JPH03225383A - Transfer device - Google Patents

Abstract

PURPOSE:To make transferring of a toner image good by either making a surface of an upstream side insulation guide on the side facing a destaticizing discharge member vertical, or making the surface inclined so that the guide leading tip is fallen in the direction of the destaticizing discharging member. CONSTITUTION:The paper carrying path 51 shown by a dotted line is the tangent of the upstream side guide roll 52 and a downstream side paper carrying roll 53. The upper stream side insulating guide 57A has its surface on the side constituting a groove 58 vertical. The outer periphery of the leading tip part P2 of the guide 57A is processed to a curved line, and is provided to proceed the paper in the direction of the downstream side guide 57B. With a leading tip of a destaticizing needle 59 as an origin, an angle formed by a vertical line 63 from this origin and a segment 64 which is passed through the origin and the downstream side edge part of the leading part P2 is made a separating charge discharge angle beta1. A discharging range shown by this angle beta1 is mainly utilized to separate the paper. Thus, the increase of the discharging angle for separation is prevented, and good transfer of a toner image against the paper can be secured.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a transfer device used in an image forming apparatus such as a copying machine, a facsimile machine, a laser printer, etc., which forms a toner image on a photoreceptor.

``Prior art'' Many copying machines use a photoreceptor, on which an electrostatic latent image corresponding to the original is formed and then developed with toner, and this toner image is transferred and fixed onto paper to create the desired image. You are now getting a copy of the . Other image forming apparatuses using photoreceptors, such as facsimile machines and printers, also create a recording surface using the same principle after forming an electrostatic latent image on the photoreceptor.

FIG. 6 shows an example of a conventionally used transfer type image forming apparatus (Japanese Unexamined Patent Publication No. 126571/1983). In this transfer type image forming apparatus, an electrostatic latent image is formed on the surface of the photoreceptor drum 111 by an electrostatic latent image forming section 112 . This electrostatic latent image is developed in a developing section 113 to create a toner image. The toner image is transferred onto paper 115 by a transfer corotron (transfer charger) 114 .

The photosensitive drum 111 of this device has a diameter φ of 35 mm.
Since a material having a large curvature is used, the paper 115 after transfer starts to separate due to the synergistic effect of its stiffness and its own weight. The paper 115 after separation is separated by the separation guide 11
6, the electric charges present on the back surface of the paper 115 are removed by the charge eliminating member 117 that is close to or in contact with the back surface of the paper. As the static eliminating member 117, for example, a static eliminating brush made of a grounded carbon wire or the like is used. After the toner image has been transferred from the photosensitive drum 111, residual toner is removed by a cleaning section 118.

In such a transfer type image forming apparatus, the discharging member 117 is arranged so that the angle θ between the terminal end of the transfer corona on the photoreceptor drum 111 and the discharging member 117 is 30 degrees or more measured from the center of the photoreceptor drum 111. It is said that it is desirable that the terminal end of the transfer corona and the static eliminating member 117 be separated by 5 mm or more. In cases other than these, it is said that the transferred corona may flow to the static elimination brush 117, causing transfer failure and making it impossible to obtain a good image.

As described above, in the conventionally proposed transfer type image forming apparatus, the paper is naturally peeled off from the photoreceptor drum. Therefore, in copying machines that use paper that is weak or uses a photoreceptor drum with a relatively small curvature, there is a drawback that the paper cannot be separated properly.

Conventional techniques for removing paper that has been electrostatically attracted to the photoreceptor drum include blowing compressed air onto the leading edge of the paper, and placing a finger member in contact with the surface of the photoreceptor drum. There existed a method of peeling off the leading edge of the paper or a method of arranging a separation charger downstream of the transfer corotron.

However, the method of blowing compressed air onto the leading edge of the paper has the problem that the toner image existing in this area is blown away by the compressed air, resulting in the image in this area appearing white. Further, the method of keeping the finger member in contact with the surface of the photoreceptor drum has the problem that the drum surface is easily damaged. Furthermore, in the method of arranging separate chargers in parallel, there is a problem that there is no space for the arrangement when the diameter of the photoreceptor drum is relatively small.

