JPH0266587A - Color picture fixing device - Google Patents

Abstract

PURPOSE:To always obtain a satisfactory discharging speed and melted condition of toner by performing an appropriate fixing operation depending on whether a sheet to be fixed is a normal sheet or an OHP sheet. CONSTITUTION:A sheet 26 to be fixed, to which toner is attached, passes between a fixing roller pair 30 and 31; at least one of the fixing rollers 30 and 31 has main heating means, 32 or 35; toner is fixed on the sheet 26, which is to be fixed, by heating and pressurizing toner while passing through the fixing roller pair. During that period of time, a discriminating means 38 first discriminates whether the sheet 26 is the normal sheet or the sheet for an OHP over sheet projector. For the recognition that the sheet 26 to be fixed is the OHP sheet, an auxiliary heating means 45 further heats the fixed sheet 26 after the toner is separated from the fixing rollers. Whichever of a normal sheet and an OHP sheet is used as a sheet to be fixed, the satisfactory discharging speed and melted condition of toner are always obtained; and trouble does not arise in the releasability of the fixing rollers.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a color image fixing device, particularly to ordinary paper and OHP sheets (sheets for overlapping projectors).
The present invention relates to a color image fixing device for fixing a color image on a computer.

[Conventional technology]

For example, an image fixing device in a color copying machine generally includes a pair of fixing rollers, at least one of which has a heater. The fixing rollers are in pressure contact with each other, so that the sheet to be fixed can pass between them. In order to obtain a translucent color image for OHP in the image fixing device, it is necessary to melt the toner in the fixing step until the toner particles attached to the OHP sheet melt and become integral with each other. In other words, if the degree of melting of the toner is increased further, the adhesion of the toner to the fixing roller will become too high, and the sheet will stick to the fixing roller and become wrapped around it. It is in a state of

For this reason, when fixing is performed using paper that is thin, stiff, and has poor toner melting properties under fixing conditions that allow the above-mentioned melting state to be obtained for an OHP sheet of a certain thickness,
The degree of melting of the toner becomes higher than necessary, resulting in problems such as paper wrapping and high-temperature offset.

In order to prevent such problems from occurring, conventional methods have been adopted: a low melting mode in which there is no need to melt the toner until it becomes translucent, and a low melting mode in which the toner does not need to be melted until it becomes translucent on the OHP sheet. The image fixing device can set two types of fixing conditions: a high melting mode for melting toner, and when an OHP sheet is detected, the circumferential speed of the fixing roller is reduced by about 45% to slowly melt the toner. A configuration (hereinafter referred to as the first prior art) is known in which a high melting state is obtained by this. In addition, the image fixing device can set two types of fixing conditions, low melting mode and high melting mode, as described above, and by manually switching the nip width increasing member to protrude and extend the heating time for the sheet, high melting mode can be set. A configuration for obtaining the state (hereinafter referred to as the second prior art) is also already known.

On the other hand, Japanese Patent Application Laid-Open No. 61-205968 discloses that the back side of the sheet to be fixed is placed along one of the fixing rollers even after passing the nip portion of the fixing roller, and the sheet to be fixed is further heated in the meantime.
A configuration for obtaining a high melting state (hereinafter referred to as the third prior art) is shown.

[Problem to be solved by the invention]

In the first and second conventional techniques, the following problems occur because the toner is melted in contact with the fixing roller until it reaches the limit where the sheet to be fixed wraps around the fixing roller.

(A) When the environmental temperature becomes high or when a weak fixing sheet is used, the fixing sheet gets wrapped around.

(B) Unless the fixing roller is heated to a temperature higher than the releasability limit, sufficient translucency of the toner cannot be obtained. That is, when trying to obtain sufficient translucency of the toner, the sheet to be fixed becomes wrapped around the toner.

(C) In order to obtain sufficient translucency of the toner, it is necessary to make the surface of the toner layer smooth, but it is not possible to make the surface of the toner layer smoother than the surface roughness of the fixing roller that the toner comes into contact with. .

In the third conventional technique, since normal paper is processed in the same way as OHP sheets, the following problems occur.

(A) When fixing is performed using paper that is thin and has a high toner melting property, the degree of toner melting becomes higher than necessary.

(B) Although it is possible to eject at high speed, normal paper can only be ejected at the same speed as OHP sheets.

(C) Since the paper is strongly curved, strong curling occurs in normal paper.

