JPH0743963A - Image forming device - Google Patents

Abstract

PURPOSE:To improve the quality of an image by controlling an image forming condition according to paper thickness. CONSTITUTION:A filler 39 which is provided in a paper carrying path 38 leading to an image forming part and which descends by the weight of a paper P, filler descending amount detection sensors 46a and 46b detecting the descending amount of the filler 39, a calculation means calculating the thickness of the paper P based on the outputs of the sensors 46a and 46b, a control means controlling the image forming condition to be a prescribed value suitable for the paper thickness based on the paper thickness calculated by the calculation means, and an alignment control means detecting the paper P based on the outputs of the sensors 46a and 46b and deriving timing for feeding the paper so as to align the image on the photoreceptor 30 of the image forming part with the paper P are provided. Then, the image forming condition is controlled based on the thickness of the paper P.

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 for forming an image on a sheet by an electrophotographic process.

[0002]

2. Description of the Related Art A basic process of a conventional example of an image forming apparatus for forming an image on a sheet by an electrophotographic process will be described below with reference to FIGS. 1: Charging First, the charging charger 1 charges the master 2 negatively by negative corona discharge. 2: Exposure The projection device 3 projects a document onto the master 2 to form an electrostatic latent image on the master 2. 3: Erase Erase LED 4 removes the charging potential of the non-image area. Erase the front and rear ends and the side. 4: Development In the developing section 5, positive toner is attached to the electrostatic latent image on the master 2 to form a visible image. 5: Transferring the toner on the master 2 to the paper P by applying a negative charge from the back surface of the paper P that is in close contact with the master 2 in the image forming unit 6. 6: Separation The sheet P after the transfer is separated from the master 2 by the separation roller 7 and the waist of the sheet P. 7: Cleaning The toner remaining on the master 2 is scraped off by the cleaning blade 8. 8: Charge elimination After cleaning, the charge elimination lamp 9 eliminates the residual charge on the master 2 to prepare for the next cycle.

Next, the carrying process at this time will be described below with reference to a.
e. a: Paper feeding The paper P fed by cassette or manually is fed to the registration rollers 11 by the feeding rollers 10. b: Registration The registration roller 11 aligns the image on the master 2 with the sheet P and sends out the sheet P. Specifically, as shown in FIG. 13, the registration roller 11 that has blocked the sheet P conveyed by the conveying roller 10 stops and rotates at the timing when the image on the master 2 and the sheet P coincide with each other to rotate the sheet P. Send out. This timing is measured based on the sheet detection by the sheet sensor 12. c: Separation and Conveyance The sheet P separated from the master 2 by the separation roller 7 and the waist of the sheet is conveyed to the fixing unit 14 by the conveyance belt 13. d: Fixing Unfixed toner on the sheet P is fixed by the fixing roller 15 and the pressure roller 16 by applying a constant temperature and pressure. e: Paper discharge The fixed paper P is discharged to the paper discharge tray by the paper discharge roller 17.

In the electrophotographic image forming apparatus for forming an image by such a process, the transfer current, the separation current, the angle of the transfer inlet guide plate, the angle of the fixing inlet guide plate, the angle of the fixing heater, and the fixing heater depend on the thickness of the paper P. It is known that image forming conditions such as temperature change.

[0005]

Therefore, it is necessary to set the image forming conditions according to the paper thickness. However, since the conventional apparatus does not always perform accurate control,
Image quality deterioration due to improper transfer and separation, separation jamming, image rubbing due to improper fixing, image quality deterioration,
There was a risk of causing fixing wrinkles.

The present invention has been made based on such a background, and an image forming apparatus capable of performing a highly reliable image forming operation by controlling the image forming conditions according to the paper thickness. The purpose is to provide.

[0007]

According to another aspect of the present invention, there is provided a filler provided in a sheet conveying path leading to an image forming unit and dropping according to the weight of the sheet, and a filler dropping amount for detecting the dropping amount of the filler. A detection sensor, a calculation means for calculating the paper thickness of the paper based on the output of the filler drop amount detection sensor, and a predetermined value suitable for the paper thickness as an image forming condition based on the paper thickness calculated by the calculation means. Position control for detecting the paper based on the output of the filler drop amount detection sensor, and measuring the paper delivery timing so that the image on the photoconductor of the image forming unit and the paper coincide with each other. And means.

According to a second aspect of the invention, in the first aspect of the invention, the filler is formed of a conductor.

