Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
2002-10-15
2004-10-19
Denion, Thomas (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090150, C123S090310
Reexamination Certificate
active
06805080
ABSTRACT:
BACKGROUND
The invention relates to a device for changing the control times of gas exchange valves of an internal combustion engine, and it can be implemented with particular advantage in a rotary piston adjustment device for rotation angle adjustment of a camshaft relative to a crankshaft.
A representative device of this type is already known from DE 196 23 818 A1. This device is fastened to the drive-side end of a camshaft mounted in the cylinder head of the internal combustion engine, and in principle is formed as a hydraulic actuator which can be controlled based on various operating parameters of the internal combustion engine. This device essentially is formed of a drive wheel drivingly connected with a crankshaft of the internal combustion engine and of a vane wheel connected to rotate with a camshaft of the internal combustion engine. The drive wheel and the vane wheel are drivingly connected each other and transfer torque from the crankshaft to the camshaft of the internal combustion engine. In a preferred embodiment, the drive wheel has a cavity formed by a hollow cylindrical circumferential wall and two sidewalls, in which two hydraulic working spaces are formed by two radial boundary walls extending to the longitudinal mid-axis of the device. The vane wheel correspondingly has, at the circumference of its hub, two vanes extending radially into the working space and dividing the working space into respectively an A pressure chamber and a B pressure chamber which, upon selective or simultaneous application of pressure with a hydraulic pressure medium, effect a pivoting motion or fixation of the vane wheel with respect to the drive wheel and hence of the camshaft with respect to the crankshaft. Furthermore, when the pressure medium pressure falls below that required for adjustment, such as occurs for example on switching off the internal combustion engine, the vane wheel can be mechanically coupled to the drive wheel by a separate locking element in a preferred basic position within its range of adjustment, in order, in particular when the internal combustion engine is restarted, to avoid chatter of the vane wheel on the boundary walls of the drive wheel resulting from the changing moment of the camshaft until the required pressure medium pressure has built up. This locking element, specifically formed as a stepped cylindrical locking pin, is arranged in a bore, parallel to the longitudinal mid-axis of the device, at the end of a vane of the vane wheel, and is displaceable by a spring element into a locking position within a seat in the sidewall of the drive wheel remote from the camshaft. The section of the locking pin that has a greater diameter is guided by the inner wall of the bore in the vane, and the section of the locking pin provided with a smaller diameter, which is also conical on the locking side for exact positioning between the vane wheel and the drive wheel, is guided by a guide bushing inserted into the bore. The seat of the locking pin is specifically formed as an elongate bore drilled into the sidewall of the drive wheel on the side remote from the cam shaft, extending in a direction transverse to the direction of rotation of the vane wheel, and connected by a groove to the A pressure chamber of the device. In addition, the annular surface arising at the transition between the cylindrical sections is also connected to the B chamber of the device via a radial bore, so that the locking pin can be moved hydraulically into an unlocked position within the bore in the vane of the vane wheel both on the application of pressure to the A pressure chambers of the device and also on the application of pressure to the B pressure chambers of the device.
It is however disadvantageous in this known device that the arrangement of the locking pin in a bore at the end of a vane of the vane wheel requires a solid construction of the vane and thus limits the number of possible hydraulic working spaces in the device to a maximum of three to four when the usual adjustment angle of about 30° nominal value is to be realizable with the device. Moreover, the relatively large distance between the longitudinal axis of the bore in the vane of the vane wheel and the longitudinal mid-axis of the device is the origin of a reduction of the rigidity of the locked connection between the vane wheel and drive wheel, and of the still considerable centrifugal forces to which the locking pin is subjected when the engine is running, which in combination with the simultaneously arising dirt sensitivity of the locking device due to the dirt particles in the hydraulic fluid deposited at the end of the vane during rotation can disadvantageously affect the locking function. Likewise, the embodiment of the locking device as a stepped cylindrical locking pin, which is connected by the annular surface arising between the cylindrical sections and by an annular surface on the locking side both to the A pressure chambers and also to the B pressure chambers of the device, is found to be disadvantageous in that locking during shutting off the engine is not possible, since at least one of the two surfaces on the locking pin still has the pressure of the pressure medium acting on it and thus holds the locking pin in its uncoupled position in the bore in the vane of the vane wheel. Thus the device cannot be operated with a specific locking, and above all is unsuitable for application to SOHC engines or to exhaust camshafts, in which a locking of the vane wheel or respectively the camshaft in an “early” control time position of the gas exchange valves of the internal combustion engine is necessary. The conical embodiment of the locking pin on the locking side with a constant cone angle furthermore has the disadvantage, in connection with its elongate seating bore in the drive wheel sidewall remote from the camshaft, that high component loads on the vane wheel and on the drive wheel occur on locking, and that the danger exists on unlocking that jamming of the locking pin in the seating bore occurs. In addition, the increased construction space requirement and the relatively high manufacturing cost for the stepped locking pin are also disadvantageous, since these are the origin of a limited applicability of the device in restricted space conditions in the engine and of the relatively high production costs of the device.
SUMMARY
The invention therefore has as its basic object to provide a device for changing the control times of gas exchange valves of an internal combustion engine, particularly a rotary piston adjusting device for rotation angle adjustment of a camshaft relative to a crankshaft, which device has a locking arrangement between a vane wheel and a drive wheel thereof which is simple and can be produced at a favorable cost, which has a small space requirement. Additionally, the device is, to the greatest possible degree, uninfluenced by centrifugal forces and is also insensitive to dirt, and is arranged or formed such that the locked connection between vane wheel and drive wheel has high rigidity, such that a universal use of the device is possible on SOHC engines or on exhaust camshafts.
This object is attained according to the invention with a device for changing the control times of gas exchange valves of an internal combustion engine including a rotary piston adjustment device for rotation angle adjustment of a camshaft relative to a crankshaft in which the adjustment device is fastened to a drive end of a camshaft mounted in a cylinder head of the internal combustion engine and comprises a hydraulic actuator which is controllable in dependence on at least one operating parameter of the internal combustion engine. The adjustment device includes a drive wheel in driving connection with the crankshaft of the internal combustion engine and a vane wheel connected to rotate with the camshaft of the internal combustion engine. The drive wheel has a cavity formed by a hollow cylindrical circumferential wall and two sidewalls, and at least one hydraulic working space is formed in the cavity by at leas
Golovatai-Schmidt Eduard
Schafer Jens
Scheidt Martin
Strauss Andreas
Denion Thomas
Eshete Zelalem
INA-Schaeffler KG
Volpe and Koenig P.C.
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