JP2003294401A - Displacement detector and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the cost of a paper thickness detection means while enhancing reliability using inexpensive parts for the purpose of solving the problem that, it is necessary to use expensive parts in a conventional paper thickness detection means in order to stably perform accurate detection, and the reliability of the paper thickness detection means is lowered if inexpensive parts are used. <P>SOLUTION: A means for putting the fulcrum 23 of a lever member 21 to the leading end of the lever member 21 to amplify the quantity of displacement of the leading end of a lever by the rear end of the lever is used, and a means for branching the rear end of a second lever 26 into a plurality of parts and detecting the presence of the passage of the rear ends of the branched levers is also used to convert the number of times of the passage of the rear end of the levers to displacement to detect the displacement. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for discriminating a minute amount of displacement and a thickness of various kinds of objects to be measured,
In particular, the present invention relates to an image forming apparatus having a recording material conveying device for passing a recording material such as an electrophotographic printer, a copying machine, and a facsimile.

[0002]

2. Description of the Related Art Conventionally, an outline of an image forming process in an apparatus such as a printer, a copying machine and a facsimile using an electrophotographic system is shown in FIG. That is, after the surface of the photosensitive drum 2 is uniformly charged by the charging roller 1 to a certain polarity, the photosensitive drum is discharged by the exposing means 3 such as a laser to form a latent image only on the under-exposed region, and a developing device is formed. The toner 5 of No. 4 is triboelectrically charged between the developing blade 4a and the developing sleeve 4b to have the same polarity as the charged surface of the photosensitive drum, and D in the developing gap portion where the photosensitive drum and the developing sleeve face each other.
C and AC biases are superimposed and applied, and the toner is floatingly vibrated by the action of the electric field and selectively adhered to the latent image forming portion of the photosensitive drum, and then to the transfer nip portion formed by the transfer roller 10 and the photosensitive drum. It is conveyed by the rotation of the photosensitive drum.

On the other hand, a recording material 7 such as a paper on which an image is recorded is conveyed from a sheet feeding section (not shown) to a pre-transfer conveying roller 6,
The pre-transfer conveying roller conveys the transfer guide plate 9 to the transfer nip portion at a predetermined approach angle. While the recording material is being conveyed from the pre-transfer conveying roller to the transfer nip, the surface of the recording material is charged by rubbing against a member that is in contact with the recording material until it reaches this area. Since it becomes a factor of disturbing the image when performing electrostatic recording, a static eliminating brush 8 for removing such unnecessary charging is provided so as to contact the back side of the recording material being conveyed, It is grounded.

The recording material conveyed in this manner has a high voltage having a polarity opposite to that of the toner so that the toner on the photosensitive drum is electrostatically attracted and moved to the recording material side at the transfer portion. Is applied to the recording material to electrostatically attract the toner to the back surface of the recording material to transfer an image, and the back surface of the recording material is charged with a polarity opposite to that of the toner, and a transfer charge for keeping the transferred toner is recorded. It is given to the back of the material.

Finally, the recording material on which the toner image has been transferred is the pressure roller 1 which forms a nip portion with the heating rotator 13.
It is conveyed to the fixing device 12 constituted by 4.

In addition to the above, since a slight amount of adhered substances such as toner having different polarities remain on the surface of the photosensitive drum after transfer, the surface of the photosensitive drum after passing through the transfer nip portion is cleaned by the cleaning container 11. The cleaning blade 11a, which is counter-contacted to the surface, scrapes off the adhering substances and cleans them, and then stands by for the next image formation.

In the above steps, a contact heating type fixing device is widely known as an image fixing method because of its high thermal efficiency and safety, and a heat fixing roller having a halogen heater inside a metal cylinder is widely known. A heat roller fixing device made up of a heat-resistant resin film with a low heat capacity and a fixing film-type fixing device that heats the inside of the fixing film with a ceramic heater are mainly used. It is used for high-speed large machines, and the latter is used for relatively low-speed small machines. In particular, the latter is attracting attention as a method in which the roller heat transfer efficiency is higher than that of a heat roller method in which a cylindrical metal enclosing a conventional halogen heater is used as a fixing roller and the apparatus starts up quickly from the viewpoint of energy saving promotion in recent years, It is also being applied to higher speed models.

