JPH06241251A - Braking device of rotary drum - Google Patents

Abstract

PURPOSE:To provide a brake of a rotary drum in an electrophotographic color printer or the like, thereby checking any variation in rotational speed in this rotary drum to be produced in the case where rotational irregularity and disturbing vibration in a driving source and a driving force transmission system have operated. CONSTITUTION:A stationary plate 4 fixed to a support frame 3 is opposed to a side part 1a of a rotary drum 1, and two O-rings 10 and 11 are constituted so as to make them chargeable and holdable in a pinched state on a concentric circle centering on a turning shaft 2 in a clearance 6 between the opposed surfaces, and then a viscous fluid 7 such as high viscous silicone oil or the like is filled up in an interval between these two O-rings 10 and 11 in the pinched and charged conditions. This viscous fluid 7 generates a shearing force in proportion to rotational speed of the rotary drum 1 in a state of being held between these two O-rings 10 and 11, effectively controlling a variation in the minute rotational speed of a high frequency to be produced in the rotary drum 1 by the damper function.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary drum braking device and is applied to a rotary drum support mechanism in an electrophotographic color printer or the like.
The present invention relates to a braking device that suppresses fluctuations in rotational speed that occur when rotational unevenness or disturbance vibrations of a driving force transmission system act and maintains a constant speed rotation of a rotating drum.

[0002]

2. Description of the Related Art Conventionally, a structure as shown in FIG. 8 has been adopted in an electrophotographic color printer, and a rotary drum 81 around which a photosensitive paper is wound is mounted on a stepping motor via a speed reduction mechanism 82 such as a harmonic gear. It is rotationally driven by (hereinafter referred to as “STEP motor”) 83, and an electrophotographic printing process is executed in the orbiting process.

A photosensitive paper 84a supplied from a photosensitive paper roll 84 is wound around the rotary drum 81 in close contact with it, and the surface of the photosensitive paper 84a is charged by corona discharge of a charger 85 during the winding process. Laser emitting section 86
While scanning the laser beam output from the polygon mirror 87 through the optical system (lens, mirror) 88, the photosensitive paper 84a
To form an electrostatic latent image by exposing the surface of the photosensitive paper 84a with a pre-wetting device 89, then develop with a toner developer 90, and squeeze 91 to roughly remove the toner developer 90. After that, the surface of the photosensitive paper 84a is dried by the heater 92 to fix the dye of the toner, and the neutralization lamp 93
Then, a series of processes for removing the charged electric charge is executed. In a color printer, the above process is repeated for each toner developer of yellow (Y) → magenta (M) → cyan (C) → black (B), and finally a color image is printed on the photosensitive material. The paper 84a is discharged.

In the above color printer, in order to improve the quality of the color image, it is an essential condition that the rotary drum 81 can be rotated with high accuracy. In that case, in the development by the electrophotographic method, the development time is mainly determined by the power of the laser and the scanning resolution, and when the semiconductor laser is used as the light source, the rotating drum 81 cannot be rotated at a very high speed.
The rotation is controlled for several tens of seconds per one rotation.

Therefore, in this type of color printer, the STEP motor 83 having excellent controllability is used as a drive source, and the reduction mechanism 82 has a large reduction ratio to ensure effective use of the drive torque and high resolution. Has been realized, and high quality image printing is possible. A timing belt or a gear is used as a driving force transmission mechanism from the STEP motor 83, and the driving system in which the speed reduction mechanism 82 is interposed has been described in the above example, but the STEP motor 83 is rotated depending on the color printer. There is also a method in which the rotary drum 81 is directly connected to the drum 81 and rotated by microstep drive.

