JPH0389370A - Image forming device - Google Patents

Abstract

PURPOSE:To independently control the correction of a delay by providing a specialized means correcting the delay of a control system executing fuzzy inference. CONSTITUTION:The device is provided with a means 801 which varies a manipulated variable obtained through fuzzy inference and corrects a delay. In response to the delay of the control system, variance between machines and a secular change, the varying amount of the varying means 801 is changed. Namely, a CPU 801 actually executes fuzzy inference. A ROM 803 stores fuzzy rules and membership functions, while a RAM 805 is used as an operating area for fuzzy inference. Thus, the correction of a delay is independently controlled and correcting amount is readily changed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image forming apparatus such as a copying machine or a laser printer, and more particularly to an image forming apparatus that controls each part of the apparatus using fuzzy inference.

[Conventional technology]

Conventionally, control devices for image forming apparatuses have performed formulaic control based on definitive judgments based on state quantities.

For example, for a fixing device in an image forming apparatus, the temperature of the fixing device is generally detected using a heat-sensitive element such as a thermistor, and a heat source such as a heater is controlled at a predetermined temperature level. For example, if the detected temperature is lower than 180°C, the heater is energized (ON) L, 18
If the detected temperature b is higher than 0° C., the heater is turned off.

In addition, various methods have been devised as improvement measures to reduce fluctuations with respect to the target temperature, such as making the heater ON time variable depending on the current temperature.

[Problems to be Solved by the Invention] However, image forming devices such as copying machines generally have large fluctuations due to the environment, and the relationship between the state quantity and the manipulated variable is often governed by an ambiguous relationship. As the number of factors increases, in most cases it is difficult to formulate control as in the conventional example.

For example, when controlling the temperature of the fixing device, if the state variables such as room temperature, number of copies, document density, type of recording medium (paper f!11), and temperature of the fixing device itself fluctuate, the toner transferred to the transfer paper Although it has been known empirically that the fixing ability for fixing changes in a complex manner, it has been difficult to formulate the relationship between these state variables and manipulated variables. Specifically, the degree of heat dissipation differs depending on the environment and the paper passing/non-passing state, and in conventional control that turns off above a certain temperature and turns on below a certain temperature, temperature change wJ (hereinafter referred to as temperature ripple) ) occurs, it is necessary to set the minimum value of this temperature ripple to a temperature sufficient for fixing the toner on the transfer paper, and therefore it is necessary to set the temperature control setting temperature higher than the ideal state. For this reason, there are problems in that extra power is consumed and it is necessary to use heat-resistant members constituting the fixing device.

Therefore, it is conceivable to calculate the manipulated variable by performing fuzzy inference on the ambiguous relationship between the state quantity and the manipulated variable.

By the way, many control systems for image forming apparatuses determine the manipulated variable to control the controlled object, detect how the manipulated variable of the controlled object changes according to the manipulated variable, and then determine the manipulated variable again. So-called feedback control is performed. Such a feedback control system inevitably involves a delay in the control system, especially in stabilizing the control response.

In fuzzy inference, this delay in the control system may be reflected in the fuzzy rules or membership functions, but with this method alone, delays due to manufacturing variations between state quantity detection means or devices, changes over time, etc. It has been difficult to adequately respond to changes in

The present invention has been developed in view of the above problems, and its purpose is to provide a change means for correcting the delay by changing the amount of operation obtained by fuzzy inference. By responding to the delay in the system and further changing the amount of change by the above-mentioned changing means in response to variations between devices and changes over time, delays in the control system can be appropriately corrected even in a control system using fuzzy inference. An object of the present invention is to provide an image forming apparatus that can perform the following functions.

[Means for Solving the Problems] To this end, the present invention provides a controlled quantity detection means for detecting a controlled quantity of a controlled object disposed in an apparatus, and a controlled quantity detection means that is involved in the controlled quantity detected by the controlled quantity detection means. a state quantity means for obtaining a state quantity to be controlled, a manipulated variable control means for providing a manipulated variable for controlling the controlled quantity, and a function memory for storing a function for defining a fuzzy set for each of the state quantity and the manipulated variable. means, a rule storage means for storing a rule that qualitatively relates the state quantity and the manipulated variable, and according to the rule, the degree to which the state quantity obtained by the state quantity means belongs to the fuzzy set, to the state quantity; A fuzzy set as an inference result of the rule is calculated from the calculated degree and the function related to the manipulated variable, and a representative value of the calculated fuzzy set is set to the manipulated variable control means. an inference means for determining the manipulated variable obtained by the inference means, and a changing means for changing the manipulated variable obtained by the inferring means according to a predetermined rule to become the manipulated variable given by the manipulated variable control means, It is characterized by controlling the controlled object according to the manipulated variable.

