JP2005163709A - Flow rate calculation method of secondary air supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately calculate flow rate of secondary air in consideration of a delivery capacity of a pump and piping resistance of a secondary air supply passage. <P>SOLUTION: The flow rate calculation method of a secondary air supply device has a secondary air supply passage for supplying secondary air to the upstream side of an exhaust emission control device provided to an exhaust passage of an internal combustion engine, a pump for supplying secondary air to the secondary air supply passage, an opening/closing means provided to the downstream part of the pump to open and close the secondary air supply passage, and a pressure sensor provided between the pump and the opening/closing means to measure pressure in the secondary air supply passage. First pressure (Pon) in the secondary air supply passage is measured by a pressure sensor when opening the opening/closing means and driving the pump. Second pressure (Pjam) in the secondary air supply passage is measured by a pressure sensor when closing the opening/closing means and driving the pump. Secondary air flow rate (Qjam) flowing through the secondary air supply passage is calculated by using the first and second pressures when opening the opening/closing means and driving the pump. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a flow rate calculation method for calculating a flow rate of secondary air of a secondary air supply device that supplies secondary air upstream 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 secondary air supply device that oxidizes HC and CO to promote purification of exhaust gas is known.

Furthermore, a secondary air supply device that can measure the flow rate of secondary air has been proposed. For example, in Patent Document 1, a secondary air supply amount is calculated from a flow rate by a flow sensor, an air-fuel ratio, or a pressure difference in a state where a throttle is provided in a secondary air supply passage, and secondary air supply is calculated from this supply amount. It is determined whether or not the apparatus is abnormal (refer to Patent Document 2 and Patent Document 3 in addition to Patent Document 1).
Japanese Patent Laid-Open No. 5-263737 JP 2003-83048 A JP-A-8-246828

  By the way, when the internal combustion engine is used for a long period of time, the fine particles mixed in the intake gas taken in from the intake system of the internal combustion engine and the fine particles generated from the lubrication part and the drive part of the pump are separated from the inner wall of the secondary air supply passage. It deposits as a deposit. In addition, fine particles in the exhaust gas also adhere to the inner wall of the secondary air supply passage and accumulate as deposits. In such a case, since the pressure in the secondary air supply passage increases due to an increase in the piping resistance of the secondary air supply passage, the flow rate of the secondary air actually decreases. There is a possibility that it is erroneously determined that the flow rate of the secondary air has increased.

  In addition, secondary air is supplied to the exhaust system of the internal combustion engine through the secondary air supply passage by driving the pump, but when the pump is used for a long time, the discharge capacity of the pump gradually decreases due to deterioration over time. To do.

  However, the secondary air supply apparatus described in Patent Literature 1 to Patent Literature 3 assumes a state in which deposits are not accumulated in the secondary air supply passage and the discharge capacity of the pump is not lowered. For this reason, when deposits are accumulated in the secondary air supply passage by using the internal combustion engine for a long period of time, or when the discharge capacity of the pump decreases due to aging, secondary air calculation in Patent Document 1 is performed. The flow rate of the secondary air calculated by the method may be different from the flow rate of the secondary air that actually flows through the secondary air supply passage.

  Further, in Patent Document 1, since it is necessary to separately provide a flow rate sensor, the manufacturing cost increases, and when calculating the secondary air supply amount from the air-fuel ratio, the accuracy of the secondary air supply amount may be inferior. It is done. Further, when the throttle is provided in the secondary air supply passage as disclosed in Patent Document 1, the pressure loss during the supply of the secondary air increases, so the secondary air supply device provided in the actual internal combustion engine It is not preferable to use it.

  The present invention has been made in view of such circumstances, and a secondary air supply capable of calculating an accurate secondary air flow rate in consideration of the discharge capacity of the pump and the piping resistance of the secondary air supply passage. An object of the present invention is to provide a flow rate calculation method for an apparatus.

