JP4266541B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus having a heat fixing unit using an electrophotographic system or the like.
[0002]
[Prior art]
As a fixing unit in an image forming apparatus using an electrophotographic process, a film heating type fixing device has been put into practical use in response to a recent demand for energy saving. A film heating type fixing device is formed by sandwiching a thin film having heat resistance between a ceramic heater as a heat generating means and a pressure roller as a pressure member to form a fixing nip. The unfixed toner image is fixed by applying heat and pressure while conveying the recording material by rotating the pressure roller together.
[0003]
In this film heating type fixing device, the heat capacity of the film as a heating member is very small compared to the conventional heat roller type fixing device, so that the heat energy from the heating means can be used efficiently in the fixing process. . Therefore, it is possible to perform a quick start that can shorten the waiting time from power-on of the image forming apparatus to a printable state. Furthermore, since the heat capacity of the heating member is small and it is not necessary to preheat the heating member during standby for printing, the power consumption of the image forming apparatus can be kept low, and energy saving can be achieved.
[0004]
Further, as a highly efficient film heating type fixing device, an electromagnetic induction heating type fixing device that heats the conductive film itself has been proposed. Japanese Utility Model Publication No. 51-109739 discloses a fixing device that induces an eddy current in a metal film by an alternating magnetic field and heats the metal film by Joule heat as an electromagnetic induction heating type fixing device. In the electromagnetic induction heating method, since the film itself can generate heat, the heat energy from the heating means can be used more efficiently in the fixing process.
[0005]
Such a fixing device using a film heating method using a heater or a film heating method using electromagnetic induction can be raised to a fixable temperature in 60 seconds or less and is called a quick start fixing device.
[0006]
[Problems to be solved by the invention]
Taking advantage of the characteristics of the quick start fixing device as described above, if it is attempted to shorten the time (first print out time, FPOT) from the start of printing to the end of the discharge of the printed transfer material, the fixing device rises. It is necessary to perform image formation in parallel with the temperature increase of the fixing device so that the temperature is expected and the transfer material reaches the fixing device when the temperature increase of the fixing device is completed.
[0007]
However, when the image forming apparatus is placed in a low temperature environment or when the voltage of the power source supplied to the image forming apparatus is lowered to the lower limit value, the temperature of the fixing device can be raised completely within the estimated time. There may not be. For this reason, if timing is set with a margin for the time from the start of printing to the start of fixing in consideration of the worst condition, the FPOT will be extended even under normal conditions.
[0008]
In view of the above situation, in the present invention, in an image forming apparatus equipped with a thermal fixing device, the image formation and the temperature of the fixing device are performed in parallel in order to minimize the FPOT. An object of the present invention is to provide an image forming apparatus capable of appropriately raising the temperature of the fixing device without imposing a burden on the constituent members of the image forming apparatus even when it is not in time for the formation.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, in the image forming apparatus of the present invention,
A drum-shaped photoreceptor;
Charging means for uniformly charging the surface of the photoreceptor;
A scanner unit that irradiates a laser beam based on image information and forms an electrostatic latent image on the photoreceptor;
A developing unit having a developing roller capable of contacting and separating from the photosensitive member and supplying toner to the photosensitive member to develop the electrostatic latent image;
Fixing means for heating and fixing the toner image on the transfer material to the transfer material while nipping and conveying the transfer material carrying the toner image transferred from the photoreceptor at the fixing nip portion;
A paper feed unit for feeding the transfer material from the transfer material storage unit;
Have
When the print signal is input, the fixing unit starts to raise the temperature toward the fixable temperature and the photosensitive member starts rotating. After the photosensitive member starts rotating, charging bias application to the charging unit starts and the fixing unit starts. The temperature of the means is lower than the fixing possible temperature If the transfer material reaches the fixing unit, the fixing unit can reach the fixing temperature regardless of the environmental temperature at which the apparatus is installed or the fluctuation of the power supply voltage. When the predetermined temperature is reached, the developing roller starts rotating and the application of a developing bias to the developing roller starts. Thereafter, the developing roller comes into contact with the photoconductor, and the transfer material is fed from the paper feeding unit. In the image forming apparatus, the electrostatic latent image formation on the photosensitive member starts, and then the scanner unit starts,
The timing at which the developing roller starts rotating and the developing bias application to the developing roller starts is the elapsed time from the start of charging bias application to the charging means. Necessary for the surface potential of the photoconductor to reach a normal potential at the time of image formation. A predetermined time has been reached, and the temperature of the fixing unit is lower than the fixable temperature. Above It is a point in time when the temperature reaches a predetermined temperature.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Exemplary embodiments of the present invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified. Absent.
[0018]
(First embodiment)
The image forming apparatus according to the first embodiment will be described with reference to FIGS.
[0019]
[overall structure]
First, the overall configuration of the image forming apparatus will be outlined with reference to FIG.
