JP4075446B2 - Secondary air supply passage opening / closing valve and secondary air supply system failure diagnosis apparatus using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an on-off valve used in a secondary air supply system for supplying secondary air to an upstream side of an exhaust purification device disposed in an exhaust system of an internal combustion engine, and a failure diagnosis device for a secondary air supply system using the same. About.
[0002]
[Prior art]
As an exhaust gas purification device for an internal combustion engine, a device is known in which a three-way catalyst is disposed in an exhaust system to purify the exhaust gas by reducing CO, HC, and NOx components. Further, by pumping air from the air pump to a secondary air supply passage having an on-off valve connected to the exhaust pipe, the secondary air is supplied into the exhaust pipe to increase the oxygen concentration, and HC in the exhaust gas, A technique for promoting the purification of exhaust gas by oxidizing CO is known.
[0003]
In such a secondary air supply system, if an abnormality occurs in a component such as an air pump or an on-off valve, the exhaust gas purification efficiency decreases, and the emission deteriorates. Therefore, it is necessary to determine the abnormality early. . Therefore, as techniques for detecting this type of abnormality, techniques disclosed in Japanese Patent Application Laid-Open Nos. 9-21312 and 9-125945 are known.
[0004]
In the former, a pressure sensor is disposed between the air pump and the on-off valve in the secondary air supply passage, and an abnormality of the secondary air supply device is detected based on the detected pressure value. In the latter, a pressure sensor is disposed in the secondary air supply passage, and an abnormality of the secondary air supply device is detected based on the difference between the detected maximum value and the minimum value of the pressure pulsation.
[0005]
[Problems to be solved by the invention]
When the pressure sensor is arranged between the air pump and the open / close valve in this way, it is easy to detect a large open failure in which the open / close valve cannot be closed while being fully opened. In the case of a small open failure such as a small foreign object being caught, it is difficult to detect. This is because a small open failure has a small pressure difference from the normal time (closed), and if the threshold is reduced to determine such a small open failure, depending on fluctuations in the discharge pressure of the air pump, the open / close valve This is because there is a risk that the on-off valve may be erroneously determined to be abnormal even though is normal.
[0006]
Therefore, an object of the present invention is to provide a secondary air supply passage opening / closing valve having a configuration capable of accurately detecting even such a small open failure and a failure diagnosis device for a secondary air supply system using the secondary air supply passage on / off valve.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems, a secondary air supply passage opening / closing valve according to the present invention supplies secondary air via a secondary air supply passage connected upstream of an exhaust purification device disposed in an exhaust passage of an internal combustion engine. The secondary air supply system is a secondary air supply passage on / off valve that switches the open / close state of the secondary air supply passage upstream of a check valve disposed in the secondary air supply passage, Is provided separately from the inlet port with a conduction path that opens into the upstream chamber of the valve body and communicates with the pressure sensor.
[0008]
A failure diagnosis device for a secondary air supply system according to the present invention includes a secondary air supply passage on-off valve according to the present invention, a pressure sensor connected to the conduction path, an air pump arranged upstream of the on-off valve, An abnormality detection device for a failure diagnosis of a secondary air supply system comprising a check valve arranged downstream of an on-off valve, which detects an on-off valve abnormality based on a pressure pulsation detected by a pressure sensor when the air pump is stopped Part.
[0009]
In the case of a small opening abnormality such as a small foreign object caught in the valve body of the on-off valve, the pressure inside the upstream chamber near the valve body is affected by the exhaust pulsation on the downstream side due to the conduction between the upstream side and the downstream side. However, since this pulsation attenuates as the distance from the valve body increases, it is difficult to detect outside the on-off valve. The on-off valve according to the present invention is capable of detecting this pressure pulsation by providing a conduction path from the upstream chamber to the pressure sensor separately from the inlet port. Even abnormalities can be detected accurately. Furthermore, it is possible to determine an abnormal level of valve opening according to the magnitude of pulsation.
[0010]
The conduction path is preferably opened at a position substantially opposite to the inlet port across the valve body in the upstream chamber. By opening the conduction path at a position away from the flow path from the inlet port of the on-off valve to the valve body, pressure detection independent of the flow in the upstream chamber can be performed, and accurate determination can be made.
[0011]
It is preferable that the conducting path extends upward from the horizontal direction from the on-off valve body in the attached state of the on-off valve. With this configuration, condensate water can be prevented from entering into the conduction path, and if it enters, it is easy to discharge, so freezing of the condensed water in the conduction path when the engine is stopped in cold weather is suppressed. Incorrect determination can be effectively prevented.
