Hydraulic Cylinder Drive Control to Prevent Stroke-End Impact
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Solution Overview
Problem
Conventional hydraulic cylinder driving apparatuses in working machines, such as hydraulic excavators, face challenges in preventing impact at the stroke end and reducing energy loss, as existing control systems are unable to completely eliminate impact and result in significant energy loss due to fluid resistance during cushioning.
Innovation Solution
A hydraulic cylinder driving apparatus with a controller that restricts the piston's movement by limiting the pilot pressure, using a drive command restriction unit to stop the piston before the stroke end, thereby preventing impact and reducing energy loss, and includes a restriction release judgment unit to allow intentional piston movement when certain conditions are met.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a cushion projection and cushion chamber with throttle flow-path are used to restrain piston impact, then impact contact between piston and cylinder body is reduced, but large fluid resistance is applied to the piston causing considerable energy loss
Solution Approach 1:
The control device restricts the drive command to the cylinder control valve before the piston reaches the stroke end, preliminarily preventing the piston from entering the cushion chamber. This avoids the large fluid resistance that would occur during cushioning while still preventing impact contact.
Solution Approach 2:
The invention replaces the mechanical cushioning system (cushion projection and cushion chamber with throttle flow-path) with a control-based solution. The control device uses detection of piston position and stroke speed to restrict drive commands, substituting active mechanical cushioning with intelligent control to eliminate both impact and energy loss.
2Object-affected harmful factors
If deceleration means is used to decelerate the piston before stroke end, then impact at stroke end is reduced, but large energy loss occurs in the vicinity of the stroke end regardless of deceleration
Solution Approach 1:
The invention replaces mechanical deceleration means with a control-based deceleration system. The control device detects piston position and stroke speed, then restricts drive commands to achieve smooth deceleration without the energy loss associated with mechanical cushioning mechanisms.
Solution Approach 2:
The control device uses feedback from stroke speed detection means to determine when to restrict the drive command. By continuously monitoring piston stroke speed and position, the system applies deceleration only when necessary (when piston is near stroke end and moving at high speed), optimizing energy efficiency while preventing impact.
3Loss of energy
If the piston is stopped before stroke end by restricting drive command, then impact and energy loss are prevented, but the piston cannot reach the full stroke end position for certain operations
Solution Approach 1:
The control device dynamically adjusts its behavior based on real-time conditions. When high stroke speed is detected near the stroke end, the drive command is restricted to prevent impact. However, when low stroke speed is detected or when the operator intentionally operates the operation member, the restriction is released, allowing the piston to reach the stroke end for operations like parking or dropping adhering materials.
Solution Approach 2:
The system changes the parameter of drive command restriction based on detected stroke speed and piston position. The restriction level is dynamically adjusted: full restriction when high speed is detected near stroke end, partial or no restriction when low speed is detected or when operational requirements demand full stroke travel.
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
Effectively prevents piston impact at the stroke end and reduces energy loss, improving the efficiency of hydraulic cylinder operations while allowing controlled piston movement for specific operations like parking or dropping adhering materials.
Implementation Method 1
a hydraulic pump that discharges hydraulic fluid to be supplied to the cylinder chamber of the hydraulic cylinder
Implementation Method 2
a cylinder control valve interposed between the hydraulic pump and the hydraulic cylinder and configured to be opened by input of a cylinder drive command to the cylinder control valve to change a direction and a flow rate of the hydraulic fluid supplied from the hydraulic pump to the hydraulic cylinder
Data Source
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AI summary
Provided is a driving apparatus capable of effectively preventing impact at the stroke end in the hydraulic cylinder. The driving apparatus includes a hydraulic pump (31,32), a cylinder control valve (37,38), an operation member (47a), a drive command input unit (34, 47b) inputting a cylinder drive command corresponding to a cylinder operation applied to the operation member (47a) to the cylinder control valve (37,38), a cylinder stroke detection unit (50,70), a cylinder drive command restriction unit (42A,42B, 50) restricting the cylinder drive command in response to the cylinder stroke to stop a piston (27p) of a hydraulic cylinder (27) before the stroke end.