JP3378075B2 - 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 system having a photoconductor contact member such as a charging member or a transfer member to which a voltage is applied in a state of being directly contacted with a rotating photoconductor or through a transfer paper. The present invention relates to an image forming apparatus.

[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 drawbacks as described above, a contact charging type charging device has been attracting attention, which charges a charging member, which is a photosensitive member contact member to which a voltage is applied, in a state of being in contact with the photosensitive member. There is.

Such a contact charging type charging device is capable of lowering the applied voltage required to obtain a desired charging potential on the surface of the charged body of the charged body such as a photoconductor, and the charging process. Since the amount of ozone generated in 1 is extremely 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, for example, in Japanese Patent Laid-Open No. 4-6567, by keeping the temperature of a charging member such as a charging roller within a range of 35 ° to 55 °, the apparatus is operated in a low temperature environment. Proposals have been made to prevent charging failure even when using.

To heat the charging member, for example, a heat source is provided in the vicinity of or inside the charging member, or the charging member is heated by utilizing heat from a heat fixing device provided in the image forming apparatus. . It is described that the temperature adjustment can be realized by using a known temperature adjusting member such as a thermostat.

[0010]

However, if the temperature of the photosensitive member contact member such as the charging roller is heated so as to fall within a predetermined temperature range, the charging potential becomes a predetermined value at which the image density is not lowered. Although it can be maintained, the heating also heats the charging member as well as the various units of the image forming system, which are arranged relatively close to the photoconductor and other heat sources. During the process of toner recycling in which the toner remaining on the surface of the body is recovered and returned to the developing device, the toner is heated, and the toner blocking and the deterioration of the toner aggregation degree are likely to occur.

Therefore, in order to solve these problems,
The temperature detection 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 is controlled according to the detected temperature, so that a stable charging potential that does not cause charging failure can be obtained. A charging device adapted to be obtained has been proposed.

According to this charging device, since a heating member such as a heater is not required, the heating has no influence on each part of the image forming system, so that toner blocking and deterioration of toner aggregation degree can be prevented. . Moreover, since the temperature detecting means is brought into direct contact with the charging roller, it is possible to accurately detect the temperature of the surface of the charging roller without being affected by the ambient temperature and apply the optimum voltage corresponding thereto.

However, the application of the voltage to the charging roller is smaller than that of the conventional charging method using the corona discharge due to the adoption of the contact charging method, but is 1-2.
Since a high voltage of KV 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 in contact with the charging roller. The control system may malfunction due to short circuit due to insufficient dielectric strength.
In the worst case, it could lead to destruction.

Further, when the temperature detecting means is brought into direct contact with the charging roller, the surface of the charging roller is abraded, foreign matter such as toner or paper powder adheres to the surface, or the charging roller is rotating. There was also a rubbing noise, which was harsh to the ear.

Therefore, if the temperature detecting means is not in contact with the charging roller, these problems can be solved.
If this is done, then the temperature of the charging roller surface cannot be measured accurately. Further, similar to the charging roller, a transfer member such as a transfer roller, which is a photosensitive member contact member to which a voltage is applied while being in contact with the photosensitive member via a transfer paper, is also used in the case of constant voltage control. When the surface temperature is low, the efficiency of transferring the toner image on the photoconductor to the transfer paper may be deteriorated.

The present invention has been made in view of the above problems, and even if a voltage is applied to a photoconductor contact member such as a charging roller or a transfer roller under environmental conditions of relatively low temperature,
The purpose is to obtain a charging potential that does not cause inconvenience.

Further, when the voltage is applied, the control system of the apparatus is prevented from malfunctioning or destroyed, and the surface of the photoconductor contact member such as a charging roller or a transfer roller is prevented. It is also an object to prevent foreign matter such as toner and paper powder from sticking to the surface of the paper and the generation of a rubbing rustling noise.

[0019]

In order to achieve the above object, the present invention provides an image forming apparatus as described above,
The temperature detecting means for detecting the surface temperature of the photoconductor contact member to which a voltage is applied in the state of being directly contacted with the photoconductor or through the transfer paper is composed of an element whose resistance value changes with temperature,
A moving means is provided for moving the temperature detecting means between a contact position in contact with the surface of the photoconductor contact member and a non-contact position in which it does not contact the surface.
And when the temperature detecting means is in the contact position.
Voltage is applied to the photoconductor contact member by voltage applying means.
It is provided with a means to prevent it.

