JP2004142871A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide new constitution to secure carriage stability not to cause image turbulence at the time when a recording medium is carried along the side of a carrier guide plate even when an environmental condition and a condition of the used recording medium are changed. <P>SOLUTION: Both ends of a suction member 11 made of an electrically conductive member grounded on an image forming apparatus main body are mounted on the carrier guide plate 8 free to slide on an eccentric shaft 13a of a stepping motor 13 through a slot 15a of a supporting member 15. An upper surface of the suction member 11 reinforces carrying force by approaching an upper surface of the carrier guide plate 8 when electrifying quantity of the recording medium is not very large due to high temperature and high humidity and prevents electric discharge from the recording medium by separating from the suction member 11 on the contrary when the electrifying quantity becomes large due to low temperature and low humidity. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
[Industrial applications]
The present invention relates to an image forming apparatus such as a copying machine, a laser beam printer, and the like, and more particularly, to a technique of transport stability from an image being transferred to a recording medium to being fixed.
[0002]
[Prior art]
FIG. 8 is a diagram illustrating an example of the image forming apparatus.
In the figure, reference numeral 1 denotes a photosensitive drum, 2 denotes a charging roller, 3 denotes an exposure device, 4 denotes a developing device, 5 denotes a paper feed tray, 6 denotes a registration roller, 7 denotes a transfer roller, 8 denotes a conveyance guide plate, and 9 denotes a fixing device. The devices 10 and 10 respectively indicate paper discharge trays.
The photosensitive drum 1 whose surface is uniformly charged by the charging roller 2 is exposed to light modulated by image information from the exposure device 3, and an electrostatic latent image corresponding to an image is formed on the surface of the photosensitive drum 1. Formed. The electrostatic latent image is visualized by the developing device 4 to become a toner image. A recording medium S such as paper or an OHP sheet is sent out from the paper feed tray 5, temporarily stopped at a registration roller 6, and further sent out in synchronization with a photosensitive drum-shaped toner image.
[0003]
A transfer roller 7 to which a predetermined transfer bias is applied is pressed against the photosensitive drum 1 at a proper timing to form a transfer nip. The recording medium S sent from the registration roller 6 is transferred from the photosensitive drum 1 to the recording medium S by passing through the transfer nip, and is sent to the fixing device 9 along the conveyance guide plate 8. The toner image on the recording medium S is fixed as a permanent image on the recording medium S by heat or other means.
[0004]
Normally, when transferring the toner image, a predetermined current is controlled to flow to the transfer roller 7, and this current flows from the transfer roller shaft to the transfer roller portion, passes through the recording medium S, and is transferred to the photosensitive drum 1. It's flowing. The resistance value of the transfer roller portion changes significantly due to environmental changes such as temperature. In particular, at low temperatures, the resistance of the transfer roller section is several tens times higher than at room temperature. Therefore, a high potential may be applied to the recording medium S in some cases.
[0005]
Further, it is more stable to change the current flowing through the transfer roller 7 depending on the type of the recording medium S, so that the toner image on the photosensitive drum 1 can be transferred. This is because if the transfer current is not increased when the thickness of the recording medium S increases, the toner image on the photosensitive drum 1 is difficult to be transferred onto the recording medium S, and a higher potential needs to be applied to a transfer material such as OHP. . Further, when the width of the recording medium S is reduced, a portion where the transfer roller 7 directly contacts the photosensitive drum 1 increases, and a transfer current flows to a portion where the transfer roller 7 contacts the photosensitive drum 1. In order to transfer the image onto the medium S, it is necessary to increase the value of the current flowing through the transfer roller 7, and therefore, the charge amount of the recording medium S increases.
[0006]
Originally, the recording medium S is conveyed along the conveyance guide plate 8. Thus, when the recording medium S is conveyed while being charged from a low potential to a high potential, the recording medium S is transferred to the conveyance guide plate 8. The recording medium S may be conveyed out of the way, and the upper surface of the recording medium S may come into contact with a guide or the like. As a result, the toner image on the recording medium S may be rubbed, resulting in an abnormal image. Therefore, a grounded conductive member is arranged as an electrostatic suction member in the vicinity of the conveyance path of the recording medium S, and the recording medium S is attracted to the conveyance guide plate 8 to be conveyed (for example, And Patent Document 1.).
