Patent Publication Number: US-2019184949-A1

Title: Manual control over electronic parking brake motor on caliper parking brake actuations

Description:
FIELD OF THE INVENTION 
     The invention relates generally to an electronic parking brake system having various configurations to control vehicle dynamic. 
     BACKGROUND OF THE INVENTION 
     Many current vehicles are equipped with an electronic parking brake (EPB). An EPB generally includes some type of brake unit having an electronic actuator in electrical communication with an electronic control unit (ECU), and there is also some type of switch which is selectively actuated by the driver of the vehicle for controlling the actuation of the EPB. The driver actuates the switch when desired such that a signal is sent to the ECU, and the ECU then sends a signal to the actuator to engage the brake unit, preventing the vehicle from moving. 
     Current EPB systems do not provide for control by the driver over the amount of clamping force generated by the brake unit. These current EPB systems typically have two configurations, where the brake unit is either fully engaged, or fully released. In some applications, such as off-road use and on-road racing, it would be beneficial for the driver to use the parking brake to adjust the vehicle dynamic. However, because of current EPB systems having limited configurations, there is limited benefit in using the EPB system to control vehicle dynamic. 
     Accordingly, there exists a need for an EPB system which has expanded functionality, allowing the driver to use the EPB system to have greater control over the vehicle dynamic. 
     SUMMARY OF THE INVENTION 
     The present invention is an electronic parking brake (EPB) system having expanding functionality, which provides the driver of a vehicle the option to manually control the clamping force of the EPB as desired, while keeping existing EPB functionalities. 
     In one embodiment, the EPB system according to the invention includes a hand lever assembly, where the hand lever assembly includes both a lever and a transducer for detecting lever position, both of which are installed in the vehicle and connected to an electronic control unit (ECU), or a hydraulic electronic control unit (HECU), of the EPB system. 
     The driver is able to move the hand lever to various positions. The position of the lever corresponds to an equivalent parking brake clamping force request. A fully retracted lever corresponds to a complete release action of the parking brake, and a fully actuated lever corresponds to a complete clamping of the parking brake. Any position in between the fully retracted and fully actuated positions corresponds to a partial apply of the parking brake using a predefined ratio of force to lever position. 
     In one embodiment, the EPB system includes actuators, such as a motor-gear-unit. In one embodiment, the current is used as an indicator for detecting force, and the EPB system software activates the actuators of EPB system to generate the requested clamping force, for example, by adjusting the switch-off current of the motor in the motor-gear-unit. Any change in the position of the hand lever assembly corresponds to an adjustment of the clamping force. In one embodiment, if the lever is pulled further, a re-clamp action is generated with a new calculated switch-off current. A partial retraction of the hand lever generates a release action to install the new requested clamping force, according to the new position of the hand lever. Once the lever is fully retracted by the driver, the software of the EPB system fully configures the actuators such that no clamping force is applied. 
     Another feature of the present invention is the use of the EPB system for complete engagement and disengagement, of the braking unit, where a switch, located in the interior of the vehicle, is used for operation of the EPB system when there is no partial apply/release request. 
     One of the advantages of the present invention is that the EPB system of the present invention may be implemented into a vehicle without changing or developing a new brake caliper for the EPB system. 
     In one embodiment, the present invention is an electronic parking brake system, which includes a control device, such as a lever operable for being pivoted between a first position and a second position, and anywhere between the first position and second position, an electronic control unit in electrical communication with the lever, at least one actuator in electrical communication with the electronic control unit, and at least one disc, the actuator operable for selectively applying a force to the disc. 
     The electronic control unit sends a signal to the actuator to allow the rotation of the disc when the lever is in the first position, and the electronic control unit sends a signal to the actuator to prevent the rotation of the disc when the lever is in the second position. 
     In one embodiment, the lever is pivoted such that the ECU sends a signal to the actuator such that the actuator applies a partial force to the rotatable element, limiting the rotation of the rotatable element. 
     At least one caliper is connected to the actuator, and the actuator configures the caliper to apply force to the disc when the lever is moved away from the first position. 
