Abstract:
An adjustment device for a variable compression ratio engine. An engine block ( 100 ) is equipped internally with a transmission device ( 1 ) including, for at least one piston ( 2 ), a transmission member ( 3 ) which co-operates with (i) a rolling guide device ( 4 ) and (ii) a sprocket wheel ( 5 ), the sprocket wheel ( 5 ) co-operating with a control rack ( 7 ), on the opposite side from the transmission member ( 3 ). Moreover, the vertical position of the control rack in relation to the engine block ( 100 ) is adjusted by a control device ( 12 ). In addition, the adjustment device includes: elements for adjusting the position of the transmission device ( 1 ), which are disposed at the rolling guide device ( 4 ); and elements for adjusting the working clearance of the transmission device ( 1 ), which are disposed at the control rack ( 7 ).

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to an adjustment device incorporated into an engine block making it possible to adjust the working clearances, and positioning of a transmission device of a variable compression ratio engine while giving it the angular freedoms necessary for it to work. 
   DESCRIPTION OF THE RELATED ART 
   Note that international patent WO98/51911 in the name of the applicant describes a device used to improve the overall efficiency of internal combustion piston engines used at variable load and speed by adapting their displacement and/or their compression ratio during operation. 
   The effective displacement of the engine is modified by forcing back into the inlet pipe cooled gases taken in excess into the cylinder and by controlling the length of stroke used to compress the gases via an additional variable closure delay inlet valve. 
   The effective compression ratio of the engine is adjusted by modifying the initial position of the stroke of a piston relative to a cylinder by means of a sprocket mounted free at the top end of a connecting rod, a transmission member fixedly attached to the piston and a control rack whose position is adjusted by a control device. 
   It is noted that, according to international patent WO00/31377 in the name of the applicant, the mechanical transmission device for a variable displacement engine comprises a piston fixedly attached in its lower portion to a transmission member interacting first with a rolling guide device and secondly with a sprocket fixedly attached to a connecting rod making it possible to transmit the movement between said piston and said connecting rod. 
   Note that, according to international patent WO03/008783 in the name of the applicant, the mechanical transmission device for a variable displacement engine comprises at least one cylinder in which there moves a piston that is fixedly attached, in its lower portion, to a transmission member interacting first by means of a small rack with a rolling guide device, and secondly by means of another large rack with a sprocket fixedly attached to a connecting rod, a control rack interacting with the sprocket, means of attaching the piston to the transmission member that provide a tightening prestress, connecting means that make it possible to stiffen the teeth of the racks, and means of reinforcing and lightening the structure of the sprocket. 
   SUMMARY OF THE INVENTION 
   Thus, the adjustment device according to the present invention is designed to adjust the working clearances and the positioning of a transmission device of a variable compression ratio engine while giving it the angular freedoms necessary for it to operate, the whole assembly being incorporated into an engine block. 
   The adjustment device according to the present invention comprises, at the rolling guide device, means of adjusting the positioning of the transmission device and, at the control rack, means of adjusting the working clearances of the transmission device. 
   The adjustment device according to the present invention comprises a control device comprising, at the thruster piston, a thruster for operating first means giving the transmission device the angular freedoms necessary for it to work. 
   The adjustment device according to the present invention comprises a control rack comprising second means giving the transmission device the angular freedoms necessary for it to work and acting more particularly between said control rack and the engine block. 
   The adjustment device according to the present invention comprises, at the rolling guide device, means of adjusting the positioning that consist of an orifice pierced in the engine block on the side of the cylinder and making it possible to insert into said block a support comprising racks providing the synchronization of the movement of a roller with that of the piston and a roller track interacting with said roller. 
   The adjustment device according to the present invention comprises a support that consists of a very thick plate which allows it to be attached to the engine block, from the outside of the latter, by means of screws. 
   The adjustment device according to the present invention comprises a body that is fitted to the support, said one body comprising roller tracks, and being attached to said support with at least one fastening screw. 