While various image forming apparatuses such as printers using the above fixing devices are required to have further improved basic performance such as improved image quality and increased print speed, they are also user friendly. There has been a demand for a device that does not bother the user. As one of the issues in this usability, the paper used by users has been diversified in recent years, It is difficult to adapt the device to the characteristics of various papers. Especially, the optimum fixing temperature in the fixing process cannot be applied to all paper types with only one setting. Currently, the user confirms the paper to be used before using the device, and the fixing temperature suitable for that paper is fixed. It is necessary to select an appropriate item from among several types of selection modes that are provided so that conditions can be selected, which not only bothers the user but also when the user makes an incorrect setting. However, there is a risk of image defects such as insufficient fixing property and offset due to excessive heating.

In order to solve such a problem, it is necessary for the main body of the apparatus to automatically detect the characteristics of the paper.
Among the various characteristics of paper, the heat capacity of paper, which is an element that affects the fixability and power consumption during heating, is particularly important in the fixing process. For this reason, it is desired to detect the paper thickness that has a strong correlation with the heat capacity of the paper, and some devices actually have a paper thickness detection function and have means for automatically switching the fixing conditions. FIGS. 3A, 3B and 3C show such a conventional example. As shown in FIG. 3A, the paper thickness detecting means 15 is provided in front of the transfer roller or the registration roller before transfer. Has been. FIG. 3B shows a paper thickness detecting means that also serves as a pair of paper conveying rollers. Of the paper thickness detecting roller pair, the upper roller bearing 16b of the paper thickness detecting upper roller 16 provided inside the frame 15 'is It is movably supported in the vertical direction by a shaft hole 16c having a gap in the vertical direction, and the upper roller is pressed against the lower roller by a pressure spring 16d. At this time, the spring strength of the pressure spring is weak enough not to hinder the conveyance of thin paper when it is fed, and it is possible to detect the accurate paper thickness by firmly pressing even thick paper with the leading edge curled. Is strongly adjusted. In this conventional example, an optical system using an LED and a PSD is used as a means for detecting the displacement amount of the upper roller.
Paper thickness detection The upper roller 16 is made of a highly rigid metal roller processed with high precision so as to reduce deflection and eccentricity. Furthermore, since PSD cannot detect specular reflection light, the surface of the upper roller is blasted. Roughened surface 16a treated
Is formed. On the other hand, a roller with high rigidity is also required to measure the accurate paper thickness on the lower roller side,
On the other hand, since the roller surface must have elasticity in order to reliably carry the paper, as shown in the figure, the metal lower roller 17a is provided at the center of the measuring portion of the roller, and the left and right end portions thereof are provided for carrying the paper. The lower rubber roller 17b is used. Further, FIG. 3C shows a further simplified structure in which the shaft of the upper roller of the metal roller pair is connected to the tip of the lever 21 and the side plate 22.
The latter half of the lever is pulled upward by a pull-up spring 24 via a fulcrum 23 provided on the upper end of the lever, so that the tip of the lever is pressed against the lower roller.
A reflection plate 21a is provided at the rear end of the lever, and when the front end of the lever is lifted by the thickness of the paper by the passage of the paper by the reflection type photosensor 19 which is arranged close to the opposite position, the rear end of the lever is lowered. The paper thickness is detected because the output signal changes. In this example, when the ratio of the distance between the lever tip and the fulcrum = a and the distance between the fulcrum and the rear end of the lever = b shown in the figure is set to be large, the displacement amount multiplied by the lever tip is calculated at the rear end. Since it is possible to amplify, minute changes can be detected relatively easily. In addition, in this conventional example, the tip of the lever can be brought into contact with the surface of the paper as it is, and the configuration can be simplified and the cost can be suppressed.

However, such a conventional example has the following problems.

(1) In the method using PSD, since the sensor itself is expensive and very high precision is required for processing the upper roller surface which becomes the reflecting surface, the cost becomes high and the method is applied to a general popular machine. Is difficult.

(2) When an inexpensive reflection type photo sensor is used instead of PSD, a change in the reflected light intensity is converted into a displacement amount, so that when the sensor unit becomes dirty or the sensitivity changes during use. False positives can occur.

