JPH08106189A - Image forming device - Google Patents

Abstract

PURPOSE: To realize the discrimination of the mat processing part of an improved OHP paper having the mat processing part whose surface coated with transparent resin is roughened and the discrimination of the front and the back surfaces. CONSTITUTION: This image forming device is provided with a light projection means 1001 emitting light and a light receiving means 1002 receiving the light which are arranged so that the optical axes are faced and the light is crossed to a paper carrying path to an image forming part. Besides, it is provided with a transmissivity detection means 105 detecting transmissivity being the ratio of the existing time of the paper with respect to the photoelectric conversion output of the light receiving means 1002 of the time when the paper does not exist stepwise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a heating roller fixing unit forming an image forming unit, such as a laser beam printer and a copying machine, and more particularly to an apparatus having a paper type and front and back detecting means.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus, a toner image transferred onto a recording material by a color laser beam printer or the like is fixed by a heating roller to form an image. By using a special OHP paper in which a transparent resin coat of the same material as the toner material has been previously applied to the printing surface on which the toner is placed, the color toner is integrated with the transparent resin to ensure its optical transparency. I am configuring.

However, if the dedicated OHP paper coated with the transparent resin is set in the paper feeding section upside down and fed, the non-resin coated surface is printed, so that the desired printing quality is obtained. In addition to not being able to obtain, in the heat fixing device with a heating roller, the transparent resin coating surface contacts the pressure roller side where the separation is not guaranteed, so the adhesiveness of the resin causes it to wind around the pressure roller and damage the fixing device. There was a problem that caused it. Therefore, as a countermeasure, a dedicated O
When the HP paper is set on the back by the front / back discriminating means, which will be described later, the paper feeding is stopped at the paper feeding unit to prevent winding around the heating roller (fixing roller).

When forming an image on the dedicated OHP paper, the fixing speed of the heat fixing device is reduced to 1/2 of that of the normal paper, and the toners of a plurality of colors are sufficiently melted and mixed to reproduce the color with the optical transparency. It is configured to improve the sex. Therefore, in order to realize the control for slowing down the fixing speed, a paper discriminating means for the special OHP paper, which will be described later, is installed, and when the special OHP paper is detected, the paper conveyance speed at the time of fixing is 1 /
It is configured to shift to OHP mode by dropping to 2.

In order to realize the above-described exclusive OHP sheet discrimination and its front and back detection, the following FIG. 9 and FIG.
The hardware configuration shown in 0 and its control configuration are configured.

The structure of the conventional optical paper type detecting means will be described below together with the structure of the image forming section.

The hardware configuration of the paper feeding device for feeding the paper to the image forming unit is such that a stepping motor (not shown) drives a paper feeding load at a predetermined speed in accordance with an instruction from a control unit (not shown).
And a half-moon roller 901 that feeds one sheet by releasing the latch by a solenoid (not shown) and mechanically controlling one rotation, and a conveying roller 902 arranged downstream thereof.
A registration roller 904 capable of switching between stop and rotation by an electromagnetic clutch, a contact type paper presence / absence detection sensor 903 (hereinafter referred to as a pre-registration sensor) arranged immediately before the registration roller 904, and a registration roller 904 downstream of the registration roller 904. A leading edge sensor 905 is provided as a leading edge detecting means which is an optical paper presence / absence detecting means.

The sheet passes through the pre-registration sensor 903 and the leading edge sensor 905 by the conveying roller 902 and the registration roller 904, and then the transfer drum 9 of the image forming section described later.
It is transported to 07. That is, a sheet conveying path is formed by these constituent members.

The hardware structure of the image forming unit that receives the sheet fed through the sheet conveying path of the sheet feeding device is such that the sheet is wound around the transfer drum 907 and a plurality of transfers are performed, and the leading edge of the sheet is sandwiched on the transfer drum 907. The gripper 908 and the gripper 9 at a position equivalent to the paper feed position in the tip sensor 905.
08, a transfer registration sensor 906 that detects that a position (grip position) where the leading edge of the paper is pinched has arrived, a photosensitive drum 911 that forms a toner image by a developing device 909, a scanner 910, and the like, and transfer completion that is separated by a separation claw 912. The fixing device 913 heat-fixes the toner image.

A control configuration for controlling the hardware configuration will be described. When the image forming signal is generated, the control unit rotates the half-moon roller 901 once, feeds one sheet at a predetermined speed, and rotates the transfer drum 907.