   The adjustment device according to the present invention comprises sealing between the support and the engine block that is provided by a seal housed in a groove made in the support. 
   The adjustment device according to the present invention comprises sealing between the support and the engine block that is provided by a seal housed in a groove made in the engine block. 
   The adjustment device according to the present invention comprises adjustment means consisting of a shim interposed between the inner face of the very thick plate and the outer face of the engine block. 
   The adjustment device according to the present invention comprises, at the control rack, means of adjusting the working clearances that consist of a bearing face whose distance relative to the engine block is adjustable. 
   The adjustment device according to the present invention comprises a flat face that is made on a cylindrical support screwed into the engine block. 
   The adjustment device according to the present invention comprises a cylindrical support that has a thread made on its periphery so that it can be screwed directly into a threaded orifice made in the engine block. 
   The adjustment device according to the present invention comprises a cylindrical support that comprises a tool socket allowing it to be tightened and held in position while it is immobilized by means of a locknut. 
   The adjustment device according to the invention comprises a locknut that comprises a tool socket allowing it to be tightened, the socket being designed so that it is possible to tighten the locknut while holding the cylindrical support by means of its tool socket. 
   The adjustment device according to the present invention comprises a cylindrical support that is fixedly attached to a very thick plate attached from the outside to the engine block by means of screws and whose distance relative to the engine block is adjusted by a shim placed between the very thick plate and the engine block. 
   The adjustment device according to the present invention comprises a thruster for controlling the control device that consists of an upper thruster rod having a threaded portion allowing it to be attached to the lower thruster rod of the control rack and a thruster piston traversed in its middle, by means of a bore, by the upper thruster rod, said upper thruster rod comprising centering means making it possible to center first the upper thruster rod on the thruster piston and secondly the lower thruster rod on the thruster piston. 
   The adjustment device according to the present invention comprises a thruster piston whose portion in contact with a thruster cylinder has a spherical profile forming a ball-and-socket type connection between said thruster piston and said thruster cylinder. 
   The adjustment device according to the present invention comprises a thruster piston that comprises seals on either side of its spherical profile. 
   The adjustment device according to the present invention comprises a thruster piston that comprises a release valve. 
   The adjustment device according to the present invention comprises a thruster piston that comprises a release valve consisting of a ball held on a seat, made in said thruster piston, by a spring. 
   The adjustment device according to the present invention comprises a control rack that comprises, on the side opposite to its teeth, a bearing face comprising a cavity in a portion of a sphere that is designed to receive a head, in a portion of a sphere, of a bearing piece housed in said cavity and producing a ball-and-socket connection between the control rack and the engine block. 
   The adjustment device according to the present invention comprises a control rack whose cavity has a housing at its pole, while the head comprises another housing at its pole, said housings making it possible to install a spring. 
   The adjustment device according to the present invention comprises a thruster piston that is traversed vertically by a bore for the passage of a control rod interacting, on either side of the thickness of the piston, with valves and springs. 
   The adjustment device according to the present invention comprises valves that are each traversed by the control rod and that press directly on the corresponding top or bottom face of the thruster piston. 
   The adjustment device according to the present invention comprises springs that are traversed by the control rod and that press first on the corresponding valve and secondly on a stop made on the control rod. 
   The adjustment device according to the present invention comprises valves that each comprise a seal that consists of a plastic, friction-resistant ring and an internal O-ring seal providing sealing between the ring and the body of the valve. 
   The adjustment device according to the present invention comprises valves that each have a small area of contact with the thruster piston, materialized by a circular peripheral rim designed to increase the pressure of contact exerted by said valves on said thruster piston. 
   The adjustment device according to the present invention comprises a thruster cylinder that is bored directly into the engine block and closed off in its upper portion by a cylinder head that is screwed onto the engine block. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The following description with respect to the appended drawings, given as nonlimiting examples, will allow a better understanding of the invention, the features that it has and the advantages that it is likely to provide. 
