JPH05107984A - Pressure fixing device - Google Patents

Abstract

PURPOSE:To miniaturize a device and to eliminate the occurrence of a defect in an image and a noise. CONSTITUTION:When an angle theta formed with a contact line as the fixing position of a fixing roller 9 and a pressure roller 10, and the top end of an image supporting body, is 0 deg.<theta<=5 deg., a rectilinear distance connecting the fixing position N1 and a transfer position D, is L1mm, the distance of a carrying part 7 where the image supporting body 1 is traveled between the fixing roller and an image carrier 6, is L2mm, the rotational speed of the image carrier is v1mm/sec, and the rotational speed of the fixing roller is v2mm/sec. L1<L2, and v1<v2, are set. In the L1<L2, the image supporting body has a deflection. and in the v1<v2, the image carrier and the fixing roller have a speed difference, so that the image supporting body has fine torsion and the degree of freedom in a lateral deviation, and while the image supporting body is pulled by the fixing roller, in this state, the torsion is relaxed, and absorbed, to resolve an influence to a transfer part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a pair of rollers which are in contact with each other under pressure, and an image support having an unfixed toner image is passed between the pair of rollers to transfer the toner image to the image support. The present invention relates to a pressure fixing device for fixing to a supporting surface of the.

[0002]

2. Description of the Related Art An electrophotographic apparatus, for example, as shown in FIG.
2 to the registration rollers 3 and 4 (hereinafter referred to as “registration rollers”), and after being temporarily stopped, the registration rollers send the image at timing with image formation.
After reaching the photoconductor drum, which is the image carrier 6, through the guide 5, the electrostatic latent image formed on the photoconductor drum is transferred to the image support and passes through the transport unit 7, and then the fixing entrance guide 8
Guided by the fixing roller 9 and the pressure roller 10 facing each other.
It is configured to be pressure-fixed by being fed in between.

In such an apparatus, the image support is conveyed with its front end and rear end parallel to the axes of the registration roller and the photosensitive drum, and enters between the fixing roller and the pressure roller. When the contact edge between the fixing roller and the pressure roller and the tip of the image support are aligned with each other, a rush shock occurs to lift the roller, which causes an image defect such as an abnormal noise or a skip due to vibration of the apparatus. Therefore, in order to mitigate the rush shock at the front edge of the image support, the fixing roller and the pressure roller are brought into contact with each other with their rotation axes having an intersecting angle as shown in FIG. It has been proposed to set the contact line R1 between the fixing roller and the pressure roller to be displaced with respect to the axis (reference axis) R0 of the image carrier so as to reduce the lateral displacement of the image carrier. An example of this device is disclosed in JP-A-63-213881.

[0004]

By the way, if the fixing (nip) position R1 and the transfer position D are set with a sufficient interval with respect to the length of the image support 11, the image support is fixed. Even if lateral displacement occurs at the position, it has no effect on the transfer. However, there is a demand for miniaturization of this type of device, and there is a tendency to move the fixing position and the transfer position closer to each other. At that time, when the distance between the fixing position and the transfer position is shorter than the length of the image support, the rear portion P2 of the image support remaining at the transfer position causes an image bend as shown in FIG. There is a problem that it ends up. This becomes more remarkable as the distance becomes shorter than the length of the image support.

FIG. 6 shows a state in which image warpage occurs when the front end P1 of the image support reaches the fixing position and the rear end P2 is nipped by the registration rollers. That is, when the front end P1 of the image support enters the fixing roller, the image support is laterally displaced, and this influence is transmitted to the transfer position, and the image is bent from the point A due to the lateral displacement.
In this state, the registration roller side acts so as to feed the image support in parallel with the roller axis, so that the lateral displacement of the image support proceeds while being slightly suppressed. However, when the trailing edge P2 of the image support leaves the registration roller, the registration roller is no longer pressed and the lateral deviation further expands from point B.

