Pumps – Expansible chamber type – Having pumping chamber pressure responsive distributor
Patent
1997-10-27
1999-11-09
Freay, Charles G.
Pumps
Expansible chamber type
Having pumping chamber pressure responsive distributor
92181R, F04B 3910
Patent
active
059802235
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a refrigerant compressor having a piston, which is movable back and forth in a cylinder, the cylinder having at its end wall a discharge opening closable by a discharge valve, into which opening a projection on the corresponding end face of the piston projects when the piston is located in the region of its end position.
Refrigerant compressors of that kind are widely used in domestic refrigerators and upright and chest freezers. In a situation of increasing environmental awareness, there have for some years been attempts to make such cooling devices of lower and lower energy consumption. Saving of energy can be achieved on the one hand by improved heat insulation, and on the other hand also by increasing the efficiency of the refrigerant compressors.
One method of increasing efficiency is to construct at the end face of the piston a projection which, in the region of the upper dead centre of the piston, that is to say when the end face of the piston is as close as possible to the end wall of the cylinder, projects into the discharge opening. By means of this projection the volume of gas remaining in the discharge opening is displaced. Without that projection, the volume of gas remaining there would merely be compressed and could subsequently expand again, which leads to energy loss because of a non-adiabatic process in the refrigerant. Such a projection is known, for example, from the compressor, type SC, manufactured by Danfoss. A similar arrangement is known from U.S. Pat. No. 5,149,254.
The projection has the disadvantage, however, that it affects the flow of the refrigerant through the discharge opening. In particular, in the end region of the movement the cross-section available for the flow can become relatively small, so that the gas flowing through is accelerated. The temperature of the gas rises correspondingly. After flowing through the discharge valve, eddies frequently form in the flow of gas, which lead to an increase in the impedance, causing higher energy consumption.
The invention is based on the problem of increasing the efficiency of a compressor.
SUMMARY OF THE INVENTION
That problem is solved in a refrigerant compressor of the kind mentioned in the introduction in that the projection is of asymmetrical construction in cross-section.
By means of this relatively simple measure, the projection can be better matched to the flow of gas through the discharge opening. Through appropriate shaping of the projection, the flow of gas can be deliberately controlled so that fewer eddies occur and the gap that forms on movement of the piston into its end position between projection and discharge opening maintains a free flow cross-section which is sufficient to allow the gas to flow through without undue resistance. The residual volume in the discharge opening can nevertheless be kept approximately as small as it was previously with a symmetrical projection.
In that case it is especially preferred for the projection to have a sloping circumferential wall, the gradient changing along the circumference. The desired asymmetry of the projection can be achieved relatively easily by such a change in the gradient. The gradient can be matched to the flow of gas to be expected in an individual case, so that it is possible to achieve the desired improvement in the flow characteristic using simple means.
The projection preferably has a gently sloping flank in the direction of a main gas flow. This gently sloping flank causes a relatively gentle redirection of the gas flow, so that formation of eddies is largely avoided by that measure. Even by a gently sloping flank the gas flow is nonetheless guided into the discharge opening. The projection is able to displace the gas volume located in the discharge opening.
In that case it is especially preferred for the projection to be arranged eccentrically on the piston end face and to have the gently sloping flank towards the middle of the piston end face. For various reasons it may be desirable to arrange the pr
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patent: 5174735 (1992-12-01), Gannaway
Iversen Frank Holm
Jensen Michael Skovgaard
Danfoss Computers GmbH
Evora Robert Z.
Freay Charles G.
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