JP2002082496A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device with which an excellent image can be formed by selecting the image forming condition or various kinds of mode corresponding to various kinds of recording material to be used. SOLUTION: This device is equipped with a recording material characteristic measuring means for measuring the characteristic of the recording material by performing the test-printing of the recording material at least once, and a control means for allowing the recording material characteristic measuring means to measure the characteristic of the recording material and controlling the image forming condition of an image forming means at the time of forming an image for forming the image on the recording material based on the measured characteristic of the recording material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine having a function of forming an image on a recording medium such as a sheet.
The present invention relates to an image forming apparatus such as a printer or a facsimile machine.

[0002]

2. Description of the Related Art FIG. 16 is a schematic sectional view showing an example of an image forming apparatus 100 utilizing a conventional electrophotographic method.

In FIG. 16, a photosensitive drum 101 as an image carrier rotates in the direction of arrow A,
The photosensitive drum 10 is uniformly and uniformly charged to about -600 V by a charging roller 102 serving as a charging means for charging the photosensitive drum 10.
1 is a laser beam 10 as an exposure means for writing an electrostatic latent image.
3, an electrostatic latent image of about -150 V is formed on the surface. This electrostatic latent image is visualized by the developing sleeve 106 carrying the toner T of the developing device 104 of the developing means. The developing sleeve 106 is connected to the photosensitive drum 101 by about 2
A predetermined AC voltage having a gap of 00 to 300 μm and being superimposed on a DC voltage of about −500 V is applied. Here, the recording material P is supplied from the paper feed cassette 107 to the paper feed roller 11.
2, the recording material P passes through the path B, and is introduced into the transfer nip portion Nt of the photosensitive drum 101 and the transfer roller 108 as a contact transfer member of the transfer means at a predetermined timing, and is applied to the transfer roller 108. About +1
The toner image on the photosensitive drum 101 is transferred onto the recording material P by a transfer voltage of up to +5 KV.

After the transfer process, the transfer residual toner on the photosensitive drum 101 is removed from the photosensitive drum 101 by a cleaning blade 109 and the cleaning device 11
Collected to 0. After the cleaning step, the photosensitive drum 101 is again subjected to an image forming process (charging → exposure → development →
By repeating (transfer → cleaning), an unfixed toner image is formed on the recording material P.

On the other hand, the recording material P carrying the unfixed toner image after the transfer process is neutralized by a static elimination needle 112 which is a static elimination means to which a ground or a bias is applied, and further a fixing nip of a heating device 111 which is a heating means. The toner image is introduced into the portion Nk, and is pressurized and heated, so that the toner image is permanently fixed on the recording material P.

As a toner image heating device represented by the heating device 111, a contact heating system such as a heat roller heating system or a film heating system has been widely used. In such a device, an electric current is applied to a halogen lamp or a heating resistor to generate heat, and the heat is generated through a fixing roller or a fixing film.
The toner image is being heated.

However, the heating device of the heating roller heating system is
Since the heat capacity of the fixing roller is large, a considerable waiting time (wait time) is required after the power is turned on until the fixing roller rises to a predetermined temperature. Even when the image forming apparatus has started up to a predetermined temperature, the heat source (halogen lamp, etc.) of the fixing roller is energized during standby of the image forming apparatus so that the image forming apparatus can output an image immediately at any time. Therefore, there is a problem that energy consumption is large because control is required to maintain the temperature.

Therefore, a heating element is formed by providing a pattern of a heating resistor on a ceramic substrate such as alumina (Al ₂ O ₃ ) or aluminum nitride (AlN), and this is heated to generate a recording material through a thin film. JP-A-63-3
13182.

[0009] Unlike the heating device of the heat roller heating type, such a heating device of the film heating type uses a heating element of a low heat capacity or a thin fixing film which heats up quickly. , So you can reduce your wait time (quick start, on demand)
Since there is no need to energize and heat the heating element during standby of the image forming apparatus, there is an advantage that power can be saved.

In the single-sided printing in the conventional image forming apparatus 100, as shown in FIG. 16, the recording material P discharged from the heating device 111 passes through the path C, and the printing surface faces upward and the printing material P is directed to the side of the image forming apparatus. The face-up (FU) sheet to be discharged and the recording material P discharged from the heating device 111 pass through the path D as shown in FIG. There is face-down (FD) discharge.

In the automatic double-sided printing in the conventional image forming apparatus 100, first, as shown in FIG.
Is taken out of the paper supply cassette 107 by the paper supply roller 112, passes through the path B, and
The recording material P is introduced into the transfer nip Nt between the transfer roller 108 and the photosensitive drum 101, and the toner image on the photosensitive drum 101 is transferred onto the recording material P.

The recording material P carrying the unfixed toner image is introduced into the fixing nip Nk of the heating device 111,
The toner image is fixed on the recording material P by being pressed and heated, and one side (the first side) of the recording material P is printed.

Next, the recording material P discharged from the heating device 111 and printed on the first side passes through the path E by the double-sided conveyance unit 201 and is reversed (switched back) by the reversing unit 202. . At this time, a configuration in which a part of the recording material P is exposed outside the image forming apparatus 100 may be employed.

The reversed recording material P passes through the path F, joins the path B again, is introduced into the transfer nip Nt of the transfer roller 108 and the photosensitive drum 101 at a predetermined timing, and the toner on the photosensitive drum 101 The image is 2 of the recording material P
The recording material P, which has been transferred onto the surface (the back surface of the first surface) and carries the unfixed toner image, is transferred to the fixing nip portion N of the heating device 111.
Then, the toner image is fixed to the second surface of the recording material P by being pressed and heated. The recording material P printed on both sides (first side / second side) passes through a path C or a path D and is discharged out of the image forming apparatus to obtain an automatic double-sided printed image.

[0015]

In recent years, copiers and printers utilizing electrophotography have become widespread throughout the world.
Further, recording material characteristics such as surface properties / resistance value / material (raw material) / thickness / strength of the recording material have also become diverse.
It is expected that the types of new recording materials will continue to increase in the future.

Under such circumstances, in the image forming apparatus, a standard recording material is specified. However, it is required to form a clear image on various recording materials other than the standard recording material.

However, there are many problems due to various recording materials, and problems due to various recording material characteristics are described below.

(1) Resistance value of recording material <at the time of transfer> In the case of a high-resistance recording material, toner cannot be retained on the recording material due to insufficient transfer current or transfer voltage, and toner scatters to a non-printing portion. An explosion splatter phenomenon occurs.

In a contact transfer type image forming apparatus, when the charging polarity of the photosensitive drum and the polarity of the transfer bias are opposite to each other, the transfer current and the transfer voltage are excessively applied to the toner in the low-resistance recording material. Charge it,
The toner is re-transferred from the recording material onto the photosensitive drum, causing white spots in the halftone image, or the "penetration" phenomenon in which the transfer current penetrates the recording material and remains as memory on the photosensitive drum. A "sandy" phenomenon in which black spots occur in a halftone image as charging failure after one round occurs. In a high-humidity environment, especially when the recording material resistance value is reduced, the above-mentioned “penetration” occurs on the entire surface, and the “transfer-loss” phenomenon occurs in which the density of the entire image is reduced.

As the above countermeasures, high-resistance recording material mode / normal recording material mode / low-resistance recording material mode / special recording material (O
It has been proposed to provide an HT mode or the like to change the transfer current value or the transfer voltage value.

(2) Recording material thickness / recording material temperature <at the time of heating> When the recording material is thick or the recording material is cooled in a low temperature environment, the amount of heat supplied to the toner and the recording material by the heating device Due to the shortage, the fixing strength (fixing property) at which the toner is fixed to the recording material is reduced.

In the case where the recording material is thin or the recording material is warm during automatic duplex printing, the heating device supplies excessive heat to the toner and the recording material. And the toner adheres to the fixing film, and a "hot offset" phenomenon occurs in which the recording material is stained after one rotation of the fixing roller or the fixing film.

As a countermeasure, the thin recording material mode / normal recording
Recording material mode / Thick recording material mode / Special recording material (OHT etc.)
Mode / automatic double-sided printing mode, etc.
/ Paper feed time / paper time / paper heating temperature can be changed
Proposed (eg, thin recording material = 60 g / m^TwoLess than
Recording material, ordinary recording material = 60 g / m^TwoMore than 105g / m ^Two
Recording material less than thick recording material = 105 g / m^TwoMore recording materials
Is).

(3) Recording material thickness / recording material resistance value / recording material curl amount (during separation of photosensitive drum) When the recording material is thin (weak in strength) and high in resistance,
The leading end of the recording material after transfer does not separate from the photosensitive drum, and the photosensitive material and the recording material are electrostatically attracted to the photosensitive drum, causing a phenomenon of “defective leading end photosensitive drum separation” in which the recording material rushes into the cleaning device. . When the recording material is thin and stiff, the separation performance is lower than the curvature separation from the photosensitive drum. Furthermore, if the recording material has high resistance, it is easy to be charged.
The separation performance is deteriorated because it is easily adsorbed to the photosensitive drum. Further, in the case of automatic double-sided printing, the recording material once passed through the heating device is curled, and when the curl is curled in the direction of the photosensitive drum, the separating performance from the photosensitive drum is further reduced.

In addition, the separation failure of the photosensitive drum at the trailing end of the recording material is caused by the fact that the trailing edge of the recording material collides with the cleaning device without disengaging from the photosensitive drum at the trailing end of the recording material and disturbs the image. The "end splash" phenomenon occurs. If the trailing edge is severe, the paper sticks to the bottom of the cleaning device, and the unfixed toner image rubs against the bottom of the cleaning device to disturb the image.

