JPH02135485A - Fixing device - Google Patents

Abstract

PURPOSE:To optimize a pressure released condition between fixing rolls correspondingly to a paper clogging degree and to prevent toner on a transfer paper from being offset with respect to the fixing rolls by reducing a pressurizing condition between the fixing roll in two stages by means of first and second pressure releasing means. CONSTITUTION:When the upper part of a paper ejecting cover 50 is opened left for the purpose of paper clogging disposal, the first depressing member 53 of the supporting part 51 of the paper ejecting cover 50 abuts on the engaging part 46c of a pressurizing board 46, which is turned counterclockwise around a supporting axis 45 against the elastic pressure of a spring member 48. Thus, a bearing 44 pushed upward by the pressurizing board 36 is dropped by its own weight and the first pressure released condition occurs between the fixing rolls 40 and 41 and a jammed paper is readily removed without causing an offset condition. When the jammed part is firmly wound around the fixing roll 41, the paper ejecting cover 50 is further opened and a second pushing-down member 54 is made to abut on the engaging part 46c of the pressurizing board 46. Thus, a pressing strength which occurs between the fixing rolls 40 and 41 is reduced to almost zero.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fixing device in an image forming apparatus such as an electrophotographic copying machine.

(Prior Art) When forming an image in an image forming apparatus such as an electrophotographic copying machine, heat fixing and pressure fixing are known as fixing methods. The heat fixing method heats one of a pair of fixing rollers to a certain temperature and passes the transfer paper between the rollers to heat and fix the toner image, while the pressure fixing method uses a pair of fixing rollers that press against each other. A transfer paper is similarly passed between rollers, and the toner image is fixed under pressure. The above-mentioned pair of rollers can be rotated by the rotation of one roller, and the other roller is driven by the rotation of the other roller, and in many cases, the pair of rollers can be used for heating and pressurizing fixing.

Now, the transfer paper on which the toner image has been fixed by the pair of fixing rollers as described above is discharged to the outside through a predetermined paper discharge section, or the paper discharge section is rotated relative to the main body of the fixing device. ,
It can be opened and closed, and if a paper jam occurs, the paper jam can be easily dealt with by opening the paper discharge section, and opening the paper discharge section is also effective for replacing parts.

If the paper discharge section is opened when a paper jam occurs, the jammed paper may become trapped in the fixing roller section, making it difficult to discharge the paper. Therefore, conventionally, the pressing force generated between the pair of fixing rollers is released in conjunction with the opening/closing operation of the paper discharge section. That is, in general, the lower roller of a pair of fixing rollers is often pressed against the upper roller via a support member by a spring member or the like, but in this case, the sheet ejection section is moved in conjunction with the Many mechanisms are used to push down the support member and release the pressing force of the lower roller against the upper roller.

Even if the pressing force between the fixing rollers is released by the above means, when pulling out the transfer paper stuck between the rollers, the toner on the unfixed transfer paper will not be rubbed off by the rollers and offset to the roller surface. Usually, the release pressing force between the rollers is often suppressed to such an extent that the pair of rollers rotates in conjunction with the movement of the paper when the transfer paper is pulled out.

(Problem to be solved by the invention) However, as described above, when the pressure is released to such an extent that the fixing roller rotates following the transfer paper, it is true that toner offset is prevented, but it is difficult to prevent the toner from being offset. This is insufficient for handling heavy paper jams such as paper jams.

In addition, in order to deal with heavy paper jams such as those described above, if the pressing force of the rollers is completely or almost completely released, the paper jams can be cleared easily, but the driven rotation of the rollers may not be sufficient when pulling out the paper. There is a possibility of unfixed toner or offset on the roller surface.

The present invention has been made in view of the above problems, and an object thereof is to provide a fixing device that can easily deal with paper jams without causing the toner on the transfer paper to be offset to the fixing roller. It is on offer.

(Means for Solving the Problems) In order to achieve the above-mentioned problems, the present invention provides a fixing device including a pair of fixing rollers that are configured as a rotating body and are pressed against each other with an appropriate pressure. and a second pressure relief means for further reducing the pressure reduced by the first pressure relief means in a second step. Characterize something.

