JPH03211580A - electrophotographic equipment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic apparatus having a fixing device for fixing a developer image on a transfer material as a permanent image.

[Prior Art] Conventionally, as a method of applying a release agent used in a fixing device of an electrophotographic apparatus, there is a method shown in FIG. 7(A), for example. The fixing device shown in FIG. 7(A) has a transfer material carrying an unfixed developer image (hereinafter referred to as an unfixed toner image) in a pressure contact area (hereinafter referred to as a nip area) between a fixing roller 1 and a pressure roller 2. The image is fixed by being conveyed under pressure. The fixing roller l is provided with a heater 3 serving as a heating source inside, and a metal core roller 4 is coated around the metal core roller 4 with a release layer 5 of a fluorine resin that is stable even at high temperatures and has high mold releasability. A pressure roller 2 is placed under pressure on the fixing roller 1, and the pressure roller 2 has a silicone rubber layer 6 on its outer layer. The silicone rubber layer 6
has sufficient elasticity, heat resistance, and durability to form the nip portion between the fixing roller 1 and the pressure roller 2, and also has high mold releasability. Further, above the fixing roller l, a release agent coating member 7 is installed above the fixing roller l.
A silicone oil reservoir 8 is provided above the release agent coating member 7 . moreover,
A meter link blade 9 is disposed in contact with the fixing roller I on the r-stream side in the rotational direction of the fixing roller I with respect to the contact portion between the release agent application member 7 and the fixing roller I.

When the fixing roller 1 rotates, silicone oil as a release agent supplied onto the fixing roller L by the release agent coating member 7 is spread by the metering blade 9 and the nip portion to form a thin film on the fixing roller L. However, this further improves the releasability of the fixing roller 1, thereby reducing offset of the toner image onto the surface of the fixing roller 1.

[Problem to be solved by the invention] However, since the silicone rubber layer 6 on the outer layer of the pressure roller 2 and silicone oil have a high affinity, the silicone oil gate spread by the meter link freight 9 is not sufficient. At the nip portion, the silicone oil on the fixing roller 1 is transferred to the pressure roller 2, and the silicone oil on the fixing roller 1 tends to be insufficient, which tends to cause offset. Therefore, in order to prevent the occurrence of this offset, it is necessary to increase the amount of oil supplied to the fixing roller l, and for this reason, it is necessary to replenish silicone oil or replace the application member frequently at short intervals. As a result, when the capacity of the oil reservoir 8 is increased or when the metering plate 9 is used for a long period of time, toner accumulates on the metering plate 9, which requires cleaning from time to time. Therefore, the method shown in FIG. 7(B) was proposed.

The applicator 7 shown in FIG. 7(B) is composed of a support member 10 and a felt 11 impregnated with silicone oil, and is used to apply oil and clean the fixing roller l at the same time. Although this method is simple and effective because it is inexpensive and allows oil application and cleaning to be performed at the same time, the absolute amount of oil contained in the felt 11 is small and oil shortage occurs at an early stage. Further, there was a problem in that the portion of Felt II that came into contact with the fixing roller became dirty, which also caused early cleaning failure. Therefore, the method shown in FIG. 7(C) was proposed.

The apparatus shown in FIG. 7(C) is similar to the apparatus shown in FIG. 7(B) in that it applies oil and cleans the rollers at the same time. As for the structure, a web 12 made of a nonwoven fabric impregnated with silicone oil is brought into contact with the fixing roller with a nip to apply oil and clean the roller. and web 12
is gradually wound up with a roller or the like, and a new web 12 always comes into contact with the fixing roller. According to this method, oil application is performed effectively, and the roller cleaning is also good, so there is no need for periodic cleaning.Furthermore, if the web 12 is wrapped in a sufficient amount, oil application can be performed effectively over a long period of time. Roller cleaning, service-free, etc. can be maintained. However, the oil application member 7 using this method has problems in that it is a large-sized apparatus, is expensive, and requires a drive mechanism for the web 12, making the mechanical configuration complicated.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide an electrophotographic apparatus having a fixing device in which an oil application member is simple, inexpensive, can be used for a long period of time, and allows good fixing without offset. It is said that

[Means for Solving the Problems] According to the present invention, the above object includes a fixing roller and a pressure roller that are rotatably disposed in pressure contact with each other, and the fixing roller and the pressure roller fix an undefined image. The image forming apparatus includes a fixing device that conveys a transfer material carrying a developing device under pressure and fixes the transfer material.

In an electrophotographic apparatus, the fixing device includes a release agent applying member that comes into contact with either the fixing roller or the pressure roller to apply a release agent.