As the above countermeasures, a thin recording material mode / normal recording material mode / special recording material (OHT, etc.) mode / automatic double-sided printing mode, etc. are provided. In a static elimination needle bias application system that applies a current or a voltage having a polarity opposite to that of a current or a transfer voltage, it has been proposed to change a static elimination needle current value or a static elimination needle voltage value.

However, if the current value of the static elimination needle or the voltage value of the static elimination needle is too large, the transfer current flows out to the static elimination needle, and if the transfer current and the transfer voltage become insufficient, or if the recording material is excessively neutralized, the recording material is left on the recording material. The toner cannot be held, and in the downstream heating device, the toner adheres to the fixing roller or the fixing film, and an "electrostatic offset" phenomenon occurs in which the recording material is soiled after one rotation of the fixing roller or the fixing film.

However, in the conventional image forming apparatus in which various modes as described above are selected by the user, the user selects an incorrect mode selection or selects the mode of the recording material to be used. There was trouble to do.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and an object thereof is to select an image forming condition or various modes according to various recording materials to be used. To provide an image forming apparatus capable of obtaining a good image.

[0030]

According to the present invention, in order to achieve the above object, a toner image obtained by developing an electrostatic latent image formed on an image carrier is formed on a recording material. In an image forming apparatus provided with an image forming means for transferring and fixing the recording material, a recording material characteristic measuring means for test-printing at least one recording material and measuring the characteristics of the recording material; Controlling the image forming condition of the image forming unit at the time of image formation for forming an image on the recording material based on the measured characteristics of the recording material. .

A recording material characteristic storage means for storing the recording material characteristic measured by the recording material characteristic measuring means, wherein the control means, based on the recording material characteristic stored in the recording material characteristic storage means, It is also preferable to control image forming conditions of the image forming means during image formation.

A recording material stacking means which is detachably provided from the apparatus main body and which stacks recording materials fed one by one to the image forming means by a feeding means; It is also preferable to be provided in the material loading means.

The recording material stacking means includes a plurality of recording material stacking means, and the recording material characteristic storing means includes a plurality of recording material stacking means, or a plurality of feeding means for conveying a recording material from the recording material stacking means to the image forming means. It is also preferable to provide a plurality of paper outlets.

A communication means capable of communicating with an external device is provided. The characteristic of the recording material measured by the recording material characteristic measuring means is communicated to the external device by the communication means, and the recording material provided in the external device is provided. The characteristic of the recording material is stored by a characteristic storage unit, and the control unit controls the image forming of the image forming unit during image formation based on the characteristic of the recording material stored in the recording material characteristic storage unit of the external device. It is also preferable to control the conditions.

Preferably, the characteristics of the recording material measured by the recording material characteristic measuring means are a resistance value of the recording material, a thickness of the recording material, a temperature of the recording material, or a size of the recording material.

The toner image formed on the image bearing member is inserted into the transfer nip portion between the image bearing member and the image bearing member when a transfer bias is applied, and the toner image formed on the image bearing member is transferred to the recording material. A transfer unit for transferring, wherein the recording material characteristic measuring unit measures a current value or a voltage value applied to the transfer unit when the recording material is sandwiched in the transfer nip portion and when the recording material is not sandwiched. And the control unit detects a transfer bias value to be applied to the transfer unit during image formation based on the resistance value of the recording material detected by the recording material characteristic measurement unit. It is also preferable to control.

A transfer means provided in the image forming means for transferring a toner image formed on the image carrier by applying a transfer bias to a recording material; and a recording material provided upstream of the transfer means. A recording material transporting member that conveys the recording material, or a static elimination unit that is provided downstream of the transfer unit and discharges the recording material, and the recording material characteristic measurement unit is configured to transfer the recording material from the transfer unit. The current value flowing through the recording material conveying member or the static elimination means is measured to detect the resistance value of the recording material, and the control means controls the resistance value of the recording material detected by the recording material characteristic measuring means. It is also preferable to control the transfer bias value applied to the transfer unit at the time of image formation based on the above.

A heating means provided in the image forming means for fixing the toner image transferred onto the recording material by inserting the recording material into a fixing nip portion between the image forming means and the pressure member; The measuring unit measures a temperature change amount of the heating unit, which is changed by the recording material inserted into the fixing nip portion, by a temperature detection unit, compares the temperature change amount with a predetermined comparison value, and The thickness or the temperature of the recording material is detected, and the control unit controls the heating during image formation based on the thickness or the temperature of the recording material detected by the recording material characteristic measuring unit. It is also suitable to control the heating mode or heating temperature of the means.

It is also preferable that the control means changes the electric power supplied to the heating means when the temperature change amount is measured by the recording material characteristic measuring means.

The control means may control whether the recording material is inserted into the fixing nip portion of the heating means to which the first power is supplied, or immediately before the recording material is inserted into the leading end region.
It is also preferable to change the power supplied to the heating means to the second power.

After the first area of the recording material inserted into the fixing nip passes through the fixing nip,
Changing the power supplied to the heating means, and the recording material characteristic measuring means measuring the temperature change amount in the first area and in the second area upstream of the first area, respectively. Are also suitable.

The control means detects the temperature of the pressure member by measuring the amount of temperature change of the heating means when the recording material is not passed through the fixing nip by the recording material characteristic measuring means. , Based on the detected temperature of the pressure member,
It is also preferable to change the heating temperature of the heating means and the predetermined comparison value.

The control means detects the temperature of the heating means at the start of the test printing by the temperature detecting means, and detects the temperature of the heating means based on the detected temperature of the heating means at the start of the test printing. It is also preferable to change the heating temperature and the predetermined comparison value.

The heating means is preferably of a film heating type.

The control means controls a bias value applied to the static elimination means at the time of image formation based on the resistance of the recording material detected by the recording material characteristic measuring means or the thickness of the recording material. Are also suitable.

The recording material on which the image is formed on the first surface by the image forming means is inverted, and the second material on the back surface of the first surface is reversed.
A double-sided image forming mechanism for forming an image on the surface of the recording medium by the image forming means, and
And the characteristics of the recording material on the second surface are measured, and during the double-sided image formation, under the respective image forming conditions controlled by the control means based on the characteristics of the recording material on the first and second surfaces. It is also preferable to form an image on the first and second surfaces.

The control means causes the recording material characteristic measuring means to measure the characteristics of the recording material when the power of the apparatus main body is turned on or when the recording material stacking means is mounted on the apparatus main body. If the characteristic of the recording material thus obtained is different from the characteristic of the recording material stored in the recording material characteristic storage unit, the recording material characteristic stored in the recording material characteristic storage unit is rewritten, or It is also preferable to display on the display means provided in the apparatus main body that the characteristics of the recording material are different, or to display on the display means provided in the external apparatus by communicating with the external device by the communication means. is there.

A recording material size detecting means for detecting the size of the recording material conveyed to the image forming means at the time of image formation is provided, and the control means controls the size of the recording material detected by the recording material size detecting means. If it is determined that the recording material characteristic is different from the recording material characteristic stored by the recording material characteristic storage unit, the recording material characteristic measuring unit performs at least one test print of the recording material to measure the characteristic of the recording material. The characteristic of the recording material stored in the storage means is rewritten, or the fact that the characteristic of the recording material is different is displayed by a display means provided in the apparatus main body, or the communication means communicates with the external device by the communication means. It is also preferable to display on a display means provided in the external device.

[0049]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the dimensions of the components described in this embodiment,
The material, shape, and relative arrangement thereof should be appropriately changed depending on the configuration of the apparatus to which the invention is applied and various conditions, and are not intended to limit the scope of the invention to the following embodiments. Note that the same components as those described in the section of the related art are denoted by the same reference numerals, and description thereof is omitted.

(Embodiment 1) An image forming apparatus according to Embodiment 1 will be described with reference to FIG.

The present embodiment is provided with a recording material characteristic measuring mode in which at least one recording material is test printed by the recording material characteristic measuring means and the recording material characteristic is measured, and the recording material measured in the recording material characteristic measuring mode is provided. By characteristic data,
It is configured to determine and select image forming conditions, and further includes a rewritable recording material characteristic storage unit that stores recording material characteristics measured in the recording material characteristic measurement mode, and stores the recording material characteristics in the recording material characteristic storage unit. The image forming conditions are determined and selected based on the recording material characteristic data thus obtained.

In the recording material characteristic measurement mode, the recording material whose image is to be output by the image forming means in the image forming apparatus is
At least one test print was made and the recording material was
Paper feed cassette 1 as a recording material loading means having a loading section
07, a transfer nip Nt of a photosensitive drum 101 as an image carrier and a transfer roller 108 as a transfer unit, and a heating device 1 as a heating unit according to a path B.
This is a mode in which the characteristics of the recording material are measured while the recording material is ejected through the path C or the path D through the fixing nip portion Nk of No. 11, and is controlled by the control unit.

The recording material characteristic measurement mode is used when the power is turned on or when a recording material is placed in a paper supply port of a paper supply cassette or the like (when replenishing paper or when the paper supply cassette is attached to the apparatus main body).
Alternatively, the image forming apparatus may perform the processing automatically, or the user may manually perform the operation by designating the paper feed port from the operation panel of the image forming apparatus main body. Alternatively, the user may manually specify a paper feed port from a computer as an external device directly connected to the image forming apparatus or connected to the image forming apparatus via a network.

