JPH07191572A - Image forming device - Google Patents

Abstract

PURPOSE:To effectively/practically use a transfer material used for the measuring work of the nip area of a fixing device, that is, a transfer material is used for the measurement of the nip area of several times. CONSTITUTION:In the fixing device, a nip part, holding, pressing and carrying the transfer material (paper sheet) by a heating part 42 having a heater 43 as a heating element and a pressure roller 44. A nip area measuring means measures the size of the area of the nip part, to recognize the strength of pressure applied to the transfer material in the nip part. At this time, a process for holding a part of the transfer material in the nip part by the stopping of a carrying means after the transfer paper is fed by a paper feeding roller 18 and a specified time Tn lapses is executed. The specified time Tn is variably set in accordance with the number of the measuring times of the nip area N obtained from a counter by a Tn setting means, to change an image forming region and measure the nip area several times in a transfer material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic copying machine,
The present invention relates to an image forming apparatus such as an electrostatic information recording device.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus such as an electrophotographic copying apparatus, an image forming means for forming a developer image (also referred to as a toner image) corresponding to an original image and an image forming means for forming the image. A transfer unit that transfers the developer image onto a transfer material (generally a sheet), a transport unit that transports the transfer material on which the developer image is formed, and a developer on the transfer material that is transported by the transport unit. Fixing means for fixing the image as a permanent image on the transfer material, temperature detecting means for detecting the fixing temperature of the fixing means on the transfer material, and fixing of the fixing means on the basis of the temperature detected by the temperature detecting means. Some include a temperature control unit that controls the temperature and a mode control unit that sets a plurality of modes related to image formation and controls each of the above units based on each mode.

The fixing means generally comprises a heating roller having a heating element therein, and a pressure roller which cooperates with the heating roller to form a nip portion for carrying the transfer material under a narrow pressure. . The quality for fixing is determined by heat and pressure, and management of this heat is performed by the temperature detecting means and the temperature control means. On the other hand, management of the pressure is performed by adjusting the pressing force of the heating roller and the pressure roller.

The size of the nip area is measured to ascertain the magnitude of pressure applied to the transfer material at the nip. To measure the size of the nip area, select the normal image forming mode, and convey the transfer material on which the solid black image is formed in advance by the conveying means from the paper feeding portion toward the fixing means. , The main power supply is turned off after a part of the transfer material reaches the nip portion, and the transfer material is pulled out from the nip portion after a predetermined time has passed since the main power supply was turned off.
There is a method in which the size of the area of the nip portion is obtained by discharging the sheet to the outside and measuring the size of the glossy gloss portion of the transfer material discharged to the outside. The above is the first conventional example.

Furthermore, a mode for measuring the nip is mounted, and by operating this mode, the transfer material on which a solid black image is formed in advance is conveyed from the paper feeding section toward the fixing means, There is a device that stops the transport motor after a certain time after the leading edge of the transfer material reaches the nip portion, and then drives the transport motor again after a certain time with the transfer material being caught in the nip portion to discharge the paper. is there. (The measuring method after discharged to the outside is the same as the first conventional example.) This is the second conventional example.

[0006]

However, in the first conventional example, it is difficult to predict which part of the transfer paper the glossy part can be formed on, and the transfer paper itself can withstand several measurements. Regardless, the transfer paper is required as many times as the size of the nip portion is measured.

Further, in the second conventional example, since the area on the transfer paper forming the glossy portion is constant in the image forming apparatus equipped with the mode for measuring the nip, the size of the nip portion is also fixed. There was a problem that the transfer paper was required for the number of times to measure, and the paper resources were not effectively used.

Therefore, an object of the present invention is to provide an image forming apparatus which enables effective use of the transfer material used for the work of measuring the nip area.

[0009]

In order to achieve the above object, the present invention provides a sheet feeding means for feeding a transfer material to an image forming means, and an image forming means for forming a developer image corresponding to an original image. A transfer means for transferring the developer image onto a transfer material, a transport means for transporting the transfer material on which the developer image is formed, and a narrow pressure transport for the transfer material sent by the transport means. The nip portion is formed, the fixing means for fixing the developer image on the transfer material as a permanent image on the transfer material, the temperature detecting means for detecting the temperature of the nip portion of the fixing means, and the temperature detecting means. Fixing temperature control means for controlling the temperature of the nip portion of the fixing means at a set temperature based on the detected temperature, mode setting means for setting a mode for nip area measurement, and nip area measurement by the mode setting means Mode against When set, a process of holding the temperature of the fixing unit at the set temperature by the fixing temperature control unit based on the setting of the mode and a predetermined first after the transfer unit feeds the transfer material Process of holding a part of the transfer material in the nip portion by stopping the conveying means after the elapse of time, and ejecting the transfer material after a predetermined second time has elapsed from the holding of the transfer material in the nip portion A mode control means for controlling the operation of the nip area measurement mode including a process and a time setting means for variably setting the predetermined first time according to the number of times of the nip area measurement are provided.

