Motors: expansible chamber type – Three or more cylinders arranged in parallel radial or... – Cylinders parallel to rotation axis
Patent
1995-06-16
1996-11-12
Freay, Charles G.
Motors: expansible chamber type
Three or more cylinders arranged in parallel radial or...
Cylinders parallel to rotation axis
417270, 417296, 417440, 417522, F04B 126
Patent
active
055729193
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an apparatus for controlling pressure in a cylinder chamber of a hydraulic pump-motor.
BACKGROUND ART
As shown in FIG. 1, there is known a piston-type hydraulic pump-motor in which a cylinder block 3 secured to a shaft 2 is disposed inside a casing 1 to be rotatable, plurality of cylinder chambers 6 are formed into which pistons 5 are respectively fitted in a plurality of cylinder bores 4 of the cylinder block 3. The respective pistons 5 are disposed to be slidable in respective axial directions thereof in accordance with the rotation of the cylinder block 3 through slidable abutment of outer end portions of the pistons 5 against a swash plate 8 through piston shoes 7. And as shown in FIG. 2, the cylinder chambers 6 are communicated with high and low pressure ports 10 and 11 formed in a valve plate 9 so as to alternately at every 180.degree. rotation.
In such a hydraulic pump-motor, as shown in FIG. 2, ports 12 open to the cylinder chambers 6 alternately communicated with the high pressure ports 10 and the low pressure port 11 at top and bottom dead points of the valve plate 9 to thereby switch the operation "from drain to suction" and "from suction to drain".
Fine grooves 10a and 11a are formed with the high and low pressure ports 10 and 11 so as not to cause a rapid pressure change at the time of this switching operation.
That is, if the port 12 is suddenly communicated with the high or low pressure port 10 or 11, the pressure in the cylinder chamber 6 rapidly changes, thus causing hydraulic pressure pulsation or large noise. In order to prevent the pressure in the cylinder chamber 6 from rapidly changing, the fine grooves 10a and 11a are formed with the high and low pressure ports 10 and 11 so that the ports 12 are gradually open thereto through the fine grooves 10a and 11a.
However, since the shapes and sizes of the fine grooves 10a and 11a are made constant and the valve plate 9 is not moved, the port 12 always assumes a constant open position. Accordingly, it is difficult to always achieve most suitable operational characteristics at the time of changing the rotating speed of the cylinder block 3 or the maximum pressure in the cylinder chamber 6 at which the hydraulic pressure pulsation or noise will be caused.
SUMMARY OF THE INVENTION
The present invention aims to provide an apparatus for controlling pressure in a cylinder chamber of a hydraulic pump-motor that is capable of solving the problems described above.
Thus, an object of the present invention is to provide an apparatus for controlling pressure in a cylinder chamber that is capable of always achieving the most suitable operational characteristics by opening or closing switching ports in response to a rotational speed or a maximum pressure in a cylinder chamber to thereby prevent the pressure in the cylinder chamber from rapidly changing, thus preventing hydraulic pressure pulsation and noise from being caused.
The apparatus for controlling a pressure in the cylinder chamber according to the present invention was conceived in consideration of the above matters, and in order to achieve the above and other objects, there is provided, in one aspect, an apparatus for controlling a pressure in a cylinder chamber of a hydraulic pump-motor in which a cylinder chamber is formed by fitting a piston in a cylinder bore that is formed to in a rotatable cylinder block. The cylinder block is rotated so that ports to the cylinder chambers are alternately opened to a high pressure port and a low pressure port, both parts being formed in a valve plate. The apparatus being has a first switching port formed at a top dead point side of the valve plate. The first switching port being is communicated with a tank through a first open-close valve. A second switching port is formed at a bottom dead point of the valve plate, and the second switching port is communicated with the high pressure port through a second open-close valve and comprises a rotational speed detection means for detecting a rotational speed
REFERENCES:
patent: 3200761 (1965-08-01), Firth et al.
patent: 3699845 (1972-10-01), Ifield
patent: 5032061 (1991-07-01), Porel
Kumamoto et al., "Research on Reduction of Pulsating Flow of Swash-Plate Axial Piston Pump", Hydraulics and Pneumatics Lecture Meeting, May 25-26, 1992, pp. 113-116.
Freay Charles G.
Kabushiki Kaisha Komatsu Seisakusho
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