That is, it is necessary to use expensive parts in order to perform accurate detection in a stable manner. On the other hand, if the parts are made of inexpensive parts, the reliability is insufficient.

[0014]

SUMMARY OF THE INVENTION The problem to be solved by the present invention is to achieve accurate detection stably in a displacement amount detecting means used for detecting the paper thickness of a conventional image forming apparatus. Need to use expensive parts,
The point is that if it is made up of inexpensive parts, the reliability will be insufficient.

An object of the present invention is to solve the above-mentioned problems and to provide a displacement amount detecting device having a more reliable detection performance even when an inexpensive component is used, and an image forming apparatus using the displacement amount detecting device. is there.

[0016]

According to the present invention, the above object is to provide a displacement amount detecting device which moves the displacement amount of a portion to be measured at a displacement amount detecting position in conjunction with the displacement amount by mechanical connection. A displacement amount number converting means for converting the number of other members to the predetermined region is used. Further, as the displacement amount number converting means, a lever-shaped member and a lever-shaped member rotation support shaft arranged as close to the front end as possible with respect to the linear distance from the front end to the rear end of the lever-shaped member. A pressing means for pressing the tip of the lever-shaped member so that the tip of the lever-shaped member can contact the object to be measured via the lever-shaped member rotation support shaft; It has a detection means for identifying the displacement of the rear end portion, and as the detection means,
By using a detection means for identifying whether or not the rear end of the lever-shaped member has passed a predetermined detection position, the rear end of the lever-shaped member is branched into a plurality according to a desired number of discriminating displacement regions, A means for converting the number of passages of the branched rear end of the lever into a displacement amount is used. Also, a plurality of lever-shaped members,
With respect to the linear distance from the front end to the rear end of each lever-shaped member, the lever-shaped member rotation support shaft arranged as close as possible to the front end and the leading lever-shaped member rotation support shaft Pressurizing means for pressurizing the tip end of the leading lever-like member so that the tip end of the lever-like member can come into contact with the object to be measured, and the tip end of the subsequent lever-like member at the rear end of each lever-like member Is provided with a means for pressurizing the lever-like members, and a plurality of lever-like members are sequentially connected in a desired direction, and a detection means for identifying the displacement of the rear end portion is provided at the rear end portion of the rearmost lever-like member, As the detecting means, a detecting means for identifying whether or not the rear end portion of the rearmost lever has passed a predetermined detection position is used, and a plurality of rear end portions of the rearmost lever are provided in accordance with a desired number of discriminating displacement regions. The number of passages of the branched rear end of the lever To be converted. Further, instead of the rear end portion of the rearmost lever that is branched into a plurality according to the number of identification displacement areas, a plate-shaped rear end portion having a plurality of slits provided according to the number of identification displacement areas is used. A photo sensor is used as the detection means. Further, a magnetic sensor is used as the detection means, and the member that passes through the predetermined region is made of a magnetized magnetic material. Further, it is realized by using the above displacement amount detecting means as the recording material thickness detecting means of the image forming apparatus.

[0017]

According to the present invention, the amount of displacement of the object to be measured is detected by the tip of the lever which is arranged with the rotation axis serving as the fulcrum close to the measurement side, and the distance from the lever tip to the rotation axis and the rotation axis The displacement amount is amplified at the lever rear end portion according to the ratio of the distance to the lever rear end, and the lever rear end portion is branched into a plurality according to the desired displacement amount measurement region. In the area that moves in the range amplified according to the displacement of the ratio measurement object, using a simple sensor that only detects whether the rear end of the lever has passed a predetermined position,
Since the detection is performed and the number of passages of the branched rear end of the lever, which changes according to the displacement amount, is converted into the displacement amount, cost reduction and reliability improvement can be realized.