Further, as one aspect of the present invention, preferably, it is arranged at either one of the upstream side position and the downstream side position of the nip portion of the fixing means, and the transfer material is placed at the one position. It has a paper detecting means for detecting the presence, and the time setting means includes a timer means for starting a time count for stopping the conveying means in response to a detection signal of the paper detecting means. You can

The present invention preferably has, as one aspect thereof, counting means for counting the number of times of the nip area measurement and number of times storing means for storing the number of times by the counting means, and the time setting means The predetermined first time can be variably set based on the content of the number-of-times storage means.

Further, preferably, as one aspect thereof, the present invention can further be characterized by further comprising means for enabling the predetermined first time to be manually settable.

Further, the present invention is preferably characterized in that the heating element of the fixing means can change the heating range according to the size of the transfer material.

[0014]

In the image forming apparatus of the present invention, the mode for nip area measurement is set. When the transfer material on which the solid black image has already been fixed is set on the conveying means and the mode for the nip area measurement is executed, the following processes are sequentially performed.

The process of transporting the transfer material toward the fixing means and the presence of the transfer material by the paper detection means are detected, and after a lapse of a predetermined time from this detection, the transfer means is stopped to remove one of the transfer materials. A process of holding the transfer material in the nip portion, and discharging the transfer material after a predetermined time has passed from the holding of the transfer material in the nip portion after a predetermined time from the holding of the transfer material in the nip portion. The processes and are performed automatically in sequence.

A glossy solid black image portion is formed on the transfer material discharged to the outside, and this glossy solid black image portion corresponds to the contact area with the nip portion. The dimension of the nip portion can be known from the plane dimension of the solid black image portion of the transfer material.

After the pressure is adjusted according to the size of the nip portion, the setting time is changed by using the setting means, and the discharged transfer material is used again to measure the nip area. When the mode is executed, the contact area of the transfer material with the nip portion is formed at a place different from the place where the transfer was performed last time. By repeating the above procedure, it is possible to perform the nip area measurement a plurality of times using the same transfer material.

[0018]

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

(Embodiment 1) FIG. 1 is a longitudinal sectional view showing the structure of an image forming apparatus showing an embodiment of the present invention. In FIG. 1, the drive system is divided into a main drive system that drives the paper feed unit, the transport unit, the photoconductor, and the fixing unit, and an optical drive system that drives the optical system that serves as a load. An AC synchronous motor 25 is used as a main drive source, and a stepping motor 26 is used as an optical drive source (including a mechanism for reading an image). The CONT is a controller unit, and includes a drive circuit including a microcomputer Q1, an expansion IC unit Q2, and the like, which will be described later (see FIG. 4).

The extension I of the microcomputer Q1
When the excitation drive method is selectively designated by the C section Q2,
The phase excitation signal applied to each phase A, A *, B, B * of the stepping motor 26 is output. Further, in this embodiment, the excitation drive system is switched to the two types of the two-phase excitation system and the one-two phase excitation system according to the speed information set in the load.

The paper feeding method can be selected from the paper feeding from the cassette 23 and the paper feeding from the multi manual feed section 24. Cassette 23
In the case of feeding from a sheet, a switch group 31 for detecting the presence or absence of the cassette 23 and a switch group 31 for detecting the size of the cassette 23
The state is managed by a switch 37 that detects the presence or absence of paper in the cassette 23, and when an abnormality is detected by the switch, the state is displayed on a display unit described later.

In the case of multi-manual feeding, the state is managed by the switch 33 for detecting the state of the manual feeding portion 24, and when an abnormality is detected, it is displayed on the display portion described later.

The photoreceptor 12 rotates clockwise (in the drawing). The potential charged on the photoconductor 12 by the primary charger 13 is exposed at a photosensitive position, which will be described in detail later, is developed in the developing unit 15, and is transferred to the transfer paper sent from the paper feeding unit in the transfer unit 14. Transfer the image. The photoconductor 12 after transfer is the cleaning unit 3
The process in which the residual toner is removed by 8 and the residual potential is removed by the pre-exposure lamp 16 and the image formation is performed again is repeated. The transfer sheet on which the image has been transferred is placed on the conveyor belt of the conveyor unit 20 and sent to the fixing unit 21.

The fixing unit 21 is composed of three rollers: a drive roller 35, a tension roller 45, and a pressure roller 44. As the heater, a heater 43 in which a resistor is printed on a ceramic substrate is used, and the heater 43 is supported by a heat resistant plastic supporter 42.
Further, a metal stay is attached to the plastic supporter 42 to make it strong. Further, the driving roller 35, the tension roller 45, the heater 43, and the endless film 47.
Is being applied.

A temperature detecting element (thermistor) 41 is attached to the metal stay, and the temperature detecting element 41 is in direct contact with the back surface of the heater 43. Similarly to the temperature detecting element 41, the other temperature detecting element 48 is attached to the metal stay. Heater 43, plastic supporter 4
2. The heater portion composed of a metal stay and the endless film 47 press the pressing roller 44.

