JP2000162919A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an image with the maximum throughput of an image forming device by the image forming device equipped with a fixing device having plural electrically heating resistance layers whose length is different in a paper width direction. SOLUTION: By providing paper width detection sensors (2nd sheet width detection means) 4b and 4c disposed at specified positions in a sheet width direction in addition to a paper width detection sensor(1st sheet width detection means) 4a, not only the optimum heating pattern of the electrically heating resistance layer is selected by the sensor 4a but also the throughput is controlled for the respective heating patterns by the sensors 4b and 4c, so that the image is formed with the maximum throughput of the image forming device according to the size of sheet material even in the case of forming the image on the irregular size sheet material or the sheet material fed from an optional paper feeding device or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming apparatus such as a copying machine and a laser beam printer.

[0002]

2. Description of the Related Art As an example of the prior art, a printer for recording an image on a sheet material using an electrophotographic process will be described with reference to FIG. FIG. 1 is a longitudinal sectional view illustrating a schematic configuration of a printer (hereinafter, referred to as an “image forming apparatus”) 100.

In an image forming apparatus 100 shown in FIG.
As the paper feed roller 102 rotates, the sheet material S is fed out of the paper feed cassette 101 one by one in the paper feed direction, and is conveyed to the registration roller pair 104 via the intermediate roller pair 103.

The sheet material S is transferred to a photosensitive drum 1 built in a cartridge 105 constituting image forming means by a registration roller pair 104 rotating at a predetermined timing.
06 and the transfer roller 107.

[0005] An electrostatic latent image is formed on the photosensitive drum 106 by laser light from the scanner unit 108, and the toner image is developed on the photosensitive drum 106 by attaching toner to the electrostatic latent image. . Then, the toner image on the photosensitive drum 106 is transferred to the sheet material S by the transfer roller 107.

[0006] The sheet material S after the transfer of the toner image is sent to the fixing device 109 by the conveying force of the photosensitive drum 106 and the transfer roller 107, where the toner image is fixed on the sheet material S. After fixing, the sheet material S is supplied to the discharge roller 11.
0, and are stacked on the stacking tray 111.

[0007]

However, the conventional image forming apparatus 100 has the following problems.

In the electrophotographic system, in the process of fixing the toner transferred to the sheet material, when the number of sheets to be continuously printed (image formed) increases, the fixing device 109 is used.
May rise more than necessary. In particular, when fixing a sheet material S such as an envelope having a narrow sheet width (a dimension in the left-right direction in the conveying direction of the sheet material S; the same applies hereinafter), the fixing device 109 is attached to the sheet material S at the end. Since the heat is not deprived, the temperature tends to rise more than when the A4 size or letter size sheet material S is fixed. Further, when a heater having an electric heating layer on a ceramic flat substrate is used, a great deal of thermal stress may act on the heater and a guide member holding the heater.

In addition, a plurality of resistance heating layers of the fixing device 109 having different lengths in the sheet width direction are prepared, and a plurality of patterns formed by a combination of whether or not power is supplied to the resistance heating layer are controlled. Accordingly, there has been proposed a method of reducing the temperature rise at the end even when the sheet materials S having different sheet widths are passed.

In the image forming apparatus 100 having the fixing device 109, the sheet feeding cassette 101 is provided with a size detecting means for detecting the size of the sheet material S. The layer pattern is set. For example, there are energized heating resistance layers a and b having a length in the sheet width direction of 222 mm and 116 mm, respectively. A sheet width detection sensor is provided at a sheet width of 122 mm, and a sheet material S having a sheet width of 122 mm or more is passed through. The control is performed such that the energized heat generating resistive layer a is used for paper, and the energized heat generating resistive layer b is used for passing the sheet material S of 122 mm or less.

