ELECTRICAL WORK EQUIPMENT

Abstract

A centrifugal impeller for an electric power tool (1) comprises an impeller body (5) and a wall section (136) that radially surrounds the impeller body. The impeller body includes a disk (51) centered about a first axis (RX) and a vane assembly (55) comprising a plurality of vanes (56). The vanes are arranged on a surface of the disk, and each vane extends radially outward from a central region of the vane assembly beyond an outer circumferential edge (D3) of the disk. The wall section is configured to define a flow path between an outer circumferential edge (D1) of the vane assembly and an inner circumferential surface of the wall section, which directs air in a first direction parallel to the first axis, conveyed radially outward by the plurality of vanes.The inner diameter (D2) of the wing unit is in the range of 45%–60% of the outer diameter (D1) of the wing unit. The outer diameter (D3) of the disc is in the range of 80%–95% of the outer diameter (D1) of the wing unit. The inner diameter (D4) of the wall section is in the range of 110%–120% of the outer diameter (D1) of the wing unit.

Description

CROSS-REFERENCE

[0001] The application claims priority from the Japanese patent application JP 2024 - 177 692, which was filed on October 10, 2024, and whose contents are fully incorporated by reference. TECHNICAL AREA

[0002] The present disclosure relates to a centrifugal fan wheel and to an electrical work device, e.g. a power tool or an outdoor electrical device, which incorporates the centrifugal fan wheel. STATE OF THE ART

[0003] Many well-known electrical power tools feature a motor and a centrifugal fan, which is rotated by the motor to generate an airflow. The airflow generated by the centrifugal fan is used, for example, to cool an internal mechanism (e.g., a motor) and / or to collect, draw in, or otherwise move dust, dirt, etc. For example, a grinding tool that incorporates a centrifugal fan for cooling a motor is disclosed in DE 10 2023 102 544 A1. BRIEF SUMMARY

[0004] In electrical power equipment, it is desirable to reduce the noise associated with the rotation of a centrifugal fan wheel. However, there is a possibility that noise reduction will lead to reduced airflow. Therefore, a non-restrictive objective of the present teachings is to disclose techniques for reducing or limiting noise generated by the centrifugal fan wheel while still ensuring sufficient airflow for the intended application of the electrical power equipment.

[0005] This problem is solved by a centrifugal fan wheel according to claim 1 or an electric working device according to claim 3. Further preferred embodiments are described in the dependent claims.

[0006] In a first non-limiting aspect of the present disclosure, a centrifugal fan wheel for an electrical power device comprises a fan wheel body and a wall portion arranged around (radially surrounding) the fan wheel body. The fan wheel body includes a disk centered about a first axis and a blade assembly comprising a plurality of blades. The blades are each arranged on a surface of the disk and extend radially outward from a central region of the blade assembly. Each blade extends radially outward beyond an outer circumferential edge of the disk. In other words, the radially outermost end of each blade extends radially outward from the outer circumferential edge of the disk.The wall section is configured to define a flow path between an outer circumferential edge of the wing unit and an inner surface of the wall section, directing (guiding, directing) air in a first direction parallel to the first axis, which is conveyed (pushed, moved) radially outward by the plurality of wing blades as the wing unit rotates.

[0007] The inner diameter of the wing unit is between 45% and 60% of its outer diameter. The outer diameter of the disc is between 80% and 95% of the outer diameter of the wing unit. The inner diameter of the wall section is between 110% and 120% of the outer diameter of the wing unit.

[0008] According to the first aspect, a centrifugal fan wheel is used, which can reduce noise while still ensuring sufficient airflow. In other words, compared to previously known centrifugal fan wheels, the same airflow can be achieved with less noise and / or a larger (stronger) airflow can be achieved with the same noise level.

[0009] In a second non-limiting aspect of the present disclosure, an electrical work tool comprises a housing, a motor, a centrifugal fan wheel, and a wall section. It is noted that in the present disclosure, the term "electric work tool" generally refers to devices and tools configured to use electricity as a power source for performing work. Non-limiting examples of electrical work tools according to the present teachings include, but are not limited to, power tools designed to perform machining work on wood, metals, concrete, or the like; dust collectors (vacuum cleaners, dust separators) that can optionally be used in conjunction with a power tool; cleaning equipment; and garden tools (outdoor power tools).

[0010] The housing has one or more air intake openings and one or more air exhaust openings. The motor is located inside the housing. The centrifugal fan wheel is located inside the housing. The centrifugal fan wheel is configured to generate an airflow from the air intake opening(s) to the air exhaust opening(s) inside the housing when it is rotated about a first axis by the motor. The wall section is arranged around (radially surrounds) the centrifugal fan wheel. The centrifugal fan wheel has a disk centered about the first axis and a blade assembly comprising a plurality of blades. Each blade is located on a surface of the disk and extends radially outward from a central region of the blade assembly. Each blade extends radially outward from (over) an outer circumferential edge of the disk.In other words, the radially outermost end of each of the vanes extends radially from (over) the outer circumferential edge of the disk. The wall portion is configured to define a flow path between an outer circumferential edge of the plurality of vanes and the inner surface of the wall portion, directing (guiding, directing) air in a first direction parallel to the first axis, which is conveyed (pushed, moved) radially outward by (through) the plurality of vanes as the vane unit rotates.

