JP3194183B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic transfer type / heat fixing type image forming apparatus.

More specifically, an image bearing member such as a photosensitive member, a dielectric member, or a magnetic member is applied to an image bearing member by an appropriate image forming process such as an electrophotographic process (ex. Carlson method), an electrostatic recording process, or a magnetic recording process. A transferable image corresponding to the target image information is formed, the transferable image is transferred to a recording material such as paper by electrostatic transfer means, and the recording material is moved through a fixing nip portion heated by a heating element. The present invention relates to an image forming apparatus such as a copying machine or a printer for thermally fixing an image by introducing and passing through the fixing nip portion of a heating and fixing unit having the same and outputting an image-formed product.

[0003]

2. Description of the Related Art Conventionally, in an image forming apparatus of the above-mentioned electrostatic transfer type and heat fixing type, a transferable image formed and carried on a surface of an image carrier such as a photoconductor (hereinafter referred to as a photoconductor). As a transfer unit for transferring a toner image (hereinafter referred to as a toner image) to a recording material (hereinafter referred to as paper), a non-contact charging type electrostatic transfer unit using a corona discharger has been used. In recent years, a contact charging type electrostatic transfer unit (for example,
No. 85572) is frequently used.

Image transfer by a corona discharger is performed by disposing a corona discharger in a non-contact manner with respect to a photoreceptor as an image carrier, and passing a paper as a recording material between the corona discharger and a back surface of the paper. By exposing the (back) surface to the discharge current from the corona discharger, the toner image on the photoconductor is charged to a polarity opposite to the charging polarity of the toner (developer), and the electrostatic force of the charging causes the toner image on the photoconductor to be charged. It is transferred and transferred to the front side of paper.

The transfer means of the contact charging system forms a transfer nip by contacting a transfer rotating member such as a conductive roller or a belt with a photosensitive member as an image carrier, and a recording nip is formed on the transfer nip. A predetermined transfer voltage is applied to the photoreceptor and the transfer rotating member by passing paper as a material, and the back surface of the paper is charged by the transfer rotating member in a contact mode with a polarity opposite to that of the toner,
The toner image on the photoreceptor side is transferred and adhered to the surface side of the paper by the electrostatic force of the charging, and is transferred.

[0006] The transfer means of the contact charging system has the advantage that the amount of ozone generated by the discharge can be greatly reduced as compared with the transfer means using a corona discharger.

As a means for heating and fixing an image transferred to paper as a recording material, a heat roller fixing device comprising a pair of rollers having a heat source has been used for a long time. In recent years, in order to save energy and shorten the waiting time until image formation, a more efficient heat fixing method has been developed. One of them is a film heating method disclosed in Japanese Patent Application Laid-Open No. 63-313182. There is a fixing device (heating device) of a system.

This film heating type apparatus has a heat-resistant film (fixing film), a heating element for forming a nip (fixing nip) with the film interposed therebetween, and a facing member.
By introducing paper between the film of the nip portion and the opposing member and passing the nip portion together with the film, the image is thermally fixed by the heat of the nip portion intensively heated by the heating element. is there.

Compared with a heat roller fixing device, a thin film having a small heat capacity is used as a film, and a low heat capacity substantially linear heating body (such as a ceramic heater) is used as a heating body, which rapidly generates heat by energization and has a low temperature. With a low heat capacity configuration, intensive heating near the nip can be performed and high-efficiency thermal fixing is realized.In addition, it is sufficient to energize the heating element from the start of image formation, so the waiting time can be reduced to almost zero , Quick start.

[0010] Further, during non-image formation, there is no power supply and no power is consumed, so that a large energy saving is achieved as compared with the conventional heat roller fixing device.

