JPH09114271A - Transferring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always obtain a very excellent transferred image, by making transferring means such as a transfer roll surely evaded form the toner soiling, even if a jamming of a transfer material occurs, in a transferring device. SOLUTION: In connection with the transferring device, it is detected that the presence or absence of sharp variation of the impressed bias voltage or current by bias impressing means, in the reaching transfer part estimated time zone (To) of the transfer material. This device is provided with controlling means for controlling, based on the described detecting information, the impressing operation of the bias impressing means in the case of the transferring device equipped with non-contact type transferring means, or for controlling the contact/uncontact operation of transferring means in the case of the transferring device equipped with contact type transferring means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer device applied to an image forming apparatus such as a copying machine or a printer, and in particular, a toner image formed on a toner image carrier such as a photoconductor is electrostatically transferred onto a transfer material. The present invention relates to a transfer device of a type that transfers images selectively.

[0002]

2. Description of the Related Art Conventionally, as a transfer device for electrostatically transferring a toner image formed on a photosensitive drum onto a transfer material such as recording paper by, for example, an electrophotographic system, it is arranged so as to contact the photosensitive drum. In addition, a transfer roll to which a transfer bias is applied is also provided. That is, in this type of transfer device, the transfer roll is a conductive rotating roll, the transfer material is sandwiched between the transfer drum and the photosensitive drum, and a predetermined bias voltage is applied, so that the toner image carried on the photosensitive drum is transferred. It is designed to be electrostatically transferred to a transfer material. Further, the transfer device of the type using such a transfer roll can perform transfer at a lower voltage as compared with the transfer device of the type using the corona discharger arranged in non-contact with the transfer material, Since the transfer material can be reliably held at the transfer portion, good transfer can be performed without transfer deviation, and ozone is very little generated as in the corotron system.

However, the transfer device using the transfer roll is left on the photosensitive drum when the image forming device is stopped due to some abnormality during image formation because the transfer roll is constantly in contact with the photosensitive drum. Toner or a toner pattern formed for controlling toner density is transferred to the transfer roll and contaminates the transfer roll. Moreover, the toner transferred to the transfer roll adheres to the back surface of the transfer material to There is a problem in that the back surface is contaminated or the transfer ability of the transfer roll is deteriorated.

Therefore, in order to solve the problems such as toner contamination of the transfer roll, for example, Japanese Patent Laid-Open No. 5-333.
In Japanese Patent Laid-Open No. 714, a transfer device is proposed in which the transfer roll is separated from the photosensitive drum except in the transfer step, and the surface of the transfer roll is cleaned when the transfer roll is separated.

However, even in this conventional apparatus, when a jam of the transfer material occurs during image formation, the transfer roll comes into contact with the photosensitive drum without the transfer material. It is unavoidable that toner adheres. Further, if a large amount of toner adheres to the transfer roll in this way, it is difficult to remove the toner from the roll surface.

Further, in Japanese Unexamined Patent Publication No. 56-126876, a detection means for detecting the length of the transfer material is provided, and the transfer roll is brought into contact with the photosensitive drum at a predetermined timing set according to the detection information. Transfer devices for separating them have been proposed.

However, even in this conventional device,
If a jam of the transfer material occurs during image formation, the jam cannot be detected and the transfer roll cannot be separated from the photosensitive drum depending on the position where the detection means is installed, as described in detail below. The toner adheres to the transfer roll as in the conventional device described above.

That is, as shown in FIG. 15a, the detecting means 100 is arranged immediately after the registration roll 104 for supplying the transfer material 101 to the transfer portion between the photosensitive drum 102 and the transfer roll 103 at a predetermined timing. In this case, if a jam occurs on the transfer material 101 after passing through the registration roll 104, the transfer roll 103 also comes into contact with the photosensitive drum 102 while the detection unit 100 recognizes that “the transfer material exists”. Because there is
As a result, the toner image on the photosensitive drum 102 directly adheres to the transfer roll 103.

Further, as shown in FIG. 15b, the detecting means 1
Even when 00 is arranged immediately before the registration roll 104, if a jam occurs on the transfer material 101 before passing through the registration roll 104, the detection means 100 recognizes that “the transfer material is present” and transfers the transfer roll. Since 103 is also in contact with the photosensitive drum 102, as a result, similar to the above case, the transfer roll 103
The toner image on the photosensitive drum 102 is directly attached to the.

[0010]

As described above, in the transfer device of the type in which the presence or absence of the transfer material is detected before the transfer material is supplied to the transfer portion and the transfer drum is brought into contact with or separated from the photosensitive drum, The roll cannot be reliably avoided from toner stains. In addition, such a problem of toner contamination is also caused in a transfer device provided with a non-contact type transfer means such as a corotron system, in which the transfer material is transferred to the transfer portion between the photosensitive drum and the non-contact type transfer means as planned. It also occurred when it was not supplied.

