Abstract:
In an electronically controllable brake unit for automotive vehicles, including a pressure generating device for generating a hydraulic pressure and a drive unit, a particularly low-noise design that is optimized with respect to the reduction of radial forces on the motor bearing is achieved because the pressure generating device is an internal gear pump ( 4 ). Preferably, the internal gear pump ( 4 ) is designed as a cartridge and attached in the valve block ( 1 ) by way of a clinch-type connection.

Description:
TECHNICAL FIELD  
         [0001]    The present invention generally relates to vehicle brakes and more particularly relates to a brake unit for automotive vehicles with a pressure generating device for generating a hydraulic pressure and with a drive unit for the pressure generating device.  
         BACKGROUND OF THE INVENTION  
         [0002]    Electronically controllable brake systems for automotive vehicles including a pressure generating device designed as a piston pump for generating a hydraulic pressure and a driving unit for this purpose are known from prior art. A pump configured as a stepped piston pump is disclosed in German publication DE 43 16 986 A1.  
           [0003]    Piston pumps in this application suffer from the disadvantage of a function-induced pressure pulsation that depends particularly on the number of pistons used. A certain noise level is thereby produced that can be unacceptable in the passenger compartment. This circumstance is likely to impair the comfort, in particular, when a piston pump is employed in EHB systems (Electro-Hydraulic Brake systems).  
           [0004]    Further, so-called internal gear pumps are known from the art. European patent application EP-A-0 848 165 A2 shall be referred to as an example. This patent application discloses an internal gear machine without a filler piece, comprised of a housing, a bearing ring that is received in a bore of the housing so as to be transversely movable, yet unrotatable, relative to its axis, a toothed ring gear circumferentially supported in the bearing ring, and a pinion pivoted in the housing.  
         BRIEF SUMMARY OF THE INVENTION  
         [0005]    An object of the present invention is to avoid the shortcomings of the state of the art, and to improve upon an electronically controlled brake system of the above-mentioned type so that only a reduced noise level occurs during the pressure generating phases, in particular in EHB systems.  
           [0006]    The object of the present invention is achieved in a brake system wherein the internal gear pump is an independent construction unit.  
           [0007]    An advantage of the present invention is that only torques are transmitted in an internal gear pump, (i.e., that lower radial forces act on the motor bearing than in a radial piston pump). Besides the low-pulsation operation, this permits a less costly design of the motor bearing in particular.  
           [0008]    According to another advantage of the present invention the assembly of the brake unit is simplified and external pre-testing of the pump is possible.  
           [0009]    Preferably, the internal gear pump is configured as a cartridge. A simple integration of the pump into a HCU (Hydraulic Control Unit) of an electronically controlled brake system is thereby achieved.  
           [0010]    To reach an especially stable connection that prevents manipulations to the brake system in particular, the internal gear pump is attached in a valve block of a hydraulic control unit by at least one clinch-type or calk-type connection.  
           [0011]    Preferably, a pressure-side port of the pressure generating device is connected to a valve assembly configured as a cartridge, wherein the valve assembly includes a non-return valve and a pressure-limiting valve. This also achieves the ability to pre-test the valve assembly externally as well as a simplified assembly.  
           [0012]    To obtain a particularly stable connection that especially prevents manipulations at the brake system, the valve assembly is attached in a valve block of a hydraulic control unit by way of a clinch-type or calk-type engagement.  
           [0013]    Advantageously, a shaft of the drive unit is guided in a bearing, the said bearing being arranged in a valve block of a hydraulic control unit. This eliminates the need for a massive motor flange to take up the bearing forces because the latter forces are received in the valve block. The bearing plate can be configured as a simple molded plastic part in this case.  
           [0014]    A particularly compact structural shape of the pump is achieved when the pump includes a housing part and a cover part, with the housing part and the cover part being interconnected by means of lanced indentations. Contamination of the system by chips is also prevented due to the connection by means of lanced indentations.  
           [0015]    Preferably, a low-pressure chamber is designed in the pump aspiration area of the pressure generating device. Especially in an OHB application, the demands placed on the shaft seals of the motor shaft, i.e., the resistance to high pressure of a shaft seal, may be reduced this way. The low-pressure chamber is favorably connected to a low-pressure accumulator or a like element.  
