Abstract:
An internal gear pump comprises an internal gear, a pinion eccentrically positioned in the internal gear and configured to mesh with the internal gear, a cover configured to close an installation space of the internal gear pump, and positioned on end sides of the pinion and the internal gear, a pump outlet leading through the cover, and a non-return valve positioned in the pump outlet in the cover and configured to open to allow flow out of the internal gear pump, and further configured to shut to disallow a return flow through the pump outlet into the internal gear pump.

Description:
[0001]    This application claims priority under 35 U.S.C. §119 to patent application no. DE 10 2013 211 615.2, filed on Jun. 20, 2013 in Germany, the disclosure of which is incorporated herein by reference in its entirety. 
         [0002]    The disclosure relates to an internal gear pump. It is provided, in particular, as a hydraulic pump instead of usually used piston pumps in slip-controlled vehicle brake systems. Hydraulic pumps of this type are often called recirculating pumps, even if this is not necessarily correct. In slip-controlled hydraulic vehicle brake systems, a pump outlet, that is to say a pressure side of a hydraulic pump, is connected to a brake line which leads from a brake master cylinder to wheel brake cylinders. A brake pressure which is generated by way of actuation of the brake master cylinder prevails at the pump outlet. 
       BACKGROUND 
       [0003]    Internal gear pumps have an internal gear, that is to say an internally toothed gearwheel, and a pinion, that is to say an externally toothed gearwheel, which is arranged eccentrically in the internal gear and meshes with the internal gear. The designation of the gearwheels as pinion and as internal gear serves to distinguish them. By way of rotation of driving of one of the two gearwheels, usually the pinion, the other gearwheel is also driven and the gearwheels convey fluid, in particular liquid, brake fluid in vehicle brake systems, in tooth spaces of the gearwheels from a suction side to a pressure side of the internal gear pump. This is known and is not to be explained in greater detail here. 
         [0004]    Patent DE 196 13 833 B4 discloses one example of an internal gear pump of this type which is not provided, however, for hydraulic vehicle brake systems, but rather for hydraulic machines, in particular construction machines. In a crescent-shaped pump space which is delimited on the inside by the pinion and on the outside by the internal gear and extends in a circumferential section between the gearwheels of the internal gear pump, in which crescent-shaped section the gearwheels do not mesh with one another, the known internal gear pump has a separating piece, against the inner side of which tooth tips of teeth of the pinion bear and against the outer side of which tooth tips of teeth of the internal gear bear. The separating piece divides the pump space into a suction space which communicates with a pump inlet and into a pressure space which communicates with a pump outlet. On account of the typical crescent shape or semi-crescent shape, separating pieces of internal gear pumps are often called a crescent piece. A further designation is a filler piece. Internal gear pumps having a separating piece in the pump space are also called crescent pumps. Internal gear pumps without a separating piece which are also called annular gear pumps are also known. The disclosure can be realized both in a crescent pump and in an annular gear pump. 
         [0005]    In a slip-regulated hydraulic vehicle brake system, an internal gear pump requires a non-return valve on or in the pump outlet, which non-return valve prevents, in the case of a stationary pump, that is to say when the slip control is not in operation, brake fluid flowing through the pump outlet into the internal gear pump and from a pump inlet out of the internal gear pump again counter to the conveying direction of the internal gear pump upon actuation of the brake master cylinder, as a result of which a brake pressure which is built up by way of actuation of the brake master cylinder is dissipated and a brake pedal would yield. 
       SUMMARY 
       [0006]    The internal gear pump according to the disclosure has a cover for closing an installation space of the internal gear pump on an end side of the pinion and of the internal gear, it not being necessary for the cover to be arranged directly next to the pinion and the internal gear, but it rather being possible for one or more components to be situated between the cover on one side and the pinion and the internal gear on another side. The installation space of the internal gear pump is, for example, a depression in a hydraulic block of a slip-controlled vehicle brake system, into which the internal gear pump is installed, or an interior space of a pump housing, it being possible for a hydraulic block, into which an internal gear pump is installed, to be considered to be a pump housing of the internal gear pump. In particular, an installation space which is open only on one end side is provided for the internal gear pump, the other end side of which installation space is closed. The cover preferably but not necessarily closes the installation space sealingly. 
