JP3356235B2 - Transfer paper separation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer paper separating apparatus applied to a copying machine and a printer using an electrophotographic system.

[0002]

2. Description of the Related Art As means for separating transfer paper electrostatically attracted to a photoreceptor and transporting it to the next step without fail,
In many cases, a transfer paper separating device is provided with a separating claw (Japanese Patent Application Laid-Open Nos. 3-245173, 3-140666, 60-184070, and 51-4).
No. 3136).

In recent years, resin-made separating claws have come to be used from the viewpoint of reducing the damage to the photoreceptor and reducing the cost. In FIG. 13 illustrating the separation claw, the separation claw 2 is adhesively held by a separation claw holder 3 that holds the separation claw. The separation claw holder 3 is rotatably fitted to a support shaft 4 provided in a rotation axis direction (a direction perpendicular to the paper surface of FIG. 13) of the drum-shaped photoconductor 1, and the transfer paper 10
During rotation of the photoconductor by means such as a cam,
It is designed to move back and forth.

The reciprocating movement is performed because the separation claw is made of a resin but has a certain degree of hardness, so that the contact with the photosensitive member may damage the photosensitive member. In order to disperse the flaw, reciprocation is performed. Alternatively, in the case of using a metal nail, the abdomen of the nail is brought into contact with the photoconductor to protect the photoconductor, and the nail position is fixed.

[0005] With respect to the separation claw that can reciprocate, the separation claw is rotatably held on a support shaft, and the tip of the separation claw is pressed by the urging means toward the center of the photosensitive member. Is to be abutted. Alternatively, a configuration is also employed in which the pressing portion does not use a pressing spring but makes contact using the rotation moment of the rear portion 3a of the separation claw holder 3 about the support shaft 4 due to its own weight.

In the image forming process, the toner image formed on the photoconductor 1 is transferred to a transfer paper 1 at a predetermined transfer position.
Transferred to 0. The transfer paper 10 after the transfer is transport belt 11
In the process of feeding, the leading end is separated from the photoreceptor and is conveyed to the fixing process unit by the conveying belt 11, but some of the toner reaches the cleaning unit 12 without being separated from the photoreceptor. In this case, since the image forming process cannot be continued, the transfer paper is separated by the separation claw 2 in advance. This is the function of the separation claw.

By the way, most of the toner forming the toner image on the photoreceptor 1 is transferred onto the transfer paper 10 as shown by the symbol Tt, but some is shown by the symbol Tr as the untransferred toner. As described above, there is a case where the whole does not transfer onto the transfer paper due to the transfer, but some remains on the photoreceptor.

When the transfer residual toner is scraped off by the separation claw, it falls on the transfer paper due to gravity and stains the image surface of the transfer paper.

The tip of the separation claw 2 is shown in FIG.
(Top view), FIG. 17 (b) (front view), FIG. 17 (c)
As shown in FIG. 17 (c) as viewed from the direction of the arrow, or as shown in FIG. 18 (a) (top view) and FIG. 18 (b).
As shown in FIG. 18C (a front view) and FIG. 18C (a cross-sectional view as viewed from the direction of the arrow in FIG. 18C), the cross section has a square or circular pointed shape. The reason why the shape is sharp is that the width of scraping off the remaining toner Tr is small when the sharp tip comes into contact with the photoconductor 1 as shown in FIG. Incidentally, compared to the contact width W ₁ as shown in FIG. 19 of narrower than the width of the residual toner Tr, if a large contact width W ₂ as shown in FIG. 20, scraped on the transfer paper by the separating claw The amount of dropped toner (hereinafter referred to as "toner drop") also increases, thereby increasing the amount and range of contamination of the transfer paper and the degree of image defects.

Further, a material having high hardness such as polyimideamide is used as a material of the separation claw, and the separation claw is reciprocated by a mechanical means such as a cam in the rotation axis direction of the photoconductor in order to reduce damage to the photoconductor. In the case of a configuration, as shown in FIGS. 21 and 22, in the case of a separation claw device that swings the separation claw 2 along the support shaft 4 in the direction of the arrow, when the swing operation is performed, Due to the gap of the fitting portion with the separation claw holder 3, the tip of the claw is inclined with respect to the photoconductor 1, and a gap d is generated.

