JP2004177430A - Fixing controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing controller for which the need of taking the variation of the constituting components of a control system into consideration with respect to the design of the control system is eliminated. <P>SOLUTION: The fixing controller by which the proper output of a heater is obtained by varying the turn-on duty of the heater 3 of a fixing unit 1 in specified control time in accordance with the detected temperature of a temperature detecting element 2 is provided with a controlling means 5 to perform control that the turn-on duty is corrected in accordance with inclination by obtaining temperature and time characteristics under the certain specified condition of the temperature detecting element 2 before assembling a machine. <P>COPYRIGHT: (C)2004,JPO

Description

本発明では、通常のヒータデューティ制御に対し、（２）式で得られたαを乗算することになる。なお、データ収集の実施タイミングとしては、ばらつき補正の対象が部品特有のばらつきであること、上記治具の条件を正規定着ユニットでは作り出せないこと等により、機械組付前に実施しておくことになる。
またそのデータから求められた（２）式の値は、機械自体に記憶させておき、通常制御中の点灯デューティに乗算することになるので、工場での機械組付後の火入れ時の調整工程などでデータ入力してメモリに保存しておくことになる。なお、ばらつきを発生するのは機械というよりは、機械に使われているサーミスタ２という部品であるのでその部品交換時、もしくは定着ユニット１の交換時には、工場出荷時と同様な調整が必要となる
また本発明のマイコン負荷を考えると、（２）式の演算は機械稼働時には行わないもので、通常制御中は（２）式で求められたαを点灯デューティに乗算するのみであるので、マイコン負荷としても非常に少ないものとなっている。
以上より、サーミスタ２の（許容公差内での）ばらつきに影響されることなく、公差±０品サーミスタと同等な検知が得られることになるので、制御系設計も部品ばらつきを考慮しなくてもすむので非常により容易なものとなる。また、結果として得られる温度制御もより正確なものとなり、定着温度を設定温度に素早くかつ不必要なオーバーシュートを生じずに、到達・維持させることが可能となる。
【００１０】
次に、本発明第２の実施例について以下に説明する。制御系要素の一つであるヒータ出力のばらつき（公差）によって、ヒータ熱量が変動しないよう補正するものである。以下、図３を用いて補正のための制御を説明する。本発明では、その使用環境での最適な制御を実現するため、ヒータ点灯デューティに補正処理を行うのだが、その補正処理のための事前データ収集を行う調整モードを用意している。
図３は、前述したようにその調整モード時の定着ユニット１内のサーミスタ２の検知温度−時間特性を示しており、動作としては、本発明の第１の実施例と同様、まずヒータ３をオンさせ、サーミスタ検知温度がある温度からある温度に到達するまでの時間をカウントし、ヒータ３をオフさせている。
図３の例では、５０℃から１００℃までの温度推移時間を計測しており、ヒータオン後、サーミスタ検知温度をＣＰＵ５が監視しており、５０℃を検知後ＣＰＵ５内のタイマをスタートさせ、１００℃検知でタイマストップ、ヒータオフとしている。その計測された時間としてはｔ_２＝ｂ−ａとなる。なお、この調整モードでのヒータ出力は固定のデューティとしておく必要があり、そのデューティとしては、サーミスタ２の検知温度の推移が図３のような１次直線となるデューティを選択する。
また、図３中５０℃−１００℃間の時間を測定しているが、サーミスタ２の特性として、温度―電圧の特性がリニアで誤差の少ない区間であれば問題ない。このような設定下で計測された時間ｔ_２は、あらかじめ測定しておいたヒータ出力公差±０品：Ｗ０での温度推移時間ｔ_０より、公差を含んだヒータでの出力Ｗが、下式より求まる。
Ｗ＝ａ・（ｔ_０／ｔ_２）・Ｗ_０ （３）
ここで、ａは任意定数となっているが、ヒータ出力のばらつきによる上式の特性をあらかじめ測定しておくことで、その制御系固有の値として求めておくことができる。これより、ヒータ点灯デューティの補正係数βは、下式となる。

【００１１】
本発明では、通常のヒータデューティ制御に対し、（４）式で得られたβを乗算することになる。なお、本発明の第１の実施例と合わせると、ヒータ点灯のデューティとしては（５）式で得られた値を乗算することになる。
α・β＝（１＋ａ・（ｔ_０／ｔ_１））・（１／（ａ・（ｔ_０／ｔ_２））） （５）なお、調整モードの実施タイミングとしては、ばらつき補正の対象がその機械特有のばらつきであり、部品であるヒータ自体の出力ばらつきだけでなく、定着ユニット自体の熱伝導ばらつきを考えると、定着ユニット組付後の調整工程とするのが望ましい。もちろん定着ユニット自体の熱伝導ばらつきが少ない場合は、本発明の第１の実施例で示したように、治具を用いて部品単体でデータ収集するのでも構わない。但し、電源が定格入力（±０％）でのデータ収集が絶対条件である。
