JPH10222003A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of forming a high-quality printed image whose image glossiness is kept, when a fixing operation is executed, in an image forming device for fixing an unfixed developer on a transfer material with heat and pressure. SOLUTION: This image forming device is provided with a fixing roller 115, a pressure roller 116 and a heating means for heating the fixing roller 115 and the pressure roller 116, respectively. In this case, the image forming device is provided with a pressure value changing device 2 for changing a value of pressure applied from the pressure roller 116 to the fixing roller 115 to a prescribed pressure value, after a prescribed time lapses from the start of a single fixing operation, so as to compensate the decrease of each of surface temperatures on the fixing roller 115 and the pressure roller 116 caused by thermal conductivity during the single fixing operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus which performs a fixing operation by heat and pressure, and in particular, can change a pressure value applied from a pressing member to a fixing member during a fixing operation. The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art As a conventional image forming apparatus, an image forming apparatus 100 shown in FIG. 14 is known.

[0005] A main body 101 of the image forming apparatus 100 includes a photosensitive drum 102 and a laser scanner 103.
, A paper cassette 112, and a fixing device 114.

The photosensitive drum 1 provided in the main body 101
Numeral 02 is rotatably supported by the main body 101, and is driven in the R1 direction at a predetermined peripheral speed by a driving means (not shown) provided in the main body 101.

Around the photosensitive drum 102, a charging roller 104, a developing device 105, and a transfer drum 106
And a cleaning device 107 for removing dirt on the surface of the photosensitive drum 102.

[0006] A charging roller 104 provided around the photosensitive drum 102 applies a predetermined charge to the photosensitive drum 102 and sets the surface of the photosensitive drum 102 to a predetermined potential.

On the other hand, a laser scanner device 103 provided in the main body 101 turns a predetermined laser La on and off toward the photosensitive drum 102 based on image information of an image (not shown) to be printed out. It has become.

Therefore, the laser La emitted from the laser scanner 103 exposes a charged area on the surface of the photosensitive drum 102 to form an electrostatic latent image on the surface of the photosensitive drum.

A developing device 105 provided around the photosensitive drum 102 is rotatably supported by the main body 101 and has magenta, cyan, yellow,
Toner container 10 containing each of the black toners
5Bk, 105M, 105C, and 105Y.

Each of the toner containers 105Bk, 105M, 105C, and 105Y provided in the developing device 105 applies toner to an electrostatic latent image at a developing position facing the photosensitive drum 102 to form a visible image (toner image). In addition, the developing device 105 is movably supported by the developing device 105 so as to be located at one of the developing position and a developing retract position described below.

Here, the developing retreat position means the toner containers 105Bk, 105M, 105 remote from the developing position.
C and 105Y are positions for retracting to stop the developing operation.

In the image forming apparatus 100,
The shortest distance between the developing position and the surface of the photosensitive drum 102 is 300 μm.

A transfer drum 106 provided around the photosensitive drum 102 is rotatably supported by the main body 101.

Around the transfer drum 106, a suction roller 108, a transfer cleaner unit 109, a separation claw 110, and a charge removing roller 111 are provided.

A suction roller 108 provided around the transfer drum 106 is rotatably supported by the main body 101.

Further, the suction roller 108 is supported by the main body 101 so as to be able to be separated from and connected to the transfer drum 106.

At the time of printing, the suction roller 108 charges the surface of the transfer drum 106 to a predetermined potential before the recording paper P is conveyed to the winding position described below. .

Here, the above-mentioned winding position means the position of the suction roller 1.
08 and the transfer drum 106 are in contact with each other.

When the recording paper P is conveyed to the winding position, the suction roller 108 moves the transfer drum 10
The recording paper P is charged to a predetermined potential so as to have a polarity opposite to that of the surface of the recording paper P.

Accordingly, the recording paper P conveyed to the winding position is wound around the surface of the transfer drum 106 by an electrostatic attraction generated between the recording paper P and the transfer drum 106.

A transfer cleaner unit 109 provided around the transfer drum 106 removes stains such as toner and paper chips remaining on the surface of the transfer drum 106 by performing a transfer operation. I have.

A separating claw 110 provided around the transfer drum 106 separates the recording paper P from the transfer drum 106 at the end of the transfer operation.

The charge removing roller 111 provided around the transfer drum 106 removes the charge remaining on the surface of the transfer drum 106 at the end of the transfer operation.

In the image forming apparatus 100,
For example, by forming the outer diameter of the photosensitive drum 102 to 40 Φ and the outer diameter of the transfer drum 106 to 164 Φ, and setting the process speed to 103 mm / sec, the throughput at the time of printing out a full-color image is realized at 3 ppm. I have.

The paper cassette 112 provided in the main body 101 previously stores recording paper P of a predetermined size.
At the time of printout, the recording paper P is taken out by a paper feed roller 113 rotatably supported by the main body 101.

A transport path Ru extends from the paper cassette 112 to the winding position.

Therefore, the recording paper P stored in the paper cassette 112 is transported from the paper cassette 112 to the winding position via the transport path Ru.

A conveyance path Ru extending from the paper cassette 112 to the winding position includes a pair of registration rollers 11.
7 and a tip sensor 118.

The registration roller pair 117 provided on the conveyance path Ru is rotatably supported by the conveyance path Ru so that the direction of the recording sheet P during conveyance is corrected to an appropriate direction for transfer. It has become.

The tip sensor 1 provided in the transport path Ru
Reference numeral 18 is provided at a position downstream of the registration roller pair 117 in the conveying direction of the recording paper P.

The leading edge sensor 118 measures the length in the direction parallel to the transport direction of the recording paper P until a part of the leading edge of the recording paper P in the middle of transport has passed through the leading edge sensor 118. Thus, the size of the recording paper P is detected.

The leading edge sensor 118 compares the time required for the leading edge of the recording paper P to pass through the leading edge sensor 118 with a predetermined passing time preset in the image forming apparatus 100. Then, the presence or absence of the paper jam of the recording paper P is detected.

The fixing device 11 provided in the main body 101
Reference numeral 4 denotes a fixing roller 115 as a fixing member and a pressing roller 116 as a pressing member, which are rotatably supported.

The fixing roller 115 rotatably supported by the fixing device 114 is driven at a predetermined process speed by driving means (not shown) provided on the main body 101.

The fixing roller 115 has a thickness of 1.25 mm on the outer peripheral surface of a hollow cored bar (not shown) formed of aluminum having an outer diameter of 40Φ and a thickness of 2.7 mm.
And a silicone rubber layer (not shown) made of LTV silicone rubber.

Therefore, the fixing roller 115 has improved toner releasability.

A halogen heater (not shown) is provided in a hollow portion of the cored bar of the fixing roller 115 as heating means for heating the fixing roller 115.

The pressure roller 116 which is rotatably supported by the fixing device 114 has a nip portion (not shown) having a predetermined width formed between the pressure roller 116 and the fixing roller 115. It is pressed into contact with the fixing roller 115 from below.

Therefore, the pressure roller 116 is driven by the rotation of the fixing roller 115.

The pressure roller 116 has a thickness of 1.75 on the outer peripheral surface of a hollow core (not shown) formed of aluminum to have an outer diameter of 39.4Φ and a thickness of 2.2 mm.
mm LTV silicone rubber is coated with a silicone rubber layer (not shown).

