JP2002244367A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably form a high-quality image by preventing the change of a transfer image caused by the change of a feeding state at the time of transfer. SOLUTION: The ambient temperature of a transfer means 5 feeding recording paper P functioning as a recording carrier while pressing the paper P to the outer peripheral surface of a photoreceptor drum 1 carrying the image is detected by a temperature sensor 52 and given to a control part 7. The control part 7 obtains the change of the outside diameter of the transfer means 5 and the change of the feeding state of the paper P caused by the change of the outside diameter from the detected result by the sensor 52, and controls to negate the change of the transfer image caused by the change of the feeding state with the transfer means 5 or an exposure means 3 as a controlled object based on the obtained result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copier, a printer, a facsimile apparatus, and more particularly, to an image forming apparatus such as an electrophotographic image forming apparatus. To an image forming apparatus configured to transfer an image onto a recording carrier such as a recording paper contacting the surface to form an image.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, a charging section, an exposure section, a development section, a transfer section and a cleaning section are arranged side by side around an outer surface of an image carrier such as a photosensitive drum or a photosensitive belt. Forming an electrostatic latent image on the outer surface of the image carrier uniformly charged by the action of the charging unit by exposure at the exposure unit;
After the electrostatic latent image is visualized by toner adhesion at the developing unit to form a toner image (supported image), the formed toner image is placed on a recording paper (recording carrier) that is brought into contact with the transfer unit. The recording paper is transferred to a fixing unit, and the transferred toner image is fixed to form an image. The outer surface of the image carrier after the transfer is cleaned in a cleaning unit, charged in the charging unit, and reused.

In the transfer section of such an image forming apparatus, as disclosed in Japanese Patent Application Laid-Open No. 9-90785 in recent years, transfer means such as a transfer roller and a transfer belt which are in rolling contact with the outer surface of an image carrier. A recording paper as a record carrier conveyed to a transfer section along an appropriate conveyance path is received and clamped between the outer surface of the image carrier and the transfer means,
A contact transfer technique has been put to practical use in which an image is transferred to the recording paper by bringing the image carrier into contact with the outer surface of the image carrier while applying a predetermined feed by the operation of the transfer means.

In an image forming apparatus employing such a contact transfer technique, an image is transferred onto a recording sheet as a record carrier by a transfer means such as a transfer roller or a transfer belt.
This is performed in a state of being pressed against the outer surface of the image carrier, and during this time, the feeding of the recording paper is reliably performed by the operation of the transfer unit. The image can be transferred satisfactorily and with high accuracy, and high image quality can be obtained.

[0005]

However, in the image forming apparatus as described above, the quality of an image transferred to a recording sheet as a record carrier depends on the feeding state applied to the recording sheet by the transfer means. Specifically, the transfer image on the recording paper expands and contracts in the feed direction due to the presence or absence of coincidence between the feed speed of the recording paper and the peripheral speed of the image carrier that carries the transferred image. However, there is a problem that desired image quality cannot be obtained.

Conventionally, in order to solve this problem, at the time of shipping before the start of use, at the time of maintenance after the start of use, etc., speed adjustment has been performed so that the operating speed of the transfer means can be correctly matched with the peripheral speed of the image carrier. The image quality is prevented from lowering due to the expansion and contraction. However, this speed adjustment is performed by adjusting the rotational speeds of the transfer unit and the drive unit of the image carrier, and even when the adjustment is performed correctly, the size of the transfer unit such as a change in the outer diameter of the transfer roller is changed. When a change occurs, the recording paper feed state (feed speed)
Changes, a transfer image that expands and contracts in the feed direction is formed,
There is a problem that the quality of an image obtained through the fixing step is reduced.

Here, a transfer roller as a transfer means is
For the purpose of preventing slippage with the recording paper and providing accurate feeding, it is strongly desired that the outer peripheral surface to be in contact with the recording paper be made of a single-cell sponge rubber. Rubber is a material that undergoes large dimensional changes due to the effect of temperature.When a transfer roller made of a single-foam sponge rubber is used, the outer diameter changes due to a change in the ambient temperature, which changes the recording paper feed state, and the resulting image There is a problem that deterioration of quality cannot be avoided.

The present invention has been made in view of such circumstances, and prevents a change in expansion and contraction of a transferred image due to a change in a feeding state of a transfer unit beforehand, and achieves a high image quality realized by employing the transfer unit. An object of the present invention is to provide an image forming apparatus capable of stably realizing high-quality image formation.