           [0016]    To avoid excessive clutch wear, a clutch device for coupling the drive unit and the pressure generating device is arranged in the low-pressure chamber. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 is a schematic cross-sectional view (partly broken away and exploded) of a motor-and-pump assembly according to a first embodiment of the present invention.  
         [0018]    [0018]FIG. 2 a  is a schematic cross-sectional view of the internal gear pump according to FIG. 1.  
         [0019]    [0019]FIG. 2 b  is a schematic view of a cross-section of the ring gear and pinion taken along line IIb-IIb of FIG. 2 a.    
         [0020]    [0020]FIG. 3 is a schematic cross-sectional view of the valve cartridge according to FIG. 1.  
         [0021]    [0021]FIG. 4 is a schematic cross-sectional view (partly broken away) of the motor-and-pump assembly according to FIG. 1 in the assembled condition.  
         [0022]    [0022]FIG. 5 is a schematic block diagram of the motor-and-pump assembly according to the first embodiment of the present invention as shown in FIGS.  1  to  4 .  
         [0023]    [0023]FIG. 6 is a schematic partial cross-sectional view of a motor-and-pump assembly according to a second embodiment of the present invention.  
         [0024]    [0024]FIG. 7 is a schematic partial cross-sectional view of a motor-and-pump assembly according to a third embodiment of the present invention.  
         [0025]    [0025]FIG. 8 is a schematic partial cross-sectional view of a motor-and-pump assembly according to a fourth embodiment of the present invention.  
         [0026]    [0026]FIG. 9 is a schematic partial cross-sectional view of a motor-and-pump assembly according to a fifth embodiment of the present invention.  
         [0027]    [0027]FIG. 10 is a schematic partial cross-sectional view of a motor-and-pump assembly according to a sixth embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0028]    A first embodiment of the present invention will be described in the following in connection with FIGS.  1  to  5 . The motor-and-pump assembly of the present invention is schematically shown in FIG. 1 in an exploded, partly cross-sectional view. Reference numeral  1  designates a valve block or HCU block of a hydraulic control unit of an electronically controlled brake system. Two essentially parallel arranged recesses  2  and  3  are provided in valve block  1 . Recess  2  accommodates an internal gear pump  4  which is explained in detail with respect to its design in connection with FIGS. 2 a  and  2   b.  While the internal gear pump  4  is mounted in a bottom part of the recess  2  and is generally flush with an opening of recess  2 . Motor  5  is fastened in the opposite top part of the recess  2 . Recess  3  is used to accommodate a valve assembly  6  configured as a cartridge. Valve assembly  6  will be explained in detail in the following by making reference to FIG. 3. The motor shaft  7  is coupled to a pin  10  that is designed at the top end of the pinion shaft  9  by way of a clutch  8 . Clutch  8  eliminates the transfer forces between shaft  7  and pin  10 . The motor shaft  7  operates in wet practice in suction chamber  11  and is sealed by a sleeve  13  at a bearing plate  12  of motor  5 . An O-ring seal  14  integrated in the bearing plate  12  is provided to seal the suction chamber  11  towards the outside. Further, valve block  1  includes a supply portion  15  of the supply reservoir. On the opposite side, a return port  16  for control valves is designed in valve block  1 . Ports  15 ,  16  are connected to the suction chamber  11 .  
         [0029]    [0029]FIG. 2 a  schematically shows a cross-sectional view of the internal gear pump  4  employed according to the present-invention. The internal gear pump  4  includes a pump housing  17 , a pump cover  18 , and a ring gear  19 . A one-part or multi-part pinion  20  (see FIG. 2 b ) moves rotatorily in sliding sleeves  21  and radial discs  22  in the ring gear  19 . The ring gear  19  is radially supported in the pump housing  17  by a slide ring  23 . The pump cover  18  is furnished with an integrated suction filter  24  and, thus, forms a suction port  25  of the internal gear pump  4 . After pre-assembly of the inner parts, the pump cover  18  is calked with the pump housing  17 . Generally, the pump housing  17  of the internal gear pump  4  has a one-part design and clinched contours  26  at its periphery. Also, the pump housing  17  receives an annular pressure port  27  and a pressure filter  28 . With respect to further details of the design and operation of the internal gear pump  4  used according to the present invention, reference again is expressly made to the publication of European patent application EP-A-0 848 165 A2 mentioned in the introductory part of the description.  
