Patent Publication Number: US-9904218-B2

Title: Heating device and image forming apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2016-041778 filed Mar. 4, 2016. 
     BACKGROUND 
     Technical Field 
     The present invention relates to a heating device and an image forming apparatus. 
     SUMMARY 
     According to an aspect of the invention, a heating device includes a conveying unit, a heating unit, a temperature detecting unit and a controller. The conveying unit conveys a recording material. The heating unit includes a plurality of heat sources which are disposed so that locations thereof are different from each other in a conveying direction of the recording material, and heats the conveyed recording material. The temperature detecting unit is positioned on an upstream side in the conveying direction of the recording material with respect to the plurality of heat sources, and detects a temperature of the heating unit. The controller controls one of the plurality of heat sources based on a detecting result obtained by the temperature detecting unit. The one of the plurality of heat sources is positioned on the upstream side in the conveying direction of the recording material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein: 
         FIG. 1  is a diagram illustrating a configuration example of an image forming apparatus: 
         FIG. 2  is a diagram illustrating a heating device; and 
         FIG. 3  is a diagram illustrating another configuration of the heating device and is a diagram illustrating a state of the heating device when viewed from above. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, the exemplary embodiment of the present invention will be described in detail with reference to accompanying drawings. 
       FIG. 1  is a diagram illustrating a configuration example of an image forming apparatus  1  according to the present exemplary embodiment. 
     The image forming apparatus  1  as shown in  FIG. 1  is a so-called tandem-type color printer, and includes an imaging forming unit  10  for forming an image based on image data. In addition, the image forming apparatus  1  includes a main controller  50 . 
     The main controller  50  as an example of a controller includes a central processing unit (CPU) controlled by a program and performs operation controlling of each device and each functional unit which are provided in the image forming apparatus  1 , communicating with a personal computer or the like, or processing with respect to the image data. 
     Furthermore, a user interface unit  30  which receives an operation unit from a user or displays various information items to the user is provided in the image forming apparatus  1 . 
     The imaging forming unit  10  as an example of an image forming unit is, for example, a functional unit for forming an image by an electrophotographic system and includes four image forming units of a yellow (Y) image forming unit  11 Y, a magenta (M) image forming unit  11 M a cyan (C) image forming unit  11 C, and a black (K) image forming unit  11 K. 
     In the following description, in a case where each of the image forming units is not specifically distinguished from each other, it is simply referred to as an “image forming unit  11 ”. 
     Each image forming unit  11  of the image forming unit  11 Y, the image forming unit  11 M, the image forming unit  11 C, and the image forming unit  11 K forms a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image, respectively. 
     In each image forming unit  11 , a photoconductor drum  12  on which a toner image of each color formed after an electrostatic latent image is formed is provided. In addition, a charging unit  13  for charging a surface of the photoconductor drum  12 , and an exposure tool  14  in which the photoconductor drum  12  which is charged by the charging unit  13  is exposed based on the image data are provided in the each image forming unit  11 . 
     Furthermore, a developing unit  15  for developing the electrostatic latent image, which is formed on the photoconductor drum  12 , with each color toner, and a cleaner  16  for cleaning the surface of the photoconductor drum  12  after transfer are provided in each image forming unit  11 . 
     In addition, an intermediate transfer belt  20  on which a toner image of each color which is formed on the photoconductor drum  12  of each image forming unit  11  is transferred, and a primary transfer roll  21  for transferring (primary transferring) a toner image of each color formed in each image forming unit  11  to the intermediate transfer belt  20  are provided in the imaging forming unit  10 . 
     In addition, a secondary transfer roll  22  for batch transferring (secondary transferring) a toner image of each color which is transferred on the intermediate transfer belt  20  in a superposed manner with respect to a recording material P is provided in the imaging forming unit  10 . 
     Furthermore, a fixing device  60  for fixing a toner image of each color secondarily transferred onto the recording material P is provided in the imaging forming unit  10 . 
     In the present exemplary embodiment, a region, where the secondary transfer roll  22  is disposed and a toner image of each color on the intermediate transfer belt  20  is secondarily transferred onto the recording material P, is referred to as a secondary transfer region Tr below. 
     Here, examples of the recording material P include paper, a resin sheet, a region film, and the like. 
