EP4493794B1

EP4493794B1 - A composite piston for an engine-generator with slotted link mechanism

Info

Publication number: EP4493794B1
Application number: EP22711509.4A
Authority: EP
Inventors: Hans RÄMMAL; Margus VILLAU
Original assignee: Lvs Motors Oue
Current assignee: Lvs Motors Oue
Priority date: 2022-03-01
Filing date: 2022-03-01
Publication date: 2025-12-24
Anticipated expiration: 2042-03-01
Also published as: EP4493794C0; EP4493794A1; WO2023165686A1

Description

Technical Field

Present invention relates to a composite piston for an engine-generator, where the internal combustion engine is embodied with a slotted link mechanism (also called Scotch yoke), and in which the composite piston comprises magnets for excitation of the generator windings, in which the generator is embodied as linear electric generator.
An engine-generator is the combination of an electrical generator and an engine (prime mover) mounted together to form a single piece of equipment. Sometimes also terms such as "engine integrated linear generator" and "hybrid power system" is used for this type of engine-generator.

Background Art

Estonian patent application EE200900001 (published 16.08.2010, Viktor Loktaevski ) discloses an internal combustion engine with a slotted link mechanism comprising a composite piston in which the slider groove is at an angle other than 90 degrees to the common longitudinal axis of the piston rods.
The closest prior art is disclosed in a German patent application DE3922986A1 (published 17.01.1991 ), which discloses an engine-generator, which comprises an internal combustion engine with a slotted link mechanism. Said engine is combined with a linear electric generator, where the windings of the generator are stationary accommodated in engine housing and the moving parts of the generator are integrated into the piston rods, between pistons and middle section comprising a slider groove.
As the pistons reciprocate in the cylinders, the magnets integrated into the piston rods move through the windings of the generator and generate a variable magnetic flux in said windings, which in turn generates an electric current.
This solution includes a composite piston engine, in which the piston rod connecting the pistons is connected to the crank mechanism by the means of a slider, which slides in a so-called slider groove in the middle section of the composite piston.
The disadvantage of this solution is that the permanent magnets integrated into the piston rods are on the sides of the piston rods and therefore the magnetic field generated by them when moving through the stationary windings to generate electromotive force is also limited.
Since the opening in the middle of the generator windings for passing through the piston rods comprising magnets, is considerably smaller in diameter than the cylinder bore and the pistons, therefore the pistons can be connected to the piston rods only after the stationary windings of the generator have been placed around the piston rods comprising magnets.
Due to the shape and arrangement of the magnets, the magnetic flux is not used as efficiently as possible to generate electromotive force in the surrounding windings and thus a generation of electricity is inefficient.
The object of the invention is to provide a composite piston on which permanent magnets can be easily mounted and which enables said composite piston including the middle section with the slider groove and the protruding piston rods therefrom to be fitted with the permanent magnets and pistons before of an installation of said composite piston into the engine. It is also an object to provide a configuration of the piston rods and the permanent magnets located on them, in which case the magnetic flux generated by the permanent magnets would maximize when passing through the generator windings surrounding them.
Another aim of the invention is to provide a compact technical solution for efficient thermal energy conversion to mechanical and electrical energy.
Since the generator is integrated in the engine, the output shaft of the engine can be used to drive, for example, an air compressor, a vacuum pump, a water pump, a fuel pump or pump for other fluid medium or another device.

