REXRTOH A4VG series 40 axial piston variable displacement pump application guide

REXRTOH A4VG series 40 axial piston variable displacement pump application guide

In modern walking machinery, engineering machinery, and heavy industrial equipment, hydraulic systems are the heart that generates powerful power. As its core power source, the performance of the axial piston pump directly determines the efficiency, response speed, and reliability of the entire system. The A4VG Series 40 axial piston variable displacement pump launched by Bosch Rexroth is designed for closed circuit applications with working pressures up to 500 bar. With its extremely high power density, rich control options, and sturdy and durable structure, it has become a benchmark product in the high-end hydraulic drive field. This article will deeply analyze its technical characteristics, control principles, selection standards, and application points.

Core Features and Design Advantages

The design concept of the A4VG Series 40 pump is to achieve maximum power output and compact structure. Its core advantages include:

Ultra high working pressure: The rated pressure can reach up to 450 bar, and the maximum pressure can reach 500 bar, significantly improving the system power density and helping to miniaturize the equipment.

Variable design of inclined disc: By changing the inclination angle of the inclined disc, the displacement can be infinitely adjusted. When the flow direction changes, the inclined disc smoothly passes through the center position, ensuring smooth operation and minimal impact.

Integrated auxiliary pump: Equipped with a built-in gear type oil replenishment pump, it provides necessary replenishment and pilot control oil source for closed circuits. It can also choose the version without a built-in oil replenishment pump, which is supplied by an external oil source.

Through drive shaft: allows for the installation of a second pump of the same diameter in series on the same axis, providing a compact solution for multi circuit systems without the need for a transfer case.

High performance high-pressure safety valve: Integrated oil replenishment function, direct acting, used to protect pumps and motors from overload pressure impact.

Diversified control methods: providing comprehensive control options from pure hydraulic to electro-hydraulic proportional, from manual to automatic speed related (DA control), to meet various application needs from simple to complex.

Interpretation of Technical Parameters and Selection Codes

1. Displacement and specifications

This series offers six specifications (NG) and geometric displacement (at 20 bar) to meet a wide range of needs:

NG 110: 110.4 cm³/rev

NG 125: 125 cm³/rev

NG 145: 145.3 cm³/rev

NG 175: 175.4 cm³/rev

NG 210: 210.6 cm³/rev

NG 280: 280 cm³/rev

Each specification comes with standard speed and high-speed (some specifications) rotor sets to meet different speed and power requirements. Its weight (excluding through drive) ranges from approximately 88 kg (NG110) to 152 kg (NG280).

2. Selection code: embodiment of modular configuration

The A4VG pump adopts a selection code of up to 23 digits, achieving high customization. The core code includes:

04- Control mode: This is the core of the selection, determining the control logic of the pump.

HP: Hydraulic proportional control, related to pilot pressure (6-18 bar). The external pilot pressure signal directly controls the displacement, and the flow rate can be ignored.

HW: Hydraulic proportional control, mechanical servo with lever. The displacement is continuously controlled through an external mechanical lever angle (± 3 ° to 32 °), with standard spring centering.

HT: Hydraulic direct control. The control pressure directly acts on the variable piston, and the displacement is related to the control pressure, system pressure, and speed.

DA: Automatic control, related to speed. The built-in DA control valve generates pilot pressure based on the driving speed to achieve adaptive adjustment of engine power, commonly used for walking drive.

EP: Electro hydraulic proportional control. Stepless control of displacement through input current (such as 400-1200mA for 12V systems), optional with manual emergency operation version.

EZ: Two point electronic control. Switch the displacement between zero and maximum through power on/off control.

ET: Direct electronic control. The pressure acting on the variable piston is controlled by the current of two proportional pressure reducing valves (DRE).

05- Pressure cutoff: optional function. When the set pressure is reached, pull the pump displacement back to the minimum to prevent frequent opening of the high-pressure relief valve, save energy, and reduce heat generation. It must be set at least 30 bar below the set value of the high-pressure safety valve.

17- Oil replenishment pump and rotor assembly configuration: Standard or high flow built-in gear oil replenishment pump can be selected, or no built-in oil replenishment pump can be selected (supplied by external oil).

18- Through drive: Specify the installation flange (SAE J744 standard) and spline shaft specifications (ANSI B92.1a or DIN 5480) for connecting the second pump in series.

20- Oil replenishment circuit filtration/external oil replenishment: Optional solutions include oil suction pipeline filtration (S), oil pressure pipeline filtration (D), accessory filter (F/B), or external oil replenishment supply (E).

