JP2007322539A - Image forming apparatus and control method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an image forming apparatus which performs fine operation control with respect to temperature change, by estimating the temperature at a desired spot in the apparatus from the results of measurements with a limited number of temperature sensors. <P>SOLUTION: The image forming apparatus is equipped with an ambient temperature sensor 42 for measuring the temperature of the installation place of the image forming apparatus; an in-machine temperature sensor 41, installed at a position separate from a fixing device that is a heat source and measuring the temperature inside the image forming apparatus; a temperature-estimating part 31 for estimating the temperature of a developing device located near the fixing device, based on the results of measurement by the ambient temperature sensor 42 and the in-machine temperature sensor 41; and a mode-switching part 32 controlling the operation of the image forming apparatus, according to the estimated value of the temperature, at a specified spot estimated by the temperature-estimating part 31. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a printer or a copying machine, and more particularly to an image forming apparatus that performs operation control in accordance with an environmental change such as an in-machine temperature.

  In an electrophotographic image forming apparatus, a developing device that develops an electrostatic latent image formed on a photoreceptor is used. This type of developing device normally contains a developer containing toner mainly composed of colored resin in a developing housing having a developing opening facing the photosensitive drum. Today, a commonly used toner is a heat-fixable toner, but this toner has a narrow temperature range suitable for optimal image formation. For this reason, the temperature inside the apparatus, particularly the temperature rise of the developing device may be a problem.

  As a conventional technique for countermeasures against this type of heat, there has been a technique for controlling the operation of the apparatus in accordance with an increase in the in-machine temperature. For example, Patent Document 1 below describes a technique in which an image forming operation is stopped when a developing device temperature exceeds a set temperature, and the developing device is cooled by a cooling unit. Japanese Patent Application Laid-Open No. 2004-228561 describes a technique for changing the driving speed of the sheet discharging unit in accordance with the temperature detected by the temperature detection sensor.

  Further, in order to effectively control the operation of the image forming apparatus in accordance with the in-machine temperature, there is also proposed a conventional technique for controlling a cooling unit provided in the apparatus by predicting a temperature change (see, for example, Patent Document 3). ). Regarding temperature prediction, there is also a conventional technique for predicting the in-machine temperature from an outside air temperature sensor (see, for example, Patent Document 4).

JP 63-142378 A JP 2004-333930 A JP 2005-215432 A JP-A-6-230660

As described above, in an electrophotographic image forming apparatus, it is important to take measures against heat such as operation control in response to a rise in the in-machine temperature.
By the way, in a small-sized image forming apparatus, there is little margin in arrangement | positioning of a developing device, a fixing device, a paper feed mechanism, etc. from the relation of the capacity of a housing. For this reason, the distance between the developing device and the fixing device is short, and the temperature of the developing device is likely to increase. Further, a color machine that combines four color images to form a color image, and in a tandem type apparatus in which process cartridges each having a developing device mounted for each of four colors are arranged side by side, a process cartridge and a fixing device for each color, Since the distances between are different, the rate of temperature rise is also different. For this reason, it is necessary to closely monitor and control the temperature rise in each place in the machine.

  As means for closely monitoring the temperature rise at each location in the machine, it is conceivable to provide a temperature sensor at each location affected by the temperature rise. For example, in the case of a tandem type apparatus, it is preferable to provide a temperature sensor for each color process cartridge and monitor the temperature of each process cartridge individually. However, since the small apparatus described above has a small casing, there are cases where temperature sensors cannot be installed at a plurality of locations in the machine.

  The present invention has been made to solve the technical problems as described above. The object of the present invention is to determine the temperature of a desired place in the machine from the measurement results of a limited number of temperature sensors. It is to estimate and realize detailed operation control with respect to temperature change.

  In order to achieve the object, the present invention is realized as an image forming apparatus configured as follows. This apparatus is based on the measurement results of the environmental temperature measuring means for measuring the temperature of the installation location of the apparatus itself, the in-machine temperature measuring means for measuring the temperature inside the image forming apparatus, and the environmental temperature measuring means and the in-machine temperature measuring means. The temperature estimation means for estimating the temperature at a specific location different from the installation position of the in-machine temperature measurement means inside the image forming apparatus, and the estimated temperature of the specific location estimated by the temperature estimation means Control means for controlling the operation.