Therefore, a transfer device has been proposed that easily removes the charge at the leading end of the paper charged by a transfer corotron and peels it off.

Japanese Patent Laid-Open No. 58-58570 proposes to provide a conductive static eliminating member with one end grounded on the downstream side of the transfer corotron, and to bring its tip close to the photoreceptor to a distance of about 0.5 to 2 mm. has been done. However, such a transfer device cannot separate thin paper from the photoreceptor. Therefore, proposals have also been made to apply a bias voltage to this static eliminating member. However, in such a proposed transfer device, since the distance between the photoreceptor and the charge eliminating member is narrow, there is a problem in that when a sheet of paper touches the charge eliminating member in a high humidity condition, an image may not be transferred.

FIG. 7 shows the main parts of a transfer device proposed to solve this problem and an image forming apparatus using the transfer device. A developing roll 122 for developing an electrostatic latent image formed by an electrostatic latent image forming means (not shown) and a developing device 123 containing the same are arranged at a predetermined position on the outer periphery of the photosensitive drum of the image forming apparatus. ing. A paper guide 124 , a registration roller 125 , and a pinch roller 126 are arranged below the developing device 123 . The registration roller 125 and the pinch roller 126 are connected to the spring 127.
are pressed against each other.

The paper sent out from a paper feed tray (not shown) is guided by the paper guide 24 and passes between the registration rollers 25 and the pinch rollers 126, and at this time, the timing at which the leading edge of the paper is sent out is adjusted. A lower guide member 131 is arranged closer to the photoreceptor drum 121 than the pinch roller 126 with a predetermined spacing from an upper guide member 129 arranged at the bottom of the developing device 123. It serves as a conveyance path for paper. Lower guide member 13
1 v! A static eliminating brush 132 is installed at the end portion so that its tip is located near the upper guide member 129, and is configured to eliminate static from the paper passing through both guides 129 and 131.

The neutralized paper is guided by a guide roll 133 and passes between the photosensitive drum 121 and the transfer device 134. At this time, a toner image is transferred from onto the photosensitive drum 121. Thereafter, the paper is neutralized by a static elimination needle 135 disposed downstream of the transfer device 134, peeled off from the photoreceptor drum 121, and transported by a paper transport roll 136 to a fixing device (not shown), where it is thermally heated. After being fixed on the image, it will be discharged outside the machine.

The path indicated by the dotted line in FIG. 7 indicates the paper conveyance path 138. The transfer device 134 includes this paper conveyance path 138.
Although it is highly unlikely that paper that has deviated from the shield case 139 will break the corotron wire 141, in order to prevent the paper from burning due to high pressure being applied to the wire while the paper is still in the transfer case, device 134
A paper entry prevention guide 142 using an insulated wire is arranged here.

FIG. 8 specifically shows the vicinity of this transfer device. The shield case 139 of the transfer device 134 is covered with an insulator 145 around the shield case 139 .

The upper part of the insulator 145 on the downstream side of the shield case 139 has a V-shaped notch, and a plate-shaped static elimination needle 135 is arranged to vertically bisect the notch from the center. has been done. This static elimination needle 135
In this specification, the portion between the shield case 139 and the shield case 139 will be referred to as an upstream insulating guide 145A, and the portion to the left of the static elimination needle 135 will be referred to as a downstream insulating guide 145B.

Now, in the transfer device 134, a high positive voltage is applied to the corotron wire 141, and a high negative voltage is applied to the static elimination needle 135. In Figure 7, the registration roller 125
After passing through the corotron wire 141 (!: rolled case 139), the toner image is transferred to the paper at a position (transfer position) directly above the transfer corotron.
5C is for preventing the discharge current from the corotron wire 141 from reaching the front side of the transfer position, thereby preventing the occurrence of blurring of the image during transfer.

When the toner image is transferred, the paper is affected by the transfer discharge current emitted from the corotron wire 41, and the photosensitive drum 121
It is in a state where it is electrostatically adsorbed. When a negative polarity charge is applied to the paper in this state from the static eliminating needle 135,
The amount of charge on the positively charged paper is reduced to a level necessary only for the transfer of the toner image. As a result, the paper is separated from the photoreceptor drum 121 by its own weight and stiffness, passes above the downstream insulated guide 145B, and is transported by the paper transport roll 136 to the fixing device.

