JP2011077002A - Luminaire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a luminaire using an LED line light source exhibiting wide light distribution characteristics. <P>SOLUTION: A light distribution adjustment lens 20 is arranged so as to cover a front surface of the LED line light source 10. The light distribution adjustment lens 20 has light distribution characteristics wherein light from a light emission surface 111 of an LED module 11 is diffused to both sides with an LED optical axis surface 292 located therebetween, and relative light flux, in a direction where an angle with an optical axis of the LED module 11 is large rather than in a direction where the angle is small, is increased in a flat surface orthogonal to the LED optical axis surface 292 and an LED light emission surface 291. Specifically, the lens has an approximately semi-cylindrical shape having an inner circumference surface (a concave curved surface) 23 functioning as a light incident surface, and an outer circumference surface (a convex curved surface) 24 functioning as a light emission surface. The inner circumference surface 23 has a quadratic surface shape in a cross section vertical to the LED optical axis surface 292. The outer circumference surface 24 has a high-order aspheric shape having an approximately flat part 28 with a gentle inclination on a top part 27. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a lighting apparatus using an LED line light source.

  A surface mounted device type LED module has high luminous efficiency and high output, and is expected as an LED light source that can be used for lighting applications.

  FIG. 8A is a front view of a general surface-mounted LED module 60, and FIG. 8B is a cross-sectional view taken along the line FF of the surface-mounted LED module 60 shown in FIG. 8A. .

  As shown in the drawing, the surface-mounted LED module 60 includes a pedestal 61 in which an inverted truncated cone-shaped recess 62 is formed, a blue LED 63 disposed at the center of the bottom surface of the recess 62, and a reflector formed on a side surface of the recess 62. 64 and a yellow phosphor dispersed resin 65 filled in the recess 62. In such a configuration, part of the blue light output from the blue LED 63 hits the yellow phosphor in the yellow phosphor dispersion resin 65 and is converted into yellow light. The blue light from the blue LED 63 and such yellow light are mixed to form white light, which is reflected directly or by the reflector 64, and then emits the concave region 62 (hereinafter, the surface region S surrounded by the edge of the concave portion 62). From the front surface-mount type LED module 60.

  By the way, the light distribution angle of the surface-mounted LED module 60 is generally about 120 degrees, which is narrower than that of a fluorescent lamp or the like. For this reason, for example, when an LED line light source in which a plurality of surface-mounted LED modules 60 are arranged in a line instead of a fluorescent lamp is used as a line light source of a shelf light fixture, the installation position of the shelf light fixture is Or depending on the display position of a display item, light cannot fully shine on a display item.

  On the other hand, Patent Document 1 discloses a condensing point variable mechanism of a lighting fixture using an LED module. This condensing point variable mechanism has a flexible wire fixed to a substrate on which a plurality of LED modules are mounted. According to this condensing point variable mechanism, the irradiation directions of the plurality of LED modules can be changed at once by twisting the flexible wire. Therefore, by applying the condensing point variable mechanism described in Patent Document 1 to the under-shelf illuminator using the LED line light source, the irradiation direction can be adjusted with a simple operation so that the display product can be sufficiently exposed to light. Can do.

JP 2003-45223 A

  However, when the condensing point variable mechanism described in Patent Document 1 is applied to the under-shelf lighting fixture using the LED line light source, the following problem occurs. That is, for example, if the irradiation direction of the LED line light source is adjusted so that light is sufficiently applied to the display in front of the shelf, the light does not reach the rear of the shelf depending on the depth of the shelf, and the entire shelf cannot be kept bright.

  This invention is made | formed in view of the said situation, The objective of this invention is providing the lighting fixture using the LED line light source which has a wider light distribution characteristic.

  In order to solve the above problems, the present invention arranges a light distribution adjustment lens so as to cover the front surface of the LED line light source. The light distribution adjusting lens diffuses light from the LED module so as to have a wider light distribution angle in a plane perpendicular to the longitudinal direction.

For example, the present invention is a luminaire including an LED line light source configured by arranging a plurality of LED modules in a line,
A light distribution adjustment lens arranged to cover the front surface of the LED line light source;
The light distribution adjustment lens is:
In a plane perpendicular to the longitudinal direction of the light distribution adjustment lens, light from the LED module increases in a relative light flux in a direction larger than the direction in which the angle formed with the optical axis direction of the LED module is small. Has light distribution characteristics.

