Timeless Power, Evolving Technology

Hydraulic technology has been developing for over 200 years. While it has become quite mature, it continues to evolve. Those working with hydraulics must always remember: it is societal needs that催生了 machines capable of meeting those needs. It is these machines that, in order to meet societal demands—driving loads and overcoming resistance—adopted hydraulic transmission. Therefore, the unwavering goal of hydraulic technology improvement and development should always be to meet societal needs.

There are several aspects that represent timeless, insatiable societal demands on hydraulic technology, influencing innovations in hydraulic valve types and other components:

The current development of hydraulic technology utilizes various means to meet these demands. Innovations in hydraulic valve types, materials science, and control systems all contribute to addressing these fundamental societal needs.

1. Energy Efficiency

Energy efficiency in hydraulic systems has long been a focus of attention for several important reasons, many of which drive innovations in hydraulic valve types and system design.

Energy Flow in Hydraulic Systems

The diagram illustrates how energy is transferred through hydraulic systems, highlighting points of potential loss and efficiency improvement opportunities, including optimized hydraulic valve types.

1. Extending fluid life: For hydraulic systems, wasted energy ultimately turns into heat, increasing fluid temperature (a 1MPa pressure loss increases oil temperature by 0.57°C). This reduces oil viscosity, increases leakage, and causes molecular chain breakage in the oil, chemical changes in additives, reduced durability, and accelerated aging. Research shows that above 80°C, oil life is halved for every 10°C temperature increase. Proper selection of hydraulic valve types can significantly reduce these pressure losses.
2. Extending equipment service life: Reduced oil viscosity decreases lubricating film thickness, increasing mechanical wear. The polymer materials used for seals in hydraulic systems tend to age quickly at high temperatures, so oil overheating reduces seal life. Advanced hydraulic valve types designed for minimal pressure drop help maintain optimal operating temperatures.
3. Temperature reduction: Using fans and radiators to reduce oil temperature brings additional energy consumption. Efficient system design incorporating appropriate hydraulic valve types can minimize the need for such cooling systems.
4. Reducing operating costs: Statistics show that the operating costs of mechanical equipment, especially energy costs (electricity and fuel), have now approached or exceeded equipment purchase costs. For example, in 2010, energy costs for mobile machinery in the United States were $56 billion, and for fixed machinery $42 billion, while the entire hydraulic components market was only $26 billion. Therefore, from a total cost perspective, energy efficiency must be considered. This economic reality drives continuous improvement in hydraulic valve types and system architectures.
5. Limited fossil fuels: Fossil energy sources on Earth, as they are consumed by humans, will become increasingly difficult to extract, leading to rising prices. Even if they are not exhausted soon, the era of energy based on coal and oil will eventually pass.
6. Uneven distribution: Fossil energy distribution on Earth is uneven: even if reserves exist globally, it does not mean every country and region has its own supply, especially when political situations are unstable.
7. Protecting public health: Using fossil energy emits pollutants harmful to human health: nitrogen oxides (NOₓ), hydrocarbons (HC), and particulate matter (PM2.5).
8. Compliance with regulations: Many countries have enacted mandatory energy conservation and emission reduction laws. Compared with other regions, Europe, America, and Japan have much stricter regulations. Under these laws, emission limits from 2014 onwards were only 10% of pre-2012 levels. Moreover, the higher the installed engine power, the stricter the emission limits. Therefore, existing main equipment must undergo significant improvements to be sold in these countries.
9. Addressing climate change: Currently, climate change caused by the greenhouse effect from CO₂ emissions from burning fossil fuels has become a serious challenge for all humanity. Countries worldwide are formulating and implementing a series of strategies, measures, and actions to address climate change, proposing more ambitious carbon emission reduction targets. In March 2022, China released the "14th Five-Year Plan for Modern Energy System," proposing comprehensive promotion of large-scale development and high-quality development of wind power and solar power. By 2025, the proportion of non-fossil energy consumption should increase to about 20%, and the proportion of non-fossil energy power generation should reach about 39%.

While natural water, wind, and solar energy are free, their supply is unstable. Obtaining stable and conveniently usable electricity from these sources requires significant investment and research and development.

Therefore, to protect the human living environment and public health, energy conservation should be considered by every citizen.

For example, Bosch Rexroth dedicated significant exhibition space at the 2022 Hannover Messe to showcase their energy management software, which can display and analyze energy consumption, efficiency, and heat generation from regional levels down to individual equipment, with specific data on how different hydraulic valve types affect overall system performance.

2. Electronic Control

Electronic control has been used in stationary hydraulics for nearly a century. For mobile hydraulics, Europe and America began implementation in the 1990s (see section 2.1 for details). Current research focuses on how to fully utilize computer intelligence, combined with hydraulic characteristics, to achieve optimal comprehensive benefits, including smart integration with various hydraulic valve types.

