JPH0546045Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus equipped with a fixing device including an upper roller, a lower roller, and the like.

[Conventional technology]

Generally, an image forming apparatus, for example, a copying machine, is divided into two parts along the conveyance path of the copy paper as shown in FIG. 1, a lower lower frame 1 side and an upper upper frame 2 side. The upper frame 2 side is placed on the lower frame 1 in a horizontal position, but if a situation such as a paper jam occurs in the copying machine, the upper frame 2 will be placed on its pivot shaft 3.
The copying machine is tilted upward with the paper as a fulcrum, and the pressure between the upper and lower rollers 4 and 5 on the conveyance path is released to open the interior of the copying machine and make it possible to easily remove jammed paper.

This upper frame 2 is normally placed horizontally as described above, and the lower end of the upper frame 2 is pressed against the lower roller 5 by the upper roller 4 via the fixing side plate 7, and between the upper and lower rollers of the fixing roller 6. The required strength of pressure is maintained.

The pressure of the fixing roller 6 is set to be quite strong, but as the upper and lower rollers rotate as the copying machine is used, the pressure position between the rollers changes, so the roller surface is The circular shape of the cross section can be maintained without distortion, and the fixing function can be maintained normally.

However, if it is not used for a long period of time, for example, from the time it is manufactured and set up by the manufacturer until it is shipped and delivered to the user's hands and they start using it,
The contact position between the upper and lower rollers of the fixing roller does not change for a long period of time, so if strong pressure is applied, the pressure contact area between the rollers will partially become distorted, which will cause uneven rotation when using the copying machine and prevent normal operation. Fixation function is impaired.

As a countermeasure against this problem, conventionally, as shown in FIG. There is an example in which the pressure at point P between the two is relaxed.

In another conventional embodiment, as shown in FIG. 5, the spring 11 is loosened by turning the screw 14, and the pressing force on the lower roller 5 side is weakened to reduce the pressure at point P between the fixing rollers 6. Some of them have taken measures to weaken them.

Generally, the pressure on the fixing roller 6 of the image forming apparatus is applied from below by the force of the spring 11 being transmitted to the lower roller 5 via the lower roller support plate 9, and from above by closing the upper frame 2. The weight is transmitted to the upper roller 4 via the fixing side plate 7, and this mutual pressure from the upper and lower directions generates inter-roller pressure, so the lower spring 11 is pushed against the upper upper frame 2. We have a compatible relationship.

That is, the force of the spring 11 not only generates pressure between the rollers, but also exerts an action of pushing up the upper frame 2.

[The problem that the idea aims to solve]

By the way, in the above structure, in the method of relieving the pressure between the rollers using the spacer S shown in FIG. The method of loosening the force had problems in workability, as there were two springs 11 on both sides of the copying machine, and it took time to set up and balance both springs to the same strength.

Further, the spring 11 originally exerts a force in the direction of pushing up the upper frame 2 in order to generate pressure between the rollers, and its original purpose is not to push up the upper frame 2.

This force pushing up the upper frame 2 is generated when the upper frame 2 is opened upward, when the fixing side plate 7 opens the upper frame 2 upward, and when the fixing side plate 7
Instead of transmitting the force of the spring 11 following the upper frame 2, the spring pressure becomes a counter pressure when the upper frame 2 is closed, and the operation of pushing up the upper frame 2 feels heavy.

The present invention solves the problems of conventional image forming apparatuses, such as the lack of repeatability of the spacer, the workability of adjusting the spring pressure, and the influence of the spring pressure on the operability of the upper frame. The purpose is to eliminate the problem.

[Means to solve the problem]

In order to achieve the above object, the present invention provides the following image forming apparatus. That is, a fixing roller consisting of an upper roller and a lower roller,
A fixing device consisting of a fixing side plate that supports an upper roller, a lower roller support plate that supports a lower roller and is equipped with a spring that presses the lower roller against the upper roller, a lower frame body to which these are attached, and the fixing side plate. an upper frame body that maintains the inter-roller pressure of the fixing roller by pressing the upper frame body; and a top frame body that applies fixing pressure to the upper and lower rollers when in use, and that regulates the rotation of the lower roller support plate when the upper frame body is opened; This image forming apparatus is equipped with a cam having a near point where the cam can be used, and a far point where the upper and lower rollers can apply pressure to an extent that does not cause distortion when not in use.

[Effect]

In the above configuration, when the upper frame is closed and the cam is rotated to press the lower roller support plate at a far point on the periphery of the cam, the lower roller moves downward and the pressure between the rollers is relieved. This is a measure taken when the device is not used for a long period of time.