Therefore, the present invention has been made in view of the above-mentioned problems of the prior art. Even when a jam of the transfer material occurs, the transfer means such as a transfer roll can be surely avoided from toner contamination. It is an object of the present invention to provide a transfer device that can always obtain a transferred image of high quality.

[0012]

In order to achieve the above-mentioned object, a transfer device of the invention according to claim 1 is a non-contact type transfer means which is arranged at a transfer portion of a toner image carrier at a distance. ,
A transfer device that includes a bias applying unit that applies a transfer bias to the transfer unit, and electrostatically transfers the toner image to a transfer material that is supplied to a transfer unit between the toner image carrier and the non-contact transfer unit. In the above, the presence or absence of a sharp change in the voltage or current of the bias applied by the bias applying means in the scheduled transfer area arrival time band of the transfer material above the set threshold value is detected, and the applying operation of the bias applying means is performed based on the detected information. It is characterized by comprising a control means for controlling the.

The transfer device of the invention according to claim 2 is
Between the toner image carrier and the contact-type transfer means, the contact-type transfer means is disposed so as to be able to come into contact with and separate from the transfer part of the toner image-bearing body, and the bias applying means for applying a transfer bias to the transfer means. In a transfer device for electrostatically transferring a toner image onto a transfer material supplied to a transfer part of the transfer material, the voltage or current of the bias applied by the bias applying means in the scheduled time band of the transfer material exceeding the set threshold value is exceeded. The present invention is characterized by including a control means for detecting the presence or absence of a sharp change and controlling the contact / separation operation of the transfer means based on the detected information.

In each of the above technical means, the control means is
Leveling detection time to detect the level of applied bias at the time of detection, and fluctuation detection to detect the presence or absence of abrupt fluctuations of the applied bias voltage or current exceeding the set threshold based on the bias level detected at that leveling detection time. Time is set, and the leveling detection time is ended before the transfer section of the transfer material is expected to reach the transfer section, and the fluctuation detection time is started before the transfer section of the transfer material is scheduled to arrive. In addition, it is desirable to set it so that it ends at a time later than the scheduled time.

Further, in each of the above-mentioned technical means, the estimated time for the transfer material to reach the transfer portion in the control means is to start the supply operation of the transfer material supply operation control means for supplying the transfer material to the transfer portion at a predetermined timing. It is desirable that the time is set as a time required for the transfer material to be supplied from the transfer material supply operation control means to the transfer portion and arrive at the transfer portion on the basis of time.

Further, in the technical means including the above-mentioned contact type transfer means, the control means makes the contact type transfer means contact the toner image carrier before the transfer material reaches the transfer portion, and applies the toner image carrier. Control is performed to continue the contact operation of the transfer means when a sharp change in the bias voltage or current is detected, and to release the contact operation of the transfer means when the change is not detected. Is desirable.

[0017]

1 to 4 show a typical example of an embodiment of a transfer device according to the present invention, and FIG. 1 is a conceptual diagram showing an example of the transfer device according to claim 1, and FIGS. FIG. 6 is a conceptual diagram showing an example of a transfer device according to claim 2. Figures 1 to 4
In FIG. 1, reference numeral 1 is a toner image carrier, 2 is non-contact type transfer means, 3 is contact type transfer means, 4 is bias applying means for transfer, 5 is transfer material, 6 is transfer material supply operation control means, and 7 is Displacement means for displacing the contact-type transfer means 3 so as to bring it into contact with or away from the toner image carrier 1, 8 is control means including the bias applying means 4 and a voltage or current detection device, and 9 is development. Shows the device.

First, in the transfer device shown in FIG. 1, a non-contact type transfer means 2 such as a corotron arranged at a predetermined distance from the toner image carrier 1, and a transfer bias to the transfer means 2. Bias applying means 4 for applying a voltage, and control means 8
The main portion of the toner image is formed on the image carrier 1 by a conventionally known image forming process using the developing device 9 and the like, from the transfer material supply operation control means 6 to the conveying path 55. The toner is transferred to the transfer material 5 supplied toward the transfer portion between the toner image carrier 1 and the transfer unit 2. Further, in this transfer device, the bias applying operation of the bias applying means 4 to the non-contact type transfer means 2 is controlled by the control means 8.

The transfer device shown in FIGS. 2 to 4 is a contact type transfer means 3 which is arranged so as to be able to come into contact with and separate from the toner image carrier 1, and a bias which applies a transfer bias to the transfer means 3. The main part is composed of the application means 4, the displacement means 7 for displacing the transfer means 3 with respect to the toner image carrier 1 in the direction of the double arrow in the figure, and the control means 8. The toner image formed on the image carrier 1 is transferred to a transfer material 5 which is supplied toward a transfer portion between the toner image carrier 1 and the transfer unit 3. In this transfer device, the contacting / separating operation of the contact type transfer means 3 is controlled by the control means 8. As the contact type transfer unit 3, a brush type transfer unit (FIG. 2) or a surface contact type transfer unit (FIG. 3) can be applied in addition to the rotary roll type transfer unit (FIG. 1).

