Patent Publication Number: US-9417577-B2

Title: Fixing device and image forming apparatus

Description:
INCORPORATION BY REFERENCE 
     This application claims priority to Japanese Patent Application No.2014-213888 filed on Oct. 20, 2014, the entire contents of which are incorporated by reference herein. 
     BACKGROUND 
     This disclosure relates to a fixing device having a detection hole for detecting an inner state from outside and an image forming apparatus provided with such a fixing device. 
     There has been a fixing device including, in a housing, a heat source, a heat transfer member heated by the heat source, and a pressure-contacting member pressure-contacting the heat transfer member, which heats recording paper passing through between the heat transfer member and the pressure-contacting member to fix a toner image on the recording paper. 
     For example, there has been a fixing device having a detection hole provided in the housing, measuring through the detection hole a temperature of the heat transfer member at time of fixation by a temperature sensor arranged outside of the fixing device. 
     SUMMARY 
     As one aspect of this disclosure, a technology obtained by further improving the technology described above will be suggested. 
     A fixing device according to one aspect of this disclosure includes: a heat source, a heat transfer member, a pressure-contacting member, a housing, and a shutter. 
     The heat transfer member is heated by the heat source. 
     The pressure-contacting member being in pressure-contact with the heat transfer member. 
     The housing stores the heat transfer member and the pressure-contacting member, and is formed with a detection hole for detecting inner property from outside. 
     The fixing device heats recording paper passing through between the heat transfer member and the pressure-contacting member to fix a toner image on the recording paper. 
     The shutter opens and closes the detection hole in accordance with supply of the recording paper to a nip part by the heat transfer member and the pressure-contacting member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective view of an image forming apparatus according to an embodiment; 
         FIG. 1B  is a perspective view of the image forming apparatus with a side cover removed; 
         FIGS. 2A and 2B  are perspective views of a fixing device; 
         FIG. 3  is a view of the fixing device from a detection hole side; 
         FIG. 4  is a view of a cross section taken along line X-X of  FIG. 3  from a direction of an arrow; 
         FIGS. 5A and 5B  are perspective views showing a state of inside of the fixing device while the detection hole is closed; 
         FIGS. 6A and 6B  are perspective views showing a state of the inside of the fixing device while the detection hole is open; 
         FIG. 7A  is a sectional view of a state in which a press roller presses a heat roller; 
         FIG. 7B  is a sectional view of a state in which the press roller does not press the heat roller; and 
         FIGS. 8A and 8B  are perspective views showing states in which the detection hole is opened and closed, respectively. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiment 
     Hereinafter, the embodiment of a fixing device according to one mode of this disclosure and an image forming apparatus provided with such a fixing device will be described with reference to the drawings. 
     1. Outline of Image Forming Apparatus 
     The image forming apparatus  1 , as shown in  FIG. 1 , includes: for example, an image formation section (not shown) which forms a toner image on recording paper; a fixing section  2  which fixes the formed toner image; a detection sensor which detects inner property of the fixing section  2 ; and a control section which, based on the detected property, controls property of the fixing section  2 . The fixing section  2  has a detection hole for the property detection, and this detection hole is used to achieve the property detection performed by the detection sensor. 
     The image forming apparatus  1  includes: in addition to the aforementioned image formation section, fixing section  2 , and detection sensor, for example, an image reading section which reads an image of a set original document; a paper feed section  4  which supplies recording paper to the image formation section; a discharge section which discharges, to a discharge tray  5 , the recording paper on which the toner image has been fixed; an operation display section  6  for displaying various functions, and for operating selection of various functions, etc.; and a main control section which controls the various sections for the purpose of executing the selected function. 
     Here, the image reading section is covered with an original document cover  3 . Moreover, a control section which controls the property of the fixing section may be incorporated in the main control section or may be provided separately from the main control section. 
     2. Fixing Section 
     The fixing section  2  corresponds to one example of the fixing device according to this disclosure, and is incorporated as a fixing section which forms a part of the image forming apparatus. Hereinafter, the fixing section is described as the fixing device. 
     The fixing section  2 , as shown in  FIGS. 2A through 4 , particularly in  FIG. 4 , a heat roller  11  and a press roller  13  are included in a housing  15 . The heat roller  11  corresponds to one example of a combination of a heat source according to this disclosure and a heat transfer member according to this disclosure. The press roller  13  corresponds to one example of a pressure-contacting member according to this disclosure. The press roller  13  makes pressure-contact with the heat roller  11 . 
     Here, a halogen lamp  17  is used as the heat source, and a roller  19  is used as the heat transfer member. The halogen lamp  17  is inserted inside the roller  19 . 
     The fixing section  2  heats the recording paper passing through between the heat roller  11  and the press roller  13  (hereinafter referred to as “nip part”) to fix the toner image on the recording paper. 
