Patent Grant
7162185
1) Field of the Invention
The present invention relates to a transmission having a transmissive member fixedly fitted with a rotary shaft, an image formation apparatus including the transmission, and a transmission manufacturing method.
2) Description of the Related Art
Transmissions are employed widely in various machines. For example, a transmission is used in image formation apparatuses to rotate a transmissive member. The rotational force is transmitted, via a rotary shaft, to a photosensitive drum that carries a toner image. The transmissive member includes gears and pulleys. Such a technology has been disclosed in, for example, Japanese Patent Application Laid-open Publication No. H7-239596 on pages 7 and 8, and in FIG. 6.
However, if the transmissive member makes an angle with the rotary shaft, there occurs variation in the speed of the rotations transmitted. This problem will be explained in detail taking the above-mentioned publication as an example. This publication discloses to fit the photosensitive drum to the rotary shaft, fit the transmissive member to the rotary shaft, and drive the rotary member by a motor. The transmissive member includes gears and shafts. The rotation axes of the gears are perpendicular to the rotary shaft. However, if the rotation axes of the gears are not perfectly perpendicular to the rotary shaft, even if the gears are rotated at constant speed, the rotations are not properly conveyed to the rotary shaft, and hence the photosensitive drum does not rotate at desired speed. As a result, a desired toner image can not be formed on the photosensitive drum and the image quality degrades.
One approach to solve the above mentioned problem is to provide a member (hereafter, “regulative member”) that regulates the angle of the gears of the transmissive member. This regulative member is, for example, fixed to the rotary shaft and pressed against the gears of the transmissive member in such a manner that the rotation axes of the gears are perfectly perpendicular to the rotary shaft. The regulative member is fit to the rotary shaft with a screw. However, when the screw is fastened, the fastening force imposes a large stress on the regulative member and deforms the regulative member. This deteriorates the state of perfect perpendicularity of the rotation axes of the gears with the rotary shaft.
It is an object of the present invention to solve at least the problems in the conventional technology.
A transmission according to one aspect of the present invention includes a rotary shaft; a transmissive member coupled with the rotary shaft and secured to the rotary shaft, the transmissive member having a first end and a second end; and a regulative member secured to the rotary shaft by press fitting and press-contacts the first end of the transmissive member in such a manner that the transmissive member is perpendicular to the rotary shaft.
An image formation apparatus according to another aspect of the present invention includes the transmission according to the above mentioned aspect.
A method of manufacturing a transmission according to still another aspect of the present invention is a method of manufacturing a transmission that includes a rotary shaft; a transmissive member coupled with the rotary shaft and secured to the rotary shaft, the transmissive member having a first end and a second end; and a regulative member secured to the rotary shaft by press fitting and press-contacts the first end of the transmissive member in such a manner that the transmissive member is perpendicular to the rotary shaft. This method includes finishing a surface of the regulative member, after securing the regulative member to the rotary shaft and before securing the transmissive member to the rotary shaft, in such a manner that the surface press-contacts with the first end of the transmissive member.
The other objects, features and advantages of the present invention are specifically set forth in or will become apparent from the following detailed descriptions of the invention when read in conjunction with the accompanying drawings.
Exemplary embodiments of the present invention are explained below while referring to the accompanying drawings.
The first to the fourth photosensitive drums 3Y, 3M, 3C and 3BK have a substantially similar configuration and perform substantially similar operation when respective toner image is formed thereon. Accordingly, only the configuration and operation of the first photosensitive drum 3Y is explained here. The first photosensitive drum 3Y is rotated in clockwise direction. A charging roller 7 electrically charges the surface of the first photosensitive drum 3Y uniformly to a certain polarity. The surface is then exposed to an optically modulated laser beam L emitted from a laser write unit 8. This results into formation of an electrostatic latent image on the first photosensitive drum 3Y. A developing device 9 sprays yellow toner on the surface. The toner sticks to the charged surface. This results into formation of a yellow tone image. The developing device 9 includes a developing roller 31 that holds the yellow toner.