[0020]
FIG. 1 is a longitudinal sectional view showing an overall configuration of a laser beam printer A which is an embodiment of an image forming apparatus. The photosensitive drum 1 is rotationally driven in the direction of the arrow in FIG. Around the photosensitive drum 1, a charging device 2 that uniformly charges the surface of the photosensitive drum 1 in order according to the rotation direction, a scanner that irradiates a laser beam based on image information and forms an electrostatic latent image on the photosensitive drum 1. Unit 3, developing device 4 for developing toner image by attaching toner to electrostatic latent image, transfer roller 5 for transferring toner image on photosensitive drum 1 to transfer material P, remaining on surface of photosensitive drum 1 after transfer A cleaning device 6 for removing the transfer residual toner is provided.
[0021]
Here, the photosensitive drum 1, the charging device 2, the developing device 4, and the cleaning device 6 are integrally formed as a cartridge to form a process cartridge 7.
[0022]
The scanner unit 3 is arranged in a substantially horizontal direction of the photosensitive drum 1, and image light corresponding to an image signal is irradiated to a polygon mirror 9 rotated at high speed by a scanner motor (not shown) by a laser diode (not shown). . The image light reflected by the polygon mirror 9 is configured to selectively expose the charged surface of the photosensitive drum 1 through the imaging lens 10 to form an electrostatic latent image.
[0023]
As the transfer roller 5 disposed facing the photosensitive drum 1, for example, a metal cored bar is used with a volume resistivity of 10 ⁷ -10 ¹¹ An EPDM (ethylene-propylene-diene terpolymer) adjusted to about Ω · cm, urethane rubber, NBR (nitrile butadiene rubber) or the like covered with an elastic body can be used. A positive bias is applied to the transfer roller 5 from a power source (not shown), and a negative toner image on the photosensitive drum 1 is transferred to the transfer material P in contact with the photosensitive drum 1 by an electric field generated by the bias. .
[0024]
The paper feed unit 8 feeds and conveys the transfer material P to the image forming unit, and a plurality of transfer materials P are stored in the paper feed cassette 11. At the time of image formation, the paper feed roller 12 (half-moon roller) and the registration roller pair 13 are driven and rotated according to the image forming operation to separate and feed the transfer material P in the paper feed cassette 11 one by one. The leading end abuts against the registration roller pair 13, stops once, forms a loop, and then feeds to a nip formed by the transfer roller 5 and the photosensitive drum 1. Reference numeral 24 denotes a registration sensor, on which image formation is performed with reference to the time when the transfer material crosses the registration sensor.
[0025]
The fixing device 14 is an electromagnetic induction heating type quick start fixing device for fixing the toner image transferred to the transfer material P, and is a cylindrical fixing as a rotating body having a heat generating layer (conductive magnetic member). It consists of a film 140 and a pressure roller 143 that presses against the film 140 and applies heat and pressure to the transfer material P (the configuration of the fixing device will be described in detail later). That is, the transfer material P onto which the toner image on the photosensitive drum 1 has been transferred is conveyed by the fixing film 140 and the pressure roller 143 while passing through the fixing device 14, and is given heat and pressure. As a result, the toner image is fixed on the surface of the transfer material P. The fixed transfer material P is discharged out of the main body by the paper discharge roller pair 15 with the image surface facing down from the paper discharge unit 16.
[0026]
The control device B controls the operation of the image forming apparatus A, and includes a CPU 17, a RAM (read / write memory) 18, and a ROM (read only memory) 19. The ROM 19 stores a program for controlling the image forming apparatus and various data, and the RAM 18 is used for storing data taken in for controlling the image forming apparatus.
[0027]
[Process cartridge]
The process cartridge containing toner according to the present embodiment will be described in detail with reference to FIGS. FIG. 2 is a longitudinal sectional view showing a schematic configuration of the process cartridge according to the first embodiment, and FIG. 3 is a perspective view showing a schematic configuration of the process cartridge according to the first embodiment.
[0028]
The process cartridge 7 is divided into a photosensitive drum 1, a photosensitive drum unit 50 having a charging unit and a cleaning unit, and a developing unit 4 having a developing unit for developing an electrostatic latent image on the photosensitive drum 1.
[0029]
The photosensitive drum 1 is configured by coating an organic optical conductor layer (OPC photosensitive member) on the outer peripheral surface of an aluminum cylinder having a diameter of 30 mm, for example.
[0030]
In the photosensitive drum unit 50, the photosensitive drum 1 is rotatably attached to the cleaning frame 51 via bearings 31 (31a, 31b) (bearings). A charging device 2 for uniformly charging the surface of the photosensitive drum 1 and a cleaning blade 60 for removing toner remaining on the photosensitive drum are disposed on the periphery of the photosensitive drum 1. The residual toner removed from the surface of the photosensitive drum 1 by the toner is sequentially sent to a waste toner chamber 53 provided behind the cleaning frame by the toner feeding mechanism 52. Then, the driving force of a driving motor (not shown) is transmitted to one end at the rear of the drawing, so that the photosensitive drum 1 is driven to rotate counterclockwise in the drawing according to the image forming operation.
