JP2008145721A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently cool a circuit board disposed in an image forming apparatus without increase of cost. <P>SOLUTION: In the image forming apparatus, an air passage 134 where exhaust stream flows from an exhaust fan 135 discharging the heat from a fixing roller 127b having a heating means incorporated is provided with an opening 132 connected to cooling space 130. In the cooling space 130, the circuit board 131 is disposed and an outside air introduction opening 142 is provided, When the exhaust fan 135 operates in print operation of a color printer 100, the air in the cooling space 130 is sucked in the air passage 134 through the opening 132 and then the circuit board 131 is cooled with a flow of air thereby generated from the outside air introduction hole 133 to the opening 132. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

  As a structure for cooling the inside of an electronic device such as an exchange, there is a configuration in which a chimney effect is used for cooling by natural convection (see, for example, Patent Document 1). In addition, as a structure for cooling the inside of an electronic device such as an exchange, a configuration is also known in which an exhaust passage by a fan is provided inside the electronic device to efficiently ventilate the air (see, for example, Patent Document 2).

JP 2001-144486 A JP-A-11-298179

  An object of the present invention is to realize effective cooling of a circuit board in an image forming apparatus without using a dedicated cooling means.

  The invention described in claim 1 includes an image fixing device, an exhaust device for exhausting heat generated by the image fixing device, and a circuit board cooled by using the exhaust force of the exhaust device. An image forming apparatus characterized by the above.

  According to a second aspect of the present invention, in the first aspect of the present invention, an air passage through which an exhaust flow from the exhaust device flows, and a cooling space provided with an opening formed in the air passage and outside air introduction means are provided. The circuit board is arranged between the opening in the cooling space and the outside air introducing means.

  The invention according to claim 3 is the invention according to claim 2, wherein the air passage has a venturi structure, and the opening is provided in a portion of the venturi structure.

  According to a fourth aspect of the present invention, in the first aspect of the present invention, an air passage through which an exhaust flow from the exhaust device flows and an opening for introducing outside air into the air passage are provided. It arrange | positions in the downstream of the opening in a path | route, It is characterized by the above-mentioned.

  According to the first aspect of the present invention, effective cooling of the circuit board can be realized without using a dedicated cooling means.

  According to the second aspect of the present invention, the circuit board can be cooled by utilizing the flow of air flowing into the exhaust flow of the exhaust device that exhausts heat generated from the fixing device. For this reason, it is possible to reduce the manufacturing cost of the apparatus, reduce the power consumption for cooling, and simplify the apparatus configuration.

  According to the third aspect of the present invention, the circuit board can be cooled using the flow of air flowing into the low-pressure portion generated by the venturi structure, and the circuit board can be cooled more effectively. Can do.

  According to the fourth aspect of the present invention, the exhaust flow of the exhaust device that exhausts heat generated from the fixing device is cooled by the outside air, and the circuit board can be cooled using the flow.

1. First embodiment (configuration of the embodiment)
Hereinafter, an embodiment using the invention will be described. This embodiment is an example when the present invention is used in a printing apparatus. FIG. 1 is a conceptual diagram showing an outline of an image forming apparatus using the invention. FIG. 1 (A) shows details of the internal structure, and FIG. 1 (B) shows FIG. 1 (A). The internal structure seen from the right is shown. Note that FIG. 1B illustrates part of the structure illustrated in FIG. 1A and omits other descriptions. FIG. 1 shows a color printer 100 which is an example of an image forming apparatus. The color printer 100 includes a one-drum type developing machine 101. The developing machine 101 includes four phenomenon units 102 corresponding to YMCK basic colors. The phenomenon unit 102 includes a toner bottle 102a and a toner supply mechanism 102b. Each of the four toner bottles 102a stores one of YMCK toners corresponding to each phenomenon unit 102.

