JP3595437B2 - Image forming device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus including a contact charging member that charges a photosensitive member when a voltage is applied to the photosensitive member while rotating the photosensitive member.
[0002]
[Prior art]
For example, an image forming apparatus such as an electrostatic copying machine or a printer includes a charging device for performing a charging process on a photoreceptor which is a member to be charged. In recent years, a charging roller which is a member for charging the photoreceptor is used as the charging device. Attention has been paid to a contact roller charging type charging device for charging a battery by contacting the same.
In such a charging device of the contact roller charging type, the material of the charging roller is, for example, a type in which the charging roller is rotated while being in contact with the photoconductor, and a portion in contact with the photoconductor is formed of a conductive rubber material. I have.
[0003]
[Problems to be solved by the invention]
However, rubber materials generally have the property that their electrical conductivity changes with changes in the environment in which they are placed, and their electrical conductivity increases under high temperature and high humidity, and under low temperature and low humidity. Conductivity decreases. Therefore, a desired charging potential cannot be obtained only by constantly applying a constant voltage to the charging roller.
[0004]
In general, when the electric conductivity decreases, the rise of the charging potential becomes unstable. Therefore, after applying a voltage to the charging roller, it takes some time until the surface of the photoconductor reaches the desired charging potential. It will cost you. Therefore, depending on the timing at which the image formation on the photosensitive member is started, there is a problem that the image density at the leading end of the formed image may become lighter or darker.
[0005]
The present invention has been made in view of the above problems, and even if an image forming apparatus having a contact charging member such as a charging roller is used in a place where the ambient temperature or humidity changes greatly, it is possible to obtain one image. An object of the present invention is to make it possible to obtain a stable image without density unevenness by making the middle charging potential constant.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a contact charging member that charges a photosensitive member by applying a voltage in contact with the rotating photosensitive member, and a temperature of the contact charging member or a temperature of the contact charging member. And a temperature detecting means for detecting a temperature in the vicinity of the image forming apparatus, wherein a voltage is applied to the contact charging member in accordance with the detected temperature detected by the temperature detecting means, Write the image A pre-charging time control means for varying the time until the start is provided.
[0007]
With this configuration, when the temperature of the contact charging member or the temperature in the vicinity of the contact charging member changes due to a change in the environmental temperature in which the image forming apparatus is placed, a voltage is applied to the contact charging member and then the photosensitive member is exposed. The charging rise time until the charging potential on the body stabilizes changes, but even in such a case, the temperature detecting means detects the temperature of the contact charging member or a temperature in the vicinity thereof, and the pre-charging time is determined according to the detected temperature. The control means applies a voltage to the contact charging member and Write the image By varying the time until the start, the time is optimized, so that the charging potential in one image can be kept constant, so that a stable image without density unevenness can be obtained.
[0008]
Further, the pre-charging time control means, when the temperature detected by the temperature detecting means is equal to or lower than a predetermined temperature, applies a voltage to the contact charging member and then applies the voltage to the photosensitive member. Write the image It is preferable that the control unit be configured to control so that the time until the start is longer than when the detected temperature is higher than a predetermined temperature.
[0009]
Then, the rise time until the charging potential becomes stable becomes longer due to the decrease in electric conductivity under a low temperature, but if the detected temperature at that time is lower than the predetermined temperature, the pre-charging time The control means applies a voltage to the contact charging member and Write the image Since the time until the start is controlled to be longer than when the temperature is higher than the predetermined temperature, the charging potential in one image can be kept constant, so that a stable image without density unevenness can be obtained. .
[0010]
Further, in an image forming apparatus provided with a humidity detecting unit for detecting the humidity of the contact charging member or the humidity near the contact charging member, a voltage is applied to the contact charging member in accordance with the detected humidity detected by the humidity detecting unit. After applying, Write the image Pre-charging time control means for varying the time until the start may be provided.
