JP4333528B2 - Secondary air supply device - Google Patents

Description

  The present invention relates to a secondary air supply device that supplies secondary air to an upstream side of an exhaust purification device provided in an exhaust passage of an internal combustion engine.

  In an internal combustion engine, a catalyst having an oxidation function is disposed in an exhaust passage, and carbon monoxide (hereinafter referred to as “CO”), hydrocarbon (hereinafter referred to as “HC”), nitrogen oxide ( It is known to provide an exhaust purification device that reduces the component (hereinafter referred to as “NOx”) to achieve purification. Further, by supplying air from the air pump to the secondary air supply passage having an on-off valve connected to the exhaust passage, the secondary air is supplied into the exhaust pipe to increase the oxygen concentration, thereby increasing the concentration of the exhaust gas in the exhaust gas. A technique is known that oxidizes HC and CO to promote purification of exhaust gas.

  In the secondary air supply passage of the secondary air supply device of the internal combustion engine having both the left and right banks disclosed in Patent Document 1, an air pump and an on-off valve are provided in order from the upstream side in the direction in which the secondary air flows. It has been. The secondary air supply passage branches into two at a branch point downstream of the on-off valve, and each branch passage is connected to an upstream side of an exhaust purification device provided in an exhaust passage extending from each bank of the internal combustion engine. Each of these branch passages is provided with a downstream on-off valve located downstream of the branch point.

Further, in the secondary air supply device in Patent Document 1, a pressure sensor is provided between an upstream on-off valve located upstream of the branch point and the air pump. In such a secondary air supply device, when 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, the pressure value detected by the pressure sensor and / or Alternatively, it is diagnosed whether there is an abnormality in these components according to the amount of pressure change (see Patent Document 1).
Japanese Patent Laid-Open No. 2003-314263 (FIG. 1)

  By the way, when detecting an abnormality of a component in Patent Document 1, the upstream on-off valve is temporarily closed with the two downstream on-off valves open, and the pressure upstream of the on-off valve is set to a predetermined value. In some cases, the control to open the upstream on-off valve is required after increasing to the value of. The detection when the secondary air is flowed after the pressure is once increased using the on-off valve in this way is called active detection. However, when active detection is performed, a larger amount of secondary air than the originally required amount is supplied to the exhaust passage through the secondary air supply passage and the branch passage. Can cause deterioration.

  In addition, if the discharge capacity of the air pump decreases due to deterioration over time, the amount of pressure fluctuation between the opening and closing of the upstream on-off valve also decreases, and the accuracy of component abnormality detection may decrease. There is also.

  The present invention has been made in view of such circumstances, and even when there is no upstream on-off valve located upstream from the branch point, it is possible to accurately detect abnormality of the component parts. An object is to provide a secondary air supply device.

  In order to achieve the above-described object, according to the first invention, a secondary air passage for taking out secondary air, a pump provided in the secondary air passage for supplying secondary air, The first and second branch passages branch from the secondary air passage, and the first and second branch passages are provided in the first and second exhaust passages extending from the internal combustion engine, respectively. A pressure sensor that is connected downstream of the pump and that is provided downstream of the pump and measures the pressure of the secondary air passage; and a first branch provided in the first branch passage Passage opening and closing means and second branch passage opening and closing means provided in the second branch passage, and the first and second branch passage opening and closing means based on the exhaust pulsation detected by the pressure sensor To detect abnormalities in The amount of attenuation of the first exhaust pulsation transmitted from the first exhaust passage through the first branch passage, and the amount of attenuation transmitted from the second exhaust passage through the second branch passage. A secondary air supply device is provided in which the amount of attenuation of the second exhaust pulsation is different from each other.

  That is, in the first invention, since the attenuation amount of the exhaust pulsation in the exhaust system differs between the first branch passage and the second branch passage, it is detected by the pressure sensor when the first and second opening / closing means are opened and closed. The value of the exhaust pulsation is also different, so that the abnormality of the first and second opening / closing means can be detected. In this way, when detecting an abnormality in the first and second opening / closing means, it is not necessary to provide an upstream opening / closing means positioned upstream from the branch point of the first and second branch passages. There is no detection. Therefore, in the first invention, it is also possible to avoid deterioration of emissions due to a flow of air larger than the required amount. Furthermore, when detecting an abnormality in the first and second opening / closing means, it is sufficient to simply open and close the first and second opening / closing means, and therefore it is not always necessary to operate the pump. Therefore, in the first invention, even if the pump discharge amount is reduced, it is possible to accurately detect the abnormality of the first and second opening / closing means.

According to the second invention, in the first invention, the attenuation amounts of the first and second exhaust pulsations are made different from each other by changing the volumes of the first and second branch passages. .
That is, in the second invention, the attenuation amount of the first exhaust pulsation and the attenuation amount of the second exhaust pulsation can be made different from each other with a relatively simple configuration.

According to a third aspect, in the second aspect, the volumes of the first and second branch passages are such that the first and second exhaust pulsations transmitted through the branch passages are the second and second exhaust pulsations, respectively. It is adjusted so that they do not cancel each other in the next air passage.
That is, in the third aspect of the invention, the first and second exhaust pulsations cancel each other at the branch points of the first and second branch passages, so that the pressure sensor of the secondary air passage does not accurately detect the exhaust pulsations. Can be avoided. Therefore, in the third aspect, the abnormality of the first and second opening / closing means can be detected more accurately.

According to a fourth aspect, in the first aspect, the attenuation amounts of the first and second exhaust pulsations are made different from each other by changing the lengths of the first and second branch passages. The
That is, in the fourth invention, the attenuation amount of the first exhaust pulsation and the attenuation amount of the second exhaust pulsation can be made different from each other with a relatively simple configuration.

According to a fifth aspect, in the fourth aspect, the volumes of the first and second branch passages are such that the first and second exhaust pulsations transmitted through the branch passages are the second and second exhaust pulsations, respectively. It is adjusted so that they do not cancel each other in the next air passage.
That is, in the fifth aspect of the invention, the first and second exhaust pulsations cancel each other at the branch points of the first and second branch passages, so that the pressure sensor of the secondary air passage does not accurately detect the exhaust pulsations. Can be avoided. Therefore, in the fifth aspect, the abnormality of the first and second opening / closing means can be detected more accurately.

According to a sixth aspect, in any one of the first to fifth aspects, the pump is driven when detecting an abnormality in the first and second branch passage opening / closing means.
That is, in the sixth aspect of the invention, when the abnormality is detected, the pump is driven to supply the secondary air so that the exhaust gas in the first and second exhaust passages becomes the first and second branch passages and the secondary air passage. It is possible to avoid backflow. Therefore, the pressure sensor and the pump are prevented from being damaged by the heat from the exhaust system.

