Hydraulic Pilot Valve Switching for Boom and Arm Flow Merging
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Solution Overview
Problem
Existing hydraulic control systems for construction machines, such as small excavators, fail to achieve desired operating speeds for boom and arm operations due to limited flow rates from hydraulic pumps, leading to increased costs and size issues when trying to enhance pump capacity, and often operate high-speed devices at unnecessary speeds.
Innovation Solution
A hydraulic control system that includes a hydraulic pump group, a main control valve, and a direction changing valve on the pilot signal line to cut off the flow of pilot pressurized oil returning to the tank, allowing pressurized oil from a third hydraulic pump to join with oil from other pumps, thereby increasing the flow rate and operating speed of working devices like the boom and arm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the capacity of the hydraulic pump is increased to increase the flow rate, then the operating speed of the working device is improved, but the prime cost increases and the exterior size of the hydraulic pump increases
Solution Approach 1:
The patent combines pressurized oil from multiple hydraulic pumps (first, second, and third pumps) into a single confluence path to supply the working device. By merging the oil flows from different pumps, the system achieves a higher total flow rate without increasing the capacity of individual pumps, thereby avoiding increased manufacturing costs and pump size.
2Productivity
If the capacity of the hydraulic pump is increased to increase the flow rate, then the operating speed of the working device is improved, but the exterior size of the hydraulic pump increases
Solution Approach 1:
The patent combines pressurized oil from multiple hydraulic pumps (first, second, and third pumps) into a single confluence path to supply the working device. By merging the oil flows from different pumps, the system achieves a higher total flow rate without increasing the capacity of individual pumps, thereby avoiding increased manufacturing costs and pump size.
3Productivity
If the confluence system joins pressurized oils from multiple pumps, then the operating speed is increased, but all devices including bucket and option device operate at high speed which is unnecessary
Solution Approach 1:
The patent employs dynamic control through spools that can be positioned in different states (first position, second position, or intermediate position) to adjust the flow distribution. The spool for the working device can selectively connect to different pump sources or the confluence path, allowing the system to adaptively control which devices receive high-speed operation based on actual operational needs.
Solution Approach 2:
The patent segments the hydraulic control system into separate controllable paths for different devices. Each device (working device, bucket, option device) has its own spool and control path, allowing independent speed control. This segmentation enables the working device to operate at high speed while other devices operate at normal speed, avoiding unnecessary high-speed operation.
4Productivity
If the internal structure of the MCV is changed to enable flow joining, then the operating speed of boom or arm is increased, but the structural complexity of the MCV increases considerably
Solution Approach 1:
The patent designs the MCV with spools that serve multiple functions. The spool for the working device can control both normal operation and high-speed operation by shifting between positions, and the confluence spool can direct oil from either the first/second pumps or the third pump. This multi-functionality allows speed enhancement without adding separate dedicated components for each function.
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 solution significantly increases the flow rate and operating speed of working devices like the boom and arm, while minimizing the need for internal structural changes to the main control valve, allowing for efficient operation pattern customization and reducing costs by only increasing speed where necessary.
Implementation Method 1
a direction changing valve equipped on the second pilot signal line configured to interconnect the spool for traveling and a tank, connected to the first pilot signal line, and configured to be switched upon switching of the spool for a working device, thereby cutting off flow of pilot pressurized oil returning to the tank
Implementation Method 2
a main control valve (MCV) including a first spool group configured to control flow rates and flows of pressurized oils to be supplied from the first hydraulic pump and the second hydraulic pump
Data Source
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AI summary
The present invention relates to a hydraulic control system for a construction machine. More specifically, the present invention provides a hydraulic control system for a construction machine comprising: a hydraulic pump group that includes a first hydraulic pump, a second hydraulic pump and a third hydraulic pump; a main control valve (MCV) that includes a first spool group that controls the amount and the flow of pressurised fluid supplied from the first hydraulic pump and the second hydraulic pump and that includes an operation apparatus spool, a driving spool and a merging spool, a second spool group that controls the amount and the flow of pressurised fluid supplied from the third hydraulic pump and that includes a rotating spool, and a straight driving valve that is installed between the first spool group and the second spool group; a first pilot signal line that is connected to the operation apparatus spool and that provides a supply path for a pilot pressurised fluid that is applied in order to switch the operation apparatus spool; a second pilot signal line that is connected to the driving spool and that provides a supply path for a pilot pressurised fluid that is applied in order to switch the driving spool; and a direction changing valve that is installed on the second pilot signal line connecting the driving spool and a tank, that is connected to the first pilot signal line, and that is switched when the operation apparatus spool is switched so as to cut off the flow of a pilot pressurised fluid that is returning to the tank.