As we know, Industry 1.0 was mechanization, which greatly expanded human strength beyond human and animal power. Industry 2.0 was assembly line production, which simplified production processes through decomposition, thereby improving efficiency and reducing costs (however, products became identical without individuality). Industry 3.0 was automation, which greatly reduced human involvement in assembly lines, improved product consistency, and laid the foundation for diversified production. Industry 4.0 is individualization, using computer and network intelligence for flexible, efficient, low-cost diversified production to meet different individual needs.

German academia and industry generally believe that Germany's hydraulic technology has basically met the requirements of Industry 4.0. Therefore, research focus is on "Predictive 4.0" to achieve predictive maintenance. These capabilities are based on various sensors related to electronic control, as well as software, algorithms, and strategies that optimize performance of all system components, including hydraulic valve types.

In January 2024, led by the German Mechanical Engineering Association, the "Fluid 4.0" working group was established with funding from the European Union and the German Ministry of Economic Affairs to advance the digitalization of fluid components and system controls, with particular attention to smart hydraulic valve types and their integration into networked systems.

3. New Materials and Processes

Technology is a combination of techniques. Hydraulics is making progress by leveraging new design methods, processes, and materials invented in other technical fields. These innovations complement advancements in hydraulic valve types to create more efficient systems.

Carbon Fiber Reinforcement

Carbon fiber winding technology increases pressure resistance and reduces weight in hydraulic cylinders and accumulators, often working in conjunction with specialized hydraulic valve types designed for high-pressure applications.

Additive Manufacturing

3D printing enables flexible, rapid production of lightweight hydraulic components with complex internal geometries, including innovative hydraulic valve types that optimize flow characteristics.

Additive manufacturing (3D printing) technology allows for flexible, rapid production of lightweight hydraulic components. Italian company Aidro showcased applications at the 2022 Hannover Messe, including multi-way valves and radiators with optimized internal structures that would be impossible to produce with traditional manufacturing methods. These advances, combined with specialized hydraulic valve types, create systems with unprecedented efficiency.

Other material innovations include advanced polymers for seals that withstand higher temperatures and pressures, nanocoatings that reduce friction and wear in hydraulic components, and composite materials that provide strength without excessive weight. These materials often enable new hydraulic valve types that can operate under more extreme conditions while maintaining precision control.

4. Electro-Hydraulic Actuators

Electro-Hydraulic Actuators (EHA) integrate motor, pump, oil tank, and hydraulic cylinder into a single unit. They comprehensively utilize the latest technologies in electronic control, volumetric speed control circuits, manifold blocks, motors, and variable frequency drives.高度集成化，只要接通电源，给人位置或速度指令，就可工作，所以，也被称为自治缸。These systems often incorporate specialized hydraulic valve types optimized for their compact form factor.

This specifically refers to differential cylinders, as they account for over 85% of hydraulic actuators in practical applications. The working principle of electro-hydraulic actuators was proposed decades ago, and volumetric speed control circuits for differential cylinders were invented long ago. At the end of the 20th century, with breakthroughs in a series of technical difficulties, particularly high power density servo motors, they began to be practically applied in aircraft.

Evolution of Electro-Hydraulic Actuators

Aerospace Applications

Jet fighters like the F-35 abandoned centralized hydraulic systems in favor of distributed EHA systems with specialized hydraulic valve types.

Early Civilian Models

Companies like VOITH showcased civilian EHA models at Hannover Messe as early as 2011, featuring innovative hydraulic valve types.

Modern High-Power Models

2017 models from Bosch Rexroth achieved 2000-2500kN thrust with advanced hydraulic valve types and materials.

For example, hydraulic lines are a vulnerability in military aircraft. In the F35 fighter jet, centralized oil supply hydraulic systems were abandoned in favor of distributed oil supply using electro-hydraulic actuators.

Today, due to their integration and energy efficiency, electro-hydraulic actuators are being used in other fields. At Hannover Messe, as early as 2011, Germany's VOITH company exhibited civilian models. Since 2013, multiple hydraulic companies have displayed their variations. Since then, Bosch Rexroth has exhibited new products at each Hannover Messe transmission exhibition.

The electro-hydraulic actuators exhibited in 2017 could achieve thrust of 2000-2500kN, while similarly sized electric actuators could only reach 290kN.

For the vast majority of German companies, in a market economy environment, meeting market demand is the direction of development. Put simply, it means using various new technologies, materials, and processes to make products more economical than competitors', better meet customers' individual needs, and satisfy societal demands, thereby legally and reasonably obtaining profits. This is their primary focus and goal. They care about whether they will infringe on others' patents and intellectual property rights, and whether others have infringed on theirs. Of course, many companies also pay attention to environmental protection and energy conservation and assume certain social responsibilities. They do not pursue advancement for advancement's sake, nor do they care much about being among the world's top performers. This philosophy applies equally to their approach to developing new hydraulic valve types and complete systems.