[0011]
Then, when the humidity of the contact charging member or the humidity in the vicinity of the contact charging member changes due to a change in the environmental humidity where the image forming apparatus is placed, a voltage is applied to the contact charging member and then the photosensitive member is charged. Although the charging rise time until the charging potential of the charging member is stabilized changes, even in such a case, the humidity detecting means detects the humidity of the contact charging member or the humidity in the vicinity thereof, and the pre-charging time controlling means according to the detected humidity. Applies voltage to the contact charging member and then Write the image By varying the time until the start, the time is optimized, so that the charging potential in one image can be kept constant, so that a stable image without density unevenness can be obtained.
[0012]
Further, the pre-charging time control means, when the detected humidity detected by the humidity detecting means is equal to or less than a predetermined humidity, applies a voltage to the contact charging member and then applies the voltage to the photosensitive member. Write the image It is preferable that the control unit is configured to control so that the time until the start is longer than when the detected humidity is higher than a predetermined humidity.
[0013]
Then, under low humidity, the rise time until the charging potential becomes stable becomes longer due to the decrease in electric conductivity, but if the detected humidity at that time is equal to or lower than the predetermined humidity, the pre-charging is performed. The time control means applies a voltage to the contact charging member and Write the image Since the time until the start is controlled to be longer than when the humidity is higher than the predetermined humidity, the charging potential in one image can be kept constant, so that a stable image without density unevenness can be obtained. .
[0014]
Still further, in an image forming apparatus including the contact charging member and a temperature and humidity detecting unit that detects a temperature and a humidity of the contact charging member or a temperature and a humidity near the contact charging member, the temperature and humidity detecting unit is According to the detected temperature and humidity, a voltage is applied to the contact charging member and then the photosensitive member is charged. Write the image It is preferable to provide a pre-charging time control means for varying the time until the start.
[0015]
In this way, even if the environmental temperature or humidity changes, both the temperature and the humidity are detected, and a voltage is applied to the contact charging member in accordance with the detected temperature and humidity, and then the photoconductor is charged. To Write the image Since the time until the start can be finely controlled to an optimum value, the charging potential in one image can be made constant, and thereby a stable image without density unevenness can be obtained.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing an example of an electrostatic copying machine as an image forming apparatus according to the present invention together with a control system. FIG. 2 detects the surface temperature of a charging roller as a contact charging member provided in the electrostatic copying machine. FIG. 3 is a schematic diagram showing a state where the temperature detection sensor is in a contact position, and FIG. 3 is a schematic diagram showing a state in which the temperature detection sensor is moved to a non-contact position.
[0017]
In an electrostatic copying machine as this image forming apparatus, as shown in FIG. 1, in a state where a charging roller 2 as a contact charging member is brought into direct contact with a drum-shaped rotating photoreceptor 1, a voltage is applied thereto. This is an image forming apparatus in which the linear velocity of the contact roller charging system for uniformly charging the image portion surface potential Vs of the surface 1a of the photoconductor 1 to, for example, -900 V is 200 mm / sec. 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 charging roller 2.
[0018]
The photoreceptor 1 is driven by a photoreceptor drive system including a drum drive timing belt, a drum drive pulley, and a motor for driving them (all not shown). , For example, with a contact pressure of 10 g / cm (substantially line contact) by the urging force of a pressure spring (not shown).
A process cartridge in which 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 10 are formed.
[0019]
Around the photoreceptor 1, an eraser 18, a developing device 6, and a transfer unit 7, which is a contact type transfer device having an endless belt, are provided. Reference numeral 13 denotes a fixing device for fixing the toner image transferred onto the transfer paper P by applying pressure while heating.
In the process cartridge 10, a temperature detection sensor 20, which is a temperature detection unit formed of, for example, a thermistor for detecting the surface temperature of the charging roller 2, is provided. The contact roller is moved to a contact position shown in FIG. 2 contacting the surface of the charging roller 2 and a non-contact position shown in FIG.
[0020]
The non-contact position is relatively close to the surface of the charging roller 2 so that the surface temperature of the charging roller 2 indirectly detected at the non-contact position is the surface temperature at the time of detection at the contact position. It is almost the same as the temperature. The contact / separation mechanism 40 constitutes a drive mechanism of means for moving the temperature detection sensor 20 to a non-contact position where the temperature detection sensor 20 does not contact 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.
