JP2021177203A - Fixing device and image forming apparatus - Google Patents

Abstract

To improve convenience by specifying a cause of an abnormal temperature of a fixing roller.SOLUTION: A fixing device (15) thermally fixes a toner image to a sheet (S), and comprises: a cylindrical fixing roller (21) that extends in a sheet width direction; a pressure roller that presses the sheet against the fixing roller; a plurality of heaters (23) that heats a plurality of portions in a longitudinal direction of the fixing roller; a plurality of temperature sensors (24) that detects the temperature at the plurality of portions of the fixing roller; a classification unit (26) that classifies rates of temperature rise of the plurality of temperature sensors into a plurality of temperature rise levels; and a determination unit (27) that determines a state of the device from the temperature rise levels of the rates of temperature rise of the plurality of temperature sensors.SELECTED DRAWING: Figure 2

Description

The present invention relates to a fixing device and an image forming device.

The image forming apparatus is provided with a fixing apparatus for thermally fixing the toner image on the sheet. In the fixing device, the fixing roller is heated by the heater, and the sheet is conveyed while being pressed against the fixing roller by the pressure roller. Since there is an optimum temperature for heat fixing of toner, the fixing device detects the temperature of the fixing roller and controls the heater. As this type of fixing device, a sensor defect is detected by detecting a plurality of locations separated in the rotation axis direction of the fixing roller with a plurality of temperature sensors and comparing the temperature rise rate obtained from the detection results of each temperature sensor. Has been proposed (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2005-234273

However, in the fixing device described in Patent Document 1, since the cause of the abnormal temperature of the fixing roller is determined to be a sensor failure, the cause of the abnormal temperature cannot be identified.

Therefore, an object of the present invention is to identify the cause of the abnormal temperature of the fixing roller and improve the convenience.

The fixing device according to one aspect of the present invention is a fixing device that heat-fixes a toner image on a sheet, and includes a tubular fixing roller extending in the sheet width direction and a pressure roller that presses the sheet against the fixing roller. A plurality of heaters for heating a plurality of locations in the longitudinal direction of the fixing roller, a plurality of temperature sensors for detecting the temperature of the plurality of locations of the fixing roller, and a plurality of temperature rise rates of the plurality of temperature sensors. It is provided with a classification unit for classifying into levels and a determination unit for determining the device state from the temperature rise level of the temperature rise rate of the plurality of temperature sensors.

The plurality of temperature rise levels include a first temperature rise level classified when the temperature rise rate is zero, and the classification unit raises some of the temperature sensors among the plurality of temperature sensors. When the temperature rate is classified into the first temperature rise level, the determination unit may determine that some of the temperature sensors are in a disconnected state.

Of the plurality of heaters, a specified value is set based on the temperature rise rate of some temperature sensors corresponding to the part of the heaters in a state where some of the heaters are stopped in advance and the other heaters are driven. The plurality of temperature rise levels include a second temperature rise level classified when the temperature rise rate is greater than zero and falls below a specified value, and the classification unit includes the plurality of temperature sensors. When the temperature rise rate of some of the temperature sensors is classified into the second temperature rise level, the determination unit may determine that some heaters corresponding to the part of the temperature sensors are in a defective state.

Multiple temperature rise levels are classified as a third temperature rise level that is classified when the temperature rise rate is equal to or higher than the specified value and falls below the lower limit of the normal rate. It includes a fourth temperature rise level that is sometimes classified and a fifth temperature rise level that is classified when the temperature rise rate exceeds the upper limit of the normal rate, and the classification unit includes the plurality of temperature sensors. When the temperature rise rate is classified into the third temperature rise level, the determination unit determines that the input voltage for the plurality of heaters is insufficient, and the classification unit determines the temperature rise rate of the plurality of temperature sensors to be the fourth. When the determination unit determines that the temperature rise level is normal, and the classification unit classifies the temperature rise rate of the plurality of temperature sensors into the fifth temperature rise level, the determination unit determines. It may be determined that the input voltage is excessive for the plurality of heaters.

The classification unit classifies the temperature rise rate of some of the plurality of temperature sensors into a third temperature rise level or a fifth temperature rise level, and sets the temperature rise rate of the remaining temperature sensors as a part of the temperature sensor. When the temperature sensor is classified into a temperature rise level different from the temperature rise rate of the temperature sensor, the determination unit may determine that some of the temperature sensors are in a defective state.

The image forming apparatus of one aspect of the present invention includes the above-mentioned fixing device and an image forming portion for forming an image on a sheet.

