A crankshaft, an internal combustion engine including variable compression ratio and a method of assembling the crankshaft

Abstract

A crankshaft (1, 40, 80) for an internal combustion engine including variable compression ratio comprises a main journal (2, 42, 82) including a crankshaft axis (5, 41, 81), a crankpin (3, 43) including a crankpin axis (7) and a crank web (4, 44, 84) located between the main journal (2, 42, 82) and the crankpin (3, 43, 83) in longitudinal direction of the crankshaft axis (5, 41, 81) and an eccentric member (6, 45, 85) which is mounted on the crankpin (3, 43, 83) and rotatable with respect to the crankpin (3, 43) about the crankpin axis (7). The eccentric member (6, 45, 85) comprises a bearing portion (8, 46, 86) for supporting a big end of a connecting rod, which bearing portion (8, 46, 86) has a centreline extending parallel to the crankpin axis (7), and an external eccentric member gear (9, 48, 87) between the bearing portion (8, 46, 86) and the crank web (4, 44, 84) as seen in longitudinal direction of the crankshaft axis (5, 41, 81). The eccentric member gear (6, 45, 85) is driveably coupled to an external central gear (12, 49, 90) through an external intermediate gear (11, 51, 89). The central gear (12, 49, 90) is fixed to a central shaft (14, 50, 92) which extends through the main journal (2, 42, 82) and through the crank web (4, 44, 84) and which is rotatable with respect to the main journal (2, 42, 82) and the crank web (4, 44, 84). The intermediate gear (11, 51, 89) is rotatably mounted to the crank web (4, 44, 84) and meshes with both the eccentric member gear (9, 48, 87) and the central gear (12, 49, 90). The intermediate gear (11, 51, 89) is mounted to an intermediate gear shaft (13, 60, 91) that is radially supported by both the crank web (4) and a separate supporting element (16), which is attached to the crank web (4) at a circumferential side thereof or by a separate supporting element (53, 94), which is attached to the crank web (44) at a side where the eccentric member (45) is located or at a circumferential side of the crank web (84)

Description

[0001] The present invention relates to a crankshaft for an internal combustion engine including variable compression ratio comprising a main journal including a crankshaft axis, a crankpin including a crankpin axis and a crank web located between the main journal and the crankpin in longitudinal direction of the crankshaft axis, an eccentric member which is mounted on the crankpin and rotatable with respect to the crankpin about the crankpin axis, wherein the eccentric member comprises a bearing portion for supporting a big end of a connecting rod, which bearing portion has a centreline extending parallel to the crankpin axis, and an external eccentric member gear between the bearing portion and the crank web as seen in longitudinal direction of the crankshaft axis, wherein the eccentric member gear is driveably coupled to an external central gear through an external intermediate gear, wherein the central gear is fixed to a central shaft which extends through the main journal and through the crank web and which is rotatable with respect to the main journal and the crank web, wherein the intermediate gear is rotatably mounted to the crank web and meshes with both the eccentric member gear and the central gear.

[0002] Such a crankshaft is known from EP 2 620 614 of the same applicant. The known crankshaft is suitable for an internal combustion engine and provides the opportunity to vary the compression ratio of the internal combustion engine by turning the eccentric member about the crankpin at a virtual standstill of the crankshaft. Increasing the compression ratio under part-load conditions of the internal combustion engine leads to improved efficiency, i.e. a lower fuel consumption.

[0003] An object of the invention is to provide a crankshaft which can be assembled in a simple manner.

[0004] This object is accomplished with the crankshaft according to the invention which is characterized in that the intermediate gear is mounted to an intermediate gear shaft that is radially supported by both the crank web and a separate supporting element, which is attached to the crank web at a circumferential side thereof or by a separate supporting element, which is attached to the crank web at a side where the eccentric member is located or at a circumferential side of the crank web.

[0005] The first option allows to first mount the central shaft and the central gear inside the main journal and the crank web, and the eccentric member to the crankpin and then mount the intermediate gear and the intermediate gear shaft to the crank web by means of the supporting element. Before mounting the intermediate gear and the intermediate gear shaft to the crank web by means of the supporting element the eccentric member can be positioned at a predetermined rotational position about the crankpin. The second option provides the opportunity to mount the intermediate gear shaft to the supporting element rather than directly to the crank web, for example into a hole of the crankshaft. This is advantageous since machining a hole in the crank web appears to be difficult in practice because of limited space between neighbouring crank webs. The third option, i.e. wherein the separate supporting element is attached to the crank web at a circumferential side of the crank web, also provides the opportunity to mount the intermediate gear shaft to the supporting element rather than directly to the crank web. All options facilitate assembling the crankshaft.

[0006] In a practical embodiment, if the intermediate gear shaft is radially supported by both the crank web and the supporting element, which is attached to the crank web at a circumferential side thereof, the intermediate gear is rotatable with respect to the intermediate gear shaft which in turn is fixed to the crank web and the supporting element and if the intermediate gear shaft is radially supported by the supporting element, which is attached to the crank web at a side where the eccentric member is located or at a circumferential side of the crank web, the intermediate gear is rotatable with respect to the intermediate gear shaft which in turn is fixed to the supporting element. The intermediate gear may be rotatable with respect to the intermediate gear shaft through a roller bearing, for example a needle bearing. In the event that the intermediate gear shaft is radially supported by the supporting element, which is attached to the crank web at a side where the eccentric member is located or at a circumferential side of the crank web, the intermediate gear shaft may be fixed to the supporting element through a press fitting.

[0007] When the intermediate gear shaft is radially supported by both the crank web and the supporting element, which is attached to the crank web at a circumferential side thereof, the intermediate gear shaft may be clamped between the crank web and the supporting element. This may be enabled by providing the crank web and the supporting element with respective recesses which accommodate the intermediate gear shaft when the supporting element is fixed to the crank web.

[0008] In an embodiment the intermediate gear shaft is radially supported by both the crank web and the supporting element, which is attached to the crank web at a circumferential side thereof, wherein the intermediate gear is a first intermediate gear, the supporting element is a first supporting element and the intermediate gear shaft is a first intermediate gear shaft, wherein the eccentric member gear is driveably coupled to the central gear through an external second intermediate gear, which is rotatably mounted to the crank web and meshes with both the eccentric member gear and the central gear, wherein the second intermediate gear is mounted to a second intermediate gear shaft that is radially supported by both the crank web and a separate second supporting element, wherein the second supporting element is attached to the crank web at a circumferential side thereof at an angular distance from the first supporting element about the crankshaft axis.

[0009] In an embodiment the first and second intermediate gears as well as the first and second supporting elements are mirror symmetrical with respect to a plane which is spanned by the crankshaft axis and the crankpin axis. This means that the first and second intermediate gears are the same and the first and second supporting elements are the same.

[0010] In an alternative embodiment, the intermediate gear shaft is radially supported by the supporting element, which is attached to the crank web at a side where the eccentric member is located or at a circumferential side of the crank web, wherein the intermediate gear is a first intermediate gear and the intermediate gear shaft is a first intermediate gear shaft, wherein the eccentric member gear is driveably coupled to the central gear through an external second intermediate gear, which is rotatably mounted to the crank web and meshes with both the eccentric member gear and the central gear, wherein the second intermediate gear is mounted to a second intermediate gear shaft that is radially supported by the supporting element. In this case the first and second intermediate gear shafts are mounted to a single supporting element. The first and second intermediate gears may be rotatable with respect to the first and second intermediate gear shafts, respectively, whereas the first and second intermediate gear shafts may be fixed to the supporting element, for example in holes of the supporting element through press fittings.

