JPH0274976A - Differential driving device in fixing device - Google Patents

Abstract

PURPOSE:To satisfy both a fixing characteristic and a paper wrinkle characteristic against a form of a large size, and to obtain a copy being in a satisfactory state by setting a peripheral velocity of a pressure roller and a speed of a heating roller so as to be low and high, respectively with respect to a speed for carrying the form. CONSTITUTION:A heating roller 11 and a pressure roller 15 for constituting a fixing device 10 are provided in a state that nip pressure of a prescribed value is obtained between both the rollers in the same way as the case of a fixing device of a regular heating roller system. Also, a peripheral velocity of the pressure roller 15 and a speed of the heating roller 11 are set so as to be low and high, respectively, and a forced slip is generated between one roller of them and a form P. Accordingly, even in the case of raising nip pressure up to a level which can satisfy enough a fixing characteristic against the form P of a large size, a slide can be generated between the heating roller 11 and the form P, and its slip quantity can be set to that of a degree which exerts no influence on an image. In such a way, before a paper wrinkle is generated, its state can be corrected by elasticity of paper itself, and a fixing action to the form P of a large size can be executed satisfactorily.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a differential drive mechanism in a roller pressing type fixing device used in a copying machine or the like, and in particular, the present invention relates to a differential drive mechanism in a roller pressing type fixing device used in a copying machine or the like. The present invention relates to a device that prevents the occurrence of wrinkles when fixing large-sized paper by setting the speed of opposing rollers quickly.

(Prior art) Like a copying machine, a toner image is formed on a photoreceptor drum, the toner image is transferred to paper, and the paper carrying the toner image is passed through a fixing device to be fused, thereby making a copy. The apparatus for forming the image is installed in a copying machine as shown in FIG.

In the general copying machine shown in FIG. 9, an image of an original provided at the top of the main body of the copying machine is read by an image reading device (not shown), and reflected light from the original is irradiated onto the photoreceptor drum 1. Then, an electrostatic latent image is formed on the surface of the photosensitive drum 1, which is charged by the charging corotron 2.

Further, a developing device 3 is provided downstream of the image light irradiation portion of the photoreceptor drum 1, and by supplying toner to the electrostatic latent image on the photoreceptor drum, the electrostatic latent image can be converted into a toner image. The image is visualized and the toner image is transferred onto the paper P by electric discharge by the transfer comitron 4.

The paper P carrying the toner image is peeled off from the photosensitive drum 1, conveyed by the transport 5, and introduced into the fixing bag @10 via the entrance guide plate 6. Then, the toner of the toner image is melted and pressed while being nipped between the heating roller 11 and the pressure roller 15 of the fixing device, and the toner is fixed on the paper to complete the copy and then discharged. It passes through the rollers 7 and is sent out toward the output tray.

In the above-mentioned xerographic process, a heating roller type device is generally used as the fixing device. This heating roller type fixing device includes a heating roller 11 containing a built-in heating source such as a halogen lamp, and a pressure roller that are in contact with each other under a predetermined pressure. Then, one of the rollers is driven, the other roller is driven and rotated, and a predetermined pressure and heat are applied to the paper nipped between both rollers.

The heating roller type fixing device mentioned above has safety, price,
It has advantageous conditions compared to other fixing devices in terms of power consumption, etc., and is the most commonly used device in devices such as copying machines.

Such heating roller type fixing devices include, for example, those disclosed in Japanese Patent Application Laid-Open No. 123877/1983. In these fixing devices, one of the two rollers is driven, The other roller is driven and rotated, and the paper is nipped between both rollers for conveyance and fixing, and the specific mechanism is as shown in Figure 10. .

In the constant IIi device 10 shown in FIG. 10, as described above, between the heating roller 11 and the pressure roller 15,
The paper P carrying the toner image is nipped. In these rollers, the surface of the heating roller 11 is coated with a relatively hard fluororesin, rubber, etc., and the surface of the pressure roller is coated with a relatively soft elastic material.

