WO2022105984A1

WO2022105984A1 - An internal combustion engine system

Info

Publication number: WO2022105984A1
Application number: PCT/EP2020/082381
Authority: WO
Inventors: Arne Andersson
Original assignee: Volvo Truck Corporation
Priority date: 2020-11-17
Filing date: 2020-11-17
Publication date: 2022-05-27
Also published as: EP4248073A1

Abstract

The invention relates to an internal combustion engine (ICE) system comprising at least one combustion cylinder housing a combustion piston, said combustion cylinder being configured to be energized by forces of combustion; a compressor cylinder housing a compressor piston, said compressor cylinder being configured to compress a volume of air and transfer the compressed air to the at least one combustion piston; an expander cylinder housing an expander piston, said expander cylinder being configured to receive exhaust gases from the at least one combustion piston; a connecting element connecting said compressor piston and said expander piston such that the compressor piston and the expander piston move in unison; and a crankshaft connected to said at least one combustion piston and said compressor piston by a respective connecting rod.

Description

AN INTERNAL COMBUSTION ENGINE SYSTEM

TECHNICAL FIELD

The present invention relates to an internal combustion engine system comprising an expander cylinder and a compressor cylinder. The invention is applicable on vehicles, in particularly heavy vehicles, such as e.g. trucks. However, although the present invention will mainly be described in relation to a truck, the internal combustion engine system may also be applicable for other types of vehicles propelled by means of an internal combustion engine. In particular, the present invention can be applied in heavy-duty vehicles, such as trucks, buses and construction equipment, but also in cars and other light-weight vehicles etc. Further, the internal combustion engine is typically a hydrogen internal combustion engine.

BACKGROUND

For many years, the demands on internal combustion engines have been steadily increasing and engines are continuously developed to meet the various demands from the market. By way of example, reduction of exhaust gases, increasing engine efficiency, i.e. reduced fuel consumption, and lower noise level from the engines are some of the criteria that have become more important aspects when designing and selecting a suitable internal combustion engine (ICE) system and its engine component. Furthermore, in the field of heavy-duty vehicles, such as trucks, there are a number of prevailing environmental regulations that set specific requirements on the vehicles, e.g. restrictions relating to maximum allowable amount of exhaust gas pollution.

In order to meet at least some of the above-mentioned demands, various engine concepts have been developed throughout the years where conventional combustion cylinders have been combined with e.g. a pre-compression stage and/or an expansion stage.

One type of ICE system that has the potential to meet prevailing and future environmental regulations is a hydrogen ICE system in which the combustion of hydrogen with oxygen produces water as its only product. In such hydrogen ICE system, there is generally a compressor for pressurizing the air before entering the combustion cylinder so as to provide an appropriate mixture of hydrogen and air in the combustion cylinder when performing and completing the combustion reaction. In addition, some of these hydrogen ICE systems typically include an expander for expanding the exhaust gases arising from the combustion reaction.

It would be desirable to further improve the operations of an ICE system using a compressor and an expander to meet the prevailing demands and the increased need in the industry for efficient ICE systems.

SUMMARY

An object of the invention is to provide an improved internal combustion engine (ICE) system comprising an expander cylinder and a compressor cylinder, in which the arrangement of the components of the ICE system allows for an efficient operation of the expander cylinder without compromising the overall size of the ICE system. The object is at least partly achieved by a system according to claim 1.

According to a first aspect of the invention, there is provided an ICE system. The ICE system comprises at least one combustion cylinder housing a combustion piston, the combustion cylinder being configured to be energized by forces of combustion so as to drive a crankshaft of the ICE system; a compressor cylinder housing a compressor piston, the compressor cylinder being configured to compress a volume of air and transfer the compressed air to the at least one combustion piston; an expander cylinder housing an expander piston, the expander cylinder being configured to receive exhaust gases from the at least one combustion piston; a connecting element connecting the compressor piston and the expander piston such that the compressor piston and the expander piston move in unison. Further, the crankshaft is connected to the compressor piston by a connecting rod.

The invention is based on the insight that the mutual operations of the combustion cylinder, the compressor cylinder and the expander cylinder may have an impact on the general efficiency of the ICE system for certain fuels, such as hydrogen-based fuels. By way of example, it has been found that ICE systems using an expander for expanding the contained gaseous medium may benefit from having responsive valves so as to permit a fast and efficient introduction of the gaseous medium into the expander cylinder, which generally may take place at the top dead centre (TDC) of the expander piston. By way of example, only, a normal valve opening-closing event duration is typically around 200 crank degrees. In regard to an expander, however, the opening-closing event duration may need to be less than 1/3 of such normal valve opening-closing event. As such, the valve flow capacity of the expander needs to be correspondingly higher than the valve flow capacity of a normal valve opening-closing event. At least for these reasons, the requirement on the expander intake valves may be considerably higher than the requirement on valves for a normal engine. Further, while a fast introduction of the gaseous medium into the expander cylinder may to some extent be accomplished with a responsive and efficient inlet valve arrangement, such arrangement is often also a relatively advanced and expensive component of the ICE system. To this end, it has been realized that one possible alternative way of improving the operation of an ICE system for use with a simpler arrangement of inlet valves at the expander side of the ICE system may be to allow the expander piston to displace slower during the intake event. By way of example, the closing of the intake valve is given by the expander piston position since there is a need for a certain expansion rate. For example, if an expansion rate of 10 is desirable, and the piston stroke is 100 mm, then the valve should close at 10 mm from TDC. However, one challenge is that a piston does not move in a perfect sinusoidal way unless the connecting rod is infinitely long. The shorter the connecting rod, the more the piston movement will deviate from the perfect sinusoidal movement. Therefore, the piston will turn faster with a correspondingly higher acceleration at the TDC compared to the acceleration of the piston at its bottom dead centre (BDC). That is, a piston travels further during the top half of its motion than during the bottom half of its motion.

