JPH05249851A - Transfer device - Google Patents

Abstract

PURPOSE:To automatically correct a transfer characteristic accompanying environmental change. CONSTITUTION:A reference resistance ring (earth ring) 6a which is externally provided at least at one end of a transfer roller 2, a terminal 7 which is brought into contact with the ring 6a and a power source means (high voltage transformer) 5a which supplies electric power to the roller 2 and the ring 6a are provided. Then, a current flowing to the terminal 7 through the ring 6a of the output current of the power source means 5a is controlled so as to be constant. Thus, even when an environmental condition is changed, a current value flowing to a photosensitive body 100 and the transfer material 2 is kept to be almost constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer device for transferring toner on a photoconductor to a transfer material such as paper in an electrophotographic copying machine, printer, facsimile or the like.

[0002]

2. Description of the Related Art Conventionally, as the transfer device, a conductive transfer roller made of a foam material is brought into contact with a photosensitive member and electricity is supplied to a core metal of the transfer roller from a bias power source. By doing so, an electric charge is given to the transfer material passing between the photoconductor and the transfer roller, and the charged toner adhering to the photoconductor is electrically transferred to the transfer material. Has been.

However, the electric resistance of the transfer roller and the transfer paper changes by about two digits depending on environmental conditions such as temperature and humidity. Specifically, the resistance value of the transfer roller is increased by several orders of magnitude in a low temperature and low humidity environment (hereinafter referred to as “L / L”) than in a room temperature and normal humidity environment (hereinafter referred to as “N / N”), and vice versa. In a high temperature and high humidity environment (hereinafter referred to as "H / H"), N /
It is 1 to 2 digits lower than N.

Therefore, in the constant voltage control for keeping the voltage applied to the transfer roller constant, a sufficient transfer current cannot be obtained at the time of L / L, which causes a transfer failure, and at the time of H / H, when the paper is not passed, the photosensitive member is not transferred. However, there is a problem that a transfer memory is generated and the background image is fogged in the output image.

On the other hand, in the simple constant current control for keeping the current applied to the transfer roller constant, when the transfer paper is small in size, the current flowing in the portion where the photoconductor and the transfer roller come into direct contact with each other increases, and There is a problem that a sufficient transfer current does not flow in a portion where the paper passes, resulting in defective transfer.

[0006]

The present invention has been made to solve the above problems, and a transfer device according to the first invention has a transfer roller which is in pressure contact with a photosensitive member. And a transfer device for transferring the toner on the photosensitive member to a transfer material that is nipped and conveyed by the photosensitive member, and a reference resistance ring that is mounted on at least one end of the transfer roller.
A terminal in contact with the reference resistance ring and power supply means for supplying electricity to the transfer roller and the reference resistance ring are provided, and the current flowing through the reference resistance ring to the terminal or the output current of the power supply means becomes constant. The control is performed as follows.

A transfer device according to a second aspect of the present invention includes a transfer roller that is in pressure contact with a photosensitive member, and transfers the toner on the photosensitive member to a transfer material that is nipped and conveyed by the transfer roller and the photosensitive member. In the apparatus, a control resistor is provided between the transfer roller and a power source that supplies electricity to the transfer roller, and a reference resistance ring is provided on at least one end of the transfer roller, and the reference resistance ring is connected in series with the control resistor. In addition, it is connected to a circuit in parallel with the circuit for the current flowing from the transfer roller to the photoconductor.

[0008]

In the transfer apparatus according to the first aspect of the present invention, the resistance value of the transfer roller and the resistance value of the transfer roller and the photoconductor or the transfer material change when the environmental conditions change, but the current flowing through the reference resistance ring is detected. The output voltage of the power supply means is adjusted so that the current flowing through the reference resistance ring or the output current of the power supply means becomes constant. Further, in the transfer device according to the second aspect of the invention, even if the resistance value of the transfer roller or the like changes according to the change in environmental conditions, the value of the current flowing through the transfer roller automatically changes according to the change in the resistance value. Is corrected to.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In FIG. 1, reference numeral 100 denotes a photoconductor 1a.
Is a transfer device. In the transfer device 1a, the transfer roller 2 is a foam sponge rubber roller (electric resistance: 10 ⁶ to 1 ⁶⁾ in which carbon black is dispersed in silicon rubber.
( ^{9 9} Ω · cm) 4 is formed by penetrating the conductive shaft 3 in the center of the rubber roller 4, and the outer peripheral surface of the rubber roller 4 is pressed against the photosensitive member 100 with a predetermined pressing force (600 g). The shaft 3 is pressed to rotate following the photoconductor 100, and the shaft 3 is electrically connected to a constant voltage type high voltage transformer 5a. The earth ring 6a is a conductive ring made of phosphor bronze and is mounted on one end of the transfer roller 2. Further, the electrode 7 is in contact with the outer peripheral surface of the earth ring 6 and is connected to the earth 9 via the resistor 8. The current flowing from the transfer roller 2 and the earth ring 6 to the earth ring 9 through the electrode 7 is the high voltage transformer 5a. It is supposed to be detected.

