Fully passive cooling system and lighting device

Abstract

The object of the present invention is to provide a heat dissipation system and a lighting device that can achieve rapid and efficient cooling. The fully passive heat dissipation mechanism includes a light-emitting device radiator, which has: a heat transfer member; a plurality of heat dissipation fins distributed along the extension direction of the heat transfer member and in physical contact with the heat transfer member; and a plurality of heat dissipation tubes distributed among the heat dissipation fins and connected to the heat dissipation fins. Since the light-emitting device radiator has a plurality of heat dissipation fins and a plurality of heat dissipation tubes are distributed and connected therebetween, the heat at the light-emitting device conducted through the heat pipe can be dissipated from the surface of the heat dissipation fins, causing the surrounding air to be heated to form a hot air flow, which is guided through the heat dissipation tubes, and cold air is supplemented and flows in continuously for cooling, forming a chimney effect, so that sufficient air flow can be generated without using active heat dissipation components, and the heat dissipation efficiency is much higher than that of a conventional passive heat dissipation system.

Description

Technical Field

[0001] The present invention belongs to the field and relates to a fully passive cooling system and a lighting device including the fully passive cooling system. Background Art

[0002] High-power semiconductor devices, such as LEDs, lasers, etc., as a new generation of lighting devices, have the advantages of low energy consumption, fast response speed, small size, long life, etc., and are commonly used in lighting devices such as projectors and lamps. However, currently, the luminous efficiency of LEDs can only reach 10% - 20%. Although the luminous efficiency of laser semiconductors is high, when used in high-definition projection, due to the frequent switching of laser semiconductors, a large amount of energy is consumed during the switching process, resulting in a low overall efficiency, and the remaining energy is converted into heat. With the improvement of user requirements, the brightness, resolution, refresh rate, and power of high-power semiconductor devices such as LEDs and laser lighting devices used in projection and lighting are getting higher and higher. If heat cannot be dissipated in time during use, it will cause the junction temperature of the semiconductor device chip to rise, thereby reducing the luminous efficiency, shortening the service life, and even causing serious problems such as color deviation of components in the projection.

[0003] In the existing applications of semiconductor lighting and projection, most heat sinks increase the convective heat transfer coefficient by increasing the fluidity of the contact between the heat sink and air, the surface area of the heat sink, or improving the structure of the heat sink, so as to improve the heat dissipation capacity of the heat sink. However, on the one hand, the heat dissipation efficiency of such a structure is very limited, and the effect is poor when used in a compact space. On the other hand, the large surface requirement of the heat sink also increases the volume, weight, and cost of the heat sink. In addition, active cooling means such as fans or water-cooled motors are often used in lighting devices such as projectors with high-power lighting devices, and the fans and motors continuously generate noise during use, which greatly affects the user experience. Summary of the Invention

[0004] To overcome the above problems and provide a cooling system and a lighting device that can meet the heat dissipation requirements without using active cooling means, the present invention adopts the following technical solutions.

[0005] The present invention provides a fully passive cooling system disposed in a lighting device including a semiconductor lighting device, characterized in that it includes: a lighting device heat sink for dissipating heat from the semiconductor lighting device, wherein the lighting device heat sink has: a heat transfer member, one end of which is connected to the semiconductor lighting device and the other end of which extends away from the semiconductor lighting device; a plurality of heat dissipation fins distributed along the extension direction of the heat transfer member and in physical contact with the heat transfer member; and a plurality of heat dissipation tubes distributed among the heat dissipation fins and connected to the heat dissipation fins.

[0006] The above-mentioned fully passive cooling system provided by the present invention may further have the following technical features: the heat transfer member is a heat pipe, the plane where the heat dissipation fins are located is perpendicular to the extension direction of the heat pipe, each heat dissipation fin is also provided with a slot and is fixed on the heat pipe through the slot, the heat dissipation pipes are arranged in multiple columns or in a matrix, and each heat dissipation pipe is cross-distributed in the heat dissipation fins far from the semiconductor light-emitting device, and its length direction is perpendicular to the extension direction of the heat pipe.

[0007] Furthermore, the above-mentioned fully passive cooling system may further have the following technical features: each heat dissipation pipe is arranged to pass through more than one heat dissipation fin, the diameter of the heat dissipation pipe is greater than 2 times and less than 5 times the distance between the heat dissipation fins, the thickness of the heat dissipation pipe is less than 1 / 5 of its diameter, and the height of the heat dissipation pipe is greater than 6 times its diameter.

[0008] Even further, the above-mentioned fully passive cooling system may further have the following technical features: one end of the heat transfer member is physically contacted with the semiconductor light-emitting device through a VC heat spreader to conduct heat.

[0009] In addition, the light-emitting device may further include a digital micromirror module cooperating with the semiconductor light-emitting device and a housing made of metal. The fully passive cooling system provided by the present invention may further include a digital micromirror module radiator for dissipating heat from the digital micromirror module. Among them, the digital micromirror module radiator has: a heat transfer plate composed of a first plate portion and a second plate portion extending perpendicular to each other; and a heat dissipation plate group installed on one of the first plate portion and the second plate portion and composed of a plurality of heat dissipation strips extending and connecting perpendicular to each other. The other of the first plate portion and the second plate portion is fixed on the digital micromirror module, and the heat dissipation strips are tightly fixed and attached to the inner wall of the housing through any one of thermal conductive adhesives, thermal conductive pastes, and thermal conductive sheets to conduct heat dissipation through the housing.

[0010] Furthermore, in the above-mentioned fully passive cooling system, the heat transfer plate may be composed of a VC heat spreader.

