JPH10186795A - Charging device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a discharge between electrodes under a controlled temperature management to prevent the density unevenness of image. SOLUTION: A lower layer electrode 3, an insulator layer 4, and an upper layer electrode 5 are formed in layered state on the surface of an insulating base 2, a heater 7 is formed on the reverse side of the insulating base 2, and a thermistor 10 arranged opposite to the heater 7 through an insulating film 8 is provided. Thus, although the heater 7 heats the insulating base 2, the thermistor 10 precisely detects the temperature of the heater 7 since it is arranged opposite to the heater 7 through the insulating film 8, and the applied voltage to the heater 7 is controlled on the basis of this detection result. Thus, a discharged can be performed between the electrodes 3, 5 under a controlled temperature management.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a charging device and an image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, a lower electrode, a dielectric layer (insulator layer), and an upper electrode are sequentially laminated on the surface of an insulating substrate, and a voltage is applied between the lower electrode and the upper electrode. An ion generator that generates high-density positive and negative ions by intensively generating a high alternating electric field in a slit portion between upper electrodes is known. It is also known to use this ion generator as a charging device for an electrophotographic image forming apparatus.

[0003] In such an ion generator, when the nitrate generated by the discharge between the lower electrode and the upper electrode adheres to the surface of the dielectric layer, the discharge stops and the ion generator itself is heated to about 70 ° C. There is a need to. On the other hand, ions generated by the ion generator are affected by temperature,
As described in JP-A-5-278258, a heating resistor having a self-heating control characteristic is provided on the back surface of an insulating substrate, and the heating substrate is used to heat the insulating substrate and to control the temperature of the insulating substrate. There is an ion generator adapted to perform this.

[0004]

When heating with a heater such as a heating resistor provided on the back surface of an insulating substrate, it is difficult to make the temperature uniform. In particular, the temperature tends to increase at the center in the width direction of the insulating substrate, and to decrease on both sides in the width direction of the insulating substrate. As a result, the discharge between the upper and lower electrodes tends to be non-uniform. Therefore, when the ion generator is used as a charging device of an image forming apparatus, image density unevenness occurs.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a charging device that can make the temperature distribution uniform, and an image forming device that can prevent image density unevenness.

[0006]

According to a first aspect of the present invention, there is provided a charging device comprising: a lower electrode formed on a surface of an insulating substrate; an insulator layer formed on the surface of the lower electrode; An upper-layer electrode formed on the front surface; a heater disposed on the back surface of the insulating substrate; and a thermistor opposed to the heater via an insulating film. Therefore, the heater heats the insulating substrate, but since the thermistor is disposed opposite to the heater via the insulating film, the temperature of the heater is accurately detected, and the voltage applied to the heater is controlled based on the detection result. It becomes possible.

According to a second aspect of the present invention, there is provided the charging device according to the first aspect, wherein the heater is configured such that one continuous heating resistance wire is folded back at an end in the longitudinal direction of the insulating substrate, and the end of the heater is connected to the end. The number of folded portions is set to an odd number, and in an intermediate portion other than the folded portion at the end, the heating resistance wire is formed in a pattern that does not exist on the center line in the width direction of the insulating substrate. Therefore, temperature rise near the center line in the width direction of the insulating substrate is suppressed. In addition, both ends (power supply positions) of the heating resistance wire of the heater can be arranged close to one end in the longitudinal direction of the insulating substrate.

The number of folded portions of the heating resistance wire of the heater is 5
By doing so, the arrangement interval of the heating resistance wires becomes narrow, and it becomes difficult to secure an insulating space. The number of folded portions is desirably 3 or less.

According to a third aspect of the present invention, in the charging device according to the first aspect, the heater is formed so that the contour of the heater pattern protrudes outside the formation region of the upper layer electrode and the lower layer electrode. Therefore, a decrease in temperature on both sides of the discharge region corresponding to the width direction of the insulating substrate is prevented.

The charging device according to claim 4, wherein the lower electrode formed on the surface of the insulating substrate; the insulator layer formed on the surface of the lower electrode; and the upper electrode formed on the surface of the insulating layer. And a heater disposed on the back surface of the insulating substrate in a pattern in which the heating resistance wire is bent in a waveform from one end to the other end of the insulating substrate. Accordingly, even when the pattern density of the heating resistance wires is relatively low, the temperature distribution in both the longitudinal direction and the width direction of the insulating substrate becomes uniform.

According to a fifth aspect of the present invention, in the charging device according to the fourth aspect, the heater is formed such that the contour of the pattern protrudes outside the formation region of the upper layer electrode and the lower layer electrode. Therefore, a decrease in temperature on both sides of the discharge region corresponding to the width direction of the insulating substrate is prevented.

