JP7235782B2 - Electronics - Google Patents

Description

The present invention relates to an electronic device with a cooling module.

An electronic device such as a notebook PC is equipped with a cooling module for cooling a heating element such as a CPU (see, for example, Patent Document 1). This type of cooling module includes a heat transport device such as a heat pipe that absorbs and transports heat generated by a CPU or the like, and a heat sink and blower fan that discharge the heat transported by the heat transport device to the outside of the housing. There is a configuration with

Japanese Patent No. 6469183

A general heat sink has a configuration in which heat transported by a heat transport device is dissipated by circulating air from a blower fan through the gaps between a plurality of fins arranged side by side. For this reason, the heat sink has a large blowing resistance. As a result, the blower fan cannot generate the original air volume, which is a factor in lowering the cooling efficiency of the module as a whole.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electronic device having a cooling module capable of enhancing cooling efficiency.

An electronic device according to a first aspect of the present invention includes a housing having a first cover member forming an outer surface on one side in a thickness direction and a second cover member forming an outer surface on the other side; and a cooling module provided in the housing for cooling the heating element, wherein the cooling module is arranged side by side with a blower fan housing an impeller portion inside the fan housing. The first surface is arranged with a first gap between it and the first cover member, and the second surface is a second surface between it and the second cover member. The fins are arranged with a gap therebetween, and a side surface orthogonal to the first surface and the second surface is arranged so as to face the exhaust port of the blower fan, so that the air from the blower fan enters the gap between the fins. a circulating heat sink; and a heat transport device partly disposed in the second gap and thermally connecting between the heating element and the second surface of the heat sink, the heat sink comprising: a notch-shaped portion that is formed by notching a corner where the first surface and the side surface intersect and forms an air flow path between the exhaust port and the first gap; and a first wall portion provided at a position facing the upstream end portion of the exhaust port in the air circulation direction of the impeller portion in (1) and blocking one side of the cutout portion in the width direction.

A cooling module according to a second aspect of the present invention has a blower fan housing an impeller portion inside a fan housing, and a plurality of fins arranged side by side. a heat sink in which the air from the blower fan flows through the gaps between the fins by arranging the first surface and the side surface perpendicular to the second surface of the other side facing the exhaust port of the blower fan; a heat transport device connected to the second surface of a heat sink, wherein the heat sink is formed by cutting out a corner where the first surface and the side surface intersect, and the air from the exhaust port is removed. along the first surface, and a position facing the upstream end of the exhaust port in the direction of air flow by the impeller in the fan housing. and a first wall portion that is provided and closes one side in the width direction of the notch shape portion.

According to one aspect of the present invention, cooling efficiency can be enhanced.

FIG. 1 is a schematic plan view looking down on an electronic device according to an embodiment. FIG. 2 is a plan view schematically showing the internal structure of the housing. FIG. 3 is a perspective view of the cooling module viewed from above. 4 is a bottom perspective view of the cooling module shown in FIG. 3. FIG. 5 is an enlarged view of the heat sink and blower fan shown in FIG. 3. FIG. FIG. 6 is a schematic cross-sectional view along line VI-VI in FIG.

BEST MODE FOR CARRYING OUT THE INVENTION An electronic device and a cooling module according to the present invention will be described in detail below with reference to preferred embodiments and with reference to the accompanying drawings.

FIG. 1 is a schematic plan view looking down on an electronic device 10 according to an embodiment. As shown in FIG. 1, the electronic device 10 is a clamshell notebook PC in which a display housing 12 and a housing 14 are connected by a hinge 16 so as to be relatively rotatable. The electronic device according to the present invention may be, for example, a desktop PC, a tablet PC, a mobile phone, a smart phone, a game machine, or the like, other than a notebook PC.

The display housing 12 is a thin flat box. A display 18 is mounted on the display housing 12 . The display 18 is composed of, for example, an organic EL (OLED: Organic Light Emitting Diode) or a liquid crystal.

Hereinafter, regarding the housing 14 and each element mounted therein, the space between the housings 12 and 14 is opened as shown in FIG. Later, the width direction will be referred to as left and right, and the height direction (thickness direction of the housing 14) will be referred to as up and down.