  According to the seventh invention, a secondary air passage for taking out secondary air, a pump provided in the secondary air passage for supplying secondary air, and first and second branch passages extending from the pump The first and second branch passages are respectively connected to the upstream side of the exhaust purification devices provided in the first and second exhaust passages extending from the internal combustion engine, respectively, A first branch passage opening / closing means provided in the first branch passage; and a first branch passage provided between the pump and the first branch passage opening / closing means for measuring the pressure of the first branch passage. A pressure sensor, a second branch passage opening / closing means provided in the second branch passage, and a pump and the second branch passage opening / closing means provided between the pump and the second branch passage opening / closing means. A second pressure sensor for measuring pressure The first and second exhaust pulsations in the first branch passage detected by the first pressure sensor and the exhaust pulsations in the second branch passage detected by the second pressure sensor. A secondary air supply device for detecting an abnormality in the branch passage opening / closing means is provided.

  That is, in the seventh invention, since each of the first and second branch passages extends independently from the pump, the exhaust pulsation transmitted to the first pressure sensor is detected when the first opening / closing means is opened / closed. Thus, the abnormality of the first opening / closing means can be detected, and the abnormality of the second opening / closing means can be detected by detecting the exhaust pulsation transmitted to the second pressure sensor when the second opening / closing means is opened / closed. In this way, when detecting an abnormality in the first and second opening / closing means, it is not necessary to provide an upstream opening / closing means positioned upstream from the branch point of the first and second branch passages. There is no detection. Therefore, in the seventh aspect, it is also possible to avoid the emission from deteriorating due to the flow of a larger amount of air than the required amount. Furthermore, when detecting an abnormality in the first and second opening / closing means, it is sufficient to simply open and close the first and second opening / closing means, and therefore it is not always necessary to operate the pump. Therefore, in the seventh aspect, even when the discharge amount of the pump is reduced, it is possible to accurately detect the abnormality of the first and second opening / closing means.

According to an eighth aspect, in the seventh aspect, the pump is driven when an abnormality of the first and second branch passage opening / closing means is detected.
That is, in the eighth aspect of the invention, when the abnormality is detected, the pump is driven to supply secondary air so that the exhaust gas in the first and second exhaust passages becomes the first and second branch passages and the secondary air passage. It is possible to avoid backflow. Therefore, the pressure sensor and the pump are prevented from being damaged by the heat from the exhaust system.

  According to the ninth invention, a secondary air passage for taking out secondary air, a pump provided in the secondary air passage for supplying secondary air, and first and second branches from the secondary air passage. Each of the first and second branch passages is connected to the upstream side of the exhaust purification device provided in the first and second exhaust passages extending from the internal combustion engine, respectively. Furthermore, a first branch passage opening / closing means provided in the first branch passage, and a first temperature sensor disposed upstream of the first branch passage opening / closing means in the first branch passage A second branch passage opening / closing means provided in the second branch passage, and a second temperature sensor disposed upstream of the second branch passage opening / closing means in the second branch passage And the first temperature sensor Secondary detecting an abnormality of the first and second branch passage opening and closing means based on the temperature in the first branch passage and the temperature in the second branch passage detected by the second temperature sensor An air supply device is provided.

  That is, in the ninth aspect, the temperature sensor indicates that the temperature of the exhaust gas from the exhaust system has passed through each of the first opening / closing means in the first branch passage and the second opening / closing means in the second branch passage. By detecting it, it is possible to detect an abnormality in the first and second opening / closing means. In this way, when detecting an abnormality in the first and second opening / closing means, it is not necessary to provide an upstream opening / closing means positioned upstream from the branch point of the first and second branch passages. There is no detection. Therefore, in the ninth aspect, it is possible to avoid the emission from deteriorating due to the flow of a larger amount of air than the required amount. In the ninth aspect, when detecting an abnormality in the first and second opening / closing means, the pump is deactivated in order to detect the temperature transmitted from the first and second exhaust passages. There is a need.

According to each invention, even if there is no upstream on-off valve located upstream from the branch point, it is possible to achieve a common effect that abnormality detection of component parts can be accurately performed.
Further, according to the second and fourth inventions, it is possible to make the attenuation amount of the first exhaust pulsation and the attenuation amount of the second exhaust pulsation different from each other with a relatively simple configuration. Can play.

Further, according to the third and fifth inventions, it is possible to achieve an effect that the abnormality of the first and second opening / closing means can be detected more accurately.
Further, according to the sixth and eighth inventions, the exhaust gas in the first and second exhaust passages can be prevented from flowing back to the first and second branch passages and the secondary air passage. sell.

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the following drawings, similar members are denoted by the same reference numerals. In order to facilitate understanding, the scales of these drawings are appropriately changed.
FIG. 1 is a schematic view of an internal combustion engine provided with a secondary air supply device according to a first embodiment of the present invention. The secondary air supply device 30 of the present invention is attached to an internal combustion engine 1, for example, a multi-cylinder V-type gasoline engine. As shown in FIG. 1, the cylinders in both the left and right banks of the internal combustion engine 1 are connected to exhaust pipes 7a and 7b via exhaust manifolds 4a and 4b that are independent of each other. Further, the exhaust pipes 7a and 7b are respectively provided with catalytic converters 5a and 5b carrying a catalyst having an oxidation function. These catalytic converters 5a and 5b serve as exhaust purification devices. Further, secondary air supply ports 8a and 8b are provided upstream of the catalytic converters 5a and 5b in the exhaust pipes 7a and 7b, respectively. These secondary air supply ports 8a and 8b are respectively connected to two branch pipes 23a and 23b described later. Further, in the exhaust pipes 7a and 7b, O ₂ sensors 6a and 6b are provided upstream of the catalytic converters 5a and 5b, respectively, and O ₂ sensors 16a and 16b are provided downstream of the catalytic converters 5a and 5b, respectively. Therefore, it is possible to calculate the amount of O ₂ consumed in the catalytic converters 5a and 5b by measuring the O ₂ concentration upstream and downstream of the catalytic converters 5a and 5b. On the other hand, a throttle valve 3 a is provided in the intake pipe 3 for supplying intake gas to the cylinders in both the left and right banks of the internal combustion engine, and the intake pipe 3 is connected to the air cleaner 2. An air flow meter 3b for measuring an air amount (primary air amount) is provided between the air cleaner 2 and the throttle valve 3a. Further, a temperature sensor 3 c for measuring the intake air temperature is provided in the intake pipe 3.

