Light emitting device

A light emitting device includes a housing; a light source unit; and a cooling unit provided in the housing to discharge heat to an outside of the housing by means of a gas, the heat being generated by the light source unit. The cooling unit includes an introduction portion, a heat exchange portion, and a circulation portion that guides the gas from the introduction portion to the heat exchange portion. The circulation portion includes a first flow path receiving the gas from the introduction portion, and a second flow path receiving the gas from the first flow path, and being connected to the heat exchange portion. The first flow path includes a portion having a flow path area larger than a flow path area of the introduction portion.

TECHNICAL FIELD

The present invention relates to a light emitting device.

BACKGROUND ART

A light source of a light emitting device generates heat when the light source emits light. The heat raises the temperature of the light source. The temperature of the light source affects a light output of the light source. Hence, the light emitting device may adopt a forced air cooling mechanism. The forced air cooling mechanism forcibly provides air to a heat radiation member.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

Patent Literature 1 discloses a light emitting device including a forced air cooling mechanism. The device of Patent Literature 1 provides an airflow to a heat radiation member by using a known air blower as the forced air cooling mechanism.

Another example of a forced air cooling mechanism is a configuration using compressed air. According to the mechanism using the compressed air, turbulence is likely to be generated in the flow of gas. When turbulence is generated in the flow of gas to be provided to a heat radiation member, a portion that is relatively cool because of easy transfer of heat and a portion that is relatively hot because of difficult transfer of heat are generated in the heat radiation member. As a result, a hot portion and a cool portion are generated in a light source. Further, a temperature difference between the hot portion and the cool portion tends to increase. The temperature of the light source affects a light output of the light source. Namely, when the temperature difference between the hot portion and the cool portion in the light source increases, a variation is generated in the light output of the light source.

An object of the present invention is to provide a light emitting device capable of making a light output as uniform as possible.

Solution to Problem

According to one aspect of the present invention, there is provided a light emitting device including: a housing; a light source unit accommodated in the housing to emit light from a light emitting window of the housing; and a cooling unit provided in the housing to discharge heat to an outside of the housing by means of a gas, the heat being generated by the light source unit. The cooling unit includes an introduction portion that receives a provision of the gas that is compressed, a heat exchange portion that causes the gas to receive the heat generated by the light source unit, and a circulation portion that guides the gas from the introduction portion to the heat exchange portion. The circulation portion includes a first flow path being connected to the introduction portion and extending along a first direction, and a second flow path being connected to the first flow path, extending along a second direction intersecting the first direction, and being connected to the heat exchange portion. The first flow path includes a portion having a flow path area larger than a flow path area of the introduction portion.

The light emitting device includes the cooling unit that discharges the heat to the outside of the housing by means of the gas, the heat being generated by the light source unit. The cooling unit receives the gas that is a heat medium from the introduction portion. Then, the received gas is provided to the heat exchange portion via the circulation portion. Since the gas is compressed, the gas has fluid energy caused by the compression. First, the gas moves from the introduction portion to the first flow path of the circulation portion. When the gas moves from the introduction portion to the first flow path, the flow path area expands. As a result, when the gas moves from the introduction portion to the first flow path of the circulation portion, the fluid energy of the gas is reduced. Further, while the gas moves to the heat exchange portion, the gas passes through the first flow path and the second flow path of the circulation portion. Here, a direction of the second flow path intersects a direction of the first flow path. In that case, a flow direction of the gas changes when the gas moves from the first flow path to the second flow path. At this time, the fluid energy of the gas is further reduced. As a result, the gas of which the fluid energy is sufficiently reduced is provided to the heat exchange portion, so that the turbulence of the flow of the gas in the heat exchange portion is suppressed. Therefore, the flow of the gas in the heat exchange portion is made uniform, so that a deviation in the amount of heat moving from the heat exchange portion to the gas is eliminated. As a result, a temperature variation of the light source unit is reduced, and the light output can be made as uniform as possible.

In the light emitting device, the introduction portion may be disposed on a back surface side of the housing opposite to a main surface of the housing, the emitting window being provided in the main surface. According to this configuration, a path that guides the gas to the heat exchange portion can be simplified.

In the light emitting device, the heat exchange portion may include a receiving port connected to the circulation portion, a heat radiation member that causes the gas to receive the heat generated by the light source unit, and an exhaust port that discharges the gas that has received the heat generated by the light source unit. According to this configuration, the gas flows in from the receiving port. Then, the gas passes through the heat radiation member, and then flows out from the exhaust port. Therefore, a flow direction of the gas can be determined to be directed from the receiving port toward the exhaust port.

In the light emitting device, the number of the receiving ports of the heat exchange portion may be 2 or more. According to this configuration, a distance by which the gas moves to reach the exhaust port after flowing out from each of the receiving ports is shortened. As a result, a deviation in the temperature of the light source unit can be further reduced.

In the light emitting device, the light source unit may include a light emitting surface on which a light emitting element emitting the light is disposed, and a connection surface opposite to the light emitting surface. The heat radiation member may be disposed on a connection surface side. According to this configuration, heat of the light source unit can be reliably transferred to the heat radiation member.

In the light emitting device, the circulation portion may be disposed inside the housing. According to this configuration, the light emitting device can be reduced in size.

In the light emitting device, the circulation portion may be disposed outside the housing. According to this configuration, the degree of freedom of a configuration of the circulation portion can be improved.

