JP3325165B2 - 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 electrophotographic apparatus provided with a charging member to which a voltage is applied in contact with a rotating photosensitive member, and temperature detecting means for detecting a surface temperature of the charging member. The present invention relates to an image forming apparatus of the type.

[0002]

2. Description of the Related Art For example, an image forming apparatus such as an electrostatic copying machine or a printer is provided with a charging device for charging a photosensitive member, which is a member to be charged. Attention has been paid to a charging device of a contact roller charging type, which performs charging by contacting a charging roller as a member.

In such a charging device of the contact roller charging type, charging efficiency expressed by charging potential / applied voltage changes depending on the surface temperature of the charging roller, and the lower the temperature, the lower the efficiency. Therefore, in the case of the constant voltage control, when the charging efficiency is reduced, the charging potential obtained by a constant applied voltage is reduced, so that there is a problem that the image density is reduced. There is also a problem that other process control for controlling the charged potential as a reference value is not normally performed.

In order to solve such a problem, for example, Japanese Patent Application Laid-Open No. Hei 4-6567 discloses a method in which the temperature of a charging member such as a charging roller is maintained in a range of 35 ° C. to 55 ° C. in a low temperature environment. Proposals have been made to prevent charging failure from occurring even when the apparatus is used.

The charging member is heated by, for example, providing a heat source near or inside the charging member, or using heat from a heat fixing device provided in the image forming apparatus. Heat. It is described that the temperature can be adjusted by using a known temperature adjusting member such as a thermostat.

However, if the temperature of a charging member such as a charging roller is heated so as to be within a predetermined temperature range,
The charging potential can be maintained at a predetermined value that does not cause a decrease in image density or the like. However, the heating system causes the image forming system to be disposed at a position relatively close to the photoconductor and other heat sources together with the charging member. Because various units of are also heated,
The toner remaining on the surface of the photoreceptor after the transfer of the toner image is recovered and returned to the developing device. In the process of recycling the toner, the toner is heated, so that toner blocking and deterioration of the toner cohesion tend to occur.

Therefore, in order to solve these problems,
Temperature detection means (sensor) for detecting the surface temperature of the charging roller
There has been proposed a charging device in which a voltage applied to a charging roller is controlled in accordance with a temperature detected thereby to obtain a stable charging potential without causing charging failure (for example, Japanese Patent Laid-Open No. -186381). According to this charging device, since a heating member such as a heater is not required, the heating does not affect each part of the image forming system, so that it is possible to prevent toner blocking and deterioration of toner aggregation.

[0008]

However, even when the surface temperature of the charging roller is detected as described above and the voltage applied to the charging roller is controlled in accordance with the detected temperature, there is still a problem. there were. That is, although the voltage applied to the charging roller is smaller than that of the conventional charging method using corona discharge due to the adoption of the contact roller charging method, it is a high voltage of 1-2 KV. And the like in various ways.

For example, when the temperature detecting means is in contact with the charging roller, when a high voltage is applied to the charging roller, the control circuit controls the applied voltage through the temperature detecting means in contact therewith. The control system may malfunction due to intrusion of electrical noise or short-circuit due to insufficient insulation withstand voltage, and in the worst case, it may lead to destruction. Also, if the temperature detecting means is in constant contact with the charging roller, the surface of the charging roller is worn, foreign matter such as toner or paper powder is fixed on the surface, or the sliding is performed when the charging roller is rotating. The sibilance may occur, and the sound may be harsh.

Therefore, it is conceivable to separate the temperature detecting means from the charging roller during image formation. In this case, the voltage applied to the subsequent charging roller according to the temperature detected when the temperature detecting means was in contact with the charging roller before the image formation was started is changed to the temperature again after the image formation is completed. If the detection means is controlled to be constant until it comes into contact with the charging roller, a problem arises when the number of images to be formed at one time is large.

For example, when a certain period of time elapses after the copying process is completed, in the case of an electrostatic copying machine that enters the standby mode by lowering the temperature of the fixing roller of the fixing device to save energy, the standby mode state is set. If the copying process is continued for a long time in a low temperature environment, the temperature may drop to about 15 ° C. immediately after restarting the copying process.

In this case, by restarting the copying process, a voltage corresponding to the surface temperature of 15 ° C. is applied to the charging roller, and the applied voltage is continuously applied until the copying of all the set number of sheets is completed. Is done. At this time, the surface temperature of the charging roller, which was low when the copying process was restarted, gradually increases with each increase in the number of times of copying, but the voltage applied to the charging roller was changed to the first sheet where copying was started. Therefore, there is a problem that a difference is generated between the surface temperature of the charging roller and the surface temperature of the charging roller, which changes every moment, and optimal charging cannot be performed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems. Even if the surface temperature of a charging member such as a charging roller changes every moment due to continuous image formation, An object is to stably obtain a desired charging potential by applying an optimum applied voltage corresponding to the changing temperature to the charging member.

In addition, when the applied voltage is applied to the charging member, the control system of the apparatus is prevented from causing a malfunction or being destroyed. It is another object of the present invention to prevent foreign substances such as paper powder from sticking and generating a jarring noise.

[0015]

According to the present invention, in order to achieve the above object, in the above-described image forming apparatus, means for moving the temperature detecting means to a non-contact position not in contact with the charging member during image formation. When the first image is formed after the image formation is started, two sheets are continuously formed according to the temperature detected when the temperature detecting means is in contact with the charging member immediately before the image formation is started. When the above image formation is performed, means for controlling the voltage applied to the charging member by the voltage applying means in accordance with the detected temperature detected by the temperature detecting means at the non-contact position for the second and subsequent sheets. It is provided.

