Adjustment device for a variable compression ratio engine

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).

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.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 to 3show an engine block100that comprises at least one cylinder110in which a piston2is moved by means of a transmission device1.

The mechanical transmission device1comprises, in the lower portion of the piston2, a transmission member3fixedly attached to said piston and interacting first with a rolling guide device4and secondly with a sprocket5.

The sprocket5interacts with a connecting rod6connected to a crankshaft9in order to transmit the movement between said piston and said crankshaft.

The sprocket5interacts, on the side opposite to the transmission member3, with another rack called the control rack7whose vertical position relative to the engine block100is controlled by a control device12comprising a control thruster8, whose thruster piston13is guided in a thruster cylinder112made in the engine block100.

The thruster cylinder112may be bored directly into the engine block100, or in a liner not shown fitted into the engine block100. The thruster cylinder112is closed in its upper portion by a thruster cylinder head113that is screwed onto the engine block100. Provision may be made for one cylinder head113for each thruster cylinder112or a cylinder head113common to all the thruster cylinders112of a multi-cylinder engine.

The transmission device1comprises a transmission member3fixedly attached to the piston2and provided on one of its faces with a first large rack35whose teeth34interact with the teeth51of the sprocket5.

The transmission member3comprises, on the side opposite to the rack35, another rack37whose small teeth38interact with those of the roller40of the rolling guide device4fixedly attached to the engine block.

The engine block100is pierced with an orifice104on one side of the cylinder110making it possible to insert into said block a support41comprising racks46synchronizing the movement of the roller40with that of the piston2and a roller track48interacting with the roller40.

The support41consists of a very thick plate42which allows it to be attached to the engine block100, from the outside of the latter, by means of screws105.

To make it easier to machine the racks46on the support41, it is possible to fit onto said support41a body45comprising the roller track48interacting with the roller40, said body being attached to said support41with at least one fastening screw107.

The sealing between the support41and the engine block100is provided by a seal47housed in a groove44that may be made either in the support41or in the engine block100.

The distance between the engine block100and the support41is adjusted by a shim106forming means of adjusting the position of the transmission device1, said shim106being interposed between the inner face of the plate42and the outer face of the engine block100.

The shim106makes it possible to adjust the control rack7in vertical position, taking account of the total dimensions of all the parts comprised between the bearing plane of the support41on the engine block100and the center of the thruster cylinder112of the control thruster8.

The thickness of the shim106is determined after measuring the total dimensions of all the parts comprised between the bearing plane of the support41on the engine block100and the center of the thruster cylinder112of the control thruster8.

FIGS. 4 and 5illustrate the control thruster8of the control device12that consists of an upper thruster rod10having a threaded portion11screwed into the lower thruster rod16of the control rack7and a thruster piston13traversed in its middle, by means of a bore17, by the upper thruster rod10.

The upper thruster rod10comprises a cylinder portion14interacting with a bore114made in the thruster cylinder head113providing the control thruster8with a ratio between displaced volume and stroke of thruster piston13that is identical for the upper chamber121and lower chamber122.

The upper thruster rod10comprises a tool socket15allowing it to be tightened.

The upper thruster rod10comprises centering means135that make it possible to center first the upper thruster rod10on the thruster piston13and secondly the lower thruster rod16on the thruster piston13.

According to a variant not shown, the lower thruster rod16may have a threaded portion screwed into the upper thruster rod10, and centering means that make it possible to center first the upper thruster rod10on the thruster piston13and secondly the lower thruster rod16on the thruster piston13.

The sealing between the upper thruster rod10and the bore114of the thruster cylinder head113is provided by a seal115.

The sealing between the lower thruster rod16and a bore116made in the bottom117of the thruster cylinder112is provided by a seal118.

The seals115and118are designed to be able to provide sealing while accommodating the large clearance provided between the upper thruster rod10and the lower thruster rod16and their respective bores114,116.