また、このデータ収集から求められた（４）式もしくは（５）式の値は、機械自体に記憶させておき、通常制御中の点灯デューティに乗算することになるので、工場での機械組付後の火入れ時の調整工程などでデータ入力してメモリに保存しておくことになる。なお、ばらつきを発生するのは機械というよりは、機械に使われているヒータ３という部品、もしくは定着ユニット１であるので、その部品交換時、もしくは定着ユニット１の交換時には、工場出荷時と同様な調整が必要となる。
また本発明のマイコン負荷を考えると、（２）式の演算は機械稼働時には行わないもので、通常制御中は（２）式で求められたβもしくは、α・βを点灯デューティに乗算するのみであるので、マイコン負荷としても非常に少ないものとなっている。
以上により、ヒータ３の（許容公差内での）ばらつきに影響されることなく、公差±０品ヒータ出力と同等な出力が得られることになるので、制御系設計も部品ばらつきを考慮しなくてもすむのでより容易なものとなる。また、結果として得られる温度制御もより正確なものとなり、定着温度を設定温度に素早くかつ不必要なオーバーシュートを生じずに、到達・維持させることが可能となる。
以上により、温度検知素子２、ヒータ３といった制御系要素ばらつきの補正がなされたのだが、これらは部品仕様として管理されているものであるため、これらの補正が行われなくても、設計の容易性、制御の追従性等を問わなければ、出力仕様からはずれることはない。
【００１２】
しかしながら、残る要素して電源事情が挙げられ、定格入力（日本国内であればＡＣ１００Ｖ）の±何％と規定して設計しても、ユーザのあらゆる条件を網羅しきれるものではなく、場合によっては狙いのヒータ出力が得られないという不具合（制御不能）が生じる。
本発明の第３の実施例はこれを補正するもので、以下、図３を用いて補正のための制御を説明する。第３の実施例では、第１、２の実施例と同様、その使用環境での最適な制御を実現するため、ヒータ点灯デューティに補正処理を行うのだが、その補正処理のための事前データ収集を行う調整モードを用意している。
図３は、前述した通り、その調整モード時の定着ユニット１内のサーミスタ２検知温度−時間特性を示しており、動作としてはまずヒータ３をオンさせ、サーミスタ検知温度がある温度からある温度に到達するまでの時間をカウントし、ヒータ３をオフさせている。
図３の例では、５０℃から１００℃までの温度推移時間を計測しており、ヒータオン後、サーミスタ検知温度をＣＰＵ５が監視しており、５０℃を検知後ＣＰＵ５内のタイマをスタートさせ、１００℃検知でタイマストップ、ヒータオフとしている。その計測された時間としてはｔ_３＝ｂ−ａとなる。
なお、この調整モードでのヒータ出力は固定のデューティとしておく必要があり、そのデューティとしては、サーミスタ２の検知温度の推移が図３のような１次直線となるデューティを選択する。また、図３中５０℃−１００℃間の時間を測定しているが、サーミスタ２の特性として、温度―電圧の特性がリニアで誤差の少ない区間であれば問題ない。
【００１３】
このような設定下で計測された時間ｔ３は、あらかじめ測定しておいた定格電源電圧Ｖ０（国内であれば１００［Ｖ］）での温度推移時間ｔ０より、その環境下での電源電圧が、下式より求まる。
Ｖ＝ａ・（ｔ_０／ｔ_３）・Ｖ_０ （６）
ここで、ａは任意定数となっているが、電源電圧のばらつきによる上式の特性をあらかじめ測定しておくことで、その制御系固有の値として求めておくことができる。電源電圧が求まると、その環境下でのヒータ出力を求めることが可能であり、定格入力でのヒータ出力をＷ０、その環境下でのヒータ出力をＷとすると、下式が成り立つ。
Ｗ＝（Ｖ／Ｖ_０）^ｂ・Ｗ_０ （７）
ここで、ｂはヒータ製品固有の値（ヒータメーカよりデータの入手可能）
（６）（７）より、ヒータ点灯デューティの補正係数γは、下式となる。

本発明では、通常のヒータデューティ制御に対し、（８）式で得られたγを乗算することになる。なお、本発明の第１の実施例と合わせると、ヒータ点灯のデューティとしては（９）式で得られた値を乗算することになる。
α・β・γ＝（１＋ａ・（ｔ_０／ｔ_１））・（１／（ａ・（ｔ_０／ｔ_２）））・（１／（ａ・（ｔ_０／ｔ_３））^ｂ） （９）
これにより、装置が設置された場所の電源事情（入力電圧）に影響されることなく、定格入力でのヒータ出力と同等な出力が得られ、素早くかつ不必要なオーバーシュートを生じずに温度を設定温度に到達・維持させることが可能となる。なお、調整モードの実施タイミングとしては、ばらつき補正の対象がその機械の使用される電源事情（入力電圧）にあるため、工場出荷時での調整は必要なく、機械設置時に最低限行われる必要がある。
機械設置時のみであれば、通常制御中は（８）式もしくは（９）式で求められたγ、もしくはα・β・γを点灯デューティに乗算するのみであるのでマイコン負荷も少なく、時々刻々と電圧事情が変化する環境であれば、より頻繁に（電源オン時毎などに）補正のためのデータ収集を行い、γを更新することで対応が可能である。
【００１４】
【発明の効果】
以上説明したように、本発明によれば、定着ユニットの温度制御において、その制御系を構成する温度検知素子、ヒータ、電源事情などの特性ばらつきを補正することにより、構成要素のばらつきを考慮するが故の設計の困難度合いを低くすることができ、また構成要素が予測したばらつきを越えた時の制御不能状態といった不具合を解消することができる。その結果、温度制御もより正確になり、定着温度を設定温度に素早くかつ不必要なオーバーシュートを生じずに到達させ、これを維持することが可能となる。
【図面の簡単な説明】
【図１】本発明の実施形態に係る定着制御装置のブロック図である。
【図２】ヒータの点灯デューティを示す図である。
【図３】データ収集時のサーミスタの検知温度−時間特性を示す図である。
【符号の説明】
１ 定着ユニット
２ 温度検出素子（サーミスタ）
３ ヒータ