Then, the heating roller 511 is heated to a predetermined temperature (usually 1
60°C to 220°C), and the heating roller 11
contacts the toner image side of the paper, and the heat is supplied to the paper nipped between both rollers and the toner image on the paper, melting the toner in the toner image, and applying pressure from the pressure roller to the toner image. The image is fixed to the paper.

In the case of the embodiment described above, the chain 21 is wound around a sprocket provided on the shaft of the heating roller 11 and a sprocket of the drive device 20, and the heating roller 11 is driven. Further, the pressure row 515 provided corresponding to the heating roller 11 has its shaft supported by an arm 16, and one end of the arm 16 is supported swingably by a pivot 17,
The other end is supported by a spring 18, and the spring 1
8 applies a predetermined nip pressure between both rollers.

In the conventional heating roller type fixing device, the pressure roller 15 is rotated at the same circumferential speed following the rotation of the heating roller, and the paper is rotated at the same circumferential speed as the circumferential speed of these rollers. It is conveyed so that it can perform the functions of fixing the toner image and conveying the paper.

(Problems to be Solved by the Invention) The conventional fixing device as described above is not suitable for small size paper (A
When performing the fixing operation on 4 to A2 size paper, the width of the paper is relatively narrow and short rollers are used, so the rigidity of the rollers may be insufficient. Therefore, the nip pressure against the paper can be maintained in a good condition.

Therefore, in the case of a small fixing device, the fixing characteristics can be sufficiently satisfied without particularly considering the configuration of the rollers, and even if a sufficient nip load is applied between both rollers. , paper wrinkles will not occur.

However, when making copies using large-sized paper such as AO or A1 size, the rollers that make up the fixing device are extremely long, and when supporting the rollers at both ends, it is difficult to make copies. An inconvenient situation occurs, such as a difference in nip pressure between the center and end portions of the nip portion.

For large-sized paper, as shown in the graph of FIG. 11, the fixing characteristic curve A and the bending characteristic curve B interact with each other with respect to the nip pressure.
It is not possible to satisfy the conditions for the double-sided version to fall within the range of target specifications.

Therefore, in conventional large size fixing devices,
In order to prevent paper wrinkles from forming on copies, methods such as reducing nip pressure may be employed to address the problems described above.

However, in a heating roller drive type fusing device, if fusing is performed with the nip pressure between both rollers reduced, problems such as poor fusing due to insufficient pressure may occur, and paper wrinkles may not occur. However, problems such as not being able to obtain copies with good fixation tend to occur.

In contrast, the present inventors set the speed of the heating roller slower than the speed of the pressure roller and set the nip pressure high when performing fusing with the heating roller slipping against the paper. He discovered that it is possible to obtain copies in good condition without the problem of paper wrinkles, even when paper is wrinkled, and established a technical means to do so.

With the configuration described above, when using a conventional heating roller drive type fixing device, by setting the speed difference between the heating roller and the pressure roller as described above, high quality can be achieved. It is now possible to obtain copies, and there is no need to make major changes to the structure of the fixing device.

However, as described above, when the speed of the heating roller is set slower than that of the pressure roller, the conveyance speed of the paper is highly dependent on the speed of the pressure roller, and the pressure roller is set at a low 1f! (20-30℃) and high temperature (120-130℃)
In this case, a problem was encountered in which the paper speed changed due to a temperature difference due to the phenomenon that the outer diameter of the pressure roller changed by about 1 second due to thermal expansion.

If there is a large change in the outer diameter of the roller,
For example, with a φ75am+ roller, as mentioned above,
It has been found that the conveyance speed by the roller changes by as much as 1.3% between low temperature and high temperature. In other words, when the above-mentioned changes occur, the AO resized paper will loosen by a maximum of 15 M, and defects such as smearing will occur. In order to prevent this situation, it is required that the system of the fixing device be constructed so as to be able to withstand practical use, on the premise of conveyance speed control.

(Object of the Invention) The present invention solves the above-mentioned drawbacks of conventionally used devices, and satisfies both fixing characteristics and paper wrinkle characteristics for large-sized paper. The object of the present invention is to provide a fixing device with which a copy of the state can be obtained.

