液压系统外文文献翻译中英文

外文文献翻译

(含：英文原文及中文译文)

英文原文

Hydraulic system

W Arnold

1 Introduction

The hydraulic station is called a hydraulic pump station and is an

independent hydraulic device. It is step by step to supply oil. And control

the direction of hydraulic oil flow, pressure and flow, suitable for the host

and hydraulic equipment can be separated on the various hydraulic

machinery.

After the purchase, the user only needs to connect the hydraulic station

and the actuator (hydraulic or oil motor) on the mainframe with different

tubings. The hydraulic machine can realize various specified actions and

working cycles.

The hydraulic station is a combination of manifolds, pump units or valve

assemblies, electrical boxes, and tank electrical boxes. Each part function

is:

The pump unit is equipped with a motor and an oil pump, which is the

power source of the hydraulic station and can convert mechanical energy

into hydraulic oil pressure energy.

Valve combination - its plate valve is mounted on the vertical plate, and

the rear plate is connected with the same function as the manifold.

Oil manifolds - assembled from hydraulic valves and channel bodies. It

regulates hydraulic oil pressure, direction and flow.

Box--a semi-closed container for plate welding. It is also equipped with

an oil screen, an air filter, etc., which is used for cooling and filtering of

oil and oil.

Electrical box - divided into two types: one is to set the external lead

terminal board; one is equipped with a full set of control appliances.

The working principle of the hydraulic station: The motor drives the oil

pump to rotate, then the pump sucks oil from the oil tank and supplies oil,

converts the mechanical energy into hydraulic pressure energy, and the

hydraulic oil passes through the manifold (or valve assembly) to adjust

the direction, pressure and flow and then passes through the external tube.

The way to the hydraulic cylinder or oil motor in the hydraulic machinery,

so as to control the direction of the hydraulic motor, the strength of the

speed and speed, to promote all kinds of hydraulic machinery to do work.

(1) Development history of hydraulic pressure

The development history of hydraulics (including hydraulic power, the

same below), pneumatics, and seals industry in China can be roughly

divided into three stages, namely: the starting stage in the early 1950s to

the early 60s; and the professional in the 60s and 70s. The growth stage of

the production system; the 80-90's is a stage of rapid development.

Among them, the hydraulic industry began in the early 1950s with the

development of hydraulic machines such as Grinding Machines,

broaching machines, and profiling lathes, which were produced by the

machine tool industry. The hydraulic components were produced by the

hydraulic workshop in the machine tool factory, and were produced for

self use. After entering the 1960s, the application of hydraulic technology

was gradually promoted from the machine tool to the agricultural

machinery and engineering machinery. The original hydraulic workshop

attached to the main engine plant was independent and became a

professional manufacturer of hydraulic components. In the late 1960s and

early 1970s, with the continuous development of mechanization of

production, particularly in the provision of highly efficient and automated

equipment for the second automobile manufacturing plant, the hydraulic

component manufacturing industry witnessed rapid development. The

batch of small and medium-sized enterprises also began to become

specialized manufacturers of hydraulic parts. In 1968, the annual output

of hydraulic components in China was close to 200,000 pieces. In 1973,

in the fields of machine tools, agricultural machinery, construction

machinery and other industries, the professional factory for the

production of hydraulic parts has grown to over 100, and its annual

output exceeds 1 million pieces. Such an independent hydraulic

component manufacturing industry has taken shape. At this time, the

hydraulic product has evolved from the original imitation Su product into

a combination of imported technology and self-designed products. The

pressure has been developed towards medium and high pressures, and

electro-hydraulic servo valves and systems have been developed. The

application of hydraulics has been further expanded. The pneumatic

industry started a few years later than hydraulics, and it was only in 1967

that it began to establish a professional pneumatic components factory.

Pneumatic components began to be manufactured and sold as

commodities. Its sealing industry including rubber seals, flexible graphite

seals, and mechanical seals started from the production of common

O-rings, oil seals, and other extruded rubber seals and asbestos seal

products in the early 1950s. In the early 1960s, it began to develop and

produce flexible products. Graphite seals and mechanical seals and other

products. In the 1970s, a batch of batches of professional production

plants began to be established one after another in the systems of the

former Ministry of Combustion, the Ministry of Agriculture, and the

Ministry of Agricultural Machinery, formally forming the industry, which

laid the foundation for the development of the seal industry.