[0011] The inner diameter of the wing unit is between 45% and 60% of its outer diameter. The outer diameter of the disc is between 80% and 95% of the outer diameter of the wing unit. The inner diameter of the wall section is between 110% and 120% of the outer diameter of the wing unit.

[0012] According to the second aspect, an electric work device is provided that features a centrifugal fan wheel, which can reduce noise while still ensuring sufficient airflow. In other words, compared to previously known electric work devices, the same airflow can be provided with less noise and / or a larger (stronger) airflow can be provided with the same noise level. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a perspective view of a grinding device according to a non-restrictive embodiment of the present teachings. Fig. Figure 2 is a cross-sectional view of the grinding device. Fig. Figure 3 is a rear view of a centrifugal fan wheel. Fig. Figure 4 is a cross-sectional view along line IV-IV in Fig. 3. Fig. 5 is an enlarged partial view of Fig. 2. Fig. Figure 6 is a cross-sectional view along line VI-VI in Fig. 2. Fig. Figure 7 is a table showing numerical values ​​relating to four factors of the centrifugal fan wheel of working examples 1 to 5 and comparison examples 1 to 3. Fig. Figure 8 is a schematic drawing to explain a test device used to measure airflow and noise. Fig. Figure 9 is an airflow-noise level scatter plot showing the correlation between the airflow and the noise level of the centrifugal fan wheels of working examples 1 to 5 and comparison examples 1 to 3. DETAILED DESCRIPTION

[0013] It is preferred that the number of wings in the wing unit is in the range of 35 to 50 in one or more embodiments of the present disclosure.

[0014] Additionally or alternatively, at least one area of ​​the wall section can be formed (defined) by an area of ​​the housing of the electrical device. According to this embodiment, the number of parts can be reduced compared to a configuration in which the wall section is provided separately from the housing.

[0015] Additionally or alternatively, the electrical tool can be a grinding machine. The motor and the centrifugal fan can be arranged between the air intake opening(s) and the air exhaust opening(s) in the first direction within the housing. The centrifugal fan can be configured to generate an airflow for cooling the motor. According to this embodiment, the grinding machine's motor can be effectively cooled by the centrifugal fan.

[0016] A grinding device 1 comprising a centrifugal fan wheel 5 (hereinafter referred to simply as the “fan wheel 5”) according to a representative and non-limiting embodiment of the present disclosure is described in more detail below with reference to the drawings.

[0017] This detailed explanation is intended solely to convey to a person skilled in the art the details of preferred examples for the implementation of the present disclosure and is not intended to limit the scope of protection of the present disclosure. Accordingly, not all combinations of the features illustrated by the embodiments are necessarily essential for the solutions to the problems described in the present disclosure. The various features disclosed in the embodiments mentioned above or below, and the various features set forth in the independent and dependent claims, need not necessarily be combined as in the specific examples mentioned herein to provide supplementary, useful embodiments of the present disclosure.

[0018] Furthermore, the various features disclosed in the embodiments mentioned above or below, and the various features set forth in the independent and dependent claims, are intended to be disclosed individually and independently of one another as limitations with respect to the disclosure and the specific subject matter claimed in the original patent application. In addition, descriptions relating to all numerical ranges are intended to disclose intermediate configurations thereof as limitations with respect to the disclosure and the specific subject matter claimed in the original patent application.

[0019] First, the general configuration of the grinding device 1 is described with reference to Fig. 1 and Fig. 2 described. The grinding device 1 is an example of an electric power tool according to the present teachings. More precisely, the grinding device 1, which can also be called a disc grinder or an angle grinder, is an example of a portable power tool according to the present teachings. The grinding device 1 is configured to perform various machining tasks (e.g., grinding, sanding, or cutting) by rotating a tool accessory 29, which has a disc shape.

[0020] The grinding device 1 has a housing 10, a motor 21, a fan wheel 5 and a spindle 25.

