JPH03168786A - Heat fixing device - Google Patents

Abstract

PURPOSE:To obtain a fixed toner image of good quality without wrinkling even a carrier formed by laminating plural materials by making a peeling layer adhere to the surface of a mandrel made of a rigid material and thus forming a couple of rolls, pressing both the rolls against each other with specific line pressure, and setting the quantities of deflection of both the rolls below a specific value. CONSTITUTION:A heat roll 1 and a pressure roll 2 are both formed of rigid materials with good heat conductivity in hollow cylinder shapes and peeling layers 3 are made to directly adhere to their surfaces. Then both the rolls 1 and 2 are pressed against each other with >=5kg/cm line pressure and the quantities of deflection of both the rolls 1 and 2 are set to <=150mum, preferably, <=100mum. Consequently, the nip width can be made small and becomes constant in the length direction of the rolls, and paper wrinkling due to a roll peripheral speed difference is eliminated, specially, when the carrier is thin. Consequently, the wrinkling is eliminated even when the carrier is formed of plural materials one over another like an envelope, and the toner image of good quality can securely be fixed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention... In an image-forming device such as a photographic device or an electrostatic printing device 1, a toner image formed on paper or other carrier is heated on at least one side thereof. It also relates to a heat fixing device that performs fixing between a pair of rolls rotating in pressure contact with each other. Not to mention passing the paper. In particular, the present invention relates to a heat fixing device that has been improved to be able to fix toner traces without causing wrinkles even on multiple carriers such as envelopes. [Prior Art] The fixing device in an image forming device is a metal core with good thermal conductivity, which has a heat source such as an infrared lamp, halogen lamp, or nichrome wire inside. A heating roll coated with a non-adhesive heat-resistant layer. A heat roll-type heat fixing device is known in which a pressure roll whose surface is coated with a heat-resistant elastic layer is disposed facing each other. FIG. 3 is a cross-sectional view of the main parts of an example of the above-mentioned conventional heat fixing device. In the same figure. 1 and 2 are a heating roll and a pressure roll, respectively. It is shaped so that its axes are approximately parallel and can be pressed and rotated in the direction of the arrow. The heating roll 1 has a heating element 12 built into a core metal 11 made of a material with good thermal conductivity, such as aluminum alloy or iron. On the other hand, the pressure roll 2 is formed by covering the surface of a core metal 21 made of the same material as described above with a heat-resistant elastic layer 22 made of silicone rubber having a hardness of about 25 to 55 degrees Hs. Note that the surfaces of the heating roll 1 and the pressure roll 2 are covered. A release layer 3 made of a low surface energy resin such as 47-fluorinated ethylene resin (PTFE) or barfluoroalkoxy resin (PFA) is coated. Therefore, due to the difference in elasticity between the two rolls, the nip portion 4 between the heating roll 1 and the pressure roll 2 as shown in FIG. The surface of the pressure roll 2 is elastically deformed to form a concave surface. In the above heat fixing device, when fixing the toner image formed on the carrier (not shown), first the heating element 12
and heats the surface of the heating roll 1 to the temperature required for fixing. When the heating roll 1 and the pressure roll 2 are brought into contact with each other with appropriate pressure and rotated, and the carrier carrying the toner image is passed between the two rolls in the direction A, the toner image is fixed on the carrier. It is possible.