In the 1980s, under the guidance of the national policy of reform and

opening up, with the continuous development of the machinery industry,

the contradiction between the basic components lags behind the host

computer has become increasingly prominent and caused the attention of

all relevant departments. To this end, the former Ministry of Machines

established the General Infrastructure Industry Bureau in 1982, and

unified the original pneumatic, hydraulic, and seal specialties that were

scattered in the industries of machine tools, agricultural machinery, and

construction machinery, etc. The management of a piece of office, so that

the industry in the planning, investment, the introduction of technology

and scientific research and development and other aspects of the basic

parts of the bureau's guidance and support. This has entered a period of

rapid development, it has introduced more than 60 foreign advanced

technology, of which more than 40 hydraulic, pneumatic 7, after digestion

and absorption and technological transformation, are now mass

production, and has become the industry's leading products . In recent

years, the industry has intensified its technological transformation. From

1991 to 1998, the total investment of national, local, and corporate

self-raised funds totaled about 2 billion yuan, of which more than 1.6

billion were hydraulic. After continuous technological transformation and

technological breakthroughs, the technical level of a group of major

enterprises has been further improved, and technological equipment has

also been greatly improved, laying a good foundation for forming a high

starting point, specialization, and mass production. In recent years, under

the guidance of the principle of common development of multiple

ownership systems in the country, various small and medium-sized

enterprises with different ownership have rapidly emerged and have

shown great vitality. With the further opening up of the country,

foreign-funded enterprises have developed rapidly, which plays an

important role in raising industry standards and expanding exports. So far

China has established joint ventures with famous manufacturers in the

United States, Germany, Japan and other countries or directly established

piston pumps/motors, planetary speed reducers, hydraulic control valves,

steering gears, hydraulic systems, hydrostatic transmissions, and

hydraulic components. The company has more than 50 manufacturing

enterprises such as castings, pneumatic control valves, cylinders, gas

processing triplets, rubber seals, and mechanical seals, and has attracted

more than 200 million U.S. dollars in foreign capital.

(2) Current status

Basic profile

After more than 40 years of hard work, China's hydraulics, pneumatics

and seals industry has formed a complete industrial system with a certain

level of production capacity and technical level. According to the

statistics of the third national industrial census in 1995, China’s

state-owned, privately-owned, cooperative, village-run, individual, and

“funded enterprises” have annual sales income of more than 1 million

yuan in hydraulic, pneumatic, and seal industrial townships and above.

There are a total of more than 1,300 companies, including about 700

hydraulics, and about 300 pneumatic and sealing parts. According to the

statistics of the international industry in 1996, the total output value of the

hydraulic industry in China was about 2.448 billion yuan, accounting for

the 6th in the world; the total output value of the pneumatic industry was

about 419 million yuan, accounting for the world’s

10 people.

2. Current supply and demand profile

With the introduction of technology, independent development and

technological transformation, the technical level of the first batch of

high-pressure plunger pumps, vane pumps, gear pumps, general hydraulic

valves, oil cylinders, oil-free pneumatic components and various types of

seals has become remarkable. Improve, and can be stable mass

production, provide guarantees for all types of host to improve product

quality. In addition, certain achievements have also been made in the

aspects of CAD, pollution control, and proportional servo technology for

hydraulic pneumatic components and systems, and have been used for

production. So far, the hydraulic, pneumatic and seal products have a total

of about 3,000 varieties and more than 23,000 specifications. Among

them, there are about 1,200 types of hydraulic pressure, more than 10,000

specifications (including 60 types of hydrodynamic products, 500

specifications); about 1350 types of pneumatic, more than 8,000

specifications; there are also 350 types of rubber seals, more than 5000

The specifications are now basically able to adapt to the general needs of

various types of mainframe products. The matching rate for major

equipment sets can reach more than 60%, and a small amount of exports

has started.

In 1998, the domestic production of hydraulic components was 4.8

million pieces, with sales of about 2.8 billion yuan (of which mechanical

systems accounted for 70%); output of pneumatic components was 3.6

million pieces, and sales were about 550 million yuan (including

mechanical systems accounting for about 60%) The production of seals is

about 800 million pieces, and the sales volume is about 1 billion yuan

(including about 50% of mechanical systems). According to the statistics

of the annual report of the China Hydraulic and Pneumatic Sealing

Industry Association in 1998, the production and sales rate of hydraulic

products was 97.5% (101% of hydraulic power), 95.9% of air pressure,

and 98.7% of seal. This fully reflects the basic convergence of production

and sales.

Although China's hydraulic, pneumatic and sealing industries have made

great progress, there are still many gaps compared with the development

needs of the mainframe and the world's advanced level, which are mainly

reflected in the variety, performance and reliability of products. . Take

hydraulic products as an example, the product varieties are only 1/3 of the

foreign country, and the life expectancy is 1/2 of that of foreign countries.

In order to meet the needs of key hosts, imported hosts, and major

technical equipment, China has a large number of imported hydraulic,

pneumatic, and sealing products every year. According to customs

statistics and relevant data analysis, in 1998, the import volume of

hydraulic, pneumatic and seal products was about 200 million U.S.

dollars, of which the hydraulic pressure was about 140 million U.S.

dollars, the pneumatics were 30 million U.S. dollars, and the seal was

about 0.3 billion U.S. dollars. The year is slightly lower. In terms of

amount, the current domestic market share of imported products is about

30%. In 1998, the total demand for hydraulic parts in the domestic market

was about 6 million pieces, and the total sales volume was 4 billion yuan;

the total demand for pneumatic parts was about 5 million pieces, and the

total sales volume was over 700 million yuan; the total demand for seals

was about 1.1 billion yuan. Pieces, total sales of about 1.3 billion yuan.

