JP2016153843A - Scanning optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scanning optical device capable of suppressing the lowering of scanning accuracy of light beams that is caused by thermal deformation of a housing, without depending on enlargement in size.SOLUTION: A scanning optical device comprises a housing 50 including: a reflection fixing part 53Y having a surface to which one surface of a reflection member 43Y is fixed; a holding part 52 with which the reflection fixing part protrudes integrally; a heat shielding wall part 54 that is integrally formed with the holding part 52 and shields heat transmitted to the reflection fixing part; and a groove-shaped relaxation part 55 formed in a portion between the reflection fixing part 53Y of the holding part 52 and the heat shielding wall part 54.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a scanning optical apparatus that irradiates an image carrier while scanning a light beam in an electrophotographic system.

  An electrophotographic image forming apparatus includes a scanning optical device that generates an electrostatic latent image on the surface of a photoconductor by irradiating a scanned light beam while rotating a charged photoconductor (image carrier). Yes. The scanning optical device includes a light source that emits a light beam, a reflection member that reflects light emitted from the light source, and a deflector that deflects and scans the light beam reflected by the reflection member toward the photosensitive member. The deflector rotates an optical element (polygon mirror) having a plurality of reflecting surfaces by a driving unit such as a motor. Then, by irradiating the rotating polygon mirror with a light beam, the light beam is scanned to irradiate the photosensitive member.

  When the angle of the reflecting surface of the reflecting member with respect to the light beam is deviated, the deviation of the irradiation position of the light beam incident on the polygon mirror increases, and a larger deviation occurs when the photosensitive member is irradiated. Therefore, in the scanning optical device, the accuracy of the position (for example, angle) with respect to the light beam required for the reflecting surface of the reflecting member is increased.

  The heat generated by the rotation of the polygon mirror is heated by the heat generated by the driving unit, and hot air is generated. In many cases, the scanning optical device is formed by integral molding of resin. When hot air reaches the fixed part of the reflecting member, the fixing part is deformed by heat, and the position of the reflecting surface of the reflecting member with respect to the light beam is changed. Shift. In order to suppress such a shift, Patent Document 1 includes a windshield member that covers the standing portion that is erected adjacent to the portion where the deflector is disposed and that can be expanded and contracted with respect to the standing portion. Have been disclosed. By applying the hot air from the motor of the deflector to this windshield member, it is possible to prevent heat from being transmitted to the standing portion. Thereby, the shift | offset | difference with respect to the light beam of the reflective surface of the reflection member accompanying the deformation | transformation of a wall is suppressed.

  Further, in Patent Document 2, a thermal expansion of the housing due to the heat of the deflector is provided by disposing a separate mounting base material having a low thermal expansion coefficient on the optical housing and attaching a plurality of light sources to the mounting base material. Is prevented from being transmitted to the light source, and a decrease in the scanning accuracy of the light beam is suppressed.

Japanese Patent No. 5127615 Japanese Patent No. 4231011

  However, the inventions described in Patent Document 1 and Patent Document 2 require a windshield member and a mounting base material, which makes the configuration complicated and makes it difficult to reduce the cost.

  In Patent Document 1, it is necessary to fix the windshield member in consideration of expansion and contraction of the windshield member. In Patent Document 2, a position for attaching the mounting base material must be secured, and scanning is performed in any configuration. The optical device becomes large.

  SUMMARY An advantage of some aspects of the invention is that it provides a scanning optical device that can suppress a decrease in scanning accuracy of a light beam due to thermal deformation of a housing without increasing the size.

  In order to achieve the above object, the present invention is a scanning optical device that scans a light beam that irradiates a surface to be irradiated, and includes a housing in which a reflecting member that reflects the light beam emitted from a light source is disposed. The housing includes a reflection fixing portion having a surface to which one surface of the reflection member is fixed, a holding portion from which the reflection fixing portion protrudes integrally, and the holding portion integrally formed with the reflection fixing portion. A heat shield wall portion that shields the transmitted heat, and a groove-shaped relaxation portion formed in a portion between the reflection fixing portion and the heat shield wall portion of the holding portion.

  According to this configuration, even if the heat shield wall portion is deformed due to thermal deformation, the strain is relieved by the groove-shaped relieving portion, so that it is difficult or not transmitted to the holding portion and the reflection fixing portion. Thereby, even if it is a case where at least one part (heat-shielding wall part) of a housing | casing is thermally deformed, the position shift of the reflection member which reflects a light beam can be suppressed effectively. In addition, since the groove-shaped relaxation portion is provided, the apparatus does not increase in size. That is, it is possible to suppress a decrease in scanning accuracy of the light beam due to thermal deformation of the housing without increasing the size.

  The said structure WHEREIN: The groove shape of the said relaxation part is extended in parallel with the reflective surface of the said reflection member fixed to the said reflection fixing | fixed part. By configuring in this way, the distortion in the direction that has the greatest influence on the scanning direction of the light beam among the changes in the angle of the reflecting surface of the reflecting member is suppressed, and the reduction in the scanning accuracy of the light beam is efficiently performed. It can be well suppressed.

  In the above configuration, the groove shape of the relaxation portion is such that the length of the reflection fixing portion in the direction along the surface to which the reflection member is fixed and the holding portion is equal to or longer than the length of the reflection fixing portion in the same direction. . According to this configuration, it is possible to minimize the configuration of the relaxing portion, suppress deformation of the reflection fixing portion, and suppress a decrease in scanning accuracy of the light beam.

  In the above configuration, one or a plurality of through holes are formed in at least one surface of the bottom or side of the relaxation portion. According to this configuration, since the relaxation portion is easily deformed, it is possible to effectively suppress the transmission of strain to other portions of the holding portion including the reflection fixing portion. As a result, deformation of the reflection fixing portion can be suppressed, and a decrease in scanning accuracy of the light beam can be suppressed.

  The said structure WHEREIN: The thickness of the at least one surface of the bottom part or side part of the said relaxation part contains the part currently formed thinner than the thickness of the other part of the said holding | maintenance part. According to this configuration, since the relaxation portion is easily deformed, it is possible to effectively suppress the transmission of strain to other portions of the holding portion including the reflection fixing portion. As a result, deformation of the reflection fixing portion can be suppressed, and a decrease in scanning accuracy of the light beam can be suppressed.

  In the above-described configuration, a plurality of the reflection members and a plurality of reflection fixing portions to which the plurality of reflection members are respectively fixed are provided, and the holding portion is fixed to the reflection fixing portion of the reflection member. A holding surface portion that comes into contact with a surface different from the surface to be formed, and the height of the reflection fixing portion in the protruding direction of the holding surface portion varies depending on the distance from the relaxation portion. With such a configuration, the holding portion can be uneven, and the strength of the holding portion itself can be raised. Thereby, a deformation | transformation of a reflection fixing | fixed part can be suppressed by this and the fall of the scanning precision of a light beam can be suppressed.

  The said structure WHEREIN: The height of the said protrusion direction of the said holding surface part becomes so low that it leaves | separates from the said relaxation part.

  The said structure WHEREIN: The height of the said protrusion direction of the bottom part of the said relaxation part is lower than a holding surface part.

  In the above-described configuration, the heat shield wall portion is a partition portion that partitions between the holding portion and a polarizer that is attached to the housing and deflects and scans the light beam.

  The said structure WHEREIN: The said heat insulation wall part is a part of wall body formed in the cylinder shape surrounding the circumference | surroundings of the said holding | maintenance part.

  According to the present invention, it is possible to provide a scanning optical device capable of suppressing a decrease in scanning accuracy of a light beam due to thermal deformation of a housing without increasing the size.

1 is a diagram illustrating an example of an image forming apparatus including a scanning optical device according to the present invention. 1 is a schematic layout diagram of a scanning optical device according to the present invention. It is the perspective view seen from the housing | casing of the scanning optical apparatus which concerns on this invention. FIG. 4 is an enlarged perspective view of a portion to which an element of the housing shown in FIG. 3 is attached. It is sectional drawing of the holding part of an example of the scanning optical apparatus which concerns on this invention. It is a bottom view of a holding part. It is a bottom view of the holding | maintenance part of the other example of a scanning optical apparatus. It is an expanded sectional view of the further another example of the scanning optical apparatus concerning this invention. It is a bottom view of the holding part of the scanning optical apparatus shown in FIG. It is an expanded sectional view of the further another example of the scanning optical apparatus concerning this invention. It is a bottom view of the holding | maintenance part of the scanning optical apparatus shown in FIG.

  The configuration of the present invention will be described with reference to the drawings.

  FIG. 1 is a view showing an example of an image forming apparatus provided with a scanning optical device according to the present invention. In the following description, there are cases where directions such as up / down / left / right or clockwise counterclockwise are described, but FIG. 1 is used as a reference unless otherwise specified.

  An image forming apparatus A shown in FIG. 1 is a tandem color digital copier, and includes an image reader unit 20 that reads an original image, a printer unit 10 that prints the read image on a transfer material such as a recording sheet, and a printer unit 10. On the other hand, a paper feeding unit 30 for supplying a transfer material (here, recording paper) and a scanning optical device 40 for forming an electrostatic latent image on the surface of the photosensitive drums 11Y, 11M, 11C, and 11K are provided. Yes. The image forming apparatus A includes a control unit Cont, and the printer unit 10, the image reader unit 20, the paper feeding unit 30, and the scanning optical device 40 are controlled by the control unit Cont.

  The image reader unit 20 reads a document placed on a document glass plate (not shown) by moving a scanner, and has a known configuration. The image reader unit 20 separates the original image into three colors of red (R), green (G), and blue (B), converts them into electrical signals using an image sensor such as a CCD (not shown),・ G / B image data is acquired. The image data for each color (R, G, B) acquired by the image reader unit 20 is subjected to various processes by the control unit Cont, and then yellow (Y), magenta (M), cyan (C), black ( K) is converted into image data of each reproduction color and stored in a recording unit (memory) provided in the control unit Cont. The image data of each reproduction color stored in the memory in the control unit Cont is subjected to positional deviation correction, and then read out for each scanning line to become a drive signal. This drive signal is a signal for driving the scanning optical device 40.

  The printer unit 10 forms an image on a recording medium such as a recording sheet by an electrophotographic method. The printer unit 10 includes photosensitive drums 11Y, 11M, 11C, and 11K corresponding to reproduction colors of yellow (Y), magenta (M), cyan (C), and black (K). The drum 11 ”).

  Around each of the photosensitive drums 11Y, 11M, 11C, and 11K, a charger 111, a developing device 112, a transfer roller 113, and a cleaning unit 114 are provided. In FIG. 1, for convenience, only the charger 111, the developing device 112, the transfer roller 113, and the cleaning unit 114 around the photosensitive drum 11Y are denoted by reference numerals, but the same applies to the periphery of each photosensitive drum. A configuration is provided.

  The charger 111 uniformly charges the surface of the photosensitive drum 11. Examples of the charger 111 include a non-contact type such as a corotron type and a scotron type, and a contact type using a charging roller or a charging brush, but are not limited thereto.

  The photosensitive drum 11 is an insulator in a dark place (dark place), and has a property that when irradiated with light (when exposed), the irradiated portion becomes a conductor. The photosensitive drum 11 utilizes this property, and an electrostatic latent image is formed by irradiating the surface of the rotating photosensitive drum 11 with a light beam scanned by the scanning optical device 40.

  The developing device 112 supplies toner having a charge to the photosensitive drum 11 on which the electrostatic latent image is formed, thereby adsorbing the toner to the surface of the photosensitive drum 11 to form a toner image. As a method of forming a toner image, a method of adsorbing toner having a charge opposite to that charged on the photosensitive drum 11 to a portion where the charge was not lost by exposure or a portion where the charge was lost is used. An example is a method of pushing in toner.

  The transfer roller 113 is a roller for transferring a toner image formed on the surface of the photosensitive drum 11 to a transfer target (here, an intermediate transfer belt 14 described later). The transfer roller 113 is disposed on the opposite side of the photosensitive drum 11 with the transfer target interposed therebetween, and sucks toner from the photosensitive drum 11 by applying a charge (transfer bias) opposite to that of the toner. As a result, the toner image formed on the photosensitive drum 11 is transferred to the transfer target.

  The cleaning unit 114 neutralizes the surface of the photosensitive drum 11 and further removes toner remaining on the photosensitive drum 11. The neutralization can be performed by using a neutralization lamp that is performed by irradiating the photosensitive drum 11 with light, but is not limited thereto. Examples of a method for removing the toner remaining on the photosensitive drum 11 include, but are not limited to, a method of adsorbing with a charging brush and a method of scraping with a blade formed of rubber or the like.