(Means and effects for solving the problem) The differential drive device in the fixing device of the present invention holds the paper bearing a toner image between both rollers, and heats the paper with a heating roller and applies pressure with a pressure roller. In a heating roller type fixing device configured to perform pressure and fixing, the peripheral speed of the pressure roller is set to be slow and the speed of the heating roller is set to be fast relative to the speed at which the paper is conveyed. be.

The present invention also provides an apparatus configured to sandwich a sheet of paper carrying a toner image between two pressure rollers and apply pressure to the sheet to melt and fix the toner. The speed of the rollers located on the toner image side of the paper may be increased, and the speed of the rollers located on the back side of the paper may be slowed relative to the speed at which the paper is moved.

Furthermore, in the above two examples of the present invention, if the speed of the roller located on the toner image side of the paper is Vf, the speed of the roller in contact with the back side of the paper is vr, and the moving speed of the paper is Vp, then each The speed relationship is set to Vf>Vp>Vr, and the sliding rate between opposing rollers [(Vf/Vr)
-1] x to.

can be set in the range of 1 to 11%.

Therefore, in the fixing device of the present invention, the speed of the heating roller is set to be slightly faster than the conveyance speed of the paper, but when fixing the toner image by melting, the image may be misaligned, etc. The slippage is so small that it does not cause any problems, and there is no paper wrinkles or poorly fixed copies, and it is possible to obtain large-sized copies in good condition.

Further, the differential drive device in the fixing device of the present invention is not only used in the heated roller type device as described above, but also a cold roller (normal temperature roller) used for -component toner, capsule toner, etc. It is also possible to apply this method to a pressure fixing device according to the present invention.

In that case, similarly to the heated roller type device, the speed of the pressure roller on the toner image side is set to high, the speed of the pressure roller on the side that contacts the back side of the paper is set to slow, and the pressure roller on the top F is set to a low speed. The paper can be configured to be moved at a speed intermediate to the speed of the pressure roller.

(Actual Example) The configuration of the differential drive device in the fixing device of the present invention will be described according to the illustrated example.

In the first embodiment of the present invention shown in FIG.
As in the case of a normal heating roller type fixing device, the rollers are provided in such a state that a predetermined value of nip pressure can be obtained between both rollers.

In this embodiment, a lamp 12 is provided inside the heating roller 11, and the lamp 12 is used as a heat source to maintain the temperature of the heating roller at a constant value. The roller 11 is driven by a drive bag W120 via a chain 21, and the circumferential speed of the roller is set.

Further, like the heating roller, the pressure roller 15 is configured to be driven by a drive bag @13 via a chain 14, and the circumferential speed of the pressure roller 15 can be set.

In the description of the present invention, the circumferential speed of the pressure roller does not simply mean the speed of the outer circumference (roller surface) of the pressure roller, but also the paper conveyance speed in the nip area with the heating roller. It is something to do.

Expressing this in a formula, the circumferential speed of the pressure roller - nDp・πX (1+Δh/h)
becomes.

(In the above formula, Dp: diameter of the pressure roller, n: rotation speed, h: thickness of the rubber layer of the pressure roller, Δh: amount of deformation of the rubber) The pressure roller 15 of the present invention described above has the following characteristics: The shaft is supported by an arm 16, and by supporting one end of the arm 16 with a pivot 17 and the other with a spring 18, it is possible to press with a predetermined pressure and obtain a constant nip pressure between both rollers. It is configured as follows.

In the fixing device 10 of the present invention configured as described above, the speed relationship between both rollers and the paper is set as shown in FIG.

That is, in the fixing device of the present invention, if the speed of the heating roller is Vf, the speed of the pressure roller is Vr, and the speed of the paper is Vp, the relationship between the respective speeds can be set as Vr < Vp < Vf. This results in ideal driving conditions.

In the relationship between the speeds of each roller and the paper described above, under the condition of Vp <Vf, (Vp - Vf )
/■p-α, the range of the value of α is set depending on the conditions of the toner image carried on the paper.

In other words, <a> * Density (ratio of toner image on paper)
is from 2 to 3% (drawing level) to 100% (solid black), α-0.04 to 0.09° (b) image density is 0%
(Mostly blank paper), α can be set within the range of 0.01 to 0.11.

