JP2008209869A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To exactly control the temperature of a paper non-passage area easily at a low cost without causing noises even when a fixing roller has an area through which recording paper is not passed, and to exactly control the temperature of the fixing roller based on the accurate temperature of the heated area of the fixing roller regardless of the speed of the fixing roller. <P>SOLUTION: The image forming apparatus includes: an induction-heating means that has the fixing roller to perform fixing processing on recording paper passed through and a coil for generating a magnetic flux, and induction-heats the fixing roller by magnetic flux generated by the coil; a simulation heat generating means that has a second coil connected to the coil in series and induction-heats by magnetic flux generated by the second coil; and a control means for controlling the drive of the induction-heating means so that the temperature of the induction heat generated by the simulation heat generating means the temperature of which has a predetermined temperature relation with the temperature of the fixing roller, is maintained at a predetermined temperature. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus including a fixing roller for fixing a recording sheet to be passed, induction heating means for induction heating the fixing roller, and control means for controlling driving of the induction heating means.

  Conventionally, an image forming apparatus has been used in which a toner image formed on a recording sheet is heated and fixed on the recording sheet by a fixing device. The fixing device includes a fixing roller that applies heat to the recording paper, and an induction heating unit that induction-heats the fixing roller by generating a magnetic flux using a coil. The fixing roller is configured as an induction heating element that is induction-heated by receiving magnetic flux.

  In recent years, the heat capacity of the fixing roller is reduced by thinning the fixing roller member so that the fixing roller can be rapidly heated. When the recording paper of a small size is passed, not the maximum size of the recording paper that passes through the full length of the fixing roller. At the peripheral portion, that is, at the end of the fixing roller, the heat of the fixing roller does not escape to the recording paper or to other portions of the fixing roller, and the end becomes higher in temperature than the central portion or the like.

  When such a temperature gradient occurs, the fixing roller and other parts are damaged, such as so-called hot offset where the toner is welded to the fixing roller at a high temperature, and the high temperature is induced by the induction heating unit. There is also a problem that the magnetic flux generation efficiency of the coil is reduced by being transmitted to the coil.

  Therefore, various techniques for suppressing the end of the fixing roller from becoming high temperature have been considered, and the main ones are as follows. In Patent Document 1, it is shown that a magnetic flux shielding plate for shielding magnetic flux in induction heat generation is provided at the end portion. Patent Documents 2 and 3 show that the fixing roller is made of a material having a constant Curie point and the temperature in the longitudinal direction of the fixing roller is made uniform. Patent Document 4 shows that a plurality of coils for generating a magnetic flux are provided in the induction heating unit in the longitudinal direction of the fixing roller, and induction heating is controlled for each location.

The induction heating unit is provided near the nip portion where the fixing roller is pressed against the pressure roller and the recording paper is passed, and heats the nip portion of the fixing roller. In the vicinity of the nip portion of the fixing roller (hereinafter referred to as a heating region), there are a pressure roller and an induction heating unit, and recording paper is passed. It is necessary to provide it close enough to the heating area, and a temperature sensor for controlling the temperature of the fixing roller cannot be provided near the heating area in terms of layout. Therefore, a temperature sensor is provided at a position downstream of the heating area in the rotation direction of the fixing roller, and each part of the fixing roller moves from the heating area to the position of the temperature sensor as it rotates. The temperature of the heating region is detected by detecting the temperature of the portion at the position where the temperature sensor is provided on the downstream side.
JP-A-2005-190728 JP 2000-35724 A JP 2000-162912 A Japanese Patent Laid-Open No. 11-15304

  However, the techniques of Patent Documents 1 to 4 that prevent the temperature at the end portion in the longitudinal direction of the fixing roller from increasing have the following drawbacks. In other words, the method using a shielding plate (Patent Document 1) requires a complicated and large mechanism that can change the area for shielding the magnetic flux according to whether the size of the paper is large or small. In addition, in the method of using a material having a certain Curie point for the fixing roller (Patent Documents 2 and 3), it is difficult to realize such a special configuration, and even if it can be realized, the accuracy of the Curie point is poor and appropriate. In addition, the temperature cannot be made uniform and the cost increases. In addition, when a plurality of coils are provided (Patent Document 4), the configuration becomes large and the cost is increased. In addition, mutual induction occurs between the coils, so that an accurate temperature distribution is generated. It is difficult to control magnetic flux generation. Further, noise is also generated due to the interference sound between the coils. While it is conceivable that heat is not generated in another coil during heat generation in one coil, this causes a temperature difference for each coil.

  Moreover, there existed the following faults in detecting temperature in the downstream of a heating area | region. In other words, if rotation of the fixing roller stops due to a mechanical lock or other cause, the temperature will decrease due to heat dissipation at the temperature sensor regardless of the temperature in the heating area. As a result, the fixing roller may be heated by mistake, as well as being unable to stop the heating. Even when such mechanical lock does not occur, even when the recording paper is passed in half speed mode instead of normal speed, the fixing device rotates in half and the fixing from the heating area to the position of the temperature sensor is performed. The moving time of each part of the roller becomes longer, and the detection of the temperature of the heating area is delayed, so that the current accurate temperature is not known.

  The present invention has been made in view of these points, and is simply, low-cost, no noise is generated, and even if there is a fixing roller region through which the recording paper does not pass, such non-passing paper is provided. It is an object of the present invention to be able to accurately control the temperature of the region and to perform temperature control based on the correct temperature of the heating region of the fixing roller regardless of the speed of the fixing roller.

  The image forming apparatus according to claim 1, wherein the image forming apparatus includes a fixing roller that performs a fixing process on a recording sheet to be passed, and a coil that generates magnetic flux, and induction heating that heats the fixing roller by the magnetic flux generated by the coil. Means, a second coil connected in series with the coil, a simulated heat generating means for generating induction heat by a magnetic flux generated by the second coil, a temperature of the fixing roller and a predetermined temperature An image forming apparatus comprising: a control unit that controls driving of the induction heating unit so as to keep a temperature of induction heat generated by the simulated heating unit below a predetermined temperature.