A paper feed unit 5 feeds a recording medium P, which may be a paper or a resinous film, in the direction of the arrow B to the rotating conveyer belt 4. As a result, the recording medium P passes below the first photosensitive drum 3Y. A transfer roller 10 presses the conveyer belt 4 and the recording medium P against the first photosensitive drum 3Y. As a result, the yellow toner image is transferred onto the recording medium P. A cleaner 11 scrapes off toner remaining on the first photosensitive drum 3Y after the yellow toner image has been transferred onto the recording medium P.
In a similar manner, the toner images of magenta, cyan, and black are transferred onto the recording medium P, in a superimposed manner, above the yellow image. These images are not yet fixed. A fixing unit 2 fixes the images. The fixing unit 2 includes a pair of hot rollers 2A and 2B through which the recording medium with the unfixed images is passed. The temperature and pressure of the rollers 2A and 2B fixes the toner images onto the recording medium P. The recording medium P with the color image printed on it is ejected a tray 6 as shown by the arrow C.
Each of the photosensitive drums 3 is supported with a support structure and a transmission conveys a force of a motor to the photosensitive drum 3 to thereby rotate the photosensitive drum 3.
This configuration includes a body frame 13, which includes a front side plate 14 located towards the F side; a rear side plate 15 located towards the R side; a stay 16 that fixedly links these side plates 14 and 15; and a body bracket 17 secured to the rear side plate 15 with a screw (not shown). A front flange 18 and a rear flange 19 are press-fitted in the photosensitive drum 3 and integrated therewith to configure a drum unit 50. The front flange 18 and the rear flange 19 are detachably secured to the rotary shaft 20 as described later, and configured to allow the rotary shaft 20 to rotate integrally with the drum unit 50.
A positioning member 22 is detachably secured to the front side plate 14 using a plurality of screws 21. The positioning member 22 rotatably supports the front flange 18 via a bearing 23. The front side end of the rotary shaft 20 is detachably fitted with the front flange 18. The front flange 18 and the front side end of the rotary shaft 20 pass through a hole 24 formed through the front side plate 14.
The rear side portion of the rotary shaft 20 extends through the rear side plate 15 and the body bracket 17, and the extended portion is rotatably supported by a pair of rolling bearings 26, 27 held in a cylindrical holder 25. The holder 25 is detachably secured to the rear side plate 15 with a screw 28. Outer rings of the rolling bearings 26, 27 are fitted, without rattling, in holes 29, 30 formed through the rear side plate 15 and the body bracket 17, respectively, to position the rolling bearings 26, 27 and the rotary shaft 20 both relative to the body frame 13. Thus, the rotary shaft 20 is positioned relative to the body frame 13 and rotatably supported, and the photosensitive drum 3 is arranged in coaxial with the rotary shaft 20 via the front flange 18 and the rear flange 19.
The transmission 12 includes the rotary shaft 20 described above; an exemplary transmissive member or gear 32 fitted with the rotary shaft 20 and secured to the rotary shaft 20 as described later; a regulative member 33 detailed later; and a link 34 configured to detachably link the rear flange 19 with the rotary shaft 20. The gear 32 is located at the rear side end of the rotary shaft 20 and arranged in coaxial with the rotary shaft 20.
A drive motor 35 is held on the body flange 17. An output gear 36 is secured around the spindle of the motor and mates with the gear 32. When the drive motor 35 rotates, its rotation is transmitted via the output gear 36 and the gear 32 to the rotary shaft 20, and the rotation of the rotary shaft 20 is transmitted via the link 34 to the rear flange 19, which rotationally drives the drum unit 50 clockwise in
A transmissive member which consists of a pulley instead of the gear 32 may be secured in coaxial with the rotary shaft 20. The pulley is rotationally driven via a belt to drive the rotary shaft 20 and the photosensitive drum 3.
When the drum unit 50 is slid as indicated with the arrow D in
As explained above, the drum unit 50 can be attached to and detached from the rotary shaft 20. Therefore, when the positioning member 22 shown in
After the drum unit 50 is assembled in the body frame 13, when the gear 32 is driven rotationally by the drive motor 35, its rotation is transmitted via the rotary shaft 20 and the rear flange 19 to the photosensitive drum 3, which is thus driven rotationally. The gear 32 has an angle of α to the axis X of the rotary shaft 20, which may largely depart from 90 degrees. In such the case, even though the gear 32 has a constant angular velocity, a constant linear velocity cannot be achieved at the teeth on the outer circumference of the gear 32. As a result, a large velocity variation is found on the gear 32, and a velocity variation is also found on the outer surface of the photosensitive drum 3. When such the velocity variation is intensive, it causes a density variation and color deviation in a toner image held on the recording medium, and deteriorates the quality of the image.
