ENGINE ARRANGEMENT WITH A FORCE DISTRIBUTOR FOR CHANGING THE COMPRESSION RATIO BY MEANS OF AN ACTUATOR

Abstract

Motor assembly (100) comprising: a crankshaft (502); a bell crank (110) pivotally mounted on the crankshaft (502), the bell crank (110) having a first end (120) and a second end (122) remote from the first end (120); a connecting rod connected to the first end (120) of the bell crank (110); a control shaft (514); a control member (114) mounted on the control shaft (514) and connected to the second end (122) of the bell crank (110); an output gear (504) fixed to the crankshaft (502); a drive gear (512) fixed to the control shaft (514); an actuator; and a power split transmission (500) that splits the torque from the output gear (504) between the input gear (512) via a first torque path and the actuator via a second torque path; characterized in that the actuator comprises a variable displacement oil pump (518) driven via the second torque path.

Description

TECHNICAL AREA

[0001] The present disclosure relates to an engine assembly according to the preamble of claim 1, having a power distributor for varying the compression ratio by means of an actuator. A generic engine assembly is essentially disclosed in JP 2009 - 85 187 A. Regarding the further prior art, reference is made to the documents DE 10 2008 059 870 A1, DE 10 2009 006 633 A1, and DE 10 2011 108 185 A1. INTRODUCTION

[0002] A variable compression ratio (VCR) engine typically comprises an engine block defining a cylinder, a piston positioned within the cylinder, a connecting rod, a crankshaft, a bell crank, a timing link, a timing shaft, and a transmission. The bell crank is pivoted to the crankshaft. The connecting rod connects the piston to one end of the bell crank. The timing link connects the other end of the bell crank to the timing shaft.

[0003] As the piston moves in the cylinder, the connecting rod exerts a force on the bell crank, and the control link transfers the force from the bell crank to the control shaft, causing the control shaft to rotate. The transmission transfers the power from the control shaft back to the crankshaft, ensuring that the rotation of the two shafts is in sync (or in phase). Additionally, the transmission couples an actuator, such as an electric motor, to the control shaft. The electric motor is operable to vary the speed of the control shaft relative to the speed of the crankshaft, thereby changing the cylinder's compression ratio.

[0004] The transmission of a VCR motor typically includes an output gear attached to the crankshaft, a drive gear attached to the timing shaft, a first gear mounted on a transmission shaft (or carrier), and a second gear mounted on the transmission shaft (or carrier). The first gear meshes with the output gear, and the second gear meshes with the drive gear. Additionally, the VCR motor's electric motor (or a shaft of the electric motor) is typically attached to the transmission shaft (or carrier) so that the electric motor rotates with the transmission shaft.

[0005] In VCR motors, such as the one described above, the electric motor may work against the full torque of the crankshaft to adjust the phase position of the timing shaft relative to the crankshaft. Therefore, the electric motor may need to be large and deliver high torque, and an expensive, high-ratio reduction gear may be required to couple the electric motor to the transmission shaft. Furthermore, the parasitic losses of such a VCR motor are high. SUMMARY

[0006] In one exemplary aspect, an engine assembly includes a crankshaft, a bell crank pivotally mounted on the crankshaft, the bell crank having a first end and a second end opposite the first end, a connecting rod connected to the first end of the bell crank, a control shaft, a control member mounted on the control shaft and connected to the second end of the bell crank, an output gear attached to the crankshaft, a drive gear attached to the control shaft, an actuator, and a split-torque transmission that splits torque from the output gear between the drive gear via a first torque path and the actuator via a second torque path. According to the invention, the actuator is a variable displacement oil pump driven via the second torque path.

[0007] In another exemplary aspect, the power split transmission includes a planetary gear set having a carrier meshing with the output gear, a sun gear meshing with the actuator, a ring gear meshing with the drive gear, and a planetary gear rotatably mounted on the carrier and meshing with the sun gear and the ring gear.

[0008] In another exemplary aspect, the power split transmission includes a cycloidal gear set having a ring gear meshing with the output gear, a sun gear meshing with the actuator, a transmission shaft meshing with the input gear, and a cycloidal reduction gear connected to the transmission shaft by a series of bolts.

