JPS597108B2 - Fusing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fixing device that has first and second rollers, such as a pair of fixing rollers, for fixing a visual image and can vary the pressure between the rollers.

Conventionally, a fixing device using a pair of fixing rollers of this kind has a heating roller for fixing a toner image on a copy material and a pressure roller for pressing the copy material against the heating roller. This configuration or heating roller,
A type having three rollers, a pressure roller and a heating roller, is known. Usually, these heating rollers and pressure rollers are composed of a rigid roller and an elastic roller, which are pressed against each other, and the fixing time of the copying material is obtained by increasing the contact area due to deformation of the elastic roller.

Conventionally, various methods of applying pressure to the elastic roller are known (for example, cam, link, pneumatic, etc.), but no particular attention has been paid to the method of releasing the pressure. If the power to the device is cut off, for example due to a power outage or other accident during copying, the pressure and residual heat will permanently damage the elastic rollers unless they are released from the pressurized state. This results in distortion, which significantly impairs the durability of the device. Therefore, it is essential to release the pressure when the device stops, and a fixing device that also takes countermeasures into consideration has become necessary. In view of the above points, the present invention provides a fixing device that reliably performs pressure contact and release of pressure contact.

That is, the present invention includes first and second rollers, a first position where the first roller is in pressure contact with the second roller at a predetermined pressure, and a position where the first roller is in light contact with the second roller. and a second position in which the first roller is in contact or not in pressure contact with the second roller, wherein the displacement means is in contact with the first roller. a roller, a first gear coaxial with the roller, a second gear that meshes with the first gear, and a second gear that provides a relative speed difference between the first and second gears; means for revolving the first gear around the gear, and displacing the first roller between the first position and the second position in accordance with the movement of the first gear. It is characterized by the ability to
The present invention will be explained below with reference to the drawings.

FIG. 1 shows the principle of the present invention.
, 3 is a heating rigid roller, 2 is a fixing elastic roller, 4 is a pressing rigid roller, and the pressure roller 4 is the heating roller 3.
and a horizontal surface, and is placed in contact with both.

The heating roller 3 is moved at a circumferential speed of V1 and a horizontal surface at a speed of V2 in the directions of the arrows in FIG. 1, and the pressure roller 4 is moved as shown in FIG.
It is assumed that the heating roller 3 rotates in synchronization with the circumferential speed V1. To move from the light contact state shown in FIG. 1A to the pressure contact state shown in FIG. 1B, if V1>V2 and the rotation direction is appropriately selected, the pressure roller While moving in the biting direction and pushing up the roller 3 from below, the first
Move to the state shown in Figure B.

If V1=V2 at the end of the pressing operation, the force relationship between the rollers is balanced in the state shown in FIG. 1B, and fixing can be performed. To release the pressure contact, set V2 to 1, or, more simply, apply force in the direction of arrow A while maintaining the state of V1=V2, and the roller 4 will be removed from the pressure position and the pressure contact force will be released. Ru.

The method described above is extremely effective in simplifying the apparatus because pressure contact and release of pressure contact are performed depending on the rotational force relationship between the rollers.

However, if a release accelerator such as silicone oil is applied to the fixing roller to improve release properties, there is a risk that the roller will slip due to the formation of a thin lubricant film on the roller surface. It may be missing.

In the following embodiment of the present invention, the above-mentioned disadvantages are solved by using a planetary gear instead of the pressure roller 4 described above to further ensure operation.

2 to 5 show one embodiment of a fixing device for an electrophotographic copying machine to which the present invention is applied.

In Fig. 2, 5 is a heating roller made of a pipe made of a material with good thermal conductivity such as copper or aluminum, and has a heater 8 inside it (Fig. 3), and both ends of the heating roller 5 are equipped with bearings. It is attached to the support plate 9 via. The support plate 9 is attached to the substrate 13 of the device via a support shaft, and is pressed downward together with the heating roller 5 by a compression spring 10.

Reference numeral 6 denotes a fixing roller made of a heat-resistant material with good mold releasability, such as silicone rubber, and an anti-offset liquid such as silicone oil is applied to the surface of the roller as necessary to promote mold releasability.

The circumferential surface of the fixing roller 6 is heated and maintained at a temperature sufficient to heat and fuse the toner image by the heat from the heating roller 5.
Both ends thereof are attached to the substrate 13 via bearings so as to be movable in the vertical direction. Reference numeral 7 denotes a pressure roller whose peripheral surface of a pipe made of a material with good thermal conductivity such as copper or aluminum is coated with a material having good mold release properties, such as Teflon (tetrafluoroethylene resin), and a heater 11 is installed inside the pressure roller. (FIG. 3), and both ends of the pressure roller 7 are attached to the swing plate 12 via pairing.

