ACTUATION SUBSYSTEM OF VARIABLE COMPRESSION RATIO CONTROL SYSTEM FOR INTERNAL COMBUSTION ENGINE

Inventor: MASAMI SAKITA

SPECIFICATION

TECHNICALL FIELD

This invention relates generally to actuation subsystems of variable compression ratio control systems for internal combustion engines, and more particularly to such systems that use mechanical actuators.

BACKGROUND ART

It is generally believed that the engine equipped with a variable compression ratio (VCR) control system should work best if operated with a lower compression ratio under higher load conditions, and with a higher compression ratio under relatively lower load conditions. The higher load conditions occur, for example, at the start from a stopped state, during climbing on a hill and during an overtaking maneuver, and the relatively lower load conditions occur, for example, during cruising on a highway.

The VCR control system should be able to respond quickly enough to cope with any changes in load conditions that occur during a trip. The quick response of the VCR control system is necessary not only to assure smooth operation of the vehicle during the change in compression ratio takes place but also to protect the engine. For example, in a four-cylinder engine, the response and execution time of the VCR control system should be as short as that spent in one half rotation of the driveshaft so that the compression ratio can be reduced by a large enough amount

to prevent another knock before the next combustion will take place in the same cylinder.

It is probably true that the super-fast responding VCR control system such as described above should generally be able to operate the engine with a higher compression ratio than the compression ratio in a slow-responding VCR control system because the potential damage from operating the engine with a higher- than-ordinary compression ratio is much smaller than operating the engine with a slow responding VCR system, and/or that the VCR control system does not have to keep changing the compression ratio continuously as long as the compression ratio is kept in a permissible range and the system is ready to respond to any sudden large changes in load conditions.

Our review of reports available in the public domain suggests that, in general, the hydraulic actuator tends to have a leak problem when operated under high pressure, and the mechanical actuator powered by an electric motor tends to have a longer response and execution time than desired.

DISCLOSURE OF INVENTION

An object of this invention is the provision of a VCR actuation subsystem that is able to change the compression ratio on a real time basis without an unwanted time lag.

An object of this invention is the provision of a VCR actuation subsystem that is able to reduce the compression ratio fast enough not to require advancing the ignition timing when knock is detected.

An object of this invention is the provision of a VCR actuation subsystem that does not keep changing the compression ratio continuously, but changes the compression ratio as the necessity of doing so occurs.

An object of this invention is the provision of a VCR actuation subsystem that is able to maximize the compression ratio under all load conditions by changing the compression ratio continuously.

An object of this invention is the provision of a VCR actuation subsystem that is sturdy enough to endure long time continuous use of the VCR control system.

BRIEF DESCRIPTION OF DRAWINGS

In the drawings, like reference characters refer to the same parts in the several views:

Fig. 1 is a top elevational view of a VCR actuation subsystem of the preferred embodiment;

Fig. 2 is an expanded cross-sectional view in partial elevational view of the drive mechanism of the VCR actuation subsystem;

Fig. 3 is a rear view in partial cross-sectional view of the actuator means of the preferred embodiment of the present invention;

Fig. 4 is cross-sectional view of the actuator means of the preferred embodiment of the present invention;

Fig. 5 is a rear elevational view in partial cross-sectional view of the actuator means of an alternative embodiment that uses a plurality of worm gear assemblies;

Fig. 6 is a top elevational view of the VCR actuation subsystem of an alternative embodiment that uses a plurality of worm gear assemblies;

Fig. 7 is a top elevational view in partial cross sectional view of the VCR actuation subsystem of another alternative embodiment that uses at least one spur gear;

Fig. 8 is an expanded cross-sectional view in partial elevational view of an alternative embodiment of the drive mechanism of the VCR actuation subsystem; and

Fig. 9 is an expanded cross-sectional view in partial elevational view of another alternative embodiment of the drive mechanism of the VCR actuation subsystem.

BEST MODE FOR CARRYING OUT THE INVENTION

As shown in Fig. 1 , an actuation subsystem 10 of a variable compression ratio control system includes a drive means 20, a connecting means 30, and an actuator means 40. The drive means 20 includes generally identical first and second clutch assemblies. The clutch assembly comprises a clutch driver plate assembly 22-1 and a clutch driven plate assembly 24-1. The clutch driver plate assembly 22-1 is rigidly mounted on the power shaft 12 of an engine and the clutch driven plate assembly 24-1 is rotatably and longitudinally slidably mounted in a groove 16 (see Fig. 2) on the power shaft in such a manner that the back surfaces of the clutch driven plate assemblies 24-1 and 24-2 are facing each other, wherein the power shaft may be a driveshaft or a crankshaft. The clutch drive plate assembly 22-2 is generally identical to the clutch drive plate assembly 22-1. The clutch driven plate assembly 24-2 is generally identical to the clutch driven plate assembly 24-1.

