JPH045676A - Image forming device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

[0001]

[Industrial application field]

The present invention relates to an image forming apparatus using an electrophotographic process. [0002]

[Prior Art] Recently, as a means of writing addresses on a large number of envelopes, it has become common practice to read address information stored in a storage means as an electrical signal, input it to a printer, and print characters corresponding to the electrical signal. It's starting to look like this. [0003] Printing using a printer is extremely fast, but when using a print head, the thickness of paper that can be printed on is limited to that of ordinary recording paper, and it is difficult to print addresses directly on envelopes. It is common practice to print on plain paper using a printer, cut it to an appropriate size, and paste it on an envelope, but this has the disadvantage of hindering work efficiency. [0004] In a laser printer that uses an electrophotographic process, a toner image is formed on a photoreceptor in accordance with an information signal, this is transferred to transfer paper, and the transferred toner image is heated by a fixing device and fused to the transfer paper. If you are using transfer paper made of multiple sheets of paper pasted together into a bag like an envelope, multiple sheets of paper bound together, or fairly thick cardboard, the following applies: There are problems like this. [0005] One of them is related to the transfer of toner images, and when the transfer paper is made of multiple sheets stacked one on top of the other, not only does the total thickness of the paper become thicker, but also a layer of air is created between each sheet of paper. For,
It is difficult for the surface to which the toner is transferred to be charged to the required charge by the corona discharger type transfer charger, resulting in transfer failure. The same applies to cardboard. [0006] Another problem is that when a heat roller fixing device consisting of a heating roller and a pressure roller is used, the envelope is passed between a pair of rollers that are pressed together with a fixing pressure suitable for fixing plain paper. If this happens, the pressure may cause wrinkles to form, or the air inside may collect at the rear end, causing the product to burst. or,
Prevents the leading edge of the paper from getting caught in the nip of the roller pair.
Timing discrepancies may occur. Furthermore, there is a difference in temperature between the paper on the side in contact with the heating roller and the paper on the side in contact with the pressure roller, and the envelope may become distorted and pressurized, which may cause wrinkles or creases. [0007] As a means to solve these problems, the power supply that applies voltage to the transfer charger is provided so that the transfer current can be changed, and the fixing pressure of the fixing device is variable. It is known to switch between the case of recording paper and the case of envelope or cardboard. [0008] Conventionally, the switching has been carried out manually depending on the transfer paper used by the operator, or by detecting the size of the transfer paper and detecting whether it is a regular paper or an envelope, and depending on the output. When switching automatically to a certain force manually, the switching operation is often forgotten, and when using a device that detects the transfer paper size to determine whether it is plain paper or an envelope, the envelope size is not always required. The size of the paper is not constant, and in cases where the circumference of ordinary paper is the same as that of large paper, accurate detection cannot be performed and there are many false detections. [0009]

[Problem to be solved by the invention]

In view of the above-mentioned circumstances, the present invention has a simple structure and is capable of more reliably detecting whether the transfer paper to be used is normal paper, a paper made of multiple papers such as an envelope, or cardboard. An object of the present invention is to provide an image forming apparatus equipped with a detecting means capable of detecting images. [0010]

[Means to solve the problem]

In order to solve the above problems, two inventions are proposed. [0011] The first invention uses the action of a transfer charger to transfer a toner image formed on a photoreceptor by an electrophotographic process to a transfer material that is fed to the photoreceptor by a conveyance roller consisting of a pair of upper and lower rollers. In an image forming apparatus that transfers images to a sheet of paper and fixes them using a fixing device consisting of a heating roller and a pressure roller that is in pressure contact with the heating roller, the shaft of each roller is attached to the end of the same side of the pair of rollers that make up the conveyance roller. A magnetic member is rotatably supported and has surfaces facing each other, and a magnetic circuit is provided to form a magnetic flux penetrating the gap between the facing surfaces.
A Hall element is provided in the gap between the two magnetic members, and the Hall element detects the magnetic flux density passing through the gap, which changes according to the amount of the gap, which changes depending on the thickness of the transfer material passing through the conveyance roller. It is characterized by detecting the thickness of the transfer material. [0012] The second invention transfers a toner image formed on a photoreceptor by an electrophotographic process to a transfer material that is fed to the photoreceptor at a timing by a pair of registration rollers that rotate intermittently, by the action of a transfer charger. In an image forming device that transfers the original material and fixes it using a fixing device consisting of a heating roller and a pressure roller that is in pressure contact with the heating roller, the amount of deflection of the transfer material formed by the intermittent rotation of the pair of registration rollers is detected. and a determining means that determines the thickness of the transfer material based on the detection signal of the range of deflection of the transfer material detected by the detection means [0013]

