JPS61184577A - Picture forming device - Google Patents

Abstract

PURPOSE:To supply a surface lubricant to the part facing to recording materials of the rotating body surface without fail and to decrease the off-set by variable- controlling the time point when the applying means starts to supply the surface lubricant to the rotating body for fixing, in accordance with the rotating speed for fixing of a pair of rotating bodies. CONSTITUTION:A control means 21 controls the rotation of a motor M in accordance with the signal from a recording material detecting means 44 to detect the size, material and thickness of the recording material, and variable-controls the peripheral speed to the first fixing speed or the second fixing speed later than the first fixing speed so that the suitable fixing characteristic may be obtained. Consequently, rollers 1-3 are maintained to the speed suitable to the recording material. After this, when the detected recording material is detected by a recording material passing detecting means provided at the prescribed position at the front side of a fixing means T, the signal is sent to the control means 21. Corresponding to the occurrence period of the detecting signal, an applying felt 10 abuts to the roller 3 formed by the fixing speed suitable to the recording material, and an applying action period to apply the surface lubricant is variable-controlled by the control means 21.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field to which the invention pertains) The present invention relates to an image forming apparatus that forms an unfixed image and fixes it on a recording material to provide a desired image. Typical examples of this equipment include printing machines, printers, electrophotographic copiers,
facsimile.

There are laser beam printers and the like, but all of them are provided with a fixing rotating body (belt, roller, etc.) that fixes an unfixed image by heating, heating and pressing, or pressure.

(Description of Prior Art) In general, a contact-type fixing rotating body is often used to efficiently fix unfixed images, but at the same time, it is essential to apply a release agent to prevent offset.

Taking a general electrophotographic device as an example, this mold release agent application is performed as follows.
For monochromatic images, it is preferable to use a small, uniform amount, but in the case of multicolor images where the material of the recording material changes or the amount of toner that makes up the image increases, the fixing speed may be lower than normal to improve fixing. Although it is conceivable to slow down the amount, it is preferable to make it relatively large since the offset occurrence rate also increases.

However, since constant application of such a relatively large amount results in unnecessary loss of release agent during non-fixing, it is usually preferable to control the supply of release agent intermittently.

On the other hand, the intermittent supply of a release agent that has been proposed and implemented in the past is performed for a fixed period of time for an image forming apparatus with a constant fixing speed. On the other hand, most conventional devices constantly supply a mold release agent.

However, when a relatively large amount of release agent is required as described above, when the fixing speed changes (taking a fixing device equipped with a fixing roller as an example), the release agent is applied to the roller and the recording material. The time it takes for the release agent to reach the point where it comes into contact and performs fixing, that is, the nip of the rollers, differs. Further, due to the speed difference, the length of the il type agent application area on the roller surface in the roller circumferential direction changes, and the area of the area changes. Due to these problems, the actual coating area on the roller surface was not as desired. Furthermore, due to the difference in arrival time of the release agent, there is a difference between the time when the release agent application area on the roller surface passes through the nip portion and the time when the recording material passes through the nip portion. Further, the area of the release agent application area on the roller surface changes, and especially when the second fixing speed is slower than the first fixing speed, the area decreases.

It cannot cover the size of the recording material.

From the above, when the fixing speed is changed, in conventional image forming apparatuses, the surface of the roller that is not wetted with the release agent may come into contact with the toner of the recording material, causing an offset problem. In addition, the release agent in the coating area that does not come into contact with the recording material is wasted, which is not only uneconomical but also causes staining of the surrounding area.

Furthermore, if the release agent is not supplied to the roller surface corresponding to the leading end of the recording material, a jam occurs in which the recording material wraps around the roller surface.

These problems were not known because a device that changes the fixing speed and performs coating intermittently had not been put into practical use, but the present invention addresses these problems with a new understanding.

(Objective of the Invention) The object of the present invention is to solve one of the above-mentioned problems. Even if the speed of the rotary body for fixing is variably controlled, the portion of the surface of the rotary body facing the recording material, especially the leading edge of the recording material. An object of the present invention is to provide an image forming apparatus that can reduce offset by reliably supplying a mold release agent to a portion of the mold, and can also prevent wrapping.