[0020]

[0021]

Further, in the image forming apparatus provided with the moving means, the moving means moves the temperature detecting means to the contact position and at the same time separates the photosensitive member contact member from the surface of the photosensitive member, and the temperature detecting means. It is advisable to have a means for bringing the photoconductor contact member into contact with the surface of the photoconductor at the same time as moving it to the non-contact position.

Further, in any one of the above image forming apparatuses, the temperature detecting means may be arranged so as to come into contact with the outside of the effective image forming area of the photoconductor contact member. In any one of the above image forming apparatuses, the photoconductor contact member is
It is preferable that the charging member is a charging member that is charged with a voltage from the voltage applying means in a state of being in contact with the surface of the photoconductor.

[0024]

According to the image forming apparatus thus constructed, the voltage applied by the voltage applying means to the photoconductor contact member is controlled according to the output signal corresponding to the detected temperature from the temperature detecting means. Even when the apparatus is used in low temperature environmental conditions, the voltage applied to the photoconductor contact member in that state is controlled according to the surface temperature of the photoconductor contact member, so that the image density is reduced due to charging failure and It is possible to prevent deterioration of transfer efficiency.

Further, since the temperature detecting means can be moved to the non-contact position by the moving means without always contacting the surface of the photoconductor contact member, the temperature detecting means can be moved to the non-contact position. The contact surface with the photoconductor contact member is less likely to be contaminated, and the rubbing noise between the temperature detecting means and the photoconductor contact member does not occur during the non-contact position.

Further, when the temperature detecting means is in the contact position, no voltage is applied to the photoconductor contact member by the voltage applying means, so that the voltage detecting means causes an electrical obstacle to the temperature detecting means and the temperature detecting means. It is possible to prevent various troubles and malfunctions due to electrical noise intruding into the control system of the entire image forming apparatus via the.

[0027]

Further, the moving means for moving the temperature detecting means moves the temperature detecting means to the contact position and at the same time separates the photosensitive member contact member from the surface of the photosensitive member and moves the temperature detecting means to the non-contact position. At the same time, by providing a means for bringing the photoconductor contact member into contact with the surface of the photoconductor, the temperature detecting means is normally exposed to light by the photoconductor contact member being pressed with the elastic portion elastically deformed. Although it is possible to obtain reliable contact with the body contact member, in this case, if only the photoconductor contact member is moved so as to be completely separated from the temperature detecting means, even the elastic deformation of the member will occur. It is necessary to move the photoconductor contact member in the separating direction by the added large movement amount. However, by simultaneously moving the temperature detecting means in the separating direction as described above, Te, it is possible to minimize the amount of movement of the photoreceptor contact member.

Further, if the temperature detecting means is disposed so as to contact with the outside of the effective image forming area of the photoconductor contact member, the temperature detecting means comes into contact with the effective image forming area of the photoconductor contact member which affects the image. Since it does not happen, it can be prevented from damaging it. Furthermore, if the photoconductor contact member is a charging member that charges the photoconductor, the photoconductor that plays an important role in affecting the image can be well charged.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a schematic view showing a state in which a temperature detecting means for detecting a surface temperature of a charging roller, which is a photosensitive member contact member of an image forming apparatus according to an embodiment of the present invention, is brought into contact with the charging system, and FIG. FIG. 3 is a schematic view 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 shows a main part of the image forming apparatus provided with the charging roller and the temperature detecting means. It is a block diagram shown.

In this image forming apparatus, as shown in FIG. 3, in a state where a charging roller (charging member) 2 which is a photoconductor contact member is directly contacted with a drum-shaped rotating photoconductor 1 which is a member to be charged, A contact charging type image forming apparatus that applies a voltage thereto to uniformly charge the surface 1a of the photoconductor 1 to a predetermined potential, in which 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 photosensitive member 1 is driven by a photosensitive member driving system including a drum driving timing belt, a drum driving pulley, a motor for driving them (all are not shown), and the surface 1a thereof is always 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).

Around the photoconductor 1, an eraser 18 in addition to the charging roller 2, a developing device 6, a contact type transfer device 7 having an endless belt 7a which is also a photoconductor contact member,
A cleaning unit 8 is provided respectively.

Then, the light from the exposure device 9 (only the mirror portion is shown) is incident on the surface 1a of the photoconductor 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 on 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.

