Pumps – With muffler acting on pump fluid
Reexamination Certificate
1999-03-17
2001-02-06
Freay, Charles G. (Department: 3746)
Pumps
With muffler acting on pump fluid
C417S540000
Reexamination Certificate
active
06183213
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to hydraulic pumps. More particularly, the present invention relates to an apparatus for reducing fluid borne noise in a hydraulic pump.
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 creates a pressure fluctuation 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 pressure ripple.
The pressure pulsations transmitted through the fluid can cause resonating of the system components downstream of the pump, which is known in the art as fluid borne noise. This pressure fluctuation can also excite structure in the pumping circuit causing them to vibrate and generate additional objectionable noise.
Typical pumps generate the majority of their noise energy at the fundamental or pumping frequency (shaft speed x the number of pumping chambers). Typical pumps also can generate appreciable noise energy in multiples of harmonics of the fundamental frequency. The sound level of the noise energy generated by typical pumps generally decreases at higher frequencies, but even fourth and fifth harmonics can have enough energy to cause noise.
Additionally, the configuration of these prior pumps is such that they require the use of hoses for fluid transfer. The hoses are typically located between the outlet of the pump and the steering gear. By adding a pressure pulse attenuator as a separate part downstream of the pump, the size of the power steering gear pack and the cost of the power steering system are increased.
It would therefore be desirable to provide a pump for use in a power steering system that is able to reduce the amount of fluid borne noise and is also compact.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an apparatus for reducing the fluid borne noise in a power steering system.
It is a further object of the present invention to provide a pressure pulse attenuator that is integral with the pump housing.
In accordance with one aspect of the invention, an apparatus for reducing the fluid borne noise in a power steering system is provided. The apparatus includes a hydraulic pump for use in a power steering system. The hydraulic pump has a pump housing with a power steering fluid inlet port formed in the pump housing. The inlet port is in fluid communication with a power steering fluid reservoir to transfer power steering fluid to a power steering fluid chamber formed in the pump housing. A first fluid conduit and a second fluid conduit are formed in the pump housing. The first fluid conduit has an inlet opening and an exit opening and the second fluid conduit has a separate inlet opening and exit opening. The first fluid conduit inlet opening is in fluid communication with the power steering fluid chamber to receive power steering fluid therethrough and the second fluid conduit inlet opening is also in fluid communication with the power steering fluid chamber to receive power steering fluid therethrough. The first fluid conduit exit opening and the second fluid conduit exit opening are in fluid communication with a pressure wave attenuator to transfer power steering fluid thereto. The second fluid conduit has a distance between the inlet opening and the exit opening that is longer than a distance of the first fluid conduit between the inlet opening and the exit opening. The pressure wave attenuator is in fluid communication with an outlet port to convey the power steering fluid to a steering gear.
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.
REFERENCES:
patent: 2732802 (1956-01-01), Eames, Jr.
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patent: 2928961 (1960-03-01), Morrill
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patent: 3434282 (1969-03-01), Shelhart
patent: 3790309 (1974-02-01), Volz
patent: 4207033 (1980-06-01), Drutchas et al.
patent: 4540354 (1985-09-01), Tuckey
patent: 4642035 (1987-02-01), Nyquist
patent: 5173034 (1992-12-01), Riffe
patent: 5785013 (1998-07-01), Sinn
patent: 4303328 (1994-08-01), None
patent: 1539393 (1990-01-01), None
Machine Design Magazine—“New Technique Muffle Hydraulic Noise” by Stanley J. Skaistis, vol. 51, No. 7, Mar. 22, 1979, pp. 120-126.
Palakodati Sunil
Robertson James Richard
Freay Charles G.
Visteon Global Technologies Inc.
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