[0011] The supporting element may have a yoke-shape which is attached to the crank web at a circumferential side of the crank web and which radially supports the first and second intermediate gear shafts. The dimensions of the central gear and the first and second intermediate gears may be such that the supporting element can be fit to the crank web in radial direction towards the crankshaft axis. The yoke-shaped supporting element may have a basis and two legs which extend from the basis. In the mounted condition the legs and the basis may contact the circumference of the crank web. The legs may be substantially parallel. The yoke-shaped supporting element and the crank web may be adapted such that the supporting element can be mounted to the crank web in a direction towards the crankshaft axis.

[0012] The main journal, the crank web and the crankpin may be made in one piece. In this case the eccentric member may be made of at least two separate mating parts.

[0013] The central shaft may extend concentrically through the main journal, which means that its axis of rotation coincides with the crankshaft axis.

[0014] In an embodiment the central gear is locked with respect to the central shaft in rotational direction of the central shaft through splines, wherein the number of splines is selected such that the relative positions of the central shaft and the eccentric member are independent from the rotational position of the central gear with respect to the central shaft. This guarantees that teeth of the central gear always have the same position with respect to the central shaft in each rotational position of the central gear with respect to the central shaft, hence facilitating assembly of the crankshaft.

[0015] In an embodiment the eccentric member gear is a first eccentric member gear and the eccentric member has a second eccentric member gear at an opposite side of the bearing portion, which is driveably coupled to an external first transfer gear through an external intermediate transfer gear, wherein the first transfer gear is fixed to one end of a transfer shaft which extends successively through a first further crank web, a further main journal and a second further crank web and which is rotatable with respect to the further main journal and the first and second further crank webs, wherein the intermediate transfer gear is rotatably mounted to the first further crank web and meshes with both the second eccentric member gear and the first transfer gear, wherein the intermediate transfer gear is mounted to an intermediate transfer gear shaft that is radially supported by both the first further crank web and a separate supporting element, which is attached to the first further crank web at a circumferential side thereof or by a separate supporting element, which is attached to the first further crank web at a side where the eccentric member is located or at a circumferential side of the first further crank web, wherein an opposite end of the transfer shaft is provided with a second transfer gear which is driveably coupled to a first eccentric member gear of a further eccentric member through a further external intermediate transfer gear, wherein the further intermediate transfer gear is rotatably mounted to the second further crank web and meshes with both the first eccentric member gear of the further eccentric member and the second transfer gear, wherein the further intermediate transfer gear is mounted to an intermediate transfer gear shaft that is radially supported by both the second further crank web and a separate supporting element, which is attached to the second further crank web at a circumferential side thereof or by a separate supporting element, which is attached to the second further crank web at a side where the further eccentric member is located or at a circumferential side of the second further crank web. In a particular embodiment the number of teeth of the first and second eccentric member gears are the same and the number of teeth of the central gear and the first and second transfer gears are the same.

[0016] In an embodiment the transfer shaft extends eccentrically with respect to the crankshaft axis through the first further crank web, the further main journal and the second further crank web. In a more particular embodiment the transfer shaft is rotatably mounted in a sleeve, which in turn is fixed to at least one of the first further crank web, the further main journal and the second further crank web, wherein the sleeve has an outer surface and an inner surface which are eccentrical with respect to each other, and wherein the outer surface fits in a central through-hole which is concentrical with respect to the crankshaft axis. The concentrical position of the through-hole facilitates the manufacturing process.

[0017] In a preferred embodiment the eccentric member and the further eccentric member are part of a plurality of eccentric members which are drivably coupled to each other in a similar way as the eccentric member and the further eccentric member, wherein each of the first and second eccentric member gears has a number of teeth that equals a whole number times the number of the plurality of the eccentric members and each of the central gear and the first and second transfer gears has a number of teeth that equals 0.5 times the number of teeth of the eccentric member gear. Hence, in case of applying the crankshaft in a six cylinder in-line engine each of the first and second eccentric member gears may have six times a whole number of teeth. This facilitates assembly of the crankshaft, since when the eccentric members are positioned in the correct angular positions about the respective crankpins this provides the opportunity to mount the intermediate gear, the intermediate transfer gear and the further intermediate transfer gear through the supporting elements, without requiring further adjustment of the rotational positions of the auxiliary gear and the first and second transfer gears. In other words, when the eccentric member and the further eccentric members are in the correct positions with respect to the respective crankpins the teeth of the central gear, the first and second transfer gears and further transfer gears are aligned.

[0018] The invention is also related to an internal combustion engine including variable compression ratio, comprising a crankshaft as described hereinbefore and an engine block which supports at least the main journal, wherein the main journal is rotatable with respect to the engine block about the crankshaft axis.

[0019] The invention is also related to a method of assembling the crankshaft as described hereinbefore, wherein the intermediate gear and the intermediate gear shaft are mounted to the crank web by the supporting element after mounting the eccentric member on the crankpin and positioning the eccentric member in rotational direction about the crankpin and after mounting the central shaft inside the main journal and the crank web and the central gear to the central shaft. This allows to position the eccentric member with respect to the central shaft before engaging the intermediate gear to the central gear and the eccentric member gear.

[0020] In an embodiment after positioning the eccentric member at the crankpin the eccentric member is temporarily fixed to the crank web during which the intermediate gear is engaged to the central gear and the eccentric member gear and the supporting element is fixed to the crank web. This provides the opportunity to mount the intermediate gear to the crank web without changing the relative position of the eccentric member and the crankpin.

[0021] The invention will hereafter be elucidated with reference to very schematic drawings showing embodiments of the invention by way of example. Fig. 1 is a perspective view of an embodiment of a crankshaft according to the invention. Fig. 2 is a perspective sectional view of the crankshaft as shown in Fig. 1. Fig. 3 is an enlarged view of a part of the crankshaft as shown in Fig. 2. Fig. 4 is a cross-sectional view of the crankshaft as shown in Fig. 1. Fig. 5 is a similar view as Fig. 1, illustrating a method of assembling the crankshaft. Fig. 6 is an enlarged perspective view of an eccentric member of the crankshaft as shown in Fig. 5. Fig. 7 is a similar view as Fig. 3, but showing an alternative embodiment of the crankshaft according to the invention. Fig. 8 is an enlarged exploded view of a part of the crankshaft as shown in Fig. 7. Fig. 9 is a similar view as Fig. 3, but showing still another embodiment of the crankshaft according to the invention. Fig. 10 is a similar view as Fig. 1, but showing an alternative embodiment of the crankshaft according to the invention. Fig. 11 is an enlarged sectional view of a part of the crankshaft as shown in Fig. 10. Fig. 12 is an enlarged view of a part of the crankshaft as shown in Fig. 10. Figs. 13 and 14 are similar views as Fig. 12, showing sub-parts of the part as shown in Fig. 12. Fig. 15 is a similar view as Fig. 10, showing a part of the crankshaft as shown in Fig. 10 on an larger scale.

[0022] Figs. 1-5 show an embodiment of a crankshaft 1 for an internal combustion engine including variable compression ratio according to the invention. The crankshaft 1 is suitable for a six-cylinder in-line four-stroke Diesel engine, but is also suitable for an Otto engine. The right side of the crankshaft 1 in Fig. 1 and the left side of the crankshaft 1 in Figs. 2, 3 and 5 are defined as a front end of the crankshaft 1, whereas the left side of the crankshaft 1 in Fig. 1 and the right side of the crankshaft 1 in Figs. 2 and 4 are defined as a rear end of the crankshaft 1.

[0023] The crankshaft 1 has seven main journals 2 which are supported by an engine block (not shown) when the crankshaft 1 is mounted to the engine block of an internal combustion engine. Furthermore, the crankshaft 1 comprises six crankpins 3 and six pairs of crank webs 4 at opposite sides of the respective crankpins 3. When mounted in an internal combustion engine the crankshaft 1 is rotatable with respect to the engine block about a crankshaft axis 5 which forms a centreline through the main journals 2. Each of the crank webs 4 is located between the adjacent main journal 2 and the adjacent crankpin 3 thereof as seen in longitudinal direction of the crankshaft axis 5. The main journals 2, the crank webs 4 and the crankpins 3 are made in one piece. In an alternative embodiment the crankshaft 1 may have a different number of main journals 2, crankpins 3 and crank webs 4 for an internal combustion engine including a different number of cylinders.