FIG. 5 shows an equivalent circuit of the transfer device 1a, in which V _T is the output voltage of the high voltage transformer 5a and Ra1.
Is a resistance value of the rubber roller 4 to the surface of the photosensitive member, Ra2 is an equivalent resistance value of the transfer paper and / or the photosensitive member 100, Rb is a combined resistance value of the rubber roller 4 and the resistor 8, and ia is a photosensitive value from the shaft 3 through the rubber roller 4. The shunt current flowing through the body 100 and ib represent the shunt current flowing through the earth ring 6a. Since the electric resistance values of the rubber roller 4, the transfer paper and the like change depending on environmental conditions, the resistances Ra1, Ra2 and Rb are represented as variable resistances.

Next, the output characteristic of the high voltage transformer 5a in the transfer device 1a will be described with reference to FIG. This figure shows a state in which the current flowing through each member changes due to environmental changes, and the horizontal axis represents the output voltage V of the high-voltage transformer 5a.
_T , the vertical axis extending upward from the origin O represents the shunt current ia, and the vertical axis extending downward from the origin O represents the shunt current ib.

The fourth quadrant shows the state in which the current flowing through the earth ring 6a changes depending on the environment.
Further, ib (L) is an example of current characteristics at L / L and ib (H) is at H / H. When L / L, the characteristic curve shifts to a high voltage side, and at H / H, the characteristic curve changes. It shows that the shift to the low voltage side.

On the other hand, in the first quadrant, the current i _{P / C} flowing from the transfer roller 2 to the surface of the photosensitive member, the current i _W flowing from the transfer roller 2 to a portion (white portion) of the transfer paper which is not in contact with the toner, and the transfer roller 2 This shows a state in which the current i _B flowing through the portion (black portion) of the transfer paper that contacts the toner changes depending on the environment. Further, i (a) is the current characteristic at L / L, i (b)
Is an example of the current characteristic at H / H. Similar to the current characteristic of the earth ring 6, the characteristic curve shifts to the high voltage side at L / L, and the characteristic curve shifts to the low voltage side at H / H. It is shown that.

In the transfer device 1a having the above structure, the high voltage transformer 5a has a shunt current ib flowing through the earth ring 6.
Is detected and the current value ib is compared with the constant current setting value ib _0, and the output voltage V _T is adjusted so that the current value ib becomes the setting value ib ₀ . For example, at the time of L / L, the electric resistance of the rubber roller 4 increases and the ib characteristic curve becomes ib.
In the state of (L), the output voltage V _T is set to V _{L / L} , and i _{P / C} , i _W , and i _B are i _{P / C} ′, i _W ′, and i _B ′, respectively.
Becomes Further, when H / H, the electric resistance of the rubber roller 4 is lowered, and when the ib characteristic curve is in the state of ib (H), the output voltage V _T is set to V _{H / H} , i _{P / C} , i _W , i _B becomes i _{P / C} ″, i _W ″, and i _B ″, respectively.

Here, as described above, i _{P / C} , i _W , i _B
The characteristic curve shifts to the high pressure side or the low pressure side according to changes in the environment, so i _{P / C} ', i _W ', i _B 'and H at L / L
I / _P ″, i _W ″, and i _B ″ at the time of / H show almost equal values. That is, i _{P / C} ,
i _W and i _B are kept almost constant.

In the above embodiment, the earth ring 6a is used.
Is provided only on one end side of the transfer roller 2, but the earth rings 6a may be provided on both ends of the transfer roller 2.
In this case, since the detected current ib is a combined current of the two earth rings, the resultant output voltage V _T also takes into consideration the environment on both sides of the photoconductor 100. Further, the outer diameter of the earth ring 6a may be set to be smaller than the outer diameter of the transfer roller 2 and may be provided in a portion facing the photoconductor 100.

Next, a second embodiment of the transfer device will be described with reference to FIGS. In the transfer device 1b, portions of the transfer roller 2 which are located outside the effective image area of the photoconductor 100 (non-image forming portion) are located at both ends of the transfer roller 2.
Has a smaller diameter than the outer diameter of the transfer roller 2, and earth rings 6b, 6b having a smaller diameter than the transfer roller 2 are mounted on the small diameter portion.
The earth rings 6b, 6b are grounded via the electrodes 7, 7. A constant current type is used as the high voltage transformer 5b. The other structure is the same as that of the first embodiment.