In the light emitting device, the cooling unit may include a cooling block in which the heat exchange portion and the circulation portion are formed. The circulation portion may be a space formed by cutting out a part of the cooling block. According to this configuration, the light emitting device including the cooling unit can be easily assembled.

In the light emitting device, the circulation portion may be a pipe member disposed in the housing. According to this configuration, the degree of freedom of a configuration of the circulation portion can be improved.

In the light emitting device, the number of the introduction portions of the cooling unit may be 2 or more. According to this configuration, the flow rate of the gas can be easily increased.

In the light emitting device, the gas may be air or nitrogen. According to this configuration, heat from the heat radiation member can be reliably received.

In the light emitting device, the heat radiation member may be a heat sink including a plurality of fins. According to this configuration, an efficiency of passing heat to the gas can be improved.

In the light emitting device, the housing may include an exhaust window that further discharges the gas to the outside, the gas being discharged from the exhaust port. The exhaust window may be provided in a central portion of the housing. According to this configuration, the gas that has received heat can be reliably discharged to the outside of the housing.

Advantageous Effects of Invention

According to the light emitting device of the present invention, the light output can be made as uniform as possible.

DESCRIPTION OF EMBODIMENTS

Hereinafter, modes for carrying out the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference signs, and duplicated descriptions will be omitted.

As illustrated inFIG.1, a light emitting device1has a long shape. The light emitting device1emits light in a predetermined direction. In the following description, a light emission direction is a Z direction (first direction). In addition, the light emitting device1includes a forced air cooling mechanism for a light source that emits light. The forced air cooling mechanism uses compressed gas to be provided from the outside as a heat medium. The forced air cooling mechanism discharges heat to the outside by causing the gas to receive heat generated from the light source. The gas may be, for example, air or nitrogen.

The light emitting device1includes a housing10, a circuit unit20, and a light emitting unit30.

The housing10accommodates the circuit unit20and the light emitting unit30. The housing10is a long rectangular parallelepiped extending in a predetermined direction. A longitudinal direction of the housing10is an X direction (second direction). The housing10includes an upper case11and a lower case12. The upper case11and the lower case12are combined with each other to form a space that accommodates the circuit unit20and the light emitting unit30.

The upper case11includes a case upper surface11a, a case front surface11b, and a case rear surface11c. The case upper surface11ais a back surface of the housing10. The upper case11includes a connector hole11hand an exhaust window11w. The connector hole11his an inlet for the compressed gas. The connector hole11his provided in the case upper surface11a. The exhaust window11wis an outlet for the gas that has received heat. The exhaust window11wis provided in the case front surface11b. The lower case12includes a case lower surface12aand a case end surface12b. The case lower surface12ais a main surface of the housing10. The lower case12includes a light emitting window12w. The light emitting window12wis provided in the case lower surface12a. Namely, in the housing10, a surface that emits light (case lower surface12a) is a surface opposite to a surface that receives the gas (case upper surface11a).

Incidentally, the discharge of the gas from the exhaust window11wmay be natural exhaust or forced exhaust. For example, a duct may be provided in the exhaust window11wto suppress the turbulence of airflows around the light emitting device1.

The circuit unit20provides electrical functions required for operation of the light emitting device1. For example, the circuit unit20supplies electric power for emitting light to the light emitting unit30. The circuit unit20includes a circuit substrate21and an electronic component22. The electronic component22is disposed on a main surface21aof the circuit substrate21. The main surface21aof the circuit substrate21faces the case front surface11b.

The light emitting unit30emits light. Further, the light emitting unit30causes heat to transfer to the outside, the heat being generated because of the generation of the light. The light emitting unit30is disposed between the circuit substrate21and the case rear surface11c. The light emitting unit30faces a back surface21bof the circuit substrate21. The light emitting unit30includes a light source unit40and a cooling unit50.

A light emitting characteristic of a light emitting element provided in the light source unit40is affected by temperature. For example, when the light source unit40becomes hot, a characteristic of light to be emitted changes. Further, when there is a temperature variation inside the light source unit40, a variation is also generated in the characteristic of the light to be emitted. Hence, the cooling unit50prevents the temperature of the light source unit40from becoming too high, and reduces the temperature variation in the light source unit40. For example, the range of the temperature variation (temperature difference) in the light source unit40may be within 10° C. Further, the temperature difference is preferably within 8° C. and more preferably within 5° C.

The light source unit40generates light. The light may be, for example, ultraviolet light. The light source unit40is accommodated in the housing10. The light source unit40includes four light emitting panels41. The light emitting panel41includes a light emitting surface41aon which light emitting diodes42(light emitting elements, refer toFIG.3) emitting ultraviolet light are disposed, and a connection surface41bon a back side with respect to the light emitting surface41a. The light source unit40is disposed between the cooling unit50and the case lower surface12a. The light emitting surface41afaces the light emitting window12w. The connection surface41bof the light emitting panel41is in contact with the cooling unit50.

As illustrated inFIG.2, the cooling unit50includes an introduction portion51, a cooling block52, a cover53, and a heat sink54as physical elements. The cooling block52includes a block upper surface52a, a block lower surface52b, a pair of block end surfaces52c, a block front surface52d, and a block rear surface52e. The cooling unit50includes the introduction portion51, a circulation portion60, and a heat exchange portion70from the viewpoint of functionality. The introduction portion51, the circulation portion60, and the heat exchange portion70are disposed in order from the block upper surface52atoward the block lower surface52b(Z direction). The arrangement order coincides with order in which the gas flows.

