JP5367745B2 - Method and electronic device for improving heat exchange rate of heat sink - Google Patents

Abstract

The invention provides a method for improving heat exchange efficiency of a radiator and an electronic device. The potential of the radiator is close to the reference potential to inhibit the accumulation of dust. A radiation unit (200) is housed in a system chassis (105) of a portable computer (100). The heat from a CPU (121) is released by the radiation unit through a heat tube (201) and the radiator (209). The radiation unit (200) is combined with a metal frame (111) only by screws (206a, 206b). The radiator (209) performs electrostatic induction to increase the potential by an electrified body (325) on a main board (113). The radiator is connected with an AC/DC adapter by a grounding layer (321), and a grounding terminal of a power supply jack (311) of a chassis (327), thus the electric charge is neutralized.

Description

  The present invention relates to a technique for improving the heat exchange rate of a heat sink, and more particularly to a technique for suppressing dust accumulation on a heat sink for heat dissipation of an electronic device.

  The computer is equipped with a heat radiating unit that forcibly exhausts heat generated in the housing by a heat radiating fan to radiate heat. A heat dissipation unit of a computer having a high mounting density of electronic components generally includes a heat dissipation fan, a heat sink, and a heat pipe. The heat sink includes a large number of heat exchange fins that form a narrow slit-like air flow path. The heat dissipating fan diffuses the heat generated by the heating element inside the housing into the air taken from the outside of the housing, and further passes the air between the slits of the heat sink and releases it out of the housing. The heat exchange fins exchange heat between the heat of the heating element and the heat of the air by direct contact with a heat sink or indirect contact through a heat pipe.

  Patent Document 1 discloses a technique for preventing dust contained in air from adhering when cooling air is blown from a fan by removing static electricity charged from the surface of a liquid crystal panel. Patent Document 2 discloses a technique for collecting dust from the inside by providing a sheet having an electrostatic force in the vicinity of an opening of a housing of an electronic device on which a fan unit is mounted.

JP 2004-219572 A JP 2009-176161 A

  The heat exchange rate of the heat sink greatly depends on the contact area between the heat exchange fin and air and the amount of air passing through the air flow path. The air flowing into the housing contains dust, but if this accumulates at the entrance or inside of the air flow path, the air flow rate decreases and the heat exchange rate decreases. If you disassemble the heat dissipation units of multiple computers that have been operating for a long time, you can observe the dust that has accumulated at the entrance of the heat sink in most of them.

  Computers that operate in dusty environments are considered difficult to suppress dust accumulation, and have been dealt with by periodic disassembly and cleaning and fan unit filters. However, disassembling and cleaning is a heavy burden for the user, and even if a filter is provided, the small dust passing through it accumulates on the heat exchange fins, and in reality there is no effective means. Therefore, it is necessary to investigate the cause of dust accumulation so that dust does not accumulate at the entrance of the heat sink.

  Accordingly, an object of the present invention is to provide an electronic apparatus or a portable computer including a heat dissipation unit that suppresses the accumulation of dust on the heat sink. It is a further object of the present invention to provide a method for improving the heat exchange rate of a heat sink.

  It is well known that dust easily adheres to charged objects, but since the heat dissipation unit is generally connected to the metal part of the housing, the cause of dust accumulation is the charge of the heat sink so far. Although not considered, in the present invention, it has been specified that the cause of dust accumulation is an increase in potential due to charging of the heat sink. The principle of the present invention is to connect the vicinity of the heat exchange fin of the heat sink to the charge neutralizing conductor so that its potential is close to the ground potential. The present invention is based on the recognition that the potential distribution of the entire heat dissipating unit is not uniform in the electronic device in operation, and at least the vicinity of the heat exchange fin of the heat sink is formed by a conductive material. Connect to a conductor and bring it closer to earth potential.