[0009] In another exemplary aspect, the gear ratio of the second torque path is higher than the gear ratio of the first torque path.

[0010] In another exemplary aspect, increasing the displacement of the variable displacement oil pump slows the speed of the variable displacement pump to advance the timing shaft and increase a compression ratio of the engine assembly.

[0011] In another exemplary aspect, by decreasing the displacement of the variable displacement oil pump, the speed of the variable displacement pump is increased to retard the timing shaft and decrease a compression ratio of the engine assembly.

[0012] In another exemplary aspect, the oil pump is connected to a variable orifice.

[0013] In another exemplary aspect, by decreasing the variable opening, the speed of the oil pump is slowed to move the control shaft forward and increase a compression ratio of the engine assembly.

[0014] In another exemplary aspect, by increasing the variable orifice, the speed of the oil pump is increased to retard the timing shaft and reduce a compression ratio of the engine assembly.

[0015] Further applicability of the present disclosure will become apparent from the detailed description provided below. It should be understood that the detailed description and specific examples are provided for purposes of illustration only.

[0016] The above features and advantages, as well as other features and advantages of the present invention, are readily apparent from the following detailed description, including the claims, and exemplary embodiments, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] This disclosure will become more fully apparent from the detailed description and the accompanying drawings, in which: Fig. 1 is a schematic sectional view of an engine assembly with a variable compression ratio (VCR) transmission; Fig. Figure 2 is a schematic diagram of a conventional VCR transmission; Fig. 3 is a schematic diagram of an exemplary embodiment of a VCR transmission according to the present disclosure; Fig. 4 is a schematic diagram of another exemplary embodiment of a VCR transmission according to the present disclosure; Fig. 5 is a schematic representation of another exemplary embodiment of a VCR transmission according to the present disclosure; and Fig. 6 is a schematic illustration of an additional exemplary embodiment of a VCR transmission according to the present disclosure. DETAILED DESCRIPTION

[0018] Reference will now be made in detail to several examples of the disclosure illustrated in the accompanying drawings. Wherever possible, the same or similar reference numerals are used throughout the drawings and the description to refer to the same or similar parts or steps. The drawings are in simplified form and not to scale. For convenience and clarity only, directional terms such as top, bottom, left, right, on, over, above, below, beneath, back, and front may be used with reference to the drawings. These and similar directional terms are not to be construed as limiting the scope of the disclosure in any way.

[0019] To solve the above-mentioned problems, a VCR engine according to the present disclosure includes a power-split transmission with a torque path from the control shaft to the crankshaft and another torque path from the actuator to the crankshaft. The torque path between the control shaft and the crankshaft carries a higher torque than the torque path between the actuator and the crankshaft. With this arrangement, the actuator operates against only a fraction of the torque of the VCR transmission. Thus, an actuator used by an exemplary embodiment of the present disclosure can be smaller than an actuator commonly used to adjust the compression ratio of a VCR engine.

[0020] According to the drawings, in which like reference numerals correspond to the same or similar components in the different figures, Fig. 1 shows an engine assembly 100 including a cylinder 102, a piston 104, a connecting rod 106, a crankshaft 108, a bell crank 110, a control shaft 112, a control member 114, and a gear 116. The piston 104 reciprocates within the cylinder 102 as an air-fuel mixture is combusted within the cylinder 102. For illustration, Fig. 1 shows only one cylinder of the engine assembly 100. However, the engine assembly 100 may include additional cylinders. The engine assembly 100 may be a gasoline engine or a compression-ignition or diesel engine.

[0021] The bell crank 110 is mounted on the crankshaft 108 such that the bell crank 110 can pivot about a rotational axis 118 of the crankshaft 108. The bell crank 110 has a first end 120 and a second end 122 facing away from the first end 120. The bell crank 110 may have nodes or bolts for connection to the crankshaft 108, the connecting rod 106, and the control member 114, wherein the nodes or bolts may be T-shaped, triangular, or arranged in series.

[0022] The connecting rod 106 connects the piston 104 to the first end 120 of the bell crank 110. The connecting rod 106 can be pivotally connected to the piston 104 and the bell crank 110, e.g., by means of bolts (not shown). The control member 114 is mounted on the control shaft 112 such that the control member 114 can pivot about a rotational axis 124 of the control shaft 112. The control member 114 is connected to the second end 122 of the bell crank 110. The connecting rod 106 can be pivotally connected to the bell crank 110, e.g., by means of a bolt (not shown).

