JP2017054026A - Non-contact temperature sensor of fixation device and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-contact temperature sensor of a fixation device which can continuously detect the temperature of a fixation member without switching a temperature conversion equation or temperature conversion table.SOLUTION: A non-contact temperature sensor of a fixation device includes: a sensor part 51 which receives an infrared ray from a fixation member; and arithmetic processing means 52 which calculates the temperature of the fixation member by processing output of the sensor part 51. The arithmetic processing means 52 includes: a steady temperature conversion table 65 or steady temperature conversion equation which converts the output of the sensor part 51 into steady temperature data of the fixation member; a transient temperature conversion table 66 or transient temperature conversion equation which converts the output of the sensor part into transient temperature data of the fixation member; and a complementary filter 67 which combines the steady temperature data and transient temperature data after gradually decreasing a prescribed frequency component of each of them. Since the complementary filter 67 combines the steady temperature data and the transient temperature data after gradually decreasing the prescribed frequency component of each of them, the temperature of the fixation member can be continuously detected without switching the steady and transient temperature conversion tables (or conversion equations).SELECTED DRAWING: Figure 5

Description

  The present invention relates to a non-contact temperature sensor for a fixing device and an image forming apparatus.

  The temperature control of the fixing device is usually performed by detecting the surface temperature of the fixing member with a temperature sensor and feeding it back. In recent years, in an image forming apparatus such as a color digital multifunction peripheral, when wear of a fixing member due to a temperature sensor occurs, image deterioration is caused. Therefore, a non-contact temperature sensor is increasingly used.

  The temperature detection by the non-contact temperature sensor generally uses the following principle. That is, the infrared rays emitted from the temperature detection target are absorbed by the absorption film inside the sensor, the temperature of the absorption film is detected by the temperature detection element, and the temperature of the target is calculated. As a temperature detection element, there are an element using a thermocouple and an element using a thermistor. The former is called a thermopile and the latter is called a non-contact thermistor. In addition, in order to remove the influence of the temperature of the sensor itself or the temperature of the absorption film due to convection heat, many non-contact temperature sensors are further provided with elements for compensating for them.

  Since the non-contact temperature sensor performs temperature detection based on such a principle, the temperature conversion formula or the temperature conversion table is tuned according to the relationship between the temperature to be detected and the sensor output (the amount of infrared rays to be detected). In general, the actual temperature is often measured with a contact-type thermocouple or the like, and the detected temperature is often fitted to the actual temperature using a temperature conversion formula.

  For example, Patent Document 1 discloses a non-contact temperature sensor detection device including a temperature detection thermistor and a temperature compensation thermistor that detects the temperature of a casing that houses the thermistor. The non-contact temperature sensor detection device includes means for selecting a data table to be used in accordance with a change amount per unit time of an output voltage from a circuit including a temperature compensation thermistor.

  However, when the data table to be used is switched, there is a problem that the sensor detection temperature changes discontinuously and adversely affects the temperature control of the fixing member. Here, “the sensor detected temperature changes discontinuously” means the occurrence of a discontinuous point of the detected temperature by switching the data table (or temperature conversion formula).

  Patent Document 1 described above also discloses that the number of data tables is further increased in order to alleviate the discontinuity of the detected temperature. However, this is not an essential measure for data table switching. Further, when the memory for the data table is increased, the memory cost increases.

  An object of the present invention is to provide a non-contact temperature sensor of a fixing device that can continuously detect the temperature of a fixing member without switching a temperature conversion formula or a temperature conversion table.

  In the non-contact temperature sensor of a fixing device, the object includes: a sensor unit that receives infrared light from the fixing member; and an arithmetic processing unit that processes an output of the sensor unit and calculates a temperature of the fixing member. Means for amplifying and discretizing the output of the sensor unit; a steady temperature conversion table or a steady temperature conversion formula for converting the amplified and discretized output of the sensor unit into steady temperature data of the fixing member; Transient temperature conversion table or transient temperature conversion formula for converting the amplified and discretized output of the sensor unit into the transient temperature data of the fixing member, the steady temperature data and the transient temperature data, respectively with predetermined frequency components This is solved by a non-contact temperature sensor of the fixing device, characterized in that it comprises a complementary filter that combines after decreasing.

