JPS604192Y2 - pressure fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure fixing device for an image recording device that forms toner images, such as an electrophotographic device or other electrostatic recording device or magnetophotographic device.

The pressure fixing device uses at least one pair of rollers to pressurize the toner image support material and fix the toner image on the support material by the pressure applied thereto.

Although this pressing force varies depending on the type of toner, it is usually required to be 9 in 10 or more per 1011 in the longitudinal direction of the roller.

Therefore, the load applied to the roller is usually several hundred or more, depending on the length of the roller.

Therefore, a large torque is required to drive the rollers, and large torque fluctuations occur as the toner image supporting material is carried into the roller pair.

This is shown in Figure 1.

In the figure, ■ indicates when the roller pair is idling with no image supporting material between the roller pair, ■ indicates when the tip of the image supporting material enters the roller pair, and ■ indicates when the image supporting material after the tip of the roller pair enters the roller pair. During pressurized conveyance, ■ indicates the time when the rear end of the image support material is discharged from the pair of rollers.

As shown in the figure, the torque fluctuation is particularly remarkable when the leading end of the image support material enters between the pair of rollers, and this tends to cause a failure of the driving force source or the driving force transmission means.

In addition, a large output power source is required as a driving force source, leading to an increase in the size and cost of the device.

Furthermore, if the driving power source is not only a pressure fixing device but also a driving power source for a means for forming a toner image on an image support material, such as an original scanning device or a photoreceptor, the torque fluctuations may be caused by the power transmission. This is also transmitted to these means via the means, and as a result, image blur etc. occur, impairing a good image forming operation.

In order to solve this problem, the tip of the toner image support material is made oblique so that it enters the roller pair to reduce the impact.
Buffer means are provided at various locations in the power transmission means, but in the former case, the image supporting material is likely to wrinkle or jam, and in the latter case, the structure becomes unnecessarily complicated. This also results in higher costs.

The main purpose of the present invention is to solve the above-mentioned disadvantages.

The pressure fixing device of the present invention uses at least one pair of rollers to pressurize and convey a toner image support material and fix the toner image under pressure. The driving force transmission means for transmitting the driving force to the chain includes a chain, an idler member engaged with the tension side portion of the chain, a support member displaceably supporting the idler member, and a drive force transmitting means that elastically connects the idler member to the chain. The chain is characterized by having an elastic member that presses the chain and changes the direction of the chain against the tension of the chain.

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

FIG. 3 shows an example of an electrophotographic copying apparatus to which the present invention can be applied.

In the figure, 1 is a fixed document table.

The original placed on this table 1 is moved back and forth parallel to the table 1.
It is scanned by two mirrors 2 and 3.

That is, the mirrors 2 and 3 are fixed to supports 4 and 5, respectively, and the supports 4 and 5 are slidably supported on the guide rail 6.

Here, pulleys 7.8 are coaxially attached to the support 5 and are rotatable relative to each other.

Since the support 5 is movable, the pulley 7.8 is a so-called movable pulley.

Reference numerals 9 and 10 indicate pulleys provided at fixed positions, so-called fixed pulleys.

11 is a drive pulley provided at a fixed position.

Reference numeral 12 denotes a wire, one end 121 of which is fixed in a fixed position, hung around a pulley 7 and folded back, and the other end 12 □ connected to the support 4.

One end 13 □ of 13 is fixed in place with another wire, looped around pulley 8, turned back, then hooked around pulley 10 to change direction, then wound around drive pulley 11 several times, and then The rear end 13□, which is turned around the pulley 9, is connected to the support 4.

As described above, when the pulley 11 is rotated in the direction of the solid line, the mirrors 2 and 3 move in the direction of the solid line arrow at a speed ratio of 1:1/2 to scan the original.

The image of the document scanned in this manner is exposed to slit light through the lens 14 and fixed mirrors 15 and 16 onto an electrophotographic photoreceptor which is uniformly charged by a charger 171 and rotates in the direction of the arrow.

When scanning of the original is completed, the pulley 11 is rotated in the direction of the broken line to move the mirrors 2 and 3 back to the forward movement starting position.

The electrostatic latent image formed by exposure during scanning of the document is developed by a developing device 17□, and the toner image thus formed is transferred onto paper by a transfer charger 17□.