[0018]

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

(Embodiment 1) FIGS. 1A and 1B are a front view and a side view of a paper thickness detecting apparatus showing a first embodiment of the present invention. In this embodiment, members having the same numbers as those in FIGS. 2 and 3 indicate the same constituent elements. In this embodiment, as shown in FIG. Ordinary metal upper roller 20 which is not treated
Using the first lever 2 provided on the shaft portion at the left end of the roller.
The displacement amount due to the paper thickness is detected via 1 '. In accordance with the configuration in which the left end side of the roller is detected, the position of the metal roller part and the rubber roller part of the lower roller in FIG. A metal lower roller 17 'is used (actually, the right end portion is also made of a metal roller in order to maintain the left-right symmetry of paper conveyance). As can be seen from the side view of FIG. 1B, the displacement detected at the tip of the first lever 21 'is divided into the distance ratio of 1:10 for the entire lever via the first fulcrum 23'. As a result, the displacement amount of the lever front end is amplified ten times at the lever rear end. Further, the displacement amount of the rear end portion of the first lever 21 'is further amplified 10 times at the rear end of the lever 26 by the second lever 26 and the second fulcrum 25 which are pressed and contacted by the pull-down spring 27. Therefore, the displacement amount due to the paper thickness is finally amplified 100 times, and the rear end portion of the lever 26 has a width of 100 times around the fulcrum according to the vertical movement of the tip portion of the lever 21 '. Rotate. At this time, the lever 26
As shown in the figure, the rear end portion is branched into five branches from 26a to 26e, and each branch is radially arranged at an equal angle about the rotation axis so that the rotation axis intersects with the extension line. Therefore, in the present embodiment, the distance between the tips of the branches is about 2 so that the distance between the tips of the levers 21 ′ corresponds to a change of 20 μm.
It is arranged at mm intervals. Further, a transmission type photo interrupter 28 is provided on the rotation orbit of the rear end of the lever 26, and its setting position is when the lever 26a in the position of zero displacement when no paper is passing detects a displacement of 80 μm. It is provided at the position to reach. With such a configuration, the paper thickness detection device can detect the paper thickness of 80 μm if the photo interrupter does not detect the paper once when the paper is passed.
It is estimated that the paper thickness is less than m, and it is 20 for each subsequent detection.
Since it is possible to identify thick paper by μm, the number of detections of the photo interrupter detected by one paper passage can be calculated by the CPU.
The paper thickness is 80 μm or less
It becomes possible to classify into 5 stages of 100 μm, 120 μm, 140 μm, 160 μm or more.

With this structure, an inexpensive sensor for identifying only whether or not the lever has passed is used to reduce the cost, and at the same time, highly reliable displacement amount detection that is not easily affected by dirt or the like of the sensor unit in use. It will be possible.

(Embodiment 2) FIGS. 4A and 4B are a front view and a side view of a paper thickness detecting device showing a second embodiment of the present invention. In the present embodiment, the members having the same numbers as those in FIG. 1 indicate the same constituent elements, and in this embodiment, the conveying roller is abolished in order to further simplify the structure.
As shown in (A), paper is fed onto the smooth plate 22 ',
The displacement amount due to the paper thickness is detected through a low friction lever 29 provided at the left end portion and having a low friction tip 29 ′ whose bottom surface is smoothly processed. As can be seen from the side view of FIG. 4B, the amount of displacement detected at the tip of the lever 29 has the same configuration as that of the first embodiment, and the lever 26
The rear end of the lever 29 moves in accordance with the vertical movement of the front end of the lever 29.
The paper thickness is 80 μm or less, 100 μm or less by rotating the rotation axis with a double width and storing the number of detections of the photo interrupter detected in one sheet passage in the CPU and adding them.
m, 120 μm, 140 μm, 160 μm or more.

According to this structure, an inexpensive sensor for identifying only whether or not the lever has passed is used, and the roller is eliminated to simplify the structure of only the lever to further reduce the cost. It is possible to detect the displacement amount with high reliability, which is less likely to be affected by dirt on the surface.

(Embodiment 3) FIG. 5 is a side view of a paper thickness detecting device showing a third embodiment of the present invention. In this embodiment, members having the same numbers as those in FIG. 1 indicate the same constituent elements, and in this embodiment, instead of the lever 26 of the second embodiment, a magnetic lever 26 ′ made of a magnetized magnetic material is used. In addition to being used, the detection sensor is also replaced with the hall element 30. Even if this configuration is used, the rear end of the lever 26 ′ rotates about the rotation axis with a width of 100 times in accordance with the vertical movement of the front end of the lever 29, similarly to the second embodiment.
By storing the number of detections of the Hall element detected in one sheet passage in the CPU and adding the result, the paper thickness is 80 μm or less, 1
It is possible to classify into five stages of 00 μm, 120 μm, 140 μm, 160 μm or more.