Here, there is a case where the temperature rise at the end becomes a problem even when an optimum pattern of the current-carrying resistance layer is used. For example, when fixing using the energizing heat generating layer a, the temperature rise at the edge does not matter in the case of the letter S or A4 size sheet material S, but the sheet width is much larger than the energizing heat generating layer a such as B5 size or A5 size. In the case of a narrow sheet material S, the temperature rise at the end becomes a problem. To prevent this, the throughput (unit) is increased by increasing the interval between the sheet material S and the succeeding sheet material S according to the detected sheet width. (The number of prints per time) is reduced to prevent the temperature of the end of the fixing device 109 from rising.

Further, one or more sheet width detecting means are provided in the image forming apparatus 100 to feed a sheet material S of an irregular size or a sheet material fed from an optional (external) sheet feeding device. There has been proposed a control method for selecting the most suitable pattern of the current-carrying resistance layer for S.

However, the sheet material S of irregular size
When printing a sheet material S fed from a sheet feeding device or an optional sheet feeding device, even when the selection of the optimal heat generation pattern of the current-carrying heating resistance layer can be set by the sheet width detection means,
The throughput cannot be set in the heat generation pattern of the energization heat generation resistance layer. For this reason, when printing a large amount of sheet material S from a sheet feeding device such as an irregular size sheet material or an envelope feeder which generally does not have a paper size detecting mechanism in the sheet feeding device, it is necessary to raise the end temperature. I print at a constant slow speed to avoid it. For example, if the sheet width is 12
In an image forming apparatus in which the heat-generating resistance layer is switched at a boundary of 2 mm, even when printing a wide sheet material S such as a letter size or an A4 size, it is the same as a narrow sheet material S such as a B5 size or an A5 size. You must print at throughput.

For the above reasons, in the conventional image forming apparatus 100, in order to prevent a temperature rise at the end of the fixing device 109, the sheet material S fed from an irregular size or an external paper feeding device is used. When printing in large quantities, the transport speed has been greatly reduced. This impairs the performance of the image forming apparatus more than necessary.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a sheet width detecting means for controlling a throughput with respect to various heating patterns of a current-carrying heating resistor layer, thereby forming a sheet of irregular size. It is an object of the present invention to provide an image forming apparatus capable of forming an image with the maximum throughput of the image forming apparatus as much as possible even when forming (printing) an image on a sheet material fed from a material or an external sheet feeding device. It is the purpose.

[0016]

According to a first aspect of the present invention, there is provided a fixing device having a plurality of current-carrying resistance layers having different lengths in a sheet width direction, wherein N is a natural number. N first sheet width detecting means when
Depending on whether or not the plurality of current-carrying resistance layers are energized (N
+1) a first control unit for switching the types of heat generation patterns by using a signal from the first sheet width detecting unit, wherein, in addition to the first sheet width detecting unit, a sheet width A second sheet width detecting means disposed at a predetermined position in the direction, and a second control means for changing the throughput in each heat generation pattern using the second sheet width detecting means. , Characterized in that. According to a second aspect of the present invention, in the image forming apparatus of the first aspect, a first sheet corresponding to a sheet member having a maximum printable width is provided.
And a second heat generation pattern corresponding to a sheet width narrower than the sheet width corresponding to the first heat generation pattern. The first heat generation pattern has the same throughput as the maximum width sheet material. The second sheet width detecting means is provided near the left and right side edges of the sheet material having the minimum sheet width that can be maintained.

According to a third aspect of the present invention, in the image forming apparatus of the second aspect, the first sheet width detecting means is disposed between 110 mm and 148 mm in the sheet width direction, and
Of the sheet width detection means in the sheet width direction
mm.

According to a fourth aspect of the present invention, in the image forming apparatus of the second aspect, the first sheet width detecting means is disposed between 110 mm and 148 mm in the sheet width direction, and
98.4 mm in the sheet width direction
mm.

According to a fifth aspect of the present invention, in the image forming apparatus of the second aspect, the first sheet width detecting means is disposed between 110 mm and 148 mm in the sheet width direction, and
Of the sheet width detection means in the sheet width direction
mm and two points between 98.4 mm and 92 mm.

According to a sixth aspect of the present invention, in the image forming apparatus of the first aspect, at least one of the first sheet width detecting means and the second sheet width detecting means is provided in the image forming apparatus main body. It is provided in a removable option.

