Fixing device of image forming apparatus

Abstract

To provide a fixing device of an image forming apparatus that can reduce the risk of temperature deviation after sensor replacement.SOLUTION: A fixing device 10 has a contact thermistor 20 that is in contact with a fixing belt 14, and a thermopile 22 that is not in contact with the fixing belt 14, and includes a control microcomputer 30 that compares a detection result of the contact thermistor 20 with a detection result of the thermopile 22 through an initial operation under a predetermined condition, and corrects the detection result of the thermopile 22. When a correction value exceeds a predetermined maximum value, the control microcomputer 30 initializes a correction value used for correction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a fixing device of an image forming apparatus. [Background technology]

[0002] Conventionally, in a fixing device of an image forming apparatus, the relationship between the rate of change per unit time of the temperature detected by a non-contact temperature detection unit during warm-up and a correction value for the temperature detected by a contact temperature detection unit provided in the fixing unit is represented, and the correction value is obtained based on previously derived relationship information, and the correction value is used to correct the temperature detected by the non-contact temperature detection unit and control the operation of the heating unit.This is disclosed, for example, in JP 2021-124555 A. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-124555 Summary of the Invention [Problem to be solved by the invention]

[0004] In a conventional image forming apparatus, when the fixing device is warming up, the temperature detected by the non-contact temperature detection unit is corrected to control the operation of the heating unit. However, in such a fixing device, when a problem occurs due to an abnormal sensor temperature, the correction value reaches its maximum value, and even if the sensor is replaced and the abnormality is resolved, the maximum correction value is used until the timing of the next correction value measurement, which creates a problem of risk of poor fixing or hot offset due to a deviation in the detected temperature.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a fixing device for an image forming apparatus that can reduce the risk of temperature deviation after sensor replacement. [Means for solving the problem]

[0006] The fixing device of the image forming apparatus according to this disclosure has a contact temperature detection unit that contacts the fixing belt and a non-contact temperature detection unit that does not contact the fixing belt, and includes a control unit that compares the detection result of the contact temperature detection unit with the detection result of the non-contact temperature detection unit during initial operation under specified conditions and corrects the detection result of the non-contact temperature detection unit, and the control unit initializes the correction value used for correction when the correction value used for correction exceeds a predetermined maximum value.

[0007] Preferably, the control unit has a memory unit that stores the correction value used for the correction, and the control unit compares the correction value obtained in the initial operation with the correction value used for the correction, uses the correction value with the larger absolute value for the correction, and overwrites the correction value stored in the memory unit.

[0008] More preferably, the control unit is connected to a server, and when the correction value used for correction is initialized, the control unit notifies an external control center via the server that the non-contact temperature detection unit is defective.

[0009] The initial operation is performed multiple times, and the correction value obtained in the previous initial operation is compared with the correction value obtained in the current initial operation. If there is a predetermined difference, an external control center is notified via the server that the non-contact temperature detection unit is faulty, and the correction value stored in the memory unit is initialized.

[0010] When initializing the correction values ​​stored in the storage unit, the correction values ​​obtained in the initial operation may be used as the correction values. [Effects of the Invention]

[0011] According to the present disclosure, when the correction value used for correction exceeds a predetermined maximum value, the correction value used for correction is initialized, thereby providing a fixing device for an image forming apparatus that can reduce the risk of temperature deviation after sensor replacement.

[0012] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description of the embodiments, which proceeds with reference to the drawings. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a diagram illustrating a fixing device of an image forming apparatus according to an embodiment of the present disclosure. [Figure 2] 5 is a flowchart illustrating an operation of the fixing device. DETAILED DESCRIPTION OF THE INVENTION

[0014] An embodiment of the present disclosure will be described in detail below with reference to the drawings. Fig. 1 is a diagram showing a fixing device of an image forming apparatus according to an embodiment of the present disclosure. Referring to Fig. 1, fixing device 10 of the image forming apparatus includes fixing unit 12. Fixing unit 12 includes fixing belt 14 and pressure roller 16. Fixing belt 14 includes heater lamp 15 therein for heating fixing belt 14.

[0015] Heater lamp 15 is heated by heater driver 18 included in heater driver unit 17. Fixing belt 14 is provided with contact thermistor 20 (contact temperature detection unit, indicated as X in FIG. 1) that contacts fixing belt 14 and detects its temperature, and thermopile 22 (non-contact temperature detection unit, indicated as A in FIG. 1) that is provided outside fixing unit 12 and detects the temperature of fixing unit 12.

[0016] [First embodiment] The contact thermistor 20 and the thermopile 22 are connected to one or more control microcomputers (controllers) 30 via an operational amplifier and protection circuit 26 for the contact thermistor and an operational amplifier and protection circuit 27 for the thermopile, which are included in a power control unit 24. The control microcomputer 30 includes a CPU 31, and memory areas A and B for storing predetermined correction values. The control microcomputer 30 is connected to the heater driver unit 17.

