Patent Publication Number: US-2023143488-A1

Title: Temperature sensor, temperature detection device and image formation device

Description:
TECHNICAL FIELD 
     The present invention relates to a temperature sensor that detects the temperature of an object, a temperature detection device and an image formation device. 
     BACKGROUND ART 
     There has been known a temperature detection device that is disposed so as to contact with a heater provided in a thermal fixing roller for controlling the temperature of the thermal fixing roller included in an image formation device such as a printer using an electrophotographic process, for example (Patent Literature 1, for example). 
     The temperature detection device in Patent Literature 1 includes a temperature detection element, a sensor main body having an insert-molded conduction member to provide the conduction between a lead wire of the temperature detection element and a covered electric wire of a circuit portion, and a heat-resistant elastic body interposed between the sensor main body and the temperature detection element. The sensor main body is elastically supported by a support body through a coil spring. The temperature detection element is pressed to the heater by the elastic force of the heat-resistant elastic body. As the heat-resistant elastic body, a ceramic paper formed from fibers composed of an inorganic material is typically used. 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: JP 2002-122489 A 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     In recent years, there has been a demand for a temperature sensor in which the ceramic paper is not used. 
     The present invention has an object to provide a temperature sensor that has heat insulation property, the pressing force to a temperature measurement object and a good responsiveness, without the ceramic paper, and a temperature detection device and an image formation device that include the temperature sensor. 
     Solution to Problem 
     The present invention is a temperature sensor that is disposed so as to maintain an abutting state with a temperature measurement object, the temperature sensor characterized by including: a thermosensitive element configured to detect the temperature of the temperature measurement object; a heat collection member configured to pressurize the temperature measurement object and to be thermally coupled with the thermosensitive element; and a holding member supporting the heat collection member and forming a space that faces the heat collection member. 
     In the temperature sensor of the present invention, it is preferable that the heat collection member be a plate spring. 
     In the temperature sensor of the present invention, it is preferable that the heat collection member include a main body portion where the thermosensitive element is disposed, and that an end portion of the main body portion be supported by the holding member, and the main body portion be pressurized to the temperature measurement object side by elastic force. 
     In the temperature sensor of the present invention, it is preferable that the heat collection member include a pair of leg portions supported by the holding member, at both end portions of the main body portion, and that the main body portion be pressurized to the temperature measurement object side by the elastic force of the leg portions. 
     In the temperature sensor of the present invention, it is preferable that an element disposition portion for disposing the thermosensitive element be formed at the main body portion. 
     In the temperature sensor of the present invention, it is preferable that the holding member include an element support portion supporting the thermosensitive element through the element disposition portion. 
     In the temperature sensor of the present invention, it is preferable that the element disposition portion be formed in a concave shape at a part of the main body portion, and that the thermosensitive element be accommodated in the element disposition portion. 
     In the temperature sensor of the present invention, it is preferable that the main body portion be formed in a substantially rectangular shape in planar view, and be supported by the holding member, at leg portions included in both end portions in a longitudinal direction, and that the element disposition portion be formed so as to extend in a short direction of the main body portion and to bend in an out-of-plane direction of the main body portion. 
     In the temperature sensor of the present invention, it is preferable that the heat collection member include a plurality of positioning pieces that are inserted into the space. 
     In the temperature sensor of the present invention, it is preferable that the holding member include a wall body forming the space, and a contact protrusion protruding from the wall body and contacting with the positioning pieces be formed on the wall body. 
     In the temperature sensor of the present invention, it is preferable that the holding member include a wall body forming the space, that the heat collection member be supported by a distal end of a part of the wall body, and that the wall body have a lower height at a position where the heat collection member is supported, than the height at the other position. 
     In the temperature sensor of the present invention, it is preferable that a first insulating material covering the heat collection member from the temperature measurement object side be disposed between the thermosensitive element and the temperature measurement object. 
     In the temperature sensor of the present invention, it is preferable that the first insulating material be formed in a film shape. 
     In the temperature sensor of the present invention, it is preferable that the thermosensitive element include a thermosensitive body having a resistance value that changes depending on temperature change, and a lead wire for electrically connecting the thermosensitive body to an external circuit, and that a second insulating material configured to insulate at least the lead wire of the thermosensitive element and the heat collection member be disposed between the thermosensitive element and the heat collection member. 
     In the temperature sensor of the present invention, it is preferable that the second insulating material be formed in a film shape, and cover the heat collection member from the temperature measurement object side. 
     In the temperature sensor of the present invention, it is preferable that the thermosensitive element include a thermosensitive body having a resistance value that changes depending on temperature change, and a pair of lead wires for electrically connecting the thermosensitive body to an external circuit, and that the pair of lead wires extend in one direction with respect to the thermosensitive element, and extend into the holding member through one side surface of the holding member. 