On the other hand, as a means of displaying addresses on multiple envelopes. Printing directly on envelopes using a printer is being considered. The problem here is that wrinkles occur when the envelope carrying the toner image is fed to the above-mentioned heat fixing device and the toner image is fixed. When wrinkles occur on an envelope, not only does the envelope become curved or deformed, but the printed address is divided by the wrinkles, and in extreme cases, there are problems such as making it impossible to decipher or read the envelope. In other words, envelopes have at least two overlapping parts due to their structure. Depending on the glued part or the overlapped part, it may be triple or quadruple. As the maximum paper thickness increases, mutual sliding movement occurs in the overlapped portion of two sheets. The above problem is a unique phenomenon caused by such sliding movement. This is a problem that is not experienced in normal copying. Considering the causes of the above-mentioned wrinkles, first of all, as shown in Fig. 3, the surface of the pressure roll 2 has a concave surface in the pressure roll 4 of the heating roll 1 and the pressure roll 2. It is forming. For this purpose, if a carrier such as paper (not shown) carrying the toner image is fed in the eight directions of the arrows. The carrier is first bent at the entrance 4a of the nip section 4 so that the upper side is concave, then bent at the niff section 4 so that the lower side is concave, and then again at the outlet 4b of the nip section 4 so that the upper side is concave. On the other hand, when the carrier has double or more polymerized parts like an envelope,
Due to the reverse bending action in the nip section 4, sliding movement occurs between the upper and lower transverse parts. Alternatively, the speed difference between the top and bottom of the envelope may occur due to the difference in movement speed due to the difference in thickness. It is estimated that it causes wrinkles. Various structures have been proposed to date to prevent the occurrence of wrinkles as described above. For example, the invention described in Japanese Patent Application Laid-Open No. 61-294477 is to lower the fixing pressure between a pair of rolls than that for plain paper and to raise the fixing temperature. Furthermore, Japanese Patent Application Laid-Open No. 63-206788 discloses an invention in which a heating roller and a pressure roller are driven individually, and the circumferential speed of the pressure roller is set 1 to 6% lower than the circumferential speed of the heating roller. is proposed.

[Problem to be solved by the invention]

Although each of the above proposals has been improved in one aspect.
It has not yet been achieved to ensure good fixing of the toner image formed on the envelope without wrinkles. In other words, both of the above proposals have problems in that the overall structure of the heating fixing device, control means, etc. are complicated, and reliability is also insufficient. Recently, there has been a demand for a fixing device for envelopes that can also perform fixing on plain paper, and there is a problem in that the above-mentioned conventional devices cannot meet this demand. The present invention solves the problems existing in the above-mentioned prior art. To provide a heat fixing device capable of obtaining a high-quality fixed toner image without causing wrinkles even on a carrier that is stacked in multiple layers, such as an envelope, as well as on plain paper. With the goal.

[Means to solve the problem]

In order to achieve the above objectives. In the present invention, a pair of rolls are arranged so as to be rotatable under pressure. In a heat fixing device in which a heating means is provided on at least one roll, and an unfixed toner image is fixed on a carrier by passing the toner image between the two rolls. Both rolls are formed by coating a mold releasable layer on the surface of a core metal made of a rigid material, and both rolls are pressed together with a linear pressure of 5 kg/cm or more, and the amount of deflection of both rolls is 150 μm or less, preferably 1
We have adopted technical means to ensure that the thickness is less than 0.00μm. In the present invention, if the pressure to be applied between a pair of rolls is a linear pressure of less than 5 kg/cs. This is undesirable because the nip width between both rolls cannot be secured and good fixing performance cannot be secured. However, if the above pressure is too high.
After fixing, the surface of the carrier becomes glossy, making it difficult to see the image. On the contrary, it may promote the formation of wrinkles. It is preferable to set it to 15 kg/(self) or less. Further, if the amount of deflection of both rolls is large, it is not possible for both rolls to come into uniform contact over the entire length in the axial direction, and the 6-nip width also becomes non-uniform, which is disadvantageous because uneven fixing occurs. Therefore, it is recommended to configure the structure so that the amount of deflection is 150 μm or less, preferably 100 μm or less. The heating means that should be installed on at least one of the pair of rolls is usually a built-in heating element such as an infrared lamp, a nitrogen lamp, or a nichrome wire. It can also be used as a heating agent. Also, both may be used together. [Operation] Due to the above configuration. By making the nip between the pair of rolls that make up the heat fixing device, that is, the passage area of the toner image carrier, substantially flat, there is an effect of preventing wrinkles from forming on the toner image carrier. Furthermore, by making the shape of the two wheels substantially flat, it is possible to expect an effect of preventing the carrier from wrapping around the roll surface after the fifth fixation. This eliminates the need for separation claws and eliminates damage to the roll surface caused by contact between the separation claws and the roll surface. Furthermore, the structure is such that the deflection of both rolls is 150 μm or less, preferably 100 μm or less.
The nip width can be made narrower. In addition, the width of the roll is constant in the longitudinal direction of the rolls, which prevents wrinkles caused by the difference in circumferential speed between the seven rolls, especially in the case of thin carriers. [Embodiment] FIG. 1 is a cross-sectional view of essential parts showing an embodiment of the present invention, and the same parts are designated by the same reference numerals as in FIG. 3. In FIG. 1, both the heating roll 1 and the pressure roll 2 are formed into hollow cylindrical shapes made of a rigid material with good thermal conductivity, such as aluminum alloy or steel, and a mold release layer 3 is directly applied to the surface. It is composed of The material forming the mold releasability N3 is PTFE or P as shown in Fig. 1 above.
By using low surface energy resin such as FA. Thickness 10~5
It is preferable to have a shape of 0 μ-. Due to the above structure. When heating roll 1 and pressure roll 2 are brought into pressure contact. As shown in FIG. The nip portion 4 has a narrow width. and is formed flat. However, it is possible to prevent undesired bending action from being applied to the holder.