A driving means for causing the release agent application member to move toward and away from the roller, a control means for the drive means for controlling the movement of the release agent application member toward and away from the roller, and an image of the document. and means for detecting the ratio, and the control means brings the release agent application member into contact with the roller with a predetermined pressing force at the latest when the transfer material reaches the roller, and after a predetermined time, The release agent applying member is set to be separated from the roller, and the predetermined pressing force or predetermined time is set to a larger value within a predetermined range as the image ratio is higher. Ru.

[Function] The present invention provides a drive means for a release agent application member that allows the release agent application member to move toward and away from a fixing roller or a pressure roller, and a means for driving the release agent application member to move the release agent application member toward and away from the fixing roller or pressure roller. It has a control means for the drive means for controlling the approaching and separating operations, and a means for detecting the image ratio of the document. Then, the control means brings the release agent coating member into contact with any of the rollers with a predetermined pressing force when the transfer material reaches the fixing roller or the pressure roller at the latest, and after a predetermined time, The release agent applying member is separated from the roller. Further, the predetermined pressing force or the predetermined time is set to a larger value within a predetermined range as the image ratio becomes higher. Therefore, the release agent of the release agent coating member is consumed only when it comes into contact with the roller, and the release agent application member comes into contact with the roller only when fixing is performed. Furthermore, in the case of a document with a low image ratio, the pressure contact force or the contact time is set to a small value within a predetermined range. As a result, wasteful consumption of mold release agent can be suppressed. In addition, at least when the transfer material enters the roller, the release agent of the predetermined lid or the roller is applied, and in the case of an original with a high image ratio, the pressure contact force or contact time has a large value within a predetermined range. is set to Therefore, offset can be prevented even in the case of an original with a high image ratio.

[Example] The first to third embodiments of the present invention are illustrated in the first to third embodiments of the attached drawings.
This will be explained using FIGS. 6 to 6.

<First Example> First, a first example will be described using FIG. 1 and FIG. 2. Note that the same reference numerals are given to the same parts as those of the conventional device shown in FIGS. 7(A) to 7(C), and the description thereof will be omitted.

In this embodiment, the fluororesin release layer of the fixing roller 1 is made of PTFE (polytetrafluoroethylene), and the surface of the silicone rubber R6 of the pressure roller 2]3
This device differs from the conventional device shown in FIGS. 7(A) to 7(C) in that it is coated with a fluororesin to improve mold releasability. Furthermore, in the apparatus of this embodiment, the 1gl type agent application member 7 can move up and down to freely approach and separate, and is arranged in contact with or not in contact with the fixing roller l, as shown in FIG. Ru. The release agent applying member 7 is the fixing roller l.
It has a silicone rubber layer 14 which is a roller body that is in contact with and can be driven to rotate freely and has a high elasticity, and a felt layer 15 impregnated with a mold release agent as an outer layer of the silicone rubber layer 14. The release agent application member 7 is connected to a solenoid 17 serving as a driving means via a coil spring I6, and by driving the solenoid 17, the release agent application member 7 is moved up and down. The solenoid 17 is connected to a DC controller 18, which is a control means, and is driven at a predetermined timing set in advance.

A transport body 19, which is movable endlessly on its surface, is disposed between the fixing device and the developing/transfer section as described above, and transports the transfer material carrying the unfixed developer image. A fixing entrance guide 20 is provided in front of the fixing roller l (on the right side in FIG. 1), and guides the conveyed transfer material -J- to the pressure contact area between the fixing roller l and the pressure roller 2. do.

Next, a description will be given of a developing/transfer section that sends a transfer material carrying an unfixed developer image to the conveying body 19. A photosensitive drum 21 serving as a latent image carrier is disposed above the conveying body 19. The photosensitive drum 21 is made of an organic semiconductor. Above the photosensitive drum 21, a corona charging device 22, which is a charge forming unit that uniformly charges the surface of the photosensitive drum 21, is disposed facing the photosensitive tram 21, and is larger than the corona charging device 22. A development forming section 23 is disposed downstream of the photosensitive drum 21 in the rotational direction so as to face the photosensitive drum 21 . The developer forming section 23 stores a developer (hereinafter referred to as toner) that visualizes the electrostatic latent image on the photosensitive drum 21 as a developer image. Below the photosensitive tram 21, a transfer charger 24 for transferring the toner image onto a transfer material is disposed facing the photosensitive tram 21, and a transfer guide disposed in front of the transfer charger 24. The transfer material is guided by the transfer charger 25, and the toner image is transferred by the transfer charger 24. The transfer material after the transfer is transferred to the static elimination needle 2 arranged in line with the transfer charger 24.
The static electricity is removed by 6.

