JP7795026B2 - Electric blower and electric vacuum cleaner equipped with same - Google Patents

Description

The present invention relates to an electric blower and an electric vacuum cleaner equipped with the same.

As an example of an electric blower (blower device) built into an electric vacuum cleaner, Patent Document 1 describes a blower device comprising: "an impeller 10 that rotates around a vertically extending central axis C; a motor 20 that is positioned below the impeller and has a stator 24 to rotate the impeller; a motor housing 21 that houses the stator; and a fan casing 2 that houses the impeller and motor housing and defines a first flow path 5 in the gap between the motor housing and the fan casing; the upper part of the fan casing covers the top of the impeller and has an air intake 3 that opens in the vertical direction; the lower part of the fan casing has an exhaust port 4 that communicates with the air intake via the first flow path; the motor housing has an inlet 21a that penetrates radially below the upper surface of the stator fixed to the inner surface of the motor housing and communicates with the first flow path; and the motor housing has a second flow path 6 that extends upward from the inlet and communicates with the space above the stator."

Japanese Patent Application Laid-Open No. 2018-105269

It is known that the operating air volume of electric vacuum cleaners varies greatly depending on operating conditions such as filter clogging due to dust and the material of the floor being cleaned. For this reason, electric blowers for electric vacuum cleaners are required to have strong suction power over a wide range of air volumes.

In addition, to improve the usability of electric vacuum cleaners, there is a demand for smaller and lighter electric blowers, but this reduces the heat dissipation area of the blower and increases the heat density inside the blower, making it necessary to improve the cooling performance of the motor and bearings.

In particular, battery-powered vacuum cleaners (secondary batteries), such as cordless stick vacuum cleaners and autonomous vacuum cleaners (robot vacuum cleaners), have low power consumption and a small maximum airflow rate due to the battery capacity. This poses the issue of reduced dust-transporting capacity and reduced suction power when the filter becomes clogged. Furthermore, battery-powered vacuum cleaners are required to be small and lightweight, and the electric blowers installed in these vacuum cleaners are required to have strong suction power over a wide range of airflow rates while also being compact.

Here, using a diffuser vane (referred to as "stationary vane 40" in Patent Document 1) allows for excellent pressure recovery at the design point airflow rate, but if the airflow rate drops below the design point airflow rate due to factors such as filter clogging, the diffuser performance will decrease due to a mismatch between the inlet angle of the diffuser vane and the inlet angle of the air flow into the diffuser, which could result in a decrease in the suction power of the vacuum cleaner.

In addition, in the blower device of Patent Document 1, as shown in Figure 4 and other figures in the same document, a portion of the airflow S flowing through the outer first flow path 5 flows into the inner second flow path 6 via the inlet 21a provided in the peripheral wall of the motor housing 21, cooling the upper bearing 26 and then the lower bearing 26. The airflow then is exhausted to the outside of the blower device 1 from the outlet (outlet 29a) of the second flow path 6 without merging with the first flow path 5. In this way, when the second flow path 6 branching off from the first flow path 5 is configured not to merge with the first flow path 5, pressure loss (resistance) occurs when a portion of the airflow S flowing through the first flow path 5 branches off into the second flow path 6, resulting in a decrease in the air volume downstream of the inlet 21a (branching point) in the first flow path 5 compared to the air volume upstream of the inlet 21a (branching point).

In addition, the second flow path 6 in Patent Document 1 is small in size, resulting in a small flow path area. Furthermore, because the air flows while bending inside the motor 20, there is a concern that the pressure loss in the flow path is large, the amount of cooling air is reduced, the temperature inside the motor 20 increases, and motor efficiency is reduced.

The present invention aims to solve the above problems by providing an electric blower that is small and lightweight, yet has high blower efficiency over a wide range of airflow volumes and high motor cooling efficiency, as well as an electric vacuum cleaner equipped with the same.

In order to solve the above-mentioned problems, the electric blower of the present invention is an electric blower in which a first flow path flows inside the blower section and a second flow path flows inside the motor section, and the motor section has a rotating shaft, a bearing that rotatably supports the rotating shaft, a rotor core fixed to the rotating shaft, a stator core arranged to surround the outer periphery of the rotor core, and a motor housing that holds the stator core and has an upstream radial opening and a downstream radial opening on its side, and the blower section has an impeller fixed to the tip of the rotating shaft, a fan casing that covers the outer periphery of the impeller, and a fan housing that is arranged upstream of the motor section. The electric blower has an upstream housing surrounding the outer periphery of the upstream housing and a downstream housing surrounding the outer periphery of the downstream housing, the first flow path running between the inner and outer walls of the upstream housing and between the inner and outer walls of the downstream housing, the second flow path running through the downstream radial opening, the interior of the motor unit, the upstream radial opening, between the motor housing and the inner wall of the upstream housing, and between the motor housing and the inner wall of the downstream housing, and a circular diffuser facing the downstream radial opening is provided on the downstream side of the downstream housing.

