Fixing device

Abstract

The present invention provides a fixing device that can detect fixing belt slippage early and prevent damage to the fixing belt. [Solution] The fixing device 10 determines slippage of the fixing belt 12 from two or more combinations of multiple determination criteria, which consist of a drive current that fluctuates according to the load that rotates the fixing member 11, the temperature gradient of the rotation of the fixing member 11, and the time difference from when the pre-fixing sensor 21 detects a sheet of paper (not shown) until the post-fixing sensor 22 detects a sheet of paper.

Description

Technical Field

[0001] The present disclosure relates to a fixing device.

Background Art

[0002] Conventionally, in a fixing device, when the slidability of the inner surface of the fixing belt deteriorates due to its lifespan, belt slip of the fixing belt may occur during startup after being left unattended for a long time or in a low-temperature environment. If there is belt slip, the fixing belt is heated and the belt is damaged, so it is necessary to stop immediately. If stopping is waited until high-temperature trouble is detected, since the belt damage is large, it is necessary to detect belt slip before belt damage. An image forming apparatus provided with a fixing device for detecting such slip of the fixing belt is disclosed in, for example, Japanese Patent Application Laid-Open No. 2016-126052 (Patent Document 1). According to Patent Document 1, it is determined whether or not belt slip of the fixing belt occurs by detecting the temperature difference between the temperature of the drive transmission surface portion and the paper passing surface portion.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A conventional fixing device for detecting slip of a conventional fixing belt was configured as described above. In the conventional fixing device, since it was determined whether or not the fixing belt slipped only based on the temperature difference between the temperature of the drive transmission surface portion and the paper passing surface portion, there was a problem that it was unclear whether or not the fixing belt had surely slipped.

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to provide a fixing device capable of detecting slip of a fixing belt before damage to the fixing belt occurs. [Means for solving the problem]

[0006] The fixing device according to this disclosure comprises a cylindrical fixing belt having a heating section and a nip-forming section inside, a pressing member that contacts the outer circumference of the fixing belt to form a nip so as to sandwich the fixing belt between itself and the nip-forming section, and rotates to drive the fixing belt, a drive device that rotates the pressing member, a pre-fixing sensor that detects paper on the upstream side of the nip in the paper transport direction, and a post-fixing sensor that detects paper on the downstream side of the nip in the paper transport direction, wherein the drive device determines the slip of the fixing belt from two or more combinations of a plurality of judgment criteria consisting of a drive current that fluctuates according to the load that rotates the fixing belt, a temperature gradient when the fixing belt is rotated while being heated, and the time difference from when the pre-fixing sensor detects paper until the post-fixing sensor detects paper.

[0007] The slip detection of the fixing belt may be performed during paper feeding while the job is running, or during non-paper feeding after the job has finished.

[0008] The system includes a pressurizing mechanism for pressurizing the anchoring belt, which can be switched between a pressurized state, a depressurized state, and an intermediate state between the pressurized and depressurized states, and may have a determination criterion for determining slippage of the anchoring belt in each state.

[0009] In other aspects of this disclosure, the image forming apparatus may include the fixing device described above and restrict image forming in response to a determination of whether the fixing belt is slipping, or it may include a notification unit and notify the outside in response to a determination of whether the fixing belt is slipping. [Effects of the Invention]

[0010] According to this disclosure, by determining the slippage of the fixing belt from two or more combinations of multiple judgment criteria, it is possible to provide a fixing device that can detect the slippage of the fixing belt before damage to the fixing belt occurs.

[0011] The aforementioned purposes, other purposes, features, and advantages of this disclosure will become even clearer from the detailed description of the embodiments described below with reference to the drawings. [Brief explanation of the drawing]

[0012] [Figure 1] This figure shows the nip portion of a fixing device according to one embodiment of the present disclosure, and illustrates the pressure release state and the pressurized state. [Figure 2] This graph shows the fluctuations of the torque obtained by converting the current value of a fixing motor (not shown) that rotates the fixing belt. [Figure 3] This graph shows whether or not there are temperature gradient anomalies at regular time intervals. [Figure 4] This diagram shows a graph that detects suspected paper feed delays. [Modes for carrying out the invention]

[0013] [First Embodiment] Hereinafter, one embodiment of the present disclosure will be described in detail with reference to the drawings. Figure 1 is a diagram showing the nip portion N of a fixing device according to one embodiment of the present disclosure. In the present disclosure, the fixing device includes a pressure mechanism (not shown) for pressurizing the fixing belt, and the pressure mechanism is switchable between a pressurized state, a depressurized state, and an intermediate state between the pressurized state and the depressurized state.

