Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
2000-05-02
2001-07-31
Lo, Weilun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090370
Reexamination Certificate
active
06267089
ABSTRACT:
Appliance for modifying the timing of gas-exchange valves of an internal combustion engine, in particular hydraulic camshaft adjustment device of rotary piston type.
1. Field of the Invention
The invention relates to an appliance for modifying the timing of gas-exchange valves of an internal combustion engine comprising a driving wheel (
2
) which is configured as an external rotor, which is in drive connection with a crankshaft of the internal combustion engine and has a hollow space (
6
) formed by a hollow-cylindrical peripheral wall (
3
) and two side walls (
4
,
5
),
at least one hydraulic working space (
8
) is formed in the hollow space (
6
) of the driving wheel (
2
) by at least two boundary walls (
7
) extending from the inside of the peripheral wall (
3
) and directed toward the longitudinal center line of the driving wheel (
2
), an impeller (
10
) which is configured as an internal rotor, is torsionally connected to a camshaft (
9
) of the internal combustion engine and is inserted in the hollow space (
6
) of the driving wheel (
2
),
on the periphery of an impeller hub (
11
), the impeller (
10
) has at least one vane (
13
) which is arranged in an axial retention groove (
12
) and which extends radially in a working space (
8
) of the driving wheel (
2
) and subdivides each working space (
8
) into two oppositely acting hydraulic pressure chambers (
14
,
15
),
the outer end surf ace (
18
) of each vane (
13
) of the impeller (
10
) is in sealing contact with the inside of the peripheral wall (
3
) of the driving of the driving wheel (
2
) due to the force of a spring element (
17
) arranged an the inner end surface (
16
) of the vane in the axial retention groove (
12
),
during optional or simultaneous pressurization by means of a hydraulic fluid, the pressure chambers (
14
,
15
) cause a pivoting motion or fixed location of the impeller (
10
) relative to the driving wheel (
2
) and, therefore, of the camshaft (
9
) relative to the crankshaft, and it can be realized in a particularly advantageous manner on hydraulic camshaft adjustment devices of rotary piston type.
2. Background of the Invention
Such an appliance, is already known from EP 818 610 A2, which forms the generic type. This appliance, configured as a so-called vane-cell adjustment device, consists of a driving wheel configured as an external rotor and of an impeller configured as an internal rotor, in this arrangement the driving wheel is in drive connection with a crankshaft of the internal combustion engine whereas the impeller is torsionally connected to a camshaft of the internal combustion engine. In addition, the driving wheel has a hollow space formed by a hollow-cylindrical peripheral wall and two side walls and in which five hydraulic working spaces are formed by five boundary walls extending from the inside of the peripheral wall and directed toward the longitudinal center line of the appliance. The impeller is inserted in the hallow space of the driving wheel and has, in turn, five vanes Arranged in an axial retention groove on the periphery of its impeller hub, each of these vanes extending radially in a working space of the driving wheel. In this arrangement the outer end surfaces of the vanes are in sealing contact with the inside of the peripheral wall of the driving wheel due to the force of a spring element arranged on each inner end surface of the vanes in the axial retention groove and, by this means, subdivide each hydraulic working space of the driving wheel into two oppositely acting hydraulic pressure chambers. During optional or simultaneous pressurization by means of a hydraulic fluid, these pressure chambers cause a pivoting motion or hydraulic clamping of the impeller relative to the driving wheel and, therefore, a relative rotation or fixed location of the camshaft relative to the crankshaft.
A disadvantageous feature of this known appliance is that during pressurization of one or both pressure chamber(s) of each hydraulic working space, a build-up of pressure occurs in the sealing gap between the outer end surface of the vane and the inside of the peripheral wall of the driving wheel in addition to the build-up of pressure which occurs in the axial retention groove of the vanes or on their inner end surface. The pressure acting on the outer end surface of the vane, and therefore causing a centripetal force, then corresponds to the pressure of the respectively pressurized pressure chamber and is, in each case, higher than the pressure acting on the inner end surface of the vane, and therefore causing a centrifugal force, because the latter pressure is throttled in an uncontrolled manner by the usually very narrow sealing gape between the vanes and their retention grooved and because of the depth of these retention grooved. If the centripetal force acting on the vanes then exceeds the sum of the spring force of the spring elements and the centrifugal force acting on the vanes, a so-called “vane immersion” can occur, i.e. a radial displacement of the vanes against the force of their spring elements. This, in turn, causes increased hydraulic fluid leakage between the individual pressure sure chambers of the hydraulic working spaces, so that the hydraulic clamping of the impeller relative to the driving wheal is impaired. In addition, these increased hydraulic fluid leaks are the cause of larger deviations from the specified adjustment angle between the camshaft and the crankshaft and of retarded adjustment times of the appliance.
OBJECT OF THE INVENTION
The invention is therefore based on the object of designing an appliance for modifying the timing of gas-exchange valves of an internal combustion engine, in particular hydraulic camshaft adjustment device of rotary piston type, in which the radial displacement of the vanes against the force of their spring elements, resulting from the build-up of pressure in the sealing gap between the outer end surface of each vane of the impeller and the inside of the peripheral wall of the driving wheel, is effectively avoided.
SUMMARY OF THE INVENTION
This object is achieved, in accordance with the invention, in such a way that the vanes of the impeller are additionally configured with pressure balance means with which, during pressurization of one or both pressure chamber(s) of each hydraulic working space of the appliance, the hydraulic fluid pressure in the pressurized chambers, which acts on the outer end surface of the vanes, can also be transmitted to the inner end surface of the vanes.
In expedient development of the invention, the pressure balance means on the vanes of the impeller are, in this arrangement, preferably configured as balance ducts extending in each case from the outer end surface of the vanes to their inner and surface.
As a particularly advantageous first embodiment of the balance ducts on the vanes of the impellers it is proposed that these should be configured as radial grooves which are machined into each of the two side surfaces, which are in sealing contact with the side walls of the driving wheel, of the vane. These radial, grooves arc are in further configuration of the balance ducts according to the invention, preferably arranged on the radial longitudinal center lines of the side surfaces of the vanes and have a profile cross section which is sufficiently large to permit compensation on for the hydraulic fluid leaks between the pressure chambers of each hydraulic working space, which necessarily occur through the axial retention grooves of the vanes because of manufacturing tolerances. From the point of view of manufacturing technology radial grooves which are configured with a triangular profile cross section and which have a width corresponding to approximately one third of the vane thickness and a depth corresponding to approximately one quarter of the vane thickness, have been found to be the most advantageous. It is, however, also possible to machine only one of these radial grooves in one of the side surfaces of each vane and/or also to provide them with a semicircular or quadrilateral profile c
Bierman, Muserlian and Lucas
Ina Walzlager Schaeffler OHG
Lo Weilun
LandOfFree
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