JP2002006651A - Image forming device - Google Patents

Abstract

(57) [Problem] To apply an optimum paper transfer bias without increasing the first print time. SOLUTION: A paper transfer roller contact / separation control circuit 32 is provided.
A sheet transfer roller resistance value measurement circuit 35; an environment change detection circuit 34; a sheet transfer bias output circuit 38; and a sheet transfer roller resistance value measurement circuit when the environment change detection circuit 34 detects an environment change in a standby state. A timer circuit 36 for measuring the time from the reading of the resistance value by the reference 35 and the detection of the environmental change by the environment change detection circuit 34 to the start of printing, the sheet transfer roller resistance value measurement circuit 35, and the operation of the sheet transfer roller resistance value measurement circuit 35 And a paper transfer bias determining circuit 37 for determining an optimum paper transfer bias based on the time from the end of printing to the start of printing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image output apparatus for printing out image data formed in an office computer, a personal computer, or the like, and an image forming apparatus used in a copying machine.

[0002]

2. Description of the Related Art In recent years, an image forming apparatus for printing a color image on a recording medium such as a color laser printer has been rapidly spread. With the spread thereof, demands for printing quality on a recording medium have been increasing, and it has been desired that the printing medium can be used for a long period of time while maintaining the printing quality stably.

Here, a configuration of a conventional image forming apparatus will be described below with reference to the drawings.

FIG. 3 is a schematic view showing a conventional image forming apparatus.

As shown in FIG. 3, the image forming apparatus includes a black photosensitive member 13, a cyan photosensitive member 14, a magenta photosensitive member 15, and a yellow photosensitive member on which a black image, a cyan image, a magenta image, and a yellow image are respectively formed. 16
Is installed.

The photosensitive members 13, 14, 15, and
Around the photoreceptor 16, a black charger 9, a cyan charger 10, a magenta charger 11, and a yellow charger 1 for uniformly negatively charging the outer peripheral surfaces of the photoconductors 13, 14, 15, 16
2. Each of the photoconductors 1, 14, 15, and 16 is provided corresponding to each of the photoconductors 1, 14, 15, and 16 and emits a laser beam according to image information.
The laser output units 1, 2, 3, and 4, which irradiate in the main scanning directions of 3, 14, 15, and 16 to form an electrostatic latent image, are formed on respective photoconductors 13, 14, 15, and 16. A black image forming unit 5, a cyan image forming unit 6, a magenta image forming unit 7, which visualizes an electrostatic latent image,
Each of the yellow image forming units 8 is arranged.

Below the photosensitive members 13, 14, 15, 16 is an intermediate endless belt-shaped intermediate member which is stretched around a driving roller 17a and a counter roller 18a which are driven to rotate by a driving means (not shown). A transfer body 17 is provided.

At the lower part of the apparatus, there is provided a cassette 21 containing a recording medium 20 such as printing paper. Then, the recording medium 20 is sent out from the cassette 21 to the transport path one by one by a paper feed roller.

On the transport path, a transport roller 19 for transporting the recording medium 20 sent to the transport path, an intermediate transfer member 1
And a paper transfer roller 18 that contacts the outer peripheral surface of the intermediate transfer member 7 for a predetermined amount to transfer the color image formed on the intermediate transfer body 17 to the recording medium 20, and holds the color image transferred on the recording medium 20 by the roller. Fixing unit 22 having a heating roller for fixing to recording medium 20 by pressure and heat due to rotation
Is arranged.

Further, a paper discharge roller 23 for discharging the recording medium 20 on which the color image is fixed, and a paper discharge tray 24 for storing the recording medium 20 discharged from the paper discharge roller 23 are provided behind the fixing device 22 in the conveyance path. Is provided.

Here, when the temperature and humidity environment suddenly changes, it takes time for the resistance value of the paper transfer roller 18 to adjust to the environment and stabilize. Therefore, the time lag detects and predicts the temperature and humidity sensor. A difference is generated between the resistance value of the paper transfer roller 18 and the actual resistance value of the paper transfer roller 18. When printing is performed in that state, an optimum paper transfer bias is applied to the paper transfer roller 18. However, there is a problem that an image defect occurs.

As the improvement, the following technique is adopted.

FIG. 4 is an enlarged schematic view showing the vicinity of the paper transfer roller in the image forming apparatus of FIG.

The paper transfer roller 18 has a paper transfer bias output circuit 38 controlled by a paper transfer roller bias output circuit control terminal 35d of the microprocessor 120 to apply a paper transfer bias current to the paper transfer roller 18.
Is connected.