According to the present invention, the temperature of a plurality of locations of the fixing roller is monitored by a plurality of temperature sensors, and the temperature rise rate obtained from the detection results of each temperature sensor is classified into a plurality of temperature rise levels. From the difference in the temperature rise level of the temperature rise rate of each temperature sensor, various device states generated in the fixing device are determined. The device state that causes the abnormal temperature of the fixing roller can be identified, and the convenience of the fixing device can be improved.

It is a schematic diagram of the printer of this embodiment. It is a schematic diagram of the detection configuration of the abnormal temperature of the fixing device of this embodiment. This is a classification example of the temperature rise level of the temperature sensor in the central portion of the present embodiment. This is an example of classification of the temperature rise level of the temperature sensor at the end of the present embodiment. This is an example of determining the device state of the present embodiment. This is an example of the amount of temperature rise of the temperature sensor in the normal state of this embodiment. This is an example of the amount of temperature rise of the temperature sensor when the sensor of the present embodiment is defective. This is an example of the amount of temperature rise of the temperature sensor when the voltage of the present embodiment is insufficient. This is an example of a flowchart of the device state determination operation of the present embodiment.

Hereinafter, an image forming apparatus to which the fixing apparatus of the present embodiment is applied will be described with reference to the drawings. In the following description, a printer will be illustrated as an image forming apparatus. FIG. 1 is a schematic view of the printer of this embodiment. Arrows Fr, Re, U, and Lo appropriately attached to each figure indicate the front side, the rear side, the upper side, and the lower side of the printer, respectively.

As shown in FIG. 1, the printer 1 includes a box-shaped housing 5 in which various devices are housed. A sheet cassette 11 in which the sheet bundle S1 is set is detachably housed in the lower part of the housing 5, and a paper output tray 12 is provided in the upper part of the housing 5. In the housing 5, a transport path L1 for the sheet S from the sheet cassette 11 to the output tray 12 is formed by a plurality of rollers. The transport path L1 is provided with a paper feeding device 13, an image forming unit 14, a fixing device 15, and a paper discharging device 16 from upstream to downstream. A toner container 17 and an exposure apparatus 18 are provided above the image forming unit 14.

At the time of image formation of the printer 1, an electrostatic latent image is formed on the surface of the photoconductor drum 19 of the image forming unit 14 by the laser light from the exposure apparatus 18, and toner is adhered to the electrostatic latent image to form the photoconductor drum 19. A toner image is formed on the surface. On the other hand, the sheet S is taken out from the sheet cassette 11 by the paper feeding device 13, and the sheet S is conveyed toward the image forming unit 14 at the timing of the image forming operation. The toner image is transferred from the surface of the photoconductor drum 19 to the surface of the sheet S in the image forming unit 14, the toner image is heat-fixed to the sheet S in the fixing device 15, and the fixed sheet S is discharged by the paper ejection device 16. It is discharged to the paper tray 12.

The fixing device 15 includes a tubular fixing roller 21 extending in the sheet width direction and a tubular pressure roller 22 extending in parallel with the fixing roller 21. The fixing roller 21 is heated by the heater 23, and the pressure roller 22 presses the sheet S against the fixing roller 21 to heat-fix the toner image on the sheet S. The temperature of the fixing roller 21 is detected by the temperature sensor 24 in order to heat-fix the toner image to the sheet S at an optimum temperature. The drive of the heater 23 is controlled so that the temperature of the fixing roller 21 becomes the optimum temperature according to the detection result of the temperature sensor 24.

When the temperature sensor 24 detects the abnormal temperature of the fixing roller 21, it is preferable to identify the cause of the abnormal temperature of the fixing roller 21 in order to improve the convenience of the user. In addition to defects in the temperature sensor 24 and the heater 23, various causes such as disconnection of the temperature sensor 24 and excess / deficiency of the input voltage to the heater 23 can be considered as causes of the abnormal temperature. Therefore, the fixing device 15 of the present embodiment classifies the temperature rise rate of the fixing roller 21 at a plurality of locations into a plurality of temperature rise levels, and utilizes the difference in the temperature rise levels of the temperature rise rates at the plurality of locations to obtain an abnormal temperature. The cause of is identified.

A configuration for detecting an abnormal temperature of the fixing device will be described with reference to FIG. FIG. 2 is a schematic diagram of an abnormal temperature detection configuration of the fixing device of the present embodiment. FIG. 3A is a classification example of the temperature rise level of the temperature sensor in the central portion of the present embodiment. FIG. 3B is a classification example of the temperature rise level of the temperature sensor at the end of the present embodiment. FIG. 4 is an example of determining the device state of the present embodiment. FIG. 5A is an example of the amount of temperature rise of the temperature sensor in the normal state of this embodiment. FIG. 5B is an example of the amount of temperature rise of the temperature sensor when the sensor of the present embodiment is defective. FIG. 5C is an example of the amount of temperature rise of the temperature sensor when the voltage of the present embodiment is insufficient.

