JPH09251250A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain excellent transporting property, and to prolong the life of a fixing roller, by forcibly operating separation means corresponding to stiffness (toughness) of paper. SOLUTION: This image forming device, provided with the means capable of deciding at least two stage of 'stiffness' of the paper on the upstream side of a fixing unit, in a recording paper transporting path, operates paper sheet separation auxiliary means based on the decision result. A recording paper 1 is introduced in between the paper transporting guide plate 51, a transporting roller 52 and the driven roller 53 held in press contact therewith. On the downstream the transporting roller, the leading end controlling plate 56, attached to a freely turning stay 58, for receiving the force in the direction interfering the course of the paper by a compression spring 57 is disposed. The controlling plate 56 is made possible to keep a state of controlling by a cam 59, and to shift the controlling plate tip to a position fleeing from becoming obstruction of the paper transport by the cam 60. In the vicinity of the paper transporting guide plate 51, the paper leading end detecting sensor 54 and a micro switch or a feeler attached photointerrupter 55 for detecting whether the paper is in the bent state or not is disposed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly to an electrophotographic fixing apparatus, and can be applied to, for example, a printing machine, a copying machine, a facsimile, a printer and the like.

[0002]

2. Description of the Related Art In a fixing device using a heat roll (fixing roller), it is possible to prevent development in which an image forming surface of a recording paper (transfer paper) is not peeled off from a fixing roller and wrapped around due to heated melted toner or static electricity. Various measures have been taken to achieve this. One example is forced separation with a separation claw, or forced separation means by applying compressed air to the leading edge of the recording paper.

In general, a separating claw system having a simple structure is often adopted, but it is unavoidable that the surface of the fixing roller is deteriorated by always applying the separating claw to the surface of the fixing roller. In order to extend the life of the recording paper, it is desirable not to have a separation claw if it does not affect the recording paper transport performance.
Even in the forced separation device using compressed air, the temperature of the air-exposed portion of the fixing roller is reduced by that amount, so that fixing unevenness is likely to occur and it is necessary to take preventive measures against it.

Further, it is considered that the stiffness of the paper, that is, the so-called "strain" of the paper has an effect on the characteristics of the paper that affect the winding. In other words, if there is a "strain" on the paper, it can be separated by itself even if the force to wind it around the fixing roller works, but if there is no "strain", it will wind up.

In Japanese Patent Laid-Open No. 60-19183, the paper peeling assisting means is operated when the paper thickness detecting means detects a paper thinner than a predetermined value, and the peeling assisting means operates without deteriorating the peeling performance. It is described to improve the drawbacks associated with. That is, in the apparatus described in the above publication, the thickness of the paper is detected, and the paper peeling auxiliary means (separation claw) arranged so as to be selectable according to the result is operated.

[0006]

However, it is difficult to accurately and inexpensively measure the thickness of the recording paper, and even if such means is available, there are the following problems. That is, particularly in an electrophotographic image forming apparatus capable of forming an image of a plurality of colors, the time from document creation to output can be shortened as compared with a conventional printing apparatus, and the cost for printing a small number of copies can be reduced. Since it is not inferior to any other purpose, it is attracting attention as a printing device. However, printed matter is required to be printed on various types of paper as compared with copying machines and printers. Among them, there is a high demand for output for paper with improved surface properties by coating clay on the surface such as coated paper and lightly coated paper.
As described above, these papers have coatings on the surface.Therefore, the weight and thickness of the paper may not be compared with the stiffness of the paper and the stiffness of the paper.Therefore, even with the same thickness, the stiffness may vary depending on the paper type. is there. In addition, the stiffness of paper is generally related to the direction in which the paper is made, and it is not possible to fully understand the separation performance from this point only by measuring the thickness of the paper.

The present invention has been made in view of the above-mentioned circumstances, and by operating the forced separating means in accordance with the stiffness of paper, good transportability is obtained and the service life of the fixing roller is improved. This is intended to be achieved.