[Effect]

According to the configuration of the first invention, the axial distance between the pair of rollers constituting the conveying roller changes depending on the thickness of the transfer paper, and
The gap between the opposing surfaces of the pair of magnetic members changes, and the magnetic flux density penetrating the gap changes accordingly. This magnetic flux density is detected by a Hall element provided in the gap, and the amount of the gap is detected from its output. [0014] According to the configuration of the second invention, as the thickness of the transfer material increases, when the tip of the transfer material collides with the nip portion of the pair of registration rollers whose rotation is stopped, the transfer material Due to its own strain, it does not easily flex.\ Slip occurs between the registration roller and the conveyance roller on the upstream side, and the amount of flex is reduced compared to paper of normal thickness. Therefore, the thickness of the transfer material can be determined by detecting the range in which the amount of deflection exists using the detection means that detects the amount of deflection of the transfer material. [0015] Therefore, by making the transfer current of the transfer charger and the fixing pressure of the heat roller fixing device variable, the transfer current and fixing pressure can be adjusted according to the output of the Hall element or the filter paper thickness detected by the deflection amount detection means. It becomes possible to change. [0016]

【Example】

Embodiments of the present invention will be described in detail below based on the drawings. [0017] FIG. 1 is a diagram showing the configuration of the main parts of a laser printer to which the present invention is applied. A writing position by a laser writing optical system 2, a developing device 3, and a transfer charger 4 are arranged around the photosensitive drum 1 in the order of the rotational direction shown by the arrow. From the paper source that does not
Transfer paper 6 is fed via a pair of registration rollers 5. In the transfer section, the toner image on the photoreceptor drum 1 is transferred to a transfer paper 6 under the action of a transfer charger 4, and then the transfer paper 6 is conveyed to a heat roller fixing device 7, where it is fixed and then transferred outside the machine. The paper is output to the output tray. [0018] A power pack 8 is connected to the transfer charger 4 and is capable of switching transfer current in two stages. Further, the tension of the pressure spring 73 that presses the pressure roller 72 against the fixing roller 71 of the fixing device 7 is variable. [0019] In the apparatus of the first invention, the thickness of the transfer material is detected by detecting a change in the gap between the pair of registration rollers. Its specific configuration is shown in FIGS. 2 and 3. [00201 The registration roller pair 5 is made up of a lower registration roller 50 made of a rubber material and a core metal and an upper registration roller 51 made of only a rigid roller, which are pressed against each other, and the transfer paper 6 is held and conveyed by the pressure contact part. be done. At one end of the upper roller 51, a magnetic relay ring 52, a permanent magnet 53, and a bearing 54 are rotatably supported on the shaft of the roller 51. On the other hand, a magnetic relay rubber 56 and a yoke plate 55 are rotatably supported on the shaft of the lower roller 50. Further, the yoke plate 55 is also fixed to the machine frame. The lower surface of the bearing 54 and the upper surface of the yoke plate 55 face each other with a gap L in between, and the outer peripheral surfaces of the magnetic relay ring 52 and the magnetic relay rubber 56 also face each other with a gap 1 in between. Therefore, 52,53
, 54, 55, and 56 constitute a magnetic circuit. Magnet ring 52, bearing 54 and yoke plate 55
is made of a magnetic material with excellent magnetic properties, and the magnetic relay rubber 56 is also made of magnetic rubber with excellent magnetic properties, and has the same hardness and outer diameter as the lower registration roller 50. [0021] Furthermore, a Hall element 31 is attached to the gap between the bearing 54 and the yoke plate 55 as shown in FIGS. 2 and 3, and the magnetic flux density B passing through this gap L can be measured. . [0022] A magnetic flow is formed as shown by the continuous arrows in FIG. 3, and the gaps 1 and L are designed to be as small as possible without the transfer material intervening. [0023] With the above configuration, when the gap 1 and L change depending on the thickness of the transfer paper 6 passing between the pair of registration rollers 50 and 51, the magnetic flux density B passing through the gear L portion changes accordingly, As a result, not only the thickness of the transfer material but also the presence or absence of the transfer material can be detected. [0024] The theory by which the thickness of the transfer material can be detected by measuring the magnetic flux density is as follows. [0025] Hm is the magnetomotive force per unit of magnet, Lm is the magnet thickness, Hg
If is the magnetomotive force per unit lost in the gap, this is expressed by the following equation. [0026]

