JP3512298B2 - Image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a contact charging member to which a voltage is applied while being in contact with a rotating photoconductor directly or while rotating via a transfer paper.

[0002]

2. Description of the Related Art For example, an image forming apparatus such as an electrostatic copying machine or a printer exposes a surface of a charging device or a charging device that charges a photosensitive member, which is a charging target, to the surface of the charging member. A transfer device that forms a latent image and transfers the developed toner image onto a transfer paper is provided, but conventionally, a corona discharge device has been widely used as these devices.

However, when this corona discharge device is used as a charging device, there are the following drawbacks. (1) It is necessary to apply a high voltage of 4 to 8 KV in order to set the charging potential of the photoconductor to, for example, 500 to 800V. (2) Since most of the discharge current from the discharge wire flows into the shield, the current used to charge the surface of the photoconductor to a predetermined potential is only a few% of the total discharge current,
Power efficiency is poor. (3) Since corona products such as ozone are generated by corona discharge, the components of the device and the surface of the photoconductor are likely to deteriorate. To prevent this, an ozone decomposition filter or a fan that generates an air flow is used. is necessary. (4) Image unevenness easily occurs due to dirt on the discharge wire.

Therefore, as a charging device having almost no such drawbacks as described above, there is a contact charging type charging device which charges a charging member such as a charging roller which is a contact charging member to which a voltage is applied, in a state of being brought into contact with a photoconductor. Attention has been paid. Such a contact charging type charging device is capable of lowering the applied voltage required to obtain a desired charging potential on a charged body such as a photoconductor, and the amount of ozone generated during the charging process is extremely high. Since the amount is very small, there is an advantage that it is not necessary to provide an ozone filter and the structure of the exhaust system can be simplified.

However, in such a contact charging type charging device, the charging efficiency represented by the charging potential / applied voltage changes depending on the surface temperature of the charging roller and tends to decrease as the temperature decreases. . Therefore, in the case of constant voltage control, there is a problem that the image density is lowered because the charging potential obtained by a constant applied voltage is lowered when the charging efficiency is lowered. Further, there is a problem that other process control in which the charging potential is controlled as a reference value is not normally performed.

Therefore, in order to solve such a problem, temperature detecting means (sensor) is brought into direct contact with the charging roller to detect the surface temperature of the charging roller, and the voltage applied to the charging roller corresponding to the detected temperature. A charging device has been proposed in which the charging device is controlled to obtain a stable charging potential without causing a charging failure. With this configuration, the temperature detecting means can accurately detect the surface temperature of the charging roller and apply the optimum voltage corresponding to the surface temperature to the charging roller without being affected by the ambient temperature.

However, even in this case, the application of the voltage to the charging roller is reduced by the adoption of the contact charging method as compared with the conventional charging method using corona discharge, but a high voltage of 1-2 KV is applied. Since the voltage is applied, there is a possibility that the temperature may be affected in various ways by the applied voltage. For example, when a high voltage is applied to the charging roller, electrical noise may enter the control circuit that controls the voltage applied to the charging roller through the temperature detecting means that is in contact with the charging roller, or the dielectric strength may increase. There is a risk that a short circuit may occur due to a shortage and the control system may malfunction, or in the worst case, it may be destroyed.

[0008] Therefore, the applicant of the present invention has previously disclosed Japanese Patent Laid-Open No. 7-248.
No. 670 (image forming apparatus) has been applied for. This image forming apparatus includes a temperature detecting means for detecting the surface temperature of a contact charging member such as a charging roller, and a voltage applying means for applying a voltage to the contact charging member according to an output signal corresponding to the detected temperature from the temperature detecting means. In the image forming apparatus provided with the applied voltage control means for controlling the voltage, the moving means for moving the temperature detecting means to the contact position in contact with the surface of the contact charging member and the non-contact position not in contact with the surface of the contact charging member is provided.

As a result, the voltage applying means controls the voltage applied to the contact charging member in accordance with the output signal corresponding to the detected temperature from the temperature detecting means, so that the apparatus can be used under environmental conditions of relatively low temperature. However, since the voltage applied to the contact charging member in that state is controlled according to the surface temperature of the contact charging member, it is possible to prevent a decrease in image density due to poor charging, deterioration of transfer efficiency, and the like.

Further, if the temperature detecting means is moved to the non-contact position by the moving means, even if a high voltage is applied to the contact charging member in that state, the temperature detecting means is separated from the contact charging member, Electrical noise may enter the control circuit that controls the voltage applied to the contact charging member, or a short circuit may occur due to insufficient dielectric strength, causing the control system to malfunction.
It won't break.

[0011]

However, in the temperature detecting means for detecting the surface temperature of the contact charging member, as shown in FIG. , Charging roller 62 and temperature detecting means 6
Since it was on the downstream side (left side in the drawing) of the charging roller 2 in the rotation direction indicated by the arrow G with respect to the contact position a with the conductive leaf spring 66 of 0, it is described in, for example, JP-A-5-188738. When the charging member continues to rotate after being separated from the photoconductor as in the contact charging device, the foreign matter such as toner and paper dust is present at the contact position a between the temperature detecting means 60 and the charging roller 62. When the friction coefficient of the portion increases due to the interposition, a large frictional force is generated between the temperature detecting means 60 and the charging roller 62, and the surface of the charging roller 62 is mechanically damaged and easily damaged. There was a problem.