The transmission 12 in the present example is provided with the regulative member 33 as described above. The regulative member 33 is secured on the rotary shaft 20, as shown also in
Conventionally, the regulative member is fit to the rotary shaft with a screw. On the other hand, in the present invention, the regulative member 33 is press-fit to the rotary shaft 20. As shown in
As described above, the regulative member 33 is fixedly press-fitted with the rotary shaft 20, and accordingly no screw is required to secure the regulative member 33. Therefore, it is possible to reject a malfunction associated with non-perpendicularity of the regulative surface 44 to the axis X, which squareness deteriorates when the screw is fastened. Thus, as the gear 32 can be fit exactly perpendicular to the axis X, desired toner image can be obtained.
To surely fit the gear 32 to the axis X at right angle, it is required to press-contact the one end 43 of the gear 32 with the regulative surface 44 of the regulative member 33 as described above. For this purpose in the art, the gear portion located outward in the radial direction from the rotary shaft 20 is secured to the regulative member 33 with a screw to press-contact the one end 43 of the gear 32 with the regulative surface 44 of the regulative member 33. This configuration, however, may deform the gear slightly when the screw is fastened, thereby tilting the gear 32 to the axis X, possibly deteriorating the squareness of the gear 32 to the axis X. In particular, if the gear is composed of a resin, the gear 32 may be deformed locally and the squareness may be deteriorated easily.
In the transmission 12 of the present example, as shown in
As shown, when the head 53 of the screw 47 screwed in the rotary shaft 20 or the washer 48 for the screw 47 presses the other end 49 of the gear 32, or the exemplary transmissive member, the one end 43 of the transmissive member is press-contacted with the regulative member 33. This is effective to improve the squareness of the gear 32 to the axis X. In addition, the gear 32 and the regulative member 33 are integrated when they are press-fitted with each other. Therefore, the rotation of the gear 32 is transmitted to the regulative member 33, of which rotation is transmitted to the rotary shaft 20 to reliably rotate the rotary shaft 20. The screw 47 is screwed in the central portion of the rotary shaft 20. Therefore, when the screw 47 is fastened intensively to press the screw 47 against the other end 49 of the gear 32, the end 49 may be deformed more or less. Even though, the portion of the end 49 in the vicinity of the central bore 51 uniformly deforms over the whole circumference. Accordingly, even if the gear 32 is resinous, the gear 32 never or rarely tilts to the axis X and can highly retain the squareness of the gear 32 to the axis X.
The regulative surface 44 of the regulative member 33, press-contacting the one end 43 of the gear 32, can be employed as a reference surface to determine the squareness of the gear 32. Accordingly, the regulative surface 44 is required to have a higher smoothness. After the regulative member 33 is processed and produced, a portion of the surface to be the regulative surface 44 is finished to improve the smoothness of the regulative surface. The whole surface of the regulative member 33, which opposes to the one end of the gear 32, may be finished to employ the whole surface as the regulative surface, but this elevates the cost of production.
