / OFF timing of laser irradiation. As a method for setting this timing, the memory circuit 224a as described above stores output variation values with respect to standard inputs of individual elements in advance, and by comparing with the monitor value by the photodiode 222a, the feedback circuit 223a The ON / OFF timing is controlled by the fixing controller 214a.

  Since the feedback circuit 223a is set to operate as a common driver for all laser elements, the circuit becomes simple and the cost can be reduced.

All the laser elements described above have been described as having the same output specifications. This is because manufacturing with the same specification is easier to manufacture and manufacturing variations can be reduced, thereby reducing costs.
However, even elements having different output specifications can be used because the output can be optimized as an array block by using the feedback circuit 223 described above. By doing so, it is possible to reduce the inventory of extra elements and to reduce the manufacturing cost.

  The array block divided into lengths corresponding to the paper size is modularized for each block, and can be easily replaced from the base member on which the array block is mounted. This not only facilitates replacement in the event of a trouble, but is economical because only the failed module needs to be replaced without replacing the entire laser unit.

40 Laser Fixing Device 50 Visible Image Forming Unit 51 Photosensitive Drum 52 Charger 53 Laser Light Irradiating Unit 54 Developer 55 Transfer Roller 56 Cleaner Unit 100 Laser Irradiating Unit 101 Laser Generating Unit 102 Collimating Lens 103 Condensing Lens 104 Transmission Type Sensor 105 Light Emitting Unit 106 Light Receiving Unit 108 Switch 110 Recording Paper Conveying Device 111 Tension Roller 112 Condensing Lens 113 Recording Paper Conveying Belt 114 Power Supply 121 Light Receiving Surface 122 Shielding Member 221 Laser Light 222 Photodiode 223 Feedback Circuit 224 Memory Circuit

Claims (8)

In a laser fixing device that fixes an unfixed toner image on a conveyed recording paper by melting the toner by irradiation of a laser beam,
Laser generating means in which a plurality of laser elements are arranged in series to form an array block, and a plurality of the array blocks are arranged in series in the conveyance width direction of the recording paper,
Fixing control means for controlling drive of laser irradiation in units of array blocks;
A detecting means provided in the vicinity of the array block for detecting the intensity of the irradiated laser beam;
Storage means for storing variation data of output characteristics of individual laser elements in advance;
Equipped with a,
The fixing control unit includes a feedback unit that obtains a laser output control value for correcting variation based on a detection value obtained by the detection unit and a variation value stored in the storage unit, and performs feedback control. Laser fixing device.   2. The laser fixing according to claim 1, wherein the laser generating unit arranges the array blocks in series by providing a plurality of blocks corresponding to the length in the transport width direction of each paper size to be used. apparatus.   3. The paper size according to claim 2, wherein the paper size is an A system, a B system, or an inch system, and the laser generation unit arranges the array block corresponding to the width of the paper size of each system. Laser fixing device. The feedback control, a laser fixing device according to claim 1, characterized in that the current value control 3. The laser element is provided with a switching transistor,
It said feedback means, by the switching transistor, a laser fixing device according to any one of claims 1 to 3, characterized in that shifting the timing of irradiation ON-OFF of each laser element. The laser element, laser fixing device according everything that has been constructed using those same output specification claims 1, wherein any of the 5. The laser element, laser fixing device according to any one of claims 1-5, characterized by being configured in combination of different output. The array block is modularized for each block, a laser fixing according to any one of claims 1 to 7, wherein the array block is replaceably configured from a base member which is mounted apparatus.

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