In view of the aforesaid, the invention addresses the problem of providing a sufficient time for the intake event at the expander side. By connecting the compressor piston with the expander piston so that the pistons move in unison, the expander will be at its TDC when the compressor is at its BDC. Further, by connecting the connecting rod directly to the compressor piston, rather than having a connecting rod from the crankshaft to the expander piston, the expander piston will turn at its TDC as if it was its BDC. As such, the expander piston will move slower at its TDC, thereby extending the time available for the intake valve(s) event at the expander. To this end, the present invention provides for extending the time period of the intake valve event at the TDC of the expander piston, so as to ensure that the expander cylinder can be filled with exhaust gases in a simple, yet efficient manner. Further, by having a connecting element rigidly connecting the compressor piston with the expander piston, and a compressor piston connecting rod transferring the reciprocating motion of both the expander and compressor pistons into a rotational motion of the crankshaft, the resulting lateral forces at the expander piston are very small. Rather, the lateral forces are taken at the compressor piston. More specifically, the lateral forces arise due to the connecting rod angle and are applied to the compressor piston at the compressor piston pin (the piston pin connecting the compressor piston to the connecting rod). As there is no piston pin at the expander piston, since the expander piston is not connected to the crankshaft via its own connecting rod, the lateral forces are mainly distributed to the compressor piston and are further transferred to an inner surface of the compressor cylinder. Stated differently, resulting forces, such as lateral forces acting on the piston(s), originating from the transferring of reciprocating motion of the piston(s) into rotational motion of the crankshaft by means of the compressor piston connecting rod can be mainly distributed to the compressor piston where the connecting rod from the crankshaft is coupled, and as there is no connecting rod directly connecting the expander piston to the crankshaft. Further, by distributing the lateral forces to the compressor piston rather than to the expander piston, it becomes possible to reduce noise from the ICE at cold start. This is at least partly due to that the expander operates with hot gases and will therefore be subject to an immediate increase in temperature. Hence, there is a need for a significant play between the expander piston and expander liner when the ICE is cold in order to allow for the expander piston thermal expansion when reaching its operation temperature. On the other hand, the temperature increase at the compressor is generally less than the temperature increase at the expander. Hence, the compressor can generally be provided with a smaller clearance to the liner.

Moreover, as the compressor piston and the expander piston are connected by the connecting element, the ICE system can be made more compact. More specifically, as the expander piston and the compressor piston are rigidly connected to each other, the total height of the expander piston and the compressor piston can be lower compared to a design in which the expander piston and the compressor piston are not rigidly connected to each other. Moreover, the connecting element provide a mechanically stiff connection between the expander piston and the compressor piston, thus increasing the mechanically stability of the ICE. In a conventional piston, the height of the piston, i.e. the piston skirt (typically being of the same size as the diameter of the piston), aims to prevent misalignment of the piston inside of the cylinder. By having a connecting element connecting the expander piston and the compressor piston, the expander piston contributes in aligning the compressor piston inside of the compressor cylinder, and the compressor piston contributes in aligning the expander piston inside of the expander cylinder. Hereby, the height (or skirt) of the respective piston can be reduced, resulting in e.g. lower friction losses.

Moreover, compared to a conventional two-stroke engine in which lubrication of the connecting rod coupling at the piston end (i.e. the small end of the connecting rod) is difficult to accomplish, the lubrication of the compressor piston connecting rod in the ICE system is relatively easy to carry out as the compressor piston is rigidly connected to the expander piston, and thus move in unison with the latter. In more detail, in a conventional two-stroke engine, the journal bearing at the small end of the connecting rod is only moving back and forth during a crankshaft revolution. A non-rotating journal bearing is difficult to lubricate. Moreover, in a four-stroke engine the small end of the connecting rod is lubricated at the top dead centre (TDC) between the exhaust stroke and the intake stroke. Hereby, the relatively low gas pressure and acceleration of the piston enable “lifting” of the piston from the piston pin whereby lubricating oil can enter the journal bearing. Comparing again with the conventional two-stroke engine, the always relatively high gas pressure at TDC is too high for the piston acceleration to overcome, and thus it is difficult to get the lubrication oil into the journal bearing. The ICE system of the example embodiments solves this problem (as for the four-stroke engine) since the gas pressure in the compressor exerts an upward force on the expander piston, and as this force is larger than the counter force from the gas in the expander cylinder during the second half of the expander power stroke. Hereby, lubricating oil can enter into the journal bearing at the small end of the expander connecting rod.

The invention is particularly useful for a hydrogen internal combustion system. In such hydrogen ICE system, the combustion of hydrogen with oxygen produces water as its only product. In addition, hydrogen can be combusted in an ICE over a wide range of fuel-air mixtures. While a hydrogen ICE system may be operated to produce low emissions during certain conditions, the amount of NOx emission may at least partly depend on the air/fuel ration, the engine compression ratio as well as the engine speed and the ignition timing. In addition, combustion of air/fuel in a hydrogen ICE system may pose higher demands on the strength and size of the engine components compared to e.g. a traditional gasoline engine.

