JPS6275253A - Oxygen concentration detecting device - Google Patents

Abstract

PURPOSE:To hold an oxygen pump element at specific temperature by calculating a resistance value from a current flowing to the oxygen pump element and a voltage applied thereto and performing control so that the resistance value is a specific value. CONSTITUTION:The pump element 1 and a battery element 2 for oxygen concentration ratio measurement face each other across a slit 3. A pump current supply circuit 20 is connected to the electrode of the element 1 and a sensor voltage detecting circuit 21 is connected to the element 2, and the oxygen concentration is detected from the pump current flowed to the circuit 20 so that the ratio of the oxygen partial pressure in the slit 3 which is detected by the circuit 21 and the atmospheric oxygen partial pressure is held constant. Further, a hole 11 is bored at a part corresponding to the electrode of the element 1 of a heating element 22, a PT wire 24 is printed at its periphery, and a heat current supply circuit 23 is connected to its electrode. Then, the current flowing from the circuit 20 to the element 1 and the voltage applied thereto are inputted to a computer 25, which sends an indication to a control circuit 26 on the basis of its arithmetic result, and the circuit 26 controls the circuit 23 according to the indication to adjust the current flowing through the Pt wire 24.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fJl gas concentration sensor for an internal combustion engine.

The original diagram of the oxygen temperature sensor, which generates an output according to the degree of oxygen concentration, is shown in FIG. 2 and will be explained.

Two plate-shaped oxygen ion conductive prisoner electrodes with electrodes on both sides. The quality sintered bodies are placed parallel to each other with a certain interval (slabs) ˜3), one side is used as a pump element 1 for pumping MA, and the other side is used as a battery element 2 for measuring acid A111 degree ratio.

When a free current (pump current) is supplied from the free current power supply 4 to both electrodes of the pump element 1 via the variable resistor 5 (the outer electrode is connected to the inner electrode and the inner electrode is -), the -electrode 0M gas is ionized. , the MA ion moves to the outer tenden (i side), and the same → −
At the electrode, 11-acid-based gas is released.

Therefore, the pump element 1 acts as a pump to pump the oxygen in the surins 1 to 3 into the external atmosphere.

This pump element 1 reduces the oxygen gas in the slit 3, causing a difference between the partial pressure of oxygen gas in the atmosphere and the partial pressure of oxygen gas in the slit. Battery tree for IJI ratio measurement 2
An electromotive force is generated between the two electrodes.

When a pump current is supplied so that this electromotive force is kept at a certain value (so that the PIi element partial pressure ratio in the atmosphere and in the slit is kept constant), this pump current Proportional to oxygen partial pressure.

Therefore, by measuring this pump current, the oxygen partial pressure in the atmosphere can be determined, and the air-fuel ratio in the exhaust gas can be measured.

The relationship between the air-fuel ratio A/F and the pump current IP is shown in a graph as shown in FIG.

As the air-fuel ratio becomes larger than the stoichiometric air-fuel ratio of 14.7, the pump current 1r increases proportionally.

In general, internal combustion engines are operated at an air-fuel ratio higher than the stoichiometric air-fuel ratio (for example, about 18) in order to improve fuel efficiency and purify exhaust gas.
r is detected and used for air-fuel ratio control.

However, (air-fuel ratio A/1: pump current 1r shown in Figure 3)
The characteristics are determined by the activation state of the pump element 1, and since this activation state changes with temperature as shown by J: 1111F11, the characteristic curve shown in FIG. 2 ultimately depends on temperature.

Therefore, it is necessary to keep the element in a certain active state by keeping the temperature above a certain level.

Therefore, an example in which a heating element was attached to the sensor (Unexamined Japanese Patent Publication No. 5
There is 8-1! 131! 15 yen public + 11).

This is shown in FIG. 4. It is made of a rectangular insulating bamboo plate 10 made of alumina, spinel, etc., and has a rectangular hole 11 inside.

A heating resistor 1 is placed on the surface of the plate-like body 10 around this hole 11.
2 are laid in a waveform and a current is passed through the plate-shaped body 10.
Heats up the whole thing.

This plate-like body 10 is attached to the pump wood 1 in 11a, and the electrode is inserted into the hole 11.
A suitable current is supplied to heat the element to make it into a living bamboo-like shape.

Here, the heating resistor 12 is made of P[ as a heat-resistant metal.

A base sheet such as ΔU is used and laid on the plate-like body 10 by printing.

(1 and 1) - As described above, if current is being supplied to the heating resistor 12, the element temperature will change due to disturbance, and a stable pump current will not be obtained. First, there is the problem that an accurate air-fuel ratio cannot be obtained.

For example, medium speed affects the element temperature (see Figure 5).

Generally, when cruising at tj115, almost complete combustion has occurred in the engine, and the temperature of the combustion gas is J:, which indicates an element temperature corresponding to the medium speed. As a result of internal combustion, the dryness of the wood has increased, and as shown by the broken line in Figure 5, the dryness level is higher than during cruise driving (solid line).

