Abstract:
The invention relates to a positive displacement pump, including a pot-shaped housing, a rotor rotatably supported in the housing, and at least one blade movably guided in the rotor, the blade tip of which contacts the inner circumferential wall of the housing and divides the interior into chambers, wherein a locking mechanism that inhibits or brakes the movement of the blade in the rotor is provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims priority to German Patent Application No. 102012210048.2, filed on Jun. 14, 2012. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates, generally, to pumps and, more specifically, to a displacement pump. 
     2. Description of the Related Art 
     Conventional displacement pumps known in the art, and in particular hydraulic pumps, typically include a pot-shaped housing, a rotor that is swivel-mounted in the housing and at least one blade that is guided movably inside the rotor. The blade tip is attached at the inner peripheral wall of the housing and divides the internal space into chambers. 
     In vehicles, the vacuum pumps generate the vacuum in the brake boosters, and usually move permanently along with the vehicle engine. Depending on the speed, this translates into an energy consumption of several hundreds of watts, even though the vacuum required for braking has already been built up. 
     In DE 2502 184 A1, a refrigerating compressor with blades has been disclosed, in which the blades when they are in a retracted position in the rotor can be locked by notched extensions provided on the blades. 
     From DE 8517622 U1, a vane pump is known in which a hook space provided between the blades is pressurized for retracting the blades into the rotor. 
     While displacement pumps known in the related art have generally performed well for their intended purpose, there remains a need in the art for a displacement pump in which the blades can be easily locked in the rotor. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the disadvantages in the related art in a displacement pump including a pot-shaped housing, a rotor that is swivel-mounted in the housing and at least one blade that is guided movably inside the rotor. The blade tip is attached at the inner peripheral wall of the housing and divides the internal space into chambers when the displacement pump is operating. A locking mechanism inhibits the displacement of the blade inside the rotor by engaging the blade tractionally or frictionally. 
     In the time period in which the vacuum pump is not required in the vehicle, the locking mechanism, which can be integrated in the rotor, ensures that the displacement pump does not perform any displacement operation and the pump is “switched off” when the rotor is rotating. This occurs in that the blades or sliders available in the displacement pump are locked by the locking mechanism in an idle position, so that the pump is no longer working and the torque and power input of the pump are reduced, except for churning losses and bearing friction losses. This drastic reduction of the energy requirement also results in a considerable reduction of the CO 2  emission of the driving combustion engine. 
     The locking mechanism engages the blade tractionally or frictionally, and not in a positive engagement, such that the retraction and extension movement of the blades can be mechanically decelerated, until the blades assume their retracted position in the rotor and the pump is no longer generating any power. Advantageously, this retraction and locking operation of the blades takes place in a transitional period, which is the period between normal operation of the pump and disconnection of the pump, when the pump is no longer generating any power and the blades are retracted in the rotating rotor and locked in an idle position. Because of the tractional or frictional connection, it can still be ensured that the blades are securely locked in their idle position. 
     This invention can be applied to all vane pumps or piston valve pumps (static rotary pumps) having any number of blades and working chambers. The principle is not limited to vacuum pumps but can also be applied to pressure pumps, as well as different media, for example, oil or water pumps and the like, if these are permanently moving along, but are not constantly required. 
     It is of advantage when in the rotor at least two blades arranged in parallel to one another are provided, wherein the blades, respectively, include a first section remaining in the rotor in such a way that the respectively first sections overlap at least sectionwise perpendicularly to the displacement plane of the blades. Each of the blades has at least a second section which comes out of the rotor when the pump is operating. Consequently, the respectively first sections are the sections which remain in the rotor when the blades are retracted. Advantageously, the locking mechanism engages at the respectively first sections of the blades. As a result, especially the locking mechanism can have a small design because the blades engage where they are located in close proximity to one another. 
     At the same time, the locking mechanism can engage in radial and/or axial direction at the respectively first section of the blade. Also in this respect the locking mechanism can have a comparatively small design. 
     Advantageously the locking mechanism is arranged in an intermediate space provided between the first sections of the blades and acts when the blades are activated in radial direction on the broadsides of the first sections of the blades facing each other. Because of the fact that the blades are arranged to overlap one another, the locking mechanism can act simultaneously on the broadsides of the blades facing each other. 
