JP3748514B2 - Sensor state detection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sensor state detection device that detects the state of a sensor that is supplied with power from the outside and detects a change in the state of a detection target.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a steering angle detection circuit using a steering angle sensor composed of an open collector output type sensor that detects a steering angle of a vehicle steering device as a detection target is configured as shown in FIG.
[0003]
FIG. 2 shows only the steering angle sensor S for one phase composed of an open collector output type sensor. However, in reality, a steering angle sensor for another phase is provided, and both steering angle sensors S are used in the vehicle. Since the basic circuit configuration is the same for both sensors, only the configuration for one phase will be described below.
[0004]
As shown in FIG. 2, the power supply terminal of the steering angle sensor S is connected to a positive power source Vcc formed from a battery (not shown) via the power supply terminal Tb, and the emitter of the transistor constituting the steering angle sensor S is grounded. One end of the current limiting resistor R1 is connected to the collector of the rudder angle sensor S, and the collector of the rudder angle sensor S is grounded via the voltage dividing resistor R2. Here, a sensor unit SU is constituted by the steering angle sensor S, the power supply terminal Tb, the current limiting resistor R1, and the voltage dividing resistor R2. The power supply terminal Tb is connected to the positive power supply Vcc via the power supply line BL.
[0005]
As shown in FIG. 2, one end of a pull-up resistor R3 is connected to the positive power source Vcc, and the other end of the pull-up resistor R3 is connected to the other end of the pull-up resistor R3 by the output line OL of the sensor unit SU. It is connected. Further, the potential Vin at the point A, which is the other end of the pull-up resistor R3, is input to the analog / digital port of the interface circuit IF composed of a dedicated IC having a resistor and an inverting circuit through the input resistor R4. The signal is input to an analog / digital port of a microcomputer (hereinafter referred to as a microcomputer) MC through a resistor R5.
[0006]
Then, the interface circuit IF compares the potential Vin at the point A with a preset first reference level Vt1, detects the on / off state of the steering angle sensor S, and inputs the detection result to the microcomputer MC. Further, the microcomputer MC compares the potential Vin at the point A with the second reference level Vt2 and the third reference level Vt3 set in advance, the ground fault of the output line OL of the sensor unit SU, and the disconnection of the output line OL. This state is detected by the microcomputer MC.
[0007]
[Problems to be solved by the invention]
However, in the above-described conventional steering angle detection circuit, when the power supply line BL connecting the power supply terminal Tb of the steering angle sensor S and the positive power supply Vcc is disconnected, the potential Vin at the point A is equal to the steering angle sensor described above. Since S is the same as when S is off, it is impossible to detect an abnormality such as disconnection of the power supply line BL.
[0008]
As described above, in the conventional configuration, the power supply terminal Tb and the positive power supply Vcc are connected even if the rudder angle sensor S is turned on and off, and the disconnection or ground fault of the output line OL of the sensor unit SU can be detected. Since the disconnection of the power supply line BL cannot be detected, there is a problem in that the steering angle sensor S is determined to be in an OFF state even though the disconnection of the power supply line BL has occurred, causing a malfunction. Further, such a problem is not limited to the steering angle sensor S, and may be caused in any case as long as the sensor is configured to operate by being supplied with power from the outside.
[0009]
SUMMARY OF THE INVENTION An object of the present invention is to make it possible to easily identify and detect a disconnection of a line connecting a power supply terminal of a sensor and an external power source as on / off of the sensor.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides the sensor, a power supply terminal connected to an external positive power source, a current limiting resistor connected to the sensor at one end, and a divided voltage connected to the sensor at one end. A sensor unit including a resistor and a switching element provided between the voltage dividing resistor and the ground and having a control terminal connected to the power supply terminal; and both ends of the positive power source and the current limiting resistor A pull-up resistor connected to an output line of the sensor unit on the side and constituting a voltage dividing circuit together with the current limiting resistor and the voltage dividing resistor, and the switching element is turned on when the sensor is turned on and off, and the positive power supply The first voltage level and the second level appearing at the detection terminal in accordance with the ON / OFF state of the sensor are identified by the voltage division of the voltage dividing circuit, and the ground fault of the output line is detected. A third level different from the first and second levels appearing at the detection terminal at a time when the output line is disconnected and a line between the power supply terminal and the positive power supply is disconnected. And a level identifying unit for identifying a fourth level different from the first to third levels that appear.