[0021]
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 with reference to FIGS. 4 and 5) of the temperature detecting sensor 20, into an electric signal such as a voltage and reads the electric signal. An electric signal conversion circuit 21 for outputting an output signal corresponding to the detected temperature, and an input signal from the electric signal conversion circuit 21 for applying a voltage to the charging roller 2 to the high voltage power supply circuit 24. And an applied voltage control circuit 22 for outputting a signal.
[0022]
Further, this electrostatic copying machine varies the time from when a voltage is applied to the charging roller 2 to when image formation on the photoreceptor 1 is started according to the temperature detected by the temperature detection sensor 20. A charging time control means 5 is provided.
The pre-charging time control means 5 inputs a signal which the temperature detection sensor 20 detects the temperature of the charging roller 2 and the electric signal conversion circuit 21 converts into a electric signal such as a voltage and outputs the signal. The time from when the high-voltage power supply circuit 24 applies a voltage to the charging roller 2 to when the image writing section 3 starts the writing operation on the photosensitive member 1 is variably controlled, and the light L is supplied to the photosensitive member at that timing. Irradiation is performed on the surface of the substrate 1 to form an electrostatic latent image thereon.
[0023]
In this electrostatic copying machine, when a copying process is started, light L from the image writing unit 3 enters the surface 1a of the photoreceptor 1, and the charged surface uniformly charged by the charging roller 2 is exposed. Then, an electrostatic latent image is formed 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 developed with the toner supplied by the developing sleeve of the developing device 6 to become a toner image (visible image).
[0024]
On the other hand, the transfer paper in a paper feed cassette (not shown) is sent out one by one by a paper feed roller rotating at a predetermined timing, and is temporarily stopped by a pair of registration rollers 14 to adjust the timing. The transfer unit 7 is conveyed to the transfer unit provided with the transfer unit 7 at an accurate timing coincident with the toner image on the body 1.
[0025]
A transfer bias is applied to the transfer paper P by the transfer unit 7 to transfer a toner image to the upper surface side in FIG. 1, and the toner image is separated from the photoreceptor 1 and transported to the fixing device 13 where the toner is fixed. Thereafter, 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 photoconductor 1 are removed by the cleaning blade 8, and the residual potential remaining on the photoconductor 1 is removed by a static eliminator (not shown). To prepare for the next charging by the charging roller 2.
[0026]
As shown in FIG. 2, the charging roller 2 has a conductive rubber roller portion 16 made of, for example, hydrin rubber, which is integrally mounted at a diameter of 14 mm, on the outside of a conductive core metal 15 made of, for example, iron having a diameter of 8 mm. Both ends of the conductive core 15 are rotatably supported by conductive bearings 17, 17, and each of the bearings 17 is moved in the direction of the photoconductor 1 by a pressing spring (not shown) via a member holding the bearing. The charging roller 2 is urged to contact the surface 1 a of the photoconductor 1 in a state where the axis of the charging roller 2 is parallel to the axis of the photoconductor 1.
[0027]
A charging bias voltage is applied to the conductive core metal 15 of the charging roller 2 from a high-voltage power supply circuit 24 that applies a voltage to the charging roller 2, so that the surface 1 a of the photoconductor 1 is uniform. Is charged.
[0028]
The temperature detecting sensor 20 has a temperature detecting element 25 between the distal end portions of the conductive leaf springs 26, 26 arranged in parallel at intervals as shown in FIG. The grease 27 is temporarily fixed by filling, and a film material 28 having a thickness of about 10 μm formed of, for example, polyimide amide is formed on the lower surface side in FIG. The film material 29 is fixedly held by adhesive so as to sandwich the conductive leaf springs 26, 26, respectively.
[0029]
Note that the temperature detecting element 25 is an element whose resistance value changes according to 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 the lead wires 36a and 36b, respectively. The insulating member 31 is fixed and held on the bracket 32 as shown in FIG.
[0030]
The bracket 32 is supported by a shaft 33 so as to be rotatable in the direction indicated by the arrow B in FIG. 2, and the conductive leaf spring 26 always contacts the charging roller 2 by a torsion spring 35 wound around the shaft 33. Is urged to rotate.