An object of the present invention is to be able to always obtain a good toner melting state and discharge speed even when using either normal paper or an OHP sheet as a fixing sheet, and also to be able to obtain a good toner melting state and discharge speed even when the environmental temperature or the material of the fixing sheet changes. It is an object of the present invention to provide a color image fixing device that does not easily cause problems such as wrapping or curling even when the fixing roller is used, and does not cause problems with the releasability or surface smoothness of the fixing roller.

[Means for Solving the Problems] A color image fixing device according to the present invention includes a fixing roller, a determining device, and an auxiliary heating device.

The fixing rollers are a pair of rollers that are in pressure contact with each other so that the toner-attached sheet can pass between them, and at least one of them has a main heating means. The determining means is a means for determining whether the sheet to be fixed is a regular paper or an OHP sheet.

The auxiliary heating means determines whether the sheet to be fixed is OHP by the determination means.
This means further heats the sheet to be fixed after the toner is separated from the fixing roller when it is determined that the sheet is a sheet.

[Operation] In the color image fixing device according to the present invention, the toner-attached sheet to be fixed passes between a pair of fixing rollers. The number of fixing rollers is small (both have the main heating means on one side,
The toner is heated and pressurized while passing through the fixing roller, thereby fixing the toner to the fixing sheet.

In this case, the determining means first determines whether the sheet to be fixed is a regular paper or an OHP sheet. The auxiliary heating means further heats the fixing sheet after the toner is separated from the fixing roller when the determining means determines that the fixing sheet is an OHP sheet. As a result, a good toner melting state and discharge speed can always be obtained regardless of whether normal paper or an OHP sheet is used as the fixing sheet, and the releasability of the fixing roller does not pose a problem.

Therefore, even if the environmental temperature or the material of the fixing sheet changes, problems such as wrapping or curling do not easily occur. In the case of HP sheets that require translucent images, the sheet to be fixed is further heated after the toner leaves the fixing roller, so the surface of the toner layer becomes smooth and the surface of the fixing roller becomes smooth. Gender is not an issue.

[Embodiment] In FIG. 1, a document table 12 on which a document 11 is placed is arranged above a copying machine body 0. As shown in FIG.

Further, a paper discharge tray 13 and a paper feed power center 14 are arranged on the side of the copying machine main body 10.

A photosensitive drum 15 is arranged inside the copying machine main body 10 . A charging device 16 is installed around the photoreceptor drum 15.
, rotary developing device 17, transfer device 18, paper separating device 19
and cleaning device 20 are arranged in this order. The rotary developing device 17 includes a yellow developing device, a magenta developing device, a cyan developing device, and the like. The transfer device 18 includes a transfer drum, a transfer corona, etc. that can grip the leading edge of the transfer material.

The paper separating device 19 has a separating claw and a separating charger. Further, above the photoreceptor drum 15, a movable exposure device 21 with an optical system is provided.

A color separation filter 22 including a blue filter, a green filter, and a red filter is arranged on the optical path between the mobile exposure device 21 and the photosensitive drum 15.

A paper feed conveyance device 23 is arranged between the lower part of the transfer device 18 and the paper feed cassette 14. Further, between the paper separation device 19 and the paper discharge tray 13, a paper discharge conveyance device 24 and an image fixing device 25 are arranged in order from the paper separation device 19 side.

FIG. 2 shows a state in which an OHP sheet is supplied to the image fixing device 25 as the sheet to be fixed 26. As shown in FIG. Second
As is clear from the figure, the paper discharge conveyance device 24 has an endless belt 27 that circulates in the direction of the arrow, and a microswitch is installed in the middle of the conveyance path of the endless belt 27 to detect the passage of the sheet to be fixed 26. 28 are arranged.

The image fixing device W25 includes a pair of upper and lower rollers 30 and 31. The upper roller 30 has a cylindrical metal core 29, a heater 32 disposed inside the cylindrical metal core 29, and an elastic body 33 made of silicone rubber or the like formed on the surface of the metal core 29. Upper roller 30 and lower roller 31
are in pressure contact with each other, and as a result, the lower roller 31 bites into the elastic body 33. On the downstream side in the fixing operation direction X, a separation claw 34 is arranged on the outer peripheral side of the elastic body 33. The lower roller 31 is a cylindrical metal member on which a layer of heat-resistant fluorocarbon resin or the like is formed, and has a heater 35 inside. On the downstream side of the fixing operation direction X,
A separation claw 36 is arranged on the outer peripheral side of the lower roller 31.

A guide plate 37 is disposed between the pair of rollers 30 and 31 and the discharged sheet conveyance device 24 for guiding the sheet to be fixed 26 from the discharged sheet conveyance device 24 between the pair of rollers 30 and 31. There is. The guide plate 37 is provided with an optical sensor 38 for detecting the type of the fixing sheet 26 and a charger 39 for charging the fixing sheet 26 in order from the paper discharge conveyance device 24 side.