The transfer material supply operation control means 6 is, for example, as shown in FIGS.
a supplies the transfer material 5 or turns off the supply by the ON / OFF operation of the electromagnetic clutch 6b. The displacing means 7 includes, for example, a supporting arm 7c pivotally supported by a fulcrum 7a and one end of which is attached to a solenoid 7b as shown in FIGS.
By the ON / OFF operation of b, the transfer means 3 attached to the other end of the support arm 7c is displaced in the direction of the double arrow in the figure. In the figure, 7d indicates a spring member. The toner image carrier 1 may be any one that carries a toner image before transfer, and may be an intermediate transfer member or the like in addition to a photosensitive drum or a belt on which a toner image is directly formed.

Then, the control means 8 in each of the transfer devices executes the transfer process when the transfer material 5 is actually supplied to the transfer portion, but the transfer material 5 is transferred to the transfer portion (due to a cause such as a jam). The control is performed so that the transfer process is not executed when the voltage is not actually supplied. Specifically, the voltage or the current of the bias applied by the bias applying unit 4 in the scheduled transfer zone arrival time band of the transfer material 5 is set. The presence or absence of a sharp change is detected, and the application operation of the bias applying means 4 or the contact / separation operation of the contact type transfer means 3 is controlled based on the detection information. Note that the abrupt change means a change that exceeds a set threshold value, which will be described later.

In fact, when there is a sharp change in the voltage or current of the applied bias, it is judged that the transfer material 5 has been supplied to the transfer portion, and the applying operation of the bias applying means 4 is executed (or continued). Or the contact-type transfer means 3 is controlled to execute (or continue) the contact / separation operation. On the contrary, when there is no abrupt change in the voltage or current of the applied bias, the transfer material 5 is transferred to the transfer portion. Is not being supplied to
The bias application means 4 is controlled so that the application operation is not executed (stopped) or the contact operation of the contact type transfer means 3 is not executed (released).

As a result, even if an abnormal situation occurs in which the transfer material 5 is not actually supplied to the transfer portion due to a jam or the like, the non-contact transfer means 2 stops applying the bias, and the contact transfer means. In 3, the contact operation of the transfer means to the toner image carrier 1 is released, so that the toner on the toner image carrier 11 electrostatically adheres to the transfer means 2 or the transfer means 3 and is contaminated. Can be avoided.

Here, the transfer material 5 is actually transferred to the transfer portion by detecting whether or not the voltage or current of the bias applied by the bias applying means 4 changes abruptly in the transfer material arrival time band of the transfer material. The point that can be discriminated as to whether or not it has been supplied to is explained.

FIG. 5 shows the output characteristics of the voltage of the applied bias when the transfer process for two sheets is executed. That is, as shown in FIG. 6, the output characteristics were controlled by a roll-shaped transfer means (transfer roll) 3a as the contact-type transfer means 3 and a constant current control (set to 20 μA in this example) as the bias application means 4. Transfer rolls 3 in a state of being in contact with the toner image carrier 1 by using respective high voltage power supplies
The transfer process is executed by applying a transfer bias from the high-voltage power source 4 to a and supplying the two transfer materials 5 to the transfer section. The output at this time is measured by the voltage measuring device 8a and the result is measured. It is recorded (specifically, input to the pen recorder via a high-voltage probe). However, the voltage waveform shown in FIG. 5 is displayed as an average value in which a noise component is added.

From the result of FIG. 5, from the start of measurement S to T ₁
The voltage waveforms during the time period of ₂ seconds, the time period of T ₃ seconds, and the time period of T ₄ seconds were all about 3.1 kV, but the voltage waveforms in the two time periods of T ₂ seconds were all about It can be seen that the voltage remained at 3.4 kV. As each time period described above is clear from the contents shown in FIG. 6, the time required times of T ₁ seconds until the transfer material 5 is fed the distance L1 to the transfer portion T L ₁ / V (V Is the transfer speed of the transfer material 5)
The time period of T ₃ seconds is from immediately after the transfer material 5 on one surface passes through the transfer portion T until the second transfer material 5 that is transported at the interval L ₃ is transported to the transfer portion T. Required time L ₃ /
The time period of T ₄ seconds corresponds to V, and the time required for the second transfer material 5 to pass through the transfer portion T and be discharged by a predetermined distance L ₄ is L ₄ / V. On the other hand, both of the two time periods of T ₂ seconds correspond to the required time L ₂ / V for the transfer material 5 having the length L _{2 in} the transport direction to enter the transfer portion T and pass therethrough.

