Abstract:
The motor/pump unit ( 10 ) comprises an electromotor ( 12 ) and at least one pump ( 14 ) for delivering brake fluid. The electromotor ( 12 ) has a motor stator ( 16 ) in which a motor rotor ( 18 ) is rotatably disposed. The pump ( 14 ) is disposed substantially within the motor rotor ( 18 ) and can be driven by the latter. In order to provide a vehicle brake system with a motor/pump unit ( 10 ) which is capable of delivering brake fluid in a highly dynamic fashion, the motor stator ( 16 ) and at least one section ( 22 ) of the motor rotor ( 18 ) which is directed towards the motor stator ( 16 ) define an electromagnetic region ( 16, 22, 24 ), and at least the pump ( 14 ) defines a hydraulic region ( 14, 26 ), wherein at least one sealing element ( 28, 96, 98 ) is provided which separates the electromagnetic region ( 16, 22, 24 ) from the hydraulic region ( 14, 26 ) in a fluid-tight fashion.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application No. PCT/EP00/12350 filed Dec. 7, 2000, which claims priority to German Patent Application No. 19958936.4 filed Dec. 7, 1999, the disclosures of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to a vehicle brake system which comprises a motor/pump unit with an electromotor and at least one pump for delivering brake fluid. The electromotor comprises a motor stator in which a motor rotor is rotatably disposed. The pump is disposed substantially within the motor rotor and can be driven by the latter. The invention also relates to a motor/pump unit of this kind. 
     The motor/pump unit serves to deliver brake fluid to and from wheel brakes of the vehicle brake system in order to actuate or release these brakes. Vehicle brake systems of this kind are also called electrohydraulic brake systems, which can be operated in so-called anti-lock braking, traction or vehicle movement dynamics control mode. The motor/pump unit may be disposed directly at a wheel brake of a vehicle or serve as a central supply member for a plurality of wheel brakes. 
     A brake system with a vehicle brake actuator in which an electromotor comprises a stator winding fitted in a stationary fashion and a rotor fitted so as to be rotatable therein is known from U.S. Pat. No. 4,435,021 A, which is hereby incorporated by reference. The rotor bears a plurality of axial pistons which are supported at an inclined end face, with which they form an inclined-plate pump. Brake fluid which flows around the rotor emerges at the axial pistons during operation of the inclined-plate pump. The brake fluid also enters a gap between the stator winding and the rotor, where it gives rise to a high fluid friction resistance and reduces the magnetic flux between the stator winding and the rotor. The electromotor therefore has a low dynamic performance level, i.e. poor starting and response characteristics. 
     The object of the invention is to remedy the above-mentioned problem and in particular to provide a vehicle brake system with a motor/pump unit which is capable of delivering brake fluid in a highly dynamic fashion. 
     SUMMARY OF THE INVENTION 
     The object is achieved according to the invention by a vehicle brake system with a motor/pump unit which has the above-mentioned features and is developed such that the motor stator and at least one section of the motor rotor which is directed towards the motor stator define an electromagnetic region, at least the pump defines a hydraulic region, and at least one sealing element is provided which separates the electromagnetic region from the hydraulic region in a fluid-tight fashion. 
     The sealing element which is disposed according to the invention separates the motor stator and the section of the motor rotor which faces it from the hydraulic region of the pump, in which brake fluid is located. It is therefore impossible for any brake fluid to enter the gap between the motor stator and the motor rotor. This means that no fluid friction resistance occurs in the gap and the dynamic performance of the electromotor is significantly augmented. This measure at the same time increases the efficiency of the electromotor. The result is a an electromotor and pump combination which is optimised in control terms. Moreover, the electromagnetic region is separated from the hydraulic region in a fluid-tight fashion, so that no dirt can reach the electromagnetic region. There is thus no possibility of the motor stator being soiled or damaged, for example due to aggressive brake fluid. The electromotor and the pump are in this case of a particularly compact configuration in a so-called cartridge construction. It is also possible for a plurality of pumps to be surrounded by the motor rotor, in particular radially, in order, for example, to provide an individual pressure source for each wheel brake. 
     The object is also achieved according to the invention by a motor/pump unit of this kind. 
