Patent Application
20050023748
This invention relates to a device for controlling the movement position of a moving member, such as a shifter which is mounted in an image forming apparatus and which switches output positions of recording paper. In particular, this invention relates to an improvement for setting a moving member to a predetermined reference position (e.g. an origin at one end of its range of movement) with a simple arrangement.
To start with, brief description is made of a conventional image forming (copying) operation by an electrophotographic image forming apparatus as represented by a digital photocopier. First, an original which is stacked on an automatic document feed tray (hereinafter referred to as original tray) is fed into a scanner unit. The scanner unit reads image data of the original, based on which an electrostatic image is formed on a photosensitive drum. On this photo-sensitive drum, the image data are visualized by toner which attaches to the electrostatic image. Next, recording paper which is transported through a paper transport path passes between the photosensitive drum and a transfer roller, so that the toner image on the photosensitive drum is transferred to the surface of the recording paper. Later, while the recording paper passes by a fuser roller, the fuser roller applies heat and pressure so as to fuse the toner image on the recording paper. After the image is formed in this manner, the recording paper is ejected through an output path to an output tray.
Among this type of image forming apparatus, some are equipped with a shifter mechanism. For example, to make a plurality of copies from a single set of originals, the shifter mechanism serves to eject each set of recording paper at different positions on the output tray. Namely, output positions for the respective sets of recording paper are offset from each other in a horizontal direction which is orthogonal to a paper output direction. Owing to the offset output, the recording paper can be picked up from the output tray and readily sorted into the respective sets. As such, Japanese Patent Application Laid-open No. H4-204668 (JP 4-204668 A) discloses an output tray which is movable in horizontal directions which are orthogonal to a paper output direction. In a copying operation for more than one kind of originals, an OC cover (an original cover) is opened and closed in order to change originals. The output tray is arranged to move in conjunction with such opening and closure of the OC cover.
With respect to a shifter mechanism, the shifter mechanism is required to recognize the position of a shifter (a moving member), to switch positions of the shifter in conjunction with a paper output operation, and to set proper output positions of recording paper on the output tray. For this purpose, the shifter position at power-on or force-reset has to be recognized correctly. In the past, a shifter position sensor (a sensor, microswitch or the like based on an optical means) is incorporated to recognize the shifter position. Such a shifter position sensor detects the shifter position at power-on or force-reset, and if the shifter is out of a predetermined reference position, the shifter is moved to the reference position.
Nevertheless, the above conventional arrangement needs a special sensor for detecting the shifter position, and hence a greater number of components. Eventually, the position control device has a complicated structure and demands a higher production cost.
This invention is made in view of the above concerns. An object of the invention is to provide a position control device for a moving member which can set a moving member (a shifter) to an exact position without a special sensor.
As a position control device for a moving member, this invention presupposes a position control device for a slidably supported moving member which controls a slide position of the moving member by powering the moving member. This position control device has a first power transmission element provided at the moving member, a second power transmission element for transmitting power from a drive source to the first power transmission element, and a stopper provided at the moving member. The second power transmission element is integrally equipped with a transmission part and a projection. This transmission part is directly connected with the first power transmission element and transmits power from the drive source to the first power transmission element. Besides, when the moving member slides closer to the second power transmission element and reaches a predetermined slide position, the projection locks the stopper and limits a position of the stopper, and thus fixes the moving member at the slide position. To put it another way, the projection fixes the moving member at its slide position by locking the stopper and limiting a position of the stopper, only when the moving member slides in a direction of bringing the stopper closer to the second power transmission element and eventually reaches a predetermined position.
According to this arrangement, when the second power transmission element transmits power from a drive source to the first power transmission element, the moving member slides in an acting direction of the power. By way of example, if adopted in a shifter mechanism of an image forming apparatus, the position control device is capable of switching output positions of recording paper in conjunction with the sliding movement. In the case where the slide position of the moving member needs to be detected (in the case where the image forming apparatus is turned on or forcibly reset), power is transmitted from the second power transmission element to the first power transmission element, thereby allowing the moving member to slide in a direction of bringing the stopper closer to the second power transmission element. Later, when the moving member slides to a predetermined slide position, the projection locks the stopper and limits a position of the stopper, thereby fixing the moving member at the slide position. Namely, it is possible to control the position of the moving member by taking the slide position of the thus fixed moving member as a reference position of the moving member. Therefore, the position of the moving member can be fixed at a predetermined reference position without a special sensor for detecting the position of the moving member.