Another object of the present invention is to optimize the operation of the apparatus by setting the position at which the stiffness determining means is provided according to the application of the image forming apparatus.

Further, it is another object of the present invention to prevent the use of a paper having a stiffness less than the standard that can be used in the image forming apparatus.

[0010]

According to a first aspect of the present invention, there is provided a plurality of photoconductors corresponding to print colors, and an electrostatic latent image is formed on the surface of the photoconductors by an electrophotographic method. The image is developed by a wet or dry developing unit, the recording paper is conveyed to the transfer position of the photoconductor by a transfer belt, and the developed image of each photoconductor is superposed on the recording paper and transferred. In a color image forming apparatus which is heat-fixed by a fixing roller and provided with a sheet peeling auxiliary means which can selectively operate on the downstream side in the vicinity of the fixing roller, at least two stages are provided upstream of the fixing unit in a recording paper conveyance path. Is provided with a means for judging the "strain" of the paper, and the paper peeling assisting means is operated based on the judgment result. Therefore, the forced separating means is operated according to the stiffness of the paper. , Good With obtaining the transportability are those aimed at improving cycle life of the fixing roller.

According to a second aspect of the present invention, in the first aspect of the invention, the paper "strain" determining means is provided in the registration mechanism in the recording paper conveyance path. Therefore, the image forming apparatus is used. The operation of the apparatus is further optimized by setting the position where the stiffness determining means is provided.

According to a third aspect of the present invention, in the first aspect of the invention, the paper "strain" determining means is provided in the recording paper feeding means, and therefore, depending on the use of the image forming apparatus. The operation of the apparatus is further optimized by setting the position where the stiffness determination means is provided.

The invention according to claim 4 is characterized in that, in the invention according to claim 3, there is provided means for warning the user that the recording paper is unsuitable by means of the "strain" judging means for the paper. It is intended to prevent the use of paper with a stiffness less than the standard that can be used in the image forming apparatus.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

(Invention of Claim 1) FIG. 1 is an overall configuration diagram of an essential part for explaining an embodiment of the present invention. The recording paper 1 fed from a paper feeding unit 10 is laterally moved by a lateral registration unit 11. After the position of is adjusted, it passes through the leading edge registration sensor 12. With this timing, the process unit 20
Image data is written by the optical writing unit 21 and each starts image formation. Recording paper 1 is transfer belt 13
Electrostatically attracted and transported by each process unit 20
The images are transferred one after another by the transfer roller 14 when the image passes. After that, the transfer belt 13 is separated by the separation charger 15.
The recording paper 1 separated from the above fixes the image by the heat and pressure of the fixing unit 30, and advances to the transport unit 16. Depending on the switching guide plate 17, the discharge tray 18 or the duplex unit 1
When 9 is selected and the duplex unit 19 is selected, the recording papers 1 are switched back, stacked several sheets, and then fed again.

2 and 3 show the fixing unit 30 shown in FIG.
2 is a detailed configuration diagram of the fixing roller 31 including a heater 32 therein.
The pressure roller 33 is pressed against the fixing roller by means (not shown), the guide plate 40, and the like. Fixing roller 3
A plurality of separation claws 34 are axially attached to a stay 35 on the downstream side in the vicinity of 1 so as to be rotatable. The separating claw 34
Is attached with a spring 36 having the other end fixed to a fixing unit housing or the like, and exerts a force to bring the separation claw 34 into contact with the fixing roller. On the other hand, a position regulating member 37 slidably attached to the fixing unit is attached near the separation claw. As shown in FIG. 3, the member 37 is usually pulled by the spring 38 and pushes down the arm-shaped portion of the separating claw 34, so that the separating claw 34 does not contact the fixing roller 31. On the other hand, when the solenoid 39 attached to the end portion of the member 37 is operated, the member 37 moves in parallel and the member 37 and the separating claw 34 are not in contact with each other.
Touch 1 The solenoid 39 can control the separation / contact of the separation claw 34 with respect to the fixing roller, and the state in which the separation claw 34 is in contact with the fixing roller 31 is the separation claw (= paper separation assisting means) 34.
Is in the operated state.

