JP3124364B2 - Fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording material carrying a visible image to be heat-fixed (hereinafter referred to as a toner image) which is brought into close contact with a heating member via a film. The present invention relates to a film heating type fixing device that applies heat energy to a recording material to heat and fix a toner image.

This apparatus is used in image forming apparatuses such as a copying machine, a laser beam printer, a facsimile, a micro film reader printer, an image display (display) device, and a recording machine. Directly or indirectly on the surface of a recording material (electrofax sheet, electrostatic recording sheet, transfer material sheet, printing paper, etc.) as an image carrier using a toner made of a heat-meltable resin or the like by an image forming process means. The present invention can be used as an image fixing device that heats and fixes an unfixed toner image corresponding to target image information formed by a (transfer) method as a permanently fixed image on a recording material surface carrying the image.

[0003]

2. Description of the Related Art Conventionally, as a fixing device of a heating type, an unfixed toner image is formed by a heating roller maintained at a predetermined temperature and a pressure roller having an elastic layer and pressing against the heating roller. A fixing device of a heat roller fixing type that heats the recording material while nipping and conveying the recording material is often used.

However, the fixing device of the heat roller fixing method firstly requires a time until the temperature rises to a predetermined temperature (a time during which the image forming operation is prohibited), that is, a so-called wait time. Third, a relatively large electric power is required, and thirdly, a heat-resistant special bearing is required for the rotating roller because the roller temperature is high.
In addition, there is a drawback that the roller comes in direct contact with the roller, which is dangerous and requires a protective member.Fifth, the recording material is wound around the roller due to the fixing temperature and the curvature of the roller, thereby causing a jam. Was.

Therefore, as a fixing device of the heating type which does not have the above-mentioned drawbacks, recently, the fixing device of the film heating type as described above has attracted attention, and research and development for practical use thereof have been promoted. .

For example, Japanese Patent Application Laid-Open No.
A method and apparatus disclosed in JP-A-3-313182 belong to this, and a thin heat-resistant film (sheet), a driving means for moving the film, and fixedly supported and arranged on one surface side with the film inside. And a pressure member disposed on the other surface of the recording material to be opposed to the heating member and closely contacting the visible image bearing surface of the recording material to be image-fixed to the heating member via the film. The film is moved at the same speed in the forward direction at the same speed as the recording material to be image-fixed which is conveyed and introduced between the film and the pressing member at least at the time of performing image fixing, and the heating element is sandwiched therebetween. The visible image carrying surface of the recording material is heated by the heating body through the film by passing through a fixing nip portion formed by the pressure contact between the recording material and the pressing member, and heat is applied to the visible image (unfixed toner image). Softening and melting by applying energy And then separating the film and the recording material, or a heating means or apparatus which is based on the toner to separate the film and the recording material after cooling and solidifying.

[0007] The heating element may be a linear or narrow strip along the length of the film on the side of the film contacting surface of a horizontally long heat-resistant, insulating and low-heat-capacity heater substrate having a longitudinal direction in the width direction of the film. A type having a low-heat-capacity energizing heat-generating resistor (heat-generating element) is used, and when power is supplied between both ends of the heat-generating element, the heat-generating element generates heat. Temperature rises rapidly, and the heat of the heating element is applied to the recording material via the film.

The temperature control of the heating element is performed by a temperature sensor provided in the heating element, a microcomputer of the image forming apparatus main body, and a heating element driving (heat generation) circuit to control the temperature to a predetermined fixing temperature. You. Although the heating element is at a high temperature, at least when the heating element generates heat, the film is driven to move at a predetermined speed on the heating element. Is executed.

Such a film heating type fixing device has features such as a short wait time, and is a fixing device meeting the needs of the times.

[0010]

However, as one of the problems, since the fixing device is heated by a heating element having a low heat capacity, the fixing device passes a recording material having a width smaller than a fixing area of the fixing device. , The portion through which the paper does not pass, that is, the temperature rise in the non-paper passing portion, compared to the conventional heat roller fixing device,
The phenomenon of being extremely high occurs. If the temperature rise in the non-sheet passing area is large, the toner may be offset at high temperature,
In some cases, the temperature exceeded the heat resistance temperature of the fixing film.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a fixing device using a heating element having a low heat capacity, in which the temperature rise of a non-sheet passing portion is suppressed. It is the purpose.

