Abstract:
Disclosed herein is a pulsation damping device of a hydraulic brake system. The pulsation damping device of a hydraulic brake system which attenuates a pressure pulsation of brake oil discharged from a pump, the device comprises a damping portion installed to be inserted into a bore in communication with an inport into which the brake oil flows and an outport through which the brake oil is discharged, and a cap coupled to one end of the bore to block the one end, wherein a flow path is formed on an outer circumferential surface of the damping portion to guide the brake oil introduced into the inport to be discharged through the outport, and the flow path is formed in a longitudinal direction of the damping portion to be continuously connected from the inport to the outport.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of Korean Patent Application No. 2015-0126783, filed on Sep. 8, 2015 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    Embodiments of the present disclosure relate to a hydraulic brake system, and more particularly, to a pulsation damping device of a hydraulic brake system which attenuates a pressure pulsation of brake oil discharged from a pump. 
         [0004]    2. Description of the Related Art 
         [0005]    In general, in order to control brake hydraulic pressure to be transferred to a brake of a vehicle, a hydraulic brake system includes a modulator block, in which a plurality of solenoid valves, a low pressure accumulator in which oil is temporarily stored, a pump disposed to be connected to an outlet of the low pressure accumulator for pumping the oil stored in the low pressure accumulator, and a motor for driving the pump are installed, and an electronic control unit (ECU) for controlling components by which the modulator block is electrically operated. 
         [0006]    Such a hydraulic brake system adopts and uses various structures including a pulsation damping device having a predetermined damping space for attenuating a pressure pulsation which is generated because hydraulic pressure of brake oil discharged from a pump is at high pressure, an orifice portion at an outport through which brake oil is discharged via the pulsation damping device, etc. For example, a generally known pulsation damping device is formed to attenuate a pressure pulsation generated according to pressure discharged from a pump by having a damping space, a spring provided in the damping space, a piston elastically supported by the spring, a sealing member for shielding the damping space from the outside, etc. 
         [0007]    However, since a structure for installation of the above-described pulsation damping device is complex, there are problems in that a manufacturing process is difficult and cost is also increased. Further, since a structure in which the pressure pulsation is attenuated using the spring is formed, there is a problem in that a pressure pulsation attenuation function is not smoothly performed because durability of the spring or the like is degraded when the spring is used for a long time. 
       SUMMARY 
       [0008]    Therefore, it is an aspect of the present disclosure to provide a pulsation damping device of a hydraulic brake system having a simple structure to be easily installed and capable of efficiently attenuating a pressure pulsation. 
         [0009]    Additional aspects of the disclosure will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the disclosure. 
         [0010]    In accordance with one aspect of the present disclosure, a pulsation damping device of a hydraulic brake system which attenuates a pressure pulsation of brake oil discharged from a pump, the device comprising: a damping portion installed to be inserted into a bore in communication with an inport into which the brake oil flows and an outport through which the brake oil is discharged; and a cap coupled to one end of the bore to block the one end, wherein a flow path is formed on an outer circumferential surface of the damping portion to guide the brake oil introduced into the inport to be discharged through the outport, and the flow path is formed in a longitudinal direction of the damping portion to be continuously connected from the inport to the outport. 
         [0011]    The flow path is formed so that size of area through which the brake oil flows is variable. 
         [0012]    The flow path includes a portion where size of area decreases as going from the inport to the outport. 
         [0013]    Size of the portion where the size of the area of the flow path decreases smoothly decreases. 
         [0014]    The flow path is formed in a spiral shape in a longitudinal direction of the damping portion. 
         [0015]    The cap and the damping portion are integrally formed. 
         [0016]    The flow path connects the inport in communication with an inner circumferential surface of the bore with the outport in communication with a closed end surface of the bore. 
         [0017]    An outer circumferential surface of the damping portion is in contact with an inner circumferential surface of the bore, and a lower end thereof is installed to be spaced a predetermined gap from a bottom surface of the bore. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    These and/or other aspects of the disclosure will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
           [0019]      FIG. 1  is a hydraulic circuit diagram schematically illustrating a hydraulic brake system provided with a pulsation damping device according to an exemplary embodiment of the present disclosure. 
           [0020]      FIG. 2  is a perspective view of an assembly illustrating a state in which a pulsation damping device provided in a hydraulic brake system according to an exemplary embodiment of the present disclosure is being assembled in a modulator block. 
           [0021]      FIG. 3  is a perspective view of the assembly shown in  FIG. 2 . 
           [0022]      FIG. 4  is a cross-sectional view illustrating a flow of brake oil whose pressure pulsation is attenuated by the pulsation damping device of the hydraulic brake system. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Hereinafter, embodiments of the present disclosure will be described in detail with reference to accompanying drawings. The accompanying drawings are examples which provide the concept of the present disclosure to those skilled in the art. The present disclosure is not limited to the accompanying embodiments and may be implemented in different forms. Parts irrelevant to description are omitted in the drawings in order to clearly describe the present disclosure, and widths, lengths, and thicknesses of components in the drawings may be exaggerated for convenience of description. 