[0011]
According to such a configuration, when the sensor is turned on and off, the switching element of the sensor unit is turned on, and the voltage value of the positive power supply is controlled by the voltage dividing circuit configured by the current limiting resistor, the voltage dividing resistor, and the pull-up resistor. Divided pressure. At this time, the first level appears at the detection terminal when the sensor is on, and the second level appears at the detection terminal when the sensor is off. When the sensor output line is grounded, a third level different from the first and second levels appears at the detection terminal, and when the sensor unit output line is disconnected, a fourth level appears at the detection terminal. Further, when the line between the power supply terminal of the sensor unit and the positive power supply is disconnected, the power supply to the sensor is cut off, the sensor stops operating, the switching element of the sensor unit is turned off, and the fourth terminal is connected to the detection terminal. A level appears.
[0012]
Therefore, the disconnection of the line connecting the power supply terminal of the sensor and the external power supply can be easily identified by detecting whether the sensor is on or off, and also by detecting the ground fault of the output line of the sensor unit. can do.
[0013]
Further, the present invention is characterized in that the sensor is a steering angle sensor including an open collector output type sensor that detects a steering angle of a vehicle steering device as the detection target.
[0014]
According to such a configuration, it is possible to detect on / off of the rudder angle sensor composed of an open collector output type sensor that operates by being supplied with power from the outside, and detects a fault such as a ground fault or a disconnection in distinction from these on / off. In addition, disconnection of the power supply line to the sensor can also be detected.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention applied to a steering angle sensor composed of an open collector output type sensor that detects a steering angle of a vehicle steering device as a detection target will be described with reference to the connection diagram of FIG. To do.
[0016]
FIG. 1 shows only a steering angle sensor for one phase composed of an open collector output type sensor as in the case of FIG. 2 showing the conventional example, but in reality, a steering angle sensor for another phase is provided. Since both steering angle sensors are arranged 90 degrees out of phase with respect to the vehicle's steering axis, the basic circuit configuration of both sensors is the same. Only the structure of the minute will be described.
[0017]
As shown in FIG. 1, the power supply terminal of the rudder angle sensor 1 is connected to a positive power source Vcc formed from a battery (not shown) via a power supply terminal 2, and the emitter of the transistor constituting the rudder angle sensor 1 is grounded. One end of the current limiting first resistor 3 is connected to the collector of the rudder angle sensor 1.
[0018]
Further, a second voltage dividing resistor 4 and an NPN transistor 5 as a switching element are connected between the collector of the rudder angle sensor 1 and the ground, and the base of the transistor 5 is connected to the power source via the third current limiting resistor 6. Connected to the supply terminal 2. Here, a sensor unit 7 is constituted by the steering angle sensor 1, the power supply terminal 2, the first resistor 3, the second resistor 4, the transistor 5, and the third resistor 6. The power supply terminal 2 is connected to the positive power supply Vcc via the power supply line 9.
[0019]
As shown in FIG. 1, one end of a fourth pull-up resistor 10 is connected to the positive power source Vcc (for example, +5 V), and the other end of the fourth resistor 10 is connected to the output line 11 of the sensor unit 7. The other end of the first resistor 3 is connected. Furthermore, the potential Vin of the detection terminal P which is the other end of the fourth resistor 10 is connected to the analog / digital of the interface circuit 14 formed of a dedicated IC (integrated circuit) having a resistor and an inverting circuit through the input fifth resistor 13. In addition to being input to the port, it is input to the analog / digital port of the microcomputer 16 via the input sixth resistor 15. Here, the interface circuit 14 and the microcomputer 16 constitute a level identification unit.