According to a sixth aspect of the present invention, in the charging device according to the fourth aspect, the heater is configured such that one continuous heating resistance wire is folded back at an end in the longitudinal direction of the insulating substrate, and the heater is connected at the end. In the intermediate portion other than the folded portion, the heating resistance wire is formed in a pattern that does not exist on the center line in the width direction of the insulating substrate. Therefore, temperature rise near the center line in the width direction of the insulating substrate is suppressed.

According to a seventh aspect of the present invention, in the charging device according to the fourth aspect, the undulation pitch of the waveform of the heating resistance wire of the heater is p, and the meandering width of the heating resistance wire in a direction orthogonal to the pitch p is p. b, the pitch p is 0.8 to the meandering width b.
It is set to 2.0 times. Therefore, it is possible to easily form the heater at a desired density while maintaining a balance in the longitudinal direction and the width direction of the insulating substrate.

The meandering width b of the heating resistance wire may be set so that the insulating substrate itself generates heat uniformly in accordance with the number of heating resistance wires of the heater in the middle portion in the longitudinal direction of the insulating substrate. Here, the number of heating resistance wires constituting the heater in the middle portion in the longitudinal direction of the insulating substrate is not assumed only when a plurality of heating resistance wires are arranged in parallel. Even when the heater is configured such that the wires are folded back at the end of the insulating substrate, the number of such heating resistors is included since a plurality of heating resistance wires are arranged in the middle portion in the longitudinal direction of the insulating substrate.

According to an eighth aspect of the present invention, there is provided an image forming apparatus according to any one of the first to seventh aspects, a photosensitive member whose surface is charged by the charging device, and an exposure for writing a latent image on a charged portion of the photosensitive member. A developing unit for developing the latent image on the photoconductor; a transfer unit for transferring the developed image on the photoconductor to transfer paper; and a fixing unit for fixing the transferred image on the transfer paper. . Accordingly, the temperature distribution of the insulating substrate of the charging device is made uniform, thereby preventing image density unevenness.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A charging device according to a first embodiment of the present invention will be described. Fig. 1 is a longitudinal side view, Fig. 2
FIG. 3 is a vertical sectional side view showing a modified example of the thermistor, and FIG. 3 is a plan view showing a heater pattern.

First, the structure of a charging device 1 using an ion generator will be described with reference to FIG. Reference numeral 2 denotes an insulating substrate formed of alumina or the like. On the surface of the insulating substrate 2 (the upper surface in FIG. 1), a lower electrode 3, an insulating layer 4 such as glass covering the surface of the lower electrode 3, and a plurality of layers disposed on the surface of the insulating layer 4. The upper electrode 5 and a protective coat 6 covering the surface of the upper electrode 5 are sequentially formed. The lower electrode 3 and the upper electrode 5 are formed by a screen printing method using a silver / palladium alloy, a silver / platinum alloy, or the like.

A heater 7 having an electric resistance of 5 to 100 Ω (10 Ω) and an insulating film 8 such as glass covering the heater 7 are provided on the back surface (the lower surface in FIG. 1) of the insulating substrate 2. It is formed by a screen printing method.
A pair of wiring conductors 9 of silver / palladium alloy, silver / platinum alloy, or the like are formed on the surface of the insulating film 8, and these wiring conductors 9 are connected to both poles of a commercially available chip-shaped thermistor 10.

FIG. 2 shows an example in which the thermistor 1 is printed.
This is an example in which No. 1 is formed. In this case, for example, a silver palladium-based conductive paste is printed and fired on the wiring conductor 9 to form the electrodes 12, and a thick-film conductive paste is printed and fired on these electrodes 12 to form the thermistor 11. .

As shown in FIGS. 3 (a) and 3 (b), the heater 7 has a single continuous heating resistance wire 7a folded at an end in the longitudinal direction of the insulating substrate 2, and at the end. The number of folded portions 7b is set to an odd number, and the intermediate portion other than the folded portion 7b at the end is formed with a pattern that does not exist on the center line C in the width direction of the insulating substrate 2.
FIG. 7A shows the case where the number of the folded portions 7b is one, and FIG. 7B shows the case where the number of the folded portions 7b is three. Therefore, both ends of the heating resistance wire 7a are connected to a commercial power supply (not shown) via the terminals 7c and 7d located at one end in the longitudinal direction of the insulating substrate 2. Further, the thermistors 10 and 11 are connected to a drive circuit system (not shown) including a power supply so that the power supply from the power supply (not shown) to the heater 7 is controlled to blink according to the detected temperature.