(3) Future developments

1. The main factors affecting development

(1) The company's product development capability is not strong, and the

level and speed of technology development can not fully meet the current

needs for advanced mainframe products, major technical equipment and

imported equipment and maintenance;

(2) Many companies have lagged behind in manufacturing process,

equipment level and management level, and their sense of quality is not

strong, resulting in low level of product performance, unstable quality,

poor reliability, and insufficiency of service, and lack of user satisfaction.

And trusted branded products;

(3) The degree of professional specialization in the industry is low, the

power is scattered, the duplication of the low level is serious, the product

convergence between the region and the enterprise leads to blind

competition, and the prices are reduced each other, thus the efficiency of

the enterprise is reduced, the funds are lacking, and the turnover is

difficult. Insufficient investment in development and technological

transformation has severely restricted the overall level of the industry and

its competitive strength.

(4) When the degree of internationalization of the domestic market is

increasing, foreign companies have gradually entered the Chinese market

to participate in competition, coupled with the rise of domestic private,

cooperative, foreign-funded, and individual enterprises, resulting in

increasing impact on state-owned enterprises. .

2. Development trend

With the continuous deepening of the socialist market economy, the

relationship between supply and demand in the hydraulic, pneumatic and

sealed products has undergone major changes. The seller market

characterized by “shortage” has basically become a buyer’s market

characterized by “structured surplus”. Replaced by. From the perspective

of overall capacity, it is already in a trend of oversupply, and in particular,

general low-grade hydraulic, pneumatic and seals are generally

oversupply; and like high-tech products with high technological content

and high value and high value-added products that are urgently needed by

the host, Can not meet the needs of the market, can only rely on imports.

After China's entry into the WTO, its impact may be greater. Therefore,

during the “10th Five-Year Plan” period, the growth of the industry’s

output value must not only rely on the growth of quantity. Instead, it

should focus on the structural contradiction of the industry and intensify

efforts to adjust the industrial structure and product structure. It should be

based on the improvement of quality. Product technology upgrades in

order to adapt to and stimulate market demand, and seek greater

development.

2. Hydraulic application on power slide

(1) Introduction of Power Sliding Table

Using the binding force curve diagram and the state space analysis

method to analyze and study the sliding effect and the smoothness of the

sliding table of the combined machine tool, the dynamics of the hydraulic

drive system of the sliding table—the self-regulating back pressure

regulating system are established. mathematical model. Through the

digital simulation system of the computer, the causes and main

influencing factors of the slide impact and the motion instability are

analyzed. What kind of conclusions can be drawn from those, if we can

reasonably design the structural dimensions of hydraulic cylinders and

self-regulating back pressure regulators ——

The symbols used in the text are as follows:

s 1 - flow source, that is, the flow rate of the governor valve outlet;

S el —— sliding friction of the sliding table;

R - the equivalent viscous friction coefficient of the slide;

I 1 - quality of slides and cylinders;

12 - self-adjusting back pressure valve core quality;

C 1, c 2 - liquid volume without cylinder chamber and rod chamber;

C 2 - Self-adjusting back pressure valve spring compliance;

R 1, R2 - Self-adjusting back pressure valve damping orifice fluid

resistance;

R 9 - Self-adjusting back pressure valve valve fluid resistance;

S e2——initial pre-tightening force of self-adjusting back pressure valve

spring;

I 4, I5 - Equivalent liquid sense of the pipeline;

C 5, C 6 - equivalent liquid capacity of the pipeline;

R 5, R7 - Equivalent liquid resistance of the pipeline;

V 3, V4 - cylinder rodless cavity and rod cavity volume;

P 3, P4—pressure of the rodless cavity and rod cavity of the cylinder;

F - the slide bears the load;

V - speed of slide motion;

In this paper, the power bond diagram and the state space splitting

method are used to establish the system's motion mathematical model,

and the dynamic characteristics of the slide table can be significantly

improved.

In the normal operation of the combined machine tool, the magnitude of

the speed of the slide, its direction and the load changes it undergoes will

affect its performance in varying degrees. Especially in the process of

work-in-process, the unsteady movement caused by the advancing of the

load on the slide table and the cyclical change of the load will affect the

surface quality of the workpiece to be machined. In severe cases, the tool

will break. According to the requirements of the Dalian Machine Tool

Plant, the author used the binding force curve diagram and the state space

analysis method to establish a dynamic mathematical model of a

self-adjusting back pressure and speed adjustment system for the new

hydraulic drive system of the combined machine tool slide. In order to

improve the dynamic characteristics of the sliding table, it is necessary to

analyze the causes and main influencing factors of the impetus and

movement of the sliding table. However, it must pass the computer's

digital simulation and the final results obtained from the research.

