Internal combustion engine

Abstract

It comprises one or more cylinders with pistons therein and mutually opposed power cams connected to respective first and second rotary shafts. The reciprocating pistons act on the power cams to impart a rotating motion to the rotary shafts. An attachment device is provided for connecting the rotary shafts to each other. The attachment device includes a shifting device for changing the relative angular position of the first and second rotary shafts. The result is engine distribution and compression ratio are changed dynamically.

Claims

1. A internal combustion engine, comprising: at least one cylinder provided with corresponding pistons arranged to reciprocate along a longitudinal axis of the at least one cylinder, and at least first and second power cams mutually opposed and connected to respective first and second rotary shafts, whereby reciprocation of the pistons results in that the pistons act on the first and second power cams to thereby impart a rotating motion to the first and second rotary shafts to drive the engine, wherein the engine further comprises an attachment device for connecting the first and second rotary shafts to each other so that the first and second rotary shafts rotate together, the attachment device comprising a shifting device for changing a relative angular position of the first and second rotary shafts, and wherein the pistons comprise at least one counter follower wheel adapted to roll on a counter cam and the cylinder has an indentation formed at opposite ends thereof so that the counter follower wheel does not collide with the cylinder; and wherein each of the indentations form a longitudinally extending open space in the cylinder wall, within which the counter follower wheel reciprocates as the pistons reciprocates along the longitudinal axis of the cylinder.

2. The engine of claim 1, wherein the shifting device comprises a slider including teeth suitable to engage with respective teeth in the first and second rotary shafts such that, as the slider is moved along the longitudinal axis of the first and second rotary shafts, the first and second rotary shafts are rotated relative to each other.

3. The engine of claim 2, wherein the teeth of both the slider and the first and second rotary shafts are helical, with the teeth of the first rotary shaft being symmetrical with respect to the teeth of the second rotary shaft.

4. The engine of claim 2, wherein a plane of symmetry of the teeth in the first and second rotary shafts is perpendicular to the first and second rotary shafts.

5. The engine of claim 2, wherein the shifting device includes a driving arrangement to actuate the slider.

6. The engine of claim 1, wherein the counter cam prevents the pistons from losing contact with the power cam.

7. The engine of claim 1, wherein each power cam is provided with at least one cam track.

8. The engine of claim 7, wherein each cam track is defined by two respective protruding areas designed such that in a power stroke exhaust ports are opened before the intake ports, and in a compression stroke exhaust ports are closed before the intake ports.

9. The engine of claim 7, wherein a profile of the cam tracks in the power cams is similar or equal to one other.

10. The engine of claim 7, wherein the respective cam tracks comprises at least an ascending or compressing portion and a descending or power portion.

11. The engine of claim 10, wherein the respective cam tracks further comprises at least an additional flat portion between the compressing and the descending portions.

12. The engine of claim 1, wherein the engine is a three stroke engine.

13. The engine of claim 1, wherein the pistons comprise a piston head, a piston body and a connector for connecting the piston head with the piston body.

14. The engine of claim 13, wherein a combustion chamber is defined within the cylinder and a space formed by the combustion chamber is between two adjacent piston heads in the cylinder.

15. The engine of claim 14, wherein the piston head carries compression piston segments arranged at one end of the piston head near the combustion chamber and lubrication piston segments arranged in a lowermost part of the piston head.

16. The engine claim 13, wherein the piston body has an indentation formed in opposite ends preventing the piston body from colliding against a cam track during a compression and power stroke of the engine.

17. The engine of claim 1, wherein the engine further comprises a locking mechanism for preventing the pistons from being rotated relative to the cylinder.

18. The engine of claim 1, wherein the engine comprises a finned area provided around the cylinder through which cooling fluid can flow.

19. The engine of claim 1, wherein the cylinder has, at one side, intake ports controlled by the pistons, which in turn are controlled by corresponding cam tracks provided in a power cam, and exhaust ports controlled by the pistons which in turn are controlled by corresponding cam tracks provided in an opposite power cam.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Particular embodiments of the present opposed piston engine will be described in the following by way of non-limiting examples, with reference to the appended drawings.