The paper that has passed through the fixing unit 21 is discharged from the fixing unit 21 by the paper discharge roller 22 and is stored on the paper discharge tray 39. The paper discharge sensor 34 is a sensor that detects whether or not the transfer paper has normally passed through the fixing unit 21.

The ceramic heater 43 has a plurality of branches, as shown in FIG. 7 described later. The positions of the branches are B4, A4R, and B5 depending on the paper size.
It corresponds to R and A5R. When the size is known by the cassette size detection switch 31, the branch of the heater 43 is switched according to the size.

The drive source of the optical drive system is the stepping motor 26 as described above. As will be described later in detail with reference to FIG. 4, this drive source is configured such that the stepping motor 26 drives a completely different load by operating the drive switching solenoid 27. One load is a unit that configures the exposure lamp 4 and the first mirror 5, the second mirror 6, and the third mirror 7, and the other load is a unit that configures the zoom lens 8. These loads that do not need to be driven synchronously can be driven by a common drive source.

This apparatus uses a stepping motor 26 of an optical drive unit to control the position of the zoom lens 8 and a multi-step magnification selection function by controlling the speed of the lamp systems 4 to 7, and the original placed on the upper surface of the original glass 3. Function to automatically select the density by the optical sensor 40 that detects the reflected light of the, the automatic selection function of the copying magnification (having the communication means) by the connection with the external device (not shown), and the possibility of paper jam or other abnormalities. Memory backup function to store various states when the occurrence of, such as remaining number of sheets, magnification value, abnormal information, etc.
Further, the exposure lamp 4 is driven by the stepping motor 26.
The page continuous shooting function by controlling the position of the developing unit 15, and further, by forming the plural color images by exchanging the developing unit 15, by providing the switch 36 for detecting the exchange of the developing unit 15, this state is provided. It has a function to switch the control by. Next, the operation of this device will be described.

A power cord (not shown) of this apparatus is connected to a predetermined power source. 2 is an operation panel of the present apparatus, which is arranged on the upper surface of the apparatus of FIG. Power switch 51
When you press the 1 side of, power is supplied to the device and
The power indicator lamp 52 is lit and displayed.

When the power is turned on, the display on the operation panel is set as the standard mode as follows. The number display 59 displays 1, the magnification display 67 displays equal magnification, and the automatic density adjustment display 76 A lights up.

Further, the display portion of the start key 56 is displayed in red at the time of initial setting when the power is turned on (moving the lens to the same magnification position, etc.) and during copying, and normally copying operation is possible in green display. Is shown.

The controlled temperature of the fixing unit 21 differs depending on the type of the developing unit 15, and the developing unit 1
The type of the developing unit 15 is discriminated by the switch 36 provided at 5, and the set temperature is switched.

Next, the operation of the optical drive system after the power is turned on will be described. The exposure lamp systems 4 to 7 scan and move the document on the document glass 3 from the left end to the right in FIG. 1 to display the document image on the first mirror 5, the second mirror 6, the third mirror 7, the zoom lens 8, and the fourth lens. Mirror 9, fifth mirror 10, sixth mirror 1
The exposure of the original document on the photoconductor 12 is performed via 1. That is, the starting point of movement is set to the left end. This position is called a home position (HP). H. H.P. A P sensor 29 is provided.

When the power is turned on, the H.V. When the P sensor 29 does not detect the position of the exposure lamp 4, the controller unit CONT by the one-chip microcomputer Q1 shown in FIG. 3 controls the stepping motor 26 to rotate the exposure lamp units 4 to 7 to H.264. Move to P side.

The start of the rotation control of the stepping motor 26 will be described with reference to FIG. 4. First, the drive switching solenoid 27 is in the off state (there is no force b'in the opposite direction to b).
At this time, the switching gear 101 moves in the direction of arrow A in FIG. 4 due to the spring pressure. As a result, the output of the stepping motor 26 is connected to the lamp driving gear 103 via the switching gear 101, and the exposure lamp units 4 to 7 are driven. When this gear is connected, the switching gear 10
When 1 and the lamp driving gear 103 are engaged, the stepping motor 26 is controlled so that the rotation speed is sufficiently lowered.

The exposure lamp units 4 to 7 are H.264. When it is located at P, the stepping motor 26 moves the zoom lens unit 8. As described above, when the power is turned on, the equal magnification value is selected as the standard mode. Further, since the home position (ZHP) of the zoom lens is set to the same size position, the position of the zoom lens 8 when the power is turned on is Z.P. H. It is unknown which side it is with respect to P. Therefore, before the power is turned off, the position of the zoom lens 8 is set to Z. H. It is stored in the non-volatile memory Q3 that stores which one is for P. The operation of driving the zoom lens 8 will be described with reference to FIG.

The drive switching solenoid 27 is turned on.
As a result, the tip of the plunger of the solenoid 27 moves in the b direction and rotates about the fulcrum. Therefore, the switching gear 101 moves in the b direction against the spring force by the force of b'in the direction opposite to b. By this movement, the fitting of the switching gear 101 and the lamp driving gear 103 is released. Further, when the tip of the plunger moves in the b direction, the switching gear 101 is fitted with the lens driving gear 105. The rotation control when the gears are fitted is the same as described above.

