JPH01197767A - Driving device for image forming device - Google Patents

Abstract

PURPOSE:To eliminate the speed fluctuation of high-frequency band based on a gear driving and a worm driving which arise from the supporting side of a photosensitive body, to reduce the unevenness of image density, and to improve the quality of image by providing an oil supplying part capable of soaking a part of a drive engaging part of the image forming device with lubricating oil and regulating the viscosity of the lubricating oil to a prescribed value. CONSTITUTION:An image signal which is read by the scanner part 1 of a color copying machine as an image forming device is converted to an electrical signal by a picture processing part 2, inputted to a printer part 3, and sent to laser beam emitting devices 12BK, 12C, 12M, and 12Y in each color. A photosensitive body for these devices 12BK-12Y is integrally fixed to the supporting shaft 24 of the photosensitive body through a flange, the shaft 24 is supported to revolve freely by a supporter 26 which is fit to a main body's side plate, and a worm wheel 28 which meshes with a worm 29 is fit to one end. A worm driving part where wheel 28 and the worm 29 engage with each other is provided with an airtight oil box 35 which contains the lubricating oil 37. The viscosity of the lubricating oil 37 is determined 300-650cst/37.8 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a drive device capable of reducing speed fluctuations of a photoreceptor in a color image forming apparatus.

(Prior art) In image forming apparatuses, especially digital image forming apparatuses that form images using dots using laser beams, etc., rotational unevenness occurring in the photoreceptor causes image density unevenness in the sub-scanning direction, which is the paper feeding direction. In the case of a color image forming apparatus, a shift occurs in the overlapping of each image, resulting in color unevenness and deterioration of image quality.

As measures to prevent such rotational unevenness that occurs in the photoreceptor, there are measures such as providing a flywheel on the photoreceptor shaft (Japanese Patent Application Laid-open No. 70547/1982), and using a vibration absorbing member in the middle of the drive transmission system (Japanese Patent Application Laid-open No. 70547/1983). No. 137361/1983), etc. have been proposed.

In the former case, the inertial load increases, which reduces durability due to the increased load on the drive unit when starting and stopping, complicates motor rotation control (slow-up, slow-down), and increases the overall weight of the device. This will cause a problem. In the latter case,
Although high-frequency vibrations are absorbed, rotational unevenness occurs at low frequencies due to the elasticity of the vibration absorbing member, and new rotational unevenness occurs at low frequencies when there is a load change on the photoreceptor.

As described above, even with the conventional means provided to remove rotational unevenness of the photoreceptor, other problems arise and it is not possible to deal with rotational unevenness due to specific vibrations, resulting in color shift, especially in color image forming apparatuses. This reduces image quality.

Note that grease has conventionally been used as a lubricant for the gear drive system in this type of image forming apparatus due to its simple structure.

(Object of the Invention) The present invention provides an image forming apparatus in which a photoreceptor shaft drive system is equipped with a drive engagement portion consisting of a worm and a worm wheel.
It is an object of the present invention to provide a means for obtaining an image without density unevenness by using lubricating oil as a lubricant for the worm drive engaging portion, reducing speed fluctuations in a high frequency band using the lubricating oil.

(Structure of the Invention) In order to achieve the above object, the present invention includes a photoreceptor, a charging means for charging the photoreceptor around the photoreceptor, and an exposure means for projecting image light onto the photoreceptor; A drive, which is provided between a photoconductor support shaft that supports a photoconductor and a drive side, and includes a developing device that visualizes the exposed electrostatic latent image and a transfer device that transfers the developed image onto transfer paper. In an image forming apparatus having an engaging portion, an oil supply portion capable of immersing a portion of the drive engaging portion in lubricating oil is provided, and the viscosity of the lubricating oil is set to 300 to 650.
cSt/37.8°C.

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a color copying machine as an image forming apparatus to which the present invention is applied.

A color copier has a scanner part 1 for reading originals.
, an image processing section 2 that electrically processes the image signal output as a digital signal from the scanner section 1, and a printer section that forms an image on copy paper based on the image recording information of each color from the image processing section 2. It has 3. The scanner part 1 has a lamp 5, for example a fluorescent lamp, for scanning and illuminating the document on the document table 4. The reflected light from the document when illuminated by the fluorescent lamp 5 is reflected by the mirrors 6, 7. 8 and enters an imaging lens 9. The image light is imaged onto a dichroic prism lO by the imaging lens 9, and is separated into light of three different wavelengths, for example, red R1 green G1 blue B, and a light receiver 11 for each wavelength light, for example, a red CCDIIR.

