FR2588954A1 - DEVICE FOR MEASURING AND INDICATING THE FILLING LEVEL OF A FUEL TANK IN A VEHICLE - Google Patents

Abstract

THE INVENTION RELATES TO A DEVICE FOR MEASURING AND INDICATING THE FILLING LEVEL OF A FUEL TANK IN A MOTOR VEHICLE. THE TAKEN DISTANCE SIGNAL PROVIDED BY THE DISTANCE SENSOR3 IS APPLIED TO A COUNTER5 OF THE EVALUATION UNIT4, WHICH GENERATES EACH TIME A PREDETERMINED DISTANCE IS TAKEN, A CONSTANT TAKEN DISTANCE SIGNAL; THE CONSTANT TAKEN DISTANCE SIGNAL EXCITES A MEMORIZATION BODY6 OF THE EVALUATION UNIT4, WHICH THEN INPUT THE SIGNAL OF THE FILLING LEVEL SENSOR2 WHICH IS APPLIED TO IT; THE SEIZED SIGNAL IS TRANSMITTED, WITH INTERMEDIATE PASSAGE THROUGH A SIGNAL PROCESSING STAGE7, TO A DIGITAL FILTER8 OF THE EVALUATION UNIT4 WHOSE OUTPUT SIGNAL CONSTITUTES THE CONTROL SIGNAL.

Description

The present invention relates to a device for measuring and indicating the

  level of filling of a fuel tank in a vehicle, comprising a level detection sensor and a distance sensing sensor, whose signals are applied via single-unit inputs evaluation circuit for processing said signals and producing a control signal at its output, said signal

  control system producing in a car contents indicator

  an indication corresponding to the filling level.

  We already know a device of the type pre-

  cited (DE 33 09 802), which is used in the context of a universal electronic system, for example in an on-board computer. In this system, the control device associated with the filling level measurement receives, in

  plus the signal from the fill level sensor

  wise, also the signal of the distance sensor traveled, but however for reasons that are related to

  determining determined cruise data.

  As is generally known, the level of filling of the fuel tank is continuously indicated to the driver of a motor vehicle so that he knows the instantaneous content available to him. According to this principle, the value indicated must decrease monotonically as the journey progresses, that is to say with the distance traveled to a refueling (Figure 1). In current fuel content indication systems, however, it is

  note that the indicated value also increases

  in the absence of refueling during the trip. One reason for this incorrect behavior of the indication system comes from the signal filtering of the

  filling level. This signal has a variable function

  over time (figure 2) which depends on the following quantities: - the level of liquid in the tank varies greatly as a result of the movements during the journey and the conditions of the road, and - the level sensor can not not, for construction reasons, be willing

  at the optimal mounting location of a sensor.

  In the devices known generally until now, the signal of the level sensor of

  filling is temporally amortized by means of a system

  low-pass filtering, for example by an output labyrinth, deflector plates mounted on the float arm of the fill level sensor, hydraulic damping effects at the center of rotation of the sensor, low-pass electronic circuits etc. These processes, however, take into account only one way

  insufficient because the filling level of the

  fuel tank varies over a certain distance of course, while it may take a long time

  without the filling level dropping significantly.

  As a result, the indication, which is amortized

  may increase when producing a fill level sensor signal that simulates a level

  higher - for example when stopping on a descent.

  The purpose of the invention is therefore to

  a device of the type defined above so as to

  exclude incorrect indications of fuel content.

  This problem is solved in that the signal

  constant distance traveled excites a memo-

  evaluation unit, which then captures the

  of the filling level sensor applied to it.

  in that the inputted signal is transmitted with intermediate passage in a signal processing stage, to a digital filter of the evaluation unit whose signal

  output is the control signal.

  A device arranged in accordance with

  graph, which receives the signal from the sensor of

  calf filling according to the distance traveled and which the filter numerically on the basis of a distance frame so that we obtain a monotonically decreasing function in time, offers by

  therefore an appropriate possibility to establish a

  because the fill level of the tank is measured during running, when

  measurable variations in this level of filling, and

  that temporally very long damping constants can be produced, since the signal of the fill level sensor is evaluated in relation to the

distance traveled.

  According to other features of the invention: the constant distance traveled signal is produced whenever a predetermined distance of 100 m to 300 m, preferably 200 m, is traveled; the digital filter is arranged as a recursive filter

  den-th order with a damping constant of about

10 to 30 km;

  - the digital filter is constituted by a pass filter

two-stage recursive bottom.

  Other features and advantages of the invention will be highlighted later in the

  description, given by way of non-limiting example, in

  reference to the accompanying drawings in which: - Figure 1 shows a diagram which gives the indication of fuel content according to the distance traveled; - Figure 2 represents an enlarged scale

  a diagram that illustrates the part, depending on the

  of the level sensor signal

  wise according to the distance traveled.