With this configuration, when the image formation is started, when the first image is formed, the charging unit detects the temperature detection unit immediately before the image formation is started when the temperature detection unit is in contact with the charging member. The voltage applied to the charging member is controlled in accordance with the surface temperature of the member, and when two or more sheets are continuously formed, the temperature detecting means does not contact the charging member after the second sheet. Since the applied voltage is controlled according to the detected temperature detected at the contact position, even when a large number of images are continuously formed in a low temperature state, the surface temperature of the charging member is changed according to the number of image formations. Even if it changes every moment, the voltage applied to the charging member is controlled according to the changed temperature, so that the photoconductor can be stably charged to a desired charging potential.

Further, since the temperature detecting means is moved to a non-contact position not in contact with the charging member at the time of image formation, an unpleasant sliding noise generated by the temperature detecting means rubbing the charging member at the time of image formation is generated. do not do. In addition, it is possible to prevent foreign matters such as toner and paper powder from sticking to the surface of the charging member.

Further, in an image forming apparatus provided with the same photosensitive member, charging member, voltage applying means, temperature detecting means, and applied voltage controlling means as described above, the temperature detecting means may be in contact with the surface of the charging member. Moving means for moving to a non-contact position not in contact with the position; means for preventing voltage from being applied to the charging member by the voltage applying means when the temperature detecting means is at the contact position; When moving from the position to the non-contact position, the image formation is started, and in the case of the first image formation, the temperature detection means detects the temperature detected at the contact position immediately before the image formation is started, When two or more images are continuously formed, the temperature detecting means moves to the above-mentioned non-contact position and the voltage is applied to each of the voltage applying means in accordance with the detected temperature. Providing a means for controlling the voltage applied to the charging member that.

In this case, when the temperature detecting means is at the contact position in contact with the surface of the charging member, no voltage is applied to the charging member from the voltage applying means. To prevent various noises, malfunctions, and destruction caused by electrical noise entering the control system of the entire image forming apparatus via a fault or its temperature detection means. Can be.

Further, in an image forming apparatus provided with the same photosensitive member, charging member, voltage applying means, temperature detecting means and applied voltage controlling means as described above, the charging member is brought into contact with and separated from the photosensitive member. Means for causing the temperature detecting means to contact the surface of the charging member when the charging member is separated from the photosensitive member, and the charging member is directly contacted with the photosensitive member or via transfer paper. When in contact, the charging member is disposed at a position separated from the surface of the charging member. When the charging member comes into contact with the photoconductor again after separating from the photoconductor, image formation is started and the first image is formed. At the time of formation, immediately before the image formation is started, the charging member is separated from the photoreceptor and the temperature detecting means is in contact with the charging member and the temperature is detected. Image shape When the charging is performed on the second and subsequent sheets, the charging member contacts the photoreceptor and is separated from the charging member according to the detected temperature detected by the temperature detecting means. Means for controlling the applied voltage is provided.

In this case, even if a means for moving the temperature detecting means is not provided, when the charging member is separated from the photoreceptor, it comes into contact with the temperature detecting means, and when the charging member comes into contact with the photoreceptor directly or via transfer paper. Since the charging member is separated from the temperature detecting means, the structure can be simplified, and the photosensitive member can be stably charged to a desired charging potential similarly to the above-described image forming apparatus.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an electrostatic copying machine, which is an image forming apparatus, for explaining an embodiment of the present invention, together with each function realizing means of the electrostatic copying machine. FIG. FIG. 3 is a schematic diagram showing a state in which a temperature detection sensor for detecting the surface temperature of a charging roller serving as an application member is in a contact position, and FIG. 3 is a schematic diagram showing a state in which the temperature detection sensor has been moved to a non-contact position.

In the electrostatic copying machine as this image forming apparatus, as shown in FIG. 1, a charging roller 2 serving as a charging member is brought into direct contact with a drum-shaped rotating photoreceptor 1, and a voltage is applied thereto. A contact roller charging type image forming apparatus for uniformly charging the surface 1a of the photoconductor 1 to a predetermined potential by applying
The photoreceptor 1 rotates at a predetermined peripheral speed in the direction indicated by the arrow A, and the charging roller 2 is driven to rotate at a constant speed in the direction indicated by the arrow while being brought into contact therewith while contacting the photosensitive member.

The photoreceptor 1 is driven by a photoreceptor drive system including a drum drive timing belt, a drum drive pulley, a motor for driving them (all not shown), and the like. The roller 2 is pressed by, for example, a contact pressure of 10 g by the urging force of a pressure spring (not shown).
/ Cm (substantially line contact).

The photosensitive member 1, a charging device having the charging roller 2, a roller cleaner 9 for cleaning the surface of the charging roller 2, a cleaning device having the cleaning blade 8, and the toner collecting unit 11 are integrated. Of the process cartridge 10.

Around the photosensitive member 1, an eraser 18 is provided.
, A developing device 6 and a transfer unit 7 which is a contact type transfer device having an endless belt.
Reference numeral 13 denotes a fixing device that fixes the toner image transferred onto the transfer paper P by applying pressure while heating.

The process cartridge 10 contains:
A temperature detecting sensor 20 which is a temperature detecting means composed of, for example, a thermistor for detecting the surface temperature of the charging roller 2 is provided, and the temperature detecting sensor 20 comes into contact with the surface of the charging roller 2 by a contact / separation mechanism 40. It is moved to the contact position shown in FIG. 2 and the non-contact position shown in FIG.

