JPH03235978A - Fixing device - Google Patents

Abstract

PURPOSE:To preclude offsetting and to obtain both a lustrous image and a nonlustrous image by making the temperature at a fixation point, where toner on a recording material fixed, and the temperature at a separation point, where a film and the recording material are separated, independent and controlling the temperature at the separation point. CONSTITUTION:A 1st heating body 1A is used for image heat fixation, a 2nd heating body 1B is used to hold the separation point of the film 7 and recording material 12 at specific temperature, and the electric feeding to heating bodies 3a and 3b is controlled respectively to control the 1st and 2nd heating bodies 1A and 1B to specific temperatures respectively. The temperature at the separation point of the film 7 and recording material 12 is held constant specifically at least while the recording material 12 passes the separation point. Consequently, the offsetting is precluded and the lustrous or nonlustrous fixed image can be selected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fixing device that applies thermal energy to a recording material through a heat-resistant film.

This device is an image heating fixing device in an image forming apparatus such as an electrophotographic copying machine, a printer, or a fax machine, that is, it is made of heat-melting resin, etc., by an appropriate image forming process means such as electrophotography, electrostatic recording, magnetic recording, etc. Recording materials (electrofax sheets, electrostatic recording sheets,
An unfixed toner image corresponding to the desired image information, formed directly or indirectly (transfer) on the surface of a transfer material sheet, printing paper, etc., is permanently fixed to the surface of the recording material that carries the image. It can be used as an image fixing device that performs heat fixing processing.

Furthermore, the present invention is not limited to image forming apparatuses, and can be widely used as a means/device for heat-treating an image carrier, such as a device that heats a recording material carrying an image to modify its surface properties.

(Prior Art) Various types and configurations of image heat fixing devices have been known and put into practice, such as a heat roller type, a hot plate type, a belt fixing type, and a flash fixing type.

Recently, a heating element (thermal heater, hereinafter referred to as heater) that is fixedly supported, a heat-resistant film (fixing film) that is conveyed while being in pressure contact with the heater, and a recording material is closely attached to the heater through the film. A fixing device having a method and configuration that has a pressure member that heats and fixes an unfixed image formed and carried on a recording material surface onto the recording material surface by applying heat from a heater to the recording material through a film. A film heating method) has been devised.

For example, Japanese Patent Application Laid-Open No. 63-3131 related to the applicant's previous proposal
The system, device, etc. disclosed in Publication No. 82 belongs to this category, and includes a thin heat-resistant film (sheet), a means for moving the film, and a fixed support arrangement on one side of the film with the film inside. and a pressure member disposed on the other side facing the heater to bring the image-bearing surface of the recording material to which the image is to be fixed into close contact with the heater through the film, and the film is At least when performing image fixing, the recording material to be image-fixed is conveyed and introduced between the film and the pressure member, and the heater and the pressure member are moved at the same speed in the same direction as the recording material to which the image is to be fixed. The image-bearing surface of the recording material is heated by the heater through the film, and thermal energy is applied to the image (unfixed toner image). This is a heating means/device that basically applies a toner, softens and melts it, and then separates the film and recording material after passing through a fixing point at a separation point.

These film heating type fixing devices include heat roller type, hot plate type, belt fixing type, flash fixing type,
In comparison with other heat fixing devices such as oven fixing systems, ■ A low heat capacity heating element can be used as the heater, which saves power and shortens wait time (quick start); Since the separation point can be set separately, offsets can be prevented, and various drawbacks of other systems can be solved, and this is an effective method.

The heater as a heating element is formed by coating a low heat capacity current-carrying heating resistor in a linear or band shape on a heat resistant, good thermal conductivity, low heat capacity insulating substrate (base material) such as ceramic. A heater having a low heat capacity of the above embodiment is used, and when the resistor is energized, the temperature of the surface of the heater rapidly rises to the required fixing temperature (for example, about 200° C.) since the heat capacity of the resistor and the substrate is small.