This arrangement allows the control rack7to orient itself in the engine block100so that the teeth74of said rack are aligned with the teeth52of the sprocket5.

Each seal115and118consists, for example, of an external ring119made of friction-resistant plastic and an internal O-ring seal120which provides the sealing between the ring119and the corresponding bore114,116.

The thruster piston13is traversed vertically by another bore18which may or may not have at least one flat19making it possible to limit the bulk of the whole control device12, for the passage of a control rod20interacting, on either side of the thickness of the piston13, with valves21and springs22.

Each valve21is traversed by the control rod20and presses directly on the corresponding top or bottom face of the thruster piston13or of the flat19.

Each spring22is traversed by the control rod20and presses first on the corresponding valve21and secondly on a stop130made on the control rod20and consisting, for example, of an elastic ring131and a washer132.

Each valve21comprises a seal that consists, for example, of a plastic, friction-resistant ring23and an inner O-ring seal24which provides the sealing between the ring23and the body of the valve21.

The valves21may be designed in two parts to make it easier to install the seal that they comprise.

The clearance between the valves21and the control rod20is sufficient to allow the thruster piston13to pivot slightly in the thruster cylinder112so that the control rack7can orient itself in the engine block100so that the teeth74of said rack are aligned with the teeth52of the sprocket5, while allowing said valves to provide the sealing between the upper chamber121and lower chamber122of the thruster cylinder112.

The valves21may therefore pivot slightly relative to the control rod20so that they always remain in contact over their whole circumference with the thruster piston13.

Each valve21may have a small area of contact with the thruster piston13, materialized by a circular peripheral rim25designed to increase the pressure of contact exerted by said valves21on said thruster piston13.

This arrangement first makes it possible to provide better sealing and secondly allows the valves21to provide a larger surface area exposed to the pressure of the fluid on the side of the thruster piston13in order to make control of the control device12easier.

The control rod20comprises, for its guidance, a cylindrical portion123interacting with a bore124made in the thruster cylinder head113. The control rod20comprises, in the extension of its cylindrical portion123, a threaded end125allowing it to be attached to a control device not shown.

The sealing between the control rod20and the bore124of the thruster cylinder head113is provided by a seal126.

The bore124may comprise a flat133in which may move the spring22and the stop130that are in the upper thruster chamber121, in order to limit the vertical bulk of the control device12.

On the opposite side of the thruster cylinder head113, the control rod20is guided in a bore127made in the bottom117of the thruster cylinder112.

The sealing between the control rod20and the bore127of the thruster cylinder112is provided by a seal128.

The bore127may comprise a flat134in which may move the spring22and the stop130that are in the lower thruster chamber122, in order to limit the vertical bulk of the control device12.

The portion of the thruster piston13in contact with the thruster cylinder112has a spherical profile26forming a ball-and-socket type connection between said thruster piston13and said thruster cylinder112.

This arrangement is designed to allow the control rack7to pivot so that its teeth74can be aligned with the teeth52of the sprocket5.

The thruster piston13comprises seals27on either side of its spherical profile26.

The seals27are designed to provide the sealing between the upper chamber121and lower chamber122of the control thruster8, despite the large clearances necessary for the orientation of the thruster piston13in the thruster cylinder112.

In a variant not shown, the seals27consist, 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 piston13.

Thus, the spherical profile26of the thruster piston13forms first means giving the angular freedoms necessary for the transmission device1to work.

The thruster piston13may comprise a release valve137that may consist, for example, of a ball138held, on a seat made in the thruster piston13, by a spring139(FIG. 10).

The release valve137makes it possible to limit the maximum pressure of the upper chamber121of the control thruster8and consequently makes it possible to limit the maximum force exerted on the teeth34,51,52,74of the transmission device1.

The control rack7comprises on the side opposite to its teeth74, a bearing face75interacting with a bearing face103made in the engine block100and whose distance relative to said engine block100is adjustable, this forming means of adjusting the working clearances of the transmission device1.