The present invention provides an electric blower that is small and lightweight, yet has high blower efficiency over a wide range of airflow volumes and high motor cooling efficiency, as well as an electric vacuum cleaner equipped with the same.

1 is an external view of an electric blower according to an embodiment of the present invention; 1 is a vertical cross-sectional view of an electric blower according to an embodiment of the present invention; FIG. 2 is a perspective view of an impeller according to an embodiment. FIG. 2 is a longitudinal cross-sectional view of an impeller according to an embodiment. FIG. 2 is a plan view of an upstream housing according to an embodiment. FIG. 3 is a longitudinal cross-sectional view of an upstream housing according to an embodiment. FIG. 2 is a partial cross-sectional view of an example upstream housing. FIG. 2 is a plan view of an embodiment of a downstream housing. FIG. 2 is a longitudinal cross-sectional view of a downstream housing according to an embodiment. FIG. 2 is a partial cross-sectional perspective view of an embodiment of a downstream housing. FIG. 2 is an external view of a motor unit according to an embodiment. FIG. 2 is a longitudinal cross-sectional view of a motor unit according to an embodiment. FIG. 4 is a longitudinal cross-sectional view showing an example of the structure of a second flow path. FIG. 4 is a longitudinal cross-sectional view showing an example of the structure of a second flow path. FIG. 4 is a longitudinal cross-sectional view showing an example of the structure of a second flow path. FIG. 4 is a longitudinal cross-sectional view showing an example of the structure of a second flow path. 1 is a perspective view of an electric vacuum cleaner according to an embodiment of the present invention; FIG. 1 is a vertical cross-sectional view of an electric vacuum cleaner according to an embodiment. 10 is a graph comparing the fan efficiency of the electric fan of the example and the comparative example. 6 is a graph comparing temperature rises of an electric blower according to an embodiment and a comparative example.

Below, an embodiment of the electric blower of the present invention and an electric vacuum cleaner equipped with the same will be described in detail with reference to the drawings.

<General configuration of the vacuum cleaner 100>
First, an electric vacuum cleaner 100 according to an embodiment of the present invention will be described with reference to Figures 7 and 8. Figure 7 is a perspective view of the electric vacuum cleaner 100, and Figure 8 is a vertical cross-sectional view of the electric vacuum cleaner 100.
The electric vacuum cleaner 100 shown in the figure is a rechargeable cordless stick vacuum cleaner in which the vacuum cleaner main body 110 is attached to a holder 120, and can be charged while placed on a charging stand 130. Note that although a rechargeable cordless stick vacuum cleaner is shown here as an example, the electric blower 200 of the present invention may also be built into a non-rechargeable stick vacuum cleaner that is equipped with a power cord.

The vacuum cleaner body 110 is a unit that can be used alone as a handheld vacuum cleaner, and has a body grip part 111 at the top that is held by the user when used as a handheld vacuum cleaner, and an intake opening 112 at the bottom that sucks in dust when used as a handheld vacuum cleaner.
The inside of the vacuum cleaner body 110 is also provided with a dust collection chamber 113 for collecting dust, an electric blower 200 for generating the suction airflow required for dust collection, a drive circuit 114 for driving the electric blower 200, and a battery unit 115 for supplying power to the drive circuit 114.

On the other hand, the holding part 120 is a unit to which the vacuum cleaner body 110 can be attached and detached, and is equipped at the top with a grip part 121 that the user holds when using it as a stick vacuum cleaner, and at the bottom with a suction body 122 that sucks in dust when using it as a stick vacuum cleaner, and a connection part 122a that connects the suction body 122 to the intake opening 112.

In addition, the main body grip portion 111 of the vacuum cleaner main body 110 is provided with a main body switch portion 111a for turning the electric blower 200 on and off when used as a handheld vacuum cleaner, and the grip portion 121 of the holding portion 120 is provided with a switch portion 121a for turning the electric blower 200 on and off when used as a stick vacuum cleaner.

