Electric handheld power tool

Abstract

A brushless DC motor having a stator, an output-side end shield which is formed in one piece and consists of plastic, a rotor which is equipped with a rotor shaft, and having a rotor bearing in which, on the one side, the rotor shaft is accommodated and which, on the other side, is supported in the output-side end shield, the output-side end shield being pressed onto an outer circumference of the stator.

Description

[0001] Electric hand tool

[0002] The present invention relates to a brushless direct current motor (BLDC motor) comprising a stator, a one-piece output-side bearing plate made of plastic, a rotor equipped with a rotor shaft, and a rotor bearing that accommodates the rotor shaft on one side and is supported by the output-side bearing plate on the other. Such BLDC motors are generally known from the prior art and are used, for example, in power tools.

[0003] DE 19542021 02 discloses a plastic bearing plate with an annular recess for receiving a winding head of an electric motor, wherein the recess for encapsulating the winding head is delimited radially inwards by an annular surface formed on the inside of the bearing plate, which extends slightly conically axially inwards on the circumferential side facing the winding head and is designed as a press fit.

[0004] EP 1 722 459 B1 describes an electrical machine with a stator, an insulating end plate positioned on the end face of the stator, a rotor having a rotor shaft, and a bearing for the rotor, wherein the bearing is supported on a bearing block which in turn rests axially on the end face of the stator or on the insulating end plate, wherein the inner wall of the insulating end plate is provided with a snap hook which effects additional axial fixing of the bearing block.

[0005] It is therefore an object of the present invention to provide a brushless DC motor which has a simple structure, which structure promotes the formation of a uniform annular gap.

[0006] The task is solved by pressing the output-side bearing shield onto an outer circumference of the stator.

[0007] In a particularly preferred embodiment, the brushless DC motor has a winding support arranged on the end face of the stator. It has proven advantageous if the winding support has a snap hook that engages with the bearing plate. In a further preferred embodiment, the snap hook has a nose pointing outwards in the radial direction. It has proven advantageous if the output-side bearing plate has a spring bar. In a particularly preferred embodiment, the spring bar extends outwards in the radial direction. It has proven advantageous if the spring bar is elastically deflectable in the axial direction.

[0008] It has also proven advantageous if the spring bar secures the snap hook against loosening.

[0009] In a further preferred embodiment, the winding support arranged on the front side of the stator is formed in one piece. It has proven advantageous if the winding support is different from the output-side bearing plate. In a particularly preferred embodiment, the winding support is completely accommodated in a volume spanned by the output-side bearing plate. In a further preferred embodiment, the snap hook is spaced apart from the rotor bearing, in particular completely. It has proven advantageous if the output-side bearing plate is pressed exclusively onto the outer circumference of the stator.

[0010] Alternatively or additionally, the output-side bearing shield can be pressed directly onto the outer circumference of the stator.

[0011] In a particularly preferred embodiment, the output-side bearing plate is an injection-molded part. It has proven advantageous if the output-side bearing plate is free of screw connections. In a further preferred embodiment, the winding support has a plurality of snap hooks, preferably six snap hooks. The bearing plate can have a plurality of spring bars, preferably six spring bars.

[0012] The task is also solved by an electric hand tool with a brushless DC motor as described above.

[0013] Further advantages will become apparent from the following description of the figures. A particularly preferred embodiment of the present invention is 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.

[0014] In the figures, identical and similar components are numbered with the same reference numerals. They show:

[0015] Figure 1 shows a preferred embodiment of a BLDC motor in a sectional view;

[0016] Figure 2 shows the embodiment of Figure 1 in perspective view; and

[0017] Figure 3 shows the bearing plate of Figures 1 and 2 in a sectional view.

[0018] Implementation example:

[0019] Figure 1 shows a preferred embodiment of a brushless DC motor 10 in a sectional view. The brushless DC motor 10 is part of a handheld power tool (not shown here).

[0020] The brushless DC motor 10 is equipped with a stator 1 and an output-side bearing plate 2 (A-end bearing plate). The output-side bearing plate is a single-piece design made of plastic. The output-side bearing plate 2 is provided as an injection-molded part. The simplicity and flexibility of the plastic allows for tight tolerances to be maintained, ensuring a uniform annular gap 11.

[0021] The brushless DC motor 10 further comprises a rotor 4 equipped with a rotor shaft 3 and a rotor bearing 5. This rotor bearing 5, provided as a ball bearing for example, accommodates the rotor shaft 3 on the one hand. The rotor bearing 5 is also supported in the output-side bearing plate 2. The rotor bearing 5 is supported in the bearing plate 2 via a bearing support ring 2' formed in the bearing plate 2.

[0022] As can be seen from Figure 1, the output-side bearing plate 2 is pressed onto an outer circumference AU of the stator 1. The output-side bearing plate 2 is pressed exclusively and directly onto the outer circumference AU of the stator 1. The pressing allows for a smaller installation space for the brushless DC motor 10 and increases reliability during assembly.