The heat-resistant film in contact with the heater also has a small heat capacity, and thermal energy from the heater side is effectively transmitted via the film to the recording material that is in pressure contact with the film, thereby performing thermal fixation of the image.

The heater temperature is controlled using an energization control configuration in which the heater temperature is detected by a temperature sensing element, and the energization to the energized heating resistor is controlled based on the temperature detection information to control the temperature of the heater to a predetermined fixing temperature. .

(Problems to be Solved by the Invention) In this type of film heating type fixing device, the temperature at the separation point is simply set lower than the temperature at the fixing point. For example, if there is black toner and red toner in a multicolor image,
Since these toners have different optimum separation temperatures, offset may occur in one toner in some cases. Also, since the temperature at the separation point is not controlled,
It is not possible to select whether the fixed image is glossy or non-glossy, and the image may have uneven gloss, with the first half of the recording material being a non-glossy image and the second half being a glossy image.

The present invention aims to solve the above problems.

(Means for Solving the Problems) The present invention involves moving a film in contact with a fixedly supported heating body, and heating the recording material together with the film by bringing the recording material into close contact with the surface of the film opposite to the heating body. The fixing device is a fixing device that applies thermal energy from a heating body to a recording material via a film by moving the position of the heating body and passing through the heating body. The fixing device is characterized in that it has means for keeping the temperature at a predetermined constant temperature while the recording material is passing through the point.

The present invention also provides that the temperature of the separation point of the above-mentioned fixing device can be changed, and that the separation of the film and recording material after moving through the heating body position is performed by changing the traveling direction of the film. The fixing device is characterized in that it includes a conveying member that is in pressure contact with a pressing member that changes the traveling direction of the recording material and that conveys the recording material.

(Function) That is, in the present invention, the temperature at the fixing point where the toner is fixed on the recording material and the temperature at the separation point where the film and the recording material are separated are made independent, so that the temperature at the separation point can be controlled. As a result, 1) with one recording material, the same glossy or non-glossy image can be obtained over the entire surface because the separation occurs at the same temperature, and 2) the temperature at the separation point can be changed by using one kind of toner (black and red toner, etc.). 3) By changing the temperature at the separation point, both glossy and non-glossy images can be produced.

(Example) Example 1 (Fig. 1) 7 is an endless belt-shaped fixing film, which includes a driving roller 8 on the left side, a driven roller 9 on the right side, and a driven roller 9 on the right side.
The first low heat capacity linear heating element IA (hereinafter referred to as
These four members 8 are parallel to each other and include a first heating element (referred to as a first heating element) and a second low heat capacity linear heating element IB (hereinafter referred to as a second heating element) on the diagonally lower right side of the drive roller 8.・9・IA・18
A suspension cable is installed in between.

The driven roller 9 also serves as a tension roller for the endless belt-shaped fixing film 7.

The fixing film 7 is rotated clockwise at a predetermined circumferential speed as the drive roller 8 is rotated clockwise (a recording material carrying an unfixed toner image 11 on its upper surface, which is conveyed from an image forming section (not shown)). Transfer material) 12 conveyance speed and interpath speed)
It is rotated without wrinkles, meandering, or uneven speed.

10a and 10b are first and second pressure rollers having rubber elastic layers with good mold releasability, such as silicone rubber, as pressure means for the first and second heating bodies IA and IB, respectively;
The first and second heating bodies IA and
The lower surface of the IB is pressed against the lower surface of the IB at a predetermined pressure, for example, a total pressure of 4 to 7 kg, by a biasing means,
The film 7 and the recording material 12 rotate in a forward and counterclockwise direction in the running/conveying direction.

The rotatably driven endless belt-shaped fixing film 7 is repeatedly used to heat and fix toner images, so it has excellent heat resistance, release properties, and durability, and has a total thickness of 100 μm for boat fishing.
Hereinafter, a thin one having a thickness of 40 μm or less is preferably used.

For example, polyimide (PI), polyetherimide (PE)
I) Single-layer film or composite layer film of heat-resistant resin such as PE5-PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin), e.g.
PTFE on at least the image contact side of the μm thick film
(Tetrafluoroethylene resin) - A releasable coating layer made of a fluororesin such as PAF and a conductive material added thereto is applied to a thickness of 10 μm.

