Abstract:
The present invention describes an innovative IBS braking system in which the regulation components are integrated with the brakes. The specific location of the fluid inlet components at the bottom of the brake and the return components positioned at the top of the brake present advantages for the renewal of the brake fluid. In the case of electronic failure, braking control is assured by a specific isolation device integrated within the brake. The general architecture of the control system can be totally decentralized due to the ability to integrate the various regulation methods of the brake: sensors, computers, and solenoid valves. This new concept, “intelligent brake”, uses the various signals supplied by the vehicle&#39;s computers to self-regulate.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to vehicle brakes and more particularly to the architecture of an hydraulic fluid regulation system integrated into individual brake assemblies.  
           [0003]    2. Description of the Prior Art  
           [0004]    As is commonly known, modern vehicles are equipped with braking systems having hydraulic controls for automobiles or pneumatic controls for heavy vehicles. When the brakes of a vehicle are applied, a braking force is generated between the wheel and the road surface that is dependent on various parameters which include the road surface condition and the amount of slip between the wheel and the road surface. This braking force increases as slip increases until a critical slip value is surpassed. Beyond the critical value of slip, the braking force decreases and the wheel rapidly is approaches lock-up. Therefore, many recent vehicles are also equipped with an anti-lock electronically controlled braking system (ABS), seeding to operate wheel slip at or near the critical slip value to achieve stable braking. This system analyses the electronic wheel speed signals and accordingly corrects the pressure in the braking circuit when it detects the beginning of a wheel lock-up. The actual controlling components are comprised of a centralized management module which integrates the electronic computer, the inlet and return solenoid valves, and the pump. Bach wheel speed sensor sends its own signal to the central computer.  
           [0005]    Applicant has developed a manufacturing technique for brakes, said ‘integrated contact’ brake, operated by a patented piston comprising an annular unrolling membrane. Applicant has also developed an electronic regulation system based on the measurements of the braking forces with a patented deformation sensor. Applicant has also developed patented control algorithms to carry out the continued regulation of braking when the available wheel traction has been surpassed. The whole electronic regulation system is called IBS—Intelligent Braking System.  
           [0006]    A known limitation of centralized solenoid valve braking regulation systems is the delay in response time caused by the fluid travelling a distance between the regulating solenoid valves situated in the central module and in each brake.  
           [0007]    Another limitation known in electronically regulated systems concerns the loss of pressure when the electronic control unit reduces the braking of one wheel at the beginning stages of wheel lock-up, due to the sudden loss of traction for example. This configuration requires significantly decreasing the brake pressure as quickly as possible, to quickly reduce the risk of braking with a locked wheel, which can contribute to pneumatic failure. The conventional electronically regulated braking systems are limited by the small size of the return solenoid valves which must satisfy a compromise between a fine regulation and a fast outlet, and also by the narrow brake source pipings which are dimensioned to resist high source pressure.  
           [0008]    Another known limitation of conventional hydraulic braking systems are: the inability to evacuate gas bubbles, created in the brake calliper if it becomes overheated during operation or as a result of poor initial purging of the circuit; and the inability to cool a fluid that is too hot.  
           [0009]    Therefore, it is desirable to have a pressure control device integrated with a brake assembly which overcomes the limitations.  
         SUMMARY OF THE INVENTION  
         [0010]    It is one object of the present invention to provide a brake pressure control device adapted to be integrated with a disk brake assembly.  
           [0011]    It is another object of the present invention to provide a disk brake integrated directly thereon with electro-hydraulic control elements.  
           [0012]    It is a further object of the present invention to provide the architecture of an hydraulic fluid regulation system for brakes of a vehicle which is integrated into each brake.  
