JP2000075761A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce postcard printing process time while keeping toner fixing property and sharp image formation by having a single latent image forming speed and to prevent errors in calculation of the amount of a residual toner resulting from variations in conveying speed. SOLUTION: During postcard printing, conveying speed is changed to low speed before insertion of a postcard into a fixing roller 114 after formation of a latent image on a photoreceptor drum 108, so that the period during which the postcard is conveyed at low speed can be minimized. While the postcard is being conveyed at low speed, the delay of the conveying speed caused by the repeated turning on and off of the transfer voltage of a transfer part 111 allows a voltage applied to the postcard to increase relatively, thus preventing the image from being fouled. Further, the sampling period of a toner sensor is extended to prevent errors in calculation of the amount of the residual toner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming apparatus, and more particularly to an electrophotographic image forming apparatus.

[0002]

2. Description of the Related Art In forming an image on a postcard, it takes a long time to conduct heat due to its thickness, and the toner is not sufficiently fixed at the same fixing temperature as ordinary recording paper (hereinafter referred to as ordinary recording paper). There is a problem. As measures against this, there are roughly two types of solutions of 1) increasing the fixing temperature and 2) decreasing the transport speed when passing through the fixing roller.

When the method 1) of raising the fixing temperature is performed, it is necessary to increase the fixing temperature only during postcard printing in order to prevent overheating during image formation on recording paper. However, the fixing roller whose width is determined assuming normal recording paper has a problem that the proportion of the portion where the recording paper does not pass during postcard printing increases, and the portion where the rollers contact each other becomes overheated. Also, this method has a problem that the effect is reduced at the time of high-speed printing.

Therefore, the conventional image forming apparatus employs a method of 2) in which the conveying speed when passing through the fixing roller is reduced. In the conventional apparatus, when the detecting means detects that the recording paper is thick paper, the transport speed of the photosensitive drum and the fixing roller is switched to a low speed.

By the way, in the conventional apparatus, the distance between the image transfer position and the image fixing position is set shorter than the length of the postcard in the conveying direction due to the demand for downsizing of the apparatus and the configuration of the recording paper conveying mechanism. This is because if a recording paper transport roller is provided between the photosensitive drum and the fixing roller, the unfixed toner transferred onto the recording paper adheres to the roller, so a roller cannot be provided, and the minimum recording paper length for printing is reduced. This is because the distance between the image transfer position and the image fixing position is set together.

For this reason, if the conveying speed is switched to a low speed immediately before the postcard is inserted into the fixing roller, a timing to switch the fixing roller to a low speed occurs during the image transfer to the postcard, and the transfer voltage changes during the transfer. Therefore, the uniformity of the image is lost. In addition, since the transport speed is reduced during the transfer, the transfer voltage becomes relatively strong, and the formed image becomes dirty.

[0007] Therefore, in the above-described conventional apparatus, the timing for switching to the low speed can be achieved immediately before the apparatus is inserted into the fixing roller. However, it is difficult to synchronize the change in the speed of the photosensitive drum with the scanning of the laser. For this reason, it is said that it is preferable to perform the process before forming a latent image by using a laser.

[0008]

However, in the above-mentioned conventional apparatus, there is a problem that the period of low-speed conveyance is long, and the processing speed in postcard printing is reduced.

Further, since the transfer speed is switched to a low speed by controlling the output of a single power source, the rotation speed of the toner stirrer is also reduced in proportion. Then
The number of samples of the toner sensor with respect to the rotation of the stirrer changes, so that one cycle of the output waveform cannot be extracted and the peak of the waveform cannot be calculated, and the remaining toner amount is erroneously calculated.

In this case, it is necessary to provide two kinds of latent image forming speeds by the laser, and the apparatus becomes complicated.

The present invention has been made in view of the above circumstances, has a single latent image forming speed, shortens a postcard printing processing time while ensuring toner fixing property and clear image formation, and further conveys. An object of the present invention is to provide an image forming apparatus that prevents erroneous calculation of the remaining amount of toner due to a change in speed.

[0012]

During postcard printing, the conveying speed is switched to a low speed before forming the latent image on the photosensitive drum and before inserting the fixing roller so that the period of the low speed conveyance is minimized. The voltage applied to the postcard is relatively increased by repeating the transfer voltage ON / OFF to reduce the conveyance speed, thereby preventing the image from being stained. Prevent erroneous calculation of remaining amount.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a first embodiment of the present invention, during postcard printing, after the formation of a latent image on a photosensitive drum and before insertion of a fixing roller for a postcard, the conveying speed of the recording paper is reduced from the first speed to the second speed. Transport speed control means for switching to a second speed lower than one speed, image transfer means provided on the postcard transport path so that the distance from the fixing roller is shorter than the vertical length of the postcard, Is adopted.