[0014] Figure 1 shows the depressurization state with the minimum load applied on the left and the pressurization state with the maximum load applied on the right. In this disclosure, the load is fixed at any load position between the depressurization state with the minimum load applied shown on the left and the pressurization state with the maximum load applied shown on the right, and slippage of the anchoring belt is detected.

[0015] First, referring to the diagram of the pressure release state on the left side of FIG. 1, the fixing device 10 includes a fixing member 11, which is a cylindrical portion arranged on the right side in the figure, and a pressing member 19, which is a cylindrical portion arranged on the left side in the figure. The fixing member 11 includes a fixing belt 12 provided on the outer periphery of the fixing member 11, a contact member 13 provided inside the fixing belt 12, an inverted L-shaped sheet metal 14 and an L-shaped sheet metal 15 provided adjacent to each other on the side opposite to the fixing belt 12 of the contact member 13, and a heater 16 provided adjacent to the L-shaped sheet metal 15.

[0016] The pressing member 19 contacts the flat portion 13a of the contact member 13 to form a nip portion N indicated by an arrow in the figure. A sheet of paper (not shown) is conveyed upward from below through this nip portion N, and a fixing operation is performed. In the present disclosure, the pressing member 19 obtains a driving force from a fixing motor (not shown) and rotates to drive the fixing belt 12 via the nip portion N. A pre-fixing sensor 21 and a post-fixing sensor 22 are provided at positions before and after the nip portion N in the paper conveyance direction to detect a suspected paper conveyance delay, which will be described later.

[0017] Here, since it is in a pressure release state, the dimension of the contact portion of the pressing member 19 with the flat portion 13a of the contact member 13 is short.

[0018] On the other hand, the right side of FIG. 1 shows a state where the fixing device 10 is pressurized with the maximum load. Here, the same reference numerals as those in the left side figure are assigned to the corresponding parts in the left side figure of FIG. 1, and the description thereof is omitted. Referring to the right side figure of FIG. 1, the length of the nip portion N is longer than that in the left side figure of FIG. 1.

[0019] In this embodiment, it is determined whether it is a factor causing slip of the fixing belt 12 from the measurement results of each of the three states shown here: the left side (pressure release state), the right side (state pressurized with the maximum load), and the intermediate load.

[0020] Next, the criteria for determining whether it is a factor causing slip of the specific fixing belt 12 will be described.

[0021] In the present disclosure, there are three criteria A to C for determining whether it is a factor for slip of the specific fixing belt 12, and the determination of the fixing belt 12 is made using any two of them. First, the first one (determination A) will be described.

[0022] The first one is to make a determination using the current value (torque) of a fixing motor (not shown) that rotates the fixing belt 12. FIG. 2 is a graph showing the fluctuations of the current value of a fixing motor (not shown) that rotates the fixing belt 12, with the values converted into torque. In the figure, the X-axis represents time, and the Y-axis represents torque. As shown in FIG. 2, a predetermined upper limit value of the torque is set in advance. During normal operation, since the fixing belt 12 is driven by the rotation of the pressing member 19 that obtains a driving force from a fixing motor (not shown), the value of the torque does not exceed the upper limit value even as time elapses, as shown by a in the figure.

[0023] On the other hand, during an abnormal situation, since the fixing belt 12 is in a state where it is difficult to be driven, a larger load than normal is applied to the pressing member 19 that obtains a driving force from a fixing motor (not shown). The greater the difficulty for the fixing belt 12 to be driven, the greater the load increases, and as shown by b in the figure, the torque exceeds the predetermined torque upper limit value.

[0024] Therefore, when the current value of the fixing motor fluctuates as shown by b in the graph shown in FIG. 2, it is determined that the fixing belt 12 is slipping.

