DEVICE FOR CONTROLLING THE PHASE ANGLE BETWEEN A FIRST AND A SECOND CRANKSHAFT

Abstract: The present invention relates to a device for regulating the phase angle between a first and a second crankshaft of an internal combustion engine. Said internal combustion engine comprises primary cylinders which communicate with secondary cylinders and in every primary cylinder there is movably arranged a primary piston which is connected to the first crankshaft and in every secondary cylinder there is movably arranged a secondary piston which is connected to the second crankshaft. Said first and second crankshafts are connected to each other by means of a transmission with the device comprising a crankshaft extension for obtaining the control of the phase angle, said extension being fixed against rotation and displaceably connected to one of said crankshafts and via a grooved portion rotationally connected to the second of said crankshafts. When the crankshaft extension in displaced rotation is obtained in said grooved portion which results in a corresponding phase angle shift.

Description: TITLE Device for controlling the phase angle between a first and a second crankshaft. TECHNICAL FIELD OF THE INVENTION The present invention relates to a device for controlling the phase angle between a first and a second crankshaft of an internal combustion engine, said internal combustion engine comprising at least one primary cylinder which communicates with at least one secondary cylinder, a primary piston being movably arranged in each primary cylinder, said primary piston being connected to the first crankshaft, and in every secondary cylinder there being movably arranged a secondary piston which is connected to the second crankshaft, with said first and second crankshafts being connected to each other by means of a transmission, and with the device comprising means for obtaining the phase shift control and a crankshaft extension intended for said phase angle control, which is connected fixed against rotation to one of said crankshafts, and rotationally connected to the second of said crankshafts, according to the preamble of appended claim 1. BACKGROUND ART In internal combustion engines of the piston engine kind, for example otto engines or diesel engines with one or several cylinders with pistons moving laterally in them, a fuel air mixture is compressed in a combustion chamber, where it is ignited and burnt when the piston is in its uppermost position. The compression of said fuel air mixture is determined by the compression ratio of the engine in question, defined as the ration between the volume in the cylinder when the piston is in its lowest and uppermost positions. Modern otto engines usually have a compression ration around 10:1 (compression figure 10), while supercharged engines, for example turbo engines, have a lower and diesel engines a considerably much higher compression ratio. The compression ratio of the engine affects the combustion of the fuel air mixture. A high compression contributes to an effective combustion, which in turn contributes to a high efficiency and low fuel consumption. At the same time there is, however, a need for a high octane fuel, particularly in the case of high engine loads, in order to avoid uncontrolled combustion. Against the above described background, it is thus desirable to be able to vary the compression ration during operation depending on fuel quality and engine load. US 5,638,777 describes an internal combustion engine with a variable compression ratio. The engine has a number of primary cylinders, a corresponding number of secondary cylinders which each communicates with a corresponding primary cylinder. In each primary cylinder, there is arranged a primary piston connected to a first crankshaft, said primary piston being arranged to carry out a movement back and forth, and in a corresponding way there is in every secondary cylinder a secondary piston connected to a second crankshaft, said secondary piston being arranged to carry out a movement back and forth. Between said first and second crankshafts there is arranged a gear wheel transmission and a device for phase angle shift between the shafts, with the purpose of obtaining a compression ratio which depends on the current load of the engine. Said device comprises a driving shaft fixedly connected to said second crankshaft, equipped with spiral-shaped splines concentrically arranged inside an outer casing. The outer casing exhibits a first gear wheel intended to interact with a second gear wheel arranged on said first crankshaft, and internal spiral- shaped splines. Between the outer casing and the drive shaft there is arranged a displaceable pipe element, the enveloping surface of which is equipped with spiral-shaped splines intended to cooperate with said internal spiral-shaped splines of the outer casing. The ' pipe element is, in addition, equipped with internal spiral-shaped splines which cooperate with said spiral- shaped splines arranged on the drive shaft. In the case of axial displacement of the pipe element, for example in the case of a hydraulic control system, a phase angle shift is obtained between said first gear wheels and said drive shaft, and thus also between the first and second crankshafts. Although the device known by said US 5,638,777 enables good control of the phase shift between the crankshafts, it does have certain drawbacks. One drawback is that it is relatively expensive to manufacture it, since it is relatively complex in its design, especially concerning the displaceable pipe element, which is equipped both on the enveloping surface and internally with spiral-shaped splines. Another drawback is that the pipe element including said hydraulic control