     In the present exemplary embodiment, a case where an image is formed with respect to the continuous recording material P (belt-like recording material P) which extends along the conveying direction of the recording material P will be described as an example without the recording material P cut one by one. 
     The operation of the image forming apparatus  1  will be described. 
     To form the image, each of the image forming units  11  forms a toner image of each color of black, cyan, magenta, and yellow by an electrophotographic process. 
     A toner image of each color formed by each of the image forming units  11  is primarily transferred on the intermediate transfer belt  20  by the primary transfer roll  21 , sequentially, and the toner image in which each toner is superposed is formed on the intermediate transfer belt  20 . 
     The toner image on the intermediate transfer belt  20  is conveyed to the secondary transfer region Tr in which the secondary transfer roll  22  is disposed in accordance with the movement of the intermediate transfer belt  20 . 
     In a recording material conveying system, the recording material P is fed out from a feeding roll (not shown) in which the recording material P is wound and the recording material P is conveyed along a predetermined convey path and reaches to the secondary transfer region Tr. In the secondary transfer region Tr, the toner image on the intermediate transfer belt  20  is secondarily transferred in a batch to the recording material P by a transfer electric field formed by the secondary transfer roll  22 . 
     Thereafter, the recording material P onto which the toner image is transferred is conveyed toward a heating device  700  and a fixing device  60  by a convey belt  28 , a convey roll  29 , or the like as an example of a conveying unit. The recording material P is heated by the heating device  700  on the way to the fixing device  60 . 
     In the fixing device  60 , the recording material P is fed with respect to a nip portion N of the fixing device  60 . Accordingly, pressing and heating of the recording material P is performed and fixing of the toner image to the recording material P is performed. Thereafter, the recording material P is wound by a winding device (not shown). 
     Here, for heating the recording material P by only the fixing device  60 , it is required to increase the output of the fixing device  60  and the size of the fixing device  60  is easily increased. By providing the heating device  700 , the increase in the size of the fixing device  60  is suppressed. 
     In addition, in the present exemplary embodiment, a fixing roll  611  provided in the fixing device  60  is press-fitted to a pressure roll  62  to form the nip portion N. 
     However, any of the fixing roll  611  and the pressure roll  62  of the present exemplary embodiment has a roll shape, and in this case, a contacted area between the fixing roll  611  and the pressure roll  62  is decreased. In this case, a heat capacity to be applied to the recording material P is easily decreased. 
     When the heating device  700  is provided, as compared to a case where heat is supplied to the recording material P by only the fixing device  60 , the heat capacity to be supplied to the recording material P is increased. 
       FIG. 2  is a diagram illustrating the heating device  700 . 
     A heating unit  710  as an example of the heating unit for heating the recording material P is provided in the heating device  700 . A heat source  800  is provided in the heating unit  710 . The heat source  800  includes a first heat source  810  and a second heat source  820 . 
     The first heat source  810  and the second heat source  820  are disposed so that locations thereof are different from each other in a conveying direction of the recording material P. In the present exemplary embodiment, in the conveying direction of the recording material P, the first heat source  810  is positioned at the upstreamside and the second heat source  820  is positioned at the downstream side. The first heat source  810  and the second heat source  820  are, for example, a halogen heater. 
     Furthermore, an accommodating housing  830 , which is formed in a rectangular parallelepiped shape, is formed by a metal material, and accommodates the first heat source  810  and the second heat source  820 , is formed in the heating unit  710 . 
     Furthermore, a contact member  840  which is in contact with the recording material P to be conveyed on the conveying path is formed on a conveying path side of the recording material P in relation to the accommodating housing  830 . 
     In the present exemplary embodiment, the contact member  840  is provided between the recording material P to be conveyed and the heat source  800 . The contact member  840  is formed by a plate material and is provided so as to extend along the conveying direction of the recording material P. Furthermore, the contact member  840  is disposed below the recording material P to be conveyed and is in contact with the recording material P from below. 
     In addition, in the present exemplary embodiment, in a case where a length of the contact member  840  in the conveying direction of the recording material P is compared to a length of the accommodating housing  830  in the conveying direction of the recording material P, the length of the contact member  840  becomes larger. 
