JPH0210930B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a guide device having a guide member for slidably guiding a movable original table in an exposure device used in an electrophotographic apparatus.

A guide device constituting a conventional exposure apparatus used a straight rail. The document image is scanned by sliding the document table guided in the scanning direction on this rail material, and the image forming body that receives the scanning light forms an image of the scanning light on the photoreceptor surface and performs exposure. Ta. For example, special public service in Showa 49-
As in the conventional example cited in No. 12184, a movable original table is guided by two straight rails, and when the copy button is pressed, this movable document table clamps the rails from above and below. The device is configured to automatically slide back and forth from side to side in the current state, and scan the original image. FIG. 1a shows a straight rail member A that guides these conventional movable document placement tables. Above the rail material A, a center of gravity G of a movable document placement table (hereinafter referred to as document placement table) B is located. In this case, the document images that successively reach the position where the exposure device receives the slit light from the document, that is, the exposure position F, are connected to the actual optical path length L ₁ between the photoconductor surface of the photoconductor drum C and the document placement surface D. It is supported and guided so that the optical path length L, that is, the conjugate length, set by the image object, for example, the imaging lens E, coincides with the optical path length L. However, as a result of the miniaturization of electrophotographic copying machines, the center of gravity G of the document mounting table B at the scanning start and end positions has shifted from the position above the rail material A, as shown in FIGS. 1b and 1c. Therefore, the document table B on the side facing the exposure position F tends to rise. When the document placement surface D moves away from the position set by the set optical path length L of this lens, the document image is formed on the photoreceptor drum at the position where the slit light from the exposure position F is imaged, that is, at the image formation position. This causes the inconvenience that the image is not correctly formed on the photoreceptor surface of C. If this lifting amount is within the range covered by the depth of focus of the lens E, it will not have a major effect on the image formed on the photoreceptor surface, but if it exceeds this range it will have an adverse effect. This effect is a problem even when a normal lens is used, but it becomes a particularly serious problem when a light-focusing optical element array with a shallow depth of focus is used. In addition, in order to simplify and lower the cost of electrophotographic copying machines, instead of the usual guide device that uses two rails with interlocking parts, a rail with only the upper surface that slides in contact with the document placement table is used. In some cases, a guide device using a material on one side is adopted, but in this case, the amount of lifting from the upper surface of the document table at the exposure position becomes larger, and there is no need to eliminate the above-mentioned negative effects. growing.

The applicant has proposed a means for eliminating the above-mentioned drawbacks in Japanese Patent Application Laid-Open No.
- Disclosed in No. 153967. That is, at the exposure position,
In order to maintain the actual optical path length from the document placement surface of the document placement table to the photoconductor surface constant, the guide member that supports the document placement table has an upward surface at the end portion of the guide member that supports the document placement table. It is formed low. As a result, even if the center of gravity of the document mounting table deviates from the edge of the guide member, and the side facing the guide member tilts significantly due to the deflection of the document mounting table itself, causing the part facing the exposure position to rise beyond the allowable range, Since the upward facing surface of the end is formed lower than the upward facing surface at the exposure position by the amount of elevation, the document mounting table always comes into contact with the upward facing surface at the exposure position, and the actual optical path length deviation is Does not occur. However, in this guide device, the document mounting table comes into contact with the upper surface of the guide member at the exposure position while moving relatively, and the optical path length tends to shift due to wear of this upper surface. It was hot.

This invention supports the document platform so that the actual optical path length from the document placement surface that successively reaches the exposure position to the photoreceptor surface is maintained constant when the document platform moves back and forth in the scanning direction; The present invention also aims to provide a guide device with enhanced wear resistance. The present invention includes a guide member having an upward surface that slides into contact with a movable document placement table, and a guide rail that restricts the inclination of the movable document placement table in the scanning direction. The guide member is formed such that the upward surface at its end is lower than the upward surface at the exposure position by the amount of lifting that would occur if the center of gravity of the document mounting table protruded from the guide member. , and the upward surface at this exposure position is formed by a part of the rotating surface of the rotating body.

According to this invention, the document mounting table that moves on the guide member makes rolling contact with the rotating surface of the rotating body,
It is supported by upward surfaces arranged on both sides of the rotating body and in sliding contact with each other. Therefore, the wear resistance of the upper surface at the exposure position where wear is most likely to occur is improved, so that deviations in the actual optical path length are less likely to occur even after long-term use. Moreover, since the entire guide device is configured to be short, the actual optical path length can always be maintained constant even if the center of gravity of the document mounting table moves away from the guide device, making it possible to downsize the entire exposure device.