  The secondary air supply device 30 has an air intake pipe 21 extending from the air cleaner 20. The air intake pipe 21 is connected to the electric air pump 9, and the secondary air supply pipe 22 extends from the electric air pump 9. As shown, the secondary air supply pipe 22 branches into two branch pipes 23a and 23b at a branch point 23, and these branch pipes 23a and 23b are secondary air supply ports 8a and 8b of the exhaust pipes 7a and 7b. Is connected to each. As shown in FIG. 1, the lengths of the branch pipe 23a and the branch pipe 23b are substantially the same, but the inner diameter of the branch pipe 23a is smaller than the inner diameter of the branch pipe 23b. That is, in the embodiment shown in FIG. 1, the volume of the branch pipe 23a is smaller than the volume of the branch pipe 23b.

  Further, as shown in FIG. 1, the branch pipe 23a is provided with a control valve V1, and the branch pipe 23b is provided with a control valve V2. These control valves V1 and V2 are an air switching valve (ASV), a vacuum switching valve (VSV) or an electromagnetic valve, and control the amount of secondary air flowing through the branch pipes 23a and 23b and the secondary air supply pipe 22 by the ECU 40 described later. Open and close to control. Further, a pressure sensor 33 is provided between the branch point 23 and the electric air pump 9 in the secondary air supply pipe 22. In the embodiment shown in FIG. 1, the first and second control valves V1 and V2 are arranged at substantially equal distances from the branch point 23, but the first and second control valves provided in the branch pipes 23a and 23b, respectively. The distances from the branch point 23 of the two control valves V1, V2 may be different from each other.

The electronic control unit 40 comprises a digital computer and is connected to each other by a bidirectional bus 41. A ROM (read only memory) 42, a RAM (random access memory) 43, a CPU (microprocessor) 44, an input port 45 and an output port 46 are connected. It comprises. As shown in FIG. 1, the output signals of the O ₂ sensors 6a and 6b provided upstream of the catalytic converters 5a and 5b and the O ₂ sensors 16a and 16b provided downstream of the catalytic converters 5a and 5b correspond to corresponding AD conversions. It is input to the input port 45 through the device 47. The output signal of the air flow meter 3 b is also input to the input port 45 via the corresponding AD converter 47. Further, the output signal of the pressure sensor 33 provided in the secondary air supply pipe 22 is also input to the input port 45 via the corresponding AD converter 47. Further, output signals from a temperature sensor 3 c provided in the intake passage and a temperature sensor (not shown) of engine cooling water are also input to the input port 45 via the corresponding AD converter 47. A load sensor 51 that generates an output voltage proportional to the depression amount L of the accelerator pedal 50 is connected to the accelerator pedal 50, and the output voltage of the load sensor 51 is input to the input port 45 via the corresponding AD converter 47. . In addition, a crank angle sensor that generates an output pulse every time the crankshaft rotates, for example, 30 °, that is, a so-called rotational speed sensor 55 is connected to the input port 45. Further, an output pulse from the vehicle speed sensor 53 representing the vehicle speed is input to the input port 45. On the other hand, the output port 46 is provided with a fuel injection valve (not shown) of the internal combustion engine 1 through a corresponding drive circuit 48, a step motor (not shown) for controlling the throttle valve 3a, and a control valve V1 of the branch pipes 23a and 23b. , V2 and the electric air pump 9.

  As the catalyst that is disposed in the catalytic converters 5a and 5b and has an oxidation function, an oxidation catalyst, a three-way catalyst, or an occlusion reduction type NOx catalyst that releases and reduces the stored NOx can be used. The NOx catalyst has a function of releasing NOx when the average air-fuel ratio in the combustion chamber becomes rich. The NOx catalyst is, for example, alumina as a support, and on this support, for example, alkali metal such as potassium K, lithium Li, cesium Cs, alkaline earth such as barium Ba, calcium Ca, rare earth such as lanthanum La, yttrium Y, and the like. At least one selected and a noble metal such as platinum Pt are supported.

  The secondary air supply device 30 mainly has a high fuel concentration at the time of cold start or the like, a low air-fuel ratio, and the catalytic converters 5a and 5b serving as exhaust purification devices have not sufficiently raised the temperature. Is used in situations where it is difficult to fully demonstrate. By supplying the secondary air to the catalytic converters 5a and 5b, the oxygen concentration in the catalytic converters 5a and 5b is increased, so that CO, HC, NOx and the like in the exhaust gas can be purified.

  Fig.2 (a) is a time chart which shows the abnormality determination operation | movement of the secondary air supply apparatus based on 1st embodiment of this invention. Hereinafter, with reference to FIG. 2 (a), the abnormality determination of the component that is included in the secondary air supply device 30 of the present invention and is determined to be abnormal will be described. The components of the secondary air supply device 30 that are abnormally detected by the secondary air supply device 30 according to the present invention are the first control valve V1 and the second control valve V2. In the present invention, abnormalities of the air pump 9, for example, ON sticking in which the power supply cannot be shut off because it remains in the ON state and OFF sticking incapable of being driven because of the OFF state are not detected.

  As shown in FIG. 2A, first, the air pump 9 is stopped and the first and second control valves V1, V2 are closed, that is, the secondary air is supplied to the secondary air supply pipe 22. Form a non-flowing state. At time t1, the air pump 9 is driven and the first and second control valves V1, V2 are simultaneously opened. Thus, the secondary air is supplied to each of the catalytic converters 5a and 5b through the secondary air supply pipe 22 and the branch pipes 23a and 23b. Next, after the predetermined time has elapsed and the state of the secondary air has stabilized, the pressure sensor 33 is used to detect the first pressure P1 in the secondary air supply pipe 22 (CHK1).

  Next, at time t2, the air pump 9 is stopped and both the first and second control valves V1, V2 are closed simultaneously. Thereby, supply of secondary air is stopped. Then, after the predetermined time has elapsed and the state of the secondary air has stabilized, the pressure sensor 33 is used to detect the second pressure P2 (CHK2).

  The pressures P1 and P2 in the secondary air supply pipe 22 detected by the pressure sensor 33 at CHK1 and CHK2 are the exhaust pulsation transmitted from the combustion chamber of the internal combustion engine 1 through the exhaust manifolds 4a and 4b and the branch pipes 23a and 23b. Contains ingredients. Therefore, by performing a predetermined process in the electronic control unit 40, only the exhaust pulsation component is extracted from these pressures P1 and P2. In the first embodiment, the exhaust pulsation obtained at CHK1 is referred to as exhaust pulsation PX0 (1), and the exhaust pulsation obtained at CHK2 is referred to as exhaust pulsation PX0 (2). Since the pressure sensor 33 is provided upstream of the branch point 23, each of the exhaust pulsations PX0 (1) and PX0 (2) is transmitted through the exhaust pipe pulsation 23a and the branch pipe 23b. And exhaust pulsation. As can be seen from FIG. 2A, the exhaust pulsation PX0 (1) is an exhaust pulsation when the first and second control valves V1, V2 are open, and the exhaust pulsation PX0 (2) is the first pulsation PX0 (2). This is the exhaust pulsation when the first and second control valves V1, V2 are closed.

