Electric work machine

Abstract

This invention provides an improvement to electric power tools that helps to suppress the noise of centrifugal fans while ensuring sufficient airflow. [Solution] The centrifugal fan for the electric work machine comprises a fan body and a wall portion arranged around the fan body. The fan body has a disk centered on a first axis and a blade portion including a plurality of blades. The plurality of blades are arranged radially on one surface of the disk and each extends radially outward from the outer edge of the disk. The wall portion is configured to define a flow path between the outer edge of the blade portion and the inner surface of the wall portion for directing the air discharged radially outward from the plurality of blades in a first direction parallel to the first axis. The inner diameter of the blade portion is in the range of 45% to 60% of the outer diameter of the blade portion. The outer diameter of the disk is in the range of 80% to 95% of the outer diameter of the blade portion. The inner diameter of the wall portion is in the range of 110% to 120% of the outer diameter of the blade portion.

Description

[Technical Field]

[0001] This disclosure relates to centrifugal fans and electric work machines equipped with centrifugal fans. [Background technology]

[0002] An electric work machine comprises a motor and a centrifugal fan rotated by the motor to generate an airflow. The airflow generated by the centrifugal fan is used, for example, to cool internal mechanisms or to collect dust. For example, Patent Document 1 discloses a grinder equipped with a centrifugal fan for cooling the motor. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-128517 [Overview of the project] [Problems that the invention aims to solve]

[0004] In electric power tools, there is a need to reduce noise associated with the rotation of centrifugal fans. However, noise reduction may lead to a decrease in airflow. One non-limiting objective of this disclosure is to provide improvements that contribute to suppressing centrifugal fan noise while ensuring sufficient airflow in electric power tools. [Means for solving the problem]

[0005] One non-limiting aspect of the present disclosure provides a centrifugal fan for an electric power machine. The centrifugal fan includes a fan body and a wall portion disposed around the fan body. The fan body includes a disk centered on a first axis and a blade portion including a plurality of blades. The plurality of blades are arranged radially on one surface of the disk and each extends radially outward beyond the outer edge of the disk. In other words, the radially outward end of each blade is radially outward beyond the outer edge of the disk. The wall portion is configured to define a flow path between the outer edge of the blade portion and the inner surface of the wall portion for directing air discharged radially outward from the plurality of blades in a first direction parallel to the first axis.

[0006] The inner diameter of the blade section is in the range of 45% to 60% of the outer diameter of the blade section. The outer diameter of the disc is in the range of 80% to 95% of the outer diameter of the blade section. The inner diameter of the wall section is in the range of 110% to 120% of the outer diameter of the blade section.

[0007] According to this embodiment, a centrifugal fan is provided that exhibits sufficient airflow while suppressing noise.

[0008] Another non-limiting aspect of this disclosure provides an electric work machine comprising a housing, a motor, a centrifugal fan, and a wall section. In this disclosure, an electric work machine refers to any machine configured to perform work using electricity as a power source. Non-limiting examples of electric work machines include power tools for processing wood, metal, concrete, etc., dust collectors used with power tools, cleaning machines, and gardening machines.

[0009] The housing has an intake port and an exhaust port. The motor is located inside the housing. The centrifugal fan is located inside the housing. The centrifugal fan is configured to be rotated by the motor around a first axis to generate an airflow within the housing from the intake port to the exhaust port. The wall is located around the centrifugal fan. The centrifugal fan comprises a disk centered on the first axis and a blade section containing a plurality of blades. The plurality of blades are arranged radially on one surface of the disk and each extends radially outward from the outer edge of the disk. In other words, the radially outward end of each blade is radially outward from the outer edge of the disk. The wall is configured to define a flow path between the outer edges of the plurality of blades and the inner surface of the wall for directing the air expelled radially outward from the plurality of blades in a first direction parallel to the first axis.

[0010] The inner diameter of the blade section is in the range of 45% to 60% of the outer diameter of the blade section. The outer diameter of the disc is in the range of 80% to 95% of the outer diameter of the blade section. The inner diameter of the wall section is in the range of 110% to 120% of the outer diameter of the blade section.

[0011] According to this embodiment, an electric work machine is provided that is equipped with a centrifugal fan that can generate sufficient airflow while suppressing noise. [Brief explanation of the drawing]

[0012] [Figure 1] This is a perspective view of a grinder. [Figure 2] This is a cross-sectional view of a grinder. [Figure 3] This is a rear view of a centrifugal fan. [Figure 4] Figure 3 shows a cross-sectional view along the line IV-IV. [Figure 5] This is a magnified view of a portion of Figure 2. [Figure 6] This is a cross-sectional view along the line VI-VI in Figure 2. [Figure 7] This table shows the numerical values ​​for the four factors of centrifugal fans in Examples 1-5 and Comparative Examples 1-3. [Figure 8]It is a schematic diagram for explaining the testing machine used in the experiment. [Figure 9] It is a scatter diagram of air volume - noise level showing the correlation between the air volume and the noise level of the centrifugal fans in Examples 1 to 5 and Comparative Examples 1 to 3.

Mode for Carrying Out the Invention

[0013] In one or more non - limiting embodiments of the present disclosure, the number of the plurality of blades of the blade part is preferably in the range from 35 to 50.

[0014] In addition to or instead of the above - mentioned embodiment, at least a part of the wall part may be formed by a part of the housing of the electric working machine. According to this embodiment, the number of parts can be reduced as compared with the configuration in which the wall part is provided separately from the housing.

[0015] In addition to or instead of the above - mentioned embodiment, the electric working machine may be a grinder. The motor and the centrifugal fan may be arranged between the air inlet and the air outlet in the first direction within the housing. The centrifugal fan may be configured to generate an air flow for cooling the motor. According to this embodiment, the motor of the grinder can be effectively cooled by the centrifugal fan.

[0016] Hereinafter, a grinder 1 provided with a centrifugal fan 5 (hereinafter simply referred to as fan 5) according to a representative and non - limiting embodiment of the present disclosure will be described in detail with reference to the drawings.

[0017] This detailed description is provided solely to illustrate to those skilled in the art details preferred examples for carrying out the disclosure and is not intended to limit the scope of the disclosure. Therefore, not all combinations of features illustrated in the embodiments are essential to solving the problems of the disclosure. The various features disclosed in the embodiments above or below, as well as the various features described in the independent and dependent claims, do not have to be combined in the same way as the specific examples described herein to provide additional and useful embodiments of the disclosure.

[0018] Furthermore, the various features disclosed in the embodiments described above or below, as well as the various features described in the independent and dependent claims, are intended to be disclosed individually and independently of each other as limitations to the specific matters disclosed and claimed in the original application. In addition, all descriptions of numerical ranges are intended to disclose intermediate configurations as limitations to the specific matters disclosed and claimed in the original application.

[0019] First, the general configuration of the grinder 1 will be described with reference to Figures 1 and 2. The grinder 1 is an example of an electric power tool. More specifically, the grinder 1 is an example of a portable electric tool also called a disc grinder or angle grinder. The grinder 1 is configured to perform various processing operations (for example, grinding, polishing, and cutting) by rotating a disc-shaped tip tool 29.

[0020] Grinder 1 comprises a housing 10, a motor 21, a fan 5, and a spindle 25.

[0021] The housing 10, also referred to as the tool body, is a long, hollow body that forms the outer shell of the grinder 1. The motor 21, fan 5, and spindle 25 are housed in the housing 10. The motor 21 is positioned such that the axis of rotation RX of the output shaft 215 of the motor 21 extends substantially parallel to the long axis of the housing 10. The fan 5 is fixed to the output shaft 215. The spindle 25 is operably connected to the motor 21 and is rotatably supported around the drive axis DX within one end of the housing 10 in the long axis direction. The drive axis DX extends in a direction that intersects (more specifically, substantially orthogonal to) the axis of rotation RX of the output shaft 215. One end of the spindle 25 in the axial direction is exposed to the outside from the housing 10 and constitutes a tool mounting section. The tip tool 29 is detachably attached to the tool mounting section of the spindle 25.

[0022] For convenience, in the following explanation, the direction of extension of the drive shaft DX is defined as the vertical direction of the grinder 1. In the vertical direction, the side where the tool mounting portion of the spindle 25 is located defines the lower side of the grinder 1, and the opposite side defines the upper side of the grinder 1. The long axis direction of the housing 10 (the direction of extension of the rotation axis RX of the motor 21) defines the front-rear direction of the grinder 1. In the front-rear direction, the side where the spindle 25 is located defines the front side of the grinder 1, and the opposite side defines the rear side of the grinder 1. The direction perpendicular to the vertical and front-rear directions defines the left-right direction of the grinder 1.