[0012]

In order to achieve the above object, there is provided a heating element having a heating element provided on a substrate, and a film sliding on the heating element. In a fixing device for fixing an unfixed image on a recording material by heat from a body, a high heat conductivity having a heat conductivity of 100 (kcal / mhr ° C.) or more is provided on a side of the heating body opposite to a side in contact with the film. A member is provided.

[0013]

In the above construction, the film of the heating element is provided.
Heat conduction of 100 [kcal / mhr ℃] or more on the side opposite to the contact side with
A high heat conductive member having a high heat transfer rate,
The temperature distribution in the hand direction, that is, the direction perpendicular to the running direction of the recording material is balanced.

[0014]

FIG. 1 is a sectional view of a fixing device according to an embodiment of the present invention, and FIG. 2 is a perspective view of the fixing device of FIG. In these figures, reference numeral 1 denotes a heating element, which has a linear or band-shaped elongated heating element 4 extending in the running direction of the recording material P. The heating element 4 is supported by the heater substrate 3 and is heated by a heat-resistant glass 6. Coated.

Reference numeral 7 denotes an endless belt-shaped fixing film, which includes a left driving roller 8 and a right driven roller 9.
And a heating element 1 as a heating element disposed below the rollers 8 and 9 and suspended between the three members 8.9.1.

The driven roller 9 also serves as a tension roller for the endless belt-shaped fixing film 7.
The fixing film 7 has a predetermined peripheral speed in the clockwise direction accompanying the clockwise rotation of the drive roller 8, that is, the conveying speed of the recording material P carrying the unfixed toner image Ta conveyed from the image forming unit side on the upper surface. It is driven to rotate at the same peripheral speed without wrinkles, meandering, and speed delay.

Reference numeral 10 denotes a pressure roller having a rubber elastic layer 12 of silicone rubber or the like having good releasability as a pressure member. The pressure roller 10 sandwiches the above-mentioned descending film portion of the endless belt-shaped fixing film 7. The lower surface of the heating element 1 is pressed against the lower surface of the heating element 1 by a biasing means (not shown) with a contact pressure of, for example, a total pressure of 4 to 7 kg. To rotate.

The heating element 1 is a low-heat-capacity linear heating element whose longitudinal direction is a direction (width direction of the film) that intersects the plane movement direction of the film 7, and includes a heater substrate 3, an energized heating resistor (heating element) 4, It is composed of a temperature measuring element 5 and the like, and is fixedly supported by being attached to and held by the heater support 2.

The heater support 2 has a heat insulating property, a high heat resistance and a rigidity for thermally supporting the heating element 1 with respect to the fixing device. For example, PPS (polyphenylene sulfide) · P
AI (polyamide imide), PI (polyimide), PE
It can be made of a high heat-resistant resin such as EK (polyetheretherketone) or liquid crystal polymer, or a composite material of these resins and ceramics, metal, glass, or the like.

The heater substrate 3 is a member having heat resistance, insulation, and low heat capacity, for example, a thickness of 1.0 mm and a width of 16 m.
It is an alumina substrate having a length of m and a length of 340 mm.

The heating element 4 is formed along the longitudinal direction substantially at the center of the lower surface of the substrate 3 (facing the film 7), for example, Ag / P.
An electric resistance material such as d (silver palladium) or Ta ₂ N is applied by screen printing or the like to a thickness of about 10 μm and a width of 1 to 3 mm.
μm coated.

As an example, the temperature detecting element 5 has a low heat capacity such as a Pt film provided by applying a screen printing or the like to a substantially central portion of the upper surface of the substrate 3 (the surface opposite to the surface on which the heating element 4 is provided). Is a resistance thermometer. Alternatively, a low-heat-capacity thermistor or the like may be arranged in contact with the substrate 3 as the temperature detecting element.

In the case of the heating element 1 of this embodiment, electricity is supplied to the linear or band-shaped heating element 4 from both ends in the longitudinal direction.
The heating element 4 is heated over substantially the entire length. Energization is AC1
The power is controlled by controlling the phase angle to be energized by an energization control circuit (not shown) including a triac according to the temperature detected by the temperature detecting element 5.

The fixing film 7 has heat resistance, releasability, durability and the like, and generally has a total thickness of 100 μm or less, preferably 40 μm or less.
A single-layer or multi-layer film of μm or less can be used.

