JPH067290B2 - Heat roll feed control method - Google Patents

Description

The present invention relates to a heat roll feeding control method for a fixing device in an electrophotographic apparatus.

[Conventional technology]

In a fixing device of an electrophotographic apparatus that forms an image on a continuous printing paper in a long shape, it is formed on the printing paper while sandwiching and transporting the printing paper between a heat roll and a backup roll rotatably pressed against each other. There is also a method of fixing an unfixed toner image.

[Problems to be Solved by the Invention]

By the way, in this type of fixing device, when printing is stopped, it is ideal to position and stop perforations provided on the printing paper in the vicinity of the facing position of the heat roll and the backup roll. Since it only applied a predetermined braking force to the heat roll at a constant timing, the load on the heat roll fluctuates with changes in the paper width and paper thickness used for printing, and as a result, the paper There is a problem that the paper stop position varies depending on the type.

An object of the present invention is to accurately stop the perforations of the printing paper near the position where the heat roll and the backup roll face each other even when the load on the heat roll fluctuates.

[Means for Solving the Problems]

The above-mentioned object has a heat roll that feeds and fixes continuous paper, a motor that drives the heat roll, an encoder that detects a rotation angle of the motor, and a motor control circuit, and the heat roll uses a pulse braking signal. In the electrophotographic device, the braking of is started at a predetermined timing for stopping the heat roll at the perforation position of the continuous paper,
At the start of braking on the heat roll, the generation cycle of the encoder pulse is detected, the duty ratio of the braking signal is increased when the generation cycle of the encoder pulse is shorter than a predetermined reference cycle, and the braking cycle is longer when it is longer than the reference cycle. This is achieved by lowering the signal duty ratio.

[Action]

According to the present invention, when the heat roll braking is started, the load applied to the heat roll can be known by detecting the generation period of the encoder pulse, and then the duty ratio of the braking signal to the heat roll is determined according to the load. By changing it, the sum of the braking force applied to the heat roll from the deceleration of the heat roll to the stop (friction force by load + electric braking force by the braking signal) is made almost constant, and the paper feed amount from the deceleration of the heat roll to the stop is set. The paper can be stopped at the target position while keeping it almost constant.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram showing an example of a fixing device for fixing a toner image on a sheet in an electrophotographic apparatus. FIG. 2 is a view of FIG. 1 as viewed in the direction of arrow A.

In the figure, 1 is a sheet. The sheet 1 has a long continuous shape, and is fed from the right side to the fixing device side in FIG. 1 through a toner image forming process by a toner image forming means (not shown). The sheet 1 sent to the fixing device side is attracted to the upper surface side of the preheater 3 by the suction blower 4, and the toner image formed on the sheet 1 is preheated by the preheater 3 before fixing. The sheet 1 that has passed through the preheater 3 is heated and pressed between the heat roll 5 and the backup roll 6 that are rotatably pressed against each other, and the toner image is fixed. The paper 1 that has passed between the heat roll 5 and the backup roll 6 is guided by the stacker roll 7, the idle roll 8 and the puller 9 and is sequentially fed to the paper folding device 10.

The heat roll 5 is connected to a drive motor 13 via gears 11 and 12, and an encoder 14 for detecting a rotation angle is attached to the drive motor 13. Further, the paper hole detector 2 is provided at the portion where the paper hole 15 passes, and detects the amount of paper sent by the heat roll 5.

Hereinafter, in the present embodiment, the upper and lower 1/3 inch (8.47 mm) of the paper perforation 16 is set as the print inhibition area, and the contact width between the heat roll 5 and the backup roll 6 is set to 1/2 inch (12.7 mm). However, a case where the paper feed speed by the heat roll is set to 35 inches (899 mm) / sec will be described as an example.

FIG. 3 is a circuit diagram showing an embodiment of a control circuit for carrying out the heat roll feeding control method according to the present invention, and FIGS. 4 to 7 are time charts showing the operation of FIG. FIG. 8 is a diagram showing the relationship between the sheet feed speed and the elapsed time according to the heat roll feed control method of the present invention.

First, the signal names and configuration of FIG. 3 will be described.

The heat roll drive signal is a signal for rotating the heat roll 5 during printing, and when the paper is stopped, the paper perforation 16 to be stopped on the heat roll 5 is 0.75 inches (19.05 mm) from the target stop position. ) It changes from low level to high level when it reaches the position in front.

