- 1 Description Title of Invention ELECTRIC VACUUM CLEANER Technical Field [0001] The present invention relates to an electric vacuum cleaner including a cyclone type dust collection unit. Background Art [0002] Conventionally, there has been an electric vacuum cleaner that includes a dust collection unit having a swirl chamber, introduces an airflow mixed with dust sucked from a cleaning surface into the dust collection unit and swirls the airflow, separates the dust from air by a centrifugal force, and holds only the dust in the dust collection unit (for example, see Patent Literature 1). Citation List Patent Literature [0003a] Patent Literature 1: Japanese Patent Laid-Open No. 2012-61093 (Figures 2 and 3) [0003b] -2 In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art. Summary of Invention Problem to be Solved by the Invention [0004] However, a dust collector that stores dust in the dust collection unit also serves as a swirl chamber that generates a swirl flow in air mixed with dust introduced therein, and has a cylindrical shape so as to efficiently generate the swirl flow. Thus, the dust collection unit must include a cylindrical dust collection container so as to efficiently separate dust from air mixed with dust, has limitations in design and size, and has a problem in a reduction in size of the electric vacuum cleaner. [0005] The present invention is achieved to solve the above described problem, and has an object to maintain a dust collection capacity of a dust collection unit, increase flexibility in design and actual size, and allow a reduction in size of the electric vacuum cleaner. An additional or alternative object of the present invention is to provide the public with a useful choice. Means for Solving the Problem [0006] -3 In accordance with an aspect of the present invention, there is provided an electric vacuum cleaner comprising: a dust collection unit; and a vacuum cleaner body to which the dust collection unit is removably mounted, wherein the dust collection unit includes an inlet portion case and a dust collection portion case, the inlet portion case has a swirl chamber that swirls air containing dust introduced therein and separates dust from an airflow containing dust, and an opening that discharges the separated dust from the swirl chamber, the inlet portion case is located in the dust collection portion case, and a dust collection chamber that holds the dust discharged from the swirl chamber is formed in a space formed between the dust collection portion case and an outer surface of the inlet portion case, wherein the dust collection portion case has an oval cylindrical shape, wherein the opening opens in a direction of a short axis of an oval that is a section of the dust collection portion case. Advantageous Effect of Invention [0007] At least preferred embodiments of the present invention increase flexibility in shape of the dust collection unit, allow a reduction in size while maintaining a dust collection capacity, and allow a reduction in visual size and actual size of the electric vacuum cleaner. Brief Description of Drawings [0008] Figure 1 shows an electric vacuum cleaner according to an embodiment. Figure 2 is a side view of a vacuum cleaner body according to the embodiment.
-4 Figure 3 is an appearance perspective view of the vacuum cleaner body of the electric vacuum cleaner according to the embodiment seen obliquely from front. Figure 4 is an appearance perspective view of the vacuum cleaner body of the electric vacuum cleaner according to the embodiment seen obliquely from behind. Figure 5 shows the state in Figure 3 with a dust collection unit 12 being removed. Figure 6 is a plan view of the dust collection unit 12 seen from a mounting side to a body 6. Figure 7 is a central sectional view of the vacuum cleaner body according to the embodiment. Figure 8 is a perspective view of the dust collection unit. Figure 9 is an exploded perspective view of the dust collection unit. Figure 10 is a D-D sectional view of Figure 12. Figure 11 is a perspective view of a D-D section of Figure 12. Figure 12 is a plan view of the dust collection unit. Figure 13 is a side view of the dust collection unit. Figure 14 is an A-A sectional view of Figure 13. Figure 15 is a B-B sectional view of Figure 12. Figure 16 is a perspective view of the dust collection unit seen from a unit side outlet. Figure 17 is a perspective view of a C-C section of Figure 12. Figure 18 is a comparison view showing a comparison between a cylindrical dust collection unit and the C-C section of Figure 12. Figure 19 is a schematic view of the C-C section of Figure 12.
