JPS6115231Y2 - - Google Patents

Description

[Detailed description of the invention] The invention is provided with a threshold switch controlled from an oxygen measurement sonde placed in the exhaust gas stream of an internal combustion engine, and the threshold switch uses the actual value of the output signal of the sonde as the threshold. In comparison, the threshold switch is configured to generate an output signal that alternates between two different values depending on the output signal of the oximetry sonde, and is operatively connected to the threshold switch for controlling the switch; During normal operation of the regulating device, the alternating output signal of this threshold switch causes the switch to be moved via a timing element into the first connecting position, and when the output signal does not alternate, the switch is transferred via a timing element to the first connecting position. The present invention relates to a regulating device for controlling a fuel mixture supplied to an internal combustion engine, which can be moved into a second connection position.

Mixture conditioning is superimposed on the basic control for the treatment of the fuel mixture that may be necessary by means of a carburetor or electronically controlled intake manifold injection system, and is carried out by means of an oxygen measuring probe to reduce the fuel mixture to a slightly ideal mixture. Its role is to maintain a constant value lower than the ratio. In this mixture composition, a particularly desirable composition of the exhaust gas of the internal combustion engine with respect to the harmful components present is obtained. Particularly with this composition, a catalytic reaction device which is additionally arranged in the exhaust system of an internal combustion engine and is used for exhaust gas aftertreatment operates particularly advantageously.

However, such a regulation only works satisfactorily if the oximetry probe delivers a sufficient available regulation amount. In particular, this occurs if the oxygen measuring probe has not yet or no longer reaches a predetermined operating temperature, which is generally above 400°C. In oxygen measuring probes that operate in the manner of ionic conduction through a solid electrolyte in the presence of an oxygen partial pressure difference, the resistance of the solid electrolyte at low temperatures allows a sufficient voltage signal to be delivered from the probe for regulation. It's too big. One of these operating states occurs, for example, during warm-up of the internal combustion engine. It also occurs during engine braking of the vehicle engine or long unloaded operation of the vehicle engine that the exhaust gas itself is not hot enough to maintain a minimum operating temperature of the measuring probe for reliable operation.

In the event of a malfunction of the oxygen measuring probe or no change in the output signal in the regulating device mentioned at the beginning,
It is already known to activate alarm devices or devices for controlling the operating characteristics of internal combustion engines. Furthermore, it is known to control a heating coil for heating the oxygen measuring probe by means of a thermoelectric element which is closely arranged on the oxygen measuring probe. This additional heating brings the oxygen probe to the required operating temperature even at low exhaust gas temperatures. However, this device has 400
The disadvantage is that the temperature sensor for this problematic temperature, which is significantly higher than °C, is expensive and, in addition, there is a risk that the temperature sensor may become inoperable in the exhaust gas stream of the internal combustion engine during rough operation. has.

The object of the invention is to provide an inexpensive device that reliably turns on the heating device of an oxygen measuring probe when the oxygen measuring probe is cold and not ready for operation.

According to the present invention, this problem is solved as follows. That is, the timing element is configured as an integrator, which integrator is configured to be controlled by the output signal of the threshold switch, and the timing element is configured to include a switching device in the heating circuit of the heating device of the oxygen measuring probe. is connected downstream and energizes the heating device if no alternation of the output signal of the threshold switch occurs for a duration determined by the time constant of the integrator. In this case, it is advantageous if the absence of the control signal emitted by the oxygen probe in the ready state is used in this case to initiate heating of the oxygen probe. This has the advantage that a temperature sensor, which also has disadvantages, can be omitted altogether.

