Abstract:
A hydraulic unit for a slip control system of a hydraulic vehicle brake system comprises a hydraulic block including a socket, a first port, a pressure change damper, and a second port. The socket has a base and defining a first interior. The first port is located at the base of the socket. The pressure change damper defines a second interior and is positioned in the socket in engagement with the first port. The first port is in fluidic communication with the second interior. The second port is in fluidic communication with the second interior via a portion of the first interior outside of the pressure change damper.

Description:
[0001]    This application claims priority under 35 U.S.C. §119 to patent application no. DE 10 2014 211 382.2, filed on Jun. 13, 2014 in Germany, the disclosure of which is incorporated herein by reference in its entirety. 
         [0002]    The disclosure relates to a hydraulic unit for a slip control system of a hydraulic vehicle brake system. 
       BACKGROUND 
       [0003]    Slip control systems of hydraulic vehicle brake systems have hydraulic units with hydraulic components for slip control. Such hydraulic components are solenoid valves, check valves, hydraulic pumps, hydraulic accumulators, damper chambers and restrictors. For mechanical fastening and hydraulic interconnection of the hydraulic components, such hydraulic units have hydraulic blocks. The hydraulic blocks are normally cuboidal flat blocks made of metal, e.g. an aluminum alloy. Sockets for the hydraulic components are formed in the hydraulic blocks, typically being embodied as blind holes of stepped diameter into which the hydraulic components are inserted, pressed or installed in some other way and fastened, for example, by swaging. Lines are produced by drilling the hydraulic block, said lines extending predominantly parallel to edges of the hydraulic block, i.e. in a Cartesian pattern, and hydraulically interconnecting the sockets and the hydraulic components installed therein. A hydraulic block equipped with the hydraulic components for slip control can be understood as a hydraulic unit. 
         [0004]    The hydraulic block or hydraulic unit is connected to a brake master cylinder by brake lines, and hydraulic wheel brakes are connected to the hydraulic unit or hydraulic block by brake lines. 
         [0005]    European Patent EP 1 623 118 B1 discloses a hydraulic block of this kind for an antilock control system in a hydraulic vehicle brake system, having a pressure change damper which is arranged in a socket in the hydraulic block and communicates via a connecting line produced as a hole with an outlet of a piston pump, which is likewise arranged in a socket in the hydraulic block. At the same time, the pressure change damper communicates via the outlet of the piston pump with an isolation valve, by means of which the hydraulic unit is connected to a brake master cylinder, and with brake pressure buildup valves, by means of which the wheel brakes are connected to the hydraulic unit. The pressure change damper is used to damp pressure surges, pressure pulsation and pressure oscillations of brake fluid at the outlet of the piston pump. The pressure change damper of the known hydraulic unit has just one port and no separate inlet and outlet. 
       SUMMARY 
       [0006]    A pressure change damper of the hydraulic unit according to an embodiment of the disclosure has two ports, one of which forms an inlet of the pressure change damper and communicates with an outlet of a piston pump of the hydraulic unit and the other forms an outlet of the pressure change damper, and having an isolation valve, by means of which the hydraulic unit can be connected or is connected to a brake master cylinder of a hydraulic vehicle brake system, and having one or more brake pressure buildup valves, by means of which the one or more wheel brakes can be connected or is/are connected to the hydraulic unit. According to the disclosure, the hydraulic block has two ports for the pressure change damper, which are drilled, for example, and can also be understood as lines or connecting lines in the hydraulic block, one of which forms an inlet and the other forms an outlet for the pressure change damper. One of the two ports issues at a base of the socket for the pressure change damper in the hydraulic block; the other port can likewise issue at the base of the socket for the pressure change damper but at a different location from the first port, or the other port does not issue at the base but, for example, at a circumference of the socket for the pressure change damper in the hydraulic block. The pressure change damper is arranged in the socket in the hydraulic block in such a way that it rests on the one port for the pressure change damper and thereby separates the two ports hydraulically, thus ensuring that brake fluid which flows in through the one port must flow through the pressure change damper in order to be able to flow out through the other port. A brake fluid flow directly from one port