     The fixing section  2  has, in the housing  15 , a detection hole  21  for detecting the inner property from outside, and includes a shutter  23  which opens and closes the detection hole  21  in accordance with supply of the recording paper to the nip part. Here, the inner property of the fixing section  2  is a temperature of the heat roller  11 . 
     The fixing section  2 , as shown in  FIGS. 5A, 5B, 6A, and 6B , includes a frame  25  which rotationally supports the heat roller  11 . The frame  25  has: side plates  27  and  29  arranged at both ends in a direction in which an axis of the heat roller  11  extends (hereinafter, the extending direction and a direction parallel to the extending direction are referred to “axial direction”); and a coupling plate  31  coupling together the pair of the side plates  27  and  29 . 
     The coupling plate  31  is provided with a detection hole  21 B at a position corresponding to the detection hole  21  of the housing  15 . The shutter  23  opens the detection hole  21 B upon supply of the recording paper as shown in  FIG. 8A , and closes the detection hole  21 B upon discharge of the recording paper as shown in  FIG. 8B . Note that the closing of the detection hole  21 B also closes the detection hole  21  of the housing  15 . The opening of the detection hole  21 B also opens the detection hole  21  of the housing  15 . 
     Moreover, disposed outside of the housing  15 , for example, at a position opposing the detection hole  21 B is a temperature sensor  70  (see  FIG. 4 ). The temperature sensor  70  detects the temperature of the heat roller  11  stored in the housing  15 . That is, the property described above is the temperature of the heat roller  11  here. The temperature sensor  70  detects, through the detection hole  21 B being opened by the shutter  23 , a temperature of the housing  15 , for example, the temperature of the heat roller  11  stored in the housing  15 . 
     The fixing device  2  includes a pressing part  33  which, in accordance with the supply of the recording paper to the nip part, presses the press roller  13  against the heat roller  11  as shown in  FIGS. 5A through 7B , and the opening and closing of the shutter  23  is interlocking with the operations of the pressing part  33 . 
     The pressing part  33  at least has: a rotary shaft  35  which rotates in accordance with the supply of the recording paper; and a pair of moving members  37  and  39  which are fitted with the press roller  13 . Note that the moving member  39  is provided at the side plate  29 , and is hidden by the side plate  29  in  FIGS. 5A, 5B, 6A, and 6B . The moving members  37  and  39 , in accordance with the rotation of the rotary shaft  35 , move in an approaching and separating direction in which the press roller  13  approaches to and separates from the heat roller  11 . The shutter  23  opens and closes the detection hole  21 B in accordance with the rotation of the rotary shaft  35 . 
     The pressing part  33  is provided at the frame  25 . More specifically, the moving members  37  and  39  and the rotary shaft  35  of the pressing part  33  are provided at the side plates  27  and  29 . Note that the rotary shaft  35  is driven into rotation by a motor, not shown, in accordance with the supply of the recording paper. 
     The moving members  37  and  39 , as shown in  FIGS. 7A and 7B , are “L”-shaped when viewed from the axial direction of the heat roller  11 . Portions located on one side forming the “L” (portions located higher than the axis of the press roller  13  although they are invisible by being hidden by a shade of the press roller  13  in  FIGS. 7A and 7B ) are fixed at the side plates  27  and  29  in a manner such as to be rotatable (oscillatable) around an axis passing through these portions (the portions which are fixed are defined as fixed portions). 
     The press roller  13  is rotationally fitted at a position away from the fixed portions of the moving members  37  and  39 . In other words, the moving members  37  and  39  oscillate (move) with respect to the fixing portions as a center whereby the press roller  13  approaches to and separates from the heat roller  11 . 
     The pressing part  33  brings, more closely to the heat roller  11 , portions located closer to the press roller  13  than the fixation portions in the moving members  37  and  39  while the press roller  13  is in contact with the heat roller  11 , whereby the press roller  13  presses the heat roller  11 . 
     The pressing part  33  may further have a function of adjusting, depending on a thickness of the recording paper, an amount of pressing the heat roller  11  by the press roller  13 . For example, the pressing part  33  presses the pressure-contacting member against the heat transfer member described above by a pressing amount predefined in accordance with a thickness of the recording paper. More specifically, the pressing part  33  may have a load generating member which generates such a load that presses the press roller  13  against the heat roller  11 . This load generating member corresponds to compression springs  40 A and  40 B. The compression spring  40 B is provided at the side plate  29 , and is hidden by the side plate  29  in  FIGS. 5A, 5B, 6A, and 6B . 