     Furthermore, the locking mechanism can include a flexible blocking element, which is arranged or engages in the intermediate space and which has a recess and an expansion element, which engages in the recess in such a way that when axially displaced the expansion element expands the blocking element in such a way that the blocking element acts on the broadsides of the first sections of the blades facing each other. Thus, it is possible to provide a tractional and frictional connection for locking the blades. At the same time, the recess and/or expansion element can have a v-shaped or cone-shaped design so that, when the expansion element is axially displaced, power deflection in radial direction and/or even power reinforcement takes place, resulting in the fact the blocking element or sections thereof act in radial direction on the blades. 
     Alternatively, it is also possible that the locking mechanism has a blocking element, which is arranged in axial extension of the blades and which can be axially displaced in such a way that, when axially displaced, the blocking element acts on the front ends of the first sections of the blades arranged in parallel to one another or located in a plane. As a result, the blocking element acts in axial direction on the blades and firmly fixes them. 
     In one embodiment, the locking mechanism or blocking element is arranged in or at the rotor and rotates with the rotor when the pump is in operation. 
     To actuate the locking mechanism, it is of advantage when provision is made for a control element on the side of the housing which can be activated in axial direction via a drive system, wherein, in one embodiment, a rotation decoupling and an axial movement coupling are provided between the control element and the locking mechanism. 
     By the rotation decoupling, it is possible to decouple the rotational movement of the locking mechanism in relation to the non-rotating control element on the side of the housing. In particular, the rotation decoupling can include a ball, which can be arranged, for example, between the control element and the blocking element or between the control element and the expansion element. In an axial forward movement of the control element, the actuating force can be initiated via the ball in the rotating blocking element or expansion element. 
     The axial movement coupling can be formed by a ring element provided at the control element and an annular groove provided at the expansion element or the blocking element, which receives the ring element, or vice versa. As a result, it is possible that, especially in a reverse movement of the control element for releasing the locking mechanism, the blocking element or expansion element is taken along by the control element. At the same time, it is advantageous, when sufficient clearance is available between the ring element and the annular groove, so as not to establish any physical contact between the ring element and the annular groove when the control element is in an extended position in which the control element acts especially on the ball and the locking mechanism is activated. 
     In a further development of the invention, the locking mechanism is provided in the rotor and/or at least in a cover which closes the internal space at the front end. As a result the locking mechanism engages radially and/or axially at the blade and blocks its radial displacement in the rotor. 
     Advantageously, the locking mechanism is driven and/or activated mechanically, pneumatically, hydraulically, magnetically and/or electromagnetically. In this way, it is possible to provide a simple and cost-effective control system and fast drive system. 
     It is possible that the locking mechanism is activated when the blade assumes its maximum retracted position in the rotor. As a result, the blade tip ends flush with the outer circumference of the rotor. Then the rotor continues to rotate virtually idle. 
     In order to reactivate the displacement pump, the locking mechanism is in one embodiment, deactivated when the rotor assumes a rotary position in which the blade tip of the locked blade shows the least distance from the inner peripheral wall of the housing. Usually, this is the case when the rotor assumes the rotary position in which the blade was locked, so that the blade tip touches down gently on the inner peripheral wall and can glide along the inner peripheral wall. 
     As mentioned above, the locking mechanism engages radially and/or axially at the blade. The axial locking operation takes place via the cover(s) at the front end and the radial locking operation takes place directly at the rotor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects, features, and advantages of the present invention will be readily appreciated as the same becomes better understood after reading the subsequent description taken in connection with the accompanying drawing wherein: 
         FIG. 1  shows a top view on a displacement pump designed in the form of a vane pump and having a deactivated locking mechanism. 
         FIG. 2  shows a top view of the displacement pump of  FIG. 1  having an activated locking mechanism. 
         FIG. 3  shows a top view on a displacement pump having a tractional radial locking mechanism. 
         FIG. 4  shows a top view on a displacement pump having a tractional radial locking mechanism. 
         FIG. 5  shows a perspective view of the displacement pump of  FIG. 4  having a mechanical control system. 
         FIG. 6  shows an embodiment of the pump of  FIG. 5 . 
         FIG. 7  shows a longitudinal section of the pump of  FIG. 6  when the locking mechanism is deactivated. 
         FIG. 8  shows a longitudinal section of the pump of  FIG. 6  when the locking mechanism is activated. 
         FIG. 9A  shows a perspective view of the expansion element and the blocking element of  FIGS. 7 and 8 . 
         FIG. 9B  shows a longitudinal section through the expansion element and the blocking element of  FIG. 9A . 
         FIG. 10  shows a perspective view of the displacement pump having a tractional axial locking mechanism which is deactivated. 
         FIG. 11  shows a perspective view of the displacement pump of  FIG. 10  having an activated locking mechanism. 
         FIG. 12  shows a longitudinal section through the pump of  FIG. 11 . 