The introduction portion51is a connecting component that connects a gas pipe (not illustrated) to the cooling block52. The introduction portion51is connected to the circulation portion60via the connector hole11hof the upper case11.

The gas to be received by the introduction portion51may be high-pressure air. The high-pressure air is compressed air to be obtained from an air supply facility that is generally disposed in a factory. Such an air supply facility is configured to include a compressor, an aftercooler, a tank, an air filter, an air dryer, an air regulator, and the like. Then, pressure is adjusted at the end of the air supply facility by the air regulator for pressure adjustment. As a result, the compressed air of a desired pressure can be used. Normally, the pressure of the compressed air to be supplied in a factory or the like is approximately 1 MPa. Therefore, the pressure of the gas to be received by the introduction portion51may be 1 MPa. Further, the introduction portion51may receive the compressed air of which the pressure is lowered less than 1 MPa. For example, the pressure of the gas to be received by the introduction portion51may be 0.3 MPa. Namely, the range of the pressure of the gas to be received by the introduction portion51may be a range from a maximum pressure of the compressed air to be supplied from a factory facility or less to higher than the atmospheric pressure.

The circulation portion60guides the gas provided to the introduction portion51to the heat exchange portion70. Namely, the circulation portion60forms a flow path for the gas. The circulation portion60is formed of some holes and grooves provided in the cooling block52, and the cover53. The circulation portion60includes a first flow path61and a second flow path62.

The first flow path61receives the gas from the introduction portion51. Then, the first flow path61passes the gas to the second flow path62. The first flow path61includes a flow path hole61aand a connection hole61b.

The flow path hole61ais a hole extending from the block upper surface52atoward the block lower surface52b. Namely, the flow path hole61aextends in the Z direction. The flow path hole61aincludes an opening formed in the block upper surface52a. The introduction portion51is connected to the opening. The flow path hole61aincludes a bottom.

The connection hole61bis a hole extending from the block rear surface52etoward the block front surface52d. Namely, the connection hole61bextends in a Y direction. An extending direction (Y direction) of the connection hole61bintersects an extending direction (Z direction) of the flow path hole61a. Specifically, the extending direction of the connection hole61bis orthogonal to the extending direction of the flow path hole61a. Namely, the flow path hole61aand the connection hole61bform an L-shaped flow path. The connection hole61bis a through-hole. One end of the connection hole61bis connected to the flow path hole61a. The other end of the connection hole61bis connected to the second flow path62.

The second flow path62receives the gas from the first flow path61. Then, the second flow path62passes the gas to the heat exchange portion70. The second flow path62includes a flow path groove62aand a connection groove62b.

The flow path groove62ais a groove extending from one block end surface52ctoward the other block end surface52c. Namely, the flow path groove62aextends in the X direction. An extending direction of the flow path groove62ais aligned with a longitudinal direction of the light emitting device1. The extending direction (X direction) of the flow path groove62aintersects the extending direction (Y direction) of the connection hole61b. Specifically, the extending direction of the flow path groove62ais orthogonal to the extending direction of the connection hole61b. The flow path groove62ais dug from the block front surface52dtoward the block rear surface52e. The flow path groove62aincludes an opening formed in the block front surface52d. The opening is closed by the cover53. A position at which the flow path groove62ais connected to the connection hole61bis substantially the center in the extending direction (X direction) of the flow path groove62a. The connection grooves62bare connected to both ends of the flow path groove62a. Namely, the cooling block52is provided with two connection grooves62b.

The flow path area is expanded in a portion in which the flow path groove62ais connected to the connection groove62b. The portion of which the flow path area is expanded is referred to as a widened portion62s(refer toFIG.3). The flow path area may be an area of a flow path cross section orthogonal to a flow line. In that case, a flow direction of the gas changes in a portion in which the flow path groove62ais connected to the connection groove62b. The flow path area changes at the corner. Specifically, the flow path area gradually increases from the flow path groove62atoward the widened portion62s. Then, the flow path area gradually decreases from the widened portion62stoward the connection groove62b. Incidentally, the flow path area may be constant from the widened portion62stoward the connection groove62b.

The connection groove62bextends from the block upper surface52atoward the block lower surface52b. Namely, the connection groove62bextends in the Z direction. Similarly to the flow path groove62a, the connection groove62bis dug from the block front surface52dtoward the block rear surface52e. A depth of the connection groove62bmay be the same as a depth of the flow path groove62a. The flow path groove62aincludes an opening formed in the block front surface52d. The opening of the flow path groove62ais closed by the cover53. One end of the connection groove62bis connected to the second flow path62. The other end of the connection groove62bis connected to the heat exchange portion70.

The heat exchange portion70causes the gas to receive heat generated by the light source unit40. The heat exchange portion70includes a third flow path71and the heat sink54(heat radiation member).

The third flow path71provides a space serving to exchange heat. Namely, the third flow path71accommodates the heat sink54. Similarly to the flow path groove62a, the third flow path71extends from the one block end surface52ctoward the other block end surface52c. Namely, the third flow path71extends in the X direction. A length of the third flow path71in the X direction may be longer than a length of the second flow path62. An extending direction (X direction) of the third flow path71intersects an extending direction (Z direction) of the connection groove62b. Specifically, the extending direction (X direction) of the third flow path71is orthogonal to the extending direction (Z direction) of the connection groove62b.

