JPH06317994A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent irregularities in an image and to obtain a sharp image by providing an image carrier and a transfer roller press-contacting with it and obtaining the gentle contact/uncontact of the transfer roller with the image carrier, when a transfer material exists between the image carrier and the transfer roller. CONSTITUTION:The shaft 2a of the transfer roller 2 is extended on the bearing part 3b of an arm 3 pivotally supported by a fixing pin 3a and the transfer roller 2 press-contacts with the image carrier 1 by a spring 5 abutted on the end part 3c of the arm 3. A circular cam 4a is abutted on the end part 3c and the arm 3 is rocked from a position where the transfer roller 2 is abutted on the image carrier 1 to a position where they are separated, against the force of the spring 5, by the turn of the cam 4a. When a resist sensor 9 detects the leading edge of the carried transfer material, the cam 4a is turned and the transfer roller 2 is gently abutted on the image carrier 1, before the leading edge reaches a transfer part. When the transfer progresses and the resist sensor 9 detects the tailing edge of the transfer material. the cam 4a is turned and the transfer roller 2 is separated from the image carrier 1.

Description

Detailed Description of the Invention

[0001]

[Object of the Invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using an electrostatic transfer process such as an electrostatic copying machine and a printer.

[0002]

2. Description of the Related Art In a known image forming apparatus including a step of transferring a toner image electrostatically formed on the surface of an image carrier to a transfer material such as paper superposed on the image, The contact nip portion between the body and the elastic transfer roller contacting the body is used as the transfer portion, and the transfer material is supplied to the transfer portion in time with the toner image on the surface of the image carrier, and the transfer bias is applied to the transfer roller. It is proposed that the toner image on the image carrier side is transferred to a transfer material by applying the voltage.

FIG. 10 schematically shows a main part of such an image forming apparatus. The surface of an image carrier 1 formed in a cylindrical shape and rotating in the direction of arrow A in the drawing is primarily charged. The device 61 is uniformly charged, and the charged surface is irradiated with image exposure T to form an electrostatic latent image. To the latent image, toner is supplied from the developing device 82 through the developing sleeve 64 to form a toner image. It is formed.

As the image carrier 1 rotates, when the toner image reaches a transfer portion formed as a pressure contact nip portion between the image carrier 1 and the transfer roller 2 in pressure contact with the image carrier 1, a transfer bias is applied to the transfer roller 2. The toner image on the image carrier side is transferred to the transfer material by the action of the applied electric field.

After that, the transfer material carrying the toner image is conveyed away from the image carrier 1 to a fixing portion (not shown), and the residual toner remaining on the surface of the image carrier without being transferred to the transfer material is transferred to the image carrier. As the body 1 rotates, it reaches the position of the cleaner 62 and is removed by the cleaning blade 65 so that the image carrier is ready for the next step.

In the illustrated apparatus, the transfer roller 2 is composed of a shaft made of a conductive member such as metal and an elastic material such as sponge whose resistance value is adjusted to an appropriate value. Both ends of the shaft are made of conductive bearings. The bearings 71 are supported by 71 (only one of which is shown in the figure), and each bearing 71 is supported by the spring 5 so that the roller 2 is constantly in pressure contact with the image carrier 1.

The transfer means configured to press the transfer roller against the image carrier does not require a high-voltage transfer bias power source, generates less ozone, and reliably grips the transfer material to prevent transfer deviation. Although it has various advantages such as being less likely to occur, on the other hand, since the transfer roller is in pressure contact with the image carrier even when there is no transfer material at the transfer site such as between adjacent transfer materials, warm air rotation, and forward / backward rotation, Since it is inevitable that a small amount of toner that remains poorly after cleaning or remains slightly after cleaning will remain on the image carrier, this will transfer to the transfer roller and cause back stain on the subsequent transfer material.

Further, in order to prevent the occurrence of a so-called hollow image phenomenon in which the toner does not get on the central portion of the linear image during printing, the peripheral speed of the image carrier and the transfer roller at the transfer portion is set to the former. Although it has been proposed to increase the size by about 1 to 3%, a small amount of toner adhering to the transfer roller is rubbed on the surface of the image carrier and gradually adheres firmly to the image carrier, resulting in deterioration of image quality. May occur.

In order to avoid such a defect, there has been proposed a method in which the transfer roller is brought into pressure contact with the image carrier only when the transfer material is present at the transfer site, and the two are separated from each other at other times. There is.

However, even in such a case, when the transfer roller comes into contact with the image carrier to enter the transfer step, the image carrier is temporarily nonuniformly rotated or vibrates due to a shocking contact. When the electrostatic latent image is generated and the laser beam is used, the pitch unevenness may occur.