  With this configuration, the temperature of the fixing roller varies between the paper passing area and the non-paper passing area, so it is difficult to control the fixing roller temperature appropriately by detecting the fixing roller temperature. In order not to be affected by the sheet passing area / non-sheet passing area, the non-sheet passing area in each area of the fixing roller is controlled by the temperature control by the driving control of the induction heating means based on the temperature by the induction heat generation of the simulated heating means. The temperature can be controlled accurately.

  With such a configuration, a complicated configuration having a mechanical movable part or the like is not required, a special material having a special curie point is not required, and a plurality of coils are not required. No complicated drive control is required, the device can be realized easily and inexpensively with a simple configuration, and noise such as interference sound due to simultaneous drive of multiple coils is not generated, and it is quiet It can be operated. The simulated heat generating means can realize the apparatus with a simple configuration, and can realize the apparatus at a low cost, compared with the case where a plurality of coils for heating the fixing roller are provided.

  In addition, with this configuration, the temperature control corresponding to the temperature of the heating region of the fixing roller heated by the induction heating of the induction heating means can be accurately performed without delay with respect to the temperature change of the heating region. Regardless of whether it is stopped by locking or not, whether the fixing roller is rotated in the half speed mode, in other words, regardless of the rotation speed of the fixing roller, the heating area of the fixing roller is surely correct without delay. Appropriate temperature control corresponding to the temperature can be performed.

  The control unit includes, for example, a storage unit that stores temperature relationship specifying information that specifies the temperature relationship, and sets a temperature that the temperature relationship stored in the storage unit corresponds to the target temperature of the fixing roller. The drive of the induction heating means is controlled as a target temperature of the temperature of the simulated heating means.

  The image forming apparatus according to claim 2, wherein the coils are connected in series to the first and second coils, and the coils are energized when the temperature of the induction heat generated by the simulated heating means is equal to or higher than a predetermined temperature. The image forming apparatus according to claim 1, further comprising an overcurrent preventer for cutting off.

  According to this configuration, when the temperature of the induction heat generation in the simulated heating means reaches a predetermined temperature by the overcurrent preventer, the induction heating of the fixing roller can be stopped, and the excessive temperature increase of the fixing roller is suppressed. Thus, the safety of the image forming apparatus can be improved.

  The overcurrent protector may include at least one of a thermostat and a thermal fuse.

  The image forming apparatus according to claim 3, wherein the simulated heat generation unit is provided at a position where the magnetic flux generated by the coil of the induction heating unit does not reach.

  With this configuration, unexpected induction heat generation occurs in the simulated heating means due to the magnetic flux generated by the induction heating means, so that the temperature of the induction heat generation by the simulated heating means becomes inaccurate, and consequently, the heating control of the induction heating means is controlled. The inaccuracy can avoid a situation in which the temperature control of the fixing roller is inaccurate, and the appropriate temperature control can be surely performed.

  The image forming apparatus according to claim 4, wherein the control unit causes the recording of the fixing roller when a recording sheet having a size smaller than the fixing roller passes through the fixing roller in a longitudinal direction of the fixing roller. When the temperature of the induction heat generated by the simulated heat generation unit, which has a predetermined temperature relationship with the temperature of the non-sheet passing region where the paper is not passed, exceeds a predetermined temperature, the induction heating unit The image forming apparatus according to claim 1, wherein the driving is suppressed.

  With this configuration, when a small size of recording paper is passed, if the temperature of the induction heat generated by the simulated heat generation unit exceeds a predetermined temperature, the induction heating unit is inhibited from being driven, thereby preventing non-passage. It is possible to suppress the occurrence of excessive temperature rise in the paper region.

  6. The image forming apparatus according to claim 5, wherein when the small size recording sheet is passed through the fixing roller, the control unit sets the temperature of the induction heat generated by the simulated heat generation unit to the predetermined temperature. If the temperature exceeds the temperature gradient between the sheet passing area of the fixing roller through which the recording paper is passed and the non-passing area through which the recording paper is not passed, the recording paper passes through the fixing roller. 5. The image forming apparatus according to claim 4, wherein the image forming apparatus is eliminated by making the interval longer than normal.

  According to this configuration, when the temperature of the induction heat generation by the simulated heat generation unit exceeds a predetermined temperature, the temperature of the non-sheet passing region is not limited by simply suppressing the drive of the induction heating unit. The temperature gradient generated between the temperature of the non-sheet-passing area and the temperature of the sheet-passing area can be eliminated, and the non-sheet-passing area can be controlled even if the induction heating means is driven to control the temperature of the sheet-passing area. Thus, even if the fixing roller temperature distribution is returned uniformly so as not to cause an excessive temperature rise and the fixing process by the fixing roller is continued, the excessive temperature rise in the non-sheet passing region is less likely to occur.

  Here, “resolving (temperature gradient)” includes not only completely eliminating, but also eliminating to some extent, and “returning the temperature distribution of the fixing roller uniformly” This includes not only the case of returning to a certain level but also the case of returning to a certain extent.

  The “normal time” refers to a time when the temperature of the induction heat generated by the simulated heat generating unit does not exceed the predetermined temperature when the small size recording paper is passed through the fixing roller. .

  According to the present invention, the temperature of the non-sheet passing area can be accurately controlled even if there is a fixing roller area through which the recording sheet does not pass, easily, at a low cost and without causing noise. Regardless of the speed of the fixing roller, the temperature of the fixing roller can be controlled based on the correct temperature of the heating area of the fixing roller.

  Hereinafter, a copying machine 1 according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram schematically showing a copying machine 1 according to an embodiment of the present invention.

