Patent Publication Number: US-2022228588-A1

Title: Variable displacement lubricant 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/EP2019/063967, filed on May 29, 2019. The International Application was published in English on Dec. 3, 2020 as WO 2020/239216 A1 under PCT Article 21(2). 
    
    
     FIELD 
     The present invention is directed to a variable displacement lubricant pump for providing a pressurized lubricant. The present invention is in particular directed to a mechanical variable displacement lubricant pump for providing a pressurized lubricant for an internal combustion engine. 
     BACKGROUND 
     The lubricant 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 variable displacement of the lubricant pump allows a pump discharge pressure of the lubricant pump to be controlled and/or stabilized, and thereby allows, for example, a lubricant galley pressure in the engine to be controlled and/or stabilized. 
     WO 2018/196991 A1 describes a typical variable displacement lubricant pump for providing a pressurized lubricant for an internal combustion engine. The lubricant pump comprises a static pump housing and a shiftable control ring which is arranged within the pump housing which radially confines a cylindrical pumping chamber. The lubricant pump comprises an inlet chamber and an outlet chamber both being partially confined by the control ring and located at opposite lateral sides of the control ring. The lubricant pump comprises a lateral slide bearing located at the outlet-chamber-sided lateral side of the control ring. The lateral slide bearing comprises a first lateral slide bearing surface which is defined by the pump housing and an opposite second lateral slide bearing surface which is defined by the control ring. The lateral slide bearing gap formed between the two vertical slide bearing surfaces is fluidically sealed by a sealing element to avoid leakage of pressurized lubricant via the lateral slide bearing gap. An undesired lubricant leakage via the lateral bearing gap can impair the pump discharge pressure control and/or the pump performance, in particular if the lateral bearing gap fluidically leads into a hydraulic control chamber of the lubricant pump. However, the sealing element increases the slide friction of the lateral slide bearing and thereby reduces the pump&#39;s efficiency. The pump housing and/or the control ring must furthermore be provided with a specific holding device to hold the sealing element in place and to avoid a slipping of the sealing element out of the lateral slide bearing gap. 
     SUMMARY 
     An aspect of the present invention is to provide a cost-efficient, reliable, and efficient variable displacement lubricant pump. 
     In an embodiment, the present invention provides a variable displacement lubricant pump for providing a pressurized lubricant. The variable displacement lubricant pump includes a static pump housing, a control ring which is arranged within the static pump housing, an inlet chamber which is partially confined by the control ring, an outlet chamber which is partially confined by the control ring, and a lateral slide bearing. The control ring is configured to be shiftable and to radially confine a pumping chamber which is substantially cylindrical. The control ring comprises a drainage channel. The outlet chamber and the inlet chamber are arranged at opposite lateral sides of the control ring. The lateral slide bearing is arranged at the lateral side of the control ring where the outlet chamber is arranged. The lateral slide bearing comprises a first lateral slide bearing surface which is defined by the static pump housing, a second lateral slide bearing surface which is arranged opposite to the first lateral slide bearing surface and which is defined by the control ring, and a lateral slide bearing gap which is defined between the first lateral slide bearing surface and the second lateral slide bearing surface. The drainage channel of the control ring fluidically connects the lateral slide bearing gap with the inlet chamber. 
    
    
     
