Abstract:
The present invention relates to a pressure sensor employed in a stability control apparatus for a vehicle. According to an aspect, there is provided a pressure sensor installed to a hydraulic unit and being in contact with a circuit board of an electronic control unit to sense brake oil pressure. The pressure sensor comprises a connecting terminal formed on the circuit board of the electronic control board and comprising a press-fit terminal; a press-fit being in slidable and movable contact with the press-fit terminal; and a spring connecting the press-fit and the press-fit terminal.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    The present invention relates to a pressure sensor employed in a stability control apparatus for a vehicle, and more particularly, to a pressure sensor, which makes it possible to be in stable contact with an electronic control unit under a condition where an excessive vibration is generated. 
         [0003]    2. Description of the Related Art 
         [0004]    In general, a vehicle is provided with a brake system for reducing speed or braking. The brake system comprises a pedal for transmitting driver&#39;s operating force, a booster and a master cylinder connected to the pedal to generate brake oil pressure, and a wheel brakes for braking wheels of the vehicle according to the brake oil pressure inputted from the booster and the master cylinder. 
         [0005]    In the brake system, when the driver steps on the brake pedal to generate the braking force, if the braking force is larger than a road friction force or the friction force generated on the wheel brake by the braking force is larger than the braking force generated on a tire or road surface, a slip phenomenon where the tire skids on the road surface is generated. 
         [0006]    In the meantime, in a state where the brake operates as described above, a steering system becomes locked, and thus, the driver cannot steer the vehicle in his or her desired direction. 
         [0007]    Accordingly, an anti-lock brake system (ABS) which electronically controls brake pedal force has been developed such that a driver can steer a vehicle in his or her desired direction when the slip phenomenon is generated. 
         [0008]    The anti-lock brake system comprises a hydraulic unit to which a plurality of solenoid valves, low-pressure accumulators and high-pressure accumulators for adjusting brake oil pressure to be transmitted to the wheel brake and an electronic control unit (ECU) for controlling components that electronically operate. 
         [0009]    The hydraulic unit is also provided with a pressure sensor for sensing brake operating pressure generated in the master cylinder in proportion to the brake pedal force generated by a driver and transmitting an electrical signal on the sensed brake operating pressure to the electronic control unit. The electronic control unit controls the operation of the brake in response to the electrical signal transmitted from the pressure sensor. 
         [0010]      FIG. 1  is an exploded perspective view of a pressure sensor  10  according to a prior art. Referring to  FIG. 1 , the pressure sensor  10  is mounted in a hole formed at a leading end of a master cylinder and electrically connected to a circuit board of an electronic control unit through additional connector and cable. 
         [0011]    The pressure sensor  10  comprises pin members  24 , which is in contact with the circuit board of the electronic control unit, and a lower guide  26 , which guides movement of the pin members  24  and to which a contact board  22  is coupled. In addition, a spring  25  is coupled to each of the pin members  24  to elastically support the pin member  24 . 
         [0012]    Furthermore, an upper guide  18  is coupled to an upper portion of the contact board  22 , and an electric component module  16  having a pressure sensing unit and a control unit provided therein is coupled to an upper portion of the upper guide  18 . In the meantime, springs  20  electrically connecting the contact board  22  and the electric component module  16  are installed to the upper guide  18 . 
         [0013]    Also, a sensor module  14  in which various kinds of sensors are mounted is installed to an upper portion of the electric component module  16 . 
         [0014]    The various kinds of components of the pressure sensor  10  are integrally configured by a housing  12 . In the meantime, O-rings  12   a  and  12   b  are installed at upper and lower portions of the housing  12 . 
         [0015]    In a case where the braking force is generated by the driver&#39;s brake pedal force, an electrical signal is generated in the pressure sensor  10  by a small vibration. Then, the pressure sensor  10  is electrically connected to the circuit board by the pin members  24  which are elastically urged by the springs  25 , whereby the electrical signal generated in the pressure sensor  10  is transmitted to the electronic control unit. 
