JP2013041212A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of accurately acquiring surface temperatures of a heat fixing member in different positions in the paper passing direction, and an image forming apparatus using the same.SOLUTION: A fixing device comprises: a plurality of Peltier elements D provided along the paper passing width direction and facing their heated surfaces Da to the surface of a fixing belt 51 as a heat fixing member; surface temperature acquisition means for detecting thermal electromotive forces generated at the Peltier elements D and acquiring surface temperatures of the fixing belt 51 in positions where the respective Peltier elements are provided; and cooling means for supplying air as a cooling medium to a cooling part 80 to cool cooled surfaces Db of the plurality of Peltier elements D. The cooling means adjusts a flow of air supplied to areas (cooling chambers 831-834) of the cooling part 80 corresponding to the respective Peltier elements D so that the temperature difference among the cooled surfaces Db of the plurality of Peltier elements D is within a predetermined range.

Description

  The present invention relates to a fixing device and an image forming apparatus using the same, and more particularly to a technique for effectively using a thermoelectric conversion element as a temperature sensor in a fixing device.

A thermoelectric conversion element is an element that generates a thermoelectromotive force according to the temperature difference when a temperature difference is generated between two thermosensitive surfaces. Recently, miniaturization has progressed and sensitivity has improved. Therefore, it has been studied to use it as a temperature sensor for measuring the surface temperature of the heating rotator by being arranged in a fixing device of an electrophotographic image forming apparatus.
However, since the inside of the fixing device is a high temperature atmosphere, there is almost no temperature difference between the thermosensitive surface of the thermoelectric conversion element facing the surface of the heating rotator and the other thermosensitive surface, making it difficult to detect the temperature.

  Therefore, a duct is arranged in the housing of the fixing device, and a cooling medium such as outside air is introduced into the duct, and a heat sensitive surface (hereinafter referred to as “cooled surface”) on the opposite side of the thermoelectric conversion element from the heating rotating body by the duct. Cooling).

JP 2008-40235 A

Recently, in order to sufficiently manage the surface temperature of the heating rotator, a plurality of temperature sensors are arranged along the sheet passing width direction of the heating rotator to detect temperatures at a plurality of locations.
Therefore, for example, as shown in FIG. 12, the present inventors arranged a plurality of thermoelectric conversion elements D in the direction of the rotation axis J along the surface of the fixing belt 951 that is a heating rotator, and a cooling duct 980. Is provided to cool the surface to be cooled Db of each thermoelectric conversion element D and acquire the surface temperature of each part of the fixing belt 951.

However, since the temperature of the fixing device 905 is high, the temperature of the cooling medium moving in the cooling duct 980 differs between the suction port 980a side and the discharge port 980b side, and as a result, a plurality of thermoelectric conversions are performed. The temperature of the cooled surface Db of the element D will be different.
The measurement principle of the temperature sensor using the thermoelectric conversion element D is to detect the temperature on the heating side by detecting the thermoelectromotive force generated according to the temperature difference with reference to the temperature on the cooled surface Db side. Therefore, if the temperature of the surface to be cooled Db differs for each position of the thermoelectric conversion element as described above, accurate temperature detection becomes difficult.

  The present invention has been made in view of the above-described problems, and uses a plurality of thermoelectric conversion elements arranged along the surface of the heat-fixing member, at different positions in the sheet passing width direction of the heat-fixing member. It is an object of the present invention to provide a fixing device and an image forming apparatus that can acquire the surface temperature more accurately.

  In order to achieve the above object, a fixing device according to the present invention forms a fixing nip by pressing a pressing member on the surface of a heat fixing member, and passes a recording sheet carrying a toner image in the fixing nip. A plurality of thermoelectric conversion elements arranged along the sheet passing width direction with the heated end face facing the surface of the heat fixing member, and heat generation generated by the thermoelectric conversion elements. Surface temperature acquisition means for detecting electric power and acquiring the surface temperature of the heat-fixing member at the position where each thermoelectric conversion element is disposed, and supplying a cooling medium to the duct to cool the plurality of thermoelectric conversion elements A cooling means for cooling the side end face, wherein the cooling means corresponds to each thermoelectric conversion element of the duct so that the temperature difference of the cooled side end faces of the plurality of thermoelectric conversion elements is within a predetermined range. The cooling supplied to the area Wherein the flow rate of the body is adjusted.

  Here, the temperature difference of the end face to be cooled being “within a predetermined range” means a range in which a decrease in detection accuracy of the surface temperature of the heating rotator does not cause a practical problem. And detection accuracy specifications.

In the fixing device configured as described above, the flow rate of the cooling medium supplied to the area corresponding to each thermoelectric conversion element of the duct is adjusted, and the temperature difference between the cooled end faces of the plurality of thermoelectric conversion elements is within a predetermined range. Thus, the temperature detection unevenness for each thermoelectric conversion element can be suppressed within an allowable range, and the surface temperatures at a plurality of positions of the heat fixing member can be detected more accurately.
The duct here has a suction path for sucking the cooling medium, and a branch path that branches from the suction path and supplies the cooling medium to each region corresponding to each thermoelectric conversion element. It is desirable that the flow rate is adjusted by changing the area. Further, it is desirable that the cross-sectional area of each branch path is determined so that the flow rate of the coolant flowing in the downstream branch path is larger than the upstream side of the coolant flowing in the suction path.

Further, it is desirable that a flow rate adjusting means for adjusting the flow rate of the cooling medium is provided for each region corresponding to each thermoelectric conversion element of the duct, and the flow rate of the cooling medium is adjusted by the flow rate adjusting means. It is preferable that the flow rate adjusting means here includes a louver, a driving means for driving the louver, and an angle control means for controlling the angle of the louver via the driving means.
The cooling means preferably includes a fan that introduces a gas as a cooling medium into the duct, and a control means that controls the overall flow rate of the introduced gas by controlling the output of the fan.

Further, temperature detection means for detecting the temperature of the cooling medium at any one of the paths from the suction to the delivery of the duct is provided, and the surface temperature acquisition means is provided for detecting the temperature of the cooling medium detected by the temperature detection means. It is desirable to obtain the surface temperature of the heat fixing member based on the thermoelectromotive force generated in each thermoelectric conversion element with reference to the temperature.
As the cooling medium here, it is desirable to use air or water taken from outside the apparatus.

  The present invention may also be an image forming apparatus provided with the fixing device.

1 is a schematic diagram illustrating a configuration of a printer according to a first embodiment of the present invention. FIG. 2 is a perspective view illustrating a configuration of a main part of a fixing unit in the printer. 2A is a cross-sectional view of the fixing unit of FIG. 2 taken along a virtual plane V, and FIG. 2B is an enlarged view of the Peltier element D of FIG. 2 is a diagram illustrating an example of a circuit configuration for detecting a thermoelectromotive force of a Peltier element D. FIG. It is a figure for demonstrating the structure of the flow volume of the air supplied to a branch pipe. It is a block diagram which shows the relationship between the structure of a control part, and the main component used as the control object by a control part. It is a perspective view which shows the structure of the principal part of the fixing | fixed part which concerns on 2nd Embodiment. It is a figure for demonstrating the operation | movement of a louver, and the flow of the air in a cooling duct. It is a figure which shows an example of control of a louver. It is a flowchart which shows operation | movement of the "louver control process" performed by a control part. It is a figure explaining the structure of the cooling duct which the fixing | fixed part which concerns on a modification has. It is a figure which shows the structure of an example of the fixing | fixed part which the present inventors considered.

