JPS58144869A - Fixing device - Google Patents

Abstract

PURPOSE:To improve fixability, by supporting the respective end parts of a pair of upper and lower fixing rolls with separate bearing boxes, and forming a clearance between the fixing rolls with the spacing forming means provided on the opposed surfaces of the upper, lower bearing boxes on the side opposite to a reference side for transferring of sheets. CONSTITUTION:Rolls 10, 11 are supported with respective a pair of right and left bearing boxes, that is, upper, lower housings 14, 15. Receiving seats 14a, 15a re projected on the upper, lower housings 14, 15 on the side opposite from a reference side for transferring of sheets so as to face each other, and the preceding end of a bolt 23 as a spacing forming means screwed into the seat 14a is brought into contact with the seat 15a so that a spacing (d) is formed between the rolls 10 and 11 on the side opposite from the reference side. The spacing (d) is adjusted according to the thickness of the sheet materials. When a sheet material 1' of a size A5 narrower than the transversely fed sheet material of a size A4 is fed longitudinally, part of the pressure is born as the bolt 23 contacts with the seat 15; therefore, the fixing is accomplished without making the sheet material transparent owing to defective fixing or overpressure.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fixing device, in particular a fixing device that transports a sheet material on one side (usually the user's side) and fixes unfixed toner on the sheet material through a pair of fixing rollers. Regarding equipment.

Hereinafter, a pressure fixing device will be explained as an example.

Some image forming apparatuses, such as electrophotographic copying machines and electrostatic recording machines, are ones in which a sheet material is manually fed for ease of operation, and those that transfer an image on an image carrier onto a sheet material and then transfer this sheet material to the image carrier. Some devices use mechanical separation means such as separation belts or separation claws to reliably separate the particles from the particles. In order to manually feed or separate the sheet material, it is necessary to transport the sheet material at least from the transport start point to the transfer separation point with one side as a reference.

However, when the sheet material is transferred on one side and passed between the pair of pressure fixing rollers, the sheet material has a maximum width (approximately equal to the length of the pressure fixing roller) and a narrow width (width smaller than the length of the pressure fixing roller). In the sheet material of , the pressure distribution in the width direction applied to the sheet material changes significantly.

The following is an explanation using specific numerical values. Figure 1 shows the pressure distribution applied to the sheet material 1 of A4 size when the sheet material 1 is fed horizontally, and the state in which the sheet material 1 is sandwiched between the pressure fixing rollers 2@3. As is clear,
Roller 2 that spans between the width a (reference side) and b of the sheet material 1
- The pressure F'i of 3 is between the fixable pressure Po and the pressure Pt at which the sheet material is pressurized and becomes transparent. In addition, as shown in Figure 2, the pressure saw fixing rollers 2 and 3 have their axes intersecting each other at a crossing angle α, and the pressure saw in the center part is higher than the side edges to form the sheet material 1 to prevent wrinkles. There is.

Next, as shown in Figure 3(b), when the A5 size sheet material 1' is fed between the pressure fixing rollers 2 and 3, the pressure distribution applied to this sheet material is as shown in Figure 3(a). On the reference side a, there is insufficient pressure and the sheet 1' is not fixed, and on the opposite side (, @, too much pressure is applied, causing the sheet 1' to become extremely thin and transparent.

Therefore, in order to eliminate the above-mentioned inconvenience, it is necessary to transport the sheet material based on the center so that it always passes through the center of the pressure fixing roller, or when transporting the sheet material based on one side, the 4 small size sheets are transferred using diagonal rollers or stock rollers. It has been considered to automatically or manually shift the sheet material to pass through the center of the pair of pressure fixing rollers, but either method has a complicated structure, or the pressure applied to the sheet material changes significantly (for small-sized sheets, Excessive pressure)・Undesirable.

The present invention has been proposed in view of the above, and it is possible to fix sheets from the maximum width to 1/2 width under exactly the same fixing conditions, and in fact, it is approximately 40% of the maximum width. To provide a pressure fixing device that has good fixing properties up to the width of a sheet material and does not make the sheet material transparent.

Embodiments of the present invention will be described below with reference to the drawings.

11E4 to JIE6, an upper roller 10 and a lower roller 11 made of rigid metal have their respective ends connected to a pair of left and right bearing boxes, that is, an upper housing 14 and a lower housing 15 via bearings 12 and 13. is supported by The housings 14 and 15 are hinged at a shaft 16 so as to be openable and closable. Numeral 17 is a bolt that is loosely passed through a hole 18 provided at the free end of the left and right upper housing 14 opposite to the opening/closing shaft 16, and is screwed into the upper housing 15 or inserted into a hole provided therein and attached to the lower end. Screw the nuts together. 19 is a bottom plate attached between the left and right lower housings 15 and 15. A compression spring %2o is a compression spring installed between the head of the bolt 17 and the upper housing 140.
It is a pressing mechanism between 1 and 2. Reference numeral 21 denotes a sprocket attached to the shaft 11a of the roller 11, to which driving force is transmitted from a drive source such as a motor (not shown) via a chain, and the roller 10 follows the roller 11 and is fed between the rollers to and ii. While fixing the unfixed toner on the surface of the sheet material
transport in the direction.

