Variable displacement type piston machine of which noise and vib

Details Variable displacement type piston machine of which noise and vib Variable displacement type piston machine of which noise and vib

1996-10-04

1998-09-15

Thorpe, Timothy

Pumps

Three or more cylinders arranged in parallel, radial, or...

92 71, F04B 112

Patent

active

058070800

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a variable displacement type piston machine such as a variable displacement type piston pump or a variable displacement type piston motor.


BACKGROUND ART

Conventionally, there has been a variable displacement type piston pump as shown in FIG. 15 (Japanese Utility Model Laid-Open Publication No. SHO 54-176102). This variable displacement type piston pump comprises a valve plate 53 provided with a suction port 51 which serves as a low pressure port and a discharge port 52 which serves as a high pressure port; a cylinder block 55 which rotates while sliding on a slide surface of the valve plate 53 and includes a plurality of cylinders 54, 54, . . . in its axial direction; and a plurality of pistons 57, 57, . . . which reciprocate inside the cylinders 54, 54, . . . by a swash plate 56 according as the cylinder block 55 rotates. As shown in FIG. 16, an oil guide groove 59 which extends from the discharge port 52 to the proximity of a bottom dead center as indicated by B in the figure is provided on a slide surface 58 between the suction port 51 and the discharge port 52 of the valve plate 53. This oil guide groove 59 is comprised of a cut portion 59a and a V-notch 59b as shown in FIGS. 16 and 17.
When a cylinder port 54a is moved from the suction port 51 to the discharge port 52 by the rotation of the cylinder block 55, a gradual back flow is generated from the discharge port 52 to the cylinders 54 by the oil guide groove 59 so that a gradual pressure variation is caused inside the cylinders 54 and the discharge port 52, by which the pressure variation inside the cylinders 54 and the discharge port 52 when the cylinder port 54a is moved from the suction port 51 to the discharge port 52 is eased to reduce the noise and vibration from the variable displacement type piston pump and its piping.
However, in the above prior art variable displacement type piston pump, a fluid flow from the discharge port 52 to the cylinders 54 takes place intermittently every time the cylinder port 54a communicates with the oil guide groove 59 according as the cylinder block 55 rotates, and this has caused the problem that the pulsation is still great and the noise and vibration are great, also impairing the operation characteristic of the whole fluid apparatus.
Accordingly, it is an object of the present invention to provide a variable displacement type piston machine having an oil guide groove that allows a high pressure port and a cylinder to intermittently communicate with each other, wherein its operating fluid is guided from the high pressure port to a drain when no back flow takes place in the oil guide groove to reduce the variation in amount of the operating fluid that is flowing from the high pressure port to a low pressure port, so that the pulsation of discharge fluid is reduced to allow the noise and vibration to be reduced and allow the operation characteristic of the whole apparatus to be improved.


DISCLOSURE OF THE INVENTION

In order to achieve the aforementioned object, the present invention provides a variable displacement type piston machine provided with: a valve plate having a slide surface at which a low pressure port and a high pressure port are opened; a cylinder block, in which pistons respectively reciprocate in a plurality of axially provided cylinders and cylinder ports respectively communicated with the cylinders are opened on a slide surface of the cylinder block that slides on the slide surface of the valve plate, and which rotates to the valve plate; and an oil guide groove which is provided between the low pressure port and the high pressure port on the slide surface of the valve plate and extends from the high pressure port toward a dead center, said high pressure port and said cylinder port being communicated with each other via the oil guide groove to cause a gradual pressure variation inside the cylinders and the high pressure port, the variable displacement type piston machine comprising valve plate and directly communicates with neither the

REFERENCES:
patent: 5538401 (1996-07-01), Schaffner et al.
patent: 5573380 (1996-11-01), Martensen et al.
patent: 5593285 (1997-01-01), Watts
patent: 5683228 (1997-11-01), Beatty

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