Abstract:
A hydraulic unit for slip-controlled braking systems has a plurality of receiving holes for transport devices associated with a plurality of hydraulic circuits bundled into groups, wherein the receiving holes are disposed at a distance from each in parallel with the upper side and a drive shaft having eccentrics located at the plane spacing for driving the transport devices. In order to provide a compromise optimized for manufacturing a small, convenient hydraulic unit, it is proposed that three theoretical planes (E 1 , E 2 , E 3 ) are arranged in parallel to the upper side, each receiving two V-shaped receiving holes for transport devices disposed at an angle to each other, and that the drive shaft includes three separate eccentrics for driving the transport devices.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. National Phase application of PCT International Application No. PCT/EP2008/063718, filed Oct. 13, 2008, which claims priority to German Patent Application No. 10 2007 050 101.5, filed Oct. 19, 2007, and German Patent Application No. 10 2008 005 279.5, filed Jan. 19, 2008, the contents of such applications being incorporated by reference herein. 
     FIELD OF THE INVENTION 
     The invention relates to a hydraulic unit. A unit of this type is suitable preferably for use within an electrohydraulic braking system, a vehicle driver expressing a braking request which is implemented by the braking system, to some extent by-wire, by means of suitable actuators—preferably while taking account of the environmental conditions detected. 
     BACKGROUND OF THE INVENTION 
     In electrohydraulic braking systems, pressure is built up in wheel brakes either directly with the aid of a pressure source, usually in the form of displacement pump devices having pistons, or indirectly by means of a pressure accumulator. These mechatronic systems always include a complex electronic unit, equipped with extensive software, and a complex hydraulic unit, which is based on a hydraulic circuit diagram and ensures correct accommodation, arrangement and connection of a multiplicity of hydraulic and electrohydraulic components which are controlled by the electronic unit in a systematic manner. 
     The systems concerned must meet multiple requirements. In particular, they must be able to deal with novel application events with the required reliability. Small size and low weight are always aimed for. Operating feel, and in particular operating comfort with regard to noise and pulsation, are to be improved, since, according to tendency, the frequency of actuation of the hydraulic unit is increasing and the noise level in the vehicle interior is being lowered, especially when electric drives are used. The system must be compatible with hybrid drive systems, while reliable, large-volume manufacture, ultimately enabling the system to be marketed profitably, must nevertheless be possible. 
     Known from WO 2004/031013 A1, which is incorporated by reference, is a hydraulic unit for slip-controlled braking systems which has three piston-type pumping devices which are integrated in a receiving body for rows of electrohydraulic valves. Proposals are made for improving a hydraulic unit with a plurality of pumping devices of the type specified in such a manner that said unit is suitable for use in electrohydraulic braking systems, with efficient utilization of the installation space within the receiving body and with little operating noise. For this purpose the receiving bores for the pumping devices are integrated regularly at an angle of 120° to one another and in a particular relationship to the receiving bores for valve rows. The configuration is capable of improvement and the document contains no indications of the implementation of more than three pumping devices in the receiving body. 
     In order to combine reduced pulsation effects with a six-piston pump for a vehicle braking system which is simple to manufacture, there is proposed according to WO 2005/050015 A1, which is incorporated by reference, a section-plane based distribution of pumping devices bundled in groups, which are driven by means of two eccentrics which are axially spaced and phase-offset with respect to one another in a circumferential direction. Two pumping devices arranged in a first section plane of the receiving body form, together with a further pump unit arranged in a section plane offset parallel thereto, a common pressure source for supplying a hydraulic circuit of the vehicle braking system. A further such grouping of pumping devices is provided to supply a second hydraulic circuit. The phase-offset positive control of the pumping devices is configured in such a way that pulsation fluctuations can hardly be felt on the suction side. This compensation of pulsations by means of positive control by two eccentrics is achieved at the expense of positioning the receiving bores for the six pump units with irregular reciprocal spacing of their angles of rotation. Although this has the advantage in principle that only two receiving bores for pumping devices are not disposed parallel to a vertical or horizontal of the receiving body, nevertheless such prioritized treatment of the receiving bores for the pumping devices produces a spatially less economical positioning of the remaining components. This way of proceeding suffers, to a degree, from the disadvantage that all the other components, with their associated connecting channels, must be designed around the receiving bores of the pumping devices. This gives rise to correspondingly high cost and complexity of the drilling technology. This applies in particular to the bundling into groups of respective connections to a pressure path and to a suction path, the particular connection requiring a very large number of bore sections which must open into the receiving body from very diverse sides and must cross multiple times. One pressure path, in particular, comprises no fewer than five individual channel sections ( 36   a - 36   e ). 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to make available a hydraulic unit with a multi-piston pump which avoids the disadvantages of the prior art and makes possible an improved compromise for a drilling configuration. 