A halogen heater (not shown) is provided in the hollow portion of the metal core of the pressure roller 116 as a heating means for heating the pressure roller 116.

In the image forming apparatus 100,
The width of the nip formed between the fixing roller 115 and the pressure roller 116 is, for example, 6 mm.

In the image forming apparatus 100, A
Fixing roller 1 at the start of fixing operation on recording paper P of four sizes
15 and the pressure roller 116 have a surface temperature of, for example, 1
It is set to 80 ° C.

Paper discharge paths Tu1 and Tu2 for paper discharge extend from the fixing device 114 to the outside of the main body 101.

Therefore, the recording paper P on which the fixing operation has been performed is
The paper is discharged to the outside of the main body 101 via one of the paper discharge paths Tu1 and Tu2.

A series of printout processes are performed by the image forming apparatus 100 having the above-described configuration in the following manner.

A laser installed in the image forming apparatus 100 based on, for example, information corresponding to black among information of an image read by an image reading apparatus (not shown) installed in the image forming apparatus 100. A driver (not shown) turns on and off an electric signal to the laser scanner device 103.
FF.

The laser scanner device 103 that has received the electric signal turns the laser La on and off toward the photosensitive drum 102 based on the ON and OFF of the electric signal.

On the other hand, the photosensitive drum 102 is
A predetermined charge is given in advance by 04 and is charged to a predetermined potential.

Accordingly, the laser La turned on from the laser scanner 103 exposes the charged area on the surface of the photosensitive drum 102 to form an electrostatic latent image corresponding to, for example, black.

The photosensitive drum 10 on which the electrostatic latent image is formed
2 rotates in the R1 direction.

At the same time, for example, the toner container 105Bk
It moves from the development retreat position to the development position.

Therefore, the latent image area and the toner container 105
When Bk faces and approaches the shortest distance of 300 μm, the electrostatic latent image becomes a visible image (toner image) with black toner applied from the toner container 105Bk.

On the other hand, the recording paper P of the size desired by the user to be printed out is taken up from the paper supply cassette 112 by the paper supply roller 113 and then directed from the base end of the transport path Ru to the above-mentioned winding position. Transported.

The recording paper P, which is being conveyed along the conveyance path Ru, is returned to the winding position at a predetermined timing after the orientation of the recording paper P is corrected by the registration roller pair 117 and a series of detections by the leading edge sensor 118 are received. Is conveyed.

On the other hand, the transfer drum 106
Before the roller reaches the winding position,
8 is charged to a predetermined potential.

Accordingly, the recording paper P is charged to a predetermined potential by the suction roller 113 at the same time or after a predetermined time when it reaches the winding position, and is wound around the transfer drum 106 by electrostatic suction.

The recording paper P wound around the transfer drum 106 is opposed to a visualized area formed on the surface of the photosensitive drum 102 by the rotation of the transfer drum 106 in the R2 direction, so that the electrostatic attractive force is applied. As a result, a toner image based on black is transferred.

Hereinafter, transfer operations based on each of magenta, cyan, and yellow are performed in the same manner as described above.

The recording paper P on which the unfixed toner layer is formed by the transfer operation based on each of black, magenta, cyan, and yellow is transferred to the transfer drum 10 by the separation claw 110.
6 separated.

The recording paper P separated from the transfer drum 106 is sent to a fixing device 114.

From the transfer drum 106 to the fixing device 114
The unfixed toner layer is melted by heat and pressure by the fixing roller 115 and the pressure roller 116, and the recording paper P sent to the recording paper P is mixed and fixed.

The recording paper P having undergone the above-described process is discharged to the paper discharge path T.
When a sheet is discharged to the outside of the main body 101 via one of the path u1 and the sheet discharge path Tu2, a series of printout processes is completed.

[0064]

However, since both the fixing roller 115 and the pressure roller 116 are covered with a silicone rubber layer having a low thermal conductivity, the heat supplied from the halogen heater is 115
Also, it takes a certain amount of time to conduct heat to the surface of each of the pressure rollers 116.

Therefore, the heat transfer from the surfaces of the fixing roller 115 and the pressure roller 116 to the recording paper P and the unfixed toner layer carried on the recording paper P causes the fixing roller 11
5 and the surface temperature of each of the pressure rollers 115 decrease as the fixing operation proceeds.

Therefore, in general, due to the property that the image glossiness increases as the fixing temperature increases, and decreases as the fixing temperature decreases, an area where the image glossiness differs greatly on one recording sheet P. It is formed at a plurality of places.

For example, when the fixing operation is performed on the recording paper P having a basis weight of 80 g / m 2, the mass per unit area, the surface temperature of both the fixing roller 115 and the pressure roller 116 is from 180 ° C. It drops to 170 ° C.

Accordingly, the result is that the image glossiness is reduced by about 10% from the middle of the recording paper P.

When a continuous printout operation is performed on a plurality of recording sheets P, the recording sheets P are conveyed to the nip one after another.

For this reason, the fixing roller 115
The surface temperature of both the pressure roller 116 and the pressure roller 116 reaches the temperature regulation temperature that is a temperature suitable for fixing while the continuous printout operation is performed on the first to fifth recording sheets P, for example. Has not been obtained.

Therefore, the first to fifth recording sheets P
Is lower than the image glossiness of the sixth and subsequent sheets of recording paper P.

Therefore, a first method has been proposed in which the thickness of the silicone layer is reduced to increase the thermal conductivity of both the fixing roller 115 and the pressure roller 116.

Further, the fixing roller 1 from the halogen heater is used.
A second method of controlling the heat supply to both the pressure roller 15 and the pressure roller 116 has been proposed.

However, in the first method, as shown in FIG. 15, since the wrapping effect described below cannot be obtained, the toner layer is formed on the recording paper P like a color image printout. When two or more layers are stacked, there is a possibility that the fixing failure of the toner layer occurs at the end of the recording paper P.

In particular, when the transparent recording paper P is used for printing out a color image, the OHP (Over
When a color image formed on the recording paper P is projected on a screen by a Head Projector, there is a possibility that a pseudo contour in which a part of the color image projected on the screen becomes dark may occur.

Here, the wrapping effect refers to an area in which the thick silicone layer wraps the unfixed toner image carried on the recording paper P, so that the unfixed toner image is supplied with heat from the fixing roller 115. This is the effect of expanding.

In the second method, the fixing roller 1
15 is coated with a silicone rubber layer having a low thermal conductivity, for example, the surface temperature of the fixing roller 115 is reduced from 180 ° C. by heating with a halogen heater to correct the degree of decrease in glossiness by 10%. Even if the temperature is increased to 188 ° C., it takes about 6 seconds for the effect to appear.

On the other hand, since the process speed of the fixing roller 115 is, for example, 100 mm / sec, the leading end of the recording paper P located at the nip at the start of the fixing operation has an effect due to the heating correction of the halogen heater. Until it appears, it has advanced by 600 mm.

For this reason, at the same time when the surface temperature of the fixing roller 115 decreases from 180 ° C. to 170 ° C., for example,
Even if the halogen heater raises the heating temperature, the end of the recording paper P passes through the nip before the heat supplied by the halogen heater reaches the surface of the silicone rubber layer.

