Light emitting module and lighting unit

A lighting unit to be used for illumination includes an LED unit having a semiconductor light emitting unit, a radiating board for directly fixing the semiconductor light emitting unit to an upper surface, and a contact formed on the radiating board and serving to input a power to cause the semiconductor light emitting unit to emit a light, an attachment having a power supply portion for surrounding and holding the LED unit and supplying a power to cause the semiconductor light emitting unit to emit a light from an external power plug to the contact in a state in which at least a part of lower and side surfaces of the radiating board and an upper part of the semiconductor light emitting unit are open.

This application claims foreign priority from Japanese Patent Application No. 2004-244435, filed Aug. 24, 2004, the entire disclosure of which is herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light emitting module and a lighting unit. More particularly, the invention relates to a light emitting module using a semiconductor light emitting unit as a light source, and a lighting unit.

2. Description of Related Art

In a lighting unit for a vehicle such as a headlamp for a vehicle, the formation of a light distribution pattern with high precision is required for safety. The light distribution pattern is formed by an optical system using a reflecting mirror or a lens. For example, JP-A-6-89601 Publication (Pages 3 to 7, FIGS. 1 to 14) discloses this type of system. In recent years, moreover, a semiconductor light emitting unit has been utilized as the light source of the headlamp for a vehicle.

In the case in which a semiconductor light emitting unit is used as the light source of a lighting unit, it is necessary to efficiently cause the semiconductor light emitting unit to emit a light, thereby satisfying a light quantity level required for the lighting unit. In order to efficiently cause the semiconductor light emitting unit to emit a light, it is necessary to prevent a reduction in luminance due to a heat. Since the semiconductor light emitting unit has a small size, it has a smaller light emitting region than that in a conventional light source. Accordingly, in order to form a light distribution pattern with high precision, the relative positions of the optical system, such as a lens or a shade, with the semiconductor light emitting unit must be managed with high precision.

SUMMARY OF THE INVENTION

A first aspect of the invention is directed to a light emitting module to be used for a lighting unit, comprising an LED unit having a semiconductor light emitting unit, a radiating board for directly fixing the semiconductor light emitting unit to an upper surface, and a contact formed on the radiating board and serving to input a power to cause the semiconductor light emitting unit to emit a light, and an attachment having a power supply portion for surrounding and holding the LED unit and supplying a power to cause the semiconductor light emitting unit to emit a light from an external power plug to the contact in a state in which at least a part of lower and side surfaces of the radiating board and an upper part of the semiconductor light emitting unit are open. According to such a structure, it is possible to implement a light emitting module in which a heat emitted from the semiconductor light emitting unit is efficiently radiated to maintain a high luminance and a light source has high precision in a position. Moreover, the attachment surrounds and holds the LED unit. Consequently, there is no possibility that hands or tools might touch the contact and foreign matters can be thus prevented from sticking to the contact.

In the light emitting module, the attachment may have an attachment body for positioning the LED unit and a lower surface support member slid and fitted in the attachment body from a side and serving to interpose and hold the LED unit together with the attachment body. According to such a structure, it is not necessary to provide a downward guide slant face which is required when the lower surface support member is to be fitted in the attachment body from below. Accordingly, it is possible to reduce the height of the light emitting module.

In the light emitting module, the attachment body may include the power supply portion, the lower surface support member may support the lower surface of the radiating board, and the power supply portion may downward energize the contact formed on an upper surface of the radiating board, thereby carrying out an electrical connection to the contact. According to such a structure, it is possible to stably implement the hold of the radiating board and the supply of a power by the energizing force of the power supply portion.

In the light emitting module, the lower surface support member may support a portion in the lower surface of the radiating board which is opposed to the contact. According to such a structure, it is possible to reliably maintain the electrical connection of a spring terminal and the contact.

Moreover, a second aspect of the invention is directed to a lighting unit to be used for illumination, comprising an LED unit having a semiconductor light emitting unit, a radiating board for directly fixing the semiconductor light emitting unit to an upper surface, and a contact formed on the radiating board and serving to input a power to cause the semiconductor light emitting unit to emit a light, an attachment having a power supply portion for surrounding and holding the LED unit and supplying a power to cause the semiconductor light emitting unit to emit a light from an external power plug to the contact in a state in which at least a part of lower and side surfaces of the radiating board and an upper part of the semiconductor light emitting unit are open, and a light source pedestal having a support surface for supporting the LED unit in direct contact with the lower surface of the radiating board, and a positioning portion for positioning the LED unit in direct abutment on the side surface of the radiating board. According to such a structure, it is possible to implement a lighting unit in which the semiconductor light emitting unit has a high light emitting efficiency and the light source has high precision in a position.