[0011] In addition, the fully passive cooling system provided by the present invention may further have the following technical features: the semiconductor light-emitting device is a part of the light-emitting optical engine in the light-emitting device, and the fully passive cooling system further includes: a circuit radiator for dissipating heat from the circuit board of the light-emitting optical engine, having: a plurality of circuit heat dissipation fins; and a plurality of circuit heat dissipation pipes. The circuit heat dissipation fins are distributed along the extension direction of the heat transfer member, and the circuit heat dissipation pipes are distributed among the circuit heat dissipation fins and connected to the circuit heat dissipation fins.

[0012] Furthermore, the above-mentioned fully passive cooling system may further have the following technical features: a part of the heat dissipation pipes in the tubular radiator also extend into some of the circuit heat dissipation fins and are connected to the circuit heat dissipation fins, so that the circuit radiator and the tubular radiator share a part of the heat dissipation pipes for heat dissipation.

[0013] The present invention also provides a multi-loop fully passive heat dissipation system, which is arranged in a device including a light-emitting optical engine and a housing made of metal. The light-emitting optical engine has a semiconductor light-emitting device, a digital micromirror module, a circuit board, a lens optical system, and a heat dissipation copper substrate. It is characterized in that it includes: a light-emitting device heat sink for dissipating heat from the semiconductor light-emitting device; a digital micromirror module heat sink for dissipating heat from the digital micromirror module; and a circuit heat sink for dissipating heat from the circuit board. Among them, the light-emitting device heat sink has: a heat transfer member, one end of which is connected to the heat dissipation copper substrate and the other end extends away from the semiconductor light-emitting device; a plurality of heat dissipation fins distributed along the extension direction of the heat transfer member and in physical contact with the heat transfer member; and a plurality of heat dissipation tubes distributed among the heat dissipation fins and connected to the heat dissipation fins. The digital micromirror module heat sink has: a heat transfer plate; and a heat dissipation plate group composed of a plurality of heat dissipation strips extending and connecting perpendicular to each other. The heat dissipation strips are fixed on the inner wall of the housing through any one of thermal conductive adhesives, thermal conductive greases, and thermal conductive sheets, so as to conduct heat dissipation through the housing. The circuit heat sink has: a plurality of circuit heat dissipation fins; and a plurality of circuit heat dissipation tubes. The circuit heat dissipation fins are distributed along the extension direction of the heat transfer member, and the circuit heat dissipation tubes are distributed among the circuit heat dissipation fins and connected to the circuit heat dissipation fins. The heat dissipation paths of the light-emitting device heat sink, the digital micromirror module heat sink, and the circuit heat sink are independent of each other.

[0014] The present invention also provides a light-emitting device, which is characterized in that it includes: a light-emitting optical engine having a semiconductor light-emitting device, a digital micromirror module, a circuit board, a lens optical system, and a heat dissipation copper substrate; a housing; and a heat dissipation system, wherein the heat dissipation system is the fully passive heat dissipation system as described in any one of the above.

[0015] The light-emitting device provided by the present invention may also have the following technical characteristics. Among them, the housing is a metal housing or a composite housing with a heat-resistant material such as plastic covered with metal on the outer surface (such as an aluminum-plastic housing). Heat dissipation holes are provided on two surfaces of the housing corresponding to the two ends of the heat dissipation tube respectively. Heat dissipation holes are provided on two surfaces of the housing corresponding to the two ends of the heat dissipation tube respectively. The total opening area of the heat dissipation holes is not less than 45% of the area of the entire surface.

[0016] Functions and effects of the invention

[0017] According to the heat dissipation system and the light-emitting device provided by the present invention, since the light-emitting device radiator has multiple heat dissipation fins and multiple heat pipes are distributed therebetween, the heat at the light-emitting device conducted through the heat pipes can be dissipated from the surface of the heat dissipation fins, causing the surrounding air to be heated and form a hot air flow. This hot air flow can be guided through the heat pipes, and cold air can flow in to supplement and continuously cool down; thus, a chimney effect can be formed in the light-emitting device radiator of the present invention. Without using active heat dissipation components, sufficient air flow can also be generated, and the heat dissipation efficiency is much higher than that of conventional passive heat dissipation systems. Description of the Drawings

[0018] Figure 1 is a structural diagram of the light-emitting device according to an embodiment of the present invention;

[0019] Figure 2 is an internal structural diagram of the light-emitting device according to an embodiment of the present invention;

[0020] Figure 3 is a structural diagram of the light-emitting device radiator according to an embodiment of the present invention;

[0021] Figure 4 is a top view structural diagram of the light-emitting device radiator in an embodiment of the present invention;

[0022] Figure 5 is a heat transfer principle diagram of the thermosyphon heat pipe according to an embodiment of the present invention.

[0023] Figure 6 is a structural diagram of the circuit radiator according to an embodiment of the present invention;

[0024] Figure 7 is a schematic diagram of tube heat dissipation according to an embodiment of the present invention;

[0025] Figure 8 is a principle diagram of the chimney effect of the present invention;

[0026] Figure 9 is a structural diagram of the digital micromirror module radiator according to an embodiment of the present invention.