By the way, in the transfer device shown in FIG. 8, the distance A between the tip of the static eliminating needle 135 and the photosensitive drum 121 is set to 8 to 12 mm, and the opposing surfaces of the upstream insulating guide 145A and the downstream insulating guide 145B are The angle (opening angle) θ formed by the opening is set from 45° to 60°. Under such conditions, thin sheets of paper can be peeled off well from the photoreceptor drum 121 even in low humidity conditions, and it is also possible to prevent image transfer omissions in high humidity conditions.

``Problem to be Solved by the Invention'' However, in such a conventional transfer device, when the leading edge of the paper becomes uneven and wavy under high humidity conditions, this leading edge partially gets between the paper entry prevention guides 142. There have been cases where the tip has hit the tip P1 of the upstream insulated guide 145A. When a collision occurs with the leading end P, the sheet is largely displaced at the leading end, which may cause a toner image to be transferred, or the toner image to be transferred to a wrong position, resulting in blurring of characters, etc.

In addition, in the example shown in FIG. 8, the upstream insulating guide 145A
is considerably higher than the height of the static eliminating needle 135 and reaches a position just below the paper entry prevention guide 142. Therefore, when paper with a wavy leading edge is conveyed, the leading edge of the paper often hits the leading edge portion P1, which causes noticeable toner image transfer failure and blurring of characters, etc. near the leading edge of the paper. became.

By the way, as shown in FIG. 8, the static eliminating needle 135 protrudes a certain distance from the bottom of the 7-shaped portion formed by the upstream insulating guide 145A and the downstream insulating guide 145B. Therefore, the negative polarity charge emitted from the static eliminating needle 135 is not emitted within the same angle range as the opening angle θ, but is emitted over an angle slightly wider than this.

Now, a vertical line 147 starting from the tip of the static elimination needle 135 and passing through this point, and a vertical line 147 passing through this point and the upstream insulating guide 14
Line segment 14 passing through the downstream end of tip portion P1 of 5A
8 is defined as the separation charge release angle α1. The discharge region indicated by the separation charge emission angle α is the portion that mainly contributes to the separation of the sheets.

FIG. 9 shows an example of a transfer device designed to prevent corrugated paper from colliding with the upstream insulating guide. The same parts as in FIG. 8 are given the same reference numerals.

In the example shown in FIG. 9, the upstream insulating guide 145A
The height is reduced by cutting only the shaded portion 145A1. As a result, the new separation charge emission angle α2 becomes wider than the previous separation charge emission angle α1. As a result, a part of the discharge region indicated by the separation charge emission angle α2 approaches the transfer position directly above the corotron wire 141. In FIG. 9, for ease of understanding, the charge emitted from the corotron wire 141 is shown as a positive charge (2), and the charge emitted from the static eliminating needle 135 is shown as a negative charge e. The chevron-shaped curve indicated by a dashed line in the figure is a transfer discharge current distribution curve 151, and represents the distribution of positive charge discharge in transfer discharge. Particularly in the upper part of the distribution curve 151, positive polarity charges are concentrated, and the transfer position is included in this part.

However, in FIG. 9, as a result of the separation charge release angle α2 being wider than that in FIG. 8, negative polarity charges arrive close to the transfer position where positive polarity charges are concentrated.
As shown by the shaded area 152, it interferes with positive charges. As a result, positive charges and negative charges cancel each other out in this part, and the positive charges become weaker. As a result, toner image transfer failure occurs when the humidity is high, and separation failure occurs when the humidity is low.

Therefore, a first object of the present invention is to provide a transfer device that can reduce the height of the upstream insulating guide without increasing the separation charge emission angle.

A second object of the present invention is to provide a transfer device in which the charge emitted from the static elimination electrode does not adversely affect the charge emitted from the transfer corotron wire.

