JP2014006172A - Measuring apparatus for on-vehicle use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measuring apparatus for on-vehicle use that can give highly accurate measurements irrespective of any ground potential difference.SOLUTION: A measuring apparatus for on-vehicle use comprises: signal wiring E connected to the ground on the vehicle body side via a fuel sensor C that varies a resistance Rs according to the remaining quantity of fuel in a fuel tank of a vehicle; control means 2 that measures the remaining quantity of fuel on the basis of a detection signal from the signal wiring E; a power supply unit 1 that is connected to the signal wiring E and supplies electric current to the fuel sensor C via a pull-up resistor; and switching means 3 that, regarding the resistance of the pull-up resistor, switches over between a first resistance Ra and a second resistance Rb different from the first resistance Ra on the basis of a control signal from the control means 2.

Description

  The present invention relates to a vehicle measurement device, and can be applied to, for example, a vehicle measurement device that notifies a vehicle user of a detection signal from a vehicle-mounted sensor as vehicle information.

  A conventional vehicle measuring device is disclosed in Patent Document 1, for example. This vehicle measuring device includes a fuel sensor that outputs a change in vehicle fuel as a resistance value change (analog signal), and a calculation that calculates a measured amount by sampling the analog signal at a predetermined period and converting it into a digital signal. It is comprised from a process part and detects a fuel remaining amount.

Japanese Patent Laid-Open No. 10-122929

  However, the vehicular measuring device described in Patent Document 1 is often located at a position where the fuel sensor and the measuring device are separated from each other, and the ground potential of the fuel sensor and the ground potential of the measuring device do not always coincide with each other. When there is a difference between the ground potential of the fuel sensor and the ground potential of the measuring device, there is a problem that it is impossible to detect a measured amount with high accuracy.

  For example, there may be a difference between the ground potential on the fuel sensor side and the ground side on the instrument side including the arithmetic processing unit due to the influence of a high load such as a headlight, which greatly affects the measured value. For this reason, it is conceivable that the ground on the fuel sensor side and the ground on the arithmetic processing unit are connected by a harness to eliminate the difference in ground potential, but as the number of connection lines from the fuel sensor to the instrument increases, There is a problem that not only the routing becomes complicated, but also the cost and weight of the vehicle are increased.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above problems and to calculate a highly accurate measurement value regardless of the ground potential difference.

  The vehicle measuring device according to the present invention includes a signal wiring connected to a ground on the vehicle body side via a detection unit that changes a resistance value according to a vehicle state, and a state of the vehicle based on a detection signal from the signal wiring. A control means for measuring the power supply, a power supply section connected to the signal wiring and supplying current to the detection means via a pull-up resistor, a first resistance value in the pull-up resistor, and the first resistance Switch means for switching a second resistance value different from the value based on a control signal from the control means.

  Further, the control means is based on the detection signal in the state pulled up through the resistor having the first resistance value and the detection signal in the state pulled up through the second resistance value. The vehicle state is calculated.

  The present invention relates to a vehicular measurement apparatus, and an object thereof is to calculate a highly accurate measurement value with a simple configuration regardless of a change in ground potential of an in-vehicle sensor.

The figure which shows the circuit structure in embodiment of this invention. The figure shown about the operation example based on the various signals of embodiment same as the above. The figure which shows the circuit structure of the other example of embodiment same as the above.

  Hereinafter, as an embodiment of the present invention, an example applied to a vehicle instrument device will be described with reference to the drawings.

  A vehicle instrument device (vehicle measurement device) A uses a vehicle-mounted battery B as a driving power source to notify a vehicle user of measured values (vehicle states) detected by various sensors. It has a meter. In this case, the vehicle display device A supplies a current to a fuel sensor (detecting means) C used for measuring the remaining amount of fuel for operating the fuel gauge.

  As the fuel sensor C, a liquid level sensor provided in a fuel tank of a vehicle can be applied, and the float floats and sinks as the fuel changes, for example, on a resistor printed on a base substrate made of a ceramic substrate or the like. A slider that slides in synchronization with the movement of the float and detects a change in the resistance value of the resistor can be applied. In this case, one end of the resistor of the fuel sensor C is connected to the ground on the vehicle body side, and the other end is connected to the signal wiring E that connects to the vehicle instrument device A.