<First Embodiment>
Hereinafter, a first embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings by taking a tandem type color printer (hereinafter simply referred to as “printer”) as an example.
<Overall configuration of printer>
FIG. 1 is a schematic diagram illustrating a configuration of a printer according to the present embodiment.

  As shown in FIG. 1, the printer 1 includes an image processing unit 3, a paper feeding unit 4, a fixing unit 5, and a control unit 60. When this printer 1 is connected to a network (for example, a LAN) and receives a print job execution instruction from an external terminal device, it forms toner images of yellow, magenta, cyan, and black colors based on the instruction. Then, these are multiplex-transferred to form a color image.

Hereinafter, the reproduction colors of cyan, magenta, yellow, and black are represented as C, M, Y, and K, and the C, M, Y, and K are added as subscripts to the numbers of the components related to the reproduction colors.
The image processing unit 3 includes image forming units 3Y, 3M, 3C, and 3K, an exposure unit 10, an intermediate transfer belt 11, and the like.
The image forming unit 3Y includes a photosensitive drum 31Y, a charger 32Y, a developing unit 33Y, a primary transfer roller 34Y, a cleaner 35Y for cleaning the photosensitive drum 31Y, and the like disposed around the photosensitive drum 31Y. A Y-color toner image is formed on 31Y. The other image forming units 3M to 3K have a configuration such as the chargers 32M to 32K as in the image forming unit 3Y except that the color of toner is different. Omitted.

The intermediate transfer belt 11 is an endless belt, is stretched around a driving roller 12 and a driven roller 13, and is driven to rotate in the direction of arrow A.
The exposure unit 10 includes a light emitting element such as a laser diode, emits a laser beam L for forming images of Y to K colors by a drive signal from the control unit 60, and is charged by the chargers 32Y to 32K. Optical scanning is performed on 31Y to 31K to form latent images on the photosensitive drums 31Y to 31K, and development is performed by the developing units 33Y to 33K to form toner images.

On the intermediate transfer belt 11, the toner images formed in the respective image forming units are transferred in a multiple manner.
The paper feed unit 4 includes a paper feed cassette 41 that accommodates the recording sheets S, a paper feed roller 42 that feeds the recording sheets S in the paper feed cassette 41 one by one onto the conveyance path 43, and a secondary feeding of the fed recording sheets S. A timing roller pair 44 and the like for taking the timing of feeding to the transfer position 46 are provided. The toner image on the intermediate transfer belt 11 is secondarily transferred to the recording sheet S fed from the paper feeding unit 4 by the action of electrostatic force by the secondary transfer roller 45 at the secondary transfer position 46. The recording sheet S that has passed through the secondary transfer position 46 is further conveyed to the fixing unit 5, and the toner image (unfixed image) on the recording sheet S is fixed to the recording sheet S by heating and pressing in the fixing unit 5. Thereafter, the sheet is discharged onto the discharge tray 72 via the discharge roller pair 71.

The control unit 60 controls the image processing unit 3, the paper feeding unit 4, the fixing unit 5, and the like, and details will be described later.
<Configuration of fixing unit>
Next, the configuration of the fixing unit 5 will be described with reference to FIGS. 2 and 3.
FIG. 2 is a perspective view showing the configuration of the main part of the fixing unit 5, and FIG. 3A is a cross-sectional view seen from the Y ′ direction when cut along the virtual plane V of FIG. 2.

The fixing unit 5 includes an endless fixing belt 51 having a resistance heating element layer 511, a pressure roller 52 loosely fitted inside the fixing belt 51, a pressure roller 53, and a power supply member 54a for supplying power to the resistance heating element layer 511. 54b, a temperature sensor unit 55, a cooling unit 80, and the like.
Both ends of the pressing roller 52 are rotatably supported by bearings (not shown) provided in the housing 50. The pressure roller 53 is also rotatably supported by a bearing portion (not shown) provided in the housing 50 and is pressed by the pressure roller 52 via the fixing belt 51, and is fixed between the fixing belt 51 and the fixing roller 51. A nip portion N is formed.

Further, the pressure roller 53 is rotationally driven via a power transmission mechanism such as a gear or belt using a motor (not shown) as a power source. The pressure roller 52 and the fixing belt 51 are driven to rotate following the rotation of the pressure roller 53. The pressure roller 53 rotates in the direction of arrow C, and the pressing roller 52 and the fixing belt 51 rotate in the direction of arrow B, respectively.
Hereinafter, each component in the fixing unit 5 will be described in detail.
(Fixing belt)
The fixing belt 51 is a cylindrical elastically deformable belt. A resistance heating element layer 511 is formed, and power is fed to both ends of the outer peripheral surface of the resistance heating element layer 511 in the width direction (rotation axis J direction). Electrode layers 512a and 512b are provided.

  The resistance heating element layer 511 is formed by dispersing a conductive filler in a resin material, and generates Joule heat upon receiving power supply. The resin material is a heat-resistant resin such as PI (polyimide), PPS (polyphenylene sulfide), or PEEK (polyether ether ketone), and the conductive filler is a metal such as silver or copper, or a carbon such as carbon nanotube. A system material and two or more of these materials mixed and dispersed can be used.

Power supply members 54 a and 54 b are slidably contacted with the electrode layers 512 a and 512 b, and the power supply members 54 a and 54 b are electrically connected to the AC power supply 500 through lead wires 501. Thereby, the power of the AC power supply 500 is supplied to the resistance heating element layer 511 through the electrode layers 512a and 512b.
In the heat generation region 51 a between the electrode layers 512 a and 512 b in the rotation axis J direction of the fixing belt 51, an elastic layer and a release layer are laminated on the outer periphery of the resistance heating element layer 511. The elastic layer is a layer for preventing the toner image from being crushed or being melted non-uniformly so as not to generate image noise. The release layer is the same as the recording sheet S after fixing. This is an insulating layer for improving the mold releasability.

For example, when the width of the electrode layers 512a and 512b is set to 15 [mm], the width dimension of the fixing belt 51 is the sum of the maximum sheet passing width (A3 lengthwise) of the recording sheet S and the widths of the electrode layers 512a and 512b. It is set to 360 [mm] which is larger than the value obtained. The inner diameter of the fixing belt 51 is set to 30 [mm].
(Pressing roller)
The pressing roller 52 has an elastic layer 522 formed around a long and cylindrical cored bar 521, and prevents heat generated in the fixing belt 51 from being radiated through the pressing roller 52. The adhesion with the fixing belt 51 at the nip portion is improved.