From the above, the applied bias voltage changes substantially constant in the time band in which the transfer material 5 does not exist in the transfer portion T (that is, the time bands of T ₁ , T ₃ , and T ₄ ). In the time zone in which 5 exists in the transfer portion T (that is, in the time zone of T ₂ ), the applied bias voltage changes abruptly unlike the other time zones. As a result, the transfer material 5 is transferred to the transfer portion T.
It is understood that whether or not the voltage is actually supplied can be determined by detecting whether or not there is a sharp change in the voltage of the bias applied by the bias applying unit 4 in the transfer portion arrival time band of the transfer material. Also, the bias applying means 4
When a similar measurement was performed using a high voltage power source controlled as a constant voltage, it was confirmed that the output waveform of the current changes in the same manner as the above depending on whether the transfer material 5 exists in the transfer portion T or not. Was done.

Therefore, the control unit 8 detects whether or not there is a sharp change in the voltage or current of the bias applied by the bias applying unit 4 in the transfer member arrival time band of the transfer material,
Based on the detection result, control to determine execution or non-execution of the transfer process may be performed as described above.

In the above detection, since the level of the applied bias at the time of detection varies depending on the type of the transfer material 5 and the environmental conditions, the level of the applied bias at the time of detection is higher from the viewpoint of more accurate detection. It is advisable to provide a leveling detection time for detecting and a fluctuation detection time for detecting the presence or absence of a sharp fluctuation in the voltage or current of the applied bias based on the bias level detected at the leveling detection time.

Further, although the scheduled time for the transfer material 5 to reach the transfer portion can be appropriately set, the operation start signal (registration signal) of the transfer material supply operation control means 6 is used as a reference from the viewpoint that it can be set more easily and accurately. It is recommended to delay the setting. That is, the scheduled transfer unit arrival time actually arrives after the transfer material 5 is supplied from the transfer material supply operation control unit to the transfer unit T with reference to the supply operation start time of the transfer material supply operation control unit 6. It is recommended to set the required time until.

[0031]

EXAMPLES The present invention will be described in more detail with reference to specific examples.

FIG. 7 shows an example of an image forming apparatus to which a transfer device having the contact type transfer means of the present invention is applied. In the figure, reference numeral 10 is a photosensitive drum as a toner carrier that rotates in the direction of the arrow, 11 is a charging device, 12 is a semiconductor laser, 13 is a polygon mirror, 14a and 14b are scanning lenses, 15 is a developing device, and 16 is a peeling device. A charger, 17 is a cleaning device, 30 is a transfer roll as a contact type transfer means, 40 is a bias power supply device as a bias applying means, 50 is a recording paper as a transfer material, 51 is a paper tray, 60 is a paper transport mechanism, Reference numeral 61 is a paper discharging mechanism, 70 is a solenoid mechanism for displacing the transfer roll 30 to and from the photosensitive drum 10, and 90 is a fixing device.

This image forming apparatus operates as follows.

That is, the photosensitive drum 10 is the charging device 11
Are uniformly charged by the laser beam, and an electrostatic latent image is formed on the charged surface by scanning the light beam from the semiconductor laser 12 modulated by the image signal through the polygon mirror 13 and the scanning system lenses 14a and 14b. After that, the electrostatic latent image is developed by the developing device 15 to form a toner image. According to this image forming cycle, the recording paper 50
Are taken out one by one from the paper tray 51 and are conveyed to the registration roll 62 through the paper conveyance mechanism 60. The roll 62 causes the photosensitive drum 10 and the transfer roll 3 to be rotated at a predetermined timing with respect to the rotation of the photosensitive drum 10.
It is supplied to 0 (transfer portion).

In the transfer process, a bias potential having a polarity opposite to the toner polarity of the toner image carried on the photosensitive drum 10 is applied to the transfer roll 30 from the bias power source device 40, and the solenoid mechanism 70 is used to apply the bias potential to the photosensitive drum 10.
To abut. The toner image formed on the photosensitive drum 10 is transferred by being electrostatically attracted to the recording paper 50 supplied to the transfer portion between the transfer roll 30 and the photosensitive drum 10. The recording paper 50 to which the toner image is transferred is separated from the photosensitive drum 10 by the electric field applied by the separation charger 16, and then the paper discharge mechanism 6 is used.
The toner image is fixed by passing through 1 to the fixing device 90 where it is heated / pressurized. On the other hand, after the transfer, the photosensitive drum 10 is uniformly charged by the charging device 11 for the next image forming cycle after the residual toner is removed by the cleaning device 17.

The image forming apparatus for performing such transfer is equipped with a control system as shown in FIG.