into the other port, past the pressure change damper, is excluded—apart from possible leakage. The compulsory flow through the pressure change damper ensures damping of pressure surges, pressure pulsation and pressure oscillations of brake fluid or at least improves damping. By way of example, the pressure change damper can rest internally against a circumference of the one port, internally against a circumference of a cylindrical or conical countersink of the one port or, while surrounding the port, can rest on the base of the socket for the pressure change damper. Sealing contact of the pressure change damper in the socket, which separates the two ports for the pressure change damper in the hydraulic block hydraulically in a pressure tight manner from one another is preferred although it is not essential for damping. In the event of leakage, a brake fluid flow from one port directly into the other port, past the pressure change damper, is small in comparison with the brake fluid flow through the pressure change damper, and the brake fluid flow flowing past the pressure change damper is greatly restricted because it has to flow through a narrow cross section between the socket of the hydraulic block and the pressure change damper resting in the socket. The high degree of restriction likewise causes damping. Pressure tight sealing of the pressure change damper in the socket of the hydraulic block is essentially indispensable for pressure tight hydraulic separation of the two ports of the pressure change damper if the pressure change damper has a check valve which closes against an inflow of brake fluid from one brake master cylinder through an isolation valve, when the latter is open, and through the port, which per se forms the outlet of the pressure change damper, into the pressure change damper. At least one such check valve is provided by embodiments of the disclosure to ensure that, in the case of brake actuation by means of the brake master cylinder, no brake fluid flows out of the brake master cylinder into the pressure change damper, something that lengthens an actuating travel of the brake master cylinder, i.e. a brake pedal travel or a brake lever travel, and would cause an unwanted “soft” brake pedal or hand brake lever feel because of elasticity of the pressure change damper. 
         [0007]    The dependent claims relate to other advantageous embodiments and developments. 
         [0008]    Further features of the disclosure will become apparent from the following description of an embodiment of the disclosure in conjunction with the claims and the drawing. The individual features can be implemented individually or jointly in any desired combination in embodiments of the disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The FIGURE shows a section through one half of a hydraulic block of a hydraulic unit according to the disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    The hydraulic unit  1  according to the disclosure, which is shown in the drawing, is part of a slip control system (otherwise not shown) of a hydraulic vehicle brake system. Such slip control systems are known and they are used for antilock control, traction control and/or vehicle-dynamics or antiskid control. The abbreviations ABS, ASR, FDR and ESP are customary for these control systems. The hydraulic unit  1  has a cuboidal hydraulic block  2 , which consists, for example, of an aluminum alloy and has been machined. In elevation, the hydraulic block  2  is rectangular, almost square, and it is flat, namely approximately ¼ to ⅓ as thick as it is long or wide. The drawing shows a section through one half of the hydraulic block  2  on one side of the longitudinal center plane  3 , with respect to which the hydraulic block  2  is symmetrical. The hydraulic block  2  has sockets  4  for hydraulic components of the slip control system. Such components are solenoid valves, of which a suction valve  5  is shown by way of example, check valves, hydraulic accumulators and piston pumps as hydraulic pumps (not shown), and pressure change dampers  6  according to the disclosure. The sockets  4  into which the hydraulic components are inserted or in which they are arranged are embodied as blind holes or through holes of stepped diameter. The sockets  4  and the hydraulic components arranged therein are interconnected hydraulically by lines  7 , which, like the socket  4 , are produced by drilling the hydraulic block  2 . The hydraulic block  2  serves for the mechanical fixing and hydraulic interconnection of the hydraulic components of the slip control system. The drilling of the hydraulic block  2  and the arrangement of the hydraulic components is Cartesian, i.e. the sockets  4  for the hydraulic components, the lines  7  for the hydraulic interconnection of the hydraulic components and the hydraulic components are arranged in a Cartesian pattern, i.e. parallel or at right angles to one another and to surfaces and edges of the hydraulic block  2 . This does not exclude one or more oblique holes. 