The present invention has been made in view of the above problems, and in order to prevent the temperature detecting means from being electrically damaged, the temperature detecting means can be brought into contact with or separated from the contact charging member. In the image forming apparatus configured as described above, the surface of the contact charging member is mechanically damaged by the frictional force generated by the contact pressure applied to the contact charging member by the temperature detecting unit when the temperature detecting unit contacts the contact charging member. The purpose is not to receive.

[0013]

[0014]

[0015]

To achieve the above object, the present invention comprises a photoconductor, a contact charging member, a voltage applying unit, and a temperature detecting unit, and the contact charging member is brought into contact with the photoconductor. In the image forming apparatus also provided with a contact charging member moving unit that moves the contact position and the non-contact position, the temperature detecting unit includes a fixed portion and an elastic member extending from the fixed portion to the contact charging member. The fixing portion is fixed to a bracket for holding a member for supporting the contact charging member, which is upstream of the contact position between the temperature detecting means and the contact charging member in the rotation direction of the contact charging member. ,
The member that supports the contact charging member has contact charging at one end.
Rotate on the bracket with the member rotatably supported
The tip end portion of the elastic member is supported so as to come into contact with the contact charging member that has moved to the non-contact position.

In this case, the contact charging member is moved to the non-contact position where it is separated from the photosensitive member without providing the moving means for moving the temperature detecting means to the contact position where it is brought into contact with the contact charging member and the non-contact position where it is separated from it. The tip of the elastic member of the temperature detecting means comes into contact with the contact charging member only by moving. Further, if the contact charging member is brought into contact with the photoconductor, the temperature detecting means is separated from the contact charging member, so that even if a voltage is applied to the contact charging member by the voltage applying means, the temperature detecting means is electrically damaged. Never.

Further, in the above image forming apparatus , the contact surface of the temperature detecting means with the contact charging member may be covered with a low friction member. Then, in general, when foreign matter such as toner or paper powder intervenes in the contact portion between the temperature detecting means and the contact charging member, the surface of the contact charging member may be damaged by them, By coating the contact surface of the temperature detecting means with the contact charging member with the low friction member, it is possible to prevent the foreign matter from adhering to the surface of the temperature detecting means. Can be prevented.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. <First Embodiment> (FIGS. 1 to 8) FIG. 1 shows a temperature detecting means for detecting the surface temperature of a charging roller which is a contact charging member of an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a schematic view showing a state of contact with the control system, FIG. 2 is a schematic view showing a state in which the temperature detecting means is moved to a non-contact position not in contact with the surface of the charging roller by the moving means, and FIG. FIG. 3 is a configuration diagram showing a main part of an image forming apparatus provided with a roller and a temperature detecting means.

In this image forming apparatus, as shown in FIG. 3, a charging roller (charging member) 2 which is a contact charging member is directly contacted with a drum-shaped rotating photosensitive member 1 which is a member to be charged. Is a contact charging type image forming apparatus for uniformly charging the surface 1a of the photoconductor 1 to a predetermined potential by applying a voltage to the photoconductor 1, and the photoconductor 1 rotates in the direction of arrow A at a predetermined peripheral speed,
While the charging roller 2 is in contact with it, the charging roller 2 is driven to rotate at a constant speed in the direction of the arrow as it rotates.

The photoconductor 1 is driven by a photoconductor drive system including a drum drive timing belt, a drum drive pulley, a motor for driving them (all are not shown), and the surface 1a is always driven. Charging roller 2
However, due to the urging force of the pressure spring described later, for example, contact pressure 1
It is pressure-welded at 0 g / cm (approximately line contact). The photoconductor 1
In addition to the charging roller 2, an eraser 18, a developing device 6, a contact type transfer device 7 having an endless belt 7a also serving as a contact charging member, and a cleaning unit 8 are arranged around the roller.

Then, the light from the exposure device 9 (only the mirror portion is shown) is incident on the surface 1a of the photosensitive member 1,
The charging surface uniformly charged by the charging roller 2 is exposed to form an electrostatic latent image thereon, and the electrostatic latent image is static in an area portion outside the size of the transfer paper P used by the eraser 18. The charges are removed (trimming), and the remaining electrostatic latent image is developed by the toner supplied by the developing sleeve 6a of the developing device 6 to form a toner image (visible image).
Becomes

On the other hand, the transfer paper in the paper feed cassette (not shown) is fed by a paper feed roller which rotates at a predetermined timing.
The transfer device 7 is fed out one by one, and is temporarily stopped between the registration roller 13 and the pressure roller 14 rotating in pressure contact therewith, and the timing is adjusted. Is conveyed toward the transfer section where is provided.

A transfer device 7 applies a transfer bias to the transfer paper P to transfer a toner image to the upper surface side in FIG. 3, and the toner image is separated from the photoconductor 1 and conveyed to a fixing device (not shown), where the toner is transferred. After the paper is fixed, the paper is ejected to a paper ejection tray or the like outside the apparatus. Then, the residual toner remaining on the photoconductor 1 after the transfer is completed and foreign matters such as paper dust are removed by the cleaning blade 8a provided in the cleaning unit 8, and the residual potential left on the photoconductor 1 is neutralized. Removed by a device (not shown),
Prepare for the next charging by the charging roller 2.