Therefore, the surface temperature of the fixing roller 115 cannot be maintained during the fixing operation.

It is not desirable to rapidly heat the fixing roller 115 with a halogen heater because the life of the fixing roller 115 is shortened.

Accordingly, the present invention provides an image forming apparatus for fixing an unfixed developer onto a transfer material by heat and pressure, when a single fixing operation and a continuous printout operation are performed, the image glossiness is maintained. It is an object of the present invention to provide an image forming apparatus capable of forming a printed high-quality print image.

[0083]

According to a first aspect of the present invention, an object of the present invention is to provide a fixing member for fixing a developer image to one surface of a sheet-like transfer material by heat; An image forming apparatus comprising: a pressing member that presses against the fixing member via the transfer material so as to press against the other surface of the material; and a heating unit that heats each of the fixing member and the pressing member. At
During a single fixing operation, which is a fixing operation on one transfer material, the temperature of each of the fixing member and the pressing member due to heat conduction from the fixing member and the pressing member to the transfer material is adjusted. In order to compensate for the decrease, after a predetermined time from the start of the single fixing operation, a pressure value changing means for changing a pressure value applied to the fixing member from the pressure member to a predetermined pressure value is provided. Is achieved by

According to a second aspect of the present invention, the above-mentioned object is achieved in the first aspect, wherein the fixing member is rolled so as to come into contact with the transfer material while rotating to perform a fixing operation by heat. The pressing value changing operation by the pressing value changing means is performed at the same time as the fixing portion of the fixing roller performing the fixing operation at the start of the single fixing operation completes one rotation or simultaneously. Achieved by being done almost simultaneously.

Further, according to the third invention of the present application,
In the first aspect, the fixing member is a fixing roller formed in a roll shape so as to perform a fixing operation by heat while rotating and contacting the transfer material. The pressure value changing operation is achieved by performing the pressure value changing operation continuously for a predetermined time before and after the fixing portion of the fixing roller performing the fixing operation at the start of the single fixing operation completes one rotation.

According to a fourth aspect of the present invention, the above object is achieved in any one of the first to third aspects, wherein the pressing value changing means comprises a plurality of transfer materials. When continuous printing is performed on the transfer material from the first sheet to a predetermined number of sheets when the continuous printing is performed, the pressure value applied from the pressing member to the fixing member is predetermined. This is achieved by changing the pressure value to.

Further, according to the fifth invention of the present application,
An object of the present invention is to provide a fixing member for fixing a developer image to one surface of a sheet-shaped transfer material by heat, and press-contact the fixing member via the transfer material so as to press the other surface of the transfer material. In an image forming apparatus including a pressing member and a heating unit for heating each of the fixing member and the pressing member, a single fixing operation as a fixing operation on one transfer material is performed. A predetermined time after the start of the single fixing operation, so as to compensate for a decrease in the temperature of each of the fixing member and the pressing member due to heat conduction from the fixing member and the pressing member to the transfer material. Pressure value changing means for changing the pressure value applied to the fixing member to a predetermined pressure value from the above, and an initial pressure which is a pressure value applied from the pressure member to the fixing member at the start of a single fixing operation. Initial pressure value setting means for setting the pressure value based on the type of the transfer material. It is achieved by.

According to a sixth aspect of the present invention, the above object is achieved in the fifth aspect, wherein the setting of the initial pressurizing value by the initial pressurizing value setting means is such that the transfer of the transfer material in the nip portion is performed. This is achieved by performing the determination in accordance with the type of the transfer material based on the detection of the type of the transfer material at a detection position located upstream in the direction.

Further, according to the seventh invention of the present application,
The above object is achieved in the sixth aspect by the fact that the detecting means is a glossiness sensor that measures the glossiness of the unfixed surface of the transfer material and detects the type of the transfer material.

According to an eighth aspect of the present invention, the above object is achieved in the sixth aspect, wherein the detecting means transmits light from one surface of the transfer material to the other surface, and This is achieved by a transmittance sensor that detects the type of the transfer material by comparing the amount of light before and after the light has passed through the transfer material.

Further, according to the ninth invention of the present application,
The above object is achieved by, in the sixth aspect, the detecting means being a whiteness sensor that measures the whiteness of the unfixed surface of the transfer material and detects the type of the transfer material.

According to a tenth aspect of the present invention, the above object is attained in one of the fifth to ninth aspects, wherein the pressurizing value changing means is provided on a plurality of transfer materials. When continuous printing is performed on the transfer material from the first sheet to a predetermined number of sheets when continuous printing is performed, the pressure applied from the pressing member to the fixing member is changed to a predetermined value. This is achieved by changing to a pressurized value.

That is, in the first invention according to the present application, the pressure value changing means is provided so as to compensate for the decrease in image gloss caused by the decrease in the temperature of each of the fixing member and the pressure member during the single fixing operation. However, after a predetermined time from the start of the single fixing operation, the pressure value applied from the pressure member to the fixing member is changed, so that a print image with uniform image gloss is formed on the transfer material. I do.

In the second invention according to the present application,
The fixing member according to the first aspect of the present invention is a fixing roller, and the fixing portion on the surface of the fixing roller, which has been performing the fixing operation at the start of the single fixing operation, completes one rotation, and at the same time, the application by the pressure value changing means is performed. Since the pressure value changing operation is performed, a print image in which the image glossiness is maintained uniformly is formed on the transfer material.

Further, in the third invention according to the present application, the fixing member of the first invention is a fixing roller, and the fixing member on the surface of the fixing roller which has been performing the fixing operation at the start of the single fixing operation. The pressurizing value changing operation is continuously performed by the pressurizing value changing means for a predetermined time before and after the part completes one rotation, so that the transfer image can be transferred to the transfer material with more uniform image glossiness. Formed.

Further, in the fourth invention according to the present application,
In one of the first to third inventions, the pressing value changing unit is configured to fix the pressing member from the pressing member during a continuous printout operation to the first to a predetermined number of transfer materials. Since the pressure value applied to the member is changed to a predetermined pressure value, uniform image glossiness is maintained over a plurality of transfer materials.

Further, in the fifth invention according to the present application, the initial pressurizing value setting means sets the initial pressurizing value corresponding to the type of the transfer material before the start of the single fixing operation. A print image having image glossiness is formed on the transfer material.

Further, in the sixth invention according to the present application,
The initial pressure value setting means of the fifth invention is based on a detection means for detecting the type of the transfer material at a detection position located upstream of a nip portion formed between the fixing means and the pressure means. Since the initial pressure value is set according to the type of the transfer material,
A print image having a suitable image gloss is formed on the transfer material.

Further, in the seventh invention according to the present application,
The detecting means of the sixth invention is a gloss sensor which detects the type of the transfer material by measuring the gloss of the unfixed surface of the transfer material. An initial pressure value corresponding to the type of the transfer material is set based on the detection of the degree sensor, and a print image having a suitable image gloss is formed on the transfer material.

In the eighth invention according to the present application,
Since the detecting means of the sixth invention is a transmittance sensor that detects the type of the transfer material by transmitting light to the transfer material and comparing the light amounts of the light before and after the light is transmitted through the transfer material, the initial sensor is used. The pressure value setting means sets an initial pressure value according to the type of the transfer material based on the detection of the transmittance sensor, and a print image having a suitable image gloss is formed on the transfer material.