The zoom lens 8 is a Z. H. The lens position is set to Z.P. with the P sensor (not shown) as a reference position. H. When it is at the position of the P sensor, it is 1 × and the Z. H. Optical system H.P. When it is on the P side, it is an enlargement, and when it is on the contrary, it is a reduction. The position control for the zoom lens 8 is performed within the range of the enlargement ratio of 200% to the reduction ratio of 50%.

At the start of driving the zoom lens, Z.
H. The operation can be understood as follows depending on the state of P.

1) Z. H. When the position of the zoom lens 8 is detected by the P sensor 1) -1 Once the zoom lens 8 is moved to the optical system H.P. P. Move to P. H. The P. sensor is brought out within a range not detected and stopped, 1) -2. H. P
It moves for a certain distance from the time when the sensor detects it and then stops.

2) Z. H. When the position of the zoom lens 8 is not detected by the P sensor 2) The moving direction of the zoom lens 8 (ZHP) is determined by the position of the zoom lens 8 stored in the nonvolatile memory Q3.
(Sensor side) and move the zoom lens. H. When the lens is moved by a predetermined distance from the time when it is detected by the P sensor and stopped, and when it is moved to the left, the zoom lens 8 is once moved to the optical system H. P. Move to P. H.
The P.P sensor does not detect and stops, and the zoom lens 8 is moved to the right and Z. H. From the time when the P sensor detects it, it moves for a predetermined distance and then stops.

The above operation is the control necessary for preventing the setting position error due to the back crash of the gears.

Thereafter, the drive switching solenoid 27 is turned off. As a result, as described above, the switching gear 1
01 moves in a direction in which the lamp drive gear 103 is fitted. However, it is necessary to rotate the switching gear 101 as described above in order to smoothly perform the fitting. At this point, the exposure lamp units 4 to 7 are H.264. It is located on the P sensor 29. Therefore, the stepping motor 2
6 rotates the exposure lamp units 4 to 7 in the direction of moving them to the right in FIG. As a result, the exposure lamp units 4 to 7 are H.264. The rotation is stopped at the time when it is disengaged from the P sensor 29 (the fitting of the switching gear 101 and the lamp drive gear 103 is completed), and the lamp drive gear 103 is rotated in the opposite direction again to make the H.264. After detecting the P sensor 29, the exposure lamp units 4 to 7 are stopped at predetermined positions.

Upon completion of the initial operation of the optical drive system described above, the preparation for the copying operation of this apparatus is completed.

Next, the copying operation by feeding the paper from the cassette 23 will be described. When the copy start key 56 in FIG. 2 is pressed by the operator, the transfer paper size data by the input signal of the switch group 31 for detecting the cassette size, the number data set by the number key 56, the magnification selection keys 61, 62, The copying operation is started based on the magnification data of 64, 65, 66 and the data of other various mode selecting means.

When the copy start key 56 is received,
The display is changed from green to red, and the mode switching keys such as the numeral keys 54 and the magnification keys 61, 62, 64, 65 and 66 are prohibited. The main drive motor 25 starts to rotate, and the driving force is transmitted to the paper feed roller 18, the photoconductor 12, the transport unit 20, the fixing unit 21, and the like.

A sheet feeding solenoid (not shown) operates 0.5 seconds (seconds) after the start of rotation of the main drive motor (AC synchronous motor) 25.
As shown in FIG.
The transfer paper inside is sent out in the direction of the paper feed roller 18. The transfer paper feed amount of the paper feed roller 17 is controlled by the cassette size data. That is, when the transfer paper is larger than the predetermined value, the feed amount is increased. When the transfer paper reaches the paper feed / feed roller 18, the transfer paper is
It is sent to the registration roller 19 by and is stopped when it reaches. A manual feed switch 33 installed between the paper feed roller 18 and the registration roller 19 detects the transfer state of the transfer paper.

At a predetermined timing until the transfer paper is sent on the paper feed path and reaches the registration roller 19,
The document scanning of the exposure lamp units 4 to 7 is permitted. At this time, the exposure lamp 4 is H.264. It is in a position detected by the P sensor 29. More specifically, during the initial operation or the backward movement of the copy operation, the H. The exposure lamp unit is stopped at a position moved backward from the position where the output of the P sensor 29 is detected by a distance corresponding to the selection magnification at that time.

When the document scanning is started, the pulse motor (stepping motor) 26, which is the optical system driving source, drives pulses corresponding to the selected magnification value in the direction in which the exposure lamp units 4 to 7 advance (to the right). The pulse rate gradually increases until the rate is reached (called slow-up control). That is, the moving speed of the exposure lamp units 4 to 7 is gradually accelerated to reach the target speed. Although not particularly shown, the pulse motor drive circuit of the present apparatus adopts a constant current control system and has a configuration in which the drive current value can be switched among a plurality of steps (two steps in the embodiment) (shown in FIG. 3). It is selected by the output signal of the output port PB4 of the optical drive pulse motor control signals).