"Means for Solving the Problem" In the invention as claimed in claim 1, (i) a corotron wire j:g toner on a light body stretched in a box-like elongated metal case having an opening at one end; A transfer corotron to which a high voltage of polarity opposite to that of the image is applied; (11) attached to the wall of the metal case on the downstream side of the photoreceptor; an insulating guide forming a wall protruding from the wall, the wall surface facing the downstream side of the wall forming a vertical plane or a front end thereof forming a plane inclined downstream at a predetermined acute angle; (iii) A voltage that is located close to the wall surface on the downstream side of this insulated guide and located at a position lower than the height of the wall on the downstream side thereof and has a polarity opposite to the voltage applied to the discharge wire of the transfer corotron. The transfer device is equipped with a discharge member for static elimination to which a voltage is applied.

Then, the surface of the upstream insulating guide facing the discharge member for static elimination is made vertical or the slope of this surface is made more inclined than before so that the tip of the guide is tilted toward the discharge member for static elimination. According to the invention as claimed in claim 2, characterized in that the first object is to prevent an increase in the separation charge emission angle due to a decrease in the height of the upstream insulating guide, (1) an opening is disposed at one end. A transfer corotron, which applies a high voltage of opposite polarity to the toner image on the photoconductor to a corotron wire stretched inside a box-shaped elongated metal case, and (u) a transfer corotron, which is attached to the wall of the metal case downstream of the photoconductor. , this attached side constitutes a wall that protrudes in the direction of the photoreceptor from the tip of the case wall surface, and the distance between the paper conveyance path for receiving the toner image transfer and the tip of this wall. 4~
(iii) an insulated guide set at 4.4 mm; The transfer device is provided with a discharge member for static elimination to which a voltage of opposite polarity to the voltage applied to the wire is applied.

By regulating the distance between the paper conveyance path and the insulating guide, the height of the upstream insulating guide can be reduced within that range.

“Example, 1 Hereinafter, the present invention will be described in detail with reference to Examples.

FIG. 2 shows a schematic configuration of a laser printer using a transfer device according to an embodiment of the present invention.

This laser beam printer 11 includes a laser scanning device 12
It is equipped with The laser scanning device 12 is provided with a semiconductor laser 13 that modulates and outputs laser light according to an image signal. A laser beam emitted from this semiconductor laser 13 is incident on a polygon mirror 14, and is deflected according to this rotation.

After the deflected laser beam passes through the fθ lens 15, its traveling direction is changed by mirrors 16 and 17, and the laser beam is output from the laser scanning device 12.

A photosensitive drum 19 that rotates at a constant speed is arranged below the laser scanning device 12. The laser beam output from the laser scanning device 12 repeatedly scans a predetermined exposure position 21 of the photosensitive drum 19 in its axial direction, that is, in the main scanning direction. A charge corotron 22 is disposed slightly in front of this exposure position 21, facing the photoreceptor drum 19, so that the surface of the photoreceptor drum 21 is uniformly charged twice. By irradiating the charged photosensitive drum 21 with a laser beam, an electrostatic latent image corresponding to image information is formed on the drum surface.

This electrostatic latent image is developed by the developing device 24 on the drum surface downstream of the exposure position. Inside the developing device 24, there is a developing roll 25 for developing an electrostatic latent image by magnetically making the toner stand up, and a toner supply mechanism 26 for supplying the toner in the cartridge to the developing roll 25.
The following parts are arranged. A predetermined developing bias is applied to the developing device 24 .

The toner image formed by the development by the developing device 24 is moved to a position facing the transfer device 28 by the rotation of the photosensitive drum 19, where it is electrostatically transferred to recording paper (plain paper). .

Next, the transport path of the recording paper will be briefly explained. Recording sheets (not shown) are stacked on a cassette tray 31 that is removably disposed at the bottom of the laser beam printer 11.

The recording paper placed in the top layer of the cassette tray 31 is
It is sent out of the tray by a half-moon roll 32 having a half-moon shape. Other means such as a retard roll may be used instead of the half-moon roll 32.