         [0007]    According to the disclosure, a pump outlet of the internal gear pump leads through the cover and there is a non-return valve in the pump outlet in the cover, which non-return valve can be flowed through out of the internal gear pump and shuts counter to a return flow through the pump outlet into the internal gear pump. When the internal gear pump is at a standstill, the non-return valve prevents throughflow of the internal gear pump counter to its conveying direction from the pump outlet to the pump inlet. If the internal gear pump is used as a hydraulic pump of a slip-controlled, hydraulic vehicle brake system, the non-return valve prevents, in the case of a stationary internal gear pump, brake fluid flowing through from the brake master cylinder of the internal gear pump counter to its conveying direction upon actuation of the brake master cylinder, a throughflow of this type of the internal gear pump counter to its conveying direction and/or through the pump outlet into the internal gear pump being called a return flow. 
         [0008]    The disclosure has the advantage of space-saving accommodation of a non-return valve in the pump outlet in the cover of the internal gear pump. 
         [0009]    The subject matter of the disclosure provides advantageous refinements and developments. 
         [0010]    One preferred refinement of the disclosure provides that the non-return valve has a damper for pressure oscillations of fluid in the cover of the internal gear pump, which fluid is conveyed by the internal gear pump. A space or volume, in which the non-return valve is accommodated, a movable, in particular sprung and/or elastic damper body or a small throughflow cross section in the pump outlet, for example in the manner of a throttle or orifice plate, can have a damping effect. The list is by way of example and is not conclusive. 
         [0011]    Another preferred refinement of the disclosure provides that the internal gear pump has a filter in the pump outlet, which filter is arranged between the gearwheels of the internal gear pump and the non-return valve as viewed in the flow direction. The filter prevents solid particles, that is to say chips, particles, etc., passing out of the internal gear pump into the non-return valve, where they can lead to a leak of the non-return valve. Refinements of the internal gear pump according to the disclosure with the filter in the pump outlet are also conceivable without a non-return valve. 
         [0012]    One development of the disclosure provides an arrangement of the filter in a pressure field. The pressure field is a typically flat, pressure-loaded depression which is situated on a side of a rotationally fixed and axially movable axial washer, which side faces away from the pinion and the internal gear, which depression extends in the circumferential direction in an arcuate or crescent-shaped manner over approximately the region or a part of the region of the pump space between the pinion and the internal gear. The pressure loading of the axial washer on the outer side loads the axial washer into bearing contact with end sides of the pinion and the internal gear, in order to seal the pump space laterally. The seal is not necessarily hermetically tight, but rather the axial washer bears against the end sides of the pinion, the internal gear and, if present, a separating piece, in a comparable manner to a hydrodynamic axial plain bearing, limited leakage out of the pump space between the pinion and the internal gear on one side and the axial washer on the other side being acceptable. A satisfactory compromise is to be found between low friction and satisfactory sealing action. Axial washers are also called thrust washers or control washers or plates. A washer or plate shape is not necessary for the disclosure. 
         [0013]    One development according to the disclosure provides that the filter which is arranged in the pressure field has a supporting element for a pressure field seal, which supporting element supports the pressure field seal from the inside. The pressure field seal is a seal which encloses the pressure field and seals on the circumference. Slip-controlled hydraulic vehicle brake systems are evacuated for filling, before they are filled with brake fluid, in order to avoid inclusions of air. The evacuation can cause a vacuum in the pressure field. The supporting element of the filter according to the disclosure prevents the pressure field seal in the pressure field being displaced from the circumference of the pressure field to the inside and holds the pressure field seal in its position which encloses the pressure field on the circumference. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    In the following text, the disclosure will be explained in greater detail using one embodiment which is shown in the drawing, in which: 
           [0015]      FIG. 1  shows an axial section of an internal gear pump according to the disclosure, and 
           [0016]      FIG. 2  shows an enlargement of a detail according to rectangle II in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    The internal gear pump  1  according to the disclosure which is shown in  FIG. 1  has a pump shaft  2  which is mounted rotatably in a cover  4  by way of a bearing, a ball bearing  3  in the embodiment. The cover  4  is a cylindrical part with a flange  5  on one side. It has an axially parallel through hole  6 , the diameter of which is stepped multiple times, for guiding through the pump shaft  2 , which through hole  6  is eccentric in the cover  4 . A gearwheel which is called a drive wheel  7  here is pressed or arranged in a rotationally fixed manner in some other way onto an end of the pump shaft  2  which projects out of the cover  4 . The drive gear  7  meshes with a gearwheel which is called a driving gear  8  here and can be driven by way of an electric motor (not shown), optionally with a gear mechanism connected in between. 
         [0018]    An externally toothed gearwheel which is called a pinion  9  here is arranged on the pump shaft  2  on another side of the ball bearing  3  to the drive gear  7 . The pinion  9  is arranged on the pump shaft  2  in an axially displaceable and rotationally fixed manner; in the embodiment, the axial displaceability and rotational fixing is achieved by way of a four-cornered shaft  10 , the disclosure not being restricted to this possibility. The pinion  9  is situated in an internally toothed gearwheel which is called an internal gear  11  here, is arranged in one plane with the pinion  9  and is the same width as the pinion  9 . The internal gear  11  is coaxial with respect to the cylindrical cover  4  and eccentric with respect to the pump shaft  2  and with respect to the pinion  9 , with the result that the pinion  9  and the internal gear  11  mesh with one another. In the case of a rotational drive of the pinion  9  with the pump shaft  2 , the pinion  9  also rotationally drives the internal gear  11  which meshes with it. The internal gear  11  is pressed into a bearing ring  12  which is mounted rotatably in the manner of a plain bearing in a hydraulic block  15 . 
         [0019]    The pinion  9  and the internal gear  11  enclose a crescent-shape pump space  13  between them in a circumferential section, in which they do not mesh with one another. A semi-crescent-shaped separating piece is arranged in the pump space  13 , which separating piece divides the pump space  13  into a suction space and a pressure space. The separating piece is the same width as the pinion  9  and the internal gear  11 . The separating piece which is also called a filler piece or, on account of its shape, a crescent is situated outside the sectional plane and therefore cannot be seen in the drawing. By way of rotational driving of the pinion  9  and the internal gear  11 , the internal gear pump  1  conveys fluid, brake fluid in the embodiment, from the suction space in tooth spaces of the pinion  9  and the internal gear  11  on the inside and outside along the separating piece into the pressure space. 
         [0020]    A seal arrangement with a sleeve seal  16 , a supporting ring  17  and a secondary seal  18  is arranged between the ball bearing  3  and the pinion  9 , which seal arrangement seals the pump shaft  2  in the cover  4 . The sleeve seal  16  is trumpet funnel-shaped and is arranged in such a way that it is loaded against the pump shaft  2  in the case of any pressure loading. The supporting ring  17  which is situated between the ball bearing  3  and the sleeve seal  16  has an annular end face which is curved concavely in accordance with a curvature of the sleeve seal  16  and against which the sleeve seal  16  bears. The secondary seal  18  is a sealing ring which is arranged in an end groove of an annular step of the through hole  6  in the cover  4 . The secondary seal  18  is situated on an outer circumference of the sleeve seal  16  on a side which lies opposite the supporting ring  17  and clamps an outer edge of the sleeve seal  16  between itself and the supporting ring  17 . 
         [0021]    An axial washer  19  which bears against end sides of the pinion  9 , the internal gear  11  and the separating piece is situated between the seal arrangement  16 ,  17 ,  18  on one side and the pinion  9  and the internal gear  11  on the other side. The axial washer  19  has a through hole for the pump shaft  2 . The axial washer  19  is rotationally fixed and axially movable. In plan view, the axial washer  19  has the shape of a circular segment which is greater than a semicircle, a step being cut out of the circular segment at one corner. The axial washer  19  covers the separating piece and the pressure space of the pump space  13  on one side. 