According to this configuration, since the speed is not changed from the speed before the photosensitive drum is inserted to the speed but from the low speed just before the fixing roller is inserted, the period for conveying at a low speed is minimized, and as a result, the time required for the postcard printing process is shortened. You. Also, only one latent image forming speed needs to be provided.

According to a second aspect of the present invention, in the first aspect, the toner sensor for detecting the remaining amount of toner and the sampling cycle of the toner sensor are set to the first when the postcard transport speed is the first speed. And a toner sensor control unit that sets the sampling cycle to a second cycle longer than the first cycle when the postcard transport speed is the second speed. take.

According to this configuration, even if the stirring of the toner is switched to a low speed in accordance with the transport speed, the sampling period is made variable in accordance with the stirring speed and the number of samples obtained is kept the same. Even in this case, the remaining amount of toner can be calculated by the same calculation method.

According to a third aspect of the present invention, a postcard is printed during the printing process when the conveyance is performed only at the first speed and when the conveyance is performed at the first speed and the second speed. And a transfer voltage control means for controlling a transfer voltage applied to a postcard per unit time during the conveyance at the second speed so that the transfer voltages applied to the transfer rollers are substantially equal.

According to this configuration, even if the transport speed is switched to a low speed during the image transfer, an excessive transfer voltage is not applied to the recording paper and the image is not dirty.

In a fourth aspect of the present invention, the transfer voltage control means reduces a transfer voltage applied to a postcard per hour during conveyance at the second speed by repeating ON / OFF of the transfer voltage. Take the configuration.

According to this configuration, the transfer voltage per time can be easily reduced by repeating ON / OFF without performing complicated voltage control.

According to a fifth aspect of the present invention, when the recording paper is a postcard, the conveying speed of the postcard is switched to a low speed after the formation of the latent image on the photosensitive drum and before the insertion of the fixing roller of the postcard. The transfer voltage is controlled such that the transfer voltage applied to the postcard per time is substantially equal, and the postcard is transferred from the transfer position to the fixing roller at a position where the distance on the transport path is shorter than the vertical length of the postcard. It was transported.

According to this method, since the speed is not changed to the low speed immediately before the photosensitive drum is inserted, but is changed to the low speed immediately before the fixing roller is inserted, the period for conveying at a low speed is minimized. As a result, the time required for the postcard printing process is reduced. You. Furthermore, even if the transport speed is switched to a low speed during image transfer, an excessive transfer voltage is not applied to the postcard, and the image is not dirty. Further, only one latent image forming speed may be provided.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

First, the configuration of an image forming apparatus according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic configuration diagram showing a configuration of the image forming apparatus according to the above embodiment.

In FIG. 1, a paper feed roller 101 takes out recording papers 103 in a cassette 102 one by one and conveys them to an image forming section described later. The paper feed roller 101 has a clutch (not shown). The clutch of the paper feed roller 101 is turned on, the paper feed roller 101 is rotated, and the recording paper 103 is rotated.
Is transported.

The registration sensor 104 senses that the registration roller 105 conveys the recording paper 103 and notifies the image forming section 106 of the timing. Image forming unit 10
In 6, the charging unit 107 charges the photosensitive drum 108, the laser 109 forms a latent image, the developing unit 110 attaches toner to the latent image on the photosensitive drum 108, and the transfer unit 111 applies toner to the recording paper 103. Transcribe. And cleaning unit 1
At 12, the excess toner on the photosensitive drum 108 is removed.

In the fixing unit 113, the surface temperature of the fixing roller 114 is detected by a temperature sensor (not shown), and ON / OFF control of a fixing lamp (not shown) in the fixing roller 114 is performed so that the fixing roller 114 is maintained at a fixed fixing temperature. keep.
When the recording paper 103 to which the toner is attached is conveyed to the fixing unit 113, the toner is melted by the heat of the fixing roller 114,
The recording paper 103 is fixed by the pressure of the fixing roller 114.

The fixed recording paper 103 is detected by a paper discharge sensor 115 and discharged. The discharge path 116 of the recording paper 103 is not necessarily straight depending on the configuration of the apparatus.

Each of the above-described mechanisms rotates by transmitting a driving force from a main motor (not shown) by a gear.
However, the ON / OFF of the rotation of the sheet feeding roller 101 and the registration roller 104 is controlled by a clutch (not shown). The transmission path of electricity and driving force will be described later.