The output voltage of the paper transfer bias output circuit 38 is inputted to an input terminal 35a of a paper transfer roller resistance value measuring circuit 35 using a comparator, and the reference voltage of the microprocessor 120 is used as the paper transfer roller resistance value measuring circuit. 35 is input to another input terminal 35b. Then, the sheet transfer roller resistance value measuring circuit 35
From the input terminal 35a to the input terminal 35
The comparison result of the voltage input to b is output to the microprocessor 120.

According to this, the paper transfer bias current supplied from the paper transfer bias output circuit 38 is transferred from the paper transfer roller 18 to the grounded opposing roller 18a via the intermediate transfer body 17 which is an image bearing member. Flows.

As described above, the paper transfer bias output circuit 38 is controlled by the paper transfer roller bias output circuit control terminal 35d of the microprocessor 120. Also, an input terminal 35 of the sheet transfer roller resistance value measuring circuit 35
A is supplied with a voltage obtained by converting the paper transfer current into a voltage value, a reference voltage from the microprocessor 120 is supplied to the input terminal 35b, and the result of comparison between the two is input to the microprocessor 120.

Therefore, the reference voltage supplied from the microprocessor 120 is sequentially changed until the output terminal 35c of the sheet transfer roller resistance value measuring circuit 35 changes.
Thus, the resistance value of the paper transfer roller 18 can be obtained from the reference voltage when the output terminal 35c of the paper transfer roller resistance value measuring circuit 35 changes, and the microprocessor 120 performs processing based on the value. Thus, the optimum paper transfer bias is determined.

This series of processing is always performed before printing starts, the resistance value of the paper transfer roller 18 is measured, and an optimum paper transfer bias is applied to the paper transfer roller 18.

FIG. 5 is a flowchart showing the operation of applying the paper transfer bias in the image forming apparatus of FIG.

In FIG. 5, before the dot data for each color of black, cyan, magenta, and yellow is sent and printing is started (step S70), the sheet transfer roller 18 is measured to measure the resistance value of the sheet transfer roller 18. Are brought into contact with each other (step S71). Then, the microprocessor 120 sets and outputs a scan start reference voltage for measuring the resistance value of the sheet transfer roller 18 (step S72), and applies a sheet transfer bias supplied from the sheet transfer bias output circuit 38 (step S73).

Next, from the microprocessor 120, the reference voltage for measuring the resistance value of the paper transfer roller 18 is from 0 to 5 V, and 0.2 V is set as one step, and the paper transfer roller resistance value is measured up to 25 times (step S76). It is checked whether the output of the circuit 35 changes (step S7).
4). This is because the distribution of the resistance value of the paper transfer roller 18 in one measurement tends to be different, and it takes one second for one rotation of the paper transfer roller 18, so that it may take up to 25 seconds.

If there is no change in step S76, the reference value is changed (step S77), and
Return to 74. If there is a change, the reference value is acquired as a resistance value (step S75). Then, the optimum paper transfer bias is determined from the value obtained in step S75 (step S78), and the paper transfer bias is switched to the optimum paper transfer bias (step S7).
9).

Thereafter, black image data is sent and input to the black laser output unit 1. The black laser output unit 1 switches between emission and extinction of laser light according to dot data, emits laser light to the black photoconductor 13 uniformly negatively charged by the black charger 9, and irradiates the laser light. The latent image is formed by the potential difference generated by the operation. In the latent image formed on the black photoconductor 13, the toner is attracted to the black photoconductor 13 by a Coulomb force generated by a developing bias which is a specified voltage value applied to the black image forming unit 5, and the toner is developed. Is performed on the black photoconductor 13 to form a toner image. Then, this toner image is transferred to the intermediate transfer body 17.

Next, the cyan charger 10, the cyan laser output unit 2, and the cyan photoconductor 14 are separated by a time delayed by the distance between the black photoconductor 13 and the cyan photoconductor 14.
The cyan toner image is formed through the same process as the above-described black image forming process using the cyan image forming unit 6 and is superimposed and transferred onto the black toner image already transferred to the intermediate transfer body 17.

Further, the magenta charger 11, the magenta laser output unit 3, the magenta photoconductor 15, and the magenta image forming unit 7 are separated by a time delayed by the distance between the cyan photoconductor 14 and the magenta photoconductor 15. A magenta toner image is formed through the same process as the black image forming process, and is transferred onto the black and cyan toner images already transferred to the intermediate transfer body 17.

