JPH07325462A - Image forming device - Google Patents

Abstract

PURPOSE:To effectively shorten a first printing time without increasing the cost for the improvement of mechanical strength, etc., by controlling the switching of an image forming speed so that it automatically restore to a first one after a prescribed number of sheets are printed, at the time of printing. CONSTITUTION:Two process speeds of a high speed mode (second image forming speed) and a normal speed mode (first image forming speed) are provided. A motor control part 18 controls the switching of the image forming speed so that it automatically restore to the first one after the printing of the prescribed number at the time of printing at the second image forming speed faster than the first one. Thus, at the time of starting consecutive printing, an image is formed at the second image forming speed faster than the first one, the first printing time can be shorten and the image forming speed is automatically restored to the first one after the printing of the prescribed number. Thus, the increase of the strength or reinforcement required for each part to be ready for the formation of the image, which is necessitated for coping with high speed can be dispensed with.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic apparatus, an electrostatic copying machine, a printer and the like.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus using an electrophotographic system such as a laser beam printer is provided with commands related to printing (print commands, commands for defining a printing state of the printer, etc.) from an external information processing device such as a personal computer or a workstation. ) And coded character and graphic information by the data receiving means, the code information is converted into pixel information by the pixel converting means, and the controller section converts the pixel information into raster information. , Intensity modulation is performed by a light output means such as a semiconductor laser, and an electrostatic latent image is formed by raster scanning on a photoconductor uniformly charged in advance by a light modulation scanning means including a rotary polygon mirror such as a polygon mirror. , Then an electrophotographic engine section for forming a desired image on a recording material by a well-known electrophotographic process. It has.

Such an electrophotographic image forming apparatus has the advantages that the printing speed is high and the printing quality is excellent. However, when printing is performed from an external information processing device, the first first page is image formed. There is a drawback in that the time until complete output from the apparatus (so-called first print time) is longer than the printing speed (the number of print output per minute).

[0004]

Since the conventional image forming apparatus is configured as described above, even when the laser scanner, which requires a relatively long time to start up, is waiting during the print preparation operation in the electrophotographic engine section. Whether the process of constantly rotating is executed, or because the first print time is governed by the relationship between the recording material conveyance path length and the recording material conveyance speed in the image forming apparatus. By increasing the transport speed, the first print time can be shortened.

For this reason, for example, according to the former, in order to rotate the laser scanner at all times during standby, in addition to the problems that noise during standby increases and power consumption increases, driving for rotating the laser scanner is also required. The life of the motor and drive shaft must be guaranteed for a long time, which results in high cost of the laser scanner.

On the other hand, the latter method of shortening the length of the recording material conveying path imposes great restrictions on the configuration of the image forming apparatus (arrangement of paper feed port, paper ejection port, arrangement of process cartridge, etc.) Not practical.

Further, the method of increasing the conveying speed of the recording material provides a higher speed image forming apparatus. Therefore, the mechanical part strength of the electrophotographic engine section is improved and the heat fixing apparatus corresponds to the higher speed. A large increase in cost will occur due to an increase in size.

The present invention has been made to solve the above problems, and an object of the first to sixth inventions is to perform printing at a second image forming speed higher than the first image forming speed. , When the image forming speed is switched according to the number of printed recording materials, or when the image forming speed is switched to the second image forming speed, the development contrast at the second image forming speed is lower than that at the first image forming speed. Setting the development contrast so as to increase, or switching the image forming speed so as to automatically return to the first image forming speed when a load torque of a predetermined value or more is detected. , The first image forming speed is slower than the second image forming speed, by changing the image forming speed, the mechanical strength is improved without increasing the cost. And to provide an image forming apparatus which can effectively shorten the lint time.

[0009]

A first invention according to the present invention is to visualize an electrostatic latent image formed on an image bearing member with a toner, and transfer the toner image onto a recording material. An image forming apparatus that prints on a recording material by fixing the above toner image has at least two stages of image forming speed, and at the time of printing at a second image forming speed higher than the first image forming speed, A control unit is provided to control switching of the image forming speed so that the first image forming speed is automatically restored after printing a predetermined number of sheets.

According to a second aspect of the present invention, the control means is
For at least a recording material having a width smaller than the maximum printable size width, the number of printouts per unit time at the first image forming speed and the number of printouts per unit time at the second image forming speed are The switching of the image forming speed is controlled so as to be substantially the same.

According to a third aspect of the present invention, when the control means switches the image forming speed to the second image forming speed,
The developing control means is provided to control the developing contrast so that the developing contrast at the second image forming speed becomes higher than that at the first image forming speed.

According to a fourth aspect of the present invention, the image resolution when the second image forming speed (V2) is set is (R2), and the image resolution when the first image forming speed (V1) is set is (R1). ), The resolution condition is V2
A resolution control means for switching and controlling the first resolution and the second resolution is provided so as to satisfy the conditional expression xR2≤V1xR1.

According to a fifth aspect of the present invention, an electrostatic latent image formed on an image carrier is visualized with toner, the toner image is transferred onto a recording material, and the toner image on the recording material is fixed. In the image forming apparatus that performs printing on the recording material by doing so, a member that has at least two stages of image forming speed and is used for image formation at the time of printing at the second image forming speed higher than the first image forming speed is provided. A detection unit that detects the load torque of the driving unit that drives, and when the detection unit detects a load torque that is equal to or greater than a predetermined value, the image forming speed is switched so as to automatically return to the first image forming speed. The control means for controlling is provided.

