JP2006145497A - Liquid level detecting device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable correspondence between a residual quantity sensor and a processing unit by means of a single signal line, during a predetermined time the residual quantity sensor concerned operates after switching off the ignition switch. <P>SOLUTION: The liquid level detecting device for vehicle comprises a residual quantity sensor 100, always connected to the first pole side of the vehicle battery, detecting the residual quantity of liquid in a tank to output the detected signal according to the residual quantity, a processing unit 200 for detecting and processing the residual quantity of liquid in the tank on the basis of the detected signal, and a signal line L2 comprising the conducting path concurrently serving as transmission of the detected signal from the residual quantity sensor 100 and the power supply from the first pole side to the second pole side of the battery; while the processing unit 200 includes a switching means 240, arranged within the conductive path, switching the conductive path, and a control means 210 for making the residual quantity sensor 100 actuated, by closing the switching means 240 and detecting and processing the residual quantity of liquid based on the detected signal during the switch-on time and a predetermined time, immediately after switching off the ignition switch. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a vehicular liquid level detection device that detects the remaining amount of liquid in an in-vehicle tank such as fuel.

2. Description of the Related Art As an example of detecting the remaining amount of liquid in an in-vehicle tank, a float type liquid level detection device that detects the remaining amount of fuel in a fuel tank has been known. This device detects, as a remaining amount sensor, the potential of the potentiometer that changes in accordance with the float position floating in the tank, on the instrument body (that is, the processing device) side at a position away from this remaining amount sensor. (For example, refer to Patent Document 1).
JP 2002-168675 A

  In such an apparatus, for example, as shown in FIG. 7, in order to measure the remaining amount when the vehicle is stopped and stable, the remaining amount sensor is only several seconds to several minutes after the ignition switch is turned off. The remaining amount data may be acquired by supplying power to 100 potentiometers. In that case, it is necessary to supply power to the potentiometer even if the ignition switch is turned off. However, if power is always supplied, the vehicle power supply is consumed quickly, so it is necessary to acquire remaining amount data. When a predetermined time has elapsed, it is necessary to stop the power supply.

  In order to construct such a device, the processing device 200 is provided with a sensor operation switch 240 for controlling energization from the in-vehicle battery 300 to the potentiometer, and the control means 210 controls the operation of the switch 240. It was.

  Therefore, between the processing device 200 side and the remaining amount sensor 100, a wire harness that constitutes an energization path from the sensor operation switch 240 provided on the processing device 200 side to the potentiometer in the remaining amount sensor 100, and the potentiometer Two wires with the wire harness constituting the energization path to the ground side in the processing apparatus 200 are required. This is also common when detecting the remaining amount of liquid in other vehicle-mounted tanks.

  The present invention has been made in view of the above points, and operates a remaining amount sensor for a predetermined time after the ignition switch is turned off. A single signal is provided between the sensor and the processing device. It aims at providing the liquid level detection apparatus for vehicles which can respond by a line.

  In order to achieve the above object, the present invention employs technical means described in claims 1 to 7.

According to the liquid level detecting device for a vehicle of the present invention described in claim 1, it is always connected to the first pole side of the battery mounted on the vehicle, and detects the remaining amount of liquid in the tank. A remaining amount sensor that outputs a detection signal corresponding to the amount, a processing device that is disposed at a position different from the remaining amount sensor, detects the remaining amount of liquid in the tank based on the detection signal of the remaining amount sensor, and a remaining amount A signal line that connects the quantity sensor and the processing device, and that constitutes an energization path that combines the transmission of the detection signal from the remaining amount sensor and the power supply from the first pole side to the second pole side of the battery; With
The processing device is disposed in the energization path and opens and closes the energization path, and closes the open / close means and activates the remaining amount sensor for a predetermined time immediately after the vehicle ignition switch is turned on and off. And control means for detecting the remaining amount of liquid based on the detection signal.

  Thus, according to the present invention, an energization path is configured via a signal line from the remaining amount sensor connected to the first pole of the battery to the second pole side of the processing device, and the detection signal from the remaining amount sensor is transmitted. By using an energization path that combines transmission (transmission) and power supply from the battery first pole side to the second pole side, a single signal line is provided between the two, and the remaining amount sensor It is possible to perform the above-described operation control and capture of the detection signal from the remaining amount sensor.

