JP4521381B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus including a fixing unit having a rotating body that fixes a developer on a medium by heat and a non-contact type temperature detecting unit that detects the temperature of the surface of the rotating body.

  In an image forming apparatus such as an electrophotographic printer, a copying machine, a facsimile machine, or a multifunction machine, a developer corresponding to a printed image is transferred to a medium, and the developer is fixed to the medium by heat and pressure. Conventionally, the temperature for fixing the developer onto the medium has been detected by contacting temperature detecting means such as a thermistor on the surface of the rotating body for fixing the developer. And based on this detected temperature, the temperature of the rotary body surface was controlled to appropriate temperature.

  However, since the temperature detecting means that contacts the surface of the rotating body is fixed, the rotating body and the temperature detecting means are rubbed by the rotating operation of the rotating body that fixes the developer. Due to this friction, there is a problem that the surface of the rotating body is scratched, and the quality of the printed image is deteriorated due to the scratch.

  Therefore, a method for detecting the temperature of the surface of the rotating body using a non-contact temperature detecting means that does not contact the surface of the rotating body has been developed. (For example, see Patent Document 1)

JP 2001-242741 A

  However, when the non-contact type temperature detecting means is used, since the temperature of the surface of the rotating body is not directly detected, there is a problem that a large detection error occurs in a situation where the ambient temperature is greatly different. .

  Accordingly, in view of the above circumstances, the present invention corrects the temperature detected in accordance with the ambient temperature condition, and more accurately detects the temperature of the surface of the rotating body using a non-contact type temperature detecting means. The purpose is to provide.

An image forming apparatus according to the present invention includes an image fixing device capable of detecting, in a non-contact manner, the temperature of a surface of a rotating body that rotates in a medium conveyance direction so as to fix a developer deposited on the medium by heat from a heating source. In the forming apparatus, the thermosensitive member that is disposed to face the rotating body and that is heated by the rotating body, the thermosensitive member temperature detecting means that detects the temperature of the thermosensitive member, the holding member that holds the thermosensitive member, From the relationship between the holding member temperature detecting means for detecting the temperature of the holding member, and the temperature of the heat sensitive member detected by the heat sensitive member temperature detecting means and the temperature of the holding member detected by the holding member temperature detecting means. A correction value holding unit that holds the obtained correction value, and the correction value held in the holding unit based on the temperature detected by the holding member temperature detecting means is corrected. The temperature detected by the heat sensitive member temperature detection means, the temperature detected by the holding member temperature detection means, by the corrected the correction value to have a temperature calculation means for calculating the temperature of the surface of the rotating member Features.

According to the image forming apparatus of the present invention, the correction value obtained in advance from the relationship between the temperature of the heat sensitive member detected by the heat sensitive member temperature detecting means and the temperature of the holding member detected by the holding member temperature detecting means is the ambient temperature. And the temperature of the surface of the rotating body can be calculated. Therefore, it is possible to detect a more accurate temperature corrected for the influence of the ambient temperature without damaging the surface of the rotating body. And the temperature control of the rotating body surface can also be performed more accurately.

  The image forming apparatus of the present invention detects the temperature of the heat sensitive member and the temperature of the holding member, and corrects the temperature of the heat sensitive member based on the temperature of the holding member. As a result, the influence of the ambient temperature can be corrected. Therefore, more accurate temperature can be detected without damaging the surface of the rotating body. And the temperature control of the rotating body surface can also be performed more accurately.

  The present invention will be described below with reference to the drawings.

[Embodiment 1]
As shown in FIG. 1, the image forming apparatus includes a charger 2, an exposure device 3, a developing device 4, a transfer device 5, a fixing device 6, a medium remaining amount sensor 7, a photosensitive drum 8, a writing sensor 9, a discharge sensor 10, and a medium. A cassette 11 is provided. A medium 12 that is a medium such as paper is stored in the medium cassette 11.

  Further, the image forming apparatus includes a control unit 1 connected to each of the above-described members as shown in FIG. The controller 1 includes a charger power source 2a, a developer power source 4a, a transfer device power source 5a, an energization controller 16, an exposure unit 3, a medium remaining amount sensor 7, a writing sensor 9, a discharge sensor 10, and a temperature detection circuit. 19 is connected.

  As shown in FIG. 1, the medium cassette 11 is a box-shaped member having an opening on the upper surface so that a medium 12 on which an image is formed is deposited and at least the medium 12 can be taken out. The medium cassette 11 is provided with a medium remaining amount sensor 7 for reading the remaining amount of the medium 12. The medium cassette 11 is provided with a paper feed roller so as to come into contact with the medium 12 in the medium cassette 11. The control unit 1 can supply the medium 12 from the medium cassette 11 to the transport path by operating the paper feed roller.

  The medium remaining amount sensor 7 is a sensor that detects whether or not there is a medium 12 in the medium cassette 11. The medium remaining amount sensor 7 is connected to the control unit 1 and transmits the remaining amount of the medium 12 in the medium cassette 11 to the control unit 1. By detecting the presence of the medium 12 in the medium cassette 11, the medium 12 is supplied to the conveyance path by the paper feed roller. The control unit 1 that has received the remaining amount of the medium 12 can display a signal indicating that the medium 12 of the medium cassette 11 has run out, for example, on a display unit (not shown) of the apparatus according to the remaining amount of the medium.

  The writing sensor 9 is provided on the downstream side of the medium cassette 11 in the conveyance path, and detects whether or not the medium 12 has been conveyed to the conveyance path. The writing sensor 9 is connected to the control unit 1 and transmits the detected signal to the control unit 1. Based on the signal transmitted from the writing sensor 9, the control unit 1 controls each member described below so as to form an image on the medium 12.

  The photosensitive drum 8 is an electrostatic latent image carrier, and is configured to be able to store charges on the surface thereof by the charger 2. For example, the photosensitive drum 8 is fixed to both ends of a frame (not shown) including the photosensitive drum 8 so as to be rotatable about a fixed shaft. The charge stored on the surface is configured such that the charge on the surface can be removed by exposure with the exposure device 3. The photosensitive drum 8 forms a toner image by adsorbing toner as a developer to the electrostatic latent image formed on the surface thereof.

  The charger 2 can store charges on the surface of the photosensitive drum 8 by applying a predetermined positive voltage or negative voltage to the photosensitive drum 8. The charger 2 is, for example, a semiconductive charging roller rotatably fixed to a frame (not shown) so as to contact the surface of the photosensitive drum 8 with a constant pressure. In order to apply a predetermined voltage to the photosensitive drum 8, a charger power source 2 a is connected to the charger 2, and the charger power source 2 a is controlled by the control unit 1. The control unit 1 controls the charger power source 2 a so as to apply a predetermined voltage to the photosensitive drum 8 based on a signal from the writing sensor 9. For example, the charger 2 generates a voltage of −1000V to −1100V.

  The exposure device 3 is provided above the photosensitive drum 8 on the downstream side of the charging device 2 in the rotation direction of the photosensitive drum 8. The exposure device 3 is, for example, an LED (Light Emitting Diode) head or a laser. The exposure device 3 removes the electric charge stored on the surface of the photosensitive drum 8 by the charger 2 by exposure, and the electrostatic latent image is transferred to the photosensitive drum 8. Form on the surface. As a result, an electrostatic latent image having a voltage of, for example, −50 V to 0 V is formed on the photosensitive drum 8. The exposure device 3 is connected to the control unit 1 and performs exposure via the control unit 1 based on print data transmitted to the image forming apparatus.

  The developing device 4 supplies the toner charged with the same charge as that charged on the surface of the photosensitive drum 8 by the charger 2 to the surface of the photosensitive drum 8 by an electric suction force. As a result, the toner adheres to the portion where the charge has been removed by exposure of the surface of the photosensitive drum 8, and a toner image is formed on the surface of the photosensitive drum 8. The developing device 4 is rotatably fixed to a frame (not shown) so as to be in contact with the surface of the photosensitive drum 8 at a constant pressure, for example, on the downstream side of the photosensitive drum 8 relative to the exposure device 3. The developing device 4 is connected to a developing device power supply 4a, and the developing device power supply 4a charges the toner with a predetermined charge. The developing device power supply 4 a is controlled by the control unit 1 based on a signal from the writing sensor 9.

  A predetermined positive voltage or negative voltage is applied to the transfer device 5 by the connected transfer device power supply 5a so that the charge opposite to the charge of the toner charged by the developing device 4 is stored on the surface thereof. As a result, the transfer unit 5 transfers the toner image formed on the photosensitive drum 8 to the medium 12 conveyed through the conveyance path by an electric suction force. The transfer unit 5 is provided on the opposite side of the photosensitive drum 8 with the conveyance path interposed therebetween, and is rotatably fixed to the shaft, for example. The transfer unit power source 5 a is controlled by the control unit 1 so as to apply a predetermined voltage to the transfer unit 5 based on a signal from the writing sensor 9. The voltage applied to the transfer device 5 is, for example, + 2000V to + 3000V. The medium 12 having the toner image is conveyed to the fixing device 6 through the conveyance path.

  As shown in FIG. 3, the fixing device 6 includes a fixing heater 6a, a fixing roller 6b, a pressure roller 6c, and a non-contact temperature detecting unit 6f. The fixing heater 6a is housed in the fixing roller 6b. The fixing heater 6 a is connected to the energization control unit 16 and heats according to the voltage applied from the energization control unit 16. This heat is transmitted from the fixing heater 6a to the fixing roller 6b. In the energization control unit 16, the voltage applied so that the fixing roller 6b reaches a predetermined temperature is controlled by the control unit 1. Instead of the fixing heater 6a, a ceramic heater may be housed in the fixing roller 6b.

  The fixing roller 6b is a rotating body whose axis is fixed so that the medium 12 can rotate in the direction in which the medium 12 flows from the upstream side to the downstream side (in the direction of arrow A in FIG. 3) so as to come into contact with the conveyed medium 12. It is. The fixing roller 6b can be heated uniformly by the heat generated by the fixing heater 6a.

  The energization control unit 16 switches the energization state of the fixing heater 6 a according to a command from the control unit 1. That is, the energization control unit 16 turns on the energization to the fixing heater 6a so that the surface temperature of the fixing roller 6b detected by the temperature detection unit 6f is within a predetermined temperature range, for example, a range of 170 ° C. ± 10 ° C. / OFF. For example, when the surface temperature of the fixing roller 6b detected by the temperature detection unit 6f is higher than a predetermined range, the energization control unit 16 receives a command to turn off the energization to the fixing heater 6a from the control unit 1, and then the fixing heater Turn off the power to 6a. On the other hand, when the surface temperature of the fixing roller 6b detected by the temperature detection unit 6f is lower than a predetermined range, the energization control unit 16 receives a command to turn on the energization of the fixing heater 6a from the control unit 1, and receives the fixing heater 6a. Turn on the power to 6a.