  In order to achieve the above-described object, according to the first aspect of the invention, a secondary air supply passage for supplying secondary air to the upstream side of the exhaust purification device provided in the exhaust passage of the internal combustion engine; A pump that supplies secondary air to the secondary air supply passage; an opening / closing means that is provided downstream of the pump to open and close the secondary air supply passage; and is provided between the pump and the opening / closing means. A flow rate calculation method for a secondary air supply device having a pressure sensor for measuring the pressure of the secondary air supply passage, wherein the secondary air supply passage is opened by the pressure sensor when the opening / closing means is opened and when the pump is driven. A first pressure in the secondary air supply passage is measured by the pressure sensor when the opening / closing means is closed and the pump is driven, and when the opening / closing means is opened. One flow rate calculation method of the secondary air supply device the flow rate of secondary air flowing through the secondary air supply passage at the time of driving is calculated by using the first pressure and the second pressure of the pump is provided.

  That is, according to the first invention, the increase degree of the pipe resistance of the secondary air supply passage based on the deposit accumulated on the inner wall or the like of the secondary air supply passage is determined from the first pressure and the second pressure. Since the discharge capacity of the pump that decreases due to the change is determined from the second pressure, the accurate secondary air flow rate is calculated considering the discharge capacity of the pump and the piping resistance of the secondary air supply passage. It becomes possible. For example, when the first pressure is relatively high when the opening / closing means is opened and the pump is driven, a relatively large amount of deposits are accumulated on the inner wall of the secondary air supply passage, etc. It is determined that the piping resistance of the supply passage is increasing, and thereby the flow rate of the secondary air is made relatively small. In addition, when the second pressure when the opening / closing means is closed and the pump is driven is relatively small, it can be determined that the capacity of the pump has decreased due to aging, so the flow rate of the secondary air is relatively small. The In the first invention, a map showing the flow rate of the secondary air as a function of the first pressure and the second pressure is prepared, and the flow rate of the secondary air is directly obtained from this map. Also good.

According to the second invention, in the first invention, if the calculated flow rate of the secondary air is smaller than a predetermined value, it is determined that the flow rate of the secondary air is reduced. In other words, according to the second invention, when the flow rate of the secondary air is smaller than a predetermined value, the amount of deposits on the inner surface of the secondary air supply passage is large, so that the flow rate of the secondary air decreases. Can be determined.

According to a third aspect, in the first or second aspect, when the first pressure is greater than a predetermined value, it is determined that the flow rate of the secondary air is decreasing. I made it.
That is, according to the third invention, when the first pressure when the opening / closing means is opened and when the pump is driven is larger than a predetermined value, the deposit on the inner surface of the secondary air supply passage is large. It can be determined that the flow rate of the secondary air is decreasing. In this case, the calculated flow rate of the secondary air supply passage is naturally reduced.

  According to the fourth aspect of the invention, the secondary air supply passage that supplies the secondary air to the upstream side of the exhaust purification device provided in the exhaust passage of the internal combustion engine, and the secondary air is supplied to the secondary air supply passage. And a pump that is provided downstream of the pump to open and close the secondary air supply passage, and is provided between the pump and the opening and closing means to measure the pressure of the secondary air supply passage. And when the pressure in the secondary air supply passage measured by the pressure sensor is larger than a predetermined value when the opening / closing means is opened and the pump is driven, Provided is a secondary air supply device that determines that the flow rate of secondary air flowing through an air supply passage is decreasing.

  That is, according to the fourth aspect of the invention, when the first pressure when the opening / closing means is opened and when the pump is driven is larger than a predetermined value, the deposit on the inner surface of the secondary air supply passage is large. It can be determined that the flow rate of the secondary air is decreasing. Further, if the pump is driven with the opening / closing means closed, the load applied to the pump and the opening / closing means is large. However, in the fourth invention, there is no need to drive the pump with the opening / closing means closed. The possibility of overloading the means can be eliminated.

According to each invention, it is possible to obtain a common effect that an accurate flow rate of secondary air can be calculated in consideration of the discharge capacity of the pump and the piping resistance of the secondary air supply passage.
Furthermore, according to the 2nd and 3rd invention, there can exist an effect that it can be judged that the flow volume of secondary air is falling.
Furthermore, according to the fourth aspect of the invention, it is possible to eliminate the possibility that an excessive load is applied to the pump and the opening / closing means.