  The printer unit 10 includes toner hoppers 12Y, 12M, 12C, and 12K and toner bottles 13Y, 13M, 13C, and 13K for supplying toner to the photosensitive drums 11Y, 11M, 11C, and 11K.

  The toner hoppers 12Y, 12M, 12C, and 12K temporarily store yellow (Y), magenta (M), cyan (C), and black (K) toners. When the amount of toner (toner density) in the developing device 112 that develops each of the photosensitive drums 11Y, 11M, 11C, and 11K becomes low, the toner is supplied to the corresponding developing device 112 via a cylindrical joint (not shown). .

  The toner bottles 13Y, 13M, 13C, and 13K are disposed above the toner hoppers 12Y, 12M, 12C, and 12K. Each of the toner bottles 13Y, 13M, 13C, and 13K contains toner of yellow (Y), magenta (M), cyan (C), and black (K), and toner hoppers 12Y, 12M, 12C, and 12K. Toner is supplied. By replacing the toner bottles 13Y, 13M, 13C, and 13K, new toner can be supplied. Examples of the toner bottles 13Y, 13M, 13C, and 13K include those in which a spiral protrusion is formed on the inner peripheral surface of a cylindrical bottle. By rotating the toner bottles 13Y, 13M, 13C, and 13K, the toner in the toner bottles 13Y, 13M, 13C, and 13K falls from the discharge port and flows into the toner hoppers 12Y, 12M, 12C, and 12K.

  The printing unit 10 superimposes yellow (Y), magenta (M), cyan (C), and black (K) color toner images formed on the photosensitive drums 11Y, 11M, 11C, and 11K, and intermediate transfer belts. After transferring to 14 (primary transfer), it is transferred (secondary transfer) to a recording sheet as a transfer material. The toner transferred onto the recording paper is heated and pressurized to print a color image. The print unit 10 includes an intermediate transfer belt 14, a secondary transfer roller 15, a fixing unit 16, and a cleaning blade 17 in order to enable such a procedure.

  The intermediate transfer belt 14 is an endless belt, and is stretched between the driving roller 141, the driven roller 142, and the tension roller 143. As shown in FIG. 1, the tension roller 143 is disposed at a position higher than the driving roller 141 and the driven roller 142. The tension roller 143 is configured to be biased upward by an unillustrated biasing member (for example, a spring), and the tension roller 143 is biased upward, whereby tension is applied to the intermediate transfer belt 14. Is given. Note that the tension roller 143 may be omitted in a configuration in which at least one of the driving roller 141 or the driven roller 142 can be urged away.

  Below the intermediate transfer belt 14, photosensitive drums 11Y, 11M, 11C, and 11K are arranged at predetermined intervals in order from the left. The photoconductive drums 11Y, 11M, 11C, and 11K are arranged so that the rotation axis thereof is orthogonal to the moving direction of the intermediate transfer belt 14. Further, a transfer roller 113 is disposed so as to sandwich the intermediate transfer belt 14 with each of the photosensitive drums 11Y, 11M, 11C, and 11K.

  The intermediate transfer belt 14 is rotated counterclockwise by the driving roller 141. By transferring toner images from the photosensitive drums 11Y, 11M, 11C, and 11K in synchronization with the intermediate transfer belt 14, yellow (Y), magenta (M), cyan (C), black ( The toner images K) are accurately superimposed and transferred (primary transfer) to the intermediate transfer belt 14. As a result, a color toner image (referred to as a primary transfer image) is formed on the surface of the intermediate transfer belt 14.

  The secondary transfer roller 15 is in pressure contact with the drive roller 141 with the intermediate transfer belt 14 interposed therebetween. A secondary transfer bias is applied to the secondary transfer roller 15 to attract toner from the primary transfer image of the intermediate transfer belt 14.

  Next, the paper feeding unit 30 that supplies recording paper to the printer unit 10 will be described. The paper feed unit 30 includes a paper feed cassette 31, a paper feed roller 32, and a registration roller 33. The paper feed cassette 31 is a storage unit for storing recording paper. The paper feed cassette 31 is detachable and can be replenished with recording paper. In the image forming apparatus A, one sheet feeding cassette 31 is shown, but the present invention is not limited to this, and a plurality of sheet feeding cassettes may be provided. When a plurality of paper feeding cassettes are provided, for example, recording papers having different sizes and colors may be stored for each paper feeding cassette, or the arrangement directions of the recording papers may be different.

  The paper feed roller 32 pulls out the recording paper disposed at the top of the paper feed cassette 31 to the transport path (indicated by a broken line) and transports it to the registration roller 33. In the case where a plurality of paper feed cassettes 31 are provided, a paper feed roller 32 may be provided for each paper feed cassette 31.

  The registration roller 33 operates in synchronization with the rotation of the intermediate transfer belt 14 so that the primary transfer image of the intermediate transfer belt 14 is transferred (secondary transfer) to a predetermined position on the recording paper. The recording paper is sent to the nip portion between the driving roller 141 and the secondary transfer roller 15.

  When the recording paper passes through the nip portion between the driving roller 141 and the secondary transfer roller 15, the recording paper comes into contact with the intermediate transfer belt 14. At this time, by applying a secondary transfer bias to the secondary transfer roller 15, the toner image on the intermediate transfer belt 14 is transferred (secondary transfer) to the recording paper. The recording paper to which the toner image has been transferred is then conveyed to the fixing unit 16.

  The fixing unit 16 heats and presses the recording paper on which the toner image is transferred, thereby fixing the toner image to the recording paper. The fixing unit 16 heats and pressurizes the conveyed recording paper, and the toner image Is fixed on the recording paper.

  The recording paper on which the toner image is fixed is discharged to the outside of the apparatus. On the other hand, the residual toner remaining on the intermediate transfer belt 14 without being transferred is collected by the cleaning blade 17 and stored in a waste toner box. The cleaning blade 17 is a plate-like member such as rubber, and is pressed toward the driven roller 142 with the intermediate transfer belt 14 interposed therebetween.