Hydraulic oil, working conditions, and filtration requirements

1. Hydraulic oil selection

Recommend using HLP mineral oil that complies with DIN 51524. The selection of oil should ensure that the operating viscosity is within the optimal range (ν _opt=36... 16 mm ²/s) at the system operating temperature to achieve maximum efficiency and component life. Bosch Rexroth's "Fluid Rating" system (technical data 90235/90245) provides important reference for oil product selection.

2. Range of work pressure

Working port A/B: rated pressure 450 bar (maximum design pressure), peak pressure 500 bar (single operation cycle ≤ 10s, total time ≤ 300h).

Oil replenishment pressure: rated at 25 bar, maximum at 40 bar.

Shell pressure (T port): It is necessary to strictly follow the pressure difference (shell environment) - speed curve to prevent damage to the shaft seal.

Pressure change rate: maximum allowable 9000 bar/s.

3. Filtering requirements

To achieve and maintain an oil cleanliness level not lower than ISO 4406 20/18/15 (19/17/14 required for short-term high-temperature operation), an efficient filtration system must be configured. Fine filtration is the key to extending the service life of pumps. For the oil replenishment circuit, various options are provided, including oil suction filters, oil pressure pipeline filters, and accessory filters directly installed on the pump. Special note: For versions with accessory filters (F, B type), a minimum conductivity of 300 pS/m is required for hydraulic oil to prevent static accumulation in the filter element.

Key functions and safety components

1. High pressure safety valve

Two integrated high-pressure safety valves (one at port A and one at port B) are the primary overload protection for the system. They set the pressure difference (Δ p_HD) between the working pressure and the refueling pressure, rather than the absolute pressure. For example, if the working pressure is designed to be 450 bar, the oil replenishment pressure is 20 bar, and a safety margin of 30 bar is considered, then Δ p_HD should be set to 460 bar. At this time, the absolute opening pressure of the safety valve is about 480 bar. When placing an order, it is necessary to clearly specify the Δ p_HD setting value.

2. Neutral valve

An electromagnetic switch valve is used to force the pump back to zero position and unload the variable cylinder when it loses power, ensuring that the drive system is "disengaged", enhancing safety, and accurately adjusting the return to zero time.

3. Mechanical travel limiter

By using two internally adjustable limit screws, the maximum displacement of the pump can be mechanically and continuously reduced, regardless of the control method used, providing the possibility of achieving power limitation or special function curves.

4. Swing angle sensor

A sensor based on the Hall effect can detect the angle of the inclined plate (i.e. displacement) in real time and output an analog signal of 0-5V (or 1-4V) for display or closed-loop control.

Installation Planning and Application Guidelines

1. Installation position and oil injection exhaust

It is recommended to install the pump under the fuel tank (with the pump located below the lowest liquid level in the tank). If it is necessary to install on top of the fuel tank, the suction height must be strictly controlled (hs_max ≤ 800 mm), and the absolute pressure at the suction port S must not be lower than 0.8 bar (not lower than 0.5 bar during cold start). The pump must be adequately oiled and vented before installation or at a specific location (such as the drive shaft level), with particular attention paid to the venting of the variable cylinder (via X1/X2 or X3/X4) and the housing (via the R vent) to prevent dry friction and cavitation. Different installation positions can affect the control characteristics, and gravity, self weight, and shell pressure may cause slight deviations in the control curve.

2. Application of combination pump

Through through drive, two A4VG pumps can be connected in series to form a combination pump, providing independent circuits for different actuators. When placing an order, the complete order models of the two pumps should be connected with a "+" sign. Installing flanges with four holes is more stable. It is necessary to verify the transmission torque of the through drive shaft to ensure that the total torque of the second pump and its driving load does not exceed the allowable value.

3. Core considerations for project planning

Professional personnel: The planning, installation, and debugging of the system must be carried out by qualified professionals.

Safety function: The pressure cutoff function is not a safety device to prevent pressure overload. The system must be equipped with a safety valve (such as a high-pressure safety valve).

Dynamic power flow: When the pump operates as a motor under braking conditions, its displacement should not exceed 95% of the maximum displacement.

Peak pressure: Transient pressure peaks may occur in applications, and must be considered when selecting measuring instruments and pipe fittings.

Electromagnetic compatibility: When using PWM signals to drive electromagnets, electromagnetic interference (EMI) may occur, and machine manufacturers need to take appropriate measures.

Natural frequency: During long-term operation at constant speed, it should be noted that the natural frequency of the hydraulic system may be excited by the pump's excitation frequency (speed frequency x number of plungers 9), and resonance should be avoided through reasonable pipeline design.

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