Further downstream of the transfer charger 24 in the rotational direction of the photosensitive drum 21, a cleaning section 27 is disposed facing the photosensitive drum 21 for cleaning the surface of the photosensitive drum after transfer.

The surface of the photosensitive drum 21 is exposed to light on the document platen glass 28.
1: Light is irradiated from the original lamp 30 onto the original 29 placed on the original 29, and the reflected light is sent to the six mirrors 3 from the first to the sixth.
1, 32, 33, 34, 35, 36 and a lens (not shown) onto the surface of the photosensitive drum. Incidentally, a reflector plate 37 is attached to the rear of the document lamp to improve the efficiency of light irradiation. Further, a light amount detection sensor 38 serving as image ratio detection means is disposed below the document table glass 28. The light amount detection sensor 38 is configured to receive reflected light from the document 29 and measure the amount of light. Further, the light amount detection sensor 38 is connected to the DC controller I8,
The image ratio is detected by reading the measurement signal by the DC controller 18. Note that the fixing roller l and the photosensitive drum 21 are rotationally driven by a driving means (not shown).

When the apparatus of this embodiment is used in a copying machine, the solenoid 17 is driven so that the release agent applying member 7 does not come into contact with the fixing roller l during non-copying operations. During operation, when the transfer material reaches the fixing roller and the pressure roller at the latest, the release agent application member 7 is brought into contact with the fixing roller l with a predetermined pressure contact force, and after a predetermined time, the release agent application member 7 is brought into non-contact again. The solenoid 17 is driven so as to.

In other words, only the minimum necessary amount of mold release agent should be applied. Furthermore, the predetermined pressing force or the predetermined time is set to a larger value within a predetermined range as the image ratio increases. In other words, when the image ratio is high, the pressing force is increased or the contact time is set longer, so that even if the image ratio is high, offset can be reliably prevented. Further, when the image ratio is low, the pressure contact force is weakened or the contact time is set short, so that the release agent is not wasted. Therefore, the mold release agent can be applied over a long period of time without using a container for supplying the mold release agent.

Next, the materials, sizes, etc. of each part in the device of the first embodiment will be explained.

First, the printing speed was 50 mm/sec, and the diameter of the photosensitive drum 2I was 60 m5.

The metal roller 4 of the fixing roller 1 is a hollow cylindrical aluminum alloy core with a wall thickness of t=3.0mm, and the surface layer serving as the release layer 5 has a PTFE (polytetrafluoroethylene) layer, which is a fluororesin. Coated. The diameter is 3
I used one from Nichoho. Further, an 850W halogen heater was used as the heater 3 which is the heat source inside the heater.

The pressure roller 2 has a thickness t=5.0m as an intermediate layer on the core metal.
The silicone rubber layer 6, which is an elastic body of m, has P on its surface 13.
Made of FA (copolymer of polytetrafluoroethylene resin and perchloroalkoxyethylene resin) with a thickness of 50
Each tube-shaped fluororesin layer is coated and has a diameter of 30 mm.

Furthermore, the release agent application roller 7, which is a release agent application member, has a silicone rubber layer 14 with a thickness t=4 ms on the core bar as an intermediate layer, that is, an elastic layer, and a heat-resistant felt layer 14 with a thickness t.
A heat-resistant felt layer 15 with a thickness of 1.5 mm and a density of 0.3 g/c is formed on each layer 3, and this release agent application roller 7 is under a relatively light load (in this embodiment) when it comes into contact with the fixing roller 1. In the example, it is configured to make contact with the contact point (zoog) and rotate as a result of the rotation. A diameter of 18 m5 was used. The heat-resistant felt layer 15 is evenly impregnated with about 10 g of silicone oil as a mold release agent having a viscosity of 10,000 cs in the longitudinal direction. The axial length of this release agent application roller rough is set to be longer than the nip length formed by the fixing roller and the pressure roller. This is because if it is too short, there will be a portion where oil is not supplied to the nip, and the fixing roller and pressure roller will be rotated slidingly without oil, making it easy for the rollers to be damaged.

Further, the nip length formed by the fixing roller and the pressure roller is 310 mm in this example.

Next, the operation of the apparatus of this embodiment will be explained using the timing chart shown in FIG.

