Patent Description:
<FIG> shows a conventional cooling fan <NUM> including a housing <NUM>. The housing has a lower housing <NUM> and an upper housing <NUM>, which can be coupled to the lower housing <NUM>. An impeller <NUM> is rotatably mounted in the lower housing <NUM>. The upper housing <NUM> includes an air inlet <NUM>. The lower housing <NUM> and the upper housing <NUM> together define an air outlet <NUM>. When the impeller <NUM> rotates, air currents pass through the air inlet <NUM>, flow axially into the lower housing <NUM>, and laterally flow out of the air outlet <NUM>. An example of the conventional cooling fan <NUM> is disclosed in <CIT>.

The operational noise of the conventional cooling fan <NUM> can be reduced by the structural design of the impeller <NUM> at the cost of a complicated structure of the impeller <NUM>, causing difficulties in making molds. Thus, it is difficult to produce the conventional cooling fan <NUM>, leading to adverse influence on the production efficiency and the yield. Furthermore, the conventional cooling fan <NUM> has no structure for increasing the airflow and/or the air pressure. Thus, there is still room for improvement to the performance of the fan.

<CIT> discloses a centrifugal blower assembly including a housing with an inner surface and an outer surface. The centrifugal blower also includes a first portion of texture applied to at least a first portion of the inner surface and the outer surface of the housing. The first portion of texture has a first height based at least in part on a local boundary layer height of an airflow moving across the inner surface and the outer surface respectively. The first portion of texture is configured to generate a turbulent flow within the airflow moving across the first portion of texture.

<CIT> discloses a centrifugal fan in which an impeller is provided in a scroll casing formed in a spiral shape with a tongue portion serving as its starting point. The scroll casing is provided with an axially expanded portion that forms an air channel expanded in a rotation axis direction at a radially outer side of an annular flange portion. In a region of an outlet between the tongue portion and a spiral-end portion of the scroll casing in the axially expanded portion, a protrusion protrudes radially outward from a radially inner side surface by a predetermined amount so as to directly face an airflow in a circumferential direction.

<CIT> discloses a double inlet centrifugal fan, in particular for the evacuation of combustion fumes in thermal power plants, producing less mechanical vibrations and lower noise levels by providing an anti-vortex fin at the fan outlet section extending on a lying plane parallel to the fluid flow direction.

<CIT> discloses a fan module comprising a casing, a fan and a plurality of fins. The casing has a mounting space, an air inlet and an air outlet. The air inlet and the air outlet are linked through the mounting space. The fan is installed inside the mounting space. The fins are installed across the air outlet with each fins aligned in parallel to each other. The fins have a plurality of protruding sections protruding from a surface of the fins. Neighboring fins are separated from each other through the protruding sections so that the fins altogether divide the air outlet into a plurality of slots whose width is less than or equal to <NUM>.

<CIT> discloses a fan flow guide structure including a centrifugal fan impeller and a case. The case includes an upper cover and a base seat. A fan impeller space and a flow passage are defined between the upper cover and the base seat. The fan impeller space serves to receive the centrifugal fan impeller. The flow passage is in communication with the fan impeller space and a lateral wind outlet. A tongue section is disposed in the flow passage in adjacency to the lateral wind outlet. A wind supplementing section is defined opposite to the tongue section. An intake gill section is disposed on the upper cover and/or the base seat in communication with the wind supplementing section. Accordingly, the airflow outside the case can be guided from the intake gill section into the wind supplementing section to enhance the flow amount of the fan.

To solve the above problems, it is an objective of the present invention to provide a cooling fan that is easy to manufacture while increasing the airflow.

It is another objective of the present invention to provide a cooling fan that is easy to manufacture while increasing the air pressure.

It is a further objective of the present invention to provide a cooling fan that is easy to manufacture while reducing the operational noise.

As used herein, the term "a" or "an" for describing the number of the elements and members of the present invention is used for convenience, provides the general meaning of the scope of the present invention, and should be interpreted to include one or at least one. Furthermore, unless explicitly indicated otherwise, the concept of a single component also includes the case of plural components.

As used herein, the term "coupling", "engagement", "assembly", or similar terms is used to include separation of connected members without destroying the members after connection or inseparable connection of the members after connection. A person having ordinary skill in the art would be able to select according to desired demands in the material or assembly of the members to be connected.