         FIG. 13  shows a perspective view from  FIG. 12 . 
         FIG. 14A  shows a diagram for controlling electromagnetically the locking mechanism when using an oil pump. 
         FIG. 14B  shows a diagram for controlling electromagnetically the locking mechanism when using a camshaft. 
         FIG. 15A  shows a diagram for internally controlling pneumatically the locking mechanism by a vacuum when using an oil pump. 
         FIG. 15B  shows a diagram for internally controlling pneumatically the locking mechanism by a vacuum when using a camshaft. 
         FIG. 16A  shows a diagram for externally controlling pneumatically the locking mechanism by a solenoid valve when using an oil pump. 
         FIG. 16B  shows a diagram for externally controlling pneumatically the locking mechanism by a solenoid valve when using a camshaft. 
         FIG. 17A  shows a diagram for externally controlling hydraulically or pneumatically the locking mechanism when using an oil pump. 
         FIG. 17B  shows a diagram for externally controlling hydraulically or pneumatically the locking mechanism when using a camshaft. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference now to the drawings,  FIG. 1  shows a displacement pump  10 , which is designed in the form of a vane pump and which has a housing  12  in which a rotor  14  is swivel-mounted. Two blades  16  are movably guided in the rotor  14  so that the blade tips  18  touch the inner peripheral wall  20  of the housing  12 . The blades  16  divide the internal space  34  of the housing  12  into chambers  22 ,  24  and  26 , wherein in the case at hand chamber  22  depicts a pressure chamber and chamber  26  a suction chamber. During the rotation operation of the rotor  14 , the blades  16  perform translational movements (indicated by the arrows  30 ) inside the rotor  14 , i.e., in vane shafts  28 . 
       FIG. 2  shows the displacement pump  10  as shown in  FIG. 1 , wherein the blades  16  are completely retracted in the rotor  14  and the blade tips  18  are located on or within the circumference  32  of the rotor  14 . The blades  16  no longer divide the internal space  34  into chambers. The position of the blades  16  is retained in a locking mechanism (as shown in  FIGS. 3-8 ). 
       FIGS. 1 and 2 , as well as other figures, show that the blades  16  are arranged in the rotor  14  in parallel to one another. Each blade  16  has a first section  80 , which remains in the rotor  14 , especially when the blades  16  are retracted, wherein, as shown in  FIG. 2 , the sections overlap at least sectionwise perpendicularly to the displacement plane of the blades  16 . Between the two blades  16  or their sections  80 , there is an intermediate space  82 , in which advantageously the locking mechanism  36  can be situated (embodiments as shown in  FIGS. 3 to 8 ). 
     In  FIGS. 3 to 8 , the displacement pump  10  has a locking mechanism  36  provided in the intermediate space, which locking mechanism  36  acts radially on the blades  16  and operates tractionally.  FIGS. 4 and 5  show that the locking mechanism  36  ensures that the blades  16  are retained in the rotor  14  when the displacement pump  10  is not needed. The blades  16  are retained in a non-use position, for example, in that the blades  16  are mechanically jammed (arrow  38 ) radially in a tractional or frictional connection that they can no longer be forced to the outside against the inner peripheral wall  20 . 
     The locking mechanism  36  includes a blocking element  84  arranged in the intermediate space  82 , which in particular can include a flexible plastic material. In the embodiment as shown in  FIGS. 3, 4 and 5 , the blocking element  84  has on its upper surface (shown in  FIGS. 3 ,  4  and  5 ) a recess  86  in the form of a taper groove, which extends in longitudinal direction of the blocking element  84 . 
     A control element  40 , which can be displaced along its longitudinal axis or the arrows  42 , engages in the taper groove. In the embodiment shown in  FIGS. 3 to 5 , the control element  40  has a cone-shaped tip  88  facing the blocking element  84 . The tip  88  engages in the recess  86  in such a way that the blocking element  84  is expanded radially to the outside when the control element  40  is displaced in axial direction into the intermediate space  82 , thus fixing tractionally the blades  16  in the rotor  14  in the region of the sections  80 . 
       FIGS. 6 to 9   b  show a further development of the embodiment as shown in  FIGS. 3 to 5 , wherein the respective components are provided with the appropriate reference numerals. 
       FIGS. 9 a  and 9 b    also show that a blocking element  84  is available in the intermediate space  82 .  FIGS. 8, 9   a  and  9   b  show that in addition to the control element  40  which can be displaced in axial direction via a drive system  90 , the embodiment as shown in  FIGS. 6 to 9   b  has an expansion element  92  which is coupled in movement in axial direction with the control element  40 . The expansion element  92  is coupled in movement in axial direction with the control element  40 . However, the expansion element  92  is rotationally decoupled from the control element  40 . 