[0031]
The developing unit 4 includes a developing roller 40 that contacts the photosensitive drum 1 and rotates in the direction of the arrow, a toner container 41 that contains toner, and a developing frame body 45. The developing roller 40 is rotatably supported by the developing frame 45 via a bearing member and rotates in the arrow Y direction. On the circumference of the developing roller 40, a toner supply roller 43 and a developing blade 44 that are in contact with the developing roller 40 and rotate in the direction of arrow Z are disposed. Further, a toner transport mechanism 42 for stirring the toner stored in the toner container 41 and transporting it to the toner supply roller 43 is provided.
[0032]
The developing unit 4 is configured such that the entire developing unit 4 is swingable with respect to the photosensitive drum unit 50 by a pin 49 a around a support shaft 49 provided on each of bearing members 47 and 48 attached to both ends of the developing unit 4. When the process cartridge 7 is a single unit (not mounted on the printer main body), the pressure spring is configured so that the developing roller 40 abuts the photosensitive drum 1 by a rotational moment about the support shaft 49 when the process cartridge 7 is a single unit (not mounted on the printer body). The developing unit 4 is always urged by 53. Further, the toner container 41 of the developing unit 4 is integrally provided with a rib 46 for contacting a separating means (described later) of the printer main body A when the developing roller 40 is separated from the photosensitive drum 1.
[0033]
[Fixing device]
The fixing device according to the present embodiment will be described in detail with reference to FIG. FIG. 4 is a longitudinal sectional view showing a schematic configuration of the electromagnetic induction heating type fixing device according to the first embodiment.
[0034]
Reference numeral 140 denotes a cylindrical fixing film as a rotating body having a heat generating layer (conductive magnetic member). Reference numerals 146a and 146b denote substantially semi-circular arc-shaped film support members (film guides) having a substantially cylindrical body with the opening sides facing each other, and the cylindrical fixing film 140 is disposed outside the film guide 146. Loosely fitted.
[0035]
Inside the film guide 146, magnetic field generating means comprising an exciting coil 148, an E-type magnetic core 147, and an exciting circuit (not shown) is disposed. Reference numeral 142 denotes a laterally long pressurizing rigid stay disposed in contact with the inner surface flat portion of the film support member 146b. Reference numeral 149 denotes an insulating member for insulating the magnetic cores 147a, 147b, 147c and the exciting coil 148 from the pressurizing rigid stay 142.
[0036]
Reference numeral 143 denotes a pressure roller. The fixing film 140 is sandwiched between the pressure roller 143 and the film guide 146, and a predetermined pressure is applied from the pressure roller 143 to the film guide 146, whereby the film guide 146 and the pressure roller 143 are fixed to each other with a predetermined width. A nip portion N is formed and mutually pressed. The magnetic core 147 of the magnetic field generating means 145 is disposed corresponding to the position where the fixing nip portion N is formed.
[0037]
The pressure roller 143 is rotationally driven by the driving means M in the direction indicated by the arrow. By the rotational driving of the pressure roller 143, a frictional force is generated between the pressure roller 143 and the outer surface of the fixing film 140, and the rotational force acts on the fixing film 140. The fixing film 140 has a circumferential speed substantially corresponding to the circumferential speed of the pressure roller 143 while sliding the inner surface of the fixing film 140 in close contact with the lower surface of the film guide 146 in the fixing nip portion N, and the clockwise direction indicated by the arrow b. The outer periphery of the film guide 146 is rotated (pressure roller drive system).
[0038]
The exciting coil 148 generates an alternating magnetic flux by an alternating current supplied from an exciting circuit (not shown). Since the E-shaped magnetic core 147 is provided corresponding to the position of the fixing nip portion N, the alternating magnetic flux is concentrated in the fixing nip portion N, and the alternating magnetic flux is transferred to the fixing film at the fixing nip portion N. An eddy current is generated in 140 heat generation layers. This eddy current generates Joule heat in the heat generating layer due to the specific resistance of the heat generating layer.
[0039]
The temperature of the fixing nip portion N is maintained at a predetermined temperature by controlling the current supply to the exciting coil 148 by a temperature control system (not shown) including a temperature sensor 141 (detection means). Adjusted.
[0040]
[Drive configuration]
Next, the operation mechanism when the process cartridge 7 is mounted on the printer main body A will be described in detail.
[0041]
As described above, when the process cartridge 7 is a single unit, the developing roller 40 is always in contact with the photosensitive drum 1 as shown in FIG.