  A photosensitive drum 103 is disposed in contact with the developing machine 101. The photosensitive drum 103 is partially exposed by the scanning light emitted from the optical writing device 104, and a latent image is formed on the surface thereof. The optical writing device 104 is a writing exposure scanning device, and includes a laser irradiation device 104a and an optical system 104b for guiding laser light. The developing machine 101 and the photosensitive drum 103 rotate in opposite directions in synchronization with each other, and at that time, the optical writing device 104 irradiates the photosensitive drum 103 with scanning light, thereby forming a latent image on the photosensitive drum 103. The The surface of the photosensitive drum 103 is charged in accordance with the latent image, and is attracted to the electric field, so that one of the YMCK toners is selectively supplied to the photosensitive drum 103 from one developing unit 102 of the developing device 101. The In this way, any toner of YMCK adheres to the surface of the photosensitive drum 103 according to the latent image formed by the optical writing device 104, and a toner image corresponding to the latent image is formed.

  A cleaning device 105 is provided in the vicinity of the photosensitive drum 103. The cleaning device 105 has a function of bringing the blade 105 a into contact with the surface of the photosensitive drum 103 and scraping off the remaining toner using the rotational force of the photosensitive drum 103. The toner scraped off is collected by a toner collecting unit (not shown).

  A transfer belt 106 is disposed in contact with the photosensitive drum 103. Further, a primary transfer roller 108 is disposed at a position facing the photosensitive drum 103 with the transfer belt 106 interposed therebetween. A bias voltage necessary for transferring a toner image can be applied between the photosensitive drum 103 and the primary transfer roller 108. The transfer belt 106 is conveyed by the driving roller 109 at a speed synchronized with the rotation of the photosensitive drum 103. At this time, the transfer belt 106 is sandwiched between the photosensitive drum 103 and the primary transfer roller 108, and at that time, a bias voltage is applied between the photosensitive drum 103 and the primary transfer roller 108. The toner image is transferred from the photosensitive drum 103 to the transfer belt 106 (primary transfer). At this time, in the case of color, the primary transfer for each color of YMCK is performed four times, and the four color images are superimposed, and a color toner image is formed on the transfer belt 106. For monochrome, transfer is performed for one color in YMCK.

  A cleaning roller 110 is disposed in the vicinity of the transfer belt 106. The cleaning roller 110 applies a DC voltage to the transfer belt 106 and positively charges the toner remaining on the transfer belt 106 after the secondary transfer. The positively charged toner is collected on the photosensitive drum 103 by the action of an electric field of a DC voltage applied between the photosensitive drum 103 and the primary transfer roller 108. The toner collected on the photosensitive drum 103 is removed by the cleaning device 105 and collected by a toner collecting unit (not shown).

  A toner sensor 111 is disposed in the vicinity of the transfer belt 106. The toner sensor 111 is an optical sensor and monitors the state of toner optically attached to the transfer belt 106. The amount of consumed toner can be known from the output of the toner sensor 111. A mark detection sensor 121 is disposed in the vicinity of the transfer belt 106. A mark for position detection (not shown) formed on the transfer belt 106 is detected by the mark detection sensor 121. This position detection mark (not shown) is used as a mark for determining a position for primary transfer on the transfer belt 106.

  A paper storage unit 123 that stores printing paper 122 is stored at the bottom of the color printer 100. The printing paper 122 is transported along the paper transport path 125 by a paper transport system typically indicated by reference numeral 124. Secondary transfer rollers 126a and 126b are arranged in the middle of the paper transport path 125. A toner image that is primarily transferred onto the surface of the transfer belt 106 by sandwiching the transfer belt 106 and the printing paper (not shown) that has been transported through the paper transport path 125 between the secondary transfer rollers 126a and 126b. Is further transferred to the printing paper.

  The printing paper on which the toner image has been transferred moves along the paper conveyance path 125 and is conveyed between fixing rollers 127a and 127b, which are examples of an image fixing device. The fixing roller 127b has a built-in heater, and heats the toner material constituting the toner image on the printing paper during the conveyance. By this heating, the toner is fixed, and an image is formed on the printing paper (that is, printing is performed). The printing paper on which printing has been performed is discharged from the discharge mechanism 128 onto the discharge surface 129. FIG. 1B shows the secondary transfer roller 126b and the fixing roller 127b shown in FIG. Note that description of other structures shown in FIG. 1A is omitted in FIG.

