JPH0412502Y2 - - Google Patents

Description

[Detailed Description of the Invention] Field of the Invention The present invention relates to a printing density control device for a copying machine (such as a diazo copying machine) that exposes and prints photosensitive paper and originals in a stacked manner. In a copying machine that has a light amount detection means, the amplification degree of the amplifier connected to the transmitted light amount detection means is determined depending on whether the amount of transmitted light is detected by the document alone or when the amount of transmitted light is detected when the document and photosensitive paper are overlapped. The present invention relates to a printing density control device for a copying machine, which is characterized in that the printing density is changed.

Prior Art A diazo copying machine that measures the amount of light transmitted through an original, controls the conveyance speed of the original and photosensitive paper (or the amount of light emitted from the exposure light source) according to the measured amount of transmitted light, and automatically adjusts the printing density. Various types of burn-in density control devices have been proposed.

However, such conventional printing density control devices only measure the amount of light transmitted through the original, so they require a mechanism (automatic photosensitive paper feeding mechanism) that transports the photosensitive paper through a path different from the original transport path. There is a problem in that it can only be applied to diazo copying machines that have the following.

Therefore, in order to make copies without using the automatic paper feeding function, such as when there is no cassette that can store the photosensitive paper to be used, first pass only the original through the transmitted light amount detection means to detect the burning level of the original. After that, there was the hassle of stacking the original and photosensitive paper and inserting them into the copying machine (manual paper feeding, that is, manually feeding the photosensitive paper) to make copies.

Purpose of the invention Therefore, the purpose of the invention is to provide a copying machine equipped with an automatic photosensitive paper feeding mechanism, whether manual paper feeding or automatic paper feeding (photosensitive paper is automatically fed). Similarly, it is an object of the present invention to provide a printing density control device for a copying machine that can make copies with appropriate printing density.

Summary of the invention This invention is applicable to a copying machine equipped with a transmitted light amount detection means and an automatic photosensitive paper feeding mechanism. The conventional problems are overcome by switching the amplification factor of the amplifier circuit that amplifies the output of the transmitted light amount detection circuit depending on the case where the photosensitive paper and the photosensitive paper are inserted in a stacked manner.

DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

Figures 1 and 2 respectively show a diazo system that measures the amount of transmitted light of an original (or stacked originals and photosensitive paper) and automatically controls the motor that drives the printing belt based on the measured amount of transmitted light. 1 is a diagram showing the main parts of a copying machine.

FIG. 1 shows the case where an automatic paper feeding mechanism for photosensitive paper is used, and FIG. 2 shows the case where the automatic paper feeding mechanism is not used and a document is inserted overlapping the photosensitive paper (manual paper feeding).

In FIGS. 1 and 2, 10 is an exposure light source, and 12 is a rotating cylinder glass (baked glass) having the exposure light source 10 inside. 14
An endless conveyor belt rotates in contact with the cylinder glass 12, and the stacked original and photosensitive paper are conveyed along the outer peripheral surface of the cylinder glass 12, during which time the photosensitive paper is exposed. 16
1 is a roller that drives or transports the conveyor belt 14, and 18 is a separation casing that separates the stacked originals from the photosensitive paper.

One end of the optical fiber 20 serving as a light guiding means is provided outside or inside the cylinder glass 12 in order to take in the light from the light source 10, and the other end is provided on the photo sensor 34 side that detects the amount of transmitted light. 38 is a table on which the original (or stacked originals and photosensitive paper) is placed; 36 is an original insertion roller;
32 is a document insertion detection sensor, 24 is a conveyance roller,
22 is a printing section conveyance roller, 26 is a photosensitive paper conveyance roller, 28 is a cassette for storing the photosensitive paper, 30 is a paper feed roller for sending out the photosensitive paper, 40 is a drive motor of the copying machine, 44 is a document, 46 (see Fig. 2) ) is photosensitive paper.

