Quantitative/variable hydraulic system of load-sensitive loader

Abstract

The invention relates to a hydraulic system of a loader, in particular to a quantitative/variable hydraulic system of a load-sensitive loader. The quantitative/variable hydraulic system comprises a logic control valve and a flow control valve, wherein an EF oil port of the logic control valve is connected with a multi-way valve through a hydraulically controlled throttling valve body of the flow control valve; and a pilot valve is connected with both a KL oil port of a hydraulically controlled reversing valve body of the logic control valve and an LS8 oil port of the hydraulically controlled throttling valve body of the flow control valve. According to the quantitative/variable hydraulic system provided by the invention, a combination of a three-way pressure compensator and the hydraulically controlled throttling valve body is additionally arranged in a current quantitative working system, so that low-pressure unloading in the working system is achieved through the bypass three-way pressure compensator, the self-adaption of load pressure is achieved through a quantitative pump, and then the accurate flow output irrelevant to load variations is achieved; and besides, the all-condition variable displacement of a variable pump is achieved and the advantage of the variable pump is exerted to the greatest extent.

Description

technical field [0001] The invention relates to engineering machinery, in particular to a loader constant variable hydraulic system. Background technique [0002] Loader is a kind of construction machinery with high working efficiency and wide application. Its hydraulic system is mainly composed of working hydraulic system and steering hydraulic system. The domestic existing loader hydraulic systems include full quantitative hydraulic system, full variable hydraulic system, fixed variable hydraulic system, etc. Among them, the full quantitative hydraulic system, that is, the steering system and the working system both use quantitative pumps, and its cost is relatively low, but it belongs to the open-center overflow speed regulation system, and there are overflow losses, throttling losses, and neutral losses. The hydraulic system has high energy consumption, high heat generation, and relatively low efficiency; the full variable hydraulic system, that is, adopts hydraulic com...

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Problems solved by technology

Among them, the full quantitative hydraulic system, that is, the steering system and the working system both use quantitative pumps, and its cost is relatively low, but it belongs to the open-center overflow speed regulation system, and there are overflow losses, throttling losses, and neutral losses. The hydraulic system has high energy consumption, high heat generation, and relatively low efficiency; the full variable hydraulic system, that is, adopts hydraulic components such as double load-sensitive variable plunger pumps, load-sensitive closed-center control valves, etc., and has better operating comfort than quantitative hydraulic systems, and can realize Power control and energy saving, but the main problem is that the cost is high, and it is very sensitive to the cleanliness of the system, and a small pollution will have a serious impact on the performance, quality, service life and reliability of the product, that is, the trouble-free working time; fixed variable hydraulic system , that is, the steering system uses a load-sensitive variable piston pump, and the working system uses a fixed-quantity pump. According to a comprehensive evaluation of its cost and energy-saving effect, the fixed-variable hydraulic system has a high cost performance, and the principle is simple and easy to implement. However, the current fixed-variable hydraulic system is in The following problems exist during use:

The load pressure of the whole machine is unstable during the working process, and the flow rate of the hydraulic pump is also constantly changing, so the speed control performance is very unstable and difficult to control; and the valve stem has a large control force, and the valve port △ is caused by the change of load pressure. The change of P and the change of hydraulic power cause the change of the operating force of the valve stem, and the irregularity of the operating force makes fine-tuning control more difficult

In short, the controllability of the oil circuit is poor, and it is very difficult for the operator to accurately control the working device, which depends entirely on the operator's feeling, experience and on-the-spot play

[0005] (3) When the quantitative pump of the existing fixed variable system is not working, its flow will flow back to the oil tank through the open center multi-way valve, resulting in a large loss along the middle position, which causes a large loss in the hydraulic system. heat, high energy consumption

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