[0021] The housing 10 is a hollow body, also referred to as a main tool body, which has an elongated shape and forms the outer wall of the grinding device 1. The motor 21, the fan wheel 5, and the spindle 25 are housed in the housing 10. The motor 21 is arranged such that a rotational axis RX of an output shaft 215 of the motor 21 extends substantially parallel (preferably parallel) to a longitudinal axis of the housing 10. The fan wheel 5 is fixed to the output shaft 215 so that it rotates with it. The spindle 25 is operationally coupled to the motor 21 and is mounted within an end region of the housing 10 in a longitudinal axis direction such that it is rotatable about a drive axis DX. The drive axis DX extends in a direction that intersects the rotational axis RX of the output shaft 215 (specifically, at least substantially perpendicular, preferably perpendicular to it).An end region of the spindle 25 in its axial direction is exposed from the housing 10 to the outside and is configured to serve as a tool mounting part. The tool accessory 29 is removably mounted to the tool mounting part of the spindle 25.

[0022] It is noted that, for the sake of simplicity in the following description, the direction of extension of the drive axis DX is defined as the top-bottom direction of the grinding device 1. In the top-bottom direction, the side on which the tool mounting part of the spindle 25 is located is defined as the bottom side of the grinding device 1, and the opposite side is defined as the top side of the grinding device 1. The longitudinal axis direction of the housing 10 (i.e., the direction of extension of the rotary axis RX of the motor 21) is defined as a front-back direction of the grinding device 1. In the front-back direction, the side on which the spindle 25 is located is defined as the front side of the grinding device 1, and the opposite side is defined as the back side of the grinding device 1.A direction that is perpendicular to the up-down direction and the front-back direction is defined as a left-right direction of the grinding device 1.

[0023] Further details regarding the configuration of the grinding device 1 are described below.

[0024] As in Fig. 1 and Fig. As shown in Figure 2, the housing 10 comprises, in order from the front, a head part 11 (also referred to as a gearbox housing), a motor housing part 13 (also referred to as a motor housing) and a main handle 15.

[0025] The head section 11 accommodates the spindle 25 and a speed reduction gear train (e.g., a bevel gear mechanism) 26. The speed reduction gear train 26 operationally couples (connects) the output shaft 215 of the motor 21 to the spindle 25 and thus transmits the rotational energy of the output shaft 215 to the spindle 25.

[0026] The motor housing part 13 has an elongated tubular shape and accommodates the motor 21 and the fan wheel 5. The motor 21 comprises a main motor body part 210, which includes a stator and a rotor, and the output shaft 215, which is configured to rotate integrally with the rotor. A front end of the output shaft 215 projects into the interior of the head part 11 and is operably coupled (connected) to the spindle 25 via the speed reduction gear train 26. The fan wheel 5 is located inside a front end of the motor housing part 13. The fan wheel 5 is fixed to the output shaft 215 at the front of the main motor body part 210 and rotates integrally with the output shaft 215. It should be noted that the configuration of the fan wheel 5 and its peripheral areas are described in more detail below.

[0027] The main handle 15 is configured to be gripped by a user and has a tubular shape with a diameter smaller than that of the motor housing part 13. A push-button switch 16 (also referred to as a lever) for manually controlling the operation of the grinder 1 is provided on the main handle 15. A power supply cable 19, which can be connected to an external power source, extends from the rear end of the housing 10, and the grinder 1 is powered by electrical power supplied by the external power source. However, in an alternative embodiment, the grinder 1 can be powered by electrical power supplied by a battery (rechargeable battery pack or battery cassette) instead of an external power supply.In addition, in another embodiment, the motor housing part 13 of the housing 10 can also function as a main handle.

[0028] The housing 10 of the present embodiment has air intake openings 101, which allow air to flow into the interior of the housing 10, and air outlet openings 105, which allow the air to be discharged to the outside of the housing 10. In the present embodiment, the air intake openings 101 are formed in a rear end region (in detail, in a right-side region and a left-side region of the rear end region) of the motor housing part 13. The air outlet openings 105 are formed in an upper region and a lower region of the head part 11. The motor 21 (the main motor body part 210) and the fan wheel 5 are arranged between the air intake openings 101 and the air outlet openings 105 in the front-to-rear direction.

[0029] When the user presses the push button 16, the motor 21 is driven, and the spindle 25 is rotated around the drive axis DX by the drive power of the motor 21. The tool accessory 29, which is mounted on the spindle 25, rotates as the spindle 25 rotates, thus enabling machining operations (e.g., grinding, sanding, cutting, polishing, etc.) to be performed on a workpiece. Furthermore, the rotation of the fan wheel 5 generates an airflow that is drawn into the interior of the housing 10 through the air intake openings 101, flows towards the inside of the housing 10, and is discharged to the outside via the air outlet openings 105. This airflow cools the motor 21 by passing around and through the interior of the main motor body 210.

[0030] The configuration of the fan wheel 5 and the circumferential areas of the fan wheel 5 are now described in more detail.