First, when the main body of the apparatus is stopped or in standby mode capable of accepting copy signals, the roller 7 of the release agent applying member is in the first position.
As shown by the dotted line in the figure, it is in a non-contact state with the fixing roller. Further, the photosensitive drum, which is a latent image carrier, the fixing roller, or the optical system are also stopped (denoted as OFF in FIG. 2).Next.

When the user places the document 29 on the document table glass 28 and presses a copy switch (not shown), the copy signal is turned on, and at the same time the copy signal is turned on, the photosensitive drum 21 and the fixing roller l rotate (in FIG. ). The purpose of rotating the fixing roller is to transfer the heat of the fixing roller to the pressure roller, and this is called pre-rotation. After the previous rotation is completed, the optical system moves forward and irradiates light from the original lamp 30 onto the original 29. The reflected light is projected from the first mirror 31 to the sixth mirror 36 and the lens, and the surface is charged by the corona charging device 22. An electrostatic latent image similar to that of the original is formed on the photosensitive tram 21 charged in the same manner. Thereafter, the electrostatic latent image formed by exposure is turned into a visible image by the development forming section 23.

On the other hand, a transfer material supplied from a paper feed section (not shown) is guided by a transfer guide 26 and comes into contact with the photosensitive drum 21, and is charged from the back side by a transfer charger 25 to transfer a visible image. Further, the transfer material is separated by a separation means (not shown, for example, a separation belt, etc.), has its back surface charge removed by a charge removal needle 26, and is conveyed to the conveyor 19. On the other hand, the surface of the photosensitive drum 21 having residual toner after the transfer is cleaned by the cleaning section 27 and prepared again for the next charging process. The transfer material carrying the unfixed image is guided to a fixing entrance guide 20 through a conveyor 19 and enters a fixing device. This point in time is indicated by T8 in FIG. At this point T.

The release agent application roller 7 starts contacting the fixing roller.

Next, how the subsequent contact time t is determined will be explained in detail using an example of an A3 size transfer material.

When the document lamp 30 exposes the document 29, part of the document pattern is exposed to the surface of the photosensitive drum through the first mirror 31, etc., as described above. However, some of the other reflected light reaches the light amount detection sensor 38. This is because the image ratio of the document can be detected based on the amount of light projected onto the light amount detection sensor 38. An image ratio of 0% means that the original is pure white, and 100% means that the original is completely black.

Normal general documents have an image ratio of 4% to 8%, at most 10%.
It is about %. However, only 10 to 20% of documents contain fine text or a portion of the document, such as a photograph.

The present invention detects the image ratio of the original using the light amount detection sensor 38, and manually inputs the signal to the DC controller 18.
The time during which the solenoid 17 is brought into contact, that is, the contact time t
It is designed to determine the The time t is set before the transfer material enters the fixing device. Fig. 3 shows the contact time for A3 size. The maximum contact time is the time required for A3 to pass through the fixing device (A3 size/process speed=8.4 seconds). Above a certain image ratio, there is a maximum contact time. The minimum contact time is approximately 2 seconds, which corresponds to one revolution of the fixing roller, and the contact time is set in proportion to the image ratio. For A4 size, the image ratio is 0 or more.
Even if it is 0%, the contact time should be short. When a predetermined contact time has been reached, the release agent applying roller 3 is separated from the fixing roller.

In this example, more than 10,000 copies were made while changing the size of the transfer material and originals with different image ratios, but no image stains due to offset or stains on the fixing roller or pressure roller occurred. Ta. Furthermore, since the release agent application roller was not in contact with the fixing roller while it was stopped, there was no oil staining that would occur if the release agent application roller was left in contact with the fixing roller.

(Second example) Next, a second embodiment will be described using FIG. 4.

This embodiment differs from the first embodiment in that a vat-type member is used as the release agent application member, and a fixing roller and a pressure roller that perform fixing only by pressure without heating are used. The release agent application member of this embodiment has a felt 40 impregnated with oil at the bottom of a support 39 molded from metal or plastic. The fixing roller l is a pressure fixing roller with hard chrome plating applied to a rigid roller. The pressure roller 2 was the same as the fixing roller 1, the pressure at the nip portion was 13 kg/cm2, and the silicone oil impregnated into the felt 40 was 30 CS.

In this example, since the temperature of the fixing roller does not rise and the viscosity of the silicone oil does not decrease, silicone oil with a viscosity at room temperature of 300 cs was used. Note that the mechanism and control method for vertically moving the support body 39 are the same as in the first embodiment.

In this embodiment, the same effects as in the first embodiment were achieved.