After the transfer is completed, the residual toner remaining on the photoconductor 1 and foreign matters such as paper dust are removed by the cleaning blade 8a provided in the cleaning unit 8, and the residual toner left on the photoconductor 1 is removed. The potential is removed by a static eliminator (not shown) to prepare for the next charging by the charging roller 2.

As shown in FIG. 1, the charging roller 2 is integrally provided with a conductive rubber roller portion 16 made of, for example, EPDM (ethylene propylene diene terpolymer) on the outside of a conductive core metal 15 made of iron or the like. Both ends of the conductive cored bar 15 are rotatably supported by bearings 17, 17, and each bearing 17 is supported by a pressure spring 12 through a member holding the bearing 17 in the direction of the photosensitive member 1. The charging roller 2 is urged to contact the surface 1a of the photoconductor 1 in a state where the axis of the charging roller 2 is parallel to the axis of the photoconductor 1.

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, which is an applied voltage control means for controlling the voltage applied to the charging roller 2 by the high-voltage power supply generation circuit 24 in response to a signal.

The applied voltage control circuit 22 determines the 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.

In the temperature detecting means 20, as shown in FIG. 4, the temperature detecting element 25 is provided between the tip portions of the conductive leaf springs 26, 26 which are arranged in parallel with a space therebetween, as shown in FIG. A film material 28 having a thickness of about 10 μm, which is temporarily fixed by filling the periphery with silicon grease 27 and is formed of, for example, polyimide amide on the lower surface side in FIG.
On the upper surface side, a film material 29 formed of, for example, a fluororesin (Teflon) and having a similar thickness is fixed and held by adhesion so as to sandwich the conductive leaf springs 26, 26.

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

The bracket 32 is rotatably supported by a shaft 33 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 rotation position of the bracket 32 is
The lower edge of the lower end is regulated at the position shown in the figure in which it contacts 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 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 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 long hole 23b and is held so as to be movable in the left-right direction in FIG. 2, and the release lever 23 is moved to the right in the figure. Tension spring 43 for urging and when activated (when on)
The release lever 23 against the biasing force of the tension spring 43.
Is moved to the left 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 timings. 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 to be 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.

As shown in FIG. 6, when the print key 51 is pressed (ON) to input a print signal as shown in FIG. 6, the microcomputer 50 solenoids before applying the charging bias voltage to the charging roller 2 after a time t1. Turn on 45.

Then, since the release lever 23 is moved from the position shown in FIG. 1 to the position shown in FIG. 2 against the biasing force of the tension spring 43, the engaging end 23 of the release lever 23 is moved.
Since a contacts the lever portion 32a of the bracket 32 and pushes it to the left side in the figure, the bracket 32 rotates about the shaft 33 in the counterclockwise 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 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 time t2 (FIG. 6) elapses after the solenoid 45 is turned on, the drive system for rotating the photoconductor 1 is driven to rotate the photoconductor 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 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, the solenoid 45 is turned 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 photosensitive member 1 through the film material 28 (FIG. 5). Sometimes, high voltage power generation circuit 2
No voltage is applied from 4 to the charging roller 2.

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, electrical noise may enter the control system of the entire image forming apparatus through the temperature detecting means 20,
Since there is no risk of a short circuit occurring in the circuit due to insufficient dielectric strength, 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 via the film material 28 having an insulating property to reduce the frictional resistance with the charging roller 2 and to reduce the electricity. Although it plays a role of electrical insulation, its thickness is set to about several tens of μm in consideration of the response of temperature detection, so that it has a perfect withstand voltage against a high voltage applied to the charging roller 2. Although it cannot be said that the temperature detecting means 2 is applied when a high voltage is applied,
The problem can be solved by separating 0 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.

By the way, it has been described above that 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 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 is a leaf spring for applying a voltage, which is pressed against the conductive cored bar 15 of the charging roller 2 by an elastic force and comes into sliding contact therewith.
Power is supplied from.

FIG. 9 is a block diagram showing the main part of an embodiment of the image forming apparatus in which the charging roller, which is a photoconductor contact member, can be brought into contact with and separated from the photoconductor. The same reference numerals are attached. In the image forming apparatus according to this embodiment, the charging roller 2 which is a photosensitive member contact member is connected to the photosensitive member 1.
It is configured to be separable from.

