Motors: expansible chamber type – Constantly applied motive fluid with controlled venting – Motive fluid constantly applied to and vented from opposed...
Patent
1994-05-25
1995-12-19
Lopez, F. Daniel
Motors: expansible chamber type
Constantly applied motive fluid with controlled venting
Motive fluid constantly applied to and vented from opposed...
91421, F15B 1302
Patent
active
054760313
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention is based on a hydraulic setting device of the generic type of the main claim. A hydraulic setting device is known, from U.S. Pat. No. 3,516,331, with a differential cylinder whose pressure space associated with the larger effective pressure surface of the differential piston is controlled by means of a 3/2-way valve. A pressure difference, which causes an adjusting motion, can be generated in the two pressure spaces by correspondingly pulsing the 3/2-way valve. Such a hydraulic setting device has the disadvantage that when the differential piston is stationary, i.e. unmoved, relatively high pressures are present in the pressure spaces, these pressures being no smaller or only slightly smaller than the adjustment pressures. Because of this, a high expenditure of energy is necessary in the hold position (stationary position) of the differential piston and this can lead to high costs in the operation of the hydraulic setting device.
A hydraulic setting device in which these disadvantages are avoided is known from German Offenlegungsschrift 40 37 824. In this known hydraulic setting device, the pressure space arranged at the large piston area of a differential cylinder is activated by means of a control valve which can be actuated electro-magnetically. This control valve is configured in such a way that it has negative overlap in its central position. It is activated in such a way that the pressures in the pressure spaces of the differential piston remain approximately constant and in such a way that, in the stationary position of the differential piston, the hold pressures are substantially smaller than the adjustment pressures. Such a hydraulic setting device is, for example, employed for actuating a device which adjusts the camshaft relative to the crankshaft in an internal combustion engine (German Offenlegungsschrift 36 16 234.) In order to seal the respective pressure-carrying connection securely against the return connection in the end positions of the control valve, guide gaps--in some cases narrow and long--are necessary for the valve element in these control valves. Because of this, these control valves are sensitive to dirt under certain circumstances, i.e. the function of the valve can be impaired in the case of dirty pressure medium (engine oil of the internal combustion engine). In addition, such control valves are expensive to manufacture because of the small tolerances necessary.
ADVANTAGES OF THE INVENTION
The hydraulic setting device according to the invention and with the characterizing features of the main claim has, in contrast, the advantage that it operates with low losses when no adjusting motion of the differential piston takes place, that it is simple in construction and that the control valve has little sensitivity to dirt.
Further advantages of the invention and advantageous further developments are given in the subclaims and the description.
DRAWING
Two embodiment examples of the invention are explained in more detail in the following description and drawing. The latter shows a simplified representation of a first embodiment example of the hydraulic setting device in FIG. 1. FIG. 2 shows a simplified representation of the pump of the hydraulic setting device and FIG. 3 shows the control valve of the hydraulic setting device in longitudinal section. FIG. 4 shows a simplified representation of a second embodiment example of the hydraulic setting device.
DESCRIPTION OF THE EMBODIMENT EXAMPLES
A hydraulic setting device is designated by 10 in FIG. 1 and this device has a differential cylinder 11 with differential pistons 12, 13. The pressure space 14 at the large piston area of the differential piston 12 is connected, via a pressure conduit 15, to a pump working space 16 of a pump 17--shown in more detail in FIG. 2. The pressure space 18 at the smaller effective piston area of the differential piston 12 is connected, via a pressure conduit 19, to a further pump working space 20, acting in opposition to the first pump working space 16, of the pump 17.
T
REFERENCES:
patent: 2983278 (1961-05-01), Heintz
patent: 3042058 (1962-07-01), Lucien
patent: 3047010 (1962-07-01), Rothfuss
patent: 3096690 (1963-07-01), Hayner
patent: 3270508 (1966-09-01), Smith et al.
patent: 3516331 (1970-06-01), Oelrich et al.
Muller Martin
Rembold Helmut
Lopez F. Daniel
Robert & Bosch GmbH
Striker Michael J.
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