  In the image forming apparatus A, the toner images of the respective photosensitive drums 11Y, 11M, 11C, and 11K are transferred onto the intermediate transfer belt 14 so as to obtain a color primary transfer image. In order to accurately superimpose the primary transfer images, as described above, the intermediate transfer belt 14 and the photosensitive drums 11Y, 11M, 11C, and 11K are accurately synchronized, and the photosensitive drums 11Y, 11M, The toner images formed on 11C and 11K, that is, electrostatic latent images, must be accurately and reliably synchronized. In the image forming apparatus A of the present invention, an electrostatic latent image is created on each of the photosensitive drums 11Y, 11M, 11C, and 11K using the scanning optical device 40.

  Next, the configuration of the scanning optical apparatus A will be described with reference to the drawings. FIG. 2 is a schematic layout diagram of the scanning optical apparatus according to the present invention.

  As shown in FIG. 2, the scanning optical device 40 includes light sources 41Y, 41M, 41C, and 41K, a collimator lens 42, reflecting members (mirrors) 43Y, 43M, 43C, and 43K, an adjustment mirror 43R, and a deflector 44. And an optical element 45, scanning reflection portions 46Y, 46M, 46C, and 46K, a detection mirror group 47, and a light receiving portion 48. In the scanning optical device 40, these members are attached to a housing 50 which is an integrally molded body of resin.

  The light sources 41Y, 41M, 41C, and 41K are light sources that emit light beams for exposing the photosensitive drums 11Y, 11M, 11C, and 11K. Here, a laser diode that emits laser light is used as the light beam. doing. The light sources 41Y, 41M, 41C, and 41K are fixed to the side wall 51 of the housing 50 while being mounted on the substrate Bd. A passage hole through which the light beam passes is formed in the side wall 51 of the housing 50. The light source 41Y, 41M, 41C, 41K receives a drive signal for each scanning line from the control unit Cont, and emits a pulsed light beam based on this drive signal.

  The collimator lens 42 is disposed on the light exit surface side of each of the light sources 41Y, 41M, 41C, and 41K, and optical that converts the light beams emitted from the light sources 41Y, 41M, 41C, and 41K from diffused light to parallel light. It is an element.

  The light beams emitted from the light sources 41Y, 41M, 41C, and 41K are reflected by the reflecting members 43Y, 43M, 43C, and 43K, and are applied to the adjustment mirror 43R. As shown in FIG. 2, when viewed from the bottom surface side, the optical paths of the light beams emitted from the light sources 41Y, 41M, 41C, and 41K overlap, but the diagram of the light sources 41Y, 41M, 41C, and 41K. Since the installation heights in the thickness direction in FIG. 2 are different, the optical paths of the respective light beams are actually different (not overlapping). The adjustment mirror 43R reflects the light beams reflected by the reflecting members 43Y, 43M, 43C, and 43K toward the deflector 44.

  The deflector 44 includes a polygon mirror 441 having a plurality of reflecting surfaces arranged side by side in the circumferential direction, and a deflection motor 442 (see FIG. 1) that rotates the polygon mirror 441. As shown in FIG. 2, the polygon mirror 441 employs a regular pentagonal prism shape having five reflecting surfaces on the outer peripheral surface, but is not limited thereto. The light beam reflected by the adjustment mirror 43R is incident at a constant angle with respect to the central axis of the polygon mirror 441. By rotating the polygon mirror 441, the incident angle and reflection angle of the light beam incident on the reflecting surface of the polygon mirror 441 change. That is, the deflector 44 scans the reflected light beam by reflecting the light beam from a certain direction on the reflecting surface on the side surface of the rotating polygon mirror 441.

  The rotation of the polygon mirror 441 of the deflector 44 and the pulsed light beams emitted from the light sources 41Y, 41M, 41C, and 41K are accurately synchronized with each other, and thereby the photosensitive drums 11Y, 11M, and 11C by the light beams are synchronized. , 11K exposure is performed with high accuracy. These synchronizations are performed by a drive signal from the control unit Cont.

  The optical element 45 is disposed in the housing 50 so that the light beam scanned by the polygon mirror 441 is transmitted. Then, the light beam transmitted through the optical element 45 is incident on the scanning reflectors 46Y, 46M, 46C, and 46K that reflect the light beam toward the photosensitive drums 11Y, 11M, 11C, and 11K, respectively. The light beam is incident on the scanning reflection portions 46Y, 46M, 46C, and 46K at points (spots), and the spot moves in the longitudinal direction of the scanning reflection portions 46Y, 46M, 46C, and 46K by scanning the light beam.

  The optical element 45 includes an optical element such as an fθ lens, and transmits light so that the moving speed of the spot of the light beam on the scanning reflectors 46Y, 46M, 46C, and 46K is constant in the linear direction. Adjust the beam.

  The light beams incident on the scanning reflection units 46Y, 46M, 46C, and 46K are further reflected by the reflecting member 46a (see FIG. 1) as necessary, and enter the photosensitive drums 11Y, 11M, 11C, and 11K. The scanning optical device 40 has a structure in which the light beam is reflected by a plurality of reflecting members, whereby the distance of the optical path from the light sources 41Y, 41M, 41C, and 41K to the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11K. Are adjusted to be equal or approximately equal.

  The scanning optical device 40 is arranged so that the scanning direction (main scanning direction) of the light beam incident on the photosensitive drums 11Y, 11M, 11C, and 11K is parallel to the rotation axis of the photosensitive drums 11Y, 11M, 11C, and 11K. Has been. Then, the scanning optical device 40 irradiates the photosensitive drums 11Y, 11M, 11C, and 11K with the scanned light beam and exposes each scanning line to form an electrostatic latent image. In the case of such a configuration, it is necessary to accurately grasp the scanning start position of the light beam (the electrostatic latent image writing position). In the scanning optical device 40, the scanning start position is detected using the detection mirror group 47 and the light receiving unit 48.

  The detection mirror group 47 includes a first mirror 471 and a second mirror 472 disposed at the scanning start position. The light beam irradiated to the scanning start position is reflected by the first mirror 471 and enters the second mirror 472. The light beam reflected by the second mirror 472 is applied to the detection opening 511 provided on the side wall 51.

  The light receiving part 48 is fixed to a fixing part 512 provided on the outer surface of the side wall 51 with a screw Sc. When a light beam is received, a light receiving sensor 481 that converts it into an electrical signal and a sensor substrate 482 on which the light receiving sensor 481 is mounted are provided. The light receiving unit 48 is fixedly attached to the outer surface of the casing 51, and is attached so that the light beam transmitted through the detection opening 511 can be received by the light receiving sensor 481. The light receiving sensor 481 detects a light beam incident on the first mirror 471 disposed at the scanning start position, and plays a role of detecting the scanning start position. The light receiving unit 48 transmits a light reception signal to the control unit Cont. This light reception signal is a detection signal of the scanning start position, and the light reception sensor 481 is a so-called SOS (Start of Scan) sensor.

  In the scanning optical system device 40, a pulsed light beam corresponding to one scanning line of the image signal is emitted from the light sources 41Y, 41M, 41C, and 41K based on the drive signal from the control unit Cont. The polygon mirror 441 scans the light beam to form electrostatic latent images on the photosensitive drums 11Y, 11M, 11C, and 11K.

  The controller Cont adjusts the exposure start timing corresponding to one scan line of the image data of each reproduction color based on the information of the scan start position from the light receiving sensor 481. That is, it is used to synchronize the pulse of the light beam of the light sources 41Y, 41M, 41C, and 41K and the rotation of the polygon mirror 441.

  Next, the housing of the scanning optical device, which is the main part of the present invention, will be described.

(First embodiment)
3 is a perspective view of the scanning optical apparatus according to the present invention as seen from the lower side, and FIG. 4 is an enlarged perspective view of a portion where the elements of the casing shown in FIG. 3 are attached. FIG. 6 is a cross-sectional view of a holding unit as an example of the scanning optical apparatus according to the present invention, and FIG. 6 is a bottom view of the holding unit. As shown in FIG. 3, the scanning optical device 40 includes a casing 50 formed by integral molding of resin. The housing 50 includes a side wall 51, a holding part 52, reflection fixing parts 53Y, 53M, 53C, 53K, 53R, a partition part 54, and a relaxing part 55.

  As shown in FIGS. 2 and 4, the housing 50 includes a first region 501 that is opened downward in which the collimator lens 42, the reflecting members 43 </ b> Y, 43 </ b> M, 43 </ b> C, and 43 </ b> K and the adjustment mirror 43 </ b> R are disposed, the deflector 44, The optical element 45, the scanning reflection portions 46Y, 46M, 46C, and 46K, and the second region 502 that is open upward are provided in which the detection mirror group 47 is disposed.

  The casing 50 is provided with a side wall 51 so as to surround the outer periphery, and the holding portion 52 is provided so as to constitute the bottom portion of the first region 501. And the partition part 54 is provided so that the 1st area | region 501 and the 2nd area | region 502 may be partitioned off. The side wall 51 and the partition part 54 are wall bodies and are formed integrally with the holding part 52. The side wall 51 and the partition part 54 constitute a part of a wall surface 56 provided so as to surround the holding part 52. The wall surface 56 is formed in a cylindrical shape, and the rigidity of the wall surface 56 is increased by being formed in a cylindrical shape. Thereby, the side wall 51 and the partition part 54 are hard to fall down. In addition, the partition part 54 is not limited to this structure, The side wall 51 and the wall surface 56 may be provided independently.

  As shown in FIGS. 2 and 3, the side wall 51 includes a detection opening 511 and a fixing portion 512. The detection opening 511 on the side wall is an opening through which the light beam reflected by the detection mirror group 47 passes, and the light beam that has passed through the opening enters the light receiving sensor 481 of the light receiving unit 48 fixed outside. The fixing portion 512 is provided to fix the sensor substrate 482 on which the light receiving sensor 481 is mounted.

  As shown in FIG. 4, the substrate Bd on which the light sources 41Y, 41M, 41C, and 41K are mounted and the sensor substrate 482 are attached to the outside of the housing 50 (the outer surface of the side wall 51). As described above, since the substrate Bd and the sensor substrate 482 are attached to the outside, the substrates can be connected to each other by the wiring Pc. In addition, the wiring from the control unit Cont can be easily attached, the manufacturing is easy, and the maintainability can be improved.

  In the deflector 44, since the polygon mirror 441 is rotated by the deflection motor 442, heat is generated from the deflection motor 442. Further, an air flow is also generated by the rotation of the polygon mirror 441 and is heated by the heat of the deflection motor 442 to generate hot air. When such hot air is blown to the holding portion 52, the reflection fixing portion 53, which is an integrally molded resin body, is deformed or the adhesive is altered, and the reflecting members 43Y, 43M, and 43C. 43K and the optical accuracy of the adjustment mirror 43R may be reduced. In the housing 50, the first area 501 and the second area 502 are partitioned by the partition portion 54, thereby suppressing the hot air from the deflector 44 from blowing to the reflecting members 43Y, 43M, 43C, 43K, and the adjustment mirror 43R. doing.

  Note that the partition portion 54 is provided with a window portion 541 for transmitting the light beam reflected by the adjustment mirror 43R. The window 541 is preferably configured to transmit a light beam and block hot air.

  As shown in FIG. 5, the holding portion 52 includes a flat portion 520 and step-like holding surface portions 521, 522, 523, and 524 formed on the lower surface (upper surface in the drawing) of the flat portion 520. Reflective fixing portions 53Y, 53M, 53C, and 53K project integrally from the holding surface portions 521, 522, 523, and 524, respectively. That is, the reflection fixing portions 53Y, 52M, 53C, and 53K are formed integrally with the holding portion 52.

  As shown in FIGS. 4 and 5, the reflecting members 43Y, 43M, 43C, and 43K contact one surface (reflecting surface) with one surface (required accuracy surface) of each of the reflection fixing portions 53Y, 53M, 53C, and 53K. Fixed in contact. Furthermore, the reflective members 43Y, 43M, 43C, and 43K are in contact with the holding surface portions 521, 522, 523, and 524, respectively. The reflecting members 43Y, 43M, 43C, and 43K make the reflecting surface and the surface adjacent to the reflecting surface contact the reflecting fixing portions 53Y, 53M, 53C, and 53K and the holding surface portions 521, 522, 523, and 524, respectively. Thus, the light beam is positioned with respect to the light beam on the reflecting surface. The reflective members 43Y, 43M, 43C, and 43K are bonded to the holding surface portions 521, 522, 523, and 524 and the reflective fixing portions 53Y, 53M, 53C, and 53K using an adhesive (such as an ultraviolet curable adhesive).

  In the present embodiment, the reflecting members 43Y, 43M, 43C, and 43K are configured to contact the holding surface portions 521, 522, 523, and 524, but are not limited thereto. The reflection members 43Y, 43M, 43C, and 43K may be configured not to contact the holding surface portions 521, 522, 523, and 524 as long as they can be accurately positioned by the reflection fixing portions 53Y, 53M, 53C, and 53K. .

  As shown in FIGS. 5 and 6, the holding surface portion 522 is configured to have the same plane as the plane portion 520. The holding surface portion 521 is provided on a convex portion protruding from the flat surface portion 520, and the holding surface portions 523 and 524 are bottom surfaces of the concave portions formed in the flat plate portion 520. The depth of the holding surface portion 524 from the surface of the flat surface portion 520 is deeper than the holding surface portion 523. By forming the concave and convex holding surface portions 521, 522, 523, and 524 on the flat surface portion 520, the strength of the holding surface portions 521, 522, 523, and 524 can be increased, and deformation is suppressed. Thereby, the deformation | transformation of the reflection fixing | fixed part 53Y, 53M, 53C, 53K is also suppressed.

  Further, as shown in FIG. 4 and the like, the adjustment mirror 43R is also fixed by bringing one surface (here, the surface opposite to the reflection surface) into contact with the fixing portion 53R protruding from the flat surface portion 520, similarly to the reflection member. ing. By fixing in this way, the adjustment mirror 43R is also positioned.

  By being fixed to the holding surface portions 521, 522, 523, and 524, the height of the reflecting surfaces of the reflecting members 41Y, 41M, 41C, and 41K with respect to the flat surface portion 520 becomes lower as the distance from the partition portion 54 increases. By setting the reflecting members 41Y, 41M, 41C, and 41K to different heights, the height from the plane portion 520 of the optical path of the light beam that forms the electrostatic latent image on each of the photosensitive drums 11Y, 11M, 11C, and 11K. It is possible to prevent the optical paths of the light beams from overlapping. Note that the height of the reflecting members 41Y, 41M, 41C, and 41K is not limited to this, but in order to prevent the optical paths of the light beams from overlapping, the reflecting members 41Y, 41M, 41C, and 41K are arranged so as to be lower toward the adjustment mirror 41R. Preferably it is.

  Further, the height of the reflecting members 41Y, 41M, 41C, and 41K is not limited to this, and may be the same height as long as the optical path can be secured so that the light beams do not overlap. Only some of the reflective members may be higher or lower than the other reflective members.

  As described above, hot air generated by the deflector 44 is blown onto the partition 54, and deformation occurs due to thermal expansion. In the partition portion 54, the second region 502 side where the deflector 44 is provided is higher than the first region 501 side. The partition 54 is deformed (inclined) so that the thermal expansion on the second region 502 side where the temperature is high becomes larger than that on the first region 501 side, and the partition 54 falls to the first region 501 side.

  Since the partition portion 54 constitutes a part of the wall surface 56, the rigidity is high, but it is impossible to completely prevent the tilting. Since the partition portion 54 is formed integrally with the holding portion 52, when distortion due to the tilt of the partition portion 54 is transmitted to the holding portion 52, the reflection fixing portions 53 </ b> Y, 53 </ b> M, 53 </ b> C formed integrally with the holding portion 52. 53K is similarly deformed (so that it falls down). When the reflection fixing portions 53Y, 53M, 53C, and 53K are deformed so as to fall down, the angles of the reflection surfaces of the reflection members 43Y, 43M, 43C, and 43K with respect to the light beam are shifted.

  Since the reflecting members 43Y, 43M, 43C, and 43K are configured to reflect the light beam on the reflecting surface, the deviation of the angle of the light beam is twice the displacement angle of the reflecting surface. Further, even if the deviation of the angle of the light beam in the vicinity of the light sources 41Y, 41M, 41C, and 41K is small, the positional deviation of the light beam (spot) is large when the photosensitive drums 11Y, 11M, 11C, and 11K are irradiated. Become. For this reason, the scanning optical device 40 according to the present invention includes the mitigation unit 55 in order to suppress the deformation of the reflection fixing units 53Y, 53M, 53C, and 53K in the falling direction.

  The relaxing portion 55 has a groove shape that is provided between the connecting portion with the partition portion 54 and the reflection fixing portion 53 </ b> Y disposed closest to the partition portion 54 and extends along the partition portion 54. The relaxation portion 55 has a groove shape that is recessed on the opposite side of the upper surface of the flat portion 520 from the protruding direction of the reflection fixing portion.

  More specifically, the relaxing part 55 is adjacent to the partition part 54, and the groove shape of the relaxing part 55 extends along the partition part 54 and the flat part 520. The groove shape of the relaxing part 55 has the same length as the partition part 54. And the relaxation part 55 has the side part 551 containing the surface connected to the partition part 54, and the surface connected to the plane part 520, and the bottom part 552 formed continuously with the side part 551, The bottom part The depth of the 552 with respect to the flat surface portion 520 is formed to be deeper than the holding surface portion 524 which is the deepest recess.

  In the scanning optical device 40 having the housing 50 having such a configuration, when the partitioning portion 54 is tilted, the distortion is transmitted and the relaxing portion 55 is deformed. The deformation transmitted to the holding surface portions 521, 522, 523, and 524 is relieved by the deformation of the relieving portion 55. In addition, it is considered that stress is easily concentrated on the bent portion 55, and the portion is deformed (distorted), so that transmission of strain to the holding surface portions 521, 522, 523, and 524 is relaxed. .

  Thus, by providing the relaxation part 55, even if it deform | transforms so that the partition part 54 may fall, the distortion by the deformation | transformation is not transmitted to the holding surface parts 521, 522, 523, and 524, or becomes difficult to transmit. Thereby, even if the partition part 54 tilts, the deformation of the reflection fixing parts 53Y, 53M, 53C, 53K is suppressed, and the angle deviation of the optical path of the light beam reflected by the reflection members 43Y, 43M, 43C, 43K is suppressed. In addition, it is possible to irradiate the photoconductor drums 11Y, 11M, 11C, and 11K with light beams at accurate positions.

  Depending on the inclination (size) of the partition portion 54, the strain may not be alleviated by the relaxing portion 55, and the strain may be transmitted to the holding surface portions 521, 522, 523, and 524. Also in this case, since the holding surface portions 521, 522, 523, and 524 are formed in the concavo-convex shape, it is difficult to deform, and deformation of the reflection fixing portions 53Y, 53M, 53C, and 53K is suppressed.

  As described above, the bottom portion 552 of the relaxing portion 55 is formed so as to be lower than the holding surface portion 524, and the relaxing portion 55 has a large effect of reducing distortion when the partition portion 54 is tilted. However, the present invention is not limited to this, and the bottom portion of the relaxing portion 55 only needs to be formed deeper than at least the holding surface portion 521 where the reflection fixing portion 53Y provided closest to the partition portion 54 is provided. In the case of such a configuration, the effect of reducing the strain is reduced, but the shape can be simplified. Such a configuration can be employed, for example, in a scanning optical device that has a small distortion due to the tilting of the partition 54.

  Further, in the present embodiment, the relaxing portion 55 is provided adjacent to the partition portion 54, but if it is provided between the partition portion 54 and the reflection fixing portion 53Y, it is formed away from the partition portion 54. May be. The groove shape of the relaxing portion 55 is formed along the entire length of the partition portion 54 when viewed from below. By setting it as this shape, the distortion of the whole partition part 54 can be relieved and the deformation | transformation of the reflection fixing | fixed part 53Y, 53M, 53C, 53K can be suppressed effectively.

  Moreover, it is preferable that the relaxation part 55 is provided so that it may become parallel with the reflective surface of a reflection fixing part. Of the change in the angle of the reflection surface of the reflection member due to the tilt of the reflection fixing portion, the influence of the change in the angle in the tilt direction tends to increase. For this reason, by making the relaxing portion 55 parallel to the reflecting surface, distortion in the direction in which the influence is greatest can be suppressed, so that the deviation of the angle of the light beam can be efficiently suppressed.

  Further, by disposing the reflective member 43Y closest to the partition portion 54 at a higher position with respect to the flat surface portion 520, the reflective surface of the reflective member 43Y that is most susceptible to the tilt of the partition portion 54 is efficiently displaced. It is possible to suppress well.

  In the present embodiment, the deflector 44 is cited as a heat source for thermally deforming the casing 50, but the present invention is not limited to this. The heat shield wall portion provided to shield (heat shield) heat from a heat source other than the deflector 44 from reaching the reflection fixing portions 53Y, 53M, 53C, 53K has the above-described configuration. By forming the holding surface portion and the relaxing portion, it is possible to suppress the deviation of the light beam based on the tilt of the heat shield wall portion due to the heat. In each of the following embodiments, the deflector is similarly used as a heat source, but a heat source other than the deflector can also be used.

(Second Embodiment)
Another example of the scanning optical apparatus according to the present invention will be described with reference to the drawings. FIG. 7 is a bottom view of a holding portion of another example of the scanning optical apparatus. As shown in FIG. 7, the length in the first direction a <b> 1 of the groove shape of the relaxing portion 55 </ b> A when the first direction a <b> 1 is perpendicular to the protruding direction of the reflection fixing portion 53 </ b> Y along the required accuracy surface of the reflection fixing portion 53 </ b> Y. L1 is the same as the length L1 of the reflection fixing portion 53Y in the same direction.

  By forming in this way, deformation of the reflection fixing portion 53Y can be suppressed. Such a configuration can be employed for the scanning optical device 40 in which, for example, the distortion due to the tilt of the partition 54 is small and the distortion affects only the reflection fixing portion 53Y closest to the partition 54. It is. In addition, the relaxation effect increases as the length of the groove shape of the relaxation portion 55A increases. Therefore, the length of the groove shape of the relaxing portion 55A is preferably longer than the length of the reflection fixing portion 53Y.

  In some cases, at least two of the reflection fixing portions 53Y, 53M, 53C, and 53K may be affected by distortion. In such a case, the relaxing portion 55 is configured to be equal to or longer than the length obtained by overlapping the plurality of reflection fixing portions. For example, when the reflection fixing portion 53Y and the reflection fixing portion 53M are affected by distortion due to thermal deformation of the partition portion 54, the length L1 in the first direction a1 of the groove shape of the relaxing portion 55A is reflected and fixed to the reflection fixing portion 53Y. The part 53M is configured to be equal to or longer than the length L2 at both ends in the first direction a1.

  By adopting such a configuration, the size of the relaxing portion 55A can be minimized, so that the influence of distortion due to the tilt of the partitioning portion 54A can be effectively reduced while minimizing the configuration change. , The shift of the light beam can be suppressed.

(Third embodiment)
Another example of the scanning optical apparatus according to the present invention will be described with reference to the drawings. 8 is an enlarged cross-sectional view of still another example of the scanning optical apparatus according to the present invention, and FIG. 9 is a bottom view of the holding portion of the scanning optical apparatus shown in FIG. The scanning optical apparatus shown in FIGS. 8 and 9 has the same configuration as that of the scanning optical apparatus of the first embodiment except that the relaxing portion 57 is different, and substantially the same parts are denoted by the same reference numerals.

  As shown in FIGS. 8 and 9, the housing 50 includes a relaxation portion 57 instead of the relaxation portion 55. The relaxation portion 57 includes a plurality of through holes 573 arranged in the same direction as the groove shape in the side portion 571 and the bottom portion 572. By providing the through hole 573, the area of the side portion 571 and the bottom portion 572 is reduced, and the side portion 571 and the bottom portion 572 are more easily deformed than the holding surface portions 521, 522, 523, and 524. Therefore, when the distortion due to the tilt of the partitioning portion 54 is transmitted, the side portion 571 and the bottom portion 572 of the relaxing portion 57 are deformed before the holding surface portions 521, 522, 523, and 524 are deformed.

  Then, the deformation of the side surface 571 and the bottom portion 572 relaxes the transmission of strain to the holding surface portions 521, 522, 523, and 524, and suppresses the deformation of the holding surface portions 521, 522, 523, and 524.

  As described above, in the relaxing portion 57 of the present embodiment, by providing the through holes 573 in the side portion 571 and the bottom portion 572, a portion that is easily deformed, that is, a portion that is intentionally reduced in strength, is formed. By deforming the part, distortion transmission is eased.

  In the present embodiment, a plurality of through holes 573 are provided side by side in the side portion 571 and the bottom portion 572 of the relaxing portion 57. However, the present invention is not limited to this, for example, provided in a planar arrangement. Alternatively, a long hole in which at least two of the plurality of through holes 573 are connected may be used. It goes without saying that a long hole shape in which all the through holes 573 are connected may be used.