  FIG. 2B is a diagram showing the relationship between the extracted exhaust pulsation and time. In FIG. 2B, the vertical axis indicates the exhaust pulsations PX0 (1) and PX0 (2) extracted from the pressures P1 and P2, respectively, and the horizontal axis indicates time.

  As shown in FIG. 2B, the exhaust pulsation PX0 (PX0 (1), PX0 (2)) is larger than the first reference value X1 in the region Z1, the first reference value X1, and the first reference value X1. A region Z2 between the second reference value X2 smaller than the reference value X1, a region Z3 between the second reference value X2 and the third reference value X3 smaller than the second reference value X2, and the first It can be in any region of the region Z4 that is smaller than the third reference value X3. These reference values X1 to X3 are values obtained in advance by experiments or the like, and are preliminarily incorporated in the ROM 42 or the RAM 43 of the electronic control unit 40.

  For example, when the exhaust pulsation PX0 (1) or the exhaust pulsation PX0 (2) is in the region Z1 exceeding the first reference value X1 (for example, the value P01 in FIG. 2B), the exhaust pulsation becomes the largest. ing. Thus, when the exhaust pulsation is in the region Z1, since both the first and second control valves V1, V2 are open, the exhaust pulsation is transmitted through both the branch pipes 23a, 23b. Therefore, it can be determined that the exhaust pulsation has increased.

  On the other hand, when the exhaust pulsation PX0 (1) or the exhaust pulsation PX0 (2) is below the third reference value X3 and is in the region Z4 (for example, the value P04 in FIG. 2B), the exhaust pulsation is the smallest. . Thus, when the exhaust pulsation is in the region Z4, both the first and second control valves V1 and V2 are closed, so the exhaust pulsation passes through both the branch pipes 23a and 23b. Therefore, it can be determined that the exhaust pulsation is small.

  Further, when the exhaust pulsation PX0 (1) or the exhaust pulsation PX0 (2) is between the first reference value X1 and the third reference value X3 (region Z2 and region Z3), the first and second Since one of the two control valves V1 and V2 is opened, the exhaust pulsation is transmitted only through one branch pipe corresponding to the opened one of the branch pipes 23a and 23b. Therefore, it can be determined that the exhaust pulsation is between the first reference value X1 and the third reference value X3.

  Here, considering the exhaust pulsation transmitted from the exhaust system of the internal combustion engine 1, such exhaust pulsation is attenuated to some extent by the influence of pipe resistance or the like when passing through the branch pipe 23a and / or the branch pipe 23b. To do. Such exhaust pulsation tends to attenuate as the branch pipes 23a and 23b become longer, and attenuate as the volume of the branch pipes 23a and 23b increases. That is, the attenuation amount of the exhaust pulsation increases as the branch pipes 23a and 23b to be transmitted become longer, and increases as the volume of the branch pipes 23a and 23b increases.

  In the embodiment shown in FIG. 1, the volume of the branch pipe 23a provided with the first control valve V1 is smaller than the volume of the branch pipe 23b provided with the second control valve V2. That is, since the attenuation amount of the exhaust pulsation transmitted through the branch pipe 23a is smaller than the attenuation amount of the exhaust pulsation transmitted through the branch pipe 23b, the magnitude of the exhaust pulsation transmitted through the branch pipe 23a is transmitted through the branch pipe 23b. Is larger than the exhaust pulsation. Therefore, the exhaust pulsation when only the first control valve V1 is open is larger than the exhaust pulsation when only the second control valve V2 is open.

  Therefore, when the exhaust pulsation PX0 (1) or the exhaust pulsation PX0 (2) is in the region Z2 between the first and second reference values (for example, the value P02 in FIG. 2B), It can be determined that the control valve V1 is open and the second control valve V2 is closed. Similarly, when the exhaust pulsation PX0 (1) or the exhaust pulsation PX0 (2) is in the region Z3 between the second and third reference values (for example, the value P03 in FIG. 2B), It can be determined that the control valve V2 is open and the first control valve V1 is closed.

In the present embodiment, the first and second exhaust pulsations PX0 (1) and PX0 (2) detected in CHK1 and CHK2 are respectively in the four regions Z1 to Z4. An abnormality of the control valves V1 and V2 can be detected.

  Here, Table 1 is a table showing an abnormality detection result by the secondary air supply device based on the first embodiment of the present invention. In Table 1, the symbol “positive” indicates that the corresponding control valve is in a normal state. Further, the symbol “open” indicates that the corresponding control valve is in an open fixed state, and the symbol “closed” indicates that the corresponding control valve is in a closed fixed state. Hereinafter, the abnormality detection of the first and second control valves V1, V2 will be described with reference to Table 1.

  In the case of the pattern A shown in Table 1, the exhaust pulsation PX0 (1) when CHK1 is in the region Z1, and the exhaust pulsation PX0 (2) when CHK2 is in the region Z4. Since both the first and second control valves V1, V2 are open at the time of CHK1, it is normal that the exhaust pulsation PX0 (1) is in the region Z1, and at the time of CHK2, the first and second control valves V1, V2 are normal. Since both the control valves V1 and V2 are closed, it is normal that the exhaust pulsation PX0 (2) exists in the region Z4. Therefore, when a behavior like the pattern A is obtained, it is determined that both the first and second control valves V1 and V2 are in a normal state.

  In the case of the pattern B shown in Table 1, the exhaust pulsation PX0 (1) when CHK1 is in the region Z1, and the exhaust pulsation PX0 (2) when CHK2 is in the region Z2. The exhaust pulsation at the time of CHK1 is similarly appropriate for the case of pattern A for the reason described above. In the case of CHK2, both the first and second control valves V1 and V2 should be closed, but the exhaust pulsation PX0 (2) in the case of CHK2 is in the region Z2. This is because the first control valve V1 is kept open even after the closing command is issued to the first control valve V1. That is, when a behavior like the pattern B is obtained, it can be determined that the second control valve V2 is in a normal state but the first control valve V1 is in an open fixed state.