Further, in the ninth invention according to the present application, the detecting means of the sixth invention may measure the whiteness of the unfixed surface of the transfer material to detect the type of the transfer material. Since it is a degree sensor, the initial pressurization value setting means sets an initial pressurization value according to the type of the transfer material based on the detection of the whiteness sensor so that a print image having a suitable image gloss level is obtained. Formed on the transfer material.

In the tenth invention according to the present application,
The pressure value changing means according to any one of the fifth to eighth inventions is characterized in that, while a continuous printout operation is performed on the transfer material from the first sheet to a predetermined number of sheets, the pressure member is fixed from the pressure member. Since the pressure value applied to the member is changed to a predetermined pressure value, uniform image glossiness is maintained over a plurality of transfer materials.

[0103]

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

(First Embodiment) First, a fixing device 1 that can be used in an image forming apparatus according to a first embodiment of the present invention will be described with reference to FIGS.

The same reference numerals are given to the same parts as those of the conventional fixing device 114 described with reference to FIG. 14, and the description is omitted.

FIG. 1 shows a state when the single fixing operation of the fixing device 1 is started, and FIG. 2 shows a state after a predetermined time Ta described below from the start of the single fixing operation of the fixing device 1. I have.

Here, the above-mentioned predetermined time Ta represents the time required for the fixing roller 115 of the fixing device 1 to make one rotation.

FIG. 3 shows an example of the relationship between the fixing pressure value, which is the pressure value applied from the pressure roller 116 to the fixing roller 115 during the single fixing operation, and the time from the start of the single fixing operation. FIG.

In FIG. 3, Pa represents the fixing pressure value at the start of the single fixing operation, and Pb represents the fixing pressure value at time Ta.

As shown in FIG. 1 or FIG. 2, the fixing device 1 is configured to change the fixing pressure value through a shaft of the pressure roller 116 during a single fixing operation. A pressurizing value changing device 2 as a pressurizing value changing means is provided.

The pressure value changing device 2 provided in the fixing device 1 includes a cam drive motor 3, a pressure spring bearing 4, a pressure spring 5, a pressure spring washer 6, a cam 7, a cam And a shaft 8.

The cam drive motor 3 provided in the pressure value changing device 2 rotates the cam shaft 8 by 180 ° after a time Ta from the start of the single fixing operation.

The cam drive motor 3 also rotates the cam shaft 8 by 180 ° at the end of the single fixing operation.

In the present embodiment, the timing for driving the cam drive motor 3 is set, for example, by using a timer (not shown) set as described below with an image forming apparatus capable of utilizing the fixing device 1. It is done by preparing for.

That is, the timer measures the time simultaneously with the start of the single fixing operation.

When the timer measures the time Ta or the time Tb required to complete the single fixing operation, the timer transmits the following drive command signal to the cam drive motor 3. Has become.

Here, the drive command signal is a signal for instructing the cam drive motor 3 to rotate the cam shaft 8 by 180 °.

Therefore, the time Ta from the start of the single fixing operation,
Alternatively, the timer from the timer after the time Tb indicates that the cam drive motor 3
, The drive timing of the cam drive motor 3 is set.

The cam shaft 8 provided in the pressure value changing device 2 is fixed to the cam 7 so as to be eccentric with respect to the center of the cam 7.

Therefore, each time the cam drive motor 3 is driven, the cam 7 rotates about the cam shaft 8 and the pressure spring washer 6 mounted on the cam 7 moves up and down in the longitudinal direction of the paper of FIG. Be moved.

Accordingly, the pressure spring 5 attached to the pressure spring bearing 4 and the pressure spring washer 6 so as to be interposed between the pressure spring bearing 4 and the pressure spring washer 6 can be moved up and down in the longitudinal direction of FIG. The pressurizing spring bearing 4 is moved up and down in the longitudinal direction of the drawing by expanding and contracting by the movement, whereby the pressing roller 116 is moved up and down in the longitudinal direction of the drawing to change the fixing pressure value.

That is, the time Ta from the start of the single fixing operation
Later, the cam drive motor 3 is driven to move the cam shaft 8 to 18
By rotating by 0 °, the cam 7 in the state of FIG. 1 rotates by 180 ° about the cam shaft 8 to the state shown in FIG. The paper is shifted upward.

Therefore, the pressing spring 5 is used as the pressing spring bearing 4
1 and the pressure spring washer 6, the elastic force applied from the pressure spring 5 to the pressure spring bearing 4 increases, and the pressure spring bearing 4 Shifted upward.

Therefore, the pressure roller 116 is strongly pressed by the fixing roller 115, and the fixing pressure value is increased from Pa to Pb as shown in FIG.

Then, a time T at the end of the single fixing operation
b, the cam drive motor 3 is driven again to move the camshaft 8 to 18
By rotating by 0 °, the cam 7 in the state of FIG. 2 rotates by 180 ° about the cam shaft 8 to be in the state of FIG.
The pressure spring washer 6 is shifted downward in FIG.

Therefore, the compression spring 5 is released from the state of being compressed between the compression spring bearing 4 and the compression spring washer 6, so that the compression spring 5 is released from the compression spring bearing 4. The elastic force applied to the pressure spring bearing 4 decreases.
Is shifted downward in FIG.

Therefore, the fixing pressure value from the pressure roller 116 to the fixing roller 115 is reduced from Pb to Pa as shown in FIG. 3, and the fixing device 1 prepares for the next single fixing operation. Can be

Next, the setting of the increasing amount of the fixing pressure value by the pressure value changing device 2 will be described with reference to FIG.

FIG. 4 is a graph showing an example of the relationship between the converted pressure value and the image glossiness described below.

Here, the above-mentioned reduced pressure value is a fixing pressure value required to realize each image glossiness shown in FIG. 4 only by pressing from the pressing roller 116 to the fixing roller 115. Value.

In this embodiment, the fixing pressure values Pa and Pb are set according to the size of the cam 7 or the combination of the cam 7 and the pressure spring 5.

Accordingly, the surface temperature of both the fixing roller 115 and the pressure roller 116 is set at, for example, 180 ° C. at the start of the single fixing operation, and after a time Ta from the start of the single fixing operation, the surface temperature of the fixing roller 115 and the pressing roller 116 is set. It is assumed that the surface temperature of both the pressure rollers 116 decreases to 170 ° C.

It is also assumed that the image glossiness of the copy image formed on the recording paper P decreases from 35% to 25% based on the decrease in the surface temperature of both the fixing roller 115 and the pressure roller 116. .

The above-mentioned numerical values are obtained by the pressurized value changing device 2
Is an example for explaining the setting operation of the increase amount of the fixing pressure value by the above, and the present invention is not limited to these.

As can be seen from FIG.
% And 35% of the image glossiness are 29 kg and 35.5 kg, respectively.

Therefore, at the same time when the surface temperature of the fixing roller 115 decreases from 180 ° C. to 170 ° C.,
After a time Ta from the start of the single fixing operation, the fixing pressure value becomes 3
If the weight is increased by 5.5 kg−29 kg = 6.5 kg, the image glossiness of the printed image can be maintained substantially uniform over one recording sheet P.