  The copying machine 1 is an example of an “image forming apparatus” in the claims.

  The copying machine 1 includes an image forming mechanism I, a recording paper conveyance path L, a fixing device 300, and a control unit 100.

  The recording paper transport path L allows the recording paper P loaded on the paper feeding apparatus to be carried into the recording paper transport path L from the paper feeding apparatus provided at the lower part of the copying machine 1, and the loaded recording paper P is recorded. The paper is conveyed downstream of the paper conveyance path L.

  The image forming mechanism I is provided in the middle of the recording paper conveyance path L and includes a photosensitive drum. The photosensitive drum is conveyed to the position of the image forming mechanism I by the recording paper conveyance path L. A toner image of an image to be printed by the copier 1 is formed on the incoming recording paper P.

  The fixing device 300 is provided on the downstream side of the image forming mechanism I in the recording paper transport path L. After the toner image is formed by the image forming mechanism I, the fixing device 300 is connected to the fixing device 300 through the recording paper transport path L. A fixing process is performed on the conveyed recording paper P, that is, the recording paper P is heated, whereby the toner image formed on the recording paper P by the image forming mechanism I is fixed on the recording paper P.

  The fixing device 300 includes a fixing roller 310 and a pressure roller 310p.

  The fixing roller 310 is an example of the “fixing roller” in the claims.

  The fixing roller 310 is heated by an induction heating unit 320 (FIG. 2) provided inside the fixing device 300 to apply heat to the recording paper P that is passed through the fixing roller 310 through the recording paper conveyance path L. Thus, the fixing process is performed on the recording paper P.

  On the other hand, the pressure roller 310p is disposed to face the fixing roller 310 with the recording paper conveyance path L in between, presses against the fixing roller 310, and the recording paper conveyance path L between the pressure roller 310p and the fixing roller 310 that makes pressure contact. When P is passed, the recording paper P to be passed is brought into close contact with the fixing roller 310, and the fixing roller 310 causes the recording paper P to be fixed.

  The control unit 100 is an information processing device that controls the operation of each part of the copying machine 1 such as the fixing device 300. For example, the control unit 100 is a computer with a built-in program equipped with a CPU, ROM, RAM, or the like, or an ASIC (Application Specific Integrated Circuit). ) Etc.

  The control unit 100 is connected to the fixing device 300 through a control signal line, acquires information from a temperature sensor or the like of the fixing device 300, and inputs a control signal to the fixing device 300. Make it work.

  FIG. 2 is a diagram illustrating a main body 300a and a simulated heat generating unit 300b included in the fixing device 300 (FIG. 1). 2 shows the recording paper conveyance direction (y direction: FIGS. 1 and 2) from the lower side of FIG. 1 (upstream side of the recording paper conveyance path L) to the upper side of FIG. 1 (downstream side of the recording paper conveyance path L). 2 is a right-to-left direction (y direction: FIG. 2) in FIG. 2, and the fixing roller 310 is on the upper side of FIG. 2 and the other pressure roller 310p is on the lower side.

  The fixing device main body 300a includes an induction heating unit 320 and a temperature sensor (first temperature sensor) 310s together with the fixing roller 310 and the pressure roller 310p. The induction heating unit 320 includes a heating coil (first heating coil) 320c and a high dielectric constant holding member 320h.

  The induction heating unit 320 is an example of the “induction heating unit” in the claims. The first heating coil 320c is an example of “(first) coil” in the claims.

  The first heating coil 320c is provided inside the fixing roller 310. The first heating coil 320c receives electric power from the wiring C to generate a magnetic flux, and an induced current is generated in the fixing roller 310 by the magnetic flux. Induction heating. Here, the first heating coil 320c is provided in the immediate vicinity of the heating region 310r of the fixing roller 310 that performs heating in order to improve heating efficiency. Here, the heating region 310r is a nip portion of the fixing roller 310 through which the recording paper P passes when the fixing roller 310 is pressed from the pressure roller 310p.

  The temperature sensor (first temperature sensor) 310 s detects the temperature of the fixing roller 310. Here, the first temperature sensor 310s is used by the control unit 100 to detect the temperature at which the fixing roller 310 performs the fixing process on the recording paper P, and to appropriately control this temperature. Although it is desired to accurately detect the temperature of the heating area 310r to be processed, the heating coil 320c, the high dielectric constant holding member 320h, the pressure roller 310p, and the recording paper P are conveyed in the vicinity of the heating area 310r. Since there is a path L and the like, layout restrictions are tight, and the first temperature sensor 310s passes the recording paper from a position slightly away from the heating area 310r, more specifically, from the heating area 310r. The fixing roller 310 is provided at a position slightly away from the rotation direction (clockwise direction in FIG. 2).

  For this reason, the first temperature sensor 310s is shifted by the time that the fixing roller 310 rotates from the heating region 310r to the first temperature sensor 310s, and is currently at the position of the first temperature sensor 310s. By detecting the temperature of the portion of the fixing roller 310 that has been in the heating area 310r in the past by this time, the temperature of the past heating area 310r that has been shifted by this deviation time is detected. However, if the rotation speed of the fixing roller 310 is a normal speed, the deviation time is small, and the first temperature sensor 310s can substantially detect the current temperature of the heating region 310r.

  However, the first temperature sensor 310s is described above when the driving mechanism of the fixing roller 310 stops due to any cause such as a lock, for example, when at least a part of the recording paper transport path L is stopped due to a mechanical lock. Since the fixing roller 310 does not rotate as described above, the correct current temperature of the heating region 310r cannot be detected without delay. At this time, the position of the first temperature sensor 310s of the fixing roller 310 is gradually lowered as heat is radiated from the fixing roller 310, so the first temperature sensor 310s detects such a temperature drop. . At this time, such a temperature drop occurs even if the heating region 310r continues to be induction heated from the induction heating unit 320.

