JP2000284549A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correctly detect the thickness of paper as recording material by having an arithmetic means for calculating the thickness of recording paper and making it unnecessary to demand the absolute accuracy of a paper thickness detection means which measures the thickness of the paper. SOLUTION: Upon receiving an instruction to print, a printer starts a paper carrying operation and rotates a pickup roller 132 in addition to a paper thickness detection roller 9, a transfer belt 4, and a fixing unit 5. The pickup roller 132 feeds out only one sheet of recording paper P onto a carrying path each time it makes one rotation. A pickup operation is started, a paper thickness is measured by a paper thickness sensor 6, the result of the measurement is outputted as t1 to an information processing means 7, in which the correct result of the measurement of the paper thickness is obtained from t1-t0. The execution of the sequence makes it unnecessary to demand the absolute accuracy of the paper thickness sensor 6. That is, measurement in which each variation of the paper thickness sensor 6 is absorbed is possible and more correct paper thickness detection is possible at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic or electrostatic recording type image forming apparatus such as a copying machine or a printer, and more particularly, to detecting a thickness of a recording material, and forming an image based on the result. The present invention relates to an image forming apparatus in which conditions are variable.

[0002]

2. Description of the Related Art A recording material, that is, printing paper used in an image forming apparatus has a resistance value,
Characteristic values such as heat capacity are different. The characteristic values of the printing paper affect the image forming conditions. For example, a laser beam printer using an electrophotographic process, an LED
In the case of a printer, the best image can be obtained by changing the image forming conditions of the electrophotographic process in accordance with the various characteristic values.

More specifically, the resistance value of the printing paper is changed by changing the transfer conditions for transferring the toner image developed on the photoreceptor to the printing paper, so that the heat capacity can be changed by applying heat to the toner image transferred to the printing paper. The image quality can be optimized by changing the fixing conditions when fixing by applying pressure.
Therefore, it has been conventionally proposed to mount a paper thickness detecting means, that is, a sensor for detecting the thickness of the printing paper (hereinafter, referred to as a “paper thickness sensor”). However, in practice, the paper thickness sensor may be expensive, and it has been mounted only on some expensive models.

An example of an optical reflection type displacement sensor will be described as a paper thickness sensor for acquiring thickness information of a printing paper.
FIG. 7 shows a schematic diagram thereof.

[0005] As shown in FIG.
Here, an LED 101 is provided as a light emitting element, and light is emitted to a detection medium, and reflected light from the detection medium or the detection area is reflected by the lens 103 and the position detection element (PSD) 1.
02 is detected. Light reflected from the detection medium, that is, the object to be measured is collected on the PSD 102 by the lens 103.

For example, when the object to be measured has the reference medium thickness x, the PS is controlled by the lens 103 as shown by the solid line.
The light is condensed at point B on D102, while when there is no measurement object, it is condensed on point A on PSD 102 as shown by the dotted line. As described above, the position of the center of gravity of the collected reflected light changes according to the distance to the measurement target. Therefore, P
By processing the output signal from the SD 102, it is possible to detect the distance to the measurement target.

FIG. 8 is a diagram showing the relationship between the output signal from the PSD 102 and its position information. Assuming that the output current from the PSD 102 is l ₁ and l ₂ , the total length of the PSD 102 is L and PSD ₁
Assuming that the distance from the center of 02 to the center of gravity of the reflected light is X, the following equation holds.

(L ₁ −l ₂ ) / (l ₁ + l ₂ ) = 2 × / L FIG. 9 is a block diagram of an electronic circuit expressing the above equation. That is, the output currents l ₁ and l ₂ reach the subtraction circuit 107 and the addition circuit 108 via the current-voltage conversion elements 104 and 105, respectively, and then are output as position information via the division circuit 108.

Next, the structure of the detecting portion of the paper thickness sensor, that is, the structure of the portion directly in contact with the printing paper will be described with reference to FIGS.

As shown in FIGS. 10 and 11, the thickness can be measured by measuring the distance from the printing paper being conveyed. FIG. 10 shows an example in which the paper thickness detecting roller 9 is used as a detecting unit. When a pressure is applied to the upper roller 9a from above by the spring 109 and the recording paper P passes between the upper and lower rollers 9a and 9b, the spring is turned on. The upper roller 9a is lifted by the thickness of the sheet against the urging force of the roller 109. The paper thickness sensor 6 reads the fluctuation of the upper roller 9a to detect the paper thickness.