[0009]

An image forming apparatus according to a first aspect of the present invention comprises: an image carrier for carrying an image; an image forming means for forming a carried image on a surface of the image carrier; An image forming apparatus comprising: a transfer unit that contacts a surface of the image carrier while feeding a record carrier to be recorded, and transfers a carried image on the surface to the record carrier. Feed detecting means for detecting a change in the state of feed applied to the recording medium, and control means for performing a control operation to cancel a change in an image transferred to the record carrier based on a detection result of the feed detecting means. It is characterized by.

In the present invention, a change in the state of feeding applied to the record carrier at the transfer section is detected by the operation of a transfer means such as a transfer roller or a transfer belt, and the change in the image transferred to the record carrier is detected in accordance with the change. By performing a control operation for canceling the generated change, deterioration of image quality due to expansion and contraction in the feed direction is prevented beforehand.

An image forming apparatus according to a second invention of the present invention is characterized in that the control means in the first invention controls the image forming means as a control object, and further, the image forming apparatus according to the third invention of the present invention. The apparatus is characterized in that the control means in the first invention makes the transfer means a control object.

In the second invention, the image forming means is controlled in accordance with the detection of the change of the feeding state, and the image formed on the surface of the image carrier is changed by the image forming means, so that the transfer image generated in the transfer section is obtained. Indirectly counteract changes in The control of the image forming means can be easily performed by changing the image data of the image to be formed. Further, in the third aspect, the transfer unit is controlled in accordance with the detection of the change in the feeding state, and the operation speed of the transfer unit is increased or decreased to directly cancel the change in the transferred image generated in the transfer unit.

Further, in the image forming apparatus according to a fourth aspect of the present invention, the transfer means according to the first to third aspects is a transfer roller which is in rolling contact with the surface of the image carrier via the recording carrier. The feed detecting means according to the third invention is an outer diameter sensor for detecting a change in the outer diameter of the transfer roller.

According to the present invention, in a configuration provided with a transfer roller as a transfer means, an expensive sensor is used to change the feed state of the record carrier which affects the transferred image, via the change in the outer diameter of the transfer roller. Detection with high accuracy.

In the image forming apparatus according to a fifth aspect of the present invention, the outer diameter sensor according to the fourth aspect is a sensor for indirectly detecting a change in the outer diameter. An image forming apparatus according to a sixth aspect is characterized in that the sensor according to the fifth aspect is a temperature sensor for detecting a peripheral temperature of the transfer roller.

In these inventions, a change in the outer diameter of the transfer roller as the transfer means is easily detected through a change in a physical quantity indirectly representing the change, for example, a change in the ambient temperature. Another physical quantity that indirectly represents a change in the outer diameter includes a change in the electrical characteristics of the transfer roller.

Further, in the image forming apparatus according to a seventh aspect of the present invention, the transfer means in the first to sixth aspects is characterized in that at least a contact portion with the record carrier is made of a single-foam sponge rubber.

According to the present invention, a transfer means in which at least the contact portion with the record carrier is made of a single-foam sponge rubber is used. The shortcomings of the easy-bubble sponge rubber are compensated for by the control operation of the control means based on the detection result of the feeding state, thereby realizing high quality image formation.

Further, the image forming apparatus according to an eighth aspect of the present invention is characterized in that the control means according to the first to seventh aspects is provided in an external device for calculating image data for image formation. .

In the present invention, control means for performing a control operation for canceling a change in a transferred image is provided in an external device having high-speed processing means and large-capacity storage means for calculating image data. A control operation corresponding to a change in the state is realized at a high speed.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments. FIG. 1 is a longitudinal sectional view schematically showing the overall configuration of an image forming apparatus according to the present invention, which is configured as a printer used for output from an external device such as a computer or a word processor. It is needless to say that the present invention is not limited to the printer apparatus described below, but can be applied to all image forming apparatuses such as copiers and facsimile apparatuses that perform similar image formation.

As shown in FIG. 1, the image forming apparatus includes a photosensitive drum 1 as an image carrier at a substantially central portion inside a housing 10 having a rectangular box shape. The photosensitive drum 1 is a large-diameter cylindrical drum provided with a photosensitive material layer on the entire outer peripheral surface serving as an image carrying surface and rotatably supported around a horizontal axis, and is transmitted by a driving source (not shown). It is rotationally driven at a predetermined speed (for example, 60 mm / sec) in a direction indicated by an arrow in the drawing. Around the photosensitive drum 1, the charging unit 2, the exposing unit 3, the developing unit 4, the transferring unit 5, and the discharging unit 6 are arranged in the rotation direction so as to face the outer peripheral surface serving as the image carrying surface. They are arranged in this order.

