JP2016130770A - Fixing device and image forming apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to perform correct temperature control even when a contact position of a contact type temperature sensor is displaced.SOLUTION: A fixing device comprises a fixing member 31, a heat source 32 for heating the fixing member 31, and a plurality of temperature detection sensors 33 and 34 for detecting the temperature of the fixing member 31, and controls the surface temperature of the fixing member 31 detected by the temperature detection sensors 33 and 34 to be a predetermined value on the basis of the surface temperature of the fixing member 31. The fixing device further comprises: temperature gradient determination means Ca that stores in advance a temperature rise gradient to be a reference, and determines whether a difference has occurred between the temperature rise gradient to be a reference and temperature rise gradients based on the surface temperature detected by the temperature detection sensors 33 and 34; and heating control means Cb that performs heating control of the heat source 32 on the basis of a temperature detected by one of the temperature detection sensors 33 and 34 that has obtained a temperature rise gradient closest to the temperature rise gradient to be a reference from among the temperature rise gradients detected by the temperature detection sensors 33 and 34.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fixing device and an image forming apparatus using the same.

  Various image forming apparatuses using an electrophotographic system have been devised as image forming apparatuses such as copying machines, facsimile machines, printers, or their combined machines, and are well known in the art. In the image forming process, an electrostatic latent image is formed on the surface of a photosensitive drum as an image carrier, and the electrostatic latent image on the photosensitive drum is developed with a toner or the like as a developer to be visualized. The developed image is transferred to a recording material such as paper or an OHP sheet (hereinafter also referred to as paper, recording paper, or recording medium) by a transfer device to carry the image, and the image is transferred onto the recording material by a fixing device using heat and pressure. This is established by the process of fixing the unfixed toner image.

Various types of fixing devices have been proposed, and the fixing device disclosed in Patent Document 1 has a heating roll having a heating source inside, and a pressure roll in pressure contact with the heating roll. Is. In this configuration, a sheet on which an unfixed image is formed is inserted between the heating roll and the pressure roll, and the sheet is heated and pressed to fix the unfixed image.

  The heating roll described in Patent Document 1 is provided with an abnormal temperature rise suppression means for suppressing an abnormal temperature increase of the heating roll. The abnormal temperature rise suppression means detects the temperature rise rate of the surface temperature of the heating roll before and after reaching the fixing standby temperature, and the temperature rising rate after reaching the fixing standby temperature is before the fixing standby temperature is reached. A predetermined abnormality process is performed when the temperature rise rate is substantially the same.

  By the way, as a contact-type temperature sensor for detecting the temperature of the heating roll described above, a so-called contact-type thermistor is often used because of cost advantages. The contact-type thermistor cannot accurately detect the temperature if the contact state with respect to the heating roll shifts. Factors that cause the contact state to shift include physical displacement of the contact position and the presence of foreign matter on the contact surface.

  In particular, when a resin material is used for a structure that holds a contact thermistor or heating roll (cost advantage), the contact position shifts with time due to the residual stress at the time of molding in the structure. May end up. Specifically, when the resin structure is affected by the warp, the contact type thermistor disposed near the center of the heating roll is most affected by the warp and the detection deviation increases.

  Further, when foreign matter is present on the contact surface, the contact-type temperature sensor and the heating roll are more suitable when the foreign matter is present at a shifted contact position than when the foreign matter is present at the correct contact position. The difference between the two becomes larger due to the synergistic effect. Thus, when the contact-type temperature sensor is displaced, the actual temperature is always shifted to the high temperature side.

  However, if the apparatus is operated in a state where the displacement of the contact position as described above is generated, there is a risk that problems such as offset and wrinkles, a shortened life of the heating roll, and a safety problem may occur.

  Accordingly, an object of the present invention is to provide a fixing device capable of performing correct temperature control even when a contact position of a contact-type temperature sensor is displaced.

