EC motor for an electric hand tool and method for producing a rotor for an EC motor

Patent metadata

Field	Value
Publication number	US-11374473-B2
Application number	US-201916674802-A
Country	US
Kind code	B2
Filing date	Nov 5, 2019
Priority date	Nov 5, 2018
Publication date	Jun 28, 2022
Grant date	Jun 28, 2022

Abstract

An EC motor for an electric hand tool having a stator in which a rotor is rotatably mounted, which comprises a rotor lamination stack, which has a passage opening and is formed of individual laminations, and a rotor shaft which is cast in the passage opening of the rotor lamination stack by means of a casting compound, and having a plurality of permanent magnets, which are received in the pockets formed in the rotor lamination stack. An annular channel, which is connected to the pockets in a fluid-conducting manner via radial channels, each of which is formed of a plurality of channel sections formed in adjacent laminations of the rotor lamination stack, is formed between the rotor shaft and the wall of the passage opening for supplying the casting compound from the annular channel to the pockets. A method is also provided for producing a rotor for an EC motor.

First claim

What is claimed is:

1. An electronically commutated (EC) motor for an electric hand tool, the EC motor comprising:
a rotor;
a stator in which the rotor is rotatably mounted;
a rotor lamination stack that has a passage opening and is formed of individual laminations; and
a rotor shaft that is cast in the passage opening of the rotor lamination stack via a casting compound;
a plurality of permanent magnets adapted to be received in pockets formed in the rotor lamination stack; and
an annular channel connected to the pockets in a fluid-conducting manner via at least two radial channels, each of the at least two radial channels being formed of at least two channel sections formed in adjacent laminations of the rotor lamination stack, the annular channel being formed between the rotor shaft and a wall of the passage opening for supplying the casting compound from the annular channel to the pockets,
wherein between 70% and 98% or between 80% and 95% the laminations of the rotor lamination stack have pocket sections that are connected to the passage opening in a fluid-conducting manner via the channel sections and a remainder of the laminations of the rotor lamination stack do not have channel sections such that the pocket sections are spatially separated from the passage opening, and
wherein the channel sections each extend from the passage opening to the pocket sections, such that a first end of each of the channel sections opens directly into the passage opening and an opposing second end of each of the channel sections opens directly into a respective one of the pocket sections.

2. The EC motor according to claim 1 , wherein the radial channel is connected in a fluid-conducting manner to at least one axial channel formed in the pockets.

3. The EC motor according to claim 2 , wherein at least the axial channel and the radial channel are provided in each case multiple times per pocket.

4. The EC motor according to claim 1 , wherein a ratio between a width of the radial channel and an axial length (L) of the annular channel as a function of a number (n) of the radial channels per pocket is between 70%×L/n and 98%×L/n, or between 80%×L/n and 95%×L/n.

5. The EC motor according to claim 1 , wherein the opening of the radial channel into the pocket is located in a center of the pocket.

6. The EC motor according to claim 1 , wherein a width of the pocket cross section is between 1% and 10% or between 2% and 5% greater than a thickness of the permanent magnets received in the pockets.

7. The EC motor according to claim 2 , wherein the at least one axial channel is formed on at least one side of the pocket.

8. The EC motor according to claim 1 , wherein the casting compound is formed of a thermosetting plastic.

9. The EC motor according to claim 1 , wherein a balance ring is disposed on at least one end face of the rotor lamination stack.

10. A method for producing a rotor for an electronically commutated (EC) motor, the method comprising:
providing a rotor shaft;
providing a rotor lamination stack having a passage opening with pockets for receiving permanent magnets, wherein between 70% and 98% or between 80% and 95% of laminations of the rotor lamination stack have pocket sections that are connected to the passage opening in a fluid-conducting manner via channel sections and a remainder of the laminations of the rotor lamination stack do not have channel sections such that the pocket sections are spatially separated from the passage opening;
inserting the permanent magnets in the pockets of the rotor lamination stack;
inserting the rotor shaft and the rotor lamination stack centered relative to one another in a casting mold such that an annular channel is formed between the rotor shaft, received in the passage opening, and the rotor lamination stack;
closing the mold;
supplying a casting compound under pressure via a sprue channel substantially exclusively in a front opening of the annular channel between the rotor shaft and the rotor lamination stack through radial channels formed in the rotor lamination stack into the pockets with the permanent magnets received therein;
curing the casting compound; and
removing the rotor from the mold,
wherein the channel sections each extend from the passage opening to the pocket sections, such that a first end of each of the channel sections opens directly into the passage opening and an opposing second end of each of the channel sections opens directly into a respective one of the pocket sections.

11. The EC motor according to claim 1 , wherein one of the laminations of the rotor lamination stack that do not have channel sections is provided in a middle of the rotor lamination stack.

12. The method according to claim 10 , wherein one of the laminations of the rotor lamination stack that do not have channel sections is provided in a middle of the rotor lamination stack.

Assignees

• Fein C & E Gmbh

Inventors

• Maier Christoph
• Adamczyk Martin
• Burkhardt Thomas

Classifications

• H02K7/04

  Balancing means · CPC title

• H02K15/03 Primary

  having permanent magnets · CPC title

• H02K2201/09

  Magnetic cores comprising laminations characterised by being fastened by caulking · CPC title

• H02K1/28

  Means for mounting or fastening rotating magnetic parts on to, or to, the rotor structures · CPC title

• H02K2213/03

  Machines characterised by numerical values, ranges, mathematical expressions or similar information · CPC title