         [0030]    [0030]FIG. 2 b  shows a schematic top view of a cross-section taken along line IIb-IIb in FIG. 2 a.  In connection with FIG. 3, the design of the valve assembly  6  configured as a cartridge will be explained in the following in further details. A pressure port  29  of the valve cartridge  6  is connected to the annular pressure port  27  of the internal gear pump  4  in the installation position as defined. The valve cartridge  6  includes a return valve  30  and a pressure-limiting valve  31 . Housing  32  of the valve cartridge  6  is of one-part design. At the outside periphery of the housing  32 , exactly as at the outside periphery of the pump housing  17 , clinched contours  33  are provided with a view to fixing the valve cartridge in the valve block  1 . An annular channel  34  of the non-return valve  30  supplies the control valves or the accumulator with the necessary supply pressure. In the event that an allowable system pressure is exceeded, the pressure-limiting valve  31  will open and connect the annular channel  34  to the suction port chamber  11  of the internal gear pump  4 . Please note that the valve cartridge  6  is also an independent construction unit that can be pre-tested from outside in particular.  
         [0031]    For further explanation of the present invention, the motor-and-pump assembly is shown in the condition as mounted into the valve block  1  in FIG. 4. FIG. 5 shows a schematic hydraulic wiring diagram of the motor-and-pump assembly as well as of the valve assembly  6 .  
         [0032]    A second embodiment of the present invention is described in the following in connection with the schematic cross-sectional view of FIG. 6. In contrast to the first embodiment described in connection with FIGS.  1  to  5 , the motor  5  includes a massive motor flange  35  that centers a bearing  36  and a sleeve or shaft sealing ring  13 . In addition, the motor forces introduced through the motor shaft  7  are received in the motor flange  35 . Together with the shaft sealing ring  13 , the sealing ring  14  ensures the sealing of the suction chamber  11  wherein the clutch  8  during operation transmits the motor torque to the pump  4  which is favorably designed as an internal gear pump. The motor flange  35  is connected to the valve block  1  by way of a contacting means  37 . On the side close to the valve block  1 , the motor flange  35  has a centering collar  38  which ensures the alignment of the motor shaft  4  and the pump shaft  9 .  
         [0033]    [0033]FIG. 7 shows an embodiment according to a third embodiment of the present invention which is improved compared to the second embodiment illustrated in FIG. 6. In contrast to the second embodiment illustrated in FIG. 6, the centering collar  38  (see FIG. 6) is omitted in the third embodiment of the present invention. At the point of passage of the motor shaft  7 , valve block  1  includes a bearing centering bore  39  which, on the one hand, accommodates the rotor force of the motor  5 , and centers the motor shaft  4 , on the other hand. Thus, sealing of the suction chamber  11  is ensured due to the side of the valve block  1  facing the motor  5  being basically closed (apart from the bearing centering bore  39 ), along with the shaft sealing ring  13 . In contrast to the second embodiment illustrated in FIG. 6, there is also no need for a massive motor flange  35  (as in FIG. 6). A simple bearing plate  40  which, due to being exposed to low loads, is favorably designed as a molded plastic part is absolutely sufficient in operation. The housing of the motor  5  is attached to the valve block  1  by way of a screw coupling  41 . The shorter overall length of the internal gear pump  4  compared to the second embodiment of the present invention shown in FIG. 6 is achieved because the two pump housing halves  17 ,  18  are interconnected by lanced indentations. This way, a coupling without a clearance is obtained which, beside the advantage of saving space due to the short construction, especially compared to screw couplings, also prevents contamination of the system by chips.  
