JP3119333B2 - Failure detection device for driving state detection circuit for vehicle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure detecting device such as an operating condition detecting circuit for a vehicle, and more particularly, to a failure detecting device or the like without being affected by the circuit configuration of the operating condition detecting circuit or the like. The present invention relates to an improvement in a failure detection device capable of detecting a failure.

[0002]

2. Description of the Related Art Conventionally, there is a detection circuit as shown in FIG. 7 for detecting an operation state of a vehicle, for example, a remaining fuel amount. In FIG. 7, V indicates a power supply voltage, and an indicator lamp 2 having a resistor R1 is provided between the power supply and the ground.
A fuel remaining amount detecting fuel sender 21 having 0 and a resistance R2 is connected in series, and thereby a fuel remaining amount detecting circuit is configured.

As the fuel remaining amount sensor 21, a thermistor whose resistance value changes with temperature is used. This thermistor has a resistance value of about 100 times R1 at room temperature, and is capable of responding to temperature rise. A resistor whose resistance value is greatly reduced is used, and is installed in a fuel tank of a vehicle.

In this conventional fuel remaining amount detection circuit, when the fuel in the fuel tank is at or above the level at which the thermistor is mounted, the thermistor generates very little heat but is cooled by the fuel and its resistance value at room temperature The indicator does not light because it remains high. On the other hand, when the fuel becomes lower than the thermistor mounting level and the thermistor is no longer cooled by the fuel, the temperature rises and the resistance decreases, so that the indicator lights up to warn of an abnormality in the fuel remaining amount. I have.

[0005] Here, in the above-mentioned conventional fuel remaining amount detection circuit, when a disconnection or short circuit occurs, the indicator 20 is used.
Does not light up irrespective of the remaining amount of fuel, there is a possibility that the vehicle will run to a gas-out state. Therefore, it is conceivable to provide a failure detection device for detecting disconnection and short circuit of the fuel remaining amount detection circuit. This is because the control unit CU includes a reserve switch SW externally at the connection point between the resistors R1 and R2.
Are connected, and a failure is detected by a change in the partial pressure Vd represented by the following equation (1). That is, when the detection circuit is disconnected, the divided voltage Vd becomes approximately equal to the power supply voltage V. By comparing the divided voltage Vd with the normal divided voltage, it is possible to detect a failure such as the disconnection. Vd = R2 / (R1 + R2) × V (1)

More specifically, when the point A in FIG. 7 is disconnected, the divided voltage Vd becomes equal to the ground voltage, and when the point B in the figure is disconnected, the divided voltage Vd is not inputted to the control unit CU. Thus, both the disconnection at the points A and B are detected by the control unit CU.

[0007]

However, the above detection circuit cannot detect the case where the point C is disconnected. That is,
Since the resistance R2 is about 100 times as large as the resistance R1, it becomes R2 / (R1 + R2) ≒ 1, and the above-mentioned divided voltage Vd ≒ V even in a normal state. The disconnection of the point cannot be detected. This is true even when the resistance R2 is extremely small compared to R1.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has an object to detect a disconnection or the like when a disconnection or the like has occurred, and to thereby appropriately perform a fail-safe. It is intended to provide.

[0009]

According to a first aspect of the present invention, there is provided a vehicle driving system comprising: a first resistor connected in series between a power supply and a ground; and a second resistor having a resistance value much larger than the first resistor. In the failure detection device of the state detection circuit, a switch means is provided between the first and second resistors, and a pull-up resistor having a resistance value larger than the first resistance is directly connected to the second resistor. The switch is turned off, and a voltage dividing means for detecting a voltage divided between the second resistor and the pull-up resistor is provided.

According to a second aspect of the present invention, in the first aspect, the first resistor is connected to the power supply side and the second resistor is connected to the ground side, and the switch means is connected between the first and second resistors. It comprises a diode interposed so that the direction of the second resistance is the forward direction from the first resistance, and an NPN transistor connected between a connection point between the diode and the first resistance and the ground. The voltage dividing means is configured to turn on the NPN transistor at the time of a failure detecting operation.

