WO2024047271A1

WO2024047271A1 - Multi-piston engine, marine vessel, power plant, method in connection with multi-piston engine and intermediate wheel

Info

Publication number: WO2024047271A1
Application number: PCT/FI2022/050570
Authority: WO
Inventors: Daniel HÄGGBLOM
Original assignee: Wärtsilä Finland Oy
Priority date: 2022-08-31
Filing date: 2022-08-31
Publication date: 2024-03-07

Abstract

A multi-piston engine (1) comprises a multi-cylinder internal combustion reciprocal piston engine. The multi-piston engine (1) comprises a plurality of combustion cylinders, a crankshaft (3), at least one camshaft (12), and a timing drive arranged at a timing drive end (13) of the multi-piston engine (1). The multi-piston engine (1) further comprises, at the timing drive end (13), an intermediate wheel (2) provided between and operationally connected to both the crankshaft (3) and the camshaft(s) (12). The intermediate wheel (2) comprises an eccentric mass configured to balance periodic forces and torques caused by the operation of the multi-piston engine (1).

Description

MULTI-PISTON ENGINE, MARINE VESSEL, POWER PLANT, METHOD IN CONNECTION WITH MULTI-PISTON ENGINE AND INTERMEDIATE WHEEL

FIELD OF THE DISCLOSURE

The present disclosure relates engines, and more particularly to a multi-piston engine, a marine vessel, a power plant, and a method in connection with multi-piston engine. The present disclosure also relates to an intermediate wheel.

BACKGROUND OF THE DISCLOSURE

The operation of piston engines causes periodic forces, more particularly gas forces caused by combustion and inertia forces caused by rotating and reciprocating movements of the engine. Unbalanced forces may cause vibrations, whereby different kinds of balancing arrangements have been provided for piston engines.

Different kinds of cylinder configurations and cylinder timings of piston engines, especially multi-piston engines, require different kinds of balancing solutions. Certain types of forces can be balanced by simple counterweights attached to a crankshaft of the piston engine, whereas certain other types of forces and torques require more complex balancing solutions. It is known to use different types of separate balancing shafts driven by the crankshaft this purpose, but this type of balancing arrangements typically increase the complexity of the system and need to be configured individually for each application, as the forces and torques involved and tolerated vary depending on the application. For instance, a different level of vibrations can be tolerated in case of a power plant engine than in a cruise ship, where the comfort of the passengers is very important. Also, a separate balancing shaft or shafts with length equal of the camshaft or engine block lead to very expensive design and use of the space already otherwise limited in these types of engine applications.

BRIEF DESCRIPTION OF THE DISCLOSURE

An object of the present disclosure is to provide a new multi-piston engine, marine vessel, power plant, intermediate wheel, and a new method in connection with a multi-piston engine.

The object of the disclosure is achieved by a method and an apparatus which are characterized by what is stated in the independent claims. Some embodiments of the disclosure are disclosed in the dependent claims.

The disclosure is based on the idea of balancing periodic forces and torques caused by the operation of the multi-piston engine at least partly by an intermediate wheel operationally connected to a crankshaft and at least one camshaft of the multi-piston engine and comprising an eccentric mass.

An advantage of the disclosure is that an easily configurable balancing arrangement can be provided for a multi-piston engine in a simple manner with a minimum number of components and with a minimal effect on the dimensions of the multi-piston engine. This makes the balancing solution disclosed particularly beneficial in connection with modular multi-piston engines, as it makes it easy to adjust the balancing to the specific multi-piston engine in question. Modular multi-piston engines enable configuring multi-piston engines to suit different requirements with a minimum number of parts different from each other. The balancing arrangement can be easily configured to adjust balancing of the periodic forces by a suitable selection of balancing eccentric mass characteristics, such as weight, position, and number of balancing weights in the intermediate wheel. The balancing arrangement is also positioned in such a manner that the balancing automatically has a correct rotating speed in relation to the operation of the multi-piston engine. The same intermediate wheel may also be used without balancing weights in applications, where further adjustment of balancing is not needed.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the disclosure will be described in greater detail by means of preferred embodiments with reference to the accompanying drawings, in which

Figure 1 illustrates schematically a multi-piston engine according to an embodiment seen from a timing drive end;

Figure 2 illustrates schematically an intermediate wheel according to an embodiment shown from a side;

Figure 3 illustrates schematically an intermediate wheel according to an embodiment shown in cross section;

Figure 4 illustrates schematically an intermediate wheel according to an embodiment;

Figure 5 illustrates schematically a balancing weight according to an embodiment;

Figure 6 illustrates schematically a balancing weight according to another embodiment;

Figure 7 illustrates schematically a multi-piston engine according to an embodiment seen from a side; and

Figure 8 illustrates a method in connection with a multi-piston engine. The figures are provided for illustrating some features of the disclosure only and are not shown to scale. Same reference numbers are used for similar features in different figures and embodiments. Not all similar features are necessarily provided with reference numbers for the sake of clarity.