(2) Dynamic Mathematical Model

The working principle diagram of the self-adjusting back pressure speed

regulation system of the combined machine tool slide hydraulic drive

system is shown in the figure. This system is used to complete the

work-cycle-stop-rewind. When the sliding table is working, the

three-position four-way reversing valve is in the illustrated position. The

oil supply pressure of the oil pump will remain approximately constant

under the effective action of the overflow valve, and the oil flow passes

through the reversing valve and adjusts the speed. The valve enters the

rodless chamber of the cylinder to push the slide forward. At the same

time, the pressurized oil discharged from the rod chamber of the cylinder

will flow back to the tank through the self-regulating back pressure valve

and the reversing valve. During this process, there was no change in the

operating status of both the one-way valve and the relief valve. The

complex and nonlinear system of the hydraulic drive system of the

self-adjusting back pressure governor system is a kind of self-adjusting

back-pressure governor system. To facilitate the study of its dynamic

characteristics, a simple and reasonable dynamic mathematical model that

only considers the main influencing factors is established. Especially

important [1][2]. From the theoretical analysis and the experimental study,

we can see that the system process time is much longer than the process

time of the speed control valve. When the effective pressure bearing area

of the rodless cavity of the fuel tank is large, the flow rate at the outlet of

the speed control valve is instantaneous. The overshoot is reflected in the

small change in speed of the slide motion [2]. In order to further broaden

and deeply study the dynamic characteristics of the system so that the

research work can be effectively performed on a miniature computer, this

article will further simplify the original model [2], assuming that the

speed control valve is output during the entire system pass. When the

flow is constant, this is considered to be the source of the flow. The

schematic diagram of the dynamic model structure of this system is

shown in Fig. 2. It consists of a cylinder, a sliding table, a self-adjusting

back pressure valve, and a connecting pipe.

The power bond graph is a power flow graph. It is based on the

transmission mode of the system energy, based on the actual structure,

and uses the centralized parameters to represent the role of the

subsystems abstractly as a resistive element R, a perceptual element I, and

a capacitive element. Three kinds of role of C. Using this method, the

physical concept of modeling is clear, and combined with the state-space

analysis method, the linear system can be described and analyzed more

accurately. This method is an effective method to study the dynamic

characteristics of complex nonlinear systems in the time domain.

According to the main characteristics of each component of the

self-adjusting back pressure control system and the modeling rules [1],

the power bond diagram of the system is obtained. The upper half of each

key in the figure represents the power flow. The two variables that make

up the power are the force variables (oil pressure P and force F) and the

flow variables (flow q and velocity v). The O node indicates that the

system is connected in parallel, and the force variables on each key are

equal and the sum of the flow variables is zero; 1 The nodes represent the

series connection in the system, the flow variables on each key are equal

and the sum of the force variables is Zero. TF denotes a transformer

between different energy forms. The TF subscripted letter represents the

conversion ratio of the flow variable or the force variable. The short bar

on the key indicates the causal relationship between the two variables on

the key. The full arrow indicates the control relationship. There are

integral or differential relationships between the force and flow variables

of the capacitive and perceptual elements in the three types of action

elements. Therefore, a complex nonlinear equation of state with nine state

variables can be derived from Fig. 3 . In this paper, the research on the

dynamic characteristics of the sliding table starts from the two aspects of

the slide's hedging and the smoothness of the motion. The fourth-order

fixed-length Runge-Kutta is used for digital simulation on the IBM-PC

microcomputer.

(3) Slide advance

The swaying phenomenon of the slide table is caused by the sudden

disappearance of the load acting on the slide table (such as drilling work

conditions). In this process, the table load F, the moving speed V, and the

pressure in the two chambers of the cylinder P3 and P4 can be seen from

the simulation results in Fig. 4. When the sliding table moves at a uniform

speed under the load, the oil pressure in the rodless cavity of the oil

cylinder is high, and a large amount of energy is accumulated in the oil.

When the load suddenly disappears, the oil pressure of the cavity is

rapidly reduced, and the oil is rapidly reduced. When the high-pressure

state is transferred to the low-pressure state, a lot of energy is released to

the system, resulting in a high-speed forward impact of the slide.

However, the front slide of the sliding table causes the pressure in the rod

cavity of the oil cylinder to cause the back pressure to rise, thereby

consuming part of the energy in the system, which has a certain effect on

the kicking of the slide table. We should see that in the studied system,

the inlet pressure of the self-adjusting back pressure valve is subject to

the comprehensive effect of the two-chamber oil pressure of the oil

cylinder. When the load suddenly disappears, the pressure of the

self-adjusting back pressure valve rapidly rises and stably exceeds the

initial back pressure value. It can be seen from the figure that

self-adjusting back pressure in the speed control system when the load

disappears, the back pressure of the cylinder rises more than the

traditional speed control system, so the oil in the rod cavity of the

cylinder absorbs more energy, resulting in the amount of forward

momentum of the slide It will be about 20% smaller than traditional

speed control systems. It can be seen from this that the use of

self-adjusting back-gear speed control system as a drive system slider has

good characteristics in suppressing the forward punch, in which the

self-adjusting back pressure valve plays a very large role.