     In the temperature sensor of the present invention, it is preferable that the thermosensitive element include a thermosensitive body having a resistance value that changes depending on temperature change, and a pair of lead wires for electrically connecting the thermosensitive body to an external circuit, and that the pair of lead wires extend in both directions with respect to the thermosensitive element, and extend into the holding member through both side surfaces of the holding member. 
     Further, a temperature detection device of the present invention is characterized by including: the above-described temperature sensor; and a circuit portion electrically connected to the temperature sensor and configured to calculate the temperature of the temperature measurement object based on a signal from the temperature sensor. 
     Further, an image formation device of the present invention that is an electrophotographic image formation device, the image formation device including: a fixing device configured to fix toner to a recording medium by heating and pressurizing; and the above-described temperature sensor configured to detect the temperature of a member included in the fixing device. 
     Advantageous Effect of Invention 
     According to the present invention, since the heat collection member pressurizes the temperature measurement object and the heat collection member is thermally coupled with the thermosensitive element, the heat input to the heat collection member is quickly transferred to the thermosensitive element, due to the heat conduction from the pressurized temperature measurement object. Due to this heat collection action and the heat insulation action of the space that faces the heat collection member, it is possible to keep the heat in the thermosensitive element more sufficiently, and therefore it is possible to realize such a good responsiveness that the detection temperature of the thermosensitive element immediately follows the temperature fluctuation of the temperature measurement object without using the so-called ceramic paper. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a perspective view showing the external appearance of a temperature sensor according to an embodiment of the present invention. 
         FIG.  2    is a plan view showing a thermosensitive element included in the temperature sensor shown in  FIG.  1   . 
         FIG.  3    is a side view showing a holding member and lead wires of the thermosensitive element as viewed in the direction of an arrow III in  FIG.  1   . 
         FIG.  4 A  is a perspective view showing the holding member. 
         FIG.  4 B  is a plan view showing the holding member. 
         FIG.  5 A  is a perspective view showing the holding member and a plate spring, two-dot chain lines showing the thermosensitive element. 
         FIG.  5 B  is a plan view showing the holding member and a plate spring, two-dot chain lines showing the thermosensitive element. 
         FIG.  6 A  is a perspective view showing the plate spring as a heat collection member. 
         FIG.  6 B  is a plan view showing the plate spring as a heat collection member. 
         FIG.  7 A  is a sectional view taken along a VIIa-VIIa line in  FIG.  1   . 
         FIG.  7 B  is an enlarged view of a VIIb portion in  FIG.  7 A . 
         FIG.  8    is a perspective view showing a state where a film on the inside is provided in the holding member. 
         FIG.  9    is a schematic view showing an internal structure of a printer equipped with the temperature sensor shown in  FIG.  1   . 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     An embodiment ( FIG.  1    to  FIG.  8   ) of the present invention will be described below with reference to the accompanying drawings. 
     [Schematic Configurations of Temperature Detection Device and Temperature Sensor] 
     Schematic configurations of a temperature detection device  1  and a temperature sensor  10  of the present invention will be described with reference to  FIG.  1    and  FIG.  7 A . As shown in  FIG.  1   , the temperature detection device  1  is configured to include the temperature sensor  10 , a circuit portion  8 , and electric wires  81 ,  82  for electrically connecting the temperature sensor  10  and the circuit portion  8 . 
     The temperature sensor  10  is disposed at a position facing a temperature measurement object  7  (see  FIG.  7 A ), so as to maintain an abutting state with the temperature measurement object  7 . As main constituent elements, the temperature sensor  10  includes a thermosensitive element  11  that detects the temperature of the temperature measurement object  7 , a holding member  20 , and a plate spring  30  as a heat collection member. 
     Further, for securing insulation and creepage distance, the temperature sensor  10  includes an inside film  41  (second insulating material) that covers the plate spring  30  and an outside film  42  (first insulating material) that covers the thermosensitive element  11  disposed on the inside film  41 . Further, the temperature sensor  10  includes a heat collection material  43  that is encapsulated in the periphery of the thermosensitive element  11  between the inside film  41  and the outside film  42 . 
     The circuit portion  8  calculates the temperature of the temperature measurement object  7 , based on an electrical signal that is output from the thermosensitive element  11 . The circuit portion  8  is electrically connected to the temperature sensor  10  through the electric wires  81 ,  82  that are drawn out from the holding member  20 . 
     A direction in which the temperature sensor  10  extends in a direction in which the electric wires  81 ,  82  are drawn out is referred to as a longitudinal direction D 1 . A direction orthogonal to the longitudinal direction D 1  in planar view is referred to as a width direction D 2 . A direction orthogonal to both of the longitudinal direction D 1  and the width direction D 2  is referred to as a height direction D 3 . The temperature measurement object  7  side in the height direction D 3  is referred to as an “upper”, and the opposite side is referred to as a “lower”. 
     Further, with respect to the position of the plate spring  30 , a front surface side Fs is defined as the temperature measurement object  7  side, and a back surface side Bs is defined as the opposite side (holding member  20  side). In the embodiment, the front surface side Fs corresponds to the upper side, and the back surface side Bs corresponds to the lower side. 
