Description:
TECHNICAL FIELD
[0001] The present subject matter relates generally to an internal combustion engine. More particularly, but not exclusively, the present subject matter relates to calibration of one or more gears of an internal combustion engine including a
5 variable compression ratio.
BACKGROUND
[0002] Nowadays, with the advancement in the technology, a variable compression ratio is used to adjust/change a compression ratio of an internal combustion engine. The internal combustion engines employing variable compression ratio permits a
10 volume above a piston of the engine at a top dead centre to be changed/varied. The internal combustion engines running at higher loads need lower compression ratios to increase power, whereas the internal combustion engines running at lower loads need higher ratios to increase the efficiency of the internal combustion engine. The variable compression ratio facilitates in lower the fuel consumption while
15 increasing the efficiency of the internal combustion engine.

BRIEF DESCRIPTION OF THE DRAWINGS

[0003] The details are described with reference to an embodiment of an internal
20 combustion engine along with the accompanying diagrams. The same numbers are used throughout the drawings to reference similar features and components. [0004] Figure 1 exemplarily illustrates a side view of the internal combustion engine.
[0005] Figure 2 exemplarily illustrates a cross section view of the internal
25 combustion engine.
[0006] Figure 3(a) exemplarily illustrates a crankshaft along with a connecting rod and one or more gears.
[0007] Figure 3(b) exemplarily illustrates a VCR shaft and the one or more gears.
[0008] Figure 4 exemplarily illustrates a localized cross sectional side view of the
30 crankshaft with the one or more gears.

[0009] Figure 5 illustrates a cross-sectional view of the internal combustion engine depicting the location and arrangement of the one or more calibrations pins corresponding to one or more components within the internal combustion engine. [00010] Figure 6 illustrates a side view of the internal combustion engine depicting
5 arrangement of electric motor along with the worm wheel and worm shaft. [00011] Figure 7 illustrates an exemplary view of the position of the third gear and corresponding position of the piston at low variable compression ratio.
[00012] Figure 8 illustrates an exemplary view of the position of the third gear and corresponding position of the piston at high variable compression ratio.
10 [00013] Figure 9 (a) illustrates one or more markings and one or more balancing holes in one or more second gears.
[00014] Figure 9 (b) illustrates one or more markings in one or more second gears. [00015] Figure 9 (c) illustrates a magnified view of the one or more second gears having a hole in the one or more second gears.
15 [00016] Figure 10 exemplarily illustrates the assembly of the one or more second gears corresponding to the one or more markings in each of the one or more second gears.

DETAILED DESCRIPTION
20
[00017] A variable compression ratio is used to increase the efficiency of an internal combustion engine while ensuring a lower fuel consumption. The Variable Compression Ratio (hereinafter to be referred as ‘VCR’) is a ratio by which fuel/air mixture is compressed before the fuel/air mixture is ignited. An engine with
25 variable compression ratio is well-known in the field of spark-ignition engines. It provides the opportunity to operate the engine at high efficiency, particularly under part-load conditions. Increasing the compression ratio leads to decreasing fuel consumption. At high-load or full-load the compression ratio must be lowered in order to avoid knocking.
30 [00018] In a typical VCR system, provided which includes one or more gears assembled in a crankshaft assembly. The one or more gear includes an eccentric

gear which is located between a connecting rod and a crank pin. A VCR gear, the eccentric gear, and an intermediate gear are connected together to form the VCR system. To vary the compression ratio, the VCR gear is adjusted, the eccentric gear rotates, which further moves the piston. The piston moves slightly up and down due
5 to the movement of the eccentric gear. This up and down movement changes the volume and thus changes the effective compression ratio in the combustion chamber.
[00019] In such variable compression ratio systems, the eccentric gear has to be assembled in such a way that crankshaft TDC and VCR shaft position are known
10 relative to each other so that calibration of VCR shaft position can be done for a given compression ratio. Also overall assembly shall ensure correct back lash at the required crank position to allow free movement of gears, otherwise this can result in gears impact/friction and durability issues. However, since the variable compression ratio mechanism described above has a large number of components
15 and a complicated structure, the compression ratio varies from engine to engine and the quality may not be stable. Further, there is a possibility that the compression ratio varies for each cylinder, and if there is such a variation, the combustion pressure between the cylinders may become non-uniform and smooth operation may not be possible.
20 [00020] The above-mentioned problems are very critical and therefore, effective calibration of the gears of the VCR system is required to be carried out for proper functioning of the internal combustion engine with variable compression ratio. Thus, there is a need to overcome the above-mentioned problems and other problems of known art.
25 [00021] An objective of the present subject matter is to provide effective and efficient calibration of gears of a VCR system of an internal combustion engine, to prevent misalignment of the gears during assembly, thereby increasing the life of the system while avoiding failure of the gears.
[00022] Thus, the objective of the present subject matter is to provide a variable
30 compression ratio mechanism for an internal compression mechanism and its piston