The charging means 2 is a urethane solid roller having a resistance value of 1 × 10 ⁶ Ω · cm, and being in rolling contact with the outer peripheral surface of the photosensitive drum 1. A charging voltage of 1200 V is applied from a power source 20. The outer peripheral surface of the photosensitive drum 1 is, for example, 600
An operation of uniformly charging V is performed. The exposure unit 3 is a laser scan unit that emits a laser beam in accordance with image data given from an external device (not shown), and selectively exposes the uniformly charged outer peripheral surface of the photosensitive drum 1,
It operates as image forming means for forming an electrostatic latent image corresponding to the image data.

The developing means 4 rotates in close proximity to the outer peripheral surface of the photosensitive drum 1 with a toner container 40 for accommodating toner T for development, and partially faces the inside of the toner container 40. And a developing roller 41. The developing roller 41 is
Due to the action of a developing bias voltage of 350 V applied from the power supply 42, the toner T in the toner container 40 is
The toner T is carried with a layer thickness of about μm, and is supplied with a charge amount of 20 μC / g to be conveyed to a portion facing the photosensitive drum 1. The toner is adhered to the electrostatic latent image formed on the outer peripheral surface, and the latent image is visualized to form a toner image 43.

The transfer means 5 is a roller having an outer diameter of 15 mm, which is in contact with the outer peripheral surface of the photosensitive drum 1, and is, for example, 1 × 10 ⁸ Ω ·
It is made of a single-foam sponge rubber (urethane sponge) having a resistance value of cm and a hardness of Asuka C40 degree. The transfer means 5 is rotated by a transmission from a motor 50 serving as a driving source so as to be in the same direction as the photosensitive drum 1 in a rolling contact means with the photosensitive drum 1 as shown by an arrow in the drawing. Being driven. Further, the transfer means 5 is supplied with
A transfer voltage of about kV is applied.

In the vicinity of the transfer means 5, a temperature sensor 52 for detecting the temperature around the transfer means 5 is provided. The detection result of the temperature sensor 52 is given to a control unit 7 that performs a control operation described later to maintain the quality of a transferred image formed by the operation of the transfer unit 5. The output of the control unit 7 is applied to the exposure unit 3 that irradiates the outer peripheral surface of the photosensitive drum 1 with a laser beam based on image data provided from an external device and operates as an image forming unit that forms an electrostatic latent image. The control operation of the control unit 7 based on the temperature around the transfer means 5 detected by the temperature sensor 52 is performed on the exposure means 3, and more specifically, is given to the exposure means 3. This is performed on image data as described below.

As shown by a broken line in FIG.
Is output to the motor 50 serving as a drive source of the transfer unit 5, and the control operation of the control unit 7 is controlled by the transfer unit 5, more specifically, the transfer unit 5 configured as a transfer roller. The rotation speed may be set as the target.

The charge removing means 6 removes electric charges remaining on the outer peripheral surface of the photosensitive drum 1 after passing through the transfer contact portion with the transfer means 5, and for example, removes the charge removing light having a uniform intensity from the photosensitive drum 1. 1 is constituted by a lamp which irradiates the outer peripheral surface. If necessary, a cleaning unit for removing the toner T remaining on the outer peripheral surface of the photosensitive drum 1 may be provided in front of the charge removing unit 6.

On both sides of the transfer section between the transfer means 5 and the photosensitive drum 1, a paper feed section and a paper discharge section for transporting a recording paper P as a recording carrier are formed. The paper supply unit is detachably mounted on one side and outside of the housing 10, and faces a paper supply cartridge 70 in which recording papers P are stacked and stored, and faces a mounting part of the paper supply cartridge 70. Roller 71 which feeds out recording paper P one by one by
And a pair of registration rollers 72, 72 for nipping and transporting the fed recording paper P from above and below, and the registration rollers 72, 72.
Paper feed guide installed between 72 and the entrance to the transfer part
73 are provided.

The paper discharge unit includes a transfer unit 5 and a photosensitive drum 1.
A discharge guide 74 extending from the exit side of the rolling contact portion to the other side of the housing 10, and a recording paper P on the discharge guide 74 facing the end of the discharge guide 74. And a pair of paper discharge rollers 75, 75 for transporting the paper from above and below, and mounted on the outside of the housing 10 so as to face these arrangement positions. The paper is conveyed above the paper discharge rollers 75, 75. And a paper discharge tray 76 for receiving the recording paper P.