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 showing a secondary air supply apparatus according to 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. Between the air cleaner 2 and the throttle valve 3a, an air flow meter 3b for measuring an air amount (primary air amount) is provided. 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 a position between the throttle valve 3 a of the intake pipe 3 and the air cleaner 2. 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 in the drawing, the secondary air supply pipe 22 is branched into two branch pipes 23a and 23b, and these branch pipes 23a and 23b are connected to the secondary air supply ports 8a and 8b of the exhaust pipes 7a and 7b, respectively. ing. 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. Further, the secondary air supply pipe 22 is also provided with a control valve V0. These control valves V0, V1, and V2 are air switching valves (ASV) or vacuum switching valves (VSV), and the amount of secondary air flowing through the branch pipes 23a and 23b and the secondary air supply pipe 22 is controlled by the ECU 40 described later. Open and close. Further, a pressure sensor 33 is provided between the control valve V 0 and the electric air pump 9 in the secondary air supply pipe 22. That is, as illustrated, the pressure sensor 33 is disposed upstream of the control valve V0.

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. Furthermore, 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. . The input port 45 is connected to a crank angle sensor 52 that generates an output pulse every time the crankshaft rotates, for example, 30 °. 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 includes 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 of the secondary air supply pipe 22. It is connected to V0, control valves V1 and V2 of the branch pipes 23a and 23b, 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 carrier, and on this carrier, 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 secondary air to the catalytic converters 5a and 5b, the oxygen concentration in the catalytic converters 5a and 5b increases, so that CO, HC, NOx, etc. in the exhaust gas can be purified.

  FIG. 2 is a flowchart showing an operation routine of the secondary air supply device according to the present invention. In step 101 of the operation routine 100 in FIG. 2, it is determined whether or not secondary air supply control (simply abbreviated as “AI” in the accompanying drawings and the following description) is currently being executed. Here, when AI is executed, both the downstream control valves V1 and V2 are open, the upstream control valve V0 is also open, and the electric air pump 9 is driven. Therefore, the secondary air is being supplied to the catalytic converters 5a and 5b. If it is determined in step 101 that the AI is being executed, the process proceeds to step 102. If it is determined that the AI is not being executed, the process proceeds to step 105 described later. In step 102, the pressure sensor 33 measures the pressure Pon of the secondary air supply pipe 22 when the control valve V0 is closed and when the electric air pump 9 is driven, that is, when AI is being executed. Next, the routine proceeds to step 103, where it is determined whether or not the pressure Pon is larger than a predetermined value P0, that is, whether or not Pon> P0. If it is determined in step 103 that the pressure Pon at the time of AI execution is not larger than the predetermined value P0, the routine proceeds to step 104 and waits until the AI ends. When the AI is finished, the electric air pump 9 is stopped, the upstream control valve V0 and the downstream control valves V1, V2 are all closed, and the supply of secondary air is stopped.

  On the other hand, if it is determined in step 103 that the pressure Pon at the time of AI execution is larger than the predetermined value P0, the process proceeds to step 114. In step 114, it is determined that the amount of secondary air passing through the secondary air supply pipe 22 is decreasing, and the process is terminated. Hereinafter, this determination will be described. As described above, the secondary air flows to the catalytic converters 5a and 5b through the air intake pipe 21, the secondary air supply pipe 22, and the branch pipes 23a and 23b by driving the electric air pump 9. The electric air pump 9 is set to operate at a predetermined upper limit voltage. As will be described later with reference to FIG. 3, the predetermined value P0 is the upper limit voltage when the deposit is not deposited on the inner walls of the air intake pipe 21, the secondary air supply pipe 22, and the branch pipes 23a and 23b. Is the pressure Pjam0 in the secondary air supply pipe 22 when AI is executed, or close to the pressure Pjam0 and less than or equal to the pressure Pjam0. For this reason, when the pressure Pon measured at the time of AI execution is larger than the predetermined value P0, deposits are deposited on the inner walls of the air intake pipe 21, the secondary air supply pipe 22, or the branch pipes 23a and 23b. Therefore, it can be presumed that the pipe resistance of these pipes has increased. For this reason, when the pressure Pon measured at the time of AI execution is larger than the predetermined value P0, the flow rate of the secondary air flowing through the secondary air piping system actually decreases because the piping resistance of the piping system has increased. Can be judged.

