Patent Application
20060071550
1. Field of the Invention
The invention relates to hydraulic actuators and, more particularly, relates to a hydraulic actuator that has an integrated pressure vessel and pedal assembly configured to supply pressurized hydraulic fluid to one or more hydraulically actuated devices, such as one or more brakes of a vehicle. The invention additionally relates to a vehicle equipped with such an actuator and to a method of fitting a vehicle with such an actuator.
2. Discussion of the Related Art
Pedal actuated hydraulic pressure vessels are used in many different systems. For example, master cylinder-based hydraulic brake systems are used on a wide variety of vehicles including trucks, automobiles, all terrain vehicles (ATVs), motorcycles, and bicycles. In all such systems, a brake such as a disk brake or drum brake is actuated by an actuator that includes a pressure vessel and a hand operated lever or foot operated pedal. (Hand levers and foot pedals are hereinafter collectively and individually referred to as “pedals” for the sake of convenience.) The pedal and pressure vessel are connected to one another such that pedal depression actuates the pressure vessel to pressurize the hydraulic fluid and deliver the pressurized hydraulic fluid to the associated brake or brakes. The pressure vessel and pedal are traditionally provided as separate components that are mounted on the vehicle independently of one another and that are connected to one another by a plunger and a mechanical linkage assembly. Brake actuators employing separate pressure vessels and pedals are well-suited for many applications but exhibit drawbacks rendering them less attractive for some applications.
For instance, the rear brake of most motorcycles is actuated by a foot pedal located in the vicinity of a footrest on the side of the motorcycle's frame. Depending upon the configuration of the frame and the location of the footrest, there may be insufficient room adjacent the brake pedal to accommodate a standard pressure vessel, requiring the use of a relatively expensive specially designed pressure vessel and/or a specially designed linkage connecting the brake pedal to a remote pressure vessel. In addition, the sprocket cover in which the typical motorcycle pressure vessel is mounted must be reinforced by a rib to support the pressure vessel. The pressure vessel is also very exposed, reducing the aesthetic appeal of the motorcycle and also exposing the pressure vessel and related components to damage.
The combined weight of the brake pedal and pressure vessel also significantly adds to the overall weight of the machine. While this is not problematic in some applications such as large motorcycles, it can be of great concern in other applications, such as racing motorcycles, where weight minimization is important.
In addition, regardless of its application, the costs of manufacturing and assembling a multi-component actuator with interconnected but separate brake pedal and pressure vessel considerably adds to the cost of a braking system.
Some of the problems cited above have been recognized and addressed by the prior art with varying degrees of success. For instance, U.S. Pat. No. 4,910,962 to Keane, U.S. Pat. No. 5,090,201 to Smith, U.S. Pat. No. 5,476,162 to Reed et al., and German Patent No. DE 39 32 529 to Schonlau all disclose systems in which a fluid pressure actuator includes a pedal and a pressure vessel or similar device that are integrated into a combined assembly as opposed to being mounted on the vehicle independently of one another. The Smith and Schonlau patents additionally propose forming the casing or housing for the system's pressure vessel or similar device directly from the pedal. All of these systems provide a more compact and, in some cases, more easily mountable, actuator than traditional actuators having separate and independently mounted pedals and pressure vessels. However, none of these systems solves or even addresses all of the problems described above.
For instance, the pressure vessels of the Keane patent and Reed patent still are formed separately from the pedals. They each are merely bolted or otherwise attached to the brake pedal to form a combined assembly that is mounted on the vehicle as a unit. As a result, although each system may be more compact than a comparable traditional system, component number reduction and weight reduction are limited, at best.
In addition, while both the Schonlau patent and Smith patent disclose an actuator in which a pressure vessel casing is integrated with a pedal, the overall design of both systems still fails to optimize compactness, weight reduction, or component part reduction. For instance, the actuator disclosed in the Schonlau patent requires an external reservoir or “backlash receiver” to supply unpressurized hydraulic fluid to the pressure vessel. The system therefore must be fitted with an additional fitting for connecting the actuator to the separate backlash reservoir, and the backlash reservoir and pressure vessel must be mounted on the vehicle at separate locations and connected to one another by an external line or hose. This situation might be acceptable for the automotive vehicular application disclosed in the Schonlau patent, but is less than optimal for motorcycle and related applications. In addition, only part of Schonlau's pressure vessel housing is integrated with the brake pedal. As a result, the pressure vessel piston is housed primarily by a cap that must be threaded into a tapped bore in the pressure vessel housing. This arrangement adds additional complexity and cost to the system. Pedal actuated hydraulic clutches and other pedal actuated systems having hydraulic pressure vessels experience similar drawbacks.