FIG. 3 is a block diagram showing an embodiment of a printing density control device for a copying machine related to the present invention. The original insertion detection circuit 50 includes the insertion detection sensor 32 shown in FIGS. 1 and 2, and outputs an original insertion detection signal to the transmitted light amount signal generation means 74 and the timing circuit 88. The transmitted light amount signal generating means 74 includes a transmitted light amount detection circuit 56 and an amplifier circuit 70. The transmitted light amount detection circuit 56 includes the photosensor 34, the resistor 52, and the operational amplifier 54 shown in FIGS. 1 and 2. Photosensor 34 is connected between the inverting input terminal of operational amplifier 54 and ground. resistance 52
is connected between the inverting input terminal and the output terminal of the operational amplifier 54, and the non-inverting input terminal of the operational amplifier 54 is grounded. The amplifier circuit 70 includes an operational amplifier 6 whose non-inverting input terminal is grounded via a resistor 68.
6. Output terminal of operational amplifier 54 and operational amplifier 66
, a feedback resistor 64 connected between the inverting input terminal and the output terminal of an operational amplifier 66 , another feedback resistor 62 connected in series, and a switch 60 . Note that the resistor 62 and switch 60 connected in series are connected in parallel to the feedback resistor 64, and the output of the operational amplifier 66 is taken out from the output terminal 72.

The output of the transmitted light amount signal generating means 74 is sent to a peak hold circuit 76, and the output of this circuit 76 is applied to an A/D converter 78. The output of converter 78 is sent to latch circuit 80 in response to timing signal T1 output from timing circuit 88. The latch circuit 80 receives the timing signal T2 output from the timing circuit 88 and holds the digital output of the A/D converter 78. The output of the latch circuit 80 is converted into an analog signal by a D/A converter 82, and the output is converted into an analog signal by a conveyance speed control signal generation circuit 84.
is applied to The output of this signal generation circuit 84 is
applied to motor speed control circuit 86 to control motor 40.
control the rotation speed of the

Next, the operation for automatic paper feeding will be described with reference to FIGS. 1 and 2.

When the power switch of the copying machine is turned on, the exposure light source 10 lights up and the motor 40 starts rotating at a predetermined speed. Subsequently, an automatic/manual selection switch (not shown) located at an appropriate location on the copying machine selects automatic paper feeding and enables the automatic paper feeding mechanism for photosensitive paper. When the automatic paper feeding function is selected, the amplifier circuit 7
0 switch 60 is closed. The switch 60 may be closed by linking the switch 60 with an automatic/manual selection switch, or by using a relay or the like. Note that automatic paper feeding may be automatically selected whenever the copying machine is turned on.

In the case of automatic feeding of photosensitive paper, when only the original 44 is inserted into the original insertion slot along the table 38, the original 44 is conveyed into the copying machine by the insertion roller 36. When the leading edge of the original 44 passes between the optical fiber 20 and the photo sensor 34 and reaches the original insertion detection sensor 32, the original insertion detection circuit 50 outputs a detection signal. This original insertion detection signal causes
Transmitted light amount signal generation means 74 and timing circuit 8
8 operates, and the paper feed roller 30 is further driven to feed the photosensitive paper from the cassette 28. The sent-out photosensitive paper is placed in the document 4 before the printing section conveyance roller 22.
Merges with 4.

On the other hand, a signal corresponding to the amount of transmitted light of the original is output from the transmitted light amount detection circuit 56 and amplified by the amplifier circuit 70. The amplification factor during automatic paper feeding is determined by setting the resistance values of resistors 58, 62, and 64 to R58 and R6, respectively.
2 and R64, it becomes (R62R64)/R58.

However, R62R64 is the parallel resistance value of resistors 62 and 64. The output voltage of the amplifier circuit 70 is
The peak voltage is applied to the peak hold circuit 76 and detected. The reason why the peak hold circuit 76 is provided is that the output voltage of the amplifier circuit 70 is
This is because it changes depending on the characters, figures, etc. to be copied. That is, by detecting the peak value, it is possible to accurately detect the amount of light transmitted through the "ground" portion of the document. The peak voltage detected by the peak hold circuit 76 is output to the A/D converter 7 according to timing signals T1 and T2 from the timing circuit 88.
8 into a digital signal and then held in a latch circuit 80. The timing signals T1 and T2 are set so that they are generated at a position before the original and the automatically fed photosensitive paper overlap and enter the printing section. The digital signal held in the latch circuit 80 is converted into an analog signal by a D/A converter 82 and applied to a conveyance speed control signal generation circuit 84. The output of this control signal generation circuit 84 controls the rotational speed of the motor 40 via a motor speed control circuit 86. In this way, the rotational speed of the motor 40 is controlled according to the amount of light transmitted through the original 44, and an appropriate printing density can be obtained.

