Patent Publication Number: US-11396811-B2

Title: Variable lubricant vane pump

Description:
CROSS REFERENCE TO PRIOR APPLICATIONS 
     This application is a U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/EP2017/082641, filed on Dec. 13, 2017. The International Application was published in English on Jun. 20, 2019 as WO 2019/114949 A1 under PCT Article 21(2). 
     FIELD 
     The present invention is directed to a variable lubricant vane pump for providing pressurized lubricant. The present invention is in particular directed to a mechanical variable displacement lubricant vane pump for providing a pressurized lubricant for an internal combustion engine. 
     BACKGROUND 
     The variable lubricant vane pump is mechanically driven by the engine, for example, via a gear or belt, and is fluidically coupled to the engine for pumping the pressurized lubricant to and through the engine. The pump outlet pressure or the lubricant gallery pressure in the engine must be controlled and stabilized to a set pressure value. 
     WO 2014/198322 A1 describes a typical variable lubricant vane pump for providing a pressurized lubricant for an internal combustion engine. The vane pump is provided with a static pump housing, a shiftable control ring, and a rotatable pump rotor comprising several rotor vanes rotating within the shiftable control ring. The control ring is shiftable with respect to the pump rotor to thereby vary the eccentricity of the control ring with respect to the pump rotor for controlling the displacement and, as a result, the volumetric pump performance. The control ring is supported radially shiftably in the static pump housing. The pump housing and the control ring radially define several hydraulic chambers actuating the control ring. 
     The shiftable control ring is normally made of sintered steel to reduce the friction-related wear caused by the rotor vanes rotating within the control ring. The static pump housing is normally made of aluminum with a low mass density compared to sintered steel to reduce the pump weight. However, aluminum has a higher thermal expansion coefficient compared to sintered steel so that the width of gaps between the aluminum pump housing and the shiftable sintered steel control ring increases with increasing temperature. This can cause leakages of the hydraulic control ring actuation system, thereby reducing the pump&#39;s efficiency. 
     SUMMARY 
     An aspect of the present invention is to provide a light-weight variable lubricant vane pump with a long lifetime. 
     In an embodiment, the present invention provides a variable lubricant vane pump for providing a pressurized lubricant. The variable lubricant vane pump includes a static pump housing which defines a pump inlet and a pump outlet, a shiftable control ring comprising at least one slide support surface, a rotatable pump rotor comprising a plurality of rotor vanes which are configured to rotate within the shiftable control ring, and at least one metal slide support pad. The shiftable control ring is configured to be shiftable with respect to the rotatable pump rotor so as to vary an eccentricity of the shiftable control ring with respect to the rotatable pump rotor so as to control a volumetric pump performance. The static pump housing comprises a static control ring housing body which is configured to radially surround and to support the shiftable control ring, and two static pump housing lids which are configured to axially support the static control ring housing body and the shiftable control ring. At least the static control ring housing body is made of a plastic. The at least one metal slide support pad is fixed to the static control ring housing body and, together with the at least one slide support surface, provides a friction bearing for the shiftable control ring. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is described in greater detail below on the basis of embodiments and of the drawings in which: 
         FIG. 1  shows a schematic side view of an embodiment of a variable lubricant vane pump according to the present invention which in particular shows the multi-part pump housing of the vane pump; and 
         FIG. 2  shows a schematic longitudinal section of the variable lubricant vane pump of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     The variable lubricant vane pump according to the present invention is provided with a rotatable pump rotor which is positioned within a shiftable control ring. The rotor comprises several rotor vanes which are in contact with the radial inside surface of the control ring and which define several pump chamber compartments. The rotor vanes and, as a result, the pump chamber compartments, rotate within the control ring. The pump rotor axis of rotation is static so that a shifting of the control ring changes the eccentricity of the pump rotor with respect to the surrounding control ring to thereby control the displacement and, as a result, the volumetric performance of the pump. 
     The variable lubricant vane pump according to the present invention is provided with a static multi-part pump housing defining a pump inlet and a pump outlet. The multi-part pump housing comprises a static control ring housing body radially surrounding and supporting the shiftable control ring, and two static pump housing lids which axially close the control ring housing body and which support the shiftable control ring. The control ring housing body and the two pump housing lids are axially attached to each other, for example, screwed, and fluid-tightly sealed, for example, by circumferential sealings. 