The paper ejection guide 74 constituting the paper ejection section as described above.
A fixing device 8 is provided in the middle. This fixing device 8
Is provided with a heat roller 80 and a pressure roller 81 which rotate while holding the recording paper P on the paper discharge guide 74 from above and below. The heat roller 80 has a built-in heater 82 that generates heat by power supply from a power supply (not shown), and is driven to rotate around an axis by transmission from a drive source (not shown). The pressure roller 81 is a roller made of silicon rubber, and the recording paper P
Is driven to rotate while being pressed against the peripheral surface of the heat roller 80.

The heat roller 80 is provided with a temperature sensor 83 for detecting the surface temperature thereof.
The detected temperature of 83 is given to the temperature control circuit 84. The temperature control circuit 84 controls the heater 82 to turn on / off the energization based on the detection result of the temperature sensor 83 to maintain the surface temperature of the heat roller 80 at a predetermined temperature, for example, 150 ° C. I do.

Each section of the image forming apparatus having the above-described configuration starts its operation in response to a printing command given from an external device (not shown). At the time of passing through the disposition position, it is uniformly charged and reaches the position facing the exposure means 3, and is exposed by laser at this position to neutralize the charge on the exposed portion, thereby corresponding to image data given from an external device. An electrostatic latent image is formed.

The electrostatic latent image thus formed on the outer peripheral surface of the photosensitive drum 1 reaches the position where the developing means 3 is provided by the rotation of the photosensitive drum 1, and the toner adhered at the position as described above. The toner image 43 is formed by being visualized by T, and the toner image 43 reaches the position where the transfer unit 5 is provided by the further rotation of the photosensitive drum 1.

On the other hand, during this time, the recording paper P accommodated in the paper feed cartridge 70 is fed out by the rotation of the pickup roller 71, is sandwiched by the pair of registration rollers 72, 72, and a conveying force is applied to feed the paper. It is transported along the guide 73. The recording paper P conveyed in this way reaches the rolling contact portion between the transfer means 5 and the photosensitive drum 1 at the same timing as the arrival of the toner image 43 forming area, and is held between the two. While being fed by the rotation of 5, the photosensitive drum 1 is pressed against the outer peripheral surface. At this time, the toner image 43 is transferred onto the recording paper P by the action of the transfer voltage applied to the transfer means 5 as described above.

The recording paper P onto which the toner image 43 has been transferred in this manner is sent out along the paper ejection guide 74, passes through the fixing device 8, and is pressed against the heat roller 80 by the action of the pressure roller 81. At this time, the toner image 43 is fixed to the recording paper P under the action of the surface temperature of the heat roller 80, and the recording paper P is fixed to the discharge rollers 75, The sheet is conveyed while being pinched by the sheet 75, and is sent out and collected on the sheet discharge tray 76.

On the other hand, after the transfer of the toner image 43, the outer peripheral surface of the photosensitive drum 1 reaches the position where the static elimination means 6 is provided, and after the residual charge is removed by the irradiation of the static elimination light, further. The rotation of the photosensitive drum 1 reaches the position where the charging means 2 is disposed, and is uniformly charged, and is used again for image formation by repeating the above-described operation.

In the image formation performed as described above, the feed applied to the recording paper P by the transfer means 5 is adjusted so that a feed speed correctly matching the peripheral speed of the photosensitive drum 1 is obtained. Initially adjusted by setting the rotation speed.

However, the roller made of a single-foam sponge rubber such as a urethane sponge used as the transfer means 5 has the advantage that it can reliably feed the recording paper P without slippage. When the temperature changes during the process, there is a disadvantage that the outer diameter is likely to change due to thermal expansion or contraction of the internal bubbles.

With respect to a roller made of urethane sponge having an outer diameter of 15 mm used as the transfer means 5 as described above, a change in the outer diameter actually caused by a temperature change was examined.
The outer diameter, which was 15 mm at normal temperature (20 ° C), should be reduced to 14.75 mm at a lower usable temperature of 5 ° C, and increased to 15.2 mm at a usable upper temperature of 35 ° C. Became clear. In addition, such a change in the outer diameter varies depending on the material of the roller to be used and various characteristics such as the expansion ratio, but when a roller made of a single-cell sponge rubber is used, its structure including bubbles is inevitable. It is a problem.

