Abstract:
An electric parking brake control system for automatically controlling one or more parking brakes in a vehicle. The parking brake control system includes an electric brake switch in communication with a low-pressure switch for automatically applying the parking brakes. The electric brake switch is preferably a latching type mechanism, which is capable of controlling a solenoid air valve external to the vehicle cab. The low-pressure switch automatically monitors an air reservoir for a low-pressure condition. The electric brake switch incorporates a time delay upon release of the switch, in order to prevent inadvertent application of the parking brakes due to a momentary loss of vehicle electrical power.

Description:
TECHNICAL FIELD 
       [0001]    Embodiments are generally related to braking systems for use with vehicles. Embodiments are also related to electric switches. Embodiments are additionally related to control systems for controlling parking brakes in vehicles. 
       BACKGROUND OF THE INVENTION 
       [0002]    A brake control system is generally utilized for engaging and disengaging a service brake and a parking brake associated with a vehicle. Service brakes are utilized to stop a moving vehicle slowly. Parking brakes are latching brakes utilized primarily for preventing the vehicle from moving from a parked position. Parking brakes may also be utilized in an emergency situation to slow the moving vehicle when the service brakes have failed to provide a redundant brake circuit. EPB (Electrical Parking Brake) systems include an EPB mechanism for applying an actuating force to the parking brake associated with the vehicle. The EPB mechanism is generally actuated in response to the operation of a push/pull hand lever located on a vehicle dash panel within a cab of the vehicle. 
         [0003]    The vehicle may include more than one push/pull knob, depending upon whether or not an additional control is available for the parking brakes, such as in the case of a trailer attached to the vehicle. The push/pull knob is generally connected to an air valve, which controls the flow of air to the parking brake. In general, when the operator pushes the valve in, air pressure can be provided to the parking brake and the brake then released, thereby allowing the vehicle to move. In order to apply the brake, the operator pulls the push/pull knob and the air pressure is then removed from the parking brake, thereby allowing the brake to be engaged. When the knob is pushed in, the air pressure acts to engage the knob and maintain the knob in the pushed position. 
         [0004]    Such push/pull knobs and air valves can be plumbed with air lines that are capable of being routed to and from the push/pull knobs located in the dash panel of the vehicle. Hence, the dash panel must be relatively large to accommodate such air lines. Additionally, such air lines are costly to install and to service because of the restricted space behind the dash panel. Furthermore, maintenance can be difficult in the case, for example, where an air leak is present in the valve or associated hoses. Such an air leak can be difficult to find and repair due to the restricted space of the dash panel. 
         [0005]    Based on the foregoing, it is believed that a need exists for an improved electric parking brake control system for automatically controlling parking brakes. A need also exists for an improved electric brake switch with time delay capabilities for preventing inadvertent application of an electric parking brake, as described in greater detail herein. 
       BRIEF SUMMARY 
       [0006]    The following summary is provided to facilitate an understanding of some of the innovative features unique to the embodiments disclosed and is not intended to be a full description. A full appreciation of the various aspects of the embodiments can be gained by taking the entire specification, claims, drawings, and abstract as a whole. 
         [0007]    It is, therefore, one aspect of the present invention to provide for an improved electric parking brake control system. 
         [0008]    It is another aspect of the present invention to provide for an improved electric brake switch with time delay for preventing inadvertent application of the electric parking brake. 
         [0009]    The aforementioned aspects and other objectives and advantages can now be achieved as described herein. An electric parking brake control system for automatically controlling at least one parking brake in a vehicle is disclosed. The parking brake control system includes an electric brake switch in communication with a low-pressure switch for automatically applying the parking brake. The electric brake switch is preferably a latching type mechanism, which controls a solenoid air valve external to the vehicle cab. The low-pressure switch automatically monitors an air reservoir for a low-pressure condition. The electric brake switch incorporates a time delay which delays release of the switch, in order to prevent the inadvertent application of the parking brake due to a momentary loss of vehicle electrical power. 