In this transfer device 1b, since the grounding rings 6b and 6b are provided at locations corresponding to the non-image forming portions of the photoconductor 100, the transfer roller 2 may have the same length as the photoconductor 100, and the device itself. Can be made compact. Further, since the earth rings 6b and 6b are provided at both ends of the transfer roller 2, the output voltage of the high voltage transformer 5b does not change so much even if the environmental condition changes, and the environmental condition changes in the axial direction of the transfer roller 2. Even if there is a variation in, it will be averaged.
Although the earth rings 6b and 6b are provided at both ends of the transfer roller 2 in the second embodiment, they may be provided only at one end side. Further, the earth ring 6 may be provided on the protruding portion by projecting the transfer roller 2 from the end portion of the photoconductor 100 as in the first embodiment.

A transfer device according to the second invention will be described with reference to FIGS.
This will be described with reference to 12. Transfer device 1c shown in FIGS.
Then, the control resistor 8 is connected on a circuit connecting the high-voltage transformer 5c and the shaft 3 of the transfer roller 2. A grounding ring 6c is mounted on one end of the transfer roller 2 and grounded via an electrode 7.

Equivalent circuit of the transfer device 1c (see FIG. 9)
In, Rs is the resistance value of the control resistor 8, V _RS is the voltage drop due to the control resistor Rs, and V _TO is the voltage drop due to the resistors Ra1, Ra2 and the resistor Rb.

The operation characteristics of the transfer device 1 will be described with reference to FIG. 10 in the case of N / N. In this figure, the horizontal axis is voltage, the vertical axis extending upward from the origin O is the shunt current ia, and the vertical axis extending downward from the origin O is the shunt current ib.
Is represented. In the fourth quadrant, L1 is an operation line by the control resistor Rs, L2 is voltage dependence of the current ib flowing through the reference resistors 6 and 6 when ia = 0, and L3 is ia.
The voltage dependence of the currents ia + ib in consideration of the voltage dependence of is shown. On the other hand, in the first quadrant, P / C is a characteristic curve of a current flowing through the photoconductor 100, W is a characteristic curve of a current flowing through a portion (white portion) where the transfer paper does not contact the toner, and B indicates a contact of the transfer paper with the toner. The characteristic curve of the electric current which flows into a part (black part) is shown. The value represented by the P / C characteristic curve is equal to the difference between the characteristic curves L2 and L3.

Then, based on the above characteristic curve and the like, the voltage drop V due to the resistors Ra1 and Ra2 and the resistor Rb.
_TO is determined from the point (voltage value) P1 on the horizontal axis corresponding to the intersection C1 between the operating line L1 and the characteristic curve L2. The current i _{P / C} flowing through the photoconductor 100 is the point P2 on the P / C characteristic curve corresponding to the intersection C2 between the operation line L1 and the characteristic curve L3.
Is determined from. Then, the current value i _W flowing in the white part of the transfer paper and the current value i _B flowing in the black part of the transfer paper are obtained from the intersections of the operation line AL connecting the points P1 and P2 with the W characteristic curve and the B characteristic curve. The operation line AL does not show a perfect constant voltage characteristic, but is relatively close to a constant voltage characteristic.

Therefore, in an actual image forming apparatus, by appropriately setting the output voltage V _T of the high voltage transformer 5c, the control resistor Rs, the size of the earth ring 6c, etc., the current i _{P / C} flowing through the photoconductor 100 can be set. The current i _W flowing in the white part of the transfer paper and the current i _B flowing in the black part of the transfer paper are determined, and the current values can be set within a predetermined range.

Specifically, at the time of H / H, the electric resistance of the rubber roller 4 and the like decreases according to changes in the environment. As a result, as shown in FIG. 11, the current i flowing through the resistors Ra1 and Ra2 is increased.
a, ib flowing through the resistor Rb rises, and a characteristic curve L of ib
2 shifts to the high current side. In addition, P / which represents the transfer characteristic
The polarities of the C, W, and B characteristics shift to the low voltage side, and also shift to the high current side due to the decrease in the resistance of the rubber roller 4, thus increasing the voltage dependence.

Then, i _{P / C} , i _W , and i _B obtained from the intersections of the operation line AL determined by the above method and the P / C, W, B characteristic curves are P / C, W, B. The voltage drop V _T0 decreases corresponding to the increase in the voltage dependence of the characteristic curve, and the slope of the operating line AL increases, and i _{P / C} , i _W , and i _B
Is set to a value almost equal to that at N / N.