The paper to which the toner image has been transferred passes through a pressure fixing device and undergoes a pressure fixing process for the image.

A broken line P is a paper conveyance path.

As the fixing device, a pressure fixing device in which a pair of rigid rollers 1B and 19 are pressed against each other with strong pressure (for example, about 10 to 50 to 9 per 10 in the longitudinal direction of the rollers) can be used.

That is, the paper carrying the toner image is conveyed between the rollers 18 and 19, and the toner image is fixed on the paper by the above-mentioned strong pressure.
A strong impact occurs when the paper enters between B and 19.

The pulley 11 is rotationally driven by a motor 20.

That is, the rotational driving force of the motor 20 is first transmitted to the rotational direction switching mechanism 22 by the chain sprocket mechanism 21 .

This mechanism 22 switches its output rotation direction to the same direction as the motor or the opposite direction by switching the clutch, but in either case, this output rotation is transmitted to the pulley 11 by a chain sprocket 23.

On the other hand, the rotational driving force of the motor 20 is transmitted to the photosensitive drum 17 by sharing the driving force transmission to the mechanism 22 and the chain, and to the fixing roller 18 by the chain-sprocket mechanism 24.
and rotates each in the direction of the arrow.

Note that the roller 19 rotates as a result of the roller 18 due to frictional force.

When the drive motor is used to drive the pressure fixing device and other driven systems in this way, the drive torque of the motor is usually
Approximately 70% is consumed by the pressure fixing device.

FIG. 4 is a detailed view of the main parts of the apparatus shown in FIG. 3.

In the figure, 24 degrees is a sprocket fixed to the output shaft 20 degrees of the motor 20 with a key or the like.

Further, 243 is a sprocket fixed to the shaft 18□ of the roller 18 with a key or the like.

A chain 241 is passed between the sprockets 24° and 243.

Therefore, when the sprocket 24□ is rotationally driven in the direction of arrow A by the motor, the chain 241 also rotates in the directions of arrows B and C, causing the sprocket 243 to rotate in the direction of the arrow.
This causes the fixing roller 18 to rotate in the direction of the arrow.

Here, the side of the chain running in the direction of arrow B, that is, the side that is paid out from sprocket 243 and pulled into sprocket 24□, is the tension side of the chain, while the side of the chain that runs in the direction of arrow C, that is, the side that is paid out from sprocket 24□, is the tension side of the chain. The side taken up by the sprocket 243 is the slack side of the chain.

Reference numeral 25 denotes an idler sprocket that is normally engaged on the slack side of the chain to prevent chain slack.

The sprocket 25 is rotatably supported by a shaft 251 fixed to a lever 27 which is rotatably supported by a shaft 26 .

One end of a tension spring 28 is attached to the immovable member 29, and the other end of the tension spring 28 is attached to the lever 27.

The spring 28 biases the lever 27 to rotate counterclockwise about the shaft 26, thereby causing the sprocket 25 to rotate against the chain 2.
41 is elastically pressed against the chain tension to change the direction of the chain and prevent it from sagging.

As the chain 241 runs, the sprocket 25 spins idly.

Note that when the sprocket changes the direction of the chain, it means that the direction of the chain when it travels to the sprocket is different from the direction of the chain when it travels from the sprocket.

Now, 30 is a shock absorbing sprocket that is engaged with the tension side of the chain 241.

This sprocket 30 is rotatably supported by a shaft 301 fixed to a lever 32 rotatably supported by a shaft 31.

One end of a tension spring 33 is attached to the immovable member 34, and the other end of the tension spring 33 is attached to the lever 32.

This spring 33 urges the lever 32 to rotate counterclockwise about the shaft 31, thereby elastically pressing the sprocket 30 against the tension side portion of the chain 24□, thereby causing the chain to resist the tension of the chain. It's changing direction.

As the chain 241 runs, the sprocket 30 spins idly.

Reference numeral 35 denotes a stopper, which locks the lever 32 and limits its rotation range in the counterclockwise direction.

This prevents the sprocket 30 from being displaced more than necessary due to the elastic force of the spring 33 against the tension of the chain 241.

Now, when the leading edge of the toner image supporting paper enters between the rollers 1B and 19, the tension in the tension side of the chain 24□ temporarily increases significantly.