According to this structure, an inexpensive sensor for identifying only whether or not the lever has passed is used, and the roller is eliminated to simplify the structure of only the lever to further reduce the cost. It is possible to detect the displacement amount with high reliability, which is less likely to be affected by dirt on the surface.

(Embodiment 4) FIG. 6 is a side view of a paper thickness detecting device showing a fourth embodiment of the present invention. In this embodiment, the members with the same numbers as in FIG. 4B indicate the same constituent elements, and in this embodiment, the configuration is basically the same as that of the second embodiment, but the amplification of the second stage is omitted. As a lever to do,
A plate 31 'having four slits from the first slit 31'a to the fourth slit 31'd at the rear end of the lever
The lever 31 provided with is used. In this configuration, the setting position of the photo interrupter is set to the same position as that of the second embodiment, and the positions of the slits provided on the plate are made to coincide with the positions of the rear ends of the levers of the branched lever 26 of the second embodiment. Therefore, basically, contrary to the second embodiment, the paper thickness is identified by storing and adding the number of times when the photo interrupter detects the non-passage time.
80μ in order to avoid increase of extra area of plate
For the determination of the paper thickness range of m or less, it is the range until the first passage of the plate front end is detected as in the above embodiments. After that, it is determined that the displacement amount is increased by 20 μm every time when the non-passage (when passing the slit) is detected, and the program is set so that the detection is not counted after the last passage of the slit. Similarly, paper thickness is 80μm or less, 100μm, 120μm, 140μ
It is possible to classify into 5 stages of m and 160 μm or more.

With this configuration, it is possible to use a plate-shaped member having higher rigidity without using a branched thin lever rear end as in the second embodiment, so that vibration or shock is applied from the outside of the device. However, it is less likely to break down, more stable performance can be expected, and the cost can be reduced, and at the same time, highly reliable displacement amount detection that is not easily affected by dirt or the like of the sensor unit in use becomes possible.

[0027]

As described above, according to the present invention, the detection of the binary state of whether or not a member has passed through a predetermined region can be applied to the detection of a minute displacement amount, so that a simple structure and an inexpensive component can be obtained. This enables stable detection of the displacement amount, and by using the device of this configuration as the paper thickness detection means of the image forming apparatus, the setting of the fixing temperature condition of the fixing means is automatically switched according to the diversification of paper types. It becomes possible to realize that at a low cost.

[Brief description of drawings]

FIG. 1A is a front view of a displacement amount detecting means representing a first embodiment of the present invention. FIG. 3B is a side view of the displacement amount detecting means representing the first embodiment of the present invention.

FIG. 2 is a sectional view of a conventional image forming apparatus.

FIG. 3A is a sectional view of an image forming apparatus having a conventional paper thickness detection unit. (B) A front view of a paper thickness detecting means of a conventional example.
(C) A side view of another paper thickness detecting means of the conventional example.

FIG. 4 (A) is a front view of a displacement amount detecting means representing a second embodiment of the present invention. (B) A side view of a displacement amount detecting means showing a second embodiment of the present invention.

FIG. 5 is a side view of a displacement amount detecting means representing a third embodiment of the present invention.

FIG. 6 is a side view of a displacement amount detecting means representing a fourth embodiment of the present invention.