Other publications? The element temperature changes depending on A Ml, the heating element capacity [n, its supply voltage, etc.

On the other hand, this element temperature also affects the life of the element.

The durability time (Il) of the element against the thermal trace ('C)
Figure 6 shows the change in r) when the element temperature is 8.
Up to about 00°C, there is no difference in durability between 1ki, but when it exceeds 900°C, the durability becomes short and the lifespan decreases.

Furthermore, if the element 'f; A is too low, the activation of the element will be insufficient and the output will not be stable.

In other words, the change in pump current 1r (m△) with respect to the element temperature (°C) with the supply voltage 1-E V S constant at 40 mV is shown as 1 and J in Figure 7, and above 600°C. If the temperature is too high, the temperature change in the pump current IP will be large.

As mentioned above, there are various factors that prevent the element temperature from changing, and if the element temperature is not stably maintained at an appropriate temperature, the value iQ will decrease and the output will become unstable.

The lignification plan was designed with this in mind, and its purpose was to determine the resistance value of the acid pump element, and by controlling it to keep it constant, the temperature of the element could be adjusted to an appropriate level (1). The object of the present invention is to provide a device for detecting acid temperature that can be maintained at a constant temperature.

The structure of the present invention will be explained with reference to FIG. 1.

It has a pair of Pli element ion conductive bamboo solid FFI dissolving materials which are protruded into the exhaust gas passage of an internal combustion engine and disposed in the gas to be measured, electrodes are formed on each of the front and back sides of 1 m, and the solid electrolyte material is They are arranged in parallel so as to face each other with a predetermined gap in between, one of the solid electrolytic materials serving as the oxygen pump element B and the other as the oxygen pump element B. 4 Battery C for concentration ratio measurement
pump current supply means I) for supplying current between the electrodes of the oxygen pump element B to the M wood concentration detection means each acting as In the PaA concentration sensor consisting of a heating element E and a heating current supply means F that supplies current to the heating element E, G is a resistance detection means; From the voltage applied between the electrodes of oxygen pump element B, the same Fl! l'Ik The resistance value of pump element B is determined.

1" is a control means for controlling the heating element E based on the resistance value, and is a control means for controlling the heating element E so that the resistance value of the liquefied acid type element B is kept constant.

Since the resistance value of M cable pump tree I3 is almost inversely proportional to the humidity of allotropy f, oxygen pump element B
From the current 1a3 flowing in and the applied voltage V, V/
The element temperature can be kept constant by keeping the resistance value determined by performing operation I constant.

The control means 1-1 can control the current supplied to the heating element E by instructing the heating current supply means F to keep the resistance value determined by the resistance detection means G constant.

In this way, by adjusting the calorific value of the heating element F and maintaining the element temperature at an appropriate value, the active state of the solid electrolytic material is stabilized, the output is stabilized and accurate, and the service life is extended. It is possible to aim for

EMBODIMENT OF THE INVENTION An embodiment of the present invention shown in FIG. 8 and subsequent figures will now be explained.

FIG. 8 is a schematic explanatory diagram of the oxygen moisture sensor according to this embodiment.

In FIG. 2, the pump element 1 and the oxygen concentration ratio measuring battery element 2 face each other via the slit 3 having a certain width, as described above.

A pump current supply circuit 20 is connected to the electrode of the pump element 1, and a sensor voltage detection circuit 21 is connected to the oxygen concentration ratio measurement battery element 2, which detects the oxygen partial pressure in the slit 3 and the atmospheric pressure. The oxygen partial pressure ratio is detected by the sensor voltage detection circuit 21, and the pump current is supplied by the pump current supply circuit 20 so as to keep this detected value constant, and the M depth is detected using this pump current.

A heating element 22 is attached to the outer surface of the pump element 1.

The heating element 22 is also made of a rectangular insulating T/I inorganic 71 plate-shaped plate 10 as described above, and a rectangular hole 11 is bored in the portion corresponding to the electrode of the pump element 1.

A line 24 is printed around the hole 11, and a heating current supply circuit 23 is connected to the end electrode.

Then, the computer 25 inputs the current flowing to the pump element 1 from the e-bomb current supply circuit 20 and the voltage to be applied.
Give an instruction to the control circuit 26 based on the calculation unity of a.
, II ta11 circuit 26 controls the heating current supply circuit 23 according to the instruction, and the pt line 24 of the heating element 22
Adjust the current flowing to the

A schematic explanatory diagram of the above circuit is shown in FIG.

A /i current S4 is connected to both electrodes of the pump element 1 via a variable resistor 5.

A voltage switch 127 is installed between the thunderbolts, and a 1.u current 6128 is installed in this heating current supply circuit (13 V), and both needles 311127.28 (7) + il
3191/l V , I + , t ] is input to the computer 2.