Next, a detailed configuration of the developing unit 110 shown in FIG. 1 and a method of detecting the remaining amount of toner in the developing unit 110 will be described with reference to FIGS. FIG. 2 shows the developing unit 11
FIG. 3 is a schematic diagram illustrating a configuration of a toner sensor, and FIG. 3 is a graph illustrating an example of a toner sensor waveform.

In FIG. 2, the developing drum 201 which is in contact with the photosensitive drum 108 rotates in accordance with the rotation of the photosensitive drum 108. The stirrer 202 rotates to attach the toner 203 to the developing drum 201. The toner 203 is agitator 2
02 also falls on the toner sensor 204 during agitation.

As shown in the output waveform of the toner sensor 204 shown in FIG. 3, when the remaining amount of toner is large, the toner touches the toner sensor 204 regardless of the rotation of the agitator 202.
The output waveform is high and the amplitude is small. On the other hand, when the remaining amount of toner decreases, only the toner lifted by the rotation of the stirrer 202 comes into contact with the toner sensor 204, and the contact depends on the rotation of the stirrer 202, that is, the amplitude of the output of the toner sensor 204 increases. . When the toner approaches the empty state, the toner hardly touches the toner sensor 204 even by the rotation of the agitator 202, so that both the output and the amplitude are reduced.

The toner sensor 204 includes a stirrer 202
The sampling period is determined in accordance with the rotation speed of the printer, and if the rotation speed is the same, the toner remaining amount is reproducible, so that the remaining toner amount can be detected. As will be described in detail later, in the present embodiment, since a single driving source is used, when the transport speed is low, the rotation speed of the stirrer 202 is also low. Therefore, by increasing the sampling cycle of the toner sensor 204 in accordance with this, the number of samples of the toner sensor 204 with respect to the rotation speed of the stirrer 202 is equal, and the remaining amount of toner is calculated by the same calculation method as before the conveyance speed becomes low. Can be calculated.

Next, the configuration of the printer control circuit will be described with reference to FIG. FIG. 4 is a block diagram showing the configuration of the printer control circuit.

In FIG. 4, an arrow pointing to the CPU 401 indicates a sensor input, and an outgoing arrow indicates a control output. The main motor 402 rotates under the control of the CPU 401, and outputs a ready signal when the main motor 402 reaches a constant speed. The main motor 402
Has two speeds, high speed and low speed, and is controlled by the CPU 401.

When the paper feed clutch 403 is turned on after confirming the ready signal from the main motor 402, the recording paper confirmation sensor 404 confirms the presence or absence of recording paper in the cassette 102, and then feeds paper (not shown in FIG. 4). The paper roller 101 starts rotating. The size sensor 405 detects the size of the recording paper 103 and transmits it to the CPU 401.

The recording paper 103 fed by the paper feed roller 101 is detected by a registration sensor 104.
The registration roller 104 temporarily stops. And CPU4
01 turns on the registration clutch 406 at a timing synchronized with the image forming unit 106, and the recording paper 103 is conveyed to the image forming unit 106 by the registration roller 105.

Laser Scan Unit (Laser Scan Unit)
A unit (LSU) 407 receives, from the CPU 401, a signal of rotation control and laser emission control of a polygon (hexagonal) motor having a laser as a line configuration, and sends a horizontal synchronization signal for detecting the formation of a latent image of one line to the CPU 401.

The toner sensor 204 indicates the remaining amount of toner by a voltage change. The CPU 401 reads the voltage change of the toner sensor 204 and recognizes the remaining amount of toner. More CPU
Reference numeral 401 changes the sampling period of the toner sensor 204 between a normal sampling period for a high-speed conveyance speed and a sampling period for a low-speed conveyance speed in accordance with a change in the recording paper conveyance speed described in detail later. As described above, this is to prevent the CPU 401 from correctly extracting one cycle of the output waveform of the toner sensor 204 and calculating the peak of the waveform when the transport speed becomes slow, thereby preventing the toner remaining amount from being erroneously detected. is there.

The high-voltage power supply 408 applies the photosensitive drum 108, and charges the charging unit 107, the developing unit 110, and the transfer unit 113.
Is generated in response to a command from the CPU 401.

The fixing lamp 409 is driven by receiving power supply from the power supply 410 to heat the fixing roller 114. The CPU 401 receives the temperature change measured by the temperature sensor 411 in contact with the fixing roller 114 as a voltage change, and controls the fixing lamp 409 to set the fixing roller 114 to an appropriate fixing temperature.

The discharge sensor 115 is, as described above,
It detects that the recording paper 103 has been fixed.