Here, the light distribution adjustment lens has a substantially semi-cylindrical shape having an inner peripheral surface functioning as a light incident surface and an outer peripheral surface functioning as a light emission surface,
The inner peripheral surface is a first aspherical shape whose inclination increases with increasing distance from the top in a cross section perpendicular to the longitudinal direction of the light distribution adjusting lens,
The outer peripheral surface may have a substantially flat second aspherical shape in which the inclination increases as the distance from the top in the cross section increases and the change in the inclination is smaller than that of the top of the inner peripheral surface.

  ADVANTAGE OF THE INVENTION According to this invention, the lighting fixture using the LED line light source which has a wider light distribution characteristic can be provided.

FIG. 1 (A) is a schematic front view of a shelf lighting fixture 1 according to an embodiment of the present invention, and FIG. 1 (B) is a cross-sectional view taken along line AA of the shelf lighting fixture 1 shown in FIG. 1 (A). FIG. 2A is a schematic front view of the LED line light source 10, and FIG. 2B is a cross-sectional view taken along the line BB of the LED line light source 10 shown in FIG. 3A is a schematic front view of the light distribution adjusting lens 20, and FIG. 3B is a cross-sectional view taken along the line CC of the light distribution adjusting lens 20 shown in FIG. 4A is a diagram for explaining the two-dimensional light distribution of the light distribution adjusting lens 20, and FIG. 4B is a diagram for explaining the light distribution characteristic in the YZ plane of FIG. 4A. It is a figure for doing. 5A is a schematic front view of the housing 40, and FIG. 5B is a DD cross-sectional view of the housing 40 shown in FIG. 5A. 6A is a diagram for explaining the light distribution characteristics of the LED line light source 10 in which the light distribution adjustment lens 20 is arranged, and FIG. 6B shows the light distribution characteristics of the under-shelf lighting fixture 1. It is a figure for demonstrating. FIG. 7 (A) is a schematic front view of a signboard lighting fixture 2 according to another embodiment of the present invention, and FIG. 7 (B) is an EE of the signboard lighting fixture 2 shown in FIG. 7 (A). It is sectional drawing. FIG. 8A is a front view of a general surface-mounted LED module 60, and FIG. 8B is a cross-sectional view taken along the line FF of the surface-mounted LED module 60 shown in FIG. 8A. . 9A is a schematic front view of Modification 1a of the under-shelf lighting fixture 1 shown in FIG. 1, and FIG. 9B is a cross-sectional view of the under-shelf lighting fixture 1a shown in FIG. It is.

  Embodiments of the present invention will be described below.

  FIG. 1 (A) is a schematic front view of a shelf lighting fixture 1 according to an embodiment of the present invention, and FIG. 1 (B) is a cross-sectional view taken along line AA of the shelf lighting fixture 1 shown in FIG. 1 (A). FIG.

  As shown in the drawing, the under-shelf lighting fixture 1 includes an LED line light source 10, a light distribution adjustment lens 20 disposed so as to cover the front surface of the LED line light source 10, and a microfoamed PET (MCPET (registered trademark)) sheet, for example. And the like, a LED line light source 10, a light distribution adjusting lens 20, and a housing 40 that holds the reflector 30. Here, reference numeral 291 denotes a surface including a light emitting surface of each LED module 11 described later mounted on the LED line light source 10 (hereinafter referred to as an LED light emitting surface), and reference numeral 292 includes an optical axis of each LED module 11. A surface (hereinafter referred to as an LED optical axis surface) is shown.

  2A is a schematic front view of the LED line light source 10, and FIG. 2B is a cross-sectional view taken along the line BB of the LED line light source 10 shown in FIG.

  As illustrated, the LED line light source 10 includes a plurality of LED modules 11 and a substrate 12 on which these LED modules 11 are mounted. The plurality of LED modules 11 are arranged in a line at predetermined intervals along the longitudinal direction of the substrate 12. Side end portions (end portions along the longitudinal direction of the substrate 12) 13 on both sides of the substrate 12 function as held portions for holding the LED line light source 10 on the housing 40. For example, a surface mount LED module 60 shown in FIG. 8 can be used for the LED module 11.