The lighting unit may further comprise an engagement surface formed in almost parallel with the support surface below the support surface in the light source pedestal and a clip for interposing an upper surface of the attachment and the engagement surface, thereby pressing the lower surface of the radiating board against the support surface through the attachment. According to such a structure, it is possible to efficiently radiate the heat of the semiconductor light emitting unit by reliably causing the back face of the radiating board to adhere to the light source pedestal.

In the lighting unit, the power supply portion may downward energize the contact formed on an upper surface of the radiating board, thereby carrying out an electrical connection to the contact, and the clip may interpose the upper surface of the attachment and the engagement surface so that the power supply portion can energize the contact more strongly. Consequently, it is possible to enhance the reliability of the electrical connection of the contact and the power supply portion.

In the lighting unit, the attachment may further have a regulating rib to abut on a side surface in the radiating board which is provided on an opposite side of the positioning portion of the light source pedestal, and the clip may press a side surface of the attachment toward the light source pedestal so that the regulating rib can press the radiating board against the positioning portion, thereby positioning the LED unit. Consequently, it is possible to reliably position the radiating board with respect to the light source pedestal.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT

Although the invention will be described below with reference to exemplary embodiment thereof, the following exemplary embodiment does not restrict the invention.

FIGS. 1 and 2illustrate an example of the structure of a lighting unit500for a vehicle according to an exemplary embodiment of the invention.FIG. 1is a front view showing the lighting unit500for a vehicle.FIG. 2is a perspective view showing the lighting unit500for a vehicle with a transparent cover400, shown inFIG. 1, removed.FIG. 2is seen from an oblique and forward view. In the exemplary embodiment, it is assumed that longitudinal, transverse and vertical directions are coincident with the longitudinal, transverse and vertical directions of the vehicle, respectively.

The lighting unit500for a vehicle is a headlamp for irradiating, for example, a low beam. The lighting unit accommodates a plurality of light source units100,200and300in a lamp housing constituted by the transparent cover400and a bracket54. The light source units are classified into the first light source unit100having a circular shape and having a comparatively large diameter, the second light source unit200having a circular shape and having a comparatively small diameter, and the third light source unit300which has a rectangular shape. Each of the light source units has, as a light source, a semiconductor light emitting unit which will be described below, and each of the light units irradiates a light generated from the semiconductor light emitting unit from the forward part of the vehicle. The semiconductor light emitting unit can be, for example, a light emitting diode unit (LED) or a laser diode.

The light source units are attached to the bracket54, which can be turned downward at an angle of approximately 0.5 to 0.6 degrees with respect to the forward part of the vehicle. The bracket54is tiltably attached to the lighting unit500for a vehicle by means of an aiming mechanism for regulating the direction of the optical axis of the light source unit. The light source units100,200and300have predetermined light distribution patterns. The light source units100,200,300collectively form a light distribution pattern required for the lighting unit500for a vehicle.

FIG. 3is an exploded perspective view showing the first light source unit100. The first light source unit100provides an intense irradiation of light on a comparatively small range in the light distribution pattern of the lighting unit500for a vehicle. The first light source unit100comprises a light emitting module10aincluding an LED unit40having a semiconductor light emitting unit44mounted thereon and an attachment16afor surrounding and holding the LED unit40, a light source pedestal50afor positioning and supporting the light emitting module10a, a clip30afor fixing the light emitting module10ato the light source pedestal50a, a reflector80afor reflecting a light emitted from the semiconductor light emitting unit44onto the forward part of the lighting unit, a lens90afor projecting the light reflected by the reflector80aonto the forward part of the lighting unit, and screws28for fastening the reflector80aand the lens90ato the light source pedestal50a. The light emitting module10aholds the LED unit40with a part of lower and side surfaces of the LED unit40exposed. The light source pedestal50adirectly positions the exposed lower and side surfaces of the LED unit40.