Disclosure of Invention

The present invention provides a composite piston for an engine-generator with a slotted link mechanism. Said composite piston comprises a middle section with a slider groove and two piston rods placed on a common longitudinal axis symmetrically to the opposite sides of said middle section, including on each side a piston and at least one permanent magnet.
In the composite piston on the side of the middle section each piston rod has a step, where at least one permanent magnet is placed onto said step around said piston rod so, that the north and south poles of said magnet are oriented along said common longitudinal axis. Said at least one permanent magnet is fixed onto said piston rod by a retainer nut between the middle section and said retainer nut.
In the present invention, each permanent magnet is substantially a disk-shaped, i.e., each permanent magnet is cylindrical, has a central opening in the centre, and has north and south poles oriented at the ends of said cylinder.
Preferably, the outer diameter of the permanent magnets is larger than the outer diameter of the pistons (piston bores).
In another preferred, the outer diameters of the pistons (diameter of piston bores) and permanent magnets are equal.
In yet another preferred embodiment, the outer diameter of the permanent magnet is smaller than the diameter of the pistons (piston bores).
In yet another preferred embodiment, the outer diameter of the permanent magnet is less than or equal to the diameter of the piston.
Preferably, when the outer diameter of the permanent magnets is at least equal to the maximum diameter of the pistons provided with piston rings, it would allow the already assembled composite piston to be installed into the cylinder assembly, since in this case the pistons with the piston rings can easily fit through the central opening of the generator windings.
The electromotive force (voltage) generated depends mainly on the material of the permanent magnets (neodymium magnets are preferred, e.g. N52), the number of turns of wire in the winding, a relative speed between the winding and permanent magnets and an air gap between the permanent magnets and the winding and also on a location of stroke of said magnets relative to the winding (maximum voltage pulse is generated in the entry section).
In a preferred embodiment, the piston rods and the middle section of the composite piston are made as one piece.
Preferably, the piston rods and the middle section are made of a light metal alloy ( e.g. aluminium alloys). The part of the slider groove in the middle section, where significantly higher wear resistance, strength and stiffness is required, can be manufactured, for example, of high-strength steel and assembled in the composite piston.
The piston rods can be made for example of aluminium alloy, titanium alloy, high-strength steel, etc.
Technologically, the piston rods with the middle section containing the slider groove can be produced by milling and turning or alternatively by additive manufacturing (3D printing).
In a preferred embodiment, the piston rods are hollow for at least half their length.
Preferably, each piston is connected at the end of the piston rod with a piston pin, said piston pin being perpendicular to the longitudinal axis of the piston rod and allowing piston to turn around said piston pin.
In this solution, the piston rotation relative to the piston rod on the piston pin is minimal as the piston rods are reciprocating linearly, and therefore a possibility of the piston to rotate on the piston pin is designed to compensate for position deviations during reciprocation movement and to minimize stresses due to minor skew and also to allow better piston centering and alignment in the cylinder bore and better fit between piston and cylinder bore during movement of the piston.
In another preferred embodiment, each piston is immovably connected to the end of the piston rod.
In another preferred embodiment, the direction of the slider groove in the middle section is at an angle of 90 to 125 degrees to the common longitudinal axis of the piston rods.

Brief Description of Drawings

Present invention is described below with reference to the accompanying schematic drawings, in which:

Figure 1 depicts an axonometric view of the composite piston with the middle section and the piston rods with the pistons removed;
Figure 2 depicts a side view the composite piston according to Figure 1 with the middle section and the piston rods with the pistons removed;
Figure 3 depicts a top view the composite piston according to Figures 1 and 2 with the middle section and the piston rods with the pistons removed;
Figure 4 depicts composite piston with generator windings surrounding said permanent magnets on the piston rods;
Figure 5 depicts a longitudinal sectional view of the composite piston according to Figure 4;
Figure 6 depicts a longitudinal sectional view of the composite piston according invention inside engine-generator with the slider in the slider groove and cylinders surrounding the pistons.