In other words, as described above, the setting range of α is determined according to the image density.

Note that the above α value may vary depending on paper quality, target fixation level, and system (technology).
It is not limited to the range mentioned above, and 0.
It may be set arbitrarily within the range of 0...1 x α x 1.

(Actually, judging from the image disturbance, it is possible to obtain copies in good condition when α-0.1 or less.) As mentioned above, the difference in the fixing device of the present invention is that In a dynamic drive device, the speed of each member is vr and Vp<v
By setting f, it is possible to prevent paper wrinkles from occurring even when the paper is nipped between both rollers, even in the case of large-sized paper.

That is, under the condition shown in FIG. 2 above, the paper P
is moved following the pressure roller 15, and its conveying action is performed in the relationship of Vp=Vr. At this time, if the heating roller 11 follows the pressure roller 15 and rotates synchronously, it is faster than the conventional method. As in the case of the heating roller drive type fixing device used, Vr = Vp #Vf.

In that case, the paper P is influenced by the friction coefficient μ (+ Coulomb force, etc.) between the heating roller 11 and the pressure roller 15, and the degree of freedom at the nip part of the paper (it is likely to wrinkle) force that allows the paper itself to avoid wrinkles when
is insufficient, and as the nip pressure increases between the two rollers, the edge characteristics deteriorate.

Therefore, if the above-described speed conditions of each member of the present invention are applied, the speed relationship between the paper and the heating roller is Vp <
Vf, slipping occurs between the two, resulting in a state of dynamic friction, and the friction coefficient μ decreases, increasing the degree of freedom of the paper at the nipped area and causing paper wrinkles on the copy. can be avoided.

When using the differential drive mechanism of the present invention, as shown in the graph of FIG. 3, the position where the fixing characteristic curve A and the wrinkle characteristic curve B intersect is on the target specification line. This allows the fixing device to have a large tolerance range C that satisfies both fixing characteristics and paper wrinkle characteristics, and even if a relatively high nip pressure is set.
This makes it possible to prevent the occurrence of paper wrinkles and maintain the fixability at a good value.

Note that in the case of the fixing device of the present invention using the above-mentioned differential drive mechanism, it is possible to exhibit good fixing performance even for small size paper such as A4 size paper. In particular, it can be made more effective for large size paper such as AO-A2 size.

Also, as shown in the graph of FIG. 4, the speed of the heating roller is set high, and the relationship between the speeds of each member is Vf>Vp.
> Vr, the slip rate between both rollers [(Vf/Vr)-1] (required tolerances).

Furthermore, the roll profile tolerance (the difference between the maximum taper and the minimum taper at the pressure roll ridge line) can also be dramatically larger than in conventional devices.

Therefore, when using the fusing device of the present invention, paper wrinkles and other defects are significantly improved compared to conventional devices, and as a result, even when using large-sized paper, It is possible to create high-quality copies without sacrificing quality.

As a differential drive mechanism for satisfying the fixing conditions of the present invention as described above, a drive system as shown in FIG. 1 and FIGS. 5 to 8 can be constructed.

The drive mechanism shown in FIGS. 5 to 7 includes a mechanism for driving the heating roller 11 by a driving device 20 via a chain 21 and driving the pressure roller 15 at a lower speed than the heating roller 11. It is set up.

In the embodiments shown in FIGS. 5 to 7 of the present invention, the pressure roller 15 is constructed as a mechanism that rotates around the heating roller 11 with paper interposed therebetween. The pressure roller is rotated within the range of the tolerance slip rate shown in FIG. 4 with respect to the rotational speed of the heating roller.

Specifically, in the embodiment shown in FIG. 5, a chain 33 is wound around the sprocket of the pressure roller 15, and a brake device 30 composed of a disk 31 and a pad 32 is connected via the chain.

Then, the brake device 30 causes the pressure roller 15 to
A brake is applied to the rotation of the heating roller 11, a resistance is applied to the rotation of the heating roller 11, and the rotation speed of the roller is lowered relative to the rotation of the pressure roller, so that the rotation speeds of both rollers are made different. This constitutes a differential drive mechanism.