According to a seventh aspect of the present invention, in the image forming apparatus of the sixth aspect, at least one of the first sheet width detecting means and the second sheet width detecting means is provided as the optional supply. The sheet width is detected by the amount of movement of a sheet width regulating plate that is provided in the paper device and regulates the width direction of the sheet material.

[Operation] In addition to selecting an optimal heating pattern of the current-carrying resistance layer by the first sheet width detecting means, the second sheet width detecting means controls the throughput for each of the heating patterns. Accordingly, even when an image is formed on a sheet material of an irregular size or a sheet material fed from an optional sheet feeding device, the image can be formed at the maximum throughput of the image forming apparatus depending on the size of the sheet material.

[0023]

Embodiments of the present invention will be described below with reference to the drawings.

<Embodiment 1> An image forming apparatus according to the present embodiment will be described with reference to FIGS. 1 to 4 and FIGS. Here, FIG. 1 is a diagram illustrating a state in which an optional cassette 20 and an envelope feeder 10 which are optional sheet feeding devices are mounted on an image forming apparatus using an on-demand fixing device as the fixing device 5. FIG. 2 shows paper width sensors (sheet width detecting means) 4a, 4b, 4c disposed between the registration roller pair 9 and the transfer roller 3.
FIG. 3 is a diagram illustrating sheet widths (sheet widths) of various sheet materials S. FIGS. 3 and 4 are views showing the configuration of the heat-generating resistance layer of the fixing device (fixing means) 5. FIG. And FIG.
FIG. 16 shows the relationship between the paper width of the sheet material S, the detection result thereof, and the heat generation pattern and the throughput depending on the presence or absence of energization to the energization heating resistance layer, and the parenthesized on or off in these figures is controlled. Will be ignored.

In this image forming apparatus, the conveyance of the sheet material S is based on the center. The maximum paper width that can be fed is 216 mm, which is the short side of the letter size. Further, this image forming apparatus can print (image formation) 16 sheets at maximum per minute.

In FIG. 1, reference numeral 1 denotes an image forming apparatus main body;
Is a paper feed cassette, 3 is a transfer roller, 4a, 4b, 4c are paper width sensors (sheet width sensors), 5 is a fixing device, 9 is a pair of registration rollers, 10 is an envelope feeder, and 20 is an optional cassette. Reference numeral 41 denotes a paper feed roller, reference numeral 42 denotes a transport roller, reference numeral 43 denotes a process cartridge in which a drum type electrophotographic photosensitive member (hereinafter, referred to as "photosensitive drum") 44 as an image carrier is incorporated, and reference numeral 45 denotes an exposure device. .

In FIG. 3, reference numeral 6 denotes a ceramic heater;
Reference numerals a and 7b denote electric heating resistance layers, each having a length of 222 m.
m, 116 mm.

Sheet material S that can be used from sheet cassette 2
Are A4 size, letter size and legal size. The optional cassette 20 is a universal cassette different from the paper feed cassette 2 and has a paper width of A5.
Almost any sheet material S having a short side of a size of 148 mm or more and 216 mm or less can be fed. The paper width sensors 4a, 4b, 4c are disposed between the transfer roller 3 and the registration roller 9,
a is set at a position closer to one side of 61 mm, which is slightly outside the energization heating resistance layer 7b from the center line C of the transport path.
In this case, the sheet material S having a paper width of 122 mm or more cuts (covers) this sensor. Since the paper width sensor 4b is installed at a position which is 47 mm closer to one side from the center line C of the conveying path, a sheet material S having a paper width of 94 mm or more cuts off this sensor. Since the paper width sensor 4c is located at a position 98 mm closer to one side from the center line C of the conveyance path, a sheet material S having a paper width of 196 mm or more cuts off this sensor. The sheet material S is used as the paper width sensor 4
When the signals a, 4b, and 4c are turned off, an on signal flows. In the present embodiment, the paper width sensor 4a corresponds to the first sheet width detecting means, and the paper width sensors 4b, 4c
Corresponds to the second sheet width detecting means.

