Patent Document

BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to a device for damping pressure pulsations, and a hydraulic unit equipped with this device, in an electronically regulatable vehicle brake system. For regulating the brake pressure required at the wheel brake cylinders, electronically regulatable vehicle brake systems require pump elements, which are acted upon as needed by a rotating drive element. This action is effected cyclically, and as a result, pressure pulsations can occur in the hydraulic circuit connected to it during the regulation cycle. The pressure pulsations can be transmitted to the brake pedal via the master cylinder located in the hydraulic circuit. The consequence is unwanted pulsating motions of this brake pedal as well as noise that is perceptible in the vehicle interior. 
   2. Description of the Prior Art 
   For damping the pressure pulsations in an electronically regulatable brake system, a device is already known from German Patent Disclosure DE 42 34 013 A1.  FIG. 3  of this reference shows a hydraulic block of an electronically controllable vehicle brake system, with a receiving bore which forms the housing of the device. The receiving bore is closed off from its surroundings by a cap anchored by positive engagement, and in its interior it defines a damping chamber. An inflow conduit arriving from a pump element discharges into this chamber, and an outflow conduit emerges from it. At the exit point of the outflow conduit there is a throttle, along with a separate filter element preceding the throttle. The filter element prevents clogging of the throttle from an accumulation of dirt. 
   It is a disadvantage of the design of this known noise-damping device that the filter and the throttle are each individual components, which must be anchored to the hydraulic block in separate assembly steps. The individual components are of metal and are relatively complicated to produce, in multiple machining steps. Their reliable fixation must be checked and assured during assembly. This makes the known device comparatively expensive. 
   OBJECT AND SUMMARY OF THE INVENTION 
   With the above background, it is the object of the present invention to provide both a device for damping pressure pulsations and a hydraulic unit equipped with this device, which preclude these disadvantages and, with a design that is as space-saving and economical as possible, have especially good damping properties. 
   The proposed device for damping pressure pulsations includes a function element, in which the throttle and the filter are combined in a single component. This function element can be anchored in the interior of a housing of the damping device, in a single work step that is simple to perform. It can be produced without metal-cutting machining and hence economically, preferably by injection molding from plastic. By means of a filter preceding the throttle, clogging of the throttle by dirt contained in the pressure fluid is averted. Otherwise, a clogged throttle could cause an impermissible pressure increase that could damage the components in the hydraulic unit. In an extreme case, the pressure increase could even cause leaks of the hydraulic unit and thus could lead to total failure of the brake system. An orientation aid can be mounted on the proposed device. With this orientation aid, the device can be oriented in a targeted way during the assembly process. With the orientation of the function element, additional prevention of an accumulation of air bubbles in the device is achieved. Since air bubbles can cause a reduction in the braking power, they are especially critical to function. Moreover, air that has already invaded the brake system can be eliminated again by a process of scavenging with pressure fluid. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood and further objects and advantages thereof will become more apparent from the ensuing detailed description of a preferred embodiment, taken in conjunction with the drawing, in which: 
       FIG. 1 , in a three-dimensional perspective view, shows the housing block of a hydraulic unit of an electronically regulatable vehicle brake system, with the device for damping pressure pulsations mounted on it; 
       FIG. 2  shows an outline of the device of the invention in the form of an enlarged detail; 
       FIG. 3  shows a cross section through this device for damping pressure pulsations; and 
       FIG. 4  shows the function element of the damping device as an individual part, viewed from its underside. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  shows a housing block  12  of a hydraulic unit  10  of an electronically regulatable vehicle brake system in which the block  12  is formed by a metal body, preferably produced by extrusion, which is machined by metal-cutting techniques to form the most various kinds of installation chambers  14 . The installation chambers  14  are intended in particular to receive electronically triggerable magnet valves, pump elements, at least one drive element for these pump elements, pressure reservoirs, connections for brake lines, or devices for damping pressure pulsations. Moreover, pressure fluid conduits  16  are embodied in the housing block  12 , which connect these various components hydraulically with one another for converting the hydraulic circuit of the vehicle brake system. 
   The installation chambers  14  are open toward at least one outer side of the housing block  12  and, together with the pressure fluid conduits  16  are oriented essentially at right angles to one another. This is favorable from a production standpoint, because then the requisite metal-cutting machining of the housing block  12  can be performed in as few chucking operations as possible. 
   For the sake of simplicity,  FIG. 1  shows only a single device  18  for damping pressure pulsations for the sake of disclosure of the invention. This damping device  18  includes an installation chamber  14   a , open toward one outer side, into the opening of which a hollow-cylindrical sleeve body  20 , closed on one end, is inserted. This sleeve body  20  protrudes, with its closed end, past that outer side of the housing block  12  where an electronic control unit is attached in a later stage of assembly. Then, the sleeve body  20  protrudes into the interior of this control unit. The end of the installation chamber  14   a  of the damping device  18  located inside the housing block  12  communicates, via two short, straight branch conduits  22 , with an installation chamber  14   b  of one pump element. As shown in  FIG. 1 , this installation chamber  14   b  is located below the installation chamber  14   a  of the damping device  18 , and its longitudinal axis extends transversely to the longitudinal axis of the installation chamber  14   a . The tie conduits  22  form the inlet  22   a  and the outlet  22   b  ( FIG. 2 ) of the damping device  18  and thus assure the flow through it of pressure fluid. A hydraulic short circuit between the inlet  22   a  and the outlet  22   b  is averted by means of the outer contour of the built-in pump element (not visible in the drawing). 
