Hydraulic braking device and valve timing adjusting apparatus

A hydraulic braking device comprising:

• a housing having a fluid chamber;
• functional fluid filled in the fluid chamber and made of base fluid into which magnetic particles are dispersed, so that viscosity of the functional fluid is changed depending on density of magnetic flux passing through the functional fluid;
• a viscosity controlling unit for controlling the density of the magnetic flux passing through the functional fluid in order to change the viscosity of the functional fluid;
• a brake rotating member having a brake shaft passing through an inside of the housing in its axial direction and outwardly extending from the housing, the brake rotating member being in contact with the functional fluid in the fluid chamber so that braking torque depending on the viscosity of the functional fluid is applied to the brake rotating member;
• and
• a sealing structure for fluid-tightly sealing a gap between the housing and the brake rotating member,
• wherein the sealing structure comprises;
• a particle sealing member for forming a sealing gap, which is communicated to the fluid chamber, between the particle sealing member and the brake shaft, wherein the particle sealing member seals the sealing gap so as to restrict movement of the magnetic particles in an axial direction from a housing-inner side to a housing-outer side;
• a fluid sealing member provided in the housing at the housing-outer side more remote from the particle sealing member in the axial direction and being in contact with the brake shaft so as to fluid-tightly seal a gap between the housing and the brake shaft;
• an intermediate fluid chamber formed in the housing between the sealing gap and the fluid sealing member in the axial direction;
• and
• an intermediate fluid made of liquid and filled in the intermediate fluid chamber.

A hydraulic braking device comprising:

• a housing having a fluid chamber;
• magnetic viscous fluid filled in the fluid chamber and made of non-magnetic base fluid into which magnetic particles are dispersed, so that viscosity of the magnetic viscous fluid is changed depending on density of magnetic flux passing through the magnetic viscous fluid;
• a viscosity controlling unit for controlling the density of the magnetic flux passing through the magnetic viscous fluid in order to change the viscosity of the magnetic viscous fluid;
• a brake rotating member having a brake shaft passing through an inside of the housing in its axial direction and outwardly extending from the housing, the brake rotating member being in contact with the magnetic viscous fluid in the fluid chamber so that braking torque depending on the viscosity of the magnetic viscous fluid is applied to the brake rotating member;
• and
• a magnetic sealing sleeve unit provided in the housing so as to surround an outer periphery of the brake shaft,
• wherein the magnetic sealing sleeve unit comprises;
• a magnetic-flux generating member for generating magnetic flux to be guided to the brake shaft,
• a magnetic-flux guiding member provided at, at least, one of axial ends of a housing-inner side and a housing-outer side of the magnetic-flux generating member, the magnetic-flux guiding member having an inner peripheral portion for forming a sealing gap between the inner peripheral portion and the brake shaft, so that the magnetic flux of the magnetic-flux generating member is guided from the magnetic-flux guiding member to the brake shaft via the sealing gap, or vice versa;
• and
• a magnetic shielding member of a sleeve-unit side having an axial end surface, which is in contact with an axial end surface of the inner peripheral portion on a housing-inner side of the magnetic-flux guiding member, for restricting passing of the magnetic flux of the magnetic-flux generating member in the axial direction to the housing-inner side of the magnetic-flux guiding member,
• wherein the magnetic shielding member forms a communication gap between the magnetic shielding member and the brake shaft so that the fluid chamber is communicated to the sealing gap via the communication gap, and
• wherein a gap width of the communication gap is made to be equal to or smaller than a gap width of the sealing gap.

A hydraulic braking device comprising:

• a housing having a fluid chamber;
• magnetic viscous fluid filled in the fluid chamber and made of non-magnetic fluid into which magnetic particles are dispersed, so that viscosity of the magnetic viscous fluid is changed depending on density of magnetic flux passing through the magnetic viscous fluid;
• a viscosity controlling unit for controlling the density of the magnetic flux passing through the magnetic viscous fluid in order to change the viscosity of the magnetic viscous fluid;
• a brake rotating member rotatably accommodated in the fluid chamber, the braking rotating member being in contact with the magnetic viscous fluid in the fluid chamber so that braking torque depending on the viscosity of the magnetic viscous fluid is applied to the brake rotating member, the brake rotating member having a brake shaft outwardly extending from the housing;
• and
• a magnetic sealing structure for fluid-tightly sealing a gap between the housing and the brake rotating member,
• wherein the magnetic sealing structure comprises;
• a magnetic-flux generating member provided in the housing for generating magnetic flux;
• a magnetic screw portion formed in the brake shaft formed in a male screw shape having a spiral projection, which is projected in a radial outward direction and spirally comes away from a housing-inner side of the brake shaft toward a housing-outer side of the brake shaft when tracing the spiral projection in a shaft rotating direction;
• a magnetic-flux guiding portion provided in the housing so as to surround an outer periphery of the brake shaft to thereby form a sealing gap portion in a radial direction between the magnetic screw portion and the magnetic-flux guiding portion, the sealing gap portion being communicated to the fluid chamber, and the magnetic-flux guiding portion guiding the magnetic flux generated by the magnetic-flux generating member to the magnetic screw portion via the sealing gap portion;
• a fluid sealing member provided in the housing so as to be in contact with the outer periphery of the brake shaft for fluid-tightly sealing a gap between the brake shaft and the housing;
• and
• a magnetic-flux restricting portion provided in the housing between the magnetic-flux guiding portion and the fluid sealing member in the axial direction so as to surround the outer periphery of the magnetic screw portion, the magnetic-flux restricting portion forming a fluid pooling gap portion in the radial direction between the magnetic screw portion and the magnetic-flux restricting portion, the fluid pooling gap portion being communicated to the sealing gap portion,
• wherein a radial distance of the fluid pooling gap portion is set to be such a value that Reynolds number of the non-magnetic fluid passing through the fluid pooling gap portion becomes smaller than a critical Reynolds number.