Engine Speed Display Device with Variable Detection Time
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Solution Overview
Problem
Conventional engine rotational speed display devices experience delays and inaccuracies, particularly when engine speed varies sharply, leading to a sense of incongruity for the driver, as they fail to immediately display '0' when the engine stops or starts improperly.
Innovation Solution
An engine rotational speed display device that includes a rotational speed sensor, an engine rotational speed calculating means, and a display means, where the calculating means determines the engine speed as '0' if no crankshaft rotational speed pulse is detected within a predetermined time, and adjusts this time based on the presence of a tooth lacking region in the crank pulse rotor, ensuring immediate display of '0' when the engine stops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the determination time for calculating moving average is lengthened to standardize variation at low rotational speed, then measurement precision is improved, but response speed deteriorates when engine stops
Solution Approach 1:
The patent applies dynamics by making the determination time variable rather than fixed. The control unit dynamically adjusts the determination time based on the detected rotational speed: using a first (longer) determination time at low rotational speeds to reduce variation, and a second (shorter) determination time at high rotational speeds to improve response. This dynamic adjustment resolves the contradiction between measurement precision and response speed.
Solution Approach 2:
The patent changes the parameter of determination time based on rotational speed conditions. By switching between different determination time values (first determination time for low speed, second determination time for high speed), the system optimizes both measurement precision and response time for different operating conditions, eliminating the sense of incongruity during engine stoppage.
2Stability of the object's composition
If the moving average calculation is used to smooth rotational speed display, then stability is improved, but the display fails to immediately reflect sharp variations when engine stops
Solution Approach 1:
The system dynamically adjusts the determination time based on rotational speed. When the engine stops or slows down, the control unit switches to the first determination time that allows for immediate detection of the stop condition, overriding the smoothing effect of moving average calculation. This ensures the display accurately reflects the engine stop state without delay, resolving the contradiction between stability and reliability.
3Speed
If the rotational speed sensor detection value is directly displayed, then response speed is improved, but variation in accuracy at low rotational speed affects display quality
Solution Approach 1:
The patent changes the determination time parameter based on rotational speed range. At low rotational speeds where sensor accuracy varies, the system uses a longer first determination time to average out variations and standardize the display. At higher speeds, it switches to a shorter second determination time for faster response. This parameter change strategy resolves the contradiction between response speed and low-speed display accuracy.
Data Source
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AI summary
To enable an engine rotational speed display device to display an engine rotational speed without causing a sense of incongruity by following changes in the engine rotational speed at times of sharp variations. An engine rotational speed display device includes: a rotational speed sensor (2) for detecting a crankshaft rotational speed pulse according to rotation of a crank pulse rotor (1) provided to a crankshaft of an engine; an engine rotational speed calculating means (7) for calculating an engine rotational speed by a moving average of a detected value of the crankshaft rotational speed pulse; and a display means (5) for displaying the engine rotational speed on a meter by electrical processing. When the crankshaft rotational speed pulse is not detected in a detection time equal to or more than a predetermined value, the engine rotational speed calculating means (7) determines that the engine rotational speed is "0" without calculating the engine rotational speed by the moving average, and the engine rotational speed of "0" is displayed on the meter.