Next, with the upper frame closed, turn the cam so that the near point on the periphery of the cam faces the lower roller support plate, and the fixing side plate pressed against the lower roller support plate and the upper frame The lower roller support plate is located at a position a little apart from the near point on the periphery of the cam via the roller and the lower roller. At this time, the inter-roller pressure has a predetermined strong pressure necessary when using the image forming apparatus;
Since the upper and lower rollers rotate with use, the rollers do not become distorted.

When a paper jam occurs while using the image forming apparatus, and the upper frame, which had been closed until now, is opened upward to remove the jammed paper, the fixing side plate is moved by the force of the spring to the lower roller support plate and the lower roller. , since it is pressed via the upper roller, it follows the upper frame and presses the upper frame upward.

However, there is a near point on the periphery of the cam in the direction in which the spring contracts, and the lower roller support plate comes into contact with this point, preventing the lower roller support plate from rotating any further rearward.

Therefore, the rise of the fixing side plate is also stopped.
It no longer follows the upper frame, and the upper frame separates from the fixing side plate and opens while tilting upward.

Since the upper frame body is opened apart from the fixing side plate in this way, there is almost no resistance pressure from the fixing side plate during the closing operation, and only the pressure necessary for the fixing roller just before closing is applied to the fixing roller against the spring. It is sufficient to press the side plate, and as a result, the operation of closing the upper frame body can be performed generally easily.

〔Example〕

Regarding one embodiment of the present invention, how the structure of the present invention is actually embodied will be described below with reference to the drawings, along with its operation.

FIG. 1 is a schematic explanatory diagram of one embodiment of the present invention, and the image forming apparatus will be described using a so-called shell-type copying machine as an example.

1 is a lower frame body, 2 is an upper frame body that covers the upper part of the lower frame body, and can be opened by tilting the upper part about the pivot shaft 3 as a fulcrum.

4 is an upper roller, 5 is a lower roller, and the upper and lower rollers 4 and 5 constitute a fixing roller 6.

A fixing side plate 7 supports the upper roller 4 and can be moved up and down using its pivot shaft 8 as a fulcrum.

9 is a lower roller support plate that supports the lower roller 5;
The lower roller 5 can be moved up and down using the pivot shaft 10 as a fulcrum.

A spring 11 serves as a driving source for the pressure between the upper and lower rollers 4 and 5.

The fixing roller 6, fixing plate 7, lower roller support plate 9, and spring 11 constitute a fixing device 13.

When a paper jam or the like occurs while using the image forming apparatus, tilt the upper frame 2 upward and open it.
You can open the inside and remove the jammed paper.

Reference numeral 12 denotes a cam, which is a main part of the present invention, and will be explained in detail in FIGS. 2 and 3.

FIG. 2 is an explanatory diagram of the state in which the fixing device of the present invention is in use.

In Figure 2, the solid line indicates the general usage condition,
The two-dot chain line shows the state when a paper jam or the like occurs during use and the upper frame body 2 is tilted upward and opened to remove the jammed paper.

Reference numeral 2a in the figure denotes a pressure contact portion at the lower end of the upper frame 2, which comes into pressure contact with the pressure contact portion 7a at the upper end of the fixing side plate 7 when the upper frame 2 is closed.

12 is a cam, 12a is a pivot shaft of the cam 12, 1
2b is the periapsis point on the periphery of the cam, and 12c is the far point on the periphery of the cam.

Here, the near point refers to the point on the periphery closest to the pivot shaft 12a of the cam 12, and the far point refers to the point on the periphery farthest from it.

When using the image forming apparatus, first, the upper frame 2 is closed, and the cam 12 is rotated to set the near point 12b of the cam 12 toward the fixing side plate 9, as shown by the solid line.

When the upper frame body 2 is rotated from the open state to the closed state, the lower roller support plate 9 resists the tensile force of the spring 11 using the pivot shaft 10 as a fulcrum via the fixing side plate 7, the upper roller 4, and the lower roller 5. It rotates clockwise and stops at the position shown by the solid line.

At this time, the lower roller support plate 9 is located away from the near point 12b of the cam 12, and the upper and lower rollers 4, 5
A strong pressure necessary for fixing is working at the point p between the two.

Next, a paper jam etc. occurs during the above operation,
In order to remove the jammed paper, when the upper frame 2 is tilted upward and opened as shown by the two-dot chain line, the fixing side plate 7 follows this and pushes up the pressure contact part 2a of the upper frame 2 with the pressure contact part 7a. However, the lower roller support plate 9 rotates counterclockwise and the cam 12
When reaching the near point 12b, the lower roller support plate 9 is restricted by the cam 12 and cannot rotate any further, and the force of the spring 11 no longer acts.