A cooling fan according to the present invention includes a fan frame and an impeller. The fan frame includes a substrate, a sidewall connected to the substrate, and a lid connected to the sidewall and opposite to the substrate. An air inlet is formed in the lid. The substrate, the sidewall, and the lid together define at least one air outlet. The impeller is rotatably mounted in the fan frame. A plurality of bulges protrudes from an inner face of the sidewall and optionally from an inner face of the lid. A cooling fan according to the present invention includes further features which are specified in claim <NUM>.

Thus, in the cooling fan according to the present invention, the fan frame can be improved by a simple structure. By providing the plurality of bulges on the inner face of the sidewall and optionally on the inner face of the lid, the effects of increasing the airflow and the air pressure and/or reducing the noise can be achieved, thereby improving the performance of the cooling fan. Furthermore, in comparison with the conventional cooling fans, the cooling fan according to the present invention is easy to manufacture and form, increasing the production efficiency and yield.

In an example, a first reference plane extends parallel to the at least one air outlet and passes through an axis of the impeller. An output zone is formed between the first reference plane and the at least one air outlet. At least a half of a quantity of the plurality of bulges is located in the output zone. Thus, the air currents passing through the output zone can be affected by the plurality of bulges to increase the airflow and the air pressure in the output zone.

In an example, a portion of the inner face of the sidewall forms a tail section which is located in the output zone and contiguous to the at least one air outlet, and at least <NUM>% of the quantity of the plurality of bulges on the sidewall is located in the tail section. Thus, the airflow can be significantly increased while excellently increasing the air pressure and excellently reducing the noise, thereby improving the performance of the cooling fan.

In an example, the sidewall includes a tongue adjacent to the at least one air outlet. The inner face of the sidewall has an outwardly enlarged section and a tail section. The outwardly enlarged section is connected to the tongue and extends to the at least one air outlet. The tail section is located in the output zone, contiguous to the at least one air outlet and opposite to the tongue. The plurality of bulges on the sidewall is disposed from the tail section along the inner face of the sidewall to a position adjacent to the tongue. The plurality of bulges is neither disposed on the tongue nor the outwardly enlarged section. Thus, the air currents can contact the plurality of bulges along the entire flow path in the fan frame, thereby improving the performance of the cooling fan.

As specified in claim <NUM>, plurality of bulges on the sidewall is located only between a half of a height of the inner face of the sidewall and an intersection of the sidewall and the substrate. Thus, the effects of increasing the airflow and the air pressure and reducing the noise can be further improved, thereby improving the performance of the cooling fan.

In an example, the plurality of bulges on the sidewall is contiguous to the intersection of the sidewall and the substrate. Thus, the effects of increasing the airflow and the air pressure and reducing the noise can be further improved, and the plurality of bulges can be more reliably disposed in predetermined locations in the fan frame, thereby improving the performance and the manufacturing convenience of the cooling fan.

In an example, all of the plurality of bulges is located on the sidewall. Thus, the fan frame is easy to manufacture and form, and the effects of increasing the airflow and the air pressure and reducing the noise can be further improved, thereby improving the manufacturing convenience and the performance of the cooling fan.

In an example, a portion of the inner face of the sidewall forms a tail section. The tail section is located in the output zone and contiguous to the at least one air outlet. A second reference plane is orthogonal to the at least one air outlet and passes through an axis of the impeller. The plurality of bulges on the lid is located between the tail section and the second reference plane. Thus, the air pressure can be significantly increased.

In an example, a first reference plane extends parallel to the at least one air outlet and passes through an axis of the impeller. An output zone is formed between the first reference plane and the at least one air outlet. The plurality of bulges is located in the output zone. Thus, the air currents passing through the output zone can be affected by the plurality of bulges to increase the air pressure in the output zone and to reduce the operational noise.

In an example, the cooling fan further includes a flow guiding plate located in the at least one air outlet. The flow guiding plate has two ends connected to the inner face of the sidewall. Thus, the sound quality of the cooling fan can be improved, thereby reducing the noise.

In an example, the fan frame includes a supporting peg located in the at least one air outlet. The supporting peg is connected to the substrate and/or the lid. The flow guiding plate is coupled to the supporting peg. Thus, the supporting peg can prevent interference between the fan frame and the impeller while improving the stability of the flow guiding plate.

In an example, a cross sectional shape of the flow guiding plate is in a form of an airfoil. Thus, the sound quality of the cooling fan can be further improved, providing a better noise-reducing effect.