The first and second heating bodies IA and IB have the same structure,
A horizontally elongated low heat capacity, heat resistant, insulating heater substrate whose longitudinal direction is the transverse direction of the fixing film (direction perpendicular to the running direction of the fixing film 7), for example, an alumina substrate 2a with a thickness of 1 mm, a medium size of 10 mm, and a length of 240 mm. 2b, and low heat capacity current-carrying heating elements 3a and 3b, for example, Ta2, provided in a linear or narrow strip shape along the longitudinal direction approximately at the center of the lower surface of the substrate.
A coating layer with a width of 1 mm made of an electrical resistance material such as N/silver palladium, and a low heat capacity temperature measuring element 6 provided on the upper surface side of the substrate.
a and 6b, for example, a measuring temperature resistor such as a thermistor or a PT film.

It is preferable to form a heat-resistant thin surface protection layer (not shown) of glass material or the like on the lower surface side of the heating elements IA and IB, which are the sliding surfaces in contact with the film.

The first and second heating bodies IA and IB are respectively connected to heat insulating holders 4a and 4b, such as PP5 (polyphenylene sulfide), FAI (polyamideimide), P■(
Heating elements 3a and 3b are installed in a holder made of highly heat-resistant resin such as polyimide (polyimide), PEEK (polyetheretherketone), and liquid crystal polymer, or composite materials of these resins and ceramics, metals, glass, etc. The heat-insulating holders 4a and 4b are held together with the heated side facing outward using heat-resistant adhesive tape or heat-resistant adhesive, and the heat-insulating holders 4a and 4b are placed on the rigid supports 5a and 5b of the device with the heating elements IA and IB sides facing downward. It is fixedly supported.

Na-Nb is applied to the lower surfaces of the heating bodies IA and IB with the film 7 in between, and the first and second heating bodies IA and IB, respectively.
and a nip portion formed by pressure contact with the second pressure rollers lOa and 10b.

The first heating body IA is for heat fixing the image, and the nip portion Na of this heating body is a fixing nip portion serving as a fixing point.

1 2 The second heating body IB is for maintaining the temperature at the separation point between the film and the recording material at a predetermined level, and the nip portion Nb of this heating body is the heating nip portion serving as the separation point.

In this example, both the first heating element IA and the second heating element IB supply electricity to the linear or band-shaped heating elements 3a and 3b from both longitudinal ends of the heating elements 3a and 3b to extend the entire length of the heating elements 3a and 3b. cause fever.

Then, the heating elements IA and IB become the heating elements 3a and 3b.

Since the heat capacity of the substrates 2a and 2b is small, the temperature of the entire substrate or at least the lower surface thereof increases rapidly.

The temperature rise of the heating bodies IA and IB is caused by the temperature measuring elements 6a and 6a, respectively.
6b, and the first temperature sensor (not shown) is detected based on the temperature detection information.
energization control circuit for the heating body IA and the second heating body IB
The energization control circuit for the first and second heating elements IA and
The temperatures of the first and second heating elements IA and IB are each controlled to a predetermined temperature by controlling the energization to the heating elements 3a and 3b of the IB, respectively.

The first heating element IA is energized at a DCI OOV period of 20
The temperature at the fixing point is controlled to, for example, 200° C. by applying a pulsed waveform of m5ec to a desired temperature controlled by the thermometer 6a and varying the pulse width according to the amount of energy released. . The pulse width is approximately 0.5 to 5 m5ec.

The second heating element IB is similarly energized to control the temperature at the separation point to a predetermined set temperature.

(2) When an image forming mechanism of an image forming apparatus (not shown) is operated in response to an image formation start signal, and the recording material 12 carrying the unfixed toner image 11 on its upper surface is conveyed to the fixing device, for example,
The leading edge of the recording material 12 is the recording material population guide 1 of the fixing device.
When detected by a recording material sensor (not shown) disposed near 6, the rotational drive of the fixing film 7 is started based on the detection signal, and energization to the first and second heating bodies IA and IB is started. and both heating bodies are heated to respective predetermined fixing temperatures.
Rapidly rises to separation temperature.