Reference numeral 14 denotes a high thermal conductive member provided on the back surface of the heater substrate 3 and preferably has a thermal conductivity of 100 [kcal / mhr ° C.] or more, and is made of, for example, an aluminum plate (hereinafter referred to as an aluminum plate). . The aluminum plate 14 is provided with a groove 14 a at a position corresponding to the area of the heating element 4. The width a of the groove is 0.5 m larger than the width of the heating element 4.
m has been increased. The thickness c of the aluminum plate 14 is 1
about mm~3mm is desirable, is 2mm in this embodiment, the depth b of the groove is preferably more than 0.3 mm, in the present embodiment is 1 mm.

Aluminum plate 14 as temperature balance member
Is held by the heater support 2 together with the heater 1,
The heater support 2 is held by a heater stay 13.
The heater stay 13 is fixed to a fixing side plate (not shown ) ,
It is a structural member having a strength that can withstand the force received from the pressing means 10.

B) Fixing operation The recording material sheet P carrying on the upper surface an unfixed toner image Ta conveyed to the fixing device by the image forming device of the above-described embodiment being image-formed by the image forming start signal is applied to the guide 18. The sheet P is guided and enters between the fixing film 7 and the pressure roller 10 at the pressure contact portion (fixing nip portion) between the heating body 1 and the pressure roller 10, and the unfixed toner image surface is adjusted to the conveyance speed of the sheet P. Mutual pressure contact between the heating element 1 and the pressure roller 10 in the overlapping state with the fixing film 7 without causing surface deviation, wrinkling, and deviation by closely adhering to the lower surface of the fixing film 7 rotated in the same direction at the same speed. It passes through between the parts while receiving pinching pressure.

Since the heating element 1 is energized and heated at a predetermined timing by an image formation start signal, the toner image Ta
Is heated at the pressure contact portion to form a softened / melted image.

The running direction of the fixing film 7 turns at a steep angle (the bending angle θ is approximately 45 °) at the edge portion S (the radius of curvature is approximately 2 mm) of the heater support 2 where the curvature is large. Accordingly, the sheet P conveyed through the pressure contact portion while overlapping the fixing film 7 is separated from the fixing film 7 at the edge portion S by a curvature, and is discharged to the discharge tray. By the time the sheet is discharged, the toner is sufficiently cooled and solidified, and is in a state of being completely fixed on the sheet P (toner image Tc).

In this embodiment, the role of the aluminum plate 14 is to carry out heat transfer in the longitudinal direction (in the direction perpendicular to the running direction of the sheet as a recording material and in the sheet width direction). It does not absorb.

FIG. 7 shows a model of heat transfer. (A) is a state at the time of starting to supply electric power to the heating element. Most of the heat generation is used for raising the temperature of the pressing member 10 and the heater substrate 3, and the movement to the aluminum plate 14 is extremely small. is there. This can be understood from the fact that the aluminum plate 14 is located at a position where the thermal resistance is large when viewed from the heating element. FIG. 2B shows a state where the temperature of the non-sheet-passing portion has risen in a steady state. In this state, since the members around the pressing member and the like are already at a high temperature, the heat transfer indicated by the downward arrow is the amount of heat supplied to the sheet. However, as shown in FIG. 3, in the non-sheet passing portion area, the sheet does not take heat, and the heat causes the heating element itself to heat up.

Next, the temperature of the heater substrate 3 rises, and heat is transmitted to the temperature balancing member 14 in contact with the heater substrate 3. In the aluminum plate 14, due to its own high thermal conductivity, heat transfer occurs from a high-temperature portion to a low-temperature portion, that is, from a non-sheet-passing portion heating region to a sheet-passing region. Therefore, as shown in FIG. 3, the temperature distribution in the longitudinal direction is balanced by the aluminum plate 14.

Further, a non-contact area is provided on a contact surface between the heating element and the aluminum plate which is the high heat conductive member, in a region corresponding to the heating element included in the heating element, so that the non-sheet passing portion rises. In addition to keeping the temperature low, it is possible to shorten the time from when power is supplied to the heating element to when fixing is possible, that is, the wait time.

FIG. 4 shows a second embodiment of the present invention. In this figure, a material having a high thermal conductivity such as aluminum is used for the heater support 15 to promote heat transfer in the longitudinal direction and to suppress the temperature rise in the non-sheet passing portion. On the other hand, the number of parts was reduced and cost was reduced. In this embodiment, the thickness of the aluminum heater support 15 is 1.6 mm, and the groove 15a is provided in a section of 3 mm × 1 mm in the entire region in the longitudinal direction (FIG. 8).

