Hydraulic Drive Torque Feedback Circuit for Construction Machines
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Solution Overview
Problem
Existing hydraulic drive systems for construction machines, such as hydraulic excavators, face challenges in performing total torque control with high precision due to errors in torque detection and complex regulator structures, particularly in small-sized machines where space is limited and installation is difficult.
Innovation Solution
A hydraulic drive system with a torque feedback circuit that modifies the delivery pressure of one hydraulic pump based on the absorption torque of another, using a variable pressure reducing valve and pressure dividing circuits to simulate the absorption torque, allowing precise detection and feedback to achieve precise total torque control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a constant set pressure is used in the pressure reducing valve for total torque control, then the rated output torque of the prime mover can be efficiently utilized in combined operations, but the torque control precision deteriorates when one pump is not undergoing torque limitation
Solution Approach 1:
The pressure reducing valve is designed with a variable set pressure characteristic that changes according to the delivery pressure of the second hydraulic pump. When the second pump's delivery pressure is high (indicating it is undergoing torque limitation), the set pressure is high, allowing efficient torque utilization. When the delivery pressure is low (indicating load sensing control is active), the set pressure is low, preventing erroneous torque reduction and maintaining control precision. This dynamic adaptation resolves the contradiction between efficient torque utilization and control precision.
2Device complexity
If the delivery pressure of the second hydraulic pump is directly led to the first hydraulic pump's regulator, then the structure remains simple, but the torque detection precision deteriorates due to errors in representing actual absorption torque
Solution Approach 1:
The pressure reducing valve serves as an intermediary device between the second hydraulic pump's delivery pressure and the first hydraulic pump's regulator. It transforms the delivery pressure signal into a modified pressure signal that accurately represents the absorption torque of the second pump. This intermediary function allows precise torque detection while maintaining a relatively simple hydraulic structure, resolving the contradiction between structural simplicity and measurement precision.
3Measurement precision
If a complex regulator structure is used to achieve precise torque control, then the torque control precision improves, but the ease of installation deteriorates in small-sized construction machines
Solution Approach 1:
The pressure reducing valve is designed to perform multiple functions: it controls the set pressure according to the second pump's delivery pressure, represents the absorption torque of the second pump, and feeds back this information to the first pump's regulator. This multi-functionality allows precise torque control to be achieved without adding complex separate systems, thereby maintaining ease of installation in small-sized construction machines while improving torque control precision.
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
Enables efficient utilization of the prime mover's rated output torque with high precision in both torque-controlled and load-sensing operational states, preventing prime mover stoppage and optimizing performance in combined operations.
Implementation Method 1
a variable pressure reducing valve and pressure dividing circuits to simulate the absorption torque
Implementation Method 2
torque feedback circuit that modifies the delivery pressure of one hydraulic pump based on the absorption torque of another
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
The object is to make it possible to efficiently utilize rated output torque of the prime mover by performing total torque control with high precision through precise detection of absorption torque of the other hydraulic pump by use of a purely hydraulic structure and feedback of the absorption torque to one hydraulic pump's side. For this purpose, the hydraulic drive system is equipped with: a torque feedback circuit 112v which is supplied with delivery pressure of a main pump 202 and load sensing drive pressure, modifies the delivery pressure of the main pump 202 to achieve a characteristic simulating the absorption torque of the main pump 202, and outputs the modified pressure; and a torque feedback piston 112f which is supplied with an output pressure of the torque feedback circuit and controls displacement of a main pump 102 so as to decrease the displacement of the main pump 102 and thereby decrease maximum torque T12max as the output pressure increases.