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液压机的工作原理,液压机工作介质的作用

液压机的工作原理,液压机工作介质的作用

作者:admin    来源:未知    发布时间:2020-07-11 23:24    浏览量:

液压机工作原理

液压机的工作原理。大、小柱塞的面积分别为S2、S1,柱塞上的作用力分别为F2、F1。根据帕斯卡原理,密闭液体压强各处相等,即F2/S2=F1/S1=p;F2=F1(S2/S1)。表示液压的增益作用,与机械增益一样,力增大了,但功不增益,因此大柱塞的运动距离是小柱塞运动距离的S1/S2倍。

基本原理是油泵把液压油输送到集成插装阀块,通过各个单向阀和溢流阀把液压油分配到油缸的上腔或者下腔,在高压油的作用下,使油缸进行运动.液压机是 利用液体来传递压力的设备。液体在密闭的容器中传递压力时是遵循帕斯卡定律。四柱液压机的液压传动系统由动力机构、控制机构、执行机构、辅助机构和工作介质组成。动力机构通常采用油泵作为动力机构,一般为积式油泵。为了满足执行机构运动速度的要求, 选用一个油泵或多个油泵。低压(油压小于2.5MP)用齿轮泵;中压(油压小于6.3MP)用叶片泵;高压(油压小于32.0MP)用柱塞泵。各种可塑性 材料的压力加工和成形,如不锈钢板的挤压、弯曲、拉深及金属零件的冷压成形,同时亦可用于粉末制品、砂轮、胶木、树脂热固性制品的压制。

液压机工作介质

液压机所用的工作介质的作用不仅是传递压强,而且保证机器工作部件工作灵敏、可靠、寿命长和泄漏少。

液压机对工作介质的基本要求是:

①有适宜的流动性和低的可压缩性,以提高传动的效率;

②能防锈蚀;

③有好的润滑性能;

④易于密封;

⑤性能稳定,长期工作而不变质。液压机最初用水作为工作介质,以后改用在水中加入少量乳化油而成的乳化液,以增加润滑性和减少锈蚀。

19世纪后期出现了以矿物油为工作介质的油压机。油有良好的润滑性、防腐蚀性和适度的粘性,有利于改善液压机的性能。20世纪下半叶出现了新型的水基乳化液,其乳化形态是“油包水”,而不是原来的“水包油”。“油包水”乳化液的外相为油,它的润滑性和防蚀性接近油,且含油量很少,不易燃烧。但水基乳化液价格较贵,限制了它的推广。

 

Working principle of hydraulic press

Working principle of hydraulic press. The area of large and small plunger is S2 and S1, and the force on plunger is F2 and F1 respectively. According to Pascal's principle, the pressure of closed liquid is equal everywhere, that is, F2 / S2 = F1 / S1 = p; F2 = F1 (S2 / S1). It indicates the gain effect of hydraulic pressure. Like mechanical gain, the force increases, but the work does not gain. Therefore, the movement distance of large plunger is S1 / S2 times of that of small plunger.

The basic principle is that the oil pump delivers the hydraulic oil to the integrated cartridge valve block, and distributes the hydraulic oil to the upper chamber or lower chamber of the oil cylinder through each one-way valve and overflow valve. Under the action of high-pressure oil, the oil cylinder moves. The hydraulic press is a device that uses liquid to transmit pressure. When liquid transfers pressure in a closed container, Pascal's law is obeyed. The hydraulic transmission system of four column hydraulic press is composed of power mechanism, control mechanism, actuator, auxiliary mechanism and working medium. The power mechanism usually uses the oil pump as the power mechanism, which is generally an integral oil pump. In order to meet the requirements of the speed of the actuator, one or more oil pumps are selected. Gear pump for low pressure (oil pressure less than 2.5MP), vane pump for medium pressure (oil pressure less than 6.3mp), plunger pump for high pressure (oil pressure less than 32.0mp). It can also be used for pressing powder products, grinding wheels, bakelite and resin thermosetting products.

Working medium of hydraulic press

The working medium used in hydraulic press is not only to transmit pressure, but also to ensure that the working parts of the machine work sensitively, reliably, with long service life and less leakage.

The basic requirements for working medium of hydraulic press are as follows:

① It has suitable fluidity and low compressibility to improve the transmission efficiency;

② It can prevent corrosion;

③ Good lubrication performance;

④ Easy to seal;

⑤ Stable performance, long-term work without deterioration. At first, water was used as the working medium of hydraulic press, and then a small amount of emulsified oil was added into the water to increase the lubricity and reduce the corrosion.

In the late 19th century, hydraulic press with mineral oil as working medium appeared. The oil has good lubricity, corrosion resistance and moderate viscosity, which is beneficial to improve the performance of hydraulic press. In the second half of the 20th century, a new type of water-based emulsion appeared, which is "water in oil" instead of the original "oil in water". The outer phase of water in oil emulsion is oil, its lubricity and corrosion resistance are close to oil, and the oil content is very small, so it is not easy to burn. However, the high price of water-based emulsion limits its popularization.

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