Next, the pre-registration sensor 903 detects the sheet and after a certain period of time, the registration roller 904 is rotated to form a loop of a certain amount in the sheet conveyance path between the conveyance roller 902 and the registration roller 904. When the skew is removed and the leading edge sensor 905 detects the leading edge of the sheet, the driving of the stepping motor is stopped and the apparatus stands by.

Next, when the transfer registration sensor 906 detects the arrival of the gripper position on the transfer drum 907, the stepping motor is restarted, and the sheet feeding speed is relatively higher than that of the transfer drum 907, and the same speed as that of the transfer drum 907 after being conveyed for a certain time. By controlling so that the gripper 908 is extended to about 30 degrees, the gripper 908 is kept in contact with the gripper 908 by a predetermined amount.
08 is closed, and the gripper 90 which is always the tip position at the time of transfer
The synchronous control is configured to stably feed the paper to the position 8.

The tip sensor 905 is an infrared light emitting diode 1 as a light projecting means for emitting light as shown in FIG.
001 and a phototransistor 1002 as a light receiving means for receiving light are arranged so as to oppose each other by optically aligning the optical axes with a prism 1003 and sandwiching the paper transport path.
With the circuit shown in FIG. 1, the photocurrent of the phototransistor 1002 is converted into a current voltage by the resistor R2.
C-MOS logic signal input port 1005 is directly input, and when the photocurrent is below a predetermined value due to the threshold characteristic of the port 1005, there is no paper, CPU 1006, and counter 1
It is configured to make a judgment at 007.

The configuration of the paper type image forming control when the dedicated OHP paper is fed by the paper feed control means and the optical paper presence / absence detection means will be described.

In order to enable image formation control according to paper type, FIG.
As indicated by reference numeral 121 in 2 (a), light-shielding printing is applied as a front-back identification transmittance pattern to the front end of the dedicated OHP paper in the transport direction.

When a dedicated OHP sheet is fed and is fed to the leading edge sensor 905 through the sheet feeding path by the feeding control, a light shielding portion 121A as a front and back side identification pattern printed in advance with a width of 10 mm downstream from the leading edge is provided. It is detected by the tip sensor 905, and the stepping motor is stopped to stand by. The transfer registration sensor 906 detects the grip position and
When the HP paper 121 is re-fed, if the leading edge sensor 905 detects the transmitted light in the transmitting portion of 20 mm or less downstream from the leading end of the dedicated OHP paper 121 by the circuit, the dedicated O
It is determined as HP paper 121.

That is, to explain with reference to the graph of light amount value of transmitted light-conveyance amount of paper (hereinafter, abbreviated as light amount value-conveyance amount) shown in FIG. 12A, the light shielding portion 121A is detected by the tip sensor 905. At this time, since it is lower than the predetermined light amount value, it is determined to be 0 according to the binary detection determination based on the transmitted light amount. After that, when the paper is re-fed, the leading edge sensor 905 detects the transparent portion, and the transmitted light is higher than a predetermined light amount value, so that it is determined to be 1 according to the binary detection determination. Based on such binary detection determination, the circuit determines that it is the dedicated OHP paper 121.

When the special OHP paper 121 is judged,
After the transfer of the toner image, the control is performed such that the paper conveying speed at the time of separating and discharging the paper and fixing the paper is reduced to 1/2 of the normal speed.

As shown at 122 in FIG. 12 (c),
When passing normal plain paper, naturally 20 m after re-feeding
After m, the sheet is shielded from light, so it is determined to be plain paper 122, and normal conveyance control is performed.

That is, to explain with reference to the graph of light amount-conveyance amount shown in FIG. 12C, when the leading edge sensor 905 detects the leading edge of the plain paper 122, it is shielded from light and falls below a predetermined light amount value. According to the binary detection judgment by, it is judged as 0. After that, even if the paper is re-fed, the light is shielded, and the light amount is held in a state of being lower than a predetermined value. Therefore, the binary detection determination is determined to be 0. Based on such binary detection determination, it is determined that the circuit is plain paper 122.