     The control ring housing body is made of plastic to reduce the weight and the cost of the pump housing and, as a result, of the vane pump. The control ring housing body comprises at least one metal slide support pad which is fixed to the control ring housing body. The shiftable control ring is provided with at least one slide support surface which is supported by the metal slide support pad of the control ring housing body, thereby providing a friction bearing for the shiftable control ring. The metal slide support pad of the plastic control ring housing body significantly reduces the friction-related wear of the control ring surface caused by the movement of the control ring within the control ring housing body. 
     In an embodiment of the present invention, the shiftable control ring can, for example, be made of metal, for example, of sintered steel, to minimize the friction-related wear of the control ring inside surface caused by the rotating rotor vanes. Sintered steel is very hard-wearing and allows a cost-efficient and durable embodiment of the shiftable control ring. 
     In an embodiment of the present invention, the shiftable control ring can, for example, be provided to be shiftable exactly linear with respect to the pump rotor axis of rotation. This allows a simple frictional bearing of the control ring within the control ring housing body which does not require any hinges or pivoting bearings. 
     In an embodiment of the present invention, the static control ring housing body can, for example, be made of plastic with a thermal expansion coefficient substantially equal to the thermal expansion coefficient of the control ring material. The difference of both thermal expansion coefficients is thus less than 5%. As a result, leakages caused by a different thermal expansion of the control ring and of the control ring housing body surrounding and supporting the control ring can be avoided or at least minimized. This provides the vane pump with a good thermal stability. 
     In an embodiment of the present invention, the static pump housing lids can, for example, be made of metal, for example, of aluminum. This allows a light-weight and also robust realization of the pump housing. 
     In an embodiment of the present invention, the metal control ring support pads can, for example, only be provided at contact areas located at the pump inlet region of the control ring housing body. Since the vane pump pressurizes the lubricant, the pressure at the pump outlet is higher than the pressure at the pump inlet so that the control ring is normally pushed toward the pump inlet. The friction at the contact areas located at the pump outlet region of the control ring housing is thus very low so that metal control ring support pads are required only at the contact areas located at the pump inlet region of the control ring housing body. 
     An embodiment of the present invention is described below under reference to the accompanying drawings. 
       FIG. 1  shows a schematic side view of variable lubricant vane pump  10  as part of a pumping system for supplying an internal combustion engine (which is not shown in the drawings) with a pressurized lubricant. A pump rotor shaft  12  co-rotatably fixed to a pump rotor  34  of the vane pump  10  is mechanically driven by the engine, for example, via a gear wheel or a transmission belt. 
     The vane pump  10  comprises a static multi-part pump housing  14  with a first static pump housing lid  16 , a static control ring housing body  18 , and a second static pump housing lid  20  which defines a pump inlet  22  and a pump outlet  24 . The two pump housing lids  16 ,  20  are made of aluminum and the control ring housing body  18  is made of a plastic having a thermal expansion coefficient which is substantially equal to the thermal expansion coefficient of sintered steel. The two pump housing lids  16 ,  20  and the control ring housing body  18  are axially attached to each other by screws  26  and are fluid-tightly sealed by circumferential sealings. 
       FIG. 2  shows a schematic longitudinal section of the vane pump  10 . The pump housing  14  and, in particular, the control ring housing body  18  radially defines a pump inlet chamber  28 , a pump outlet chamber  30 , a pumping chamber  32  with a rotatable pump rotor  34  and with a shiftable control ring  36 , a spring chamber  38  with a control ring preload spring  40 , and defines a pilot chamber  42 . The pump inlet chamber  28  is fluidically connected to a lubricant tank  44  via the pump inlet  22  and is provided with atmospheric pressure PA. The pump outlet chamber  30  is pressurized with a pump outlet pressure PO and is fluidically connected with the internal combustion engine via the pump outlet  24 . 