[0027] Reference numerals: 100 - light emitting device; 10 - housing; 11 - optical engine accommodating portion; 111 - power switch; 12 - arm portion; 20 - projection optical engine; 21 - heat dissipation substrate; 22 - semiconductor light emitting device; 23 - digital micromirror device module; 24 - lens; 30 - circuit board; 40 - heat dissipation system; 41 - heat sink for light emitting device; 410 - heat transfer plate for light emitting device; 4101 - first heat spreader portion; 411 - heat pipe; 412 - heat dissipation fins; 412A - proximal fins; 412B - distal fins; 413 - connecting plate; 414 - heat dissipation pipe; 42 - heat sink for circuit; 421 - heat dissipation fins for circuit; 422 - connecting plate for circuit; 423 - heat dissipation pipe for circuit; 43 - heat sink for digital micromirror device module; 431 - heat transfer plate for digital micromirror device module; 4311 - heat transfer plate portion for digital micromirror device module; 432 - heat dissipation plate group; 4321 - heat dissipation strip. Detailed implementation manners

[0028] The following takes a projector as an example in conjunction with the accompanying drawings to illustrate the full passive heat dissipation structure of the present invention and the specific implementation manners of the light emitting device.

[0029] <Example>

[0030] Figure 1 is a structural diagram of the light emitting device according to an embodiment of the present invention, Figure 2 is an internal structural diagram of the light emitting device according to an embodiment of the present invention. Figure 2 In, the housing is omitted in order to show the internal structure.

[0031] As Figures 1 - 2 shown, the light emitting device 100 of the present embodiment has a housing 10 and a light emitting optical engine 20, a circuit board 30, and a heat dissipation system 40 accommodated in the housing 10.

[0032] The housing 10 is a hollow shell made of a plastic-coated aluminum plate, and has an optical engine accommodating portion 11 and an arm portion 12.

[0033] The optical engine accommodating portion 11 has a cylindrical outer shape and is hollow inside, and a power switch 111 is provided on one surface. Among them, the power switch 111 is used to control the power on and off of the entire light emitting device 100.

[0034] The arm portion 12 has a rectangular columnar outer shape and is hollow inside. One end thereof is installed on one side of the optical engine accommodating portion 11 and is communicated with the inside of the optical engine accommodating portion 11. The other end can be rotatably installed on other brackets by means of a rotating shaft or the like during use, so as to support the entire light emitting device 100.

[0035] The light emitting optical engine 20 of the present embodiment includes a heat dissipation substrate 21, a semiconductor light emitting device 22, a digital micromirror device module 23, and a lens 24.

[0036] Among them, the number of heat dissipation substrates 21 is multiple, which are respectively arranged corresponding to the semiconductor light-emitting device 22 and the digital micromirror module 23, and are used to conduct the heat generated by the semiconductor light-emitting device 22 and the digital micromirror module 23 outward respectively.

[0037] The semiconductor light-emitting device 22 is an LED light-emitting device, and the number is three; the digital micromirror module 23 is a DMD (Digital Micromirror Device, that is, a digital micromirror module) that cooperates with the semiconductor light-emitting device 22 to achieve projection.

[0038] The lens 24 is installed on one side of the optical engine accommodating portion 11 opposite to the power switch 111. When the light-emitting device 100 operates, the semiconductor light-emitting device 22 and the digital micromirror module 23 cooperate with each other to form an image, and the imaging light is projected outward through the lens 24 from one side of the optical engine accommodating portion 11, thereby forming a projection image.

[0039] In this embodiment, since the arm portion 12 is rotatably installed on other brackets, different orientation states can be presented. For the convenience of description, the following description will be made in the state where the arm portion 12 is horizontally arranged and the lens 13 faces downward. At the same time, the direction close to the light-emitting optical engine 20 is called the near side, and the direction far from the light-emitting optical engine 20 is called the far side.

[0040] The circuit board 30 is used to drive and control the light-emitting optical engine 20, and various components related to drive control are installed thereon. In this embodiment, the number of the circuit boards 30 is two, which are located inside the arm portion 12 close to the light-emitting optical engine 20, and are respectively fixedly installed on two opposite inner side walls of the arm portion 12 by bolts.

[0041] The heat dissipation system 40 includes a light-emitting device heat sink 41, a circuit heat sink 42, and a digital micromirror module heat sink 43. Among them, the light-emitting device heat sink 41 is used to dissipate heat from the semiconductor light-emitting device 22, the digital micromirror module heat sink 43 is mainly used to dissipate heat from the digital micromirror module 23, and the circuit heat sink 42 is mainly used to dissipate heat from the circuit board 30.

[0042] Figure 3 is the structural diagram of the light-emitting device heat sink according to the embodiment of the present invention, Figure 4 is the top view structural diagram of the light-emitting device heat sink in the embodiment of the present invention.

[0043] As Figures 2 - 4 shown, the light-emitting device heat sink 41 includes a light-emitting device heat transfer plate 410, a heat transfer member 411, multiple heat dissipation fins 412, a connection plate 413, and multiple heat dissipation tubes 414.

[0044] As Figure 3As shown, the heat transfer plate 410 of the light-emitting device in this embodiment is an L-shaped VC heat pipe (i.e., Vapor Chamber heat pipe, vacuum chamber heat pipe), and has two heat transfer plate portions 4101 of the light-emitting device that extend perpendicular to each other. Both of these two heat transfer plate portions 4101 of the light-emitting device are fixed to the outside of the heat dissipation substrate 21 corresponding to the light-emitting device 22.

[0045] The heat transfer member 411 is a thermosyphon heat pipe, one end of which is the installation end, and the installation end is bent into an L shape and is fitted and installed on the outside of one heat transfer plate portion 4101 of the light-emitting device. The remaining part of the heat transfer member 411 is perpendicular to its installation end and extends in the distal direction to reach a position close to the distal end of the support arm portion 12.

