JPH07111413B2 - Exhaust gas concentration detector - Google Patents

Description

TECHNICAL FIELD The present invention relates to a characteristic adjusting device for an exhaust gas concentration sensor that proportionally detects the concentration of components in exhaust gas.

[Conventional technology]

Exhaust gas concentration sensors that detect the concentration of components in exhaust gas are already widely known.

By the way, this exhaust gas concentration sensor has a drawback that it is difficult for the sensor section to maintain the uniformity of product characteristics during its production, and as a result, output characteristics differ for the same exhaust gas concentration.

That is, as shown in FIG. 6, with respect to the originally required target output voltage range TB, one sensor has characteristic A, and other sensors have characteristic B.

Therefore, in order to calibrate this characteristic variation, an adjustment resistor is provided in the output circuit so as to be adjusted within the target output voltage range TB as shown in Japanese Utility Model Laid-Open No. 61-140957.

[Problems to be solved by the invention]

By the way, the adjustment resistor described above is, for example, (i) a method of being housed inside the sensor body, (ii) a method of serially interposing between the sensor and the processing circuit, and (iii) a method of being housed inside the connector. And are proposed respectively.

However, the method (i) has a problem that the sensor itself is heated to a high temperature, so that an appropriate adjustment resistance value cannot be maintained.

Also, in the methods (ii) and (iii), the adjustment resistor and the output signal lead are connected mechanically in series and mechanically, so when installing the sensor or inspecting the engine room, the cable When pulling out, a large pull-out force may act between the output lead and the adjusting resistor, which causes problems when the adjusting resistor is damaged or the resistance characteristic changes.

The present invention has been made in view of the above circumstances, and the adjustment resistor is not adversely affected by high heat, and is not likely to be damaged by external force, and stably maintains a high-precision resistance value for a long time. It is an object of the present invention to provide an exhaust gas concentration detection device that can be used.

[Means for solving problems]

The device of the present invention created to achieve the above object calibrates the characteristics of the exhaust gas concentration sensor, the drive circuit that issues a control signal in response to the detection signal from the exhaust gas concentration sensor, and the characteristics of the exhaust gas concentration sensor. Is applied to an exhaust gas concentration detection device having a resistor for controlling the exhaust gas concentration sensor, and at least one of the resistors is pulled out from a drive circuit and at least the drive is provided in the middle of a lead wire branched from the lead of the exhaust gas concentration sensor. A side that is connectable / disconnectable with respect to the circuit is provided with a pair of connectors that are separate from the exhaust gas concentration sensor and its lead wire, and a side of the resistor that is connectable / disconnectable with respect to the drive circuit is connected to the resistor. At least one is accommodated and the voids are filled with an electrically insulating material and buried.

[Action]

According to the above configuration, (a) since the calibration resistor (adjustment resistor) is drawn out by the lead wire, it is possible to dispose this adjustment resistor away from the high temperature part, and It is possible to maintain a proper resistance value without being affected by.

(B) Do not fix the adjustment resistor and the lead wire directly to the above,
Since the lead wire is provided through the connector, the adjustment resistor is not subjected to excessive force even if the lead wire is pulled strongly due to some circumstances (for example, something is hung up).

(C) In addition, since the adjusting resistor is stored on the detachable side of the connector (the side that is not fixed to the lead wire but can be freely connected or disconnected), it has a different resistance value. If it is prepared in advance, attachment / detachment / replacement can be easily and quickly performed.

(D) Since the adjusting resistor is housed in the connector and the gap is filled with an electrically insulating material and embedded, the sealing property of the resistor housed in the connector, insulation, vibration resistance, and pull pull-out prevention of the lead As a result, it is possible to maintain a proper resistance value.

〔Example〕

FIG. 1 is a wiring diagram showing an embodiment of an exhaust gas concentration detecting device according to the present invention.