     The pump rotor  34  is radially surrounded by the control ring  36  and rotates in a counterclockwise direction about a static axis of rotation A. The pump rotor  34  is provided with seven rotor vanes  46  which are supported radially slidable within corresponding vane slits  48 . The two pump housing lids  16 ,  20 , the control ring  36 , and the rotor vanes  46  define seven pumping chamber compartments  50   a    50   g . The rotor vanes  46  and, as a result, the pumping chamber compartments  50   a - 50   g  rotate within the control ring  36 . The control ring  36  is made of hard-wearing sintered steel so that the wear of the control ring  36  inside surface caused by the rotating rotor vanes  46  is minimized. 
     The control ring  36  is shiftable exactly linear with respect to the pump rotor  34  and the pump housing  14 . The volumetric pump performance of the pump  10  can be controlled by moving the control ring  36  and thereby varying the eccentricity of the pump rotor  34  with respect to the surrounding control ring  36 . 
     The control ring  36  is preloaded by the control ring preload spring  40  pushing the control ring  36  into a high-eccentricity direction H. As a result, if no other forces in the shifting direction of the control ring  36  are effective with respect to the control ring  36 , the control ring  36  is pushed into the maximum-eccentricity position providing the maximum volumetric pump performance. 
     The control ring  36  is loaded in the opposing low-eccentricity direction L by the pressure of the pilot chamber  42 . The pilot chamber  42  is fluidically connected with the pump outlet chamber  30  by a pilot chamber channel  56  and, as a result, is pressurized with the pump outlet pressure PO. 
     The control ring  36  is loaded in the high-eccentricity direction H by the pressure of the spring chamber  38 . The spring chamber  38  is fluidically connected with the pump outlet chamber  30  via a spring chamber channel  58  and is fluidically connected with a lubricant tank  44  via a control valve  60 . The lubricant tank  44  is provided with atmospheric pressure PA. As a result, the control valve  60  allows controlling the spring chamber  38  pressure in the pressure range between the atmospheric pressure PA and the pump outlet pressure PO. 
     The radial position of the control ring  36  depends on the ratio of the spring chamber  38  pressure to the pilot chamber  42  pressure and, as a result, can be controlled via the control valve  60 . Since the control ring  36  and the control ring housing body  18  have substantially equal thermal expansion coefficients, leakages of the spring chamber  38  or of the pilot chamber  42  caused by different thermal expansions of the control ring  36  and of the surrounding and supporting control ring housing body  18  are avoided or at least minimized. This allows a temperature-stable control of the pump performance and, as a result, a temperature-stable pump efficiency. 
     The control ring  36  is axially supported by the two pump housing lids  16 ,  20  and is radially supported by two metal slide support pads  52   a ,  52   b  being attached to the control ring housing body  18 . The control ring is radially loaded toward the pump inlet chamber  28  via the pressure difference between the pump outlet chamber  30  and the pump inlet chamber  28 . The metal slide support pads  52   a ,  52   b  are thereby located at the pump inlet  22  region of the control ring housing body  18 . The metal slide support pads  52   a ,  52   b  support the control ring  36  via corresponding slide support surfaces  54   a ,  54   b  being provided at the control ring  36  outside surface. 
     The metal slide support pads  52   a ,  52   b  and the slide support surfaces  54   a ,  54   b  provide a low-friction friction bearing for the control ring  36 . The friction-related wear of the control ring  36  outside surface caused by the control ring  36  movement within the control ring housing body  18  is thereby minimized. 
     The present invention is not limited to embodiments described herein; reference should be had to the appended claims. 
     LIST OF REFERENCE NUMERALS 
       10  variable lubricant vane pump 
       12  pump rotor shaft 
       14  static multi-part pump housing 
       16  first static pump housing lid 
       18  static control ring housing body 
       20  second static pump housing lid 
       22  pump inlet 
       24  pump outlet 
       26  screws 
       28  pump inlet chamber 
       30  pump outlet chamber 
       32  pumping chamber 
       34  rotatable pump rotor 
       36  shiftable control ring 
       38  spring chamber 
       40  control ring preload spring 
       42  pilot chamber 
       44  lubricant tank 
       46  rotor vanes 
       48  vane slits 
       50   a - 50   g  pumping chamber compartments 
       52   a ,  52   b  metal slide support pads 
       54   a ,  54   b  slide support surfaces 
       56  pilot chamber channel 
       58  spring chamber channel 
       60  control valve 
     A static axis of rotation 
     H high-eccentricity direction 
     L low-eccentricity direction