Further, when the dedicated OHP paper 121 is set upside down, the leading edge sensor 905 will be the dedicated O
Since the HP paper 121 is arranged so as to be displaced from the center of the HP paper 121 by about 25 mm, the position of the scanning portion of the leading edge sensor 905 accompanying conveyance is different from that of the solid line arrow in FIG. In order to continue to detect the transmitted light from the front end to the rear end of 121, that is, FIG.
In the graph of the light amount value-conveyance amount, the light amount value is held at a high value (see the dotted line in the figure), so the dedicated OH
The P-paper 121 is considered to be the reverse side or the black-and-white OHP paper, and the conveyance is stopped.

[0022]

However, according to the above-mentioned conventional example, since the front and back of the dedicated OHP paper 121 is determined,
Since the printing process is performed on the front end of the dedicated OHP paper 121, when the light is projected by the projector, the light-shielding portion 121A can be seen as it is, and there is a problem that the appearance is significantly impaired.

Further, in recent years, according to a design aiming at personalization of a color laser printer, since a good transferability is obtained even on a transfer drum material having a longer life and a higher durability, a transfer defect called a hollow image is particularly caused. Easy-to-use dedicated OH
In P paper 121, an improved OHP paper 123 (see FIG. 12B) in which the surface of the transparent resin coated surface is roughened (hereinafter referred to as matte treatment) is proposed.

In the matte processing portion of the improved OHP paper 123, the transparent resin portion is melted at the time of fixing and becomes transparent. Therefore, the matte processing portion is made transparent by heat or the like to form a detection mark 123A (FIG. If it can be used as a hollowed-out portion), it will be a means for solving the aesthetic problem. However, in the conventional method of directly detecting the transmitted light quantity by binary detection, the light quantity does not become lower than a predetermined value as shown in the graph of light quantity value-conveyance quantity of FIG. As shown in FIG. 12 (b), there is a drawback that the mat processing portion side, which can be easily identified visually, cannot be stably identified. Of course, it was not possible to make a judgment as to whether it was upside down.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and its purpose is to:
An object of the present invention is to provide an image forming apparatus capable of discriminating between a matte processing portion and a front and back surface of an improved OHP sheet having a matte processing portion having a roughened transparent resin coated surface.

[0026]

In order to achieve the above object, according to the present invention, the light is arranged so that the optical axes thereof are opposed to each other and the light is arranged so as to traverse the sheet conveying path to the image forming section. In an image forming apparatus having a light emitting means for emitting light and a light receiving means for receiving light, a transmittance detecting means for stepwise detecting a transmittance which is a ratio of a photoelectric conversion output of the light receiving means to a photoelectric conversion output when the paper is absent. Image forming control means for switching control of the image forming portion according to the photoelectric conversion output of the transmittance detecting means.

[0027]

In the image forming apparatus having the above-mentioned structure, since the transmissivity is detected stepwise, for example, the transmissivity of 25% and 80%, the transmissivity detecting means is provided. Since it is not shielded from light, the transmittance becomes 25% or more, and it is possible to determine from this output that it is the matte processing section, and the output allows the image forming control section to control the image forming section from the ordinary OHP paper. The control can be switched to.

Further, by making the front and back identifying transparent pattern of the improved OHP paper transparent, the transmittance of this pattern is 80%.
As described above, it is possible to discriminate between the front and the back by this output.

[0029]

【Example】

(First Embodiment) The present invention will be described below based on the illustrated embodiment. A color laser beam printer will be described as an example of the image forming apparatus according to the present invention. Since the schematic hardware configuration of this color laser beam printer is the same as that of the conventional example, the description will be given with the same reference numerals based on FIGS. 9 and 10.

First, the construction of the optical paper type detecting means will be described together with the construction of the image forming section.

The hardware structure of the paper feeding device for feeding the paper to the image forming unit is a stepping motor (not shown) that drives the paper feeding load at a predetermined speed in accordance with an instruction from the control unit (not shown).
And a half-moon roller 901 that feeds one sheet by releasing the latch by a solenoid (not shown) and mechanically controlling one rotation, and a conveying roller 902 arranged downstream thereof.
A registration roller 904 capable of switching between stop and rotation by an electromagnetic clutch, a contact type paper presence / absence detection sensor 903 (hereinafter referred to as a pre-registration sensor) arranged immediately before the registration roller 904, and a registration roller 904 arranged downstream of the registration roller 904. It is composed of a leading edge sensor 905 as a leading edge detecting means which is an installed optical paper presence detecting means.