[0031] As in Fig. 3 and Fig. As shown in Figure 4, the fan wheel 5, according to the present embodiment, is an open-type impeller (vane wheel) and comprises a disc 51, a hub 53, and a blade assembly 55, which are arranged coaxially. In the present embodiment, the fan wheel 5 is a single component manufactured by integral molding (casting) of a polymer (synthetic resin). However, in a further embodiment, the fan wheel 5 can be formed by coupling (connecting) a plurality of components that are manufactured separately. Furthermore, in another embodiment, the fan wheel 5 can be made of a metal or can be manufactured from a combination of a metal and a polymer by injection molding (e.g., the disc 51 and the hub 53 can be made of metal for structural robustness, and the blades 56 can be made of plastic to reduce weight).

[0032] The disc 51 is a disc-shaped (round, circular) part and can also be referred to as a main plate, a back plate, or the like. A hole is formed in the center of the disc 51. The hub 53 is a circular tube-shaped area which is fitted onto and thus to the output shaft 215 of the motor 21 (preferably by interference fit or friction fit) and is thereby fixed to it. The hub 53 is arranged around the hole in the disc 51 and projects from a surface of the disc 51 in the axial direction of the fan wheel 5 (i.e., the direction of extension of the axis of rotation RX). It should be noted that, since the fan wheel 5 is mounted coaxially with the output shaft 215, the (rotational) axis of the fan wheel 5, which is referred to in the following description, can also be understood as the axis of rotation RX of the output shaft 215.

[0033] The wing unit 55 comprises a plurality of wings 56. The wings 56 are arranged on a surface (i.e., the surface on which the hub 53 is arranged) of the disk 51 and project in the axial direction of the fan wheel 5. The wings 56 extend radially outward from a central region of the wing unit 55. In the present embodiment, the wings 56 all have the same shape and are arranged with a substantially uniform spacing (“pitch”) in the circumferential direction of the disk 51.

[0034] In more detail, each of the wings 56 extends radially outward from a predetermined location on the disk 51 in the radial direction. It is noted that the “wings 56 extend radially outward” can also be described as “the wings 56 extend away from the center (axis of rotation RX) of the disk 51.” In the present embodiment, the radially inner ends (hereinafter referred to simply as the “inner ends”) of the wings 56 are located at radial positions that are the same as the radial position of the outer circumferential surface of the hub 53; however, the inner ends of the wings 56 may be located at positions that differ from these examples.

[0035] The blades 56 extend in a straight line along the radius of the disk 51 or can extend away from the center of the disk 51 while curving. Furthermore, the blades 56 can be inclined in a direction relative to the radius of the disk 51. In the fan wheel 5 shown in the drawings, the blades 56 are so-called rearward-facing blades, which rotate in the opposite direction to the direction of rotation (the clockwise direction). Fig. 3) of the fan wheel 5 are inclined and extend radially outwards as they curve.

[0036] All of the radially outer (outermost) ends (hereinafter simply referred to as the "outer ends") of the blades 56 are located along the circumference of a circle C1, which is centered on the axis (rotation axis RX) of the fan wheel 5; the diameter of circle C1 defines an outer diameter D1 of the blade assembly 55 (hereinafter simply referred to as "blade outer diameter D1"). In the present embodiment, each of the blades 56 extends radially outward from (over) the outer circumferential edge of the disk 51. That is, the blade outer diameter D1 is larger than the outer diameter D3 of the disk 51 (hereinafter simply referred to as "disc outer diameter D3").

[0037] The height of each of the blades 56 in the axial direction of the fan wheel 5 increases from the inner end of the blade 56 as it extends radially outward along the blade. The height of each of the blades 56 is at its maximum at a predetermined location in the radial direction and decreases from this predetermined location as it extends toward the outer end of the blade 56. Specifically, the location at which the height of the blade 56 is at its maximum is preferably along the circumference of a circle C2, which is centered on the axis of the fan wheel 5 and has a diameter smaller than the blade outer diameter D1 and the disc outer diameter D3. The diameter of the circle C2 defines an inner diameter D2 of the blade assembly 55 (hereinafter simply referred to as "blade inner diameter D2").It is noted that the height of each of the wings 56 need not necessarily vary as the wings 56 extend radially outwards. For example, the height of each of the wings 56 can be uniform (constant) from the inner to the outer end. Alternatively, the height of each of the wings 56 can increase from the inner end to a predetermined point in the radial direction and then be uniform (constant) from that point to the outer end.

[0038] As in Fig. As shown in Figure 5, the fan wheel 5, which has the configuration described above, is fixed to the output shaft 215 such that the surface of the disk 51, on which the blade assembly 55 is arranged, is oriented (facing) to the rear (i.e., so that the projecting ends of the blades 56 face the main motor body part 210). A guide plate 133 is arranged between the fan wheel 5 and the main body part 210 in the front-to-back direction, enabling the fan wheel 5 to draw in air more efficiently. A circular suction opening 134, which has essentially the same or a slightly larger diameter than the inner diameter D2 of the blades, is formed at the center of the guide plate 133.Accordingly, when the fan wheel 5 rotates, air is drawn in axially (forward) through the suction opening 134, flows radially outwards through flow paths defined between adjacent blades 56, and flows out of openings between the outer ends of the adjacent blades 56. The flow paths between the blades 56 are hereinafter also referred to as "internal flow paths".