The encoder pulse signal is a signal for detecting the rotation of the drive motor 13. For example, assuming that the number of pulses of the encoder 14 is 240 per rotation of the drive motor 13, and the paper 1 is fed by the heat roll 5 of about 2 inches (50.8 mm) per rotation of the drive motor, 2 inches (50 .8 mm) / 240 pulses = 0.0083 inch (0.21 mm) An encoder pulse signal is generated every time the paper 1 is fed.

The paper hole pulse signal is a signal for detecting the paper hole 15. Space between paper holes 15 is 1/2 inch (12.7 mm)
The paper hole pulse signal is 1/2 inch (1
(2.7 mm) each time it is fed, it occurs at the center of the paper hole (diameter 4 mm).

The position counter 17 is loaded by the paper hole pulse signal, and the output of the position counter 17 becomes -30. The output of the position counter 17 is counted up from -30 by the encoder pulse signal. Paper hole pulse signal is 1 for paper
Since it is generated every 1/2 inch (12.7 mm), the output of the position counter 17 is incremented from -30 by +60 by the encoder pulse signal to be +30. Next, when the paper hole pulse signal is generated, the output of the position counter 17 changes from +30 to -30. The operation described above is repeated during paper feeding.

The heat roll stop pulse signal is a signal for instructing to stop the heat roll 5, and is generated when the output of the position counter 17 becomes +8. 38 pulses x 0.0083 inch (0.21 mm) / pulse = 0.32 inch (8.13) after the paper hole pulse signal is generated.
mm) Emitted every time the paper is fed.

The brake signal is a signal for causing the drive motor 13 to generate a counter electromotive force, which is opposite to that when the paper is running, to brake the heat roll 5, and a low level indicates that the heat roll is being braked.

Next, a heat roll feed control method will be described.

In this embodiment, when braking the heat roll 5, the paper feed speed by the heat roll 5 is 25 inches (635 m).
m) / sec or more, 8.5 inches (215.9 mm)
8.5 to 8.5 inches per second to 25 inches (635 mm) per second
The duty ratio of the brake signal of the heat roll 5 is changed depending on the case of inches (215.9 mm) / second or less.

First, generation of a brake signal with a 25% duty as shown in FIG. 4 will be described. The heat roll drive signal goes high, and then the position counter 17 outputs +8.
Then, a heat roll stop pulse signal is generated. Since the heat roll drive signal is at high level, the output of the NAND gate 18 becomes low level, the flip-flop 19 is reset, and the 0 side output of the flip-flop 19 changes from low level to high level. And one shot 2
0 oscillates only for 5 msec, and 25% duty lock is generated as a brake signal for 5 msec. At the start of the heat roll braking, the load applied to the heat roll 5 can be known by detecting the encoder pulse generation period by applying a constant brake signal to the heat roll 5 for a predetermined time. Such control is performed.

When the 25% duty brake signal is generated for 5 msec, the 0-side output of the one-shot 20 becomes high level.
After this, the heat roll feed rate is 25 inches (635 m
If it is faster than m) / sec, a brake signal as shown in FIG. 5 is generated. As the paper travels 1 inch (25.4 mm), 120 encoder pulse signals are generated, so the heat roll feed speed is 25 inches (63 mm).
In the case of 5 mm) / sec or more, the generation period of the encoder pulse signal is 1 / (25 × 120) = 333 μs or less. Each time the encoder pulse signal is generated, the retriggerable one-shot 23 oscillates and the oscillation time is set to 980
Since it is set to μs, the 0-side output of the retriggerable one shot 23 remains at the low level. Therefore, the retriggerable one-shot 24 also oscillates every time the encoder pulse signal is generated, and the oscillation time is set to 333 μs, so that the output on the first side of the retriggerable one-shot 24 remains high. Then, the output of the NAND gate 25 goes low and the brake signal remains generated through the NOR gate 26.

When the heat roll feed rate is between 25 inches (635 mm) / sec and 8.5 inches (215.9 mm) / sec, the brake signal shown in FIG. 6 is generated. The generation cycle of the encoder pulse signal is from 333 μs to 980 μs (1
/(8.5×120)=980). The 0-side output of the retriggerable one-shot 23 remains at the low level, and the retriggerable one-shot 24 oscillates for 333 μs each time the encoder pulse signal is generated. Therefore, 3 is generated every time the encoder pulse signal is generated.
The brake signal is generated for 33 μs, and the duty ratio of the brake signal decreases as the heat roll feed speed decreases.