As such, in one example embodiment, the ICE system is a hydrogen ICE system. The hydrogen ICE system comprises the combustion cylinder for combusting hydrogen, the expander and the compressor. According to at least one embodiment, the at least one combustion cylinder is configured for combustion of hydrogen gas. It should also be conceivable that the ICE system may be configured for combustion of another gaseous fuel. Hence, according to one example embodiment, the ICE system is a conventional diesel-type ICE system.

According to at least one embodiment, the expander piston is a connecting rod-free expander piston. In other words, the compressor piston connecting rod transfers the reciprocating motion of the expander piston and the compressor piston to a rotational motion of the crankshaft.

According to at least one embodiment, the connecting rod of the compressor piston is operable to reciprocate the compressor piston between its bottom dead centre (BDC) and top dead centre (TDC), whereby the expander piston reciprocates between its TDC and BDC via the connecting element, such that the expander piston is at its TDC when the compressor piston is at its BDC.

According to at least one embodiment, the ICE system further comprises at least one expander intake valve for introducing exhaust gases into the expander cylinder. The expander intake valve may be controllable to initiate an intake event of the exhaust gases into the expander cylinder when the connecting rod of the compressor piston is at its bottom half of movement, corresponding to the BDC of the compressor piston. When the compressor piston is at its BDC, the expander piston is at its TDC. Accordingly, there is provided an even more improved operation of the expander of the ICE system, in which the intake event is initiated in response to a given position of the compressor piston so as to permit that the intake event of the expander can occur when the expander piston is at its TDC.

According to one example embodiment, the crankshaft comprises an integrated cam lobe arranged to operate the expander intake valve. In this manner, it becomes possible to drive the valve of the expander directly via the crankshaft. Hence, it becomes possible to further reduce the number of components of the ICE system and thus generally also reduce the weight of the ICE system. The crankshaft is thus arranged to operate the at least one valve of the expander by means of the integrated cam lobe. Typically, although strictly not required, the integrated cam lobe may be arranged to mechanically operate the expander intake valve. By way of example, the integrated cam lobe is arranged to mechanically operate the expander intake valve by means of an intermediate member displaceable arranged between the integrated cam lobe and the at least one valve. The intermediate member may e.g. be a conventional cam follower, rocker arm or the like. The integrated cam lobe may be integrally formed with the crankshaft. Alternatively, the integrated cam lobe may be mounted on the crankshaft. The crankshaft may include a number of integrated cam lobes. The cam lobe of the crankshaft is generally arranged on the crankshaft so that a rotation of the crankshaft provides the cam lobe to operate the expander intake valve between an open position and a closed position relative the expander cylinder. Further, the cam lobe is arranged on the crankshaft to rotate at the crankshaft speed. Typically, the crankshaft is rotatable about a longitudinal axis and having at least one integrated cam lobe arranged thereon for rotation therewith. As such, the at least one integrated cam lobe is driven in rotation about the longitudinal rotational axis of the crankshaft and further engageable with a displaceable intermediate member in the form of cam follower for operating the valve of the expander. The fluid medium regulated by the at least one valve is typically exhaust gases received from the combustion. Hence, by way of example, the at least one valve is arranged to regulate the flow of exhaust gases into the cylinder of the expander.

According to one example embodiment, the expander intake valve is a side valve arranged at a side of the expander piston, whereby the integrated cam lobe of the crankshaft is arranged to drive the expander intake side valve.

According to at least one embodiment, the expander piston is connected to the crankshaft via the compressor piston, such that a rotational motion of the crankshaft is transferred into a reciprocating motion of the expander piston via the compressor piston connecting rod. Thus, according to at least one embodiment, the compressor piston and the expander piston are arranged with a common connecting rod. That is, the expander piston is connected to the crankshaft via the compressor piston connecting rod.

It should be understood that at least one combustion piston is arranged inside the at least one combustion cylinder, and is adapted for reciprocating motion therein. Correspondingly, the compressor piston and the expander piston are arranged inside the compressor cylinder and the expander cylinder, respectively, and are adapted for reciprocating motion therein. Moreover, a “downward” stroke of the compressor piston is referred to a stroke of the compressor piston in which the air in the compressor cylinder is compressed. Correspondingly, an “upward” stroke of the compressor piston is referred to a stroke of the compressor piston in the opposite direction. Moreover, as the compressor piston is connected to the expander piston by the connecting element and thereby move in unison with expander piston, the downward and upward strokes of the expander piston coincides with the respective strokes of the compressor piston.

In other words, the crankshaft is driven by the at least one combustion piston via its connecting rod, i.e. a combustion piston connecting rod. Moreover, the crankshaft drives the compressor piston via its connecting rod, i.e. the compressor piston connecting rod.