[0011]

As described above, even when the contact area of the separation claw with the photosensitive member is reduced, the tip of the separation claw wears over time, and the contact width with the photosensitive member tends to increase. Is inevitable. Contact width as shown in FIG. 19 compared to the case is narrow and W _1, when the contact width as shown in FIG. 20 becomes greater and W ₂ is scraped residual toner is on the image bearing member (photosensitive member) There is a problem that the amount of toner dropping due to the increase in the amount of toner taken out increases the image quality.

Further, as shown in FIGS. 21 and 22, in a configuration in which the separation claw always reciprocates on the support shaft by a mechanical means such as a cam, the separation claw is moved during the movement. A gap is created by the inclination, and the toner enters the gap, and the toner passes through the separation claw while being rubbed by the separation claw. In the case of a separation claw having a small contact width as shown in FIG. 14, the contact width W is increased due to abrasion as shown in FIG. 15 (front view) and FIG. Problem.

Further, if the hardness of the separating claw is too high, the image carrier is damaged, so that the image has an influence such as a streak.
If it is too low, the abrasion of the separation claw is accelerated, and the image quality is degraded due to toner drop.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a transfer paper separating apparatus capable of appropriately selecting conditions of a separating claw and preventing a deterioration in image quality due to toner drop.

[0015]

In order to achieve the above object, the present invention is configured as follows.

(1). The tip of the separation claw contacting the image carrier is shaped like a cone, the angle between the tangent line of the image carrier at the separation claw contact point and the separation claw contact surface is α (°), and the top surface of the separation claw is projected. The weight angle is θ ₂ (°), the top projection tip radius of the separation claw is R (μm), the projection weight angle of the separation claw in the rotation axis direction of the image carrier is θ ₁ (°), and the rotation axis is When the projected tip radius of the separation claw in the direction is r (μm), ₂ tan (θ 2/2) [R ｛1 / sin (θ ₂ /
2) -1} + r _{[cos (θ 1/2) /} tan {α +
_{(Θ 1/2)} -} sin satisfy (theta _{1/2) +1]] <200, θ 1, θ} 2, r, we decided to use the separation claw having a value of R, alpha (claim 1) .

(2). In (1), the separation claw has a material whose Rockwell hardness is H ≦ 109 (M scale) (Claim 2).

(3). In (2), the separation claw is movable in the direction of the rotation axis of the image carrier, and has means capable of being fixed so as not to move in the direction of the rotation axis.

[0019]

According to the first aspect, when such conditions are set, the wear width of the separation claw with time (= contact width with the image carrier) is obtained.
Is 200 μm or less, and when it is more than this, it is difficult to increase. According to the second aspect, it is possible to reduce the abrasion speed of the separation claw while reducing the generation and progress of the flaw on the image carrier. According to the third aspect, the separation claw does not always reciprocate, but can be fixed at a predetermined position for separating the transfer paper during the rotation of the latent image carrier. There is no room for the separation claw to be tilted with respect to the image carrier at the time of swinging, and the abrasion caused by the gap is not promoted.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The separation claw is applied to a photoreceptor, and a drum-shaped or belt-shaped dielectric is disposed opposite to the photoreceptor so as to be mainly used in a color image copying machine or the like. There is also a method of transferring the toner image formed on the photoreceptor onto the above-mentioned dielectric, and then further transferring it to transfer paper. In such a method, a separating claw is applied to the dielectric. In some cases, the image carrier to which the present invention is applied includes a dielectric material in addition to the photoconductor.

(1). Description corresponding to claim 1.

Regarding the wear of the separation claw, the wear width (= contact width:
FIG. 2 summarizes the relationship between W) and the toner removal level. Here, regarding the determination of the toner drop level, items such as the number of black spots per unit area on the transfer paper, the size of black spots, the frequency of occurrence of black spots (how many copies occur during copying), and the like are determined. Visual judgment was performed using the scale.