(4) The smoothness of the slide

When the load acting on the slide changes periodically (such as in the

case of milling), the speed of the slide will have to fluctuate. In order to

ensure the processing quality requirements, it must reduce its speed

fluctuation range as much as possible. From the perspective of the

convenience of the discussion of the problem, assume that the load

changes according to a sine wave law, and the resulting digital simulation

results are shown in Figure 5. From this we can see that this system has

the same variation rules and very close numerical values as the

conventional speed control system. The reason is that when the change of

the load is not large, the pressure in the two chambers of the fuel tank will

not have a large change, which will eventually lead to the self-regulating

back pressure valve not showing its effect clearly.

(5) Improvement measures

The results of the research show that the dynamic performance of a

sliding table with self-regulating back pressure control system as a drive

system is better than that of a traditional speed control system. To reduce

the amount of kick in the slide, it is necessary to rapidly increase the back

pressure of the rod cavity when the load disappears. To increase the

smoothness of the sliding table, it is necessary to increase the rigidity of

the system. The main measure is to reduce the volume of oil. From the

system structure, it is known that the cylinder has a large volume between

the rod cavity and the oil discharge pipe, as shown in Fig. 6a. Its

existence in terms of delay and attenuation of the self-regulating back

pressure valve function, on the other hand, also reduces the rigidity of the

system, it will limit the further improvement of the propulsion

characteristics and the smoothness of the motion. Thus, improving the

dynamic characteristics of the sliding table can be handled by two

methods: changing the cylinder volume or changing the size of the

self-regulating back pressure valve. Through the simulation calculation of

the structural parameters of the system and the comparison of the results,

it can be concluded that the ratio of the volume V4 between the rod cavity

and the oil discharge pipe to the volume V3 between the rodless cavity

and the oil inlet pipe is changed from 5.5 to 5.5. At 1 oclock, as shown in

the figure, the diameter of the bottom end of the self-adjusting back

pressure valve is increased from the original 10mm to 13mm, and the

length of the damper triangle groove is reduced from the original lmm to

0.7mm, which will enable the front of the slide table. The impulse is

reduced by 30%, the transition time is obviously shortened, and the

smoothness of the slide motion will also be greatly improved.

中文译文

液压系统

W Arnold

1. 绪论

液压站称液压泵站,是独立的液压装置。它是按逐级要求供油。 并控制液压油流方向、 压力和流量, 适用在主机与液压装置可分离的各种液压机械上面。

用户在购后只要将液压站与主机上执行机构 (油缸或油马达) 用不同的油管相连, 液压机械即实现各种规定的动作与工作循环。

液压站是由集成块、泵装置或阀组合、电气盒、油箱电气盒组合而成。各个部件 功能为:

泵装置——上装有电机和油泵, 其是液压站的动力源, 能将机械能转化为液压油压力能。

阀组合--其板式阀装在立板上,板后管连接,与集成块的功能相同。

油集成块--是由液压阀及通道体组装而成。 其对液压油实行压力、 方向和流量 调节。

箱--是板焊的半封闭容器, 上面还装有滤油网、 空气滤清器等, 是用来储油与 油的冷却及过滤。

电气盒--分两种型式:一种是设置外接引线的端子板; 一种是配置了全套控制 电器。

液压站工作原理:电机带动油泵转动, 然后泵从油箱中吸油并供油,

将机械能转 化为液压站压力能,液压油通过集成块(或阀组合)实现方

向、压力、流量调节后 经过外接管路并至液压机械里的油缸或油马达中,从而控制液动机方向变换、力量 的大小及速度的快慢,来推动各种液压机械做功。

(1)液压的发展历程

在我国液压(含液力,下同) 、气动和密封件工业的发展历程,大致可分成三个 阶段,即:在 20世纪 50年代初到 60年代初是起步阶段;

60-70年代为专业化生产 体系的成长阶段; 80-90年代为快速发展阶段。在其中,液压工业始于 50年代初从 机床行业生产的仿苏的磨床、拉床、仿形车床等液压传动来起步,液压元件由机床 厂里的液压车间生产, 自产自用。 在进入 60年代后, 液压技术应用从机床逐渐推广

到农业机械与工程机械等领域,原来附属于主机厂里的液压车间有些独立出来,成 为液压件的专业生产厂。在 60年代末、 70年代初,随着生产机械化的不断发展, 特别是在为第二汽车制造厂等提供了高效、自动化设备的带动下,液压元件制造业 出现了不断迅速发展的局面,一批中小企业也开始成为液压件专业制造厂。 1968年中国的液压元件年产量已接近 20万件;而在 1973年在机床、农机、工程机械等行 业里,生产液压件的专业厂已发展到 100余家,其年产量超过 100万件,这样一个 独立的液压件制造业已初步形成。于此这时,液压件产品已从开始的仿苏产品发展 为引进技术和自行设计相结合的产品,压力向中、高压发展,开发了电液伺服阀及 系统,液压的应用领域进一步扩大。而气动工业的起步比液压稍晚几年,到 1967年开始才建立气动元件专业厂,气动元件才开始作为商品生产和销售。其含橡塑密