According to the invention of claim 3, claim 1 or 2
In the invention described above, a filler having a shielding plate protruding upward that blocks the paper conveyance path is formed, and the filler is arranged downstream of a conveyance roller that conveys the paper in the paper conveyance path,
A moving unit is provided to move the filler to the outside of the sheet conveyance path based on the control of the alignment control unit that matches the image on the photoconductor of the image forming unit with the sheet.

According to a fourth aspect of the present invention, in the first, second or third aspect of the present invention, a humidity sensor is provided and the calculation means for correcting the calculated value of the paper thickness based on the output of the humidity sensor.

[0011]

According to the first aspect of the invention, when the sheet moves in the sheet conveying path, the filler drops due to the weight of the sheet. Then, the calculation unit calculates the paper thickness from the filler drop amount detected by the filler drop amount detection sensor, and the control unit controls the image forming condition based on the calculated paper thickness. Further, the alignment control means detects the sheet based on the output of the filler drop amount detection sensor, and measures the sheet delivery timing so that the image on the photoconductor of the image forming unit and the sheet coincide with each other.

According to the second aspect of the present invention, since the filler is formed of a conductor, the static electricity charged on the paper escapes through the filler.

According to the third aspect of the present invention, the leading edge of the sheet comes into contact with the shielding plate formed on the filler during the transportation by the transportation roller, and the transportation of the sheet stays. Then, according to the timing measured by the alignment control means, the moving means moves the filler to the outside of the paper conveyance path to release the shielding of the paper conveyance path. Then, the paper is fed to the image forming unit at the timing when the image on the photoconductor of the image forming unit and the paper match.

According to the fourth aspect of the invention, the calculating means corrects the calculated value of the paper thickness based on the humidity detected by the humidity sensor, and the correct paper is not affected by the weight of the paper which changes depending on the humidity. Calculate the thickness.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a vertical cross-sectional side view showing the whole of the image forming apparatus of this embodiment.
A charging charger 31 for charging along the circumference of
An exposing unit 32 for exposing, a developing unit 33 for developing, an image forming unit 34 for transferring and separating, a cleaning unit 35 for cleaning, and a discharging lamp 36 for discharging are provided.

Next, the paper feed path 3 from the paper feed cassette 37 through the image forming unit 34 to a paper discharge unit (not shown).
No. 8 is provided, a filler 39 is provided in the vicinity of the upstream side of the image forming unit 34 of the paper transport path 38, and a fixing device 40 is provided in the vicinity of the downstream side. A sheet feeding roller 41 is provided at the front end of the sheet feeding cassette 37, and a conveying roller 42 is provided between the sheet feeding roller 41 and the filler 39.

As shown in FIG. 1, the filler 39 is arranged so that the upper surface of the filler 39 can be slightly seen through the cutout portion of the paper guide 43 forming the paper transport path 38 so as to be lowered. And is supported by a spring 44 from below. The spring 44 is supported by a solenoid 45 which is a moving means, and the solenoid 45 operates so that the filler 39 is retracted from the paper transport path 38. Further, the tip end of the filler 39 is formed as an inclined surface so that the paper P in the paper transport path 38 can easily climb up. Further, on the upper surface of the filler 39, a shield plate 39a that shields the paper transport path 38 is provided upright. The sensor plate 39b protruding below the filler 39 is sandwiched between five photosensors 46a and 46b, which are filler drop amount detection sensors. The filler 39 is made of a conductor.

Next, FIGS. 3 and 4 show the image forming unit 3
4, a transfer inlet flap 47 is arranged in the image forming portion 34 at a position upstream of the photosensitive drum 30 which is an inlet thereof. This transfer entrance flap 4
Reference numeral 7 is connected to the motor shaft 48a of the motor 48 at the hanging side 47a at the upstream end, and the angle can be changed by the rotation of the motor 48. The angle of the transfer entrance flap 47 determines the angle of the paper P facing the photoconductor drum 30, and the contact pressure between the photoconductor drum 30 and the paper P due to the waist of the paper P is determined.

FIG. 5 shows the fixing device 40. A fixing roller 49 and a pressure roller 50 are provided so as to face each other, and the fixing inlet flap 5 is provided on the upstream side thereof.
1 is arranged. As shown in FIG. 6, the fixing inlet flap 51 has a motor shaft 52a of the motor 52 on its side surface.
The rotation angle of the motor 52 allows the angle to be changed.