The fed recording paper travels along the path indicated by the broken line by the conveyance roll 33, and its progress is temporarily stopped when it reaches the tip of the registration roll 34. Thereafter, an electromagnetic clutch (not shown) starts rotation of the registration roll 34 in synchronization with the rotational position of the photosensitive drum 19, and the recording paper starts to be stably transported at a constant speed. In this way, the recording paper passes between the photosensitive drum 19 and the transfer device 28 at a desired timing. Only at the time of this passage, the transfer corotron of the transfer device 28 discharges, whereby the toner image on the photoreceptor drum 19 is electrostatically attracted toward the transfer device 28, and the toner image is transferred onto the recording paper. It will be done. The recording paper on which the transfer has been performed is charged from its back surface by a charge eliminating needle (not shown) disposed in the transfer device 28, and is peeled off from the drum surface.

The peeled recording paper is conveyed along a conveyance path of a predetermined length to release the tension, and then conveyed to a fixing device consisting of a pair of heat roll 6 and pressure roll 8. In the fixing device, the recording paper passes between a heat roll 6 and a pressure roll 8 that are nipped at a predetermined width. At this time, the side of the recording paper onto which the toner image has been transferred becomes the heat roll 6 side, and the pressure roll 8 presses the recording paper against the heat roll 6 to enable efficient heat transfer. The heat roll 6 is controlled to a constant high temperature. In this state, the toner image on the recording paper is thermally fixed to the paper surface.

A switching valve 38 is provided on the exit side of the fixing device to switch the conveyance path of the recording paper after fixing. Depending on the switching operation of the switching valve 38, the recording paper after fixing will either go straight and be ejected in the first ejection direction 39, or it will be conveyed in an inverted U-shape within the device and will be ejected in the first ejection direction 39. It is discharged from the upper part of the laser beam printer 11 in a second discharge direction 41 in the opposite direction. The reason why two types of ejecting directions can be selected is to enable the selection of ejecting with the recording surface facing up or with the recording surface facing down. If the second ejection direction 41 is selected and the paper is ejected with the recording surface facing down, pages printed one by one can be bound with a stapler in the order in which they were ejected.

By the way, the toner image that has not been transferred to the recording paper is removed from the drum surface by the cleaning device 43. The cleaning device 43 includes a blade 44 for scraping toner from the drum surface and a rotating body 45 for evacuating toner particles accumulated under the blade 44 to a rear storage location.

FIG. 1 specifically shows the transfer device and its surroundings used in this laser printer.

The paper conveyance path 51 indicated by a dotted line in FIG. Paper transport roll 53 located immediately downstream of
It is a tangent line.

The point where the vertical line passing through the corotron wire 54 of the transfer device 28 intersects with the lower part of the photoreceptor drum 21 is the transfer position, and this point almost coincides with the point where the paper conveyance path 51 contacts the photoreceptor drum 21 . Corotron wire 5 of transfer device 28
The outer periphery of a shield case 56 surrounding 4 is covered with 57, similar to the conventional transfer device 134 shown in FIG. A groove 58 is cut in the axial direction of the photoreceptor drum 21 in the upper part of the insulator 57 on the downstream side of the remote from the shield case 56, and a plate-shaped static eliminator is cut in the axial direction of the photoreceptor drum 21. A needle 59 is arranged.

FIG. 3 shows the shape of the static eliminating needle.

The static eliminating needle 59 is almost connected to the photosensitive drum 121 (see Fig. 1)
It has a plate shape with the same length as , and has a sharp protrusion 59A on its side edge in the elongated direction. cusp 5
The pitch of 9A is 1 to 2 mm, and negative polarity charges are emitted from these protrusions. The pointed protrusion 59A can be created, for example, by etching. The smaller the pinch, the more uniform the discharge and the better the paper separation effect.

The base portion 59B of the static eliminating needle 59 excluding the etched portion is held between the insulators 57.

In FIG. 1, the static eliminating needle 59 and the shield case 59
The part between is called the upstream insulation guide 57A, and the part between the static elimination needle 5
The portion to the left of 9 in the figure will be referred to as the downstream insulating guide 57B.