           [0013]    In accordance with one aspect of the present invention, a device is adapted to be securely attached to an annular radial support wall of a disk brake and includes a solenoid valve having a first opening to be connected to a pressurized hydraulic fluid source, a second opening to be connected in fluid communication with a chamber in the disk brake assembly to apply an hydraulic pressure on a piston for a brake action, and a third opening to be connected to the hydraulic system for draining the hydraulic fluid from the disk brake assembly. The device includes an electronic control box associated with the regulating solenoid valve and housing an electrical brake control system, so that the pressurized hydraulic fluid supplied into and drained from the piston chamber is controlled by the regulating solenoid valve responding to a signal sent from the electronic control box. The device further includes a pressurized accumulator in fluid communication with the first passage of the valve body to directly feed the regulating solenoid valve.  
           [0014]    The device is preferably integrated with a torque sensor which is operatively attached to the brake assembly so that when the hydraulic fluid pressure is applied in the brake and while the wheel turns, the metal portion on which the sensor is affixed, is submitted to forces which determine the elongation in the structure of the brake and of the sensor. The sensor is electronically connected to the electrical brake control system in the electronic control box to send input signals to the system for the brake control.  
           [0015]    In accordance with another aspect of the present invention an hydraulic brake system is provided. The hydraulic brake system includes a central pump connected with an hydraulic fluid tank and driven by a motor to supply pressurized hydraulic fluid to individual disk brakes of a vehicle. Each disk brake is integrated with a regulating solenoid valve electronically controlled by an integrated electronic brake control system so that the pressurized hydraulic fluid supplied to and drained from the brake is controlled by the regulating solenoid valve in response to signals from the brake control system. Each brake is integrated with a pressurized accumulator in fluid communication with the system, to directly feed the valve when a brake action is required.  
           [0016]    Each disk brake preferably includes an additional outlet valve electronically connected to the brake control system in order to facilitate the hydraulic fluid drainage from the brake when the brake action is not required.  
           [0017]    The hydraulic brake system preferably further includes a backup system which includes a master cylinder connected in fluid communication with the hydraulic fluid tank and further connected to at least one pair of front or rear disk brakes for supplying the pressurized hydraulic fluid to the brakes when the brake control system fails. The backup system includes brake isolation-valves, each being positioned in fluid communication with the individual disk brake and the regulating solenoid valve associated with that disk brake, in order to ensure that the pressurized fluid is supplied to the disk brake only from the central pump through the regulating solenoid valve in a default condition, and the pressurized fluid is supplied to the disk brake only through the master cylinder when the master cylinder is actuated. The hydraulic fluid connection between the master cylinder and the brake isolation-valve of the disk brakes is further controlled by a master-cylinder isolation-valve which is electronically connected to the electronic control system, which permits the pressurized hydraulic fluid supply from the master cylinder to the disk brakes only when the brake control system fails.  
           [0018]    The present invention provides a simple but effective hydraulic brake system adapted to be integrated in each brake to form an intelligent brake assembly. Nevertheless, it is understood that the present invention is applicable to a similar pneumatic brake system.  
           [0019]    Other advantages and features of the present invention will be better understood with reference to the preferred embodiment described hereinafter.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    Having thus generally described the nature of the present invention, reference will now be made to the accompanying drawings by way of illustration of the preferred embodiments in which:  
         [0021]    [0021]FIG. 1. is an hydraulic brake system according to a preferred embodiment of the present invention, for use with an intelligent brake system to individually control brake pressures of a vehicle;  
         [0022]    [0022]FIG. 1A is an hydraulic brake system according to another preferred embodiment of the present invention, showing a radiator used in the hydraulic fluid return lines for cooling the fluid;  
         [0023]    [0023]FIG. 2 is a perspective view of a disk brake assembly integrated with a brake pressure control device according to one embodiment of the present invention;  
         [0024]    [0024]FIG. 3 is a partial perspective view of the brake assembly in FIG. 2 in a larger scale, showing the brake pressure control device;  
         [0025]    [0025]FIG. 4 is a partial cross-sectional view of the brake assembly showing the fluid passages in the regulating solenoid valve seat;  
         [0026]    [0026]FIG. 5 is a partial cross-sectional view of the disk assembly, showing the pressurized accumulator;  
         [0027]    [0027]FIG. 6 is a perspective view of a disk assembly according to another embodiment of the present invention, with a portion of the disk assembly removed, showing the brake pressure control device having an additional brake outlet-valve; and  
         [0028]    [0028]FIGS. 7 and 8 are cross-sectional views of a brake isolation-valve used in the hydraulic brake system shown in FIG. 1.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0029]    [0029]FIG. 1 illustrates an hydraulic brake system  10  including a force generation module  11 , an emergency activation module  15 , front brake assemblies  16   a  and rear brake assemblies  20   a , and a hydraulic fluid tank  26 .  