[0046] In this embodiment, both the heat transfer member 411 and the heat transfer plate 410 of the light-emitting device are hollow structures. The distal end of the heat transfer member 411 is a closed end, and the proximal end is connected to the inside of the heat transfer plate 410 of the light-emitting device. Both the inside of the heat transfer member 411 and the heat transfer plate 410 of the light-emitting device are filled with a heat transfer liquid, such as water.

[0047] Figure 5 It is the heat transfer principle diagram of the thermosyphon heat pipe of the embodiment of the present invention.

[0048] As Figure 5 shown, as a thermosyphon heat pipe, a capillary structure layer (such as a material layer similar to a sponge) is provided on the inner side of the tube wall of the heat transfer member 411. The heat dissipation substrate 21 conducts the heat generated by the semiconductor light-emitting device 22 to the heat transfer plate 410 of the light-emitting device. The heat transfer liquid is heated and evaporated in the heat transfer plate 410 of the light-emitting device and in the installation end of the heat transfer member 411 (equivalent to the evaporation section), and then flows to the distal end and releases heat at the distal end (the distal end is equivalent to the condensation section), thereby achieving high-efficiency heat conduction. In addition, the heat transfer plate 410 of the light-emitting device also has the same structure as the heat transfer member 411 (i.e., it contains a heat transfer liquid and the inner wall is provided with a capillary structure layer), and the heat conduction principle is the same as that, and will not be elaborated here.

[0049] The heat dissipation fins 412 are distributed along the extension direction of the heat transfer member 411, and the plane of each heat dissipation fin 412 is perpendicular to the extension direction of the heat transfer member 411. Specifically, slots are provided at the lower ends of the heat dissipation fins 412, and they are fixed to the heat transfer member 411 by being snapped into the slots of the heat transfer member 411.

[0050] In this embodiment, the heat dissipation fins 412 have two sizes, and their widths are different; among them, the width of the heat dissipation fins 412 on the proximal side is smaller than that of the heat dissipation fins 412 on the distal side. This height difference causes cavities to be formed on both sides of the heat dissipation fins 412 on the proximal side. Refer to Figure 2 for this, and these two cavities are used to accommodate the circuit board 30.

[0051] For convenience of description, the proximal heat dissipation fins 412 are hereinafter denoted as proximal fins 412A, and the distal heat dissipation fins 412 are denoted as distal fins 412B.

[0052] The number of the connecting plates 413 is two. The two connecting plates 413 are formed around the two ends of each heat dissipation fin 412. The two ends of each heat dissipation fin 412 are respectively connected to one connecting plate 413, so that the heat dissipation fins 412 can be fixed to each other and will not spread out.

[0053] In this embodiment, a plurality of heat dissipation tubes 414 are distributed in the distal fins 412B. These heat dissipation tubes 414 are arranged in two columns along the extending direction of the heat transfer member 411. The length direction of each heat dissipation tube 414 is consistent with the length direction of the distal fins 412B (that is, perpendicular to the extending direction of the heat transfer member 411), and the diameter D of each heat dissipation tube 414 is three times the distance L between the two distal fins 412B. The distance between two adjacent heat dissipation tubes 414 in the same column is L.

[0054] Thus, each heat dissipation tube 414 completely penetrates through the two distal fins 412B, and the outer peripheral edges on both sides of the heat dissipation tube 414 are respectively tangent to the other two distal fins 412B adjacent to the two distal fins 412B. That is, each heat dissipation tube 414 is actually connected or in contact with four distal fins 412B. Since the distance between two adjacent heat dissipation tubes 414 in the same column is L, which is exactly the distance between the distal fins 412B, there is no situation where each heat dissipation tube 414 and the adjacent heat dissipation tubes 414 on both sides in the same column are connected or in contact with the same distal fin 412B.

[0055] In addition, in this embodiment, the height of the heat dissipation tube 414 is greater than 6 times its diameter D, and the thickness is less than 1 / 5 of its diameter D. At the same time, the top ends of the heat dissipation tubes 414 are all higher than the top ends of the distal fins 412B, so they all protrude from the top ends of the distal fins 412B.

[0056] As Figure 3 shown, the distal fins 412B are further divided into two groups. The height of the distal fins 412B near the proximal fins 412A is less than that of the distal fins 412B far from the proximal fins 412A (the height is about 1 / 3), so that the upper parts of the heat dissipation tubes 414 in this area are exposed. These heat dissipation tubes 414 with the upper parts exposed are shared by the light-emitting device radiator 41 and the circuit radiator 43, and are denoted as shared heat dissipation tubes 414'. The shared heat dissipation tubes 414' will be further described in combination with the structure of the circuit radiator 43 later.

[0057] Figure 6 is the structural diagram of the circuit radiator according to the embodiment of the present invention.

[0058] As Figure 2 and Figure 6As shown, the circuit radiator 42 is disposed at a position above the proximal fins 412A, and the two circuit boards 30 are respectively located on both sides of the circuit radiator 42.

[0059] The circuit radiator 42 has multiple heat dissipation fins 421 for the circuit, two connecting plates 422 for the circuit, and several heat dissipation tubes 423 for the circuit.

[0060] Similar to the heat dissipation fins 412, the heat dissipation fins 421 for the circuit are distributed along the extension direction of the heat transfer member 411, and there are also two types with different widths: the proximal heat dissipation fins 421 for the circuit have the same width as the proximal fins 412A and are correspondingly disposed above each proximal fin 412A; the distal heat dissipation fins 421 for the circuit have the same width as the distal fins 412B and are correspondingly disposed above the lower distal fins 412B. At the same time, the upper part of the shared heat dissipation tube 414' is also connected to these distal heat dissipation fins 421 for the circuit, and the distribution and connection methods of these shared heat dissipation tubes 414' on the distal heat dissipation fins 421 for the circuit are the same as those in the distal fins 412B. In addition, the upper end of the shared heat dissipation tube 414' also protrudes from the upper end of the heat dissipation fins 421 for the circuit.

