Swash plate type hydraulic pump or motor

Abstract

A swash plate type hydraulic pump or motor has a first swash plate (30) and a second swash plate (40) which cause a first piston (8) and a second piston (9), respectively, to move reciprocally, opposing each other, so as to expand and contract a volume chamber (10) according to rotation of a cylinder block (4). A rod shape valve body (60) is disposed pushed into a through hole (12) of a shaft axis of the cylinder block (4) so as to be free to rotate relative to the cylinder block (4). A pair of supply and discharge ports (61) that open and supply high pressure and low pressure, respectively, are formed in an outer circumferential surface of the valve body (60). A cylinder port (11) is formed connecting the volume chamber (10) and an inner circumferential surface of the through hole of the cylinder block. The cylinder port (11) is arranged in a position opposite to the supply and discharge port (61).

Description

FIELD OF THE INVENTION [0001] This invention relates to a swash plate type hydraulic pump or motor capable of being applied to hydrostatic transmission (hereinafter called HST), which is used in a running gear or the like in agricultural machinery, industrial vehicles, and construction machinery. BACKGROUND OF THE INVENTION [0002] HST is a combination of a hydraulic pump and a hydraulic motor. Consequently, by Changing the tilt angle of a swash plate in the hydraulic pump, and by changing the discharge amount in a range from zero to a maximum discharge amount, the rotational velocity of the hydraulic motor changes. A vehicle can thus continuously change speeds from a stopped state to a maximum forward or reverse speed. [0003] Structures that comprise a single swash plate, a cylinder block, and a plurality of pistons that are housed on only one side of the cylinder block are often used as HST hydraulic pumps or hydraulic motors. [0004] However, the size of the HST hydraulic pump or t...

AI Technical Summary

Benefits of technology

[0008] However, a hydraulic fluid passage and a valve mechanism that switches flow of the hydraulic fluid in order to supply and discharge the hydraulic fluid to and from the pistons disposed on both sides of the cylinder block become complex. Further, the hydraulic fluid passage becomes complex, and the supply and discharge efficiency for the hydraulic fluid worsens.

[0009] It is an object of this invention to provide a swash plate hydraulic pump or motor in which a valve mechanism for switching the flow of hydraulic fluid and a passage configuration are simplified.

Problems solved by technology

However, a hydraulic fluid passage and a valve mechanism that switches flow of the hydraulic fluid in order to supply and discharge the hydraulic fluid to and from the pistons disposed on both sides of the cylinder block become complex.

Further, the hydraulic fluid passage becomes complex, and the supply and discharge efficiency for the hydraulic fluid worsens.

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