The outer diameter of the pressing roller 52 is smaller than the inner diameter of the fixing belt 51, and is set to about 30 [mm], for example.
(Pressure roller)
In the pressure roller 53, an elastic layer 532 and a release layer 533 are laminated in this order around a long and cylindrical cored bar 531. Also in this case, by providing the elastic layer 532, the pressure roller 53 and the fixing belt 51 are brought into elastic contact so as to eliminate the uneven contact pressure as much as possible and to prevent uneven fixing. The outer diameter of the pressure roller 53 is set to about 30 [mm].
(Power supply member)
The power feeding members 54a and 54b are block-like carbon brushes, which are made of a material such as copper graphite or carbon graphite having slidability and conductivity, each of which is in the direction of arrow E (not shown) by a guide member (not shown). 3 (a)) and is urged toward the fixing belt 51 by a biasing member such as a spring (not shown) so as to ensure electrical connection.

The power source 500 is, for example, a household power source with a voltage of 100 [V], and is connected to the lead wire 501 and the power feeding members 54a and 54b. A known relay switch (not shown) for controlling ON / OFF of power supply is inserted into the lead wire 501 based on an input signal from the control unit 60, and thereby energization of the fixing belt 51 is controlled. .
(Temperature sensor)
The temperature sensor unit 55 includes a plurality of Peltier elements D arranged in a line in the rotation axis J direction along the surface of the fixing belt 51. The number and arrangement of the plurality of Peltier elements D are determined so that any of the Peltier elements D are opposed to each other in substantially the entire region of the heat generating area 51 a of the fixing belt 51 in the rotation axis J direction.

As shown in the enlarged view of FIG. 3B, the Peltier element D has a plurality of sets formed by joining N-type semiconductor pieces 91n and P-type semiconductor pieces 91p with conductive electrodes 92, and sandwiching them between them. And a pair of ceramic substrates 93 to be mounted on.
In FIG. 3, only two sets of an N-type semiconductor piece 91n and a P-type semiconductor piece 91p are drawn for easy understanding.

In the Peltier element D, when a temperature difference occurs between the heat sensitive surfaces Da and Db, electrons move in the N-type semiconductor piece 91n and holes in the P-type semiconductor piece 91p move from the high temperature side to the low temperature side, respectively. However, a thermoelectromotive force is generated by the so-called Seebeck effect, and a current flows in the direction of the arrow in FIG. The electric power thus generated is transmitted to and stored in the secondary battery.
During operation of the fixing unit 5, the heat-sensitive surface Da of each Peltier element D is heated by the heat of the fixing belt 51, and the opposite heat-sensitive surface Db is cooled by the cooling unit 80. As a result, a temperature difference Td is generated between the heat-sensitive surfaces Da and Db, and each Peltier element D generates heat by generating a thermoelectromotive force according to the temperature difference Td. Hereinafter, the heat sensitive surface Da of each Peltier element D is referred to as a heated surface Da, and the heat sensitive surface Db is referred to as a cooled surface Db.

Each Peltier element D is disposed at a position where the shortest distance g between the heated surface Da and the surface of the fixing belt 51 is 0.25 mm to 1.5 mm, and is close to the fixing belt 51. Following the change in the surface temperature of the fixing belt 51, the temperature of the heated surface Da is likely to change, and the responsiveness of the output voltage is improved.
FIG. 4 is a diagram illustrating an example of a circuit configuration for detecting the thermoelectromotive force of the plurality of Peltier elements D.

In FIG. 4, 20 Peltier elements D (D1 to D20 in order from the left are set so as to face substantially the entire region of the heat generating area 51a of the fixing belt 51 in the rotation axis J direction. In this case, a configuration in which “Peltier elements D” are simply arranged) is shown.
The Peltier elements D <b> 1 to D <b> 20 are connected in series, and the element array connected in series is connected to the secondary battery 7 via the lead wire 502. A relay switch 502 a that is controlled to open and close based on an input signal from the control unit 60 is inserted into the lead wire 502. The power stored in the secondary battery 7 is used, for example, for driving a fan 87 (FIG. 2) provided in the cooling unit 80 and also used as standby power for the printer 1.

Each of the Peltier elements D1 to D20 is connected to the voltage detection unit 59 via a lead wire and a relay, and the thermoelectromotive force is detected by the voltage detection unit 59.
Specifically, the Peltier element D1 is connected to the voltage detection unit 59 via the lead wire L1 and the relay RS1. The relay RS1 includes a known relay switch, and is controlled to open and close based on an input signal from the control unit 60. When the relay RS1 is closed, the thermoelectromotive force of the Peltier element D1 is detected by the voltage detection unit 59, and the detection result is output to the control unit 60.

The Peltier element D2 is also connected to the voltage detection unit 59 via the lead wire L2 and the relay RS2, and when the relay RS2 is closed based on the input signal from the control unit 60, the thermoelectromotive force of the Peltier element D2 is It is detected by the voltage detector 59. Each of the Peltier elements D3 to D20 is configured similarly.
The control unit 60 closes only the relay RS corresponding to the Peltier element D at the position where the temperature is to be detected among the relays RS1 to RS20, and the other relays RS1 to RS12 are in an open state. An input signal is output to RS20. For example, if the control unit 60 controls the relays RS1, RS2,... RS20 to be closed one by one in this order, the thermoelectromotive forces of the Peltier elements D1, D2,. Can do.

In general, the thermoelectromotive force of the Peltier element D that is detected is proportional to the temperature difference Td between the heated surface Da and the cooled surface Db. Therefore, the correlation between the thermoelectromotive force and the temperature difference Td is measured or obtained in advance. Therefore, based on the correlation, the temperature difference Td can be obtained from the thermoelectromotive force.
In the present embodiment, the surface temperature of the fixing belt 51 is acquired from the temperature difference Td obtained from the thermoelectromotive force of each Peltier element D by a method described later.

Accordingly, each of the Peltier elements D1 to D20 can function as a temperature sensor that acquires the surface temperatures of the regions R1 to R20 of the heat generating region 51a of the fixing belt 51. Regions R <b> 1 to R <b> 20 are regions formed by dividing the heat generating region 51 a into 20 pieces in the rotation axis J direction, and the Peltier elements D <b> 1 to D <b> 20 face each other when the fixing belt 51 is driven to rotate.
(Cooling section)
2 and 3A, the cooling unit 80 secures the temperature difference Td between the heat sensitive surfaces Da and Db by cooling the cooled surface Db of each Peltier element D, and each Peltier element D The amount of power generated from the plant is increased.

  The cooling unit 80 includes a suction pipe 81, a discharge pipe 82, a cooling pipe 83, a fan device 87, and the like. The cooling pipe 83 is divided into four cooling chambers 831 to 834 in the rotation axis J direction. The suction pipe 81 and the cooling chambers 831 to 834 communicate with each other via communication pipes 811 to 814, respectively, and the discharge pipe 82 and the cooling chambers 831 to 834 communicate with each other via communication pipes 821 to 824, respectively. The cooling pipe 83 is arranged inside the housing 50 of the fixing unit 5, and the suction pipe 81 and the discharge pipe 82 are arranged outside the housing 50.

