FR2466626A1 - Variable compression ratio piston - has outer part telescopically mounted on upper end of inner part - Google Patents

Abstract

An upper hydraulic chamber is formed between the ends of the inner and outer members. A lower chamber is fluidly connected to the upper chamber and disposed adjacent the piston ring area of the piston assembly. Both a lubricant supply passage and a discharge passage are formed through the piston inner member and are fluidly connected with the upper chamber. Both the supply inlet valve and the discharge valve are contained within a single housing and, together with the housing, form a valve assembly. The valve assembly in turn is slidable within a bore in the upper end of the inner member and locked into position by a snap ring.

Description

 The present invention relates to a piston system with variable compression ratio It7CR) as described for example in US Patents No. 3,156,162, 3,161,112, 3,185,137, 3,185,137, 3,185,138, 3.3a3. 831, 3.311.09: 6, 3.402.662, 4.418.982, 3.450.111, 3.417.738, 3.417.739,3.450.112, 3.527.265, 3.405.698, 3.405.697,3.405.6-97, 3,405,113, 3,407,791, 3,667,433, 3,704,695, 4,016,841 and 4,031,868, all belonging to the Depositing Company and more particularly an improved construction of these piston systems.

 In the constructions described in the aforementioned patents, an internal element of the piston type is joined in the usual way by a connecting rod while an external element is carried to and movable axially with respect to the internal element.

The relative displacement of these elements modifies the compression ratio of the cylinder in which the piston moves. Free spaces are formed between the upper and lower ends of the internal and external elements respectively, and these spaces constitute upper and lower chambers whose volume varies in opposite directions with respect to the relative displacement of the elements of the piston. An essentially incompressible fluid such as engine lubricating oil is sent to these chambers in a manner which automatically adjusts the movement of the elements so as to gradually change the compression ratio until a predetermined combustion pressure has been reached. The hydraulic system thus modifies the displacement of the elements in a way which tends to maintain a uniform maximum pressure in the combustion chamber. It is conventional that the hydraulic system in these known VCR piston systems includes both a supply passage and an evacuation passage through the internal element of the piston, these two passages being joined to the upper chamber. A one-way valve in the supply passage allows the fluid only to exit the supply passage to enter the upper chamber while, conversely, a normally closed valve in the discharge passage opens under the pre ssion predetermined above in the upper chamber and allows the fluid to exit through the discharge passage into the engine housing.

 In these known VCR piston systems, it has been customary to mount and trap both the feed inlet valve and the normally closed discharge valve between a plate and the upper end of the internal element of the piston. The plate is in turn fixed to the internal element by bolts or similar fixing means.

 These systems thus have the drawback that it is practically necessary to completely disassemble the VCR piston system in order to access either the inlet valve or the discharge valve. Such access is necessary for example to check, maintain and / or repair these valves.

Another disadvantage of these prior systems is that the discharge valve, frequently a Belleville washer, is tensioned or prestressed against the mounting plate fixed to the upper end of the internal element of the piston.

As the mounting plate is directly fixed to the upper end of the internal element of the piston, individual adjustment of the tension on the discharge valve is impossible. On the contrary, to modify the voltage on the relief valve it has hitherto been necessary to modify the timing of the discharge valve.

 The invention overcomes these drawbacks of previous VCR piston systems by means of a piston system in which the supply and discharge valves are relatively easy to access and in which the tension on the discharge valve can be adjusted 'easily and very finely.

 Briefly, the VCR piston system according to the invention comprises an internal piston element and an external piston elements telescopically mounted on the upper end of the internal piston element. As in the known systems, an upper hydraulic chamber is formed between the upper end of the internal element and the internal end of the external element while a lower chamber is joined to the upper chamber in the vicinity of the region of the piston system segment. A supply passage and a lubricant discharge passage are formed through the internal member of the piston and joined to the upper chamber.

 Unlike the already known VCR piston systems, however, both the supply valve and the discharge valve are formed in a single housing, and, with this housing, constitute a valve system. This valve system is in turn slidably mounted in a practical bore in the upper end of the internal element of the piston and locked in position by a washer or other suitable means. This construction thus eliminates the mounting plate previously used to trap the supply and discharge valves in the internal element of the piston.

 In the preferred embodiment of the invention, the housing of the valve system comprises a first part and a second part. The first part is cylindrical and tubular, closed at one end by defining a cylindrical chamber in which are arranged both the supply valve and the discharge valve so that the discharge valve abuts against the closed end of this first part. The second part acts as a plug which is fixed in the other end of the first part, trapping the supply and discharge valves between the two parts. In addition, the tension on the discharge valve can be easily and precisely changed by adjusting the axial and / or angular position of the second part relative to the first.

