JP3121447B2 - Fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device having a fixing roller which is drivingly connected to a driving source via a driving transmission means and is heated by a heating means.

[0002]

2. Description of the Related Art A fixing device of the above-mentioned type is well known and is used in copiers, printers, facsimile machines and the like. In this type of fixing device, a toner image is transferred by an image carrier, for example, a photoreceptor, and the paper separated from the photoreceptor is sent to a fixing unit by a suitable conveyance means such as a conveyance belt, and is nipped and conveyed by a fixing roller pair. Thus, the toner image is fixed on the sheet. In this case, if the conveyance length from the transfer / separation part of the photoconductor to the fixing roller pair is longer than the maximum length in the conveyance direction of the sheet, the paper may not straddle both the transfer / separation part of the photoconductor and the fixing roller pair. Absent. However, in a machine capable of copying long paper such as A0 size paper, the paper reaches the fixing roller during transfer / separation, so that the paper is either pulled or loosened therebetween.

In such a case, the image being transferred is usually blurred when pulled, so that the image is loosened. That is, with respect to the transport speed V1 of the paper being transferred,
Assuming that the transport speed of the sheet during fixing is V2, the configuration is such that V1 ≧ V2. At this time, if V1 = V2, the diameter of the fixing roller changes due to thermal expansion.
It is common to set V1> V2.

However, when V1> V2 is set, if the speed difference is too large, the amount of slack in the sheet also increases, causing wrinkles and the like. Therefore, an empirical value is applied to the speed difference.

Japanese Patent Application Laid-Open No. 1-267237 discloses that a loop detecting means is provided upstream of a fixing device to detect a slack amount of a sheet, and to switch a conveying speed of the fixing device to keep the loop amount constant. Have been.

[0006]

However, V1>
Even if the speed difference of V2 is set as an empirical value, the magnitude of the slack varies depending on the slip ratio, the thickness of the paper, the width of the paper, and the like. Therefore, V1> V2
If the speed difference is set to a small value, thermal expansion of the fixing roller is also applied to paper that is unlikely to be loosened, so that the speed of the fixing roller increases and the paper during transfer may be pulled. Further, when the speed difference is set to be relatively large, there is a problem that when the sheet is easily loosened, a large slack is generated and wrinkles are generated.

On the other hand, such a problem does not occur in the configuration in which the transport speed of the fixing device is switched to keep the loop amount constant, but since the slack must be detected and controlled at all times,
In addition to the increase in cost, the speed of the fixing roller is switched stepwise, so that a shock is applied to the paper and the drive system, which causes another problem that image abnormalities such as jitter are likely to occur.

The present invention solves the above-mentioned conventional problems,
It is an object of the present invention to provide a fixing device capable of reducing a change in speed by a thermal expansion of a fixing roller with a simple configuration and maintaining a substantially constant speed difference between the transfer / separation unit and the fixing roller.

[0009]

According to the present invention, there is provided a fixing apparatus having a fixing roller which is drivingly connected to a driving source via a driving transmission means. A substantially pulley formed in a substantially V-shaped groove serving as the drive transmission means attached to the other end of the fixing roller; A drive V-pulley attached to a shaft and having a substantially V-shaped groove formed therein, and a V-belt having a substantially V-shaped cross section wound around the drive V-pulley and the V-pulley; Pulley is V
The side corresponding to one end of the fixing roller of the drive V-pulley divided into two at the lowermost point of the V-shaped groove is fixed to the drive shaft, and the fixing roller of the drive V-pulley divided into two is A side corresponding to the other end is slidably mounted on the drive shaft.

Further, according to the present invention, the V angle of the V-pulley and the driving V-pulley is determined by adjusting the material, thickness,
It is characterized by being set from a length, a temperature control range, a permissible value of the sheet thickness, and the like.

[0011]

According to the above construction, the driving V-pulley is divided into two parts at the lowermost point of the V-shaped groove with respect to the driving shaft, and the side corresponding to one end of the fixing roller of the divided driving V-pulley is formed. The fixing roller is fixed to the driving shaft, and the side corresponding to the other end of the fixing roller is slidably mounted on the driving shaft. Therefore, when the diameter of the fixing roller increases due to thermal expansion, the length of the fixing roller also increases, and the V-belt increases. The V-belt is wound around the small-diameter portion of the drive V-pulley by dropping between the two divided drive V-pulleys. Therefore, the speed increase due to the diameter of the fixing roller increasing due to thermal expansion and the deceleration due to the V-belt being wound around the small-diameter portion of the driving V-pulley are corrected. The transport speed difference can be kept at a speed difference at which the amount of paper pallet is in an appropriate amount range.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a sectional view of a fixing device according to the present invention. In FIG. 1, reference numeral 1 denotes a fixing roller 1 and 2 denotes a heater built in the fixing roller 1. The temperature of the fixing device is controlled by a thermistor (not shown) or the like.
The surface temperature of the fixing roller 1 is controlled to 160 to 195 ° C. The fixing roller is rotatably supported by left and right side plates 3 and 4 via bearings 5 and 6, respectively. In this case, the fixing roller 1 is regulated by the ring 7 with respect to the right side plate 3 and supported at a fixed position, but is supported by the left side plate so as to be expandable and contractible without restriction.