The present invention will be described below with reference to the accompanying drawings. Second
The figure shows a guide device 3 for a document table 2 in an exposure apparatus 1 as an embodiment of the present invention. The exposure device 1 is installed approximately in the center of the electrophotographic copying machine, and is rotated at a predetermined speed by a motor (not shown), and is positioned at an image forming position H on a photoconductor drum 4 having a photoconductor layer on its circumferential surface. Then, slit light from the document J is sequentially irradiated through an image forming body 13 consisting of an array of light-converging optical elements to perform exposure (see FIG. 3). In order to sequentially slit scan the entire surface of the original J, the original placing table 2 on which the original J is placed is reciprocated by a guide device 3 attached to a substrate 5.

This guide device 3 supports the document placement table 2 at both ends. On one side, precision rail 6 (product name:
Akyuride) is used, and a transparent plate 7 is used on the other side.
A guide member 8 is used which supports the image sensor so as to be movable toward and away from the image sensor and to be movable in the scanning direction. This precision rail 6 is a straight guide rail 601 fixed to the board 5.
This guide rail 601 has a large number of steel balls 6.
The sliding body 6 is slidably moved from 02 through a steel ball row.
03 is fitted. An elongated glass holding member 10 is connected to this sliding body 603 via a hinge 9. This glass holding member 10 is
It is configured to be moved in the scanning direction by the endless chain 12 via the connecting arm 11 hanging down from the sliding body 603. That is, the connecting arm 11 is fitted with a pin 121 extending horizontally from the endless chain 12 and has an elongated hole 111 bored in the vertical direction, and moves under the pressure of the pin 121. . The precision rail 6 is configured so that when the sliding body 603 moves along the guide rail 601, the steel ball array moves in the same direction by half the amount of movement. Such a precision rail 6 can control the inclination of the document mounting table 2 to a range that does not cause a problem as a deviation in the optical path length by the action of its meshing portion. Note that when the scanning direction position of the center of gravity C of the document platform 2 deviates from the steel ball array and the upper surface 801 of the guide member 8, the document platform 2 receives a holding moment caused by the engagement portion of the precision rail at the same time as a reversing moment. is applied inversely, but an inclination within a small range where the two are balanced is allowed. For this reason, at the start and end of scanning, the center of gravity G of the document mounting table 2 was removed from the steel ball array, and the document mounting table 2 sometimes tilted. That is, the precision rail 6 allows the original table 2 to tilt by an amount corresponding to the slight play that the steel balls 602 and the sliding body 603 have with respect to the guide rail 601 and the deflection of the original table 2 and the like.

The other guide member 8 is fixed to the substrate 5, and has an upward surface 801 for guiding the original platen 2 on its upper side. Like the guide rail 601, this guide member 8 also has a length that is approximately equal to the entire length of the document placement table, and the upper surface 8 of this guide member
As shown in FIG. 3, No. 01 forms a slightly downwardly sloped surface to the left and right with the exposure position F as the center. That is, in this guide member 8, the upward surface 801 at the exposure position F is formed by the circumferential surface a of the roller 802 as a rotating body, and the upward surface 801 is formed by a part of the circumferential surface a on this roller. Two rail members 80 each having an upward surface 801 that is continuous and slopes toward the end.
3,804. The upper surface 801 of the end portion of the guide member is formed to be lower than the upper surface 801 of the exposure position by Δh. The document placement table 2 on the upward surface has a transparent plate 7, and the actual optical path length between the document placement surface D on the transparent plate and the photoreceptor surface 401.
L ₁ is arranged so as to match the optical path length set by the light-focusing optical element array 13 as an image forming body, that is, the conjugate length L.

Note that, as shown in FIG. 4, the transparent plate 7 comes into contact with the roller 802 as a rotating body used here between the 0 point and the 01 point on the circumferential surface a as the rotating surface. This means that when the transparent plate 7 is in a position offset to both ends, it will come into contact with point 0 or 01, and when the center of gravity G of the transparent plate is close to the exposure position F, it will come into contact with point P, respectively. An error l occurs in the height position of the 0 or 01 point with respect to the point. The transparent plate 7 that causes such an error l is the actual optical path length.
This is not preferable in terms of keeping L ₁ constant. In order to suppress this influence within an allowable range, the roller 802 used here has a length of optical path due to wear on its circumferential surface a.
It is desirable to use a material with an outer diameter as small as possible within the range that does not cause an error in _L1 .

Although the roller 802 is used as the rotating body shown in FIG. 3, a spherical body 805 as shown in FIG. 5 may be used instead. This sphere 805
is attached to the substrate 5 by a ball holder 806, and is loosely fitted into a ball holder hole 807 formed in the ball holder to support the transparent plate 7 by rolling contact. The rotating surface b of this sphere 805 and the transparent plate 7 come into point contact. In this case, it is easy to downsize the rotating body itself.