         [0011]    The pressure change damper  6  has a damper housing  8  which is dome-shaped, i.e. is in the form of a cylindrical tube and closed by a hemisphere at one end. At its open end, which is situated in the socket  4  in the hydraulic block  2 , the damper housing  8  of the pressure change damper  6  has a diameter step  9  of enlarged diameter, into which an oppositely oriented valve housing  10  is inserted. The valve housing  10  has a stepped diameter with frustoconical diameter steps, although radial diameter steps are also possible. One of the diameter steps has holes distributed over a circumference as inlet openings  11  of the pressure change damper  6 . An outlet opening  12  is provided coaxially in an end wall of the valve housing  10  remote from the damper housing  8  of the pressure change damper  6 . In the damper housing  8 , the pressure change damper  6  has a damper body  13  in the form of a corrugated tube made of an elastomer, one end of which is closed and the end of which that is adjacent to the valve housing  10  is open. A retaining ring  14  holds the open end of the damper body  13  in the damper housing  8  of the pressure change damper  6 . The retaining ring  14  has an encircling bead  15 , which engages in a groove in the open end of the damper body  13  and in this way holds the open end of the damper body  13 . The retaining ring  14  furthermore has a flange  16 , which is fixed between the segment  9  of increased diameter of the damper housing  8  and the valve housing  10 . 
         [0012]    Two ports  17 ,  18 , of which one port  17  forms an inlet and the other port  18  forms an outlet, issue into the socket  4  for the pressure change damper  6 . The port  17  forming the inlet issues eccentrically at a base  19  of the socket  4  for the pressure change damper  6 , close to a circumference of the socket  4 . This port  17  extends obliquely and is aligned in such a way that it can be drilled through a mouth of the socket  4 . The other port  18 , which forms the outlet, extends parallel to the axis and close to the center and issues by means of a coaxial cylindrical countersink  20  into the base  19  of the socket  4  for the pressure change damper  6 . A hollow-cylindrical end of the valve housing  10  of the pressure change damper  6  is pressed into the countersink  20  of the port  18  forming the outlet, ensuring that it rests with a pressure tight seal on the circumference of the countersink  20 . In this way, the two parts  17 ,  18  for the pressure change damper  6  in the hydraulic block  2  are separated hydraulically from one another, ensuring that brake fluid cannot flow directly from one port  17  into the other port  18  but has to flow into and out of the housing  10  and hence into and out of the pressure change damper  6  through the inlet opening  11  and the outlet opening  12  in order to pass from one port  17  to the other port  18 . 
         [0013]    A valve seat part  21 , which has a central hole forming a valve seat  22  for a springless check valve  23 , is pressed into the valve housing  10 . The check valve  23  has a ball as a shutoff member  24 , although this is not compulsory for the disclosure. The shutoff member  24  of the springless check valve  23  is arranged in a coaxial countersink in a cylindrical shutoff member  25  of a spring-loaded check valve  26 . An axial through hole  27  leads from the countersink in which the shutoff member  24  of the springless check valve  23  is accommodated, through the shutoff member  25  of the spring-loaded check valve  26 . The through hole  27  has a segment of small diameter, which forms a restrictor  28 . In the segment of larger diameter, the through hole  27  has longitudinal ribs  29  projecting radially inwards, which extend as far as the entry of the through hole  27  into the countersink in which the shutoff member  24  of the springless check valve  23  is arranged. The longitudinal ribs  29  prevent the shutoff member  24  of the springless check valve  23  from blocking the through hole  27 . On its outer side, the cylindrical shutoff member  25  of the spring-loaded check valve  26  has outward-projecting longitudinal ribs  30 , which guide shutoff member  25  in an axially movable manner in the valve seat part  21  and allow a flow around shutoff member  25 . As a valve spring  31 , the spring-loaded check valve  26  has a helical compression spring, which is supported on the end wall of the valve housing  10  and presses shutoff member  25  against an end wall of the valve seat part  21 , which forms a valve seat of the spring-loaded check valve  26 . 