Further, as shown in FIG. 1, the heater 7 has a pattern whose profile is projected outside a region B in which the upper electrode 5 and the lower electrode 3 are formed by about A (0.1 to 0.2 mm), and is insulated. A heating resistance wire 7a is provided at the center line C in the width direction of the substrate 2.
Are formed with a pattern that does not exist.

In such a configuration, when a high-frequency, high-voltage AC voltage is applied to the lower electrode 3 and the upper electrode 5 while the heater 7 is driven and the insulating substrate 2 is heated, the voltage between the upper electrode 5 is reduced. A high alternating electric field is intensively generated in the slit portion 5a (see FIG. 1), and high-density ions are generated. Regarding the mechanism of ion generation, regarding positive ions, the species of electrons generated in the air are reversible by the electric field in the slit portion 5a, and are multiplied as they sequentially move while colliding with gas molecules in the air. After the transfer of electrons, about the same number of positive ions as the increased electrons are generated.

The heater 7 provided on the back surface of the insulating substrate 2 has a thermistor 10 or 1 through an insulating film 8.
Since the heaters 1 are opposed to each other, the temperature of the heater 7 can be accurately detected by the thermistor 10 or 11, and the voltage applied to the heater 7 can be appropriately controlled based on the detection result. That is, it is possible to cause uniform discharge between the lower electrode 3 and the upper electrode 5 under precisely controlled temperature management.

The heater 7 has a configuration in which one continuous heating resistance wire 7 a is folded at the longitudinal end of the insulating substrate 2,
Since the number of the folded portions 7b at the ends is set to an odd number, both ends of the heating resistance wire 7a can be arranged close to one end of the insulating substrate 2 in the longitudinal direction. Accordingly, the heater 7 can be easily connected to a power source or the like at one end in the longitudinal direction of the insulating substrate 2.

Further, as shown in FIG. 3, since the heater 7 is formed with a pattern in which the intermediate portion other than the folded portion 7b at the end does not exist on the center line C in the width direction of the insulating substrate 2, The temperature rise near the center line C in the width direction of the insulating substrate 2 can be suppressed. Therefore, since the temperature distribution of the insulating substrate 2 can be made uniform, the discharge between the lower electrode 3 and the upper electrode 5 can be made more uniform.

Further, since the heater 7 is formed so that the contour of the pattern protrudes outside the formation region B of the lower layer electrode 3 and the upper layer electrode 5, the heater 7 has a discharge region corresponding to the width direction of the insulating substrate 2. It is possible to prevent a temperature decrease on both sides.

Next, a charging device according to a second embodiment of the present invention will be described. The same parts as those in the previous embodiment are denoted by the same reference numerals and description thereof is omitted. FIG. 4 is a longitudinal side view, and FIG. 5 is a plan view showing a pattern of a part of the heater 7.

This embodiment is different from the previous embodiment in that the number of the lower electrode 3 and the upper electrode 5 is increased, the pattern of the heater 7 is different, and the thermistor 10 or 11 is not provided. is there. The increased number of lower-layer electrodes 3 and upper-layer electrodes 5 are arranged along the width direction of the insulating substrate 2.

The features of the heater 7 in this embodiment are as follows.
The heat-generating resistance wire 7a is formed in a pattern that bends in a waveform from one end of the insulating substrate 2 to the other end. Therefore, even if the pattern density of the heating resistance wires 7a is relatively low, the temperature distribution in both the longitudinal direction and the width direction of the insulating substrate 2 can be made uniform. The fact that the pattern density of the heating resistance wires 7a can be made relatively small means that there is a margin in the interval between the heating resistance wires 7a,
Since the insulating space can be made large, it is advantageous in manufacturing.

In this case, when the pitch of the undulation of the waveform of the heating resistance wire 7a constituting the heater 7 is p, and the meandering width of the heating resistance wire 7a in a direction orthogonal to the pitch p is b, the pitch p is the meandering width. By setting the value of b to 0.8 to 2.0 times, the heater 7 can be easily formed with a desired density while maintaining a balance in the longitudinal direction and the width direction of the insulating substrate 2.

In the pattern of the heater 7, a plurality of heating resistance wires 7 a may be arranged in parallel, or one heating resistance wire 7 a is folded at the end of the insulating substrate 2, as in the previous embodiment. You may do so. In any case, the meandering width b of the heating resistor wire 7a is set so that the insulating substrate 2 itself generates heat uniformly according to the number of the heating resistor wires 7a of the heater 7 at the middle portion in the longitudinal direction of the insulating substrate 2. Good.