     In one embodiment, the actuator is a motor-gear-unit, however it is within the scope of the invention that other types of actuators may be used, such as, but not limited to, a stand-alone DC motor, a brushless DC motor, a stepper motor, or the like. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a diagram of a vehicle having an electronic parking brake system, according to embodiments of the present invention; 
         FIG. 2  is a diagram of an electronic parking brake system, according to embodiments of the present invention; and 
         FIG. 3  is an enlarged view of the circled portion of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     A diagram showing a vehicle  10 A having an electronic parking brake (EPB) system according to the present invention is shown in  FIG. 1 , generally at  10 . Referring to the Figures generally, the system  10  includes a control device, shown generally at  12 , which in this embodiment is a lever  12  in electrical communication with an electronic control unit (ECU)  14 . The ECU  14  is in electrical communication with at least one brake unit, which in this embodiment is two brake units, shown generally at  16 A, 16 B, where each brake unit  16 A, 16 B is able to prevent the rotation of a corresponding rotatable element, which in this embodiment are two discs  18 A, 18 B connected a corresponding wheel (not shown). Each brake unit  16 A, 16 B includes an actuator  20 A, 20 B, and each actuator  20 A, 20 B is connected to and is able to actuate a corresponding caliper  22 A, 22 B. Each caliper  22 A, 22 B has two brake pads  24 A, 24 B, 24 C, 24 D, and is able to apply force to the brake pads  24 A, 24 B, 24 C, 24 D. Two of the brake pads  24 A, 24 B are located on opposite sides of the first disc  18 A, and the other two brake pads  24 C, 24 D are located on opposite sides of the second disc  18 B. The first actuator  20 A is able to control the operation of the first caliper  22 A such that the pads  24 A, 24 B apply force to the first disc  18 A, limiting or preventing rotation of the first disc  18 A. The second actuator  20 B is able to control the operation of the second caliper  22 B such that the pads  24 C, 24 D apply force to the second disc  18 B, limiting or preventing rotation of the second disc  18 B. 
     The lever  12  is able to be moved to various positions. More specifically, the lever  12  is able rotate about an axis  26  from a first position, shown in  FIG. 3 , to a second position, where the lever  12  has rotated an angular distance indicated by an angle  28 , also shown in  FIG. 3 . The lever  12  also includes a transducer, which generates a voltage signal corresponding to the degree of which the lever  12  is pivoted about the axis  26 , where the voltage signal from the transducer is sent to the ECU  14 , and the ECU  14  sends a signal to each actuator  20 A, 20 B representing the desired clamping force corresponding to the position of the lever  12 , and therefore the corresponding clamping force is applied to each disc  18 A, 18 B by each corresponding caliper  22 A, 22 B. The actuators  20 A, 20 B are able to maintain clamping force such that once the desired clamping force is achieved, the actuators  20 A, 20 B are able to be deactivated (such that no current is applied to the actuators  20 A, 20 B), while still maintaining the desired clamping force on the corresponding discs  18 A, 18 B. The ECU  14  includes software such that the ECU  14  is programmed to command the actuators  20 A, 20 B to generate a requested clamping force on the discs  18 A, 18 B based on the position of the lever  12 . In one embodiment, the actuators  20 A, 20 B are motor-gear-units, each of which includes a DC motor connected to a gear box for torque amplification, where the current consumption by the DC motors is used as a force estimation (i.e., the current consumption by the DC motors corresponds to the force applied to the discs  18 A, 18 B), and the switch-off current to the DC motors is adjusted to achieve the desired clamping force on the discs  18 A, 18 B by the calipers  22 A, 22 B. In this embodiment, the “switch-off” current is the current level of the DC motors once the desired clamping force is achieved. Once the desired clamping force is achieved, the DC motors are deactivated, and the level of current at the time the DC motors are switched off is the “switch off” current. Although the actuator  20 A, 20 B has been described as a motor-gear-unit, it is within the scope of the invention that other types of actuators may be used, such as, but not limited to, a stand-alone DC motor (no gear box), a brushless DC motor, a stepper motor, or the like. 
