JP2016126261A - Fixation device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the temperature rise in an image forming apparatus along with the actual state of use of the image forming apparatus and reduce the standby time to prevent the deterioration in productivity of image formation.SOLUTION: A fixation device having a fixation roller 14 for fixing toner on a recording medium at a fixation nip N, and a pressure roller 16 includes an inner temperature thermistor 22 that detects the atmospheric temperature inside an image forming apparatus 40 having the fixation device disposed therein; and temperature control means 25 that controls the temperature of the fixation roller 14 on the basis of the atmospheric temperature. The temperature control means 25 sets the setting temperature of the fixation roller 14 to a second temperature lower than a first temperature, which is a prescribed stipulated temperature, when the atmospheric temperature exceeds a prescribed threshold. The temperature control means 25 sets the setting temperature of the fixation roller 14 to the first temperature for a prescribed certain period of time even when the atmospheric temperature exceeds the prescribed threshold in the case in which the image forming apparatus 40 receives a printing signal in a state of not being operated.SELECTED DRAWING: Figure 1

Description

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

  In general, an electrophotographic image forming apparatus performs fixing by heating and pressurizing a recording medium onto which a toner image is transferred in a fixing device. In such an image forming apparatus, when image forming processing is continuously performed, a developing device of an image forming unit that forms a toner image or a fixing device is driven for a long time to generate heat, and the ambient temperature in the image forming apparatus The component temperature of the image forming apparatus may rise excessively. When the ambient temperature or the component temperature rises excessively, toner agglomerates occur in the toner replenishment portion or inside the developing device, causing abnormal images such as black spot image defects (so-called “black spots”). In order to solve this problem, when the ambient temperature or the component temperature reaches a predetermined limit temperature, which is a predetermined temperature, execution of image formation is temporarily stopped and control is performed to lower the temperature in the image forming apparatus. ing.

  In order to prevent a temperature rise in the image forming apparatus, the set temperature of the fixing device is also lowered.

  Patent Document 1 discloses a fixing unit that heats and fixes a developer image transferred to a recording material, a fixing temperature detecting unit that detects a fixing temperature of the fixing unit, and a detection value of the fixing temperature detecting unit. In addition, the image forming apparatus includes a temperature control unit that controls a fixing temperature of the fixing unit. The image forming apparatus includes an atmospheric temperature detection unit that detects an ambient temperature in the vicinity of the fixing unit. It is described that the fixing temperature is controlled to be high when the ambient temperature detected by the means is low, and the fixing temperature is controlled to be low when the ambient temperature is high.

  However, as in the conventional image forming apparatus, if the image formation is temporarily stopped and the temperature inside the apparatus and the temperature of the developing device of the image forming means are lowered, a waiting time for image formation occurs, and the image forming process There is a problem that productivity decreases.

  In addition, since the fixing temperature is uniformly kept low regardless of the state of use of the image forming apparatus, the one described in Patent Document 1 may not match the actual use of the image forming apparatus. There is a problem that the performance is lowered.

  Accordingly, the present invention includes a fixing device that can suppress a temperature rise in the image forming apparatus in accordance with the actual use of the image forming apparatus, reduce a waiting time, and prevent a decrease in image forming productivity, and the fixing device. An object is to provide an image forming apparatus.

  The fixing device according to the present invention is a fixing device including a fixing member that heats and fixes toner on a recording medium, and detects an atmospheric temperature in an image forming apparatus in which the fixing device is arranged. And a temperature control means for controlling the temperature of the fixing member based on the ambient temperature. The temperature control means includes a first temperature that is a preset temperature for the fixing member, and the first temperature. When the ambient temperature exceeds a predetermined threshold, the setting temperature of the fixing member is changed from the first temperature to the second temperature, and the image forming apparatus is not operating. When a print signal is received in a state, the set temperature of the fixing member is set to the first temperature for a predetermined time even when the ambient temperature exceeds a predetermined threshold value. .

  According to the present invention, it is possible to suppress an increase in temperature in the image forming apparatus in accordance with the actual use of the image forming apparatus, and it is possible to reduce a waiting time and prevent a decrease in image forming productivity.