  As shown in FIG. 1, the vehicular instrument device A includes a power supply unit 1, a control unit 2, a switch unit 3, and a display unit 4.

  The power supply unit 1 includes a power supply wiring F connected to the in-vehicle battery B and a diode. The power supply unit 1 inputs and outputs driving power of the vehicle instrument device A and supplies current to the fuel sensor C through a pull-up resistor. . The power supply wiring F is connected to the vehicle side equipment (the vehicle battery B and the fuel sensor C) through the connector together with the signal wiring E.

  The control means 2 can be applied with calculation means such as a microcomputer, and is based on a program stored in a storage unit such as a ROM, vehicle information input via an input / output interface, and a voltage detection signal. 4 can be used to generate and issue a control signal that prompts a desired output including the remaining amount of fuel. For example, the control unit 2 is also used as a control unit for causing the display unit 4 to display information such as the vehicle speed and the travel distance.

  The switch means 3 can be a transistor such as an FET, can switch between two resistance values in the pull-up resistor based on a control signal from the control means 2, and changes the power supplied to the fuel sensor C. It is. In this case, as the pull-up resistor, two resistance elements connected in series are prepared, and the switch means 3 supplies a current via a resistance element having a resistance value (first resistance value) Ra and a combined resistance value. (Second resistance value) The current supply through the two resistance elements Rb is switched.

  The display means 4 can be a fuel gauge that displays the remaining amount of fuel based on a control signal from the control means 2, and may be a display device that displays an image such as a liquid crystal panel or an organic EL panel. It may be a pointer indicator that can be read in comparison with a pointer that rotates in response to the indicator portion such as a scale or a numerical value that is the target of the pointer.

  Next, a method for calculating the remaining amount of fuel by the control means 2 will be described.

  The control means 2 controls to switch the resistance value of the pull-up resistor alternately by turning on / off the switch means 3 at a predetermined cycle (for example, every 100 milliseconds). Further, the control means 2 detects the potential of the signal wiring E when the switch means 3 is in the on state, that is, when the current is supplied from the power supply unit 1 to the signal wiring E via the resistance value Ra. Enter as. Then, the control means 2 detects the potential of the signal wiring E when the switch means 3 is in the off state, that is, when the current is supplied from the power supply unit 1 to the signal wiring E via the combined resistance value Rb. Enter as Vy.

  The control means 2 receives the output voltage Ve of the power supply unit 1 and can calculate the resistance value Rs of the fuel sensor C from the output voltage Ve and the two detection signals Vx and Vy. .

  Rs = (Vx−Vy) / [(Ve−Vx) / Ra− (Ve−Vy) / Rb] Equation 1

  For example, since the resistance value Rs can be calculated based on the above equation 1, even if there is a difference between the ground potential on the fuel sensor C side and the ground potential on the control means 2 side, the accurate fuel sensor C The resistance value Rs can be calculated, and the remaining fuel amount can be accurately measured by separately calculating the remaining fuel amount based on the resistance value Rs. Moreover, the control means 2 performs the process which controls the display means 4 so that this fuel remaining amount may be displayed.

  The calculation of the remaining amount of fuel takes into account the liquid level fluctuations during vehicle travel and the like by averaging the calculated values (Rs0, Rs1,... Rsn) of the fuel sensor C a plurality of times in the past. The value Rs is calculated. Further, as the remaining amount of fuel, in addition to the measurement of the remaining amount in the fuel tank based on the resistance value Rs of the fuel sensor C, information on the fuel consumption (fuel injection amount) from the engine control unit is also used to determine the remaining amount of fuel. It is also possible to increase accuracy by computing The sampling of the detection signals Vx and Vy is preferably as short as possible (for example, 10 to 100 milliseconds) in consideration of the liquid level fluctuation.

  ΔVg = [Vy (Ve−Vx) Ra−Vx (Ve−Vy) Rb] / [(Ve−Vx) Ra− (Ve−Vy) Rb] Equation 2

  Further, since the potential difference ΔVg between the fuel sensor C side and the control means 2 side can be calculated by the above formula 2, an abnormal state can be estimated, for example, when there is a large potential difference of 1 V or more. . When the control unit 2 determines the abnormal state, the control unit 2 determines that the fuel sensor C is unreliable, stops the display of the remaining amount of fuel by the display unit 4, and sets a value different from the measured value (for example, zero point). Controls such as displaying or displaying an alarm can be performed.