  Further, in order to control the remaining amount sensor immediately after the ignition switch is turned off, the opening / closing means for opening and closing the energization path on the processing apparatus side is controlled without increasing a new signal line with respect to the remaining amount sensor. Thus, the operation control of the remaining amount sensor can be easily performed.

  According to the second aspect of the present invention, the remaining amount sensor outputs a digital signal with a duty ratio indicating a current level corresponding to the remaining amount of liquid as a detection signal, so that a signal line or connector Even if there is a wiring resistance or contact resistance inside, and a voltage drop occurs there, it is possible to suppress the influence on the current output. In addition, since the detection signal is transmitted in a digital signal format, it is not easily affected by external noise or the like. As a result, even if the signal line is also used, it is possible to ensure stable detection accuracy in the processing device.

  According to the third aspect of the present invention, the remaining amount sensor detects the remaining amount of the liquid and generates an analog signal corresponding to the remaining amount of the liquid, and according to the analog signal as the detection signal. And a PWM output circuit for switching and outputting two constant current values with a duty ratio, thereby generating two constant current values alternately corresponding to the H level and L level signals of the PWM signal, and detecting signals To the signal line, and a stable detection signal can be transmitted to the processing apparatus side against external noise, wiring resistance, and the like.

  According to the present invention described in claim 4, in the processing apparatus, a current detection resistor is inserted in the energization path, and a detection signal indicating a voltage level generated in the current detection resistor is given to the control means. It becomes easy to detect the average current value of the detection signal.

  According to the fifth aspect of the present invention, the processing device is provided with the shaping circuit that shapes the detection signal indicating the voltage level and applies the waveform to the control means, thereby facilitating edge detection of the detection signal. By simplifying the reading process, it is possible to reduce the burden of the input process on the control means side.

  According to the sixth aspect of the present invention, the processing device includes the constant voltage circuit that stabilizes the potential between the first pole side of the remaining amount sensor and the output side of the detection signal of the remaining amount sensor. Thus, for example, even when the battery voltage fluctuates or external noise or the like gets on the first pole side of the battery, the potential in the above section can be stabilized. It is possible to use an element with a low withstand voltage, and the cost of the entire apparatus can be reduced.

  According to the seventh aspect of the present invention, the constant voltage circuit includes a series circuit of a Zener diode and a resistor, and the first pole side of the remaining amount sensor and the second pole side of the current detection resistor. Since a Zener diode is connected between the two sections, it is possible to stabilize both sections within a voltage range determined by the Zener voltage with a relatively simple configuration.

  Hereinafter, embodiments of the liquid level detection device for a vehicle of the present invention will be described. In this example, a case where the present invention is applied to a residual fuel detection device for detecting residual fuel in a fuel tank of a vehicle will be described as an example. However, the present invention can also be applied to liquid level detection of liquids other than fuel. .

(First embodiment)
FIG. 1 is a block diagram showing the overall configuration of a vehicle liquid level detection device according to a first embodiment of the present invention.

  In FIG. 1, the remaining fuel sensor 100 is disposed in an in-vehicle fuel tank. In this case, the remaining fuel sensor 100 is always connected to the (+) pole (first pole) side of the vehicle-mounted battery 300 without passing through the ignition switch 400. As a detection signal, a digital signal having a duty ratio indicating a current level corresponding to the amount of remaining fuel is output to the instrument body 200 which is a processing device via one wire harness L2 which is a signal line.

  In this case, the wiring length of the harness L1 connected to the (+) pole (first pole) side of the in-vehicle power source 300 is shortened by taking it from the power source closest to the remaining fuel sensor 100 in mounting the vehicle. It is possible.

  In the remaining fuel sensor 100, the constant voltage power supply 110 operates by connecting one end of the wire harness L2 to the ground side, that is, in this case, to the (−) pole (second pole) side of the battery 300 through the vehicle body. For example, a constant voltage of 5 V is applied to the Hall IC sensor 120 and the PWM output circuit 130. The Hall IC sensor 120 incorporates a Hall element and its signal processing circuit, and generates an analog voltage that changes according to the magnetic flux density of the magnetic flux passing through the Hall element. The magnetic flux density of this magnetic flux changes according to the float position indicating the remaining fuel amount as will be described later. The PWM circuit 131 generates a duty ratio corresponding to the analog voltage, in other words, a pulse width modulation signal (PWM signal) that generates an average current corresponding to the analog voltage, and the constant current switching circuit 132 generates an H of the PWM signal. The two constant current sources 1321 and 1322 are alternately switched corresponding to the level and L level signals, and two constant current values i1 and i2 are alternately generated and output to the harness L2 side as the detection signal S1.