         [0022]    The cover  4  has a pressure field  20  on an inner side which faces the axial washer  19 , that is to say on an outer side of the axial washer  19 , which outer side faces away from the pinion  9  and the internal gear  11 . The pressure field  20  is a flat depression with an approximately semi-crescent-shaped form which extends approximately over the pressure space of the pump space  13  and over part of the separating piece. The pressure field  20  is enclosed by a pressure field seal  21  which seals the pressure field  20  between the cover  4  and the axial washer  19 . Instead of in the cover  4  as illustrated, the pressure field  20  can also be provided in the outer side of the axial washer  19  (not shown). The axial washer  19  has a through hole  22  which leads from the pressure space of the pump space  13  into the pressure field  20 . The pressure field  20  communicates with the pressure space of the pump space  13  of the internal gear pump  1  through the through hole  22 , with the result that the same pressure prevails in the pressure field  20  as in a pump outlet. By way of the pressure loading in the pressure field  20 , the axial washer  19  is loaded into sealing contact with the end sides of the pinion  9 , the internal gear  11  and the separating piece. In the manner of a plain bearing, the axial washer  19  bears against the end sides of the pinion  9 , the internal gear  11  and the separating piece, but it does not seal hermetically; an optimum or at least favorable ratio is to be selected between friction between the rotating pinion  9  and the rotating internal gear  11  on one side and the rotationally fixed axial washer  19  on the other side and a low leakage, which can be selected substantially by way of size, shape and position of the pressure field  20 . An angled-away bore in the cover  4  leads away from the pressure field  20  in an axially parallel manner for a short distance and subsequently radially to the outside to a circumference of the cover  4 . The through hole  22  in the axial washer  19  and the angled-away bore in the cover  4  are constituent parts of a pump outlet of the internal gear pump  1 . The angled-away bore in the cover  4  opens into an annular groove  23  in the abovementioned hydraulic block  15 , which annular groove  23  encloses the cover  4  at the level of the radial part of the angled-away bore. The annular groove  23  is intersected by an outlet bore  24  which is likewise made in the hydraulic block  15  and, like the annular groove  23 , is part of the pump outlet. The outlet bore  24  communicates via a separating valve with a brake master cylinder and via pressure build-up valves with wheel brakes. The separating valve, the pressure build-up valves, the brake master cylinder and the wheel brakes are not shown. 
         [0023]    The separating valve and the pressure build-up valves are solenoid valves which are installed into the hydraulic block  15 , but outside the sectional plane, for which reason they cannot be seen in the drawing. The brake master cylinder and the wheel brakes are situated outside the hydraulic block  15 ; they are connected by way of brake lines. 
         [0024]    On both sides of the opening of the angled-away bore on the circumference of the cover  4  and therefore on both sides of the annular groove  23  in the hydraulic block  15 , the cover  4  has two sealing rings  25  which are arranged in the circumferential grooves in the cover  4  and which seal on both sides of the annular groove  23  between the hydraulic block  15  and the cover  4 . 
         [0025]    On an opposite side of the pinion  9  and the internal gear  11  to the axial washer  19 , the internal gear pump  1  has a thrust washer  26  which bears sealingly against the end sides of the pinion  9 , the internal gear  11  and the separating piece. The thrust washer  26  is arranged immovable, that is to say in a rotationally, radially and axially fixed manner in the hydraulic block  15 . The thrust washer  26  is circular. The thrust washer  26  has an eccentric, cylindrical through hole which is coaxial with respect to the pump shaft  2  and which forms a bearing  27 , in which an end of the pump shaft  2  which is remote from the drive gear  7  is mounted rotatably in the manner of a plain bearing. In order to mount the pump shaft  2  in the manner of a plain bearing, a sliding bearing bush (not shown) can be pressed into the hole  27  in the axial washer  26  or can be fastened there in some other way. Anti-friction mounting of the pump shaft  2  by way of an anti-friction bearing (not shown) in the thrust washer  26  is also possible. 