This control system comprises a main control section 80 which controls the entire image forming apparatus and a sub control section 81 which mainly controls the transfer apparatus. In FIG. 8, reference numeral 71 is a drive device that drives the solenoid mechanism 70, 40 is a bias power supply device that applies a transfer bias to the transfer roll 30, and 41 is a voltage detection device that detects the output voltage of the bias applied by the bias power supply device 40. , 62a are drive devices including a registration electromagnetic clutch for driving the registration rolls 62, and 10a is a drive device for driving the photosensitive drum 10. Then, each of these devices 71, 4
0, 41, 62a, 10a are the sub control unit 81 and the main control unit 8
0, and the sub control unit 81 and the main control unit 80 are also connected to each other, so that desired signals can be exchanged (output / input) with each other. In this example, the sub control unit 81 functions as the control means 8 in the present invention.

Further, the bias power supply device 40 and the voltage detection device 41 are constructed in detail as shown in FIG. That is, the bias power supply device 40 is used for the transfer roll 3
A constant voltage controlled high voltage power supply circuit 42 for transfer bias for outputting a transfer bias, and a cleaning bias for cleaning the surface of the transfer roll 30 (having a polarity opposite to that of the transfer bias) are output. Cleaning bias high-voltage power supply circuit 43, and both of the high-voltage power supply circuits 42 and 43 are controlled by the control signal S ₁ or S ₂ from the sub-control unit 81. Further, the voltage detection device 41 uses the voltage output from the high voltage power supply circuit 42 for transfer bias as resistances R ₁ and R _2.
And the divided signal is amplified by the amplifier circuit 44 and then input to the A / D conversion circuit 45 to be an 8-bit DATA signal, and the DATA signal is also sent to the sub-control unit 81 as the detection signal S _3. It is designed to be entered. Moreover, the voltage detection device 41 is controlled by the control signal S ₄ from the sub control unit 81.

Further, in this embodiment, as described in detail below, the presence or absence of voltage fluctuation of the applied bias is detected in the sub-control unit 81 by providing a leveling detection time and a fluctuation detection time. There is.

First, the voltage characteristic actually obtained by measuring the voltage of the transfer bias output from the bias power supply device 40 by the voltage detection device 41 has a voltage waveform as shown in FIG. That is, this voltage waveform is
In addition to changing depending on whether 0 is present in the transfer portion, it also changes depending on the noise component. This noise component is generally generated due to resistance unevenness in the rotation direction of the transfer roll 30, a change in the contact state between the transfer roll 30 and the photosensitive drum 10, and the like. Therefore, in detecting the fluctuation of the output voltage of the transfer bias, it is necessary to first detect the bias voltage level for detection in consideration of the noise margin β.

Therefore, in this example, prior to detecting a sharp voltage change, the bias voltage at each detection is digitally sampled a predetermined number of times to detect the bias level (characteristic). This is the leveling detection time. Then, the maximum value (M) and the minimum value (N) of the voltage information obtained by sampling at that time are stored in memory, and at the same time as the end of the leveling detection time, the difference between the maximum value (M) and the minimum value (N) stored in memory is stored. ΔA (= M−N) is calculated, and a value obtained by adding a half value of this difference ΔA (that is, this is regarded as noise margin β) to the maximum value (M) is
A so-called "threshold" was used as a criterion for determining the presence or absence of a sharp change (that is, the change detection time). That is,
This threshold is represented by “M + ΔA / 2”. Then, at the fluctuation detection time, when the measured bias voltage level exceeds this threshold value, it is set so as to be judged as "there is a sharp fluctuation". Incidentally, in this example, since the maximum value (M) = 3.2 kV and the minimum value (N) = 3.0 kV, the threshold value was set to 3.3 kV.

In addition, the leveling detection time (RE) and
The motion detection time (HE) is as shown in FIG.
Of the recording paper 50, which is the transfer material, to reach the transfer portion
Time T ₀Based on, the leveling detection time (R
E) is the estimated transfer time T₀Ends earlier
And one fluctuation detection time (HE) reaches the transfer part.
Scheduled time T₀Start earlier and the scheduled time
T₀It was set to end at a later time. Follow
Then, the sub-control unit 81 detects whether there is a bias voltage fluctuation.
Estimated time is T₀Before and after
(ST) will be performed.