Each of the tubes 81 to 83, 811 to 814, 821 to 824, and 831 to 834 is made of, for example, a heat resistant insulating resin.
Each of the suction pipe 81 and the discharge pipe 82 extends in parallel along the direction of the rotation axis J, the ends 81a and 82a opposite to each other open, and the openings 81a and 82a are separated from each other. It is arranged with a gap.

The opening-side end 81a can suck air outside the printer 1 (hereinafter also referred to as outside air) through a through-hole formed in a housing (not shown) of the printer 1.
A ventilation fan device 87 is provided at the end 82 a of the discharge pipe 82. By driving the fan device 87, outside air flows from the suction port 81 a of the suction pipe 81 and is discharged from the discharge port 82 b of the discharge pipe 82 through the cooling chambers 831 to 834.

Normally, a printer is used in an office, and in the office, the room temperature is set within a predetermined range (for example, 20 ° C. to 28 ° C.) by air conditioning. Therefore, the temperature of the outside air sucked into the cooling unit 80 is extremely lower than the temperature inside the fixing unit 5 during operation, and can be sufficiently utilized as a cooling medium.
FIG. 3A shows a schematic cross section of the cooling chamber 831 among the cooling chambers 831 to 834.

As shown in FIG. 3A, the cooling chamber 831 is provided with an attachment portion 831a to which the Peltier element D is attached. The attachment portion 831a includes a slit-like opening formed on the peripheral surface of the cooling chamber 831 and a rib surrounding the opening.
In order to prevent the air flowing in the cooling chamber 831 from leaking from the attachment portion 831a, between the attachment portion 831a and each Peltier element D and between the Peltier elements D is sealed with, for example, a heat resistant resin, The cooled surface Db of each Peltier element D is cooled by the outside air supplied into the cooling chamber 831.

The basic configuration of the cooling chambers 832 to 834 is the same as that of the cooling chamber 831.
Since the suction pipe 81 for supplying air to the cooling chambers 831 to 834 is arranged outside the housing 50, the influence of the heat of the fixing belt 51 is less than that in the case where it is arranged inside the housing 50. Absent. For this reason, the temperature of the air flowing through the suction pipe 81 becomes higher as it goes downstream, so that when the flow rate of air supplied to each of the cooling chambers 831 to 834 is the same, the cooling effect of the cooling chamber is lower in the downstream side. Becomes lower. According to the present inventors, it has been confirmed that the temperature difference between the upstream and downstream air in the suction pipe 81 is about 5 to 10 ° C.

The cooling effect becomes higher as the temperature of the air serving as the cooling medium is lower and as the flow rate is higher. Therefore, in this embodiment, the flow rate of the supplied air is made different between the cooling chambers 831 to 834. The same cooling effect is obtained.
FIG. 5 is a diagram schematically showing the air flow in each duct in the cooling unit 80.
As shown in FIG. 5, the Peltier elements D1 to D20 are divided into four groups G1 to G4 in the rotation axis J direction, and the group G1 (Peltier elements D1 to D5) is included in the cooling chamber 831 in the cooling chamber 832. Includes a group G2 (Peltier elements D6 to D10), a cooling chamber 833 includes a group G3 (Peltier elements D11 to D15), and a cooling chamber 834 includes a group G4 (Peltier elements D16 to D20). .

The communication pipes 811 to 814 that supply the air flowing through the suction pipe 81 to the cooling chambers 831 to 834 are connected in this order from the upstream side to the downstream side of the suction pipe 81.
Among these, the inner diameter of the communication pipe 811 connected to the most upstream side is indicated by Φ1, and the flow rate of the air flowing into the cooling chamber 831 through the communication pipe 811 is indicated by F1.
In the communication pipe 812, the inner diameter is indicated by Φ2, and the flow rate flowing in is indicated by F2. The inner diameter Φ2 is set to a size larger than the inner diameter Φ1 of the communication pipe 811 (Φ2> Φ1), and the flow rate F2 is configured to be larger than the flow rate F1 (F2> F1). Similarly, the inner diameter of the communication pipe 813 is Φ3 (Φ3> Φ2), the flow rate is F3 (F3> F2), the inner diameter of the communication pipe 814 on the most downstream side is Φ4 (Φ4> Φ3), and the flow rate is F4 (F4). > F3).

As described above, the communication pipe connected to the downstream side of the suction pipe 81 has a larger inner diameter (Φ1 <Φ2 <Φ3 <Φ4), thereby increasing the cross-sectional area of the flow path, thereby supplying the air supplied to the cooling chamber. The flow rate is adjusted so as to increase (F1 <F2 <F3 <F4).
The sizes of the flow rates F1 to F4 are determined in advance so that the cooling effects of the cooling chambers 831 to 834 are equal in anticipation of the temperature rise of the air flowing through the suction pipe 81.

The temperature of the air supplied to each of the cooling chambers 831 to 834 includes (a) the temperature of the outside air to be introduced, (b) the temperature gradient in the suction pipe 81, and (c) the communication pipes 811 to 811 from the suction port 81 b. The distance k1 to k4 to the connection position 814 can be easily calculated by proportional distribution.
Therefore, at the stage of development or design, a temperature sensor such as a thermistor is disposed at the open end 81b of the suction pipe 81 and the closed end on the opposite side of the suction pipe 81, and the outside air introduced in (a) is measured. And the temperature gradient in the suction pipe 81 of (b) are acquired. Each distance in (c) is also determined at the design stage.

  Since it is understood that the temperature of the gas increases in proportion to the distance flowing through the duct, the air temperature at the connection point between the suction pipe 81 and each of the communication pipes 811 to 814 is easily calculated by proportional distribution based on the above information. be able to. And based on the temperature of these air, the flow volume of F1-F4 can be determined so that the cooling effect in each cooling room 831-834 may become equal, and also based on the flow volume and the total ventilation volume of a fan device, Inner diameters Φ1 to Φ4 of the communication pipes 831 to 834 are determined.

Note that the temperature gradient in (b) varies somewhat depending on the temperature of the fixing belt 51a. Therefore, in the present embodiment, the measurement is performed with the fixing belt 51a heated to the actual fixing temperature (here, 160 ° C.). Each inner diameter is determined based on the result. This is because temperature management near the actual fixing temperature is the most important.
However, even if the cooling effects of the respective cooling chambers 831 to 834 are made equal in this way, the temperature of the cooled surface Db is higher in the downstream Peltier element D than in the upstream side for each of the cooling chambers 831 to 834. Thus, a temperature difference Tu occurs.

However, the detection accuracy necessary for the temperature control of the fixing belt 51a is not limited to a small level of 1 ° C. and 2 ° C., but is allowed to a certain range (about 10 ° C. depending on the model). If the temperature difference between the surfaces to be cooled Db is within this range, the temperature can be detected with the required accuracy.
In the present embodiment, as compared with the configuration of the fixing device 905 in FIG. 12, in this embodiment, the Peltier elements D1 to D20 are cooled using four cooling chambers 831 to 834 having the same cooling effect. Therefore, the temperature difference Tu of the cooled surface Db between the Peltier elements D can be made smaller than that of the fixing device 905 using a cooling duct composed of a single pipe, and was actually less than 5 ° C.