  Such a vehicle meter device A includes a signal wiring E connected to the ground on the vehicle body side via a fuel sensor C that changes a resistance value Rs in accordance with the remaining amount of fuel in the fuel tank of the vehicle, A control means 2 for measuring the fuel remaining amount based on a detection signal, a power supply unit 1 connected to the signal wiring E and supplying a current to the fuel sensor C via a pull-up resistor, and a resistance of the pull-up resistor Switch means 3 for switching a first resistance value Ra with respect to a value and a second resistance value Rb different from the first resistance value Ra based on a control signal from the control means 2.

  Therefore, even when the ground potential of the fuel sensor C and the ground potential of the vehicular instrument device A do not match, it is possible to detect a measured amount with high accuracy. For example, even when there is a difference between the ground potential on the fuel sensor C side and the ground side on the instrument side including the control means 2 due to the influence of a high load such as a headlight, the wiring of the harness is complicated. The remaining amount of fuel can be detected with high accuracy with a simple configuration without increasing the cost and weight of the vehicle.

  Further, the control means 2 includes a detection signal Vx pulled up through a resistor having a first resistance value Ra, and a detection signal Vy pulled up through a resistor having a second resistance value Rb. By calculating the fuel remaining amount based on the above, it is possible to detect the remaining fuel amount with high accuracy regardless of the ground potential difference due to the variation in the ground potential on the fuel sensor C side with a simple configuration.

  The vehicle measurement device of the present invention has been described by way of example in the configuration of the embodiment described above, but the present invention is not limited to this, and the gist of the present invention is also provided in other configurations. It goes without saying that various improvements and display changes can be made without departing from the scope. For example, even if it is not the calculation of the resistance value according to the above-described formula 1, it can be realized by a calculation that approximates this or calculation based on table data, and the same effect as the above-described embodiment can be obtained. .

  Further, as shown in FIG. 3, a stabilized power source may be used as the power supply unit 10. In this case, since the output voltage Ve is constant, it is not necessary to detect this voltage value, and it is easier. This is advantageous in that the calculation process becomes simple. In FIG. 3, the same parts as those of the above-described embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In addition, an example using two resistance elements connected in series as a pull-up resistor has been described, but any configuration that can switch between two types of resistance values Ra and Rb may be used. For example, as shown in FIG. In addition, a plurality of transistors 31 and 32 respectively corresponding to resistance elements having different resistance values Ra and Rb can be used for switching. In this case, the current supply to the fuel sensor C can be stopped when the detection signals Va and Vb are not required to be input.

  Moreover, in embodiment mentioned above, although the fuel meter was mentioned as an example and it demonstrated taking as an example what measured the fuel remaining amount as a state of a vehicle, it is applicable also to the water temperature meter using a thermistor.

  The present invention relates to a vehicle measuring apparatus, for example, a vehicle using an in-vehicle sensor that detects a change in a resistance value such as a fuel gauge or a water temperature gauge mounted on a moving body including an automobile, a motorcycle, an agricultural machine or a construction machine It can be applied to a measuring instrument.

DESCRIPTION OF SYMBOLS 1 Power supply part 2 Control means 3 Switch means 4 Display means A Vehicle measuring device (vehicle measuring device)
B On-board battery C Fuel sensor (detection means)

Claims (2)

A signal wiring connected to the ground on the vehicle body side via a detecting means that changes a resistance value according to the state of the vehicle;
Control means for measuring the state of the vehicle based on a detection signal from the signal wiring;
A power supply unit connected to the signal wiring and supplying a current to the detection means via a pull-up resistor;
Switch means for switching between a first resistance value in the pull-up resistor and a second resistance value different from the first resistance value based on a control signal from the control means;
A vehicular measuring device.   Based on the detection signal in a state pulled up through the resistor having the first resistance value and the detection signal in the state pulled up through the second resistance value, the control means The vehicle measuring device according to claim 1, wherein the state is calculated.

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