５ ＣＰＵ（制御手段）[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fixing control device that controls a heater of a fixing unit used in an image forming apparatus such as a copying machine, a facsimile, and a printer.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus having a fixing unit using a heater, a control method in which an appropriate heater output is obtained by making a heater lighting time (lighting duty) variable within a predetermined control time. Is commonly used.
For example, when controlling the heater lighting so that the temperature at the position where the temperature detecting element in the fixing unit is attached becomes a predetermined set temperature, an amount obtained by multiplying a difference between the set temperature and the current temperature by a proportional constant is used. Commonly known automatic control techniques such as P (proportional) control that determines the lighting time with PID, PI (proportional / integral) control that also considers the temperature transition, and PID (proportional / integral / derivative) control that also considers the time response There are many examples of application.
However, these controls do not take into account the variation of each element that composes the control system. Therefore, when designing as a product, design a control system with a high margin considering the variation tolerance or detect and correct the variation. Either a control system to be designed is adopted. In the latter case, various studies have been made and many technologies have been announced.
[0003]
For example, in Japanese Patent No. 2867766 (first conventional example), a variation in heater resistance value is corrected by calculating a temperature rise rate from the start of energization to a control temperature and selecting a control pattern prepared in advance. Technology has been proposed.
Japanese Patent Application Laid-Open No. 10-161466 (second conventional example) presupposes that the temperature rise gradient is measured to correct the time delay of the thermistor output and that the thermistor output is corrected. There has been proposed a technique of detecting a change in input voltage based on a gradient and correcting the on / off duty of a heater.
Further, Japanese Patent Application Laid-Open No. 2000-147942 (third conventional example) finds a temperature control method from heater turn-on time and temperature rise data within a predetermined time, thereby reducing variation in characteristics such as thermal conductivity of a heat fixing device. On the other hand, there has been proposed a technology that enables appropriate temperature control and always realizes optimum temperature control even when the heat fixing device is replaced.