In an example, the impeller includes a plurality of blades. An edge of the flow guiding plate facing the impeller is aligned with <NUM>-<NUM>% of a height of the plurality of blades. Thus, the sound quality of the cooling fan can be further improved, providing a better noise-reducing effect.

In an example, the substrate includes a slot extending parallel to the at least one air outlet. The slot is located below the flow guiding plate. An area of a vertical projection of the flow guiding plate on the substrate at least partially overlaps with the slot. Thus, the effects of increasing the airflow and the air pressure and reducing the noise can be improved, thereby improving the performance of the cooling fan.

In an example, a height of the inner face of the sidewall is smaller than or equal to eight times a thickness of each of the plurality of bulges protruding from the inner face. Thus, the size of the plurality of bulges is proper to provide a better effect in improving the performance of the cooling fan.

In an example, each of the plurality of bulges has a thickness protruding beyond the inner face and ranging between <NUM> and <NUM>. Thus, the size of the plurality of bulges is proper to provide a better effect in improving the performance of the cooling fan.

In an example, each of the plurality of bulges has a maximum width ranging between <NUM> and <NUM>. Thus, the size of the plurality of bulges is proper to provide a better effect in improving the performance of the cooling fan.

The present invention will become more fully understood from the detailed description given hereinafter and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:.

When the terms "front", "rear", "left", "right", "up", "down", "top", "bottom", "inner", "outer", "side", and similar terms are used herein, it should be understood that these terms have reference only to the structure shown in the drawings as it would appear to a person viewing the drawings and are utilized only to facilitate describing the invention, rather than restricting the invention.

<FIG> shows a cooling fan F of a first embodiment according to the present invention. The cooling fan F includes a fan frame <NUM>, an impeller <NUM>, and a plurality of bulges <NUM>. The impeller <NUM> is rotatably mounted in the fan frame <NUM>. The plurality of bulges <NUM> protrudes from an inner face W of the fan frame <NUM>.

The fan frame <NUM> includes a substrate <NUM>, a sidewall <NUM> connected to the substrate <NUM>, and a lid <NUM> connected to the sidewall <NUM>. The lid <NUM> is opposite to the substrate <NUM>. Each of the sidewall <NUM> and the lid <NUM> has an inner face W facing an interior of the fan frame <NUM>. The fan frame <NUM> includes an air inlet <NUM> located in the lid <NUM>. The substrate <NUM>, the sidewall <NUM>, and the lid <NUM> together define an air outlet <NUM>. In this embodiment, the substrate <NUM> may be made of metal, the sidewall <NUM> may be made of plastic material, and the sidewall <NUM> may be integrally formed with the substrate <NUM> by injection molding. Thus, the fan frame <NUM> may have a proper structural strength, and the sidewall <NUM> can be easily formed to have various shapes according to different needs. The lid <NUM> may be made of metal or plastic material according to need.

With reference to <FIG> and <FIG>, a stator <NUM> can be coupled to the substrate <NUM> of this embodiment. Furthermore, the fan frame <NUM> of this embodiment may include at least one auxiliary air inlet <NUM>. The at least one auxiliary air inlet <NUM> may be formed in the substrate <NUM>, such that air can enter via the air inlet <NUM> and the at least one auxiliary air inlet <NUM> when the cooling fan F operates. The sidewall <NUM> of this embodiment may include a tongue <NUM>. The tongue <NUM> is adjacent to the air outlet <NUM> and is in the form of a protrusion. A portion of the inner face W of the sidewall <NUM> may form an outwardly enlarged section <NUM>. The outwardly enlarged section <NUM> may be connected to the tongue <NUM> and extends to the air outlet <NUM>. A portion of the inner face W of the sidewall <NUM> may further form a tail section <NUM>. The tail section <NUM> is contiguous to the air outlet <NUM> and is substantially opposite to the tongue <NUM>. For example, when the tongue <NUM> is located on the left side of the air outlet <NUM>, the tail section <NUM> may be substantially located on the right side of the air outlet <NUM>. In this embodiment, the tail section <NUM> is approximately on the right side of <FIG> and begins from an intersection of an arcuate line and a rectilinear line of the inner face W of the sidewall <NUM> to the air outlet <NUM>. In another embodiment, the tail section <NUM> may extend non-rectilinearly.