Further, at the time of L / L, the electric resistances of the rubber roller 4, the reference resistances 6, 6 and the like increase according to the change of the environment. As a result, as shown in FIG. 12, the current ia flowing through the resistors Ra1 and Ra2 and the ib flowing through the resistor Rb decrease, and ib decreases.
The characteristic curve L2 of is shifted to the low current side. Further, the polarities of the P / C, W, and B characteristics representing the transfer characteristics shift to the high voltage side, and also shift to the low current side due to the increased resistance of the rubber roller 4 and the like, and the voltage dependence decreases.

Then, i _{P / C} , i _W , and i _B are P / C,
The voltage drop V _T0 increases corresponding to the decrease in the voltage dependence of the W and B characteristic curves, and the inclination of the operation line AL decreases, and i _{P / C} , i _W , and i _B are N / N. It is set to a value almost equal to.

As described above, in the transfer device 1c, when the electric resistance of the rubber roller 4, the transfer paper, or the like changes due to the change of environment, the voltage automatically applied to the transfer roller 2 changes accordingly, and the photosensitive member 100, the transfer current of the transfer paper is automatically corrected within a certain width.

[0029]

As is apparent from the above description, in the transfer device according to the first aspect of the invention, the resistance value of the transfer roller changes according to the change of the environmental conditions, but the resistance value of the transfer roller flows to the reference resistance ring. The current or the output current of the power supply means is controlled to be constant. Therefore, even if the environment changes, the value of the current flowing from the transfer roller to the white part and the black part of the photoconductor or the transfer paper is kept substantially constant, and a high-quality image without background fog or transfer failure can be obtained.

In the transfer device according to the second invention,
Even if the resistance values of the transfer member and the resistor change due to environmental changes, the value of the current flowing through the transfer roller is automatically corrected to a substantially constant value based on the change, and as in the first invention, a high-quality image is obtained. Is obtained. Further, the present invention has an advantage that a feedback circuit for adjusting the output of the power supply means is unnecessary and the configuration is simple.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a transfer device according to a first embodiment of the first invention.

FIG. 2 is a perspective view of a transfer roller.

FIG. 3 is a schematic configuration diagram of a transfer device according to a second embodiment of the first invention.

FIG. 4 is a perspective view of a transfer roller.

FIG. 5 is an equivalent circuit diagram of the transfer device according to the first embodiment of the first invention.

FIG. 6 is a voltage-current characteristic diagram of the transfer device according to the first example of the first invention.

FIG. 7 is a schematic configuration diagram of a transfer device according to a second invention.

FIG. 8 is a perspective view of a transfer roller.

FIG. 9 is an equivalent circuit diagram of the transfer device according to the second invention.

FIG. 10 is a voltage-current characteristic diagram in the NN environment of the transfer device according to the second invention.

FIG. 11 is a voltage-current characteristic diagram in an HH environment of the transfer device according to the second invention.

FIG. 12 is a voltage-current characteristic diagram in the LL environment of the transfer device according to the second invention.

[Explanation of symbols]

1a, 1b, 1c ... Transfer device, 2 ... Transfer roller, 4 ... Rubber roller, 5a, 5b, 5c ... High-voltage transformer, 6a, 6
b, 6c ... Earth ring, 100 ... Photoconductor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Uno 2-3-13 Azuchi-cho, Chuo-ku, Osaka-shi, Osaka, Osaka International Building Minolta Camera Co., Ltd. (72) Inventor Hitoshi Saito Azuchi, Chuo-ku, Osaka-shi, Osaka 2-3-13 Machi, Osaka International Building Minolta Camera Co., Ltd. (72) Inventor Yasuo Tanaka 2-3-3 Azuchicho, Chuo-ku, Osaka City, Osaka Prefecture International Building Minolta Camera Co., Ltd.

Claims (2)

[Claims] 1. A transfer device, comprising: a transfer roller that is in pressure contact with a photoconductor, wherein the toner on the photoconductor is transferred to a transfer material that is nipped and conveyed by the transfer roller and the photoconductor. A reference resistance ring provided on one end, a terminal in contact with the reference resistance ring, and a power supply means for supplying electricity to the transfer roller and the reference resistance ring are provided, and a current flowing through the reference resistance ring to the terminal, or A transfer device characterized in that the output current of the power supply means is controlled to be constant. 2. A transfer device, comprising: a transfer roller that is brought into pressure contact with a photosensitive member, wherein toner on the photosensitive member is transferred to a transfer material that is nipped and conveyed by the transfer roller and the photosensitive member. A control resistor is provided between the power supply means for supplying the control roller and the transfer roller, and a reference resistor ring is provided on at least one end of the transfer roller. The reference resistor ring is connected in series with the control resistor and from the transfer roller to the photosensitive member. A transfer device, which is connected to a circuit in parallel with a circuit for flowing current.