Next, let us consider the amount of deflection when the heating roll 1 and the pressure roll 2 are brought into pressure contact. Figure 2 is an explanatory diagram schematically showing the deformation state when a load is applied to both ends of the roll pair, and the same parts are designated by the same reference numerals as in Figure 1 above. In Fig. 2, when a load W is applied to both ends of the heating roll 1 and the pressure roll 2 to press them together, both rolls l,
2 is bent with a concave center. The amount of deflection δ in this case is 5wj! ' / 384EI (E: material forming o-ru? modulus of longitudinal elasticity, I second moment of inertia of two rolls, W: contact pressure (linear pressure) per unit length of roll,
l: length of roll). Therefore, the nip section 4 shown in FIG. Usually, the width at the center appears smaller than the width at both ends. That is, the radius of both rolls 1.2 in the nip portion 4 is Rc>Re, where Re is the center and Re is the both ends. On the other hand, both rolls 1
, since the rotation speed of 2 is constant. The circumferential speed at the two-pipe portion 4 is Vc>V, where Vc is at the center and Ve is at both ends.
It becomes e. The circumferential speed at the center is greater than the circumferential speed at both ends.
This difference in circumferential speed, that is, the feed speed of the carrier, causes undesirable wrinkles or undulations in the carrier. In the present invention, δ1 shown in FIG. δ■ is 150 μm or less, preferably 1 (10 μm or less).
Note that if the heating roll 1 and the pressure roll 2 are each made of the same rigid material and have the same shape and dimensions, δ, - δ8 will be obtained, so these will be referred to as δ. By forming δ as described above. That is, the heating roll 1 and the pressure roll 2 are made of aluminum alloy (E=7.3x
lO' kg/c4), the outer diameter is 2 8 u, l
= 2431Ilm, wall thickness 7. when w-10kg/cm. Formed into a hollow cylindrical shape of 5 mm and δ=
It was confirmed that if the oscillation was set to 100μ, good fixation could be achieved without causing warping or waving on the carrier. In this embodiment, an example in which the heating roll is disposed above is described, but the heating roll may be disposed below, or heating means may be provided on both of the pair of rolls. [Effect of the invention] Since the present invention has the structure and operation as described above,
It has the effect of reliably fixing a high-quality toner image without wrinkles, not only on plain paper, but also on carriers such as envelopes, which are stacked in multiple layers.

[Brief Description of the Drawings] Figure 1 is a cross-sectional view of a main part showing an embodiment of the present invention, Figure 2 is an explanatory diagram schematically showing a deformed state when a load is applied to both ends of a pair of rolls, Figure 3 is a cross-sectional view of the main parts of an example of a conventional heating device. 1: heating roll, 2: pressure roll,
11.21: Core metal, arm type layer.

Claims (1)

[Claims] In a heat fixing device in which a pair of rolls are disposed so as to be rotatable under pressure, at least one of the rolls is provided with a heating means, and an unfixed toner image is fixed on a carrier by passing between the two rolls. , both rolls are formed by applying a releasable layer to the surface of a core metal made of a rigid material, both rolls are pressed together with a linear pressure of 5 kg/cm or more, and the deflection amount of both rolls is preferably 150 μm or less, preferably A heat fixing device characterized in that the heating fixing device is configured such that the diameter is 100 μm or less.