The invention will be better understood by referring to the description below corresponding to the appended drawing in which: - Figure 1 is a longitudinal section of an udder system
your VCR with a preferred embodiment of the pre
invention, the valve system being in a position
adjustment ; - Figure 2 is a IongJtuddnaledu section of the valve system
according to the invention, enlarged for clarity; - Figure 3 is a longitudinal section similar to that of
Figure 2, but showing a variant of the
valve for a VCR piston system according to the invention.

Referring to Figure 1, there is shown a piston system with variable compression ratio (VCR), 10 according to the present Snvetfton, comprising an internal element 12, the upper portion 14 is of reduced diameter. An external element
16 is mounted on the external surface of the reduced portion 14.

The external element 16 has a crown 18 which
serves as a piston head and compatible with the chosen combustion system '. The crown 18 constitutes a movable wall dela lower limit of the combustion chamber of the engine (not
shown) and is mounted axially sliding or telescoping
that on the external surface of the reduced portion 14 of the element
12. An annular retaining ring 22 is mounted on the top of
the internal element 12-by suitable renon means shown)
around the periphery of the reduced portion 14 of the element
12.A ring 24 having an external thread -26 is disposed
around the reduced diameter portion 14 of the internal element
12 and cooperates by this net with internal threads 28 formed
on the inner surface of the lower portion of the element
external of the piston, it being understood that other means of
fixing between the ring 24 and the external element 16 can also
be employed. Limiting locking means
displacement such as a locking pin 30 prevents
cost the rotation of the ring 24 relative to the external element
ne 16 and consequently the axial displacement of the ring 24 by
relative to the external element 16. Appropriate seals 32 and 34
are provided between the element - internal 12 and external element 16
of the system 10 so as to seal the fluid between
the piston elements in the region of their frictional contact
seriously. An upper chamber 36 is formed between the former
upper end 37 of the internal element of the piston and the
internal surface of the external element of the piston 16, while
that a lower annular chamber 38 is formed between
the annular element 22, the external element of the piston 16 and the ex
upper end of the ring 24 in the vicinity of the region of the
segment 35 of the piston system 10. Joints 32 and 34
prevent oil leakage from the lower chamber 28, at
except for a passage 40 made through the annu element
area 22 and which joins the upper room 36 to the room
lower 38. The passage 40 allows the passage of the fluid between
the upper chamber 36 and the lower chamber 38. The element
internal of the piston 12 is joined to a connecting rod 42 by a pin 44 in a conventional manner to assemble a piston
to a connecting rod. A passage 58 in the connecting rod 42 communicates with the engine lubrication system by means not shown.

 A single valve system 60 which is best seen in FIGS. 2 and 3, is provided to regulate the flow of fluid to and from the upper chamber 36 of the system 10. This valve system 60 comprises a housing 62 consisting of a first part 64 and a second part 66.

The first part 64 is generally tubular and cylindrical in shape and has a radial wall 68 at its upper end, with a central opening 76. The first part 64 defines an internal cylindrical chamber 70.

 A tubular body for one-way valve 72, in which is placed a ball of one-way counter valve 92, is formed in the cylindrical chamber 70 in such a way that its upper end corresponds to the central opening 76 and has a fluid passage 78 which crosses. The clearance between the opening 76 and the body 72 constitutes a filter as is well known in this technique. An external radial rim 80 at the other end of the body 72 constitutes a support for a valve 82 of the frustoconical washer or Belleville washer type, mounted on the body 72 as seen in FIG. 2. The other end of the washer 82 rests against the rim 68 of the first part 64 of the housing.

 The second part of the housing of the valve system 66 has the shape of a disc and has an external thread 84 on its external periphery, cooperating with an internal thread 86 formed at the lower end of the first part 64.

By screwing the second part 66 onto the first part 64, the tubular body 72 and the elastic washer 82 are trapped between the parts 64 and 65 in the chamber 70. An axial passage of fluid 88 through the second part 66 determines a communication of fluid coming from the passage 58 towards the interior 73 of the body 72. The upper end of the passage 88 is of conical shape and constitutes a seat 90 for a ball 92 housed inside 73 of body 72.