If the number of divisions of the plurality of Peltier elements D is 5 or more and the length of each cooling chamber in the direction of the rotation axis J is further shortened, the temperature difference on the cooled surface side of each Peltier element D can be further reduced. This improves detection accuracy.
With the above configuration, the temperature difference on the cooled surface side of each Peltier element D can be within an allowable range. Therefore, if the temperature on the cooled surface side of any one Peltier element D is known, each temperature is determined based on that. Temperature detection by the Peltier element D becomes possible.

  In the present embodiment, a duct internal temperature sensor 88 (for example, a thermistor) is provided at a position that does not obstruct the flow of air in the cooling chamber 831 in the vicinity of the cooled surface Db of the Peltier element D3. The temperature is detected by regarding the temperature of the surface to be cooled of the Peltier element D. In this way, by using the temperature of the cooled surface of the Peltier element D at the center of the group G1 as a reference, the temperature difference between the cooled surfaces of the other Peltier elements D in the group can be reduced.

  Note that the mounting position of the temperature sensor 88 is not limited to the above position. Assuming that the outside air temperature to be sucked is within a certain range (20 ° C. to 28 ° C.) as described above, it is provided at another location in the duct, for example, in the vicinity of the open end portion 82b of the discharge pipe 81 and fixed. While the temperature of the belt 51a is maintained at the fixing temperature, the temperature of the cooled surface Db of a specific Peltier element D (for example, the same Peltier element D3 as described above) and the detection of the temperature sensor near the open end 82b of the discharge pipe 82 If the temperature is actually measured and a correlation table is stored in the ROM 602 (see FIG. 6), the surface to be cooled Db of the specific Peltier element D is referred to by referring to the detection value and table of the temperature sensor. It is also possible to estimate the temperature.

<Control unit>
FIG. 6 is a block diagram illustrating a relationship between the configuration of the control unit 60 and main components that are controlled by the control unit 60.
As illustrated in FIG. 6, the control unit 60 includes a CPU (Central Processing Unit) 601, a ROM (Read Only Memory) 602, a RAM (Random Access Memory) 603, a communication interface (I / F) unit 604, and an image data storage unit. 605 and the like.

  The CPU 601 executes a program for controlling the image processing unit 3, the paper feeding unit 4, the fixing unit 5, the operation panel 6, the secondary battery 7, and the like. The ROM 602 is a storage that stores various programs executed by the CPU 601. The RAM 603 is a work area when the CPU 601 executes a program. The communication I / F unit 604 is an interface for connecting to a LAN such as a LAN card or a LAN board. The image data storage unit 605 stores image data for printing input via the communication I / F unit 604 or an image reading unit (not shown).

The operation panel 6 is disposed at an easy-to-operate position on the upper part of the printer 1 and includes a liquid crystal display for displaying a print setting operation screen and a print result, a touch panel stacked on the liquid crystal display, operation buttons, and the like. The control unit 60 can accept various instructions from the user via the operation panel 6 and causes the corresponding program to be executed.
In addition to the various programs, the ROM 602 stores output characteristics indicating the correlation between the thermoelectromotive force of the Peltier element D and the temperature difference Td between the thermal surfaces Da and Db.

The control unit 60 acquires the surface temperature at each position of the fixing belt 51 using the stored output characteristics and the thermoelectromotive force detected from the Peltier element D.
(A) The control unit 60 acquires the detected temperature Ts of the temperature sensor 88.
(B) The thermoelectromotive force of the target Peltier element D is detected by the voltage detector 59, and the detected thermoelectromotive force is converted into a temperature difference Td based on output characteristics obtained in advance.

(C) A temperature difference Td of the heated surface Da is calculated by adding the temperature difference Td to the detected temperature Ts.
This temperature Ta may be evaluated as it is as the temperature of the fixing belt 51a, but since there is a slight gap between the fixing belt 51 and Ta + α (α is a correction constant previously determined by experiment) The temperature can be more accurate.
The controller 60 can acquire the surface temperature of the entire heat generating area 51a of the fixing belt 51 by repeating the operations (B) and (C) for each of the Peltier elements D1 to D20.

For example, the control unit 60 causes the fixing belt 51 to perform a warm-up process for raising the fixing belt 51 to the fixing temperature, a temperature control process for maintaining the fixing temperature, a process for detecting local abnormal heat generation due to scratches on the fixing belt 51, and the like. The surface temperature is acquired.
As described above, according to the present embodiment, the Peltier elements D1 to D20 arranged in the rotation axis J direction along the surface of the fixing belt 51 are divided into four groups G1 to G4, and each group G1 to G4 is divided. The cooling chambers 831 to 834 are provided corresponding to the above, and the flow rates F1 to F4 of the air supplied to the cooling chambers 831 to 834 are adjusted so that the cooling effects of the cooling chambers 831 to 834 are equal.

Thereby, the temperature difference Tu of the cooled surface Db between the Peltier elements D1 to D20 can be set within a predetermined range (10 ° C.), so that the surface temperature of the fixing belt 51 can be obtained with high accuracy.
In the present embodiment, the suction pipe 81 that supplies air to the cooling chambers 831 to 834 is arranged outside the housing 50, thereby minimizing the influence of the heat of the fixing belt 51, so that each cooling chamber The temperature difference of the air supplied to 831 to 834 is made small.

In the present embodiment, the control unit 60 functions as a surface temperature acquisition unit that acquires the surface temperature of the fixing belt 51.
<Second Embodiment>
In the second embodiment, the cooling duct of the cooling unit is configured by a T-shaped tube, and a louver that changes the flow direction of the cooling medium is provided in the cooling duct. By changing the angle of the louver, This is different from the first embodiment in that the flow rate of the cooling medium toward the Peltier element D is adjusted.

Since the configuration other than the cooling unit is basically the same as that of the printer 1 of the first embodiment, the same configuration is denoted by the same reference numeral, and the description thereof is omitted.
<Configuration of cooling unit>
FIG. 7 is a perspective view illustrating a configuration of a main part of the fixing unit 105 according to the second embodiment.
As shown in FIG. 7, the cooling unit 190 in the fixing unit 105 in the present embodiment includes an inverted T-type cooling duct 180, a fan device 187, louvers Lv1 to Lv4, and the like.

The cooling duct 180 includes a suction pipe 181 extending in the rotation axis J direction along the surface of the fixing belt 51, and a discharge pipe 182 connected so as to protrude from the central portion in the longitudinal direction of the suction pipe 181. The fan device 187 is installed at the discharge port 182 a of the discharge pipe 182.
The suction pipe 181 passes through the housing 50 of the fixing unit 5 in the direction of the rotation axis J, and both ends thereof are opened, and through holes (not shown) formed in the housing of the printer 1 (see FIG. 1). The outside air outside the printer 1 can be sucked through.