According to a sixth aspect of the present invention, a polygon mirror rotatably driven by a scanner motor scans a light beam on an image carrier to visualize an electrostatic latent image formed on the image carrier with toner. In the image forming apparatus, the toner image is transferred onto the recording material, and the toner image on the recording material is fixed to print on the recording material.
Having a stepwise image forming speed, the first on the conveyed recording material
After performing the second printing, a recording material conveying path for performing printing on the printing surface or the non-printing surface of the recording material again and performing multiplex or double-sided printing is provided. A control means for switching and controlling the image forming speed so that the first image forming speed is lower than the image forming speed is provided.

[0015]

According to the first aspect of the invention, when printing at the second image forming speed which is higher than the first image forming speed, the control means automatically returns to the first image forming speed after printing a predetermined number of sheets. By controlling the switching of the forming speed, image formation is executed at the second image forming speed which is faster than the first image forming speed at the start of continuous printing, and the first print time is shortened, and after the predetermined number of sheets are automatically printed. Returns to the first image forming speed, and does not require the increase in strength or reinforcement required for each unit provided for image formation, which is required for higher speed.

In the second aspect of the invention, the control means, at least for a recording material having a width smaller than the maximum printable size width, the number of print output sheets per unit time at the first image forming speed, and the second When the thermal fixing means having a heating film with a small heat capacity is used by controlling the switching of the image forming speed so that the number of printed output per unit time at the image forming speed of 1 is almost the same. As the same number regardless of the image forming speed, the temperature rise of the non-sheet passing portion when passing a small-sized recording material does not depend on the image forming speed, No heat measures required.

In the third invention, when the control means switches the image forming speed to the second image forming speed, the developing control means sets the developing contrast at the second image forming speed at the first image forming speed. The development contrast is controlled so as to be larger than that, and deterioration of image quality due to switching of the image forming speed is prevented, and uniform image quality is obtained from the start of continuous printing to the final printing.

In the fourth invention, the image resolution and (R2) at the time of setting the second image forming speed (V2) are defined as:
When the image resolution is set to (R1) when the first image forming speed (V1) is set, the resolution control means sets the first resolution so that the resolution condition satisfies the conditional expression of V2 × R2 ≦ V1 × R1. The second resolution is switched and controlled, and the resolution switching control procedure is simplified while suppressing the lengthening of the first print time until the start-up of the scanner is completed.

According to the fifth aspect of the invention, the detection means for detecting the load torque of the drive unit for driving the member used for image formation has a predetermined value or more when printing at the second image formation speed higher than the first image formation speed. When the load torque is detected, the control means controls the switching of the image forming speed so as to automatically return to the first image forming speed, and the load torque increases in the developing device due to the drive failure. However, the image formation can be continuously started.

In the sixth invention, after the first printing is performed on the conveyed recording material, the printing surface of the recording material,
Alternatively, when the printing is performed again on the non-printing side, and the multiplex or double-sided printing is performed via the recording material conveying path for performing the multiplex or double-sided printing, the control means is slower than the second image forming speed. The image forming speed is switched and controlled so as to become the image forming speed, and an increase in load torque in multiplex or double-sided printing that does not affect the reduction of the first print time is reduced.

[0021]

【Example】

[First Embodiment] FIG. 1 is a schematic diagram illustrating the configuration of an image forming apparatus according to a first embodiment of the present invention.

In the figure, reference numeral 1 denotes an electrophotographic cartridge, which is an electrophotographic photosensitive member 2, a charging roller 3, a developing device 4, and a cleaner 5 which are integrated. Electrophotographic photoreceptor 2 is OP
A photosensitive material such as C, amorphous Se, or amorphous Si is formed on a cylindrical substrate such as aluminum or nickel, and is called a photosensitive drum.

The charging roller 3 uniformly charges the surface of the photosensitive drum 2. Next, the laser scanner 6 raster scans the image signal and exposes it. The laser scanner 6 scans the blinking of the semiconductor laser with a polygon scanner, and forms an optical spot image on the photosensitive drum by the optical system and the folding mirror 7. This creates an electrostatic latent image. The produced electrostatic latent image is developed by the developing device 4. For the development, jumping development, two-component development, FEED development, etc. are used, and a combination of image exposure that turns on the laser at the recording position to eliminate the latent image charge and reversal development that attaches toner to the one with less charge Often used as.

The developed image is transferred to a transfer material.
The transfer material is stored in the cassette 8 and is fed by the paper feed roller 9
Will be fed one by one. When a print signal is sent from the host device, paper is fed by the paper feed roller 9,
The toner image is transferred onto the transfer material by the transfer roller 11 in synchronization with the image signal by the timing roller 10.

The transfer roller 11 is a conductive elastic material having a low hardness, and is electrostatically transferred by a bias electric field at a nip portion formed by the photosensitive drum 2 and the transfer roller 11. The transfer material on which the image has been transferred is fixed by the fixing device 12, sent by the paper discharge roller 13, and discharged to the paper discharge tray 14. On the other hand, the transfer residual toner is cleaned by the blade of the cleaner 5.

The semiconductor laser of the laser scanner 6 is modulated by the exposure controller 16. The bias applied to the charging roller 3, the bias applied to the developing device 4, and the bias applied to the transfer roller 11 are controlled by a high voltage controller 17.

A main motor and a scanner motor (not shown) are controlled by a motor controller 18. Fixer 12
The temperature of is controlled by the fixing controller 19. The operation of the paper feed roller 9 and the timing roller 10 is performed by the paper feed control unit 2
Controlled by 0.

Here, in the image forming apparatus, at least the normal mode (process speed 72 mm / s
ec) and a high speed mode (high speed (second image forming speed) and normal speed (first image forming speed)), which has a process speed of 108 mm / sec and a normal speed of 72 mm.
mm / sec. ) Has two modes,
The user can select whether to use the normal mode or the high speed mode. As the method for the user to select, there is a method in which the user instructs the normal mode or the high speed mode from the print screen on the personal computer. There is a method in which the user uses the printer body to instruct the normal mode or the high speed mode.