A V-pulley 8 formed in a substantially V-shaped groove is fixed to an end of the fixing roller 1 on the expandable side, that is, a left end, as a drive transmission means from a driving source for rotating the fixing roller 1. Have been. The driving source of the fixing roller 1 in this embodiment is a motor 9 mounted on the left side plate 4, and a driving shaft 10 of the motor 9 is mounted so as to be parallel to the axis of the fixing roller 1. This drive shaft 1
A drive V pulley 11 is attached to the drive belt 0, and a V belt 12 having a substantially V-shaped cross section is wound around the drive V pulley 11 and the V pulley 8. Note that the cross-sectional shape of the V-belt 12 of this example is formed in an inverted trapezoidal shape in which a lower part of a V-shape is cut off.

The drive V pulley 11 is divided into a right half portion 11a and a left half portion 11b in a plane perpendicular to the axis of the drive shaft 10 and at approximately the lowest point of the V-shaped groove. I have.
The right half 11a of the drive V pulley 11 is
The left half 11b corresponding to the telescopic side of the fixing roller 1 is mounted movably in the axial direction via a ring 13 provided on the drive shaft 10. The drive shaft 10 is mounted on the left half 11 b of the drive V pulley 11.
By pressing the other end of the spring 15 whose one end is pressed against the ring 14 provided at the left end of the right side, the pressing force in the direction of contacting the right half 11a is constantly urged. Note that a gear 16 is provided at the right end of the fixing roller 1 to transmit rotational drive to other members.

In the fixing device having such a configuration, when the fixing roller 1 has a large diameter due to thermal expansion, the length in the axial direction also increases. When the length of the fixing roller 1 in the axial direction becomes longer, the fixing roller 1 is supported at a fixed position with respect to the right side plate 3, but is supported to be expandable and contractible with respect to the left side plate. Extends to For example, if the fixing roller 1 is 20
When the temperature rises from ℃ to 195 ° C., and the material of the fixing roller 1 is aluminum, the thermal expansion coefficient is 23.9 × 10 to ⁶ and when the length is 1000 mm, the left end extends about 4 mm.

For this reason, the V pulley 8 also moves from the position indicated by the dashed line to the position indicated by the solid line in FIG.
Also move to the left. The movement of the V-belt 12 also applies a moving force to the drive V-pulley 11 to the left. Then, the left half portion 11b of the drive V pulley 11 movably mounted on the drive shaft 10 separates the spring 15 from the position of the chain line to the position of the solid line by moving the leftward moving force away from the right half portion 11a by the urging force. , The drive V-pulley 11 expands, and the V-belt 12 falls into it. At this time, since the rotation speed of the motor 9 is constant, the rotation speed transmitted to the fixing roller 1 decreases,
The peripheral speed of the fixing roller 1 decreases.

In this manner, the paper is increased by the fixing roller 1 due to the speed increase due to the diameter of the fixing roller 1 increasing due to thermal expansion and the deceleration due to being wound around the small diameter portion of the driving V pulley due to the drop of the V belt 12. The transport speed is corrected, and the peripheral speed due to thermal expansion can be changed slightly, and the speed correction is performed steplessly. Therefore, the speed difference between the transfer / separation unit and the fixing roller 1 can be maintained at a speed difference at which the thickness of the paper is within an appropriate range.

Conversely, when the fixing roller 1 is lowered due to continuous paper passing or the like, the diameter is reduced, the peripheral speed is reduced, and the amount of slack in the paper is increased. Since the roller 1 returns from the position indicated by the solid line to the position indicated by the chain line, the left half 11b of the drive V pulley 11 also returns due to the action of the spring 15, and the speed of the fixing roller 1 substantially disappears.

The V pulley 8 and the driving V pulley 11
And the V-angle of the V-belt 12 are set based on the material, thickness, length, temperature control range, allowable value of the thickness of the paper, and the like of the fixing roller 1, so that the peripheral speed due to thermal expansion hardly changes. A stable and appropriate amount of paper thickening can be obtained.

[0020]

According to the above arrangement, when the diameter of the fixing roller becomes large due to thermal expansion, the width of the drive V pulley divided into two is spread and the winding position of the V belt is lowered. Correction is made between the speed at which the fixing roller becomes faster and the speed at which the drive V pulley becomes substantially smaller with a smaller diameter.
The speed difference between the transfer / separation unit and the fixing roller can be kept at a speed difference at which the thickness of the paper is within an appropriate range.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view showing a driving unit of a fixing device according to the present invention.

FIG. 2 is an explanatory sectional view showing the operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing roller 8 V pulley 9 Motor 11 Drive V pulley 11a Right half of drive V pulley 11b Left half of drive V pulley 12 V belt

Claims (2)

(57) [Claims] 1. A fixing device having a fixing roller which is drivingly connected to a driving source via a driving transmission means and is heated by a heating means, wherein one end of the fixing roller is substantially fixed to thermal expansion and the other end is fixed. A V pulley formed in a substantially V-shaped groove serving as the drive transmission means attached to the other end of the fixing roller, which is attached to the other end of the fixing roller; A drive V-pulley having a V-shaped groove formed thereon, and a V-belt having a substantially V-shaped cross-section wound around the drive V-pulley and the V-pulley, wherein the drive V-pulley is arranged with respect to a drive shaft. A portion corresponding to one end of the fixing roller of the drive V pulley divided into two along substantially the lowest point of the V-shaped groove is fixed to the drive shaft, and the fixing of the drive V pulley divided into two is performed. The side corresponding to the other end of the roller is Fixing apparatus characterized by being slidably mounted on the rotary shaft. 2. The V of the V-pulley and the driving V-pulley
2. The fixing device according to claim 1, wherein the angle is set based on a material, a thickness, a length, a temperature control range, an allowable value of a sheet thickness, and the like of the fixing roller.