The present invention has been made in view of the above circumstances, and is only for an image forming apparatus including an image carrier and a transfer roller that is in pressure contact with the image carrier, and only when the transfer material is present between the two. In a case where both are brought into contact with each other, the transfer roller is gradually brought into contact with or separated from the image carrier, and it is possible to provide an apparatus capable of obtaining a high quality image while avoiding the above-mentioned drawbacks. It is intended.

[0012]

[Constitution of the invention]

In order to achieve the above object, the present invention comprises an image bearing member and a transfer means abutting against the image bearing member, and there is no transfer material at a transfer portion which is a contact nip portion of both. In an image forming apparatus configured so that they are sometimes separated from each other, the transfer means is elastically biased in a direction in which the transfer means always comes into contact with the image carrier, and the image carrier is moved from a position where the transfer means is separated from the image carrier. When the image carrier is displaced to the position where it comes into contact with the image carrier, the proximity means is provided to bring the image carrier into contact with the image carrier without giving an impact.

With this arrangement, it is possible to prevent the written image from being disturbed by the transfer means impactingly contacting the image carrier, thereby obtaining a clear image.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS "FIGS. 1" and "FIG. 2" are side views of an image forming apparatus showing an embodiment of the present invention, particularly in the vicinity of a transfer portion, in which arrows are provided with axes in the direction perpendicular to the plane of the drawing. A
It is assumed that a toner image is formed on the surface of the image carrier 1 that rotates in the direction by an image forming member (not shown).

When this toner image reaches the transfer portion where the image carrier 1 and the transfer roller 2 are in contact with each other, the transfer material P is conveyed from the conveying path 10 to the transfer portion at the same timing. , A transfer bias is applied to the transfer roller 2, and the toner image is transferred from the image carrier to the transfer material P.
After that, the transfer material is separated from the image carrier 1 and is conveyed to a fixing portion (not shown) via the conveying path 8. The above basic image forming operation is performed by the known apparatus shown in FIG. It is no different from the case.

In the apparatus shown in the figure, the shaft 2b of the transfer roller 2 is mounted on the bearing portion 3b of the arm 3 which is axially supported by the fixed pin 3a.

Further, a spring 5 is in contact with the end portion 3c of the arm 3, whereby the arm 3 is pivotally biased counterclockwise in the drawing, and thus the transfer roller 2 is pressed against the image carrier 1. ing.

A fixing pin 4 is attached to the end 3c of the arm 3.
A cam 4a that is attached to b and rotates is abutted, and by the rotation of the cam 4a, the arm 3 becomes a cam follower and the transfer roller 2 resists the force of the spring 5 and the transfer roller 2 moves. It is assumed that the roller 2 is swung from a position ("FIG. 1") in contact with the image carrier to a position ("FIG. 2") separated from the image carrier.

Reference numeral 9 is a resist sensor for detecting the transfer material by tilting the photo interrupter 9b in contact with the tip of the transfer material to release the light blocking of the photo interrupter, and the reference numeral 7 is conductive. It is a power source for applying a bias to the transfer roller via the arm 3 made of a member, the spring 5, and the electrode 6.

With the above-described structure, when the transfer material is conveyed and the registration sensor 9 detects the tip of the transfer material, the cam 4a moves to a position as shown in FIG. 1 before the tip reaches the transfer portion. Then, the transfer roller 2 is brought into pressure contact with the image carrier 1, and the toner image is transferred onto the transfer material P in the manner described above. When the registration sensor 9 detects the rear end of the transfer material as the transfer progresses, the cam 4b reaches the position shown in FIG. 2 depending on the timing when the rear end passes through the transfer portion. 2 is separated from the image carrier 1.

When the transfer material is supplied to the transfer portion, slightly before the transfer material reaches the transfer portion in order to stabilize the operation relationship between the image carrier and the transfer roller, which is placed at the time of transfer.
The image carrier and the transfer roller are positioned as shown in FIG. 1, and the image carrier and the transfer roller are moved to the position shown in FIG. 2 after a small time has elapsed since the trailing edge of the transfer material was detected. It is preferable to set the sequence so as to take the position shown in FIG.

Since it is preferable that the transfer roller 2 contact the image carrier 1 as gently as possible, a circular cam is used in the illustrated apparatus to contact and separate the transfer roller 2 and the cam as described above. FIG. 3 shows the relationship between the rotation angle of the cam and the movement of the arm 3 for bringing the transfer roller into contact with the image carrier in this case.

As shown in FIGS. 3A and 3B, the angle θ formed by the arm 3 with respect to the horizontal direction is θ _A when the transfer roller 2 is in contact, and θ _B when the transfer roller 2 is at the maximum separation. Assuming that the rotation angle position of α is α, from FIG. 3, when α is 0 ° (or 360 °), the change of θ with respect to the change of α is the smallest. In other words, the transfer roller 2 is set to the image carrier 1. It can be seen that it is possible to make a slow contact with the. It goes without saying that the shape of the cam is not limited to the circular shape shown in the drawing.

