Working principle and system analysis of electric forklift

1、 Core system composition and working principle

1. Power system

Battery pack:

Type: Lead acid battery (mainstream) or lithium-ion battery (high-end model).

Function: Store electrical energy and supply power to the motor through wires. Lead acid batteries need to be regularly replenished with distilled water, while lithium-ion batteries are optimized for charging and discharging through BMS (Battery Management System).

Voltage level: ranging from 12V to 80V, configured according to forklift tonnage and usage.

Motor system:

Walking motor:

Type: DC series excited motor (traditional) or three-phase AC motor (modern).

Speed control:

DC motor: regulates the speed through armature voltage or excitation current. Armature voltage control is suitable for low-speed segments, while excitation control is suitable for high-speed segments.

AC motor: adopts variable frequency drive (VFD), combined with CAN bus to achieve precise control and support energy recovery.

Hydraulic motor:

Function: Drive hydraulic pump to generate high-pressure oil to control fork lift and gantry tilt.

Starting method: Independently controlled from the walking motor to ensure the separation of loading and unloading operations from driving operations.

2. Hydraulic system

Hydraulic pump: The gear pump converts the mechanical energy of the motor into hydraulic energy and outputs high-pressure oil (usually at a pressure of 10-20MPa).

Control valve group:

Multi way valve: distributes high-pressure oil to the lifting cylinder or tilting cylinder to achieve fork lifting and gantry angle adjustment.

Return valve: Ensure that the completed oil is filtered and returned to the tank, forming a closed circuit.

Executing Agency:

Lifting cylinder: Push the gantry up, and the fork lifts accordingly.

Tilt cylinder: Adjust the forward/backward tilt angle of the gantry to meet the requirements of cargo stacking.

Auxiliary devices: Filter purifies hydraulic oil, cooler controls oil temperature to ensure stable system operation.

3. Control system

Electronic Control Unit (ECU):

Function: Receive operation commands (accelerator pedal, joystick signals), and control motor speed and torque through pulse width modulation (PWM).

Battery management: monitoring battery level and temperature, supporting energy recovery (converting kinetic energy into electrical energy during braking to recharge the battery).

Operation interface:

Control lever: controls the lifting, tilting, and gantry movement of the fork.

Accelerator pedal: Adjust the driving speed and switch forward/backward with the direction switch.

safeguard:

Fault diagnosis: Real time monitoring of motor temperature, battery voltage and other parameters, automatic shutdown and alarm when exceeded.

Overload protection: Cut off abnormal current to prevent motor burnout.

4. Mechanical structure

Door frame system:

Composition: Inner frame, outer frame, fork, chain, roller.

Working principle: The hydraulic cylinder drives the inner frame to slide along the outer frame, and the chain pulls the fork to lift synchronously.

Steering system:

Steering wheel: Connected to the steering motor, the rear wheel direction is controlled through gear transmission.

Steering bridge: Adopting Ackermann steering geometry to ensure the minimum turning radius.

Chassis:

Tires: front drive wheels (solid rubber tires), rear steering wheels (polyurethane tires), suitable for indoor and outdoor ground.

Frame: High strength steel welded structure, bearing the weight of the entire vehicle and cargo load.

2、 Detailed explanation of workflow

1. Startup phase

The operator inserts the key and starts, the battery supplies power to the control system, and the ECU initializes sensors (such as angle sensors and pressure sensors).

2. Driving control

Acceleration: Press the accelerator pedal, and the ECU adjusts the motor voltage according to the pedal opening, driving the walking motor to rotate and transmitting power to the front wheels through the reducer.

Steering: Rotate the steering wheel, activate the steering motor, adjust the rear wheel direction, and achieve precise steering.

Braking: Release the accelerator pedal or press the brake, the ECU cuts off the power supply to the walking motor, and starts energy recovery to convert braking kinetic energy into electrical energy storage.

3. Loading and unloading operations

Lifting cargo:

Operate the lifting control lever, start the hydraulic motor, and drive the hydraulic pump to generate high-pressure oil.

High pressure oil enters the lifting cylinder through a multi way valve, pushing the piston to raise the gantry and the fork accordingly.

Adjust angle:

Operate the tilt control lever, high-pressure oil enters the tilt cylinder, and adjust the forward or backward tilt angle of the gantry.

Decreased goods:

Release the lifting control lever, the lifting cylinder returns oil, and the fork slowly descends under the action of gravity. The hydraulic system provides damping to prevent impact.

4. Special working conditions

Climbing: The motor provides high torque output, combined with the differential to distribute power, ensuring smooth uphill climbing.

Energy recovery: When braking or going downhill, the motor acts as a generator to convert kinetic energy into electrical energy, which is then recharged to the battery to extend the range.

3、 Key technical points

1. Speed control technology

DC motor: Combining armature control (low-speed section) with excitation control (high-speed section) to achieve wide range speed regulation.

AC motor: Combining variable frequency drive (VFD) with vector control to enhance dynamic response and efficiency.

2. Hydraulic efficiency optimization

Gear pump: Provides stable oil pressure and reduces energy loss.

Multi way valve: Accurately allocate flow to ensure smooth and impact free operation.

Load sensitive system: Automatically adjust oil pressure based on load to reduce energy consumption.

3. Battery management

Lead acid batteries: Regular water replenishment and maintenance, balanced charging to prevent sulfurization.

Lithium ion battery: BMS monitors cell voltage and temperature in real-time, supports fast charging and deep discharging.

4. Intelligent functions

CAN bus communication: realizes high-speed data transmission between ECU, display, and sensors, and supports fault self diagnosis.

Remote control operation: Some models are equipped with wireless remote control, suitable for dangerous or narrow environments.

4、 Advantages and application scenarios

1. Core advantages

Environmental friendliness: zero exhaust emissions, meeting indoor storage environmental protection requirements.

Low noise: The operating noise is below 70dB, improving the working environment.

Easy maintenance: The motor has no complex transmission mechanism, the hydraulic system has good sealing, and the failure rate is low.

High efficiency: Energy recovery technology improves battery life, with AC motor efficiency reaching over 90%.

2. Typical applications

Storage and logistics: Handling of goods in e-commerce warehouses and cold chain warehouses.

Manufacturing industry: material distribution on production lines, stacking of finished products.

Special environment: Clean workshops in the food and pharmaceutical industries, chemical warehouses that require explosion-proof forklifts.

The main equipment produced by Hebei Makita: stage electric hoist, electric chian hoist, wire rope electric hoist，Hand chain hoist, lever hoist, pneumatic hoist and other lifting equipment