FIG. 7 shows the influence on the image when the front end P1 of the image support enters the fixing roller or when the rear end P2 of the image support is released from the fixing roller or the registration roller. When the front end P1 of the image support 11 plunges into the fixing roller, vibration occurs due to the plunge as described above, and due to this influence, an image defect due to skipping occurs at point A. At the same time, the electrostatic latent image is disturbed by the carriage jumping due to the vibration, and an image defect occurs at the point D due to the influence on the development. Similarly, when the rear end P2 of the image support is released from the registration roller, the effect of image bending appears at the point B. Further, the influence of the vibration of the carriage when the image support plunges into the fixing roller in the previous copy cycle is C
Appear in dots.

The running property of the image support of the apparatus itself, especially the running property of the sheet until the image support reaches the fixing position, is always stable with respect to the contact line between the fixing roll and the pressure roll. It is not sent. Therefore, even if the alignment of the pressure fixing device is finely adjusted so as to correct the running property of the image support, it is not possible to completely eliminate the image bending and the like. An object of the present invention is to improve the speed of the fixing roller drive torque due to a rush shock when the image support enters between the fixing roller and the pressure roller, an image defect such as a skip due to the vibration of the entire apparatus, and the image support is fixed. Image defect such as plunge noise when pushing up the roller, collision noise between the fixing roller and pressure roller due to discharge shock at the trailing edge of the image support and skip due to vibration of the entire device at that time, and image due to lateral displacement of the image support It is an object of the present invention to provide a pressure fixing device in which an image defect such as bending does not occur.

[0008]

In order to achieve the above object, the present invention provides a fixing roller and a pressure roller which bring an image support having an unfixed toner image transferred by an image carrier into contact with each other under pressure. In the pressure fixing device for fixing the toner image by passing through the gap between the fixing roller and the pressure roller, the angle θ formed by the contact line serving as the fixing position and the tip of the image support is 0 ° <θ.
≦ 5 °, L1 (mm) is the linear distance connecting the fixing position of the roller and the transfer position of the image carrier, and the conveying distance traveled until the image support separates from the image carrier and reaches the fixing position of the roller. L2 (mm), the rotation speed of the image carrier is v1 (m
m / sec) and the rotation speed of the fixing roller are v2 (mm
/ Sec), L1 <L2 and v1 <v2
Is configured.

[0009]

The function of L1 <L2 is to give the image support a flexure, and at the same time, to give a speed difference between the fixing roller and the image support by v1 <v2. In this state, while being pulled by the fixing roller, the twist is relaxed and absorbed, and the influence on the transfer portion is eliminated. Of course, at this time, the image support is electrostatically adsorbed to the image support at the transfer portion over the entire area, so that image bending is less likely to occur.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of the main part of an electrophotographic copying apparatus to which the pressure fixing device of the present invention is applied. The same components as those of the electrophotographic copying machine shown in FIG. 4 are designated by the same reference numerals, and detailed description thereof will be omitted. In the present embodiment, the distance L2 that the image support 11 travels from the transfer section formed of the image carrier 6 to the fixing section formed of the fixing roll 9 and the pressure roll 10 is set to the above-mentioned both parts (transfer position D). And fixing position N
1) is set larger than the linear distance L1 between them, and the rotational speed v1 of the image carrier at the transfer portion and the rotational speed v of the roll at the fixing portion are set.
2 is made to have a speed difference by making v2 larger than v1 in accordance with the amount of deflection (L2-L1). Here, as the configuration of L2> L1, the shapes of the transport unit 7 and the fixing entrance guide 8 are set so that the image support 11 bends downward in the direction of gravity.

An experiment was conducted in a copying machine equipped with a fixing device of a type in which a fixing roller and a pressure roller have a crossing angle. This device has a process speed (rotational speed v1 of the image carrier) of 1
It is 00 mm / sec. As the developer, particles having an average particle diameter of 10 to 16 μm and having a function of being pressure-bonded to the image support were used. The experiment was conducted by mounting the fixing device on the copying machine (alignment) by swinging from 0 ° to 20 °. The angle θ between the contact line N1 between the fixing roller 9 and the pressure roller 10 and the tip P1 of the image support 11 shown in FIG. 2 is 0 ° <θ ≦ 5 °, and the contact line N1 between the fixing roller and the pressure roller (fixing position ) And the image carrier 6 are in contact with the image support 11 and a linear distance connecting a position D (transfer position) at which the electrostatic latent image is transferred onto the image support L1 (m
m), the traveling distance is L2 (m) until the image support separates from the image support and reaches the contact line between the fixing roller and the pressure roller.
m), when the rotational speed of the image carrier is v1 (mm / sec) and the rotational speed of the fixing roller is v2 (mm / sec), good results are obtained when L1 <L2 and v1 <v2. It was

