JPS6095303A - Liquid level indicator for vehicle - Google Patents

Abstract

PURPOSE:To hold an indicating state basing on a variation state of a liquid level by generating a signal only for a prescribed time required for a convergence only when a transient variation state of a detecting signal exceeds a prescribed allowable range, and cutting off a power supply to an indicating mechanism from a DC power source. CONSTITUTION:When an ignition switch IG is closed, in case when a detecting voltage Va generated from a liquid level detecting circuit 20 is stable, a monostable multivibrator 40 does not generate a high level signal due to a relation to a differential voltage generated from a differentiation circuit 30, and a transistor 51 conducts. Also, a stable composite magnetic field is generated, and a needle is also stabilized by controlling a inflow current to a coil due to a relation to a current flowing into a resistance 66 by an operation of a differential amplifier 63 and a transistor 67 to the voltage Va and a voltage Vb. Also, when the liquid level changes suddenly and the voltage Va changes suddenly, a high level signal is generated, the transistor 51 becomes non-conducting, a driving force from a driving part 10 is eliminated, and the needle holds its immediately previous position.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a vehicle indicator, and in particular detects the level of liquid in each housing container, such as fuel in a fuel tank mounted on a vehicle. This invention relates to a vehicle liquid level indicator suitable for use in vehicles.

(Prior art) Conventionally, this type of liquid level V/I/indicator for vehicles was as follows:
For example, it detects the liquid level of fuel existing in a fuel tank of a vehicle, detects the inclination angle or acceleration/deceleration of the vehicle, and indicates the detected liquid level while being supplied with power from a DC power source, and Some devices are designed to cut off the power supply when the detected inclination angle or detected acceleration/deceleration reaches a predetermined value, and maintain the indicated state at the time of the cutoff.

However, in such a configuration, the fuel level may not change appropriately in response to changes in the tilt angle or acceleration/deceleration of the vehicle, so the power supply may be cut off by mistake and the above-mentioned instruction There is a risk that the state will be maintained inappropriately. Furthermore, in the above configuration, in addition to the means for detecting the level of fuel in the armpit, it is also necessary to employ means for detecting the inclination angle or acceleration/deceleration of the vehicle.

(Objective of the Invention) The present invention has been made in response to the above-mentioned problems, and its purpose is to provide a liquid level indicator for a vehicle in which the power supply to the liquid level indicator is cut off. The reason is that the indicated state is maintained based on the fluctuation of the liquid level itself.

(Structure of the Invention) In order to achieve the above object, the structural feature of the present research is a detection means that detects the level of liquid present in a container mounted on a vehicle and generates the detection result as a detection signal. and an indicating mechanism that indicates the liquid level in response to the detection signal in a state where power is supplied from a DC power supply, and maintains the indicated state at the time of cutoff when the power supply is cut off. In the surface level indicator,
Signal generating means for generating an output signal only when the transient fluctuation state of the level of the detection signal exceeds a predetermined tolerance range, and for a certain period of time necessary for the transient fluctuation state to converge within the tolerance range. and a cutoff means for cutting off power supply from the DC power source to the indicating mechanism for the predetermined period of time in response to the output signal.

(Effects of the Invention) By configuring the present invention in this way, the transient fluctuation state of the level of the detection signal can be directly utilized.
Only when this transient fluctuation state exceeds the allowable range, the cutoff means cuts off the power supply to the indicating mechanism for a certain period of time in cooperation with the signal generation means, so that it is possible to determine what driving state the vehicle is in. Even if the above-mentioned power supply is cut off, that is, the indicated state is maintained by the above-mentioned indicating mechanism, whenever the transient fluctuation state of the liquid level exceeds the allowable range described in f5iJ, the power supply is always properly added. As a result, it is possible to reliably prevent the occurrence of transient fluctuations in the indicated value by the indicating mechanism. In this case, since only the detection signal of the detection means is used, there is no need to add unnecessary detection means.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings. The drawings show an example in which the present invention is applied to a cross-coil type liquid level indicator for a vehicle. This crossed coil type liquid level indicator detects and indicates the liquid level of the fuel existing in the fuel tank of the vehicle as the remaining amount of this fuel.
A drive unit 10 provided in the instrument body (located inside the vehicle) together with a pointer, a liquid level detection circuit 20 connected to a DC power supply B via an ignition mailer check G of the vehicle, and a drive unit 10. and liquid level detection circuit 20
A differentiating circuit 3 which is connected between and constitutes the main part of the present invention
0, a monostable multivibrator 40, a transistor circuit 50, and a drive circuit 60.

When the ignition mailer chain G is closed, the drive unit 10 is supplied with power from the DC power supply B under the action of the transistor circuit 50 as described below, and becomes in operation. Accordingly, a composite magnetic field is generated based on each current flowing in the coils/l'11.12 wound in a crosswise manner around the magnetic body in accordance with the temperature compensation resistor 14, and the magnetic body is rotated by this composite magnetic field. and wave the pointer. This means that the drive unit 10 generates a driving force corresponding to the composite magnetic field, and causes the pointer to swing by a deflection angle corresponding to this driving force. Also,
When the drive unit 10 eliminates its driving force by cutting off the DC power source B, the pointer maintains the indicated position immediately before the disappearance due to the relationship with its indicating structure, regardless of the disappearance of the driving force. It is supposed to be done. Note that the reference numeral 15 indicates a current limiting resistor.

