review 液压传动与控制英文课件

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1.3 Viscosity
1.3.1 cohesion force and adhesion force
There are cohesion forces among fluid particles, while there are adhesion forces among fluid particles and solid wall.
Adhesion forces are usually greater than cohesion force except mercury. 1.3.2 dynamic viscosity
Consider two parallel plates, placed a small distance Y apart, the space between the plates being filled with the fluid.
Hydraulics and Pneumatics
Transmission
FLUID MECHANICS WITH HYDRAULICS
1 Fluid Properties 2 Mechanics of fluids at rest 3 Mechanics of fluids in motion 4 Energy loss of fluids in motion 5 Flow of fluids in clearances and orifices 6 Hydraulically sticking 7 Hydraulically shocking 8 Cavitation

不能变量
e ，就可改变泵的进、
出油口(双向泵)
3. 叶片式变量泵 （Pressure-limiting variable vane pumps）
结构（Fig. 3-13） 与单作用叶片泵相似，但带有压力控制弹
簧和排量调节螺钉。 工作原理（Fig. 3-14）
液压泵压力油作用于定子上所产生径向力 的水平分力与弹簧力进行比较，以决定定子与 转子间的偏心距大小。
特点 每转各叶片吸压油各一次（单作用） 转子径向受力不平衡 为消除困油，配流盘上开有三角槽（卸荷槽） 叶片沿旋转方向后倾，利于叶片甩出
（改变偏心距 e 可改变输出流量 q，制成变量泵）
2. 双作用叶片泵（Double-acting vane pumps）
结构 类似于单作用式，区别在于： 定子内表面由圆弧面(四段)和过渡曲面组成 配流盘有四个油口轴对称分布 转子与定子同心安装
Separating inlet port from outlet port 高、低压工作腔分开 Conclusion 结论
Working based on the oil tight chamber variation 密闭工作腔容积的变化进行工作
－－Displacement pumps 容积式液压泵
Fig. 3-1 Operating principle of a single piston pump
Conditions 工作条件 Forming oil tight chamber 密封工作容积的形成 Changing the oil tight chamber 密封容积变化
（increasing: suction oil; decreasing: delivery oil） （容积变大:吸油；容积变小:压油）

9.1.4 Hydraulic components calculation and selection
9.1.5 Performance check for a hydraulic system designed 9.1.6 Drawing of working diagrams and technical documents
Hydraulic and pneumatic pressure transmission
Chapter 9 Design of Hydraulic Transmission System
Chapter 9 Design of Hydraulic Transmission systems Introduction The design of hydrostatic transmission systems is an important part of the whole mechanical design and also a summarizing and comprehensive application of knowledge in previous chapters. The aim of this chapter is to show through an example how hydrostatic transmission circuits can be designed to satisfy a given set of requirements.
dynamic parameters (Fig.9-2a) Includes two parts of movement parameters (Fig.9-2b)
1）Dynamic parameters analysis A load diagram can be drawn out based on the determined extrinsic loads, see Fig.9-2a, which is load chart. The load chart is actually a load-displacement （F-l）curve .

11*24*300*4 = 316,800 kw.h **还没有计算由于功耗产生的冷却费用。
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基本闭式液压传动回路
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闭式回路用液压泵
最大摆角 = 最大流量=执行机构最大速度
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闭式回路用液压泵
摆角减小 = 流量减小=执行机构运动速度减慢
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闭式回路用液压泵
摆角为零 = 无流量输出=执行机构停止运动 液压泵仍在运转
对液压工作参数实行控制
压力控制 - 压力阀 流量控制 - 流量阀 方向控制 - 方向阀
执行机构
将液压能转换为机 械能 液压缸- 直线运动 液压马达- 旋转运动
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典型回路，液压缸伸出
开式液压传动回路
液压泵 溢流阀
方向控制阀
(非完整回路)
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液流换向使液压缸缩回
开式液压传动回路
液压泵 溢流阀
方向控制阀
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闭式回路用液压泵
斜盘摆角方向相反= 液流方向 相反
液压泵仍按原方向运转
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最大反向摆角 = 最大反向流量
闭式回路用液压泵
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问题：
内部泄漏 会引起液压 泵产生气穴 现象
基本闭式液压传动回路
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加入充液 / 补油泵
基本闭式液压传动回路
液流方向
补油泵的加入容许主泵提高工作转速
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可双向工作
流量控制回路
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调速阀
可选项
调节螺钉
主要零件
补偿阀芯 主阀芯 调节装置 阀体 (板式)
调速阀
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调速阀回路
调速阀，带二通型压力补偿器
流量控制回路
pLxA+F
pC x A
pL A F pC A

Low-speed motors are usually radial piston motors. They possess high pressure and large delivery to meet the needs of low speed rotation and large torque. Because of their large size and large moment of inertia, they are not suitable for the applications which require rapid response and frequent direction changing.
Hydraulic and pneumatic pressure transmission
Chapter 4 Hydraulic Actuators
Chapter 4 Hydraulic Actuators
Chapter list
1. Hydraulic Motors 2. Hydraulic Cylinders
（2）Torques and mechanical efficiencies （a）The theoretic torque
Or （b）Startup torque
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(4-4) (4-5)
Chapter 4 Hydraulic Actuators
（c） Mechanical efficiencies thus
Fig. 4-5 Operating principle of crank and connecting rod type radical-plunger motor 15
Chapter 4 Hydraulic Actuators