       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 top view of an opened variable displacement lubricant pump according to the present invention; and 
         FIG. 2  shows a partially sectioned side view of a control ring section and a pump housing section of the lubricant pump of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     The variable displacement lubricant pump according to the present invention is provided with a static pump housing which defines a pump inlet and a pump outlet. The pump inlet is typically fluidically connected with a lubricant tank, and the pump outlet is fluidically connected with an engine for providing the engine with the pressurized lubricant. 
     The variable displacement lubricant pump according to the present invention is also provided with a shiftable control ring which is arranged within the pump housing. The control ring radially confines a substantially cylindrical pumping chamber. The control ring can, for example, be linearly shiftable with respect to the pump housing, but the control ring is in any case not pivotably hinged within the pump housing. The pumping chamber is typically provided with an exactly circular radial cross section. The pumping chamber can, however, also be provided with a non-exactly circular radial cross section (for example, with a slightly elliptical cross section) to improve the pump efficiency and/or the pump pressure control. 
     The variable displacement lubricant pump according to the present invention is also provided with an inlet chamber and with an outlet chamber which are both partially confined by the control ring and partially confined by the pump housing. The inlet chamber and the outlet chamber are located radially outwardly of the pumping chamber at opposite lateral sides of the control ring. The inlet chamber is fluidically connected with the pump inlet, and the outlet chamber is fluidically connected with the pump outlet. During pump operation, the inlet chamber is filled with lubricant having a relatively low pressure; the inlet chamber is typically filled with a lubricant substantially having atmospheric pressure. The outlet chamber is filled with pressurized lubricant during pump operation. 
     The variable displacement lubricant pump according to the present invention is also provided with a lateral slide bearing which is located at the outlet-chamber-sided lateral side of the control ring and via which the control ring is frictionally supported within the pump housing. The lateral slide bearing comprises two parallel and opposite lateral slide bearing surfaces, a first lateral slide bearing surface defined by the pump housing, and a second lateral slide bearing surface defined by the control ring. Both lateral slide bearing surfaces each extend in a pump plane which is parallel to the sliding direction of the control ring as well as to the axial direction of the cylindrical pumping chamber. A typically relatively narrow lateral slide bearing gap is formed between the two corresponding lateral slide bearing surfaces. The lateral slide bearing is typically located between the outlet chamber and a control chamber, wherein the control ring position and, as a result, the volumetric pump performance, is controlled via the hydraulic pressure of the control chamber. 
     According to the present invention, the control ring is provided with a drainage channel which fluidically connects the lateral slide bearing gap with the inlet chamber. The drainage channel can directly lead into the inlet chamber or alternatively can lead into a pump region which is in fluidic contact with the inlet chamber. The drainage channel is in any case provided substantially with the inlet chamber pressure. Pressurized lubricant which is pressed into the lateral slide bearing gap from the outlet chamber is as a result reliably conveyed out of the lateral slide bearing and toward the low-pressure inlet chamber. This avoids or at least significantly suppresses a lubricant leakage via the lateral slide bearing into the adjoining hydraulic chamber, for example, into the control chamber, not requiring any separate sealing element in the lateral slide bearing gap. 
     The variable displacement lubricant pump according to the present invention provides a reliable and efficient pump operation. The variable displacement lubricant pump according to the present invention can be realized very cost-efficiently since no sealing element is required to seal the lateral slide bearing. 
     The drainage channel can, for example, be partially defined by a lateral groove which is provided within the second lateral slide bearing surface of the control ring and which is fluidically connected with the inlet chamber. The lateral groove can, for example, extend over the entire axial height of the control ring and, as a result, over the entire axial height of the lateral slide bearing to efficiently collect any lubricant which leaks into the lateral slide bearing gap. The lateral groove can be realized cost-efficiently and allows for a reliable avoidance of lubricant leakage via the lateral slide bearing gap. 
     The control ring is typically frictionally supported within the pump housing also at its top side and its bottom side. In an embodiment of the present invention, a top-side slide surface of the control ring can, for example, be provided with top-side groove and/or a bottom-side slide surface of the control ring can, for example, be provided with bottom-side groove, wherein the top-side groove and/or the bottom-side groove as a result fluidically leads into the lateral groove and partially defines the drainage channel. The top-side groove and/or the bottom-side groove can, for example, lead into the inlet chamber or into a region which is in direct fluidic contact with the inlet chamber so that no additional arrangements are required in/at the control ring to fluidically connect the lateral slide bearing gap with the inlet chamber. This allows for a very cost-efficient realization of the drainage channel and thereby provides a cost-efficient lubricant pump. The top-side groove and/or the bottom-side groove also allows for a drainage of lubricant which leaks via the top side and/or the bottom side of the control ring. This minimizes the total lubricant leakage and thereby provides a very reliable and efficient lubricant pump. 