[0061] The connecting plates 422 for the circuit are formed around both ends of each heat dissipation fin 421 for the circuit, and both ends of each heat dissipation fin 421 are respectively connected to a connecting plate 421 for the circuit.

[0062] As described above, the heat dissipation fins 421 for the circuit are correspondingly disposed above the heat dissipation fins 412. However, in this embodiment, these heat dissipation fins 412 and the heat dissipation fins 421 for the circuit are not connected but have a small interval from each other. In addition, the connecting plates 421 for the circuit and the connecting plate 414 also have a small interval from each other instead of being connected.

[0063] The heat dissipation tubes 423 for the circuit are distributed between the proximal heat dissipation fins 421 for the circuit with a smaller width and are arranged in a row along the extension direction of the connecting member 411. In this embodiment, the distribution and connection methods of the heat dissipation tubes 423 in the heat dissipation fins 421 for the circuit are the same as those of the heat dissipation tubes 414 in the distal fins 412B, and will not be elaborated here.

[0064] As Figure 1 shown, through holes 121 penetrating the housing are provided on both the upper surface and the lower surface of the arm portion 12 of this embodiment, and the positions where these through holes 121 are distributed exactly correspond to each heat dissipation tube 414 (including the shared heat dissipation tube 414').

[0065] Figure 7 is a schematic diagram of the tube heat dissipation of the embodiment of the present invention. Figure 7Among them, the solid arrow indicates the heat flow direction, and the hollow arrow indicates the gas flow direction.

[0066] As Figure 7 shown, when the light-emitting optical machine 20 works and the circuit board 30 works, both generate a large amount of heat.

[0067] The heat generated at the semiconductor light-emitting device 22 in the light-emitting optical machine 20 can be efficiently conducted to the heat transfer member 411 through the heat transfer plate 410 of the light-emitting device, and then conducted by the heat transfer member 411 to each heat dissipation fin 412 and the heat dissipation tube 414 respectively. When the heat is conducted to each heat dissipation fin 412 and the heat dissipation tube 414, the air around the heat dissipation fin 412 and the heat dissipation tube 414 is heated to generate an upward air flow, and the upward air flow continues to flow upward under the guidance of the heat dissipation tube 414 and the heat dissipation fin 412, and flows out through the through hole 121 on the upper surface; at the same time, since the gas flows upward, the gas volume decreases, and the outside cold air enters through the through hole 121 on the lower surface and flows upward to form a supplement, and continues to cool the heat dissipation fin 412 and the heat dissipation tube 414.

[0068] As Figure 7 shown, the vertical space formed by the staggered connection between the heat dissipation tube 414 and the heat dissipation fin 412 constitutes a structure similar to a chimney. Due to the existence of this chimney structure, on the one hand, the natural convection of air is strengthened, making the air flow smoother, and producing the effect of sufficient cold air cooling without a fan; on the other hand, the structure of the chimney through hole further expands the heat dissipation area and further strengthens the heat dissipation effect. That is, the structure similar to a chimney formed between the heat dissipation tube 414 and the heat dissipation fin 412 forms a chimney effect during the heat dissipation process.

[0069] Figure 8 is the schematic diagram of the chimney effect of the present invention.

[0070] The chimney effect is mainly produced by thermal pressure, which is specifically divided into two parts: the suction of cold air at a certain tube wall temperature (specifically in this embodiment, the temperature finally generated by the heat transfer member 411 transferred to the heat dissipation fin 412 and then conducted to the tube wall of the heat dissipation tube 414); the heat exchange between the hot air in the upper part of the heat dissipation tube above the bottom heat pipe and the tube wall. As Figure 8 shown, for a chimney-type heat dissipation tube structure, the air densities inside and outside the tube are ρ i and ρ o respectively. When the height of the tubular fin is h, the magnitude of the thermal pressure Δp caused is:

[0071] Δp = gh(ρ o – ρ i )

[0072] According to the definition of the air thermal expansion coefficient, the above formula can be written as:

[0073] Δp = ρ o ghβ(T o – T i )

[0074] In the formula, g is the gravitational coefficient, h is the height of the heat dissipation pipe, β is the average value of the air volume expansion coefficient, T o is the air temperature outside the heat dissipation pipe, and T i is the air temperature inside the heat dissipation pipe. Due to the action of the density difference, when the air temperature inside the pipe is higher than that outside the pipe, the air flow inside the pipe flows from bottom to top. According to the thermal pressure principle, the mass flow rate m of the air sucked inside the pipe can be deduced as:

[0075] m = C D A{ρ o ghΔρ} 0.5 = C D A{ρ i ghΔρ} 0.5

[0076] Among them, C D is the local resistance coefficient, generally taking a value of 0.5, and A is the heat dissipation area of the heat dissipation pipe.

[0077] If the cross-sectional area of the heat dissipation pipe is S, the flow velocities at the bottom and top of the heat dissipation pipe can be obtained as:

[0078]

[0079]

[0080] In the formula, V 1 is the air flow velocity at the bottom of the heat dissipation pipe, V 2 is the air flow velocity at the top of the heat dissipation pipe. Since ρ 0 > ρ i , therefore V 1 < V 2 , indicating that the air flow inside the heat dissipation pipe is continuously accelerating.