  The meter body 200 includes a microcomputer 210 which is a control means for performing a remaining fuel amount detection process, a stabilized power supply 220 which adjusts the voltage of the battery 300 to generate a stabilized voltage of, for example, 5 V and supplies the stabilized voltage to the microcomputer 210, and various information. A display device 230 to be displayed, a sensor operation switch 240 serving as an opening / closing means connected in series in an energization path from the remaining fuel sensor 100 to the ground (second electrode of the battery 300) through the wire harness L2, and a wire harness And a current detection resistor 250 that detects a current flowing through L2 and generates a voltage corresponding to the current.

  The microcomputer 210 is always connected to the battery 300 and receives an on / off signal of the ignition switch 400. Although not shown, the microcomputer 210 detects and processes various information such as vehicle speed, engine speed, and cooling water temperature necessary for vehicle instrument display in addition to the remaining fuel amount detection process, and displays the display device 230. It is also used to control the display on the instrument panel in the passenger compartment. The switch 240 is composed of a bipolar transistor, a MOS transistor, a relay, or the like.

  Here, an example of a specific structure of the remaining fuel sensor 100 will be described with reference to FIG.

  In FIG. 2, the remaining fuel sensor 100 is fixed to a bracket 1 that hangs down from a ceiling inner surface (not shown) of a fuel tank of a vehicle. The float 2 is made of resin and is set so as to float on the liquid level 10 of the fuel. The left end is prevented from being removed by the snap ring 9 and is connected to the metal arm 3. The arm 3 is also connected to the magnet holder 4, and interlocks with the vertical movement according to the liquid level position 10 of the float 2, so that the magnet holder 4 rotates about the shaft portion 51 as a rotation axis.

  The magnet holder 4 is made of resin, and the movement in the left direction in FIG. 2 is restricted by the locking portion 53, and the magnet holder 4 is held rotatably on the body 5. A housing chamber 52 is formed inside the shaft portion 51, and a constant voltage power source 110, a Hall IC sensor 120, and a PWM output circuit 130 are mounted in the housing chamber 52. In this case, two external extraction terminals 6 are provided. A connector portion 54 having the shape is formed.

  The magnet 7 is fixed in close contact with the ferromagnetic cover 8, and a magnetic flux is applied in a direction intersecting the substrate surface of the Hall IC sensor 120 from the magnet 7. The magnetic flux density of the magnetic flux applied to the substrate surface is set so as to change according to the position of the magnet 7 that rotates according to the liquid surface position of the float 2.

  With the above configuration, the Hall IC sensor 120 generates an analog voltage of a level corresponding to the liquid level position, and the PWM output circuit 130 applies a (+) polarity battery voltage from the fuel pump side closest to one of the external extraction terminals 6. The detection signal S1 having a duty ratio (that is, a current level corresponding to the liquid surface position) corresponding to the analog voltage is output from the other external extraction terminal 6 toward the (−) pole side of the meter body 200. Become.

(Operation)
Next, the operation of the vehicle liquid level detection device shown in FIG. 1 will be described with reference to FIGS.

  First, when the ignition switch 400 is off, the microcomputer 210 opens (turns off) the sensor operation switch 240 (steps 501, 503, and 509). At this time, since the energization path from the remaining fuel sensor 100 is opened, the constant voltage power source 110 in the remaining fuel sensor 100 is not energized, and the remaining fuel sensor 100 stops operating. However, since the microcomputer 210 is always supplied with power, the microcomputer 210 performs necessary control as appropriate.

  Next, when the ignition switch 400 is turned on at time t1, the sensor operation switch 240 is turned on (steps 501 and 502), and the remaining fuel sensor 100 is operated. Therefore, the PWM output circuit 130 outputs a signal with a duty ratio corresponding to the analog voltage from the Hall IC sensor 120, and two constant current sources 1321, 1322 corresponding to the H level and L level signals of the PWM signal. Are switched alternately, and two constant current values i1 and i2 are alternately generated and output to the harness L2 side as a detection signal S1 (see FIG. 4C). Here, the detection signal S1 is shown as a signal in which the time width of the H level and the L level changes with respect to the fixed period T as a duty ratio. May be a modulated signal.

