Hydraulic Pump Flow Compensation to Eliminate Lever Dead Zone
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Solution Overview
Problem
Conventional hydraulic pump systems for construction machines experience a 'dead zone' where the discharge flow rate remains unchanged with operation lever movement, leading to abrupt flow rate increases and reduced operation sensibility and workability.
Innovation Solution
A method that compensates the discharge flow rate by determining a required discharge volume and a compensation ratio based on the operation lever's signal pressure and engine RPM, controlling the hydraulic pump to adjust the flow rate proportionally with the pilot pressure, ensuring the flow rate aligns with the operator's intention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the discharge flow rate is compensated by taking engine RPM into account, then the initial sense of operation becomes consistent across different engine speeds, but a dead zone is created where the discharge flow rate does not change with operation lever movement
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the compensation ratio based on pilot pressure. The compensation ratio varies from 100% at low pilot pressure to 0% at high pilot pressure, allowing the system to transition between different control modes. This resolves the contradiction by eliminating the dead zone while maintaining operation consistency across different engine RPMs.
Solution Approach 2:
The patent implements dynamics by making the compensation ratio variable rather than fixed. The compensation ratio changes dynamically with pilot pressure, enabling the system to adapt its behavior based on operating conditions. This dynamic adjustment eliminates the dead zone where flow rate remains unchanged, while preserving the benefits of RPM-based compensation.
2Productivity
If the required pump volume is adjusted to compensate for low engine RPM, then the discharge flow rate matches the required volume, but the discharge flow rate does not respond to operation lever movement in the dead zone
Solution Approach 1:
The patent uses parameter changes by adjusting the compensation ratio based on pilot pressure. When pilot pressure is low (dead zone condition), the compensation ratio is high (100%), allowing operation lever movement to directly affect the required pump volume. When pilot pressure is high, the compensation ratio decreases, maintaining flow rate matching. This resolves the contradiction between flow rate matching and response speed.
3Speed
If the discharge flow rate is set based on pilot pressure alone, then the flow rate responds to operation lever movement, but the initial sense of operation differs depending on engine RPM
Solution Approach 1:
The patent applies parameter changes by using engine RPM as a variable to determine the compensation ratio. The compensation ratio is calculated based on the ratio of actual engine RPM to reference engine RPM, ensuring that the discharge flow rate responds consistently to operation lever movement across different engine speeds. This resolves the contradiction between operation response and operation consistency.
Data Source
Figure 1a~1c
Figure 1d~2
Figure 3a~4
AI summary
Disclosed is a method for compensating for the flow rate of a variable capacity-type hydraulic pump such that, when a manipulation lever is manipulated, a discontinuous section, which has no change in the discharge flow rate of the hydraulic pump, is eliminated. The present invention provides a method for compensating for the flow rate of a hydraulic pump of a construction machine comprising a hydraulic pump, which is connected to an engine, a hydraulic actuator, which is driven by operating oil of the hydraulic pump, a control valve, which is installed in a channel of the hydraulic pump, a manipulation lever, a means for detecting the amount of manipulation of the manipulation lever, a means for detecting the number of revolutions of the engine, and a controller for controlling the control valve according to a signal pressure, which follows the amount of manipulation of the manipulation lever, and a signal resulting from detection of the number of revolutions of the engine, the method being characterized by comprising the steps of: detecting a signal pressure, which results from the amount of manipulation of the manipulation lever, and the number of revolutions of the engine; setting a required volume, which results from the amount of manipulation of the manipulation lever, and a compensation ratio and setting a required volume, which is obtained by compensating for the number of revolutions of the engine; and controlling the hydraulic pump so as to discharge a flow rate that corresponds to the sum of the required volume, which results from the amount of manipulation of the manipulation lever, and a flow rate that follows a calculation value obtained by multiplying a value of difference between a value of the required volume, which is obtained by compensating for the number of revolutions of the engine, and a value of the required volume, which results from the amount of manipulation of the manipulation lever, by the percentage of the compensation ratio.