The tip of the downstream insulated guide 57B is connected to the paper conveyance path 51.
A paper entry prevention guide 61 is arranged between this portion and the upper end of the shield case 59 to prevent paper from entering. The height of the upstream insulating guide 57A is lower than that of the downstream insulating guide 57B, and the distance B between the paper conveyance path 51 and the upstream insulating guide 57A is 4.0 to 4.4 mm. This means that the leading edge of the paper being conveyed is located at the upstream insulating guide 5.
This is to eliminate the possibility of contact with 7A as much as possible. The height of the static eliminating needle 59 is several mm lower than this.

The distance between the static eliminating needle 59 and the side surface 57A1 of the upstream insulating guide 57 is 0.5 to 0.7 mm.

The upstream insulating guide 57A has a vertical surface forming the a58. Further, the outer periphery of the tip portion P2 of the upstream insulating guide 57A is processed to form a curve that gently descends toward the portion that contacts the side wall of the shield case 59, such as a part of a circle. This is to ensure that even if the leading edge of the paper should come into contact with the upstream insulating guide 57A, the paper will move smoothly toward the downstream insulating guide 57B.

Now, the angle formed by the vertical line 63 starting from the tip of the static eliminating needle 59 and passing through this point, and the line segment 64 passing through this point and the downstream end of the tip portion P2 of the upstream insulating guide 57A. Let the separation charge release angle be β. The discharge area indicated by the separation charge emission angle β1 is the part that mainly contributes to separation of sheets.

As shown in FIG. 4, in the transfer device 28 of this embodiment, the groove 5
Since the side surface 57A1 of the upstream insulating guide constituting 8 is vertical, when the separation charge release angle β1 is set to be the same as the separation charge release angle α1 explained in FIG. The height of the upstream insulating guide 57A can be lowered by several mm than that of the upstream insulating guide 145A.

When the separation charge release angle β1 is equal to α1, there is no fear that the negative charges released from the static eliminating needle 59 cancel out the positive charges existing near the transfer position, and the paper can be transferred well. .

Moreover, since the height of the upstream insulating guide 57A has been significantly reduced, even if the leading edge of the paper is undulated when the moisture content is high, there is a risk that it will collide with the leading end P2 of the upstream insulating guide 57A. from 1/100 to 10
It can be reduced by a factor of 2. Moreover, since the outer periphery of this leading edge portion P2 is formed to be, for example, a part of a circle, there is no risk that the leading edge of the paper will be significantly deformed by this leading edge portion P2, and the toner image may not be transferred at the leading edge of the paper. Inconveniences such as blurring and blurring of characters can be virtually eliminated.

It should be noted that if the height of the upstream insulating guide 57, A is made lower than this, the separation charge emission angle β1 will expand accordingly, and there is a possibility that a transfer failure of the paper at the transfer position may occur. However, the side surface of the upstream insulating guide 57A does not need to be vertical, and its tip may protrude or be inclined slightly toward the static elimination needle 59 side. In this way, by configuring a surface where the wall surface is angled toward the downstream side by a predetermined acute angle, the separation charge emission angle β1 is pinched, and the toner image is Adverse effects on transcription can be avoided.

"Modification" FIG. 5 shows a modification of the transfer device applied to the laser printer shown in FIG. 2.

Components that are the same as those in FIG. 4 are designated by the same reference numerals, and their description will be omitted as appropriate.

In the transfer device 71 of this modification, the upstream insulating guide 57A
The distance between the leading edge of the sheet and the paper conveyance path 138 is set to 4.0 to 4.4 mm as in the previous embodiment. The separation charge release angle β2 at this time is set to be the same as the separation charge release angle β1 of the previous embodiment. For this reason, the width of the tip of the upstream insulating guide 57A' is wider than that of the conventional upstream insulating guide 145A.

Generally, when the width of the upstream insulating guide 57A' becomes wider,
If this is molded from plastic, sink marks, warpage, etc. may occur and dimensional accuracy may not be obtained. In such a case, there is a possibility that uneven discharge of negative polarity charges necessary for static elimination may occur. If there is such a possibility, the surface 57A'2 of the upstream insulating guide 578' on the transfer corotron side may be shaped as shown in FIG. 4 by appropriately cutting it.

