JPS5853723B2 - Automotive digital fuel level display device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a digital fuel remaining amount display device that measures the liquid level of a fuel tank mounted on a vehicle such as an automobile and displays the remaining fuel amount in a digital amount. .

Generally, for displaying the remaining fuel level in vehicles such as cars,
A bimetallic or differential coil type meter is used, which is connected to a variable resistance level sensor whose resistance value changes depending on the liquid level in the fuel tank, and which indicates a pointer deflection angle proportional to the resistance value. The amount is displayed as an analog amount.

In recent years, there has been a trend toward the adoption of digital fuel level display devices that use digital display elements to display the remaining fuel level in digital amounts, instead of these hole-in-hole and open-type fuel level display devices. .

However, since the liquid level in a fuel tank mounted on a vehicle such as an automobile can fluctuate greatly due to the vibrations of the vehicle, the liquid level may vary greatly due to the lag characteristic of the remaining fuel level indicator, such as an analog type. Digital types that do not have a fluctuation suppressing function that prevents the display from fluctuating much even if the fuel level fluctuates have the disadvantage that the display of the remaining fuel level fluctuates as the fuel level fluctuates.

The disadvantage of this is that the level sensor that measures the liquid level has a structure that is not easily affected by liquid level fluctuations, but it is possible to integrate the output of the level sensor, but the fluctuations in the liquid level are relatively large, and both of the above methods In particular, the latter method does not process the signal as a series of digital data signals, and is not suitable for signal processing by general-purpose IC circuits or microcomputers. Ultimately, both of the above methods are not optimal as methods for suppressing display fluctuations in a digital fuel remaining amount display system.

Therefore, it is an object of the present invention to provide a novel display device capable of suppressing the above-mentioned display fluctuations by processing digital data signals, and to cope with the above-mentioned problems.

For the above purpose, the present invention emits a digital data signal indicating the remaining amount of fuel at regular timing, compares the digital data signal at the current timing and the previous timing, and based on the comparison result, outputs the digital data signal currently displayed. It is designed to control.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the outline of the digital fuel remaining amount display device according to the present invention. In the figure, 1 is an analog signal that measures the liquid level of a fuel tank (not shown) and indicates the remaining fuel amount. It is a level sensor that emits a signal.

This level sensor 1 is constituted by, for example, a known variable resistance type level sensor whose resistance value changes depending on the liquid level.

Reference numeral 2 denotes an A-D converter that converts the analog signal generated by the level sensor 1 into an n-bit digital data signal, and the level sensor 1 and the A-D converter 2 constitute digital data signal generating means. .

3 is a signal comparator which is means for comparing the digital quantities of the digital data signals; 4 is a timing generator that generates timing pulses for controlling the A-D converter 2 and the signal comparator 3; 5 is the signal comparator 3; The display section is a fuel remaining amount display means, which is composed of, for example, a 7-segment digital display element (not specifically shown) whose display is switched according to a digital data signal issued from the fuel tank.

Incidentally, reference numeral 6 denotes an initialize section that initializes the display on the display section 5 to the engine starting time.

Therefore, first, at the time of starting the engine, receiving the initial set pulse emitted from the initializing section 6,
The signal comparator 3 applies a digital data signal indicating the remaining fuel amount, which is an output signal of the A-D converter 2, to the display section 5 without performing signal comparison, which will be described later. Display the value.

Thereafter, the A-D converter 2 receives a timing pulse from the timing generator 4 and outputs a digital data signal indicating the remaining amount of fuel at regular timings.

On the other hand, the signal comparator 3 executes a signal comparison, which will be described later, according to the timing pulse generated by the timing generator 4, and also applies the signal to the display unit 5 depending on whether the comparison result satisfies the conditions described later. The digital data signal generated by the converter 2 is changed in accordance with the digital data signal generated by the A-D converter 2.

In this way, the display on the display unit 5 is prevented from changing due to changes in the liquid level.
This will be explained along with the specific circuit of the block in the figure.

FIG. 2 is a circuit diagram showing a specific circuit example of the blocks in FIG. 1, in which portions corresponding to the blocks in FIG. 1 are surrounded by dashed-dotted lines and designated by the same reference numerals as in FIG. 1.

As described above, the level sensor 1 includes a variable resistor 11 whose resistance value changes depending on the liquid level, and a resistor 12 that applies a power supply voltage (Vcc) to the variable resistor 11. Generates an analog signal with a voltage value proportional to the amount of fuel remaining.

The output terminal 13 of the level sensor 1 is connected to the input terminal of the AD converter 2.