In this arrangement, the first power transmission element may be a rack which is provided along sliding directions of the moving member. The transmission part of the second power transmission element may be a sector gear which rotates in mesh with the rack and thus powers the moving member via the rack. In addition, the stopper extends orthogonally to the sliding directions of the moving member, and the projection locates away from a rotation shaft of the second power transmission element. When the moving member slides to a predetermined slide position, the stopper may move into a space between the projection and the transmission part of the second power transmission element, and the projection may establish contact with the stopper and may limit a position of the stopper.
While the position of the moving member is fixed, the projection and the transmission part can be disposed in the following arrangement. When the projection locks the stopper and limits a position of the stopper, the stopper may be interposed between the projection and the transmission part which maybe opposed to each other in the sliding directions of the moving member. In other words, the projection and the transmission part locate on either side of the stopper (on either side in the sliding directions of the moving member), respectively. Owing to this arrangement, the position of the moving member can be fixed at the reference position without fail.
Moreover, in order to fix the moving member at the reference position, the following specific arrangement is available. In a state where the moving member slides to a predetermined slide position at which the stopper moves in between the projection and at which the transmission part (the sector gear) and the projection establishes contact with the stopper, the second power transmission element may be driven further so as to press the projection against the stopper.
The contact force of the projection against the stopper acts as a fixing force for fixing the moving member at the reference position. This arrangement can increase the contact force by pressing the projection against the stopper, thereby stabilizing the stop position of the moving member.
Further, the slide position of the moving member where the projection locks the stopper and limits a position of the stopper may be set as an origin for the moving member. This origin may be taken as a reference for controlling the slide position of the moving member.
According to this arrangement, an origin can be set as a position where the projection locks the stopper in order to fix the moving member. On the other hand, a steady position for the moving member can be set as a slide position to which the moving member moves from the origin by a predetermined amount. In particular, suppose that the moving member is fixed at the origin, with use of an electric motor as the drive source. In this case, the moving member which has reached the origin does not slide any further even though the electric motor transmits power to the second power transmission element. Eventually, the electric motor steps out. Namely, such step-out of the electric motor indicates that the moving member has reached the origin and has been fixed at the position.
Regarding the power transmission system to the moving member, the following action may occur at the moment when the projection locks the stopper. Namely, when the projection locks the stopper and limits a position of the stopper, the transmission part of the second power transmission element maybe disengaged from the first power transmission element. To put it differently, once the projection locks the stopper, there is no power transmission from the second power transmission element to the first power transmission element, and the slide position of the moving member is limited merely by the locking of the stopper with the projection. Now, suppose that the projection has locked the stopper and power is still transmitted from the second power transmission element to the first power transmission element. Under such circumstances, if the sliding amount of the moving member due to the power transmission is not equal to the sliding amount of the moving member due to the locking of the stopper with the projection, these power transmission points will receive such a heavy load that any of the components may possibly break. In contrast, according to this solution, power transmission from the second power transmission element to the first power transmission element stops once the projection locks the stopper. As a result, this arrangement is free from such a load and can prevent breakage of the position control device.
Regarding a specific application of a position control device according to any of the above arrangements, the device can be mounted in an image forming apparatus and can control a slide position of a shifter (a moving member) which switches output positions of recording paper.
When the image forming apparatus is turned on or forcibly reset, it needs to detect a slide position of the shifter. In this situation, if the position control device according to any of the above arrangements is applied to a shifter mechanism of an image forming apparatus, the shifter can be quickly fixed at the slide position. Hence, it is unnecessary to detect the position of the shifter with a special sensor, thereby simplifying the structure of the image forming apparatus.