[0007]
When the charging of the recording medium S is at a low potential, the recording medium S cannot follow the conveyance guide plate 8 unless the suction member is brought close. In the case of a high potential, if the suction member is brought too close, the charge on the transfer paper is discharged to the conductive member at a stretch, and the toner on the recording medium S is scattered by this discharge, and the image may be disturbed. is there. As a configuration for solving such a problem and stabilizing the conveyance of the recording medium, there is known a method in which the suction force of the suction member is varied depending on the location along the conveyance direction of the recording medium S (for example, see Japanese Patent Application Laid-Open No. H11-163873). Reference 2).
[0008]
[Patent Document 1]
JP 2001-199592 A (Claims 1 and 3)
[Patent Document 1]
JP-A-8-96325 (Claim 1, FIG. 1)
[0009]
[Problems to be solved by the invention]
The present invention provides a new configuration that ensures transport stability without image disturbance when the recording medium is transported along the transport guide plate side even when the environmental conditions and the conditions of the recording medium to be used change. The purpose is to do.
[0010]
[Means for Solving the Problems]
In the image forming apparatus according to the first aspect of the present invention, the image forming apparatus includes a transfer unit, a fixing unit, and a guide member that guides a recording medium on which the toner image has been transferred by the transfer unit to the fixing unit. A conductive suction member, which is grounded and electrostatically sucks the recording medium, is disposed near the passage surface of the recording medium, and the distance between the suction member and the passage surface is variable. It is characterized by.
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the suction member changes a distance between the suction member and the recording medium passage surface in accordance with a change in environmental temperature.
[0011]
According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, a bimetal is used as a means for changing a distance between the suction member and the passage surface.
According to a fourth aspect of the present invention, in the image forming apparatus according to the second aspect, a shape memory alloy is used as a means for changing a distance between the suction member and the passage surface.
According to a fifth aspect of the present invention, in the image forming apparatus according to the first aspect, the suction member changes a distance between the suction member and the passage surface in accordance with an environmental temperature change and a type of a recording medium. I do.
[0012]
According to a sixth aspect of the present invention, in the image forming apparatus according to the first aspect, the suction member changes a distance between the suction member and the passage surface in accordance with an environmental temperature change and a size of a recording medium. I do.
According to a seventh aspect of the present invention, in the image forming apparatus according to the first aspect, the suction member sets a distance from the passage surface to an environmental temperature change, a type of a recording medium, and a size of the recording medium. It is characterized by changing.
[0013]
According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first, second, and fifth to seventh aspects, a stepping motor is provided as means for changing a distance between the suction member and the passage surface. It is characterized by having.
According to a ninth aspect, in the image forming apparatus according to any one of the first to eighth aspects, the upper surface of the suction member is parallel to the passage surface.
According to a tenth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects, the upper surface of the suction member is closer to the transfer unit than the fixing device side with respect to the passage surface. It is characterized by being distant from the side.
[0014]
【Example】
Hereinafter, the present invention will be described with reference to Examples.
FIG. 1 is a perspective view of a unit including the transport guide unit of the present invention.
In the figure, reference numeral 11 indicates a suction member. Other symbols are the same as those in FIG.
In this unit, the lower registration roller 6, the transfer roller 7, and the conveyance guide plate 8 are integrated, but the registration roller 6 is not necessarily required to be integrated.
In the transport guide plate 8, a plurality of elongated plates connected to each other are arranged with a gap at substantially equal intervals, and the suction member 11 formed in a plurality of elongated plates does not contact each of the gaps. They are integrally supported by a movable member so as to be able to enter and exit up and down with a margin.
[0015]
FIG. 2 is a sectional view of a substrate portion of the unit shown in FIG. 1 including a transport guide plate.
In the drawing, reference numeral 12 denotes a bimetal as a movable member, and a denotes a distance from the upper surface of the transport guide plate 8 to the upper surface of the suction member 11, respectively. Since there is no risk of confusion, hatching of the cross section is omitted. The same applies to the following drawings.
