Patent Grant
7530439
This application claims priority to Japanese Patent Application No. 2004-077048 filed in the Japanese Patent Office on Mar. 17, 2004, the entire contents of which is hereby incorporated herein by reference.
1. Field of the Invention
The present invention relates to a drive device including a reverse preventing mechanism that prevents a roller shaft from being rotated in a reverse direction. The present invention further relates to a sheet conveying device using the drive device, and an image forming apparatus such as a copying machine, a facsimile machine, a laser beam printer, or other similar image forming apparatus, including the sheet conveying device.
2. Discussion of the Background
In an image forming apparatus such as a copying machine, a facsimile machine, a laser beam printer, or other similar image forming apparatus, it is necessary to prevent sheet conveying rollers from being reversed for various reasons. For example, to correct a skew feed of a sheet, a leading edge of the sheet is abut against a nip portion of a pair of registration rollers, and the sheet is conveyed for some distance by sheet conveying rollers disposed upstream of the registration rollers in a sheet conveying direction to form a loop of the sheet. At this time, if a reverse preventing mechanism for preventing the sheet conveying rollers from being reversed is not provided, the sheet conveying rollers are rotated in a reverse direction (i.e., in the direction opposite to the sheet conveying direction) due to a tension of the sheet. As a result, the loop of the sheet disappears, resulting in an inferior sheet skew correction. At worst, the leading edge of the sheet goes back from the nip portion of the registration rollers toward the sheet conveying rollers, so that a mis-feeding of the sheet occurs. Generally, a sheet separation roller is disposed upstream of the sheet conveying rollers in the sheet conveying direction, which rotates in a reverse direction to separate the uppermost sheet from the sheets fed out from a sheet feeding cassette. The above-described inferior sheet skew correction and mis-feeding of sheets are typically caused when a force is exerted in a sheet returning-back direction.
To obviate the above-described problems, a reverse preventing mechanism for preventing sheet conveying rollers from being reversed is provided in an apparatus that performs a sheet conveying operation.
In this configuration of the roller clutch 100, when the roller shaft 135 is rotated in a direction indicated by arrow A in
In the above-described sheet conveying roller mechanism provided with the roller clutch 100, the following problems typically arise. Generally, to convey sheets, the sheet conveying rollers 103 convey sheets by use of a frictional force produced by contacting the driven rollers 137 with the sheet conveying rollers 103 with a predetermined pressure as described above. Accordingly, a load is generated in the roller shaft 135 in its radial direction. Thereby, the roller shaft 135 is pressed against the needle pins 120, and the needle pins 120 are pressed against the outer ring 160 facing the clearance 140. The rotation and halt of the roller shaft 135 are repeated in this condition.
Although a rust preventing oil is applied to the needle pins 120, it is difficult to use a lubricating oil because a slip occurs at the time of halt (locking) of the roller clutch 100. The needle pins 120 are generally formed from a hard material of iron and steel and are subjected to quench hardening in view of the needle pins 120 abrading over time. In the above-described use conditions of the roller clutch 100, the roller shaft 135 wears over time, and abrasion powders accumulate in the roller clutch 100. The diameter of the roller shaft 135 decreases, and/or abrasion powders enter portions between the roller shaft 135 and the needle pins 120. As a result, the roller shaft 135 becomes unable to be locked, an abnormal noise is produced, and a useful life of the roller shaft 135 decreases. The roller shaft 135 may be subjected to quench hardening to extend its useful lifetime. However, because the roller shaft 135 needs to be formed from a special stainless material free from rusting, subjecting the roller shaft 135 to quench hardening increases the cost of the roller shaft 135. Further, as the length of the roller shaft 135 is generally greater than a width of a sheet, the cost of the roller shaft 135 increases that much more.
In addition to the above-described problems, in a high-speed apparatus in which a rotational speed of the roller shaft 135 is high, heat produced by friction between the needle pins 120 and the roller shaft 135 and heat produced by friction between the needle pins 120 and the outer ring 160 facing the clearances 140 increase. As a result, seizing up of metallic members typically occurs, and an abnormal noise tends to be produced.
In an image forming apparatus, the sheet conveying rollers 103 and an image forming device are generally disposed between the pair of side plates 131 and 132. A drive system such as gears, motors, and clutches is disposed at the outside of one of the side plates 131 and 132. Such a drive system may be disposed on each side of the side plates 131 and 132 instead of one side thereof. However, because wires and gear trains used for a motor and reduction gears need a predetermined space for their layouts, if such a drive system is disposed on each side of the side plates 131 and 132, the width of the apparatus increases. Therefore, the layout of a drive system concentrates on one side of the apparatus.