More specifically, the specific portion is a developing device, the in-machine temperature measuring means is a temperature sensor provided in a location farther from the fixing device that is a heat source than the developing device in the image forming apparatus, and the temperature estimating means is The temperature of the developing device is estimated based on the measurement value of the temperature sensor.
Further, the temperature estimation means includes the measured value of the in-machine temperature measuring means, the measured value of the environmental temperature measuring means, the rate of temperature rise of the measured value by the in-machine temperature measuring means, the heat transfer coefficient at a specific location, and the heat transfer coefficient of the in-machine temperature measuring means. Is used as a parameter to calculate the temperature rise rate at the specific location, and the temperature at the specific location is estimated based on the calculated temperature rise rate at the specific location.
Alternatively, the temperature estimation means may include the measured value of the in-machine temperature measuring means, the measured value of the environmental temperature measuring means, the rate of temperature rise of the measured value by the in-machine temperature measuring means, the heat capacity of a specific location, the heat capacity of the in-machine temperature measurement means, and the specific location. The temperature increase rate at the specific location is calculated using the amount of heat applied and the amount of heat applied to the in-machine temperature measurement means as parameters, and the temperature at the specific location is estimated based on the calculated temperature increase rate at the specific location.

More preferably, a coefficient for calculating a temperature rise rate of a specific portion (developing device) is stored in the storage device for each operation mode of the image forming apparatus, and the temperature estimation unit is in the operation mode of the image forming apparatus. In response, the corresponding coefficient is read out, and the estimated value of the temperature at the specific location is calculated.
Further, the temperature estimation unit calculates an estimated value of the temperature of each of the plurality of developing devices provided for each color.

  The present invention is also grasped as a method for controlling an image forming apparatus as follows. In this method, an internal temperature which is a temperature of an installation place of the image forming apparatus and an internal temperature which is an internal temperature of the image forming apparatus are measured, and the internal temperature is measured based on the measured environmental temperature and the internal temperature. For controlling the operation of the image forming apparatus in accordance with the step of estimating the temperature of the developing device set at a position closer to the fixing device that is the heat source than the temperature sensor and the estimated value of the temperature of the developing device Including the step of. More specifically, in the step of controlling the operation of the image forming apparatus, the output speed of the image forming apparatus is changed or the operation of the image forming apparatus is stopped according to the estimated value of the temperature of the developing device.

  According to the present invention configured as described above, a limited temperature sensor is used, the temperature at a desired location in the machine is estimated from the measurement result, and fine operation control with respect to temperature change can be performed.

The best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a diagram illustrating an image forming apparatus to which the exemplary embodiment is applied.
This image forming apparatus 10 is a so-called tandem type in which four color process cartridges (image forming units, drum cartridges) 11a, 11b, 11c, and 11d are arranged in the vertical direction in a main body 10a. Further, a conveyance path 12 through which the paper P is conveyed from a substantially vertical lower side to an upper side is arranged at a corresponding position of each of the process cartridges 11a to 11d. Further, a paper feed cassette 13 for storing the paper P that is transported through the transport path 12 and to which the toner images are sequentially transferred is disposed further below (upstream) of the lowermost (uppermost) process cartridge 11a. Has been. In the illustrated example, a part of the paper feed cassette 13 protrudes to the back side (rear side, in side) of the main body 10a due to the size of the paper P stored in the paper feed cassette 13. However, if the paper P is small, it does not protrude from the main body 10a.

  The process cartridges 11 a to 11 d as one of the image forming cartridges are provided with toner images for yellow (Y), magenta (M), cyan (C), and black (K) in order from the upstream side of the conveyance path 12. To form. Each of the process cartridges 11a to 11d is a cartridge in which a photosensitive drum (image holding member) 14 and various electrophotographic devices sequentially arranged around the photosensitive drum 14 are integrally formed. It is.

FIG. 2 is a diagram schematically showing an example of the configuration of the process cartridge 11d. The other process cartridges 11a, 11b, and 11c have the same configuration as the process cartridge 11d except for the color of the built-in toner.
The process cartridge 11d in the present embodiment includes a photosensitive drum 14, and a charging device 111, a developing device 112, and a cleaning device 113 that are disposed around the photosensitive drum 14. The photosensitive drum 14 functioning as a latent image holding member is rotatably arranged and is driven by a drive motor (not shown). A photosensitive layer (not shown) is formed on the outer peripheral surface of the photosensitive drum 14. The charging device 111 is disposed in contact with the photosensitive drum 14 and is applied with a charging bias for charging the photosensitive drum 14 by a power source (not shown). The charging device 111 and an exposure device 15 described later function as a latent image forming unit. The developing device 112 includes a developing unit that develops the electrostatic latent image on the photosensitive drum 14 with toner, and a main toner supply unit that supplies toner to the developing unit. The main toner supply unit is appropriately supplied with toner from the sub toner supply unit. The cleaning device 113 places the cleaning blade in pressure contact with the photosensitive drum 14 and removes residual toner remaining on the photosensitive drum 14 without being transferred to the paper P after the developing process.