The rotation position is regulated at a position where the lower edge of the bracket 32 abuts against the stopper shaft 34 as shown.
The bracket 32 has a lever portion 32a formed thereon, and the engagement end 23a of the release lever 23 of the contact / separation mechanism 40 can be engaged with the lever portion 32a.
[0031]
The contact position shown in FIG. 2 in which the temperature detecting element 25 of the temperature detecting sensor 20 is brought into contact with the surface of the charging roller 2 via the film material 28 (FIG. 5) by the contact / separation mechanism 40, and the contact position shown in FIG. 3 can be moved to the non-contact position.
[0032]
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. 3, and biases the release lever 23 rightward in FIG. And a solenoid 45 for moving the release lever 23 to the left in the drawing against the urging force of the tension spring 43 when activated (when turned on).
[0033]
In this electrostatic copying machine, when the copying process described in FIG. 1 is executed, the microcomputer 50 shown in FIG. 2 detects when the temperature detection sensor 20 is in contact with the charging roller 2 immediately before starting the copying process. The time from application of voltage to the charging roller 2 to the start of image formation on the photoreceptor 1 is controlled according to the temperature, and the image writing unit 3 is driven at that time (timing) to perform a writing operation. To start.
Therefore, in this electrostatic copying machine, the microcomputer 50 functions as the pre-charging time control means 5 described with reference to FIG.
[0034]
The microcomputer 50 includes a central processing unit (CPU) having various determination and processing functions, a ROM which is a program memory storing various programs and fixed data necessary for performing various operations at predetermined timings, It is composed of a RAM which is a data memory for storing input data and data processed by the CPU, an input / output circuit (I / O), and also has a timer.
[0035]
The start of the copying process by this electrostatic copying machine is to apply a charging bias voltage (applied voltage) to the charging roller 2 after the print key 51 shown in FIG. 2 is pressed and the print key 51 is pressed. Prior to that, the solenoid 45 is turned on.
Then, since the release lever 23 is moved to the position shown in FIG. 3 against the urging force of the tension spring 43, the engagement end 23a of the release lever 23 comes into contact with the lever portion 32a of the bracket 32 and In order to push to the left side in the figure, the bracket 32 rotates around the shaft 33 in the counterclockwise direction in the figure.
[0036]
Therefore, the temperature detection sensor 20 fixed and held by the bracket 32 is rotated in the same direction, and the temperature detection element 25 fixed to the distal end portion of the conductive leaf spring 26 is separated from the surface of the charging roller 2, The temperature detection sensor 20 is at the non-contact position shown in FIG.
[0037]
When a preset time 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 photoreceptor 1 at a predetermined contact pressure rotates in the direction indicated by the arrow.
[0038]
Thereafter, a charging bias voltage is applied to the charging roller 2 from the high-voltage power supply circuit 24, and after the application of the voltage is completed, the solenoid 45 is turned off.
When the print key 51 is pressed again at an arbitrary timing after the solenoid 45 is turned off, the above-described copying process is repeatedly executed.
[0039]
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 in contact with the photosensitive member via the film material 28 (FIG. 5). When the charging roller 2 is in contact with the surface of the charging roller 2, no voltage is applied from the high voltage power supply circuit 24 to the charging roller 2.
[0040]
Then, the voltage is applied to the charging roller 2 when the copying process is being performed, and at that time, the solenoid 45 is turned on, so that the temperature detection sensor 20 is at 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 fear that electric noise may enter the control system of the entire electrostatic copying machine via the temperature detection sensor 20 or a short circuit may occur in the circuit due to insufficient insulation withstand voltage, so that malfunction does not occur.
[0041]
By the way, as described above, if the temperature of the place where the charging roller 2 is placed is low, the charging roller 2 has low electric conductivity, and thus the rising time until the charging potential is stabilized becomes long.