system needs relatively much space in the axial direction, which makes it difficult to install it in cars with lateral multi- cylinder engines. Furthermore, assembly/disassembly of this known device is relatively difficult to carry out. SUMMARY OF THE INVENTION The object of the present invention is to create the possibility to achieve a device for controlling the phase angle between a first and a second crankshaft of an internal combustion engine, which, relative to previous technology is more cost-efficient to manufacture. This purpose is obtained by means of the invention described in claim 1. In the claims which follow claim 1 , preferred embodiments of the invention are described. The device according to the invention is, as mentioned previously, arranged between a first and a second crankshaft of an internal combustion engine which comprises at least one primary cylinder which communicates with at least one secondary cylinder, with a primary piston being movably arranged in each primary cylinder, said primary piston being connected to the first crankshaft, and in every secondary cylinder there is movably arranged a secondary piston which is connected to the second crankshaft, with said first and second crankshafts being connected to each other by means of a transmission, with the device comprising means for obtaining the phase shift control and a crankshaft extension intended for said phase control, the extension being connected fixed against rotation to one of said crankshafts, and rotationally fixed to the other of said crankshafts. By means of said crankshaft extension being displaceably arranged relative to one of said crankshafts, a mechanical interface is obtained at which phase angle shift can be done without introducing further components. According to a preferred embodiment, said means is arranged to bring about axial displacement of the crankshaft extension, as a result of which the phase angle will shift. Said means preferably consist of a hydraulic piston arranged in a housing for affecting the crankshaft extension in at least one direction. This enables quick phase angle shift with good precision at high engine loads. According to another preferred embodiment, said hydraulic piston is also arranged to affect the crankshaft extension in a second direction, to enable optimal control of the phase angle between said first and second crankshaft, for example in the case of rapid shifts in engine load. Since the hydraulic piston according to the present invention is arranged to not rotate relative to said housing, a simplified oil sealing is obtained between the piston and the housing. Furthermore, this creates favourable conditions for obtaining a simple and durable arrangement for supplying oil to the piston. In a third preferred embodiment of the present invention, said crankshaft extension in its one end is equipped with splines which enables a displaceable connection fixed against rotation to one of said crankshafts. The crankshaft extension is, additionally, at its other end equipped with a grooved portion, preferably trapeze grooves, for said rotateable connection. By providing the crankshaft extension according to the present invention with a flange between said spline equipped portion and the grooved portion which the hydraulic piston is arranged to affect, a compact and axially short device for controlling the phase angle is enabled, which is extremely advantageous in motor vehicles. Other advantages and objects of the invention can be found in the appended claims and in the description below. DESCRIPTION OF THE FIGURES The invention will in the following be described in connection to examples of preferred embodiments and in the appended figures in which Fig. 1 shows a perspective view partially in cross-section of an internal combustion engine provided with a device for controlling the phase angle according to the present invention, and Fig. 2 shows a side view in partial cross-section of a preferred embodiment of a device for regulating the phase angle according to the present invention. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Fig. 1 shows, in a perspective view in partial cross-section, an internal combustion engine 1 with an engine block 2 with primary cylinders 3a, 3b, 3c, 3d, which communicate via channels 4a, 4b, 4c, 4d with secondary cylinders 5a, 5b, 5c, 5d arranged in the cylinder head 6 of the internal combustion engine 1. In every primary cylinder, primary pistons 7a, 7b, 7c, 7d are movingly arranged, which by means of primary crankshafts 8a, 8b, 8c, 8d are connected to a first crankshaft 9, and in every secondary cylinder 5a, 5b, 5c, 5d there are movingly arranged secondary pistons 10a, 10b, 10c, 10d which by means of secondary connecting rods 11a, 11b, 11c, 11d are connected to the second crankshaft 12. Said first crankshaft 9 is mounted in bearings in the engine block 2, and said second crankshaft 12 is mounted in bearings in . the cylinder head 6. The crankshafts 9, 12 are connected to each other by means of a transmission 13 comprising a cogged driving belt 14 which runs over a first 15 and a second 16 driving wheel, the size of the driving wheels 15, 16 being chosen so that the second crankshaft 12 rotates with half the rpm's of the first crankshaft 9. The second driving wheels 16 partially envelope the housing 18 of the device for phase shift control 17 which is arranged on the cylinder head 6. With reference to Fig. 2, a preferred embodiment of the device or phase shift control 17 will now be described. In the embodiment shown, the second driving wheel 16 is mounted in the housing 18 by means of ball bearings 19, preferably an angle contact layer with double rows. The driving wheel 16 is in addition equipped