  According to the present invention, the steady-state temperature data and the transient temperature data are synthesized by decreasing the respective predetermined frequency components by the complementary filter and set as the temperature of the fixing member. Therefore, the temperature of the fixing member can be continuously detected without switching the steady / transient temperature conversion table (or conversion formula).

1 is a schematic diagram illustrating an image forming apparatus according to an embodiment of the present invention. 1 is a schematic diagram illustrating a fixing device according to an embodiment of the present invention. 3 is a schematic circuit of a non-contact temperature sensor of the fixing device according to the embodiment of the present invention. 6 is a graph showing a temperature change of a fixing member. 2 is a block diagram of a non-contact temperature sensor of a fixing device according to an embodiment of the present invention. FIG.

(Embodiment)
FIG. 1 is a schematic diagram showing an image forming apparatus according to an embodiment of the present invention. The illustrated image forming apparatus 100 employs an electrophotographic system, and an image reading apparatus 200 is installed on the image forming apparatus 100 to constitute a copying apparatus. A duplex unit 300 is attached to the right side of the image forming apparatus 100 in the drawing. The image forming apparatus 100 includes an intermediate transfer device 10. The intermediate transfer device 10 is provided so as to run around an endless intermediate transfer belt 11 while being wound around a plurality of rollers almost horizontally and running counterclockwise.

  Under the intermediate transfer device 10, cyan, magenta, yellow, and black image forming devices 12 c, 12 m, 12 y, and 12 k are arranged in a quadruple tandem manner along the stretch direction of the intermediate transfer belt 11. Each of the image forming devices 12c, 12m, 12y, and 12k is configured by installing a charging device, a developing device, a transfer device, a cleaning device, and the like around a drum-shaped image carrier that rotates clockwise in the drawing. Primary transfer devices 25c, 25m, 25y, and 25k are provided at positions inside the intermediate transfer belt 11 that face each image carrier. An exposure device 13 is provided below the image forming devices 12c, 12m, 12y, and 12k.

  A sheet feeding device 14 is provided below the exposure device 13. The paper feeding device 14 includes two stages of paper feeding cassettes 15 for storing paper 20 as recording media. A paper feed roller 17 is provided at the upper right of each paper feed cassette 15 to feed out the paper 20 in each paper feed cassette 15 one by one and put it into the paper transport path 16.

  The sheet conveyance path 16 is formed on the right side in the drawing in the image forming apparatus 100 from the lower side to the upper side, and communicates with the in-body sheet discharge unit 18 formed between the image forming apparatus 100 and the image reading apparatus 200. Provide as follows. In the paper transport path 16, a secondary transfer device 21, a fixing device 22, a paper discharge device 23 including a pair of paper discharge rollers, and the like are provided in this order so as to face the transport roller 19, the intermediate transfer belt 11. A paper feed path 37 that re-feeds paper from the duplex unit 300 or manually feeds from the manual paper feeder 36 and joins the paper 20 to the paper transport path 16 is provided upstream of the transport roller 19. Further, a refeed conveyance path 24 to the duplex unit 300 is provided downstream from the fixing device 22.

  When the image forming apparatus 100 takes a copy, first, the image reading apparatus 200 reads a document image and the exposure apparatus 13 writes it. Next, each color toner image is formed on the image carrier of each of the image forming devices 12c, 12m, 12y, and 12k, and the toner image is sequentially transferred by the primary transfer devices 25c, 25m, 25y, and 25k, and intermediate transfer is performed. A color image is formed on the belt 11.

  On the other hand, one of the paper feed rollers 17 is selectively rotated to feed the paper 20 from the corresponding paper feed cassette 15 and put it into the paper transport path 16. Alternatively, the manual paper 20 is fed from the manual paper feeder 36 into the paper feed path 37. Next, the sheet is conveyed by the conveyance roller 19 through the sheet conveyance path 16 and sent to the secondary transfer position in a timely manner, and the color image formed on the intermediate transfer belt 11 is transferred to the sheet 20 by the secondary transfer device 21. To do. The paper 20 after the image transfer is fixed by the fixing device 22, discharged by the paper discharge device 23, and stacked on the in-body paper discharge unit 18.

