Internal-combustion engines – Accessories – Covers – trays – vibrators – corrosion inhibitors – air filters
Reexamination Certificate
1999-05-19
2001-06-26
McMahon, Marguerite (Department: 3747)
Internal-combustion engines
Accessories
Covers, trays, vibrators, corrosion inhibitors, air filters
Reexamination Certificate
active
06250276
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a drive mechanism for accessory assemblies of a reciprocating internal combustion engine.
BACKGROUND INFORMATION
French Unexamined Patent Application No. 2 644 866 discloses a drive mechanism for accessory assemblies of a reciprocating internal combustion engine having a switchable planetary transmission. The planetary transmission is positioned concentrically to the crankshaft and includes a planetary gear carrier attached to the crankshaft, planet gears, a ring gear that can be locked against an end shield using a braking device and a sun gear that is connected to a belt pulley. The sun gear is positioned in the end shield and can be connected to the planetary gear carrier via a one-way clutch.
Switchable planetary transmissions of this type are intended to provide adequate power to accessory assemblies, such as an air conditioner compressor and electric generator, at engine idling speeds without causing those assemblies to race at high engine speeds, which may cause damage. This makes it possible to guarantee the operation of the vehicle electrical system even if the accessory assembly size might be reduced. This is so even if an electrically heated windshield and an electrically heated (pre)-catalytic converter are needed in addition to the equipment now present. The latter is an important prerequisite in reducing pollutant emissions during a cold start.
However, the switchable planetary transmission described in French Unexamined Patent Application 2 644 866 has a large volume and poor efficiency, since it is difficult to lubricate. Because it is connected rigidly to the free end of the crankshaft, this planetary transmission is subjected to the latter's vibratory load, making it susceptible to failures and producing noise emissions.
A switchable planetary transmission whose drive provides damping of the torsional vibrations stemming from the crankshaft is known from German Patent Application No. 1 526 560. This damping is achieved by a combination of compression springs and rubber cushions that are arranged in the planetary gear carrier. However, this has no effect on radial or axial vibrations of the crankshaft end, but only on its tangential vibrations which, unlike radial and axial vibrations, can be corrected by torsional vibration isolators and vibration dampers.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a switchable planetary transmission which is reliable, compact, and quiet and has a high level of efficiency and a long service life.
The present invention provides a drive mechanism for accessory assemblies of a reciprocating internal combustion engine comprising a switchable planetary transmission (
1
) which is positioned concentrically to the crankshaft (
2
) and which has a planetary gear carrier (
12
) connected to the crankshaft (
2
) with planet gears (
15
), as well as a ring gear (
17
) that can be locked against an end shield (
19
) by a braking device and a sun gear (
16
) that is connected to a belt pulley (
21
). The sun gear is positioned in the end shield (
19
) and can be connected to the planetary gear carrier (
12
) via a one-way clutch (
22
). The present invention is characterized in that the planetary gear carrier (
12
) is connected to the crankshaft (
2
) by a vibration isolator (
8
).
To prevent the vibrations produced by the crankshaft end from being transmitted to the planetary transmission, a vibration isolator is connected between the units. The vibration isolator is connected to the crankshaft end and the planetary gear carrier, but does not allow passage of the vibrations produced by the crankshaft end, due to its elasticity or its geometry.
Isolating the vibrations produced by the crankshaft end makes it possible to design a much more light-weight and thus more compact planetary transmission. This also reduces its susceptibility to failures and its noise emissions, in particular the belt pulley noise emissions.
In principle, it is conceivable to connect the crankshaft and planetary gear carrier to the vibration isolator by screwing, riveting, or gluing, etc. An especially simple mounting method, however, is to provide both parts with axial claws which need only to be inserted into corresponding slots in the vibration isolator. An identical number of claws produces a more symmetrical, and thus smaller, load and allows the vibration isolator to be centered before it is mounted. The number of claws is not specified. Two or three per part are usual.
If the vibration isolator is made of an elastic material (such as polyurethane), it is capable of filtering out tangential and axial vibrations as well as radial vibrations.
The tangential vibrations produced by the crankshaft end can be eliminated on the latter by torsional vibration isolators or vibration dampers. It is therefore also possible to use vibration isolators made of an inelastic material. Although their torsional rigidity prevents them from filtering out torsional vibrations, the radial and axial clearance of the claws allows the latter to move radially and axially within the slots, thus eliminating radial and axial vibrations.
Similarly, the vibration isolator can also be designed in the shape of a square or hexagon, with the claws being tangential to its circumferential sides. A vibration isolator known as a cross-recess coupling is characterized by an especially simple design, since it has only four radial slots distributed evenly across its circumference, each accepting two claws.
According to one preferred embodiment of the present invention, the ring gear is mounted on the planet gears so that it can move in an axial direction, and the brake disc is integrally molded onto the ring gear. The one-piece design of the ring gear and brake disk, the floating attachment of the ring gear onto the planet gears, and the ability of corresponding brake pads to move within a retaining ring with an integrated axial stop give the brake a simple design.
A cylindrical piston actuated by oil pressure ensures that the brake pads apply a uniform pressure on the brake disk, thus allowing the latter to operate with little wear and tear. Positioning the cylindrical piston between an outer and an inner guide ring also allows the latter to be operated with little wear and tear and offers freedom in selecting the material for the end shield. The linear contact between a rounded torus of the cylindrical piston and the brake pad facing it avoids twisting and thus wear and tear.
An electronic controller inhibits switching pressure or a variation in engine speed when the planetary transmission is switched on and off.
Because it is placed in the timing box, the planetary transmission is reliably lubricated with motor oil, thereby achieving a high level of efficiency and reducing wear and tear. This solves one problem that could never be controlled by positioning the planetary transmission on the free crankshaft end outside the engine housing. In addition, arranging the planetary transmission in this manner requires only one dynamic gear oil sealing ring, just like in a standard engine. This ring does not have to provide a seal against differential oil pressure, but must merely withstand the vacuum in the crankcase.
REFERENCES:
patent: 3469473 (1969-09-01), Förster et al.
patent: 4569252 (1986-02-01), Harper
patent: 4760757 (1988-08-01), Svab
patent: 4854192 (1989-08-01), Churchill et al.
patent: 4862770 (1989-09-01), Smith
patent: 4870875 (1989-10-01), Morishita
patent: 5263906 (1993-11-01), Antonov
patent: 5372106 (1994-12-01), Botterill
patent: 5470285 (1995-11-01), Schneider et al.
patent: 5800298 (1998-09-01), Kanehara et al.
patent: 1526560 (1970-04-01), None
patent: 2 644 866 (1990-09-01), None
patent: 630788 (1949-10-01), None
patent: 10288044 (1998-10-01), None
Benton Jason
Daimler-Chrysler AG
Kenyon & Kenyon
McMahon Marguerite
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