Next, FIG. 7 is a block diagram showing the hardware configuration of the image forming apparatus, which includes a CPU 53 and a ROM.
Microcomputer 56 comprising 54 and RAM 55
The five photosensors 46, the operation board 57, etc. are connected to (calculation means, control means, alignment control means) via an input interface 58, and the solenoid 4 is connected.
5, the motors 48 and 52, transfer and separation output control circuit 5
9, the fixing heater control circuit 60, the operation board 57, etc. are connected via an output interface 61.

Then, the microcomputer 56
Is programmed to calculate a paper thickness that is a function of weight from the output of the five-series photosensor 46 that changes depending on the amount of fall of the filler 39 due to the weight of the paper P.

Further, the optimum image forming conditions are determined from the obtained paper thickness of the paper P, and the transfer current, the separation current, the angle of the transfer inlet flap 47, the angle of the fixing inlet flap 51, and the temperature of the fixing heater are determined. Programmed to control.

Further, the microcomputer 56 is
The paper P is detected from the output of the five-series photosensor 46 which changes depending on the amount of the drop of the filler 39 due to the weight of the paper P, and the solenoid 45 is activated at the timing when the image on the photoconductor drum 30 and the paper P coincide with each other. It is programmed to drive and retract the filler 39 from the paper transport path 38.

In such a structure, the paper feed roller 41
The paper P pulled out from the paper feed cassette 37 is conveyed by the conveyance rollers 42. Then, when the sheet P rides on the filler 39, the filler 39 descends due to the weight of the sheet P as shown in FIG. Then, the microcomputer 56 calculates the paper thickness of the paper P as a function of the weight from the amount of fall of the filler 39, and the transfer current and the separation current are set so that the image forming condition suitable for the paper thickness of the paper P is obtained. , Angle of transfer entrance flap 47, fixing entrance flap 5
The angle of 1 and the temperature of the fixing heater are controlled.

Therefore, the image forming apparatus can always obtain good print quality regardless of the change in the paper thickness. Moreover, since the paper thickness of the paper P is calculated from its weight, unlike the case of using a transmissive sensor, the amount of transmitted light differs depending on the type of paper, which is different from the discrimination method that often causes malfunctions. The paper thickness can be accurately obtained, and stable performance can be obtained.

The sheet P is conveyed by the conveying roller 42, but is temporarily blocked by the shielding plate 39a of the filler 39 as shown in FIG. Then, the filler 39 is retracted from the inside of the paper transport path 38 and the shielding of the paper transport path 38 by the shield plate 39a is released, so that the image of the paper P coincides with the image on the photosensitive drum 30. Is sent to the image forming unit 34 (FIG. 10).

As described above, since the filler 39 blocks the sheet P, the image forming apparatus does not need a conventional registration roller for blocking the sheet P and can be constructed at low cost.

Further, since the detection of the paper P, which is the reference for the timing of retracting the filler 39, is performed by detecting the fall of the filler 39, the conventional paper detection sensor is not required, and the construction can be made inexpensively. it can.

Further, since the filler 39 is made of a conductive material, the static electricity charged on the paper P can escape through the filler 39, and the adsorption of the paper P and the paper guide 43 by the static electricity can be prevented.

Further, the five-series photo sensor 46 is turned on and off.
The size of the paper P can also be obtained from F.

Next, the second embodiment of the present invention is shown in FIG.
It will be described based on. The same parts as those shown in the above-mentioned embodiment are designated by the same reference numerals and the description thereof will be omitted. FIG. 11 shows
In the block diagram showing the hardware configuration, a humidity sensor 62 is provided in the image forming apparatus of this embodiment.

The microcomputer 56 is programmed to correct the calculated paper thickness of the paper P based on the output of the humidity sensor 62.

In such a configuration, the microcomputer 56 calculates the paper thickness of the paper P based on the amount of fall of the filler 39 due to the weight of the paper P, and further corrects the calculated paper thickness with humidity. Determine the final paper thickness,
Each unit is controlled so that the image forming condition suitable for the paper P having this paper thickness is obtained.

Therefore, the correct paper thickness can be calculated without being affected by the weight of the paper P which changes depending on the humidity, and the optimum image forming conditions can always be prepared.