FIGS. 4 and 5 are schematic views for explaining the mechanism for determining the stiffness of the paper, and are shown between the paper transport guide plate 51 and the transport roller (or roller) 52 and the driven roller 53 pressed against this. The recording paper 1 is introduced. Transport roller 52
Can control the feed amount of the recording paper 1 by a driving unit and a control device (not shown). At the downstream side of the transport roller, a tip regulation plate 56 is provided which is attached to a rotatable stay 58 and receives a force by a compression spring 57 in a direction that impedes the path of the paper. The regulation plate 56 maintains a state of being regulated by the cam 59, and the cam 60 can move the tip of the regulation plate to a position where it does not hinder the sheet conveyance. Each cam is driven by drive means (rotary solenoid or the like) not shown. Further, in the vicinity of the paper conveyance guide plate 51, a paper front end detection sensor 54 and a micro switch or a photo interrupter (sensor) 55 with a filler for detecting whether or not the paper is bent are provided.

6 to 9 are views for explaining the operation of the mechanism for judging the strain of the recording paper according to the present invention, and the recording paper 1 sent to the mechanism is sent by the conveying roller.
First, as shown in FIG. 6, the regulating plate 56 is held by the cam in a posture such that the leading edge of the paper cannot pass through. Sensor 54
After the leading edge is detected by, the paper is conveyed by L + α. Here, L is a distance from the sensor 54 to the regulation plate 56, and α is a feed amount such that the paper whose tip is regulated sags and hits the sensor 55.

From this state, the cam 59 is rotated so that the regulating plate 56 can move in the tilting direction. At this time recording paper 1
When the strainer is strong, the force of the spring 57 is overcome and the regulation plate is tilted as shown in FIG. At this time, the sensor 55 does not detect the paper.
On the other hand, if the recording paper 1 is weak, the force of the spring 57 is applied to the recording paper 1.
Stays in the state of. Therefore, the force of the spring 57 is appropriately selected so that a paper having a weak strain such as being wound around the fixing roller can be determined here. Ie cam 5
When the sensor 55 continues to detect the paper as shown in FIG. 7 after releasing 9, the recording paper 1 is determined to be weak and the paper peeling agent assisting means is operated when the recording paper 1 passes through the fixing roller. On the other hand, after releasing the cam 59, it becomes as shown in FIG.
When the sensor 55 no longer detects the recording paper 1, it is determined that the recording paper 1 has a strong stiffness, and the paper peeling assisting means is not operated when the recording paper passes through the fixing roller. After the judgment of the paper strain, as shown in FIG. 9, the cam 60 is driven to forcibly depress the regulation plate 56 to eliminate the obstacle on the conveyance path and allow the paper having a weak strain to pass through the judgment means. .

(Invention of Claim 2) FIG. 10 is a view for explaining another embodiment of the present invention. In this image forming apparatus, as shown in FIG.
The recording paper 1 from 9 is conveyed to the transfer process via the lateral registration unit 11. Horizontal registration unit 11
As shown in FIG. 10, is composed of a ball roller 61, an inclined roller 62, a conveyance roller 63, and the above-described paper strain determination mechanism,
The recording paper 1 that has passed through the spherical roller 61 abuts the side surface of the recording paper 1 on the side block by the inclined roller 62 to ensure accuracy in the lateral direction. The recording sheet 1 corrected by the side block is conveyed to the transfer portion while being surely held by the conveying roller 63. Positioning in the vertical direction is controlled by the tip registration sensor 12 provided downstream of this. Here, FIG.
Install the paper strain determination mechanism described using. With this configuration, the recording paper 1 that has passed the strain determination mechanism has a time delay until the recording paper reaches the fixing roller in accordance with the result, and the paper peeling auxiliary means is operated / not operated. The transport rollers 63 and the transport rollers 52, 5 of the determination mechanism
The number of parts can be reduced by using the same function as 3.