  Further, in the relaxing portion 57 of the present embodiment, the through holes 573 are formed in the side portion 571 and the bottom portion 572. However, the present invention is not limited to this. 573 may be formed.

(Fourth embodiment)
Another example of the scanning optical apparatus according to the present invention will be described with reference to the drawings. 10 is an enlarged cross-sectional view of still another example of the scanning optical device according to the present invention, and FIG. 11 is a bottom view of the holding portion of the scanning optical device shown in FIG. The scanning optical apparatus shown in FIGS. 10 and 11 has the same configuration as that of the scanning optical apparatus of the first embodiment except that the relaxing portion 58 is different, and substantially the same parts are denoted by the same reference numerals.

  As shown in FIG. 10, the housing 50 includes a relaxation portion 58 instead of the relaxation portion 55. The relaxing part 58 is formed such that the side part 581 and the bottom part 582 are thinner than the holding surface parts 521, 522, 523, and 524. By configuring the side portion 581 and the bottom portion 582 in this manner, the side portion 581 and the bottom portion 582 are more easily deformed than the holding surface portions 521, 522, 523, and 524. Therefore, when the distortion due to the tilt of the partition portion 54 is transmitted, the side portion 581 and the bottom portion 582 of the relaxing portion 58 are deformed before the holding surface portions 521, 522, 523, and 524 are deformed.

  Then, deformation of the holding surface portions 521, 522, 523, and 524 is relieved by the deformation of the side portions 581 and the bottom portion 582, and the deformation of the holding surface portions 521, 522, 523, and 524 is suppressed.

  As described above, in the relaxing portion 58 of the present embodiment, the side portion 581 and the bottom portion 582 are thinner than the holding surface portions 521, 522, 523, and 524, so that they are easily deformed, that is, the strength is intentionally increased. The transmission of distortion is eased by dropping and deforming the part.

  In the relaxation portion 58 of the present embodiment, both the side portion 581 and the bottom portion 582 are formed thinner than the holding surface portions 521, 522, 523, and 524, but the present invention is not limited to this, and the side portion 581 , At least one of the bottom portions 582 may be formed thin.

  In the present embodiment, the entire side portion 581 and bottom portion 582 of the relaxing portion 58 are thinner than the holding surface portions 521, 522, 523, and 524, but the present invention is not limited to this. It is good also as the thin part 583 (refer FIG. 10) formed only thinly. At this time, the thin portion 583 may be continuous in the direction in which the groove shape extends (thin portion 5831, see FIG. 11), or may be formed intermittently (see the thin portion 5832, FIG. 11). Moreover, the thin part 583 may be arranged side by side in the tilting direction of the partition part 54.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this content. The embodiments of the present invention can be variously modified without departing from the spirit of the invention.

11Y, 11M, 11C, 11K Photoconductor drum 111 Charger 112 Developing device 113 Transfer roller 114 Cleaning unit 12Y, 12M, 12C, 12K Toner hopper 13Y, 13M, 13C, 13K Toner bottle 14 Intermediate transfer belt 141 Drive roller 142 Driven roller 143 Tension roller 15 Secondary transfer roller 16 Fixing unit 17 Cleaning blade 20 Image reader unit 30 Paper feed unit 31 Paper feed tray 32 Paper feed roller 33 Registration roller 40 Scanning optical devices 41Y, 41M, 41C, 41K Light source 42 Collimator lens 43Y , 43M, 43C, 43K Reflective member 43R Adjustment mirror 44 Deflector 441 Polygon mirror 442 Deflection motor 45 Optical element 46Y, 46M, 46C, 46K Scanning reflection unit 50 Housing 51 Side wall 511 Detection Opening 512 fixing unit 52 holding portion 520 planar portion 521, 522, 523 and 524 holding surface 53Y, 53M, 53C, 53K reflective fixing portion 54 partition portion (Saeginetsukabe portion)
55 Relaxation part 551 Side part 552 Bottom part 56 Wall surface 57 Relaxation part 571 Side part 572 Bottom part 573 Through hole 58 Relaxation part 581 Side part 582 Bottom part 583 Thin part 5831 Thin part 5832 Thin part

Claims (10)

A scanning optical device that scans a light beam applied to an irradiation target surface,
A housing in which a reflecting member that reflects a light beam emitted from a light source is disposed;
The housing is
A reflection fixing portion having a surface to which one surface of the reflection member is fixed;
A holding portion from which the reflection fixing portion protrudes integrally;
A heat shield wall portion that blocks heat transmitted to the reflection fixing portion integrally formed with the holding portion;
A scanning optical device comprising a groove-shaped relaxation portion formed in a portion between the reflection fixing portion and the heat shield wall portion of the holding portion.   The scanning optical device according to claim 1, wherein a groove shape of the relaxation portion extends in parallel with a reflection surface of the reflection member fixed to the reflection fixing portion.   The groove shape of the relaxation portion is such that the length of the reflection fixing portion in the direction along the surface to which the reflecting member is fixed and the holding portion is equal to or longer than the length of the reflection fixing portion in the same direction. The scanning optical device according to claim 2.   4. The scanning optical device according to claim 1, wherein one or a plurality of through holes are formed in at least one surface of a bottom portion or a side portion of the relaxing portion.   5. The scanning optical device according to claim 1, wherein a thickness of at least one surface of a bottom portion or a side portion of the relaxing portion includes a portion formed thinner than a thickness of another portion of the holding portion. . A plurality of reflection members, and a plurality of reflection fixing portions to which each of the plurality of reflection members is fixed,
The holding portion has a holding surface portion that comes into contact with a surface different from a surface fixed to the reflection fixing portion of the reflecting member;
5. The scanning optical device according to claim 1, wherein a height of the holding surface portion in a protruding direction of the reflection fixing portion is different depending on a distance from the relaxation portion.   The scanning optical device according to claim 6, wherein a height of the holding surface portion in the protruding direction is lowered as the distance from the relaxing portion is increased.   The scanning optical device according to claim 7, wherein a height of the bottom portion of the relaxation portion in the protruding direction is lower than a holding surface portion.   The said heat shield wall part is a partition part which partitions off between the polarizer which is attached to the said housing | casing, and deflects and scans the said light beam, and the said holding | maintenance part. Scanning optical device.   The scanning optical device according to claim 1, wherein the heat shield wall portion is a part of a wall body formed in a cylindrical shape surrounding the holding portion.