It should be noted that, in FIG. 2, it is assumed that the fixing device is provided with the usual configuration, and the description thereof will be omitted. Further, in the following description, when one of the plurality of heaters 23a-23c is not specified, the heater 23 is described, and when one of the plurality of temperature sensors 24a-24c is not specified, the temperature sensor 24 is used. Describe.

As shown in FIG. 2, the fixing device 15 includes heaters 23a for small size sheets and heaters 23b and 23c for large size sheets as a plurality of heaters 23 for heating a plurality of locations in the longitudinal direction of the fixing roller 21. , Are provided. The heater 23a is a lamp heater in which the light distribution peak is located at the center of the fixing roller 21 in the longitudinal direction, and the heaters 23b and 23c are lamp heaters in which the light distribution peak is located at both ends in the longitudinal direction of the fixing roller 21. Only the heater 23a lights up when the small size sheet is heat-fixed, and the heaters 23a-23c light up when the large size sheet is heat-fixed.

Further, in the fixing device 15, as a plurality of temperature sensors 24 for detecting the temperature of a plurality of locations of the fixing roller 21, a temperature sensor 24a corresponding to the heater 23a, temperature sensors 24b and 24c corresponding to the heaters 23b and 23c, and the like. Is provided. The temperature sensor 24a is a center thermistor that detects the temperature at the central portion of the fixing roller 21 in the longitudinal direction, and the temperature sensors 24b and 24c are end thermistors that detect the temperature at both ends of the fixing roller 21 in the longitudinal direction. The detection result of the temperature sensor 24a-24c is output to the control unit 25, and the control unit 25 executes the drive control process of the heaters 23a-23c or the cause identification process of the abnormal temperature.

The control unit 25 includes a classification unit 26 that classifies the temperature rise rate of the temperature sensor 24a-24c into a plurality of temperature rise levels, and a determination unit that determines the device state from the temperature rise level of the temperature sensor 24a-24c. 27 and a timer unit 28 for counting the elapsed time from the start of heating are provided. The classification unit 26 records the temperature output from the temperature sensor 24a-24c during the period from the start of heating of the fixing roller 21 by the heaters 23a-23c to the reaching the printable temperature. Then, the classification unit 26 calculates the temperature rise rate, which is the amount of temperature rise per unit time, from the detection result of the temperature sensor 24a-24c, and raises the temperature rise rate of the temperature sensor 24a-24c in the 1st to 5th steps. Classify into temperature levels.

In the classification unit 26, a part corresponding to the part of the heaters 23 is supported in a state where some of the heaters 23 are stopped in advance and the other heaters 23 are driven for the classification of the second temperature rise level. A specified value is set based on the heating rate of the temperature sensor 24 of. Further, in the classification unit 26, an upper limit value and a lower limit value of the normal speed are set for classifying the third to fifth temperature rise levels. The temperature rise rate of the temperature sensor 24 is classified with the specified value, the lower limit value and the upper limit value of the normal speed as threshold values. As the specified value for these classifications, the lower limit value and the upper limit value of the normal speed, values obtained empirically, experimentally, or theoretically from past data and the like are used.

The first temperature rise level indicates a state in which there is no temperature change of the temperature sensor 24, and is classified into the first temperature rise level when the temperature rise rate of the temperature sensor 24 is zero. The second heating level is such that a part of the fixing roller 21 is not heated by some heaters 23 and another part of the fixing roller 21 is heated by another heater 23, so that the other part of the fixing roller 21 is heated. It shows the state where heat is transferred from one part to another. Therefore, the temperature rise rate of some temperature sensors 24 corresponding to some heaters 23 is larger than zero but very low. When the temperature rising rate of the temperature sensor 24 is higher than zero and falls below the above-mentioned specified value, it is classified into the second temperature rising level.

The third temperature rise level indicates a state in which the temperature rise rate of the temperature sensor 24 is insufficient with respect to the normal speed, and when the temperature rise rate of the temperature sensor 24 is equal to or higher than the specified value and falls below the lower limit of the normal speed, the third temperature rise level. It is classified into 3 temperature rise levels. The fourth temperature rise level indicates a state in which the temperature rise rate of the temperature sensor 24 is normal, and when the temperature rise rate of the temperature sensor 24 is equal to or greater than the lower limit of the normal rate and equal to or less than the upper limit, the fourth temperature rise is achieved. It is classified into levels. The fifth temperature rise level indicates a state in which the temperature rise rate of the temperature sensor 24 is excessive with respect to the normal speed, and when the temperature rise rate of the temperature sensor 24 exceeds the upper limit of the normal speed, the fifth rise Classified as temperature level.