  The present invention described in claim 1 for solving the above problem includes a fixing member, a heating source for heating the fixing member, and a plurality of temperature detection sensors for detecting the temperature of the fixing member. A fixing device that controls the surface temperature of the fixing member to a predetermined value based on the surface temperature of the fixing member detected by the plurality of temperature detection sensors, and previously stores a temperature increase gradient serving as a reference for the fixing member. The temperature gradient determination means for determining whether or not there is a difference between the stored temperature increase gradient as a reference of the fixing member and each temperature increase gradient based on the surface temperature detected by each temperature detection sensor. And the temperature detected by the temperature detection sensor that obtains the temperature increase gradient closest to the reference temperature increase gradient stored in the storage unit among the temperature increase gradients detected by each temperature detection sensor. Based, and a heating control means for heating control of the heating source.

  According to the present invention, correct temperature control can be performed even when the contact position of the contact-type temperature sensor is displaced.

1 is a schematic cross-sectional side view showing a configuration of an image forming apparatus using a fixing device according to a first embodiment of the present invention. 1 is a front sectional view showing a schematic configuration of a fixing device according to a first embodiment of the present invention. It is a graph which shows transition of the temperature in the normal detection state by a temperature detection sensor. It is a graph which shows transition of the temperature when deviation arises in the contact state of the temperature detection sensor arrange | positioned in the center part. (A) shows a state in which the temperature detection sensor is normally in contact with the fixing member, and (B) shows a state in which the temperature detection sensor is in contact with the fixing member due to deformation of the casing. It is a side view. (A) is a front sectional view showing a state in which the fixing device is attached to a housing that is not deformed, and (B) shows a state in which the fixing device is attached to a housing that is deformed. It is a front sectional view. (A) is a graph showing a change in temperature when a deviation occurs in the contact state of the temperature detection sensor 34 arranged in the center, and (B) is a graph showing a change in temperature in a state where the temperature is corrected. is there. FIG. 5 is a schematic sectional side view showing a configuration of a fixing device according to a second embodiment of the present invention. FIG. 9 is a graph showing a change in temperature in a normal detection state in the fixing device shown in FIG. 8. FIG. 8A is a graph showing a change in temperature in a detection state in which the contact of the temperature detection sensor 34 disposed in the center portion is shifted in the fixing device shown in FIG. 8, and FIG. It is a graph which shows transition of the temperature of. (A) is a graph which shows transition of the temperature in the structure using one heating source, (B) is a graph which shows transition of the temperature in the structure using two heating sources. 3 is a flowchart illustrating an operation in the fixing device according to the first embodiment of the present invention.

Hereinafter, an image forming apparatus using a fixing device according to the present invention will be described with reference to the drawings.
FIG. 1 is a schematic sectional side view showing a configuration of an image forming apparatus using a fixing device according to a first embodiment of the present invention.

  Hereinafter, a color laser printer (hereinafter simply referred to as “printer”) will be described as an example of the image forming apparatus. The printer 10 shown in FIG. 1 is provided with four image forming units 11Y, 11M, 11C, and 11K in the center of the printer body. Each image forming unit 11Y and the like is the same except that it contains developers of different colors of yellow (Y), magenta (M), cyan (C), and black (K) corresponding to the color separation components of the color image. It becomes the composition of.

  Each of the image forming units 11Y, 11M, 11C, and 11K includes a drum-shaped photoconductor 12, a charging device 13 that charges the surface of the photoconductor 12, a developing device 14, a cleaning device 15, and the like. The developing device 14 supplies toner to the surface of the photoconductor 12, and the cleaning device 15 cleans the surface of the photoconductor 12.

  In FIG. 1, only the photoconductor 12, the charging device 13, the developing device 14, and the cleaning device 15 included in the black image forming unit 11 </ b> K are denoted by reference numerals, and the other image forming units 11 </ b> Y, 11 </ b> M, and 11 </ b> C are illustrated. Is omitted.

  Below the image forming units 11Y, 11M, 11C, and 11K, an exposure device 16 for exposing the surface of each photoconductor 12 is disposed. The exposure device 16 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates the surface of each photoreceptor 12 with laser light based on image data.

  A transfer device 17 is disposed above the image forming units 11Y, 11M, 11C, and 11K. The transfer device 17 includes an intermediate transfer belt 18, four primary transfer rollers 19, a secondary transfer roller 20, a secondary transfer backup roller 21, a cleaning backup roller 22, a tension roller 23, and a belt cleaning device 24.