[0006]

By the way, a STEP motor
When the rotation control of the rotary drum 81 is performed by using the 83 as a drive source, the rotation unevenness peculiar to the driving force transmission mechanism including the STEP motor 83 and the speed reduction mechanism 82 occurs. Also, other mechanisms that are driven at the same time generate mechanical vibration,
It is not uncommon for the location where the color printer is installed to be subject to external vibration. Then, the rotation unevenness and the vibration described above act on the rotating drum 81 in a manner in which they are superposed, and when actually measuring the rotating speed of the rotating drum 81, due to the influence, a minute fluctuation of the rotating speed at a high frequency is caused. It is demonstrated that is continuously occurring.

On the other hand, in the electrophotographic color printer, the laser beam is scanned on the assumption that the rotary drum 81 is rotated at a constant speed, and in a color printer having a high resolution, the rotational speed of the rotary drum 81 varies only slightly. However, a fine shade or color shift is generated in the recorded image, resulting in deterioration of the quality of the recorded image. Further, not only in the field of image recording such as a color printer, but also in a device that generally controls a rotating drum with high accuracy at a constant speed, it is often the case that a minute fluctuation in the rotating speed due to various factors must be suppressed. Absent.

Therefore, the present invention provides a braking device for maintaining the constant speed rotation of the rotating drum even when the rotation unevenness of the drive source / driving force transmission system or the external vibration is applied. It was created with the purpose of applying it to the rotating drum mechanism of a printer to achieve high quality recorded images.

[0009]

According to the present invention, there is provided a gap between a side surface of a rotary drum and a fixed plate facing the side surface, or a side outer peripheral surface of the rotary drum and a fixed ring externally fitted to the side outer peripheral surface. The present invention relates to a braking device for a rotating drum, characterized in that a viscous fluid is held in a gap between the bodies.

Here, the viscous fluid holding means fits the two annular seal members into the two annular grooves formed on the opposing surfaces forming the gap, and the annular seal members are opposed to each other. It can be realized by a mechanism in which a viscous fluid is filled between the annular seal members in the gap, and when a magnetic fluid is used as the viscous fluid, the magnetic fluid in the facing surfaces forming the gap is This can be realized by a mechanism in which an annular magnet is embedded in the boundary portion to be interposed.

[0011]

In general, when a fluid is present between opposing surfaces and one surface has a relative velocity with respect to the other surface and performs parallel motion, the two layers in the fluid are separated by a distance dy. Is τ = μ ・ (du
/ dy) shear stress acts. Where μ is the viscosity coefficient of the fluid and (du / dy) is the velocity gradient between the two layers. Therefore, between each facing surface, S is the facing area of the region where the fluid is interposed, U is the relative speed, and Y is the distance (gap) between the facing surfaces, and T = S.
A shearing force T expressed by μ · (U / Y) acts.

In the present invention, since the viscous fluid is interposed and held in the gap between the side surface of the rotary drum and the fixed plate, the shearing force of the viscous fluid increases in proportion to the rotational speed of the rotary drum, and the damper element is added. Has been done. As a result, in the case where uneven rotation or disturbance vibration of the drive source / driving force transmission system acts on the rotating drum to cause minute fluctuations in its rotation speed at high frequencies, it is It is suppressed and the constant speed rotation of the rotating drum is maintained.

On the other hand, if the viscous fluid is simply placed in the gap, it will flow out from the gap due to gravity and rotation of the rotary drum. Therefore, a means for holding the viscous fluid in the gap is essential in the present invention. Therefore, as the holding means,
Although a means for sealing a viscous fluid between two annular seal members fitted and loaded in the gap between the facing surfaces and a means for holding the viscous fluid as a magnetic fluid by an annular magnet are proposed. Even if the rotating drum rotates, each annular seal member maintains a sealed state while slidingly contacting the rotating drum side and the fixed part side (fixed plate / fixed ring body), and the latter holds the magnetic fluid only by the magnetic attraction force. Therefore, the rotary drum can be rotated while maintaining the mechanically non-contact state between the facing surfaces.