with a grooved portion 20, which interacts with the corresponding grooved portion 22 on a crankshaft extension 21. Said grooved portions 20, 22 are equipped with grooves of the trapeze groove kind with twelve inlets which afford a shift in angle of 120 degrees at 20 mm axial displacement of the crankshaft extension 21. The crankshaft extension 21 in addition exhibits a portion equipped with splines 23 which cooperates with a corresponding portion 24 equipped with splines on the second crankshaft 12 for said connection which is displaceable and fixed against rotation. The axis of rotation of the crankshaft extension 21 thus coincides with the axis of rotation of the second crankshaft 12. The crankshaft extension 21 is made of steel and is, at the grooved portion 22 and the portion 23, equipped with splines, covered with a layer consisting of chemically deposited nickel, which has been impregnated and surface coated with a fluoral plastic and thermically hardened. In this way, low friction is obtained, which means that reduced forces will be necessary for said phase shift control. Coatings of this kind are commercially available under the brand name Nedox®, and have previously been used, among other things, as surface coating on gear cogs and on molding tools for plastic products with small trailing angles. The device 17 in addition comprises means 25 to achieve the displacement of the crankshaft extension 21. For this purpose, the crankshaft extension 21 is thus provided with a flange 26 between said grooved portion 22 and the spline equipped portion 23, on which a hydraulic piston 27 which is displaceably arranged in the housing 18 is arranged to work. Between the flange 26 and the hydraulic piston 27 there are arranged bearings 28, 29 of the needle bearings kind, which are arranged to absorb the axial forces which will arise as a result of the torque transferred over said grooved portions 20, 22. Since the hydraulic piston 27 is arranged to surround the crankshaft extension 21 , the arrangement 17 will become compact and short in the axial direction, which is extremely advantageous in motor vehicles. In addition, the hydraulic piston 27 on its enveloping surface exhibits an abutment 30 which divides a chamber into a first 31 and a second 32 sub- chamber, which each communicate with a first 33 and a second 34 oil conduit, respectively. The oil conduits 33, 34 are connected to a not shown hydraulic control valve which, depending on a control system of the engine 1 , controls the oil supply to one or the other sub-chamber 31 , 32, and in so doing causes a phase angle shift between said first 9 and second 12 crankshaft. By using part of the oil which is pressurized by the servo control pump which is usually to be found on the engine 1 , there is no need for an extra oil pump. The housing 18 is additionally provided with o-rings 35, 36, which are arranged to be in contact with the piston 27, one on each side of said abutment 30, and to function as oil sealings for the sub-chambers 31 , 32. On the outer perimeter of the abutment 30 there is arranged a corresponding o- ring for oil sealing between said first 31 and second 32 sub-chamber. Since the crankshaft extension 21 is connected to the piston 27 via the bearings 28, 29 there is, in principle, no torque transferred to the piston 27 when the crankshaft extension 21 rotates. As a result of this, the piston 27, due to friction between it and the o-rings 35, 36, 37, will not rotate with the crankshaft extension 21 when it rotates, which simplifies said oil sealing. According to what has been described above, the function of the device 17 is as follows: Supply of oil through the conduit 33 to the sub-chamber 31 results in a build-up of pressure in the sub-chamber 31 , whose volume is limited by the abutment 30 arranged on the piston 27. This in turn causes the piston 27 to be pressed in the direction of the cylinder head 6. Since the crankshaft extension 21 via the bearings 28, 29 is connected to the piston 27, there is thus a relative axial displacement in the spline coupling 23, 24 between the crankshaft extension 21 and the crankshaft 12. At the same time, there is a corresponding relative axial displacement between the crankshaft extension 21 and the second driving wheel 16, while the driving wheel 16 rotates in the trapeze grooves 20, 22, which causes a phase angle shift between the first 9 and the second 12 crankshaft. In a corresponding manner, a shift in phase angle in the opposite direction is obtained when supplying oil through the conduit 34 to the sub-chamber 32. The invention is not limited to that which has been described above, other embodiments are also possible. For example, an electrical engine instead of said hydraulic piston can be arranged to influence the flange of the crankshaft extension. Displacement of the crankshaft extension can also take place against a coil, for example a spiral coil, with said hydraulic piston or electrical engine only being arranged to cause displacement in one direction. According to an alternative embodiment, the crankshaft extension is arranged in the opposite direction, so that said spline coupling can be arranged at the second driving wheel, and said trapeze groove is arranged between the crankshaft extension and the second crankshaft. In yet another alternative embodiment, the device for control of phase angle, in contrast to the above described embodiment, is arranged at the first crankshaft. Finally, the crankshaft extension can, instead of said splines, be equipped with another cross-section, for example a square cross-section which interacts with a corresponding square hole on the crankshaft for obtaining said displaceable connection which is fixed against rotation.