Also in this embodiment, the heater 7
Is formed, as in the previous embodiment, one continuous heating resistance wire 7a is folded at the longitudinal end of the insulating substrate 2 and the number of the folded portions 7b at the end is set to an odd number. By doing so, both ends of the heating resistance wire 7 a can be arranged close to one end in the longitudinal direction of the insulating substrate 2. Further, in an intermediate portion other than the folded portion 7b at the end,
By forming the heater 7 with a pattern in which the heating resistance wire 7 a does not exist on the center line C in the width direction of the insulating substrate 2, it is possible to suppress a temperature rise near the center line C in the width direction of the insulating substrate 2. it can. Further, as shown in FIG. 4, the contour of the pattern of the heater 7 has a dimension A (0.1 to 0.2) outside the formation region B of the upper electrode 5 and the lower electrode 3.
By forming the film so as to protrude by about mm), it is possible to prevent a temperature decrease on both sides of the discharge region corresponding to the width direction of the insulating substrate 2.

Next, an image forming apparatus according to a third embodiment of the present invention will be described. FIG. 6 is a front view schematically showing the internal structure of an electrophotographic image forming apparatus (laser printer) LP.

In the drawing, reference numeral 20 denotes a photosensitive member which is driven to rotate clockwise. Around the photoconductor 20, the charging device 1, the exposing unit 21, the developing unit 22, the transfer unit 23, and the cleaning unit 24 described in FIGS. 1 to 5 are arranged. A paper feed cassette 25 stores a large number of transfer papers (not shown) in a stacked state. A transfer paper in the paper feed cassette 25 is stored in a paper passage 27 extending from the paper feed cassette 25 to the fixing unit 26. A sheet feeding roller 28 for feeding sheets one by one; a registration roller 29 that rotates in synchronization with an image forming process on the photoconductor 20;
3 are arranged.

In such a configuration, the surface of the photosensitive member 20 is charged by the charging device 1 in the process of being driven to rotate clockwise, and the charged portion is exposed to a laser beam modulated based on an image signal in the exposure section 21. Irradiates a latent image. This latent image is developed by the developing unit 22.
On the other hand, the transfer paper fed by the paper feed roller 28 reaches the nip of the registration roller 29 and waits. When the registration roller 29 is driven in synchronization with the image forming process, the transfer paper is brought into contact with the photoconductor 20. The sheet is fed between the transfer unit 23. The developed image on the photoreceptor 20 is transferred to a transfer sheet by a transfer unit 23, and the transferred image is transferred to a fixing unit 26.
Is reached by the fixing unit 26. The fixed transfer sheet is discharged to a discharge tray (not shown). The remaining toner remaining on the photoconductor 20 is wiped by the cleaning unit 24.

In this case, the charging device 1 is, as described above,
Since the photoconductor 20 is charged by discharging under precisely controlled temperature management, the photoconductor 20 can be charged evenly. As a result, it is possible to form a high quality image while keeping the optical density of the latent image and the developed toner density constant.

[0037]

According to the first aspect of the present invention, since the heater for heating the insulating substrate is provided with the thermistor opposed to the heater via the insulating film, the temperature of the heater is accurately detected, and the detection result is obtained. Based on this, the voltage applied to the protection heater can be accurately controlled. Thus, the discharge between the lower electrode and the upper electrode can be uniformly performed under the controlled temperature control.

According to the second aspect of the present invention, in the first aspect of the present invention, the heater is configured such that one continuous heating resistance wire is folded at the longitudinal end of the insulating substrate, and the folded portion at the end is formed. Is set to an odd number, it is possible to arrange both ends of the heating resistance wire of the heater close to one end in the longitudinal direction of the insulating substrate. Thereby, the connection structure between the heater and the power supply can be facilitated. Also, since the heater is formed in a pattern that does not exist on the center line in the width direction of the insulating substrate in an intermediate portion other than the end portion of the insulating substrate where the heating resistor wire is folded, the heater is formed in the width direction of the insulating substrate. Suppress the temperature rise near the center line at
Discharge between the lower electrode and the upper electrode can be performed more uniformly.

According to the third aspect of the present invention, in the first aspect of the present invention, the heater is formed such that the contour of the pattern protrudes outside the formation region of the upper electrode and the lower electrode. In addition, it is possible to prevent the temperature from being lowered on both sides of the discharge region corresponding to the width direction of the insulating substrate, and to make the discharge between the lower electrode and the upper electrode more uniform.

According to the fourth aspect of the present invention, since the heater is provided on the back surface of the insulating substrate with a pattern in which the heating resistance wire is bent in a waveform from one end to the other end of the insulating substrate, Even when the pattern density of the heating resistance wires is relatively low, the temperature distribution in both the longitudinal direction and the width direction of the insulating substrate can be made uniform. Thereby, the discharge between the lower electrode and the upper electrode can be uniformly performed.