That is, when the charging roller 2 is at a high temperature such as 30 ° C. as shown in FIG. 6 or at a normal temperature such as 23 ° C. as shown in FIG. However, when the charging roller 2 is at a low temperature such as 10 ° C. as shown in FIG. 8, when the time A has elapsed after the voltage was applied to the charging roller 2, the charging potential is still The stable range of -900V has not been reached.
[0042]
Therefore, for example, at the timing of the voltage application time A in FIG. 8, the image writing unit 3 shown in FIG. 1 is controlled to perform the writing operation, and the light L is irradiated on the surface of the photoconductor 1 to start the image formation. In this case (when the leading edge of the image comes at the time of the voltage application time A), the charged potential of the surface 1a of the photosensitive member 1 corresponding to the leading edge of the image has not yet reached the stable range of -900 V, so that the image density Becomes thinner.
[0043]
In this case, if the image writing unit 3 shown in FIG. 1 is caused to perform the writing operation at the timing after the voltage application time B at which the charging potential is stabilized at −900 V in FIG. Since the leading end also has a stable charge potential region, a normal image density can be obtained.
[0044]
Therefore, for example, if the writing operation is always started at the timing of the voltage application time B to start the image formation irrespective of the temperature of the charging roller 2, the high temperature of 30 ° C. shown in FIG. Also at the normal temperature of 23 ° C., image formation starts at the timing of the voltage application time B. Therefore, in that case, the first copy time (the copy time when an image is first formed and discharged) becomes significantly longer (is delayed).
[0045]
However, in the electrostatic copying machine according to the present embodiment, the pre-charging time control means 5 is provided so that the pre-charging time control means 5 applies a voltage to the charging roller 2 and then applies the voltage to the photosensitive member 1. The time until the image formation is started (pre-charging time t) is variably controlled as shown in FIG. 9 according to the temperature detected by the temperature detection sensor 20.
[0046]
As a result, the temperature of the charging roller 2 and the temperature in the vicinity thereof change due to a change in the environmental temperature in which the electrostatic copying machine is placed, and after a voltage is applied to the charging roller 2, Even if the charging rise time until the charging potential stabilizes, the pre-charging time control means 5 varies the time (pre-charging time t) in accordance with FIG. 9 according to the detected temperature detected by the temperature detection sensor 20. Therefore, the charging potential in one image can be made constant in the shortest time, and a stable image without density unevenness can be obtained even at a low temperature without sending a first copy time at a high temperature and a normal temperature.
[0047]
In this manner, in this electrostatic copying machine, as is apparent from the diagram shown in FIG. 9, when the temperature detected by the temperature detection sensor 20 is equal to or lower than the predetermined temperature of approximately 20 ° C., the charging roller 2 The time from application of the voltage to the start of image formation on the photoreceptor 1 (pre-charging time t) is set to be longer than when the detected temperature is higher than the predetermined temperature (20 ° C.). I have to.
[0048]
FIG. 10 is a configuration diagram similar to FIG. 1 showing another embodiment of an electrostatic copying machine as an image forming apparatus according to the present invention, and portions corresponding to FIG. 1 are denoted by the same reference numerals.
In this electrostatic copying machine, the temperature detection sensor 20 of the embodiment described with reference to FIG. 1 is changed to a humidity detection sensor 60, and the precharge time control means 5 is replaced with a humidity detection sensor 60 which detects the humidity. The only difference is that a pre-charging time control means 5 'for changing the time (pre-charging time) from when a voltage is applied to the charging roller 2 to when image formation on the photoreceptor 1 is started is provided.
[0049]
According to this electrostatic copying machine, when the humidity of the charging roller 2 or the humidity in the vicinity of the charging roller 2 changes, a period from when a voltage is applied to the charging roller 2 to when the charging potential on the photoconductor 1 is stabilized. The charging rise time changes, but even in such a case, the humidity detecting sensor 60 detects the humidity of the charging roller 2 or the humidity in the vicinity thereof, and the pre-charging time control means 5 ′ controls the charging roller 2 according to the detected humidity. Since the time from the application of the voltage to the start of image formation on the photoreceptor 1 (pre-charging time t) is variable, the charging potential in one image can be kept constant, so that there is no density unevenness. A stable image can be obtained.