Both ends of the suction member 11 are fixed to the transport guide plate 8 via bimetals 12, respectively. The suction member is made of a conductive material and is grounded to the main body of the image forming apparatus.
[0016]
FIG. 3 is a diagram showing a case where the environmental temperature is low in the configuration of FIG.
The upper surface of the suction member 11 is formed parallel to the upper surface of the transport guide plate 8, and the distance a between the upper surfaces changes depending on the degree of bending corresponding to the environmental temperature of the two bimetals 12. When the environmental temperature is high, the value of a is set to be approximately 0, and the upper surface of the suction member 11 and the upper surface of the transport guide plate 8 are set to be substantially flush. When the environmental temperature is low, the value of “a” increases, and as shown in FIG. 3, the upper surface of the suction member 11 becomes lower.
[0017]
Therefore, when the environmental temperature is high and the charge amount of the recording medium S is not so large, the suction member 11 approaches the passage of the recording medium S and increases the suction force. When the charge amount is large, the suction member 11 is moved away from the passage of the recording medium S so that the suction force is appropriately reduced, and no discharge from the recording medium S to the suction member 11 occurs.
[0018]
2 and 3, a shape memory alloy may be used instead of the bimetal. The shape memory alloy has a property of returning to a previously stored shape when the temperature is increased and reaches a specific transition temperature, even if the alloy is deformed to some extent. There are alloys whose shape does not change even when the temperature is lowered, and alloys which return to the shape before the temperature is raised when the temperature is lowered. If the transition temperature of the alloy is properly selected within the range of the temperature change inside the image forming apparatus, a change similar to a bimetal can be made.
[0019]
As described above, since the charge amount of the recording medium S changes depending on the type and size of the recording medium S, the distance between the suction member 11 and the recording medium S is changed in accordance with the change, so that a better guide of the recording medium S is achieved. The method of carrying is shown below.
FIG. 4 is a block diagram showing a relationship for controlling a stepping motor according to environmental conditions and recording medium conditions.
In the figure, reference numeral 13 denotes a stepping motor, 14 denotes a motor drive control unit, ST denotes a temperature sensor, SH denotes a humidity sensor, and OP denotes an operation panel.
[0020]
The charge amount of the recording medium S is affected not only by the environmental temperature but also by the humidity. If the humidity is high, depending on the type of the recording medium, the resistance value may decrease and the charge amount may decrease. Therefore, a sensor SH for detecting humidity is provided as an environmental condition in addition to the temperature sensor ST. As described above, the width and size of the recording medium S are important as conditions for the recording medium S. Means for designating and inputting these by the operator are provided on the operation panel OP, and the CPU having obtained the respective conditions issues necessary instructions to the motor drive control means 14 to drive the stepping motor 13. The use of a stepping motor can be used without any problem even in the above-described device corresponding only to the environmental temperature. In such a case, only the temperature sensor ST needs to be used as condition detecting means.
[0021]
FIG. 5 is a diagram showing a configuration in which the value of the distance a is changed in consideration of the environmental conditions and the conditions of the recording medium.
FIG. 6 is a diagram showing a state in which the value of the distance a is increased in the configuration shown in FIG.
In both figures, reference numeral 15 denotes a support member.
[0022]
Both ends of the suction member 11 are supported by the support member 15 and are regulated by a known mechanism (not shown) so that the suction member 11 can move vertically in parallel. The stepping motor 13 has an eccentric shaft 13a at a position slightly distant from the rotation shaft, and is slidably attached to an elongated hole 15a provided substantially at the center of the support member 15. The amount of eccentricity of the eccentric shaft 13a is set to one half or more of the maximum size required for the distance a.
[0023]
The motor drive control means 14 instructed by the CPU for the control amount rotates the stepping motor 13 to move the suction member 11 up and down to the target position.
Accordingly, the suction member 11 can be moved closer to or farther from the passage of the recording medium S in response to changes in environmental conditions and recording medium conditions, so that stable conveyance of the recording medium can be guaranteed. Become.