  The pressure roller 6c is provided on the opposite side of the fixing roller 6b via the conveyance path, and the medium 12 flows from the upstream side of the conveyance path to the downstream side so that a predetermined pressure is applied to the medium 12 being conveyed. The center is axially fixed so as to be rotatable in the direction (the direction of arrow A ′ in FIG. 3). Thereby, a predetermined pressure can be applied to the medium 12 conveyed through the conveyance path. The toner image can be fixed to the medium 12 so that the toner on the conveyed medium 12 is fused by the heat from the fixing roller 6b and the pressure from the fixing roller 6b and the pressure roller 6c.

  As shown in FIG. 4, the temperature detection unit 6f includes a non-contact thermistor 6fa and a compensation thermistor 6fb. This non-contact thermistor 6fa has a plate-like holding member 6fa1. On the holding member 6fa1, a heat-sensitive film 6fa2 smaller than the holding member 6fa1 is held by the holding member 6fa1. The heat-sensitive film 6fa2 is a film-like heat-sensitive member that is heated by absorbing infrared rays emitted from the fixing roller 6b. Therefore, the temperature of the heat sensitive film 6fa2 changes according to the change in the temperature of the surface of the fixing roller 6b. And the temperature of holding member 6fa1 holding heat-sensitive film 6fa2 changes according to the change of the temperature of heat-sensitive film 6fa2. The holding member 6fa1 holds a non-contact thermistor element 6fa3 which is a thermal member temperature detecting means for detecting the temperature of the thermal film 6fa2 via the thermal film 6fa2.

  The non-contact thermistor element 6fa3 is provided with a wiring 6fa4 for forming a temperature detection circuit 19 to be described later in order to detect the temperature of the thermal film 6fa2, and this temperature detection circuit 19 is connected to the control unit 1. Yes. The dimensions of the non-contact thermistor 6fa are not particularly limited. For example, the length is 20.3 mm, the width is 11.0 mm, and the thickness is 12.5 μm.

  The compensation thermistor 6fb has a plate-like member compensation thermistor frame 6fb1. The compensation thermistor element 6fb2 is held on the compensation thermistor frame 6fb1. As shown in FIG. 5, the compensation thermistor 6fb is provided in the non-contact thermistor 6fa so that the compensation thermistor element 6fb2 can detect the temperature of the holding member 6fa1 of the non-contact thermistor 6fa. The compensation thermistor element 6fb2 serves as a holding member temperature detecting means for detecting the temperature of the holding member 6fa1.

  The compensation thermistor element 6fb2 is also provided with a wiring 6fb3 for forming a temperature detection circuit 19 to be described later in order to detect the temperature of the holding member 6fa1, similarly to the non-contact thermistor element 6fa3. The circuit 19 is connected to the control unit 1.

  Here, the non-contact thermistor element 6fa3 and the compensating thermistor element 6fb2 used are elements whose resistance values change according to temperature as shown in FIG. There are types that change so that the resistance value decreases as the temperature increases, and conversely, those that change so that the resistance value decreases as the temperature decreases. In the present invention, the thermistor element that changes so that the resistance value decreases as the temperature increases is used. However, a thermistor element that changes so that the resistance value decreases as the temperature decreases may be used.

  In order for the controller 1 to detect the temperatures of the heat sensitive film 6fa2 and the holding member 6fa1, the non-contact thermistor element 6fa3 and the compensation thermistor element 6fb2 form a temperature detection circuit 19 as shown in FIG.

  The temperature detection circuit 19 includes a non-contact thermistor element 6fa3, a compensation thermistor element 6fb2, and detection resistors Rs1 and Rs2. One end of the power supply unit Vdd, the non-contact thermistor element 6fa3 and the compensation thermistor element 6fb2 is connected, the other end of the non-contact thermistor element 6fa3 is connected to one end of the detection resistor Rs1, and the other end of the compensation thermistor element 6fb2 is connected. Connected to one end of the detection resistor Rs2. The other ends of the detection resistors Rs1 and Rs2 are connected to the ground part (GND), respectively. This temperature detection circuit 19 has a detection voltage point Vout1 between the non-contact thermistor element 6fa3 and the detection resistor Rs1, and has a detection voltage point Vout2 between the compensation thermistor element 6fb2 and the detection resistor Rs2. ing.

  As described above, the resistance value of the non-contact thermistor element 6fa3 and the compensation thermistor element 6fb2 provided in the temperature detection circuit 19 varies depending on the temperature as shown in FIG. Therefore, according to the temperature of the non-contact thermistor element 6fa3 and the compensation thermistor element 6fb2, the voltage changes at the voltage detection points Vout1 and Vout2, as shown in FIG. That is, output voltages from the non-contact thermistor element 6fa3 and the compensation thermistor element 6fb2 can be detected at the voltage detection points Vout1 and Vout2. Therefore, by supplying a predetermined voltage from the power supply unit Vdd to the control unit 1 connected to the temperature detection circuit 19 and detecting the voltages at the voltage detection points Vout1 and Vout2, respectively, for example, as shown in FIG. The respective temperatures of the non-contact thermistor element 6fa3 and the compensation thermistor element 6fb2 can be detected using the graph.

  Thereby, the non-contact thermistor element 6fa3 can detect the temperature of the thermal film 6fa2 based on the voltage detected at the voltage detection point Vout1 of the control unit 1. Similarly, the compensation thermistor element 6fb2 can detect the temperature of the holding member 6fa1 based on the voltage detected at the voltage detection point Vout2 of the control unit 1.

  The temperature detector 6f including the non-contact thermistor 6fa and the compensation thermistor 6fb is provided apart from the fixing roller 6b. The distance between the temperature detector 6f and the fixing roller 6b is not particularly limited, but is, for example, 0.90 mm. The heat sensitive film 6fa2 changes according to a change in the temperature of the surface of the fixing roller 6b, and the holding member 6fa1 changes according to a change in the temperature of the heat sensitive film 6fa2. As described above, the heat of the fixing roller 6b is transmitted to the heat sensitive film 6fa2, but the heat transmitted to the heat sensitive film 6fa2 is also transmitted to the holding member 6fa1. Therefore, the temperature of the surface of the fixing roller 6b can be corrected based on the temperatures detected by the heat sensitive film 6fa2 and the holding member 6fa1.

  The discharge sensor 10 is provided on the downstream side of the conveyance path with respect to the fixing device 6 and detects whether or not the medium 12 conveyed from the fixing device 6 is discharged. The discharge sensor 10 is connected to the control unit 1 and transmits to the control unit 1 as a signal whether or not the medium 12 is discharged.

  The control unit 1 includes a microprocessor, a ROM (Read Only Memory), an EEPROM (Electrically Erasable Programmable Read Only Memory), a RAM (Random Access Memory) input / output port, a timer, and the like. Printed in response to a video signal consisting of control signals from a host controller or the like that is connected to an external information processing apparatus such as a personal computer and controls the operation of the image forming apparatus of the present invention, and data in which pit map data is centrally arranged. Processes such as operations are executed.

  The control unit 1 is connected to each member described above and forms an image on the medium 12 based on print data transmitted to the image forming apparatus. Then, the temperature of the heat sensitive film 6fa2 and the holding member 6fa1 is detected from the voltage detected by the temperature detection circuit 19, and the temperature calculation means for calculating the surface temperature of the fixing roller 6b, which is a rotating body, from this temperature.

  Hereinafter, a method for calculating the temperature of the surface of the fixing roller 6b from the temperatures of the thermal film 6fa2 and the holding member 6fa1 by the control unit 1 will be described.

  First, using the same fixing device as the fixing device 6 of the image forming apparatus of the present invention, the surface temperature (Tc) of the fixing roller 6b and the temperature (Tnc) of the thermal film 6fa2 detected by the non-contact thermistor element 6fa3. 9 and 10 are detected when a change with time in the temperature (Tamb) of the holding member 6fa1 detected by the compensation thermistor element 6fb2 is detected. FIG. 10 is an enlarged view of part A of FIG. FIG. 11 shows the difference between Tc and Tnc with respect to time. Thereby, even if Tc shows a substantially constant value, it is understood that Tamb is lowered and Tnc is lowered. This is because the amount of heat (heat radiation amount) flowing out from the held heat-sensitive film 6fa2 to the holding member 6fa1 increases due to a decrease in the temperature of the holding member 6fa1.

  Here, the correlation between the difference between Tc and Tamb and the difference between Tnc and Tamb is shown in FIG. That is, the difference between the surface temperature (Tc) of the fixing roller 6b and the temperature (Tamb) of the holding member 6fa1 detected by the compensation thermistor element 6fb2, and the temperature (Tnc) of the thermal film 6fa2 detected by the non-contact thermistor element 6fa3. It can also be seen that there is a strong correlation with the difference in temperature (Tamb) of the holding member 6fa1 detected by the compensation thermistor element 6fb2. When this relationship is expressed by an approximate expression, the following expression 1 is obtained.

  When this expression 1 is expanded, the following expression 2 is obtained.

  As a result, the actual surface temperature (Tc) of the fixing roller 6b includes the temperature (Tnc) of the thermal film 6fa2 detected by the non-contact thermistor element 6fa3 and the temperature (Tamb) of the holding member 6fa1 detected by the compensation thermistor element 6fb2. ). From Equation 2, the actual surface temperature (Tc) of the fixing roller 6b can be derived from the relationship between the temperature (Tnc) of the heat sensitive film 6fa2 and the temperature (Tamb) of the holding member 6fa1. The controller 1 can obtain this relationship in advance, and can calculate the surface temperature of the fixing roller 6b based on this relationship. Thereby, the temperature of the surface of the fixing roller 6b can be calculated with high accuracy. That is, by correcting the temperature (Tnc) of the thermal film 6fa2 detected by the non-contact thermistor element 6fa3 with the temperature (Tamb) of the holding member 6fa1 detected by the compensation thermistor element 6fb2, the correction according to the ambient temperature can be performed. It becomes possible. Therefore, a more accurate temperature can be detected without damaging the surface of the fixing roller 6b. Further, the temperature control of the surface of the fixing roller 6b can be performed more accurately.