-5 Modes for Carrying Out the Invention [0009] Embodiment (Configuration of electric vacuum cleaner) With reference to Figures 1 to 7, an embodiment will be described. As shown in Figure 1, an electric vacuum cleaner 1 includes attachments such as a suction port body 2 and an extension pipe 3, a connection pipe 4, a suction hose 5, and a vacuum cleaner body 6 (hereinafter referred to as "body 6") as essential portions. The suction port body 2 sucks dust on a floor with air through an opening formed downward. A connection portion 2a for exhausting air is provided in a substantially middle portion in a longitudinal direction of the suction port body 2. [0010] An end on one side (an intake side) of the extension pipe 3 is connected to the connection portion 2a of the suction port body 2. The extension pipe 3 is telescopically configured by a combination of cylindrical members 3a, 3b having different inner diameters. An end on one side (an intake side) of the connection pipe 4 is connected to the other end of the extension pipe 3. The connection pipe 4 is formed of a cylindrical member. [0011] A handle 7 is provided on the connection pipe 4. The handle 7 is held by a user of the electric vacuum cleaner 1 for operation. The handle 7 has an operation switch 8 for controlling operation of the electric vacuum cleaner 1. An end on one side (an intake side) of the suction hose 5 is connected to the other end of the connection pipe 4. The suction hose 5 is formed of a flexible member having a bellows shape.
-6 [0012] (Configuration of vacuum cleaner body) As shown in Figures 2 to 7, the body 6 separates dust from air containing sucked dust (air containing dust), and discharges air from which the dust is removed (clean air) (for example, returns the air to a room). A hose connection port 9 is formed in a front end of the body 6. The other end of the suction hose 5 is connected to the hose connection port 9 of the body 6. Wheels 10 are mounted on both sides and the bottom surface of the body 6. [0013] The body 6 includes a power cord 11. A cord plug 11 a is mounted to one end of the power cord 11, and the power cord 11 is wound around a cord reel portion (not shown) in the body 6 from the other end. A pair of edges to be inserted into a socket protrude from the cord plug 11 a. A power cord takeout port 6h through which the power cord 11 is taken into and out of the body and where the cord plug 11 a is located when the power cord 11 is stowed in the cord reel opens rearward in an upper portion of the body 6 so that the user can easily pull the power cord 11. [0014] The cord plug 11 a is held to protrude from the power cord takeout port 6h so that the user can easily hold the cord plug Ila. The cord plug 11 a is connected to the socket as an external power source to energize an internal device such as an electric air blower 13 described later. The electric air blower 13 is driven by energization, and performs predetermined suction depending on operation with the operation switch 8. [0015] -7 The suction port body 2, the extension pipe 3, the connection pipe 4, and the suction hose 5 have inner portions continuously formed. If the electric air blower 13 described later performs suction, dust on a floor is sucked with air into the suction port body 2. The air containing dust sucked into the suction port body 2 is fed through the suction port body 2, the extension pipe 3, the connection pipe 4, and the suction hose 5 in this order, and fed to the body 6. As such, the suction port body 2, the extension pipe 3, the connection pipe 4, and the suction hose 5 form an air trunk for allowing the air containing dust to flow from outside into the body 6. [0016] Next, a dust collection unit 12 is removably mounted to the body 6. Figure 5 shows the dust collection unit 12 being removed from the body 6. The body 6 includes an electric air blower housing unit 6a and a dust collection unit housing portion 6b. [0017] The electric air blower housing unit 6a is formed of a box-like member (for example, a molded product). A portion from a rear end to a predetermined position closer to a front side of the electric air blower housing unit 6a has an inclined upper surface with a high rear side and a low front side. A portion on a front side of the predetermined position of the electric air blower housing unit 6a has an inclined upper surface with a low rear side and a high front side. [0018] Thus, a part of the upper surface of the electric air blower housing unit 6a is substantially recessed when seen from a side. The substantially recessed portion in the electric air blower housing unit 6a has a dust collection unit housing portion 6b formed thereon. The dust collection unit housing portion 6b houses the dust collection unit 12.