The impeller <NUM> includes a hub <NUM> and a plurality of blades <NUM> disposed around the hub <NUM>. The impeller <NUM> includes a shaft <NUM> and a magnetic member <NUM> which are separately and securely positioned on the hub <NUM>. A longitudinal axis of the shaft <NUM> defines an axis X of the impeller <NUM>. The shaft <NUM> is rotatably mounted to a center of the stator <NUM>. The magnetic member <NUM> and the stator <NUM> are opposite to each other and are spaced from each other by a magnetic induction gap. Thus, when the stator <NUM> is energized to generate a magnetic field, the whole impeller <NUM> is driven to rotate, driving air currents to flow via the air inlet <NUM> into the interior of the fan frame <NUM> and then flow outward via the air outlet <NUM>. A first reference plane S1 extends parallel to the air outlet <NUM> and passes through the axis X of the impeller <NUM>. An output zone Z is formed between the first reference plane S1 and the air outlet <NUM>. The tongue <NUM>, the outwardly enlarged section <NUM>, and the tail section <NUM> of the sidewall <NUM> may be located in the output zone Z. A second reference plane S2 is orthogonal to the air outlet <NUM> and passes through the axis X of the impeller <NUM>.

The plurality of bulges <NUM> protrudes from the inner face W of the sidewall <NUM> and optionally also from the inner face W of the lid <NUM> to affect the air currents flowing in the interior of the fan frame <NUM>. In this embodiment, all of the plurality of bulges <NUM> may be located on the inner face W of the sidewall <NUM>. Furthermore, at least a half of the plurality of bulges <NUM> may be located in the output zone Z. Thus, the air currents passing through the output zone Z can be affected by the plurality of bulges <NUM>. Turbulence can be generated on the surfaces of the plurality of bulges <NUM> to delay separation of the air currents, thereby generating small vortexes and reducing the resistance. Thus, effects of increasing the airflow and the air pressure and/or reducing the noise can be provided, and these effects can be proven by experiments, which will be set forth hereinafter.

With reference to <FIG> and <FIG>, the plurality of bulges <NUM> protrudes from the inner face W of the sidewall <NUM>. In this embodiment, the plurality of bulges <NUM> may be formed while proceeding with injection molding of the sidewall <NUM> made of plastic material, such that the plurality of bulges <NUM> can be integrally formed and connected with the sidewall <NUM>. Nevertheless, the present invention is not limited in this regard. The plurality of bulges <NUM> may be identical or different in sizes or shapes. Each of the plurality of bulges <NUM> is preferably in the form of a hemisphere protruding from the inner face W of the sidewall <NUM> and is connected to the inner face W of the sidewall <NUM> by the maximum width D of the respective bulge <NUM>. With reference to <FIG>, the height H1 of the inner face W of the sidewall <NUM> is preferably smaller than or equal to eight times the thickness T of each of the plurality of bulges <NUM> protruding from the inner face W. In this embodiment, each of the plurality of bulges <NUM> has a thickness T protruding beyond the inner face W and ranging between <NUM> and <NUM> and has a maximum width D ranging between <NUM> and <NUM>.

With reference to <FIG> and <FIG>, in this embodiment of this claimed invention, the plurality of bulges <NUM> is located between a half of the height H1 of the inner face W of the sidewall <NUM> and an intersection J of the sidewall <NUM> and the substrate <NUM>. The plurality of bulges <NUM> is preferably contiguous to the intersection J of the sidewall <NUM> and the substrate <NUM>. Preferably, at least <NUM>% of the plurality of bulges <NUM> is located in the tail section <NUM>. Thus, the effects of increasing the airflow and the air pressure and reducing the noise can be further improved.

<FIG> shows a cooling fan F of a second embodiment according to the present invention. This embodiment is substantially the same as the first embodiment. Similarly, all of the plurality of bulges <NUM> of the cooling fan F is located on the inner face W of the sidewall <NUM>. The main difference resides in that the plurality of bulges <NUM> of this embodiment is disposed in a wider area.

Specifically, the plurality of bulges <NUM> may be disposed from the tail section <NUM> along the inner face W of the sidewall <NUM> to a position adjacent to the tongue <NUM>, and the tongue <NUM> and the outwardly enlarged section <NUM> are free of the plurality of bulges <NUM>. Thus, the air currents can contact the plurality of bulges <NUM> along the entire flow path in the interior of the fan frame <NUM>.