Therefore, at the time Ta, the pressure roller 116
From the fixing pressure value Pb applied to the fixing roller 115 from P
For example, the cam 7 and the pressure spring 5 may be combined so that a + 6.5 is obtained.

The fixing pressure value is increased by a predetermined amount after the time Ta from the start of the single fixing operation by the pressure value changing device 2 having the above-described configuration, so that the surface temperatures of the fixing roller 115 and the pressure roller 116 decrease. Thus, the user can be provided with a printed image having an image gloss maintained almost uniformly by compensating for the decrease in the image gloss based on the image.

(Second Embodiment) Next, a fixing device 9 which can be used in an image forming apparatus according to a second embodiment of the present invention is shown in FIG.
This will be described with reference to FIG.

Incidentally, the same reference numerals are given to the common parts and the like between the conventional fixing device 114 described with reference to FIG. 14 and the fixing device 1 of the first embodiment, and the description will be omitted.

FIG. 5 is a diagram showing a state of the fixing device 9 when the operation of changing the fixing pressure value is performed.

FIG. 6 is a graph showing an example of the relationship between the fixing pressure value and the time from the start of the single fixing operation.

In FIG. 6, Pb 'represents the maximum fixing pressure value during the single fixing operation.

The pressure value changing device 10 as the pressure value changing means provided in the fixing device 9 includes a cam drive motor 11 set as follows.

The cam drive motor 11 provided in the pressurized value changing device 10 is different from the cam drive motor 3 in the first embodiment in that the cam shaft 8 is moved for a predetermined period ΔT with time Ta interposed therebetween as shown in FIG. After being vibrated to the left and right on the paper, it is rotated by 180 degrees.

The cam drive motor 11 rotates the cam shaft 8 by 180 ° at the end of the single fixing operation.

Therefore, the cam drive motor 11 is driven for a predetermined period ΔT with the time Ta interposed therebetween to oscillate the cam shaft 8 to the left and right in FIG. Since the pressure spring washer 6 is moved up and down in the longitudinal direction of the paper by vibrating left and right, the pressure roller 116 is moved up and down in the longitudinal direction of the paper of FIG.

Therefore, as shown in FIG. 6, during the predetermined period ΔT including the time Ta, the fixing pressure value is set to Pa
And Pb ′ continuously vibrate, so that the fixing roller 11
5 and the decrease in the image glossiness due to the decrease in the surface temperature of the pressure roller 116 is continuously compensated for a predetermined period ΔT, and the print image with the image glossiness maintained more uniformly than in the first embodiment. Can be provided to the user.

In this embodiment, the predetermined period ΔT
During this time, the cam drive motor 11 is driven to oscillate the cam 7 to the left and right on the paper surface to continuously increase the fixing pressure value. However, the present invention is not limited to this method. Similar effects can be obtained by a method in which the cam drive motor 11 is set so as to change the fixing pressure value as shown in FIGS.

Further, the pressure value changing means is not limited to the pressure value changing device having the configuration described in the first embodiment and the second embodiment. An electromagnetic solenoid having an access portion that can be put in and out when turned off may be used.

(Third Embodiment) Next, an image forming apparatus 12 according to a third embodiment of the present invention will be described with reference to FIGS.

Note that the same reference numerals and the like as those of the conventional image forming apparatus 100 described with reference to FIG. 14 and the fixing device 1 of the first embodiment denote the same parts, and a description thereof will be omitted.

The image forming apparatus 12 includes a fixing device 13
And a gloss sensor 17 as a detecting means for detecting the type of the recording paper P, and a controller 18.

The fixing device 13 provided in the image forming apparatus 12 has the same configuration as the fixing device 1 of the first embodiment, except that a push-pull solenoid 14 as an initial pressure value setting means is provided. Has become.

The push-pull solenoid 14 provided in the fixing device 13 includes a solenoid body 15 and a telescopic part 1.
And the telescopic part 16 is provided with the solenoid body 1.
5 so as to be extendable and contractible.

When an elongation command signal described below is turned on by the controller 18, the solenoid main body 15 provided in the push-pull solenoid 14 moves the expansion / contraction section 16 upward by a predetermined amount in FIG. 9 based on the elongation command signal. It is designed to be lengthened.

Here, the extension command signal is a signal for instructing the solenoid body 15 to extend the extendable portion 16 by a predetermined length upward in FIG.

The gloss sensor 17 provided in the image forming apparatus 12 has a light emitting element 17a and a light receiving element 17b.

The light emitting element 17a provided in the glossiness sensor 17 emits a predetermined amount of light toward an unfixed surface of the recording paper P on which the recording paper P is not fixed.

The light receiving element 17b provided in the glossiness sensor 17 receives light reflected from the unfixed surface. In the present embodiment, the angle between the normal direction of the light emitting element 17a and the normal direction of the light receiving element 17b is, for example, 75 °.

The glossiness sensor 17 having the above-described configuration determines the glossiness of the unfixed surface by comparing the amount of light emitted from the light emitting element 17a toward the unfixed surface with the amount of light received by the light receiving element 17b. The degree is detected, and a detection signal based on the detection is transmitted to the controller 18.

Table 1 shows the measurement results of the glossiness of the unfixed surface of the following four types of recording paper measured by the glossiness sensor 17.

The recording paper P used for measuring the glossiness by the glossiness sensor 17 is the recording paper 1 [Xerox4
024 (registered trademark, basis weight = 75 g / m ² )], recording paper 2
[Voice Cascade (registered trademark, basis weight = 80 g /
m ² )], recording paper 3 [CLC SK (registered trademark, basis weight =
80 g / m ² )] and recording paper 4 [Xerox 4024 (registered trademark, basis weight = 105 g / m ² )].

[0164]

[Table 1] As can be seen from Table 1, it is possible to distinguish the basis weight 80 g / m ² or less of plain paper as a boundary glossiness 7.0%, and a basis weight 80 g / m ² or more thick.

Therefore, in the present embodiment, the controller 18 provided in the image forming apparatus 12 compares the value of 7.0% of the glossiness with the glossiness detected by the glossiness sensor 17 in advance. Is recorded in advance as a glossiness comparison value.

Incidentally, the recording of the glossiness comparison value of 7.0% by the controller 18 may be achieved by incorporating a CPU having a memory capable of recording predetermined information or the like in the controller 18, for example.

The controller 18 compares the detection signal from the gloss sensor 17 with the gloss comparison value 7.0%, and determines the gloss value based on the detection signal as the gloss comparison value 7. When it is 0.0% or more, it is recognized that thick paper has been fed, and the extension command signal to the solenoid body 15 is turned ON.

The ON / OFF of the elongation command signal from the controller 18 to the solenoid body 15 is recorded on the controller 18 with the glossiness corresponding to each of various types of recording paper. 17 may be performed based on a comparison with the detection signal from the control unit 17.

With the fixing device 13 having the above structure, an initial pressure value, which is a fixing pressure value at the start of the single fixing operation, is determined in the following manner.

The glossiness of the recording paper P of the size selected by the user is detected by the glossiness sensor 17 during the conveyance.