According to an advantageous embodiment of the invention, there is a pulse-controlled transistor switch in the input feed of the integrator, the frequency of which is dependent on the rotational speed of the internal combustion engine. With this arrangement, the delay time of the integrator is limited to the time of conducting the transistor switch with a pulse of constant width and frequency dependent on the rotational speed. The delay until heating begins in the absence of a change in the output signal of the threshold switch or the oximetry probe can thus be related to the rotational speed, so that the onset of heating is even more difficult at high rotational speeds. done rapidly. This means increasing the reliability of the function and response at higher rotational speeds, especially with respect to the fact that the output signal of the oximetry probe changes more rapidly at higher rotational speeds. In this way a decrease in the operating temperature of the oxygen measuring probe can be detected already very early.

Embodiments of the present invention will be described below with reference to the drawings.

The figure shows a part of an exhaust pipe 1 of an exhaust system of an internal combustion engine, which is not shown further. A known oxygen measurement sonde 2 is inserted into the exhaust pipe, and this sonde operates by means of ion conduction using a solid electrolyte. If the oxygen concentration or oxygen partial pressure on the side of the electrolyte exposed to the exhaust gas of the internal combustion engine differs from the oxygen concentration on the other side of the solid electrolyte exposed to the reference medium, the sonde generates a voltage signal that The signal causes a sudden change in voltage in the range of excess air ratio λ=1 in the exhaust gas of the internal combustion engine. Such sondes are known. The probe has the disadvantage that ion conduction through the solid electrolyte, which is suitable for generating a sufficiently clear voltage signal, only occurs in the measuring probe at an operating temperature of approximately 400° C. As a result, the internal resistance of the measuring probe is too high at low temperatures. Such sondes are simply shown symbolically in the figures. This sonde is once again shown in the diagram as a voltage source 2 within the circuit frame. The voltage signal of this sonde is supplied to the base of a transistor 4 whose collector is connected to a common power supply line 5 and whose emitter is connected to a resistor 6. A resistor 6 connected in series between the collector and emitter of the transistor 4 forms the first side of the bridge circuit 7. There is a resistor 8 in series with this side, which is connected to a common feed line 1 which supplies the positive voltage via another resistor 9.
Connected to 0. There is a Zener diode 11 in parallel to the first bridge leg formed by the transistor and the resistor 6 and to the second bridge leg formed by the resistor 8 . Furthermore, there is a resistor 13 on the third side of the bridge circuit 7 in parallel with the resistor 8, and an emitter resistor 14 on the fourth side in series with the resistor 13, after which the emitter-collector of the transistor 15 is connected. Subsequently, the collector of this transistor is connected to a common power supply line 5. The base of transistor 15 is connected to a voltage divider consisting of resistors 16 and 16' in parallel to the third and fourth sides of bridge circuit 7. The diagonal of the bridge circuit is connected to an operational amplifier 17. The connection point between resistors 8 and 6 is connected to the inverting input terminal of the operational amplifier, and the connection point between resistors 13 and 14 is connected to the non-inverting input terminal of operational amplifier 17.

The output terminal of the operational amplifier is connected via a resistor 18 to a common power supply line 10 and further to a regulating amplifier 19 with integral characteristics. In the circuit connected to the regulating amplifier 19 there is a normally known regulating device, at the output of which there is an actuator, not shown in further detail, for controlling the fuel-air mixture of the internal combustion engine. is connected.

The operation of the circuit arrangement described above is as follows. That is, the output signal of the oxygen sonde 2 is supplied to the first side of the bridge circuit via the transistor 4.
This electrical signal, which represents the oxygen content in the exhaust gas of the internal combustion engine, constitutes the actual value for the regulating device. The desired value, ie the value of the excess air ratio λ for which the fuel-air mixture is to be adjusted, is applied as a voltage stabilized by the Zener diode 11 to the base of the transistor 15 via voltage dividers 16 and 16'. Resistor 13 of bridge circuit 7
At the tap point between . In this case, the operational amplifier is used as a threshold switch which, depending on the signal of the oximetry sensor, outputs a signal to the power supply lines 5 and 10, depending on whether the actual value is above or below the actual value. sends out a positive or negative signal depending on the voltage. These signals are fed to a conditioning amplifier 19 for further processing. Due to the dead time of the regulating circuit consisting of oxygen measuring probe - mixture conditioning - internal combustion engine - oxygen measuring probe, the exhaust gas composition is constantly changing at the oxygen measuring probe when the mixture conditioning is operating. arise. When adjusting the fuel mixture to λ=1, the oxygen measuring probe in the exhaust system sends out a constantly changing signal, sometimes indicating an excess of oxygen and sometimes an insufficient amount of oxygen. The frequency of this voltage change in the oxygen sonde increases with increasing rotational speed. The varying voltages correspondingly present at the output of the operational amplifier 17 are detected by a regulating amplifier 19, which integrates these voltages in one direction or the other depending on the potential and correspondingly controls the internal combustion. Controls the operating section that controls the engine's fuel-air mixture.