Another object of the present invention is to convert an unfixed image into a multicolor image,
Even at extremely slow fixing speeds when heat-fixing onto films such as resin sheets, which are different from normal recording materials, offset can be largely prevented and clear images with excellent color mixing can be obtained. The purpose of the present invention is to provide a color image forming apparatus that can perform the following tasks.

Other objects of the invention will be understood from the following description, and the gist of the invention will be understood from the structures described in the claims and the following description.

(Description of Examples) The following example applies the present invention to a color electrophotographic device, but the present invention is not limited thereto, and the scope of the technical idea of the present invention is applicable to image forming devices in general. It is applicable.

The outline of the apparatus shown in FIG. 1 will be explained.

The original (not shown) on the original table glass 23 is irradiated with illumination means 26 (iodine lamp and reflective shade) integrated with the first scanning mirror 24, and the original is illuminated by the first scanning mirror 24 and the second scanning mirror 25. scanned above. 1st and 2nd
The scanning mirror scans the original while keeping the optical path length of the first half of the lens 27 constant by moving at a speed ratio of 1:1/2.

The reflected light image passes through a lens 27 and reaches a color separation filter 28, which converts the light image into three colors - red, green, and blue - 28a.

28b or 28c.

The separated optical image passes through a fixed third mirror 29 and a fourth mirror 30, and further through a dust-proof sealing glass 31, and forms an image on a photosensitive drum 32. The photosensitive drum 32 is rotatably supported on a shaft 33, rotates in the direction of the arrow in response to the operation of the copy button, is charged (for example, with a positive electrode) by a primary charger 34, and is then charged with the color-separated light. While irradiating the image, static electricity is removed by the AC static eliminator 35, and then the entire surface exposure lamp 3
6, the entire surface is uniformly irradiated to obtain a high contrast electrostatic latent image.

The electrostatic latent image on the photosensitive drum 32 is then visualized by a developer 37. The developing device 37 is 37a for cyan-magenta-yellow and black.

Consisting of four developing means 37b, 37c, and 37d,
The image is visualized by a developing means 37C corresponding to the color separation filter (for example, a yellow developing means for a blue filter). Each developing means has a non-magnetic sleeve, a magnet, a developer stirring screw, etc. inside the sleeve. After this.

After development, the powder image on the photosensitive drum is charged with an arbitrary polarity by a post charger 22, and then reaches a transfer section.

The recording material P is stored in a cassette 40 that is detachably attached to the main body.In this apparatus, two similar cassettes are provided to store recording materials of different sizes. When either the upper or lower cassette is selected using the selection button 17a in the operation section provided at the top of the main body, the recording material size and recording material material in the selected cassette are detected (this may be done automatically or manually). and the results are displayed.

The display unit 17 displays the size of the recording material in rows A and B of the wood industry standard.
The display section 16 shows the column and a 7-segment numerical display indicating its number, and the display section 16 shows the material of the recording material, that is, paper or resin (O
HP19), thick paper 18, or paper 20 with a thickness equivalent to normal use. These signals are sent to the control means 21, and based on these information, the control means 21 controls the rotational peripheral speed of the roller of the fixing means T in order to obtain appropriate fixing performance. This control includes changing the rotational speed (rpm) of the motor M, changing the gear ratio of the transmission system from the motor M to the rollers, and the like.

By the way, the selected recording material P is moved to the photosensitive drum 32 at a predetermined timing by a pair of registration rollers or the like.
Sent in synchronization with the powder image above. At this time, the recording material P contacts the transfer roll 38 through the guide, and then receives a corona discharge of the same polarity as the post charger 39 from the back side of the recording material P by the electrostatic adsorption charger 40. P is transfer roll 38
electrostatically adheres to the surface. The transfer roll 38 includes an elastic roll wrapped around the outer periphery of a metal roll, and a conductive rubber wrapped around the outermost layer.
Grounded.