  In the first aspect of the present invention, the heat radiating unit of the electronic device is housed in a heat sink including a plurality of heat exchange fins forming an air flow path and a fan chamber coupled to the heat sink. Including a heat dissipation fan. The charge neutralizing conductor has a predetermined capacitance as an independent conductor and can exchange charges with the heat sink to neutralize the heat sink charge. The neutralizing means connects the vicinity of the heat exchange fin and the charge neutralizing conductor. Therefore, the potential in the vicinity of the heat exchange fin approaches the potential of the charge neutralizing conductor.

  When the heat sink is charged, the positive charge is charged and the potential is increased, and the negative charge is charged and the potential is decreased. In either case, the absolute value of the potential with respect to the ground potential is large. Then, it becomes easy to adhere dust. The causes of the heat sink charging include frictional charging due to friction between air and heat exchange fins, and induction charging due to electrostatic induction from a charged body in the vicinity of the heat sink. Here, a case where the potential of the heat sink increases due to charging will be described as an example.

  In the case of frictional charging, it is possible to suppress an increase in potential to some extent as long as it is connected to the charge neutralizing conductor even at a portion away from the heat sink in the entire heat dissipation unit. However, in the case of induction charging, as long as a charged body is present in the vicinity of the heat sink, even if a portion away from the heat sink is connected to the charge neutralization conductor, the increase in the potential of the heat sink cannot be suppressed. According to the present invention, the increase in the potential of the heat sink can be suppressed by connecting the vicinity of the heat exchange fin to the charge neutralizing conductor. The heat dissipating unit has a heat pipe connected to the heat sink and a heat receiving part connected to the heat pipe and directly contacting the central processing unit, so that the heat dissipating unit is coupled to the housing at the heat receiving part. Can be configured. At this time, it is conceivable that the heat receiving portion and the charge neutralizing conductor are electrically connected.

  However, in this case, the heat receiving portion and the heat sink are farthest apart from each other, and even if the potential of the heat receiving portion matches the potential of the charge neutralizing conductor, the potential of the heat sink may increase due to induction charging. . In the present invention, even in the heat dissipating unit configured as described above, the potential of the heat sink can be brought close to the potential of the charge neutralizing conductor. When the heat receiving unit is in direct contact with the central processing unit, the heat sink cannot be coupled to the housing because it is particularly necessary to ensure that contact. Connect the neutralization object with the vicinity of the heat exchange fin so that the can move freely.

  The static elimination means can be constituted by a lead wire. It is desirable to connect the lead wires so as to suppress the potential increase at the entrance of the heat sink where dust is most likely to accumulate. For example, the leads can be connected to the surface of the heat sink or fan chamber along the boundary between the heat sink heat exchange fins and the fan chamber. When the power cable for supplying power to the electronic device is provided with a ground line, the static elimination means can be connected to the ground terminal of the power jack. By connecting to the ground terminal, the potential of the heat sink can be brought close to the ground potential most effectively. The charge neutralizing conductor can be a ground plane to which a ground terminal of an electronic component or an electrical component is connected.

  In the second aspect of the present invention, the static eliminator is applied to a portable computer having a system housing for storing electrical components and a palm rest. The portable computer includes a ground plane that provides a reference potential for the electrical components. One of the neutralizing means is connected to the surface of the heat sink or fan chamber that is near the boundary between the heat sink and the fan chamber, and the other is connected to the ground plane.

  One of the static eliminating means is connected from one side surface to the other side surface in the width direction of the heat sink. By doing so, all the heat exchange fins can be brought close to the reference potential effectively. When the portable computer has a power jack having a voltage terminal to which the voltage line of the AC / DC adapter is connected and a ground terminal to which the ground line is connected, by connecting the ground terminal and the ground plane, An AC / DC adapter can be used as the charge neutralizing conductor.

  The ground plane can be part of the EMI shield. Specifically, when the portable computer has a mother board on which an electronic device is mounted and a metal frame that is arranged on the upper side of the mother board and connected to the ground plane, the ground plane is connected to the mother board. Located on the underside of the board, the ground plane and metal frame can constitute EMI shielding for electrical components. EMI shielding is an effective charge neutralization conductor due to its large area for enclosing and shielding the electrical components as a whole, and thus large capacitance. Further, when the system casing is made of a conductive material, the capacitance of the charge neutralizing conductor can be increased by providing a connection means for connecting the ground plane and the system casing.