[0039] Inside the motor housing part 13, a flow path is defined that directs the air conveyed (supplied) by the internal flow paths in the axial direction (i.e., forwards) around the blade assembly 55 of the fan wheel 5. The flow path around the blade assembly 55 is also hereinafter referred to as the "external flow path 63". As in Fig. 5 and Fig. As shown in Figure 6, in the present embodiment, a tubular wall section 136, which is the area of ​​the motor housing section 13 arranged around the impeller unit 55, has a substantially circular cross-section and is arranged coaxially with the fan wheel 5. Accordingly, the inner diameter D4 of the tubular wall section 136 (hereinafter simply referred to as "inner diameter D4") is larger than the outer diameter D1 of the impeller. Due to this tubular wall section 136, the external flow path 63 is defined between the outer circumferential edge of the impeller unit 55 and an inner surface of the tubular wall section 136. That is, the inner diameter D4 of the tube can also be referred to as the outer diameter of the external flow path 63. It should be noted that the outer circumferential edge of the impeller unit 55 is defined by the outer ends of the impeller 56.

[0040] A subdivision 138, which divides an interior of the motor housing part 13 and an interior of the head part 11, is arranged on the front of the tube wall part 136. A communication opening (connection opening) is provided in the subdivision 138, and the air conveyed (supplied) by the fan wheel 5 flows forward through the external flow path 63, passes through the connection opening in the subdivision 138, and flows into the upper and lower regions of the head part 11, after which the air is discharged to the outside through the air outlet openings 105 (see Fig. 1).

[0041] Furthermore, among the many factors used to determine the specifications of a centrifugal fan wheel, the fan wheel 5 of the present embodiment exhibits properties with respect to specific factors that are not present in previously existing centrifugal fan wheels.

[0042] For example, factors such as the outer diameter of the fan wheel, the shape of the blades, the height of an inlet, an inlet angle, an outlet angle, the number of blades, and the like are generally known to be used to determine the specifications of a centrifugal fan wheel. However, it is not easy to identify, among these numerous factors, a combination of specific factors that significantly influence the airflow and noise of the centrifugal fan wheel, and to establish suitable numerical ranges for these factors. The inventors of the present application conducted various tests by changing different factors and, based on the test results, developed embodiments of the present invention.Specifically, it was determined that airflow can be increased (enlarged) while noise is reduced by appropriately setting the numerical ranges for at least two factors among the following four factors, i.e.: (i) inner diameter of the blade D2, (ii) outer diameter of the disc D3, (iii) inner diameter of the pipe D4 and (iv) number of blades 56 (hereinafter referred to simply as "blade number B").

[0043] Furthermore, it was found that it is particularly effective when the ratios (percentages) of the aforementioned factors (i), (ii), and (iii) to the wing outer diameter D1 satisfy the following conditions (a)-(c). It should be noted that in all cases of a “range of XX-YY” in the following description, XX is intended to represent the lower limit and YY the upper limit. In other words, the expression “range of XX-YY” means “XX or greater and YY or less.” (a) The inner wing diameter D2 lies in the range of 45%-60% of the outer wing diameter D1. In other words, the ratio (percentage) of the inner wing diameter D2 to the outer wing diameter D1 (hereinafter referred to simply as the ‘inner wing diameter ratio’) lies in the range of 0.45-0.60 (0.45 ≤ D2 / D1 ≤ 0.60). (b) The disk outer diameter D3 lies in the range of 80%-95% of the blade outer diameter D1. In other words, the ratio (percentage) of the disk outer diameter D3 to the blade outer diameter D1 (hereinafter referred to simply as the ‘disc outer diameter ratio’) is in the range of 0.80-0.95 (0.80 ≤ D3 / D1 ≤ 0.95). (c) The pipe inner diameter D4 is in the range of 110%-120% of the impeller outer diameter D1. In other words, the ratio (percentage) of the pipe inner diameter D4 to the impeller outer diameter D1 (hereinafter simply referred to as the ‘pipe inner diameter ratio’) is in the range of 1.10-1.20 (1.10 ≤ D4 / D1 ≤ 1.20). Furthermore, it was confirmed that, in addition to the conditions (a)-(c) described above, it is even more effective if the number of wings (iv), which is the fourth factor, satisfies the following condition (d). However, the following range is a preferred range because determining the number of wings B within the following range becomes difficult if the inner wing diameter D2 becomes too small to accommodate the preferred number of wings 56. (d) The number of wings B is in the range of 35-50 (35 ≤ B ≤ 50).