The recording material P electrostatically attracted to the transfer roll 38 synchronizes with the powder image on the photosensitive drum and transfers the pressed powder image,
A yellow powder image is formed on the recording material.

Repeat the same process with sequential exposure using other red and green filters,
The recording material P on the transfer roll that undergoes repeated development and transfer is
In the case of an apparatus in which transfer is repeated a total of three times while being electrostatically attracted, the diameter of the photosensitive drum and the diameter of the transfer drum are 2=1, and since they are directly connected by gears, the synchronization between the two never goes out of order. Further, the color separation filter 7 is changed to the next filter during the reversal process of the optical system, and the filter and the corresponding developing means are set in a 1:1 correspondence by the programming device.

Color separation exposure using red, t & blue filters as above,
Development with cyan, magenta, and yellow toners and 3
After performing the multiple transfer, the separation claw 41 is
is actuated to transfer the electrostatically attracted recording material P to the transfer roller 38.
The film is peeled off from the film, passes through the conveyor belt 15, and reaches the fixing means T.

FIG. 2 shows the structure of this fixing means T.

In this example, the fixing speed is changed as shown in Figs. 4 to 7 so that the surface of the roller that is not coated with the release agent does not come into contact with the toner image surface on the recording material when changing the fixing speed. When changing the release agent application sequence control,
Use mold release agents effectively.

In the figure, 1.3 is a roller whose surface is coated with Teflon to improve the releasability of toner.
The rollers 2 located between these and rotating relative to each other are made of silicone rubber and have a soft surface layer. Further, these rollers 1 and 3 are hollow, and heaters 4 and 5 are inserted into the centers of their shafts to heat them appropriately.Therefore, the silicone rubber roller 2 that comes into contact with both rollers is also indirectly heated, and eventually the roller 1 .2.3 plasticizes the thermoplastic toner 9 of the unfixed toner image on the recording material 8 inserted into the nip 6 between the rollers 1 and 2 by heat, and
It becomes a fixing rotating body for fusing. Furthermore, during the operation of this device, a load is applied to the roller 3 in the direction of the rollers 1, 2, and 2, and the space between the rollers 1 and 2°3 becomes pressurized.
The silicone rubber layer of the roller 2 is deformed under pressure at the nip portions 6 and 7 between the roller 1 and the roller 2 and between the roller 2 and the roller 3, respectively, so that the surfaces are in contact with each other.

Further, a coating felt 10 can be appropriately contacted with the surface of the roller 3 in order to apply a mold release agent. That is, the coated felt 10 is backed and supported by a support plate 11, and this support plate 11 is fixed to a rotation shaft 12 that rotates under the drive of a drive means 22. The lower end of the coated felt 10 is immersed in the silicone oil 14 in the oil pan 13, and the zero rotation shaft 12 is configured such that the silicone oil 14 permeates to the upper part of the coated felt 10 by capillary action. It is provided so that it can reciprocate in the direction of the arrow in the figure by applying appropriate rotational force by a drive means 22 operated by an electric signal from a control means 21, and the support plate 11 rotates together with the rotation/movement shaft 12. The coated felt 10 is brought into contact with or separated from the surface of the roller 3 by moving. During this pressure contact, the silicone oil 14 impregnated in the coating felt 10 is applied to the surface of the roller 3 (at this time, the roller 2 acts as a coating roller), and this silicone oil is sequentially transferred to the roller 2 and the roller 1. This prevents the toner from adhering to the toner and from offsetting.

The control means 21 controls the motor M in response to a signal from a recording material detection means 44 (for example, determines the recording material using a cassette signal, a light transmission signal, etc.) that detects the size, material, and thickness of the recording material. The peripheral speed of the rollers 1, 2, and 3 is variably controlled to a first fixing speed or a second fixing speed slower than the first fixing speed in order to obtain appropriate fixing performance.