         [0010]    The electric parking brake control system further includes a push/pull knob connected to a return spring. The electric brake switch can be depressed, which in turn provides a signal to the solenoid air valve, thereby causing the valve to move to an open position. In the open position, air from the reservoir can pass through the solenoid air valve and release the parking brake. When the electric brake switch is pulled, a circuit is opened, which moves the solenoid air valve to an exhaust position. The pressure to the parking brake then goes to atmospheric pressure and the parking brake can be applied. The low-pressure switch automatically returns the electric brake switch to the pulled position thereby opening the circuit and moving the latching solenoid air valve to an exhaust position when the pressure from a reservoir drops below a preset limit. The control system delays the application of the parking brake for a suitable short time interval, thereby preventing the inadvertent application of the parking brake due to a momentary loss of vehicle electrical power. Additionally, the control system can include a unique combination of electric brake switch, pressure switch, and control for desired automation and/or semi-automatic operations. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The accompanying figures, in which like reference numerals refer to identical or functionally-similar elements throughout the separate views and which are incorporated in and form a part of the specification, further illustrate the embodiments and, together with the detailed description, serve to explain the embodiments disclosed herein. 
           [0012]      FIG. 1  illustrates a schematic view of an electric parking brake control system for automatically controlling a parking brake, in accordance with a preferred embodiment; and 
           [0013]      FIG. 2  illustrates a schematic view of an electric brake switch associated with the electric parking brake control system, in accordance with a preferred embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    The particular values and configurations discussed in these non-limiting examples can be varied and are cited merely to illustrate at least one embodiment and are not intended to limit the scope thereof. 
         [0015]      FIG. 1  illustrates a schematic view of an electric parking brake control system  100 , in accordance with a preferred embodiment. The electric parking brake control system  100  can be utilized in the operation of a wide variety of different types of vehicles such as, for example, construction vehicles, according to the embodiment of the present invention. The electric parking brake control system  100  can be utilized for controlling at least one parking brake  190  associated with the vehicle. The parking brake control system  100  utilizes a series of electrically controlled valves that are in turn utilized to operate at least one valve to apply or release the vehicle&#39;s parking brakes  190 . The electrically controlled valves are solenoid valves that can be utilized to induce a “change of state” in the vehicle&#39;s parking brakes, as described below. 
         [0016]    The automatic electric parking brake control system  100  generally includes a solenoid air valve  180  that can be connected to an electric brake switch  150 . In general, the solenoid air valve  180  is basically a simple electromechanical unit utilized to control the opening and closing of the valve  180 . The parking brake system  100  further includes an air source  170 , such as an air reservoir, for supplying air pressure. The air can be routed from the air reservoir  170  to the solenoid valve  180 . A low-pressure switch  175  electrically communicates with the electric brake switch  150  via a connector  160 . The low-pressure switch  175  automatically returns the electric brake switch to the pulled position thereby opening the circuit and moving the solenoid air valve  180  to an exhaust position when the pressure from the air reservoir  170  goes below a preset limit. The solenoid valve  180  can be electrically grounded via a grounding terminal (GND). 
         [0017]    The electric brake switch  150  includes a PCB  110  incorporated with a time delay circuit  115 . The PCB  110  generally includes a number of resistors  112 , a number of diodes  114  and at least one capacitor  116  for electrical connections. A coil  130  can be connected to the resistor  112  and the capacitor  116 . A switch  120  can be connected to the battery  165  and the solenoid air valve  180  for controlling the parking brakes  190 . The connector  160  can be utilized to electrically connect the solenoid air valve  180 , the battery  165 , and the low-pressure switch  175  to the electric brake switch  150 . Note that the term PCB refers generally to a printed circuit board, which can be utilized to mechanically support and electrically connect electronic components (e.g. resistors  112 , diodes  114  and capacitors  116 ) via conductive pathways, or traces, etched from copper sheets laminated onto a non-conductive substrate. 
         [0018]    The electric brake switch  150  can be a single pole momentary contact switch and is spring loaded to a normally off position. However, it will be apparent to those skilled in the art that other type of switches can be utilized as desired without departing from the scope of the invention. The electric brake switch  150  can be depressed which provides a signal to the solenoid air valve  180  causing the valve  180  to move to an open position. In the open position, air from the reservoir  170  can pass through the solenoid air valve  180  and release the parking brakes  190 . When the electric brake switch  150  is pulled, a circuit is opened which moves the solenoid air valve  180  to an exhaust position. The pressure to the parking brake  190  then goes to atmospheric pressure and the parking brakes  190  can be applied. 