[Operation] According to the above configuration, by having a means for changing the manipulated variable calculated by fuzzy inference according to a predetermined rule, correction for delay can be independently controlled, and furthermore, the correction amount can be easily changed. becomes possible.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

1. Control System (Part 1) FIG. 1 shows an embodiment in which the present invention is applied to a fixing device of an image forming apparatus. 801 is a CPU, which will be described later, and actually performs fuzzy inference. 803 is a ROM which will be described later;
Store fuzzy rules and membership functions. 80
Reference numeral 5 denotes a RAM, which will be described later, and is used as a work area when performing fuzzy inference. 807 is a human output unit (Ilo) which will be described later.
), 813 is an A/D converter that converts an analog signal into a digital signal, 163 is a fixing device that heats the conveyed recording medium such as paper to fix the image, and 163-1 applies heat to the fixing roller. Heater, 163-2 is a thermistor that detects the temperature of the fixing heater, 163-3 is cpuao
This is a control circuit that drives the fixing heater according to commands from t.

20 Internal Configuration of Image Forming Apparatus FIG. 2 shows an example of the internal configuration of the image forming apparatus according to this embodiment. In FIG. 2, 100 is a main body that has an image reading function and an image recording function, and 200 is a double-sided processing function that turns the recording medium (paper) over during double-sided recording, and a double-sided processing function that can record multiple times on the same recording medium. 300 is a circulating document feeder (hereinafter referred to as RDF) that automatically feeds documents; 400 is a T-combining device with a stibble (hereinafter referred to as stable sorter);
Each of these 200 to 400 devices has a main body of 100
However, they can be used in any combination.

(^) About the main body (100) In the main body 10G, 101 is the document table glass on which the original is placed, and 103 is the illumination lamp (exposure lamp) that illuminates the original.
, 105, 107, and 109 are scanning reflecting mirrors (scanning mirrors) that change the optical path of the reflected light from the original, respectively.
, 111 is a lens having focusing and variable magnification functions, 113
1 is a fourth reflection cellar (scanning mirror) that changes the optical path; 115 is an optical system motor that drives the optical system;
19 and 121 are sensors, respectively.

131 is a photosensitive drum, 133 is a main motor that drives the photosensitive drum 131, 135 is a high voltage unit, 137 is a blank exposure unit, 139 is a developing device, 141 is a transfer charger, 147 is a separation charger, and 145 is a cleaning device. be.

151 is the upper cassette, 153 is the lower cassette, 171
1 is a manual paper feed slot, 155 and 157 are paper feed rollers, 1
59 is a registration roller. Further, 161 is a conveyor belt that conveys the recording paper on which an image has been recorded to the fixing side, 183 is a fixing device that fixes the conveyed recording paper by heat fixing, and 1
67 is a sensor used for double-sided recording.

The surface of the photosensitive drum 131 described above is made of a seamless photoconductor using a photoconductor and an electric conductor. The motor 133 starts rotating in the direction of the arrow in the figure. Next, when the predetermined rotation control and potential control processing (preprocessing) of the drum 131 are completed, the original placed on the original platen glass 101 is moved to the first scanning mirror 1.
The light reflected from the original is illuminated by an illumination lamp 103 that is integrated with the illumination lamp 103, and the reflected light from the original is sent to the first scanning mirror 105, the second scanning mirror 107, the third scanning mirror 109, and the lens illumination.
, and a fourth scanning mirror 131 to form an image on the drum 131.

The drum 131 is corona charged by a high pressure unit 135. After that, the image illuminated by the illumination lamp 103 (
The original image) is exposed to slit light, and an electrostatic latent image is formed on the drum 131 using a known Carlson process.

Next, the electrostatic latent image on the photosensitive drum 131 is transferred to a developing device 139.
The toner image is developed by a developing roller 140 and visualized as a toner image, and the toner image is transferred onto a transfer paper by a transfer device 141 as described below.

That is, the upper cassette 151 or the lower cassette 1
The transfer paper in 53 or the transfer paper set in the manual paper feed port 171 is fed into the main unit by a paper feed roller 155 or 157, and the leading edge of the latent image is aligned with the leading edge of the transfer paper. Thereafter, the transfer paper passes between the transfer charger 141 and the drum 131 and is discharged to the outside of the main body 100.

After the transfer, the drum 131 continues to rotate, and its surface is cleaned by a cleaning device 145 composed of a cleaning roller and an elastic blade.