For example, as shown in FIG. 3A, the temperature rise amount per second is obtained as the temperature rise rate of the temperature sensor 24a, and the temperature rise amount per second of the temperature sensor 24a becomes the first to fifth temperature rise levels. being classified. Here, 9 [° C.] is set as a specified value for determining the second temperature rise level, and 45 [° C.] is set as the lower limit of the normal speed for determining the third to fifth temperature rise levels. , 55 [° C.] is set as the upper limit of the normal speed. The specified value is set based on the amount of temperature rise of the temperature sensor 24a when the heaters 23b and 23c are driven with the heater 23a stopped in advance.

When the temperature rise amount of the temperature sensor 24a is 0 [° C.], it is classified into the first temperature rise level where there is no temperature rise. When the temperature rise amount of the temperature sensor 24a is 1-8 [° C.], the temperature rise is classified into a minute second temperature rise level. When the temperature rise amount of the temperature sensor 24a is 9-44 [° C.], it is classified into a third temperature rise level in which the temperature rise is insufficient. When the temperature rise amount of the temperature sensor 24a is 45-55 [° C.], the temperature rise is classified into a normal fourth temperature rise level. When the temperature rise amount of the temperature sensor 24a is 56 [° C.] or more, it is classified into a fifth temperature rise level in which the temperature rise is excessive.

Similarly, as shown in FIG. 3B, the amount of temperature rise of the temperature sensor 24b is classified into the first to fifth temperature rise levels. Here, 11 [° C.] is set as a specified value for determining the second temperature rise level, and 40 [° C.] is set as the lower limit of the normal speed for determining the third to fifth temperature rise levels. , 50 [° C.] is set as the upper limit of the normal speed. The specified value is set based on the amount of temperature rise of the temperature sensor 24b when the heater 23a is driven with the heaters 23b and 23c stopped in advance. The classification of the temperature sensor 24c is the same as that of the temperature sensor 24b, and thus the description thereof will be omitted.

When the temperature rise amount of the temperature sensor 24b is 0 [° C.], it is classified into the first temperature rise level where there is no temperature rise. When the temperature rise of the temperature sensor 24b is 1-10 [° C.], the temperature rise is classified into a minute second temperature rise level. When the temperature rise amount of the temperature sensor 24b is 11-39 [° C.], it is classified into a third temperature rise level in which the temperature rise is insufficient. When the temperature rise amount of the temperature sensor 24b is 40-50 [° C.], the temperature rise is classified into a normal fourth temperature rise level. When the temperature rise amount of the temperature sensor 24b is 51 [° C.] or more, it is classified into a fifth temperature rise level in which the temperature rise is excessive.

As shown in FIG. 4, the determination unit 27 determines the fixing device 15 into 13 types of device states based on the classification result of the temperature sensor 24. Here, for convenience of explanation, the device state of the fixing device 15 is determined using the two classification results of the temperature sensors 24a and 24b, but the device state is further determined by using the three classification results of the temperature sensors 24a-24c. It may be determined in detail. In the state number 1, the temperature rise amount (temperature rise rate) of the central temperature sensor 24a is the first temperature rise level, and the temperature rise amount of the end temperature sensor 24b is the first to fifth temperature rise levels by the classification unit 26. Classified as one of the levels. In this case, since there is no temperature change of the temperature sensor 24a, the determination unit 27 determines that the temperature sensor 24a is in a disconnected state.

In the state number 2, the classification unit 26 classifies the temperature rise amount of the temperature sensor 24a into any of the first to fifth temperature rise levels, and the temperature rise amount of the temperature sensor 24b into the first temperature rise level. In this case, since there is no temperature change of the temperature sensor 24b, the determination unit 27 determines that the temperature sensor 24b is in a disconnected state. In the state number 3, the temperature rise amount of the temperature sensor 24a is classified into one of the second temperature rise levels, and the temperature rise amount of the temperature sensor 24b is classified into one of the first to fifth temperature rise levels by the classification unit 26. In this case, since the temperature rise of the temperature sensor 24a is very small, the determination unit 27 determines that the heater 23a is in a poor lighting state.

In the state number 4, the temperature rise amount of the temperature sensor 24a is classified into one of the first to fifth temperature rise levels, and the temperature rise amount of the temperature sensor 24b is classified into the second temperature rise level by the classification unit 26. In this case, since the temperature rise of the temperature sensor 24b is very small, the determination unit 27 determines that the heater 23b is in a poor lighting state. In the state number 5, the temperature rise amount of the temperature sensors 24a and 24b is classified into the third temperature rise level by the classification unit 26. In this case, since it is unlikely that the temperature sensors 24a and 24b fail at the same time and the temperature rise is insufficient, the determination unit 27 determines that the input voltage to the heaters 23a and 23b is insufficient.