         [0026]    By way of the pressure loading of the outer side of the axial washer  19  in the pressure field  20 , the axially movable axial washer  19  is loaded against the end sides of the pinion  9 , the internal gear  11  and the separating piece, and those end sides of the axially movable pinion  9 , of the axially movable internal gear  11  and of the axially movable separating piece which face away from the axial washer  19  are loaded against the facing inner side of the thrust washer  26 , with the result that the end sides of the pinion  9 , the internal gear  11  and the separating piece also bear sealingly against the thrust washer  26 . Here too, the contact is in the manner of a plain bearing, and the seal is not hermetic, but rather has a leak. 
         [0027]    The hydraulic block  15  has a stepped blind bore as installation space  28  for the internal gear pump  1 , into which blind bore the gear pump  1  is inserted and is fastened, for example, by way of caulking. The hydraulic block  15  is part of a slip control means (not shown) of a hydraulic vehicle brake system. The hydraulic block  15  is a rectangular part which is made from an aluminum alloy and has a second depression as installation space  28  for a second internal gear pump  1  and further depressions for hydraulic structural elements of the slip control means. Structural elements of this type are solenoid valves and hydraulic accumulators (not shown). The abovementioned electric motor (not illustrated) is flange-connected to the outside of the hydraulic block  15 , on the motor shaft of which electric motor or on a gear mechanism shaft of a gear mechanism which is flange-connected to the electric motor the driving gear  8  is seated which drives the two internal gear pumps  1  via the drive gears  7 . The seats for the hydraulic structural elements are connected to one another by way of bores in the hydraulic block  15 , as a result of which the hydraulic structural elements (not shown) of the slip control means are connected to one another hydraulically. Fitted with the hydraulic structural elements and provided with the electric motor and further electric, electromechanical and electronic components, the hydraulic block  15  forms a hydraulic assembly and a slip control assembly of the hydraulic vehicle brake system. 
         [0028]    A pump inlet which is arranged offset at an angle with respect to the pump outlet  29  can be brought about, like the pump outlet  29 , through the cover  4  and the axial washer  19  or, on the bottom of the depression in the hydraulic block  13  which forms the installation space  28 , through a through hole in the thrust washer  26 . The pump inlet is situated outside the sectional plane and therefore cannot be seen. 
         [0029]    The pressure field seal  21  is a sealing ring which encloses the semi-crescent-shaped pressure field  20  with a step-shaped annular cross section. An annular end face of the pressure field seal  21  bears against the outer side of the axial washer  19 . Offset to the outside and in the direction of the cover  4  with respect thereto, the pressure field seal  21  has a sealing bead which bears against the bottom of the pressure field  20  in the cover  4 . In an annular step on the outside of the pressure field seal  21  and facing the axial washer  19 , a supporting ring  30  encloses the pressure field seal  21  and supports the pressure field seal  21  from the outside. 
         [0030]    A filter  31  is arranged in the pressure field  20  inside the pressure field seal  21 . The filter  31 , for example a filter fabric, is encapsulated on its edge by a flange-like frame  32  which is semi-crescent-shaped in a manner which corresponds to the pressure field  20  and/or an inner side of the pressure field seal  21 . A clearance within the frame  32 , in which the filter  31  is situated, is likewise semi-crescent-shaped, in order to ensure a large filter area. The flange-shaped frame  32  of the filter  31  is smaller than an internal circumference of the pressure field seal  21 , with the result that there is a gap  33  (see  FIG. 2 ) on the circumference between the frame  32  of the filter  31  and the pressure field seal  21 . The flange-like frame  32  of the filter  31  is flatter than the depth of the pressure field  20 , with the result that there is a gap  34  between a side of the frame  32  of the filter  31 , which side faces the axial washer  19 , and the axial washer  19 . The pressure field  20  communicates with the pressure space of the pump space  13  of the internal gear pump  1  through the through hole  22  in the axial washer  19  and the gaps  33 ,  34  between the frame  32  of the filter  31  and the axial washer  19  and the pressure field seal  21 . By way of the pressure loading, the pressure field seal  21  is loaded into sealing contact both with the axial washer  19  and with the circumference and/or the bottom of the pressure field  20  in the cover  4 . The gap  33  between the frame  32  of the filter  31  and the axial washer  19  is part of the pressure field  20 . 
