JPS5934570A - Picture forming device - Google Patents

Abstract

PURPOSE:To perform stable, excellent transfer, by grounding members in front of and behind a transfer position where a transferring material is contacted through respective impedance elements, and setting the values of the impedance elements correlatively. CONSTITUTION:A current iT flows through paper P by the discharge of a transfer corona discharger 5; a current i1 flows to a grounding part through transferring material guides 2 and 3 and a current i2 flows through fixing rolls 6 and 7 respectively. In this case, iT=i1+i2, VT(R1R2/R1+R2)iT, where VT is the transfer part potential of the transferring material P and R1=Crho+A and R2=Drho+ B, where C and D are distances between a transferring device, and transfer material guides 2 and 3 and fixing rolls 6 and 7 and P is the resistance value of the transferring material P per unit length at high humidity. It is necessary to apply an enough transfer electric field to the transferring material P at the transfer part for an excellent transfer picture free of transfer defect and for this purpose, the transfer part potential VT is only set higher than a minimum potential Vmin for transfer; the resistance values A and B of the impedance elements 8 and 9 are therefore determined correspondingly.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus, and more specifically, the developed image on an image carrier is transferred by corona onto a transfer blade guided by a transfer material guide, and the transferred image on the transfer material is transferred. ll1j fixed by fixing means
The present invention relates to an image forming apparatus.

Conventionally, in PPC type image forming apparatuses, corona transfer is commonly used in which corona discharge is applied to the back side of a transfer material for transfer.

By the way, in the case of the corona transfer method, it is necessary to maintain a predetermined transfer voltage and apply sufficient transfer corona discharge for good transfer. However, since the resistance of the transfer material decreases when the humidity is high, the transfer current is very likely to leak.

For this reason, when the transfer material is in the transfer section, all the members that the transfer material comes into contact with are insulated or electrically suspended.
Under high humidity conditions, the flow of transfer current from the transfer material causes the transfer material guide and other conveyance members that come into contact with the transfer material in the vicinity of the transfer area to become high potential, resulting in permanent stains due to toner scattering. 5. In order to prevent the leakage of transfer current that causes such transfer defects, it has been proposed that a transfer material guide or the like that comes into contact with the transfer material is grounded via an impedance element.

However, in experiments conducted by the present inventors, it was found that even if the impedance elements connected to each member were individually set to optimal conditions, efficient transfer could not necessarily be achieved.

The present invention has been made in view of the above points, and relates to an image forming apparatus that enables efficient transfer.

Hereinafter, details of the present invention will be explained by way of specific examples with reference to the drawings.

FIG. 1 is an explanatory diagram of main parts of a specific example image forming apparatus according to the present invention.

S denotes an image carrier that supports a photoreceptor or the like in the form of a drum, and rotates in the direction of the arrow. A latent image forming means and a developing means (not shown) are arranged along the circumference of the image carrier S, and a transfer corona discharger 1 is arranged at the transfer position. A cleaning means (not shown) is arranged to act on the image carrier after the transfer is completed. 2 and 6 are transfer material guides that guide the transfer material to a transfer position, and 4 is a timing roller. 5 is a shield case of the transfer corona discharger 1, and 06 and 7 are fixing rollers of the fixing means.

8 and 9 are resistors provided as impedance elements interposed between the transfer material guide, the fixing means, and the ground, respectively. 1
0 is a high-voltage power supply for the transfer corona discharger, and 11 is a separation roller for the transfer material. 12 is a conveyance guide. In the illustrated apparatus, the transfer material guides 2 and 3 and the fixing roller 7 of the fixing means are substantially used as transfer current leak starter members.

In the above-described apparatus, a latent image is formed on the image carrier S by a latent image forming means (not shown), and the latent image is developed by a developing means. In synchronization with the development images on the image carrier reaching the transfer position, the transfer material P fed by the timing roller 4 passes between the transfer material guides 2 and 3 and is guided to the transfer position. At the transfer position, a transfer corona is first applied from the back side near the leading edge of the transfer material by the transfer corona discharger 1, and the leading edge of the transfer material passes through the rollers 11 and the conveyance guide 12, and is then transferred between the rollers 6 and 7 of the fixing means. reach. At this time as well, the transfer corona is applied to the central portion of the transfer material from the back surface, and the rear end of the -1 transfer material remains in contact with the transfer material guides 2 and 6. (First illustrated state) Next, the rear end of the transfer material also passes through the transfer position, and successively passes through the fixing means position. This completes the transfer and fixing onto the transfer material. As described later, the impedance element connected to the transfer material guide and the fixing means is
Since they are set in a correlated manner, good transfer conditions can be maintained even in the case where the leading edge of the transfer material is at the transfer material guide position.

That is, in the apparatus of the present invention, there are two cases in which the transfer material contacts a member on the intrusion side with respect to the transfer position and a transfer current leak occurs only from the intrusion side, and another case in which the transfer material contacts a member on the ejection side with respect to the transfer position. In addition to the case where transfer current leakage occurs only from the discharge side, the case where transfer current leakage occurs from both the intrusion side and the discharge side is also well countered.