[0025] The second one (determination B) is to determine the presence or absence of abnormal temperature gradients at regular time intervals. FIG. 3 is a graph showing the presence or absence of abnormal temperature gradients at regular time intervals. In the figure, graphs showing two temperature gradients in the vertical direction are shown. In the figure, the X-axis represents time, and the Y-axis represents the temperature of the fixing belt 12. The temperature of the fixing belt 12 is measured by a thermometer (not shown) provided near the fixing belt 12.

[0026] The figure shown above is a diagram showing the normal temperature gradient. As shown in the figure, here the normal heat gradient (solid line) and the heating R of the fixing belt 12 (dotted line) overlap. That is, the temperature of the fixing belt 12 is rising with a rightward upward slope as time elapses.

[0027] The diagram below shows the case where slippage of the fixing belt 12 occurs, in addition to the normal temperature gradient shown above. As shown in the diagram, in this case, the heating R (dotted line) of the fixing belt 12 does not rise steadily to the right over time, but rather shows an irregular temperature increase.

[0028] Therefore, in the graph shown in Figure 3, if the thermal gradient shown below does not rise steadily over time, but instead shows an irregular temperature increase, it is determined that the fixing belt 12 is slipping.

[0029] Next, we will explain the third method (Judgment C). The third method determines slippage of the fuser belt 12 by detecting a suspected paper transport delay. Figure 4 shows a graph for detecting a suspected paper transport delay. Here, from top to bottom, three patterns are shown: normal operation, paper transport delay (JAM), and suspected paper transport delay detection. In each graph, the X axis is time, and the Y axis is detection time. The Y axis shows the design value, the suspected abnormal value, and the value at the time of error detection.

[0030] First, let's explain the normal case shown at the top. In this case, the detection time is basically lower than the suspected abnormality value, and although it occasionally exceeds the suspected abnormality value, it never exceeds the error detection value.

[0031] Next, we will explain paper lag (JAM). Referring to the case of paper lag (JAM), the detection time is basically lower than the suspected abnormality value, but occasionally it may exceed the suspected abnormality value and may exceed the error detection value. When this error detection value is exceeded, it is a paper lag (JAM).

[0032] Next, we will explain the case when a suspected paper feed delay is detected. Referring to the case when a suspected paper feed delay is detected, the detection time is basically lower than the suspected abnormality value, although it may occasionally exceed the suspected abnormality value. Within the range that does not exceed the error detection value, there are cases where the value continuously exceeds a predetermined level value for a certain period of time, as shown by the dotted ellipse in the figure. When such a value is detected, it is determined that a suspected paper feed delay has been detected.

[0033] Therefore, in the graph shown in Figure 4, if it is detected that the specified level value is continuously exceeded for a certain period of time, within the range that does not exceed the error detection value shown at the bottom, it is determined that the fixing belt 12 is slipping.

[0034] [Second Embodiment] Furthermore, the slip detection of these fixing belts 12 may be performed during paper feeding while a job is in progress, or during non-paper feeding after a job is completed. Alternatively, a pressure mechanism (not shown) for pressurizing the fixing member 11 may be provided as described above, and it may be possible to switch between a pressurized state, a depressurized state, and an intermediate state between the pressurized state and the depressurized state, with a determination criterion for determining slip in each state. The above information is shown in the table below. Table 1 shows the timing of the judgment, and the judgment is made when there is no paper feeding, such as after the job is finished or in test mode, or when there is paper feeding during paper feeding. The judgment is made using the three judgments A to C described above.

[0035] [Table 1] Next, we will explain the relationship between the evaluation criteria and the pressurized state. Table 2 shows the relationship between the evaluation criteria and the pressurized state, and also indicates whether or not paper is being passed through for each pressurized state.

[0036] [Table 2] Referring to Table 2, for A and B, the determination is made regardless of the pressure state, both when there is no paper flow and when there is paper flow. However, for C, the determination is made only when there is paper flow in each pressure state.

[0037] Next, we will explain how the presence or absence of slippage is determined from the results of A to C when there is no paper feed and when there is paper feed. Table 3 shows how the presence or absence of slippage is determined from the results of A to C.