The swing plate 12 is attached to the substrate 13 so as to rotate about a shaft 14 fixed to the substrate 13. axis 14
A drive gear 16 coupled to a drive source (not shown) is rotatably attached to the drive gear 16, and the drive gear 16 meshes with a pressure roller gear 17. The pressure roller gear 17 is connected to the pressure roller 7, and when the pressure roller gear 17 rotates, the pressure roller 7 rotates. A copying material (transfer paper) 15 carrying an unfixed toner image is sent between the fixing roller 6 and the pressure roller 7 with the toner image side facing the fixing roller 6, as shown in the third figure, and is sent between the fixing roller 6 and the pressure roller 7. , 7, the toner image is heated and pressurized to fix the toner image.

When one drive force is transmitted from one drive source to one drive gear 16 , the pressure roller 7 rotates via the pressure roller gear 17 .

When the fixing is not performed, the rollers 5, 6, and 7 rotate in light contact with each other (non-pressure contact), and the fixing roller 6 is kept in a heated state by the heating roller 5 and the pressure roller 7. The pressure roller gear 17 meshes with a planetary gear 18 rotatably provided on the swing shaft 27.

The planetary gear 18 meshes with a control gear 19 rotatably provided on a fixed shaft 21 fixed to the substrate 13.

The control gear 19 is operatively connected to a fixed shaft 21 via a spring clutch 20.

As shown in FIGS. 4 and 6, the spring clutch 20 includes a coil spring 24 and a coil spring 24 wound around a fixed shaft 21.
It has a control ring provided at 4. This spring clutch 20 is controlled via a lever 23 by an electromagnetic plunger SLl. As shown in FIG.
is rotatably mounted on a shaft 23', and is given the habit of rotating counterclockwise by a tension spring 25.

When the electromagnetic plunger SLl is not energized and is inactive, the lever 23 is moved against the shaft 23 by the action of the tension spring 25.
The lever 23 rotates counterclockwise around 1, and the claw 23' at the tip of the lever 23 engages with the spring clutch 20.

As a result, the coil spring 24 of the spring clutch 20 is expanded as shown in FIG. 6, so that the connection between the control gear 19 and the fixed shaft 21 is broken, and the control gear 19 can freely rotate relative to the fixed shaft 21. It becomes possible. Also, when the electromagnetic plunger SLl is energized and activated, the lever 23
rotates clockwise around the shaft 23, and the lever 23
The pawl 23'' is removed from the spring clutch 20.

As a result, the coil spring 24 of the spring clutch 20 is compressed, so that the control gear 19 and the fixed shaft 21 are connected, and the rotation of the control gear 19 is forcibly prevented. Note that other known mechanical or electrical clutches may be used in place of the spring clutch.

A first lever 26 and a second lever 26'' are attached to the fixed shaft 21.
is rotatably provided (Fig. 2), and the first lever 2
A swing shaft 27 is attached to the other end of the lever 6 and the second lever 26'.

The first lever 26 is given the habit of rotating clockwise about the fixed shaft 21 by the action of the tension spring 32.

Even if the swing shaft 27 moves to the fifth illustrated position, each gear 16,
A stopper (not shown) that engages with the second lever 265 is provided at an appropriate position so that the levers 17, 18, and 19 are always engaged. A roller 28 is further rotatably provided on the swing shaft 27 and in contact with the pressure roller 7, and movement of the swing shaft 27 moves the pressure roller 7 up and down.

A lock arm 29 having a notch 39'' for regulating the movement of the swing shaft 27 is rotatably attached to the shaft 30, and the lock arm 29 is rotated counterclockwise about the shaft 30 by a tension spring 31. It has a habit of rotating.

This lock arm 29 is connected to an electromagnetic plunger SL2.

Next, the operation of the above device will be explained.

When fusing is not performed, each element of the device is in the position shown in FIG. The rollers are rotating in contact and each roller is in a non-pressure state.

Therefore, the fixing roller 6 is uniformly heated and maintained by the rollers 5 and 7. Now, when a signal for applying pressure is sent to this device according to a predetermined sequence of the copying machine, the electromagnetic plunger SLl is actuated (energized) by this signal, and the lever 23 is centered around the shaft 23'. (Fig. 3), and the pawl 23' of the lever 23 engages the spring clutch 2.
0, the control gear 19 is connected to the fixed shaft 21,
Rotation of control gear 19 is forcibly prevented.