  When an image is also formed on the back side of the paper 20, the paper 20 is put into the refeed conveyance path 24, reversed by the duplex unit 300, and then fed again through the paper feed path 37. Next, a color image separately formed on the intermediate transfer belt 11 is secondarily transferred to the paper 20, fixed again by the fixing device 22, and discharged to the in-body paper discharge unit 18 by the paper discharge device 23.

  FIG. 2 is a schematic diagram illustrating a fixing device according to an embodiment of the present invention. As shown in FIG. 2, the fixing device 22 is a fixing belt 40 as a fixing member that rotates in contact with an unfixed image, and a pressure member that forms a fixing nip N between the fixing belt 40. And a pressure roller 45. Further, the fixing device 22 energizes the halogen heaters 41 a and 41 b based on the temperatures of the halogen heaters 41 a and 41 b as heating means, the non-contact temperature sensor 50 as temperature detection means, and the temperature of the non-contact temperature sensor 50. The temperature control means 60 etc. to control are provided.

  The fixing belt 40 is a thin and flexible endless belt member. As the belt member, for example, a metal belt such as nickel or SUS or a resin material such as polyimide can be used. On the inner peripheral side of the fixing belt 40, two halogen heaters 41 a and 41 b and a reflection member 42 that reflects heat from the halogen heaters 41 a and 41 b to the fixing belt 40 are provided. The fixing belt 40 is directly heated by radiant heat from the inner peripheral side by the halogen heaters 41a and 41b and the reflecting member 42.

  Further, a nip forming member 43 that forms a fixing nip portion N in contact with the pressure roller 45 and a stay 44 as a support member that supports the nip forming member 43 are provided on the inner peripheral side of the fixing belt 40. ing.

  The pressure roller 45 is a rotatable roller member, and includes a core 46, an elastic layer 47 formed of solid rubber or foamed sponge, and a surface layer 46 for improving toner releasability. Is done. The pressure roller 45 is rotationally driven by a driving source such as a motor provided in the image forming apparatus 100. The pressure roller 45 is pressed against the fixing belt 40 by a spring or the like, and has a predetermined nip width when the elastic layer 47 is crushed and deformed.

  The halogen heaters 41 a and 41 b are fixed to the side plate of the fixing device 22 at both ends. The halogen heaters 41 a and 41 b are heated by electric power from a power supply unit provided in the image forming apparatus 100.

  The non-contact temperature sensor 50 is a thermometer that measures the temperature of an object by measuring the intensity of infrared rays emitted from the object, and detects the surface temperature of the fixing belt 40. The installation position of the non-contact temperature sensor 50 cannot be installed anywhere because of the layout limitation of the fixing device 22. Details of the non-contact temperature sensor 50 will be described later.

  The temperature control means 60 is composed of a computer including a CPU, ROM, RAM, I / O, and the like. Based on the temperature detected by the non-contact temperature sensor 50, the temperature controller 60 controls energization of the halogen heaters 41a and 41b so that the surface temperature of the fixing belt 40 becomes a constant temperature (fixing temperature). For example, PID control is used for energization control.

  FIG. 3 is a schematic circuit diagram of the non-contact temperature sensor of the fixing device according to the embodiment of the present invention. As shown in FIG. 3, the non-contact temperature sensor 50 includes a sensor unit 51 that receives infrared rays from the fixing member, and an arithmetic processing unit 52 that processes the output of the sensor unit 51 and calculates the temperature of the fixing belt 40. Have. The sensor unit 51 includes an absorption film 53 that absorbs infrared rays, a temperature detection element 54 that detects the temperature of the absorption film 53, and a compensation element 55 for temperature compensation. The arithmetic processing unit 52 includes an amplifier circuit unit 56, an A / D converter 57, and a calculation unit 58.

  In the sensor unit 51, the absorption film 53 receives infrared rays from the fixing member and generates heat. And the temperature detection element 54 detects the temperature rise of the absorption film 53, and outputs it as an electric current or a voltage. The compensation element 55 detects the temperature in the sensor unit 51 and outputs it as a current or voltage. Outputs from the sensor unit 51 (temperature detection element 54 and compensation element 55) are amplified by the amplification circuit unit 56 of the arithmetic processing means 52 and sent to the calculation unit 58 as sensor outputs discretized by the A / D converter 57. It is done.