     The configuration proposed according to aspects of the invention consists substantially in arranging the relatively large-volume receiving bores for the pumping devices in respective V-shaped pairs at an angle to one another within three imaginary horizontal planes E 1 , E 2 , E 3 . Because the pumping devices are positioned within these horizontal planes E 1 -E 3  to some extent in a stratified manner, but with only a relatively small offset from a common vertical plane V 1 , relatively extensive zones without receiving bores for pumping devices are produced in the receiving body, which to a large extent can be utilized entirely—without regard to the pumping devices—for arranging other components therein. Furthermore, a configuration bundled in this way makes possible a simplified drilling process together with a more compact construction. 
     The receiving bores for the pumping devices are provided with constant aperture angles in all the horizontal planes. 
     However, the aperture angle is offset alternately by a constant offset angle from one horizontal plane to another. 
     Dimensional control as well as programming of production machines is simplified if the drilling pattern of the receiving body is configured substantially symmetrically with respect to an imaginary vertical plane. The same is true in principle if the distances between the different horizontal planes are selected equally. 
     The number of chucking and rechucking operations is reduced if the receiving bores for the pumping devices of a hydraulic circuit each start uniformly from one side of the receiving body. 
     Furthermore, with a view to standardizing the drilling pattern it is especially advantageous if two each of the receiving bores of the pumping devices of a common hydraulic circuit are arranged perpendicularly to the upper face and congruently one above the other, and if one receiving bore for a pumping device of this hydraulic circuit is offset at an acute angle with respect to the other two receiving bores. 
     Very generally, each plane or section plane has two receiving bores, the receiving bores being arranged in each case in a V-formation at an angle to one another, the included angle being greater than 90° and not more than 180°. If the plane containing the receiving bore which is offset at an acute angle is arranged between the section planes of the receiving bores positioned congruently in a vertical direction, this makes possible an especially space-saving, compact construction. 
     The complexity and cost of drilling are further reduced if receiving bores for valves are arranged substantially perpendicularly above the receiving bores for pumping devices, so that, for a bundled group of pumping devices on the suction side, there are provided substantially linear, vertical channel sections which, starting from these valve receiving bores, enter the receiving body perpendicularly and open into the receiving bores of the pumping devices. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is best understood from the following detailed description when read in connection with the accompanying drawings. Included in the drawings is the following figures: 
         FIG. 1  is a schematic circuit diagram of a vehicle braking system with three pumping devices connected in parallel for each hydraulic circuit; 
         FIGS. 2   a - 2   c  show a section through a hydraulic unit with a total of six pumping devices, shown rotated in the drawing plane; 
         FIG. 3  shows a simplified hydraulic unit in a perspective schematic view; 
         FIG. 4  is a perspective top view of an upper face of a hydraulic unit with receiving bores for valve rows; 
         FIG. 5  is a perspective view of a hydraulic unit from below; 
         FIG. 6  is a perspective view of the suction path of the pumping devices, and 
         FIG. 7  is a perspective view of the pressure path of the pumping devices. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in  FIG. 1 , an electrohydraulic braking system  1  comprises an actuating unit  2  with a master cylinder  3  and wheel brakes FR, FL, RR, RL organized in pairs in two different hydraulic circuits, which wheel brakes FR, FL, RR, RL are each connected both in a bundled manner and independently of one another either to a primary pressure chamber PC or to a secondary pressure chamber SC of the master cylinder  3 . 