[0023] The following describes the configuration of Grinder 1 in detail.

[0024] As shown in Figures 1 and 2, the housing 10 includes, in order from the front, a head section 11 (also called a gear housing), a motor housing section 13 (also called a motor housing), and a main handle 15.

[0025] The head unit 11 houses the spindle 25 and the reduction gear train 26. The reduction gear train 26 is operably connected to the output shaft 215 of the motor 21 and the spindle 25, and transmits the rotational power of the output shaft 215 to the spindle 25.

[0026] The motor housing 13 is a long, cylindrical shape and houses the motor 21 and the fan 5. The motor 21 comprises a motor body 210 including a stator and rotor, and an output shaft 215 configured to rotate integrally with the rotor. The front end of the output shaft 215 protrudes into the head portion 11 and is operably connected to the spindle 25 via a reduction gear train 26. The fan 5 is located within the front end of the motor housing 13. The fan 5 is fixed to the output shaft 215 at the front of the motor body 210 and rotates integrally with the output shaft 215. The configuration of the fan 5 and its surrounding parts will be described in detail later.

[0027] The main handle 15 is configured to be gripped by the user and is cylindrical in shape with a smaller diameter than the motor housing 13. The main handle 15 is provided with a trigger switch 16 (also called a switch lever). A power cord 19, which can be connected to an external power source, extends from the rear end of the housing 10, and the grinder 1 is driven by power supplied from the external power source. However, in another embodiment, the grinder 1 may be driven by power supplied from a battery instead of an external power source. In yet another embodiment, the motor housing 13 of the housing 10 may function as the main handle.

[0028] The housing 10 of this embodiment has an intake port 101 for introducing air into the housing 10 and an exhaust port 105 for discharging air to the outside of the housing 10. In this embodiment, the intake port 101 is formed at the rear end of the motor housing 13 (specifically, the right and left sides of the rear end). The exhaust port 105 is formed at the upper and lower parts of the head portion 11. The motor 21 (motor body portion 210) and the fan 5 are arranged between the intake port 101 and the exhaust port 105 in the front-rear direction.

[0029] When the trigger switch 16 is pressed by the user, the motor 21 is driven, and the power of the motor 21 rotates the spindle 25 around the drive shaft DX. As the spindle 25 rotates, the tip tool 29 attached to the spindle 25 rotates, performing machining operations on the workpiece. In addition, the rotation of the fan 5 creates an airflow that is drawn into the housing 10 through the intake port 101, flows forward inside the housing 10, and flows out to the outside through the exhaust port 105. This airflow passes around and inside the motor body 210, cooling the motor 21.

[0030] The configuration of fan 5 and its surrounding components will be described in detail below.

[0031] As shown in Figures 3 and 4, the fan 5 according to this embodiment is a so-called open-type impeller and includes a coaxially arranged disk 51, a hub 53, and a blade portion 55. In this embodiment, the fan 5 is a single component manufactured by integrally molding synthetic resin. However, in another embodiment, the fan 5 may be formed by connecting a plurality of separately manufactured components. In yet another embodiment, the fan 5 may be made of metal.

[0032] The disk 51 is a disc-shaped part, also referred to as the main plate, back plate, etc. A hole is formed in the center of the disk 51. The hub 53 is a cylindrical part that is fitted onto and fixed to the output shaft 215 of the motor 21. The hub 53 is positioned around the hole in the disk 51 and protrudes from one surface of the disk 51 in the axial direction of the fan 5 (the direction in which the rotation axis RX extends). Since the fan 5 is mounted coaxially to the output shaft 215, the axis of the fan 5 referred to in the following description may be read as the rotation axis RX of the output shaft 215.

[0033] The fan section 55 includes a plurality of blades 56. The blades 56 are arranged radially on one surface of the disk 51 (the surface on which the hub 53 is located) and protrude in the axial direction of the fan 5. In this embodiment, all blades 56 have the same shape and are arranged at a substantially uniform pitch in the circumferential direction of the disk 51.