The non-contact position is the position of the charging roller 2
The surface temperature of the charging roller 2 detected indirectly at the non-contact position is substantially the same as the surface temperature detected at the contact position by setting the position relatively close to the surface. The contact / separation mechanism 40 constitutes a drive mechanism of a means for moving the temperature detection sensor 20 to a non-contact position not in contact with the charging roller 2 during execution of a copying process for forming an image. The drive is controlled by a drive system operation control means 39 shown in FIG.

The electrostatic copying machine converts a change in electric resistance, which changes according to a temperature detected by a temperature detecting element 25 (described later in FIGS. 4 and 5) of the temperature detecting sensor 20, into an electric signal such as a voltage. And an electric signal conversion circuit 21 for outputting an output signal corresponding to the detected temperature, and a high voltage power supply circuit 24 serving as a voltage applying means for applying a voltage to the charging roller 2 according to an output signal from the electric signal conversion circuit 21. An applied voltage control circuit 22 serving as applied voltage control means for controlling an applied voltage;
And

The application voltage control circuit 22 responds to the output signal from the electric signal conversion circuit 21 by a charging roller surface temperature stored in a microcomputer 50 shown in FIG. A signal for applying the applied voltage determined according to the control table (see FIG. 6) indicating the relationship with the voltage to the charging roller 2 is output to the high-voltage power supply circuit 24.

At this time, the microcomputer 50 starts the copying process and executes the first copying process.
(At the time of image formation), when the temperature detection sensor 20 is in contact with the charging roller 2 immediately before the start of the copying process, and when two or more copying processes are continuously performed, Is the temperature detection sensor 2
Control is performed such that a voltage is applied to the charging roller 2 by the high-voltage power supply circuit 24 in accordance with the detected temperature where 0 is detected at a non-contact position away from the charging roller 2.

Then, the microcomputer 50
Input from the copy number counter 38 the number of copies continuously performed by executing the copy process. Further, this electrostatic copying machine is provided with a voltage application stopping means 30 for preventing the high voltage power supply circuit 24 from applying a voltage to the charging roller 2 when the temperature detection sensor 20 is at the contact position as shown in FIG. ing.

In this electrostatic copying machine, when a copying process is started, light L from an exposure device (not shown) is incident on the surface 1a of the photosensitive member 1, and the charged surface uniformly charged by the charging roller 2 Is exposed to form an electrostatic latent image thereon.
At this time, on the charged surface, the static charge in the area outside the size of the transfer paper used by the eraser 18 is removed (trimmed). Then, the electrostatic latent image is transferred to the developing device 6.
Is developed by the toner supplied by the developing sleeve of (1) to become a toner image (visible image).

On the other hand, the transfer paper in a paper feed cassette (not shown) is fed by a paper feed roller which rotates at a predetermined timing.
The sheet is fed one by one, and is temporarily stopped by the pair of registration rollers 14 and adjusted in timing. Then, the sheet is conveyed toward the transfer unit provided with the transfer unit 7 at an accurate timing coincident with the toner image on the photoreceptor 1. Is done.

A transfer bias is applied to the transfer paper P by the transfer unit 7, and a toner image is transferred to the upper surface side in FIG. 1 and is separated from the photoreceptor 1 and conveyed to the fixing device 13, where the toner is removed. After fixing, the sheet is discharged to a discharge tray or the like outside the apparatus.

After the transfer is completed, foreign matters such as residual toner and paper dust remaining on the photosensitive member 1 are removed by the cleaning blade 8, and the residual potential remaining on the photosensitive member 1 is removed by a charge removing device (not shown). ) To prepare for the next charging by the charging roller 2.

As shown in FIG. 2, the charging roller 2 has a conductive rubber roller 16 made of, for example, epichlorohydrin rubber integrally mounted on the outside of a conductive core 15 made of iron or the like. Both ends of the gold 15 are rotatably supported by conductive bearings 17, 17, respectively.
Each of the bearings 17 is urged toward the photoconductor 1 by a pressure spring (not shown) via a member holding the bearing 17, so that the axis of the charging roller 2 is parallel to the axis of the photoconductor 1. It is in contact with surface 1a.

The conductive core 15 of the charging roller 2 includes
A charging bias voltage (an applied voltage that changes according to the surface temperature of the charging roller as described later with reference to FIG. 6) is applied from a high-voltage power supply circuit 24 that applies a voltage to the charging roller 2. 1 is uniformly charged.

The temperature detecting sensor 20 for detecting the surface temperature of the charging roller 2 has a temperature detecting element 25 between the distal end portions of conductive leaf springs 26, 26 arranged in parallel at intervals as shown in FIG. As shown in FIG. 5, the periphery is temporarily fixed by filling it with silicon grease 27, and a film material 28 having a thickness of about 10 μm formed of, for example, polyimide amide is formed on the lower surface in FIG. A film material 29 of the same thickness made of fluororesin (Teflon) is fixed and held by bonding so as to sandwich the conductive leaf springs 26, 26, respectively.

The temperature detecting element 25 is an element whose resistance value changes depending on the temperature, and is in contact with the surface of the charging roller 2 via a polyimide amide film material 28. The pair of conductive leaf springs 26, 26 to which the temperature detecting element 25 is attached are fixed at one end to a resin insulating member 31 in a non-contact state as shown in FIG. They are connected to lead wires 36a and 36b, respectively. The insulating member 31 is fixedly held by a bracket 32 as shown in FIG.