In the present invention, seats 14a and 15a are provided in a protruding manner opposite to the upper and lower housings 14 and 15 on the side opposite to the transfer reference side of the sheet material (in the illustrated example, the right side of the page). The tip of a bolt 23 serving as a gap forming means screwed into 14a is brought into contact with the seat 15a of the lower screw/gug 15 to form a gap d between the rollers 10 and 11 on the side opposite to the reference side. .

This gap d is adjusted according to the thickness of the sheet material.
The adjusted position is fixed with a nut 24 that functions as a double nut. In addition, if the sheet material used is constant, a convexity may be provided on the opposing surfaces of the upper and lower hinges 14 and 15 to form a constant gap, or a metal washer 25 may be used between the bolt and nut. Alternatively, it may be interposed between the upper and lower catch seats 14a and 15a.

This embodiment has the above-mentioned configuration, and when the A4 size sheet material 1 is fed horizontally as shown in Figure 7 (b), at this time,
The pressure distribution applied to the sheet material, as shown in FIG. 1(a), is generally the same as that in FIG. 1(a).

Next, when the A5 size sheet *41' is fed vertically as shown in Figure 2 (b) of WN2, the pressure distribution applied to the sheet material when it is in the center becomes as shown in Figure (a). In other words, A4 size horizontal feed (width 29
If a sheet material with a width narrower than 7 mm is used, part of the pressure is shared by the contact between the bolt 23 and the seat 15a, so fixing can be achieved without the sheet material becoming transparent due to poor fixing or excessive pressure. .

The following is an explanation using specific numerical values.

The thickness of commonly used sheet materials is about 85μ. The upper limit of the pressure at which this sheet material can be fixed without making it transparent is about 35 Af/am, and when the sheet material is passed between the pressure fixing rollers at this pressure, the thickness becomes about 65 μm. That is, if pressure is applied to make the sheet material thinner, the sheet material will become transparent. Therefore, the distance d between the pressure fixing rollers according to this embodiment is preferably set to about 65 μm. This value is approximately 80 degrees thicker than the thickness of the sheet material before the sheet material was deformed.

Therefore, if the distance d is set to about 65 μm for commonly used sheet materials, it can be applied to most sheet materials. In addition, the pressure fixing roller is hardened steel and hard J-ROM plated for its durability, but conventionally, when sheet material is not passed through, excessive pressure is applied to the center due to the intersection angle α, causing point contact there. Therefore, the durability of the plating became a problem. However, in the pressure fixing device according to this embodiment, when the paper is not passed, one end of the rollers 10 and 11 (reference @
) are in contact with each other, and the other end (opposite to the reference side) is in contact with the catch 15a of the lower housing 15 and the stopper (bolt 23
Since the tip of the roller is in contact with the roller, it is possible to prevent the plating in the center, which is the paper passing area, from peeling off, resulting in uneven fixing and rust on the roller.

In the present invention, both ends of a pair of upper and lower fixing rollers are supported by separate bearing boxes, and a gap forming means is provided on the facing surface of the upper and lower bearing boxes on the side opposite to the sheet material transfer reference side. Since a gap is formed between them, when a small-sized sheet material is transferred on one side basis, part of the pressure that should be applied to this sheet material is received by the above-mentioned gap forming means, so that excessive pressure is applied to the sheet material and the object is affected. The sheet material does not become transparent.

Further, since the gap between the fixing rollers is configured to be adjustable according to the thickness of the sheet material, effects such as the fact that the sheet material used is not limited by the thickness can be obtained.

Although the present embodiment has been described using a pressure fixing device as an example, the present invention is not limited to this, and can of course be applied to, for example, a heating roller fixing device.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are a pressure distribution diagram and a front view of a pair of rollers when a sheet of maximum width is transferred between the pressure fixing rollers of a conventional pressure fixing device, and a front view of the roller pair, @2
The figure is a plan view of the pair of O rollers. @3 Figures (a) and (b) are the distribution of pressure applied to a sheet material whose width is narrower than the maximum width when it is transferred between the pressure fixing rollers in Figure 1. 4 is a perspective view of the pressure fixing device of the present invention, FIG. 5 is a side view thereof, and FIG. 6 is a longitudinal sectional front view thereof.
FIGS. 7(a) and 7(b) are a pressure distribution diagram and a front view of the pair of rollers when a sheet material of the maximum width is transferred between the pressure fixing rollers of the pressure fixing device of the present invention;
Figures (a) and (b) are a pressure distribution diagram and a front view of the roller pair, respectively, when a sheet material having a width smaller than the maximum width is transferred between the pressure fixing rollers. 1 and 1' are sheet materials, 10 and 11 are rollers, and 14 and 15
d is the distance between the upper and lower horns, 14a@15a is the catch seat, and 23 is the bolt as the distance forming means. Figure 8 Figure 7

Claims (1)

[Claims] (1) In a fixing device that transports a sheet material on a one-sided basis and passes between a pair of fixing rollers to fix unfixed toner on the sheet material, both ends of each pair of rollers are supported by bearing boxes on each side. A gap forming means is provided on the facing surface of the upper and lower bearing boxes on the opposite side to the sheet material transfer reference side to form a gap between the fixing rollers on the same side, and this gap can be adjusted according to the thickness of the sheet material. A fixing device characterized by comprising: