Motors: expansible chamber type – Three or more cylinders arranged in parallel radial or... – Cylinders parallel to rotation axis
Patent
1990-01-30
1993-02-02
Bertsch, Richard A.
Motors: expansible chamber type
Three or more cylinders arranged in parallel radial or...
Cylinders parallel to rotation axis
91504, 91505, F01B 1304
Patent
active
051829789
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a bent axis type variable displacement hydraulic machine which is suitable for use as a hydraulic pump, hydraulic motor or the like, and, more particularly, to a bent axis type variable displacement hydraulic machine adapted to support a rotational shaft by partial and/or total-hydrostatic bearings.
BACKGROUND OF THE INVENTION
Generally, a bent axis type hydraulic machine has the drive disc of a rotational shaft coupled with a cylinder block through pistons which are reciprocally received in the cylinder block. Therefore, when the bent axis type hydraulic machine is used as a hydraulic pump, the hydraulic reaction forces acting on pistons on the high pressure side in the discharge stroke are supported by the rotational shaft through the drive disc. Similarly, when applied as a hydraulic motor, the hydraulic reaction forces acting on pistons on the high pressure side in the suction (feeding) stroke are supported by the rotational shaft through the drive disc.
Accordingly, in a bent axis type hydraulic machine of this type, the rotational shaft is subject to radial and thrust load of the hydraulic reaction forces and therefore it is necessary to hold the rotational shaft in suitable condition for supporting these loads.
In this regard, it has been the general practice in the prior art to resort to the so-called mechanical support type which mechanically supports the rotational shaft rotatably by ball or roller bearings capable of supporting the radial and thrust loads, with the partial hydrostatic support type which mechanically supports either the radial or thrust loads by a roller or ball bearing while supporting the other load hydraulically by a hydrostatic bearing, or the total hydrostatic support type which supports the entire loads hydraulically by hydrostatic bearings.
Of these various shaft supporting means, a hydraulic machine employing a shaft support bearing of the partial hydrostatic type is described in, for example, Japanese Laid-Open Patent Application 60-224981, wherein a rotational shaft is supported by a hydrostatic thrust bearing composed of a stationary bearing and a movable bearing, each movable bearing being provided with springs and an outer ring to counteract the thrust load which acts on the rotational shaft, along with pistons which are located on the side of the outer ring to generate a pressure in the same direction as the springs and to which oil pressure is applied from the high pressure area in the cylinder block.
On the other hand, a hydraulic machine supporting a shaft by total-hydrostatic bearings is described in Japanese Laid-Open Patent Application 59-131776, which is provided with a radial load bearing sleeve and a thrust load bearing plate within a casing, in combination with a drive flange which is movably disposed between the bearing sleeve and the bearing plate to serve also as a drive disc. The one end face of the drive flange is securely connected to a rotational shaft and the other end face is coupled with pistons. Further, pressure chambers, constituting a hydrostatic radial bearing, are defined between the outer peripheral surface of the drive flange and the bearing sleeve, and drive shoes, constituting a hydrostatic thrust bearing, are provided on one end face of the drive flange. The pistons have oil passages bored therein for supplying high pressure oil to the radial and thrust bearings from cylinders in the cylinder block, to thereby hydrostatically support the radial and thrust loads.
In this connection, even if the hydraulic reaction forces which are applied to the rotational shaft through pistons are the same, the resulting radial and thrust loads vary in dependence upon the tilt angle of the cylinder block. More specifically, the radial load F.sub.R and thrust load F.sub.T are expressed as ##EQU1## where: F is the hydraulic reaction force by the piston,
When the tilt angle .THETA. is minimum, the radial load F.sub.R becomes minimum while the thrust load F.sub.T becomes maximum. On the other hand, when t
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patent: 4765228 (1988-08-01), Wagenseil
patent: 4788902 (1988-12-01), Akasaka
patent: 4836693 (1989-06-01), Stroze
Akasaka Yoshimichi
Gotoh Yasuharu
Nakamura Ichiro
Bertsch Richard A.
Hitachi Construction Machinery Co. Ltd.
Korytnyk Peter
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