Next, a flow of an image forming operation on a postcard according to the present embodiment will be described with reference to FIGS. FIG. 5 is a schematic diagram illustrating the relationship between the position of the postcard on the transport path and the motor speed, and FIG. 6 is a schematic diagram illustrating the state of transfer control.

The postcard position 501 indicates a state in which one postcard is taken out of the cassette 102 by the paper feed roller 101 and is started to be conveyed. At this time, the main motor 402
As shown in the motor speed change flow at the bottom of FIG.
Spinning at high speed.

When the start-up of the image forming section 106 is completed, the main motor 402 is switched to a low speed, and the paper feed roller 101 starts to transport the postcard from the state of the postcard position 501. The low speed here is about half of the high speed. The reason why the conveyance from the paper feed roller 101 to the registration roller 105 is performed at a low speed is that the postcard after the second sheet is conveyed from the paper feed roller 101 in the case of continuous paper feeding, and the postcard immediately before will be described later. This is because the fixing step is performed so that the conveying speed is adjusted on the conveying path.

The postcard position 502 indicates a state where the postcard conveyed by the paper feed roller 101 reaches the registration roller 105 and is temporarily stopped. Paper feed roller 101
Is completed, the CPU 401 sets the paper feed clutch 4
03 is turned off, and the rotation of the paper feed roller 101 is stopped.

In order for the postcard to be conveyed from the postcard position 502 by the registration roller 105, the registration clutch 406 must be turned on by a command from the CPU 401. In the case of continuous paper feeding, the CPU 401 turns on the registration clutch 406 after waiting for the discharge sensor 115 to detect the end of the fixing of the previous postcard. If the fixing of the previous postcard has been completed, the CPU 401
The registration clutch 406 is turned on in synchronization with the formation of a latent image on the photosensitive drum 108 by U407,
Postcard image forming unit 106 using registration roller 105
Starts transport to. Since it is not necessary to convey the image at a low speed in this image forming step, the motor speed is set to a high speed.

The distance A in FIG.
08 along the roller surface of the photosensitive drum 10
8, a position equal to the distance from the position where the latent image is formed to the transfer unit 111 and separated from the transfer unit 111 by a distance A on the recording paper conveyance path is defined as an image forming position 503.

From the postcard position 502, the registration roller 10
5, the postcard is conveyed, and when the leading end of the postcard in the conveying direction reaches the image forming position 503, the laser 109 starts forming a latent image on the photosensitive drum. By adjusting the timing in this way, the postcard is transferred to the transfer unit 11.
When the number reaches 1, transfer can be started.

The leading end of the postcard in the transport direction is the transfer portion 11.
When it reaches 1, transcription starts. Further, the operation of the fixing roller 114 is started as shown in FIG.

The postcard position 504 indicates a state where the rear end of the postcard in the transport direction has reached the image forming position 503. Here, while the postcard passes through the fixing roller 114 in order to sufficiently transmit heat to the postcard and fix the toner, the main motor 4
Set 02 to low speed.

The reason why the speed is switched to the low speed at the postcard position 504 is that the LSU 407 needs to be set at a single setting. That is, if the speed is switched to a low speed before the postcard position 504, the LSU 407 has not yet formed a latent image on the photosensitive drum 108, and therefore it is necessary to provide another setting corresponding to the low transport speed. On the other hand, postcard position 5
If the speed is switched to low speed after 04, the distance B between the transfer unit 111 and the fixing unit 113 is shorter than the vertical length of the postcard, so it is not possible to start fixing. (Distance A) + (Distance B) is longer than the vertical length of the postcard.
If the speed is switched to low speed in 04, it is in time for the start of fixing.

On the other hand, when the speed is switched to the low speed at the postcard position 504, as described above, the photosensitive drum 10 by the LSU 407 is used.
The formation of the latent image on the photosensitive drum 108 has been completed, but the process of transferring the latent image on the photosensitive drum 108 to a postcard is in progress. Therefore, by switching the transport speed to a low speed, the transfer voltage applied to the postcard becomes relatively high, and the image becomes dirty.

As a countermeasure, the transfer unit 111 performs ON / OFF control of the transfer voltage as shown in FIG. That is, by periodically generating ON and OFF of the voltage, the voltage per time applied to the recording paper during the low-speed conveyance is reduced, and as a result, the entire transfer voltage applied to the postcard during the printing process is reduced by the high-speed conveyance. It is made to be substantially equal between the case where a constant application is made and the case where the conveyance is switched at a low speed on the way.

The postcard position 505 indicates a state where the fixing process has been completed. When the paper discharge sensor 115 detects completion of fixing, the CPU 401 returns the conveying speed to the high speed, and the postcard is discharged.