  In the case of the pattern C shown in Table 1, the exhaust pulsation PX0 (1) when CHK1 is in the region Z1, and the exhaust pulsation PX0 (2) when CHK2 is in the region Z3. The exhaust pulsation PX0 (1) at the time of CHK1 is similarly appropriate in the case of the pattern A for the reason described above. In the case of CHK2, both the first and second control valves V1 and V2 should be closed, but the exhaust pulsation PX0 (2) in the case of CHK2 is in the region Z3. This is because the second control valve V2 is kept open even after the closing command is issued to the second control valve V2. That is, when a behavior like the pattern C is obtained, it can be determined that the first control valve V1 is in a normal state but the second control valve V2 is in an open fixed state.

  In the case of the pattern D shown in Table 1, the exhaust pulsation PX0 (1) when CHK1 is in the region Z3, and the exhaust pulsation PX0 (2) when CHK2 is in the region Z4. Since the first and second control valves V1, V2 are closed at the time of CHK2, it is appropriate that the exhaust pulsation PX0 (2) exists in the region Z4. In the case of CHK1, both the first and second control valves V1, V2 should be open, but the exhaust pulsation PX0 (1) in the case of CHK1 is in the region Z3. This is because the first control valve V1 continues to be closed even after an opening command is issued to the first control valve V1. That is, when a behavior like the pattern D is obtained, it can be determined that the second control valve V2 is in a normal state, but the first control valve V1 is in a closed fixed state.

  In the case of pattern E shown in Table 1, the exhaust pulsation PX0 (1) when CHK1 is in the region Z2, and the exhaust pulsation PX0 (2) when CHK2 is in the region Z4. The exhaust pulsation PX0 (2) at the time of CHK2 is similarly appropriate for the case of the pattern D for the reason described above. In the case of CHK1, both the first and second control valves V1 and V2 should be open, but the exhaust pulsation PX0 (1) in the case of CHK1 is in the region Z2. This is because the second control valve V2 continues to close even after the opening command is issued to the second control valve V2. That is, when a behavior like the pattern E is obtained, it can be determined that the first control valve V1 is in a normal state, but the second control valve V2 is in a closed fixed state.

  Next, in the case of the pattern F shown in Table 1, both the exhaust pulsation PX0 (1) at CHK1 and the exhaust pulsation PX0 (2) at CHK2 are in the region Z1. Since the same level of exhaust pulsation is detected in both CHK1 and CHK2, it can be seen that there is an abnormality in both the first and second control valves V1, V2. In the case of CHK2, both the first and second control valves V1 and V2 should be closed, but the exhaust pulsation PX0 (2) in the case of CHK2 is in the region Z1. This means that both the first and second control valves V1, V2 continue to open even after the closing command is issued to the first and second control valves V1, V2. Is the cause. That is, when a behavior like the pattern F is obtained, it can be determined that both the first and second control valves V1 and V2 are in the open fixing state.

  In the case of the pattern G shown in Table 1, both the exhaust pulsation PX0 (1) at CHK1 and the exhaust pulsation PX0 (2) at CHK2 are in the region Z4. Since the same level of exhaust pulsation is detected in both CHK1 and CHK2, it can be seen that there is an abnormality in both the first and second control valves V1, V2. In the case of CHK1, both the first and second control valves V1 and V2 should be open, but the exhaust pulsation PX0 (1) in the case of CHK1 is in the region Z4. This means that both the first and second control valves V1, V2 continue to close even after an opening command is issued to the first and second control valves V1, V2. Is the cause. That is, when a behavior like the pattern G is obtained, it can be determined that both the first and second control valves V1 and V2 are in the closed fixed state.

  In the case of the pattern H shown in Table 1, both the exhaust pulsation PX0 (1) at CHK1 and the exhaust pulsation PX0 (2) at CHK2 are in the region Z2. Since the same level of exhaust pulsation is detected in both CHK1 and CHK2, it can be seen that there is an abnormality in both the first and second control valves V1, V2. Since the exhaust pulsation is in the region Z2 in both CHK1 and CHK2, when the behavior like the pattern H is obtained, the first control valve V1 is in the open fixing state, and the second control valve V2 is It can be judged that it is in a closed fixed state.

  Finally, in the case of the pattern I shown in Table 1, both the exhaust pulsation PX0 (1) at CHK1 and the exhaust pulsation PX0 (2) at CHK2 are in the region Z3. Since the same level of exhaust pulsation is detected in both CHK1 and CHK2, it can be seen that there is an abnormality in both the first and second control valves V1, V2. Since the exhaust pulsation is in the region Z3 in both CHK1 and CHK2, when the behavior like the pattern I is obtained, the first control valve V1 is in the closed fixing state, and the second control valve V2 is It can be judged that it is in an open fixed state.

  Thus, in the first embodiment of the present invention, the exhaust pulsation PX0 (1) when the air pump 9 is driven and the first and second control valves V1 and V2 are open is CHK1. ) And the exhaust pulsation PX0 (2) at the time of CHK2 in which the air pump 9 is stopped and the first and second control valves V1, V2 are closed, the first and second It is possible to detect an abnormal state of the control valves V1, V2. In such a case, there is no need to provide another on-off valve upstream from the branch point 23, and therefore active detection is not performed in the first embodiment of the present invention. It is possible to avoid the emission from being deteriorated by the flow of air.

  In the first embodiment described with reference to FIG. 2, the air pump 9 is driven when CHK1 and the air pump 9 is stopped when CHK2. However, in the present invention, only the exhaust pulsation transmitted from the exhaust system of the internal combustion engine 1 through the branch pipe 23a and / or the branch pipe 23b is used as an index for determining the abnormality of the first and second control valves V1, V2, and the air pump The pressure of the secondary air supplied by driving 9 is not taken into consideration. For this reason, even when the discharge capacity of the air pump 9 is lowered due to deterioration over time, it is possible to accurately detect an abnormality related to the first and second control valves V1 and V2.

  Further, in the case of the present embodiment, since abnormality detection is performed based on the magnitude of exhaust pulsation, the air pump 9 is driven when the air pump 9 is stopped at CHK1 and / or at CHK2. Even if it is, abnormality detection can be performed. However, the air pump 9 is preferably driven when an opening command is issued to at least one of the first and second control valves V1, V2. In such a case, it is possible to prevent high-temperature exhaust gas from the exhaust system of the internal combustion engine 1 from reaching the pressure sensor 33 and / or the air pump 9 through the branch pipe 23a and / or the branch pipe 23b. And / or it can avoid that the air pump 9 is damaged by heat.