Note that the brake device used in this embodiment is not limited to a disc brake, and a drum brake or other devices similar to commonly used mechanical brake mechanisms may be used as the brake device. It is possible.

In the embodiment shown in FIG. 6, a fluid brake device 35 is provided in place of the mechanical brake device. This fluid brake device N35 utilizes the viscous resistance of fluid, and rotates a rotating body 37 having protruding fins inside a case 36.
The inside is filled with oil 38.

Then, following the rotation of the heating roller 11, the pressure roller 51
5 is rotated, a rotating body 37 that is linked to the pressure roller 15 via a chain is driven,
When the rotating body 37 receives resistance from the oil, it generates a constant torque with respect to its rotational speed, thereby making it possible to reduce the rotational speed of the pressurizing row 515.

Of course, in the case of this embodiment, it is natural to use a highly stable oil that does not change its viscosity or resistance value due to agitation as the oil housed inside the case 36. It is.

In the embodiment shown in FIG. 7, an electric brake device 40 is used to apply resistance to the pressure roller 15. This electric brake device 40 is provided with a brake motor 41 that is interlocked with a heating roller, and the motor acts as a generator by the rotation of the heating roller, and the electricity is consumed by a variable resistor 42. There is.

3 applicable to the differential drive mechanism of the present invention as described above
In two basic brake mechanisms, synchronous rotation is performed in contact with a heated roller using a mechanical device that presses the brake pad against a disc, control using fluid density, control using electrical resistance, etc. A predetermined resistance is applied to the pressure roller, and the rotational speed of the pressure roller is varied within the range of α-0.11 or less as described above, thereby making it possible to configure a differential drive mechanism. .

As mentioned above, by providing a brake mechanism,
Apart from the differential drive mechanism configured to reduce the rotation speed of the pressure roller, in the fixing device of the present invention, as shown in FIG. 8, the drive device 50 includes sprockets with different numbers of teeth. It is also possible to provide the heating roller and the pressure roller at different speeds using the same drive device.

In the embodiment shown in FIG. 8, the drive device Fi50
Two sprockets 51 and 53 are provided on the output shaft of
The sprocket 51 is used to drive the pressure roller 15, and the sprocket 53 is used to drive the heating roller 11.

In this embodiment, the pressure roller 15 is connected to the chain 52
However, the chain 54 that drives the heating roller 11 has a drive force transmitted through a plurality of idler sprockets 55, 55, etc. It has become.

Then, by arbitrarily selecting the number of sprocket teeth in these drive mechanisms or by making the diameters of both rollers different, the circumferential speed of both rollers can be arbitrarily set, and a differential drive mechanism is constructed. It is something to do.

The drive system shown in FIG. 8 does not require fine adjustment or the like to the differential drive mechanism, compared to the case where a brake device as described above is provided. When setting the circumferential speed of each roller, driving can be performed accurately using the differential value set based on the number of sprocket teeth, roller diameter, etc., and general-purpose parts can be used, reducing costs. This is advantageous and also facilitates maintenance.

As described above, the differential drive mechanism shown in the embodiments of the present invention is basically configured to drive the heating roller and drive the pressure roller to follow the heating roller. Set the heating roller drive speed faster than the pressure roller. Then, by creating a speed difference between the two rollers and the paper, the heating roller slides on the surface of the paper, reducing the friction coefficient μ between the rollers and the paper, and To improve the flexibility of paper.

Furthermore, in a device that drives both rollers at the same time and makes the driving speeds of both rollers different, as in the case of the differential drive mechanism using the brake mechanism described above,
This causes slippage between the paper and the heating roller, and the differential drive mechanism shown in these embodiments of the present invention must be configured so that the amount of differential movement can be reliably set (and controlled). is possible.

Note that the differential drive mechanism of the present invention described above is not limited to the differential drive mechanism shown in the embodiments, and may be any other mechanism as long as it can generate a speed difference between both rollers. It is possible to use a device having the following configuration, and the differential m can be easily set, and the device can be configured to reduce manufacturing costs and power consumption.