(2) In the drawings:

(3) FIG. 1 is a general perspective view of one embodiment of a twin cylinder opposed piston direct injection petrol engine in which the engine block has been illustrated in its assembled condition, that is, assembled on the engine;

(4) FIG. 2 is a general perspective view of the engine shown in FIG. 1 in which the engine block has been shown with the intake and exhaust collectors, the side crankcases and the cooling housings removed;

(5) FIG. 3 is a general perspective view of the engine shown in FIG. 1 with the engine block in its disassembled condition, that is, removed from the engine;

(6) FIG. 4 is a perspective general view of the engine shown in FIG. 3 with the attachment device removed from the rotary shafts;

(7) FIG. 5 is a perspective view of the attachment device;

(8) FIG. 6 is a perspective view of the slider of the attachment device;

(9) FIG. 7 is a side elevational view of one piston;

(10) FIG. 8 is a cross-sectional view taken along line A-A in FIG. 7;

(11) FIGS. 9 and 10 are perspective views of the piston shown in FIGS. 7 and 8 taken from different sides;

(12) FIG. 11 is a perspective view showing one of the power cams and the respective counter cams;

(13) FIG. 12 is a perspective view showing the other power cam and respective counter cam;

(14) FIG. 13 is a side elevational view of the opposed piston engine shown in FIG. 1;

(15) FIG. 14 is a cross-sectional view taken along line B-B in FIG. 13;

(16) FIG. 15 is a perspective view of the engine block; and

(17) FIG. 16 is a perspective view of one side crankcase of the engine.

(18) FIG. 17 shows a relationship among a piston and follower-wheel, cylinder and indentation in the cylinder.

DETAILED DESCRIPTION OF EMBODIMENTS

(19) A twin cylinder, three-stroke, opposed piston, direct injection petrol engine is shown in the figures by way of an example. It been indicated as a whole by reference numeral 100.

(20) As shown in FIG. 1 of the drawings, the opposed piston engine 100 comprises a cylindrical engine block 110. The embodiment shown in FIG. 1 is one possible example of an engine block 110. However, it could be different in shape, such as prismatic or irregular, according to the specific requirements. As shown in FIG. 1, holes 118, 119 are formed in the engine block 110 for cooling purposes.

(21) Intake collectors 116 and exhaust collectors 115 are provided on the engine block 110. The intake and exhaust collectors 116, 115 lead to corresponding exhaust and intake ports (not shown).

(22) From the perspective view of the engine 100 shown in FIG. 3, in which the engine block 110 has been removed from the engine 100, it can be seen two cylinders 120, 130. Cylinders 120, 130 have been depicted through dashed lines in order to shown the corresponding pistons 140, 150 and 160, 170 provided therein as it will be explained further below.

(23) Cylinders 120, 130 are arranged inside the engine block 110 separated 180 from each other in the axial direction of their corresponding longitudinal axes X, parallel to each other. The cylinders 120, 130 are formed integral with the engine block 110 although they could be separated parts coupled to the engine block 110. The cylinders 120, 130 may be arranged to work in any desired position, such as horizontal, vertical or inclined.

(24) The engine block 110 is further provided with side crankcases 117 located at its opposites ends as shown in FIG. 1, surrounding cylinders 120, 130. The side crankcases 117 house power cams 300, 400, that will be explained further below, within the engine block 110. The side crankcases 117 absorb piston expansion forces and define lubrication areas.

(25) As stated above, two pistons 140, 150 and 160, 170 are provided within each cylinder 120, 130. Pistons 140, 150 and 160, 170 in their respective cylinder 120, 130 are aligned to each other such that in use, pistons 140, 150 and 160, 170 reciprocate along the longitudinal axis of the cylinder, that is, along their longitudinal axes X.