The configuration is substantially the same as the configuration in which an eccentric cam is used instead of the eccentric shaft 13a and the elongated hole 15a and the support member 15 is brought into contact with the eccentric cam with a pressing force.
[0024]
The force of the suction member 11 for sucking the recording medium S does not need to be constant at all positions in the transport direction. As the recording medium S moves away from the transfer nip, the resistance that the recording medium S receives from the conveyance guide plate 8 increases. In the case of a so-called stiff recording medium, a phenomenon in which the vicinity of the leading end sticks to the conveyance guide plate 8 and becomes immobile tends to occur. In view of this, the upper surface of the suction member may not be parallel to the passage surface of the recording medium S, and may be inclined and installed so that the distance on the fixing device side is larger than that on the transfer unit side. However, the vertical movement of the suction member is in principle parallel movement.
FIG. 7 is a diagram illustrating a configuration in which the upper surface of the suction member is not parallel to the passage surface of the recording medium.
In the case of this configuration, the distance a between the upper surface of the suction member and the passing surface is an average value of the distances, in other words, the distance at the center of the upper surface of the suction member 11 in the length direction.
[0025]
【The invention's effect】
According to the present invention, in response to changes in environmental conditions, changes in the recording medium to be used, and the like, the transferred recording medium can be sent to the fixing device while being conveyed with an appropriate suction force. Abnormalities such as rubbing of the toner image and toner scattering during conveyance can be eliminated. .
[Brief description of the drawings]
FIG. 1 is a perspective view of a unit including a transport guide section of the present invention.
FIG. 2 is a sectional view of a substrate portion of the unit shown in FIG. 1 including a transport guide plate.
FIG. 3 is a diagram showing a case where the environmental temperature is low in the configuration of FIG. 2;
FIG. 4 is a block diagram showing a relationship for controlling a stepping motor according to environmental conditions and recording medium conditions.
FIG. 5 is a diagram showing a configuration in which the value of a distance a is changed in consideration of environmental conditions and recording medium conditions.
FIG. 6 is a diagram showing a state when the value of a distance a is increased in the configuration shown in FIG. 5;
FIG. 7 is a diagram illustrating a configuration in which an upper surface of a suction member is not parallel to a passage surface of a recording medium.
FIG. 8 is a diagram illustrating an example of an image forming apparatus.
[Explanation of symbols]
8 Conveyance guide plate 11 Suction member 12 Bimetal 13 Stepping motor 14 Motor drive control means

Claims (10)

In an image forming apparatus including a transfer unit, a fixing unit, and a guide member that guides a recording medium onto which a toner image has been transferred by the transfer unit to the fixing unit, the guide member has a vicinity of a passage surface of the recording medium. An image recording apparatus, wherein a conductive suction member that is grounded and electrostatically suctions the recording medium is arranged, and a distance between the suction member and the passage surface is variable. . 2. The image forming apparatus according to claim 1, wherein the suction member changes a distance between the suction member and the recording medium passage surface in accordance with a change in environmental temperature. 3. The image forming apparatus according to claim 2, wherein a bimetal is used as a unit that changes a distance between the suction member and the passage surface. 3. The image forming apparatus according to claim 2, wherein a shape memory alloy is used as a means for changing a distance between the suction member and the passage surface. 2. The image forming apparatus according to claim 1, wherein the suction member changes a distance between the suction member and the passage surface in accordance with a change in environmental temperature and a type of a recording medium. 2. The image forming apparatus according to claim 1, wherein the suction member changes a distance between the suction member and the passage surface in accordance with a change in environmental temperature and a size of a recording medium. 2. The image forming apparatus according to claim 1, wherein the suction member changes a distance from the passage surface in accordance with a change in environmental temperature, a type of a recording medium, and a size of the recording medium. 3. Image forming device. The image forming apparatus according to claim 1, wherein a stepping motor is used as a unit that changes a distance between the suction member and the passage surface. Forming equipment. 9. The image forming apparatus according to claim 1, wherein an upper surface of the suction member is parallel to the passage surface. 9. The image forming apparatus according to claim 1, wherein the upper surface of the suction member is further away from the passage unit on the fixing device side than on the transfer unit side. 9. Characteristic image forming apparatus.

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