Cylindrical member and electrophotographic apparatus employing the same

Abstract: A cylindrical member has a sleeve, a flange (12b) bonded to the end portion of the sleeve (12a), and a space-controlling member (18) provided at the end portion of the sleeve (12a). The flange (12b) is press-fitted into the end portion of the sleeve (12a) to be bonded thereto. A space-controlling portion of the space-controlling member (18) is located more apart from the end of the sleeve (12a) than the press-fitted portion of the flange (12b).

Description: The present invention relates to photosensitive drums and developing rollers for electrophotographic apparatus, and also to an electrophotographic apparatus, process cartridge, developing device and facsimile machine which may include such a developing roller or photosensitive drum. Conventionally, a developing roller of a development device of a conventional image-forming apparatus, as shown in Fig. 5, comprises a cylindrical sleeve 12a, and a developing roller end-member or flange 12b bonded permanently at the end portion thereof. At the fitting portion, the inside diameter of the sleeve 12a is larger than the outside diameter of the flange 12b, usually by approximately 30 µm, for the purpose of applying a prescribed amount of an adhesive 9 between the sleeve 12a and the flange 12b for bonding them. The bonding is practiced specifically such that an adhesive 9 is applied uniformly onto the inside peripheral face of the end portion of the sleeve 12a where the flange 12b is fitted, then the flange 12b is inserted thereto, and the adhesive 9 is completely cured at a constant temperature and humidity. Usually, the adhesive includes instantaneous adhesives, and combinations of an adhesion primer and an anaerobic adhesive. The adhesive is selected depending on the required bonding strength for the use and the purpose. The above constitution of conventional developing rollers has disadvantages shown below. (1) When the adhesive is applied and completely cured at a high temperature and a high humidity (e.g., at a temperature of 32.5°C, and a relative humidity of 85 %), the moisture in the air affects adversely the adhesion during the curing process, causing instable bonding such as separation of the sleeve and the flange, and slipping between them owing to the deterioration of the adhesion. (2) Some adhesives require a very long time for complete curing, which necessitates a storage space for a long time, and installation for keeping a constant temperature and a constant humidity of the storage environment, and therefore is disadvantageous from the standpoint of cost, management and productivity. (3) Conventionally, the constitution around the developing roller is as shown in Fig. 2, comprising a magnet roller 14, a developing sleeve 12a, a developing roller flange 12b, a spacer roller 18, a developing roller bearing 16, a developing roller gear 17, a holder 15, a photosensitive drum 1, and a photosensitive drum gear 1b. In Fig. 2, the flange 12b is inserted into the sleeve 12a with a gap, and is bonded by use of an adhesive. Therein the magnet roller 14 is enclosed. The developing roller is supported at both ends thereof by the bearings 16. The bearing is fixed on the holder 15 by a positioning pin and a hole which are not shown in the drawing. The magnet roller is also fitted to the holder 15. On the other hand, the photosensitive drum comprises the sleeve 1a and the gear 1b which are bonded with an adhesive. The developing roller and the photosensitive drum are pressure-contacted through the spacer roller 18 by aid of a spring 8. The spacer roller keeps constant the distance between the developing roller and the photosensitive drum. The photosensitive drum is rotated by receiving rotational driving force from the main body of an image-forming apparatus through the gear 1b to rotate the developing roller in the arrow-marked direction through the developing roller gear 17. Therefore, if the sleeve 12a and the developing roller flange 12b is not coaxial and deviate from each other by the distance A as shown in Fig. 5, then the outside diameter of the flange 12b swings with an amplitude of twice the dimension A relative to the outside diameter of the sleeve 12a when the developing roller is rotated through the developing roller gear 17 by the driving action of the photosensitive drum gear 1b. Accordingly, the magnet roller 14 moves by a distance of twice the distance A in one rotation relative to the surface of the photosensitive drum 1. As the result, the magnetic force exerted to the photosensitive drum swings, causing irregularity of image density corresponding to the rotation cycle of the developing roller. Examples of the use of a space-controlling member between a developing roller and a photosensitive drum are shown in patent documents JP-A-58-108562 & EPA-0389267. The present invention is concerned with providing a cylindrical member which exhibits stable rotational performance without axial deviation and which enables the spacing between the cylindrical member and a surface parallel thereto to be controlled. In accordance with one aspect of the present invention, there is provided a photosensitive drum or a developing roller for an electrophotographic apparatus, comprising: a sleeve, an end-member which has a portion which is press-fitted into an end portion of the sleeve, and a space-controlling member having a portion provided adjacent the end portion of the sleeve and spaced apart axially from the end of the sleeve more than the press-fitted portion of the end-member for controlling the spacing between the sleeve and an opposing surface parallel to the sleeve. Other aspects of the invention and preferred features thereof are defined in the claims. Specific embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a cross-sectional view of an embodiment of the invention in the