The bracket 32 is rotatably supported by a shaft 33 in a direction indicated by an arrow B in FIG.
The conductive leaf spring 26 is constantly urged to rotate in the direction in which the conductive leaf spring 26 comes into contact with the charging roller 2 by the torsion spring 35 wound around the roller 3. The pivoting position is regulated at a position shown in the drawing where the lower edge of the bracket 32 abuts against the stopper shaft 34. A lever portion 32a is formed on the bracket 32, and the engaging end 23a of the release lever 23 of the contact / separation mechanism 40 can be engaged with the lever portion 32a.

Then, the temperature detecting element 25 of the temperature detecting sensor 20 is moved by the contact / separation mechanism 40 to the film material 28.
(FIG. 5) FIG.
Can be moved to a contact position shown in FIG. 3 and a non-contact position shown in FIG.

The contact / separation mechanism 40 includes a release lever 23 in which a stepped screw 41 is fitted into the elongated hole 23b and held so as to be movable in the left-right direction in FIG. Tension spring 43 for urging, when activated (on)
Release lever 23 against the urging force of the tension spring 43.
Is moved to the left in the figure.

In this electrostatic copying machine, when the copying process described with reference to FIG. 1 is executed, when the copying process for the first sheet is executed, before the temperature detection sensor 20 executes the copying process. The temperature detection sensor 20 detects the non-contact position near the charging roller 2 in accordance with the detected temperature detected when the surface of the charging roller 2 is in contact with the charging roller 2 and when performing a copying process continuously for two or more sheets. The voltage applied to the charging roller 2 is controlled in accordance with the detected temperatures.

In other words, the microcomputer 50 shown in FIG. 2 responds to the signal corresponding to the number of copies inputted from the copy number counter 38 to determine whether the process is the first copy process or two or more continuous copy processes. It is determined whether it is the second and subsequent sheets when the operation is performed.

If the copying process is the first copying process, the temperature detecting sensor 20 immediately before the copying process is started.
According to the temperature detected when the battery was in contact with the charging roller 2,
In the copying process for the second and subsequent sheets, a control signal is sent to an applied voltage control circuit 22 so as to control the applied voltage applied to the charging roller 2 in accordance with the detected temperature detected by the temperature detection sensor 20 at the non-contact position. Is output. Therefore, the applied voltage control circuit 22 determines an applied voltage to be applied to the charging roller 2 by the high-voltage power supply circuit 24 based on the control signal, and controls the output voltage of the high-voltage power supply circuit 24 to be the applied voltage. .

The control of the applied voltage performed here is performed according to the relationship between the surface temperature of the charging roller and the applied voltage necessary for maintaining the charging potential constant as shown in FIG. As is clear from FIG. 6, the applied voltage changes each time according to the surface temperature of the charging roller 2 detected by the temperature detection sensor 20. When the applied voltage is determined in this way, the high-voltage power supply circuit 24 applies an output voltage corresponding to the determined applied voltage to the charging roller 2.

The start of the copying process by this electrostatic copying machine is started when the print key 51 (FIG. 2) is pressed and a print signal is inputted (ON) as shown in FIG. That is, after time t1 after the print signal is turned on, the solenoid 45 is turned on before applying the charging bias voltage (applied voltage) to the charging roller 2.

Then, the release lever 23 shown in FIG. 2 is moved to the position shown in FIG. 3 against the urging force of the tension spring 43, so that the engagement end 23a of the release lever 23 The bracket 32 pivots about the shaft 33 in the counterclockwise direction in the figure to come into contact with the part 32a and push it to the left in the figure.

Therefore, the temperature detection sensor 20 fixed and held by the bracket 32 is rotated in the same direction,
The temperature detecting element 25 fixed to the tip of the conductive leaf spring 26 is separated from the surface of the charging roller 2, and the temperature detecting sensor 20 is brought into the non-contact position shown in FIG.

When a time t2 (FIG. 7) elapses after the solenoid 45 is turned on, the drive system for rotating the photosensitive member 1 is driven to rotate the photosensitive member 1 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 photoreceptor 1 at a predetermined contact pressure is rotated in the direction indicated by the arrow.

Further, when a time t3 (longer than the time t2) has elapsed since the solenoid 45 was turned on, a charging bias voltage is applied from the high voltage power supply circuit 24 to the charging roller 2, and the application of the voltage is completed. Time after t4
Later, the solenoid 45 is turned off. When the print key is pressed again to input a print signal (ON) after time t5 (arbitrary timing) after the solenoid 45 is turned off, the above-described copying process is repeatedly executed.

As described above, in this embodiment, when the solenoid 45 is off, the temperature detection sensor 20 is at the contact position (the position in FIG. 2), and the temperature detection element 25 is connected via the film material 28 (FIG. 5). When the charging roller 2 is in contact with the surface of the photosensitive member 1, no voltage is applied to the charging roller 2 from the high-voltage power supply circuit 24.

The voltage is applied to the charging roller 2 during the copying process. At this time, the solenoid 45 is turned on as shown in FIG. The non-contact position shown in FIG. Therefore, even if a high voltage is applied to the charging roller 2 at this time, the temperature detection sensor 20 located at a position separated from the charging roller 2 has no electrical influence and does not cause any trouble. Therefore, there is no risk of electric noise entering the control system of the entire electrostatic copying machine via the temperature detection sensor 20 or short-circuiting of the circuit due to insufficient insulation withstand voltage, so that no malfunction occurs.