As shown in Fig. 2, the clutch driver plate assembly 22-1 includes a solenoid 25 and a clutch driver plate 29. The clutch driven plate assembly 24-1 includes a core 19 with a cylindrical outer wall, a clutch driven plate 28 affixed to the sidewall of the core 19 facing the clutch driver plate 29 of the paired clutch driver plate assembly 22-1, a back plate 23 affixed to the sidewall of the core 19 facing the back plate 23 of the other clutch driven plate assembly 24-2, a spring 27, and a pulley tire 26 longitudinally (in the direction of the power shaft) slidably mounted on the core's 19's cylindrical outer wall. The spring 27 holds the clutch driven plate assembly 24- 1 away from the clutch driver plate assembly 22-1 , and pushes the clutch driven plate assembly 24-1 toward the other clutch driven plate assembly 24-2 so that their back plates 23 are always pressed against each other to prevent the drive

gear shaft 42 described blow from rotating in either direction when neither of the clutch assemblies is activated.

As shown in Fig. 1 , the connecting means includes an idler shaft 34, a drive gear shaft 42, a pulley 32-1 mounted on the idler shaft 34, a pulley 32-2 mounted on the drive gear shaft 42, a spur gear set 37 mounted on the idler shaft 34 and the drive gear shaft 42. Note that the expression "mounted on a shaft" without any adverb such as rotatably or longitudinally slidably implies "rigidly mounted on a shaft" as usually done in mounting gears etc. on a shaft. The power shaft, the drive gear shaft, and the idler shaft are all in parallel to one another. The first clutch driven plate assembly 24-1 and the pulley 32-1 on the idler shaft 34 are rotatably connected by a belt 33-1 ; and the second clutch driven plate assembly 24-2 and the pulley 32-2 on the drive gear shaft 42 are rotatably connected by a belt 33-2. The gear ratio of the gears of the spur gear set 34 is 1 to 1 ; the diameter of the pulley 24-1 is larger than that of the pulley 32-1 ; and similarly, the diameter of the pulley 24-2 is larger than that of the pulley 32-2. The ratio of diameters of the pulleys 24-2 and 32-2 equals the ratio of diameters of the pulleys 24-1 and 32-1.

As shown in Figs. 3 and 4, the actuator means 40 of the preferred embodiment of the present invention is a plurality of jackscrew assemblies. The jackscrew assembly includes a jackscrew 47 comprising a thimble with a worm gear 46, a worm gear 44 mounted on the drive gear shaft 42 and meshes with the worm gear 46, a spindle 45 and a base plate 49, an upper plate 48, and a hexahedron-shaped arm holder 43. The spindle 45 is affixed to the bottom of the arm holder 43. The worm gear 46 is disposed between the base plate 49 and the upper plate 48 of the worm gear housing. A thrust bearing may be placed between the top surface of the worm gear 46 and the upper plate 48, and another thrust bearing may be placed between the bottom surface of the worm gear 46 and the base plate 49. The jackscrew assembly shown in Fig. 3 is generally the same as that shown in U.S. Patent Number 7,174,865 B2 by the inventor of the present invention. A self contained jackscrew including a worm gear set and thrust roller bearings named Joyce Machine Screw Jack is available in the market. A jackscrew such as the

Joyce Machine Screw Jack may be used as a building block of the actuation subsystem.

The hexahedron-shaped arm holder 43 has front and rear walls, top and bottom walls, and a hollow hexahedron-shaped inner space with open-ended two sides. The hollow inner space of the arm holder 43 slidably receives the arm member (or a control lever) 14 of the variable compression ratio control system in such a manner that the front and rear walls of the arm holder 43 generally slidably covers the square window 51 (of the arm member), and is able to hold the arm member 14 inside the hexahedron-shaped inner space 53. The arm holder 43 is pivotally connected to a hexahedron-shaped metal piece 55 by a pin 41 wherein the hexahedron metal piece 55 is laterally slidably received by a square window 51 of an arm member 14 of the variable compression ratio control system.