When such an outer diameter change occurs, the peripheral speed of the transfer means 5 changes under the initially set rotational speed as described above, and the feed speed applied to the recording paper P is changed to the peripheral speed of the photosensitive drum 1. No longer matches speed. As a result, the transfer image transferred to the recording paper P at the rolling contact portion between the photosensitive drum 1 and the transfer means 5 expands and contracts in the feed direction with respect to the toner image 43 formed on the outer peripheral surface of the photosensitive drum 1. Then, the formed image on the recording paper P sent to the paper discharge tray 76 after being fixed by the fixing device 8 becomes different from the original image, and the desired image quality cannot be obtained.

As described above, the transfer means (transfer roller) 5 made of urethane sponge is provided with ±
An outer diameter change of about 1.5% occurs. In this case, the expansion and contraction of the image reaches, for example, up to ± 4.5 mm in the longitudinal direction of the A4 size recording paper P.

The control section 7 cancels out the expansion and contraction of the transfer image generated as described above due to the change in the outer diameter of the transfer means 5 due to the influence of the peripheral temperature, and improves the quality of the image formed on the recording paper P. The control operation for maintaining is performed. As described above, this control operation is performed as follows with the exposure unit 3 or the transfer unit 5 as a control target.

First, the case where the exposure means 3 is to be controlled will be described. In this case, image data provided from the external device to the exposure unit 3 is targeted, and a control operation for expanding or reducing the image data as described below in order to cancel the expansion and contraction of the image which occurs as described above in the process of transfer by the transfer unit 5. Is made.

The controller 7 monitors the ambient temperature of the transfer means 5 given as an input from the temperature sensor 52 and applies the detected temperature to a preset calculation formula or calculation table to transfer the current transfer means (transfer means). The outer diameter of the roller 5 is calculated. If the calculated outer diameter is larger or smaller than the reference outer diameter at room temperature, an expansion / contraction ratio with respect to the reference outer diameter (= calculated outer diameter / reference outer diameter) is obtained. It is given to the exposure means 3.

Exposure means 3 given such a scaling ratio
Performs an operation of performing data processing for enlarging / reducing image data provided from an external device in accordance with the reciprocal of the enlargement / reduction ratio, and emitting laser light for exposure based on the processed image data.

For example, when the outer diameter of the transfer means 5 is reduced by 1% due to use in a low temperature environment, the controller 7 calculates an enlargement / reduction ratio of 99%. Is extended to 101% in the sub-scanning direction of the exposure laser light, that is, in the circumferential direction of the photosensitive drum 1 irradiated with the laser light. The data processing is performed, and the laser light is emitted based on the processed image data.

By the irradiation of the laser beam, an electrostatic latent image whose length in the sub-scanning direction, that is, the circumferential direction is extended to 101% with respect to the original image on the outer peripheral surface of the photosensitive drum 1. As a result, an image is formed, and the toner image 43 that has reached the position where the transfer unit 5 is disposed after the development by the developing unit 4 also expands by 101% in the circumferential direction.

On the other hand, the feeding speed of the recording paper P fed to the rolling contact portion between the photosensitive drum 1 and the transfer means 5 is the same as that of the transfer means 5.
Is reduced to 99% of the original feed speed by the diameter reduction
As described above, the toner image 43 reduced to 101% in the circumferential direction of the photosensitive drum 1, that is, in the feed direction of the recording paper P, is transferred to the recording paper P thus decelerated, as described above. On the transfer surface of the recording paper P, an image that correctly corresponds to the image data before the data processing is formed. Therefore, high image quality which should be originally obtained by adopting the transfer means 5 made of a single-foam sponge rubber which can be accurately fed without slipping on the recording paper P is favorably maintained without being affected by the ambient temperature. be able to.

When the diameter of the transfer means 5 is increased, the exposure means 3 emits a laser beam in accordance with image data obtained by reducing image data provided from an external device. A toner image 43 contracted in the circumferential direction is formed on the outer peripheral surface of the drum 1, and the toner image 43 is transferred onto the recording paper P whose feed speed has been increased by enlarging the diameter of the transfer unit 5. Similarly, an image correctly corresponding to the original image is formed.

In the above embodiment, the exposure means 3
The problem can be solved by appropriately calculating when the image data given to the image data is expanded into a bit map, or by rescaling the image data by recalculating the image data itself. It is not necessary to control the drive unit, and the like, and it is possible to prevent an increase in cost due to addition of components for these controls. The enlargement / reduction processing of the image data may be performed stepwise or continuously based on the result of the temperature detection.