         [0031]    The frame  32  of the filter  31  has a collar  35  which protrudes toward the bottom of the pressure field  20  and bears with an outwardly protruding sealing bead in a sealing manner against a mating collar  14  of the cover  4  in the pressure field  20 , which mating collar  14  encloses the collar  35 . The collar  35  of the frame  32  of the filter  31  encloses the clearance in the frame  32 , in which the filter  31  is arranged. 
         [0032]    The frame  32  of the filter  31  forms a supporting element which supports the pressure field seal  21  from the inside. If the hydraulic block  15  is evacuated by way of the internal gear pump  1  before filling of the vehicle brake system with brake fluid, the frame  32  of the filter  31  which forms the supporting element prevents the pressure field seal  21  being displaced into the pressure field  20  to the inside and holds the pressure field seal  21  in its provided position on the circumference of the pressure field  20 . 
         [0033]    Within the collar  35 , a through hole  36  opens into the bottom of the pressure field  20 . The through hole  36  penetrates the cover  4  of the internal gear pump  1  in an axially parallel manner. As viewed from the pressure field  20 , the through hole  36  first of all widens conically with the formation of a valve seat  37  and subsequently by way of two annular steps. A non-return valve  38  is arranged in the through hole  36 , which non-return valve  38  has a disk-shaped valve body  39  with a ball ring-shaped bearing face  40  which interacts with the valve seat  37 , and a valve stem  41 . 
         [0034]    The valve stem  41  protrudes into a tubular damper body  42  which has a transverse wall  43  with a hole in its interior, through which hole the valve stem  41  reaches. The hole in the transverse wall  43  of the damper body  42  is larger than the valve stem  41 , with the result that there is a passage. 
         [0035]    On a side which faces away from the pressure field  20 , the stepped through hole  36  in the cover  6  is closed in a pressure-tight manner by way of a cap  44 . The cap  44  is pressed into the through hole  36  and is held in a pressure-tight manner, for example, by way of a calked connection (not shown). The cap  44  bears against an annular step of the through hole  36 . The damper body  42  is movable in the through hole  36 ; a spring element  45  in the form of a compression coil spring which is arranged between the cap  44  and the transverse wall  43  of the damper body  42  loads the damper body  42  and, via the latter, the closing body  39  of the non-return valve  38  against the valve seat  37 . On account of its movability in the through hole  36 , the damper body  42  damps pressure oscillations of brake fluid which occur during operation of the internal gear pump  1  as a result of the non-return valve  38 . 
         [0036]    The closing body  39  of the non-return valve  38  and of one end of the damper body  42  which faces it are enclosed by an annular channel  46  which is configured as an undercut in the through hole  36  adjacently to the valve seat  37 . The pump outlet  29  which runs radially in the cover  4  opens into the annular channel  46 . The pump outlet  29  is offset axially with respect to the annular channel  46 , with the result that the pump outlet  29  intersects the annular channel  46 . This results in a step with a small through flow cross section, which step likewise damps pressure oscillations in the pump outlet. 
         [0037]    The through hole  22  in the axial washer  19 , which through hole  22  communicates with the pressure space in the pump space  13  of the internal gear pump  1 , the pressure field  20 , the clearance in the frame  32  of the filter  31 , the through hole  36  as far as the damper body  42 , the annular channel  46  which encloses the closing body  39  of the non-return valve  38 , the annular groove  23  in the hydraulic block  15 , which annular groove  23  encloses the cover  4  between the sealing rings  25  and into which annular groove  23  the radial part of the pump outlet  29  opens, and the outlet bore  24  in the hydraulic block  15 , which outlet bore  24  intersects the annular groove  23 , form the pump outlet.