In the case of the present embodiment, as shown in FIG.
Temperature was controlled at 0 ° C.

Therefore, small-size paper (width 182 × length 25)
When 7,80 g / m ² ) was continuously passed, the temperature of the non-sheet passing portion was 235 ° C. Therefore, the temperature rise of the non-sheet passing portion is ΔT =
35 ° C. Further, in the conventional example in which PEEK (polyetheretherketone) was used in the same shape (groove 14a pear) as the material of the heater support 15, the temperature of the non-paper passing portion was 283 ° C. Therefore, the temperature rise in the non-sheet passing portion is ΔT = 83 ° C.
It is.

Further, the second embodiment differs from the conventional type of the PEEK heater support in that the power is turned on after the fixing device is cooled.
The time required for the heating body to reach 200 ° C., that is, the wait time, is equivalent to about 4 seconds. In other words, the temperature rise in the non-sheet passing portion can be kept low without lengthening the wait time.

FIG. 5 shows a third embodiment of the present invention. In the figure, a member having a high thermal conductivity such as aluminum is used for the heater stay 16 to promote heat transfer in the longitudinal direction and to suppress the temperature rise in the non-sheet passing portion. On the other hand, the number of parts was reduced and cost was reduced. 16a is a groove.

FIG. 6 shows a fourth embodiment of the present invention. In the figure, a heat-resistant and heat-insulating sheet material 17 is interposed at the contact surface between the heating element 1 and the aluminum plate 14 at a position corresponding to the area of the heating element 4. The sheet material 17
Preferably, PEEK (polyetheretherketone) is used in this embodiment. The thickness of the sheet material 17 is desirably 0.1 mm to 1 mm.
6 mm.

In the first embodiment, since the force of the pressing member 10 is received on both sides of the back surface of the heating element and no force is applied to the groove, the heating element may be broken due to accidental abnormal pressure or the like. There is. Therefore, as shown in FIG.
By interposing, the same performance as thermal insulation by space was achieved, and high reliability against accidents such as accidental abnormal pressurization could be provided.

[0041]

As described above, according to the present invention,
By providing the high heat conductive member on the back surface of the heating element, the temperature distribution in the longitudinal direction of the heating element can be balanced, and the temperature of the non-sheet passing portion can be reduced.

Further, by providing a space or a heat insulating sheet between the high thermal conductive member and the back surface of the heating element , the rise time from the cold state to the fixable state, that is, the wait time is lengthened. Never.

As a result, the temperature rise of the non-sheet passing portion exceeding the heat resistant temperature of each component does not occur, and high reliability and high durability of the fixing device can be realized.

[Brief description of the drawings]

FIG. 1 is a sectional view of a fixing device according to a first embodiment of the present invention.

FIG. 2 is a perspective view of the fixing device of FIG.

FIG. 3 is a perspective view of a temperature balancing member in FIG. 1;

FIG. 4 is a sectional view of a fixing device according to a second embodiment of the present invention.

FIG. 5 is a sectional view of a fixing device according to a third embodiment of the present invention.

FIG. 6 is a sectional view of a fixing device according to a fourth embodiment of the present invention.

FIG. 7 is a heat transfer model around a heating element in the fixing device according to the present invention.

FIG. 8 is a view for explaining the operation of the fixing device of FIG. 4;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heating body 2 ... Heater support 3 ... Heater board 4 ... Heating body 13 ... Heater stay 14 ... Aluminum
Rate 14a: groove 15: heater support 16: heater stay 17: heat insulating sheet

Claims (3)

(57) [Claims] 1. A heating element having a heating element provided on a substrate, and a film sliding on the heating element, wherein an unfixed image is formed on a recording material by heat from the heating element via the film. In the fixing device for fixing to the film, 100
A fixing device comprising a high heat conductive member having a heat conductivity of [kcal / mhr ° C.] or more. 2. A contact surface between said high heat conductive member and said heating element.
The part corresponding to the area of the heating element is not
2. A groove having a contact so as to be in contact therewith.
The fixing device as described in the above. 3. The thermal conductivity of the same width as the heat generating element in a portion corresponding to the area of the heat generating element between the high heat conductive member and the heat generating element . 2. The fixing device according to claim 1, wherein a heat insulating sheet having a temperature of 3 [kcal / mhr.degree.