       FIG. 7  shows the control element  40  in its retracted position. As a result, the locking mechanism  36  is deactivated. In  FIG. 8 , the drive system  90  is activated. Consequently, the control element  40  is extended. As a result, the locking mechanism  36  is activated. 
       FIG. 9 b    shows that the free end  94  of the expansion element  92  facing the blocking element  84  has a cone-shaped design.  FIGS. 9 a  and 9 b    also show that the free end  94  engages in a recess  86  of the blocking element  84  which also has a cone-shaped design. As a result, the blocking element  84  is expanded in radial direction when the expansion element  92  or its end  94  is retracted in axial direction. As shown in  FIG. 8 , the blades  16  are fixed frictionally or tractionally in their position. 
     The expansion element has a first sleeve-like section which receives the control element  40 . The expansion element  92  has a pin section with the free end  94  on the side facing the blocking element  84 . A ring element  96  is arranged in the radially inner region of the sleeve-like section. A ball  102  is arranged in the bottom area of the sleeve-like section. 
     For an axial movement coupling of the control element  40  and the expansion element  92 , the ring element  96  is provided between the control element  40  and the expansion element  92 , wherein the ring element  96  is sectionwise situated in one embodiment with large clearance in an annular groove  98  on the side of the expansion element  92  and sectionwise in one embodiment with large clearance in an annular groove  98  situated on the side of the control element  40 . As a result, especially when retracting the control element  40  into the position shown in  FIG. 7 , the expansion element  42  is taken along. 
     Furthermore, a ball  102  is provided for rotational decoupling in axial direction between the control element  40  and the expansion element  92 . This allows the expansion element  92  to rotate in relation to the control element  40 , especially in the retracted position of the control element  40  shown in  FIG. 8  in which the expansion element  92  rotates with the rotor  14 . The arrangement is made in such a way that in one embodiment in the region of the ring element  96  no physical contact takes place between the control element  40  and the expansion element  92  when the locking mechanism  36  is activated. As a result, the expansion element  92  can rotate comparatively contact-free in the region of the ring element  96  in relation to the control element  40 . 
     Consequently, the embodiment as shown in  FIGS. 6 to 9   b  functions in the following way: 
     Based on  FIG. 7 , the drive system  90  is actuated. The drive system  90  can involve a pneumatic drive system or a magnetic drive system which causes the control element  40  to be extended in axial direction. In  FIG. 7 , the control element  40  is retracted. Therefore, the expansion element  92  arranged at the control element  40  has no physical contact with the rotor  14  or the blocking element  84  arranged in the rotor  14  between the blades  16 . If now the control element  40  is moved into the position as shown in  FIG. 8 , the free end  94  of the expansion element  92  submerges into the recess  86  of the blocking element  84 . Because of the physical contact between the expansion element  94  and the blocking element  84 , the expansion element  92  starts to rotate with the rotor  14 . Via the ball  102  a rotation of the expansion element  92  takes place, wherein at the same time, power is transmitted in axial direction from the control element  40  to the blocking element  84 . When the free end  94  of the expansion element  92  submerges again into the recess  86 , the blocking element  84  is expanded in radial direction. The axial force is deflected in a radially effective force. Depending on the inclination of the cones, it is possible to reinforce the power in radial direction. 
     The radial force generates a friction force which inhibits the movement of the blades  16 . Because of the fact that the rotor continues to rotate, the free ends of the blades  16  are gliding along the inner peripheral wall  20 , thus automatically moving the blades  16  into the rotor  14 . Because of the tractional or frictional connection of the blocking element  84 , the blades  16  are retained in the rotor  14 . As a result, the locking mechanism  36  is activated; the pump  10  is deactivated and does not supply any power when the rotor  14  is rotating. 
     To resume the operation of the pump  10 , the control element  40  is retracted in axial direction into the position shown in  FIG. 7 . Because of the translational movement coupling, the expansion element  92  is retracted in axial direction by the ring element  96 . In operation, the free end  94  is disengaged from the recess  86  of the blocking element. As a result, the expansion element  92  is no longer driven rotationally by the blocking element  84 . It stops to rotate. 
     Because of the elastic flexibility of the blocking element  84 , the tractional or frictional connection with the blades  16  is released in radial direction. As a result, the blades  16  can freely move again in the rotor  14 . The pump  10  starts to perform again. 