This A-D converter 2 has a conversion command signal input terminal co
nv is the output terminal Q of the timing generator 4, which will be described later.
4, and converts the analog signal into an n-bit digital data signal every time a timing pulse issued from the output terminal Q4 is input to the input terminal conv as a conversion command signal.

On the other hand, the signal comparator 3 has a latch record 31. It is composed of an up/down counter 32 and a comparison circuit 33.

The latch circuit 31 has a clock terminal T connected to an OR circuit 34.
When the output of the OR circuit 34 is input as a trigger pulse to the clock terminal T, the output signal of the A-D converter 2 applied to the data terminal is read and output from the output terminal. do.

The output signal of this latch circuit 31 is sent to a decoder 51 which will be described later.
and is input to the counter 32.

The load terminal of the counter 32 is connected to the conversion completion signal output terminal 5ta of the A-D converter 2 via the inverter 35.
The down-count input terminal dow and the up-count input terminal up are respectively connected to the output terminal Q1 of the timing generator 4 and the output terminal of the OR circuit 41, and first, the output of the inverter 35 is connected to the load terminal as a preset pulse. , the counter output is preset by the output E of the latch circuit 31.

Thereafter, the counter 32 receives count pulses input to both count input terminals dow and up, performs step countdown and countup, and changes the count output.

The count output of this counter 32 is transmitted to the A-D converter 2.
(This is input to the comparison circuit 33 above.

The comparator circuit 33 is a circuit for detecting coincidence between two circuits, which is configured by an exclusive-or circuit, etc., provided according to the number of bits of the input signal, and its output terminal Q
is connected to one input terminal of the OR circuit 34, and outputs an output to trigger the latch circuit 31 when the outputs of the counter 32 and the AD converter 2 match.

Therefore, the signal comparator 3 compares the magnitude of the digital data signal applied to the decoder 51 and the digital data signal issued from the AD converter 2 indicating the remaining amount of fuel.

The timing generator 4 has a reset terminal R and timing pulse output terminals Q1, Q2, Q3.

Q4, and the reset terminal R is connected to the conversion completion signal output terminal sta of the A-D converter 2, and the output terminal Q1
is connected to the down-count input terminal of the counter 32, output terminals Q2 and Q3 are connected to both input terminals of the OR circuit 41, and output terminal Q4 is connected to the conversion command signal input terminal c onv of the AD converter 2. .

Although the timing generator 4 is not specifically shown, it is composed of an oscillator, a counter, a decoder, etc., and while the conversion completion signal issued from the A-D converter 2 is input to the reset terminal R (A - During the signal conversion operation of the D converter) is reset, and then each output terminal Q
Timing pulses are issued sequentially from 1 to Q4.

The display unit 5 includes a decoder 51 and, for example, a 7-segment digital display element 52 that displays at least two decimal digits.
It is composed of.

The decoder 51 receives the output of the latch circuit 31 of the signal comparator 3 as a BCD input, and generates a code signal for displaying a decimal number.

On the other hand, the digital display element 52 receives the code signal,
Displays a number indicating the amount of fuel remaining.

Note that the minimum increment of the remaining fuel amount displayed on the display section 5 is the amount (liter) obtained by dividing the capacity of the fuel tank by the maximum value of the digital data signal, and is not necessarily in increments of 1 liter.

The initialization section 6 includes a key switch 61 and a resistor 62.
and a differentiator circuit consisting of a capacitor 63, and outputs a differential pulse obtained by differentiating the switch signal of the key switch 61 from an output terminal 64.

This output terminal 64 is connected to one input terminal of an AND circuit 65 whose output terminal is connected to the other input terminal of the OR circuit 34.

Note that the other input terminal of the AND circuit 65 is connected to the output terminal Q1 of the timing generator 4.

Next, the operation of the circuit of FIG. 2 constructed as described above will be explained based on the time chart shown in FIG. 3.

Note that A in FIG. 3 indicates the output terminal 6 of the initialize section 6.
The outputs of 4, mouth, ha, 2, and ho are timing generator 4.
Each output terminal Q1. Q2. Q3. Q4 output to A
-The output of the conversion completion signal output terminal sta of the D converter 2,
G indicates the output of the AND circuit 65, and H indicates the output of the output terminal Q of the comparison circuit 33, respectively.

Upon starting the engine, time t.

When the key switch 61 is turned on, a differential pulse P is output from the output terminal 64 of the initializing section 6.

[See Figure 3 A] is emitted.

Therefore, the AND circuit 65 generates an initial set pulse P6 (see FIG. 3) when the timing pulse P1 (see FIG. 3) output from the output terminal Q1 of the timing generator 4, which is another input signal, is generated. It comes out.