         [0014]    The pressure change damper  6  is fixed in the socket  4  of the hydraulic block  2  by a “self-clinch” technique: for this purpose, a swaging collar  32  is arranged on the damper housing  8  in the socket  4 , close to the mouth, said collar having on its outer side an encircling groove  33 , into which material of the hydraulic block  2  is plastically deformed when it is pressed into the socket  4 , holding the swaging collar  32  and sealing it pressure tightly in the mouth of the socket  4 . The swaging collar  32  rests against the diameter step  9  of the damper housing  8  and in this way holds the pressure change damper  6  in the socket  4  and the end of the valve housing  10  in the countersink  20  of port  18  at the base of the socket  4 . 
         [0015]    The two ports  17 ,  18  issue into a socket  4  for a slip control piston pump (not shown). The ports  17 ,  18  are arranged in such a way that the port  17  forming the inlet of the pressure change damper  6  communicates with an outlet of the piston pump and the port  18  forming the outlet of the pressure change damper  6  communicates by means of a line  7  with the isolation valve (not shown), by means of which the hydraulic block  2  is connected to the brake master cylinder (likewise not shown), and to brake pressure buildup valves (not shown), by means of which the wheel brakes (not shown) are connected to the hydraulic block  2 . Brake fluid delivered by the piston pump (not shown) flows through the port  17  forming the inlet, the socket  4  and the inlet openings  11  into the pressure change damper  6 . The damper body  13  and, by virtue of their restricting effect, the check valves  23 ,  26  and the restrictor  26  damp pressure surges, pressure pulsation and pressure oscillations of the brake fluid from the piston pump. The brake fluid flows out of the pressure change damper  6  through the springless check valve  23  into the port  18  forming the outlet. During this process, the brake fluid must flow through the restrictor  28 , improving damping. An increased pressure in the pressure change damper  6  opens the spring-loaded check valve  26 , making available an additional flow cross section for the brake fluid from the piston pump. The two check valves  23 ,  26  are connected hydraulically in parallel with one another and the restrictor  28  is arranged hydraulically downstream of the springless check valve  23 . Moreover, both check valves  23 ,  26  and the restrictor  28  are arranged hydraulically downstream of the pressure change damper  6 . 
         [0016]    If a brake pressure which passes through the socket  4  for the piston pump (not shown) is built up for brake actuation in the line  7  by means of the brake master cylinder (not shown), the check valves  23 ,  26  shut off, with the result that no brake fluid flows out of the brake master cylinder into the pressure change damper  6 . As a result, the brake master cylinder does not displace any brake fluid volume into the pressure change damper  6 , which would lengthen an actuating travel of the brake master cylinder and would cause an unwanted, soft “pedal feel” owing to elasticity of the damper body  13 . 
         [0017]    The pressure change damper  6  is arranged in the hydraulic block  2  in an axial plane of the socket  4  for the piston pump (not shown). The damper housing  8  projects perpendicularly from a flat side of the hydraulic block  2 , which is here referred to as valve side  34 . The solenoid valves of the hydraulic unit  1 , of which the suction valve  5  is shown, also project from the valve side  34 . The suction valve  5  is arranged in the hydraulic block  2  between the pressure change damper  6  and the longitudinal center plane  3  of the hydraulic block  2 , parallel to the pressure change damper  7 , in the same axial plane as the socket  4  for the piston pump. Like the pressure change damper  6 , the suction valve  5  is secured and sealed off pressure tightly in the socket  4  by means of a self-clinch technique. The socket  4  for the piston pump issues radially into an eccentric space  35 , which is formed as a blind hole of stepped diameter in the longitudinal center plane  3  of the hydraulic block  2 . The eccentric space  35  serve to accommodate an eccentric (not shown), which can be driven by electric motor, for driving the piston pump (not shown). 
         [0018]    When fitted with the hydraulic components, the hydraulic block  2  forms the hydraulic unit  1  of the slip control system of the hydraulic vehicle brake system (otherwise not shown).