Finally, a yellow charger 12, a yellow laser output unit 4, a yellow photosensitive member 16, and a yellow image forming unit 8 are used at a time delayed by the distance between the magenta photosensitive member 15 and the yellow photosensitive member 16. Then, a yellow toner image is formed through a process similar to the above-described black image forming process, and is transferred over the black, cyan, and magenta toner images already transferred to the intermediate transfer body 17.

The paper transfer roller 18 sets the paper transfer bias to OF after the toner image passes through the paper transfer roller 18.
F to enter the separated state. The recording medium 20 is the intermediate transfer body 17
The image is picked up from the cassette 21 and transported by the transport roller 19 such that the timing at which the top of the upper image reaches the paper transfer roller 18 and the timing at which the top of the recording medium 20 reaches the paper transfer roller 18 coincide. When the recording medium 20 and the toner image pass between the abutted paper transfer roller 18 and the intermediate transfer body 17, an optimal paper transfer bias is applied to the paper transfer roller 18 as described above. As a result, the toner image held on the intermediate transfer body 17 is transferred onto the recording medium 20.

The four-color composite toner image transferred onto the recording medium 20 is fixed to the recording medium 20 by melting the toner by heat and pressure in a fixing unit 22. After fixing, the sheet is discharged onto a sheet discharge tray 24 by a sheet discharge roller 23.

Through the above steps, a color image is formed.

[0031]

However, according to the above technique, it takes time to measure the resistance value of the paper transfer roller. Further, it takes time to switch the state of contact and separation of the sheet transfer roller with respect to the intermediate transfer member. As a result, there is a problem that the first print time becomes long. When the paper transfer roller is adapted to the environment, the measurement of the resistance value of the paper transfer roller is an unnecessary operation.

Accordingly, it is an object of the present invention to provide an image forming apparatus capable of applying an optimum paper transfer bias without increasing the first print time.

[0033]

To solve this problem, an image forming apparatus according to the present invention comprises a paper transfer roller for transferring a toner image formed on an intermediate transfer member to a recording medium;
Sheet transfer roller contact / separation control means for switching between a contact state in which the sheet transfer roller is in contact with the intermediate transfer member and a separated state in which the sheet transfer roller is separated from the intermediate transfer member; and a resistance of the sheet transfer roller. Paper transfer roller resistance value measuring means for measuring the value, environmental fluctuation detecting means for detecting environmental fluctuation in the image forming apparatus, paper transfer bias output means for applying a bias to the paper transfer roller, and environmental fluctuation in a standby state. When the detecting means detects the environmental change, a measuring means for reading the resistance value by the paper transfer roller resistance value measuring means and measuring a time from the environmental change detection by the environmental change detecting means to the start of printing, and a paper transfer roller resistance value measuring The optimal paper transfer bias is determined by the time from the end of the operation of the paper transfer roller resistance value measuring means measured by the means and the measuring means to the start of printing. It is obtained by a structure having a paper transfer bias determining means for determining by calculation.

This makes it possible to apply an optimum paper transfer bias without prolonging the first print time.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to a first aspect of the present invention, there is provided a sheet transfer roller for transferring a toner image formed on an intermediate transfer member to a recording medium, and the sheet transfer roller abuts on the intermediate transfer member. Paper transfer roller contact / separation control means for switching between a contact state where the paper transfer roller is separated from the intermediate transfer member and a paper transfer roller resistance value for measuring a resistance value of the paper transfer roller Means, environmental fluctuation detecting means for detecting environmental fluctuations in the image forming apparatus, paper transfer bias output means for applying a bias to the paper transfer roller, and when the environmental fluctuation detecting means detects an environmental fluctuation in a standby state, Measuring means for measuring the time from the reading of the resistance value by the paper transfer roller resistance value measuring means and the detection of the environmental change by the environmental fluctuation detecting means to the start of printing; and a paper transfer roller resistance value measuring means. Paper transfer bias determining means for calculating and determining an optimum paper transfer bias based on the time from the end of the operation of the paper transfer roller resistance value measuring means measured by the measuring means to the start of printing. This has the effect that the optimum paper transfer bias can be applied without increasing the first print time.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. Since the basic configuration of the apparatus is substantially the same as that shown in FIG. 3 described above, FIG. 3 will be used in the following description and redundant description will be omitted.

FIG. 1 is a block diagram showing a control system of the image forming apparatus according to one embodiment of the present invention, and FIG. 2 is a flowchart showing the operation of the image forming apparatus shown in FIG.