position calibration method capable of easily adjusting the position of a piston without deviation.
[00023] As per an aspect of the subject matter, an internal combustion engine comprising a crankcase, a crankshaft, one or more connecting rod, and a piston. The
5 crankshaft is supported by said crankcase and said crankshaft is rotatable about a crankshaft axis. The one or more connecting rod includes a first end and a second end. The piston is connected to said first end of said one or more connecting rod. One or more gear members being disposed on said crankshaft and said one or more gear members being connected in a transmission path forming a variable
10 compression ratio system. one or more gear members being disposed on said crankshaft, and said one or more gear members being connected in a transmission path forming a variable compression ratio system, said one or more gear members include a first gear, a second gear and a third gear. The said internal combustion engine includes a control shaft , said control shaft being connected to said first gear;
15 one or more calibration pins; and a measuring device, said measuring device being connected at one end of said control shaft, and said measuring device being capable of measuring a position of said control shaft; wherein said one or more calibration pins being assembled to ensure correct relation between compression ratio and said measuring device values; and wherein said rotation of said control shaft enables
20 rotation of said third gear to a predetermined position corresponding to a set of predefined variable compression ratios, said rotation of third gear to said predetermined position enables movement of said piston to achieve variable compression ratio.
[00024] As per an aspect of the subject matter, the one or more gears include a first
25 gear, a second gear, and a third gear, said first gear, said second gear, and said third gear are connected in said transmission path forming said variable compression ratio system. The third gear is disposed between said connecting rod and a crank pin. The crank pin is supported by said crankshaft. The second gear and the third gear are supported by said crankshaft, said first gear and said second gear are
30 configured to mesh with said third gear.

[00025] As per an aspect of the subject matter, the first gear is is a VCR (Variable Compression Ratio) gear, the second gear is one or more intermediate gears and the third gear is an eccentric gear.
[00026] As per another aspect of the subject matter, the internal combustion engine
5 wherein said second gear and said third gear being supported by said crankshaft, said first gear and said second gear being configured to mesh with said third gear. [00027] As per another aspect of the subject matter, one or more calibration pins includes a gear calibration pin and a measuring device pin.
[00028] As per an aspect of the subject matter, the gear calibration pin being
10 configured to pass through one or more holes in a cover clutch, a crankcase, a web of a crankshaft and one or more second gears.
[00029] As per another aspect of the subject matter, said measuring device pin being configured to pass through one or more holes in a cover clutch.
[00030] As per an aspect of the subject matter, said one or more gears being
15 connected in said transmission path forming said variable compression ratio system. [00031] As per yet another aspect of the subject matter, a control mechanism comprises a worm gear, a worm shaft and an electric motor, said worm gear being fixed to said control shaft at a first end and to said worm shaft at a second end is disclosed.
20 [00032] As per another aspect of the subject matter, said electric motor being capable of rotating said worm shaft, said worm shaft being capable of rotating said worm gear and said worm gear being capable of rotating said control shaft. [00033] As per an aspect of the subject matter, said electric motor being configured to receive inputs from an electronic control unit of said vehicle based on one or
25 more throttle position values, said throttle position values being determined by a throttle position sensor of said vehicle.
[00034] As per an aspect of the subject matter, said electronic control unit being configured to store one or more predefined positions of said control shaft and said third gear corresponding to a set of predefined variable compression ratios, wherein
30 said one or more predefined positions being determined based on one or more throttle position values and one or more engine speed values.