Furthermore, if the width of the upstream insulating guide 57A' is simply widened, the side surface 57A'l of the upstream insulating guide on the side forming the groove 58' and the tip of the static eliminating needle 59 may become too close to each other, resulting in dielectric breakdown. This part may deteriorate. Therefore, it is desirable to determine the degree of inclination of the side surface 57A'l so that the distance between the side surface 57A'l and the tip of the static eliminating needle 59 can be kept at least 0.5 mm.

"Effects of the Invention" As explained above, according to the invention as claimed in claim 1, the surface of the upstream insulating guide facing the discharge member for static elimination is made vertical or the inclination of this surface is made more than before. The tip of the guide is tilted toward the discharge member for static elimination, which prevents the separation charge release angle from increasing due to the decrease in the height of the upstream insulated guide, and improves the transfer of the toner image onto the paper. can be ensured.

According to the second aspect of the invention, the distance between the tip of the insulating guide attached to the side wall of the shield case of the transfer corotron and the paper conveyance path is 4 to 4.4 m.
Since the spacing is set to m, even if the leading edge of the paper is wavy, the risk of the leading edge of the paper hitting this leading edge of the insulating guide can be largely avoided. Moreover, since this tip portion regulates the direction of the charge emitted by the discharge member for static elimination, there is an effect that the transfer of the toner image onto the paper is not adversely affected.

[Brief explanation of drawings]

Figures 1 to 4 are for explaining one embodiment of the present invention, of which Figure 1 is a front view specifically showing the transfer device and its surroundings, and Figure 2 is a front view of the transfer device. A schematic configuration diagram of the laser printer used, Fig. 3 is a plan view of the static elimination needle, Fig. 4 is a front view comparing the transfer device of this embodiment with a conventional one, and Fig. 5 is a modification of the transfer device. As an example, FIG. 6 is a front view showing the main parts, FIG. 6 is a principle diagram showing the main parts of an example of a conventionally used transfer type image forming apparatus, and FIG.
The figure is a front view showing the main parts of a conventionally proposed transfer device and an image forming apparatus using the same, FIG. 8 is a front view specifically showing the vicinity of the transfer device of the device shown in FIG. 7, and FIG. The figure is an explanatory diagram for explaining problems caused by lowering the upstream insulating guide. 21...Photosensitive drum, 28...Transfer device, 51...Paper transport path, D4...Corotron wire, D6... Shield case, 57...Insulator, 57A...Upstream insulation guide, 57B
...Downstream insulation guide, 9...Static elimination needle.

Claims (1)

[Claims] 1. A transfer corotron in which a high voltage of opposite polarity to the toner image on the photoreceptor is applied to a corotron wire stretched within a box-shaped elongated metal case with an opening at one end; attached to the wall surface of the metal case downstream of the photoconductor;
This attached side constitutes a wall that protrudes toward the photoreceptor than the tip of the case wall surface, and the wall surface facing downstream of this wall is a vertical plane or the tip of the case wall is vertical. an insulating guide having a surface inclined at a predetermined acute angle toward the downstream side; and an insulating guide disposed adjacent to the downstream wall surface of the insulating guide at a position downstream of this and lower than the height of the wall. A transfer device comprising: a discharge member for neutralizing static electricity to which a voltage of opposite polarity to the voltage applied to the discharge wire of the transfer corotron is applied. 2. A transfer corotron, in which a high voltage of opposite polarity to the toner image on the photoreceptor is applied to a corotron wire stretched inside a box-shaped elongated metal case with an opening at one end, and the photoreceptor in the metal case. Attached to the downstream wall,
This attached side constitutes a wall that protrudes toward the photoconductor from the tip of the case wall surface, and there is a gap between the paper conveyance path for receiving the toner image transfer and the tip of this wall. is set to 4 to 4.4 mm, and an insulated guide disposed close to the downstream surface of the insulated guide at a position lower than the height of the wall on the downstream side thereof, and the electric discharge of the transfer corotron. 1. A transfer device comprising a discharge member for static elimination to which a voltage of opposite polarity to a voltage applied to a transfer wire is applied.