  Further, in the first embodiment shown in FIG. 1, the inner diameters of the branch pipe 23a and the branch pipe 23b are different from each other. For example, the inner diameters of the branch pipes 23a and 23b are equal to each other. It may be formed to be longer than 23a. Also in this case, since the attenuation amount of the exhaust pulsation in the branch pipe 23b is larger than the attenuation amount of the exhaust pulsation in the branch pipe 23a, it is possible to perform the same abnormality detection as described with reference to Table 1. Become. Naturally, if the attenuation amount of the exhaust pulsation in the branch pipe 23b is larger than the attenuation amount of the exhaust pulsation in the branch pipe 23a, the length, inner diameter, shape, and surface roughness of the inner wall of these branch pipes 23a and 23b. Etc. may be different from each other. In order to avoid the exhaust pulsations transmitted from the branch pipes 23a and 23b from canceling each other at the branch point 23, the length, inner diameter, shape, inner surface roughness, etc. of the branch pipes 23a and 23b are appropriate. It shall be adjusted to.

  FIG. 3 is a schematic view of an internal combustion engine provided with a secondary air supply device according to the second embodiment of the present invention. Of the configuration of the secondary air supply device 30 shown in FIG. 3, description of members that are the same as those of the secondary air supply device 30 based on the first embodiment shown in FIG. 1 is omitted.

  Hereinafter, differences from the first embodiment of the second embodiment shown in FIG. 3 will be described. In the second embodiment of the present invention shown in FIG. 3, the secondary air supply pipe 22 does not exist, and each of the branch pipes 23 a and 23 b extends from the air pump 9. A part of these branch pipes 23a and 23b shall play the role of a secondary air supply pipe. Further, as shown in the drawing, the lengths and inner diameters of the branch pipes 23a and 23b are equal to each other. Further, as shown in FIG. 3, the pressure sensor 33a is provided upstream of the first control valve V1 in the branch pipe 23a, and the pressure sensor 33b is provided upstream of the second control valve V2 in the branch pipe 23b. It has been. The output signals of the pressure sensors 33a and 33b are input to the input port 45 via the corresponding AD converter 47 in the same manner as the pressure sensor 33 described above. In the embodiment shown in FIG. 3, it is assumed that the distance between the pressure sensor 33a and the secondary air supply port 8a and the distance between the pressure sensor 33b and the secondary air supply port 8b are equal to each other.

  4 is a schematic diagram showing the internal state of the air pump shown in FIG. FIG. 4 shows the rotor 9 </ b> A of the air pump 9. The rotor 9A is disposed in the air pump 9 so as to be rotatable in the direction of the arrow in FIG. As illustrated, an annular flange 9B is provided at the center of the peripheral surface 9C of the rotor 9A. The rotor 9A is divided into an upper part and a lower part by the annular flange 9B.

  Furthermore, a plurality of blades 90 are provided at equal intervals in the circumferential direction above and below the annular flange 9B on the circumferential surface 9C. As can be seen from FIG. 5, these blades 90 have the same curved shape, and are disposed at a predetermined angle with respect to the peripheral surface 9 </ b> C so that the secondary air can be appropriately pumped.

  Incidentally, although not shown in the drawing, the air intake pipe 21 branches into two branch passages inside the air pump 9. The air flowing through one of the branch passages is supplied to the upper portion of the rotor 9a in parallel with the axis of the rotor 9A as indicated by the arrow XA1. Next, the air flows in the circumferential direction (see arrow XA2) in the upper portion of the rotor 9A by the rotation of the rotor 9A, and is introduced into one branch pipe 23a.

  Similarly, the air flowing through the other branch passage is supplied to the lower portion of the rotor 9a in the direction opposite to the arrow XA1 described above, as indicated by the arrow YA1. Next, the air flows through the lower portion of the rotor 9A in the circumferential direction (see arrow YA2) as the rotor 9A rotates, and is introduced into the other branch pipe 23b.

  Since the annular flange 9B is provided on the peripheral surface 9C of the rotor 9A, the air supplied to the branch pipe 23a and the air supplied to the branch pipe 23b do not mix with each other in the air pump 9. In the second embodiment, since the annular flange 9B is provided in the center of the peripheral surface 9C, the amount of air supplied to the branch pipe 23a and the amount of air supplied to the branch pipe 23b are equal to each other. The

  FIG. 5A is a time chart showing an abnormality determination operation of the secondary air supply device according to the second embodiment of the present invention, and CHK1 and CHK2 are performed at the same timing as in FIG. . In the second embodiment, the exhaust pulsation calculated using the pressure sensor 33a is the exhaust pulsation PXA (1), the exhaust pulsation calculated using the PXA (2) and the pressure sensor 33b is the exhaust pulsation PXB (1). , PXB (2).

  FIG. 5B is a view similar to FIG. 2B showing the relationship between the extracted exhaust pulsation and time. In FIG. 5B, the vertical axis represents exhaust pulsations PXA (1) and PXA (2) calculated using the pressure sensor 33a and exhaust pulsations PXB (1) and PXB (2) calculated using the pressure sensor 33b. ), And the horizontal axis represents time.

  As shown in FIG. 2B, the exhaust pulsations PXA (1), PXA (2), PXB (1), and PXB (2) are a region Z5 larger than the fifth reference value X5, and a fifth reference. It can be in any region of the region Z6 that is smaller than the value X5. These reference values X5 and X6 are values obtained in advance by experiments or the like, and are incorporated in the ROM 42 or RAM 43 of the electronic control unit 40 in advance.

  In the second embodiment, since the determination is separately performed using the exhaust pulsation PXA (PXA (1), PXA (2)), PXB (PXB (1), PXB (2)), hereinafter, the exhaust pulsation PXA The determination using (PXA (1), PXA (2)) will be described. For example, when the exhaust pulsation PXA is in the region Z5 beyond the fifth reference value X5 (for example, the value P05 in FIG. 5B), the exhaust pulsation is large. Thus, when the exhaust pulsation is in the region Z5, the first control valve V1 is open, so the exhaust pulsation is detected through the branch pipe 23a, and therefore the exhaust pulsation is large. It can be judged.

  On the other hand, when the exhaust pulsation PXA is below the fifth reference value X5 and is in the region Z6 (for example, the value P06 in FIG. 2B), the exhaust pulsation is the smallest. When the exhaust pulsation is in the region Z6 as described above, the exhaust pulsation is not transmitted through the branch pipe 23a because the first control valve V1 is closed, and therefore the exhaust pulsation is reduced. I can judge.

In the present embodiment, exhaust pulsations PXA (PXA (1), PXA (2)) and PXB (PXB (1), PXB (2)) detected in CHK1 and CHK2 are respectively in these regions Z5 and Z6. The abnormality of the corresponding control valves V1 and V2 can be detected depending on whether or not the control valve is present.

  Here, Table 2 is the same table as Table 1 described above showing the abnormality detection result by the secondary air supply device based on the second embodiment of the present invention. Hereinafter, the abnormality detection of the first and second control valves V1 in the second embodiment of the present invention will be described with reference to Table 2.