     Also located in the connection between master cylinder  3  and wheel brakes FR, FL, RR, RL is a hydraulic unit  4  with electronic control unit ECU which makes possible slip control for braking or drive. For this purpose the hydraulic unit  4  includes in a receiving body  21  currentlessly open inlet valves  5 - 8  and currentlessly closed outlet valves  9 - 12 , which valves are connected in pairs upstream of the wheel brakes FR, FL, RR, RL. 
     Unnecessarily high pressure build-up within the ABS control cycles is reduced by activating the currentlessly closed outlet valves  9 - 12  and draining hydraulic fluid into respective low-pressure accumulators  13 , 14 . In addition, three pumping devices  15   a,b,c ; 16   a,b,c  are connected in parallel in each hydraulic circuit in order to return the hydraulic fluid from the low-pressure accumulators  13 , 14  in the direction of the master cylinder  3 . The three pumping devices  15   a,b,c ; 16   a,b,c  for each hydraulic circuit make possible not only a largely uniform, pulsation-free return function but also, in comparison to conventional single-piston pumps, an accelerated pressure build-up and increased volume flow. 
     In addition, in order to be able to build up pressure with the pumping devices  15   a,b,c ; 16   a,b,c  in one or more wheel brakes FR, FL, RR, RL independently of the driver for the stability control processes or for comparable requested functions, a currentlessly open block valve  17 , 18  and a currentlessly closed change-over valve  19 , 20  are provided in each hydraulic circuit. The block valve  17 , 18  is used to block the normally open hydraulic connection between the master cylinder  3  and the wheel brakes FR, FL, RR, RL. By contrast, the change-over valve  19 , 20  makes it possible to change the suction path and the pressure path for the pumping devices  15   a,b,c ; 16   a,b,c  in such a manner that, for the driver-independent control processes, fluid is drawn not from the low-pressure accumulators  13 , 14  but from the pressure chambers PC, SC of the master cylinder  3 , in order not to pump the fluid in the direction of the master cylinder  3  but to build up pressure in the direction of the wheel brakes  15   a,b,c ; 16   a,b,c.    
     The precise arrangement of the pumping devices  15   a,b,c ; 16   a,b,c  is apparent in detail from  FIGS. 2 and 3 . With regard to the configuration of the receiving body  21 , in principle a plurality of horizontal planes E 1 , E 2 , E 3  can be distinguished from a plurality of vertical planes V 1 , V 2 . For reasons of clarity, the corresponding planes E 1 , E 2 , E 3  are indicated only by straight lines in the figures. The horizontal planes E 1 , E 2 , E 3  each extend parallel to the upper face  22  of the receiving body  21 . The vertical planes V 1  and V 2  are disposed perpendicularly to the upper face  22  and are arranged at right angles to one another. Although the planes mentioned are represented as lines in the drawing for reasons of clarity, it is self-evident that a planar extent is meant in each case. 
     Accordingly, all the receiving bores  23 - 28  for the pumping devices  15   a,b,c ; 16   a,b,c  are arranged in layers in a total of three horizontal planes E 1 , E 2  and E 3 . In addition, the pumping devices  15   a,b,c ; 16   a,b,c  of a hydraulic circuit are bundled in respective groups on the right or left of the vertical plane V 2 . The receiving bores arranged inside the respective horizontal planes E 1 , E 2 , E 3  are not located diametrically opposite one another, but are arranged in a V-formation with a constant aperture angle α of, for example, 148°. In this case the aperture angle α denotes in each case the angle with reference to the axes of movement WL 1 , WL 2  in a horizontal plane of the pump pistons, which are driven by a common pump eccentric. 
     However, depending on the horizontal plane, the aperture angle α is rotated through an offset angle β 1 =6° or β 2 =26° (exemplary values in each case), the pumping devices of the horizontal planes E 1  and E 3  each being positioned with an identical offset angle β 1 . The schematic sectional representations along the respective horizontal planes E 1 , E 2  and E 3  shown in  FIGS. 2   a  to  2   c  serve to clarify this stratified distribution of the pumping devices. 