According to a third aspect of the present invention, in the first aspect, the second resistor is connected to the power supply side and the first resistor is connected to the ground side, and the switch means is connected between the first and second resistors. The diode includes a diode interposed so that the direction of the first resistance from the second resistance is the forward direction, and a PNP transistor connected between a power supply and a connection point between the diode and the first resistance. The voltage detecting means is configured to turn on the PNP transistor during a failure detecting operation.

[0012]

According to the first aspect of the present invention, when a failure such as a disconnection is detected, the partial pressure detecting means turns off the switching means provided between the first and second resistors. Thus, a series circuit of the pull-up resistor and the second resistor is formed between the power supply and the ground to detect the divided voltage of the second resistor with the pull-up resistor, and the divided voltage value is compared with the divided voltage value in the normal state. The disconnection and the like are detected by comparison.

Thus, when a failure such as a disconnection is detected, the first
Since I switched between the resistor and the pull-up resistor,
Even when the value of the second resistor is much larger than the first resistor, it is possible to accurately detect an abnormality in the operation state detection circuit by comparing the divided voltage values, and to thereby reliably perform control such as fail-safe by the detection circuit. be able to.

According to the second and third aspects of the present invention, the switch means is composed of a transistor and a diode, and the transistor is turned on by the voltage division detecting means, thereby providing the first switch.
Switching between the resistor and the pull-up resistor can be realized quickly, accurately and with high reliability.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIGS. 1 to 4 are diagrams for explaining a failure detecting device of a vehicle operating condition detecting circuit according to a first embodiment of the present invention, and FIG. 1 is a schematic diagram of a configuration of an operating condition display device. FIG. 2 is a circuit diagram for explaining the failure detection device, FIG. 3 is a graph showing the display of the engine tachometer with respect to time during normal operation of the display device, and FIG. 4 is abnormal operation of the display device. It is a graph which shows the display of the engine tachometer with respect to time in time.

In FIG. 1, reference numeral 1 denotes an engine speed sensor for detecting an engine speed of a vehicle, and the speed sensor 1 is connected to a control unit 2. A display signal corresponding to the number of revolutions is generated to cause the tachometer 3 to display the engine revolution number in an analog manner.

In FIG. 2, V indicates a power supply voltage. An indicator lamp 5 having a resistor R1 and a fuel remaining amount detecting fuel sender 4 having a resistor R2 are connected in series between the power supply voltage V and the ground. Connected to form a fuel remaining amount detection circuit 6. Here, the resistance value of the resistor R2 at normal temperature is set to be much larger (for example, about 100 times) than the resistance value of the resistor R1. The thermistor 4 uses a thermistor whose resistance greatly decreases when the temperature rises.

The control unit 2 functions as abnormality detection means (failure detection device) for detecting an abnormality such as a disconnection of the fuel remaining amount detection circuit 6, and an abnormality detection signal when the abnormality is detected. Sg1 and abnormal code display signal Sg
2 also functions as an abnormal time display signal generating means. The abnormality detection signal Sg1 causes the engine tachometer 3 to display zero rotation, and the abnormality code display signal Sg2 causes the engine tachometer 3 to display rotation near the maximum rotation speed.

The fault detecting device includes a switch means 8 provided between the first and second resistors R1 and R2, and a connection point between the switch means 8 and the resistor R2 and the power supply. In addition, the pull-up resistor Rp having a resistance value substantially equal to the resistance R2 and the switch means 8 being turned off during the abnormality detection operation, and the pull-up resistor Rp of the resistor R2 represented by the equation (1) being added. And a partial pressure detecting means 7 for detecting the pressure Vd. Vd = R2 / (Rp + R2) × V (1)

The switch means 8 is connected between a diode 9 interposed so that the direction from the resistor R1 to the resistor R2 is a forward direction, and between a connection point between the diode 9 and the resistor R1 and ground. And an NPN transistor 10.

Next, the operation and effect of the display device of the first embodiment will be described. If the remaining fuel level is equal to or higher than the fuel sender 4 arrangement level, the resistance R2 is increased and the indicator lamp 5
Does not light up, but when the remaining fuel amount falls below the above level, the resistance R2 decreases and the indicator lamp 5 lights up,
This function of detecting the remaining amount of fuel is the same as the conventional one.