[0020]
Then, the interface circuit 14 compares the potential Vin of the detection terminal P with a preset first reference level Vt1 (for example, +2.5 V), and detects whether the steering angle sensor 1 is on or off. The detection result is input to the microcomputer 16, and the microcomputer 16 compares the potential Vin of the detection terminal P with the second reference level Vt2 (≈0V) and the third reference level Vt3 (≈5V) set in advance. The microcomputer 16 detects the ground fault of the output line 11 of the unit 8 and the disconnection of the output line 11 or the disconnection of the power supply line 9 connecting the power supply terminal 2 and the positive power supply Vcc. Yes.
[0021]
Next, the detection operation will be described in detail. First, a case where the power supply line 9 is not disconnected will be described. Here, since the power supply line 9 is not disconnected, the transistor 5 is in an on state.
[0022]
In this state, when the steering angle sensor 1 is on, the second resistor 4 is short-circuited, so that the potential Vin of the detection terminal P is obtained by dividing the voltage value of the positive power supply Vcc between the fourth resistor 10 and the first resistor 3. The first level Vi1 is divided by the pressure circuit, and the first level Vi1 and the first reference level Vt1 are compared by the interface circuit 14. As a result, Vi1 <Vt1 is established and the steering angle sensor 1 is identified as ON. .
[0023]
At this time, the microcomputer 16 compares the first level Vi1 of the detection terminal P with the second and third reference levels Vt2 and Vt3, but the second reference level Vt2 is approximately 0V and the third reference level Vt3 is approximately 5V. Therefore, Vt2 <Vi1 <Vt3, and the comparison result by the microcomputer 16 and the comparison result by the interface circuit 14 are combined to identify whether the steering angle sensor 1 is on.
[0024]
On the other hand, when the rudder angle sensor 1 is off, the voltage level of the positive power supply Vcc becomes the second level Vi2 obtained by dividing the voltage value of the fourth, first, and second resistors 10, 3, and 4, and this second level. Vi2 is compared with the first reference level Vt1, and as a result, Vi2> Vt1 is established, and turning off of the steering angle sensor 1 is identified.
[0025]
At this time, the microcomputer 16 compares the second level Vi2 of the detection terminal 12 with the second and third reference levels Vt2 and Vt3, resulting in Vt2 <Vi2 <Vt3. The comparison result of the microcomputer 16 and the interface circuit 14 Together with the comparison result, the turning-off of the rudder angle sensor 1 is identified.
[0026]
Further, when the output line 11 of the sensor unit 7 is grounded, the fourth and fifth resistors 10 and 15 and the detection terminal P are grounded. Therefore, the detection terminal P has a third potential substantially equal to the ground potential (= 0 V). A level Vi3 is generated. As a result of comparison between the third level Vi3 and the second reference level Vt2 (≈0V), the ground fault of the output line 11 of the steering angle sensor 8 is identified by the microcomputer 16.
[0027]
At this time, the interface circuit 14 compares the third level Vi3 of the detection terminal P with the first reference level Vt1 and determines that the steering angle sensor 8 is on from the result of Vi3 <Vt1. The ground fault of the output line 11 of the steering angle sensor 1 is identified by combining the comparison result and the comparison result by the interface circuit 14.
[0028]
Subsequently, when the output line 11 of the rudder angle sensor 1 is disconnected or has a power fault (shorted to the positive power supply Vcc), a fourth level Vi4 substantially equal to the positive power supply Vcc (= 5 V) is generated at the detection terminal P. As a result of the comparison between the fourth level Vi3 and the third reference level Vt3 (≈5V), the microcomputer 16 identifies the disconnection or power fault of the output line 11 of the steering angle sensor 1.
[0029]
At this time, the interface circuit 14 compares the fourth level Vi4 of the detection terminal P with the first reference level Vt1 and determines that the rudder angle sensor 1 is turned off from the result of Vi4> Vt1. The disconnection or the power fault of the output line 11 of the rudder angle sensor 1 is identified by combining the comparison result and the comparison result by the interface circuit 14.
[0030]
Next, a case where the power supply line 9 is disconnected will be described. Now, when the power supply line 9 is disconnected, the transistor 5 is turned off. With the transistor 5 turned off, the positive power supply Vcc (= 5 V) is applied to the detection terminal P as in the case of the disconnection of the output line 11 of the steering angle sensor 1 or the power failure. ) Is generated, which is substantially equal to the first level Vi4). As a result of comparison between the fourth level Vi3 and the third reference level Vt3 (≈5V), and the fourth level Vi4 of the detection terminal P by the interface circuit 14 and the first level Vi4. Based on the result of the comparison with the reference level Vt1, the disconnection of the power supply line 9 is identified by the microcomputer 16.