Therefore, the rollers 1.2.3 are maintained at a speed suitable for the recording material. After this, when the detected recording material is detected by a recording material passage detection means provided at a predetermined position in front of the fixing means T, a signal thereof is sent to the control means 21. Corresponding to the period during which this detection signal is generated, the application timing at which the coating felt 10 contacts the roller 3 rotating at a fixing speed suitable for the recording material and applies the release agent is variably controlled by the control means 21. be done. Assuming that the point of contact between the coated felt 10 and the roller 3 is point C, and the starting point of the pressure contact portion 6 of roller 1.2 is point C, the silicone oil as a mold release agent is applied to roller 3.2. As the circumferential surface of the roller 2 rotates, it moves by a distance ML of arc CE+ED at a given fixing speed. Here, point E is the curvature change point of roller 2.3. By varying the fixing speed, the time it takes for the silicone oil to travel the distance flllL also changes, so the application timing is controlled to be different for each fixing speed. Regarding this timing, the fourth
This will be explained in detail with reference to FIGS. 6 to 6.

The conveyor belt 15 located in front of the fixing means T in this example is conveyor rollers 15a and 1 rotated by a drive means (not shown).
5b, the recording material 8 rotates counterclockwise in the figure, and conveys the recording material 8 to which the image has been transferred in the image transfer section of the image forming apparatus to the nip section 6. This conveyance speed is always constant regardless of the fixing speed. As mentioned above, these rollers 1
, 2.3 have their rotational speeds variably controlled in response to signals from the control means 212, but for the sake of simplicity in the following example, (a) the first fixing speed v in the case of normal paper is
1 and (b) Thick paper or OHP (resin recording sheet)
It is assumed that the second fixing speed V2 (lower than the first fixing speed) is switched to the second fixing speed V2 (lower than the first fixing speed).

The reason for this setting is as follows.

In an image fixing device that passes a recording material between a pair of rollers as described above, when the material of the recording material changes, the amount of heat supplied to the toner on the recording material changes depending on the thermal conductivity and thickness of the recording material.
Fixation status changes. That is, depending on the type of recording material, the image may not be well fixed and may peel off. In addition, when obtaining a color copy image using a color copying device, it is necessary to apply an appropriate amount of heat to the toner in order to smoothly mix the three primary color toners and develop a predetermined color during fixing. If there is a change in the recording material, the color tone of the color copy image will change. Furthermore, when obtaining a color copy image on Trapen film for 0HP (Overhead Rad projector), Trapen film has a smaller thermal conductivity than paper, so it provides sufficient heat to flow the toner better. In order to minimize the refraction and scattering of the OHP projection light due to the unevenness of the toner layer, the toner layer must be flattened, but this cannot be achieved by supplying heat in the same way as with paper. Therefore, in order to cope with changes in the amount of heat supplied due to changes in the recording material, it has been considered to change the fixing speed.

This is intended to increase the amount of heat supplied per unit time by slowing down the fixing speed for recording materials that have poor thermal conductivity or require more heat.

Here, the problem when the present invention is not used will be explained using FIG. Hereinafter, the size of the recording material is the same in both (, a) and (b). In FIG.
At time 1 and time t2, when the application of the silicone oil 14 is started, the rotational force is cut off to the rotation shaft 12, and the application felt 10 is separated from the roller 3, and the application of the silicone oil 14 is completed. At time t3, the silicone oil 14 applied at the start of application reaches the nip portion 7 together with the roller 3 rotating at the first fixing speed V1, is transferred to the roller 2 here, and is roughly transferred to the nip portion 6 as the roller 2 rotates. The entry time, time t4, is the time when the recording material 8 enters the nip portion 6, time t5 is the time when the rear end of the recording material 8 passes through the nip portion 6, and time t6 is the time when the recording material 8 is coated just before the coating end time t2. At time t7, when the silicone oil 14 passes through the nip portion 6 through the rotation of the rollers 3 and 2, the silicone oil applied at time t1 passes through the rotation of the rollers 3 and 2, which rotate at the second fixing speed v2. Time t8 is the time when the trailing edge of the recording material 8 passes through the nip 6 at the second fixing speed V2, and time t9 is just before the end of coating at time t2 at the second fixing speed V2. This is the time when the applied silicone oil 14 passes through the nip portion 6 through the rotation of the rollers 2 and 3, and the time t□
is the time at which the rotational speed of the rollers 1, 2.3 is switched to the second fixing speed v2.