     The vehicle brake system is advantageously developed such that there is just an air gap between the motor stator and the motor rotor. The entire motor rotor is located in the hydraulic region in the case of the vehicle brake actuator which is described in U.S. Pat. No. 4,435,021 A. The motor winding is therefore surrounded internally by a partition which separates it off from the hydraulic region and also from the motor rotor. However this partition may be dispensed with in order to achieve the object according to the invention. The spacing between the motor stator and the motor rotor may therefore be very small. This additionally improves the efficiency and response and starting characteristics of the electromotor. 
     According to an advantageous development, the motor stator is fitted in a stationary fashion in a casing, and the sealing element is formed in an annular fashion between the motor rotor and the casing. In this particularly simple configuration of the invention the sealing element which is used may be a conventional, inexpensive sealing ring which is selected from a wide range and can therefore be adapted particularly well to the sealing object which is to be achieved. 
     In an advantageously developed vehicle brake system the motor rotor is rotatably supported in the casing about a rotational axis by means of two bearings which are disposed at the axial end regions of the motor rotor. The bearings enable the motor rotor to be precisely guided, with the possibility of adjusting its position independently of the pump. 
     The motor rotor is advantageously substantially cup-shaped and comprises at its bottom a coaxially fitted drive shaft, which is connected in a driving fashion, for driving the pump. Because the cup shape is only open to one side, a configuration of this kind enables a closed space for the pump to be sealed off particularly easily in the motor rotor. For example, a sealing element may be disposed at the opening of the cup-shaped motor rotor for this purpose. 
     However the casing advantageously comprises a substantially hollow cylindrical casing section which projects radially inwards and coaxially into the cup-shaped motor rotor, and the sealing element is advantageously disposed between the hollow cylindrical casing section and the drive shaft. The motor rotor is thereby sealed off at a relatively small area, and a sealing element of a small diameter can be used. Sealing elements of this kind have a relatively low frictional resistance and require little construction space. Moreover, because the casing section is disposed between the motor rotor and the pump, there is no fluid friction between the motor rotor and the pump. 
     In an advantageous configuration the motor rotor is substantially of a hollow cylindrical shape and connected in a driving fashion to the pump at an inner circumferential surface. This constitutes a particularly simple coupling between the pump and the motor rotor which may, for example, be in the form of a tongue-and-groove joint. The motor rotor and the pump may in this respect be elastically connected such that little structure-borne sound is transmitted outwards from the pump to the motor rotor and the casing. 
     A respective sealing element is advantageously disposed between the axial end sections of the motor rotor and the casing in this configuration. This means that a particularly large construction space is available for the pump. The pump may also pass axially through the motor rotor. 
     The pump is advantageously formed as an inclined-plate pump, in which a pump rotor is coupled in a driving fashion to the motor rotor, in which pump rotor at least one axial piston can be displaced, the latter being supported at an inclined plate fitted in a stationary fashion to the casing. This configuration is used together with a hollow cylindrical motor rotor, to which the pump rotor is directly coupled. The pump rotor may then also be integral with the motor rotor. 
     The pump may alternatively be in the form of a swash-plate pump, with a swash plate being coupled in a driving fashion to the motor rotor and supporting at least one axial piston which can be axially displaced in a piston guide which is fitted in a stationary fashion to the casing. This configuration can be used to particular advantage together with a cup-shaped motor rotor, to the bottom of which the swash plate is coupled. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features and properties are illustrated on the basis of the description of two embodiments with reference to the accompanying drawings. 
     FIG. 1 is a longitudinal sectional view of a first embodiment of a motor/pump unit according to the invention. 
     FIG. 2 is a longitudinal sectional view of a second embodiment of a motor/pump unit according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A motor/pump unit  10  is represented in FIG. 1, this unit comprising an electromotor  12 , which in the represented embodiment is a brushless d.c. motor, and a pump  14 . 
     The electromotor  12  is formed with a hollow cylindrical motor stator  16  and a motor rotor  18 , which is disposed in the latter. The motor rotor  18  can rotate about a rotational axis  20 , and its section which radially faces the motor stator  16  comprises permanent magnets  22 . The motor rotor  18  is substantially of a hollow cylindrical shape. The pump  14  is disposed coaxially with the rotational axis  20  in its cavity. The pump  14  is driven by means of the motor rotor  18  during operation of the motor/pump unit  10  in order to deliver brake fluid to wheel brakes, which are not represented, or away from these. 