DETAILED DESCRIPTION OF THE DISCLOSURE

The disclosure relates to a multi-piston engine 1 , a marine vessel, a power plant, an intermediate wheel, and a method in connection with a multi-piston engine 1. More particularly, the disclosure related to balancing periodic forces caused by an operation of the multi-piston engine 1 and arrangement, in other words balancing arrangements, for implementing this balancing or adjustment of this balancing.

Figure 1 illustrates schematically a multi-piston engine 1 seen from a timing drive end 13; Figure 2 illustrates schematically an intermediate wheel 2 according to an embodiment shown from a side; and Figure 3 illustrates schematically an intermediate wheel 2 according to an embodiment shown in cross section, more particularly seen in the direction A-A indicated in Figure 2.

A multi-piston engine 1 , such as the multi-piston engine 1 of Figure 1 , may comprise a multi-cylinder internal combustion reciprocal piston engine. The multi-piston engine 1 comprises a plurality of combustion cylinders (not shown), a crankshaft 3 and a timing drive arranged at a timing drive end 13 of the multi-piston engine to connect the crankshaft and the camshaft(s) to rotate in a mutually synchronized manner. A multi-piston engine 1 may, thus, comprise a plurality of pistons and combustion cylinders.

The multi-piston engine 1 preferably further comprises an intermediate wheel 2, which intermediate wheel 2 is operationally connected to the crankshaft 3. The intermediate wheel 2 being operationally connected to the crankshaft 3 refers the operation of the crankshaft also affecting the operation of the intermediate wheel 2 and/or vice versa. Such operational connection and/or rotating in a mutually synchronized manner may be provided, directly or indirectly, by toothing or in other suitable manner.

On the other hand, according to an aspect, an intermediate wheel 2, is configured to be provided at a timing drive end of a multi-piston engine 1 , wherein the intermediate wheel 2 comprises an eccentric mass configured to balance periodic forces and torques caused by the operation of the multi-piston engine 1 .

According to an embodiment, the eccentric mass may comprise at least one balancing weight 6 provided in the intermediate wheel 2. According to an embodiment, the intermediate wheel 2 may be provided with at least one opening 4, and the eccentric mass may comprise at least one balancing weight 6 mounted to the opening 4. According to an embodiment, the opening 4 may be provided for reducing the mass of the intermediate wheel 2. According to another embodiment, the eccentric mass may comprise a mass permanently attached to the intermediate wheel 2 or forming an integral part of the intermediate wheel 2. In other words, according to an embodiment, the eccentric mass and the intermediate wheel 2 may form a uniform structure.

According to an embodiment, the intermediate wheel 2 is operationally connected to the crankshaft 3 in such a manner that the rotational motion of the crankshaft 3 causes, directly or indirectly, rotational motion of the intermediate wheel 2. The intermediate wheel 2 is at provided at the timing drive end 13 of the multi-piston engine 1. The intermediate wheel 2 may comprise an eccentric element configured to balance periodic forces and torques caused by the operation of the multi-piston engine 1 .

According to an embodiment, the multi-piston engine 1 may further comprise at least one camshaft 12. According to an embodiment, the multi-piston engine 1 may comprise a plurality of camshafts 12. According to an embodiment, the multi-piston engine 1 may comprise exactly one camshaft 12 or exactly two camshafts 12. According to an embodiment, the multi-piston engine 1 may comprise an intake camshaft and an exhaust camshaft.

According to an embodiment, the intermediate wheel 2 is provided between and operationally connected to both the crankshaft 3 and the camshaft(s) 12.

According to an embodiment, the multi-piston engine 1 may comprise a modular design. The modular design multi-cylinder engine, such as a modular design multi-cylinder internal combustion reciprocal piston engine, may comprise individual power packs, preferably one power pack per each cylinder assembled into an engine block. The engine block may comprise a crankshaft 3, one or more camshafts 12, preferably modular camshafts, and a timing drive arranged into engine block connecting the crankshaft 3 and the one or more camshafts 12 to rotate in mutually synchronized manner.

According to an embodiment, the multi-piston engine 1 with a modular design may comprise a plurality of individual power packs. In this disclosure, a power pack refers to a module, which can be mounted to an engine block configured to receive a predetermined number of cylinders. According to an embodiment, each power pack may comprise in each case one of the combustion cylinders of the multi-piston engine 1. According to an embodiment, each power pack may comprise a cylinder sleeve, a piston provided within the cylinder sleeve, a rotary head coupled to the piston, and/or a cylinder head. According to an embodiment, the power pack may have only some of these parts and/or further parts, such as mounting members, like mounting screws, for the cylinder head.

According to an embodiment, the at least one camshaft 12 may comprise a modular camshaft comprising a plurality of camshaft portions. In other words, the camshaft 12 may be formed of separate camshaft portions attached to each other, for instance by bolts or other suitable manner, instead of being formed as one uniform part. This may be beneficial, as a suitable camshaft 12 for a particular multi-piston engine type may be provided by mounting a suitable number of camshaft portions to each other. According to an embodiment, the number of camshaft portions may be equal to or larger than the number of combustion cylinders. Thereby, the length of the camshaft 12 may be adjusted to the number of combustion cylinders in the multi-piston engine.

According to an embodiment, the individual power packs may be assembled into an engine block, and wherein the engine block comprises the crankshaft 3, the one or more modular camshafts 12, and the timing drive.

According to an embodiment, the intermediate wheel 2 may be provided with at least one opening 4. According to an embodiment, the opening 4 may be provided in the intermediate wheel 2 for reducing the mass of the intermediate wheel 2. It may be desirable to reduce weight of structural parts for instance for reasons related to structural strength requirements and minimizing energy consumption. One option for reducing weight of the intermediate wheel 2 is, thus, providing the intermediate wheel 2 with one or more openings 4. According to an embodiment, two or more openings 4 may be provided symmetrically in relation to the centre 5 of the intermediate wheel 2. The centre 5 of the intermediate wheel 2 may refer to the dimensional centre and/or the centre of mass of the intermediate wheel 2.

According to an embodiment, all the openings 4 are round and have a same diameter 15. According to an embodiment, at least one of the openings 4 has a different shape and/or diameter 15 than another one of the openings 4.

According to an embodiment, two or more openings 4 may be provided at a same distance 14 from the centre 5 of the intermediate wheel 2. According to an embodiment, all openings 4 may be provided at a same distance 14 from the centre 5 of the intermediate wheel 2. According to an embodiment, two or more openings 4 may be provided at different distances 14 from the centre 5 of the intermediate wheel 2, such as in the embodiment of Figure 4. According to an embodiment, two or more openings 4 of same or different shape and diameter 15 may be provided at different distances 14 from the centre 5 of the intermediate wheel 2. According to an embodiment, the dimensional centre and the centre of mass of the intermediate wheel 2 are provided at a same point or within a normal manufacturing tolerance from each other. According to an embodiment, two or more series of openings 4 may be provided symmetrically in relation to the centre 5 of the intermediate wheel 2, wherein each series of openings 4 is provided within a same distance from the centre 5 of the intermediate wheel 2 and are of a same diameter 15 with each other, but at a different distance 14 from the centre 5 of the intermediate wheel 2 and/or of a different diameter 15 than at least one other series of openings 4. These types of embodiments may further increase the possibilities of balancing different types of engines, as the weight and distance from the centre 5 of the intermediate wheel 2 of the balancing weight 6 can be selected to best suit balancing requirements of a multi-piston engine 1 in question.

According to an embodiment, at least one balancing weight 6, in the embodiment of Figure 2 exactly one balancing weight 6, is provided in the intermediate wheel 2. According to an embodiment, at least one balancing weight 6, in the embodiment of Figure 2 exactly one balancing weight 6, is mounted to the intermediate wheel 2. According to an embodiment, at least one balancing weight 6, in the embodiment of Figure 2 exactly one balancing weight 6, is mounted to an opening 4, namely an opening 4 provided in the intermediate wheel 2, for instance an opening 4 provided in the intermediate wheel for reducing the mass of the intermediate wheel 2. In such embodiments, the balancing weight(s) 6, thus, receives its rotating force from the timing drive. In other words, the eccentric movement of the balancing weight 6 is caused by the rotation of the intermediate wheel 2 driven by the timing drive and the position of the balancing weight 6 with respect to the central axis of the intermediate wheel 2. Some embodiments of balancing weights are shown in Figures 5 and 6, where a balancing weight 6 in each case is shown from a side, namely from the same direction as the intermediate wheel 2 in Figure 2, on the left, and in cross section, such as the intermediate wheel 2 in Figure 3, on the right.

According to an embodiment, the intermediate wheel 2 may be provided with two or more balancing weights 6, such as for instance in the embodiment of Figure 4. According to an embodiment, the number of the balancing weights 6 and the position and weight of each balancing weights 6 may be selected according to a balancing need of the multi-piston engine 1 in question based on at least the structure and the use environment of the multipiston engine 1.

According to an embodiment, the balancing weight(s) 6 may form the eccentric element of the intermediate wheel. According to an embodiment, one, two or more balancing weights 6 may each be mounted to different openings 4 provided in the intermediate wheel 2. According to an embodiment, two or more balancing weights 6 may be mounted to one opening 4. According to an embodiment, at least one balancing weight 6 may be mounted to two or more openings 4. In other words, according to an embodiment, one balancing weight 6 may cover, at least partly, at least two openings 4.

According to an embodiment, such as the embodiments of Figures 1 and 2, the intermediate wheel 2 may comprise a gear wheel. Such embodiments may be particularly beneficial, as they enable using a same component, namely a gear wheel, which is used to transfer forces at the timing drive end 13 of the multi-piston engine 1 , for adjusting balancing of the periodic forces in the multi-piston engine 1 . This enables using a minimum number of components in the balancing arrangement.

According to an embodiment, such as the embodiments of Figures 2 and 3, the balancing weight 6 may comprise at least one weight plate 7 mounted to the opening 4. A weight plate 7 may comprise a plate-like structure configured to be mounted to the intermediate wheel 2.

According to an embodiment, the balancing weight 6 may comprise two weight plates 7 configured to be provided on opposite sides of the intermediate wheel 6 and attached to each other. According to an embodiment, the weight plates 7 may be identical with each other. According to another embodiment, the weight plates 7 may be different from each other, for instance different in form or weight.

According to an embodiment, wherein the balancing weight 6 comprises at least two weight plates 7, the weight plates 7 may be attached to each other through the opening 4. According to an embodiment, at least one of the weight plates 7 may be formed to lock to the other weight plate 7, when the weight plates 7 are pressed against each other.

According to an embodiment, at least one balancing weight 6, for instance a balancing weight 6 comprising one, two or more weight plate(s) 7, may be formed to lock to the opening 4 in the intermediate wheel 2, when the balancing weight 6 is pressed against the intermediate wheel 2. According to an embodiment, the balancing weight 6 may be formed to lock to the opening 4 by form-locking.

According to an embodiment, the balancing weight 6 may comprise two or more weight plates 7, and at least one of the weight plates 7 may be formed to lock, instead of the other weight plate 7 or in addition to the other weight plate 7, to the opening 4 in the intermediate wheel 2, when the balancing weight is pressed against the intermediate wheel 2. According to an embodiment, the weight plate 7 may be formed to clamp to the other weight plate 7 and/or to the opening 4, when the weight plate 7 is pressed against the other weight plate 7 and/or the intermediate wheel 2, respectively.

Locking a balancing weight 6 or a weight plate 7 to another structure refers to the balancing weight 6 or the weight plate 7 attaching to the other structure in an immovable manner in at least one direction, such as in a radial direction 8 of the balancing weight 6 or the weight plate 7, such that the balancing weight 6 or the weight plate 7 cannot be detached from the other structure without using force or a tool.

According to an embodiment, the balancing weight 6 may be mounted removably to the intermediate wheel 2. According to an embodiment, the balancing weight 6 may be mounted to the intermediate wheel 2 by bolts or screws (not shown). An advantage of such embodiments is that the same intermediate wheel 2 can be used in connection with different multi-piston engine types and configured to adjust balancing of the periodic forces to suit the specific multi-piston engine in question by a suitable selection of balancing weight characteristics, such as weight, position, and number of balancing weights in the intermediate wheel. The same intermediate wheel 2 may also be used without balancing weights in applications, where further adjustment of balancing is not needed.

According to an embodiment, the weight of the balancing weight 6 may be at least 3 percent of the weight of the intermediate wheel 2. According to an embodiment, the weight of the balancing weight 6 may be at least 5 percent of the weight of the intermediate wheel 2. An advantage of this type of embodiments may be that the weight is sufficiently heavy in relation to the weight of the intermediate wheel 2 to effectively balance the forces caused by the multi-piston engine 1 operation. According to an embodiment, the weight of the intermediate wheel 2 may be at least 1 kg, preferably at least 2 kg.

According to an embodiment, balancing weights 6 of different weights may be provided, and a balancing weight 6 of a suitable weight may be selected to balance the forces in a multi-piston engine 1 in question. This may enable using the same intermediate wheel 2, in other words a similar intermediate wheel 2, with balancing weights 6 of different weights in connection with different multi-piston engines 1 and multi-piston engine configurations.

