JPH11265630A - Monitoring method and monitoring device for switching means - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely identify the error of a switching means by providing a capacitor charged through the switching means and discharged through a discharging means, and estimating the function performance of the switching means from the charged state of the capacitor. SOLUTION: A switch contact (switching means) 107 connects a feed voltage Ubat to a capacitor 140 through a diode 160 and a resistor 170. When an error occurs, a control unit 110 outputs a signal to a relay control switch 115 to interrupt the current carried in a coil 105, the switch contact 107 is moved to an open position, and a load 120 is separated form the feed voltage Ubat. When a low side switch 127 is then opened, the current carried in the load is interrupted to induce a high voltage to the terminal of the load 120, and it reaches the capacitor 140 through a diode 130, in which it is temporarily stored, and reaches the load 120 through a booster switch 150 in the following control. Thus, the voltage of the capacitor 140 becomes abnormal, whereby the error can be identified.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for monitoring switching means.

[0002]

2. Description of the Related Art DE40055609 (US Pat. No. 5,304,304)
238), a device for monitoring the function of an electric load is known. There, the RC element distinguishes whether there is a line cut or a short to ground. Here, the fact that different discharge times occur when discharging through the RC element and the RL element is used.

[0003] The switching means is not monitored by this device. It simply monitors the connection to the load for errors.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and a device for monitoring switching means, for example, a relay.

[0005]

According to the present invention, a capacitor is charged from a voltage source via a switching device and discharged via a discharging device, and the functional capability of the switching device is estimated from the charged state of the capacitor. It is solved by doing.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, switching means,
For example, an error in a normally closed switching means is reliably identified. Only a few additional components are required for this. Existing components are advantageously used.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Normally, the loads used in motor vehicles are connected to the supply voltage Ubat via relays. At this time, a plurality of loads are commonly supplied via one relay 100 to supply voltage UBa.
can also be connected to t. For safety reasons, it must be identified when the switch contacts of the relay remain in their closed position. This means that relay sticking must be reliably identified.

Hereinafter, a method and an apparatus which can reliably identify the stuck relay will be described. The means of the present invention is not limited to a relay, and can be applied to other switching means.

In the embodiment shown, the supply voltage Ubat is connected via relay 100 to various loads. This relay is essentially a relay coil 105 and a switching means 107.
This switching means is hereinafter referred to as a switch contact 107. FIG. 1 shows only the load 120. Here, the switch contact 107 of the relay 100 connects the load 120 with the supply voltage UBat. The relay coil 105 is connected to the ground via a relay control switch 115.

A control signal is applied to the relay control switch 115 from the control unit 110.

Supply voltage UB via switch contact 107
at is connected to the high side switch 125. This high-side switch is connected in series with the load 120 and the low-side switch 127. This configuration is merely selected as an example, and only a low-side switch or a high-side switch can be provided.

A connection point between the low-side switch 127 and the load 120 is connected to a first terminal of a capacitor 140 via a first diode 130. The second terminal of the capacitor 140 is connected to the ground. The first terminal of the capacitor 140 is further connected to the booster switch 15.
0, it is connected to a connection point between the load 120 and the high-side switch 125. Low side switch 12
7. Similarly, a control signal is applied from the control unit 110 to the high-side switch 125 and the booster switch 150. Relay 110, especially switch contact 1
A voltage is supplied to the load via 07.

Such a configuration is used, for example, for controlling an electromagnetic valve. This means that the load 120 is configured as a solenoid valve. Such solenoid valves are used for controlling fuel metering, in particular for controlling fuel injection in internal combustion engines.

Further, the switch contact 107 is connected to the supply voltage UB.
At is connected to the anode terminal of the diode 160. The cathode of diode 160 is connected via resistor 170 to the first terminal of capacitor 140 and resistor 180. The second terminal of the resistor 180 is connected to the control unit 110
, And to the ground via a resistor 190.

Switches 115, 125, 127 and 1
50 is preferably designed as a transistor, in particular a field-effect transistor. The resistors 180 and 170 have a larger value than the resistor 190. Resistance 170 and 1
80 has a value of about 1 MΩ, for example, and the resistor 190 has a value of about 50 MΩ.
Take the value of kΩ. The capacitor has a capacitance of, for example, 15 μF.

This device operates as follows. Depending on the various operating parameters, the control unit 110 forms control signals for application to the various switching means 115, 125, 127 and 150. In a normal operation, the relay control switch 115 is controlled so that a current flows. This brings the switch contact 107 into its closed position as well. Accordingly, a supply voltage is applied to a series circuit including the high-side switch 125, the load 120, and the low-side switch 127.

When an error occurs, the control unit 110
Outputs a signal to the relay control switch 115. As a result, the current flowing through the coil 105 of the relay 100 is cut off, and the switch 107 moves to its open position. This ensures that the load 120 is isolated from the supply voltage UBa. A corresponding decoupling between the supply voltage and the load preferably takes place when the internal combustion engine is switched off.

The current flowing through the load is controlled by the control of the low-side switch 127 and the high-side switch 125. When the low-side switch 127 is opened, the current flowing through the load is shut off, which induces a high voltage at the load terminal. This released energy reaches the capacitor 140 via the diode 130. This energy there is temporarily stored and reaches the load via booster switch 150 during the next control. This is to promote load connection. Capacitor 14
A zero can therefore be referred to as a booster capacitor.