The bearing face75comprises a cavity28in a portion of a sphere which may or may not have at its pole a cylindrical housing29for a spring30which may, for example, be of the helical or “belleville” type.

The function of the spring30is to keep the various members of the transmission device1in contact when a slight force is exerted on the teeth51,52of the sprocket5.

The cavity28is designed to receive the head31in a portion of a sphere of a bearing piece76housed in said cavity producing a ball-and-socket connection between the control rack7and the engine block100(FIG. 5).

The head in a portion of a sphere31of the bearing piece76may have at its pole a cylindrical housing36for the spring30.

The bearing piece76comprises, on the side opposite to its head in a portion of a sphere31, a flat face32interacting with the bearing face103made in the engine block100.

This arrangement allows the control rack7to move relative to the engine block100.

The bearing piece76may comprise a network of ducts33making it possible to deliver the lubricating oil first to its flat face32and secondly to its head in a portion of a sphere31.

Thus, the ball-and-socket type connection between the control rack7and the engine block100formed by the spherical profile of the cavity28of said control rack7and by the head in a portion of a sphere31of the bearing piece76forms second means giving the angular freedoms necessary for the transmission device1to work.

The bearing face103of the engine block100is made, for example, on a cylindrical support102screwed into said block.

The cylindrical support102has a thread108made on its periphery in order to be screwed directly into a threaded orifice101made in the engine block100.

The cylindrical support102comprises a tool socket109allowing it to be tightened and held in position while it is immobilized by means of a locknut129.

The locknut129comprises a tool socket111allowing it to be tightened. The tool socket111is designed so that it is possible to tighten the locknut129while holding the cylindrical support102by means of its tool socket109.

Thus, the cylindrical support102and its locknut129screwed into the threaded orifice101of the engine block100form a device for adjusting the working clearances of the transmission device1in the engine block100.

As a variant, the cylindrical support102may be fixedly attached to a very thick plate, not shown, attached from the outside to the engine block100by means of screws.

For this variant, the working clearances of the transmission device1in the engine block100are adjusted by means of a shim, not shown.

This shim, placed between the very thick plate and the engine block100makes it possible to adjust the distance between said plate and said engine block.

According to a variant, not shown, the cavity28in a portion of a sphere used as a housing for the head31in a portion of a sphere of the bearing piece76may be made in the cylindrical support102.

In this variant, the flat face32of the bearing piece76slides on a flat face made on the control rack7, 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 10show a variant embodiment of the second means giving the angular freedoms necessary for the transmission device to work provided at the control rack7and more particularly at its ball-and-socket type connection pressing on the engine block100.

In this variant, the second means consist of a pressure thruster62whose piston61, thanks to a spherical profile, makes a ball-and-socket type connection between the control rack7and the engine block100.

A directional flow valve65makes it possible to permanently compare the pressures existing in the upper chamber121and the lower chamber122in order to connect the one with the higher pressure to the chamber66of the pressure thruster62.

Thus, the directional flow valve65makes it possible to connect the upper chamber121or the lower chamber122whose pressure is the higher with the chamber66of the pressure thruster62.

The pressure thruster62comprises a spring63which makes it possible to keep the various members of the transmission device1in contact when the pressure existing in the chamber66is low.

The spring63may be of the helical or “belleville” type.

As an example, the directional control valve65may be housed in the thickness of the thruster piston13. In this case, it is connected to the pressure thruster62via ducts64made in the thruster piston13, the upper thruster rod10and lower thruster rod16and in the control rack7.

Note that the engine block100may 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 cylinders110, directly bored into said engine block100.

The engine block100may comprise at least one duct and/or at least one chamber in which an engine-cooling fluid circulates.

The engine block100may 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 block100comprises bearing caps141attached via at least two screws, said bearing caps141being able to be incorporated into a bearing casing140.

Note that the engine block100may 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 block100. The engine block100may 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.