When the failure detection timing of the fuel remaining amount detection circuit 6 comes, the partial pressure detection means 7 turns on the transistor 10 for 10 ms, for example. Then, the diode 9 functions as a switching element to turn off between the resistors R1 and R2. The partial pressure Vd at this time is detected by the partial pressure detecting means 7. If the partial pressure Vd is approximately 1/2 V, it is normal, otherwise, it is determined that the fuel sender 4 is abnormal due to, for example, disconnection of the control unit 2 at point C shown in the drawing, and the control unit 2 After displaying zero rotation on the engine tachometer 3, rotation near the maximum rotation speed is displayed. The current flows through the indicator lamp 5 when the transistor 10 is turned on. When the ignition switch is turned on, the partial pressure detecting means 7 sets the transistor 10 to 1.
It is turned on for about 4 seconds, and the indicator lamp 5 is turned on. Thus, the disconnection of the indicator lamp 5 itself can be checked.

Here, the abnormality detection display and the abnormality code display by the engine tachometer 3 will be specifically described with reference to FIGS. When the vehicle is operating normally, the display of the rotation speed of the tachometer 3 changes as shown in a graph G1 in FIG. On the other hand, when the control unit 2 detects an abnormality such as disconnection of the fuel sender 4, the abnormality detection signal Sg
1 and the subsequent error code display signal Sg2. Thus, as shown in the solid line graph G2 in FIG. 4, the tachometer 3 displays 0 rpm for 1 second indicating abnormality detection, and then displays 8000 rpm for 2 seconds near the maximum rotation speed indicating a fuel sender disconnection, Thereafter, the detected engine speed is displayed for 3 seconds, and this cycle is repeated. When displaying multiple types of codes,
Different error codes are displayed in order for each cycle.

As described above, in the first embodiment, the resistance R
1 and a resistor R2, a switch means 8 including a diode 9 and an NPN transistor 10 is provided, and the resistor R2 is switched between the resistor R1 and the pull-up resistor Rp.
Is detected, the abnormality such as the disconnection of the fuel remaining amount detection circuit 6 can be accurately detected even when the resistance R2 is much larger than R1.

Further, when the control unit 2 detects an abnormality on the fuel sender 4 side, an abnormality is displayed on the engine tachometer 3, so that an abnormality can be displayed without providing a dedicated indicator. Then, in this abnormal display, after displaying 0 rpm on the engine tachometer, 8000 rpm is displayed. Therefore, it is determined whether or not the display of the engine tachometer 4 is an abnormal code at the time of abnormality. It can be done easily. Also,
It is also possible to display a plurality of different abnormality codes.

Next, referring to FIG. 5, a description will be given of a failure detecting device for a vehicle operating state detecting circuit according to a second embodiment of the present invention. FIG. 5 is a circuit diagram for explaining the detection device, and the same reference numerals as those in FIG. 2 indicate the same or corresponding parts. This embodiment is an example in which the fuel sender 4 of the device of the first embodiment is provided on the power supply side, and the switch means 8a of this embodiment is provided so that the direction from the resistor R2 to the resistor R1 is the forward direction. PN connected between a power supply and a diode 9a, and a connection point between the diode 9 and the resistor R1.
The pull-up resistor Rp is connected between the connection point of the switch means 8a and the resistor R2 and the ground.

Next, the operation and effect of the display device according to the second embodiment will be described. The operation of detecting the remaining amount of fuel is the same as in the first embodiment. Further, at the time of failure detection, the partial pressure detecting means 7 turns off the switch means 8a and detects the partial pressure Vd. Based on the partial pressure value, the C shown in FIG. An abnormality due to a broken wire or the like is detected and displayed on the engine tachometer 3 in the same manner as described above.

As described above, even when the fuel sender 4 is provided on the power supply side, an abnormality on the fuel sender 4 side can be detected as in the first embodiment provided on the ground side.
It can be displayed on the engine tachometer 3.