[0042]
On the other hand, a cam 20 for separating the developing roller 40 from the photosensitive drum 1 against the urging force of the developing unit 4 is disposed on the back side in the insertion direction of the process cartridge 7 of the printer main body A. The cam 20 is rotated by drive means (not shown), and the cam 20 raises the rib 46 so that the developing roller 40 is separated from the photosensitive drum 1, and when the cam 20 releases the pushing up of the rib 46, the developing roller 40 moves to the photosensitive drum 1. Abut. Normally, when the process cartridge is mounted on the printer main body, the cam 20 pushes up the rib 46 so that the developing roller 40 is separated from the photosensitive drum 1.
[0043]
Accordingly, even when the process cartridge 7 is mounted and not used for a long time, the developing roller 40 is always separated from the photosensitive drum 1, so that the developing roller 40 is applied to the photosensitive drum 1 for a long time. It is possible to reliably prevent permanent deformation of the roller layer generated by contact. The photosensitive drum 1 and the developing roller 40 of the process cartridge 7 mounted on the image forming apparatus main body A can be separately driven by a motor (not shown).
[0044]
[Image forming operation]
The image forming operation according to the present embodiment will be described in detail with reference to FIGS. FIG. 5 is a timing chart showing an operation sequence of the image forming apparatus according to the first embodiment. FIG. 6 is a flowchart showing the operation of the image forming apparatus according to the first embodiment.
[0045]
When the operation of the image forming apparatus is started by inputting a print signal to the image forming apparatus main body (Start, S600), the CPU 17 first sets a fixing temperature for controlling the fixing device 14 to a predetermined temperature as a first sequence group. Adjustment, rotation of the photosensitive drum 1 and rotation of the scanner 3 are started (Heat-on, S601). In the present embodiment, the above three sequences are collectively referred to as a first sequence group. At this time, the developing roller 40 remains stopped.
[0046]
Next, application of a charging bias is started after a predetermined time from the start of rotation of the photosensitive drum 1 (Ch-on, S602). This is because if the rotation of the photosensitive drum and the application of the charging bias are performed simultaneously, a memory may be formed on the photosensitive drum. This charging bias application is also included in the first sequence group.
[0047]
Next, the CPU 17 determines whether or not the temperature T of the fixing device 14 has reached a predetermined temperature T1 (S603). If the temperature of the predetermined temperature T1 is kept as it is, the transfer material P reaches the fixing device 14 even when the image forming apparatus is in a low temperature environment or when the supplied power supply voltage is at the lower limit value. The temperature of the fixing device 14 is sufficient to fix the transfer material. (Fixable temperature) This is the temperature that is expected to be reached.
[0048]
If the temperature T of the fixing device 14 reaches T1, rotation of the developing roller 40 and application of the developing bias are started after a predetermined time T_dev from the start of charging bias application (Ch-on) (Dev-on, S604). At this time, if the temperature T of the fixing device does not reach T1, the temperature of the fixing device 14 is continuously monitored. If the temperature reaches T1 within T_dev, it waits until it reaches T_dev (S605). The rotation of 40 and the application of the developing bias are started. In the present embodiment, control of developing bias application, developing roller rotation, and the like corresponds to the second sequence group, and whether or not the detected temperature of the fixing device has reached the predetermined temperature T1 as described above. The operation timing of the second sequence group is determined.
[0049]
If T1 reaches after T_dev, rotation of the developing roller 40 and application of the developing bias are started when T1 is reached. Normally, a sufficient separation distance is provided between the photosensitive drum 1 and the developing roller 40. If the developing roller 40 is separated, the surface of the photosensitive drum 1 is exposed to light even if it is not properly charged. The toner does not fly to the drum 1.
[0050]
However, the rotation of the developing roller 40 and the application of the developing bias are started after a time T_dev when the photosensitive drum 1 is charged and becomes a normal potential so that the toner does not fly even if the separation distance becomes short for some reason. I am doing so. Therefore, even if the temperature T of the fixing device has already reached T1 within T_dev, the developing roller 40 is not rotated and the developing bias is not applied until T_dev, and the developing roller 40 is rotated and the developing bias is applied at T_dev. The image forming operation that has started is the shortest printing time.
[0051]
After T_dev, the developing roller is brought into contact with the photosensitive drum 1 after a predetermined time with respect to T_dev (D_R-on, S606), and then a transfer material is picked up (P-pick, S607) to form an image (Print, S608).
[0052]
If the fixing device temperature rise is determined after the transfer material is picked up, if the fixing device temperature is determined to be insufficient, the image forming operation is temporarily stopped and only the fixing device temperature rise is performed. There is a risk of reducing accuracy. Therefore, the determination of the temperature rise must be made before the transfer material is picked up.