When the printing paper P is conveyed by the belt 4 as shown in FIG. 2B, the distance between the printing paper P and the upper part of the actuator 120 pressed against the belt 4 by the pressure spring 121 is determined. By measuring, the thickness of the paper can be measured.

[0012]

However, the paper thickness sensor 6 having the above-mentioned configuration is not suitable for the LED 101 or the PSD 10.
Very high accuracy is required for mounting accuracy of 2. This is one of the causes of the cost increase of the paper thickness sensor 6. For example, in FIG. 12, if the mounting position of the PSD 102 moves in the direction indicated by the arrow and shifts to the position indicated by the dotted line, the reflected light originally applied to the position a of the PSD 102 is applied to the position a ′. Will be. PS
Due to the element characteristics of D102, the output value fluctuates by the amount of the deviation, so that a correct distance from the object to be measured cannot be measured.

FIG. 13 shows an output change when the mounting position of the PSD 102 is shifted. When the PSD 102 is at the normal position, the output characteristic of the solid line 123 in FIG. 13 is shown. On the other hand, when the PSD 102 is mounted shifted as shown by the dotted line in FIG. Output characteristics. If an attempt is made to detect the thickness of the printing paper having the thickness t, an incorrect detection result of ta 'will be obtained where the output of ta should originally appear.

To correct this, the mounting accuracy of the PSD 102 is increased, or the relationship between the thickness of the printing paper and the output value is measured at a factory using printing paper of known thickness. It is necessary to store the data in a nonvolatile memory in the printer, and to detect the paper thickness using the result. Writing to the non-volatile memory in this factory has caused an increase in assembly costs due to an increase in the number of work steps. Also, in the market, even when the paper thickness sensor fails and needs to be replaced, it is necessary to store the paper thickness data in the same manner as in the factory.

Accordingly, a main object of the present invention is to provide an image forming apparatus capable of accurately detecting the paper thickness of a recording material with a simple configuration without increasing the cost.

Another object of the present invention is to provide an image forming apparatus which can accurately detect the thickness of a recording material without requiring absolute accuracy for a paper thickness detecting means for measuring the thickness of the paper. is there.

[0017]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
Image forming means for forming an image on a recording material, and paper thickness detecting means for detecting the thickness of the recording material, wherein image forming conditions for the image forming means are varied based on the detection result of the paper thickness detecting means In the apparatus, the output value of the paper thickness detecting means when there is no recording material in the detecting unit of the paper thickness detecting means, and the output value of the paper thickness detecting means when there is a recording material in the detecting part of the paper thickness detecting means An image forming apparatus comprising an arithmetic unit for calculating a thickness of a recording material from a value.

Preferably, a paper feeding means for feeding the recording material onto a conveying path of the recording material, a recording material conveying means for conveying the recording material on the conveying path, and a recording medium on the conveying path, The first recording material presence / absence detecting means for detecting the presence / absence, and no recording material is present on all the transport paths including the transport path where the first paper presence / absence means is not located, without performing the paper feeding operation by the paper feeding means. Control means having a staying paper absence diagnostic sequence for detecting that there is no recording material in the detecting section of the paper thickness detecting means. From that point,
This is a time before the recording material is fed by the paper feeding unit and before the recording material reaches the detecting unit of the paper thickness detecting unit.

According to an embodiment of the present invention, the condition that there is no recording material in the detecting portion of the paper thickness detecting means means that the next recording material starts when the recording material passes through the detecting portion of the paper thickness detecting means. Until it reaches the detecting section of the paper thickness detecting means. Further, in order to detect the presence / absence of a recording material in the detecting section of the paper thickness detecting means, there is provided second recording material detecting means arranged near the detecting section, and the recording in the detecting section of the paper thickness detecting means is performed. It is preferable that the presence or absence of a material is determined by the second recording material detecting means. Alternatively, the output value of the recording material having the smallest output from the paper thickness detecting means is held, and when the difference between the output value and another output value of the paper thickness detecting means is equal to or smaller than a predetermined value, the detection is performed. It is preferable to determine that there is no recording material in the section.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described in more detail with reference to the drawings. The same members as those described above are denoted by the same reference numerals, and detailed description thereof will be omitted.