[0023] Here, a grain of the toner drop black spot size up to 0.5 mm (average particle size of 7.5 [mu] m (-) use of charged toner), the black spot there rate per 1 cm ² is good to 3% Level.

According to this, toner particle size, toner shape,
Depending on the combination of factors such as the toner material, toner charging polarity, and the material of the photoreceptor, the toner adhesion and the amount of toner adhered to the photoreceptor fluctuate, and the level of toner drop varies. When the width (W) was 200 μm or less, it was found that the toner elimination level was within an allowable level and was in a range where the image quality was not significantly deteriorated.

In order to keep the wear width (= contact width: W) within a predetermined value, that is, within 200 μm, there is a problem how to set the condition of the separation claw. In this regard, as shown in FIG. 5, in a state where the R shape (rounded shape) of the tip of the separation claw 2 remains, the photosensitive member 1 is placed in the gap between the sharp edges of the tip shown by arrow j. The remaining toner easily enters, and therefore the wear proceeds due to the polishing effect of the toner. When the wear progresses and the tip R-shaped portion disappears as shown in FIG. 1, the residual toner on the photoreceptor 1 flows to the upper part of the separation claw as shown by an arrow k,
Alternatively, even if the pier is blocked, it does not enter under the separation claw, so that the above-described polishing effect does not occur.

Therefore, the present inventor has found that the contact width W when the tip R-shaped portion of the separation claw disappears can be obtained by the following equation, and that the contact width W is within 200 μm as described above. It has been found that, by setting a condition that abrasion is hardly caused when the value is set to, an increase in the contact width can be suppressed and toner dropping can be prevented.

Referring to FIG. 1, a description will be given of a calculation formula for obtaining the contact width W when the tip R-shaped portion of the separation claw disappears. FIG.
FIG. 1A is an enlarged view of a portion surrounded by a circle when the separation claw 2 shown in FIG. 1B is viewed from the rotation axis direction of the photoconductor 1, and FIG. FIG. 1D is an enlarged view of a portion surrounded by a circle when the separation claw 2 is viewed from above, as shown in FIG.

In FIG. 1, the angle between the tangent line of the image carrier at the separation claw contact point and the separation claw contact surface is α.
(°), the upper surface projected weight angle of the separation claw is θ ₂ (°), the upper surface projected tip radius of the separation claw is R (μm), and the projected weight angle of the separation claw in the rotation axis direction of the photoconductor 1 is θ ₁ ( °), the projected tip radius of the separation claw in the rotation axis direction of the photoconductor 1 is r (μm).

In the case where the separation claw 2 is worn until the rounded end portion loses its shape, in FIG. 1A, the symbol LL indicates a wear line. Assuming that the distance from the intersection Q between the center line OO and the wear line LL to the tip of the separation claw is indicated by a symbol d, the wear width (= contact width: W) can be obtained using the distance d. .

D = c + rb (1) where c is the distance on the center line OO from the intersection Q to the intersection H of the wear line LL and the contour of the separation claw. Also, b is the intersection J (the center of the projected tip radius r of the separation claw) where the perpendicular on the contour line of the separation claw that rises from the intersection H intersects the center line OO, and the center line OO through the intersection H. The distance on the center line OO between the lowered intersection K is shown. b, c
Can be obtained as follows.

The a / c = tan {α + (θ 1/2)} c = a / tan {α + (θ 1/2)} = r · cos (θ 1/2) / tan {α + (θ 1/2 )｝ (2) where a is the distance from intersection K to intersection L.