According to another embodiment, the weight of the balancing weight 6 may be at most 20 percent of the weight of the intermediate wheel 2.

According to an embodiment, the balancing weight 6 may be arranged to the intermediate wheel 2 symmetrically in relation to a central radial plane 9 of the intermediate wheel. The central radial plane 9 of the intermediate wheel 2 refers to a plane perpendicular to a longitudinal direction of the crankshaft 3 and extending through the centre 5 of the intermediate wheel. According to an embodiment, the balancing weight 6 may be arranged to the intermediate wheel 2 dimensionally symmetrically in relation to a central radial plane

9 of the intermediate wheel. In other words, at each point, where the balancing weight overlaps with the central radial plane 9, the balancing weight 6 extends to a same distance from the central radial plane 9 on each side of the central radial plane 9. It is clear for a person skilled in the art that the same distance comprises a normal manufacturing tolerance. According to an embodiment, the balancing weight 6 may be arranged to the intermediate wheel 2 symmetrically mass-wise in relation to a central radial plane 9 of the intermediate wheel centre of mass of the intermediate wheel 2. In other words, the centre of mass of the balancing weight 6 may be arranged to be provided on the central radial plane 9 of the intermediate wheel 2 or within a normal manufacturing tolerance from the central radial plane 9 of the intermediate wheel 2.

According to an embodiment, the largest dimension of the balancing weight 6 in a direction parallel to the longitudinal direction 10 of the crankshaft 3 does not exceed the largest dimension of the intermediate wheel 2 in the direction parallel to the longitudinal direction

10 of the crankshaft 3 on either side of the intermediate wheel 2. In other words, the largest dimension of the balancing weight 6 in a direction perpendicular to the central radial plane 9 of the intermediate wheel 2 does not exceed the largest dimension of the intermediate wheel 2 in the direction perpendicular to the central radial plane 9 of the intermediate wheel 2 on either side of the intermediate wheel 2.

According to an embodiment, the intermediate wheel 2 may be operationally connected to the crankshaft 3 by engaging with a second gear wheel 11 , for instance the primary gear wheel, mounted on the crankshaft 3 to rotate at the same speed with the crankshaft 3, but in such a manner that the intermediate wheel 2 is configured to rotate in the opposite direction in relation to the crankshaft 3, and wherein the diameter 16 of the intermediate wheel 2 is equal to the diameter 17 of the second gear wheel 11 . Thus, the second gear wheel 11 may be configured to rotate at the same speed and in the same direction as the crankshaft 3, and the intermediate wheel 2 may be configured to rotate at the same speed but in an opposite direction than the crankshaft 3 and the second gear wheel 11 . An advantage of such embodiments is that the rotation speed of the balancing is naturally and without additional parts synchronized with the operation of the multi-piston engine 1 and, thus, optimal for balancing the periodic forces caused by the operation.

According to an embodiment, a diameter 19 of a gear wheel provided on the camshaft 12 may be equal to the diameter 16 of the intermediate wheel 2. According to an embodiment, the diameter 19 of the gear wheel provided on the camshaft 12 may be smaller than the diameter 16 of the intermediate wheel 2.

According to an embodiment, the multi-piston engine 1 may comprise an odd number of cylinders. According to an embodiment, the multi-piston engine 1 may comprise 7 or 9 cylinders. Embodiments of this disclosure may be particularly beneficial in connection with such multi-piston engines 1 , as the balancing is typically needed in such multi-piston engines. According to another embodiment, the multi-piston engine 1 may comprise an even number of cylinders, such as 6 or 8 cylinders.

According to an embodiment, the multi-piston engine 1 may comprise a reciprocatingpiston internal combustion engine.

Figure 7 illustrates schematically a multi-piston engine according to an embodiment seen from a side.

According to an embodiment, such as the embodiment of Figure 7, the multi-piston engine 1 may further comprise a balancing element 18 provided at the opposite end of the camshaft 12 with respect to the intermediate wheel 2. In other words, the intermediate wheel 2 may be provided at the timing drive end 13 of the camshaft 12 and the balancing element 18 may be provided at the opposite end of the camshaft 12.

According to an embodiment, the weight and position of the balancing weight 6 may be adjusted to a weight and position of the balancing element 18 and provided in a coaxially eccentric manner with respect to the intermediate wheel 2.

According to an embodiment, the balancing element 18 may comprise an axially eccentric structure.

According to an embodiment, the balancing element 18 may comprise a wheel.