<Electric blower 200>
Next, the details of the electric blower 200 of this embodiment will be described using Figures 1A to 6, 9 and 10. The electric blower 200 of this embodiment mainly includes an impeller 1, a rotating shaft 2, a fan casing 3, an upstream housing 4, a downstream housing 5, an upstream motor housing 6, a downstream motor housing 7, an upstream diffuser blade 8, and a downstream diffuser blade 9, which together form a blower section 201 and a motor section 202.

1A is an external view of electric blower 200, and FIG. 1B is a longitudinal cross-sectional view of electric blower 200. In this embodiment, electric blower 200 is a blower that draws in air through upper air intake 200a and expels air through lower exhaust 200b when impeller 1 rotates, so upstream and downstream directions are defined as shown. Focusing on the installation direction of rotating shaft 2, axial and radial directions are also defined as shown. Note that electric blower 200 is installed inside electric vacuum cleaner 100 with air intake 200a facing downward and exhaust 200b facing upward so that dust can be sucked up from suction body 122 at the bottom of electric vacuum cleaner 100 to dust collection chamber 113 above (see FIG. 8).

As shown in Figure 1A, the outer periphery of the electric blower 200 is covered by an outer shell that integrates the fan casing 3, upstream housing 4, and downstream housing 5. The specific method for integrating these components will be described later.

As shown in Figure 1B, a rotating shaft 2 is rotatably disposed inside the electric blower 200, and an impeller 1 that rotates integrally with the rotating shaft 2 is fixed to its upper end. In Figure 1B, the impeller 1 is fixed with a nut threaded onto the upper end of the rotating shaft 2, but the impeller 1 may also be fixed by press-fitting it onto the tip of the rotating shaft 2.

When the impeller 1 rotates, as illustrated on the left side of Figure 1B, the electric blower 200 forms an air flow path indicated by solid arrows (hereinafter referred to as the "first flow path F1") that flows through the blower section 201 from the intake port 200a to the exhaust port 200b, and an air flow path indicated by dotted arrows (hereinafter referred to as the "second flow path F2") that branches off downstream from the first flow path F1 and flows from downstream to upstream within the motor section 202. Below, the structure of the electric blower 200 of this embodiment, which allows the desired airflow to flow through the first flow path F1 and the second flow path F2 and can sufficiently cool the inside of the motor section 202 while maintaining suction power over a wide range of airflow, will be described separately for the blower section 201 and the motor section 202.

<Blower section 201>
1B , the blower section 201 is a unit that generates an airflow that sucks up dust in the vacuum cleaner 100, and as shown in FIG. 1B , from upstream to downstream, includes an impeller 1, which is a rotary blade, an upstream diffuser vane 8 provided on the inner periphery of the upstream housing 4, and a downstream diffuser vane 9 provided on the inner periphery of the downstream housing 5. In this embodiment, upper and lower diffuser vanes are provided to control the flow velocity and static pressure of the airflow downstream of the impeller 1, but some or all of the diffuser vanes may be omitted as long as the Venturi effect, which will be described later, is sufficiently maintained. Each section will be described below in order.

<Impeller 1 and fan casing 3>
First, the impeller 1 will be described using Figures 2A and 2B. Figure 2A is a perspective view of the impeller 1, and Figure 2B is a longitudinal cross-sectional view of the impeller 1. The impeller 1 in both figures is an open-type mixed-flow impeller without a shroud plate, and has a hub 11, a plurality of blades 12, and a boss 13 for inserting the rotating shaft 2, which are integrally molded from engineering plastic or thermoplastic resin. Note that the impeller 1 of this embodiment may be a mixed-flow impeller with a shroud plate, or may be a centrifugal impeller or an axial-flow impeller.

A metal sleeve 14 is integrally molded on the back side of the hub 11, coaxially with the boss 13 of the impeller 1. The use of this sleeve 14 reduces the variation in the fit gap between the impeller 1 and the rotating shaft 2, which is likely to occur when a sleeve is not used, and reduces imbalance in the impeller 1, thereby reducing vibration and noise when the impeller 1 is driven to rotate. Furthermore, a protrusion 14a is provided on the downstream side of the sleeve 14. The function of this protrusion 14a will be described later.

The fan casing 3 is a cover that covers the outer periphery of the impeller 1 and is integrally molded from engineering plastic or thermoplastic resin. As shown in Figure 1B, it has an air intake port 200a opening on the upstream side and also functions as a shroud plate for the impeller 1.