According to one embodiment, the crankshaft is driven by the at least one combustion piston by means of the combustion piston connecting rod, and is driven by the compressor piston by means of the compressor piston connecting rod. Further, the expander piston is driven by the crankshaft by means of the compressor piston. That is, the crankshaft is driven, i.e. receives power from, the combustion cylinder and combustion piston due to forces of combustion, and from the expander cylinder and expander piston due to forces of expansion. Moreover, the crankshaft drives, i.e. deliver power to, the compressor piston and the compressor cylinder in order to compress the air. Thus, the crankshaft is rotatably driven by at least the at least one combustion piston, by means of the corresponding connecting rod, and the crankshaft drives the power consuming piston, i.e. at least the compressor piston, by means of its corresponding connecting rod. The expander piston is then driven by means of the already existing connecting rod of the compressor cylinder and the connecting element between the compressor piston and the expander piston. By having a connecting element connecting the compressor piston and the expander piston, the height, or the skirt, of the compressor piston can be reduced. In other words, the connecting element provides mechanical stability enabling the height, or skirt, of the compressor piston to be reduced. According to one example embodiment, the height, or skirt, of the compressor piston is sized and dimensioned relative the compressor piston sealing arrangement. It should be understood that the height of the respective piston is often referred to as the skirt of the piston, and that the diameter of the expander piston is typically the diameter of the expansion volume facing surface, and the diameter of the compressor piston is typically the diameter of the compression volume facing surface. By reducing the height, or skirt, of the expander piston and/or the compressor piston, the respective piston can move inside of their respective cylinder with less friction.

According to one example embodiment, the diameter of the compressor piston is smaller compared to the diameter of the expander piston. For example, the diameter of the compressor piston is between 1/2 to 1/99 of the diameter of the expander piston, such as e.g. about 2/3 of the diameter of the expander piston. According to one embodiment, the compressor piston, the expander piston and a portion of the crankshaft are arranged along a geometrical axis, and wherein the portion of the crankshaft is arranged along the geometrical axis in between the compressor piston and the expander piston. Hereby, a compact design of the ICE can be achieved. The portion of the crankshaft can be described as being intermediary of the expander piston and the compressor piston. The portion of the crankshaft may e.g. be a segment of the crankshaft along a longitudinal direction of the crankshaft.

According to one embodiment, a reciprocating motion of the expander piston inside of the expander cylinder occurs along an expander axis, and a reciprocating motion of the at least one combustion piston inside the combustion cylinder occurs along a combustion axis. According to one embodiment, the geometrical axis coincides with the expander axis and the compressor axis. According to one embodiment, the compressor piston, the expander piston and the portion of the crankshaft are arranged in a geometrical plane extending at least along one of the expander axis and the compressor axis, and perpendicular to a longitudinal axis of the crankshaft, wherein the portion of the crankshaft is arranged in the geometrical plane in a direction perpendicular to the longitudinal axis of the crankshaft between the compressor piston and the expander piston. According to one embodiment, at least a portion of the compressor piston, at least a portion of the expander piston and at least a portion of the connecting element together form a compressor-expander arrangement surrounding the portion of the crankshaft. According to one embodiment, the compressor-expander arrangement encloses, or encompasses, the portion of the crankshaft. Thus, a compact design of the ICE can be achieved. Stated differently, at least a portion of the expander piston, at least a portion of the connecting element, and at least a portion of the compressor piston may form a geometrical frustum, or geometrical cylinder, which surrounds, or houses or encloses, the portion of the crankshaft. Stated differently, the expander piston may comprise at least an expander volume facing surface, and a crankshaft facing surface, and correspondingly the compressor piston may comprise at least a compressor volume facing surface, and a crankshaft facing surface, wherein the portion of the crankshaft is arranged in between the respective crankshaft facing surfaces.

According to one embodiment, the expander piston has a circular cross section extending in a first geometrical plane, and the compressor piston has a circular cross section extending in a second geometrical plane, the first and second geometrical planes being positioned in a parallel configuration on opposite sides of a longitudinal axis of the crankshaft.

It should be noted that the pistons may not be entirely circular in their respective cross section due to considerations of thermal expansion of the pistons. Thus, the expander piston cross section may be referred to as a round or elliptical cross section, extending perpendicular to the expander axis (i.e. the expander axis extends perpendicular into the cross section), and the compressor piston cross section may be referred to as a round, or elliptical cross section, extending perpendicular to the compressor axis (i.e. the compressor axis extends perpendicular into the cross section), and wherein the portion of the crankshaft is arranged between the cross section of the expander piston and the cross section of the compressor piston.

According to one embodiment, the expander cylinder and the compressor cylinder are co-axially arranged. Thus, alignment of the expander cylinder and the compressor cylinder inside the respective cylinder are facilitated. According to one embodiment, the crankshaft is located closer to the compressor cylinder compared to the expander cylinder. According to one embodiment, the combustion piston connecting rod is coupled to the crankshaft (i.e. the large end of the connecting rod) on the same crankshaft side as the compressor connecting rod, opposite to the expander piston. Hereby, the risk of colliding of internal components is reduced. Thus, a compact design of the ICE can be achieved. Moreover, the resulting lateral forces previously described can be kept at a minimum.

According to one embodiment, a reciprocating motion of the expander piston inside of the expander cylinder occurs along an expander axis, and a reciprocating motion of the at least one combustion piston inside the combustion cylinder occurs along a combustion axis, and wherein the expander cylinder and the at least one combustion cylinder is arranged inside the ICE in such way that the expander axis is angled in relation to the combustion axis by about 90 degrees. Thus, the internal components, such as e.g. the various pistons and corresponding connecting rods with their reciprocating and/or rotational motions, can be adapted to be kept out of the way from each other as the move internally inside the ICE. Hereby, the ICE may be made compact. The at least one combustion cylinder may thus be described as protruding laterally from the crankshaft compared to the expander cylinder.

According to one embodiment, the compressor piston connecting rod and the combustion piston connecting rod are coupled to the crankshaft by a respective crank pin. Thus, the compressor piston and the at least one combustion piston may individually be phased relative each other in relation to the crankshaft. Hereby, an even distribution of torque pulses can be achieved. According to one embodiment, the compressor piston connecting rod and the combustion piston connecting rod are coupled to the crankshaft by the same crank pin.