         [0016]    However, the pressure sensor  10  according to the prior art has a problem in that if large vibration is generated, the springs  20  and  24  may be compressed and thus the pin member  24  may be separated from the circuit board of the electronic control unit. Also, in the conventional pressure sensor  10 , the pin members  24  are not accurately connected to terminals of the circuit board, whereby signal transmission or electrical connection becomes unstable due to a contact error caused by the inaccurate connection. Furthermore, in the conventional pressure sensor  10 , since the pin members  24 , which are in contact with the circuit board, are made of a rigid material, when shock is applied, the pin members  24  are inertially moved by vibration and the like, so that a contact error can be easily generated. There is a problem in that a connecting terminal of the circuit board is damaged by shock or friction generated between the pin members  24  and the circuit board. Also, there is a problem in that when lateral vibration is generated, the conventional pressure sensor  10  cannot absorb this lateral vibration appropriately. As described above, if the contact error between the conventional pressure sensor  10  and the electronic control unit is generated, this contact error acts as the factor affecting the steering and braking performances of a vehicle. Accordingly, development for a pressure sensor that can be connected to a circuit board of an electronic control unit through a new method is desired. 
       BRIEF SUMMARY 
       [0017]    The present invention is conceived to solve the aforementioned problems in the prior art. According to one embodiment, a pressure sensor is provided, which can be in stable connect with a circuit board of an electronic control unit, has a simple coupling structure without soldering, and can be securely mounted to prevent signal transmission or electrical connection caused by vibration and the like from being interrupted. 
         [0018]    According to one embodiment, a pressure sensor has an improved inner structure to allow the pressure sensor to be stably connected to a circuit board, can prevent a coupling error from occurring to easily perform an assembling process, and can absorb lateral vibration. 
         [0019]    According to one aspect, there is provided a pressure sensor installed to a hydraulic unit and being in contact with a circuit board of an electronic control unit to sense brake oil pressure. The pressure sensor comprises a connecting terminal formed on the circuit board of the electronic control board and comprising a press-fit terminal; a press-fit being in slidable and movable contact with the press-fit terminal; and a spring connecting the press-fit and the press-fit terminal. 
         [0020]    Further, the press-fit terminal preferably comprises a central portion having a lower end coupled to the connecting terminal of the circuit board and electrically connected thereto, and a pair of extension portions extending upward from both sides of the central portion, the press-fit terminal having elasticity for allowing the ends of the extension portions to be in elastic contact with the press-fit. Furthermore, the press-fit terminal may comprise a guide portion formed on the end of the extension portion to be inclined outwardly for allowing the press-fit to be easily inserted thereinto. 
         [0021]    In addition, according to another aspect, there is provided a pressure sensor installed to a hydraulic unit and being in contact with a circuit board of an electronic control unit to sense brake oil pressure. The pressure sensor comprises a contact terminal being in contact with the circuit board of the electronic control unit, wherein the contact terminal consists of a first coil spring portion being in contact with the circuit board of the electronic control unit and a second coil spring portion extending from the first coil spring portion to connect to the pressure sensor, the first coil spring portion having a winding density larger than that of the second coil spring portion. 
         [0022]    Here, the first coil spring portion preferably has a spring constant larger than that of the second coil spring portion. In addition, the first coil spring portion preferably has a winding diameter smaller than that of the second coil spring portion. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0023]      FIG. 1  is an exploded perspective view of a pressure sensor according to a prior art; 
           [0024]      FIG. 2  is a schematic side view of the configuration of an anti-lock brake system, showing a pressure sensor according to one embodiment; 
           [0025]      FIG. 3  is an exploded perspective view of the pressure sensor of  FIG. 2 . 