(Function) According to the present invention, the pressing force between the fixing rollers is
Since the pressure can be reduced in two stages using the pressure release means and the second pressure release means, in the case of a normal paper jam, the pressure between the fixing rollers can be reduced to the first stage using the first pressure release means. Even in the case of a heavy paper jam, the pressure between the fixing rollers can be further reduced to the second stage using the second pressure release means. Therefore, the state of pressure release between the fixing rollers can be changed depending on the state of the paper jam, and it is possible to avoid a situation where unfixed toner is offset to the fixing roller.

(Example) A first example of the present invention will be described below based on the attached FIGS. 1 and 5.

FIG. 1 is a side sectional view of the fixing device, FIG. 2 is a perspective view of the main part of the fixing device, FIGS. 3 and 4 are diagrams showing the operating state, and FIG.
The figure is a sectional view of the main body of the copying apparatus.

First, the main body of the copying apparatus will be explained with reference to FIG. 0 is illuminated by the illumination lamp L, and its reflected light image is slit-exposed onto the photosensitive tram 3 by the short-focus small-diameter imaging element array 2. Since the surface of the photosensitive drum 3 is uniformly charged in advance by the charger 4, an electrostatic latent image corresponding to the original image is sequentially formed on the photosensitive drum 3 by the element array 2. The toner T is visualized by the developing device 5 containing the toner T.

On the other hand, the transfer paper P sent to the registration rollers 7 via the paper feed roller 6 is fed onto the photosensitive tram 3 at a certain timing by the registration rollers 7, and is transferred onto the photosensitive tram 3 by the transfer charger 8. toner image is transferred. Next, the transfer paper P separated from the photosensitive drum 3 is moved to a guide 9
is sent to the fixing device 10 by a pair of fixing rollers 40.
After the toner image on the transfer paper P is fixed by being heated and pressurized by the transfer paper P, the paper is discharged to the outside by the paper discharge roller 42 of the fixing device IO.

Next, as shown in FIGS. 1 and 2, the fixing bag 221 according to the present invention
O will be explained. Note that, in order to clearly show the content of the invention, the paper ejection roller 42 is omitted in the drawings.

In the figure, reference numerals 40 and 41 denote a pair of fixing rollers formed in the shape of a hollow vibrator.
Three rollers are rotatably supported horizontally at both ends via bearings (not shown), and rod-shaped heaters or the like are inserted as necessary to function as heating rollers. Note that the fixing roller 40 is rotationally driven by a drive device (not shown). The fixing roller 41, which is disposed diagonally below the fixing roller 40, has both ends 41a,
41a is pivotally supported by a bearing 44.44 (only one of which is shown in FIGS. 1 and 2), and the bearing 44.44 is inserted into a U-groove (not shown) of the support side plate 43.43 toward the fixing roller 40. The fixing roller 40 is supported so as to be slidable in the direction of the fixing roller 40 . The lower part of the bearing 44 becomes a substantially circular pressing protrusion 44a that protrudes downward, and the pressing protrusion 44a is attached to the upper surface of a pressing plate 46 that is supported by the support side plate 43 via a support shaft 45 so as to be able to swing up and down. are in contact.

The pressure plate 46 extends from the support shaft 45 toward the upper left in FIG.
A diagonal piece 46a that comes into contact with the pressing protrusion 44a of the bearing 44
It consists of a thick horizontal part 46b extending further leftward from the diagonal piece part 46a and a cylindrical engagement part 46c at the left end, and the horizontal part 46b is compressed onto the lower support part 43a of the support side plate 43. It is elastically biased upward by a spring member 48 installed therein. Therefore, the pressure plate 46.46 (only one of which is shown in FIG. 1) presses the bearing 44° 44 around the support shaft 45.45, and presses the fixing roller 40 through its pressing protrusions 44a, 44a.
As a result, the fixing roller 41 is also pushed upward toward the fixing roller 41 diagonally above, and the two fixing rollers 40 and 41 are brought into pressure contact with each other on their outer surfaces. That is, the fixing roller 41 functions as a pressure roller and rotates as the fixing roller 40 rotates.