  A, B, and C in the above formulas 1 and 2 are constants and are correction values for calculating the surface temperature of the fixing roller 6b. For example, in the approximate straight line as shown in FIG. 12, A in Expression 1 and Expression 2 is 1.3, C is 1.5, and B in Expression 2 is −0.3. The correction values A, B, and C calculated in this way are calculated in advance by performing an experiment for obtaining the above approximate expression, and are held in the control unit 1. In this experiment, a detection unit that directly detects the surface temperature Tc of the fixing roller 6b in substantially the same state as in a normal use is provided, and can be calculated from the actually detected temperature and the temperature detected by the thermistor element. . The controller 1 uses the correction values A, B, and C from the detected temperature of the thermal film 6fa2 detected by the non-contact thermistor element 6fa3 and the temperature of the holding member 6fa1 detected by the compensation thermistor element 6fb2. The surface temperature of the fixing roller 6b can be calculated more accurately. The correction values A, B, and C are determined by experiment for each model of the image forming apparatus. Therefore, different models have different values. For example, if the model is different, the correction value A is 1.45, the correction value B is -0.45, and the correction value C is 0.00. As described above, the coefficient varies depending on the positional relationship between the fan in the apparatus and the fixing device 6.

  As described above, the control unit 1 that holds the correction value controls the temperature of the surface of the fixing roller 6b to an appropriate temperature as described below. Hereinafter, a method for controlling the surface temperature of the fixing roller 6b will be described with reference to FIG.

  When receiving the print data, the control unit 1 performs the following processing. This process is performed every time the temperature is detected by the thermistor element. First, the control unit 1 detects the output voltages of the non-contact thermistor element 6fa3 and the compensation thermistor element 6fb2 at the voltage detection points Vout1 and Vout2 of the temperature detection circuit 19 and reads the values. In step S2, the control unit 1 converts the output voltage into a temperature, and detects the temperatures of the non-contact thermistor element 6fa3 and the compensation thermistor element 6fb2. Since the output voltage varies depending on the temperatures of the contactless thermistor element 6fa3 and the compensation thermistor element 6fb2, the detected voltage varies from the detected output voltage with the contactless thermistor element 6fa3 and the compensation thermistor element 6fb2. Each temperature can be detected.

  The temperature detected by the non-contact thermistor element 6fa3 is the temperature (Tnc) of the thermal film 6fa2. The temperature detected by the compensation thermistor element 6fb2 is the temperature (Tamb) of the holding member 6fa1. In step S3, the control unit 1 calculates the calculation formula represented by the above-described formula 2 from the temperatures detected by the temperatures of the non-contact thermistor element 6fa3 and the compensation thermistor element 6fb2 and the correction values A, B, and C held therein. Is used to calculate the surface temperature of the fixing roller 6b. At this time, the calculated temperature of the surface of the fixing roller 6b is Tc '.

  Using the calculated surface temperature (Tc ′) of the fixing roller 6b, the control unit 1 controls the temperature of the surface of the fixing roller 6b in step S4. At this time, the control unit 1 sends an ON / OFF command for energizing the fixing heater 6a to the energization control unit 16 connected to the fixing heater 6a in the fixing roller 6b. Upon receiving this command, the energization controller 16 turns on / off the fixing heater 6a, controls the temperature of the surface of the fixing roller 6b, and ends this processing. By repeating this, the temperature can be controlled to be suitable for fixing the toner on the medium 12.

  In this way, by controlling the surface temperature of the fixing roller 6b by the control unit 1, the actual surface temperature (Tc) of the fixing roller 6b and the calculated surface temperature (Tc) of the fixing roller 6b (see FIG. 14). The difference from Tc ′) is almost eliminated. As a result, even if the temperature of the surface of the fixing roller 6b is detected by the non-contact type temperature detector 6f, the temperature is corrected according to the temperature detected by the compensation thermistor element 6fb2, that is, the ambient temperature. The temperature of the surface of the fixing roller 6b can be calculated. That is, the correction value used for calculating the surface temperature of the fixing roller 6b can be calculated from the temperatures of the heat sensitive film 6fa2 and the holding member 6fa1, and a more accurate temperature can be detected.

  As a method of calculating the temperature of the surface of the fixing roller 6b, a method of holding the correction values A, B, and C and calculating using the above-described equation 1 has been described. However, the present invention is not limited to this. Absent. For example, instead of Equation 1, a method using a conversion table may be used. In this case, the thermistor element characteristics and temperature detection circuit constants are determined, and the detected voltage value and the temperature at that time are stored in the control unit 1 as one-to-one data for each predetermined voltage.

  Further, the equation for calculating the surface temperature of the fixing roller 6b is calculated by using the difference between the actual surface temperature (Tc) of the fixing roller 6b and the temperature (Tamb) of the holding member 6fa1 detected by the compensation thermistor element 6fb2, and non-contact. Although this is obtained from the correlation between the temperature (Tnc) of the thermal film 6fa2 detected by the thermistor element 6fa3 and the temperature (Tamb) of the holding member 6fa1 detected by the compensation thermistor element 6fb2, the first embodiment is It is not limited to. For example, the difference between the surface temperature (Tc) of the fixing roller 6b and the temperature (Tnc) of the thermal film 6fa2 detected by the non-contact thermistor element 6fa3 and the temperature (Tnc) of the thermal film 6fa2 detected by the non-contact thermistor element 6fa3. Further, an equation for calculating the surface temperature of the fixing roller 6b may be obtained from the correlation with the difference in temperature (Tamb) of the holding member 6fa1 detected by the compensation thermistor element 6fb2. In this case, the above formula 1 becomes the following formula 3.

  When this expression 3 is expanded, the following expression 4 is obtained.

  Correction values A ′, B ′, and C ′ that are constants in Expressions 3 and 4 are held in the control unit 1 and detected by the non-contact thermistor element 6fa3 using Expression 4 instead of Expression 2 described above. From the temperature (Tnc) of the heat sensitive film 6fa2 and the temperature (Tamb) of the holding member 6fa1 detected by the compensation thermistor element 6fb2, the surface temperature of the fixing roller 6b can be calculated. Even using this equation, the surface temperature of the fixing roller 6b can be accurately calculated.

  The image forming apparatus of the present invention configured as described above operates as follows when print data is transmitted.

  First, when the control unit 1 receives the print data, the fixing heater 6a and the like are passed through the energization control unit 16 so that the fixing roller 6b has a temperature suitable for fixing the toner onto the medium 12 as shown in FIG. Control. After the fixing roller 6 b reaches a temperature suitable for fixing the toner onto the medium 12, the control unit 1 detects the presence or absence of the medium 12 set in the medium cassette 11 by the medium remaining amount sensor 7. As a result, when it is detected that the medium 12 to be used for printing exists, the medium 12 is sent to the transport path by the paper feed roller as described above.

  When the medium 12 sent to the transport path reaches the writing sensor 9, the signal is sent to the control unit 1. Receiving this signal, the control unit 1 applies a voltage to the charger 2 through the charger power source 2 a to charge the surface of the photosensitive drum 8. Then, based on the supplied print data, the control unit 1 causes the exposure device 3 to expose a portion where toner is attached to the photosensitive drum 8, and erases the electric charge charged on the photosensitive drum 8. Thereafter, the control unit 1 charges the toner so as to have a predetermined charge in the developing device 4 through the developing device power supply 4a, supplies the toner to the photosensitive drum 8, and exposes the toner in the exposure device 3 by an electric suction force. A toner image is formed on the photosensitive drum 8 by adhering to the spot.

  Then, the controller 1 applies a charge to the surface of the transfer device 5 through the transfer device power supply 5a. Then, the toner image formed on the surface of the photosensitive drum 8 is transferred to the medium 12 sent to the conveyance path by the electric suction force of the transfer unit 5. Then, the medium 12 onto which the toner image has been transferred is sent to the fixing device 6 on the downstream side of the conveyance path of the photosensitive drum 8. The control unit 1 causes the toner on the medium 12 to be fused on the medium 12 sent to the fixing device 6 by the temperature of the fixing roller 6b controlled as described above and the pressure roller 6c. Toner is fixed on the toner. The medium 12 on which the toner is fixed is sent to the downstream side of the conveying path of the fixing device 6, passes through the discharge sensor 10, and is discharged outside the apparatus such as a discharge stacker. As described above, the image forming apparatus described in the first embodiment can form an image on the medium 12 based on the transmitted print data.

  Therefore, the image forming apparatus described in the first embodiment includes the non-contact type temperature detection unit 6f that detects the temperature of the surface of the fixing roller 6b, so that the surface of the fixing roller 6b is not damaged. Therefore, it is possible to prevent the quality of the formed image from being deteriorated. Then, as described above, the control unit 1 uses the correction value calculated from the temperature of the thermal film 6fa2 and the temperature of the holding member 6fa1, and corrects the temperature of the thermal film 6fa2 based on the temperature of the holding member 6fa1. By calculating the temperature of the surface of the fixing roller 6b, a more accurate temperature can be detected. Therefore, it is possible to detect a more accurate temperature corrected for the influence of the ambient temperature without damaging the surface of the fixing roller 6b. Further, the temperature control of the surface of the fixing roller 6b can be performed more accurately, and the toner can be reliably fixed to the medium 12.

  In the first embodiment, the temperature control of the surface of the fixing roller 6b when printing data is received, that is, during printing is described. However, the present invention is not limited to this, and the state where the medium 12 is not conveyed to the photosensitive drum 8, that is, Similar temperature control is possible during warm-up. Since the fixing device 6 is deprived of heat when the medium 12 passes, the correction values A, B, and C different from the correction values A, B, and C at the time of printing described above are obtained in advance, and the control unit 1 The correct temperature on the surface of the fixing roller 6b may be calculated using the correction values A, B, and C. For example, in detecting the temperature of the landing roller 6b during warm-up, the control unit 1 sets the correction value described above so that the correction value A is 1.40, the correction value B is −0.40, and the correction value C is 0.00. Temperature detection may be performed using values different from A, B, and C. As a result, the temperature of the fixing roller 6b can be controlled more accurately.

[Embodiment 2]
As shown in FIG. 15, the image forming apparatus described in the second embodiment includes a time measuring unit 20 that is a time measuring unit and a non-contact thermistor detected temperature storage unit 25 that is a thermal member temperature storage unit in the control unit 1. It has further. Since other than that is the same as Embodiment 1, it attaches | subjects the same number and abbreviate | omits description.

  Since the fixing roller 6b and the temperature detecting unit 6f are provided apart from each other, there is a delay in heat transfer from the fixing roller 6b to the temperature detecting unit 6f. Due to the delay in heat transfer, the temperature (Tnc) detected by the non-contact thermistor element 6fb3 of the temperature detection unit 6f may change abruptly as shown in part A of FIG. In this case, as shown in FIG. 17, the difference (Tc−Tc ′) between the actual temperature (Tc) of the fixing roller 6b and the temperature (Tc ′) calculated by the control unit 1 serving as the temperature calculation means is greatly different. End up. That is, a detection error from the actual temperature of the surface of the fixing roller 6b occurs.

