BRUSHLESS ELECTRIC MOTOR

Description

[0001] The present invention relates to a brushless electric motor for an electric hand-held power tool. The electric motor has a bearing plate and a Hall effect board arranged on the bearing plate.

[0002] Brushless electric motors of the type mentioned above are generally known from the state of the art and are used, for example, in modern handheld power tools. The Hall effect board typically has one or more Hall sensors for detecting the rotor position of the electric motor's rotor, allowing sensor-based electronic commutation.

[0003] It is an object of the present invention to provide an electric motor that is easy to assemble / disassemble.

[0004] This object is achieved by axially securing the Hall plate to the bearing plate by means of an elastic O-ring. The invention incorporates the finding that Hall plates in prior art electric motors are typically attached by screwing or hot-staking. Screwing leads to increased assembly effort. Hot-staking prevents, or at least significantly complicates, non-destructive disassembly of the Hall plate. DE 10 2008 037737 A1 discloses securing the Hall plate by means of an elastic O-ring that axially secures the Hall plate to the bearing plate.

[0005] In the brushless electric motor according to the invention, the Hall effect board is also axially fixed to the bearing plate by means of an elastic O-ring. This reduces assembly effort (with a comparatively compact design) and, in the interests of functional integration, ensures precise axial positioning of the Hall effect board through the clamping effect of the elastic O-ring. It has proven advantageous if the Hall effect board is axially fixed to the bearing plate exclusively by means of the O-ring.

[0006] Preferably, the bearing plate is a B-bearing plate, i.e., the bearing plate opposite the drive side of the electric motor. The Hall effect plate and the O-ring are preferably located on a side of the bearing plate facing away from the rotor. The bearing plate can be connected to a stator of the electric motor. The bearing plate and the stator can be formed integrally with one another.

[0007] According to the invention, the bearing plate has a central bearing for accommodating a rotor shaft. The central bearing can be attached to the bearing plate via at least one radial retaining web.

[0008] It has proven advantageous if the Hall effect plate is supported in the axial direction against the at least one radial retaining web. According to the invention, at least one support collar is formed on the central bearing, against which the O-ring is supported. Preferably, three equally spaced support collars are provided. The support collar can have a contact surface for the O-ring that is oriented obliquely to the rotor axis. An angle enclosed between the rotor axis and the surface normal of the contact surface can be, for example, less than 90 degrees, preferably between 40 and 60 degrees.

[0009] In a further preferred embodiment, the Hall plate is disc-shaped with a concentric hollow cylindrical recess. Preferably, the inner diameter of the recess is larger than the outer diameter of the central bearing, including the at least one support collar. In this way, the Hall plate can be pushed axially onto the central bearing and then secured in the axial direction by the O-ring.

[0010] The invention is also achieved by an electric hand-held power tool, preferably a battery-operated hand-held power tool, with an electric motor according to the type described above.

[0011] Further advantages will become apparent from the following description of the figures. Various embodiments of the present invention are illustrated in the figures. The figures, the description, and the claims contain numerous features in combination. Those skilled in the art will expediently consider the features individually and combine them into useful further combinations.

[0012] In the figures, identical and similar components are numbered with the same reference numerals. They show: Figure 1 shows a first preferred embodiment of a brushless electric motor according to the invention, viewed from the side facing away from the rotor; Figure 2 shows a section through the bearing plate of the electric motor of the Figure 1 ; and Figure 3 a rotor-side view of the bearing plate of the electric motor of the Figure 1 . Example:

[0013] A preferred embodiment of a brushless electric motor 10 according to the invention with a view of the side RS facing away from the rotor is shown in Figure 1 The electric motor 10 has a bearing plate 1 and a Hall plate 3 arranged on the bearing plate 1. In the exemplary embodiment shown here, the bearing plate 10 is a B-bearing plate, ie the bearing plate opposite the drive side of the electric motor 10. For reasons of clarity, the electric motor 10 is not shown in its entirety, ie in particular a stator winding or a stator package (apart from some stator segments connected to the bearing plate 1) is shown in Figure 1 not shown.

[0014] According to the invention, the Hall plate 3 is fixed axially, ie in the axial direction AR, to the bearing plate 1 by means of an elastic O-ring 5. In the present case, the Hall plate 3 is fixed axially to the bearing plate 1 exclusively by means of the O-ring 5. The Hall plate 3 and the O-ring 5 are both on the Figure 1 shown side RS of the bearing shield 1 facing away from the rotor.

[0015] In Figure 1 It can be clearly seen that the bearing plate 1 has a central bearing 2 for receiving a rotor axis 6. A rotor of the electric motor 10 itself is shown in Figure 1 not shown. Three support collars 8 are formed on the central bearing 2, against which the O-ring 5 is supported in the axial direction AR.