[00035] As per an aspect of the subject matter, said one or more gears include one or more markings.
[00036] As per an aspect of the subject matter, said one or more second gears include said one or more markings, said one or more markings being configured to
5 enable assembly of said one or more second gears in alignment with each other. [00037] As per yet another aspect of the subject matter, said third gear include said one or more markings, said one or more markings being configured to enable assembly of said third gear at a predetermined crankshaft position.
[00038] As per an aspect of the subject matter, said one or more gears includes one
10 or more balancing holes to balance for rotational mass forces.
[00039] As pet yet another aspect of the subject matter, said one or more balancing holes being opposite to said one or more calibration holes in said one or more gears. [00040] The embodiments of the present invention will now be described in detail with reference to an internal combustion engine along with the accompanying
15 drawings. However, the present invention is not limited to the present embodiments. The present subject matter is further described with reference to accompanying figures. Wherever convenient, the same reference numbers are used throughout the drawings to refer to the same or like parts. While examples and features of disclosed principles are described herein, modifications, adaptations,
20 and other implementations are possible without departing from the scope of the disclosed embodiments. It should be noted that the description and figures merely illustrate principles of the present subject matter. Various arrangements may be devised that, although not explicitly described or shown herein, encompass the principles of the present subject matter. Moreover, all statements herein reciting
25 principles, aspects, and examples of the present subject matter, as well as specific examples thereof, are intended to encompass equivalents thereof.
[00041] Fig.1 and Fig. 2 exemplarily illustrates a side view and a cross-sectional view of the internal combustion engine 100. Fig. 1 and Fig.2 have been explained here together for the sake of brevity. Fig. 1 and Fig. 2 shows an embodiment of a
30 four-stroke internal combustion engine 100 according to the invention. The engine
100 comprises a crankcase 208, which supports a crankshaft 204 through a

crankshaft bearing 206. The crankcase 208 is divided into a left-side crankcase 208a and a right-side crankcase 208b. The crankshaft 204 includes a crankpin 210 which is located between two crank arms and is rotatable with respect to an engine block 202 about a crankshaft axis 212. The crankshaft 204 includes at least a central main
5 portion, the crankpin 210 and a crankshaft web, where the crankshaft web is located between the central main portion and the crankpin 210. One or more piston 216 is rotatably connected to a first end of the one or more connecting rod 214. The engine 100 further has an electric motor 102 configured for converting electrical energy into mechanical energy to rotate internal components within the engine 100. The
10 engine 100 further comprises of a measuring device 104 which could be a potentiometer or any other measuring device to detect the position of one or more connected components.
[00042] Fig.3(a) exemplarily illustrates the crankshaft 204 along with the connecting rod 214 and which shows a part of the embodiment of Fig. 1 in a more
15 schematic way, in which parts are omitted for brevity. Fig.3(b) exemplarily illustrates a VCR shaft 340 and the one or more gears 302, 304, 306. The internal combustion engine 100 includes one or more gears 302, 304, 306 being disposed on the crankshaft 204. The one or more gears 302, 304, 306 forms a VCR (variable compression ratio) system of the internal combustion engine 100. The one or more
20 gears 302, 304, 306 are connected in a transmission path forming the VCR system. The one or more gears include a first gear 302, a second gear 304, and a third gear
306. The first gear 302, the second gear 304, and the third gear 306 are connected in the transmission path forming said variable compression ratio system. The third gear 306 is disposed between the connecting rod 214 of the piston 216 (shown in
25 fig.1) and the crank pin 210 (shown in fig.1), the crank pin 210 is supported by the crankshaft 204. In an embodiment, the third gear 306 is an eccentric gear which is an external gear and which meshes with a second gear 304 which is the intermediate gear. In an embodiment, the first gear 302 is a VCR gear. The first gear 302 is attached to and end of a VCR shaft 340. In an embodiment, the first gear 302 is
30 integrated to the end of the VCR shaft 340. In an embodiment, the second gear 304
is an intermediate gear which is also an external gear. The second gear 304 includes