Hereinafter, the principle of the device of the present invention will be schematically explained using an equivalent circuit.

FIG. 2 is an equivalent circuit of the first illustrated device.

A and B are the resistance values of resistors 8 and 9, respectively, C and D are the distances between the transfer device, transfer material guides 2 and 3, and fixing rows 26 and 7, respectively, and 9 is the unit length of the transfer material T at high humidity. This is the resistance value of the satatashi.

Due to the discharge of the transfer corona discharger 5, a current LT flows through the paper, a current tl flows to the grounding portion through the transfer material guide, and a current ill flows to the grounding portion through the fixing roller.

In this circuit, y =, = illis (1). Here, 7 is the transfer part potential of the transfer material, and R, l
-Cρ1A, R*-firstborn B.

Incidentally, in order to obtain a good transferred image without transfer defects, it is necessary to apply a sufficient transfer electric field to the transfer material at the transfer section. For this purpose, the transfer part potential VT of the transfer material is
must be set higher than the minimum potential required for transfer.

Letting Vvmin be the minimum potential required for transfer, a good image without transfer defects can be obtained by satisfying Vvmin. For this reason, the values of the aforementioned impedance elements 8 and 9 are determined accordingly.

For example, process speed 66 nul/See,
Drum diameter 60φ, transfer high pressure 5-5KV, C-2C
In the image forming apparatuses II+ and D-15cn+, the current il flowing from the transfer material guide is measured, and the transfer material potential required for an image without transfer defects is calculated using the following formula (%).
1 That is, in the above-mentioned inverted image forming apparatus, Vrm r n −1
ooav). Based on this, determine A and B.

In addition, in the above-mentioned image forming apparatus, guide stains occur depending on the transfer material potential, so the relationship is shown in Table 2. Therefore, when considering transfer material guide stains, VT-13
It is effective to set the voltage to 00 (V). Taking these points into consideration, by setting R1 and Rs to the values of A and B based on the conditions, it is possible to obtain a good image without transfer defects, and further improve the transfer material. It won't stain the guide.

In addition, in the specific example image forming apparatus described above, if the current ir flowing through the paper is set to 20 (μA), and A-9Q (MΩ) and B-so (MΩ) are set so as to satisfy equation (4), Transfer defects such as transfer omissions do not occur. At this time, a high humidity environment (3
0'C, 90% RH) and fix it under 6.
With anti-H6 conversion, when evaluating □, the results are as shown in Table 3.

Table 3 As shown in Table 3, by satisfying the above-mentioned formula (5), good transfer is possible and guide stains can be prevented.

Fig. 6 shows an example in which constant voltage elements (varistors) 8' and 9' are used in place of the resistors as impedance elements in the device shown in Fig. 1. Common parts are indicated by the same numbers as in Fig. 1. .

The equivalent circuit of the device shown in FIG. 6 is shown in FIG.

Let F and G be the rated voltages of the varistors 8' and 9', respectively. For example, in an image forming apparatus with the same process conditions as described above, it is desirable that %1000≦VT≦1200, so by satisfying the following, it is possible to avoid transfer defects (・images can be borrowed).

FIG. 5 shows a further modification of the device according to the present invention, in which a resistor is used as the impedance element on one side and a constant voltage element is used on the other side. In this case as well, it goes without saying that suitable conditions can be set in the same manner as described above.

The above-mentioned specific example was explained using a single contact member both before and after the transfer position, but it goes without saying that even if there is a plurality of contact members, one or both can be similarly correlated and conditioned. .

As described above in detail in the specific examples, the present invention provides an image forming apparatus that corona-transfers developed images on an image carrier onto a transfer material, in which the members before and after the transfer position that come into contact with the transfer material are connected via impedance elements. The impedance element is grounded, and the values of each impedance element are set in a correlated manner.

The present invention enables stable and good transfer with the above-described configuration.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the main parts of a specific example image forming apparatus based on the present invention, FIG.
FIG. 5 is an explanatory diagram of a device according to a further modified example of the present invention. In the figure, 1; transfer corona discharger; 2, 3; transfer material guide;
4; Timing roller. Applicant Canon Co., Ltd.

Claims (1)

[Claims] Raccoon (1) In an image forming apparatus that corona-transfers the developed images on an image holding member onto a transfer material, the members before and after the transfer position that come into contact with the transfer material are each grounded through an impedance element. An image forming apparatus whose special mission is to set the values of each impedance element in a correlated manner. (2. In the invention described in claim 1, the impedance element values of the plurality of members are R1, &, each member and the front and back of the transfer position are 141@, transfer material unit resistance, transfer voltage t, current An image forming apparatus characterized in that each impedance element R1, R* is set under the conditions when the impedance element is 1t. An image forming apparatus comprising a transfer guide and a fixing means.