  Next, at step 105, whether or not the pressure Pon at the time of AI execution is measured, that is, an execution condition for performing the closing operation for driving the electric air pump 9 with the control valve V0 closed as described later is established. It is determined whether or not. If the pressure Pon at the time of AI execution has already been measured, the routine proceeds to step 106. If the pressure Pon has not been measured, the process proceeds to step 111 described later.

  In step 106, the electric air pump 9 is driven. As described above, when the step 106 is reached, the AI process has already been completed or the AI process has not been performed. Therefore, when the electric air pump 9 is driven, the upstream control valve V0 and the downstream side All of the control valves V1, V2 are closed. That is, in step 106, the electric air pump 9 is driven with the control valve V0 closed. Next, the routine proceeds to step 107, where it is determined whether or not a predetermined time has elapsed since the electric air pump 9 was driven. The predetermined time in step 107 means a time sufficient to drive the electric air pump 9 in a stable state. If it can be determined that the electric air pump 9 is driven in a stable state, the routine proceeds to step 108. If the predetermined time has not elapsed in step 107, the process proceeds to step 111 described later.

  In step 108, the shutoff pressure Pjam of the secondary air supply pipe 22 upstream of the control valve V 0 is measured by the pressure sensor 33 when the control valve V 0 is closed and the electric air pump 9 is driven. Since the electric air pump 9 is driven in a state where the control valve V0 is closed, the cutoff pressure Pjam measured in step 108 is, as will be described later, when the control valve V0 is opened and when the electric air pump 9 is driven. That is, it is considerably larger than the pressure Pon during AI execution. Next, the routine proceeds to step 109, where the flow rate Qjam of the secondary air that actually flows when the AI is executed is calculated using the pressure Pon and the cutoff pressure Pjam when the AI is executed.

  FIG. 3 is a diagram showing the relationship between the pressure and flow rate of secondary air in the secondary air supply passage of the present invention. In FIG. 3, the vertical axis indicates the flow rate Q of the secondary air in the secondary air supply pipe 22, and the horizontal axis indicates the pressure P of the secondary air. Hereinafter, calculation of the actual flow rate Qjam of secondary air at the time of AI execution will be described with reference to FIG. Between the secondary air pressure P and the flow rate Q in the secondary air supply passage, there is a relationship that generally draws an exponential function as shown by the solid line X0 in FIG. That is, the flow rate Q increases exponentially as the pressure P increases. However, when deposits accumulate on the inner wall of the secondary air supply pipe 22 and the like and the pipe resistance increases, the flow rate Q becomes small even at the same pressure P. Therefore, the relationship between the pressure P and the flow rate Q. Moves in the direction of the dashed arrow Z1. For example, if the solid line X0 is in a state where no deposit is deposited on the inner wall of the secondary air supply pipe 22 or the like, the pipe resistance of the secondary air supply pipe 22 or the like increases as the deposit accumulates. Accordingly, the solid line X0 changes in the direction of the broken line arrow Z1 to, for example, the broken line X1.

  On the other hand, considering the flow rate Q when the electric air pump 9 is driven when the degree of closing of the secondary air supply pipe 22 by the control valve V0 is changed while the electric air pump 9 is being driven, the control valve V0 is completely closed. In this case, the pressure P becomes maximum and the flow rate Q becomes zero. When the control valve V0 is completely open, the flow rate Q becomes maximum and the pressure P approaches zero. Furthermore, if the control valve V0 is semi-closed, each of the flow rate Q and the pressure P is positioned between the control valve V0 fully opened and the control valve V0 fully closed. Therefore, when the control valve V0 is gradually changed from the fully opened state to the completely closed state when the electric air pump 9 is being driven, the pressure P and the flow rate Q are shown in FIG. A relationship such as a PQ characteristic curve Y0 is obtained. Here, the intersection between the PQ characteristic curve Y0 and the X axis is the cutoff pressure Pjam0, and the intersection between the PQ characteristic curve Y0 and the Y axis is the flow rate Qon0. Assuming that this PQ characteristic curve Y0 is a PQ characteristic curve obtained when no deterioration of the electric air pump 9 is observed, the intersection Pjam0 between the PQ characteristic curve Y0 and the X axis is the control valve. This is the maximum value of the cutoff pressure Pjam obtained when the electric air pump 9 is driven when V0 is closed. Further, the flow rate Qon0 at the intersection between the PQ characteristic curve Y0 and the Y-axis is the theoretical maximum value of the flow rate Qon obtained when the electric air pump 9 is driven when the control valve V0 is fully opened. Note that the theoretical flow rate Q when the control valve V0 is opened is the flow rate Qon0 shown in FIG. 3. However, since there is actually a pressure loss in the piping system, the pipe resistance increases in the secondary air supply pipe 22 and the like. Even when the above is not observed, the pressure P and the flow rate Q have a relationship as indicated by the solid line X0.