The liquid level detection circuit 20 has a liquid level detector 21, and this liquid level V bell detection? i? J21 is composed of a variable resistor 2111+ disposed at a suitable location in the fuel tank, and a slider 21b that changes the resistance value of the variable resistor 21a in accordance with fluctuations in the liquid level of the fuel in the fuel tank. Further, the variable resistor 21a is grounded at one end, and connected to the positive side terminal of the DC power supply B via the resistor 22 and the ignition mailer chain G at the other end.

This means that the variable resistance value of the variable resistor 21a connected to the resistor 22 changes in inverse proportion to the height of the fuel level. The liquid level detection circuit 20 is supplied with power from the DC power supply B when the ignition switch G is closed, and is connected to the variable resistor 2111+ from the common terminal (i.e., output terminal) of the variable resistor 21a and the resistor 22. A detection voltage ■α that is proportional to the variable resistance value of (that is, a detection voltage ■α that is inversely proportional to the liquid level) is generated.

The differentiating circuit 60 differentiates the detected voltage α from the liquid level detecting circuit 20 using its capacitor 31 and resistor 62, and generates a differential voltage. Monostable multipipe lake 4
0 is the addition of the reference voltage defined by the sum of the Zener voltage of the Zener diode 46 and the forward voltage of the diode 48, the differential voltage from the differentiating circuit 60, the Zener voltage of the Zener diode 46, and the voltage drop of the resistor 46. The voltage is compared by a comparator 45, and only when the added voltage is higher than the reference voltage, a high level signal is generated from the comparator 45 for a certain period of time. In such a case, the reference voltage represents a permissible limit value during transient fluctuations (for example, rapid fluctuations) in the fuel level based on the relationship between the added voltage and the differential voltage. The generation time of the high level signal from the monitor and comparator 45 represents the time expected to be required for the transient fluctuation state of the liquid level exceeding the permissible limit value to decay below the permissible limit value after its occurrence. . Note that the permissible limit value is determined in consideration of preventing the occurrence of a transient needle vibration phenomenon of the pointer.

The transistor circuit 50 has a transistor 51 which has a resistor 52 at its base.
It is connected to the output terminal of the comparator 45 via.

Further, the transistor 51 is connected to the positive side terminal of the DC power supply B via the ignition switch G at the solenoid emitter, and the collector of this transistor 51 is connected to the current limiting resistor 15 of the drive section 10. ing. Thus, when the ignition switch G is closed, the transistor 51 becomes conductive in response to the generation of a high-level signal from the comparator 45, and becomes non-conductive in response to the disappearance of this high-level signal. . In other words, the transistor 51 is conductive only during the generation time of the high level signal from the comparator 45, allowing power to be supplied from the DC power supply B to the drive unit 10 via the ignition switch G.

The drive circuit 60 includes a series resistor 61.6 forming a voltage dividing circuit.
One terminal of the resistor 61 is grounded, and the other terminal is connected to the positive terminal of the DC power source B via the resistor 62 and the ignition switch G. Thus, the voltage dividing circuit receives the power supply voltage from the DC power supply B when the ignition switch G is closed, divides the voltage by both resistors 61.62, and applies this divided voltage Vb to the common terminal of both resistors 61.62. arises from. Differential amplifier 6
The non-inverting input terminal of the differential amplifier 63 is connected to the common terminal of both resistors 61 and 62, and the inverting input terminal of the differential amplifier 63 is connected to the liquid level I via the resistor 64 and is connected to the output terminal of the detection circuit 20. and is grounded via both resistors 65 and 66. The amplification transistor 67 has its base connected to the output terminal of the differential amplifier 63 and its emitter grounded via a resistor 66. The collector of the amplification transistor 67 is connected to the coil 11 of the drive unit and is connected to a current limiting resistor 15 via a temperature compensation resistor 14.

Therefore, in the drive circuit 60 configured in this manner, the differential amplifier 66 calculates the difference between the detected voltage va from the liquid level detection circuit 20 and the divided voltage Vb from the resistor 61 between the two resistors 64 and 65. The amplification transistor 67 current-amplifies the output of the differential amplifier 66 while working together to differentially amplify it, and the output voltage 0 is produced at its emitter in cooperation with the resistor 66.

In such a case, the resistance value of each resistor 64.65 is Ra
, 'Rb, the above-mentioned output voltage vO is expressed by the following equation.

Therefore, if the resistance value of the resistor 66 is RC, then this resistor 6
The current i flowing into 6 is expressed by the following equation.

However, in this embodiment, each resistance value of the sheet resistance 61.62 and the resistance value Rα of each resistance 64, 65.66.

Rb and Re are the variable resistor 212 of the liquid level detector 21 instead of the transistor 67 and the resistor 66)v12
When connected in parallel to the variable resistor 2112, the current flowing into the variable resistor 2112 according to the change in the variable resistance value is determined to match the current 1.