Due to the stoppage of the control gear 19, the rotating planetary gear 1
8 revolves counterclockwise around a fixed shaft 21 while rolling on a control gear 19 .

Due to the revolution of the planetary gear 18, the rollers 28 coaxial with the planetary gear 18 rotate counterclockwise about the fixed shaft 21, pushing up the pressure roller 7 from below. By pushing up the pressure roller 7, the fixing roller 6 also moves upward. The pushed up fixing roller 6 and pressure roller 7
Since the heating rollers 5 are pressed downward from above by the compression spring 10, they are in pressure contact with each other. In addition, compression spring 1
By appropriately selecting a spring constant of 0, each roller can be maintained in an equilibrium state with a desired pressing force. On the other hand, planetary gear 1
When the second lever 26' rotates counterclockwise due to the revolution of 8, the end of the second lever 26' touches the micro switch SW.
Turn it on by engaging micro switch SWl.
The electromagnetic plunger SL2 is actuated (energized) by an electric signal from the electromagnetic plunger SL2. The lock arm 29 rotates clockwise around the shaft 30 due to the operation of the electromagnetic plunger SL2. are fitted, and movement of the swing shaft 27 is prevented.At this time, the tip of the lock arm 29 engages with the micro switch SW2 to turn it on, and the electromagnetic plunger SLl is activated by an electric signal from the micro switch SW2. It becomes inoperative (no electricity is applied).As a result, the lever 23 rotates counterclockwise, the pawl 23'' engages with the ratchet 20'', and the control gear 19 is released from its fixed state and rotates freely. The pressure operation is completed, and the copying material is fixed in this pressurized state.Next, when the fixing operation is completed, a signal to release the pressure is sent to this device according to a predetermined sequence of the copying machine, and the , this signal causes the electromagnetic plunger SL to
2 becomes inoperative (no electricity is applied).

Therefore, the lock arm 29 is rotated counterclockwise by the tension spring 31, the notch 39' is separated from the swing shaft 27, the swing shaft 27 is pulled back by the tension spring 32, and the first The lever 26 and the second lever 2V rotate clockwise about the fixed shaft 21. Due to the movement of the swing shaft 27, the planetary gear 18 revolves clockwise around the fixed shaft 21, and the rollers 28 also move.
As a result, the rollers 5, 6, and 7, which were in pressure contact with each other, return from the pressure contact state to the non-press contact state in which they are in light contact, as shown by the broken line in FIG.

In the case of this embodiment, since the configuration is as described above, when power to the device stops due to a power outage or the main switch being turned off due to an accident while pressurizing, the electromagnetic plunger SL
2 becomes inoperative and the lock arm 29 is separated from the swing shaft 27 by the spring 31, so the pressure is immediately released.
Deformation of the fixing rubber roller 6 can be prevented and the safety of the apparatus can be maintained.

In addition, it is preferable to keep the deformation period of the elastic rubber roller as short as possible during the pressure contact period and the pressure release time. By setting this, the fixing roller can be kept in a heated state during the fixing wait period.
In another embodiment of the present invention, the control gear 19 is driven by another drive source, and the pressure roller gear 17 and the control gear 1
By creating a relative speed difference between the planetary gear 1 and the
It is also possible to make the pressurizing or releasing operation by rotating the pressurizing member 8.

Although this embodiment has been described using three rollers, it can also be implemented with a two-roller configuration.

Furthermore, when applying silicone oil or the like to the elastic rollers to improve mold release properties, the rollers 5 and 6 may not rotate due to slippage.
Alternatively, even if 1 drive is given to 6, this does not hinder implementation of the present invention.

[Brief explanation of drawings]

1 is a diagram showing the principle of the present invention, FIG. 2 is a perspective view of a main part of a fixing device showing an embodiment of the invention, FIG. 3 is a sectional view, and FIG. 4 is a side view showing a press-contact state. FIG. 5 is a side view of the main parts showing the pressure release state, and FIG. 6 is a view showing the spring clutch. 5, 6, 7, 8...Roller, 16, 17, 18
,19...Gear.

Claims (1)

[Claims] 1 first and second rollers, a first position where the first roller is in pressure contact with the second roller at a predetermined pressure, and a first position where the first roller is in light contact or pressure contact with the second roller; In the fixing device, the fixing device includes means for displacing the first roller relative to the second roller to a second position in which
A roller in contact with the first roller, a first gear coaxial with the roller, and a second gear meshing with the first gear.
a gear, and means for giving a relative speed difference between the first gear and the second gear and causing the first gear to revolve around the second gear, A fixing device characterized in that the first roller is displaced between the first position and the second position according to the movement.