           [0026]      FIG. 4  is a sectional view showing a state where the pressure sensor of  FIG. 2  is connected to a circuit board by a connecting unit; 
           [0027]      FIG. 5  is a schematic side view of an anti-lock brake system, showing a pressure sensor according to another embodiment; 
           [0028]      FIG. 6  is an exploded perspective view of the pressure sensor of  FIG. 5 ; and 
           [0029]      FIG. 7  is an enlarged front view of a contact terminal of the pressure sensor of  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    Hereinafter, some embodiments will be explained in detail with reference to the accompanying drawings. 
         [0031]      FIG. 2  is a view of the configuration of an anti-lock brake system, showing a pressure sensor according to a first embodiment of the present invention. 
         [0032]    As shown in  FIG. 2 , a pressure sensor  80  according to one embodiment is mounted to a hydraulic unit  60  of an anti-lock brake system  50 . The anti-lock brake system  50  comprises the hydraulic unit  60  to which a plurality of solenoid valves, low-pressure accumulators and high-pressure accumulators for adjusting brake oil pressure to be transmitted to the wheel brake, and an electronic control unit (ECU)  70  for controlling components that electronically operate. 
         [0033]    The solenoid valve of the hydraulic unit  60  can adjust brake oil pressure of a wheel brake installed on a wheel. The wheel brake is rubbed with a wheel by the oil pressure of the solenoid valve to directly generate braking force. To this end, a pump for pumping brake oil is connected to the solenoid valve. The operation of the solenoid valve or the pump is electrically controlled by the electronic control unit  70 . 
         [0034]    In addition to the hydraulic unit  60  and the electronic control unit  70 , the anti-lock brake system  50  comprises a boosting device  54  for generating boost force by a brake pedal force of a brake pedal  52  and a master cylinder  56  communicating with an oil storage tank  58  to transmit brake oil pressure to the wheel brake. 
         [0035]    Furthermore, wheel sensors are installed to front and rear wheels for sensing a wheel speed and transmitting an electrical signal on the wheel speed to the electronic control unit  70 . 
         [0036]    The electronic control unit  70  receives an electrical signal on brake pressure of the master cylinder  56  sensed by the pressure sensor  80 . Then, the electronic control unit  70  controls the opening/closing operation of the respective solenoid valves and the additional operation of a motor depending on the transmitted electric signal to thereby control the anti-lock operation of the brake. To this end, the electronic control unit  70  comprises a circuit board  72  to which an integrated circuit (IC) chip is mounted, wherein a program for anti-lock control is inputted in the IC chip. 
         [0037]    Referring to  FIG. 3 , which is an exploded perspective view of the pressure sensor  80  according to one embodiment, the pressure sensor  80  comprises a housing  82 , and the housing  82  has O-rings  82   a  and  82   b  provided at upper and lower portions thereof. A sensor module  84  to which various sensors  85  are mounted is embedded in the upper portion of the housing  82 . In addition, an electric component module  86  having a pressure-sensing unit and a control unit is coupled to a lower portion of the sensor module  84 . Further, a lower portion of the electric component module  86  is provided with a connecting member to connect to the circuit board  72  of the electronic control unit  70  ( FIG. 4 ). 
         [0038]    The connecting member comprises an upper guide  88  coupled to the lower portion of the electric component module  86 . In addition, a contact board  92  is installed to a lower portion of the upper guide  88 . A connecting member is installed to the upper guide  88  to connect the contact board  92  and connecting terminals  87  provided at a lower portion of the electric component module  86  to each other. In order to stably transmit the signal when the contact board  92  is vibrated, the connecting member may comprise springs  90 . Furthermore, the upper guide  88  is formed with a plurality of through holes  89  for providing spaces allowing the springs  90  to be inserted thereinto. The springs  90  inserted into the through holes  89  can be elastically and freely deformed in the longitudinal direction. 
         [0039]    Further, in the pressure sensor  80 , a connecting unit which is in direct contact with the circuit board  72  of the electronic control unit  70  is provided at a lower portion of the contact board  92 . 