  The portable computer may include a power jack including a voltage terminal to which the voltage line of the AC / DC adapter is connected and a ground terminal to which the ground line is connected. If the ground plane is connected to the ground terminal of the power jack, and the static eliminator is connected to the ground terminal, the capacitance of the charge neutralizing conductor can be increased by the AC / DC adapter connected to the power jack. .

  When the secondary circuit of the AC / DC adapter is electrostatically insulated from the primary circuit, the capacitance held by the secondary circuit of the AC / DC adapter reduces the potential of the heat sink. Can do. Further, when the ground line of the secondary circuit of the AC / DC adapter is electrostatically connected to the ground line of the primary circuit, the potential of the heat sink can be brought close to the ground potential.

  When the palm rest is made of metal, the capacitance of the charge neutralization conductor can be increased by providing a connection means to connect the ground plane to the palm rest, When the hand is touched, the capacitance of the user's body can also be used as a charge neutralizing conductor. Further, when the palm rest is plastic, a metal part is embedded therein, and the electrostatic capacity of the human body can be used as a charge neutralization conductor by electrically connecting the heat sink and the metal part.

  According to the present invention, it is possible to provide an electronic apparatus or a portable computer including a heat dissipation unit that suppresses the accumulation of dust on the heat sink. Furthermore, the present invention has provided a method for improving the heat exchange rate of the heat sink.

It is the perspective view which looked at notebook PC100 concerning an embodiment of the invention from the front and back. It is a disassembled perspective view of notebook PC100. 2 is a perspective view showing an outer shape of a heat dissipation unit 200. FIG. FIG. 4 is a perspective view showing a state in which the heat radiating unit 200 of FIG. 3 is turned over and the cover of the fan chamber 215 is removed. It is the figure which modeled notebook PC100 in order to show the mode of an electrostatic field. It is a figure which shows the result of having performed the dust accumulation acceleration test for measuring the effect when lead wire 317,319 is connected to heat sink 209,211. 3 is a plan view of the fan unit 200 with the heat sink 209 as the center. FIG.

  FIG. 1 is a perspective view of a notebook PC 100 according to an embodiment of the present invention as viewed from the front and rear. FIG. 2 is an exploded perspective view of the notebook PC 100. FIG. 3 is a perspective view showing the outer shape of the heat dissipation unit 200. FIG. 4 is a perspective view showing a state in which the heat radiating unit 200 of FIG. 3 is turned over and the cover of the fan chamber 215 is removed. FIG. 5 is a diagram in which the notebook PC 100 is modeled to show the state of the electrostatic field.

  In FIG. 1, the notebook PC 100 is in a state where a display housing 101 that holds a liquid crystal display device (LCD) 102 is opened from a system housing 105. A keyboard 104 and an optical disk drive (ODD) 103 are attached to the system casing 105. Exhaust ports 106 and 107 and intake ports 108 and 109 each having a louver are formed on the side surface of the system housing 105.

  A palm rest 313 is disposed on the surface of the system housing 105 in front of the keyboard 104 to fix the palm when the keyboard is operated. The palm rest 313 is made of non-insulating ABS resin. An elongated metal band 315 is embedded in the palm rest 313 over the entire left and right direction of the system housing 105. A power jack 311 for connecting an AC / DC adapter that supplies power to the notebook PC 100 is provided on the side surface of the system housing 105. In this specification, the term “connection” is used in the sense of being electrically connected, and the term “coupling” is used regardless of whether it is coupled and electrically connected for mechanical purposes. Used in. The power jack 311 includes a voltage terminal 311a to which a DC voltage is supplied from an AC / DC adapter and a ground terminal 311b (FIG. 5).