As shown in FIG. 1, the control system of the image forming apparatus according to the present embodiment includes an intermediate transfer member drive motor control circuit 21 for controlling an intermediate transfer member drive motor 22 for rotating the intermediate transfer member around the periphery, a transport roller. , A recording medium transport motor control circuit 23 that controls a recording medium transport motor 24 that drives the image forming unit (black image forming unit 26, cyan image forming unit 27, and magenta image forming unit 2).
8, image forming unit control circuit 25 for controlling yellow image forming unit 29), pickup device control circuit 30 for controlling pickup device 31, paper transfer roller 3
A sheet transfer roller contact / separation control circuit (sheet transfer roller contact / separation control means) 32 for controlling contact / separation with the intermediate transfer member 3; and an environment fluctuation detection circuit (meaning an environment in the image forming apparatus). Environment fluctuation detecting means) 34, paper transfer roller 3
3, a paper transfer roller resistance value measurement circuit (paper transfer roller resistance value measurement means) 35, a timer circuit (measurement means) 36, a paper transfer bias determination circuit (paper transfer bias determination means) 37, a paper transfer bias The output circuit (paper transfer bias output means) 38 comprises a microprocessor 120 for controlling the operation of the entire apparatus via these blocks.

Here, the environment change detecting means 34 detects whether or not the environment in the image forming apparatus has changed during standby. When the environment change is detected, the microprocessor 120 controls the paper transfer roller. The contact / separation control circuit 32 is activated to bring the sheet transfer roller 33 into contact, and upon receiving the operation, the sheet transfer roller resistance value measuring circuit 35 repeats the operation of measuring the resistance value. The timer circuit 36 measures the time from the end of the resistance value measurement operation of the sheet transfer roller resistance value measurement circuit 35 to the start of printing. The paper transfer bias determination circuit 37 is a part of the paper transfer roller resistance value measurement circuit 3.
5 and the time from the end of the operation of the sheet transfer roller resistance value measurement circuit 35 measured by the timer circuit 36 to the start of printing, an optimum sheet transfer bias is calculated and determined. The paper transfer bias output circuit 38 outputs the obtained optimum paper transfer bias to the paper transfer roller 33.
Is applied.

Next, the operation of the image forming apparatus of the present embodiment having such a configuration will be described with reference to FIG.

In FIG. 2, first, it is checked whether or not there is an environmental change during standby by using, for example, a temperature and humidity sensor (step S50).

If an environmental change is detected in step S50, the paper transfer roller 33 is brought into a contact state in order to measure the resistance value of the paper transfer roller 33 (step S51). Next, the microprocessor 120 sets and outputs a scan start reference voltage for measuring the resistance value of the sheet transfer roller 33 (step S52), and applies a sheet transfer bias supplied from the sheet transfer bias output circuit 38 (step S53). Then, the microprocessor 120 sets the reference voltage for measuring the resistance value of the paper transfer roller 33 to 0 to 5
The process is repeated up to 25 times at intervals of 0.2 V as one step until the output of the sheet transfer roller resistance value measuring circuit 35 changes (steps S54 and S56).

If there is no change in this process, the reference value is changed (step S57), and the process returns to step S54. If there is a change, the reference value is obtained as a resistance value (step S55).

When the measurement is completed, the paper transfer bias is turned off (step S58), the time T from the measurement to the start of printing is initialized (step S59), and the paper transfer roller 33 is brought into a contact state (step S60). ). Then, it is determined whether or not printing has been started (step S61).
If printing is not started, only the time T is counted up and the process waits (step S62). If printing is started, an optimum paper transfer bias is determined based on the time T and the measurement result in step S55 (step S6).
3).

This makes it possible to apply an optimum paper transfer bias without increasing the first print time.

Here, for example, if 20 minutes have passed since the environmental change, the resistance value becomes constant. During that time, the relationship between time and resistance value is determined by previously determining the coefficient a and the constant b by experiments. In other words, it can be estimated by a linear equation of “resistance = −a × time T + b”. After a certain time has elapsed, the resistance value of the sheet transfer roller 33 does not fluctuate, and the environment is adjusted. Therefore, the sheet transfer bias can be determined by the value of the temperature and humidity sensor.

Thereafter, in FIG. 3, black image data is sent and input to the black laser output unit 1. The black laser output unit 1 switches between emitting and extinguishing laser light in accordance with the dot data, emits laser light to the black photoconductor 13 uniformly negatively charged by the black charger 9, and emits laser light on the black photoconductor 13. A latent image is formed due to the potential difference generated by irradiating the laser beam with the laser beam. In the latent image formed on the black photoconductor 13, the toner is attracted to the black photoconductor 13 by a Coulomb force generated by a developing bias which is a specified voltage value applied to the black image forming unit 5, and the toner is developed. Is performed on the black photoconductor 13 to form a toner image. Then, this toner image is transferred to the intermediate transfer body 17.