According to one embodiment, the ICE system further comprises an expander piston sealing arrangement sealing the expander piston to an inner surface of the expander cylinder, and a compressor piston sealing arrangement sealing the compressor piston to an inner surface of the compressor cylinder, wherein the expander piston sealing arrangement is independent from the compressor piston sealing arrangement. That is, the expander cylinder and the compressor cylinder may be individually sealed. That is, the expander piston sealing arrangement may be configured and arranged with no, or very little, adaptation to the compressor piston sealing arrangement. In other words, as the expander piston is physically separated from the compressor piston by the connecting element, the expander piston may be sealed independently of the sealing of the compressor piston.

According to one embodiment, the expander piston is an oil-free piston arrangement. That is, the expander piston is arranged in the expander cylinder in an oil-free arrangement. In other words, no lubricating oil is used to seal the piston to the cylinder wall. Thus, any disadvantage related to the use of lubrication oil is avoided, e.g. the production of soot or particles as lubricating oil is leaked into the first compartment where it is combusted.

According to one embodiment, the compressor piston is physically separated from the expander piston by the connecting element. That is, the expander piston and the compressor piston are not a common piston, but rather two separate pistons rigidly connected by the connecting element. Thus, the expander piston, the compressor piston and the connecting element may be referred to as a compressor-expander arrangement in which the two pistons are rigidly connected to each other by the connecting element. The expander piston, the compressor piston and the connecting element may according to one embodiment be made in one piece, and/or be comprised in one single unit.

According to one embodiment, the at least one combustion cylinder is a first combustion cylinder and the combustion piston is a first combustion piston, and the ICE further comprises a second combustion cylinder housing a second combustion piston, the second combustion cylinder being configured to be energized by forces of combustion. Thus, the at least one combustion cylinder may be referred to as at least two combustion cylinders. The second combustion piston is according to one embodiment connected to the crankshaft via a connecting rod. That is, the first and the second combustion pistons are connected to the same crankshaft. It should be understood that the at least one combustion cylinder, or the at least two combustion cylinders, is according to one embodiment at least partly arranged between the expander piston and the compressor piston. For example, the connecting rod(s) of the combustion cylinder(s) may be arranged between the expander piston and the compressor piston. According to one embodiment, the first and second combustion cylinders operate in a four-stroke configuration, and each one of the compressor and expander cylinders operate in a two-stroke configuration. According to one embodiment, the first and second combustion cylinders operate in common in a four-stroke configuration. According to one embodiment, the first and second combustion cylinders each operate in a two-stroke configuration. According to one embodiment, the first and second combustion cylinders each operate in a four-stroke configuration. Thus, the overall stroke of the ICE may be referred to as an eight-stroke engine (the respective two- stroke configuration of the expander and the compressor cylinders, and the four-stroke configuration of the combustion cylinders). According to one embodiment, the ICE is referred to as a dual compression expansion engine, DCEE.

It should also be readily appreciated that the engine cycle in e.g. a hydrogen ICE system may vary for different types of engine concepts. In a four-stroke engine, the cylinder performs four strokes in a cycle, i.e. intake, compression, power and exhaust. For example, in a four-stroke ICE working by e.g. the conventional Otto cycle or the Diesel cycle, each cylinder in the engine performs four strokes per cycle. Thus, each power stroke results in two revolutions of the crank shaft. In contrast, a two-stroke engine completes a power cycle with two strokes of the cylinder during only one crankshaft revolution, as the end of the power stroke and the beginning of the compression stroke happen simultaneously, and the intake and exhaust functions occurring at the same time.

According to at least a second aspect of the present invention, the object is achieved by a vehicle according to claim 12. The vehicle comprises an internal combustion engine according to the first aspect of the invention.

Effects and features of this second aspect of the present invention are largely analogous to those described above in connection with the first aspect of the inventive concept. Embodiments mentioned in relation to the first aspect of the present invention are largely compatible with the second aspect of the invention.

Further advantages and advantageous features of the invention are disclosed in the following description and in the dependent claims. It should also be readily appreciated that different features may be combined to create embodiments other than those described in the following, without departing from the scope of the present invention.

The terminology used herein is for the purpose of describing particular examples only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" "comprising," "includes" and/or "including" when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, as well as additional objects, features and advantages of the present invention, will be better understood through the following illustrative and non-limiting detailed description of exemplary embodiments of the present invention, wherein:

Fig. 1 is a side view of a vehicle comprising an internal combustion engine system according to an example embodiment of the present invention;

Fig. 2 is a perspective view of the internal combustion engine system according to an example embodiment of the present invention;

Figs. 3a and 3b are side views of the internal combustion engine system of Fig. 2 according to an example embodiment of the present invention;

Fig. 4 is a cross-sectional perspective view of the internal combustion engine system of Fig. 2 according to an example embodiment of the present invention. DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which an exemplary embodiment of the invention is shown. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiment set forth herein; rather, the embodiment is provided for thoroughness and completeness. Like reference character refer to like elements throughout the description.

With particular reference to Fig. 1 , there is provided a vehicle 1 with an internal combustion engine (ICE) system 100 according to the present invention. The vehicle 1 depicted in Fig. 1 is a truck for which the ICE system 100, which will be described in detail below, is particularly suitable for. The ICE system 100 includes an internal combustion engine (ICE). In this example, the ICE system is a hydrogen ICE system. The combustion in such hydrogen ICE system is based on a combustion of air and hydrogen, as is commonly known in the art. Hence, the ICE system here comprises a hydrogen ICE.