       FIG. 1  is a view in section illustrating an adjustment device incorporated into an engine block allowing the adjustment of the working clearances, and of the positioning of a transmission device of a variable compression ratio engine while giving it the angular freedoms necessary for it to work. 
       FIG. 2  is a view in perspective showing an adjustment device incorporated into an engine block allowing the adjustment of the working clearances, and of the positioning of a transmission device of a variable compression ratio engine while giving it the angular freedoms necessary for it to work. 
       FIG. 3  is an exploded view in perspective representing the engine block into which the device for adjusting the mechanical transmission device according to the present invention is incorporated. 
       FIGS. 4 and 5  are views illustrating the adjustment device allowing the adjustment of the working clearances of a transmission device of a variable compression ratio engine while giving the angular freedoms necessary for it to work. 
       FIG. 6  is a view representing the device allowing the adjustment of the positioning of the transmission device according to the present invention. 
       FIGS. 7 to 10  are views showing a variant of the adjustment device incorporated into an engine block allowing the adjustment of the working clearances, and of the positioning of a transmission device of a variable compression ratio engine while giving it the angular freedoms necessary for it to work. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1 to 3  show an engine block  100  that comprises at least one cylinder  110  in which a piston  2  is moved by means of a transmission device  1 . 
   The mechanical transmission device  1  comprises, in the lower portion of the piston  2 , a transmission member  3  fixedly attached to said piston and interacting first with a rolling guide device  4  and secondly with a sprocket  5 . 
   The sprocket  5  interacts with a connecting rod  6  connected to a crankshaft  9  in order to transmit the movement between said piston and said crankshaft. 
   The sprocket  5  interacts, on the side opposite to the transmission member  3 , with another rack called the control rack  7  whose vertical position relative to the engine block  100  is controlled by a control device  12  comprising a control thruster  8 , whose thruster piston  13  is guided in a thruster cylinder  112  made in the engine block  100 . 
   The thruster cylinder  112  may be bored directly into the engine block  100 , or in a liner not shown fitted into the engine block  100 . The thruster cylinder  112  is closed in its upper portion by a thruster cylinder head  113  that is screwed onto the engine block  100 . Provision may be made for one cylinder head  113  for each thruster cylinder  112  or a cylinder head  113  common to all the thruster cylinders  112  of a multi-cylinder engine. 
   The transmission device  1  comprises a transmission member  3  fixedly attached to the piston  2  and provided on one of its faces with a first large rack  35  whose teeth  34  interact with the teeth  51  of the sprocket  5 . 
   The transmission member  3  comprises, on the side opposite to the rack  35 , another rack  37  whose small teeth  38  interact with those of the roller  40  of the rolling guide device  4  fixedly attached to the engine block. 
   The engine block  100  is pierced with an orifice  104  on one side of the cylinder  110  making it possible to insert into said block a support  41  comprising racks  46  synchronizing the movement of the roller  40  with that of the piston  2  and a roller track  48  interacting with the roller  40 . 
   The support  41  consists of a very thick plate  42  which allows it to be attached to the engine block  100 , from the outside of the latter, by means of screws  105 . 
   To make it easier to machine the racks  46  on the support  41 , it is possible to fit onto said support  41  a body  45  comprising the roller track  48  interacting with the roller  40 , said body being attached to said support  41  with at least one fastening screw  107 . 
   The sealing between the support  41  and the engine block  100  is provided by a seal  47  housed in a groove  44  that may be made either in the support  41  or in the engine block  100 . 
   The distance between the engine block  100  and the support  41  is adjusted by a shim  106  forming means of adjusting the position of the transmission device  1 , said shim  106  being interposed between the inner face of the plate  42  and the outer face of the engine block  100 . 
   The shim  106  makes it possible to adjust the control rack  7  in vertical position, taking account of the total dimensions of all the parts comprised between the bearing plane of the support  41  on the engine block  100  and the center of the thruster cylinder  112  of the control thruster  8 . 