Then, by driving a fan device 187 provided in the discharge pipe 182, outside air flows into the cooling duct 180 from the suction ports 181 a and 181 b at both ends of the suction pipe 181, and a plurality of pieces attached to the lower surface of the suction pipe 181. While cooling the surface to be cooled of the Peltier element D, it is discharged from the discharge port 182a of the discharge pipe 182.
Further, four louvers Lv1 to Lv4 made of long plate members are arranged in the suction pipe 181.

Each motor M is formed of, for example, a stepping motor, and is disposed outside the housing 50 of the fixing unit 105. The drive shaft m1 passes through the housing 50 and the suction pipe 181 and is introduced into the suction pipe 181 to be described above. It is connected to louvers Lv1 to Lv4.
The control unit 60 controls the rotation of the motor M to adjust the flow rate of air toward the surface to be cooled of the Peltier element D by changing the swing angles of the louvers Lv1 to Lv4.

FIG. 8 is a diagram for explaining the operation of the louvers Lv <b> 1 to Lv <b> 4 and the flow of air in the cooling duct 180.
The louvers Lv <b> 1 to Lv <b> 4 are configured to be switchable between a basic posture shown by a solid line and an inclined posture shown by a broken line in FIG.
Louver Lv1 is arranged at a position corresponding to group G1 of Peltier elements D. The louver Lv2 is arranged at a position corresponding to the group G2, the louver Lv3 is arranged at a group G3, and the louver Lv4 is arranged at a position corresponding to the group G4.

The air flow sucked from the suction port 181a toward the discharge pipe 182 is divided into flows F11 and F12 by the louvers Lv1 and Lv2. The flow F11 is a flow of air flowing between the louvers Lv1 and Lv2 and the Peltier elements D1 to D10, and the flow F12 is a flow of air on the opposite side of the louvers Lv1 and Lv2 from the Peltier element D side.
Further, the air flow sucked from the suction port 181b and directed to the discharge pipe 182 is divided into flows F13 and F14 by the louvers Lv3 and Lv4. The flow F13 is a flow of air flowing between the louvers Lv3 and Lv4 and the Peltier elements D11 to D20, and the flow F14 is a flow of air on the opposite side of the louvers Lv3 and Lv4 from the Peltier element D side.

For example, by changing the posture of the louver Lv1 from the basic posture to the inclined posture, the flow rate distribution ratio between the flows F11 and F12 can be changed, and the flow rate of the flow F11 on the Peltier element D side can be increased. The cooling effect for cooling the cooled surface Db of the element D can be enhanced. The same applies to louvers Lv2 to Lv4.
FIG. 9 is an example of a table showing the louver attitude control, and louver control examples 1 to 7 controlled based on the thermoelectromotive force (output voltage) for each of the groups G1 to G4 of the Peltier element D are shown. ing.

The output voltage for each of the groups G1 to G4 here is obtained, for example, by electrically connecting the Peltier elements D included in the group when the warm-up is completed after the power is turned on. . Further, during the warm-up process, all the louvers Lv1 to Lv4 are started in the basic posture state.
When the warm-up is completed after the power is turned on, it is understood that there is no temperature difference in the fixing belt 51a. Therefore, the variation in the output voltage at this time, that is, the surface to be cooled of the Peltier element D belonging to each group. It shows that there is a difference in temperature.

Therefore, when the variation in the output voltage between the groups G1 to G4 is within the allowable range as in Control Example 1, it is determined that there is no temperature difference that would hinder the detection accuracy between the groups. The louvers Lv1 to Lv4 are maintained in the basic posture.
Here, “the variation in the output voltage is within the allowable range” means that the difference between the maximum voltage and the minimum voltage among the output voltages of each group is within 10 ° C. when converted into a temperature difference. .

Control examples 2 to 7 are examples when the variation in the output voltage is outside the allowable range. In this case, whether the difference from the reference voltage is within an allowable range based on the highest output voltage (that is, the group having the lowest temperature on the surface to be cooled) among the output voltages of the groups G1 to G4. It is determined whether or not the variation is within the allowable range.
The louvers facing the groups included in the allowable range maintain the basic posture, and the louvers facing the groups outside the allowable range (groups with low output voltage) are changed to the inclined posture.

This is because the output voltage is lower than the others because it is understood that the surface to be cooled Db of the Peltier element D is not sufficiently cooled. Therefore, by inclining the louvers, the flow rate flowing to the Peltier element D side of the group is increased, the cooling effect is enhanced, and the variation in the output voltage is reduced to fall within the allowable range.
If abnormal heat is generated in the fixing belt 51a at the time of warm-up, the output voltage becomes extremely higher than others, so that abnormal heat can be detected. Therefore, in this case, the warm-up process is stopped. For example, when the printer 1 is connected to the manager terminal via the network, an error message may be transmitted to the manager terminal. .

  The control example 2 is a case where the output voltage of the group G1 is low and is out of the allowable range, and the louver Lv1 is changed to the inclined posture. In control example 3, the output voltage of group G2, the output voltage of group G3 is low in control example 4, and the output voltage of group G4 is low because the output voltage of group G4 is outside the allowable range. This is an example in which the louvers Lv2 to Lv4 are changed to an inclined posture.

The control example 6 is a case where the output voltages of the two groups G1 and G2 are low, so that they are out of the allowable range, and the louvers Lv1 and Lv2 are changed to an inclined posture.
The control example 7 is a case where the output voltages of the three groups G1 to G3 are low, so that they are outside the allowable range, and the louvers Lv1 to Lv3 are changed to the inclined posture.
It goes without saying that there are other louver control patterns.
<Louvre control processing>
FIG. 10 is a flowchart showing the operation of the “louver control process” executed by the control unit 60, and is executed as a subroutine of a main flowchart (not shown) for controlling the entire printer 1. For example, it is called and executed in the warm-up process for raising the surface temperature of the fixing belt 51 to the fixing temperature.

Specifically, the warm-up process is started in a state where all the louvers Lv1 to Lv4 are in the basic posture, and the surface temperature of the fixing belt 51 is determined at a predetermined timing, for example, one of the Peltier elements D1 or D20. The following “louver control process” is performed at a timing at which it can be considered that the toner has reached the fixing temperature (160 ° C.).
The acquisition of the surface temperature of the fixing belt 51 at this time is executed based on, for example, the output value of the Peltier element D1 or D20. Since the Peltier elements D1 and D20 are closest to the suction ports 181a and 181b, the temperature of the cooled surface Db is considered to be almost the same as the outside air. As described above, the environment in which a general apparatus is used is considered to be about 20 ° C. to 28 ° C. Therefore, for example, the median value of 24 ° C. is set to the temperature (reference temperature) of the cooled surface Db of the Peltier elements D1 and D20. Therefore, the electromotive force of the Peltier elements D1 and D20 is detected at a predetermined sampling timing, converted into a temperature difference between the surface to be cooled and the surface to be heated, and added to the reference temperature, whereby the Peltier element D1 , D20, the surface temperature of the fixing belt 51a is obtained. Even if the actual room temperature is slightly different from the above 24 ° C., it is within the range of error.