The control system as described above is as shown in FIG.
It operates according to various control sequences.
FIG. 11 shows the transfer application voltage obtained by the voltage detection device 41.
The voltage characteristics (voltage waveform) of Iias are also shown. Also,
In FIG. 11, time t₁Registration low
ON signal (S₇) Is input (RS)
The leveling detection time (RE) is started with a delay from
Until the end, or via a cleaning via
Switch OFF operation and transfer bias ON operation are performed.
Time. Similarly time t_TwoIs when the above ON signal is input
The leveling detection time (RE) ends from the point (RS)
Until the sudden change detection time (HE) starts
Time. Similarly time t_ThreeIs when the above ON signal is input
The steep fluctuation detection time (HE) ends from the point (RS)
Until the time. Similarly time t _FourIs the ON signal
From the time of input until the recording paper 50 reaches the transfer section
This is a required time, and in this embodiment, this time t_FourRecording paper 5
Scheduled arrival time T of 0₀Is set to Also time
Interval t_FiveThe recording paper 50 passes after it reaches the transfer section.
It is the time required to finish. Furthermore, time t₆Is the time
Interval t_ThreeAnd t_FourIt is the time difference of the recording sheet 50 reaches the transfer section.
Until the abrupt change detection time (HE) ends.
It corresponds to the time required in. Abrupt change detection time (HE)
Is preferably this time t₆End before. In particular, this
Time t₆Is an image generated at the leading edge of the recording paper 50.
It also corresponds to the transit time of the image area (non-image area).
You. The length of the image loss part in the transport direction is usually about 5 mm.
However, if this length is as short as possible, the transfer roll
-You don't have to be dirty.

FIG. 12 shows the above times t ₁ , t ₂ , t ₃ , t _4.
(= T ₀ ) and t ₆ are shown in association with the conveyance state of the recording paper 50 from the registration roll 62 to the transfer unit (transfer roll 30). That is, the recording paper 50 is shown as (a), (b),
It is proceeding in the order of (b). Although the time t ₅ cannot be illustrated, t ₅ = L ₂ / V from the conditions described in the figure (the length of the recording sheet 50 in the carrying direction is L ₂ and the carrying speed is V). I understand.

Next, the operation of the image forming apparatus (mainly the transfer apparatus) controlled according to such a control sequence will be described with reference to the flow charts shown in FIGS.

First, when a start command for the image forming process is issued, the sub controller 81 turns on the drive unit 10a.
The signal S ₅ is sent and the photosensitive drum 10 is driven by the motor (step S1). At the same time (after the solid image for detection is formed on the photosensitive drum when the image is formed for process control), an ON signal S ₆ is sent from the sub control unit 81 to the drive unit 71, and the solenoid mechanism 70 is sent. Is activated,
As a result, the transfer roll 30 contacts the photosensitive drum 10 (step S2). At the same time, the sub control unit 8
An ON signal S ₂ is sent from 1 to the cleaning bias high-voltage power supply circuit 43 of the bias power supply device 40, and a cleaning bias (negative electrode in this example) is applied to the transfer roll 30 (step S3). Cycle start cleaning is performed.

When the main controller 80 issues an ON signal S ₇ to the drive unit 62a at a timing set corresponding to the image forming cycle on the photosensitive drum 10, the registration roll (registration roll) 62 is rotated. The recording paper 50 starts to be supplied to the transfer portion by the operation, while the registration signal S ₇ is input to the sub control portion 81.

Then, the sub control unit 81 determines whether or not a predetermined time (t ₁ described above) has elapsed with reference to the registration signal S ₇ (step S 4), and the time t ₁
When the above condition has passed, the application of the cleaning bias is stopped (step S5) and the sub-control unit 8
The ON signal S ₁ is sent from 1 to the transfer bias high-voltage power supply circuit 42 of the bias power supply device 40, and the transfer bias is applied to the transfer roll 30 (step S6). Moreover,
When this time t ₁ has elapsed, the leveling detection time (RE) is reached, and the ON signal S ₄ is sent from the sub control unit 81 to the voltage detection device 41 to start the voltage detection of the transfer bias (step S7). ).

When the time t ₁ has elapsed in step S6, a transfer bias is applied to the transfer roll 30 which is in the middle of cleaning, whereby the reversely charged toner which could not be removed by the negative cleaning bias is transferred to the positive electrode. A cleaning effect that can be removed by the transfer bias is obtained.

The voltage information detected by the voltage detection device 41 is A / D converted and then input to the sub control unit 81 as the DATA signal S ₃ , and the sub control unit 81 outputs the maximum value (M) and the minimum value (M). N) is stored (step S)
8, S9). In this leveling detection, it is determined whether or not a predetermined time (t ₂ described above) has elapsed from the input time (RS) of the registration signal S ₇ (step S10).
When the time t ₂ has elapsed, the OF from the sub control unit 81
The process is ended by the F signal S ₄ (step S11).

When the time t ₂ has elapsed in step S10, the sub-control unit 81 reaches the fluctuation detection time (HE) and the voltage detection device 41 detects the voltage of the transfer bias (step S12), and the voltage information is the DATA signal. It is input to the sub control unit 81 as S ₃ . At this variation detection time, whether or not the detected bias voltage BV exceeds the threshold value based on the threshold value [M + (M−N) / 2)] calculated and set in the sub control unit 81 immediately after the end of the leveling detection. Is determined (step S13).