[0023] The connecting rod 106, the bell crank 110, and the control member 114 together convert the translational movement of the piston 104 into a rotational movement of the crankshaft 108. In other words, the connecting rod 106, the bell crank 110, and the control member 114 cause the crankshaft 108 to rotate as the piston 104 reciprocates within the cylinder 102. As the piston 104 reciprocates within the cylinder 102, the connecting rod 106 pivots about the first end 120 of the bell crank 110 (e.g., rocks back and forth). The pivoting movement of the connecting rod 106 causes the bell crank 110 to pivot about the rotational axis 118 of the crankshaft 108 (e.g., rocks back and forth). The pivoting movement of the reversing lever 110 causes a pivoting (e.g. rocking back and forth) of the control member 114 about the rotational axis 124 of the control shaft 112.

[0024] As will be further described, the transmission 116 synchronizes the rotation of the crankshaft 108 with the rotation of the control shaft 112. In addition, the transmission 116 connects an actuator (in Fig. 1 not shown) with the control shaft 112 in a manner that allows the actuator to vary the speed of the control shaft 112 relative to the speed of the crankshaft 108. Varying the speed of the control shaft 112 relative to the speed of the crankshaft 108 varies the stroke and top dead center (TDC) position of the piston 104, thereby varying the compression ratio of the engine assembly 100.

[0025] Fig. Figure 2 is a schematic representation of a conventional VCR transmission 200. The transmission 200 includes a crankshaft 202, a second output gear 204, a second input gear 206, an actuator shaft 208, an actuator 210, a first output gear 212, a first input gear 214, a control shaft 216, and an in-line phaser 218. The second output gear 204 is fixedly connected to the crankshaft 202. The second output gear 204 meshes with the second input gear 206. The second input gear 206, the actuator shaft 208, the in-line phaser 218, and the first output gear 212 form components of a high-ratio reduction system. The in-line phaser 218 may be, for example, a strain wave gear drive, a cycloidal gear drive, or the like, as is known in the art.The first output gear 212 meshes with the first drive gear 214 mounted on the control shaft 216 of a VCR motor system as shown in FIG. Fig. 1. In this way, the actuator 210 can be controlled to change the phase angle via the in-line phaser 218 between the crankshaft and the control shaft and thereby change the compression ratio of an engine arrangement as shown in Fig. 1 shown.

[0026] One problem with the VCR transmission 200 is that the actuator 210 must work against the full torque of the crankshaft 202. If an electric motor is used as the actuator, the electric motor must be very large to provide sufficient torque to operate the VCR transmission 200. Large electric motors also have correspondingly high parasitic losses, which significantly reduces the efficiency of the overall system. Furthermore, the fact that the VCR transmission 200 works against the full torque of the system also means that the cost and size of the transmission become extremely high. In addition, VCR transmissions, such as the one in Fig. 2 have a very high gear ratio, which limits the type of gearboxes that can be used in this type of system.

[0027] To solve the above-mentioned problems, a VCR engine according to the present disclosure includes a power-split transmission with a torque path from the crankshaft to the timing shaft and another torque path from the actuator to the crankshaft. The torque path between the crankshaft and the timing shaft carries a higher torque than the torque path between the actuator and the crankshaft. With this arrangement, the actuator operates against only a fraction of the torque of the VCR transmission. Thus, an actuator used by an exemplary embodiment of the present disclosure can be smaller than an actuator commonly used to adjust the compression ratio of a VCR engine.

[0028] In an exemplary aspect of the present invention, a variable compression ratio engine assembly includes a power-split transmission having a first torque path and a second torque path. The first torque path carries higher torque than the second torque path. The first torque path carries higher torque between the crankshaft of the engine assembly and a control shaft of a VCR transmission than the torque carried by the second torque path between the crankshaft and the actuator. The higher torque carried by the first torque path of the power-split transmission is phase-shifted by any variation in the lower torque carried by the second torque path. In this way, the actuator does not have to work against the full torque of the system.Rather, the actuator only has to work against a portion of the system's torque. This significant reduction in the actuator's torque handling requirements allows for the use of a much smaller actuator than previously required. This also reduces the actuator's cost, the overall system complexity, and the parasitic losses it generates.