 The axial position of the second part 66 relative to the second part 64, that is to say the quantity of which the second part 66 is screwed or placed by rotation on the first part 64, determines the preload or tension on the washer elastic 82. For example, the second part 66 is seen on the second part 64 to a much greater degree in FIG. 2 than in FIG. 2 so that the preload on the elastic washer 82 is much greater on Figure 1 as in Figure 2 and exaggerated for clarity. The degree of tension on the washer 82 in turn determines the pressure under which the washer 82 suddenly opens, as will be apparent below.

 Any suitable means can be used to prevent rotation of the second part 66 relative to the first part 64 once the two parts are fixed together at the desired relative position. For example, in the preferred embodiment of the invention, an adjusting screw 94 of the Allen type is screwed into a threaded bore 96 made in the bottom of the second part 66 in the immediate vicinity of the thread 84. The bore 96 is however smaller than the screw 94 so that as one screws the screw 94 into the bore 96, it spreads the threads 97 and 97 'of the second part 66 which prevents in a simple way but effective any new rotation of the elements 64 and 66 relative to each other.

Other means, such as a radial pin 98 (Figure 3) passing through the parts 64 and 66 can also be used to prevent the rotation of the elements 64 and 66 relative to each other.

 Referring to Figure 1, the elements 64 and 66 being appropriately placed and locked against any rotation relative to one another, the complete valve system 60 is then put in position in a cylindrical bore 100 made axially in the upper end of the internal element of the piston 12 and practically immediately above the connecting rod 42. An elastic washer 102 is housed in an annular groove 104 formed in the upper end of the bore 100 and through the valve system 60 so as to detachably lock the valve system in the bore 100. At the opposite end of the system 60, a slide 106 having a central orifice 108 is pushed against the upper end of the connecting rod 42 by a res leaves the dia.PosQé between the gii-ssÀère 10 and the bottom of the second housing part 66 :. The valve system is retained axially by the elastic washer 1a2.

 The sowpape-unifidifirectivonnealle 92 of the valve system 60 establishes the communication of the fluid between the feed passage 58, through the passage 88 and towards the upper chamber 36, via the passage 78. Conversely, a passage evacuation is established from the upper chamber 36 through the orifice 76, through the radial wall portion 68 and around the tubular body 72. When the elastic valve evacuation valve 82 opens, that is to say is in the lowered position, the fluid can flow through the openings 112 made through the first part 64 of the housing towards the evacuation passages 114 of the element 12 of the piston. The passages 114 are open at their lower end towards the motor housing.

 As the invention has just been described, it appears clearly that the internal element 12 being connected to the connecting rod 42 in the conventional manner moves up and down in the cylinder of a conventional motor between fixed limits and in the manner of a conventional piston.

The external element 16 is driven in an alternating movement with the piston, between defined axial limits, at their external limit, by the contact of the crown 18 with the top of the internal element 12 and at the upper limit by the contact of the top of the washer 24 with 1 lower edge of the radial portion of the annular element 22. Thus, when the piston is driven by its reciprocating movement, the external element 16 moves under the influence of inertia towards its extreme high point, while the oil volume is lost from the upper chamber 36 to the sump by the discharge valve 82, from which it results in a displacement of the external element 16 towards its extreme low position. The lubricant sent to rooms 36 and 38, however, regulates this movement in a manner which ensures an increased compression ratio for the engine while at the same time it maintains a maximum predetermined pressure in the combustion chamber which is established by adjusting the pressure of the opening of the discharge valve 82.

 The inertia and the oil pressure act on the external element 16 at the upper end of the exhaust stroke and in the front part of the downward intake stroke, which causes the element to separate. external 16 of external element 12. As the elements move apart and the upper chamber 36 expands, the ball 92 acting as a one-way inlet valve moves in a direction allowing the oil to be sent in the upper chamber 36 in expansion from the passages 58 and 88. The ball 92 prevents the oil from returning via the supply valve from the upper chamber 36 during the downward stroke of the piston.

Preferably, the upper chamber is connected directly to the lower chamber 38 by the passage 40. The passage 40 however is preferably restricted and limits the flow between the chambers 36 and 38 to prevent excessive movement of the piston on each stroke,
As described more fully in the patents
US 4,016,801 and 4,031,868, the conical spring discharge valve 82 used in the present invention provides a damping of the lubricant coming from the chamber 36 towards the crankcase when it reaches a predetermined maximum pressure in the upper chamber 36 As described above, the adjustment of the opening pressure of the discharge valve 82 can be preset with precision by adjusting the rotation or the path towards the interior of the second part 66 relative to the first. part 64.