  By the way, as is well known, the discharge capacity of the electric air pump 9 gradually decreases due to aging. As the discharge capacity of the electric air pump 9 decreases, both the cutoff pressure Pjam when the control valve V0 is closed and the flow rate Qon when the control valve V0 is opened are smaller than the cutoff pressure Pjam0 and the flow rate Qon0 shown in FIG. . That is, as shown in FIG. 3, as the discharge capacity of the electric air pump 9 decreases, the PQ characteristic curve Y0 changes in the direction of the solid arrow Z2, for example, another PQ characteristic curve Y1 indicated by a broken line. Will gradually move until.

  Here, when neither the increase in the piping resistance of the secondary air supply pipe 22 or the like nor the decrease in the discharge capacity of the electric air pump 9 occurs, for example, almost no time has elapsed since the use of the secondary air supply device 30 was started. Consider the case where it has not elapsed. At this time, it is assumed that the pressure Pon0 at the time of AI execution is obtained by driving the electric air pump 9 when the control valve V0 is opened, and then the cutoff pressure Pjam0 is obtained by driving the electric air pump 9 when the control valve V0 is closed. Then, by obtaining the cutoff pressure Pjam0, a PQ characteristic that passes through the cutoff pressure Pjam0 when neither an increase in piping resistance of the secondary air supply pipe 22 or the like nor a decrease in the discharge capacity of the electric air pump 9 occurs. Curve Y0 is determined. Next, as can be seen from FIG. 3, the actual flow rate Qjam00 during AI execution is determined from the Y coordinate of the intersection W00 between the perpendicular line passing through the pressure Pon0 during AI execution and the PQ characteristic curve Y0. Since the flow rate Qjam00 is the flow rate Q at the time of AI execution when neither an increase in piping resistance of the secondary air supply pipe 22 or the like nor a decrease in the discharge capacity of the electric air pump 9 occurs, the flow rate Qjam00 is actually at the time of AI execution. This is the maximum flow rate that can be obtained.

  Next, let us consider a case where the piping resistance of the secondary air supply pipe 22 and the like has not increased, but the electric air pump 9 has deteriorated over time and the discharge capacity has decreased. In this case, since the piping resistance of the secondary air supply pipe 22 and the like has not increased, the pressure Pon at the time of AI execution remains the pressure Pon0 shown in FIG. However, since the discharge capacity of the electric air pump 9 is reduced, the cutoff pressure Pjam for driving the electric air pump 9 when the control valve V0 is closed is smaller than the maximum cutoff pressure Pjam0. For example, the cutoff pressure Pjam is shown in FIG. The cut-off pressure Pjam1 as shown in FIG. Since a new cutoff pressure Pjam1 is obtained, a PQ characteristic curve Y1 passing through the cutoff pressure Pjam1 is determined. This PQ characteristic curve Y1 is selected from a plurality of PQ characteristic curves Y obtained in advance by experiments or the like. Next, the actual flow rate Qjam10 at the time of AI execution is obtained from the Y coordinate of the intersection W10 between the perpendicular line passing through the pressure Pon0 at the time of AI execution and the PQ characteristic curve Y1. As a matter of course, the actual flow rate Qjam10 when the discharge capacity of the electric air pump 9 is reduced is smaller than the flow rate Qjam00. Here, although the piping resistance of the secondary air supply pipe 22 and the like has not increased, when the electric air pump 9 has deteriorated over time and the discharge capacity has decreased, according to the flow rate calculation method of the prior art, the pressure Pon0 The flow rate Qjam00 is obtained as the actual flow rate from the PQ characteristic curve Y0. However, in the present invention, since the reduction of the discharge capability of the electric air pump 9 is taken into consideration, the flow rate Qjam 10 during AI execution can be determined more accurately than in the case of the prior art.