As described above, by changing the transport speed to a low speed at the same time as the completion of the formation of the latent image on the photosensitive drum so as to minimize the period of the low speed transport, the postcard printing processing time can be reduced.

Next, a procedure in which the CPU 401 sets the sampling cycle of the toner sensor 204 will be described with reference to FIG. FIG. 7 is a flowchart showing a procedure in which the CPU 401 sets the sampling cycle of the toner sensor 204.

Steps ST701 to ST706 are procedures for collecting data of a required number of samples according to the sampling period that has been set. Since a sampling period suitable for the number of rotations of the stirrer 202 is set, the number of samples is set to be the same in any sampling period, and the arithmetic processing is performed in the same manner.

In ST707, it is determined whether the transport speed is high or low. If the transport speed is high, a sampling cycle for high-speed transport, which is a normal cycle, is set in ST708. A long sampling period is set.

[0060]

As described above, according to the present invention,
It has a single latent image forming speed, shortens postcard printing processing time while securing toner fixability and clear image formation, and prevents erroneous calculation of toner remaining amount due to change in transport speed. it can.

[Brief description of the drawings]

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

FIG. 2 is a schematic diagram illustrating a configuration of a developing unit according to the embodiment.

FIG. 3 is a graph showing an example of a toner sensor waveform according to the embodiment.

FIG. 4 is a block diagram showing a configuration of a printer control circuit according to the embodiment.

FIG. 5 is a schematic diagram showing the relationship between the position of the postcard on the transport path and the motor speed according to the embodiment.

FIG. 6 is a schematic diagram showing the movement of each electric signal along the flow of image formation according to the embodiment.

FIG. 7 is a flowchart showing a procedure for setting a sampling cycle of the toner sensor according to the embodiment.

[Explanation of symbols]

 Reference Signs List 101 feed roller 102 cassette 103 recording paper 104 registration sensor 105 registration roller 106 image forming unit 107 charging unit 108 photosensitive drum 109 laser 110 developing unit 111 transfer unit 112 cleaning unit 113 fixing unit 114 fixing roller 115 discharge sensor 116 discharge path 201 Developing drum 202 Stirrer 203 Toner 204 Toner sensor 401 CPU 402 Main motor 403 Feed clutch 404 Recording paper confirmation sensor 405 Size sensor 406 Registration clutch 407 Laser scan unit (LSU) 408 High voltage power supply 409 Fixing lamp 410 Power supply 411 Temperature sensor 503 Image formation position

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 2H027 DD02 DE09 EA03 ED02 ED16 ED24 ED25 EE02 EE03 EE04 EF09 FA30 FC02 ZA10 2H032 AA02 BA12 BA13 CA04 CA13 2H033 AA02 AA20 AA47 BB00 CA21 CA22 CA36 2AD07 DA02 DA01 DB16 DB22

Claims (5)

[Claims] At the time of postcard printing, after the formation of a latent image on a photosensitive drum and before insertion of a fixing roller of the postcard, the conveyance speed of the recording paper is changed from a first speed to a second speed lower than the first speed. Transport speed control means for switching, image transfer means provided such that the distance from the fixing roller on the transport path of the postcard is shorter than the vertical length of the postcard,
An image forming apparatus comprising: 2. A toner sensor for detecting a remaining amount of toner,
When the transport speed of the postcard is the first speed, the sampling period of the toner sensor is set to the first period, and when the transport speed of the postcard is the second speed, the sampling period is set to be longer than the first period. The image forming apparatus according to claim 1, further comprising: a toner sensor control unit that sets a second cycle having a long cycle. 3. A transfer voltage applied to a postcard during a printing process when the sheet is conveyed only at the first speed and when the sheet is conveyed at the first speed and the second speed. 3. The image according to claim 1, further comprising a transfer voltage control unit configured to control a transfer voltage applied to a postcard per time during the conveyance at the second speed so as to be substantially equal. Forming equipment. 4. The transfer voltage control means according to claim 1, wherein
4. The image forming apparatus according to claim 1, wherein a transfer voltage applied to a postcard per unit time is reduced during conveyance at the second speed by repeating N-OFF. 5. When the recording paper is a postcard, the conveying speed of the postcard is switched to a low speed after the formation of the latent image on the photosensitive drum and before the fixing roller of the postcard is inserted, and the postcard is applied per time before and after the switching. An image forming method in which a transfer voltage is controlled so that the transfer voltage is substantially equal to each other, and the postcard is conveyed from the transfer position to the fixing roller at a position on the conveyance path shorter than the vertical length of the postcard.