<Upstream Housing 4 and Upstream Diffuser Vanes 8>
Next, the upstream housing 4 and the upstream diffuser vanes 8 will be described with reference to Figures 3A to 3C. Figure 3A is a plan view of the upstream housing 4 as seen from the upstream side, Figure 3B is a vertical cross-sectional view of the upstream housing 4, and Figure 3C is a partial cross-sectional view of the upstream housing 4 as seen from the outer periphery.
In FIG. 3C, the shroud of the upstream housing 4 is partially omitted to show the shape of the upstream diffuser vane 8 (particularly the positions of the leading edge 8a and the trailing edge 8b).

The upstream housing 4 and upstream diffuser vanes 8 are integrally molded from engineering plastic or thermoplastic resin, and as shown in Figures 3A to 3C, multiple upstream diffuser vanes 8 integrally molded with the inner wall 4a (hub) and outer wall 4b (shroud) of the upstream housing 4 are arranged at equal intervals in the circumferential direction between them.

The length (chord length) from the leading edge 8a to the trailing edge 8b of the upstream diffuser vanes 8 is longer on the outer wall 4b side than on the inner wall 4a side. This is because, downstream of the impeller 1, the wind speed is faster on the outer peripheral side than on the inner peripheral side, so by making the outer side of the upstream diffuser vanes 8 longer than the inner side, losses are reduced and the efficiency of the blower is improved. Note that while a configuration with 15 upstream diffuser vanes 8 is shown here, the number of upstream diffuser vanes 8 can be changed depending on the specifications of the electric blower 200.

In addition, as shown in Figures 3A and 3C, protrusions 4c are provided at three equally spaced locations on the outer periphery of the outer wall 4b of the upstream housing 4. By fitting the claws 5c of the downstream housing 5 (described below) into these protrusions, the upstream housing 4 and the downstream housing 5 can be integrated while being centered (see Figure 1B).

In addition, as shown in Figures 3A and 3B, fastening portions 4d are provided in two locations on the top surface of the upstream housing 4, and the motor portion 202 can be fastened to these portions while being centered (see Figure 1B).

Furthermore, as shown in Figures 3A to 3C, a fitting portion 4e is provided on the outer wall 4b of the upstream housing 4 in the area other than the outer periphery of the protrusion 4c. By fitting the lower end of the fan casing 3 into this fitting portion and adhesively fixing it, the fan casing 3 and the upstream housing 4 can be integrated while being centered (see Figure 1B).

<Downstream Housing 5 and Downstream Diffuser Vanes 9>
Next, the downstream housing 5 and the downstream diffuser vanes 9 will be described with reference to Figures 4A to 4C. Figure 4A is a plan view of the downstream housing 5 as seen from the upstream side, Figure 4B is a vertical cross-sectional view of the downstream housing 5, and Figure 4C is a partially cross-sectional perspective view of the downstream housing 5 as seen from the outer periphery. Note that Figure 4C shows the shape of the downstream diffuser vanes 9 (particularly the positions of the leading edge 9a and the trailing edge 9b) by partially omitting the shroud of the downstream housing 5.

The downstream housing 5 and downstream diffuser vanes 9 are integrally molded from engineering plastic or thermoplastic resin. As shown in Figures 4A to 4C, multiple downstream diffuser vanes 9 integrally molded with the inner wall 5a (hub) and outer wall 5b (shroud) of the downstream housing 5 are arranged at equal intervals in the circumferential direction. Note that a configuration with 15 downstream diffuser vanes 9 is shown here; this is because the number of upstream diffuser vanes 8 and downstream diffuser vanes 9 is the same, as each downstream diffuser vane 9 is positioned downstream of each upstream diffuser vane 8.

As shown in Figures 4A to 4C, the downstream housing 5 has three equally spaced claws 5c on its upper periphery, and fittings 5d are provided on the entire upper periphery excluding the claws 5c. By pressing the lower end of the upstream housing 4 against the fittings 5d on the downstream housing 5 and fitting the three claws 5c into the three protrusions 4c, the upstream housing 4 and downstream housing 5 can be integrated while being centered (see Figure 1B).

Furthermore, as shown in Figures 4B and 4C, an annular diffuser 5e without downstream diffuser vanes 9 is provided downstream of the downstream housing 5. Details of this annular diffuser 5e will be described later.