         [0030]    The force generation module  11  includes a central pump  12  connected through high pressure lines  14  to annular pistons  16  of the front brake assemblies  16   a  and annular pistons  20  of the rear brake assemblies  20   a , which are identical and will be referenced only as brake  16  hereinafter unless otherwise indicated. The central pump  12  is also connected through line  24  to the hydraulic fluid tank  26  and coupled with an electric motor  28  so that the pump  12  is driven by the electric motor  28  to pump the hydraulic fluid from the tank  26  to the individual brakes  16 . A check valve  30  is provided to ensure a predetermined maximum fluid pressure limit in the system. A pressurized accumulator  32  is also provided to ensure pressure stability in the high pressure lines  14 .  
         [0031]    The brake  16  is provided with a regulating solenoid valve  34  which is electronically connected to an intelligent braking system which allows the braking torque to be maintained at the maximum allowed by adherence to which the wheel is submitted, and is therefore to able to obtain the maximum efficiency for braking. The intelligent braking system upon receiving information signals from a torque sensor attached to the disk brake  16  processes the information signals and sends control signals to the regulating solenoid valve  34 , in order to control the introduction and drain of the pressurized hydraulic fluid into and from the brake  16 . The regulating solenoid valve  34  further proportionally controls the pressure of the hydraulic fluid supplied to the brake  16  according to the control signals from the intelligent braking system. The intelligent braking system is described in U.S. patent application Ser. No. 09/712,180, filed on Nov. 15, 2000 and assigned to the Applicant of this application. The intelligent brake system can be housed in an electric control box integrated into the regulating solenoid valve  34  and attached to the brake  16 .  
         [0032]    A pressurized brake accumulator  36  is provided for each of the brakes  16 , being connected with the high pressure lines  14  and positioned adjacent to the regulating solenoid valve  34  for directly feeding the pressurized hydraulic fluid through the valve  34  and into the brake  16 . Therefore, the time taken to transfer the fluid contained in the accumulator to the interior of the brake is reduced to a minimum when the regulating solenoid valve is situated at a position for supplying the fluid. The pressurized accumulator  36  will ensure that the brake  16  is actuated promptly.  
         [0033]    The regulating solenoid valve can be either opened proportionally, or can be operated fully opened or closed. It can have two channels when it is only managing the admission of the fluid into the brake, or three channels when it is also managing the outlet of the fluid to the reservoir with the use of an outlet return pipe  6 . All electronic control techniques are applicable to the desired performances.  
         [0034]    The hydraulic fluid drained from the brake  16  through the regulating solenoid valve  34  is directed through return lines  38  to the hydraulic fluid tank  26 .  
         [0035]    Additional drainage for each of the brakes  16  is provided through an additional outlet solenoid valve  40  which has a large opening integrated with the inner passage of the brake  16 , connected with a larger return line. The additional outlet solenoid valve  40  is also electronically connected to the intelligent braking system so that when a control signal for terminating a brake action is sent from the intelligent braking system, both the regulating solenoid valve  34  and the solenoid valve  40  are actuated to drain the hydraulic fluid from the brake  16  into the return lines  38 . This set up increases the speed of the pressure drop because of the large cross-section opening of the return solenoid valve  40  and the large cross-section of the return line. The solenoid valve  40  can be of the fully opened or closed variety, continually fed during a regulated time period, or electronically controlled to have a variable cyclic ratio for example, or proportionally opened and servo-controlled by flow or by pressure.  