(Invention of Claim 3) FIG. 11 is a view for explaining still another embodiment of the present invention. In this image forming apparatus, as shown in FIG. A large amount of recording paper is stocked and sequentially fed, and particularly when the present image forming apparatus is used as a printing apparatus, the types of paper stocked at one time are all the same. As shown in FIG. 11, the paper feeding unit 10 picks up the recording paper 1 stocked in the elevating tray 70 that is lifted and lowered by the pinion 71 and the rack 72 by the pickup roller 73, and feeds the roller 74, the reverse roller 75, and the separation plate. At 76, the sheet is reliably fed one by one. In the present embodiment, the paper strain determining means described with reference to FIG. 4 is provided at the portion after the paper is fed by the feed roller 74. In this configuration, at the start of printing, it is determined whether the first sheet of recording paper 1 that has been fed first is strained to determine whether or not to operate the sheet peeling auxiliary means in the fixing unit for the recording paper 1. However, the following recording sheets can be continuously fed without operating the paper strain determination mechanism. The number of parts can be reduced by using the feed roller 74 also as the conveyance roller 52 of the strain determination mechanism.

(Invention of Claim 4) FIG. 12 is a block diagram for explaining still another embodiment of the present invention, FIG. 13 and FIG.
FIG. 4 is a diagram for explaining the operation of the recording paper strain determination mechanism shown in FIG. 12, and as shown in FIG. A force is applied to the obstacle in the direction. The force obstructing the regulating plate 70 is set to be weaker than the force obstructing the regulating plate 56 by the spring 57. That is, for a paper without sticking that is stuck to the fixing roller from the front end of the paper and cannot be separated even by the paper peeling assisting means, as shown in FIG. Even if it is done, the regulation plate 70 cannot be repelled, and the force exerted on the paper by the regulation plate 70 is set so that it stops. In this case, the printing operation is stopped, and the display unit (not shown) notifies the user that the recording paper is not suitable for the image forming apparatus. As shown in FIG. 14, the regulation plate 70 can be repelled without problems for paper that can be separated without the paper peeling assisting means or paper that can be separated by operating the paper peeling assisting means.
The cam 6 on the regulation plate 56 cannot interfere with the paper conveyance.
The forced waiting means such as 0 does not have to be provided, but may be provided. As shown in FIG. 5, it is desirable that the regulation plate 56 has a comb-teeth shape, and the regulation plate 70 is arranged in the gap so as to be on the same straight line with respect to the front end of the paper.

[0022]

According to the first aspect of the present invention, the fixing unit section of the image forming apparatus and the selectively operable sheet peeling auxiliary unit are provided in the vicinity of the fixing roller, and the sheet peeling auxiliary unit is provided in the recording sheet conveying path at an upstream side of the fixing unit. At least two levels of paper "strain"
If it is determined that the recording paper has a weak stiffness, the paper peeling assisting means is activated, and if it is determined that the recording paper has a strong stiffness, the paper peeling assistance means is not operated. As a result, it is possible to ensure the separation of the paper in the fixing unit, improve the paper transportability, and minimize the adverse effect of the paper peeling auxiliary means on the fixing roller.

According to the second aspect of the invention, the paper "strain" determining means of the first aspect is provided in the registration mechanism in the recording sheet conveyance path, and the sheet strain is determined for all the recording sheets passing through the registration mechanism. By doing so, in addition to the effect of claim 1, in double-sided printing, it is possible to determine an image on one side and a change in the stiffness of the paper due to passing through the fixing unit once, and more stable paper transport performance is obtained. be able to.

According to a third aspect of the present invention, the paper "strain" determining means of the first aspect is provided in the paper feeding unit, and the operation of the paper peeling assisting means is performed by the stiffness of the first sheet of paper at the start of printing. By determining the presence / absence, by not operating the paper “brush” determination means for the succeeding recording paper, it is possible to obtain the effect of speed improvement during continuous recording in addition to the effect of claim 1.