  An exposure device 15 common to the process cartridges 11a to 11d is disposed on the opposite side of the transport path 12 of the process cartridges 11a to 11d. The exposure device 15 drives and drives four semiconductor lasers (not shown) based on image data corresponding to each color. The light from the four semiconductor lasers is deflected and scanned by a polygon mirror (not shown) and guided to an exposure point on the photosensitive drum 14 through an fθ lens (not shown) and a plurality of reflection mirrors, thereby the photosensitive drum 14. It is configured to draw a light image on top.

  A conveyance belt 16 that circulates along the conveyance path 12 is disposed at a location corresponding to each photosensitive drum 14 of the process cartridges 11a to 11d. The transport belt 16 is made of a belt material that can electrostatically attract the paper P, and is stretched around a pair of driving roller 17A and driven roller 17B. Further, an adsorption roller 18 for electrostatically adsorbing the paper P to the conveyance belt 16 is disposed in the conveyance path 12.

  A transfer roller 19 is disposed on the back side of the conveyance belt 16 corresponding to each photosensitive drum 14 of the process cartridges 11a to 11d. The transfer roller 19 is for transferring the toner image formed on the photosensitive drum 14 onto the paper P by bringing the photosensitive drum 14 and the paper P on the transport belt 16 into close contact with each other.

  A fixing device 20 is provided in the conveyance path 12 further above (downstream side) of the uppermost (most downstream) process cartridge 11d. On the upper part of the main body 10a, a paper discharge unit 21 is provided integrally with the main body 10a for storing the paper P discharged after the toner image is fixed by the fixing device 20. The main body 10 a is provided with a reversing conveyance path 22 for reversing the paper P, one side of which has been fixed by the fixing device 20, and sending it again to the conveyance path 12.

  The main body 10a of the image forming apparatus 10 is provided with a front cover 25 that is rotatable about a rotation fulcrum J provided at the lower end. The front cover 25 constitutes a side wall portion on the upper side of the paper feed cassette 13 and on the near side of the image forming apparatus 10, and functions as an external cover together with the main body 10 a in the closed state. Further, the front cover 25 is provided with a manual feed tray 23 that is rotatable about a rotation fulcrum J provided at the lower end. That is, the manual feed tray 23 is configured to be openable and closable on the front side (front side and out side). When the manual feed tray 23 is rotated in the opening direction, a desired paper P can be set in an insertion window (not shown). As described above, the image forming apparatus 10 is configured to feed paper P other than the paper P stored in the paper feed cassette 13 from the manual feed tray 23.

  Further, a control device 30 for controlling the operation of each device and each mechanism is provided in the main body 10a of the image forming apparatus 10. Furthermore, in an appropriate position inside the main body 10a, an in-machine temperature sensor 41 which is a measuring means for the in-machine temperature, and an environmental temperature sensor which is a measuring means for the temperature (environment temperature) where the image forming apparatus 10 is installed. 42 is provided. In the illustrated example, the in-machine temperature sensor 41 is installed in the vicinity of the photosensitive drum 14 of the lowermost (uppermost) process cartridge 11a. The environmental temperature sensor 42 is installed near the side wall of the main body 10a opposite to the front cover 25.

  Here, in a state where the paper P on which the toner image is to be transferred is set, either a paper P in the paper feed cassette 13 or a paper P in the manual feed tray 23 is instructed by a user to a control device 30 (not shown). One is sent at a predetermined timing. The sent paper P is transported to the transport path 12 via a plurality of transport rollers 24 and sent to the transfer positions of the process cartridges 11 a to 11 d via the transport belt 16. In addition, the control device 30 of the present embodiment reads the measured values of the in-machine temperature sensor 41 and the environmental temperature sensor 42, and estimates the temperature of each developing device in a desired location inside the device, specifically, the process cartridges 11a to 11d. To do. The control device 30 controls the image forming operation by the process cartridges 11a to 11d and the operation of the driving roller 17 and the conveying roller 24 that drive the conveying belt 16 according to the estimation result.

FIG. 3 is a diagram illustrating a functional configuration of the control device 30 in the present embodiment.
As shown in FIG. 3, the control device 30 of the present embodiment includes a temperature estimation unit 31 that estimates the temperature of a specific place in the machine based on the measured values (temperatures) of the in-machine temperature sensor 41 and the environmental temperature sensor 42. A mode switching unit 32 that switches the operation mode of the image forming apparatus 10 based on the estimation result by the temperature estimation unit 31. As described above, the control device 30 has a function of receiving various inputs and controlling various operations of the image forming apparatus 10. FIG. 3 shows only the characteristic functions of the present embodiment. Yes.

