Magnetic encoder and bearing
A magnet portion 27 of a magnetic encoder 26 includes a magnetic member and a resin, and a highly reliable magnetic encoder 26 having a high magnetic property and enabling to detect a rotational number with high accuracy, and a hub unit bearing 2 a are provided. Further, the resin is preferably a thermoplastic resin and further preferably includes a thermoplastic resin including a soft segment in a molecule. Further, the magnetic encoder 26 further includes a fixed member 25 attached with the magnet portion 27 and comprising a magnetic material, and the magnet portion 27 and the fixed member 25 are bonded by an adhering agent including at least one of a phenolic resin based and an epoxy resin based.
1. A bearing for a wheel comprising:
a fixed ring,
a rotating ring,
a plurality of rolling members rollably arranged in a circumferential direction between the fixed ring and the rotating ring, and
a magnetic encoder, wherein:
the magnetic encoder comprises a magnet portion substantially in a circular ring shape magnetized in multipoles in a circumferential direction and a fixed member,
the magnet portion is bonded to the fixed member and includes a magnetic member and a thermoplastic resin,
the magnet portion and the fixed member are bonded by at least one of a phenolic resin based adhering agent and an epoxy resin based adhering agent, and
the adhering agent is baked to the fixed member in a semicured state and further cured in a process of forming the magnet portion by insert molding.
2. The bearing according to claim 1 , wherein the thermoplastic resin is polyamide based resin or polyphenylene sulfide (PPS).
3. The bearing according to claim 2 , wherein the thermoplastic resin is polyamide 6, polyamide 12, polyamide 612 or polyamide 11.
4. The bearing according to claim 3 , wherein the thermoplastic resin contains a silane coupling agent or an oxidization preventing agent.
5. The bearing according to claim 2 , wherein the thermoplastic resin is polyamide 12, polyamide 612, polyamide 11 or polyphenylene sulfide (PPS).
6. The bearing according to claim 1 , wherein a flexural deflection at 23° C. of the magnet portion (thickness t =3.0 mm, ASTM D790; span distance of 50 mm) is within a range of 2 to 10 mm.
7. The bearing according to claim 6 , wherein the thermoplastic resin includes a thermoplastic resin at least having a soft segment in a molecule.
8. The bearing according to claim 6 , wherein a plasticizer is included by about 0.1 through 4 weight % in total weight.
9. The bearing according to claim 1 , wherein
the magnet portion includes at least ferrite as the magnetic member, and
the magnetic member includes 60 through 80 volume % of a magnet portion.
10. The bearing according to claim 9 , wherein the magnetic member of the magnet portion is an anisotropic magnet which is orientated by a magnetic field.
11. The bearing according to claim 9 , wherein the magnetic property of the magnet portion is in a range of 1.3 through 15 MGOe as a maximum energy product (BHmax).
12. The bearing according to claim 11 , wherein the magnetic property of the magnet portion is in a range of 1.63 through 2.38 MGOe as a maximum energy product (BHmax).
13. The bearing according to claim 12 , wherein a flexural deflection at 23° C. of the magnet portion (thickness t =3.0 mm, ASTM D790; span distance of 50 mm) is n a range of 2 through 10 mm.
14. The bearing according to claim 9 , wherein
a number of poles of the magnet portion is about 70 through 130 poles, and
a single pitch error is equal to or smaller than ±2 %.
15. The bearing according to claim 1 , wherein the magnet portion and the fixed member are bonded by said phenolic resin based adhering agent.
16. The bearing according to claim 1 , wherein the magnet portion and the fixed member are bonded by said epoxy resin based adhering agent.
17. The bearing according to claim 1 , wherein the bonding surface of the fixed member has recesses and projections having 0.2 through 2.0 μm by an arithmetic mean height Ra and about 1.5 through 10 pm by a maximum height Rz.
18. The bearing according to claim 1 , wherein the magnet portion pinches a flange portion of the fixed, member so that the magnet portion and the fixed member are mechanically bonded.
19. The bearing according to claim 18 , wherein the bonding surface of the fixed member has recesses and projections having 0.2 through 2.0 μm by an arithmetic mean height Ra and about 1.5 through 10 μm by a maximum height Rz.
20. The bearing according to claim 18 , wherein said phenolic resin based adhering agent or said epoxy resin based adhering agent are used together.
21. The bearing according to claim 1 , wherein
a notched portion is provided on an outer circumference of a flange portion of the fixed member, and
the magnet portion and the fixed member are mechanically bonded by the notched portion.
22. The bearing according to claim 21 , wherein the bonding surface of the fixed member has recesses and projections having 0.2 through 2.0 μm by an arithmetic mean height Ra and about 1.5 through 10 μm by a maximum height Rz.
23. The bearing according to claim 21 , wherein said phenolic resin based adhering agent or said epoxy resin based adhering agent are used together.
24. The bearing according to claim 1 , wherein the fixed member includes a plurality of members, and is mechanically bonded to the magnet portion.