(8) About pedestal (200) pedestal z
00 can be separated from the main body 100, and 2000
It has a deck 201 capable of storing sheets of transfer paper and an intermediate tray 203 for double-sided copying. I wrote it, part 200
The lifter 205 of the deck 201 that can accommodate 0 sheets raises the amount of transfer paper (according to the amount) so that the transfer paper always comes into contact with the paper feed roller 207.

Further, 211 is a paper ejection flapper that switches the path between the double-sided recording side or multiplex recording side and the ejection side path; 213;
215 is a conveyance path of the delivery belt, and 217 is an intermediate tray weight for holding down the transfer paper. The transfer paper that has passed through the paper discharge flapper 211 and the transport paths 213 and 215 is turned over and stored in the intermediate tray 203 for double-sided copying. Reference numeral 219 denotes a multiplex flapper for switching between double-sided recording and multiplex recording paths, which is disposed between conveyance paths 213 and 215, and guides the transfer paper to the multiplex recording conveyance path 211 by rotating upward. Reference numeral 223 is a multiple sheet discharge sensor that detects the end of the transfer sheet passing through the multiple flapper 219. A paper feed roller 225 feeds the transfer paper to the drum 131 through a path 227.

229 is a discharge roller that discharges the transfer paper to the outside of the machine.

When performing double-sided recording (duplex copying) or multiplex recording (multiple overlapping copying), first raise the paper ejection flapper 211 of the main body 100 to information, and then move the copied transfer paper to the conveyance path 21 of the bediskle 200.
3, 215 and stored in the intermediate tray 203. At this time, the multiplex flapper 219 is lowered during double-sided recording, and the multiplex flapper 219 is raised during multiplex recording. This intermediate tray 203 can store up to 99 sheets of transfer paper, for example.

The transfer paper stored in the intermediate tray 203 is held down by the intermediate tray weight 217.

During the next back-side recording or multiplex recording, the transfer paper stored in the intermediate tray 203 is moved one by one from the bottom to the path 2 by the action of the paper feed roller 225 and the weight 217.
27 to the registration rollers 159 of the main body 100.

(C) RDF (Recirculating Original Feeder) (300) In the RDF 300, 301 is a stacking tray on which a bundle of originals 302 is set. First, in the case of single-sided originals, the half-moon roller 304 and separation roller 303
The originals are separated one by one from the bottom of the document 02, and the separated originals are conveyed to the exposure position on the platen glass 101 through buses 1 to 11 and stopped by conveying rollers 305 and a full-surface belt 306, and then the copying operation is started. After completing the copying path, the originals on the platen gala 101 are sent to the bus v1■ by the transport large roller 307 through buses III and IV, and roughly returned to the top surface of the original bundle 302 by the paper ejection roller 308.

Reference numeral 309 denotes a recycle lever for detecting document circulation. When the original g4 feeding starts, this recycle lever 309 is placed on top of the document bundle, and the documents are rapidly fed one after another until the trailing edge of the final document passes through the recycle lever 309. One circulation of the original is detected by the original falling onto the stacking tray 301 due to its own weight.

Next, for double-sided originals, the originals are placed on the I%I! bus as described above. After copying is completed, the leading edge of the document is guided to the bus by switching the drivable switching flapper 310, and the leading edge of the document is transferred to the bus If by the transport roller 305.
The document is conveyed and stopped on the platen glass 101 by the full-surface belt 306. In other words, the large transport roller 307
The configuration is such that the rotation of the document causes the document to be reversed along the routes of buses III to ■ to II.

Also, the document bundle 302 is transferred one by one to the bus ■~11~■~■~
It is also possible to count the number of originals by conveying them through V to ■ until one cycle is detected by the recycle lever 309.

(D) Stable sorter (collating device with stable)
(400)? The staple sorter 400 has a fixed non-sort tray 411 with 20 bins, and performs 7 bins.

In the sort mode, the copied sheets are sequentially discharged from the paper feed roller 229 of the main body, enter the conveyance roller 401 of the sorter 400, pass through the conveyance bus 403, and are discharged from the discharge roller 405 to each bin of the tray 412. Each time, a bin shift motor (not shown) moves each bin up and down to complete 7 bins. Also, when the stable mode is selected and a stapling signal is input from the main body 100, the bin shift motor moves one bin While moving the sheets one by one, the stabilizing device 420 stabilizes the sheets in each bin.
aple) and go.

3. Operation Panel FIG. 3 shows an example of the arrangement of the operation panel provided on the main body 100 described above. The operation panel has a key group 600 and a display group 700 as described below.

(A) Regarding the key group (60G) In FIG. 3, 601 is an asterisk (0 key), which is used when the operator (user) is in the setting mode to set the binding substitution and the size of the document frame eraser. 606
is the all reset key, which is pressed to return to standard mode. This key 602 is also pressed when returning from the auto-shutoff state to the standard mode.