         [0034]    The embodiment of the present invention illustrated in FIG. 8 shows a connection between motor  5  and pump  6  by means of the valve block  1  which is optimized in terms of components. In particular, it becomes apparent from the illustration of FIG. 8 that at the pump cover  18 , i.e., the top housing half of the internal gear pump  4 , there is designed a stepped bore or step  42  which especially adopts the function of centering the clutch  8  for the assembly of the electric motor  5 . A filter (not shown) is optionally integrated in the suction chamber  6 . A partial press fit between the pump housing  17  and the valve block  1  ensures the support of torques and prevents the pump  4  from detaching from the valve block  1 . Due to the optimized connection, the screw coupling  41  (see FIGS. 6 and 7) can be replaced by a rivet connection indicated by reference numeral  43 .  
         [0035]    Due to the operation of the internal gear pump  4  which additionally ensures a pressure increase, a fourth embodiment of the present invention is illustrated schematically in a cross-sectional view in FIG. 9. Pressure fluid propagates into an accumulator (not shown) through the suction bore  25 , and through the pressure bore  29  also in the embodiment of FIG. 9. The design of the fourth embodiment of the present invention illustrated in FIG. 9 is advantageous especially in connection with an EHB application (electro-hydraulic brake). Reference is made especially to the description and the drawing of the first embodiment for further details with respect to the embodiment illustrated in FIG. 9. It will be appreciated that the sealing sleeve  13  in the preferred EHB case is loaded with low suction pressures only.  
         [0036]    In contrast thereto, a sixth embodiment of the present invention is schematically shown in a cross-sectional view in FIG. 10, which is preferred especially for an OHB application or for an OHB circuit (Optimized Hydraulic Brake). The design of the pumps in FIGS. 9 and 10 is generally similar, however, the pump preferred for the OHB application has larger dimensions. In contrast to the case of the EHB application, the pressures introduced through the suction port  25  can be considerably higher than in the EHB case and e.g. amount to 200 bar approximately. Therefore, a low-pressure chamber  44  is provided in the pump aspiration area beside the sealing sleeve  13  in the embodiment of FIG. 10, which is in contrast to the embodiment illustrated in FIG. 9. The low-pressure chamber is connected to a (non-illustrated) low-pressure accumulator or reservoir by way of channels  45  (in the motor housing  5 ) and  46  (in the valve block  1 ). The low-pressure chamber  44  is provided by a cylindrically shaped sleeve portion  47  that is sealed by an inward sealing ring  48  and an outward sealing ring  49 . The inward sealing ring  48  is designed in a corresponding recess on the side of the sleeve portion  47  facing the motor  5 . The outward sealing ring  49  is arranged in a stepped bore between motor  5  and valve block  1 . The pressurization of the sealing sleeve  13 , that is especially high in an OHB application, is minimized in the embodiment illustrated in FIG. 10. The problem of a rotating radial shaft seal that is subjected to high pressure is otherwise difficult to solve. Leakage of the pump may thus flow off.  
         [0037]    It shall be noted that valve assembly  6  was not shown or described in connection with the second to sixth embodiments of the present invention. Of course, a corresponding valve assembly may be provided optionally, and a design as a valve cartridge is especially preferred.  
                                         List of Reference Numerals:                                1   valve block or HCU block       2   recess       3   recess       4   (internal gear) pump       5   (electric) motor       6   valve assembly or valve cartridge       7   motor shaft       8   clutch       9   pinion       10   pin       11   suction chamber       12   bearing plate       13   sleeve or shaft sealing ring       14   O-ring seal or sealing ring       15   supply port       16   return port       17   pump housing       18   pump cover       19   ring gear       20   pinion       21   sliding sleeve       22   radial disc       23   slide ring       24   suction filter       25   suction port       26   clinched contours       27   pressure port       28   pressure filter       29   pressure port       30   non-return valve       31   pressure-limiting valve       32   housing       33   clinched contour       34   annular channel       35   motor flange       36   bearing       37   contacting means       38   centering collar       39   bearing centering bore       40   bearing plate       41   screw coupling       42   stepped bore       43   rivet connection       44   low-pressure chamber       45   channel       46   channel       47   sleeve portion       48   inward sealing ring       49   outward sealing ring