According to an embodiment, the balancing element 18 may comprise a wheel structurally similar to an intermediate wheel 2 according to an embodiment or a combination of embodiment disclosed in this description and/or the accompanying drawings but provided at the opposite end of the piston multi-piston engine 1 with respect to the intermediate wheel 2.

According to an embodiment, the intermediate wheel 2 may comprise a straight toothing. This may be beneficial in embodiments, where strength and durability are essential. According to another embodiment, the intermediate wheel 2 may comprise a skewed toothing. This may be beneficial in embodiments, where a low noise level of the engine is particularly important. According to an embodiment, the crankshaft 3 may be coupled to the camshaft(s) 12 at the timing drive end by a full gear arrangement. In other words, the crankshaft 3 may be coupled to the camshaft(s) 12 at the timing drive end 13 by gears only, that is without any belt or chain transmission or similar. According to an embodiment, the crankshaft 3 may be coupled to the camshaft(s) 12 at the timing drive end 13 by a maximum of intermediate shaft 20 only. In other words, the timing drive comprises a maximum of one intermediate shaft 20 with one, two or more gear wheels and/or toothings provided on the intermediate shaft 20 and coupled to gear wheels and/or toothing provided on the crankshaft 3 and the camshaft(s) 12, respectively. At least one of the gear wheels provided on the one intermediate shaft 20 may comprise the intermediate wheel 2.

According to an embodiment, such as the embodiments of Figures 1 and 7, the intermediate wheel 2 may be provided on the intermediate shaft 20 and coupled to a gear wheel provided on the crankshaft 3. According to an embodiment, such as the embodiment of Figures 1 and 7, the multi-piston engine 1 and/or the balancing arrangement may comprise one intermediate shaft 20 with two gear wheels provided on the intermediate shaft 20. One of the gear wheels may be the intermediate wheel 2. In these embodiments, the intermediate wheel 2 may be coupled to a gear wheel provided on the crankshaft 3 and the other gear wheel provided on the intermediate shaft 20 may be coupled to a gear wheel provided on the camshaft 12. According to an embodiment, the diameter of the other gear wheel provided on the intermediate wheel 20 may be smaller than the diameter 16 of the intermediate wheel 2.

According to an embodiment, the multi-piston engine 1 may be configured to be mounted to a marine vessel or a power plant. Such a use environment of the multi-piston engine 1 may further affect the type and amount of balancing needed, which may affect the number, weight, and position, namely the distance from the centre 5 of the intermediate wheel 2, of the balancing weight(s) 6 configured to be mounted to the intermediate wheel 2.

According to an embodiment, a marine vessel may comprise a multi-piston engine 1 according to an embodiment or a combination of embodiments disclosed in this description and/or accompanying claims and drawings.

According to an embodiment, a power plant may comprise a multi-piston engine 1 according to an embodiment or a combination of embodiments disclosed in this description and/or accompanying claims and drawings.

Figure 8 illustrates a method in connection with a multi-piston engine. A method in connection with a multi-piston engine 1 , such as a method of Figure 8, may be partly or fully implemented by a multi-piston engine 1 according to an embodiment or a combination of embodiments disclosed in this description and/or accompanying claims and drawings. Such a method comprises balancing 81 periodic forces and torques caused by the operation of the multi-piston engine at least partly by the eccentric mass, such as the balancing weight, of the intermediate wheel 2. Balancing periodic forces and torques caused by the operation of the reciprocating-piston internal combustion engine, at least partly, by the eccentric mass refers to the multi-piston engine 1 possibly comprising, in some embodiments, other balancing arrangements besides those disclosed in this disclosure, including the intermediate wheel 2 provided with the eccentric mass and/or the balancing element, and/or some periodic forces and/or torques possibly remaining unbalanced.

According to an embodiment, the intermediate wheel 2 may be operationally connected to the crankshaft 3, and the method may further comprise providing the intermediate wheel 2 with at least one opening 4 for reducing the mass of the intermediate wheel 2 and mounting at least one balancing weight 6 to the opening 4.

According to an embodiment, the intermediate wheel 2 may be provided between and operationally connected to both the crankshaft 3 and the camshaft 12.

According to an embodiment, the method may further comprise adjusting the balance needed for a particular multi-piston engine 1 type by selecting suitable at least one balancing weight 6 to be mounted to the opening 4.

According to an embodiment, the method may further comprise unmounting at least one balancing weight 6, or all the balancing weights 6, from the intermediate wheel 2 in response to absence or reduced need for balancing.