As shown in FIG. 1B, in this embodiment, the inner wall 4a of the upstream housing 4 and the inner wall 5a of the downstream housing 5, and the outer wall 4b of the upstream housing 4 and the outer wall 5b of the downstream housing 5, are integrated while their radial positions are approximately aligned. This smooths the inner surface of each flow path and reduces losses in each flow path. Furthermore, in this embodiment, the circumferential positions of the trailing edge 8b of the upstream diffuser vane 8 and the leading edge 9a of the downstream diffuser vane 9 are aligned so that a pair of upstream and downstream diffuser vanes 8 and 9 function as a single diffuser vane, and the curved surfaces of the upstream and downstream diffuser vanes 8 and 9 are smoothly continuous. Furthermore, in this embodiment, the thickness of each diffuser vane increases from the upstream side to the downstream side, thereby increasing static pressure and achieving high efficiency in the blower section 201.

<Motor section 202>
Next, the motor section 202 will be described using Figures 5A and 5B. Figure 5A is a side external view of the motor section 202, and Figure 5B is a longitudinal cross-sectional view of the motor section 202. The illustrated motor section 202 is a unit for rotating the impeller 1 of the blower section 201 within a range of, for example, 50,000 to 200,000 rpm, and is composed of a rotating shaft 2, an upstream bearing 21, a downstream bearing 22, a rotor core 23, a stator core 24, a collar 25, an upstream motor housing 6, and a downstream motor housing 7. Each section will be described in order below.

<Housing of motor unit 202>
As shown in both figures, the motor section 202 has an upstream motor housing 6 and a downstream motor housing 7 as housings for holding the stator core 24 and other components, and the motor section 202 can be built into the electric blower 200 by fixing the upper surface of the upstream motor housing 6 to the lower surface of the upstream housing 4 with screws or the like (see Figure 1B).

The upstream motor housing 6 is a metal (aluminum alloy, steel, etc.) housing that covers the upstream side of the motor section 202, and as shown in Figure 5A, has multiple (e.g., six) radial openings 6a on its side. As shown in Figure 5B, the center of the top surface of the upstream motor housing 6 protrudes upward, and an upstream bearing 21 that rotatably supports the upstream side of the rotating shaft 2 is provided inside this protrusion. The upstream bearing 21 is positioned in the axial direction by an upstream spacer 21a below the upstream bearing 21. An axial opening may be provided in the upstream motor housing 6, in which case cooling air can flow over the bearing 21 for cooling.

On the other hand, the downstream motor housing 7 is a metal (aluminum alloy, steel, etc.) casing that covers the downstream side of the motor section 202, and as shown in FIG. 5A, it has multiple (e.g., six) radial openings 7a on its side and multiple axial openings 7b on its underside. Furthermore, as shown in FIG. 5B, the center of the underside of the downstream motor housing 7 protrudes downward, and within this protrusion is provided a downstream bearing 22 that rotatably supports the downstream side of the rotating shaft 2. The downstream bearing 22 is positioned axially by a downstream spacer 22a above it.

As shown in FIG. 5A, in this embodiment, the upstream radial opening 6a and the downstream radial opening 7a are arranged so that they do not overlap in the axial direction. The radial openings 6a and 7a of each motor housing are arranged so that they axially overlap with the axial end of the coil 24b (described later). The radial openings of each motor housing are uniformly arranged in the circumferential direction, and the number of openings and the number of diffuser vanes are set so that the greatest common divisor of the number of radial openings and the number of diffuser vanes is 3. This creates an identical flow field at three circumferential locations inside the motor section 202, thereby reducing the circumferential temperature distribution. The number of radial openings and the number of diffuser vanes may also be set using a predetermined value other than 3 as the greatest common divisor.

In this embodiment, in order to improve the cooling performance of the motor section 202, each motor housing is made of metal to improve heat dissipation performance, and an area where the stator core 24 is exposed (exposed portion 24a) is provided between the upper and lower motor housings so that the stator core 24 can be cooled from the outside. However, in cases where the amount of heat generated by the motor section 202 is relatively small, each motor housing may be made of heat-resistant resin, or the upper and lower motor housings may be connected to create a structure where the stator core 24 is not exposed.

In addition, while the radial opening 7a and axial opening 7b of the downstream motor housing 7 can cool the motor using only the radial opening 7a, the presence of the axial opening 7b reduces pressure loss when taking in motor cooling air, increasing the amount of motor cooling airflow and enabling motor cooling.

<Rotor of motor unit 202>
5B, a rotor core 23 is fixed to the rotating shaft 2 in an area sandwiched between upper and lower spacers. This rotor core 23 is the rotor of the motor section 202, which incorporates a rare earth bonded magnet such as a samarium-iron-nitrogen magnet or a neodymium magnet.