(a) First fixing speed v1 At time t1, a rotational force is applied to the rotation shaft 12, and the coating felt 10 comes into contact with the roller 3, and the silicone oil 14 is applied until time t2.

During this time, silicone oil 14 is applied on the surface of roller 3 at time t.
The area coated at time L2 is the leading edge, and the area coated at time L2 is the trailing edge. The tip of this coated surface moves with the rotation of the roller 3 at the first fixing speed v1 and reaches the nip portion 6. The silicone oil 14 in this portion is transferred to the roller 2 at this nip portion 6, moves roughly with the rotation of the roller 2, and enters the nip portion 6 at time t3. The silicone oil behind the tip of the coating surface is also applied to the nip portion 6.
Finally, the rear end of the coated surface reaches the nip portion 6 at time t6.
enter. In this case, the leading edge of the transfer material 8 starts to enter the nip portion 6 at time t4, and the rear end of the transfer material 8 passes through the nip portion 6 at time t5. t3 t4. Since t5<t6, while the recording material 8 is passing through the nip portion 6, the surface of the a-ra 2 facing the recording material 8 is the surface coated with the silicone oil 14, so that a female type effect is applied to the roller 2. Therefore, the toner 1 on the recording material 8 is not offset to the roller 2.

However, (b) even at the second fixing speed v2, the same process conditions and the same sequence a control as the first fixing speed v1 are performed from the start of the copy operation to the time t□, and at the time t□, the rollers 1, 2.3 is switched to the rotational speed corresponding to the second fixing speed and driven, the silicone oil 14 is applied from time t1 to time t2 in the same way as at the first fixing speed v1. As described above, the coating surface on the roller 3 is transferred to the roller 28 by the rotation of the roller, and roughly moves toward the nip portion 6. The rotation of the roller 3 is a rotation corresponding to the second fixing speed v2, which is slower than the first fixing speed v1. Since it is rotating at a high speed, the time at which the tip of the coated surface enters the nip portion 6 is much later than time t3, and becomes time t7. Further, the rear end of the coated surface passes through the nip portion 6 at time t9. On the other hand, since the recording material 8 is being transported by the transport section 20 at the same transport speed as when operating the first fixing wave, it similarly enters the nip section 6 at time t4.

However, since the roller is rotating slower than at the first speed,
The rear end of the recording material 8 passes through the nip portion 6 later than time t5, and a timer 8 is reached.

Therefore, unlike when operating the first fixing speed v1, when operating the second fixing speed v2, the time is t4 minus t7, and the surface of the roller 2 facing the recording material 8 while the recording material 8 is passing through the nip portion 6 is not necessarily made of silicone. The surface is not coated with oil 14.

In particular, since the tip of the recording material 8 comes into contact with the surface of the roller that is not coated with oil, offset and winding around the roller occur. As explained above, conventional devices that change the fixing speed depending on the material of the recording material,
The main purpose is to change the rotation speed of the roller of the fixing device.
Other conditions, especially the sequence control, are not changed. Therefore, when the roller is rotated at the second fixing speed v2, the release agent coated surface on the roller surface shows that the recording material passes through the nip portion at times t4 and t7. As a result, the applied release agent is not used effectively and some of it is wasted. Especially in the case of color image formation, which is relatively easy to offset compared to monochromatic copying, there is a great risk of offset. therefore,
Even though a release agent is applied and consumed, the releasing effect of the release agent cannot be exerted, which is very uneconomical. When the fixing speed is slowed down, the amount of rotation of the roller is reduced, so the distance between the leading edge and the trailing edge of the release agent-coated surface on the roller surface is shortened, and the area of the coated surface is reduced. Therefore, the above-mentioned problem also occurs depending on the size of the recording material.