The housing 14 is a thin flat box. The housing 14 is composed of a cover member 14A forming an upper surface and four peripheral side surfaces, and a cover member 14B forming a lower surface. The upper cover member 14A has a substantially bathtub shape with an open bottom surface. The lower cover member 14B has a substantially flat plate shape and serves as a lid that closes the lower opening of the cover member 14A. The cover members 14A and 14b are overlapped in the thickness direction and detachably connected to each other. A keyboard 20 and a touch pad 21 are provided on the upper surface of the housing 14 . The housing 14 is connected to the display housing 12 using a hinge 16 at its rear end.

FIG. 2 is a plan view schematically showing the internal structure of the housing 14. As shown in FIG. FIG. 2 schematically shows a state in which the housing 14 is cut slightly below the keyboard 20 .

As shown in FIG. 2 , a cooling module 22 , a motherboard 24 and a battery device 26 are provided inside the housing 14 . Various electronic components, mechanical components, and the like are further provided inside the housing 14 .

Motherboard 24 is the main board of electronic device 10 . The motherboard 24 is arranged toward the rear of the housing 14 and extends in the left-right direction. The motherboard 24 is a printed circuit board on which various electronic components such as a CPU (Central Processing Unit) 30 and a GPU (Graphics Processing Unit) 31 as well as a communication module and memory are mounted. The motherboard 24 is arranged under the keyboard 20 and screwed to the back surface of the keyboard 20 and the inner surface 14Aa of the cover member 14A. The motherboard 24 has an upper surface that serves as a mounting surface for the cover member 14A, and a lower surface that serves as a mounting surface for the CPU 30, the GPU 31, and the like.

The CPU 30 performs calculations related to main control and processing of the electronic device 10 . The GPU 31 performs calculations necessary for rendering images such as 3D graphics. In the case of the electronic device 10 of the present embodiment, the GPU 31 is a heat generator that generates the largest amount of heat among the electronic components mounted in the housing 14 . The CPU 30 is a heat generating element that generates the second largest amount of heat after the GPU 31 .

The battery device 26 is a rechargeable battery that serves as a power source for the electronic device 10 . The battery device 26 is arranged in front of the motherboard 24 and extends left and right along the front end portion of the housing 14 .

The motherboard 24 is arranged behind the battery device 26 and extends in the left-right direction. The CPU 30 and the GPU 31 are arranged horizontally in the center of the mother board 24, and are installed in a valley between blower fans 38L and 38R, which will be described later. The motherboard 24 may be divided into a plurality of sections by the blower fans 38L and 38R.

Next, the configuration of the cooling module 22 will be described.

The cooling module 22 is a cooling device that absorbs and diffuses heat generated by the CPU 30 and GPU 31 and discharges the heat to the outside of the housing 14 . The electronic component to be cooled by the cooling module 22 may be either one of the CPU 30 and the GPU 31, or other than these. The cooling module 22 is laminated on the underside of the motherboard 24 .

FIG. 3 is a perspective view of the cooling module 22 viewed from above. FIG. 4 is a perspective view of the cooling module 22 shown in FIG. 3 as seen from below. As shown in FIGS. 2 to 4, the cooling module 22 includes a pair of left and right heat sinks 36L and 36R, a pair of left and right fans 38L and 38R, a pair of front and rear heat pipes 40 and 41, a vapor chamber 42, and a heat sink. conductive plates 44, 45;

The left and right heat sinks 36L and 36R are substantially bilaterally symmetrical in structure, although their sizes are slightly different. Similarly, the left and right blower fans 38L, 38R are also substantially bilaterally symmetrical. Therefore, the left heat sink 36L and blower fan 38L will be mainly described below, and the right heat sink 36R and blower fan 38R will be given the same reference numerals as those on the left side, and detailed description thereof will be omitted.

As shown in FIGS. 2 to 4, the heat sink 36L (36R) has a structure in which a plurality of plate-like fins 36a extending in the front-rear direction and erected in the vertical direction are arranged at regular intervals in the horizontal direction. . Between the adjacent fins 36a, 36a, a gap G0 is formed through which the air sent from the blower fan 38L (38R) passes. That is, the gap G0 penetrates in the front-rear direction, and a plurality of gaps are arranged in the left-right direction. Each fin 36a is integrated by joining, for example, a plate 36b at its lower end surface (see FIG. 6). The fins 36a and the plate 36b are plates made of metal with high thermal conductivity, such as aluminum or copper. In FIGS. 3 to 5, the fins 36a and plates 36b are collectively shown schematically as one block. The heat sink 36L (36R) of the present embodiment has a cut-out portion 46 at the upper corner on the blower fan 38L (38R) side, the details of which will be described later.