  The intermediate transfer belt 18 is formed in an endless shape and is stretched by a secondary transfer backup roller 21, a cleaning backup roller 22, and a tension roller 23. Here, the secondary transfer backup roller 21 is driven to rotate, so that the intermediate transfer belt 18 travels (rotates) in the direction indicated by the arrow in the figure.

  The four primary transfer rollers 19 sandwich the intermediate transfer belt 18 between the respective photoreceptors 12 to form primary transfer nips. Each primary transfer roller 19 is connected to a power source (not shown) so that a predetermined DC voltage or AC voltage is applied.

  The secondary transfer roller 20 sandwiches the intermediate transfer belt 18 between the secondary transfer backup roller 21 and forms a secondary transfer nip. Similarly to the primary transfer roller 19, a power source (not shown) is also connected to the secondary transfer roller 20, so that a predetermined DC voltage or AC voltage is applied.

  The belt cleaning device 24 includes a cleaning brush and a cleaning blade (not shown) disposed so as to contact the intermediate transfer belt 18. The waste toner transfer hose extending from the belt cleaning device 24 is connected to the entrance of the waste toner container (none of them are shown).

  A bottle container 25 is provided on the upper part of the printer main body, and four toner bottles 25Y, 25M, 25C, and 25K that contain toner for replenishment are detachably attached to the bottle container 25. .

  A replenishment path (not shown) is provided between each of the toner bottles 25Y, 25M, 25C, and 25K and each of the developing devices 14. The toner is supplied to each developing device 14 from each of the toner bottles 25Y, 25M, 25C, and 25K through this supply path.

  On the other hand, at the lower part of the printer main body, a paper feed tray 26 for storing the paper 1 as a recording medium, a paper feed roller 27 for carrying out the paper 1 from the paper feed tray 26, and the like are provided. Here, the paper 1 includes thick paper, postcard, envelope, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheet and the like in addition to plain paper. Further, a manual sheet feeding mechanism (not shown) may be provided.

  In the printer main body, a conveyance path 2 is disposed for discharging the paper 1 from the paper feed tray 26 through the secondary transfer nip and out of the printer main body. In the transport path 2, a pair of registration rollers 28 for transporting the paper 1 to the secondary transfer nip is disposed upstream of the position of the secondary transfer roller 20 in the paper transport direction.

  Further, a fixing device 30 for fixing the unfixed image transferred to the paper 1 is disposed downstream of the position of the secondary transfer roller 20 in the paper transport direction. Further, a pair of paper discharge rollers 29 for discharging the paper 1 out of the printer main body is provided downstream of the fixing device 30 in the paper transport direction of the transport path 2. In addition, a paper discharge tray 5 for stocking the paper 1 discharged outside the printer main body is provided on the upper surface of the printer main body.

  Next, the details of the fixing device 30 will be described. FIG. 2 is a front sectional view showing a schematic configuration of the fixing device according to the first embodiment of the present invention. As shown in FIG. 2, the fixing device 30 according to the first embodiment of the present invention includes a fixing member 31, a heating source 32, and two temperature detection sensors 33 and 34.

  The heating source 32 is a so-called heater, and heating portions 32 a, 32 a, 32 b, and 32 b are formed corresponding to the end portion and the center portion of the fixing member 31. The fixing member 31 is formed in a cylindrical shape, and one heating source 32 is disposed at the center of rotation. Reference numeral 35 denotes a driving gear, and 36 denotes a bearing. This bearing 36 is supported by the structure.

  The temperature detection sensors 33 and 34 are contact thermistors, and reference numerals 33 a and 34 a in the figure are contact terminals that are in contact with the fixing member 31. Of the two temperature detection sensors 33, 34, one temperature detection sensor 33 is shifted to one end side of the fixing member 31, and the other temperature detection sensor 34 is disposed at the center.

  In the present embodiment, the temperature detection sensor 34 is disposed within the paper passing range, and the temperature detection sensor 33 is disposed outside the paper passing range. The “sheet passing range” is a range in which the sheet 1 is assumed to be inserted.