  Further, when the copying machine 1 is operating in the half speed mode in which the recording paper P is transported at half speed by the recording paper transport path L, the fixing roller 310 is only at half speed as normal. Without being rotated, the first temperature sensor 310s detects the temperature of the rather old heating region 310r that has been delayed by twice the normal time. Also at this time, the first temperature sensor 310s detects an incorrect temperature.

  The high dielectric constant holding member 320h suppresses unnecessary radio waves from being emitted by the magnetic flux of the heating coil 320c.

  On the other hand, the simulated heating unit 300b includes a second heating coil 350c, a heating element 350h, a second temperature sensor 350s, and a thermostat 350Sw.

  The simulated heat generating section 300b is an example of the “simulated heat generating means” in the claims. The second heating coil 350 is an example of the “second coil” in the claims.

  The simulated heating section 300b is connected in series to the induction heating section 320 of the main body section 300a described above by the wiring C. When the connected induction heating section 320 induction heats the fixing roller 310, the induction heating section 320b Simultaneously with heating, induction heat is generated.

  The second heating coil 350c is connected to the wiring C connected to the simulated heat generating part 300b, and thereby the first heating coil 320c included in the induction heating part 320 on the main body part 300a side described above is connected to the first heating coil 350c. When the first heating coil 320c generates a magnetic flux and the induction heating unit 320 performs induction heating on the fixing roller 310, the magnetic flux is generated at the same time.

  The heating element 350h receives the magnetic flux generated by the second heating coil 350c, generates an induced current, and performs induction heat generation.

  The simulated heating section 300b uses the second heating coil 350c and the heating element 350h to simultaneously generate magnetic flux with the second heating coil 350c when the induction heating section 320 performs induction heating on the fixing roller 310 on the main body section 300a side. The induced heat is generated by causing an induced current to flow through the heating element 350h.

  The simulated heating unit 300b is not affected by the magnetic flux generated by the above-described first heating coil 320c on the fixing device main body 300a side. In particular, the heating element 350h generates induction heat by the magnetic flux of the first heating coil 320c. It is provided in a position that does not.

  Hereinafter, the temperature of the heating element 350h of the simulated heating unit 300b is simply referred to as the temperature of the simulated heating unit 300b in contrast to the temperature of the heating region 310r of the fixing roller 310 and the like.

  The temperature of the simulated heating unit 300b (the temperature of the heating element 350h) is determined by the induction heating of the fixing roller 310 at the same time as the fixing roller 310 is induction-heated from the induction heating unit 320. The temperature changes in accordance with the change in the amount of heat applied to 310r, and becomes a temperature having a certain correlation such as approximately proportional or approximately linear with respect to the amount of heat applied to the heating region 310r of the fixing roller 310. Thus, the temperature of the simulated heat generating portion 300b becomes a temperature that specifies the temperature (of the non-sheet passing portion) of the heating region 310r. Here, “identify” may be completely specified, and of course, includes specifying with a certain degree of error, specifying within a certain range, and the like.

  The second temperature sensor 350s detects the temperature of the simulated heating unit 300b that specifies the temperature of the heating region 310r.

  The thermostat 350Sw is a switch that is turned off when its own temperature is equal to or higher than a certain temperature (hereinafter referred to as a safety device operating temperature). Then, the thermostat 350Sw detects the temperature of the simulated heat generating unit 300b, and is turned off when the temperature of the simulated heat generating unit 300b is equal to or higher than the safety device operating temperature. The thermostat 350Sw is connected in series to the above-described wiring C connecting the two heating coils 320c and 350c together with the two heating coils 320c and 350c, and the temperature of the simulated heating unit 300b is the safety device. When the temperature is equal to or higher than the operating temperature, power supply to the two heating coils 320c and 350c by the wiring C is cut off, and thereby the induction heating of the fixing roller 310 by the induction heating unit 320 is stopped.

  The thermostat 350Sw is an example of an “overcurrent preventer”.

  The second temperature sensor 350s and the thermostat 350Sw are less restricted in the layout in the vicinity of the simulated heat generating portion 300b, unlike the first temperature sensor 310s that cannot be provided in the vicinity of the heating region 310r of the fixing roller 310. The positions where the second temperature sensor 350s and the thermostat 350S are provided can be freely selected in the vicinity of the simulated heat generating portion 300b. For this reason, the second temperature sensor 350s and the thermostat 350Sw have their detected temperatures without delay with respect to the temperature of the simulated heat generating unit 300b, and when the temperature of the simulated heat generating unit 300b changes, these detected temperatures are immediately the same. It is arranged by selecting the position to change.

  As described above, the temperature of the simulated heat generating unit 300b changes simultaneously with the temperature change of the heating region 310r of the fixing roller 310, and a temperature having a correlation such as a substantially proportional relationship with the temperature of the heating region 310r. Therefore, these detected temperatures also change at the same time in accordance with the temperature change of the heating region 310r of the fixing roller 310, and become a temperature having a correlation such as approximately proportional.

  FIG. 3 shows a region 310 c where the recording paper Ps of the fixing roller 310 is passed and a region 310 t where the recording paper Ps is not passed when the small size recording paper Ps (see FIG. 4) is passed through the fixing roller 310. FIG.

  With reference to FIG. 3, the detected temperature of the second temperature sensor 350s and the thermostat 350Sw will be further described.

  The recording sheet Ps is a recording sheet having a relatively small size among various types of recording sheets P.

  In the recording paper Ps, the width w1 in the longitudinal direction of the fixing roller 310, that is, the direction in which the rotation axis of the fixing roller 310 extends (z direction: FIG. 3) is shorter than the length w2 of the fixing roller 310 in the longitudinal direction. For this reason, when the recording paper Ps is passed through the fixing roller 310, the fixing roller 310 simply passes the recording paper Ps through the region 310c having the width w1 of the recording paper Ps in the longitudinal direction. This is a width of “width w2−width w1” obtained by subtracting the width w1 of the central area 310c from the width w2 of the entire fixing roller 310 in the longitudinal direction outside the area 310c. The recording paper Ps is not passed through the end (peripheral) area 310t.