As shown in FIG. 1, the charging roller 2 is formed by integrally mounting a conductive rubber roller portion 16 formed of a medium resistance rubber layer on the outside of a conductive cored bar 15 made of iron or the like. Both ends of the core metal 15 are rotatably supported by bearings 17, 17, and each of the bearings 17 is pressed by the pressure spring 12 via a member holding the bearing 17.
The axis of the charging roller 2 is biased in the direction
Is in contact with the surface 1a of the photoconductor 1 in a state parallel to the axis line of.

The conductive core metal 15 of the charging roller 2 includes
A charging bias voltage (which changes according to the surface temperature of the charging roller as will be described later with reference to FIG. 8) is applied from a high-voltage power supply generation circuit 24 that serves as a voltage applying unit that applies a voltage to the charging roller 2. As a result, the surface 1a of the photoconductor 1 is uniformly charged.

Further, this image forming apparatus has the charging roller 2
Temperature detecting means 20 which is, for example, a thermistor for detecting the surface temperature of the device, and a temperature detecting element 25 of the temperature detecting means 20.
The electric signal conversion circuit 21 that converts the change in electric resistance that changes according to the detected temperature into an electric signal such as a voltage and reads the electric signal, and outputs an output signal corresponding to the detected temperature, and the output from the electric signal conversion circuit 21. An applied voltage control circuit 22 that controls the applied voltage to the charging roller 2 by the high-voltage power supply generation circuit 24 according to the signal.

The applied voltage control circuit 22 determines a correction amount for the reference applied voltage according to the output signal from the electric signal conversion circuit 21 according to a predetermined control table (see FIG. 8 described later), A signal for applying the charging bias voltage having the adjusted correction amount to the charging roller 2 is output to the high-voltage power generation circuit 24.

The temperature detecting means 20 includes a temperature detecting element 25 between the tip portions of the conductive leaf springs 26, 26 arranged in parallel at a distance as shown in FIG. It is temporarily fixed by filling the periphery with silicon grease 27. In the figure, a low friction member such as a fluororesin thin film material 28 is formed on the lower surface side, and a film material 29 formed of polyimide amide is formed on the upper surface side. The conductive leaf springs 26, 26 are fixed and held by bonding so as to sandwich them.

In this way, by covering the contact surface of the temperature detecting means 20 with the charging roller 2 with the thin film material 28 of the low friction member, generally foreign matter such as toner or paper powder is absorbed by the temperature detecting means 20. If it intervenes in the contact portion with the charging roller 2, the surface of the charging roller 2 may be damaged by them, and thus the contact surface of the temperature detecting means 20 with the charging roller 2 has low friction. By covering with a member, it is possible to prevent the above-mentioned foreign matter from sticking to the surface of the temperature detecting means 20, so that the surface of the charging roller 2 can be prevented from being scratched.

The temperature detecting element 2 of the temperature detecting means 20
Reference numeral 5 is an element whose resistance value changes with temperature, and is in contact with the surface of the charging roller 2 via the thin film material 28. A pair of conductive leaf springs 2 to which the temperature detecting element 25 is attached
6, 26 and 26 are in a non-contact state with each other as shown in FIG.
One ends of the insulating members 31 made of resin are fixed, and they are connected to the lead wires 36a and 36b, respectively. The insulating member 31, which is the fixing portion, is fixedly held by the bracket 32 as shown in FIG.

The bracket 32 is supported by a shaft 33 so as to be rotatable in the direction of arrow B in FIG.
The conductive leaf spring 26 is constantly urged to rotate in a direction in which the conductive leaf spring 26 contacts the charging roller 2 by a torsion spring 35 wound around 3. The position of the shaft 33, which is the center of rotation for rotating the temperature detecting means 20, is located upstream of the contact position a between the charging roller 2 and the temperature detecting means 20 in the rotation direction of the charging roller 2 (see FIG. 1). On the right).

The rotational position of the temperature detecting means 20 is
The lower edge of the bracket 32 is regulated at the position shown in the figure where it abuts on the stopper shaft 34. Bracket 3
2, a lever portion 32a is formed, and the engaging end 23a of the release lever 23 of the moving means 40 can be engaged therewith.

Then, by the moving means 40, the temperature detecting element 25 of the temperature detecting means 20 is brought into contact with the surface of the charging roller 2 through the thin film material 28 (FIG. 5) and the contact position shown in FIG. It can be moved to the non-contact position shown in FIG.

The moving means 40 includes a release lever 23 in which a stepped screw 41 is fitted in the elongated hole 23b and is held so as to be movable in the left and right directions in FIG. 2, and the release lever 23 is moved to the left side in FIG. Tension spring 43 for urging and when activated (when on)
The release lever 23 against the biasing force of the tension spring 43.
And a solenoid 45 for moving the right side in the figure.

In this image forming apparatus, as shown in the timing chart of FIG. 6, when the temperature detecting means 20 is in the contact position, the charging roller 2 is driven by the high voltage power supply generating circuit 24.
The applied voltage control circuit 22 is controlled so that the voltage is not applied to. The control is performed by the microcomputer 50 shown in FIG. 1 which controls the entire image forming apparatus.