         [0019]    The electric brake switch  150  can be ultimately connected to the vehicle&#39;s battery  165 , which itself is grounded via the grounding terminal (GND). The time-delay circuit  115  can be utilized to change the state of the solenoid valve  180 . Activation of the switch  120  moves the solenoid valve  180  in a position that disengages the parking brake. The time delay circuit  115  delays the de-activation of switch  120  for a short period of time when power is disrupted. Accordingly, the possibility of inadvertent brake application due to electrical failure can be avoided. 
         [0020]      FIG. 2  illustrates a schematic view of the electric brake switch  150  associated with the electric parking brake control system  100 , in accordance with a preferred embodiment. Note that in  FIGS. 1-2 , identical or similar blocks are generally indicated by identical reference numerals. The basic function of the parking brake system  100  according to the present invention is actuating or releasing the parking brake  190  when the vehicle stands still by operating a push/pull knob  210 . The electric parking brake system  100  can be applied and released (on/off function) with regard to a predefined maximum force. When the push/pull knob  210  is in the pushed position, it can be released by the mechanical actuation of the operator or momentary loss of vehicle electrical power after a predetermined time delay. The electronic parking brake system  100  of the present invention includes the parking brake switch  150  adapted to deliver power from the battery  165  to desired elements of the parking brake system  100 . 
         [0021]    The electric brake switch  150  can be located in a dash panel (not shown) of the vehicle connected to the battery  165  for electric current and the solenoid air valve  180 . The electric brake switch  150  generally includes the push/pull knob  210 , a return spring  220 , a hold in coil  230 , and the PCB  110 . The push/pull knob  210  can be operated by an operator of the vehicle, is pushed in to release the parking brakes  190 , and pulled out to engage the parking brakes  190 . When an operator pushes in the push/pull knob  210 , the electric brake switch  150  is closed and the solenoid valve  180  is actuated, thus providing air pressure to the parking brakes  190 . 
         [0022]    As described above, when a low pressure is encountered in the air reservoir  170 , the low-pressure switch  175  automatically moves the solenoid air valve  180  to the exhaust position by deactivating coil  130  and thereby opening switch  120 . The electric brake switch  150  is of the latching type, which incorporates the time delay on release of the electric brake switch  150 . The control system  100  delays the application of the parking brakes  190  for a suitable short time interval, thereby allowing the inadvertent application of the parking brakes  190  due to momentary loss of the vehicle&#39;s electrical power. Note that the electric brake switch  150  may also be applied to other types of electro-hydraulic systems. 
         [0023]    Furthermore, the invention can include a unique combination of electric switch  150 , low-pressure switch  175 , and control for desired automation and/or semi-automatic operations. The switches  150  and  175  control solenoid air valves  180  external to the vehicle cab. The electric brake switch  150  is in communication with the pressure switch  175  for automatically applying the parking brakes  190 . The electric parking brake control system  100  also includes a parking brake control unit and/or an output contact (OC)  270  for receiving an output signal  260  and generating a control signal for controlling a desired driving element of the parking brake system  100 , based on the received signal. 
         [0024]    In addition to realizing a control strategy for controlling the electric parking brake system  100 , the OC  270  converts the driver&#39;s request signalized by the push/pull knob  210  into the relative control signals for the control of the electric parking brake system  100 . The OC  270  includes an electronic controlling device with an alarm function (not shown), especially for controlling the application force and detecting the wear of the brake linings, as well as with diagnostic means and safety logic. On the basis of the information on the vehicle speed and the operating status of the vehicle, the electric parking brake control system  100  is operated according to the driving situation. 
         [0025]    As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for the claims and/or as a representative basis for teaching one skilled in the art to variously employ the present invention. The brake control system  100  described herein also can be adapted for automatically controlling the parking brakes due to momentary loss of vehicle electrical power. Such system also reduces the space occupied in the dash panel due to the replacement of air-operated controls with the electric brake switch  150 . 
         [0026]    it will be appreciated that variations of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.