The sheet passes through the pre-registration sensor 903 and the leading edge sensor 905 by the conveying roller 902 and the registration roller 904, and then the transfer drum 9 of the image forming section described later.
It is transported to 07. That is, a sheet conveying path is formed by these constituent members.

The hardware structure of the image forming unit that receives the sheet fed through the sheet conveying path of the sheet feeding device is such that the sheet is wound around the transfer drum 907 and a plurality of transfer operations are performed. The gripper 908 and the gripper 9 at a position equivalent to the paper feed position in the tip sensor 905.
08, a transfer registration sensor 906 that detects that a position (grip position) where the leading edge of the paper is pinched has arrived, a photosensitive drum 911 that forms a toner image by a developing device 909, a scanner 910, and the like, and transfer completion that is separated by a separation claw 912. The fixing device 913 heat-fixes the toner image.

A control configuration for controlling the hardware configuration will be described. When the image forming signal is generated, the control unit rotates the half-moon roller 901 once, feeds one sheet at a predetermined speed, and rotates the transfer drum 907.

Next, the pre-registration sensor 903 detects the sheet and after a certain time, the registration roller 904 is rotated to form a loop of a certain amount in the sheet conveyance path between the conveyance roller 902 and the registration roller 904. When the skew is removed and the leading edge sensor 905 detects the leading edge of the sheet, the driving of the stepping motor is stopped and the apparatus stands by.

Next, when the transfer registration sensor 906 detects the arrival of the gripper position on the transfer drum 907, the stepping motor is restarted, and the sheet feeding speed is relatively faster than that of the transfer drum 907. By controlling so that the gripper 908 is extended to about 30 degrees, the gripper 908 is kept in contact with the gripper 908 by a predetermined amount.
08 is closed, and the gripper 90 which is always the tip position at the time of transfer
The synchronous control is configured to stably feed the paper to the position 8.

Next, the schematic structure of the transmittance detecting means of the color laser beam printer according to the first embodiment of the present invention will be described with reference to FIG.

Reference numeral 905 denotes a tip sensor, which turns the optical axis back by an optical prism 1003 as shown in FIG.
Infrared light emitting diode 10 as a light projecting means for emitting light
The optical axis of 01 and the optical axis of a phototransistor 1002 as a light receiving means for receiving light are made to face each other across the sheet conveyance path. Reference numeral 101 denotes a sheet feeding unit as a sheet feeding control unit, which controls sensors and actuators 901 to 905 of the sheet feeding device in synchronization with control of an image forming unit by a communication function (not shown) built in the microcomputer 102. .

Reference numeral 103 is a resistor R1 for setting the light emitting current of the infrared light emitting diode 1001, and 104 is a resistor R2 for converting the photocurrent of the phototransistor 1002 into a current voltage.

Reference numeral 105 is a sample and hold circuit,
Analog switch 106 consisting of MOS type transistor
Is connected to the output port 117 from the CPU 118 of the microcomputer 102, the photoelectric current-voltage conversion value input to the capacitor 107 via the input resistor 112 (R3, R4, R5) is charged, and the hold from the microcomputer 102 is held. Hold by signal. Reference numeral 108 is an operational amplifier having an FET input configuration, which impedance-converts the hold voltage by the hold signal and outputs it.

Reference numerals 109, 110, and 111 denote resistors R6, R7, and R8 that determine the threshold level, and the transmittance (phototransistor 1002) at which the hold voltage is detected.
The ratio is divided according to the level of the photocurrent voltage conversion value when there is no paper (the ratio when there is paper) level, and is input as a reference level to the minus inputs of the comparators 113 and 114. The comparators 113 and 114 input the photocurrent-voltage conversion value to the plus input via the input resistor 112 (R3, R4, R5), compare with the reference level, and output the output from the C-MOS logic input port of the microcomputer 102. It is input to 115 and 116.

Each sheet will be described with reference to FIG. Since the respective sheets are the same as those shown in the above-mentioned conventional example, the same portions will be described with the same reference numerals.

Reference numeral 121 is a dedicated OHP paper, the surface of which is coated with a transparent resin of the same material as the toner material, and the front and rear identification transparent patterns are provided at the front end in the conveying direction as a light-shielding portion 1.
21A is being printed.

Reference numeral 122 is plain paper.