This initial set pulse P6 is applied to the clock terminal T of the latch circuit 31 of the signal comparator 3 via the BOA circuit 34.

As a result, the latch circuit 31 operates at time t.

The output of the A-D converter 2, which previously converted the analog signal of the level sensor 1 into a digital data signal, is read and the digital data signal is output.

This digital data signal is applied to the decoder 51 of the display section 5, and therefore, the remaining fuel amount displayed by the digital display element 52 becomes the initial value indicated by the digital data signal.

Next, at time t1, when a timing pulse P4 (see FIG. 3E) is issued from the output terminal Q4 of the timing generator 4, the A-D converter 2 receives the timing pulse P4 as a conversion command signal. Time t
1 starts the operation of converting the analog signal of the level sensor 1 into a digital data signal (hereinafter simply referred to as an A-D conversion operation).

Until the A/D conversion operation is completed, a sta pulse P5 (see FIG. 3) is output from the conversion completion signal output terminal sta, and the timing generator 4 is reset.

On the other hand, an inverted pulse of the sta pulse P5 is applied to the load terminal of the counter 32 as a preset pulse, and when the A-D conversion operation based on the timing pulse P4 at time t1 is completed (the sta pulse (at fall) The output of the counter 32 is preset to the output of the latch circuit 31, in other words, the digital data signal currently displayed on the display section 5.

After this, the reset of the timing generator 4 is released, and the timing pulses P1. P2. P3
is each output terminal Q1゜Q2. In response to the timing pulses P1 to P3 generated by Q3, the counter 32 first counts down by one step and then counts up by two steps.

Therefore, the output of the counter 32 is the timing pulse P
1 is subtracted from the digital amount of the digital signal preset in response to the timing pulse P2. After receiving P3, the digital amount subtracted above is
1" is added to the digital amount.

Now, time t.

Assuming that the output of the level sensor 1 at times t1 and t is the same, the comparator circuit 33 outputs a trigger pulse P7 (see FIG. 3, h) when the timing pulse P2 is generated.

Upon receiving this trigger pulse P7, the latch circuit reads the output of the AD converter 2 at that point in time, but this output is the same as the digital data signal currently displayed, and the display unit 5 displays the initial value. It remains as it is.

At time t2, when the timing pulse P4 is issued again from the output terminal q of the timing generator 4,
Thereafter, the same operation as above is performed.

If the remaining fuel amount is decreasing at time t2, the digital amount of the digital data signal emitted from the A-D converter will be smaller than the digital amount of the currently displayed digital data signal, and therefore, the comparison When the output of the counter 32 changes to the value obtained by subtracting "1" from the digital amount of the preset digital data signal (measured value at time t1), in other words, when the timing pulse P1 is emitted, A trigger pulse P71 shown by a broken line in FIG. 3H is output.

Upon receiving this trigger pulse P7', the latch circuit 31 reads the output of the AD converter 2 at that time and outputs it to the display section 5.

As a result, the display on the display section 5 changes to display the remaining fuel amount with "1" subtracted.

The operation when the fuel gradually decreases as described above will be explained using specific numerical values.

Time t. The digital data signal at I is indicating the remaining fuel level “2”.
0 liter", and assuming that the fuel gradually decreases from this state, the analog quantity from the level sensor 1 changes linearly, whereas the A-D converter Since the digital quantity converted in step 2 changes stepwise, even if the analog quantity of level sensor 1 is decreasing moment by moment, the amount of decrease must reach the amount of "1" in terms of digital quantity. For example, when timing pulse P4 is issued at time t1, the A/D converter outputs a digital data signal representing a digital quantity of "20 liters".

Thereafter, the counter 32 outputs the timing pulse P1. P2.
After receiving P3, "19 liters" and "20 liters"
, outputs a digital data signal indicating a digital amount of "21 liters".

The comparison circuit 33 for detecting the coincidence of the two human forces is A-D.
When the data signal from the converter 2 and the data signal from the counter 32 match, in other words, when the counter 32 receives the timing pulse P2 and emits a digital data signal indicating a digital amount of "20 liters", the trigger pulse P
Outputs 7.

As a result, the latch circuit 31 has A= at the current timing.
A digital data signal indicating the digital amount of "20 liters" output from the D converter 2 is read and output to the display section 5.

Therefore, at this time t. The display in does not change.

Next, the analog amount from the level sensor 1 further decreases until the amount of decrease reaches the amount of "1" in terms of analog amount, and when the timing pulse P4 is emitted at time t2, the A-D converter 2 A digital data signal indicating a digital amount of "19 liters" is output.

