Countershaft Brake Using Adjustable Flow Restrictor
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Solution Overview
Problem
Heavy-duty vehicles with non-synchronous manual transmissions require skilled operators to avoid gear clashes, and existing countershaft brakes are expensive and prone to wear.
Innovation Solution
A transmission with a countershaft brake system that includes a positive displacement pump driven by the countershaft and an adjustable flow restrictor to increase resistance, allowing for controlled retardation of the countershaft rotation without complex mechanical systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If clutch and countershaft brakes are employed to facilitate gear shifting, then gear shifting speed is improved, but device complexity and cost increase
Solution Approach 1:
The oil pump is designed to serve dual functions: its primary function of lubricating transmission components is maintained, while its secondary function as a braking device is achieved by utilizing the pump chamber as a braking chamber and the outlet passage as a braking passage. This eliminates the need for separate brake mechanisms, reducing device complexity while maintaining gear shifting speed improvement
Solution Approach 2:
The system uses the existing oil pump structure and oil circulation system to provide braking functionality. The oil pump chamber and outlet passage, which already exist for lubrication purposes, are repurposed to create braking effect through flow restriction, allowing the system to serve itself rather than requiring additional dedicated brake components
2Productivity
If traditional countershaft brakes are used to slow countershaft rotation, then gear shifting is facilitated, but wear resistance deteriorates
Solution Approach 1:
The invention replaces traditional mechanical friction brake systems with a hydraulic braking mechanism. Instead of using friction pads and discs that are prone to wear, the system uses oil flow restriction through the pump outlet passage to create braking effect, substituting mechanical friction with hydraulic resistance that does not cause wear
Solution Approach 2:
The braking function is achieved through hydraulic means by restricting oil flow through the pump outlet passage. The resistance to oil flow creates a braking torque on the countershaft without direct mechanical contact, eliminating the wear issues associated with traditional friction-based brake systems
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 provides an inexpensive and low-wear countershaft brake system that facilitates quick gear shifting by increasing torque and resistance, reducing wear and operational complexity.
Implementation Method 1
a positive displacement pump driven by the countershaft to pump liquid out of an outlet opening of the oil pump
Implementation Method 2
increasing resistance to driving of the pump by increasing a restriction to flow in a restriction at or downstream of the outlet opening
Data Source
AI summary
A transmission with a countershaft brake includes a countershaft, a positive displacement pump including a pump housing having a chamber with an inlet and an outlet, the pump being driven by the countershaft, and a flow restrictor disposed at or downstream of the chamber outlet, the flow restrictor being adjustable to increase and decrease an amount of flow restriction from, the outlet of the chamber. Torque needed to drive the pump increases with an increasing flow restriction by the flow restrictor. A method for braking a countershaft in a transmission is also provided.