In the state number 6, the temperature rise amount of the temperature sensor 24a is classified into the third temperature rise level, and the temperature rise amount of the temperature sensor 24b is classified into the fourth temperature rise level by the classification unit 26. In this case, since the temperature rise of the temperature sensor 24a is insufficient, the determination unit 27 determines that the temperature sensor 24a is in a defective state. In the state number 7, the temperature rise amount of the temperature sensor 24a is classified into the third temperature rise level, and the temperature rise amount of the temperature sensor 24b is classified into the fifth temperature rise level by the classification unit 26. In this case, since the temperature rise of the temperature sensor 24a is insufficient and the temperature rise of the temperature sensor 24b is excessive, the determination unit 27 determines that the temperature sensors 24a and 24b are in a defective state.

In the state number 8, the temperature rise amount of the temperature sensor 24a is classified into the fourth temperature rise level, and the temperature rise amount of the temperature sensor 24b is classified into the third temperature rise level by the classification unit 26. In this case, since the temperature rise of the temperature sensor 24b is insufficient, the determination unit 27 determines that the temperature sensor 24b is in a defective state. In the state number 9, the temperature rise amount of the temperature sensors 24a and 24b is classified into the fourth temperature rise level by the classification unit 26. In this case, since the amount of temperature rise of the temperature sensors 24a and 24b changes normally and there is no problem with the heaters 23a and 23b, the determination unit 27 determines that the fixing device 15 is in a normal state.

In the state number 10, the temperature rise amount of the temperature sensor 24a is classified into the fourth temperature rise level, and the temperature rise amount of the temperature sensor 24b is classified into the fifth temperature rise level by the classification unit 26. In this case, since the temperature rise of the temperature sensor 24b is excessive, the determination unit 27 determines that the temperature sensor 24b is in a defective state. In the state number 11, the temperature rise amount of the temperature sensor 24a is classified into the fifth temperature rise level, and the temperature rise amount of the temperature sensor 24b is classified into the third temperature rise level by the classification unit 26. In this case, the temperature rise of the temperature sensor 24a is excessive, and the temperature rise of the temperature sensor 24b is insufficient. Therefore, the determination unit 27 determines that the temperature sensors 24a and 24b are in a defective state.

In the state number 12, the temperature rise amount of the temperature sensor 24a is classified into the fifth temperature rise level, and the temperature rise amount of the temperature sensor 24b is classified into the fourth temperature rise level by the classification unit 26. In this case, since the temperature rise of the temperature sensor 24a is excessive, the determination unit 27 determines that the temperature sensor 24b is in a defective state. In the state number 13, the temperature rise amount of the temperature sensors 24a and 24b is classified into the fifth temperature rise level by the classification unit 26. In this case, since it is unlikely that the temperature sensors 24a and 24b fail at the same time and the temperature rise becomes excessive, the determination unit 27 determines that the input voltage to the heaters 23a and 23b is excessive.

For example, as shown in FIG. 5A, the detection temperature of the central temperature sensor 24a rises by 50 [° C.] and the detection temperature of the end temperature sensor 24b rises by 50 [° C.] in 1 second from 1 second to 2 seconds after the start of heating. It is rising by 45 [° C]. The temperature rise of the temperature sensor 24a is included in the fourth temperature rise level of 45-55 [° C.] (see FIG. 3A), and the temperature rise of the temperature sensor 24b is the fourth temperature rise of 40-50 [° C.]. Included in the level (see Figure 3B). In this way, since the temperature rise amount of the temperature sensors 24a and 24b is classified into the fourth temperature rise level by the classification unit 26, the determination unit 27 determines that the fixing device 15 is in a normal state (FIG. FIG. See state number 9 of 4).

As shown in FIG. 5B, the detection temperature of the central temperature sensor 24a rises by 50 [° C.] and the detection temperature of the end temperature sensor 24b is 38 [] in 1 second from 1 second to 2 seconds after the start of heating. ℃] It is rising. The temperature rise of the temperature sensor 24a is included in the fourth temperature rise level of 45-55 [° C.] (see FIG. 3A), and the temperature rise of the temperature sensor 24b is the third temperature rise of 11-39 [° C.]. Included in the level (see Figure 3B). As described above, since the temperature rise amount of the temperature sensor 24a is classified into the fourth temperature rise level by the classification unit 26 and the temperature rise amount of the temperature sensor 24b is classified into the third temperature rise level by the determination unit 27, the temperature sensor 24b is classified by the determination unit 27. Is determined to be in a defective state (see state number 8 in FIG. 4).