As described above, in the electrostatic copying machine, when the copying process is started, when the first copying process is executed,
Immediately before the copying process is started, the temperature detection sensor 2
0 controls the voltage applied to the charging roller 2 in accordance with the surface temperature of the charging roller 2 detected when the charging roller 2 is in contact with the charging roller 2. After the first sheet, the applied voltage is controlled according to the detected temperature detected by the temperature detection sensor 20 at a non-contact position where the temperature detection sensor 20 does not contact the charging roller 2.

Therefore, even when the surface temperature of the charging roller 2 is changed (increased) every time when a large number of copies are continuously made in a low temperature state in accordance with the number of image formations, the changed surface temperature is changed. Therefore, the applied voltage applied to the charging roller 2 is controlled in each case, so that the photosensitive member 1 can be stably charged to a desired charging potential.

The microcomputer 50 shown in FIG. 2 controls the voltage applied to the charging roller 2 according to the surface temperature of the charging roller 2 in accordance with the number of copies. The microcomputer 50 has a central processing unit (CPU) having various judgment and processing functions, a ROM which is a program memory storing various programs and fixed data necessary for performing various operations at predetermined timings, A RAM, which is a data memory for storing input data and data processed by the CPU, and an input / output circuit (I /
O).

Then, the microcomputer 50
Is a step 1 when the routine shown in FIG. 8 starts.
From the copy number counter 38, the number of copies indicating the number of the transfer sheet on which an image is to be transferred from the start of the copying process is input. Next, in step 2, it is determined whether or not the input copy number is the first copy. If the copy is the first copy, the process proceeds to step 3, where the temperature detection sensor 20 is contacted immediately before the copy process is started. The voltage applied to the charging roller 2 by the high-voltage power supply circuit 24 (FIG. 1) is changed according to the detected temperature when the charging roller 2 is in contact with the charging roller 2 at the position shown in FIG.
Is controlled in accordance with the relationship between the surface temperature of the charging roller and the applied voltage shown in FIG.

If it is determined in step 2 that the number of copies is not the first copy, it is the second copy or later, and thus the
To the charging roller 2 in accordance with the temperature detected by the temperature detection sensor 20 at a non-contact position away from the charging roller 2.
Similarly, the applied voltage is controlled according to the relationship between the surface temperature of the charging roller and the applied voltage shown in FIG.

In the next step 5, it is determined whether or not the number of copies has reached the set number of copies to be copied. If not, the copying process is continued, so that the process returns to step 1 and the above-described processing and determination are performed. Repeat, step 5
When it is determined that the number of copies has reached the set number, all the processes in this routine are terminated.

FIG. 9 is a schematic diagram showing the vicinity of the charging device of an electrostatic copying machine, which is an image forming apparatus in which the temperature detection sensor is fixed and the charging roller contacts and separates from the photosensitive member. FIG. 11 is a perspective view showing a temperature detection sensor provided in the charging device, FIG. 11 is a side view of the temperature detection sensor, and FIG. 12 is a diagram showing a state in which a microcomputer 70 provided in the image forming apparatus shown in FIG. It is a flowchart which shows the routine which concerns on applied voltage control. Note that, in FIG. 9, the portions corresponding to FIG. 2 are denoted by the same reference numerals.

In the charging roller 2 according to this embodiment, as shown in FIG. 9, both ends of a conductive core 15 are rotatably supported by conductive bearings 17, 17, respectively. Tension spring 52 made of a conductive material
Is always urged in a direction away from the photoconductor 1. When the charging is not performed, the charging roller 2
It is in the separated position shown by the solid line in the figure due to the urging force of the tension urging spring 52.

In FIG. 9, reference numeral 53 denotes a fixing member made of an insulating material, to which one end of a tension urging spring 52 is engaged. A charging bias voltage is applied to the conductive core 15 from the high-voltage power supply circuit 24 via the tension urging spring 52 and the bearing 17 while the charging roller 2 is in contact with the surface 1 a of the photoconductor 1. So that the photosensitive member 1
Is uniformly charged.

The charging roller 2 is rotatably held via a bearing 17 at one end of an arm 55 whose center is swingably supported by a shaft 54, and the other end of the arm 55 is provided with a solenoid 56. The movable shaft 56a is attached via a spring 57. The solenoid 56 has a main body fixed to a fixing portion of the apparatus. When the solenoid 56 is in an off state, the arm 55 swings to a position shown by a solid line in FIG. 2 is separated from the photoconductor 1.

When the solenoid 56 is turned on, the arm 55 swings clockwise against the tension urging force of the tension urging spring 52 and moves to a position shown by a virtual line. The charging roller 2 comes into contact with the surface 1a of the photoreceptor 1 with a predetermined contact pressure suitable for charging by slightly extending 57.

A temperature detecting sensor 60 for detecting the surface temperature of the charging roller 2 is provided close to the charging roller 2, and the temperature detecting sensor 60 is connected to the charging roller 2 and the photosensitive member 1.
Is in contact with the surface of the charging roller 2 when the charging roller 2 is in a separated state, and is fixed at a position shown in the drawing that is separated from the surface of the charging roller 2 when the charging roller 2 and the photosensitive member 1 are in a contacting state. .

As shown in FIG. 11, the temperature detecting sensor 60 has a cushion material 59 made of foamed polyurethane placed on a substrate 58 made of, for example, epoxy resin, and the upper surface of the cushion material 59 is shown in FIG. The temperature detecting element 25 is placed so as to cover the temperature detecting element 25 from above with a thickness of 10 μm formed of polyimide amide.
The film material 28 of about m is fixed and held.

