HMT Shuttle Control via Clutch and Motor Coordination
Solution Overview
Problem
Work vehicles equipped with HMT or EMT transmissions lack the braking performance when switching between forward and rearward movement, as they do not have a torque converter to absorb braking forces, leading to inefficient deceleration and increased engine load.
Innovation Solution
A control system that includes a clutch controlling unit and a motor controlling unit to manage clutch pressure and motor torque, allowing for equivalent braking performance by disengaging and re-engaging clutches based on vehicle speed and operator input, reducing relative rotational speed and clutch pressure to prevent over-rotation and vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If HMT or EMT transmission is used to replace torque converter type transmission, then power transmission efficiency is improved and continuously variable speed change is enabled, but braking performance during shuttle operation deteriorates because there is no torque converter to absorb braking force
Solution Approach 1:
The control unit acts as an intermediary that manages the transition between forward and reverse movement by controlling clutch engagement timing. It detects vehicle speed and determines optimal clutch disengagement timing to enable the engine to absorb braking force during shuttle operations, thereby resolving the braking performance deficiency of HMT/EMT transmissions while maintaining their efficiency advantages
Solution Approach 2:
The system implements feedback control by detecting vehicle speed and using this information to determine clutch control timing. The control unit continuously monitors vehicle speed and adjusts clutch engagement/disengagement timing accordingly, allowing the engine to effectively absorb braking force during direction changes while maintaining efficient power transmission during normal operation
2Speed
If clutch is disengaged quickly during direction switching to enable rapid response, then operational responsiveness is improved, but engine load increases and clutch abrasion worsens due to lack of torque converter cushioning
Solution Approach 1:
The control unit performs preliminary action by detecting vehicle speed in advance and determining the optimal timing for clutch disengagement. This advance preparation allows the system to execute clutch control at the precise moment needed for effective braking force absorption, achieving rapid response while protecting the engine and clutch from excessive loads
Solution Approach 2:
The system dynamically adjusts clutch control timing based on real-time vehicle speed conditions. Rather than using fixed timing, the control unit adapts clutch disengagement timing to the current operating state, enabling rapid response when conditions permit while preventing excessive engine load and clutch wear under adverse conditions
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 system effectively prevents over-rotation, reduces engine load, and alleviates clutch abrasion by managing clutch pressure and motor torque, enabling smooth transitions between forward and rearward movements.
Implementation Method 1
a gear mechanism that has a planetary gear mechanism and transmits a rotation of an input shaft to an output shaft
Implementation Method 2
configured to change a rotational speed ratio of the output shaft to the input shaft by changing a rotational speed of the motor
Implementation Method 3
a first clutch that connects with the gear mechanism to drive the travelling apparatus in one of a forward moving direction and a rearward moving direction
Data Source
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AI summary
A work vehicle and a method of controlling the work vehicle are provided, whereby a braking performance equivalent to that of a conventional torque converter type work vehicle can be exerted when an operator switches between forward movement and rearward movement in a power transmission of an HMT or EMT type. A control unit embedded in the work vehicle includes a clutch controlling unit and a motor controlling unit. The clutch controlling unit is configured to disengage a first clutch in a condition that the first clutch is engaged and a second clutch is disengaged, when a first moving direction inputted through an FR operating device as an instruction of the operator and a second moving direction determined based on a vehicle speed detected by a vehicle speed detecting unit are different from each other, and in addition, when and the vehicle speed falls in a preliminarily set first range. The motor controlling unit is configured to control a motor so as to reduce a relative rotational speed of the second clutch after the first clutch is disengaged.