The computer 25 outputs the bell of V/l as tr -3-(1
The resistance is 1 direct R80, and the same resistance + fJ R is 1. The control signal t is then outputted to the terminal i to transistor 290 gate 1.

Transistor 291, connect the heated water f-22 l) to line 24
1g is connected in series with d3 and power supply 30 to perform switching control.

As shown in FIG. 10, the control signal output from the computer 25 is a duty pulse signal that changes the duty ratio to adjust the ON/OFF state of the transistor 29, thereby changing the average current value flowing through the Pt wire 24. fever i
control fi.

In this example, the water temperature ranges from 650°C to 70°C.
A temperature between 0°C is optimal, and a resistance value Rrat corresponding to this temperature is set in the computer 25.]
The computer 2 compares the resistance value R derived from the measured voltage value V and current value I with the set resistance value RrOr, and determines the duty ratio so that the set resistance value R2° is reached according to the difference.

1/, when the temperature is low, the resistance value R as a result of the input by the computer 25 is larger than the set resistance value Rrat, and the duty ratio is increased according to the difference.
Extends the ON time of

Then Pl! The average current flowing through the oxygen pump element 324 increases and the amount of heat generated by the heating element 22 increases, raising the element temperature of the oxygen pump element 1.

When the water temperature is higher than a predetermined temperature, the −j′neity ratio of the control signal from the computer 25 is reduced, the ON time of the two transistors is shortened, and the amount of heat generated by the heating element 22 is reduced.

The element humidity can be kept at a predetermined temperature (approximately constant) by setting ε.

If the water temperature is stable at a predetermined temperature between 650°C and 100°C, the life of the wood itself can be maintained for a long time (see Figure 6), and the element can be kept in a stable active state. to eliminate variations in the output (pump current 1r) (7th
(see figure), the accuracy of the air-fuel ratio control 20 can be maintained at a high level.

The present invention is lI! The resistance +tfi is calculated from the current a3J- flowing through the pump element and the applied voltage, and by controlling the resistance value to a predetermined resistance value, the element temperature is maintained at a predetermined humidity and humidity changes due to disturbances are avoided. As a result, accurate output values can be obtained by keeping the element in a stable active state at all times.

Therefore, accurate output (air-fuel ratio control as high as 1!llI degree with n and b) is possible.

Furthermore, by keeping the temperature of the element at an appropriate value, it is possible to extend the life of the element.

Furthermore, since the present invention uses the oxygen pump element itself as a temperature sensor, there is no need to separately provide a temperature sensor.

[Brief explanation of drawings]

Figure 1 is a diagram corresponding to the claims of the present invention, Figure 2 is an original raccoon diagram of the oxygen concentration sensor, and Figure 3 is the air-fuel ratio Δ/F and pump current 1.
Fig. 4 is a perspective view of the heating element, Fig. 5 is a perspective view of the heating element;
Figure 1 shows the relationship between medium speed and element temperature, Figure 6 shows the relationship between water element temperature and durability opening, and Figure 7 shows the relationship between water element temperature and pump current. 9 is an explanatory diagram of an oxygen concentration 1α sensor according to an embodiment of the present invention, FIG. 9 is a schematic explanatory diagram of a circuit according to this embodiment, and FIG. 10 is a diagram showing a υ1111 signal output from a monitor. 1...Pump element, 2...lli! 2: Raichi Soryo for measuring ratio of power, 3: Slit, 4: DC power supply,
5... Variable resistor, 10... Insulating non-T11 plate-like body, 11... Hole, 12... Heat generating resistor, 20... Pump current supply circuit, 21... Heating current detection Circuit, 22... Heating element, 23... Heating current supply circuit, 24... PE wire, 25... ]] Nbicoater 2
G... Control circuit, 27... Electric meter, 28... Ammeter, 29... Transistor, 30... Power supply.

Claims (1)

[Claims] A pair of oxygen ion conductive solid electrolyte materials are provided that protrude into an exhaust gas passage of an internal combustion engine and are disposed in a gas to be measured, and electrodes are formed on each of the front and back surfaces of the solid electrolyte materials, and the solid electrolyte materials are arranged in a predetermined manner. oxygen concentration detection means arranged in parallel so as to face each other with a gap in between, one of the solid electrolyte materials acting as an oxygen pump element and the other acting as a battery element for measuring oxygen concentration ratio; and the oxygen pump element. A heating element that generates heat according to the supplied current value to heat the solid electrolyte material, and a heating current supply means that supplies current to the heating element. In the oxygen concentration sensor, a resistance detection means for determining a resistance value of the oxygen pump element from a current flowing through the oxygen pump element and a voltage applied between electrodes of the oxygen pump element; An oxygen concentration detecting device comprising: a control means for controlling the oxygen concentration, the control means controlling the resistance value of the oxygen pump element so as to be constant.