  In the image forming apparatus described in the second embodiment, the unit time is measured by the time measuring unit 20 of the control unit 1, and the temperature of the thermal film 6fa2 detected every unit time is determined as the non-contact thermistor detected temperature storage unit 25. Is remembered. The above-described detection error can be corrected by calculating a temperature change amount in a predetermined time from the temperature of the heat sensitive film 6fa2 per unit time and using this temperature change amount. That is, the temperature of the surface of the fixing roller 6b can be calculated more accurately.

  The time measuring unit 20 is provided in the control unit 1 and includes, for example, a clock. The time measuring unit 20 measures the unit time when the control unit 1 performs temperature detection by the non-contact thermistor 6fa every unit time. That is, the control unit 1 detects the temperature of the thermal film 6fa2 with the non-contact thermistor 6fa every unit time measured by the time measurement unit 20. The unit time is not particularly limited, but may be 1 second or 1/100 second, for example.

  The non-contact thermistor detection temperature storage unit 25 is a fixed storage area secured in a RAM (not shown) of the control unit 1. And the non-contact thermistor detection temperature memory | storage part 25 memorize | stores the temperature detected by the non-contact thermistor element 6fa3 of the non-contact thermistor 6fa in the storage area for every unit time. At this time, the non-contact thermistor detection temperature storage unit 25 divides the storage area into a predetermined number of elements. And the non-contact thermistor detection temperature memory | storage part 25 memorize | stores so that the temperature for every unit time detected may be stored in each element divided | segmented sequentially.

  For example, when divided into 100 elements, the non-contact thermistor detection temperature storage unit 25 stores the temperature first detected by the non-contact thermistor element 6fa3 in Tnc [0]. Then, after the unit time has elapsed, the temperature stored in Tnc [0] is moved to Tnc [1], and the temperature detected next by the non-contact thermistor element 6fa3 is stored in Tnc [0]. The non-contact thermistor detected temperature storage unit 25 repeats this and stores the temperature detected every unit time. When the temperature is stored up to Tnc [99] and the next temperature is newly stored in Tnc [0], the non-contact thermistor detection temperature storage unit 25 erases the temperature stored in Tnc [99]. . Then, the temperature is sequentially shifted so that the temperature stored in Tnc [98] is transferred to Tnc [99], and the newly detected temperature is stored in Tnc [0].

  When detecting the surface temperature of the fixing roller 6b, the control unit 1 serving as a temperature calculating unit calculates a correction value using the temperature detected for each unit time. Hereinafter, the calculation method of the correction value will be described, where t is the unit time and n is the number of elements that delimit the non-contact thermistor detection temperature storage unit 25.

  First, the amount of change in the temperature (Tnc) of the thermal film 6fa2 detected by the non-contact thermistor element 6fa3 at the predetermined time T will be described. The temperature change amount (dTnc / dT) of the thermal film 6fa2 at the predetermined time T can be calculated from the temperature stored for each unit time as each element in the non-contact thermistor detection temperature storage unit 25. When calculating the temperature change amount from the predetermined time T to the present, the temperature detected before the predetermined time T is stored in Tnc [n−1] of the non-contact thermistor detection temperature storage unit 25. The currently detected temperature is stored in Tnc [0] of the non-contact thermistor detection temperature storage unit 25. Assuming that the temperatures are Tnc [n−1] and Tnc [0], the temperature change amount (dTnc / dT) of the thermal film 6fa2 at the predetermined time T is calculated by the following equation (5). The predetermined time T is a time used as a reference when calculating the temperature change amount of the thermal film 6fa2, and is the same as the unit time t measured by the time measurement unit or a natural number times the unit time t. There is no particular limitation. The predetermined time T is determined by the product of the unit time t and the number n of elements that delimit the non-contact thermistor detection temperature storage unit 25.

  Then, using the same fixing device as the fixing device 6 of the image forming apparatus of the present invention, the actual surface temperature (Tc) of the fixing roller 6b with respect to the temperature change amount (dTnc / dT) of the thermal film 6fa2 at a predetermined time T. ) And the surface temperature (Tc ′) of the fixing roller 6b calculated by the expression 2 described in the first embodiment, the difference is as shown in FIG. That is, the difference (Tc′−Tc) between the amount of change in the temperature of the heat-sensitive film 6fa2 during the predetermined time T (dTnc / dT) and the actual surface temperature of the fixing roller 6b and the surface temperature of the fixing roller 6b calculated by Expression 2. ) Has a strong correlation. When this relation is expressed by an approximate expression, the following expression 6 is obtained. Since this expression 2 is the same as that of the first embodiment, the description thereof is omitted.

  That is, the detection error of the surface temperature of the fixing roller 6b due to the heat transfer delay due to the fixing roller 6b and the temperature detecting unit 6f being provided apart from each other is a change in the temperature of the heat sensitive film 6fa2 during the predetermined time T. It is represented by the product of the quantity (dTnc / dT) and the constant D. Tc ′ is obtained by the equation 2 shown in the first embodiment. Accordingly, the surface temperature of the fixing roller 6b is calculated by the following formula 7 obtained by subtracting D × (dTnc / dT) from the right side of the formula 2. That is, D × (dTnc / dT) is a correction value calculated based on the temperature change amount at the predetermined time T.

  A, B, and C in Equation 1 and Equation 2 are calculated in the same manner as in the first embodiment. And D of Formula 6 and Formula 7 can be calculated | required from the inclination of the approximate formula calculated | required by a correlation diagram as shown in FIG. As the correction values A, B, C, and D, for example, the correction value A is 1.45, the correction value B is −0.45, the correction value C is 0.00, and the correction value D is 1.20. is there. The correction values A, B, C, and D calculated in this way are calculated in advance and held in the control unit 1. The controller 1 detects the temperature of the thermal film 6fa2 detected by the detected non-contact thermistor element 6fa3, the temperature of the holding member 6fa1 detected by the compensation thermistor element 6fb2, and the temperature of the thermal film 6fa2 at a predetermined time T. The surface temperature of the fixing roller 6b can be accurately calculated from the amount of change using the correction values A, B, C, and D. The correction values A, B, C, and D are determined by experiment for each model of the image forming apparatus. Therefore, different models have different values.

  As described above, the control unit 1 that holds the correction value controls the temperature of the surface of the fixing roller 6b to an appropriate temperature as described below. Hereinafter, a method for controlling the surface temperature of the fixing roller 6b will be described with reference to FIG.

  When receiving the print data, the control unit 1 performs the following processing. This process is performed every time the temperature is detected by the thermistor element. First, the control unit 1 detects output voltages of the non-contact thermistor element 6fa3 and the compensation thermistor element 6fb2 at the voltage detection points Vout1 and Vout2 of the temperature detection circuit 19 and reads the values. In step S12, the control unit 1 converts the output voltage into a temperature, and detects the temperatures of the non-contact thermistor element 6fa3 and the compensation thermistor element 6fb2. Since the output voltage varies depending on the temperatures of the contactless thermistor element 6fa3 and the compensation thermistor element 6fb2, the detected voltage varies from the detected output voltage with the contactless thermistor element 6fa3 and the compensation thermistor element 6fb2. Each temperature can be detected.

  The temperature detected by the non-contact thermistor element 6fa3 is the temperature (Tnc) of the thermal film 6fa2. The temperature detected by the compensation thermistor element 6fb2 is the temperature (Tamb) of the holding member 6fa1. In step S <b> 13, the control unit 1 stores the temperature detected by the non-contact thermistor element 6 fa <b> 3 in the element Tnc [0] divided into a predetermined number in the non-contact thermistor detection temperature storage unit 25. The temperature of the thermal film 6fa2 detected before the predetermined time T is stored in the nth element Tnc [n−1] of the non-contact thermistor detection temperature storage unit 25. And the control part 1 judges whether the temperature detected before predetermined time T is stored in Tnc [n-1] in step S14. When the temperature is not stored in Tnc [n−1], the control unit 1 proceeds to step S18.

  On the other hand, when the temperature is stored in Tnc [n−1] in step S14, the control unit 1 determines in step S15 the temperature Tnc [0] currently detected by the non-contact thermistor element 6fa3 and the predetermined time T. From the temperature Tnc [n−1] detected by the non-contact thermistor element 6fa3, the amount of change in the temperature detected by the non-contact thermistor element 6fa3 at the predetermined time T is calculated using the above equation 5. That is, the control unit 1 calculates the amount of change in the temperature of the thermal film 6fa2 at the predetermined time T.

  Then, the controller 1 detects the temperature detected by the temperatures of the non-contact thermistor element 6fa3 and the compensation thermistor element 6fb2, the change amount of the temperature detected by the non-contact thermistor element 6fa3 at a predetermined time T, and the correction value A held. In step S16, the temperature (Tc ′) of the surface of the fixing roller 6b is calculated from B, C, and D using the calculation formula shown in Formula 7 above.

  Using the calculated Tc ', the control unit 1 controls the temperature of the surface of the fixing roller 6b in step S17. At this time, the control unit 1 sends an ON / OFF command for energizing the fixing heater 6a to the energization control unit 16 connected to the fixing heater 6a in the fixing roller 6b. Upon receiving this command, the energization control unit 16 turns on / off the fixing heater 6a and controls the temperature of the surface of the fixing roller 6b.

  In step S18, the control unit 1 shifts the temperatures stored in the separated elements of the non-contact thermistor detection temperature storage unit 25 so that Tnc [i] becomes Tnc [i + 1]. At this time, i represents 0 to n-1. After the end of step S18, the control unit 1 ends this process. The control unit 1 repeats this series of processing every time the temperature is detected by the thermistor element. Thereby, the temperature can be controlled to be suitable for fixing the toner on the medium 12.

  In this way, by controlling the temperature of the surface of the fixing roller 6b as described above by the control unit 1, the actual temperature (Tc) of the surface of the fixing roller 6b is calculated as shown in FIG. There is almost no difference from the surface temperature (Tc ′). Thereby, even if the temperature detector 6f is provided apart from the fixing roller 6b, it is possible to accurately correct the temperature error of the surface of the fixing roller 6b caused by the heat transfer delay. That is, a more accurate temperature can be detected based on the temperature of the heat sensitive film 6fa2 and the holding member 6fa1 and the amount of change in the temperature of the heat sensitive film 6fa2 at the predetermined time T.

  The image forming apparatus described in the second embodiment accurately detects the surface temperature of the fixing roller 6b as described above. Then, as described in Embodiment 1, an image can be formed on the medium 12.