The third flow path71is dug from the block front surface52dtoward the block rear surface52e. A depth of the third flow path71is deeper than the depth of the flow path groove62aof and the depth of the connection groove62bof the second flow path62. In other words, a bottom surface of the third flow path71is located closer to a block rear surface52eside than a bottom surface of the second flow path62. The third flow path71includes an opening formed in the block front surface52d. The opening of the third flow path71is closed by the cover53.

The third flow path71includes a receiving port71aconnected to the connection groove62b. As described above, the cooling block52includes the two connection grooves62b. Therefore, the third flow path71includes two receiving ports71a. The receiving port71amay be provided, for example, at a position at which a distance from the one block end surface52cto the receiving port71ais ¼ the length of the cooling block52. For example, when the first flow path61is assumed as being provided at the center of the cooling block52, the receiving port71amay be provided at the center of a distance from the block end surface52cto the first flow path61. In addition, the receiving ports71amay be provided directly above the heat sinks54disposed at both ends among four heat sinks54.

The third flow path71includes an exhaust port71b. The exhaust port71bis provided in the cover53. The exhaust port71bis provided between a pair of the receiving ports71a. Specifically, the exhaust port71bis provided substantially at the center in a longitudinal direction (X direction) of the cover53.

The heat sinks54pass heat to the gas. The heat sinks54are disposed in the third flow path71. The heat sinks54do not protrude from the third flow path71. In other words, a width of the heat sink54is shorter than the depth of the third flow path71. The heat sinks54are disposed symmetrically with respect to the center of the cooling block52as an axis. The heat sink54includes a fin base56and a plurality of fins57. The fin base56is in contact with a lower wall surface71cof the third flow path71. The lower wall surface71cis located on a back surface side with respect to the block lower surface52b. In other words, the lower wall surface71cand the block lower surface52bare interposed between the fin base56and the light source unit40.

The plurality of fins57are plate-shaped members extending upward from the fin base56. Upper ends of the fins57are not in contact with an upper wall surface71dof the third flow path71. The plurality of fins57are disposed to be separated from each other in a depth direction (Y direction) of the third flow path71. As a result, a plurality of grooves are formed in a direction from the one block end surface52ctoward the other block end surface52c. In addition, a plurality of the fins57may be disposed in the X direction.

As illustrated inFIG.3, the gas moves in order of the introduction portion51(refer toFIG.1), the circulation portion60, and the heat exchange portion70. First, the gas moves from the gas pipe to the introduction portion51. Next, the gas moves from the introduction portion51to the circulation portion60. Next, the gas moves in order of the first flow path61and the second flow path62in the circulation portion60. In more detail, the gas moves from the flow path hole61aof the first flow path61to the second flow path62via the connection hole61b.

Here, a flow path area of the flow path hole61ais larger than a flow path area of the introduction portion51. In a case where each of the flow path hole61aand the introduction portion51is assumed as being a pipeline, when the size of a cross-sectional area of the pipeline changes, a fluid energy loss is generated because of a change in the cross-sectional area. The fluid energy loss causes a pressure loss. The gas moving through the introduction portion51has a high pressure. However, the pressure of the gas decreases because of an expansion from the flow path area of the introduction portion51to the flow path area of the flow path hole61a. Namely, the momentum of the high-pressure gas weakens. Further, the extending direction of the connection hole61bis different from the extending direction of the flow path hole61a. According to this configuration, the gas moving inside the flow path hole61acollides with a bottom surface of the flow path hole61a. The collision dissipates a part of the fluid energy of the gas. As a result, the fluid energy of the gas is further reduced.

Next, the gas that has moved to the flow path groove62aof the second flow path62branches into a flow toward the one block end surface52cand a flow toward the other block end surface52c. Next, the branched gas moves to the heat exchange portion70via the connection grooves62b(refer to arrow G2). Here, the extending direction of the flow path groove62ais different from the extending direction of the connection groove62b. In that case, the gas collides with a wall surface of the flow path groove62aor the connection groove62b, and then flows along the wall surface of the connection groove62b. The collision further reduces the fluid energy of the gas. Namely, while the gas moves from the introduction portion51to the heat exchange portion70, in other words, while the gas moves through the circulation portion60, the gas loses fluid energy. Namely, the gas loses fluid energy as the gas moves downstream. In this state, the movement of the gas located on a downstream side is not governed by fluid energies such as the kinetic energy and the pressure energy of the gas. It can rather be said that the gas on a downstream side is pushed out by the movement of the gas on an upstream side. The turbulence of flow is unlikely to be generated because of such movement of the gas.

The gas that has moved to the heat exchange portion70moves to the third flow path71via the receiving ports71a. The gas flows and falls from the receiving ports71atoward the lower wall surface71cof the third flow path71. Then, the gas that has moved to the third flow path71moves between the fins57. In more detail, the gas flows along base portions of the fins57. Alternatively, it can be said that the gas flows along a main surface of the fin base56to which the base portions of the fins57are connected.

The fin base56is in contact with the lower wall surface71c. Heat generated by the light source unit40transfers to the cooling block52via the connection surface41band the block lower surface52b(refer to arrow H1). Further, the heat transfers to the fin base56via the lower wall surface71c(refer to arrow H2). Namely, the fin base56is relatively hot in the heat sinks54. Then, when the main flow of the gas is formed in a portion that is relatively hot, a temperature difference between the heat sinks54that are a high-temperature side and the gas that is a low-temperature side increases. A heat flow rate moving from the high-temperature side to the low-temperature side is proportional to the temperature difference. Therefore, heat transfers more efficiently from the heat sinks54to the gas, for example, when the main flow of the gas is formed on a base end side of the fins57(fin base56side) than when the main flow of the gas is formed on a tip side of the fins57. The gas flows toward the exhaust port71bwhile receiving heat (refer to arrow HG).