[Patent Document 1] Japanese Patent No. 2867766 [Patent Document 2] Japanese Patent Application Laid-Open No. 10-161466 [Patent Document 3] Japanese Patent Application Laid-Open No. 2000-147942 [0004]
[Problems to be solved by the invention]
In the first conventional example, the object of the variation correction is only the heater resistance value, and it is not possible to consider the variation of other control system elements.
In the second conventional example, since the correction is based on the table method, accurate control that follows the variation amount is impossible.
In the third conventional example, the correction is performed by a complicated calculation process (least square method), so that there is a problem that the load of the microcomputer for controlling is very heavy.
Further, in the conventional fixing control device, even if the design is regulated to ±% of the rated input (100 V AC in Japan) with respect to the variation in the power supply condition, it cannot cover all the conditions of the user. In some cases, there is a problem that a desired heater output cannot be obtained.
SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing control device which does not need to consider variations in control system components in control system design.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 is a fixing control for obtaining a proper heater output by varying a lighting duty of a heater of a fixing unit within a fixed control time according to a temperature detected by a temperature detecting element. In the apparatus, a temperature-time characteristic under a predetermined condition of the temperature detecting element is obtained before mechanical assembly, and a fixing control device including a control unit that performs control to correct a lighting duty according to the inclination is provided. The most important feature.
According to a second aspect of the present invention, there is provided a fixing control device which obtains an appropriate heater output by varying a lighting duty of a heater of a fixing unit within a predetermined control time according to a temperature detected by a temperature detecting element. Control means for determining the temperature-time characteristics under different conditions before the machine is assembled or before the factory is shipped after the machine is assembled, and performing control to correct the lighting duty according to the inclination. The most important feature is a fixing control device characterized by the following.
According to a third aspect of the present invention, there is provided a fixing control device for obtaining a proper heater output by varying a lighting duty of a heater of a fixing unit within a certain control time according to a temperature detected by a temperature detecting element. The main feature of the fixing control device is that the temperature-time characteristics below are obtained when the user installs the machine or when the power is turned on, and the control unit performs control to correct the lighting duty in accordance with the inclination. .
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of a fixing control device according to an embodiment of the present invention. The fixing control device includes a fixing unit 1 having a temperature detecting element 2 and a heater 3 to be controlled, a base engine control unit (BCU) 4 having a CPU 5 mounted thereon, and an AC control plate 6 having a bidirectional switching element 7. I have.
The heater 3 is connected to a commercial AC power supply 8 via a bidirectional switching element 7 such as a triac and a current detection fuse or the like (not shown) as a safety circuit. The input / output insulated photocoupler or the like is often used to drive the switching element 7, and the ON / OFF F control is performed by the CPU 5 operated by the secondary power supply.
The temperature detecting element 2 is disposed near a roller surface (belt surface), not shown, and generally uses an inexpensive thermistor. Hereinafter, the thermistor will be described as an example. The thermistor 2 has the characteristic that the resistance value changes according to the detected temperature. The temperature is converted into a voltage by the thermistor 2, and this voltage is taken into the A / D input of the CPU 5 mounted on the BCU 4 and detected as the temperature. .
With the configuration of the control system as described above, the CPU 5 controls the heater on / off so that the roller (belt) surface temperature of the fixing unit 1 can be changed or maintained at a predetermined set temperature.
[0007]
Hereinafter, specific control will be described. The basic control method is a known automatic control technique as described above. For example, in the case of P control, for example, first, a temperature is detected by the thermistor 2, a difference between the detected temperature and a set target temperature is obtained, and the difference is calculated. The lighting duty (time) of the heater 3 is determined by the value multiplied by the proportional constant Kp.
To explain with reference to FIG. 2, the value of how much time (t ₁ , t ₂ , t ₃ ,...) Of the thermistor temperature is detected at every control unit time t ₀ and the cycle of the t ₀ cycle is turned on. And ON / OFF control is performed. At this time, the lighting time increases as the difference from the set temperature increases, and the lighting time decreases as the difference from the set temperature decreases. The control unit time is determined by the CPU performance and the required resolution of the lighting time.
The above is the case where the basic control is the P control. However, if the microcomputer is used to determine the lighting duty in consideration of the temperature transition and the temperature change rate, the PI control and the PID control are performed.
Although these are established as conventional techniques, the design of the control constants Kp, Ki, and Kd is generally performed in consideration of the tolerance (variation) of the elements constituting the control system. It is a target. However, the variation that occurs due to this consideration depends on the control operation target, that is, in the present control system, the heater lighting time (the amount of heater heat to be supplied) varies from device to device.