FIG. 10 is a schematic view showing an example of a contacting / separating mechanism for contacting / separating the charging roller 2 with respect to the photosensitive member 1.
In the charging roller 2, both ends of the conductive core 15 have bearings 17,
Each of which is rotatably supported by 17, and its bearing 1
7 is always urged in a direction away from the photoconductor 1 by a tension urging spring 52 formed of a conductive material. When the not performed charging the charging roller 2 is, by the biasing force of the tension biasing spring 52 is <br/> the separated position indicated by a solid line in FIG.

In FIG. 10, reference numeral 53 is a fixing member made of an insulating material, and one end of the tension urging spring 52 is engaged with the fixing member.
The charging roller 2 is connected to the conductive cored bar 15 with the high voltage power supply generating circuit 24 while it is in contact with the surface 1a of the photoconductor 1.
From the above, a charging bias voltage is applied via the tension urging spring 52 and the conductive bearing 17, whereby the surface 1a of the photoconductor 1 is uniformly charged.

The charging roller 2 is provided with a conductive bearing 1 at one end of an arm 55 whose center is supported by a shaft 54 so as to be swingable.
It is rotatably held via 7 and its arm 55
A movable shaft 56a of a solenoid 56 is attached to the other end side of the spring via a spring 57.

The solenoid 56 has its main body fixed to the fixing portion of the apparatus, and when it is in the off state, the arm 55 swings to the position shown by the solid line in FIG. 10 by the urging force of the tension urging spring 52. The charging roller 2 is separated from the photoconductor 1.

When the solenoid 56 is turned on, the arm 55 swings in the clockwise direction against the tension urging force of the tension urging spring 52 and moves to the position indicated by the phantom line. The charging roller 2 comes into contact with the surface 1a of the photoconductor 1 with a predetermined contact pressure suitable for charging due to a slight extension of 57.

A temperature detecting means 60 for detecting the surface temperature of the charging roller 2 is provided in the vicinity of the charging roller 2.
The temperature detecting means 60 contacts the surface of the charging roller 2 when the charging roller 2 and the photoconductor 1 are in a separated state,
When the charging roller 2 and the photoconductor 1 are in contact with each other, the charging roller 2 is fixed at a position shown in the drawing which is separated from the surface of the charging roller 2.

As shown in FIG. 12, the temperature detecting means 60 has a cushion material 59 made of foamed polyurethane placed on a substrate 58 made of, for example, an epoxy resin, and the cushion material 59 shown in FIG. The temperature sensing element 25 is placed as described above, and the thickness is 10 μm formed by polyimide amide so as to cover the temperature sensing element 25 from the upper side.
A film material 28 of about m is covered and fixedly held.

The role of the film material 28 covering the surface of the temperature detecting element 25 is the same as that of the film material 28 of the temperature detecting means 20 described with reference to FIGS. 4 and 5. In this embodiment, as shown in FIG. 10, the temperature detecting means 60 contacts the surface of the charging roller 2 and the photosensitive member 1 when the charging roller 2 and the photosensitive member 1 are in a separated state, and the temperature detecting means 60 contacts the charging roller 2 and the photosensitive member 1. Is fixed to a position separated from the surface of the charging roller 2 when the charging roller 2 is in contact with the charging roller 2, the temperature detecting means 60 correspondingly causes the charging roller 2 to move when the charging roller 2 is brought into contact with or separated from the photoconductor 1. Away from or contact the surface of.

Therefore, the same effect as the embodiment described with reference to FIGS. 1 to 7 can be obtained. FIG. 13 is a block diagram showing an embodiment of an image forming apparatus provided with a moving means for moving the temperature detecting means and the charging roller at the same time, and the portions corresponding to those in FIG. 1 are designated by the same reference numerals.

In the image forming apparatus according to this embodiment, the moving means 70 for moving the temperature detecting means 20 moves the temperature detecting means 20 to a contact position in contact with the surface of the charging roller 2 and at the same time exposes the charging roller 2 to light. Surface 1a of body 1
And the temperature detecting means 20 is moved to a non-contact position with respect to the surface of the charging roller 2, and at the same time, the charging roller 2 is brought into contact with the surface 1a of the photoconductor 1.

The means will be described below. The swing lever 74 is rotatably supported by a holding bracket 76 around a support shaft 77, and the charging roller 2 is rotatably supported by a bearing 17 at one end of the swing lever 74.