-8 When the dust collection unit 12 is appropriately mounted to the electric air blower housing unit 6a, essential portions of the dust collection unit 12 are placed in the dust collection unit housing portion 6b, that is, above the electric air blower housing unit 6a. [0019] Also with reference to Figure 7, an internal configuration of the body 6 will be described. The electric air blower housing unit 6a of the body 6 houses the electric air blower 13, the cord reel portion, or the like. The electric air blower housing unit 6a has an intake air trunk 14 (Figure 5) formed therein for leading air containing dust having flowed in through the hose connection port 9 to the dust collection unit 12 in the body 6. [0020] One end of the intake air trunk 14 opens in a front surface of the body 6 to form the hose connection port 9. The intake air trunk 14 passes through an internal space of the electric air blower housing unit 6a. The other end of the intake air trunk 14 opens in an upper surface of the electric air blower housing unit 6a (that is, a side of the dust collection unit housing portion 6b) to form a body side outlet 15. The body side outlet 15 is placed closer to a rear end and one side of the upper surface of the electric air blower housing unit 6a. [0021] Next, with reference to Figure 6, the dust collection unit 12 separates dust from air containing dust, and temporarily stores the separated dust. The dust collection unit 12 swirls the air containing dust therein to separate dust from air by a centrifugal force. Specifically, the dust collection unit 12 has a cyclone separation function therein. [0022] -9 A unit side inlet 18 opens in a side surface of the dust collection unit 12. The unit side inlet 18 is an opening for introducing an airflow mixed with dust from the body side outlet 15 into the dust collection unit 12. A unit side outlet 19 opening downward is provided in an upper portion of the dust collection unit 12. The unit side outlet 19 is an opening for exhausting an airflow separated from dust in the dust collection unit 12 toward the electric air blower housing unit 6a. [0023] An exhaust air trunk 16 for leading air discharged from the dust collection unit 12 (clean air from which dust is removed by the dust collection unit 12) to an exhaust port (not shown) in the body 6 is formed in the electric air blower housing unit 6a. One end of the exhaust air trunk 16 opens in the upper surface of the electric air blower housing unit 6a to form a body side inlet 17. [0024] The exhaust air trunk 16 passes through the internal space of the electric air blower housing unit 6a. The other end of the exhaust air trunk 16 opens outward of the electric air blower housing unit 6a to form the exhaust port. The body side inlet 17 is placed substantially at a middle close to the rear end of the upper portion of the body 6. [0025] When the dust collection unit 12 with the components configured as described above is housed in the dust collection unit housing portion 6b, the unit side inlet 18 and the body side outlet 15 are connected to face each other, and the unit side outlet 19 and the body side inlet 17 are connected to face each other. [0026] - 10 The electric air blower 13 generates an airflow in the air trunks formed in the electric vacuum cleaner 1 (the air trunk for allowing air containing dust to flow into the body 6, the intake air trunk 14, an air trunk described later in the dust collection unit 12, and the exhaust air trunk 16). The electric air blower 13 is placed in the exhaust air trunk 16 in a predetermined position closer to the rear end in the electric air blower housing unit 6a. [0027] When the electric air blower 13 starts suction, an airflow (suction air) is generated in each air trunk formed in the electric vacuum cleaner 1. The air containing dust sucked by the suction port body 2 is taken from the hose connection port 9 into the body 6. The air containing dust having flowed into the body 6 passes through the intake air trunk 14, and is fed from the body side outlet 15 through the unit side inlet 18 to the dust collection unit 12. [0028] The airflow separated from dust in the dust collection unit 12 is discharged from the unit side outlet 19 toward the body side inlet 17. The air (clean air) discharged from the dust collection unit 12 flows into the exhaust air trunk 16, and passes through the electric air blower 13 in the exhaust air trunk 16. The air having passed through the electric air blower 13 further travels through the exhaust air trunk 16, and is discharged from the exhaust port to the outside of the body 6 (electric vacuum cleaner 1). [0029] (Dust collection unit 12) Next, with reference to Figures 8 to 18, the dust collection unit 12 will be described in detail. As shown in the drawings, the dust collection unit 12 generally has - 11 a substantially oval cylindrical shape. The dust collection unit 12 includes a discharge portion case 12a, a filter portion case 12b, an inlet portion case 12c, and a dust collection portion case 12d. [0030] The discharge portion case 12a, the filter portion case 12b, the inlet portion case 12c, and the dust collection portion case 12d are formed of, for example, molded products. The discharge portion case 12a, the filter portion case 12b, the inlet portion case 12c, and the dust collection portion case 12d are configured to be disassembled into a state in Figure 9 or assembled into a state in Figure 8 by predetermined operation (for example, operation of a lock mechanism). Also, only the dust collection portion case 12d may be removed from the state in Figure 8. [0031] Now, the dust collection unit 12 configured by an appropriate combination of the discharge portion case 12a, the filter portion case 12b, the inlet portion case 12c, and the dust collection portion case 12d will be described. In the descriptions on the dust collection unit 12 below, upper and lower sides are specified with reference to the direction in Figure 12. [0032] As shown in Figures 10, 13, and 15, the unit side inlet 18 is formed in one side of the inlet portion case 12c of the dust collection unit 12. Also, the unit side outlet 19 is formed substantially at a middle of the discharge portion case 12a of the dust collection unit 12. The unit side outlet 19 is placed above the unit side inlet 18. The unit side inlet 18 and the unit side outlet 19 open toward the same side. The unit side outlet 19 is placed above the unit side inlet 18.