  Furthermore, although the discharge capacity of the electric air pump 9 is not changed, a case is considered in which deposits are accumulated on the inner wall of the secondary air supply pipe 22 and the like and the pipe resistance is increased. Since the discharge capacity of the electric air pump 9 has not changed, the cutoff pressure Pjam remains the maximum cutoff pressure Pjam0. Therefore, the PQ characteristic curve Y0 passing through the cutoff pressure Pjam0 is employed. Next, when the control valve V0 is opened and when the electric air pump 9 is driven, that is, when AI is executed, a pressure higher than the pressure Pon0, for example, the pressure Pon1, is obtained because the pipe resistance is increased. The pressure Pon1 is naturally smaller than the maximum cutoff pressure Pjam0. Then, the actual flow rate Qjam01 at the time of AI execution is obtained from the Y coordinate of the intersection W01 between the PQ characteristic curve Y0 and the perpendicular passing through the pressure Pon1 when the discharge capacity of the electric air pump 9 is not lowered. As a matter of course, the flow rate Qjam01 is smaller than the flow rate Qjam00. Although the discharge capacity of the electric air pump 9 has not changed, according to the flow rate calculation method of the prior art when deposits are accumulated on the inner wall of the secondary air supply pipe 22 or the like and the pipe resistance is increased. The flow rate Q is calculated from the pressure Pon1 using a predetermined formula. However, in the present invention, since an increase in piping resistance of the secondary air supply pipe 22 and the like is taken into consideration, the flow rate is more accurate than in the case of the prior art. Qjam01 can be obtained.

  Finally, considering the case where the piping resistance of the secondary air supply pipe 22 and the like is increased and the discharge capacity of the electric air pump 9 is also reduced, the pressure Pon at the time of AI execution for the same reason as described above A pressure higher than the pressure Pon0, for example, the pressure Pon1, is obtained, and the cutoff pressure Pjam is a pressure lower than the maximum cutoff pressure Pjam0, for example, the cutoff pressure Pjam1. As in the case described above, the actual flow rate Qjam11 at the time of AI execution is calculated from the Y coordinate of the intersection W11 between the PQ characteristic curve Y1 passing through the cutoff pressure Pjam1 and the perpendicular passing through the pressure Pon1. Naturally, the flow rate Qjam when the piping resistance of the secondary air supply pipe 22 and the like is increased and the discharge capacity of the electric air pump 9 is also decreased is the flow rate Qjam00, the flow rate Qjam01 and the flow rate Qjam10 shown in FIG. Is smaller than As in the case described above, the present invention takes into account the decrease in the discharge capacity of the electric air pump 9 and the increase in the piping resistance of the secondary air supply pipe 22 and the like, so that the flow rate Qjam11 is more accurate than in the prior art. Can be requested.

  As described above, the case where the cutoff pressure Pjam is reduced to the cutoff pressure Pjam1 due to a decrease in the discharge capacity of the pump and / or the case where the pressure Pon at the time of AI execution is increased to the pressure Pon1 due to an increase in the piping resistance of the secondary air supply pipe 22 has been described. However, the cutoff pressure Pjam and the pressure Pon differ depending on the degree of decrease in the discharge capacity of the electric air pump 9 and / or the degree of increase in the piping resistance of the secondary air supply pipe 22, and a different PQ characteristic curve Y is used each time. Obviously it will be done. Accordingly, in FIG. 3, the flow rate decreases in the order of the flow rate Qjam01, the flow rate Qjam10, and the flow rate Qjam11. However, depending on the degree of decrease in the discharge capacity of the electric air pump 9 and / or the degree of increase in the pipe resistance, The order of may change.

  As described above, in the present invention, the degree of decrease in the discharge capacity of the electric air pump 9 is determined by the cutoff pressure Pjam obtained when the control valve V0 is closed and when the electric air pump 9 is driven. The actual flow rate Qjam during AI execution is calculated after the degree of increase in the piping resistance of the secondary air supply pipe 22 is determined based on the pressure Pon and the cutoff pressure Pjam obtained when the air pump 9 is driven, that is, when AI is executed. Yes. For this reason, the actual value at the time of AI execution is more accurate than in the case of the prior art in which these two factors (the degree of decrease in the discharge capacity of the electric air pump 9 and the degree of increase in the piping resistance of the secondary air supply pipe 22) are not considered. It becomes possible to calculate the flow rate Qjam.