  Inside the image forming apparatus 10, the influence of the temperature rise becomes a serious problem in the developing device 112 containing toner. On the other hand, there are various heat sources in the image forming apparatus 10, but the fixing device 20 for heat-fixing the toner has a particularly large heat generation amount. The image forming apparatus 10 shown in FIG. 1 includes four process cartridges 11 a to 11 d corresponding to four colors. However, the process cartridge 11 d located at the uppermost stage is closest to the fixing device 20, and thus the fixing device 20. It will be most affected by the heat generated. When performing duplex printing, the sheet P heated by the fixing device 20 dissipates heat when it is sent to the conveyance path 12 via the reverse conveyance path 22. In this case, the heat is radiated from the paper P in order from the process cartridge 11 a located at the uppermost stream of the transport path 12. Therefore, the temperature estimation unit 31 of the present embodiment estimates the temperatures of the developing devices 112 of the process cartridges 11a to 11d individually.

ただし、Ｔは物体の温度、Ｔ０は雰囲気温度、Ｃは物体の熱容量、Ｑは物体に与えられる熱量、ｈは熱伝達係数である。 Here, a temperature estimation method by the temperature estimation unit 31 will be described.
In general, the temperature change of an object is expressed by the following equation (1) model.

Where T is the temperature of the object, T0 is the ambient temperature, C is the heat capacity of the object, Q is the amount of heat given to the object, and h is the heat transfer coefficient.

The above model is applied to the developing device 112 and the in-machine temperature sensor 41. For the second term, the ambient temperature is unknown, but in order to express the general behavior, instead of the ambient temperature, when the model is applied by replacing the ambient temperature Ta measured by the ambient temperature sensor 42, the following Equations 2 and 3 are obtained. Note that each variable and coefficient subscript d represents the developing device 112, and s represents the in-machine temperature sensor 41.

Further, although the positions of the developing device 112 and the in-machine temperature sensor 41 are separated from each other, both are similarly affected by the temperature rise factor (heat source) in the apparatus. Therefore, the amount of heat Qd given to the developing device 112 and the amount of heat Qs given to the in-machine temperature sensor 41 can be expressed by the following equation (4).

数５式によれば、現像装置１１２の温度Ｔｄ、機内温度センサ４１の温度Ｔｓおよび機内温度センサ４１の温度上昇率ｄＴｓ／ｄｔを与えると、現像装置１１２の温度の上昇率ｄＴｄ／ｄｔが求まる。これにより、現像装置１１２の温度を逐次推定することができる。具体的には、現像装置１１２に対する前回の推定温度Ｔｄ（前回）、前回の測定時と今回の測定時との時間差Δｔから、現像装置１１２の温度Ｔｄ（今回）は、次の数６式により推定される。

When Qd and Qs are eliminated from the above formulas 2 to 4, the following formula 5 is obtained.

According to Equation 5, when the temperature Td of the developing device 112, the temperature Ts of the in-machine temperature sensor 41, and the temperature increase rate dTs / dt of the in-machine temperature sensor 41 are given, the rate of increase dTd / dt of the temperature of the developing device 112 is obtained. . Thereby, the temperature of the developing device 112 can be estimated sequentially. Specifically, from the previous estimated temperature Td (previous) for the developing device 112 and the time difference Δt between the previous measurement and the current measurement, the temperature Td (current) of the developing device 112 is expressed by the following equation (6). Presumed.

  During the printing operation, the amount of heat Qd given to the developing device 112 and the amount of heat Qs given to the in-machine temperature sensor 41 change from time to time depending on printing conditions and the like, so that prediction and measurement are difficult. For example, in the case of single-sided printing, the temperature of the paper P is deprived of heat, so the temperature rise is suppressed. However, in the case of double-sided printing, the paper P warmed by the fixing device 20 conversely accelerates the temperature rise. Therefore, the values of Qd and Qs are different. Similarly, the size of the paper P and the interval of the transported paper P also affect the values of Qd and Qs. However, Qd and Qs are not directly included in the above equation (5). Therefore, by using this equation, the rate of change in the temperature of the developing device 112 can be calculated easily and accurately even if the printing conditions change.

On the other hand, in the so-called standby time when the printing operation is not performed, there is slight heat generation due to the energized state, but since there is no change in the heat generation amount due to the printing operation, the amount of heat Qd given to the developing device 112 and the in-machine temperature sensor The amount of heat Qs given to 41 can be obtained in advance. On the other hand, when the front cover 25 is opened to remove paper jams or replace consumables, outside air directly enters the machine and changes the ambient temperature. Two terms will change. When the change in the atmospheric temperature is expressed by changes in the heat transfer coefficients hd and hs, and the ratio between the value of hd and the value of hs is kh, these relationships are expressed as shown in Equation 7.