The structure and operation of the fixing device 5 will be described. As shown in FIG. 3, the heating and heating resistor layer of the fixing device 5 includes one long heating and heating resistor layer 7a and one shorter heating and heating resistor layer 7b. The heat generation pattern is fixed by using the long energization heat generation resistive layer 7a depending on the presence or absence of energization of the energization heat generation resistance layer (first heat generation pattern), and fixed using the short energization heat generation resistance layer 7b (second heat generation). Pattern). Paper width sensor 4
“a” is used for controlling switching of these two types of heat generation patterns by the first control means (not shown). The relationship between the paper width of the sheet material S, the detection results by the paper width sensors 4a, 4b, and 4c, the heat generation pattern, and the control of the throughput is shown in FIG.
As described above, the switching of the heat generation pattern by the first control means and the control of the throughput by the second control means (not shown) are performed according to the change in the paper width.
In the present embodiment, the second heat generation pattern is provided near the left and right side edges of the sheet material S having the minimum sheet width capable of maintaining the same throughput as the sheet material S having the maximum width in the first heat generation pattern.
The paper width sensor 4b as the sheet width detecting means is disposed.

Next, the actual printing operation (image forming operation) will be described.

First, the case where paper is fed from the paper feed cassette 2 will be described. Since only the wide sheet material S such as A4 size, letter size, and legal size is supplied from the paper feed cassette 2, the throughput is always 16 ppm as shown in FIG.

Next, a case where paper is fed from the optional cassette 20 will be described. When the sheet material S of A4 size, letter size and legal size is fed, the description is omitted.
Consider the case of printing a sheet material S of B5 size or A5 size. In this case, as shown in FIG.
In order to prevent the temperature from increasing only at the end of the fixing device 5 through which the sheet material S does not pass, the throughput is reduced to 12 ppm and 9 ppm for every fixed number of sheets, and the paper interval (sheet material S) is started. (The distance between the sheet material S and the subsequent sheet material S), the temperature distribution in the width direction in the fixing device 5 is kept constant. In the case of feeding a sheet material S of an irregular size, printing is performed according to the heat generation pattern of FIG.

Next, a case where paper is fed from the envelope feeder 10 will be described. Envelope feeders are C5, B5, DL, mon
Feed an envelope of size arch, com10, 63/4. Further, in addition to envelopes of irregular sizes other than these standard sizes, sheet materials S of the same size can be fed. FIG.
As shown in the figure, the envelopes C5 and B5 are printed by the following method. DL, monarch, and com10 are printed by the method described in the above. If you want to print 6 3/4, print it in the following way.

With the above configuration, the image forming apparatus 1 can be used with the sheet width S of 196 mm or more and 94 to 122 mm by using the three paper width sensors 4a, 4b, and 4c in combination. It is possible to print at the maximum possible speed.

In the above description, the heating and heating resistor layer of the fixing device 5 is composed of two long heating and heating resistor layers 7a and one shorter heating and heating resistor layer 7b as shown in FIG. However, a similar effect can be obtained with another configuration of the energized heating resistor layer. For example, as shown in FIG. 4, a long current-carrying resistance layer 7a, 7c and a short current-carrying resistance layer 7b are formed as a current-carrying resistance layer, each of which is a total of three. Depending on whether the heating resistor layer is energized, fixing is performed using two long heating resistor layers 7a and 7c, and fixing is performed using one long heating resistor layer 7a and a short heating resistor layer 7b. Consider the case where there are two types. At this time, the relationship between the sheet width of the sheet material S and the detection result, the heat generation pattern and the throughput is shown in FIG.
It is represented as

Although the present embodiment has been described using an on-demand fixing device as the fixing device 5, a similar effect can be obtained with the fixing device 5 using a heat roller. Also,
In the present embodiment, the center of the paper conveyance is set at the center, but the same effect can be obtained by an image forming apparatus based on the left end or the right end instead. Further, in this embodiment, the sheet width of the sheet material S on which printing (image formation) can be performed is a letter size,
The same effect can be obtained by changing the position of the paper width sensor in an image forming apparatus which is legal size but has a wider or narrower sheet material S as the maximum paper passing width.
In addition, the same effect can be obtained for an image forming apparatus having a maximum printing speed other than 16 sheets per minute.