     Furthermore, the contact member  840  includes an upstream side end portion  841  on the upstream side in the convening direction of the recording material P and a downstream side end portion  842  on the downstream side in the conveying direction of the recording material P. 
     Furthermore, in the present exemplary embodiment, the upstream side end portion  841  of the contact member  840  is positioned on the upstream side in the conveying direction of the recording material P in relation to an upstream end  831 A (end portion positioned furthest toward the upstream side in the conveying direction of the recording material P) of the accommodating housing  830 . 
     In addition, the downstream side end portion  842  of the contact member  840  is positioned on the downstream side in the conveying direction of the recording material P in relation to an downstream end  832 A (end portion located furthest toward the downstream side in the conveying direction of the recording material P) of the accommodating housing  830 . 
     Furthermore, in the present exemplary embodiment, an upstream side temperature, sensor S 1  and a downstream side temperature sensor S 2  for detecting the temperature of the heating unit  710  are provided. 
     The upstreamside temperature sensor S 1  as an example of the temperature detecting unit is positioned on the upstream side of the recording material P in the conveying direction in relation to the first heat source  810  and the second heat source  820  provided in the heating unit  710 . 
     The upstreamside temperature sensor S 1  detects the temperature of the upstream side end portion  841  (a portion positioned at the upstream side in relation to the accommodating housing  830 ) of the contact member  840 . 
     The downstream side temperature sensor S 2  as an example of the downstream side detecting unit is positioned on the downstream side of the recording material P in the conveying direction in relation to the first heat source  810  and the second heat source  820  provided in the heating unit  710 . The downstream side temperature sensor S 2  detects the temperature of the downstream side end portion  842  (a portion positioned at the downstream side in relation to the accommodating housing  830 ) of the contact member  840 . 
     A heating process of the recording material P by the heating device  700  will be described. 
     In the age forming apparatus  1  according to the present exemplary embodiment, the main controller  50  as an example of the controller outputs a control signal at a predetermined timing such as at a time of power input or at a time of return from a power-saving mode. Therefore, the first heat source  810  and the second heat source  820  are in the turned-off state until then are turned on. Accordingly, the temperature of the entire heating unit  710  is increased. 
     When the temperature detected by the upstream side temperature sensor S 1  and the temperature detected by the downstream side temperature sensor S 2  reach the predetermined temperature (when an upper limit value to be described is reached), the control signal is output from the main controller  50  and the first heat source  810  and the second heat source  820  are turned off once. 
     In the present exemplary embodiment, the signals from the upstream side temperature sensor S 1  and the downstream side temperature sensor S 2  are output from the main controller  50 . 
     The main controller  50  is configured to control the first heat source  810  and the second heat source  820  based on the detecting result by the upstream side temperature sensor S 1  and the downstream side temperature sensor S 2 . 
     Thereafter, in the present exemplary embodiment, conveying of the recording material P is started and forming of the image onto the recording material P by the imaging forming unit  10  is started. In the recording material P, a portion in which an image is not formed by the imaging forming unit  10  is toward the fixing device  60  (refer to  FIG. 1 ) via the heating device  700  and in the fixing device  60 , fixing the image to the recording material P is performed. A portion in which the fixing of the image is terminated in the recording material P is discharged to the outside the image forming apparatus  1 . 
     Here, when the image forming onto the recording material P is sequentially performed, the heat of the heating unit  710  (refer to  FIG. 2 ) is lost by the recording material P, and the temperature of the heating unit  710  is gradually lowered. 
     Specifically, in the present exemplary embodiment, since the recording material P comes into contact with the portion on the upstream side of the recording material P in the conveying direction in the heating unit  710 , at first, the temperature is lowered from the portion on the upstream side of the heating unit  710 . More specifically, the temperature is lowered from the portion of the upstream side end portion  841  of the contact member  840  (refer to  FIG. 2 ). In this case, the temperature of the heating unit  710  is lower than the originally planned temperature, and the heat capacity to be supplied to the recording material P is decreased. 
     In the present exemplary embodiment, in a case where the temperature of the heating unit  710  is lowered, the first heat source  810  is turned on to increase the temperature of the heating unit  710 . 