         [0024]      FIG. 1  is a hydraulic circuit diagram schematically illustrating a hydraulic brake system provided with a pulsation damping device according to an exemplary embodiment of the present disclosure. 
         [0025]    Referring to  FIG. 1 , the hydraulic brake system includes a brake pedal  10  to which an operating force of a driver is applied, a brake booster  11  which increases pedal effort due to the pedal effort of the brake pedal  10 , using a pressure difference between vacuum pressure and atmospheric pressure, a master cylinder  20  which generates pressure using the brake booster  11 , a first hydraulic circuit  40 A which connects a first port  21  of the master cylinder  20  and wheel cylinders  30  provided on two wheels FR and RL and controls hydraulic pressure transmission, and a second hydraulic circuit  40 B which connects a second port  22  of the master cylinder  20  and wheel cylinders  30  provided on the two remaining wheels FL and RR and controls hydraulic pressure transmission. The first hydraulic circuit  40 A and the second hydraulic circuit  40 B are compactly installed in a modulator block  40 . 
         [0026]    Each of the first hydraulic circuit  40 A and the second hydraulic circuit  40 B includes solenoid valves  41  and  42  for controlling brake hydraulic pressure transferred to two pairs of wheel cylinders  30 , a pump  44  for suctioning and pumping brake oil discharged from wheel cylinders  30  or brake oil discharged from the master cylinder  20  by driving a motor  45 , a low pressure accumulator  43  for temporarily storing the brake oil discharged from the wheel cylinders  30 , a main flow path  47   a  which connects an outlet of the pump  44  to the master cylinder  20 , an auxiliary flow path  48   a  which guides the brake oil from the master cylinder  20  to an inlet of the pump  44  to be suctioned, and an electronic control unit (ECU) (not shown) which controls driving of the plurality of solenoid valves  41  and  42  and the motor  45 . 
         [0027]    Here, as shown in the drawing, the solenoid valves  41  and  42 , the low pressure accumulator  43 , the pump  44 , the main flow path  47   a,  and the auxiliary flow path  48   a  are provided in each of the first and second hydraulic circuits  40 A and  40 B. 
         [0028]    More specifically, the plurality of solenoid valves  41  and  42  are related to upstream side and downstream side of each of the wheel cylinders  30  and are classified as a normal open type solenoid valve  41 , which is disposed at the upstream side of each wheel cylinder  30  and usually maintains an open state, and a normal closed type solenoid valve  42  which is disposed at the downstream side of each wheel cylinder  30  and usually maintains a closed state. Opening and closing operations of the solenoid valves  41  and  42  are controlled by the ECU, and the normal closed type solenoid valve  42  is opened by decompression braking so that brake oil discharged from the wheel cylinder  30  is temporarily stored in the low pressure accumulator  43 . 
         [0029]    The pump  44  is driven by the motor  45  and suctions and discharges the brake oil stored in the low pressure accumulator  43 , and hydraulic pressure is thus transferred to the wheel cylinder  30  or the master cylinder  20 . 
         [0030]    Further, a normal open type solenoid valve  47  (hereinafter, a TC valve) for a traction control system (TCS) is installed in the main flow path  47   a  which connects the master cylinder  20  to an outlet of the pump  44 . The TC valve  47  usually maintains an open state and, during a general braking using the brake pedal  10 , transfers brake hydraulic pressure generated from the master cylinder  20  to the wheel cylinder  30  through the main flow path  47   a.    
         [0031]    Further, the auxiliary flow path  48   a  is branched from the main flow path  47   a  to guide brake oil discharged from the master cylinder  20  to be suctioned at the inlet of the pump  44 , and a shuttle valve  48  is installed on the auxiliary flow path  48   a  so that the brake oil is only introduced into the inlet of the pump  44 . The shuttle valve  48  which is electrically operated is installed in the middle of the auxiliary flow path  48   a,  is usually closed, and is operated to be open in a TCS mode. 
         [0032]    Meanwhile, the unmentioned reference number ‘ 49 ’ is a check valve installed at a suitable position in a flow path for preventing a backflow of brake oil, the reference number ‘ 50 ’ is a pressure sensor which detects a brake pressure transferred to the TC valve  47  and the shuttle valve  48 , and the reference number ‘ 51 ’ is an orifice. 
         [0033]    When braking is performed in the hydraulic brake system described above, a pressure pulsation is generated from a hydraulic pressure pumped from the pump  44  according to operation of the motor  45 . Thus, according to one embodiment of the present disclosure, a pulsation damping device  100  connected to the outlet of the pump  44  of each of the hydraulic circuits  40 A and  40 B is provided for attenuating a pressure pulsation. 
         [0034]      FIG. 2  is a perspective view of an assembly illustrating a state in which a pulsation damping device provided in a hydraulic brake system according to an exemplary embodiment of the present disclosure is being assembled in a modulator block,  FIG. 3  is a perspective view of the assembly shown in  FIG. 2 , and  FIG. 4  is a cross-sectional view illustrating a flow of brake oil whose pressure pulsation is attenuated by the pulsation damping device of the hydraulic brake system. 