The reflector80ais an almost dome-shaped member fixed above the semiconductor light emitting unit44. The reflector80ahas, on an inside surface, a reflecting plane having the shape of part of an almost elliptical sphere, with the optical axis of the first light source unit100as a central axis of the elliptical sphere. Specifically, the reflecting plane is formed so that a section of the reflecting plane has the shape of almost ¼ ellipse, in which common vertex is provided rearward from the semiconductor light emitting unit44. By such a shape, the reflector80acollects a light emitted from the semiconductor light emitting unit44and reflects the light forward close to the optical axis of the lens90a. The lens90aincludes a shade92aon a side of the lens90athat is provided close to the LED unit40. The shade92ashields or reflects a part of a light reflected from the reflector80a, thereby causing a ray forming the light distribution pattern of the first light source unit100to be incident on the lens portion.

The light source pedestal50ahas an assembly reference plane59. The assembly reference plane59determines positions in the direction of the optical axis of the reflector80aand the lens90ain relation to the direction of irradiation of the lighting unit500for a vehicle with high precision with respect to the light source pedestal50a, and a positioning projection57protruded from the assembly reference plane59almost perpendicularly. The positioning projection57determines the positions of the reflector80aand the lens90ain a perpendicular direction to the optical axis with high precision.

Thus, all of the LED unit40, the reflector80aand the lens90acan be positioned with respect to the light source pedestal50awith high precision and are fixed in this state. Consequently, the relative positions of the reflector80aand the lens90awith respect to the semiconductor light emitting unit44are determined with high precision. Accordingly, the light generated from the semiconductor light emitting unit44can be caused to be incident on the lens90awith high precision, thereby forming a light distribution pattern with high precision in the forward part of the vehicle. The reflector80aand the lens90aare taken as a non-limiting example of the optical member according to the invention.

FIG. 4is an exploded perspective view showing the third light source unit300. The third light source unit300is designed to irradiate a light having the largest range in a transverse direction in the light distribution pattern of the lighting unit500for a vehicle. The third light source unit300includes an oblong light emitting module10bhaving a plurality of LED units40arranged and mounted in a line, a light source pedestal50bfor positioning the light emitting module10bthereon in a downward and transverse direction, a clip30bfor fixing the light emitting module10bwith respect to the lower surface of the light source pedestal50b, and a reflector80bfor irradiating a light emitted downward from the semiconductor light emitting unit44over the forward part of the lighting unit500for a vehicle.

The inner reflecting plane of the reflector80bhas a section that is vertical with respect to the longitudinal direction of the lighting unit500for a vehicle. The vertical section includes a portion that is the shape of an almost ¼ ellipse. The vertex of a major axis of the ellipse is provided in contact with the light source pedestal50b. The whole region of the internal reflecting plane of the reflector is provided behind the semiconductor light emitting unit44. By such a shape, the reflector80birradiates lights emitted from the semiconductor light emitting units44arranged in the transverse direction over the largest range in the transverse direction in the light distribution pattern of the lighting unit500for a vehicle, and furthermore, provides a light within a constant range which is smaller in the vertical direction than that in the transverse direction.

FIGS. 5,6and7are perspective views showing the light emitting module10a.FIGS. 5 and 6are exploded perspective views showing the light emitting module10aseen from above and below, respectively.FIG. 7is an assembled perspective view showing the light emitting module10aseen from below.

The light emitting module10aincludes the LED unit40and the attachment16a. The LED unit40has the semiconductor light emitting unit44, a radiating board42, and a contact46. The semiconductor light emitting unit44is directly fixed to an upper surface of the radiating board42The contact46formed on the radiating board42serves to input a power for causing the semiconductor light emitting unit44to emit a light. The attachment16asurrounds and holds the LED unit40in a state in which at least a part of the lower and side surfaces of the radiating board42and the upper part of the semiconductor light emitting unit44are open. In the example, the LED unit40is held in a state in which most of the lower surface of the radiating board42is exposed. Moreover, the attachment16ahas a power supply portion162for supplying a power that causes the semiconductor light emitting unit44to emit a light from an external power plug to the contact46.

The radiating board42is a material having a high thermal conductivity and a low coefficient of thermal expansion, for example, ceramic. The radiating board has an almost rectangular shape. A pair of contacts46are formed on both ends in the longitudinal direction of the radiating board42with the semiconductor light emitting unit44interposed therebetween. The LED unit40further has a dome lens48fixed to the upper surface of the radiating board42and serving to cover the semiconductor light emitting unit44. The dome lens48is, for example, a hollow glass lens and has a diameter which is almost equal to that of the side surface of the radiating board42.

The light emitting module10aholds the LED unit40in a state in which most of the lower surface of the radiating board42is open. Therefore, a heat generated with the light emission of the semiconductor light emitting unit44is radiated efficiently. Accordingly, a rise in the temperature of the semiconductor light emitting unit44is suppressed and a high light emitting efficiency is obtained. Consequently, it is possible to continuously emit a light having a high luminance. Moreover, the light emitting module10aholds the LED unit40in a state in which at least a part of the side surface of the radiating board42is exposed. In the case in which the light emitting module10ais to be fixed to the lighting unit, consequently, the radiating board42can be directly positioned. Thus, it is possible to enhance precision in the position of the semiconductor light emitting unit44, that is, precision in the position of the light source. Furthermore, the attachment16asurrounds and holds the LED unit40. Therefore, there is no possibility that hands or tools might touch the contact46of the LED unit40, and foreign matters can be prevented from sticking to the contact46.

The attachment16aincludes an attachment body160aand a lower surface support member170a. The attachment body160aenergizes the LED unit40downward. The lower surface support member170ais slid and fitted in the attachment body160afrom a side and interposes and holds the LED unit40together with the attachment body160a. According to such a structure, the LED unit40can be stably held by the pressing force of the attachment body160a. Because of the structure in which the lower surface support member170ais slid and fitted in the attachment body160afrom the side, moreover, the height of the light emitting module10acan be reduced.

The attachment body160ahas the power supply portion162. The power supply portion162includes an input portion163connected electrically and a spring terminal164. The input portion163acquires a power for causing the semiconductor light emitting unit44to emit a light when an external power plug is inserted. The spring terminal164presses the upper surface of the contact46downward and is thus connected electrically to the contact46, thereby supplying a power for causing the semiconductor light emitting unit44to emit a light. The positive and negative sides of the spring terminal164come in contact with the contact46by means of a plurality of independent springs, respectively. Accordingly, the contact46and the spring terminal164have a highly reliable electrical connection. More specifically, the light emitting module10acan stably implement the hold of the LED unit40and the supply of a power by the energizing force of the spring terminal164.

As shown inFIG. 6, the attachment body160ahas board guides165and166for positioning the LED unit40with respect to the attachment body160a. The board guides165and166are provided at an almost identical interval to the external shape of the radiating board42, and the side surfaces of the radiating board42are guided by slanted faces provided on their inside surfaces, thereby positioning the LED unit40.

The lower surface support member170ahas an almost U shape. A tip engagement portion174is provided on each of the tips of open ends of the U-shaped lower surface support member, and a rear end engagement portion176is provided in a central part on the side opposite the tip engagement portion174. The attachment body160ais provided with an engagement click167engaged with each of the tip engagement portions174and serving to hold the tip engagement portion174on the attachment body160aside. Furthermore, the attachment body160ais provided with an engagement click168for holding the rear end engagement portion176on the attachment body160aside when the engagement click167and the tip engagement portion174are engaged with each other. The lower surface support member170afurther has a contact holding portion172for holding the lower surface of the LED unit40and maintaining contact between the contact46and the spring terminal164.

The light emitting module10ais assembled by following procedure. First, the LED unit40is assembled into the attachment body160ain a state in which the contact46of the LED unit40is opposed to the spring terminal164of the attachment body160a. Next, the tip engagement portion174and the rear end engagement portion176are slid to be engaged with the engagement click167and the engagement click168respectively with the contact holding portion172of the lower surface support member170aplaced on a lower side. Consequently, the contact holding portion172is guided along the lower surface of the LED unit40and the LED unit40is fixed in a state shown inFIG. 7. Thus, the assembly of the light emitting module10ais finished.

FIGS. 8,9and10are perspective views showing a light emitting module10bfor mounting a plurality of LED units40thereon.FIGS. 8 and 9are exploded perspective views showing the light emitting module10bseen from above and below, respectively.FIG. 10is a perspective view showing a state in which the light emitting module10bis assembled. Although the light emitting module10baccording to the example has three LED units40arranged in a transverse line, the number and array of the LED units40is not restricted by the example. Moreover, the structures that are the same as those as the light emitting module10ashown inFIGS. 5,6and7have been provided the same reference numerals and, therefore, description of these structures will be omitted. Description will be given to different structures from the light emitting module10a.