In the present invention, the above-described variation of the control system element is corrected so as not to affect the control operation amount. In the first embodiment of the present invention, the variation of the temperature sensing element, which is one of the control system elements, is corrected. The correction is performed so that the heater output (heater heat amount) does not fluctuate due to the tolerance.
[0008]
Hereinafter, the control for correction will be described with reference to FIG. In the present invention, correction processing is performed on the heater lighting duty in order to realize optimum control in the usage environment. However, a jig for performing preliminary data collection for the correction processing is prepared. Although the basic configuration is the same as that of FIG. 1, it is stipulated that the output of the heater 3 is a standard (tolerance ± 0%) product and that the commercial AC power supply 8 has a rated input (± 0%). In addition, since the jig is used only for collecting data, it has a structure in consideration of convenience of removal. The thermal conductivity to the thermistor 2 in this jig must be the same as that of the regular fixing unit.
FIG. 3 is a diagram showing the detected temperature-time characteristics of the thermistor at the time of data collection. As an operation, the heater 3 is first turned on, the time until the thermistor detection temperature reaches a certain temperature from a certain temperature is counted, and the heater 3 is turned off. In the example of FIG. 3, the temperature transition time from 50 ° C. to 100 ° C. is measured. After the heater is turned on, the thermistor detection temperature is monitored by the CPU 5. After detecting 50 ° C., the timer in the CPU 5 is started. Timer stop and heater off at ° C detection. The measured time is t ₁ = ba.
Note that the heater output in this adjustment mode needs to have a fixed duty, and the duty is selected such that the transition of the temperature detected by the thermistor 2 becomes a primary straight line as shown in FIG. Although the time between 50 ° C. and 100 ° C. is measured in FIG. 3, there is no problem as long as the characteristics of the thermistor 2 are such that the temperature-voltage characteristics are linear and have few errors.
[0009]
Such time t ₁ measured by the under configuration, previously measured in advance thermistor 2 tolerance ± 0 goods: the temperature transition time t ₀ at r _0, tolerance d thermistor 2 [%] is lower Obtained from the formula.
d = a · (t ₀ / t ₁ ) (1)
Here, although a is an arbitrary constant, it can be obtained as a value specific to the control system by measuring the characteristics of the above equation due to the variation of the thermistor 2 in advance. Thus, the heater lighting duty correction coefficient α is given by the following equation.

In the present invention, the normal heater duty control is multiplied by α obtained by the equation (2). The data collection should be performed before the machine is assembled because the target of the variation correction is the component-specific variation and the condition of the jig cannot be created by the regular fixing unit. Become.
Further, the value of the expression (2) obtained from the data is stored in the machine itself and multiplied by the lighting duty during the normal control. The data is input and stored in the memory. It is to be noted that since the variation is caused by the thermistor 2 used in the machine rather than by the machine, the same adjustment as that at the time of factory shipment is required at the time of replacement of the component or replacement of the fixing unit 1. Considering the microcomputer load of the present invention, the calculation of the expression (2) is not performed when the machine is operating, and during normal control, only the lighting duty is multiplied by α obtained by the expression (2). The load is very low.
As described above, the same detection as the thermistor with a tolerance of ± 0 can be obtained without being affected by the variation (within the allowable tolerance) of the thermistor 2, so that the control system design does not need to consider the component variation. So much easier. In addition, the resulting temperature control becomes more accurate, and the fixing temperature can be quickly reached and maintained at the set temperature without causing unnecessary overshoot.
[0010]
Next, a second embodiment of the present invention will be described below. The correction is performed so that the heater calorific value does not fluctuate due to the variation (tolerance) of the heater output, which is one of the control system elements. Hereinafter, the control for correction will be described with reference to FIG. In the present invention, in order to realize optimal control in the usage environment, correction processing is performed on the heater lighting duty. However, an adjustment mode is provided for performing preliminary data collection for the correction processing.
FIG. 3 shows the detected temperature-time characteristic of the thermistor 2 in the fixing unit 1 in the adjustment mode as described above, and the operation is similar to that of the first embodiment of the present invention. The heater 3 is turned on, the time from when the thermistor detection temperature reaches a certain temperature to a certain temperature is counted, and the heater 3 is turned off.