1 is a block diagram illustrating a fixing device according to an embodiment of the present invention. 6 is a graph showing changes in a heating roller, a pressure roller, and an atmospheric temperature in a fixing device that is not controlled by the atmospheric temperature. 6 is a flowchart showing the operation of the fixing device according to the embodiment of the present invention. 6 is a graph showing changes in a heating roller, a pressure roller, and an ambient temperature in the fixing device according to the embodiment of the present invention. 4 is a graph showing changes in a heating roller, a pressure roller, and an ambient temperature in the fixing device. 6 is a graph showing changes in a heating roller, a pressure roller, and an ambient temperature in the fixing device according to the embodiment of the present invention. 1 is a cross-sectional view illustrating an overall structure of an image forming apparatus according to an embodiment of the present invention. It is sectional drawing which shows the whole structure of the other image forming apparatus which concerns on embodiment of this invention.

  Hereinafter, a fixing device and an image forming apparatus according to an embodiment for carrying out the present invention will be described. First, a fixing device according to an embodiment of the present invention will be described. FIG. 1 is a block diagram showing a fixing device according to an embodiment of the present invention. The fixing device 8 is disposed inside the image forming apparatus 40. The fixing device 8 includes a fixing roller 14 and a pressure roller 16 as fixing members. The fixing roller 14 incorporates a heater 15 composed of a halogen heater or the like. The fixing roller 14 and the pressure roller 16 are in contact with each other to form a fixing nip N.

  The fixing device 8 passes the transfer paper P, which is a recording medium on which a toner image is formed, to the fixing nip N, and fixes the toner image on the transfer paper P by applying heat and pressure. Further, a fixing roller thermistor 24 that measures the temperature of the fixing roller 14 is disposed on the fixing roller 14. In the image forming apparatus 40, an in-machine temperature thermistor 22 serving as an atmospheric temperature detecting unit is disposed, and the atmospheric temperature in the image forming apparatus 40 is measured.

  A temperature control means 25 for controlling the temperature of the heater 15 is connected to the fixing roller 14. The temperature control means 25 controls the heater 15 based on the fixing roller temperature from the fixing roller thermistor 24 and the ambient temperature from the in-machine temperature thermistor 22. The temperature control means 25 controls the heater 15 based on the detection value of the fixing roller thermistor 24, and the temperature of the heater 15 is a first temperature which is a specified temperature (for example, 150 ° C.) and a temperature lower than the specified temperature (for example, 130 ° C.). ) Can be set to the second temperature. Switching of the set temperature to the first temperature or the second temperature by the temperature control means 25 is performed according to the following procedure based on the atmospheric temperature detected by the in-machine temperature thermistor 22. The first temperature and the second temperature can be set to appropriate values depending on the type of toner, the type of image forming apparatus, performance, and other factors.

  The fixing temperature is controlled based on the ambient temperature of the image forming apparatus for the following reason. The temperature rise of the image forming apparatus is influenced not only by the self-heating of the developing device but also by the fixing device which is a large heat source. The temperature of the fixing device is set with a margin in order to ensure the image fixing property on the assumption of a temperature drop immediately after the start of paper feeding. The temperature drop in the fixing device occurs because heat is taken from the fixing roller having a heater inside to the transfer paper and the pressure roller. However, the temperature of the pressure roller rises as it rotates continuously, and the amount of heat taken by the pressure roller from the fixing roller decreases. For this reason, the heat amount of the fixing roller becomes excessive, and the ambient temperature inside the image forming apparatus rises.

  At this time, even if the thermistor is brought into contact with the surface of the pressure roller to detect the temperature rise and the amount of heat taken from the fixing roller is detected, the measured temperature is that of the surface of the pressure roller. The temperature drop of the device cannot be detected stably. In contrast, the atmospheric temperature inside the image forming apparatus is stable with little influence from the fixing roller. Therefore, when the ambient temperature rises and reaches a certain temperature, it can be estimated that the temperature drop of the fixing device is small, and in this state, even if the set temperature of the fixing device is lowered, the image fixing property can be secured. . As a result, the amount of heat generated by the fixing device, which is a large heat source inside the image forming apparatus, can be suppressed at the same time, so that an increase in the ambient temperature inside the image forming apparatus can be suppressed.