         [0036]    Gas bubbles may be created in the inner passages of the brake if the brake becomes overheated during operation or as a result of poor initial purging of the hydraulic circuit, and the inability to cool the overheated hydraulic fluid. In order to evacuate the gas bubbles, the solenoid valve  40  is positioned next to the highest position of the brake piston  16 , replacing a purge screw, as shown in FIG. 1A, in which the large circle  16   a  indicates the entire brake assembly. Therefore, automatic purging with each action of the solenoid valve  40  occurs, and the gas infused fluid is evacuated by the return lines  38  into the hydraulic tank  26 , where the gas will come out of the fluid when the fluid comes into contact with atmospheric pressure.  
         [0037]    When the regulating solenoid valve  34  is positioned next to the lowest point of brake piston  16  as shown in FIG. 1A, a flush of the fluid inside the brake piston  16  cavity occurs with each action of the brake control. The fluid sucked from the tank by the pump  12  is transferred by the line  14  to the regulating solenoid valve  34 . The fluid used in the brake  16  returns to the tank  26  through the return line  38  when the braking pressure is released, and exchanges its heat with the fluid contained in the tank  26 . This device therefore regulates the temperature of the brake fluid.  
         [0038]    When a radiator element  18  is placed between the exit of the brake  16  and the tank  26  as shown in FIG. 1A, or if the tank  26  is itself a radiative element, a permanent exchange of caloric energy is realized between the brake  16  and the exterior surroundings. A low pressure fluid circulation can then be programmed when cooling of the brakes outside of the braking phases is to be done, for example, for a predetermined time after hard braking. This temperature regulation can then be controlled by one of several temperature sensors placed throughout the brake circuit or in close proximity of the hot elements of the braking system. The radiator can also be placed at other points along the hydraulic circuit.  
         [0039]    The emergency activation module  15  is used as a backup system which includes a master cylinder  42  connected through hydraulic fluid supply lines to the hydraulic fluid tank  26  and through safety lines  46  to each of the front brakes  16 .  
         [0040]    The backup safety line  46  to each of the front brakes  16  is controlled by a master cylinder isolation valve  48  which is a solenoid valve and electronically connected to the intelligent braking system. The master cylinder isolation valve  48  is normally closed and disconnects the safety line  46  from the master cylinder  42  to provide a resistance to the force applied by the driver to the brake pedal, if the IBS system works properly. When the IBS computer is in failure mode, or the driver turns the IBS system off, or if the vehicle&#39;s electric power has failed, the isolation solenoid valves  40  of the emergency activation module  15  are released to the open position and connect the master cylinder  42  to the front brakes  16  through the safety line  46 . The driver can then push the fluid of the master-cylinder  42  into the lines  46 . The safely lines  46  to each of the front brakes  16  can be a single pipe or a double pipe if imposed by regulations.  
         [0041]    A brake isolation valve  50  is provided for each of the brakes  16  to ensure a proper switch of the pressurized hydraulic fluid from the central pump  28  to the master cylinder  42 , or vice versa.  
         [0042]    The brake isolation valve  50  will now be described in detail with reference to FIGS. 7 and 8. The brake isolation valve  50  includes a body member  52  having a cylindrical chamber  54  formed therein. The cylindrical chamber  54  includes at one end, a section  56  having a smaller diameter (see FIG. 8). The body member  52  includes a first opening  58  at one end thereof and a second opening  60  at the other end thereof. The openings  58  and  60  are coaxial and extend inwardly, the opening  58  communicating with the smaller section  56  of the chamber  54  and the opening  60  communicating with the major section of the chamber  54 . The body member  52  further includes a third opening  62  at one side thereof, extending inwardly to communicate with the major section of the chamber  54 . A cylindrical valve body  64  is provided in the chamber  54 . One end section  66  of the valve body  64  which is provided with a seal ring  68 , is slidably received in the small section  56  of the chamber  54 . The valve body  64  includes a conical section  70  at the other end thereof. The valve body  64  has a central cylindrical cavity  72  slidably receiving a valve core  74  with a surrounding seal ring  76 . Axial passages  78  and  80  extend from the opposite ends of the valve body inwardly to the central cavity  72  and radial passages  82  extend from the periphery of the valve body  64  inwardly to an end of the central cavity  72  adjacent to the end section  66  of the valve body  64 . In a default condition the valve body  64  is forced to its left hand extremity position by the spring  84 , and the valve core  74  is forced to its left hand extremity position by spring  86 , as shown in FIG. 7, so that the opening  58  which is connected to the master cylinder  42  is closed while the opening  60  which is connected to the fluid supply controlled by the intelligent braking system is in fluid communication with the opening  62 , which is in turn connected to the brake  16 . In this default condition, the brake isolation valve  50  permits pressurized hydraulic fluid to be supplied and drained only through the regulating solenoid valve  34  controlled by the intelligent system.  