  In addition, as shown in FIG. 2, it is not restricted to using two temperature detection sensors, You may use three or more temperature detection sensors. In this case, at least any one of the plurality of temperature detection sensors is disposed outside the paper range.

  FIG. 3 is a graph showing a change in temperature in a normal detection state by the temperature detection sensor. The vertical axis is temperature and the horizontal axis is time. In the figure, “end temperature” indicates the temperature detected by the temperature detection sensor 33, and “center temperature” indicates the temperature detected by the temperature detection sensor 34. Further, what is indicated as “target temperature” is a predetermined temperature. The same applies to each graph shown below.

  As is clear from FIG. 3, the end portion (indicated by a thin line) of the fixing member 31 generally has a lower temperature at the rise than the central portion (indicated by a thick line). This is because the heat generation range of the heating source 32 does not reach the end of the fixing member 31 and the bearing 36 and the driving gear 35 are attached to the end of the fixing member 31. Because.

  In the case of a configuration in which only one heating source 32 as shown in FIG. 2 is provided, the temperature detection sensor used for temperature control uses the temperature detection sensor 34 disposed in the center. This is because all paper sizes can be accommodated. When transporting with the central portion as a reference, the temperature detection sensor 34 is normally in contact with both the central portion and the end portion, so that the temperature detected by the temperature detection sensor 34 matches the actual temperature of the fixing member 31. .

  FIG. 4 is a graph showing the transition of temperature when a deviation occurs in the contact state of the temperature detection sensor 34 arranged in the center. The vertical axis is temperature and the horizontal axis is time. In this case, since the temperature detected by the temperature detection sensor 34 (shown by a thick broken line) is low, the actual temperature (shown by a thick solid line) is controlled to be high.

  As described above, the temperature detection sensor 34 disposed at the center is likely to be displaced due to deformation and accumulation of foreign matters such as toner and paper powder when a resin casing is used as the structure.

  5A shows a state in which the temperature detection sensor is normally in contact with the fixing member 31, and FIG. 5B shows that the temperature detection sensor is in contact with the fixing member 31 due to deformation of the casing. It is a side view which shows the state which exists. FIG. 6A is a front cross-sectional view showing a state where the fixing device is attached to a housing that is not deformed, and FIG. 6B is a state where the fixing device is attached to the housing that is deformed. FIG. FIG. 7A is a graph showing a change in temperature when a deviation occurs in the contact state of the temperature detection sensor 34 disposed in the center, and FIG. 7B is a change in temperature in a state where the temperature is corrected. It is a graph which shows.

  5 and 6, when the temperature detection sensor 34 is in contact with the fixing member 31 in a state in which the temperature detection sensor 34 is shifted due to deformation of the casing 37, the temperature detection sensor 33 has a temperature shift. The correct temperature is detected because it is difficult to do.

  That is, as shown in FIG. 6B, the deformation of the resin casing 37 tends to warp toward the center due to warpage. The adhesion of toner and foreign matter is caused by paper passing, and is not affected by the temperature detection sensor 33 being installed outside the paper passing range.

  In particular, if the temperature detection sensor 33 is set outside the paper range, the influence of foreign matter is eliminated and reliable temperature detection can be performed. As shown in FIG. 7A, when the temperature detection sensor 34 can detect a temperature increase gradient based on the detected temperature detected by the temperature detection sensor 33, it is determined that the temperature detection sensor 34 is shifted. In this case, as shown in FIG. 7B, the temperature deviation is calculated from the temperature rise gradient of the temperature detection sensor 33 and corrected to the correct temperature.

  If the temperature rise gradient is not correct because the input voltage is low or the like, the temperature rise gradient detected by the temperature detection sensors 33 and 34 at both the center and the end is shifted. Thereby, it can be seen that there is no abnormality in the temperature detection, and can be distinguished from the deviation of the temperature detection sensor 34 arranged in the center.

  FIG. 8 is a schematic sectional side view showing the configuration of the fixing device according to the second embodiment of the present invention. FIG. 9 is a graph showing a temperature transition in a normal detection state in the fixing device shown in FIG. The vertical axis is temperature and the horizontal axis is time.

  The fixing device 40 according to the second embodiment of the present invention is different in that the fixing device 30 described above has one heating source, whereas the fixing device 30 has two heating sources. . In FIG. 8, the same components as those described in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted.

  In the present embodiment, the two heating sources 41 and 42 are disposed at the center of the fixing member 31 at a predetermined interval. The heating source 41 is a so-called heater, and heating portions 41 a and 41 a are formed corresponding to the end portions of the fixing member 31. The heating source 42 is a heater similar to the heating source 41, and heating portions 42 a and 42 a are formed corresponding to the central portion of the fixing member 31.

  The heating source 42 is controlled to be heated so that the surface temperature of the fixing member 31 becomes a predetermined value based on the temperature detected by the temperature detection sensor 34 disposed in the center. The heating source 41 is controlled to be heated so that the surface temperature of the fixing member 31 becomes a predetermined value based on the temperature detected by the temperature detection sensor 33 disposed at the end.

  In this configuration, since the two heating sources 41 and 42 are optimized, the temperature difference between the central portion and the end portion can be made smaller than when a single heating source is used.

  FIG. 10A is a graph showing a change in temperature in a detection state in which a deviation occurs in the contact of the temperature detection sensor 34 disposed in the center in the fixing device shown in FIG. 8, and FIG. 10B is a temperature correction. It is a graph which shows transition of temperature when performing. The vertical axis is temperature and the horizontal axis is time.

  As shown in FIG. 10A, since the temperature detected by the temperature detection sensor 34 is low, the actual temperature is controlled to be high. As described above, the temperature detection sensor 34 at the center is likely to be displaced due to deformation of the resin casing 37. At this time, the temperature detection sensor 33 disposed at the end portion hardly detects temperature deviation, and thus detects the correct temperature. When this state can be detected with a temperature increase gradient based on the temperature detected by the temperature detection sensor 33, it is determined that the temperature detection sensor 34 is deviated, and the temperature difference from the gradient of the temperature detection sensor 33 at the end is determined. Is calculated and corrected to the correct temperature (FIG. 10B).

  On the other hand, if the temperature rise gradient is not correct due to low input voltage or the like, the temperature rise gradients of the temperature detection sensors 33 and 34 at both the center and the end are shifted. It can be distinguished from the deviation of the sensor 34. In the case of a contact-type temperature detection sensor, it is necessary to set in consideration that the detected temperature value does not become higher than the actual value.

  FIG. 11A is a graph showing the transition of temperature in a configuration using one heating source, and FIG. 11B is a graph showing the transition of temperature in a configuration using two heating sources. As shown in FIGS. 11A and 11B, when the detection deviation of the temperature detection sensors 33 and 34 is larger than a preset value, the temperature detection sensors 33 and 34 are abnormal, such as jamming of jammed paper. It is conceivable that this has occurred.

  That is, when a deviation larger than expected occurs, danger can be avoided by stopping the temperature control and stopping the fixing operation of the printer 10.

  By the way, as shown in FIG. 2 above, the heating source 32 is connected to the output side of the control unit C, and the two temperature detection sensors 33 and 34 are connected to the input side of the control unit C. . The control unit C is provided with a storage unit (not shown), and a temperature increase gradient that serves as a reference for the fixing member 31 is stored in advance in the storage unit.

The control unit C is a control center of the fixing device 30 and realizes the following required functions by executing a predetermined program.
(1) A function of discriminating whether or not there is a difference between the stored temperature increase gradient serving as a reference of the fixing member 31 and each temperature increase gradient based on the surface temperature detected by each of the temperature detection sensors 33 and 34. This function is referred to as “temperature gradient discrimination means Ca”.

(2) Heating is performed based on the temperature detected by the temperature detection sensor that has obtained the temperature increase gradient closest to the stored reference temperature increase gradient among the temperature increase gradients detected by the temperature detection sensors 33 and 34. Function to control the heating of the source. This function is referred to as “heating control means Cb”.
The specific procedure for realizing the above function is as follows.

FIG. 12 is a flowchart showing the operation of the fixing device 30 described above.
Step 1 (abbreviated as “S1” in the figure): It is determined whether or not the temperature increase gradient of the detected temperature detected by the temperature detection sensor 34 disposed at the center of the fixing member 31 is within a normal range. Here, if it is determined that the gradient is within the normal range, the process proceeds to step 2; otherwise, the process proceeds to step 3.

  Step 2: It is determined whether or not the temperature is capable of printing at the center. If it is determined that the temperature is the temperature, the process proceeds to Step 8 to execute printing, and if not, the process returns to Step 1.

  Step 3: It is determined whether or not the temperature increase gradient based on the temperature detected by the temperature detection sensor 33 disposed at the end is within the normal range. If it is determined that the gradient is within the normal range, the process proceeds to step 4; otherwise, the process proceeds to step 6.

  Step 4: It is determined whether or not the temperature increase gradient based on the temperature detected by the temperature detection sensor 34 disposed in the center is A or more. If the temperature increase gradient is equal to or greater than the predetermined value A, the process proceeds to Step 5. The “predetermined value A” is a reference temperature rise gradient stored in the storage unit. If the temperature increase gradient is not equal to or greater than the predetermined value A, the process proceeds to step 9 and the operation of the printer 10 is stopped. That is, it is determined as a failure. By stopping the operation when the difference is larger than the predetermined value A set in advance, when the contact position of the temperature detection sensor 34 is displaced, it is possible to reliably prevent safety problems such as smoke, melting, and ignition. it can.

  Step 5: It is determined whether or not it is a temperature at which printing can be performed at the edge. If it is determined that the temperature is reached, the process proceeds to Step 8 to execute a printing operation. If not, the process returns to Step 1. .

  Step 6: It is determined whether or not the temperature increase gradient based on the temperature detected by the temperature detection sensor 34 disposed in the center is equal to or greater than a predetermined value B. If the temperature increase gradient is equal to or greater than B, the process proceeds to Step 7. If the temperature increase gradient is not greater than or equal to the predetermined value B, the process proceeds to step 9 where the fixing operation of the printer 10 is stopped. That is, it is determined as a failure.

  Step 7: It is determined whether or not the temperature is capable of printing in the central portion. If it is determined that the temperature is the temperature, the process proceeds to Step 9 to execute the printing operation. If not, the process returns to Step 1.

DESCRIPTION OF SYMBOLS 1 Sheet | seat 2 Conveyance path 11Y, 11M, 11C, 11K Image-forming part 12 Photoconductor 14 Developing device 15 Cleaning device 18 Intermediate transfer belt 19 Primary transfer roller 21 Secondary transfer backup roller 24 Belt cleaning device 25 Bottle accommodating part 25Y, 25M, 25C, 25K toner bottle 28 registration roller 29 paper discharge roller 31 fixing member 32 heating source 33 temperature detection sensor 34 temperature detection sensor 36 bearing 40 fixing device 41 heating source 42 heating source C control unit

JP 2007-133247 A

Claims (6)

A fixing member, a heating source for heating the fixing member, and a plurality of temperature detection sensors for detecting the temperature of the fixing member, and the surface temperature of the fixing member detected by the plurality of temperature detection sensors In the fixing device for controlling the surface temperature of the fixing member to a predetermined value based on
A temperature rise gradient that serves as a reference for the fixing member is stored in advance,
A temperature gradient determination means for determining whether or not a difference has occurred between the stored temperature increase gradient and each temperature increase gradient based on the surface temperature detected by each of the temperature detection sensors;
Heating control of the heating source is performed based on the temperature detected by the temperature detecting sensor that has obtained the temperature rising gradient closest to the stored temperature rising gradient among the temperature rising gradients detected by each temperature detection sensor. And a heating control unit.   The fixing device according to claim 1, further comprising a plurality of heating sources.   3. The fixing device according to claim 1, wherein any one of the plurality of temperature detection sensors is disposed outside a sheet range.   The temperature control means controls the surface temperature of the fixing member to a predetermined value based on a temperature detection sensor that obtains a temperature increase gradient closest to a reference temperature increase gradient. The fixing device described.   The fixing operation is stopped when a difference between a stored reference temperature increase gradient and a temperature increase gradient based on a temperature detected by each temperature detection sensor is larger than a preset value. The fixing device according to 1. An image forming apparatus using the fixing device according to claim 1.

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