  3A is a schematic front view of the light distribution adjusting lens 20, and FIG. 3B is a cross-sectional view taken along the line CC of the light distribution adjusting lens 20 shown in FIG.

  As shown in the figure, the light distribution adjusting lens 20 is configured by connecting a plurality of substantially semi-cylindrical lens blocks 21 made of, for example, polycarbonate. A light diffusion surface 22 for diffusing incident light is formed on the joint surface of the lens block 21 with the other lens block 21. As shown in the figure, the light diffusing surface 22 may have a jagged shape that meshes with the light diffusing surface 22 of the lens block 21 to be connected, or may have fine irregularities formed thereon.

  The lens block 21 includes an inner peripheral surface (a concave curved surface surrounding the array of the LED modules 11) 23 that functions as an incident surface for light emitted from the LED line light source 10, and a radiation surface for light incident on the inner peripheral surface 23. An outer peripheral surface (convex curved surface) 24 that functions as a holding portion, and a held portion 25 that is formed at both end portions along the longitudinal direction and holds the light distribution adjusting lens 20 on the housing 40.

  In the cross section perpendicular to the longitudinal direction of the lens block 21, the inner peripheral surface 23 is inclined (parallel to the LED light emitting surface 291) as the distance from the top (intersection line between the inner peripheral surface 23 and the LED optical axis surface 292) 26 increases. The angle α1) formed with the surface becomes large and has an aspherical shape terminating at the LED light emitting surface 291. For example, the inner peripheral surface 23 has a quadratic curved surface shape represented by the following aspheric shape formula (1) in a cross section perpendicular to the longitudinal direction of the lens block 21.

Aspherical shape formula (1):
z = c ₁ × y ² / (1 + sqrt (1− (1 + K ₁ ) × c ² × y ² ))
Here, c ₁ is a curvature (1 / mm), K ₁ is a negative conic coefficient, y is a distance from the LED optical axis surface 292 to a point on the inner peripheral surface 23, and z is a top portion of the inner peripheral surface 23. 26 is a distance (a zag amount) from a surface in contact with 26 to a point on the inner peripheral surface 23.

  On the other hand, the outer peripheral surface 24 has a substantially flat portion 28 having a gentle inclination at the top (intersection line between the outer peripheral surface 24 and the LED optical axis surface 292) 27 in a cross section perpendicular to the longitudinal direction of the lens block 21. However, the inclination (angle α2 formed by the surface parallel to the LED light emitting surface 291) increases as the distance from the top portion 27 increases, and the shape is an aspherical shape that terminates in the vicinity of the LED light emitting surface 291 (held portion 25). For example, the outer peripheral surface 24 has a higher-order aspheric shape represented by the following aspheric shape formula (2) in a cross section perpendicular to the longitudinal direction of the lens block 21.

Aspherical shape formula (2):
z = c ₂ × y ² / (1 + sqrt (1− (1 + K ₂ ) × c ² × y ² )) + A × y ⁴ + B × y ⁶
Here, c ₂ is a curvature (1 / mm), K ₂ is a positive conic coefficient, A is a fourth-order coefficient, B is a sixth-order coefficient, and y is a distance from the LED optical axis surface 292 to a point on the outer peripheral surface 24. The distance z is a distance (a zag amount) from a surface in contact with the top 27 of the outer peripheral surface 24 to a point on the outer peripheral surface 24. Then, the curvature c ₂ of the aspheric shape formula (2) representing the outer peripheral surface 24 is set to an aspheric shape formula (1) representing the inner peripheral surface 23 so that the outer peripheral surface 24 becomes flatter than the inner peripheral surface 23. absolute value than the curvature c ₁ of) is set to a small value.

  4A is a diagram for explaining the two-dimensional light distribution of the light distribution adjusting lens 20, and FIG. 4B is a diagram for explaining the light distribution characteristic in the YZ plane of FIG. 4A. It is a figure for doing. Here, the optical axis of an arbitrary LED module 11 on the LED line light source 10 is defined as the Z axis, and the longitudinal direction of the light distribution adjustment lens 20 arranged at an appropriate position with respect to the LED line light source 10 (LED module). 11 in the LED light emitting surface 291 along the X axis along the width direction (direction perpendicular to the longitudinal direction). In addition, the code | symbol 111 shows the light emission surface of the LED module 11, and the code | symbol 112 shows the angle | corner which the light emission direction which passes along an origin, and a Z-axis make.

  As shown in the drawing, the light distribution adjusting lens 20 diffuses light from the light emitting surface 111 of the LED module 11 in the Y-axis direction, and in the ZY plane, a direction in which the angle 112 formed with the Z-axis is larger than a small direction ( For example, it has a light distribution characteristic that increases the relative luminous flux in a direction from about 50 degrees to about 90 degrees. Therefore, for example, when the surface-mounted LED module 60 shown in FIG. 8 is used as the LED module 11 of the LED line light source 10, as shown in FIG. 6A, the light distribution is centered on the LED optical axis plane 292. The angle can be expanded from about 120 degrees to about 180 degrees.

  5A is a schematic front view of the housing 40, and FIG. 5B is a DD cross-sectional view of the housing 40 shown in FIG. 5A.

  As illustrated, the housing 40 includes a holding portion 41 for holding the side end portion 13 of the LED line light source 10, a holding portion 42 for holding the held portion 25 of the light distribution adjusting lens 20, and a reflector. 30 includes a holding portion 43 for holding side end portions on both sides (end portions along the longitudinal direction of the reflector 30), and a receiving portion 44 for receiving a power supply, wiring to the LED line light source 10, and the like. .

  As shown in FIG. 1, the holding unit 41 holds the LED line light source 10 so that the LED optical axis surface 292 is inclined toward the housing unit 44 with respect to the attachment surface (back surface) 45 under the shelf. The holding unit 42 is held by the holding unit 41 so that the light from the LED module 11 is irradiated from one edge of the inner peripheral surface 23 to the other edge (see FIG. 6A). The light distribution adjustment lens 20 is fixed at an appropriate position with respect to the LED line light source 10. Specifically, the top portion 26 of the inner peripheral surface 23 and the top portion 27 of the outer peripheral surface 24 are arranged on the plurality of LED modules 11, and the distance between the edge portion of the inner peripheral surface 23 and the LED light emitting surface 291 is equal to or smaller than a predetermined dimension. The light distribution adjusting lens 20 is positioned so that

  And the holding | maintenance part 43 fixes the reflector 30 between the LED line light source 10 and the accommodating part 44 so that the longitudinal direction of the reflector 30 may follow the longitudinal direction of the LED line light source 10. FIG. Here, the reflection surface of the reflector 30 is inclined with respect to the back surface 45 at a predetermined angle slightly smaller than the inclination angle of the LED optical axis surface 292.

  In this way, for example, when the surface-mounted LED module 60 shown in FIG. 8 is used as the LED module 11 of the LED line light source 10, as shown in FIG. Of the light L1 and L2 that are irradiated and have a large relative luminous flux directed in the direction of about 50 degrees to 90 degrees on both sides of the LED optical axis surface 292 through the light distribution adjustment lens 20, one light L1 is: The other light L2 is radiated to the outside of the housing 40 without being blocked, and is reflected by the reflecting surface of the reflector 30 and is emitted to the outside of the housing 40 so as to irradiate the irradiation region side of the one light L1.

  The embodiment of the present invention has been described above.

  In the present embodiment, the light distribution adjustment lens 20 is disposed so as to cover the front surface of the LED line light source 10. The light distribution adjusting lens 20 sandwiches the optical axis of the LED module 11 (Z axis in FIG. 4A) in a plane perpendicular to the arrangement direction of the LED modules 11 (ZY plane in FIG. 4A). The light distribution characteristic is such that light from the LED module 11 is diffused on both sides, and the relative luminous flux is increased in a direction in which the angle formed with the optical axis of the LED module 11 is large. Specifically, the light distribution adjusting lens 20 has a substantially semi-cylindrical shape having an inner peripheral surface (concave surface) 23 that functions as a light incident surface and an outer peripheral surface (convex surface) 24 that functions as a light emission surface. The inner peripheral surface 23 has a first aspherical shape in which the inclination α1 increases as the distance from the top portion 26 increases in the cross section perpendicular to the LED optical axis surface 292, and the outer peripheral surface 24 increases as the distance from the top portion 27 increases in the cross section. This is a second aspherical shape in which the inclination α2 is large and the top part 27 has a substantially flat part 28 having a gentle inclination.