  In the case of the pattern J shown in Table 2, the exhaust pulsation PXA (1) at CHK1 is in the region Z5, and the exhaust pulsation PXA (2) at CHK2 is in the region Z6. Since the first control valve V1 is open at the time of CHK1, it is normal that the exhaust pulsation PXA (1) exists in the region Z5, and at the time of CHK2, the first control valve V1 is closed, so that the exhaust gas is exhausted. It is normal that the pulsation PXA (2) is in the region Z6. Therefore, when a behavior like the pattern J is obtained, it is determined that the first control valve V1 is in a normal state.

  In the case of the pattern K shown in Table 2, the exhaust pulsation PXA (1) when CHK1 is in the region Z5, and the exhaust pulsation PXA (2) when CHK2 is also in the region Z5. Since the first control valve V1 is open at the time of CHK1, it is normal that the exhaust pulsation PXA (1) is in the region Z5. In the case of CHK2, the first control valve V1 is kept open because the exhaust pulsation PXA (2) is in the region Z5 even though the closing command is issued to the first control valve V1. This can be determined. Therefore, when the behavior like the pattern K is obtained, it is determined that the first control valve V1 is in the open fixing state.

  In the case of the pattern L shown in Table 2, the exhaust pulsation PXA (1) at CHK1 is in the region Z6, and the exhaust pulsation PXA (2) at CHK2 is also in the region Z6. Since the first control valve V1 is closed at the time of CHK2, it is normal that the exhaust pulsation PXA (2) exists in the region Z6. Although the opening command is issued to the first control valve V1 at the time of CHK1, the first control valve V1 is kept closed because the exhaust pulsation PXA (1) is in the region Z6. This can be determined. Therefore, when the behavior like the pattern L is obtained, it is determined that the first control valve V1 is in the closed and fixed state.

  Although not described in detail, also in the case of the second control valve V2, the first control is performed using the exhaust pulsations PXB (1) and PXB (2) with reference to FIG. It is assumed that the same abnormality determination as in the case of the valve V1 is performed.

  Thus, also in the second embodiment of the present invention, the exhaust pulsation PXA (1) when the air pump 9 is driven and the first and second control valves V1, V2 are open is CHK1. ), PXB (1) and the behavior of the exhaust pulsations PXA (2) and PXB (2) when the first and second control valves V1 and V2 are closed and the air pump 9 is stopped are detected. By doing so, it becomes possible to detect an abnormal state of the first and second control valves V1, V2. Even in this case, there is no need to provide another on-off valve upstream from the branch point 23, so active detection is not performed in the second embodiment of the present invention. It is possible to avoid the emission from getting worse by flowing. Further, in the case of the second embodiment, since the abnormality is detected based on the exhaust pulsation, even if the discharge capacity of the air pump 9 is deteriorated due to aging, the first and second control valves It is possible to accurately detect abnormality relating to V1 and V2.

  As in the case of the first embodiment, it is preferable that the air pump 9 is driven when pressure is detected by the pressure sensor 33a and the pressure sensor 33b, so that high-temperature exhaust gas from the exhaust system flows backward. Can be prevented.

  FIG. 6 is a schematic view of an internal combustion engine including a secondary air supply device according to the third embodiment of the present invention. Of the configuration of the secondary air supply device 30 shown in FIG. 6, description of members that are the same as those of the secondary air supply device 30 based on the first embodiment shown in FIG. 1 is omitted.

  Hereinafter, differences from the first embodiment of the third embodiment shown in FIG. 6 will be described. In the third embodiment of the present invention shown in FIG. 6, the lengths and volumes of the branch pipes 23a and 23b are equal to each other. The secondary air supply pipe 22 is not provided with the pressure sensor 33. Instead of the pressure sensor 33, a thermocouple TC1 is provided upstream of the first control valve V1 in the branch pipe 23a. Similarly, a thermocouple TC2 is provided on the upstream side of the second control valve V2 in the branch pipe 23b. The output signals of these thermocouples TC1 and TC2 are input to the input port 45 via the corresponding AD converter 47. In the embodiment shown in FIG. 6, the distance between the thermocouple TC1 and the secondary air supply port 8a and the distance between the thermocouple TC2 and the secondary air supply port 8b are equal to each other. And

  FIG. 7 is a time chart showing an abnormality determination operation of the secondary air supply device based on the third embodiment of the present invention. Further, the behavior of the temperature detected by the thermocouples TC1 and TC2 is shown in the lower part of FIG. Hereinafter, with reference to FIG. 7, the abnormality determination of the component parts (first and second control valves V1, V2) that are provided in the secondary air supply device 30 of the present invention and are determined to be abnormal will be described.

  As shown in FIG. 7, the air pump 9 is initially stopped and the first and second control valves V <b> 1 and V <b> 2 are closed, that is, the secondary air is not flowing into the secondary air supply pipe 22. Form a state. Then, at time t3 shown in FIG. 7, the air pump 9 is driven and the first and second control valves V1 and V2 are simultaneously opened. Thus, the secondary air is supplied to each of the catalytic converters 5a and 5b through the secondary air supply pipe 22 and the branch pipes 23a and 23b. At this time, since the secondary air is flowing, the heat of the exhaust gas from the exhaust system is not transmitted through the branch pipes 23a and 23b. Therefore, the thermocouple TC1 and the thermocouple TC2 detect the temperature of the secondary air introduced from the outside, and since this temperature is normal temperature, there is no temperature change.

  Next, at time t4, the air pump 9 is stopped and both the first and second control valves V1, V2 are closed simultaneously. Since each of the thermocouples TC1 and TC2 is arranged on the upstream side of the first and second control valves V1 and V2, even if the air pump 9 is stopped, the first and second control valves V1 and V2 are closed. Therefore, the temperature in the branch pipes 23a and 23b does not rise.

  On the other hand, when the temperature detected by the thermocouple TC1 rises above the predetermined reference value X6 at time t4 as indicated by the broken arrow YA1 in FIG. 7, the first control valve V1 is closed. It can be determined that the device is in an open fixed state that remains open even when the button is released.

  Similarly, since the closing command is issued to the second control valve V2 at time t4, if the temperature detected by the thermocouple TC2 rises above the predetermined reference value X7 at time t4, the second command is issued. It can be determined that the second control valve V2 is in an open stuck state that remains open even when a closing command is issued (see broken line arrow YB1 in FIG. 7). The reference values X6 and X7 are values obtained in advance by experiments or the like, and are preliminarily incorporated in the ROM 42 or the RAM 43. These reference values X6 and X7 may be equal to each other.