数８式は、数５式と同様に、現像装置１１２の温度Ｔｄ、機内温度センサ４１の温度Ｔｓおよび機内温度センサ４１の温度上昇率ｄＴｓ／ｄｔを与えると、現像装置１１２の温度の上昇率ｄＴｄ／ｄｔが求まる。そして、得られたｄＴｄ／ｄｔを用いて、上記の数６式により、現像装置１１２の温度を逐次推定することができる。また、数８式には、機内温度の変化に伴って値が変化する可能性のある熱伝達係数ｈｄ、ｈｓが直接含まれていない。したがって、同式を用いることにより、フロントカバー２５の開閉等で雰囲気温度等の機内環境が変化しても、容易にかつ精度良く現像装置１１２の温度の変化率を算出することができる。 Therefore, when the hd and hs are deleted from the formulas 2, 3, and 7, the following formula 8 is obtained.

In the same way as Equation 5, Equation 8 gives the temperature Td of the developing device 112, the temperature Ts of the in-machine temperature sensor 41, and the temperature rise rate dTs / dt of the in-machine temperature sensor 41. dTd / dt is obtained. Then, using the obtained dTd / dt, the temperature of the developing device 112 can be sequentially estimated by the above equation (6). Further, Equation 8 does not directly include the heat transfer coefficients hd and hs whose values may change with changes in the in-machine temperature. Therefore, by using this equation, even if the in-machine environment such as the ambient temperature changes due to opening / closing of the front cover 25, the rate of change in the temperature of the developing device 112 can be calculated easily and accurately.

  By the way, parameters such as Qs / Cs, Qd / Cd, k, hs, and hd used in the above formula are the device configuration such as whether or not the image forming apparatus 10 has a duplex printing mechanism, color printing, or monochrome printing. The appropriate value should be selected depending on the operation mode such as single-sided printing or double-sided printing, the printing speed, and the like. Therefore, more preferably, a table in which values of the parameters determined in advance according to various device configurations and operation modes are registered and stored in the nonvolatile memory. When the temperature estimation unit 31 estimates the temperature of the developing device 112, appropriate parameters are read out and used according to the device configuration and operation mode of the image forming device 10. The values registered in the parameter table are used to actually measure the temperature changes of the in-machine temperature sensor 41, the environmental temperature sensor 42, and the developing device 112 by operating the image forming apparatus 10 under various conditions (apparatus configuration and operation mode). Then, the actual measurement values are determined so as to match the above equations.

FIG. 4 is a diagram illustrating a configuration example of a parameter table for setting parameters.
In the illustrated parameter table, whether or not a double-sided printing mechanism is provided, whether color printing or monochrome printing is provided, and if a double-sided printing mechanism is provided, single-sided printing or double-sided printing, and a printing speed (PPM: pages / minute) The parameter value is registered according to the above. This parameter table is created for each individual parameter. In FIG. 4, idling is a state in which a part of the apparatus in the image forming apparatus 10 is operating for warm-up, error detection, and the like, although the printing operation is not performed. Although not shown, parameters such as standby Qs / Cs, Qd / Cd, and kh used in Equation 8 are also measured in advance and stored in the nonvolatile memory together with the parameter table.

  As described above, development is performed when the amount of heat Qd given to the developing device 112 during the printing operation and the amount of heat Qs given to the in-machine temperature sensor 41 change, and when the in-machine environment may change during standby. An equation for estimating the temperature of the device 112 was obtained. The temperature of the developing device 112 estimated by these equations is stored in the memory and used as Td (previous) at the next estimation.

  After the temperature of the developing device 112 is estimated, the mode switching unit 32 operates the operation mode of the image forming apparatus 10 based on the estimation result so that the temperature of the developing device 112 of each of the process cartridges 11a to 11d does not rise too much. Switch. Specifically, the printing speed is reduced or the printing operation is stopped.

FIG. 5 is a chart showing the relationship between the estimated temperature of the developing device 112 by the temperature estimation unit 31 and the operation mode to be selected.
In FIG. 5, reference temperature 1 is a reference temperature for stopping the printing operation, reference temperature 2 is a reference temperature for restarting the printing operation in the half speed mode, and reference temperature 3 is a half speed from the full speed mode (normal printing speed). The reference temperature for shifting to the high speed mode (half the printing speed of the full speed mode) and the reference temperature 4 are the reference temperatures for returning from the half speed mode to the full speed mode. The actual value becomes higher in the order of reference temperature 1, reference temperature 2, reference temperature 3, and reference temperature 4.

