JPH0128522Y2 - - Google Patents

Description

[Detailed description of the invention] This invention includes a pair of rollers that pinch and convey a transfer material carrying an unfixed toner image for fixing, and a means for supplying an anti-offset agent to at least one of the rollers. Regarding a fixing device.

In a transfer type electrophotographic copying machine, a toner image formed on a photoconductor by a predetermined process is transferred to transfer paper, and then the transfer paper is separated from the photoconductor and transported to a fixing section where it is heated and/or Pressure is applied to fuse or press the toner image onto the transfer paper and fix it.

As this fixing device, a roller fixing device is widely used in which a transfer paper carrying an unfixed toner image is conveyed while being held between a pair of rollers consisting of a heating roller and a pressure roller, and is heated and pressurized to fix the transfer paper.

An example of this type of fixing device will be explained with reference to FIG. 1. Transfer paper S conveyed to the fixing device by a separation conveyance belt 1 can be pressed against and removed from a fixing roller 3 having a heater 2 inside. The toner image is fused to the transfer paper by passing between the roller pair of the pressure roller 4, and is bitten by the conveyance roller 7 along the peeling claw 5 and the guide plate 6, and then transferred to the guide plate 8.
is discharged through.

Now, important technical issues regarding the roller fixing device include prevention of offset of the toner image to the fixing roller and separation of the transfer paper from the fixing roller. For this purpose, it is common practice to use Teflon, silicone rubber, or the like, which has good releasability, on the surface layer of the fixing roller, or to apply an anti-offset agent such as silicone oil to at least one of the pair of fixing rollers.

In the apparatus shown in FIG. 1, in order to apply an anti-offset agent (hereinafter abbreviated as oil) to the fixing roller 3, the upper surface of a coating felt 10 whose lower part is immersed in an oil tank 9 provided at the lower part of the fixing device is used. , and the fixing roller 3, an oil supply roller 11 and an oil application roller 12 are sequentially provided. The application felt 10 is constantly pressed against the oil supply roller 11 by a spring 13 via a felt holding plate 14, and the pressure lever 1 is pressed by a spring 15.
6. The oil application roller 12 is constantly in pressure contact with the fixing roller 3 via the oil supply roller 11, and due to the friction between the oil application roller 12 and the fixing roller 3, the oil supply roller rotates following the fixing roller 3. - The fixing roller 3 is stopped so that an appropriate amount of oil is applied to the fixing roller 3.

However, since oil starts to be supplied when the fixing roller 3 rotates, a considerable amount of oil is supplied to the fixing roller 3 by the time the transfer paper reaches the fixing roller. Therefore, a large amount of oil accumulates at the tip 5a of the peeling claw 5, and this oil adheres to the tip of the transfer paper when it passes through, causing stains on the transfer paper, and furthermore, re-adhering to the inside of the machine and staining it. . In particular, if a wide transfer paper is passed after passing several sheets of narrow transfer paper, the oil supplied outside the width of the narrow transfer paper will be directly transferred to the tip of the peeling claw. This phenomenon is noticeable in that area because of the accumulation of water.

For the purpose of improving this, for example, Japanese Patent Application Laid-Open No. 53-7338
No. 53-68240 and JP-A-53-68240 each disclose a device in which an oil supply felt is divided into two parts in the longitudinal direction, and one part is brought into contact with and separated from the surface of a supplied roller using a solenoid. . Also, Japanese Patent Application Publication No. 1973-
Publication No. 5441 discloses a device in which an oil coating roller provided between an oil coating felt and a fixing roller is rotated independently according to the paper passing width, so that oil is supplied only to the paper passing width. has been done. All of these devices are complicated and expensive, and it is difficult to change the oil application width in multiple stages. Japanese Unexamined Patent Publication No. 55-89878 discloses a fixing device in which the width of the oil application can be changed steplessly using an oil application member whose width changes continuously, but it is difficult to adjust the rotational position. It's complicated.

In consideration of the above-mentioned problems of the conventional roll fixing device with variable oil application width, the present invention has a relatively simple configuration and operation that allows the oil application width to be adjusted to correspond to the width of each paper size used in actual production. An object of the present invention is to provide a switchable roll fixing device.

The present invention will be described in detail below with reference to drawings showing embodiments thereof.

FIG. 2 is a diagram showing an offset prevention agent supply section of an embodiment of the fixing device of the present invention, and other parts are omitted because they are the same as the conventional device shown in FIG.