Generally, the characteristics of the pulse motor are such that the pull-in torque decreases as the pulse rate increases. Therefore, a means for switching the constant current set value is provided,
Switch the current value as necessary. In this device, the set current is lowered during a relatively low pulse rate from the start of movement, and the set current value is controlled to increase when the speed exceeds a predetermined value. The control for lowering the set current value is performed again with the passage of. This is mainly intended to prevent noise, temperature rise, and step-out phenomenon of the pulse motor.

Next, a method for forming a margin at the leading edge of the image and a method for aligning the leading edge with the transfer sheet will be described with reference to FIG.

As a means for preventing toner adhesion in the non-image area, a charge eliminating means using a light source such as an LED (light emitting diode) lamp or a fuse lamp is generally used. In this apparatus, a grid provided in the primary charging unit 13 is used. 13a
The same effect is realized by controlling the voltage value of. This is due to downsizing of the device
This is an important method in the present situation where it is difficult to arrange a plurality of members around the.

The distance L5 between the exposure point and the grid is H.264. P
Since it cannot be arranged sufficiently shorter than the distance L2 between the sensor 29 and the document abutting position, in order to form a 2 mm margin at the leading edge of the document, a predetermined time corresponding to the magnification selection value has elapsed from the start of the movement of the exposure lamp 4. The grid 13a is switched from the L level to a predetermined voltage. That is, when the voltage of the grid (grid voltage) is at the L level, the photoconductor 12 is not charged with the electric potential, so that the toner image is not formed and the image is formed from the timing when the voltage is switched to the predetermined voltage. As a result, a margin is formed at the leading edge of the image.

Next, regarding alignment of the leading edge of the image with the transfer paper, the distance L3 between the exposure point and the transfer portion is set to the registration roller 1
9 is shorter than the distance L4 between the transfer portion and the transfer portion. Therefore, before the image at the front end of the original is actually exposed on the photoconductor 12, it is necessary to re-feed the transfer paper waiting on the registration roller 19 and feed it toward the transfer unit.

In the present apparatus, when the exposure lamp 4 starts moving and reaches the target speed, the exposure lamp unit is still in the H.V. It is detected by the P sensor 29. The exposure lamp unit is H.264. A value obtained by dividing the value of the exposure L2 + 2 mm by the speed according to the selected magnification from the timing when the P sensor 29 has passed is the H. It is the time required for the exposure lamp 4 to reach the end portion of the white plate after passing the P sensor 29, and this time is defined as x.

A value obtained by subtracting the time required for the image at the exposure point of the photoconductor 12 to reach the transfer portion from the time from the start of re-feeding by the registration rollers 19 until the transfer sheet reaches the transfer portion. Is defined as y, and the time required to feed the transfer paper by 2 mm to this y (2 mm / 100 mm / s = 0.02 se
c ... Transport speed = 100 mm / s) is added. The above numerical values are calculated by the following formula.

[0058]

## EQU00001 ## x- (y + 0.02) = Z (sec) (1) That is, the exposure lamp 4 is a H. When the registration roller 19 is operated at the timing when the value Z of the above formula (1) has passed from the time when the P sensor 29 is passed and re-feeding is executed, a transfer sheet having a margin of 2 mm formed according to the selected magnification An image is obtained.

As for the scanning distance of the exposure lamp units 4 to 7, the exposure lamp unit moves a predetermined distance according to the cassette size data, magnification data, etc., and when the target position is reached, the pulse rate is gradually reduced (slow down control). Called),
After stopping, H. This is the distance for moving backward by the slow-up control and the low-speed control in the P sensor 29 direction. And H. P
At the time when the sensor 29 is detected, slowdown control for stopping the exposure lamp unit at a position corresponding to the selected magnification is performed, and the exposure lamp units 4 to 7 are stopped.

Further, control of the document scanning distance is also executed by the trailing edge detection signal of the transfer sheet. The control operation described above is controlled by the one-chip microcomputer Q1 shown in FIG. Q1 in FIG. 3 shows a one-chip microcomputer with built-in ROM and RAM. FIG. 6 shows the basic structure of the program of the microcomputer Q1. It should be noted that the detailed description of FIG. 6 is well known and is not a characteristic part of the present invention, and therefore will be omitted.

Next, the control of the exposure lamp 4 will be described. A halogen lamp is used as the exposure lamp, and the AC regulator is phase-controlled by a lamp regulator (not shown) so that the lighting voltage of the halogen lamp is constant. This lamp regulator has a lamp lighting voltage Vc even if the AC input voltage changes and the power supply frequency changes.
Is controlled to be constant. Therefore, the trigger signal of the exposure lamp for phase control is output from this lamp regulator and input to the controller CONT of FIG. The trigger signal of the exposure lamp is always output regardless of whether the lamp 4 is turned on.

Further, a zero-cross generation circuit (not shown)
Zero cross signal created in
Input to T and connect to the microcomputer Q1 therein. By monitoring the time Tc from the zero-cross signal to the trigger signal of the exposure lamp, it is possible to read the change in the input voltage.