(26) Pistons 140, 150 and 160, 170 are associated with the above mentioned intake and exhaust ports. Thus, exhaust ports are driven by exhaust pistons and intake ports are driven by intake pistons. Opening and closing of intake and exhaust ports is controlled as set out below.

(27) Within each cylinder 120, 130 a combustion chamber 250 is defined. Specifically, each combustion chamber 250 is formed by the space between two adjacent pistons 140, 150 and 160, 170 in each cylinder 120, 130, as shown in FIG. 4. Corresponding spark plugs are provided inside the combustion chamber 250 in each cylinder 120, 130. The spark plugs 230, 231 can be fitted through corresponding access holes 225, 226 formed in an upper housing and received inside the engine block 110, as shown in FIGS. 1-3 of the drawings. The above mentioned intake and exhaust ports are formed in correspondence with said chambers 250.

(28) FIGS. 7-10 show one embodiment of the pistons 140, 150 and 160, 170. Pistons 140, 150 and 160, 170 each comprises a piston head 180, a piston body 190 and a connector 200. The connector 200 can be shown in the sectional view of FIG. 8. The connector 200 is formed like a connecting rod for connecting the piston head 180 with the piston body 190 to each other with no or little oscillating movement. In the embodiment shown in FIG. 8, the connector 200 comprises three parallel rods 210 mutually joined by a bottom common shaft 220 and an upper common shaft 221 which connect the piston head 180 and the piston body 190.

(29) The piston head 180 carries compression and lubrication piston segments 185, 186 as shown in FIGS. 7-10. The compression piston segments 185 are arranged at one end of the pistons 140, 150 and 160, 170, near the combustion chamber 250. The lubrication piston segments 186 are arranged in the lowermost part of the piston head 180, close to the compression piston segments 185 taking into account that in the compression stroke ports can not be opened for preventing oil from entering ports and therefore the cylinder 120, 130.

(30) Each piston body 190 has an indentation 280 as shown in FIG. 10. The indentation 280 is formed at one end of each piston 140, 150 and 160, 170 and it is suitable for preventing the piston body from hitting the corresponding cam track. On the other hand, the cylinders 120, 130 have an indentation 125, 135 formed in opposite ends for allowing the counter cam follower wheel 228 to not collide with the cylinders 120, 130. This can be seen in FIG. 15 of the drawings.

(31) FIG. 17 shows the relationship among the piston 180, follower wheel 228, and the cylinder 130, within which the piston 180 and follower wheel 228 reciprocate, and the indentation 125 in the cylinder 130. As shown in FIGS. 15 and 17, the indentiation 125 forms a longitudinally extending open space in the wall of the cylinder 130 and extends along the x axis. This open space allows the piston 180 and follower wheel 228 to reciprocate along the x-axis within the cylinder 130 without the follower wheel 228 colliding with the cylinder 130.

(32) Pistons 140, 150 and 160, 170 are provided with locking means for preventing the pistons 140, 150 and 160, 170 from being rotated. The locking means, as shown in FIGS. 3 and 4, comprise a groove 260 formed along the piston body 190 intended for receiving a projection 270 formed in the cylinder 120, 130. The projection 270 may be attached to the cylinder 120, 130 or it may be integral therewith.

(33) The engine 100 shown in the figures further comprises two mutually opposed power cams 300, 400 as shown in FIGS. 2 and 3 of the drawings and in greater detail, disassembled from the engine 100, in FIGS. 11 and 12. The power cams 300, 400 are rotatably fitted inside the engine block 110 at the opposite ends thereof, facing each other.

(34) As shown in FIGS. 11 and 12, each power cam has cam tracks 315, 316, 415, 416. The cam tracks 315, 316, 415, 416 are shaped such that each half turn of the first and second rotary shafts 500, 600 causes a complete combustion and completes the thermodynamic cycle.

(35) Specifically, FIGS. 11 and 12 illustrates intake cam tracks 315, 316 and exhaust cam tracks 415, 416 of the power cams 300, 400. Intake cam tracks 315, 316 are equal to one another. Exhaust cam tracks 415, 416 are equal to one another.