[0012]
It is preferable that the leading end of the conduction path is disposed so as to protrude to the vicinity of the valve body. As a result, it is possible to detect smaller pulsations, and it is possible to expand the abnormality level that can be determined.
[0013]
If the check valve is further integrated, the system can be easily assembled and the individual difference in pressure pulsation can be reduced, so that the detection accuracy can be improved.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same reference numerals are given to the same components in the drawings as much as possible, and duplicate descriptions are omitted.
[0015]
FIG. 1 is a schematic configuration diagram of a secondary air supply system including a secondary air supply passage opening / closing valve according to the present invention, and FIG. 2 is a first embodiment of a secondary air supply passage opening / closing valve according to the present invention. FIG.
[0016]
The secondary air supply device (hereinafter referred to as AI supply device) 1 is attached to a multi-cylinder gasoline engine (hereinafter simply referred to as engine) 2 that is an internal combustion engine. Here, an intake pipe 20 and an exhaust pipe 21 are connected to the engine 2, and a throttle 24 is disposed on the intake pipe 20 and connected to an intake filter 25. On the other hand, an exhaust purification device 22 made of a three-way catalyst is disposed downstream of the exhaust pipe 21.
[0017]
The AI supply device 1 includes a secondary air (AI) supply passage 11 that connects a position between the intake filter 25 and the throttle 24 of the intake pipe 20 and the engine 2 and the exhaust purification device 22 of the exhaust pipe 21. An air pump (AP) 12 driven by an electric motor is disposed on the AI supply passage 11, and a secondary air supply passage opening / closing valve (hereinafter referred to as an opening / closing valve at the end) 13 according to the present invention is provided downstream thereof. Be placed. A pressure sensor 15 is connected to the on-off valve 13. A pipe 16 extending from the downstream side of the throttle 24 of the intake pipe 20 is connected to the on-off valve 13, and an electromagnetic three-way valve 17 is further disposed on the pipe 16 (for convenience of explanation, the pipe 16 is connected to the three-way valve 13. The valve 17 is divided into two parts, and the intake pipe 20 side is represented by reference numeral 16a and the on-off valve 13 side is represented by reference numeral 16b). The three-way valve 17 is connected to the outside air via a passage 18 and an air filter 19.
[0018]
Here, the on-off valve 13 is an integrated check valve. As shown in FIG. 2, the main body 130 is divided into four air chambers 130a to 130d. Between the air chamber 130a and the air chamber 130b, there is a diaphragm 131, a valve body 133 in the connecting hole portion of the air chamber 130b with the air chamber 130c, and a connecting hole portion of the air chamber 130d in the connecting hole portion with the air chamber 130c. Reed valve bodies 134 serving as stop valves are respectively disposed, and the valve body 133 is directly connected to the diaphragm 131 by a rod 133a. The reed valve body 134 includes a leaf spring portion 134a and a valve body 134b, and the leaf spring portion 134a presses the valve body 134b against the valve seat portion of the body 130 with a predetermined force.
[0019]
The air chamber 130a is connected to the pipe 16b via the connection port 135, and a spring 132 that presses the diaphragm 131 toward the air chamber 130b is disposed therein. An inlet port 136 is provided on a side surface of the air chamber 130b and is connected to the AI supply passage 11 connected to the AP 12. And the conduction path 137 is provided in the side surface facing this, and the pressure sensor 15 is attached through the tube 138. The tube 138 is arranged to bend upward from the horizontal when the vehicle is mounted. An outlet port 139 is provided at the lower end of the air chamber 130 d and is connected to the AI supply passage 11 connected to the exhaust pipe 21.
[0020]
The control device 10 that controls the operation of the AI supply device 1 is electrically connected so as to be able to exchange information with the engine ECU 23 that controls the engine, and also receives an output signal of the pressure sensor 15 and AP 12 The motor drive and the opening / closing of the three-way valve 17 are controlled. This control device also serves as an abnormality detection unit of the failure diagnosis device for the secondary air supply system according to the present invention. Note that the control device 10 may form part of the engine ECU 23.