         [0040]      FIG. 4  is a view showing a state where the pressure sensor  80  is connected to the circuit board by the connecting unit. Referring to  FIG. 4 , the pressure sensor  80  is connected to connecting terminals formed on the circuit board  72  of the electronic control unit  70 . To this end, press-fit terminals  74  are utilized as the connecting terminals of the circuit board  72  of the electronic control unit  70 . Also, the connecting unit of the pressure sensor  80  comprises press-fits  94  respectively connected to the press-fit terminals  74 . 
         [0041]    The movement of the press-fits  94  is guided by the lower guide  96  coupled to the lower portion of the contact board  92 . The lower guide  96  is formed with a plurality of through holes  97 , into each of which the press-fit  94  is movably inserted. 
         [0042]    In a state where the press-fit  94  is inserted in and connected to the press-fit terminal  74 , the press-fit slides therein to maintain the contact with the circuit board of the electronic control unit  70 . In addition, a spring  95  which is in contact with the contact board  92  of the pressure sensor  80  is provided around each press-fit  94 . The spring  95  is elastically deformed when the press-fit  94  is vibrated, and maintains the electrical connection with the contact board  92  of the pressure sensor  80 . Accordingly, when the pressure sensor  80  and the electronic control unit  70  are vibrated, the elastic deformation of the springs  95  or the slide of the press-fits  94  in the press-fit terminals  74  absorbs the vibration. 
         [0043]    Here, the press-fit terminal  74  comprises a central portion  74   a  having a lower end coupled to the connecting terminal of the circuit board  72  and electrically connected thereto, and a pair of extension portions  74   b  extending upward from both sides of the central portion  74   a.    
         [0044]    In addition, the press-fit terminal  74  is made of a material having predetermined elasticity, and ends of the pair of extension portions  74   b  are arranged to face each other, so that it possible to maintain the contact between the press-fit terminal and the press-fit  94  inserted by the elastic force. 
         [0045]    Accordingly, when the press-fit  94  is inserted into the press-fit terminal  74 , a gap between the extension portions  74   b  widens and the extension portions  74   b  come into contact with the press-fit, so that an electrical connection therebetween is maintained. 
         [0046]    More preferably, the press-fit terminal  74  is formed with guide portions  74 c for guiding the insertion of the press-fit  94 . The guide portions  74   c  are respectively formed on the ends of the extension portions  74   b  to be inclined outward. Accordingly, when the press-fit  94  is inserted into the press-fit terminal  74 , an end of the press-fit  94  comes into contact with the guide portions  74   c,  so that the extension portions  74   b  are bent outward, and then, the press-fit  94  is inserted into the press-fit terminal  74  and electrically connected thereto. 
         [0047]    An operation of the pressure sensor according to the above-described embodiment will be described as follows. 
         [0048]    First, the pressure sensor  80  senses brake pressure, which is generated by the driver&#39;s brake pedal force and increased by the master cylinder  56 , and then transmits a signal on the increased pressure to the electronic control unit  70 . Accordingly, the operation of the brake is controlled according to a pattern programmed in the electronic control unit  70 . 
         [0049]    The pressure sensor  80  is installed to the hydraulic unit  60  which is mounted with a plurality of solenoid valves, low pressure-accumulators and high pressure-accumulators. Then, the pressure sensor  80  is electrically connected to the circuit board  72  of the electronic control unit  70  to enable the electrical signal to be transmitted to the circuit board  72 . 
         [0050]    In such a pressure sensor  80 , the press-fits  94  which are the electrical connecting terminals are inserted into the press-fit terminals  74  of the circuit board. The end of the press-fit  94  comes into contact with the guide portions  74   c  formed on the extension portions  74   b  of the press-fit terminal  74 , and the press-fit  94  pushes the extension portions  74   b  outwardly and inserted in the press-fit terminal  74  as the press-fit  94  is continuously inserted therein. 
         [0051]    When vibration is transmitted from the electronic unit  70  to the press-fit  94 , the press-fit  94  is moved up and down in the press-fit terminal  74  to absorb the vibration. 