In the embodiments of the present invention described above, an example is shown in which the fixing device is configured as a heated roller type device, but the differential drive mechanism of the present invention can be applied only to a heated roller type device. Alternatively, the present invention can also be applied to a pressure fixing device in which a sheet carrying a toner image is sandwiched between upper and lower pressure rollers and the fixing operation is performed by pressure.

This pressure fixing device is used to fix a toner image made of -component toner or capsule toner, but in the case of this fixing device as well, among the pair of upper and lower pressure rollers that carry the toner image, By making the speed of the pressure roller on the toner image side faster than the pressure roller in contact with the back side of the paper, a differential drive mechanism is constructed, and as in the case of the heating roller type fixing device described above, It can have a fixing effect. It should be noted that even in the case of this pressure fixing device, the differential drive mechanism of each embodiment provided for the heating roller type fixing device of the present invention described above is similarly applied.

(Effects of the Invention) Since the differential drive device in the fixing device of the present invention has the above-described configuration, the nip can be adjusted to a level that sufficiently satisfies the fixing characteristics for large-sized paper. Even when the pressure is increased, it is possible to cause slippage between the heating roller and the paper, and it is possible to keep the amount of slippage to a level that does not affect the image.

Therefore, in the heated roller type fixing device using the differential drive mechanism of the present invention, the degree of freedom of the paper between both rollers can be increased, and as a result, the paper becomes white before wrinkles occur. This state can be corrected by the elasticity of the body, and it is possible to perform a good fixing action on large size paper such as AO size.

[Brief explanation of the drawing]

FIG. 1 is a side view of a heating roller type fixing device of the present invention;
Fig. 2 is an explanatory diagram showing the relationship between the speeds of both rollers of the fixing device and paper, and Fig. 3 shows the relationship between nip pressure, fixing characteristics, and paper wrinkle characteristics when using the differential drive mechanism of the present invention. The graph shown in FIG. 4 is a graph showing the relationship between the slip rate and roll profile tolerance when using the method of the present invention, and FIGS. 5 to 7 respectively show the configuration when a brake device is provided on the heating roller. FIG. 8 is an explanatory diagram of a device in which both rollers are driven at different circumferential speeds by the same drive source, and FIG. 9 is an explanatory diagram showing the configuration of a general copying machine.
FIG. 10 is an explanatory diagram showing the configuration of a conventional fixing device, and FIG. 11 is a graph showing the relationship between fixing characteristics and paper wrinkle characteristics in the conventional fixing device. Code 1 in the diagram: Copying machine, 10: Fixing device, 1
1... Heat roller, 15... Pressure roller, 13... Pressure roller drive device, 30...
...Brake device, 35...Fluid brake device, 40...Electric brake device, 50...
...Drive device. Fig. 1 Fig. 3 =...y7'Mp Fig. 4 Fig. 7 Fig. 8 Fig. 9 Fig. 10 Fig. 2...7 de repulsion (kl shi8♂)

Claims (3)

[Claims] (1) In a heating roller type fixing device configured to hold a sheet carrying a toner image between both rollers, heat it with a heating roller, and pressurize it with a pressure roller to perform fixing. A differential drive device for a fixing device, characterized in that the circumferential speed of the pressure roller is set low and the speed of the heating roller is set high, thereby causing accentuated slippage between one of the rollers and the paper. (2) In an apparatus configured to sandwich a sheet of paper bearing a toner image between two pressure rollers and apply pressure to the sheet, the toner is melted and fixed. 1. A differential drive device for a fixing device, characterized in that the speed of a roller located on the toner image side of a sheet of paper is set to be high, and the speed of a roller located on a back side of the sheet is set to be slow relative to the speed of movement of the sheet. (3) The speed of the roller located on the toner image side of the paper is V
f, the speed of the roller in contact with the back side of the paper is Vr, and the moving speed of the paper is Vp, then the relationship between the respective speeds is set as Vf>Vp>Vr, and the sliding rate between the opposing rollers [(Vf/ Vr)-1]×100
3. A differential drive device in a fixing device according to claim 1 or 2, wherein: is set in a range of 1 to 11%.