<FIG> and <FIG> show a cooling fan F of a third embodiment but not belonging to the claimed invention. This embodiment is substantially the same as the second embodiment. The main difference resides in that the plurality of bulges <NUM> of this embodiment is located on the inner face W of the lid <NUM> rather than the inner face W of the sidewall <NUM>.

Specifically, the plurality of bulges <NUM> of this embodiment may be distributed on the inner face W of the lid <NUM> in an array. The plurality of bulges <NUM> may be located between the tail section <NUM> and the second reference plane S2. Preferably, the plurality of bulges <NUM> is adjacent to the tail section <NUM> and remote from the second reference plane S2. Alternatively, all of the plurality of bulges <NUM> may be located in the output zone Z. Thus, the effects of increasing the air pressure and reducing the noise can also be achieved, and the effect of increasing the air pressure is more obvious (which can be proven by experiments set forth hereinafter). Furthermore, since the plurality of bulges <NUM> is disposed on the lid <NUM> in this embodiment, the plurality of bulges <NUM> may be formed by a pressing process when the lid <NUM> is made of metal, such that a plurality of dimples can be formed on an outer face of the lid <NUM> while forming a plurality of bulges <NUM> on the inner face W of the lid <NUM>. Furthermore, in a case that the lid <NUM> is made of plastic material, the plurality of bulges <NUM> may be formed while forming the lid <NUM>, such that the plurality of bulges <NUM> can be integrally formed and connected with the lid <NUM>. Alternatively, the plurality of bulges <NUM> can be adhered to the inner face W of the lid <NUM> after formation of the lid <NUM>. The present invention is not limited in this regard.

<FIG> shows a cooling fan F of a fourth embodiment according to the present invention. In this embodiment, a portion of the plurality of bulges <NUM> protrudes from the inner face W of the sidewall <NUM>, and another portion of the plurality of bulges <NUM> protrudes from the inner face W of the lid <NUM>. Nevertheless, the disposition of the bulges <NUM> is not limited to the patterns disclosed in this figure. Furthermore, the auxiliary air inlet <NUM> (<FIG>) may be omitted in the fan frame <NUM> of this embodiment. Nevertheless, in the present invention, it is not limited to dispose the bulges <NUM> on the frame <NUM> without the auxiliary air inlet <NUM>. Namely, the fan frame <NUM> of each embodiment according to the present invention may or may not include the auxiliary air inlet <NUM>, and disposition of the auxiliary air inlet <NUM> is irrelevant to the disposition pattern of the plurality of bulges <NUM>.

<FIG> shows a cooling fan F of a fifth embodiment according to the present invention. This embodiment is substantially the same as the first embodiment. The main difference resides in that the fan frame <NUM> of this embodiment has two air outlets <NUM>, and the orientations of the two air outlets <NUM> may be different.

Specifically, in the fan frame <NUM> of this embodiment, the sidewall <NUM> may include a first section 12a and a second section 12b discontinuous to the first section 12a. As viewed from top of the fan frame <NUM>, the substrate <NUM> may be substantially rectangular. The first section 12a of the sidewall <NUM> may be substantially L-shaped and is connected to two adjoining edges of the substrate <NUM>. The second section 12b of the sidewall <NUM> may be connected to an intersection of another two adjoining edges of the substrate <NUM>. After the lid <NUM> is connected to the first section 12a and the second section 12b of the sidewall <NUM>, one of the two air outlets <NUM> may be located between the second section 12b and an end of the first section 12a, and another of the two air outlets <NUM> may be located between the second section 12b and another end of the first section 12a, such that the orientations of the two air outlets <NUM> are substantially orthogonal to each other. Nevertheless, the present invention is not limited in this regard.

The outwardly enlarged section <NUM> and the tail section <NUM> of the sidewall <NUM> may be located on the two ends of the first section 12a of the sidewall <NUM>, respectively. The second section 12b of the sidewall <NUM> may also form a tongue <NUM>. Generally, the air outlet <NUM> between the tail section <NUM> and the tongue <NUM> of the second section 12b of the sidewall <NUM> is the primary air outlet <NUM>, whereas the air outlet <NUM> between the outwardly enlarged section <NUM> and the tongue <NUM> of the second section 12b of the sidewall <NUM> is the auxiliary air outlet <NUM>. Thus, the plurality of bulges <NUM> is preferably disposed adjacent to the primary air outlet <NUM>. The first reference plane S1 and the second reference plane S2 (see <FIG>) of the cooling fan F of this embodiment are defined with respect to the primary air outlet <NUM>.