Numeral 123 is an improved OHP paper which is provided with a matte portion having a roughened transparent resin coated surface on its surface, and the detection mark 123A is made transparent by heat treatment or the like at the front end in the conveying direction as a front and back identifying transparent pattern. It is marked (white part in the figure).

FIG. 2 is a flow chart for explaining the software control configuration in the hardware configuration, and FIG. 3 is a conceptual diagram for explaining the timing sequence and threshold control in the software control configuration.

The following is a description with reference to the flowchart of FIG.

When an image forming signal is input from a host (not shown), the state of the pre-registration sensor 903 is confirmed, and when a sheet is detected (201), an abnormal process is performed by staying sheet (202, 203).

When it is confirmed that there is no accumulated paper, the sample and hold signal is set to the hold state, and the photocurrent level when there is no paper is held in the sample and hold circuit 105 (20
4).

Next, the timer T1 is set, the motor and the solenoid are controlled to start the paper feeding operation, and one sheet is fed (205).

The leading edge of the paper is detected by the pre-registration sensor 903 at time T1
If it does not reach within the range, it is considered as a paper feed jam and abnormality processing is performed (206, 207, 208). When the leading edge of the sheet reaches the pre-registration sensor 903 within the time T1, the registration roller 904 is driven by the electromagnetic clutch, the skew-corrected sheet is sent to the leading edge sensor 905, and the timer T2 is set (206, 209, 210). ).

Next, the input port 115 of the microcomputer 102
Input the port 1 which is the transmittance threshold characteristic in
If it is higher than a threshold value (transmittance 80%) preset by the ratio of R6: R7 + R8 three times consecutively within the time T2, it is regarded as the leading edge detection, the timer T3 is set and the motor is stopped. The leading edge of the sheet is made to stand by at the position of the leading edge sensor 905 (211, 214, 215). If the value is lower than the threshold value (transmittance 80%) three times consecutively within the time T2, an abnormal process is performed as a paper feed jam (211;
212, 213).

The rotation of the transfer drum 907 causes a time T3.
When the arrival of the grip position is detected within the transfer registration sensor 906, the timer interrupt T4 is set and the motor is restarted (216, 219, 220). Time T
If the arrival of the grip position is not detected within 3 (3), it is regarded as a failure and abnormal processing is performed (216, 217, 21).
8).

After waiting for a time T4 corresponding to 2 mm from the leading edge of the paper by the timer interrupt (211), the port 2 which is the transmittance threshold characteristic of the input port 116 of the microcomputer 102 is input and the ratio of R6 + R7: R8 is input. When the value is lower than a preset threshold value (transmittance 25%), the special OHP paper 121 and plain paper 122 shown in FIG.
As can be seen from the graphs of (a) and (c) of the sheet transmittance value-the sheet transport amount (hereinafter abbreviated as the transmittance value-transport amount), both are 25% or less. It becomes 0 by the binary detection judgment by the special OHP paper 121
On the assumption that the light-shielding portion 121A and the front end of the plain paper 123 have been detected, the interrupt timer T6 is set, and the processing 224 is executed (222, 223). Also, the threshold value (transmittance 2
5%), the modified OHP paper 123 of FIG.
As can be seen from the graph of the transmittance-conveyance amount shown in (b), the transmittance is 25% or more, so that it is 0 by the binary detection judgment.
Then, assuming that the matte processing section at the front end of the improved OHP paper 123 is detected, the interrupt timer T5 is set, and the processing 229 is executed (222, 228).

When it is assumed that the light-shielding portion 121A of the dedicated OHP paper 121 has been detected and the processing 224 is executed, after waiting for a time T6 corresponding to 20 mm from the leading edge of the paper, the port 1 of the input port 115 of the microcomputer 102 is waited. When the value is lower than the threshold value (transmittance 80%), the transmittance is low (25% or less) as can be seen from the graph of the transmittance value-conveyance amount shown in FIG. Since it is held at
Then, the normal paper 122 is regarded and the image forming control including the normal conveyance speed fixing is executed (224, 225,
226). If it is higher than the threshold value (transmittance 80%), as shown in the graph of transmittance value-conveyance amount shown in FIG.
Because of the above, the binary detection judgment based on the transmittance is 1, which is regarded as the dedicated OHP paper 121 having the transparent portion, and the dedicated OH which is formed by fixing the conveyance speed 1/2 as compared with the plain paper 122.
OHP control of P paper 121 is performed (224, 225,
227).

