JPS58205849A - Oxygen concentration detector - Google Patents

Abstract

PURPOSE:To correct variation in characteristics of an oxygen concentration sensor unavoidably generated in the manufacture by providing a variable resistor in series on a signal line for connecting a constant voltage power source and oxygen concentration sensor. CONSTITUTION:An oxygen concentration sensor 10 for lean burning is connected to a constant voltage power source 16 with a signal line 11 and a part of the signal line 11 is out off to provide terminals 14 and 15 at cut ends thereof while a variable resistor 13 is provided between the two ends 14 and 15 thereof. The resistance value of the variable resistor 13 is varied with output current characteristics of the oxygen concentration sensor so that the voltage across the variable resistor is kept almost at a fixed value with respect to the air/fuel ratio. This can reduce the variations in characteristics of output current unavoidably generated in the manufacture of the oxygen concentration sensor to a level free from problem in practice.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention is a book related to a device for detecting the air-fuel ratio of an engine from the oxygen concentration in the exhaust gas of an internal engine (hereinafter referred to as the engine).

In recent years, there has been a demand for cars with low fuel consumption, and as one means of achieving this, a lean burn system is being considered in which the engine is operated in a region leaner than the stoichiometric air-fuel ratio. In this lean burn system, it is necessary to control the engine air-fuel ratio according to the engine operating state, so W, 1
A sensor is required in which the air-fuel ratio A/F and the output value have a linear relationship of 1 over a wide range of air-fuel ratios as shown in the figure. In order to meet this demand, a lean burn oxygen concentration sensor (hereinafter referred to as a lean sensor) has been proposed that detects the air-fuel ratio A/F' by replacing it with the oxygen concentration in the exhaust gas of the engine. As shown in Fig. 2, this lean sensor consists of a plate-shaped electrolyte body 2, electrode layers 37 attached to both sides of the plate-shaped electrolyte body 2, and a diffusion rate-determining rate @4 of oxygen molecules attached to the outer surface of one of the electrode layers 3. I have Hikoru Motoko 1. Moreover, one element shown in FIG. 3 has a structure in which an electrode retainer 5 is attached to the outer surface of the electrode layer 3 on the opposite side of the diffusion control 14 shown in FIG. 2, and the element shown in FIG. 1B has a structure in which an electric current (R3) is deposited on one surface of the electrolyte body 2 shown in FIG. 2, and a diffusion-controlled electrode layer 6 is deposited on the other surface.

The above element 1. When a constant voltage is applied between the electrode layers on both sides of the element while IA and IB are heated and maintained at a constant temperature, a current with a strength proportional to the oxygen concentration in the exhaust gas is output. FIG. 5 shows the relationship between the oxygen concentration and the output current, which is replaced by the air-fuel ratio A/F of the intake air of the engine and the output current, and the air-fuel ratio A/F and the output current have an if dose relationship.

However, the output current characteristics of this lean sensor are realized as a result of a complex interplay of the resistance of the solid electrolyte 2 of the element 1, the resistance of the mFM layer 3, the performance of the diffusion control 114, etc., so there are large individual differences between lean sensors, as shown in Fig. 6, for example. As shown, the output current varies over a wide range depending on the individual lean sensor, so even if the output current is the same, the air-fuel ratio is not necessarily the same.

This invention is based on the correlation between the air-fuel ratio of the intake air of the engine and the output W flow of the lean sensor, the correlation between the air-fuel ratio and the output voltage, and the correlation between the air-fuel ratio and the output current of the lean sensor. The purpose of the present invention is to provide a mounting in which the correlation between the air-fuel ratio and the output voltage is always kept constant even if it varies between units.

In order to achieve the above object, the present invention has a configuration in which a usable resistor is attached in series with the signal MK that connects the lean sensor and the constant voltage power supply, and this variable resistor has a configuration in which the variable resistor has a correlation between the air-fuel ratio and the output voltage. It is designed to be used so that it is always constant.