[0017] The control microcomputer 30 is connected to a control center (not shown) via a server 32 .

[0018] Next, the operation of the control microcomputer 30 will be described. Figure 2 is a flowchart showing the operation of the control microcomputer 30. Referring to Figure 2, when the image forming apparatus is powered on or restarted, the following process starts (step S11; steps will be omitted below). First, correction value A is called up (the initial value is called up the first time the power is turned on) to be used to correct the detection result of thermopile 22 (shown as sensor A in Figure 2) based on the detection result of contact thermistor 20, and the temperature of thermopile 22 is corrected (step S12).

[0019] Here, an example of the initial value will be described. The initial value is a correction value according to the circuit offset measured during the production process, and is written in memory area B. This initial value is not overwritten. The upper limit of the initial value is an AD value, which is, for example, 10 counts. If the upper limit is exceeded, the value is processed in a board check process in the production process (not shown).

[0020] Next, the temperature of the temperature sensor (thermopile 22) is detected (S13), and an initial operation is determined (S14). Here, the initial operation is determined by determining whether or not the contact thermistor 20 and the thermopile 22 are both 30° C. or less before the heater lamp 15 is turned on after the power is turned on.

[0021] If the initial judgment is OK (YES) in S14, the temperature of the contact thermistor 20 (shown as sensor X in FIG. 2) is set as the reference temperature, the AD value of the contact thermistor 20 at the reference temperature is set as the origin, and the difference between the AD value of the thermopile 22 and the origin is set as difference A, and a correction value A corresponding to the temperature difference with the thermopile 22 is calculated (S15).

[0022] Here, an upper limit and a lower limit of the difference A are determined in advance, and when the difference A falls below the lower limit, the correction value is rounded to 0. In other words, when the difference A is less than the lower limit, the correction value is 0, and when the difference A is greater than or equal to the lower limit, the correction value A is equal to the difference A - the lower limit.

[0023] On the other hand, if the difference A exceeds the upper limit, the correction value A is rounded to the upper limit.

[0024] That is, when the upper limit value<the difference A, the correction value A=the upper limit value.

[0025] Here, an example of how to calculate the correction value A will be described. The AD value of the contact thermistor 20 at the reference temperature (for example, the temperature of the contact thermistor 20 is 20°C) is set to 400 (origin). The lower limit is set to the AD value of the thermopile 22, which corresponds to the temperature error of the contact thermistor 20, of 2. The upper limit is set to the AD value of 8, which is an offset including the periphery of the operational amplifier plus α.

[0026] As an example, if the AD value of the thermopile 22 is 409, the difference A is the AD value of the thermopile 22 minus the origin, ie, 409-400=9.

[0027] Since the lower limit value is 2 and the upper limit value is 8, the correction value A (difference A-lower limit value) is 9-2=7.

[0028] As another example, if the AD value of the thermopile 22 is, for example, 412, the difference A is 412-400=12.

[0029] Since the lower limit value is 2 and the upper limit value is 8, the correction value A is 12-2=10. In this way, if the correction value exceeds the upper limit value, it is considered a detection error, and the correction value A is rounded to the upper limit value so that the detection error is not included. Therefore, in this case, the correction value A is 8.

[0030] Next, the process proceeds from S15 to S16, where it is determined whether correction value A is equal to or greater than the upper limit abnormal value. Here, the upper limit abnormal value is, for example, set to AD=20, which corresponds to the detected temperature expected when the thermopile 22 fails. If correction value A is equal to or greater than the upper limit abnormal value (YES in S16), it is detected that the sensor (thermopile 22) is abnormal, and the sensor abnormality is notified to a control center (not shown) via server 32 (S24). At this time, the sensor (thermopile 22) is replaced.

[0031] If correction value A is not greater than or equal to the upper limit abnormal value (NO in S16), it is determined whether or not correction value A has suddenly changed (S17). If it is determined that correction value A has suddenly changed (YES in S17), a sensor abnormality is detected as in S16, and the sensor abnormality is notified to a control center (not shown) via server 32 shown in FIG. 1 (S24).

[0032] Here, we will explain the sudden change in correction value A. Here, the correction value acquired in the initial operation and stored in memory area B is compared with the previous correction value (the correction value before overwriting stored in memory area A), and if the difference is, for example, AD value = 5 or more, it is determined that there is a sudden change in correction value A.

[0033] By detecting not only upper limit abnormalities but also sudden changes in the correction value, sensor (thermopile 22) abnormalities are not overlooked.

[0034] This sudden change in the correction value may occur in the early stages of an abnormality in the sensor (thermopile 22), and may occur several times before the abnormality is detected. Therefore, if a sudden change in the correction value is detected three times, it may be determined that the sensor is abnormal.