[0034] More specifically, each blade 56 extends radially outward from a predetermined position in the radial direction of the disk 51. Note that "the blade 56 extends radially outward" can also be rephrased as "the blade 56 extends away from the center (rotation axis RX) of the disk 51." In this embodiment, the radially inner end of the blade 56 (hereinafter simply referred to as the inner end) is at the same radial position as the outer circumferential surface of the hub 53, but the inner end of the blade 56 may be at a different position than in this example.

[0035] The blades 56 may extend linearly along the radius of the disk 51, or they may extend in a curved manner away from the center of the disk 51. Furthermore, the blades 56 may be inclined in any direction with respect to the radius of the disk 51. In the fan 5 illustrated in the drawings, the blades 56 are so-called backward-facing blades, inclined in the opposite direction to the rotation direction of the fan 5 (clockwise direction in Figure 3), and extending radially outward in a curved manner.

[0036] The radially outer ends of all the blades 56 (hereinafter simply referred to as the outer ends) lie on the circumference of a circle C1 centered on the axis of the fan 5 (rotation axis RX), and the diameter of circle C1 defines the outer diameter D1 of the blade portion 55 (hereinafter simply referred to as the blade outer diameter D1). In this embodiment, each blade 56 extends radially outward beyond the outer edge of the disk 51. In other words, the blade outer diameter D1 is larger than the outer diameter D3 of the disk 51 (hereinafter simply referred to as the disk outer diameter D3).

[0037] The height of each blade 56 of the fan 5 in the axial direction increases from the inner end of the blade 56 toward the radially outward direction. The height of each blade 56 is maximum at a predetermined position in the radial direction and decreases from this position toward the outer end. Specifically, the position where the height of the blade 56 is maximum lies on the circumference of a circle C2 centered on the axis of the fan 5, with a diameter smaller than the outer diameter D1 of the blade and the outer diameter D3 of the disk. The diameter of circle C2 defines the inner diameter D2 of the blade portion 55 (hereinafter simply referred to as the inner blade diameter D2). Note that the height of the blade 56 does not necessarily have to change toward the radially outward direction. For example, the height of the blade 56 may be uniform from the inner end to the outer end. Alternatively, the height of the blade 56 may increase from the inner end to a predetermined position in the radial direction and then be uniform from this position toward the outer end.

[0038] As shown in Figure 5, the fan 5 having the above configuration is fixed to the output shaft 215 such that the surface on which the blade portion 55 of the disk 51 is arranged faces rearward (that is, the protruding ends of the blades 56 face the motor body 210). In the front-rear direction, a guide plate 133 is positioned between the fan 5 and the motor body 210 to efficiently draw air into the fan 5. A circular intake port 134 is formed in the center of the guide plate 133, having a diameter that is approximately the same as or slightly larger than the inner diameter D2 of the blades. Therefore, as the fan 5 rotates, air is drawn into the fan 5 axially (forward) through the intake port 134, flows radially outward through a flow path defined between adjacent blades 56, and flows out through an opening between the outer ends of adjacent blades 56. Hereinafter, the flow path between the blades 56 will also be referred to as the internal flow path.

[0039] Within the motor housing 13, a flow path is defined around the blade portion 55 of the fan 5 to direct the air sent from the internal flow path axially (forward). Hereinafter, the flow path around the blade portion 55 will also be referred to as the external flow path 63. As shown in Figures 5 and 6, in this embodiment, the cylindrical wall portion 136 arranged around the blade portion 55 in the motor housing 13 has a substantially circular cross-section and is arranged coaxially with the fan 5. Therefore, the inner diameter D4 of the cylindrical wall portion 136 (hereinafter simply referred to as the inner diameter D4) is larger than the outer diameter D1 of the blade. The external flow path 63 is defined by this cylindrical wall portion 136 between the outer edge of the blade portion 55 and the inner surface of the cylindrical wall portion 136. In other words, the inner diameter D4 can also be said to be the outer diameter of the external flow path 63. The outer edge of the blade portion 55 is defined by the outer end of the blade 56.