Preferably, in the surface of the regulative member 33 that opposes to the transmissive member, the one end 43 of the gear 32 in this example, only a part is employed as the regulative surface 44 that press-contacts the one end 43 of the transmissive member. In this case, the other part of the surface of the regulative member 33 is preferably designed as a no contacting surface that never contacts the transmissive member. Specifically, as shown in
As in the example shown in
Thus, by producing the regulative member 33 larger in the radial direction, and press contacting the regulative surface formed in the outer portion in the radial direction with the one end 43 of the gear 32, the gear 32 and the axis X can be positioned at right angles. The regulative member 33 thus produced larger, however, elevates its cost. Further, the shown image formation apparatus is configured to employ the rolling bearings 26, 27 held in the holder 25, during its assembly, to support the rotary shaft 20 with the regulative member 33 secured thereon as shown in
In the transmission 12 of the present example, as shown in
The regulative member 33 catches the gear 32 using the plural protruded portions 56. This is effective to secure the gear 32 in stable. When the protruded portions 56 are provided three, the stability of the gear 32 can be improved particularly. In addition, the protruded portions 56 locate on the outer portion of the regulative member 33 in the radial direction. Accordingly, the gear 32 can be fit to the axis X at perfect right angle. Further, the regulative member 33 has radii, which are not entirely larger over the whole circumference but only larger at the protruded portions 56. Therefore, it is possible to prevent the regulative member 33 from being upsized and suppress the elevation of its cost. In addition, the hole 30 of the body bracket 17 can be made in a form that sets back from the protruded portions 56 of the regulative member 33, as shown in
In the transmission 12 of the present example, as described earlier, the screw 47 is fastened in the rotary shaft 20 to press-contact the one end 43 of the gear 32 with the regulative member 33. Therefore, even only with this configuration, it is possible to secure the gear 32 to the regulative member 33, to transmit the rotation of the gear 32 to the regulative member 33, and to transmit the rotation of the regulative member 33 to the rotary shaft 20. If the screw 47 loosens a little over time, the press-contacting force between the end 43 of the gear 32 and the regulative surface 44 of the regulative member 33 lowers and may cause slight sliding between both possibly. In such the case, the rotation of the gear 32 cannot be transmitted to the rotary shaft 20 correctly.
Preferably, a relative rotation protector is provided to inhibit the transmissive member and the regulative member to rotate relatively. For example, as shown in
As shown in
As shown in
The engagement protrusions 61 also form a relative rotation protector, which can transmit the rotation of the gear 32 to the regulative member 33 reliably. When the gear 32 is assembled to the rotary shaft 20, the engagement protrusions 61 formed on the gear 32 are engaged with the protruded portions 56 on the regulative member 33, respectively, to position the gear 32 relative to the regulative member 33.
As described above, the relative rotation protector comprises the engagement protrusions 61, which are formed on the one end 43 of the gear 32 that is an example of the transmissive member, and engaged with the regulative member 33. The engagement protrusions 61 are provided plural. The plural engagement protrusions 61 are arranged in the circumferential direction of the transmissive member. The engagement protrusions 61 are each located between the protruded portions 56 formed on the regulative member 33 and engaged with the protruded portions 56, respectively.
As shown in
The relative rotation protectors are described above as including the stepped screw 57, the engagement protrusions 61, and the projection 62, respectively. When at least one of these is applied, the rotation of the gear 32 can be transmitted to the rotary shaft 20 reliably even though the screw 47 loosens.
The gear 32 is attached to the rotary shaft 20 when the rotary shaft 20 is fitted in the central bore 51 formed in the gear 32, and the gear 32 is secured to the regulative member 33 using the screw 47. In order to further improve the squareness of the gear to the axis X, it is preferable to configure the whole length in the direction of the axis X on the circumferential surface of the rotary shaft 20 at a portion fitted in the central bore 51 such that the rotary shaft 20 can fit in the central bore 51 without rattling to improve the concentricity of the gear 32 to the rotary shaft 20. Such the configuration, however, results in a difficult fitting work and a lowered workability when the gear 32 is fitted with the rotary shaft 20 because no or little spacing is present between both.
In the transmission 12 of the present example, as shown in
In the outer circumferential surface of the rotary shaft 20 fitted in the central bore 51 of the gear 32, only the portion 64 near the regulative member 33 contacts the inner circumferential surface of the central bore of the gear 32 and, with no or little rattling, fits in the bore. The other portion 65 of the rotary shaft is formed to have a smaller diameter than that of the portion 64 and is configured not to contact the inner circumferential surface of the central bore. In this case, when the gear 32 is fitted with the rotary shaft 20, the small diameter portion 65 of the rotary shaft is inserted into the central bore 51 of the gear 32 at the beginning of the fitting. Therefore, the gear 32 can be smoothly fitted with the rotary shaft 20 with easy fitting work. It is found from experiments that the gear 32 can be easily fitted with the rotary shaft 20 in particular if the portion 64 of the outer circumferential surface of the rotary shaft 20 has a length of equal to or less than 5 millimeters in the axial direction, which contacts and fits the inner circumferential surface of the central bore of the gear 32.