Embodiment 1 A first embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 1, the image forming apparatus of this embodiment, ie, a printer, conveys a photosensitive drum 1, which is a photosensitive medium, a laser scanner unit 2, a developing unit 3, and a recording paper P, which is a recording material. A transfer belt 4 for transferring the toner image on the photosensitive drum 1 to the recording paper P; a fixing device 5 for fixing the toner image on the recording paper P to the recording paper P by heat and pressure;
Paper thickness sensor 6 as paper thickness detecting means for detecting the thickness of
An information processing means 7 as an arithmetic means for processing information from the paper thickness sensor 6 and a paper thickness detecting roller 9 constituting a detection unit of the paper thickness detecting means are provided.

In the photosensitive drum 1, the laser scanner unit 2, and the developing device 3, the laser scanner unit 2 scans the photosensitive drum 1 according to image data from a controller (not shown) to form an electrostatic image. The electrostatic image is visualized by the toner stored in the toner container 3.

At the same time, the recording paper P is
The sheet is picked up by a pickup roller 132 serving as a paper supply unit, passed through a paper presence / absence sensor 131 serving as a recording material presence / absence detection unit, and then sent to a paper thickness detection roller 9. As the paper presence sensor, for example, a known optical sensor or the like can be employed. The detecting operation of the paper thickness detecting roller 9 is as described with reference to FIG.

The output from the paper thickness sensor 6 is transmitted to an information processing unit 7.
Sent to The information processing means 7 performs predetermined processing described later to calculate thickness information of the recording paper P. Based on the accurate paper thickness data calculated by the information processing unit 7, the engine control unit 8 selects appropriate image forming conditions, that is, transfer / fixing conditions.

Thereafter, the image formed on the photosensitive drum 1 is transferred onto the recording paper P conveyed by the transfer belt 4. Thereafter, the recording paper P is conveyed to the fixing device 5, where the toner is melted by heat and then pressed to apply the melted toner to the recording paper P.
Is completely fixed to the sheet, and the sheet is discharged to a sheet discharge tray 134 outside the apparatus.

Next, features of the present invention will be described mainly with reference to FIGS. 2 and 4 show a calculation sequence in the information processing means 7, FIG. 2 shows a sequence for obtaining the output level of the paper thickness sensor in a state where the recording paper P is not present, and FIG. This is a sequence for detecting.

In FIG. 2, when the power is turned on, the printer starts a predetermined initialization sequence.
In the description of the present embodiment, only a sequence related to paper thickness detection will be described. The initialization sequence includes a sequence for detecting whether or not the in-machine retained paper exists.

First, the paper thickness detecting roller 9, the transport belt 4,
Then, a roller for conveying the recording paper P such as the fixing device 5 is rotated (S101). At the same time, while checking whether or not the recording paper P is detected by the paper presence / absence sensor 131 provided on the recording paper transport path (S102), the roller is continuously rotated for a specified time (S103). By this operation, if the recording paper P is not detected by the paper presence / absence sensor 131, it can be determined that there is no stagnant paper in the apparatus. This is called an in-machine retained paper detection sequence. In the in-machine retained paper detection sequence, it is necessary to detect whether or not the recording paper P is present in the machine, so that the paper feeding operation is not performed, that is, the pickup roller 132 is not rotated.

If it is determined in the in-machine retained paper detection sequence that there is in-machine retained paper, an automatic paper discharge sequence is started (S104). In this automatic paper ejection sequence, sufficient time is required for paper remaining in the machine to be discharged outside the machine,
Continue to rotate the rollers required for transport. When the above specified time has elapsed (S103) or when the automatic paper ejection sequence is completed (S104), the paper thickness sensor 6
Is measured (S105). This result is stored in the information processing means 7 as t0 (S106). This value may be stored in a non-volatile memory as storage means,
Alternatively, it may be stored in a volatile memory. The sequence for measuring the offset of the paper thickness sensor 6 has been described above.

In this sequence, the reason why the data of the paper thickness sensor 6 is acquired after each transport roller of the transport path is rotated is that there is no paper in the detection unit 9 of the paper thickness sensor 6 without fail. To do that. Now, assuming that the transport roller sequence (S101) is not performed, for example, as shown in FIG. The output of the thickness sensor 6 is erroneously detected as the output when there is no recording paper.

This leads to acquisition of erroneous paper thickness detection information, which causes transfer failure and fixing failure. Therefore, it is important to confirm that there is no residual paper in the machine.

Next, a sequence for actually measuring the thickness of the recording paper P will be described with reference to FIG.

