Hydraulic Flow Control With Fluid Temperature Compensation
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Solution Overview
Problem
Existing hydraulic excavators face challenges in maintaining control accuracy of actuators due to temperature variations in hydraulic operating fluids, as temperature sensors are not directly measuring the fluid temperature, leading to deviations and reduced flow rate control performance.
Innovation Solution
The system includes a work machine with a hydraulic drive system that incorporates a temperature sensor on a sampling hydraulic line branching from the main hydraulic line, allowing the controller to correct command electrical signals based on the measured temperature of the hydraulic operating fluid, ensuring accurate flow rate control irrespective of temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the temperature sensor is disposed in the valve housing to sense the valve housing temperature, then the temperature measurement is easier to implement, but a large deviation is caused between the measured temperature and the actual hydraulic operating fluid temperature
Solution Approach 1:
A thermal conductor is introduced as an intermediary between the hydraulic operating fluid and the temperature sensor. The thermal conductor is in direct contact with the fluid and conducts heat to the temperature sensor, which is mounted on the valve housing. This mediator enables accurate fluid temperature measurement while keeping the sensor accessible on the housing exterior.
Solution Approach 2:
The patent replaces direct mechanical contact between the temperature sensor and the hydraulic fluid with a thermal conduction system. Instead of immersing the sensor directly in the fluid, a thermal conductor pathway is established that transfers thermal energy from the fluid to the sensor mounted on the housing.
2Reliability
If the temperature sensor is placed far from the restrictor part to avoid high pressure, then the sensor safety is improved, but the temperature measurement deviates from the actual fluid temperature at the restrictor
Solution Approach 1:
The thermal conductor acts as a mediator that bridges the spatial gap between the restrictor part and the temperature sensor. It conducts thermal energy from the high-pressure restrictor area through the hydraulic operating fluid to the sensor location, enabling accurate temperature measurement without exposing the sensor to high pressure.
Solution Approach 2:
The patent utilizes the hydraulic operating fluid itself as a medium for thermal energy transmission. The fluid circulating through the restrictor part carries thermal energy that is conducted through the thermal conductor pathway to the temperature sensor, leveraging the existing hydraulic system for both fluid power and thermal measurement.
3Measurement precision
If the temperature sensor is directly exposed to the hydraulic operating fluid to measure accurate temperature, then the measurement precision is improved, but the risk of sensor breakdown increases
Solution Approach 1:
The thermal conductor serves as a protective intermediary between the temperature sensor and the hydraulic operating fluid. It transfers thermal energy from the fluid to the sensor while physically isolating the sensor from the high-pressure fluid environment, preventing sensor breakdown while maintaining measurement accuracy.
Solution Approach 2:
The patent replaces direct mechanical exposure of the sensor to the hydraulic fluid with a thermal conduction interface. The sensor remains mounted on the valve housing in a safe, low-pressure environment while still accurately measuring fluid temperature through the thermal conductor pathway.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration maintains actuator control accuracy by adjusting flow rates to target values, reducing the risk of sensor breakdown and facilitating easy replacement, while improving robustness against temperature fluctuations.
Implementation Method 1
a temperature sensor set on the sampling hydraulic line
Implementation Method 2
solenoid proportional pressure reducing valves that reduce the pressure of the hydraulic fluid supplied from the pilot pump and output a resulting pressure as an operation pressure
Implementation Method 3
a hydraulic pump, flow rate controllers that are connected in parallel to a delivery line of the hydraulic pump
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A work machine that can keep the control accuracy of actuators irrespective of temperature variation of a hydraulic operating fluid that passes through flow rate controllers that control the flow rates of supply to the actuators is provided. For this purpose, the flow rate controllers each have a valve body that is disposed on a main hydraulic line connecting a delivery line of a hydraulic pump and the actuator and that moves according to an operation pressure from a solenoid proportional pressure reducing valve, a sampling hydraulic line that branches from the main hydraulic line, and a temperature sensor set on the sampling hydraulic line. The controller is configured to correct a command electrical signal to the solenoid proportional pressure reducing valve according to a signal from the temperature sensor.