 A variant of the valve system 60 for the VCR system 10 according to the present invention is shown in FIG. 3. It differs from that shown in FIGS. 1 and 2 in that the conical washer or belleville 82 is reversed inside the chamber 70. In this case, the upper chamber 36 of the system 10 communicates through the opening 76 with the internal face 83 of the conical washer 82. Thus, when the predetermined pressure necessary to open the discharge valve 82 is reached , the discharge valve 82 suddenly expands upwards and establishes a communication of the fluid coming from the opening 76 through the radial orifices 112 towards the engine casing.

 From the foregoing, it can yol'lr that the valve system 6Q encapsulated according to the present i? Nventi'on has several advantages unknown to systems used in prior VCR piston systems. In particular, the entire valve system 60 can be easily, simply and quickly removed or returned to the piston system 10 when necessary for maintenance, repair or replacement. In addition, the adjustment of the opening pressure of the discharge valve 82 can be preset simply and precisely by simply rotating the elements 64 and 66 relative to one another in a manner which does not was so far not known in the disassembly of the piston.

 Of course, this invention is not limited to the embodiment which has just been described but on the contrary covers all the variants which may be envisaged by specialists in this question.

Claims (11)

1. Combustion engine of the type comprising at least one piston  consisting of an internal element and an external element  telescopically mounted on this internal element, these elements  being mobile under the effect of the reciprocating movement of the piston  in the engine combustion chamber, a fluid chamber  of variable volume under the effect of this relative movement  and variations in the amount of fluid it contains  and means for sending fluid into this chamber,  these means including a feed passage in this udder  your, gathered in this room and a means of evacuatinn gathered  to this chamber and with the motor housing, characterized in  what this piston contains  - a valve system comprising a housing mounted in  a bore of the internal element of the piston,  - a unidirectional supply valve mounted in  this housing and in this feed passage,  - a normally closed valve mounted in this housing and  in this discharge passage, said valve normally  closed opening under the effect of a predetermined pressure  in this chamber and thus allowing the fluid to be  evacuated from this chamber to the housing and  - means for detachably locking this  housing of the valve system in this bore of the element  internal piston. 2. Motor according to claim 1, characterized in that the  valve system housing includes a first part  and a second part, means for bringing together in a way  detachable these two parts together, so that  these parts define an internal chamber between them,  said one-way intake valve and said penny  normally closed pope being housed inside said  bedroom. 3. Engine according to claim 2, characterized in that the  said first part of the housing is tubular and  cylindrical and has a radial wall internal to one of  its ends-, the second part of this housing being in  disc shape and joined axially detachable to  the first part of this housing at its other end. 4. Motor according to reyendihcatibn 3, characterized in that the  means' of fiatiÙn detached'ablas of-s two-s- of housing  together consist of threads-cooperating between the  first and second part in such a way that the lon  axial runner of the interior chamber of this accommodation depends  of the axial position of the second part relative to the  first. 5. Motor according to claim 2, characterized in that the  said normally closed valve is constituted by a  elastic conical washer having its outer edge at  tight contact of the internal radial wall of the first  part of the accommodation, means being provided for varying  the axial length of said interior chamber and make  vary the preload voltage on this washer  elastic. 6. Motor according to claim 5, character-ized in that the  last mentioned means exist in an assembly by  axial thread hampered first part and second part  of the housing so that the rotation of a part by rap  port to port changes the axial length of the interior of the  housing. 7. Motor according to claim 6, characterized in that the  one-way intake valve consists of a lodge  tubular cylindrical with a radial rim towards  the exterior at its lower end, the so-called washer  elastic being disposed on this housing and supported by  the upper face of this radial rim, the lower face  of this radial flange being in contact with the second part  of housing and supported by it. 8. Motor according to claim 4, characterized in that it  includes means for locking parts of the housing  together at a preset angular position relative to  to each other. 9. Motor according to claim 8, characterized in that the  last means mentioned above consist of a threaded bore  substantially parallel and in the immediate vicinity of the assembly  threaded connection between the two parts of the housing in one  of these parts and a threaded element cooperating with these file  tages separating them from each other, -the said threaded element  having a larger diameter than the threaded bore.  inside the bore of the internal element of the piston.  valve system housing to retain this housing at  this washer comprising a portion projecting above the  quées at the top of the bore in the internal element of the piston,  annular elastic removably mounted in the grooves  detacX locking means: ables-consist of a washer  10.Motor according to claim 1, characterized in that the 11. Motor according to claim 1, characterized in that  normally closed valve includes an annular washer  elastic whose internal edge is in leaktight contact with  the internal radial wall of the first part of the housing and  whose outer edge is in leaktight contact with the outer rim  of the one-way intake valve.