  Before describing the control of the embodiment, a case where temperature control based on the ambient temperature is not performed will be described. FIG. 2 is a graph showing changes in the heating roller, the pressure roller, and the ambient temperature in the fixing device that is not controlled by the ambient temperature. When the fixing roller 14 reaches 150 ° C. in the power-on state, the printing operation is started, and the fixing sheet 14 is heated and fixed at the fixing nip N while conveying the transfer paper P onto which the toner image is transferred. For this reason, the temperature rises while the pressure roller 16 also rotates. At this time, the ambient temperature of the image forming means inside the image forming apparatus 40 also increases.

  In this state, the fixing roller 14 is set to a set temperature of 150 ° C., the temperature drop is eliminated by the paper passing immediately after the start-up, and the paper passing operation continues while maintaining the temperature of 150 ° C. by increasing the temperature. When the paper is continued, the pressure roller 16 and the ambient temperature rise. In this state, aggregates are generated in the toner replenishment portion and the developing device, and an abnormal image such as “black spots” is generated. For this reason, conventionally, the printing operation of the image forming apparatus is temporarily stopped and cooled.

  In contrast, the fixing device 8 according to the present embodiment performs the following control. FIG. 3 is a flowchart showing the operation of the fixing device according to the embodiment of the present invention. First, the temperature control unit 25 determines whether or not the image forming apparatus 40 is in operation (step S1). When the image forming apparatus 40 is in operation (Yes in step S1), the temperature control unit 25 determines whether the ambient temperature of the image forming apparatus 40 exceeds a predetermined threshold from the detection result of the in-machine temperature thermistor 22. (Step S2). When the ambient temperature does not exceed the threshold value (No in step S2), the temperature control unit 25 controls the heater 15 of the fixing device 8 to set the temperature of the fixing roller 14 to the first temperature (step S3).

  In this state, an image forming process, that is, a fixing process in the fixing device 8 is executed (step S4). When these printing processes are completed, the ambient temperature is determined again (steps S5 and S2). Thus, in a state where the ambient temperature is lower than the threshold value, the fixing roller 14 of the fixing device 8 is set to the first temperature of 150 ° C., and stable fixing can be performed. Here, the threshold value of the ambient temperature is a value lower than a value that decreases the productivity of image formation due to an increase in ambient temperature. This threshold value prevents the temperature of the image forming productivity from decreasing.

  In the present embodiment, the temperature control means 25 performs the following process when the atmospheric temperature detected by the in-machine temperature thermistor 22 is lower than the threshold (No in step S2). That is, the temperature of the fixing roller 14 of the fixing device 8 is set to the second temperature (130 ° C.) (step S6). In this state, image formation is performed (step S4). Thereby, it is possible to prevent the ambient temperature in the image forming apparatus 40 from rising excessively. Further, it is possible to prevent the fixing roller 14 from being too low in temperature and being unable to be fixed satisfactorily.

  FIG. 4 is a graph showing changes in the heating roller, the pressure roller, and the ambient temperature in the fixing device according to the embodiment of the present invention. The control temperature immediately after rising of the fixing roller 14 is 150 ° C. in a state where the ambient temperature of the image forming means exceeds the threshold value from the detection data of the in-machine temperature thermistor 22 when the image forming apparatus starts up. In this state, the temperature control unit 25 has a small temperature drop of the fixing roller 14 when the sheet is passed immediately after the start-up. In this state, the temperature control means 25 maintains the temperature of the fixing roller 14 at 130 ° C. Even when the fixing roller 14 is at 130 ° C., the lower limit temperature of 120 ° C. or higher for securing the fixing property can be maintained, so that the fixing quality can be ensured.

  At this time, it can be seen that an increase in the ambient temperature of the image forming means is suppressed as compared with the state in which the temperature of the fixing roller 14 shown in FIG. That is, it is possible to delay the time until the printing operation of the image forming apparatus is temporarily stopped due to an increase in the ambient temperature of the image forming apparatus, and to improve the printing productivity. Note that the timing of switching from a higher temperature setting to a lower temperature setting immediately after the start-up is controlled from a preset operating time of the fixing device or from a temperature change detected by the fixing device.

