Gas sensor arrangement structure

Abstract

To provide a gas sensor arrangement structure that can suppress the temperature of the gas sensor's detection element from dropping below its activation temperature due to the influence of airflow during vehicle operation, thereby reducing the frequency of heater activation. [Solution] The arrangement structure of the gas sensor 21 includes a gas sensor 21 having a detection element 21a for detecting the concentration of NOx in the exhaust gas flowing through the exhaust pipe 4, and a heater 23 for heating the detection element 21a to an activation temperature. The gas sensor 21 is positioned behind the cross member 5 in the front-rear direction, and is mounted on the exhaust pipe 4 such that the detection element 21a is positioned lower than the upper end 5a of the cross member 5 and higher than the lower end 5b of the cross member 5.

Description

Technical Field

[0001] The present invention relates to an arrangement structure of gas sensors.

Background Art

[0002] Conventionally, there has been known a sensor control device that is attached to an exhaust pipe of an internal combustion engine of an automobile and detects the concentration of a specific gas component in the gas flowing through the exhaust pipe (see Patent Document 1).

[0003] This sensor control device includes a gas sensor that detects the concentration of a specific gas contained in the gas to be detected, and a heater that heats the gas sensor to a temperature equal to or higher than the activation determination temperature, and suppresses deterioration of the gas sensor while reducing the power consumption of the heater of the gas sensor during idling stop.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, in the case of a gas sensor, since the gas detection accuracy decreases unless the temperature of the gas sensor reaches a predetermined temperature (for example, from 600°C to 700°C), it is heated to a temperature equal to or higher than the activation temperature by a heater.

[0006] However, when the pipe portion of the exhaust pipe where the gas sensor is disposed is exposed to the traveling wind during vehicle travel, the gas sensor is cooled and tends to become lower than the activation temperature.

[0007] As a result, the frequency of heating by the heater increases, and there is a possibility that the power consumption of the heater increases. For this reason, it is desirable to reduce the frequency of heating the heater.

[0008] This invention has been made in view of the above circumstances, and aims to provide an exhaust gas detection device that can suppress the temperature of the gas sensor's detection element from dropping below its activation temperature due to the influence of wind during vehicle operation, thereby reducing the frequency of heater operation. [Means for solving the problem]

[0009] The present invention relates to a gas sensor arrangement structure comprising: an exhaust pipe extending from an internal combustion engine to below the floor surface of a vehicle and through which exhaust gas discharged from the internal combustion engine flows; a cross member positioned behind the internal combustion engine and extending in the vehicle width direction; a gas sensor attached to the exhaust pipe and having a detection element for detecting a specific gas component in the exhaust gas flowing through the exhaust pipe; and a heater for heating the detection element to an activation temperature, wherein the gas sensor is positioned behind the cross member in the longitudinal direction of the vehicle, and is attached to the exhaust pipe such that the detection element is positioned lower than the upper end of the cross member and higher than the lower end of the cross member. [Effects of the Invention]

[0010] As described above, according to the present invention, it is possible to suppress the temperature of the gas sensor's detection element from dropping below its activation temperature due to the influence of wind while the vehicle is in motion, thereby reducing the frequency with which the heater needs to be operated. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a left side view of a vehicle equipped with an exhaust gas detection device according to one embodiment of the present invention. [Figure 2] Figure 2 shows a vehicle equipped with an exhaust gas detection device according to one embodiment of the present invention, and is a longitudinal cross-sectional view of the side member, dash panel, floor panel, and rear of the exhaust pipe (viewed along arrow II-II in Figure 3). [Figure 3] Figure 3 shows a vehicle equipped with an exhaust gas detection device according to one embodiment of the present invention, and is a plan view of the side member and the rear of the exhaust pipe. [Modes for carrying out the invention]

[0012] A gas sensor arrangement structure according to one embodiment of the present invention comprises an exhaust pipe extending from an internal combustion engine to below the floor of the vehicle and through which exhaust gas discharged from the internal combustion engine flows, a cross member positioned behind the internal combustion engine and extending in the vehicle width direction, a gas sensor attached to the exhaust pipe and having a detection element for detecting a specific gas component in the exhaust gas flowing through the exhaust pipe, and a heater for heating the detection element to an activation temperature. The gas sensor is positioned behind the cross member in the longitudinal direction of the vehicle, and is attached to the exhaust pipe such that the detection element is positioned lower than the upper end of the cross member and higher than the lower end of the cross member.

