JPH09214309A - Fault detecting method for switching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely detect a device fault in inexpensive circuit configuration at the time of detecting the faults of a hydraulic control solenoid and a wheel speed sensor by changing either one of analog inputs of two systems. SOLUTION: A hydraulic control solenoid S1 is forcedly driven by impressing the duty signal of OFF/ON/OFF from a control CPU 1 to a solenoid driving element T, and the analog signal of the solenoid S1 is inputted through a line L1 and a switching device 2 to a terminal P of the CPU 1. On the other hand, the analog signal of a wheel speed sensor S2 is inputted through a line L2 to the terminal P2 as well. When the line L1 is fixed due to a fault at the device 2, only the analog signal of the solenoid S1 is inputted to the terminal P and when the line L2 is fixed, only the analog signal of the sensor S2 is inputted to the terminal P. Thus, since the analog signal inputs of two systems are alternately monitored based on the change of the analog signal monitored by the CPU 1, the fault of the device 2 can be detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure detection method for a switching device, and, for example, two systems of analog inputs for monitoring the operating states of a hydraulic control solenoid of an ABS of an automobile and a wheel speed sensor are time-shared. The present invention relates to a failure detection method for a switching device, which is switched to monitor each operation state with one system of analog input.

[0002]

2. Description of the Related Art Conventionally, for example, two analog inputs are required to monitor each operating state of a hydraulic control solenoid of an automobile ABS and a wheel speed sensor, and each analog input is individually monitored on the control controller side. By doing so, the respective operating states are monitored.

[0003]

However, in the conventional failure detection method as described above, if one hydraulic control solenoid and one wheel speed sensor are mounted for each wheel, at least eight per vehicle. Input terminal is required, and trying to monitor each analog input individually increases the load on the calculation of the controller,
There is a drawback that the circuit becomes expensive as much as a controller having a higher processing capability is required.

Further, in a circuit in which two systems of analog inputs to the control controller are switched by time division, if the switching device fails, it will be fixed to one of the analog input sides. Depending on the abnormality determination voltage of (for example, when the abnormality determination voltages are the same), the failure that the failure of the switching device cannot be detected occurs.

The present invention has been proposed in order to solve the above-mentioned conventional problems, and an object thereof is to provide a switching device for switching between two analog inputs by time division, regardless of an inexpensive circuit configuration. Another object of the present invention is to provide a failure detection method for a switching device capable of reliably detecting the failure.

[0006]

SUMMARY OF THE INVENTION To solve the above problems,
In order to achieve the object, a failure detection method for a switching device according to the present invention has the following features. That is, a switching device which is output from a predetermined circuit and switches each monitor signal input for monitoring the operation state of the predetermined circuit by time division so that each operation state is monitored by one system of signal input. In the failure detection method, at least one monitor signal is changed while switching the plurality of monitor signal inputs by time division, and a failure of the switching device is detected based on the input monitor signal and other monitor signals. To do.

Further, preferably, the failure detection method for a switching device according to claim 1, wherein the monitor signal is changed by forcibly operating the predetermined circuit.

Also, preferably, the predetermined circuit is connected to a hydraulic control solenoid and a wheel speed sensor of an antilock brake system in an automobile, and outputs a monitor signal for monitoring the respective operating states.

Further, preferably, the failure detection is executed every time the ignition switch is turned on.

As described above, in the failure detection method for a switching device according to the present invention, each monitor signal input that is output from a predetermined circuit and is used for monitoring the operating state of the predetermined circuit is switched in a time-division manner, and the respective monitor signal inputs are switched. When detecting a failure of a switching device in which the operating state is monitored by a single signal input, at least one monitor signal is changed while switching a plurality of monitor signal inputs by time division, and the input monitor signal And acts to detect faults in the switching device based on other monitor signals.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, according to an embodiment of the present invention, a failure detection circuit (hereinafter, abbreviated as failure detection circuit) for monitoring respective operating states of an ABS hydraulic control solenoid and a wheel speed sensor of an automobile. ) Will be described in detail with reference to the accompanying drawings.

FIG. 1 is a fault detection circuit diagram including a switching device according to an embodiment of the present invention.

In FIG. 1, a failure detection circuit 100 includes a control CPU 1 and a switching device 2, and the switching device 2 is, for example, a JFET (Junction Fie).
an analog input line L1 connected to a drive circuit (not shown) of the hydraulic control solenoid S1 of the ABS and an analog input line L2 connected to a detection circuit (not shown) of the wheel speed sensor S2. Two analog input lines are switched by the control CPU1 in a time-sharing manner to control the analog input lines as one control CPU1.
Is input to the input port P. Control CP
The U1 is supplied with the power supply V, is switched by the switching device 2, and monitors an analog input that is alternately input, and the hydraulic control solenoid S1 or the wheel speed sensor S2 is monitored.
Detect the fault condition of.

The hydraulic control solenoid S1 is a linear solenoid connected to a + B power source such as a battery, and drives, for example, a valve that controls the line pressure of an ABS (antilock brake system). Hydraulic control solenoid S
1 is driven by on / off controlling a solenoid drive element T formed of a transistor with a predetermined duty signal, and a voltage based on the duty signal from the control CPU 1 is applied to its base. When a voltage is applied to the base of the solenoid drive element T (transistor on state), the hydraulic control solenoid S1 is energized as a solenoid. When the hydraulic control solenoid S1 is energized, the analog signal of the hydraulic control solenoid S1 is input to the control CPU 1 via the resistors R1 and R2 while the switching device 2 is connected to the input line L1.

