Patent Application
20180037207
The subject invention relates to a vehicle brake-by-wire (BBW) system, and more particularly, to a brake pedal emulator with an emulator override device.
Traditional service braking systems of a vehicle are typically hydraulic fluid based systems actuated by a driver depressing a brake pedal that generally actuates a master cylinder. In-turn, the master cylinder pressurizes hydraulic fluid in a series of hydraulic fluid lines routed to respective actuators at brakes located adjacent to each wheel of the vehicle. Such hydraulic braking may be supplemented by a hydraulic modulator assembly that facilitates anti-lock braking, traction control, and vehicle stability augmentation features. The wheel brakes may be primarily operated by the manually actuated master cylinder with supplemental actuation pressure gradients supplied by the hydraulic modulator assembly during anti-lock, traction control, and stability enhancement modes of operation.
When a plunger of the master cylinder is depressed by the brake pedal to actuate the wheel brakes, pedal resistance is encountered by the driver. This resistance may be due to a combination of actual braking forces at the wheels, hydraulic fluid pressure, mechanical resistance within the booster/master cylinder, the force of a return spring acting on the brake pedal, and other factors. Consequently, a driver is accustomed to and expects to feel this resistance as a normal occurrence during operation of the vehicle. Unfortunately, the ‘feel’ of conventional brake pedals are not adjustable to meet the desires of a driver.
More recent advancements in braking systems include BBW systems that actuate the vehicle brakes via an electric signal typically generated by an on-board controller. Brake torque may be applied to the wheel brakes without a direct hydraulic link to the brake pedal. The BBW system may be an add-on, (i.e., and/or replace a portion of the more conventional hydraulic brake systems), or may completely replace the hydraulic brake system (i.e., a pure BBW system). In either type of BBW system, the brake pedal ‘feel’, which a driver is accustomed to, must be emulated.
Accordingly, it is desirable to provide a brake pedal emulator that may simulate the brake pedal ‘feel’ of more conventional brake systems, and an emulator that is generally robust.
In one exemplary embodiment of the invention, a brake pedal apparatus for actuating a vehicle brake assembly includes a stationary structure, a brake pedal emulator assembly, and an emulator override device. The brake pedal emulator assembly includes a brake pedal operatively engaged to the stationary structure, and a brake pedal emulator operatively engaged between the stationary structure and the brake pedal along a centerline. The brake pedal emulator is configured to electrically operate the brake assembly. The emulator override device includes a mechanical linkage operatively engaged to the brake assembly, and a latch configured to selectively connect and disconnect the mechanical linkage from the brake pedal emulator assembly. The mechanical linkage is configured to mechanically operate the brake assembly via at least in-part movement of the brake pedal along the centerline.
In another exemplary embodiment of the invention, a vehicle includes a BBW system that has a brake assembly, a brake pedal emulator assembly and an emulator override device. The brake pedal emulator assembly is electrically connected to the brake assembly and the emulator override device is mechanically connected to the brake assembly.
The above features and advantages and other features and advantages of the invention are readily apparent from the following detailed description of the invention when taken in connection with the accompanying drawings.
Other features, advantages and details appear, by way of example only, in the following detailed description of embodiments, the detailed description referring to the drawings in which:
The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. As used herein, the terms module and controller refer to processing circuitry that may include an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality.
In accordance with an exemplary embodiment of the invention,
Each brake assembly 28 of the BBW system 26 may include a brake 34 and an actuator 36 configured to operate the brake. The brake 34 may include a caliper (not shown) and may be any type of brake including disc brakes, drum brakes, and others. As non-limiting examples, the actuator 36 may be an electro-hydraulic brake actuator (EHBA) or other actuators capable of actuating the brake 34 based on an electrical input signal that may be received from the controller 32. More specifically, the actuator 36 may be, or may include, any type of motor capable of acting upon a received electric signal and as a consequence, converting energy into motion that controls movement of the brake 34. Thus, the actuator 36 may be a direct current motor configured to generate electro-hydraulic pressure delivered to, for example, the calipers of the brake 34. It is further contemplated and understood that the brake 34 and or the actuator 36 may further include a redundant actuating means that may include more traditional techniques such as a mechanical linkage between the brake 34 and the brake pedal (e.g., push/pull cable, hydraulics, and others).
The controller 32 may include a computer-based processor (e.g., microprocessor) and a computer readable and writeable storage medium. In operation, the controller 32 may receive one or more electrical signals from the brake pedal apparatus 30 over a pathway (see arrow 38) indicative of driver braking intent. In-turn, the controller 32 may process such signals, and based at least in-part on those signals, output an electrical command signal to the actuators 36 over a pathway (see arrow 40). Based on any variety of vehicle conditions, the command signals directed to each wheel 24 may be the same or may be distinct signals for each wheel 24. The pathways 38, 40 may be wired pathways, wireless pathways, or a combination of both.