[0081] From the energy balance of the microelement section of the air inside the heat dissipation pipe, the energy equation can be listed along the air flow direction inside the heat dissipation pipe:

[0082]

[0083] In the formula, R represents the inner radius of the heat dissipation pipe, and the specific heat capacity at constant pressure Cp is the energy absorbed or released by a unit mass of substance when the temperature rises or falls by 1°C or 1K under the condition of constant pressure; T f represents the final air temperature inside the heat dissipation pipe, T s represents the average temperature of the outer surface of the heat dissipation pipe, and x represents the boundary condition. If the average temperature T s, and according to the boundary condition x = 0, T f (0) = T ∞ ,

[0084] The solution of the differential equation can be obtained as follows:

[0085] T f (x) = Ts - (Ts - T∞)exp(-kx)

[0086] where

[0087] The average temperature of the air sucked inside the tube:

[0088]

[0089] It can be obtained that:

[0090]

[0091] Once the average temperature T s of the outer surface of the heat dissipation tube is given, the average temperature of the air sucked inside the tube can be obtained from the above formula, and thus the following can be obtained:

[0092]

[0093] Then, the natural convection heat transfer coefficient inside the tube can be obtained according to the following criterion relation:

[0094]

[0095] From the assumed average temperature, the natural convection heat transfer coefficient λ outside the tube can be obtained in the same way, and thus it is easy to obtain the total heat transfer amount Q of the tubular finned heat dissipation tube.

[0096] After measuring the average temperature of the heat dissipation tube through experiments, the average natural convection heat transfer coefficient can be deduced from the following formula:

[0097]

[0098] In the above formula, λ is the average natural convection heat transfer coefficient of the heat dissipation tube, Q is the heating air film power, A is the heat dissipation area of the heat dissipation tube, and Δt is the heat transfer temperature difference.

[0099] Based on the calculation theory of the total heat transfer of the above-mentioned tubular finned heat dissipation tube, the total heat dissipation is calculated according to the heat generated in the light-emitting optical engine 20 adopted in this embodiment, and then it is possible to calculate how many heat dissipation tubes 414 and heat dissipation fins 412 need to be provided in the heat dissipation mechanism 40 in total, as well as the dimensional relationship between these heat dissipation tubes 414 and heat dissipation fins 412. The results show that when the diameter of the heat dissipation tube is 4 times the distance between the heat dissipation fins, the thickness of the heat dissipation tube is less than 1 / 5 of its diameter, and the height of the heat dissipation tube is greater than 6 times its diameter, the convection formed by the chimney effect is more significant than the natural convection of simple radiation and open surfaces, and an obvious upward heat flow can be formed in the middle chimney channel. In addition, a sufficient heat dissipation area must be ensured, and the heat dissipation fins 412 cannot be too dense. The total opening area of the upper and lower through holes 121 of the housing 10 is not less than 45% of the total upper and lower surface areas, so as not to seriously lose the pressure head generated by the air density difference.

[0100] In addition, when the arm portion 12 rotates 180° to the state where the lens 24 faces downward and the power switch 111 faces upward, the air flow direction of this chimney effect will also reverse, and the same cooling and heat dissipation effect can be achieved.

[0101] Similarly, the heat generated by the circuit board 30 is conducted to the circuit heat dissipation fins 421, the circuit heat dissipation tubes 422, and the shared heat dissipation tubes 414' through the circuit connection plate 422, causing the surrounding air to be heated and generate an upward air flow. The upward air flow is guided by the shared heat dissipation tubes 414' and flows upward, while new cold air enters and replenishes from below.

[0102] Thus, a chimney effect can also be formed at the positions of the heat dissipation tubes 414 (including the shared heat dissipation tubes 414') and the circuit heat dissipation tubes 422, thereby forming a continuous air flow. Even without using active heat dissipation components (such as fans or water cooling), heat dissipation can be continuously carried out through the flowing air.

[0103] Figure 9 It is a structural diagram of the digital micromirror module radiator according to the embodiment of the present invention.

[0104] As Figure 9 shown, the digital micromirror module radiator 43 includes a digital micromirror module heat transfer plate 431 and a heat dissipation plate group 432.

[0105] The digital micromirror module heat transfer plate 431 is an L-shaped VC heat pipe, having two digital micromirror module heat transfer plate portions 4311 extending perpendicular to each other. Among them, one of the digital micromirror module heat transfer plate portions 4311 is fixed on the heat dissipation substrate 21 on the side of the light-emitting optical engine 20, and the other is used to fix the heat dissipation plate group 432. In addition, the digital micromirror module heat transfer plate 431 of this embodiment has the same internal structure as the light-emitting device heat transfer plate 410 (that is, it is hollow inside, contains a heat transfer liquid, and has a capillary structure layer on the inner wall).

[0106] The heat dissipation plate group 432 is composed of a plurality of heat dissipation fins 4321 whose long sides are perpendicularly connected to each other. These heat dissipation fins 4321 form a multi-layer frame structure including a plurality of rectangular cylinders, and the number of rectangular cylinders formed by the heat dissipation fins 4321 in each layer gradually decreases from the side close to the second plate portion 4312 to the side far from the second plate portion 4312, so as to adapt to the cylindrical shape of the optical engine accommodating portion 11 where the light-emitting optical engine 20 is located. In addition, the ends of the heat dissipation fins 4321 in the heat dissipation plate group 432 are adhered to the inner wall of the optical engine accommodating portion 11 through heat-conducting glue.