     In order to obtain a highly dynamic motor/pump unit  10 , the motor stator  16  and the radially outer part of the motor rotor  18 , i.e. the permanent magnets  22 , are surrounded by a gas space  24  (marked by dots) containing air. This part of the motor/pump unit  10  is called the electromagnetic region. The pump  14  is also surrounded by a fluid space  26  (marked by wavy lines) which is filled with brake fluid, this part being called the hydraulic region of the motor/pump unit  10 . An annular sealing element  28  is disposed between the electromagnetic and the hydraulic region, which element separates these regions in a fluid-tight fashion. As the electromagnetic region is therefore without brake fluid, no fluid friction is produced between the motor stator  16  and the motor rotor  18 . The dynamic performance of the motor/pump unit  10  is as a result improved. There is also no possibility of the motor stator  16  and the motor rotor  18  being soiled or damaged by brake fluid. 
     The embodiment which is represented in FIG. 1 is described in detail in the following. The motor/pump unit  10  is externally bounded by a cup-shaped casing part  30 , which is rotationally symmetrical about the rotational axis  20  and is closed by a casing cover  32  at an end side which is on the left in FIG. 1. A spacer ring  34  and then the motor stator  16  are inserted axially in the casing part  30 . The motor stator  16  is held axially between the spacer ring  34  and the casing cover  32  and is supported radially at the casing part  30 . 
     At the end wall which is opposite the casing cover  32  the cup-shaped casing part  30  comprises an opening through which a feed line  36  is passed into the interior of the casing part  30 . Here the lead-through of the feed line  36  is sealed off by means of an elastomer sleeve  38 . 
     The motor stator  16  comprises a stator winding  40 , which is positioned around an iron core  42 . There is just a small air gap  44  between the iron core  42  and the permanent magnets  22 . 
     The motor rotor  18  comprises a cup-shaped rotor body  46  which bears a backing portion  22 A of the permanent magnets  22  on the outside in the radial direction as shown in FIG.  1 . The cup-shaped rotor body  46  is mounted at its end section which is on the right in FIG. 1 by means of a ball bearing  48 , which is held in the cup-shaped casing part  30  by a spring ring  50 . The end section of the cup-shaped rotor body  46  which is axially opposite the ball bearing  48  is supported by means of a second ball bearing  52  in the casing cover  32 . The rotor body  46  is positioned precisely in relation to the motor stator  16  by the bearings  48  and  52 . The air gap  44  may therefore be particularly small. A drive shaft  54  projects coaxially into the cavity formed by the rotor body  46  at a bottom of the cup-shaped rotor body  46 . A hollow cylindrical casing section  56  of the casing cover  32  projects into the cavity from the side which is opposite the bottom of the cup-shaped rotor body  46 . This casing section  56  is stepped at the end region which faces the drive shaft  54  and bears here the annular sealing element  28 , which provides a seal with respect to the drive shaft  54 . The sealing element  28  is pressed into the casing section  56  and comprises two sealing lips  58  and  60 , which lie against the drive shaft  54 . The sealing element  28  is U-shaped, with the opening of the U shape being directed towards the hydraulic region. The sealing lip  58  is therefore pressed against the drive shaft  54  by hydraulic pressure. 
     An inclined plate  62  is disposed axially next to the sealing element  28  in the casing section  56  and is fixed by means of a feather key  64  engaging in a longitudinal groove  66  which is formed in the hollow cylindrical casing section  56 . A coaxial bore  68  is formed in the inclined plate  62 , in which bore the drive shaft  54  passes through the inclined plate  62 . The drive shaft  54  projects into a cylindrical pump rotor  70 , which is disposed axially next to the inclined plate  62  in the casing section  56 , in which it is rotatably mounted. The cylindrical outer surface of the pump rotor  70  also co-operates with a part of the cylindrical inner surface of the casing section  56  as a sliding-contact bearing. 