  By doing in this way, as shown to FIG. 6 (A), the lighting fixture using the LED line light source 10 which has a wider light distribution characteristic is realizable.

  In the present embodiment, the light distribution adjusting lens 20 is configured by connecting a plurality of lens blocks 21 each having a substantially semicylindrical shape. The lens block 21 has a light diffusion surface 22 formed on the joint surface with another lens block 21. By doing in this way, when the LED line light source 10 is lighted, it can prevent that a dark part is formed in the junction part between the lens blocks 21. FIG.

  Further, in the present embodiment, the LED line light source 10 is held such that the LED optical axis surface 292 is inclined toward the accommodating portion 44 side with respect to the under shelf mounting surface (rear surface) 45 of the housing 40, and the reflector 30 The reflection surface is held so as to be inclined with respect to the back surface 45 of the housing 40 at a predetermined angle slightly smaller than the inclination angle of the LED optical axis surface 292.

  By doing so, as shown in FIG. 6B, the relative luminous flux directed to the direction of about 50 degrees to 90 degrees on both sides with respect to the LED optical axis surface 292 via the light distribution adjustment lens 20. Of the many lights L1 and L2, one light L1 irradiates the outside of the housing 40 without being blocked, and the other light L2 is reflected by the reflecting surface of the reflector 30 toward the irradiation direction of the one light L1. Thus, an area different from the irradiation area of the one light L1 is irradiated.

  Therefore, by attaching the storage unit 44 of the present embodiment to the bottom of the shelf (or to the front of the upper surface of the showcase) with the accommodating portion 44 facing the front of the shelf (or the front of the showcase), the lower shelf (or the showcase) The light L2 can be sufficiently applied to the display on the front side of the display stand), and the light L1 can reach the back of the shelf (or the back of the showcase). For this reason, the whole shelf (or the whole showcase) can be kept bright.

  In addition, this invention is not limited to said embodiment, Many deformation | transformation are possible within the range of the summary.

  For example, in the above-described embodiment, the light distribution adjustment lens 20 is configured by connecting a plurality of lens blocks 21. This is because, depending on the length of the LED line light source 10, it is technically difficult to form the lens block 21 having a length necessary for covering the front surface by injection molding. However, when the LED line light source 10 is short or when an extrusion molding capable of forming a sufficiently long lens block 21 can be used, the light distribution adjusting lens 20 is constituted by one lens block 21. You may make it do.

  In the above embodiment, the case where the present invention is applied to the under-shelf lighting fixture 1 has been described as an example. However, the present invention is used for various lighting fixtures that require light irradiation over a relatively wide range. Is possible. For example, the present invention can also be applied to a planar light source (surface light source) such as a sign illuminator or a viewer.

  FIG. 7 (A) is a schematic front view of a signboard lighting fixture 2 according to another embodiment of the present invention, and FIG. 7 (B) is an EE of the signboard lighting fixture 2 shown in FIG. 7 (A). It is sectional drawing. Here, the same code | symbol as the code | symbol used in FIG. 1 is attached | subjected to the structure which has the same function as the shelf lighting fixture 1 shown in FIG.

  As illustrated, the signboard luminaire 2 includes an LED line light source 10, a light distribution adjustment lens 20 disposed so as to cover the front surface of the LED line light source 10, and the LED line light source 10 and the light distribution adjustment lens 20. And a transparent or translucent housing 50 for accommodating. Here, the LED line light source 10 and the light distribution adjusting lens 20 are attached to the back surface 52 inside the housing 50 so as to illuminate the inside of the housing 50.

  As described above, by arranging the light distribution adjusting lens 20 so as to cover the front surface of the LED line light source 10, a wider light distribution characteristic can be realized, so that the front surface 51 of the housing 50 can be achieved with only one LED line light source 10. Not only can the light be emitted from both side surfaces 53 and 54.

  In the above embodiment, the case where the inclination of the reflector 30 held by the housing 40 is fixed has been described. However, the inclination may be adjusted. 9A is a schematic front view of Modification 1a of the under-shelf lighting fixture 1 shown in FIG. 1, and FIG. 9B is a cross-sectional view of the under-shelf lighting fixture 1a shown in FIG. It is. Here, the same code | symbol as the code | symbol used in FIG. 1 is attached | subjected to the structure which has the same function as the shelf lighting fixture 1 shown in FIG.