[0014]

Embodiments of the present invention will be described below in detail with reference to FIGS. 1 to 7. Embodiment 1 This embodiment is shown in FIG. 1 (a sectional view of a supporting mechanism portion of a rotary drum), in which 1 is a rotary drum and 2 is a rotary drum.
Is a rotary shaft fixed to the rotary drum 1, 3 is a support frame, 4 is a fixed plate attached to the support frame 3, and the rotary shaft 2 is axially supported in a hole of the fixed plate 4 via a radial bearing 5. ing.

In this apparatus, the side end surface 1a of the rotary drum 1 and the inner side surface 4a of the fixed plate 4 are opposed to each other.
It is characterized in that a silicone oil 7 having a large viscosity coefficient is interposed in the gap 6 of 4a. And silicone oil 7
As a means for holding the two annular grooves 8a, 8b, 9a, 9 on concentric circles centering on the rotating shaft 2 on the respective facing surfaces 1a, 4a.
b are formed to face each other, and two O-rings 10 and 11 are fitted in the annular grooves 8a, 8b, 9a and 9b, and the O-rings 10 and 11 are sandwiched between the facing surfaces 1a and 4a. While being pressed, silicon oil 7 is filled between the O-rings 10 and 11 in the gap 6.

Therefore, the silicon oil 7 is filled in a thin annular disk space in a sealed state, the flat area of the space is S, the viscosity coefficient of the silicon oil 7 is μ, and the rotary drum is
When the rotation speed of 1 is U and the space of the gap 6 is Y, the shearing force of the silicone oil 7 against the rotating drum 1 is T = S ・ μ ・ (U / Y)
To exert a damper function for the rotary drum 1. That is, the damper function described above can prevent the rotation speed of the rotating drum 1 from being slightly changed at a high frequency due to the rotation unevenness or the disturbance vibration of the drive source / driving force transmission system. The constant speed rotation can be maintained.

Further, in the rotating state of the rotary drum 1,
The O-rings 10 and 11 are mounted concentrically with respect to the rotary shaft 2 and slide in a manner that a lubricating layer of silicone oil 7 is formed between the O-rings 10 and 11 and the annular grooves 8a, 8b, 9a and 9b. It does not generate so much load torque on the drum 1.

Looking at this embodiment, T = S · μ ·
As shown in the formula (U / Y), the flat area of the annular disc space is increased, the viscosity coefficient of the silicone oil 7 is increased, and the spacing of the gap 6 is decreased, the above braking performance is improved. It is possible, but if the braking performance is increased excessively, the rotating drum 1
There is also a disadvantage that the drive torque for the motor must be increased and the mechanical strength of the drive system must be increased accordingly. Therefore, optimum braking performance can be obtained by selecting these parameters appropriately. It will be.

Embodiment 2: The supporting mechanism portion of the rotating drum of this embodiment is shown in FIG. 2, in which 21 is a rotating drum, 22 is a supporting frame, and 23 is laterally fixed to the supporting frame 22. It is a fixed shaft, and the rotary drum 21 is a bearing portion of a bearing side plate 24 attached to the side surface of the rotary drum 21.
It is rotatably supported by the fixed shaft 23 via.

In the supporting mechanism of the rotary drum in this apparatus, the side portion of the rotary drum 21 has a double structure, and an inward flange portion 21a is formed inside the bearing side plate 24 from the cylindrical portion of the rotary drum 21. In addition, it has a structure in which an outward flange-shaped fixed plate 26 attached to the fixed shaft 23 is interposed between the bearing side plate 24 and the inward flange portion 21a. Further, in this device, a gap 27 having an annular U-shaped cross section formed between the rotating drum 1 side and the fixed plate 26.
On the other hand, it is characterized in that silicone oil 7 is interposed. In this case, as means for holding the silicone oil 7, both surfaces of the fixed plate 26, the bearing side plate 24, and the inward flange portion 21 are used.
Two annular grooves are formed opposite to each other on a concentric circle centered on the fixed shaft 23 on the facing surface of a, and two O-rings 28 and 29 are fitted into the annular grooves, and the two O-rings 28 and 29 are fitted to each other. While pressing the O-rings 28 and 29 between them,
The silicone oil 7 is filled between the O-rings 28 and 29 in FIG. However, since the gap 27 in this embodiment has an annular U-shaped cross-section as described above, by loading O-rings 28 and 29 of the same diameter on both sides of the fixed plate 26, both ends of the gap 27 can be loaded. It has a sealing function in the vicinity.