Regarding a position control device for a moving member according to this invention, when the moving member moves to a predetermined position (a reference position for position control), movement of the moving member is limited by a part of the power transmission elements which have transmitted power to the moving member. To control the position of the moving member, the thus fixed position is taken as a reference position for the moving member. Hence, it is unnecessary to detect the position of the moving member with a special sensor. Consequently, while attempting to reduce the number of components and to simplify the device structure, this position control device is capable of setting the moving member at a predetermined reference position.
FIGS. 4(a)-(f) are illustrations for describing an operation of setting a shifter position concerning the embodiment of this invention, wherein the operation is effected in conjunction with rotation of a transmission gear.
FIGS. 5(a)-(c) are illustrations for describing reference positions of a shifter, concerning the embodiment of this invention.
An embodiment of the invention is hereinafter described with reference to the drawings. In the following embodiment, a position control device of the invention is applied to a multifunction machine which combines the functions of a copier, a printer and a scanner. Overall structure of a multifunction machine
<Scanner Unit 2>
The scanner unit 2 reads the image of an original and creates image data. An original is either placed on a platen 41 made of transparent glass or the like, or fed one sheet after another by the automatic document feeder unit 4. The scanner unit 2 is equipped with an exposure light source 21, a plurality of reflection mirrors 22, 23, 24, an imaging lens 25, and a charge coupled device (CCD) 26.
The exposure light source 21 irradiates an original which is either placed on the platen 41 of the automatic document feeder unit 4 or transported through the automatic document feeder unit 4. The light reflected from the original follows an optical path indicated by the dash-dot line AA of
As an image reading operation from an original, when an original is placed on the platen 41 (“fixed sheet type” image reading), the exposure light source 21 and the reflection mirrors 22, 23, 24 horizontally scan the original along the platen 41 in order to read an entire image of the original. On the other hand, when an original is transported through the automatic document feeder unit 4 (“sheet transfer type” image reading), the exposure light source 21 and the reflection mirrors 22, 23, 24 are fixed at the locations shown in
After reflected by the reflection mirrors 22, 23, 24 and passing through the imaging lens 25, the light is guided to the CCD 26, where the reflected light is converted to electric signals (original image data).
<Printer Unit 3>
The printer unit 3 is composed of an image formation system 31 and a paper transport system 32.
The image formation system 31 has a laser scanning unit 31a and a photosensitive drum 31b which is a drum-shaped image carrier. Based on the original image data converted by the CCD 26, the laser scanning unit 31a irradiates the surface of the photosensitive drum 31b with a laser beam. The photosensitive drum 31b rotates in the direction indicated by an arrow in
Aside from the laser scanning unit 31a, the photosensitive drum 31b is externally surrounded by a developer (a development mechanism) 31c, a transfer unit 31d (a transfer mechanism), a cleaner (a cleaning mechanism) 31e, a static eliminator (not shown), and a charger unit 31f, all of which are circumferentially arranged in this order. The developer 31c develops an electrostatic image formed on the surface of the photosensitive drum 31b to a visible image by toner (a printing material). The transfer unit 31d transfers a toner image formed on the surface of the photosensitive drum 31b to image formation paper (a recording medium). After toner transfer, the cleaner 31e removes any toner remaining on the surface of the photosensitive drum 31b. The static eliminator removes residual charges on the surface of the photosensitive drum 31b. The charger unit 31f charges the surface of the photosensitive drum 31b to a given electric potential prior to formation of an electrostatic image.
In this image formation system 31, an image is formed on image formation paper in the following cycle. To start with, the charger unit 31f charges the surface of the photosensitive drum 31b to a given electric potential. Then, based on image data of an original, the laser scanning unit 31a irradiates the surface of the photosensitive drum 31b with a laser beam. Next, the developer 31c develops a visible image by toner on the surface of the photosensitive drum 31b. Later, the transfer unit 31d transfers the toner image on image formation paper. Lastly, the cleaner 31e removes any toner remaining on the surface of the photosensitive drum 31b, and the static eliminator removes residual charges from the surface of the photosensitive drum 31b. These steps make up a cycle of image forming operation (print operation) on image formation paper. Repetition of this cycle enables successive image formation on more than one sheet of image formation paper.