[0024] The crankshaft 1 is provided with six eccentric members 6 which are rotatably mounted on the respective crankpins 3. One of the eccentric members 6 is shown in Fig. 6. Each of the eccentric members 6 is rotatable with respect to the corresponding crankpin 3 about a crankpin axis 7, see Fig. 3, and comprises a bearing portion 8 for supporting a big end of a connecting rod (not shown). The bearing portion 8 of each eccentric member 6 is circular cylindrical and has a centreline parallel to the crankpin axis 7 of the corresponding crankpin 3. Each of the eccentric members 6 has a circular cylindrical inner wall including a centreline which coincides with the crankpin axis 7 of the corresponding crankpin 3. Since the centreline of the bearing portion 8 is parallel to the crankpin axis 7 they extend at a distance from each other. Hence, the bearing portion 8 and the inner wall of each eccentric member 6 are disposed eccentrically with respect to each other.

[0025] For clarity reasons, in Figs. 2 and 3 several parts of the crankshaft 1 are not shown. Since the main journals 2, the crank webs 4 and the crankpins 3 are made in one piece, each of the eccentric members 6 is made of at least two mating pieces in order to enable assembly of the crankshaft 1. Such eccentric members are disclosed in EP 2 873 835 of the same applicant.

[0026] The eccentric member 6 closest to the front end of the crankshaft 1 has an external front eccentric member gear 9 and an external rear eccentric member gear 10. The front eccentric member gear 9 is located between the bearing portion 8 and the crank web 4 closest to the front end as seen in longitudinal direction of the crankshaft axis 5. The bearing portion 8 lies between the front eccentric member gear 9 and the rear eccentric member gear 10.

[0027] The front eccentric member gear 9 meshes with two external intermediate gears 11, which in turn mesh with an external central gear in the form of an auxiliary gear 12. The front eccentric member gear 9 and the auxiliary gear 12 are located behind each other as seen along the crankshaft axis 5. For this reason, the intermediate gears 11 are wider than each of the front eccentric member gear 9 and the auxiliary gear 12. In an alternative embodiment (not shown) the intermediate gears 11, the auxiliary gear 12 and the front eccentric member gear 9 may lie in a single plane.

[0028] The intermediate gears 11 are rotatably mounted to respective intermediate gear shafts 13, see Fig. 1, for example through needle bearings. The intermediate gears 11 are rotatable with respect to the respective intermediate gear shafts 13 about intermediate gear axes which extend parallel to the crankshaft axis 5. The intermediate gear shafts 13 are fixed to the crank web 4 closest to the front end of the crankshaft 1.

[0029] Fig. 3 shows that the auxiliary gear 12 is fixed to a central shaft in the form of an auxiliary shaft 14 through a bolt 15. The auxiliary gear 12 may be locked to the auxiliary shaft 14 in rotational direction thereof through splines but alternative means are conceivable. The auxiliary shaft 14 extends concentrically through a central through-hole through the main journal 2 and through the adjacent crank web 4 thereof at the front end of the crankshaft 1. The auxiliary shaft 14 has a centreline that coincides with the crankshaft axis 5 and is rotatable with respect to the corresponding main journal 2 about the crankshaft axis 5.

[0030] When the crankshaft 1 is applied in an internal combustion engine the angular position of the auxiliary shaft 14 can be adjusted with respect to the engine block in order to vary the compression ratio of the internal combustion engine, for example through a hydraulic control system or a worm - worm wheel mechanism as disclosed in EP 2 620 614 of the same applicant.

[0031] The front eccentric member gear 9, the intermediate gears 11 and the auxiliary gear 12 are dimensioned such that under operating conditions, in case of a standstill of the auxiliary shaft 14 with respect to the engine block, the corresponding eccentric member 6 is rotated with respect to the corresponding crankpin 3 at half speed of the speed of the crankshaft 1 with respect to the engine block and is rotated with respect to the corresponding crankpin 3 in opposite direction of the rotational direction of the crankshaft 1 with respect to the engine block. For this reason the gear ratio between the front eccentric member gear 9 and the auxiliary gear 12 equals two.

[0032] Each of the intermediate gear shafts 13 is radially supported by both the corresponding crank web 4 and a separate supporting element 16, see Fig. 1. Each of the supporting elements 16 is provided with a semi-circular cylindrical recess and the crank web 4 is provided with two semi-circular cylindrical recesses in which the respective intermediate gear shafts 13 are accommodated. The supporting elements 16 are located at opposite sides of the crank web 4 at a circumferential side thereof. They are fixed to the crank web 4 through bolts. Each of the intermediate gear shafts 13 is fixed to the corresponding crank web 4 and supporting element 16 by a clamping force between the crank web 4 and the supporting element 16.

[0033] In an alternative embodiment (not shown) the intermediate gears 11 may be fixed to the intermediate gear shafts 13, which in turn are rotatable with respect to the corresponding crank web 4 and supporting element 16.

[0034] In the embodiment as shown in Figs. 1-5 the intermediate gears 11 as well as the corresponding supporting elements 16 are mirror symmetrical with respect to a plane which is spanned by the crankshaft axis 5 and the crankpin axis 7 of the crankpin 3 closest to the front end of the crankshaft, but this may be different in an alternative embodiment.

[0035] Fig. 4 shows a cross-section of the crankshaft 1 at the bearing portion 8 of the eccentric member 6 closest to the front end of the crankshaft 1. It can be seen that the rear eccentric member gear 10 of the eccentric member 6 meshes with two external first intermediate transfer gears 17 which in turn mesh with an external first transfer gear 18. The rear eccentric member gear 10 and the first transfer gear 18 are located behind each other as seen along the crankshaft axis 5. For this reason, the first intermediate transfer gears 17 are wider than each of the rear eccentric member gear 10 and the first transfer gear 18. In an alternative embodiment (not shown) the first intermediate transfer gears 17, the first transfer gear 18 and the rear eccentric member gear 10 may lie in a single plane.

[0036] The first intermediate transfer gears 17 are rotatably mounted to respective first intermediate transfer gear shafts 13', for example through needle bearings. The first intermediate transfer gear shafts 13' are mounted to the corresponding crank web 4 by clamping them between the crank web 4 and respective separate supporting elements 16' in a similar manner as the intermediate gear shafts 13 through their corresponding supporting elements 16.

[0037] The first transfer gear 18 is fixed to a front end of a transfer shaft 19 through a bolt 20, see Fig. 3. An external second transfer gear 21 is fixed to a rear end of the transfer shaft 19 through a bolt 20', as well. The first and second transfer gears 18, 21 may be locked to the transfer shaft 19 in rotational direction thereof through splines, but alternative means are conceivable. The transfer shaft 19 is mounted inside a second one of the main journals 2 as counted from the front end of the crankshaft 1 and its adjacent crank webs 4 and rotatable with respect to that second one of the main journals 2 about the crankshaft axis 5.

[0038] The second transfer gear 21 meshes with two external second intermediate transfer gears 22 which in turn mesh with an external front eccentric member gear 23 of a second one of the eccentric members 6 as counted from the front end of the crankshaft 1. The front eccentric member gear 23 of the second one of the eccentric members 6 has the same dimensions as the rear eccentric member gear 10 of the eccentric member 6 closest to the front end. The first and second transfer gears 18, 21 are also the same, and the first and second intermediate transfer gears 17, 22 are also the same. This means that the second one of the eccentric members 6 rotates with respect to its corresponding crankpin 3 in the same direction and at the same speed as the eccentric member 6 closest to the front end with respect to its corresponding crankpin 3.