The microcomputer 50 includes a central processing unit (CPU) having various judgment and processing functions, and a program memory storing various programs and fixed data necessary for controlling various operations at predetermined timing. Is a ROM, a RAM is a data memory for storing input data and processing data by the CPU, and an input / output circuit (I / O). The microcomputer 50 inputs a print signal output when the microcomputer 50 is pressed when starting the image forming operation from a print key 51 provided outside the main body of the image forming apparatus.

Although not shown in FIG. 1, various signals selected by the operator are input from a group of keys for selecting various image forming conditions such as transfer paper size and transfer density. Further, it outputs a drive signal for rotating and driving the drive system of the photoconductor 1 and a signal for operating the solenoid 45 to move the temperature detecting means 20 to the non-contact position.

When the print key 51 is pressed (ON) to input a print signal as shown in FIG. 6, the microcomputer 50 solenoids prior to applying the charging bias voltage to the charging roller 2 after time t1. Turn on 45. Then, the release lever 23
From the position shown in FIG. 1 to the position shown in FIG.
Since it is moved against the biasing force of the
The engaging end 23a of the bracket abuts against the lever portion 32a of the bracket 32 and pushes it toward the right side in FIG.
Rotates about the shaft 33 in the clockwise direction in the figure.

Therefore, the temperature detecting means 20 fixedly held by the bracket 32 is rotated in the same direction, and the temperature detecting element 25 fixed to the tip portion of the conductive leaf spring 26 is removed from the surface of the charging roller 2. After being separated, the temperature detecting means 20 becomes the non-contact position shown in FIG. Further, when the time t2 (FIG. 6) elapses after the solenoid 45 is turned on, the drive system for rotating the photoconductor 1 is driven to drive the photoconductor 1
Is rotated in the direction of arrow A in FIG. As a result, the charging roller 2, which is in contact with the surface 1a of the photoconductor 1 with a predetermined contact pressure, rotates in the direction of the arrow C along with it.

Further, when time t3 (longer than time t2) elapses after the solenoid 45 is turned on, as shown in FIG.
A charging bias voltage is applied to the charging roller 2 from the high-voltage power supply generation circuit 24 shown in FIG. 3, and the solenoid 45 is turned off after a time t4 after the application of the voltage is completed. Therefore, in this embodiment, when the solenoid 45 is off, the temperature detecting means 20 is in the contact position, and the temperature detecting element 25 is in contact with the surface of the photoconductor 1 through the thin film material 28 (FIG. 5), No voltage is applied to the charging roller 2 from the high voltage power supply generation circuit 24.

The voltage is applied to the charging roller 2 when the solenoid 45 is turned on and the temperature detecting means 20 is in the non-contact position shown in FIG. Even if a high voltage is applied to the temperature detecting means 20, there is no electrical influence on the temperature detecting means 20 located away from the charging roller 2 and no trouble occurs. Further, there is no possibility that electrical noise will enter the control system of the entire image forming apparatus through the temperature detecting means 20 or that a short circuit will occur in the circuit due to insufficient dielectric strength, so that no malfunction occurs.

Therefore, the temperature detecting element 25 of the temperature detecting means 20 described with reference to FIG. 5 is brought into contact with the charging roller 2 through the thin film material 28 having an insulating property, so that the friction resistance with the charging roller 2 is reduced and the electricity is reduced. It plays the role of static insulation, but its thickness is several 1 considering the response of temperature detection.
Since it is set to about 0 μm, it cannot be said that it has a perfect withstand voltage against a high voltage applied to the charging roller 2, but the temperature detection means 20 when a high voltage is applied in this way.
The problem can be solved by separating the charging roller 2 from the charging roller 2.

During the charging operation in which the charging bias voltage is applied to the charging roller 2, the temperature detecting means 20 separates from the charging roller 2, so that the surface of the charging roller is not rubbed by the temperature detecting means 20 during that time. It is possible to prevent abrasion of the surface and prevent foreign matters such as toner and paper powder from sticking to the surface. Further, it is possible to prevent the generation of a rubbing noise that is harsh.

As described above, the charging bias voltage applied to the charging roller 2 is corrected with respect to the reference applied voltage according to the surface temperature of the charging roller 2 detected by the temperature detecting means 20. The correction of the applied voltage is performed based on, for example, the content of the diagram showing the relationship between the charging roller surface temperature and the charging bias voltage shown in FIG.

As described above, in this image forming apparatus, the charging bias voltage applied to the charging roller 2 is controlled according to the surface temperature of the charging roller 2 detected by the temperature detecting means 20, so that the image forming apparatuses are compared with each other. Since it is possible to prevent the charging failure even when used under an environmental condition where the target temperature is low (for example, 25 ° C. or lower), it is possible to prevent a decrease in image density.

