JPS6342790B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly relates to a safety device for a copying machine that prevents paper jams occurring in a pressure fixing device.

As shown in FIG. 1, a conventional safety device installed in the fixing device of a copying machine includes a detector c near the fixing roller a during fixing to detect paper b wrapped around the fixing roller a. In many cases, the copying machine is stopped or the copying cycle is slowed down based on the signal detected by the detector c.

In addition, in a pressure fixing device in which paper jams in the vicinity of the fixing roller a are relatively rare, a peeling claw d whose tip end touches the fixing roller a circumferentially is provided on the discharge side of the paper b, and
A safety device is generally provided with a paper jam detector e for detecting passage of paper 6 behind these peeling claws d. However, once a paper jam occurs in the pressure fixing device, such as when paper b gets wrapped around fixing roller a,
It takes a lot of effort and time to remove this, and even if double feeding occurs, it is necessary to forcibly eject it to prevent paper jams, etc., so the fixing roller is driven. There were some problems, such as the need to install a large-capacity motor.

This invention was made with the aim of improving this problem, and includes a drive torque detector provided in the drive system of the fixing roller, and an abnormal torque signal detected by the detector that stops or reverses the drive of the fixing roller. The purpose of this invention is to provide a safety device for a copying machine that switches the drive system to prevent paper jams, damage to paper due to double feeding of paper, defective fixing, and the like.

The present invention will be described in detail below with reference to an embodiment shown in FIG. 2 and subsequent figures. In the figure, reference numeral 1 denotes a pressure fixing device provided in a copying machine (not shown), which has a pair of fixing rollers 2 and 3 that are pressed against each other with strong force.One fixing roller 3 is connected to a transmission means 4 such as a chain. is connected to the drive source 5 via the drive source 5.
Accordingly, both the fixing rollers 2 and 3 are rotated simultaneously while being in pressure contact with each other. Reference numeral 6 denotes a sheet of paper on which transfer has been completed; 7 is a peeling claw provided on the ejection side of the sheet 6; 6 is peeled off, and the paper 6 peeled off by a peeling claw 7 is stored in a paper discharge tray 8. Note that 9 is the fixing roller 2,
3 is a pad for applying mold release agent.

On the other hand, FIG. 3 is a circuit diagram of a safety device that detects an abnormality from the load applied to the drive source 5 and stops or reverses the rotation of the fixing rollers 2 and 3 to prevent paper jams, double feeding, etc. , has a control circuit 11 connected to a drive source 5. The control circuit 11 has a function of detecting the drive torque of the drive source 5 and a function of controlling forward/reverse rotation and stop of the drive source 5, and the torque detection signal b of the drive source 5 detected by the control circuit 11 is The signal is input to comparators 12 and 13. Voltages V _{1 and V 2 set by setters R 1 , R 2} and R ₃ are input to the comparators 12 and 13 as the other inputs. These voltages V ₁ ,
V ₂ is a voltage corresponding to the drive torque generated in the drive source 5 during normal operation and the drive torque during abnormal conditions such as double feeding or paper jam, and is set as V ₁ and V ₂ respectively by the setting device R ₁ ,
The control circuit 11 is set by R ₂ and R ₃ .
When the input torque detection signal b becomes larger than _V1 , the output side of the comparator 12 becomes "1" and
When it becomes larger than V ₂ , the output side of comparator 13 becomes “1”
become.

14, 15 and 16 are the comparators 12, 1
The latch circuit connected to the output side of 3 resets the contents by the sending signal _a1 generated every time paper 6 is sent out, and when there is an input, the input contents are held until the next sending signal _a1 is input. do. 17 and 18 are monostable multivibrator circuits, which output "1" for a certain period of time when the input changes from "0" to "1", and 19 and 20 are monostable multivibrator circuits.
The control circuit 11 controls the driving and stopping of the drive source 5 using the control signal 19 and the normal rotation and reverse rotation of the drive source 5 using the control signal 20.

Next, to explain the operation of each part, when the paper 6 sending signal _a1 is inputted at the same time as copying starts, the latch circuits 14, 15 and 16 are reset and the output Q is set to "0". It becomes "1".
At the same time, by inputting the drive signal _a2 , the AND gate 24
output 19 is "1", normal rotation inversion signal 20 is "1"
In this state, the drive source 5 starts rotating in the forward rotation direction. As a result, each of the fixing rollers 2 and 3 is driven to rotate, but since the paper 6 to be fixed has not yet arrived, they are in an idling state, and therefore the control circuit 1
Torque detection signal b of the drive source 5 detected by 1
does not even reach the voltages V ₁ and V ₂ set by the setters R ₁ and R ₂ , and the outputs of the comparators 12 and 13 are both "0".

Next, the paper 6 on which the transfer has been completed is transferred to the fixing rollers 2 and 3.
When only one sheet enters between them, the driving torque of the driving source 5 that drives the fixing rollers 2 and 3 increases, and the torque detection signal b becomes larger than the voltage _V2 .

As a result, only the output of one of the comparators 13 becomes "1", and the latch circuit 15 is set, and the output Q of the latch circuit 15 causes the monostable multivibrator circuit 17 to output a pulse of a certain time to AND.
However, since the output of the other comparator 14 remains "0", fixing continues without any change.