[0035] [Second embodiment] When it is determined in S17 that the correction value A has not changed suddenly (NO in S17), the correction value A is compared with the initial value stored in the memory area B, and the correction value with the larger absolute value is adopted as the correction value A, and the correction value A is overwritten in the memory area A (S18).

[0036] Next, correction value A is called up and the temperature of thermopile (sensor A in FIG. 2) 22 is corrected (S19), after which heater lamp 15 is controlled (S20).

[0037] On the other hand, if it is determined in S14 that the temperature is not the temperature for initial determination (NO in S14), the heater lamp 15 is controlled (S20).

[0038] Next, a temperature abnormality is detected (S21), and if a temperature abnormality is detected (YES in S21), a temperature abnormality notification is made (S22), and after the notification is addressed, the device is restarted (S23), and the process ends.

[0039] An example of detecting a temperature abnormality will now be described. A detected temperature abnormality does not necessarily mean that the thermopile 22 sensor is abnormal, so simply notifying the temperature abnormality does not set the initial value as the correction value A. This temperature abnormality corresponds to, for example, a heater lamp burning out.

[0040] Next, the process of S24 will be described in the case where the result of S16 is YES (correction value A≧upper limit abnormal value). When a sensor abnormality is detected in S24, the initial value stored in memory area B is written to memory area A as correction value A (S25), and the process ends.

[0041] As described above, in the present disclosure, when the correction value used for correction exceeds a predetermined maximum value (upper limit abnormal value) (YES in S16, S24 to S25), the control microcomputer 30 replaces the sensor (thermopile 22) and initializes the correction value. In this way, after the occurrence of a problem due to an abnormal sensor temperature is resolved, the correction value can be returned to the initial value, thereby reducing the risk of temperature deviation after replacing the sensor.

[0042] If there is no temperature abnormality in S21 (NO in S21), the process proceeds to detecting the temperature of the thermopile 22 (S13).

[0043] In the above embodiment, the heater lamp is shown as one element, but the heater lamp includes a main lamp and a sub-lamp, and the thermopile is provided at a position corresponding to the main lamp and the sub-lamp.

[0044] Furthermore, the upper and lower limit abnormal values ​​of the correction value for correcting the thermopiles corresponding to the main lamp and the sub-lamp may be set separately.

[0045] The present disclosure can be implemented in various other forms without departing from its spirit or main features. Therefore, the above-described embodiments are merely examples and should not be interpreted as being limited. All modifications and variations within the scope of the claims of the present disclosure are within the scope of the present disclosure. [Industrial Applicability]

[0046] According to the present disclosure, when the correction value exceeds a predetermined maximum value, the correction value is initialized, thereby providing a fixing device that can reduce the risk of temperature deviation after sensor replacement, and is therefore useful as a fixing device to be installed in an image forming apparatus. [Explanation of symbols]

[0047] 10 Fixing device 12 Fuser unit 14 Fixing belt 15 Heater lamp 16 Pressure roller 17 Heater driver unit 18 Heater driver 20 Contact thermistor (contact temperature detection unit, X) 22 Thermopile (non-contact temperature detection unit, A) 24 Power control unit 26 Operational amplifiers and protection circuits for contact thermistors 27 Thermopile operational amplifiers and protection circuits 30 Control microcomputer (control unit) 31 CPU 32 servers

Claims

1. a contact-type temperature detection unit that contacts the fixing belt and a non-contact-type temperature detection unit that does not contact the fixing belt; a control unit that compares the detection result of the contact temperature detection unit with the detection result of the non-contact temperature detection unit during an initial operation under predetermined conditions and corrects the detection result of the non-contact temperature detection unit; The fixing device of the image forming apparatus, wherein the control unit initializes the correction value used for correction when the correction value exceeds a predetermined maximum value.

2. the control unit has a storage unit that stores a correction value used for the correction, 2. The fixing device of the image forming apparatus according to claim 1, wherein the control unit compares the correction value acquired in the initial operation with the correction value used for the correction, uses the correction value with the larger absolute value for the correction, and overwrites the correction value used for the correction stored in the memory unit.

3. The control unit is connected to a server, 2. The fixing device of the image forming apparatus according to claim 1, wherein when the correction value used for the correction is initialized, a notification of a malfunction of the non-contact temperature detection unit is sent to an external control center via the server.

4. The initial operation is performed multiple times, 4. The fixing device of the image forming apparatus according to claim 3, wherein the control unit compares the correction value acquired in the previous initial operation with the correction value acquired in the current initial operation, and when there is a predetermined difference, notifies an external control center via the server that the non-contact temperature detection unit is defective, and initializes the correction value used for the correction stored in the memory unit.

5. 3. The fixing device of the image forming apparatus according to claim 2, wherein the correction value used for the correction stored in the storage unit is initialized using the correction value acquired in the initial operation.

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