Referring next to the paper transport system 32, this system transports image formation paper one sheet after another from a paper cassette 33 (a paper holder) and have an image formed thereon by the image formation system 31. After image formation, the paper transport system 32 ejects the image formation paper to an output tray 35 (a paper output part).
This paper transport system 32 is composed of a main transport path 36 and a reverse transport path 37. One end of the main transport path 36 is opposed to the output side of the paper cassette 33, and the other end is opposed to the output tray 35. The reverse transport path 37 is joined with the main transport path 36, one end at the upstream side (the lower section in
A pickup roller 36a having a semicircular cross-section locates at the upstream end of the main transport path 36 (a section opposed to the output side of the paper cassette 33). With rotation of this pickup roller 36a, image formation paper stored in the paper cassette 33 can be intermittently fed to the main transport path 36 one sheet after another.
Along the main transport path 36, resist rollers 36d, 36d are provided upstream of the transfer unit 31d. These resist rollers 36d, 36d deliver image formation paper in alignment with a toner image on the surface of the photosensitive drum 31b. Further along the main transport path 36, a fuser 39 is provided downstream of the transfer unit 31d. The fuser 39 has a pair of fuser rollers 39a, 39b and thermally fuses a toner image which is transferred to the image formation paper. At the downstream end of the main transport path 36, there is an output mechanism 5 for ejecting image formation paper to the output tray 35. The output mechanism 5 will be mentioned later.
A switcher claw 38 is provided at an upstream end of the reverse transport path 37 where it joins the main transport path 36. The switcher claw 38 is freely swingable around a horizontal shaft between a first position (shown in solid line in
<Automatic Document Feeder Unit 4>
The automatic document feeder unit 4 is a so-called automatic double-sided original transport device. The automatic document feeder unit 4 is available for the sheet transfer type image reading, and is composed of an original tray 43 (an original stacking part), a middle tray 44, an original ejection tray 45 (an original ejection part), and an original transport system 46 for transporting an original to and from the trays 43, 44, 45.
The original transport system 46 contains a main transport path 47 and an auxiliary transport path 48. The main transport path 47 sends an original from the original tray 43, via the original reading part 42, to the middle tray 44 or to the original ejection tray 45. The auxiliary transport path 48 feeds an original from the middle tray 44 to the main transport path 47.
An original pickup roller 47a and an alignment roller 47b are provided at the upstream end of the main transport path 47 (a section opposed to the output side of the original tray 43). An alignment plate 47c lies under the alignment roller 47b. Along with the rotation of the original pickup roller 47a, one of the originals stacked on the original tray 43 is drawn between the alignment roller 47b and the alignment plate 47c and fed into the main transport path 47. PS rollers (Paper Stop rollers) 47e, 47e are disposed down stream of a joint where the main transport path 47 meets the auxiliary transport path 48 (Point B in
The original reading part 42 is equipped with a platen glass 42a and an original hold-down plate 42b. While an original fed from the PS rollers 47e, 47e passes between the platen glass 42a and the original hold-down plate 42b, light from the exposure light source 21 irradiates the original through the platen glass 42a. This is when the scanner unit 2 acquires image data of the original. The original hold-down plate 42b is biased at the back face (the top face) by a coil spring (not shown). As a consequence, the original hold-down plate 42b maintains contact with the platen glass 42a under a certain pressure, and thereby prevents the original from floating over the platen glass 42a while the original passes the original reading part 42.
Located downstream of the platen glass 42a are transport rollers 47f and original ejection rollers 47g. After passing over the platen glass 42a, the original travels through the transport rollers 47f and the original ejection rollers 47g to be ejected to the middle tray 44 or the original ejection tray 45.
A middle-tray swing plate 44a situates between the original ejection rollers 47g and the middle tray 44. The middle-tray swing plate 44a is capable of swinging around its edge beside the middle tray 44, between Position 1 (shown in solid line in
<Basic Operations of the Multifunction Machine>
The above-described multifunction machine 1 performs following operations. As a printer, the multifunction machine 1 receives data for printing (image data or text data) which are transmitted from a host device such as a PC. The received data for printing (print data) are temporarily stored in a buffer or memory (not shown). Thus, the print data are stored in the buffer and then successively read out from the buffer. Based on the read-out print data, the printer unit 3 forms an image on image formation paper according to the image formation operation as mentioned above.