[0044] The effects of the fan wheel 5 according to the present embodiment are described below with reference to the results of the measurements of the airflow and noise for fan wheels 5A-5E according to working examples 1-5 and fan wheels 6A-6C according to comparative examples 1-3.

[0045] Fig. Figure 7 shows the numerical values ​​relating to the four factors for each of the fan wheels 5A-5E according to Working Examples 1-5 and the fan wheels 6A-6C according to Comparative Examples 1-3. It is noted that the blade outer diameter D1 is 85 millimeters (mm) in all Working Examples 1-5 and Comparative Examples 1-3.

[0046] Each of the fan wheels 5A-5E fulfills the aforementioned conditions (a)-(c) concerning the aforementioned factors (i)-(iii). Furthermore, each of the fan wheels 5A-5E also fulfills the aforementioned condition (d) concerning factor (iv). In contrast, each of the fan wheels 6A-6C fails to fulfill at least one of the conditions (a)-(c) concerning the aforementioned three factors (i)-(iii). Furthermore, only the fan wheel 6A fulfills the aforementioned condition (d) concerning factor (iv).

[0047] It is noted that all of the fan wheels 5A-5E, 6A-6C are the same in that each has the disc 51, the hub 53, and the blade assembly 55 (the plural of blades 56), similar to the fan wheel 5 described above. In contrast, with regard to measuring airflow and noise, the pipe wall section 136 used was not the area of ​​the housing 10 described above, but was instead an enclosure 14 (see Fig. 8), which was integrally formed with the guide plate 133.

[0048] In detail, how Fig. As can be seen from Figure 7, the inner diameter ratio (D2 / D1) of the fan wheel 5A according to Working Example 1 was 0.47, the outer diameter ratio (D3 / D1) of the disc of the fan wheel 5A according to Working Example 1 was 0.83, and the inner diameter ratio (D4 / D1) of the pipe of the fan wheel 5A according to Working Example 1 was 1.14. The number of blades B of the fan wheel 5A was 35. The inner diameter ratio of the blades of the fan wheel 5B according to Working Example 2 was 0.47, the outer diameter ratio of the disc of the fan wheel 5B according to Working Example 2 was 0.82, and the inner diameter ratio of the pipe of the fan wheel 5B according to Working Example 2 was 1.20. The number of blades B of the fan wheel 5B was 35. The blade inner diameter ratio of the fan wheel 5C according to working example 3 was 0.47, the disc outer diameter ratio of the fan wheel 5C according to working example 3 was 0.91, and the pipe inner diameter ratio of the fan wheel 5C according to working example 3 was 1.20.The number of blades B of the fan wheel 5C was 35. The blade inner diameter ratio of the fan wheel 5D according to Working Example 4 was 0.59, the disc outer diameter ratio of the fan wheel 5D according to Working Example 4 was 0.83, and the pipe inner diameter ratio of the fan wheel 5D according to Working Example 4 was 1.14. The number of blades B of the fan wheel 5D was 35. The blade inner diameter ratio of the fan wheel 5E according to Working Example 5 was 0.59, the disc outer diameter ratio of the fan wheel 5E according to Working Example 5 was 0.91, and the pipe inner diameter ratio of the fan wheel 5E according to Working Example 5 was 1.20. The number of blades B of the fan wheel 5E was 35.

[0049] In contrast, the inner diameter ratio of the blades of fan wheel 6A according to comparison example 1 was 0.67, the outer diameter ratio of the disc of fan wheel 6A according to comparison example 1 was 1.00, and the inner diameter ratio of the tube of fan wheel 6A according to comparison example 1 was 1.16. The number of blades B of fan wheel 6A was 42. The inner diameter ratio of the blades of fan wheel 6B according to comparison example 2 was 0.65, the outer diameter ratio of the disc of fan wheel 6B according to comparison example 2 was 1.00, and the inner diameter ratio of the tube of fan wheel 6B according to comparison example 2 was 1.14. The number of blades B of the fan wheel 6B was 29. The blade inner diameter ratio of the fan wheel 6C according to comparison example 3 was 0.62, the disc outer diameter ratio of the fan wheel 6C according to comparison example 3 was 0.89, and the pipe inner diameter ratio of the fan wheel 6C according to comparison example 3 was 1.02.The number of blades B of the fan wheel 6C was 30.

[0050] Suitable methods for measuring airflow and noise are each described below.

[0051] The test device 9, which is in Fig. The test apparatus shown in Figure 8 was used to measure the airflow. The test apparatus 9 was equipped with an air chamber 91, a measuring line 92, a perforated plate (nozzle plate, measuring / perforated orifice plate) 93, an additional fan wheel 94, and differential pressure measuring devices 96, 97. It is noted that the test apparatus used for this test apparatus 9 is the one described in the "Procedure for Testing and Inspecting a Fan Wheel" in JIS (Japan Industrial Standard) B8330:2000 for "the case of a fan wheel in which neither a discharge pipe nor a suction pipe is provided in the operating condition."