     In the embodiments shown in  FIGS. 1 to 13 , the displacement pump  10  has a locking mechanism  36  which acts axially on the blades  16  and operates tractionally or frictionally. As shown in  FIG. 11 , the locking mechanism  36  ensures that the blades  16  are retained in the rotor  14  when the displacement pump  10  is not needed. For example, the blades  16  are retained in that they are mechanically jammed axially to the extent that they can no longer be forced to the outside against the inner peripheral wall  20 . Control takes place via a mechanical force which acts in the direction of the arrows  46  on the front ends  104  of the blades  16 , thus locking the blades  16  in the rotor  14 . 
       FIGS. 12 and 13  show such specification, wherein components already shown in the preceding figures are identified with the appropriate reference numerals. 
       FIGS. 12 and 13  clearly show the blocking element  84  which has a plate-like design. The blocking element  84  has a first sleeve-like section for receiving the free end of the control element  40 . On the surface facing the blades  16 , the blocking element  84  has a plate-like design so that it can act on the front ends  104  of the blades  16 , which are arranged next to one another in a plane. As a result, the blades  16  are retained tractionally or frictionally and actively locked in the rotor  14 . 
     The blocking element  84  is activated in axial direction by the control element  40  of the drive system  90 . At the same time, the control element  40  is coupled in movement in axial direction with the blocking element  84  and rotationally decoupled (via the ring element  96  and the ball  102 , as described in  FIGS. 6 to 10  with regard to the control element  40  and the expansion element  92 ). 
     If now the control element  40  is displaced from its axially retracted position by actuating the drive system  90  into its axially extended position, the blocking element  84  is impinged in axial direction against the front ends  104  of the blades  16 . As a result, the blades  16  can be fixed in the rotor  14 . 
     Because of the fact that the blocking element  84  is housed in the rotor  14 , it is also rotating with the rotor  14 . The rotation decoupling can be provided by the ball  102 , so that power can be transmitted in axial direction despite the fact that the blocking element  84  is rotating and the control element  40  is not rotating. 
     The control element  40  is retracted in axial direction so as to deactivate the locking mechanism  36 . Via the ring element  96 , the control element  40  takes along the blocking element  84  in axial direction. Then the blocking element  84  is lifted off the front ends  104  of the blades  16 . The blades  16  are now able to freely move in the rotor  14 . As a result, the pump  10  is activated again. 
       FIGS. 14 a  and 14 b    show a diagram for an electromagnetic control system of the locking mechanism  36 . Via a drive shaft  50  (camshaft  62  of an engine  64 ) a lubrication pump  52  is actuated which, in turn, actuates the displacement pump  10  and supplies a brake booster  54  with low pressure. The pressure in the brake booster  54  is acquired by a sensor  56  and transmitted to control electronics  58  which, on its part, controls an electromagnet  60 . The electromagnet  60  actuates the locking mechanism  36  which acts on the blades  16  in the displacement pump  10 . As soon as a predetermined low pressure has been reached in the brake booster  54 , the locking mechanism  36  is activated and the blades  16  are blocked in the rotor  14 . A return valve  66  prevents a reduction of the pressure in the brake booster  54 . 
       FIGS. 15 a  and 15 b    show a diagram for an internal pneumatic actuation of the locking mechanism  36 . The pressure in the brake booster  54  is directly transmitted via a line  68  to an internal pneumatic vacuum control  70  which, on its part, actuates the locking mechanism  36  which, in turn, acts on the blades  16  in the displacement pump  10 . The reference numeral  10  refers to the displacement pump as a whole. 
       FIGS. 16 a  and 16 b    show a diagram for an external pneumatic control system of the locking mechanism  36 . The pressure in the brake booster  54  is transmitted via the line  68  to an external magnetic valve  72 , which controls the pneumatic vacuum control  70  which, on its part, actuates the locking mechanism  36  which, in turn, acts on the blades  16  in the displacement pump  10 . 
       FIGS. 17 a  and 17 b    show a diagram for an external hydraulic or pneumatic control system of the locking mechanism  36 , similar to the control system as shown in  FIGS. 10 a  and 10 b   . The pressure in the brake booster  54  is acquired by the sensor  56  and transmitted to control electronics  58  which, on its part, controls the hydraulic or pneumatic vacuum control  70 , which is indicated by arrows  74  and  76 . As soon as a predetermined low pressure has been reached in the brake booster  54 , the locking mechanism  36  is activated and the blades  16  are blocked in the rotor  14 . 
     The invention has been described in an illustrative manner. It is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the invention may be practiced other than as specifically described.