  Therefore, the image forming apparatus described in the second embodiment includes the non-contact type temperature detection unit 6f that detects the temperature of the surface of the fixing roller 6b, so that the surface of the fixing roller 6b is not damaged. Therefore, it is possible to prevent the quality of the formed image from being deteriorated. By correcting the temperature detected by the non-contact thermistor element 6fa3 based on the temperature change amount of the heat-sensitive film 6fa2 during a predetermined time, heat transfer to the non-contact thermistor element 6fa3 that occurs when the temperature of the surface of the fixing roller 6b changes. Can cope with the delay. That is, it is possible to correct an error caused by a delay in heat transfer to the non-contact thermistor element 6fa3. Therefore, correction according to the change in the ambient temperature of the fixing roller 6b can be performed, and the surface temperature of the fixing roller 6b can be detected more accurately. Further, the temperature control of the surface of the fixing roller 6b can be performed more accurately, and the toner can be reliably fixed to the medium 12.

  In the second embodiment, the temperature control of the surface of the fixing roller 6b when printing data is received, that is, during printing, has been described. However, the present invention is not limited to this, and the state where the medium 12 is not conveyed to the photosensitive drum 8, that is, Similar temperature control is possible during warm-up. Since the fixing device 6 is deprived of heat when the medium 12 passes through, the correction values A, B, C, and D different from the correction values A, B, C, and D at the time of printing described above are obtained in advance and controlled. The unit 1 may calculate the accurate temperature of the surface of the fixing roller 6b using the correction values A, B, C, and D. For example, in detecting the temperature of the landing roller 6b during warm-up, the control unit 1 determines that the correction value A is 1.40, the correction value B is −0.40, the correction value C is 0.00, and the correction value D is 1.20. Thus, temperature detection may be performed using a value different from that at the time of printing. As a result, the temperature of the fixing roller 6b can be controlled more accurately.

[Embodiment 3]
The configuration of the image forming apparatus described in the third embodiment is the same as that of the image forming apparatus described in the second embodiment. In the image forming apparatus described in the third embodiment, the correction value A of Expression 7 described in the second embodiment changes according to the ambient temperature, that is, the temperature of the holding member detected by the compensation thermistor element 6fb2. Focus on that. The image forming apparatus described in the third embodiment can correct an error caused by this change. The members constituting the image forming apparatus described in the third embodiment are the same as those in the first and second embodiments, and thus the same reference numerals are given and description thereof is omitted.

  The actual surface temperature (Tc) of the fixing roller 6b, the temperature of the thermal film detected by the non-contact thermistor element 6fa3 (Tnc), and the temperature of the holding member detected by the compensation thermistor element 6fb2, which is the ambient temperature ( Tamb) is as shown in FIG. Then, the difference (Tc−Tc ′) between the actual surface temperature of the fixing roller 6b and the surface temperature (Tc ′) of the fixing roller 6b calculated by Expression 7 of Embodiment 2, the temperature of the thermal film, and the actual fixing. The difference in the surface temperature of the roller 6b (Tnc−Tc) is as shown in FIG. Thus, when the difference between the temperature of the heat sensitive film and the actual surface temperature of the fixing roller 6b (Tnc−Tc) is large, the difference between the actual surface temperature of the fixing roller 6b and the calculated surface temperature of the fixing roller 6b (Tc− It can be seen that Tc ′) increases. When the difference between the temperature of the heat sensitive film and the actual surface temperature of the fixing roller 6b (Tnc−Tc) is large, as described in the first embodiment, the temperature detected by the compensation thermistor element 6fb2 is low. Indicates that the temperature is low. Therefore, when the ambient temperature is low, an error occurs in the calculated surface temperature of the fixing roller 6b. This is because when the ambient temperature is greatly different, the spatial thermal resistance between the fixing roller 6b and the temperature detection unit 6f changes, and the optimum correction value varies accordingly.

  The image forming apparatus described in the third embodiment can calculate the surface temperature of the fixing roller 6b more accurately by changing the correction value according to the ambient temperature that can be detected by the compensation thermistor element 6fb2.

  First, FIG. 23 shows the relationship between the temperature detected by the compensation thermistor element 6fb2 that is the ambient temperature and the correction value A used in Equation 7 described above. That is, it can be seen that there is a strong correlation between the ambient temperature and the correction value A. When this relationship is expressed by an approximate expression, the following expression 8 is obtained.

  That is, it can be seen that the correction value A of the above-described equation 7 is proportional to the ambient temperature Tamb and shows a value corresponding to the ambient temperature. Here, by obtaining the constants a and b in advance, the correction value A can be corrected according to the ambient temperature. The constants a and b can be obtained from an approximate expression obtained from a correlation diagram as shown in FIG. The constants a and b are obtained in advance in the same manner as the correction values A, B, C, and D, and are held in the control unit 1. The controller 1 calculates a value A [Tamb] obtained by correcting the correction value A using the constants a and b from the detected temperature of the compensation thermistor element 6fb2. Substituting this correction value A [Tamb] into A in Equation 7 described above yields Equation 9 below. The constants a and b are determined by experiment for each model of the image forming apparatus. Therefore, different models have different values. For example, the constant a is 0.33 and the constant b is 1.10.

  The control unit 1 calculates the correction value A from the detected temperature of the non-contact thermistor element 6fa3, the temperature detected by the compensation thermistor element 6fb2, and the amount of change in the temperature of the thermal film 6fa2 at a predetermined time T. Using [Tamb], B, C, and D, the surface temperature of the fixing roller 6b can be accurately calculated.

  As described above, the control unit 1 that holds the correction value controls the temperature of the surface of the fixing roller 6b to an appropriate temperature as described below. Hereinafter, a method for controlling the surface temperature of the fixing roller 6b will be described with reference to FIG.

  When receiving the print data, the control unit 1 performs the following processing. This process is performed every time the temperature is detected by the thermistor element. First, the control unit 1 detects the output voltages of the non-contact thermistor element 6fa3 and the compensation thermistor element 6fb2 at the voltage detection points Vout1 and Vout2 of the temperature detection circuit 19 and reads the values. In step S22, the control unit 1 converts the output voltage into a temperature, and detects the temperatures of the non-contact thermistor element 6fa3 and the compensation thermistor element 6fb2. Since the output voltage varies depending on the temperatures of the contactless thermistor element 6fa3 and the compensation thermistor element 6fb2, the detected voltage varies from the detected output voltage with the contactless thermistor element 6fa3 and the compensation thermistor element 6fb2. Each temperature can be detected.

  The temperature detected by the non-contact thermistor element 6fa3 is the temperature (Tnc) of the thermal film 6fa2. The temperature detected by the compensation thermistor element 6fb2 is the temperature (Tamb) of the holding member 6fa1. In step S23, the controller 1 stores the temperature detected by the non-contact thermistor element 6fa3 in the element Tnc [0] divided into a predetermined number in the non-contact thermistor detection temperature storage unit 25. The temperature of the thermal film 6fa2 detected before the predetermined time T is stored in the nth element Tnc [n−1] of the non-contact thermistor detection temperature storage unit 25. Then, in step S24, the control unit 1 determines whether or not the temperature detected before the predetermined time T is stored in Tnc [n−1]. When the temperature is not stored in Tnc [n−1], the control unit 1 proceeds to step S29.

  On the other hand, if the temperature is stored in Tnc [n] in step S24, the control unit 1 determines that the temperature Tnc [0] currently detected by the non-contact thermistor element 6fa3 in step S25 is not equal to the predetermined time T. From the temperature Tnc [n−1] detected by the contact thermistor element 6fa3, the change amount of the temperature detected by the non-contact thermistor element 6fa3 at the predetermined time T is calculated using the above equation 5. That is, the control unit 1 calculates the amount of change in the temperature of the thermal film 6fa2 at the predetermined time T.

  After calculating the amount of change in the temperature of the thermal film 6fa2 at the predetermined time T, the control unit 1 uses the temperature detected by the compensation thermistor element 6fb2 and the constants a and b calculated in advance in step S26. The obtained correction value A is corrected to a correction value A [Tamb] based on Equation 8.

  Then, the controller 1 detects the temperature detected by the temperatures of the non-contact thermistor element 6fa3 and the compensation thermistor element 6fb2, the amount of change in the temperature detected by the non-contact thermistor element 6fa3 at a predetermined time T, and the correction value B held. , C, D and the correction value A [Tamb] calculated in step S26, the temperature (Tc ′) of the surface of the fixing roller 6b is calculated in step S27 by using the calculation formula shown in the above-described formula 9. To do.

  Using the calculated Tc ', the control unit 1 controls the temperature of the surface of the fixing roller 6b in step S28. At this time, the control unit 1 sends an ON / OFF command for energizing the fixing heater 6a to the energization control unit 16 connected to the fixing heater 6a in the fixing roller 6b. Upon receiving this command, the energization control unit 16 turns on / off the fixing heater 6a and controls the temperature of the surface of the fixing roller 6b.

  Then, in step S29, the control unit 1 shifts the temperatures stored in the separated elements of the non-contact thermistor detection temperature storage unit 25 so that Tnc [i] becomes Tnc [i + 1]. At this time, i represents 0 to n-1. After the end of step S18, the control unit 1 ends this process. The control unit 1 repeats this series of processing every time the temperature is detected by the thermistor element. Thereby, the temperature can be controlled to be suitable for fixing the toner on the medium 12.

  As described above, in the image forming apparatus described in the third embodiment, the control unit 1 changes the value of the correction value A according to the ambient temperature, that is, the temperature detected by the compensation thermistor element 6fb2. . Thus, the calculated temperature of the surface of the fixing roller 6b is changed as in the case where the ambient temperature is greatly changed such as when the ambient temperature is low and the spatial thermal resistance between the fixing roller 6b and the temperature detecting unit 6f is changed. 25, the difference between the actual surface temperature (Tc) of the fixing roller 6b and the calculated surface temperature (Tc ′) of the fixing roller 6b is almost eliminated as shown in FIG. . In this way, by changing the correction value according to the ambient temperature, it is possible to perform correction according to the ambient temperature situation. Therefore, the temperature of the surface of the fixing roller 6b can be detected more accurately.

  As described above, the image forming apparatus described in the third embodiment accurately detects the surface temperature of the fixing roller 6b. Then, as described in Embodiment 1, an image can be formed on the medium 12.

  Therefore, in the image forming apparatus described in the third embodiment, the surface of the fixing roller 6b is damaged by providing the non-contact type temperature detecting unit 6f that detects the temperature of the surface of the fixing roller 6b apart from the fixing roller 6b. In other words, it is possible to prevent the quality of the formed image from being deteriorated. Then, by changing the correction value according to the ambient temperature, it is possible to perform correction according to the situation of the ambient temperature. Therefore, the temperature of the surface of the fixing roller 6b can be detected more accurately. Further, the temperature control of the surface of the fixing roller 6b can be performed more accurately, and the toner can be reliably fixed to the medium 12.