[0035]

According to the first aspect of the invention, when the sheet moves in the sheet conveying path, the filler drops due to the weight of the sheet, and the filler is detected by the filler drop amount detection sensor by the calculating means. The paper thickness is calculated from the amount of fall of the paper, and the control means controls the image forming conditions based on the calculated paper thickness, so that good image quality can be obtained, and the alignment control means can adjust the filler fall amount. Since the paper is detected based on the output of the detection sensor and the paper delivery timing is measured, the conventional paper sensor for detecting the paper can be omitted, and therefore, the cost can be reduced, and further,
Since the paper thickness of the paper is calculated from its weight, unlike the case where a transmission type sensor is used, the amount of light transmitted differs depending on the type of paper, which is different from the discrimination method that often causes malfunctions The paper thickness can be obtained, and stable performance can be obtained.

In this case, according to the second aspect of the present invention, since the filler is made of a conductor, static electricity charged on the paper escapes through the filler and is caused by static electricity on the paper and the paper guide for guiding the paper. Adsorption can be prevented.

Further, according to the third aspect of the present invention, the leading edge of the sheet comes into contact with the shielding plate formed on the filler during the transportation by the transportation roller, and the transportation of the sheet stays. According to the timing, the moving unit moves the filler to the outside of the paper transport path to release the blocking of the paper transport path, and the paper is fed to the image forming section at the timing when the image on the photoconductor of the image forming section matches the paper. The conventional registration roller can be omitted, and thus the cost can be reduced.

Further, according to the invention described in claim 4, the calculating means corrects the calculated value of the paper thickness based on the humidity detected by the humidity sensor, without being influenced by the weight of the paper which changes due to the humidity. Since the correct paper thickness is calculated, the correct paper thickness can be calculated without being affected by the weight of the paper that changes due to humidity. Therefore, it is possible to maintain good image quality without being affected by humidity changes. it can.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view showing a first embodiment of the present invention.

FIG. 2 is a vertical sectional side view showing the entire apparatus.

FIG. 3 is a vertical side view showing an image forming unit.

FIG. 4 is a perspective view showing an image forming unit.

FIG. 5 is a vertical sectional side view showing a fixing device.

FIG. 6 is a perspective view showing a fixing inlet flap.

FIG. 7 is a block diagram showing a hardware configuration.

FIG. 8 is a vertical cross-sectional side view showing a state in which the filler has dropped due to the weight of the paper.

FIG. 9 is a vertical cross-sectional side view showing a state in which the leading edge of the sheet is in contact with the shielding plate and the sheet feed is retained.

FIG. 10 is a vertical cross-sectional side view showing a state in which the filler has retracted from the sheet conveyance path.

FIG. 11 is a block diagram showing a hardware configuration of a second embodiment of the present invention.

FIG. 12 is a vertical sectional side view showing an example of a conventional image forming apparatus.

FIG. 13 is a vertical cross-sectional side view showing a state where sheet feed is retained by registration rollers.

[Explanation of symbols]

 30 Photoreceptor 34 Image Forming Section 38 Paper Conveying Path 39 Filler 39a Shielding Plate 42 Conveying Roller 45 Moving Means 46 Filler Drop Detection Sensor 56 Calculating Means, Control Means, Positioning Control Means 62 Humidity Sensor P Paper

Claims (4)

[Claims] 1. A filler provided in a sheet conveying path leading to an image forming section and lowered by the weight of the sheet, and a filler drop amount detection sensor for detecting the drop amount of the filler.
Calculation means for calculating the paper thickness of the paper based on the output of the filler drop amount detection sensor, and control for controlling the image forming condition to a predetermined value suitable for the paper thickness based on the paper thickness calculated by the calculation means. And a positioning control unit that detects the sheet based on the output of the filler drop amount detection sensor and adjusts the sheet delivery timing so that the image on the photoconductor of the image forming unit matches the sheet. An image forming apparatus characterized by the above. 2. The image forming apparatus according to claim 1, wherein the filler is formed of a conductor. 3. A filler having a shield plate protruding upward that blocks the paper transport path is formed, and the filler is disposed downstream of a transport roller for transporting the paper in the paper transport path, and is placed on the photoconductor of the image forming section. 3. The image forming apparatus according to claim 1, further comprising a moving unit that moves the filler to the outside of the sheet conveying path based on the control of the alignment control unit that matches the image of FIG. 4. The image forming apparatus according to claim 1, wherein a humidity sensor is provided, and the calculation means corrects the calculated value of the paper thickness based on the output of the humidity sensor.