         [0035]    Referring to  FIGS. 2 to 4 , the pulsation damping device  100  according to one embodiment of the present disclosure is provided at an inport  102  through which brake oil discharged from the pump  44  (see  FIG. 1 ) flows and a bore  101  in communication with an outport  103  through which brake oil is discharged. Here, as the pulsation damping device  100  is provided in the main flow path  47   a  (see  FIG. 1 ), the inport  102  is connected to the main flow path  47   a  connected to the outlet of the pump  44 , and the outport  103  is connected to the main flow path  47   a  connected to the master cylinder  20 . The pulsation damping device  100  includes a damping member  110  installed in the bore  101  and configured to guide the brake oil introduced into the inport  102  to be discharged through the outport  103 . 
         [0036]    The damping member  110  includes a cap  115  which blocks one end of the bore  101  and a guide portion  111  which guides the flow of brake oil. Here, the cap  115  and the guide portion  111  are integrally formed. 
         [0037]    The cap  115  is installed to block one open end of the bore  101 . That is, the cap  115  prevents oil introduced into the bore  101  from leaking to the outside. 
         [0038]    The guide portion  111  is installed to be in contact with an inner circumferential surface of the bore  101 . A flow path  112  is formed in the guide portion  111  to guide the brake oil introduced into the inport  102  to be discharged through the outport  103 . 
         [0039]    The flow path  112  is formed on an outer circumferential surface of the guide portion  111 . More specifically, the flow path  112  is formed in a spiral shape on the outer circumferential surface of the guide portion  111 . Thus, brake oil is guided along the flow path  112  and discharged through the outport  103 . That is, the pulsation damping device  100  according to one aspect of the present disclosure forcibly guides the flow of the brake oil so that the brake oil is discharged through the outport  103 . In the flow path  112 , size of area through which brake oil passes is formed to be variable. For example, in the flow path  112 , the size of area decreases as going from the inport  102  to the outport  103 . Accordingly, when brake oil introduced into the inport  102  flows along the flow path  112 , the size of the area through which the brake oil flows is reduced and resistance against the oil flow is thus generated. Thus, a pressure pulsation of brake oil at high pressure decreases, and the brake oil flows along the flow path  112 . It is illustrated and described that the size of area of the flow path  112  through which the brake oil flows is smoothly decreased, but the present invention is not limited thereto and the size may be irregularly decreased. Further, pitch of the flow path  112  formed in the guide portion  111  may be selectively increased or decreased. 
         [0040]    A lower end of the damping member  110  is installed to be spaced a predetermined gap from a bottom surface of the bore  101  so that brake oil introduced into the bore  101  is discharged through the flow path  112 . That is, the flow path  112  is connected to each of the inport  102  and the outport  103  via a predetermined space formed between the damping member  110  and the bottom surface of the bore  101 , guides the flow of the brake oil, and attenuates a pressure pulsation of brake oil discharged from the pump  44 . 
         [0041]    Meanwhile, the damping member  110  may be formed of a steel or plastic material having high stiffness using an injection-molding or forging method. Accordingly, cost can be reduced. Further, the damping member  110  may be formed of a rubber material having elasticity. That is, when a rubber material is used for the damping member  110 , a volume of the flow path  112  is changed according to an inflow of brake oil at high pressure so as to improve damping effect and mitigate impacts, and thus a pressure pulsation may be attenuated. 
         [0042]    Subsequently, a state in which a pressure pulsation is attenuated by the pulsation damping device  100  will be described. 
         [0043]    Brake oil discharged at high pressure by pumping of the pump  44  is transferred to the pulsation damping device  100  through the inport  102 . The brake oil introduced through the inport  102  is forcibly guided by the flow path  112  formed in the damping member  110  and is discharged through the outport  103 . Here, size of area of the flow path  112  is formed to decrease toward the outport  103  so that pressure is changed by a change in speed of the brake oil. That is, the size of area through which the brake oil passes is decreased, resistance against an oil flow is increased, and thus a pressure pulsation can be attenuated. 
         [0044]    As is apparent from the above description, it is advantageous that a pressure pulsation can be attenuated because the pulsation damping device of a hydraulic brake system according to one embodiment of the present disclosure is provided with a flow path in a spiral shape formed on an outer circumferential surface of a damping member so that a flow path has an increased length. 
         [0045]    Further, it is advantageous that a pressure pulsation can be attenuated by inducing a change in pressure based on a change in flow speed of brake oil by forming size of area of a flow path to be variable and decreasing as going from an inport to an outport, and thus operating noise can be reduced. 
         [0046]    Meanwhile, it is advantageous that, in addition to installation time reduction, manufacturing cost can be reduced by manufacturing a pulsation damping device using an injection-molding or forging method, by providing the pulsation damping device as a single member. 
         [0047]    As described above, while the present disclosure has been described with reference to specific embodiments and drawings, the present disclosure is not limited thereto. It should be clear to those skilled in the art that various modifications and alterations may be made without departing from the spirit and scope of the present disclosure and equivalents of the appended claims. 
       REFERENCE NUMERALS 
       [0000]    
       
           100 : Pulsation Damping Device 
           101 : Bore 
           102 : Inport 
           103 : Outport 
           110 : Damping Member 
           112 : Flow Path