- 12 [0033] As shown in Figures 14 and 15, the inlet portion case 12c introduces air containing dust from outside, and includes the swirl chamber 20. An upper portion of the swirl chamber 20 is constituted by a cylindrical portion 20a. A lower portion of the swirl chamber 20 is constituted by a conical portion 20b. [0034] The cylindrical portion 20a has a hollow cylindrical shape. The cylindrical portion 20a is placed so that a central axis thereof is vertically directed. The conical portion 20b has a hollow truncated conical shape. The conical portion 20b is vertically placed so that a central axis thereof matches the central axis of the cylindrical portion 20a. An upper end of the conical portion 20b is connected to a lower end of the cylindrical portion 20a, and the conical portion 20b is provided to extend downward from the lower end of the cylindrical portion 20a with a diameter decreasing downward. [0035] A continuous space formed by an internal space of the cylindrical portion 20a and an internal space of the conical portion 20b formed in this manner constitutes the swirl chamber 20. The swirl chamber 20 is a space for swirling air containing dust introduced through the unit side inlet 18. [0036] As shown in Figures 10 and 11, the inlet 21 is formed in the upper portion of the cylindrical portion 20a (an uppermost portion of a side wall that forms the swirl chamber 20). One end of an inlet pipe 22 is connected to the inlet 21. The other end of the inlet pipe 22 is connected to the unit side inlet 18.
- 13 The inlet pipe 22 leads air containing dust having passed through the intake air trunk 14 into the cylindrical portion 20a (swirl chamber 20). An internal space of the inlet pipe 22 forms an inlet air trunk. The inlet air trunk is an air trunk for allowing air containing dust to flow from the intake air trunk 14 into the swirl chamber 20. [0037] The inlet pipe 22 has, for example, a hollow square shape and is formed of a straight member. The inlet pipe 22 has an axis perpendicular to the central axis of the cylindrical portion 20a, and placed tangentially of the cylindrical portion 20a (a side wall of the swirl chamber 20). [0038] Next, as shown in Figures 14, 15, and 17, a zero-order opening 28 is formed in the side wall of the cylindrical portion 20a of the swirl chamber 20. The zero-order opening 28 is placed below the unit side inlet 18 in a central axis direction of the swirl chamber 20. More specifically, the zero-order opening 28 is placed below the inlet 21 in the central axis direction of the swirl chamber 20, that is, on a downstream side of a swirl flow generated in the swirl chamber 20. [0039] Next, a lower end of the conical portion 20b that constitutes the swirl chamber 20 opens downward (in the central axis direction). The opening formed at a lower end of the conical portion 20b is a primary opening 29. Thus, the primary opening 29 is placed on the downstream side of the zero-order opening 28 in the swirl flow generated in the swirl chamber 20. A partition 30 is provided outside the conical portion 20b. The partition 30 has a substantially cylindrical shape having substantially the same diameter - 14 as the cylindrical portion 20a. An upper end of the partition 30 is connected near the connection portion between the cylindrical portion 20a and the conical portion 20b. [0040] Next, the dust collection portion case 12d has a substantially oval cylindrical shape like a cup with a closed lower side and an open upper side. The dust collection portion case 12d is placed outside and on a lower side of the inlet portion case 12c. Specifically, the cylindrical portion 20a and the conical portion 20b that form the swirl chamber 20 therein are placed inside the dust collection portion case 12d. In this state, a lower side from an upper end of the zero-order opening 28 in the cylindrical portion 20a of the inlet portion case 12c, the conical portion 20b, and the partition 30 are entirely housed in the dust collection portion case 12d. A lower end of the partition 30 engages a protrusion formed on a bottom surface of the dust collection portion case 12d. An opening 121d in the dust collection portion case 12d is closed by a lid 121c protruding like a flange from an outer peripheral surface of the inlet portion case 12c. [0041] With reference to Figure 19 that is a schematic view of a section (C-C section of Figure 12) laterally cut in the position of the zero-order opening 28, the swirl chamber 20 is located in the dust collection portion case 12d so that a center 01 of the swirl chamber 20 substantially matches a center 