Hydromatik

Hydromatik is a brand name for axial piston pumps and axial piston motors that were originally developed and manufactured by Brüninghaus Hydromatik GmbH, based in Elchingen. The components are characterized by high power density, variable displacement, and operating pressures of up to 450 bar, and are used in demanding hydrostatic drives for mobile and industrial hydraulics. Today, Hydromatik is integrated into the Bosch Rexroth Group as a product line.

Origins and History of Hydromatik

Hydromatik’s roots date back to the mid-20th century. The company established itself as a specialist in axial piston units and made a name for itself with robust, high-pressure-resistant pumps and motors that became indispensable in heavy-duty hydraulics. From the very beginning, the product range was geared toward applications requiring stepless speed and torque control at high pressures.

Acquisition by Rexroth and Integration into Bosch Rexroth

In 1972, Rexroth acquired Hydromatik GmbH, thereby expanding its portfolio to include the proven axial piston pumps and motors. Shortly thereafter, in 1976, Rexroth was fully integrated into the Mannesmann Group, and Hydromatik continued as part of Mannesmann Rexroth. The company’s final integration into the current group took place in 2001, when Mannesmann Rexroth merged with Robert Bosch’s automation technology division to form Bosch Rexroth AG. Since then, the Hydromatik product lines have been further developed, manufactured, and marketed under the Bosch Rexroth umbrella brand. The name Hydromatik is retained to designate the proven axial piston series.

Hydromatik Product Lines and Series

The Hydromatik product range includes axial piston pumps and axial piston motors with swivel disc or skewed-axis designs. The series are coded alphabetically and numerically, with the prefixes indicating the design and adjustability. The main series are divided into open and closed circuits as well as fixed and variable displacement volumes.

Variable-displacement pumps for open circuits

Variable-displacement pumps with a swivel-disc design form the backbone of the Hydromatik product line. They continuously adjust their flow rate to meet demand by changing the swivel angle of the disc. At a swivel angle of zero degrees, the pump delivers no flow; at the maximum angle, it reaches its rated flow rate. This design enables demand-based power delivery without throttling losses.

With displacement volumes ranging from 18 to 140 cm³ per revolution, the A10V series covers the mid-range performance levels. Rated pressures of 280 bar and peak pressures up to 450 bar make them the standard solution for mobile machinery such as excavators and wheel loaders. The A4VSO series, with displacement volumes ranging from 71 to 750 cm³ per revolution, is designed for industrial applications with nominal pressures of 350 bar. For particularly demanding heavy-duty applications, the A11V series offers displacement volumes of up to 600 cm³ per revolution at pressures up to 450 bar.

Fixed-displacement pumps and motors

Fixed-displacement units in the A2F series deliver a constant flow rate or a constant displacement volume. They are used in applications where the required flow or drive power remains constant or where control is achieved via external valves. The series covers sizes ranging from 5 to 1, 000 cm³ per revolution and achieves nominal pressures of 350 to 400 bar. Their compact design and high power density make them particularly attractive for installation situations with limited space.

Variable-displacement motors

Hydromatik’s variable-displacement motors allow the displacement volume to be adjusted during operation. This enables the speed and torque to be varied while maintaining a constant flow rate. The A6V series, for example, covers displacement volumes ranging from 28 to 500 cm³ per revolution and is primarily used in travel drives for mobile machinery, where a wide speed range combined with sufficient starting torque is required.

Technical Features and Design Principles

Hydromatik components are based on the axial piston principle. The pistons are arranged parallel to the drive shaft and are immersed in a cylinder block that is inclined relative to the drive shaft or driven by a swivel disc. Depending on the design, the piston stroke is generated either by the inclined position of the cylinder block (inclined-axis design) or by the angle of the swivel disc (swivel-disc design).