The light is input to CCDIIG for green and CCDIIB for blue. Each CCDIIR, IIG, and IIB converts the incident light into a digital signal and outputs it, and the output is subjected to necessary processing in the image processing section 2 to produce recorded color information for each color, such as black (hereinafter abbreviated as Bk). , yellow (abbreviated as Y), magenta (abbreviated as M), and cyan (abbreviated as C).

Although FIG. 1 shows an example of forming four colors, Bk, C, M, and Y, it is also possible to form a color image using only three colors. In that case, the number of recording devices can be reduced by one compared to the example shown in FIG.

The signal from the image processing section 2 is manually input to the printer section 3,
12C, 1 to the laser beam emitting device 128 of each color.
2M, 12Yi will be sent.

In the example shown in the figure, the printer section includes four sets of recording devices 138,
13C, 13M, and 1°3Y are arranged side by side. Since each recording device 13 is made of the same constituent members, in order to simplify the explanation, the recording device for C will be explained, and the explanations for other colors will be omitted. Note that for each color, the same parts are given the same reference numerals, and in order to distinguish the configuration of each color, a subscript indicating each color is added to the reference number.

The recording device 13C includes a photoreceptor 14C1, for example, a photoreceptor drum, outside the laser beam emitting device 12C.

The photoreceptor 14C is provided with a charger 15C, an exposure device including a laser light emitting device 12C, a developing device 16C, a transfer charger 17C, etc., as in a known copying apparatus.

Photoreceptor 1 uniformly charged by charger 15C
4C forms a cyan latent image by exposure by the laser beam emitting device 12C, and develops it by the developing device 16C to form a developed image. Copy paper is fed by a paper feed roller 18 from a paper feed unit 19, for example, one of two paper feed cassettes, and the leading edge of the copy paper is aligned by a registration roller 20 and sent to a transfer belt 21 at the same timing. Transfer belt 2
The copy paper conveyed by 1 is sequentially sent to photoreceptors 148, 14C, 14M, and 14Y, each having a developed image formed thereon, and the developed image is transferred under the action of the transfer charger 17.

The transferred copy paper is fixed by a fixing roller 22,
The paper is ejected by the paper ejection roller 23.

By being electrostatically attracted to the transfer belt 21, the copy paper can be conveyed with high precision at the speed of the transfer belt.

Next, the force shown in FIG.
48, the drive systems of 14C, 14M, and 14Y are shown in a plan view in FIG.

Each photoreceptor 14 is driven in a predetermined direction by rotation of the shaft of the motor 31. That is, the shaft of the motor 31 is connected to one end of a worm shaft 30 via a timing belt drive section 32, and the worm shaft 30 includes a worm 29Bk for driving each photoreceptor 14.

29C, 29M, and 28Y are provided, and are engaged with the worm wheel 288 on the side of each photoreceptor 14. Each worm wheel 28 and photoreceptor 14
Since the relationship between them is the same, one of them will be described (in this case, the subscripts for each color attached to each symbol will be omitted). The photoreceptor is integrally fixed to a photoreceptor support shaft 24 via a flange 27, and the photoreceptor support shaft 24 is rotatably supported by a supporter 26 attached to a side plate 25 of the main body, and a worm 29 is attached to one end of the supporter 26. A worm wheel 28 is attached that engages with the worm wheel 28.

Further, a worm shaft bracket 33 is attached to the supporter 26, and a worm shaft support portion 3 is attached to the bracket 33.
4 is formed to support the worm shaft 30.

Each worm drive portion in which the worm wheel 28 and the worm 29 are engaged is provided with a sealed oil box 35 serving as an oil supply portion containing lubricating oil. A drawing showing this state is shown in FIG.

In FIG. 3, a worm wheel 28 is fixed to one end of the photoreceptor support shaft 24, and a portion of the worm wheel 28 is immersed in lubricating oil 37 in an oil box 35 to lubricate the tooth surface and prevent wear. The oil box 35 is hermetically covered by a cover 36, and a thrust stopper collar 38 is provided around the photoreceptor support shaft 24 in the portion extending into the oil box 35, and a thrust stopper collar 38 is provided from the oil box 35 to the supporter 26 side. This prevents the lubricating oil 37 from leaking to.