02 of the dust collection portion case 12d. The zero order opening 28 is directed in a direction of a short axis YY' of an oval that is a section of the dust collection portion case 12d. [0042] Specifically, a distance a between the zero-order opening 28 and an inner surface of the dust collection portion case 12d (a distance between the dust collection portion - 15 case 12d and the cylindrical portion 20a facing each other in the direction of the short axis YY' of the oval that is the section of the dust collection portion case 12d) and a distance b between an outer surface of the cylindrical portion 20a at a position rotated 90 degrees with reference to the center 01 of the swirl chamber 20 and the inner surface of the dust collection portion case 12d (a distance between the dust collection portion case 12d and the cylindrical portion 20a facing each other in a direction of a long axis XX' of the oval that is the section of the dust collection portion case 12d) have a relationship of a<b. [0043] A space formed between the inlet portion case 12c and the dust collection portion case 12d is partitioned into two by the partition 30. Among two spaces thus formed, the space formed outside the cylindrical portion 20a and the partition 30 is a zero-order dust collection chamber 31, and the space formed below and outside the conical portion 20b and inside the partition 30 is a primary dust collection chamber 32. Specifically, the spaces formed between the dust collection portion case 12d and the outer surface of the inlet portion case 12c are the dust collection chambers 31, 32 that hold dust discharged from the swirl chamber. [0044] The zero-order dust collection chamber 31 communicates with the zero-order opening 28, and surrounds the entire outer periphery of the swirl chamber 20. The zero order dust collection chamber 31 extends downward from the zero-order opening 28. The primary dust collection chamber 32 extends around the entire periphery of the conical portion 20b from below the primary opening 29. [0045] - 16 A mesh-like discharge port 34 is provided at a center of an upper end of the cylindrical portion 20a. The discharge port 34 is formed of micropores opening in a part of a side wall and a lower side of a pipe having a substantially cylindrical upper portion and a substantially conical lower portion. Thus, as compared to a discharge port opening only in the lower side of the pipe, a force to suck an airflow in the swirl chamber 20 in a swirl direction is increased to allow a swirl airflow in the swirl chamber 20 to easily travel in the swirl direction. [0046] Thus, a swirl force of the airflow in the upper side of the swirl chamber 20 can be increased to further improve separation performance. A discharge pipe 33 provides communication between the discharge port 34 and the unit side outlet 19. In other words, a part of the mesh-like discharge port 34 described above is formed of the micropores opening in a part of a side wall of the discharge pipe 33. The discharge pipe 33 is mainly constituted by the discharge portion case 12a. The discharge port 34 is formed in the filter portion case 12b, and an upper end wall of the swirl chamber 20 is formed of a part of a bottom surface of the filter portion case 12b. [0047] If the dust collection unit 12 having the above described configuration is appropriately mounted to the dust collection unit housing portion 6b, a central axis of the swirl chamber 20 or the like is obliquely placed to match a slope of the dust collection unit housing portion 6b. The unit side inlet 18 and the unit side outlet 19 are placed to face the slope, and the unit side inlet 18 is connected to the body side outlet 15. The unit side outlet 19 is connected to the body side inlet 17 (Figure 7). In such a state, the zero-order opening 28 opens in a direction opposite to the body 6, that is, in an upward - 17 direction R (Figures 2 to 4). The upward direction R refers to a direction opposite to a floor G with the vacuum cleaner being placed on the floor G. [0048] Next, a function of the dust collection unit 12 having the above-described function will be described. When the electric air blower 13 starts suction, the air containing dust passes through the intake air trunk 14 and reaches the body side outlet 15 as described above. The air containing dust successively passes through the body side outlet 15 and the unit side inlet 18, and flows into the inlet pipe 22, that is, into an inlet air trunk. The air containing dust having flowed into the inlet air trunk travels in the axial direction of the inlet pipe 22 (travels straight), and flows through the inlet 21 into the cylindrical portion 20a (swirl chamber 20). Such a path is shown as a path A by a solid arrow. [0049] The air containing dust taken from the inlet 21 into the swirl chamber 20 forms a swirl airflow that turns in a predetermined direction along a side wall in the swirl chamber 20. The swirl airflow flows downward by a path structure and gravity thereof while forming a forced vortex region near the central axis and a free vortex region outside the forced vortex region. A centrifugal force is applied to the dust contained in the swirl airflow (airflow in the swirl chamber 20). For example, relatively large dust such as fiber dust or hair (such dust is hereinafter referred to as "dust a") falls in the swirl chamber 20 while being pressed against the inner peripheral surface of the cylindrical portion 20a (inner wall surface of the swirl chamber 20) by the centrifugal force. When reaching the height of the zero-order opening 28, the dust a is separated from the swirl airflow, and fed through the zero-order opening 28 to the zero-order dust collection chamber 31.
- 18 [0050] With reference to Figure 19, the dust a discharged from the zero-order opening 28 to the zero-order dust collection chamber 31 is discharged from the zero-order opening 28 tangentially of the cylindrical portion 20a because of the swirl airflow. Specifically, the dust a is discharged from the zero-order opening 28 in the direction of the long axis XX' of the oval that is the section of the dust collection portion case 12d, and thus flows to a relatively large space in the zero-order dust collection chamber 31 with a large clearance between the cylindrical portion 20a and the dust collection portion case. Then, the dust a having flowed from the zero-order opening 28 into the zero-order dust collection chamber 31 falls in the zero-order dust collection chamber 31 while moving in the same direction as the direction of the airflow swirling in the swirl chamber 20 (swirl direction). The dust a reaches a bottom of the zero-order dust collection chamber 31 and is collected. [0051] Dust that has not entered the zero-order dust collection chamber 31 from the zero order opening 28 travels downward while swirling in the swirl chamber 20 on the airflow in the swirl chamber 20. Relatively small dust such as sand dust or fine fiber dust (such dust is hereinafter referred to as "dust P") passes through the primary opening 29. Then, the dust P falls into the primary dust collection chamber 32 and is captured. [0052] When the airflow swirling in the swirl chamber 20 reaches the lowermost portion of the swirl chamber 20, the airflow changes its traveling direction to an upward direction, and rises along the central axis of the swirl chamber 20. The dust a and the dust P are removed from the air that forms the rising airflow by the action described above. The - 19 airflow from which the dust a and the dust P are removed (clean air) passes through the discharge port 34 and is discharged to the outside of the swirl chamber 20. The air discharged from the swirl chamber 20 passes through the inside of the discharge pipe 33, and reaches the unit side outlet 19. Then, the clean air successively passes through the unit side outlet 19 and the body side inlet 17, and is fed to the exhaust air trunk 16. [0053] The electric air blower 13 performs suction, and thus as described above, the dust a accumulates in the zero-order dust collection chamber 31 and the dust P accumulates in the primary dust collection chamber 32. The dust a and the dust P can be easily disposed of by removing the dust collection portion case 12d from the dust collection unit 12. [0054] In the dust collection unit 12 configured as described above, the air containing dust flows from the inlet 21 into the swirl chamber 20 so as to successively push the swirl airflow in the swirl chamber 20 from behind. Specifically, the air containing dust newly taken into the swirl chamber 20 flows into the swirl chamber 20 so as to accelerate the swirl airflow already formed in the swirl chamber 20. [0055] This can increase a swirl force, particularly above the zero-order opening 28, in the swirl chamber 20 and significantly improve a function of separating dust (particularly relatively large dust a) (separation function). Thus, there is no need to provide a different separation device on the upstream side or the downstream side of the dust collection unit 12. This can reduce the size of the dust collection unit 12, and reduce the sizes of the body 6 and the electric vacuum cleaner 1.