However, the high speed mode is to print at a high speed (process speed 108 mm / sec, paper distance 225 mm) first, and after printing a predetermined number of sheets, normal speed (process speed 72 mm /
sec, paper distance 50 mm)
The resolution is 300d for both high speed and normal speed.
pi.

On the other hand, the normal speed mode means the normal speed (process speed 72 mm / se from the beginning).
c, the distance between sheets is 50 mm), but the resolution is 600 dpi, which is double the high speed mode. Hereinafter, the correspondence between the present embodiment and each means of the first invention and the operation thereof will be described.

A first aspect of the present invention visualizes an electrostatic latent image on an image bearing member (photoreceptor 2) with toner, transfers the toner image onto a recording material, and fixes the toner image on the recording material. An image forming apparatus for printing on a recording material by means of a second image forming speed having at least two stages (high speed, normal speed) and higher than the first image forming speed.
At the time of printing at the image forming speed, a control unit (motor control unit 18) is provided to control switching of the image forming speed so as to automatically return to the first image forming speed after printing a predetermined number of sheets. Image formation is performed at a second image formation speed that is faster than the first image formation speed, the first print time is shortened, and the first image formation speed is automatically restored after printing a predetermined number of sheets, resulting in high speed. It is not necessary to increase the strength or reinforce required for each part to prepare for image formation which is required in response to the trend. Below, FIG.
This embodiment will be described with reference to the timing chart of FIG.

FIG. 2 is a timing chart for explaining the image forming sequence by the image forming apparatus shown in FIG.

First, at the time of pre-rotation, the main motor is started at timing a to start the primary charging, and the laser scanner 6
Start up. Next, at timing b, the printer main body sends a signal to the formatter that the main motor, the primary charging, the scanner, etc., have completed the preparations for printing and are ready to start printing.

Then, at timing c, the formatter sends a signal to the printer body to start printing,
Start printing the first sheet. 1 on the drum surface according to the image information developed by the formatter at timing d
Start laser exposure for the first print.

At timing e, a transfer bias is applied to the transfer roller to start the first transfer of the image information drawn on the paper on the drum.

At timing f, fixing of the first unfixed image is started. At timing i, the ejection of the first sheet is completed.

However, since continuous printing is performed, at timing g before timing i, the main body of the printer, the primary charging, the scanner 2 and the like are transferred from the printer body to the formatter.
Send a signal that the first sheet is ready for printing. At timing h, the formatter sends a signal to the printer body to start printing the second sheet, and starts printing the second sheet. Laser exposure for printing the second sheet is started at timing j, but immediately after the laser exposure is finished, the rotation speed of the scanner is reduced at timing m to prepare for printing at normal speed.

However, the resolution at normal speed is also 3
It is 00 dpi. Next, at timing k, biasing of the transfer roller is started for transfer of the second sheet.

At timing 1, the second unfixed image is fixed. At timing n, the ejection of the second sheet ends. At this timing n, the rotation speed of the main motor is also reduced at the same time to prepare for printing at normal speed.

At timing p, the printer main body sends a signal to the formatter that the main motor, primary charging, scanner, etc. are ready to print the third sheet. At timing q, the formatter sends a signal to the printer body to start printing the third sheet, and the third sheet is ready for printing.

At this time, the third sheet of paper stands by at the registration roller. At timing r, laser exposure for printing the third sheet is started. However, since the process speed became slower, the laser exposure time was 3
At the time of the first piece, it is longer. The same applies to transfer, fixing, and paper ejection times.

At timing s, a transfer bias is applied to the transfer roller 11 for transferring the third sheet. The third sheet is fixed at timing t. At timing u, the discharge of the third sheet is completed. After that, since printing is performed at normal speed, the same operation as that for printing the third sheet is performed for the fourth and fifth sheets.

By performing the above process, the first print time becomes 14 seconds when printing in the high speed mode, and the first print time when printing only in the normal mode is 20 seconds, which is faster than when printing only in the normal mode. There is an effect that the print time is shortened by 6 seconds.

At this time, the paper path is 936 mm, and the rise of the laser scanner 6 is linear.

However, in the case of printing at high speed, it is generally necessary to devise the following mechanical structure.

That is, in order to drive at a high speed, it is necessary to increase the strength of the mechanical parts, and especially when used continuously for a long time, for example, gear wear and bearing wear are accelerated by the temperature rise inside the machine.

Further, in the fixing device 12, the wattage of the heater must be increased in order to compensate for the decrease in the temperature of the fixing roller due to the heat being absorbed by the transfer material during continuous printing, and therefore the electric AC driver is used. Costs more.

Similarly, in order to increase the nip width, it is necessary to increase the diameter of the fixing roller and the diameter of the pressure roller and simultaneously increase the pressure. Therefore, the load torque of the entire image forming apparatus becomes large, and it is necessary to use a main motor having a large torque.

The above measures not only increase the cost of the image forming apparatus but also increase the size thereof.

However, by automatically returning to the normal mode after printing a predetermined number of sheets in the high speed mode described in this embodiment, for example, in order to increase the strength of mechanical parts, even when printing in the high speed mode, continuous printing is performed. Since it returns to the normal mode with a few sheets, the strength of the mechanical parts is greatly affected. In the state where the temperature rise inside the machine is large, there is almost no need to increase the strength because it is not used in the high speed mode. In other words, the process speed of 72 mm / sec can be configured with optimum strength, and even if the fixing device prints in high speed mode, it returns to the normal mode with several sheets during continuous printing. The amount of temperature drop is small, and the pressure roller side is sufficiently warm for the first number of sheets during continuous printing. Therefore, the fixing speed is 72 mm / sec, and the fixing speed is 72 mm / sec. Therefore, the fixing speed is 72 mm / sec. Also, in the high speed mode, sufficient fixing property can be obtained.