[0032] _{b = r · sin (θ 1} /2) ... (3) (2), is substituted into (3) Equation (1), ∴d = r _{[cos (θ 1/2) /} tan { _{α + (θ 1/2}} -sin (θ 1/2) +1 ] (4) On the other hand, in FIG. 1 (c), the intersection of both the contour of the separating claw O _3, from to the intersection point Q the intersection point O ₃ e the distance on the center line O-O of the wear width (= contact width: W) center O-O of the central distribution distance g, from the intersection O ₃ to the center M of the upper surface projecting tip radius R of the separation claw When the distance on the f, W = 2g ... (5 ) g = e · tan (θ 2/2) ... (6) e = f + d-R ... (7) where, f · sin (θ ₂ / 2) = when seeking f from R, f = R / sin (theta _2/2) ... (8) where (7), (4), = e from (8) R [{1 / _{sin (θ 2/2)}} - 1 ] + r [co _{(Θ 1/2) / tan} {α + (θ 1/2)} - sin (θ 1/2) +1 ]] ... (9) (9), (5), (6) where, W = 2tan (θ
_{2/2) [R {1} / sin (θ 2/2) -1} + r [co
_{s (θ 1/2) /} tan {α + (θ 1/2)} - sin
(Θ _1/2) +1]].

Therefore, the value of W obtained by this equation is 200 μm.
θ that satisfies the condition of within m ₁, Θ_Two, R, R, α
When the condition of the separation claw is determined to have the value of
Even if the number is increased, the increase in the contact width can be suppressed,
-It can prevent falling.

FIG. 3 shows the results of an experiment conducted to confirm this. FIG. 3 shows data obtained by measuring the actual wear width for each number of transfer sheets using three types of separation claws satisfying the condition of W <200 in calculation. The condition of the separation nail shown by the solid line is R = 75 μm, r = 60 μm, the condition of the separation nail shown by the broken line is R = 75 μm, r = 35 μm, and the condition of the separation nail shown by the dashed line is R = 50 μm, r = 25 μm, and a common condition for each of these separation claws is α = 13
(°), θ ₁ = θ ₂ = 30 (°), pressure f = 1 on the separation claw
g / f, the material of the separation claw is polyetherimide (PE
I), the tip of the separation claw is a quadrangular pyramid as shown in FIG. In FIG. 3, the actual wear width W (μm) is measured and graphed for each copy number (transfer number) for each of these separation claws.

In FIG. 3, in any of the separation claws,
The actual wear width (W) is 200 even for a separation claw having a large wear width.
The calculated value does not exceed about μm, and the calculated value is in good agreement with the experimental value. In fact, these separation claws did not cause deterioration in image quality due to toner dropping over time.

(2). Generally, a resin such as a polycarbonate resin that is hard to be worn and hard to be scratched is used for the surface of the photoconductor. During rotation of the photoconductor, the separation claw is fixed so as not to swing in the direction of the rotation axis of the photoconductor, and the tip of the separation claw is configured to abut on the same point in the rotation axis direction of the photoconductor, The depth of the scratch on the surface of the photoconductor relative to the number of copies (the number of copies) was measured for each material by changing the material of the photoconductor. The result shown in FIG. 4 was obtained.

In FIG. 4, reference numeral PAI indicates an experimental result in the case of using polyamideimide (Rockwell hardness, 119 on M scale) as the material of the separation nail.

The symbol PEI is polyetherimide (Rockwell hardness, 109 on M scale), the symbol PEEK.
Is polyetheretherketone (Rockwell hardness M
The scale 106) and the symbol PEEK 'indicate the experimental results when polyetherketone (Rockwell hardness, M scale 99) was used as the material of the separation nail.

In this example, when polyimide amide is used, the rising of the straight line is steeper than in the other examples, and the transfer number (200,000 sheets) which is the life level of the image bearing member (photosensitive member) is obtained. It can be seen that since the depth of the flaw received by the image carrier before reaching the level reaches a level at which a streak is generated in the image, it is impossible to set an appropriate material condition.

Codes PAI, PEI, PEEK, PEE
In the case of other material conditions indicated by K ', the depth of the flaw on the surface of the image carrier reaches the level at which streaks occur in the image and still reaches the life level of the image carrier. It turns out to be appropriate.

It is considered that the hardness of the material is mainly related, and if the hardness of the material of the separation claw is 109 or less in Rockwell's M scale, it is considered to be appropriate as the material. That is, with this hardness, an image defect due to damage to the image carrier does not occur until the life of the image carrier.