[Explanation of symbols]

1 charging roller 2 photosensitive drum 3 exposure means 4 developing device, 4a Development blade 4b Development sleeve 5 toner 6 Transport roller before transfer 7 Recording material 8 conductive brush 9 Transfer guide plate 10 Transfer roller 11 Cleaning container 11 'cleaning blade 12 Fixing device 13 Heating rotor 14 Pressure roller 15 Displacement amount detection means 15 'frame 16 Paper thickness detection upper roller 16a roughened surface 16b Upper roller bearing 16c bearing 16d pressure spring 16e Spring support member 17 Paper thickness detection lower roller 17a metal lower roller 17b Rubber lower roller 18 Non-contact displacement detection sensor 18 'LED 18 "PSD 19 Reflective photo sensor 21 lever 21 'first lever 21a reflector 22 Side plate 22 'smooth plate 23 fulcrum 23 'First fulcrum 24 Lifting spring 25 Second fulcrum 26 Second lever 26a First branch lever 26'a first branch magnetic lever 26b Second branch lever 26'b Second branch magnetic lever 26c Third branch lever 26'c Third branch magnetic lever 26d 4th branch lever 26'd Fourth branch magnetic lever 26e Fifth branch lever 26'e fifth branch magnetic lever 27 Pull-down spring 28 Transmissive Photointerrupter 29 Low friction resistance lever 29 Low friction resistance tip 30 Hall element 31 Plate type lever 31 'plate 31'a 1st slit 31'a second slit 31'b Third slit 31'c Third slit 31'd fourth slit

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2F062 AA01 AA27 BB14 BC08 CC02                       EE05 EE22 EE62 GG41 GG72                       HH22 NN02                 2F077 AA21 AA41 AA42 AA46 CC01                       CC02 DD01 NN06 NN27 PP12                       PP19                 3F048 AA02 AA04 AA05 AB01 BA06                       BB03 BB10 CA02 DA06 DC09                       DC12 DC19 EB37

Claims (7)

[Claims] 1. A displacement amount detecting device, wherein the displacement amount of a measured portion at a displacement amount detecting position is converted into the number of times a predetermined region is passed by another member that moves in conjunction with the displacement amount by mechanical connection. A displacement amount detection device characterized by using a conversion means. 2. The device according to claim 1, wherein the displacement amount number conversion means is a lever-shaped member and a lever-shaped member which is as close to the tip as possible with respect to a linear distance from the tip to the rear of the lever-shaped member. Lever-shaped member rotation support shaft arranged as
Pressurizing means for pressing the tip of the lever-shaped member so that the tip of the lever-shaped member can contact the object to be measured via the lever-shaped member rotation support shaft, and the rear end of the lever-shaped member. A rear end of the lever-shaped member, which has a detection unit for identifying the displacement of the section, and which detects whether or not the rear end of the lever-shaped member has passed a predetermined detection position. A displacement amount detecting device characterized by using a means for branching a plurality of parts according to a desired number of discriminating displacement regions and converting the number of passages of the branched rear end of the lever into a displacement amount. 3. The apparatus according to claim 2, wherein a plurality of lever-shaped members and a lever-shaped member arranged as close to the tip as possible with respect to a linear distance from the tip to the rear of each lever-shaped member. Pressurizing means for pressing the tip of the leading lever-shaped member so that the tip of the leading lever-shaped member can contact the object to be measured via the member rotation support shaft and the leading lever-shaped member rotation support shaft. And a means for pressurizing the front end of the subsequent lever-shaped member is provided at the rear end of each lever-shaped member so as to abut,
A plurality of lever-shaped members are sequentially connected in a desired direction, and a detection means for discriminating the displacement of the rear end portion is provided at the rear end portion of the rearmost lever-shaped member. Using the detection means for identifying whether or not the rear end of the rearmost lever has passed, the rear end of the rearmost lever is branched into a plurality according to the desired number of discriminating displacement regions, and the branched rear end of the lever is divided. A displacement amount detecting device, characterized in that the number of passages of a part is converted into a displacement amount. 4. The apparatus according to claim 2, wherein instead of the rear end portion of the rearmost lever that is branched into a plurality according to the number of identification displacement regions, a plurality of units are provided according to the number of identification displacement regions. Displacement amount detection device characterized by using a plate-shaped rear end having a slit. 5. The displacement amount detecting device according to claim 1, wherein a photo sensor is used as the detecting means. 6. The displacement amount detecting device according to claim 1, wherein a magnetic sensor is used as the detecting means, and a member for passing a predetermined region is made of a magnetized magnetic material. 7. An image forming apparatus, wherein each of the apparatuses according to claim 1 is used as a recording material thickness detecting means.