   The thickness of the shim  106  is determined after measuring the total dimensions of all the parts comprised between the bearing plane of the support  41  on the engine block  100  and the center of the thruster cylinder  112  of the control thruster  8 . 
     FIGS. 4 and 5  illustrate the control thruster  8  of the control device  12  that consists of an upper thruster rod  10  having a threaded portion  11  screwed into the lower thruster rod  16  of the control rack  7  and a thruster piston  13  traversed in its middle, by means of a bore  17 , by the upper thruster rod  10 . 
   The upper thruster rod  10  comprises a cylinder portion  14  interacting with a bore  114  made in the thruster cylinder head  113  providing the control thruster  8  with a ratio between displaced volume and stroke of thruster piston  13  that is identical for the upper chamber  121  and lower chamber  122 . 
   The upper thruster rod  10  comprises a tool socket  15  allowing it to be tightened. 
   The upper thruster rod  10  comprises centering means  135  that make it possible to center first the upper thruster rod  10  on the thruster piston  13  and secondly the lower thruster rod  16  on the thruster piston  13 . 
   According to a variant not shown, the lower thruster rod  16  may have a threaded portion screwed into the upper thruster rod  10 , and centering means that make it possible to center first the upper thruster rod  10  on the thruster piston  13  and secondly the lower thruster rod  16  on the thruster piston  13 . 
   The sealing between the upper thruster rod  10  and the bore  114  of the thruster cylinder head  113  is provided by a seal  115 . 
   The sealing between the lower thruster rod  16  and a bore  116  made in the bottom  117  of the thruster cylinder  112  is provided by a seal  118 . 
   The seals  115  and  118  are designed to be able to provide sealing while accommodating the large clearance provided between the upper thruster rod  10  and the lower thruster rod  16  and their respective bores  114 ,  116 . 
   This arrangement allows the control rack  7  to orient itself in the engine block  100  so that the teeth  74  of said rack are aligned with the teeth  52  of the sprocket  5 . 
   Each seal  115  and  118  consists, for example, of an external ring  119  made of friction-resistant plastic and an internal O-ring seal  120  which provides the sealing between the ring  119  and the corresponding bore  114 ,  116 . 
   The thruster piston  13  is traversed vertically by another bore  18  which may or may not have at least one flat  19  making it possible to limit the bulk of the whole control device  12 , for the passage of a control rod  20  interacting, on either side of the thickness of the piston  13 , with valves  21  and springs  22 . 
   Each valve  21  is traversed by the control rod  20  and presses directly on the corresponding top or bottom face of the thruster piston  13  or of the flat  19 . 
   Each spring  22  is traversed by the control rod  20  and presses first on the corresponding valve  21  and secondly on a stop  130  made on the control rod  20  and consisting, for example, of an elastic ring  131  and a washer  132 . 
   Each valve  21  comprises a seal that consists, for example, of a plastic, friction-resistant ring  23  and an inner O-ring seal  24  which provides the sealing between the ring  23  and the body of the valve  21 . 
   The valves  21  may be designed in two parts to make it easier to install the seal that they comprise. 
   The clearance between the valves  21  and the control rod  20  is sufficient to allow the thruster piston  13  to pivot slightly in the thruster cylinder  112  so that the control rack  7  can orient itself in the engine block  100  so that the teeth  74  of said rack are aligned with the teeth  52  of the sprocket  5 , while allowing said valves to provide the sealing between the upper chamber  121  and lower chamber  122  of the thruster cylinder  112 . 
   The valves  21  may therefore pivot slightly relative to the control rod  20  so that they always remain in contact over their whole circumference with the thruster piston  13 . 
   Each valve  21  may have a small area of contact with the thruster piston  13 , materialized by a circular peripheral rim  25  designed to increase the pressure of contact exerted by said valves  21  on said thruster piston  13 . 
   This arrangement first makes it possible to provide better sealing and secondly allows the valves  21  to provide a larger surface area exposed to the pressure of the fluid on the side of the thruster piston  13  in order to make control of the control device  12  easier. 