[0053]
However, when the transfer material is picked up immediately before the pickup, the rotation of the photosensitive drum and the developing roller has already started, and if the temperature of the fixing device is insufficient, the pickup operation is continued until the predetermined temperature is reached. When waiting, the photosensitive drum and the developing roller continue to rotate during that time. Since the life of the developing device is greatly affected by the number of rotations of the developing roller, the rotation time of the developing roller should be minimized.
[0054]
On the other hand, the surface potential of the photosensitive drum once charged does not decay unless a transfer bias is applied or exposed, so that the photosensitive drum is charged only if it is rotated by being charged. Because of this, the discharge will not continue to occur. Accordingly, there is no possibility that the surface of the photosensitive drum is scraped by the discharge and the life is shortened.
[0055]
Therefore, as in the present embodiment, the temperature T of the fixing device 14 is detected by the temperature sensor 141, and it is determined in S603 whether the temperature T has reached T1, and the second sequence group operates according to the determination result. If the image forming apparatus is in a low temperature environment, the power supply voltage to be supplied is lower than the lower limit if the timing of starting the rotation of the developing roller 40 and the timing of applying the developing bias are controlled in this embodiment. Even when the value is lowered, it is possible to reliably raise the temperature of the fixing device without shortening the life of the developing device.
[0056]
Even if the second sequence group does not have the above-described operation, the fixing device operates when the transfer material reaches the fixing device based on the detected temperature of the fixing device after a predetermined time from the input of the print signal. An operation for determining the timing of an image forming operation such as picking up a transfer material so as to be at a temperature is also included.
[0057]
Therefore, as described above, image formation and fixing device temperature increase are performed in parallel, and when the fixing device temperature increase is not in time for image formation, after the fixing device reaches a predetermined temperature, Since the image forming operation such as the rotation of the developing roller which is the second sequence group is performed, unnecessary image forming operations such as the developing device are reduced, and the life of the developing device or the photosensitive drum is extended without extending the FPOT. It can be extended.
[0058]
(No. 1 of Reference example No. 1 of Reference example The image forming operation according to the above will be described in detail with reference to FIGS. FIG. 1 of Reference example 6 is a timing chart illustrating an operation of the image forming apparatus according to the embodiment. Figure 8 shows the first 1 of Reference example 6 is a flowchart showing an operation of the image forming apparatus according to the embodiment.
[0059]
When the operation of the image forming apparatus is started by the input of a print signal to the image forming apparatus main body (Start, S800), the CPU 17 first sets a fixing temperature for controlling the fixing device 14 to a predetermined temperature as a first sequence group. And the rotation of the scanner 3 is started (Heat-on, S801). Book Reference example However, unlike the first embodiment, the rotation of the photosensitive drum and the application of the charging bias are not included in the first sequence group.
[0060]
Next, the CPU 17 determines whether the temperature T of the fixing device 14 has reached a predetermined temperature T1 (S802). If the predetermined temperature T1 is kept as it is, the transfer material P reaches the fixing device 14 even when the image forming apparatus is in a low temperature environment or when the supplied power supply voltage is at the lower limit. Sometimes the temperature of the fixing device 14 is expected to reach a temperature sufficient for fixing the transfer material. The heating is continued until the temperature T of the fixing device 14 reaches T1, and when the temperature reaches T1, the rotation of the photosensitive drum (Ph-on, S803), the application of the charging bias (Ch-on, S804), the development roller 40 Rotation and development bias application (Dev-on, S805), development roller contact (D_R-on, S806), transfer material pickup (P-pick, S807), image formation (Print, S808) at predetermined intervals Open and start. Book Reference example In this case, the control of the rotation of the photosensitive drum, the application of the charging bias, the application of the developing bias, the rotation of the developing roller corresponds to the second sequence group, and the detected temperature of the fixing device reaches the predetermined temperature T1 as described above. The timing of the operation of the second sequence group is determined depending on whether or not it is.
[0061]
In the first embodiment, the photosensitive drum continues to rotate while waiting for the temperature of the fixing device to rise. In the first embodiment, if the photosensitive drum is merely rotated, the discharge for charging does not continue to occur, so the photosensitive drum is not scraped by the discharge. However, since the cleaning blade 60 is actually in contact with the photosensitive drum 1, it may be slightly scraped off. In particular, when the efficiency of transferring the toner image on the photosensitive drum 1 to the transfer material at the time of image formation is very good, the amount of toner scraped off by the cleaning blade 60 as a transfer residue on the photosensitive drum 1 is reduced. Since the amount of toner acting as a lubricant between the photosensitive drum 1 and the cleaning blade 60 is reduced, the frictional resistance of the cleaning blade 60 is increased and the photosensitive drum 1 is easily scraped.
[0062]
Book Reference example As described above, the temperature T of the fixing device 14 is detected by the temperature sensor 141, and it is determined whether or not the temperature T has reached T1 in S802, and the timing at which the second sequence group starts operating based on the determination result, Book Reference example In this case, if the timing of each image forming sequence after the start of rotation of the photosensitive drum 1 is controlled, even if the image forming apparatus is in a low temperature environment or the supplied power supply voltage is lowered to the lower limit value. It is possible to reliably raise the temperature of the fixing device without shortening the life of the photosensitive drum and the developing device.