On the other hand, when the transfer means 5 is to be controlled,
The control unit 7 calculates the outer diameter of the transfer unit 5 using the ambient temperature of the transfer unit 5 given as a detection result by the temperature sensor 52, and based on the result, the driving motor of the transfer unit 5
A control command is issued to 50 to perform a control operation for accelerating and decelerating the rotation speed of the transfer means 5. This control operation is more direct, and when the outer diameter of the transfer means 5 is increased and the feeding speed of the recording paper P is increasing, a deceleration command is sent to the motor 50 to cancel this. Conversely, if the outer diameter of the transfer means 5 is reduced and the feed speed of the recording paper P is reduced, the motor 50 is designated to increase the speed in order to cancel this.

According to this configuration, it is necessary to add an additional configuration for controlling the driving of the transfer unit 5, and it is unavoidable that the cost is increased. Therefore, it is possible to respond instantaneously to a sudden change in the feed state, and it is possible to obtain high responsiveness.

In order to perform the above control operation with high accuracy, it is necessary that the temperature sensor 52 accurately detects the temperature around the transfer means 5. For this purpose, it is desirable to dispose the temperature sensor 52 as close to the transfer means 5 as possible. However, if it is difficult to dispose the temperature sensor 52 due to space problems or scattering of paper dust or toner, Inside, the temperature sensor 52 is disposed at a position considered to be in the same temperature environment as the vicinity of the transfer unit 5, and the same operation is performed by regarding the detected temperature of the temperature sensor 52 as the ambient temperature of the transfer unit 5. It may be performed.

The temperature around the transfer means 5 can be detected without using the temperature sensor 52 by utilizing the electrical characteristics of the transfer means 5. That is, as shown in FIG. 2, after the image forming operation is started, a predetermined time t is applied while the transfer voltage V _T applied to the transfer unit 5 is applied over the time t _2.
A constant current control of IμA over _one measures the required voltage V _t this time. This voltage V _t, the transfer unit 5
A required temperature detection value is obtained by comparing with a reference voltage V ₀ measured in advance at normal temperature, which depends on the ambient temperature including the internal temperature of the device.

The internal resistance of the single-foam sponge rubber roller used as the transfer means 5 decreases as the temperature rises, and increases as the temperature drops. Therefore, for example, the reference voltage V ₀ at normal temperature is 500 V,
If the measured voltage V _t during the constant current control described above may be had been 700 V, ambient temperature internal resistance has been increased found to be lower than the room temperature, contrary to the measured voltage V _t was 300 V, the internal It can be seen that the resistance has decreased and the ambient temperature is lower than normal temperature. The actual temperature, ratio or between the V ₀ and V _t can be known by previously obtained temperature relationships for the difference.

It is also possible to perform constant voltage control instead of the above-described constant current control, and to obtain the ambient temperature based on the measurement result of the current flowing during this time. Such temperature detection is suitable when it is difficult to dispose the temperature sensor 52 near the transfer unit 5.

In the above embodiment, the change in the outer diameter of the transfer means 5 is indirectly detected by using the detection result of the peripheral temperature of the transfer means (transfer roller) 5. Can be directly detected, and the control operation of the control unit 7 can be performed based on the detection result.

FIG. 3 is a diagram showing an example of a configuration for detecting the outer diameter of the transfer means 5. This figure shows a front view of a transfer contact portion between the photosensitive drum 1 and the transfer means 5, and as shown, the transfer means 5 configured as a transfer roller that comes into contact with the outer peripheral surface of the photosensitive drum 1 has two ends. Support shafts 53, 53 projecting into the part
Are supported by separate bearings 54, 54 and are rotatably supported by shafts. These bearings 54, 54 are urged by pressing springs 55, 55 interposed between the bearings and fixed portions inside the housing 10. The photosensitive drum 1 is pressed against the outer peripheral surface of the photosensitive drum 1.

When the outer diameter of the transfer means 5 changes, the positions of the bearings 54 on both sides are displaced. That is, when the outer diameter of the transfer means 5 is reduced, the pressing springs 55 extend to fill the gap formed between the transfer means 5 and the photosensitive drum 1, and the support position by the bearings 54 approaches the photosensitive drum 1. It is displaced away from the fixed part. Conversely, when the outer diameter of the transfer means is increased, the pressure applied to the rolling contact portion with the photosensitive drum 1 causes the compression springs 55, 55 to contract, and the bearings 54, 55 to contract.
The support position by 54 moves away from the photosensitive drum 1 and moves closer to the fixed portion.

