Patent Application
20150143991
The present invention relates generally to vehicle master cylinders (e.g., for hydraulic clutches or brakes) and more specifically to the interface between a piston and a rod in a master cylinder assembly.
Vehicles commonly use hydraulics to actuate certain vehicul components, such as clutches and brakes. In such hydraulic arrangements, a master cylinder is commonly used to pressurize the hydraulic fluid and thereby transmit force to a remote location.
Master cylinders typically include a main housing that defines a cylinder that retains fluid. A hydraulic piston is positioned in the cylinder and can reciprocate relative to the housing to force hydraulic fluid out of the housing. A spring is commonly used to bias the piston toward one end of the cylinder. A hydraulic rod includes an inner end that engages the piston and an outer end positioned outside the housing to facilitate movement of the piston from an external source. An actuator (e.g., a hand lever or foot pedal) can be used to provide the external force on the rod. With this arrangement, pressing on the actuator will provide movement to the rod and the piston, to thereby displace hydraulic fluid in the system.
The present invention provides a hydraulic brake assembly comprising a fluid conduit containing hydraulic fluid, a cylinder having a port fluidly connected to the conduit, and a piston positioned in the cylinder. The piston includes a recess having a depth that is at least 30% (preferably at least 50%) of a length of the piston. The assembly further includes a rod having an inner end positioned in the recess and an outer end outside the recess, and an actuator (e.g., a hand or foot lever) coupled to the outer end of the rod. If desired, the assembly can further include a reservoir fluidly coupled to the cylinder.
In one embodiment, the piston moves relative to the cylinder along an axis, and the piston further includes a primary piston seal and a secondary piston seal separated by a seal spacing. In this embodiment, the rod can axially overlap the secondary piston seal. For example, the inner end of the rod can be positioned axially between the primary piston seal and the secondary piston seal, and is preferably axially closer to the primary seal than to the secondary seal. In addition, the depth of the recess can be at least 70% (preferably at least 85% and more preferably at least 100%) of the seal spacing.
Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.
Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.
Referring to
The master cylinder assembly 12 further includes a piston assembly 32 positioned in the cylinder housing 22 and adapted to reciprocate relative to the cylinder housing 22 along a piston axis 34. A piston return spring biases the piston toward the actuator. The piston assembly includes a piston body 36 and primary and secondary piston seals 38, 40 between the piston body 36 and the cylinder housing 22. The piston body 36 includes a deep recess 42 extending axially into an outer end of the piston body 36. The illustrated piston assembly 32 has an overall length L of 47.1 millimeters, and the illustrated recess 42 has a depth D1 of 25.3 millimeters. The primary and secondary piston seals 38,40 are spaced by a distance D2 of 21.5 millimeters. As shown in
In light of the above arrangement, it can be seen that the depth D1 of the recess 42 is greater than the distance D2 between the piston seals 38,40. In addition, it can be seen that the depth D1 of the recess 42 is greater than 50% of the overall length L of the piston body 36.
The master cylinder assembly 12 further includes a rod 50 positioned between the brake lever 30 and the piston body 36. An outer end 52 of the rod 50 engages the brake lever 30, and an inner end 54 of the rod 50 engages the bottom surface 46 of the recess 42 in the piston body 36. With this arrangement, it can be seen that the rod 50 axially overlaps (i.e., extends from one side to the other in the axial extent) the secondary piston seal 40. In other words, the secondary piston seal 40 defines a plane that is generally perpendicular to the piston axis 34, and one portion of the rod 50 is on one side of the plane and another portion of the rod 50 is on the other side of the plane. In addition, by virtue of the illustrated arrangement, the inner end 54 of the rod 50 is positioned axially between the primary and secondary piston seals 38,40, and is axially closer to the primary seal than to the secondary seal. That is, the primary and secondary seals 38,40 each define a plane substantially parallel to the piston axis 34, and the inner end 54 of the rod 50 is positioned between those two planes and is closer to the plane defined by the primary seal 38.
While the illustrated embodiment discloses an ATV, it should be understood that the features of the present invention can also be applied to other vehicles, such as motorcycles, bicycles, and snowmobiles.