FIG. 4 is a time chart showing the sequence control of the present invention, of which FIG. 3(a) is a time chart showing the sequence control at the first fixing speed, and FIG. 3(b) is a time chart showing the sequence control at the first fixing speed. 5 is a time chart showing sequence control at speed.

The mechanical configuration of the fixed M device is the same as that shown in FIG.

At the first fixing speed, zero time T1, which is the same as in FIG. 3, is the time until time t3 when the release agent applied at time t1 moves together with rollers 3 and 2 and reaches the nip portion 6. That is, T 1 = L / v 1 in FIG.

Time t11 at the second fixing speed v2 is the coating start time corresponding to time t1, which is earlier than time t1. In this example, the time t3 at which the tip of the application surface of the roller 2 reaches the nip portion is the same time t12 for the speeds vi, I, and V2.
represents the end of coating at the second fixing speed, and the time (t
12-to) = time l! JI (tts-tS), time (
t tS - t4) time (tls - tS), tS<t
Give the relationship of 4. Here, time ttS corresponds to time t5, and time t16 corresponds to time t6, when the trailing edge of the recording material at the second fixing speed passes through the nip portion 6, and the oil-applied surface at the second fixing speed. This is the time when the rear end passes through the nip portion 6. Therefore, in this example, tls>tls.

Using a constant α for the first fixing speed v1 and the second fixing speed v2, v
2=vt/α (v2<vl, α>>1), it takes time at the first fixing speed for the silicone oil 14 applied onto the roller 3 by the coating film 10 to reach the nip “6”. If it takes only T1, the time αT at the second fixing speed
In this embodiment, the application start time is set before time αT1 from time L3 so that the tip of the applied oil surface reaches the nip portion 6 at the second fixing speed at the same time as the above-mentioned time t3 at the first fixing speed. t11 is set. Further, the time for the recording material 8 to pass through the nip portion 6 is T2 at the first fixing speed.
Then, the second fixing speed becomes αT2. Therefore, in order to maintain the oil-applied surface on the roller 2 in contact with the entire surface of the recording material 8 at the second fixing speed,
The time it takes for the oil-applied surface to pass through the nip 6 (tls-t
4) = αT2 must also be longer by this amount, so the coating time (t12-tu) should be (t12-t11)≧
αT2 is set.

If you set the oil application sequence as above,
Even if the fixing speed of the roller changes, there is no offset problem because the oil-applied surface of the roller 2 contacts the entire recording material 8 at both the 1st and 2nd fixing speeds; More specifically, the silicone oil 14 applied at time t1i enters the nip portion 6 at time E3, which is the same as that at the first fixing speed, after time αTl. Therefore, time t
4, the tip of the recording material 8 begins to pass through the nip portion 6.
It comes into contact with the oil-applied surface on La 2. On the other hand, time t 12
The silicone oil 14 applied immediately before the end of application reaches the nip portion 6 at time t16 after time αT1. At this time, the rear end of the recording material 8 has passed through the nip portion 6 at time t15 before this. Therefore, the entire surface of the recording material 8 comes into contact with the oil-applied surface of the roller 2.

In this way, when the fixing speed of the fixing device is changed, the surface other than the oil-applied surface of the roller 2 is prevented from coming into contact with the toner image on the recording material, and offset can be prevented.

FIG. 5 shows another embodiment of sequence control, which is a modification of the (&) normal (vl) timing chart of the embodiment in FIG. The feature is that the coating start time t11 is the same at the first fixing speed and at the second fixing speed.

In this case, the control parameter for sequence control is only the application end time t22 or t12, and when performing program sequence control, the program structure is simple and the memory capacity used can be small.

FIG. 5 has many parts in common with FIG. 4, and can be easily understood by comparing it with FIG. As explained in FIG. 4, time t11 ensures that the leading edge of the recording material at the second fixing speed comes into contact with the silicone oil coated roller surface. In FIG. 5, the time t of the first fixing speed
1 is changed to this time t1 to advance the start of coating, and to control only the coating end time variably according to the length of the recording material. The time tei at which the end passes through the nip is t
It is set so that 5<t61.

