JPS601567B2 - Vehicle fuel level gauge - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel level meter for a vehicle that improves the responsiveness of remaining level display.

Conventionally, fuel gauges that measure the amount of fuel remaining in a vehicle's fuel tank have been known, and one type of fuel gauge is a fuel gauge that averages the remaining fuel detection signal and displays the remaining amount. There is.

In other words, when a vehicle is driving, when it turns a curve, accelerates or decelerates, starts climbing a slope, finishes climbing, starts descending, or finishes descending, weight is applied to the fuel tank and the fuel fluctuates greatly. To detect the amount of fuel, it is necessary to average the fuel amount detection signals. A fuel gauge that displays the remaining amount by averaging the remaining amount detection signal is convenient because it can display the average amount of fuel remaining, but normally the responsiveness of the remaining fuel gauge, that is, changes in remaining fuel amount, is The responsiveness of the remaining amount display is selected based on when the vehicle is running, so if the amount of fuel in the fuel tank increases in a short period of time, such as when refueling, the increase in fuel amount will not be reflected until a certain period of time has elapsed. The problem is that it is not displayed. On the other hand, when starting to drive the vehicle, the remaining amount of fuel needs to be displayed the moment the ignition key is turned to the accessory position, but if the averaging processing time of the remaining amount detection signal is long, the ignition key is turned There is a problem in that the remaining amount is not displayed until a certain amount of time has passed after turning it to the position or ignition position. The present invention has been made in view of the above points, and it switches the averaging processing time of the remaining amount detection signal depending on the state of the vehicle, and reduces fluctuations in the remaining amount detection signal by using a long averaging processing time while the vehicle is running. The responsiveness of the remaining amount display is improved by measuring the remaining amount detection signal using a short averaging processing time during refueling or just before starting the engine.

The present invention will be explained below based on the drawings. FIG. 1 is a block diagram showing an embodiment of a fuel level meter according to the present invention, and this embodiment measures the capacitance between a pair of electrodes disposed facing each other in a fuel tank. This is a capacitance type fuel gauge that measures the remaining amount of fuel.

The remaining amount detector 1 measures the capacitance C of the gap between the electrodes to obtain a remaining amount detection signal, and this signal is applied to the RC oscillator 2 and converted into a frequency f (or period T). Next, this oscillation frequency f (or oscillation period T) is passed through a frequency divider 3 and divided by a frequency f''. The average frequency (or period) of the divided frequency f' is counted through a counter 6 or 7 which is switched by a changeover switch 5 which is switched based on a signal from a position discriminator 4' of the ignition switch 4. Alternatively, the averaged output from 7 is supplied to an arithmetic unit 8 to calculate the remaining amount, and the remaining amount is displayed on a display 9. Next, the operation of the above circuit will be explained.

For example, assume that the capacitance between the electrodes constituting the remaining amount detector 1 is 1000 pF when the fuel tank is empty and 2000 pF when it is full.

At this time, the oscillation frequency of the RC oscillator 2 changes from 10 KHz to 1 Hz (in the case of the oscillation cycle, from 0.1 milliseconds to 0.2 milliseconds), which is divided by the frequency divider 3 into 1/min (of the oscillation cycle). In that case, divide the frequency by 5 times). Next, a changeover switch 5 is actuated in response to a signal from the ignition switch 4, and the counter 6 or 7 for measuring the oscillation frequency is switched. The counters 6 and 7 are the oscillation frequency (or period) f′ after frequency division.
It has a function of counting the average value of a certain number of pulse signals or the number of pulse signals during a certain gate time, and the number of pulse signals to be averaged or the gate time differs.

For example, when ignition switch 4 is off, 1
The remaining amount detection signal is counted by a counter 6 having an average value of 00 pulse signals or a gate time of 1 to 2 seconds, but when the ignition switch 4 is on (that is, the ignition key is in the ignition position), The remaining amount detection signal is counted by a counter 7 having an average value of pulse signals or a gate time of 10 acids. In this way, the counters 6 and 7 are switched by a signal representing the vehicle status from the ignition switch 4, but in place of the ignition switch 4, a vehicle distance sensor is used and the counters are switched depending on whether the vehicle distance is zero or not. In this way, counter 6
Alternatively, the calculation unit 8 calculates the remaining amount from the average value (or average period) of the oscillation frequencies counted in step 7, and the display 9 displays the remaining amount. Next, as is already known, float-type sliding resistance type or wire-wound resistance type fuel gauges, in which the amount detection signal is an analog signal, use a float floating on the fuel surface and a brush sliding on a resistor. are integrated, and when the liquid level changes, the position of the float moves, and as a result, the brush moves, and the resistance value of the superdynamic resistor or wire-wound resistor changes.