In this figure, in order to directly detect a change in the outer diameter of the transfer means 5 by utilizing the displacement generated as described above, the support shafts 53, 53 on both sides of the transfer means 5 are provided at the fixed portion. A pair of distance sensors 56, 56 are arranged to face each other. These are sensors that output an output corresponding to the separation distance to the corresponding support shafts 53, 53, and these outputs allow the support shafts 53, 53 to be output.
And the change in the outer diameter of the transfer means 5 can be determined from the result.

The distance sensors 56, 56 receive the reflected light of the light emitted toward the support shafts 53, 53 serving as objects,
A non-contact type sensor configured to detect the distance based on the time until this light reception, and a contact type sensor configured to detect expansion and contraction of a detection bar having its tip abutting on the peripheral surface of the support shafts 53, 53. For example, an appropriate sensor can be used. Further, the distance sensors 56, 56 may be attached to the support of the photosensitive drum 1 to detect the relative displacement of the transfer means 5 with respect to the photosensitive drum 1.

The direct detection of the change in the outer diameter of the transfer means 5 is as follows.
Not only the distance sensors 56, 56 as described above, but also other appropriate sensors may be used. However, this type of sensor requires an accurate arrangement in accordance with the position of the transfer means 5, is generally expensive, and is liable to cause erroneous detection due to the influence of electric noise generated in controlling a high voltage such as a transfer voltage. Temperature sensor
It is desirable to perform indirect outer diameter detection using 52 or the like.
However, when the change in the outer diameter of the transfer unit 5 due to the wear over time is also targeted, a detection unit for direct detection is required.

The detection of the outer diameter of the transfer means 5 as described above is performed by detecting a change in the feeding state of the recording paper (recording carrier) P fed by the transfer means 5, more specifically, a change in the feeding speed. It is for detecting. The change in the outer diameter of the transfer unit 5 is a physical quantity that most affects the feeding state and is easily detected indirectly or directly. Detecting this is small in error and efficient.

However, a physical quantity other than the change in the outer diameter, such as a change in hardness of the transfer means 5 and a driving torque of the transfer means 5 may be detected, and the change in the feeding state may be known from the result. Recording paper P near the means 5
The feed speed may be directly detected using the passage of the front and rear ends as a medium, and the control operation of the control unit 7 may be performed based on the result.

An image forming apparatus having a transfer unit 5 having another configuration such as a transfer belt in addition to the above-described roller has been put into practical use. In such an image forming apparatus, means other than the outer diameter detection is used. It is necessary to detect a change in the feeding state.

FIG. FIG. 4 is a block diagram illustrating an example of an image data processing unit for performing scaling of image data. The image data processing unit 9 includes an I / O for sending and receiving image data.
Interface 90, CP for performing arithmetic processing of image data
U91, R which stores enlargement / reduction data necessary for enlargement / reduction such as the relationship between the outer diameter change of the transfer means 5 and the enlargement / reduction ratio, and an arithmetic procedure.
An OM 92 and a RAM 93 for storing image data before and after processing are provided, and these are connected as shown in the figure.

The detection results obtained by the outside diameter sensors such as the temperature sensor 52 and the distance sensor 56 are converted into outside diameter change data via a conversion unit (not shown), and are transmitted to the I / O interface 90 together with image data given from an external device. Via CPU
Given to 91. The CPU 91 temporarily stores the given image data in the RAM 93, first determines whether to perform expansion or reduction processing based on the outer diameter change data, and stores the same in accordance with the procedure stored in the ROM 92. The image data is expanded or reduced using the enlarged / reduced data. The processed image data (processed data)
After storing in the RAM 93, the I / O interface 90
Are sequentially output via the.

The detection result obtained by the outer diameter sensor may be fetched every time image data is input.
When the power is turned on, it may be performed at a predetermined appropriate timing, such as each time a predetermined number of images are formed. The image data processing unit 9 as described above is a dedicated processing unit.
The control unit 7 may be attached to the exposure unit 3.
For example, it may be provided in a control unit for performing various control operations.

The image data processing section 9 may be provided in an external device for providing image data when the external device has a high-speed processing means and a large-capacity storage means. In this case, the image data processing unit 9 that requires high-speed processing is not required inside the image forming apparatus.
Cost reduction becomes possible. When the external device does not have a function of processing image data, a magnetic disk,
The processing program stored in a recording medium such as an optical disk may be installed in an external device so as to have a processing function.