[0040] A partition wall 138 is positioned on the front side of the cylindrical wall 136, separating the internal space of the motor housing 13 from the internal space of the head section 11. The partition wall 138 is provided with a communication port, and the air sent out from the fan 5 flows forward through the external flow path 63, enters the upper and lower parts of the head section 11 through the communication port of the partition wall 138, and is then discharged to the outside through the exhaust port 105 (see Figure 1).

[0041] Furthermore, the fan 5 of this embodiment has features not found in conventional centrifugal fans with respect to certain factors among the many factors used to determine the specifications of a centrifugal fan.

[0042] Generally, factors used to determine the specifications of a centrifugal fan include, for example, the fan's outer diameter, blade shape, inlet height, inlet angle, outlet angle, and number of blades. However, it is not easy to identify specific combinations of factors that significantly affect the airflow and noise of a centrifugal fan from among these numerous factors and to appropriately set their numerical ranges. The inventors of this invention conducted various experiments by changing various factors and diligently researched based on the experimental results. As a result, the inventors found that by appropriately setting the numerical ranges of at least two of the four factors—(i) blade inner diameter D2, (ii) disk outer diameter D3, (iii) cylinder inner diameter D4, and (iv) the number of blades 56 (hereinafter simply referred to as blade count B)—it is possible to increase airflow while reducing noise.

[0043] Furthermore, the inventors found that it is particularly effective when the relationship between the three factors of the above four factors—(i) blade inner diameter D2, (ii) disc outer diameter D3, and (iii) cylinder inner diameter D4—and the blade outer diameter D1 satisfies the following conditions (a) to (c). Note that in the following description, "range from XX to YY" includes XX as the lower limit and YY as the upper limit.

[0044] (a) The inner diameter D2 of the blade is in the range of 45% to 60% of the outer diameter D1. In other words, the ratio of the inner diameter D2 to the outer diameter D1 (hereinafter also simply called the inner diameter ratio) is in the range of 0.45 to 0.60 (0.45 ≤ D2 / D1 ≤ 0.60).

[0045] (b) The outer diameter of the disc D3 is in the range of 80% to 95% of the outer diameter of the blade D1. In other words, the ratio of the outer diameter of the disc D3 to the outer diameter of the blade D1 (hereinafter also simply referred to as the disc outer diameter ratio) is in the range of 0.80 to 0.95 (0.80 ≤ D3 / D1 ≤ 0.95).

[0046] (c) The inner diameter D4 of the cylinder is in the range of 110% to 120% of the outer diameter D1 of the blade. In other words, the ratio of the inner diameter D4 to the outer diameter D1 of the blade (hereinafter also simply called the inner diameter ratio) is in the range of 1.10 to 1.20 (1.10 ≤ D4 / D1 ≤ 1.20).

[0047] Furthermore, it was confirmed that the fourth factor, (iv) the number of blades B, is more effective when it satisfies the following condition (d), in addition to the above conditions (a) to (c). However, as the inner diameter of the blade D2 becomes somewhat small, it becomes difficult to keep the number of blades B within this range, so this range is a preferred range.

[0048] (d) The number of feathers B is in the range of 35 to 50 (35 ≤ B ≤ 50).

[0049] The effects of fan 5 according to this embodiment will be explained below with reference to the measurement results of airflow and noise for fans 5A to 5E in Examples 1 to 5 and fans 6A to 6C in Comparative Examples 1 to 3.

[0050] Figure 7 shows the numerical values ​​for the four factors for each of the fans 5A to 5E in Examples 1 to 5 and fans 6A to 6C in Comparative Examples 1 to 3. In all of Examples 1 to 5 and Comparative Examples 1 to 3, the outer blade diameter D1 is 85 millimeters (mm).

[0051] Each of fans 5A to 5E satisfies all of the above conditions (a) to (c) regarding the three factors (i) to (iii). Furthermore, each of fans 5A to 5E also satisfies the above condition (d) regarding factor (iv). On the other hand, each of fans 6A to 6C lacks at least one of the above conditions (a) to (c) regarding the three factors (i) to (iii). Also, only fan 6A satisfies the above condition (d) regarding factor (iv).

[0052] Fans 5A-5E and 6A-6C, like fan 5 described above, all include a disk 51, a hub 53, and a blade section 55 (multiple blades 56). On the other hand, for the measurement of airflow and noise, the cylindrical wall section 136 used was a casing 14 (see Figure 8) integrally formed with the guide plate 133, rather than a part of the housing 10 described above.