  Therefore, a voltage signal corresponding to the detection signal S1 is also input to the microcomputer 210. The microcomputer 210 measures T as a cycle and ts as an ON (H level) time, obtains a duty ratio from these, and stores them in the storage unit 211. In the second and subsequent times, the obtained duty ratio is averaged every predetermined number to reduce the influence of fluctuations in the detection signal S1 due to liquid level fluctuations (steps 504 to 506, FIG. 4C). (D)).

  Subsequently, based on this averaged average value, based on a predetermined average duty ratio-remaining fuel amount table, the remaining fuel amount is detected, stored in the storage means 211, and output to the display device 230 and the like. (Steps 507 and 508).

  Subsequently, at time t2, even if the ignition switch 400 is turned off, the sensor operation switch 240 is turned on for a predetermined time T0 (steps 502 and 503), and the above-described remaining fuel detection process is continued (steps 504 to 508). FIG. 4 (b)). At time t3, the sensor operation switch 240 is turned off, and the remaining fuel detection operation is stopped (steps 503 and 509).

  As this fixed time T0, in order to measure a more accurate remaining fuel amount, a value between several seconds to several minutes until the vehicle stops and the liquid level in the tank is stabilized is selected.

  As described above, according to the present invention, the remaining fuel sensor 100 is configured to generate the detection signal S1 of the digital signal indicating the average current level corresponding to the remaining fuel amount, that is, the current variable digital (PWM) signal. Thus, it is possible to reduce the influence on the detection accuracy due to the wiring resistance in the wire harness L2.

  In addition, an energization path is formed from the remaining fuel sensor 100 connected to the (+) pole of the battery 300 to the ground side of the instrument body 200 via the wire harness L2, and the detection signal S1 is transmitted (transmitted) from the remaining fuel sensor 100. ) And a power supply path that combines power supply from the (+) pole (first pole) side to the ground (second pole) side of the battery 300, so that the wire harness L <b> 2 between the two 100 and 200 is used. Thus, the instrument body 200 can control the operation of the remaining fuel sensor 100 and take in the detection signal S1 from the remaining fuel sensor 100.

  Further, in order to control the remaining fuel sensor 100 immediately after the ignition switch 400 is turned off, a sensor that opens and closes the above-described energization path on the instrument body 200 side without adding a new wire harness to the remaining fuel sensor 100. By controlling the operation switch 240, the remaining fuel sensor 100 can be easily controlled.

(Second Embodiment)
Next, FIG. 5 is a block diagram showing the overall configuration of the vehicle liquid level detection device according to the second embodiment of the present invention.

  The difference from the first embodiment is that the sensor operation switch 240 is connected to the ground side of the current detection resistor 250 in the energization path from the remaining fuel sensor 100 to the ground (second electrode of the battery 300) through the wire harness L2. And a pulse width modulation signal (PWM signal) of the detection signal S1 flowing through the wire harness L2 is caused to flow through the current detection resistor 250, and a comparator 260 for shaping the voltage generated at the current detection resistor 250 is provided. It is to have established.

  Accordingly, in the present invention, since the input side of the operational amplifier 261 of the comparator 260 has a high input impedance, it can be connected to the comparator 260 without generating a sneak current from the energization path, and the waveform of the detection voltage can be shaped. By doing so, the burden of input processing on the microcomputer 210 side can be reduced.

(Third embodiment)
Next, FIG. 6 is a block diagram showing an overall configuration of a vehicle liquid level detection device according to a third embodiment of the present invention.

  The difference from the first embodiment is that the sensor operation switch 240 is connected to the ground side of the current detection resistor 250 in the energization path from the remaining fuel sensor 100 to the ground (second electrode of the battery 300) through the wire harness L2. And a pulse width modulation signal (PWM signal) of the detection signal S1 flowing through the wire harness L2 is caused to flow through the current detection resistor 250, and a comparator 260 for shaping the voltage generated at the current detection resistor 250 is provided. And a constant voltage circuit 270 including a Zener diode 271 and a resistor 272 are provided, and the (+) pole (first pole) side of the remaining fuel sensor 100 and the ground (second second) of the current detection resistor 250 are provided. The zener diode 271 is connected to the pole) side, and a resistor for generating the threshold voltage of the comparator 260 Even across 62,263 is that of connecting the Zener diode 271.

  Accordingly, in the present invention, since the input side of the operational amplifier 261 of the comparator 260 has a high input impedance, it can be connected to the comparator 260 without generating a sneak current from the energization path, and the waveform of the detection voltage can be shaped. By doing so, the burden of input processing on the microcomputer 210 side can be reduced.