   The control rod  20  comprises, for its guidance, a cylindrical portion  123  interacting with a bore  124  made in the thruster cylinder head  113 . The control rod  20  comprises, in the extension of its cylindrical portion  123 , a threaded end  125  allowing it to be attached to a control device not shown. 
   The sealing between the control rod  20  and the bore  124  of the thruster cylinder head  113  is provided by a seal  126 . 
   The bore  124  may comprise a flat  133  in which may move the spring  22  and the stop  130  that are in the upper thruster chamber  121 , in order to limit the vertical bulk of the control device  12 . 
   On the opposite side of the thruster cylinder head  113 , the control rod  20  is guided in a bore  127  made in the bottom  117  of the thruster cylinder  112 . 
   The sealing between the control rod  20  and the bore  127  of the thruster cylinder  112  is provided by a seal  128 . 
   The bore  127  may comprise a flat  134  in which may move the spring  22  and the stop  130  that are in the lower thruster chamber  122 , in order to limit the vertical bulk of the control device  12 . 
   The portion of the thruster piston  13  in contact with the thruster cylinder  112  has a spherical profile  26  forming a ball-and-socket type connection between said thruster piston  13  and said thruster cylinder  112 . 
   This arrangement is designed to allow the control rack  7  to pivot so that its teeth  74  can be aligned with the teeth  52  of the sprocket  5 . 
   The thruster piston  13  comprises seals  27  on either side of its spherical profile  26 . 
   The seals  27  are designed to provide the sealing between the upper chamber  121  and lower chamber  122  of the control thruster  8 , despite the large clearances necessary for the orientation of the thruster piston  13  in the thruster cylinder  112 . 
   In a variant not shown, the seals  27  consist, for example, of an external ring made of friction-resistant plastic and an internal O-ring seal which provides the sealing between the ring and the thruster piston  13 . 
   Thus, the spherical profile  26  of the thruster piston  13  forms first means giving the angular freedoms necessary for the transmission device  1  to work. 
   The thruster piston  13  may comprise a release valve  137  that may consist, for example, of a ball  138  held, on a seat made in the thruster piston  13 , by a spring  139  ( FIG. 10 ). 
   The release valve  137  makes it possible to limit the maximum pressure of the upper chamber  121  of the control thruster  8  and consequently makes it possible to limit the maximum force exerted on the teeth  34 ,  51 ,  52 ,  74  of the transmission device  1 . 
   The control rack  7  comprises on the side opposite to its teeth  74 , a bearing face  75  interacting with a bearing face  103  made in the engine block  100  and whose distance relative to said engine block  100  is adjustable, this forming means of adjusting the working clearances of the transmission device  1 . 
   The bearing face  75  comprises a cavity  28  in a portion of a sphere which may or may not have at its pole a cylindrical housing  29  for a spring  30  which may, for example, be of the helical or “belleville” type. 
   The function of the spring  30  is to keep the various members of the transmission device  1  in contact when a slight force is exerted on the teeth  51 ,  52  of the sprocket  5 . 
   The cavity  28  is designed to receive the head  31  in a portion of a sphere of a bearing piece  76  housed in said cavity producing a ball-and-socket connection between the control rack  7  and the engine block  100  ( FIG. 5 ). 
   The head in a portion of a sphere  31  of the bearing piece  76  may have at its pole a cylindrical housing  36  for the spring  30 . 
   The bearing piece  76  comprises, on the side opposite to its head in a portion of a sphere  31 , a flat face  32  interacting with the bearing face  103  made in the engine block  100 . 
   This arrangement allows the control rack  7  to move relative to the engine block  100 . 
   The bearing piece  76  may comprise a network of ducts  33  making it possible to deliver the lubricating oil first to its flat face  32  and secondly to its head in a portion of a sphere  31 . 
   Thus, the ball-and-socket type connection between the control rack  7  and the engine block  100  formed by the spherical profile of the cavity  28  of said control rack  7  and by the head in a portion of a sphere  31  of the bearing piece  76  forms second means giving the angular freedoms necessary for the transmission device  1  to work. 