封、 柔性石墨密封和机械密封的密封件工业, 从 50年代初生产普通

O 型圈、 油封等 挤压橡塑密封和石棉密封制品起步, 在到 60年代初, 开始研制生产柔性石墨密封和 机械密封等制品。 70年代,原燃化部、一机部、农机部所属系统内,一批批专业生 产厂开始相继成立,正式形成行业,为密封件工业发展成长奠定了基础。

在进入 80年代, 国家改革开放的方针指引下, 随着机械工业的不断发展, 基础 件滞后于主机的矛盾日益突出,引起各有关部门的重视。为此,原一机部在 1982年组建了通用基础件工业局,将原有分散在机床、农业机械、工程机械等的行业归 口的气动、液压和密封件专业厂,统一划归为通用基础件局管理,从而使该行业在 规划、投资、引进技术以及科研开发等方面得到基础件局的指导和支持。由此进入 了快速发展期,其先后引进了 60余项国外先进技术,而其中液压 40余项、气动 7项,经过消化吸收和技术改造,现均已批量生产,并成为了行业的主导产品。近年 来,行业加大技术改造力度, 1991-1998年国家、地方及企业自筹资金总投入共约 20多亿元,而其中液压 16亿多。经过不断技术改造和技术攻关,一批主要企业技 术水平进一步提高,工艺装备也得到很大改善,为形成了高起点、专业化、批量生 产打下良好基础。近几年来,在国家多种所有制共同发展的方针指引下,各种不同 所有制的中小企业迅猛崛起,展现出勃勃生机。随着国家进一步的开放,三资企业 迅速发展,这对提高行业水平和扩大出口起着重要作用。目前为止我国已和美国、 德国、 日本等国著名厂商合资或直接由外国厂商独资建立了柱塞泵 /马达、 行星减速 机、液压控制阀、

转向器、液压系统、静液压传动装置、液压件的铸造、气动控制 阀、气缸、气源处理的三联件、橡塑密封、机械密封等类产品生产企业 50多家,总 共引进外资 2亿多美元。

(2) 目前状况

1. 基本概况

在经过 40多年的努力, 我国的液压、 气动和密封件行业已形成了一个门类比较 齐全, 并有一定生产能力与技术水平的工业体系。 据

1995年的全国第三次工业普查 统计,我国在液压、气动和密封件工业乡及乡以上年销售收入在 100万元以上的国营、私营、合作经营、村办、个体、“三资”等企业总共有 1300余家,而其中液压 约 700家,

气动和密封件各约 300余家。 在按 1996年国际同行业的统计, 我国液压 行业总产值约 23.48亿元, 占世界第 6位; 气动行业总产值约 4.19亿元, 占世界第

10位。

2. 当前供需概况

在通过技术引进,自主开发和技术改造下,高压柱塞泵、叶片泵、齿轮泵、通 用液压阀门、油缸、无油润滑气动件与各类密封件第一大批产品的技术水平有了显 著的提高,并可以稳定的批量生产,为各类主机提高产品水平提供保证。另外,在 液压气动元件与系统的 CAD 、污染控制、比例伺服技术等方面也取得了一定成果, 并已用于生产。

目前为止, 液压、 气动和密封件产品总计大概有 3000个品种、

23000多个规格。其中,液压约有 1200个品种、 10000多个规格(其

中含液力产品 60个 品种、 500个规格) ;气动约有 1350个品种、

8000多个规格;橡塑密封也有 350个 品种、 5000多个规格,现已基本能适应各类主机产品的一般需要,为重大的成套装 备的品种配套率也可达 60%以上,并开始有了少量出口。

1998年国产的液压件产量 480万件, 销售额约为 28亿元 (其中机械系统占 70%) ; 气动件产量有 360万件,销售额约为 5.5亿元(其中机械系统约占 60%) ;密封件产 量约有 8亿件,销售额约为 10亿元(其中机械系统约占 50%) 。据中国液压气动密 封件工业协会在 1998年年报统计中,液压产品产销率为 97 .5%(液力为 101%) ,气 动为

95.9%,密封有 98.7%。这充分反映了产销的基本衔接。

我国液压、气动和密封工业虽然取得了很大的进步,但与主机发展的需求,以 及和世界先进水平相比较下,还存在不少差距,主要反映在产品的品种、性能和可 靠性等方面。如以液压产品为例,产品的品种只有国外 1/3,寿命为国外 1/2。为了 满足重点主机、进口主机和重大技术装备的需要,我国每年都有大量的液压、气动 和密封产品进口。

据海关统计及有关资料分析, 在 1998年液压、 气动和密封件产品

的进口额约为 2亿美元,其中液压约为 1.4亿美元,气动有 0.3亿美元,密封约为 0.3亿美元,与 1997年相比稍有下降。按金额计,目前进口产品国内市场占有率约 30%。 1998年国内市场的液压件需求总量约

600万件,销售总额有 40亿元;气动件 的需求总量约 500万件, 销售总额有 7亿多元; 密封件的需求总量约 11亿件, 销售 总额约为 13亿元。

(3) 今后发展走势

1. 影响发展的主要因素

(1)企业产品的开发能力不强, 技术开发的水平与速度不能完全满足当前先进主机产品、重大技术装备与进口设备的配套和维修需要;