Further, since it is not necessary to increase the pressing force of the fixing device, the load torque of the main motor is also slightly increased, so that the cost is not increased in this respect as well. [Second Embodiment] Correspondence between the present embodiment and each means of the second invention and its operation will be described below.

A second aspect of the invention is basically provided with the configuration shown in FIG. 1, and the control means (motor control section 18) at least for the recording material having a width smaller than the maximum printable size width is the first aspect. By controlling the switching of the image forming speed so that the number of printouts per unit time at the image forming speed and the number of printouts per unit time at the second image forming speed are substantially the same, heating with a small heat capacity is performed. When using a heat fixing unit having a film, the number of printouts is the same regardless of the image forming speed, and the temperature rise of the non-sheet passing portion when a small-sized recording material is passed does not depend on the image forming speed. The heat countermeasures required for each unit for image formation required for higher speeds are unnecessary. The operation of the second embodiment will be described in detail below with reference to FIG.

FIG. 3 is a timing flowchart for explaining the image forming sequence of the image forming apparatus showing the second embodiment of the present invention.

The image forming apparatus to which this embodiment is applied is the same as the first embodiment in the main part, and the description thereof will be omitted.

In this embodiment, the printing interval of the transfer material is controlled in the high speed mode described in the first embodiment, and the print output per unit time of the image forming apparatus is substantially at the high speed and the normal speed. The number of sheets (hereinafter referred to as throughput) is the same.

The present embodiment will be described below with reference to the timing chart of FIG.

The image forming apparatus of this embodiment is similar to the above-described embodiment in the normal speed mode (process speed: 7
2 mm / sec) and high speed mode (process speed: 108 mm / sec → 75 mm / sec), the user can specify the high speed on the monitor of the host computer or operate the image forming apparatus. High speed mode is specified by a method such as specifying a high speed mode from the section (normal mode is set as default).

When the high speed mode is set, the resolution of the image forming apparatus is set to 300 dpi. When the high speed mode is designated in the electrophotographic engine section, the transfer material is fed, the laser scanner 6 is started up, and the photosensitive drum 2 is instructed by a print command from the controller.
Starts the print preparation operations such as rotation start of the printer, rise of high voltage for primary charging, and rise of development high voltage, and after completion of the print preparation operations, sends a VSREQ signal to the controller section to notify that it is ready to print .

Next, VSYNC from the controller section
The signal starts the printing operation. When the electrophotographic engine unit receives the print signal for the second page within a predetermined timing, the paper feeding operation for the second page is started at the control timing inside the electrophotographic engine.

In this embodiment, at high speed, the paper feed interval is set longer than that at normal speed so that the number of printed output per unit time (1 minute) is substantially the same at high speed and at normal speed. Control. When the fed transfer material for the second page is conveyed to the registration roller section, the electrophotographic engine section sends a VSREQ signal to the controller section.

After that, the printing operation is performed at the same timing as the first page. The printing operation is controlled for the third and subsequent pages at the same timing as that for the second page.
The same control is not performed up to the 0th page, and for the 11th and subsequent pages, the process speed is switched to the normal speed as described in the first embodiment. The timing control at this time is the same as that of the first embodiment, and the description thereof is omitted.

By controlling the printing operation at the above timing, the following actions and effects are produced.

That is, the first print time can be shortened by increasing the process speed as described in the above embodiment.

As for the device on the side of the image forming apparatus for coping with the high speed, as described in the above embodiment, in order to return to the normal speed during the high speed mode, the strength and fixing of the mechanical parts are increased. Since there is no need to increase the size of the container structure, there is almost no factor that increases the cost of the image forming apparatus.

Further, as in the present embodiment, the printing interval is controlled at high speed, and the throughput is substantially the same at high speed and normal speed, so that the fixing property is not particularly lowered and the high speed is improved. The number of printed sheets at that time can be increased as compared with the above-described embodiment. This is because the distance between the transfer material and the next transfer material to reach the fixing device is long even during continuous printing, and the pressure roller can be sufficiently heated during that time, so that the temperature drop of the pressure roller is small and good. This is because it is easy to maintain the fixability.

In addition to this effect, the temperature rise in the non-sheet-passing portion when a small-sized sheet is passed, which is a problem when a heating film having a small heat capacity such as surf fixing is used, is generally used. It is known that the higher the process speed and the higher the throughput, the higher the temperature rise in the non-sheet passing area. According to the study by the present inventor, it was found that the temperature rise in the non-sheet passing portion depends on the throughput rather than the process speed.

The temperature rise in the non-sheet-passing area is maintained by keeping the heating member temperature in the sheet-passing area constant by replenishing the amount of heat deprived of the transfer material in the sheet-passing area. This is a phenomenon that occurs due to excess.

Therefore, if the throughput is the same, the amount of heat absorbed by the transfer material is almost the same even if the process speed is different, and the non-sheet-passage temperature rise amount does not change. Therefore, unlike the present embodiment, it is not necessary to take a special non-sheet passing temperature rise measure by providing the high speed mode by making the throughputs at the high speed and the normal speed substantially the same.

Therefore, for example, the maximum size paper (A4 size in this embodiment) has a throughput of 12 sheets / min at normal speed, and does not pass through a narrow transfer material such as an envelope at normal speed. 6 to suppress part temperature rise
In an image forming apparatus that achieves a throughput of one sheet / minute,
Maximum size paper is 12 sheets / minute even in high speed mode,
A transfer material having a narrow width is set at a throughput of 6 sheets / minute.