[0039] It is noted that the dimensions of the front eccentric member gear 23 of the second one of the eccentric members 6, the rear eccentric member gear 10 of the eccentric member 6 closest to the front end and the first and second transfer gears 18, 21 may be different as long as their dimensions are selected such that the eccentric members 6 have the same motions about the respective crankpins 3, respectively, under operating conditions in an internal combustion engine. The dimensions of the first intermediate transfer gears 17 and the second intermediate transfer gears 22 do not influence these motions; it is even possible, for example, that the first and second transfer gears 18, 21 are identical, and the front eccentric member gear 23 of the second one of the eccentric member 6 and the rear eccentric member gear 10 of the eccentric member 6 closest to the front end are identical, whereas the first and second intermediate transfer gears 17, 22 are different.

[0040] The second intermediate transfer gears 22 are rotatably mounted to respective second intermediate transfer gear shafts 13'' . The second intermediate transfer gear shafts 13'' are clamped between the corresponding crank web 4 and respective separate supporting elements 16'' in a similar manner as the intermediate gear shafts 13 through their corresponding supporting elements 16. The third to sixth one of the eccentric members 6 of the crankshaft 1 as counted from its front end are drivably coupled to each other in a similar way through further transfer shafts, transfer gears, intermediate transfer gears and supporting elements such that the eccentric members 6 have the same motions about the respective crankpins 3.

[0041] Fig. 5 illustrates a method of assembling the crankshaft 1 as described hereinbefore. After mounting the eccentric members 6, the auxiliary shaft 14, the auxiliary gear 12, the transfer shaft 19 and the further transfer shafts, the first and second transfer gears 18, 21 and further transfer gears, and before mounting the intermediate gears 11, the first and second intermediate transfer gears 17, 22 through the supporting elements 16, 16', 16'', and the further intermediate transfer gears through the corresponding further supporting elements, the eccentric members 6 should be positioned with respect to their corresponding crankpins 3 in rotational direction such that each eccentric member 6 has a predetermined relative position to its corresponding crankpin 3 during engine running. More specifically, when the crankshaft 1 is applied in an internal combustion engine each of the eccentric members 6 must have the same relative position to its crankpin 3 when a piston in the corresponding cylinder is at top dead centre at the end of its compression stroke. For this reason each of the eccentric members 6 is provided with six reference locations, in this case six reference holes 24 which can be temporarily fixed to the adjacent crank web 4 through a calibration pin (not shown) that fits in one of the reference holes 24 and has a fixed position with respect to the adjacent crank web 4. In this case there are six reference locations because of applying the crankshaft 1 in a six cylinder engine, but the number will be different in case of a different number of cylinders.

[0042] Referring to Fig. 6, the reference holes 24 of each eccentric member 6 lie at equiangular distances from each other about the corresponding crankpin axis 7 at an axial side of the eccentric member 6. Since the crankshaft 1 as shown in Figs. 1-5 is suitable for a six-cylinder in-line engine the angular distance between two neighbouring reference holes 24 is 60°. The reference holes 24 have numbers 1 to 6 in a sequence of 1-5-3-6-2-4 in counter-clockwise direction as seen from the front end to the rear end of the crankshaft 1. This sequence corresponds to the firing sequence of the engine.

[0043] In this case the crankshaft 1 rotates in clockwise direction as seen from the front end to the rear end. As mentioned hereinbefore each of the eccentric members 6 rotates about the corresponding crankpin 3 at half speed of the crankshaft speed and in opposite direction of the rotational direction of the crankshaft 1 with respect to the engine block. Fig. 5 shows a situation in which the reference hole 24 having number 1 of the eccentric member 6 that is closest to the front end is located at a top end of the adjacent crank web 4. At the second one of the eccentric members 6 as counted from the front end the reference hole 24 having number 2 is located at a top end of the adjacent crank web 4, whereas at the third one of the eccentric members 6 as counted from the front end the reference hole 24 having number 3 is located at a top end of the adjacent crank web 4, and so on. After temporarily fixing the eccentric members 6 to the respective crankpins 3 through calibration pins as described above the intermediate gears 11, the first and second intermediate transfer gears 17, 22 and the further intermediate transfer gears can be mounted to the respective crank webs 4 through the corresponding supporting elements 16, 16', 16'' and the further supporting elements.

[0044] Referring to Figs. 5 and 6, when the crankshaft 1 is applied in an internal combustion engine the second cylinder as counted from the front end of the crankshaft 1 fires four times 120° later than the first cylinder as counted from the front end. Since each of the eccentric members 6 rotates about the corresponding crankpin 3 at half speed of the crankshaft speed and in opposite direction thereof, the second one of the eccentric members 6 as counted from the front end must have the same angular position with respect to its corresponding crankpin 3 four times 60° later than the first one of the eccentric members 6 as counted from the front end of the crankshaft 1. For that reason the reference hole 24 having number 2 is located 240° from the reference hole 24 having number 1 in counter clockwise direction in Fig. 6.

[0045] Similarly, the third cylinder as counted from the front end fires two times 120° later than the first cylinder, which means that the third one of the eccentric members 6 must have the same angular position with respect to its corresponding crankpin 3 two times 60° later. For that reason the reference hole 24 having number 3 is located 120° from the reference hole 24 having number 1 in counter clockwise direction in Fig. 6. Fig. 5 illustrates that the sequence of numbering of the reference holes 24 at the eccentric members 6 facilitates the process of assembly, since the numbers of the reference holes 24 must be located at the same relative positions of the crank webs 4 which correspond to the respective eccentric members 6 as counted from the front end of the crankshaft 1, indicated by arrows in Fig. 5.

[0046] In the embodiment as shown in Figs. 1-6 the front and rear eccentric member gears 9, 10, 23 of each of the eccentric members 6 have 60 teeth. The auxiliary gear 12, the first and second transfer gears 18, 21 and the further transfer gears have 30 teeth. The gear ratio of two between the front eccentric member gear 9 and the auxiliary gear 12 is essential for the motion of the first one of the eccentric members 6 as counted from the front end under operating conditions. However, the gear ratios at the first and second transfer gears 18, 21 and at the further transfer gears may be different as long as all of the eccentric members 6 have the same motions about the respective crankpins 3 under operating conditions. It is even possible that the transfer shaft 19 and the further transfer shafts extend eccentrically through the respective main journals 2. In this case the transfer shaft 19 and the further transfer shafts may be accommodated in respective sleeves which each have an inner and outer circumference that are eccentrical with respect to each other, whereas the sleeves are mounted in respective through-holes in the respective main journals 2, which through-holes are concentrical with respect to the crankshaft axis 5. In this case the concentrical through-holes can be made relatively simple.

[0047] For simply assembling the crankshaft 1 for a six cylinder engine as shown in Figs. 1-6 each of the front and rear eccentric member gears 9, 10, 23 of each eccentric member 6 has six times a whole number of teeth, i.e. the number of eccentric members 6 times a whole number of teeth, and the auxiliary gear 12 as well as each of the first and second transfer gears and the further transfer gears has half the number of teeth of each of the front and rear eccentric member gears 9, 10, 23. This means that when the eccentric members 6 are in the correct positions with respect to the respective crankpins 3 the teeth of the auxiliary gear 12, the first and second transfer gears 18, 21 and the further transfer gears are aligned. In other words, during assembly, when the eccentric members 6 are positioned in the correct angular positions about the respective crankpins 3 this provides the opportunity to mount the intermediate gears 11, the first and second intermediate transfer gears 17, 22 and the further intermediate transfer gears through the supporting elements 16, 16', 16'' and the further supporting elements, without requiring further adjustment of the rotational positions of the auxiliary gear 12, the first and second transfer gears 18, 21 and the further transfer gears.