  Throughout this specification, a ground line or a ground terminal means a system connected to the ground plane 321 (FIG. 5) of two wirings of a DC power supply system. It shall mean a system connected to the ground that can be regarded as zero potential. When the ground line is connected to the ground line through the ground line of the AC / DC adapter or power cable, it approaches the ground potential. When the notebook PC 100 is placed on a highly insulating object such as a desk and the ambient air humidity is low, the notebook PC 100 becomes an independent conductor from an electrostatic point of view, and the ground line is different from the ground. Although it becomes a potential, it can be treated as being much closer to the ground potential than the potential of the heat sinks 209 and 211 when charged.

  The system casing 105 is entirely formed of a conductive magnesium alloy. As described in JP 2009-169498 A, the system housing 105 is formed of glass fiber reinforced resin (GFRP), which is a non-conductive material, in the peripheral portion of the bottom surface that communicates with the side wall, The central portion of the bottom surface can also be formed of a carbon fiber reinforced resin (CFRP) that is a conductive material.

  In FIG. 2, a metal frame 111, a mother board 113, a hard disk drive (HDD) 117, a battery pack 119, and the like are mounted on a system housing 105. The metal frame 111 is a strength member formed of a magnesium alloy, and the heat dissipation unit 200 is also attached thereto. On the mother board 113, a central processing unit (CPU) 121, a video chip 125, a north bridge 127, a main memory 129, and other semiconductor elements are mounted.

  Since the notebook PC 100 contains electronic devices and electrical components that operate with high-frequency signals inside the system housing 105, the notebook PC 100 is likely to emit electromagnetic waves to the outside or to be affected by electromagnetic waves entering from the outside. Therefore, the notebook PC 100 is electromagnetically shielded to prevent such electromagnetic interference (EMI). Hereinafter, this electromagnetic shielding is referred to as EMI shielding. EMI shielding has a structure in which electromagnetic waves emitted from the inside and electromagnetic waves entering from the outside are reflected or absorbed and not allowed to pass by covering the electronic device with a plate material formed of a conductive material such as aluminum or copper. Yes.

  In the notebook PC 10, a ground plane 321 (see FIG. 5) and a metal frame 111 disposed over almost the entire lower surface of the mother board 113 are electrically connected to each other and function as EMI shielding. The electronic device and other electrical components mounted on the mother board 113 are composed of a signal line through which a high-frequency pulse signal passes and a ground line that applies a reference potential to the signal line. The EMI shield provides a common reference potential to the electronic devices and electrical components of the notebook PC 100, and the ground line is connected to the EMI shield. The metal frame 111 is fixed to the system housing 105 with screws 323a and 323b (see FIG. 5).

  In FIG. 3, the heat radiating unit 200 includes a fan chamber 215, a centrifugal heat radiating fan 213, heat pipes 201 and 203, heat sinks 209 and 211, and heat receiving portions 205 and 207. The fan chamber 215 and the heat sinks 209 and 211 are each formed of a metal material having good thermal conductivity such as aluminum or copper. Fan chamber 215 is thermally coupled to heat sink 209 and heat sink 211. The fan chamber 215, the heat pipes 201 and 203, the heat sinks 209 and 211, and the heat receiving units 205 and 207 are electrically connected.

  The heat sinks 209 and 211 are formed with a plurality of slit-like air flow paths in order to increase the contact area between the metal material and air to increase the heat exchange rate. The heat sink 211 will be described as an example. A plurality of heat exchange fins 211c are arranged in parallel between the upper plate 211a and the lower plate 211b (FIG. 4), and a plurality of air flow paths are provided between the heat exchange fins 211c. Slits are formed. The end of the heat pipe 203 on the low temperature side is coupled to the upper plate 211a.

  The heat sinks 209 and 211 can dissipate a large amount of heat as the temperature of the air passing through the interior is lower and as the amount of air is larger. The heat receiving unit 205 absorbs the heat generated by the CPU 121 and transmits the heat to the heat pipe 201, and the heat pipe 201 transmits the heat to the heat sink 209. The heat receiving unit 207 absorbs heat from the video chip 125 and the north bridge 127 and transmits the heat to the heat pipe 203, and the heat pipe 203 transmits to the heat sink 211.

