Embodiments of the invention relate generally to a digital display type gauge for numerically displaying rapidly changing values, and more particularly to a vehicle digital display type gauge for numerically displaying changing engine rotation speed or vehicle speed.
Various types of digital display type vehicle gauges for numerically displaying values are known, including digital displays representing automotive performance elements such as, for example, engine revolutions, oil temperature, fuel pressure, and voltage. One of the major disadvantages of digital displays, such as LED (light-emitting diode) and LCD (liquid crystal display) displays, is the poor readability of their least significant digits during rapid changes in the displayed value. In other words, the digits being shown may change so quickly, e.g., more than four changes per second, that the operator cannot accurately comprehend the digits being displayed. This problem is especially prominent in tachometers and speedometers during moments of great acceleration. To make matters worse, a vehicle driver may be subject to multiple digital images from different gauges.
In some instances, manufacturers have chosen to retard the rate of impulse current reporting the particular value, e.g., engine rotation or vehicle speed, in order to control the rate of digital display fluctuations or changes. Such measures, however, contravene the ultimate purpose of the gauge: timely reporting of vehicular performance and/or operations.
In the following description, reference is made to the accompanying drawings, which form a part hereof. The description is provided to set forth a best mode of the embodiments of the invention and to enable those of ordinary skill in the art to make and use them. The following disclosure provides non-limiting embodiments of particular aspects of the invention, which are described with reference to an automobile. Structural, logical, procedural changes and the like may be made to the specific embodiments without departing from the spirit and scope of the invention.
The BCD signals are then latched by latch circuits 2, 3 and 4 at a predetermined timing respectively and converted into decimal character signals by decoder/driver circuits 5, 6 and 7 which character signals in turn are applied to a digital display device 8 having display sections 8a, 8b and 8c for the 1000's, 100's and 10's digits, each comprising seven segments to numerically display the rotation speed of the engine. A display section 8d for the 1's digit is constructed to display always “zero” and is driven together with a display section 8e for “RPM” by closing an ignition switch 9.
Even slight variations of the engine rotation speed in driving an automobile would cause the 10s digit display section (8a) to vary unsteadily and frequently. Thus, especially during times of intense acceleration, the driver would not be able to determine the value of the 10's digit (8a). Accordingly, the present invention implements a process by which a tachometer, speedometer, or other type of vehicle gauge maintains the respective rate of display of one or more digits according to predetermined thresholds or ranges (i.e., minimum and maximum acceptable rate of changes). These parameters may establish the same or different thresholds or ranges for the display rates of respective digital numeric position.
For example, if the rate of change increases for the tens digit, then the numerical display of that digit may be ceased or locked on its current value or a preset value until the rate of change falls within an acceptable range. Conversely, should the tachometer be showing only the thousands and hundreds digits and the rate of revolutions begins to decrease, the tens digit would become visible or “unlocked” as the input pulse reports a rate of change within the predetermined acceptable ranges for the respective digits. The same approach may be respectively applied to any digital position in the readout, such as, for example the tenths, ones, tens, hundreds, or even thousands digits, etc. The range of acceptable rates of change may vary in accordance with the particular numerical placement.
Because of the prevalent use of software for automobile display systems, the algorithm can be implemented via numerous software code implementations well known in the art. However, for illustrative purposes, a non-limiting example of a possible processing circuit for a hardware implementation is provided below.
The processing circuit 80 is thus adapted to detect a difference between the actual value of the engine revolution speed and the displayed value. More particularly, in this example, when either the first AND gate 87 or the second AND gate 89 emits an output, the OR gate 90 is adapted to indicate the difference signal 104 as “1”. The difference signal can be used to indicate that a particular digit should be “frozen” at the displayed value, “blacked out” or “set” to a predetermined value (e.g. 0) in order to minimize distractions that would otherwise result from the rapid changing of that particular digit. For instance, if sudden acceleration causes the engine revolution speed to increase by greater than 10 rpm over the period of ¼ second, then the processing circuit 80 would output a signal “1” indicating that the tens digit should be frozen, blacked out, or set.
Those skilled in the art will appreciate that the above non-limiting example is merely one possible hardware implementation for halting (e.g., freezing, blacking out, or setting to zero) a particular digit of a digital-type display; and appreciate that processing can be implemented in software or other hardware configurations known in the art. Such “halting” may also be performed for more than one digit, e.g., the tens and hundreds digits.
In the above example, the output of the processing circuit 80 indicates whether the tens digit of the display will change in a span of less than ¼ second, which may be the shortest duration required for an average person to comprehend a newly displayed value. This required duration may vary in accordance with a particular individual or desired setting. Therefore, this embodiment may implement a design by which an individual variably sets the rate of change that triggers the halting of a particular digit; and by which the variably set rate of change may be different for respective digits. However, the rate of change may be permanently or otherwise preset into the device; and may be the same for all digits. Those skilled in the art will appreciate that such features can be easily added to a particular software or hardware implementation.
The variable setting of the display rate may be input to the controller from the user control module 26, which may in turn process this user setting information to accordingly control the display 32. The control module 26 may include or employ a combination of hardware and software, e.g., employ software to control the display 32 in accord with the signal output by the processor 80. As noted, however, a full software implementation or full hardware implementation could be easily created by those skilled in the art.
In step 440, the rate of change in speed, as determined based on the difference between the actual and displayed speeds, is calculated for the least significant digit. For instance, if the driver has set the device such that the tens digit is the least significant digit (i.e., if the ones digit is never changed) and such that it cannot be changed at a rate greater than ¼ second, then the device may determine, every ¼ second, whether the difference between the actual and displayed speeds is greater than 10. If that is the case, then the rate is exceeded.
If the rate of change is not exceeded, then the least significant digit is renewed and process ended at step 440A. However, if the rate of change is exceeded, then the process proceeds to step 450 where the least significant digit is halted; and where the it is determined whether the rate of change is exceeded for the second least significant digit. For instance, if the driver has set the device such that the hundred digit also cannot be changed at a rate greater than ¼ second, then the device may determine, every ¼ second, whether the difference between the actual and displayed speeds is greater than 100. If the rate is not exceeded, then the second least significant digit is renewed and the process is halted at step 450A. If that is the case, i.e., the rate is exceeded, then the second least significant digit is halted and the process is continued for the remaining positions at step 460.
While the embodiments have been described in detail in connection with preferred embodiments known at the time, it should be readily understood that the invention is not limited to the disclosed embodiments. Rather, the embodiments can be modified to incorporate any number of variations, alterations, substitutions, or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. For example, while the embodiments are described in connection with a tachometer, they can be practiced with any other type of vehicle gauge, such as a speedometer.
Number | Date | Country | |
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60881181 | Jan 2007 | US |