     The arrangement of the receiving bores  23 - 28  for pumping devices  15   a,b,c ; 16   a,b,c  which has been described makes possible, to an extent, a bundling into groups, so that relatively large regions of the receiving body  21  are kept completely free of pumping devices  15   a,b,c ; 16   a,b,c , and for this reason can be utilized entirely for receiving any other components, channels or bores. 
     The perspectivally oriented  FIGS. 4 and 5  illustrate a drilling concept with the individual receiving bores for the components of the receiving body  21  on the basis of the bundled arrangement of the receiving bores  23 - 28  for the pumping devices  15   a,b,c ; 16   a,b,c . While  FIG. 4  is based, to an extent, on a primary top view of the upper face  22  of the receiving body  21 , and makes visible the valve receiving bores  29 - 40  for the valve rows I, II and III, as well as separate receiving bores  41 - 45  in particular for hydraulic sensors, and also connections  46 - 49  for wheel brakes FR,FL,RL,RR as well as connections  50 ,  51  for the master cylinder  3 , a primary view from below of the receiving body  21  rotated through 180° is shown in  FIG. 5 . This view from below makes visible, in particular, a receiving bore  52  for the drive shaft as well as receiving bores  53 , 54  for low-pressure accumulators  13 , 14 . Common to both views is that they reveal the extensive axial symmetry in the drilling of the receiving body  21 , in each case with respect to the vertical plane V 2 . 
     As a further, central feature of the receiving body  21 , it should be added that the angles α, β between the receiving bores  23 - 28  for the pumping devices  15   a,b,c ; 16   a,b,c  are arranged in such a manner that, according to tendency, all the working lines WL 1 , WL 2  of the pumping devices  15   a,b,c ; 16   a,b,c  are oriented away from the end face  55  of the receiving body  21  from which the receiving bores  53 , 54  for the low-pressure accumulators  13 , 14 , and the receiving bores  56 , 57  for damping chambers  58 , 59 , open into the receiving body  21  substantially perpendicularly to the end face  55 . 
     An additional clear, perspective overview of the configuration of the suction path of the pumping devices, b,c;  16   a,b,c  is given in  FIG. 6 . As described previously, the change-over valve  19 , 20 , in conjunction with the block valve  17 , 18 , primarily makes it possible for fluid to be drawn both from a low-pressure accumulator  13 , 14  and from a master cylinder  3 . For this purpose it is provided that for each hydraulic circuit one chamber each of the master cylinder  3  is connected via channel sections to a receiving bore  38 , 39  for the associated change-over valve  19 , 20 . Furthermore, the receiving bore  53 , 54  of the associated low-pressure accumulator  13 , 14  is also connected via a channel to the receiving bore  38 , 39  for this change-over valve  19 , 20 . Starting from the respective outlets of these change-over valves  19 , 20 , there extend two channels, arranged substantially perpendicularly to the upper face  22 , which lead to the suction region of the associated receiving bores  23 - 28  for the pumping devices  15   a,b,c ; 16   a,b,c .  FIG. 6  shows clearly that in the present configuration a single channel makes possible in each case a common connection of two pumping devices  15   a,c ; 16   a,c  arranged in alignment one above the other, while an adjacent channel essentially effects the connection of the pumping devices  15   b , 16   b  positioned in a somewhat angled manner. 
     By contrast,  FIG. 7  gives a clear overview of the comparatively simple connection of the pumping devices  15   a,b,c ; 16   a,b,c  of the hydraulic circuits on the pressure side, each to a respective wheel connection  46 , 47 ; 48 , 49 . For this purpose a damping chamber  58 , 59  is provided, for each hydraulic circuit, between the pumping devices  15   a,b,c ; 16   a,b,c  and the corresponding wheel connections  46 , 47 ; 48 , 49 . Each damping chamber  58 , 59  is connected via three channel sections to the respective wheel connection  46 , 47 ; 48 , 49 . The connection of the relevant pumping devices  15   a,b,c ; 16   a,b,c  to the respective damping chamber  58 , 59  is effected by substantially two channels which open into the receiving body perpendicularly to the upper face and largely parallel to one another, and by a collecting channel which connects these channels and which, starting from the end face  55  having the damping chamber  58 , 59 , is disposed substantially perpendicularly in the receiving body  21 .