Furthermore, the output terminal of the operational amplifier 17 is connected to a resistor 21.
The emitter of this transistor is connected to the common feed line 5, and the collector of this transistor is connected to the common feed line 10 via resistors 23 and 24. It is connected. The collector of transistor 22 is further connected to transistor 2.
5 and is connected to the base of transistor 25
The emitter of this transistor is likewise connected to a common power supply line 5, and the collector of this transistor is connected to a resistor 26.
It leads to the power supply line 10 via. The collectors of transistors 22 and 25 are directly connected via capacitor 27. This circuit, consisting of transistors 22 and 25, resistors 23 and 26, and capacitor 27, forms a known Miller integrator 28 whose output terminal, which is at the collector terminal of transistor 25, is connected via resistor 30. Connected to the base of transistor 31. The collector of this transistor is connected to the base of the transistor 33 , the emitter of the transistor 33 is connected to the power supply line 5 , and the collector is connected to the power supply line 10 via the coil of the relay 35 . The transistor 31 is provided with a collector resistor 32 at a connection portion of the collector to the power supply line 10 .

A switch is operable via a relay 35, and this switch is connected to the heating device 3 of the oxygen sonde 2.
It is inserted into the power supply line 37 of No. 8. This heating device consists of a heating coil surrounding the oxygen sonde as closely as possible, which coil is connected to the exhaust pipe 1 as earth on the one hand and passes through the exhaust pipe insulated on the other hand to a positive power supply, e.g. Connected to the positive terminal of the vehicle battery.

A transistor 40 is connected in parallel to the resistor 24 in the connection of the transistor 22 to the power supply line 10.
The base of this transistor is controlled by a pulse shaper 41. The pulse shaper 41 receives, for example, rotation speed-dependent pulses from a power distribution device 42 of an internal combustion engine;
These pulses are converted into rectangular pulses with a frequency and constant width that also depend on the rotational speed.

This circuit operates as follows. Operational amplifier 1 as described above when the oxygen measuring sonde is operational
At the output terminal of 7, a signal is generated that constantly changes between a high potential H and a low potential L. Each H potential is
Transistor 22 becomes conductive, thereby causing transistor 2 to become conductive after a short charging and discharging time of capacitor 27.
The low potential of the feed line 5 is applied to the base of 5, and this transistor is completely cut off. The collector terminal of transistor 25 thereby becomes positive, so that a positive voltage is applied to the base of transistor 31 with respect to supply line 5, and this transistor becomes conductive. As a result, the base of the transistor 33 becomes at the potential of the power supply line 5, whereby the transistor 33 is cut off and the flow of current through the relay 35 is cut off. Therefore, the power supply line 3 of the heating device
Switch 36 in 7 is opened and heating is stopped.

When the L potential reaches the base of transistor 22, this transistor is turned off. From this point on, the function of Miller integrator 28 begins. At this time, it is assumed that the transistor 40 is first conductive. The precharged capacitor 27 can now be discharged via the resistor 23 and the transistor 25. The discharge time is then determined by the resistor 23. As the discharge state of capacitor 27 progresses, the base of transistor 25 becomes more positive, until it becomes completely conductive and transistor 31 is turned off at the same time. A positive voltage with respect to the supply line 5 applied at this time to the base of the transistor 33 makes this transistor conductive. This energizes relay 35 and closes switch 36.