(2)不少企业制造工艺、 装备水平和管理水平都较为落后, 加上质量意识感不强, 导致产品性能的水平低、质量不稳定、可靠性差,及服务不及时,缺乏使用户能满 意和信赖的名牌产品;

(3)行业内的生产专业化程度低, 力量较为分散, 低水平重复严重, 地区与企业 之间产品趋同,导致盲目竞争,相互压价,从而使企业效益下降,资金缺乏、周转 困难等,产品开发和技术改造的投入不足,严重地制约了行业整体水平提高以及竞 争实力的增强;

(4)当国内市场国际化程度日益提高,国外公司陆续进入中国市场参与竞争,再 加上国内私营、合作经营、三资、个体等企业的崛起,从而给国有企业造成愈来愈 大的冲击。

2. 发展走势

随着社会主义市场经济不断深化,液压、气动与密封产品的市场供求关系发生 了较大变化,长期以来“短缺”为特征的卖方市场已基本成为了以“结构性过剩” 为特征的买方市场所取代。而从总体能力看,已处于供大于求的态势,而且特别是 一般低档次的液压、气动和密封件,普遍供过于求;而像主机急需的技术含量高的 高参数与高附加值的高档产品,又不能满足市场的需要,只能依赖进口。在我国加 入 WTO

后,其受冲击有可能更大。因此,在“十五”期间行业产值的增长,决不能

只依赖于量的增长,而是应针对行业自身结构性矛盾,加大力度调整产业结构和产 品结构,就是应依靠质的提高来促进产品技术升级,以适应和拉动市场的需求,而 求得更大的发展。

2. 液压在动力滑台上的应用

(1) 动力滑台介绍

利用有束缚力曲线图和状态空间分析法来对组合机床滑台的滑动影响与运动平 稳性问题进行分析和研究,从而建立起滑台的液压驱动系统——自调背压调速系统 的动态数学模型。通过计算机数字的仿真系统,分析滑台产生滑动影响与运动不平 稳的原因和主要影响因素。从那些当中可以得出什么样的结论,如果能合理地设计 出液压缸与自调背压调压阀的结构尺寸 . ——

文中所使用的符号如下:

s 1——流源,即调速阀出口流量;

S el ——滑台滑动摩擦力;

R ——滑台等效粘性摩擦系数;

I 1——滑台与油缸的质量;

12——自调背压阀阀心质量;

C 1、 c 2——油缸无杆腔及有杆腔的液容;

C 2——自调背压阀弹簧柔度;

R 1, R2——自调背压阀阻尼孔液阻;

R 9——自调背压阀阀口液阻;

S e2——自调背压阀弹簧的初始预紧力;

I 4, I5——管路的等效液感;

C 5、 C 6——管路的等效液容;

R 5, R7——管路的等效液阻;

V 3, V4——油缸无杆腔及有杆腔内容积;

P 3, P4——油缸无杆腔及有杆腔的压力;

F ——滑台承受负载;

V ——滑台运动速度;

文中采用的是功率键合图和状态空间分折法来建立系统的运动数学模型,而滑 台的动态特性可以得到显著的改善。

在组合机床正常工作中,滑台的运动速度大小和它的方向及所承受负载变化都 将以程度不同地影响着其工作性能。特别是工进过程中,滑台上负载突然消失引起 的前进及负载的周期性变化从而引起的运动不平稳性,都将影响被加工件的表面质 量,在严重的情况下会使刀具折断。根据大连机床厂的要求,作者采用有束缚力的 曲线图与状态空间分析法来建立组合机床滑台的新型液压驱动系统——自调背压调

速系统的动态数学模型。为改善滑台的动态特性,有必要分析找出滑台产生的前冲 和运动不平稳的原因及主要的影响因素,但那必须通过计算机的数字仿真和研究得 出的最后结果。

(2)动态数学模型

组合机床滑台液压驱动系统——自调背压调速系统的工作原理图如图所示。这 系统是用来完成 " 工进——停止——快退” 的工作循环。当滑台在工进时,三位四通 换向阀处于图示位置,油泵的供油压力

会在滥流阀的有效作用下近似地保持恒定, 该油液流经过换向阀与调速阀后进入油缸的无杆腔,来推动滑台向前移动。与此同 时, 从油缸有杆腔排出的压力油将经自调背压阀和换向阀流回油箱。 在这个过程中, 两个单向阀和溢流阀工作状态始终都没有任何改变。对像组合机床滑台的液压驱动 系统——自调背压调速系统这种复杂非线性系统,为便于研究它的动态特性,建立 一个仅着重考虑主要影响因素的简单合理的动态数学模型是尤为重要的 [1][2]。 从理 论上分析和试验研究的列举中可得知:该系统过程时间是远大于调速阀的过程时间, 当油缸的无杆腔有效承压面积很大时,在调速阀出口流量瞬时的超调反映为滑台运 动速度变化是很小的 [2]。为了来更加拓宽和深入研究系统动态特性,使研究工作能 在微型的计算机上有效地进行,本文章将对原模型 [2]做出进一步简化处理,假定调 速阀在系统整个通过过程中输出时候恒定的流量,这被看成其为流源。这样系统的 动态模型结构简图如图 2所示,它是由油缸、滑台、自调背压阀和联接管路等组成 的。

