The hydraulic circuit for the lifting of the harvesting section of the combine harvester

Abstract

The purpose of the present invention is to reduce a time lag generated when lowering a reaper at high speed. To this end, a hydraulic circuit comprise: a pilot-operated check valve (11); a first switching valve (7); a first throttle (9) which is connected to the first switching valve (7) in parallel and restricts the flow of hydraulic fluid supplied from a hydraulic pump (4) to a hydraulic cylinder (2); a resistance valve (10) which is connected to the first throttle (9) in series and opens a valve when a primary fluid pressure reaches a predetermined pressure; a second throttle (12b) for restricting the flow of hydraulic fluid which flows into the pilot-operated check valve (11) backward to be drained; a third throttle (18) which has a flow path sectional area smaller than the second throttle (12b) and restricts the flow of the drained hydraulic fluid; and a second switching valve (19) for selectively switching a flow path of the drained hydraulic fluid into a flow path of the hydraulic fluid drained through the third throttle (18).

Description

technical field [0001] The present invention relates to a hydraulic circuit for raising and lowering a harvesting section of a combine harvester. Background technique [0002] In the prior art, combine harvesters are usually equipped with a free-rising harvesting section at the front of the body. For the harvesting section, for example, it is required to raise and lower at a low speed when setting the harvesting height, and to raise and lower at a high speed after the work is finished or before the work starts. Therefore, there has been proposed a hydraulic circuit capable of changing the speed of a hydraulic cylinder for raising and lowering a harvesting section (for example, JP-A-H06-113603). [0003] In the hydraulic circuit of the Japanese Patent Publication No. H06-113603, when the harvesting section is lowered, the electromagnetic on-off valves connected in parallel with different flow rates are selectively operated to control the flow rate of the hydraulic oil discha...

AI Technical Summary

Problems solved by technology

[0009] According to the hydraulic circuit disclosed in Japanese Patent No. 4994296, fluctuations in the rising speed of the reaping section caused by the escape flow rate of hydraulic oil are suppressed, and the excellent effect of low-speed rising can be exerted even when the engine rotates at a low speed, but according to the circuit Especially when the hydraulic oil flow rate is small and the oil temperature is high under no-load conditions, when the harvesting unit is lowered at high speed, there will be some time lag from the start of the high-speed lowering operation to the actual lowering of the harvesting unit

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