Hydrostatic Transmission Clutch Calibration via Control Device
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Solution Overview
Problem
Existing traction drive systems with hydrostatic transmissions face challenges in efficiently calibrating the clutch's grinding point, requiring complex and costly procedures on a roller test stand, which are impractical for real-world applications due to wear and tear, leading to reduced switching comfort over time.
Innovation Solution
A transmission combination with a control device that calibrates the clutch's grinding point based on the response of the hydraulic pump's expulsion volume, pressure medium volume flow, and rotational speed of hydraulic motors, allowing for on-site calibration without the need for complex pressure load detection, and incorporating a closed-loop control system for precise adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the clutch is closed quickly by supplying pressure medium to the hydraulic cylinder, then the clutch engagement speed is improved, but the piston movement becomes too rapid and causes discomfort
Solution Approach 1:
The clutch closing process is divided into two distinct phases: a first phase for rapid piston movement to reach the grinding point, and a second phase for gentle torque transmission. This segmentation allows each phase to be optimized independently - the first phase prioritizes speed while the second phase prioritizes comfort.
Solution Approach 2:
The nozzle cross-sectional area is varied dynamically during the clutch closing process. The switching valve changes the nozzle area from a larger value in the first phase (enabling rapid piston movement) to a smaller value in the second phase (providing gentle torque increase). This dynamic adaptation resolves the contradiction between speed and comfort.
2Ease of operation
If the clutch closing process is controlled gently to ensure comfort, then the switching comfort is improved, but the clutch engagement speed decreases
Solution Approach 1:
The clutch closing process is divided into two distinct phases: a first phase for rapid piston movement to reach the grinding point, and a second phase for gentle torque transmission. This segmentation allows each phase to be optimized independently - the first phase prioritizes speed while the second phase prioritizes comfort.
Solution Approach 2:
The nozzle cross-sectional area is varied dynamically during the clutch closing process. The switching valve changes the nozzle area from a larger value in the first phase (enabling rapid piston movement) to a smaller value in the second phase (providing gentle torque increase). This dynamic adaptation resolves the contradiction between speed and comfort.
3Measurement precision
If calibration is performed on a roller test stand before delivery, then the initial grinding point accuracy is improved, but the complexity and cost of calibration increases
Solution Approach 1:
The clutch calibration is performed autonomously by the control device using the hydraulic circuit already present in the traction drive. The control device supplies pressure medium to the hydraulic cylinder and detects the actual grinding point automatically, eliminating the need for external roller test stand equipment and manual calibration procedures.
Solution Approach 2:
The mechanical calibration process on a roller test stand is replaced by an automated control system that uses the existing hydraulic circuit. The control device electronically controls the switching valve and monitors the clutch closing process, substituting complex mechanical calibration equipment with a simpler electronic control approach.
4Measurement precision
If recalibration is performed frequently to maintain accuracy, then the grinding point precision is improved, but the time and resource expenditure increases
Solution Approach 1:
The clutch calibration is performed autonomously by the control device using the hydraulic circuit already present in the traction drive. The control device supplies pressure medium to the hydraulic cylinder and detects the actual grinding point automatically, eliminating the need for external roller test stand equipment and manual calibration procedures.
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 efficient and precise calibration of the clutch's grinding point in real-time, maintaining shifting comfort despite mechanical wear, by using the control device to adjust the expulsion volume and rotational speed, allowing for field-based calibration rather than relying on a roller test stand.
Implementation Method 1
The clutch is activated, for example, by means of a hydraulic cylinder. Depending on the design, the closing of the clutch is brought about here either by the application of pressure medium to the hydraulic cylinder or by the discharging of pressure medium from the hydraulic cylinder.
Implementation Method 2
a hydraulic pump with an adjustable expulsion volume and with at least one hydraulic motor which can be supplied with pressure medium by the hydraulic pump
Data Source
AI summary
A transmission combination includes a hydrostatic transmission and a mechanical transmission having a clutch and a control device for calibrating a grinding point of the clutch. A traction drive includes the transmission combination. A method includes calibrating the clutch.