(3). In a case where the position of the separation claw is always fixed to an arbitrary position in the rotation axis direction of the photoconductor and used, for example, when the image is a key line, the position of the key line is used. If the position of the separation claw coincides with the position of the separation claw, the separation claw continues to be located at the position corresponding to the key line, so that the toner remaining after transfer continuously drops occurs, and the image quality is significantly deteriorated. . Even in the case of the method in which the separation claw is swung in the rotation axis direction of the photoreceptor, if there is a key line, a band-shaped image, a specific format, etc. Toner drop occurs intermittently, which degrades image quality.

In the method in which the separation claw swings in the rotation axis direction of the photosensitive member during rotation of the photosensitive member, as described with reference to FIGS. It promotes abrasion and causes deterioration of image quality due to toner drop. An object of the present invention is to provide a technique capable of avoiding such deterioration of image quality.

In FIG. 7, the two separation claws 2 are both
Although it is rotatable about the support shaft 4, its movement is restricted in the longitudinal direction of the shaft and moves together with the support shaft 4. The separation claw 2 is adhered to a separation claw holder 3, and the separation claw holder 3 is
It is urged to contact the photoreceptor ₁ by a spring S1 hung between the upper protrusion.

The support shaft 4 includes a rib 13 provided on a stationary member 14.
And is supported in a state where it can move in the axial direction. The right end of the support shaft 4 are formed stepped portions 4a, between the stepped portion 4a and the ribs 13, though the spring S ₂ extensibility is interposed, the right side in the drawing the pivot shaft 4 It is energizing. The movement of the support shaft due to this bias is prevented by the right end of the support shaft 4 abutting on the positioning plate 5 provided on the immobile member 14.

The positioning plate 5 is fixed to the immovable member 1 by a screw 6 through an elongated hole having a longitudinal direction in the rotation axis direction of the photosensitive member 1.
4 is fixed. Therefore, if the positioning plate 5 is moved after the screw 6 is loosened, the separation claw 2 is also moved together with the support shaft 4 in the rotation axis direction of the photoconductor.

Here, the spring S ₂ , the positioning plate 5, the elongated hole and the screw 6 constitute an example of a fixing means for making the position of the separation claw movable and fixing the position.

With such a configuration, for example, FIG.
Even if the transfer residual toner is generated at the position of the separation claw 2 as shown by r, the separation claw 2 is transferred to the transfer claw 2 as shown in FIG.
In such a case, the phenomenon of toner falling due to the separation claw 2 shaving off the transfer residual toner Tr does not occur.

FIGS. 9 and 10 show another example. Instead of attaching the support shaft 4 to the positioning plate 5 as shown in FIGS. 7 and 8, the end of the support shaft 4 is screwed. The screw portion 9 is screwed through a drum face plate 8 as an immovable member.

A knob 7 is provided at an end of the screw portion 9. By rotating this knob 7, the support shaft 4
Can be moved in the rotation axis direction of the photoconductor 1. Therefore, also in this example, since the position of the separation claw can be appropriately changed by the movement of the separation claw and the fixing means at a predetermined position, by shifting the position of the transfer residual toner or the position of the separation claw, It is possible to avoid a decrease in image quality due to toner drop. 9 and 10 are particularly convenient because no tools are required.

In a mechanism in which two separation claws positioned at regular intervals are used and the transfer paper is conveyed on the basis of a center, as shown in FIG. It is necessary to set the movable range of the separation claw so as to cover the area.

Also, in this embodiment, once the position of the separation claw is set, the position of the separation claw is set to the position in either the case of FIGS. 7 and 8 or the case of FIGS. Since the separation claw does not swing during the rotation of the photoconductor, the gap d as shown in FIGS. 21 and 22 does not occur, and the separation claw as shown in FIG. Of the separation claw does not occur due to the gap, because the tip of the second member is in close contact with the photoreceptor 2 and does not form a gap.

The degree of wear of the separation claw is different between the method of fixing the separation claw without moving it during rotation of the photosensitive member as in this example and the method of swinging the separation claw. FIG. 12 shows the experimental results of the examination.