According to this structure, the rotary drum 21 and the fixed plate
Since the opposing surfaces of 26 can be composed of both surfaces of the fixed plate 26 and its outer peripheral surface, the shearing force due to the rotation of the rotary drum 21: T = S ・ μ ・ (U / Y)
Of S can be made larger, and the braking function can be further improved as compared with the case of the first embodiment.

Embodiment 3: The supporting mechanism of the rotating drum of this embodiment is shown in FIG. 3, and the rotating drum 1, the rotating shaft 2, the supporting frame 3, the fixed plate 4, the radial bearing 5, the annular grooves 8a and 9a,
The basic structure including the O-ring 10 is the same as that of the first embodiment (FIG. 1). In this embodiment, a magnetic fluid 31 having a large viscosity coefficient is used instead of silicon oil as the viscous fluid interposed in the gap 6, and an annular magnet 32 is used instead of the O-ring 11 in the first embodiment. It is characterized in that it is embedded in the side end surface 1a and the outer peripheral side of the magnetic fluid 31 interposed in the gap 6 is held by the magnetic attraction force of the annular magnet 32.

As in the case of the first embodiment, the shearing force T proportional to the rotation speed of the rotary drum 1 acts on the rotary drum based on the viscosity of the magnetic fluid 31 held in the gap 6 also in this configuration. However, the damper function makes it possible to suppress minute fluctuations in the rotational speed at high frequencies, and to maintain the constant speed rotation of the rotating drum 1. In particular, the O-ring 11 of the first embodiment tends to generate a relatively large load torque due to the sliding contact with the fixed plate 4, but according to this embodiment, the mechanism is a magnetic fluid 31 which is mechanically non-contact. Since the holding mechanism is replaced by the holding mechanism of No. 1, the driving torque for the rotary drum 1 can be reduced, and the ripple and the like that are likely to occur due to the sliding contact relationship can be eliminated.

In this embodiment, in order to effectively use the magnetic flux of the annular magnet 32, the annular magnetic plates 33 and 3 are provided on the fixed plate 4 side corresponding to the back surface of the annular magnet 32 and the facing surface thereof.
Although the 4 is embedded, the annular magnetic plates 33 and 34 may not be provided as long as the magnetic attraction force of the annular magnet 32 is sufficient to hold the magnetic fluid. Further, in this embodiment, only the outer peripheral side of the magnetic fluid 31 is held by the annular magnet 31, but the O-ring 10 is also held on the inner peripheral side.
A similar configuration can be adopted instead of the above, and the advantages described above can be made more effective.

Embodiment 4: The support mechanism of the rotary drum of this embodiment is shown in FIG. 4, and the rotary drum 1, the rotary shaft 2, the support frame 3, the fixed plate 4, the radial bearing 5, the annular grooves 8a, 8b, 9 are provided.
The basic structure consisting of a and 9b and O-rings 10 and 11 is the same as that of the first embodiment (FIG. 1), but the rotary drum 1 between the O-rings 10 and 11 is the intervening region of the silicone oil 7. The side end surface 1a and the inner side surface 4a of the fixed plate 4 are formed so that the convex portion and the concave portion face each other, and the intervening region of the silicon oil 7 in the gap 6 is made to meander.

Therefore, since the meandering portion 41 is provided, the rotary drum 1 and the fixed plate 4 are the same as in the second embodiment.
You can increase the facing area of the silicone oil 7
Since the shearing force T due to becomes large, it becomes possible to improve the braking characteristics. Further, according to this embodiment,
There is no need to make the structure of the rotary drum 21 complicated as in the case of the second embodiment, and there is an advantage that it is sufficient to simply perform the processing on the rotary drum 1 and the fixed plate 4. The means for providing the meandering portion 41 as in this embodiment can be applied even when the configurations of the second and third embodiments are adopted.