[0013] As a result, the arrangement structure of the gas sensor according to one embodiment of the present invention can suppress the temperature of the detection element of the gas sensor from dropping below the activation temperature due to the influence of airflow during vehicle operation, thereby reducing the frequency of heater operation. [Examples]

[0014] The arrangement structure of a gas sensor according to one embodiment of the present invention will be described below with reference to the drawings. Figures 1 to 3 show the arrangement structure of a gas sensor according to one embodiment of the present invention.

[0015] First, let me explain the structure. In Figures 1 to 3, the vertical, horizontal, and vertical directions are based on the engine as it is positioned in the vehicle. The horizontal direction of the vehicle is defined as the horizontal direction, the horizontal direction (vehicle width direction) as the horizontal direction, and the vertical direction (height direction) as the vertical direction.

[0016] As shown in FIG. 1, the vehicle 1 includes an engine 2 as an internal combustion engine for a vehicle. The engine 2 has a cylinder block 2A, a cylinder head 2B provided on the upper part of the cylinder block 2A, a cylinder head cover 2C provided on the upper part of the cylinder head 2B, and an oil pan 2D provided on the lower part of the cylinder block 2A. The engine 2 burns fuel to convert thermal energy into mechanical energy and transmits power to a transmission (not shown).

[0017] On the front surface of the engine 2, a catalytic converter 3 is connected to the cylinder head 2B. The catalytic converter 3 has a catalyst (not shown) inside, removes harmful components from the exhaust gas discharged from the engine 2 by the catalyst, purifies the exhaust gas, and discharges it into an exhaust pipe 4.

[0018] The exhaust pipe 4 is connected to the downstream end of the catalytic converter 3, and the exhaust gas purified by the catalytic converter 3 is introduced into the exhaust pipe 4.

[0019] A cross member 5 is provided behind the engine 2. The cross member 5 extends in the vehicle width direction, and its left and right ends are respectively connected to a left side member and a right side member that extend in the front-rear direction of the vehicle.

[0020] A dash panel 6 is provided above the cross member 5, and the dash panel 6 extends in the vertical direction.

[0021] An engine room 7 is arranged in front of the dash panel 6, and a passenger compartment 8 is arranged behind the dash panel 6.

[0022] The engine 2 is arranged in the engine room 7, and passengers including a driver can board in the passenger compartment 8.

[0023] A floor panel 9 that constitutes the floor surface of the vehicle 1 is connected to the lower part of the dash panel 6, and the floor panel 9 extends rearward from the lower part of the dash panel 6. A floor tunnel 9A is provided on the floor panel 9.

[0024] The floor tunnel 9A is located between the driver's seat and the passenger seat (not shown) in the vehicle width direction, and bulges upward from the floor panel 9, extending in the front-rear direction.

[0025] The exhaust pipe 4 has an upstream exhaust pipe section 11, a curved exhaust pipe section 12, and a downstream exhaust pipe section 13. The upstream end 11a of the upstream exhaust pipe section 11 is connected to the downstream end of the catalytic converter 3, and the upstream exhaust pipe section 11 extends from the downstream end of the catalytic converter 3, passing under the engine 2 and to the rear.

[0026] Here, "upstream" and "downstream" refer to the upstream and downstream directions relative to the direction of exhaust gas flowing through the catalytic converter 3 and exhaust pipe 4. In other words, the catalytic converter 3 is located upstream of the exhaust pipe 4, and the exhaust pipe 4 is located downstream of the catalytic converter 3.

[0027] The downstream end 11b of the upstream exhaust pipe section 11 is positioned in front of the cross member 5. The upstream end 12a of the curved exhaust pipe section 12 is connected to the downstream end 11b of the upstream exhaust pipe section 11.

[0028] The curved exhaust pipe section 12 is bent upward from its upstream end 12a, which is located in front of the cross member 5, and then bent downward from its apex as it passes over the cross member 5.