1. Pump pressure: 1) Rated pressure: It is that pressure below which no
mechanical damage due to overpressure will occur to the pump and the result will be a long reliable service life.
The initial spring force:
Fs = k • x0
The horizontal force produced by pressure :
Fx = p A x
If Fx < Fs , maximum eccentricity and maximum flow rate.
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2) Actual pressure: 2. Pump flow rate and displacement volume
1)Pump displacement volume q p(排量): The volume of oil per revolution of the pump shaft displaced by the pump.
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3. Cavitation contributes to noise.
Cavitation
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Cavitation
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The following rules will control or eliminate cavitation of a pump .(1) Keep suction line velocities below 0.5~1.5 m/s. (2) Keep pump inlet lines as short as possible. (3) Minimize the number of fittings in the inlet line. (4) Mount the pump as close as possible to the reservoir. (5) Use lowpressure drop inlet filters or strainers. (6) Use the proper oil.

(2)動態性能
定義最高暫態壓力峰值與額定壓力調定值的差值△P為壓力超調 量，它是衡量溢流閥動態定壓誤差的一個重要指標。
圖3.17所示t1稱之為回應時間，t2稱之為過渡時間。t1越小， 溢流閥的回應越快；t2越小，動態回應過程時間越短。
2．順序閥
順序閥是利用油路中壓力的變化來控制閥口啟閉，以實現各工 作部件依次順序動作的液壓元件，常用在控制多個執行元件 的順序動作，故名順序閥。順序閥按結構不同分為直動式和 先導式兩種，一般先導式用於壓力較高的場合。當順序閥利 用外來液壓力進行控制時，稱液控順序閥。不論是直動式還 是先導式順序閥都和對應的溢流閥原理相類似，主要不同為 溢流閥的調壓彈簧腔的洩漏油和出油口相連，而順序閥單獨 接回油箱。
液控單向閥按控制活塞背壓腔的泄油方式不同，分為內泄式和 外泄式。內泄式如圖3.2，控制活塞的背壓腔通過內泄油孔a 連通單向閥的P1口；外泄式如圖3.3，控制活塞的背壓腔通過 外泄油孔a直接通油箱。一般情況下在反向出油口的壓力P1較 低時採用內泄式，較高時採用外泄式，以減小所需控制壓力。
如圖3.4，卸載式液控單向閥帶有卸載閥，當控制活塞向右運動 時首先頂開卸載閥的小閥芯，使主油路油壓P2卸壓，繼續運 動再頂開單向閥芯，反向導通油路。這樣可大大減小控制壓 力，實際應用這種結構的液控單向閥可以使控制壓力與工作 壓力之比降低到4.5％左右，常用於高壓系統。
1．單向閥
單向閥有普通單向閥和液控單向閥等。
1）普通單向閥
如圖3.1a和3.1b，分別是管式連接的直通式單向閥和板式連接的 直角式單向閥。 。圖3.1c為單向閥的圖形符號。
2）液控單向閥
除普通單向閥外，還有液控單向閥，它是液壓系統經常使用的 液壓元件。如圖3.2，液控單向閥由閥體2、閥芯5、彈簧6、 控制活塞3、推杆4等組成。閥芯為一般錐芯，彈簧的剛度較 小。

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c. To keep oil pressure in hydraulic control circuit constant
Main circuit
Control circuit
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5. Counterbalance valve 1) Operation: The purpose of a counterbalance valve is
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3) Applications of pressure relief in hydraulic circuit a. To limit the force or torque
Pressure relief valve is normally open.
b. To provide protection against any overloads Pressure relief valve is normally closed.
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(5) Solenoid-controlled, pilot-operated The upper pilot stage spool (which is solenoid-actuated) controls the pilot pressure, which can be directed to either end of the main stage spool.
Solution: Power P = p·Q =100 ×20/600 = 3.33 KW
Example 8-2
An unloading valve is used to unload the pump of example 8-1. If the pump discharge pressure (during unloading) equals 5 bar, how much hydraulic power is being wasted?

vehicle engineering
总学时
50
其中实验（上机）学时
6
三、本课程与其他课程的联系
先修课程
机械类基础课程，流体力学，高等数学，控制理论基础 The basic courses of enginery, fluid mechanics, mathematics and the control theory
1
（重点：液/气压传动与控制的基本工作原理，系统组成） Difficulties: to grasp the two important characters that obtain fluid transmission. （难点：实现液压传动两个重要特征的理解）
1.1 Study on Hydraulic and Pneumatic Pressure Transmission （液压与气压传动的研究内 容） 1.2 Principles of Hydraulics Transmission （液压传动的工作原理） 1.3 Composing in Hydraulic System （液压传动系统的组成） 1.4 Features of Hydraulic and Pneumatic Transmission （液压与气压传动的特点） 1.5 History of Hydraulic and Pneumatic Technology Development and Application （液压与 气压传动发展及应用概况）
Emphasis: The principle and feature of variable pumps. 2
（重点：变量泵结构特点及工作原理。）
Difficulties: to grasp the features and variable method of the constant power pumps. （难点：恒功率变量泵的结构特点及变量原理）