a first intermediate gear 304a and a second intermediate gear 304b. The second gear 304 and the third gear 306 form a common external gear which is rotatably mounted to the crankshaft 204 about a common axis of rotation which extends parallel to the crankshaft axis 212. The combination of first gear 302, the second
5 gear 304, and the third gear 306 facilitates in increasing the compression ratio to reduce fuel consumption.
[00043] Fig.4 exemplarily illustrates a localized cross sectional side view of the crankshaft 204 with the one or more gears 302, 304 and 306 and Fig.5 illustrates a cross-sectional view of the internal combustion engine depicting the location and
10 arrangement of the one or more calibrations pins 510,520 corresponding to one or more components within the internal combustion engine 100. The one or more calibration pins include a measuring device pin 510 and a gear calibration pin 520. The measuring device pin 510 is configured to pass through a hole in cover clutch
535. The gear calibration pin 520 is configured to pass through a hole in web of
15 crankshaft 410, a hole in crankcase 536 and a hole in first intermediate gear 420. [00044] Herein, the gear calibration pin 520 and the measuring device pin 510 are assembled to ensure correct relation between variable compression ratio system and measuring device 104 values. The gear calibration pin 520 passing through the hole in crankcase 536, the hole in web of crankshaft 410, one or more holes in
20 intermediate gear 420 ensures that the VCR shaft 340 and measuring device 104 in known values for this position.
[00045] Further, the measuring device 104 is connected at one end of the control shaft 340, and the measuring device 104 is capable of measuring a position of the control shaft 340. Herein, the one or more calibration pins 510, 520 is assembled to
25 ensure correct relation between compression ratio and the measuring device 104 values. Upon rotation of the control shaft 340, the control shaft 340 enables rotation of the third gear 306 to a predetermined position corresponding to a set of predefined variable compression ratios. The rotation of the third gear 306 to the predetermined position further enables movement of the one or more piston 216 to
30 achieve variable compression ratio.

[00046] Fig. 6 illustrates a side view of the internal combustion engine depicting arrangement of electric motor along with the worm wheel and worm shaft. The internal combustion engine 100 includes a control mechanism that comprises a worm gear 530, a worm shaft 610 and the electric motor 102. The worm gear 530
5 is fixed to the control shaft (not shown) at a first end and to the worm shaft 610 at a second end. The electric motor 102 is capable of rotating the worm shaft 610, which in turn rotates the worm gear 530 and the worm gear 530 in turn rotates the control shaft 340. Herein, the electric motor 102 is configured to receive inputs from an electronic control unit of a vehicle based on one or more throttle position
10 values, said throttle position values being determined by a throttle position sensor of said vehicle.
[00047] Fig. 7 and Fig.8 have been explained together for the sake of brevity. Fig. 7 illustrates an exemplary view of the position of the third gear and corresponding position of the piston at low variable compression ratio and Fig. 8 illustrates an
15 exemplary view of the position of the third gear and corresponding position of the piston at high variable compression ratio. Herein, the electronic control unit (not shown) is configured to store one or more predefined positions of said control shaft
340 and the third gear 306 corresponding to a set of predefined variable compression ratios during assembly of the internal combustion engine 100. Once
20 the electronic control unit (not shown) receives one or more inputs in the form of one or more throttle position values and one or more engine speed values, one or more predefined positions are determined based on such inputs. Further, corresponding to these determined predefined positions of the control shaft 340, the control shaft 340 moves the third gear 306, which in turn moves the one or more
25 pistons 216 to a first position at low variable compression ratio. For a high variable compression ratio, the control shaft 340 moves the third gear 306 in another position, which in turn moves the one or more pistons 216 to a second position. In this way, the piston 216 top dead center position or bottom dead center position can be more accurately set to an appropriate position. According to the present subject
30 matter, the position of the third gear 306 is controlled by rotating the control shaft
340 and the third gear 340 in turn moves the piston 216 up or down. By doing so,