Next, the paper discharge section disposed on the left side in FIG. 1 will be described, and the pressure release mechanism for the fixing rollers 40 and 41 will be described. A paper ejection cover 50 is disposed in the paper ejection section and extends longitudinally and vertically along the fixing rollers 40, 41 so as to cover the sides of the fixing rollers 40, 41. Both front and rear ends of the lower part of the paper ejection cover 50 As shown in FIG.
1.51, and the supporting portion 51.51
Upper and lower ribs 51a, 51a protruding inward of the device are formed on the upper and lower sides. The paper discharge cover 50 has the ribs 51a, 51
The front and rear support side plates 43 are attached to the lower part of a through the support shafts 49 and 49.
．． 43, so that the upper part of the paper discharge cover 50 can be opened and closed to the left in FIG.

The support portion 51.51 of the paper discharge cover 50 is connected to the pressure plate 4.
6.46 is disposed slightly diagonally above the engaging parts 46c, 46c, and the lower part of the support part 51.51 is bent so that the side plate 52 of the paper ejection cover 50 is bent below the support shaft 49.49 inside the apparatus. Bent portion 52a.

52a, and the lower end of the support portion 51.51 has a semicircular shape together with the ribs 51a, 51a. The side plate bent portions 52a, 52a of the supporting portions 51, 51 and the linear portion slightly above the side plate portions protrude outward in a substantially arc shape, and serve as a pressure release mechanism for the fixing rollers 40, 41. Second
A push-down member (cam) 53, 53, 54, 54 is attached.

The operation of the pressure release mechanism described above will be explained below with reference to FIGS. 3 and 4.

When the upper part of the paper ejection cover 50 is opened to the left as shown in FIG. 3 to clear a paper jam or for other purposes, the support portion 51 of the paper ejection cover 50
．． 51 first pressing member 53 53 or pressure plate 46.46
Press down the engaging portions 46c, 46c of the pressure plate 46.46.
rotates counterclockwise in the figure about the support shaft 45.45 against the elastic force of the spring member 48.48. For this reason, the bearings 44, 44, which had been pushed up toward the fixing roller 40 by the pressure plates 46.46,
The fixing roller 41 also descends due to the lowering of the bearings 44 and 44, and the fixing rollers 40, 41
The suppressed state in between is slightly released (hereinafter, this state will be referred to as the first pressure released state). This makes it possible to easily remove jammed paper that remains in the fixing device 1i10 due to poor conveyance or poor ejection. In this case, the fixing roller 40,
Even if the jammed paper between the fixing rollers 40 and 41 is removed, the fixing rollers 40 and 41 rotate following the movement of the transfer paper, so that no offset occurs in which unfixed toner adheres to the fixing rollers 40 or 41.

If the jammed paper is tightly wrapped around the fixing roller 41 due to poor separation, etc., move the paper ejection cover 50 to the fourth
When opened further as shown in the figure, the second push-down member 54 of the paper ejection cover 50 further pushes down the engagement portion 46c of the pressure plate 46, and as in the case of the first push-down member 53, the fixing roller 41 is lowered. The pressing force generated between the two fixing rollers 40 and 41 can be released to almost zero (this state is referred to as a second pressure release state). By rotating the roller, hard jammed paper wrapped around the roller can be easily disposed of. If the amount of pressure released between the pair of fixing rollers 40 and 41 increases, the fixing roller 41, which rotates as a result, will stop rotating, and there is a concern that toner from the jammed paper may offset the roller 41. Since it is considered that the toner is almost fixed on the jammed paper that has been wrapped around the roller 41, the above problem does not occur.

Now, as a specific amount of pressure release, for example, if the fixing roller 41 is crushed by 1+as in the initial pressure state, the amount of collapse in the first pressure release state is 0.5I.
l + * binding, the amount of collapse is 0.1 mm in the second pressure release state
Moreover, if O■ is used, the above-mentioned effects can be sufficiently obtained.

As described above, between the pair of fixing rollers 40 and 41, the first and second
Since it is possible to generate the two pressure release states of It can be added to and installed on a computer, and its configuration is not complicated.