[0021]
This AI supply device 1 has a high fuel concentration mainly during cold start, an air-fuel ratio (A / F) is small, and the exhaust purification device 22 has not sufficiently raised its temperature to fully perform its function. In a state where it is difficult to do so, the control device 10 drives the air pump 12 and causes the pipe 16 a and the pipe 16 b to communicate with each other by the three-way valve 17 to guide the negative pressure in the intake pipe 20 to the air chamber 130 a of the on-off valve 13. In the on-off valve 13, the pressure on the air chamber 130b side becomes higher than the pressure on the air chamber 130a side, and the diaphragm 131 moves to the air chamber 130a side, so that the valve body 133 connected thereto moves upward in FIG. To make the air chambers 130b and 130c communicate with each other. Further, since the exhaust pipe 21 side also has a negative pressure, the pressure on the air chamber 130c side becomes higher than the pressure on the air chamber 130d side, so that the reed valve body 134 is pushed out to the air chamber 130d side, and the air chambers 130c and 130d. Is also communicated. As a result, part of the air (secondary air) that has passed through the intake filter 25 is guided into the exhaust pipe 21 via the AI supply passage 11. As a result, the oxygen concentration in the exhaust gas is increased, the A / F is increased, the secondary combustion of the HC and CO in the exhaust gas in the exhaust pipe 21 is promoted to purify the exhaust gas, and the exhaust gas temperature is increased. In this way, the exhaust emission control device (three-way catalyst) 22 is accelerated in temperature to suppress the deterioration of the emission.
[0022]
When the AI supply is stopped, the control device 10 stops the AP 12 and closes the on-off valve 13. Specifically, by controlling the three-way valve 17 to connect the passage 18 and the pipe 16b, outside air is introduced into the air chamber 130a of the on-off valve 13 via the air filter 19, the passage 18, and the pipe 16b. The pressure in the chamber 130a is set to atmospheric pressure, and the valve body 133 is pressed against the valve seat of the main body 130 by the spring 132 to block communication between the air chambers 130b and 130c.
[0023]
The AI supply device 1 has a function of detecting abnormalities in the component parts, that is, the AP 12 and the on-off valve 13 using the pressure behavior detected by the pressure sensor 15. Specifically, first, when the AI system is stopped, that is, the AP 12 is stopped, and the on-off valve 13 is closed, the pressure sensor 15 detects the pulsation amount of the pressure value P. FIG. 3 is a graph showing this pulsation. Hereinafter, it is assumed that the AP 12 is operating as controlled.
[0024]
If the valve body 133 of the on-off valve 13 completely shuts off the communication between the air chambers 130b and 130c, the pressure detected by the pressure sensor 15 should be almost atmospheric pressure. On the other hand, as shown in FIG. 2, when so-called biting occurs in which the foreign matter 14 exists between the valve body 133 and the valve seat, the air chamber 130b and the air chamber 130c are communicated with each other. The pulsation in the exhaust pipe 21 is transmitted. If the reed valve body 134 functions normally, the communication between the air chambers 130c and 130d is blocked when the pressure on the exhaust pipe 21 side, that is, the air chamber 130d is higher than that of the air chamber 130c. The pressure value P detected by the pressure sensor 15 according to the magnitude pulsates as shown in FIG.
[0025]
Further, if the reed valve body 134 fails and an open failure occurs in which the air chambers 130c and 130d are always in communication, the pulsation in the exhaust pipe 21 is transmitted to the air chamber 130b, and is detected by the pressure sensor 15. The pressure value P to be pulsated as shown in FIG. In this way, the abnormality of the valve body 133 and the reed valve body 134 can be determined from the pulsation state of the pressure value P. In particular, it is possible to accurately determine the clogging of a small foreign object that has been difficult to determine in the past, and it is possible to estimate the degree of abnormal opening, that is, the size of a foreign object based on the magnitude of pulsation.
[0026]
The pulsation in the exhaust pipe 21 attenuates as the distance from the exhaust pipe 21 increases. The on-off valve 13 according to the present invention directly pulls out the conduction path 137 from the air chamber 130b and measures the pressure with the pressure sensor 15, so when detecting the pressure in the pipe 11 upstream of the on-off valve 13. In comparison, the pressure can be measured with a large pulsation width, and the pulsation can be detected with high accuracy. In particular, accurate detection is possible by taking out pressure from the side facing the inlet port 136 across the valve body 133. Further, when mounted on the vehicle, the condensate enters the conducting path 137 and the tube 138 from the exhaust pipe 21 side by arranging the conducting path 137 and the tube 138 leading to the pressure sensor 15 so as to face upward from the horizontal. Even in such a case, it is possible to facilitate the discharge and prevent freezing when the engine 2 is stopped to perform accurate measurement.
[0027]
4-6 is a block diagram which shows the 2nd-4th embodiment of the on-off valve 13 based on this invention, respectively. In any embodiment, the basic configuration is the same as that of the first embodiment shown in FIG. 2, and only the configurations of the conduction path 137 and the tube 138 are different.
[0028]
In the second embodiment shown in FIG. 4, the conduction path 137 itself is formed so as to extend obliquely upward rather than horizontally when mounted on a vehicle, and a tapered portion 137 a is provided at a connection portion to the tube 138. The intrusion of the condensed water into the conduction path 137 is suppressed, and even when it enters, the discharge is easy.