In a recent space-saving printer or multi-function apparatus, the space for the layout of units is restricted, and therefore some units need to be disposed on a side opposite from a drive source relative to a sheet conveying area. For example, a waste toner tank may be applied to this case. The waste toner tank is preferably disposed at the outside of one of the side plates 131 and 132 for easy maintenance. On the side where a drive system is provided, a motor, a structure for supporting the motor, and shafts for transmitting a drive force of the motor to each unit are disposed. Further, a waste toner conveying path for conveying waste toner from an image forming device, which is disposed between the side plates 131 and 132, to the waste toner tank needs to protrude through one of the side plates 131 and 132. Therefore, it is difficult to dispose the drive system and the waste toner tank on the same side of one of the side plates 131 and 132.
To drive a unit such as a waste toner tank disposed on a side opposite from a first drive source such as a motor, a second drive source needs to be provided on a side opposite from the first drive source. In this case, it costs extra money for a motor, a driver, attaching parts, and electric wires. Further, measures against waves and noises produced from electric wires and motors need to be taken on the both sides of the side plates 131 and 132.
Moreover, to enhance maintenance of a waste toner tank in an image forming apparatus, it is desirable that the waste toner tank is disposed at the outside of a side plate located on a side opposite from a drive system. This location of the waste toner tank is convenient for a user who replaces the full waste toner tank. Generally, the maintenance of a drive system is conduced by a customer engineer for safety. Further, a user replaces a photoreceptor/cleaning unit (PCU) and an intermediate transfer belt unit, for example, by opening a cover disposed on a side opposite from the drive system. It is preferable that the number of covers to be opened for maintenance is reduced to a minimum. Therefore, the same cover to be opened for maintenance is preferably shared among the waste toner tank, the PCU, and the intermediate transfer belt unit.
In view of the above-noted recognized drawbacks in the background art, it is desirable to provide a drive device, a sheet conveying device using the drive device, and an image forming apparatus including the sheet conveying device that can use a reverse preventing mechanism preventing at least one sheet conveying roller from being reversed and having a high durability without increasing costs.
Further, it is desirable to provide a drive device, a sheet conveying device using the drive device, and an image forming apparatus including the sheet conveying device in which a waste toner tank can be driven without providing a drive source on the installation side of the waste toner tank and without requiring extra costs.
The present invention can provide a novel drive device including a first shaft, a second shaft disposed at a position deviated from a shaft line of the first shaft, a drive source configured to drive the first shaft to rotate, and a drive force transmitting unit connecting the first shaft to the second shaft via the drive force transmitting unit to transmit a drive force of the drive source from the first shaft to the second shaft. The drive force transmitting unit includes a reverse preventing mechanism configured to prevent the first shaft from being rotated in a reverse direction.
The reverse preventing mechanism may include a one-way clutch, and the drive force transmitting unit may further include a reduction mechanism configured to reduce a rotational speed of the one-way clutch to be lower than a rotational speed of the first shaft.
The present invention can further provide a novel sheet conveying device including at least one sheet conveying roller configured to convey a sheet, a first shaft on which the at least one sheet conveying roller is attached, a second shaft disposed at a position deviated from a shaft line of the first shaft, a drive source configured to drive the first shaft to rotate, and a drive force transmitting unit connecting the first shaft to the second shaft via the drive force transmitting unit to transmit a drive force of the drive source from the first shaft to the second shaft. The drive force transmitting unit includes a reverse preventing mechanism configured to prevent the first shaft from being rotated in a reverse direction.
The reverse preventing mechanism may include a one-way clutch, and the drive force transmitting unit may further include a reduction mechanism configured to reduce a rotational speed of the one-way clutch to be lower than a rotational speed of the first shaft.
The present invention can further provide a novel image forming apparatus including the above-described novel sheet conveying device and a novel image forming device configured to form an image on the sheet conveyed by the sheet conveying device.
A more complete appreciation of the present invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
Preferred embodiments of the present invention are described with reference to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the views.