Here, the throughput is determined by the process speed and the feeding interval of the transfer material. For example, if the throughput is 12 mm / min at the process speed of 72 mm / sec, the feeding interval of the transfer material is about 50 mm. If the speed is 108 mm / sec and the throughput is 12 sheets / min, the feeding interval of the transfer material is about 220 mm.

Generally speaking, the relationship between the feeding distance of the transfer material at the time of high speed and the normal speed is as follows: the feeding distance of the transfer material at the normal speed is L1 and the process speed is V1. When the sheet feeding interval of the transfer material is L2 and the process speed is V2, L2 = (L0 + L1) × V1 / V2-L0 for the length L0 of the transfer material.
Should be satisfied.

In order to achieve the object of the present embodiment, it goes without saying that the above relationship may be slightly deviated.
If the difference in throughput between high speed and normal speed is within ± 1 sheet / minute, there is no problem in practical use. [Third Embodiment] Correspondence between the present embodiment and each means of the third invention and its operation will be described below.

The third invention is basically provided with the structure shown in FIG. 1, and when the control means (motor controller 18) switches the image forming speed to the second image forming speed, the developing control means (high voltage The control unit 17) controls the development contrast so that the development contrast at the second image forming speed is made higher than that at the first image forming speed to prevent deterioration of image quality due to switching of the image forming speed, and continuous Uniform image quality from the start of printing to the final printing. Hereinafter, the operation of this embodiment will be described in detail with reference to FIG.

FIG. 4 is a diagram showing normal speed and high speed process conditions (developing bias) in the high speed mode in the image forming apparatus according to the present invention.

This embodiment is characterized in that, in the image forming apparatus described in the first embodiment, process conditions are changed when printing in high speed mode and when printing at high speed and when printing at normal speed. The purpose is to minimize the image quality difference between high speed and normal speed.

If the normal speed and high speed process conditions are the same in the high speed mode, an image output at the high speed in the high speed mode has a problem that the line width is narrower than that in the normal speed. This occurs because the process speed is high, and when the laser output light amount is the same, the laser light amount received by the drum surface becomes weak and the latent image contrast becomes small.

On the other hand, in the method of increasing the laser light amount at high speed, the mechanism is complicated because the laser light amount is controlled in two steps, and the threshold current between the laser chips, slope efficiency, FFP efficiency, etc. However, the allowable range is narrowed and the cost increases.

Therefore, in order to prevent image deterioration even in the high speed mode, the process conditions are switched between the normal speed and the high speed in the high speed mode.

Specifically, as shown in FIG. 4, at high speed, since the process speed is fast, the amount of laser light received on the drum surface is weak, the absolute value of V1 becomes high, and the latent image contrast becomes low. Vd at normal speed
= -700V / V1 = -150V, Vd at high speed
= -700 / V1 = -250V) In order to prevent this, in the normal mode, the developing bias is DC voltage -500V,
Peak voltage 1600V superimposed on DC voltage, frequency 1
While the rectangular wave of 800 Hz was applied to the developing sleeve, in the high speed mode, the same developing bias as in the normal mode is applied to the developing sleeve in the normal speed, while in the high speed mode, the developing bias has a DC voltage of −550V. Peak voltage 1 superimposed on DC voltage
A rectangular wave of 600 V and a frequency of 1800 Hz is applied to the developing sleeve.

As described above, by making the DC voltage of the developing bias stronger at the high speed than at the normal speed, the image thinning in the high speed mode can be eliminated without increasing the cost, and it is equivalent to the image output in the normal mode. There is an effect that an image of is obtained. [Fourth Embodiment] Correspondence between the present embodiment and each means of the fourth invention and its operation will be described below.

The fourth invention is the second image forming speed (V
2) The image resolution when set is (R2), and the image resolution when the first image forming speed (V1) is set is (R2).
In the case of 1), the resolution control means (motor control unit 18) controls the switching between the first resolution and the second resolution so that the resolution condition satisfies the conditional expression of V2 × R2 ≦ V1 × R1. The resolution switching control procedure is simplified while suppressing a long first print time until the scanner startup is completed. Hereinafter, the operation of this embodiment will be described in detail with reference to FIG.

FIG. 5 is a diagram showing the relationship between the high speed mode (normal speed, high speed) in the image forming apparatus according to the present invention and the process speed and resolution in the normal mode.

In this embodiment, the image forming apparatus described in the first embodiment has the same resolution when printing in the high speed mode in the normal speed but in the normal mode in the high speed. It is characterized by lowering the resolution when printing.

In the normal mode, the process speed V1
= 72 mm / sec and resolution R1 = 600 dpi, printing is performed without changing the conditions.

On the other hand, in the high speed mode, printing is performed at high speed at first, but the process speed and resolution at that time are the process speed V2 = 108 mm / se.
In c, the resolution is R2 = 300 dpi, which is lower than the resolution of normal speed.

Next, after printing a predetermined number of sheets, it returns to the normal speed. At this time, the process speed and resolution are process speed V3 = 72 mm / sec and resolution R3.
= 600 dpi, the process speed and resolution during normal speed printing in the high speed mode are the same as those during normal mode printing. Here, the process speed V2 and the resolution R2 at the time of high-speed printing in the high-speed mode satisfy the relationship of V2 × R2 ≦ V1 × R1.

By satisfying the relationship of V2 × R2 ≦ V1 × R1, at least the rotational speed of the laser scanner does not become larger at the high speed than at the normal speed, so the influence of the first print time by the rise time of the scanner is affected. Does not change.

Further, in order to control the engine speed to the second speed with the same controller, it is preferable that the clock of the image control signal from the controller be an even multiple. Therefore, the resolution at high speed in the high speed mode is expressed by the above relational expression. Is satisfied and it is preferable that the resolution is set to be an even fraction of the resolution in the normal mode.