During the discharge time determined by the capacitance of the resistor 23 and capacitor 27, the transistor 2
2, the heating circuit of the heating device remains closed.

Before the end of this time, when the L potential applied to the base of transistor 22 changes again to H potential, transistors 25 and 33 are turned off and switch 36 is opened. In this embodiment, the delay time of the Miller integrator is determined as follows. That is, a change in the output signal always occurs before this time has elapsed when the oxygen measurement probe is ready for operation, and in fact transistors 25 and 33 always remain turned off when the probe is ready for operation. Make it. According to this circuit arrangement, the still cold oxygen probe is therefore heated up at the start of the regulation, and this heating occurs only after the moment when the probe repeatedly sends out control signals with different potentials at a sufficiently rapid rate. will be stopped.

Basically, this circuit arrangement also operates when the resistor 23 and the power supply line 10 are directly connected instead of the resistor 24 and the transistor 40. However, the transistor 4 connected to the pulse shaper 41
0 allows the time course of the mirror integrator to be controlled as a function of the rotation speed. The transistor is then turned off and on at a frequency that depends on the rotational speed. During the period in which transistor 40 is turned off, the discharge process proceeds only slowly through additional resistor 24. This discharge process occurs more rapidly when the transistor conducts, so that a stepped discharge characteristic is obtained. As the rotational speed increases, the period of conduction of the transistor 40 per unit time becomes longer, so that in the case of high rotational speeds, which results in rapid repetition of the voltage signal even when the oxygen measuring probe is ready for operation, the time of the Miller integrator increases. The course is shortened for the case of low speed rotation. This has the advantage that in all operating ranges of the internal combustion engine, it is possible to quickly detect that the oxygen probe is too cold and to initiate heating.

In an alternative configuration of the circuit instead of the relay provided in this embodiment, the heating device can also be placed between the emitter and collector of the transistor as a collector resistor.

[Brief explanation of the drawing]

The figure is a circuit diagram showing one embodiment of the adjustment device according to the present invention. 2... Oxygen measurement sonde, 17... Threshold switch, 22... Transistor, 28... Integrator, 3
1... Transistor, 33... Semiconductor power switch, 33, 35, 36... Switch device, 37...
...Heating circuit, 38...Heating device, 40...Transistor switch.

Claims (1)

[Claims for Utility Model Registration] 1. A threshold switch is provided which is controlled from an oxygen measurement sonde placed in the exhaust gas stream of an internal combustion engine, the threshold switch comparing the actual value of the output signal of the sonde with a threshold value. the threshold switch is configured to generate an output signal that alternates between two different values depending on the output signal of the oximetry sonde, and has a timing element operatively connected to the threshold switch for controlling the switch; During normal operation of the device, the alternating output signal of this threshold switch causes the switch to move via the timing element to the first connection position, and when the output signal does not alternate, the switch via the timing element moves the switch to the first connection position. In the regulating device for controlling the fuel mixture supplied to the internal combustion engine, which can be moved into the connecting position of The integrator is configured to be variable depending on the number, and the integrator is configured to be controlled by the output signal of the threshold switch 17, and the timing element is configured to be variable depending on the heating device 38 of the oxygen measuring probe 2. If the switch devices 33, 35, 36 in the circuit 37 are connected downstream and no alternation of the output signal of the threshold switch 17 occurs during a period determined by the time constant of the integrator 28, the heating device A regulating device that controls the fuel mixture supplied to an internal combustion engine by energizing the engine. 2. Regulating device according to claim 1, in which a semiconductor power switch 33 in the heating circuit is used as the switch device, which semiconductor power switch is controlled via a transistor 31. 3. The utility model according to claim 1 or 2, wherein there is a transistor switch 40 controlled by a pulse having a frequency corresponding to the rotational speed of the internal combustion engine in the input feed line of the integrator. Adjustment device.