In this image forming apparatus, the lamp lighting voltage Vc is adjusted so that the illuminance on the surface of the photosensitive drum 12 is constant for each apparatus, and the lamp lighting voltage Vc is stored in the nonvolatile memory Q3. . Based on the stored lamp lighting voltage Vc and the time Tc from the zero cross signal to the trigger signal of the exposure lamp 4, from the following equations (2) to (4), A
It is possible to obtain the C input voltage Emax.

[0064]

[Equation 2]

[0065]

[Equation 3] Erms ² / Vc ² = 1 / {1-2 × Tc / T + sin (4πTc / T) / 2π} (4) Time Tc from the zero-cross signal to the exposure lamp trigger signal by the above equation (4) By entering the Erm
It is possible to obtain s ² / Vc ² and obtain the AC input voltage Erms from the lamp lighting voltage Vc stored in the nonvolatile memory Q3. In this embodiment, the microcomputer Q1
From the table stored in the internal ROM to Tm to Erm ²
/ Vc ² is required.

Next, the control of the heater 43 will be described. The heater 43 is a heater in which a resistor is printed on the ceramic substrate as described above, and has a very excellent thermal response. Therefore, in the normal ON / OFF control, the ripple becomes large with respect to the temperature control temperature, or the electric power is excessively applied to the heater 43, and the heater is damaged. Therefore, in this heater control, power control is performed so that a constant power is applied. In addition, in order to reduce the ripple, control is performed to switch the power according to the temperature detected by the thermistor.

Further, the power control of the heater will be described in detail. The power control of the heater 43 is also performed by the phase control similarly to the control of the exposure lamp 4 described above. Since the heater is a purely resistive load, the power W is

[0068]

## EQU4 ## W = V _H ² / R (5) V _H : voltage applied to heater R: resistance value of heater

Since the resistance value R of the heater is stored in the non-volatile memory Q3 for each image forming apparatus and the electric power supplied to the heater 43 is known in advance, the voltage V _H applied to the heater 43 can be calculated by the above equation. From (5)

[0070]

Equation 5] ^{_{V H 2 = R × W ...}} (6) Further, the voltage V _H to give the expression of the effective voltage to the heater,

[0071]

[Equation 6]

V _H ² is calculated from the above equation (6) to obtain the above equation (4)
From the equation (9), the time T _H from the zero-cross signal to the trigger signal to the heater can be obtained by calculating Erms ² from the above and calculating Erms ² / V _H ² . In this embodiment, the table is used to determine Erms ² / V.
We are looking for T _H from _H ² .

The electric power of the heater 43 is controlled by the algorithm as described above. The power control of the heater 43 is always performed during the copying period so that the temperature of the heater 43 is constant.

Next, the control circuit of the heater 43 of the fixing unit 21 will be described. The portion of the heater 43 is as shown in FIG. 7, and the portion of the resistor in which 43a is printed is
In this figure, an example is shown in which five branches are made from the middle.
The energization to each branch is controlled according to the paper size. The reason is that in the heater 43, the paper passing portion (the portion through which the paper passes)
Since the temperature of the non-paper passing part (the part where the paper does not pass) becomes too high compared to the temperature of, the resistor is branched from the non-paper passing part and the branching part is moved to the front (non-paper passing part). This is to reduce the total electric power applied and lower the temperature. Of course, in the case of branch energization, the total electric power applied is controlled so that the temperature of the paper passing portion becomes constant. The energization of each branch according to the paper size will be described with reference to FIG.

FIG. 8 shows the electric wiring of the heater 43 of the fixing unit 21. Here, T1 to T6 are terminals of the heater, of which T1 to T5 are the controller unit CO
Relays RL1 to RL5 set A according to the signal from NT
It is designed to be connected to the neutral N of the C power supply. The triac TRA1 functions as a switch between the terminal T6 and the hot H of the AC power supply according to the signal from the controller CONT.

As an actual operation, for example, when using B4 size copy paper, the controller CONT is HIGH (high level) on the bases of the transistors Q3 and Q4.
Outputs a signal and turns on the relays RL3 and RL4
Then, connect the branch end connected to it and the AC-N line. Then, by applying a signal to turn on the triac TRA1, the resistors connected to the terminals T3 and T4 are energized.

The controller CONT turns on / off the triac TRA1 so that the voltage (effective value voltage) applied to the heater 43 becomes a predetermined constant voltage (performed by phase control). Further, based on a signal from a temperature detection element (thermistor) 41 attached to the heater 43, energization is controlled so that the temperature of the heater becomes a predetermined temperature. It is to be noted that FIG. 9 shows ON / OFF states of energization of the branch end portion of the heater according to the size of each copy.

Next, consideration will be given to suppressing ripple (overshoot) when the temperature of the heater 43 of the fixing unit 21 is kept at a predetermined temperature. Conventionally, the maximum electric power to be applied is applied until the temperature reaches a predetermined temperature, and when the temperature exceeds the predetermined temperature is detected, the power supply to the heater 43 is turned off, and when the temperature becomes lower than the predetermined temperature, the maximum power is supplied again. Was being supplied. Therefore, there was a large variation in temperature due to overshoot. Therefore, in the present embodiment, the applied power (voltage) P is changed as follows according to the difference between the temperature detected by the temperature detection element 41 attached to the heater 43 and the predetermined temperature.