  In FIG. 1B, reference numeral 131 denotes a circuit board stored in the color printer 100. The circuit board 131 includes a control system and image processing system circuit board, and a power supply system circuit board. The circuit board of the image processing system includes various integrated circuits for performing digital operations, and these integrated circuits generate heat during operation. Since the color printer 100 handles images, the operation of these integrated circuits is fast and the amount of data handled is large. Therefore, the integrated circuit on the circuit board 131 generates a large amount of heat, and some kind of cooling (or exhaust heat) mechanism is required. Also, the circuit board of the power supply system generates heat from the regulator circuit and the like and needs to be cooled.

  In the present embodiment, the cooling mechanism includes the following configuration. That is, the circuit board 131 is disposed in the cooling space 130. The cooling space 130 is provided with an opening 132 at the upper part thereof and an outside air introduction port 133 as an example of an outside air introduction means at the lower part thereof. The opening 132 is formed so as to be connected to the air passage 134, and the circuit board 131 is disposed between the opening 132 and the outside air inlet 133.

  The air path 134 functions as a path for exhausting an exhaust flow from an exhaust fan 135, which is an example of an exhaust device, to the outside of the color printer 100. The exhaust fan 135 faces the space where the fixing rollers 127a and 127b are disposed, and sucks air in the space. The fixing roller 127b has a built-in heater, and an image is fixed on the printing paper using the heat generated by the heater. The air containing heat from the heater is sucked by the exhaust fan 135 and discharged to the outside through the air passage 134. On the exhaust side of the exhaust fan 135, an activated carbon filter (or catalyst filter) 136 for absorbing (or decomposing) the odor generated when the image is fixed is disposed. The configuration shown in FIG. 1B is arranged on the back side (the other side of the sheet) of the configuration shown in FIG.

  When the exhaust fan 135 is operated and an air flow toward the outside is generated in the air passage 134, the pressure in the air passage 134 is relatively lowered from Bernoulli's theorem, and the air in the cooling space 130 is discharged from the opening 132. It is sucked into the air passage 134. Accordingly, outside air flows from the outside air inlet 133 into the cooling space 130. Since the circuit board 131 is located on the downstream side of the air flow when viewed from the outside air introduction port 133, the circuit board 131 is cooled by the air flowing in from the outside air introduction port 133. In other words, the amount of heat generated from the circuit board 131 is carried away by the air flowing in from the outside air inlet 133 and discharged from the air path 134 to the outside.

  The circuit board 131 includes the following two circuit boards 131a and 131b. FIG. 2 is a block diagram showing an outline of a control system including the circuit board 131a. The circuit board 131a is a board on which circuits of a control system and an image processing system are arranged, on which a CPU (central processing unit) 201, a ROM (read only memory) 202, a RAM (random access memory) 203, An image data input circuit 204 and an image processing circuit 205 are arranged.

  The CPU 201 has a function of supervising the operation of the entire control system shown in FIG. 2 and executing various operation procedures. The ROM 202 stores an operation program for executing various operation procedures and data necessary for the operation. The RAM 203 functions as a working area for temporarily storing program data and various data when executing various operation procedures, and a storage unit for storing data obtained in the various operation procedures. The RAM 203 includes a nonvolatile memory, and necessary data is retained even when the power is turned off.

  The image data input circuit 204 has a function of taking in image data sent from a terminal (not shown) (for example, a personal computer) into the color printer 100. The image processing circuit 205 performs various processes such as color conversion processing, image processing for adjusting gradation, image processing for determining resolution, image enlargement / reduction processing, and generation of control signals that can be interpreted by the optical writing unit 104. It is a circuit for performing.