Therefore, the time t31 when the tip of the oil-applied surface passes through the nip is earlier than the time t3, and t3t=(twe+Tt
), and time t22 is approximately equal to time t2. When compared with the example in FIG. 4, (α-1)T1
However, since the fixing speed is faster than the second fixing speed, the amount of oil consumed is not so large, and on the contrary, oil is supplied to the surface of the roller 1. This is a preferred embodiment.

FIG. 6 shows an example in which each time in the above timing chart is not determined based on direct detection of the recording material, but is replaced with the elapsed time during the image process, and the movement of the recording material is indirectly grasped and determined. .

As for the structure, the coating is controlled by the control means 21 according to the count number of the counter 45 shown in FIG. The counter 45 may detect the rotation angle of the photosensitive drum 32 or transfer roller 38 shown in FIG. 1, or may detect a pulse emitted during image formation such as clock pulse detection, or may detect a normal timer. You should adopt.

The explanation will be based on a flowchart. When the start of recording is performed, counting is started, and the fixing speed based on the recording material or other factors is determined in a judgment 46. In the 0 judgment 46, it is judged whether or not the above-mentioned first fixing speed is reached. In the fusing speed mode, decision 47.48 is made, and in the second fusing speed mode, decision 49.50 is made. In either determination, it is determined whether the count number has reached a predetermined value. Predetermined values NQ, Nl.

N2. For N3, NO≦N1<N2゜NQ<N3
There is a relationship between When the predetermined value falls, coating is started in the second fixing speed mode at a time corresponding to the aforementioned time t11, and sufficient silicone oil is coated on the roller surface when the leading edge of the recording material enters the nip portion. guarantee that the relationship is Similarly, the predetermined value N1 is the above-mentioned time t 1
, t11, the coating is started in the first fixing speed mode to ensure the above relationship.

The predetermined value N3 corresponds to time t16, and the application is completed at the second fixing speed, so that sufficient silicone oil is applied to the surface of the roller that comes into contact with the trailing edge of the recording material when it passes through the nip. to prevent future unnecessary losses. Similarly, the predetermined value N2 is set at time t8. Corresponding to the time corresponding to t61, in the first fixing speed mode, the predetermined value N
Performs the same action as 3.

After this, when the image process is finished, the count is reset and ready for the next step. In addition, in the continuous copy mode, the predetermined values No., Nl, N2 and N3 may be determined by considering the image forming speed and the distance between each recording material, and the coating period is determined to satisfy the above technical concept. , it goes without saying that these predetermined values are determined to be changed depending on the different sizes of recording materials.

° The embodiment shown in FIG. 7 utilizes the fixing means T shown in FIGS. 1 and 2 to improve the fixability of color images (multiple colors) and to utilize the release agent more effectively. It is a σ thing to present.

As previously mentioned, coating at a slower second fixing speed generally increases coverage, but when the speed is much lower, a significant coverage is obtained, especially at the beginning of coating. However, when a large amount of toner is used to form a color image (multicolor) or an unfixed image, a large amount of release agent tends to cause image deletion.

This embodiment solves this problem and provides a coating sequence that allows fixing from the leading edge to the trailing edge of the recording material without image blurring or offset even at a fairly slow fixing speed.

To briefly describe the characteristics, the application period of the application member at a low fixing speed does not affect the entire length of the recording material as shown in Figure 4.5.6, but the application period is shorter than the entire length and is based on the leading edge of the recording material. That is to say. Then, the release agent remaining on the roller surface is used to supply the remaining recording material to the surface of the roller that comes into contact with the recording material. Therefore, the application period is determined by taking into consideration the amount of the remaining #type agent, but the period for supplying the release agent to the roller by the application member should be shorter than the time to fix the entire length of the recording material. is important.