When receiving the print instruction, the printer starts a paper transport operation. The pickup roller 132 is rotated in addition to the paper thickness detection roller 9, the transfer belt 4, and the fixing device 5 (S201). The pickup roller 132 can send only one sheet of the recording paper P onto the transport path by one rotation. The pick-up operation is started, and a predetermined time, that is, a time when the recording paper P reliably reaches the paper thickness sensor 9 elapses (S202). After the prescribed time has elapsed, the paper thickness is measured by the paper thickness sensor 6. Then, the measurement result is output to the information processing means 7 as t1 (S203). The information processing means 7 obtains a formal paper thickness measurement result from t1-t0.

As described above, by executing these sequences, it is not necessary to request the paper thickness sensor 6 for absolute accuracy, that is, it is possible to perform measurement while absorbing individual variations of the paper thickness sensor 6, and to reduce the cost. More accurate paper thickness detection becomes possible. In turn, this leads to the selection of accurate process conditions during the printing sequence, resulting in higher printing quality.

Embodiment 2 Next, a second embodiment of the present invention will be described with reference to FIG.

In the first embodiment, data for canceling the offset of the paper thickness sensor 6 is obtained in the initial sequence when the printer is started. Acquisition of this offset cancellation data is not limited to the initialization sequence, and may be performed at any time as long as no paper exists in the detection unit 9 of the paper thickness sensor 6. For example, as shown in FIG. 5, the measurement may be performed between sheets in continuous printing or intermittent printing mode.

Therefore, in this embodiment, in FIG. 5, the configuration is such that the measurement is performed from the state where the preceding paper 136 has passed through the paper thickness detecting roller 9 to the time when the next succeeding paper 137 enters the paper thickness detecting roller 9. did. In addition, when these papers are present, or
The measurement without paper may be performed at only one point, or may be performed at a plurality of points and averaging processing. However, the averaging processing enables more accurate measurement.

In the case of a printer used for mass printing, there is a case where the printer is continuously operated without turning off the power for tens of days. In such a case, in the method of the first embodiment, the paper thickness detecting roller 9 and the actuator 120 (FIG. 1) are used.
1), the measurement error gradually increases. However, according to this embodiment, since the data for offset cancellation is continuously taken, the wear of the paper thickness detecting roller 9 and the actuator 120 does not affect the measurement result, and even when the printer is used for a long time, Accurate paper thickness detection can be maintained.

Embodiment 3 Next, a third embodiment of the present invention will be described with reference to FIG. In the present embodiment, as shown in FIG. 6, an arrangement is provided in which a second paper presence / absence detection sensor 139 as a second recording material presence / absence detection means is provided in the detection section of the paper thickness sensor 6. This arrangement is used in the first and second embodiments to arrange the detection unit 120 of the paper thickness sensor 6 and the second paper presence / absence detection sensor 139 in the main scanning direction, that is, in the longitudinal direction of the photosensitive drum 1. The paper thickness detecting roller 9 is not suitable, and in this case, FIG.
The actuator 120 described in 1 is more suitable.
Since the actuator 120 occupies only one point in the main scanning direction, it is possible to arrange the second paper presence / absence detection sensors 139 side by side.

According to the above configuration, it is possible to reliably detect the absence of paper, so that it is particularly suitable for an image forming apparatus requiring reliability.

On the other hand, if the printer must be made very inexpensively, the output of the paper thickness sensor 6
A method of detecting the presence or absence of paper is also conceivable. That is, the output of the paper thickness sensor 6 is constantly detected, and when a result corresponding to the thinnest recording paper is obtained, it is determined that there is no paper. According to this method, even if the second paper presence / absence sensor 139 is not provided, the detection unit 120 of the paper thickness sensor 6 can be used.
It is possible to identify whether or not the recording paper P exists.

Of course, it is also possible to make a determination from information of a paper presence / absence sensor near the paper thickness sensor.

According to the above embodiment, the offset component of the paper thickness sensor is canceled by subtracting the output value in the absence of paper from the output value in the presence of paper when measuring the paper thickness. Thickness detection can be performed. This makes it possible to obtain an inexpensive paper thickness sensor that does not require acquisition of paper thickness data at the factory and does not require strict values for LED and PSD mounting tolerances.

In the above embodiment, the present invention
The present invention is applied to the paper thickness sensor of the PSD method, but is not limited to this. In general, various sensors such as a sensor for measuring the thickness of the recording paper, for example, a method for measuring magnetic force, a method using inductance, and the like. Can be applied to

[0046]

As is apparent from the above description, according to the image forming apparatus of the present invention, the output value of the paper thickness detecting means when there is no recording material in the detecting section of the paper thickness detecting means, By having a calculating means for calculating the thickness of the recording material from the output value of the paper thickness detecting means when the recording material is present in the detecting section of the detecting means, the structure is simple, without increasing the cost, and The paper thickness of the recording material can be accurately detected without requiring absolute accuracy for the paper thickness detecting means for measuring the thickness. Therefore, appropriate image forming conditions can be selected based on accurate paper thickness detection, and a high-quality image can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a sequence for acquiring a value for canceling an offset of the paper thickness sensor according to the first embodiment.