Swivel-Disc Design Versus Inclined-Axis Design

Both design principles have specific strengths. The swivel-disc design allows for a more compact configuration and is particularly suitable for variable-displacement pumps, as the swivel angle can be continuously varied between zero and the maximum value. The inclined-axis design, on the other hand, offers higher efficiency at large displacement volumes and is primarily used in fixed-displacement units and high-performance motors. Hydromatik utilizes both principles, depending on the series and application requirements.

Operating Pressures and Efficiency

The Hydromatik series operate at nominal pressures between 280 and 450 bar, with peak pressures briefly reaching up to 500 bar. In modern units, volumetric efficiencies exceed 90 percent, while overall mechanical-hydraulic efficiencies reach values above 92 percent. These efficiency figures result from optimized piston and control disc geometries that minimize leakage losses and improve flow control within the units.

Applications of Hydromatik Components

The range of applications extends from mobile hydraulics and industrial hydraulics to maritime and offshore-specific requirements. The following overview shows typical areas of application:

Variable-displacement pumps and motors dominate the mobile hydraulics sector, as work cycles impose highly fluctuating power requirements. An excavator, for example, requires high pressure and high flow rate when lifting a load, whereas only a fraction of that power is needed during an empty stroke. The infinitely variable adjustment of Hydromatik pumps precisely adapts the flow to current demand, thereby reducing energy consumption and heat generation in the system.

In industrial hydraulics, the large variable-displacement pumps of the A4VSO series are used when constant pressure, constant flow rate, or constant power is required. Injection molding machines utilize their precise controllability to precisely regulate injection pressure, holding pressure, and ejection time. Hydraulic presses benefit from the ability to switch between fast feed and high pressing pressure without having to change the pump.

Maintenance and Servicing of Hydromatik Units

The service life of Hydromatik pumps and motors depends largely on adherence to maintenance specifications and oil quality. Typical operating times of over 5, 000 hours are not uncommon with proper maintenance. The most common signs of wear affect the piston-bore pairing, the control disc, and the seals.

Oil Quality and Filtration

Axial piston units are sensitive to contaminants in the hydraulic oil. Particles larger than 10 micrometers can already cause scoring on the sensitive control discs. Compliance with the oil cleanliness class specified in DIN ISO 4406 is therefore absolutely essential. For most Hydromatik series, Bosch Rexroth requires a cleanliness class of at least 20/18/15; for high-pressure applications, this requirement is even 18/16/13. Filtration must meet these requirements, and the filter elements must be replaced according to the recommended intervals.

The viscosity of the hydraulic oil also significantly affects service life. The recommended viscosity ranges from 12 to 60 mm²/s during operation. Too low a viscosity increases leakage and reduces volumetric efficiency; too high a viscosity impairs suction capacity and can lead to cavitation damage. HLP oil, as defined by DIN 51524, is the minimum requirement for most applications.

Typical Signs of Wear and Diagnosis

Wear on units first becomes apparent through increasing leakage losses. The housing leakage volume increases, and volumetric efficiency decreases. Acoustically, incipient damage often manifests as increased pulsation or unusual noises, which indicate piston or bearing wear. Regular monitoring of the casing leakage volume and oil temperature enables condition-based maintenance, which minimizes downtime and maximizes the service life of the units.

Hydromatik in Today’s Market Environment

Under the leadership of Bosch Rexroth, the Hydromatik series is continuously being further developed. Current generations feature electrohydraulic control systems that can be integrated into digital control architectures. Sensors measure pressure, temperature, and speed directly at the unit and transmit the data to higher-level control systems. This integration enables predictive maintenance concepts and optimized operational management, which further reduces energy consumption.

At the same time, the spare parts market for older Hydromatik units remains vibrant. Many machine operators rely on maintaining existing systems rather than purchasing new ones. Specialized hydraulic service providers such as HK Hydraulik offer overhauls, spare parts procurement, and repairs for these proven series, underscoring the enduring relevance of Hydromatik technology in everyday industrial operations.