The recording material characteristic storage means for storing the recording material characteristic data measured in the recording material characteristic measurement mode may be provided on an electric substrate inside the image forming apparatus main body or separately provided in a paper feed cassette. But it's fine. Further, a recording material characteristic storage unit may be provided inside the computer.

When the image forming apparatus has a plurality of paper feed cassettes and a plurality of paper feed ports, a plurality of recording material characteristic storage means are provided for each paper feed port on the electric board inside the image forming apparatus main body. Is preferred. By having the recording material characteristic data for each paper feed port, even if there is a different recording material in each paper feed port, the image forming conditions of the image forming apparatus can be optimized correspondingly.

Further, by separately providing a recording material characteristic storing means in the paper feeding cassette, when another different paper feeding cassette is mounted on the image forming apparatus, the recording material characteristic storing means provided in the paper feeding cassette is provided. Since the recording material characteristics are stored in the recording material characteristics storage device, the image forming apparatus can read and set appropriate image forming conditions corresponding to the recording material characteristics stored in the recording material characteristic storage means of the sheet cassette. Is more preferable.

Further, by providing the recording material characteristic storage means inside the computer, there is no need to provide the recording material characteristic storage means in the image forming apparatus, so that there is an advantage that the cost of the image forming apparatus can be reduced.

In this embodiment, a configuration for detecting a recording material resistance value as a recording material characteristic in an image forming apparatus having a contact transfer unit will be described.

FIG. 1 is a schematic configuration diagram of the transfer unit. The photosensitive drum 101 is made of a grounded conductive material 20 such as aluminum.
1 is coated with a photosensitive layer 202. Transfer roller 108
Is a medium resistance (approximately 10 ⁵ -10 ¹¹⁾
Ω · cm) of an elastic layer 204 such as foamed EPDM.

When a transfer roller is used as the contact transfer unit, the transfer bias applied to the transfer roller during printing is controlled by an image forming apparatus control unit (CPU) 3 as a control unit.
02 and constant current control for applying a constant current or constant voltage control for applying a constant voltage,
Different control schemes are used.

In the case of a high-resistance recording material, the toner T cannot be held on the recording material P in the printing portion due to a shortage of the transfer current or the transfer voltage, and the toner T scatters in the non-printing portion. The phenomenon occurs.

In the case of a low-resistance recording material, the toner T is charged to the opposite polarity due to a transfer current or an excessive transfer voltage, and the toner T is re-transferred from the recording material P onto the photosensitive drum 101, and is "Punch-through" phenomenon in which white spots occur in a tone image, or transfer current passes through a recording material,
It remains as a memory on the photosensitive drum 101, and after one round of the photosensitive drum 101, a "sand background" phenomenon occurs in which black spots occur in a non-printed portion or a halftone image as charging failure. Further, in a high-humidity environment or the like, particularly when the recording material resistance value is reduced, the "penetration" occurs on the entire surface, and the "transfer loss" phenomenon in which the density of the entire image is reduced occurs.

The high-resistance recording material and the low-resistance recording material described above are specific to various types and thicknesses of the recording material, and even if the high-resistance recording material contains moisture in a high-humidity environment,
There are various types such as those that become low-resistance recording materials.

Therefore, in the recording material characteristic measurement mode, the resistance value of the recording material is detected, and the constant current value of the constant current control or the constant voltage value of the constant voltage control is changed according to the recording material resistance value. By doing so, it is possible to obtain a good image even on the recording material P having various resistance values.

In FIG. 1, the recording material characteristic measurement mode is automatically or manually performed, and a test printing of one recording material P is performed. The measurement of the recording material resistance value is performed such that when the recording material P is inserted into the transfer nip portion Nt of the photosensitive drum 101 and the transfer roller 108, a predetermined constant voltage value is applied to the transfer roller 108 by the transfer bias power supply 301 controlled by the CPU 302. Is applied, and the value of the current flowing from the transfer roller 108 to the photosensitive drum 101 via the recording material P is measured. Alternatively, constant current control for applying a predetermined constant current value to the transfer roller 108 is performed.
A voltage value applied to the transfer roller 108 is measured in accordance with a predetermined constant current value flowing through the photosensitive drum 101 via the control unit 102.

The recording material resistance value is estimated from the measured current value or voltage value, and the recording material resistance value is stored in the recording material characteristic storage means 601 as recording material characteristic data.

At the time of printing, the recording material characteristic storage means 60
Based on the recording material resistance value, which is the recording material characteristic data stored in No. 1, a constant current value for constant current control or a constant voltage value for constant voltage control at the time of printing by the CPU 302 using a predetermined table or a predetermined calculation formula. Or correct a predetermined constant current value or constant voltage value to apply an appropriate transfer current value or transfer voltage value to the transfer roller 108 in accordance with the recording material P to be printed, so that there is no image defect. A clear image can be obtained.

Actually, in an image forming apparatus of A4 length 8 ppm (process speed 50 mm / sec), transfer roller constant voltage control at the time of printing, at the time of test printing in the recording material characteristic measuring mode, first, when manufacturing the resistance value of the transfer roller 108 In response to variations, environmental fluctuations, and endurance fluctuations,
When the transfer nip portion Nt is not passing the paper, the applied voltage value V0 of the transfer roller 108 is measured by the constant current control of +2.0 μA, and the resistance value of the transfer roller 108 is measured. Next, the voltage V1 applied to the transfer roller 108 by the constant current control of +2.0 μA is measured in the same manner when the transfer nip Nt is passed.

A recording material resistance value Vk = | V0−V1 | is calculated from the measured V0 and V1, and the recording material resistance value Vk is calculated as follows.
The recording material characteristic data is stored in the recording material characteristic storage unit 601 as the recording material characteristic data.

During printing for outputting an image, the transfer roller 108 is again controlled by a constant current control of +2.0 μA when the transfer nip Nt is not passed in response to the manufacturing variation of the resistance value of the transfer roller 108, environmental fluctuations, and durability fluctuations. 108
Is measured, and the resistance value of the transfer roller 108 is measured. Next, the CPU 302 uses the recording material resistance value Vk, which is the recording material characteristic data stored in the recording material characteristic storage unit 601, to calculate the constant voltage value at the time of printing at the transfer nip portion Nt at the time of printing according to the following equation (A). Determine Vt,
A voltage Vt is applied to the transfer roller 108 to transfer the toner image on the photosensitive drum 101 onto the recording material P.

[0071]

Vt = a · V2 + b + (cVk + d) (where a, b, c, and d are predetermined constants including zero) (cVk + d) in the above formula is the recording material resistance value This is the corresponding correction term.

In this embodiment, a = 1.0, b = 1.
Assuming that 1, c = 1.0 and d = −1.1, the image transferred by the transfer bias determined by the above formula (A) is “explosion splattered” under various recording materials and various environments. , "Penetration", "sandy ground", "transfer loss" and the like, and a clear image without image defects could be obtained.

In the recording material characteristic measurement mode, the recording material size (width and length of the recording material) is automatically input, or recording is manually performed from the operation panel of the image forming apparatus or a computer connected to the image forming apparatus. By inputting the material size, the recording material resistance can be measured more precisely.

The automatic detection of the recording material size is performed by a recording material size detection sensor (not shown) arranged between the paper supply port of the image forming apparatus and the transfer nip portion Nt, and a recording material arrangement regulating plate (not shown) of the paper supply cassette 107. This is detected by a recording material size detecting means such as a recording material size detection sensor (not shown) for detecting the position.

At the time of printing an image, for example, the recording material size is monitored, and if a recording material having a recording material characteristic different from the recording material characteristic data stored in the recording material characteristic storage means 601 is detected, a warning is issued, or By newly performing the recording material characteristic measurement mode and rewriting the recording material characteristic data stored in the recording material characteristic storage unit 601, a clear image can be always obtained.

Further, when the power of the image forming apparatus is turned on or when the recording material is supplied, the recording material characteristic measurement mode is automatically or manually performed, so that the recording material characteristic data different from the recording material characteristic data stored in the recording material characteristic storage means 601 is obtained. Is detected, or a recording material characteristic storage unit 601 is issued.
By rewriting the recording material characteristic data stored in the printer, it is possible to always obtain a clear image.

In the above description, the transfer bias control based on the calculation formula in the constant voltage control during printing has been described as an actual configuration. However, the constant current control during printing, the method of setting the transfer bias by a predetermined table, and the plural calculation formulas It can also be applied to systems with

In the above description, the transfer roller has been described.
Other contact transfer means such as a transfer blade, a transfer brush, and a transfer belt may be used.

(Second Embodiment) FIGS. 2 to 4 show a second embodiment. In the first embodiment, the configuration in which the recording material resistance value is detected at the transfer nip portion Nt has been described. In the present embodiment, however, the pair of registration rollers 701 disposed upstream of the transfer nip portion Nt, or static elimination as static elimination means This relates to a configuration in which a recording material resistance value is detected by a needle 112. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 2, a pair of registration rollers 701 for regulating the leading end position of the recording material and conveying the recording material P to the transfer nip Nt at a predetermined timing are arranged upstream of the transfer nip Nt. I have. Registration roller pair 7
01 is a grounded conductive upper resist roller 7 made of iron or the like.
02 and a core 703a such as iron for transporting the recording material P.
Lower registration roller 7 having an elastic rubber layer 703b coated thereon
It consists of 03. The upper registration roller 702 and the lower registration roller 703 are driven and rotated by driving means (not shown) at the ends. The distance between the nip portion of the registration roller pair 701 and the transfer nip portion Nt is set smaller than the minimum size recording material.

