Hydraulic Pump for Concrete Mixer Truck
1. Core Functions and Working Principles
The hydraulic pump of a concrete mixer truck is the core power source for rotating the mixing drum and unloading materials. Its working principles are as follows:
• Power Transmission: Power is drawn from the engine via a Power Take-Off (PTO) and transmitted to the hydraulic pump through a drive shaft.
• Hydraulic Energy Conversion: The hydraulic pump (e.g., piston pump, gear pump) converts mechanical energy into hydraulic energy, which is delivered to the hydraulic motor through oil pipes.
• Kinetic Energy Output: The hydraulic motor converts hydraulic energy into kinetic energy, which is transmitted to the mixing drum via a reducer to drive its forward and reverse rotation for mixing and unloading.
• Pumping Control: The piston reciprocates to suck in and push out concrete, while the S-valve swings to change direction, enabling continuous concrete delivery.
Technical Parameter Examples:
• Displacement: 90–180 mL/r (e.g., SAUER 90L series piston pumps).
• Pressure: Rated pressure up to 35–40 MPa, meeting high-torque requirements.
• Efficiency: Volumetric efficiency ≈95%, total efficiency ≈90%.
2. Types and Selection Recommendations
Based on truck requirements, hydraulic pumps can be classified as follows:
【表格】
Type Characteristics Applicable Scenarios
Fixed-Displacement Piston Pump Constant displacement, simple structure, low cost. Small mixer trucks or low-load conditions.
Variable-Displacement Piston Pump Adjustable displacement (e.g., constant-pressure variable pump), adapts to varying loads, high efficiency. Large mixer trucks or high-load, variable-condition demands.
Gear Pump Strong resistance to contamination, but lower pressure and efficiency. Budget-limited models or low-performance requirements.
Key Selection Parameters:
• Displacement (Vg): Must match the mixing drum’s rotational speed requirements; higher displacement = higher flow rate.
• Pressure Rating: Should exceed the system’s maximum working pressure (typically with 10%–20% margin).
• Volumetric Efficiency: Prefer ≥90% to minimize energy loss.
3. Typical Applications and Component Synergy
The hydraulic pump must collaborate with the following components:
• Hydraulic Motor: Converts hydraulic energy into kinetic energy to drive the mixing drum.
• Reducer: Reduces rotational speed and increases torque to suit the mixing drum’s load characteristics (typically with a gear ratio of 50:1–100:1).
• S-Valve and Piston: In concrete pumping, these components enable suction, pushing, and direction change.
Case Examples:
• 8m³ Mixer Truck: Uses an Eaton hydraulic pump (120 mL/r displacement) paired with a Bonfiglioli reducer, achieving a mixing drum speed of 0–14 r/min for construction needs.
• High-Pressure Pumping Scenarios: Adopts a Rexroth A4VG variable pump (max pressure 40 MPa) to deliver concrete via high-pressure pipes to high-rise buildings.
4. Common Faults and Maintenance Recommendations
Fault Phenomena:
• Overheating Pump Body: May result from elevated system oil temperature or excessive motor current.
• Pressure Fluctuations: Caused by aged skeleton shaft seals, worn main shaft seals, or abnormal noises inside the pump.
• Oil Leakage: Due to worn shaft seal seals or loose oil pipe connections.
Maintenance Recommendations:
• Regular Inspections: Check hydraulic oil cleanliness every 500 hours and replace hydraulic oil every 2,000 hours.
• Lubrication: Ensure proper gear oil levels in the reducer to avoid dry friction.
• Spare Parts Inventory: Stock critical wear parts (e.g., skeleton shaft seals, oil seals) to minimize downtime.
5. Leading Market Brands and Models
【表格】
Brand Typical Models Features
SAUER 90L Series (e.g., 90L250) Closed-loop hydraulic system, high pressure/large displacement, suitable for heavy-duty mixer trucks.
Rexroth A4VG Series (e.g., A4VG125) Variable displacement, high efficiency, adapts to variable working conditions.
Eaton A4VTG090 Series Strong contamination resistance, long lifespan, low maintenance costs.
Danfoss
90RLFRL Series
High integration, suitable for compact mixer truck designs.