Furthermore, the fan frame <NUM> may further include at least one supporting peg <NUM>. The supporting peg <NUM> is connected to the substrate <NUM> and/or the lid <NUM> to prevent interference with the rotating impeller <NUM> when the substrate <NUM> or the lid <NUM> is subject to pressure. The supporting peg <NUM> is located in the air outlet <NUM> to achieve a better supporting effect. In this embodiment, each of the two air outlets <NUM> has a supporting peg <NUM> disposed therein to thoroughly prevent interference between the fan frame <NUM> and the impeller <NUM>.

<FIG> shows a cooling fan F of a sixth embodiment according to the present invention. This embodiment is substantially the same as the fifth embodiment. The main difference resides in that the cooling fan F of this embodiment further includes at least one flow guiding plate <NUM>.

Specifically, when there is only one flow guiding plate <NUM>, the flow guiding plate <NUM> is preferably located in the primary air outlet <NUM>. When there are two flow guiding plates <NUM>, the two flow guiding plates <NUM> are disposed in the two air outlets <NUM>, respectively. Two ends of the flow guiding plate <NUM> may be connected to the inner face W of the sidewall <NUM>. According to the type of the fan frame <NUM> of this embodiment, an end of the flow guiding plate <NUM> may be connected to the first section 12a of the sidewall <NUM>, whereas the other end of the flow guiding plate <NUM> may be connected to the second section 12b of the sidewall <NUM>, such that the flow guiding plate <NUM> extends transversely in the air outlet <NUM>. In the embodiment including the supporting peg <NUM>, the flow guiding plate <NUM> may be coupled to the supporting peg <NUM>. For example, the supporting peg <NUM> is coupled by extending through the flow guiding plate <NUM> to improve the stability of the flow guiding plate <NUM>.

With reference to <FIG>, the cross sectional shape of the flow guiding plate <NUM> may be rectangular, elliptic or, preferably, in the form of an airfoil. An edge P of the flow guiding plate <NUM> facing the impeller <NUM> is aligned with <NUM>-<NUM>% of a height H2 of the plurality of blades <NUM>, preferably <NUM>% of the height H2. Thus, when the air outlet <NUM> has the flow guiding plate <NUM> disposed therein, the flow guiding plate <NUM> may generate an effect similar to the plurality of bulges <NUM>.

<FIG> shows a cooling fan F of a seventh embodiment according to the present invention. This embodiment is substantially the same as the sixth embodiment. The main difference resides in that the substrate <NUM> may further include a slot <NUM> adjacent to the air outlet <NUM>.

Specifically, the slot <NUM> of the substrate <NUM> may extend parallel to the air outlet <NUM>. In this embodiment, two ends of the slot <NUM> extends to the sidewall <NUM>. Nevertheless, the present invention is not limited in this regard. Furthermore, the slot <NUM> of the substrate <NUM> may be located below the flow guiding plate <NUM>, such that an area of a vertical projection of the flow guiding plate <NUM> formed on the substrate <NUM> at least partially overlaps with the slot <NUM>.

To prove the above effects, the present invention uses a comparative cooling fan, a first cooling fan, a second cooling fan, a third cooling fan, and a fourth cooling fan to proceed with tests of airflow, air pressure, and noise (such as by computer software simulation and numerical analysis). Each of the fan frames of the comparative cooling fan and the first to fourth cooling fans includes only one air outlet, and the comparative cooling fan does not include the features of the bulges, the flow guiding plate, and the slot mentioned above. Using the comparative cooling fan as a reference, each of the first to third cooling fans further includes a plurality of bulges <NUM>. Furthermore, the disposition pattern of the plurality of bulges <NUM> of the first cooling fan is shown in <FIG>, the disposition pattern of the plurality of bulges <NUM> of the second cooling fan is shown in <FIG>, and the disposition pattern of the plurality of bulges <NUM> of the third cooling fan is shown in <FIG>, such that the variable of the first to third cooling fans relative to the comparative cooling fan is the disposition pattern of the plurality of bulges <NUM>. Furthermore, using the first cooling fan as a reference, the fourth cooling fan further includes a flow guiding plate <NUM> and a slot <NUM> (see <FIG>), but the fourth cooling fan is not the type shown in <FIG>. Namely, the fourth cooling fan includes the features of the plurality of bulges <NUM>, the flow guiding plate <NUM>, and the slot <NUM>. Furthermore, the disposition pattern of the plurality of bulges <NUM> is shown in <FIG>, such that the variables of the fourth cooling fan relative to the comparative cooling fan are the plurality of bulges <NUM>, the flow guiding plate <NUM>, and the slot <NUM>, whereas the variables of the fourth cooling fan relative to the first cooling fan are the flow guiding plate <NUM> and the slot <NUM>.