[0029] Fig. 3 is a schematic representation of a VCR transmission 300 operating as a planetary gear set according to an exemplary embodiment of the present disclosure. The VCR transmission 300 includes a crankshaft 302, an output gear 304, a carrier 306, a planetary gear 308, a ring gear 310, a drive gear 312, a control shaft 314, a sun gear 316, and an actuator 318. The output gear 304 is fixedly connected to the crankshaft 302 and meshes with the carrier 306. The carrier 306 meshes with at least one of a plurality of planetary gears 308. The planetary gear 308 meshes with the ring gear 310, which in turn meshes with the drive gear 312 fixed to the control shaft 314. The VCR transmission 300 forms a first torque path from the crankshaft 302, which extends through the output gear 304, the carrier 306, the ring gear 310 and the drive gear 312 to the control shaft 314.The carrier 306 also meshes with the sun gear 316, which is fixedly connected to the actuator 318. The VCR transmission 300 forms a second torque path from the crankshaft 302, extending through the output gear 304, the carrier 306, and the sun gear 316 to the actuator 318. The VCR transmission 300 splits the torque between the first and second torque paths such that the first torque path carries a higher torque than the second torque path. In this way, any change in the torque driving the actuator 318 causes a change in the phase of the control shaft 314 relative to the crankshaft 302, which in turn changes the compression ratio of a VCR engine assembly including the VCR transmission 300.

[0030] In addition to reducing the size, cost, and torque capacity of a VCR transmission actuator, the present disclosure eliminates the need to provide an actuator dedicated exclusively to the VCR transmission system. In one exemplary aspect, the VCR transmission of the present disclosure may be configured to provide torque to a component already present in a motor assembly, thereby eliminating the need to provide a dedicated actuator. This reduces cost, complexity, space, and parasitic losses while improving efficiency and performance. The actuator 318 of the VCR transmission according to the present disclosure may be any power-consuming component.By splitting the torque within the VCR gearbox and driving the actuator with only a portion of the torque flowing through the gearbox, the actuator can be used with significantly reduced power requirements. This allows for the use of significantly smaller actuators and improved efficiency and performance.

[0031] Fig. 4 is a schematic representation of a VCR transmission 400 operating as a cycloidal gear according to another exemplary embodiment of the present disclosure. The VCR transmission 400 includes a crankshaft 402, an output gear 404, a ring gear 406, a cycloidal reduction gear 408, a sun gear 410, an actuator 412, a transmission shaft 414, a drive gear 416, and a control shaft 418. The output gear 404 is fixedly connected to the crankshaft 402 and meshes with the ring gear 406. The ring gear 406 meshes with the cycloidal reduction gear 408. The cycloidal reduction gear 408 is engaged with the transmission shaft 414, which in turn is engaged with the drive gear 416 fixed to the control shaft 418.The VCR transmission 400 forms a first torque path from the crankshaft 402, extending through the output gear 404, the ring gear 406, the cycloidal reduction gear 408, the transmission shaft 414, the input gear 416, and the control shaft 418. The cycloidal reduction gear 408 also meshes with the sun gear 410, which is attached to an output of the actuator 412. The VCR transmission 400 therefore also forms a second torque path extending from the crankshaft 402 through the output gear 404, the ring gear 406, the cycloidal reduction gear 408, and the sun gear 410 to the actuator 412. The VCR transmission 400 divides the torque between the first and second torque paths such that the first torque path carries a higher torque than the second torque path.In this manner, any change in the torque driving actuator 412 causes a change in the phase of control shaft 418 relative to crankshaft 402, which in turn changes the compression ratio of a VCR engine assembly including VCR transmission 400.