Then, as illustrated inFIG.4, the gas moves from the exhaust port71bto the outside of the third flow path71(refer to arrow HG1). As described above, the exhaust port71bis provided in the cover53. The circuit substrate21is disposed on a back side of the cover53with respect to a surface of the cover53which is in contact with the cooling block52. Therefore, the gas discharged from the exhaust port71bflows between the cover53and the circuit substrate21(refer to arrow HG2). Then, the gas passes through a gap between the circuit substrate2and the lower case12(refer to arrow HG3), and flows between the circuit substrate21and the case front surface11b. The electronic component22is disposed in a space between the circuit substrate21and the case front surface11b. Therefore, the gas is also capable of receiving heat from the electronic component22while moving through the space. Namely, the gas is used not only to cool the light source unit40, but also to cool the circuit unit20. Then, the gas is discharged from the exhaust window11wof the upper case11(refer to arrow HG4).

The light emitting device1includes the cooling unit50that discharges heat to the outside of the housing10by means of the gas, the heat being generated by the light source unit40. The cooling unit50receives the gas that is a heat medium from the introduction portion51, and provides the gas to the heat exchange portion70via the circulation portion60. Since the gas is compressed, the gas has fluid energy caused by the compression. First, the gas moves from the introduction portion51to the first flow path61of the circulation portion60. When the gas moves from the introduction portion51to the first flow path61, the flow path area expands. As a result, when the gas moves from the introduction portion51to the first flow path61of the circulation portion60, the fluid energy of the gas is reduced. Further, while the gas moves to the heat exchange portion70, the gas passes through the first flow path61and the second flow path62of the circulation portion60. Here, a direction of the second flow path62intersects a direction of the first flow path61. In that case, a flow direction of the gas changes when the gas moves from the first flow path61to the second flow path62. At this time, the fluid energy of the gas is further reduced. As a result, the gas of which the fluid energy is sufficiently reduced is provided to the heat exchange portion70, so that the turbulence of the flow of the gas in the heat exchange portion70is suppressed. Therefore, the flow of the gas in the heat exchange portion70is made uniform, so that a deviation in the amount of heat moving from the heat exchange portion70to the gas is eliminated. As a result, the temperature variation of the light source unit40is reduced, and the light output can be made as uniform as possible.

Second Embodiment

As shown inFIG.5, a light emitting device1A of the second embodiment includes a housing10A, the circuit unit20, and a light emitting unit30A. A length of a light receiving region of the light emitting device1A of the second embodiment is longer than a length of a light receiving region of the light emitting device1of the first embodiment. Therefore, a region that has to be cooled by a cooling unit50A of the second embodiment is larger than a region that has to be cooled by the cooling unit50of the first embodiment. Hence, the cooling unit50A of the second embodiment adopts a configuration for reducing the temperature difference in an expanded region to be cooled. Namely, the cooling unit50A of the light emitting device1A is different from the cooling unit50of the light emitting device1of the first embodiment. Hereinbelow, the cooling unit50A will be described in detail. The other housing10A and the circuit unit20will be described as necessary and a detailed description will be omitted.

As illustrated inFIG.6, the cooling unit50A includes the introduction portion51, a cooling block52A, a cover53A, and the heat sink54. A length of the cooling block52A is longer than the length of the cooling block52of the first embodiment. Hence, five heat sinks54are disposed in a third flow path71A of the cooling unit50A. In addition, the number of the introduction portions51of the cooling unit50of the first embodiment is 1. On the other hand, the number of the introduction portions51of the cooling unit50A of the second embodiment is 3. Namely, the cooling unit50A receives a supply of the gas from three places.

As illustrated inFIG.7, a first flow path61A includes three flow path holes61aand three connection holes61b. One flow path hole61ais connected to one connection hole61b. Namely, one flow path hole61ais not connected to two or more connection holes61b. Therefore, the first flow path61A includes three paths, in each of which the flow path hole61ais connected in series to the connection hole61b.

A second flow path62A includes three flow path grooves62aand three connection grooves62b. One flow path groove62ais connected to one connection hole61b. Namely, one flow path groove62ais not connected to two or more connection holes61b. Further, one flow path groove62ais connected to one connection groove62b, and one flow path groove62ais not connected to two or more connection grooves62b. According to the above-described connection configuration, the second flow path62A includes three paths, in each of which the flow path groove62ais connected in series to the connection groove62b.

The third flow path71A has three receiving ports71aand two exhaust ports71b(refer toFIG.6). A first receiving port71ais disposed in the vicinity of the one block end surface52cof the cooling block52. A second receiving port71ais disposed in the vicinity of the other block end surface52cof the cooling block52. A third receiving port71ais disposed at the center of the cooling block52A.

Incidentally, the connection grooves62bdisposed on both sides may not have a constant groove width. Namely, the connection groove62bmay include a portion of which the groove width is expanded. For example, the widened portion of the connection groove62bis provided between an inlet of the flow path groove62aand an outlet that is the receiving port71a, the inlet having the same groove width as that of the widened portion. The widened portion is provided at a corner at which the flow direction changes. A groove width of the widened portion is larger than the groove width of the flow path groove62a. In addition, the groove width of the widened portion is larger than a width of the receiving port71a.