[0050]
That is, when the charging roller 2 is at a high humidity of 80% as shown in FIG. 11 or at a humidity of 50% as shown in FIG. Although the potential stabilizes at −900 V, when the charging roller 2 is in a low humidity state of 20% as shown in FIG. 13, when the time A has elapsed since the voltage was applied to the charging roller 2, The charging potential has not yet reached the stable range of -900V.
[0051]
Therefore, when the image writing unit 3 shown in FIG. 10 is controlled to perform the writing operation at the timing of the voltage application time A to start the image formation (timing of the image at the time of the voltage application time A). Since the charged potential of the surface 1a of the photoconductor 1 corresponding to the leading end of the image has not yet reached the stable range of -900V, the image density is reduced.
[0052]
In this case, if the image writing unit 3 is caused to perform the writing operation at the timing after the voltage application time B at which the voltage in FIG. 13 stabilizes at −900 V, the image formed thereby has a stable charging potential even at the leading end. , A normal image density can be obtained.
Therefore, in the electrostatic copying machine according to the present embodiment, the pre-charging time control unit 5 ′ sets the time from when a voltage is applied to the charging roller 2 to when image formation on the photoconductor 1 is started (the pre-charging time t) is variably controlled according to the humidity detected by the humidity detection sensor 60 as shown in FIG.
[0053]
As a result, even if the humidity of the charging roller 2 and the humidity in the vicinity thereof change, and the charging rise time from when a voltage is applied to the charging roller 2 to when the charging potential on the photoconductor 1 stabilizes, Since the pre-charging time control means 5 'changes the time (pre-charging time t) according to FIG. 14 according to the detected humidity detected by the humidity detection sensor 60, the charging potential in one image can be made constant. Therefore, a stable image without density unevenness can be obtained.
[0054]
Thus, in this electrostatic copying machine, as is apparent from the diagram shown in FIG. 14, when the detected humidity detected by the humidity detection sensor 60 is equal to or lower than the predetermined humidity of about 50%, the charging roller 2 The time from application of the voltage to the start of image formation on the photoreceptor 1 (pre-charging time t) is set to be longer than when the detected humidity is higher than the predetermined humidity (50%). Thus, a stable image without density unevenness is obtained.
[0055]
In this way, when the humidity is low, the change in the electrical characteristics of the conductive rubber roller portion of the charging roller becomes large, so that the charging rise time changes because, for example, the elastic layer of the conductive rubber roller portion is It is likely to occur when formed of hydrin rubber and the outer surface layer is formed by dispersing carbon in nylon resin.
[0056]
Further, instead of the temperature detection sensor 20 and the humidity detection sensor 60 described with reference to FIGS. 1 and 10, a temperature and humidity detection sensor for detecting the temperature and humidity of the charging roller 2 or the temperature and humidity near the charging roller 2 is provided. And a pre-charging time control means for varying the time from when a voltage is applied to the charging roller 2 to when image formation on the photoreceptor 1 is started in accordance with the temperature and humidity detected by the temperature and humidity detection sensor. You may do so.
[0057]
In this way, even if the environmental temperature or humidity changes, both the temperature and humidity are detected, and a voltage is applied to the charging roller 2 in accordance with the detected temperature and humidity, and then the photosensitive member 1 is charged. Since the time until the start of image formation on the upper side can be obtained from the matrix of temperature and humidity and can be finely controlled, a stable image with less density unevenness can be obtained.
[0058]
【The invention's effect】
As described above, according to the image forming apparatus provided with the temperature detecting unit and the pre-charging time control unit according to the present invention, the temperature of the contact charging member or the temperature in the vicinity thereof changes due to the change of the environmental temperature of the installation location. Even if it changes, the pre-charging time control means varies the time from when a voltage is applied to the contact charging member to when image formation on the photoreceptor is started, according to the temperature. Since an image is formed on a portion where the charged potential on the surface of the body is stable, a stable image without density unevenness in one image can be obtained.
