JPS6118749B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fixing device in a copying machine, and more particularly to a fixing device in an electrophotographic copying machine that uses a pair of fixing rollers to fix a heat-adhesive visible image on a copying material under heat and pressure. be.

Conventionally, this type of heating/pressure fixing device has a structure in which a pair of fixing rollers is always kept in contact with each other under a substantially constant pressure, or a pair of fixing rollers is kept in contact with a pair of fixing rollers under a substantially constant pressure during a copying cycle. A structure having a mechanism for releasing pressure contact between a pair of fixing rollers when a copying cycle is stopped (when the machine is stopped) or when a paper jam occurs is known.

However, with the former structure, when a paper jam occurs, the paper (copying material) cannot be placed in the fixing unit (fixing roller pair).
If this exists, it is necessary to manually release the pressurized contact between the pair of fixing rollers, which is cumbersome. Since the fixing roller pair maintains a pressurized contact state for a long period of time, the contact portion is deformed. It has various problems such as a short lifespan of the pair of fixing rollers.

The latter structure has the advantage of eliminating the above-mentioned problems, but the pressure contact release mechanism of the pair of fixing rollers is complex and needs to be electrically controlled, resulting in high cost and difficult control. This method has disadvantages such as complexity and frequent failures, and abnormal noises due to impact when the pair of fixing rollers is pressed into contact and released.

The present invention was made in view of the above circumstances, and its purpose is to make it possible to bring the pressure roller into pressure contact with and release from the heating roller, and to make it possible to bring the pressure roller into contact with and release the heat roller through simple control such as controlling the operation of the drive device. To provide a fixing device for a copying machine that can adjust the pressure, does not generate abnormal noise due to impact when pressure contact is released, and can set the pressure according to the internal temperature of the copying machine.

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

The output shaft 1a of the motor 1 is transmitted to the input side 3a of the fluid coupling 3 via a transmission mechanism 2 such as a sprocket 2a and a chain 2b, and the base of an arm 4 is fixed to the output side 3b of the fixing device 3. A pressure roller 5 is rotatably attached to the tip of the arm 4, and a heating roller 6 is mounted above the pressure roller 5.
is arranged.

7 is a stopper fixedly installed on the fixed side 8, facing the lower end surface 4a of the arm 4, and facing the lower end surface 4a of the arm 4.
When a comes into contact with the stopper 7, the pressure contact between the pressure roller 5 and the heating roller 6 is released, and when the arm 4 rotates clockwise, the pressure roller 5 contacts the heating roller 6.
It is configured to come into pressure contact with.

Therefore, when the motor 1 is stopped, the fluid coupling 3 does not generate transmission torque due to viscous resistance, so the arm 4 equipped with the pressure roller 5 rotates counterclockwise while remaining in contact with the stopper 7 due to its own weight. Then, the pressure contact between the pressure roller 5 and the heating roller 6 is released.

Furthermore, when the motor 1 is rotationally driven, the fluid coupling 3
Since transmission torque is generated due to viscous resistance,
The output side 3b is rotated clockwise, the arm 4 is rotated clockwise, the pressure roller 5 is brought into pressure contact with the heating roller 6, and the transmission torque of the fluid coupling 3 is applied while the motor 1 continues to rotate. Pressure contact is maintained with the appropriate pressure.

Here, the transmission torque T of the fluid coupling 3 is expressed by the following equation.

T=μ・△v/△z・A・r ...(1) However, μ is the kinematic viscosity coefficient, △v is the relative velocity, △z
is the gap, A is the contact area, and r is the effective radius.

As is clear from equation (1), the transmitted torque T is the gap △
If z, contact area A, effective radius r, and kinematic viscosity coefficient μ are the same (if they are the same fluid coupling), they will be proportional to the relative speed △v, so if the rotational speed of the motor 1 is increased or decreased, the transmitted torque will be By changing T, the pressing force (pressing contact state) between the pressure roller 5 and the heating roller 6 can be adjusted.

Also, when the motor 1 is stopped, the pressure roller 5
Since the arm 4 equipped with this rotates gradually due to the kinematic and viscous resistance of the fluid coupling 3, it quietly contacts the stopper 7 and no impact force is generated, so that no abnormal noise is generated.

Furthermore, as is clear from equation (1), the transmission torque of the fluid coupling 3 increases or decreases in proportion to the kinematic viscosity resistance μ, and the kinematic viscosity resistance μ is the environment in which the fluid coupling 3 is placed, that is, inside the copying machine. It changes depending on the temperature.

For this reason, the transmission torque of the fluid coupling 3 is large when the temperature inside the copying machine is low, and becomes small when the temperature inside the copying machine is high.

On the other hand, in a heat fusion fixing type fixing device, it is preferable to increase the pressure when the thermal energy applied to the copy material is small, and to decrease the pressure when it is large. The reason for this is that if the pressure is low when the thermal energy is small, it will cause a fixing failure, and if the pressure is high when the thermal energy is large, it will cause the image to collapse.

Therefore, according to the fixing device according to the present invention using the fluid coupling 3, when the inside of the copying machine is cold, such as in the early morning, the pressure of the pair of fixing rollers 5 and 6 is automatically increased due to the above-mentioned characteristics. Since the pressure is automatically lowered when the inside of the copier is warm during continuous copying of multiple sheets, the pressure is appropriate depending on the internal temperature of the multiple machines and good fixing operation can be performed. can.

When the fixing device 3 is continuously operated, the change in the transmitted torque due to self-heating is as shown by a characteristic curve A shown in FIG.