In the example of FIG. 3, the temperature transition time from 50 ° C. to 100 ° C. is measured. After the heater is turned on, the thermistor detection temperature is monitored by the CPU 5. After detecting 50 ° C., the timer in the CPU 5 is started. Timer stop and heater off at ° C detection. The measured time is t ₂ = ba. Note that the heater output in this adjustment mode needs to have a fixed duty, and the duty is selected such that the transition of the temperature detected by the thermistor 2 becomes a primary straight line as shown in FIG.
Although the time between 50 ° C. and 100 ° C. is measured in FIG. 3, there is no problem as long as the characteristics of the thermistor 2 are such that the temperature-voltage characteristics are linear and have few errors. Time t ₂ which is measured under such setting, the heater output tolerance ± 0 goods measured in advance: the temperature transition time t ₀ at W0, the output W of a heater including a tolerance, the following formula Find more.
W = a · (t ₀ / t ₂ ) · W ₀ (3)
Here, a is an arbitrary constant, but can be obtained as a value specific to the control system by previously measuring the characteristics of the above equation due to variations in the heater output. Thus, the correction coefficient β for the heater lighting duty is given by the following equation.

[0011]
In the present invention, normal heater duty control is multiplied by β obtained by equation (4). When combined with the first embodiment of the present invention, the heater lighting duty is multiplied by the value obtained by equation (5).
α · β = (1 + a · (t ₀ / t ₁ )) · (1 / (a · (t ₀ / t ₂ ))) (5) As for the execution timing of the adjustment mode, the target of variation correction is Considering not only the variation of the output of the heater itself, which is a component, but also the variation of the heat conduction of the fixing unit itself, it is desirable that the adjustment process be performed after the fixing unit is assembled. Of course, when the variation in the heat conduction of the fixing unit itself is small, as shown in the first embodiment of the present invention, it is also possible to collect the data of the parts alone using a jig. However, data collection with the power supply at the rated input (± 0%) is an absolute condition.
Further, the value of the expression (4) or (5) obtained from this data collection is stored in the machine itself and multiplied by the lighting duty during normal control. The data will be input and stored in the memory in the adjustment process at the time of the subsequent burning. It is to be noted that the variation occurs not in the machine but in the component called the heater 3 or the fixing unit 1 used in the machine. Therefore, when the component is replaced or when the fixing unit 1 is replaced, the same as at the factory shipment. Adjustment is required.
Considering the microcomputer load of the present invention, the calculation of the expression (2) is not performed during the operation of the machine, and only the light duty is multiplied by β or α · β obtained by the expression (2) during normal control. Therefore, the load on the microcomputer is very small.
As described above, it is possible to obtain an output equivalent to the heater output of the product having the tolerance of ± 0 without being affected by the variation (within the allowable tolerance) of the heater 3. Therefore, the control system design does not need to consider the component variation. It is easier to use. In addition, the resulting temperature control becomes more accurate, and the fixing temperature can be quickly reached and maintained at the set temperature without causing unnecessary overshoot.
As described above, the correction of the control system element variation such as the temperature detecting element 2 and the heater 3 has been performed. However, since these are managed as part specifications, even if these corrections are not performed, the design is easy. There is no deviation from the output specifications, as long as the performance, the control followability, etc. are not asked.
[0012]
However, the remaining factor is the power supply situation. Even if the design is defined as ±% of the rated input (AC100V in Japan), it is not possible to cover all conditions of the user. There is a problem that a desired heater output cannot be obtained (control is impossible).
The third embodiment of the present invention corrects this, and control for the correction will be described below with reference to FIG. In the third embodiment, similarly to the first and second embodiments, correction processing is performed on the heater lighting duty in order to realize optimum control in the usage environment. However, prior data collection for the correction processing is performed. An adjustment mode for performing is provided.
FIG. 3 shows the temperature-time characteristic of the thermistor 2 detected in the fixing unit 1 in the adjustment mode, as described above. First, as an operation, the heater 3 is turned on, and the temperature of the thermistor detected temperature changes from a certain temperature to a certain temperature. The time until it reaches is counted, and the heater 3 is turned off.
In the example of FIG. 3, the temperature transition time from 50 ° C. to 100 ° C. is measured. After the heater is turned on, the thermistor detection temperature is monitored by the CPU 5. After detecting 50 ° C., the timer in the CPU 5 is started. Timer stop and heater off at ° C detection. The measured time is t ₃ = b−a.