■ The conveyed recording material 12 from the image forming mechanism side is guided by the population guide 16 and is attached to the fixing film 7 at the pressure nip between the first heating body IA and the pressure roller 10a, that is, the fixing nip (fixing point) Na. The unfixed toner image surface enters between the pressure roller 10a and the surface of the fixing film 7, which is moving in the same direction at the same speed as the conveyance speed of the recording material 12, to prevent surface misalignment and wrinkles. The film passes through the fixing nip portion Na in an overlapping state together with the fixing film 7 without being pressed by the clamping force. During this passing process, the toner image bearing surface of the recording material 12 receives the heat of the first heating body IA via the fixing film, and the toner image is melted at a high temperature and fixed by heating on the surface of the recording material 12.

■The recording material that has passed through the fixing nip part Na is fixed to the fixing film 7.
The pressure nip portion between the second heating body IB and the pressure roller 10b, that is, the heating nip portion (
Separation point) Enters Nb and is pressurized and heated to a predetermined temperature set in this heating nip.

■The direction of movement of the fixing film 7 is changed toward the upper driving roller 8 at the exit of the heating nip Nb, so that the recording material 12 that has come out of the heating nip Na is separated from the bottom surface of the fixing film 7 by the curvature. The paper is guided by the paper discharge guide 17 and reaches the paper discharge section.

Regarding the set temperature of the heating nip portion Nb by the second heating body IB in (2) above, that is, the separation point temperature, the separation point temperature is set to be higher than the glass transition point of the toner, and the temperature is set at least on the recording material 12. By keeping the toner image constant while passing through the heating nip portion Nb, the toner image immediately after the recording material 12 is separated from the fixing film 7 (Nato image heated and fixed on the surface of the recording material 12 at the fixing nip portion Na). Since the surface has appropriate rubber properties at temperatures higher than the glass transition point, it does not mimic the smooth surface properties of the fixing film 7 surface, but has a moderately uneven and rough surface, and this surface property is maintained as it cools and solidifies. As a result, the surface of the fixed toner image becomes completely non-glossy.

5 6 In addition, by setting the separation point temperature to a temperature lower than the glass transition point of the toner, the surface of the toner image that appears immediately after the recording material 12 is separated from the fixing film 7 has the smooth surface property of the fixing film 7 surface. As a result, the surface of the fixed toner image becomes glossy as a whole because it becomes smooth and solidified by cooling.

That is, by setting the separation point temperature as high or low as desired and keeping the set temperature constant at least while the recording material passes through the separation point, the glossiness and non-glossyness of the output image can be adjusted freely and unevenness can be prevented. This makes it possible to perform reliable and stable control without any problems.

Furthermore, even when toners with different offset temperatures coexist in a multicolor image, etc., it is possible to prevent the occurrence of offsets due to differences in the type of toner by controlling the separation point temperature.

In this embodiment, the operation panel of the image forming apparatus has, for example, "Non-glossy/
A "glossy" selection changeover switch is provided, and by switching the switch, the temperature control temperature setting of the temperature control circuit of the second heating element IB is changed to a high temperature setting (for non-glossy) or a low temperature setting (for gloss). By controlling the separation point temperature, it is possible to select matte/glossy.

Further, the separation point temperature may be switched by automatically pressing a selection switch in conjunction with replacing the developing device (for example, from red toner to black toner) or switching the selection. It may also be linked with switching of the fixing temperature.

Table 1 shows an example of the difference in separation point temperature and image quality depending on the type of toner.

Table 1 Example 2 (Figure 2) This example is a modification of the device shown in Figure 1 above, and in this example, the first and second heating bodies IA and IB are attached to a common heat insulating holder 4. are supported, and the holder 4 is fixedly supported by a common rigid support 5.