Next, a specific example of the present invention will be explained with reference to FIG. Note that the same members as in FIG. 1 have the same reference numerals.

A shaft 11 having first and second pulleys 9 and 10 is integrally connected to the output side 3b of the fixing device 3.

On the other hand, the support shaft 5a of the pressure roller 5 is fitted and supported by a pair of left and right upwardly inverted U-shaped guides 12 and 13 so as to be movable up and down. , 15 are rotatably provided, and the first and second wires 16 and 17 wound around the first and second pulleys 9 and 10 are connected to the third and fourth pulleys 14 and 1.
5 is hooked onto the fixed side 8 and fixed thereto.

Further, the heating roller 6 is rotatably supported by a frame (not shown), and is transmitted to the motor 1 by an appropriate transmission means (not shown), and a heater rod 18 is inserted inside the heating roller 6.

Next, its operation will be explained.

FIG. 3 shows a state in which the motor 1 has stopped and the pressure roller 5 has descended due to its own weight and is separated from the heating roller 6 (pressure contact release state).

From this state, when the motor 1 rotates clockwise (hereinafter referred to as normal rotation direction) when viewed from the output shaft 1a, the heating roller 6 rotates and at the same time, the fixing device 3 applies a transmission torque proportional to the rotational speed of the motor 1 in the normal rotation direction. Since the wires rotate while being generated, the first and second pulleys 9 and 10 fixed to the shaft 11 also rotate in the same direction and wind up the first and second wires 16 and 17.

As a result, the pressure roller 5 is pulled up, brought into pressure contact with the heating roller 6, and rotates together with the heating roller 6.

As the motor 1 continues to rotate in this state, the pressure on the pair of fixing rollers 5 and 6 gradually increases.
When the pressure obtained by the maximum transmission torque that can be generated by the fixing device 3 is reached, the pressure does not increase any further, and a constant pressure contact state is maintained.

Further, when the motor 1 is stopped due to a paper jam or other abnormality or a copy end signal, the transmission torque of the fixing device 3 decreases as the speed of the input side 3a decreases, so the first and second wires 16, 17 The winding force also decreases, and the pressure roller 5 falls due to its own weight W.

As a result, the fixing device 3 is rotated in the reverse direction, but since the fixing device 3 generates a transmitted torque due to kinematic and viscous resistance even during reverse rotation, this transmitted torque is used as a braking force when the pressure roller 5 descends. The pressure roller falls gently and quietly stops at the lower ends of the guides 12 and 13.

Therefore, no abnormal noise is generated due to impact when the pressure contact is released.

In addition, as shown in FIG. 4, the guides 12 and 13 are crushed, and the bolts 19 are attached to the cross members 12a and 13a.
They may be screwed together and fixed with a lock nut 20. 21 is a bearing.

In this way, the upper limit of the pressure roller can be regulated by the bolt 19, and for example, the transmitted torque can be limited to T in FIG. This torque T is set so as to apply a pressing force that does not cause fixing failure even when the inside of the copying machine is cold.

FIG. 5 shows a modification of the fixing device shown in FIG. 3, in which the pressure roller 5 is rotatably supported horizontally on a pair of left and right swing arms 23 and 24, which are swingably supported on a support shaft 22. , third and fourth pulleys 14 and 15 are provided at the swinging ends of the pair of swinging arms 23 and 24, and stoppers 25 and 26 are provided on the fixed side 8 facing the lower end surfaces of the swinging arms 23 and 24. It is a fixed structure. Note that since the operation is substantially the same as that shown in FIG. 3, the explanation will be omitted.

FIG. 6 shows a modification of the fixing device shown in FIG. 5, in which a segment gear 27 is integrally formed on the swing levers 23 and 24, and a gear 28 meshing with the segment gear 27 is provided on the output side 3b of the fixing device 3. Since it is a fixed structure and the operation is substantially the same as that in FIG. 3, the explanation will be omitted.

Since the present invention is configured as described above, the pressure roller 5 is brought into pressure contact with the heating roller 6. In addition to being able to release the pressurized contact, it is possible to release the pressurized contact and adjust the pressurizing force by simply controlling the operation of the motor 1. Moreover, when the pressurized contact is released, there is no abnormal noise caused by impact, and
The pressure can be set according to the internal temperature of the copying machine.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of the present invention, FIG. 2 is a diagram showing the relationship between the usage time of the fixing device and the transmitted torque,
FIG. 3 is an explanatory diagram showing one specific example of the present invention, FIG. 4 is an explanatory diagram of a partially improved version thereof, and FIGS. 5 and 6 are explanatory diagrams of other different specific examples of the present invention. 1 is a motor, 5 is a pressure roller, 6 is a heating roller, and 3 is a fluid coupling.

Claims (1)

[Claims] 1. In a fixing device in a copying machine, which is composed of a heating roller 6 and a pressure roller 5 disposed opposite to the heating roller 6, the pressure roller 5 is moved toward and away from the heating roller 6 in the vertical direction. The pressure roller 5 is held movably in the vertical direction, and the pressure roller 5 is connected to a rotation means that moves in the vertical direction, and the rotation means is connected to the output side of a fluid coupling 3 containing a viscous fluid. By connecting the motor 1 to the input side motor 1, the motor 1 is rotated to raise the fluid coupling 3, the pressure roller 5 is raised via the rotating means, and the motor 1 is stopped to raise the fluid coupling 3. A fixing device characterized in that only the output side of the pressure roller 5 rotates so that the pressure roller 5 falls under its own weight.