As shown in FIGS. 2 to 4, the blower fan 38L (38R) is arranged in front of the heat sink 36L (36R), and the exhaust port 38a opened rearward faces the front side surface 36c of the heat sink 36L (36R). are doing. The blower fan 38L (38R) is a centrifugal fan that rotates an impeller portion 38c (see FIG. 6) accommodated inside the fan housing 38b by a motor portion. The fan housing 38b is composed of a cover plate 38d forming upper and side surfaces and a cover plate 38e forming a lower surface. In the blower fan 38L (38R) of the present embodiment, intake ports 38f and 38g are opened in the cover plates 38d and 38e, respectively. One of the intake ports 38f and 38g may be omitted. The blower fan 38L (38R) of this embodiment has an auxiliary exhaust port 48 at the rear edge of the lower cover plate 38e, the details of which will be described later.

As shown in FIGS. 2 and 4, the heat pipes 40 and 41 are, for example, pipe-shaped heat transport devices with curved central portions. In this embodiment, the two heat pipes 40 and 41 are used in parallel in a set of two in the front and rear, but the heat pipes may be used in one or three or more. The heat pipes 40 and 41 are thin and flat metal pipes in which a working fluid is sealed in a sealed space. Metal pipes are made of metals with high thermal conductivity, such as aluminum, copper, or stainless steel. The sealed space serves as a flow path through which the sealed working fluid flows while undergoing a phase change. Examples of working fluids include water, CFC alternatives, acetone, butane, and the like. A wick that transfers the condensed working fluid by capillary action is disposed in the sealed space. The wick is formed of, for example, a porous body such as a mesh or a microchannel made by weaving thin metal wires in a cotton-like fashion.

As shown in FIGS. 2 to 4, the vapor chamber 42 is a plate-type heat transport device, which is a type of heat pipe. The vapor chamber 42 forms a closed space between two thin metal plates and encloses a working fluid in this closed space. In the vapor chamber 42, the material of the metal plate, the type of working fluid, the structure of the wick installed in the closed space, and the like may be the same as those of the heat pipes 40 and 41 described above.

As shown in FIGS. 2-4, the thermally conductive plates 44, 45 are bonded to the leading and trailing edges of the vapor chamber 42 and extend therefrom. The thermally conductive plates 44 and 45 are plates made of a material having high thermal conductivity, such as metal such as aluminum or copper, or graphite. The heat conduction plates 44 and 45 are auxiliary heat diffusion members that further diffuse and dissipate the heat diffused by the vapor chamber 42 . Since the heat-conducting plates 44 and 45 can be configured to be thinner than the vapor chamber 42, they can be easily installed even in areas where the space in the housing 14 in the height direction is narrow.

In the cooling module 22 configured as described above, the upper surface of the vapor chamber 42 contacts the CPU 30 and the GPU 31 via the heat receiving plates 30a and 31a, respectively. The heat receiving plates 30a and 31a are plates made of metal with high thermal conductivity such as copper and aluminum. The heat pipes 40 and 41 are joined to the lower surface of the vapor chamber 42 at the central portion, which is the heat receiving portion, and are joined to the lower surfaces 36d of the heat sinks 36L, 36R at both end portions, which are the heat radiating portions, respectively.

The heat generated by the CPU 30 and GPU 31 is absorbed and diffused in the vapor chamber 42, and is efficiently transported to the heat sinks 36L and 36R through the heat pipes 40 and 41. is discharged to the outside of the housing 14 by . At the same time, the heat diffused in the vapor chamber 42 is further diffused and radiated through the heat conducting plates 44,45.

FIG. 5 is an enlarged view of the heat sink 36R and the blower fan 38R shown in FIG. As described above, the basic configuration of the left heat sink 36L and blower fan 38L is bilaterally symmetrical to that shown in FIG. FIG. 6 is a schematic cross-sectional view along line VI-VI in FIG.