[0053] More specifically, as shown in the figures, the blade inner diameter ratio (D2 / D1) of fan 5A in Example 1 was 0.47, the disk outer diameter ratio (D3 / D1) was 0.83, and the cylinder inner diameter ratio (D4 / D1) was 1.14. The number of blades B for fan 5A was 35. The blade inner diameter ratio of fan 5B in Example 2 was 0.47, the disk outer diameter ratio was 0.82, and the cylinder inner diameter ratio was 1.20. The number of blades B for fan 5B was 35. The blade inner diameter ratio of fan 5C in Example 3 was 0.47, the disk outer diameter ratio was 0.91, and the cylinder inner diameter ratio was 1.20. The number of blades B for fan 5C was 35. The blade inner diameter ratio of fan 5D in Example 4 was 0.59, the disk outer diameter ratio was 0.83, and the cylinder inner diameter ratio was 1.14. The number of blades B for fan 5D was 35. The blade inner diameter ratio of fan 5E in Example 5 was 0.59, the disk outer diameter ratio was 0.91, and the cylinder inner diameter ratio was 1.20. The number of blades B for fan 5E was 35.

[0054] On the other hand, the blade inner diameter ratio of fan 6A in Comparative Example 1 was 0.67, the disk outer diameter ratio was 1.00, and the cylinder inner diameter ratio was 1.16. The number of blades B for fan 6A was 42. The blade inner diameter ratio of fan 6B in Comparative Example 2 was 0.65, the disk outer diameter ratio was 1.00, and the cylinder inner diameter ratio was 1.14. The number of blades B for fan 6B was 29. The blade inner diameter ratio of fan 6C in Comparative Example 3 was 0.62, the disk outer diameter ratio was 0.89, and the cylinder inner diameter ratio was 1.02. The number of blades B for fan 6C was 30.

[0055] The methods for measuring airflow and noise are as follows:

[0056] The test machine 9 shown in Figure 8 was used to measure the airflow rate. The test machine 9 is equipped with an air tank 91, a measuring pipe 92, an orifice plate 93, an auxiliary blower 94, and differential pressure gauges 96 and 97. This test machine 9 is based on the test machine used in "the case of a blower that does not have both a discharge pipe and a suction pipe in the operating state" as specified in JIS (Japan Industrial Standard) B8330:2000 "Test and inspection methods for blowers".

[0057] The air tank 91 has an opening 910 and is covered by a casing 14. The cylindrical wall portion 136 of the casing 14 is attached to the outside of the air tank 91 to prevent air from leaking between the opening 910 and the cylindrical wall portion 136. A measuring pipe 92 is connected to the air tank 91, and an orifice plate 93 is provided in the measuring pipe 92. An auxiliary blower 94 is located at the end of the measuring pipe 92. A differential pressure gauge 96 is positioned to measure the pressure inside the air tank 91. A differential pressure gauge 97 is positioned to measure the pressure difference between the upstream and downstream sides of the orifice plate 93.

[0058] Motors 21, each attached to fans 5A-5E and 6A-6C respectively, were installed sequentially in the air tank 91 and driven at the same rotational speed. In the experiment in this embodiment, the rotational speed of the motors 21 was uniformly 18,000 revolutions per minute (18,000 rpm). While adjusting the rotational speed of the auxiliary blower 94, the measured values ​​of the differential pressure gauges 96 and 97 at arbitrary operating points (flow resistance) were obtained, and the airflow corresponding to fans 5A-5E and 6A-6C was calculated.

[0059] For noise measurement, a device utilizing a portion of the test machine 9 was used. Specifically, to eliminate the influence of the operating noise of the auxiliary blower 94, the part of the test machine 9 downstream of the orifice plate 93 of the measurement conduit 92 was removed. Furthermore, the air tank 91 was placed in the center of the semi-anechoic chamber with sound-absorbing material laid inside to avoid resonance. A microphone for noise measurement was placed 1 meter (m) away from the intake port 134 of the casing 14. Motors 21, each attached to fans 5A-5E and 6A-6C respectively, were sequentially installed in the air tank 91 and driven at 18,000 rpm. The opening area at the end of the measurement conduit 92 was adjusted so that the pressure inside the air tank 91 was substantially the same as the pressure during the airflow measurement described above. In this state, noise was measured by the microphone and recorded as an evaluation value (noise level corresponding to airflow).

