Vehicle Control Apparatus Downhill Shift Inhibition
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Solution Overview
Problem
Engine stalls can occur when switching between forward and reverse drive ranges on a downhill road, reducing brake booster assistance and impairing operational convenience due to increased vehicle inertia and torque input.
Innovation Solution
A vehicle control apparatus that rejects switching requests to the opposite-direction drive range during downhill driving, maintaining the current drive range or switching to neutral/parking range to prevent engine stalls, while informing the operator of potential engine stalling and allowing switching after stopping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the given value for inhibiting shift range switching is reduced to prevent engine stall on downhill road, then engine stall is prevented, but operational convenience is impaired due to more limitation on shift range switching even on flat road
Solution Approach 1:
The control apparatus applies different speed threshold values for different road conditions: a first given value for flat roads and a second given value (lower than the first) for downhill roads. This localized adjustment of the threshold parameter prevents engine stalls on downhill roads while maintaining operational convenience on flat roads, as the system adapts the inhibition criterion to the specific running condition.
2Ease of operation
If shift range switching is allowed during running on downhill road, then operational convenience is maintained, but engine stall occurs due to larger inertia and torque input
Solution Approach 1:
The control apparatus preemptively inhibits shift range switching when it detects that the vehicle is running on a downhill road at a speed not lower than the second given value. By applying the inhibition before engine stall can occur, the system prevents the harmful effect of engine stall while maintaining brake booster assistance, thus prioritizing reliability over operational convenience in this specific condition.
3Ease of operation
If engine stop is allowed during downhill running, then vehicle can be stopped easily, but brake booster assistance is reduced due to reduced vacuum pressure
Solution Approach 1:
The control apparatus performs preliminary action by inhibiting shift range switching before engine stall occurs. This preventive measure ensures that the engine continues running and maintaining vacuum pressure, thereby preserving brake booster assistance. The system proactively prevents the condition that would lead to loss of brake assistance, rather than reacting after engine stop has occurred.
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
Prevents engine stalls and ensures easy vehicle stopping by maintaining drive range or switching to neutral/parking range during downhill driving, thus maintaining brake booster assistance and operational convenience.
Implementation Method 1
The occurrence of the engine stall causes a vacuum pressure in an intake of the engine to be reduced, and accordingly reduces a force which is generated by a brake booster using the vacuum pressure
Implementation Method 2
when the switching between the forward drive range and the reverse drive range is made on a downhill road, a larger inertia of the vehicle is generated, as compared with on a flat road, so that a larger torque inputted to the engine is generated on the downhill road
Data Source
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AI summary
A control apparatus (60) for a vehicle (10) provided with (a) an automatic transmission (12) and (b) a shifting device (58) including (b-1) a shift actuator (76) and (b-2) a shift lever (74). The shift actuator (76) establishes one of shift ranges (D, N, R, P) in the transmission (12) such that the established one of the shift ranges (D, N, R, P) corresponds to a selected one of shift-lever operating positions in which the shift lever (74). When a switching request is made to request the transmission (12) to be switched to an opposite-direction drive range (D, R) that is for driving the vehicle (10) in a direction opposite to a current running direction of the vehicle (10), during running of the vehicle (10) with a running speed (V) being not lower than a given value (Va), the control apparatus (60) rejects the switching request. The control apparatus (60) rejects the switching request, also during running of the vehicle (10) with the running speed (V) being lower than the given value (Va), if the vehicle (10) is running on a downhill road.