  The drive control circuit 207 is a circuit that controls a motor that drives the developing device 102, the photosensitive drum 103, the transfer belt 106, the fixing rollers 127a and 127b, the printing paper conveyance system 124, and the like. Further, the drive control circuit 207 performs ON / OFF and temperature control of the heater built in the fixing roller 127b, and further controls the operation of the exhaust fan 135.

  The sensor 206 detects the rotation state and rotation angle of the motor driven by the drive control circuit 207, the toner image formation state, the printing paper conveyance state, the number of image formations, the image formation amount, and the like. The sensor 206 also includes a mark detection sensor 121 and a toner sensor 111.

  FIG. 3 is a block diagram showing a configuration of a circuit arranged on the circuit board 131b. The circuit board 131b is a power system circuit board. Stabilized power supply circuits 302 and 303 and a heater power supply circuit 304 are arranged on the circuit board 131b. Here, as an example, a stabilized power supply circuit that generates DC12V and DC5V from a DC24V power supply source and a heater power supply circuit that generates a voltage to be applied to the heater in the fixing roller 127b are shown. A power supply circuit can be arranged. The voltage generated by the heater power supply circuit 304 may be set according to the standard of the heater to be used.

  Each power supply circuit is equipped with a regulator circuit, a booster circuit, etc. according to the supplied voltage and power, and a semiconductor device (3-terminal regulator, transistor, etc.) constituting these circuits adopts a heat dissipation structure as necessary. Has been.

(Operation of the embodiment)
First, when a main power supply (not shown) of the color printer 100 is turned on, activation processing of various functions is performed. In addition, after the main power is turned on, power is supplied to various devices that perform an idling operation even during a non-printing operation. At this time, power is supplied to the heater built in the fixing roller 127b, and the heater is preheated. Further, the operation of the exhaust fan 135 is appropriately controlled based on the temperature detected by a temperature detection sensor (not shown), and temperature management is performed so that the temperature in the color printer 100 does not exceed a predetermined temperature.

  When printing is started, image data sent from a terminal (for example, a personal computer) or the like is taken into the image data input circuit 204 and sent to the image processing circuit 205. In the image processing circuit 205, the image data is color-separated into YMCK basic color image data, and predetermined image processing is performed on these image data. The image processing circuit 205 generates a control signal that instructs the optical writing device 104 to form an image based on the image data after the image processing. When this operation is started, rotation of the photosensitive drum 103 and the transfer belt 106 is started, the developing machine 101 further rotates, and the corresponding phenomenon unit 102 faces the photosensitive drum 103. Further, the voltage applied to the heater built in the fixing roller 127b is higher than the preheated state, and the heater is in a state of generating heat necessary for actually fixing the image. At this time, the amount of rotation of the exhaust fan 135 is controlled in accordance with the amount of heat generated by the heater, and heat is exhausted from the color printer 100.

  The control signal generated by the image processing circuit 205 is sent to the optical writing device 104. The optical writing device 104 irradiates the rotating photosensitive drum 103 while scanning the laser beam, and latently irradiates the surface of the photosensitive drum 103. Form an image. Toner is supplied from the developing unit 102 to the photosensitive drum 103 on which the latent image is formed, and a toner image is formed on the photosensitive drum 103 in a pattern corresponding to the latent image. This toner image is primarily transferred to the transfer belt 106 by the action of the primary transfer roller 108.

  Thus, a toner image of one basic color of YMCK is formed on the transfer belt 106. This operation is performed for each basic color, and a YMCK toner image is superimposed on the transfer belt to form a color toner image. The color toner image is secondarily transferred onto the printing paper conveyed from the paper storage unit 123 through the conveyance path 125 by the function of the secondary transfer rollers 126a and 126b. The color toner image transferred to the printing paper is fixed on the printing paper by the printing paper being sandwiched between the fixing rollers 127a and 127b and simultaneously being heated from the fixing roller 127b. Thereafter, the printing paper is discharged from the discharge mechanism 128 onto the discharge surface 129. Thus, one sheet is printed. When there are a plurality of sheets to be printed, the above operation is repeated.