On production of the regulative member 33, if its surface is subjected to a rust preventing process, the regulative member 33 can be prevented from rusting for a long time period. When the regulative member 33 is finished by cutting or lapping to form the regulative surface 44 of the regulative member 33, which press-contacts the one end 43 of the gear 32 as described above, the process of finishing removes the rust-prevented portion. If this portion is left as such, it may possibly rust. Preferably, the regulative member 33 is composed of a material that causes no rust, for example, stainless steel or aluminum. In particular, the stainless steel is excellent in strength and stiffness, and accordingly it is suitable for the material of the regulative member 33.
After the regulative member 33 is finished to form the regulative surface 44, the regulative member 33 may be fixedly press-fitted around the rotary shaft 20. In this case, even if the processing accuracy of the central bore 45 in the regulative member 33 can be elevated, its slight variation may possibly cause the regulative surface 44 of the regulative member 33 secured on the rotary shaft 20 to have a deteriorated squareness relative to the axis X. Preferably, on production of the transmission 12, after the regulative member 33 is secured on the rotary shaft 20 and before the transmissive member consisting of the gear 32 is attached to the regulative member 33, the regulative member 33 is finished. The finished surface is employed as the regulative surface 44 that is press-contacted with the one end 43 of the gear 32. In such the production of the transmission 12, the squareness of the regulative surface 44 to the axis X of the rotary shaft 20 can be improved even though the regulative member 33 is secured on the rotary shaft 20 with the screw as is in the art. This is because the regulative surface is finished and formed after the regulative member 33 is secured on the rotary shaft 20. Preferably, the regulative member 33 is secured on the rotary shaft 20 by press-fitting also in this case.
The portion 64 of the rotary shaft 20, which fits in the central bore 51 of the gear 32 without rattling, may also be finished to improve the surface accuracy thereof and improve the squareness of the gear 32 to the axis X. Preferably, after the regulative member 33 is secured on the rotary shaft 20 and before the gear 32 is attached to the regulative member 33, a portion of the outer circumferential surface of the rotary shaft 20 is finished also in this case. The finished surface is employed as a regulative surface 64 that contacts and fits the inner circumferential surface of the central bore in the gear 32 with no or little rattling. If the rotary shaft 20 is finished before the gear 32 is attached to the regulative member 33, the finished portion of the rotary shaft suffers damage from the regulative member 33 and lowers its surface accuracy possibly when the regulative member 33 is fitted with the rotary shaft 20. To the contrary, as described above, if the rotary shaft 20 is finished after the regulative member 33 is secured on the rotary shaft 20, such the malfunction can be prevented from arising.
If the regulative member 33 and the rotary shaft 20 are finished at the same time after the regulative member 33 is secured on the rotary shaft 20, the accuracy of the finished surfaces of both can be further improved.
In the processes of finishing, for example, the regulative member 33 is secured on the rotary shaft 20, the rotary shaft 20 is then secured with a tool. Thereafter, the regulative member 33 is finished to form the regulative surface 44 so as to square the axis X of the rotary shaft 20, and similarly the rotary shaft is finished.
In the configuration of the transmission 12 described above, secured to the rotary shaft 20 is the rotator consisting of the photosensitive drum 3 that is rotatable together with the rotary shaft 20, and the rotation of the transmissive member consisting of the gear 32 is transmitted to the rotator. Other rotators, shown in
The present invention is widely applicable to an image formation apparatus consisting of, other than the printer, a copier, a facsimile, a printing machine, or a complex machine thereof, and an image formation apparatus that forms a monochromic image, as well as transmissions in other machines and devices.
According to the present invention, the squareness of the transmissive member to the axis of the rotary shaft can be improved with a simple configuration.
The present document incorporates by reference the entire contents of Japanese priority documents, 2002-268922 filed in Japan on Sep. 13, 2002.
Although the invention has been described with respect to a specific embodiment for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art which fairly fall within the basic teaching herein set forth.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2002-268922 | Sep 2002 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 2473417 | Essl | Jun 1949 | A |
| 3985432 | Hou et al. | Oct 1976 | A |
| 5210574 | Kita | May 1993 | A |
| 6661986 | Kitayama | Dec 2003 | B1 |
| 6907205 | Himes et al. | Jun 2005 | B1 |
| Number | Date | Country |
|---|---|---|
| 7-239596 | Sep 1995 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20040126137 A1 | Jul 2004 | US |