  In the end region 310t, the heat applied to the fixing roller 310 by induction heating (see FIG. 2) of the induction heating unit 320 is not deprived by the recording paper Ps to be passed, that is, the fixing roller by the recording paper Ps. The end region 310t of 310 is not cooled, and the temperature of the end region 310t is relatively higher than that of the central region 310c. As a result, a temperature gradient is generated in the longitudinal direction in the fixing roller 310 in which the temperature is high in the end region 310t and the temperature is low in the central region 310c.

  FIG. 4 is a diagram illustrating a temperature gradient generated in the fixing roller 310 and each configuration of the copying machine 1 that performs an operation for eliminating the temperature gradient.

  The lower graph in FIG. 4 shows a temperature gradient that occurs in the longitudinal direction of the fixing roller 310 when a small size recording paper Ps (see FIG. 3) is passed through the fixing roller 310.

  In the graph of FIG. 4, the horizontal axis represents each position in the longitudinal direction of the fixing roller 310, the vertical axis represents the temperature of the fixing roller 310 at each position, and the data SmlT is recorded in a small size. The temperature of the fixing roller 310 when the paper Ps is passed through the fixing roller 310 is larger than the recording paper Ps as data BigT, and the width of the fixing roller 310 in the longitudinal direction with respect to the fixing roller 310 w2 shows the temperature of the fixing roller 310 when a large-sized recording sheet to be fully fed is fed to the fixing roller 310, respectively.

  In this graph, among the positions of the respective portions in the longitudinal direction of the fixing roller 310 shown on the horizontal axis, the end region 310t of the fixing roller 310 described above with reference to FIG. 3 and the central region The position with respect to 310c is shown by being divided by a two-dotted line and a broken line, respectively.

  In this graph, as shown in the large-size recording paper data BigT, when a large-size recording paper is passed, the heat of the fixing roller 310 is recorded at all positions in the longitudinal direction. Since the sheet escapes to the paper, the fixing roller 310 has a substantially uniform temperature at any position.

  On the other hand, as shown in the data SmlT of the small size recording paper Ps (FIG. 3), when the small size recording paper Ps is passed, the fixing roller at the position indicated by the broken line in FIG. In the central area 310c of 310, the temperature is about the same as the data BigT of the large-size recording paper, but in the data in the end area 310t at the position indicated by the two-dot chain line in FIG. The temperature is higher than the temperature of the region 310c.

  For this reason, when recording paper Ps of a small size is passed through the fixing roller 310, the first temperature sensor 310s of the main body 300a (see FIGS. 3 and 4) is in the longitudinal direction of the central region 310c. Since the temperature in the central region 310c is detected from the temperature gradient provided at the position of, the incorrect and incorrect low temperature is detected with respect to the above-described high temperature in the end region 310t. It will be.

  With respect to such an erroneously low detection temperature T1 of the first temperature sensor 310s, the detection temperatures of the second temperature sensor 350s and the thermostat 350Sw are as follows.

  As described above, the temperature of the simulated heat generating unit 300b specifies the temperature of the fixing roller 310. As shown in the graph of FIG. 4, when the temperature gradient occurs in the fixing roller 310, the simulated heat generating unit 300b. In this case, the recording paper Ps (P) is not passed, heat is not taken away by the recording paper Ps, and the temperature is the same as that of the end region 310t, and the temperature of the end region 310t is specified. Become.

  For this reason, as shown in the graph of FIG. 4, when the temperature gradient of the simulated heating unit 300b is generated in the fixing roller 310, the high temperature portion of the temperature gradient shown in the data SmlT of FIG. A change correlated with the temperature of the region 310t at the end of the fixing roller 310 to be configured becomes a correlated temperature. That is, the detected temperature T2 of the second temperature sensor 350s and the thermostat 350Sw that detect the temperature of the simulated heat generating unit 300b is approximately proportional to the temperature of the end region 310t through which the recording paper Ps is not passed, for example. A correlated change is made to achieve a correlated temperature.

  Eventually, the detected temperature is a temperature correlated with the heating area 310r of the fixing roller 310 without delay, and the small size recording paper Ps described above with reference to FIGS. When the paper is passed, it is not simply correlated with the temperature of the heating region 310r of the fixing roller 310, but when a temperature gradient occurs, it particularly correlates with the temperature of the end region 310t that has become higher due to the temperature gradient. It will be a thing.

  The thermostat 350Sw (FIGS. 2 to 4) causes the induction heating unit 320 (see FIG. 2) to perform induction heating of the fixing roller 310 only when the detected temperature is lower than the operating temperature of the safety device based on the self-detected temperature. When the detected temperature is equal to or higher than the operating temperature of the safety device, the induction heating unit 320 (FIG. 2) is turned off, and the induction heating of the fixing roller 310 by the induction heating unit 320 is stopped.

  FIG. 5 is a diagram showing the high-frequency ON / OFF circuit 100x.

  On the other hand, the high-frequency ON / OFF circuit 100x shown in FIGS. 4 and 5 is provided on the wiring C, and the power supply from the commercial power source to the two heating coils 320c and 350c through the wiring C is turned on and off. Switch between.

Further, the paper passing motor Mtr (FIG. 4) is a motor that passes the recording paper to the fixing roller 310, and is provided, for example, in a part of the recording paper transport path L (FIG. 1).

  The controller 100 implements a roller temperature control function unit 100f.

  The roller temperature control function unit 100 f is a functional block of the function of the control unit 100 that controls the temperature of the fixing roller 310.