On the other hand, assuming that the mat processing unit at the front end of the improved OHP paper 123 has been detected, when the processing 229 is executed, after waiting for a time T5 corresponding to 7 mm cumulatively from the front end of the paper, the input port of the microcomputer 102 is reached. When the port 1 in 115 is input and the value is lower than the threshold value (transmittance 80%), it is considered that the improved OHP sheet 123 is upside down or the direction is abnormal, and the image formation is stopped and the abnormal process is executed (22).
9, 230, 232). Also, the threshold value (80% transmittance)
If higher, the modified OHP paper 121 in FIG.
As can be seen from the graph of transmittance value-conveyance amount in (b),
Since the detection mark 123A is transparent, the transmittance is 8
It becomes 0% or more, and becomes 1 by the binary detection judgment based on the transmittance, and it is regarded as the improved OHP sheet 121, and the OHP control of the improved OHP sheet 123 made up of the 1/2 conveyance speed fixing is performed (229, 230, 231).

As described above, the sample and hold circuit 105 and the voltage divider (R6, R7,
R8), a combination of comparators 113 and 114, a paper type, and transmission threshold value data representing a front / back side identifying transmission pattern are non-volatilely stored as a ratio of the voltage dividing resistors R6, R7, and R8. As a result, an image forming control means for switching between image forming control (fixing speed control in this embodiment) by performing paper type discrimination and front / back discrimination by implementing a transmissivity spatial code reading means for making a comparison at a predetermined timing from the front end is provided. It is a thing.

(Second Embodiment) FIG. 4 is a schematic structural view for explaining the hardware structure of a color laser printer as an image forming apparatus according to the second embodiment of the present invention. 5 and 6 are flow charts for explaining software control according to the second embodiment of the present invention. A conceptual diagram for explaining the timing sequence and the threshold control in the software control configuration is FIG. 3 as in the first embodiment, and the other hardware configurations are the same as those in the first embodiment.
Descriptions thereof are omitted.

The second embodiment differs from the first embodiment in that the sample-hold circuit, the voltage divider, and the comparator are combined to constitute the transmittance detecting means, whereas the photocurrent-voltage conversion value is directly measured. It is characterized in that it is configured by inputting to an A / D converter and comparing data at the time of calibration and data at the detection timing in a microcomputer.

The hardware configuration will be described below with reference to FIG. The same reference numerals are given to the same components explained in FIG. 1 in the first embodiment.

Reference numeral 401 denotes an A / D converter, which is built in the microcomputer chip in this embodiment. 402, 403
Is a constant voltage generator and inputs a reference voltage to the A / D converter 401. A ROM 404 stores transmittance threshold data for detecting the transmittance set in advance on the paper. A RAM 405 stores data obtained by converting the transmittance into a threshold value of a light amount value, which is set by a calibration process described later.

The software control configuration of the hardware configuration will be described below with reference to FIG. The same steps as those described in FIG. 2 in the first embodiment are designated by the same reference numerals.

Step 501 is a calibration process, which is the process shown in FIG. Proceeding to the calibration process 601, the average value of the photocurrent of three times when there is no paper is taken in, and when the level is below a predetermined level, the tip sensor 905.
If it is determined to be abnormal and the level is equal to or higher than a predetermined level, it is written in the RAM 405 (601, 602, 603, 604, 605).

Next, the set transmittance data (in the present embodiment, light passes through twice, a square value) is read out, and the threshold data obtained by multiplying the calibration data by the RAM 40.
It is set at a predetermined address on No. 5, and the process returns from the calibration process (606, 607).

Steps 502, 503, 504, 505
Is a determination process at each transmittance detection timing, which is determined by comparing the threshold data set on the RAM 405 in the calibration process with the A / D converter conversion value. Other controls are performed according to the first embodiment.

(Third Embodiment) FIG. 7 is a schematic view showing the hardware arrangement of a color laser beam printer as an image forming apparatus according to the third embodiment of the present invention.
FIG. 8 is a flow chart for explaining the peculiar software control according to the third embodiment of the present invention. Also, FIG. 5 shows the second
It is a flowchart figure explaining the soft control of the 3rd Example similarly to the Example of this. A conceptual diagram for explaining the timing sequence and the threshold control in the software control configuration is FIG. 3 as in the first and second embodiments. Other hardware configurations are the same as those of the first and second embodiments.