         [0043]    As shown in FIG. 8, when the intelligent braking system fails, the master cylinder  42  in FIG. 1 is actuated and no pressurized hydraulic fluid is directed to opening  60  of the brake isolation valve  50 . The pressurized hydraulic fluid from the master cylinder  42  enters the opening  58  of the brake isolation valve  50  to push the valve body  64  to its right hand extremity against the spring  84  to close the opening  60 , while the pressurized hydraulic fluid entering through the axial passage  78  into the central cavity  72  pushes the valve core  74  to move to the right hand extremity against the spring  86 . Thus, the pressurized hydraulic fluid is able to flow through the axial passages  60  into the chamber  54  and further to the brake  16  through the opening  62 . When the brake action is terminated, the hydraulic fluid from the brake  16  is drained through the opening  62  and opening  60  until the force exerted on the end of the valve body  64  and the end of the valve core  74  by the hydraulic fluid pressure at the opening  58 , is smaller than the respective spring forces applied by the springs  84  and  86 . At this point, the valve body  64  and the valve core  74  under the spring forces will return to the default condition as shown in FIG. 7, ready for the next brake action controlled by the intelligent braking system.  
         [0044]    The installation of a computer (not shown) on the brake assembly permits the creation of the intelligent brake in which sensors, solenoid valves, accumulator, and computer are mounted and cabled together. Thus, the brake becomes capable of self-regulating the braking torque according to the signals received from the various computers on board the vehicle, such as driver actions (personalised to the identity of the driver for example), vehicle behaviour, (electronic stability control program for example), anti-theft system (lock-up of the brakes in case of break-in for example), traction control, etc.  
         [0045]    Structural embodiments of the present invention, as examples, are described below with references to FIGS. 2-6.  
         [0046]    In FIG. 2, a disk brake, generally indicated by numeral  100  includes a device  102  for individual pressure control of the brake. The device  102  is integrated with a disk brake assembly  104  of the type described in U.S. patent application Ser. No. 09/678,092, filed on Oct. 4, 2000 and assigned to the Applicant of this application, which is incorporated by reference herewith. Nevertheless, it is understood that the device  102  is adapted to be integrated with any type of disk brake which uses pressurized hydraulic fluid or pressurized air to produce the brake force.  
         [0047]    The device  102  includes an hydraulic fluid pressure control assembly  106  with an inlet connector  108  and an outlet connector  110  to be connected with the respective high pressure line  14  and return line  38  shown in FIG. 1 for receiving and draining the hydraulic fluid. The device  102  further includes a torque sensor  112  which is described in Applicant&#39;s U.S. patent application Ser. No. 09/712,180 and is operatively attached to a support plate  114 . The support plate  114  has three mounting arms  116  secured to an annular radial support wall  118  of the disk brake assembly  104  by means of threaded bolts  120 . The support plate  114  has a central opening  122  to permit an end section of a drive shaft (not shown) extending therethrough, to transmit a torque to rotate the wheel. The torque sensor  112  is attached to one of the axial arms  116  so that when a brake force is applied and the wheel still turns, the side of the radial arm  116  of the support plate  114  on which the torque sensor  112  is attached is submitted to forces which determine the elongation of the radial arms  116  and of the torque sensor  112 . The torque sensor  112  transforms the changes of the torque forces to electronic information signals to be sent to the intelligent braking system housed in an electronic box  146 , in which the information signal is processed and converted into the control signals. The control signals are then sent to the hydraulic fluid pressure control assembly  106  to control the brake pressure.  