FIG. 3 is an explanatory diagram showing a state in which there is staying paper in the apparatus.

FIG. 4 is a diagram for explaining a paper thickness detection sequence in the first embodiment.

FIG. 5 is an explanatory diagram showing a state in which a sheet thickness is measured between sheets in the second embodiment.

FIG. 6 is a schematic configuration diagram illustrating a state in which an actuator and a paper presence / absence sensor are provided side by side in a paper thickness detection unit according to a third embodiment.

FIG. 7 is a schematic configuration diagram showing an example of a conventional paper thickness sensor applied to the first to third embodiments.

8 is an explanatory diagram of an operation of a PSD used in the paper thickness sensor of FIG. 7;

9 is an electronic circuit block diagram for calculating position information from the output of the paper thickness sensor of FIG. 7;

FIG. 10 is an explanatory view showing a mechanism of a conventional paper thickness sensor used in the first and second embodiments.

FIG. 11 is an explanatory view showing a mechanism of a conventional paper thickness sensor used in the third embodiment.

12A and 12B are diagrams illustrating a sheet thickness sensor (a) and a PSD (b) for explaining a mounting error of a PSD of the sheet thickness sensor.

FIG. 13 is a graph showing a change in output when a mounting position of a PSD is shifted.

[Explanation of symbols]

6 Paper thickness sensor (paper thickness detection means) 7 Information processing means (computing means) 9 Paper thickness detection roller (detection unit) 131 Paper presence / absence detection sensor (first recording material presence / absence detection means) 132 Pickup roller (paper feed means) 139 second paper presence / absence detection sensor (second recording material presence / absence detection means)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H027 DA38 DC02 DC07 DE02 DE09 DE10 EA18 EC06 EC20 ED17 EE02 EE07 EE08 EF06 EF09 2H072 AA04 AA05 AA09 AA16 AA22 AB07 3F048 AA02 AB01 BA14 BA26 CA02 DA06 DC14 EB22

Claims (5)

[Claims] An image forming means for forming an image on a recording material, and a paper thickness detecting means for detecting a thickness of the recording material, and an image forming condition of the image forming means based on a detection result of the paper thickness detecting means. In the image forming apparatus, the output value of the paper thickness detecting means when there is no recording material in the detecting section of the paper thickness detecting means, and the output value of the paper when there is a recording material in the detecting section of the paper thickness detecting means. An image forming apparatus comprising: an arithmetic unit that calculates a thickness of a recording material from an output value of a thickness detecting unit. 2. A sheet feeding means for sending a recording material onto a conveyance path of a recording material, a recording material conveyance means for conveying the recording material on the conveyance path, and a presence / absence of a recording material on the conveyance path which is located on the conveyance path. A first recording material presence / absence detecting means for detecting the presence of a recording material, and no recording material is present on all of the conveyance paths including a conveyance path where the first recording material presence / absence means is not located, without performing a sheet feeding operation by the sheet feeding means. Control means having a staying paper absence diagnostic sequence for detecting that there is no recording material in the detecting section of the paper thickness detecting means. 2. The image forming apparatus according to claim 1, wherein the time from when the recording material is fed by the paper feeding unit and before the recording material reaches the detection unit of the paper thickness detection unit. 3. The state in which no recording material is present in the detection section of the paper thickness detection means means that the next recording material is detected by the paper thickness detection means from the time when the recording material passes through the detection section of the paper thickness detection means. 2. The method according to claim 1, wherein the process is performed until the detection unit is reached.
Image forming apparatus. 4. A detecting device for detecting the presence or absence of a recording material in a detecting portion of the paper thickness detecting device, the device further comprising a second recording material detecting device disposed in the vicinity of the detecting portion. 2. The image forming apparatus according to claim 1, wherein the presence or absence of a recording material in the unit is determined by the second recording material detection unit. 5. An output value of a recording material having the smallest output of the paper thickness detecting means is held, and when a difference between the output value and another output value of the paper thickness detecting means is equal to or less than a predetermined value. And determining that there is no recording material in the detection unit.
Image forming apparatus.