  FIG. 3 represents a block diagram of the device according to the invention, and FIG. 4 represents the corresponding flowchart. This chart should be considered as

  incorporated into the description by reference to it

  made here. The device, generally designated 1, for measuring and indicating the level of filling of a fuel tank in a vehicle is essentially composed of a suitable level sensor 2, detecting the level filling, a distance sensor 3 detecting the distance traveled, an evaluation unit 4 and a fuel content indicator 15. Within the evaluation unit 4, which can be arranged in the form of a single-chip microcomputer, a counter 5, a storage device 6, a signal processing stage 7 and a digital filter 8 are provided, the evaluation unit 4 being it. - even powered by the battery voltage (in 9 and 10). The evaluation unit 4 has three inputs 11, 12 and 13 and an output 14, in which case the reserve input 11 is not used here. Through the input 12, the storage device 6 receives the signals from the filling level sensor 2, while, via the input 13, the counter 5 receives the distance traveled signals. from the distance sensor 3. After a predetermined constant distance traveled (for example 200 m), that is to say when the counter has received a determined number of distance traveled signals, this counter produces a signal of

  constant distance traveled, which excites

  of a connection 5 'the memory organ 6.

  it then captures the signal applied to it by the fill level sensor 2 and which is transmitted to the filter 8 after having passed into the signal processing stage 7 - in which specific parameters and characteristics of the type

  such as the geometry of the tank, the

  the actual sensor, the geometry of the wheels,

  etc., with a view to a corresponding conditioning. Thread-

  8 is for example constituted by a filter

  recursive second order having a damping constant

  approximately 30 km; in particular, with a filter arranged in this way, it is also possible to obtain maximum consumption without significant phase shift of the indication with respect to the level of filling. The filtered output signal which then appears at the output 14 simultaneously constitutes the control signal used to

  establish the indication, corresponding to the level of

  pleating, in the fuel content indicator 15.

  Corresponding to the predetermined constant distance traveled, ie 200 m in the example considered, the signal of the filling level sensor is thus entered every 200 m and the program flow described above is triggered so that gets a filtering of the fill level sensor signals according to the distance traveled. The repetition frequency of the program is thus function

the speed of the vehicle.

  It is only when refueling the vehicle that, when stopped, the function of

  temporal growth of the filling level of the reservoir

  see is measured, i.e. the time variation of the signal voltages of the fill level sensor,

  so that the driver immediately has an indication of

  cation of the instantaneous level. This can be done so that, when no distance traveled signal is entered for a time which is for example 500 ms, it is then admitted that the vehicle is stationary. Then the filling level is entered in an analysis cycle

  500 ms and, from the temporal variation function,

  the level of filling thus obtained, it is defined if there is refueling or if the vehicle is simply not stopped horizontally. If it is detected

  that a refueling of the vehicle takes place, the indica-

  following without significant damping the level of filling so that the driver has

  immediately from the indication of the actual fuel content.

  Furthermore, if, during vehicle operation, the reserve contact closes so that a signal is applied to the evaluation unit 4 via the reserve input 11, it occurs, for prohibit an indefinite and incorrect floating of the indication of fuel reserve between "filling level" and "reserve", a switching of the indication on "reserve"

  when the reserve contact is closed

  for example, over a distance of 3 km.

  Thanks to the invention, however, no

  only an erroneous indication of

  but we also obtain a greater precision

  indication that it is possible to obtain both an assessment of any indication in liters and a numerical

remaining amount of fuel.

Claims (4)

  1 - Device for measuring and indicating the level of filling of a fuel tank in a vehicle, comprising a sensor for detecting the level of   filling and a sensor for detecting   the signals are applied through inputs to an evaluation unit for processing said signals and outputting a control signal, said control signal producing in a fuel content indicator a indication corresponding to the filling level, characterized in that the distance signal supplied by the distance sensor (3) is applied to a counter (5) of the evaluation unit (4), which produces whenever 'a   predetermined distance is traveled, a warning signal   constant flow, in that the signal of dis-   constant flow rate excites a memory device   (6) of the evaluation unit (4), which then captures the   of the filling level sensor (2) applied to it, in that the signal input is transmitted, with intermediate passage in a processing stage of   signal (7), to a digital filter (8) of the   evaluation (4) whose output signal constitutes the signal control.   2 - Device according to claim 1, characterized in that the constant distance traveled signal is produced whenever a predetermined distance of 100 m to 300 m, preferably 200 m, is covered.   3 - Device according to claim 1,   characterized in that the digital filter (8) is   killed by a n-first order recursive filter with a constant   damping of about 10 to 30 km.   4 - Device according to claim 2, characterized in that the digital filter (8) is constituted   by a two-stage recursive low-pass filter.