The transparent plate 7 is moved from the right end toward the left end by an endless chain 12 on the guide device 3 via the connecting arm 11. In this case, the transparent plate 7 gradually loosens its inclination, and when the center of gravity G of the transparent plate reaches near the exposure position F, it maintains a substantially horizontal document placement surface D. When the document placement surface D is further moved to the left, the document placement surface D is tilted downward to the left. During this operation, the original images that successively reach the exposure position F are received by the light-converging optical element array 13 as an image forming body, so that the images are transferred to the photoreceptor drum 4.
is formed as an electrostatic latent image on the photoreceptor surface 401.

In the exposure apparatus 1 as described above, the image forming body 13
The shape of the exposure apparatus 1 is determined based on this. That is, the document mounting table 2 extends by an equal amount to the left and right with the image forming body 13 at the center, but if the image forming body is placed directly above the photoreceptor drum for compactness, the guide device 3
are configured to have the same minimum length on the left and right sides of the image forming body 13, that is, to have approximately the same length as the entire length of the document table. This allows the guide device 3 to have the most compact shape. The document mounting table 2 supported by such a guide device has its center of gravity G removed from the guide device at the scanning start and end positions. At this time, the side of the document table 2 placed on the guide member 8 is tilted more than the side of the precision rail 6 due to its own deflection, causing the portion facing the exposure position to rise beyond the permissible range. However, both ends of the guide member 8 are arranged in advance at the upper surface 801 of the exposure position.
The inclined upward surface 801 is formed to be lowered by a predetermined amount Δh, that is, by the amount of floating that would occur if the center of gravity of the document mounting table protrudes from the guide member. Therefore, even if the center of gravity G of the document table 2 at both ends of the guide member 8 is removed from the guide member 8, the center of gravity of the document table 2 will already be lowered by Δh and will be tilted by that amount, causing the above-mentioned reversal moment and hold. Balance with the moment has been achieved.
For this reason, any further lifting of the edge of the document table at the exposure position is suppressed, and since it comes into contact with the upper surface 801, no image deviation occurs. Furthermore, the roller 802 that regulates the actual optical path length L ₁ is in rolling contact with the document table 2, and the rate at which the upward surface 801 on the roller is deformed due to wear is much greater than that due to wear due to sliding contact. has been reduced.

By using an electrophotographic copying machine incorporating this invention, clear copies can always be obtained. In particular, when the image forming body consists of the light-focusing optical element array 13, the depth of focus is shallow, so the actual optical path length is
The effect of adjusting L ₁ is large.

The above-mentioned guide device 3 has a precision rail 6 on one side and a guide member 8 on the other side, and sets the actual optical path length L ₁ between the document placement surface D at the exposure position F and the photoreceptor 401 to the set optical path length of the image forming body 13. That is, it is configured to always match the conjugate length L, and can be changed within this range. For example, as shown in FIG. 6, the guide member 8 used in the embodiment in FIG. 2 is also provided near the precision rail side. This makes it more stable,
A tilted posture can be obtained as the transparent plate 7 moves back and forth.

In the embodiment shown in FIG. 7, the upward surface 801 at both ends of the guide member 8 at the exposure position F is
1 is formed to be lower by a predetermined amount Δh, and a roller 802 that can be finely adjusted vertically is provided at this exposure position F. By adjusting the support piece 808 in the vertical direction, the roller 802 can easily perform a correction operation to arrange the document placement surface D at the position of the set optical path length L. In this case, if the light-focusing optical element array 171 is connected to the support piece 808 so that it can move up and down integrally, the attachment work can be easily performed. The copying machine 15 shown in FIG. 8 has a light focusing optical element array 13 as an image forming body.
This is a so-called EF copying machine 15 in which a photoreceptor surface 401 that receives an image is provided on the surface of photosensitive paper P. The exposure device 1 of this copying machine includes a light-converging optical element 13 that focuses scanning light from a document placement surface D irradiated by a document illumination device 16 onto an imaging position H, and a light-converging optical element 13 that reflects this scanning light and The mirror 17 projects a normal image onto the photoreceptor surface 401, and a glass plate 171 allows the reflected light from the mirror to pass therethrough and forms an image on the lower surface of the scanning light from the document placement surface. The copying machine 15 shown in FIG. 8 has its exposure position F shifted to the right side in the figure. The guide member 8 of this copying machine has a roller 802 disposed at the exposure position F, and a flat rail member 80 on the left side of the roller 802.
9, the right side is a rail material 81 that slopes toward the end.
0, an upward surface 801 is formed respectively. The transparent plate 7 indicated by a solid line in the figure is in its original position before the scanning of the document placement surface D begins, and in this state, the center of gravity G of the transparent plate 7, that is, the document placement table 2, is on the flat upward surface 801. positioned. While moving with the center of gravity G positioned on the flat upward surface 801, the document mounting table 2 does not lift the surface facing the exposure position F upward. Furthermore,
When the document placing table 2 moves and the center of gravity G passes over the roller 802, and the center of gravity G is located on the inclined upward surface 801, the document placing table 2 moves parallel to the inclined upward surface 801. The center of gravity is gradually lowered from the surface of the exposure position F, and is moved to the position shown by the one-dot chain line to perform one scan. Thereafter, it returns to its original position (the position indicated by the solid line) and completes one copying process. At the position indicated by the one-dot chain line, the document mounting table 2 is placed with its center of gravity G lowered by Δh than the surface of the exposure position F, and is off the upward surface 801. For this reason, the left end side of the document platform 2 facing the guide member tends to rise upward, but since the center of gravity of the document platform 2 facing the guide member itself has already been lowered by Δh, exposure The document placement surface D at the position F is supported at a set position according to the set optical path length L. In this way, in this invention, it is only necessary to form the inclined upward surface 801 on the side where the center of gravity G of the document mounting table 2 deviates from the guide member 8 due to the deviation of the exposure position F, and the structure is simple and the effect is large. It is what it is. In this copying machine, the left side of the upward surface 801 may not be flat, but may be configured to form a continuous slope with the slope on the right side.

In each of the above-mentioned embodiments, a light-converging optical element array is used as the image forming body 13, but the invention is not limited to this, and conventionally used image forming bodies 13,
For example, an imaging lens (not shown) may be used. In this case, the set optical path length L is the distance from the document placement surface D to the imaging surface of the lens, that is, the imaging position H. This set optical path length L is a value that is determined individually depending on the focal length of the image forming body 13 and the copying magnification, and when the copying machine is equipped with a variable magnification device (not shown), each setting for the same magnification and variable magnification If the optical path lengths L are different, each set optical path length L needs to be maintained constant during scanning.

Since a portion of the transparent plate 7 placed on the side member 8 always faces the exposure position F, the transparent plate 7 is never removed from the exposure position F.
For this reason, it is desirable that a hook-shaped jaw portion 811 be formed extending from the guide member 8 in the vicinity of the exposure position to maintain the transparent plate 7 in a slidable manner but not detachable. For example, as shown in FIG.
A jaw portion 811 may be formed at the upper end of the support base 812 on which the roller 802 is attached. By using such a guide member 8, for example, when moving the copying machine itself, it is possible to prevent inconveniences such as when an operator carelessly lifts the transparent plate 7 and causes it to fall, causing wave damage. can. Furthermore, as shown in FIG.
01, there is an advantage that the document J on the transparent plate can be set without being caught by the jaws 811.

As described above, the present invention can prevent the set optical path length L of the exposure device 1 from shifting due to the lifting of the document placement surface D that occurs when the center of gravity G of the document placement table 2 is removed from above the guide member. Moreover, since the upward surface 801 of the exposure position F that regulates the set optical path length L is formed by the roller 802 with little wear, there is an advantage that the set optical path length L can be maintained constant over a long period of time.

[Brief explanation of drawings]

Fig. 1 is a functional explanatory diagram of a conventional guide device, Fig. 2 is a schematic vertical sectional view of a copying machine equipped with a guide device as an embodiment of the present invention, and Fig. 3 is a diagram showing a copying machine equipped with the same guide device. A schematic side view, FIG. 4 is an enlarged explanatory view of essential parts of the guide device as described above, FIG. 5 is a side view of a rotating body as another embodiment used in the guide device as described above, and FIG. A schematic longitudinal sectional view of a copying machine with a guide device attached as an example,
FIG. 7 is an enlarged side view of essential parts of a guide device as another embodiment of the present invention, FIG. 8 is a schematic side sectional view of a copying machine equipped with a guide device as another embodiment of the present invention, and FIG. Figures 1 and 10 are sectional views of main parts showing different embodiments of the rail material used in the above guide device. DESCRIPTION OF SYMBOLS 1...Exposure device, 2...Document mounting table, 3...Guide device, 8...Guide member, 801...Upper surface, 802...Roller, 803, 804, 80
9,810...Rail material, a, b...Rotating surface, D
...Original placement surface, F...Exposure position.

Claims (1)

[Claims] 1. In an exposure device that sequentially receives scanning light from a document placement surface on a movable document placement table at an exposure position, scanning of the movable document placement table and a guide member having an upwardly facing surface that slides into contact with the movable document placement table is performed. The guide device includes a guide rail for regulating inclination in the direction and sequentially guides the document placement surface in the scanning direction, and the guide member is configured to prevent the document placement surface from being tilted when the center of gravity of the document placement table protrudes from the guide member. The upper surface at the end is formed lower than the upper surface at the exposure position by the amount of uplift, and the upper surface at this exposure position is formed by a part of the rotating surface of the rotating body. A guide device for a movable original table in an exposure apparatus.