  When the heat dissipation unit 200 is attached to the frame 111, the position of the heat sink 209 is aligned with the exhaust port 106, and the position of the heat sink 211 is aligned with the exhaust port 107. In the heat dissipation unit 200, the four corners of the heat receiving portion 205 are fixed to the metal frame 111 with four screws 206a to 206d. The heat receiving unit 205 absorbs the heat of the CPU 121 that generates the largest amount of heat in the notebook PC 100. The heat receiving unit 205 absorbs heat by directly contacting the flat surface of the CPU 121 with a flat contact surface.

  Therefore, the contact surface of the heat receiving unit 205 and the surface of the CPU 121 need to be in close contact so that no gap is opened. Therefore, the heat radiation unit 200 is fixed with screws 206a to 206d while bringing the heat receiving portion 205 and the surface of the CPU 121 into complete contact. When the heat radiating unit 200 is fixed, the heat sinks 209 and 211, the fan chamber 215, and the heat pipes 201 and 203 move freely so that they do not come into contact with any part of the system casing. If the heat sinks 209 and 211 are fixed to the metal frame 111, there is a gap between the heat receiving unit 205 and the CPU 121, resulting in poor contact or mechanical stress on the heat radiating unit 200. It is not desirable to fix the part other than the heat receiving part 205 to the frame 111.

  Further, the gap between the outlets of the heat sinks 209 and 211 and the inner surfaces of the exhaust ports 106 and 107 is filled with a plastic sponge. Therefore, in the heat dissipation unit 200, there is little possibility that a portion other than the heat receiving portion 205 coupled by the four screws 206 a to 206 d is electrically connected to the metal frame 111 and the side wall of the system housing 105. Further, since the screws 206a to 206d are intended for mechanical coupling, there may be a case where an electrical connection suitable for discharging electric charges is not made. The present invention can be applied regardless of whether or not the heat receiving portion 205 and the metal frame 111 are electrically connected.

  The heat dissipating unit 200 heats the air by sucking air in the axial direction of the heat dissipating fan 213 from the openings formed on the upper surface and the lower surface of the fan chamber 215 when the heat dissipating fan 213 mounted in the fan chamber 215 rotates. The heat is dissipated outside the system housing 105 by exhausting from the sinks 209 and 211. The heat dissipating unit 200 dissipates not only the heat received from the heat receiving units 205 and 207 but also the heat of other electronic devices housed in the system housing 105.

  In addition to the air inlets 108 and 109, the system housing 105 is substantially formed with openings in terminals such as a network cable, a USB device, an external display, and a memory card mounting portion. When the heat radiating fan 213 rotates, the inside of the system housing 105 becomes negative pressure, and the air flow generated by the inflow of air from these openings diffuses the heat of the electronic device and is exhausted through the exhaust ports 106 and 107. To dissipate heat to the outside. The air flowing into the system housing contains small dust.

  When dust adheres to the entrance of the charged heat sinks 209 and 211 that communicate with the fan chamber 215, it is charged and adsorbs other dust. The dust once adsorbed does not leave even when the electric charges of the heat sinks 209 and 211 are discharged, and further adsorbs other dust when the notebook PC 100 is operated next time. If dust accumulates at the entrance of the heat sinks 209 and 211, the flow rate of air passing through the heat sinks 209 and 211 decreases, so that sufficient heat exchange cannot be performed, and the temperature of the heat sinks 209 and 211 increases. The rotational speed of the heat radiating fan 213 increases or the system stops. Further, the increase in the temperature of the heat sinks 209 and 211 causes the temperature of the system housing 105 to increase, which causes discomfort to the user who works with the notebook PC 100 placed on the knee.

  In FIG. 4, lead wires 317 and 319 for preventing charging are connected to the heat sinks 209 and 211 by solder. The lead wires 317 and 319 are stripped at positions where they come into contact with the heat sinks 209 and 211. Lead wires 317, 319 are connected from one end of heat sink 209, 211 to the other end so as to be connected to lower plates 209b, 211b at positions corresponding to all heat exchange fins of heat sink 209, 211 It extends.

  In FIG. 4, lead wires 317 and 319 are connected to the surfaces of the lower plates 209 b and 211 b along the boundary between the heat sinks 209 and 211 and the fan chamber 215. As shown in FIG. 5, the ends of the lead wires 317 and 319 are connected to the ground terminal 311 b of the power jack 311. The ground terminal 311b is connected to the ground plane 321 by a lead wire 329. The ends of the lead wires 317 and 319 are further connected to a metal band 315 formed on the palm rest 313.

  Here, with reference to FIG. 7, a desirable position where the lead wire 319 is connected on the heat sink 2011 side will be described. FIG. 7 is a plan view of the fan unit 200 with the heat sink 211 as the center. Since the position where dust accumulates is the entrance of the heat sink 211, it is effective for preventing dust accumulation to bring the potential of the heat exchange fin 211c at this position as close to the reference potential as possible.

  Now, the direction of the air flow A of the heat sink 211 is referred to as the depth direction, and the direction perpendicular thereto is referred to as the width direction. In the width direction, the lead wire 319 is connected from one side surface 211d to the other side surface 211e along a boundary 211f between the heat sink 211 and the fan chamber 215. By doing so, the positions of the lower plate 211b corresponding to all the heat exchange fins 211c are connected to the ground terminal 311b and the ground plane 321.

  The range 251 in the depth direction connecting the lead wire 319 may be the surface of the fan chamber 215 that is within the range of the depth dimension L of the heat sink 209 from the entire area of the heat sink 209 and the boundary 211f. When connecting the lead wire to the surface of the fan chamber 215, it is desirable to connect from one side surface of the fan chamber 215 to the other side surface like the lead wire 319a. The lead wire 319 may be connected only to the upper plate 211a, or may be connected to both the upper plate 211a and the lower plate 211b. The same applies to the fan chamber 215 and the heat sink 209.

  As shown in FIG. 5, the ground plane 321 and the system housing 105 are electrically connected by a lead wire 327. It is desirable that there are a plurality of connection points between the ground plane 321 and the system chassis 105. A charged body 325 exists in the vicinity of the heat sink 209. The charged body 325 gradually accumulates negative charges while the notebook PC 100 is operating, and charges the heat sink 209 by electrostatic induction.

  The charged body 325 is a semiconductor device on the mother board 113 or a wiring pattern. The charged body 325 is not limited to an electronic device mounted on the mother board 113, and may be an electrical component or a metal body that exists inside the system housing 105 and causes electrostatic induction in the heat sink 209. Good. The charged body 325 may be an object that accumulates electric charges or an object that is charged by the influence of electrostatic induction from another charged body 325.

  Until now, the fan unit 200 has been connected to the metal frame 111 with screws 206a to 206d, and it has not been known that the cause of dust accumulation is the charging of the heat sinks 209 and 211. In the model of FIG. 5, even if the heat receiving portion 205 of the fan unit 200 is electrically connected to the metal frame 111, the heat sinks 209 and 211 are charged and adsorb dust. Next, based on FIGS. 5 and 6, the principle of suppressing charging will be described using the heat sink 209 as an example.

  FIG. 6 is a diagram showing the results of a dust accumulation acceleration test for measuring the effect when the lead wires 317 and 319 are connected to the heat sinks 209 and 211. FIG. 6A shows the relative value of the potential of the heat sink 209 with respect to the time when the notebook PC 100 operates in the acceleration tester, and FIG. 6B is attached to the entrances of the heat sinks 209 and 211. Indicates the weight of dust. Lines 401 and 405 indicate a case where the lead wires 317 and 319 are not connected to the ground terminal 311b, and lines 403 and 407 indicate a case where the lead wires 317 and 319 are connected to the ground terminal 311b. FIG. 6A shows a relative value where the voltage of the heat sink 209 is 100 when 10 hours have passed on the line 401.