[0031]
However, although it cannot be distinguished whether the failure in this case is a disconnection (or power supply) of the output line 11 of the rudder angle sensor 1 or a disconnection of the power supply line 9, at least the positive power supply Vcc (= It can be determined that a failure has occurred in which a fourth level Vi4 that is substantially equal to 5V) occurs.
[0032]
Therefore, according to the first embodiment described above, in addition to turning the steering angle sensor 1 on and off, it is possible to identify the ground fault of the output line 11 of the sensor unit 7 as well as the output line 11. It is possible to detect a disconnection (or power fault) or a disconnection of the power supply line 9 clearly from these failures, and prevent a malfunction of the vehicle steering device that operates based on the output of the steering angle sensor 1. And the reliability of the steering device can be improved.
[0033]
In the first embodiment described above, the switching element constituting the sensor unit 7 has been described as the transistor 5, but it is needless to say that the switching element is not particularly limited to the transistor.
[0034]
Further, in the first embodiment described above, an example in which the present invention is applied to the steering angle sensor 1 that is an open collector output type sensor that detects the steering angle of the vehicle steering device is shown. The applicable open collector output type sensor is not limited to such a steering angle sensor, and can be applied to any sensor as long as it is configured to operate with power supplied from outside. It is possible and the same effect as the above-described embodiment can be obtained.
[0035]
The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention.
[0036]
【The invention's effect】
As described above, according to the first aspect of the present invention, the disconnection of the line connecting the power supply terminal of the sensor and the external power supply can be easily identified and detected as the on / off state of the sensor. In addition, it is possible to identify and detect the ground fault of the output line of the sensor unit, so that it is possible to prevent malfunction of a device that operates based on the sensor output, and to improve the reliability of such a device. It becomes possible.
[0037]
According to the second aspect of the invention, it is possible to distinguish and detect a failure such as a ground fault or disconnection in addition to turning on and off the rudder angle sensor composed of an open collector output type sensor that operates by being supplied with power from the outside. In addition, it is possible to detect disconnection of the power supply line to the sensor.
[Brief description of the drawings]
FIG. 1 is a connection diagram of an embodiment of the present invention.
FIG. 2 is a connection diagram of a conventional example.
[Explanation of symbols]
1 Steering angle sensor 2 Power supply terminal 3 First resistance (current limiting resistance)
4 Second resistance (voltage dividing resistance)
5 Transistor (switching element)
7 Sensor unit 9 Power line 10 4th resistor (pull-up resistor)
11 Output line 14 Interface circuit (level identification unit)
16 Microcomputer (level identification unit)
Vcc positive power supply P detection terminal

Claims (2)

In the sensor state detection device that detects the state of the sensor that is supplied with power from the outside and detects the change in the state of the detection target,
The sensor, a power supply terminal connected to an external positive power source, a current limiting resistor connected to the sensor at one end, a voltage dividing resistor connected to the sensor at one end, and between the voltage dividing resistor and ground A sensor unit comprising a switching element provided at a control terminal connected to the power supply terminal;
A pull-up resistor that is connected to an output line of the sensor unit, both ends of which are the positive power supply and the other end of the current limiting resistor, and constitutes a voltage dividing circuit together with the current limiting resistor and the voltage dividing resistor;
When the sensor is turned on and off, the switching element is turned on, and the voltage value of the positive power supply appears at the detection terminal in response to the sensor on and off due to the voltage division of the voltage dividing circuit, respectively. And a third level different from the first and second levels appearing at the detection terminal when the output line is grounded, and when the output line is disconnected, the power supply terminal and the positive power source And a level identification unit for identifying a fourth level different from the first to third levels appearing at the detection terminal when the line between the two is disconnected. The sensor state detection device according to claim 1, wherein the sensor is a steering angle sensor including an open collector output type sensor that detects a steering angle of a vehicle steering device as the detection target.

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