  Further, in the fixing device 8 according to the present embodiment, when the image forming apparatus is stopped (No in Step S1), when the printing instruction is received (Yes in Step S7), the temperature control unit 25 has an ambient temperature of It is determined whether a predetermined threshold is exceeded (step S8). Even when the ambient temperature exceeds the predetermined threshold (No in step S8), the temperature control unit 25 maintains the fixing roller 14 at the first temperature for a certain period of time (step S9), and image forming processing ( Step S4) is performed. When the next printing signal is received in a state where the operation of the fixing device is stopped, the temperature of the fixing roller 14 decreases when paper feeding is started while the surface temperature of the pressure roller 16 having no heat source is decreasing. End up. In the present embodiment, this situation is prevented. If the ambient temperature exceeds a predetermined threshold, normal processing is performed.

  Next, control of the temperature control means 25 in another state will be described. The temperature of the fixing roller 14 at the time of rising is controlled to 150 ° C. by the temperature control means 25. If the temperature control of the fixing roller 14 is changed to the second temperature (130 ° C.) at the timing when the temperature rise starts from this state, the temperature is maintained, and the fixing roller 14 is set to the first temperature when a printing signal is received. It becomes excessive heating and the ambient temperature rises.

  FIG. 5 is a graph showing changes in the heating roller, the pressure roller, and the ambient temperature in the fixing device. In the present embodiment, as shown in FIG. 5, the temperature control is performed at the second temperature 130 at the timing when the temperature drop is eliminated by the passage of paper immediately after the start-up when the temperature of the fixing roller 14 is 150 ° C. and the temperature rise starts. Change to ° C to maintain temperature. In this state, when the ambient temperature of the image forming means exceeds a certain threshold value from the detection data of the in-machine temperature thermistor 22, even when the next print signal is received, the paper passing operation is not performed immediately after the start-up. Start. By this control, the quality of the fixed image is ensured as in the case of continuous paper feeding, and the temperature rise in the apparatus can be suppressed.

  When the next printing signal is received in a state where the operation of passing the printing signal is completed and the operation of the fixing device is stopped, the surface temperature of the pressure roller 16 having no heat source is lowered. The temperature of the fixing roller 14 falls. For this reason, the same control as the higher temperature setting immediately after the rise in FIG. 4 is performed.

  Further, the set temperature of the fixing device is set to the second temperature for suppressing the in-machine temperature while ensuring the image quality, but the in-machine temperature rise is unavoidable as the image forming apparatus operates. For this reason, when the temperature detected by the in-machine temperature thermistor 22 further increases and exceeds a certain threshold value, the temperature rise is suppressed by lowering the set temperature of the fixing device even when the image forming apparatus is in a standby state.

  Next, an image forming apparatus according to an embodiment of the present invention will be described. FIG. 7 is a cross-sectional view showing the overall structure of the image forming apparatus according to the embodiment of the present invention. The image forming apparatus 40 according to the present embodiment includes the fixing device 8 according to the above-described embodiment.

  In the image forming apparatus 40, the image forming unit 10 includes a drum-shaped photosensitive member 1 that is an image carrier that rotates counterclockwise. Around the photoreceptor 1, a charging roller 2, a developing device 3, and a cleaning device 6 are provided. A writing device 11 that emits writing light is provided on the left side of the image forming means 10 in the drawing. Further, a toner bottle 13 is provided on the upper side of the image forming means 10 in the drawing. The toner bottle 13 is driven to rotate to supply toner to the image forming means 10.

  While the transfer roller 5 is pressed against the photoconductor 1 at the transfer position so as to come into contact with the photoconductor 1 by an urging member, it contacts the toner image carrying surface of the photoconductor 1 to form a transfer nip. A transfer bias is applied to the transfer roller 5, and a transfer electric field is formed in a transfer nip positioned between the grounded photoreceptor 1. Examples of the transfer roller 5 include a metal roller, or a roller in which a conductive elastic layer is coated around a cored bar. The elastic layer may be foamable. In FIG. 7, a contact type transfer roller is described as the bias application unit, but a transfer charger including a non-contact type corona discharger may be used.