Therefore, when a constant current is passed through the resistor and the resistance value of the resistor changes, the voltage changes, so the remaining amount can be determined by detecting this voltage change. By the way, while the vehicle is running, the voltage value of the remaining fuel gauge fluctuates due to changes in the fluid level due to vibrations and rocking of the vehicle, so the remaining fuel detection signal is averaged through an integrator to smooth out fluctuations in voltage changes while the vehicle is running. However, according to experiments conducted by the present inventors, it takes an average time of about 1 to 2 minutes to smooth out fluctuations in the remaining amount detection signal due to fluctuations in the liquid level during driving. However, it is inconvenient for the driver that there is a delay of about 1 to 2 minutes from when the vehicle's power is zero to when the remaining amount is displayed after the ignition key is turned to the accessory or ignition position or after the vehicle starts driving. Therefore, two integrators with different time constants are provided, and the integrator is switched depending on whether the vehicle is stopped or running. That is, in Fig. 2, 1 is a float type sliding resistance type remaining amount detector, and 4 and 5 are the first
The ignition switch and changeover switch are the same as in the embodiment shown in the figure, 10 and 11 are two integrators with different time constants, the time constant of integrator 10 being shorter than the time constant of integrator 11, shall be taken as a thing. In the above embodiment, when the ignition switch 4 is not in the on state, the remaining amount detector 1
The remaining amount detection signal from the changeover switch 5 is passed through an integrator 10' having a short time constant and averaged, and when the ignition switch 4 is in the ignition position, the remaining amount detection signal is passed through the changeover switch 5. The signal is passed through an integrator 11 having a longer time constant and averaged.

In this way, when the vehicle is stopped, the remaining amount detection signal is averaged in a short averaging time, so the time required to display the remaining amount is shortened, and the driver can know the remaining amount almost immediately. As explained above, in the present invention,
The averaging processing time for the remaining amount detection signal is changed depending on whether the vehicle is stopped or moving, and the remaining amount is calculated in a short time when the vehicle is stopped, and the remaining amount is displayed over a longer period of time when the vehicle is moving. As a result, the remaining amount can be displayed with good responsiveness when necessary and with good stability while driving.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a capacitive fuel level meter as an embodiment of the fuel level meter according to the present invention, and FIG. 2 is a block diagram of a float-type tank dynamic resistance fuel level gauge as another embodiment of the present invention. It is a block diagram of a fuel gauge. 1, 1'...Remaining amount detector, 2...RC
Oscillator, 3... Frequency divider, 4... Ignition switch, 5... Changeover switch, 6, 7...
...Counter, 8...Calculation section, 9...
Display, 10, 11...Integrator. Figure 1 Figure 2

Claims (1)

[Scope of Claims] 1. Remaining amount detection signal generation means for generating a remaining amount detection signal corresponding to the remaining amount of fuel, and different averages for averaging the remaining amount detection signals output from the remaining amount detection signal generation means. an averaging circuit having an averaging time; a state determining means for determining the state of the vehicle; a switching means for switching the averaging time of the averaging circuit according to a state signal output from the state determining means; A fuel level meter for a vehicle, comprising a calculation means for calculating the remaining amount of fuel from an averaged remaining amount detection signal, and a remaining amount indicator for displaying the remaining amount output from the calculation means. . 2. The vehicle according to claim 1, wherein the state determining means comprises a vehicle speed sensor and a switching signal generating means that outputs a different state signal depending on a vehicle speed signal from the vehicle speed sensor. fuel level gauge. 3. The device according to claim 1, wherein the state determining means comprises an ignition switch and a switching signal output means that outputs a different state signal depending on the on/off state of the ignition switch. Vehicle fuel level gauge. 4. Claim 1, wherein the remaining amount detection signal is a digital signal, and the averaging circuit has different digital signal count values or digital signal transit times.
The fuel level meter for a vehicle according to any one of Items 1 to 3. 5. According to any one of claims 1 to 3, wherein the remaining amount detection signal is an analog signal, and the averaging circuit includes a plurality of integrators having different time constants. Fuel level gauge for vehicles.