         [0048]    The device  102 , particularly the hydraulic fluid pressure control assembly  106  will now be described in detail with reference to FIGS. 3-5. The hydraulic fluid control assembly  106  includes a base member  124 . The base member  124  has a first cavity  126  for receiving a solenoid valve core member  128  therein and an inlet  130  and an outlet  132  in fluid communication with the first cavity  128 . The inlet connectors  108  and outlet connector  110  are installed in the inlet  130  and the outlet  132  respectively The base body member  124  further includes a passage  134  extending inwardly from a contacting surface  136  to the first cavity  126  and is adapted to be in fluid communication with a passage  138  which extends through the annular radial support wall  118  to an annular chamber  140  of the bladder assembly of the disk brake assembly  104 , The bladder assembly applies a brake force to the brake shoe  142  when pressurized hydraulic fluid is introduced therein. When the hydraulic fluid pressure control assembly  106  is attached to the disk brake assembly  104 , the contacting surface  136  of the base body member  124  abuts a corresponding contacting surface of the annular radial support wall  118 . The passage  128  should be aligned with the passage  138  and then the base body member  124  is secured to the annular radial support wall  118  using three threaded bolts  144 .  
         [0049]    The electronic box  146  which houses a micro-computer and electric circuits of IBS (not shown), is secured to the base body member  124 . One end of the regulating solenoid valve core member  128  extends into the electric box  146 , integrated with the electric circuits in the electronic box  146  to form a regulating solenoid valve which can control the axial proportional displacement of the regulating solenoid valve core member  128  located in the first cavity  126  according to the control signals sent from the computer installed in the electric box  146 , thereby controlling the hydraulic fluid flow through the solenoid valve into or out of the brake. The regulating solenoid valve is well known in the art and will not be further described.  
         [0050]    The electronic box may not include a micro-computer but may be linked with an IBS computer on board the vehicle to achieve the IBS control.  
         [0051]    The base body member  124  further includes a second cavity  148  in a cylindrical shape and having a passage  150  in fluid communication with the inlet passage  130  and the first cavity  126 . A piston  152  with sealing rings  153  is snuggly and slidably received in the second cylindrical cavity  148 , and is biased towards the passage  150  under a force exerted by a spring (not shown). Thus, the second cavity  148  acts as a pressurized accumulator to receive the pressurized hydraulic fluid and maintain a quantity of the hydraulic fluid with pressure, when the pressurized hydraulic fluid is supplied through the inlet  130  into the brake assembly  104 . The hydraulic fluid with pressure maintained in the second cavity  148  is then ready to feed into the annular chamber  140  of the bladder assembly in the next brake action. The second cylindrical cavity  148  is positioned adjacent to the regulating solenoid valve core member  128  so that the brake action will take place instantly when the brake action is requested.  
         [0052]    For the reasons discussed above with reference to FIG. 1A, the hydraulic fluid pressure control assembly should be attached to the annular radial support wall  118  at a lowest position adjacent to the annular chamber  140  of the bladder assembly. Therefore, the passage  138  in the annular radial support wall  118  should be positioned accordingly.  
         [0053]    Another embodiment of the present invention is shown in FIG. 6 in which a disk brake  110   a  includes a device for individual hydraulic fluid pressure control  102  integrated into the disk brake assembly  104 , which is similar to the embodiment described above and will not be redundantly described. Nevertheless, the disk brake  110   a  is provided with an additional hydraulic fluid outlet  156  controlled by an outlet solenoid valve  158  which is equivalent the outlet solenoid valve  40  shown in FIG. 1. A second outlet connector  160  is installed in the additional outlet  156  to be connected to the return line of the hydraulic fluid control system shown in FIG. 1. The operation and the feature of the additional hydraulic fluid outlet has been well described with reference to FIG. 1, and will not be redundantly described again (redundant because in this context it has roughly the same meaning as “redundantly”).