605 is a copy start key (copy start key);
Pressed to start copying.

A clear/stop key 604 functions as a clear key during standby and as a stop key during copy recording. This clear key is also used to cancel the set number of copies. Also, press the stop key to interrupt continuous copying. The copying operation stops after the copying at the time when the button is pressed is completed.

Numeric keys 603 are pressed to set the number of copies. It is also used to set the * (asterisk) mode. A memory key 619 allows the user to register frequently used modes. Here, Ml
You can register four modes: ~M4.

Copy density keys 611 and 612 are pressed when manually adjusting the copy density. 613 is the AE key, which is pressed to automatically adjust the copy density according to the density of the original, or to cancel ^E (automatic density adjustment) and switch the density adjustment to manual. Ru. 607 is a cassette selection key, and upper end cassette 1
51. It is pressed when selecting the suspended cassette 153 and lower vapor deck 201. Further, when a document is placed on the RDF 300, ^PS (automatic paper cassette selection) can be selected using this key 607. When ^PS is selected, a cassette of the same size as the original is automatically selected.

Reference numeral 610 is a same size key, which is pressed when making a same size (original size) copy. Reference numeral 618 denotes an auto-magnification key, which is pressed to automatically reduce or enlarge the original image according to the specified transfer paper size.

A double-sided key 626 is pressed when making a double-sided copy from a single-sided original, a double-sided copy from a double-sided original, or a single-sided copy from a double-sided original. A binding key 625 can create a binding margin of a specified length on the left side of the transfer paper. 624 is a photo key, which is pressed when copying a photo original.

Reference numeral 623 is a multiple key, which is pressed when creating (combining) images from two originals on the same side of transfer paper.

Reference numeral 820 denotes a document frame erase key, which is pressed by the user when erasing the frame of a standard size document. At this time, the size of the document is set using the asterisk key 601. Reference numeral 621 denotes a sheet frame erase key, which is pressed to erase the frame of the document according to the cassette size.

Reference numeral 614 is a paper ejecting method selection key for selecting the ejecting method of stapling, sorting, and grouping, and when a stapler is connected to record paper, it is used to select the stable mode and sort mode, or to cancel the selected mode. For sorting, if a tray (sorter) is connected, you can select sort mode and group mode, or cancel the selected mode.

Reference numeral 615 is a paper fold selection key, which selects either Z-fold, which folds recorded paper of ^3 or B4 size into a Z-shaped cross section, or half-fold, which folds recorded paper of 83 or B4 size in half. You can make selections and cancel selections.

(B) Display group (700) &: In Fig. 3, 701 is an LCD that displays information regarding copying.
It is a (liquid crystal) type message display, for example, 5 x 7 dots make up one character, and it has a message display and fixed magnification keys 608, 609. Same size key 610. The copy magnification set using the zoom keys 617 and 618 can be displayed for 40 characters. This display 701 is a transflective liquid crystal display and uses two colors for the backlight. Normally, the green backlight is lit, and the orange backlight is lit when there is an abnormality or when copying is not possible.

Reference numeral 706 denotes a true-size display, which lights up when true-size copying is selected. A color developer display 703 displays the number of copies or a self-diagnosis code.

705 is a used cassette indicator, which indicates the upper cassette 15.
1. Middle cassette 153. Displays whether any of the lower cassettes 201 is selected.

704 is a ^E display, and the AE key 613
Lights up when (automatic density adjustment) is selected.

A preheating indicator 709 lights up when a double-sided copy is made from a double-sided original or a double-sided copy is made from a single-sided original.

Note that when using the RDF300 in standard mode, the settings are 1 copy, density AE mode, automatic paper selection, same size, and 1-sided copying from a 1-sided original.

When the RDF300 is not in use, the standard mode is set to 1 copy, manual density mode, same size, and 1-sided copying from a 1-sided original. The difference between when the RDF 300 is used and when it is not used is determined by whether or not a document is set on the RDF 300.

A power lamp 710 lights up when a power switch (not shown) is turned on.

(Leaving space below) 4. Control system (Part 2) Figure 4 shows an example of the configuration of the control device 800 of the embodiment shown in Figure 's2. For example, a 16-bit microcomputer such as V50 manufactured by NEC Corporation can be used. 803 is a read-only memory (ROM) in which the control procedure (control program) of this embodiment is stored in advance;
O301: (7) Controls each component device stored in ROM803. Reference numeral 805 denotes a random access memory (RAM) which is a main storage device used for storing input data and as a working storage area.