The role of the film member 28 covering the surface of the temperature detecting element 25 is the same as that of the film member 28 of the temperature detecting sensor 20 described with reference to FIGS. In this embodiment, as shown in FIG.
Is in contact with the surface of the charging roller 2 when the charging roller 2 and the photoconductor 1 are separated from each other, and is separated from the surface of the charging roller 2 when the charging roller 2 and the photoconductor 1 are in contact with each other. Since the charging roller 2 is fixed at the position, when the charging roller 2 is moved toward and away from the photosensitive member 1, the temperature detection sensor 60 is separated and comes into contact with the surface of the charging roller 2. Therefore, effects similar to those of the embodiment described with reference to FIGS. 1 to 8 can be obtained.

In this electrostatic copying machine, the control of the voltage applied to the charging roller 2 is performed by the microcomputer 5 described with reference to FIG.
The processing is performed by the microcomputer 70 similar to the microcomputer 70. That is, when the routine shown in FIG. 12 starts, the microcomputer 70 determines whether or not the charging roller 2 has come into contact with the photosensitive member 1 again after the charging roller 2 has been separated from the photosensitive member 1 in Step 11, and if NO, YES. Wait until it becomes YES, and proceed to step 12 if it becomes YES.
Steps 12 to 16 perform exactly the same processing and judgment as the processing and judgment from step 1 to step 5 described in FIG.

According to this embodiment, when the charging roller 2 is separated from the photosensitive member 1 without contacting the photosensitive member 1, even if a means for moving the temperature detecting sensor 60 is not provided, the charging roller 2 contacts the temperature detecting sensor 60 and directly contacts the photosensitive member 1. Alternatively, the charging roller 2 is separated from the temperature detection sensor 60 when it comes into contact with the transfer paper, so that the structure of the entire apparatus can be simplified, and the photosensitive member 1 is moved in the same manner as in the embodiment of FIGS. It can be stably charged to a desired charging potential.

FIG. 13 shows that when a jam occurs, the temperature detection sensor is in contact with the charging roller immediately before the start of the copying process when the first copy process after the jam has been performed is performed according to the detected temperature. FIG. 4 is a diagram for describing an embodiment in which a voltage applied to a charging roller is controlled.

In this embodiment, when a jam (paper jam) occurs during the execution of the copying process (copying operation), the front cover provided on the image forming apparatus main body is opened and the jam is cleared. When the front cover is closed, the temperature detection sensor 60 that has been separated from the charging roller 2 comes into contact with the charging roller 2, and after that, when the print key is pressed again and a copy restart signal is input, the jam processing is performed. When the first first copy process is executed later, immediately before the copy is started (immediately after the front cover is closed).
The voltage applied to the charging roller 2 is controlled according to the temperature detected when the temperature detection sensor 60 is in contact with the charging roller 2. When two or more copies are continuously made, the second and subsequent copies are charged by the voltage application means in accordance with the detected temperature detected by the temperature detection sensor 60 at the non-contact position separated from the charging roller 2. The voltage applied to the roller 2 is controlled.

In this embodiment, for example, the linear speed of the photoconductor is 200 mm / sec and the copy speed is 35 mm in the electrostatic copying machine.
Use an analog type copier of sheets / minute (at the time of A4 size horizontal feed). The charging roller 2 has a conductive rubber roller portion made of epichlorohydrin rubber having an outer diameter of φ14 mm.
A conductive rubber roller having a thickness of 3 mm is used. Further, a thermistor is used for the temperature detecting sensor 60 for detecting the surface temperature of the charging roller 2, and the thermistor sets a thermal time constant, that is, an ambient (air) temperature to t1.
When the temperature is changed from t2 to t2, the time required to reach 63.2% of the temperature difference between t1 and t2 is 10 seconds. The distance between the temperature detector of the thermistor and the surface of the charging roller 2 is set to 3 mm.

Next, when a jam occurs during continuous copying operation using this electrostatic copying machine,
The case where the copying operation is resumed after the jam processing and the copying is continued will be described with reference to FIG. In FIG. 13, the horizontal axis indicates the elapsed time after the occurrence of the jam, and the vertical axis indicates the temperature of each part when the surface temperature of the charging roller at the time of the occurrence of the jam is 0 ° C.

In this electrostatic copying machine, when a jam occurs during a continuous copying operation (continuous copying operation), each drive system in the image forming apparatus main body stops operating, and an exhaust fan provided in the fixing device. Also stop rotating. Here, the front cover provided on the image forming apparatus main body is opened in order to perform the jam processing. At this time, the air heated to a very high temperature stored in the fixing roller portion of the fixing device fills the inside of the apparatus. . Therefore, the ambient temperature of the portion where the charging roller 2 is provided increases, and the roller surface temperature of the charging roller 2 also increases.

At this time, the roller surface temperature rises later than the rise in the ambient temperature of the charging roller 2 as shown in FIG. The temperature difference between the two gradually increases with the lapse of time, as seen in the portion of the elapsed time from the occurrence of the jam of 0 to 9 minutes in FIG. If
9 minutes after the occurrence of the jam, the jam processing is completed. At that time, if the front cover opened when the jam is cleared is closed, the charging roller 2 which has been in contact with the surface of the photoconductor at that time is assumed. However, as shown in FIG.
Away from the surface. Then, the charging roller 2 comes into contact with the temperature detection sensor (thermistor) 60.