  Referring to FIG. 5, when the estimated temperature is equal to or higher than the reference temperature 1, the printing operation is stopped. When the estimated temperature is lower than the reference temperature 1 and higher than the reference temperature 2, if the previous state is the stop state, the operation is performed in the full speed mode or the half speed mode. It becomes operation. If the estimated temperature is equal to or lower than the reference temperature 2 and equal to or higher than the reference temperature 3, the operation is performed in the half speed mode regardless of the previous state. If the estimated temperature is lower than the reference temperature 3 and higher than the reference temperature 4, if the previous state was operating in the full-speed mode, the half-speed mode is used as it is if the previous state was operating in the full-speed mode. It becomes the operation. When the estimated temperature is equal to or lower than the reference temperature 4, the operation is performed in the full speed mode.

FIG. 6 is a flowchart for explaining the flow of control operations by the temperature estimation unit 31 and the mode switching unit 32.
Referring to FIG. 6, first, the temperature estimation unit 31 reads the measured values of the in-machine temperature sensor 41 and the environmental temperature sensor 42 (step 601). Then, the temperature estimation unit 31 reads the previous estimated value Td (previous) and the measured value (previous in-machine temperature) of the in-machine temperature sensor 41 at the previous estimation from the memory (step 602). Next, the temperature estimation unit 31 calculates the rate of change dTs / dt between the previous and current in-flight temperature from the previous in-flight temperature and the measured value (current in-flight temperature) of the in-flight temperature sensor 41 read in Step 601 ( Step 603). Further, the current in-machine temperature read in step 601 is recorded in the memory (step 604).

  Next, the temperature estimation unit 31 determines whether a printing operation (including idling) has been performed from the previous estimation time to the present time (step 605). Since this printing operation is executed under the control of the control device 30, the temperature estimation unit 31 can easily obtain information regarding the presence or absence of the printing operation. If it is determined in step 605 that the printing operation has been performed (including during the operation), the temperature estimation unit 31 next determines the heat transfer coefficient hs of the in-machine temperature sensor 41, the heat transfer coefficient hd of the developing device 112, the developing device. An appropriate value is read from the parameter table (see FIG. 5) of the coefficient k used in Formula 4 showing the relationship between the heat quantity Qd given to 112 and the heat quantity Qs given to the in-machine temperature sensor 41 (step 606). Here, the value read from the parameter table is determined by calculating a weighted average according to the type of operation (color double-sided printing, monochrome single-sided printing, idling, etc.) determined in step 605 and the ratio thereof, for example. Thereafter, the temperature estimation unit 31 obtains the temperature increase rate dTd / dt of the developing device 112 using Equation 5 (step 607).

  On the other hand, if it is determined that the printing operation has not been performed, the temperature estimation unit 31 reads the values of Qs / Cs, Qd / Cd, and kh at the time of standby (step 608), and the temperature of the developing device 112 is calculated according to equation (8). An increase rate dTd / dt is obtained (step 609).

  If the rate of increase dTd / dt of the temperature of the developing device 112 is obtained in step 607 or step 608, then the temperature estimation unit 31 calculates an estimated value of the current temperature of the developing device 112 using equation 6 (step 610). The calculated value (estimated temperature) is recorded in the memory (step 611).

Next, the mode switching unit 32 compares the estimated temperature calculated in step 610 with the reference temperatures 1 to 4 shown in FIG. 5 and switches the operation mode of the image forming apparatus 10 as necessary (step). 612).
The above operations by the temperature estimation unit 31 and the mode switching unit 32 are repeatedly executed at regular time intervals (Δt).

  By the way, in the normal temperature estimating operation, as described above, the estimated value of the current temperature can be obtained by the equation 6 using the previous estimated value. In the estimation operation, since there is no previous estimated value, it is necessary to set an initial value by an appropriate method. For example, the last estimated value before turning off the power and the measured value of the in-machine temperature sensor 41 obtained by this estimation operation are stored in the nonvolatile memory. Then, in the first temperature estimation after startup, the last measured value of the in-machine temperature read from the nonvolatile memory is compared with the current measured value of the in-machine temperature sensor 41, and the ratio and the last estimated value are obtained. Based on this, the temperature of the developing device 112 may be estimated.

  In addition, when the apparatus has been stopped for a long time without turning off the power (standby state), the temperature change rate dTs / dt of the in-machine temperature sensor 41 and the estimated value dTd / dt of the temperature of the developing device 112. The difference with is small. In this case, the temperature of the developing device 112 is calculated by a regression equation obtained in advance from the measured value of the in-machine temperature sensor 41 and the measured value of the environmental temperature sensor 42, and the obtained value is sequentially used in the above-described procedure (FIG. 6). The estimated temperature of the developing device 112 may be replaced.