Claims

1. A multi-piston engine, the multi-piston engine comprising a multi-cylinder internal combustion reciprocal piston engine comprising a plurality of combustion cylinders, a crankshaft, at least one camshaft, and a timing drive arranged at a timing drive end of the multi-piston engine to connect the crankshaft and the camshaft(s) to rotate in mutually synchronized manner, wherein the multi-piston engine comprises, at the timing drive end, an intermediate wheel, the intermediate wheel is provided between and operationally connected to both the crankshaft and the camshaft(s), and wherein the intermediate wheel comprises an eccentric mass configured to balance periodic forces and torques caused by the operation of the multi-piston engine.

2. A multi-piston engine according to claim 1 , wherein the intermediate wheel is provided with at least one opening, and wherein the eccentric mass comprises at least one balancing weight mounted to the opening.

3. A multi-piston engine according to claim 1 or 2, wherein the multi-piston engine comprises a modular design comprising a plurality of individual power packs, wherein each power pack comprises in each case one of the combustion cylinders.

4. A multi-piston engine according to any one of claims 1 - 3, wherein the at least one camshaft comprises a modular camshaft comprising a plurality of camshaft portions, wherein the number of camshaft portions is equal to or larger than the number of combustion cylinders.

5. A multi-piston engine according to claim 3 or 4, wherein the individual power packs are assembled into an engine block, and wherein the engine block comprises the crankshaft, the one or more modular camshafts, and the timing drive.

6. A multi-piston engine according to any one of claims 1 - 5, wherein the intermediate wheel comprises a gear wheel.

7. A multi-piston engine according to any one of claims 2 - 6, wherein the balancing weight comprises at least one weight plate mounted to the opening. 8. A multi-piston engine according to claim 7, wherein the weight of the balancing weight is at least 3 percent of the weight of the intermediate wheel.

9. A multi-piston engine according to claim 7 or 8, wherein the weight of the balancing weight is at most 20 percent of the weight of the intermediate wheel.

10. A multi-piston engine according to any one of claims 2 - 9, wherein the intermediate wheel is operationally connected to the crankshaft by engaging with a second gear wheel mounted on the crankshaft to rotate at the same speed with the crankshaft, but in such a manner that the intermediate wheel 2 is configured to rotate in the opposite direction in relation to the crankshaft, and wherein the diameter of the intermediate wheel is equal to the diameter of the second gear wheel.

11 . A multi-piston engine according to any one of claims 1 - 10, wherein the multi-piston engine further comprises a balancing element provided at the opposite end of the camshaft with respect to the intermediate wheel.

12. A multi-piston engine according to claim 11 , wherein the weight and position of the balancing weight is adjusted to a weight and position of the balancing element and provided in a coaxially eccentric manner with respect to the intermediate wheel.

13. A multi-piston engine according to claim 11 or 12, wherein the balancing element comprises an axially eccentric structure.

14. A multi-piston engine according to any one of claims 11 - 13, wherein the balancing element comprises a wheel.

15. A multi-piston engine according to claim 14, wherein the balancing element comprises a wheel structurally similar to an intermediate wheel according to any one of claims 1 - 10 but provided at the opposite end of the multi-piston engine with respect to the intermediate wheel.

16. A multi-piston engine according to any one of claims 1 - 15, wherein the intermediate wheel comprises a straight toothing.

17. A multi-piston engine according to any one of claims 1 - 15, wherein the intermediate wheel comprises a skewed toothing.

18. A multi-piston engine according to any one of claims 1 - 17, wherein the crankshaft is coupled to the camshaft at the timing drive end by a full gear arrangement. 19. A multi-piston engine according to an any one of claims 1 - 18, wherein the crankshaft is coupled to the camshaft at the timing drive end by a maximum of one intermediate shaft only.

20. A multi-piston engine according to any one of claims 1 - 19, wherein the multi-piston engine comprises an odd number of cylinders.

21. A multi-piston engine according to any one of the claims 1 - 20, wherein the multipiston engine is configured to be mounted to a marine vessel or a power plant.

22. A multi-piston engine according to claim 7, wherein the balancing weight comprises two weight plates configured to be provided on opposite sides of the intermediate wheel and attached to each other.

23. A multi-piston engine according to claim 22, wherein the weight plates are identical with each other.

24. A multi-piston engine according to claim 22 or 23, wherein the weight plates are attached to each other through the opening.

25. A multi-piston engine according to any one of claims 22 - 24, wherein at least one of the weight plates is formed to lock to the other weight plate, when the weight plates are pressed against each other.

26. A multi-piston engine according to any one of claims 2 - 25, wherein at least one balancing weight is formed to lock to the opening in the intermediate wheel, when the balancing weight is pressed against the intermediate wheel.