Turning to Figs. 2, 3a and 3b, there is illustrated an ICE system 100 according to an example embodiment of the present invention. It should be noted a that full illustration of the cylinders housing the respective pistons have been omitted from Figs. 2, 3a and 3b for simplicity of understanding the invention and the piston configuration.

Hence, while it should be noted that the ICE system may include several cylinders, the ICE system 100 here comprises at least a piston combustor assembly 110 having at least one combustion cylinder 111 housing a first combustion piston 112, and a second combustion cylinder 114 housing a second combustion piston 116. The ICE system 100 further comprises a compressor 120 having a compressor cylinder 121 housing a compressor piston 122. The compressor is a two-stroke machine. Also, as depicted in Fig. 2, the ICE system 100 comprises an expander 130. In this example embodiment, the expander 130 is a two-stroke machine. The expander 130 comprises an expander cylinder 131 housing an expander piston 132. In this context, it should be noted that the term cylinder generally refers to a component having an interior space for accommodating a reciprocating piston, as is commonly known in the art.

Turning again to the combustor assembly 110, it should be understood that the first and second combustion pistons 112, 116 are individually arranged inside the first and second combustion cylinders 111 , 114, respectively, and are adapted for reciprocating motion therein. Correspondingly, the compressor piston 122 and the expander piston 132 are arranged inside the compressor cylinder 121 and the expander cylinder 131 , respectively, and are adapted for reciprocating motion therein.

Moreover, as shown in e.g. Fig. 2, the ICE system 100 comprises a crankshaft 140. As will be further described hereinafter, the crankshaft 140 is driven by the combustion piston and arranged to operate the compressor piston 122. The crankshaft further operates the expander piston 132 indirectly via the compressor piston 122 and one or more connecting elements extending between the compressor piston and the expander piston. The crankshaft 140 is rotatable arranged around an axis of rotation, generally corresponding to a longitudinal axis LA of the crankshaft 140 (see Fig. 2).

Turning to Fig. 3a and 3b, the ICE system 100 comprises a compression piston connecting rod 154 connecting the compression piston 122 to the crankshaft 140, as illustrated in Figs. 2 to 4. Further, as shown in Figs. 2, 3a and 3b, the expander piston 132 is connected to the compressor piston 122 by a connecting element 150.

Correspondingly, as illustrated in Figs. 2 to 4, a first combustion piston connecting rod 163 connects the first combustion piston 112 to the crankshaft 140, and a second combustion piston connecting rod 164 connects the second combustion piston 114 to the crankshaft 140. Thus, the above-mentioned reciprocating motions of the pistons 112, 114 can be transferred into a rotational motion of the crankshaft 140.

By way of example, as illustrated in e.g. Fig. 3a, the expander piston 132 is connected to the compressor piston 122 by the connecting element 150 in the form of two connecting element arms 152, 156 arranged in a respective periphery portion of the expander and compressor pistons 132, 122. Each one of the connecting element arms 152, 156 typically extends from the expander piston 132 to the compressor piston 122, respectively. Even though two connecting element arms 152, 156 are shown in Fig. 3a, it should be understood that other number of connecting elements, or only one connecting element, may likewise be conceivable. Moreover, the connecting element 150 may be arranged with no connecting element arms, but instead as e.g. a connecting element envelope extending from the expander piston 132 to the compressor piston 122, such that the expander piston 132 and the compressor piston 122 move in unison. In other words, the connecting element is adapted to connect the compressor piston 132 to the expander piston 122, such that the expander piston 132 and the compressor piston 122 move in unison when the crankshaft effects a movement of the compressor piston connecting rod 154. By way of example, the connecting element 150 rigidly connects the compressor piston 132 with the expander piston 122 such that when the compressor piston 122 moves in a down-stroke (i.e. in order to compress the air in the compressor cylinder 121), the expander piston 132 moves in a stroke following the motion of the compressor piston 122. Correspondingly, as the expander piston 132 moves in an upstroke, the compressor piston 122 moves in a stroke following the motion of the expander piston 132.

As shown in Figs. 2 to 4, the compressor cylinder 121 and the expander cylinder 132 are positioned on opposite sides of, and in close proximity to, the crankshaft 140. Stated differently, a substantial portion of the crankshaft 140 is generally arranged in between the expander piston 132 and the compressor piston 122, such that the substantial portion of the crankshaft is arranged between respective crankshaft facing surfaces of the compressor piston and the expander piston, as illustrated in e.g. Fig. 2. In other words, the compressor piston 122, the expander piston 132 and the substantial portion of the crankshaft 140 are arranged along a geometrical axis GA, and the substantial portion of the crankshaft 140 is arranged along the geometrical axis GA in between the compressor piston 122 and the expander piston 132. In this manner, there is provided a so-called compressor-expander arrangement enclosing a substantial portion of the crankshaft 140. The internal position of the components in the ICE system 100 may, however, also be described in a different manner. In at least a third way of describing the internal position of the components in the ICE system 100, the expander piston 132 has a circular, or round, cross section extending in a first geometrical plane, and the compressor piston 122 has a circular, or round, cross section extending in a second geometrical plane, the first and second geometrical planes being positioned in a parallel configuration on opposite sides of the longitudinal axis LA of the crankshaft 140.

