Patent Application
20090229402
None.
1. Field of the Invention
The present invention relates to a brake system suited for use with a hybrid vehicle having both regenerative and friction braking on one or more axles.
2. Disclosure Information
Hybrid vehicles, whether powered by an internal combustion engine or otherwise, and using electric, hydraulic, or compressed gas or another energy storage medium, typically utilize regenerative and friction braking on one or more axles. Regenerative braking is a fixture of hybrid vehicles simply because energy which is usually lost during the braking process may be recovered and used for powering the vehicle. Because, however, regenerative braking is not available at times, due to, for example, the lack of storage capacity in a traction battery or pump storage reservoir, or during certain operating modes, it is necessary to provide hybrid vehicles with not only regenerative braking, but also friction braking.
When a vehicle is being braked regeneratively, it is desirable for the brake pedal travel and effort to be, to the extent possible, equivalent to the travel and effort necessary to achieve a given level of braking during operation solely with friction brakes. In order to achieve the desired transparency needed of operation both with and without regenerative capability, it is required that the vehicle's brake pedal be displaceable by the motorist, during regenerative braking, without resistance from the master cylinder used to apply the friction brakes. This requirement of non-interaction from the master cylinder may be satisfied by the accommodation of lost motion between the master cylinder push rod and the arm to which the brake pedal is attached. Known attachments between the brake cylinder push rod and brake pedal arm are very complex and difficult to assemble. Moreover, known devices use a drive pin centered by the outer surfaces of a clevis attached to the master cylinder, and this causes friction to develop between the drive pin's head and the clevis surfaces.
It would be desirable to provide a brake pedal and master cylinder arrangement allowing rapid and relatively effortless coupling of the brake booster/master cylinder push rod to the brake pedal arm, using a structure which minimizes annoying vibration and noise during operation of the vehicle.
It would further be desirable to employ a drive pin and pedal arm combination which center the drive pin through its interaction with the pedal arm, rather than through interaction of the drive pin with a clevis attached to the master cylinder or brake booster. In this manner, friction between the head of the drive pin and adjoining surfaces of the clevis is eliminated.
According to an aspect of the present invention, a brake system for a hybrid vehicle includes a master cylinder connected with a number of wheel cylinders, and a brake pedal mounted upon a pivoted brake pedal arm which is adapted for mounting within the passenger compartment of the vehicle. The brake pedal arm has a bore extending therethrough. A compliance device extends between the brake pedal arm and the master cylinder. The compliance device includes a push rod having a first end attached to a master cylinder and a second, free end. A clevis is attached to the second end of the push rod. The clevis has a base engaging the push rod. A pair of opposing connecting members are integral with the clevis base. In a first embodiment, the opposing connection members each have a linear aperture extending generally parallel to a longitudinal axis of the push rod. A composite drive pin extends through the linear apertures and through the bore formed in the brake pedal arm in a direction generally perpendicular to the push rod. The composite drive pin includes a metallic core and a resin sheath applied to the core. The resin sheath has a generally cylindrical outer surface adapted to engage with both the bore formed in the brake pedal arm, and with the linear apertures. The resin sheath has a number of axial location abutments including at least one abutment which is radially displaceable so as to permit the drive pin to be readily assembled to the clevis and the brake pedal arm.
The composite drive pin preferably includes an anti-rotation cam extending radially outward from a portion of the generally cylindrical outer surface of the resin sheath. The anti-rotation cam is adapted to fit within a non-circular portion formed in the brake pedal arm bore.
In a first embodiment of the present invention, the opposing connecting members incorporated in the clevis are generally planar and configured such that the linear apertures in the connecting members have major axes which extend generally parallel to the longitudinal axis of the push rod. This is shown in
According to another aspect of the present invention, a master cylinder used with the present brake system is preferably configured as an active booster master cylinder, with the compliance device allowing the brake pedal to be depressed for a fraction of its normal travel, without applying the hydraulic brake system. This allows the use of regenerative braking in conjunction with friction braking in a manner which is transparent to the driver of the vehicle.
According to another aspect of the present invention, the axial location abutments formed on the resin sheath of the composite drive pin include a number of abutments positioned between the brake pedal arm and each of the opposing connecting members of the clevis. The axial location abutments are formed integrally with the resin sheath and are preferably created when the resin sheath is molded in place upon a metallic core. The abutments are preferably configured as radial displaceable sprags which are cantilevered to the resin sheath so as to normally project from the outer cylindrical surface of the resin sheath, with each sprag having a selectively retracted position enabling insertion of the composite drive pin within the clevis and bore formed in the brake pedal arm.
According to another aspect of the present invention, the axial abutments of the installed composite drive pin may be positioned within an internal annular groove formed within the bore of the brake pedal arm. As an alternative, the axial abutments may include an abutment positioned within an internal annulus defined by an outer surface of the composite drive pin and a bore formed within a doubler applied to the brake pedal arm such that the bore formed within the doubler is concentric with the bore formed in the brake pedal arm.
According to another aspect of the present invention, a brake system includes an active booster master cylinder connected with a number of wheel cylinders, with a brake pedal having a linear aperture extending through a brake pedal arm. A clevis has opposing connecting members which each have a generally cylindrical bore extending therethrough in a direction generally perpendicular to a push rod having a first end attached to the master cylinder and a second free end which is attached to the clevis. A composite drive pin extends through the bores formed in the connecting members and through the linear aperture formed in the brake pedal arm.
It is an advantage of a system according to the present invention that compliance may be provided between a brake pedal and an active booster master cylinder, with a minimum number of components in the compliance device, while avoiding undesirable noise, vibration and harshness from the connection between the master cylinder push rod and the brake pedal arm.
It is yet another advantage of a brake system according to the present invention that a connection may be made up between a brake pedal arm and a master cylinder push rod without the need for attaching threaded fasteners under the dash of a vehicle during the final assembly process.
It is yet another advantage of a brake system according to the present invention that necessary compliance between a brake pedal and a master cylinder is provided with minimal tooling cost.
It is an advantage of a system according to the present invention that compliance may be provided between a brake pedal and an active booster master cylinder with a minimum amount of friction within the compliance device.
Other advantages, as well as features of the present invention, will become apparent to the reader of this specification.
As shown in
A brake pedal, 14, is attached to a brake pedal arm, 18, which is mounted to a bracket, 20, by means of a pivot shaft 22.
Composite drive pin 64 further includes at least one fixed abutment, 80, and at least one cantilevered, radially displaceable abutment or sprag, 84. As shown in
Composite drive pin 64 is inserted, as shown in
In the embodiment shown in
In the embodiment of
In the embodiment of
Although the present invention has been described in connection with particular embodiments thereof, it is to be understood that various modifications, alterations, and adaptations may be made by those skilled in the art without departing from the spirit and scope of the invention set forth in the following claims.