<Embodiment 2> FIGS. 3, 5 to 8, 1
This embodiment will be described with reference to FIG. FIG. 5 is a longitudinal sectional view showing a state in which an envelope feeder 10 as an external paper feeder is mounted on the image forming apparatus 1 using an on-demand fixing device as a fixing device. FIG. 6 is a diagram showing one sheet width sensor 4a disposed between the registration roller pair 9 and the transfer roller 3 and the sheet width of various sheet materials S.
7 and 8 are top views of the envelope feeder 10. FIG. In this image forming apparatus 1, paper transport is based on the center. The maximum paper width that can be fed is 216 mm, which is the long side of the letter size and the short side of the legal size. The image forming apparatus 1 can print up to 16 sheets per minute at a maximum.
FIG. 17 shows the relationship between the heat generation pattern and the throughput depending on whether or not current is supplied to the current-carrying resistance layer. In the control pattern, the photointerrupter 11 (FIGS. 7 and 8) is used.
The reason why there is no item is that the sheet material S of this size cannot be fed from the envelope feeder 10. Note that the same reference numerals are given to members having the same configuration, operation, and the like as those in the first embodiment, and description thereof will not be repeated.

7 and 8, 11 is a photo interrupter, 12 sensor levers, 13 is a right rack, 14 is a left rack, 15 is a right side regulating plate (sheet width regulating plate), and 16 is a left side. A regulating plate (sheet width regulating plate).

The envelope feeder 10 will be described. The sheet material S having a width of 90 mm or more and 182 mm or less can be fed from the envelope feeder 10. The user adjusts the paper width by moving the side regulating plates 15 and 16 according to the size of the envelope to be used. The racks 13 and 14 are respectively provided with side regulating plates 15 and 1
Slide 6 in the paper width direction.

Now, the sensor lever 12 is connected to the left rack 14
, The sensor lever 12 also slides in the paper width direction in accordance with the movement of the left side regulating plate 16. In order to allow the user to set a 63/4 size envelope having a paper width of 92 mm in the envelope feeder 10, the side regulating plate 1 is used.
5 and 16, when the sensor lever 1 is moved as shown in FIG.
Since 2 interrupts the photo interrupter 11, the first control means (CPU) detects that 63/4 envelopes are set. 6 3/4 with the narrowest paper width for standard size envelopes
Only the photo interrupter 11 is blocked. Sensor lever 1
When the photo interrupter 2 interrupts the photo interrupter, an on signal flows.

FIG. 1 shows the relationship between the sheet width of the sheet material S to be fed, the detection result, the current-carrying resistance layer, and the throughput.
As shown in FIG.

With the above-described configuration, by using two paper width sensors in combination, the maximum width of the image forming apparatus 1 that can be exhibited by the sheet material S having a paper width of 196 mm or more and 94 to 122 mm is used. It is possible to print at a speed.

Although the present embodiment has been described using an on-demand fixing device as the fixing device 5, a similar effect can be obtained with the fixing device 5 using a heat roller. Further, in the present embodiment, the center is set as a reference for paper conveyance, but the same effect can be obtained with an image forming apparatus based on the left end or the right end. Further, unlike the above-described first embodiment, a paper width sensor for controlling throughput, which is unnecessary when paper is supplied only from the paper supply cassette 2, is provided in the envelope feeder 10 which is an external paper supply device. Therefore, there is also an effect that the cost can be reduced for a user who does not need the envelope feeder 10. In addition, in the present embodiment, the paper width of the sheet material S that can be printed is a letter size or a legal size, but the position of the paper width sensor is also set in an image forming apparatus in which a wider or narrower sheet material S has a maximum width. A similar effect can be obtained by changing.

The same effect can be obtained for an image forming apparatus having a maximum printing speed other than 16 sheets per minute.