As shown in FIG. 5C, the detection temperature of the central temperature sensor 24a rises by 43 [° C.] and the detection temperature of the end temperature sensor 24b rises by 38 [° C.] in 1 second from 1 second to 2 seconds after the start of heating. ℃] It is rising. The temperature rise of the temperature sensor 24a is included in the third temperature rise level of 9-44 [° C.] (see FIG. 3A), and the temperature rise of the temperature sensor 24b is the third temperature rise of 11-39 [° C.]. Included in the level (see Figure 3B). In this way, since the temperature rise amount of the temperature sensors 24a and 24b is classified into the third temperature rise level by the classification unit 26, the determination unit 27 determines that the input voltage for the heaters 23a and 23b is insufficient. (See state number 5 in FIG. 4).

Each part of the control unit 25 may be realized by software using a processor, or may be realized by a logic circuit (hardware) formed in an integrated circuit or the like. When a processor is used, various processes are performed by the processor reading and executing a program stored in the memory. As the processor, for example, a CPU (Central Processing Unit) is used. The memory is composed of one or a plurality of storage media such as ROM (Read Only Memory) and RAM (Random Access Memory) depending on the intended use.

The flow of the device state determination operation will be described with reference to FIG. FIG. 6 is an example of a flowchart of the device state determination operation of the present embodiment. Here, for convenience of explanation, a determination operation for determining the device state of the fixing device 15 using the classification results of the temperature sensors 24a and 24b will be described. In addition, the reference numerals in FIG. 2 will be described as appropriate.

As shown in FIG. 6, when the heaters 23a-23c are driven (step S01), the timer unit 28 counts the elapsed time from the start of heating by the heaters 23a-23c (step S02). Next, when the count value of the timer unit 28 reaches the specified count value (Yes in step S03), the classification unit 26 calculates the temperature rise amounts (heating rate) ta and tb of the temperature sensors 24a and 24b per unit time. (Step S04). Next, the classification unit 26 classifies the temperature rise amounts ta and tb of the temperature sensors 24a and 24b in parallel (steps S05 and S11).

In the classification process of the temperature rise amount ta of the central temperature sensor 24a, when the temperature rise amount ta is 0 [° C.], the temperature rise amount ta is classified into the first temperature rise level (step S06). When the temperature rise amount ta is 1-8 [° C.], the temperature rise amount ta is classified into the second temperature rise level (step S07). When the temperature rise amount ta is 9-44 [° C.], the temperature rise amount ta is classified into the third temperature rise level (step S08). When the temperature rise amount ta is 45-55 [° C.], the temperature rise amount ta is classified into the fourth temperature rise level (step S09). When the temperature rise amount ta is 56 [° C.] or more, the temperature rise amount ta is classified into the fifth temperature rise level (step S10).

In the classification process of the temperature rise amount tb of the temperature sensor 24b at the end, when the temperature rise amount tb is 0 [° C.], the temperature rise amount tb is classified into the first temperature rise level (step S12). When the temperature rise amount ta is 1-10 [° C.], the temperature rise amount tb is classified into the second temperature rise level (step S13). When the temperature rise amount tb is 11-39 [° C.], the temperature rise amount tb is classified into the third temperature rise level (step S14). When the temperature rise amount tb is 40-50 [° C.], the temperature rise amount tb is classified into the fourth temperature rise level (step S15). When the temperature rise amount tb is 51 [° C.] or more, the temperature rise amount tb is classified into the fifth temperature rise level (step S16).

Next, the determination unit 27 determines the device state of the fixing device 15 based on the combination of the temperature increase amount ta of the central temperature sensor 24a and the temperature increase amount tb of the temperature sensor 24b at the end. (Step S17). When the temperature rise amount ta is the first temperature rise level and the temperature rise amount tb is any of the first to fifth temperature rise levels, it is determined that the temperature sensor 24a is in a disconnected state (step S18). .. When the temperature rise amount ta is any of the first to fifth temperature rise levels and the temperature rise amount tb is the first temperature rise level, it is determined that the temperature sensor 24b is in a disconnected state (step S19). ..

When the temperature rise amount ta is the second temperature rise level and the temperature rise amount tb is any of the first to fifth temperature rise levels, it is determined that the heater 23a is in a lighting failure state (step S20). .. When the temperature rise amount ta is any of the first to fifth temperature rise levels and the temperature rise amount tb is the second temperature rise level, it is determined that the heater 23b is in a lighting failure state (step S21). .. When the temperature rise amounts ta and tb are the third temperature rise levels, it is determined that the input voltage for the heaters 23a-23c is insufficient (step S22). When the temperature rise amount ta is the third temperature rise level and the temperature rise amount tb is the fourth temperature rise level, it is determined that the temperature sensor 24a is in a defective state (step S23).