Here, for example, when the recording paper 50, which should be supplied from the registration roll 62 to the transfer portion, jams (paper jam) during the conveyance and has not actually reached the transfer portion, At the fluctuation detection time, the bias voltage BV does not exceed the threshold value, and during that time, the registration signal S ₇
It is determined whether or not a predetermined time (t ₃ described above) has elapsed from the point of input of (step S14). In other words, this fluctuation detection is performed until at least the scheduled transfer unit arrival time T _{0 of the} recording paper has elapsed.

When this time t ₃ has elapsed, it is determined that the recording paper 50 has not arrived at the transfer portion as scheduled, and the sub control portion 81 sends the bias power source device 40 to the OF state.
At the same time when the F signal S ₁ is sent and the bias application to the transfer roll 30 is stopped (step S15), the sub controller 8
The OFF signal S ₆ is sent from 1 to the driving device 71, and the transfer mechanism 30 separates the transfer roll 30 from the photosensitive drum 10 by the solenoid mechanism 70 (step S16). At the same time, the photosensitive drum 10 also stops its rotation by the OFF signal S ₅ from the sub control unit 81 to the driving device 10a (step S1).
7). As a result, the transfer process is not executed and the transfer roll is separated from the photosensitive drum, so that the toner on the photosensitive drum does not transfer to and adhere to the transfer roll. Further, in this case, since the information after the time t ₃ has passed is sent from the sub control unit 81 to the main control unit 80 as a paper jam error signal, the main control unit 80 causes “paper jam” on the display unit of the apparatus. It is displayed (step S18).

On the other hand, when the recording paper 50 is normally supplied to the transfer portion, the bias voltage BV exceeds the threshold value at the fluctuation detection time of step S13, and the information is sent to the sub control portion 81. In this case, the recording paper 5
It is determined that 0 has reached the transfer portion as scheduled, and the normal transfer process is executed.

That is, the timer for controlling the operation of the transfer process is started in the sub control unit 81 (step S19), and the time (nipped) until the recording sheet 50 passes through the transfer unit (the above-mentioned t _It is determined whether or not ₅ ) has passed (step S20). When this time t ₅ has elapsed, it is considered that the recording sheet 50 has passed through the transfer section, and the sub-control section 81 sends an OFF signal S ₁ to the bias power supply device 40.
Is sent to stop the application of the transfer bias to the transfer roll 30 (step S21), and at the same time, the cleaning bias is applied from the bias power supply device 40 to the transfer roll 30 (step S22). As a result, inter-image cleaning is performed on the transfer roll 30 (the cycle end cleaning is performed when the final transfer process is completed).

Then, it is judged whether or not the time required from the end of the transfer process to the next transfer process elapses (step S23), and at the time when this time elapses, the cleaning for the transfer roll 30 is performed. At the same time that the bias application is stopped (step S24), it is judged whether or not the set number of image formations is completed (step S2).
5). If the set number of sheets has not been completed in step S25, the process from step 6 onward is repeated again to execute the next transfer step. On the other hand, when the set number of sheets is completed, the transfer mechanism 30 separates the transfer roll 30 from the photosensitive drum 10 by the solenoid mechanism 70 (step S26), the rotation of the photosensitive drum 10 is stopped (step S27), and the image forming process is completed. .

In this embodiment, the sampling frequency (digital processing method) of the leveling detection time is set to the time t ₆ (recording paper 5 shown in FIG. 11 and FIG. 12).
The frequency is set so that the sampling is performed a plurality of times during the passage time of the image loss portion occurring at the leading edge of 0). This is because the bias voltage level may not be detected in one sampling at time t ₆ . In this example, the frequency is set so that sampling is performed 10 times at time t ₆ . That is,
When the process speed is 250 mm / s, t ₆ is 20
Therefore, the sampling frequency is 20/10 = 2 and 1 / 0.002 = 500 (Hz).

[0058]

As described above, according to the transfer device of the present invention, it is possible to detect the presence or absence of a sharp change in the voltage or current of the bias applied to the transfer means in the scheduled time band in which the transfer material reaches the transfer portion. By detecting the presence (presence) of the transfer material in real time by doing so, even when the transfer material is jammed before the transfer material is supplied to the transfer portion, the transfer material is transferred to the transfer unit. By stopping the bias application or separating the transfer means from the toner image carrier, the transfer means can be surely avoided from toner contamination. As a result, it is possible to always obtain a high quality transferred image.

Further, according to the present invention, it is not necessary to install a paper detection sensor or the like, or to secure a space for the installation, which does not lead to unnecessary cost increase, and the apparatus There is no need for complications such as layout changes. Further, according to the present invention, unlike the case where the paper detection sensor is provided, it is not necessary to delay the original transfer process to execute the control operation of the transfer device based on the detection information of the sensor. The transfer means is not contaminated by a jam of the transfer material or the like that occurs during the delay time period.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an example of an embodiment of a transfer device of the invention according to claim 1.