[0063]
(No. 2 of Reference example ) 2 of Reference example An image forming operation according to the above will be described. Book Reference example The image forming apparatus according to the first embodiment is characterized in that the fixing device is preheated when the operation of the image forming apparatus is stopped (during standby).
[0064]
Unlike the conventional heat roller type fixing device, the electromagnetic induction heating type quick start fixing device as in the first embodiment can perform preheating with a small amount of electric power because the heating member has a small heat capacity. Book Reference example In the standby mode, the fixing device is preheated to about 120 ° C., and normal heating is performed simultaneously with the start of the image forming operation.
[0065]
In this way, unlike the case where the temperature is raised from room temperature, the temperature has already reached about 120 ° C., so the temperature rises up to the fixing temperature and the timing of rotation of the developing roller and the start of application of the developing bias is hardly delayed. It does not occur and can maintain a stable FPOT. Further, even when the apparatus is placed in an extremely low temperature environment or the power supply voltage reaches the lower limit value, the rotation time of the developing roller and the application time of the developing bias can be minimized.
[0066]
However, even in such a preheating state, the temperature control time after the start of printing varies. Therefore, even during the printing operation following preheating, 1's The FPOT can be further shortened by similarly using the present invention described in the embodiment and the like.
[0067]
(No. 3 of Reference example )
The following 3 of Reference example Will be described. Book Reference example Is an application of the first embodiment to a color image forming apparatus. Note that the same configurations and functions as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
[0068]
[overall structure]
Book Reference example The image forming apparatus according to FIG. 9 will be described in detail with reference to FIG. Figure 9 shows 3 of Reference example 1 is a longitudinal sectional view showing an overall configuration of a full-color laser beam printer C that is an aspect of a color image forming apparatus according to FIG.
[0069]
The color image forming apparatus C shown in the figure has a process cartridge 7 (7a, 7b, 7c, 7d) in which toner of each color of yellow, magenta, cyan, and black is stored in the process cartridge described in the first embodiment. Are vertically stacked.
[0070]
The scanner unit 3 (3a, 3b, 3c, 3d) is vertically stacked in the same manner as the process cartridge 7 (7a, 7b, 7c, 7d), and substantially in the horizontal direction with the photosensitive drum 1 (1a, 1b, 1c, 1d). Is arranged.
[0071]
Next, an electrostatic transfer belt 21 that circulates and moves so as to face and contact all the photosensitive drums 1a, 1b, 1c, and 1d is disposed. The electrostatic transfer belt 21 has a thickness of 50 to 300 μm and a volume resistivity of 10 ⁹ -10 ¹⁶ Resin materials such as PVdF (polyvinylidene fluoride) of about Ω · cm, polyamide, polyimide, PET (polyethylene terephthalate), polycarbonate, etc., thickness 0.5-2 mm, volume resistivity 10 ⁹ -10 ¹⁶ A rubber material such as chloroplane rubber of about Ω · cm, EPDM, NBR, urethane rubber is used. In addition, carbon, ZnO, SnO may be added to these materials as necessary. ₂ TiO ₂ The volume resistivity is 10 by dispersing a conductive filler such as ⁷ -10 ¹¹ It may be adjusted to about Ω · cm. The electrostatic transfer belt 21 is supported by four-axis rollers 22a, 22b, 22c, and 22d in the vertical direction. , 1c, 1d) is circulated to bring the transfer material P into contact therewith. As a result, the transfer material P is conveyed to the transfer position by the electrostatic transfer belt 21, and each toner image on the photosensitive drum 1 (1a, 1b, 1c, 1d) is transferred.
[0072]
The transfer roller 5 (5a, 5b, 5c, 5d) is arranged in parallel at a position in contact with the inside of the electrostatic transfer belt 21 and facing the four photosensitive drums 1a, 1b, 1c, 1d.
[0073]
The transfer roller 5 (5a, 5b, 5c, 5d) electrostatically transfers the toner image formed on the photosensitive drums 1a, 1b, 1c, 1d to the transfer material P on the transfer belt 21. For example, a metal core bar has a volume resistivity of 10 ^Five -10 ⁸ An EPDM (ethylene-propylene-diene terpolymer) adjusted to about Ω · cm, urethane rubber, NBR (nitrile butadiene rubber) or the like covered with an elastic body can be used. A positive bias is applied to the transfer rollers 5 (5a, 5b, 5c, 5d) from a power source (not shown), and the transfer material P in contact with the photosensitive drum 1 is applied to the transfer material P on the photosensitive drum 1 by an electric field generated by the bias. The negative toner image is transferred.
