Shift Control Logic for Preventing Unintended Vehicle Start
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Solution Overview
Problem
Electrically driven vehicles can inadvertently start in unintended modes due to self-resetting shifters being operated by obstacles, leading to safety concerns and the need for additional components or wire harnesses to prevent this.
Innovation Solution
A control apparatus with system activation detecting means, shift abnormality detecting means, and traveling mode transfer inhibiting means that prevents the vehicle from transferring to unintended modes by detecting the activation state and shift position without additional components or wire harnesses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a self-resetting shifter is used to enable momentary shift operation, then ease of operation is improved, but reliability deteriorates due to unintended shift operations caused by obstacles
Solution Approach 1:
The control unit preemptively prevents unintended shift operations by detecting shift abnormality (when the shifter is held away from reference position) and inhibiting the activation switch function. This counter-action occurs before the vehicle can inadvertently start, neutralizing the reliability problem while preserving the ease of operation benefit
Solution Approach 2:
The system continuously monitors the shifter position and provides feedback to the control unit. When the shifter is detected at a position other than the reference position during activation switch operation, the control unit receives this feedback and responds by preventing the traveling drive system from activating, thus resolving the reliability issue
2Reliability
If a shift allowance switch is added to prevent unintended shift operations, then reliability is improved, but device complexity increases
Solution Approach 1:
The control unit is given multiple functions: it controls the traveling drive system activation, monitors shifter position, detects shift abnormality, and prevents unintended activation. By making the control unit universal and multi-functional, the patent avoids adding a separate shift allowance switch, thus improving reliability without increasing device complexity
Solution Approach 2:
The patent merges the shift abnormality detection function and the activation control function into a single control unit. Instead of having separate components for detecting shifter position and controlling vehicle activation, these functions are combined, simplifying the overall system while preventing unintended vehicle start
3Reliability
If the vehicle is prevented from activating when shifter abnormality is detected, then safety is improved, but productivity deteriorates due to delayed vehicle start
Solution Approach 1:
The system dynamically adjusts its behavior based on real-time shifter position. When the shifter is at the reference position, normal activation proceeds quickly. When the shifter is abnormal, the system dynamically prevents activation only during the abnormal state. Once the shifter returns to the reference position, activation is immediately permitted again, making the system responsive and minimizing any delay in vehicle start
Data Source
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AI summary
When a traveling drive system is activated at a time t2 in response to a turning of an ignition switch to an ON state at a time t1, a request of P/N (a park lock release inhibit) from an electrically operated motor controller vanishes. Therefore, originally, according to an execution of a park lock release, the vehicle is started in response to a holding of a D position of a shifter. However, in a case where a park lock release inhibit state occurs at a time immediately before a time t2 and the shifter is at the D position at time t2, a present shift inhibit flag takes over the park lock inhibit state at the time immediately before t2 until a time t3 at which the shifter returns to a home (H) position so that the above-described start of the vehicle is prevented. Since, after time t3, the present shift inhibit flag is in a park lock release allowance state, the shifter is operated to the D position at a time t4 and the park lock release is carried out so that the vehicle is travelable. In this way, without addition of another component, the vehicle is, at a low cost, not started even though a re-activation of the traveling drive system, when the shifter is shifted to the position other than the reference position occurs.