Torque converter using magnetic viscous fluid as working fluid

1. A torque converter for performing torque transmission by circulating a working fluid between a pump impeller and a turbine runner, characterized in that:

the working fluid is a magnetic viscous fluid;

in a torque converter housing, outside a circulation path of the working fluid, a yoke member connected to the pump impeller and provided with a coil and a magnetic member connected to the turbine runner are concentrically arranged with a predetermined space kept therebetween; and

a magnetic circuit is established between the yoke member and the magnetic member upon energization of the coil.

2. A torque converter as claimed in claim 1 , in which the yoke member and the magnetic member are concentrically arranged in such a manner that a plurality of the spaces are formed between the yoke member and the magnetic member.

3. A torque converter as claimed in claim 2 , in which the yoke member and the magnetic member are each provided with a member with a small magnetic permeability in order to prevent a flow of a magnetic flux along the respective cylindrical surfaces.

4. A torque converter as claimed in claim 1 , in which mutually opposed portions of the yoke member and the magnetic member are arranged outside in the radial direction from the circulation path, and in which the yoke member and the magnetic member are opposed to each other in the radial direction.

5. A torque converter comprising:

a converter housing adapted to be connected to a power source to be driven;

a pump impeller constituting part of the converter housing, the pump impeller having an annular yoke member that constitutes a cylindrical outer body portion of the converter housing;

a turbine runner rotatably installed in the converter housing and adapted to be connected to a transmission device, the turbine runner being arranged to face the pump impeller;

a magnetic viscous fluid filled in the converter housing and serving as a working fluid, the magnetic viscous fluid being circulated between the pump impeller and the turbine runner for performing torque transmission therebetween; and

a magnetic force applying mechanism for changing a viscosity of the magnetic viscous fluid by applying the fluid with a magnetic force, the magnetic force applying mechanism being installed in the converter housing at a position outside a circulation path of the magnetic viscous fluid, the magnetic force applying mechanism comprising:

a coil concentrically held by the annular yoke member; and

an annular plate unit of magnetic material concentrically installed inside the coil and connected to the turbine runner through a disc member,

wherein upon energization of the coil, there is produced a magnetic circuit between the annular yoke member and the annular plate unit.

6. A torque converter as claimed in claim 5 , in which the magnetic force applying mechanism further comprises a cylindrical plate of magnetic material that is connected to the converter housing and concentrically installed inside the coil in the vicinity of the annular plate unit.

7. A torque converter as claimed in claim 6 , in which the annular plate unit is shaped to have an annular recess into which the cylindrical plate is received while being spaced from an inner surface of the annular recess.

8. A torque converter as claimed in claim 7 , in which the annular recess of the annular plate unit is defined by a second cylindrical plate portion, a third cylindrical plate portion and an annular connecting ridge portion through which the second and third cylindrical plate portions are connected.

9. A torque converter as claimed in claim 6 , in which the annular plate unit and the cylindrical plate of the magnetic force applying mechanism have given portions that are low in magnetic permeability.

10. A torque converter as claimed in claim 5 , in which the annular plate unit of the magnetic force applying mechanism has given portions that are low in magnetic permeability.

11. A torque converter as claimed in claim 5 , in which the annular yoke member is formed with a coil accommodating groove for tightly receiving the coil.

12. A torque converter as claimed in claim 11 , in which the coil accommodating groove has a generally triangular cross section sharpened in two stages toward the center of the torque converter.

13. A torque converter as claimed in claim 12 , in which the annular plate unit of the magnetic force applying mechanism has, at a portion facing the sharpened end of the coil accommodating groove, a part that is low in magnetic permeability.