The detection of the recording material resistance value is performed by a test print in the recording material characteristic measurement mode. When the recording material P passes through the transfer nip portion Nt, a predetermined transfer bias (constant voltage or constant current) is applied to the transfer roller 108 from the transfer bias power supply 301. )
To detect the current value flowing from the transfer nip portion Nk to the pair of registration rollers 701 (the upper registration roller 702 in the present embodiment) via the recording material P. The value of the current flowing from the registration roller pair 701 to the ground decreases as the recording material resistance increases, and increases as the recording material resistance decreases. When the current value of the registration roller pair 701 is detected, the CPU 302 estimates the recording material resistance value and stores it in the recording material characteristic storage unit 601.

At the time of printing, the recording material characteristic storage means 60
Based on the recording material resistance value, which is the recording material characteristic data stored in No. 1, a constant current value or a constant current value of constant current control applied to the transfer roller 108 at the time of printing is determined by the CPU 302 by a predetermined table or a predetermined calculation formula. By determining a constant voltage value for voltage control or correcting a predetermined constant current value or constant voltage value, an appropriate transfer current or transfer voltage is applied to the transfer roller 108 in accordance with the recording material P to be printed. A clear image without image defects can be obtained.

In the above description, the current value flowing from the registration roller pair 701 to the ground is detected. However, a resistor (not shown) is arranged between the registration roller pair 701 and the ground.
A configuration for detecting a voltage value generated in the resistor may be used. In the above description, the pair of registration rollers 701 is used. However, the configuration is not limited to the pair of registration rollers 701, and a configuration may be used in which a current value flowing into an arbitrary conductive roller is measured.

As shown in FIG. 3, the transfer nip N
Downstream of t, a grounded discharging needle 1 for discharging the recording material P is grounded.
12 are arranged.

At this time, when the recording material P passes through the transfer nip Nt by the test print in the recording material characteristic measurement mode, the recording material resistance value is detected by a transfer bias power supply 301 from the transfer bias power supply 301 to a predetermined transfer bias (constant voltage). Or a constant current), and detects a current value flowing from the transfer nip portion Nk to the charge eliminating needle 112 via the recording material P. The value of the current flowing from the static elimination needle 112 to the ground decreases as the recording material resistance increases, and increases as the recording material resistance decreases. The CPU 302 detects the current value of the static elimination needle 112, estimates the recording material resistance value, and stores it in the recording material characteristic storage unit 601.

At the time of printing, the recording material characteristic storage means 60
Based on the recording material resistance value, which is the recording material characteristic data stored in No. 1, a constant current value or a constant current value of constant current control applied to the transfer roller 108 at the time of printing is determined by the CPU 302 by a predetermined table or a predetermined calculation formula. By determining a constant voltage value for voltage control or correcting a predetermined constant current value or constant voltage value, an appropriate transfer current or transfer voltage is applied to the transfer roller 108 in accordance with the recording material P to be printed. A clear image without image defects can be obtained.

In the above description, the current value flowing from the static elimination needle 112 to the ground is detected. However, a configuration in which a resistor (not shown) is disposed between the static elimination needle 112 and the ground and the voltage value generated at the resistance is detected. good.

As shown in FIG. 4, in a static elimination needle bias applying system for applying a voltage having a polarity opposite to that of the transfer bias applied to the transfer roller 108 by the static elimination needle bias power supply 801 to the static elimination needle 112 in the same manner as described above. Even in a configuration in which the current value flowing into the static elimination needle 112 via the recording material is detected, the recording material resistance value can be similarly detected, and the current value flowing into the static elimination needle 112 is larger in the static elimination needle bias application system. Therefore, there is an advantage that the detection accuracy is improved.

In the above description, the case of the static elimination needle has been described, but any other neutralization means such as a neutralization brush or a neutralization corona may be used as long as the static elimination means.

(Embodiment 3) Embodiment 3 according to the present invention will be described with reference to FIGS. Note that the same components as those in the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 5 is a schematic sectional view of the film heating device 401. Reference numeral 403 denotes an endless heat-resistant film, which is outer-circularly mounted on a heater support 404 which is a guide member of the film 403 including the heater 405. The inner peripheral length of the endless heat-resistant film 403 is
3 mm from the outer peripheral length of the heater support 404 including
Therefore, the film 403 has a loose outer ring with a margin around the heater support 404 with a margin.

The film 403 is used to enhance heat transfer, reduce heat capacity, and improve quick start.
The film thickness is 100 μm or less, preferably 10 to 50
Single layer of PTFE, PFA, FEP with heat resistance of about μm, or polyimide, polyamideimide, PEE
PTFE, PFA, on the outer surface of K, PES, PPS, etc.
A composite film coated with FEP or the like can be used. In this embodiment, the outer peripheral surface of the polyimide is made of PTFE.
Was used.

Reference numeral 405 denotes a heating element, and an electric resistance material such as Ag / Pd (silver palladium) is screen-printed to a thickness of 10 μm and a width of 1 to 3 mm as a heating resistor 405 b on the surface of a ceramic substrate 405 a of alumina or the like. And a glass or fluororesin is coated thereon as a protective layer 405d.

Reference numeral 402 denotes a film 4 between the heating element 405 and the heating element 405.
03, a fixing nip portion Nk is formed, and the film 40
3, a pressure roller of a rotating body as a pressure member for driving the motor 3, which is composed of a core bar 402a and a heat-resistant rubber 402b having good releasability, such as silicon rubber, and a drive (not shown) from the end of the core bar 402a. Drive by means.

As shown in FIG. 6, the heating temperature is controlled by a thermistor which is a temperature detecting element as a temperature detecting means provided in the sheet passing area on the opposite side (back side) of the heating resistor 405b on the heating element 405. A / D conversion of the output of 405c (502)
Then, the power is supplied to the heating element 405 by controlling the phase of the AC voltage applied to the heating resistor 405b of the heating element 405 by the triac 501 based on the information, and controlling the power supply to the heating element 405 based on the wave number control or the like. ing.

FIG. 7 shows an example of heating temperature control during continuous printing.

If the main body has not been operated for 5 to 6 hours,
The heating device has cooled to about room temperature. The temperature of the heating element 405, which is the thermistor output at that time, indicates a [° C.]. When printing is started, the temperature of the heating element 405 starts to rise, and the heating element 405 is necessary for permanently fixing the unfixed toner image to the recording material P before the leading end of the recording material P enters the fixing nip portion Nk. Heating temperature, for example 190
Temperature rises to ° C.

When the recording material P passes through the fixing nip portion Nk, the heating element 405 is controlled so that the heating temperature is maintained at 190 ° C., and the rear end of the recording material P passes through the fixing nip portion Nk. (C), the sheet-to-sheet heating temperature at c to d during (d) when the leading end of the next recording material P is inserted into the fixing nip portion Nk is controlled to, for example, 170 ° C. of “heating temperature−20 deg”. You. Then, the temperature is again controlled to 190 ° C. during the time d to J when the leading end of the second recording material P enters the fixing nip portion Nk (d) and the rear end passes through the fixing nip portion Nk (J).

As described above, in the conventional heating control, the heating amount is controlled by “heating temperature ≧ inter-sheet heating temperature”. When the heating temperature is controlled by “heating temperature <inter-sheet heating temperature”, the amount of heat is deprived by the recording material P. Since the temperature inside the image forming apparatus rises, the toner T in the developing device 104 solidifies, and the temperature of the pressure roller 402 rises too much to deteriorate the pressure roller 402. For this purpose, the heating element 405 is controlled so as to satisfy the relationship “heating temperature ≧ inter-sheet heating temperature”.

In the conventional heating temperature control at the time of continuous printing, the heating temperature is set in a plurality of steps. For example, as shown in FIG. 7, the heating temperature is set in four steps (190 ° C., 180 ° C., 170 ° C.).
℃, 160 ° C).
The number-of-sheets control means that, for example, during continuous printing from the first state in the morning when the fixing device is cold, for example, the heating temperature is set at 19 degrees.
Pass 1 to 3 sheets at 0 ° C, 4th to 6th sheets at 180 ° C, 7
When the recording material is continuously passed, the heating temperature is changed according to the number of sheets passed, such as 170 ° C. for the 15th sheet and 160 ° C. for the 16th and subsequent sheets.

This is because the temperature of the pressure roller rises as the number of prints is increased, and the amount of heat applied to the recording material P is determined by “the heat generation amount of the heating member + the heat generation amount of the pressure roller = constant” to improve the fixing property. It is preferable to keep the temperature constant, and when the temperature of the pressure roller rises and the calorific value of the pressure roller increases, the heating temperature of the heating body is reduced to reduce the calorific value of the heating body and applied to the recording material. This is because it is necessary to make the amount of heat generated constant.

The above is the control during the continuous printing. At the time of the intermittent printing, as is known from Japanese Patent Application Laid-Open No. Hei 5-165368, the member to be heated is determined based on the temperature of the heating member at the start of temperature control (at the start of printing). Control means for determining the heating temperature of the first sheet has been proposed.

The heating temperature of the heating element 405 is controlled by controlling the voltage or current applied to the heating resistor 405b or by controlling the energizing time. Methods of controlling the energization time include zero-crossing wave number control for controlling energization and non-energization for each half-wave of the power supply waveform, and phase control for controlling the phase angle of energization for each half-wave of the power supply waveform.

