Hydraulic Pump Flow Control via Auxiliary Pressure
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Solution Overview
Problem
Existing load-controlled pump devices cannot modify the discharge flow as desired when the workload remains the same, as they rely on operator-specific required speeds for the drive actuator, which can vary between operators.
Innovation Solution
A pump device with a variable capacity first pump, tilt actuator, regulator, fixed capacity second pump, resistor, control actuator, auxiliary passage, and switch valve, allowing for independent control of discharge flow by varying the control pressure and tilt angle of the swash plate, regardless of workload.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If load control is executed to vary pump discharge amount in accordance with actuator workload, then actuator speed can be controlled according to control valve opening, but discharge flow cannot be modified independently when workload remains the same
Solution Approach 1:
The pump device is divided into two independent pumps: a variable capacity first pump for load-controlled operation and a fixed capacity second pump for auxiliary flow control. This segmentation allows independent adjustment of discharge flow through the second pump without affecting the load control function of the first pump, thereby achieving discharge flow modifiability while maintaining system stability
Solution Approach 2:
A control actuator is introduced as an intermediary device that responds to front-rear differential pressure of the resistor to drive the regulator and reduce control pressure. This intermediary mechanism enables indirect control of the second pump's discharge flow through pressure differential sensing, providing flow adjustment capability without direct mechanical linkage and reducing control system complexity
2Ease of operation
If auxiliary pressure is supplied to control actuator through auxiliary passage, then discharge flow can be reduced to match operator requirements, but system pressure control becomes more complex
Solution Approach 1:
The control actuator automatically responds to front-rear differential pressure changes across the resistor and self-regulates the control pressure through the regulator, eliminating the need for complex external control mechanisms. The system uses its own internal pressure differentials to control itself, achieving operator-specific speed control while keeping the pressure control mechanism relatively simple
Solution Approach 2:
The auxiliary pressure supplied through the auxiliary passage changes the effective pressure differential acting on the control actuator, which in turn modifies the control pressure output from the regulator. By varying the auxiliary pressure parameter, the system can adjust discharge flow to match different operator requirements without changing the fundamental control mechanism structure
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 modification of discharge flow to match operator-specific requirements, maintaining consistent drive speed and workload independence, improving controllability and energy efficiency by adjusting the auxiliary pressure and engine rotation speed.
Implementation Method 1
a variable capacity first pump (10) configured to supply the working fluid to the drive actuator (3), the first pump having a discharge capacity that varies in accordance with a tilt angle of a swash plate (11)
Implementation Method 2
the control actuator (70) operates in accordance with a front-rear differential pressure of the resistor (65) so as to drive the regulator (60) to reduce the control pressure (Pcg) in response to an increase in the front-rear differential pressure of the resistor
Data Source
AI summary
A pump device includes a variable capacity first pump, a tilt actuator that controls a tilt angle of a swash plate of the first pump in accordance with the control pressure, a regulator that regulates the control pressure in accordance with a front-rear differential pressure of a control valve, a fixed capacity second pump driven by the same drive source as the first pump, the control actuator that operates in accordance with the front-rear differential pressure a resistor so as to drive the regulator to reduce the control pressure in response to an increase in the front-rear differential pressure of the resistor, an auxiliary passage that leads an auxiliary pressure to the control actuator, the auxiliary pressure acting on the control actuator against a upstream pressure of the resistor, and a switch valve that switches between connecting and shutoff the auxiliary passage.