As a scanner, the multifunction machine 1 reads the image of an original by the scanner unit 2 and temporarily stores its scan image data in the buffer. Thus, the scan image data are stored in the buffer and successively transmitted to the host device, so that the image can be shown on a display or the like of the host device.
As a copier, the multifunction machine 1 obtains image data of an original by the above scanner function. Based on the original image data, it forms an image on image formation paper by the image formation operation of the printer unit 3.
<Output Mechanism 5>
The output mechanism 5 locates at the downstream end of the main transport path 36 and, after image formation, ejects image formation paper to the output tray 35. The output mechanism 5 has a shifter mechanism for ejecting the image formation paper to different positions on the output tray 35. For example, to make a plurality of copies from a single set of originals, output positions for the respective sets of recording paper are offset from each other in a horizontal direction which is orthogonal to a paper output direction. Owing to the offset output, recording paper can be picked up and readily sorted into the respective sets. This output mechanism 5 is detailed below.
As illustrated in these drawings, the shifter 6 is a substantially cuboidal member and has a pair of ejection rollers (not shown). These ejection rollers hold image formation paper therebetween and eject the paper to the output tray 35. In a machine body (not shown), the shifter 6 is supported in such a manner as to reciprocate (slide) freely in its lengthwise directions (horizontal directions which are orthogonal to the paper output direction, as indicated by Arrows A1, B1 in
The position control device 7 is disposed close to and upstream of the shifter 6 in the paper output direction. The position control device 7 is composed of a rack 71 (a first power transmission element) which is integrally attached to a side surface 61 of the shifter 6, an electric motor 72 (a drive source), a transmission gear 73 (a second power transmission element) which transmits power from the electric motor 72 to the rack 71, and a stopper 74 which is integrated with the rack 71. Each of these components is detailed below.
The rack 71 is screwed or otherwise attached to the shifter 6 at a side surface (a vertical surface) which faces upstream in the paper output direction. On this side surface, the rack 71 locates in either half in the lengthwise direction (on the left in
Integrated with this rack 71, the stopper 74 is provided to the shifter 6 at a side surface (a vertical surface) which faces upstream in the paper output direction. On this side surface, the stopper 74 locates in either half in the lengthwise direction (on the left in
The electric motor 72 is screwed or otherwise attached to a device frame 7A. The electric motor 72 has a drive shaft 72a which stands upright and a pulse motor which can optionally regulate the amount of rotation for the drive shaft 72a. The drive shaft 72a of the electric motor 72 is equipped with a pinion gear 72b.
The transmission gear 73 is integrally made of a round gear 75, a sector gear 76, and a retention pin 77 (a projection). In
The round gear 75 is a spur gear which has teeth around the entire periphery. The round gear 75 can freely rotate around a vertical shaft (in directions indicated by Arrows C1, D1 in
The sector gear 76 is integrated at the bottom surface of the round gear 75. The sector gear 76 rotates around the rotation shaft of the round gear 75, and its teeth are formed in the range of about 180 degrees. Namely, the transmission gear 73 has a dual structure of the round gear 75 and the sector gear 76. The outside diameter of the sector gear 76 is slightly smaller than that of the round gear 75. When the rotation driving force of the electric motor 72 is transmitted via the pinion gear 72b to the round gear 75, the transmission gear 73 rotates as a whole, accompanied by rotation of the sector gear 76. The teeth of the sector gear 76 are in mesh with the rack 71 only in the range of certain rotation angles. With this meshing engagement, the rotation force of the sector gear 76 is transmitted to the shifter 6 via the rack 71 (e.g. the states in FIGS. 4(a), (b)).