[0016] On the lower right side of the Figure 1 An electric hand-held power tool 100 is shown schematically, which is equipped with an electric motor 10 according to the invention.

[0017] Figure 2 shows a section through the bearing plate 1 of the electric motor 10 of the Figure 1 . It can be clearly seen that the central bearing 2 is attached to the bearing plate 1 via a radial retaining web 7 (see on Figure 3 ). On the one hand, the Hall plate 3 is supported in the axial direction AR against the radial retaining web 7. On the other hand, the elastic O-ring 5 is supported in the axial direction AR on the support collar 8 formed on the central bearing 2. Thus, the Hall plate 3, which here, for example, has a Hall sensor 4, is axially fixed to the bearing plate 1 by means of the elastic O-ring 5.

[0018] The support collar 8 has a contact surface 8' for the O-ring 5, which is oriented obliquely to the rotor axis 6. The angle W enclosed between the rotor axis 6 and the surface normal N of the contact surface 8' is less than 90 degrees. In the presently illustrated embodiment, the angle W is approximately 45°, which represents a good compromise between clamping effect and assembly capability.

[0019] Again Figure 2can be removed, the Hall plate 3 is disc-shaped with a concentric hollow cylindrical recess 9. An inner diameter ID of the recess 9 is larger than an outer diameter AD of the central bearing 2 including the support collar 8. Thus, the Hall plate 3 can be pushed onto the central bearing 2 in the axial direction AR and then secured in a form-fitting manner in the axial direction AR by the O-ring 5. Exact positioning of the Hall plate 5 in the axial direction AR is ensured by the clamping effect of the elastic O-ring 5.

[0020] Figure 3 now shows a rotor-side view RB of the bearing plate of the electric motor of the Figure 1. The central bearing 2 and the rotor axis 6 arranged coaxially to it can be clearly seen. In the exemplary embodiment shown here, the central bearing 2 is fastened to the bearing plate 1 via six retaining webs 7, each of which extends in the radial direction RR.

[0021] Again Figure 3 As can be seen, the disk-shaped Hall plate 3 is precisely positioned in the radial direction RR by the O-ring 5, which can be seen partially through the Hall plate 3. This is in the sense of functional integration at the same time as the already described with reference to Figure 2 mentioned exact positioning of the Hall board 5 in the axial direction AR by the clamping effect of the elastic O-ring 5. List of reference symbols

[0022] 1End shield 2Central bearing 3Hall board 4Hall sensor 5O-ring 6Rotor axis 7Radial retaining web 8Support collar 8Contact surface 9Recess 10Brushless electric motor 100Electric hand tool ADOuter diameter ARAxial direction IDInner diameter NFace normal RBRotor-facing side RRRadial direction RSRotor-facing side WAngle

Claims

1. Brushless electric motor (10) for an electric handheld power tool (100), wherein the electric motor (10) has an end plate (1) and a Hall board (3) which is arranged on the end plate (1), wherein the Hall board (3) is axially fixed to the end plate (1) by means of an elastic O-ring (5), and wherein the end plate (1) has a central bearing (2) for receiving a rotor axis (6), characterized in that at least one radially outwardly projecting supporting collar (8), against which the O-ring (5) is supported, is formed on the central bearing (2).

2. Electric motor (10) according to Claim 1, characterized in that the Hall board (3) is axially fixed to the end plate (1) exclusively by means of the O-ring (5).

3. Electric motor (10) according to Claim 1, characterized in that the central bearing (2) is fastened to the end plate (1) by means of at least one radial retaining web (7).

4. Electric motor (10) according to Claim 3, characterized in that the Hall board (3) is supported against the at least one radial retaining web (7) in the axial direction (AR).

5. Electric motor (10) according to Claim 1, characterized in that the supporting collar (8) has a contact area (8') for the O-ring (5), which contact area is oriented obliquely in relation to the rotor axis (6).

6. Electric motor (10) according to Claim 5, characterized in that an angle (W) which is enclosed between the rotor axis (6) and the surface normal (N) of the contact area (8') is less than 90 degrees, preferably between 40 and 60 degrees.

7. Electric motor (10) according to one of the preceding claims, characterized in that the Hall board (3) is designed, in the form of a disc, with a concentric hollow-cylindrical recess (9).

8. Electric motor (10) according to Claim 7, characterized in that an inside diameter (ID) of the recess (9) is greater than an outside diameter (AD) of the central bearing (2) including the at least one supporting collar (8).

9. Electric motor (10) according to one of the preceding claims, characterized in that the Hall board (3) and the O-ring (5) are located on a side of the end plate (1) that is averted from the rotor.

10. Electric handheld power tool (100) comprising an electric motor (10) according to one of the preceding claims.