the piston 216 of the variable compression ratio mechanism can be moved, and the engine 100 compression ratio can be changed. As a result, the piston 216 top dead center position and bottom dead center position can be changed, so that the piston 216 position for each engine can be easily adjusted, and the compression ratio can
5 be stabilized during engine operation. Markings on first intermediate gear 304(a) and second intermediate gear 304(b), third gear 306 and to assemble at minimum backlash at specified crank orientation. Gear calibration pin 520 passing through a hole in crankcase 536, a hole in web of crankshaft 410, second gear 304 ensures VCR shaft 340 and measuring device 104 in known values for this position. Thus,
10 markings in Intermediate gear assembly and eccentric gear & assembly at the given position to get minimum back lash at the required crank position and or given compression ratio position
[00048] Fig. 9(a), 9(b), 9(c) and 10 are explained together for brevity purposes. Figure 9 (a) and Figure 9 (b), 9(c) illustrates one or more markings and one or more
15 balancing holes in one or more second gears and Figure 10 exemplarily illustrates the assembly of the one or more second gears corresponding to the one or more markings in each of the one or more second gears. Herein, the one or more gears 302, 304, 306 include one or more markings 905. Such one or more markings 905 is configured to enable assembly of said one or more second gears 304 in alignment
20 with each other. The third gear 306 also includes the one or more markings 905, which enable assembly of the third gear 306 at a predetermined crankshaft 204 position. The one or more gears 302, 304, 306 also has one or more balancing holes 901 to balance for rotational mass forces. Herein, the one or more balancing holes 901 are placed opposite to the one or more markings 905 in the one or more gears
25 302, 304, 306. Therefore, assembly of first intermediate gear 304a and second intermediate gear 304b is done in such a manner with markings 905 so that combined gear maximum runout is in same position. Markings 905 in third gear 306 which is the eccentric gear enables to position the gears lowest backlash to come at specified crankshaft 204 position. As the crankshaft 204 rotates highest
30 backlash comes at specified crank position. The first intermediate gear 304a has a hole 420 which is used for calibration pin location. To balance the unbalance due

to the hole 420, additional one or more balancing holes 901 are put on opposite side. This reduces friction torque due to unbalance. Therefore, one or more markings 905 on the one or more gear 302, 304 and 306 is made to position the highest runout of the gear in a particular crank shaft and or compression ratio position.
5 [00049] It is an advantage of the present subject matter that the position of third gear 306 or the eccentric gear decides the compression ratio. Calibration ensures correct assembly/fault proof assembly in service and engine assembly, for the relation between measuring device 104 and compression ratio.
[00050] In light of the above-mentioned advantages and the technical
10 advancements provided by the disclosed method and system, the claimed steps as discussed above are not routine, conventional, or well understood in the art, as the claimed steps enable the following solutions to the existing problems in conventional technologies. Further, the claimed steps clearly bring an improvement in the functioning of the device itself as the claimed steps provide a technical
15 solution to a technical problem.
[00051] While the present disclosure has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made, and equivalents may be substituted without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a
20 particular situation or material to the teachings of the present disclosure without departing from its scope. Therefore, it is intended that the present disclosure may not be limited to the particular embodiment disclosed, but that the present disclosure will include all embodiments falling within the scope of the appended claims.

25

30

List of Reference Numerals 100: Internal combustion engine 102: Electric motor
5 104: Measuring device
202: Engine block
204: Crankshaft
206: Bearing
208: Crankcase
10 208(a): Left side crankshaft 208(b): Right side crankshaft 210: Crankpin
212: Crankshaft axis
214: One or more connecting rod
15 216: One or more piston 302: First gear (VCR gear)
304: Second gear (Intermediate gear) 304(a): First intermediate gear 304(b): Second intermediate gear
20 306: Third gear (Eccentric gear)
340: control shaft
410: hole in web of crankshaft 420: hole in first intermediate gear 510: measuring device pin
25 520: gear calibration pin
530: worm gear
535: holes in cover clutch 536: hole in crankcase

610: Worm shaft
901: one or more balancing holes 905: one or more markings
, Claims:We claim:
1. An internal combustion engine (100), said internal combustion engine (100) comprising:
a crankcase (208),

5 a crankshaft (204), said crankshaft (204) being supported by said crankcase

(208) and rotatable with respect thereto about said crankshaft axis (212),

one or more connecting rods (214), said one or more connecting rods (214) including a first end and a second end;
one or more piston (216), said one or more piston (216) being rotatably

