JPS61129674A - Pressure fixing device - Google Patents

Abstract

PURPOSE:To prevent slip of a driven roll of a pair of fixing rolls by interlocking the driven roll with the other driving roll through a one-direction clutch which is provided for the driven roll so that the peripheral speed of the driven roll is lower than that of the driving roll. CONSTITUTION:A sprocket 10 having a tooth number Z1 is set to a shaft end 1a of a fixing roll 1, and a sprocket 11 having a tooth number Z2 (<Z1) is set to a shaft end 3a of a pressuring roll 3 through a one-direction clutch 12, and sprockets 10 and 11 are connected by a roll chain 13 which a motor 14 drives. When the motor 14 is started, rolls 1-3 are rotated in directions of arrows if an image carrier 16 does not exist between fixing rolls 1 and 2. If the image carrier 16 enters between fixing rolls 1 and 2 and the roll 2 slips, a counterclockwise force acts upon the one-direction clutch 12, and the clutch 12 is rotated synchronously with the sprocket 10. Thus, the pressuring roll 3 is driven by the roll chain 13, and rolls 1-3 cancels the slip synchronously with one another to extent the life of rolls.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a pressure fixing device in which a support carrying a toner image is passed between a pair of fixing rolls and fixed by pressure.

Conventional Technology In dry type electrophotographic copying machines, facsimile machines, printers, etc., a pressure fixing device, for example, is used to fix a toner image formed on a paper or plastic sheet support after development or transfer. It is used. For this pressure window 1vt12, a pair of rolls (for example, steel rolls whose surfaces are plated with hard chrome) are brought into pressure contact with each other, as described in, for example, Japanese Patent Publication No. 35-47751 and Japanese Utility Model Publication No. 54-151343. It is well known that the axes of the rolls are crossed with each other in order to obtain a uniform pressing force. However, although this pressure fixing device has a relatively simple structure, in order to obtain a predetermined pressing force (usually 10 to 25 kg/c+++), it is necessary to increase the roll diameter to about 40 to 60 IllI, resulting in an increase in the size of the device. It also has disadvantages of increasing the size and weight of Nm.

Recently, in order to reduce the weight and size of the device, a pair of fixing devices with different diameters have been developed, for example, as described in Japanese Patent Application Laid-Open No. 55-4075, for pressurizing and fixing a support holding a toner image. A pressure fixing device equipped with a roll and a pressure roll for correcting the deflection of a smaller diameter roll among the fixing rolls has been proposed and put into practical use. This pressure fixing device crosses the axis of the fixing roll, which is smaller than the diameter of the roll, by a small angle θ (usually about 1° to 2°) with the axis of the fixing roll on the side that contacts the toner image. The axis of the pressure roll is parallel to the axis of the fixing roll on the side that contacts the toner image, and the shaft end is connected to an external drive source.

In addition, from the point of view of preventing paper loss, for example,
A pressure fixing device has also been proposed, as described in Japanese Patent No. 315, in which the axes of a pair of fixing rolls and a pressure roll cross each other.

In the pressure fixing devices of the various structures described above, only one roll (usually the fixing roll on the side that contacts the toner image) is driven by a motor or the like, and the other rolls are driven by friction between the rolls. Therefore, especially when the support holding the toner image is a thick paper (80 μm or more) or a plastic sheet with a smooth surface, this support may be scratched between the fixing rolls (for example, hard chrome plating may peel off).
Or, a problem arises in that the support does not get caught.

Therefore, in order to eliminate such problems, for example, Japanese Utility Model Application Publication No. 56-128663, Japanese Patent Application Publication No. 59-18976 have been proposed.
As described in the publication, rolls other than the rolls connected to the drive source can be forcibly driven by connecting the rolls (fusing rolls or the fixing roll and pressure roll) with gears or chains. Conceivable.

Problems to be Solved by the Invention However, even if the above-mentioned coupling means such as gears or chains are provided and the driven side fixing roll is forcibly driven, the driven side fixing roll may slip due to the following reasons. You can't get rid of it.

If the outer diameters of both fixing rolls match a predetermined size, the circumferential speeds of both rolls will be the same, and theoretically no slip will occur. However, like general mechanical parts, the fixing roll also has a predetermined dimensional tolerance (±0.05m to ±0.3110m).
1), and therefore the circumferential speeds of both rolls actually differ, making it impossible to prevent the driven-side fixing roll from slipping.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pressure fixing device that can eliminate the above-mentioned drawbacks and reliably prevent the driven fixing roll from slipping.

Means for Solving the Problems The present invention provides a roll type having a pair of fixing rolls that are in pressure contact with each other and whose axes cross each other at a small angle, or a roll type 30 that has a pressure roll in addition to the above-mentioned pair of fixing rolls.
- The target is a type of pressure fixing device.

In the pressure fixing device of the present invention, a first sprocket with a diameter of 71 is attached to the driving side fixing roll of a pair of fixing rolls, and
Or a pressure roll (22 teeth in case of 30-wheel method)
(However, Z2>Zl) A second sprocket is attached via a one-sided clutch, and these sprockets are connected by a driving roller chain.

Effect According to the above configuration, when there is no support between a pair of fixing rolls, the driving side fixing roll is driven by the rotation of the roller chain, but the other fixing roll (or pressure roll) is Since it is Zl and has a one-sided clutch, it is not driven by a roller chain (that is, the second sprocket idles), but is driven by the frictional force with the fixing roll on the drive side.