In this case, in order to sufficiently distinguish between the first pressure release state and the second pressure release state, the first and second push-down members 53.
It goes without saying that the shape and spacing of the paper discharge cover 54 should be adjusted so that a sufficient click feeling can be obtained when opening and closing the paper discharge cover 50. In addition, in order to distinguish between the first and second pressure release states, a stopper (not shown) stops the rotation of the paper ejection cover 50 in the first pressure release state, and this stopper is used when moving to the second pressure release state. The paper discharge cover 50 may be made rotatable by removing it.

Next, second and third embodiments of the present invention will be explained with reference to the attached FIGS. 6 and 7. Since both FIGS. 6 and 7 are the same as FIG. 1 of the first embodiment except for the paper ejection cover, the same parts are given the same numbers and the explanation thereof will be omitted.

FIG. 6 shows a second embodiment, in which a first push-down member 61L serving as a first pressure release means is not attached to the paper discharge cover 60. As a second pressure release means, a lever 62 movable up and down is provided for the paper ejection cover 60, and the second push-down member 5 of the first embodiment is located at the lower left side of the lever 62.
A push-down portion 62a having the same shape as 4 is formed. The push-down portion 62a is positioned such that when the lever 62 is pressed down, the push-down portion 62a of the lever 62 is located at the same position as the second push-down member 54 of the first embodiment. do.

Therefore, after opening the paper ejection cover 60 to the first pressure release state as shown in FIG. is opened as shown in FIG.
The second pressure release state can be created by pushing down the engaging portion 46c.

The configuration of this embodiment is slightly more complicated than that of the first embodiment.
Since the second pressure release state can be generated using a lever 62 that is separate from the paper ejection cover 60, the paper ejection cover 60 is not needed until it reaches the second pressure release state unconsciously as in the first embodiment. There is no tendency for the part to open, and the second pressure release state can be reliably generated only when necessary.

FIG. 7 shows a third embodiment, in which the first and second pressure release states are generated in conjunction with the opening and closing of the paper ejection cover 70, as in the first embodiment. There is no pressure release lever 71. It is set up separately. The lever 71 supports the paper ejection cover 7 with the support shaft 49 of the paper ejection cover 70 as the center.
0, and second push-down parts 71a and 71b of the same shape are formed at the same positions as the first and second push-down members 53 and 54 of the paper discharge cover 50 of the first embodiment. has been done. Therefore, even if the paper ejection cover 70 is not opened, the lever 7
1 in the same direction as the paper ejection cover 70. Since the first and second pressure release states can be caused by the second push-down portions 71a and 71b, it is possible to easily clear a jam from the paper feed side in a short time.

In both the second and third embodiments, only one pressure plate side was used.
Although the pressure release mechanism has been explained, the fixing rollers 40, 41
Of course, a similar mechanism is also provided for the pressure plate 46 on the other end side. In this case, the mechanism on the other side may be linked to the one side, or may be operated separately.

(Effects of the Invention) As is clear from the above description, according to the present invention, the pressure state between the fixing rollers can be reduced to two stages by the first pressure release means and the second pressure release means, so that the pressure inside the fixing device can be reduced. When a paper jam occurs in the fixing device, it is possible to obtain an optimal pressure release state between the fixing rollers depending on the degree of the paper jam, and it is possible to easily deal with any kind of paper jam in the fixing device, and also to remove unfixed toner. The inconvenience of offset to the fixing roller can also be avoided.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of the fixing device according to the first embodiment, FIG. 2 is a perspective view of the main parts of the fixing device, and FIGS. 3 and 4 are exhaust views of the fixing device according to the first embodiment. FIG. 5 is a sectional view of the main body of the copying apparatus, and FIGS. 6 and 7 are side sectional views of the fixing device showing the second and third embodiments. 40.41... Fixing roller, 50... Paper ejection cover 5
3.61...first push-down member (first pressure release means),
54... second push-down member (second pressure release means), 62
．． 71... Lever, 62a... Push-down part (first pressure release means), 71a... First push-down part (first pressure release means), 71b... Second push-down part ( second pressure release means).

Claims (1)

[Claims] In a fixing device comprising a rotating body and having a pair of fixing rollers that are pressed against each other with an appropriate pressure, a first pressure release means that reduces the pressure between the pair of fixing rollers as a first step; A fixing device comprising: a second pressure release means for further reducing the pressurizing force reduced by the first pressure release means to a second stage.