The light emitting module10bhas three LED units40and an attachment16bfor surrounding and holding each of the three LED units40. The attachment16bincludes an attachment body160band a lower surface support member170b. The attachment body160bhas three pairs of spring terminals164for supplying a power to the three LED units40, respectively. The power is supplied to each of the three pairs of spring terminals164through an input portion163. The lower surface support member170bincludes a contact holding portion172for supporting the back face of a portion in which the spring terminal164and the contact46come in contact with each other.

FIG. 11is a sectional view taken along the contact46and the spring terminal164of the light emitting modules10aand10b. As shown inFIG. 11, the contact holding portion172supports a portion of the lower surface of the radiating board42which is opposite the contact46. Accordingly, it is possible to reliably maintain contact of the spring terminal164with the contact46.

FIG. 12is a perspective view showing a state in which the light emitting module10ais fixed to a light source pedestal50awith a clip30a. Moreover,FIG. 13shows a state in which the clip30aand the attachment16aare omitted fromFIG. 12. As shown inFIG. 13, the light source pedestal50ahas a positioning portion56for directly abutting the side surface of the radiating board42in order to position the radiating board42. The light source pedestal also has a support surface55for directly coming in contact with the lower surface of the radiating board42to support the LED unit40. Furthermore, the light source pedestal50ahas an engagement surface51formed almost parallel with the support surface55below the support surface55.

As shown inFIG. 12, the clip30ahas a pair of upper surface pressing portions32for pressing both left and right ends of the upper surface of the attachment16aagainst the light source pedestal50a. The clip30aalso has a lower surface engagement portion36to be engaged with the engagement surface51shown inFIG. 13. Left and right ends of the upper surface of the attachment16aand the engagement surface51are interposed between the upper surface pressing portions32and the lower surface engagement portion36of the clip30a, thereby pressing the lower surface of the radiating board42against the support surface55through the attachment16a. The upper surface of the attachment16aand the engagement surface51being interposed by the portions clip30acauses the spring terminal164to strongly press against the contact46. Consequently, it is possible to enhance the reliability of the electrical connection of the contact46and the spring terminal164.

Moreover, the light source pedestal50ahas a holding portion58for abutting on the upper surface of the tip of the upper surface pressing portion32. The holding portion58holds the tip of the upper surface pressing portion32so that the light emitting module10can be pressed against the light source pedestal50amore reliably. Accordingly, the clip30acan stably fix the light emitting module10ato the light source pedestal50a, and furthermore, a heat generated from the semiconductor light emitting unit44can be efficiently radiated to the light source pedestal50athrough the radiating board42. Consequently, a reduction in the quantity of a light of the semiconductor light emitting unit44caused by the heat can be prevented.

FIGS. 14 and 15are sectional views showing an A cross-section and a B cross-section ofFIG. 12, respectively. A cutback37is provided on the tip of the lower surface engagement portion36of the clip30a. The cutback37is engaged with an engagement surface53provided vertically below the engagement surface51so that the clip30ais fixed. The clip30ahas a side surface pressing portion34that abuts the side surface of the attachment16a. The side surface pressing portion34presses the side surface of the attachment16aagainst the inner part of the light source pedestal50a(a rightward direction of the drawing) when the cutback37is engaged with the engagement surface53. The attachment16ahas a regulating rib60that abuts a side surface in the radiating board42, the side surface being provided on the opposite side of radiating board42with respect to the positioning portion56. When the side surface pressing portion34presses the side surface of the attachment16aagainst the light source pedestal50a, the regulating rib60presses the radiating board42against the positioning portion56as shown inFIG. 15. Consequently, the LED unit40is directly positioned so that it abuts the light source pedestal50a. There is a constant clearance in a horizontal direction between the attachment16aand the light source pedestal50awhen the radiating board42abuts on the positioning portion56. According to such a structure, the LED unit40is directly positioned with high precision by the light source pedestal50a.