Then, when the fixing of the paper 6 is completed and the paper 6 passes between the fixing rollers 2 and 3, the driving torque of the drive source 5 decreases and the torque detection signal b becomes lower than the voltage V ₂ . The output becomes "0" and the latch circuit 1 is activated by the next paper feed signal _a1 .
5 is reset and the output Q becomes "0".

The above is a normal operation in which paper jam or double feeding does not occur on paper 6. However, to explain the operation when double feeding occurs on the next paper 6, the paper 6
When two or more overlapping sheets enter between the fixing rollers 2 and 3, the driving torque of the drive source 5 increases rapidly and the torque detection signal b reaches the voltage V ₁ via the voltage V ₂ , but the torque detection signal When the signal b reaches the voltage _V2 , the output of the comparator 13 becomes "1" and the latch circuit 15 is set.
The monostable multivibrator circuit 17 is operated by the output Q of 5, and the monostable multivibrator circuit 17 outputs pulses for a certain period of time to the AND gate 25.
Output to.

And from monostable multivibrator circuit 17
While the pulse is being output to the AND gate 25,
When the torque detection signal b reaches the voltage _V1 , the comparator 12
Since the output of is "1", the latch circuit 14 is set and "1" is outputted from the output Q of the latch circuit 14 to the AND gate 25.
Since the output of the AND gate 25 becomes "1" and the latch circuit 16 is set by this output "1", the output of the latch circuit 16 becomes "0".

Therefore, even if the output Q of the latch circuit 14 changes from "0" to "1", the output of the NAND gate 22 remains "1" and does not change, but "1" is sent to the NAND gate 23 from the output Q of the latch circuit 14. As a result, the output of the NAND gate 23 becomes "0" and the output of the AND gate 24, that is, the drive stop signal 19, becomes "0", and the control circuit 11 instantly stops the drive source 5. Therefore, the fixing rollers can be stopped before the double-fed sheets 6 are wound around the fixing rollers 2 and 3.

In addition, the operation in case of paper jam or tangled double feed is explained below.
When torque detection signal b reaches voltage _V2 , comparator 1
3 becomes "1" and the latch circuit 15 is set, and the output Q of the latch circuit 15 causes the unit stable multivibrator circuit 17 to output a pulse of a fixed time.

However, unlike the case of double feed, in the case of paper jam or tangled double feed, the torque detection signal b is higher than the voltage V ₂ than V ₁
Since it takes time to reach , during this time the AND gate 2 is
The signal output to the AND gate 25 becomes "0" and then the output of the comparator 12 becomes "1" and the latch circuit 14 is set, so the output of the AND gate 25 remains "0" and the latch circuit 14 is set. Circuit 16 is not set.

Therefore, the output of the latch circuit 16 remains "1" and does not change, so the output of the NAND gate 22 changes from "1" to "0", and the reverse signal 20 is output to the control circuit 11 (note that the signal 20 is "1"). 1" means forward rotation, "0" means reverse rotation).

As a result, the control circuit 11 causes the drive source 5 to reverse the fixing rollers 2 and 3, and this reversal is caused by the output of the monostable multivibrator circuit 18 operated by the output Q of the latch circuit 14 changing from "1" to "0". ”, the output of the comparator 13 becomes “0”, that is, the torque detection signal b becomes less than the voltage _V2 , and the rotation continues until the torque is detected. The paper 6 that has been jammed, tangled or double fed is fixed to the fixing rollers 2 and 3.
When the output of the monostable multivibrator circuit 18 becomes "0" and the output of the comparator 13 becomes "0", the output of the OR gate 26 becomes "0".
Therefore, the output of the NAND gate 22 becomes "1", and the output of the NAND gate 23 becomes "0" with the output "1" of the latch circuit 14, so the output of the AND gate 24, that is, the drive stop signal 19 becomes "1". 0'' and the drive source 5 is stopped by the control circuit 11.

As described in detail above, in this invention, the stopping and forward/reverse rotation of the drive source for driving the fixing roller is controlled by the torque detection signal detected from the drive source for driving the fixing roller. This prevents paper from getting jammed or jammed before it occurs, which prevents paper from being wasted due to paper wrinkles or poor fixing caused by double feeding, and prevents paper jams from occurring. There is no need to spend much time or effort removing the paper. It is also economical because there is no need to provide a large-capacity drive source in advance to forcibly eject sheets that are double fed.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a conventional fixing device, FIG. 2 is an explanatory diagram of a fixing device according to an embodiment of the present invention, and FIG.
The figure is the same control circuit diagram. 2 and 3 are fixing rollers, 5 is a drive source, and 6 is paper.

Claims (1)

[Claims] 1. A drive source that drives the fixing rollers 2 and 3 in a device that fixes the toner image on the paper 6 by passing the transferred paper 6 between the fixing rollers 2 and 3 that are in pressure contact with each other. A safety device for a copying machine is provided with means for detecting drive torque at 5, and controls rotation, stop, and forward/reverse rotation of the drive source 5 based on a torque detection signal detected by the detection means.