Hydrostatic Transmission Braking Torque Control
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Solution Overview
Problem
Existing hydrostatic transmission devices lack ease of control for modulating braking torque and are prone to cavitation due to difficulties in modifying the spring rate, leading to inefficient braking modulation.
Innovation Solution
The device incorporates a displacement selector with restriction means that activate when exhaust pressure exceeds a threshold, controlled by a control pressure in a control chamber, allowing for adjustable fluid flow in the bypass connection, and regulates supply pressure to an equilibrium pressure proportional to the control pressure, independent of fluid flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a spring-based pressure reducer is used to restrict the bypass connection, then the downstream pressure can be balanced, but the braking torque cannot be modulated and the spring rate is difficult to modify
Solution Approach 1:
The invention changes the control parameter from spring rate to control pressure. By using a pressure regulator to control the pressure in the control chamber, the braking torque can be easily modulated without modifying mechanical spring characteristics. The force balance equation F_spring = k*x becomes F_control = P_control * A, where P_control can be independently adjusted via a pressure regulator, enabling easy modulation of braking torque.
Solution Approach 2:
The invention replaces the mechanical spring-based pressure reduction system with a pressure-controlled restriction means. Instead of using a spring's mechanical properties to balance pressure, the system uses a control chamber with adjustable control pressure acting on a piston or diaphragm, substituting mechanical spring adjustment with hydraulic/pneumatic pressure control for easier modulation.
2Ease of operation
If the spring rate is too low to allow braking modulation, then the downstream pressure balance is achieved, but cavitation occurs due to excessive pressure loss
Solution Approach 1:
The invention introduces a feedback mechanism where the control pressure is regulated to maintain proper pressure balance. The pressure regulator adjusts the control pressure based on system conditions to ensure the restriction means provide appropriate restriction without causing excessive pressure loss that would lead to cavitation. This feedback control ensures both braking modulation capability and cavitation prevention.
Solution Approach 2:
The invention introduces a control chamber and pressure regulator as intermediary elements between the supply and exhaust enclosures. This intermediary system allows precise control of the restriction means, enabling the system to achieve both braking modulation and prevent cavitation by maintaining appropriate pressure levels through the control pressure.
3Power
If the bypass connection is restricted during braking, then braking torque is generated, but the control mechanism is complex and difficult to activate
Solution Approach 1:
The invention enables the system to self-regulate the bypass restriction based on operating conditions. The restriction means are automatically activated or deactivated based on the control pressure, which can be linked to system pressure conditions. During braking, the pressure differential automatically triggers the restriction, eliminating the need for complex external activation mechanisms.
Solution Approach 2:
The control chamber serves multiple functions: it acts as both the activation mechanism for the restriction means and the control element for braking torque modulation. The same control pressure that activates the restriction also modulates the braking torque magnitude, combining activation and control functions in a single mechanism.
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 enables easy control of braking torque, avoiding cavitation and ensuring consistent braking performance by leveraging pressure increases during braking, and allows for independent regulation of braking torque from fluid flow, enhancing the device's control and efficiency.
Implementation Method 1
when the selector is in the bypass position, the restriction means are able to be activated to restrict the flow of fluid in the bypass connection when an exhaust pressure prevailing in the enclosure exhaust exceeds a restriction threshold, said threshold being a function of a control pressure prevailing in a control chamber
Implementation Method 2
when they are activated, said restriction means are capable of regulating the supply pressure of the first motor to an equilibrium pressure depending on the control pressure, and more particularly at an equilibrium pressure substantially proportional to the control pressure
Implementation Method 3
when the restriction means are activated, if the motor is driven in rotation, it exerts a braking torque
Data Source
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AI summary
The invention relates to a hydrostatic transmission device (10) including an elementary motor (22A) having supply (22A) and exhaust chambers (22B); a displacement selector capable of adopting a bypass position, in which the supply and exhaust chambers are connected via a bypass link (62); and a means (70, 72) for restricting said bypass link. When the selector is in the bypass position, the restriction means can be activated to restrict fluid circulation in the bypass link when the exhaust pressure in the exhaust chamber exceeds a restriction threshold, said threshold depending on a current control pressure in a control chamber (58). On account of said arrangement, the elementary motor can generate braking torque via the bypass link, and said torque can be controlled easily using the pressure in the control chamber.