In FIG. 12, the solid line shows the case without swinging.
The broken line indicates the case with swing. As can be seen from this example, in the method in which the separation claw is fixed without swinging, it is possible to reduce the abrasion of the contact width of the separation claw tip with time, leading to image failure. Can be increased, that is, the life of the separation claw can be extended.

[0055]

According to the present invention, it is possible to prevent the deterioration of the image quality due to the toner drop without damaging the image carrier by appropriately selecting the condition of the separation claw.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a separation claw.

FIG. 2 is a diagram illustrating a relationship between a wear width of a separation claw and a toner drop level.

FIG. 3 is a diagram illustrating a relationship between a wear width of a separation claw and the number of copies.

FIG. 4 is a diagram illustrating the relationship between the depth of a flaw caused by the separation claw on the image carrier and the number of copies.

FIG. 5 is a diagram illustrating the shape of a separation claw before wear.

FIG. 6 is a diagram illustrating the shape of the separation claw after abrasion.

FIG. 7 is a view for explaining a position fixing means of the separation claw capable of fixing the position after the position adjustment, before the position adjustment.

FIG. 8 is a diagram illustrating the position fixing means of the separation claw capable of fixing the position after the position adjustment, in a state after the position adjustment.

FIG. 9 is a perspective view illustrating the position fixing means of the separation claw that can fix the position after the position is adjusted.

FIG. 10 is a sectional view of a main part of the position fixing means of the separation claw capable of fixing the position after the position is adjusted.

FIG. 11 is a diagram illustrating a relationship between a movable range of a separation claw and a transfer paper size.

FIG. 12 is a diagram illustrating the relationship between the contact width and the number of copies when the separation claw is swung or fixed.

FIG. 13 is a front view of the separation claw and peripheral members illustrating the function of the separation claw.

FIG. 14 is a front view illustrating an initial contact state of the separation claw with the photoconductor.

FIG. 15 is a front view illustrating a contact state of the separation claw on the photosensitive member after being worn.

FIG. 16 is a plan view illustrating a state after the separation claw is worn.

FIG. 17 is a diagram illustrating the shape of a separation claw having a square cross section.

FIG. 18 is a diagram illustrating the shape of a separation claw having a circular cross section.

FIG. 19 is a diagram illustrating a relationship between a contact width of a separation claw and a width of remaining toner.

FIG. 20 is a diagram illustrating a relationship between a contact width of a separation claw and a width of remaining toner.

FIG. 21 is a front view illustrating a gap formed between the separation claw and the photoconductor when the separation claw is moved to the left.

FIG. 22 is a front view illustrating a gap formed between the separation claw and the photoconductor when the separation claw is moving rightward.

FIG. 23 is a front view illustrating that there is no gap between the separation claw and the photoconductor when the separation claw is fixed.

[Explanation of symbols]

 2 Separating claws

Claims (3)

(57) [Claims] 1. A transfer paper separating apparatus using a separation claw made of a resin that abuts on an image carrier and separates transfer paper, wherein a tip of the separation claw that abuts on the image carrier has a cone shape,
The angle between the tangent line of the image carrier at the contact point of the separation claw and the contact surface of the separation claw is α (°), the upper surface projected weight angle of the separation claw is θ ₂ (°), and the upper surface projected tip of the separation claw The radius is R (μm), the projected weight angle of the separation claw in the rotation axis direction of the image carrier is θ ₁ (°), and the projection tip radius of the separation claw in the rotation axis direction is r (μ).
m), when _{a, 2tan (θ 2/2)} [R {1 / sin (θ 2/2) -
1} + r _{[cos (θ 1/2) /} tan {α + (θ 1 /
_{2)} - sin (θ 1} /2) +1 ] <meet _{200, θ 1, θ 2,} r, R, the transfer sheet separating device which is characterized by using a separation claw having a value of alpha. 2. The transfer paper separating apparatus according to claim 1, wherein the material of the separation claw has a Rockwell hardness of H ≦ 109 (M scale). 3. The image forming apparatus according to claim 2, wherein the separation claw is movable in the direction of the rotation axis of the image carrier, and has means capable of being fixed so as not to move in the direction of the rotation axis. A transfer paper separating device.