As shown in FIG. 7, the temperature detecting means 20 contacts the outside of the effective image forming area W of the charging roller 2 with the temperature detecting element 25 through the thin film material 28 (FIG. 5). It is good to arrange. In this way, the temperature detecting means 20 does not come into contact with the effective image forming area W of the charging roller 2 which affects the image and does not damage it, so that a good image can be obtained. Reference numeral 46 in FIG. 7 denotes a plate spring for applying a voltage, which is pressed against the conductive cored bar 15 of the charging roller 2 by an elastic force and slidably contacts,
Power is supplied from there to the high-voltage power supply generation circuit 24.

By the way, in this image forming apparatus, as described with reference to FIG. 1, the position of the shaft 33, which is the center of rotation for rotating the temperature detecting means 20, is located at the charging roller 2 and the temperature detecting means 20.
It is located on the upstream side (right side in FIG. 1) in the rotation direction of the charging roller 2 with respect to the contact position a. By doing so, the rotation center of the temperature detecting means 20 is located on the upstream side in the rotation direction of the charging roller 2 with respect to the contact position a between the charging roller 2 and the temperature detecting means 20. The contacting side is the side approaching / separating from the charging roller 2. That is,
The contact of the temperature detecting means 20 with the charging roller 2 is the contact of the charging roller 2 from the forward direction of rotation.

Therefore, foreign matter such as toner and paper powder adheres to the portion where the temperature detecting means 20 contacts the charging roller 2, so that the friction coefficient of the contact portion increases, which causes a large frictional force. Even if there is, the free end side of the temperature detecting means 20 in contact with the charging roller 2 escapes in the direction away from the charging roller 2 according to the excessively acting frictional force, so that the surface of the charging roller 2 is mechanically damaged. Can be prevented from being given.

<Second Embodiment> (FIG. 9) In the image forming apparatus according to this embodiment, the contact charging member is moved to move the charging roller 2 between a contact position in contact with the photosensitive member 1 and a non-contact position in which it does not contact the photosensitive member 1. A charging roller moving mechanism 70, which is a means, is provided, and the charging roller moving mechanism 70 causes the charging roller 2 separated from the surface of the photoconductor 1 to come into contact with the temperature detecting means 20 standing by at a fixed position. . The image forming apparatus is not provided with a mechanism for moving the temperature detecting means 20.

In this embodiment, the portion of the insulating member 31, which is the fixed portion of the temperature detecting means 20, is located upstream of the contact position a with the charging roller 2 in the rotational direction of the charging roller (right side in FIG. 9). ) Fixed to the holding bracket 76,
The tip end of the conductive leaf spring 26, which is an elastic member extending from the insulating member 31 to the charging roller 2, comes into contact with the charging roller 2 that has moved to the non-contact position as indicated by a virtual line. .

The charging roller moving mechanism 70 includes a swing lever 7
4 is rotatably supported on a holding bracket 76 about a support shaft 77, and the charging roller 2 is rotatably supported on one end of a swing lever 74 via a bearing 17. In the state shown by the solid line in FIG. 9, the charging roller 2 has a predetermined contact pressure due to the urging force of the tension spring 75 whose one end is attached to the spring receiver formed at the end of the swing lever 74.
Is in contact with the surface 1a. The moving operation of the charging roller 2 is performed by moving the release lever 73, which is held so as to be movable only in the left-right direction in FIG.

One end of a swing arm 72 is rotatably attached to the upper surface side of the release lever 73 by a shaft, and a connecting plate 78 is rotatably attached to the other end of the swing arm 72. Through the movable shaft 45a of the solenoid 45
Are connected. The swing arm 72 is constantly biased by the biasing force of the tension spring 43 in the clockwise direction in FIG.

In the charging roller moving mechanism 70, when the solenoid 45 is in the off state, the swing arm 72 is swung by the urging force of the tension spring 43 and the release lever 73 is at the position shown by the solid line in FIG. In this state, the swing lever 74 that supports the charging roller 2 is slightly separated from the cam portion 73b fixed to the end portion of the release lever 73 by the projecting piece portion 74a thereof, so that the urging force of the tension spring 75 causes The charging roller 2 is swung to the position shown in the figure, and is in contact with the surface 1a of the photoconductor 1 with a predetermined contact pressure by the urging force of the tension spring 75.

When the solenoid 45 is turned on, its movable shaft 45a moves to the left in FIG. 9, so that the swing arm 72 swings counterclockwise against the urging force of the tension spring 43. The release lever 73 is moved to the position shown by the phantom line. Therefore, the cam portion 73b of the release lever 73 moves to the position shown by the phantom line to move the swing lever 74.
In order to push the protruding piece 74a of the
4 rotates clockwise against the biasing force of the tension spring 75. Therefore, the charging roller 2 is separated from the surface 1a of the photoconductor 1 as shown by a virtual line.

At the non-contact position where the charging roller 2 is separated from the photoconductor 1, the tip portion of the conductive leaf spring 26 of the temperature detecting means 20 comes into contact therewith. Then, when the charging roller 2 is brought into contact with the photoconductor 1, the tip end portion of the conductive leaf spring 26 of the temperature detecting means 20 separates from the charging roller 2.
Therefore, even if a high voltage is applied to the charging roller 2 while it is in contact with the photoconductor 1, the temperature detecting means 20 will not be electrically damaged.