27. A multi-piston engine according to any one of claims 2 - 26, wherein the balancing weight is mounted removably to the intermediate wheel.

28. A multi-piston engine according to claim 27, wherein the balancing weight is mounted to the intermediate wheel by bolts or screws.

29. A multi-piston engine according to any one of claims 2 - 28, wherein the balancing weight is arranged to the intermediate wheel symmetrically in relation to a central radial plane of the intermediate wheel.

30. A multi-piston engine according to any one of claims 2 - 29, wherein the largest dimension of the balancing weight in a direction parallel to the longitudinal direction of the crankshaft does not exceed the largest dimension of the intermediate wheel in the direction parallel to the longitudinal direction of the crankshaft on either side of the intermediate wheel.

31 . A marine vessel comprising a multi-piston engine according to any one of claims 1 - 30.

32. A power plant comprising a multi-piston engine according to any one of the claims 1 - 30.

33. A method in connection with a multi-piston engine, wherein the multi-piston engine comprises a multi-cylinder internal combustion reciprocal piston engine according to any one of claims 1 - 30, wherein the method comprises balancing periodic forces and torques caused by the operation of the multi-piston engine at least partly by the eccentric mass of the intermediate wheel.

34. A method according to claim 33, wherein the method further comprises providing the intermediate wheel with at least one opening for reducing the mass of the intermediate wheel, and mounting at least one balancing weight to the opening.

35. A method according to claim33 or 34, wherein the method further comprises adjusting the balance needed for a particular multi-piston engine type by selecting suitable at least one balancing weight to be mounted to the opening.

36. A method according to any one of claims 33 - 35, wherein the method further comprises unmounting at least one balancing weight from the intermediate wheel in response to absence or reduced need for balancing.

37. An intermediate wheel, wherein the intermediate wheel is configured to be provided at a timing drive end of a multipiston engine, and wherein the intermediate wheel comprises an eccentric mass configured to balance periodic forces and torques caused by the operation of the multi-piston engine. An intermediate wheel according to claim 37, wherein the eccentric mass comprises at least one balancing weight provided in the intermediate wheel. An intermediate wheel according to claim 37 or 38, wherein the intermediate wheel is provided with at least one opening, and wherein the eccentric mass comprises at least one balancing weight mounted to the opening. An intermediate wheel according to claim 39, wherein the at least one opening is provided for reducing the mass of the intermediate wheel. An intermediate wheel according to any one of claims 37 - 40, wherein the intermediate wheel comprises a gear wheel. An intermediate wheel according to any one of claims 37 - 41 , wherein the balancing weight comprises at least one weight plate mounted to the opening. An intermediate wheel according to claim 42, wherein the balancing weight comprises two weight plates configured to be provided on opposite sides of the intermediate wheel and attached to each other. An intermediate wheel according to claim 43, wherein the weight plates are identical with each other. An intermediate wheel according to claim 43 or 44, wherein the weight plates are attached to each other through the opening. An intermediate wheel according to any one of claims 43 - 45, wherein at least one of the weight plates is formed to lock to the other weight plate, when the weight plates are pressed against each other. An intermediate wheel according to any one of claims 37 - 46, wherein at least one balancing weight is formed to lock to the opening in the intermediate wheel, when the balancing weight is pressed against the intermediate wheel. An intermediate wheel according to any one of claims 37 - 47, wherein the balancing weight is mounted removably to the intermediate wheel. 49. An intermediate wheel according to claim 48, wherein the balancing weight is mounted to the intermediate wheel by bolts or screws.

50. An intermediate wheel according to any one of claims 37 - 49, wherein the weight of the balancing weight is at least 3 percent of the weight of the intermediate wheel.

51 . An intermediate wheel according to any one of claims 37 - 50, wherein the weight of the balancing weight is at most 20 percent of the weight of the intermediate wheel.

52. An intermediate wheel according to any one of claims 37 - 51 , wherein the balancing weight is arranged to the intermediate wheel symmetrically in relation to a central radial plane of the intermediate wheel.

53. An intermediate wheel according to any one of claims 37 - 52, wherein the largest dimension of the balancing weight in a direction parallel to the longitudinal direction of the crankshaft does not exceed the largest dimension of the intermediate wheel in the direction parallel to the longitudinal direction of the crankshaft on either side of the intermediate wheel.

54. An intermediate wheel according to any one of claims 37 - 53, wherein the multi-piston engine further comprises a camshaft, and wherein the weight and position of the balancing weight is adjusted to a weight and position of a balancing element provided in a coaxially eccentric manner at the opposite end of the camshaft with respect to the intermediate wheel.