The third embodiment differs from the first and second embodiments in that a quantizing means for comparing transmittances is provided with means for stepwise adjusting the amount of light emitted from the sensor and the second embodiment is used. In the method of inputting to the A / D converter of the example and comparing the data at the time of calibration and the data of the detection timing in the microcomputer, the amount of emitted light is adjusted at the time of the calibration process, and the comparison information is combined to perform the comparison process. By doing so, the transmittance detecting means is configured, and a wide dynamic range and accuracy are secured.

The hardware configuration will be described below with reference to FIG. The same parts as those described in FIGS. 1 and 4 in the first and second embodiments are designated by the same reference numerals.

Reference numeral 701 denotes an output port of the microcomputer, which has a current setting resistor R10 (70
When the output is connected to the cathode of the infrared light emitting diode 1001 through 2) and low is output, the infrared light emitting diode 1001 is brightened by pulling more by a predetermined current.

Reference numerals 703 and 704 are constant voltage generating circuits,
Infrared light emitting diode 1001 and phototransistor 10
02 to the A / D converter 40 through the infrared light emitting diode 1001 while applying a stabilized bias voltage.
By connecting to the reference voltage input of 1, the influence of the non-linear characteristic due to the saturation voltage of the phototransistor 1002 is avoided.

The software control configuration in the hardware configuration will be described below with reference to FIG. In FIG. 8, only the explanation of the calibration process is given, and the process calling program is the same as that of FIG. 5 in the second embodiment.

When proceeding to the calibration processing 801,
The average value of the photocurrent of three times when there is no paper is taken in, and when it is below a predetermined level, it is confirmed whether the infrared light emitting diode 1001 has been brightened, and if it is not brightened, it is brightened (801, 80
2, 803, 804, 805), when the level is lower than a predetermined level, it is determined that the tip sensor 905 is abnormal (808, 809).

When the infrared light emitting diode 1001 is brightened as a result of being below a predetermined level, it is determined that the tip sensor 905 is abnormal (806, 807).
The average value of the times is recorded in the RAM 405 (804, 80
5). When the level is equal to or higher than the predetermined level in step 803, the above (804, 805) is executed.

Next, the set transmittance data (in the present embodiment, the light passes through twice, the square value) is read out, and the threshold data obtained by multiplying the calibration data by the RAM 40 is read.
It is set at a predetermined address on No. 5 and returns from the calibration process (805, 806).

Other controls are controlled according to the first and second embodiments.

In each of the above embodiments, the optical prism 10
Although the type in which the optical axes are opposed to each other via 03 is described as an example, the type is not particularly limited to this type.

[0077]

As described above, according to the present invention, the light emitting means and the light receiving means for receiving the light, which are arranged such that the optical axes are opposed to each other and the light crosses the sheet conveying path to the image forming portion, are provided. In the image forming apparatus having the means, the matte of the improved OHP paper is provided by providing the transmittance detecting means for stepwise detecting the transmittance which is the ratio of the photoelectric conversion output of the light receiving means to the photoelectric conversion output when the paper is present. An effect that enables the processing unit to be discriminated and enables control of the image forming unit (for example, a fixing device) (for example, conveyance speed) by discriminating between the front and back sides of a dedicated OHP sheet including an improved OHP sheet and plain paper. There is.

Therefore, by using the improved OHP paper, the front and back identifying transparent pattern in the mat processing section becomes transparent, and the transparent resin section in the other mat processing sections becomes transparent at the time of fixing and becomes transparent. When this is done, there is an effect that the problem of remarkably impairing the aesthetics due to the front and back distinguishing transmission pattern can be solved.

Further, according to the improved OHP paper, it is possible to obtain a good transfer property without causing a transfer defect, which is referred to as a hollow defect, even in a transfer drum material forming an image forming portion having a long life and high durability in recent years. You can Therefore, a highly durable transfer drum material can be used, and the maintenance-free property of the transfer drum can be ensured. As a result, the color laser beam printer as the image forming apparatus can be personalized and reduced in cost.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram illustrating a hardware configuration of a color laser beam printer as an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a flow chart illustrating a control configuration of a color laser beam printer as an image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is a diagram for explaining a control configuration by comparing the control configuration according to the first embodiment of the present invention with a conventional technique. FIG. 3 is a graph of light amount value-conveyance amount of a conventional detection method and binary detection determination, The transmittance value-conveyance amount graph and binary detection judgment of the method of the present invention,
FIG. 3A shows a special OHP paper, FIG. 2B shows an improved OHP paper, and FIG. 3C shows plain paper.