  In the image forming apparatus described in the third embodiment, the correction value A has been described. However, the present invention is not limited to this. Similarly, the correction values B, C, and D can be corrected from the ambient temperature, that is, the relationship between the temperature detected by the compensation thermistor element 6fb2 and the correction values B, C, and D. As a result, correction according to the situation of the ambient temperature is possible, and the temperature of the surface of the fixing roller 6b can be calculated more accurately. In addition, by correcting this correction value D with the ambient temperature, the temperature change amount of the heat sensitive film 6fa2 for a predetermined time can be corrected with the ambient temperature. Further, like the correction of the correction value A described in the third embodiment, the relationship between the ambient temperature and the temperature change amount of the thermal film 6fa2 for a predetermined time is obtained, and similarly, the ambient temperature and the thermal film 6fa2 for the predetermined time are determined. The amount of temperature change may be corrected.

  In the third embodiment, the temperature control of the surface of the fixing roller 6b when printing data is received, that is, during printing is described. However, the present invention is not limited to this, and the state where the medium 12 is not conveyed to the photosensitive drum 8, that is, Similar temperature control is possible during warm-up. Since the fixing device 6 is deprived of heat when the medium 12 passes, constants a and b different from the constants a and b for correcting the correction value A at the time of printing described above are obtained in advance. However, the correction values A [Tamb] may be obtained for the constants a and b, and the correct temperature of the surface of the fixing roller 6b may be calculated using the correction values A [Tamb] and the correction values B, C, and D. For example, in detecting the temperature of the fixing roller 6b during warm-up, the control unit 1 uses a value different from that used during printing, such as a constant a of 0.00 and a constant b of 1.40. May be corrected to a correction value A [Tamb]. As a result, the correction value A [Tamb] becomes 1.40, the correction value B is -0.40, the correction value C is 0.00, and the correction value D is 1.20. It may be used for temperature detection. As a result, the temperature of the fixing roller 6b can be controlled more accurately.

[Embodiment 4]
The configuration of the image forming apparatus described in the fourth embodiment is the same as that of the image forming apparatus described in the first embodiment. In the image forming apparatus described in the fourth embodiment, attention is paid to the fact that the ambient temperature of the heat sensitive film 6fa2 is lowered by the air flow in the fixing device 6 generated by the rotation of the fixing roller 6b. The image forming apparatus described in the fourth embodiment can correct an error caused by the decrease in the ambient temperature. The members constituting the image forming apparatus described in the fourth embodiment are the same as those in the first to third embodiments, and thus the same reference numerals are given and description thereof is omitted.

  The actual surface temperature (Tc) of the fixing roller 6b decreases as the fixing roller 6b rotates as shown in FIG. The difference between the surface temperature (Tc) of the fixing roller 6b and the temperature (Tnc) of the thermal film detected by the non-contact thermistor element 6fa3 is as shown in FIG. 27 when the fixing roller 6b is rotated and when it is stopped. And different. That is, if the correction value used at the time of rotation is also used at the time of stopping, an error occurs in the actual surface temperature of the fixing roller 6b. This is because the fixing roller 6b and the temperature detection unit 6f are provided apart from each other, so that the air in the fixing device 6 flows due to the rotation of the fixing roller 6b, so that the ambient temperature is lowered and the heat dissipation amount is large. It is to become.

  In the image forming apparatus described in the fourth embodiment, as an operation state of the fixing roller 6b, a correction value used at the time of rotation and a correction value used at the time of stop are obtained in advance, and according to the operation state of the fixing roller 6b. Thus, the temperature of the surface of the fixing roller 6b can be calculated more accurately using either one of them.

  First, the difference between the surface temperature (Tc) of the actual fixing roller 6b and the temperature (Tamb) of the holding member detected by the compensation thermistor element 6fb2 which is the ambient temperature, and the non-contact thermistor element 6fa3. The relationship between the temperature (Tnc) of the heat-sensitive film and the temperature (Tamb) of the holding member is as shown in FIG. Thus, as in the first embodiment, the difference between the surface temperature (Tc) of the fixing roller 6b and the temperature (Tamb) of the holding member 6fa1 detected by the compensation thermistor element 6fb2, and the non-contact thermistor element 6fa3 are detected. It can be seen that there is a strong correlation between the difference between the temperature (Tnc) of the heat-sensitive film 6fa2 and the temperature (Tamb) of the holding member 6fa1 detected by the compensation thermistor element 6fb2. When this relationship is expressed by an approximate expression, the above expression 1 is obtained, and the above expression 2 can be derived as in the first embodiment. As a result, the actual surface temperature (Tc) of the fixing roller 6b can be derived from the relationship between the temperature (Tnc) of the thermal film 6fa2 and the temperature (Tamb) of the holding member 6fa1.

  A, B, and C in the above formulas 1 and 2 are calculated in the same manner as in the first embodiment, separately when the fixing roller 6b is rotated and stopped. For example, the correction values A, B, and C during rotation of the fixing roller 6b are 1.45, the correction value B is −0.45, and the correction value C is 0.00. Further, as the correction values A, B, and C when the fixing roller 6b is stopped, for example, the correction value A is 1.34, the correction value B is -0.34, and the correction value C is 0.00. The correction values A, B, and C calculated in this way are calculated in advance and held in the control unit 1. The control unit 1 calculates the correction values A, B, and C from the detected temperature of the thermal film 6fa2 detected by the non-contact thermistor element 6fa3 and the temperature of the holding member 6fa1 detected by the compensation thermistor element 6fb2. By using this, the surface temperature of the fixing roller 6b can be accurately calculated. The correction values A, B, and C are determined by experiment for each model of the image forming apparatus. Therefore, different models have different values.

  As described above, the control unit 1 that holds the correction value controls the temperature of the surface of the fixing roller 6b to an appropriate temperature as described below. Hereinafter, a method for controlling the surface temperature of the fixing roller 6b will be described with reference to FIG.

  When receiving the print data, the control unit 1 performs the following processing. This process is performed every time the temperature is detected by the thermistor element. First, the control unit 1 detects output voltages of the non-contact thermistor element 6fa3 and the compensation thermistor element 6fb2 at the voltage detection points Vout1 and Vout2 of the temperature detection circuit 19 and reads the values. In step S102, the control unit 1 converts the output voltage into a temperature, and detects the temperatures of the non-contact thermistor element 6fa3 and the compensation thermistor element 6fb2. Since the detected voltage varies depending on the temperatures of the contactless thermistor element 6fa3 and the compensation thermistor element 6fb2, the output voltage varies from the detected output voltage to the contactless thermistor element 6fa3 and the compensation thermistor element 6fb2. Each temperature can be detected.

  In step S103, the control unit 1 determines whether or not the fixing roller 6b is rotating. When the fixing roller 6b is rotating, the control unit 1 selects correction values A, B, and C at the time of rotation of the fixing roller 6b obtained in advance in step S104-1, and proceeds to step S105. On the other hand, if the fixing roller 6b is stopped in step S103, the control unit 1 selects the correction values A, B, and C obtained when the fixing roller 6b is stopped in advance in step S104-2, and step S105. Migrate to

  The temperature detected by the non-contact thermistor element 6fa3 is the temperature (Tnc) of the thermal film 6fa2. The temperature detected by the compensation thermistor element 6fb2 is the temperature (Tamb) of the holding member 6fa1. In step S105, the controller 1 determines from the temperatures detected by the temperatures of the non-contact thermistor element 6fa3 and the compensation thermistor element 6fb2 and the correction values A, B, and C selected in step S104-1 or step S104-2. The temperature of the surface of the fixing roller 6b is calculated using the calculation formula shown in Formula 2 above. At this time, the calculated temperature of the surface of the fixing roller 6b is Tc '.

  Using the calculated temperature (Tc ′) of the surface of the fixing roller 6b, the control unit 1 controls the temperature of the surface of the fixing roller 6b in step S106. At this time, the control unit 1 sends an ON / OFF command for energizing the fixing heater 6a to the energization control unit 16 connected to the fixing heater 6a in the fixing roller 6b. Upon receiving this command, the energization controller 16 turns on / off the fixing heater 6a, controls the temperature of the surface of the fixing roller 6b, and ends this processing. By repeating this, the temperature can be controlled to be suitable for fixing the toner on the medium 12.

  For example, the controller 1 calculates the surface temperature (Tc ′) of the fixing roller 6b using the correction values A, B, and C when the fixing roller 6b is stopped when the fixing roller 6b rotates, and the control unit 1 calculates the surface temperature of the fixing roller 6b. When the temperature is controlled, as shown in FIG. 30, the fixing roller 6b is rotated to cause a difference from the actual surface temperature of the rotating roller 6b. Further, when the fixing roller 6b is stopped, the surface temperature (Tc ′) of the fixing roller 6b is calculated using the correction values A, B, and C when the fixing roller 6b is rotated, and the control unit 1 calculates the surface temperature of the fixing roller 6b. When the temperature is controlled, a difference from the actual surface temperature of the rotating roller 6b occurs when the fixing roller 6b is stopped as shown in FIG.

  As shown in FIG. 29, when the control unit 1 controls the surface temperature of the fixing roller 6b, the correction values A, B, and C when the fixing roller 6b is rotated are used when the fixing roller 6b is rotated. By using the correction values A, B, and C when the fixing roller 6b is stopped at the time of stopping, as shown in FIG. 32, the actual surface temperature (Tc) of the fixing roller 6b and the calculated surface temperature of the fixing roller 6b are calculated. (Tc ′) is substantially the same value. Accordingly, a correction value corresponding to the operation state of the fixing roller 6b is obtained in advance, and the control unit 1 selects to use the correction value obtained in advance according to the operation state, thereby detecting a more accurate temperature. be able to.

  The image forming apparatus according to the fourth embodiment calculates the surface temperature of the fixing roller 6b by dividing the correction values A, B, and C used for calculating the surface temperature of the fixing roller 6b during rotation and when stopped. This can also be applied to the second embodiment. That is, correction values A, B, C, and D used for calculating the surface temperature of the fixing roller 6b are also obtained in advance when the fixing roller 6b is rotated and stopped, and are stored in the control unit 1. For example, as the correction values A, B, C, and D when the fixing roller 6b is rotated, the correction value A is 1.45, the correction value B is −0.45, the correction value C is 0.00, and the correction value D. Is 1.20. As the correction values A, B, C, and D when the fixing roller 6b is stopped, for example, the correction value A is 1.34, the correction value B is -0.34, the correction value C is 0.00, The correction value D is 1.20. Then, according to the operation state of the fixing roller 6b, one of the correction values A, B, C, D at the time of rotation or the correction values A, B, C, D at the time of the stop is selected, and the surface temperature of the fixing roller 6b is selected. (Tc ′) is calculated. Thereby, a more accurate temperature can be detected.

