Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
2001-09-17
2004-03-09
Lopez, F. Daniel (Department: 3745)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C091S031000, C123S090310, C137S625690, C464S002000
Reexamination Certificate
active
06701877
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns a control device for adjusting a relative angular position of a driven shaft, particularly a camshaft of an internal combustion engine, with the following features
the control device comprises a drive pinion that is rotatably connected to the shaft,
the control device comprises an adjusting element (
1
) for the angular adjustment of the drive pinion relative to the shaft, and further comprises chambers (
2
,
3
) that are alternately supplied with hydraulic fluid,
the control device further comprises a control valve (
6
) for actuating the adjusting element (
1
), said control valve being connected to the chambers (
2
,
3
) of the adjusting element (
1
) through pressure medium channels (
4
,
5
),
the control valve (
6
) comprises a valve body (
7
) comprising working connections A and B for the pressure medium channels (
4
,
5
), a delivery connection P for the supply of hydraulic fluid and a discharge connection T for the discharge of hydraulic fluid,
the control valve (
6
) further comprises a sliding valve control piston (
8
) for setting different hydraulic resistances W between the individual connections,
in a first adjusted position of the valve control piston (
8
), the connections between the connections P and A and between the connections B and T have a low resistance W and the connections between the connections P and B and between the connections A and T have a high resistance W,
in a second adjusted position of the valve control valve (
8
), the connections between the connections P and B and between the connections A and T have a low resistance W and the connections between the connections P and A and between the connections B and T have a high resistance W,
in a third adjusted position of the valve control valve (
8
), the connections between the connections A and T and between the connections B and T and the connections between the connections P and A and between the connections P and B have a high resistance W. The invention further concerns a control valve for actuating the adjusting element of a control device for adjusting the relative angular position of a driven shaft.
BACKGROUND OF THE INVENTION
A control device of the pre-cited type is known from U.S. Pat. No. 5,483,930. Through an adequate positioning of the valve control piston of the control valve in a hold position by a control circuit it is assured that one of the chambers of the adjusting element of the control device is supplied with an additional quantity of hydraulic fluid for compensating fluid leakage and stabilizing the position of the adjusting piston of the adjusting element.
OBJECT OF THE INVENTION
The object of the invention is to provide a control device for adjusting a relative angular position of a driven shaft, particularly a camshaft of an internal combustion engine, which device enables a compensation of fluid leakage in a hold position of the valve control piston without a controlled positioning of the valve control piston.
SUMMARY OF THE INVENTION
This and other objects of the invention, which will also become obvious from the following description of the invention, are achieved by the fact that, in a third adjusted position (hold position) of the valve control piston of the control valve of the control device of the invention, to compensate for fluid leakage from the pressure medium channel of the connection A, the resistance in the connection between the connections P and A is lower than the resistance in the connection between the connections P and B, whereas to compensate for fluid leakage from the pressure medium channel of the connection B, the resistance in the connection between the connections P and B is lower than the resistance in the connection between the connections P and A.
With a control device of this type, the phase angle of the camshaft of an internal combustion engine can be set by an angular displacement between the camshaft and the belt- or chain-driven drive pinion not only for two end positions, namely, a first adjusted position with the phase angle “advance” and a second adjusted position with the phase angle “delay”, but also for an intermediate, third adjusted position (hold position) in which the value of the phase angle lies between the two extremes.
When an intermediate phase angle corresponding to a third adjusted position of the valve control piston of the control valve of the control device is set, a medium drive torque of the internal combustion engine having a dynamic and a static component is applied to the camshaft and, thus, to the chambers of the adjusting element of the control device. The dynamic torque component is applied substantially uniformly to the two chambers thus assuring an alternating supply of hydraulic fluid thereto, while the static torque component loads only one of the two chambers and thus the pressure medium channel connected to this chamber and the associated working connection of the valve body of the control valve.
A force and torque analysis taking into consideration the structure of the control device and the internal combustion engine makes it possible to predict which of the chambers and, thus also, which of the pressure medium channels and working connections of the valve body will be loaded by the static component of the torque of the internal combustion engine. During operation of the control device, increased leakage of fluid is to be expected at the loaded pressure medium channel and the associated working connection.
By the inventive structural measures implemented in the control valve, it is achieved that, in an intermediate adjusted position (hold position), for stabilizing the valve control piston for setting an intermediate phase angle, the pressure medium channel and the associated working connection of the control valve which will predictably be loaded by the static torque component have a lower hydraulic resistance to the delivery connection P than the pressure medium channel and the associated working connection that are not loaded by the static torque component.
Due to the lower hydraulic resistance set at the loaded connection, a larger volume of hydraulic fluid is supplied to the loaded pressure medium channel for compensating leakage of hydraulic fluid. This, at the same time, also stabilizes the position of the piston of the adjusting element.
By the inventive structural measures implemented in the valve control piston and/or in the valve body of the control valve, it is achieved that a larger volume of hydraulic fluid is supplied to the pressure medium channel and the associated working connection of the control valve loaded by the static torque component for compensating for the fluid leakage that has occurred there. In contrast to the prior art, there is no need for an expensive and interference-prone positioning of the valve control piston by a control circuit. Rather, it is possible in the control device of the invention, to use a 4/3 proportional valve, known per se, with a structurally modified valve control piston and/or valve body and defined adjusted positions (first position “advance”, second position “delay” and third position “hold”). Compared to the prior art, in the control device of the invention, the pressure rigidity of the control valve and the torque rigidity of the entire hydraulic system of the control device are improved.
In an advantageous embodiment of the invention, for compensating for fluid leakage, the delivery connection P is connected through a connecting duct to the loaded pressure medium channel of the respective working connection of the control valve, so that more hydraulic fluid is supplied to this pressure medium channel than to the other channel. Such a connecting duct having a by-pass function can also be added subsequently to the control valve without structural modifications to the valve control piston and/or the valve body. The arrangement of a throttle in the connecting duct assures that a larger amount of hydraulic fluid is supplied to the loaded pressure medium channel as a compensation for leakage, above
Auchter Jochen
Kohrs Mike
Ottersbach Rainer
Strauss Andreas
Ina Walzlager Schaeffler oHG
Lopez F. Daniel
Muserlian Lucas and Mercanti
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