ただし、Ｔｄｓａｔは現像装置１１２の温度Ｔｄの飽和値を表す。 Hereinafter, a method for obtaining a predetermined coefficient will be described.
For example, when obtaining the coefficients hd, hs, and k corresponding to a certain printing mode, k can be expressed by the above equation 4, so it is only necessary to obtain hd, hs, Qd / Cd, and Qs / Cs.
First, printing is continuously performed in a predetermined printing mode, and the temperature Td of the developing device 112 whose temperature is to be estimated is recorded using a thermocouple or the like. Also, the temperatures Ts and Ta of the in-machine temperature sensor 41 and the environmental temperature sensor 42 are recorded simultaneously. At this time, the temperature Td of the developing device 112 and the temperature Ts of the in-machine temperature sensor 41 gradually increase as shown in FIG. 7, and show a behavior of being saturated at a specific temperature. Here, since the temperature Td of the developing device 112 is saturated because dTd / ds = 0, for example, when the left side of Equation 2 is modified to 0, the following Equation 9 is obtained.

Tdsat represents the saturation value of the temperature Td of the developing device 112.

以上の数９式および数１０式の関係から、ｈｄ、ｈｓ、Ｔｄｓａｔ、Ｔｓｓａｔが求められれば良いことになる。すなわち、現像装置１１２の温度Ｔｄの測定結果と環境温度センサ４２の温度Ｔａから、ｈｄとＴｄｓａｔを求め、機内温度センサ４１の温度Ｔｓと環境温度センサ４２の温度Ｔａの温昇挙動からｈｓとＴｓｓａｔを求める。具体的には、温度上昇中の適当な時点の温度Ｔｄの測定値を初期値として数２式を用いて逐次計算した温度Ｔｄの推定値が、温度Ｔｄの測定値に最も良く一致するように係数ｈｄ、Ｔｄｓａｔを決めれば良い。 Similarly, for the saturation value Tssat of the temperature Ts of the in-machine temperature sensor 41, the following formula 10 is obtained.

It is only necessary to obtain hd, hs, Tdsat, and Tssat from the relationship of the above formula 9 and formula 10. That is, hd and Tdsat are obtained from the measurement result of the temperature Td of the developing device 112 and the temperature Ta of the environmental temperature sensor 42, and hs and Tssat are obtained from the temperature rise behavior of the temperature Ts of the in-machine temperature sensor 41 and the temperature Ta of the environmental temperature sensor 42. Ask for. Specifically, the estimated value of the temperature Td, which is sequentially calculated using Equation 2 with the measured value of the temperature Td at an appropriate time during the temperature rise as the initial value, is best matched with the measured value of the temperature Td. The coefficients hd and Tdsat may be determined.

  As described above, the coefficients hd and Tdsat are coefficients related to the rate of temperature rise and the temperature at the time of saturation, respectively. Therefore, when each is larger than the appropriate value and when it is smaller, the deviation as shown in FIG. 8 is shown, so that the appropriate value can be easily obtained. Even when the coefficients are fitted so that the error is mathematically minimized, a convergent solution can be obtained without divergence. Similarly, appropriate values can be determined for the coefficients hs and Tssat.

1 is a diagram illustrating an image forming apparatus to which the exemplary embodiment is applied. FIG. 2 is a diagram illustrating an example of a configuration of a process cartridge provided in the image forming apparatus of FIG. 1. It is a figure which shows the function structure of the control apparatus in this embodiment. It is a figure which shows the structural example of the parameter table which sets the parameter used for estimation of the temperature of the control apparatus by this embodiment. It is a graph which shows the relationship between the estimated temperature of the image development apparatus by the temperature estimation part of this embodiment, and the operation mode which should be selected. It is a flowchart explaining the flow of control operation by the temperature estimation part and mode switching part of this embodiment. It is a figure which shows the relationship between the temperature of the image development apparatus in this embodiment, and the temperature of an in-machine temperature sensor. It is a figure which shows the relationship between the measured temperature of the image development apparatus in this embodiment, and estimated temperature.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Image forming apparatus, 11a-11d ... Process cartridge, 20 ... Fixing device, 30 ... Control device, 31 ... Temperature estimation part, 32 ... Mode switching part, 41 ... In-machine temperature sensor, 42 ... Environmental temperature sensor, 112 ... Development apparatus

Claims (12)