Next, a third embodiment according to the first and second aspects of the present invention will be described with reference to FIG. FIG. 6 is a circuit diagram for explaining the apparatus of this embodiment, and the same reference numerals as those in FIG. 2 indicate the same or corresponding parts. In this embodiment, the fall detection circuit 11
1 is an example of a failure detection device that detects a disconnection or the like of a device. The fall detection circuit 11 includes an indicator 5 having a resistance R1 and a second
A fall detection switch S that is turned on when a fall occurs with the resistor R2
W1.

When the vehicle falls and the fall detection switch SW1 is connected, the indicator 5 is turned on and the control unit 2 performs a fall control such as stopping the engine as a retreat action when the vehicle falls and the fall detection switch SW1 is connected. It has become.

Further, at the time of failure detection, similarly to the first embodiment, the partial pressure detecting means turns off the switch means and detects the partial pressure Vd. Then, an abnormality in the overturn detection circuit 11 is detected based on the partial pressure value,
Display on the engine tachometer 3 as described above.

In the third embodiment, the resistance R2 is
Although the example in which it is provided on the ground side as in the first embodiment has been described, it may be provided on the power supply side as in the second embodiment.

[0033]

As described above, according to the failure detecting device for the vehicle operating condition detecting circuit according to the first aspect of the present invention, since the switching device, the pull-up resistor and the partial pressure detecting device are provided,
The switch means can switch between the first resistor and the pull-up resistor to detect the voltage division on the second resistor side, thereby detecting an abnormality such as a disconnection on the operation state detection circuit side of the first and second resistors. There is an effect that can be detected regardless of the value.

According to a second aspect of the present invention, there is provided a failure detecting device for a driving state detecting circuit for a vehicle, wherein the switching means comprises a diode and a transistor, and the transistor is turned on by the voltage dividing detecting means. Because
The switching between the first resistor and the pull-up resistor can be performed quickly and accurately, and there is an effect that abnormality detection such as disconnection on the operation state detection circuit side can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a configuration of a failure detection device of a vehicle operation state detection circuit according to a first embodiment of the present invention;

FIG. 2 is a circuit diagram for explaining the device of the first embodiment.

FIG. 3 is a characteristic diagram for explaining a display of an engine tachometer in a normal state of the first embodiment.

FIG. 4 is a characteristic diagram for explaining a display of an engine tachometer when the device of the first embodiment is abnormal.

FIG. 5 is a circuit diagram for explaining an apparatus according to a second embodiment of the present invention;

FIG. 6 is a circuit diagram for explaining a device according to a third embodiment of the present invention;

FIG. 7 is a circuit diagram for explaining a conventional vehicle operating state detection circuit.

[Explanation of symbols]

2 Control unit (failure detection device, abnormality detection means) 6,11 Fuel remaining amount detection circuit, overturn detection circuit (vehicle operation state detection circuit) 7 Partial pressure detection means 8,8a Switch means 9,9a Diode 10 NPN transistor 10a PNP transistor R1 First resistor R2 Second resistor Rp Pull-up resistor

Claims (3)

(57) [Claims] A first resistor connected in series between a power supply and a ground; and a second resistor having a resistance that is significantly larger than the first resistor. Switch means is provided between the first and second resistors, and a pull-up resistor having a larger resistance value than the first resistor is connected to the second resistor.
A driving state for a vehicle, comprising: a voltage dividing means connected in series with a resistor for turning off the switch means at the time of a failure detecting operation and detecting a partial pressure of the second resistor with a pull-up resistor. Failure detection device for the detection circuit. 2. The device according to claim 1, wherein the first resistor is connected to a power supply, and the second resistor is connected to a ground.
The switch means includes a diode interposed between the first and second resistors so that a direction from the first resistor to the second resistor is forward, and a connection point between the diode and the first resistor and ground. And an NPN transistor connected between the NPN transistors.
A failure detection device for a vehicle operation state detection circuit, wherein the failure detection device is configured to turn on an N transistor. 3. The device according to claim 1, wherein the second resistor is connected to a power supply, and the first resistor is connected to a ground.
A diode interposed between the first and second resistors so that the direction of the first resistance is the forward direction from the second resistor; and a connection point between the diode and the first resistor and a power supply. And a PNP transistor connected between the PNP transistors.
A failure detection device for a driving state detection circuit for a vehicle, wherein the failure detection device is configured to turn on a transistor.