  The compensation element 55 is used to remove the influence of the temperature of the sensor unit 51 itself from the temperature detected by the temperature detection element 54. Therefore, when the influence on the detected temperature can be ignored, the compensation element 55 need not be provided.

  The calculation unit 58 is configured by a computer including a CPU, ROM, RAM, I / O, and the like. The calculation unit 58 converts the sensor output into the surface temperature of the fixing belt 40 using a temperature conversion formula or a temperature conversion table, and sends the surface temperature to the temperature control means 60.

  Next, the temperature conversion formula / temperature conversion table will be described.

  FIG. 4 is a graph showing a temperature change of the fixing member. The horizontal axis of the graph is time, and the vertical axis is the fixing member temperature. The fixing member temperature in a transient state that rises or falls is called transient temperature data, and the fixing member temperature in a steady state that changes substantially constant is called steady temperature data. If the temperature of the fixing member is controlled as shown in FIG. 4, the sensor output and the actual fixing member temperature are obtained and the relationship between the two is subjected to multiple regression analysis, a temperature conversion formula or a temperature conversion table can be created.

  In the present embodiment, a transient temperature conversion formula or transient temperature conversion table for converting sensor output into transient temperature data of the fixing member, and a steady temperature conversion formula or steady temperature conversion table for converting sensor output into steady temperature data of the fixing member Use.

  Conventionally, a temperature conversion formula or a temperature conversion table has been created by performing fitting by multiple regression analysis using only steady temperature, or by fitting data obtained by combining steady temperature and transient temperature. However, due to the heat balance inside the non-contact temperature sensor, it has been difficult to improve the accuracy at both the steady temperature and the transient temperature, such as an error increasing with respect to the transient temperature.

  In order to improve the accuracy in both the steady temperature and the transient temperature of the fixing member, it is conceivable to switch the temperature conversion formula or the temperature conversion table. However, when the temperature conversion formula or the temperature conversion table is switched, there is a problem that the sensor detection temperature changes discontinuously and adversely affects the temperature control of the fixing member. Here, “the sensor detected temperature changes discontinuously” means the occurrence of a discontinuous point of the detected temperature by switching the data table (or temperature conversion formula). Increasing the temperature conversion formula and the temperature conversion table to alleviate the discontinuity of the detected temperature does not provide an essential solution. Rather, the memory of the conversion formula or conversion table increases, causing a problem that the memory cost increases.

  Therefore, in the present embodiment, the temperature is continuously detected by combining the steady temperature data and the transient temperature data converted by the temperature conversion formula or the temperature conversion table with weighting using the complementary filters.

  FIG. 5 is a block diagram of a non-contact temperature sensor of the fixing device according to the embodiment. FIG. 5 shows the configuration of the calculation processing means 52 (calculation unit 58) of FIG. The flow of processing for calculating the temperature of the fixing member will be described with reference to FIG.

First, the output V from the sensor unit 51 is amplified and discretized by the amplifier circuit unit 56 and the A / D converter 57 which are circuit units. Then, the amplified and digitized output V ^*, as well is converted to a steady temperature data T _S at constant temperature conversion table 65 are translated into transient temperature data T _TR transient temperature conversion table 66. Next, the steady temperature data T _S and the transient temperature data T _TR are sent to the complementary filter 67.

  The complementary filter 67 includes a low-pass filter 68 and a high-pass filter 69, and is a digital filter that synthesizes and outputs data generated by both filters. The sum of the gains of the low-pass filter 68 and the high-pass filter 69 is 1 in the entire frequency region.

In steady temperature data, a low frequency component (long period of temperature fluctuation) indicates an accurate temperature, but a high frequency component (short period of temperature fluctuation) is considered a noise component. On the other hand, in the transient temperature data, the high frequency component (the cycle of temperature fluctuation is short) indicates an accurate temperature, but the low frequency component (the cycle of temperature fluctuation is long) is considered an offset component. Thus, declining high frequency components of the steady state temperature data T _S, after declining the low frequency components of the transient temperature data T _TR, if synthesizing the continuous appropriate temperature depending on the state of the temperature of the fixing member Can be output.

  From the data output from the complementary filter 67, noise is removed by the noise removal filter 70 and output as the detected temperature T.

  The steady temperature conversion table 65 and the transient temperature conversion table 66 may be replaced with a steady temperature conversion formula and a transient temperature conversion formula, respectively.