When the temperature rise amount ta is the third temperature rise level and the temperature rise amount tb is the fifth temperature rise level, it is determined that the temperature sensors 24a and 24b are in a defective state (step S24). When the temperature rise amount ta is the fourth temperature rise level and the temperature rise amount tb is the third temperature rise level, it is determined that the temperature sensor 24b is in a defective state (step S25). When the temperature rise amounts ta and tb are the fourth temperature rise level, it is determined that the fixing device 15 is in a normal state (step S26). When the temperature rise amount ta is the fourth temperature rise level and the temperature rise amount tb is the fifth temperature rise level, it is determined that the temperature sensor 24b is in a defective state (step S27).

When the temperature rise amount ta is the fifth temperature rise level and the temperature rise amount tb is the third temperature rise level, it is determined that the temperature sensors 24a and 24b are in a defective state (step S28). When the temperature rise amount ta is the fifth temperature rise level and the temperature rise amount tb is the fourth temperature rise level, it is determined that the temperature sensor 24a is in a defective state (step S29). When the temperature rise amounts ta and tb are the fifth temperature rise level, it is determined that the input voltage is excessive with respect to the heaters 23a-23c (step S30). If it is determined that the device is in a state other than the normal state, the user may be notified of the device state by the display or the like of the printer 1.

As described above, according to the present embodiment, the temperatures of the fixing rollers 21 at a plurality of locations are monitored by the plurality of temperature sensors 24a-24c, and the temperature rising rate obtained from the detection results of the respective temperature sensors 24a-24c is the first to fifth. It is classified into the temperature rise level of. Due to the difference in the temperature rise level of the temperature rise rate of each temperature sensor 24a-24c, not only the detection abnormality of the temperature sensor 24a-24c, but also the input voltage abnormality, the lighting abnormality of the heater 23a-23c, and the disconnection of the temperature sensor 24a-24c. Various device states generated in the fixing device 15 such as the above are determined. The device state that causes the abnormal temperature of the fixing roller 21 can be identified, and the convenience of the fixing device 15 can be improved.

Further, in the present embodiment, since the device state is determined by the existing temperature sensors 24a-24c used for the drive control of the heaters 23a-23c, it is not necessary to newly increase the number of sensors, and the number of parts and the cost can be reduced. Can be done. Further, by providing the fixing device 15 in the printer 1, it is possible to appropriately determine the cause of the abnormality of the fixing device 15 and improve the workability of the maintenance work.

Further, in the present embodiment, when the temperature rising rate of some temperature sensors 24 is classified into the first temperature rising level by the classification unit 26, the determination unit 27 determines that some of the temperature sensors 24 are in a disconnected state. (See status numbers 1 and 2 in FIG. 4). As a result, the abnormal temperature caused by the disconnection of the temperature sensor 24 is identified. Further, when the temperature rise rate of some temperature sensors 24 is classified into the second temperature rise level by the classification unit 26, the defective state of some heaters 23 corresponding to some temperature sensors 24 by the determination unit 27. (See status numbers 3 and 4 in FIG. 4). Thereby, the abnormal temperature caused by the lighting failure of the heater 23 or the like is specified.

When the temperature rise rate of the plurality of temperature sensors 24 is classified into the third temperature rise level by the classification unit 26, the determination unit 27 determines that the input voltage for the plurality of heaters 23 is insufficient (state of FIG. 4). See number 5). Further, when the temperature rise rate of the plurality of temperature sensors 24 is classified into the fifth temperature rise level by the classification unit 26, the determination unit 27 determines that the input voltage is excessive for the plurality of heaters 23 (FIG. 4). See state number 13). From these, the abnormal temperature caused by the excess or deficiency of the input voltage is specified. Further, when the temperature rise rate of the plurality of temperature sensors 24 is classified into the fourth temperature rise level by the classification unit 26, the determination unit 27 determines the normal state (see the state number 9 in FIG. 4).

Further, the temperature rise rate of some temperature sensors 24 is classified into a third temperature rise level or a fifth temperature rise level by the classification unit 26, and the temperature rise rate of the remaining temperature sensors 24 is a part of the temperature sensors 24. When the temperature rise is classified into a temperature rise level different from the temperature rise rate of No. 1, the determination unit 27 determines that some of the temperature sensors 24 are in a defective state (see state numbers 6, 7, and 10-12 in FIG. 4). Thereby, the abnormal temperature caused by the defect of the temperature sensor 24 is specified.

In the present embodiment, the fixing device 15 is configured to include three heaters 23a-23c, but the fixing device 15 may include two or more heaters 23. Further, in the present embodiment, the fixing device 15 is configured to include three temperature sensors 24a-24c, but the fixing device 15 may include two or more temperature sensors 24.