Similarly, the wheel speed sensor S2 has a coil wound around an iron core, and a gear-shaped exciter 3 provided on each wheel.
Is rotated, electromagnetic induction is generated on the sensor S2 side and is input as a pulse signal to the control CPU1 as a wheel speed detection circuit. Further, the pulse signal output from the sensor S2 is smoothed by the smoothing circuit 50 including the capacitor C and the resistor R4, and the resistor R3 to which the voltage V is applied in the state where the switching device 2 is connected to the input line L2. And an analog signal of the sensor S2 via the binarization circuit 4 and the terminal Q to the control CPU 1.

The above two systems of analog input line L
Reference numerals 1 and L2 are circuits that are provided separately from a solenoid drive circuit and a wheel speed detection circuit, which are not shown, and are provided only for failure detection.

Since the solenoid drive circuit and the wheel speed detection circuit are well known, their illustration and description are omitted.

<Switching Device Failure Detection Method>
Next, a method of detecting a failure of the switching device will be described.

FIG. 2 is a diagram showing waveforms of two systems of analog input signals for explaining the failure detection method of the switching device according to the embodiment of the present invention.

1 and 2, the failure detection of the switching device according to the present embodiment is executed only once during the self-function diagnosis (during the initial check) when the ignition switch is turned on and the control CPU is activated. It This is because during normal traveling, the hydraulic pressure control solenoid S1 is not energized unless the ABS operates, so that the analog signal input to the analog input line L1 does not change and failure detection cannot be performed.

The failure detection of this embodiment is performed by the two analog input lines L1 and L during the initial check.
Forcibly change any one of the two analog signals,
The switching device 2 is switched based on the change, and the analog inputs of two systems are alternately monitored.

Specifically, failure detection is performed as follows. That is, as shown in FIG. 2A, when the control CPU 1 applies a duty signal of “OFF → ON → OFF” to the solenoid drive element T to forcibly drive the hydraulic control solenoid S1, ), With the switching device 2 connected to the input line L1, the control solenoid S
The analog signal b of 1 is input to the terminal P of the control CPU 1.

Further, as shown in FIG. 2 (c), the analog signal c of the wheel speed sensor S2, which is made constant via a predetermined filter circuit, is controlled in the state where the switching device 2 is connected to the input line L2. It is input to the terminal P of the CPU 1.

In the above state, when the connection of the switching device 2 is switched in a time division manner at the timings of the period A and the period B shown in FIG. 2D, when the switching device 2 is in a normal state, FIG. The irregular rectangular wave e shown in is input to the terminal P of the control CPU 1.

On the other hand, in the case where the switching device 2 fails and is stuck to the analog input line L1 side, as shown in FIG.
As shown in (f), only the analog signal b of the control solenoid S1 is input to the terminal P of the control CPU1.

When the switching device 2 fails and is stuck to the analog input line L2 side, as shown in FIG.
As shown in (g), only the analog signal c of the wheel speed sensor S2 is input to the terminal P of the control CPU 1.

As described above, the failure of the switching device 2 is detected by alternately monitoring the analog signal inputs of the two systems based on the change of the analog signal monitored by the control CPU 1.

When the switching device 2 is detected to be out of order as described above, the ABS control during the subsequent traveling of the vehicle is prohibited and the occupant is notified by a warning lamp.

As described above, in the failure detection method for the switching device of this embodiment, the hydraulic control solenoid S1 is changed by changing one of the two analog inputs.
The failure of the switching device 2 at the time of detecting the failure of the wheel speed sensor S2 can be reliably detected, and it can be realized with an inexpensive circuit configuration.

The present invention can be applied to a modification or change of the above embodiment without departing from the spirit of the present invention.

In the present embodiment, two analog input lines have been described, but the present invention can also be applied to switching a plurality of analog input lines.

[0032]

As described above, according to the present invention, each monitor signal input from the predetermined circuit and for monitoring the operation state of the predetermined circuit is switched in a time-sharing manner to obtain the respective operation states. At the time of detecting a failure of a switching device in which a single-system signal input is monitored, at least one monitor signal is changed while switching a plurality of monitor signal inputs by time division, and the input monitor signal and other Since the failure of the switching device is detected based on the monitor signal of 1, the failure of the switching device for switching the analog inputs of the two systems by time division can be surely detected despite the inexpensive circuit configuration.

[0033]

[Brief description of drawings]

FIG. 1 is a fault detection circuit diagram including a switching device according to an embodiment of the present invention.

FIG. 2 is a diagram showing waveforms of analog input signals of two systems for explaining a failure detection method for a switching device according to an embodiment of the present invention.

[Explanation of symbols]

 1 ... Control CPU 2 ... Switching device 3 ... Exciter L1, L2 ... Analog input line S1 ... Hydraulic control solenoid S2 ... Wheel speed sensor T ... Solenoid drive element

Claims (4)

[Claims] 1. A monitor signal input, which is output from a predetermined circuit and is used to monitor the operating state of the predetermined circuit, is switched by time division, and each operating state is monitored by a single system signal input. In a failure detection method for a switching device, at least one monitor signal is changed while switching the plurality of monitor signal inputs by time division, and the switching device of the switching device is changed based on the input monitor signal and another monitor signal. A failure detection method for a switching device, which is characterized by detecting a failure. 2. The failure detection method for a switching device according to claim 1, wherein the monitor signal is changed by forcibly operating the predetermined circuit. 3. The predetermined circuit is connected to a hydraulic control solenoid and a wheel speed sensor of an antilock brake system in an automobile, and outputs a monitor signal for monitoring respective operating states. 2. A failure detection method for a switching device according to 1. 4. The failure detection method for a switching device according to claim 1, wherein the failure detection is executed each time an ignition switch is turned on.