As illustrated in
A roller shaft 35 is disposed to cross a center opening portion of the main body frame 2. A plurality of sheet conveying rollers 3 are attached on the roller shaft 35. A drive force transmitting unit (described below) including a one-way clutch for transmitting a drive force to the auger 5 is disposed on the left end side of the roller shaft 35 in
As illustrated in
After a registration sensor 20 (illustrated in
The front cover 22 is closed at the time of feeding sheets. The registration drive roller 17, the sheet conveying rollers 3, and the sheet feeding roller 13 are started to rotate in alignment with a timing of forming a latent image on the photoconductive drum 4a. The sheet feeding roller 13 stops rotating after feeding a trailing edge portion of a sheet. The sheet conveying rollers 3 keep rotating until a loop of the sheet is formed. The registration drive roller 17 stops at a predetermined timing when the registration sensor 20 detects the leading edge of the sheet to perform a sheet skew correction. Thus, when a sheet is fed out and conveyed from the sheet feeding tray 12, the sheet conveying rollers 3 keep rotating except when a loop of the sheet is formed for a sheet skew correction. The sheet having passed through the nip portion between the registration drive roller 17 and the registration driven roller 18 is conveyed toward an image transfer section along a sheet guide plate (not shown). Subsequently, images of different colors formed on an intermediate transfer belt 23a of the intermediate transfer belt unit 23 are sequentially transferred to the sheet conveyed by the registration drive roller 17 and the registration driven roller 18 while being superimposed on one another.
With reference to
The image forming apparatus has a configuration that allows images to be formed on dual sides (the first and second sides) of a sheet. When a dual-side image-forming mode is selected, the sheet passed through the fixing device 27 is directed to a reversing mechanism. The reversing mechanism includes a pair of reversing rollers 30, a separation pick 36, and a sheet conveying path 37. When forming images on dual sides of a sheet, the separation pick 36 moves to the position illustrated by dotted lines in
The above-described reversing mechanism, the transfer roller 26, the registration driven roller 18, and the manual feeding roller 21 are provided to the front cover 22. A sheet conveying path for conveying a sheet fed out from the sheet feeding tray 12 is formed by closing the front cover 22. Further, toner bottles 38 containing respective color toners are provided below the sheet discharging tray 29. The toner bottles 38 can be replaced by opening the sheet discharging tray 29. That is, the sheet discharging tray 29 also acts as an upper cover of the image forming apparatus.
As illustrated in
As illustrated in
As illustrated in
As described above, the one-way clutch (roller clutch) 8c is inserted into the double gears 8b of the idler unit 8 with pressure. In order not to reverse the sheet conveying rollers 3 when the sheet conveying rollers 3 form a loop of a sheet, when the roller shaft 35 is about to rotate in the direction opposite from the drive direction, the one-way clutch is locked with respect to the shaft 8d of the idler unit 8 so as not to rotate the roller shaft 35 and the sheet conveying rollers 3. Thus, the one-way clutch 8c acts as a reverse preventing mechanism configured to prevent the roller shaft 35 from being rotated in a reverse direction. By this arrangement, because a radial load exerted on the shaft 8d of the idler unit 8 is minimized, the shaft 8d may be formed from a material such as stainless, and steel such as nickel-plated mild steel (SUM), which need not be subjected to quench hardening.
The combination of the helical gears 6 and 8b1 constructs a reduction mechanism configured to reduce a rotational speed of the one-way clutch 8c to be lower than a rotational speed of the roller shaft 35. With the reduction mechanism, a frictional force between the shaft 8d and the one-way clutch 8c decreases, so that the abrasion of the shaft 8d can be lessened.
Even if the shaft 8d is subjected to a surface hardening processing, the surface hardening processing for the shaft 8d can be performed at a low cost, as the axial length of the shaft 8d is only slightly longer than that of the double gears 8b. As the idler unit 8 is unitized as described above, in the event of failure of the one-way clutch 8c, for example, the idler unit 8 can be repaired just by replacing the one-way clutch 8c, thereby allowing easy maintenance.
When a sheet is fed by the manual feeding roller 21 without being conveyed by the sheet conveying rollers 3, the drive force of the sheet feeding motor 10 is transmitted to the auger 5 of the waste toner tank 1 by turning on the electromagnetic clutch 11 at a predetermined timing.
In the above-described embodiments, the drive force transmitting direction of the roller shaft 35 is set to be substantially orthogonal to the drive force transmitting direction of the shaft of the auger 5. Therefore, a twist angle of each of the helical gears 6 and 8b1 is set to about 45 degrees. However, the twist angle of each of the helical gears 6 and 8b1 may be changed according to a relative angle between the respective drive force transmitting directions of the roller shaft 35 and the shaft of the auger 5, that is, according to a positional relationship between the roller shaft 35 and the shaft of the auger 5.