Further, in the present embodiment, the central portion and the end portion of the fixing roller 21 are heated by the heaters 23a-23c, but the heating portion by the heater 23 is not particularly limited. Further, in the present embodiment, the temperature of the central portion and the end portion of the fixing roller 21 is detected by the temperature sensor 24a-24c, but the temperature detection portion by the temperature sensor 24 is not particularly limited.

Further, in the present embodiment, the temperature rise rate of the temperature sensor 24 is classified into five levels of the first to fifth temperature rise levels by the classification unit 26, but the temperature rise rate of the temperature sensor 24 is determined by the classification unit 26. It suffices if it is classified into a plurality of temperature rise levels. For example, the temperature rising rate of the temperature sensor 24 may be classified into four or less levels, or may be classified into six or more levels.

Further, in the present embodiment, the printer is exemplified as the image forming apparatus, but the image forming apparatus may be a multifunction device having a printing function, a copying function, a fax function, and the like in addition to the copier and the facsimile.

Further, in the present embodiment, the sheet S may be a sheet-like sheet to be formed as an image, and may be, for example, plain paper, coated paper, tracing paper, or an OHP (Over Head Projector) sheet.

Although this embodiment has been described, as another embodiment, the above-described embodiment and modifications may be combined in whole or in part.

Further, the technique of the present invention is not limited to the above-described embodiment, and may be variously modified, replaced, or modified without departing from the spirit of the technical idea. Furthermore, if the technical idea can be realized in another way by the advancement of the technology or another technology derived from it, it may be carried out by using that method. Therefore, the claims cover all embodiments that may be included within the scope of the technical idea.

1: Printer (image forming device)
14: Image forming unit 15: Fixing device 21: Fixing roller 22: Pressurizing roller 23: Heater 24: Temperature sensor 26: Classification unit 27: Judgment unit S: Sheet

Claims (6)

A fixing device that heat-fixes a toner image on a sheet.
A cylindrical fixing roller that extends in the seat width direction,
A pressure roller that presses the sheet against the fixing roller, and
A plurality of heaters for heating a plurality of locations in the longitudinal direction of the fixing roller, and
A plurality of temperature sensors for detecting the temperature of the plurality of locations of the fixing roller, and
A classification unit that classifies the temperature rise rates of the plurality of temperature sensors into a plurality of temperature rise levels,
A fixing device including a determination unit for determining a device state from the temperature rise level of the temperature rise rate of the plurality of temperature sensors. The plurality of heating levels include a first heating level that is classified when the heating rate is zero.
When the classification unit classifies the temperature rise rate of some of the temperature sensors among the plurality of temperature sensors into the first temperature rise level, the determination unit determines that some of the temperature sensors are in a disconnected state. The fixing device according to claim 1, wherein the fixing device is characterized. Of the plurality of heaters, a specified value is set based on the temperature rise rate of some temperature sensors corresponding to the part of the heaters in a state where some of the heaters are stopped in advance and the other heaters are driven. Has been
The plurality of heating levels include a second heating level classified when the heating rate is greater than zero and below a specified value.
When the classification unit classifies the temperature rise rate of some of the temperature sensors among the plurality of temperature sensors into the second temperature rise level, the determination unit selects some heaters corresponding to the part of the temperature sensors. The fixing device according to claim 1 or 2, wherein it is determined to be in a defective state. The plurality of temperature rise levels are classified as a third temperature rise level classified when the temperature rise rate is equal to or higher than the specified value and falls below the lower limit of the normal rate. It includes a fourth temperature rise level that is sometimes classified and a fifth temperature rise level that is classified when the rate of temperature rise exceeds the upper limit of the normal rate.
When the classification unit classifies the temperature rise rate of the plurality of temperature sensors into a third temperature rise level, the determination unit determines that the input voltage for the plurality of heaters is insufficient.
When the classification unit classifies the temperature rise rate of the plurality of temperature sensors into the fourth temperature rise level, the determination unit determines that it is in a normal state.
The claim is characterized in that when the classification unit classifies the temperature rise rate of the plurality of temperature sensors into a fifth temperature rise level, the determination unit determines that the input voltage is excessive with respect to the plurality of heaters. The fixing device according to 3. The classification unit classifies the temperature rise rate of some of the plurality of temperature sensors into a third temperature rise level or a fifth temperature rise level, and sets the temperature rise rate of the remaining temperature sensors as a part of the temperature sensor. The fixing device according to claim 4, wherein the determination unit determines that the temperature sensor is in a defective state when the temperature sensor is classified into a temperature rise level different from the temperature rise rate of the temperature sensor. The fixing device according to any one of claims 1 to 5.
An image forming apparatus including an image forming portion for forming an image on a sheet.

Images