[0029]
In the third embodiment shown in FIG. 5, the conduction path 137 is formed in an L shape and is connected to the tube 138 at a portion extending upward. Also in this embodiment, a tapered portion 137a is provided at the connection portion to the tube 138, as in the second embodiment. As a result, the condensed water does not easily accumulate at the joint portion between the conduction path 137 and the tube 138, and can easily be discharged when it enters.
[0030]
In the fourth embodiment shown in FIG. 6, the conduction path 137 in the second embodiment is extended into the air chamber 130 b, and the tip 137 b is disposed in the vicinity of the valve body 133. With this arrangement, the pressure pulsation in the vicinity of the valve body 133 can be grasped, so that even a minute foreign object can be detected.
[0031]
Further, as shown in FIG. 7, the upstream valve of the on-off valve 13 may be a solenoid valve instead of a diaphragm type. In this case, when the valve body 133 is disposed in the air chamber 130b and opened when moving upward in the figure, the valve body 133 is disposed in the air chamber 130c and moved downward. It is good also as a structure which opens to. Further, the check valve may be provided separately from the on-off valve 13 instead of being integrated.
[0032]
【The invention's effect】
As described above, according to the present invention, it is possible to more accurately measure the pressure in the air chamber upstream of the valve body of the on-off valve, which is an on-off means in the secondary air supply system. Based on the pressure pulsation of this portion at the time, it is possible to accurately detect abnormalities that have been difficult to distinguish in the past, such as, for example, clogging of foreign matter in the valve body.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a secondary air supply system including a secondary air supply passage opening / closing valve according to the present invention.
FIG. 2 is a cross-sectional view showing a first embodiment of a secondary air supply passage opening / closing valve according to the present invention.
FIG. 3 is a graph showing pressure pulsation used in abnormality detection.
FIG. 4 is a cross-sectional view showing a second embodiment of the secondary air supply passage opening / closing valve according to the present invention.
FIG. 5 is a cross-sectional view showing a third embodiment of the secondary air supply passage opening / closing valve according to the present invention.
FIG. 6 is a cross-sectional view showing a fourth embodiment of the secondary air supply passage opening / closing valve according to the present invention.
FIG. 7 is a cross-sectional view showing a fifth embodiment of the secondary air supply passage opening / closing valve according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Secondary air supply device, 2 ... Engine, 10 ... Control device, 11 ... Secondary air supply passage, 12 ... Air pump, 13 ... Secondary air supply passage on-off valve, 14 ... Foreign matter, 15 ... Pressure sensor, 16 ... Piping, 17 ... three-way valve, 18 ... passage, 19 ... air filter, 20 ... intake pipe, 21 ... exhaust pipe, 22 ... exhaust purification device, 23 ... engine ECU, 24 ... throttle, 25 ... intake filter, 130 ... main body, 130a to 130d ... air chamber, 131 ... diaphragm, 132 ... spring, 133 ... valve body, 134 ... reed valve body, 135 ... connection port, 136 ... inlet port, 137 ... conduction path, 138 ... tube, 139 ... outlet port.

Claims (6)

In a secondary air supply system that supplies secondary air via a secondary air supply passage that is connected to an upstream side of an exhaust purification device that is disposed in an exhaust path of an internal combustion engine, a reverse arrangement that is disposed in the secondary air supply passage. A secondary air supply passage opening / closing valve for switching the open / close state of the secondary air supply passage upstream from the stop valve,
The on-off valve body is a secondary air supply passage on-off valve that is provided in the upstream chamber of the valve body and has a conduction path that communicates with the pressure sensor separately from the inlet port. 2. The secondary air supply passage opening / closing valve according to claim 1, wherein the conduction path opens at a position substantially opposite to the inlet port across the valve body in the upstream chamber. 3. The secondary air supply passage opening / closing valve according to claim 1, wherein the conduction path extends upward from the opening / closing valve main body in a mounted state of the opening / closing valve. 4. The secondary air supply passage opening / closing valve according to claim 2, wherein a leading end of the conduction path protrudes toward the vicinity of the valve body. 5. The secondary air supply passage opening / closing valve according to any one of claims 1 to 4, wherein the check valve is further integrated. The secondary air supply passage opening / closing valve according to any one of claims 1 to 5, a pressure sensor connected to the conduction path, an air pump disposed upstream of the opening / closing valve, and disposed downstream of the opening / closing valve. A failure diagnosis device for a secondary air supply system comprising a check valve,
A failure diagnosis device for a secondary air supply system, comprising: an abnormality detection unit that detects an abnormality of the on-off valve based on a pressure pulsation detected by the pressure sensor when the air pump is stopped and the on-off valve is closed.

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