[0059]
Further, even if the image forming apparatus is configured by providing the humidity detecting unit and the pre-charging time control unit, if the ambient temperature changes and the humidity of the contact charging member or the vicinity thereof changes, the humidity may be changed according to the humidity. Since the pre-charging time control means varies the time from when a voltage is applied to the contact charging member to when image formation on the photoreceptor is started, image formation is performed on a portion where the charging potential on the surface of the photoreceptor is stable. As a result, a stable image without density unevenness in one image can be obtained.
[0060]
Furthermore, if the temperature and humidity detecting means and the pre-charging time control means are provided, both the temperature and humidity of the contact charging member or the vicinity thereof are detected, and the contact charging member is provided in accordance with the detected temperature and humidity. Since the time from when the voltage is applied to when image formation on the photoreceptor is started can be finely controlled to an optimum value, a stable image with less density unevenness can be obtained. .
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an example of an electrostatic copying machine, which is an image forming apparatus according to the present invention, together with a control system.
FIG. 2 is a schematic diagram showing a state in which a temperature detection sensor for detecting a surface temperature of a charging roller serving as a contact 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 showing charging rise when the temperature of the charging roller is 30 ° C.
FIG. 7 is a diagram showing charging rise when the temperature of the charging roller is 23 ° C.
FIG. 8 is a diagram showing the rise of charging when the temperature of the charging roller is 10 ° C.
FIG. 9 is a diagram showing a relationship between a temperature detected by a temperature detection sensor and a precharge time t.
FIG. 10 is a configuration diagram similar to FIG. 1, showing another embodiment of an electrostatic copying machine that is an image forming apparatus according to the present invention.
FIG. 11 is a diagram illustrating charging rise when the humidity of the charging roller is 80%.
FIG. 12 is a diagram showing charging rise when the humidity of the charging roller is 50%.
FIG. 13 is a diagram showing the rise of charging when the humidity of the charging roller is 20%.
FIG. 14 is a diagram showing a relationship between a humidity detected by a humidity detection sensor and a precharge time t.
[Explanation of symbols]
1: Photoconductor
2: Charging roller (contact charging member)
3: Image writing unit
5, 5 ': pre-charge time control means
20: temperature detection sensor (temperature detection means)
60: humidity detection sensor (humidity detection means)
50: microcomputer

Claims (5)

A contact charging member that charges the photoconductor by applying a voltage in contact with the rotating photoconductor, and a temperature detecting unit that detects a temperature of the contact charging member or a temperature near the contact charging member. In the image forming apparatus provided with
Pre-charging time control means for varying the time from applying a voltage to the contact charging member to starting writing an image on the photoconductor is provided according to the detected temperature detected by the temperature detecting means. An image forming apparatus comprising: The pre-charging time control means, when the temperature detected by the temperature detection means is equal to or lower than a predetermined temperature, from applying a voltage to the contact charging member to starting writing an image on the photoconductor. 2. The image forming apparatus according to claim 1, wherein the control unit controls the time to be longer than when the detected temperature is higher than the predetermined temperature. A contact charging member that charges the photoconductor by applying a voltage in contact with the rotating photoconductor, and a humidity detecting unit that detects humidity of the contact charging member or humidity near the contact charging member. In the image forming apparatus provided with
In accordance with the detected humidity detected by the humidity detecting means, a pre-charging time control means for changing a time from applying a voltage to the contact charging member to starting writing an image on the photoconductor is provided. An image forming apparatus comprising: The pre-charging time control means, when the detected humidity detected by the humidity detecting means is equal to or less than a predetermined humidity, from applying a voltage to the contact charging member to starting writing an image on the photoconductor. 4. The image forming apparatus according to claim 3, wherein the control unit controls the time to be longer than when the detected humidity is higher than the predetermined humidity. A contact charging member for charging the photosensitive member by applying a voltage in contact with the rotating photosensitive member, and a temperature for detecting the temperature and humidity of the contact charging member or the temperature and humidity near the contact charging member. An image forming apparatus provided with a humidity detecting unit;
Pre-charging time control means for varying the time from applying a voltage to the contact charging member to starting writing an image on the photoreceptor in accordance with the temperature and humidity detected by the temperature and humidity detecting means. An image forming apparatus, comprising:

Images