Reference numeral 10 is an oxygen concentration detector, which includes an electrolyte 1, an electrode 2,
3 and a diffusion hole 4 are provided. That is, the electrodes 2 and 3 are provided inside and outside the partition wall of the zirconia electrolyte 1 and
Is exposed to the atmosphere and the outer electrode 3 is introduced through the diffusion hole 4. Exposed to vehicle exhaust gas. Since this zirconia electrolyte 1 has a large internal resistance at low temperatures, it is used in combination with a heater 5 while being constantly heated. The internal resistance of the zirconia electrolyte 1 is R ₁ , the electromotive force is E, and this can be combined with a bridge circuit for driving to obtain an output. Resistance R ₂ , Rs,
A bridge is formed by R ₃ and Ri, and each side has a resistance. E'is a set voltage commensurate with the super power E. Assemble an operational amplifier A1 that can differentially amplify the voltage generated at the middle point of each bridge resistor array, increase or decrease the heater current according to the differential amplification amount, and automatically change the heating amount to produce a zirconia electrolyte. Always keep 1 in the specified temperature range. Vc is a bias voltage applied in advance so that the output can be maintained positive in the latch region where the excess air ratio λ is 1 or less. V _B is the power supply voltage, and Vo is the output voltage value. Tr is a transistor for receiving the output of the differential amplifier and determining the value of the current flowing through the heater 5. Such a drive circuit unit 11 of the air-fuel ratio detector 10 is housed inside a case 12 in which a circuit board in which a microcomputer used for controlling an engine of an automobile is housed. The difference in the film thickness and the density of the diffusion film is absorbed by absorbing the variation of the detection part including the zirconia electrolytic solution 1 of the air-fuel ratio detector 10 (the difference in the density is the number of gas diffusion holes inside, the hole diameter, the Adjustment resistors R ₂ and Rs are provided in order to eliminate the influence of the variation due to variations in length, etc.).

The adjusting resistors R ₂ and Rs above are connected to the lead wire L from the drive circuit 11.
It is drawn out via ₁ , L ₂ and L _3, and is connected via the connectors 13 and 14, and further via the lead wires L ₈ , L ₉ , L ₁₀ and the connector 15.

The connector 15 is fitted and connected to the outer casing of the adjusting resistor assembly 16 '.

In other words, the connector 15 is a so-called female connector, and the adjusting resistors R ₂ and Rs are housed in a male connector that can be connected / disengaged with the connector 15 to form the adjusting resistor Ass'y 16.

FIG. 3 (A) is an external view including the lead wires L _{1 to} L ₁₀ and the connectors 13, 14 and 15. FIG. 4 is a sectional view of the connector 15 and the adjusting resistor assembly 16 '. A view taken along the line VV of FIG. 4 is shown in FIG.

The oxygen concentration detector portion 10 shown in FIG. 1 is connected to the above-mentioned connector 14 via lead wires L ₁₁ , L ₁₂ , L ₁₃ , and L ₁₄ . The appearance of this part is shown in FIG.

(Refer to FIG. 4) The adjusting resistor assembly 16 constructed by applying the present invention is combined with the connector 15 at the tip thereof with the retaining mechanism 17. A rubber waterproof plug 20 is fitted to the ready-made connector 15, and an automobile low-voltage electric wire 26 is in contact with the inside. A ready-made metal terminal 21 with a stopper is attached to the tip thereof, and is fitted into the connector case 15.

The adjustment resistor assembly 16 is attached to a new resin housing 23 via a prevention rubber 22. The metal terminal 21
Is fitted in the metal terminal 24, and one or two combinations of adjusting resistors R ₂ , RS, and R ₃ are attached to the other end of each pair of metal terminals. An insulating coating 27, which can be processed at a low temperature, is provided in these adjusting resistors, and is wrapped and embedded. Finally, the lid 25 is fixed, for example, by ultrasonic fusion at the outer peripheral contact surface portion. As an application example, the connector 15 and the adjustment resistor assembly 16 are attached to the adjustment resistor attachment leads directly out of the computer storage case 12.

FIG. 2 is a wiring diagram of an embodiment different from the embodiment of FIG. 1, but the external appearance of this embodiment is similar to that of FIG. 3 (A).

As a modified example of the embodiment shown in FIG. 3 (A) (a wiring diagram is omitted, the entire structure can be as shown in FIG. 3 (B).

FIG. 7 is an explanatory view schematically showing the internal structure of FIG. 3 (A).

FIGS. 8A and 8B are an external view of an embodiment different from FIGS. 3A and 7 and a schematic view of the internal structure. This example is an example in which the adjusting resistors R ₂ and Rs are housed in the connector 16 ′ so that they can be inserted and removed freely.