Specifically, L1 = 170 mm, L2 = 1
80 mm, rotation speed v1 of image carrier = 100 mm / se
c and the rotation speed v2 of the fixing roller are 80 to 120 mm
The experiment was conducted by changing the range to / sec. When θ = 0 °, the impact is increased because the fixing roller is instantly lifted by the thickness of the image support (about 50 to 150 μm) over the entire width of the image support at the time of entry, resulting in an abnormal noise. And the device vibrated. The maximum drive torque of the fixing roller is also generated at that moment, and the rotation of the fixing roller may be stopped depending on the output of the motor. Even if the rotation does not stop, the optical system 12 (carriage) is affected by the vibration of the device at that time.
Vibrates, causing an image defect called skip. Here, depending on the configurations of the fixing roller and the pressure roller, it is possible to suppress the lateral displacement of the image support in the fixing device itself to almost 0 mm.

That is, in the pressure fixing device in which the roller is provided with a tapered shape of an inverted crown to make it suitable, the angle θ has no upper limit if the enlargement of the device can be ignored. Of course, θ is 5 even in a pressure fixing device (a type that causes lateral deviation) in which a conventional fixing roller and a pressure roller have an intersecting angle.
Image bending was acceptable up to °. In either case θ
When the angle exceeds 5 °, for example, when using a commonly used A3 (vertical 420 mm * horizontal 297 mm) size image support, the axial length (width) of the fixing roller and the pressure roller is designed to be about 10 mm. % (About 33 mm), which increases the weight and volume of the device. In order to obtain an electrophotographic apparatus of the same size as a conventional one, a preferable mode is set to 0 ° <θ ≦ 3 °. A good copy could be obtained when the rotation speed v2 of the fixing roller was in the range of 101 to 104 mm / sec.

By the way, when v2 = 100 mm / sec or less, the peeling time of the image support from the image bearing member was delayed at the transfer portion, and the image bearing member was wrapped around the image bearing member, resulting in defective transfer. In some cases, the unfixed toner image on the image support may come into contact with the casing inside the copying machine and disturb the toner image.

Further, when v2 = 105 mm / sec or more, the image support is pulled between the central portion and the rear end of the image support, and the speed fluctuation of the image support and the image support occurs at the transfer portion. , The electrostatic latent image on the image bearing member was rubbed by the image bearing member and disturbed the toner image. Image support 11 is L1
If the length is longer, and the distance from the rear end of the image support to the transfer portion when the front end of the image support contacts the fixing position is L3, the relationship between L1, L2, L3, v1, and v2 is (L2-
It can also be expressed as L1) / v2> L3 / v1. Here, (L2-L1) / v2 is the time until the deflection of the image support disappears. L3 / v1 is the time from the time when the front end of the image support comes into contact with the fixing position until the rear end of the image support finishes passing through the transfer portion.

As a preferred embodiment of the present invention, the fixing roller and the pressure roller constituting the pressure fixing device of the type having a crossing angle may be made of a material that gives a predetermined pressing force to the contact portion between the rollers, Although not particularly limited, it is, for example, an induction-hardened surface made of steel and hard-chrome plated on the surface. Alternatively, a metal roller whose surface is coated with resin may be used. At least one of the rollers may have a tapered shape with an inverted crown. As shown in FIG. 3, both the fixing roller and the pressure roller may be tapered. When a metal is used as a material for either or both of the hollow roll and the solid roll, it is preferable to provide the metal roll with a tapered shape of an inverted crown.

