Utility Vehicle Engine Brake Control at Low Engine Speed
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Solution Overview
Problem
Utility vehicles face challenges in maintaining engine brake functionality when traveling downhill, as the clutch disconnects power transmission at low engine rotational speeds, leading to increased vehicle speed and increased load on the brake device.
Innovation Solution
Incorporating a controller with engine brake necessity determination circuitry and rotational speed control circuitry that automatically increases engine rotational speed to or above the engage rotational speed when necessary, allowing the engine brake to operate by connecting the clutch, thereby eliminating the need for manual driver intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the clutch disconnects power transmission when engine rotational speed is low, then the engine can operate independently without driving the wheels, but the engine brake cannot operate when traveling downhill causing vehicle speed to increase
Solution Approach 1:
The control unit continuously monitors engine rotational speed and vehicle operating conditions, and automatically adjusts the clutch engagement state to maintain engine brake functionality when needed. The system provides feedback control by comparing actual engine speed with target speed and adjusting clutch slip ratio accordingly.
Solution Approach 2:
The clutch is operated in a dynamic manner with variable engagement states rather than simple on/off control. The control unit adjusts the clutch slip ratio continuously based on operating conditions, allowing the clutch to transmit varying amounts of torque while maintaining engine brake effectiveness at low engine speeds.
2Reliability
If the driver manually operates the accelerator to maintain engine rotational speed above engage rotational speed, then the engine brake can operate, but the ease of operation deteriorates due to requiring constant manual intervention
Solution Approach 1:
The control unit automatically manages engine rotational speed by controlling the clutch engagement state, eliminating the need for driver intervention. The system monitors its own operating conditions and self-adjusts the clutch slip ratio to maintain engine brake functionality, making the vehicle operate itself without constant driver input.
3Reliability
If the clutch remains engaged to maintain engine brake, then engine brake functionality is preserved, but the ability to disconnect power transmission when engine speed is low is lost
Solution Approach 1:
The clutch operates in dynamic engagement states with variable slip ratios rather than fixed engaged or disengaged positions. This allows the clutch to maintain partial power transmission sufficient for engine brake functionality while still providing the capability to fully disconnect when needed, achieving both objectives simultaneously through continuous adjustment.
Data Source
AI summary
A utility vehicle includes: an engine; a drive wheel; a power transmission path between the engine and the drive wheel; a clutch that is provided in the power transmission path and configured to disconnect power transmission when an engine rotational speed is lower than an engage rotational speed; an engine rotational speed sensor configured to sense the engine rotational speed; and a controller configured to control an operation of the engine, the controller including an engine brake necessity determination circuitry configured to determine necessity of engine braking, and an engine rotational speed control circuitry configured to control the engine rotational speed, and when the engine brake necessity determination circuitry determines that engine braking is necessary, the engine rotational speed control circuitry is configured to perform automatic engine brake control that increases the engine rotational speed so as to be equal to or higher than the engage rotational speed.