FIG. 4 shows another embodiment. In the apparatus shown in the figure, the transfer roller 2 attached to the end of the swing arm 21 is arranged to face the image carrier 1. In the arm 21, a spring 22 is arranged on a spring washer 22 which is slidable in a guide portion 22a, and a cam 24a supported by a pin 24b abuts on the bottom of the spring washer 22. There is.

By configuring in this way, the cam 2
Immediately, the washer 22 slides in the guide portion 22a by the rotation of 4a, the transfer roller 2 can be brought into contact with and separated from the image carrier 1, and the same operation as in the case of the above-described apparatus can be achieved. You can understand. Further, in this case, when the same cam as in the above-described embodiment is used, the transfer roller 2 is brought into contact with the image carrier 1 at a rotation angle of 180 °.
Since the vicinity is used, as can be seen from the graph of FIG. 3, the swing angle of the arm 21 with respect to the rotation angle of the cam is reduced, that is, the transfer roller is gently brought into contact with the image carrier 1. You can

FIG. 5 shows still another embodiment of the present invention, in which the transfer roller 2 disposed on the bearing portion 13b of the arm 13 axially supported by the pin 13a provided at a fixed position in the apparatus is The spring 5 presses the image carrier 1.

An end portion 13c of the arm 13 is connected to a member 14a which is rotationally displaced by the energizing force of the solenoid 14, and a pin 13d formed on the arm 13 is further provided.
Further, the lever 16 is always engaged by the spring 17 in the counterclockwise direction so that the lever 16 can be rotated.

With this construction, the transfer roller 2 can be brought into contact with or separated from the image carrier 1 by energizing the solenoid 14 and rotating the arm 13 by a signal indicating the presence or absence of the transfer material. At the same time, as the roller 2 approaches the image carrier, the spring 17 and the lever 16 strongly brake the rotation of the arm 13, so that the impact of the collision of the transfer roller on the image carrier is prevented. Can be relaxed.
It goes without saying that a suitable material such as a damper or rubber can be used as the shock absorbing member.

FIG. 6 shows still another embodiment. In this apparatus, the transfer roller 2 is attached to a support member 40 that is swingably supported by a drive shaft 43a and is biased toward the image carrier 1 by a spring 44 at all times. , A gear 43 provided on the shaft 43a and driven by a motor M, an idler 42, and a gear 41 provided on the transfer roller 2.

By rotating the cam 4a provided on the pin 4b, the supporting member 40 rotates clockwise against the action of the spring 44, and the transfer roller 2 comes into contact with and separates from the image carrier 1. In this apparatus, since the transfer roller 2 is rotated at any time when the transfer roller 2 comes into contact with or separates from the image carrier 1, the shock caused by the abrupt rotation of the transfer roller in the stopped state when the two come into contact with each other is mitigated. be able to.

FIG. 7 shows still another embodiment. The mechanism for bringing the transfer roller 2 into and out of contact with the image carrier 1 is the same as that shown in FIG.

In this case, when the transfer roller 2 is in contact with the image carrier 1, the transfer roller 2 is rotated accordingly, and when separated, the gear 52 driven by a drive source (not shown) is A gear 51 attached to the shaft of the transfer roller 2 meshes with and rotates.

With this structure, when the transfer roller 2 comes into contact with the image carrier 1, the shock caused by the rapid rotation of the roller can be alleviated.

FIG. 8 shows still another embodiment of the present invention. In this apparatus, the transfer roller 2 attached to one end of the lever 54 attached to the pin 54b is attached to the image carrier 1. Approach and separate.

A rack 54a is provided at the other end of the lever 54 and is engaged with a gear 53 driven by a drive source (not shown). A spring 5 contacts the lever 54 so that the transfer roller 2 always contacts the image carrier 1.

The gear 53 is activated by a signal indicating the presence or absence of the transfer material.
Is driven to bring the transfer roller 2 into and out of contact with the image carrier 1, and at this time, the rotational speed of the gear 53 is controlled so as to become smaller as the transfer roller 2 approaches the image carrier 1 It is possible to reduce the shock when the roller comes into contact.

FIG. 9 shows another embodiment of the image carrier 1.
FIG. 3 is an end view of the transfer roller 2. In the illustrated case, a cam for bringing the transfer roller into and out of contact with the image carrier is provided only at one end.