     FIG. 2  shows a view into the interior of the installation chamber  14   a  of the damping device  18 . Inserted into it according to the invention is a one-piece function element  24 , which includes a tubular first part  24   a  and a radially protruding second part  24   b  integrally formed onto the first. The tubular first part  24   a  extends onward on both sides of the second part  24   b . The lower extension, not visible in  FIG. 1 , of the tubular part  24   a  is inserted into the tie conduit, forming the inlet  22   a , far enough that the end face, toward the tie conduits  22 , of the second part  24   b  rests on the bottom of the installation chamber  14   a . This end face covers the orifice cross section of the second tie conduit, forming the outlet  22   b , into the interior of the damping device  18 . In the exemplary embodiment shown, the second part  24   b  of the function element  24  is disk-shaped, with two opposed, parallel end faces. The end face toward the bottom of the installation chamber  14   a  has an inward-oriented chamfer extending all the way around. Three flow grooves  26 , for example, emerge at the outer circumferential surface of this chamfer and together form a (gap) filter, which traps contaminants in the pressure fluid. 
     FIG. 2  furthermore shows an orientation aid, in the form of a flat face  28  which is embodied for example on the circumferential surface of the upward-protruding portion of the tubular first part  24   a . This orientation aid  28  is oriented relative to the flow grooves  26  in order to determine the desired position of these flow grooves  26  in the installation of the function element  24  from above into the installation chamber  14   a . The background for such an arrangement will now be described in conjunction with  FIG. 3 . 
     FIG. 3  shows a detail of circular shape of the housing block  12 , with the installation chamber  14   a  embodied in it for the damping device  18 . The part of  FIG. 3  that is not shaded indicates the bottom face of the installation chamber  14   a . It can be seen that the installation chamber  14   a  has a cross section in the form of a circular area flattened on one side. Approximately at the center point of this circular area, the inlet  22   a  discharges into the interior of the installation chamber  14   a . Radially offset from the inlet  22   a , the outlet  22   b  of larger cross section can be seen. The latter is covered by the disk-shaped second part  24   b  of the function element  24 . The visible free portion of the outlet  22   b  is in communication with a crescent-shaped, groovelike recess  30 , which begins at the end face, toward the bottom of the installation chamber  14   a , of the function element  24 . This crescent-shaped recess  30  is opposed by a corresponding second recess. However, the latter is present only for production reasons, to avoid an accumulation of material; otherwise, it is of no further technical importance. The three flow grooves, for example, already mentioned in conjunction with the description of  FIG. 2  discharge into the first crescent-shaped recess  30 . These three flow grooves  26  are given a course such that they meet in a node in the immediate vicinity of the associated crescent-shaped recess  30 . This node forms the throttle restriction  32 , whose cross section, while larger than the cross sections of the individual flow grooves  26 , is nevertheless smaller than the total flow cross section of the three grooves  26 . Remote from the throttle restriction  32 , the three flow cross sections  26  emerge into the installation chamber  14   a  of the damping device  18 . These discharge points are oriented in a targeted way, with the aid of the orientation aid  28  referred to in conjunction with  FIG. 2 , and specifically are oriented such that they are located in the region of the highest point of the damping device  18 .  FIG. 3  shows the damping device  18  in a later installed position. The orientation of the function element  24  assures that any gas bubbles occurring in a brake system and collecting at the highest point will be carried away with the pressure fluid flowing out through the damping device  18 . Accordingly, relatively large bubbles cannot accumulate in the interior of the damping device  18 . On the occasion of brake system maintenance, any gas that has already entered can furthermore be removed again in this way by means of a scavenging process. 
   The function element  24  already described is shown again in  FIG. 4  in perspective, from its underside. The same reference numerals used thus far are also used in  FIG. 4 .  FIG. 4  once again clearly shows the region of the tubular first part  24   a  of the function element  24  that protrudes into the inlet  22   a . This region forms a neck, which is inserted, preferably press-fitted, into the inlet  22   a  in pressure-fluid-tight fashion. The pressure fluid flows through this tubular part  24   a  and emerges at its end into the interior of the installation chamber  14   a . The outflow from the installation chamber  14   a  takes place through the flow cross sections  26  that form the filter and onward to the throttle restriction  32  and from there, finally, through the crescent-shaped recess  30 , which is closed at the top, to the outlet  22   b . A plane contact of the end face of the second part  24   b  with the bottom face of the installation chamber  14   a  assures that no pressure fluid can reach the outlet  22   b  without passing through the filter or the throttle restriction  32 . Accordingly, with the function element  24  described, both the filter and the throttle restriction  32  are combined in a single component, which is simple to produce and can be anchored without problems on the housing block  12  of a hydraulic unit  10  of a vehicle brake system. Especially favorably, the function element  24  can be made by injection molding from plastic in one operation. Metal-cutting postmachining can be dispensed with as a result. 
   It is understood that additions or further refinements of the exemplary embodiment described are conceivable without departing from the fundamental concept of the invention. 
   The foregoing relates to a preferred exemplary embodiment of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.

Technology Category: 4