The standards landscape for axial piston units is shaped by DIN ISO 4413 (Safety Requirements for Hydraulic Systems) and the VDMA standard sheets. Hydromatik components meet these standards and are also certified according to Bosch Rexroth’s internal guidelines, which define additional tests and quality requirements.

Hydromatik is a brand name for axial piston pumps and axial piston motors that were originally developed and manufactured by Brüninghaus Hydromatik GmbH, based in Elchingen. The components are characterized by high power density, variable displacement, and operating pressures up to 450 bar, and are used in demanding hydrostatic drives for mobile and industrial hydraulics. Today, Hydromatik is integrated into the Bosch Rexroth Group as a product line.

Origins and History of Hydromatik

Hydromatik’s roots date back to the mid-20th century. The company established itself as a specialist in axial piston units and made a name for itself with robust, high-pressure-resistant pumps and motors that became indispensable in heavy-duty hydraulics. From the very beginning, the product range was geared toward applications requiring stepless speed and torque control at high pressures.

Acquisition by Rexroth and Integration into Bosch Rexroth

In 1972, Rexroth acquired Hydromatik GmbH, thereby expanding its portfolio to include the proven axial piston pumps and motors. Shortly thereafter, in 1976, Rexroth was fully integrated into the Mannesmann Group, and Hydromatik continued as part of Mannesmann Rexroth. The company’s final integration into the current group took place in 2001, when Mannesmann Rexroth merged with Robert Bosch’s automation technology division to form Bosch Rexroth AG. Since then, the Hydromatik product lines have been further developed, manufactured, and marketed under the Bosch Rexroth umbrella brand. The name Hydromatik is retained to designate the proven axial piston series.

Hydromatik Product Lines and Series

The Hydromatik product range includes axial piston pumps and axial piston motors with swivel disc or skewed-axis designs. The series are coded alphabetically and numerically, with the prefixes indicating the design and adjustability. The main series are divided into open and closed circuits, as well as fixed and variable displacement volumes.

Variable-displacement pumps for open circuits

Variable-displacement pumps with a swivel-disc design form the backbone of the Hydromatik product line. They continuously adjust their flow rate to meet demand by changing the swivel angle of the disc. At a swivel angle of zero degrees, the pump delivers no flow; at the maximum angle, it reaches its rated flow rate. This design enables demand-based power delivery without throttling losses.

With displacement volumes ranging from 18 to 140 cm³ per revolution, the A10V series covers the mid-range performance levels. Rated pressures of 280 bar and peak pressures up to 450 bar make them the standard solution for mobile machinery such as excavators and wheel loaders. The A4VSO series, with displacement volumes ranging from 71 to 750 cm³ per revolution, is designed for industrial applications with nominal pressures of 350 bar. For particularly demanding heavy-duty applications, the A11V series offers displacement volumes of up to 600 cm³ per revolution at pressures up to 450 bar.

Fixed-displacement pumps and motors

Fixed-displacement units in the A2F series deliver a constant flow rate or a constant displacement volume. They are used in applications where the required flow or drive power remains constant or where control is achieved via external valves. The series covers sizes ranging from 5 to 1, 000 cm³ per revolution and achieves nominal pressures of 350 to 400 bar. Their compact design and high power density make them particularly attractive for installation situations with limited space.

Variable-displacement motors

Hydromatik’s variable-displacement motors allow the displacement volume to be adjusted during operation. This enables the speed and torque to be varied while maintaining a constant flow rate. The A6V series, for example, covers displacement volumes ranging from 28 to 500 cm³ per revolution and is primarily used in travel drives for mobile machinery, where a wide speed range combined with sufficient starting torque is required.

Technical Features and Design Principles

Hydromatik components are based on the axial piston principle. The pistons are arranged parallel to the drive shaft and are immersed in a cylinder block that is inclined relative to the drive shaft or driven by a swivel disc. Depending on the design, the piston stroke is generated either by the inclined position of the cylinder block (inclined-axis design) or by the angle of the swivel disc (swivel-disc design).