The gloss sensor 17 that has detected the gloss of the recording paper P transmits a detection signal based on the detection to the controller 18.

The controller 18 having received the detection signal from the gloss sensor 17 compares the detection signal with a gloss comparison value 7.0% of the controller 18 previously recorded in, for example, a memory. .

Next, when the glossiness detected by the glossiness sensor 17 is equal to or greater than the glossiness comparison value of 7.0%, the controller 18 turns on a predetermined extension command signal to the solenoid body 15.

The solenoid body 15 which has received the predetermined elongation command signal from the controller 18 extends the expansion / contraction section 16 by a predetermined length upward in FIG. 9 on the basis of the elongation command signal.

Therefore, since the pressure value changing device 2 provided in the fixing device 13 is shifted upward in the drawing, the fixing pressure value applied from the pressure roller 116 to the fixing roller 115 is increased, which is suitable for thick paper. Initial pressurization value is set.

Therefore, there is an advantage that a high quality print image can be formed not only on plain paper but also on thick paper.

(Fourth Embodiment) Next, an image forming apparatus 19 according to a fourth embodiment of the present invention will be described with reference to FIG.

Note that the same reference numerals are given to the common parts and the like between the conventional image forming apparatus 100 described with reference to FIG. 14 and the fixing device 13 of the third embodiment, and description thereof will be omitted.

The image forming apparatus 19 includes a transmittance sensor 20 as detecting means for detecting the type of the recording paper P.

The transmittance sensor 20 provided in the image forming apparatus 19 has a light emitting element 20a and a light receiving element 20b.

The light emitting element 20a provided in the transmittance sensor 20 emits a predetermined amount of light toward the unfixed surface.

The light receiving element 20b provided in the transmittance sensor 20 receives light transmitted through the unfixed surface. The transmittance sensor 20 having the above configuration includes:
By comparing the amount of light emitted from the light emitting element 20a toward the unfixed surface and the amount of light received by the light receiving element 20b, the transmittance of the unfixed surface is detected, and a detection signal based on this detection is generated. The data is transmitted to the controller 18.

Table 2 shows the measurement results of the transmittance of the following four types of recording paper on the unfixed surface of the recording paper measured by the transmittance sensor 20.

The recording paper P used for the measurement of the transmittance by the transmittance sensor 20 was recording paper 1 [DK (registered trademark, basis weight = 64 g / m ² )], recording paper 2 [Xerox4
024 (registered trademark, basis weight = 75 g / m ² )], recording paper 3
[Xerox 4024 (registered trademark, basis weight = 90 g /
m ² )], recording paper 4 [Xerox 4024 (registered trademark,
Basis weight = 105 g / m ² )] and recording paper 5 [silver ring (registered trademark, basis weight = 128 g / m ² )].

[0185]

[Table 2] As can be seen from Table 2, the plain paper and the cardboard can be distinguished from each other at a transmittance of 2.0%.

Thus, in the present embodiment, the controller 18 provided in the image forming apparatus 19 compares the value of the transmittance of 2.0% with the transmittance based on the detection signal from the transmittance sensor 20. The above-mentioned transmittance comparison value is previously recorded in, for example, the above-mentioned memory.

The controller 18 compares the detection signal from the transmittance sensor 20 with the transmittance comparison value of 2.0%, and determines the transmittance value based on the detection signal as the transmittance comparison value 2. When it is 0% or less, it is recognized that thick paper has been fed, and the extension command signal to the solenoid body 15 is turned ON.

As described in the third embodiment, ON / OFF of the extension command signal from the controller 18 to the solenoid body 15 is controlled by the controller 1.
8, the transmittance corresponding to each of the various types of recording paper may be recorded, and the determination may be made based on a comparison between these and a detection signal from the transmittance sensor 20.

Thus, the initial pressure value suitable for thick paper is set by the image forming apparatus 19 in the same manner as in the third embodiment. It has the advantage that it can also be formed on cardboard.

(Fifth Embodiment) Next, an image forming apparatus 21 according to a fifth embodiment of the present invention will be described with reference to FIG.

The conventional image forming apparatus 100 described with reference to FIG. 14 and the image forming apparatus 13 of the third embodiment
The same reference numerals are given to common parts and the like, and the description is omitted.

The image forming apparatus 21 has a whiteness sensor 22 as a detecting means for detecting the type of the recording paper P.

The whiteness sensor 22 provided in the image forming apparatus 21 has a light emitting element 22a and a light receiving element 22b.

The light emitting element 22a provided in the whiteness sensor 22 emits a predetermined amount of light toward the unfixed surface.

The light receiving element 22b provided in the whiteness sensor 22 receives light reflected on the unfixed surface. By the way, when light is irradiated on a completely white object, it is not absorbed by the white object at all,
That is, the light is reflected from the white object without decreasing the light amount based on the energy of the light.

Therefore, as the object irradiated with light has a color closer to white, the amount of light reflected by the object shows a value closer to the amount of light at the time of irradiation.

Therefore, the transmittance sensor 22 having the above-described structure can be used.
Detects the whiteness of the unfixed surface by comparing the amount of light emitted from the light emitting element 22a toward the unfixed surface with the amount of light received by the light receiving element 22b, and performs detection based on this detection. A signal is transmitted to the controller 18.

Table 3 shows the measurement results of the whiteness on the unfixed surface of the following four types of recording paper measured by the whiteness sensor 22.

The recording paper P used for measuring the whiteness by the whiteness sensor 22 was recording paper 1 [DK (registered trademark, basis weight = 64 g / m ² )] and recording paper 2 [Xerox4
024 (registered trademark, basis weight = 75 g / m ² )], recording paper 3
[CLC SK (registered trademark, basis weight = 80 g / m ² )],
Recording paper 4 [Xerox 4024 (registered trademark, basis weight = 10
5 g / m ² )].

[0200]

[Table 3] As can be seen from Table 3, the plain paper and the cardboard can be distinguished from each other at a whiteness of 84%.

Therefore, in the present embodiment, the controller 18 provided in the image forming apparatus 21 compares the value of 84% whiteness with the whiteness based on the detection signal from the whiteness sensor 22. Is previously recorded in, for example, the above-mentioned memory.

The controller 18 compares the detection signal from the whiteness sensor 22 with the whiteness comparison value of 84%, and determines the whiteness value based on the detection signal as the whiteness comparison value 8.
When it is 4% or more, it is recognized that thick paper has been fed, and the extension command signal to the solenoid body 15 is turned ON.

The ON / OFF of the extension command signal from the controller 18 to the solenoid body 15 is performed as described in the third embodiment and the like.
The whiteness corresponding to each of the various types of recording paper may be recorded in advance, and the determination may be made based on a comparison between the whiteness and a detection signal from the whiteness sensor 22.

Therefore, the initial pressure value suitable for thick paper is set by the image forming apparatus 21 in the same manner as in the third embodiment. It has the advantage that it can also be formed on cardboard.

(Sixth Embodiment) Next, a continuous printout operation performed by an image forming apparatus according to a sixth embodiment of the present invention will be described with reference to FIGS.

Note that the image forming apparatus according to the present embodiment
Since the configuration is the same as that of any one of the image forming apparatuses 12, 19, and 21 described in the third to fifth embodiments, the apparatuses included in the image forming apparatus and the image forming apparatus The description of the single fixing operation process according to the first embodiment will be omitted.