  As described above, the non-contact temperature sensor of the fixing device according to the present embodiment includes a steady-state / transient temperature conversion table (or conversion formula), synthesizes the converted steady-state / transient temperature data with a complementary filter, and detects it. Calculated as temperature. Therefore, the temperature of the fixing member can be continuously detected without switching the steady / transient temperature conversion table (or conversion formula).

  In addition, since the non-contact temperature sensor of the fixing device according to the present embodiment calculates temperature data in a predetermined frequency band with a complementary filter, it is possible to improve measurement accuracy at both steady temperature and transient temperature.

  Subsequently, an advantageous configuration of the non-contact temperature sensor of the fixing device of the present invention will be described.

  The two filters of the complementary filter 67 are preferably composed of a finite impulse response filter (FIR filter) or an infinite impulse response filter (IIR filter). In the case of a finite impulse response filter, there is an advantage that the mounting is relatively simple. On the other hand, the infinite impulse response filter has an advantage that it has better filter characteristics than the infinite impulse response filter.

  The present invention has been described in detail above using the embodiment. This embodiment is an example, and can be used with various modifications within a range not departing from the gist.

DESCRIPTION OF SYMBOLS 10 Intermediate transfer device 11 Intermediate transfer belt 12c, 12m, 12y, 12k Image forming device 13 Exposure device 14 Paper feed device 15 Paper feed cassette 16 Paper feed path 17 Paper feed roller 18 In-body paper discharge unit 19 Transport roller 20 Paper 21 2 Next transfer device 22 Fixing device 23 Paper discharge device 24 Refeed conveyance path 25c, 25m, 25y, 25k Primary transfer device 36 Manual paper feed device 37 Paper feed path 40 Fixing belt 41a, 41b Halogen heater 42 Reflecting member 43 Nip forming member 44 Stay 45 Pressure Roller 46 Core Wire 47 Elastic Layer 48 Surface Layer 50 Non-Contact Temperature Sensor 51 Sensor Unit 52 Arithmetic Processing Unit 53 Absorption Film 54 Temperature Detection Element 55 Compensation Element 56 Amplification Circuit Unit 57 A / D Converter 58 Calculation Unit 60 Temperature control means 65 Steady temperature conversion table 66 Transient temperature conversion table Bull 67 complementary filter 68 low-pass filter 69 a high-pass filter 70 removing noise filter 100 image forming apparatus 200 the image reading device 300 duplex unit T detected temperature T _S steady state temperature data T _TR transient temperature data V output V ^* amplified and digitized output

JP 2003-28722 A Japanese Patent Laid-Open No. 06-66639

Claims (6)

A sensor unit that receives infrared rays from the fixing member;
In the non-contact temperature sensor of the fixing device, which includes an arithmetic processing unit that processes the output of the sensor unit and calculates the temperature of the fixing member.
The arithmetic processing means is
A circuit unit for amplifying and discretizing the output of the sensor unit;
A steady temperature conversion table or a steady temperature conversion formula for converting the amplified and discretized output of the sensor unit into steady temperature data of the fixing member;
A transient temperature conversion table or a transient temperature conversion formula for converting the amplified and discretized output of the sensor unit into transient temperature data of the fixing member;
A non-contact temperature sensor of a fixing device, comprising: a complementary filter that synthesizes the steady temperature data and the transient temperature data after decreasing respective predetermined frequency components. The complementary filter is:
A low-pass filter that gradually reduces high-frequency components of the steady-state temperature data;
A high-pass filter that gradually reduces the low-frequency component of the transient temperature data,
The non-contact temperature sensor of the fixing device according to claim 1, wherein the two filters have a sum of gains of 1 at all frequencies.   The non-contact temperature sensor of the fixing device according to claim 2, wherein the complementary filter includes a finite impulse response filter.   The non-contact temperature sensor of the fixing device according to claim 2, wherein the complementary filter is an infinite impulse response filter.   5. The non-contact temperature sensor of a fixing device according to claim 1, wherein the arithmetic processing unit further includes a noise removal filter that removes noise from the output of the complementary filter. 6. An image forming apparatus, wherein the temperature of the fixing device is controlled using the non-contact temperature sensor of the fixing device according to claim 1.

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