The present invention will be described below based on drawings showing embodiments. 7th
In the figure, a lean sensor 10, a constant voltage source 1, and a source 16 are connected by a μ line 11, a part of the signal line 11 is cut off, and terminals 14 and 15 are provided at the cut end.
．． A variable resistor 13 is provided between the resistors 15 and 15. As shown in Fig. 8, the output q of the two lean sensors 10A and 10B
Flow i a is 1mj, /F', 2mAA/ respectively.
F'teal note variable resistor 13 resistance sensor 1 [
10Ω for IA, 5Ω for lean sensor 10B
When set to , the output voltage Ea between terminals 14° and 15 is 0°01vA/F for both lean sensors 10A and 10BK.
Therefore, even if the relationship between the output current of the signal line lean sensor after terminals 14 and 15 and Al2 is different, it can be kept constant as shown in Fig. 9.

Also, it is not inventive to prepare several resistors with different resistance values in place of the usable resistor 13, and select and use the resistor with the resistor II most suitable for each lean sensor with different output current. For example, as shown in Figure 10, the output current characteristics are g 1.2 mA/
A/F', 1.4mA/i/F', 1.5mA/
When resistors with resistance values of 8.3Ω, 7.1Ω, and 6.30 are used for the lean sensors I QC, 10D, and 10E, which are F', the output voltage Ea between terminals 14 and 15 is as shown in Fig. 9. As shown in 0. OI V/A/r.

Furthermore, the output voltage Ea between terminals 14 and 15 and the air-fuel ratio A/F
If some variation is allowed in the relationship between lean sensors, the lean sensors are classified according to the range of change in the output current of the lean sensor, and a resistor having a resistance value corresponding to the median value of the classification range is prepared. Even with a lean sensor whose output current characteristics vary over a wide range, as shown in the shaded area in Figure 11, it is possible to suppress the variation in output voltage characteristics within a narrow, constant range, as shown in the shaded area in Figure 12. can.

As described above, the present invention connects the power source to an oxygen concentration sensor that detects the air-fuel ratio of the engine by generating a current with a strength proportional to the oxygen concentration in the exhaust gas of the engine under a constant voltage power source. Since a usable resistor is installed in series with the signal line, and the voltage across the variable resistor is always at a constant value in relation to the air-fuel ratio, the output that is inevitably generated in the manufacture of the oxygen concentration sensor is Variations in current characteristics can be absorbed to such an extent that they are practically negligible. Therefore, inspection regulations in the manufacturing process can be relaxed without impairing the original performance of the oxygen concentration sensor, making it possible to reduce costs. Furthermore, this device is extremely simple in construction and is therefore easy to implement.

[Brief explanation of the drawing]

FIG. 1 shows the desired output value of the oxygen concentration sensor with respect to the air-fuel ratio A/F' of the engine. FIG. 2 shows a sectional view of an example of an element constituting an oxygen concentration sensor, FIG. 3 shows a sectional view of another example of the element, and FIG. 4 shows a sectional view of still another example of the element. FIG. 5 is a diagram showing the output current characteristics of the oxygen concentration sensor with respect to the air-fuel ratio A/F' of the engine. Figure @6 is a diagram showing variations in the output current characteristics of the oxygen concentration sensor. Figure 7 shows one example of this invention! It is a block diagram of an example. 8th
The figure is a diagram showing the difference in output current characteristics of two oxygen concentration sensors. FIG. 9 is a diagram showing the voltage characteristics with respect to the air-fuel ratio of the device of this invention. FIG. 10 is a diagram showing differences in output current characteristics of three oxygen concentration sensors. FIG. 11 is a diagram showing the fluctuation range of the output current characteristics of the oxygen concentration sensor. FIG. 12 shows a diagram in which the output current shown in FIG. 11 is converted into voltage by the device of the present invention. 10... Lean sensor (oxygen concentration sensor) 11...
Signal line 13...Possible resistor 16...Constant voltage power supply Output Person: ToHori Automatic 11f Industrial Co., Ltd. Agent: Patent attorney Oka, 1) Hidehiko 257-Machi/Rami Pashi (A/Hi)

Claims (1)

[Claims] An output signal for the air-fuel ratio is connected in series with a signal line connecting a constant voltage power supply and an oxygen concentration sensor that generates a current with a strength proportional to the oxygen concentration in the exhaust gas of the internal combustion engine to detect the air-fuel ratio of the internal combustion engine. Oxygen that is characterized by having a variable resistor that keeps the voltage almost constant at all times? I Liao detection device.