The exhaust port71bis disposed between a pair of the receiving ports71aadjacent to each other.

The gas moves in order of the introduction portion51, a circulation portion60A, and a heat exchange portion70A. As described above, the circulation portion60A includes three paths, in each of which the flow path hole61a, the connection hole61b, the flow path groove62a, and the connection groove62bare connected in series to each other. Therefore, the number of the paths through which the gas is supplied to the heat exchange portion70A is 3.

Similarly to the light emitting device1of the first embodiment, the light emitting device1A of the second embodiment is capable of making a temperature distribution of a light source unit40A as uniform as possible. As a result, the light emitting device1A of the second embodiment is capable of making the light output as uniform as possible.

Further, according to this configuration, the distance from the receiving port71ato the exhaust port71bis shortened. For example, when the distance from the receiving port71ato the exhaust port71bis long, a large amount of heat easily transfers from the heat sink54to the gas in the vicinity of the receiving port71ain which the temperature difference is large. Namely, the temperature of the light source unit40A is easily lowered. Hence, the gas continues to receive heat as the gas approaches the exhaust port71b, so that the temperature of the gas gradually rises. In that case, since the temperature difference between the gas and the heat sinks54decreases, the transfer of heat from the heat sinks54to the gas becomes difficult as the gas approaches a downstream side. Namely, the decreasing of the temperature of the light source unit40A becomes difficult.

On the other hand, when the distance from the receiving port71ato the exhaust port71bis short, the distance at which the gas receives heat from the heat sinks54is shortened. As a result, the rising of the temperature of the gas that has reached the exhaust port71bbecomes difficult. In that case, the temperature difference between the heat sinks54and the gas can be prevented from decreasing too much. Therefore, a state is easily maintained where heat easily transfers from the heat sinks54to the gas.

The light emitting device of the present invention is not limited to the above embodiments.

First Modification Example

FIG.8illustrates a light emitting device1B of a first modification example. A circulation portion60B of the light emitting device1B may be formed of a pipe member. The circulation portion60B receives the gas from one inlet, and provides the gas to a heat exchange portion70B from two outlets.

The circulation portion60B includes a receiving pipe63a, a branch pipe63b, and supply pipes63c. A flow path area (cross-sectional area) of each of the receiving pipe63aand the branch pipe63bmay be the same as a flow path area of the supply pipe63c. The receiving pipe63aforms the first flow path61. The branch pipe63band the supply pipes63cform the second flow path62. The receiving pipe63aextends from the case upper surface11atoward the case lower surface12a. An upstream end of the receiving pipe63aprotrudes from the case upper surface11a. The introduction portion51is connected to the protruding portion. A downstream end of the receiving pipe63ais disposed inside a housing10B. The branch pipe63bis connected to the downstream end of the receiving pipe63a.

The branch pipe63bextends from the one case end surface12btoward the other case end surface12b. One end portion of the branch pipe63bis disposed in the vicinity of the one case end surface12b. The other end portion of the receiving pipe63ais disposed in the vicinity of the other case end surface12b.

The supply pipe63cis a separate component from the branch pipe63b. The supply pipes63care connected to end portions of the branch pipe63b. The supply pipe63cdirects a flow direction of the gas toward the heat sink54of the heat exchange portion70B. A supply port of the supply pipe63cfaces the heat sink54of the heat exchange portion70B.

Incidentally, the branch pipe63band the supply pipes63cmay be formed by bending the vicinities of both ends of one cylindrical member. Namely, the branch pipe63band the supply pipes63cmay be an integral component.

The light emitting device1B including the circulation portion60B formed of a pipe-shaped component is also capable of obtaining the same effects as those of the light emitting device1of the first embodiment.

Second Modification Example

FIG.9illustrates a light emitting device1C of a second modification example. Similarly to the light emitting device1B of the first modification example, in the light emitting device1C of the second modification example, a circulation portion60C disposed inside a housing10C is formed of a pipe-shaped member. On the other hand, in the first modification example, the gas is received from one inlet, and the gas is provided to the heat exchange portion70B from two outlets. In the second modification example, two sets of configurations are provided in each of which the gas is received from one inlet and the gas is provided to a heat exchange portion70C from one outlet. The circulation portion60C includes the receiving pipes63a, connection pipes63d, and the supply pipes63c. One receiving pipe63a, one connection pipe63d, and one supply pipe63care connected in series to each other to form one path.

The light emitting device1C including the circulation portion60C of the second modification example is also capable of obtaining the same effects as those of the light emitting device1of the first embodiment. In addition, the circulation portion60C of the second modification example receives the gas from two receiving pipes63a. Therefore, the flow rate of the gas to be supplied to the heat exchange portion70C is easily increased.

Third Modification Example

FIG.10illustrates a light emitting device1D of a third modification example. In the light emitting device1B of the first modification example, the receiving pipe63a, the branch pipe63b, and the supply pipe63chave the same flow path area. The light emitting device1D of the third modification example includes the branch pipe63band supply pipes63ethat are disposed inside a housing10D. The receiving pipe63a, the branch pipe63b, and the supply pipe63ehave different flow path areas. The flow path area of the receiving pipe63ais the same as the flow path area of the branch pipe63b. In other words, the flow path area is constant from an inlet of the receiving pipe63ato an outlet of the branch pipe63b. On the other hand, the flow path area of the supply pipe63echanges continuously along a flow direction.