In light of the foregoing, a hydraulic actuator is required that has a more fully integrated pressure vessel and pedal assembly and that better achieves the advantages of compactness, weight reduction, component reduction, and/or assembly time reduction achieved by the prior art cited above.
The need has also arisen to provide a vehicle brake actuator that does not require the vehicle frame to be reinforced to support the system's pressure vessel and that does not obstruct access to the vehicle's footrest or other components in the vicinity of the brake pedal.
In accordance with a first aspect of the invention, one or more of the above-identified needs is met by providing a hydraulic actuator that comprises a pedal and a pressure vessel that is integral to the pedal and that has an outlet in fluid communication with an outlet of the pressure vessel, an unpressurized reservoir, and a piston that is slidably disposed in the pressure vessel and that is responsive to pedal pivoting to selectively fluidically connect the pressurizable chamber and the reservoir to one another and isolate them from one another. In accordance with a preferred embodiment of the invention, at least a portion of the pressure vessel and at least a portion of the pedal are formed integrally with one part. In addition, at least a portion of the reservoir is formed in a hollow interior portion of the pedal at a location that is spaced from the pressure vessel. The actuator is well suited for use as a brake or clutch actuator.
The actuator may additionally include a mounting arrangement that is configured to mount the actuator on a mounting surface of the vehicle as a preassembled unit. The mounting arrangement may comprise a mounting bracket and a bolt configured for attaching the mounting bracket to the mounting surface. In this case, a return spring is preferably provided that acts on the pedal and the mounting bracket and that is configured to bias the pedal to a deactuated position thereof. The return spring imposes a preload force that holds the pedal and the mounting bracket together as a subassembly with the pedal biased into the deactuated position thereof. The return spring is preferably a torsion spring having a first end attached to the pedal and a second end attached to the mounting bracket.
The mounting arrangement may additionally comprise a reaction pin that is configured, when the actuator is mounted on the vehicle mounting surface, to extend through the mounting block and into the vehicle mounting surface along a line that is at least generally parallel to but offset from the pedal pivot axis. In this case, the pressure vessel further comprises a plunger that rests against the reaction pin and that translates upon pedal pivotal motion from a deactuated position thereof toward an actuated position thereof to drive the pressure vessel piston to move within the bore.
In order to render the actuator as self-contained and compact as possible, the reservoir could be formed entirely from the hollow interior portion of the pedal.
The benefits provided by the inventive actuator are particularly (but by no means exclusively) applicable to brakes or clutches for motorcycles or other vehicles. Hence, in accordance with other aspects of the invention, a vehicle system having an actuator configured at least generally as described above and a vehicle equipped with such as system are additionally provided.
In accordance with still other aspects of the invention, a method of making an actuator configured at least generally as described above and a method of using such an actuator are additionally provided.
Other objects, features, and advantages of the invention will become apparent to those skilled in the art from the following detailed description and accompanying drawings. It should be understand, however, that the detailed description and specific examples, while indicating the preferred embodiments of the present invention, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.
Preferred exemplary embodiments of the invention are illustrated in the accompanying drawings in which like reference numerals represent like parts throughout, and in which:
A wide variety of different hydraulic actuators for a variety of different applications could be constructed in accordance with the invention as defined by the claims. Hence, while preferred embodiments of the invention will now be described with reference to a foot pedal actuated motorcycle rear brake actuator, it should be understood the invention is in no way so limited. For example, it is also usable with a variety of foot operated or hand operated clutch and brake systems for a variety of different vehicles such as ATVs and snowmobiles.
Referring now to the drawings, a brake actuator 40 constructed in accordance with one embodiment of the invention is shown as being installed on a conventional motorcycle 10. The motorcycle 10 includes front and rear wheels 12, 14 and a frame 16 that is supported on the front and rear wheels 12, 14 in a conventional manner. The frame 16 supports the remaining components of the motorcycle including an engine 18, a seat 20, handlebars 22, footrests 24, etc. The front and rear wheels 12 and 14 are each equipped with associated hydraulic disk brakes 26 and 28, respectively. The front brake 26 is actuated by a conventional squeeze grip type lever 30 located adjacent one of the handlebars 22. The rear brake 28 is actuated by the actuator 40.