As described above, in the high speed mode, the resolution is lowered during the high speed printing as compared with the printing in the normal mode so as to satisfy the above relational expression, and the rotational speed of the scanner during the high speed printing at the high speed is set to the normal value. The cost of the scanner is prevented from increasing without increasing it when printing in the mode, and the resolution is reduced during high-speed printing at high speed, so the startup of the scanner can be made faster, so the first print time can be shortened, In addition, by returning the resolution at the time of normal speed printing in the high speed mode to the resolution at the time of printing in the normal mode, there is an action / effect that image deterioration can be prevented. [Fifth Embodiment] Correspondence between the present embodiment and each means of the fifth invention and its operation will be described below.

According to a fifth aspect of the invention, the electrostatic latent image on the image bearing member is visualized with toner, the toner image is transferred onto a recording material, and the toner image on the recording material is fixed, whereby the electrostatic latent image is fixed on the recording material. In an image forming apparatus that performs printing, a load torque of a driving unit that drives a member used for image formation at the time of printing at a second image forming speed that has at least two stages of image forming speed and is faster than the first image forming speed. When the detection means for detecting the load torque (in the present embodiment, the current detection portion DET monitors and detects the current of the driver DR) detects a load torque equal to or more than a predetermined value, the control means automatically performs the first image formation. By controlling the switching of the image forming speed so as to return to the speed, even if the load torque increases due to a drive failure in the developing device,
The image formation can be continuously started. Below, FIG.
The operation of this embodiment will be described in detail with reference to FIG.

FIG. 6 is a diagram showing a mechanism for detecting the load torque of the motor during high speed mode and high speed mode printing in the image forming apparatus according to the present invention.

FIG. 7 is a diagram showing the rising time of the motor and the number of revolutions of the motor in the normal mode and the high speed mode (at the time of high speed) in the image forming apparatus according to the present invention, and the vertical axis represents the number of revolutions of the motor. The horizontal axis represents time.

In this embodiment, in the image forming apparatus described in the first embodiment, even when printing in the high speed mode, the first first sheet is started up at the normal speed,
The load torque of the motor MM at that time is detected by the current detection unit DET to detect the current applied to the driver DR, and when the load torque becomes larger than the load torque when printing in the normal mode, the printing is automatically performed in the normal mode. In addition, the control unit CPU controls each unit.

In this embodiment, the photosensitive drum, the developing device, the charger,
This is particularly effective for an image forming apparatus that uses a cartridge that is integrally configured with a cleaner and that is detachable from the main body. In the cartridge system, there is a case where new toner is erected and a notification is given, and at this time, there is a case where a tapping phenomenon occurs in which the toner is pushed downward in the developing container and hardened. At the normal speed when the toner is in the above state (process speed V1 = 72 m
It has been confirmed that the load torque during high-speed printing (process speed V2 = 108 mm / sec) is much larger than that when the toner tapping phenomenon does not occur. Therefore, when high-speed printing is performed in the high-speed mode, the printer body may stop.

Therefore, in order to prevent the above problem, the load torque of the motor MM is detected as follows.

First, when the user selects the high speed mode, printing of the first sheet is started at normal speed. At this time, when the first recording material is made to stand by at the registration roller (registration roller), the rotation speed of the motor is as shown in FIG.
When the position A is reached, the motor control unit 1 shown in FIG.
At 8, the load torque of the motor (cartridge, fixing device, scanner, etc.) is detected.

Here, the load torque detection processing will be described with reference to FIG.

ON / OFF of the motor MM by the control unit CPU
However, since the motor MM is rotating, the motor MM is ON. Since the motor MM is ON, the load current of the motor MM and the voltage applied to the resistor are in a proportional relationship, so that the monitor current is supplied from the main body to the motor M.
The current flowing in the motor M and the current flowing in the motor MM is detected by the current detector DET
Since it flows to the internal resistor, the load torque of the motor MM is detected by A / D converting the voltage applied to the resistor by the control unit CPU and monitoring the voltage.

If the load torque exceeds a predetermined value, the normal mode is automatically restored, and the first recording material waiting on the registration rollers is conveyed at normal speed.

On the other hand, if the load torque does not exceed the predetermined value, the high speed mode is continued, and the first recording material waiting by the registration rollers is conveyed at high speed.
It is set to start high speed printing.

As a result, even if the user selects the high speed mode when the tapping phenomenon occurs in the developing container, the image forming apparatus does not operate or fails. [Sixth Embodiment] Correspondence between the present embodiment and each means of the sixth invention and its operation will be described below.

A sixth aspect of the present invention is provided with each control unit shown in FIG. 1 and further has a basic structure shown in FIG. 8 which will be described later, and visualizes the electrostatic latent image on the image carrier with toner. An image forming apparatus that prints on a recording material by transferring the image onto the recording material and fixing the toner image on the recording material has an image forming speed of at least two stages, After the first printing, a printing material or a non-printing surface of the printing material is printed again, and a control means (motor control unit 18) performs multiplex or double-sided printing. Automatic double-sided transport path 23 (see FIG. 8)),
The image forming speed is switched and controlled so that the first image forming speed becomes slower than the second image forming speed, and an increase in load torque in multiplex or double-sided printing that does not affect the reduction of the first print time is reduced.

FIG. 8 is a schematic view showing a paper conveying path for automatic both sides in the image forming apparatus according to the present invention. The same parts as those in FIG. 1 are designated by the same reference numerals.

FIG. 9 is a diagram showing whether the high speed mode can be selected when the image forming apparatus shown in FIG. 8 performs double-sided printing, multiplex printing, or single-sided printing.

In the figure, ◯ means that the mode can be selected, and x means that the use of the mode is prohibited.