  Further, as described with reference to FIG. 3, the flow rate Qjam may be calculated based on the PQ characteristic curve Y obtained in advance, for example, the PQ characteristic curve Y1, but as shown in FIG. 4, for example. The actual flow rate Qjam at the time of AI execution may be stored in the ROM in the form of a map as a function of the pressure Pon and the cutoff pressure Pjam at the time of AI execution. In this case, the actual flow rate Qjam at the time of AI execution can be obtained directly without performing the calculation as described above.

  Referring again to FIG. 2, after obtaining the flow rate Qjam in step 109, the routine proceeds to step 110, where the electric air pump 9 is stopped. The electric air pump 9 may be stopped after measuring the cutoff pressure Pjam in step 108. Next, the routine proceeds to step 111 where it is determined whether or not the flow rate Qjam is calculated, that is, whether or not an execution condition that can determine the actual flow rate Qjam is satisfied. When the flow rate Qjam has been calculated, the process proceeds to step 112, and when it has not been calculated, the process ends.

  In step 112, it is determined whether or not the flow rate Qjam during AI execution is larger than a predetermined flow rate Q0, that is, whether or not Qjam> Q0. Here, the predetermined flow rate Q0 is smaller than the flow rate Qjam00 in the case where neither an increase in piping resistance of the secondary air supply pipe 22 or the like nor a decrease in the discharge capacity of the electric air pump 9 occurs, and the predetermined flow rate Q0 is relatively smaller than the flow rate Qjam00. The predetermined flow rate Q0 may be close to the flow rate Qjam00. If it is determined in step 112 that the flow rate Qjam is greater than the predetermined flow rate Q0, the process proceeds to step 113, where the flow rate of the secondary air is determined to be normal, and the process ends. In this case, the calculated flow rate Qjam may be smaller than the flow rate Qjam00, but normal determination is made assuming that an increase in piping resistance and / or a decrease in discharge capacity of the electric air pump 9 can be ignored.

  On the other hand, if it is determined in step 112 that the flow rate Qjam is not greater than the predetermined flow rate Q0, the routine proceeds to step 114, where the pipe resistance increases and / or the discharge capacity of the electric air pump 9 decreases. In addition, it is determined that the flow rate of the secondary air is decreasing, and the process is terminated.

  Since the cutoff pressure Pjam is measured when the control valve V0 is closed and when the electric air pump 9 is driven, an excessive load can be applied to the control valve V0 and the electric air pump 9. Therefore, when the cutoff pressure Pjam is frequently measured, the control valve V0 and the electric air pump 9 may be damaged. However, when the pressure Pon is determined as YES in step 103 of FIG. Since it is not necessary to measure Pjam, it is possible to avoid the load described above from being applied to the control valve V0 and the electric air pump 9. In the flowchart shown in FIG. 2, if NO is determined in step 103, it is determined that the flow rate of the secondary air is decreasing, and the process ends. However, after NO is determined in step 103, Proceeding to step 107, after calculating the actual flow rate Qjam during AI execution, it may be determined again in step 112 whether or not the flow rate Qjam has decreased. Even such a case is clearly included within the scope of the present invention.