     Each constituent element of the temperature sensor  10  will be described below. 
     [Thermosensitive Element] 
     As shown in  FIG.  2   , the thermosensitive element  11  is a thermistor element that includes a thermosensitive body  110 , electrodes  110 A,  110 B provided in the thermosensitive body  110 , a pair of lead wires  111 ,  112  electrically connected to the electrodes  110 A,  110 B, and a covering portion  113  covering the thermosensitive body  110 . In addition, as the thermosensitive element  11 , resistors having temperature coefficients, as exemplified by a thin film thermistor and a platinum temperature sensor, can be widely used. 
     The lead wires  111 ,  112  are respectively conducted to the electric wires  81 ,  82  through a pair of conductive members  121 ,  122  ( FIG.  7 A ) described later, which are provided in the holding member  20 . 
     The thermosensitive body  110  of the thermosensitive element  11  is disposed so as to face the temperature measurement object  7  ( FIG.  7 A ) through the heat collection material  43  and the outside film  42 . 
     [Holding Member] 
     The holding member  20  will be described with reference to  FIG.  4 A  and  FIG.  4 B . 
     The holding member  20  in the embodiment is formed in a substantially rectangular shape in planar view, and includes a main body portion  22 , a seat  201  including a wall body  21  that is formed so as to protrude in the height direction D 3  from a nearly central portion of the main body portion  22  in the longitudinal direction D 1 , and an electric wire connection portion  25  to which the electric wires  81 ,  82  are connected. A space  20 S surrounded by the wall body  21  and having a rectangular parallelepiped shape is formed on the inside of the seat  201 . The plate spring  30  described later is arranged on the front surface side Fs (the upper side in the height direction D 3 ) of the space  20 S. 
     The holding member  20  may be formed in a square shape or a circular shape in planar view, depending on the shape of the space  20 S, the disposition of bosses  221 ,  231  described later, and the like. 
     The holding member  20  is integrally formed by injection molding, using an insulating resin material. For example, an upper surface  22   a  of the main body portion  22  and an upper surface  25   a  of the electric wire connection portion  25  exist on an identical plane. Moreover, a plurality of first bosses  221  formed so as to protrude in the height direction D 3  are provided on the upper surface  22   a  of the main body portion  22 , and a plurality of second bosses  231  formed so as to protrude in the width direction D 2  are provided on a side surface  23  of the main body portion  22 . The first bosses  221  and the second bosses  231  are used for attaching the films  41 ,  42  to the holding member  20 . 
     The electric wire connection portion  25  is a site for attaching the electric wires  81 ,  82  for electrically connecting the thermosensitive element  11  and the circuit portion  8 , and is formed integrally with the main body portion  22  at one end portion of the main body portion  22  in the longitudinal direction D 1 . Connection holes  251 ,  252  for respectively connecting the electric wires  81 ,  82  to the conductive members  121 ,  122  described later are formed on the electric wire connection portion  25 . 
     The seat  201  is a site for attaching the plate spring  30 , and is formed in a rectangular shape in planar view. The seat  201  is constituted by the wall body  21  and the space  20 S. 
     The wall body  21  includes a pair of first walls  211 ,  211  that extend in the longitudinal direction D 1  and that face each other in the width direction D 2 , and second walls  212 ,  212  that connect the respective both ends of the first walls  211 ,  211  in the longitudinal direction D 1 . Each of the first walls  211 ,  211  and the second walls  212 ,  212  is formed so as to stand in the height direction D 3  from a bottom portion  213  of the seat  201 , and upper ends of the first walls  211 ,  211  and the second walls  212 ,  212  form an opening  210  having a rectangular shape. Cutouts  211 A,  211 A formed so as to be cut in a concave shape are respectively formed at the centers of the first walls  211 ,  211  in the longitudinal direction D 1 . Moreover, positioning pieces  321  to  324  ( FIG.  6   ) each of which is a part of the plate spring  30  are inserted into the space  20 S through the opening  210 . 
     The space  20 S maintains heat in the thermosensitive element  11 , due to the heat insulation action that restrains the heat conduction from the thermosensitive element  11  to the exterior. Thereby, the resistance value of the thermosensitive element  11  is quickly changed in response to the temperature fluctuation of the temperature measurement object  7  that inputs heat to the thermosensitive element  11 , and the responsiveness of the temperature sensor  10  is enhanced. Cross-sectional areas (areas in the directions D 1  and D 2 ) and a thickness (a size in the direction D 3 ) that realize a necessary thermal resistance are given to the space  20 S. 
     For keeping the heat conductivity of the space  20 S as low as possible, it is preferable that substances other than air be not disposed in the space  20 S. The existence of substances such as gas and liquid other than air is not entirely excluded in the space  20 S, and substances other than air is not avoided from being encapsulated into the space  20 S, as long as a low heat conductivity can be maintained. Further, it is allowable to dispose a member having a plate shape or the like in the space  20 S, for restraining the generation of a convective flow in the space  20 S. The space  20 S may be formed in another shape, for example, in a cylindrical shape. 