  Furthermore, in the present invention, even when the battery voltage increases due to external noise or the like, it is possible to prevent a voltage higher than the Zener voltage from being constantly applied to the remaining fuel sensor 100 side. Thus, the potential between the first pole of the remaining fuel sensor 100, that is, the (+) pole side of the battery 300 and the output side of the detection signal S1 of the remaining fuel sensor 100 including the current detection resistor 250 is stabilized. By providing the constant voltage circuit 270, an element having a low withstand voltage can be used in the remaining fuel sensor 100, and the cost of the entire apparatus can be reduced.

  In the present invention, any circuit configuration that does not use the Zener diode 271 and the resistor 272 may be applied as long as the circuit does not apply a voltage exceeding a specified value to the remaining fuel sensor 100.

1 is a block diagram illustrating an overall configuration of a vehicle liquid level detection device according to a first embodiment of the present invention. 2 is a schematic cross-sectional view showing an example of a specific structure of a remaining fuel sensor 100. FIG. It is a flowchart which shows the remaining fuel measurement process by the microcomputer 210. FIG. It is a timing chart used for description of a remaining fuel measurement process. It is a block diagram which shows the whole structure of the liquid level detection apparatus for vehicles used as the 2nd Embodiment of this invention. It is a block diagram which shows the whole structure of the liquid level detection apparatus for vehicles used as the 3rd Embodiment of this invention. It is a block diagram which shows the whole structure of the liquid level detection apparatus for vehicles which shows a prior art example.

Explanation of symbols

2 Float 4 Magnet holder 5 Body 7 Magnet 52 Storage chamber 100 Remaining fuel sensor (remaining amount sensor)
110 Constant voltage power supply 120 Hall IC sensor (Main part of liquid level sensor)
130 PWM Output Circuit 131 PWM Circuit 132 Constant Current Switching Circuit 200 Instrument Body (Processing Device)
210 Microcomputer (control means)
240 Sensor operation switch (open / close means)
250 Current detection resistor 260 Comparator (shaping circuit)
270 Constant voltage circuit 271 Zener diode 300 Battery 400 Ignition switch L2 Wire harness (signal line)

Claims (7)

A remaining amount sensor that is always connected to the first pole side of the battery mounted on the vehicle, detects the remaining amount of liquid in the tank, and outputs a detection signal according to the remaining amount;
A processing device that is arranged at a position different from the remaining amount sensor and detects the remaining amount of the liquid in the tank based on the detection signal of the remaining amount sensor;
Energization that connects the remaining amount sensor and the processing device and combines the transmission of the detection signal from the remaining amount sensor and the power supply from the first pole side to the second pole side of the battery Signal lines constituting the path,
The processing device is arranged in the energizing path to open and close the energizing path, and the opening / closing means is closed for a predetermined time immediately after the ignition switch of the vehicle is turned on and off. A liquid level detection device for a vehicle, comprising: a control unit that operates a quantity sensor and detects the remaining amount of the liquid based on the detection signal.   The liquid level detection device for a vehicle according to claim 1, wherein the remaining amount sensor outputs a digital signal having a duty ratio indicating a current level corresponding to the remaining amount of the liquid as the detection signal.   The remaining amount sensor detects a remaining amount of the liquid and generates an analog signal corresponding to the remaining amount of the liquid, and two detection ratios with a duty ratio corresponding to the analog signal. The liquid level detection device for a vehicle according to claim 1, further comprising a PWM output circuit that switches and outputs a current value.   3. The processing apparatus according to claim 2, wherein a current detection resistor is inserted in the energization path, and the detection signal indicating a voltage level generated in the current detection resistor is provided to the control means. The liquid level detection device for a vehicle according to claim 3.   The liquid level detection device for a vehicle according to claim 4, wherein the processing device includes a shaping circuit that shapes the detection signal indicating the voltage level and applies the waveform to the control means.   The processing apparatus includes a constant voltage circuit that stabilizes a potential between the first pole side of the remaining amount sensor and an output side of the detection signal of the remaining amount sensor. 5. The vehicle level detecting device according to 4.   The constant voltage circuit includes a series circuit of a Zener diode and a resistor, and the Zener diode is disposed between the first pole side of the remaining amount sensor and the second pole side of the current detection resistor. The liquid level detecting device for a vehicle according to claim 6, wherein:

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