Embodiment 5: The supporting mechanism portion of the rotating drum of this embodiment is shown in FIG. 5, in which the rotating drum 51 rotates integrally with the rotating shaft 2, and the rotating shaft 2 is fixed to the supporting frame 3. The basic structure in which the hole 52 is rotatably supported via the radial bearing 5 is the same as that of the first embodiment (FIG. 1). In this embodiment, the ring body portion 53 formed on the fixed plate 52 is externally fitted to the outer peripheral surface of the side portion of the rotary drum 51, and the rotary drum 51 and the ring body portion 53 have circumferentially facing surfaces 51a and 53a.
Two circumferential grooves 54a, 54b, 55a, 55b are formed in each of the two circumferential grooves 54a, 54b, 55a, 55b.
6 and 57 are fitted to each other so that the pressure is applied between the circumferentially opposed surfaces 51a and 53a, and the gap formed between the O-rings 56 and 57 is filled with silicone oil 7. There is.

In the structure of this embodiment, the braking mechanism is not provided on the side surface of the rotary drum 1 as in the first to fourth embodiments,
It is provided on the outer peripheral surface of the side portion of the rotary drum 51. That is, the shearing force of the silicon oil 7 generates a reverse rotation direction torque in the rotating drum 51 in proportion to the peripheral speed of the outer peripheral surface of the rotating drum 51, and the damper function thereof provides a braking function for rotating the rotating drum 51 at a constant speed. To be

From the standpoint of the braking function, as is clear from the above mathematical formula relating to the shearing force: T = S.μ. (U / Y), the higher the peripheral speed of the rotary drum 51, the higher the silicon. oil
Since the shearing force generated in 7 also increases and the reverse rotation direction torque that acts on the rotating drum 51 also increases, it is possible to more effectively demonstrate the damper function by providing the braking mechanism on the outer peripheral surface of the rotating drum 51. it can. Therefore, this embodiment makes it possible to further improve the braking characteristics as compared with the case of the first to fourth embodiments. However, in the electrophotographic color printer, since the photosensitive paper is wound around the outer peripheral surface of the rotating drum, the portion where the braking mechanism is provided (the circumferential facing surfaces 51a, 53a
It is necessary to lengthen the rotating drum 51 by (corresponding to).

Experimental Example: The same drive system was used for the case where the braking device was not provided and the case where the braking device was provided as shown in FIG. The rotation speed of the rotating drum 1 was measured. 6 and 7 are graphs showing the measurement results of the former and the latter, respectively, and each figure shows time in the horizontal axis [scale is 5 se.
[Each c]], the rotational angular velocity in the vertical direction [scale is 0.375 (° / sec)
Every] to show the fluctuation of the rotational angular velocity.

As is clear from comparing FIG. 6 and FIG.
Since a braking device is provided, the change in rotational angular velocity is PP.
It is understood that the values are suppressed to 1/3 or less and the average value is suppressed to about 1/2. That is, the damper function of the braking device eliminates minute fluctuations in the rotation speed at high frequencies, and the constant speed rotation characteristics of the rotary drum 1 are greatly improved.