Both ends of the shaft of the transfer roller 2 are supported by bearings 56, which are biased upward in the drawing by a spring 5 and are in pressure contact with the image carrier 1. In the illustrated case, the cam 55b comes into contact with the bearing 56 on the right side, which is the input shaft 5
The cam is driven by a signal entering 5a to rotate only the bearing on the left side in the drawing in the counterclockwise direction to separate the transfer roller 2 from the image carrier 1. Even with this configuration,
Since the image carrier and the transfer roller are separated from each other over the required length, the same operation as that of each of the above-described embodiments can be achieved.

Further, in this apparatus, since the transfer roller and the image bearing member are constantly in contact with each other at the end portion (the side where the cam does not exist), the transfer roller rotates, and the impact when the both contact next is generated. Can be tempered. Further, it is advantageous in terms of space and cost when the drive source is provided only on one side such as an image forming apparatus adopting the one-sided conveyance method.

[0040]

As described above, according to the present invention, the image carrier and the transfer means contacting the image carrier are provided, and when the transfer material is not present at the transfer site formed as the nip portion of the both, both are carried. In the image forming apparatus configured to be separated from each other, when the transfer unit is displaced in the direction of the image carrier to be in contact with the image forming apparatus, the transfer unit is gently contacted so as to alleviate the shock caused by the collision. Not only is it possible to prevent the deterioration of the image quality at night due to toner adhesion to the means, but also to effectively prevent the image distortion due to the occurrence of pitch unevenness due to the impact at the time of writing the image signal to obtain a high quality image. It has a remarkable effect.

[Brief description of drawings]

FIG. 1 is a side view of a main part of an image forming apparatus showing an embodiment of the present invention when a transfer roller is at a transfer position;

FIG. 2 is a side view showing a case where the transfer roller is separated from the image carrier, FIG.

FIG. 3 is a graph showing a relationship between a rotation angle of a cam and a rotation angle of an arm that is rotated by the rotation angle of the cam;

FIG. 3A

FIG. 3B is an explanatory view schematically showing the same aspect as above.

[Figure 4]

[Figure 5]

[Figure 6]

[Figure 7]

FIG. 8 and

FIG. 9 is a schematic side view of an essential part of an image forming apparatus, which shows another embodiment of the present invention;

FIG. 10 is a schematic side view schematically showing the configuration of a known image forming apparatus, 1 image carrier 2 transfer roller 3, 13 arm 4a cam 5, 17 spring 14 solenoid 40 support member 41, 42, 43 gear 54 lever 55b cam 56 bearing

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[Procedure amendment]

[Submission date] May 23, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a side view of a main part of an image forming apparatus according to an embodiment of the present invention when a transfer roller is at a transfer position.

FIG. 2 is a side view showing a case where the transfer roller is separated from the image bearing member.

FIG. 3 is a graph showing a relationship between a rotation angle of a cam and a rotation angle of an arm which is rotated by the rotation angle of the cam.

FIG. 4 is an explanatory view showing a state at the time of contact with a transfer roller showing the same operation.

FIG. 5 is an explanatory view showing a state when the transfer roller showing the same operation is separated.

FIG. 6 is a side view of an essential part showing another embodiment of the present invention.

FIG. 7 is a side view of an essential part showing another embodiment.

FIG. 8 is a side view of an essential part showing another embodiment.

FIG. 9 is a side view of essential parts showing another embodiment.

FIG. 10 is a side view of an essential part showing another embodiment.

FIG. 11 is a side view of essential parts showing another embodiment.

FIG. 12 is a schematic side view schematically showing the configuration of a known image forming apparatus.

[Explanation of reference symbols] 1 image carrier 2 transfer roller 3, 13 arm 4a cam 5, 17 spring 14 solenoid 40 support member 41, 42, 43 gear 54 lever 55b cam 56 bearing

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 3]

[Figure 4]

[Figure 5]

[Figure 6]

[Figure 7]

[Figure 8]

[Figure 9]

[Figure 10]

FIG. 11

[Fig. 12]

Claims (5)

[Claims] 1. An image forming apparatus having an image carrier and a transfer means contacting the image carrier, and when the transfer material is not present at a transfer site which is a contact nip portion between the two, the two are separated from each other. The transfer means is elastically biased in the direction in which the transfer means is always in contact with the image carrier, and when the transfer means is displaced from the position separated from the image carrier to the position in contact with the image carrier, the image carrier is given a shock. An image forming apparatus provided with a proximity unit that abuts without contact. 2. The image forming apparatus according to claim 1, wherein the proximity means is a circular cam. 3. The image forming apparatus according to claim 1, wherein the approaching means is a braking mechanism whose braking force becomes stronger as the transfer means approaches the image carrier. 4. The image forming apparatus according to claim 1, wherein the proximity means is a gear whose rotation speed decreases as the transfer means approaches the image carrier. 5. The image forming apparatus according to claim 1, wherein the proximity means is provided only at one end of the transfer means.