  In the above operation, when the exhaust fan 135 is operated, an air flow toward the outside is generated in the air passage 134, and the pressure in the air passage 134 is lower than that in the cooling space 130 by Bernoulli's theorem. As a result, air flows from the inside of the cooling space 130 into the air passage 134 through the opening 132, and an air flow 137 from the outside air inlet 133 toward the opening 132 in the cooling space 130 is generated. The circuit board 131 is cooled by the air flow 137.

  At this time, since the air drawn from the outside air inlet 133 is air taken from the outside of the color printer 100, high cooling efficiency can be obtained. Further, since the outside air inlet 133 is relatively in the lower part (vertically below) and the opening 132 is in the upper part (vertically above), the upward flow of the air deprived of the heat of the circuit board 131 in the cooling space 130 is obtained. Realized efficiently. That is, in the cooling space 130, the force drawn into the air flow flowing in the air passage 134 and the force that takes the heat of the circuit board 131 to increase the temperature of the heated air synergistically act efficiently. An air flow indicated by an arrow 137 is formed.

  As described above, in the color printer 100 according to the present embodiment, the circuit board 131 is disposed between the opening 132 of the cooling space 130 and the outside air inlet 133, and the opening 132 discharges heat from the fixing device. It arrange | positions so that it may connect with the air path 134 through which the air which flows. As a result, an air flow 137 is generated inside the cooling space 130 due to the air flow in the air passage 134, thereby cooling the circuit board 131. Since the heat generated from the fixing roller 127b is the portion that generates the most heat inside the color printer 100, the exhaust fan 135 has a relatively large exhaust capacity and a long operation time. For this reason, the circuit board 131 can be efficiently cooled by cooling the circuit board 131 by using a part of the capacity.

2. Second Embodiment The present embodiment is an example of a configuration that more efficiently generates an air flow from the cooling space 130 to the air passage 134 by adopting a venturi structure in the first embodiment. FIG. 4 is a conceptual diagram showing an example of an embodiment using the invention. Here, FIG. 4B shows an internal structure of FIG. 4A viewed from the right direction. Note that FIG. 4B illustrates part of the structure illustrated in FIG. 4A and omits other descriptions.

  Similar to the color printer shown in FIG. 1, the color printer 100 shown in FIG. 4 includes an exhaust fan 135 that exhausts heat generated by the fixing roller 127b. In this embodiment, the venturi structure 138 is formed in the air passage 134 on the downstream side of the exhaust fan 135. The venturi structure is a structure in which the flow rate in the part is increased and the pressure in the part is relatively lowered by restricting the flow of fluid (partially reducing the diameter of the flow path). An opening 132 is provided at the outlet portion of the venturi structure 138. Since this portion is a portion where the flow velocity is high and the pressure is low, air is efficiently sucked from the cooling space 130 into the air passage 134 via the opening 132.

  The other parts are the same as those of the color printer 100 shown in FIG. The operation of the color printer 100 and the principle of cooling the circuit board 131 are the same as those of the color printer 100 shown in FIG.

3. Third Embodiment (Configuration of Embodiment)
The present embodiment is an example in which the circuit board is cooled by using an air flow different from that of the first embodiment. FIG. 5 is a conceptual diagram showing an example of an embodiment using the invention. FIG. 5B shows the internal structure of FIG. 5A viewed from the right direction. Note that part of the structure illustrated in FIG. 5A is illustrated in FIG. 5B, and other description is omitted.

  In this example, the exhaust flow from the exhaust fan 135 that exhausts the heat generated by the fixing roller 127 b is guided to the cooling space 130 and discharged from the exhaust port 143 to the outside. Outside air introduction ports 141 and 142 are provided on the upstream side of the cooling space 130 (upstream side when viewed from the circuit board 131). In the cooling space 130, a circuit board 131 is disposed between the outside air inlets 141 and 142 and the exhaust port 143. The other parts are the same as those of the color printer 100 shown in FIG.