A pair of paper ejection rollers 40 are arranged on the paper ejection side of the pair of rollers 30 and 31 with an interval therebetween.

On the paper ejection side of the paper ejection roller 40, a paper ejection tray 13 (FIG. 1) is arranged. Upper roller 30. A guide plate 4 disposed above is located between the lower roller 31 and the paper ejection roller 40.
1 and a guide plate 42 arranged below it.

The guide plate 41 is a member that extends generally in the horizontal direction, and its rear end is disposed near the contact portion of the paper discharge roller 40 .

A switching pawl 43 is arranged on the front end side of the guide plate 41. The switching claw 43 is driven by a solenoid 44, and the tip of the switching claw 43 is connected to the upper roller 30.
It is rotatable between the posture shown in FIG. 2 where it is placed on the side and the posture shown in FIG. 3 where it is placed on the lower roller 31 side. That is, when the switching claw 43 is in the attitude shown in FIG.

Further, when the switching claw 43 is in the position shown in FIG. 3, the fixing sheet 26 that has come out from between the rollers 30 and 31 is guided toward the guide plate 41 by the switching claw 43.

The guide plate 42 is grounded to eliminate static electricity from the fixing sheet 26, and its rear end is disposed near the contact portion of the paper discharge roller 40. The guide plate 42 is arranged to be inclined downward from the paper discharge roller 40 side toward the lower roller 31 side, and its front end is curved so as to be smoothly continuous with the separation claw 36. Between the separating claw 36 and the switching claw 43, an auxiliary heater 45 as an auxiliary heating means is arranged radially outward of the lower roller 31.

FjT The microswitch 28, the optical sensor 38, the charger 39, the solenoid 44, and the auxiliary heater 45 are each electrically connected to a control circuit 50. The control circuit 50 includes a microswitch 28 and an optical sensor 38
As will be described later, the charger 39, solenoid 44, and auxiliary heater 45 are operated and controlled at predetermined timing according to input signals from the controller.

Next, the operation will be explained.

In response to a copy command, the photosensitive drum 15 shown in FIG. 1 starts rotating, and its surface is uniformly charged by the charging device 16. Next, the reflected light image obtained by irradiating the document 11 on the document table 12 with the movable exposure device 21 is color-separated by the color separation filter 22, and the photoreceptor drum 15
formed as a latent image on the surface. Furthermore, rotating developing bag ff1
At step 17, a toner of a color corresponding to the filter color used in the color separation filter 22 is selected, and the latent image is visualized on the photoreceptor drum 15 using the toner.

On the other hand, the sheet to be fixed 26 stored in the paper feed cassette 14 is supplied to the transfer device 18 through the paper feed conveyance device 23 and wound around the transfer drum of the transfer device 18 . The transfer drum and the photosensitive drum 15 rotate synchronously, and a developed image is transferred to a predetermined position on the fixing sheet 26.

With the fixing sheet 26 wrapped around the transfer drum of the transfer device 18, the filter of the color separation filter 22 and the color of the toner in the rotary developing device 17 are changed to perform exposure, latent image formation,
By repeating the image formation and transfer operation, the original 11
A color image corresponding to the color image is transferred to the fixing sheet 26. When the transfer is completed, the sheet to be fixed 26 is peeled off from the transfer device 18 by the paper separation device 19, and the sheet to be fixed 26 is conveyed to the image fixing device 25 side by the paper discharge conveyance device 24.

When the to-be-fixed sheet 26 turns on the microswitch 28 of the paper discharge conveyance device 24, the control circuit 50 performs the following control. When the microswitch 28 detects that the sheet to be fixed 26 approaches the image fixing device 25, the optical sensor 38 is activated. When the fixing sheet 26 is an OHP sheet, the optical sensor 38 detects that the fixing sheet 26 is an OHP sheet because light passes through the fixing sheet 26 as shown in FIG. Based on this detection, the charger 39 and the auxiliary heater 45 are activated, and the solenoid 44 is activated.
As a result, the switching claw 43 is placed in the position shown in FIG. The sheet to be fixed 26 is charged when passing over a charger 39 and then supplied between an upper roller 30 and a lower roller 31 .