     Support portions  214  supporting the plate spring  30  are formed on an upper end (distal end) of the second wall  212 . The support portions  214  are formed so as to be flat, and the height of the support portions  214  is set so as to be lower than the height of the upper end of the first wall  211 . 
     Outer surfaces  212 A of the pair of the second walls  212  are inclined in such directions that the outer surfaces  212 A come close to each other upward. Therefore, the holding member  20  is formed in a frustum shape in side view. 
     Element support portions  215  supporting the thermosensitive element  11  through the plate spring  30 , first contact protrusions  216  and second contact protrusions  217  are formed on the inside of the wall body  21 . 
     The element support portions  215  are formed so as to respectively protrude to the inside in the width direction D 2  from positions where the cutouts  211 A,  211 A of the pair of the first walls  211  are formed. Upper end surfaces of the element support portions  215  are continuous with bottom surfaces of the cutouts  211 A formed on the first walls  211 . Each element support portion  215  is positioned at the center of the space  20 S in the longitudinal direction D 1 , and supports the plate spring  30  at a position corresponding to the thermosensitive body  110 . 
     The first contact protrusion  216  ( FIG.  4 A  and  FIG.  4 B ) is formed at two spots on both sides of the element support portions  215  of each of the pair of the first walls  211 . The respective first contact protrusions  216  protrude from the first walls  211 , and distal ends of the first contact protrusions  216  contact with surfaces of the positioning pieces  321  to  324  of the heat collection member  30 . Further, the second contact protrusions  217  are formed at four corners of the bottom portion  213  in the vicinity of the first contact protrusions  216 , and distal ends of the second contact protrusions  217  contact with side surfaces of the positioning pieces  321  to  324 . With the first contact protrusions  216  and the second contact protrusions  217 , the positioning of the plate spring  30  in the longitudinal direction D 1  and the width direction D 2  is performed, and the plate spring  30  is maintained in a state of being away from the wall body  21  as much as possible. 
     As shown in  FIG.  4 B , the first contact protrusions  216  are formed so as to protrude from the first walls  211  in a circular arc shape. Further, upper ends of the first contact protrusions  216  have a taper shape for guiding the positioning pieces  321  to  324  at the time of the insertion of the plate spring  30 . The height of the first contact protrusions  216  is set so as to be lower at a distal end side than at a proximal end on the first wall  211  side. Similarly, upper ends of the second contact protrusions  217  are formed in a taper shape. 
     By adopting the shapes of the first contact protrusions  216  and the second contact protrusions  217 , the contact area between the holding member  20  and the plate spring  30  is reduced, and therefore it is hard for heat to escape from the thermosensitive element  11  to the holding member  20  through the plate spring  30 . 
     As shown in  FIG.  7 A , the conductive members  121 ,  122  having a plate shape are provided in the bottom portion  213  of the seat  201 . The insert molding can be performed while the conductive members  121 ,  122  are disposed in a mold for the injection molding of the holding member  20 . Connection holes  241 ,  242  are formed so as to penetrate the bottom portion  213  in the height direction D 3 . The conductive members  121 ,  122  are disposed so as to protrude to the insides of the connection holes  241 ,  242 . The lead wires  111 ,  112  ( FIG.  3   ) extend to one side of the plate spring  30  in the width direction D 2 , and extend to the inside of the bottom portion  213  through the side surface  23  of the holding member  20 . 
     The first bosses  221  and the second bosses  231  are formed integrally with the holding member  20 . 
     The first bosses  221  are disposed on the upper surface of the main body portion  22  such that two first bosses  221  face two first bosses  221  in the longitudinal direction D 1  through the seat  201 , and the second bosses  231  are disposed such that two second bosses  231  are disposed on each of both side surfaces  23  of the holding member  20 . This is an example, and the first bosses  221  and the second bosses  231  can be formed at appropriate positions of the holding member  20 . 
     [Plate Spring (Heat Collection Member)] 
     The plate spring  30  ( FIG.  5 A  to  FIG.  7 B ) pressurizes the temperature measurement object  7  from the back surface side Bs by elastic force, and is thermally coupled with the thermosensitive element  11 . 
     For quickly transferring the heat from the temperature measurement object  7  to the thermosensitive element  11 , the plate spring  30  can be integrally formed using a metal material generally having a higher heat conductivity than resin material and the like, or another material having a heat conductivity that is comparable to the heat conductivity of the metal material, for example, using a metal material such as a copper alloy and stainless steel, a material containing carbon, or the like. In the case where the metal material is used, the plate spring  30  can be formed by press working such as punching and bending. The material that is used for the plate spring  30  can be appropriately selected in consideration of heat conductivity, spring property and heat resistance property. 