Although the secondary air supply device 30 of the present invention has been described with reference to FIG. 1, the internal combustion engine in which the secondary air supply device 30 can be mounted is a multi-cylinder V-type gasoline divided into left and right banks as shown in FIG. It is not limited to the engine. FIG. 5 is a view showing another internal combustion engine in which the secondary air supply device of the present invention can be mounted. As shown in FIG. 5, the internal combustion engine 1 in this case is configured as a single bank. An intake manifold 3d extending from the intake pipe 3 is connected to one side of the internal combustion engine 1 and an exhaust manifold 4 is provided. The other side of the internal combustion engine 1 is connected. The secondary air supply device 30 ′ in FIG. 5 includes an air intake pipe 21, an electric air pump 9, and a secondary air supply pipe 22, and a pressure sensor 33 and a control valve V 0 are upstream of the secondary air supply pipe 22. It is provided in order from the side. Further, the secondary air supply pipe 22 is provided with a control valve V 3 downstream of the control valve V 0, and the secondary air supply pipe 22 is connected to the exhaust pipe 7 of the internal combustion engine 1. As shown in the figure, the exhaust pipe 7 is provided with a catalytic converter 5 carrying a catalyst having an oxidation function, and O ₂ sensors 6 and 16 are provided upstream and downstream of the catalytic converter 5. In FIG. 5, the ECU 40 is omitted for easy understanding. Even in the case of the internal combustion engine 1 and the secondary air supply device 30 ′ configured as shown in FIG. 5, the electric air pump is in a state in which the upstream control valve V0 is closed while the downstream control valve V3 is opened. Since the cutoff pressure Pjam is measured by driving 9, and the electric pressure pump Pn can be measured by driving the electric air pump 9 with the downstream side control valve V3 and the upstream side control valve V0 being opened. Even in the case of an internal combustion engine, the actual flow rate Qjam during AI execution can be accurately calculated from the operation routine 100 described above with reference to FIG.

  Further, as described above, the operation routine 100 is performed in a state in which the downstream control valves V1 and V2 (see FIG. 1) and the control valve V3 (see FIG. 5) are open. In addition, even when these control valves V1, V2, and V3 are not provided, it is clear that the operation routine 100 of the secondary air supply device 30 can be performed, and such a case is also within the scope of the present invention. include.

It is the schematic which shows the secondary air supply apparatus based on this invention. It is a flowchart which shows the operation | movement routine of the secondary air supply apparatus based on this invention. It is a figure which shows the relationship between the pressure and flow volume of the secondary air in the secondary air supply path of this invention. It is a figure which shows the map of the actual flow volume Qjam at the time of AI execution. It is a figure which shows the other internal combustion engine which can use the secondary air supply apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 5a, 5b ... Catalytic converter 7a, 7b ... Exhaust pipe 9 ... Electric air pump 21 ... Air intake pipe 22 ... Secondary air supply pipe 23a, 23b ... Branch pipe 30, 30 '... Secondary air supply apparatus Pjam ... Cut-off pressure Pon ... AI execution pressure Qjam ... AI execution actual flow rate V0 ... Control valve

Claims (4)

A secondary air supply passage for supplying secondary air upstream of an exhaust purification device provided in an exhaust passage of the internal combustion engine; a pump for supplying secondary air to the secondary air supply passage; and a downstream of the pump An opening / closing means that opens and closes the secondary air supply passage, and a pressure sensor that is provided between the pump and the opening / closing means and measures the pressure of the secondary air supply passage. In the air flow rate calculation method,
A first pressure in the secondary air supply passage is measured by the pressure sensor when the opening / closing means is opened and the pump is driven;
A second pressure in the secondary air supply passage is measured by the pressure sensor when the opening / closing means is closed and the pump is driven;
The flow rate of the secondary air supply device that calculates the flow rate of the secondary air flowing through the secondary air supply passage when the opening / closing means is opened and when the pump is driven using the first pressure and the second pressure Calculation method.   2. The secondary air supply device according to claim 1, wherein when the calculated flow rate of the secondary air is smaller than a predetermined value, it is determined that the flow rate of the secondary air is decreasing. Flow rate calculation method.   The flow rate of the secondary air supply device according to claim 1 or 2, wherein when the first pressure is greater than a predetermined value, it is determined that the flow rate of the secondary air is decreasing. Calculation method. A secondary air supply passage for supplying secondary air to the upstream side of the exhaust purification device provided in the exhaust passage of the internal combustion engine;
A pump for supplying secondary air to the secondary air supply passage;
Opening and closing means provided downstream of the pump and opening and closing the secondary air supply passage;
A pressure sensor provided between the pump and the opening / closing means for measuring the pressure of the secondary air supply passage;
When the pressure in the secondary air supply passage measured by the pressure sensor is larger than a predetermined value when the opening / closing means is opened and the pump is driven, the secondary air flowing through the secondary air supply passage A secondary air supply device for determining that the flow rate of the air is decreasing.

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