The sheet to be fixed 26 is heated by the heat of the heaters 32 and 35, and is heated by the heat of the upper roller 30 and the lower roller 3.
Pressure is applied between 1 and 1. As a result, the fixing sheet 2
The toner on No. 6 is melted to some extent. Since the fixing sheet 26 is charged by the charger 39, even after it leaves the nip between the upper roller 30 and the lower roller 31,
The state in which the sheet 26 to be fixed is adhered to the surface of the lower roller 31 is maintained. Therefore, the sheet 26 to be fixed passes between the lower roller 31 and the switching claw 43, and after passing between the lower roller 31 and the auxiliary heater 45, it is peeled off from the lower roller 31 by the separation claw 36.

During this time, the fixing sheet 26 is further heated by the heater 35 and the auxiliary heater 45, and is melted until the toner on the fixing sheet 26 becomes sufficiently translucent.

In this way, the final heating is performed after the fixing sheet 26 is separated from the upper roller 30, so the releasability of the upper roller 30 does not limit the degree of toner melting. Therefore, for example, in a low temperature environment, a 100 μm thick OH
Even if a 75 μm thick OHP sheet, which exhibits higher toner meltability, is used as the fixing sheet 26 after setting the conditions to obtain a good translucent image when using the P sheet, problems such as entrainment still occur. do not. Further, the surface of the toner layer is finished by supplementary heating by the auxiliary heater 45 based on the surface tension of the molten resin, so that a toner image with a smoother surface can be obtained.

Furthermore, the sheet 26 to be fixed reaches the guide plate 42, where the static electricity is removed and the sheet 26 is transported to the paper discharge roller 40 side. Then, the sheet to be fixed 26 is discharged onto the paper discharge tray 13 by a paper discharge roller 40 .

On the other hand, in the above-described operation, when the fixing sheet 26 is a normal paper, after the fixing sheet 26 turns on the microswitch 28, the optical sensor 26 turns on the optical sensor 26 as shown in FIG.
Since the light does not pass through the fixing sheet 26 at step 8, it is detected that the fixing sheet 1-26 is a normal paper. Based on this detection, the charger 39 and the auxiliary heater 45 are not activated, and the solenoid 44 causes the switching claw 43 to take the position shown in FIG. The sheet to be fixed 26 is supplied between the upper roller 30 and the lower roller 31 without being charged by the charger 39 .

The sheet to be fixed 26 is heated by the heat of the heaters 32 and 35, and is heated by the heat of the upper roller 30 and the lower roller 3.
Pressure is applied between 1 and 1. As a result, the fixing sheet 2
The toner above 6 melts appropriately. The sheet to be fixed 26 is
After leaving the nip between the upper roller 30 and the lower roller 31,
The paper passes over the switching claw 43 and is linearly guided toward the paper discharge roller 40 by the guide plate 41 . Then, the sheet 26 to be fixed is discharged onto the paper discharge tray 13 by the paper discharge roller 40 .

In this way, when a regular paper is supplied as the fixing sheet 26, no supplementary heating is performed and the toner is fused to a state suitable for the regular paper. Furthermore, since the paper ejection path is simple, the ejection speed can be increased.

In carrying out the present invention, instead of the optical sensor 38, the type of the fixing sheet 26 may be determined by the paper feed cassette 14, or the type may be set manually.

[Effects of the Invention] According to the color image fixing device according to the present invention, the fixing operation is performed depending on whether the sheet to be fixed is normal paper or OHP sheet. Even when used as a sheet, a good toner melting state and discharge speed can always be obtained.
The releasability of the fixing roller is no longer a problem. Therefore, according to the present invention, problems such as wrapping and curling do not easily occur even if the environmental temperature or the material of the fixing sheet changes. Moreover, according to the present invention, in the case of an OHP sheet that requires a translucent image, the sheet to be fixed is further heated after the toner leaves the fixing roller, so that the surface of the toner layer is smoothed. Therefore, the surface smoothness of the fixing roller does not become a problem.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical cross-sectional view of a color copying machine adopting an embodiment of the present invention, FIG. 2 is a schematic vertical cross-sectional view showing one operating state of the embodiment of the present invention, and FIG. 3 is an embodiment thereof. FIG. 3 is a schematic vertical cross-sectional view showing another operating state of the device. 26...Fixing sheet, 32.35...Heater, 3
8... Optical sensor, 45... Auxiliary heater.

Claims (1)

[Scope of Claims] 1 which is in pressure contact with each other so that the toner-adhered sheets can pass therebetween, and has a main heating means on at least one of them;
a pair of fixing rollers; a determining means for determining whether the sheet to be fixed is a regular paper or an OHP sheet; and when the determining means determines that the sheet to be fixed is an OHP sheet, toner is removed from the fixing roller. A color image fixing device comprising: auxiliary heating means for further heating the fixing sheet after the fixing sheet is separated.