In the state shown in FIG. 13, the charging roller 2 is provided with a predetermined contact pressure by a biasing force of a tension spring 75 having one end attached to a spring receiver formed at the end of the rocking lever 74. 1 is in contact with the surface 1a. Also,
The bracket 32 to which the temperature detecting means 20 is fixed is attached to the shaft 33.
Is rotatably held by the holding bracket 76, and the temperature detecting means 20 and the charging roller 2 are both the same holding bracket 76.
By holding at, the positional relationship between them is maintained.

The moving operation of the temperature detecting means 20 and 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. 13, to a position shown by a solid line and a virtual line in FIG. .

On the release lever 73, one end of a swing arm 72 is rotatably attached to the upper surface 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 oscillating arm 72 is always urged by the urging force of the tension spring 43 in the clockwise direction in FIG.

In this mechanism, when the solenoid 45 is off, the swing arm 72 is swung by the urging force of the tension spring 43, and the release lever 73 is in the position shown by the solid line. Therefore, the engaging end 73a pushes the lever portion 32a of the bracket 32 leftward in the drawing to rotate the bracket 32 counterclockwise, so that the temperature detecting means 20 fixed to the bracket 32 is charged by the charging roller 2. In the illustrated non-contact position away from.

On the other hand, in this state, the swinging lever 74 that supports the charging roller 2 has the projecting piece 74a with the release lever 7.
Since it is slightly separated from the cam portion 73b fixed to the end portion of 3, the charging roller 2 is swung to the position shown in the figure by the urging force of the tension spring 75, and the charging roller 2 makes a predetermined contact by the urging force of the tension spring 75. It is in contact with the surface 1a of the photoconductor 1 by pressure.

When the solenoid 45 is turned on, the movable shaft 45a moves leftward in FIG.
The swing arm 72 swings counterclockwise against the biasing force of the tension spring 43, and the release lever 73 moves to the position indicated by the imaginary line.

Therefore, since the engaging end 73a is separated from the lever portion 32a of the bracket 32, the bracket 32 is rotated clockwise by the urging force of the torsion spring 35. Therefore, the temperature detecting means 20 moves to the contact position, and the portion of the temperature detecting element 25 becomes the film material 28.
(See FIG. 5) to contact the surface of the charging roller 2.

Further, the cam portion 73b of the release lever 73 is
The protrusion 7 of the swing lever 74 is moved to the position shown by the phantom line.
4a is pushed to the right in the figure, the swing lever 74 rotates clockwise against the urging force of the tension spring 75.

Therefore, the charging roller 2 is separated from the surface 1a of the photoconductor 1 as shown by the phantom line. Note that, also in this embodiment, the timing for operating the solenoid 45 (ON / OFF control) is the solenoid 45 shown in FIG.
It is the same as the operation of, and it does not matter.

As described above, in this embodiment, the temperature detecting means 20 is moved to the contact position where it comes into contact with the charging roller 2, and at the same time, the charging roller 2 is separated from the surface 1a of the photoconductor 1 and the temperature detecting means 20 is operated. By providing a means (mechanism) for moving the charging roller 2 to the surface 1a of the photoconductor 1 at the same time as moving it to the non-contact position, the temperature detecting means 20 is moved to the charging roller 2 while minimizing the movement amount of the charging roller 2. To be completely separated from the surface.

That is, at the non-contact position shown in FIG. 14 (b) and FIG. 15 (b), the temperature detecting means 20 and 60 are provided.
When the distances G and G ′ between the contact portions of the charging roller 2 and the surface of the charging roller 2 are to be obtained, the temperature detecting means 20 and 60 are in contact with the charging roller 2. In order to obtain reliable contact with
4 (a) and the elastic displacements ΔG, Δ shown in FIG. 15 (a).
In the case where G'is provided, if only the charging roller 2 is moved to obtain the distances G and G ', the moving distances L and L'are L = G + ΔG and L' = G '. +
ΔG 'is required.

On the other hand, in the embodiment of FIG. 13,
At the same time that the charging roller 2 moves, the temperature detecting means 20 also moves in a direction away from the charging roller 2, so that, for example, as shown in FIG.
When (a) the elastic displacement ΔG or more is set as the movement amount for the temperature detecting means 20 itself to move, the movement amount is offset from the movement amount of the charging roller 2, and therefore the movement for moving the charging roller 2 is performed. The distance L can be a distance G or less.