As shown in FIGS. 5 and 6, the heat sink 36L (36R) has a top surface 36e and the inner surface 14Aa of the cover member 14A with a gap G1 therebetween, and a bottom surface 36d with the heat pipes 40 and 41 interposed therebetween. A gap G2 is provided between the cover member 14B and the inner surface 14Ba of the cover member 14B. The ends of the heat pipes 40, 41 are arranged in the gap G2 and connected to the lower surface 36d. Furthermore, the front side surface 36c is arranged facing the exhaust port 38a of the blower fan 38L (38R).

Accordingly, in the heat sink 36L (36R), the air discharged from the exhaust port 38a flows rearward through the gap G0 between the fins 36a. The air that has passed through the gap G0 is discharged to the outside through a housing exhaust port 14Ab formed in the rear end surface of the housing 14. As shown in FIG.

The heat sink 36L (36R) has a structure in which a plurality of fins 36a arranged in the horizontal direction are supported by a plate 36b. For this reason, the upper surface 36e is actually formed by the upper end surfaces of the fins 36a arranged in the left-right direction with the gap G0 interposed therebetween. be. On the other hand, the lower surface 36d is composed of a plate 36b. The heat sink 36L (36R) may be installed upside down. That is, the heat sink 36L (36R) may have the upper surface 36e arranged on the lower cover member 14B side and the lower surface 36d arranged on the upper cover member 14A side.

The cooling module 22 of the present embodiment also has a structure that circulates air not only along the gap G0 but also along the upper surface 36e and the lower surface 36d of the heat sink 36L (36R). This air flow is formed by a notched portion 46 provided in the heat sink 36L (36R) and an auxiliary exhaust port 48 provided in the blower fan 38L (38R).

First, the configuration of the notch-shaped portion 46 and its peripheral portion will be described.

As shown in FIGS. 3, 5 and 6, the heat sink 36L (36R) has a notch portion 46 and a pair of left and right walls 50a and 50b at the corners where the top surface 36e and the side surface 36c intersect. .

The notch-shaped portion 46 is a chamfered portion obtained by notching the corners of the left and right fins 36a except for a few (for example, about 1 to 5) left and right ends of the fins 36a. is. The lower end (rear end) of the notch-shaped portion 46 is positioned at or near the vertical center of the exhaust port 38a of the opposing blower fan 38L (38R). Thus, the notch-shaped portion 46 forms an air flow path 46a between the exhaust port 38a and the gap G1 for circulating the air from the exhaust port 38a. An arrow indicated by a one-dot chain line in FIG. 6 schematically shows the flow of air from the exhaust port 38a toward the housing exhaust port 14Ab.

Circular arrows indicated by dashed lines in FIGS. 3 and 5 indicate the rotation direction of the impeller portion 38c in the blower fan 38L (38R). One wall portion 50a is provided at a position facing the upstream end portion 38a1 of the exhaust port 38a in the air circulation direction of the impeller portion 38, and blocks one side of the notch portion 46 in the width direction (FIGS. 2 and 3). See also Figure 6). The other wall portion 50b is provided at a position facing the downstream end portion 38a2 of the exhaust port 38a in the air circulation direction of the impeller portion 38, and blocks the other side in the width direction of the notch portion 46 (see also FIG. 2). reference).

The walls 50a and 50b are located on both left and right sides of the fins 36a arranged laterally, except for the fins 36a forming the notch-shaped portion 46 at the center, that is, the number of the walls 50a and 50b where the notch-shaped portion 46 is not formed. It is composed of a sheet of fins 36a. Each of the walls 50a and 50b may be composed of at least one fin 36a. In this embodiment, the walls 50a and 50b are formed by four or five fins 36a in order to secure a space for attaching the sealing member 52 to the upper surface 36e. The heat sink 36L (36R) may be configured such that the corners of all the fins 36a are cut to form the notched portion 46. In this case, the wall portions 50a and 50b are formed on the left and right side surfaces of the heat sink 36L (36R). Another plate or the like may be fixed and configured.

A sealing member 52 is provided on the upper surface 36e of the wall portions 50a and 50b. The sealing member 52 is provided so as to close the space between the walls 50a and 50b and the inner surface 14Aa of the cover member 14A. The sealing member 52 is, for example, a strip of sponge or rubber. The sealing member 52 prevents the air inside the housing 14 from flowing back to the exhaust port 38a through the gap between the wall portions 50a and 50b and the cover member 14A. The sealing member 52 of the present embodiment is provided not only on the upper surfaces of the walls 50a and 50b, but also on the outer edge of the upper surface of the blower fan 38L (38R) (see FIG. 5).