  Similarly, the present invention can be applied to the third embodiment. That is, correction values A [Tamb], B, C, and D used for calculating the surface temperature of the fixing roller 6b are also obtained in advance when the fixing roller 6b is rotated and stopped, and are stored in the control unit 1. The correction value A [Tamb] is calculated from the correction value A and the constants a and b as in the third embodiment. For example, the constants a and b and the correction values A, B, C, and D during rotation of the fixing roller 6b include a constant a of 0.33, a constant b of 1.10, and a correction value A of 1.45. The value B is -0.45, the correction value C is 0.00, and the correction value D is 1.20. The constants a and b and the correction values A, B, C, and D when the fixing roller 6b is stopped include, for example, a constant a of 0.17, a constant b of 1.10, and a correction value A of 1. 34, the correction value B is -0.34, the correction value C is 0.00, and the correction value D is 1.20. Based on these, the correction value A [Tamb] is calculated. Then, depending on the operation state of the fixing roller 6b, one of the constants a and b at the time of rotation and the correction values A, B, C and D, or the constants a and b at the time of stop and the correction values A, B, C and D. And the surface temperature (Tc ′) of the fixing roller 6b is calculated. Thereby, a more accurate temperature can be detected.

[Embodiment 5]
The configuration of the image forming apparatus described in the fifth embodiment is the same as that of the image forming apparatus described in the fourth embodiment. The image forming apparatus described in the fifth embodiment pays attention to the fact that the heat radiation condition changes when an image is formed on a medium narrower than usual in the previous image formation. The image forming apparatus described in the fourth embodiment can correct an error caused by the decrease in the ambient temperature. The members constituting the image forming apparatus described in the fourth embodiment are the same as those in the first to fourth embodiments, and thus the same reference numerals are given and description thereof is omitted.

  When an area narrower than the contact area of the fixing roller 6b with the medium 12 is used in the previous image formation, that is, a medium having a width smaller than that of the normal medium 12, it is an end portion of the fixing roller 6b and a medium having a narrow width. The temperature of the portion not in contact with the temperature is higher than that in the portion where the fixing roller 6b and the narrow medium are in contact with each other. As a result, the ambient temperature of the non-contact thermistor 6fa increases, so that the heat dissipation condition changes. Further, since the temperature does not immediately return to the normal time even after the printing is finished and the fixing roller 6b is stopped, when the correction value at the time of stop is used, as shown in FIG. 33, the surface temperature calculated for the fixing roller 6b ( There is a difference between Tc ′) and the actual surface temperature (Tc) of the fixing roller 6b. Accordingly, it is necessary to use a correction value different from the correction value at the stop for a certain period (hereinafter referred to as Tw) after the fixing roller stops.

  The image forming apparatus described in the fifth embodiment is used in a state where the fixing roller 6b is stopped within a period Tw after using a narrow medium as a predetermined operation state of the fixing roller 6b. By obtaining a correction value in advance and using this correction value according to the operation state of the fixing roller 6b, the temperature of the surface of the fixing roller 6b can be calculated more accurately.

  As in the fourth embodiment, a medium having a narrow width is used in the immediately preceding image formation, and the above-described expressions 1 and 2 can be derived when the fixing roller 6b is stopped within the period Tw after the end of the image formation. Then, the correction values A, B, and C at the time of stopping after narrow paper printing as the second correction values of the above-described Expressions 1 and 2 are calculated by experiments. For example, as the correction values A, B, and C at this time, the correction value A is 1.30, the correction value B is −0.30, and the correction value C is 0.00. As described above, the correction values A, B, and C at the time of stopping after narrow paper printing are calculated in advance and held in the control unit 1 in the same manner as the correction values at the time of rotation and stop of the fixing roller 6b. The control unit 1 calculates the correction values A, B, and C from the detected temperature of the thermal film 6fa2 detected by the non-contact thermistor element 6fa3 and the temperature of the holding member 6fa1 detected by the compensation thermistor element 6fb2. By using this, the surface temperature of the fixing roller 6b can be accurately calculated. The correction values A, B, and C are determined by experiment for each model of the image forming apparatus. Therefore, different models have different values.

  As described above, the control unit 1 that holds the correction value controls the temperature of the surface of the fixing roller 6b to an appropriate temperature as described below. Hereinafter, a method for controlling the surface temperature of the fixing roller 6b will be described with reference to FIG.

  When receiving the print data, the control unit 1 performs the following processing. This process is performed every time the temperature is detected by the thermistor element. First, the control unit 1 detects output voltages of the non-contact thermistor element 6fa3 and the compensation thermistor element 6fb2 at the voltage detection points Vout1 and Vout2 of the temperature detection circuit 19 and reads the values. In step S202, the control unit 1 converts the output voltage into a temperature, and detects the temperatures of the non-contact thermistor element 6fa3 and the compensation thermistor element 6fb2. Since the output voltage varies depending on the temperatures of the contactless thermistor element 6fa3 and the compensation thermistor element 6fb2, the detected voltage varies from the detected output voltage with the contactless thermistor element 6fa3 and the compensation thermistor element 6fb2. Each temperature can be detected.

  In step S203, the control unit 1 determines whether or not the fixing roller 6b is rotating. When the fixing roller 6b is rotating, the control unit 1 selects the correction values A, B, and C at the time of rotation of the fixing roller 6b obtained in advance in step S206-1, and proceeds to step S207. On the other hand, when the fixing roller 6b is stopped in step S203, the control unit 1 determines in step S204 whether or not a narrow medium has been used in the immediately preceding image formation. As a result, when a narrow-width medium is used in the previous image formation, the control unit 1 performs the image formation on the narrow-width medium in step S205, that is, the control unit 1 It is determined whether or not it is within the period Tw after the fixing roller 6b is stopped.

  If it is within the period Tw after the fixing roller 6b is stopped in step S205, the control unit 1 obtains the correction values A, B, and C at the time of stopping after narrow paper printing obtained in advance in step S206-2. The process proceeds to step S207. In step S204, if a narrow medium is not used in the previous image formation, or if the period Tw is exceeded after the fixing roller 6b is stopped in step S205, the control unit 1 performs step S206-3. In step S207, correction values A, B, and C obtained when the fixing roller 6b is stopped in advance are selected, and the process proceeds to step S207.

  The temperature detected by the non-contact thermistor element 6fa3 is the temperature (Tnc) of the thermal film 6fa2. The temperature detected by the compensation thermistor element 6fb2 is the temperature (Tamb) of the holding member 6fa1. The controller 1 detects the temperature detected by the temperature of the non-contact thermistor element 6fa3 and the compensation thermistor element 6fb2, and the correction values A, B, selected in step S206-1, step S206-2, or step S206-3. From C, in step S207, the temperature of the surface of the fixing roller 6b is calculated using the calculation formula shown in the above-described formula 2. At this time, the calculated temperature of the surface of the fixing roller 6b is Tc '.

  Using the calculated surface temperature (Tc ') of the fixing roller 6b, the control unit 1 controls the temperature of the surface of the fixing roller 6b in step S208. At this time, the control unit 1 sends an ON / OFF command for energizing the fixing heater 6a to the energization control unit 16 connected to the fixing heater 6a in the fixing roller 6b. Upon receiving this command, the energization controller 16 turns on / off the fixing heater 6a, controls the temperature of the surface of the fixing roller 6b, and ends this processing. By repeating this, the temperature can be controlled to be suitable for fixing the toner on the medium 12.

  As shown in FIG. 34, when the control unit 1 controls the surface temperature of the fixing roller 6b, the correction values A, B, and C when stopping after narrow paper printing are used according to the operation state of the fixing roller 6b. Thus, as shown in FIG. 35, the actual surface temperature (Tc) of the fixing roller 6b and the calculated surface temperature (Tc ′) of the fixing roller 6b become substantially the same value. Accordingly, a correction value corresponding to the operation state of the fixing roller 6b is obtained in advance, and the control unit 1 selects to use the correction value obtained in advance according to the operation state, thereby detecting a more accurate temperature. be able to.

  In the image forming apparatus according to the fifth embodiment, in addition to the correction values at the time of rotation and stop of the fixing roller 6b, a narrow medium is used in the immediately preceding image formation, and the period Tw after the narrow medium is used. Among them, correction values A, B, and C at the time of stopping after narrow paper printing as second correction values used when the fixing roller 6b is stopped are further obtained in advance. These correction values are selected according to the operating condition of the fixing roller 6b, and the surface temperature of the fixing roller 6b is calculated. This can also be applied to the second embodiment. That is, the correction values A, B, C, and D used for calculating the surface temperature of the fixing roller 6b are further obtained in advance by controlling the time when the fixing roller 6b is stopped within the period Tw after the narrow medium is used. Held in part 1. For example, as the correction values A, B, C, and D when the fixing roller 6b is stopped after printing on narrow paper, the correction value A is 1.30, the correction value B is -0.30, and the correction value C is 0. 00 and the correction value D is 1.20. Then, depending on the operation state of the fixing roller 6b, the correction values A, B, C, D at the time of rotation, the correction values A, B, C, D at the time of stop, or the correction value at the time of stopping after printing narrow paper One of A, B, C, and D is selected, and the surface temperature (Tc ′) of the fixing roller 6b is calculated. Thereby, a more accurate temperature can be detected.

  Similarly, the present invention can be applied to the third embodiment. That is, the correction values A [Tamb], B, C, and D used to calculate the surface temperature of the fixing roller 6b are further set in advance during the period Tw after the narrow medium is used. It is obtained and held in the control unit 1. The correction value A [Tamb] is calculated from the correction value A and the constants a and b as in the third embodiment. For example, the constants a and b and the correction values A, B, C, and D when the fixing roller 6b of the fixing roller 6b is stopped after printing on narrow paper are as follows: the constant a is 0.15, the constant b is 1.20, The correction value A is 1.30, the correction value B is -0.30, the correction value C is 0.00, and the correction value D is 1.20. Based on these, the correction value A [Tamb] is calculated. Depending on the operation status of the fixing roller 6b, the constants a and b at the time of rotation and the correction values A, B, C, and D, the constants a and b at the time of the stop and the correction values A, B, C, D, or One of constants a and b and correction values A, B, C, and D when stopped after narrow paper printing is selected, and the surface temperature (Tc ′) of the fixing roller 6b is calculated. Thereby, a more accurate temperature can be detected.