The rear brake actuator 40 comprises a preassembled unit mounted on a mounting location of the motorcycle 10 at a convenient location for access by the operator's foot. In the illustrated embodiment, that location is on the right side of the motorcycle's frame 16 inboard of the right footrest 24. Significantly, the actuator 40 is sufficiently compact so as not to interfere with standard footrest placement. The actuator 40 can also be mounted directly to the frame 16 without having to provide reinforcing ribs on a sprocket cover to accommodate a separate pressure vessel. Referring to
The mounting arrangement 42 preferably is configured to support the brake pedal 44, the piston end 46, and a reaction device for the pressure vessel piston while holding the brake pedal 44 together as a preassembled, preferably preloaded, unit. The mounting arrangement 42 of the illustrated embodiment includes a mounting block 48, a main mounting bolt 50, and a reaction pin 52. The mounting block 48 comprises a metal (preferably aluminum) casting having an outer surface 54 and an inner surface 56 that is configured to rest against the vehicle mounting surface. The vehicle mounting surface comprises the motorcycle frame 16 in this embodiment. First and second cylindrical bores 58 and 60 extend through the mounting block 48 from the outer surface 54 to the inner surface 56. The first or main cylindrical bore 58 is configured to receive the brake pedal 44 and the mounting bolt 50. The second, smaller bore 60 is offset from the first bore 58 and is configured to receive the reaction pin 52. As explained in more detail below, the bolt 50 is coincident with the pivot axis of the brake pedal 44. The reaction pin 52 is positioned relative to this pivot axis so that, as the brake pedal 44 pivots about the bolt 50, the piston end 46 rotates about the reaction pin 52 to actuate the pressure vessel piston 92 as detailed below.
Referring now to
Referring to
The brake pedal 44 includes a pressure vessel 86 that has an inner bore 88, a piston 90 that slides disposed in the bore 88, and a plunger portion of piston 92 that interacts with the reaction pin 52 upon brake pedal pivoting motion to drive the piston 90 to move relative to the pressure vessel 86 to apply the brake 28. At least part, and preferably the entire, pressure vessel 86 is cast integrally with the remainder of the brake pedal 44 as seen in
The integrated brake pedal 44 and pressure vessel 86 assembly preferably is cast in a lost core casting process. A particularly preferred process involves the casting of a thixotropic aluminum alloy around a zinc core and subsequently melting the zinc core from the alloy. This process permits the formation of interior structures of the brake pedal and pressure vessel, such as the ports, 74, 78, 82, etc., directly during the casting process without requiring the use of mechanical pins and without post casting drilling, milling, or other functions. Such a thixotropic alloy melt away melting process is described in greater detail in U.S. Pat. Nos. 6,564,856 and 6,427,755, the subject of both of which are hereby incorporated by reference.
Referring to
Referring to
Referring to
To assemble the actuator 44, the torsion spring 110 is mounted over the shank 62 on the brake pedal 44, the shank 62 is then inserted into the bore 58 of the mounting block 48. First and second tangs 112 and 114 on the ends of the torsion spring 110 are then attached to corresponding receptacles 116 and 118 formed on the mounting block 48 and the brake pedal 44, respectively. The torsion spring 110 is pre-stressed to provide a preload on the brake pedal 44. This preload holds the brake pedal 44 in its deactuated position and also holds the brake pedal 44 and mounting block 48 together as a unit. The spring 108 and piston 90 are then inserted into the bore 88 and held in a forward position within the bore 88 while the reaction pin 52 is inserted through a bushing 120 and then through the bore 60 in the mounting block 48 and clipped in place against the mounting block using a clip 122. The plunger 92 can then be released, whereupon it is held against the bushing 120 by the return spring 108. Finally, a conventional brake light switch 124 is mounted in a slot 126 on the mounting block 48 in a position in which it is responsive to brake pedal pivotal movement to actuate a brake light (not shown).
The actuator 40 is now fully preassembled and ready for mounting on the motorcycle 10 as a unit. All of these operations can be performed at the factory so that the motorcycle manufacturer or other end user can receive the actuator 40 as a preassembled unit ready for mounting on the motorcycle 10.
Referring to
The assembled actuator 40 has approximately 50% fewer parts than a comparable traditional multi-component motorcycle rear brake actuator. It also weighs approximately 50% less than the comparable traditional motorcycle rear brake actuator.
To operate the rear brake 28 of the motorcycle 10, the operator simply places his or her foot on the foot pad 68 of the brake pedal 44 and depresses the brake pedal to pivot it from the position illustrated in
When the operator removes his or her foot from the pad 68, the brake pedal 44 returns immediately to its deactuated position under the return force of the torsion spring 110 and hydraulic pressure. The piston 90 simultaneously returns to its deactuated position under the return force of the return spring 108, hence increasing the volume of the chamber 98 and permitting fluid to flow back into the chamber 98 from the brake 28 and, ultimately, re-opening the combined timing and spill ports 96 to reconnect the chamber 98 to the reservoir 72.
Referring now to
Referring to
As indicated above, many changes and modifications may be made to the present invention without departing from the spirit thereof. The scope of some of these changes are discussed above. The scope of others will become apparent from the appended claims.