<Third Embodiment> (FIGS. 10 to 13) In this embodiment, the charging roller 2 is rotated even after it is separated from the photosensitive member 1. As shown in FIG. 10, both ends of the conductive cored bar 15 of the charging roller 2 are rotatably supported by bearings 120 and 121 made of resin. The bearing 120 has the charging roller 2 at one end side.
Hole 120 formed on the other end side for supporting the conductive core metal 15 of
The a is rotatably fitted into the conductive support shaft 123.
Then, both ends of the support shaft 123 are formed on a steel plate by bending the U-shape into a U-shape.
It is supported by 0a.

Therefore, this bearing 120 is
Rotate around 3. Conductive core metal 1 of charging roller 2
5, the upper end portion 15a in FIG. 10 is formed in a spherical shape, and the end portion 15a is in contact with the flat surface portion 127a of the power feeding terminal 127. Similarly, the bearing 121 for rotatably supporting the lower end of the conductive core 15 in FIG. 10 also has the support shaft 129 rotatably fitted to the other end thereof.
The both ends of 29 are connected to the drive side support portion 17 of the bracket 170.
We support with 0b. Therefore, the bearing 121 is the support shaft 1
Rotate around 29.

An intermediate gear 131 and a gear 132 meshing with the intermediate gear 131 are rotatably supported by the bearing 121, and the intermediate gear 131 is formed of a conductive metal core 1 of the charging roller 2.
5 meshes with a roller drive gear 138 fixed to one end. The gear 132 also meshes with a transmission gear 133 fixed to one end of a gear support shaft 134 rotatably supported by the device fixing portion 10, and a one-way clutch 137 is attached to the other end of the gear support shaft 134. A drive gear 135 which is built in and mounted on the gear support shaft 134 via the one-way clutch 137 is provided. Further, a driving force transmission gear 136 rotatably supported by the apparatus fixing portion 10 meshes with the driving gear 135, and the driving force transmission gear 136 drives the motor 13 that drives the photoconductor 1.
It is designed to be rotated by 0.

The one-way clutch 137 functions when the surface peripheral speed when the charging roller 2 is separated from the photosensitive member 1 is made slower than the surface peripheral speed when rotating while contacting the photosensitive member 1. Therefore, when the charging roller 2 contacts the photoconductor 1, the rotational force from the motor 130 is stopped from being transmitted to the charging roller 2 via the rotational force transmission means, and the charging roller 2 is separated from the photoconductor 1. At times, the rotational force from the motor 130 is transmitted to the charging roller 2 via the rotational force transmission means by connecting the gear support shaft 134 and the drive gear 135.

As shown in FIG. 11, the bearing 121 for rotatably supporting the conductive cored bar 15 of the charging roller 2 has a contact lever portion 121b projecting from the upper surface of the bracket 170 on the upper right end in FIG. The spring engaging portions 121c are formed in the respective. Further, a spring engagement portion 170c is formed on the bracket 170 corresponding to the spring engagement portion 121c, and a tension spring 125 is attached between the spring engagement portions 121c and 170c.

Therefore, the bearing 121 is centered on the support shaft 129 by the urging force of the tension spring 125, as shown in FIG.
It is urged to rotate in the counterclockwise direction by 1, so that the charging roller 2 comes into contact with the surface 1a of the photoconductor 1 with a predetermined contact pressure suitable for charging, and the photoconductor 1 can rotate together.

Similarly, the bearing 120 shown in FIG.
Abutment lever portion 12 protruding from the upper surface of the bracket 170
0b, a spring engaging portion 120c is formed in the lower portion, a spring engaging portion 170d is formed in the bracket 170, and a tension spring 125 is attached between the spring engaging portions 120c and 170d. Therefore, the bearing 120
Also, due to the urging force of the tension spring 125, the support shaft 123
Is urged to rotate about the center of the charge roller 2
Contacts the surface 1a of the photoconductor 1.

FIG. 13 is a schematic structural view showing the internal structure of the one-way clutch 137. The one-way clutch 137 is a clutch housing 8 integrally fixed to the drive gear 135.
On the inner peripheral surface of No. 1, linear portions 81a for forming a plurality of wedge portions with the outer peripheral surface 134a of the gear support shaft 134 are formed at predetermined intervals along the circumferential direction, and the clutch housing 81 thereof is formed. A plurality of spring bearing blocks 83 are inserted between the gear bearing shaft 134 and the gear support shaft 134, and the spring bearing blocks 83 are fixed to the inner peripheral surface of the clutch housing 81, and the bearing surfaces 83a of the spring bearing blocks 83 are used to gear the gears. The support shaft 134 is rotatably supported.

Further, needle rollers 85 are rotatably inserted between the spring receiving blocks 83 and 83 adjacent to each other in the circumferential direction, and the needle rollers 85 are inserted between the adjacent spring receiving blocks 83 and 83. Allow to move slightly in the circumferential direction. Then, the springs 86 are attached to the spring receiving grooves of the spring receiving blocks 83, respectively, and each needle roller 85 is biased in the direction of arrow E in FIG. 13 by its biasing force.