First, in step S <b> 101, the control unit 60 acquires output voltages V <b> 1 to V <b> 4 for the groups G <b> 1 to G <b> 4 of the Peltier elements D via the voltage detection unit 59.
Then, it is determined whether or not the obtained variations in the output voltages V1 to V4 are within an allowable range (step S102). As described above, “within the allowable range” here means that the variation in the temperature difference Td obtained by converting the output voltage based on the output characteristics stored in the ROM 602 is within 10 ° C.

If it is determined in step S102 that it is within the allowable range (Yes), the process returns to the main flowchart (not shown) while maintaining the basic postures of the louvers Lv1 to Lv4.
When it is determined that it is not within the allowable range (step S102: No), the louver facing the low output voltage group whose difference is not included in the allowable range with the highest output voltage among the output voltages V1 to V4 as a reference. The inclined posture is set (step S103).

Thereby, since the cooling effect with respect to the group with a low output voltage can be heightened, the output voltage of the said group becomes large and it can suppress variation.
Here, the basic posture is maintained for the louvers facing the output voltage group determined to be within the allowable range.
After step S103, the control unit 60 again obtains the output voltages V1 to V4 for the groups G1 to G4 of the Peltier elements D via the voltage detection unit 59 after a predetermined time T1 (step S104), and outputs them. It is determined whether or not the variations in the voltages V1 to V4 are within an allowable range (step S105). The predetermined time T1 is set to a time (for example, 2 to 3 seconds) sufficient to obtain the cooling effect due to the louver inclination.

If it is determined that the value is within the allowable range (step S105: Yes), the process returns to the main flowchart (not shown) while maintaining the current posture of the louvers Lv1 to Lv4.
If it is determined again that it is not within the allowable range (step S105: No), the number of rotations of the fan 187 is increased (step S106), and the flow rate of the air flowing through the cooling duct 180 is increased to enhance the cooling effect.

In this case, the group in which the flow rate is increased by inclining the louver can obtain a higher cooling effect, and therefore, variation in output voltage can be more effectively suppressed.
Thereafter, the control unit 60 returns to step S104 after a predetermined time T2, and repeats the operations of steps S104 and S105. The predetermined time T2 is set to a time (for example, 2 to 3 seconds) sufficient to obtain a cooling effect by increasing the number of rotations of the fan 187.

With the above operation, the louver control process is executed.
According to the fixing unit 105 configured as described above, first, the louvers are controlled so that the louvers Lv1 to Lv4 are provided corresponding to the groups G1 to G4 of the Peltier element D and the cooling effects on the groups G1 to G4 are equal. Thus, the flow rate of the cooling medium toward the Peltier element D is adjusted. Thereby, also in the present embodiment, the temperature difference Tu of the cooled surface Db between the Peltier elements D1 to D20 can be set within a predetermined range (10 ° C.), so that the surface temperature of the fixing belt 51 can be accurately set. Can be acquired.

  In the present embodiment, although the suction pipe 181 is disposed in the housing 50 and provided along the fixing belt 51, air is sucked from both ends of the suction pipe 181, and from the central portion of the suction pipe 181. Since the air flows along the discharge pipe 182, the flow path length of the air flowing along the fixing belt 51 is shortened to about ½ of the cooling duct 980 shown in FIG. It can be suppressed.

In the present embodiment, the control unit 60 functions as an angle control unit that controls the angles of the louvers Lv1 to Lv4. The flow rate is adjusted by the control unit 60, the louvers Lv1 to Lv4, the motor M, and the rotation shaft m1. Means are configured.
[Modification]
As described above, the present invention has been described based on the embodiment. However, the present invention is not limited to the above-described embodiment, and the following modifications can be implemented.
(1) In the above-described embodiment, the configuration in which the fixing belt 51 having the resistance heating element layer 511 is used as the heat fixing member for thermally fixing the toner image on the recording sheet is described, but the present invention is not limited to this. . For example, a fixing roller heated by a halogen heater or a fixing roller heated by electromagnetic induction can be used.
(2) In the above-described embodiment, the configuration in which all of the plurality of Peltier elements D are used as temperature sensors is shown. However, the present invention is not limited to this, and only a part of the Peltier elements D are used as temperature sensors. It is good.

For example, when a fixing roller heated by a halogen heater is used, unlike the fixing belt 51 having the resistance heating element layer 511, local abnormal heat generation due to scratches or the like does not occur on the surface of the fixing roller. There is no problem even if the entire temperature is not acquired.
(3) In the above-described embodiment, a configuration in which one Peltier element functions as one temperature sensor is shown. However, the present invention is not limited to this, and a plurality of Peltier elements are connected in series and connected in series. It is also possible to adopt a configuration in which the element rows used are used as one temperature sensor. For example, each group G1 to G4 of Peltier elements D can be configured as one temperature sensor. The number of Peltier elements constituting the temperature sensor can be appropriately selected based on the specifications of the Peltier elements and the fixing device.
(4) The number of Peltier elements arranged along the surface of the fixing belt 51, the arrangement (including gaps), and the like can be appropriately selected according to the specifications and application of the fixing device.
(5) In the above embodiment, the configuration using air as the cooling medium in the duct is shown, but the cooling medium is not limited. For example, water may be used as the cooling medium. In this case, a water tank and a pump for circulating water are required.
(6) In the above embodiment, in order to reduce the influence of heat of the fixing belt 51, it is preferable to provide a heat insulating material on the outer periphery of each pipe constituting the cooling units 80 and 180.
(7) In the first embodiment, the configuration in which the in-duct temperature sensor 88 for detecting the temperature of the air in the vicinity of the cooled surface Db of the Peltier element D3 is provided in the cooling chamber 831 is shown. However, the present invention is not limited to this, and in some cases, a configuration may be adopted in which the duct temperature sensor is not provided.

For example, the flow rate of air supplied to each cooling chamber 831 to 834 is relatively increased so that the temperature change in each cooling chamber 831 to 834 is within the allowable range even if the temperature of the fixing belt 51 rises. Then, the temperature of the cooled surface Db of a specific Peltier element D (for example, the same Peltier element D3 as in the first embodiment) is measured in advance through experiments, and the temperature information is stored in the ROM 602 (see FIG. 6). ), The temperature information can be regarded as the temperature of the cooled surface Db of the specific Peltier element D.
(8) In the first embodiment, the configuration in which the four cooling chambers 831 to 834 are provided is shown, but the present invention is not limited to this. The number, size, arrangement, and the like of the cooling chamber can be appropriately selected according to the specifications of the cooling duct and the fixing unit.
(9) Instead of the duct internal temperature sensor, for example, a non-contact temperature sensor represented by an infrared temperature sensor or the like is disposed at an appropriate position along the surface of the fixing belt 51 to detect the surface temperature, A value obtained by converting the output voltage detected by the Peltier element D corresponding to the detection position into a temperature difference may be subtracted from the detected temperature to be regarded as the temperature of the cooled surface Db of the Peltier element D.