[0079]

Equation 7] _{P = K P (T G -T} R) ... (10) K P: proportional constant [W / ℃] T _G: target temperature T _R: by changing the detected temperature proportional constant K _P, various You can control. If the proportional constant K _P is reduced, temperature control with less overshoot can be performed, but the response speed becomes slower. On the contrary, if the proportional constant K _P is increased,
The response speed becomes faster, but the overshoot becomes larger. Since the electric power P is changed according to the paper size (that is, how to energize the branch), the optimum value of the proportional constant K _P is obtained in advance by experiments. Next, the nip area measurement mode will be described with reference to the configuration diagrams of FIGS. 1 and 2 and the flowchart of FIG.

The solid black paper is set in advance in the multi-manual feeding section 24 or the cassette 23 (S1). By pressing a service switch (not shown) on the controller unit, the service mode is entered and "[3]" is displayed on the number display 59.

By pressing the sort key 57, the AC
The synchronous motor (main drive motor) 25 starts to drive, and the solid black copy paper stored in the manual feed section 24 or the cassette 23 is fed by the paper feed roller 18 and the paper feed roller 17 (S3). . Almost at the same time, the control for raising the heater 43 to the normal fixing temperature is started.

Simultaneously with the start of feeding, the grid of the primary charger is controlled so that the latent image does not get on the photosensitive member 12. The fed copy paper passes through the photoconductor 12 and is then sent to the fixing unit 21 by the carrying unit 20.

The copy paper passes through the nip portion, and the paper discharge sensor 3
When the position 4 is reached, the paper discharge sensor 34 outputs a copy paper detection signal (S4). The timer is started based on the output of this detection signal (S5), and the motor 25 continues to be driven until the time Tn set by the timer setting means described later elapses. After the time is over, A
The driving of the C synchronous motor 25 is stopped (S
6).

When the stop time of the AC synchronous motor 25 reaches a predetermined time (S7), the AC synchronous motor 25 is driven again and the copy sheet is discharged to the outside (S8).

After the sheet is discharged, the AC synchronous motor 25
Is stopped again, and the power supply to the heater 43 is stopped (S9).

The copy sheet discharged to the outside is observed by the operator, and a solid black image portion having gloss on the copy sheet is found. The plane dimension of the solid black image portion is measured by the operator, and it is determined whether the pressure at the nip portion is proper or not based on the counted value of the measurement.

The timer setting time Tn indicated by Tn in step S5 of FIG. 10 is a parameter for determining which part of the transfer paper (copy paper) the glossy part showing the nip width is specifically generated. FIG. 11 schematically shows the image forming position on the transfer material to which the developer (toner) generated by the image forming apparatus in this embodiment is attached. A for transfer paper
Use 3 sizes. When the timer setting time Tn = 0,
Due to the distance from the nip portion of the fixing unit 21 to the paper discharge sensor 34 and the time from when the motor 25 stops until the transfer paper actually stops, about 7 cm from the front end of the paper.
A glossy portion indicating the nip width is generated in the area. When the value of Tn is sequentially increased, the place where the nip is generated retracts from the conveyance direction by that amount. In this embodiment, a unit time tn is calculated and a multiple thereof is used to calculate Tn.

For example, t when the unit width is desired to be 5 cm
The calculation formula for n is that the transport speed of the copying machine as the image forming apparatus in this embodiment is 100 mm / sec.

[0089]

## EQU8 ## It can be obtained by tn = 5 (cm) × 10/100 (mm / sec) (sec) = 0.5 sec (11). Here, if N is the number of nip area measurements,

[0090]

By setting Tn = N × tn (12), it is possible to shift the position of the glossy portion on the transfer paper for each number of measurements, and even if the same transfer paper is used, the glossy portion on the transfer paper Do not overlap. Therefore, the nip area measurement can be performed several times with one sheet of transfer paper. The value of N is stored in the non-volatile memory Q3 and is cleared to 0 as necessary.

Further, referring to FIGS. 12 and 13, the above T
A method of setting n will be described. When the nip area measurement means 401 completes the nip area measurement (S12), the counter 402 counts up (S13). Upon receiving this count-up, the Tn setting means 403 causes
Tn in the next nip area measurement is calculated by the above formula (11).
And calculated based on the above equation (12) and set (S1
4).

When the nip area measurement mode is performed again, the nip area measurement control is performed based on the previously calculated Tn.

When the set number of times clear mode is entered (S1
5), the counter reset means 404, the counter 402
N (the number of measurements) is cleared to 0 (S16). This clear mode will not be described in detail, but this mode is executed when a new solid black transfer paper is used.