Claims: CLAIMS 1. Device for controlling the phase angle between a first (9) and a second (12) crankshaft of an internal combustion engine (1 ), said internal combustion engine (1) comprising at least one primary cylinder (3a, 3b, 3c, 3d) which communicates with at least one secondary cylinder (5a, 5b, 5c, 5d), in each primary cylinder (3a, 3b, 3c, 3d) there being arranged a primary piston (7a, 7b, 7c, 7d) which is connected to the first crankshaft (9), and in every secondary cylinder (5a, 5b, 5c, 5d) there being movingly arranged a secondary piston (10a, 10b, 10c, 10d) which is connected to the second crankshaft (12), with said first (9) and second (12) crankshaft being connected to each other by means of a transmission (13), with the device (17) comprising means (25) for obtaining the phase shift control, and a crankshaft extension (21) intended for said phase angle control, which is connected fixed against rotation to one of said crankshafts (9, 12) and rotationally attached to the second of said crankshafts (9, 12) characterized in that said crankshaft extension (21 ) is axially movably arranged relative to one of said crankshafts (9, 12). 2. Device according to claim 1, characterized in that said means (25) is arranged to obtain an axial displacement of the crankshaft extension (21). 3. Device according to claim 2, characterized in that said displacement means comprise a hydraulic piston (27) arranged in a housing (18) for influencing the crankshaft extension (21) in at least a first direction. 4. Device according to claim 3, characterized in that said hydraulic piston (27) is also arranged for influencing the crankshaft extension (21) in a second direction. 5. Device according to claim 3 or 4, characterized in that said hydraulic piston (27) is arranged rotationally fixed relative to said housing (18). 6. Device according to any of claims 1-5, characterized in that said crankshaft extension (21) exhibits a first portion (23) equipped with splines for said connection fixed against rotation. 7. Device according to claim 6, characterized in that said first portion (23) is arranged to admit said axial displaceability. 8. Device according to claim 6 or 7, characterized in that said crankshaft extension (21) exhibits a second portion (22) equipped with grooves for said rotational connection. 9. Device according to claim 8, characterized in that said crankshaft extension (21) exhibits a flange (26) between said first and second portions (22, 23) with the hydraulic piston (27) being arranged to affect said flange (26).

Inventors: HALLENSTVEDT ODDBJOERN, KRISTIANSSON BO, NILSSON STEFAN, RYDBERG ANDERS, HALLENSTVEDT, ODDBJOERN, KRISTIANSSON, BO, NILSSON, STEFAN, RYDBERG, ANDERS
Applicants: HALLENSTVEDT ODDBJOERN, KRISTIANSSON BO, NILSSON STEFAN, RYDBERG ANDERS, VOLVO LASTVAGNAR AB, HALLENSTVEDT, ODDBJOERN, KRISTIANSSON, BO, NILSSON, STEFAN, RYDBERG, ANDERS
Application year: 2001
Main classification: F02D15
IPC codes: F02D15, F16C3, F16D3