[0029] The upstream end 13a of the downstream exhaust pipe section 13 is connected to the downstream end 12b of the curved exhaust pipe section 12, and the downstream exhaust pipe section 13 extends horizontally from the upstream end 13a behind the cross member 5. In this embodiment, the downstream exhaust pipe section 13 constitutes the exhaust pipe section. The curved exhaust pipe section 12 includes a connecting section connected by a pair of flanges 12F.

[0030] The upstream end of the muffler 24 is connected to the downstream end 13b of the downstream exhaust pipe section 13. The downstream end of the muffler 24 is connected to the furthest downstream exhaust pipe section (not shown), and the exhaust gas discharged from the muffler 24 is discharged to the outside (atmosphere) from the furthest downstream exhaust pipe section.

[0031] As shown in Figure 2, a gas sensor 21 is located in the downstream exhaust pipe section 13. That is, the curved exhaust pipe section 12 is located behind the cross member 5 in the front-rear direction, and the gas sensor 21 is located behind the cross member 5.

[0032] The gas sensor 21 consists of, for example, a sensor that detects the concentration of NOx as a specific gas component in the exhaust gas.

[0033] The gas sensor 21 may include sensors that detect specific gas components in the exhaust gas, such as oxygen concentration, carbon monoxide concentration, carbon dioxide concentration, and nitrogen carbide concentration, or air-fuel ratio sensors that detect the air-fuel ratio.

[0034] The gas sensor 21 includes a sensor body 21A, which is fixed to the upper end portion 13c of the downstream exhaust pipe section 13.

[0035] A detection element 21a is provided at the lower end (one end) of the sensor body 21A. The detection element 21a is positioned inside the downstream exhaust pipe section 13 and exposed to the exhaust gas, and detects the concentration of NOx in the exhaust gas.

[0036] A wiring connection section 21b is provided at the upper end (other end) of the sensor body 21A, and one end of the wiring 22 is connected to the wiring connection section 21b. The other end of the wiring 22 is connected to a control circuit (not shown), and information regarding NOx detected by the detection element 21a is output to the control circuit through the wiring 22.

[0037] A heater 23 is housed inside the sensor body 21A, and the heater 23 heats the detection element 21a to a temperature above its activation temperature (for example, 600°C to 700°C).

[0038] The wiring 22 consists of a bundle of signal wiring that transmits information about NOx detected by the detection element 21a to the control circuit, and power supply wiring that heats the heater 23.

[0039] The gas sensor 21 is mounted on the downstream exhaust pipe section 13 such that the detection element 21a is positioned lower than the upper end 5a of the cross member 5 and higher than the lower end 5b of the cross member 5.

[0040] Specifically, the upper end portion 13c of the downstream exhaust pipe section 13 is located lower than the upper end portion 5a of the cross member 5, and the detection element 21a is positioned in the downstream exhaust pipe section 13 so as to be located below the upper end portion 13c of the downstream exhaust pipe section 13.

[0041] In Figure 2, a virtual plane 25 is shown that passes horizontally through the upper end 5a of the cross member 5, and a virtual plane 26 is shown that passes horizontally through the lower end 5b of the cross member 5.

[0042] The wiring connection section 21b is positioned above the upper end 5a of the cross member 5. In other words, the sensor body 21A is positioned above the upper end 13c of the downstream exhaust pipe section 13, and the wiring connection section 21b located at the upper end of the sensor body 21A is exposed to the outside air.

[0043] Next, the effects of the arrangement structure of the gas sensor 21 in this embodiment will be explained. The arrangement structure of the gas sensor 21 in this embodiment includes an exhaust pipe 4 that extends from the engine 2 to below the floor panel 9 of the vehicle 1 and through which exhaust gas discharged from the engine 2 flows, a cross member 5 positioned behind the engine 2 and extending in the vehicle width direction, a gas sensor 21 attached to the downstream exhaust pipe section 13 of the exhaust pipe 4 and having a detection element 21a for detecting the concentration of NOx in the exhaust gas flowing through the exhaust pipe 4, and a heater 23 for heating the detection element 21a to an activation temperature.