<Embodiment 3> This embodiment will be described with reference to FIGS. 9 to 11 and FIG. FIG. 9 is a vertical cross-sectional view showing a state in which an optional paper cassette 20 capable of feeding an envelope is mounted as an external paper feeding device to the image forming apparatus 1. 10 and 11 are top views of the optional cassette 20. FIG. The members having the same configuration and operation as those in the first embodiment and the second embodiment are given the same reference numerals, and the description thereof will not be repeated.

In FIG. 9, reference numeral 20 denotes an optional cassette. 10 and 11, the feeding direction of the sheet S is rightward, 21 is a right side regulating plate, 22 is a left side regulating plate, 23 is a right rack, 24 is a left rack, 25
Is a pinion, 26 is a sensor lever, 27a, 27b, 2
7c is a photo interrupter. FIG. 18 shows the relationship between the sheet material S, the detection result thereof, and the heat generation pattern and the throughput depending on the presence / absence of power supply to the current-carrying resistance layer.

The user adjusts the paper width by moving the side regulating plates 21 and 22 according to the size of the sheet material S to be used. The racks 23 and 24 are respectively provided with side regulating plates 21 and 2
Slide in the paper width direction according to 2.

Since the sensor lever 26 is now attached to the right rack 23, the sensor lever 26 also slides in the paper width direction in accordance with the movement of the right side regulating plate 21. When the sensor lever 26 covers the photo interrupter, o
The signal of n flows. For example, in the case of FIG. 11, when the side regulating plate 21 is slid in accordance with an envelope of 63/4 size, the sensor lever 26 covers all the photo interrupters 27a, 27b, 27c. The relationship between the sheet width of the sheet material S and the on / off of the photo interrupter is as shown in FIG.

FIG. 18 shows the relationship between the sheet width of the sheet S to be fed, the current-carrying resistance layer to be energized, and the throughput.

With the above configuration, by using three paper width sensors in combination, the maximum speed that the image forming apparatus 1 can exhibit with a sheet material S having a paper width of 196 mm or more and 94 to 122 mm is used. To print.

Although the present embodiment has been described using the on-demand fixing device as the fixing device, the same effect can be obtained with the fixing device 5 using a heat roller. In the present embodiment, the center is set as the reference for paper conveyance, but the same effect can be obtained with an image forming apparatus based on the left end or the right end. Further, unlike the above-described first embodiment, a paper width sensor for controlling throughput, which is unnecessary when paper is supplied only from the paper supply cassette 2, is provided in the optional cassette 20 which is an external paper supply device. Therefore, there is also an effect that the cost is reduced for a user who does not need the optional cassette 20. In addition, in the present embodiment, the paper width of the sheet material S that can be printed is a letter size or a legal size, but the position of the paper width sensor is also set in an image forming apparatus in which a wider or narrower sheet material S has a maximum width. A similar effect can be obtained by changing.

<Embodiment 4> FIGS. 12, 13 and 19
This embodiment will be described with reference to FIG. FIG. 12 shows an image forming apparatus using an on-demand fixing device as a fixing device, and an optional cassette 2 as an optional paper feeding device.
FIG. 3 is a vertical cross-sectional view showing a state in which a paper discharge unit 28, which is an optional paper discharge device, is mounted on top of the envelope feeder 10 mounted thereon. FIG. 13 is a diagram showing the widths of the sheet width sensors 29a, 29b, and 29c and the various sheet materials S disposed near the sheet discharge roller 30. Members having the same configuration and operation as those of the first to third embodiments are denoted by the same reference numerals, and description thereof will not be repeated.

In FIG. 12, reference numeral 28 denotes a paper discharge unit, 2
9a, 29b and 29c are paper width sensors, and 30 is a paper discharge roller pair. FIG. 19 shows the relationship between the sheet material S, the detection result thereof, and the heat generation pattern and the throughput depending on the presence or absence of energization to the energization heating resistance layer.