form of a process cartridge employing a photosensitive drum and a developing roller. Fig. 2 is a partial cross-sectional view of the process cartridge shown in Fig. 1. Fig. 3 is a partial cross-sectional view of the developing roller. Fig. 4 is a partial cross-sectional view of a photosensitive drum forming another embodiment of the present invention. Fig. 5 is a partial cross-sectional view of a conventional cylindrical member. Fig. 6 is a block diagram of another embodiment of the invention in the form of a facsimile system employing an electrophotographic apparatus as its printer in which a cylindrical member of the present invention is used. The present invention provides a cylindrical member which comprises a sleeve, a flange forced into the end portion of the sleeve and bonded thereto, and a space-controlling member provided at the end portion of the sleeve and having the space controlling portion located apart from the end portion. The present invention also provides an electrophotographic apparatus employing a photosensitive drum and/or a developing roller having the cylindrical member of the above construction. In the photosensitive drum or the developing roller of the developing device of the electrophotographic apparatus, the portion of the flange to be press-fitted into the end of the sleeve has an outside diameter larger than the inside diameter of the sleeve, and is forced into the sleeve to be bonded thereto. The outside diameter of the sleeve is expanded by forced insertion of the flange, but the expanded portion of the sleeve in the axis direction does not reach the contact portion of the spacer roller. The difference between the inside diameter of the sleeve and the outside diameter of the flange, and the press-fitting length are selected such that no gap is formed between the flange and the sleeve on thermal contraction and the required rotational strength is obtained. The deviation of the axis from the rotation axis as is met in conventional cylindrical members can be avoided and stable rotation state can be obtained invariably by press-fitting the flange into the sleeve without a gap therebetween and by keeping the expanded portion of the sleeve so as not to reach the portion of the space-controlling member for contacting with another member. Use of the cylindrical member of the present invention as a developing roller or a photosensitive drum gives the effects as below. 1. The absence of a gap between the sleeve and the flange at the fitting portion ensures the concentricity of the two axes, and obviates swing of the flange relative to the sleeve surface, keeping the magnet roller at the fixed position and eliminating non-uniformity of image density in the rotation cycle of the developing roller. 2. The absence of adhesive or the like improves and stabilizes the quality of the bonding between the sleeve and the flange, and simplifies the assemblage process, lowering the production cost. By press-fitting of the flange into the sleeve, the sleeve is expanded in the radial direction. The height of the expansion is preferably not more than 80 µm, more preferably not more than 50 µm. The press-fitting length is preferably in the range of from 5 to 150 µm, more preferably from 40 to 150 µm, particularly preferably from 60 to 120 µm. The present invention is explained by reference to the drawings. (First Embodiment) Fig. 1 illustrates a cross-section of a process cartridge 6 provided with a photosensitive drum and/or a developing roller having a cylindrical member according to the present invention. In Fig. 1, a photosensitive drum 1 is an image holding member which rotates in a predetermined direction. Around the photosensitive drum 1, are provided processing devices including an electrostatic charger 2, a developing device 3, and a cleaning device 4. These devices are assembled integrally in the cartridge case 6a which is set to be demountable in the main body of an image-forming apparatus. Therefore, when the life of the photosensitive drum is over, or when the toner (a developing agent) in the developing device 3 has been consumed completely, the processing cartridge 6 is exchanged as a whole, thereby the maintenance being facilitated. The developing device 3 faces to the photosensitive drum 1, and comprises a developing section 10 having a developing roller 12 as a developing-agent supporter, and a developing agent storing section 11 for storing a toner T and supplying the toner T to the developing section 10. A lid member 13 having an opening 13a is provided between the developing section and the toner-storing section. To the opening 13a of the lid member 13, a sealer 13b is attached so as to prevent the toner T in the developing-agent storing section 11 from leaking through the developing section 10 to the outside of the cartridge 6 during the time when the toner is not used. When the cartridge 6 is mounted on a main body of an image-forming apparatus, the sealer 13b is handled to open the opening 13a to supply the toner from the developing agent-storing section 11 to the developing section 10. The cleaning device 4 is provided for cleaning any remaining toner on the photosensitive drum 1 to make ready the photosensitive drum for subsequent image formation. The cleaning device comprises a cleaning blade 4a which slides on the photosensitive drum 1 and removes remaining toner thereon, and a waste toner container 4b which stores the waste toner removed by the cleaning blade 4a. A protecting shutter 5 protects the photosensitive drum 1. On mounting the processing cartridge 6 on a main body of an image-forming apparatus, the shutter 5 is displaced to a side of the photosensitive drum 1 (toward the waste toner container). The photosensitive drum 1 is electrically charged uniformly by the electrostatic charger 2. When the photosensitive drum 1 is exposed to imaging light L from a scanning optical system