In the photoreceptor drive device configured as described above, the worm shaft 3
Even if the speed fluctuation at
It has been observed that this occurs largely over the 07 frequency bands.

Among the causes of these speed fluctuations, those in the low frequency band are due to the eccentricity of the worm Hoinope worm.
Those in the high frequency band are the worm, the tooth profile error of the worm wheel, the play between teeth in backlash, and the worm shaft 30.
It is understood that this is due to the vibration of the

Therefore, although speed fluctuations in the low frequency band could be resolved by using a worm wheel and means for reducing the eccentricity of the worm, no means for solving speed fluctuations in the high frequency band could be found.

In the present invention, it has been confirmed through experiments that the speed fluctuation in the high frequency band changes by changing the viscosity of the lubricating oil stored in the oil box in the worm drive section.

Experiments have shown that when a lubricating oil with a viscosity of approximately 300 cSt/37.8°C is used, speed fluctuations in the high frequency band are reduced; /1 for lubricating oil at 37.8℃! It exhibits a similar speed fluctuation rate and causes problems such as an increase in load due to viscosity and a decrease in lubricity due to air bubbles being mixed into the lubricant due to agitation. is 300~650c
St/37.8°C is preferred.

Figures 4(a) and 4(b) show the case where a lubricating oil with a viscosity of 50 cSt/37.8°C was used as an experimental example (a).
) and (when using one with a viscosity of 650 cSt/37.8° C.), the results of frequency analysis of speed fluctuations (rotation unevenness) of the photoreceptor support shaft are shown. The horizontal axis represents the fluctuation frequency, and the vertical axis represents the speed fluctuation rate at each frequency.

Comparing (a) and (6) in Figure 4, there is not much difference in the range of 0 to 1507, but in the range of 1507 and above, the speed at 1621 (z, 172Hz, 2067) in (a) (from fluctuations) has been reduced.

This phenomenon is thought to be due to an increase in the viscous damping coefficient in the degree-of-freedom oscillating system. By using lubricating oil of a predetermined viscosity in this way, the effect of reducing leakage from the sealed oil box through the gap is exerted.

As an application example of the present invention, a color copying machine using a plurality of photoreceptors has been described, but the present invention is not limited to this, and the present invention can also be applied to a photoreceptor drive unit of a boat-type copying machine, a printer, etc. This is useful for reducing uneven rotation and improving image quality in these cases.Although an example of a worm drive consisting of a worm and a worm wheel was shown in the drive unit, it cannot be applied to a normal gear drive. However, rotational unevenness due to occlusal errors on the tooth surfaces can be reduced.

(Effects of the Invention) With the configuration of the present invention, it is possible to eliminate speed fluctuations in the high frequency band caused by gear drive and worm drive that occur on the photoreceptor support shaft side, and it is possible to reduce rotational unevenness, thereby improving the image quality. Image quality can be improved by reducing density unevenness. Further, there is no need to separately provide a damper, a flywheel, etc. in the drive system as in the conventional case, and there is no need to deal with load fluctuations caused by separately providing such members.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a color copying machine to which the present invention is applied, FIG. 2 is a schematic plan view of the photoreceptor drive section of FIG. 1, and FIG. 3 is a side view of the drive engagement section of the present invention. Figure 4 (a), (b)
are experimental data showing the difference in speed fluctuation rate based on different viscosities of lubricating oil. 28... Worm wheel, 29... Worm, 3
5... Oil box, 37... Lubricating oil.

Claims (1)

[Claims] A photoreceptor, around the photoreceptor, a charging means for charging the photoreceptor, an exposure means for projecting image light onto the photoreceptor, a developing means for visualizing the exposed electrostatic latent image; In an image forming apparatus including a transfer means for transferring a developed image onto a transfer paper, and having a drive engagement part disposed between a photoreceptor support shaft supporting a photoreceptor and a drive side, a part of the drive engagement part An oil supply section is provided that can soak the lubricating oil in the lubricating oil, and the viscosity of the lubricating oil is set to 3.
A driving device for an image forming apparatus, characterized in that the temperature is 00 to 650 cSt/37.8°C.