The positions in the width direction when the paper width sensors 29a, 29b and 29c are provided are the same as those of the paper width sensors 4a, 4b and 4c in the first embodiment (see FIG. 2), and are the same as the center lines of the transport path. They are located at positions 61mm, 47mm and 98mm from C, respectively, on one side.

The sheet material S discharged to the paper discharge unit 28
Are paper width sensors 29a, 29b, 29c according to the paper width.
Cut or not cut (covered or uncovered)
I do. The sheet width of the sheet material S and the ON / OFF of the sheet width sensor
The relationship of f is as shown in FIG.

When a paper width sensor is provided in the paper discharge unit 28, the detection result of the sheet material S that has passed through the paper discharge unit is fed back to the second and subsequent prints. It is always printed in the pattern shown in FIG. And 2
The sheet material S after the first sheet is determined according to the detection result of the first sheet.
Is printed with one of the control patterns.

With the above configuration, by using three paper width sensors in combination, the maximum speed that the image forming apparatus 1 can exhibit with a sheet material S having a paper width of 196 mm or more and 94 to 122 mm is used. To print.

Although the present embodiment has been described using the on-demand fixing device as the fixing device, the same effect can be obtained with the fixing device 5 using a heat roller. In the present embodiment, the center is set as the reference for paper conveyance, but the same effect can be obtained with an image forming apparatus based on the left end or the right end. Further, unlike the above-described first to third embodiments, the paper width detection sensor is provided in the optional paper ejection unit 28, so that a plurality of optional paper feeding devices 2 as in this embodiment are provided.
Since the paper width detection sensor only needs to be provided in the paper discharge unit 28 for the image forming apparatus 1 in which the envelope feeder 10 or the image forming apparatus 10 is mounted, there is an effect that the cost can be reduced for the user. In addition, in the present embodiment, the paper width detection sensor is provided in the optional paper discharge unit 28, but the same effect can be obtained by providing the paper width detection sensor in the double-sided printing unit (not shown) which is also an optional device. can get. In the present embodiment, the sheet width of the printable sheet material S is the letter size or the legal size. However, the position of the paper width sensor may be changed even in an image forming apparatus in which a wider or narrower sheet material S has the maximum width. A similar effect can be obtained.

[0059]

As described above, according to the present invention,
Since the first sheet width detecting means can not only select the optimal heat generation pattern of the energized heat generating resistance layer but also control the throughput for each of the heat generation patterns by the second sheet width detecting means, the irregular size When an image is formed on a sheet material supplied from an optional sheet feeding device or the like, an image can be formed at the maximum throughput of the image forming apparatus depending on the size of the sheet material.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus according to a first embodiment with an envelope feeder and an optional cassette mounted.

FIG. 2 is a diagram illustrating a relationship between a sheet width sensor disposed between a registration roller pair and a transfer roller and the width of various sheet materials according to the first embodiment.

FIG. 3 is a diagram illustrating a configuration of a current-carrying resistance layer of the fixing device according to the first embodiment.

FIG. 4 is a diagram illustrating a configuration of another energized heating resistor layer of the fixing device according to the first embodiment.

FIG. 5 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to a second embodiment with an envelope feeder attached.

FIG. 6 is a diagram illustrating a relationship between a sheet width sensor disposed between a registration roller pair and a transfer roller and the width of various sheet materials according to the second embodiment.

FIG. 7 is a top view of the envelope feeder according to the second embodiment.

FIG. 8 is a top view of the envelope feeder according to the second embodiment.

FIG. 9 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to a third embodiment with an optional cassette mounted.

FIG. 10 is a top view of an optional cassette according to the third embodiment.

FIG. 11 is a top view of an optional cassette according to the third embodiment.

FIG. 12 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to a fourth embodiment with an envelope feeder, an optional cassette, and a paper discharge unit mounted.

FIG. 13 is a diagram illustrating a relationship between a sheet width sensor disposed near a sheet discharge roller and widths of various sheet materials according to the fourth embodiment.

FIG. 14 is a longitudinal sectional view illustrating a schematic configuration of a conventional image forming apparatus.