  The control unit 100 constitutes an example of “control means”.

  Here, the control unit 100 may be configured, for example, by simply rewriting software of a conventional product using a conventional product. In this regard, in FIG. 4, the roller temperature control function unit 100f, which is a functional block of the function realized by the control unit 100 by such rewriting, is clearly shown in addition to the control unit 100. ing.

  In this embodiment, the properties, functions, operations to be executed, and the like of the roller temperature control function unit 100f are all realized by the control unit 100f having or executing it.

  The roller temperature control function unit 100f controls induction heating of the fixing roller 310 by the induction heating unit 320 using the high frequency ON / OFF circuit 100x. Further, the roller temperature control function unit 100f controls the passing of the recording sheet to the fixing roller 310 by the sheet passing motor Mtr. The roller temperature control function unit 100f controls the temperature of the fixing roller 310 by performing these controls.

  The high-frequency ON / OFF circuit 100x and the paper passing motor Mtr used by the roller temperature control function unit 100f for controlling the temperature of the fixing roller 310 are referred to as a temperature changing device 100m. The high-frequency ON / OFF circuit 100x and the paper passing motor Mtr included in the temperature changing device 100m can change the temperature of the fixing roller 310 by controlling the operation of the roller temperature control function unit 100f. .

  FIG. 6 is a timing chart showing the timing at which the roller temperature control function unit 100 f controls the temperature of the fixing roller 310.

  In FIG. 6, the detected temperature T1 detected by the first temperature sensor 310s in the fixing device main body 300a is shown in the upper stage (A), and the second temperature sensor 350s and the thermostat 350Sw in the lower stage (B). A detected temperature T2 of the detected temperature of the simulated heat generating unit 300b is shown.

  The timing t0 is a timing at which the copying machine 1 starts to start up the fixing device 300 when the user presses a print start button.

  Timing t1 is timing when the copying machine 1 completes the start-up. At this time, as shown in the upper part (A) of FIG. 6, the fixing roller 310 is at a temperature at which the fixing process to the recording paper can be appropriately performed, that is, a fixing temperature (for example, 180 ° C.).

  The copying machine 1 starts printing on the recording paper P by the image forming mechanism I (FIG. 1) or the like from this timing t1.

  FIG. 7 is a flowchart showing a temperature control process performed by the roller temperature control function unit 100f to keep the temperature of the fixing roller 310 at 180 ° C.

  In FIG. 7, timings t1 to t3 indicate a period during which the roller temperature control function unit 100f maintains the temperature of the fixing roller 310 at 180 ° C. by the process of step S1.

  In step S11, the roller temperature control function unit 100f specifies whether printing performed by the copying machine 1 is normal mode printing that is not the half speed mode or printing in the half speed mode. .

  In step S12, when it is determined in step S11 that the copying machine 1 is printing in the normal mode other than the half speed mode in step S11 (step S11: NO), the roller temperature control function unit 100f The temperature control is performed based on the detected temperature T1 of the first temperature sensor 310s of the fixing device main body 300a. At this time, since the fixing roller 310 is rotating at a normal speed, the detected temperature T1 of the first temperature sensor 310s is the temperature at which the temperature of the heating region 310r of the fixing roller 310 is correctly detected without delay. Therefore, at this time, the roller temperature control function unit 100f uses the high-frequency ON / OFF circuit 100x (see FIG. 4) based on the detected temperature T1 of the first temperature sensor 310s to cause the fixing roller 310 to move by the induction heating unit 320. By controlling induction heating, the heating region 310r is set to 180 ° C.

  On the other hand, in step S13, the roller temperature control function unit 100f determines in step S11 that the copying machine 1 is printing in the half speed mode (step S11: YES). The process which maintains 310 at 180 degreeC is performed.

  At this time, as described above, the detected temperature T1 of the first temperature sensor 310s is different from the current correct temperature of the heating region 310r of the fixing roller 310 and is an inaccurate temperature with a delay.

  In the half speed mode, the amount of heat required for one sheet is constant, but the conveyance speed is halved and the fixing time is doubled. By reducing the amount of heat taken away by the recording paper, the temperature difference between the non-new passing area and the paper passing area of the fixing roller 310 is reduced.

  Therefore, the roller temperature control function unit 100f uses the detected temperature T2 of the second temperature sensor 310s in this step S13.

  The roller temperature control function unit 100f stores in advance a target temperature (for example, 90 ° C.) of the second temperature sensor 310s that sets the temperature of the heating region 310r of the fixing roller 310 to 180 ° C. The second temperature sensor 310s When the detected temperature T2 becomes equal to or higher than the target temperature (90 ° C.), the induction heating of the fixing roller 310 by the induction heating unit 320 is stopped by the high frequency ON / OFF circuit 100x (see FIG. 4), and thereby the simulated heating unit The temperature of 300b is maintained at the target temperature 100 ° C., and the temperature of the heating region 310r of the fixing roller 310 is maintained at the fixing temperature (180 ° C.), which is the temperature on the fixing roller 310 side corresponding to the target temperature (90 ° C.). Let

  At the timing t1 to t2 in the lower part of FIG. 6, during the period of the target temperature (90 ° C.) detected by the second temperature sensor 310s, the roller temperature control function unit 100f performs the process of step S13, The period during which the temperature of the heating region 310r of the fixing roller 310 is maintained at the fixing temperature (180 ° C.) is shown, and the temperature of the heating region 310r (fixing temperature: 180 ° C.) is a detection delay time due to the rotation of the fixing roller 310. While being delayed by a minute (see the description of FIG. 2), the first temperature sensor 310s detects 180 ° C. (fixing temperature) as shown at timings t1 to t2 in the upper part of FIG.

  In step S1r, the roller temperature control function unit 100f repeatedly executes the processes in steps S11 to S13 described above (step S1r: NO), and continuously maintains the temperature of the fixing roller 310 at a fixing temperature of 180 degrees. The iterative control process is shown.