[Equation 1] HmLm=Hg (L+l) [0027] Assume that the effective cross-sectional area of the gap and the first part are the same, and that there is no leakage coefficient or magnetomotive force loss at the joint surface of the relay plate. . [0028] According to equation (1), when the transfer material is thin, L+1 becomes small and Hm becomes small. When the transfer material is thick, L+1 becomes large and Hm becomes large. -H if there is no transfer material. Thin case→Ha ri Thick case −Hb (Ho<Ha<Hb) Then, from the demagnetization curve shown in Fig. 4, the respective operating points o, a, and b can be found, and the magnetic flux densities Bo and Ba at that time are ,Bb
is found. Note that Po, Pa, and Pb in the figure are permeance coefficients at respective operating points. Magnetic flux density Bo, Ba
, Bb are as follows. B o > B a > B b , B○: Magnetic flux density when there is no transfer material Ba: ri thin ri Bb: // thick ri Based on the above theory, the thickness of the transfer material can be detected by the Hall element. As shown in FIG. 5, the output of the Hall element 31 is input to the CPU 32, and the thickness of the transfer material is calculated based on the above theory.
The output voltage of the screw 8 and the fixing pressure of the fixing device 7 are changed as necessary. [0029] Next, the configuration of an embodiment of the second invention will be described. [0030] FIG. 6 shows this embodiment. It is a diagram showing the configuration near the registration roller pair 5 of the example device.The lower side of a pair of guide members forming a transfer paper conveyance path between the registration roller pair 5 and the conveyance roller pair 9 on the upstream side thereof. The guide member 10 is provided just below and generally parallel to the straight line connecting the respective nips of the pair of transport rollers 9 and the pair of registration rollers 5;
Registration rollers arranged such that the distance from the lower guide member 10 is wider at the transport roller pair 9 than near the nip between the registration roller pair 5, and the leading end of the transfer material 6 sent out from the transport roller pair 9 is stopped. After colliding with the nip portion of the pair 5, the transfer paper 6 is fed for a predetermined amount of time, allowing the transfer paper 6 to protrude upward and bend as shown in the figure. The transfer material 6 is strained so that its leading edge collides with the nip of the pair of registration rollers to correct skew feeding, and at the same time, the leading edge of the transfer material 6 is brought into contact with the registration rollers at the timing when the leading edge of the image area on the photoconductor 1 is aligned with the leading edge of the image area at the transfer section. When the pair 5 starts rotating, it is immediately conveyed at a predetermined conveyance speed. In the apparatus of this embodiment, in order to detect the amount of deflection δ of the transfer material 6 caused by the pair of registration rollers 5, the upper conveyance guide 11 is provided with a portion of the transfer paper that is pushed near the peak of the deflection of the transfer paper so as to be rotatable around the fulcrum 12. a feeler 13 that moves and a light shielding plate 1 that rotates integrally with the feeler 13;
4 and a photosensor 15 operated by a light shielding plate 14 are provided. Depending on the deflection that occurs when normal transfer paper is fed, the feeler 13 and light shielding plate 14 move to the position shown by the broken line, and the photo sensor 15, which had been blocked, moves to the position shown by the broken line.
to open the optical path. However, when conveying envelopes, cardboard, etc. as transfer materials, they are stiff and difficult to bend.・They slip with the conveyance roller pair 9, and the deflection caused by the registration roller pair results in the condition shown by the broken line in FIG. 6, for example, and the feeler 13 and therefore the light shielding plate 14 does not activate the photosensor 15. [0031] The output of the photosensor 15 is as shown in FIG.
is input to determine whether the transfer material is regular paper or thick material such as an envelope or cardboard. Based on the results, the power pack 8 is switched to a transfer current suitable for the transfer material,
Switching the tension of the pressure spring 73 of the fixing device 7 is the same as in the case of the device of the first invention. [0032] As shown in FIG. 6, when a photosensor operated by a feeler is used as a deflection amount detection sensor, it can be used as a force plate sensor that can only detect two levels of deflection: above or below a certain value. If a differential transformer is used, as shown in Fig. 8, it is possible to obtain a voltage that corresponds to the change in the amount of deflection δ, so it is possible to distinguish between three or more types of transfer materials, and the transfer current etc. can be adjusted in several steps accordingly. It is also possible to control the [0033]

【Effect of the invention】

As described above, according to the present invention, it is possible to reliably determine the presence or absence of a transfer material and the thickness of the transfer material, and it is possible to automatically switch the transfer current and fixing pressure to values suitable for the thickness of the transfer material. Therefore, it is possible to obtain a good image without wrinkles, curls, damage, etc. of the transfer material.