[0052] An opening 910 is provided in the air tank 91 and is covered by the housing 14. The tube wall section 136 of the housing 14 is mounted on the outside of the air tank 91 so that air cannot escape between the opening 910 and the tube wall section 136. The measuring line 92 is in fluid communication with the air tank 91, and the perforated plate 93 is provided in the measuring line 92. The additional fan wheel 94 is arranged at the connection end (end) of the measuring line 92. The differential pressure measuring device 96 is arranged such that it measures the pressure inside the air tank 91. The differential pressure measuring device 97 is arranged such that it measures the pressure difference on an upstream side and a downstream side of the perforated plate 93.

[0053] The motor 21, to which the fan wheels 5A-5E, 6A-6C were attached, was installed in the air chamber 91 and was driven at the same speed for each airflow measurement. Specifically, in the test of the present embodiments, the speed of the motor 21 was 18,000 revolutions per minute (18,000 rpm) for all airflow measurements. The measured values ​​were acquired from each of the differential pressure measuring devices 96, 97 at an arbitrary operating point (a flow path resistance) by adjusting the speed of the additional fan wheel 94, and the corresponding airflow from each of the fan wheels 5A-5E, 6A-6C was calculated.

[0054] A device utilizing part of the test fixture 9 was used for noise measurement. Specifically, to eliminate the influence of the operating noise of the additional fan wheel 94, the components (i.e., a downstream section of the measuring line 92 and the additional fan wheel 94) located downstream of the perforated plate 93 of the measuring line 92 in the test fixture 9, which are in Fig. Figure 8 was removed. Furthermore, the air chamber 91 was positioned in the center of a semi-anechoic chamber in the condition in which a sound-absorbing material was arranged to dampen resonances inside the chamber (walls and ceiling, but not the floor). A noise-measuring microphone was positioned at a distance of one meter from the suction opening 134 of the enclosure 14. The motor 21, to which the fan wheels 5A-5E, 6A-6C were attached, was installed in the air chamber 91 and was driven at 18,000 rpm for each noise measurement. The open area of ​​the connecting end of the measuring line 92 was adjusted such that the pressure inside the air chamber 91 was essentially equal to the pressure during the airflow rate measurements described above.The noise was measured in a specific state using the microphone and used as a data point (the noise level corresponding to the airflow).

[0055] Fig. Figure 9 shows the results in which the airflow and noise level were measured according to the procedures described above for each of the fan wheels 5A-5E according to work examples 1-5 and the fan wheels 6A-6C according to comparison examples 1-3.

[0056] The airflow of fan wheel 5A was 1.66 cubic meters per minute (m³). 3 / min), and the noise level was 77.0 A-weighted decibels (dBA). The airflow of fan wheel 5B was 1.73 m 3 / min, and the noise level was 77.0 dBA. The airflow of the fan wheel 5C was 1.51 m. 3 / min, and the noise level was 74.0 dBA. The airflow of the 5D fan wheel was 1.67 m. 3 / min, and the noise level was 78.9 dBA. The airflow of the fan wheel 5E was 1.52 m. 3 / min, and the noise level was 75.9 dBA.

[0057] The airflow of fan wheel 6A was 1.33 m 3 / min, and the noise level was 83.3 dBA. The airflow of the fan wheel 6B was 1.50 m 3 / min, and the noise level was 86.7 dBA. The airflow of the fan wheel 6C was 1.00 m 3 / min, and the noise level was 74.6 dBA.

[0058] From the airflow-noise level dispersion diagram, which is in Fig. As shown in Figure 9, it can be deduced that, when airflow and noise level are fully considered, all of the 5A-5E fan impellers are superior to the 6A-6C fan impellers. Specifically, all 5A-5E fan impellers were able to achieve an airflow of 1.5 m³ / h. 3 / min or greater under the measurement conditions described above and were able to limit the noise level to 80 dBA or less. It is noted that when comparing impeller 5C according to Working Example 3 and impeller 6C according to Comparison Example 3, while noise levels were at the same height, impeller 5C showed a significantly greater airflow. Accordingly, impeller 5C is superior overall. Furthermore, when comparing impellers 5C and 5E according to Working Examples 3 and 5 and impeller 6B according to Comparison Example 2, while airflows were at the same height, each of impellers 5C and 5E had a significantly lower noise level. Accordingly, impellers 5C and 5E are superior overall.

[0059] It is noted that in the present embodiments, the measurement results are shown as an example under the conditions that the outer diameter of the blade D1 was 85 mm for all fan wheels 5 and the speed of the motor 21 was 18,000 rpm for all measurements. However, as long as a fan wheel is geometrically similar to the fan wheels 5A-5E, 6A-6C described above, the correlation between the airflow and the noise level will exhibit the same trend as shown in Fig. 9 shown, also in the case in which the outer wing diameter D1 and / or the rotational speed of the motor 21 was (were) modified.