[0011]

In the transfer section, the toner image on the photoreceptor side as the image carrier is electrostatically transferred to and held on paper as a recording material, and the paper is fixed to a fixing nip portion of a heat fixing unit. When the toner image is thermally fixed by introducing the toner into the paper, a phenomenon in which the toner image scatters in a whisker-like manner toward the downstream side in the paper traveling direction (hereinafter, referred to as fixing scattering) may appear.

The phenomenon of the scattering of the fixing is caused by the fact that the heating fixing device heats the fixing nip in a concentrated manner, as typified by the above-mentioned film heating type fixing device, and makes it possible to conduct electricity only during image formation. This is particularly noticeable when the device has a certain characteristic.

The mechanism of the scattering of the fixation is that the toner image is heated for the first time and immediately in a very close place where the toner image enters the fixing nip portion. It is presumed that a part of the unfixed toner image adhered to the paper only by electrostatic force is blown off, and such scattering occurs.

As a countermeasure, it is conceivable to increase the voltage applied to the transfer means in order to increase the electrostatic force between the toner image and the paper, and to increase the charging potential of the paper by flowing a large amount of current. In fact, when the transfer voltage was greatly increased, the fixing scattering was improved.

However, if the transfer voltage is increased and the transfer current is increased, the discharge current under a high electric field flows into the photoreceptor and roughens the surface of the photoreceptor. There was a problem of damage.

Accordingly, the present invention provides an image forming method of a heat fixing method in which a recording material on which an image is electrostatically transferred is passed through a fixing nip portion heated by a heating body to thermally fix the image. It is an object of the present invention to suppress an adverse effect on an image carrier due to a transfer voltage applied to a transfer unit, and to prevent the occurrence of fixing scattering, or to prevent the level thereof from deteriorating.

[0017]

SUMMARY OF THE INVENTION The present invention is an image forming apparatus having the following configuration.

[0018]

[0019]

(1) An image carrier, a unit for forming a transferable image on the image carrier, an electrostatic transfer unit for applying a transfer voltage to transfer the transferable image to a recording material, An image forming apparatus having a heat-fixing unit that heat-fixes a transferred image by passing a recording material through a fixing nip heated by a heating unit, wherein the image forming operation is completed, and power is supplied to the heating unit of the heating-fixing unit. Measuring means for measuring the time between the stop of the image forming operation and the start of the next image forming operation, a temperature measuring means for measuring the temperature of the heating body of the heat fixing unit or the vicinity thereof, and the start of the next image forming operation And a transfer voltage control unit that controls a voltage applied to the electrostatic transfer unit based on the stop time information obtained by the clock unit and the temperature information obtained by the temperature measurement unit. Characteristic image forming apparatus.

(2) The electrostatic transfer means causes the transfer rotating member to abut on the image carrier to form a transfer nip portion, and the recording material is passed through the nip portion to be pinched and conveyed. The image forming apparatus according to (1 ), wherein the image forming apparatus is of a contact type in which a transfer voltage is applied to a transfer rotating member during the transfer.

(3) The heating and fixing means has a quick start property by intensively heating the fixing nip portion by the heating element, and the power supply to the heating element is stopped immediately after the end of the image forming operation. The image forming apparatus according to any one of (1) and (2) , wherein

(4) The heating and fixing means comprises: a film member;
A heating element and a facing member forming a fixing nip portion with the film member interposed therebetween, and a recording material is introduced between the film member and the facing member of the fixing nip portion to form a fixing nip portion together with the film member. (1) A film heating type heating device in which an image is thermally fixed by applying heat to a nip portion which is intensively heated by a heating element.
The image forming apparatus according to any one of ( 1 ) to (3) .

(5) The image forming apparatus according to (4) , wherein the film member is an endless belt-shaped rotating body.

[0025]

A) That is, various studies have been made on the phenomenon of "fixation scattering", which is a problem to be solved by the present invention, and the following facts have been found.

When the image formation is performed in a state where the heating and fixing means is sufficiently cooled, the level of the occurrence of the fixing scattering phenomenon is the worst. After that, the image formation is repeatedly performed at short pause intervals, or the image is continuously formed. This is the fact that, when an image is formed, the level of the fixing scattering phenomenon gradually increases, and reaches a level at which no problem occurs.

The state in which the heating and fixing means has been sufficiently cooled corresponds to a case where the image is formed for a long period of time after the image formation, a start of use of a day (hereinafter, referred to as a state in the morning). Concentrated heating of the fixing nip like a device,
In the case of an apparatus having a quick start property in which energization heating is enabled only during image formation, a relatively large number of cool states appear when power is not applied during non-image formation.

The reason why the level of the fixing scattering phenomenon is improved after one state in the morning is that the toner image is not located immediately near the fixing nip because the entire heating and fixing means is warmed including its atmosphere by continuous or intermittent use. It is presumed that while the toner is heated in front of it, the cohesive force of the toner is increased, and the rapid air expansion is alleviated, and as a result, fixing scattering is reduced.

B) As described above, the present invention is based on the fact that the level of the degree of scattered fixing development varies depending on the temperature state of the heating / fixing means at the start of the image forming operation. To fix the fixing scatter around the first state in the morning, and as described above, the temperature state of the heating and fixing means at the start of the next image forming operation after the image forming operation is completed, of the stop time measured by the measuring means said stop time information, is determined based on both the temperature information by the temperature measuring means is for controlling the applied transfer voltage for the transfer means according to the determination.

More specifically, if the determination of the temperature state of the heating / fixing means at the start of the image forming operation is one in the morning when the heating / fixing means is completely cooled, the degree of the fixing / scattering phenomenon generated in the heating / fixing means is considered. Since the level becomes the worst, the transfer voltage applied to the transfer means is controlled to a higher set value than usual, thereby increasing the electrostatic force of the recording material and the transferred image, and suppressing the occurrence of the remarkable fixing scattering phenomenon. . Thereafter, control is performed to reduce the transfer voltage to an appropriate set value.

If the temperature condition of the heating and fixing means at the time of the start of the image forming operation is still in a state of being warm to a predetermined level or more, the level of the generated fixing scattering phenomenon is in a good state or does not matter. In the state, the transfer means voltage applied to the transfer means can be controlled by a set value at a normal time, or by a set value of an appropriately higher level than that.

Therefore, the reason why a high transfer voltage is applied to the transfer means, which is significantly higher than that in the normal state, is that at least the minimum required at the time of image formation of the first sheet in the case where the judgment temperature state is the first state in the morning. In this case, the excessive transfer current to the image carrier becomes temporary in this case, and the duration can be minimized. The image carrier can be used stably for a long period of time, and the fixing scattering phenomenon can be prevented at the time of each image forming operation, or the level of deterioration can be reduced. Can be prevented.

[0033]

EXAMPLES <Example 1> (FIGS. 1-4) (1) Example of Image Forming Apparatus Figure 1 is a schematic diagram of images forming apparatus example. The image forming apparatus of this embodiment is a copying machine or a printer of an electrostatic transfer type and a heat fixing type using an electrophotographic process.

Reference numeral 1 denotes a rotating drum type electrophotographic photosensitive member serving as an image carrier, which is rotated at a predetermined peripheral speed (process speed) in a clockwise direction indicated by an arrow.

During the rotation of the photosensitive member 1, the peripheral surface thereof is uniformly charged to a predetermined polarity and potential by the primary charger 2 to which a predetermined charging bias voltage is applied from the power supply 7.
The primary charger 2 of the present embodiment is a contact charging roller, which is pressed against the photosensitive member 1 with a predetermined pressing force by a pressing means such as a spring (not shown), and rotates following the rotation of the photosensitive member 1.

Next, the charged surface of the photoreceptor 1 is subjected to image exposure A of target image information by an image exposure means (not shown) such as a slit exposure means for a document image or a laser scanner. An electrostatic latent image of the target image information is formed.

The electrostatic latent image is developed by the developing device 3 as a toner image.

In the transfer nip portion, which is a contact portion between the photoreceptor 1 and a transfer roller 4 serving as a transfer unit brought into contact with the photoreceptor 1, a predetermined amount is applied to the transfer nip portion from a paper supply unit (not shown). It is sequentially transferred to the paper P as the recording material fed at the timing.

The transfer roller 4 as the transfer means in this embodiment is
Semi-conductive (about 105 to 106Ω) around the cored bar 4a
(Cm), a solid elastomer layer or a sponge layer or a layer 4b obtained by laminating them.

The paper P is fed to the transfer nip and is nipped and conveyed. When the leading end of the paper P reaches the transfer section, a transfer bias voltage of, for example, about 1 to several kV, which is opposite to the polarity of the toner, is applied to the metal core 4a of the transfer roller 4 from the power supply 8, and the transfer roller 4 comes into contact. The back surface of the paper P is charged by a contact charging method with a polarity opposite to that of the toner, and the toner image on the photoconductor 1 is electrostatically transferred to the front surface of the paper P.

The paper P to which the toner image has been transferred through the transfer nip portion is separated from the surface of the photoreceptor 1 and sent to the heat fixing unit 6, where the transferred toner image is fixed on the paper P as a permanently fixed image. , And are discharged out of the apparatus as a copy or a print.

On the other hand, the surface of the photoreceptor 1 after passing through the transfer nip and separating the paper is cleaned by removing the residual developer and other deposits by the cleaner 5, and is repeatedly used for image formation.

The above is an outline of a series of processes of the image forming operation.

(2) Heat Fixing Unit 6 FIG. 2 is a schematic configuration diagram of the heating fixing unit 6. The heat fixing device 6 of the present embodiment is a film heating type heating device using an endless belt-like heat-resistant film (fixing film).

Reference numeral 15 denotes a heating element, which is a horizontally long, low-heat-capacity ceramic heater whose longitudinal direction is a direction perpendicular to the direction of transport of the paper P as a recording material. This ceramic heater has a basic structure consisting of a ceramic substrate such as alumina and a linear conductive resistance heating element formed along the length of the substrate surface. The temperature is adjusted to a predetermined fixing temperature by the system. The heater 15 is held by a holder 14 made of a heat-resistant resin (for example, PEEK), and is fixedly provided by attaching the holder 14 to a supporting metal plate 16.

Reference numerals 12 and 13 denote a driving roller and a tension roller disposed substantially in parallel with the heater 15 as the heating element.

An endless belt-shaped fixing film 9 is stretched between the three members of the heater 15, the driving roller 12, and the tension roller 13. Fixing film 9
Is formed by forming a base layer of, for example, a heat-resistant resin film (eg, polyimide) or a thin metal (several μm to several tens of μm), and a fluororesin layer or a rubber layer (eg, silicon rubber) or a laminate thereof formed thereon. is there.

Reference numeral 10 denotes a heater 1 with the fixing film 9 interposed therebetween.
5 is a pressure roller in which a fixing nip portion is formed by pressing the roller 5.

When the drive roller 12 is driven to rotate,
The fixing film 9 is driven to rotate clockwise as indicated by an arrow while the inner surface thereof slides in close contact with the surface of the heater 15. The pressure roller 10 rotates following the rotation of the fixing film 9.

The fixing film 9 is driven to rotate and the heater 1
5 is energized to raise the temperature to a predetermined fixing temperature, the paper P as the recording material to be image-fixed between the fixing film in the fixing nip portion and the pressure roller 10 is fixed to the fixing surface of the fixing film 9. The paper P is guided and guided by the entrance guide 17 so that the paper P
The toner image is heat-fixed to the surface of the paper P by the heat of the fixing nip portion, which is intensively heated by the heater 15 in the process, while being held in close contact with the outer surface of the paper P and the fixing film 9. You.

The paper P that has passed through the fixing nip is separated from the surface of the fixing film 9 and discharged and conveyed through a guide plate 21 and a discharge roller pair 22 on the fixing outlet side.

(3) Control System FIG. 3 is a block diagram of a control system for controlling the transfer voltage applied to the transfer roller 4 and energizing the heater 15 of the heat fixing unit 6.

The heater 15 of the fixing device 6 is controlled by a control circuit (CP
U) The element 18 such as a triac is turned on at a predetermined timing by 100, and is supplied with power from the power supply 19 to rapidly generate heat to heat the fixing nip portion. Element 18
Is turned off, the power supply is stopped.

A temperature sensing element 20 such as a thermistor is disposed on the back surface of the heater 15, and the temperature of the heater 15 is detected by the temperature sensing element 20 and fed back to the control circuit 100. During the image forming operation, the control circuit 1
00 is the temperature of the heater 15 according to the input temperature information,
That is, the power supply to the heater 15 is controlled by turning on and off the element 18 so as to control the temperature of the fixing nip to a predetermined fixing temperature.

Reference numeral 8 denotes a transfer voltage application power supply to the transfer roller 4, which is a voltage-variable DC power supply. Control circuit 100
As a result, on / off control of the transfer voltage applied to the transfer roller 4 is performed at a predetermined timing, and the applied voltage value of the transfer voltage to the transfer roller 4 is controlled.

The power supply to the heater 15 of the heat fixing unit 6 is stopped when the image forming operation is completed. The control circuit 100
A timer means for counting the time (stop time) from the end of the image forming operation to the stop of the power supply to the heater 15 of the heating / fixing unit 6 to the next press of the image forming start button 21 (hereinafter referred to as a copy button) is provided. The stop time is integrated and reset when the copy button 21 is pressed.

FIG. 4 is an operation flow of the control system.

1) When the image formation is completed and the power supply to the heater 15 of the heat fixing unit 6 is turned off, the time measurement starts in the control circuit 100 as described above (steps S1 and S2).

2) When the copy button 21 is pressed at the time of the next image formation, the next image formation operation is started, the timekeeping operation of the timekeeping means is stopped, and after the stop time t is obtained, the timekeeping means is reset. (Step S3).

3) The measured stop time t seconds is compared with a preset time level T0 seconds, and t
If <T ₀ , the transfer output (transfer voltage applied to the transfer roller 4) is at a necessary and sufficient voltage level (referred to as output L) that does not cause image loss due to image transfer from the photoconductor 1 to the paper P in the transfer nip portion. A command is issued from the control circuit 100 to the power supply 8 to make the setting, and the voltage _VL is applied to the transfer roller 4 (steps S4 → S5).

4) However, if t ≧ T ₀ , a command is issued from the control circuit 100 to the power supply 8 so that the transfer output is set to a voltage level higher than the output L (referred to as output H). Is applied with the voltage VH. However, in the case of continuous copying, the comparison is omitted for only the first sheet and the second and subsequent sheets are reduced to _VL (step S4 → S
6).

In such an operation, if the stop time t from the end of the image forming operation to the start of the next image forming operation is short, the temperature of the entire heating and fixing unit does not decrease so much, and thus the operation described in the above-mentioned section. Thus, also in the next image formation, the scattering of the fixing is small, and it is within an acceptable level.

However, if the stop time t is long, the fixing device 6 cools and returns to the first state in the morning. Therefore, the transfer output is increased to increase the electrostatic force of the toner and the paper P at the time of transfer, thereby suppressing an increase in fixing scattering. .

If the image forming operation continues, the level of the scattering phenomenon of the fixing is improved due to the rise in the temperature of the fixing unit 6, so that there is no problem even if the transfer output is reduced to the original normal value (minimum necessary voltage).

Further, since the transfer output is set high only for one sheet, the damage to the photosensitive member 1 is kept extremely small.

In this embodiment, the set value T ₀ may be set to a time at which the fixing scattering level is allowed, as can be understood from the above description.

In the above example, the output H is set only for the first sheet. However, the output H may be set to the nth sheet, which is not so large that the level of the degree of the splattering phenomenon can be sufficiently recovered. Even in this case, damage to the photoconductor 1 is increased only by the number of sheets.

Reference Example 2 (FIG. 5) In this reference example, the control accuracy is higher than that in the above-described reference example 1 . FIG. 5 is a flowchart of the transfer output determination in this example.

Steps S1 to S3 are the same as the flow of FIG. 4 described above. The feature of this reference example is that the set value of the stop time t is divided into multiple stages, and the transfer output is switched in a plurality of stages according to which level each is.

1) In this example, the set values are determined in three stages T ₀ , T ₁ , T
₂ (steps S4, S5, S6) and T ₀
<T ₁ <T ₂ of a relationship segment times for (setting value), if the measured stop time t is T ₂ or more, the distance from 1 to n ₀ th in the next successive imaging transfer output H ₂ , n ₀ +1
n ₁ th H ₁ transcription output until, n ₁ + 1 to n H ₀ of the transfer output to _second sheet, then returns the output to the normal value L (step S4 → S8 → S9 → S10 → S7). Of course, n ₀ <
n ₁ <n ₂ .

Here, the magnitude of the transfer output is H ₂ > H ₁ > H ₀ >
Since the relationship is L, the output is gradually reduced from high to low.

[0072] 2) the next time the stop time t is in T _2> t ≧ T ₁ segment, a transcription outputs as H1 ₀ th 1 to m, m ₀ +
1~m lowered transfer output to _{the first} sheet in H _0, returns then further transfer output lower then similarly transfer output back down to L to L (step S5 → S11 → S12 → S7) . In addition,
m ₀ <m ₁ .

3) Further, when the pause time t is in the section T ₁ > t ≧ T ₀ , the transfer output is set to H ₀ from the first to the first sheet, and thereafter the transfer output is similarly reduced to L (steps S 6 → S 13).
→ S7).

4) If the stop time t <T ₀ , the transfer output is kept at the normal value L (steps S 6 → S 7).

By doing so, it is possible to control the transfer output more finely than in the above example while suppressing the scattering of the fixing in accordance with the length of the pause time, and the damage to the photoconductor is further reduced.

Each value T _{0 to} T ₂ , L, H _{0 to} H ₂ , n _{0 to} n ₂ ,
m ₀ , m ₁ , and l may be arbitrarily set as the minimum values that allow the fixing scattering to be within an allowable range based on the above-described concept.

Further, it is easy to increase the number of stages more than in this embodiment.

Reference Example 3 (FIG. 6) FIG. 6 is a flowchart for determining a transfer output in this reference example .

[0079] In this reference example, instead of the time measurement in Reference Examples 1 and 2, the temperature of the fixing unit 6 is measured by temperature measuring means, obtained by surveying raising means at the beginning of the next image forming operation The voltage applied to the transfer roller 4 is controlled based on the temperature information. The system used is the same as that shown in FIGS. 1 to 3, and the temperature of the fixing device 6 is detected by the temperature sensing element 20.

[0080] 1) When the copy button 21 is pressed, comparison is made between the fuser temperature C and a predetermined temperature C ₀ detected by the thermosensitive element 20 at that time (step S1 to S3).

2) If the detected temperature C is equal to or higher than the predetermined temperature C ₀ , the transfer output is set to L (step S3 → S6).

3) If the temperature C is lower than the predetermined temperature C ₀ , the transfer output is set to H, and if continuous image formation is performed, this is repeated (steps S3 to S5).

In the present embodiment , the temperature of the heater 15 as a heating element is detected by using a temperature-controlling temperature-sensitive element 20 as the temperature detecting means of the fixing device 6. However, the present invention is not limited to this. A separate temperature sensing element may be provided in the vicinity of the heater 15, particularly on the upstream side in the paper transport direction or outside the heat insulating material to detect the temperature.

<Embodiment> (FIGS. 7 and 8) FIG. 7 is a flowchart of the transfer output determination in the embodiment of the present invention .

[0085] This example, in addition to the time measurements as described in Reference Example 1 and the 2 indicates the control in consideration of the temperature of the fixing unit 6 of Reference Example 3. The system used is the same as that shown in FIGS. 1 to 3, and the temperature of the fixing device 6 is detected by the temperature sensing element 20.

1) When the image formation is completed, the heater 1 of the heat fixing unit 6
5 and the time measurement starts (steps S1 and S2). The temperature sensing element 20 monitors the temperature from the back surface of the heater 15 even during this pause, and the control circuit 10
The detected temperature information to 0 is transmitted.

2) When the next copy button 21 is pressed,
The timing stops and is reset (step S3).

3) If the stop time t measured at this time is less than the predetermined value T ₀ , the image forming process is started with the transfer output L (step S 4 → S 7).

4) If the stop time t ≧ T ₀ , the temperature C measured by the element 20 at the time when the copy button is turned on is determined. If the temperature C is equal to or more than the predetermined value C ₀ , the continuation of the next image formation m The transfer output is H up to the first sheet (however, m = 1 if one image is formed), or up to the nth continuous sheet if C <C ₀ (however, n = 1 if one image is formed). Level
Thereafter, the transfer output is lowered to the L level (step S5 → S
8 → S7 or S5 → S6 → S7).

Here, there is a relation of n> m. That is, if a sufficient time has passed since the end of the previous image formation and the temperature of the heater 15 has been sufficiently lowered, it means that the time of the transfer output H is set to be longer.

By doing so, the accuracy of control for fixing output scattering of transfer output can be further improved. This point will be described with reference to FIG.

FIG. 8 shows the heater 1 detected by the temperature sensing element 20.
FIG. 5 shows the change in the temperature C due to the stop time t, but the speed at which the heater temperature C decreases depends on the previous image forming conditions. For example, after continuous copying, the temperature of the entire fixing unit 6, particularly around the heater 15, is sufficiently warmed, so that the temperature decreases slowly as indicated by the dotted line in the figure.

However, after one copy, the heater is easily cooled because the entire fixing device is not sufficiently heated.
As shown by the solid line in FIG.

In other words, it can be said that the temperature detected by the temperature sensing element 20 during the rest is the ambient temperature including the area around the heater. As described above, if the temperature around the heater is high, the scattering of the fixing is small. Therefore, if the temperature is equal to or higher than the predetermined temperature, the scattering of the fixing will be within the allowable range without setting the transfer output unnecessarily long and high.

Accordingly, the transfer output is determined by both the stop time t and the detected temperature C to determine the number of transfer outputs H and L and the number of sheets at the transfer output H, so that the transfer output can be kept in a state in which the fixing scatter is small, and It is possible to control with high precision so as to minimize the damage to the object.

As can be seen from the above, the values C ₀ , T ₀ , n, and m may be set to the minimum necessary levels that fall within a range in which fixing scattering is allowed.

It is also conceivable to provide a separate temperature sensing element from the heater temperature sensing element 20 to detect the temperature around the heater 15. However, in practice, another element is provided in a narrow space around the heater. This makes the device complex and expensive. From this aspect (simplified and inexpensive), it is preferable to use the temperature-controlling temperature-sensitive element 20 of the heater 15 also.

In this embodiment, as in the second embodiment, if the time section and the detected temperature section are multi-staged and the transfer output is controlled in a plurality of stages, it goes without saying that the accuracy is further improved.

[0099] <Others> Although actual施例image forming apparatus is of an electrophotographic process, image forming process in the present invention, or an electrostatic recording process using a dielectric as an image carrier, a magnetic a magnetic material is used Needless to say, the recording process is optional.

The transfer roller 4 may be another type of transfer rotating member such as a belt or a cylindrical film. The present invention is not limited to a contact-type electrostatic transfer unit, but may be applied to a non-contact-type electrostatic transfer unit such as a corona discharger.

The heating device of the film heating type as the heating fixing device 6 is not limited to the configuration of the embodiment, and as disclosed in JP-A-4-44075 and the like.
A pressure roller drive type that uses a cylindrical film as the fixing film and rotates it with the rotational driving force of the pressure roller.
The device may be a tensionless type device, or may be a device in which a fixing film is formed into a rolled long endless film and the film is run and moved.
The fixing nip may be heated by an electromagnetic heating method. Further, the present invention is not limited to a film heating type apparatus. The present invention is broadly applicable to heat fixing means and devices in which heat is concentrated in and around the fixing nip.

[0102]

As described above, according to the present invention, a recording material on which an image has been electrostatically transferred by an electrostatic transfer method is passed through a fixing nip portion heated by a heating element to heat the image. With respect to the heat fixing type image forming apparatus for fixing, it is possible to suppress the adverse effect on the image carrier due to the transfer voltage applied to the transfer unit and prevent the occurrence of the fixing scattering, or to prevent the level thereof from deteriorating. The purpose of the period is achieved well.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an image forming apparatus according to a reference example 1 .

FIG. 2 is a schematic diagram of a fixing device.

FIG. 3 is a block diagram of a control system.

FIG. 4 is a flowchart of transfer output control.

FIG. 5 is a flowchart of transfer output control according to Reference Example 2 ;

FIG. 6 is a flowchart of transfer output control according to a third embodiment.

FIG. 7 is a flowchart of the transfer output control in Embodiment

FIG. 8 is a temperature transition diagram of a heating element (heater).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor (image carrier) 2 Charging device (charging roller) 3 Developing device 4 Transfer device 5 Cleaner 6 Fixing device 8 Transfer power supply 9 Fixing film 10 Pressure roller 15 Heating body (heater) 20 Temperature sensing element

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/16 G03G 15/00 303 G03G 15/20 101

Claims (5)

(57) [Claims] And 1. A image bearing member, means for forming a transferable image on the image bearing member, and an electrostatic transfer unit for transferring the movable transfer image transfer voltage is applied to the recording material,該被recording Wood,
Transfer by passing through the fixing nip heated by the heater
An image forming apparatus having a heating fixing means for thermally fixing an image, measures the time from stop energization to the heating body of the heating fixing unit ends the imaging operation until the next image forming operation start A temperature measuring means for measuring the temperature of the heating body of the heating / fixing means or the vicinity thereof; information on stop time obtained by the time measuring means at the start of the next image forming operation; Based on the temperature information obtained by the means,
An image forming apparatus comprising a transfer voltage control unit for controlling a voltage applied to the electrostatic transfer unit. An electrostatic transfer means for causing a transfer rotating member to abut on the image carrier to form a transfer nip portion, passing a recording material through the nip portion to nip and transport the recording material; 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is of a contact type that applies a transfer voltage to an inter-transfer rotating member. 3. The heating and fixing means is characterized in that the heating element heats the fixing nip portion intensively and has a quick start property, and immediately after the image forming operation is completed, the power supply to the heating element is stopped. the image forming apparatus according to claim 1 or 2, characterized. 4. A fixing device comprising a film member, a heating member forming a fixing nip portion with the film member interposed therebetween, and an opposing member, wherein recording is performed between the film member and the opposing member in the fixing nip portion. It is a film heating type heating device which heat-fixes an image by heat of the nip portion which is intensively heated by a heating body by introducing a material and energizing the fixing nip portion together with the film member. The image forming apparatus according to claim 1 . 5. The image forming apparatus according to claim 4 , wherein the film member is an endless belt-shaped rotating body.