     Axial pistons can be displaced in the pump rotor  70 , two of which pistons are designated by reference numbers  72  and  74  in FIG.  1 . The axial pistons  72  and  74  are supported at the inclined plate  62 , so that an axial piston pump in the form of an inclined-plate machine is created. At the end side of the pump rotor  70  which is opposite the inclined plate  62  this rotor  70  is supported at a plate-shaped pump shield  76 , which is positioned by means of a feather key  78  in the longitudinal groove  66  so as to be non-rotatable with respect to the casing section  56 . 
     The pump shield  76  is adjoined on the outside in the axial direction by a pump cover  80 , which comprises a shoulder which is directed towards the casing section  56  and has a radial external tooth system  82 . The external tooth system  82  meshes with a corresponding internal tooth system formed at the casing cover  32 . A sealing ring  84  is inserted in the casing cover  32  at the end side which faces the pump cover  80 . The pump cover  80  is therefore disposed such that it cannot rotate and closes the casing cover  32  in a fluid-tight fashion. 
     Two connections  86  and  88  are formed in the pump cover  80  in order to connect the pump shield  76  and the pump rotor  70  to brake fluid lines, which are not represented. 
     The motor rotor  18  rotates relative to the motor stator  16  when the motor/pump unit  10  is operating and in the process rotates the drive shaft  54 . The drive shaft  54  rotates the pump rotor  70 , and the axial pistons  72  and  74  move and deliver brake fluid. As the pump  14  has no valve control system, the direction in which the pump  14  delivers can be changed by reversing the direction of rotation of the drive shaft. 
     The embodiment which is represented in FIG. 2 resembles in functional terms that which is represented in FIG.  1 . The motor stator  16  is fitted in the casing part  30 , in which stator the motor rotor  18  is rotatably mounted on the inside in the radial direction. The motor rotor  18  comprises a hollow cylindrical rotor body  90 , which is mounted at its axial end regions with the ball bearing  48  in the casing part  30  and with the ball bearing  52  in the casing cover  32 . The ball bearing  48  is likewise fixed by means of the spring ring  50  and forms a rigid bearing, whereas the ball bearing  52  forms a movable bearing. An external thread  92 , onto which a lock ring  94  is screwed, is formed at the cup-shaped casing part  30 . The casing cover  32  is coupled to the casing part  30  by means of the lock ring  94  in order to position the ball bearings  48  and  52  relative to one another and the motor rotor  18  in the motor stator  16 . 
     An annular sealing element  96  and  98 , respectively, is disposed on the outside in the radial direction about the ball bearings  48  and  52 , respectively, in the cup-shaped casing part  30  and in the casing cover  32 , which element provides a seal between the hollow cylindrical rotor body  90  and the casing part  30  or the casing cover  32 . The electromagnetic region is thus separated from the hydraulic region as described above. 
     In this embodiment the inclined plate  62  is fitted directly to the casing part  30  and secured so as not to rotate by means of the feather key  64  in the groove  66  in the casing part  30 . The pump rotor  70  is disposed axially next to the plate  62  and comprises three axial pistons. A longitudinal groove  100  is formed in the inner surface of the hollow cylindrical rotor body  90 . A feather key  102 , which is mounted so as to be stationary at the outer surface of the pump rotor  70 , engages in the longitudinal groove  100 . The pump rotor  70  is coupled via the feather key  102  to the motor rotor  18  so as to rotate with it. An axial through-bore  104  is also formed in the pump rotor  70 , via which bore the connection  88  communicates with the fluid space  26 . 
     A recess is formed in the casing cover  32  in a region of the circumference, in which recess a lug  106  of the casing part  30  engages. The casing cover  32  is therefore positioned so as not to rotate. A sealing ring  108 , which provides a seal with respect to the casing cover  32 , is also inserted in the pump shield  76 . 
     The motor rotor  18  drives the pump rotor  70  via the feather key  102  when the motor/pump unit  10  which is represented in FIG. 2 is operating. The motor rotor  18  is in this case only separated from the motor stator  16  by the air gap  44 , so that a high magnetic flux is guaranteed and the frictional resistance between the parts rotating relative to one another is negligible. The pump rotor  70  rotates with the motor rotor  18 , so that there is also no friction between these components—for example due to fluid friction of brake fluid. The motor/pump unit  10  therefore has a particularly high dynamic performance level and very good starting and response characteristics. 
     In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.