FIG. 4 is a schematic configuration diagram illustrating a hardware configuration of a color laser beam printer as an image forming apparatus according to a second embodiment of the present invention.

FIG. 5 is a flow chart illustrating a control configuration of a color laser beam printer as an image forming apparatus according to a second embodiment of the present invention.

FIG. 6 is a flowchart illustrating the calibration process of FIG.

FIG. 7 is a schematic configuration diagram illustrating a hardware configuration of a color laser beam printer as an image forming apparatus according to a third embodiment of the present invention.

FIG. 8 is a flow chart illustrating the calibration process of FIG. 5 according to the third embodiment of the present invention.

FIG. 9 is a schematic configuration diagram illustrating a hardware configuration of a color laser beam printer as an image forming apparatus according to an embodiment of the present invention.

FIG. 10 is an enlarged schematic configuration diagram of the tip sensor unit in FIG. 9.

FIG. 11 is a schematic configuration diagram illustrating a hardware configuration of a color laser beam printer as a conventional image forming apparatus.

FIG. 12 illustrates a conventional control configuration.
A graph of light amount value-conveyance amount, binary detection judgment, and a sheet are shown. In the figure, (a) is a dedicated OHP sheet, (b) is an improved OHP sheet, and (c) is a plain sheet. is there.

[Explanation of symbols]

 101 paper feeding unit (paper feeding control means) 102 microcomputer 105 sample and hold circuit (transmittance detecting means) 113, 114 comparator (transmittance detecting means) 901 half-moon roller 902 transport roller 903 pre-registration sensor (contact type paper presence / absence detection) Sensor) 904 Registration roller 905 Tip sensor (tip detecting means) 906 Transfer registration sensor 907 Transfer drum 908 Gripper 909 Developer 910 Scanner 911 Photosensitive drum 912 Separation claw 913 Fixer 1001 Infrared light emitting diode (light emitting means) 1002 Phototransistor (light receiving) Means) 1003 Optical prism

Claims (5)

[Claims] 1. An image forming apparatus having a light projecting means for emitting light and a light receiving means for receiving the light, wherein the light axes are opposed to each other, and the light is arranged to cross a sheet conveying path to the image forming section. Transmittance detecting means for stepwise detecting the transmittance, which is the ratio of the light receiving means to the photoelectric conversion output when there is no paper, and the transmittance detecting means, and the photoelectric conversion output of the transmittance detecting means An image forming apparatus comprising: an image forming control unit that switches control. 2. The image forming control means, a leading edge detection means for detecting the transmissivity of the sheet in stages to determine the leading edge of the sheet,
The image forming apparatus according to claim 1, further comprising a paper feed control unit that controls the sheet conveyance to the image forming unit in synchronization with the output of the leading edge detection unit. 3. The image forming control means stores, in a non-volatile manner, transmittance threshold data corresponding to a paper type, a photoelectric conversion output of the transmittance detecting means, and the transmittance threshold data of the storage means. The image forming apparatus according to claim 1, further comprising: a paper type determination unit that compares the types and determines a paper type. 4. The image forming control means has a storage means for storing the transmittance threshold value data corresponding to the paper type in a nonvolatile manner corresponding to the position information on the paper, and is stored in advance in the paper space. Based on the position information, the transmissivity code information is read by the transmissivity detecting means, the transmissivity space code reading means is compared with the transmissivity space code information and the transmissivity threshold data of the storage means, and the paper type The image forming apparatus according to claim 1, further comprising a paper type determining unit that determines whether the image forming apparatus is a sheet. 5. The image forming control means has a storage means for storing non-volatilely the transmittance threshold value data corresponding to the position information on the paper, which corresponds to the front and back discrimination transmittance pattern previously formed on the paper. The transmissivity code information stored in advance in the paper space is read by the transmissivity detecting means based on the position information, and the transmissivity code information and the transmissivity of the storage means are stored. The image forming apparatus according to claim 1, further comprising: a paper attitude determination unit that compares the threshold value data to determine whether the sheet is front side or back side.