         [0052]    In addition, as the contact board  92  slides in a state where the press-fit  94  is inserted into the press-fit terminal  74 , it is possible to maintain the electrical connection between the contact board  92  and the circuit board  72 . The electrical connection therebetween can also be maintained by the elastic deformation of the spring  95 . 
         [0053]    When the driver steps on the brake pedal  52  to transmit the brake pedal force to the master cylinder  56 , the master cylinder  56  increases the brake pressure in proportion to the magnitude of the brake pedal force. Then, the brake pressure increased in the master cylinder  56  is sensed by the pressure sensor  80  of the hydraulic unit  60  ( FIG. 2 ). 
         [0054]    Then, the pressure sensor  80  senses the pressure of the master cylinder  56  and converts the sensed pressure into an electrical signal, and transmits the electrical signal to the circuit board  72  of the electronic unit  70  through the connecting means provided at the lower portion of the pressure sensor  80 . 
         [0055]    In the pressure sensor  80 , the sensed pressure is converted into the electric signal through the sensor module  84  mounted with the sensor  85  and the electric component module  86  comprising the pressure-sensing unit and the control unit, and the electrical signal is transmitted to the contact board  92  via the springs  90  acting as the connecting member  90  and then transmitted to the press-fits  94  through the springs  95 . Then, the press-fits  94  are connected to the press-fit terminals  74  of the circuit board  72  to transmit the electrical signal thereto. 
         [0056]    On the other hand, it will be apparent that a structure of the contact terminal of the pressure sensor can be modified to withstand a lateral load. 
         [0057]      FIG. 5  is a view of an anti-lock brake system, showing a pressure sensor according to another embodiment, and  FIG. 6  is an exploded perspective view of the pressure sensor of  FIG. 5 . 
         [0058]    The pressure sensor  50  of this embodiment differs from and the pressure sensor according to the aforementioned embodiment in the connecting member connected to the circuit board of the electronic control unit. In other words, there is a difference in that the second embodiment has no press-fit employed therein and no press-fit terminal provided on the circuit board of the electronic control unit. 
         [0059]    The connecting member is provided with the upper guide  88  coupled to the lower portion of the electric component module  86  and the contact board  92  at the lower portion of the upper guide  88 . The upper guide  88  is provided with the connecting members  90  for connecting the contact board  92  and the connecting terminals  87  provided at the lower portion of the electric component module  86 . In order to stably transmit the signal when the contact board  92  is vibrated, springs  90  may be employed as the connecting members  90 . Furthermore, the upper guide  88  is formed with a plurality of through holes  89  for allowing the connecting members  90  to be elastically and freely deformed in the longitudinal direction. 
         [0060]    Referring to  FIG. 6 , contact terminals  194 , which are in direct contact with the circuit board  72  of the electronic control unit  70 , are connected to the lower portion of the contact board  92 . The movement of the contact terminals  194  is guided by the lower guide  96  coupled to the lower portion of the contact board  92 . To this end, the lower guide  96  is formed with a plurality of through holes  97  in which the contact terminals  194  can be movably inserted. 
         [0061]    Referring to  FIG. 7 , the contact terminal  194  comprises a coil spring, which can be elastically deformed to a predetermined length in a state where the coil spring is in contact with the circuit board  72  of the electronic control unit  70 . In addition, even though the circuit board  72  of the electronic control unit is laterally moved, the contact terminal  194  is bent and absorbs the deformation. 
         [0062]    In the meantime, the contact terminal  194  is formed such that its upper portion differs from lower portion in winding density. That is, the contact terminal  194  consists of a first coil spring portion  194   a  to be in contact with the circuit board  72  and a second coil spring portion  194   b  extending from the first coil spring portion  194   a  and connected to the pressure sensor  80  through the contact board  92 . 