Next, the configuration of the auxiliary exhaust port 48 and its peripheral portion will be described.

As shown in FIGS. 4 and 6, the blower fan 38L (38R) has an auxiliary exhaust port 48 at the rear edge of the lower cover plate 38e of the fan housing 38b.

The auxiliary exhaust port 48 is formed by cutting out a part of the cover member 14B of the fan housing 38b. The auxiliary exhaust port 48 is an opening for circulating part of the air sent by the impeller portion 38c to the gap G3.

A sealing member 54 is provided on the lower surface of the blower fan 38L (38R). The seal member 54 is provided so as to block the space between the lower surface (cover plate 38e) of the fan housing 38b and the inner surface 14Ba of the cover member 14B. The sealing member 54 is, for example, a strip of sponge or rubber. The seal member 54 prevents the air inside the housing 14 from flowing backward from the gap between the fan housing 38b and the cover member 14B to the auxiliary exhaust port 48 . The seal member 54 of this embodiment is provided to surround the outer edge of the lower surface of the fan housing 38b, and is also provided on the lower surfaces of the heat pipes 40 and 41 along the left and right edges of the heat sink 36L (36R). ing.

Next, the functions of the notch portion 46 and the auxiliary exhaust port 48 will be described.

Most of the air discharged from the exhaust port 38a of the blower fan 38L (38R) flows from the opposing side surface 36c of the heat sink 36L (36R) into the gap G0 between the fins 36a, 36a. However, since the gap G0 is a narrow gap formed between the fins 36a, 36a, it has a high flow resistance. Therefore, part of the air from the exhaust port 38a passes through the air flow path 46a formed by the cutout portion 46 and flows into the gap G1. Further, part of the air sent from the blower fan 38L (38R) is discharged from the auxiliary exhaust port 48 and flows into the gap G3 between the lower surfaces of the heat pipes 40, 41 and the inner surface 14Ba of the cover member 14B.

Therefore, in the housing 14, the air sent from the blower fan 38L (38R) is divided into three directions, upper and lower, as indicated by the three dashed line arrows in FIG. It is discharged to the outside of the housing 14 through the port 14Ab. As a result, in the electronic device 10, the air discharged from the blower fan 38L (38R) does not flow only through the gap G0 between the fins 36a, 36a, and the amount of air blown is limited by pressure loss in the gap G0. Suppressed. Therefore, the blower fan 38L (38R) can maximize its blowing capacity.

That is, first, the heat sink 36L (36R) has a notch portion 46 at a corner facing the exhaust port 38a of the blower fan 38L (38R). As a result, of the air discharged from the exhaust port 38a, surplus air that is likely to remain due to pressure loss in the gap G0 passes through the gap G1 along the upper surface 36e of the heat sink 36L (36R). As a result, the upper surface 36e of the heat sink 36L (36R) is efficiently cooled, and the heat dissipation amount as a whole is improved. In addition, since the low-temperature air flows through the gap G1, it is possible to suppress the temperature rise of the upper surface (cover member 14A) of the housing 14 on which the user places his/her hands and fingers.

At this time, both ends of the notched portion 46 are closed by the walls 50a and 50b. Therefore, the air in the housing 14 is prevented from flowing backward from the side portion of the cutout portion 46 into the exhaust port 38a. In addition, the wall part should just have only the wall part 50a of at least one side. That is, the wall portion 50a is located at a position facing the upstream end portion 38a1 of the exhaust port 38a in the air circulation direction of the impeller portion 38c inside the fan housing 38b. The upstream end 38a1 has a higher wind speed than the opposite downstream end 38a2. For this reason, the wall portion 50a on the upstream end portion 38a1 side is more effective than the wall portion 50b in suppressing the suction that causes wall backflow and the discharge that causes a decrease in the air volume from the exhaust port 38a.

Further, the notch-shaped portion 46 is provided not on the lower surface 36d of the heat sink 36L (36R) to which the heat pipes 40 and 41 are connected, but on the upper surface 36e side. Thereby, the notch-shaped portion 46 can reliably communicate between the gap G1 and the exhaust port 38a. In the case of this embodiment, even if the corners of the fins 36a are notched, the heat pipes 40 and 41 (and the plate 36b) will interfere with the lower surface 36d, making it difficult for air to flow through the gap G3. be.