Next, the cyan charger 10, the cyan laser output unit 2, and the cyan photoconductor 14 are separated by a time delayed by the distance between the black photoconductor 13 and the cyan photoconductor 14.
Then, a cyan toner image is formed through the same process as the black image forming process using the cyan image forming unit 6 and is transferred onto the black toner image already transferred to the intermediate transfer body 17.

Further, the magenta charger 11, the magenta laser output unit 3, the magenta photoconductor 15, and the magenta image forming unit 7 are separated by a time delayed by the distance between the cyan photoconductor 14 and the magenta photoconductor 15. A magenta toner image is formed through a process similar to the black image forming process, and is transferred onto the black and cyan toner images already transferred to the intermediate transfer body 17.

Finally, the yellow charger 12, the yellow laser output unit 4, the yellow photosensitive member 16 and the yellow image forming unit 8 are used with a time delayed by the distance between the magenta photosensitive member 15 and the yellow photosensitive member 16. Then, a yellow toner image is formed through a process similar to the black image forming process, and is transferred over the black, cyan, and magenta toner images already transferred to the intermediate transfer body 17.

The paper transfer roller 18 comes into contact with the toner image on the intermediate transfer body 17 at the timing when the toner image reaches the paper transfer roller 18, and the optimum paper bias obtained in step S63 is applied. Then, after the toner image passes through the paper transfer roller 18, the paper transfer bias becomes O.
It becomes FF and it becomes a separated state. The recording medium 20 is picked up from the cassette 21 so that the timing at which the leading end of the image on the intermediate transfer body 17 reaches the paper transfer roller 18 coincides with the timing at which the leading end of the recording medium 20 reaches the paper transfer roller 18. Transported by
Then, the contacted paper transfer roller 18 and the intermediate transfer body 1
When the recording medium 20 and the toner image pass between the intermediate transfer member 1 and the intermediate transfer member 1, the optimal paper transfer bias is applied to the paper transfer roller 18 as described above.
The toner image held on 7 is transferred onto recording medium 20.

The four-color composite toner image transferred onto the recording medium 20 is fixed on the recording medium 20 by melting the toner by heat and pressure in a fixing unit 22. After the fixing, the sheet is discharged onto a sheet discharge tray 24 by a sheet discharge roller 23.

Through the above steps, a color image is formed.

[0054]

As described above, according to the present invention, it is possible to obtain an effective effect that an optimum paper transfer bias can be applied without increasing the first print time.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a control system of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating an operation of the image forming apparatus of FIG. 1;

FIG. 3 is a schematic view showing a conventional image forming apparatus.

4 is an enlarged schematic view showing the vicinity of a sheet transfer roller in the image forming apparatus of FIG.

5 is a flowchart showing an operation of applying a sheet transfer bias in the image forming apparatus of FIG. 3;

[Explanation of symbols]

32 paper transfer roller contact / separation control circuit (paper transfer roller contact / separation control means) 33 paper transfer roller 34 environmental change detection circuit (environmental change detection means) 35 paper transfer roller resistance value measurement circuit (paper transfer roller resistance value) Measuring means) 36 timer circuit (measuring means) 37 paper transfer bias determining circuit (paper transfer bias determining means) 38 paper transfer bias output circuit (paper transfer bias output means)

Claims (1)

[Claims] A sheet transfer roller for transferring a toner image formed on an intermediate transfer member to a recording medium; a contact state in which the sheet transfer roller is in contact with the intermediate transfer member; Paper transfer roller contact / separation control means for switching between a state of separation from the transfer body, paper transfer roller resistance value measurement means for measuring the resistance value of the paper transfer roller, and environmental change in the image forming apparatus. An environmental change detecting means for detecting, a paper transfer bias output means for applying a bias to the paper transfer roller, and a paper transfer roller resistance value measuring means when the environmental change detecting means detects an environmental change in a standby state. Measuring means for reading the resistance value and measuring the time from the detection of the environmental fluctuation by the environmental fluctuation detecting means to the start of printing; a paper transfer roller resistance value measuring means; Paper transfer bias determining means for calculating and determining an optimum paper transfer bias based on the time from the end of the operation of the paper transfer roller resistance value measuring means measured by the measuring means to the start of printing. Image forming apparatus.