The retention pin 77 is a columnar element which projects vertically downward from the bottom surface of the round gear 75. On this bottom surface, the retention pin 77 locates in a different area from the sector gear 76. Namely, when the round gear 75 rotates by the rotation driving force of the electric motor 72, the retention pin 77 revolves around the rotation shaft of the round gear 75. The location of the retention pin 77 is described in detail, with reference to FIGS. 4(b)-(f). While the sector gear 76 transmits power to the rack 71 and causes sliding movement of the shifter 6, the rotation shaft of the transmission gear 73 will move so close to the stopper 74 that the retention pin 77 comes into contact with the tilted surface 74a of the stopper 74. With further rotation of the transmission gear 73, the retention pin 77 advances along an external surface 74b of the stopper 74. Eventually, the stopper 74 moves in between the sector gear 76 and the retention pin 77.
<Action of the Position Control Device 7>
The action of the position control device 7 of the above structure is now described. When the multifunction machine 1 is turned on or forcibly reset, the slide position of the shifter 6 needs to be recognized. The position control device 7 sets (initializes) the position of the shifter 6 by the following actions.
To start with, the electric motor 72 is driven counterclockwise in
FIGS. 4(a)-(f) represent positional relationships of the sector gear 76 and the retention pin 77 relative to the rack 71. As shown in these drawings, as the shifter 6 slides toward the predetermined origin, the stopper 74 moves in between the retention pin 77 and the sector gear 76 which are revolving. When the transmission gear 73 rotates from the state of
Still referring to FIGS. 4(a)-(f), while the transmission gear 73 is rotating, the sector gear 76 is disengaged from the rack 71 at the moment when the retention pin 77 starts to lock the stopper 74. Hence, the meshing engagement between the sector gear 76 and the rack 71 is released at the transition from the state of
Now, suppose that the retention pin 77 has locked the stopper 74 and power is still transmitted from the sector gear 76 to the rack 71. Under such circumstances, if the sliding amount of the shifter 6 due to the power transmission is not equal to the sliding amount of the shifter 6 due to the locking of the stopper 74 with the retention pin 77, these power transmission points will receive such a heavy load that any of the components may possibly break. In contrast, according to this embodiment, power transmission from the sector gear 76 to the rack 71 stops once the retention pin 77 locks the stopper 74. As a result, this embodiment is free from such a load and can prevent breakage of the device (the gears, etc.).
The position of the shifter 6 is fixed at the origin when the electric motor 72 steps out in the above manner, and this condition is set as its normal operation position. In an image formation operation which does not call for the shifter function, the shifter 6 is fixed at this normal operation position throughout the above-described image formation operation. In this situation, the stopper 74 is interposed between the retention pin 77 and the sector gear 76 which are opposed to each other in the sliding directions of the shifter 6. In other words, the retention pin 77 is next to one side of the stopper 74 and the sector gear 76 is next to the other side (i.e. the stopper 74 has obstacles on both sides in the sliding directions of the shifter 6). Even when the power to the electric motor 72 is shut down, the position of the shifter 6 can be fixed without fail.
On the other hand, if a user desires an image formation operation with the shifter function, the shifter 6 is allowed to move between the fixed position as defined above, and a slide position to which the shifter 6 slides with the drive of the electric motor 72 (a position displaced by a predetermined amount in the direction of A1 in
In
Preferably, the position of the shifter 6 is set to the origin when the multifunction machine 1 is shipped from the factory. This is intended to avoid troubles during shipment of the multifunction machine 1, because, for example, the shifter 6 may slide and break due to shock or other causes. To give a specific example, the shifter 6 may be set at the position shown in
In the above embodiment according to the invention, the position control device for a moving member is applied to a multifunctional image forming apparatus (a multifunction machine) 1 which combines the functions of a copier, a printer and a scanner. Additionally, this invention is applicable, without limitation, to an image forming apparatus with any one of these functions or an image forming apparatus of any other type.
Also in the above embodiment according to the invention, the position control device for a moving member is applied to a shifter mechanism of an image forming apparatus (a multifunction machine). Additionally, this invention is applicable, without limitation, to other slidable moving members in order to control its position.
The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The above embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-281947 | Jul 2003 | JP | national |
This nonprovisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2003-281947 filed in Japan on Jul. 29, 2003, the entire contents of which are hereby incorporated by reference.