[0023] The brushless DC motor 10 also has a winding support 6 arranged on the front side of the stator 1. The winding support 6 arranged on the front side of the stator 2 is formed in one piece and is a separate component from the output-side bearing plate 2. The winding support 6 is completely accommodated in a volume VL defined by the output-side bearing plate 2 (see Figure 3).

[0024] The winding support 6 is equipped with a snap hook 7 that engages with the bearing plate 2. For this purpose, the snap hook 7 has a lug 8 directed outward in the radial direction RR. The output-side bearing plate 2, in turn, has a spring bar 9 that extends outward in the radial direction RR and is elastically deflectable in the axial direction AR.

[0025] As can be seen from Figure 1, the spring bar 9 secures the snap hook 7 against loosening. This makes a non-destructive release of the connection between the output-side bearing plate 2 and the winding support 6 practically impossible. The output-side bearing plate 2 is free of screw connections. Figure 2 shows the embodiment of Figure 1 in a perspective view. In Figure 2 it is clearly visible that the output-side bearing plate 2 has a total of six spring bars 9. The spring bars 9 are arranged at equal distances from one another along a circumference UL of the output-side bearing plate 2. The winding support 6 - which is completely enclosed by the bearing plate 2 in both the axial direction AR and the radial direction RR - in turn has six snap hooks 7, each of which engages with the bearing plate 2. Locking in the bearing plate 2 is achieved by a respective lug 8 of the snap hook 7.

[0026] All snap hooks 7 are spaced apart from the rotor bearing 9 in the radial direction RR.

[0027] Finally, Figure 3 shows a sectional view of the output-side bearing plate shown in Figures 1 and 2. The output-side bearing plate 2 occupies a volume VL in which the winding support (not shown here) is completely accommodated. A recess 9' formed in the bearing plate 2 and surrounding the spring web 9 is part of the volume VL occupies by the output-side bearing plate 2.

[0028] Each spring bar 9 extends outward in the radial direction RR from the bearing support ring 2' formed centrally in the bearing plate 2. The spring bars 9 are elastically deflectable in the axial direction AR in the sense of a flexible mechanism. This allows the spring bars 9 to yield in the axial direction AR during the joining of the bearing plate 2 and the winding support 6 (shown in dashed lines). As soon as the bearing plate 2 and the winding support 6 are joined and the snap hooks 7 or their lugs 8 are engaged with the bearing plate (see Figure 1), the spring bars 9 are in a non-deflected position and secure the snap hooks 7 against loosening.

[0029] List of reference symbols

[0030] 1 stator

[0031] 2 bearing shield

[0032] 2' bearing support ring

[0033] 3 Rotor shaft

[0034] 4 Rotor

[0035] 5 rotor bearings

[0036] 6 Changing support

[0037] 7 snap hooks

[0038] 8 Nose of the snap hook

[0039] 9 spring bar

[0040] 9' recess

[0041] 10 Brushless DC motor

[0042] 11 Annular gap

[0043] AR Axial direction

[0044] AU Outer circumference of the stator

[0045] RR Radial Direction

[0046] UL circumference of the bearing shield

[0047] VL volume bearing shield

Claims

Patent claims 1. Brushless DC motor (10) with a stator (1), an output-side bearing plate (2) which is formed in one piece and consists of plastic, a rotor (4) equipped with a rotor shaft (3), and with a rotor bearing (5) in which the rotor shaft (3) is received on the one hand and which is supported in the output-side bearing plate (2) on the other hand, characterized in that the output-side bearing plate (2) is pressed onto an outer circumference (AU) of the stator (1).

2. Brushless DC motor (10) according to claim 1, characterized in that the brushless DC motor (10) has a winding support (6) arranged on the end face of the stator (1), wherein the winding support (6) has a snap hook (7) which engages with the bearing plate (2).

3. Brushless DC motor (10) according to claim 2, characterized in that the snap hook (7) has a nose (8) directed outwards in the radial direction (RR).

4. Brushless DC motor (10) according to 3, characterized in that the output-side bearing plate (2) has a spring web (9) which extends outwards in the radial direction (RR) and is elastically deflectable in the axial direction (AR).

5. Brushless DC motor (10) according to 4, characterized in that the spring bar (9) secures the snap hook (7) against loosening.

6. Brushless DC motor (10) according to one of claims 2 to 5, characterized in that the winding support (6) arranged on the end face of the stator is formed in one piece and is different from the output-side bearing plate (2).

7. Brushless DC motor (10) according to one of claims 2 to 6, characterized in that the winding support (6) is completely accommodated in a volume (VL) spanned by the output-side bearing plate (2).

8. Brushless DC motor (10) according to one of claims 2 to 7, characterized in that the snap hook (7) is spaced from the rotor bearing (9).

9. Brushless DC motor (10) according to one of the preceding claims, characterized in that the output-side bearing plate (2) is pressed exclusively and / or directly onto the outer circumference (AU) of the stator (1).

10. Brushless DC motor (10) according to one of the preceding claims, characterized in that the output-side bearing plate (2) is an injection-molded part.

11. Brushless DC motor (10) according to one of the preceding claims, characterized in that the output-side bearing plate (2) is free of screw connections.

12. Electric hand-held power tool with a brushless DC motor (10) according to one of the preceding claims.

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