[0048] When the first and second transfer gears 18, 21 are mounted to the transfer shaft 19 and the further transfer gears are mounted to the further transfer shafts via splines it is desired that an angular shift of a spline in rotational direction of the mentioned gears does not change a shift in axial projection of teeth. Since each of the transfer gears has 30 teeth, an angular shift of one tooth is 12°, so an angle between two neighbouring splines must correspond to a whole number times 12°. For example, an angle of 24° corresponds to 15 splines and two teeth. In other words, shifting a transfer gear with respect to its transfer shaft by one spline should not change the axial projection of its teeth.

[0049] Fig. 9 shows a part of an alternative embodiment of the crankshaft 1 according to the invention. In this case the crankshaft 1 is provided with a lubrication system for supplying lubricant to needle bearings 25 through which the intermediate gears 11 and the first and second intermediate transfer gears 17, 22 are mounted to the intermediate gear shaft 13 and the first and second intermediate transfer gear shafts 13', 13", respectively. Fig. 9 shows that a first oil channel 26 extends through the main journal 2 and the adjacent crank web 4 to an outer side of that crank web 4 where the first intermediate transfer gear shafts 13' is mounted. The first oil channel 26 communicates with a second oil channel 27 in the first intermediate transfer gear shaft 13' at the adjacent supporting element 16' of the crank web 4. This allows lubricant to flow from the inner side of the main journal 2 to the needle bearing 25 under operating conditions.

[0050] Fig. 7 shows another alternative embodiment of a crankshaft 40 according to the invention. In this case the crankshaft 40 is suitable for a multi-cylinder Diesel engine including variable compression ratio, but could also be applied in an Otto engine. The crankshaft 40 has a crankshaft axis 41. Fig. 7 shows two main journals 42, two crankpins 43 and four crank webs 44. Each crank web 44 lies between an adjacent crankpin 43 and an adjacent main journal 42 as seen in longitudinal direction of the crankshaft axis 41.

[0051] Similar to the embodiment as shown in Figs. 1-6 the crankshaft 40 is provided with eccentric members 45, which are rotatably mounted on the respective crankpins 43 and rotatable about respective crankpin axes. Each of the eccentric members 45 is also provided with a bearing portion 46 for supporting a big end of a connecting rod. Similar to the embodiment as shown in Figs. 1-6 the bearing portion 46 of each eccentric member 45 has a centreline parallel to the corresponding crankpin axis. An external rear eccentric member gear 47 of one of the eccentric members 45 is drivably coupled with an external front eccentric member gear 48 of a neighbouring eccentric member 45. The front eccentric member gear 48 is located between the bearing portion 46 of the corresponding eccentric member 45 and the adjacent crank web 44 as seen in longitudinal direction of the crankshaft axis 41.

[0052] The front eccentric member gear 48 is drivably coupled to an external first central gear in the form a first transfer gear 49 through two external intermediate transfer gears 51. The first transfer gear 49 is fixed to a first end of a central shaft in the form of a transfer shaft 50 through a bolt 61. In order to fix the first transfer gear 49 to the transfer shaft 50 appropriately, the first transfer gear 49 and the transfer shaft 50 may be provided with mating splines. Each of the intermediate transfer gears 51 meshes with the first transfer gear 49 and the front eccentric member gear 48. The widths of the intermediate transfer gears 51 are larger than the width of the front eccentric member gear 48 and larger than the width of the first transfer gear 49. The transfer shaft 50 extends concentrically through a central through-hole in one of the main journals 42 and the crank webs 44 at opposite sides of that main journal 42. The transfer shaft 50 is rotatable with respect to the corresponding main journal 42 and crank webs 44. In an alternative embodiment (not shown) the transfer shaft 50 may extend through the main journals 42, but eccentrically with respect to the crankshaft axis 41. Similar to the embodiment as shown in Figs. 1-6 it is relevant that the eccentric members 45 have the same motions about the respective crankpins 43.

[0053] In a similar way the rear eccentric member gear 47 of the left eccentric member 45 in Fig. 7 is drivably coupled to an external second central gear in the form of a second transfer gear 52 through two external intermediate transfer gears. The second transfer gear 52 is fixed to a second end of the transfer shaft 50 through a bolt 61. This configuration urges the eccentric members 45 to rotate in the same direction and at the same speed about the respective crankpins 43 under operating conditions when mounted in an internal combustion engine.

[0054] The transfer shaft 50 is radially supported by separate supporting elements 53 which are attached to the respective crank webs 44 at sides where the respective adjacent eccentric members 45 are located. One of the separate supporting elements 53 is shown in Fig. 8. Each supporting element 53 has a sleeve 54 in which a needle bearing 55 is provided through a press fitting. The transfer shaft 50 fits in inner sides of the respective needle bearings 55. The sleeve 54 fits in a central through-hole through the corresponding main journal 42 and crank webs 44 with play. An oil guide tube 56 is located between the needle bearings 55 of the transfer shaft 50 in order to guide lubricant from an inner side of the main journal 42 to the eccentric member 45.

[0055] In an alternative embodiment (not shown) the oil tube 56 may have an inner and outer circumference that are eccentrical with respect to each other and fit in the central through-hole in the corresponding main journal 42, which central through-hole is concentrical with respect to the crankshaft axis 41; in this case the transfer shaft 50 can be mounted eccentrically with respect to the crankshaft axis 41, whereas the central through-hole is concentrical. This is analogue to the eccentrical sleeve as described hereinbefore in relation to the embodiment as shown in Figs. 1-6. The transfer shaft 50 may be supported by the oil guide tube rather than by the sleeves 54 of the supporting elements 53.

[0056] The crankshaft 40 is provided with covers 57 which can be fixed to the respective supporting elements 53 and crank webs 44 through bolts 58. Each of the bolts 58 can be successively inserted into through-holes in the crank web 44 and the supporting element 53 and screwed into a threaded hole 59 in the cover 57 such that the supporting element 53 is clamped between the crank web 44 and the cover 57. The intermediate transfer gears 51 are located between the supporting element 53 and the cover 57. Each of the intermediate transfer gears 51 is rotatably mounted on an intermediate gear shaft 60, for example through needle bearings, which intermediate gear shaft 60 is fixed in both the supporting element 53 and the cover 57, for example through press fittings.

[0057] The transfer shaft 50 is locked with respect to the corresponding main journal 42 in a direction along the crankshaft axis 41 through the first and second transfer gears 49, 52 which abut against the respective supporting elements 53.

[0058] It is noted that the transfer shaft 50 is not necessarily supported by the supporting elements 53. This means that the supporting element 53 is applied for supporting the intermediate transfer gears 51, whereas the transfer shaft 50 may be supported by the corresponding main journal 42 and the adjacent crank webs 44. Hence, in the embodiment as shown in Figs. 1-6 the intermediate gear shafts 13 are radially supported by both the crank web 4 and a separate supporting element 16, wherein the supporting element 16 is attached to the crank web 4 at a circumferential side thereof and the first and second intermediate transfer gear shafts 13, 13'' are radially supported by both the crank webs 4 and separate supporting elements 16', 16'', wherein the supporting elements 16, 16'' are attached to respective crank webs 4 at circumferential sides thereof, whereas in the embodiment as shown in Figs. 7 and 8 the intermediate transfer gears 51 are mounted to intermediate gear shafts 60 that are radially supported by a separate supporting element 53, wherein the supporting element 53 is attached to the crank web 44 at a side where the eccentric member 45 is located.

[0059] Figs. 10-15 show still another alternative embodiment of a crankshaft 80 according to the invention. The crankshaft 80 is suitable for a six-cylinder in-line four-stroke Diesel engine, but is also suitable for an Otto engine. The left side of the crankshaft 80 in Figs. 10 and 11 is defined as a front end of the crankshaft 80 and the right side of the crankshaft 1 in Fig. 10 is defined as a rear end of the crankshaft 80.