According to the invention of claim 4, further, there is provided a judging means capable of judging the paper without the strain and a means for warning the user that the recording paper is not suitable. If so, the recording operation is stopped and the user is warned, so that it is possible to prevent the non-standard paper of the image forming apparatus from being used.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a main part for explaining an embodiment of the present invention.

2 is a configuration diagram of a fixing unit 30 shown in FIG.

3 is an exploded perspective view of a main part of a fixing unit 30 shown in FIG.

FIG. 4 is a schematic configuration diagram for explaining a mechanism for determining stiffness of paper.

FIG. 5 is a perspective view of a main part for explaining a mechanism for determining the stiffness of paper.

FIG. 6 is a diagram for explaining the operation of the mechanism for determining the strain of the recording paper shown in FIG.

FIG. 7 is another diagram for explaining the operation of the mechanism for determining the stiffness of the recording paper shown in FIG.

FIG. 8 is a further diagram for explaining the operation of the mechanism for determining the strain of the recording paper shown in FIG.

FIG. 9 is still another view for explaining the operation of the mechanism for determining the strain of the recording paper shown in FIG.

FIG. 10 is a main part configuration diagram for explaining another embodiment of the present invention.

FIG. 11 is a main part configuration diagram for explaining still another embodiment of the present invention.

FIG. 12 is a main part configuration diagram for explaining still another embodiment of the present invention.

FIG. 13 is a diagram for explaining the operation of the recording paper strain determination mechanism shown in FIG. 12.

FIG. 14 is a diagram for explaining the operation of the recording paper strain determination mechanism shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Recording paper, 10 ... Paper feeding unit, 11 ... Horizontal registration unit, 12 ... Front-end registration sensor, 13 ... Transfer belt, 14 ... Transfer roller, 15 ... Separation charger, 16 ...
Transport unit, 17 ... switching guide plate, 18 ... paper discharge tray, 19 ... duplex unit, 20 ... process unit,
21 ... Optical writing unit, 30 ... Fixing section, 31 ... Fixing roller, 32 ... Heater, 33 ... Pressure roller, 34 ... Separation claw, 35 ... Stay, 36 ... Spring, 37 ... Position regulating member,
38 ... Spring, 39 ... Solenoid, 40 ... Guide plate, 51
... Paper transport guide plate, 52 ... Followed roller, 53 ... Transport roller, 54 ... Paper tip detection sensor, 55 ... Font interrupter with filler, 56 ... Regulation plate, 57 ... Spring, 58 ... Stay, 59, 60 ... Cam, 61 ... Sphere roller, 62 ... Inclined roller, 63 ... Conveying roller, 70 ... Elevating tray, 71 ... Pinion, 72 ... Rack, 73 ... Pickup roller, 7
4 ... Feed roller, 75 ... Reverse roller, 76 ... Separation plate.

Claims (4)

[Claims] 1. An electrostatic latent image is formed on a surface of a plurality of photoconductors corresponding to printing colors by an electrophotographic method,
The electrostatic latent image is developed by a wet-type or dry-type developing unit, the recording paper is conveyed to a transfer position of the photoconductor by a transfer belt, and the developed images of the respective photoconductors are superposed and transferred onto the recording paper, In a color image forming apparatus in which the transfer image is heat-fixed by a fixing roller and a sheet peeling auxiliary means that can be selectively operated is provided on the downstream side in the vicinity of the fixing roller, in a recording paper conveyance path, an area upstream of the fixing unit. An image forming apparatus characterized in that it has means capable of determining at least two levels of "strain" of paper, and based on the determination result, the paper peeling assisting means is operated. 2. The image forming apparatus according to claim 1, wherein the paper “brush” judging means is provided in a registration mechanism in a recording paper conveyance path. 3. The image forming apparatus according to claim 1, wherein the paper “strain” judging means is provided in a recording paper feeding means. 4. The image forming apparatus according to claim 3, wherein the paper “brush” judging means has means for warning a user that the recording paper is unsuitable.