     It is preferable that the plate thickness of the plate spring  30  be as small as possible, as long as the strength can be secured, for avoiding the decrease in responsiveness due to the increase in heat capacity. For example, the plate thickness of the plate spring  30  is about 0.05 to 0.2 mm. 
     Due to not only the heat insulation action of the above-described space  20 S but also the heat collection action of the plate spring  30 , it is possible to quickly change the resistance value of the thermosensitive element  11  in response to the temperature fluctuation of the temperature measurement object  7 , and to further enhance the responsiveness of the temperature sensor  10 . The “heat collection” in the specification means that the heat input from the temperature measurement object  7  is quickly transferred to the thermosensitive element  11 . With this heat collection action of the plate spring  30 , the heat is maintained in the thermosensitive element  11  and the vicinity of the thermosensitive element  11 . 
     The plate spring  30  includes a main body portion  31  on which the thermosensitive element  11  is disposed and the plurality of positioning pieces  321  to  324  for the positioning of the plate spring  30  on the holding member  20 . 
     The main body portion  31  is formed in a substantially rectangular shape in planar view. The main body portion  31  includes an abutting portion  310  that is pressed against the temperature measurement object  7 , and spring pieces  311 ,  312  as a pair of leg portions that form both end portions of the abutting portion  310  in the longitudinal direction D 1 . 
     A groove  310 A as an element disposition portion where the thermosensitive body  110  and parts of the lead wires  111 ,  112  are disposed is provided on the abutting portion  310 . The groove  310 A extends in the short direction (width direction D 2 ) of the main body portion  31  and is bent in an out-of-plane direction of the main body portion  31  to form a concave shape. The groove  310 A is formed from one end of the abutting portion  310  to the other end of the abutting portion  310  in the width direction D 2 . 
     The groove  310 A is set so as to have a width (the size in the longitudinal direction D 1 ) and a depth that allow the thermosensitive body  110  to be accommodated even when the sizing of the thermosensitive body  110  varies due to tolerance. 
     When heat is sufficiently input from the temperature measurement object  7  to the lead wires  111 ,  112  (particularly, Dumet wires in the vicinity of the thermosensitive body  110 ) having a higher heat conductivity than the thermosensitive body  110 , the responsiveness can be enhanced, and therefore it is preferable that sections of the lead wires  111 ,  112  that are disposed in the groove  310 A be as long as possible, in consideration of the position where the thermosensitive body  110  of the thermosensitive element  11  is disposed. For example, the thermosensitive body  110  is disposed so as to be shifted to the outside of the center in the width direction D 2  of the groove  310 A formed on the plate spring  30 , and thereby it is possible to elongate the sections of the lead wires  111 ,  112  that are disposed in the groove  310 A. 
     The abutting portion  310  is formed so as to be substantially flat except the groove  310 A, and the whole in the length direction D 1  is pressed against the temperature measurement object  7 . 
     In order to avoid the abutting portion  310  supported by the spring pieces  311 ,  312  at both ends from warping between both ends due to reaction force from the temperature measurement object, thereby causing the thermosensitive element  11  to move away from the temperature measurement object  7 , the abutting portion  310  is supported at the position of the groove  310 A by the element support portion  215  of the holding member  20 . 
     Instead of the groove  310 A, a concave portion having the same shape as the outer shape of the thermosensitive body  110  may be formed on the abutting portion  310 . 
     The spring pieces  311 ,  312  protrude from the abutting portion  310  to both sides in the longitudinal direction D 1 , and are bent so as to be inclined downward with respect to the surface of the abutting portion  310 , and the respective distal ends  311 A,  312 A are bent in the surface direction of the abutting portion  310  so as to perform surface contact with the support portions  214 . Between the pair of first walls  211  of the holding member  20 , the spring pieces  311 ,  312  are respectively supported by the support portions  214  formed at positions lower than the first walls  211 . Therefore, when the abutting portion  310  is pressed against the temperature measurement object  7  and the spring pieces  311 ,  312  are displaced on the support portions  214 , the spring pieces  311 ,  312  elastically deform without interfering with the second walls  212 , and therefore it is possible to sufficiently pressurize the temperature measurement object  7 , as the plate spring  30 . 
     The respective distal ends  311 A,  312 A of the spring pieces  311 ,  312  are formed so as to be bent and to perform surface contact with the support portions  214 , and therefore, when the spring pieces  311 ,  312  slide on the support portions  214 , it is hard for the spring pieces  311 ,  312  to damage the holding member  20 . 
     It is preferable that the contact area between the plate spring  30  and the holding member  20  be as small as possible. This is because heat escapes to the holding member  20  through the portion of the contact. Therefore, the spring pieces  311 ,  312  of the plate spring  30  in the embodiment are formed in a biforked shape for decreasing the contact area with the support portions  214 . 