As shown in FIG. 5A, a collar 25 is fixed to the rotary shaft 2 protruding from the upper part of the upstream motor housing 6, and a recess 25a is provided on the upper part of the collar 25.
By fitting this recess 25a into the protrusion 14a of the sleeve 14 of the impeller 1 described above, the torque of the rotating shaft 2 can be reliably transmitted to the impeller 1, and freewheeling of the impeller 1 can be prevented.

<Stator of motor section 202>
As shown in Fig. 5B, a stator core 24, which is the stator of the motor section 202, is arranged on the outer periphery of the motor section 202 so as to surround a rotor core 23, which is the rotor of the motor section 202. A coil 24b, which is made of aluminum wire or copper wire covered with a coating material, is wound around the winding frame of the stator core 24, and the stator core 24 can be made into an electromagnet by supplying a desired AC power to the coil 24b from the drive circuit 114 shown in Fig. 8, and the rotor core 23, the rotating shaft 2, and the impeller 1 can be rotated at high speed together.

Furthermore, by fixing the upstream motor housing 6 to the upstream side of the stator core 24 with a driven adhesive and fixing the downstream motor housing 7 to the downstream side with a driven adhesive, the stator core 24, the upstream motor housing 6, and the downstream motor housing 7 can be integrated. This allows a radial opening 6a in the upstream motor housing 6 to be formed at the height of the upstream end of the coil 24b, and a radial opening 7a in the downstream motor housing 7 to be formed at the height of the downstream end of the coil 24b.

<Structures of First Flow Passage F1 and Second Flow Passage F2>
Next, the structures of the first flow path F1 and the second flow path F2 of this embodiment will be described in detail with reference to FIGS. 1B and 6A.

As shown in Figure 1B, if the dimensions defining the shapes of the first flow path F1 and the second flow path F2 are the radial height H1 of the downstream diffuser vane 9, the radial distance H2 between the inner surface of the annular diffuser 5e and the outer surface of the downstream motor housing 7, the axial length L1 of the inner wall 5a, the axial length L2 of the downstream diffuser vane 9, and the axial length L3 of the annular diffuser 5e, in the electric blower 200 of this embodiment, the dimensions are set using the following equations to improve both the blower efficiency of the blower section 201 and the cooling efficiency of the motor section 202. The function of each equation will be explained below using Figure 6A, which is an enlarged cross-sectional view of the right-hand flow path in Figure 1B.

H1 ≧ 0.5×H2 ... (Formula 1)
More preferably, H1≧0.66×H2 (Equation 1′)
0.5×L2 ≦ L1 ≦ L2 ... (Formula 2)
More preferably, L1≈0.5×L2 (Equation 2′)
L3 ≧ 2.5×H1... (Formula 3)
More preferably, L3≧3×H1 (Equation 3′)
6A, when power is supplied to motor section 202 to rotate impeller 1, a first flow path F1 through blower section 201 and a second flow path F2 that mainly flows within motor section 202 are formed inside electric blower 200. Second flow path F2, which branches off from first flow path F1, passes through the following flow paths (1) to (5) and is exhausted from exhaust port 200b of electric blower 200.

(1) First, the airflow branching off from the first flow path F1 inside the annular diffuser 5e flows into the interior of the motor section 202 through the downstream radial openings 7a and axial openings 7b. In this embodiment, by positioning the annular diffuser 5e on the outer periphery of the downstream radial openings 7a, the airflow flowing out from the downstream diffuser vanes 9 is prevented from diffusing in the outer periphery direction, allowing the airflow branching off from the first flow path F1 to be efficiently guided into the interior of the motor section 202.

(2) The airflow that flows into the motor section 202 from the downstream radial opening 7a flows from downstream to upstream, efficiently cooling the downstream bearing 22, rotor core 23, stator core 24, upstream bearing 21, etc., which are in a high temperature state.

(3) The airflow that flows upstream inside the motor section 202 flows out of the motor section 202 through the upstream radial opening 6a, and then flows downstream through the gap between the inner surface of the inner wall 4a of the upstream housing 4 and the outer surface of the upstream motor housing 6, further cooling the exposed portion 24a of the stator core 24.