[0032] In an exemplary embodiment of the present disclosure, the VCR transmission may be used with a power split configuration to drive an existing component, such as a variable displacement oil pump. The displacement of a variable displacement oil pump driven by the VCR transmission may be controlled to vary not only the amount of oil delivered to the engine assembly, but also to change the compression ratio. The inventors of the present disclosure have discovered that the compression ratio of an engine is generally a function of engine speed and load, and the same is true for the displacement of the oil pump. The power requirements for the engine and the oil pump are consecutive. By selecting the correct gear ratios for the VCR transmission so that the appropriate torque is distributed to the oil pump, the displacement orthe displacement of the oil pump can be varied to control the speed of the eccentric shaft (control shaft) and accordingly control the compression ratio of the engine.

[0033] Fig. 5 is a schematic representation of an exemplary VCR transmission 500 including a variable displacement pump 518 according to the present disclosure. The variable displacement pump 518 can be controlled in a manner that varies the phase of a control shaft 514 relative to the crankshaft 502 to vary the compression ratio of an engine assembly including the VCR transmission 500. The VCR transmission 500 includes a crankshaft 502, an output gear 504, a carrier 506, a planetary gear 508, a ring gear 510, a drive gear 512, a control shaft 514, a sun gear 516, and the variable displacement pump 518. The VCR transmission 500 operates similarly to the one described with reference to Fig. 3 by incorporating a planetary gear assembly. The VCR transmission 500 forms a first torque path from the crankshaft 502, extending through the output gear 504, the carrier 506, the ring gear 510, and the drive gear 512 to the control shaft 514. The carrier 506 also meshes with the sun gear 516, which is fixedly connected to the variable displacement pump 518. The VCR transmission 500 forms a second torque path from the crankshaft 502, extending through the output gear 504, the carrier 506, and the sun gear 516 to the variable displacement pump 518. The VCR transmission 500 divides the torque between the first and second torque paths such that the first torque path carries a higher torque than the second torque path.In this way, any change in the torque driving the variable displacement pump 518 causes a change in the phase of the control shaft 514 relative to the crankshaft 502, which in turn changes the compression ratio of a VCR engine assembly including the VCR transmission 500. The variation in the torque driving the variable displacement pump 518 can be controlled by varying the displacement of the variable displacement pump 518. Increasing the displacement of the variable displacement pump 518 results in a slowing of the speed of the variable displacement pump 518, thereby increasing the speed of the ring gear 510, thereby moving the control shaft 514 forward and increasing the compression ratio of a VCR engine assembly including the VCR transmission 500.In contrast, decreasing the displacement of the variable displacement pump 518 results in an increase in the speed of the variable displacement pump 518, thereby decreasing the speed of the ring gear 510, thereby retarding the control shaft 514 and reducing the compression ratio of a VCR engine assembly including the VCR transmission 500. In a preferred embodiment of the present disclosure, the variable displacement pump 518 may provide oil flow to the VCR engine assembly including the VCR transmission 500.

[0034] Fig.6 is a schematic representation of an exemplary VCR transmission 600 including a pump 612 in conjunction with a variable orifice 620 according to the present disclosure. The pump 612, along with the variable orifice 620, can be controlled in a manner that varies the phase of the control shaft 618 relative to the crankshaft 602 to vary the compression ratio of an engine assembly including the VCR transmission 600. The VCR transmission 600 includes a crankshaft 602, an output gear 604, a ring gear 606, a cycloidal reduction gear 608, a sun gear 610, the pump 612, a transmission shaft 614, a drive gear 616, a control shaft 618, and the variable orifice 620. The output gear 604 is fixedly connected to the crankshaft 602 and meshes with the ring gear 606. The ring gear 606 meshes with the cycloidal reduction gear 608.The cycloidal reduction gear 608 meshes with the transmission shaft 614, which in turn meshes with the drive gear 616 attached to the control shaft 618. The VCR gear 600 forms a first torque path from the crankshaft 602, extending through the output gear 604, the ring gear 606, the cycloidal reduction gear 608, the transmission shaft 614, the drive gear 616, and the control shaft 618. The cycloidal reduction gear 608 also meshes with the sun gear 610 attached to an output of the pump 612. The VCR transmission 600 therefore also forms a second torque path extending from the crankshaft 602 via the output gear 604, the ring gear 606, the cycloidal reduction gear 608 and the sun gear 610 to the pump 612.The VCR transmission 600 splits the torque between the first and second torque paths such that the first torque path carries more torque than the second torque path. In this way, any change in the torque driving the pump 612 causes a change in the phase of the control shaft 618 relative to the crankshaft 602, which in turn changes the compression ratio of a VCR engine assembly that includes the VCR transmission 600. More specifically, decreasing the size of the variable orifice 620 increases the flow resistance of the pump, thereby slowing the speed of the pump 612. This increases the speed of the transmission shaft 614, which moves the control shaft 618 forward and increases the compression ratio of a VCR engine assembly with the VCR transmission 600. In contrast, increasing the size of the variable orifice 620 decreases the flow resistance of the pump 612.This increases the speed of pump 612, which decreases the speed of transmission shaft 614, thereby retarding control shaft 618 and reducing the compression ratio of a VCR engine assembly including VCR transmission 600. In a preferred embodiment of the present disclosure, pump 612 may provide oil flow to the VCR engine assembly including VCR transmission 600.