Embodiment 3 (FIG. 3) The fixing film 7 does not have to be an endless type, but as in this example, a film with an end is rolled around the feed roller 13 and then passed through the first and second heating elements IA and IB. It is also possible to adopt a configuration in which the winding roller 14 winds up the winding roller 14 and controls the running at a predetermined speed.

Embodiment 4 (FIG. 4) In this example, a heat roller 28 is provided at the separation point, and this heat roller 28 is heated by heat generated by a heater 27 provided inside, so that the surface temperature of the heat roller 28, that is, the separation point, is heated. The temperature is controlled to a predetermined set temperature by a heater energization control circuit (not shown) including a surface temperature measuring element 6b of the heat roller 28.

Embodiment 5 (FIG. 5) In this embodiment, in place of the heat roller 28 in the example shown in FIG. 4, a roller is used in which the roller 20 itself has resistance to electricity and generates heat when a voltage is applied to the roller. A voltage application control circuit (not shown) including a surface temperature detection element 6b of the roller 20 controls the roller temperature, that is, the separation point temperature, to a predetermined set temperature.

Embodiment 6 (FIG. 6) In this embodiment, the temperature at the separation point is controlled by applying hot or cold air to the separation point formed by the upper and lower separation rollers 23 and 24 using two fans and a heater 22. The temperature of the upper separation roller 23 is measured by the temperature measuring element 6b, and the temperature information is used to control energization of the heater 22 and drive of the fan 21, thereby controlling the separation point temperature to a predetermined set temperature.

9 0 Embodiment 7 (FIG. 7) In this example, a plurality of conveying rollers 25.
-25. are sequentially provided on the upper surface side of the film 7 with the fixing film 7 sandwiched therebetween. --- A plurality of movable separation rollers 26, each corresponding to 254. . . 264 is provided, and the movable separation rollers 26, . . . 264 are selectively transferred to the conveying rollers 25, .
- By controlling the release movement from 254, the distance from the fixing point Na to the separation point can be changed in length as L4, L3, L2, and Ll.

The temperature of the toner image heated and melted at the fixing point Na and fixed on the surface of the recording material decreases as the conveyance distance increases.

Therefore, we measured the relationship between the distance and temperature drop in advance,
By changing and controlling the separation point distance as described above, the separation point temperature can be controlled to be high or low.

The configurations of Examples 1 to 7 may be used in combination. In both cases, the desired effects were obtained.

(Effects of the Invention) As explained above, in the present invention, the temperature at the fixing point where the toner is fixed on the recording material and the temperature at the separation point where the film and recording material are separated are made independent, and the temperature at the separation point is made independent. By making it possible to control the temperature, effects such as 1), 2), 3), etc. described in the above (effects) section can be obtained, and the intended purpose can be achieved.

[Brief explanation of drawings]

1 to 7 show the first to seventh parts of the fixing device of the present invention, respectively.
1 is a schematic diagram of the configuration of an example device. IA and IB are the first and second heating elements, 7 is the fixing film, 10a and 10b are the first and second pressure rollers, Na is the fixing nip (fixing point), and Nb is the heating nip (separation point). ), 12 is a recording material, 11 is a toner image, 20 and 28 are heating rollers, 21 is a fan, 22 is a heater, and 23 and 24 are upper and lower separation rollers.

Claims (3)

[Claims] (1) A film is brought into contact with a fixedly supported heating body and moved, a recording material is brought into close contact with the surface of the film opposite to the heating body, and the film is moved and passed through the heating body together with the film, and the film is removed from the heating body. It is a fixing device that applies thermal energy to the recording material through the heating body, and the temperature at the separation point between the film and the recording material after moving through the heating body position is controlled at least during the process of the recording material passing through this separation point. A fixing device characterized in that the fixing device has means for maintaining a predetermined constant temperature. (2) The fixing device according to claim 1, wherein the temperature of the separation point can be changed. (3) When the film and recording material are separated from each other after moving through the heating body position by changing the direction of travel of the film, the film is pressed against a pressing member that changes the direction of travel of the film;
3. The fixing device according to claim 1, further comprising a conveyance member for conveying the recording material.