In the image forming apparatus,
Environmental temperature measuring means for measuring the temperature of the installation place of the image forming apparatus;
In-machine temperature measuring means for measuring the temperature inside the image forming apparatus,
Based on the measurement results of the environmental temperature measuring means and the in-machine temperature measuring means, a temperature estimating means for estimating the temperature at a specific location different from the installation position of the in-machine temperature measuring means inside the image forming apparatus,
An image forming apparatus comprising: control means for controlling the operation of the image forming apparatus in accordance with an estimated value of the temperature at the specific location estimated by the temperature estimating means. The in-machine temperature measuring means is a temperature sensor provided in the image forming apparatus,
The specific portion is a developing device,
The image forming apparatus according to claim 1, wherein the temperature estimation unit estimates a temperature of the developing device based on a measurement value of the temperature sensor provided at a position distant from the developing device.   The image forming apparatus according to claim 2, wherein the temperature sensor is installed at a location farther from a fixing device that is a heat source than the developing device.   The temperature estimating means includes a measured value of the in-machine temperature measuring means, a measured value of the environmental temperature measuring means, a rate of temperature increase of the measured value by the in-machine temperature measuring means, a heat transfer coefficient at the specific location, and the in-machine temperature measuring means. The temperature increase rate of the specific location is calculated using the heat transfer coefficient of the parameter as a parameter, and the temperature of the specific location is estimated based on the calculated temperature increase rate of the specific location. Image forming apparatus.   The temperature estimation means includes a measurement value of the in-machine temperature measurement means, a measurement value of the environmental temperature measurement means, a rate of temperature increase of the measurement value by the in-machine temperature measurement means, a heat capacity of the specific location, a heat capacity of the in-machine temperature measurement means The temperature increase rate of the specific location is calculated using the amount of heat given to the specific location and the amount of heat given to the in-machine temperature measuring means as parameters, and the temperature of the specific location is calculated based on the calculated temperature rise rate of the specific location. The image forming apparatus according to claim 1, wherein   A coefficient used for calculating the temperature increase rate at the specific location is stored in a storage device for each operation mode of the image forming apparatus, and the temperature estimation unit corresponds to the coefficient corresponding to the operation mode of the image forming apparatus. The image forming apparatus according to claim 4, wherein an estimated value of the temperature at the specific location is calculated. The image forming apparatus according to claim 1, wherein the temperature estimation unit calculates an estimated value of the temperature at the specific location using a temperature increase rate dTd / dt at the specific location obtained by the following equation.

However, Td is the temperature at a specific location, Ts is the measured value by the in-machine temperature measuring means, Ta is the measured value by the environmental temperature measuring means, dTs / dt is the rate of temperature rise of the measured value by the in-machine temperature measuring means, and hd is the specific location Heat transfer coefficient, hs is a heat transfer coefficient of the in-machine temperature measuring means, and k is a coefficient satisfying the following relationship.

However, Cd is the heat capacity of a specific location, Cs is the heat capacity of the in-machine temperature measurement means, Qd is the amount of heat given to the specific location, and Qs is the heat quantity given to the in-machine temperature measurement means. The image forming apparatus according to claim 1, wherein the temperature estimation unit calculates an estimated value of the temperature at the specific location using a temperature increase rate dTd / dt at the specific location obtained by the following equation.

Where Td is the temperature at a specific location, Ts is the measured value by the in-machine temperature measuring means, Ta is the measured value by the environmental temperature measuring means, dTs / dt is the rate of temperature rise of the measured value by the in-machine temperature measuring means, and Cd is the specific location Heat capacity, Cs is the heat capacity of the in-machine temperature measuring means, Qd is the amount of heat given to a specific location, Qs is the amount of heat given to the in-machine temperature measuring means, and kh is a coefficient that satisfies the following relationship.

Where hd is the heat transfer coefficient at a specific location, and hs is the heat transfer coefficient of the in-machine temperature measurement means.   The image forming apparatus according to claim 1, wherein the specific portion is a developing device for each color, and the temperature estimation unit calculates an estimated value of the temperature of the developing device. An image forming apparatus control method comprising:
Measuring an environmental temperature, which is a temperature of an installation place of the image forming apparatus, and an in-machine temperature, which is a temperature inside the image forming apparatus;
Estimating the temperature of the developing device set at a position closer to the fixing device that is a heat source than the temperature sensor for measuring the temperature inside the device based on the measured ambient temperature and the inside temperature; and
And a step of controlling the operation of the image forming apparatus in accordance with the estimated value of the temperature of the developing device.   The control of the image forming apparatus according to claim 10, wherein in the step of controlling the operation of the image forming apparatus, the output speed of the image forming apparatus is changed according to an estimated value of the temperature of the developing device. Method.   The method for controlling an image forming apparatus according to claim 10, wherein in the step of controlling the operation of the image forming apparatus, the operation of the image forming apparatus is stopped according to an estimated value of the temperature of the developing device. .

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