FIG. 16 is a block diagram showing an embodiment of the image forming apparatus in which the temperature detecting means is moved in the axial direction from the surface of the charging roller so that it can be retracted to a position where it does not contact the surface of the charging roller. The same parts as those in FIG. 9 are designated by the same reference numerals. In this embodiment, the moving means 80 moves the temperature detecting means 60 to a contact position shown by a solid line and a non-contact position shown by a virtual line.

The moving means 80 fixes the temperature detecting means 60 to the lower surface of the holding bracket 81, and holds the holding bracket 81 on the guide shaft 82 so as to be slidable in the E direction. The upper part of the holding bracket 81 is rotatably supported on the lower end of the swing arm 72, and the movable shaft 45a of the solenoid 45 is rotatable on the upper end of the swing arm 72 via a connecting plate 78. Is attached to.

The swing arm 72 has a shaft 83 near the center.
It is swingably supported by, and when the solenoid 45 is turned on, it moves to the position shown by the phantom line in FIG. Therefore, the holding bracket 81 has the temperature detecting means 6
The temperature detecting means 60 moves away from the surface of the charging roller 2 because the temperature detecting means 60 moves to the position indicated by the phantom line together with 0.

When the solenoid 45 is turned off, the swing arm 72 is moved to the position shown by the solid line in FIG. Move to. Therefore, the holding bracket 81 has the temperature detecting means 6
The temperature detecting means 60 is moved to the position indicated by the solid line with 0.
Contacts the surface of the charging roller 2.

As described above, the retreating direction of the temperature detecting means 60 can be the axial direction of the charging roller 2. that's all,
Although each embodiment has been described, the temperature detecting means 20 or 60 in each embodiment is not limited to the thermistor, and may be another temperature detecting means as long as it is a temperature sensor capable of converting the detected temperature into an electric signal. Good.

For example, the temperature of the platinum resistance thermometer, the base-emitter forward voltage drop VBE of the bipolar transistor, in which the temperature is measured by using a thermocouple, platinum as a resistance element, and its electric resistance changes with temperature. Utilizing a coefficient of about 2.3 mV / ° C, an IC temperature sensor in which an amplifier circuit and an output transistor are integrated in the same silicon chip can be used.

Further, in each of the above embodiments, the case where the photoconductor contact member for detecting the surface temperature by the temperature detection means is the charging roller has been described, but the transfer member (FIG. 3 and FIG. 3) which is also the photoconductor contact member is described. 9 shows the case of the transfer belt type, but the present invention is applied to the transfer roller type), the surface temperature of the transfer member is detected by the temperature detecting means, and an output signal corresponding to the detected temperature is obtained. If the voltage applied to the transfer member is controlled according to
It is possible to always transfer the toner image on the photoconductor onto the transfer paper under the optimum transfer condition regardless of the operating temperature of the device.

Although the temperature detecting means having different shapes are used in each of the embodiments of FIGS. 1 and 9, these have exactly the same function of detecting the temperature of the surface of the charging roller, and in each of these embodiments. The peculiar effect to be obtained is not due to the difference in the type such as the shape of the temperature detecting means, but to the difference in the configuration of the entire apparatus.

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

[0099]

As described above, according to the image forming apparatus of the present invention, the voltage applied to the photoconductor contact member is controlled according to the surface temperature of the photoconductor contact member, so that the device can be relatively operated. Even when used in low temperature environment conditions, a voltage corrected according to the surface temperature of the photoconductor contact member at that time is applied to the photoconductor contact member. Since a predetermined charging potential that does not cause charging failure can be obtained, it is possible to prevent a decrease in image density and obtain a good image. When the photoconductor contact member is a transfer member, efficient and good transfer can be performed. .

Further, since the temperature detecting means can be moved to the non-contact position where it does not contact the surface of the photoconductor contact member by the moving means, when the non-contact position is reached, the temperature detecting means comes into contact with the photoconductor contact member. As the surface becomes harder to stain,
The rubbing noise between the temperature detecting means and the photoconductor contact member also does not occur during the non-contact position.