     Specifically, in the present exemplary embodiment, as described above, since the temperature is gradually lowered from a portion positioned on the upstream side in the heating unit  710 , firstly, the first heat source  810  is turned on to increase the temperature of the portion on the upstream side of the heating unit  710 . 
     More specifically, in the present exemplary embodiment, the temperature of the portion on the upstream side of the heating unit  710  is detected by the upstream side temperature sensor S 1 , and in a case where the temperature of the portion on the upstream side of the heating unit  710  is lower than the predetermined threshold value, the control signal is output from the main controller  50  and the first heat source  810  is turned on. Therefore, the temperature of the portion on the upstream side of the heating unit  710  increases. 
     In the present exemplary embodiment, in a case where even when the temperature of the portion on the upstream side of the heating unit  710  is lowered, the temperature of a portion on the downstream side is not lowered (in a case where the temperature detected by the downstream side temperature sensor S 2  does not fall below the predetermined threshold value), the second heat source  820  is not turned on. 
     In the portion on the downstream side of the heating unit  710 , the temperature is not yet lowered, and when the second heat source  820  is turned on, the portion on the downstream side is heated more than necessary. 
     On the other hand, in a case where the temperature of the portion on the downstream side of the heating unit  710  is lowered, the second heat source  820  is turned on. More specifically, in the present exemplary embodiment, the temperature of the portion on the downstream side of the heating unit  710  is detected by the downstream side temperature sensor S 2 , and in a case where the temperature of the portion on the downstream side of the heating unit  710  is lower than the predetermined threshold value, the control signal is output from the main controller  50 , and the second heat source  820  is turned on. 
     Accordingly, the decrease in the temperature of the portion on the downstream side of the heating unit  710  is suppressed, and the predetermined heat capacity is supplied with respect to the recording material P. 
     In the present exemplary embodiment an upper limit value relating to the temperature is set, and in a case where the temperature detected by each of the upstream side temperature sensor S 1  and the downstream side temperature sensor S 2  exceeds the predetermined upper limit value, the main controller  50  controls the first heat source  810  and the second heat source  820  to be turned off. 
     Specifically, in a case where the temperature detected by the upstream side temperature sensor S 1  exceeds the predetermined temperature (upper limit value), the main controller  50  controls the first heat source  810  to be turned off, and in a case where the temperature detected by the downstream side temperature sensor S 2  exceeds the predetermined temperature, the main controller  50  controls the second heat source  820  to be turned off. 
     Here, in the present exemplary embodiment, a thickness of a portion in which a temperature is detected by the upstream side temperature sensor S 1  and the downstream side temperature sensor S 2  in the heating unit  710  is smaller than a thickness of a portion positioned between the heat source  800  and the recording material P to be conveyed (a portion positioned between the heat source  800  and the recording material convey path), in the heating unit  710 . 
     Specifically, a thickness T 2  of a portion shown by the reference numeral  2 B in  FIG. 2  is smaller than a thickness T 1  of a portion shown by the reference numeral  2 A in  FIG. 2 . Additionally remarking, in a case where thicknesses in a direction perpendicular to the conveying direction of the recording material P with each other, the thickness T 2  of the portion shown by the reference numeral  2 B is smaller than the thickness T 1  of the portion shown by the reference numeral  2 A. 
     In this case, as compared with a case where the thicknesses of the portions where the temperatures are detected by the upstream side temperature sensor S 1  and the downstream side temperature sensor S 2  are large, the response is improved upon detecting of the temperature of the heating unit  710 . Furthermore, in this case, an accumulating section of the heat is provided between the heat source  800  and the recording material P to be conveyed (between the heat source  800  and the recording material convey path) and the heat capacity of the heating unit  710  is further increased. 
     In the present exemplary embodiment, a case where two heat sources the first heat source  810  and the second heat source  820  are used is described as an example. 
     However, the number of the heat sources is not limited to two, and may be three or more. 
     Here, for example, if the number of the heat sources is three, in a case where the temperature detected by the upstream side temperature sensor S 1  is lower than the predetermined threshold value, for example, one heat source positioned furthest toward the upstream side among three heat sources is turned on, and in a case where the temperature detected by the downstream side temperature sensor S 2  is lower than the predetermined temperature, the other two heat sources positioned on the downstream side are turned on. 