     When the lever  12  is in the first position, shown in  FIG. 3 , a voltage signal of zero volts is sent from the lever  12  to the ECU  14 , such that no signal is sent from the ECU  14  to each actuator  20 A, 20 B, and therefore no clamping force is generated by the actuators  20 A, 20 B. When the lever  12  is in the second position, a voltage signal of twelve volts is sent from the lever  12  to the ECU  14 , such that a signal corresponding to maximum clamping force is sent from the ECU  14  to each actuator  20 A, 20 B, and the maximum clamping force is generated by the actuators  20 A, 20 B. The lever  12  may also be placed anywhere between the first position and the second position such that a corresponding voltage signal anywhere between zero and twelve volts is sent from the lever  12  to the ECU  14 , such that a signal representing the desired clamping force corresponding to the position of the lever  12  is sent from the ECU  14  to each actuator  20 A, 20 B, and the desired clamping force is generated by the actuators  20 A, 20 B. In the embodiment shown in  FIGS. 1-3 , there is a linear relationship between the position of the lever  12  and the clamping force applied to the discs  18 A, 18 B by the actuators  20 A, 20 B. However, it is within the scope of the invention that the relationship between the position of the lever  12  and the clamping force applied to the discs  18 A, 18 B by the actuators  20 A, 20 B may be non-linear, exponential, or have some other correlation such that the EPB system  10  of the present invention may be best suited for a specific application. 
     The EPB system  10  also includes a switch  30 , which is also in electrical communication with the ECU  14 . The switch  30  may also be used to actuate the brake units  16 A, 16 B. The switch  30  has two configurations, in the first configuration, or “off position,” the switch  30  is configured such that the ECU  14  does not send a signal to the actuators  20 A, 20 B, and no force is applied to the discs  18 A, 18 B. When the switch  30  is in the off position, the actuators  20 A, 20 B configure the calipers  22 A, 22 B to release the discs  18 A, 18 B, such that the discs  18 A, 18 B, and therefore the wheels, are allowed to rotate freely. In the second configuration, or “on position,” the switch  30  is configured to send a signal to the ECU  14 , and a signal corresponding to maximum clamping force is sent from the ECU  14  to each actuator  20 A, 20 B, and the clamping force is generated by the actuators  20 A, 20 B is maximized. When the switch  30  is in the on position, the clamping force applied to the discs  18 A, 18 B by the actuators  20 A, 20 B is maximized, and the discs  18 A, 18 B, and therefore the wheels, are stationary, and prevented from rotating. The switch  30  may be used when the vehicle  10 A is in a parked location, and it is desired to prevent the vehicle  10 A from moving, such as when the vehicle  10 A is parked on a hill. 
     In operation, the driver of the vehicle  10 A may desire to change the vehicle dynamic. This may occur under different driving conditions, such as on-road racing, or when traveling off-road over various types of terrain. When the driver desires to change the vehicle dynamic, the driver may change the position of the lever  12 , and rotate the lever  12  about the axis  26  from the first position to the second position, or anywhere between the first position and second position. When the lever  12  is in the first position, shown in  FIG. 3 , a voltage signal of zero volts is sent from the lever  12  to the ECU  14 , no signal is sent from the ECU  14  to the actuators  20 A, 20 B, and there is no force applied to the discs  18 A, 18 B, and the discs  18 A, 18 B, and therefore the wheels, are allowed to rotate freely. When the lever  12  is in the second position, a voltage signal of twelve volts is sent from the lever  12  to the ECU  14 , and a signal corresponding to maximum clamping force is sent to the actuators  20 A, 20 B by the ECU  14 , such that the clamping force applied to the discs  18 A, 18 B by the actuators  20 A, 20 B is maximized, and the discs  18 A, 18 B, and therefore the wheels, are stationary, and prevented from rotating. The lever  12  may also be placed in any position between the first position and the second position, where a partial clamping force is applied to the discs  18 A, 18 B, reducing the rotational speed of the discs  18 A, 18 B, and therefore the wheels, allowing the driver to change the vehicle dynamic. 
     Any adjustment in the position of the lever  12  changes the corresponding clamping force applied to the discs  18 A, 18 B by the calipers  22 A, 22 B. When the lever  12  is located anywhere between the first position and the second position, and the lever  12  is pulled further, a “re-clamp action” is generated, having a new switch-off current. However, if the lever  12  is partially retracted, a “release action” is generated, to implement the new requested clamping force which corresponds to the new position of the lever  12 . 
     While the control device has been described above using the embodiment of the lever  12 , it is within the scope of the invention that the lever  12  may be replaced with other types of control devices, such as knobs and different types of levers. Furthermore, while it has also been described above that each rotating element is a disc, the rotating element may be a drum, or any other type of rotating element such that the EPB system  10  described above may be suitable for use with various types of braking units. 
     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.