Therefore, at the moment when the front cover is closed, the temperature detected by the temperature detecting sensor 60 is still close to the ambient temperature of the charging roller 2 (depending on the thermal time constant of the thermistor). As shown by the dashed line, the roller surface temperature is detected. When the front cover is closed, the operation of each drive system in the image forming apparatus main body which has been stopped is restarted, and the exhaust fan of the fixing device is rotated again. Accordingly, since the air in the image forming apparatus main body is discharged to the outside of the apparatus by the exhaust fan, the ambient temperature of the charging roller 2 gradually decreases as seen from 9 to 10.5 minutes in FIG. I do.

By the way, the fixing device needs a waiting time of about one and a half minutes to return to a temperature at which a predetermined fixing operation can be performed. Therefore, after closing the front cover,
At the time when half an hour has elapsed, that is, when about 10.5 minutes have elapsed after the occurrence of the jam, the print key is pressed again to restart copying. Then, the exhaust fan of the fixing device at the start of the copying operation rotates more strongly than at the time of standby, so that the ambient temperature drops more rapidly than at the time of standby (about 10.5 minutes of the elapsed time in FIG. 13). 1
See around 2 minutes). In the example shown in FIG. 13, when about one and a half minutes have elapsed from the restart of the copy operation, the copying of all the specified number of sheets has been completed, and the operation of each image forming system in the image forming apparatus main body is stopped. Stop.

When the copying operation is restarted, the charging roller 2 separates from the temperature detection sensor 60 and comes into contact with the surface of the photosensitive member 1 as shown in FIG. Therefore,
The temperature detection sensor 60 detects the ambient temperature of the charging roller 2 as shown in FIG. 13 (see near 11 minutes elapsed time). At this time, since the ambient temperature has already rapidly dropped, the difference from the roller surface temperature is as small as 0.5 ° C. at the maximum, so that the applied voltage can be controlled almost in accordance with the roller surface temperature.

Here, if the temperature detection sensor 60 always detects the ambient temperature of the charging roller 2, the temperature difference between the temperature detected by the temperature detection sensor 60 and the roller surface temperature is shown in FIG. As shown, the temperature can reach 1.5 ° C. Therefore, in this case, the error of the applied voltage due to the temperature difference is fatal to the charging roller 2. In addition to the above-mentioned jam occurrence, the ambient temperature of the charging roller and the surface of the charging roller as described above may be reduced even when the apparatus is reused after a long-time stoppage of the apparatus, or after performing many continuous copies. The temperature difference from the temperature increases.

In this embodiment, when the copy is started and the first copy operation is performed (when the copy operation is temporarily interrupted due to a jam or the like, the first copy operation is resumed after the restart). Immediately before the copying operation is started, the temperature detection sensor 60
According to the temperature detected when the battery was in contact with the charging roller 2,
When two or more copies are continuously made, the voltage applied to the charging roller 2 is controlled for the second and subsequent copies according to the temperature detected by the temperature detection sensor 60 at the non-contact position. Even when the temperature difference between the ambient temperature of the charging roller 2 and the surface temperature of the charging roller 2 is large, such as when a jam occurs, a voltage almost corresponding to the roller surface temperature can be applied to the charging roller 2. , A desired charging potential can be stably obtained.

[0082]

As described above, according to the present invention, during image formation, the temperature detecting means moves to a non-contact position not in contact with the charging member, so that the temperature detecting means slides on the charging member during image formation. It is possible to prevent the generation of harsh rubbing noise caused by the rubbing and the adhesion of foreign substances such as toner and paper powder to the surface of the charging member.

Further, by continuously forming a large number of images in a low temperature state, the surface temperature of the charging member gradually increases in accordance with the number of times of image formation, or the image is continuously formed. Even if the ambient temperature near the charging member rises sharply due to the air heated by the fixing device during the jam processing,
The first sheet after the image formation is started, or the first sheet after the image formation is resumed, depends on the temperature detected when the temperature detecting means is in contact with the charging member. The voltage applied to the charging member is controlled according to the detected temperature of the atmosphere detected at the non-contact position not in contact with the charging member, so the second and subsequent sheets almost correspond to the surface temperature of the charging member Since the applied voltage is applied to the charging member, the photosensitive member can be stably charged to a desired charging potential.

Further, if a means is provided for preventing the voltage from being applied to the charging member by the voltage applying means when the temperature detecting means is at the contact position in contact with the surface of the charging member, the temperature detecting means can be used to When a voltage is applied to the charging member from the voltage applying unit when the charging unit is at the contact position in contact with the surface, an electrical obstacle to the temperature detecting unit due to the application of the voltage, and the entire image forming apparatus through the temperature detecting unit are damaged. It is possible to prevent various noises and malfunctions from being caused by the intrusion of electrical noise into the control system, and to prevent the malfunctions from being broken.

Further, the temperature detecting means contacts the surface of the charging member when the charging member is separated from the photosensitive member, and the charging member contacts the photosensitive member directly or via the transfer paper. If the charging member is disposed at a position separated from the surface of the charging member when the charging member is in the state, the charging member can be separated from the photoreceptor without providing a means for moving the temperature detecting means to a non-contact position not in contact with the charging member. When it comes apart, it comes into contact with the temperature detecting means, and when it comes in contact with the photoreceptor directly or via transfer paper, the charging member separates from the temperature detecting means. It can be charged to a desired charging potential.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an electrostatic copying machine, which is an image forming apparatus, for explaining an embodiment of the present invention, together with each function realizing means of the electrostatic copying machine.