Swivel-Disc Design Versus Inclined-Axis Design

Both design principles have specific strengths. The swivel-disc design allows for a more compact configuration and is particularly suitable for variable-displacement pumps, as the swivel angle can be continuously varied between zero and the maximum value. The inclined-axis design, on the other hand, offers higher efficiency at large displacement volumes and is primarily used in fixed-displacement units and high-performance motors. Hydromatik utilizes both principles, depending on the series and application requirements.

Operating Pressures and Efficiency

The Hydromatik series operate at nominal pressures between 280 and 450 bar, with peak pressures briefly reaching up to 500 bar. In modern units, volumetric efficiencies exceed 90 percent, while overall mechanical-hydraulic efficiencies reach values above 92 percent. These efficiency figures result from optimized piston and control disc geometries that minimize leakage losses and improve flow control within the units.

Applications of Hydromatik Components

The range of applications extends from mobile hydraulics and industrial hydraulics to maritime and offshore-specific requirements. The following overview shows typical areas of application:

Variable-displacement pumps and motors dominate the mobile hydraulics sector, as work cycles impose highly fluctuating power requirements. An excavator, for example, requires high pressure and high flow rate when lifting a load, whereas only a fraction of that power is needed during an empty stroke. The infinitely variable adjustment of Hydromatik pumps precisely adapts the flow to current demand, thereby reducing energy consumption and heat generation in the system.

In industrial hydraulics, the large variable-displacement pumps of the A4VSO series are used when constant pressure, constant flow rate, or constant power is required. Injection molding machines utilize their precise controllability to precisely regulate injection pressure, holding pressure, and ejection time. Hydraulic presses benefit from the ability to switch between fast feed and high pressing pressure without having to change the pump.

Maintenance and Servicing of Hydromatik Units

The service life of Hydromatik pumps and motors depends largely on adherence to maintenance specifications and oil quality. Typical operating times of over 5, 000 hours are not uncommon with proper maintenance. The most common signs of wear affect the piston-bore pairing, the control disc, and the seals.

Oil Quality and Filtration

Axial piston units are sensitive to contaminants in the hydraulic oil. Particle sizes larger than 10 micrometers can already cause scoring on the sensitive control discs. Compliance with the oil cleanliness class specified in DIN ISO 4406 is therefore absolutely essential. For most Hydromatik series, Bosch Rexroth requires a cleanliness class of at least 20/18/15; for high-pressure applications, this requirement is even 18/16/13. Filtration must meet these requirements, and the filter elements must be replaced according to the recommended intervals.

The viscosity of the hydraulic oil also significantly affects service life. The recommended viscosity ranges from 12 to 60 mm²/s during operation. Too low a viscosity increases leakage and reduces volumetric efficiency; too high a viscosity impairs suction capacity and can lead to cavitation damage. HLP oil, as defined by DIN 51524, is the minimum requirement for most applications.

Hydromatik in Today’s Market Environment

Under the leadership of Bosch Rexroth, the Hydromatik series is continuously being further developed. Current generations feature electrohydraulic control systems that can be integrated into digital control architectures. Sensors measure pressure, temperature, and speed directly at the unit and transmit the data to higher-level control systems. This integration enables predictive maintenance strategies and optimized operational management, which further reduces energy consumption.

At the same time, the spare parts market for older Hydromatik units remains vibrant. Many machine operators rely on maintaining existing systems rather than purchasing new ones. Specialized hydraulic service providers such as HK Hydraulik offer overhauls, spare parts procurement, and repairs for these proven series, underscoring the continued relevance of Hydromatik technology in everyday industrial operations.

The standards landscape for axial piston units is shaped by DIN ISO 4413 (Safety Requirements for Hydraulic Systems) and the VDMA standard sheets. Hydromatik components meet these standards and are also certified according to Bosch Rexroth’s internal guidelines, which define additional tests and quality requirements.