FIG. 15 is a diagram showing a relationship between a paper width of a sheet material, a detection result thereof, and a heat generation pattern depending on whether or not power is supplied to a current-carrying resistance layer according to the first embodiment;

FIG. 16 is a diagram illustrating a relationship between a heat generation pattern and a throughput depending on whether or not power is supplied to a current-carrying resistance layer according to another embodiment of the present invention.

FIG. 17 is a diagram illustrating a relationship between a heat generation pattern and a throughput based on whether or not power is supplied to a current-carrying resistance layer according to the second embodiment.

FIG. 18 is a diagram showing a relationship between a paper width of a sheet material, a detection result thereof, and a heat generation pattern depending on whether or not power is supplied to a current-carrying resistance layer according to the third embodiment;

FIG. 19 is a diagram illustrating a relationship between a paper width of a sheet material, a detection result thereof, and a heat generation pattern depending on whether or not power is supplied to a current-carrying resistance layer according to the fourth embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Paper feed cassette 3 Transfer roller 4a, 27b, 29a 1st sheet width detecting means (paper width sensor) 4b, 4c, 29b, 29c 2nd sheet width detecting means (paper width sensor) 5 Fixing means (fixing) 6) Ceramic heaters 7a, 7b, 7c9 Registration roller pair energized heating resistance layer 10 Optional (paper feeder, envelope feeder) 11 Second sheet width detecting means (photo interrupter) 12, 26 Sensor lever 16, 21 Sheet width regulation Plate (side regulating plate) 20 Optional (sheet feeder, optional cassette) 27a, 27c Second sheet width detecting means (photo interrupter) 27b First sheet width detecting means (photo interrupter) 28 Option (discharge unit) 29a First sheet width detecting means (paper width sensor) S sheet material

Claims (7)

[Claims] 1. A fixing means having a plurality of current-carrying resistance layers having different lengths in a sheet width direction; N first sheet width detecting means when N is a natural number; An image forming apparatus comprising: a first control unit that switches (N + 1) types of heat generation patterns based on the presence or absence of energization of the heat generation resistance layer using a signal of the first sheet width detection unit. In addition to the sheet width detecting means, a second sheet width detecting means disposed at a predetermined position in the sheet width direction, and using the second sheet width detecting means to change the throughput in each heat generation pattern An image forming apparatus, comprising: 2. A first heat generation pattern corresponding to a sheet material having a maximum printable width, and a second heat generation pattern corresponding to a sheet width smaller than the sheet width corresponding to the first heat generation pattern. The second sheet width detecting means is arranged near the left and right side edges of the sheet material having the minimum sheet width capable of maintaining the same throughput as the sheet material having the maximum width in the first heat generation pattern. The image forming apparatus according to claim 1, wherein: 3. The first sheet width detecting means is disposed between 110 mm and 148 mm in the sheet width direction, and the second sheet width detecting means is disposed 210 mm in the sheet width direction.
The image forming apparatus according to claim 2, wherein the image forming apparatus is disposed between the image forming apparatus and the image forming apparatus. 4. The first sheet width detecting means is disposed between 110 mm and 148 mm in the sheet width direction, and the second sheet width detecting means is 98.4 in the sheet width direction.
The image forming apparatus according to claim 2, wherein the image forming apparatus is disposed between mm and 92 mm. 5. The first sheet width detecting means is disposed between 110 mm and 148 mm in the sheet width direction, and the second sheet width detecting means is set to 210 mm in the sheet width direction.
3. The image forming apparatus according to claim 2, wherein the image forming apparatus is disposed at two positions between a distance between 9.4 mm and 182 mm and between 98.4 mm and 92 mm. 6. The image forming apparatus according to claim 1, wherein at least one of the first sheet width detecting unit and the second sheet width detecting unit is provided as an option detachable from the image forming apparatus main body. Item 2. The image forming apparatus according to Item 1. 7. At least one of the first sheet width detecting means and the second sheet width detecting means is provided in the optional sheet feeding device, and regulates a width direction of the sheet material. The image forming apparatus according to claim 6, wherein the sheet width is detected based on a movement amount of the sheet width regulating plate.