[0060] Figure 9 shows the results of measuring the airflow and noise levels of fans 5A to 5E in Examples 1 to 3 and fans 6A to 6C in Comparative Examples 1 to 3 using the method described above.

[0061] The airflow of fan 5A is 1.66 cubic meters per minute (m³). 3 The airflow rate was 1.73 m³ / min, and the noise level was 77.0 dBA. The airflow rate of fan 5B was 1.73 m³ / min. 3 The noise level was 77.0 dBA. The airflow of fan 5C was 1.51 m³. 3 The noise level was 74.0 dBA. The airflow of fan 5D was 1.67 m³. 3 The noise level was 78.9 dBA. The airflow of fan 5E was 1.52 m³. 3 The noise level was 75.9 dBA, with a minimum output of / min.

[0062] The airflow of fan 6A is 1.33 m³. 3 The noise level was 83.8 dBA. The airflow of fan 6B was 1.50 m³. 3 The airflow rate was / min, and the noise level was 86.7 dBA. The airflow rate of fan 6C was 1.00 m³. 3 The noise level was 74.6 dBA, with a minimum output of / min.

[0063] From the air volume-noise level scatter diagram of Fig. 9, considering the air volume and noise level comprehensively, it can be seen that all of the fans 5A to 5E are superior to the fans 6A to 6C. Specifically, all of the fans 5A to 5E can exhibit an air volume of substantially 1.5 m 3 / min or more under the above measurement conditions, and the noise level is substantially suppressed to 80 dBA or less. When comparing the fan 5C according to Example 3 with the fan 6C according to Comparative Example 3, although the noise levels are comparable, the air volume of the fan 5C is significantly larger. Therefore, overall, the fan 5C is superior. Also, when comparing the fans 5C and 5E according to Examples 3 and 5 with the fan 6B according to Comparative Example 2, although the air volumes are comparable, the noise levels of the fans 5C and 5E are significantly lower. Therefore, overall, the fans 5C and 5E are superior.

[0064] In addition, in this embodiment, the measurement results under the conditions that the outer diameter D1 of the blade is uniformly 85 mm and the rotational speed of the motor 21 is uniformly 18,000 rpm are illustrated. However, if it is geometrically similar to the above fans 5A to 5E and 6A to 6C, even when the outer diameter D1 of the blade and / or the rotational speed of the motor 21 are changed, the correlation between the air volume and the noise level shows a tendency similar to that shown in Fig. 9.

[0065] As described above, it was confirmed that the fan 5 according to this embodiment can suppress noise while ensuring a sufficient air volume.

[0066] Furthermore, it is not necessary for all four factors—(i) blade inner diameter D2, (ii) disc outer diameter D3, (iii) cylinder inner diameter D4, and (iv) number of blades B—to satisfy the corresponding conditions from the above conditions (a) to (d). In other words, the effect of increasing airflow while reducing noise can be obtained if at least two of these factors satisfy the corresponding conditions. For example, it is sufficient if (i) blade inner diameter D2 and (iii) cylinder inner diameter D4 each satisfy the corresponding conditions (a) and (c). Alternatively, it is sufficient if (ii) disc outer diameter D3, (iii) cylinder inner diameter D4, and (iv) number of blades B each satisfy the corresponding conditions (b), (c), and (d).

[0067] The correspondence between each component (feature) of the above embodiment and each component (feature) of the present disclosure is shown below. However, each component of the embodiment is merely an example and does not limit the components of the present disclosure.

[0068] Grinder 1 is an example of an "electric work machine" and a "grinder". Fans 5, 5A to 5E are examples of "centrifugal fans" and "fan bodies". Disc 51 is an example of a "disk". Blade section 55 and blade 56 are examples of "blade section" and blades, respectively. Cylinder wall section 136 is an example of a "wall". Housing 10 is an example of a "housing". Intake port 101 and exhaust port 105 are examples of "intake port" and "exhaust port", respectively. Motor 21 is an example of a "motor".

[0069] The above embodiments are merely illustrative, and the centrifugal fan and electric work machine relating to this disclosure are not limited to the illustrated fan 5 (5A to 5E) and grinder 1. For example, the non-limiting modifications described below can be made.