[0060] Similar to the crankshaft 1 as shown in Fig. 1 the crankshaft 80 has seven main journals 82 which are supported by an engine block (not shown) when the crankshaft 80 is mounted to the engine block of an internal combustion engine. Furthermore, the crankshaft 80 comprises six crankpins 83 and six pairs of crank webs 84 at opposite sides of the respective crankpins 83. When mounted in an internal combustion engine the crankshaft 80 is rotatable with respect to the engine block about the crankshaft axis 81 which forms a centreline through the main journals 82. Each of the crank webs 84 is located between the adjacent main journal 82 and the adjacent crankpin 83 thereof as seen in longitudinal direction of the crankshaft axis 81. The main journals 82, the crank webs 84 and the crankpins 83 are made in one piece. In an alternative embodiment the crankshaft 80 may have a different number of main journals 82, crankpins 83 and crank webs 84 for an internal combustion engine including a different number of cylinders.

[0061] The crankshaft 80 is provided with six eccentric members 85 which are rotatably mounted on the respective crankpins 83. The eccentric members 85 may be similar to the eccentric member 6 as shown in Fig. 6. Each of the eccentric members 85 is rotatable with respect to the corresponding crankpin 83 about a crankpin axis and comprises a bearing portion 86 for supporting a big end of a connecting rod (not shown). The bearing portion 86 of each eccentric member 85 is circular cylindrical and has a centreline parallel to the crankpin axis of the corresponding crankpin 83. Each of the eccentric members 85 has a circular cylindrical inner wall including a centreline which coincides with the crankpin axis of the corresponding crankpin 83. Since the centreline of the bearing portion 86 is parallel to the crankpin axis they extend at a distance from each other. Hence, the bearing portion 86 and the inner wall of each eccentric member 85 are disposed eccentrically with respect to each other.

[0062] The eccentric member 85 closest to the front end of the crankshaft 80 has an external front eccentric member gear 87 and an external rear eccentric member gear 88. The front eccentric member gear 87 is located between the bearing portion 86 and the crank web 84 closest to the front end as seen in longitudinal direction of the crankshaft axis 81. The bearing portion 86 lies between the front eccentric member gear 87 and the rear eccentric member gear 88.

[0063] The front eccentric member gear 87 meshes with two external intermediate gears 89, which in turn mesh with an external central gear in the form of an auxiliary gear 90. The front eccentric member gear 87 and the auxiliary gear 90 are located behind each other as seen along the crankshaft axis 81. For this reason, the intermediate gears 89 are wider than each of the front eccentric member gear 87 and the auxiliary gear 90. In an alternative embodiment (not shown) the intermediate gears 89, the auxiliary gear 90 and the front eccentric member gear 87 may lie in a single plane.

[0064] The intermediate gears 89 are rotatably mounted to respective intermediate gear shafts 91, see Figs. 10 and 11, for example through needle bearings. The intermediate gears 89 are rotatable with respect to the respective intermediate gear shafts 91 about intermediate gear axes which extend parallel to the crankshaft axis 81. The intermediate gear shafts 91 are fixed to the crank web 84 closest to the front end of the crankshaft 80.

[0065] Fig. 11 shows that the auxiliary gear 90 is fixed to a central shaft in the form of an auxiliary shaft 92 through a bolt 93. The auxiliary gear 90 may be locked to the auxiliary shaft 92 in rotational direction thereof through splines but alternative means are conceivable. The auxiliary shaft 92 extends concentrically through a central through-hole through the main journal 82 and through the adjacent crank web 84 thereof at the front end of the crankshaft 80. The auxiliary shaft 92 has a centreline that coincides with the crankshaft axis 81 and is rotatable with respect to the corresponding main journal 82 about the crankshaft axis 81.

[0066] When the crankshaft 80 is applied in an internal combustion engine the angular position of the auxiliary shaft 92 can be adjusted with respect to the engine block in order to vary the compression ratio of the internal combustion engine, for example through a hydraulic control system or a worm - worm wheel mechanism as disclosed in EP 2 620 614 of the same applicant.

[0067] The front eccentric member gear 87, the intermediate gears 89 and the auxiliary gear 90 are dimensioned such that under operating conditions, in case of a standstill of the auxiliary shaft 92 with respect to the engine block, the corresponding eccentric member 85 is rotated with respect to the corresponding crankpin 83 at half speed of the speed of the crankshaft 80 with respect to the engine block and is rotated with respect to the corresponding crankpin 83 in opposite direction of the rotational direction of the crankshaft 80 with respect to the engine block. For this reason the gear ratio between the front eccentric member gear 87 and the auxiliary gear 90 equals two.

[0068] The intermediate gear shafts 91 are supported by a yoke-shaped separate supporting element 94 which in turn is fixed to the corresponding crank web 84 at a circumferential side thereof. In an alternative embodiment (not shown) the intermediate gears 89 may be fixed to the intermediate gear shafts 91, which in turn are rotatable with respect to the supporting element 94. In this case the yoke has a basis and two parallel legs extending from the basis. The yoke can be fit radially to the corresponding crank web 84 by moving it towards the crankshaft axis 81.

[0069] In the embodiment as shown in Figs. 10 and 11 the intermediate gears 89 as well as the corresponding supporting element 94 are mirror symmetrical with respect to a plane which is spanned by the crankshaft axis 81 and the crankpin axis of the crankpin 83 closest to the front end of the crankshaft 80, but this may be different in an alternative embodiment.

[0070] Fig. 15 shows a cross-section of the crankshaft 80 at the bearing portion 86 of the eccentric member 85 closest to the front end of the crankshaft 80. It can be seen that the rear eccentric member gear 88 of the eccentric member 85 meshes with two external first intermediate transfer gears 95 which in turn mesh with an external first transfer gear 96. The rear eccentric member gear 88 and the first transfer gear 96 are located behind each other as seen along the crankshaft axis 81. For this reason, the first intermediate transfer gears 95 are wider than each of the rear eccentric member gear 88 and the first transfer gear 96. In an alternative embodiment (not shown) the first intermediate transfer gears 95, the first transfer gear 96 and the rear eccentric member gear 88 may lie in a single plane.

[0071] The first intermediate transfer gears 95 are rotatably mounted to respective first intermediate transfer gear shafts 91', for example through needle bearings. The first intermediate transfer gear shafts 91' are mounted to the corresponding crank web 84 by a separate yoke-shaped supporting element 94' which in turn is fixed to the corresponding crank web 84 in a similar manner as the intermediate gear shafts 91 through their corresponding supporting element 94, see Figs. 10 and 11.

[0072] The first transfer gear 96 is fixed to a front end of a transfer shaft 97 through a bolt 98, see Figs. 11 and 15. An external second transfer gear 99 is fixed to a rear end of the transfer shaft 97 through a bolt 98', as well. The first and second transfer gears 96, 99 may be locked to the transfer shaft 97 in rotational direction thereof through splines, but alternative means are conceivable. The transfer shaft 97 is mounted inside a second one of the main journals 82 as counted from the front end of the crankshaft 80 and its adjacent crank webs 84 and rotatable with respect to that second one of the main journals 82 about the crankshaft axis 81.

[0073] The second transfer gear 99 meshes with two external second intermediate transfer gears 100 which in turn mesh with an external front eccentric member gear 101 of a second one of the eccentric members 85 as counted from the front end of the crankshaft 80. The front eccentric member gear 101 of the second one of the eccentric members 85 has the same dimensions as the rear eccentric member gear 88 of the eccentric member 85 closest to the front end. The first and second transfer gears 96, 99 are also the same, and the first and second intermediate transfer gears 95, 100 are also the same. This means that the second one of the eccentric members 85 rotates with respect to its corresponding crankpin 83 in the same direction and at the same speed as the eccentric member 85 closest to the front end with respect to its corresponding crankpin 83.