Heat roll feed rate is 8.5 inches (215.9m
In the case of m) / sec or less, the brake signal is not generated as shown in FIG. The generation cycle of the encoder pulse signal is 980 μs or more, and the retriggerable one shot 23 is 980 μs each time the encoder pulse signal is generated.
Oscillates for a while. When the encoder pulse signal is generated, the 0-side output of the retriggerable one shot 23 is at a high level, so the retriggerable one shot 24 does not oscillate. Therefore, no brake signal is generated.

FIG. 8 shows the relationship between the heat roll feed speed and the elapsed time according to the heat roll feed control method described above. S1 shows the case where the load on the heat roll is small, and S2 shows the case where the load on the heat roll is large. In the case of S1, even after the 25% duty brake signal is generated for 5 msec, the heat roll feed speed is 25 inches (6
Since it is faster than 35 mm) / sec, a brake signal is generated at 100% duty, and the heat roll is rapidly decelerated.
When the heat roll feed rate becomes slower than 25 inches (635 mm) / sec, the duty ratio of the brake signal decreases as the heat roll feed rate becomes slower, and the brake is applied when it becomes slower than 8.5 inches (215.9 mm) / sec. Instead, the heat roll gradually slows down and stops only by the frictional force. In the case of S2, if a 25% duty brake signal is generated for 5 msec, the heat roll feed rate is 2
It becomes 5 inches (635 mm) / sec or less, and a 100% duty brake like S1 cannot be applied. After that, as with S1, the duty ratio of the brake signal decreases as the heat roll feed speed becomes slower, and when it becomes slower than 8.5 inches (215.9 mm) / sec, it gradually heats only by friction without applying the brake. Roll slows down and stops. As a result, even if the load on the heat roll fluctuates, the amount of paper sent from deceleration to stop of the heat roll can be made almost constant, and when the printing is stopped, the perforation position of the printing paper is backed up with the heat roll. The paper can be stopped while being positioned at the opposite portion of the roll.

In the present embodiment, the method of generating the brake signal is divided into three stages according to the heat roll feed speed, but it may be divided into any number of stages according to the load applied to the heat roll.

〔The invention's effect〕

According to the present invention, when the heat roll is stopped, the duty ratio of the braking signal applied to the heat roll changes according to the load fluctuation applied to the heat roll, that is, the generation cycle of the encoder pulse, so that the stop position accuracy of the sheet is improved. Can be made.

Further, since the accuracy of the stop position of the paper can be improved, the print prohibited area of the paper can be set narrow.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a fixing device, FIG. 2 is a view taken in the direction of the arrow in FIG. 1, and FIG. 3 is a circuit diagram showing an embodiment of a control circuit for carrying out the heat roll feeding control method according to the present invention. , Fig. 4,
FIGS. 5, 6, and 7 are time charts showing the operation of FIG. 3, and FIG. 8 is a diagram showing the relationship between the sheet feed speed and the elapsed time by the heat roll feed control method according to the present invention. 1 ... Paper, 2 ... Paper hole detector, 3 ... Preheater, 4 ... Suction blower, 5 ... Heat roll, 6 ... Backup roll, 7 ... Stacker roll, 8 ... Idle roll, 9
... puller, 10 ... paper folding device, 11, 12 ... gear, 13 ... drive motor, 14 ... encoder, 15 ... paper hole, 16 ... paper perforation, 17 ... position counter, 18,
21, 25 ... NAND gate, 19 ... Flip-flop,
20 ... One shot, 22 ... Inverter, 23, 24 ...
Retriggerable one shot, 26 ... Noah Gate.

Claims (1)

[Claims] 1. A heat roll that feeds and fixes continuous paper, a motor that drives the heat roll, an encoder that detects a rotation angle of the motor, and a motor control circuit, and heat by a pulse braking signal. In an electrophotographic apparatus in which the braking of the roll is started at a predetermined timing for stopping the heat roll at the perforation position of the continuous paper, when the braking of the heat roll is started, the generation cycle of the encoder pulse is detected and the encoder A heat roll feed control method comprising increasing the duty ratio of the braking signal when the pulse generation period is shorter than a predetermined reference period, and lowering the duty ratio of the braking signal when the pulse generation period is longer than the reference period.