According to the fifth aspect of the present invention, in the invention of the fourth aspect, the heater is formed so that the contour of the pattern protrudes outside the formation region of the upper layer electrode and the lower layer electrode. It is possible to prevent a temperature drop on both sides of the discharge region corresponding to the width direction of the substrate, and to make the discharge between the lower electrode and the upper electrode more uniform.

According to a sixth aspect of the present invention, in the invention of the fourth aspect, the heater is such that one continuous heating resistance wire is folded at an end in the longitudinal direction of the insulating substrate, and a folded portion at the end is formed. Since the heating resistance wires are formed in a pattern that does not exist on the center line in the width direction of the insulating substrate in the intermediate portion other than the above, the temperature rise near the center line portion in the width direction of the insulating substrate is suppressed, and the lower electrode and the upper layer Discharge between the electrodes can be performed more uniformly.

According to a seventh aspect of the present invention, in the invention of the fourth aspect, the undulation pitch of the waveform of the heating resistance wire of the heater is p, and the meandering width of the heating resistance wire in a direction orthogonal to the pitch p is b. Then, the pitch p is 0.8 to 2.
Since it is set to 0 times, the heater can be easily formed with a desired density by balancing in the longitudinal direction and the width direction of the insulating substrate.

According to the present invention, the surface of the photoreceptor is charged by the charging device according to any one of claims 1 to 7 to form an image, so that the temperature distribution of the insulating substrate of the charging device is obtained. Can be made uniform to prevent image density unevenness.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional side view showing a charging device according to a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional side view showing a modified example of a thermistor.

FIG. 3 is a plan view showing a pattern of a heater.

FIG. 4 is a longitudinal sectional side view showing a charging device according to a second embodiment of the present invention.

FIG. 5 is a plan view showing a partial pattern of a heater.

FIG. 6 is a front view schematically showing the internal structure of an image forming apparatus according to a third embodiment of the present invention;

[Explanation of symbols]

 1: Charging device 2: Insulating substrate 3: Lower electrode 4: Insulator layer 5: Upper electrode 7: Heater 7a: Heating resistance wire 7b: Folding portion 8: Insulating film 10, 11: Thermistor 20: Photoconductor 21: Exposure portion 22: developing section 23: transfer section 26: fixing section

Claims (8)

[Claims] A lower electrode formed on the surface of the insulating substrate; an insulator layer formed on the surface of the lower electrode; an upper electrode formed on the surface of the insulating layer; and a back surface of the insulating substrate. And a thermistor disposed opposite the heater with an insulating film interposed therebetween. 2. The heater according to claim 1, wherein one continuous heating resistance wire is folded at an end in the longitudinal direction of the insulating substrate, the number of folded portions at the end is set to an odd number, and a folded portion at the end is set. 2. The charging device according to claim 1, wherein the heating resistance wire is formed in a pattern that does not exist on a center line in a width direction of the insulating substrate in an intermediate portion other than the intermediate portion. 3. The charging device according to claim 1, wherein the heater is formed such that the contour of the pattern protrudes outside the formation region of the upper layer electrode and the lower layer electrode. A lower electrode formed on the surface of the insulating substrate; an insulator layer formed on the surface of the lower electrode; an upper electrode formed on the surface of the insulator layer; A heater disposed on the back surface of the insulating substrate with a pattern bent in a waveform from one end of the insulating substrate to the other end;
A charging device comprising: 5. The charging device according to claim 4, wherein the heater is formed such that the contour of the pattern protrudes outside the formation region of the upper electrode and the lower electrode. 6. The heater, wherein one continuous heating resistance wire is folded at an end in the longitudinal direction of the insulating substrate, and an intermediate portion other than the folded portion at the end is on the center line in the width direction of the insulating substrate. The charging device according to claim 4, wherein the charging device is formed with a pattern that does not exist in the charging device. 7. When the undulation pitch of the waveform of the heating resistance wire of the heater is p, and the meandering width of the heating resistance wire in a direction orthogonal to the pitch p is b, the pitch p is 0.8 to less than the meandering width b.
5. The charging device according to claim 4, wherein the setting is 2.0 times. 8. A charging device according to claim 1, a photoconductor whose surface is charged by the charging device, an exposure unit for writing a latent image on a charged portion of the photoconductor, and a latent image on the photoconductor. An image forming apparatus comprising: a developing unit that develops an image; a transfer unit that transfers a developed image on the photoconductor onto a transfer sheet; and a fixing unit that fixes a transferred image on the transfer sheet.