Non-limiting examples of the controller 32 may include an arithmetic logic unit that performs arithmetic and logical operations; an electronic control unit that extracts, decodes, and executes instructions from a memory; and, an array unit that utilizes multiple parallel computing elements. Other examples of the controller 32 may include an engine control module, and an application specific integrated circuit. It is further contemplated and understood that the controller 32 may include redundant controllers, and/or the system may include other redundancies, to improve reliability of the BBW system 26.
Referring to
The brake pedal 42 may be supported by, and in moving relationship too, a fixed structure 46 of the brake pedal apparatus 30. Illustrated as one non-limiting example, the brake pedal 42 may be pivotally engaged to the fixed structure 46 about a first pivot axis 48. The brake pedal emulator 44 may be supported by and extend between the brake pedal 42 and the fixed structure 46. More specifically, the emulator 44 may be pivotally engaged to the brake pedal at a second pivot axis 50, and may be in operable contact with the stationary structure 46 at a contact 52. The second pivot axis 50 may be spaced from and substantially parallel to the first pivot axis 48. It is contemplated and understood that the brake pedal 42 may not be pivotally connected to the stationary structure 46, and instead, may be in sliding contact with the stationary structure with limited degrees of motion. It is further contemplated and understood that the contact 52 may include a third pivotal axis, or may be a sliding contact between the emulator 44 and the stationary structure 46 with limited degrees of motion.
The brake pedal emulator 44 may include a damping device 54 and a force induction device 56 to at least simulate the desired or expected ‘feel’ of the brake pedal 42 during operation by the driver. The damping device 54 is constructed and arranged to generally produce a damping force that is a function of the speed upon which a driver depresses the brake pedal 42. The force induction device 56 produces an induced force (e.g., spring force) that is a function of brake pedal displacement. Both the damping device 54 and the force induction device 56 may be controlled, individually or in combination, by the controller 32 to at least simulate the desired pedal ‘feel.’
One example of the force induction device 56 may be a resiliently compressible, coiled, spring. Other non-limiting examples of a force induction device 56 include elastomeric foam, a wave spring, and any other device capable of producing a variable force generally as a function of brake pedal displacement. One example of the damping device 54 may include a hydraulic cylinder having at least one internal orifice for the flow and exchange of hydraulic fluid between chambers. Such a damping device (and others) may be designed to exert a constant force when a constant speed is applied to the brake pedal throughout the brake pedal throw. One example of such a ‘constant force’ damping device 54 may be a hydraulic cylinder with a single orifice. Another non-limiting example of a damping device 54 may include a device designed to increase a force with increasing pedal displacement and when the brake pedal 42 is depressed at a constant speed. Such ‘variable force’ damping devices may be passive and dependent solely upon the brake pedal position and/or displacement, or may be active and controllable by the controller 32. One example of a ‘passive variable force’ damping device may include a hydraulic cylinder with multiple orifices, sequentially exposed, based on brake pedal position. Other non-limiting examples of a damping device 54 may include a friction damper, and any other device capable of producing a variable force generally as a function of pedal actuation speed. Although illustrated in a parallel (i.e., side-by-side) relationship to one-another, it is further contemplated and understood that the orientation of the devices 54, 56 with respect to one-another may take any variety of forms. For example, the devices 54, 56 may be concentric to one-another along the centerline C (see
Referring to
To optimize system reliability, the brake pedal emulator 44 may include more than one displacement sensor located at different locations of the brake pedal apparatus 30. Similarly, the brake pedal emulator 44 may include more than one pressure sensor (i.e., force) configured to, for example, output redundant signals to more than one controller to facilitate fault tolerance for sensor faults.
In operation, the controller 32 is configured to receive a displacement signal (see arrow 64) and a pressure signal (see arrow 66) over pathway 38 and from the respective sensors 60, 62 as the brake pedal 42 is actuated by a driver. The controller 32 processes the displacement and pressure signals 64, 66 then sends appropriate command signal(s) 68 to the brake actuators 36 over the pathway 40. It is contemplated and understood that the signal pathways 38, 40 may be wireless, hard wired, or a combination of both.
Referring to
Referring to
Referring to
The brake pedal emulator 44 of the brake pedal emulator assembly 41 (also see
The emulator override device 43 of the brake pedal apparatus 30 may include a mechanical linkage 80 (e.g., input rod) and a latch 82. When the brake pedal apparatus 30 is in the BBW mode, the latch 82 generally engages, and holds rigid, the base member 72 to the stationary structure 46. In one embodiment, the latch 82 may include an electric solenoid 84 and a bolt 85 configured to extend and retract from the solenoid based on whether the solenoid is electrically energized or not. The solenoid 84 may be controlled by the controller 32 and may be energized when the brake pedal apparatus 30 is in the BBW mode. In one embodiment, the solenoid 84 may be carried by the base member 72. When the solenoid 84 is energized, the bolt 85 may project from the solenoid and into an opening 86 or other arrangement carried by the stationary structure 46. With the bolt 85 in the opening 86, the base member 72 is prevented from moving (i.e. at least axially along centerline C) with respect to the stationary structure 46, and the devices 54, 56 may be compressed axially between the base member 72 and the linking member 58 which moves axially as the brake pedal 42 is actuated.
