Hydraulic Pump Flow Staging for Fine Work Machine Actuation
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Solution Overview
Problem
The operability of hydraulic actuators in fine operations is impaired due to delayed response and variability in starting behavior, especially when the operation lever is moved slowly, as the thrust force required to overcome static friction is not adequately managed, leading to inconsistent timing and speed of actuator activation.
Innovation Solution
A work machine with a variable displacement hydraulic pump, equipped with first and second timing sensors, controls the pump delivery flow rate to a minimum before actuation, then increases it to a predetermined rate just before and after actuation, ensuring the thrust force surpasses static friction, thus improving the synchrony of actuator response with lever operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the pump capacity is minimized to reduce fuel consumption, then the pump delivery flow rate decreases, but the meter-in flow rate becomes excessively high relative to the operation lever speed, degrading operability in fine operations
Solution Approach 1:
The invention segments the flow control function by introducing a separate flow control valve that bypasses the directional control valve. This allows independent control of the meter-in flow rate from the pump delivery flow rate, enabling the pump to operate at minimum capacity while the flow control valve restricts flow to match the slow operation lever speed in fine operations.
Solution Approach 2:
The flow control valve acts as an intermediary device between the pump and the hydraulic actuator. It mediates the flow rate mismatch by providing a controllable restriction that matches the meter-in flow rate to the slow operation speed, while allowing the pump to maintain minimum delivery flow rate for fuel efficiency.
2Loss of energy
If the engine speed is decreased to reduce pump delivery flow rate, then fuel consumption decreases, but the flow rate to all hydraulic actuators decreases uniformly, degrading operability when multiple actuators act simultaneously
Solution Approach 1:
The invention applies local quality control by providing individual flow control for each hydraulic actuator through separate flow control valves. This allows the pump to maintain minimum delivery flow rate for fuel efficiency while each actuator receives the appropriate flow rate independently, ensuring consistent operability whether one or multiple actuators are operating simultaneously.
3Measurement precision
If the operation lever is moved slowly for fine operation, then precision control is achieved, but the thrust force increases slowly and fails to overcome static friction promptly, causing delayed and inconsistent actuator response
Solution Approach 1:
The flow control valve is pre-adjusted to provide the optimal restriction that enables the meter-in flow rate to increase at the appropriate rate during slow lever operation. This preliminary setup ensures that when the lever is moved slowly for fine operation, the hydraulic pressure builds up at the correct rate to overcome static friction consistently, producing reliable and repeatable actuator response without delay.
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 enhances the operability of hydraulic actuators during fine operations by ensuring timely and consistent activation, reducing dispersion in start timing and speed rise, thereby improving overall performance.
Implementation Method 1
a pump is driven by an engine and hydraulic operating fluid delivered from the pump is supplied to a hydraulic actuator
Implementation Method 2
a directional control valve is interposed between the pump and the hydraulic actuator and adjusts the direction and the flow rate of hydraulic fluid that is to flow into the hydraulic actuator
Implementation Method 3
The pump is a variable displacement pump whose capacity is controllable and can adjust the flow rate of the hydraulic fluid that flows into the directional control valve
Implementation Method 4
it is further necessary for the thrust force to exceed the friction force of a sliding portion of the cylinder. In general, the friction force of the sliding portion is in the maximum in a standstill state (static friction)
Data Source
AI summary
The object of the invention of the present application resides in provision of a work machine that can be improved in operability at start of an action of a hydraulic actuator in a fine operation in which an operation lever is operated by a small amount. To this end, on the basis of a signal from a first timing sensor and a signal from a second timing sensor, a machine body controller controls, before the first timing is sensed, the pump delivery flow rate to a minimum delivery flow rate, controls, after the first timing is sensed but before the second timing is sensed, the pump delivery flow rate to a predetermined delivery flow rate that is greater than the minimum delivery flow rate, and controls, after the second timing is sensed, the pump delivery flow rate to a delivery flow rate according to an operation amount of the operation lever.