It is assumed that the charging roller 2 is in contact with the photoconductor 1 and is being driven to rotate. In FIG.
Assuming that the rotation direction of the photoconductor 1 is the arrow A direction, the charging roller 2 is rotated in the arrow C direction in FIG. 10, and the rotation of the charging roller 2 is the rotation of the roller driving gear 138 and the intermediate gear 13.
1, transmitted to the transmission gear 133 via the gear 132.
The rotation direction of the transmission gear 133 is the same as the rotation direction of the photoconductor 1 (the direction of arrow A), and the gear support shaft 134 is rotated in the same direction as the transmission gear 133. On the other hand, drive gear 1
35, the rotational force of the motor 130 is transmitted to the driving force transmission gear 136.
The rotation direction of the drive gear 135 is also the same as the rotation direction of the photoconductor 1 (direction of arrow A).

When the charging roller 2 is in contact with the photoconductor 1 and is being driven to rotate, the rotation speed of the gear support shaft 134 is higher than the rotation speed of the drive gear 135. Therefore,
The gear support shaft 134 rotates relative to the drive gear 135 in the direction opposite to arrow E in FIG. As a result, each needle roller 85 rolls in the same direction against the biasing force of each spring 86.

For this reason, each needle roller 85 moves to a wide portion in the wedge portion, and the one-way clutch 1
37 is unlocked. That is, the clutch housing 81 and the gear support shaft 134 are relatively rotatable,
The gear support shaft 134 becomes idle with respect to the drive gear 135. In summary, when the charging roller 2 is in sliding contact with the photoconductor 1 and is being driven to rotate, the roller drive gear 138, the intermediate gear 131, the gear 132, the transmission gear 133, and the gear support shaft 134 in FIG. The photoconductor 1 is rotated by the rotational driving force of the photoconductor 1.

Next, when the charging roller 2 shifts from the state where it is in contact with the photosensitive member 1 to the separated state, this charging roller 2
The rotational speed of the gear support shaft 134 in the direction of arrow A decreases with the transition from the contact state to the photoconductor 1 to the separated state. On the other hand, since the drive gear 135 rotates at a constant speed in the arrow A direction, the rotation speed of the drive gear 135 becomes higher than the rotation speed of the gear support shaft 134, and the gear support shaft 13
4 is an arrow E with respect to the drive gear 135 as shown in FIG.
It will rotate relative to the direction.

Therefore, the outer peripheral surface 1 of the gear support shaft 134 is
A force acts to move each needle roller 85, which is in point contact with 34a, in the direction of arrow E. As a result, the needle rollers 85 are moved to the narrow portion of the wedge portion, and the needle rollers 85 are moved to the outer peripheral surface 134 a of the gear support shaft 134.
Then, the one-way clutch 137 is locked by being strongly pressed against the linear portion 81a.

That is, the clutch housing 81 and the gear support shaft 134 are locked through the needle rollers 85, the drive gear 135 and the gear support shaft 134 are connected, and the charging roller 2 shown in FIG. 12 is rotated by the rotating force of the photosensitive member 1 in the direction opposite to the rotating direction of the photosensitive member 1 and separated from each other, and the charging roller 2 is fixed to the inner surface of the bracket 170 as shown in FIG.
Touch 1.

Then, at the moment when the charging roller 2 separates from the photoconductor 1, the rotational force from the motor 130 described in FIG. 10 is transmitted from the driving force transmission gear 136, the driving gear 135 to the one-way clutch 137 via a gear. The rotation force is transmitted to the support shaft 134, and the rotational force thereof is further transmitted to the transmission gear 133 and the gear 13.
2, transmitted to the intermediate gear 131 and the roller drive gear 138.

Therefore, while the charging roller 2 rotates while the surface peripheral speed V is instantly switched to the surface peripheral speed V 0 slower than the surface peripheral speed V 0 when rotating while contacting the photoreceptor 1, As shown in 12, cleaning member 1
Since it comes into contact with 11, the foreign matter such as toner and paper dust attached to the surface of the charging roller 2 is reliably removed.

By the way, as shown in FIG. 14 (the parts corresponding to those in FIG. 1 are designated by the same reference numerals), the charging roller 2 is always brought into contact with the photosensitive member 1 so that the charging roller 2 rotates together with the photosensitive member 1. A high voltage may be applied from the high-voltage power supply generation circuit 24 at a predetermined timing with the image forming operation to charge the surface of the photoconductor 1. In this image forming apparatus, the portion of the insulating member 31 that is the fixed portion of the temperature detecting means 20 is located upstream of the contact position a between the charging roller 2 and the temperature detecting means 20 in the rotation direction of the charging roller 2 (see FIG. It is fixed to the fixing portion 30 of the device located on the right side) via the bracket 32.

Therefore, the moving means for bringing the temperature detecting means 20 into and out of contact with the charging roller 2 and the charging roller 2 are connected to the photosensitive member 1.
Although it has no means for contacting and separating with the temperature detecting means 20,
Even if the friction coefficient of the contact portion increases due to the adhesion of foreign matter such as toner or paper powder to the portion of the temperature detecting means 20 that contacts the charging roller 2, the free end side of the temperature detecting means 20 that contacts the charging roller 2 is separated from the charging roller 2. Since it escapes in the moving direction in accordance with the excessively acting frictional force, it is possible to prevent mechanical damage to the surface of the charging roller 2.