not shown in the drawing, an electrostatic latent image is formed thereon. This latent image is moved to face to the developing device 3 with rotation of the photosensitive drum 1, and is developed to form a toner image with the toner T supplied by the developing roller 12 of the developing device 3. The resulting toner image is transferred onto a transfer-receiving paper sheet by a transfer means not shown in the drawing. The photosensitive drum 1, after the image transfer, is cleaned to remove remaining toner by cleaning device 4 to make it ready for subsequent image formation. The transfer-receiving paper sheet is fed from a paper-feeding cassette not shown in the drawing to the photosensitive drum 1, and, after receiving the transferred image, is sent to a fixing device not shown in the drawing to fix the toner image. The processing cartridge 6 according to the present invention is explained below in more detail by reference to Fig. 2. The photosensitive drum 1 comprises a sleeve 1a and a gear flange port ion 1b which are fixed with each other by bonding, and is supported rotatably with a centering axis 7 by the cleaning vessel 4c. The developing device 3 has a magnet roller 14. This magnet roller 14 is held by a magnet holder 15. A developing roller 12, which is provided with a developing roller sleeve 12a, is held rotatably with a flange 12b by a roller bearing 16 which is fixed to a magnet holder 15 by means of a positioning pin/hole means not shown in the drawing. The magnet holder 15 is fixed by a screw to a development vessel not shown in the drawing. At the end portion of the developing roller 12, a spacer roller 18 in a cap shape is fitted rotatably to keep constant the distance from the photosensitive drum 1 outside the development region. The cleaning vessel 4c is supported rotatably around a rotation center (not shown in the drawing) relative to the magnet holder 15, and is energized by a spring 8 in one direction. Therefore, the spacer roller 18 is pressed to the external face of the pipe 1a of the photosensitive drum 1 and the distance between the sleeve 12a and the sleeve 1a of the photosensitive drum 1 is invariably kept constant. A rotational driving force is transmitted to the developing roller gear 17 from a driving gear not shown in the drawing of the main body of an image forming apparatus through the gear flange 1b of the photosensitive drum, so that the photosensitive drum 1 and the developing roller 12 rotate respectively in the directions shown by the arrow marks. The invention is explained in more detail by reference to Fig. 3. The outside diameter of the developing roller flange 12b is slightly larger than the inside diameter of the sleeve 12a, for example, by about 100 µm, and the developing roller flange 12b is press-fitted into the sleeve 12a having a smaller inside diameter. If the sleeve 12a is made of aluminum and the flange 12b is made of a plastic which is softer than aluminum, the outside diameter of the sleeve 12a expands, for example, by about 10 µm. However, the length of fitting of the sleeve 12a and the flange 12b in the axial direction is short, and the expanded portion does not reach the position of the contacting portion 18a of the spacer roller 18. Therefore, the distance between the developing roller 12 and the photosensitive drum 1 is controlled to be constant invariably by the thickness of the contacting portion 18a. The elasticity of the sleeve 12a and the flange 12b to restore the original dimensions thereof prevents the slipping and the falling-off. The expansion of the sleeve 12a is less than the difference between the thickness of the contacting portion 18a and the thickness of the other portion of the spacer roller 18. If the expanded portion caused by the press-fitting reaches the contacting collar of the spacer roller (i.e., the space-controlling portion), the distance between the photosensitive drum and the developing roller comes to be changed, or otherwise the thickness of the drum-contacting collar of the spacer roller needs to be adjusted to compensate the expansion by estimating the degree of expansion. However, the adjustment is not easy. Therefore, the expanded portion is required not to reach the contacting collar. Since the sleeve 12a and the flange 12b are press-fitted without gap, the axes thereof coincide to prevent the swing of the flange 12b, as met in prior art, relative to the sleeve 12a. Therefore, the position of the magnet roller 14 is invariable. Consequently, the accuracy of bonding of the sleeve and the flange is improved with an economical assemblage process, and the lowering of the image quality can be avoided. (Second Embodiment) In the above first embodiment, the sleeve of the developing roller 12 is made of aluminum, and the flange is made of a plastic. In the case where both of the sleeve and the flange are made of metal, the same effect can be achieved as long as the elasticity of the metal prevents the slipping and falling-out of the flange and the amount of the expansion of the sleeve is less than the difference between the thickness of the contacting collar and the thickness of the other portion of the spacer roller. It is preferred, however, to select a hard material such as aluminum, stainless steel, and other metals for the sleeve, and a soft material such as a plastic for the flange from the standpoint of reducing the expansion of the sleeve. (Third Embodiment) In the above embodiments, the description is made regarding the developing roller. The photosensitive drum may also be provided according to the present invention. This is shown by Fig. 4. In this embodiment, the developing roller 12 is the same as in the above embodiments, and the explanation therefor is not repeated here. In this embodiment also, the gear flange 1c is press-fitted into the sleeve 1a of the photosensitive drum 1, and the expanded portion of the