FIG. 9 is a schematic view of a further different embodiment, and FIG. 10 is a schematic view of a further different embodiment.

In any of the embodiments described above, (I) the mounting portion of the adjusting resistor is not affected by heat conduction through the air-fuel ratio detector and its leads, so that the adjusting resistor is It can be used within the range. Therefore, the accuracy of the output voltage can be kept high for a long period of time.

(II) When trying to attach an air-fuel ratio detector, or when working in the vicinity of the device of the present invention, such as when inspecting the engine room, even if a strong lead is given by hooking the lead wire, Does not damage the adjusting resistor.

(III) The adjusting resistor Ass'y uses a combination of resistances on each side of the bridge, and if one resistance value is determined, the other is uniquely determined. Therefore, the number of assembling steps can be reduced.

(IV) The adjusting resistor assembly is, for example, an adjusting resistor when the output voltage after adjustment is slightly higher than the specified value.
Since the Ass'y can be replaced with another Ass'y immediately after removing the retainer, it is possible to improve the yield.

(V) Since the length of the lead using the heat resistant coating on the air-fuel ratio detector side can be minimized, the cost can be kept low.

(VI) Preventive measures, insulation measures, anti-vibration measures, lead pull-out prevention measures, etc. can be implemented by gathering existing parts, so reliability can be improved at low cost.

〔The invention's effect〕

As described above in detail, when the present invention is applied, the adjustment resistor can maintain the resistance value with high accuracy without being affected by high heat, and moreover, the adjustment can be performed even if the lead wire is subjected to excessive tension. There is no risk of damaging the resistor.

[Brief description of drawings]

1 and 2 are wiring diagrams in one embodiment of the present invention. FIG. 3 (A) is an external view common to both of the above embodiments, and FIG. 3 (B) is an external view of an embodiment different from the above. FIG. 4 is a sectional view of the connector 15 and the adjusting resistor Ass'y shown in the embodiment of FIG. 3, and FIG. 5 is a V-V arrow view thereof. FIG. 6 is a characteristic chart showing the relationship between the excess air ratio and the output voltage. FIG. 7 is an explanatory view schematically showing the internal structure of the above-mentioned embodiment (FIG. 3 (A)). FIGS. 8A and 8B are an external view of an embodiment different from FIGS. 3A and 7 and a schematic view of the internal structure. 9 to 10 are explanatory views of further different embodiments. 1 …… Zirconia electrolyte, 2,3 …… Electrode, 4 …… Diffusion hole, 5 …… Heater, 10 …… Oxygen concentration detector (air-fuel ratio detector), 12 …… Case, 13,14,15 …… Connector, 16 …… Adjusting resistor assembly, 27 …… Coating, L _{1 to} L ₁₄ ……
Lead wire, R ₂ , Rs, R ₃ …… Adjusting resistor (each resistor forming one side of the bridge), Ri …… Internal resistance of zirconia electrolyte, E …… Electromotive force of zirconia electrolyte, E ′ …… above Set voltage commensurate with electromotive force E, A1 ... Operational amplifier, Vc ...
… Bias voltage, V _B …… Power supply voltage, Vo …… Output voltage, Tr
... transistor.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location G01N 27/58 B (72) Inventor Sadane Ueno 2520 Takaba, Katsuta, Ibaraki Hitachi, Ltd. Factory Sawa Factory (56) Bibliography Sho 61-140957 (JP, U) Sho 61-140956 (JP, U)

Claims (1)

[Claims] 1. Exhaust gas comprising an exhaust gas concentration sensor, a drive circuit for receiving a detection signal from the exhaust gas concentration sensor and issuing a control signal, and a resistor for calibrating the characteristics of the exhaust gas concentration sensor. In the gas concentration detection device, at least one of the resistors is pulled out from the drive circuit, and at least in the middle of the lead wire branched from the lead of the exhaust gas concentration sensor, at least the side that can be connected to and disconnected from the drive circuit is the exhaust gas. A pair of connectors separate from the gas concentration sensor and its lead wire are provided, and at least one of the resistors is housed on the side of the connector which can be connected / disconnected to / from the drive circuit and is made of an electrically insulating material. An exhaust gas concentration detector characterized in that it is filled with a void and buried.