(Second Embodiment) In the image forming apparatus described in the first embodiment of the present invention, the Tn setting means 4 shown in FIG. 12 is used.
03 may have a mode means for setting Tn regardless of the number of times N of measurement. By inputting the number corresponding to the number of times of measurement N by the setting mode means, the glossy portion for measuring the nip area can be formed at an arbitrary position among the positions on the transfer paper shown in the first embodiment.

(Third Embodiment) In the image forming apparatus according to the first embodiment of the present invention, N as an initial value may be set not only to 0 but to an arbitrary number. Further, when N reaches a certain number, N may be automatically returned to 0 and may be controlled to count up again. It is also possible to issue an alarm when N is automatically returned to 0. As described above, the transfer paper in use can be used, and the transfer paper can be further saved.

[0096]

As described above, according to the image forming apparatus of the present invention, the paper resources required for measuring the nip area can be saved.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing the configuration of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view showing an operation panel of the apparatus shown in FIG.

3 is a block diagram showing a one-chip microcomputer Q1 of a control unit of the apparatus shown in FIG.

4 is a front view showing a rotation control mechanism near a stepping motor of the apparatus of FIG.

FIG. 5 is a schematic diagram illustrating a method of forming a margin of an image leading end portion and a leading end alignment direction of a transfer sheet according to an embodiment of the present invention.

6 is a flowchart showing a basic configuration of a program of the microcomputer Q1 of FIG.

7 is an enlarged plan view showing a heater of a fixing unit of the apparatus shown in FIG.

8 is a circuit diagram showing electric wiring of a heater portion of the fixing unit shown in FIG.

FIG. 9 is a diagram illustrating switching control of energization of a branch end portion of a heater according to a size of each copy according to an embodiment of the present invention.

FIG. 10 is a flowchart showing an operation procedure of a nip area measurement mode according to an embodiment of the present invention.

FIG. 11 is a diagram showing an image forming position on a transfer material to which a developer generated by the image forming apparatus according to the embodiment of the present invention is applied.

FIG. 12 is a block diagram showing a configuration of a nip area measurement controller according to an embodiment of the present invention.

FIG. 13 is a flowchart showing a processing procedure of the Tn setting means of FIG. 12 according to an embodiment of the present invention.

[Explanation of symbols]

3 Original glass 4 Exposure lamp 12 Photoconductor 14 Transfer unit 15 Developing unit 21 Fixing unit 22 Paper ejection roller 23 Cassette 25 AC synchronous motor (main drive motor) 26 Stepping motor (pulse motor) 27 Drive switching solenoid 29 H. P sensor 30 Z. H. P sensor 31 Switch group (including cassette size detection switch) 34 Paper ejection sensor 35 Drive roller 39 Paper ejection tray 40 Optical sensor 41 Temperature detection sensor (thermistor) 42 Plastic supporter 43 Heater 44 Pressure roller 45 Tension roller 48 Temperature detection element 51 Power switch CONT controller Q1 microcomputer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Teruo Mitsui Inventor Teruo Mitsui 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Takahiro Takahiro 3-30-2 Shimomaruko, Ota-ku, Tokyo Kya Non non corporation

Claims (5)

[Claims] 1. A paper feeding means for feeding a transfer material to an image forming means, an image forming means for forming a developer image corresponding to an original image, and a transfer means for transferring the developer image to the transfer material. Conveying means for conveying the transfer material on which the developer image is formed, and a nip portion for narrow-pressure conveying the transfer material fed by the conveying means are formed. The fixing means for fixing the image on the transfer material as a permanent image, the temperature detecting means for detecting the temperature of the nip portion of the fixing means, and the temperature of the nip portion of the fixing means based on the temperature detected by the temperature detecting means. The fixing temperature control means for controlling to maintain the set temperature, the mode setting means for setting the mode for the nip area measurement, and the mode for the nip area measurement set by the mode setting means, based on the setting of the mode, The above The process of holding the temperature of the fixing unit at a preset temperature by the deposition temperature control unit, and the transfer member being stopped after a lapse of a predetermined first time after the paper feeding unit feeds the transfer member. Of holding a part of the transfer material in the nip portion and holding the transfer material in the nip portion
Mode control means for controlling the operation of the nip area measurement mode consisting of a process of discharging the transfer material after the passage of time, and a time setting means for variably setting the predetermined first time according to the number of times the nip area is measured. An image forming apparatus comprising: 2. A paper detection unit arranged at either one of the upstream side position and the downstream side position of the nip portion of the fixing unit and detecting the presence of the transfer material at the one position. The image forming apparatus according to claim 1, wherein the time setting means includes a timer means for starting a time count for stopping the conveying means in response to a detection signal of the paper detecting means. 3. A counting means for counting the number of times of the nip area measurement, and a number of times storing means for storing the number of times by the counting means, wherein the time setting means is based on the contents of the number of times storing means. The image forming apparatus according to claim 1 or 2, wherein the first time of is set variably. 4. The image forming apparatus according to claim 1, further comprising means for manually setting the predetermined first time. 5. The image forming apparatus according to claim 1, wherein the heating element of the fixing unit can change the heating range according to the size of the transfer material.