     The pressing part  33  further has cams  41  and  43  fitted to the rotary shaft  35 , and the moving members  37  and  39  move by interlocking with operation of the cams  41  and  43 . More specifically, the pressing part  33 , as shown in  FIGS. 5A through 7B , includes: oscillating members  45  and  47  which oscillate while abutting on outer circumferential surfaces of the cams  41  and  43 ; and coupling members  49  and  51  which couple the oscillating members  45  and  47  to the moving members  37  and  39 . 
     The oscillating members  45  and  47  are elongated as shown in  FIGS. 7A and 7B , and with middle portions in contact with the cams  41  and  43 , each have one end thereof (an end part on a side closer to the heat roller  11 ) oscillatably fitted to the frame  25  (coupling plate  31 ). As a result, the oscillating members  45  and  47  oscillate in accordance with the rotation of the rotary shaft  35 . 
     The cams  41  and  43  are eccentric cams which are eccentric with respect to the axis of the rotary shaft  35 , and a contacting portion between the outer circumferential surfaces of the cams  41  and  43  and the oscillating members  45  and  47  approaches to and separates from the axis of the rotary shaft  35 . 
     The coupling members  49  and  51  couple together another ends of the oscillating members  45  and  47  and end parts (another end parts) on a side on which the press roller  13  is fitted from the fixation portions in the moving members  37  and  39 . 
     Consequently, upon approach of the position of contact between the outer circumferential surfaces of the cams  41  and  43  and the oscillating members  45  and  47  to the axis of the rotary shaft  35  as a result of the rotation of the rotary shaft  35 , the another end parts of the moving members  37  and  39  approach the heat roller  11  side, and a force with which the press roller  13  presses the heat roller  11  increases. On the contrary, upon separation of the position of contact between the outer circumferential surfaces of the cams  41  and  43  and the oscillating members  45  and  47  from the axis of the rotary shaft  35  as a result of the rotation of the rotary shaft  35 , the another end parts of the moving members  37  and  39  separate from the heat roller  11 , and the force with which the press roller  13  presses the heat roller  11  decreases. 
     Note that when the recording paper is supplied to the nip part, the rotary shaft  35  stops in a state in which the contact position is located closely to the axis of the rotary shaft  35 , and when the recording paper is discharged from the nip part after completion of fixation of the recording paper, the rotary shaft  35  rotates and stops in a state in which the contact position is located away from the axis of the rotary shaft  35 . Directions in which the rotary shaft  35  rotates when the recording paper is supplied and when it is discharged may be fixed or may be reversed therebetween. 
     The pressing part  33  includes the load generating member which generates a load in a direction in which the oscillating members  45  and  47  are caused to abut on the outer circumferential surfaces of the cams  41  and  43 . Here, the load generating member are compression springs  53  and  55 . 
     The shutter  23 , as shown in  FIGS. 8A and 8B , is formed of a plate member supported in a manner such as to be slidable along the coupling plate  31 . The shutter  23  slides in a guide groove  63  of a guide plate  61  provided at the coupling plate  31 . The guide plate  61  is provided at the coupling plate  31  orthogonally thereto. 
     The support of the shutter  23  is, for example, performed by a first locking part  65  which locks on a top surface of the guide plate  61  at a middle portion in a moving direction of the shutter  23  and by a second locking part  67  which locks on a top end of the shutter  23 . 
     The opening and closing of the shutter  23  are performed through sliding in accordance with the rotation of the rotary shaft  35 . The rotary shaft  35  is arranged in parallel to the heat roller  11  as shown in  FIGS. 5A, 5B, 6A, and 6B . That is, the rotary shaft  35  is arranged along a wall (coupling plate  31 ) at which the detection hole  21 B is formed. 
     The shutter  23  has an engaging part  73  engaging with a projection part  71  provided in a screw form on the rotary shaft  35 . As a result, the shutter  23  moves in accordance with the rotation of the rotary shaft  35  (that is, in accordance with the supply and discharge of the recording paper). 
     3. Operation 
     Operation performed from the supply of the recording paper to the discharge thereof will be described. A state before the recording paper is supplied is a state of  FIG. 7B , and a state in which the oscillating members  45  and  47  are separated from the axis of the rotary shaft  35 . 
     (1) At time of Supply of Recording Paper 
     Approach of the recording paper to the nip part rotates the rotary shaft  35 . In accordance with this rotation, the oscillating members  45  and  47  oscillate in a manner such that the point of contact between the outer circumferential surfaces of the cams  41  and  43  and the oscillating members  45  and  47  approaches the axis of the rotary shaft  35  (see  FIG. 7A ). 
     As a result of this oscillation, the moving members  37  and  39  are caused by the coupling members  49  and  51  to approach the heat roller  11  side, and the press roller  13  presses the heat roller  11 . 