[0070] For example, the centrifugal fan according to this disclosure is applicable to electric power tools other than grinders 1, in which the air blown radially outward from the blades of the centrifugal fan is directed axially by the surrounding wall portion of the blades. Such electric power tools include, for example, power tools, dust collectors used with power tools, cleaning machines, and gardening machines. Non-limiting specific examples of electric power tools to which the centrifugal fan according to this disclosure can be applied include circular saws, backpack vacuums, upright vacuums, robotic vacuums, and stick vacuums.

[0071] Furthermore, the wall surrounding the blades of the centrifugal fan does not necessarily have to be part of the housing of the electric work machine. As with the casing 14 used in the experiment described above (see Figure 8), the flow path around the blades may be defined within the housing by a separate component (for example, a cylindrical component). [Explanation of Symbols]

[0072] 1: Grinder, 10: Housing, 101: Intake port, 105: Exhaust port, 11: Head section, 13: Motor housing section, 133: Guide plate, 134: Suction port, 136: Cylinder wall section, 138: Partition, 14: Casing, 15: Main handle, 16: Trigger switch, 19: Power cord, 21: Motor, 210: Motor body section, 215: Output shaft, 25: Spindle 26: Reduction gear train, 29: Cutting tool, 5, 5A, 5B, 5C, 5D, 5E, 6A, 6B, 6C: Centrifugal fan (fan), 51: Disc, 53: Hub, 55: Blade section, 56: Blade, 63: External flow path, 9: Testing machine, 91: Air chamber, 92: Measurement conduit, 93: Orifice plate, 94: Auxiliary blower, 96: Differential pressure gauge, 97: Differential pressure gauge, 910: Opening, DX: Drive shaft, RX: Rotating shaft

Claims

1. A centrifugal fan for electric work machines, The fan itself, The fan body is surrounded by a wall portion, The aforementioned fan body is A disk centered on the first axis, The disc includes a wing portion comprising a plurality of wing blades arranged radially on one surface of the disc, each extending radially outward from the outer edge of the disc, The wall portion is configured to define a flow path between the outer edge of the blade portion and the inner surface of the wall portion for directing the air discharged radially outward from the plurality of blades in a first direction parallel to the first axis. The inner diameter of the blade portion is in the range of 45% to 60% of the outer diameter of the blade portion. The outer diameter of the disc is in the range of 80% to 95% of the outer diameter of the blade portion. A centrifugal fan characterized in that the inner diameter of the wall portion is in the range of 110% to 120% of the outer diameter of the blade portion.

2. A centrifugal fan according to claim 1, A centrifugal fan characterized in that the number of blades in the blade section is in the range of 35 to 50.

3. It is an electric work machine, A housing having an air intake and an exhaust port, A motor arranged inside the housing, A centrifugal fan is disposed within the housing and rotated around a first axis by the motor to generate an airflow within the housing from the intake port to the exhaust port. The centrifugal fan comprises a wall portion arranged around it, The aforementioned centrifugal fan is A disk centered on the first axis, The disc comprises a wing portion including a plurality of fins arranged radially on one surface of the disc, each extending radially outward from the outer edge of the disc, The wall portion is configured to define a flow path between the outer edges of the plurality of blades and the inner surface of the wall portion for directing the air discharged radially outward from the plurality of blades in a first direction parallel to the first axis. The inner diameter of the blade portion is in the range of 45% to 60% of the outer diameter of the blade portion. The outer diameter of the disc is in the range of 80% to 95% of the outer diameter of the blade portion. An electric work machine characterized in that the inner diameter of the wall portion is in the range of 110% to 120% of the outer diameter of the blade portion.

4. An electric work machine according to claim 3, An electric work machine characterized in that the number of blades in the blade section is in the range of 35 to 50.

5. An electric work machine according to claim 3 or 4, An electric work machine characterized in that at least a portion of the wall portion is formed by a portion of the housing.

6. An electric work machine according to any one of claims 3 to 5, The aforementioned electric work machine is a grinder, The motor and the centrifugal fan are arranged within the housing between the intake port and the exhaust port in the first direction. The electric work machine is characterized in that the centrifugal fan is configured to generate an airflow for cooling the motor.

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