Among the above two control methods, the wave number control used in the present embodiment has an advantage that the noise is smaller than the phase control. The wave number control is a method of turning on some of a specific wave number (hereinafter referred to as a fundamental wave number) and turning off the remaining waves.

In the conventional contact heating method, the fixing strength (fixing property) at which the toner is fixed to the recording material greatly changes depending on the recording material thickness and the recording material temperature.

In the case where the recording material is thick or the recording material is cooled in a low temperature environment, the fixing strength (fixing property) at which the toner adheres to the recording material in the heating device due to insufficient heat supplied to the toner and the recording material. ) Decreases. When the recording material is thin or the recording material is warm in a high-temperature environment, the toner is excessively supplied to the toner and the recording material in the heating device, and the toner is excessively melted. And a "hot offset" phenomenon occurs in which the recording material is soiled after one rotation.

Therefore, in the present embodiment, the recording material characteristic measurement mode is automatically or manually performed, and a test printing of one recording material P is performed. At this time, a constant power is supplied to the heating resistor 405b of the heating element 405, the recording material P is inserted into the fixing nip portion Nk, and the heat of the heating element 405 is deprived by the recording material P and the temperature changes. 405 temperature change ΔT
Is detected by the thermistor 405c of the temperature detecting element, the recording material thickness and the recording material temperature, that is, the recording material heat capacity are detected, and the recording material thickness (temperature) data is recorded as the recording material characteristic data. To memorize.

At the time of printing, the recording material characteristic storage means 60
Based on the recording material thickness (temperature) data stored in No. 1, from among a plurality of heating modes, an optimal heating mode is set according to the recording material, so that recording with various thicknesses and temperatures is performed. It is a configuration that can obtain a good image even for a material.

Actually, the configuration of the heating device used in this embodiment is such that the ceramic substrate 405a has a width of 7 mm and a length of 270 mm.
The heating resistor 405b has a width of 2 mm and a resistance value of 24Ω. Heating resistor 405
b is covered with a 50 μm glass layer 405d. The film 2 has a cylindrical shape with a diameter of 24 mm and a total thickness of 50 μm.
The pressure roller has a release layer of 30 μm of PFA or the like on silicone rubber having a diameter of 20 mm and a thickness of 3 mm. A4 length 8
ppm (process speed is 50 mm / sec).

As shown in FIG. 8, for controlling the heating temperature of the heating element 405, a wave number control in which a half wave of the input power supply AC is set to one wave number and the fundamental wave number is set to 15 waves is used. For example, if the input power is 5
In the case of 0 Hz, “AC half wave = 1 wave number = 10 msec” becomes “fundamental wave number = 15 waves = 150 msec”. By turning ON / OFF the wave number in the 15 fundamental wave numbers, 150 m is obtained.
The heating temperature was controlled by switching the input wave number every second.

The thermistor 405c detects the temperature of the heating element 405 at the start of test printing in the recording material characteristic measurement mode, and the heating element temperature Ti [° C.] at the start of test printing.
However, for example, in the case of a [° C.] of less than 70 ° C., as shown in FIG. 9, immediately after the test print, the temperature of the heating body 405 is quickly raised to an arbitrary initial temperature Ta [° C.] = 190 ° C. As shown in FIG. 8A, all 15 waves are turned ON (start-up control), and PID control (normal temperature control) is applied from 180 ° C., for example, to prevent overshoot. After reaching 190 ° C., the ON wave number changes every 150 msec to maintain 190 ° C.

FIG. 10 is an enlarged view showing the temperature change of the thermistor before and after the recording material P is inserted into the fixing nip portion Nk. In FIG. 10, about 5 to 7 waves are turned ON to maintain 190 ° C., and the wave number fluctuates (（f). In this state, before (f) about 20 mm (400 msec) immediately before the leading end of the recording material P enters the fixing nip portion Nk (f), FIG.
As shown in (b), six waves of constant power are used as fixed wave numbers and O
N (fe) and supply to the heating resistor 405b of the heating element 405.

Then, the recording material P enters the fixing nip portion Nk (b), and the pressure roller 402 makes a 60 mm
(Between about 1.2 sec) (between b and e)
The amount of temperature change ΔT at which the temperature of the temperature 05 changes varies with the thermistor 40
5c senses and sets ΔT [° C.] to a predetermined comparison value (for example, +
| S1 | [° C.], − | S2 | [° C.), as the recording material characteristic data, “thin paper”, “plain paper”, “thick paper”
Detect which of the following applies. The detected recording material characteristic data is stored in the recording material characteristic storage unit 602.

In FIGS. 10 to 10, solid lines indicate the thermistor 4 when about 75 g / m ^{2 of} ordinary paper is passed.
05c output. In this case, ΔT1 = G2−G1
[° C] and + | S1 | [° C] <ΔT1 <− | S2 |
From [° C.], “plain paper” is stored in the recording material characteristic storage unit 601 as recording material characteristic data.

The dashed line in FIGS.
This is the thermistor 405c output when 0 g / m ² paper is passed. In this case, ΔT2 = G3−G1 [° C.], and from ΔT2 <− | S2 | [° C.], “thick paper” is used as recording material characteristic data. Is stored in the recording material characteristic storage unit 601.

In FIGS. 10 to 10, the two-dot chain line is about 50
g / m ² paper is output when the thermistor 405c is passed. In this case, ΔT3 = G4-G1 [° C.]
Since “+ | S1 | [° C.] <ΔT3”, “thin paper” is stored in the recording material characteristic storage unit 601 as recording material characteristic data.

The temperature of the heating element 405 at the start of test printing in the recording material characteristic measurement mode is set to the thermistor 40.
5c, the heating element temperature Ti at the start of test printing
When [° C.] is, for example, k [° C.] of 70 ° C. or more, the initial heating temperature Ta [° C.] is 180 ° C. lower than 190 ° C. by 180 ° C.
Set to ° C.

As shown in FIG. 11, immediately after the test printing, the temperature of the heating element 405 is increased quickly to an arbitrary initial temperature Ta [° C.].
= 180 ° C., all 15 waves are turned ON (start-up control) as shown in FIG.
PID control (normal temperature control) is applied from 0 ° C. to prevent overshoot. After reaching 180 ° C, 18
The ON wave number changes every 150 msec to maintain 0 ° C.

FIG. 12 is an enlarged view showing the thermistor temperature change before and after the recording material P is inserted into the fixing nip Nk. In FIG. 12, about 4 to 6 waves are turned on to maintain 180 ° C., and the wave number fluctuates (〜f). In this state, about 20 mm (400 msec) immediately before (f) immediately before the leading end of the recording material enters the fixing nip portion Nk, five waves of constant power are turned on as fixed wave numbers (f to e), and the heating element 4 is turned on.
05 to the heating resistor 405b. Then, the recording material enters the fixing nip portion Nk (b) and reaches 60 mm (1.2 mm).
Thermistor 405c detects a temperature change amount ΔT at which the temperature of the heating element 405 changes during the passage (b to e) for about sec), and ΔT [° C.] is compared with a predetermined comparison value (for example, + | M1 |).
[° C], − | M2 | [° C]), it is detected which of “thin paper”, “plain paper”, and “thick paper” as the recording material characteristic data. The detected recording material characteristic data is stored in the recording material characteristic storage unit 601.

[0120] The thermistor 4 when the solid line was passed ordinary plain paper about 75 g / m ² paper used in b~e of 12
05c output. In this case, ΔT4 = I2-I1
[° C] and + | M1 | [° C] <ΔT4 <− | M2 |
From [° C.], “plain paper” is stored in the recording material characteristic storage unit 601 as recording material characteristic data.

The dashed line in FIGS.
This is the output of the thermistor 405c when 0 g / m ² paper is passed. In this case, ΔT5 = I4−I1 [° C.], and ΔT2 <− | M2 | [° C.] indicates that “thick paper” is used as recording material characteristic data. Is stored in the recording material characteristic storage unit 601.

A double-dot chain line in FIGS.
g / m ² is the output of the thermistor 405c when the paper is passed. In this case, ΔT6 = I3-I1 [° C.]
+ | M1 | [° C.] <ΔT6, “thin paper” is stored in the recording material characteristic storage unit 601 as recording material characteristic data.

In the above description, in test printing in the recording material characteristic measurement mode, the temperature of the pressure roller 402 differs between the state where the heating device is cooled down to room temperature and the state where the heating device is warmed. The temperature change amount ΔT of the heating element 405 due to the passage of the recording material at Nk is different between the same recording material when the heating device is cold and when the heating device is warm. Therefore, in the recording material characteristic measurement mode, the initial heating temperature Ta before the temperature change amount detection is started according to the heating element temperature Ti [° C.] at the start of test printing.
By changing the predetermined comparison value to [° C.], it is possible to accurately detect the recording material thickness, which is the characteristic of the recording material.

At the time of actual image printing, the temperature of the heating element 405 at the start of printing is detected by the thermistor 405c, and when the heating element temperature Ti [° C.] at the start of printing is, for example, a [° C.] less than 70 ° C. As shown in FIG. 13, when the recording material characteristic data stored in the recording material characteristic storage means 601 is “thin paper”, the thick line “thin paper mode” in FIG. 13 is used, and the recording material characteristic data is “plain paper”. Figure 1 in case of
When the recording material characteristic data is "thick paper" in the thin line 3 in "normal mode" and the recording material characteristic data is "thick paper", the heating temperature is controlled according to each heating temperature according to FIG. 13 in the dotted line "thick paper mode" in FIG. In each heating mode, the heating temperature is set to be different by 10 ° C.