Mode(s) for Carrying Out the Invention

For the sake of clarity of the drawings, the same details and elements are denoted by the same reference numerals in the various figures. In the case of an engine, for the sake of simplicity and clarity of the drawing, no valves, ignition system, lubrication system or other elements are shown which are not necessary for an understanding of the invention.
Figures 1, 2 and 3 depict the middle section 1 of the composite piston and the piston rods 2 with the pistons removed (pistons 3 are shown in Figures 4, 5 and 6). The middle section 1 comprises a slider groove 4, which in the embodiments shown in the figures is at an angle with respect to the common longitudinal axis of the piston rods, where said angle is greater than 90 degrees.
In the embodiment shown in the figures, both piston rods 2 have a piston pin bore 5 for the piston pin 12 of the piston 3, and on the side of the middle section 1 each piston rod 2 has a step 6 on the piston rod 2, which ends at the middle section 1 with a seating 7. In front of the step 6 there is a threaded part 8 for a retaining nut 9.
In the embodiments shown on Figures 5 and 6, three washer-shaped permanent magnets 10 are placed on step 6 on each side of the middle section 1, where the north and south poles of said permanent magnets 10 are aligned in a direction of the common longitudinal axis of the piston rods 2.
As can be seen from said drawings, the diameter of the permanent magnets 10 is slightly smaller than the diameter of the piston 3 or the cylinder 13 bore. The permanent magnets 10 are fastened on the step 6 against the seating 7 using the retaining nut 9.
In the embodiment of Figure 6, a diameter of a central opening in the winding 11 is equal to the diameter of the cylinder 13 bore or piston 3 - for the sake of clarity it should be mentioned, that term "central opening of winding" refers to a central opening of core, which carries a winding wire of the winding 11 wound around said core.
This allows the composite piston, together with the pistons 3 and the permanent magnets 10, to be assembled before being inserted into the engine and to be fitted to the engine and connect in the slider groove 4 the slider 14 to a crankpin.
It also simplifies the placement of the cylinders 13 with the windings 11 attached to their lower parts (Figure 6) over the pistons 3 and permanent magnets 10, since the pistons 3 fit through the central opening of the windings 11.
As can be seen from the embodiment of the composite piston in Figures 2 and 6, the piston rods 2 are made hollow over half their length to reduce weight.
In the embodiments shown in the figures, the angle of the slider groove 4 with respect to the common axis of the piston rods 2 is more than 90 degrees.
When the engine is running, the permanent magnets 10 are reciprocating through the windings 11 and generate electromotive force therein.

REFERENCE NUMBER LIST

1.: middle section
2.: piston rod
3.: piston
4.: slider groove
5.: piston pin bore
6.: step
7.: seating
8.: threaded part
9.: retaining nut
10.: permanent magnet
11.: winding
12.: piston pin
13.: cylinder
14.: slider

Claims

A composite piston for an engine-generator with a slotted link mechanism, where said composite piston comprises a middle section (1) with a slider groove (4) and two piston rods (2) placed on a common longitudinal axis symmetrically to the opposite sides of said middle section (1), including on each side a piston (3) and at least one permanent magnet (10), characterized in that, on the side of the middle section (1) each piston rod (2) has a step (6), where at least one permanent magnet (10) is placed onto said step around said piston rod so, that the north and south poles of said magnet are oriented along said common longitudinal axis and said at least one permanent magnet (10) is fixed onto said piston rod by a retainer nut (9) between the middle section (1) and said retainer nut (9).
The composite piston according to any previous claim, characterised in that, the middle section (1) and the piston rods (2) are made in one piece.
The composite piston according to any previous claim, characterised in that, the piston rods (2) are hollow for at least half their length.
The composite piston according to any previous claim, characterised in that, each piston (3) is connected at the end of the piston rod (2) with a piston pin (12), said piston pin (12) being perpendicular to the longitudinal axis of the piston rod (2).
The composite piston according to any previous claim 1 to 3, characterised in that, each piston (3) is immovably connected to the end of the piston rod (2).
The composite piston according to any previous claims, characterized in that, the direction of the slider groove (4) in the middle section (1) is at an angle of 90 to 125 degrees to the common longitudinal axis of the piston rods (2).
The composite piston according to any previous claims, characterized in that, the outer diameter of each permanent magnet (10) is larger than the diameter of the piston (3).
The composite piston according to any previous claims, characterized in that, the outer diameter of each permanent magnet (10) is smaller than the diameter of the piston (3).
The composite piston according to any previous claims, characterized in that, the outer diameter of each permanent magnet (10) and diameter of the piston (3) are equal.