(Operation of the embodiment)
When the exhaust fan 135 operates, the exhaust flow from the exhaust fan 135 flows into the cooling space 130 from the upper side to the lower side in the figure, and the outside air flows from the outside air inlets 141 and 142 due to the low pressure state caused by the flow. To do. Thereby, the air flowing from the upper side to the lower side in the cooling space 130 is cooled. That is, since the exhaust fan 135 sucks and exhausts exhaust including heat generated by the fixing roller 127b, the exhaust flow of the exhaust fan 135 has a relatively higher temperature than the air outside the color printer 100. The temperature can be lowered by mixing the warm air with the outside air flowing from the outside air inlets 141 and 142 (the air outside the color printer 100).

  The circuit board 131 is cooled by the cooled air flow 144. The air deprived of heat from the circuit board 131 is discharged from the exhaust port 143 to the outside of the color printer 100. The operation of the color printer 100 is the same as that of the color printer 100 shown in FIG.

  According to this aspect, the circuit board 131 is cooled using the mechanism for exhausting heat generated by the fixing roller 127b. At this time, the outside air is mixed with the heated exhaust flow from the exhaust fan 135 to lower the temperature and enhance the cooling effect of the circuit board 131.

4). Other Embodiments In the first to third embodiments, an example of a color printer is shown as an example of an image forming apparatus. However, examples of an image forming apparatus to which the present invention can be applied include a copying apparatus, a FAX communication apparatus, and a monochrome printer. be able to. The present invention can also be applied to a composite apparatus having a plurality of functions selected from a printer, a copying apparatus, and a FAX communication apparatus.

  Further, as the fixing device, a fixing device provided with a heating means by irradiation with light from a lamp can be adopted. In the first to third embodiments, an example of a one-drum type image forming apparatus using a developing unit in which four colors of YMCK are integrated and one photosensitive drum has been described. The present invention can also be applied to a tandem type image forming apparatus including a pair of a developing machine and a photosensitive drum.

  The present invention can be used in an image forming apparatus having a mechanism for cooling a circuit board.

1 is a conceptual diagram illustrating an example of an image forming apparatus using the invention. It is a block diagram which shows the structure of a control system. It is a block diagram which shows the outline | summary of the circuit arrange | positioned on the circuit board of a power supply system. 1 is a conceptual diagram illustrating an example of an image forming apparatus using the invention. 1 is a conceptual diagram illustrating an example of an image forming apparatus using the invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Color printer, 101 ... Developing machine, 103 ... Photosensitive drum, 105 ... Cleaning device, 105a ... Blade for removing toner, 106 ... Transfer belt, 108 ... Primary transfer roller, 110 ... Cleaning roller, 126a ... Secondary transfer roller, 126b ... secondary transfer roller, 127a ... fixing roller, 127b ... fixing roller (with built-in heater), 130 ... cooling space, 131 ... circuit board, 131a ... circuit board for control system and image processing system, 131b ... Circuit board of power supply system, 132 ... Opening, 133 ... Outside air inlet, 134 ... Air path, 135 ... Exhaust fan, 136 ... Filter, 137 ... Air flow, 138 ... Venturi structure, 141 ... Outside air inlet, 142 ... Outside air introduction port, 143... Exhaust port.

Claims (4)

An image fixing device;
An exhaust device for exhausting heat generated by the image fixing device;
An image forming apparatus comprising: a circuit board that is cooled by using an exhaust force of the exhaust device. An air passage through which an exhaust flow from the exhaust device flows;
A cooling space provided with an opening formed in the air passage and an outside air introduction means,
The image forming apparatus according to claim 1, wherein the circuit board is disposed between the opening in the cooling space and the outside air introduction unit. The air passage has a venturi structure,
The image forming apparatus according to claim 2, wherein the opening is provided in a portion of the venturi structure. An air passage through which an exhaust flow from the exhaust device flows;
An opening for introducing outside air into the air passage,
The image forming apparatus according to claim 1, wherein the circuit board is disposed on the downstream side of the opening in the air passage.

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