The image forming apparatus is designed so that a user can instruct a continuous printout operation.
For example, a continuous printout execution button (not shown) having a function of instructing execution of a continuous printout operation is provided.

In the image forming apparatus, for example, the photosensitive drum 102 or the transfer drum 10
For example, the photosensitive drum 102, the transfer drum 106, and the like are set to a predetermined potential or the like by rotating the 6 or the like several times in the clockwise direction, for example, by performing multiple forward rotations, to prepare for the next single fixing operation. It has become.

In the present embodiment, the setting of the photosensitive drum 102, the transfer drum 106, and the like to a predetermined potential or the like is performed by causing the photosensitive drum 102, the transfer drum 106, or the like to perform the pre-multiple rotation. However, the photosensitive drum 102, the transfer drum 106, and the like are rotated several times in a counterclockwise direction, that is, by rotating the photosensitive drum 102, the transfer drum 106, and the like a number of times, so that the potential of the photosensitive drum 102, the transfer drum 106, and the like is set to a predetermined potential. Settings may be made.

Further, during continuous printout, the image forming apparatus does not set the photosensitive drum 102 and the transfer drum 106 by the preceding multi-rotation, but sequentially prints a plurality of recording sheets. A transfer operation, a fixing operation, and the like are performed.

Further, the image forming apparatus is provided with a detecting means (not shown) for detecting whether or not the setting to the photosensitive drum 102, the transfer drum 106, and the like by the preceding multi-rotation is performed. Based on the detection, it is also determined whether or not a continuous printout operation is being performed.

In the image forming apparatus, when a continuous printout operation is performed while the fixing pressure value is kept constant, heat conduction from the surface of the fixing roller 115 to the recording paper, Due to the small thermal conductivity of the silicone rubber layer covering the outer peripheral surface of the fixing roller 115, it takes a certain time for the surface temperature of the fixing roller 115 to reach a predetermined temperature.

For this reason, for the first to several sheets, for example, the fifth sheet, the surface temperature of the fixing roller 115 does not reach the temperature regulation temperature which is a temperature suitable for fixing. Thus, the fixing operation is performed.

Therefore, the image glossiness of the print image formed on the first to several sheets, for example, the fifth sheet of recording paper is as follows:
As a result, for example, the image glossiness of the print image formed on the sixth and subsequent recording sheets is reduced by, for example, 10% from 40%, for example.

Therefore, when the image forming apparatus receives an instruction to execute a continuous printout operation from a continuous printout execution button (not shown), the image forming apparatus sends the image to the photosensitive drum 102, the transfer drum 106, and the like by the preceding multiple rotations. Is set, the fixing pressure value is changed to the pressure value changing device 2.
Thus, a predetermined amount, for example, 37-35.5 = 1.5 kg, is increased.

In the above image forming apparatus, when the continuous printout operation on a plurality of recording sheets starts from the first sheet to a predetermined number, for example, the sixth sheet, the first to fifth sheets. The fixing pressure value which has been applied to the recording paper up to the above is increased by a predetermined value by the pressure value changing device 2, for example, 37-35.5 = 1.5.
kg.

Next, the procedure of the continuous printout operation in the image forming apparatus will be described with reference to FIG.

FIG. 13 is a flowchart showing the procedure of a continuous printout operation in the image forming apparatus.

First, the power of the image forming apparatus is turned on (step 200).

Next, when the user presses, for example, a continuous printout execution button, execution of continuous printout by the image forming apparatus is instructed (step 20).
1).

The image forming apparatus that has received the continuous printout execution command resets the number counter provided in the image forming apparatus to 0 so as to display the number of recording sheets for which continuous printout has been completed (step 202). .

Next, the image forming apparatus includes the photosensitive drum 1
02, the transfer drum 106, and the like are detected to make multiple forward rotations (step 203).

The photosensitive drum 102 and the transfer drum 106
The image forming apparatus that has detected the pre-multiple rotations such as the above increases the fixing pressure value by a predetermined value (step 204).

Thus, the fixing operation on the first sheet of recording paper is performed by the fixing device 12 whose fixing pressure value has been increased by a predetermined value (step 205).

Thereafter, the fixing operation is performed on the second to fifth recording sheets at the fixing pressure value applied to the first recording sheet (step 206).

Next, before the fixing operation on the sixth recording sheet is performed, the fixing pressure value is returned to the value before the increase (steps 207 and 208).

Thereafter, the fixing operation is performed on the seventh and subsequent recording sheets at the fixing pressure value applied to the sixth recording sheet (step 209).

Therefore, uniform image glossiness can be maintained over all recording sheets on which continuous printout operation has been performed, and a high-quality continuous print image can be provided to the user.

[0229]

As described above, according to the first aspect of the present invention, the decrease in the image glossiness caused by the decrease in the temperature of each of the fixing member and the pressure member during the single fixing operation is prevented. To compensate, the pressure value changing means changes the pressure value applied to the fixing member from the pressure member a predetermined time after the start of the single fixing operation, so that the image glossiness is maintained uniform. High-quality print image can be provided to the user.

Further, according to the second invention of the present application, the fixing member of the first invention is a fixing roller, and the fixing member on the surface of the fixing roller performing the fixing operation at the start of the single fixing operation. At the same time that the fixing portion has completed one rotation, the pressure value changing operation is performed by the pressure value changing means, so that it is possible to provide a user with a high quality print image in which the image glossiness is maintained uniformly. it can.

Furthermore, according to the third invention of the present application,
The fixing member according to the first aspect of the present invention is a fixing roller, which is pressurized for a predetermined period of time before and after the fixing portion on the surface of the fixing roller that has been performing the fixing operation at the start of the single fixing operation completes one rotation. Since the pressure value changing operation by the value changing means is performed continuously, it is possible to provide the user with a higher quality print image in which the image glossiness is maintained more uniformly.

Further, according to the fourth invention of the present application, one of the first to third inventions, the pressurizing value changing means is provided for transferring the first to the predetermined number of transfer materials. While the continuous printout operation is performed, the pressure value applied from the pressure member to the fixing member is changed to a predetermined pressure value until the temperature of the fixing unit and the pressure unit rises to the predetermined temperature. To compensate for the decrease in image gloss due to the fixing operation performed.
A uniform image glossiness is maintained over a plurality of transfer materials, and a high-quality print image can be provided to the user.

Further, according to the fifth invention of the present application,
Before the start of the single fixing operation, the initial pressure value setting means sets the initial pressure value according to the type of the transfer material. A print image having high image glossiness can be provided to the user.

According to the sixth invention of the present application, the initial pressure value setting means of the fifth invention is arranged upstream of the nip formed between the fixing means and the pressure means. Since the initial pressure value according to the type of the transfer material is set based on the detection unit that detects the type of the transfer material at the detected detection position, the fixing is suitably performed on the transfer material, and the high-quality image is obtained. A print image having a gloss level can be provided to the user.

Further, according to the seventh invention of the present application,
The detecting means of the sixth invention is a gloss sensor for detecting the type of the transfer material by measuring the gloss of the unfixed surface of the transfer material. Since a suitable initial pressurization value is set for the transfer material based on the type of the transfer material based on the detection of the sensor, a print having a high-quality image glossiness can be performed by suitably fixing the transfer material. Images can be provided to the user.