807 is a load such as the main motor 133 with CPt1801
Output signal transfer interface that outputs control signals (
Ilo), 809 is an input signal transfer interface that inputs human input signals such as the image tip sensor 121 and sends them to the CPt18Q1, 811 is a key group 600 and a display group 700
This is an interface for controlling human output. For these interfaces 807, 809, and 811, for example, an input/output circuit board μPD8255 manufactured by NEC Corporation is used.

Note that the display group 700 is each display device shown in FIG. 3, and uses, for example, an LED (light emitting diode) or an LCD (liquid crystal display). Further, the key group 600 is each key shown in FIG. 3, and is configured so that the CPO 301 can know which key has been pressed using a known key matrix. Further, 1630 is a fixing system unit, which includes each part 183, 807, 813, etc. in FIG.

5. Example of Operation Next, an example of the operation of controlling temperature, which is a controlled variable, when the present invention is applied to a fixing device, which is a controlled object of an image forming apparatus, will be described. Examples of state quantities used in temperature control include ■Temperature deviation between the target temperature and current temperature; ■Temperature gradient, which is the amount of temperature change per unit time; and ■Paper surface area of paper passing through the fixing device per unit time.

We use three state quantities.

In addition, as a manipulated variable when performing temperature control, for example, ■Heater 183-1 ON time Use.

FIG. 5 shows membership functions that define fuzzy sets for each of the state quantities and manipulated variables shown in (1) to (2) above. That is, each of the temperature deviation, the temperature gradient after 0 paper, and the heater ON time belongs to at least one of several fuzzy sets defined by the amount and the degree to which the amount belongs (hereinafter referred to as the degree of fitness). For example, in the case of temperature deviation, as shown in FIG. 5(a), NO (Negative Big) temperature deviation has a negative value and a large absolute value.

NS (Negative Small) A negative value with a small absolute value.

20 (Zero) Near 0.

PS (f'ositive Small) is a positive value and has a small absolute value.

PB (Positive Big) It is a positive value and has a large absolute value.

There are five sets, and the suitability of the temperature deviation for each set is expressed as a value from O to 1. In Figure 5, (a) is the membership function of temperature deviation, (b) is the membership function of temperature gradient, (c) is the membership function of paper sheet, and (d) is the membership function of heater. The membership functions of ON time are shown respectively.

To explain more specifically using the case of the temperature deviation shown in Fig. 5(a) e, for example, the degree of fitness for the set zO with a temperature deviation of 0°C is 1,0, and the degree of fit for other sets is O. It means that. Further, for example, it means that the degrees of fitness for sets ZO and PS with a temperature deviation of 145° C. are each 0.5, and the degrees of fit for other sets are O. The same meaning applies to other values of temperature deviation, other state variables, or manipulated variables C.

Note that among the membership functions of each state quantity or manipulated variable shown in Fig. 5, the limits of the sections in which the membership functions indicated by NB, SM, PB, and LA are defined are not clearly indicated in the figure. Of course, it is determined by an appropriate value for control purposes.

It goes without saying that if the ON time is negative in the membership function of the heater ON time shown in FIG. 5(d), it means that the heater is turned off for that period.

Next, a method of calculating the heater ON time, which is a manipulated variable, from each state quantity of the temperature deviation, temperature gradient, and paper area by fuzzy reasoning will be described.

To determine the heater ON time, a fuzzy rule called a rule is used, for example, as shown below.

(Rule 1) If Temperature deviation = PBand Temperature gradient = ZOan
d Paper area = ME then Heater ON time = NS (Rule 2) If Temperature deviation = PSand Temperature gradient = ZOan
d Paper area = ME then Heater ON time = 20 Such fuzzy rules are not set by a mechanical combination of membership functions shown in Figure 5, but are set appropriately according to the controlled object, control environment, etc. FIG. 6 shows an example of the fuzzy rules set in the case of fixing device control with zero lines set to . Here, E is the temperature deviation, DE is the temperature gradient, SP is the paper score, and H is the heater ON time.

FIG. 7 shows an example of calculating the heater ON time by fuzzy reasoning using Rule 1 and Rule 2.

Temperature deviation = x, temperature gradient =
Consider the case where = y2 paper area = 2.

In rule 1, according to the membership function of temperature deviation, human power X is included in the set PR with fitness μ8, and according to the membership function of temperature gradient, input y is included in set
Furthermore, due to the membership function of paper area, input 2 is included in set ME with fitness μ2.