  FIG. 8 is a flowchart illustrating a temperature control process in which the roller temperature control function unit 100 f suppresses the temperature gradient of the fixing roller 310.

  In step S21, the roller temperature control function unit 100f specifies whether or not a small size recording paper Ps (see FIG. 3) is passed through the fixing roller 310, and the small size recording paper Ps is passed. If it is specified (step S21: YES), the processing of steps S22 to S23 is performed.

  In step S22, the roller temperature control function unit 100f determines whether or not the temperature detected by the second temperature sensor 350s is higher than a fixing roller allowable temperature limit (for example, 100 ° C.).

  Here, the allowable temperature limit of the fixing roller is the simulated heat generating portion 300b that matches the temperature rise when the temperature of the region 310t at the end of the fixing roller 310 increases to an allowable limit level (for example, 200 ° C.). This is the temperature at which the simulated heat generating portion 300b is formed by the temperature rise due to the induction heat generation.

  Here, the allowable limit level of the temperature of the fixing roller 310 is, for example, a temperature at which a so-called hot offset does not occur in the fixing roller 310.

  The fixing roller allowable temperature limit is an example of a “predetermined temperature” in claim 4 of the claims.

  When the temperature T2 detected by the second temperature sensor 350s is higher than the allowable temperature limit (100 ° C.) of the fixing roller 310 (step S22: YES), the roller temperature control function unit 100f performs the process of the next step S23. Execute.

  In step S23, the roller temperature control function unit 100f suppresses induction heating of the fixing roller 310 by the induction heating unit 320, so that the region 310t at the end of the fixing roller 310 that has reached the allowable temperature limit of the fixing roller further increases in temperature. To prevent.

  In step S23, the roller temperature control function unit 100f controls the paper passing motor Mtr so that the paper passing interval of the recording paper Ps to the fixing roller 310 is wider than the normal paper passing interval. Let the interval. Here, the normal sheet passing interval refers to the case where the roller temperature control function unit 100f determines in step S22 that the detected temperature T2 of the second temperature sensor 350s is equal to or lower than the fixing roller allowable temperature limit (step S22: NO). Sometimes the interval at which paper is passed. Thus, the roller temperature control function unit 100f can transfer the heat accumulated in the end region 310t due to the temperature gradient (refer to the data SmlT in the lower graph of FIG. 4) to the center region 310c. By making the length longer, heat is transferred from the end region 310t to the central region 310c, and a small recording paper Ps is passed, and a large amount of heat is required to perform the fixing process on the small recording paper Ps. Heat is supplied from the end region 310t to the center region 310c.

  The roller temperature control function unit 100f stops the induction heating by the induction heating unit 320 and the fixing roller 310 until the detected temperature T2 of the second temperature sensor 350s is equal to or lower than the fixing roller allowable temperature limit (100 ° C.) described above. The temperature of the end region 310t is equal to or lower than the allowable temperature level (200 ° C.) while eliminating the temperature gradient of the fixing roller 310 by extending the sheet passing interval without passing the next recording sheet Ps to the sheet. Let me.

  At timings t3 to t4 in the lower part of FIG. 8, the roller temperature control function unit 100f repeatedly executes the process of step S2 of FIG. 8 (step S2r: NO), thereby detecting the temperature T2 detected by the second temperature sensor 350s. Changes around 100 ° C., indicating that the temperature of the end region 310t does not exceed the allowable temperature level. At this time, as described above, the roller temperature control function unit 100f lengthens the sheet passing interval, and the temperature gradients in the end region 310t and the central region 310c are eliminated. As shown in the upper temperature T1, the temperature of the central region 310c is continuously maintained at the fixing temperature (180 ° C.).

  FIG. 9 is a flowchart showing the operation of the thermostat 350Sw.

  The operation of the thermostat 350Sw will be described in detail with reference to FIG.

  At timing t4 in FIG. 6, the fixing roller 310 is locked by the driving mechanism of the fixing roller 310, for example, a gear between the fixing roller 310 and the paper passing motor Mtr (FIG. 4) is locked. The stop timing is shown.

  At this time, since the fixing roller 310 is stopped, the detected temperature T1 of the first temperature sensor 310s is lowered. An example of this temperature drop is shown at timings t4 to t5 in the upper part (A) of FIG.

  At this time, the thermostat 350 </ b> SW erroneously recovers the temperature of the fixing roller 310 as the detected temperature decreases, and after the timing t <b> 4 when the induction heating unit 320 erroneously continues the induction heating of the fixing roller 310 in the copying machine 1. When the temperature of the thermostat 350Sw shown in the lower part (B) of FIG. 7 is increased, the self temperature, that is, the self-detected temperature T2 reaches the safety device operating temperature (125 ° C. in FIG. 6) (timing t5, step S31: YES), the induction heating to the fixing roller 310 by the induction heating unit 320 is stopped (step S32). The thermostat 350Sw continues to stop induction heating while the detected temperature T2 of the thermostat 350Sw is the safety device operating temperature (step S3r: NO, step S31: YES).

  As shown in the period of the timing t4 to t5, the thermostat 350Sw has the fixing roller 310 erroneously stopped due to the lock and the detected temperature T1 of the first temperature sensor 310s is lowered as shown in the period of the timing t4 to t5 ( (A) in FIG. 6, as a result of the induction heating of the fixing roller 310 by the induction heating unit 320 being silently performed, as a result of the induction heat generation of the simulation heat generation unit 300b at the same time as the induction heating (see FIG. 6A) 125 ° C. (refer to the lower part (B) of FIG. 6).

  An example of the “(temperature at which the power is turned off)” in claim 2 is an example of the temperature set as the safety device operating temperature of the thermostat 350Sw.