  When the notebook PC 100 starts operating, the heat radiating fan 213 rotates and air flows out from the slit of the heat sink 209 through the exhaust port 106. Electric charges are generated in the heat sink 209 by frictional charging due to friction between the air flow and the heat exchange fins. If the heat receiving unit 205 and the metal frame 111 are electrically connected, the generated charge moves to the ground plane 321 and is neutralized, and the potential of the ground plane 321 and the heat dissipation unit 200 approach each other.

  If the electrical connection between the heat receiving unit 205 and the metal frame 111 is insufficient, electric charge is accumulated in the heat sink 209 with the passage of time, and the potential thereof rises or falls with respect to the ground potential. Here, a case where the charged body 325 is charged with a negative charge and a positive charge is generated in the heat sink 209 and the potential is increased will be described as an example. However, the case where a negative charge is generated should be understood similarly. Can do. The phenomenon occurring in the heat sink 211 may be considered in the same manner.

  The electronic device and other electrical components on the mother board 113 are operated by the operation of the notebook PC 100, and the negative charge is gradually accumulated in the charged body 325, and the positive charge is generated in the heat sink 209 by induction charging by electrostatic induction. Is done. The positive charge induced in the heat sink 209 is not neutralized as long as the charged body 325 exists even if the heat receiving unit 205 and the metal frame 111 are connected. When the polarities of the charges generated by the frictional charging and the induction charging are the same, they are superimposed and the potential of the heat sink 209 is increased.

  When the lead wire 317 is not connected, the potential of the heat sink 209 rises as indicated by a line 401 and dust increases as indicated by a line 405. Next, the heat sink 209 is connected to the ground terminal 311b by the lead wire 317 and is connected to the ground plane 327 by the lead wire 329. Therefore, the charge generated in the heat sink 209 is neutralized with the charge of the ground plane 321 and the potential of the heat sink 209 drops close to the potential of the ground plane. The ground plane 321 acts as a charge neutralizing conductor for neutralizing charges with respect to the heat sink 209.

  When the potential of the ground plane 321 is close to the ground potential before the heat sink 209 is charged, it is desirable that the potential of the ground plane 321 does not increase as much as possible due to the connection of the lead wire 317. For this purpose, it is desirable that the ground plane 321 as the charge neutralizing conductor has a large capacitance. If the potential of the charge neutralizing conductor is close to the ground potential and the capacitance is large, the potential of the heat sink 209 and the ground plane 321 that are electrically integrated even if the charge is transferred from the heat sink 209 is grounded. It can be kept close to the potential.

  In order to bring the heat sink 209 to ground potential, the heat sink 209 needs to be connected to the ground through the ground line. However, the notebook PC 100 exists as an isolated conductor when operating with the battery pack 119 or when the secondary circuit of the AC / DC adapter connected to the power jack 311 is electrostatically insulated from the primary circuit. To do.

  However, even if the secondary circuit is an AC / DC adapter that is insulated from the primary circuit, when it is connected to the power jack 311, its capacitance is added to the ground plane 321 to charge neutralizing conductor. This contributes to a decrease in the potential of the heat sink 209. Further, when the system housing 105 is made of metal, the capacitance of the charge neutralization conductor including the ground plane 321 is connected by connecting the ground plane 321 and the system housing 105 with the lead wire 327. Can be increased. When the palm rest 313 is made of metal, it can be similarly connected to increase the electrostatic capacity of the charge neutralizing conductor.

  In some AC / DC adapters, the power plug on the AC side includes a ground line, and the ground line of the secondary circuit is connected to the ground line. In this case, the potential of the heat sink 209 can be brought close to the ground potential most effectively through the ground line on the AC side. In this experiment, an AC / DC adapter with a ground terminal was connected to the power jack 311 on the AC side power plug. Accordingly, the lines 403 and 407 show the state when the ground terminal 311b is connected to the earth line.

  When the notebook PC 100 is operated by the battery pack 119, the effect as a charge neutralizing conductor of the AC / DC adapter or the connection effect to the ground cannot be obtained. However, the user cannot use the metal band 315 when using the notebook PC 10. In order to touch the palm, the human body can act as a charge neutralizing conductor to neutralize the heat sink 209 charge. As apparent from FIGS. 6A and 6B, by connecting the lead wire 317, the potential of the heat sinks 209 and 211 is lowered, and the amount of accumulated dust is reduced.