(4) The airflow that has cooled the exposed portion 24a merges with the first flow path F1 near the lower end of the inner wall 5a of the downstream housing 5. In this embodiment, as shown in (Equation 1) or (Equation 1'), the radial height H1 of the downstream diffuser vanes 9 is set large, allowing the downstream diffuser vanes 9 to be closer to the downstream motor housing 7 and increasing the flow velocity in the outer peripheral region of the downstream motor housing 7. Furthermore, as shown in (Equation 2'), by positioning the lower end of the inner wall 5a of the downstream housing 5 at a position approximately half the axial length of the downstream diffuser vanes 9 (e.g., L1/L2 = 0.5 to 0.6), the second flow path F2 can be merged with the first flow path F1 in the region where high-speed air flows through the downstream diffuser vanes 9. Therefore, the Venturi effect of the high-speed first flow path F1 allows air inside the motor section 202 to be efficiently sucked in through the upstream radial opening 6a, and as a result, cooling air can be efficiently drawn into the negative pressure inside the motor section 202 through the downstream radial opening 7a and axial opening 7b. In other words, the Venturi effect of the first flow path F1 improves the cooling efficiency of the motor section 202 regardless of the operating range of the electric blower 200.

(5) The airflow that joins the first flow path F1 is exhausted from the exhaust port 200b. In this embodiment, as shown in (Equation 3) or (Equation 3'), an annular diffuser 5e is provided with an axial length L3 that corresponds to the radial height H1 of the downstream diffuser vane 9. Because the axial length L3 of the annular diffuser 5e is sufficiently longer than the radial height H1 of the downstream diffuser vane 9, sudden expansion of the flow path downstream of the downstream diffuser vane 9 is suppressed, and as a result, the blowing efficiency of the blower section 201 is improved.

<Effect of the annular diffuser 5e>
Next, the effects of the annular diffuser 5e of this embodiment will be described with reference to the experimental results shown in Figures 9 and 10. The comparative example shown in Figures 9 and 10 corresponds to an electric blower in which the annular diffuser 5e has been removed from electric blower 200 in Figure 6A.

In the electric blower of the comparative example, the annular diffuser 5e is not located opposite the downstream radial opening 7a, so the flow path rapidly expands downstream of the trailing edge 9b of the downstream diffuser vane 9, through which high-speed air flows. In this case, as shown in the experimental results in Figure 9, the efficiency of the electric blower is significantly reduced compared to the electric blower 200 of this embodiment, which is equipped with the annular diffuser 5e. As a result, the amount of air flowing into the motor section 202 is reduced in the electric blower of the comparative example. As shown in Figure 10, the temperatures of the bearings (upstream bearing 21, downstream bearing 22), stator core 24, coil 24b, etc. inside the motor section 202 are approximately 25 to 40 K higher than in the electric blower 200 of this embodiment.

As is clear from Figures 9 and 10, the electric blower 200 of this embodiment, which is equipped with the annular diffuser 5e, not only improves the air-blowing efficiency of the blower section 201, but also improves the cooling efficiency of the motor section 202, compared to the electric blower of the comparative example, which does not have a circular diffuser.

<Modification>
Next, a modified example of the structure of FIG. 6A will be described with reference to FIGS. 6B to 6D.

In Figure 6B, the downstream radial opening 7a is positioned further downstream than in Figure 6A. In this case, the second flow path F2 branches off from the first flow path F1 near the position where the innermost airflow in the first flow path F1, shown by the solid line, adheres to the downstream motor housing 7. This increases the amount of air drawn into the motor section 202 from the downstream radial opening 7a, further improving the cooling efficiency of the motor section 202 compared to Figure 6A.

In Figure 6C, the downstream radial opening 7a is positioned further upstream than in Figure 6A. In this case, of the airflow in the first flow path F1, shown by the solid line, the innermost airflow adheres to the outer peripheral surface of the downstream motor housing 7 further upstream, which suppresses separation of the airflow in the area of the annular diffuser 5e where the flow path expands, and further improves the blowing efficiency of the blower section 201 compared to Figure 6A.

Figure 6D shows a configuration in which, instead of the radial opening 7a and axial opening 7b described above, a corner opening 7c is provided, which combines the functions of both. In this case, the same effect as in Figure 6B can be achieved with a simplified configuration.

In Figures 6A to 6D, an annular diffuser 5e is provided downstream of the downstream housing 5, but the annular diffuser 5e may be omitted. In that case, to prevent the flow path of the first flow path F1 from suddenly expanding near the downstream radial opening 7a, the downstream diffuser vanes 9 should be extended at least to the axial position opposite the downstream radial opening 7a.

In addition, the Venturi effect cooling of this configuration makes it possible to cool the motor even without diffuser vanes on the upstream or downstream housing.