The switching means 125, 127, 150 of the load 120, the diode 130 and the capacitor 140 are shown by way of example only. Other circuit arrangements for storing energy in the capacitor can be provided to connect the load at an accelerated rate.

If the switch contact 107 remains in its closed position, it is no longer possible to reliably isolate the load from the supply voltage in the region of the low-side switch or the high-side switch in the event of an error. For this reason, the switch contact 10
Seven such errors must be reliably identified.

The switch contact 107 connects the capacitor 140 to the voltage source Ubat. Switch contact 1 closed
The capacitor is charged via 07. Resistance 180 and 1
The capacitor is discharged via 90. These resistors can also be called discharge means. The functional ability of the switch contact 107 is estimated based on the state of charge of the capacitor, that is, based on the voltage applied to the capacitor 140.

In the present invention, the switch contact 107 is connected to the booster capacitor 1 via the diode 160 and the high resistance 170.
40 is connected. Control unit 1 when starting internal combustion engine
During the initialization of 10, the voltage applied to the capacitor 140 is read. If the switch contact 100 operates without error, the control unit 110 reads a booster voltage of about 0V. This is because the charging time constant is much larger than the initialization phase of the control device.

With the example of the above values for the resistance, about 15 s
Charging time occurs. The initialization phase of the control device is much smaller than 1 s.

If the relay fails, the capacitor 140
Is already charged to a much higher voltage. Diode 16
A conduction voltage of 0 is known. Furthermore, the supply voltage UBat is likewise known in the control device 110. Because the control device is connected via a separate relay or directly to the supply voltage U
This is because it is connected to Bat.

A corresponding measure is shown in FIG. The inquiry 200 checks whether a start procedure exists, ie whether the control unit 110 is initialized. If not, an inquiry 200 is newly executed. If yes, that is, if there is an initialization phase, the voltage UC of the capacitor 140 is read in step 210. Following the inquiry 220, the voltage UC has the value Umi
It is checked whether it is greater than n and less than the value Umax. If affirmative, that is, the voltage U of the capacitor 140
If C is within the predetermined value range, an error is identified at step 230. Otherwise, step 240 identifies that relay 100 is error free. That is, if the voltage of the capacitor differs from its expected value when the internal combustion engine is started, an error is identified.

According to the invention, a fault of the relay is identified when the voltage of the booster capacitor reaches a predetermined value earlier than expected when the control device is switched on, or when the voltage does not fall within a predetermined value range. You.

After the controller 110 is turned off, the booster capacitor 140 discharges to 0V through a voltage divider consisting of resistors 180 and 190. If the discharge voltage is in the tolerance zone for fault identification and the control unit is restarted, this leads to an error identification even if there is no fault in the relay. Therefore, in the present invention, post-operation is performed. That is, the cutoff phase is terminated only when the voltage of the booster capacitor 140 falls below the value Umin. In addition, the maximum duration for the after-run operation is set via the discharge time constant. Beyond this time ST, a relay error is identified. A corresponding measure is shown in FIG.

In a first query 250, it is checked whether a post-run is present. In the case of post-operation, various inspection procedures are processed as usual. Furthermore, the detected data is stored in a suitable memory so that it can be used again when the internal combustion engine is restarted. At the end of the after-run, the control unit 110 is disconnected from the supply voltage Ubat.

If not, inquiry 250 is repeated. When the after-run is identified, i.e., for example, when the relay control switch 115
When controlled to be separated from at, step 25
5 is executed. In step 255, the capacitor 14
A voltage UC of 0 is detected. The following inquiry 260
It is checked whether the voltage UC is smaller than a threshold value. If it is, the program ends at step 265.

If not, an inquiry 270 checks whether the time T since identification of the after-run is greater than a threshold value ST. If so, an error is identified at step 290 and the program ends at step 295. If the query 270 identifies that the time T is not greater than the threshold ST, the time counter T is incremented by a value 1 at step 280. Subsequently, the voltage UC is newly detected in step 255.

In this configuration, during post-operation, an error is identified when the voltage on the capacitor does not drop to the expected value within a predetermined time. In particular, it is advantageous to combine the two embodiments.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram of the main elements of the device of the present invention.

FIG. 2 is a flowchart of the method of the present invention.

FIG. 3 is a flowchart of another method of the present invention.

Continued on the front page (72) Inventor Hans-Heinrich Millevskiy Schwieberdingen-Gilcherweg 13 Germany

Claims (6)

[Claims] 1. The switching means according to claim 1, wherein the capacitor is charged from a voltage source via the switching means, discharged via the discharging means, and the functional capability of the switching means is estimated from the charged state of the capacitor. Monitoring method. 2. The method according to claim 1, wherein the switching means is a relay, and supplies a voltage to a load for controlling fuel metering via the relay. 3. The method according to claim 1, wherein a capacitor is used for controlling the load. 4. The method according to claim 1, wherein at the start the error is identified when the voltage of the capacitor differs from an expected value. 5. The method according to claim 1, further comprising the step of identifying an error when the voltage of the capacitor does not drop to an expected value within a predetermined time during post-operation. 6. A capacitor having a capacitor, wherein the capacitor is charged from a voltage source via a switching unit and discharged via a discharging unit, and a unit is provided for identifying a functional capability of the switching unit from a charged state of the capacitor. A monitoring device for a switching unit.