Pumps – Expansible chamber type – Having pulsation dampening fluid receiving space
Reexamination Certificate
1999-08-24
2001-10-23
Freay, Charles G. (Department: 3746)
Pumps
Expansible chamber type
Having pulsation dampening fluid receiving space
C417S312000, C417S543000
Reexamination Certificate
active
06305919
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to hydraulic pumps. More particularly, the present invention relates to an apparatus for reducing pressure pulses in a hydraulic pump that create fluid borne noise.
BACKGROUND ART
The use of hydraulic pumps, such as power steering pumps, is well known in the automotive industry. Conventional hydraulic pumps, such as those used in power steering systems, are positive displacement pumps. Positive displacement pumps, such as gear pumps, have a pumping action that can create pressure fluctuations in the pump discharge flow. Any variations in this pump discharge flow are converted to pressure pulsations when they encounter circuit resistance. This conversion is referred to in the art as a pressure ripple.
One such example of a positive displacement pump is a vane rotor pump. During normal operation of pumps of this type, pressure pulsations are generated. Each rotation of the pump causes chambers that exist between the vanes to go through two expansion and compression phases, as is well known. The transitions between the expansion and compression phases can create pressure changes in the fluid which can create pressure pulsations. As the fluid is compressed, the pressure in the fluid builds up. This pressure can be different than the pressure in the pumping chamber at the high pressure side of the pump (outlet). Thus, when the compressed fluid at a higher pressure is added to the fluid in the pumping chamber, pressure pulsations can be created as the fluid equalizes in pressure as a whole.
The pressure pulsations transmitted through the fluid can cause resonating (vibrating) of the system components downstream of the pump. These pressure pulsations can also excite structure in the pumping circuit causing them to vibrate and generate additional objectionable noise. For example, if there is grounding of the hoses, i.e., direct contact of the hoses to the vehicle with no isolation, the system can create noises that are unacceptable to the vehicle user.
Typical pressure pulsation noises are tuned out by the use of various tuning methods in the hoses. The utilization of these tuning methods, however, is expensive. Additionally, accumulators have also been used as another possible way to tune out pressure pulsations. The use of accumulations, however, adversely affects the reaction time of the pump. It would therefore be desirable to provide a pump for use in a power steering system that is able to minimize pressure pulsations in an effective, cost efficient manner.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an apparatus for reducing the pressure pulsations in a power steering system.
It is a further object of the present invention to provide an integral dampening chamber in a pump housing for reducing pressure pulsations.
In accordance with one aspect of the invention, an apparatus for reducing pressure pulsations in a power steering system is provided. The apparatus includes a hydraulic pump for use in a power steering system. The hydraulic pump is positioned within a pump reservoir formed in a pump housing. The pump housing has an upstream portion and a downstream portion. The upstream portion receives fluid from a fluid source and is in communication with a pump inlet. The downstream portion receives fluid expelled from a pump outlet and conveys it to a steering gear. The downstream portion includes a dampening chamber integrally formed in the pump housing which increases the volume of the downstream section allowing fluid expelled from the pump outlet to equalize in pressure whereby pressure pulsations are minimized.
Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.
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Robertson James Richard
Staton Timothy Matthew
Freay Charles G.
Kajander John E.
Solak Timothy P.
Visteon Global Technologies Inc.
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