<Effects of this embodiment>
According to the present embodiment described above, it is possible to provide an electric blower that is small and lightweight, yet has high blower efficiency over a wide range of air volume and high motor cooling efficiency, and an electric vacuum cleaner equipped with the same.

The present invention is not limited to the above-described embodiment, but includes various modifications.
For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is also possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

DESCRIPTION OF SYMBOLS 100 Electric vacuum cleaner 110 Vacuum cleaner main body 111 Main body grip portion 111a Main body switch portion 112 Air intake opening 113 Dust collection chamber 114 Drive circuit 115 Battery unit 120 Holding portion 121 Grip portion 121a Switch portion 122 Suction mouth body 122a Connection portion 130 Charging stand 200 Electric blower 200a Air intake port 200b Exhaust port 201 Blower portion 202 Motor portion 1 Impeller 11 Hub 11a Hub protrusion 12 Blade 13 Boss 13a Boss curved surface 14 Sleeve 14a Protrusion 2 Rotating shaft 21 Upstream bearing 21a Upstream spacer 22 Downstream bearing 22a Downstream spacer 23 Rotor core 24 Stator core 24a Exposed portion 24b Coil 25 Collar 25a Recess 3 Fan casing 4 Upstream housing 4a Inner wall 4b Outer wall 4c Protrusion 4d Fastening portion 4e Fitting portion 5 Downstream housing 5a Inner wall 5b Outer wall 5c Claw portion 5d Fitting portion 5e Annular diffuser 6 Upstream motor housing 6a Radial opening 7 Downstream motor housing 7a Radial opening 7b Axial opening 7c Corner opening 8 Upstream diffuser vane 8a Leading edge 8b Trailing edge 9 Downstream diffuser vane 9a Leading edge 9b Trailing edge F1 First flow passage F2 Second flow passage

Claims (8)

An electric blower in which a first flow path flows inside a blower unit and a second flow path flows inside a motor unit,
The motor unit includes a rotating shaft, a bearing that rotatably supports the rotating shaft, a rotor core fixed to the rotating shaft, a stator core that is disposed so as to surround the outer periphery of the rotor core, and a bearing that holds the stator core.
a motor housing having an upstream radial opening and a downstream radial opening on a side surface, the blower unit including an impeller fixed to the tip of the rotary shaft, a fan casing covering the outer periphery of the impeller,
an upstream housing surrounding an outer periphery of the motor unit on the upstream side; and a downstream housing surrounding an outer periphery of the motor unit on the downstream side;
the first flow path extends between the inner wall and the outer wall of the upstream housing and between the inner wall and the outer wall of the downstream housing;
the second flow path passes through the downstream radial opening, the interior of the motor section, the upstream radial opening, a space between the motor housing and an inner wall of the upstream housing, and a space between the motor housing and an inner wall of the downstream housing;
an annular diffuser provided downstream of the downstream housing and facing the downstream radial opening; The electric blower according to claim 1,
an upstream diffuser vane is provided between an inner wall and an outer wall of the upstream housing;
a downstream diffuser blade provided between the inner wall and the outer wall of the downstream housing; The electric blower according to claim 2,
an electric blower, wherein one of the following formulas is satisfied, where H1 is a radial height of the downstream diffuser vanes and H2 is a radial distance between the inner surface of the annular diffuser and the outer surface of the motor housing:
H1 ≧ 0.5×H2,
H1 ≧ 0.66×H2 The electric blower according to claim 2,
1. An electric blower, wherein when the axial length of the inner wall of the downstream housing is L1 and the axial length of the downstream diffuser vanes is L2, any one of the following formulas is satisfied:
0.5×L2 ≦ L1 ≦ L2,
L1 ≒ 0.5 × L2 The electric blower according to claim 2,
1. An electric blower, wherein when a radial height of the downstream diffuser vanes is H1 and an axial length of the annular diffuser is L3, any one of the following formulas is satisfied:
L3 ≧ 2.5×H1,
L3 ≧ 3 × H1 The electric blower according to claim 1,
The motor housing is an electric blower characterized in that an upstream motor housing covering the upstream side of the stator core and a downstream motor housing covering the downstream side of the stator core are connected together so that the stator core is not exposed. The electric blower according to any one of claims 1 to 6,
An electric blower having an axial opening in either an upstream motor housing, a downstream motor housing, or both. An electric vacuum cleaner equipped with the electric blower described in any one of claims 1 to 7.