The flow path area of an inlet of the supply pipe63eis the same as the flow path area of the outlet of the branch pipe63b. The flow path area of the supply pipe63eexpands continuously toward a downstream side. Then, the flow path area is maximized in a portion of the supply pipe63eof which the curvature is maximized. Thereafter, the flow path area decreases continuously toward an outlet of the supply pipe63e.

The light emitting device1D including the circulation portion60D of the third modification example is also capable of obtaining the same effects as those of the light emitting device1of the first embodiment. In addition, since the flow path area of the supply pipe63eis made variable, a state (flow speed, pressure) of the gas to be supplied to a heat exchange portion70D can be controlled to a more suitable state.

Fourth Modification Example

FIG.11illustrates a light emitting device1E of a fourth modification example. In the light emitting device1of the first embodiment, the gas is received from one inlet, and the gas is provided to the heat exchange portion70from two outlets. In the light emitting device1E of the fourth modification example, the gas is received from two inlets, and the gas is provided to a heat exchange portion70E from one outlet. Similarly to the light emitting device1of the first embodiment, a cooling unit50E of the light emitting device1E of the fourth modification example includes a groove provided in a cooling block52E and a cover that closes the groove.

A first flow path61E includes two flow path holes61aand two connection holes61b. One flow path hole61ais disposed in the vicinity of the one block end surface52c. The other flow path hole61ais disposed in the vicinity of the other block end surface52c. A second flow path62E includes one flow path groove62aand one connection groove62b. The flow path groove62aextends from the one block end surface52ctoward the other block end surface52c. The connection holes61bare connected to both ends of the flow path groove62a. The connection groove62bis connected to the center of the flow path groove62a. The receiving port71aof a third flow path71E is provided at the center of a distance from the one block end surface52cto the other block end surface52c. The exhaust ports71bof the third flow path71E are provided at both ends of the third flow path71E.

The light emitting device1E including the cooling unit50E of the fourth modification example is also capable of obtaining the same effects as those of the light emitting device1of the first embodiment.

Fifth Modification Example

FIG.12illustrates a light emitting device1F of a fifth modification example. As described above, the circulation portion60of the light emitting device1of the first embodiment is provided inside the housing10. Here, from the viewpoint of obtaining a cooling effect of making the light output as uniform as possible, the fluid energy of the gas may be reduced until the gas is supplied to the heat exchange portion, and the reduction of the fluid energy is achieved by a flow path configuration from the introduction portion to the heat exchange portion. Namely, when such a flow path configuration is provided, a satisfactory cooling characteristic can be obtained. At this time, whether the flow path configuration is disposed inside the housing or is disposed outside the housing is important from a perspective of the assembly of the light emitting device or from a perspective of the size of the light emitting device. However, the flow path configuration does not affect an effect of making the light output as uniform as possible.

Hence, the light emitting device1F of the fifth modification example includes a circulation portion60F disposed inside a housing10F and a heat exchange portion70F disposed outside the housing10F. The circulation portion60F includes a receiving pipe63aF, a branch pipe63bF, and supply pipes63cF. An introduction portion51F is connected to the receiving pipe63aF. Further, the receiving pipe63aF is connected to substantially the center of the branch pipe63bF. The branch pipe63bF extends in a longitudinal direction of the housing10F. The supply pipes63cF are connected to both ends of the branch pipe63bF. An output port60hof the circulation portion60F which is an output port of the supply pipe63cF is connected to the case upper surface11aof the housing10F. The gas of which the momentum is reduced flows from the output port60htoward the heat sink54of the heat exchange portion70F. Incidentally, the housing10F may be provided with at least one or more holes to which the output ports60hare connected. The light emitting device1F including the circulation portion60F of the fifth modification example is also capable of obtaining the same effects as those of the light emitting device1of the first embodiment.

Hereinafter, results of confirmation of the actions and effects of the light emitting devices of the embodiments using analysis or the like will be described.

Comparative Example 1

As Comparative Example 1, in a cooling structure of a configuration that was different from the cooling unit50of the present embodiment, the flow of gas was confirmed by numerical calculation. In the cooling structure of Comparative Example 1, high-pressure gas is directly provided to a heat sink. As illustrated inFIG.13, in the cooling structure of Comparative Example 1, a heat sink154is disposed on an extension line of a flow direction of the gas that has flowed out from an introduction portion151. Then, a member that obstructs the flow of the gas is not disposed between the introduction portion151and the heat sink154.

FIG.13illustrates the flow direction of the gas ejected from the introduction portion151to a space in which the heat sink154is disposed. Referring toFIG.13, the gas flows linearly from the introduction portion151, and then collides with the heat sink154. The colliding gas receives a reaction force from the heat sink154to change the flow direction. The change of the flow direction is irregular. As a result, the flow of the gas is turbulent in the space in which the heat sink154is disposed. Namely, it can be said that the gas is in a turbulent state. The turbulent state simply means that the flow direction is irregularly turbulent, and does not necessarily have to coincide with the definition of a turbulent flow in fluid dynamics. According to such a flow of the gas, fresh gas is supplied to a region on the heat sink154, the region being located on a flow line of the gas to be ejected from the introduction portion151. Namely, heat easily transfers from the heat sink154to the gas. As a result, the heat sink154is cooled. On the other hand, fresh gas is not provided to a region on the heat sink154, the region being not located on the flow line of the gas. As a result, a portion of which the cooling is easily and a portion of which the cooling is difficult are generated in the heat sink154. Namely, a non-uniform temperature distribution is generated in a light source unit that is thermally connected to the heat sink154. From a result of Comparative Example 1, it could be predicted that a large temperature gradient was generated to cause an increase in temperature difference between a high-temperature portion and a low-temperature portion of the light source unit.