However, depending on the material of the charging roller 2, the abnormal contact of the charging roller 2 with the photosensitive member 1 may cause an abnormal image due to the contact mark formed on the surface of the photosensitive member 1. As it happens,
As described above, it is desirable to provide a means (contact charging member moving means) for bringing the charging roller 2 into and out of contact with the photoconductor 1.

In each of the above-mentioned embodiments, the case where the contact charging member for detecting the surface temperature by the temperature detecting means is the charging roller has been described, but the transfer member (transfer belt in FIG. 3) which is also the contact charging member is described. The present invention is applied to a transfer roller type), the surface temperature of the transfer member is detected by a temperature detecting means, and the surface temperature of the transfer member is detected according to an output signal corresponding to the detected temperature. If the voltage applied to the transfer member is controlled, the toner image on the photoconductor can be always transferred onto the transfer paper under optimum transfer conditions regardless of the operating temperature of the apparatus.

When the contact charging member that detects the surface temperature and applies the applied voltage according to the detected surface temperature is a charging member, the charging member is not limited to the roller type, but may be a belt type, a blade type, or a brush type. It may be a type. Further, the photoconductor is not limited to the drum type, but may be a belt type.

[0078]

As described above, according to the image forming apparatus of the present invention, the fixing portion of the temperature detecting means rotates the contact charging member with respect to the contact position between the contact charging member and the temperature detecting means. Since the elastic member is located on the upstream side in the direction of contact with the contact charging member, the friction coefficient changes due to the presence of foreign matter such as toner or paper dust in the portion of the temperature detecting unit contacting the contact charging member. Even if a large frictional force is generated, the excessive frictional force escapes as the portion of the temperature detecting means that contacts the contact charging member moves away from the contact charging member. It is possible to prevent the physical damage and to always perform accurate temperature detection.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing, together with a control system, a state in which a temperature detecting means for detecting a surface temperature of a charging roller, which is a contact charging member of an image forming apparatus according to a first embodiment of the present invention, is brought into contact with the charging roller. .

FIG. 2 is a schematic diagram showing a state in which the temperature detecting means is moved to a non-contact position where it does not contact the surface of the charging roller by the moving means.

FIG. 3 is a configuration diagram showing a main part of an image forming apparatus which is also provided with the charging roller and temperature detecting means.

FIG. 4 is a perspective view showing the structure of the temperature detecting means.

FIG. 5 is a vertical cross-sectional view showing a structure around a temperature detecting element of the temperature detecting means.

FIG. 6 is a timing chart showing operation timings of respective parts of the image forming apparatus of FIG.

FIG. 7 is a front view showing a state in which the temperature detecting means is brought into contact with the outside of the effective image forming area of the charging roller.

FIG. 8 is a diagram showing the relationship between the charging bias voltage applied to the charging roller and the surface temperature of the charging roller.

FIG. 9 is a schematic configuration diagram showing a second embodiment of the present invention.

FIG. 10 is a plan view showing the vicinity of a charging roller of an image forming apparatus showing a third embodiment of the invention.

11 is a sectional view taken along line D-D of FIG. 10 showing a state in which the charging roller is brought into contact with the photoconductor in the image forming apparatus.

FIG. 12 is a sectional view taken along the line DD of FIG. 10, showing a state in which the charging roller is also separated from the photoconductor.

FIG. 13 is a schematic configuration diagram showing an internal configuration of a one-way clutch that transmits a driving force to a charging roller, which is also provided in the image forming apparatus.

FIG. 14 is a schematic view similar to FIG. 1, showing an embodiment in which a charging roller is always brought into contact with a photoconductor to rotate together.

FIG. 15 is a schematic view showing an example of a conventional rotatable temperature detecting means.

[Explanation of symbols]

1: photoconductor 2: charging roller (contact charging member) 7a: Endless belt (contact charging member) 20: Temperature detecting means 24: High-voltage power supply generation circuit (voltage application means) 26: Conductive leaf spring (elastic member) 28: Thin film material (low friction material) 31: Insulation member (fixed part) 33: Shaft 40: means of transportation 70: Charging roller moving mechanism (contact charging member moving means)

Claims (2)

(57) [Claims] 1. A rotating photoconductor, a contact charging member to which a voltage is applied while being in contact with the photoconductor directly or via a transfer paper while rotating, and a voltage is applied to the contact charging member. A voltage applying means, a temperature detecting means for detecting the surface temperature of the contact charging member, and a contact charging member moving means for moving the contact charging member to a contact position in contact with the photoreceptor and a non-contact position not in contact with the photoreceptor. In the image forming apparatus, the temperature detecting means has a fixing portion and an elastic member extending from the fixing portion to the contact charging member, and the fixing portion contacts the temperature detecting means and the contact charging member. The member, which is located upstream of the contact charging member in the rotation direction of the contact charging member and is fixed to a bracket that holds the member that supports the contact charging member, supports the contact charging member at one end thereof.
With the contact charging member rotatably supported,
An image forming apparatus , which is rotatably supported by a roller, and the tip of the elastic member comes into contact with the contact charging member that has moved to the non-contact position. 2. The image forming apparatus according to claim 1 ,
An image forming apparatus, wherein a contact surface of the temperature detecting means with the contact charging member is covered with a low friction member.