This increased tension then displaces the sprocket 30, and thus the lever 32, clockwise about the shaft 31 against the elastic force of the spring 33.

That is, the sprocket 30 is displaced to the position 30, and the running path of the chain 24□ also becomes 241.

Therefore, the increase in chain tension, in other words, the torque fluctuation, is buffered by the spring 33, and the rollers 1B and 1 at the leading edge of the paper are buffered by the spring 33.
The torque fluctuation at the time of entry into the interval 9 is as shown at 0 in FIG.

Comparing 0 in FIG. 2 with ■ in FIG. 1, it can be seen that the peak value is significantly smaller.

Note that the elastic force of the spring 33 is such that when there is no paper between the rollers 1B and 19 and they are idling (indicated by ■), and after the leading edge of the paper enters, the rollers 18 and 19 pressurize and convey the paper. When (
2), press the sprocket 30 against the chain against the tension of the chain 241, and move the lever 32 to the stopper 35.
The pressing force is set to .

When the leading edge of the paper passes between the rollers 18 and 19, the lever 32 suddenly returns to its original position and violently collides with the stopper 35. Therefore, the stopper 35 is made of a rigid core coated with an elastic material such as rubber. An elastic material is placed on the engaging part of the
It would be better if this could prevent shocks and noises.

Incidentally, when the torque fluctuation peak value at (2) in FIG. 1 is relatively small, a spring 33 having a relatively small spring constant can be used.

In such cases, the stopper 35 should be eliminated and the spring 3
3 only, and when ■ and ■, the idler sprocket 30 is kept at a substantially constant position against the tension of the chain 241, and only when the leading edge of the paper enters between the rollers 1B and 19, the chain 2
It is also possible to balance the sprocket 30 by displacing the sprocket 30 by varying the tension of the sprocket 41.

Furthermore, the present invention can also be applied to an image recording apparatus in which the driving force of the driving force source is used only to drive the pressure fixing device.

In any case, according to the present invention, it is possible to reduce the torque fluctuation when the image support material rushes into the pair of pressure fixing rollers with a simple configuration, and it has an excellent effect on downsizing the driving power source and preventing failures. Furthermore, even in an apparatus in which the driving force of the driving force source is used to drive a means for forming a toner image, problems such as image blurring can be prevented.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining torque changes in a conventional pressure fixing device, FIG. 2 is a diagram for explaining torque changes in a pressure fixing device according to the present invention, and FIG. 3 is a diagram for explaining torque changes in a pressure fixing device according to the present invention. An explanatory diagram of an applicable electrophotographic apparatus, FIG. 4 is an explanatory diagram of an embodiment of the present invention. 18.19 is a pressure fixing roller, 20 is a drive motor, 2
41 is chain, 24□, 243 is sprocket, 30
is the idler sprocket, 31 is the shaft, 32 is the lever,
33 is a spring.

Claims (1)

[Claims for Utility Model Registration] 1. In a pressure fixing device that fixes a toner image under pressure by transporting a toner image support material under pressure using at least one pair of rollers,
The driving force transmission means for transmitting the driving force from the driving force source to the roller includes a chain, an idler member engaged with the tension side portion of the chain, and a support member that displaceably supports the idler member. and an elastic member that elastically presses the idler member against the chain and changes the direction of the chain against the tension of the chain. 2. The elastic force of the elastic member is strong enough to allow the idler member to be displaced by the tension of the chain when the leading end of the toner image support material enters between the pair of rollers. The pressure fixing device according to item 1. 3. The utility model according to claim 2, further comprising a stopper member that engages with the support member and limits displacement of the idler member in a direction that resists the tension of the chain due to the elastic member. Pressure fixing device. 4. The elastic force of the elastic member is strong enough to press the support member against the stopper member against the tension of the chain when there is no toner image support member between the pair of rollers. The pressure fixing device according to item 3. 5. The elastic force of the elastic member is such that the support member is pressed against the stopper member against the tension of the chain while the toner image support material is passing after the tip enters between the pair of rollers. A pressure fixing device according to claim 4 of the utility model registration claim. 6. The pressure fixing device according to claim 3, claim 4, or claim 5, wherein the stopper member has an elastic material at the engagement portion with the support member. 7. The driving force source also supplies driving force to a means for forming a toner image on a toner image support material. Section 5 or Section 6
Pressure fixing device as described in section.