  Further, the bias applying unit may be a type using a transfer belt as shown in FIG. 8 instead of the transfer roller. In the case of using a transfer belt, the transfer belt 4 is wound around the driving roller 17, the driven roller 18 and the transfer roller 5 so as to be able to run clockwise in the drawing. A belt cleaning device 9 that cleans the surface of the transfer belt 4 is provided opposite the driven roller 18.

  The transfer belt 4 is an endless belt, and has a two-layered seamless structure in which a fluorine coating is applied as a toner filming prevention layer on the outside of a semiconductive film substrate to which various conductive agents are added in order to impart conductivity to a synthetic resin. A belt can be used.

  A paper feed tray 20 on which the transfer paper P is disposed is provided below the image forming apparatus 40. The transfer paper P fed from the paper feed tray 20 by the paper feed roller 21 reaches the registration roller pair 19, where the skew is corrected and then conveyed by the registration roller pair 19 at a predetermined timing.

  The fixing device 8 relates to the above-described embodiment, and includes a fixing roller 14, a heater 15 serving as a heat source disposed inside, and a pressure roller 16. The fixing device 8 is temperature-controlled by the temperature control means 25 based on the detected temperatures from the in-machine temperature thermistor 22 and the fixing roller thermistor 24. The transfer paper P on which the toner image has been transferred is fixed at the fixing nip N formed by the pressure roller 16 to which the fixing roller 14 is also pressed, and an image is formed. The transfer paper P on which the image is formed is discharged to the paper discharge tray 31 by the paper discharge roller pair 30. Reference numeral 32 in the drawing denotes a document reading device that reads a document and outputs an image signal.

  The image forming apparatus according to the present invention includes the fixing device according to the above-described embodiment, and can control the atmospheric temperature in the image forming apparatus so as not to increase, thereby ensuring image quality and durability quality. Further, the waiting time can be reduced to prevent the image forming productivity from being lowered.

8: Fixing device 9: Cleaning device 10: Image forming means 11: Writing device 14: Fixing roller (fixing member)
15: Heater 16: Pressure roller (fixing member)
22: In-machine temperature thermistor 24: Fixing roller thermistor 25: Temperature control means 40: Image forming apparatus

JP 2005-292449 A

Claims (6)

A fixing device including a fixing member that heats and fixes toner on a recording medium,
An atmospheric temperature detecting means for detecting an atmospheric temperature inside the image forming apparatus in which the fixing device is disposed;
Temperature control means for controlling the temperature of the fixing member based on the ambient temperature,
The temperature control unit can set the fixing member to a first temperature which is a predetermined set temperature and a second temperature lower than the first temperature, and when the ambient temperature exceeds a predetermined threshold, This is a case where the set temperature of the fixing member is changed from the first temperature to the second temperature, and the ambient temperature exceeds a predetermined threshold when a print signal is received in a state where the image forming apparatus is not operating. However, the fixing device is characterized in that the set temperature of the fixing member is set to the first temperature for a predetermined time. The fixing device according to claim 1,
The temperature control unit is set when the fixing member is set to the second temperature in a state where the ambient temperature exceeds the threshold, and when the next print signal is received, the set temperature of the fixing member The fixing device is characterized in that the operation is started in a state where the temperature is set to the second temperature. The fixing device according to claim 1 or 2,
The temperature control means performs a sheet passing operation by a next print signal in a state where the image forming apparatus is operating with the set temperature of the fixing member as the second temperature in a state where the ambient temperature exceeds the threshold value. The fixing device is characterized in that the driving of the fixing device is not stopped until the operation is started. The fixing device according to any one of claims 1 to 3,
The fixing device according to claim 1, wherein the threshold value is lower than a value that decreases image forming productivity due to the increase in the ambient temperature. In the fixing device according to any one of claims 1 to 4,
When the ambient temperature reaches a threshold value, the fixing device sets the temperature of the fixing member to the second temperature even when the image forming apparatus is in a standby state. A fixing device according to any one of claims 1 to 5,
Image forming means for forming a toner image on a recording medium fixed by the fixing device;
An image forming apparatus comprising: