JP2003122225A - Heater, heat fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that throughput is lowered more than necessary in the view of the reduction of warming at a part through which no paper passes since throughput in the case of using a paper of 150 mm length, e.g. with which warming at the part through which no paper passes is small is not different from that in the case of a paper of 249 length with which warming at the part through which no paper passes is large, because there is only one step of the distinction level of small sizes and the sizes are sorted only to a normal size not shorter than 250 mm and a small size shorter than 250 mm. SOLUTION: There are at least two steps of paper feeding intervals corresponding to a material to be heated shorter than a prescribed length, and a relation between the paper feeding interval I1 of the shortest material to be heated and the paper feeding interval I2 of a material to be heated which is longer than this by one step is I1<I2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device which heats and discharges a recording material, a transfer material, an OHT (hereinafter also referred to as a recording material) as a heated material which is conveyed and introduced by a heating section, A heat-fixing device that conveys recording materials having different lengths and widths by using an apparatus and heat-fixes an unfixed toner image directly or indirectly formed on the recording material to the recording material, and an electronic device including the heat-fixing device The present invention relates to an image forming apparatus using a photographic method.

[0002]

2. Description of the Related Art Conventionally, for example, a laser printer as shown in FIG. 1 is known as an image forming apparatus using this type of electrophotography.

In this laser printer, as shown in FIG. 1, a sheet as a recording material is guided from a sheet feeding cassette 10 to a sheet feeding guide 7, and the guided sheet is a lever of a top sensor 13 on the conveying path. Then, it is detected that the leading edge of the paper has passed the position of the top sensor 13. The lever of the top sensor 13 returns to its original position when the trailing edge of the sheet passes, and it is detected that the trailing edge of the sheet has passed the position of the top sensor 13. The sheet of which the leading edge has passed the top sensor 13 reaches a transfer portion facing the transfer roller 6 below the photosensitive drum 1, and the toner image on the photosensitive drum 1 is transferred.

The photosensitive drum 1 has a charging roller 1 on the surface thereof.
A uniform and uniform charge is made by 1 and a laser beam L corresponding to the image signal emitted from the laser scanning exposure device 2 is irradiated to form an electrostatic latent image on the surface. The electrostatic latent image is selectively developed by toner by the developing device 2 and developed, and is visualized as a toner image, and is conveyed to the transfer portion as the photosensitive drum 1 rotates. In the transfer section, the transfer roller 6 transfers a toner image onto the paper by applying an electric field having a polarity opposite to that of the toner from the back surface (back surface) of the paper.

The sheet on which the toner image has been transferred is guided to the conveyance guide and reaches the heat fixing device 12, where heat and pressure are applied, and the toner image is fixed on the sheet from the front end of the sheet.

The heat-fixing device 12 is a heat-fixing device using a so-called film heating system having a structure as shown in FIG. A heater 22 serving as a heating body is supported by a heater holder 23, and the nip N is formed by pressing the heater 22 against a pressure roller 25 via a fixing film 21 by a pressure means (not shown). The fixing film 21 is a pressure roller 25.
The recording material introduced into the nip N is conveyed by the rotation of the recording material, and the heat of the heating body is applied to the recording material through the film.

[0007]

Generally, a recording material having various widths and lengths is passed through the image forming apparatus and the heating device thereof. By the way, when a recording material having a particularly narrow width such as an envelope is continuously fed, a temperature rise occurs in a portion which does not pass due to a difference in heat consumption between a portion where the recording material passes and a portion where the recording material does not pass in the heating device. A so-called non-sheet-passing portion temperature increase occurs.

When this phenomenon becomes severe, the thermal expansion of the pressure roller becomes non-uniform, the rubber breaks, the feed speed of the film varies, and twisting occurs. Also,
If the temperature exceeds the heat-resistant temperature of the device, the surface of the pressure roller and the heater holder will melt. Alternatively, if the large size paper is passed immediately after passing the small size paper, the non-paper passing portion of the small size paper becomes hot, so that the toner is excessively melted and the small size paper is not passed. A high temperature offset also occurs in the part corresponding to the part.

Therefore, in order to prevent such a problem, in the conventional apparatus, when a small size paper such as an envelope is passed, the paper feeding interval of the recording material is lengthened, that is, the so-called throughput is lowered to reduce the paper interval. The temperature rise of the non-sheet passing area is reduced for a long time. That is, since the excessive temperature rise of the non-sheet passing portion occurs during the sheet passing, it is possible to suppress the temperature rise to some extent by lengthening the time when there is no sheet, that is, the sheet interval.

As a method for discriminating between small size paper and normal size paper, another sensor is provided on the transport path in addition to the top sensor, and as shown in FIG. There is a method of arranging the sheets of paper at positions where they can be identified.

In the case of FIG. 3, a device which uses the center of the sheet-passage as the reference for the sheet-passage is 68 mm from the center of the sheet-passage reference.
When the top sensor 13 detects the paper and the paper width detection sensor 14 detects the paper, it is recognized as a normal size. When the top sensor 13 detects the paper and the paper width detection sensor 14 does not detect the paper, it is determined that the size is small and narrow.

Although this method can reliably detect small size paper, it is not preferable in terms of cost reduction and downsizing of the apparatus. Therefore, a method of simply recognizing a sheet having a short length as a sheet having a narrow width by using a top sensor is often used. That is, the size of the paper is determined according to the paper presence detection time of the top sensor 13, and for example, a paper having a length of 250 mm or more is a normal size, 250
A size less than mm is determined as a small size with a narrow width, and if the size is small, the throughput is reduced.

By the way, since the mechanism of the temperature rise of the non-sheet passing portion is due to the difference in heat consumption between the portion where the recording material passes and the portion where the recording material does not pass in the heating device, it is the same narrow sheet. However, the degree of temperature rise changes depending on the length. The shorter the length, the shorter the time the sheet stays in the heating nip, and the smaller the difference in heat accumulation between the non-sheet passing portion and the sheet passing portion. Therefore, the temperature rise in the non-sheet passing portion becomes small.

However, conventionally, there is only one level of recognition level for small sizes, and only the normal size having a length of 250 mm or more and the small size having a length of less than 250 mm are classified. Therefore, for example, even if the length of the paper is 150 mm and the temperature of the non-sheet passing portion is slight, the throughput is the same as the paper of the length 249 mm and the temperature of the non-sheet passing portion is large.
There was a case where the throughput was unnecessarily reduced from the viewpoint of reducing the temperature rise in the non-sheet passing portion.

This cannot be said to be a configuration that maximizes the performance of the apparatus in terms of the number of printed sheets per unit time,
There is a problem that it can be said that the configuration is extremely unfavorable.

The present invention has been made to solve the above problems, and prevents destruction / ignition of a heating device and high temperature offset caused by a temperature rise in a non-sheet-passing portion when a small-sized sheet is passed. However, a heating device that improves the performance degradation caused by lowering the throughput at a uniform feeding interval for small size paper and maximizes the capacity of the device with the optimum throughput for each paper size, An object of the present invention is to obtain a heat fixing device using this heating device as a heat source and an image forming apparatus to which the heat fixing device is applied.

[0017]

The present invention is a heating device, a heat fixing device, and an image forming apparatus having the following configurations.

(1) In a heating device which heats and discharges a material to be heated introduced and conveyed in a heating section, it is detected that the length of the material to be heated in the conveying direction is shorter than a predetermined length. At this time, the sheet feeding interval is changed so that at least two sheet feeding intervals corresponding to the material to be heated shorter than the predetermined length are provided, and the sheet feeding interval I1 of the material to be heated having the shortest length is Also, the heating device is characterized in that the relationship with the sheet feeding interval I2 of the material to be heated, which is also one step long, is I1 <I2.

(2) When it is detected that the length of the material to be heated introduced into the apparatus in the conveying direction is shorter than a predetermined length, the heating temperature of the material to be heated and the sheet feeding interval are changed. , The relationship between the heating temperature T1 of the shortest heated material and the heating temperature T0 of the longest heated material longer than the predetermined length is T.
The heating device according to (1), characterized in that 1 <T0.

(3) In a heating and fixing device for conveying under pressure a heated material having an unfixed toner image formed thereon and heating and fixing the unfixed toner image on the heated material, the heated material A heating / fixing device comprising the heating device according to (1) or (2) as a heating device for heating.

(4) Conveying means for conveying the heated material from the feeding section to the discharging section, image forming means for directly or indirectly forming an unfixed toner image on the heated material being conveyed, and An image forming apparatus having a heat fixing means for heat-fixing an unfixed toner image formed on a material to be heated on the material to be heated, comprising the heat fixing device according to (3) as the heat fixing means. An image forming apparatus characterized by.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings.

(Embodiment 1) Since the mechanical constitution of the heat fixing device using the heating device of the present invention and the image forming apparatus to which the heat fixing device is applied is the same as the constitution shown in FIG. 1 and FIG. A duplicate description will be omitted.

In this embodiment, the maximum paper width is LETTER.
Size, process speed 150mm / sec, A4
An apparatus that outputs 24 sheets / minute of size paper will be described as an example.

In FIG. 1, when a print command is input to the apparatus, the sheet as a recording material fed from the sheet feeding cassette 10 is guided to the sheet feeding guide 7 and is finally on the conveyance path. Then, it is detected that the leading edge of the paper has passed the position of the top sensor 13.
After this, until the trailing edge of the paper passes the top sensor 13,
The top sensor 13 continues to detect the presence of paper.

Eventually, the paper reaches the transfer portion facing the transfer roller 6 below the photosensitive drum. On the photosensitive drum 1,
After being uniformly and uniformly charged by the charging roller 11,
A laser beam L corresponding to an image signal emitted from the laser scanning exposure device 3 is irradiated to form an electrostatic latent image on the surface.
The electrostatic latent image is visualized as a toner image by selectively adhering toner to it by the developing device 2.
It is conveyed to the transfer unit as the paper rotates.

In the transfer section, the transfer roller 6 transfers the toner image onto the paper by applying an electric field having a polarity opposite to that of the toner from the back surface of the paper. The sheet on which the toner image has been transferred is guided to a conveyance guide and reaches a fixing device 12, which is a film heating type heating device, where heat and pressure are applied, and the toner image is fixed on the sheet from the leading edge of the sheet. Go.

When the trailing edge of the sheet passes the position of the top sensor 13, the lever of the top sensor 13 returns to its original position, and it is detected that the trailing edge of the sheet has passed the position of the top sensor 13. That is, the top sensor 13 detects that there is no sheet (no sheet). Then, in the case of continuous printing, feed the next paper at regular intervals,
Prints are generated through a similar process.

The paper throughput is determined by the top sensor 13
Is maintained by feeding the next sheet after a lapse of a certain time after detecting the leading edge or the trailing edge of the sheet. When so-called small size paper is passed with a narrow width, the time during which the top sensor detects the presence of paper is shorter than when normal size paper is passed. By doing this, the normal size paper and the small size paper are discriminated, and when it is judged that the small size paper is used, the paper feeding interval is widened to reduce the throughput,
To reduce the temperature rise in the non-sheet passing area when passing small size paper.

In this embodiment, there are two detection levels for this small size paper.

When a normal A4 sheet (length 297 mm) is passed, it is detected that the length of the sheet is 250 mm or more, so the sheet feeding interval I0 for the regular sheet is set. Since the throughput is maintained at 24 sheets / minute, the sheet feeding interval I0 is 2.5 sec.

On the other hand, when it is detected that the length is less than 250 mm, the sheet feeding interval I2 in the small size is set, and the continuous printing of the sheet is performed at the throughput of 10 sheets / minute and the sheet feeding interval of 6 sec. Further, when a smaller size sheet is passed and it is detected that the length is 200 mm or less, the sheet feeding interval I1 for the small size is set, the throughput is 12 sheets / minute, and the sheet feeding interval is 5 sec.

As described above, the temperature rise of the non-sheet passing portion due to the narrow paper becomes higher as the paper is passing through the heating nip for a longer time = the longer the paper is. In that respect, the width of the paper is narrow and the length of the paper is A4 size or more.

However, according to the knowledge of the inventor of the present invention, in the paper generally used in the printer, the length which is the most strict for the temperature rise in the non-sheet passing portion is the length in the width direction and the length direction. Most envelopes are about 250 mm. Therefore, in this embodiment, the length is 250 mm or less, the throughput is reduced, and the temperature rise of the non-sheet passing portion is suppressed.

On the other hand, even when the width of the paper is narrow, the time during which the paper is passing through the heating nip is short = the length of the paper is short, the shorter the paper is, the smaller the temperature rise of the non-sheet passing portion is. Become. That is, in comparison with the throughput assuming an envelope with a length of about 250 mm and a width of about 100 mm in which the temperature rise in the non-sheet passing portion is the most severe in actual use, if the paper length is shorter than this, the throughput will not increase. The temperature rise in the paper passing area does not matter.

Therefore, in this embodiment, the length is 200 mm.
The throughput applied to a sheet of up to 250 mm is set to the minimum, and the throughput is increased for a sheet shorter than 200 mm and a length of less than 200 mm.

The relationship between the paper length, the paper feed interval, and the throughput in this embodiment is shown in Table 1 below.

[0038]

[Table 1]

If the conventional paper having a length of about 250 mm and the temperature at which the most non-sheet passing portion is heated is the standard, and the lengths shorter than this are treated as the same small size paper, how is it processed? Even if a short paper size was passed, the throughput could not be increased, resulting in a decrease in performance.

On the other hand, in the present embodiment, the standard for small size paper is set to the size where the temperature rise of the non-sheet passing portion is the most severe and the size of which the length is shorter and the temperature rise of the non-sheet passing portion is slight. By finely dividing and setting the paper feed interval respectively, problems such as device destruction due to temperature rise in the non-sheet passing area do not occur, and printing is performed with optimal throughput according to the paper size compared to the conventional one. It was possible to improve the performance.

By the way, in the above example, the setting level of the sheet feeding interval of the small size paper is set to two stages, but it is naturally possible to divide it more finely. For example, when the setting level for small size paper is set to four levels, a switching table as shown in Table 2 below can be used.

[0042]

[Table 2]

As is clear from this example, in the case of a paper having a size smaller than that of the normal size paper, particularly an extremely small width in the width direction orthogonal to the length in the carrying direction such as an envelope, the paper length The shorter the length, the shorter the paper feed interval. Therefore, the feeding interval I2 of the sheet having a length one step longer than the feeding interval I2 of the sheet having the shortest length.
Can always be I1 <I2.

(Embodiment 2) In this embodiment, as in the case of Embodiment 1, when the small size paper is passed, the throughput is switched in several steps according to the length of the paper in the conveying direction and the fixing of the heat fixing device 12 is carried out. Control to switch the temperature.

When the toner image is fixed on the paper by heat and pressure, the fixing property is generally worse at the rear end of the paper than at the front end of the paper. This is because the amount of heat stored in the heat fixing device before it enters the heat fixing device is gradually taken away by the passage of the paper, and the physical property verification is that the temperature drop of the pressure roller 25 during paper passing is performed. It can be easily confirmed by measuring that the heat storage amount of the heat fixing device itself decreases toward the trailing edge of the paper.

Usually, as the fixing temperature of the heat fixing device,
The fixing property at the trailing edge is set to a satisfactory level.

From this fact, it can be presumed from the fact that the paper having a short length has a shorter length and thus is more advantageous to the deterioration of the fixing property at the trailing edge than the normal size such as A4 size. That is, in the case of small-sized paper having a short length, it is possible to fix the image at a temperature lower than the fixing temperature set for the normal-sized paper. It can be said that the fixing temperature can be lowered.

Needless to say, the lower the fixing temperature, the lower the temperature rise in the non-sheet passing portion. On the contrary, the lower the fixing temperature, the lower the fixing temperature according to the length. so,
It is shown that the throughput can be further increased as compared with the case of the first embodiment.

In view of the above, in the present embodiment, the switching between the throughput and the fixing temperature corresponding to the length when the small size paper is passed is set as shown in Table 3 below.

[0050]

[Table 3]

With the above-mentioned configuration, problems such as melting and ignition of the apparatus when the temperature of the non-sheet passing portion is raised during passing of a small size sheet are not caused, and the apparatus performance is further improved as compared with the first embodiment. It has become possible to improve.

By the way, in the above table, the fixing temperatures are all different values for each paper size, but in the case of the present embodiment, it is not always necessary to do so, and for example, shown in Table 4 below. As described above, the fixing temperature may be switched in two steps with respect to three steps in the sheet feeding interval including the normal size.

[0053]

[Table 4]

Needless to say, the detection setting level for small size paper is not limited to two levels in this embodiment as in the first embodiment.

[0055]

As described above, according to the present invention,
In a heating device that heats and discharges the heated material that is conveyed and introduced in the heating unit, it is detected that the heated material that is conveyed and introduced into the device has a length in the conveying direction that is shorter than a predetermined length. When the sheet feeding interval changes, the sheet feeding interval changes, and at least two sheet feeding intervals corresponding to the material to be heated shorter than the predetermined length are provided, and the sheet feeding interval I1 for the material to be heated having the shortest length, Since the relation with the sheet feeding interval I2 for the material to be heated, which is one step longer than this, is set to I1 <I2, the throughput is conventionally reduced with a uniform sheet feeding interval for small size paper. It has become possible to improve the performance degradation caused by the above-mentioned problems and to bring out the capability of the device with the optimum throughput for each paper size.

According to the present invention, when it is detected that the length of the heated material conveyed and introduced into the apparatus is shorter than the predetermined length, the heating temperature and supply of the heated material are increased. Since the paper interval changes and the heating temperature T1 for the material to be heated having the shortest length and the heating temperature T0 for the material to be heated longer than the predetermined length are set to T1 <T0, While preventing the destruction / ignition of the heating device and the high temperature offset caused by the temperature rise in the non-sheet passing area during size passing, the performance is further improved and the throughput of the device is optimized for each paper size. It has become possible to create a configuration that maximizes the ability.

According to the present invention, in the heat fixing device for heating and fixing the unfixed toner image on the heated material, the heated material having the unfixed toner image formed on the surface thereof is conveyed under pressure. Since the heating device of the present invention is provided as a heating device for heating the material to be heated, it is possible to realize a highly efficient heat fixing device with less power loss, and it is possible to prevent deterioration of device reliability due to heat generation or the like. Therefore, it is possible to always perform stable heat fixing processing.

According to the present invention, the image forming means for directly or indirectly forming the unfixed toner image on the heated material, and the unfixed toner image formed on the heated material on the heated material. In the image forming apparatus, the heat fixing unit for heat fixing is provided with the heat fixing device of the present invention as the heat fixing unit, so that it is possible to prevent deterioration of the reliability of the device due to heat generation, etc. It has become possible to perform stable and high-precision printing.

[Brief description of drawings]

FIG. 1 is a schematic view showing an image forming apparatus of the present invention and a conventional image forming apparatus.

FIG. 2 is a schematic sectional view showing a heating device of the present invention.

[Fig.3] Layout of sensors for detecting small size paper

[Explanation of symbols]

P paper (recording material) 1 photosensitive drum 2 Development device 3 Laser scanning exposure equipment 6 Transfer roller 11 charging roller 12 Heating device 13 Top sensor

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H027 DA12 DC05 DC10 DE01 DE07                       DE09 EA12 EA15 EC02 EC06                       EC09 ED17 ED25 EE02 EE05                       EF09                 2H033 AA20 BA09 BA10 BA11 BA25                       BA59 BB18 BB28 BB33 BB34                       BB37 BE03 CA07 CA17 CA22                       CA23 CA35 CA37 CA44

Claims (4)

[Claims] 1. A heating device that heats and discharges a material to be heated that is conveyed and introduced by a heating unit, when it is detected that the length of the material to be heated in the conveying direction is shorter than a predetermined length. The paper feed interval is changed to have at least two stages of paper feed intervals corresponding to the material to be heated shorter than the predetermined length, and the paper feed interval I1 of the material to be heated having the shortest length.
And the feeding interval I of the heated material which is one step longer than this
The heating device characterized in that the relation with 2 is set so that I1 <I2. When wherein the length in the conveying direction of the material to be heated introduced transport device in is detected as being shorter than the predetermined length, changing the heating temperature Contact and feeding interval of the heated material ,
The relationship between the heating temperature T1 of the material to be heated having the shortest length and the heating temperature T0 of the material to be heated longer than the predetermined length is T1 <T.
The heating device according to claim 1, wherein the heating device is set to 0. 3. A heating fixing device for conveying a heated material having an unfixed toner image formed on its surface with a pressure to heat and fix the unfixed toner image on the heated material. Claim 1 or Claim 2 as a heating device for heating
A heating and fixing device comprising the heating device according to any one of the above. 4. A conveying means for conveying a heated material from a feeding section to a discharging section, an image forming means for directly or indirectly forming an unfixed toner image on the heated material being conveyed, An image forming apparatus having a heat fixing means for heat-fixing an unfixed toner image formed on a heating material onto the heated material, comprising the heat fixing device according to claim 3 as the heat fixing means. A characteristic image forming apparatus.