The chart of FIG. 7 is based on the chart of the embodiment of FIG. 4, with the features of this embodiment added. (a),
(b) The coating area by the coating felt in the chart indicates the time it takes for the oil in the coating area where the coating felt actually comes into contact and supplies silicone oil to pass through the nip portion.

Therefore, in (a), if the application period (t2-tl) is Δt, the application area is Δ=vl and the passing period of the application surface (ts
-ts).

In (b), if the application period (t21-tll) is Δt', it is shorter than (tl2-tu) in the example in Fig. 4, and ts<t4
The coating area satisfies the following, and the coating area is Δt'・v2, which is shorter than the passing period of the coated surface (t-t3).
2-ts) after this period (txsx-t 16
2), in the example shown in FIG.
3 provides sufficient silicone oil.

In this way, image disturbance due to excess oil is prevented, and efficient use of the fa type agent and reliable offset prevention are achieved.

(Effects of the Invention) As explained above, by changing the application sequence of the release agent in accordance with the change in fixing speed, the toner image surface on the recording material is always on the surface of the fixing roller wetted with the release agent. This will prevent image offset. In addition, by setting appropriate values for the sequence parameters at the start and end of coating at any fixing speed, it is possible to apply the release agent only to the areas on the surface of the fixing roller that are in contact with the recording material. It is possible to achieve the maximum effect in preventing offset with the minimum required amount of application. Therefore, it is not only more economical than the conventional example, but also prevents staining of the apparatus due to unnecessary application of mold release agent.

Although the present invention is particularly effective for color recording devices, it can also be applied to devices using various types of recording materials.

[Brief Description of the Drawings] Fig. 1 is a schematic explanatory diagram of a color copying machine to which the present invention is applied;
FIG. 2 is an enlarged view of the main parts of FIG. 1, and is an explanatory diagram of the intermittent application means of the release agent, the fixing device and the conveying device that can switch the fixing speed, and FIG. 3 is an illustration of the case where the present invention is not implemented. FIG. 4 is an explanatory diagram of the time chart (a) of the release agent application sequence at the first fixing speed and the time chart (b) of the release agent application sequence at the second fixing speed used in the conventional apparatus; 5 and 7 are examples showing a comparison of the release agent application sequence (a) at the first fixing speed and the release agent application sequence (b) at the second fixing speed of the present invention, respectively. Explanatory diagram, No. 6
The figure is a flowchart for explaining another embodiment of the coating sequence of the present invention. 1.2.3 is a roller, 10 is a coated felt, 21 is a control means, 44 is a recording material detection means, vl is a first fixing speed, and v2 is a second fixing speed.

Claims (4)

[Claims] (1) A means for forming an unfixed image on a recording material, and a fixing means having a pair of rotating bodies that nip and convey the recording material in order to fix the unfixed image onto the recording material. Speed control means for variably controlling the fixing rotational speed of the pair of rotating bodies between a first fixing speed and a second fixing speed that is slower than the first fixing speed, and intermittently supplying a release agent to at least one of the pair of rotating bodies. Coating means; Coating control for variably controlling the point in time at which the coating means starts supplying a release agent to the rotary body for fixing according to the rotational speed for fixing of the pair of rotary bodies variably set by the speed control means; An image forming apparatus comprising: means. (2) The application means has a first application member that contacts one of the pair of rotating bodies to transmit the mold release agent, and a second application member that contacts the application member, and supplies the mold release agent. 2. The image forming apparatus according to claim 1, wherein the starting point is when the second applicator comes into contact with the first applicator. (3) the forming means is capable of forming a multicolor image;
Claim 1 or 2, wherein the second fixing speed is selected depending on a mode in which the recording material is thick paper or a resin sheet and a multicolor image is formed on the recording material. image forming device. (4) The application control means controls the length of the application area applied by the application means to the surface of the rotary body for the same recording material by the first method.
4. The image forming apparatus according to claim 1, further comprising a coating area length control means that makes the coating area length shorter in the second fixing speed mode than in the fixing speed mode.