According to the embodiments of the present invention, the one-way clutch 8c and the roller shaft 35 of the sheet conveying rollers 3 are not in a coaxial relationship. By this arrangement, the roller shaft 35 is not abraded at the attachment portion of the one-way clutch 8c, and the durability of the roller shaft 35 can thereby be enhanced. Therefore, the roller shaft 35 need not be formed from a material having a high hardness, and can be formed from a low-cost material.
In the above-described embodiments, when a rotational force of the roller shaft 35 is transmitted from the helical gear 6 attached on the end portion of the roller shaft 35 to the helical gear 8b1 of the idler unit 8, the rotational speed of the one-way clutch 8c is reduced to be lower than the rotational speed of the roller shaft 35. Accordingly, a frictional force exerted on the shaft 8d can be decreased. Consequently, the abrasion of the shaft 8d at the attachment portion of the one-way clutch 8c can be minimized, and abrasion powders are not significantly produced. Thus, the durability of the one-way clutch 8c can be enhanced.
A generally-used shaft is formed from steel such as nickel-plated mild steel (SUM). However, a shaft used for a one-way clutch is often formed from an expensive stainless material or a special stainless material subjected to quench hardening to increase the hardness of the shaft. If a plated shaft is used for a one-way clutch, a plating layer is removed from the shaft due to contact with the one-way clutch, causing a lock failure. However, if the rotational speed of and the radial load exerted on a shaft used for a one-way clutch is low, the shaft can be formed from steel such as nickel-plated mild steel (SUM) as similarly in the generally-used shaft.
Further, in the above-described embodiments, because the auger 5 obtains a drive force by the rotations of the roller shaft 35, a drive source for driving the auger 5 need not be disposed independently. Therefore, the cost of the image forming apparatus can be decreased. As described above, the roller shaft 35 of the sheet conveying rollers 3 is connected to the shaft of the auger 5 via the idler unit 8, and they are in a substantially orthogonal positional relationship. In this arrangement, the drive source for driving the roller shaft 35, namely the sheet feeding motor 10, is provided on the side opposite from the side where the idler unit 8 is provided in a direction of the shaft line of the roller shaft 35. Thus, a drive mechanism, for example the drive system 25 for driving the image forming device and the sheet feeding motor 10 for driving the sheet feeding roller 13 and the roller shaft 35 of the sheet conveying rollers 3, can be concentrated on the same side surface side of the main body frame 2 in the image forming apparatus, achieving a space-saving configuration of the image forming apparatus.
Moreover, according to the embodiments of the present invention, the one-way clutch 8c is provided in the idler unit 8 to act as a reverse preventing mechanism configured to prevent the roller shaft 35 and the sheet conveying rollers 3 from being rotated in a reverse direction. Thus, the roller shaft 35 is not abraded by the reverse preventing mechanism (i.e., the one-way clutch 8c), and therefore the durability of a sheet conveying mechanism can be enhanced. The idler unit 8 acts as a drive force transmitting unit connecting the roller shaft 35 (first shaft) to the shaft (second shaft) of the auger 5 via the idler unit 8 to transmit the drive force of the sheet feeding motor 10 from the roller shaft 35 to the shaft of the auger 5.
The present invention has been described with respect to the exemplary embodiments illustrated in the figures. However, the present invention is not limited to these embodiments and may be practiced otherwise.
In the above-described embodiments, the drive force of the sheet feeding motor 10 is transmitted from the roller shaft 35 (first shaft) to the shaft (second shaft) of the auger 5 that moves waste toner, via the idler unit 8. In another embodiment, the drive force of the sheet feeding motor 10 may be transmitted from the roller shaft 35 to a shaft of the transfer roller 26, the fixing roller 27a, the sheet discharging rollers 28, or any other roller used in the image forming apparatus. Further, the reverse preventing mechanism of the present embodiment can be applied to any roller shaft that is desirable to be prevented from being reversed.
Moreover, aspects of the present invention can be applied to any type of image forming apparatus, such as, a copying machine, printer, facsimile machine, a multi-functional image forming apparatus, etc.
Numerous additional modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-077048 | Mar 2004 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 1400687 | Kurtz | Dec 1921 | A |
| RE17489 | Anderson | Nov 1929 | E |
| 2003963 | Banker | Jun 1935 | A |
| 3803934 | Yokel | Apr 1974 | A |
| 4944375 | Ohta et al. | Jul 1990 | A |
| 20050230900 | Yamada et al. | Oct 2005 | A1 |
| Number | Date | Country |
|---|---|---|
| 07-146606 | Jun 1995 | JP |
| 07-168491 | Jul 1995 | JP |
| 11-139626 | May 1999 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20050230900 A1 | Oct 2005 | US |