The temperature of the heating element 405 at the start of printing is detected by the thermistor 405c. When the temperature of the heating element Ti [° C.] at the start of printing is, for example, k [° C.] of 70 ° C. or more, FIG. As shown in FIG.
When the recording material characteristic data stored in No. 01 is “thin paper”, the thick line “thin paper mode” in FIG. 14 is used, and when the recording material characteristic data is “plain paper”, the thin line “normal mode” in FIG.
When the recording material characteristic data is "thick paper", the heating temperature is controlled according to each heating temperature according to FIG. 14 in the dotted line "thick paper mode" of FIG. When the pressure roller is warm, the heating temperature is controlled in each heating mode according to the heating temperature lower by 10 ° C. than in FIG.

As described above, the thickness (temperature) of the recording material as the recording material characteristic data is detected by the test print in the recording material characteristic measurement mode, and the detected data is stored in the recording material characteristic storage means 601. When printing,
By adopting a configuration in which the heating temperature is determined based on the stored recording material characteristic data and the printing start temperature of the heating device, a clear image with good fixability and no hot offset can be obtained.

In the recording material characteristic measurement mode of the present embodiment, the heating device detects necessary and appropriate amount of heat according to various recording materials and various environments, and stores it in the recording material characteristic storage means 601 at the time of printing. By shifting to the appropriate heating mode based on the recording material characteristic data obtained, a good fixed image can be obtained, and it is possible to eliminate user selection mistakes in the heating mode and the complexity of the user selecting the heating mode. it can.

In the above description, the temperature change amount detection time is set to 60 mm (1.2 sec) at the front end of the recording material, but may be set arbitrarily depending on the configuration of the heating device. Although the film heating device has good responsiveness, it can be operated in a short time, but the heat roller heating device has poor responsiveness, so that it is preferable to set the detection time to be long.

In the above description, one heating element temperature branch at the start of test printing is set at 70 ° C., two predetermined comparison values with ΔT are set, and three heating modes are set.
Further, the temperature may be further subdivided to set two or more heating element temperature branches at the start of test printing, set three or more predetermined comparison values, and set four or more heating modes.

In the heating mode, not only the heating temperature but also a time interval between sheets, a heating temperature between sheets, and the like may be changed.

Further, before or after the recording material P is inserted into the fixing nip portion Nk, when the paper is not passed, a constant power is supplied to the heating resistor 405b of the heating element 405, and the heat quantity of the heating element 405 is increased. The temperature change amount ΔTk of the heating element 405 whose temperature is changed by being robbed by the roller 402 is measured.
By detecting the temperature and changing a predetermined comparison value to be compared with ΔT measured during the passage of the recording material P at the fixing nip portion Nk described above, the recording material thickness and the recording material characteristics more strictly The recording material temperature can be accurately detected.

In the above description, the method of determining the predetermined heating mode by comparing ΔT with a predetermined comparison value has been described. However, instead of selecting the predetermined heating mode, a predetermined heating temperature calculation, for example, described below, is performed from ΔT. By the method of determining the heating temperature by the formula, the heating temperature suitable for the recording material can be set more strictly.

[0133]

Tk = T (0) + (xΔT + y) (heating temperature (Tk) calculation formula) where x and y are constants including zero> T (0) is a predetermined heating temperature. (X · ΔT + y) is a correction term corresponding to the recording material thickness.

In the above description, the heating resistor 40 of the heating element 405
5b, the recording material P is fixed at the fixing nip N
k, the amount of heat of the heating element 405 is deprived by the recording material P, and the temperature change ΔT of the heating element 405 whose temperature changes is detected by the thermistor 405c of the temperature detecting element.
Although the recording material thickness and the recording material temperature are detected, it is possible to more accurately detect the recording material thickness, the recording material temperature, and the recording material heat capacity by changing the electric power.

For example, the heating resistor 405 of the heating element 405
b is turned off as the first power, and immediately before or immediately after the recording material enters the fixing nip portion Nk, or after the recording material P passes through the fixing nip portion Nk for a predetermined distance (predetermined time), the fixing nip portion Nk When there is a recording material, a constant power is supplied to the heating resistor 405b as the second power, and the amount of heat change of the heating body 405 at which the amount of heat of the heating body 405 is deprived by the recording material P and the temperature changes is determined. The thickness of the recording material and the temperature of the recording material may be detected by detecting with the thermistor 405c of the temperature detecting element.
There is an advantage that the type of recording material can be detected with higher accuracy, and the power consumption during test printing in the recording material characteristic measurement mode can be reduced.

Further, for example, a constant power or a power for maintaining a constant temperature is supplied as the first power to the heating resistor 405b of the heating element 405 so that the recording material P is fixed to the fixing nip portion Nk.
Immediately before or immediately after the recording material P is inserted into the fixing nip portion Nk, or after the recording material P is inserted through the fixing nip portion Nk and passes through the fixing nip portion Nk for a predetermined distance (predetermined time).
When the recording material is present, the power supplied to the heating resistor 405b is turned off as the second power, and the amount of heat change ΔT of the heating body 405 at which the amount of heat of the heating body 405 is deprived by the recording material P and the temperature changes. The recording material thickness and the recording material temperature may be detected by detecting with the thermistor 405c of the temperature detecting element. By turning on and off the power as in this configuration, the temperature change amount ΔT of the heating element 405 becomes large. Therefore, there is an advantage that the temperature change amount ΔT can be detected more accurately.

Further, for example, a constant power (for example, 6 waves) is supplied to the heating resistor 405b of the heating element 405, and the recording material P is inserted through the fixing nip Nk for a predetermined distance (predetermined time, first area). After the recording material P has passed through the fixing nip portion Nk, the constant power supplied to the heating resistor 405b is changed (for example, reduced to three waves) in the second region of the recording material, and heating is performed at each constant power. The amount of heat of the body 405 is the recording material P
Are detected by the thermistor 405c of the temperature detecting element, where ΔTb (for example, when three waves are supplied) and ΔTb (for example, when three waves are supplied) of the heating element 405 whose temperature is changed by being deprived by the first and second regions. Thus, a configuration in which the thickness of the recording material and the temperature of the recording material are detected may be used. As in this configuration, a plurality of temperature changes ΔT of the heating element 405 are detected by changing the constant power supplied to the heating resistor 405b. Therefore, there is an advantage that the temperature change amount ΔT can be detected more accurately.

Although the above description has been made with respect to the film heating method, the present invention can also be applied to a heat roller heating method having a low thermal response.

[0139] In a contact heating device of a heat roller heating system and a film heating system, a paper property measurement mode is used.
Supply constant power to halogen heater and heating element,
The temperature change amount ΔT of the fixing roller and the heating element by the recording material inserted into the fixing nip portion Nk is detected by a temperature detecting element, and ΔT is compared with a predetermined comparison value to determine the recording material thickness and the recording material temperature. Obtain an image with good fixability by detecting and automatically selecting the heating mode of thin paper mode / plain paper mode / cardboard mode, or determining the heating temperature using a calculation formula based on ΔT Can be.

In the above, the configuration using the existing heating device as the recording material thickness (temperature) detecting means has been described.
Separately, even when a recording material thickness detecting means and a recording material temperature detecting means are arranged, the recording material thickness and the recording material temperature, that is, the recording material heat capacity can be detected in the same manner.

(Embodiment 4) Embodiment 4 according to the present invention will be described with reference to FIG. Note that the same components as those in the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

Conventionally, when the thickness of the recording material is thin, the strength (stiffness) of the recording material is weak, the recording material after transfer does not separate from the photosensitive drum, and the photosensitive drum and the recording material are electrostatically adsorbed.
The phenomenon of “defective leading end photosensitive drum separation” in which the recording material spills into the cleaning device 110 occurs. Recording materials with a thin recording material and weak stiffness have poor separation performance against curvature separation from the photosensitive drum, and a high-resistance recording material is easily charged and easily adsorbed on the photosensitive drum. Decreases. In addition, the separation failure of the photosensitive drum at the rear end of the recording material causes the rear end to collide with the cleaning device without separating from the photosensitive drum at the rear end of the recording material, thereby generating “rear end splash” which disturbs an image. If the trailing edge is severe, the recording material sticks to the bottom of the cleaning device, and the image is disturbed.

Therefore, it has been proposed to prevent the above-described separation failure by applying a current elimination needle bias for applying a current or a voltage having a polarity opposite to that of the transfer current or the transfer voltage to the static elimination needle disposed downstream of the transfer means.

However, if the current value of the static elimination needle or the voltage value of the static elimination needle is too large, the transfer current flows to the static elimination needle, and if the transfer current / transfer voltage becomes insufficient or the recording material is excessively neutralized,
The toner cannot be held on the recording material, and in the downstream heating device, the toner adheres to the fixing roller or the fixing film, and an “electrostatic offset” phenomenon occurs in which the recording material is soiled after one round of the fixing roller or the fixing film. Resulting in.

Therefore, it is necessary to set the static elimination needle bias value to an appropriate value according to the recording material.

Therefore, in the present embodiment, in the image forming apparatus of the static elimination needle bias system, the recording material resistance value detected in the first and second embodiments or the recording material resistance value in the test printing in the recording material characteristic measurement mode. The bias value applied to the static elimination needle during printing is changed based on the recording material characteristic data stored in the recording material characteristic storage unit 601 such as the recording material thickness detected in the third embodiment.