Referring to
The base member 72 may include a first side 92 and an opposite second side 94, both substantially disposed normal to the centerline C. The first side 92 may generally bear upon the damping and force induction devices 54, 56. The second side 94 may bear upon the mechanical linkage 80 of the emulator override device 43. When the brake pedal apparatus 30 is in the mechanical backup mode 88 and the brake pedal 42 is being actuated by the driver, the base and linking members 72, 58 move axially with the pedal 42 causing the second side 94 of the base member 72 to make contact with and move the mechanical linkage 80 in, for example, the axial direction. This motion (see arrow 96 in
Referring to
The brake pedal emulator 44′ may include a damping device 54′, a force induction device 56′, a linking member 58′, and a base member 72′. The devices 54′, 56′ may be orientated for compression along the centerline C and between the linking and base members 58′, 72′ during normal operation and as the brake pedal 42′ is actuated. The linking member 58′ may be pivotally engaged directly to the brake pedal 42′ at the second pivot axis 50′, and the base member may be pivotally engaged directly to the stationary structure 46′ at the third pivot axis 52′.
The emulator override device 43′ may include a mechanical linkage 80′ and an electric latch 82′ configured to engage and release at least a portion of the mechanical linkage 80′ from the brake pedal emulator 44′. The mechanical linkage 80′ may include a push/pull cable 100 that may be mounted to and/or guided through the base member 72′, and a pivot arm 102 pivotally engaged to the base member at a pivot axis 104. A first end portion 106 of the pivot arm 102 may project radially outward from the pivot axis 104 and may pivotally connect to the linking member 58′ at a pivot axis 108. A second end portion 110, which may be opposite the first end portion 106 (i.e., end portions project in diametrically opposite directions), may carry an electric solenoid (not shown) of the latch 82′. A bolt (not shown) of the latch 82′ may be configured to retract and project, in and out of the solenoid 84′.
When the brake pedal apparatus 30′ is in a mechanical backup mode and the solenoid may be de-energized, the bolt of the latch 82′ may be located in an opening 112 (e.g., hole) defined by an enlarged end segment 114 of the cable 100 that projects out of the base member 72′. With the linking member 58′ thus engaged to the cable 100 of the mechanical linkage 80′, the cable 100 will move with the linking member 58′ and thereby mechanically actuate the brake assembly 28. When the bolt of the latch 82′ is retracted and not in the opening 112, the brake pedal apparatus 30′ is operating normally in BBW mode.
The opening 112 in the enlarged end segment 114 of the cable 100 may be a plurality of openings (e.g., holes) generally aligned side-by-side forming an arcuate pattern that extends substantially axially with respect to the centerline C. The distance between the outer openings along the path may correspond to the total throw (i.e., axial displacement) of the emulator 44′. The multiple openings 112 facilitate actuation of the emulator override device 43′ regardless of the brake pedal position. In this way, the linking member 58′ may continue to move toward the base member 72′, thus compressing the damping and force induction devices 54, 56 even though the BBW mode of operation may not be operative (i.e., the brake assemblies 28 are not receiving a wire brake command).
Referring to
The emulator override device 43″ may include a mechanical linkage 80″ and an electric latch 82″ configured to engage and release at least a portion of the mechanical linkage 80″. The mechanical linkage 80″ may include a pivot arm 102″ pivotally engaged to the stationary structure 46″ at a pivot axis 104″. A first end portion 106″ of the pivot arm 102″ may project radially outward from the pivot axis 104″ for intermittent contact with the brake pedal 42″. A second end portion 110″ having a series of openings (e.g., holes) may be positioned opposite the first end portion 106″. The latch 82″ (e.g., electric solenoid with throw bolt) may be supported by the structure 46″, and may be configured to insert the throw bolt into one of the series of openings in the second end portion 110″.
Advantages and benefits of the present disclosure include a low cost back-up brake system that may automatically override a BBW system if an electric fault is present. Another advantage may include a means for providing a mechanical backup with minimal changes required to a pure BBW emulator. Yet another advantage may include an entire braking system without any need for hydraulic fluid. A further advantage includes an emulator capable of being packaged inline between a master cylinder and a pedal push rod. Yet further, the present disclosure may enable a compact mechanical part envelope that simplifies design and physical integration of a pedal module, along with simplifying diagnosis and servicing of the module.
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the application.