(36) Said cam tracks 315, 316, 415, 416 are defined by respective protruding areas or protrusions formed therein as shown in said FIGS. 11 and 12. The intake cams track control the movement of intake pistons, that is, pistons associated with the engine intake stroke while exhaust cam tracks control the movement of exhaust pistons, that is, pistons associated with the engine exhaust stroke depending upon the stroke in use.

(37) Opening and closing of the ports is thus controlled by the profile of each of the cam tracks 315, 316, 415, 416 in a way that the exhaust piston is advanced with respect to the intake piston. Therefore, before at the end of the power stroke, opening of the exhaust port is carried out before opening of the intake port and at the beginning of the compression exhaust port closes before closing the intake port.

(38) Respective output shafts 310, 410 are connected to the respective power cams 300, 400, as shown in FIGS. 11 and 12. The output shafts 310, 410 can be attached to the power cams 300, 400 or they can be integrally formed therewith.

(39) First and second rotary shafts 500, 600 are also provided inside the engine block 110, in a substantially central portion, as shown in FIG. 4. The first and second rotary shafts 500, 600 are aligned to each other, with their free ends next to each other but not in contact with each other. The first and second rotary shafts 500, 600 are connected to or are formed integral with the respective power cams 300, 400, as shown in FIGS. 11 and 12.

(40) Turning to FIGS. 7-10, the pistons 140, 150 and 160, 170 have a respective drive end. The drive end in each of the pistons 140, 150 and 160, 170 comprises three cam follower wheels 227. The follower wheels 227 are adapted to roll on the respective power cams 300, 400. The drive end in each of the pistons 140, 150 and 160, 170 further comprises the above mentioned counter cam follower wheel 228. Said counter cam follower wheel 228 is adapted to roll on respective counter cams 305, 405 which will be described in greater detail according to FIGS. 3, 4, 11, 12 and 15 of the drawings. The four wheels 227, 228 in the drive end of each piston 140, 150 and 160, 170 are mounted on the above mentioned common shaft 220 as shown in FIGS. 7, 8 and 10. The common shaft 220 is arranged perpendicular to said first and second shafts 500, 600 and to the longitudinal axis X of the pistons 140, 150 and 160, 170.

(41) In operation, the follower wheels 227 roll on the respective first and second power cams 300, 400. Reciprocation of pistons 140, 150 and 160, 170 against the power cams 300, 400 results in that a rotating motion is imparted to the first and second rotary shafts 500, 600 to drive the engine 100, causing the output shafts 310, 410 to be rotated.

(42) Reference is now made to FIGS. 3-6 of the drawings. As shown in FIG. 3, the first and second rotary shafts 500, 600 of the engine 100 are linked to each other through an attachment device 700. The attachment device 700, that has been removed from the engine 100 in FIG. 4 for the sake of clarity in order to show the first and second rotary shafts 500, 600, is arranged inside the engine block 110. The attachment device 700 connects the first and second rotary shafts 500, 600 to each other so that they can be rotated together in operation.

(43) Said attachment device 700 is shown in detail in FIG. 5. The attachment device 700 comprises shifting means 705. In the embodiment shown in FIG. 5, the shifting means 705 include a slider 710. The slider 710 comprises two main bodies 711, 712 attached to each other. The slider 710 is commanded by a control unit (not shown) causing it to be displaced along the longitudinal axis of the first and second rotary shafts 500, 600 through a motor means comprising a servomotor M. Other motor means controlled by the control unit (not shown) for displacing the slider 710 are not rule out, such as motor means comprising a hydraulic motor.

(44) The slider 710 includes an inner bushing 720 rotatably mounted therein through bearings 721. In an inner surface of bushing 720, shown in detail in FIG. 6, a number of helical teeth 730 are provided. The inner bushing helical teeth 730 are arranged to engage the respective helical teeth 505, 605 formed at the respective mutually adjacent or proximate ends of the first and second rotary shafts 500, 600 as shown in FIGS. 4, 11 and 12.