[0032]

The braking device for a rotary drum according to the present invention has the following effects due to the above-mentioned configuration. According to the invention of claim 1, when uneven rotation or disturbance vibration of the drive source / driving force transmission system acts on the rotating drum to cause a minute fluctuation at a high frequency in the rotating speed,
The damper function using the shearing force of the viscous fluid suppresses fluctuations in the rotation speed, and greatly improves the constant speed rotation characteristics of the rotating drum. In particular, by applying it to the rotary drum mechanism of an electrophotographic color printer, fine light and shade and color misregistration are eliminated, and high quality of a recorded image is realized. Claim 2
The invention of (1) provides means for rationally holding the viscous fluid exhibiting the damper function by the seal member, and realizes stable braking performance for the rotating drum. According to the third aspect of the invention, since the magnetic fluid is used as the viscous fluid and the magnetic fluid is held by the magnetic attraction force of the magnet, the damper function is exerted in a mechanically non-contact state with the rotating drum. It is possible to realize high-precision constant-speed rotation without mechanical friction. According to the invention of claim 4, the area in which the damper function of the viscous fluid acts is enlarged by a simple structure, and the braking characteristic is improved.

[Brief description of drawings]

FIG. 1 is a sectional view of a support mechanism portion of a rotary drum according to a first embodiment to which a rotary drum braking device of the present invention is applied.

FIG. 2 is a sectional view of a support mechanism portion of a rotary drum according to a second embodiment.

FIG. 3 is a cross-sectional view of essential parts of a support mechanism portion of a rotary drum according to a third embodiment.

FIG. 4 is a cross-sectional view of a main part of a support mechanism portion of a rotary drum according to a fourth embodiment.

FIG. 5 is a sectional view of a supporting mechanism portion of a rotary drum according to a fifth embodiment.

FIG. 6 is a graph showing fluctuations in the rotation speed of the rotary drum when the braking device is not applied to the mechanism of the first embodiment.

FIG. 7 is a graph showing fluctuations in the rotation speed of the rotating drum when the braking device is applied to the mechanism of the first embodiment.

FIG. 8 is a schematic configuration diagram centering on a rotating drum in an electrophotographic color printer.

[Explanation of symbols]

1,21,51 ... Rotating drum, 1a, 4a, 51a, 53a ... Opposing surface, 2 ... Rotating shaft, 3,22 ... Support frame, 4,26,52 ... Fixing plate, 5,25 ...
Radial bearings, 6,27 ... Gap, 7 ... Silicon oil
(Viscous fluid), 8a, 8b, 9a, 9b ... Annular groove, 10,11,28,29,56,57
... O-ring (annular seal member), 21a ... Inward flange portion, 23 ... Fixed shaft, 24 ... Bearing side plate, 31 ... Magnetic fluid, 32 ... Annular magnet, 33, 34 ... Annular magnetic plate, 41 ... Meandering part of gap , 53 ... Ring part of fixed plate (fixed ring), 54a, 54b, 55a, 55
b ... circumferential groove (annular groove), 81 ... rotary drum, 82 ... speed reduction mechanism, 83 ... STEP motor (stepping motor), 84 ... photosensitive paper roll, 84a ... photosensitive paper, 85 ... charger, 86 ... laser emitting section , 87 ... Polygon mirror, 88 ... Optical system, 89 ... Prewetting device, 90 ... Toner developer, 91 ... Squeeze, 92 ... Heater, 93 ... Static elimination lamp.

Claims (4)

[Claims] 1. A viscous fluid is retained in a gap between a side surface of a rotary drum and a fixed plate facing the side surface, or in a clearance between a side outer peripheral surface of a rotary drum and a fixed ring body externally fitted on the side outer peripheral surface. A braking device for a rotating drum, which is characterized in that 2. The viscous fluid holding means fits two annular seal members into two annular grooves formed in the opposing surfaces forming a gap, and the annular seal members are provided between the opposing surfaces. The braking device for a rotating drum according to claim 1, wherein the viscous fluid is filled between the annular seal members in the gap by compressing. 3. The rotary drum according to claim 1, wherein the viscous fluid holding means uses a magnetic fluid as the viscous fluid, and an annular magnet is embedded in a boundary portion of the facing surface forming the gap, in which the magnetic fluid is to be interposed. Braking system. 4. The viscous fluid intervening region is formed so that each facing surface is formed so that the convex portion and the concave portion are opposed to each other, and the gap in the intervening region of the viscous fluid is meandered. Rotating drum braking system.