The present embodiment is particularly effective in the image forming apparatus of the automatic double-sided machine shown in FIG. 8 and is characterized in that the automatic double-sided machine body of FIG. 8 automatically enters the normal mode when performing double-sided printing or multiplex printing. And

First, the transfer material P is fed from the cassette 22 by the paper feed roller 21, the transfer material P is conveyed to the conveying roller 17 and the registration roller 10, and the transfer material P is once image-formed on the drum by the registration roller 10. Wait until the end. After image formation on the drum, register roller 1
The transfer material P, which has been waiting at 0, is conveyed again, is transferred to the transfer material P at the nip portion N by the transfer roller 11, is fixed by the fixing roller 12, the image formation on the first surface (front surface) is completed, and B2 is set. Be transported.

Here, the transfer material P is reversed, passes through the automatic double-sided conveying path 23, passes through the re-feeding roller 25, and is conveyed again to the sheet-feeding roller 17 and the registration roller 10, and the image on the second side (back side) is transferred. Form. Fix with the fixing roller 12 2
The image formation on the first side (back side) is completed, and this time, the sheet passes through B1 and is discharged.

FIG. 10 is a flow chart showing an example of a print mode setting processing procedure for double-sided printing, multiplex printing, and single-sided printing of the image forming apparatus shown in FIG. Note that (1) to (10) indicate each step.

First, a controller having a CPU (not shown) determines the print mode set (1),
If it is determined to be the automatic double-sided mode (6) and if it is determined to be the multiplex mode (9), the normal mode is set (8) and (10).

On the other hand, when it is judged in the step (1) that the mode is the one-sided mode (2), it is judged whether the speed mode selected by the user is the normal speed mode or the high speed mode. (3) Select the normal mode and proceed to step (8). If the high speed mode is selected, enter the high speed mode (4). After printing a predetermined number of sheets, enter the normal mode ( 5) The print processing for the set number of sheets is executed, and the processing is ended.

As described above, the printing method has one side on one side.
There is a single-sided mode that prints only once, a multiplex mode that prints four times on one side like color printing, and an automatic double-sided mode that prints both sides by forming an image as described above, but the first print time is important in the single-sided mode. Therefore, it is meaningless to enter the high speed mode in the multiplex mode and the automatic double-sided mode, and the image deterioration may occur and the life of the printer body may be shortened by entering the high speed mode. When printing with, control the printer so that it is in normal mode.

On the other hand, when printing on one side, the user can select two print modes, the normal mode and the high speed mode. As a method for the user to select, the user can select the normal mode from the print screen on the personal computer. There are a method of instructing the high speed mode and a method of the user specifying the normal mode or the high speed mode on the printer main body. If the image forming apparatus main body is network compatible, the normal mode or the high speed mode may be designated by any one of a plurality of host computers connected via a predetermined network.

As described above, the load torque is increased in the high speed mode, and the load torque is further increased in the multiplex mode or the double-sided mode. Therefore, the margin of the load torque must be increased and the cost is increased. In the double-sided mode, it is possible to prevent image deterioration without unnecessarily entering the high speed mode, because it is not necessary to mechanically increase the strength of the image forming apparatus, which does not increase the cost. Action /
effective.

[0115]

As described above, the first aspect of the present invention
According to the invention, when the printing is performed at the second image forming speed which is higher than the first image forming speed, the control means switches the image forming speed so as to automatically return to the first image forming speed after printing a predetermined number of sheets. Is controlled, the image formation is performed at the second image formation speed higher than the first image formation speed at the start of continuous printing, the first print time is shortened, and the first image is automatically printed after the predetermined number of prints. By returning to the image forming speed, it is possible to eliminate the need for increasing the strength or reinforcing required for each part for image formation, which is required for the higher speed.

According to the second aspect of the invention, the control means, for at least the recording material having a width smaller than the maximum printable size width, the number of print output sheets per unit time at the first image forming speed, Since the switching of the image forming speed is controlled so as to be almost the same as the number of printed output sheets per unit time at the image forming speed of 2, the number of printed output sheets is increased when the heat fixing means having a heating film with a small heat capacity is used. However, the same number does not depend on the image forming speed, and the temperature rise of the non-sheet passing portion when a small-sized recording material is passed is not dependent on the image forming speed and is prepared for the required image formation corresponding to the speeding up. It is possible to eliminate the heat countermeasure required for each part.

According to the third aspect of the invention, when the control means switches the image forming speed to the second image forming speed, the developing control means sets the developing contrast at the second image forming speed to the first image forming speed. Since the development contrast is controlled so as to be larger than that at the time, it is possible to prevent the image quality from being degraded due to the switching of the image forming speed, and to obtain the uniform image quality from the start of the continuous printing to the final printing.

According to the fourth aspect, the image resolution when the second image forming speed (V2) is set is (R2), and the image resolution when the first image forming speed is set (V1) is (R1). In this case, the resolution control means controls the switching between the first resolution and the second resolution so that the resolution condition satisfies the conditional expression of V2 × R2 ≦ V1 × R1. The resolution switching control procedure can be simplified while suppressing an increase in print time.

According to the fifth aspect of the invention, at the time of printing at the second image forming speed which is higher than the first image forming speed, the detecting means for detecting the load torque of the driving unit for driving the member used for image forming has a predetermined value. When the above load torque is detected, the control unit automatically controls the switching of the image forming speed so as to return to the first image forming speed. Therefore, the load torque increases in the developing device due to the drive failure. Even in this case, at least the image formation can be continuously started so that the user cannot avoid the image formation.