     Alternatively, for example, in a case where the temperature detected by the upstream side temperature sensor S 1  is lower than the predetermined temperature, two heat sources positioned on the upstream side among three heat sources are turned on, and in a case where the temperature detected by the downstream side temperature sensor S 2  is lower than the predetermined temperature, the other one heat source positioned furthest toward the downstream side is turned on. 
     In addition, in the above description, a case where the first heat source  810  and the second heat source  820  are turned on or turned off is described as an example, but it is not limited to control of the turning on or turning off. 
     The adjusting of the output may be performed. 
     Specifically, in a case where the temperatures detected by the upstream side temperature sensor S 1  and the downstream side temperature sensor S 2  exceed the predetermined temperature (upper limit value), the outputs of the first heat source  810  and the second heat source  820  decrease. In addition, in a case where the temperatures detected by the upstream side temperature sensor S 1  and the downstream side temperature sensor S 2  are lower than the predetermined temperature, the outputs of the first heat source  810  and the second heat source  820  increase. 
     In addition, in the above description, a case where an image is formed onto the continuous recording material P which extends along the conveying direction of the recording material P is described as an example. 
     However, even in a case where an image is formed onto the recording material P which one by one, the above-described processes are performed. 
       FIG. 3  is a diagram illustrating another configuration of the heating device  700  and is a diagram illustrating a state of the heating device  700  when viewed from above. 
     In the heating device  700  shown in  FIG. 3 , four heat sources of a first heat source  831  to a fourth heat source  834  are provided. Furthermore, in the image forming apparatus  1  including the heating device  700 , two types of recording materials P having a difference size are conveyed. 
     Furthermore, in the heating device  700 , a total of four temperature sensors of a first upstream side temperature sensor S 11 , a second upstream side temperature sensor S 12 , a first downstream side temperature sensor S 21 , and a second downstream side temperature sensor S 22  are provided. 
     In the heating device  700  as shown in  FIG. 3 , the recording material P is conveyed in a so-called side standard, and a side of the recording material P passes above a predetermined conveying standard  4 A, regardless of the size of the recording material P. 
     The first heat source  831  and the third heat source  833  are disposed on the conveying standard  4 A side and the second heat source  832  and the fourth heat source  834  are disposed on a side facing the conveying standard  4 A. 
     In addition, the first upstream side temperature sensor S 11  and the first downstream side temperature sensor S 21  are disposed on the conveying standard  4 A side and the second upstream side temperature sensor S 12  and the second downstream side temperature sensor S 22  are disposed on a side facing the conveying standard  4 A side. 
     In the configuration example, a used heat source is switched depending on the size of the recording material P to be conveyed. 
     When the size of the recording material P is large at a time of power input, four heat sources of the first heat source  831  to the fourth heat source  834  are turned on. 
     When the temperatures detected by the first upstreamside temperature sensor S 11 , the second upstreamside temperature sensor S 12 , the first downstream side temperature sensor S 21 , and the second downstream side temperature sensor S 22  reach the predetermined temperature, the first heat source  831  to the fourth heat source  834  are turned off. 
     In a case where the temperatures detected by the first upstream side temperature sensor S 11  and the second upstream side temperature sensor S 12  are lower than the predetermined temperature in accordance with the conveying of the recording material P, the first heat source  831  and the second heat source  832  are turned on, and the temperatures detected by the first downstream side temperature sensor S 21  and the second downstream side temperature sensor S 22  are lower than the predetermined temperature, the third heat source  833  and the fourth heat source  834  are turned on. 
     On the other hand, when the size of the recording material P is small and at a time of the power input, two heat sources of the first heat source  831  and the third heat source  833  are turned on, and when the temperatures detected by the first upstream side temperature sensor S 11  and the first downstream side temperature sensor S 21  reach the predetermined temperature, the first heat source  831  and the third heat source  833  are turned off. 
     In a case where the temperature detected by the first upstream side temperature sensor S 11  is lower than the predetermined temperature in accordance with the conveying of the recording material P, the first heat source  831  is turned on, and in a case where the temperature detected by the first downstream side temperature sensor S 21  is lower than the predetermined temperature, the third heat source  833  is turned on. 
     The foregoing description of the exemplary embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.