First, according to the antecedent part of the above rule, these μ8゜μ2. μ
Take the logical product of 2, ie, the minimum value in this case. As is clear from the figure, the minimum value obtained is μ, and this value is the degree of fitness of the antecedent part of Rule 1. In order to reflect this degree of fitness in the fuzzy set of the consequent part, A fuzzy set as an inference result of Rule 1 is obtained by performing an AND operation on the fitness μ and the membership function NS of the heater ON time. This inference result is shown as the surrounding area of the shaded area S excluding the bottom.

Similar calculations are performed in Rule 2 to obtain the inference result of the fuzzy set shown as the surrounding area of the shaded area T excluding the base.

After that, in order to obtain the final inference result from the inference results of the individual rules, the logical sum of the set corresponding to the shaded part S and the set corresponding to the shaded part T, in this case the maximum value, is taken, and the bottom of the shaded part U is excluded. A new fuzzy set represented by the surrounding area is obtained as the final inference result.

In actual control, a definite value is required as the output of fuzzy inference, so the center of gravity for the heater ON time of this set is further calculated, and the obtained value is set as the heater ON time obtained by fuzzy inference. do.

The types and number of rules used for the above inference are as follows:
A dominant rule is appropriately determined from among the rules shown in FIG. 6 according to the state quantities, that is, the values of the inputs X, Y, and Z, and the type and number thereof are not limited to the above embodiments. .

Next, the result obtained by fuzzy inference is multiplied by a predetermined coefficient to correct the delay in the control system.In this embodiment, the heater ON time is multiplied by 1 to suppress the influence of the delay.
Multiply by the smaller value. In other words, this allows the heater to be turned on for a shorter time than the result obtained by fuzzy inference.
Or it will be turned off. ' By suppressing and applying the manipulated variable in advance in this way, it is possible to suppress the amount of delay in the control system that appears in the output of the control system.

Furthermore, in embodiments of the invention, this correction factor is R
This is stored in the AM1105, and its initial value is determined by each device at the time of factory shipment, and then the function shown in FIG. The correction coefficient is changed accordingly.

The function in FIG. 8 shows the ratio to the initial setting value.

In other words, the table of relationships shown in FIG. 8 is stored in the ROM 803.
Further, means is provided for accumulating the total heater energization time in the apparatus, and, for example, when the power is turned on, a table is referred to based on the value of the accumulating means, and a correction coefficient at that time is determined.

6. Control Means Next, the control procedure of this embodiment will be explained with reference to FIG. This is an example of a control procedure that is activated by an interrupt every predetermined time (1 hs in this example).

First, it is determined whether t is O based on the heater ON time 1 (1 is set as a value with 1 Gms as a unit) set by the control procedure shown in FIG. 1) If O, the heater is turned on by fuzzy reasoning.
Call a fuzzy inference subroutine to set time t, then return.

On the other hand, if the judgment in step 9-1 is negative, the heater is turned on.
Determine whether time t is positive or negative (step 9-3); if positive, subtract 1 from the value of t (step 9-4); then determine whether heater ON time t is O ( Step 9L
5). If this judgment is O, the fuzzy inference subroutine of step 9-7 is called, and then the process returns. If the judgment in step 9-5 is negative, the heater O
Output the N signal (step 9-6) and return.

If the heater ON time t is negative in step 9-3, the value of t is added by 1 (step 9-8), and then it is determined whether the heater ON time t is O (step 9-9).
). If this judgment is 0, the fuzzy inference subroutine of step 9-7 is called, and then the process returns. If the judgment in step 9-9 is negative, the heater OF
Output the F signal (steps 9-10) and return.

Next, the control procedure of the fuzzy inference subroutine will be explained with reference to the flowchart of FIG.

First, the temperature of the fixing roller is measured by the thermistor 163-2 (Step 1O-1), and the deviation of the current temperature from the target temperature and the temperature gradient, which is the temperature change per unit time, are calculated (Step 1O-2).

Furthermore, the area of paper that passes through the fixing roller per unit time is calculated based on the paper size specified by the user or the RDF 300 (step 1O-3).

After that, for the set fuzzy rules, use the method described above to calculate the fuzzy set of manipulated variables that reflects the degree of fitness for the fuzzy set of state variables, that is, the degree of fitness, according to each fuzzy rule (step 10-4.1O-5). , calculate the maximum value of the fuzzy set obtained by each rule (Step 1O-6), calculate the most likely operation amount by determining the center of gravity (Step 1O-7), and apply the calculation value as described above. Multiply by correction coefficient (step 1O-
8) Set as heater ON time t (Step 1
O-9).

The heater ON time t is used when controlling the heater ON time in the 10m5 interrupt as described above, and the 10m5
Set the value in units of .

7. Other Embodiments Below, another embodiment of the means for changing the manipulated variable calculated by fuzzy inference according to a predetermined rule in order to correct the delay in the control system will be shown.