In this case, a non-contact type temperature sensor is arranged at a position corresponding to the area of the sheet passing portion of the fixing belt 51, and the temperature of the fixing belt 51 is controlled based on the detected value. The output from the temperature sensor unit composed of a plurality of Peltier elements D may be used exclusively for detecting abnormal heat generation.
(10) As a modification of the second embodiment, a configuration as shown in FIG. 11 may be adopted. The fixing unit 205 of FIG. 11 and the fixing unit 105 (see FIG. 8) of the second embodiment have different louver and ventilation fans, and the direction of the air flowing in the duct is reversed. Is different. The rest of the configuration is the same. In the fixing unit 205 in FIG. 11, driving of the fan 287 causes the outside air to be sucked from the opening 182 a of the tube 182, and the sucked outside air is discharged from the openings 181 a and 181 b at both ends of the tube 181. At this time, the air flow toward the opening 181a is divided into flows F15 and F16 by the louvers Lv5 and Lv6, and the air flow toward the opening 181b is divided into the flows F17 and F18 by the louvers Lv7 and Lv8. By changing the posture of these louvers from the basic posture to the inclined posture, the flow rates of the flows F15 and F17 can be increased, and the cooling effect on the Peltier element D can be enhanced.

Inside the fixing unit, the temperature of the central part is higher than that of the peripheral part. Thus, if the outside air is allowed to flow from the central part in the direction of the rotation axis J to both ends in this way, the Peltier located at the central part. The groups G2 and G3 of the element D can be cooled more effectively.
(11) In the second embodiment and the modification of FIG. 11, the configuration in which one louver is provided for each group G1 to G4 of the Peltier element D is shown, but the present invention is not limited to this. . For example, a plurality of louvers may be provided by reducing the size of the louvers. The number, size, arrangement, and the like of the louvers can be appropriately selected according to the specifications of the louvers and the specifications of the fixing unit.
(12) In the second embodiment and the modification, the configuration in which each louver can be switched between two attitudes of the basic attitude and the inclined attitude is shown, but the present invention is not limited to this. For example, the tilt posture may be finely controlled in a plurality of postures such as two steps or three steps. In this case, since the adjustment of the flow rate flowing to the Peltier element D side can be finely controlled, the temperature difference of the cooled surface Db between the Peltier elements D can be further reduced.

In addition, the louver may be inclined not only to incline so as to increase the flow rate flowing to the Peltier element D side but also to decrease the flow rate flowing to the Peltier element D side. It is only necessary that the temperature difference of the cooled surface Db between the Peltier elements D can be reduced.
Moreover, although the structure which rotates centering on the center part of the longitudinal direction of a louver was shown, it is not limited to this, For example, it is good also as a structure which rotates centering on the edge part of a longitudinal direction.
(13) In the second embodiment, the configuration using the stepping motor to switch the louver posture is shown, but a servo motor may be used instead of the stepping motor. Here, it is only necessary that the louver can be switched to a desired posture, and the configuration is not particularly limited.
(14) In the above-described embodiment, each tube constituting the cooling duct has a cylindrical shape. However, the present invention is not limited to this. For example, the cooling duct may be configured using a rectangular tube.
(15) In the above embodiment, the tandem color printer is used as the image forming apparatus. However, the scope of the present invention is not limited to this, and the present invention is applicable to other printers, copiers, facsimile machines, and the like. can do.

  Further, the contents of the above-described embodiment and modification examples may be combined as much as possible.

  The present invention relates to a fixing unit and an image forming apparatus using the fixing unit, and in particular, can be used as a technique for effectively utilizing a thermoelectric conversion element in a fixing device including a thermoelectric conversion element for utilizing exhaust heat.

DESCRIPTION OF SYMBOLS 1 Printer 3 Image process part 4 Paper feed part 5 Fixing part 6 Operation panel 7 Secondary battery 10 Exposure part 11 Intermediate transfer belt 31 Photoreceptor drum 32 Charger 33 Developing device 41 Paper feed cassette 50 Housing 51 Fixing belt 51a Heat generation area 52 Pressure roller 53 Pressure roller 55 Temperature sensor unit 60 Control unit 80 Cooling unit 81 Suction tube 82 Discharge tube 83 Cooling tube 831 to 834 Cooling chamber 87 Fan 88 Temperature sensor 105 Fixing unit 180 Cooling duct 181 Suction tube 182 Discharge tube 190 Cooling unit 511 Resistance heating element layer 512a, 512b Electrode layer D, D1-D20 Peltier element (thermoelectric conversion element)
Da Heated surface Db Cooled surface F1-F4 Flow rate G1-G4 Group of Peltier elements L, L1-L20 Lead wire RS, RS1-RS20 Relay

Claims (10)

A fixing device that forms a fixing nip by pressing a pressing member on the surface of a heat fixing member, and passes a recording sheet carrying a toner image in the fixing nip to fix it.
A plurality of thermoelectric conversion elements arranged along the sheet passing width direction with the heated side end face facing the surface of the heat fixing member,
Surface temperature acquisition means for detecting a thermoelectromotive force generated in the thermoelectric conversion element and acquiring a surface temperature of the heating and fixing member at a position where each thermoelectric conversion element is disposed;
Cooling means for supplying a cooling medium to the duct and cooling the cooled side end surfaces of the plurality of thermoelectric conversion elements,
In the cooling means, the flow rate of the cooling medium supplied to the region corresponding to each thermoelectric conversion element of the duct is adjusted so that the temperature difference between the cooled end faces of the plurality of thermoelectric conversion elements is within a predetermined range. A fixing device characterized by that. The duct has a suction path for sucking a cooling medium, and a branch path that branches from the suction path and supplies the cooling medium to each region corresponding to each thermoelectric conversion element,
The fixing device according to claim 1, wherein the flow rate is adjusted by making a flow path cross-sectional area of each branch path different. The cross-sectional area of each of the branch paths is determined so that the flow rate of the coolant flowing in the downstream branch path is larger than the upstream side of the coolant flowing in the suction path. Fixing device. A flow rate adjusting means for adjusting the flow rate of the cooling medium is provided for each region of the duct,
The fixing device according to claim 1, wherein the flow rate of the cooling medium is adjusted by the flow rate adjusting unit. The fixing device according to claim 4, wherein the flow rate adjusting unit includes a louver, a driving unit that drives the louver, and an angle control unit that controls an angle of the louver via the driving unit. . The cooling means is
A fan for introducing a gas as a cooling medium into the duct;
The fixing device according to claim 1, further comprising a control unit that controls an output of the fan to control an entire flow rate of the introduced gas. Temperature detection means for detecting the temperature of any one of the paths from the suction of the cooling medium to the delivery of the cooling medium is provided;
The surface temperature acquisition means refers to the temperature of the cooling medium detected by the temperature detection means, and acquires the surface temperature of the heating and fixing member based on the thermoelectromotive force generated in each thermoelectric conversion element. The fixing device according to claim 1. The fixing device according to claim 1, wherein the cooling medium is air taken from outside the device. The fixing device according to claim 1, wherein water is used as the cooling medium.   An image forming apparatus comprising the fixing device according to claim 1.

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