Next, when the support is caught between both fixing rolls and the fixing roll on the driven side C slips, the rotation of the second sprocket is transferred to the driven side via the one-sided clutch because Z2>Zl. The fixing roll (pressure roll) is transmitted to the fixing roll (pressure roll), and the fixed roll (pressure roll) on the driven side is also driven by the roller chain. That is, the fixing roll on the driven side may be interlocked with the fixing roll on the driving side via a one-way clutch so that the circumferential speed of the fixing east side roll on the driving side is slowed, regardless of the size of the outer diameter of the roll.

Example The details of the present invention will be explained below with reference to the drawings.

FIG. 1 is a sectional view of a pressure fixing device according to an embodiment of the present invention, FIG. 2 is a view taken along the line A-A in FIG. 1, and FIG. 3 is a view taken along the line B-B in FIG. be.

In FIGS. 1 to 3, reference numeral 1 denotes a fixing roll, which is rotatably supported by a side plate 4.4' via a bearing (not shown). The fixing roll 2 has a guide plate 5.5' (however, 5
(only shown) via bearings (not shown). The guide plates 5 and 5' are mounted in the side plates 4 and 4', respectively, so as to be vertically movable. The pressure roll 3 has a bearing (not shown) on a guide plate 6.6' (only 6 is shown).
The guide plates 6 and 6' are respectively mounted in the side plates 4 and 4' so as to be movable up and down. Further, a disc spring 7 and a washer 8 are interposed between the lower surface of the guide plate 6 (6') and the side plate 4 (4'), and the lower surface of the washer 8 is provided with a The pressure bolt 9 is in contact with it. By appropriately tightening the pressure bolt 9, the fixing roll 1 and the fixing roll 2 and the fixing roll 2 and the pressure roll 3 are brought into pressure contact. Note that the axis of the fixing roll 2 and the axis of the pressure roll cross in opposite directions with respect to the axis of the fixing roll 1, and such a roll arrangement can provide uniform pressure and prevent the occurrence of paper wrinkles.

Next, a sprocket 10 having 71 teeth is attached to the shaft end 1a of the fixing roll 1, as shown in FIG.

Further, a sprocket 11 having the number of teeth Z2 (<Zl) is attached to the shaft end 3a of the pressure roll white via a latch 12 in the -h direction. Sprocket 10.11. are connected by a roller chain 13 driven by a motor 14.

According to the above configuration, the motor 14 is started and the low mouth 1-
When the roller 13 is driven in the direction of the arrow χ shown in the figure, the fixing roll 1 rotates counterclockwise. When there is no support 16 holding the toner image 15 between the fixing rolls 1 and 2, frictional force acts between the rolls and the rotation of the fixing roll 1 causes the fixing roll 2 and pressure roll 3 to move clockwise and counterclockwise, respectively. Rotate to. In this case, since the sprocket 11 is attached to the shaft end 3a via the one-sided clutch 12, even if the sprocket 11 is rotated by the roller chain 13, its force is not transmitted to the pressure roll 3.

Next, when the support body 16 is caught between the fixing rolls 1 and 2 and the fixing roll 2 slips, since Zl is set to >22, a counterclockwise rotational force acts on the one-way clutch 12. The one-way clutch 12 rotates 1° in synchronization with the sprocket 10. As a result, since the pressure roll 3 is driven by the roller chain 13, the pressure roll 3 and the fixing roll 2 rotate in synchronization with the fixing roll 1, so that the above-mentioned slip is immediately eliminated.

When the slip disappears, the rotational force of the one-way clutch 10 is not transmitted to the pressure roll 3, and the sprocket 11 idles and returns to its original state.

As described above, in this embodiment, the sprocket 11 of the pressure roll 3 is attached via the one-sided clutch 12, so even if there is a variation in the dimensions between the rolls, the fixing roll 1
．． Only when a slip occurs between the rollers 2 and 2, the one-sided clutch is activated to drive the pressure roll 3, thereby driving the fixing roll 2, and the slip is immediately eliminated. Therefore, damage to the roll due to slipping as in the conventional case does not occur.

In the present invention, Zl < 22 is set for the sprocket, but if Z2 is extremely larger than 71, the roll cannot rotate smoothly, so it is preferable that Z2 is larger than Zl by 1 to 2.

In the above embodiment, only a 30-hole type pressure fixing device was described, but it is of course applicable to a 20-hole type pressure fixing device.

As described above, since the pressure fixing device of the present invention employs a specific forced drive mechanism, it can achieve an excellent effect of improving the life of the roll.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a pressure fixing device according to an embodiment of the present invention, FIG. 2 is a view taken along the line A-A in FIG. 1, and FIG. 3 is a view taken along the line B-B in FIG. be. 1.2: Fixing, roll, 3: Pressure roll, 10.11:
Sprocket, 12 unidirectional clutch, 13: roller chain

Claims (1)

[Claims] 1. A pressure fixing device comprising a pair of fixing rolls that are in pressure contact with each other and whose axes cross each other by a small angle, and a support holding a toner image is passed between the fixing rolls. In the fixing roll pair, a one-way clutch is provided on the driven roll so that the peripheral speed of the driven roll is slower than the peripheral speed of the driving roll of the pair of fixing rolls, and the driven roll is interlocked with the driving roll via the one-way clutch. Pressure fixing device. 2. A pair of fixing rolls that are in pressure contact with each other and whose axes cross each other at a slight angle, and that sandwich and convey a support holding a toner image, and a pair of fixing rolls that are in pressure contact with one of the fixing rolls on the side that does not contact the toner image. In a pressure fixing device having a pressure roll, the pressure roll is fixed in one direction such that the circumferential speed of the pressure roll is slower than the circumferential speed of the fixing roll on the side of the fixing roll that contacts the toner image. 1. A pressure fixing device, comprising: a unidirectional clutch, which is interlocked with a fixing roll on the side that contacts the toner image via the unidirectional clutch.