  Note that when the detected temperature of the thermostat 350Sw becomes the operating temperature of the safety device (step S31: YES), the thermostat 350Sw is detected even if the detected temperature T1 of the first temperature sensor 310s is equal to or lower than the fixing temperature (180 ° C.) (FIG. 6). The induction heating of the induction heating unit 320 is stopped regardless of the operation of the control unit 100 in accordance with the temperature detected by the first temperature sensor 310s.

  Finally, another embodiment will be described.

  (A) A thermal fuse may be used instead of the thermostat 350Sw. This thermal fuse is also connected in series to the first and second heating coils 320c and 350c, and, similarly to the above-described thermostat 350Sw, when the temperature of the thermostat 350Sw itself becomes the safety device operating temperature ( Step S31: YES), induction heating by the induction heating unit 320 is stopped (step S32).

  (B) The roller temperature control function unit 100f may control the temperature of the fixing roller 310 based on the safety device operating temperature of the thermostat 350Sw in the description of FIG. For example, the roller temperature control function unit 100f detects the second temperature sensor 350s even if the detected temperature T1 of the first temperature sensor 310s is lower than the fixing temperature 180 ° C. (timing t4 to t5 in FIG. 6 (A), etc.). If the detected temperature T2 is equal to or higher than the operating temperature of the safety device (see step S31 in FIG. 9), induction heating of the fixing roller 310 by the induction heating unit 320 is stopped by the high frequency ON / OFF circuit 100x. (See step S32 in FIG. 9). In this case, unlike the case where the thermostat 350Sw stops the induction heating, the temperature to be stopped can be easily changed according to the setting of the roller temperature control function unit 100f, and adjustment such as fine adjustment can be easily performed.

  Note that the operating temperature of the safety device of the thermostat 350Sw may be set to the fixing roller allowable temperature limit described in the explanation of FIG. The thermostat 350Sw is connected to the wiring C only when a small-size sheet is passed by a switch operation by the control unit 100 (see step S21 in FIG. 8), and is fixed by the induction heating unit 320. It is assumed that the induction heating of the roller 310 can be stopped. By so doing, the thermostat 350Sw can easily suppress the occurrence of a temperature gradient.

1 is a diagram schematically showing a copier according to an embodiment. It is a figure which shows the main-body part with which a fixing device is provided, and the simulation heat generating part. It is a figure which shows the area | region where a recording paper is passed, and the area | region where a paper is not passed. 2 is a diagram illustrating a temperature gradient generated in a fixing roller and a configuration of each part of a copier that performs an operation for eliminating the temperature gradient. FIG. It is a figure which shows a high frequency ON / OFF circuit. 6 is a timing chart showing timing at which the roller temperature control function unit controls the temperature of the fixing roller. 7 is a flowchart of a temperature control process performed by a roller temperature control function unit to keep the temperature of the fixing roller at 180 ° C. 6 is a flowchart illustrating a temperature control process for suppressing a temperature gradient of a fixing roller, which is performed by a roller temperature control function unit. It is a flowchart which shows operation | movement of a thermostat.

Explanation of symbols

BigT Fixing roller temperature when large size recording paper is passed SmlT Fixing roller temperature when small size recording paper is passed C Wiring I Image forming mechanism L Recording paper transport path Mtr Passing motor P recording paper Ps small size recording paper w1 width of recording paper Ps w2 width of fixing roller 310 1 copier (image forming apparatus)
100 Control unit (control means)
100f Roller temperature control function unit 100m Temperature change device 100x High frequency ON / OFF circuit 300 Fixing device 300a Fixing device main body 300b Simulated heating unit (simulated heating unit)
310 Fixing roller (fixing roller)
310p pressure roller 310r heating area 310c area through which the fixing roller 310 passes (sheet passing area)
310t Area where the fixing roller 310 is not passed (non-passage area)
310s first temperature sensor 320 induction heating unit (induction heating means)
320c first heating coil ((first) coil)
320h High dielectric constant holding member 350c Second heating coil (second coil)
350h Heating element 350s Second temperature sensor 350Sw Thermostat (overcurrent protector)

Claims (5)

A fixing roller for fixing the recording paper to be passed;
An induction heating means having a coil for generating magnetic flux, and induction heating the fixing roller by the magnetic flux generated by the coil;
A second heating coil connected in series to the coil, and a simulated heating means for generating induction heat by a magnetic flux generated by the second coil;
An image provided with control means for controlling the drive of the induction heating means so as to keep the temperature of the induction heat generated by the simulated heat generation means which is in a predetermined temperature relationship with the temperature of the fixing roller below a predetermined temperature. Forming equipment.   2. An overcurrent preventer that is connected in series to the first and second coils, and that cuts off the energization of each coil when the temperature of induction heat generated by the simulated heat generating unit is equal to or higher than a predetermined temperature. The image forming apparatus described.   The image forming apparatus according to claim 1, wherein the simulated heat generation unit is provided at a position where magnetic flux generated by the coil of the induction heating unit does not reach.   When the recording paper having a size smaller than that of the fixing roller is passed through the fixing roller in the longitudinal direction of the fixing roller, the control unit is configured to detect a non-passing area in which the recording paper of the fixing roller is not passed. The image according to claim 1, wherein when the temperature of the induction heat generated by the simulated heat generation unit having a predetermined temperature relationship with respect to the temperature exceeds a predetermined temperature, the drive of the induction heating unit is suppressed. Forming equipment.   When the temperature of the induction heat generated by the simulated heat generating unit exceeds the predetermined temperature when the small size recording sheet is passed through the fixing roller, the control unit is configured to record the recording sheet of the fixing roller. By making the temperature gradient between the paper passing area through which the recording paper passes and the non-paper passing area through which the recording paper is not passed, the interval between passing the recording paper to the fixing roller is longer than usual. The image forming apparatus according to claim 4, wherein the image forming apparatus is eliminated.

Images