Next, the blower fan 38L (38R) has an auxiliary exhaust port 48 on the lower surface facing the exhaust port 38a. As a result, surplus air that has not been discharged from the exhaust port 38a to the gaps G0 and G1 passes through the auxiliary exhaust port 48 and the gap G3. As a result, the lower surface 36d of the heat sink 36L (36R) is also efficiently cooled, further improving the heat dissipation amount as a whole. In addition, since low-temperature air flows through the gap G3, it is possible to suppress the temperature rise of the lower surface (cover member 14B) of the housing 14, which may be placed on the user's knee or the like. The auxiliary exhaust port 48 may be omitted.

In the present embodiment, the notch shape portion 46 is provided on the heat sink 36L (36R), and the auxiliary exhaust port 48 is provided on the blower fan 38L (38R). The reason for this is that, as shown in FIG. 3, the fan housing 38b has a single large hole in the intake port 38f of the cover plate 38ed on the upper side. This is because there is a possibility of causing a problem with the strength of the body 38b.

It goes without saying that the present invention is not limited to the above-described embodiments, and can be freely modified without departing from the gist of the present invention.

The blower fans 38L, 38R and the heat sinks 36L, 36R may be configured by only one of them instead of a left and right pair. Also, the heat receiving plates 30a, 31a, the vapor chamber 42, and the heat conducting plates 44, 45 may be omitted.

REFERENCE SIGNS LIST 10 Electronic device 12 Display housing 14 Housing 14A, 14B Cover member 22 Cooling module 36L, 36R Heat sink 38L, 38R Blower fan 40, 41 Heat pipe 46 Cut-out portion 48 Auxiliary exhaust port 50a, 50b Wall portion 52, 54 Sealing member

Claims (3)

an electronic device,
a housing having a first cover member forming one side of the outer surface in the thickness direction and a second cover member forming the other side of the outer surface;
a heating element provided in the housing;
a cooling module provided in the housing for cooling the heating element;
with
The cooling module is
A blower fan that accommodates an impeller part inside a fan housing,
It has a plurality of fins arranged side by side, the first surface being arranged with a first gap between the first cover member and the second surface being arranged between the second cover member and the second cover member. 2, and the side surface orthogonal to the first surface and the second surface is arranged to face the exhaust port of the blower fan, so that the gaps between the fins are filled with the air from the blower fan. a heat sink through which air flows;
a heat transport device partially disposed in the second gap and thermally connecting between the heating element and the second surface of the heat sink;
has
The heat sink
A part of the plurality of fins in the height direction at a corner where the first surface and the side surface intersect is chamfered so that the exhaust port and the first fin are notched. a notched portion forming an air flow path between the air outlet and the gap to introduce part of the air from the exhaust port into the first gap;
a first wall portion provided at a position facing an upstream end portion of the exhaust port in the air circulation direction of the impeller portion in the fan housing and blocking one side in the width direction of the notch-shaped portion;
a second wall portion provided at a position facing the downstream end portion of the exhaust port in the air circulation direction in the fan housing and blocking the other side of the notched portion in the width direction;
has
Furthermore, by blocking the space between the first wall portion and the first cover member and the space between the second wall portion and the first cover member, the air inside the housing is prevented from flowing into the first wall portion and the first cover member. A sealing member is provided for preventing backflow to the exhaust port from a gap between the second wall portion and the first cover member.
An electronic device characterized by: The electronic device according to claim 1 ,
The notch-shaped portion is formed in each of the plurality of fins except for the plurality of fins positioned on one side and the other side in the width direction,
The first wall portion and the second wall portion are located on one side and the other side in the width direction, respectively, and are configured by the plurality of fins in which the notch-shaped portion is not formed,
The sealing member is interposed between the upper surfaces of the plurality of fins and the first cover member.
An electronic device characterized by: The electronic device according to claim 1 or 2 ,
a portion of the heat transport device connected to the second surface is arranged with a third gap from the second cover member;
The electronic device according to claim 1, wherein the fan housing has an auxiliary exhaust port that opens on the outer surface on the side of the second cover member and allows the air sent by the impeller section to flow to a third gap.

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