[0074] The second intermediate transfer gears 100 are rotatably mounted to respective second intermediate transfer gear shafts 91'', see Figs. 11 and 12. The second intermediate transfer gear shafts 91" are mounted to the corresponding crank web 84 by a separate yoke-shaped supporting element 94'' in a similar manner as the first intermediate transfer gear shafts 91' through their corresponding supporting element 94'. The third to sixth one of the eccentric members 85 of the crankshaft 80 as counted from its front end are drivably coupled to each other in a similar way through further transfer shafts, transfer gears, intermediate transfer gears and supporting elements such that the eccentric members 85 have the same motions about the respective crankpins 83.

[0075] In this case all of the eccentric members 85 have the same dimensions, i.e. the front and rear eccentric member gears 87, 88, 101 of each eccentric member 85 are the same.

[0076] In the embodiment as shown in Figs. 10-15 the auxiliary gear 90 comprises 27 teeth and the front eccentric member gear 87 of the eccentric member 85 closest to the front end comprises 54 teeth. Each of the intermediate gears 89 has 41 teeth, which allows to fit the corresponding supporting element 94 including the intermediate gears 89 in radial direction towards the crankshaft axis 81 to the corresponding crank web 84. In a mounted condition centrelines of the intermediate gear shafts 91 span a plane which is close to the crankshaft axis 81 or in which the crankshaft axis 81 lies.

[0077] Fig. 10 shows that the dimensions of the intermediate gears 89 and the first intermediate transfer gears 95 are different. The first and second intermediate transfer gears 95, 100 and the further intermediate transfer gears have 35 teeth each. Furthermore, the first and second transfer gears 96, 99 comprise 24 teeth each, which is also different from the dimensions of the auxiliary gear 90. The mentioned dimensions cause the first and second transfer gears 96, 99 and the further transfer gears to rotate with respect to the auxiliary shaft 92 when the main journals 82 are rotated about the crankshaft axis 80 and the auxiliary shaft 92 is kept at a fixed position. This is different from the embodiment as shown in Figs. 1-6, in which the dimensions are such that the first and second transfer gears 18, 21 and the further transfer gears would stand still together with the auxiliary shaft 14 during the same motion.

[0078] Fig. 12 shows a part of the crankshaft 80 where the second one of the eccentric members 85 as counted from the front end of the crankshaft 80 is located and Figs. 13 and 14 show separate subparts thereof. Fig. 14 illustrates that the yoke-shaped supporting element 94'' can be provided with a fitting plate 102 in order to adjust the positions of the second intermediate transfer gears 100 with respect to the corresponding crank web 84 before fixing them to each other through bolts 103. The adjustment may be desired in order to achieve an appropriate meshing of the intermediate transfer gears 100 with the second transfer gear 99 and the front eccentric member gear 101 of the second one of the eccentric members 85 as counted from the front end of the crankshaft 80. This also applies to the supporting element 94 which supports the intermediate gears 89 and the supporting element 94' which supports the first transfer gears 95.

[0079] It is noted that it is also possible to fit the supporting elements 94, 94' and 94'' including the intermediate gears 89 and the first and second intermediate transfer gears 95, 100 to the corresponding crank webs 84 in axial direction of the crankshaft axis 81.

[0080] In the embodiments as shown in Figs. 7 and 8 and Figs. 10-15 the separate supporting elements 53, 94', 94'' each support two intermediate transfer gears 51, two first intermediate transfer gears 95 and two second intermediate transfer gears 100. In order to achieve appropriate meshing of the gear train between two neighbouring eccentric members 45, 85, it may be required to mount the transfer shaft 50, 97 eccentrically with respect to the crankshaft axis 41, 81. In such a case the locations of the intermediate transfer gears 51 and the first and second intermediate transfer gears 95, 100 may be asymmetrical with respect to the crankshaft axis 41, 81. This depends on the angle between the crankpins 43, 83 at the neighbouring eccentric members 45, 85. This condition is defined in the following aspect of the invention: A crankshaft for an internal combustion engine including variable compression ratio comprising a main journal including a crankshaft axis, a first crankpin including a first crankpin axis, a first and second crank web at opposite sides of the first crankpin, a second crankpin including a second crankpin axis, a third and fourth crank web at opposite sides of the second crankpin, wherein the second and third crank web are adjacent to each other and the first crank web is adjacent to the main journal, a first eccentric member which is rotatably mounted on the first crankpin and which comprises a first bearing portion for supporting a big end of a connecting rod and an external first eccentric member gear located between the first bearing portion and the second crank web, a second eccentric member which is rotatably mounted on the second crankpin and which comprises a second bearing portion for supporting a big end of a connecting rod and an external second eccentric member gear located between the second bearing portion and the third crank web, a transfer shaft which extends through the second and third crank web and which is rotatable with respect to the second and third crank web about a transfer shaft axis, wherein an external first transfer gear is fixed to the transfer shaft at a side of the second crank web where the first eccentric member is located and an external second transfer gear is fixed to the transfer shaft at a side of the third crank web where the second eccentric member is located, wherein the first and second eccentric members are drivably coupled to each other through the transfer shaft such that rotation of the first eccentric member about the first crankpin causes the second eccentric member to rotate about the second crankpin by the same angle and in the same direction, wherein the first transfer gear meshes with two external first intermediate transfer gears which in turn mesh with the first eccentric member gear, wherein the second transfer gear meshes with two external second intermediate transfer gears, which in turn mesh with the second eccentric member gear, wherein preferably the first intermediate transfer gears are rotatably mounted to the second crank web through a separate supporting element that is fixed to the second crank web and the second intermediate transfer gears are rotatably mounted to the third crank web through a separate supporting element that is fixed to the third crank web, wherein the first and second transfer gears are the same and the first and second eccentric member gears are the same, wherein the first and second intermediate transfer gears are dimensioned and positioned such that the transfer shaft axis intersects an adjusting line which is perpendicular to a reference plane that is spanned by the first and second crankpin axes and which adjusting line intersects the crankshaft axis. This allows appropriate meshing between the mentioned gears. Depending on the angle between the neighbouring crankpins about the crankshaft axis the transfer shaft axis intersects the adjusting line at a certain location. This location may lie at the crankshaft axis or eccentrically thereof.

[0081] The invention is not limited to the embodiments shown in the drawings and described hereinbefore, which may be varied in different manners within the scope of the claims and their technical equivalents.

Claims

1. A crankshaft (1, 40, 80) for an internal combustion engine including variable compression ratio comprising a main journal (2, 42, 82) including a crankshaft axis (5, 41, 81), a crankpin (3, 43) including a crankpin axis (7) and a crank web (4, 44, 84) located between the main journal (2, 42, 82) and the crankpin (3, 43, 83) in longitudinal direction of the crankshaft axis (5, 41, 81), an eccentric member (6, 45, 85) which is mounted on the crankpin (3, 43, 83) and rotatable with respect to the crankpin (3, 43) about the crankpin axis (7), wherein the eccentric member (6, 45, 85) comprises a bearing portion (8, 46, 86) for supporting a big end of a connecting rod, which bearing portion (8, 46, 86) has a centreline extending parallel to the crankpin axis (7), and an external eccentric member gear (9, 48, 87) between the bearing portion (8, 46, 86) and the crank web (4, 44, 84) as seen in longitudinal direction of the crankshaft axis (5, 41, 81), wherein the eccentric member gear (6, 45, 85) is driveably coupled to an external central gear (12, 49, 90) through an external intermediate gear (11, 51, 89), wherein the central gear (12, 49, 90) is fixed to a central shaft (14, 50, 92) which extends through the main journal (2, 42, 82) and through the crank web (4, 44, 84) and which is rotatable with respect to the main journal (2, 42, 82) and the crank web (4, 44, 84), wherein the intermediate gear (11, 51, 89) is rotatably mounted to the crank web (4, 44, 84) and meshes with both the eccentric member gear (9, 48, 87) and the central gear (12, 49, 90), characterized in that the intermediate gear (11, 51, 89) is mounted to an intermediate gear shaft (13, 60, 91) that is radially supported by both the crank web (4) and a separate supporting element (16), which is attached to the crank web (4) at a circumferential side thereof or by a separate supporting element (53, 94), which is attached to the crank web (44) at a side where the eccentric member (45) is located or at a circumferential side of the crank web (84).