     On the other hand, as a result of the rotation of the rotary shaft  35 , the engaging part  73  of the shutter  23  is threaded to the projection part  71  of the rotary shaft  35 , and thus the shutter  23  moves and the detection hole  21 B is opened as shown in  FIG. 8A . As a result, through the detection hole  21 B, an inner temperature, for example, the temperature of the heat roller  11  can be detected by the temperature sensor  70 . 
     As described above, the shutter  23  opens the detection hole  21 B in accordance with the supply of the recording paper, and thus compared to a case where it is constantly open, inner heat loss can be reduced. Moreover, a mechanism of opening and closing the shutter  23  utilizes the rotary shaft  35  forming the pressing part  33  which presses the press roller  13  against the heat roller  11 , thus making it possible to carry it out easily at low costs. 
     In view of the reduced heat loss inside of the fixing device  2 , the shutter  23  had better always close the detection hole  21 B, in which case the inner temperature detection cannot be performed by the temperature sensor  70 . In this embodiment, it is one of objects to reduce the heat loss caused by opening the detection hole  21 B as much as possible while making it possible to detect the inner temperature by the temperature sensor  70 . 
     For example, in a fixing device simply having a detection hole, the detection hole is kept open, thus causing a problem that a warmth retention force in a housing is lost. With the fixing device  2  and the image forming apparatus  1  according to this embodiment, however, the heat loss can be suppressed by the aforementioned detection hole  21 B which is opened and closed by the shutter  23 . 
     (2) At time of Discharge of Recording Paper 
     Upon separation of the recording paper, which has already went through fixation, from the nip part, the rotary shaft  35  rotates in a direction opposite to that at the time of the discharge of the recording paper. In accordance with this rotation, the oscillating members  45  and  47  oscillate in a manner such that the point of contact between the outer circumferential surfaces of the cams  41  and  43  and the oscillating members  45  and  47  separate from the axis of the rotary shaft  35  (see  FIG. 7B ). 
     As a result of this oscillation, the another end parts of the moving members  37  and  39  are separated from the heat roller  11  by the coupling members  49  and  51 , whereby the pressing of the press roller  13  against the heat roller  11  is released. 
     On the other hand, as a result of the rotation of the rotary shaft  35 , the shutter  23  moves in a direction opposite to that at the time of discharge of the recording paper, whereby the detection hole  21 B is closed as shown in  FIG. 8B . This can suppress the inner heat loss. 
     MODIFIED EXAMPLE 
     The fixing device and the image forming apparatus according to this embodiment have been described above, but this disclosure should not be limited to the embodiment described above, and thus may be, for example, a modified example as described below. Moreover, the embodiment and the modified example or modified examples may be combined together. 
     Moreover, even an example not described in the embodiment or the modified examples and a design change without departing from the spirits of this disclosure may be included in this disclosure. 
     1. Shutter Opening and Closing 
     In the embodiment, the rotary shaft  35  of the pressing part  33  is used to open and close the shutter  23 , but a mechanism of opening and closing the shutter in accordance with the supply of the recording paper may be separately provided from the rotary shaft. For example, a new rotary shaft may be used separately from the rotary shaft of the pressing part. Note that using components forming the pressing part  33  can better prevent an increase in the number of components. 
     For the opening and closing, a screw mechanism of the rotary shaft  35  is used, but another mechanism, for example, a gear mechanism such as a rack and a pinion or such a mechanism which winds a wire attached to the shutter may be used. 
     The shutter slides at time of opening and closing, but the opening and closing may be performed in a different movement method. Permitted as the different movement method may be a method of rotating a blade (shutter) fitted to the rotary shaft. In this case, it can be carried out by using, for example, a step motor to achieve rotation through a predetermined angle or by using, for example, the rotary shaft and an umbrella gear to rotate the rotary shaft. 
     2. Inner Property of Housing 
     In the embodiment, the temperature in the housing (the temperature of the heat roller) is detected, but any different properties may be detected. The different property includes, for example, a rotation speed and humidity of the heat roller. 
     3. Pressing Part 
     Used in the embodiment is the pressing part having a structure such that the moving members are coupled to the oscillating members which use the cams, but any different pressing parts may be used. Used as the different pressing part can be, for example, a cylinder or an electric magnet which performs absorption and repelling by energization. 
     The compression springs are used for adjusting the pressing of the oscillating members against the cams and the force of pressing the pressure-contacting member against the heat transfer member, but a tensile spring may be used. Shapes of the oscillating members and the moving members described in the embodiment may be each one example, and may be in different shapes. 
     4. Heat source 
     In the embodiment, the heat source is arranged inside the heat transfer member, but the heat source may be arranged outside of the heat transfer member. 
     Various modifications and alterations of this disclosure will be apparent to those skilled in the art without departing from the scope and spirit of this disclosure, and it should be understood that this disclosure is not limited to the illustrative embodiments set forth herein.