Under the normal condition, neither of the clutch assemblies is activated. In operation, only one of the clutch assemblies is activated at a time. When the first clutch assembly is activated, the arm member 14 is lifted/lowered (or pushed/pulled) in one direction, and when the second clutch assembly is activated the arm member 14 is lifted/lowered (or pushed/pulled) in the other direction.

ALTERNATIVE MODES FOR CARRYING OUT THE INVENTION

As shown in Fig. 5, an actuator means 4OA of an alternative embodiment includes a plurality of worm gear assemblies each of which includes worm gears 44A and 71 wherein the worm gear 44A is mounted on the drive gear shaft 42A, and the worm gear 71 is mounted on the worm gear assembly shaft 72. A variable-diameter worm gear 73 that has an arc-shaped concave cross section is mounted on the gear assembly shaft 72. The teeth of the worm gear 73 mesh with the gear teeth 15 that are disposed on an arc-shaped convex surface of the arm member 14A of a VCR control system. The worm gear assemblies may be disposed not only vertically as shown in Fig. 5 but also horizontally as shown in Fig. 6. The worm gear assembly shown in Fig. 5 is generally the same as that shown in U.S. Patent Numbers 7,007,640 and 7,174,865 by the inventor of the present invention.

As shown in Fig. 6, another alternative embodiment 1OB of the present invention includes a plurality of actuator means having bevel gears 44B mounted on the drive gear shaft 42B and bevel gears 71 B mounted on the worm gear assembly shaft 72B disposed horizontally.

As shown in Fig. 7, another alternative embodiment 1OC of the present invention includes at least one spur gear 44C that is mounted on the drive gear shaft 42C wherein the spur gear 44C meshes a partial spur gear 46C mounted on an arm member 14C of the variable compression ratio control system.

The drive means 2OD of an alternative embodiment shown in Fig. 8 includes generally identical first and second clutch assemblies. The first clutch assemblies comprises a clutch driver plate assembly 22-1 D and a clutch driven plate assembly 24-1 D, and the second clutch assembly comprises a clutch driver plate assembly 22-2D and a clutch driven plate assembly 24-2D. The clutch driver plate assemblies 22-1 D and 22-2D are longitudinally slidably mounted on a power shaft 12D of an engine and the clutch driven plate assemblies 24-1 D and 24-2D are rotatably mounted on the power shaft wherein the power shaft may be a driveshaft or a crankshaft. The clutch driver plate assembly 22-1 D (or 22-2D) includes a solenoid 25D, a driver plate 29D, a spring 27D that holds the driver plate away from the paired clutch driven plate assembly 24-1 (or 24-2). The clutch driven plate assembly 24-1 D (or 24-2D) includes a clutch driven plate 28D and a pulley tire affixed to its outer cylindrical wall. The connecting means 3OD includes a brake 82D that prevents the drive gear shaft 42D from rotating when neither of the clutch assemblies is activated, and the gear sets 37D with a gear ratio not having to be 1 to 1.

The drive means 2OE of another alternative embodiment shown in Fig. 9 includes a pair of generally identical clutch driver plate assemblies 62-1 and 62-2 each of which including a clutch driver plate and a pulley tire mounted on its cylindrical outer wall, rotatably mounted on the power shaft 12E; and the clutch driven plate assembly 64 that includes a clutch driven plate and a pair of springs 67,

longitudinally slidably mounted on the power shaft 12E. The clutch driver plate assembly 62-1 is rotatably connected to the pulley 32-1 E mounted on the idler shaft by a belt 33-1 E, and the other clutch driver plate assembly 62-2 is rotatably connected to the pulley 32-2E mounted on the drive gear shaft by a belt 33-2E. The connecting means 3OE includes a brake 82E that prevents the drive gear shaft 42E from rotating, and the gear sets 37E with a gear ratio not having to be 1 to 1.

Another alternative embodiment of the drive means 2OG includes generally identical drive means to that of the embodiment 2OD except that the pair of the clutch assemblies are mounted on the drive gear shaft 42G.

Another alternative embodiment of the drive means 2OH includes generally identical drive means 2OE except that the pair of the clutch driver plate assemblies and the clutch driven plate assembly are mounted on the drive gear shaft 42H.

Various other changes and modifications will suggest themselves to those skilled in this art. For example, the pulleys and belts may be replaced by gears, or the pulley ratios may be different from that described above, or the brake mounted on the drive gear shaft in some of the alternative embodiment may not be necessary. It is intended that the above and other such changes and modifications shall fall within the spirit and scope of the invention defined in the appended claims.