2. A crankshaft (1) according to claim 1, wherein the intermediate gear shaft (13) is radially supported by both the crank web (4) and the supporting element (16), which is attached to the crank web (4) at a circumferential side thereof and wherein the intermediate gear (11) is rotatable with respect to the intermediate gear shaft (13) which in turn is fixed to the crank web (4) and the supporting element (16) or wherein the intermediate gear shaft (60, 91) is radially supported by the supporting element (53, 94), which is attached to the crank web (44, 84) at a side where the eccentric member (45) is located or at a circumferential side of the crank web (84) and wherein the intermediate gear (51, 89) is rotatable with respect to the intermediate gear shaft (60, 91) which in turn is fixed to the supporting element (53, 94).

3. A crankshaft (1) according to claim 2, wherein the intermediate gear shaft (13) is radially supported by both the crank web (4) and the supporting element (16), which is attached to the crank web (4) at a circumferential side thereof and wherein the intermediate gear shaft (13) is clamped between the crank web (4) and the supporting element (16).

4. A crankshaft (1) according to any one of the preceding claims, wherein the intermediate gear shaft (13) is radially supported by both the crank web (4) and the supporting element (16), which is attached to the crank web (4) at a circumferential side thereof, wherein the intermediate gear (11) is a first intermediate gear, the supporting element (16) is a first supporting element and the intermediate gear shaft (13) is a first intermediate gear shaft, wherein the eccentric member gear (9) is driveably coupled to the central gear (12) through an external second intermediate gear, which is rotatably mounted to the crank web (4) and meshes with both the eccentric member gear (9) and the central gear (12), wherein the second intermediate gear is mounted to a second intermediate gear shaft that is radially supported by both the crank web (4) and a separate second supporting element, wherein the second supporting element is attached to the crank web (4) at a circumferential side thereof at an angular distance from the first supporting element about the crankshaft axis (5).

5. A crankshaft (1) according to claim 4, wherein the first and second intermediate gears (11) as well as the first and second supporting elements (16) are mirror symmetrical with respect to a plane which is spanned by the crankshaft axis (5) and the crankpin axis (7).

6. A crankshaft (1) according to any one of the claims 1-2, wherein the intermediate gear shaft (60, 91) is radially supported by the supporting element (53, 94), which is attached to the crank web (44, 84) at a side where the eccentric member (45) is located or at a circumferential side of the crank web (84), wherein the intermediate gear (51, 89) is a first intermediate gear and the intermediate gear shaft (60, 91) is a first intermediate gear shaft, wherein the eccentric member gear (48, 87) is driveably coupled to the central gear (49, 90) through an external second intermediate gear, which is rotatably mounted to the crank web (44, 84) and meshes with both the eccentric member gear (48, 87) and the central gear (49, 90), wherein the second intermediate gear is mounted to a second intermediate gear shaft that is radially supported by the supporting element (53, 94).

7. A crankshaft (1) according to claim 6, wherein the supporting element (94) has a yoke-shape which is attached to the crank web (84) at a circumferential side of the crank web (84) and which radially supports the first and second intermediate gear shafts (91).

8. A crankshaft (1) according to any one of the preceding claims, wherein the main journal (2), the crank web (4) and the crankpin (3) are made in one piece.

9. A crankshaft (1) according to any one of the preceding claims, wherein the central shaft (14, 50) extends concentrically through the main journal (2, 42).

10. A crankshaft (1) according to any one of the preceding claims, wherein the central gear (12, 49) is locked with respect to the central shaft (14, 50) in rotational direction of the central shaft (14, 50) through splines, wherein the number of splines is selected such that the relative positions of the central shaft (14, 50) and the eccentric member (6, 45) are independent from the rotational position of the central gear (12) with respect to the central shaft (14).

11. A crankshaft (1) according to any one of the preceding claims, wherein the eccentric member gear is a first eccentric member gear (9, 87) and the eccentric member (6, 85) has a second eccentric member gear (10, 88) at an opposite side of the bearing portion (8, 86), which is driveably coupled to an external first transfer gear (18, 96) through an external intermediate transfer gear (17, 95), wherein the first transfer gear (18, 96) is fixed to one end of a transfer shaft (19, 97) which extends successively through a first further crank web (4, 84), a further main journal (2, 82) and a second further crank web (4, 84) and which is rotatable with respect to the further main journal (2, 82) and the first and second further crank webs (4, 84), wherein the intermediate transfer gear (17, 95) is rotatably mounted to the first further crank web (4, 84) and meshes with both the second eccentric member gear (10, 98) and the first transfer gear (18, 96), wherein the intermediate transfer gear (17, 95) is mounted to an intermediate transfer gear shaft (13') that is radially supported by both the first further crank web (4) and a separate supporting element (16'), which is attached to the first further crank web (4) at a circumferential side thereof or by a separate supporting element (94'), which is attached to the first further crank web (44, 84) at a side where the eccentric member is located or at a circumferential side of the first further crank web (84), wherein an opposite end of the transfer shaft (19, 97) is provided with a second transfer gear (21, 99) which is driveably coupled to a first eccentric member gear (23, 101) of a further eccentric member (6, 85) through a further external intermediate transfer gear (22, 100), wherein the further intermediate transfer gear (22, 100) is rotatably mounted to the second further crank web (4, 84) and meshes with both the first eccentric member gear (23, 101) of the further eccentric member (6, 85) and the second transfer gear (21, 99), wherein the further intermediate transfer gear (22, 100) is mounted to an intermediate transfer gear shaft (13'', 91'') that is radially supported by both the second further crank web (4) and a separate supporting element (16''), which is attached to the second further crank web (4) at a circumferential side thereof or by a separate supporting element (94''), which is attached to the second further crank web (44, 84) at a side where the further eccentric member (45) is located or at a circumferential side of the second further crank web (84).

12. A crankshaft (1) according to claims 11, wherein the eccentric member (6, 85) and the further eccentric member (6, 85) are part of a plurality of eccentric members (6, 85) which are drivably coupled to each other in a similar way as the eccentric member (6, 85) and the further eccentric member (6, 85), wherein each of the first and second eccentric member gears (9, 10, 22, 87, 88, 101) has a number of teeth that equals a whole number times the number of the plurality of the eccentric members (6, 85) and each of the central gear and the first and second transfer gears has a number of teeth that equals 0.5 times the number of teeth of the first eccentric member gear (9, 87) .

13. An internal combustion engine including variable compression ratio, comprising a crankshaft (1) according to any one of the preceding claims and an engine block which supports at least the main journal (2), wherein the main journal (2) is rotatable with respect to the engine block about the crankshaft axis (5).

14. A method of assembling the crankshaft (1) according to any one of the claims 1-12, wherein the intermediate gear (11) and the intermediate gear shaft (13) are mounted to the crank web (4) by the supporting element (16) after mounting the eccentric member (6) on the crankpin (3) and positioning the eccentric member (6) in rotational direction about the crankpin (3) and after mounting the central shaft (14) inside the main journal (2) and the crank web (4) and the central gear (12) to the central shaft (14).

15. A method according to claim 14, wherein after positioning the eccentric member (6) at the crankpin (3) the eccentric member (6) is temporarily fixed to the crank web (4) during which the intermediate gear (11) is engaged to the central gear (12) and the eccentric member gear (9) and the supporting element (16) is fixed to the crank web (4).

Images