[0107] Thus, the heat generated by the digital micromirror module 23 in this embodiment can be dissipated outward through the digital micromirror module heat sink 43 and the optical engine accommodating portion 11 in a heat conduction manner.

[0108] As described above, in this embodiment, the heat generated by the semiconductor light-emitting device 22 is dissipated through the light-emitting device heat sink 41, the heat generated by the circuit board 30 is dissipated through the circuit heat sink 42, and the heat generated by the digital micromirror module 23 is dissipated through the digital micromirror module heat sink 43. That is, the heat is dissipated simultaneously and efficiently through three relatively independent heat dissipation circuits. In these three heat dissipation circuits, although the common heat dissipation pipe 414' is connected to the far-side fins 412B and the far-side circuit heat dissipation fins 421 at the same time, such that there is a certain connection relationship between the circuit heat sink 42 and the light-emitting device heat sink 41, due to the weak heat conduction ability of the structure of the common heat dissipation pipe 414', the heat conduction effect between the circuit heat sink 42 and the light-emitting device heat sink 41 can be ignored. Therefore, the three heat dissipation circuits formed by the light-emitting device heat sink 41, the circuit heat sink 42, and the digital micromirror module heat sink 43 can still be regarded as independent of each other.

[0109] Functions and Effects of the Embodiment

[0110] According to the heat dissipation system and the light-emitting device provided in this embodiment, since the light-emitting device heat sink has a plurality of heat dissipation fins and a plurality of heat dissipation pipes are distributed therebetween, the heat at the light-emitting device conducted through the heat pipes can be dissipated from the fin surfaces, causing the surrounding air to be heated to form a heat flow. This heat flow can be guided through the heat dissipation pipes, and cold air can be supplemented and flowed in to continuously cool down. Thus, the light-emitting device heat sink in this embodiment can form a chimney effect, and sufficient air flow can be generated without using active heat dissipation components, and the heat dissipation efficiency is much higher than that of conventional passive heat dissipation systems.

[0111] Furthermore, in the embodiment, the diameter of the heat dissipation tube is 4 times the spacing of the heat dissipation fins. The thickness of the heat dissipation tube is less than 1 / 5 of its diameter, and the height of the heat dissipation tube is greater than 6 times its diameter. Under these dimensional conditions, the convection formed by the chimney effect is more significant than the natural convection of simple radiation and open surfaces, and an obvious upward heat airflow can be formed in the middle chimney channel. In addition, since the heat dissipation fins have a sufficient heat dissipation area and their density distribution is reasonable, the total opening area of the upper and lower through holes of the housing is not less than 45% of the entire upper and lower surface areas, so the pressure head generated by the air density difference will not be seriously lost.

[0112] The heat dissipation system in the embodiment further includes a circuit heat sink. The heat dissipation fins and heat dissipation tubes for the circuit in this circuit heat sink can also form a chimney effect. Further, the circuit heat sink also shares a part of the heat dissipation tubes with the light-emitting device heat sink, so that the space of the two can be made more compact, the chimney effect can be strengthened, and the heat dissipation efficiency can be improved.

[0113] In addition, in the embodiment, a light-emitting device heat sink is also provided at the light-emitting device. The heat dissipation plate group therein is composed of a plurality of heat dissipation strips extending and connecting perpendicularly to each other, and has a large heat dissipation surface area. Therefore, heat can be further dissipated to the light-emitting device by heat conduction in another direction.

[0114] Furthermore, in the embodiment, the heat dissipation substrate and the heat sink of the light-emitting device are both connected through a VC heat pipe. Its thickness is only about 1 / 10 of the thickness of the traditional copper heat dissipation plate, and its weight is about 1 / 20 of the traditional copper heat dissipation plate. It is very thin and light. It can not only make the light-emitting device thinner and lighter, but also transfer heat efficiently, so as to better cooperate with the heat sink and improve the heat dissipation efficiency.

[0115] As described above, this embodiment adopts three heat sink structures, and accordingly forms three heat dissipation circuits. These three heat dissipation circuits are relatively independent, with a compact space and no interference with each other. After testing, when using the light-emitting device and circuit board of this embodiment with a conventional passive heat sink, the highest temperature on the outside of the housing reaches 63°C, and the highest local temperature inside can reach 89°C, and active heat dissipation means must be used; while when using the heat dissipation system of this embodiment, the highest temperature on the outside of the housing reaches 48°C, and the highest local temperature is only 71°C, and this temperature can be maintained during the operation of the light-emitting device. Therefore, no additional active heat dissipation means are required at all, and full passive and silent heat dissipation can be achieved.

[0116] The above embodiments are used to illustrate the specific implementation manners of the present invention, and the light-emitting device of the present invention is not limited to the forms described in the above embodiments.

[0117] For example, in the embodiment, the light-emitting device is described by taking a projector with a semiconductor device LED as the light-emitting device as an example. However, the light-emitting device of this embodiment can also be a semiconductor laser device, a semiconductor infrared device, a semiconductor holographic light-emitting and imaging device, etc., as well as other light-emitting devices other than projectors, such as LED lamps, LED displays, OLED displays, mini-LED displays, micro-LED displays, as long as they have corresponding semiconductor light-emitting devices; moreover, the digital micromirror module can also be other imaging modules other than the DMD in the embodiment.

[0118] In the embodiment, the diameter of the heat dissipation tube is 4 times the spacing of the heat dissipation fins, the thickness of the heat dissipation tube is less than 1 / 5 of its diameter, and the height of the heat dissipation tube is greater than 6 times its diameter, so that the chimney effect can be the best; but in the present invention, the diameter of the heat dissipation tube only needs to be greater than 2 times the spacing of the heat dissipation fins and less than 5 times the spacing of the heat dissipation fins, and the effect of not using active heat dissipation means can be achieved within this size range.