The recording material resistance value is detected by the test method in the recording material characteristic measurement mode by the detection method described in the first and second embodiments, and the recording stored in the recording material characteristic storing means 601 is performed. Depending on the material resistance value,
At the time of printing, the CPU 302 increases the predetermined static elimination needle bias value in the case of “high-resistance recording material” by comparing it with a predetermined comparison value. Alternatively, the separation failure can be prevented by applying the static elimination needle bias value calculated by the CPU 302 based on the recording material resistance value by the static elimination needle bias power supply 801.

Alternatively, the recording material thickness detection is performed by the detection method described in the third embodiment, and based on the recording material thickness stored in the recording material characteristic storing means 601, the CPU 302 compares the recording material thickness with a predetermined comparison value during printing. Then, in the case of "thin paper", the predetermined static elimination needle bias value is increased. Alternatively, the separation failure can be prevented by applying the static elimination needle bias value calculated by the CPU 302 based on the recording material resistance value by the static elimination needle bias power supply 801.

As described above, not only is the static elimination needle bias value changed only when "high-resistance recording material" or "thin paper" is used, but also a static elimination needle having a plurality of static elimination needle bias values using a predetermined table or the like. A bias value variable mode may be provided, and the bias value of the static elimination needle may be arbitrarily determined by a calculation formula according to the recording material thickness of the recording material resistance value.

In an image forming apparatus in which an A4 length of 10 ppm (process speed 50 mm / sec) and a positive voltage is applied to the transfer roller 108, a "high resistance recording material" or a "high resistance recording material" “Thin paper” is detected, and recording material characteristic data is stored in the recording material characteristic storage unit 601.

At the time of printing, when the static elimination needle bias control is a constant voltage, the static elimination needle bias value in the normal paper mode is -600 V, but the static elimination needle bias value in the high-resistance recording material or thin paper mode is -1. By setting to 2KV,
The occurrence of “defective separation of the photosensitive drum at the front end”, “splash at the rear end”, and “electrostatic offset” were prevented.

When the static elimination needle bias control at the time of printing is a constant current control, the static elimination needle bias value in the normal paper mode is -1 μA, but the static elimination needle bias value in the high-resistance recording material or the thin paper mode is changed to -1 μA. -2 μA,
The occurrence of “defective separation of the photosensitive drum at the front end”, “splash at the rear end”, and “electrostatic offset” were prevented.

The static elimination needle bias value may be changed according to the individual data of the recording material resistance value and the recording material thickness, or the static elimination needle bias value may be changed in combination. Furthermore, in the above description, the static elimination needle bias value is changed on the entire surface of the paper according to the recording material characteristic value. , "Rear-end fly" can be prevented.

In the above description, the case of the static elimination needle has been described. However, any other neutralization means such as a neutralization brush or a neutralization corona may be used as long as the static elimination means.

(Embodiment 5) In Embodiments 1-4,
Although one-sided printing has been described, in an image forming apparatus equipped with an automatic two-sided printing function (two-sided image forming mechanism), in the recording material characteristic measurement mode, the recording material characteristics are set to the first surface (first side).
Surface), the second surface (second surface), and each of the recording material characteristic data is transferred to the image forming apparatus main body or a paper supply port (paper supply cassette or the like), a computer connected to the image forming apparatus, or the like. Stored in the recording material characteristic storage means 601 provided in
Embodiments 1 to 3 according to the paper characteristic data of the first side and the second side
By setting the transfer bias control, the heating temperature control of the heating unit, and the bias control of the static elimination needle described in 4 to be variable on the first side and the second side, a good image can be obtained even during automatic double-sided printing.

In the transfer bias control, during test printing in the recording material characteristic measurement mode, for example, when the environment is a high humidity environment, the first surface absorbs moisture and is detected as a low resistance recording material.
The second side is dehumidified by passing through a heating device during printing on the first side and is detected as a high-resistance recording material, and recording material characteristic data is stored in the recording material characteristic storage unit 601. At the time of printing, the first side is “sandy”, “penetration”, “transfer missing” according to the stored first / second side recording material characteristic data.
To prevent this phenomenon, set the transfer bias value low,
On the first side, good transfer images could be obtained on both the first and second sides by setting the transfer bias value high to prevent the phenomenon of "explosion scattering".

In the heating temperature control, at the time of test printing in the recording material characteristic measurement mode, for example, when the environment is a low temperature environment, the first surface requires a large amount of heat because the recording material is cooled, and the second surface has the first surface. Since the recording material is warmed by passing through the heating device during printing, the required amount of heat may be small. In this case, since the temperature change ΔT described in the third embodiment differs between the first surface and the second surface, the first surface and the second surface
The recording material characteristic data of the surface is stored in the recording material characteristic storage unit 601. At the time of printing, the heating temperature for the first side is set high to ensure the fixability, and the heating temperature is set low for the second side to prevent the "hot offset" phenomenon, based on the stored recording material characteristic data for the first side / second side. Like
By changing the heating temperature on the first and second surfaces, good fixed images were obtained on both the first and second surfaces.

In the static elimination needle bias control, at the time of test printing in the recording material characteristic measurement mode, the recording material resistance values and the recording material thickness of the first and second surfaces are detected, and the recording material characteristic data of the first and second surfaces are recorded. The information is stored in the characteristic storage unit 601.

For example, if the recording material characteristic data is “thin paper” at the time of printing, the first surface has a static elimination needle bias value = −
Since the curl amount is large since the second surface has passed through the heating device once, the bias of the static elimination needle bias value is set to prevent "defective separation of the photosensitive drum at the front end" and "splash at the rear end". By setting a predetermined value higher than the first surface and setting the static elimination needle bias value to −2.0 KV,
Good images could be obtained on both sides.

For example, if the recording material characteristic data is “plain paper” at the time of printing, the first surface has a static elimination needle bias value = −
Since the curl amount is large because the second surface has passed through the heating device once, the bias value of the static elimination needle is set to 1 in order to prevent “distortion of the photosensitive drum at the front end” and “splash at the rear end”. By setting a predetermined value higher than the first surface and setting the static elimination needle bias value to -1.2 KV,
Good images could be obtained in both aspects.

For example, when the recording material characteristic data is “thick paper” at the time of printing, “the leading end photosensitive drum separation failure”
Since the "rear end splash" is unlikely to occur, the static elimination needle bias is turned off for both the first and second surfaces, and the static elimination needle bias value is 0 V
By setting, good images could be obtained on both the first and second surfaces.

The first to fifth embodiments may be used in any combination.

Further, the present invention is not limited to the recording material characteristic detecting means described in the embodiment, and the other recording material characteristic detecting means can be used to perform recording material resistance test printing in the recording material characteristic measuring mode. A configuration may be adopted in which values, recording material thickness, recording material temperature, and other recording material characteristics are detected, and image forming conditions other than those described in the embodiment are changed.

Further, at the time of test printing in the recording material characteristic measuring mode, an image may be written on the recording material and a toner image may be arranged on the recording material to measure the recording material characteristics.
In this case, for example, the change in the resistance value of the toner under each environment and the temperature of the toner can be measured, so that the characteristics of the recording material can be more suitably measured.

Although the above description has been made with reference to a monochrome image forming apparatus, the present invention can also be applied to a color image forming apparatus.

[0166]

As described above, according to the present invention,
A recording material characteristic measuring means for performing test printing of at least one recording material and measuring the characteristics of the recording material; and measuring the characteristics of the recording material by the recording material characteristic measuring means, based on the measured characteristics of the recording material. Control means for controlling image forming conditions of the image forming means at the time of image formation for forming an image on a recording material, so that the image forming apparatus can adjust the image forming conditions based on the recording material characteristic data at the time of image printing. Since it can be automatically determined and selected, it eliminates the user's misselection of various modes and the complexity of selecting various types of recording materials used by the user, eliminating various existing recording materials and new ones in the future. The image forming apparatus judges and selects the image forming conditions or various modes for the recording material to be developed and for various environments, and always obtains a good image. It is possible to provide an image forming apparatus capable.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of detecting a recording material resistance value in a transfer unit according to a first embodiment.

FIG. 2 is a schematic configuration diagram of detecting a recording material resistance value at a transfer unit and a pair of registration rollers according to a second embodiment.

FIG. 3 is a schematic configuration diagram of detection of a recording material resistance value at a transfer unit and a grounding needle according to a second embodiment.

FIG. 4 is a schematic configuration diagram of recording material resistance detection at a transfer unit and a bias application static elimination needle unit according to a second embodiment.

FIG. 5 is a schematic sectional view of a heating device of a film heating type according to a third embodiment.

FIG. 6 is a schematic configuration diagram of heating temperature control according to a third embodiment.

FIG. 7 is an example of heating temperature control during continuous printing of a film heating device according to a third embodiment.

FIG. 8 is an explanatory diagram of wave number control according to the third embodiment.

FIG. 9 is an explanatory diagram of heating temperature control in a recording material characteristic measurement mode (test print) when the heating device is at a low temperature according to the third embodiment.

FIG. 10 is a diagram illustrating detection of a heating element temperature change amount ΔT when a heating device is at a low temperature according to the third embodiment.

FIG. 11 is an explanatory diagram of heating temperature control in a recording material characteristic measurement mode (test print) at a high temperature of the heating device according to the third embodiment.

FIG. 12 is an explanatory diagram of detection of a heating element temperature change amount ΔT at the time of a high temperature of a heating device according to a third embodiment.