  As shown in the drawing, the difference between the under-shelf luminaire 1a and the under-shelf luminaire 1 shown in FIG. 1 is that a housing 40a is used instead of the housing 40. The housing 40 a includes a stopper 46 that defines a moving range of one movable end 43 a of the holding portion 43 that holds the side ends on both sides of the reflector 30, and a side surface of the housing 40 that is rotatable about the longitudinal axis of the reflector 30. A rotating shaft 47 held on the side, a disc 48 eccentrically attached to the rotating shaft 47, and an elastic member 49 such as a spring or rubber for urging the movable end 43a toward the housing portion 44 are provided in the housing 40. It has the structure added to. In such a configuration, when the rotating shaft 47 is rotated, the back end surface of the reflector 30 and the outer peripheral surface of the disc 48 are urged by the elastic member 49 toward the accommodating portion 44 side. The contact position changes. As a result, the movable end 43a moves within the movement range defined by the stopper 46, and the inclination of the reflector 30 with respect to the back surface 45 of the housing 40 changes. By setting it as such a structure, the inclination of the reflector 30 can be adjusted.

  The rotation angle of the rotary shaft 47 may be adjusted via a gear that engages with a gear of a knob at one end portion of the rotary shaft 47. By doing in this way, the rotation angle of the rotating shaft 47 can be adjusted more accurately.

  1: Under-shelf lighting fixture, 2: Signboard lighting fixture, 10: LED line light source, 11: LED module, 12: Substrate, 13: Side edges on both sides of the substrate, 20: Lens for adjusting light distribution, 21: Lens block, 22 : Light diffusing surface, 23: inner peripheral surface, 24: outer peripheral surface, 25: held portion, 26: top portion, 27: top portion, 28: substantially flat portion, 30: reflector, 40: housing, 41: holding portion, 42 : Holding part, 43: holding part, 44: accommodating part, 45: back face, 46: stopper, 47: rotating shaft, 48: disc, 49: elastic member, 50: housing, 51: front face, 52: back face, 53 : Side surface, 54: Side surface, 60: Surface mount type LED module, 61: Base, 62: Recessed part, 63: Blue LED, 64: Reflector, 65: Yellow phosphor dispersed resin

Claims (5)

A lighting fixture including an LED line light source configured by arranging a plurality of LED modules in a line,
A light distribution adjustment lens arranged to cover the front surface of the LED line light source;
The light distribution adjustment lens is:
In a plane perpendicular to the longitudinal direction of the light distribution adjustment lens, light from the LED module increases in a relative light flux in a direction larger than the direction in which the angle formed with the optical axis direction of the LED module is small. A luminaire characterized by having a light distribution characteristic. The lighting fixture according to claim 1,
The light distribution adjustment lens is:
A substantially semi-cylindrical shape having an inner peripheral surface functioning as a light incident surface and an outer peripheral surface functioning as a light emitting surface;
The inner peripheral surface is
In the first aspherical shape, the inclination increases with increasing distance from the top in a cross section perpendicular to the longitudinal direction of the light distribution adjusting lens,
The outer peripheral surface is
The lighting apparatus is characterized in that the inclination increases as the distance from the top in the cross section increases, and the top has a substantially flat second aspherical shape with less change in inclination than the top of the inner peripheral surface. The lighting apparatus according to claim 2,
The light distribution adjustment lens is:
A plurality of substantially semi-cylindrical lens blocks are connected,
The lens block is
A light diffusing surface is formed on a joint surface with another lens block. It is a lighting fixture as described in any one of Claim 1 thru | or 3, Comprising:
A reflector for reflecting light emitted toward one side with respect to a surface including an optical axis of the plurality of LED modules toward the other side;
The LED line light source, the light distribution adjustment lens, and a housing that holds the reflector;
The housing is
The reflector is held on one side with respect to the surface so as to be arranged along the array of the plurality of LED modules. It is a lighting fixture as described in any one of Claim 1 thru | or 3, Comprising:
Housing the LED line light source and the light distribution adjustment lens, further comprising a housing through which light from the LED line light source is transmitted;
The light distribution adjustment lens is:
The lighting apparatus is installed on an inner wall of the casing with an outer peripheral surface facing the inner side of the casing.

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