     The positioning pieces  321  to  324  are formed on both sides of the abutting portion  310  in the width direction D 2 . The positioning pieces  321  to  324  are respectively provided close to four corners of the abutting portion  310 , and are formed so as to protrude downward by bending the abutting portion  310  in the thickness direction D 3 . The positioning pieces  321  to  324  communicate with portions  313  of the abutting portion  310  where the width is decreased. In the abutting portion  310 , the width is decreased from steps  310 B, on both sides of the groove  310 A in the longitudinal direction D 1 . 
     When the positioning pieces  321  to  324  are inserted into the space  20 S, the positioning is performed on the holding member  20  by the above-described first contact protrusions  216  and second contact protrusions  217 . 
     When the temperature sensor  10  is pressed against the temperature measurement object  7  ( FIG.  7 A ), the abutting portion  310  performs surface contact with the temperature measurement object  7 , and the plate spring  30  is pressed by the temperature measurement object  7 . Then, the spring pieces  311 ,  312  of the plate spring  30  elastically deform while being displaced on the support portions  214  to the outsides in the longitudinal direction D 1  orthogonal to the pressing direction (D 3 ). At this time, the main body portion  31  is pressurized to the temperature measurement object  7  by the elastic force of the spring pieces  311 ,  312 . 
     [Inside Film] 
     The inside film  41  is provided on the holding member  20 , for insulating the plate spring  30  and the thermosensitive element  11 . 
     The inside film  41 , which has insulation property, is inserted into the inside of the groove  310 A, and is interposed between the plate spring  30  and the thermosensitive element  11 , as shown in  FIG.  7 B  and  FIG.  8   . In addition, for sufficiently securing the creepage distance from the thermosensitive element  11 , the inside film  41  covers the whole of the surface of the plate spring  30  from the temperature measurement object  7  side. 
     For the inside film  41 , for example, a resin material such as polyimide and a fluorocarbon resin is used. For example, the thickness of the inside film  41  is about 10 to 20 μm. 
     The inside film  41  has a width equivalent to the width of the seat  201 , and is formed in a rectangular shape. 
     In the case where insulating coatings are provided on the lead wires  111 ,  112 , the inside film  41  is not always necessary even when the plate spring  30  has conductive property. Similarly, in the case where the plate spring  30  is a member having no conductive property, as exemplified by a resin molded article, it is possible to omit the arrangement of the inside film  41 . 
     Moreover, the plate spring  30  and the thermosensitive element  11  are thermally coupled through the inside film  41 . 
     [Heat Collection Material] 
     For collecting heat in the thermosensitive element  11 , it is preferable that a gap G 1  ( FIG.  7 B ) in the periphery of the thermosensitive element  11  disposed in the groove  310 A be filled with the insulating heat collection material  43  ( FIG.  7 B  and  FIG.  8   ) that is thermally coupled with the thermosensitive element  11 . 
     As the heat collection material  43 , for example, a material containing a disperse medium such as a silicone resin that has a high heat conductivity among resin materials, and an insulating dispersoid such as a ceramic powder is used. Further, as the heat collection material  43 , a so-called heat conductive grease or silicone oil compound can be used. 
     The filling with the heat collection material  43  is performed on the inside film  41 . 
     The heat collection material  43  tightly contacts with the thermosensitive element  11  and tightly contacts with the plate spring  30  through the inside film  41 , and thereby it is possible to thermally couple the plate spring  30  with the thermosensitive element  11  more sufficiently, and to further enhance the responsiveness. 
     [Outside Film] 
     The outside film  42  has insulation property, and is provided for insulating the thermosensitive element  11  and the temperature measurement object  7  by covering the plate spring  30  and the holding member  20  from the temperature measurement object  7  side while being interposed between the thermosensitive element  11  and the temperature measurement object  7 . Further, the outside film  42  holds the thermosensitive element  11  on the plate spring  30 . As shown in  FIG.  1    and  FIG.  7 A , the outside film  42  covers the thermosensitive element  11  on the inside film  41 , and is fixed to both side surfaces  23  of the holding member  20 . Furthermore, for sufficiently securing the creepage distance from the thermosensitive element  11  and the conductive members  121 ,  122 , the outside film  42  covers most of the holding member  20  that includes both side surfaces  23  of the holding member  20 , in addition to the whole of the plate spring  30 . 
     For the outside film  42 , for example, a resin material such as polyimide and a fluorocarbon resin is used. As shown in  FIG.  7 B , the outside film  42  may be a film in which two or more film materials are laminated. For example, the whole thickness of the outside film  42  is about 10 to 20 μm. 
     [Assembly Procedure for Temperature Sensor] 
     For example, the temperature sensor  10  can be assembled in the following procedure. 
     Each procedure will be described. 
     (1) Terminals of the lead wires  111 ,  112  of the thermosensitive element  11  are joined to the conductive members  121 ,  122  ( FIG.  7 A ) in a state where the insert molding has been performed in the holding member  20 , by electric welding or the like. 