Comparative Example 2

In Comparative Example 1, in the cooling structure of the configuration that was different from the cooling unit50of the present embodiment, an increase in temperature difference between the high-temperature portion and the low-temperature portion of the light source unit was predicted. In Comparative Example 2, this prediction was confirmed.

FIG.14is a graph illustrating a result of the confirmation. The horizontal axis of the graph indicates a position in a longitudinal direction of a light emitting device. The vertical axis of the graph indicates a temperature of a light source unit. 0 in on the horizontal axis indicates the position of one block end surface. 0.38 m indicates the position of the other block end surface. Then, the light emitting device of Comparative Example 2 supplies high-pressure gas from three places such as the one end portion, the other end portion, and the center. The pressure of the gas was, for example, 0.3 MPa. Namely, a heat exchange portion includes three receiving ports. In the graph, arrows A1, A2, and A3indicate the positions of the receiving ports. Then, the heat exchange portion includes two exhaust ports. Arrows B1and B2indicate the positions of the exhaust ports.

Referring to the graph, it was found that the temperature of the light source unit decreased at its maximum at the positions (arrows A1, A2, and A3) of the receiving ports. Then, it was found that the temperature of the light source unit increased from the receiving port toward the exhaust port and a highest temperature was reached in the vicinity of the exhaust port. For example, a temperature difference between a lowest temperature and the highest temperature difference was approximately 12° C. Namely, it was found that satisfactory heat transfer from the light source unit to the gas became difficult as the gas approached the exhaust port from the receiving port. Therefore, as predicted in Comparative Example 1, it could be confirmed that a large temperature gradient was generated to cause an increase in temperature difference between a high-temperature portion and a low-temperature portion of the light source unit.

In Example 1, the effects of the cooling unit50A of the second embodiment were confirmed. In Example 1, a central portion of the cooling unit50E of the second embodiment was adopted as an analysis model.FIG.15illustrates a result of analysis of the flow of gas moving from the first flow path61A to the third flow path71A. InFIG.15, the flow speed of the gas is illustrated by shading. Referring toFIG.15, it was found that the flow speed of the gas was reduced in each of a portion in which the flow path hole61awas connected to the connection hole61b, a portion in which the connection hole61bwas connected to the flow path groove62a, and a portion in which the flow path groove62awas connected to the connection groove62b. Further, it was found that the main flow of the gas was formed on a lower side of the third flow path71A, namely, on a lower side of the heat sinks54. From this result, it was found that according to structures for securing an air volume such as the connection hole61band the connection groove62b, the generation of a turbulent flow was suppressed and the gas could be provided to the heat sinks54in a laminar flow state. As a result, it was confirmed that the heat exhaust efficiency of the heat sinks54was improved since the flow of the gas was formed without waste.

In Example 2, the effects of the cooling unit50A of the second embodiment were confirmed. In Example 2, the cooling unit50A of the second embodiment was adopted as an analysis model.FIG.16illustrates a result of analysis of the flow of gas moving from the second flow path62to the third flow path71A. InFIG.16, the flow speed of the gas is illustrated by shading. Referring toFIG.16, it was found that the flow speed of the gas was relatively large on upstream sides of corners of the flow path groove62aand the connection groove62b. On the other hand, it was found that the flow speed of the gas was significantly reduced on a downstream side of the corner of the connection groove62band particularly, on a downstream side of the receiving port71aof the third flow path71A. Further, it was found that the main flow of the gas was formed on the lower side of the third flow path71A, namely, a bottom portion side of the heat sinks54. From this result, it was confirmed that similarly to the cooling unit50of the first embodiment, the heat exhaust efficiency of the heat sinks54was also improved by the cooling unit50A of the second embodiment.

In Example 3, the same confirmation as in Comparative Example 2 was performed. Namely, a temperature distribution of a light source unit in a longitudinal direction of a light emitting device was confirmed. Analysis conditions (for example, pressure of high-pressure air: 0.3 MPa) are the same as those in Comparative Example 2. In Example 3, the same configuration as the cooling unit50A of the light emitting device1A of the second embodiment was adopted as an analysis model.FIG.17is a graph illustrating a result of the confirmation.

Referring to the graph, a tendency of a rough temperature distribution was similar to that of Comparative Example 2 (FIG.14). Namely, it was found that the temperature of the light source unit decreased at its maximum at the positions (arrows A1, A2, and A3) of receiving ports. Then, it was found that the temperature of the light source unit40increased from the receiving port71atoward the exhaust port71band a highest temperature was reached in the vicinity of the exhaust port71b. On the other hand, a temperature difference between a lowest temperature and a highest temperature was clearly smaller than that in Comparative Example 2. The temperature difference in Comparative Example 2 was approximately 12° C. On the other hand, the temperature difference in Example 3 was approximately 4° C. Namely, as a result of an improvement in temperature gradient, it was found that heat transfer from the light source unit40to the gas was performed even when the gas approached the exhaust port71b(for example, arrow B1) from the receiving port71a(for example, arrow A1). From this result, it could confirmed that a flow direction of the gas having a momentum was changed by the connection groove62bor the like to generate the flow of the gas having a good cooling efficiency and thus, a temperature distribution of the light source unit40could be made as uniform as possible.

REFERENCE SIGNS LIST