FIG. 13 is an explanatory diagram of a heating mode during continuous printing of the film heating device when the heating device is at a low temperature according to the third embodiment.

FIG. 14 is an explanatory diagram of a heating mode at the time of continuous printing of the film heating device when the heating device is at a high temperature according to the third embodiment.

FIG. 15 is an explanatory diagram of static elimination needle bias control according to the fourth embodiment.

FIG. 16 is a schematic sectional view of a conventional image forming apparatus.

FIG. 17 is a schematic sectional view of a conventional image forming apparatus having an automatic double-sided function.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Image forming apparatus 101 Photosensitive drum 108 Transfer unit 111 Heating device 201 Double-sided conveyance unit 202 Inversion (switchback) unit 301 Transfer bias power supply 302 CPU 401 Film heating type heating device 402 Pressure roller 403 Fixing film 404 Heating body support 405 Heating element 405a Heating element substrate 405b Heating resistor 405c Temperature detecting element 701 Registration roller pair 801 Static electricity removal needle bias power supply B Recording material transport path C Face-up discharge path D Face-down discharge path E Automatic two-sided (second side) print transport path F Automatic double-sided (second side) print conveyance path P Recording material T Toner Nt Transfer nip portion Nk Fixing nip portion ΔT Heating member temperature change when passing through fixing nip portion ΔTk Heating member temperature change when not passing through fixing nip portion

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 1/29 H04N 1/29 Z F term (Reference) 2C061 AQ06 HK07 HK10 HK11 KK12 KK25 KK32 2H027 DA01 DA12 DC00 DC02 DC05 DC19 EA03 EA12 EA15 ED16 ED24 EE08 EJ08 EJ15 FA12 GA30 GB07 GB09 HA07 2H032 AA05 BA12 BA13 BA19 BA23 CA02 CA11 CA12 DA02 DA23 DA26 DA27 2H033 AA02 AA32 AA47 BA08 BA30 BA59 BE03 CA07 CA16 CA27 CA24 DD EE03 EE08 EE11 GG15 GG16 HH02

Claims (19)

[Claims] An image forming apparatus comprising an image forming means for forming a toner image obtained by developing an electrostatic latent image formed on an image carrier on a recording material, and transferring and fixing the toner image. A recording material characteristic measuring means for test-printing one recording material to measure the characteristics of the recording material; and measuring the characteristics of the recording material by the recording material characteristic measuring means, and recording based on the measured characteristics of the recording material. A control unit for controlling image forming conditions of the image forming unit at the time of image formation for forming an image on a material. 2. A recording material characteristic storage means for storing a recording material characteristic measured by the recording material characteristic measuring means, wherein the control means is configured to store the recording material characteristic based on the recording material characteristic stored in the recording material characteristic storage means. And controlling image forming conditions of said image forming means during image formation.
An image forming apparatus according to claim 1. 3. A recording material loading means which is provided detachably from the apparatus main body and which loads recording materials fed one by one to said image forming means by a feeding means, wherein said recording material characteristic storage means, The image forming apparatus according to claim 2, wherein the image forming apparatus is provided in the recording material stacking unit. 4. A recording material stacking means comprising a plurality of recording material loading means, wherein said plurality of recording material property storing means comprises a plurality of recording material loading means or a plurality of recording material transporting means from said recording material loading means to said image forming means. The image forming apparatus according to claim 2, wherein a plurality of image forming apparatuses are provided corresponding to the sheet feeding ports. 5. A communication device for communicating with an external device, wherein the characteristic of the recording material measured by the recording material characteristic measuring device is communicated to the external device by the communication device, and provided in the external device. The characteristics of the recording material are stored by a recording material characteristics storage unit, and the control unit controls the image forming unit during image formation based on the characteristics of the recording material stored in the recording material characteristics storage unit of the external device. The image forming apparatus according to claim 1, wherein an image forming condition is controlled. 6. A recording material characteristic measured by the recording material characteristic measuring means is a resistance value of the recording material, a thickness of the recording material, a temperature of the recording material, or a size of the recording material. The image forming apparatus according to claim 1. 7. A toner image formed on the image carrier by applying a transfer bias to the image forming means and passing a recording material through a transfer nip portion between the image carrier and the image carrier. A transfer unit for transferring the recording material to the transfer material, wherein the recording material characteristic measuring unit is configured to control a current value or a voltage value applied to the transfer unit in a case where the recording material is sandwiched between the transfer nip portion and a case where the recording material is not sandwiched. And the control unit detects the transfer material bias based on the resistance value of the recording material detected by the recording material characteristic measuring unit. The image forming apparatus according to claim 1, wherein the value is controlled. 8. A transfer means provided in the image forming means, and to which a transfer bias is applied to transfer a toner image formed on the image carrier to a recording material, and a transfer means provided upstream of the transfer means. A conductive recording material transporting member for transporting the recording material, or a static elimination unit provided on the downstream side of the transfer unit for neutralizing the recording material, wherein the recording material characteristic measuring unit performs recording from the transfer unit. Through the recording material, the resistance value of the recording material is detected by measuring a current value flowing to the recording material conveying member or the static elimination unit, and the control unit detects the resistance of the recording material detected by the recording material characteristic measuring unit. The image forming apparatus according to claim 1, wherein a transfer bias value applied to the transfer unit at the time of image formation is controlled based on a resistance value. 9. A recording apparatus comprising: a heating unit provided in the image forming unit, the recording unit penetrating a recording material into a fixing nip portion between the recording material and a pressing member, and fixing the toner image transferred onto the recording material. The material characteristic measuring means measures a temperature change amount of the heating means, which changes due to the recording material inserted into the fixing nip portion, by a temperature detecting means, compares the temperature change amount with a predetermined comparison value, and performs the recording. The thickness of the recording material, or, while detecting the temperature of the recording material, the control means, based on the thickness of the recording material detected by the recording material characteristic measuring means, or the temperature of the recording material, at the time of image formation A heating mode of the heating means, or
The image forming apparatus according to claim 1, wherein a heating temperature is controlled. 10. An image forming apparatus according to claim 9, wherein said control means changes the power supplied to said heating means when said temperature change amount is measured by said recording material characteristic measuring means. 11. The heating device according to claim 1, wherein the control unit controls the heating unit immediately before the recording material is inserted into the fixing nip portion of the heating unit to which the first power is supplied or when the leading end region of the recording material is inserted. The image forming apparatus according to claim 10, wherein the power supplied to the unit is changed to the second power. 12. The recording material characteristic, wherein the control unit changes the power supplied to the heating unit after the first region of the recording material inserted into the fixing nip passes through the fixing nip. 11. The apparatus according to claim 10, wherein the measuring unit measures the temperature change amount in each of the first region and a second region upstream of the first region.
2. The image forming apparatus according to 1. 13. The control means according to claim 1, wherein said recording material characteristic measuring means controls the recording material when the recording material is not passed through said fixing nip.
A temperature change amount of the heating unit is measured to detect a temperature of the pressing member, and a heating temperature of the heating unit and the predetermined comparison value are changed based on the detected temperature of the pressing member. 13. The method of claim 9, 10, 11 or 12.
An image forming apparatus according to claim 1. 14. The control means detects the temperature of the heating means at the start of the test print by the temperature detection means, and controls the heating based on the detected temperature of the heating means at the start of the test print. The heating temperature of the means and the predetermined comparison value are changed.
The image forming apparatus according to claim 1. 15. An image forming apparatus according to claim 9, wherein said heating means is of a film heating type. 16. The control unit controls a bias value applied to the charge removing unit during image formation based on a resistance value of the recording material detected by the recording material characteristic measuring unit or a thickness of the recording material. 8. The method according to claim 8, wherein
6. The image forming apparatus according to claim 5. 17. A double-sided image in which a recording material having an image formed on a first surface by said image forming means is reversed and an image is formed by said image forming means on a second surface on the back surface of said first surface. A forming mechanism, wherein the characteristics of the recording material on the first and second surfaces are respectively measured by the recording material characteristic measuring means, and when forming a double-sided image,
An image is formed on the first and second surfaces under respective image forming conditions controlled by the control unit based on characteristics of the recording material on the first and second surfaces. An image forming apparatus according to any one of claims 1 to 16. 18. The control means according to claim 1, wherein a power supply of an apparatus main body is turned on.
When the recording material is loaded, or when the recording material stacking means is mounted on the apparatus main body, the recording material characteristics are measured by the recording material characteristic measuring means, and the measured characteristics of the recording material are stored in the recording material characteristic storage. If the characteristics of the recording material are different from the characteristics of the recording material stored in the means, the characteristics of the recording material stored in the recording material characteristics storage means are rewritten, or the fact that the characteristics of the recording material are different is provided in the apparatus main body. 18. The display device according to claim 2, wherein the display is performed by a display unit, or the communication unit communicates with the external device to display the display on a display unit provided in the external device. Image forming device. 19. A recording material size detecting means for detecting a size of a recording material conveyed to said image forming means at the time of image formation, wherein said control means controls a size of the recording material detected by said recording material size detecting means. If it is determined that the recording material characteristic is different from the recording material characteristic stored by the recording material characteristic storage unit, the recording material characteristic measurement unit performs at least one test print of the recording material to measure the characteristic of the recording material. The characteristic of the recording material stored in the material characteristic storing means is rewritten, or the fact that the characteristic of the recording material is different is displayed on a display means provided in the apparatus main body, or
19. The image forming apparatus according to claim 2, wherein the communication unit communicates with the external device to display the image on a display unit provided in the external device.