FIG. 2 is a conceptual diagram showing an example of an embodiment of a transfer device of the invention according to claim 2;

FIG. 3 is a conceptual diagram showing another example of the embodiment of the transfer device of the invention according to claim 2;

FIG. 4 is a conceptual diagram showing another example of the embodiment of the transfer device of the invention according to claim 2;

FIG. 5 is a voltage characteristic diagram of a transfer bias before and after a transfer process.

FIG. 6 is an explanatory diagram for explaining the measurement content of the voltage characteristics of FIG.

FIG. 7 is a conceptual diagram of a main part showing an image forming apparatus (one embodiment) to which a transfer device of the present invention including a contact type transfer means is applied.

FIG. 8 is a block diagram showing a control system of the embodiment apparatus.

FIG. 9 is a circuit diagram showing a detailed configuration of a bias voltage device and a voltage detection device of the embodiment device.

FIG. 10 is a voltage characteristic diagram for explaining the principle of voltage fluctuation detection of the transfer bias.

FIG. 11 is a timing chart showing the sequence of the control system of the embodiment apparatus.

FIG. 12 is an explanatory diagram showing various set times related to the control system of the embodiment apparatus in association with a transfer material conveyance progress state.

13 is a part of a flowchart for explaining the sequence of FIG.

FIG. 14 is the remaining part (continuation of FIG. 13) of the flowchart for explaining the sequence of FIG. 11;

FIG. 15 is an explanatory diagram for explaining a problem in a conventional transfer device.

[Explanation of symbols]

1, 10 ... Toner image carrier, 2 ... Non-contact type transfer means,
3, 30 ... Contact transfer means, 4, 40 ... Bias applying means, 5, 50 ... Transfer material, 6, 62 ... Transfer material supply operation control means, 8, 81 ... Control means, T ₀ ... Scheduled arrival time of transfer portion , RE ... Leveling detection time, HE ... Fluctuation detection time. Body part, 21a ... Top surface of main body part, 30 ... Transfer material holding member pasting part, 33 ... Lower surface part, 34 ... Top surface part, 40 ... Elastic member.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhisa Mashiko 2274 Hongo, Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd. (72) Inventor Toshihiro Kanematsu 2274 Hongo, Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd.

Claims (5)

[Claims] 1. A non-contact type transfer means provided separately from a transfer portion of the toner image carrier and a bias applying means for applying a transfer bias to the transfer means, and the non-contact type transfer means is provided. In a transfer device for electrostatically transferring a toner image onto a transfer material supplied to a transfer part between contact type transfer means, a voltage or a current of a bias applied by a bias applying means in a time band at which the transfer material is expected to reach the transfer part. 2. A transfer device comprising: a control unit that detects the presence or absence of a sharp change exceeding a set threshold value and controls the application operation of the bias applying unit based on the detection information. 2. A contact-type transfer means disposed so as to be capable of coming into contact with and separated from a transfer portion of the toner image carrier, and a bias applying means for applying a transfer bias to the transfer means, and contacting the toner image carrier. In a transfer device for electrostatically transferring a toner image onto a transfer material supplied to a transfer section between the transfer units, a bias voltage or current of a bias applied by the bias applying unit in the transfer member scheduled transfer time band is transferred. A transfer device comprising: a control unit that detects the presence or absence of a sharp change exceeding a set threshold value and controls the contact / separation operation of the transfer unit based on the detection information. 3. The apparatus according to claim 1, wherein the control means detects the level of the applied bias at the time of detection, and the level of the applied bias based on the bias level detected at the leveling detection time. A fluctuation detection time for detecting the presence or absence of a sharp fluctuation in voltage or current exceeding a set threshold value is provided, and the leveling detection time is ended at a time point before the scheduled arrival time of the transfer material in the transfer portion. A transfer apparatus, wherein the fluctuation detection time is set to start at a time point before the scheduled time for the transfer material to reach the transfer portion and to end at a time point after the scheduled time. 4. The apparatus according to claim 1 or 2, wherein the scheduled time for the transfer material to reach the transfer portion in the control means is determined by the transfer material supply operation control means for supplying the transfer material to the transfer portion at a predetermined timing. A transfer device, wherein the time required for the transfer material to be supplied from the transfer material supply operation control means to the transfer portion and to reach it is set based on the supply operation start time. 5. The apparatus according to claim 2, wherein the control means brings the contact type transfer means into contact with the toner image carrier before the transfer material reaches the transfer portion, and applies the voltage or current of the applied bias. The transfer device is characterized in that the contact operation of the transfer means is continued when a sudden change is detected, and the contact operation of the transfer means is released when the change is not detected. .