  Next, at time t5, the first control valve V1 is opened, and the second control valve V2 is kept closed. Since the air pump 9 is stopped at this time, the heat of the exhaust system is detected by the thermocouple TC1 through the branch pipe 23a by opening the first control valve V1, and the temperature rises beyond the reference value X6 (solid line). (See arrow YA0).

  On the other hand, if the temperature detected by the thermocouple TC1 does not rise beyond the reference value X6 at time t5 as indicated by the dashed arrow YA2, the first control valve V1 may issue an opening command. It can be determined that it is in a closed adhering state that remains closed.

  Next, after the first control valve V1 is closed again at time t6, the second control valve V2 is opened at time t7, and the first control valve V1 remains closed. At this time, since the air pump 9 is stopped, the heat of the exhaust system is detected by the thermocouple TC2 through the branch pipe 23b by opening the second control valve V2, and the temperature rises beyond the reference value X7 (solid line). (See arrow YB0).

  On the other hand, if the temperature detected by the thermocouple TC2 does not rise beyond the reference value X7 even at time t7 as indicated by the dashed arrow YB2, the second control valve V2 may issue an opening command. It can be determined that it is in a closed adhering state that remains closed. Next, at time t8, the second control valve V2 is closed, and the process ends.

  Therefore, also in the third embodiment of the present invention, by using the temperature of the branch pipes 23a and 23b detected by the thermocouples TC1 and TC2, there is no need to provide another on-off valve upstream from the branch point 23. It becomes possible to detect an abnormal state of the first and second control valves V1, V2. Accordingly, active detection is not performed in the third embodiment, and it is possible to prevent the emission from deteriorating due to a flow of air larger than the required amount.

  In the third embodiment, since it is necessary to detect heat transmitted from the exhaust system, the air pump 9 stops when the first and second control valves V1, V2 are opened at time t5 and time t7, respectively. It is required that In other words, even in the third embodiment, even when the discharge capacity of the air pump 9 is lowered due to aging, it is possible to accurately detect the abnormality related to the first and second control valves V1, V2. is there.

It is the schematic of the internal combustion engine provided with the secondary air supply device based on 1st embodiment of this invention. (A) It is a time chart which shows the abnormality determination operation | movement of the secondary air supply apparatus based on 1st embodiment of this invention. (B) It is a figure which shows the relationship between exhaust pulsation and time. It is the schematic of the internal combustion engine provided with the secondary air supply apparatus based on 2nd embodiment of this invention. 4 is a schematic diagram showing an internal state of the air pump shown in FIG. 3. (A) It is a time chart which shows the abnormality determination operation | movement of the secondary air supply apparatus based on 2nd embodiment of this invention. (B) It is a figure which shows the relationship between exhaust pulsation and time. It is the schematic of the internal combustion engine provided with the secondary air supply device based on 3rd embodiment of this invention. It is a time chart which shows abnormality determination operation | movement of the secondary air supply apparatus based on 3rd embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 5a, 5b Catalytic converter 7a, 7b Exhaust pipe 9 Air pump 21 Air intake pipe 22 Secondary air supply pipe 23a, 23b Branch pipe 30 Secondary air supply apparatus V1 On-off valve V2 On-off valve

Claims (9)

A secondary air passage for taking out secondary air;
A pump provided in the secondary air passage for supplying secondary air;
First and second branch passages branched from the secondary air passage, and these first and second branch passages are exhaust gas provided in first and second exhaust passages extending from the internal combustion engine, respectively. It is connected to the upstream side of the purification device,
further,
A pressure sensor provided downstream of the pump and measuring the pressure of the secondary air passage;
First branch passage opening / closing means provided in the first branch passage;
Comprising a second branch passage opening and closing means provided in the second branch passage,
An abnormality of the first and second branch passage opening / closing means is detected based on exhaust pulsation detected by the pressure sensor,
Attenuation amount of the first exhaust pulsation transmitted from the first exhaust passage through the first branch passage, and a second amount transmitted from the second exhaust passage through the second branch passage. Secondary air supply device in which the amount of attenuation of exhaust pulsation is different from each other.   The secondary air supply device according to claim 1, wherein the attenuation amounts of the first and second exhaust pulsations are made different from each other by changing the volumes of the first and second branch passages.   The volumes of the first and second branch passages are adjusted so that the first and second exhaust pulsations transmitted through the branch passages do not cancel each other in the secondary air passage. The secondary air supply device according to claim 2.   The secondary air supply device according to claim 1, wherein the attenuation amounts of the first and second exhaust pulsations are made different from each other by changing the lengths of the first and second branch passages.   The volumes of the first and second branch passages are adjusted so that the first and second exhaust pulsations transmitted through the branch passages do not cancel each other in the secondary air passage. The secondary air supply device according to claim 4.   The secondary air supply device according to any one of claims 1 to 5, wherein when the abnormality of the first and second branch passage opening / closing means is detected, the pump is driven. A secondary air passage for taking out secondary air;
A pump provided in the secondary air passage for supplying secondary air;
First and second branch passages extending from the pump, the first and second branch passages being more than the exhaust gas purification devices provided in the first and second exhaust passages extending from the internal combustion engine, respectively. Connected to the upstream side,
further,
First branch passage opening / closing means provided in the first branch passage;
A first pressure sensor provided between the pump and the first branch passage opening / closing means and measuring the pressure of the first branch passage;
Second branch passage opening / closing means provided in the second branch passage;
A second pressure sensor provided between the pump and the second branch passage opening / closing means for measuring the pressure of the second branch passage;
The first and second branches based on the exhaust pulsation in the first branch passage detected by the first pressure sensor and the exhaust pulsation in the second branch passage detected by the second pressure sensor. A secondary air supply device for detecting an abnormality in the passage opening / closing means.   The secondary air supply device according to claim 7, wherein when the abnormality of the first and second branch passage opening / closing means is detected, the pump is driven. A secondary air passage for taking out secondary air;
A pump provided in the secondary air passage for supplying secondary air;
First and second branch passages branched from the secondary air passage, and these first and second branch passages are exhaust gas provided in first and second exhaust passages extending from the internal combustion engine, respectively. It is connected to the upstream side of the purification device,
further,
First branch passage opening / closing means provided in the first branch passage;
A first temperature sensor disposed upstream of the first branch passage opening / closing means in the first branch passage;
Comprising a second branch passage opening and closing means provided in the second branch passage,
A second temperature sensor disposed upstream of the second branch passage opening / closing means in the second branch passage;
The first and second branch passages are opened and closed based on the temperature in the first branch passage detected by the first temperature sensor and the temperature in the second branch passage detected by the second temperature sensor. Secondary air supply device for detecting abnormality of means.

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