sleeve does not reach the contacting portion 18a of the spacer roller 18, whereby the assemblage process is simplified and the bonding is stabilized. In an electrophotographic apparatus employing a developing roller or a photosensitive drum of the present invention, two or more of the constituting elements such as a photosensitive member, a developing means, and a cleaning means may be integrated into one unit as shown in Fig. 1, and the unit may be made demountable from the main body of the apparatus. For example, at least one of the electrostatic charging means, the developing means, and the cleaning means is integrated with the photosensitive member into one unit which is made demountable from the main body of the apparatus by aid of a guiding means such as a rail in the main body of the apparatus. The device unit may comprise the electrostatic charging means and/or the developing means. In the case where the electrophotographic apparatus is used as a copying machine or a printer, the optical image exposure light may be projected onto the photosensitive member as reflected light or transmitted light from an original copy, or otherwise the information read out from an original may be signalized, and light is projected, onto a photosensitive member, by scanning with a laser beam, driving an LED array, or driving a liquid crystal shutter array according to the signal. In the case where the electrophotographic apparatus is used as a printer of a facsimile machine, the optical image exposure light is employed for printing the received data. Fig. 6 is a block diagram of an example of this case. A controller 21 controls the image-reading part 20 and a printer 29. The entire of the controller 21 is controlled by a CPU 27. Readout data from the image reading part 20 is transmitted through a transmitting circuit 23 to the other communication station. Data received from the other communication station is transmitted through a receiving circuit 22 to a printer 29. The image data is stored in image memory 26. A printer controller 28 controls a printer 29. The numeral 24 denotes a telephone set. The image received through a circuit 25, namely image information from a remote terminal connected through the circuit, is demodulated by the receiving circuit 22, treated for decoding of the image information in CPU 27, and successively stored in the image memory 26. When at least one page of image information has been stored in the image memory 26, the images are recorded in such a manner that the CPU 27 reads out the one page of image information, and sends out the decoded one page of information to the printer controller 28, which controls the printer 29 on receiving the one page of information from CPU 27 to record the image information. During recording by the printer 29, the CPU 27 receives the subsequent page of information. Images are received and recorded in the manner as described above.

Claims: A photosensitive drum (1), or a developing roller (12), for an electrophotographic apparatus, comprising: a sleeve (12a; 1a); an end-member (12b; 1c) which has a portion which is press-fitted into an end portion of the sleeve, and a space-controlling member (18) having a portion (18a) provided adjacent the end portion of the sleeve and spaced apart axially from the end of the sleeve more than the press-fitted portion of the end-member for controlling the spacing between the sleeve and an opposing surface parallel to the sleeve. A drum or roller according to claim 1, wherein, prior to press fitting of the end member into the end portion of the sleeve, the outside diameter of the press-fitted portion of the end-member is between 5 µm and 150 µm greater than the inside diameter of the end portion of the sleeve. A drum or roller according to claim 1 or 2, wherein the press-fitted portion of the end member causes the sleeve to have an expanded portion, the space-controlling portion being spaced apart axially from the expanded portion. A drum or roller according to any preceding claim, wherein the end-member is made of a material softer than that of the sleeve. A drum or roller according to claim 4, wherein the end-member is made of a plastics material and the sleeve is made of a metal. An electrophotographic apparatus comprising a developing roller (12) as claimed in any preceding claim, a photosensitive drum (1) extending parallel to the developing roller, and means (8) for urging the roller and drum towards each other so that the space-controlling portion engages the drum and controls the spacing between the roller and the drum. An electrophotographic apparatus comprising a photosensitive drum (1) as claimed in any of claims 1 to 5, a developing roller (12) extending parallel to the drum, and means for urging the roller and drum towards each other so that the space-controlling portion engages the roller and controls the spacing between the roller and the drum. A process cartridge (6) comprising an electrophotographic apparatus as claimed in claim 6 or 7, and means for removably mounting the electrophotographic apparatus in a main body of an image forming apparatus. A developing device (3), comprising a developing agent storing section, and a developing roller as claimed in any of claims 1 to 5 for carrying developing agent from the developing agent storing section. A facsimile machine (20, 21, 29) having a developing roller or photosensitive drum as claimed in any of claims 1 to 5, or an electrophotographic apparatus as claimed in claim 6 or 7, or a process cartridge as claimed in claim 8, or a developing device as claimed in claim 9.

Inventors: MIURA KOJI, SASAKI SHINICHI, SHISHIDO KAZUO, MIURA, KOJI, SASAKI, SHINICHI, SHISHIDO, KAZUO, Miura, Koji, c/o Canon K. K., Sasaki, Shinichi, c/o Canon K. K., Shishido, Kazuo, c/o Canon K. K.
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1992
Main classification: G03G15
IPC codes: G03G15