[0119] In the embodiment, the heat transfer member is a heat pipe, but in the present invention, other heat transfer components can also be used; similarly, the heat transfer plates of the light-emitting device and the digital micromirror module in the embodiment are also VCs with a hollow structure, a heat transfer liquid, and a capillary structure layer, which is equivalent to a kind of heat pipe heat transfer plate, but in the present invention, other heat transfer components can also be used to form the heat transfer plates of the light-emitting device and the digital micromirror module, as long as the purpose of efficient heat transfer is achieved. In addition, the number of heat transfer members in the embodiment is one, but the number of heat transfer members in the present invention can also be two or more. For example, a heat transfer member can be added between the heat dissipation fins for the circuit and the proximal fins, or a heat transfer member can be added at other positions, as long as the heat of the heat sources (light-emitting device, digital micromirror module, and circuit board) can be effectively conducted to the heat dissipation components.

[0120] In the embodiment, the heat dissipation strips are adhered to the inner wall of the optical engine housing by thermal conductive adhesive, but in the present invention, they can also be fixed by other thermal conductive connection materials, such as thermal conductive paste, thermal conductive sheet, etc. In addition, components such as heat dissipation fins and heat dissipation tubes can also be fixed to the inner wall of the housing by any thermal conductive connection materials such as thermal conductive adhesive, thermal conductive paste, and thermal conductive sheet.

Claims

1. A multi-loop fully passive cooling system is provided in a lighting device containing semiconductor lighting devices. It is characterized in that it includes: A lighting device heat sink for dissipating heat from the semiconductor lighting device. Among them, the lighting device heat sink has: At least one heat transfer member, one end of which is connected to the semiconductor lighting device, and the other end extends away from the semiconductor lighting device. Multiple heat dissipation fins distributed along the extension direction of the heat transfer member and in physical contact with the heat transfer member; and Multiple heat dissipation tubes distributed among the heat dissipation fins and connected to the heat dissipation fins. The lighting device further includes a digital micromirror module and a housing that cooperate with the semiconductor lighting device. The fully passive cooling system further includes a digital micromirror module heat sink for dissipating heat from the digital micromirror module. Among them, the digital micromirror module heat sink has: A heat transfer plate composed of a first plate portion and a second plate portion extending perpendicular to each other; and A heat dissipation plate group installed on one of the first plate portion and the second plate portion, composed of multiple heat dissipation strips extending and connected perpendicular to each other. The other of the first plate portion and the second plate portion is fixed on the digital micromirror module. The heat dissipation strips are tightly fixed and attached to the inner wall of the housing through any one of thermal conductive glue, thermal conductive paste, and thermal conductive sheet, so as to conduct heat dissipation through the housing. The semiconductor lighting device is a part of the light engine in the lighting device. The fully passive cooling system further includes: A circuit heat sink for dissipating heat from the circuit board of the light engine, having: Multiple circuit heat dissipation fins; and Several circuit heat dissipation tubes. The circuit heat dissipation fins are distributed along the extension direction of the heat transfer member. The circuit heat dissipation tubes are distributed among the circuit heat dissipation fins and connected to the circuit heat dissipation fins.

2. The fully passive cooling system according to claim 1, characterized in that: Among them, The heat transfer member is composed of a heat pipe. The plane where the heat dissipation fins are located is perpendicular to the extension direction of the heat pipe. Each heat dissipation fin is also provided with a slot and is fixed on the heat pipe through the slot. The heat dissipation tubes are arranged in multiple columns or in a matrix, and each heat dissipation tube is cross-distributed in the heat dissipation fins far from the semiconductor lighting device, and its length direction is perpendicular to the extension direction of the heat pipe.

3. The fully passive cooling system according to claim 2, characterized in that: Among them, Each heat dissipation tube is arranged to pass through more than one heat dissipation fin. The diameter of the heat dissipation tube is greater than 2 times the fin pitch and less than 5 times the fin pitch. The thickness of the heat dissipation tube is less than 1 / 5 of its diameter. The height of the heat dissipation tube is greater than 6 times its diameter.

4. The fully passive cooling system according to claim 3, characterized in that: Among them, One end of the heat transfer member is in physical contact with the semiconductor lighting device through a VC heat spreader for heat conduction.

5. The fully passive cooling system according to claim 1, characterized in that: Among them, The heat transfer plate is composed of a VC heat spreader, and the heat transfer member is composed of a heat pipe.

6. The all-passive heat dissipation system according to claim 1, wherein: Among them, A part of the heat dissipation tubes in the light-emitting device heat sink also extends into a part of the heat dissipation fins for the circuit and is connected to the heat dissipation fins for the circuit, so that the circuit heat sink and the light-emitting device heat sink share a part of the heat dissipation tubes for heat dissipation.

7. A light-emitting device, Characterized in that, Comprising: A light-emitting optical engine, having a semiconductor light-emitting device, a digital micromirror module, a circuit board, a lens optical system, and a heat dissipation copper substrate; A housing; And A heat dissipation system, Wherein, the heat dissipation system is the all-passive heat dissipation system according to any one of claims 1 to 6, The housing is a metal housing or a composite housing with a heat-resistant material such as plastic covered with metal on the outer surface, and heat dissipation holes are provided on two surfaces of the housing corresponding to the two ends of the heat dissipation tube respectively, The total opening area of the heat dissipation holes is not less than 45% of the entire upper and lower surface area of the housing.

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