[0074]
[Drive configuration]
Next, the operation mechanism when the process cartridge 7 is mounted on the printer main body C will be described in detail.
[0075]
In the first embodiment, there is a cam for separating the developing roller 40 from the photosensitive drum 1 against the urging force of the developing unit 4 on the back side in the insertion direction of the process cartridge. Book Reference example Then, a separation plate 23 is arranged so that the four color developing rollers can be separated and contacted at the same time. The spacing plate 23 can be moved up and down by a drive motor (not shown). When the separating plate 23 is raised, the developing roller 40 is separated from the photosensitive drum 1. When the separating plate 23 is lowered, the developing roller 40 is in contact with the photosensitive drum 1.
[0076]
Normally, when the developing roller comes into contact with the photosensitive drum, the photosensitive drum vibrates due to the shock of the contact. Therefore, the contact of the developing roller is not performed in the order of four colors, Reference example As described above, it is preferable to perform the four colors at the same time and to generate the abutment shock once, because the influence on the image can be suppressed.
[0077]
When the process cartridge 7 is mounted on the printer main body C, the separation plate 23 is pushed up, and accordingly, the rib 46 provided on the developing unit 4 along the insertion operation of the process cartridge 7 is attached to the separation plate 23. As a result, the developing roller 40 is separated from the photosensitive drum 1 by a predetermined gap. This separated state is always maintained when the power is turned off and when development is not performed.
[0078]
Accordingly, even when the process cartridge 7 is mounted and not used for a long time, the developing roller 40 is always separated from the photosensitive drum 1, so that the developing roller 40 is applied to the photosensitive drum 1 for a long time. It is possible to reliably prevent permanent deformation of the roller layer generated by contact. The photosensitive drum 1 and the developing roller 40 of the process cartridge 7 mounted on the image forming apparatus main body C can be independently driven by a motor (not shown).
[0079]
[Image forming operation]
Next book Reference example The image forming operation will be described with reference to the schematic diagram of FIG. 9, the timing chart of FIG. 10, and the flowchart of FIG.
[0080]
When the operation of the image forming apparatus is started by the input of a print signal to the image forming apparatus main body (Start, S1100), the CPU 17 first controls the fixing temperature to control the fixing device 14 to a predetermined temperature as a first sequence group. Then, rotation of the photosensitive drums 1a, 1b, 1c, and 1d and rotation of the electrostatic transfer belt 21 are started (Heat-on, S1101). Next, after a predetermined time, rotation of the scanners 3a, 3b, 3c, 3d is started (Scan-on, S1102). This is because there is a possibility that the capacity of the power supply will be exceeded if four motors that drive the photosensitive drums 1a, 1b, 1c, and 1d, one motor that drives the electrostatic transfer belt 21, and four scanner motors are activated simultaneously. The startup timing is shifted. At this time, the developing rollers 40a, 40b, 40c, and 40d remain stopped.
[0081]
Next, in order to prevent memory, application of a charging bias is started a predetermined time after the photosensitive drums 1a, 1b, 1c, and 1d start rotating (Ch-on, S1103). Next, the CPU 17 determines whether or not the temperature T of the fixing device 14 has reached a predetermined temperature T1 (S1104). If the predetermined temperature T1 is kept as it is, the transfer material P reaches the fixing device 14 even when the image forming apparatus is in a low temperature environment or when the supplied power supply voltage is at the lower limit. Sometimes the temperature of the fixing device 14 is expected to reach a temperature sufficient for fixing the transfer material.
[0082]
If the temperature T of the fixing device 14 reaches T1, rotation of the developing roller 40 and application of the developing bias are started after a predetermined time T_dev from the start of charging bias application (Ch-on) (Dev-on, S1105).
[0083]
At this time, if the temperature T of the fixing device does not reach T1, the temperature of the fixing device 14 is continuously monitored. If the temperature reaches T1 within T_dev, it waits for it to reach T_dev (S1106), and then the developing roller 40 Rotation and application of a developing bias is started. If T1 reaches after T_dev, rotation of the developing rollers 40a, 40b, 40c, and 40d and application of the developing bias are started when T1 is reached. After T_dev, the developing roller is brought into contact with the photosensitive drum 1 after a predetermined time with respect to T_dev (D_R-on, S1107). Next, the transfer material is picked up (P-pick, S1108) to form an image. (Print, S1109).
[0084]
Book Reference example As described above, the temperature T of the fixing device 14 is detected by the temperature sensor 141, and it is determined whether or not the temperature T has reached T1 in S1104. The timing at which the second sequence group starts to operate according to the determination result, Book Reference example If the timing of starting rotation of the developing rollers 40a, 40b, 40c, and 40d and applying the developing bias is controlled, the supplied power supply voltage is lowered to the lower limit value even when the image forming apparatus is in a low temperature environment. Even in this case, it is possible to reliably raise the temperature of the fixing device without shortening the life of the developing device.
