Hydraulic Stepless Transmission Neutral Control via Dynamic Orifice Sealing
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Solution Overview
Problem
Hydraulic oil leakage through an orifice in existing traveling hydraulic stepless transmissions leads to reduced transmission efficiency under high load conditions, affecting vehicle performance and stopping reliability.
Innovation Solution
A traveling hydraulic stepless transmission design that includes a first and second valve mechanism to control oil passage connections to a tank based on pressure and discharge rate, featuring a sealing system to prevent oil leakage and an internal damping system with pistons and a plate to manage oil flow and stop the vehicle effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an orifice is provided in the charge valve unit to expand the neutral region, then the neutral position range is extended, but hydraulic oil leakage occurs under high load conditions causing deterioration of transmission efficiency
Solution Approach 1:
The patent applies dynamics by making the orifice opening state changeable based on operating conditions. The movable plate shifts position according to swash plate angle, dynamically opening or closing the orifice to adapt between neutral region expansion needs and transmission efficiency requirements under different load conditions
Solution Approach 2:
The patent changes the physical state parameter of the orifice (open/closed) based on operating conditions. By varying the swash plate angle, the plate position changes, which in turn changes the orifice opening area from fully open to fully closed, adapting the system behavior to different operational requirements
2Reliability
If hydraulic oil leakage is allowed to expand the neutral position, then stopping reliability is improved, but transmission efficiency deteriorates under high load conditions
Solution Approach 1:
The system dynamically adjusts the orifice opening state based on the swash plate angle. During stopping operations, the orifice remains open to provide leakage that expands the neutral region and improves stopping reliability. During high load driving, the orifice closes to eliminate unnecessary leakage and maintain transmission efficiency
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
The solution enables smooth starting and stopping under both low and high load conditions, reduces oil leakage, and maintains vehicle position by closing orifices during high load conditions, while allowing increased leakage for neutral range expansion under low load conditions, enhancing driving efficiency and feeling.
Implementation Method 1
a hydraulic pump and a hydraulic motor are fluidly connected. Conventionally, in such a hydraulic stepless transmission, it is possible to switch between forward movement and backward movement of a vehicle by changing an angle of a movable swash plate of a variable displacement hydraulic pump
Implementation Method 2
an orifice is provided in a charge valve unit so as to bypass a check valve and a relief valve
Implementation Method 3
a first valve mechanism and a second valve mechanism that enable the first oil passage and the second oil passage to be fluidly connected to the tank
Data Source
AI summary
A traveling hydraulic stepless transmission (“HST”), ensures stopping of a vehicle on a slope under high load conditions, maintains stopping the vehicle on flat ground under low load conditions, and enables smooth starting from a stop. The HST includes a neutral check valve (“NCV”) and an internal damping system (“IDS”). The NCV includes a first orifice that opens a first oil passage to a transaxle case when a pressure in the first oil passage is equal to or less than a predetermined pressure, and that connects the second oil passage to the transaxle case when a pressure in a second oil passage is equal to or less than the predetermined pressure. The IDS includes second orifices that connect a high pressure side of the oil passages to the transaxle case when a discharge rate of the hydraulic pump is equal to or less than a predetermined discharge rate.