[0038] Referring to Table 3, in A, "OK" indicates that the fuser motor current value is normal, and "NG" indicates that the fuser motor current value is abnormal. Also, in B, "OK" indicates that the temperature gradient at regular time intervals is normal, and "NG" indicates that the fuser belt 12 is slipping. Also, in C, "OK" indicates that there is no suspicion of paper transport delay, and "NG" indicates that a suspected paper transport delay has been detected.

[0039] [Table 3] The slip detection shows the result of belt slip detection based on conditions A, B, and C. Referring to the upper left part of Table 3, if both A and B are "OK" when no paper is being fed, the slip detection is NO (no slip). If A is "OK" and B is "NG" when no paper is being fed, the slip detection is YES (slip present).

[0040] Referring to Table 3 as a whole, if both A and B are "OK", the slip is "NO" regardless of C. If either A or B is "NG", the slip is judged "YES" regardless of C.

[0041] Even if A is NG when no paper is being fed, if B is OK, the slip will be judged as "NO".

[0042] The image forming apparatus disclosed herein may further include a notification unit (not shown). When a slip is detected, the notification unit (not shown) can prompt the user or administrator to perform an early inspection or replace the fixing belt. The notification unit here may include general notification means or combinations thereof, such as displaying a message on a display unit (not shown), lighting or flashing a light-emitting unit (not shown), or transmitting information about the slip to an external device (not shown) via a communication means (not shown).

[0043] The image forming apparatus disclosed herein may determine whether or not a notification is given by the notification means based on the cumulative number of times a slip has been detected. Alternatively, it may be determined based on whether or not a slip has been detected within a unit period. Alternatively, it may be determined based on whether or not a slip has been detected after a predetermined cumulative number of sheets of paper that have passed through the fuser. Alternatively, it may be determined based on whether or not a slip has been detected after a predetermined period of time since the fuser was incorporated into the main body of the image forming apparatus.

[0044] The image forming apparatus disclosed herein may be configured to regulate heating to the fixing device based on whether or not slippage is detected.

[0045] This disclosure can be implemented in various other forms without departing from its spirit or main features. Therefore, the embodiments described above are illustrative and should not be constrained. Any modifications or changes within the equivalent scope of the claims of this disclosure are within the scope of this disclosure. [Industrial applicability]

[0046] According to this disclosure, the fixing belt can be detected before damage to the fixing belt occurs, making it useful as a fixing device. [Explanation of Symbols]

[0047] 10 Fixing device 11 Fixing member 12 Fixing belt 13 Contact Member 13a Flat area 14 Inverted L-shaped sheet metal 15 L-shaped sheet metal 16 Heater 19 Pressurizing member 21 Pre-fixation sensor 22. Sensor after fixing

Claims

1. A cylindrical fixing belt having a heating section and a nip-forming section inside, A pressing member that contacts the outer circumference of the fixing belt to form a nip, so as to sandwich the fixing belt between itself and the nip-forming portion, and rotates to drive the fixing belt, A drive device for rotating the pressurizing member, The system includes a pre-fixing sensor that detects paper on the upstream side of the paper transport direction of the nip, and a post-fixing sensor that detects paper on the downstream side of the paper transport direction of the nip, A fixing device that determines slippage of the fixing belt based on two or more combinations of a plurality of judgment criteria, which consist of a drive current that fluctuates according to the load that rotates the fixing belt, a temperature gradient when the fixing belt is rotated while being heated, and the time difference from when the pre-fixing sensor detects the paper until the post-fixing sensor detects the paper.

2. The fixing device according to claim 1, wherein slip detection of the fixing belt is performed during paper feeding while a job is being executed.

3. The fixing device according to claim 1, wherein slip detection of the fixing belt is performed during the non-paper-feeding period after job execution.

4. The system includes a pressurizing mechanism for pressurizing the aforementioned fixing belt, The fixing device according to claim 1, wherein the pressurizing mechanism is switchable between a pressurized state, a depressurized state, and an intermediate state between the pressurized state and the depressurized state, and has a determination criterion for determining slippage of the fixing belt in each state.

5. An image forming apparatus comprising the fixing device described in claim 1, wherein image formation is restricted according to the determination of whether or not the fixing belt is slipping.

6. The image forming apparatus according to claim 5, further comprising a notification unit that notifies an external party in response to a determination of whether or not the fixing belt has slipped.

Images