[0085]
The image forming apparatus according to the present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the gist. Ie, on Real In the embodiment, the photosensitive drum and the developing roller of the process cartridge are driven by separate motors. However, a method may be used in which driving is separated from one motor by using a gear and a clutch. Another method such as using a cam instead of the separation plate may be used.
[0086]
Further, the start timing of the fixing device, the photosensitive drum, and the scanner, and the timing of contact of the developing roller and the timing of picking up the transfer material may be other than the above order. Up Real In the embodiment, an image scanning type scanner is used, but an exposure apparatus using an LED array may of course be used. In that case, the startup timing is different from that of the scanner because the startup operation like the scanner is not necessary. In addition to the tandem type color image forming apparatus, the present invention can be applied to a color image forming apparatus provided with a plurality of developing devices for one photosensitive drum well known in the art.
[0087]
【The invention's effect】
As described above, in the image forming apparatus according to the present invention, particularly in the image forming apparatus provided with the quick start fixing device, the image forming and the fixing device are heated in parallel in order to minimize the FPOT, When the temperature of the fixing device cannot keep up with the image formation, the image forming operation such as the rotation of the developing roller or the rotation of the photosensitive drum is performed after the fixing device reaches a predetermined temperature. The temperature of the fixing device can be appropriately increased without affecting the life of the components of the image forming apparatus such as the photosensitive drum and the photosensitive drum.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to a first embodiment.
FIG. 2 is a longitudinal sectional view showing a schematic configuration of a process cartridge according to the first embodiment.
FIG. 3 is a perspective view showing a schematic configuration of a process cartridge according to the first embodiment.
FIG. 4 is a longitudinal sectional view showing a schematic configuration of the fixing device according to the first embodiment.
FIG. 5 is a timing chart illustrating the operation of the image forming apparatus according to the first embodiment.
FIG. 6 is a flowchart showing the operation of the image forming apparatus according to the first embodiment.
FIG. 7 1 of Reference example 6 is a timing chart illustrating an operation of the image forming apparatus according to the embodiment.
FIG. 8 1 of Reference example 6 is a flowchart showing an operation of the image forming apparatus according to the embodiment.
FIG. 9 3 of Reference example 2 is a longitudinal sectional view showing a schematic configuration of the image forming apparatus according to FIG.
FIG. 10 3 of Reference example 6 is a timing chart illustrating an operation of the image forming apparatus according to the embodiment.
FIG. 11 3 of Reference example 6 is a flowchart showing an operation of the image forming apparatus according to the embodiment.
[Explanation of symbols]
1, 1a, 1b, 1c, 1d Photosensitive drum
2, 2a, 2b, 2c, 2d Charging device (charging roller)
3, 3a, 3b, 3c, 3d scanner
4 Development device
5, 5a, 5b, 5c, 5d Transfer roller
6 Cleaning device
7 Process cartridge
14 Fixing device
21 Electrostatic transfer belt
23 Spacing plate
40, 40a, 40b, 40c, 40d Developing roller
140 Fixing film
141 Temperature sensor
143 Pressure roller
A, C Image forming apparatus

Claims (1)

A drum-shaped photoreceptor;
Charging means for uniformly charging the surface of the photoreceptor;
A scanner unit that irradiates a laser beam based on image information and forms an electrostatic latent image on the photoreceptor;
A developing unit having a developing roller capable of contacting and separating from the photosensitive member and supplying toner to the photosensitive member to develop the electrostatic latent image;
Fixing means for heating and fixing the toner image on the transfer material to the transfer material while nipping and conveying the transfer material carrying the toner image transferred from the photoreceptor at the fixing nip portion;
A paper feed unit for feeding the transfer material from the transfer material storage unit;
Have
When the print signal is input, the fixing unit starts to raise the temperature toward the fixable temperature and the photosensitive member starts rotating. After the photosensitive member starts rotating, charging bias application to the charging unit starts and the fixing unit starts. the fixing means the fixing when regardless deflection of environmental temperature or the power supply voltage the temperature of means the fixable temperature than the low Ku and apparatus Continuing with warm operation is installed transfer material reaches the fixing unit When a predetermined temperature at which the possible temperature can be reached is reached, the developing roller starts to rotate and application of a developing bias to the developing roller starts, and then the developing roller comes into contact with the photosensitive member and comes from the paper feeding unit. In the image forming apparatus, the feeding of the transfer material starts, and then the electrostatic latent image formation on the photoconductor starts by the scanner unit.
The timing at which the developing roller starts rotating and the developing bias application to the developing roller starts is such that the elapsed time from the start of applying the charging bias to the charging unit is the normal potential at the time of image formation. image forming apparatus which is a time when the temperature reaches the lower fixable temperature the predetermined temperature of which and the fixing unit reaches a predetermined time required to reach.

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