[0071]

As described above in detail, in the image forming apparatus according to the first aspect of the present invention, a change in the state of feeding applied to the record carrier by the transfer means is detected, and the record carrier is detected based on the detection result. Since the control operation for canceling the change of the transferred image is performed, the change of the transferred image including the expansion and contraction in the feeding direction can be surely suppressed, and the high-quality image formation can be stably realized.

Further, in the image forming apparatus according to the second aspect of the present invention, the image forming means for forming the carried image on the surface of the image carrier is controlled, and the image data of the image to be formed is expanded and contracted to change the transferred image. Since the configuration is such that the indirect cancellation is performed, an additional configuration for controlling the driving unit such as the transfer unit and the image carrier becomes unnecessary, and high-quality image formation can be performed with a simple configuration.

Further, in the image forming apparatus according to the third aspect of the invention, the transfer means for feeding the recording paper is controlled, and the change in the transferred image is directly canceled by controlling the speed of the transfer means. High-quality image formation can be realized with high response.

Further, in the image forming apparatus according to the fourth aspect of the invention, since the change in the feeding state is detected based on the change in the outer diameter of the transfer roller as the transfer means, the detection can be performed with high accuracy. In the image forming apparatus according to the fifth and sixth aspects of the present invention, the change in the outer diameter of the transfer roller is indirectly detected through the ambient temperature of the transfer roller, the change in the electrical characteristics of the transfer roller, and the like. Accordingly, the object can be easily achieved without difficulty in arranging the detection sensor.

Further, in the image forming apparatus according to the seventh aspect of the present invention, since the transfer means in which the contact portion with the record carrier is made of single-foam sponge rubber is used, the size based on the influence of temperature is controlled by the control based on the detection result of the feeding state. While compensating for the shortcomings of the single-cell sponge rubber, which is liable to change, reliable feeding without slippage can be applied to the record carrier, and high-quality image formation can be performed stably.

Further, in the image forming apparatus according to the eighth aspect of the present invention, since a control unit for performing the above control is provided in an external device for calculating image data for image formation, high-speed processing can be performed. The present invention provides excellent effects, such as allowing a control operation according to a change in state to be performed at a high speed without complicating the configuration of the image forming apparatus itself.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view schematically showing the entire configuration of an image forming apparatus according to the present invention.

FIG. 2 is an explanatory diagram of a method of detecting a peripheral temperature of a transfer unit without using a temperature sensor.

FIG. 3 is a diagram illustrating an example of a configuration for detecting an outer diameter of a transfer unit.

FIG. 4 is a block diagram illustrating an example of an image data processing unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum (image carrier) 3 Exposure means (imaging means) 5 Transfer means 7 Control part 9 Image data processing part 52 Temperature sensor 56 Distance sensor P Recording paper (recording carrier)

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Kokazu Kamei 22-22, Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Hideki Onishi 22-22, Nagaike-cho, Abeno-ku, Osaka-shi, Osaka (72) Inventor Hiroshi Doshoda 22-22, Nagaike-cho, Abeno-ku, Osaka-shi, Osaka F-term in Sharp Corporation (reference) MA08 MC18 PB07 PB15 PB27

Claims (8)

[Claims] 1. An image carrier for carrying an image, an image forming means for forming a carried image on the surface of the image carrier, and an image carrier on a surface of the image carrier while feeding a recording carrier on which an image is to be recorded. An image forming apparatus comprising: a transfer unit that transfers the carried image on the surface to the record carrier by contacting the transfer unit, wherein a feed detection unit that detects a change in a state of a feed applied to the record carrier by the transfer unit; An image forming apparatus comprising: a control unit that performs a control operation based on a detection result of a feed detection unit to cancel a change in an image transferred to the record carrier. 2. The image forming apparatus according to claim 1, wherein the control unit controls the image forming unit. 3. The image forming apparatus according to claim 1, wherein the control unit controls the transfer unit. 4. The transfer means is a transfer roller which is in contact with the surface of the image carrier via the recording carrier, and the feed detecting means is an outer diameter sensor for detecting a change in the outer diameter of the transfer roller. The image forming apparatus according to claim 1, wherein: 5. The image forming apparatus according to claim 4, wherein the outer diameter sensor is a sensor that indirectly detects a change in the outer diameter. 6. The image forming apparatus according to claim 5, wherein the sensor is a temperature sensor that detects a temperature around the transfer roller. 7. The transfer device according to claim 1, wherein at least a contact portion with the record carrier is made of a single-cell sponge rubber.
The image forming apparatus according to claim 6. 8. The image forming apparatus according to claim 1, wherein the control unit is provided in an external device that calculates image data for image formation.