  In addition, the case where an AC / DC adapter without a ground terminal is connected to the power plug on the AC power source side, the case where the AC / DC adapter is not connected, and the case where the human body is brought into contact with the metal band 315 are not as large as the line 403 However, it has been confirmed that the potential of the heat sink 209 is lower than that of the line 401. Some computers receive AC voltage from the outside via a power cable including a ground line and convert it into DC voltage inside the computer. In this case, the heat sink 209 can be brought close to the ground potential by connecting the lead wire 319 to the ground terminal of the power jack to which the power cable is connected.

  The heat dissipation unit according to the present invention is not obtained only when the effect of suppressing dust accumulation is mounted on a computer. The present invention is used in game machines used for computer games, electronic devices such as projectors used in office and business, household electrical equipment used for music playback and video playback, navigation systems mounted on automobiles, or factories. The present invention can be widely applied to electrical equipment such as industrial electrical equipment.

  Although the present invention has been described with the specific embodiments shown in the drawings, the present invention is not limited to the embodiments shown in the drawings, and is known so far as long as the effects of the present invention are achieved. It goes without saying that any configuration can be adopted.

105 ... System housing 111 ... Metal frame 113 ... Mother board 121 ... CPU
200 ... Heat radiation unit 201, 203 ... Heat pipe 205, 207 ... Heat receiving part 209, 211 ... Heat sink 225 ... Fan chamber 311 ... Power jack 313 ... Palm rest 315 ... Metal bands 317, 319, 327, 329 ... Lead wire 321 ... ground plane 325 ... charged body

Claims (6)

A portable computer comprising a system housing containing electrical components and formed of a conductive material, and a palm rest,
A ground plane capable of supplying a reference potential to the electrical component and exchanging charges with other objects ;
A plurality of heat exchange fins that are aligned with an exhaust port formed in the system casing and coupled to an upper plate and a lower plate to form an air flow path for exhausting air inside the system casing; A heat sink, a heat dissipating fan housed in a fan chamber coupled to the heat sink and sending air to the air flow path, and a heat pipe thermally and electrically coupled to the heat sink; A heat dissipating unit including a heat receiving unit that is thermally and electrically coupled to the heat pipe and directly contacts the central processing unit;
A charging body disposed in the vicinity of the heat sink and charging the heat sink by electrostatic induction during operation of the portable computer ;
One is connected to the surface of the heat sink or the fan chamber along the vicinity of the boundary between the heat sink and the fan chamber from one side to the other side in the width direction of the heat sink. The other lead connected to the ground plane;
A metal frame connected to the ground plane;
The heat radiating unit is mechanically and electrically coupled to the system housing via the metal frame at the heat receiving unit, and the lead wire is configured to allow the heat sink to freely move when the heat receiving unit is coupled. A portable computer connected to a ground plane . A power jack having a voltage terminal to which a voltage line of an AC / DC adapter is connected and a ground terminal to which a ground line is connected; the other of the lead wires is connected to the ground terminal; and the ground terminal is the ground A portable computer according to claim 1 connected to a plane. Has a motherboard which electronic device is mounted, wherein the metal frame is arranged on the upper side of the mother board, the ground plane is disposed on the lower side of the mother board, the said ground plane metal The portable computer according to claim 2 , wherein the frame constitutes an EMI shield that suppresses electromagnetic interference with respect to the electrical component. The portable computer according to any one of claims 1 to 3, further comprising connection means for electrically connecting the system casing and the ground plane. The palm rest is made of metal,
The portable computer according to any one of claims 1 to 4 , wherein the other of the lead wires is connected to the palm rest. The palm rest is formed by plastic, provided with a metal portion embedded in a portion of the palm rest, the other of the leads of claims 1 to 4, which is connected to the metal part A portable computer according to any one of the above.

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