     The control ring is typically provided with a suction opening which fluidically connects the pumping chamber with the inlet chamber. The suction opening is typically provided via a top-side and/or a bottom-side recess within the control ring. The drainage channel can, for example, lead into the suction opening which is in direct fluidic contact with the inlet chamber. Since the suction opening typically extends over a relatively large circumferential sector of the pumping chamber, the drainage channel can be realized to be relatively short and thereby relatively cost-efficient. 
     An embodiment of the present invention is described below with reference to the enclosed drawings. 
       FIG. 1  shows a variable displacement lubricant pump  10  for providing a pressurized lubricant to an internal combustion engine  12 . The lubricant pump  10  is provided with a static pump housing  14 , with a shiftable control ring  16 , and with a rotatable pump rotor  18 . The control ring  16  is arranged within the pump housing  14  and radially confines a substantially cylindrical pumping chamber  20 . 
     The lubricant pump  10  comprises an inlet chamber  22  which is fluidically connected with a lubricant tank  24  and which is filled with a lubricant having substantially atmospheric pressure during pump operation. The inlet chamber  22  is partially confined by the control ring  16  and is directly fluidically connected with the pumping chamber  20  via a suction opening  26  of the control ring  16 . 
     The lubricant pump  10  comprises an outlet chamber  28  which is fluidically connected with the internal combustion engine  12  and which is filled with the pressurized lubricant during pump operation. The outlet chamber  28  is located at an opposite lateral side of the pumping chamber  20  with respect to the inlet chamber  22 . The outlet chamber  28  is partially confined by the control ring  16  and is directly fluidically connected with the pumping chamber  20  via a discharge opening  30  of the control ring  16 . 
     The lubricant pump  10  comprises a control chamber  32  which is located circumferentially between the inlet chamber  22  and the outlet chamber  28  at a front side of the control ring  16 . During pump operation, the control chamber  32  is filled with lubricant, wherein the lubricant pressure within the control chamber  32  is controllable to thereby hydraulically control the position of the control ring  16  and, as a result, the volumetric pump performance. 
     The lubricant pump  10  comprises a lateral slide bearing  34  via which the control ring  16  is frictionally supported within the pump housing  14 . The lateral slide bearing  34  is located at an outlet-chamber-sided lateral side of the control ring  16 . The lateral slide bearing  34  directly adjoins the outlet chamber  28  as well as the control chamber  32  and thereby fluidically separates the control chamber  32  and the outlet chamber  28  from each other. The lateral slide bearing  34  comprises two parallel and opposite lateral slide bearing surfaces  36 ,  38  which are in a touching frictional contact with each other. The first lateral slide bearing surface  36  is defined by the pump housing  14 , and the second lateral slide bearing surface  38  is defined by the control ring  16 . The two lateral slide bearing surfaces  36 ,  38  define a lateral slide bearing gap  40  therebetween. 
     According to the present invention, the control ring  16  is provided with a drainage channel  42  which fluidically connects the lateral slide bearing gap  40  with the inlet chamber  22 . In the shown embodiment of the present invention, the drainage channel  42  is formed and defined by a lateral groove  44 , a top-side groove  46 , and a bottom-side groove  48 . 
     The lateral groove  44  is formed within the second lateral slide bearing surface  38  of the control ring  16 . The lateral groove  44  extends substantially linear along the entire axial height of the control ring  16 . 
     The top-side groove  46  is formed within a top-side slide surface  50  of the control ring  16 . In the assembled (closed) pump, the top-side slide surface  50  is in frictional contact with a (not shown) pump housing cover body. The top-side groove  46  fluidically leads into the lateral groove  44  at one end and fluidically leads into a top-side region  51  of the suction opening  26  at its opposite end. The top-side groove  46  directly fluidically connects the lateral groove  44  with the suction opening  26  and thereby fluidically connects the lateral slide bearing gap  40  with the inlet chamber  22 . 
     The bottom-side groove  48  is formed within a bottom-side slide surface  52  of the control ring  16 . The bottom-side slide surface  52  is in frictional contact with the pump housing  14 . The bottom-side groove  48  is shaped symmetrically to the top-side groove  46  in the shown embodiment of the present invention. The bottom-side groove  48  fluidically leads into the lateral groove  44  at one end, and fluidically leads into a (not shown) bottom-side region of the suction opening  26  at its opposite end. The bottom-side groove  48  directly fluidically connects the lateral groove  44  with the suction opening  26  and thereby fluidically connects the lateral slide bearing gap  40  with the inlet chamber  22 . 
     The present invention is not limited to embodiments described herein; reference should be had to the appended claims. 
     LIST OF REFERENCE NUMERALS 
     
         
         
           
               10  Variable displacement lubricant pump 
               12  Internal combustion engine 
               14  Pump housing 
               16  Control ring 
               18  Pump rotor 
               20  Pumping chamber 
               22  Inlet chamber 
               24  Lubricant tank 
               26  Suction opening 
               28  Outlet chamber 
               30  Discharge opening 
               32  Control chamber 
               34  Lateral slide bearing 
               36  First lateral slide bearing surface 
               38  Second lateral slide bearing surface 
               40  Lateral slide bearing gap 
               42  Drainage channel 
               44  Lateral groove 
               46  Top-side groove 
               48  Bottom-side groove 
               50  Top-side slide surface 
               51  Top-side region (of suction opening  26 ) 
               52  Bottom-side slide surface