On the other hand, the counter 32 receives a digital data signal I, r-iJ, roJ, r+i indicating the currently displayed digital quantity.
, J is added/subtracted, so at time t
In 2, "19 liters", "20 liters", "
21 liters of digital data signals are sequentially output.

Therefore, the comparator circuit 33 outputs a trigger pulse P7' when the counter 32 receives the timing pulse P1 and issues a digital data signal indicating a digital amount of "19 liters".

This causes the latch circuit 31 to
A digital data signal indicating the digital amount of "19 liters" output from the D converter 2 is read and output to the display section 5.

Therefore, the display at this time t21 is r 201
It changes from ``J ttle'' to ``19 liters''.

Contrary to the above operation example, if the fuel is increasing at time t2 due to refueling, then the digital amount of the digital data signal emitted from the A-D converter 2 is greater than the currently displayed digital data amount. Therefore, the comparison circuit 33 outputs the preset digital data signal (measured value at time t1) from the output of the counter 32.
In other words, when the timing pulse P3 is emitted, the latch circuit 31 receives the trigger pulse P7n indicated by the broken line in FIG. -Read the output of the D conversion 2 and output it to the display unit 5.

As a result, the display on the display section 5 changes to a display of the remaining amount of fines to which "1" has been added.

Also, at time t2, due to liquid level fluctuation, the A-D converter 2
If the output of is greatly decreased or increased, the amount of variation exceeds the digital quantity r+l1r-IJ, so the output due to this variation will not match the output of the counter 32, and the above comparison condition is not satisfied.

Therefore, the comparator circuit 33 does not output the trigger pulse P7'1 or P7'1, and the display on the display section 5 continues to display the previous display, thereby preventing the display from fluctuating due to the liquid level fluctuation.

Such a signal comparison for comparing the magnitude of both the digital data signal indicating the remaining fuel amount and the digital data signal currently displayed is repeatedly executed after time t3, and the display section 5 is updated according to the comparison result. change the display,
The remaining fuel amount is displayed stably without being affected by fluid level fluctuations.

In the explanation of the above embodiment, the measurement timing of the remaining fuel amount, that is, the frequency of the timing pulse, was not particularly mentioned. However, since the decrease or increase in the remaining fuel amount changes relatively slowly, the measurement timing is set to seconds. By setting the timing pulse frequency to about 1 to 10 Hz, the display on the display can sufficiently follow the change in the remaining fuel amount.

Further, in the above-mentioned embodiment, it is desirable that the display on the display section be linked with, for example, a key switch, so that the remaining fuel amount is displayed only while the engine is operating.

Furthermore, in the above embodiment, if the level sensor is a digital level sensor, the A-D converter is of course unnecessary.

However, a latch circuit or the like is required to store the output of the level sensor at each measurement timing.

Note that the signal processing performed by the circuit shown in FIG. 2 can also be performed by, for example, operating a microcomputer according to a predetermined program; therefore, the present invention is not limited to the circuit example described above.

As explained above, according to the present invention, a digital data signal indicating the remaining amount of fuel is emitted at regular timing,
A signal comparison is performed to compare the magnitude of both the digital amounts of the digital data signal at the current timing and the digital data signal currently displayed, and the digital data signal currently displayed is changed based on the comparison result.
Through a series of digital data signal processing, it has the ability to suppress fluctuations in the remaining fuel level display due to changes in the liquid level, and is a highly responsive digital fuel level display device that eliminates the above-mentioned conventional drawbacks. can do.

The present invention is a digital fuel remaining amount display device that uses a series of digital data signal processing, and when an IC circuit or a microcomputer is installed for the purpose of controlling various loads, etc. of an automobile fuel cell, this can be used. Easy to implement.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a digital fuel level display device according to the present invention, Fig. 2 is a circuit diagram showing a specific circuit example of the block in Fig. 1, and Fig. 3 is for explaining the operation of the circuit shown in Fig. 2. This is a time chart. 1...Level sensor, 2...A-D'
X[1%! , 3... Signal comparator, 4... Timing generator 5... Display section, 6... Initialization section.

Claims (1)

[Claims] 1 Digital data signal generation means for measuring the remaining amount of fuel in a fuel tank mounted on a vehicle at regular timings and generating a digital data signal indicating the remaining amount of fuel; and generating the digital data signal at the current measurement timing t. A signal comparison that detects a match between the digital amount of the digital data signal from the means and the digital amount obtained by adding and subtracting "+1", rol, and "-1" to the currently displayed digital data signal and generates a digital data signal at the current measurement timing. What is claimed is: 1. A digital fuel remaining amount display device for a motor vehicle, comprising: a means for displaying a remaining fuel amount;