In this embodiment configured in this way, it is assumed that the vehicle is running at a low constant speed on a flat road, for example, with the ignition switch G closed and the device of the present invention operating. Then, the liquid level of the fuel existing in the fuel tank is almost stable. Therefore, in such a state, the detection voltage α generated from the liquid level detection circuit 20 is almost stable without any transient fluctuations, and is equal to the differential voltage generated from the differentiation circuit 3'0 in response to the detection voltage VtL. Due to this relationship, the added voltage formed in the monostable multivibrator 4o is lower than the reference voltage, and a high level signal is not generated from the monostable multipipe rake 40, and the DC power supply via the ignition switch G is generated. Power is supplied from B to the drive unit 10 by the transistor circuit 50 while the transistor 51 is conductive, and the current 1 is supplied from the detection voltage Vα from the liquid level detection circuit 20 and the resistance 61 of the drive circuit 60. The voltage flows into the resistor 66 under the differential amplification effect of the differential amplifier 66 and the current amplification effect of the transistor 67 on the divided voltage V1). As a result, the drive section 10 controls the current flowing into the coil 1v12 in relation to the current 1 flowing into the resistor 66 under power supply from the transistor 51, thereby generating a composite magnetic field. As a result, the pointer indicates the level of the fuel, that is, the remaining amount, in a stable state by the rotating force of the magnetic body based on the combined magnetic field.

In such a state, if the fuel level in the fuel tank transiently (e.g., suddenly) fluctuates (for example, suddenly) due to sudden acceleration/deceleration of the vehicle, rapid vibration, etc. and exceeds the above-mentioned allowable limit value, the liquid level will change. The detection voltage α from the level detection circuit 20 transiently fluctuates, and a monostable multi is formed in the break 40 by the relation with the differential voltage generated in response to the detection voltage α applied from the differentiating circuit 60. becomes higher than the reference voltage, and a high level signal is generated from the monostable multi-bibreak 40 under the action of its comparator 45, rendering the transistor 51 non-conducting. Therefore, even if the current 1 flowing into the resistor 66 fluctuates transiently while the drive circuit 60 is operating, the drive unit 10 is cut off from the DC power supply B due to the non-conduction of the transistor 51 immediately before such fluctuation occurs. Eliminate that driving force. As a result, the pointer maintains the indicated position in a stable state immediately before the driving force from the drive unit 10 disappears, despite transient fluctuations in the liquid level.

This means that, despite transient fluctuations in the liquid level that exceed the permissible limit value, the occurrence of rapid needle vibration of the pointer can be reliably prevented.

Furthermore, the high-level signal from the monostable multivibrator 40 disappears after the predetermined period of time has elapsed, that is, after the transient fluctuation of the liquid level has attenuated to below the allowable limit value, so that the needle vibration phenomenon of the pointer is suppressed. It cannot be caused by mistake.

In the above embodiment, an example was explained in which the monostable multivibrator 40 was adopted as a means for making the transistor 51 of the transistor circuit 50 non-conductive for a certain period of time, but the invention is not limited to this, and an appropriate timer circuit may be simply used. Instead of the stable multi-vibration τ of 4°, the transistor 51 may be made non-conductive for a certain period of time.

Further, in the embodiment, the drive unit 1 is connected to the DC power supply B.
Although the transistor circuit 50 is used to cut off the power supply to 0, the present invention is not limited to this, and an electromagnetic relay circuit, a thyristor circuit, etc. can be used instead of the transistor circuit 50 to perform the above-mentioned cutoff of the power supply. Good too.

Further, in the embodiment, the liquid level is detected by the liquid level detector 21, but instead of this, a potentiometer type, capacitance type, or electromagnetic induction type 4 type liquid level detection may be used. The liquid level may be detected by a device.

In addition, in the above embodiment, an example was described in which the present invention was applied to a crossed coil type liquid level indicator used for indicating the detection of the fuel level in a fuel tank of a vehicle. However, the present invention may also be applied to an indicator used for indicating the level of oil or other various liquids in a vehicle's heating system.

[Brief explanation of drawings]

The drawing is an electrical circuit diagram showing an example in which the present invention is applied to a cross-coil type liquid level indicator for a vehicle. Explanation of symbols 10... Drive unit, 21... Liquid level detector, 30
... Differential circuit, 40 ... Monostable multipipe V-type, 50 ... Transistor circuit. Applicant Nippondenso Co., Ltd. Agent Patent Attorney Teru Hase −

Claims (1)

[Claims] a detection means that detects the liquid level of the liquid existing in a container mounted on a vehicle and generates the calibration result as a detection signal; and an indicating mechanism that maintains the indicated state at the time of cutoff from the power supply when the transient fluctuation state of the level of the detection signal reaches a predetermined level. signal generating means for generating an output signal for a predetermined period of time necessary for the transient fluctuation state to converge within the permissible range only when the permissible range is exceeded; A liquid level indicator for a vehicle, comprising: a cutoff means for cutting off power supply from the DC power source to the indicating mechanism.