   The bearing face  103  of the engine block  100  is made, for example, on a cylindrical support  102  screwed into said block. 
   The cylindrical support  102  has a thread  108  made on its periphery in order to be screwed directly into a threaded orifice  101  made in the engine block  100 . 
   The cylindrical support  102  comprises a tool socket  109  allowing it to be tightened and held in position while it is immobilized by means of a locknut  129 . 
   The locknut  129  comprises a tool socket  111  allowing it to be tightened. The tool socket  111  is designed so that it is possible to tighten the locknut  129  while holding the cylindrical support  102  by means of its tool socket  109 . 
   Thus, the cylindrical support  102  and its locknut  129  screwed into the threaded orifice  101  of the engine block  100  form a device for adjusting the working clearances of the transmission device  1  in the engine block  100 . 
   As a variant, the cylindrical support  102  may be fixedly attached to a very thick plate, not shown, attached from the outside to the engine block  100  by means of screws. 
   For this variant, the working clearances of the transmission device  1  in the engine block  100  are adjusted by means of a shim, not shown. 
   This shim, placed between the very thick plate and the engine block  100  makes it possible to adjust the distance between said plate and said engine block. 
   According to a variant, not shown, the cavity  28  in a portion of a sphere used as a housing for the head  31  in a portion of a sphere of the bearing piece  76  may be made in the cylindrical support  102 . 
   In this variant, the flat face  32  of the bearing piece  76  slides on a flat face made on the control rack  7 , that is to say, the opposite of what has been previously described, without, for all that, changing the object of the present invention. 
     FIGS. 7 to 10  show a variant embodiment of the second means giving the angular freedoms necessary for the transmission device to work provided at the control rack  7  and more particularly at its ball-and-socket type connection pressing on the engine block  100 . 
   In this variant, the second means consist of a pressure thruster  62  whose piston  61 , thanks to a spherical profile, makes a ball-and-socket type connection between the control rack  7  and the engine block  100 . 
   A directional flow valve  65  makes it possible to permanently compare the pressures existing in the upper chamber  121  and the lower chamber  122  in order to connect the one with the higher pressure to the chamber  66  of the pressure thruster  62 . 
   Thus, the directional flow valve  65  makes it possible to connect the upper chamber  121  or the lower chamber  122  whose pressure is the higher with the chamber  66  of the pressure thruster  62 . 
   The pressure thruster  62  comprises a spring  63  which makes it possible to keep the various members of the transmission device  1  in contact when the pressure existing in the chamber  66  is low. 
   The spring  63  may be of the helical or “belleville” type. 
   As an example, the directional control valve  65  may be housed in the thickness of the thruster piston  13 . In this case, it is connected to the pressure thruster  62  via ducts  64  made in the thruster piston  13 , the upper thruster rod  10  and lower thruster rod  16  and in the control rack  7 . 
   Note that the engine block  100  may be made of steel, cast iron or light alloy. It may comprise one or more dry or wet liners. It may also comprise one or more cylinders  110 , directly bored into said engine block  100 . 
   The engine block  100  may comprise at least one duct and/or at least one chamber in which an engine-cooling fluid circulates. 
   The engine block  100  may comprise at least one duct and/or at least one chamber in which there circulates a fluid for lubricating the various engine components. 
   Note that the engine block  100  comprises bearing caps  141  attached via at least two screws, said bearing caps  141  being able to be incorporated into a bearing casing  140 . 
   Note that the engine block  100  may comprise balance shafts to limit the effect of the vibrations, said balance shafts being able to be mounted in an independent casing attached to the engine block  100 . The engine block  100  may comprise a lubricant casing made either of pressed metal sheeting or of light alloy or of plastic, which may or may not comprise reinforcing structures. 
   It should furthermore be understood that the foregoing description has been given only as an example and that it in no way limits the field of the invention which would not be departed from by replacing the described embodiment details with any other equivalent.