According to the eighth aspect of the present invention, the detecting means of the sixth aspect transmits light to the transfer material and compares the amount of light before and after transmission through the transfer material. A transmittance sensor for detecting the type of the transfer material, and an initial pressure value setting unit sets an initial pressure value suitable for the transfer material according to the type of the transfer material based on the detection of the transmittance sensor. Since the setting is performed, the transfer material is appropriately fixed, and a print image having high-quality image gloss can be provided to the user.

Further, according to the ninth invention of the present application,
The detecting means of the sixth invention is a whiteness sensor for detecting the type of the transfer material by measuring the whiteness of the unfixed surface of the transfer material, and the initial pressure value setting means includes Since a suitable initial pressure value for the transfer material is set in accordance with the type of the transfer material based on the detection of the sensor, fixing is performed at an initial pressure value suitable for the transfer material, and a high quality image is formed. A print image having a gloss level can be provided to the user.

In the tenth invention according to the present application,
The pressure value changing means according to any one of the fifth to eighth inventions is characterized in that, while a continuous printout operation is performed on the transfer material from the first sheet to a predetermined number of sheets, the pressure member is fixed from the pressure member. The pressure value applied to the member is changed to a predetermined pressure value to compensate for a decrease in image glossiness due to a fixing operation performed until the temperature of the fixing unit and the pressure unit rises to the predetermined temperature. The uniform image glossiness is maintained over the transfer material, and a high quality print image can be provided to the user.

[Brief description of the drawings]

FIG. 1 shows a state when a single fixing operation of a fixing device according to a first embodiment of the present invention is started.

FIG. 2 shows a state after a predetermined time from the start of a single fixing operation of the fixing device of FIG.

FIG. 3 is a graph showing an operation of changing a fixing pressure value by the pressure value changing device according to the first embodiment of the present invention.

FIG. 4 is a graph showing a relationship between a converted pressure value and image glossiness.

FIG. 5 illustrates a state after a predetermined time from the start of a single fixing operation of the fixing device according to the second embodiment of the present invention.

FIG. 6 is a graph showing an operation of changing a fixing pressure value by a pressure value changing device according to a second embodiment of the present invention.

FIG. 7 is a graph showing an operation of changing a fixing pressure value by a pressure value changing device according to a second embodiment of the present invention.

FIG. 8 is a graph showing an operation of changing a fixing pressure value by a pressure value changing device according to a second embodiment of the present invention.

FIG. 9 illustrates a state after a predetermined time from the start of a single fixing operation of the fixing device according to the third embodiment of the present invention.

FIG. 10 illustrates a schematic configuration of an image forming apparatus that can utilize the fixing device of FIG. 9;

FIG. 11 shows a schematic configuration of an image forming apparatus according to a fourth embodiment of the present invention.

FIG. 12 shows a schematic configuration of an image forming apparatus according to a fifth embodiment of the present invention.

FIG. 13 is a flowchart illustrating a procedure of a continuous printout operation performed by an image forming apparatus according to a sixth embodiment of the present invention.

FIG. 14 shows a schematic configuration of a conventional image forming apparatus.

FIG. 15 is a diagram illustrating a thickness effect.

[Explanation of symbols]

 2 Pressure value change device (Pressure value change means) 10 Pressure value change device (Pressure value change means) 14 Push-pull solenoid (Initial pressure value setting means) 17 Glossiness sensor (Detection means) 20 Transmittance sensor (Detection means) 22 Whiteness sensor (detection means)

Claims (10)

[Claims] 1. A fixing member for fixing a developer image to one surface of a sheet-shaped transfer material by heat, and a pressure contact with the fixing member via the transfer material so as to press the other surface of the transfer material. A fixing operation as a fixing operation on one transfer material is performed in an image forming apparatus having a pressing member to be heated and a heating unit for heating each of the fixing member and the pressing member. In order to compensate for a decrease in the temperature of each of the fixing member and the pressing member due to heat conduction from the fixing member and the pressing member to the transfer material, the pressing is performed after a predetermined time from the start of the single fixing operation. An image forming apparatus comprising: a pressure value changing unit configured to change a pressure value applied from a member to the fixing member to a predetermined pressure value. The fixing member is a fixing roller formed in a roll shape so as to perform a fixing operation by heat while rotating and contacting a transfer material. The image forming apparatus according to claim 1, wherein the fixing operation is performed simultaneously or almost simultaneously when the fixing portion of the fixing roller that has performed the fixing operation at the start of the single fixing operation completes one rotation. 3. The fixing member is a fixing roller formed in a roll shape so as to contact with the transfer material while rotating and perform a fixing operation by heat. 2. The image forming apparatus according to claim 1, wherein the fixing is performed continuously for a predetermined time before and after the fixing portion of the fixing roller that has performed the fixing operation at the start of the single fixing operation completes one rotation. 4. The pressurizing value changing means performs continuous printout on a first to a predetermined number of transfer materials when continuous printout is performed on a plurality of transfer materials. 4. The image forming apparatus according to claim 1, wherein a pressure value applied from the pressure member to the fixing member is changed to a predetermined pressure value during the interval. 5. A fixing member for fixing a developer image to one surface of a sheet-like transfer material by heat, and press-contacting the fixing member via the transfer material so as to press the other surface of the transfer material. A fixing operation as a fixing operation on one transfer material is performed in an image forming apparatus having a pressing member to be heated and a heating unit for heating each of the fixing member and the pressing member. In order to compensate for a decrease in the temperature of each of the fixing member and the pressing member due to heat conduction from the fixing member and the pressing member to the transfer material, the pressing is performed after a predetermined time from the start of the single fixing operation. A pressure value changing means for changing a pressure value applied from the member to the fixing member to a predetermined pressure value, and an initial value which is a pressure value applied from the pressure member to the fixing member at the start of a single fixing operation. Initial pressure value setting means for setting the pressure value based on the type of the transfer material. An image forming apparatus comprising: 6. The setting of the initial pressure value by the initial pressure value setting means is based on the detection of the type of the transfer material at a detection position located upstream of the nip portion in the transport direction of the transfer material. 6. The image forming apparatus according to claim 5, wherein the transfer is performed in accordance with the type of the transfer material. 7. The image forming apparatus according to claim 6, wherein the detection unit is a gloss sensor that measures the gloss of the unfixed surface of the transfer material and detects the type of the transfer material. 8. A transmittance for transmitting light from one surface of the transfer material to the other surface, and detecting the type of the transfer material by comparing the amount of light before and after the light is transmitted through the transfer material. The image forming apparatus according to claim 6, wherein the image forming apparatus is a sensor. 9. The image forming apparatus according to claim 6, wherein the detecting means is a whiteness sensor that measures the whiteness of the unfixed surface of the transfer material and detects the type of the transfer material. 10. The pressurizing value changing means performs continuous printout on a first to a predetermined number of transfer materials when continuous printout is performed on a plurality of transfer materials. 11. The image forming apparatus according to claim 4, wherein a pressure value applied from the pressure member to the fixing member is changed to a predetermined pressure value during the interval.