[0044] The gas sensor 21 is positioned behind the cross member 5 in the front-rear direction, and is mounted on the exhaust pipe 4 such that the detection element 21a is positioned lower than the upper end 5a of the cross member 5 and higher than the lower end 5b of the cross member 5.

[0045] This allows the airflow from the front to the rear of the vehicle 1 to collide with the cross member 5 and be blocked, splitting it into airflow W1 flowing above the cross member 5 and airflow W2 flowing below the cross member 5 (see Figure 2), thereby preventing the downstream exhaust pipe section 13 located behind the cross member 5 from being cooled by the airflow W1 and W2.

[0046] Therefore, the detection element 21a located in the downstream exhaust pipe section 13 can be prevented from being cooled by the airflow W1 and W2 and falling to a temperature lower than its activation temperature. As a result, the heater 23 can be prevented from frequently heating the detection element 21a to raise it to its activation temperature, thereby reducing the power consumption of the heater 23.

[0047] Furthermore, according to the arrangement structure of the gas sensor 21 in this embodiment, the gas sensor 21 comprises a sensor body 21A fixed to the downstream exhaust pipe section 13 and having a detection element 21a at its lower end, and a wiring connection section 21b located at the upper end of the sensor body 21A to which the wiring 22 is connected, with the wiring connection section 21b located above the upper end 5a of the cross member 5.

[0048] In this way, by positioning the wiring connection portion 21b, which has a relatively lower heat resistance temperature within the sensor body 21A, above the upper end portion 5a of the cross member 5, it is possible to prevent the airflow W1 flowing from the front to the rear of the vehicle 1 from being obstructed by the cross member 5, thereby supplying the airflow W1 to the wiring connection portion 21b.

[0049] Therefore, the airflow W1 ensures that the wiring connection section 21b is reliably cooled, and the temperature of the wiring connection section 21b is suppressed.

[0050] Furthermore, according to the arrangement structure of the gas sensor 21 in this embodiment, the exhaust pipe 4 is located behind the cross member 5 and has a downstream exhaust pipe section 13 where the upper end 13c is located lower than the upper end 5a of the cross member 5, and the gas sensor 21 is arranged in the downstream exhaust pipe section 13.

[0051] In this way, by positioning the detection element 21a at a lower position than the upper end portion 13c of the downstream exhaust pipe section 13, the cooling of the detection element 21a by the airflow W1 and W2 can be more effectively suppressed.

[0052] While embodiments of the present invention have been disclosed, it will be apparent to those skilled in the art that modifications can be made without departing from the scope of the invention. All such modifications and equivalents are intended to be included in the following claims. [Explanation of Symbols]

[0053] 1 vehicle 2. Engine (internal combustion engine) 4 Exhaust pipes 5 Cross Member 5a Upper end (upper end of the cross member) 5b Lower end (lower end of cross member) 13 Downstream exhaust pipe section (exhaust pipe section) 21 Gas Sensor 21A Sensor Body 21a Detection element 21b Wiring connection section 23 Heater

Claims

1. An exhaust pipe extending from the internal combustion engine to below the vehicle floor, through which exhaust gas discharged from the internal combustion engine flows, A cross member positioned behind the internal combustion engine and extending in the vehicle width direction, A gas sensor attached to the exhaust pipe and having a detection element for detecting a specific gas component in the exhaust gas flowing through the exhaust pipe, A gas sensor arrangement structure comprising a heater for heating the detection element to an activation temperature, The gas sensor arrangement structure is characterized in that the gas sensor is positioned behind the cross member in the longitudinal direction of the vehicle, and the detection element is mounted on the exhaust pipe such that it is positioned lower than the upper end of the cross member and higher than the lower end of the cross member.

2. The aforementioned gas sensor is A sensor body fixed to the exhaust pipe and having the detection element at one end, The sensor body is provided with a wiring connection section located at the other end to which wiring is connected, The arrangement structure for a gas sensor according to claim 1, characterized in that the wiring connection portion is positioned above the upper end of the cross member.

3. The exhaust pipe has an exhaust pipe section located behind the cross member, with its upper end positioned lower than the upper end of the cross member. The arrangement structure for a gas sensor according to claim 1 or 2, characterized in that the gas sensor is located in the exhaust pipe section.

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