(45) The driving assembly 715 comprises a driving arm 716 acting on a connecting rod 717. The connecting rod 717 of the driving assembly 715 connects the driving arm 716 with the main bodies 711, 712 of the slider 710 through a fork element 718 attached to them.

(46) As the slider 710 is actuated, that is, as it is displaced along the first and second rotary shafts 500, 600 by the servomotor M that is commanded by the control unit, through driving assembly 715, engagement of helical teeth 730 of the slider 720 with helical teeth 505, 605 of the first and second rotary shafts 500, 600 causes the relative angular position of the first and second rotary shafts 500, 600 to be changed so that they are mutually rotated slightly. This occurs due to the symmetric arrangement of the helical teeth 730, 505, 605 of the slider 720 and the first and second rotary shafts 500, 600.

(47) The intake and exhaust power cams 300, 400 in this specific example are equal to each other. Therefore a suitable angular shift exists between the power cams 300, 400. In this specific example, the angular shift is of the order of 4.5. This means that the exhaust power cam is advanced relative to the intake power cam. This is an initial angular shift between the power cams which is not caused by the attachment device 700 but is due to the design of the helical teeth 730, 505, 605 of the slider 720 and the first and second rotary shafts 500, 600. Then, from the starting position (idling), as the engine 100 is running the slider 710 can travel a maximum displacement of the order of 16 mm and as a consequence the power cams 300, 400 are rotated to each other, that is, the exhaust power cam is advanced relative to the intake power cam, up to 12.8 in this specific example. This however may vary depending upon gear pitch, teeth shape (whether they are constant or variable radius teeth, etc).

(48) In operation, pistons 140, 150 and 160, 170 act, through their respective drive end, on the power cams 300, 400 causing them, together with the first and second rotary shafts 500, 600, to be rotated in the same direction while the slider 710 is actuated, that is, displaced along them, causing the engine distribution and compression ratio are changed.

(49) As stated above and as shown in FIGS. 3, 4, 11, 12, respective counter cams 305, 405 are provided in correspondence with each power cam 300, 400. The counter cams 305, 405 are received in respective recesses 240 formed at both ends of the engine block 110 as shown in FIG. 15. The counter cams 305, 405 are attached to or are part of the respective first and second shafts rotary 500, 600. The counter cams 305, 405 are attached to or are part of the respective power cams 300, 400. As shown in FIGS. 11, 12, the diameter of the counter cams 305, 405 is smaller than that of the power cams 300, 400. The counter cams 305, 405 have the same shape and they are facing each other. The counter cams 305, 405 are adapted to prevent pistons 140, 150 and 160, 170 from losing contact with the cam tracks 315, 316, 415, 416 of the power cams 300, 400 and thus to prevent possible collisions with each other which might occur when inertial forces of the pistons 140, 150 and 160, 170 are in opposite direction to those of the power cams 300, 400 and the gas pressure inside the cylinder or cylinders 120, 130 is lower than said inertial forces.

(50) Although only a number of particular embodiments and examples of the present engine have been disclosed and shown herein, it will be understood by those skilled in the art that other alternative embodiments and/or uses and obvious modifications and equivalents thereof are possible.

(51) For example, although shifting means 705 have been disclosed herein as comprising a slider 710 such that as it is moved along the longitudinal axis of the first and second rotary shafts 500, 600, said first and second rotary shafts 500, 600 are rotated to each other, other alternative mechanical embodiments are possible. For example, the shifting means 705 might comprise a rotary actuator. As such actuator is rotated, the first and second rotary shafts 500, 600 are rotated to each other resulting in that the engine distribution and compression ratio are changed as stated above.

(52) The present disclosure thus covers all possible combinations of the particular embodiments of the engine described. Reference signs related to drawings and placed in parentheses in a claim, are solely for attempting to increase the intelligibility of the claim, and shall not be construed as limiting the scope of the claim. Thus, the scope of the present disclosure should not be limited by particular embodiments, but should be determined only by a fair reading of the claims that follow.