That is, the lower roller support plate 9 pushes up the fixing side plate 7 via the upper and lower rollers 4 and 5 from the solid line position to the two-dot chain line position in the figure, but does not push it up any further.

Therefore, when the upper frame body 2 is opened upward, the range in which the pressure contact portion 7a of the fixing side plate 7 follows the pressure contact portion 2a of the upper frame body 2 is also the range shown by the two-dot chain line, and beyond that, the upper frame body Even if the fixing side plate 7 is opened upward, the fixing side plate 7 does not follow the fixing side plate 7, and the two separate from each other.

When the upper frame body 2 is closed again after removing the jammed paper, the range of the force exerted by the spring is limited because the rotation is restricted at the near point 12b of the cam 12, as described above. The range in which the pressure contact portion 7a of the fixing side plate pushes up the pressure contact portion 2a of the upper frame body 2 is reduced and limited, and the operation of pressing the upper frame body 2 is performed easily.

FIG. 3 is an explanatory diagram of the state of the fixing device of the present invention when it is not in use.

The period of non-use here refers to the period of non-use for a relatively long period of time, such as the period from when the product is manufactured by the manufacturer, set up, shipped, delivered to the user, and used. This refers to cases where it is not used across the board.

In such cases, applying strong roller pressure at one point between the upper and lower rollers for a long period of time may cause partial distortion of the roller, which has a circular cross section, making it difficult to rotate smoothly or maintain constant pressure during use. This can lead to chipping and poor fixing.

In order to prevent this, the present invention rotates the cam 12 and supports the lower roller support plate 9 at the far point 12c on the periphery of the cam, thereby lowering the position of the lower roller 5, thereby causing a long period of failure. This reduces harmful strong pressure between the upper and lower rollers during use, and prevents partial distortion of the fixing roller with a simple operation.

Note that in the image forming apparatus described above, the upper pressing means is of a type in which the upper frame presses the fixing side plate to apply fixing pressure between the fixing rollers, but the present invention is not limited to this. Instead, it is possible to separately provide an upper pressing means for pressing the fixing side plate, and it is also possible to separately provide a pressing means in a normal copying machine that is not a shell type.

[Effects of the invention] The present invention provides a cam as described above and utilizes the far point and near point on the periphery of the cam to prevent the image forming apparatus from being used for a long time, for example, until the image forming apparatus is transferred from the manufacturer to the user's hands. In between, the lower roller support plate is supported at the far point of the cam, and pressure is applied to the extent that the upper and lower rollers do not become distorted to prevent deterioration of the fixing function.

When using the image forming apparatus, set the cam near the periphery toward the lower roller support plate, and when the upper frame is closed, the near point between the lower roller support plate and the cam should be set. Since the cams are far apart, the force of the spring is acting to enable fixing. If you open the upper frame to remove jammed paper, etc., the lower roller support plate will rotate backwards at the near point of the cam. Since the range of the distance by which the force of the spring pushes up the upper frame is restricted, it acts as a counterpressure only immediately before closing the upper frame, and as a result, the operation of the upper frame becomes easier.

Furthermore, the image forming apparatus of the present invention can easily and accurately switch between the far point and the near point of the cam by rotating a single cam to set the pressure between the rollers that is required when in use and when not in use. It has the advantage that it can be used repeatedly.

[Brief explanation of the drawing]

Figure 1 is a schematic explanatory diagram of one embodiment of the present invention;
The figure is an explanatory diagram of the fixing device of the present invention when it is used, FIG. 3 is an explanatory diagram of the same when it is not used, FIG. 4 is an explanatory diagram of an embodiment of the conventional fixing device, and FIG. 5 is an explanatory diagram of the conventional fixing device. It is an explanatory view of another example. 1...Lower frame body, 2...Upper frame body, 4...Upper roller, 5...Lower roller, 6...Fixing roller, 7...
... Fixing side plate, 9 ... Lower roller support plate, 11 ... Spring, 12 ... Cam, 12b ... Cam's periapsis, 12
c... Far point of the cam.

Claims (1)

[Scope of utility model registration request] a fixing roller consisting of an upper roller and a lower roller;
A fixing device consisting of a fixing side plate that supports an upper roller, a lower roller support plate that supports a lower roller and is equipped with a spring that presses the lower roller against the upper roller, a lower frame body to which these are attached, and the fixing side plate. an upper frame body that maintains the inter-roller pressure of the fixing roller by pressing the upper frame body; and a top frame body that applies fixing pressure to the upper and lower rollers when in use, and that regulates the rotation of the lower roller support plate when the upper frame body is opened; An image forming apparatus comprising a cam having a near point where the cam can be used, and a far point where the cam can apply pressure to the extent that the upper and lower rollers do not become distorted when not in use.