That is, in this example, a predetermined value is added or subtracted from the result obtained by fuzzy inference.

Here, the influence of the delay is suppressed, that is, subtraction is performed when the calculated value is positive, and addition is performed when the calculated value is negative.

This correction coefficient is stored in the RAM 805 as in the above embodiment, and its value is determined at the time of factory shipment.
Thereafter, the correction coefficient is changed according to the function shown in FIG. 11 to reflect changes in the amount of delay due to changes in the thermistor and the like over time.

Next, the control procedure of this embodiment will be explained with reference to FIG. This is the same control procedure for the 10m5 interrupt as in the previous embodiment.

First, it is determined whether t is 0 or not according to the heater ON time t set in FIG. Calls a subroutine and then returns.

On the other hand, if the judgment in step 12-1 is negative, the heater is turned on.
Determine whether time t is positive or negative (Step 12-3); if positive, subtract 1 from the value of t (Step 12-4);
Thereafter, it is determined whether the heater ON time t is 0 (step 12-5). If this judgment is 0, step 12
-7 fuzzy inference subroutine is called and then returns. If the determination in step 12-5 is negative, a heater ON signal is output (step 12-6);
Return.

If the heater ON time t is negative in step 12-3, the value of t is added by 1 (step 12-8), and it is determined whether the subsequent heater ON time t is O (step 12-8). 9) If this judgment is 0, step 12-
7, and then returns. If the judgment in step 12-9 is negative,
Output a heater OFF signal (step 12-10),
Return.

Next, the control procedure of the fuzzy inference subroutine will be explained with reference to the flowchart of FIG.

First, the temperature of the fixing roller is measured by the thermistor 163-2 (step 13-1), and the deviation of the current temperature from the target temperature and the temperature gradient, which is the temperature change per unit time, are calculated (step 13-2).

Further, the paper area is calculated from the paper size specified by the user or the RDF 300 (step 13-3).

After that, for the set fuzzy rules, use the method described above to calculate the fuzzy set of manipulated variables that reflects the degree of fitness for the fuzzy set of state quantities, that is, the degree of fitness, according to each fuzzy rule (step 13-4.13-5). , calculate the maximum value of the fuzzy set obtained by each rule (step 13-6), and calculate the most likely operation amount by determining the center of gravity (step 13-7).

After the above processing, the calculated value is multiplied by a value smaller than 1 in the embodiment described above, whereas in this embodiment, a predetermined correction coefficient is subtracted or added in order to suppress delay in the control system.

In other words, determine whether the calculated value is positive or negative (Step 13-8)
, if positive, subtract the correction coefficient (Step 13-9)
, if it is negative, add the correction coefficient step 13-10
) and set as the heater ON time t (step 13-
11).

In the above embodiments, the fixing means was used as an example of the control target, but the same control can be applied to charging means, exposure means, transfer means, recording medium feeding means, conveying means, etc. can. For example, the state quantity in the transfer means can be room temperature, humidity, atmospheric pressure, etc., and the operation quantity can be the current applied during charging.

Further, as the state quantity in the exposure means, the potential of the photoreceptor, the developing bias, etc. can be taken, and the operating quantity can be taken as the lighting voltage of the exposure lamp.

In addition, the state quantity in the conveying means can be a conveyance speed, a conveyance speed gradient, humidity, etc., and the operation variable can be a conveyance speed control voltage.

Further, in this embodiment, a fixing device of an electrophotographic copying machine is used as an example, but the image forming apparatus of the present invention is not necessarily limited to an electrophotographic copying machine, but can also be applied to an inkjet printer, a thermal printer, etc. For example, although heater control has been taken as an example of the fixing device in this embodiment, if a means for drying ink recorded in an inkjet printer is used, this can also be said to be a fixing device in a broad sense.

Furthermore, the present invention is applicable to means other than the fixing device, such as optical system drive motor control.

Further, the above-mentioned fuzzy inference algorithm is just an example, and the algorithm may be modified. For example, instead of taking the center of gravity of the maximum area when combining multiple rules,
The value on the horizontal axis relative to the maximum value on the vertical axis may be used as the inference result. Furthermore, the number and content of fuzzy rules can be modified based on empirical rules.

In addition, instead of storing fuzzy sets and rules independently in RAM or ROM and performing fuzzy inference calculations during control, we can look up the pre-inferred results by combining the inputs of all state quantities in advance. Table (R
If it is stored in OM), the output can be easily obtained according to the human power of the state quantity.

Furthermore, the multiplication of the correction coefficients may not be performed by the CPIJ801, but may be performed by providing a separate multiplication circuit.