     (2) The positioning pieces  321  to  324  of the plate spring  30  are inserted into the inside of the wall body  21  of the holding member  20  shown in  FIG.  4 A  and  FIG.  4 B . At this time, distal ends (lower ends) of the positioning pieces  321  to  324  do not contact with the bottom portion  213 . When the plate spring  30  is further pushed to the inside of the wall body  21 , the distal ends of the positioning pieces  321  to  324  come in contact with the bottom portion  213 , and the positioning pieces  321  to  324  function as a stopper at this time. 
     As shown in  FIG.  5 A , the plate spring  30  is assembled to the holding member  20  in a state where the spring pieces  311 ,  312  are supported by the support portions  214 . At this time, the abutting portion  310  protrudes upward of the upper ends of the first walls  211 . The space  20 S is defined on the back surface side Bs of the plate spring  30 . 
     (3) Next, as shown in  FIG.  8   , the plate spring  30  is covered by the inside film  41 , and the inside film  41  is fixed to the holding member  20  by a heat caulking in which heat and pressure are applied to the first bosses  221  that are inserted into holes provided at four corners of the inside film  41 . 
     (4) The lead wires  111 ,  112  are routed while being shaped, and the thermosensitive element  11  is assembled to the holding member  20  and the plate spring  30 . Specifically, the lead wires  111 ,  112  are bent upward along the side surfaces  23  of the holding member  20  from the conductive members  121 ,  122 , and thereafter are also bent at the position of the groove  310 A of the plate spring  30 . Then, the thermosensitive body  110  is accommodated in the groove  310 A on which the inside film  41  is laid. 
     (5) Subsequently, the heat collection material  43  is applied to the thermosensitive body  110 . The heat collection material  43  adheres to the thermosensitive body  110  and the lead wires  111 ,  112  drawn out from the thermosensitive body  110 . 
     (6) Finally, as shown in  FIG.  1   , most of the holding member  20  that includes the thermosensitive element  11  and the heat collection material  43  is covered by the outside film  42 , and the outside film  42  is fixed to the holding member  20  by the heat caulking of the second bosses  231 , similarly to the first bosses  221 . 
     Thereby, the assembly of the temperature sensor  10  is completed. 
     [Main Function Effect of Temperature Sensor] 
     When the temperature sensor  10  is installed so as to face the temperature measurement object  7  ( FIG.  7 A ), the abutting portion  310  of the plate spring  30  is pressed against the temperature measurement object  7 , and thereby the spring pieces  311 ,  312  elastically deform while smoothly sliding on the support portions  214 . As a result, the abutting portion  310  supported by the element support portions  215  is evenly pressurized to the temperature measurement object  7  through the inside film  41  and the outside film  42 . Furthermore, the heat radiated from the temperature measurement object  7  is sufficiently input to the abutting portion  310  pressed against the temperature measurement object  7 , and the heat is sufficiently transferred from the abutting portion  310  to the thermosensitive element  11  through the heat collection material  43  supplied to the inside of the groove  310 A. At this time, the abutting portion  310  is thermally coupled with not only the thermosensitive element  11  but also the temperature measurement object  7 . 
     Even when void remains between the thermosensitive element  11  and the abutting portion  310  at the time of the completion of the assembly of the temperature sensor  10 , the thermosensitive body  110  and the vicinity of the thermosensitive body  110  are filled with the heat collection material  43  substantially with no gap, by the pressurization from the plate spring  30  to the temperature measurement object  7 . Therefore, it is possible to thermally couple the thermosensitive element  11  and the plate spring  30  more sufficiently. 
     Furthermore, the positioning pieces  321  to  324  and spring pieces  311 ,  312  of the plate spring  30  contact with the holding member  20  by the minimum necessary contact, and therefore the outflow of the heat to the holding member  20  through the plate spring  30  is restrained. By the synergy of this, the heat collection action of the plate spring  30 , and further the heat insulation action of the space  20 S having a lower heat conductivity than a heat insulating material such as a ceramic paper, it is possible to more surely keep the heat transferred from the temperature measurement object  7  in the thermosensitive element  11  and the vicinity of the thermosensitive element  11 . 
     Accordingly, with the temperature sensor  10  in the embodiment, it is possible to cause the thermosensitive element  11  to immediately follow the temperature change of the temperature measurement object  7 , and to realize a good responsiveness of the detection temperature. Due to the thin plate spring  30  and the space  20 S defined on the back surface side Bs, the temperature sensor  10  has both the heat insulation performance and the elastic force for pressurizing the temperature sensor  10  to the temperature measurement object  7 , and therefore without using the so-called ceramic paper, it is possible to realize a responsiveness equal to or higher than that of the ceramic paper, while maintaining the small size of the temperature sensor  10 . 
     [Application Example for Image Formation Device] 
     An example in which the temperature detection device  1  including the temperature sensor  10  is applied to the laser printer  9  as an example of the image formation device will be briefly described with reference to  FIG.  9   . 
