Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
  • B60T11/00—Transmitting braking action from initiating means to ultimate brake actuator without power assistance or drive or where such assistance or drive is irrelevant
  • B60T11/10—Transmitting braking action from initiating means to ultimate brake actuator without power assistance or drive or where such assistance or drive is irrelevant transmitting by fluid means, e.g. hydraulic
  • B60T11/16—Master control, e.g. master cylinders
  • B60T11/236—Piston sealing arrangements
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B7/00—Systems in which the movement produced is definitely related to the output of a volumetric pump; Telemotors
  • F15B7/06—Details
  • F15B7/08—Input units; Master units
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16J—PISTONS; CYLINDERS; SEALINGS
  • F16J1/00—Pistons; Trunk pistons; Plungers
  • F16J1/001—One-piece pistons
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16J—PISTONS; CYLINDERS; SEALINGS
  • F16J1/00—Pistons; Trunk pistons; Plungers
  • F16J1/02—Bearing surfaces

Definitions

• the present invention relates generally to hydraulic brake systems and specifically to pistons of master cylinders for such systems.
• Hydraulic brake systems are commonly used on vehicles (e.g., automobiles, snowmobiles, ATVs, motorcycles) to provide a braking function.
• vehicles e.g., automobiles, snowmobiles, ATVs, motorcycles
• Such systems typically include a master cylinder designed to be moved by the user (e.g., by a foot pedal or hand lever) to pressurize hydraulic fluid and impart motion to brake pads.
• Master cylinders commonly include a housing defining a bore, and a piston movable in the bore.
• the piston has an outer diameter slightly smaller than the inner diameter of the bore so that the piston can reciprocate within the bore.
• One or more resilient seals are mounted on the piston to seal the gap between the piston and the bore.
• the sidewalls of the piston adjacent the seal(s) are called the“lands.”
• the present invention provides a brake master cylinder comprising a housing having an inner surface defining a bore (e.g., a substantially cylindrical bore), and a piston positioned in the bore and movable relative to the bore along a piston axis.
• the piston includes two spaced apart lands defining the radially outermost surfaces capable of contacting the inner surface. At least one of the lands (and preferably both of the lands) is longitudinally curved at the radially outermost surface.
• the radially outermost surface can be curved at a radius of less than 1 inch (e.g., between 0.15 inch and 0.75 inch) and preferably less than 0.5 inch.
• the longitudinally curved land includes two edges that define an axial length of the land.
• the two edges have a radius of less than 0.2 inch, and preferably about 0.1 inch.
• the relative positions of the edges and lands are such that neither of the two edges is capable of contacting the inner surface of the bore during reciprocating movement of the piston in the bore.
• FIG. 1 illustrates an ATV with a brake master cylinder assembly embodying the present invention.
• Fig. 2 is a perspective view of the master cylinder assembly of Fig. 1.
• Fig. 3 is an exploded view of the master cylinder assembly of Fig. 2.
• Fig. 4 is a section view taken along line 4-4 in Fig. 2.
• Fig. 5 is an enlargement of a portion of the section view of Fig. 4.
• Fig. 6 is an enlargement of another portion of the section view of Fig. 4.
• Fig. 7 illustrates a piston member embodying the present invention is an askewed position relative to a bore.
• FIG. 1 illustrates an ATV 10 having a master cylinder assembly 12 embodying the present invention.
• the illustrated master cylinder assembly 12 is used in connection with a braking system to actuate the vehicle brakes.
• a braking system to actuate the vehicle brakes.
• the features of the present invention are also applicable to a master cylinder assembly used in connection with other actuating systems, such as transmission clutches.
• the illustrated master cylinder assembly 12 includes a cylinder housing 14 defining a bore 16, a fluid reservoir 18 that supplies fluid to the bore 16, and a lever 20 pivotally attached to the housing 14.
• the lever 20 is positioned to actuate a piston assembly 22 along a piston axis 24 in the bore 16.
• the illustrated bore 16 has a diameter D of about 11/16 inch.
• the piston assembly 22 includes a piston member 26, a piston O-ring 28 mounted on the piston member 26, a piston wiper 30 mounted on the piston member 26, and an end cap 32 removably mounted on one end of the piston member 26.
• a compression spring 34 and spring retainer 36 are position between the piston member 26 and the bottom of the bore 16 to bias the piston member 26 is a direction out of the bore 16 (i.e., to the right in Figs. 2-3).
• the piston member 26 includes front and rear lands 40,42, which are the radially outermost surfaces of the piston member 26 and position the piston member 26 in the bore 16.
• the lands 40,42 are spaced along the piston axis 24 to provide contact points between the piston member 26 and the sidewalls defining the bore 16.
• each land 40,42 is an annular member that protrudes radially and has a diameter slightly smaller than the diameter of the bore 16 to provide a stable sliding interface between the piston member 26 and the sidewalls defining the bore to facilitate smooth reciprocating motion of the piston assembly 22 in the bore 16.
• the illustrated front land 40 has a width Wl of about 0.080 inch
• the illustrated rear land 42 has a width W2 of 0.125 inch.
• the illustrated lands 40,42 are spaced from each other by a length L of about 0.75 inch.
• each of the lands 40,42 is longitudinally convexly curved. That is, in addition to being convexly curved in the circumferential direction to define the annular shape, each of the illustrated lands 40,42 is convexly curved longitudinally to create a partial torus shape.
• the partial torus shape provides a large-diameter, curved surface for contacting the inner surface of the bore 16.
• the longitudinal curve of the front land 40 has a radius R2 of 0.25 inches and the longitudinal curve of the rear land 42 has a radius Rl of 0.40 inches.
• the lands each have a radius Rl,R2 that is roughly proportional to the width Wl,Wl of the corresponding land.
• the illustrated radii Rl,R2 are chosen to be about 2 - 5 times (and preferably 2.5 - 4 times) the corresponding width Wl,W2.
• the radii Rl,R2 are about 3.1 - 3.3 times the corresponding width Wl,W2.
• This 3.1 - 3.3 multiplier is related to the length L between the lands. As the length L between the lands increases, the size of the radius on each land can also increase (i.e., the multiplier can increase), all other factors remaining the same. Preferably, the ratio of the multiplier (R/W) to the length L is 3.0 to 5.5, and more preferably 4.0 to 4.5. In the current embodiment, the lands are spaced by a length L of 0.75 inch, and the ratio of the multiplier (R/W) to the length L is about 4.3.
• Each illustrated land 40,42 is defined between two edges 44 that define an axial length of each land.
• the illustrated edges 44 have radii that are smaller than the radii of the longitudinal curve of the corresponding land.
• each of the edges 44 has a radius R3 of about 0.010 inches. It is noted that, because of the longitudinal curvature of the lands 40,42, the corresponding edges 44 are spaced from and do not contact the inner surface of the bore 16.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Transportation (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Transmission Of Braking Force In Braking Systems (AREA)
• Arrangement And Mounting Of Devices That Control Transmission Of Motive Force (AREA)

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Citations (6)

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• 2017
  • 2017-12-01 US US15/829,462 patent/US10518759B2/en active Active
• 2018
  • 2018-11-29 WO PCT/US2018/063161 patent/WO2019108852A1/en not_active Ceased
  • 2018-11-29 JP JP2020527811A patent/JP6968999B2/ja not_active Expired - Fee Related
  • 2018-11-29 EP EP18882453.6A patent/EP3672852B1/en active Active

Patent Citations (6)

Non-Patent Citations (1)

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