- 20 [0056] The increased swirl force above the zero-order opening 28 in the swirl chamber 20, which prevents the swirl airflow from moving downward, simply represents that a component of the airflow in the swirl direction above the zero-order opening 28 in the swirl chamber 20 is larger, and a component of the airflow moving downward is smaller. This can prevent the dust a accumulating on the bottom surface of the zero-order dust collection chamber 31 from being swirled up and scattered by the airflow having flowed into the zero-order dust collection chamber 31, and improve collection performance. [0057] Further, in the dust collection unit 12, the dust collection chambers 31, 32 are formed around the swirl chamber 20 as independent spaces. Thus, the shapes of the dust collection chambers 31, 32 do not influence the shape of the swirl chamber 20, and thus the shapes of the dust collection chambers 31, 32 are irrelevant to cyclone separation performance of separating dust from the airflow in the swirl chamber 20. Thus, the dust collection portion case 12d of various shapes may be used. This can easily reduce the size of the dust collection portion case 12d and also reduce the size of the vacuum cleaner, and further increases flexibility in design. [0058] Further, the shape of the dust collection portion case 12d can be determined without impairing cyclone performance as described above. Thus, as in this embodiment, the dust collection portion case 12d having the substantially oval cylindrical shape can reduce the entire height of the vacuum cleaner body when mounted to the vacuum cleaner body. For example, as shown in Figure 18, a height (AT) can be - 21 reduced while maintaining a dust collection capacity as compared to a cylindrical dust collection portion case (dashed dotted line). [0059] Further, since the zero-order opening 28 opens in the direction of the short axis YY', the dust a discharged from the zero-order opening 28 to the zero-order dust collection chamber 31 is discharged from the zero-order opening 28 tangentially of the cylindrical portion 20a because of the swirl airflow. Thus, the dust a is discharged from the zero-order opening 28 in the direction of the long axis XX' of the oval that is the section of the dust collection portion case 12d, and thus flows to a relatively large space in the zero-order dust collection chamber 31 with a large clearance between the cylindrical portion 20a and the dust collection portion case. As such, the direction of the dust discharged from the zero-order opening 28 is oriented to the large space in the zero-order dust collection chamber 31, thereby preventing the discharged dust from accumulating near the zero-order opening 28. [0060] Further, when the dust collection unit 12 is mounted to the body 6, the zero-order opening 28 is oriented upward, thereby preventing the zero-order opening 28 from being closed by the dust accumulating in the dust collection unit 12. [0061] Further, the dust collection unit 12 has the oval cylindrical shape, and thus the air having flowed from the zero-order opening 28 into the zero-order dust collection chamber 31 can smoothly flow, thereby preventing noise. [0062] - 22 The term 'comprising' as used in this specification and claims means 'consisting at least in part of. When interpreting statements in this specification and claims which include the term 'comprising', other features besides the features prefaced by this term in each statement can also be present. Related terms such as 'comprise' and 'comprised' are to be interpreted in a similar manner. Description of Reference Characters [0063] 1; vacuum cleaner 2; suction port body 3; extension pipe 3 4; connection pipe 5; suction hose 6; vacuum cleaner body 6a; electric air blower housing unit 6b; dust collection unit housing portion 7; handle 8; operation switch 9; hose connection port 10; wheels 11; power cord lla; cord plug 12; dust collection unit 12a; discharge portion case - 23 12b; filter portion case 12c; inlet portion case 12d; dust collection portion case 13; electric air blower 14; intake air trunk 15; body side outlet 16; exhaust air trunk 17; body side inlet 18; unit side inlet 19; unit side outlet 20; swirl chamber 20a; cylindrical portion 20b; conical portion 21; inlet 22; inlet pipe 28; zero-order opening 29; primary opening 30; partition 31; zero-order dust collection chamber 32; primary dust collection chamber