功率键合图是一功效流图, 是按着系统能量的传递方式, 以实际结构作为基础, 用集中参数把子系统间的作用关系抽象表示为阻性元

R 、感性元 I 和容性元 C 的三 种作用元。采用此方法建模物理概念清晰,能结合状态空间分析法可较准确地描述 和分析线性系统, 该方法在时域中研究复杂的非线性系统动态特性的一种有效方法。 据自调背压调速系统各元件的主要特性及建模规则 [1],得出了系统的功率键合 图。图中每根键上半箭头表示功率流向,构成了功率的两个

变量是力变量(油压 P 与作用力 F )和流变量(流量 q 与速度 v ) 。

O 结点表示在该系统中属于并联连接, 各键上力变量相等而流变量之和为零; 1结点表示在该系统中属于串联连接,各键 上的流变量相等而力变量之和为零。 TF 表示在不同能量形式间的变换器, TF 下标 的字母表示流变量或力变量的转换比值。 键上短横杠表示该键上两变量间因果关系。 全箭头则表示控制关系。在三种作用元中容性元与感性元的力变量和流变量之间具 有积分或微分关系。 因此, 根据图 3可推具有九个状态变量的复杂非线性状态方程。 文中对滑台动态特性研究是从滑台的前冲与运动平稳性两方面入手的,用四阶定步 长 Runge-Kutta 在 IBM-PC 微型计算机上来进行数字仿真。

(3)滑台前冲

滑台的前冲现象是作用在滑台上负载突然消失 (如钻削工作情况 )

引起的。 在此 过程中,滑台负载 F 、运动速度 V 、油缸两腔压力 P3与 P4的变化可从图 4中仿真 结果看出。当滑台在负载作用下作匀速运动时,油缸无杆腔油液压力较高,油液中 聚集大量的能量;而当负载突然消失时,该腔的油压随之迅速降低,油液从高压态 转入低压态过程中向系统释放出很多能量,从而致使滑台高速的向前冲击。然而滑 台前冲使油缸有杆腔油液受压而引起背压升高,从而耗掉系统中的一部分能量,对滑台的前冲起到了一定的抑制作用。我们应当看出,在所研究系统中,自调背压阀 入口压力要受到油缸两腔油压综合性作用。在负载突然消失之时,自调背压阀的压 力会迅速地上升,并稳定地在高于初始背压数值以上。从图可见,自调背压的调速 系统在负载

消失之时油缸背压力升高幅度大于传统调速系统,所以其油缸的有杆腔 中油液吸收的能量就多,结果滑台的前冲量将比传统调速系统要小约 20%。由此可 见采用自调背庄调速系统来作为驱动系统滑台在抑制前冲方面具有良好特性,其中 自调背压阀起了非常大的作用。

(4)滑台的运动平稳性

当作用在滑台上的负载作周期变化时 (比如像铣削加工的情况) , 滑台运动速度 将要产生一定波动。为保证加工质量要求,必须尽可能减小其速度波动范围。而从 讨论问题的方便性出发看,假设负载按正弦波规律变化,从而得出的数字仿真结果 如图 5所示。由此看出这个系统与传统调速系统有着相同变化规律以及非常接近的 数值数字。其中原因是负载的变化幅度不大时,油缸两腔的压力也就没有较大的变

化,从而最终导致自调背压阀作用不够明显显示。

(5)改善措施

通过研究的结果表明,以自调背压调速系统来作为驱动系统的滑台,其动态特 性会比传统的调速系统好。要减少滑台前冲量,就必须在负载消失瞬间之时迅速提 高油缸有杆腔的背压力。提高滑台的运动平稳性就需增加系统刚性,主要措施在于 减小油液体积。从系统结构知道,油缸有杆腔与排油管间有一很大容积,如图 6a 所示。 它在存在方面的延迟和衰减了自调背压阀作用, 另一方面也降低系统的刚性, 它会限制前冲特性与运动平稳性的进一步改善。由此,改善滑台动态特性可以从两 个方法进行处理:即改变油缸容积或改变自调背压阀结构尺寸。通过系统结构性参 数的仿真计算及结果的比较可得出这样的

结果:当把油缸有杆腔与排油管间的容积 V4同无杆腔与进油管间的容积 V3之比由原来 5.5改为 1时,如图所示,同时把自 调背压阀的阀芯底端直径由原来的 10mm 增加为 13mm, 阻尼三角槽边长从原来 lmm 减小到 0.7mm 时,将可使滑台前冲量减小 30%,过渡过程时间明显的缩短,滑台运 动平稳性也将会得到很大的改善。