<Third Embodiment> Next, a third embodiment will be explained using FIGS. 5 and 6. This embodiment differs from the first embodiment in that the release agent application roller is brought into contact with the pressure roller. Further, the contact time of the #type agent application roller was always constant regardless of the image ratio, and the pressing force was varied according to the image ratio as shown in FIG. In other words, when there are many black images and the image ratio is high, the contact force is increased and the amount of oil discharged increases. This example also achieved the same effects as the first example.

Although the first to third embodiments have been described above in 1-1, the point at which the release agent applying member starts contacting the fixing roller or the pressure roller may be before the transfer material enters the fixing device. good.

Further, the contact time or pressure may be changed during one fixing operation according to the image ratio.

[Effects of the Invention] As explained above, the present invention provides a drive means for a release agent application member that drives the release agent application member so as to be able to move toward and away from a fixing roller or a pressure roller, and It has a control means for the driving means for controlling the movement of the application member toward and away from the fixing roller or the pressure roller, and means for detecting an image ratio, so that the transfer material reaches the two rollers at the latest. At times, the release agent applying member is brought into contact with the roller with a predetermined pressing force, and separated after a predetermined time. Further, the predetermined pressing force or the predetermined time is set to a larger value within a predetermined range as the image ratio becomes higher. Therefore, the mold release agent is not wasted and can be used for a long period of time. Furthermore, the release agent is always applied when the transfer material enters, and when the image ratio is high, the amount of application increases, making it possible to prevent offset. In addition, the release agent applicator comes into contact with the roller only when necessary, and the amount of application can be suppressed when the image ratio is low, so the life of the release agent applicator itself is extended, and the release agent applicator comes into contact with the roller only when necessary. Toner does not accumulate at the contact portion with the roller. Furthermore, since the drive mechanism for the release agent applying member only needs to be vertically movable, the mechanical configuration becomes simple.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a schematic configuration of the device of the first embodiment of the present invention, FIG. 2 is a timing chart of the operation of an experimental example device using the device of FIG. 1, and FIG. 3 is an image of the device of FIG. 1. A diagram showing the relationship between ratio and contact time, FIG. 4 is a sectional view showing a schematic configuration of a device according to a second embodiment of the present invention, and FIG. 5 is a sectional view showing a schematic configuration of a device according to a third embodiment of the present invention. FIG. 6 is a diagram showing the relationship between the image ratio and the pressing force in the device shown in FIG. 5, FIG.
B) is a sectional view showing the schematic structure of another conventional device, and FIG. 7(C) is a sectional view showing the schematic structure of another conventional device. 1... Fixing roller 2... Pressure roller 7... Release agent application member (release agent application roller) 1
7... Drive means (solenoid) 18...
- Control means (DC controller) 38... Means for detecting image ratio (light amount detection sensor)

Claims (5)

[Claims] (1) It has a fixing roller and a pressure roller that are rotatably arranged in pressure contact with each other, and the fixing roller and the pressure roller pinch-convey the transfer material carrying the unfixed developer image and fix it. In an electrophotographic apparatus, the fixing device is equipped with a release agent application member that comes into contact with either the fixing roller or the pressure roller to apply a release agent. A driving means for freely moving the release agent application member toward and away from the roller, a control means for the drive means for controlling the movement of the release agent application member toward and away from the roller, and detecting an image ratio of the original. The control means brings the release agent application member into contact with the roller with a predetermined pressing force at the latest when the transfer material reaches the roller, and releases the mold after a predetermined time. The electrophotographic device is configured to separate the agent applying member from the roller, and the predetermined pressing force or the predetermined time is set to a larger value within a predetermined range as the image ratio is higher. Device. (2) The release agent applying member is a roller body having a felt layer around a core metal, and is arranged to be driven to rotate when it comes into contact with a fixing roller or a pressure roller. The electrophotographic device according to item (1). (3) The maximum contact time during which the release agent coating member contacts the fixing roller or pressure roller is the time from when a transfer material of a predetermined size reaches the fixing roller and pressure roller to when it passes through the fixing roller or pressure roller. Claim (1) or claim (
2) The electrophotographic device according to item 2). (4) The fixing roller is a heating roller that has a fluororesin layer or a rubber layer on a core metal that includes a heating source, and the pressure roller has an elastic body on a core metal or a fluororesin film is formed on the surface layer. The electrophotographic apparatus according to claim 1 or 2, wherein the roller has an elastic body. (5) The electrophotographic apparatus according to claim 1 or 2, wherein both the fixing roller and the pressure roller are formed of rigid bodies, and the fixing device is a pressure fixing device.