With reference to <FIG>, regarding the simulation result of the airflow, given the same impeller rotating speed of <NUM> RPM, the maximum airflow of the fourth cooling fan can be increased by about <NUM>% in comparison with the comparative cooling fan, the maximum airflow of the first cooling fan can be increased by about <NUM>% in comparison with the comparative cooling fan, and the maximum airflow of the second cooling fan can be increased by about <NUM>% in comparison with the comparative cooling fan. Therefore, the fourth cooling fan has the most significant airflow increasing effect, and the first cooling fan is the second best. Thus, it is proven that disposition pattern of the plurality of bulges <NUM> according to <FIG> can achieve a significant airflow increasing effect, and provision of the flow guiding plate <NUM> and the slot <NUM> (see <FIG>) can further increase the airflow.

With reference to <FIG>, regarding the simulation result of the air pressure, given the same impeller rotating speed of <NUM> RPM, the maximum static pressure of the third cooling fan can be increased by about <NUM>% in comparison with the comparative cooling fan, and the maximum static pressure of the fourth cooling fan can be increased by about <NUM>% in comparison with the comparative cooling fan. Therefore, the third cooling fan has the most significant air pressure increasing effect, and the fourth cooling fan is the second best. Thus, it is proven that disposition pattern of the plurality of bulges <NUM> on the inner face W of the lid <NUM> (see <FIG>) can achieve a significant static pressure increasing effect, and provision of the flow guiding plate <NUM> and the slot <NUM> (see <FIG>) also assist in the increase of the static pressure.

Regarding the simulation result of the operational noise, given the same impeller rotating speed of <NUM> RPM, the comparative cooling fan has the largest acoustic power, whereas the acoustic powers of the first to fourth cooling fans are lowered, and the sound quality of the first cooling fan is the best. Thus, each of the cooling fans of the various embodiments according to the present invention has the effect of improving the sound quality to reduce operational noise.

According to the above simulation results, when the primary objective is increasing the airflow, the plurality of bulges <NUM> is disposed according to the disposition pattern shown in <FIG>, and the flow guiding plate <NUM> and the slot <NUM> (see <FIG>) are also provided, such that the airflow can be more significantly increased. When it is desired to increase the airflow and to reduce the noise, the plurality of bulges <NUM> may be disposed according to the disposition pattern shown in <FIG>, and it is not necessary to provide the flow guiding plate <NUM> and the slot <NUM>, such that the airflow can be obviously increased and the noise can be obviously reduced. When the primary objective is to increase the air pressure, the plurality of bulges <NUM> is disposed according to the disposition pattern shown in <FIG>, such that the air pressure can be increased more significantly. When it is desired to increase both the airflow and the air pressure, the plurality of bulges <NUM> is disposed according to the disposition pattern shown in <FIG>, and the flow guiding plate <NUM> and the slot <NUM> are also provided, such that the airflow can be significantly increased and the air pressure is slightly increased.

Claim 1:
A cooling fan (F) comprising:
a fan frame (<NUM>) including a substrate (<NUM>), a sidewall (<NUM>) connected to the substrate (<NUM>), and a lid (<NUM>) connected to the sidewall (<NUM>) and opposite to the substrate (<NUM>), wherein an air inlet (<NUM>) is formed in the lid (<NUM>), and wherein the substrate (<NUM>), the sidewall (<NUM>), and the lid (<NUM>) together define at least one air outlet (<NUM>);
an impeller (<NUM>) rotatably mounted in the fan frame (<NUM>); and
a plurality of bulges (<NUM>) protruding from an inner face (W) of the sidewall (<NUM>) and optionally also from an inner face (W) of the lid (<NUM>);
wherein the cooling fan is characterized in that:
the plurality of bulges (<NUM>) on the sidewall (<NUM>) is located only between a half of a height (H1) of the inner face (W) of the sidewall (<NUM>) and an intersection (J) of the sidewall (<NUM>) and the substrate (<NUM>).