1 is a schematic diagram illustrating an outline of an image forming apparatus according to a first embodiment. 1 is a block diagram of an image forming apparatus according to a first embodiment. 2 is a diagram illustrating a fixing device of the image forming apparatus according to Embodiment 1. FIG. FIG. 3 is a diagram for explaining the structure of a temperature detection unit of the image forming apparatus according to the first embodiment, which is disassembled. It is a figure which shows the state which accumulated the temperature detection part shown by decomposition | disassembly of FIG. 3 is a diagram illustrating characteristics of a thermistor element used in the temperature detection circuit of the image forming apparatus according to Embodiment 1. FIG. 2 is a circuit diagram illustrating a temperature detection circuit of the image forming apparatus according to Embodiment 1. FIG. 3 is a diagram illustrating a relationship between a voltage and a temperature detected by a thermistor element provided in a temperature detection circuit of the image forming apparatus according to Embodiment 1. FIG. FIG. 3 is a diagram illustrating a temperature relationship among a fixing roller, a thermal film, and a holding member in the image forming apparatus according to the first embodiment. It is the figure which expanded the A section of FIG. FIG. 3 is a diagram illustrating a difference between a surface temperature of a fixing roller and a temperature of a heat sensitive film in the image forming apparatus according to the first embodiment. 6 is a diagram illustrating a correlation between a difference between the actual surface temperature of the fixing roller and the temperature of the holding member and a difference between the temperature of the heat-sensitive film and the temperature of the holding member in the image forming apparatus according to Embodiment 1. FIG. FIG. 3 is a flowchart for controlling the surface temperature of the fixing roller by the control unit of the image forming apparatus according to the first embodiment. FIG. 3 is a diagram showing a difference between the surface temperature of the fixing roller calculated in the image forming apparatus of Embodiment 1 and the actual surface temperature of the fixing roller. 6 is a block diagram of an image forming apparatus according to Embodiment 2. FIG. 6 is a diagram illustrating a temperature relationship between a heat-sensitive film and a holding member in the image forming apparatus according to Embodiment 2. FIG. FIG. 10 is a diagram illustrating a relationship between a difference between an actual surface temperature of a fixing roller and a calculated surface temperature of a fixing roller, and a difference between a surface temperature of the fixing roller and a temperature of a heat sensitive film in the image forming apparatus according to the second embodiment. FIG. 10 is a diagram illustrating a correlation between the amount of change in the temperature of the heat-sensitive film during a predetermined time, the actual surface temperature of the fixing roller, and the calculated surface temperature of the fixing roller in the image forming apparatus according to the second embodiment. FIG. 10 is a flowchart for controlling the surface temperature of the fixing roller by the control unit of the image forming apparatus according to the second embodiment. FIG. 6 is a diagram showing a difference between the surface temperature of the fixing roller calculated in the image forming apparatus of Embodiment 2 and the actual temperature of the surface of the fixing roller. FIG. 10 is a diagram illustrating a temperature relationship among a fixing roller, a thermal film, and a holding member in the image forming apparatus according to the third embodiment. FIG. 10 is a diagram illustrating a difference between an actual fixing roller surface temperature and a calculated fixing roller surface temperature, and a difference between an actual fixing roller surface temperature and a thermal film temperature in the image forming apparatus according to the third embodiment. . 6 is a diagram illustrating a correlation between an ambient temperature and a correction value A in the image forming apparatus of Embodiment 3. FIG. FIG. 10 is a flowchart for controlling the surface temperature of the fixing roller by the control unit of the image forming apparatus according to the third embodiment. FIG. 10 is a diagram showing a difference between the surface temperature of the fixing roller calculated in the image forming apparatus of Embodiment 3 and the actual surface temperature of the fixing roller. FIG. 10 is a diagram showing the relationship between the surface temperature of the fixing roller, the temperature of the heat-sensitive film, and the temperature of the holding member when the fixing roller rotates and stops in the image forming apparatus according to the fourth embodiment. FIG. 10 is a diagram illustrating a relationship between a surface temperature of a fixing roller and a temperature of a heat sensitive film when the fixing roller rotates and stops in the image forming apparatus according to the fourth embodiment. The relationship between the surface temperature of the fixing roller and the temperature of the holding member when the fixing roller rotates and stops in the image forming apparatus according to the fourth embodiment, and the relationship between the temperature of the thermal film and the temperature of the holding member are as follows. FIG. FIG. 10 is a flowchart for controlling the surface temperature of the fixing roller by the control unit of the image forming apparatus according to the fourth embodiment. FIG. 6 is a diagram illustrating a relationship between a surface temperature of a fixing roller and a temperature of a heat sensitive film when temperature control is performed using a correction value when the fixing roller is stopped. FIG. 5 is a diagram illustrating a relationship between the surface temperature of the fixing roller and the temperature of the heat sensitive film when the temperature is controlled using a correction value when the fixing roller rotates. In the image forming apparatus according to the fourth embodiment, the surface temperature of the fixing roller calculated when the temperature is controlled using the correction value at the time of rotation of the fixing roller and the correction value at the time of stop and the actual fixing roller. It is a figure which shows the relationship with the temperature of the surface. In the image forming apparatus according to the fifth embodiment, the actual surface temperature of the fixing roller, the calculated surface temperature of the low adhesion roller, and the thermal film when the image is formed on the medium with the narrow fixing roller and when the fixing roller is stopped thereafter. It is a figure which shows the relationship between this temperature and the temperature of a holding member. FIG. 10 is a flowchart for controlling the surface temperature of the fixing roller by the control unit of the image forming apparatus according to the fifth embodiment. Relationship between the calculated temperature of the surface of the fixing roller and the actual temperature of the surface of the fixing roller when the temperature is controlled using the correction value at the time of stopping after narrow paper printing in the image forming apparatus according to the fourth embodiment. It is a figure which shows

Explanation of symbols

2 Charging device 3 Exposure device 4 Developing device 5 Transfer device 6 Fixing device 6a Fixing heater 6b Fixing roller 6c Pressure roller 6f Temperature detection unit 7 Remaining medium sensor 8 Photosensitive drum 9 Write sensor 10 Discharge sensor 11 Media cassette 12 Medium

Claims (7)

In an image forming apparatus provided with a fixing unit capable of detecting, in a non-contact manner, the temperature of a surface of a rotating body that rotates in the medium conveyance direction so as to fix the developer deposited on the medium by heat from a heating source.
A heat-sensitive member disposed opposite to the rotating body and heated by the rotating body;
Thermal member temperature detecting means for detecting the temperature of the thermal member;
A holding member for holding the heat sensitive member;
Holding member temperature detecting means for detecting the temperature of the holding member;
A correction value holding unit that holds a correction value obtained in advance from the relationship between the temperature of the heat sensitive member detected by the heat sensitive member temperature detecting means and the temperature of the holding member detected by the holding member temperature detecting means;
The correction value held in the holding portion is corrected based on the temperature detected by the holding member temperature detection means, and the temperature detected by the thermal member temperature detection means and the detection value detected by the holding member temperature detection means. An image forming apparatus comprising: a temperature calculating unit that calculates the temperature of the surface of the rotating body based on the corrected temperature and the corrected correction value . A thermal member temperature storage means for storing the temperature detected by the thermal member temperature detection means for each unit time measured by the time measurement means;
The temperature calculating means includes
The temperature calculated by the temperature detected by the thermal member temperature detection means and the temperature detected by the holding member temperature detection means is calculated from the temperature for each unit time stored in the thermal member temperature storage means. The image forming apparatus according to claim 1, wherein the temperature of the surface of the rotating body is calculated while being corrected based on the calculated temperature change amount in a predetermined time. The amount of temperature change in the predetermined time is
The image forming apparatus according to claim 2, wherein the correction is performed based on a temperature detected by the holding member temperature detecting means. As the correction value,
A rotation correction value used by the temperature calculating means when the rotating body is rotating;
The stop correction value used by the temperature calculation means when the rotating body is stopped is obtained in advance,
The temperature calculation means determines the operating status of the rotating body,
If the rotating body is rotating, use the rotation correction value,
4. The image forming apparatus according to claim 1, wherein the stop correction value is used when the rotating body is stopped. 5. As the correction value,
A second stop correction value used in the temperature calculating means when the rotating body is stopped and the rotating body has performed a predetermined operation immediately before is obtained;
The temperature calculating means determines an operating condition of the rotating body and an immediately preceding operating condition;
5. The image forming apparatus according to claim 4 , wherein when the rotating body is stopped and the rotating body is performing a predetermined operation immediately before, the second stop correction value is used.

In an image forming apparatus provided with a fixing unit capable of detecting, in a non-contact manner, the temperature of a surface of a rotating body that rotates in the medium conveyance direction so as to fix the developer deposited on the medium by heat from a heating source.
A heat-sensitive member disposed opposite to the rotating body and heated by the rotating body;
Thermal member temperature detecting means for detecting the temperature of the thermal member;
A holding member for holding the heat sensitive member;
Holding member temperature detecting means for detecting the temperature of the holding member;
Temperature calculating means for correcting the temperature detected by the thermal member temperature detecting means based on the temperature detected by the holding member temperature detecting means and calculating the temperature of the surface of the rotating body;
A thermal member temperature storage means for storing the temperature detected by the thermal member temperature detection means for each unit time measured by the time measurement means;
The temperature calculating means includes
The temperature calculated by the temperature detected by the thermal member temperature detection means and the temperature detected by the holding member temperature detection means is calculated from the temperature for each unit time stored in the thermal member temperature storage means. An image forming apparatus, wherein the temperature of the surface of the rotating body is calculated with correction based on the calculated temperature change amount for a predetermined time. In an image forming apparatus provided with a fixing unit capable of detecting, in a non-contact manner, the temperature of a surface of a rotating body that rotates in the medium conveyance direction so as to fix the developer deposited on the medium by heat from a heating source.
A heat-sensitive member disposed opposite to the rotating body and heated by the rotating body;
Thermal member temperature detecting means for detecting the temperature of the thermal member;
A holding member for holding the heat sensitive member;
Holding member temperature detecting means for detecting the temperature of the holding member;
From the relationship between the actual temperature of the surface of the rotating body, the temperature detected by the heat sensitive member temperature detecting means, and the temperature detected by the holding member temperature detecting means, a correction value obtained in advance is used, and the heat sensitive member is used. Temperature calculating means for correcting the temperature value detected by the temperature detecting means based on the temperature detected by the holding member temperature detecting means and calculating the temperature of the surface of the rotating body,
As the correction value,
A rotation correction value used by the temperature calculating means when the rotating body is rotating;
A correction value at stop used by the temperature calculation means when the rotating body is stopped;
A second stop correction value used in the temperature calculation means when the rotating body is stopped and the rotating body has performed a predetermined operation immediately before is obtained;
The temperature calculation means determines the operating status of the rotating body,
If the rotating body is rotating, use the rotation correction value,
When the rotating body is stopped, use the correction value at the time of stop,
2. The image forming apparatus according to claim 1, wherein when the rotating body is stopped and the rotating body is performing a predetermined operation immediately before, the second stop correction value is used.