According to the sixth aspect of the invention, after the first printing is performed on the conveyed recording material, the printing surface or the non-printing surface of the recording material is printed again to perform multiplex or double-sided printing. When performing the multiplex or double-sided printing through the recording material conveying path, the control means controls the switching of the image forming speed so that the first image forming speed is slower than the second image forming speed. It is possible to reduce an increase in load torque in multiplex or double-sided printing that does not affect the reduction of the first print time.

Therefore, by selecting the second image forming speed, the image forming apparatus operates at a high image forming speed at the start of continuous printing, so that the first print time can be shortened and at the same time, the predetermined number of sheets can be automatically printed. Since the first image forming speed is restored after printing, in the case of coping with the higher speed, there is no need to deal with the problem that occurs when the image forming apparatus is continuously operated for a long time, and almost no increase in cost occurs.

Further, at least for a recording material having a width smaller than the maximum printable size width of the image forming apparatus, the number of printouts per unit time at the first image forming speed and the second image forming speed Since the number of printouts per unit time is almost the same, even in a fixing device that uses a heating film with an extremely small heat capacity such as surf fixing, the number of printouts is the same regardless of the image forming speed, so it passes through a small size. The temperature rise of the non-sheet passing portion at that time does not depend on the image forming speed, and it is not necessary to take special measures for raising the temperature of the non-sheet passing portion in response to the increase in speed.

Further, since the developing contrast at the second image forming speed is made higher than that at the first image forming speed, it is possible to obtain the same image quality when the image forming speeds are different.

Further, since the resolution of the image forming apparatus at the second image forming speed and the resolution of the image forming apparatus at the first image forming speed are controlled so that a predetermined condition is satisfied, the first print time by the rise of the scanner is set. The effect of is minimized, and the control of the controller section can be simplified.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating a configuration of an image forming apparatus according to a first exemplary embodiment of the present invention.

FIG. 2 is a timing chart for explaining an image forming sequence by the image forming apparatus shown in FIG.

FIG. 3 is a timing flowchart for explaining an image forming sequence of the image forming apparatus showing the second embodiment of the present invention.

FIG. 4 is a diagram showing process conditions of normal speed and high speed in a high speed mode in the image forming apparatus according to the present invention.

FIG. 5 is a diagram showing a relationship between process speed and resolution in a high speed mode and a normal mode in the image forming apparatus according to the present invention.

FIG. 6 is a diagram showing a mechanism for detecting a load torque of a motor during high speed mode and high speed mode printing in the image forming apparatus according to the present invention.

FIG. 7 is a diagram showing a motor rising time and a motor rotation speed in a normal mode and a high speed mode in the image forming apparatus according to the present invention.

FIG. 8 is a schematic view showing a paper transport path for automatic both sides in the image forming apparatus according to the present invention.

FIG. 9 is a diagram showing whether the high speed mode can be selected when performing double-sided printing, multiplex printing, or single-sided printing in the image forming apparatus shown in FIG.

10 is a double-sided print of the image forming apparatus shown in FIG.
7 is a flowchart showing an example of a print mode setting processing procedure at the time of multiplex printing and single-sided printing.

[Explanation of symbols]

 2 Photoconductor 3 Charging Roller 4 Developing Device 5 Cleaner 8 Cassette 9 Paper Feed Roller 10 Registration Roller 11 Transfer Roller 12 Fixing Roller 18 Motor Control Section

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location G03G 21/00 378 (72) Inventor Yuko Ogama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Satoru Izawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Koichi Tanigawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (6)

[Claims] 1. An electrostatic latent image formed on an image bearing member is visualized with toner, and the toner image is transferred onto a recording material,
In an image forming apparatus that prints on a recording material by fixing a toner image on the recording material, printing at a second image forming speed that has at least two stages of image forming speed and is faster than the first image forming speed. At times, the image forming apparatus is provided with a control unit that controls switching of the image forming speed so as to automatically return to the first image forming speed after printing a predetermined number of sheets. 2. The control means, at least for a recording material having a width smaller than the maximum printable size width, the number of print output sheets per unit time at the first image forming speed, and the second
2. The image forming apparatus according to claim 1, wherein the switching of the image forming speed is controlled so that the number of printouts per unit time at the image forming speed is substantially the same. 3. When the control means switches the image forming speed to the second image forming speed, the developing contrast is set so that the developing contrast at the second image forming speed is made larger than that at the first image forming speed. The image forming apparatus according to claim 1, further comprising a developing control unit for controlling. 4. The resolution condition in the case where the image resolution when the second image forming speed (V2) is set is (R2) and the image resolution when the first image forming speed (V1) is set is (R1). 2. The image forming apparatus according to claim 1, further comprising resolution control means for switching and controlling the first resolution and the second resolution so as to satisfy the conditional expression of V2 × R2 ≦ V1 × R1. 5. An electrostatic latent image formed on an image carrier is visualized with toner, and the toner image is transferred onto a recording material,
In an image forming apparatus that prints on a recording material by fixing a toner image on the recording material, printing at a second image forming speed that has at least two stages of image forming speed and is faster than the first image forming speed. Sometimes, a detection unit that detects a load torque of a drive unit that drives a member used for image formation,
An image forming apparatus comprising a control means for controlling switching of the image forming speed so as to automatically return to the first image forming speed when the detecting means detects a load torque of a predetermined value or more. apparatus. 6. An electrostatic latent image formed on an image carrier is visualized with toner, and the toner image is transferred onto a recording material,
An image forming apparatus that prints on a recording material by fixing a toner image on the recording material, has an image forming speed of at least two stages, and performs the first printing on the conveyed recording material. A recording material conveying path for performing multiplex or double-sided printing by performing printing again on the printing surface or non-printing surface of the recording material, and at the time of the multiplex or double-sided printing, a second image forming speed slower than the first An image forming apparatus, comprising: a control unit for switching and controlling the image forming speed so that the image forming speed becomes the same.