[0060] As described above, it has been confirmed that the fan wheel 5, according to the present embodiment, can reduce noise while ensuring sufficient airflow. In other words, for a specific airflow rate, less noise is generated compared to fan wheels that do not meet the conditions (a)-(c) described above.

[0061] It is noted that not all four factors – (i) inner diameter of the blade D2, (ii) outer diameter of the disc D3, (iii) inner diameter of the pipe D4, and (iv) number of blades B – need to be fulfilled; as long as at least two of the factors satisfy the corresponding condition under the four conditions (a)-(d) described above, the effect of increasing airflow while reducing noise can be achieved. Accordingly, (i) inner diameter of the blade D2 and (iii) inner diameter of the pipe D4, for example, can each easily satisfy the corresponding conditions (a) and (c). Alternatively, (ii) outer diameter of the disc D3, (iii) inner diameter of the pipe D4, and (iv) number of blades B, for example, can each easily satisfy the corresponding conditions (b), (c), and (d).

[0062] The corresponding relationships between the structural elements (features) of the embodiment described above and the structural elements (features) of the present disclosure are shown below. However, the structural elements of the embodiment are merely an example and do not limit the structural elements of the present disclosure.

[0063] Grinding device 1 is an example of an "electrical power tool" and a "grinding device". Fan wheels 5, 5A-5E are each an example of a "centrifugal fan wheel" and a "fan wheel body". Disc 51 is an example of a "disc". Blade assembly 55 and blades 56 are examples of a "blade assembly" and "blades", respectively. Pipe wall section 136 is an example of a "wall section". Housing 10 is an example of a "housing". Air intake openings 101 and air exhaust openings 105 are each an example of an "air intake opening" and an "air exhaust opening", respectively. Motor 21 is an example of a "motor".

[0064] It is noted that the embodiment described above is merely an illustrative example, and centrifugal fan wheels and electrical working devices according to the present disclosure are not limited to the fan wheels 5 (5A-5E) and the grinding device 1 described herein by way of example. For instance, the non-restrictive modifications described below are possible while remaining within the scope of protection of the present teachings.

[0065] In addition to its application in the grinding device 1 according to the present disclosure, the centrifugal fan wheel is also applicable, for example, to an electrical power tool configured such that the air conveyed radially outwards from the impeller unit is guided (directed) in the axial direction by the wall portion surrounding the impeller unit of the centrifugal fan wheel. For example, power tools, dust collectors (dust separators, vacuum cleaners) or cleaning devices that can be used alone or optionally in conjunction with power tools, and garden tools (outdoor power tools) are included within the scope of protection of the electrical power tools according to the present teachings. Furthermore, for example,Circular saws, backpack vacuum cleaners, stand-up vacuum cleaners, robot vacuum cleaners and stick vacuum cleaners are further non-restrictive specific examples of electrical work equipment which can advantageously utilize the centrifugal fan wheel of the present disclosure.

[0066] Furthermore, the wall section around the blade assembly of the centrifugal fan wheel does not necessarily have to be formed by a portion of the housing of the electrical device. As shown in housing 14 (see Fig. 8), which was applied in the above described test procedures, the flow path around the wing unit inside the housing may be defined by a structure (e.g. a tubular component) that is separate from the housing.

[0067] It is explicitly emphasized that all features disclosed in the description and / or the claims are to be considered separate and independent of one another for the purposes of the original disclosure as well as for the purpose of limiting the claimed invention, irrespective of the combinations of features in the embodiments and / or the claims. It is explicitly stated that all range specifications or specifications of groups of units disclose every possible intermediate value or subgroup of units for the purposes of the original disclosure as well as for the purpose of limiting the claimed invention, in particular also as a boundary of a range specification. Reference symbol list 1 grinding machine 10 cases 101 Air intake opening 105 Air vent 11 Headboard 13 Engine housing part 133 Guide plate 134 Suction opening 136 Pipe wall section 138 subdivisions 14 Enclosure 15 Main handle 16 push buttons 19 Power supply cables 21 engine 210 Main engine body part 215th issue wave 25 spindle 26 Reduction gear train 29 Tool accessories 5, 5A, 5B, 5C, 5D, 5E, 6A, 6B, 6C Centrifugal fan wheel (fan wheel) 51 disc 53 hub 55 wing units 56 wings 63 external flow path 9 Test device 91 air chambers 92 Measuring leads 93 perforated plate 94 additional fan wheel 96 Differential pressure measuring device 97 Differential pressure measuring device 910 Opening DX drive axle RX rotary axis QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2024 - 177 692

[0001] DE 10 2023 102 544 A1

[0003] Cited non-patent literature

[0000] Method for testing and inspection of a fan wheel” in JIS (Japan Industrial Standard) B8330:2000

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