According to the structure, the reference position of the light emitting region of the semiconductor light emitting unit44is positioned with high precision in a horizontal direction with respect to the positioning portion56of the light source pedestal50a. The reflector80aand the lens90aare positioned with high precision with respect to the assembly reference plane59and the positioning projection57as described above. By managing high precision from the positioning portion56to the assembly reference plane59and the positioning projection57, it is possible to maintain the relative positions in the horizontal direction of the reference position of the light emitting region of the semiconductor light emitting unit44with the reflector80aand the lens90awith high precision.

Furthermore, the LED unit40is stably fixed to the support surface55of the light source pedestal50ain a vertical direction. The positions of the reflector80aand the lens90ain the vertical direction are determined with high precision by the positioning projection57as described above. By managing a distance in the vertical direction from the support surface55for supporting the LED unit40to the positioning projection57with high precision, it is possible to maintain the relative positions in the vertical direction of the center of the light emitting region of the semiconductor light emitting unit44with the reflector80aand the lens90awith high precision.

As described above, the relative positions of the light emitting region of the semiconductor light emitting unit44with the reflector80aand the lens90aare maintained with high precision in both the horizontal and vertical directions of the first light source unit100. Accordingly, the first light source unit100can irradiate a light generated from the semiconductor light emitting unit44to an outside with high precision. Furthermore, the radiating board42is mainly made of a material having a high thermal conductivity and a low coefficient of thermal expansion, for example, a metal or ceramic. Therefore, the external shape of the radiating board42is not easily changed by the heat generated from the semiconductor light emitting unit44. Accordingly, the relative positions of the light emitting region of the semiconductor light emitting unit44with the reflector80aand the lens90aare not changed by the generation of the heat of the semiconductor light emitting unit44so that the first light source unit100can irradiate the light of the semiconductor light emitting unit44to the outside with higher precision.

Since all of the light source units100,200and300according to the exemplary embodiment have the same structures, the relative positions of the reflector80aand the lens90awith the semiconductor light emitting unit44are maintained with high precision. In particular, the reference of the semiconductor light emitting unit44, for example, the center of an optical region is aligned with the optical center of the reflector80awith high precision. Accordingly, the lighting unit500for a vehicle can form a predetermined light distribution pattern with high precision.

As is apparent from the above description, according to the exemplary embodiment, the lighting unit500for a vehicle effectively radiates the heat generated from the semiconductor light emitting unit44so that a reduction in the luminance of the semiconductor light emitting unit44can be prevented. By maintaining the relative positions of optical systems such as the reflector80aand the lens90awith the semiconductor light emitting unit44with high precision, moreover, it is possible to form a light distribution pattern with high precision.

In another exemplary embodiment, the attachment16includes a power circuit in the middle of a power supply path between the input portion163and the spring terminal164. The power circuit converts a voltage and a current to be supplied from an external power plug to the input portion163into a current and a voltage for operating the LED unit40. The power circuit is formed on a circuit board incorporated in the attachment16. The circuit board and the power supply portion162are connected to each other through a soft flexible substrate. The flexible substrate is a sufficient length for the incorporation and connection of the circuit board. Since the flexible substrate has a predetermined flexure, it can be prevented from being disconnected even if a vibration is applied to the lighting unit500for a vehicle. Moreover, the attachment16may further include a fail safe circuit or an interface circuit in the middle of the power supply path from the input portion163to the spring terminal164.

The circuit board is provided apart from the radiating board42. Accordingly, the temperature of the semiconductor light emitting unit44can be prevented from being raised by the heat generated from the power circuit. Moreover, it is desirable that the circuit board should be covered with a metal case having a high thermal conductivity and a high radiating property. Consequently, it is possible to efficiently radiate the heat generated from the power circuit. Furthermore, it is desirable that the metal case should be connected to the ground plane of the circuit board. Consequently, it is possible to effectively block the radiation of a noise generated from the power circuit onto an outside.

Moreover, it is desirable that the circuit board should be exchange able with respect to the attachment16. By exchanging power circuits having different properties, for example, current values, consequently, it is possible to easily implement a light emitting module10having a different property, while using the same LED unit40. By causing one power circuit to correspond to one LED unit40, thus, it is possible to advantageously standardize the LED unit40.

While the invention has been described with reference to the exemplary embodiment, the technical scope of the invention is not restricted to the description of the exemplary embodiment. It is apparent to the skilled in the art that various changes or improvements can be made. It is apparent from the description of claims that the changed or improved configurations can also be included in the technical scope of the invention.