Further, when the temperature detecting means is in a contact position in contact with the surface of the photoconductor contact member , no voltage is applied to the photoconductor contact member by the voltage applying means, so that the voltage is applied to the temperature detecting means electrically. It is possible to substantially completely prevent various troubles and malfunctions from occurring due to noises and noises entering the control system of the entire image forming apparatus through the temperature detecting means.

[0102]

Further, the moving means for moving the temperature detecting means moves the temperature detecting means to the contact position and at the same time separates the photosensitive member contact member from the surface of the photosensitive member, and moves the temperature detecting means to the non-contact position. At the same time, if a means for bringing the photoconductor contact member into contact with the surface of the photoconductor is provided, when the temperature detecting means is separated from the photoconductor contact member, both of them move toward the separation side, so that the photoconductor contact Since the amount of movement of the member can be minimized, the device can be downsized accordingly.

Further, if the temperature detecting means is arranged so as to contact the outside of the effective image forming area of the photoconductor contact member, the effective image forming area of the photoconductor contact member which affects the image is not rubbed by the temperature detecting means. Therefore, scratches on that portion can be prevented and a good image can be obtained.

[Brief description of drawings]

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

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 configuration diagram showing a configuration of a main part of an embodiment of an image forming apparatus in which a charging roller which is a photoconductor contact member can be separated from a photoconductor.

FIG. 10 is a schematic view showing an example of a contact / separation mechanism for contacting and separating the charging roller with respect to the photoconductor in the embodiment of FIG.

11 is a perspective view showing a temperature detecting means 60 in the embodiment of FIG.

FIG. 12 is a side view showing the temperature detecting means 60 of the same.

FIG. 13 is a configuration diagram showing an embodiment of an image forming apparatus provided with a moving unit that simultaneously moves a temperature detecting unit and a charging roller.

FIG. 14 is a schematic diagram for explaining how the temperature detecting means can be completely separated from the surface of the charging roller while minimizing the movement amount of the charging roller according to the embodiment of FIG.

FIG. 15 is a schematic view for explaining a state in which the temperature detecting means can be completely separated from the surface of the charging roller by minimizing the moving amount of the charging roller, using a temperature detecting means of a different type from FIG. Is.

FIG. 16 is a configuration diagram showing an embodiment of an image forming apparatus in which the temperature detecting means is moved from the surface of the charging roller in the axial direction thereof and can be retracted to a position not in contact with the surface of the charging roller.

[Explanation of symbols]

1: photoconductor 2: charging roller (photoconductor contact member) 7a: Endless belt (photosensitive member contact member) 20, 60: Temperature detecting means 21: Electric signal conversion circuit 22: Applied voltage control circuit 24: High-voltage power supply generation circuit (voltage application means) 32: Bracket 40, 70, 80: Moving means 73: Release lever 74: Swing lever 45, 56: Solenoid

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Claims (4)

(57) [Claims] 1. A rotating photoconductor, a photoconductor contact member to which a voltage is applied in contact with the photoconductor directly or via a transfer paper, and a voltage application to apply a voltage to the photoconductor contact member. Means, temperature detecting means for detecting the surface temperature of the photoconductor contact member, and voltage applied to the photoconductor contact member by the voltage applying means in response to an output signal corresponding to the detected temperature from the temperature detecting means. In an image forming apparatus having an applied voltage control unit for controlling, the temperature detecting unit is an element whose resistance value changes with temperature, and the temperature detecting unit is not in contact with a contact position in contact with the surface of the photoconductor contact member. A moving means for moving to the non-contact position is provided, and a means for preventing the voltage applying means from applying a voltage to the photoconductor contact member when the temperature detecting means is at the contact position is provided. An image forming apparatus comprising and. 2. The image forming apparatus according to claim 1,
A moving means for moving the temperature detecting means moves the temperature detecting means to the contact position and at the same time separates the photosensitive member contact member from the surface of the photosensitive member and moves the temperature detecting means to the non-contact position. At the same time, the image forming apparatus is provided with means for bringing the photoconductor contact member into contact with the surface of the photoconductor. 3. The image forming apparatus according to claim 1 ,
An image forming apparatus, wherein the temperature detecting means is arranged so as to come into contact with the outside of the effective image forming area of the photoconductor contact member. 4. The image forming apparatus according to claim 1 ,
An image forming apparatus, wherein the photoconductor contact member is a charging member that charges the photoconductor by applying a voltage from the voltage applying means in a state of being in contact with the surface of the photoconductor.