[Brief explanation of the drawing]

FIG. 1 is a side cross-sectional view showing the configuration of essential parts of a laser printer as an example of an image forming apparatus to which the present invention is applied.

FIG. 2 is an exploded perspective view showing the configuration of a transfer material thickness detection mechanism as an embodiment of the first invention.

[Figure 3] FIG.

[Figure 4] It is a curve diagram showing an example of a demagnetization curve of a permanent magnet.

FIG. 5 is an example of a block diagram of transfer current and fixing pressure control based on transfer material thickness detection according to the first invention.

[Figure 6] FIG. 7 is a sectional view showing a transfer material thickness detection mechanism of a second invention.

FIG. 7 is an example of a block diagram of transfer current and fixing pressure control based on transfer material thickness detection according to the second invention.

FIG. 8 is a curve diagram showing the relationship between the amount of deflection and the amount of voltage when a differential transformer is used as means for detecting the amount of deflection of the transfer material by the registration rollers.

[Explanation of symbols]

1 Photoconductor 4 Transfer charger 5 Registration roller (conveyance roller) 6 Transfer paper (transfer material) 7 Fixing device 8 Power back (transfer current application device) 9 Conveyance roller pair 11 Upper guide member 13 Feeler 14 Light shielding plate 15 Photo sensor (transfer Material deflection amount detection means) 31
Hall element 32 CPU (transfer material thickness determining means) 50 Lower registration roller 51 Upper registration roller 52, 53, 54, 55° 52 Magnetic ring 53 Permanent magnet 54 Bearing 55 Yoke plate 56 Magnetic rubber 71 Fixing roller 72 Pressure roller 73 Pressure spring L Gear rough magnetic circuit forming part

【Document name】

drawing

[Figure 1]

[Figure 2]

[Figure 3]

[Figure 4]

[Figure 6]

[Figure 8]

Claims (6)

[Claims] Claim 1: A toner image formed on a photoreceptor by an electrophotographic process is transferred to a transfer material, which is fed to the photoreceptor by a conveyance roller consisting of a pair of upper and lower rollers, under the action of a transfer charger. In an image forming apparatus that performs fixing using a fixing device consisting of a heating roller and a pressure roller that is in pressure contact with the heating roller, the shafts of each roller are rotatably attached to ends on the same side of a pair of rollers constituting the transport roller. A magnetic member having surfaces facing each other is provided, a magnetic circuit is provided for forming a magnetic flux passing through the gap between the opposing surfaces, a Hall element is provided in the gap between the two magnetic members, and the conveying roller is provided with a magnetic member having surfaces facing each other. An image forming apparatus characterized in that the thickness of the transfer material is detected by using the Hall element to detect the magnetic flux density penetrating the gap that changes depending on the amount of the gap that changes depending on the thickness of the transfer material passing through. 2. The transfer current of the transfer charger is variable, and the transfer current is controlled to be changed in accordance with the thickness of the transfer material detected from the output of the Hall element. The image forming apparatus according to claim 1. 3. The pressing force between the heating roller and the pressure roller of the fixing device is variable, and the pressing force is changed according to the thickness of the transfer material detected from the output of the Hall element. The image forming apparatus according to claim 1, further comprising means for controlling. 4. A toner image formed on a photoreceptor by an electrophotographic process is transferred to a transfer material fed to the photoreceptor at a timing by a pair of intermittently rotating registration rollers under the action of a transfer charger. In an image forming apparatus that performs fixing using a fixing device that includes a heating roller and a pressure roller that is in pressure contact with the heating roller, there is provided a detection means for detecting the amount of deflection of the transfer material formed by the intermittent rotation of the pair of registration rollers. , a determining means for determining the thickness of the transfer material based on the detection signal of the range in which the amount of deflection of the transfer material is detected by the detecting means. 5. A method of controlling the transfer current of the transfer charger so as to make the transfer current variable, and controlling the transfer current to vary according to the thickness of the transfer material determined by the determining means. The image forming apparatus according to item 4. 6. The pressing force between the heating roller and the pressure roller of the fixing device is variable, and the pressing force is controlled to be changed in accordance with the thickness of the transfer material determined by the determining means. The image forming apparatus according to claim 4, further comprising means.