As explained above, according to the above embodiments of the present invention, image forming apparatuses, which have conventionally been controlled in a fixed manner in response to changes in the environment, can be efficiently controlled by taking into account complex factors. image formation processing can be performed. Furthermore, since the control amount is determined based on a plurality of parameters, even if there is an error in part of the input data, it is possible to prevent a large error from occurring in the control amount.

[Effects of the Invention] As is clear from the above description, according to the present invention, by providing a dedicated means for correcting delay in a control system that performs fuzzy inference, correction for delay can be independently controlled.
The correction amount can be easily changed according to variations between machines or changes over time.

This reduces the power consumption of the image forming apparatus.

Since paper jams, damage, etc. can be kept to a minimum at all times, and process control can be optimally performed, the quality of images can be improved and the reliability of image formation can be significantly improved.

[Brief explanation of drawings]

FIG. 1 is a basic block diagram showing an example of the configuration of a control system when the present invention is applied to a fixing device according to an embodiment of the present invention, and FIG. 2 is an overall internal view of an image forming apparatus according to the present embodiment. 3 is a plan view showing an example of the external configuration of the operation panel of the embodiment; FIG. 4 is a block diagram showing an example of the overall circuit configuration of the control system according to the embodiment; FIG. 5 is a diagram for explaining membership functions that can be adopted in this embodiment, FIG. 6 is an explanatory diagram showing fuzzy rules that can be applied to this embodiment, and FIG. 7 is a diagram for explaining fuzzy inference according to an embodiment of the present invention. Fig. 8 is a diagram showing the ratio of the correction coefficient to the initial setting value according to the present embodiment, and Fig. 9 is a diagram showing the control procedure for the controlled object (heater) according to the present embodiment. A flowchart showing an example; FIG. 10 is a flowchart showing an example of the fuzzy inference procedure according to the present embodiment; FIG. 11 is a diagram showing the ratio of the correction value to the initial setting value according to the second embodiment of the present invention; FIG. 12 shows the controlled object (heater) according to the second embodiment C.
FIG. 13 is a flowchart showing an example of the fuzzy inference procedure according to the second embodiment. DESCRIPTION OF SYMBOLS 100... Image forming apparatus main body, 163... Fixing device, 163-1... Heater, 183-2... Thermistor, 183-3... Drive circuit, 200... Bedistal, 300...・RDF. 400... stable sorter, 600... key carp, 700-... display group, 801... cpu. 803...ROM. 805...RAM. (d) Menno〈Ship group yield - 180-90 0 80 Heater 0 Nllj time (msec) Futonjiime brother °j request 1 failure Fig. 6 Fig. 8 Fig. 9 Fig. 11

Claims (1)

[Scope of Claims] 1) Controlled quantity detection means for detecting a controlled quantity of a controlled object disposed in an apparatus, and a state quantity for obtaining a state quantity related to the controlled quantity detected by the controlled quantity detection means. means, a manipulated variable control means for providing a manipulated variable for controlling the controlled variable; a function storage means for storing a function for defining a fuzzy set for each of the state quantity and the manipulated variable; a rule storage means for storing a rule that qualitatively relates a manipulated variable to a manipulated variable; inference means that calculates a fuzzy set as an inference result of the rule from the determined degree and the function related to the manipulated variable, and obtains a representative value of the calculated fuzzy set as the manipulated variable of the manipulated variable control means; and a changing means for changing the manipulated variable obtained by the inference means according to a predetermined rule to make it the manipulated variable given by the manipulated variable control means, and changing the controlled object according to the manipulated variable obtained by the changing means. An image forming apparatus characterized by controlling. 2) The device is an image forming device that forms a latent image on a photoreceptor, visualizes it with a developing device, and transfers the visible image onto a transfer paper, and the control target includes a charging device, an exposing device, and a developing device. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is at least one of a transfer means, a paper feeding means, a conveying means, a fixing means, and an image forming mode setting means. 3) The image forming apparatus according to claim 1, wherein the changing means multiplies the operation amount obtained by the inference means by a predetermined coefficient. 4) The image forming apparatus according to claim 3, wherein the predetermined coefficient is variable. 5) The image forming apparatus according to claim 4, wherein the coefficient is changed according to a predetermined qualitative rule. 6) The image forming apparatus according to claim 1 or 2, wherein the changing means adds or subtracts a predetermined value to or from the operation amount calculated by the inference means. 7) The image forming apparatus according to claim 6, wherein the predetermined value to be added or subtracted is variable. 8) The image forming apparatus according to claim 7, wherein the predetermined value to be added or subtracted is changed according to a predetermined qualitative rule.