         [0063]    The first coil spring portion  194   a  has a winding density higher than the second coil spring portion  194   b.  Preferably, the first coil spring portion  194   a  is larger than the second coil spring portion  194   b  in spring constant, so that a gap between the windings of the first coil spring portion  194   a  becomes smaller than that of the second coil spring portion  194   b.  Furthermore, the contact terminal  194  is formed such that a winding diameter d 1  of the first coil spring portion  194   a  is smaller than a winding diameter d 2  of the second coil spring portion  194   b.  Accordingly, as compared with the second coil spring portion  194   b,  the first coil spring portion  194   a  can withstand larger pressure. 
         [0064]    In addition, it is preferable that a length L 1  of the first coil spring portion  194   a  and a length L 2  of the second coil spring portion  194   b  are designed such that each of the first coil spring portion  194   a  and the second coil spring portion  194   a  has the appropriate elasticity depending on an amount of vibration of the circuit board  72  and the like. 
         [0065]    The operation of the pressure sensor  80  according to this embodiment will be described as follows. 
         [0066]    First, as the driver steps on the brake pedal  52  to transmit the brake pedal force to the master cylinder  56 , the master cylinder  56  increases brake pressure in proportion to the magnitude of the brake pedal force. Then, the brake pressure increased in the master cylinder  56  is sensed by the pressure sensor  80  of the hydraulic unit  60 . 
         [0067]    Then, the pressure sensor  80  senses the pressure of the master cylinder  56  and converts the sensed pressure into an electrical signal, and is connected to, and transmits the electrical signal to, the circuit board  72  of the electronic unit  70  through the connecting means provided at the lower portion of the pressure sensor  80 . 
         [0068]    In the pressure sensor  80 , the sensed pressure is converted into the electric signal through the sensor module  84  mounted with the sensor  85  and the electric component module  86  comprising the pressure-sensing unit and the control unit, and the electrical signal is transmitted to the contact board  92  via the springs acting as the connecting members  90  and then transmitted to the contact terminal  194  through the contact board  92 . Then, the contact terminal  194  is connected to the circuit board  72  to transmit the electrical signal thereto. 
         [0069]    In the meantime, if vibration is generated between the hydraulic unit  60  and the electronic control unit  70 , the contact terminal  194  of the pressure sensor  80  absorbs the vibration. The second coil spring portion  194   b  of the contact terminal  194 , which is in contact with the contact board  92 , is rapidly deformed in the longitudinal or lateral direction, and the first coil spring portion  194   a  formed integrally with the second coil spring portion  194   b  absorbs small vibration as well as an elastic deformation to maintain the electrical connection with the circuit board  72 . 
         [0070]    Based on the foregoing, a pressure sensor according to one embodiment has a press-fit installed therein and connected to a press-fit terminal of the electronic control unit, so that there are advantages in that the pressure sensor can be stably connected to an electronic control unit and there is no need to perform a soldering work to allow an assembling work to be simply performed and the pressure sensor is simply installed. In addition, since the pressure sensor is stably connected to the electronic control unit, an electrical connection therebetween is not interrupted although a vibration is generated, and the electrical connection can be maintained stably and continuously. In addition, in a pressure sensor according to one embodiment has a coil spring consisting of two coil spring portions having different winding densities may be used as the contact terminal that is in electrical contact with the circuit board of the electronic control unit. Thus, the difference in winding density of the contact terminal makes it possible to rapidly absorb vibration and elastic deformation, so that a continuous electrical connection can be achieved. 
         [0071]    Although the pressure sensor according to the present invention has been described with reference to the drawings and the preferred embodiments, the present invention is not limited thereto but defined by the appended claims. It will be understood by those skilled in the art that various modifications and changes can be made thereto within the scope of the invention defined by the appended claims. 
         [0072]    The various embodiments described above can be combined to provide further embodiments. All of the U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet are incorporated herein by reference, in their entirety. Aspects of the embodiments can be modified, if necessary to employ concepts of the various patents, applications and publications to provide yet further embodiments. 
         [0073]    These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.