[0035] As explained above, the actuator of the VCR transmission according to the present disclosure can be any power-consuming component. It is advantageous to use an actuator that may already be present in an engine assembly. While the detailed description of the present disclosure addresses VCR transmissions having a planetary or cycloidal configuration, it should be understood that the present disclosure is not limited to any particular configuration, as long as the VCR transmission splits the torque from the crankshaft between the actuator and the control shaft. Other examples of a VCR transmission that may be used in an exemplary embodiment of the present disclosure include, without limitation, a stretch shaft transmission, a roller reduction transmission, and the like.

[0036] Preferably, the VCR transmission has a high gear ratio, so that the torque delivered to the actuator is significantly lower than that delivered to the control shaft. This allows the use of an actuator with significantly reduced power consumption, while still allowing control of the engine's compression ratio by varying the actuator's power consumption.

Claims

[1] Motor assembly (100) comprising: a crankshaft (502); a bell crank (110) pivotally mounted on the crankshaft (502), the bell crank (110) having a first end (120) and a second end (122) remote from the first end (120); a connecting rod connected to the first end (120) of the bell crank (110); a control shaft (514); a control member (114) mounted on the control shaft (514) and connected to the second end (122) of the bell crank (110); an output gear (504) fixed to the crankshaft (502); a drive gear (512) fixed to the control shaft (514); an actuator; and a power split transmission (500) that splits the torque from the output gear (504) between the input gear (512) via a first torque path and the actuator via a second torque path; characterized by , that the actuator comprises a variable displacement oil pump (518) driven via the second torque path. [2] The engine assembly (100) of claim 1, wherein the power split transmission (500) comprises a planetary gear system comprising: a carrier (506) engaging with the output gear (504); a sun gear (516) coupled to the actuator; a ring gear (510) meshing with the drive gear (512); and a planetary gear (508) rotatably mounted on the carrier (506) and meshing with the sun gear (516) and the ring gear (510). [3] The engine assembly (100) of claim 1, wherein the power split transmission (400) comprises a cycloidal transmission comprising: a ring gear (406) meshing with the output gear (404); a sun gear (410) coupled to the actuator (412); a transmission shaft (414) engaging with the drive gear (416); and a cycloidal reduction gear (408) rotatably connected to the transmission shaft (414). [4] The engine assembly (100) of claim 1, wherein the gear ratio of the second torque path is higher than the gear ratio of the first torque path. [5] The engine assembly (100) of claim 1, wherein increasing the displacement of the variable displacement pump (518) slows the speed of the variable displacement pump (518) to advance the control shaft (514) and increase a compression ratio of the engine assembly (100). [6] The engine assembly (100) of claim 1, wherein decreasing the displacement of the variable displacement pump (518) increases the speed of the variable displacement pump (518) to retard the control shaft (514) and decrease a compression ratio of the engine assembly. [7] The engine assembly (100) of claim 1, wherein the oil pump (518) communicates with a variable orifice. [8] The engine assembly (100) of claim 7, wherein decreasing the size of the variable orifice slows the speed of the oil pump (518) to advance the timing shaft (514) and increase a compression ratio of the engine assembly (100). [9] The engine assembly (100) of claim 7, wherein increasing the size of the variable orifice (620) increases the speed of the oil pump (518) to retard the control shaft (514) and reduce a compression ratio of the engine assembly (100).

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