The same effect can be obtained even if the hollow roller is used only on one side of the pressure side, only one side of the pressure side, or both of the pressure side and the pressure side. The pressure distribution can be made uniform. Furthermore,
In the pressure fixing device of the type having no crossing angle, one roller is a hollow cylindrical roller 13 and the other roller is a solid roller 14, as shown in FIG. A support shaft 15 is disposed inside the hollow roller 13 along the axial direction thereof, and constitutes a center support roller in which the hollow roller and the support shaft are fixed at a substantially central portion in the axial direction of the hollow roller 13. .. The material of the roller is not particularly limited to hollow rollers and solid rollers, and may be metal, for example. Further, it may be formed by coating with resin, rubber, hard urethane, polycarbonate, or the like.

The material of the soft elastic body to be coated may be one having a compressibility capable of dispersing the concentration of the pressing force transmitted from the support shaft 15, and the linear load acting on the roller (per unit length of the roller) Load). Specifically, for example, when the linear load is 20 Kg / cm, it is 50 to 500 Kg.
/ Mm ² compressive modulus is good, preferably 80-2
Good compression modulus between 00 Kg / mm ² . The thickness of the soft elastic body depends on the pressing force applied to the hollow roller and the compression elastic modulus of the soft elastic body, but it must be a thickness that can disperse at least the concentration of the pressing force transmitted from the support shaft. Specifically, for example, when the linear load is 5 to 40 kg / cm, the thickness of 0.2 to 1.5 mm is preferable, and the thickness of 0.3 to 1.0 mm is preferable.

[0019]

As described above, according to the present invention, the angle θ between the contact line of the fixing roller and the pressure roller at the fixing position and the tip of the image support is 0 ° <θ ≦ 5 °, The linear distance connecting the fixing position and the transfer position of the image carrier is L1 (m
m), the distance that the image support travels from the image support until it reaches the fixing position of the roller is L2 (mm), the rotational speed of the image support is v1 (mm / sec), and the rotational speed of the fixing roller. Is v2 (mm / sec), L1 <L
2. Since v1 <v2 is set, the size of the electrophotographic apparatus can be reduced, and the lateral displacement of the image support and the vibration of the apparatus do not occur, so that image defects due to image bending and skipping are eliminated, and at the same time, the image support is The impact noise due to the up and down movement of the fixing roller when entering and discharging the fixing roller is also eliminated.

[Brief description of drawings]

FIG. 1 is an explanatory view of an arrangement of an image carrier and a fixing device and a locus along which an image support travels in an electronic copying apparatus to which a pressure fixing device of the present invention is applied.

FIG. 2 is an explanatory diagram of a plunge angle of an image support (an angle θ formed by the contact line between the fixing roller and the pressure roller and the image support) in the pressure fixing device of the present invention.

FIG. 3 is a cross-sectional view showing a roller structure of the pressure fixing device.

FIG. 4 is a side view of a main portion of an electrophotographic apparatus incorporating a conventional pressure fixing device.

FIG. 5 is an explanatory diagram showing a state in which the tip of the image support in the conventional pressure fixing device projects into the fixing roller.

FIG. 6 is an explanatory diagram of an image defect (image bending).

FIG. 7 is an explanatory diagram of an image defect (skip).

[Explanation of symbols]

1, 2 paper feed rollers, 3, 4 registration rollers, 5 guides, 6 image carrier, 7 transport section, 8 fixing inlet guide, 9 fixing roller, 10 pressure roller, 11
Image support, 12 Optical system, 13 Hollow roller, 14 Solid roller

Continuation of the front page (72) Inventor Ken Mizomi 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Zero Tux Co., Ltd.

Claims (1)

[Claims] 1. A pressure fixing device for fixing a toner image by passing an image support having an unfixed toner image transferred by an image carrier between a fixing roller and a pressure roller which are in contact with each other under pressure, The angle θ formed by the contact line at the fixing position of the fixing roller and the pressure roller and the tip of the image support is 0 ° <θ ≦ 5 °, and the linear distance connecting the fixing position of the roller and the transfer position of the image carrier is L
1 (mm), the transport distance traveled until the image support separates from the image support and reaches the fixing position of the roller is L2 (m).
m), L1 <L2 and v1 <v2, where v1 (mm / sec) is the rotational speed of the image carrier and v2 (mm / sec) is the rotational speed of the fixing roller. Fixing device.