10 connected to said first end of said at one or more connecting rods (214);

one or more gear members (302, 304, 306), said one or more gear members (302, 304, 306) being disposed on said crankshaft (204), and said one or more gear members (302, 304, 306) being connected in a transmission path forming a variable compression ratio system, said one or more gear members include a first gear (302),
15 a second gear (304) and a third gear (306);

a control shaft (340), said control shaft (340) being connected to said first gear (302) and said control shaft (340) being configured to rotate about said crankshaft axis (212);
one or more calibration pins (510, 520); and

a measuring device (104), said measuring device (104) being connected at one end of said control shaft (340), and said measuring device (104) being capable of measuring a position of said control shaft (340);
wherein said one or more calibration pins (510, 520) being

5 assembled to ensure correct relation between compression ratio and said

measuring device (104) values; and

wherein said rotation of said control shaft (340) enables rotation of said third gear (306) to a predetermined position corresponding to a set of predefined variable compression ratios, said rotation of third gear (306) to said
10 predetermined position enables movement of said one or more piston (216) to

achieve variable compression ratio.

2. The internal combustion engine (100) as claimed in claim 1, wherein said internal combustion engine (100) includes a variable compression ratio engine.
3. The internal combustion engine (100) as claimed in claim 1, wherein said

15 second gear (304) and said third gear (306) being supported by said crankshaft

(204), said first gear (302) and said second gear (304) being configured to mesh with said third gear (306).
4. The internal combustion engine (100) as claimed in claim 1, wherein said one or more calibration pins includes a gear calibration pin (520) and a measuring
20 device pin (510).

5. The internal combustion engine (100) as claimed in claim 4, wherein said gear calibration pin (520) being configured to pass through one or more holes in a

cover clutch (535), a hole in crankcase (536), a hole in a web of a crankshaft

(410) and one or more hole in second gears (420).

6. The internal combustion engine (100) as claimed in claim 4, wherein said measuring device pin (510) being configured to pass through one or more holes
5 in a cover clutch (535).

7. The internal combustion engine (100) as claimed in claim 1, wherein a control mechanism comprises a worm gear (530), a worm shaft (610) and an electric motor (102), said worm gear (530) being fixed to said control shaft (340) at a first end and to said worm shaft (610) at a second end.
10 8. The internal combustion engine (100) as claimed in claim 1, wherein said

electric motor (102) being capable of rotating said worm shaft (610), said worm shaft (610) being capable of rotating said worm gear (530) and said worm gear
(530) being capable of rotating said control shaft (340).

9. The internal combustion engine (100) as claimed in claim 1, wherein said

15 electric motor (102) being configured to receive inputs from an electronic

control unit of a vehicle based on one or more throttle position values, said throttle position values being determined by a throttle position sensor of said vehicle.
10. The internal combustion engine (100) as claimed in claim 9, wherein said

20 electronic control unit being configured to store one or more predefined

positions of said control shaft (340) and said third gear (306) corresponding to a set of predefined variable compression ratios, wherein said one or more

predefined positions being determined based on one or more throttle position values and one or more engine speed values.
11. The internal combustion engine (100) as claimed in claim 1, wherein said one or more gears (302, 304, 306) include one or more markings (905).
5 12. The internal combustion engine (100) as claimed in claim 11, wherein said one

or more second gears (302, 304, 306) include said one or more markings (905), said one or more markings (905) being configured to enable assembly of said one or more second gears (304) in alignment with each other.
13. The internal combustion engine (100) as claimed in claim 11, wherein said

10 third gear (306) include said one or more markings (905), said one or more

markings (905) being configured to enable assembly of said third gear (306) at a predetermined crankshaft (204) position.
14. The internal combustion engine (100) as claimed in claim 1, wherein said one or more gears (302, 304, 306) includes one or more balancing holes (901) to
15 balance for rotational mass forces.

15. The internal combustion engine (100) as claimed in claim 14, wherein said one or more balancing holes (901) being opposite to one or more markings (905) in said one or more gears (302, 304, 306).