1. A bearing unit comprising:
a cylindrical oil-impregnated bearing, in which a bearing bore to support a turning shaft is formed so as to enable the turning shaft to turn;
a bearing holder, in which the oil-impregnated bearing is fixed by an inner bore;
a first groove being formed in an axial direction on an inner circumferential surface of the oil-impregnated bearing;
a second groove being formed in an axial direction on at least one of an outer circumferential surface of the oil-impregnated bearing and an inner circumferential surface of the bearing holder;
said second groove being formed so as to have a greater depth than that of the first groove; and
said second groove being formed so as to have a larger cross section than that of the first groove;
wherein the first groove and the second groove are each formed in plural numbers;
wherein a total cross section of the second grooves is greater than a total cross section of the first grooves; and
wherein a part of the plurality of second grooves is formed so as to be shallower in the depth direction than the other second grooves.
2. The bearing unit according to claim 1;
wherein the first groove and the second groove are laid out in such a manner that the first groove and the second groove are not oriented in the same radial direction.
3. The bearing unit according to claim 1;
wherein the first groove is a stepped groove being protruded in a radial direction with a stepped shape.
4. A bearing unit comprising:
a cylindrical oil-impregnated bearing, in which a bearing bore to support a turning shaft is formed so as to enable the turning shaft to turn;
a bearing holder, in which the oil-impregnated bearing is fixed by an inner bore;
a first groove being formed in an axial direction on an inner circumferential surface of the oil-impregnated bearing;
a second groove being formed in an axial direction on at least one of an outer circumferential surface of the oil-impregnated bearing and an inner circumferential surface of the bearing holder;
said second groove being formed so as to have a greater depth than that of the first groove; and
said second groove being formed so as to have a larger cross section than that of the first groove;
wherein the first groove and the second groove are each formed in plural numbers;
wherein a total cross section of the second grooves is greater than a total cross section of the first grooves; and
wherein a part of the plurality of second grooves is formed so as to have a rougher porous structure than the other second grooves.
5. The bearing unit according to claim 4;
wherein the first groove and the second groove are laid out in such a manner that the first groove and the second groove are not oriented in the same radial direction.
6. The bearing unit according to claim 4;
wherein the first groove is a stepped groove being protruded in a radial direction with a stepped shape.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A compound of formula 2f,
wherein R2 and R3 are each independently hydrogen or a protecting group and R4 is hydrogen or a an optionally substituted alkyl, cycloalkyl, aryl, heterocycloalkyl or heteroaryl group.
2. A compound of formula 3
3. A compound of formula S-3
4. A compound of formula R-3