As may be gleaned from Fig. 2, or Fig. 3a, the expander piston 132 is configured for a reciprocating motion inside of the expander cylinder 131 along an expander axis EA. Correspondingly, the compressor piston 122 is configured for a reciprocating motion inside of the compressor cylinder 121 along a compressor axis CA. Correspondingly, the first combustion piston 112 is configured for a reciprocating motion inside of the first combustion cylinder 111 along a combustion axis CoA1 , and the second combustion piston 116 is configured for a reciprocating motion inside of the second combustion cylinder 114 along a combustion axis CoA2. As seen in e.g. Fig. 2, the expander cylinder 130 and the compressor cylinder 120 are co-axially arranged, i.e. the expander axis EA and the compressor axis CA are aligned.

Turning back to Fig. 2, it is further shown that the first combustion cylinder 111 , and the second combustion cylinder 114 may be described as protruding laterally from the crankshaft 140 compared to the expander cylinder 130. Thus, the expander cylinder 130, and the first and second combustion cylinders 111 , 114 are arranged inside the ICE system 100 in such way that the expander axis EA is angled in relation to each one of the combustion axis CoA1 , CoA2 by about 90 degrees. However, the expander axis may be angled in relation to each one of the combustion axes by between 40 degrees and 140 degrees, preferably between 50 degrees and 130 degrees, and more preferably between 80 degrees and 110 degrees. Analogously, the first combustion cylinder 111 , and the second combustion cylinder 114 may be described as protruding laterally from the crankshaft 140 compared to the compressor cylinder 120.

The function of the ICE system 100 will now be further elucidated with reference to Fig. 2. The compressor cylinder 120 is configured to draw a volume of ambient air, compress the air, and transfer the compressed air to the first and second combustion cylinders 111 , 114. The first and second combustion cylinders 111 , 114 are configured to be energized by forces of combustion, e.g. by ignition of the fuel, such as fuel in the form of hydrogen, by means of a spark plug (e.g. as for a petrol or gasoline driven engine) or heat originating from compression (e.g. as for a diesel driven engine). The expander cylinder 130 is configured to receive exhaust gases from the first and second combustion pistons 112, 116. The generated exhaust is generally fed via an exhaust passage (not shown) to the expander 130, where the pressure and temperature of the exhaust reduce during expansion thereof. Transportation of air, fuel and gases are carried out by means of inlet valves, transfer ports, and outlet valves known by the skilled person in the art, and which fluidly interconnects the compressor cylinder 121 , the first and second combustion cylinders 111 , 114 and the expander cylinder 131.

The crankshaft 140 is driven by at least one of the combustion pistons by means of a corresponding combustion piston connecting rod. In regard to the other power piston, i.e. the expander piston 132, the expander piston 132 is connected to the crankshaft 140 via the connecting element 150, the compressor piston 122 and the compressor piston connecting rod 154. Hereby, the rotational motion of the crankshaft 140 is transferred into a reciprocating motion of the expander piston 132 via the compressor piston connecting rod 154. Thus, the crankshaft 140 is driven by the first and second combustion pistons 112, 116 by means of the respective combustion piston connecting rods, while the compressor piston is driven by means of the crankshaft and the compressor piston connecting rod 154. The expander piston 132 is thus driven by means of the compressor piston 122 and the compressor piston connecting rod 154.

As should be readily appreciated from the positions of the compressor piston 122 and the expander piston 132 in Figs. 3a and 3b, the connecting rod 154 of the compressor piston 122 operates the compressor piston between its BDC and TDC, whereby the expander piston 132 reciprocates between its TDC and BDC via the connecting element 150. In this manner, the expander piston 132 is at its TDC when the compressor piston 122 is at its BDC, as illustrated in fig. 3a, while the expander piston 132 is at its BDC when the compressor piston 122 is at its TDC, as illustrated in fig. 3b.

Optional, the rotatable crankshaft is further arranged in the ICE system so as to cooperate with at least one valve of the expander 130. Accordingly, the expander 130 comprises at least one valve 136 (see Fig. 2) for regulating a flow of fluid medium, such as exhaust gases. While the valve can be designed in several different manners to cooperate with the crankshaft, the crankshaft 140 typically has a cam lobe 142 for effecting a movement of the valve 136 upon rotation of the crankshaft 140 about the longitudinal axis LA. In this example, as illustrated in Figs. 2 to 4, the integrated cam lobe 142 is integrally formed with the crankshaft 140. The cam lobe may thus generally be denoted as the integrated cam lobe. The cam lobe 142 is generally arranged on the crankshaft 140 so that a rotation of the crankshaft provides the cam lobe to operate the valve 136 between an open position and a closed position relative the expander 130. The cam lobe 142 is driven in rotation about the longitudinal axis of the crankshaft 140 and subsequently engages with an intermediate displaceable member in the form of a cam follower that effect a displacement of the valve 136 relative the expander 130 (i.e. relative the expander cylinder 131). The intermediate member is configured to translate the rotational movement of the cam lobe 142 into a linear motion so as to effect actuation of the valve 136. Hence, by way of example, the integrated cam lobe 142 is arranged to mechanically operate the valve 136 by means of the cam follower 138 (see Fig. 3a) rotationally arranged between the integrated cam lobe and the valve. Typically, as illustrated in Figs. 2 to 4, the cam lobe 142 of the crankshaft 140 is arranged to operate the intake valve of the expander 130. That is, the cam lobe 142 of the crankshaft 140 is arranged to operate the intake valve 136 of the expander between the open position and the closed position so as to regulate the flow of exhaust gases into the expander cylinder. While not explicitly illustrated in the Figures, the crankshaft 140 may optionally have a plurality of integrated cam lobes for operating a number of valves, e.g. a number of intake valves of the expander.