As shown in FIG. 2, in the oil supply section of the present invention, the oil tank 9 is also
The pumped up oil is supplied to the fixing roller 3 via an oil supply roller 11 and an oil application roller 12, which rotate following the fixing roller 3.
A spring 13 and a felt holding plate 14 that constantly press the coated felt 10 against the oil supply roller 11
is not provided, and instead a coated felt 10 is provided.
is the oil supply roller 11 holding the felt 10.
A spring 21 is held in tension between the lower end of the coating felt 10 and the bottom plate of the oil tank 9.
Therefore, the applied felt 10 is always kept under the control roller 20.
It is designed to be in close contact with the upper side of the.

As shown in FIG. 3, the regulation roller 20 is provided with wings 20a, 20b, and 20c radially arranged in a T-shaped cross section, each having a length corresponding to the width of each size of transfer paper handled by this copying machine. ing. In addition,
Since the paper passing reference of this copying machine is a one-sided reference, one end of each wing is at the same position. The regulation roller 20 is operated by a drive device (not shown) in three operating positions: one in which one of the blades faces the oil supply roller 11;
The upper surface of the horizontal side of the letter-shaped cross section is the oil supply roller 11
The blades 20a, 20b, or 20c are selectively displaced and positioned in one of the non-operating positions opposite to the blades 20a, 20b, and 20c. The application felt 10 is pressed against the oil supply roller 11 and is separated from the oil supply roller 11 in the non-operating position.

The coated felt 10 is divided into widths that, when combined as shown in FIG. 3, have the width of each transfer paper, and is hung on a regulating roller 20.

The operation of this device will be explained below. Normally, when the transfer paper is not passing between the pair of fixing rollers, the regulating roller 20 is held in the non-operating position as shown in FIGS. Oil is not supplied to the fixing roller 3.

During copying, by receiving a signal of the size of the transfer paper passing from the transfer paper size detection means or size setting means and a signal indicating that the leading edge of the transfer paper has reached a position close to the pair of fixing rollers, the image shown in FIGS. As shown, the regulation roller 20 rotates so that the wings whose length corresponds to the width of the transfer paper of that size presses the coated felt 10 against the oil supply roller 11, and only the coated felt 10 corresponding to that width is supplied with oil. The fixing roller 3 is pressed against the roller, and oil is supplied to the fixing roller 3 within the width thereof. The starting point of oil application is shown in Figure 5a.
As shown in the figure, oil application position A to the fixing roller 3
When the leading edge of the transfer paper reaches a position C such that the circumferential length l of the roller from to the nip start position B of the pair of fixing rollers is the same as the distance until the leading edge of the transfer paper reaches point B, then the fixing is completed. It is possible to prevent the oil applied to the roller from being wasted and accumulated at the tip 5a of the peeling claw 5. When it is detected that the trailing edge of the transfer paper has reached the point C, the regulating roller 20 is returned to the non-operating position as shown in FIG. You can apply oil until then.

As described above, according to the present invention, the anti-offset agent can be supplied only to the area where the transfer paper passes between the pair of fixing rollers and within the width of the transfer paper. This prevents the anti-offset agent from accumulating in the transfer paper, prevents oil stains from forming on the transfer paper, prevents oil stains inside the machine, and prevents the anti-offset agent from being wasted.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of a conventional roller fixing device, FIG. 2 is a sectional view showing an offset prevention agent supply section of an embodiment of the fixing device of the present invention, and FIG. 3 is a perspective view showing the regulating roller thereof. , Fig. 4a is a sectional view of the main part of the device when the regulating roller is in the non-operating position, b
5 is a front view of the same, FIG.
FIG. 6 is a cross-sectional view of the main parts of the apparatus at the time when the application of the same agent is completed. 3, 4...Fixing roller pair, 5...Peeling claw, 9...
...Offset prevention agent storage tank, 10...Felt-like member, 11, 12...Rotating member, 20...Regulating roller (rotating member contact/separation means).

Claims (1)

[Scope of utility model registration request] In a fixing device that supplies an anti-offset agent from a storage tank through a felt-like member to at least one roller of a roller pair that pinches and conveys a transfer material holding an unfixed toner image at its edges and performs fixing, the above-mentioned felt-like member is used. By combining the members, the members are divided to correspond to the width range of each size of transfer material, and correspond to the width range of each size of transfer material for pressing the felt member against the surface to which the offset prevention agent is supplied. 1. A fixing device comprising a roller having a plurality of convex portions provided on one rotating shaft, the width of which an anti-offset agent is applied is made variable depending on the rotational position of the roller.