Note that the heater output in this adjustment mode needs to have a fixed duty, and the duty is selected such that the transition of the temperature detected by the thermistor 2 becomes a primary straight line as shown in FIG. Although the time between 50 ° C. and 100 ° C. is measured in FIG. 3, there is no problem as long as the temperature-voltage characteristics are linear and have a small error as the characteristics of the thermistor 2.
[0013]
The time t3 measured under such a setting is based on the previously measured temperature transition time t0 at the rated power supply voltage V0 (100 [V] in Japan). It is obtained from the following equation.
V = a · (t ₀ / t ₃ ) · V ₀ (6)
Here, although a is an arbitrary constant, it can be obtained as a value specific to the control system by previously measuring the characteristics of the above equation due to variations in the power supply voltage. When the power supply voltage is obtained, the heater output under the environment can be obtained. If the heater output at the rated input is W0 and the heater output under the environment is W, the following equation is established.
W = (V / V ₀ ) ^b · W ₀ (7)
Here, b is a value specific to the heater product (data is available from the heater manufacturer)
(6) From (7), the heater lighting duty correction coefficient γ is given by the following equation.

In the present invention, normal heater duty control is multiplied by γ obtained by equation (8). When combined with the first embodiment of the present invention, the heater lighting duty is multiplied by the value obtained by equation (9).
α · β · γ = (1 + a · (t ₀ / t ₁ )) · (1 / (a · (t ₀ / t ₂ ))) · (1 / (a · (t ₀ / t ₃ )) ^b ) (9)
As a result, an output equivalent to the heater output at the rated input can be obtained without being affected by the power supply situation (input voltage) at the place where the device is installed, and the temperature can be quickly and unnecessarily increased without causing overshoot. It is possible to reach and maintain the set temperature. As for the execution timing of the adjustment mode, there is no need to make adjustments at the time of factory shipment, and it is necessary to perform the adjustments at the minimum at the time of installation of the machine, because the object of variation correction is the power supply condition (input voltage) used by the machine. .
If only the machine is installed, during normal control, only the lighting duty is multiplied by γ or α, β, or γ obtained by equation (8) or (9), so that the microcomputer load is small and momentarily. In an environment where the voltage situation changes, it is possible to cope with the problem by collecting data for correction more frequently (every time the power is turned on, etc.) and updating γ.
[0014]
【The invention's effect】
As described above, according to the present invention, in the temperature control of the fixing unit, the variation in the constituent elements is taken into account by correcting the variation in the characteristics of the temperature detecting element, the heater, the power supply, and the like constituting the control system. Therefore, it is possible to reduce the degree of difficulty in designing due to the above, and it is possible to eliminate a problem such as an uncontrollable state when the components exceed the predicted variation. As a result, the temperature control becomes more accurate, and the fixing temperature can be quickly reached to the set temperature without causing unnecessary overshoot, and can be maintained.
[Brief description of the drawings]
FIG. 1 is a block diagram of a fixing control device according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a lighting duty of a heater.
FIG. 3 is a diagram showing a detected temperature-time characteristic of a thermistor at the time of data collection.
[Explanation of symbols]
1 fixing unit 2 temperature detection element (thermistor)
3 heater 5 CPU (control means)

Claims (3)

In a fixing control device that obtains an appropriate heater output by varying the lighting duty of the heater of the fixing unit within a certain control time according to the temperature detected by the temperature detection element, the temperature of the temperature detection element under a predetermined condition -A fixing control device characterized by comprising a control means for obtaining a time characteristic before mechanical assembly and correcting the lighting duty in accordance with the inclination thereof. In a fixing control device that obtains an appropriate heater output by varying the lighting duty of the heater of the fixing unit within a certain control time according to the temperature detected by the temperature detecting element, the temperature-time under a predetermined condition of the heater A fixing control device comprising: a control unit that obtains characteristics in an adjustment process before a machine is assembled or before a factory is shipped after the machine is assembled, and performs control for correcting a lighting duty according to the inclination. In a fixing control device that obtains an appropriate heater output by varying a lighting duty of a heater of a fixing unit within a fixed control time according to a temperature detected by a temperature detecting element, a temperature-time characteristic under a predetermined condition is determined. A fixing unit which is obtained when the machine is installed by the user or when the power is turned on, and which performs control for correcting the lighting duty in accordance with the inclination thereof.

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