FIG. 2 is a schematic diagram showing a state in which a temperature detection sensor for detecting a surface temperature of a charging roller as a charging member provided in the electrostatic copying machine is in a contact position.

FIG. 3 is a schematic diagram showing a state where the temperature detection sensor is moved to a non-contact position.

FIG. 4 is a perspective view showing the configuration of the temperature detection sensor.

FIG. 5 is a longitudinal sectional view showing a configuration near a temperature detecting element of the temperature detecting sensor.

FIG. 6 is a diagram illustrating a relationship between an applied voltage applied to a charging roller and a charging roller surface temperature.

FIG. 7 is a timing chart showing the operation timing of each section of the electrostatic copying machine of FIG. 1;

FIG. 8 is a flowchart relating to a process of applying a voltage to a charging roller performed by the microcomputer 50 of FIG. 2;

FIG. 9 is a schematic configuration diagram showing the vicinity of a charging device in an embodiment of an image forming apparatus in which a temperature detection sensor is fixed and a charging roller contacts and separates from a photosensitive member.

FIG. 10 is a perspective view showing a temperature detection sensor provided in the charging device.

FIG. 11 is a side view of the temperature detection sensor.

FIG. 12 is a flowchart illustrating a routine related to control of a voltage applied to a charging roller performed by a microcomputer provided in the image forming apparatus of FIG. 9;

FIG. 13 shows that when a jam occurs, the temperature of the charging roller is determined according to the temperature detected when the temperature detection sensor was in contact with the charging roller immediately before the start of copying when executing the first copy process after the jam processing. FIG. 3 is a diagram for describing an embodiment in which an applied voltage to the dc is controlled.

[Explanation of symbols]

 1: Photoconductor 2: Charging roller (charging member) 20, 60: Temperature detection sensor (Temperature detection means) 22: Applied voltage control circuit (Applied voltage control means) 24: High voltage power supply circuit (Voltage application means) 30: Voltage Application stopping means 40: contact / separation mechanism 50, 70: microcomputer

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-248670 (JP, A) JP-A-7-134470 (JP, A) JP-A 4-186381 (JP, A) 48870 (JP, A) JP-A-1-207768 (JP, A) JP-A-6-348115 (JP, A) JP-A-5-181350 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) G03G 15/02 G03G 15/00 303

Claims (3)

(57) [Claims] 1. A rotating photoreceptor, a charging member to which a voltage is applied in contact with the photoreceptor, voltage applying means for applying a voltage to the charging member, and a surface of the charging member An image forming apparatus comprising: a temperature detection unit configured to detect a temperature; and an application voltage control unit configured to control a voltage applied to the charging member by the voltage application unit in accordance with a temperature detected by the temperature detection unit. A means for moving the temperature detection means to a non-contact position not in contact with the charging member; and, when image formation is started, immediately before the image formation is started at the time of the first image formation, the temperature detection means The temperature detected by the temperature detecting means at the non-contact position according to the detected temperature at the time of contact with the charging member, and when two or more sheets are continuously formed, from the second sheet onward. In response Te image forming apparatus is characterized by providing a means for controlling the respective voltage applied to the charging member by said voltage applying means. 2. A rotating photosensitive member, a charging member to which a voltage is applied in contact with the photosensitive member, voltage applying means for applying a voltage to the charging member, and a surface of the charging member. An image forming apparatus comprising: a temperature detection unit configured to detect a temperature; and an application voltage control unit configured to control an applied voltage to the charging member by the voltage application unit in accordance with a temperature detected by the temperature detection unit. Moving means for moving the detecting means to a contact position in contact with the surface of the charging member and a non-contact position not in contact with the charging member; and applying a voltage to the charging member by the voltage applying means when the temperature detecting means is in the contact position. Means for preventing the voltage from being applied; and when the temperature detecting means moves from the contact position to the non-contact position, image formation is started, and when the first image is formed, the image formation is started. In response to the detected temperature detected by the temperature detection means at the contact position immediately before
When two or more images are formed continuously,
Means for controlling the voltage applied to the charging member by the voltage applying means in accordance with the detected temperature detected by the temperature detecting means moving to the non-contact position after the first sheet. Image forming apparatus. 3. A rotating photoreceptor, a charging member to which a voltage is applied in contact with the photoreceptor, voltage applying means for applying a voltage to the charging member, and a surface of the charging member. An image forming apparatus comprising: a temperature detection unit configured to detect a temperature; and an application voltage control unit configured to control an applied voltage to the charging member by the voltage application unit in accordance with a temperature detected by the temperature detection unit. Means for contacting / separating the charging member from / to the photosensitive member; and contacting the temperature detecting means with the surface of the charging member when the charging member is separated from the photosensitive member, and When the charging member is in contact with the photoreceptor directly or via transfer paper, the charging member is disposed at a position separated from the surface of the charging member. After the charging member is separated from the photoreceptor, the charging member contacts the photoreceptor again. When contacted, Immediately before the image formation is started at the time of the first image formation after the image formation is started, the charging member is separated from the photoreceptor and the temperature is detected in a state where the temperature detection unit is in contact with the charging member. When two or more images are continuously formed according to the detected temperature and when the second and subsequent images are formed, the temperature detecting means is in a state where the charging member is in contact with the photosensitive member and is separated from the charging member. An image forming apparatus, comprising means for controlling a voltage applied to the charging member by the voltage applying means in accordance with a detected temperature detected by the image forming apparatus.