Further, in an example when the expander intake valve 136 is arranged for introducing exhaust gases into the expander cylinder 131 , the expander intake valve 136 is here typically controllable to initiate an intake event of the exhaust gases into the expander cylinder 131 when the connecting rod 154 of the compressor piston 122 is at its bottom half of movement. The bottom half of the compressor piston connecting rod corresponds to the BDC of the compressor piston 122, as illustrated in Fig. 3a. To this end, the expander piston is at its TDC, as also illustrated in Fig. 3a. In this example, as shown in Figs. 2 to 4, the expander 130 is arranged in a so-called side-valve arrangement. In such arrangement, the intake and exhaust valves are located at the side portions of the axis of the expander cylinder 131. To this end, the intake valves are considered side valves of the expander cylinder. Analogously, the exhaust valves are side valves to the expander cylinder. Further, the intake valves 136 are opened and closed by the cam lobe 142 arranged on the crankshaft. Typically, the crankshaft 140 extends perpendicular to the expander, i.e. the longitudinal axis LA is arranged perpendicular to the axis of the expander EA.

As may be gleaned from Figs. 2 to 4, and if the expander 130 is considered to be arranged in a vertical orientation relative to a horizontal oriented crankshaft 140, the intake valve 136 of the expander 130 is a side valve arranged at a vertical side of the expander 130, whereby the cam lobe 142 of the crankshaft 140 is arranged to drive the vertical side valve of the expander 130. In such arrangement, the inlet valve is located at a side portion of the expander cylinder 131. Analogously, in such sidevalve expander arrangement, the exhaust valve of the expander is also typically located at a side portion of the expander cylinder.

Moreover, it should also be noted that the expander here comprises an oil-free piston arrangement. Such arrangement is particularly suitable for hydrogen ICE systems, in which the combustion cylinders are configured for combustion of hydrogen gas.

It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.

Claims

22 CLAIMS

1. An internal combustion engine, ICE, system comprising:

- at least one combustion cylinder housing a combustion piston, said combustion cylinder being configured to be energized by forces of combustion so as to drive a crankshaft of the ICE system;

- a compressor cylinder housing a compressor piston, said compressor cylinder being configured to compress a volume of air and transfer the compressed air to the at least one combustion piston;

- an expander cylinder housing an expander piston, said expander cylinder being configured to receive exhaust gases from the at least one combustion piston;

- a connecting element connecting said compressor piston and said expander piston such that the compressor piston and the expander piston move in unison; wherein said crankshaft is further connected to said compressor piston by a connecting rod.

2. Internal combustion engine system according to claim 1 , wherein the connecting rod of the compressor piston is operable to reciprocate the compressor piston between its bottom dead centre, BDC, and top dead centre, TDC, whereby the expander piston reciprocates between its TDC and BDC via the connecting element, such that the expander piston is at its TDC when the compressor piston is at its BDC.

3. Internal combustion engine system according to any one of the preceding claims, further comprising at least one expander intake valve for introducing exhaust gases into the expander cylinder, wherein the expander intake valve is controllable to initiate an intake event of said exhaust gases into the expander cylinder when the connecting rod of the compressor piston is at its bottom half of movement, corresponding to the BDC of the compressor piston.

4. Internal combustion engine system according to claim 3, wherein the crankshaft comprises an integrated cam lobe arranged to operate the expander intake valve.

5. Internal combustion engine system according to 4, wherein the expander intake valve is a side valve arranged at a side of the expander piston, whereby the integrated cam lobe of the crankshaft is arranged to drive the expander intake side valve.

6. Internal combustion engine system according to any one of the preceding claims, wherein the expander piston is an oil-free piston arrangement.

7. Internal combustion engine system according to any one of the preceding claims, wherein said crankshaft is driven by said at least one combustion piston by means of the combustion piston connecting rod, and wherein said compressor piston is driven by said crankshaft by means of said compressor piston connecting rod.

8. Internal combustion engine system according to any one of the preceding claims, wherein at least a portion of said compressor piston, at least a portion of said expander piston and at least a portion of said connecting element together form a compressorexpander arrangement surrounding a portion of said crankshaft.

9. Internal combustion engine system according to any one of the preceding claims, wherein said expander piston has a circular cross section extending in a first geometrical plane, and said compressor piston has a circular cross section extending in a second geometrical plane, said first and second geometrical planes being positioned in a parallel configuration on opposite sides of a longitudinal axis of the crankshaft.

10. Internal combustion engine system according to any one of the preceding claims, wherein said expander cylinder and said compressor cylinder are co-axially arranged.

11 . Internal combustion engine system according to any one of the preceding claims, wherein said at least one combustion cylinder is a first combustion cylinder and said combustion piston is a first combustion piston, and said ICE system further comprises a second combustion cylinder housing a second combustion piston, said second combustion cylinder being configured to be energized by forces of combustion.

12. Internal combustion engine system according to claim 11 , wherein said first and second combustion cylinders operate in a four-stroke configuration, and each one of said compressor and expander cylinders operate in a two-stroke configuration.

13. Internal combustion engine system according to any one of the preceding claims, wherein the at least one combustion cylinder is configured for combustion of hydrogen gas.

14. A vehicle (1) comprising an internal combustion engine system according to any one of the preceding claims.