     As shown in  FIG.  9   , the laser printer  9  includes a photoreceptor belt  91 , an electrifier  92 , an exposure device  93 , developing devices  901  to  904 , a guide roller  94 , an intermediate transfer unit  95 , a paper feed cassette  96 , a paper feed roller  97 , a transfer roller  98 , a fixing device  99 , a resist roller  910 , a paper ejection roller  911 , a paper ejection tray  912 , and a control device  900  that controls each unit of the laser printer  9 . 
     The fixing device  99  includes a pressure roller  991  and a heating roller  992 . The heating roller  992  incorporates an unillustrated heater as a heat source. 
     For measuring the temperature of the heater incorporated in the heating roller  992  and the temperature of a member provided on the heater, the temperature sensor  10  is installed so as to be pressed against the heater or the member. 
     After electrification, exposure, development and transfer as processes of the image formation by the laser printer  9 , a recording paper  913  on which a color toner image is transferred is fed to between the pressure roller  991  and heating roller  992  of the fixing device  99 , in the process of fixation. The recording paper  913  is pressurized and heated while passing through between the pressure roller  991  and the heating roller  992 , and thereby the color toner image is fixed to the recording paper  913 . Thereafter, the recording paper  913  is ejected to the paper ejection tray  912  through the paper ejection roller  911 . 
     The control device  900  controls the energization state of the heater of the heating roller  992 , using the temperature measurement value obtained from the temperature sensor  10  and the circuit portion  8  to which the temperature sensor  10  is connected. For example, when the temperature measurement value exceeds a threshold, the control device  900  stops the energization of the heater of the heating roller  992 . 
     With the temperature sensor  10 , the surface temperature of the heating roller  992  is measured at a high following capability, and therefore, it is possible to adequately control the energization state of the heater without needlessly heating the heating roller  992  with the heater in prospect of the delay of the response of the measurement. 
     In addition to the above description, configurations described in the above embodiment can be chosen, or can be appropriately altered to other configurations, without departing from the spirit of the present invention. 
     The case of using the thermistor element having a configuration in which the lead wires  111 ,  112  extend from one side of the thermosensitive body  110  in one direction as shown in  FIG.  2    has been exemplified and described in the above embodiment, but a thermistor element in which the lead wires  111 ,  112  extend in both directions of the thermosensitive body  110  may be used. In this case, the lead wires  111 ,  112  pass through both side surfaces  23  of the holding member  20 , and extend into the holding member  20 . 
     Further, the case where the lead wires  111 ,  112  are drawn out from the thermosensitive body  110  in the width direction D 2  has been exemplified and described in the embodiment, but the lead wires  111 ,  112  may be drawn out from the thermosensitive body  110  in the longitudinal direction D 1 . 
     The shape of the plate spring  30  is not limited to the above embodiment, and various modifications can be made. 
     For example, a protrusion for performing the positioning of the plate spring  30  on the holding member  20  can be formed between portions of the biforked shape of each of the spring pieces  311 ,  312 . In that case, the positioning pieces  321  to  324  extending downward from the abutting portion  310  is not necessary. 
     REFERENCE SIGNS LIST 
     
         
           1  temperature detection device 
           7  temperature measurement object 
           8  circuit portion 
           9  laser printer 
           10  temperature sensor 
           11  thermosensitive element 
           20  holding member 
           20   s  space 
           21  wall body 
           22  main body portion 
           23  side surface 
           25  electric wire connection portion 
           30  plate spring (heat collection member) 
           31  main body portion 
           41  inside film (second insulating material) 
           42  outside film (first insulating material) 
           43  heat collection material 
           81 ,  82  electric wire 
           91  photoreceptor belt 
           92  electrifier 
           93  exposure device 
           94  guide roller 
           95  intermediate transfer unit 
           96  paper feed cassette 
           97  paper feed roller 
           98  transfer roller 
           99  fixing device 
           110  thermosensitive body 
           111 ,  112  lead wire 
           113  covering portion 
           121 ,  122  conductive member 
           201  seat 
           210  opening 
           211  first wall 
           211 A cutout 
           212  second wall 
           212 A outer surface 
           213  bottom portion 
           214  support portion 
           215  element support portion 
           216  first contact protrusion (contact protrusion) 
           217  second contact protrusion (contact protrusion) 
           221  first boss 
           231  second boss 
           241 ,  242  connection hole 
           251 ,  252  connection hole 
           310  abutting portion 
           310 A groove (element disposition portion) 
           310 B step 
           311 ,  312  spring piece (leg portion) 
           311 A,  312 A distal end 
           321  to  324  positioning piece 
           900  control device 
           901  to  904  developing device 
           910  resist roller 
           911  paper ejection roller 
           912  paper ejection tray 
           913  recording paper (recording medium) 
           991  pressure roller 
           992  heating roller 
         Bs back surface side 
         Fs front surface side 
         D 1  longitudinal direction 
         D 2  width direction 
         D 3  height direction 
         G 1  gap