When not using the automatic paper feed mechanism for photosensitive paper (second
(in the case shown in the figure), that is, in the case of manual paper feeding, select manual paper feeding with the automatic/manual selection switch. In response to this, automatic paper feeding of photosensitive paper is prohibited, and the amplifier circuit 7
0 switch 60 is opened. As shown in FIG. 2, the insertion roller 36 holds the original 44 and the photosensitive paper 4.
Insert 6 overlapping. The insertion roller 36 transports the original 44 and the photosensitive paper 46 into the copying machine in an overlapping state. The original 44 and the photosensitive paper 46 are
When the tip passes between the optical fiber 20 and the photo sensor 34 and reaches the document insertion detection sensor 32,
As in the case of automatic paper feeding described above, measurement of the amount of transmitted light is started. However, in this case, the amount of transmitted light between the original 44 and the photosensitive paper 46 is measured in a state where they are overlapped. Therefore, as a matter of course, the amount of transmitted light in this case is reduced compared to the case of only the original 44. On the other hand, since the switch 60 is opened, the amplification degree of the amplifier circuit 70 becomes R64/R58, which is higher than (R62R64)/R58 in the case of automatic sheet feeding. In other words, this increase in amplification compensates for the decrease in the amount of transmitted light, and it is possible to measure the amount of transmitted light from only the document when automatically feeding photosensitive paper, and from the stacked original and photosensitive paper when manually feeding paper. In this case, the transmitted light amount signal generating means 74
It is possible to prevent the output signal from changing. Therefore, in any case, if the document is of the same type, the motor rotational speed is the same and the optimum printing density can be obtained.

The other operations in manual paper feeding are the same as those in automatic paper feeding, so a description thereof will be omitted.

Effects of the invention As explained above, according to the invention, the amplification degree of the amplification circuit 70 of the transmitted light amount signal generation means 74 is
Since we have provided a means to switch between automatic and manual feeding of photosensitive paper, even when manually feeding paper in a copying machine equipped with an automatic paper feeding mechanism, you can simply stack the original on the photosensitive paper and insert it into the copying machine. Just by doing this, you can make copies with the appropriate printing density, just as you would with automatic paper feeding. The circuit configuration is extremely simple because the amplification degree can be changed by simply adding a resistor and a switch to the conventional circuit. Therefore, there is also the advantage that it can be easily applied to conventional copying machines.

Modifications and Modifications of the Idea Although only one embodiment has been described above, various modifications and changes are possible. For example, the amplifier circuit 7
The zero resistors 62 and 64 may be made variable resistors so that the printing density can be adjusted according to the printing sensitivity and paper thickness of the photosensitive paper. Further, although a method of controlling the speed of the drive motor has been shown to control the printing density, a method of changing the amount of light emitted from the exposure light source may also be adopted.

[Brief explanation of the drawing]

1 and 2 are diagrams showing the main parts of a copying machine to which the present invention is applied, and FIG. 3 is a block diagram of an embodiment of the printing density control device according to the present invention. 56...Transmitted light amount detection circuit, 79...Amplification circuit, 60...Switch.

Claims (1)

[Scope of utility model registration request] A printing density control device for a copying machine that has an automatic photosensitive paper feeding mechanism and exposes and prints photosensitive paper and a document in a stacked manner, comprising: a transmitted light amount detection means; an amplification means for amplifying the output of the transmitted light amount detection means; and a switching means for switching the amplification degree of the amplification means, and the transmitted light amount detection means measures the amount of transmitted light of only the original, and the transmitted light amount detection means measures the amount of transmitted light by overlapping the original and photosensitive paper. 1. A printing density control device for a copying machine, characterized in that the amplification degree of the amplifier is changed by the switching means according to the change in the amplification degree of the amplifier.