- You do not have any products in your shopping cart yet.
Axial Piston Pumps Variable Displacement
Variable displacement axial piston pumps are key components in closed hydraulic systems. They allow for a variable delivery flow as well as a reversible flow direction. The displacement is controlled via a swash plate. More on variable displacement axial piston pumps
Axial piston variable displacement pumps – a selection
1 to 8 (from a total of 8)
Due to the precise adjustment of the flow rate, these pumps are ideal for mobile and industrial applications with high power requirements.
W0 / C1: Compact aluminum design, suitable for low to medium pressures.
W1: Cast iron construction for increased durability.
C2 / C3: Large displacements and high pressure ratings, SAE flange systems, extensive control options.
Every variable displacement axial piston pump is available with different control systems: manual, hydraulic proportional, or electric (ON/OFF, proportional, pulse control). The C2 and C3 series additionally support automatic power adjustment via automotive control.
Integrated charge pumps ensure reliable operation by maintaining charge pressure. Complementary accessories such as pressure filters, bypass valves, flushing valves, or power limiters extend the range of functions.
Hydromot's variable displacement axial piston pumps are available in single or tandem versions. Flexible connection variants (BSPP, UNF, SAE flanges) and various shaft ends enable easy integration into existing hydraulic systems.
Variable Displacement Axial Piston Pumps - Frequently Asked Questions
What are variable displacement axial piston pumps and how do they work?
Variable displacement axial piston pumps are hydraulic pumps used in closed loop systems. Their main function is to generate a continuously variable oil flow with reversible flow direction. The displacement variation is achieved through rotation of a swash plate. When the swash plate is moved beyond the zero point, the oil flow direction changes. These pumps are available in various series such as C1, C2, C3, W0, and W1.
Which series of axial piston pumps are offered and what are their main differences?
We offer several series of axial piston pumps with different specifications:
- Series W0 (14/18 cc/rev): For low-power applications with low cost. Rated pressure 170 bar, peak pressure 250 bar. Aluminum housing, manual controls only
- Series C1 (14/18 cc/rev): Higher rated pressure of 230 bar, peak pressure 270 bar. Aluminum housing with wide range of controls (manual, hydraulic, electric)
- Series W1 (14/20 cc/rev): Robust construction with cast iron housing. Rated pressure 280 bar, peak pressure 350 bar. Various control options available
- Series C2 (21/28/35 cc/rev): Larger displacement volumes, rated pressure 270 bar, peak pressure 350 bar. SAE "B" flange system, comprehensive control selection
- Series C3 (46/50/64 cc/rev): Largest series with rated pressure 320 bar, peak pressure 400 bar. SAE "B" flange system, wide control range
What types of controls are available for these pumps?
The axial piston pumps offer a variety of control options:
Manual Controls:
- Without zero position: Displacement adjustment by turning a control pin
- With zero position: With internal return spring to zero displacement
- With lever and feedback: Displacement proportional to lever angle
Hydraulic Proportional Controls:
- With and without feedback: Displacement proportional to control pressure
Electric Controls:
- Two-position (ON-OFF): Switch to maximum displacement
- Pulse control: Displacement as a function of current inputs
- Proportional with/without feedback: Displacement proportional to input current
Automotive Control: For C2/C3 series, automatic adjustment to pump speed
What is a charge pump and what role does it play?
A charge pump is a small auxiliary pump that is integrated into these variable axial piston pumps or can be added as an option. Its main function is to maintain a minimum pressure in the closed loop (charge pressure), which is crucial for the proper operation of the pump and its controls. This charge pressure ensures that the main pump is always adequately supplied with oil and cavitation is prevented, especially at high speeds. The displacement varies by series (e.g., 5.4 cc/rev for C1/W0/W1 and 11-13 cc/rev for C2/C3).
What precautions should be observed when operating these pumps?
For longevity and proper operation, important precautions must be observed:
- Peak operation: Peak loads must not exceed 1% of each minute
- Maximum operation: Simultaneous operation at maximum speed and maximum pressure is not recommended
- Suction pressure: Must always be ≥ 0.8 bar (≥ 11.6 psi) to prevent cavitation
- Oil type: Specified values are based on operation with mineral oil
What additional options and accessories are available for the pumps?
The pump series offer various additional options to extend functionality:
- Pressure filters: To protect the system from contamination
- Filter with electric clogging sensor: Enables monitoring of filter condition
- Bypass valve: Connects pressure ports A and B when needed (standard on C2 and C3)
- Power limiter: Only for C2 and C3, limits power consumption
- Electric shut-off valve: Brings pump displacement to zero in case of power interruption
- Flushing valve: Enables oil cooling at high speeds
- Inching (Hydraulic/Mechanical): Variable throttling for fine control (C2 and C3 only)
- Through-drive options: Various SAE and Bosch flange types for gear pumps (for example for separate circuit for hydraulic oil coolers)
What are "tandem pumps" and what configurations are possible?
Tandem pumps are combinations of two or more axial piston pumps mechanically connected together to increase total power or the number of independent hydraulic circuits. There are two main configurations:
- Short version: Only the second pump includes the charge pump. More compact arrangement, but certain options are not available
- Long version: Both pumps have their own charge pump. More installation flexibility and improved overall performance
For tandem pumps, the shaft type and through-drive option must be specified for each individual pump when ordering.
What role do connection variants and drive shafts play in the pumps?
Connection variants and shaft ends are crucial for integration into various hydraulic systems:
Connection Variants:
- Various thread types for pressure, suction, charge pressure, and drain connections
- BSPP threads (G) and SAE-UNF threads (U)
- C3 series additionally offers SAE 6000 flanges for pressure lines
Drive Shafts:
- Various drive shafts (cylindrical, splined)
- Through-drive options (SAE "A", "B", "B-B", Bosch Gr.1, Gr.2)
- Enable connection to drive motor and direct mounting of additional auxiliary pumps
How does swash plate technology work in variable axial piston pumps?
The swash plate technology is the heart of variable displacement. The swash plate can be tilted at a specific angle, changing the piston stroke and thus the delivery volume. At zero position, the plate stands perpendicular to the drive axis and no oil is delivered. By tilting the plate in one direction, oil is delivered in the forward direction; tilting in the other direction reverses the flow direction. The tilt angle directly determines the delivery rate.
What advantages do closed loop systems with variable axial piston pumps offer?
Closed loop systems with variable axial piston pumps offer several decisive advantages:
- Energy efficiency: Demand-based delivery reduces energy losses
- Precise control: Stepless speed and direction changes
- Compact design: Smaller tanks and reduced piping
- Lower heat generation: Less throttling means less power loss
- Fast response times: Direct relationship between control and output
- Reversibility: Easy reversal of rotation direction without mechanical changes
How do I select the right series for my application?
Series selection depends on several factors:
- Power requirements: W0 for low cost/low power, C3 for highest power
- Pressure range: From 170 bar (W0) to 320 bar (C3) rated pressure
- Displacement volume: 14-18 cc/rev (W0/C1) to 46-64 cc/rev (C3)
- Control requirements: Simple manual to complex automotive control
- Construction: Aluminum for lighter applications, cast iron for robust operations
- Additional functions: Bypass valves, power limiters only available on C2/C3