JP2009293480A - Secondary-air supply system for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary air supply system which controls optimally activation of a plurality of catalysts, while restraining a voltage drop in driving a plurality of electric air-pumps. <P>SOLUTION: The secondary-air supply system includes a plurality of exhaust pipes 5, 6 in which catalysts 8, 9 are provided respectively. The electric air-pumps P1, P2 are arranged in the respective exhaust pipes so as to supply air into the exhaust pipes upstream of the catalysts. Timing for driving each of the electric air-pumps P1, P2 are adjusted by shifting it by a specified time period. In the control of the air pumps, one of the air-pumps which has a lower-temperature of the catalysts 8, 9 is preferentially driven. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a secondary air supply control device that controls a secondary air supply device that supplies secondary air into an exhaust pipe.

  Conventionally, in order to purify harmful components (CO, HC, NOx) in the exhaust gas of the engine, a three-way catalyst or the like is provided in the middle of the exhaust passage. However, such a catalyst has a predetermined activation temperature. Without sufficient purification performance.

Therefore, in recent years, when the catalyst is in a low temperature state, such as when the engine is cold started, a secondary air supply device is used to activate the catalyst at an early stage. This secondary air supply device is configured by arranging piping for supplying secondary air to an exhaust pipe on the upstream side of the catalyst, and supplies secondary air to the catalyst. That is, the amount of fuel supplied to the engine is made larger than usual to exhaust unburned components from the cylinder, while secondary air is supplied to the upstream side of the catalyst via the secondary air supply pipe to remove the unburned components. React. Thereby, the catalyst can be warmed in a short time by the reaction heat generated by the reaction.
On the other hand, in addition to the engine having a plurality of cylinders arranged in series to exhaust the exhaust gas from one exhaust pipe, the engine is divided into a plurality of cylinders connected to the intake pipe as in a V-type engine. Some are arranged in banks. In such an engine, a plurality of exhaust pipes are provided corresponding to each bank, and a catalyst is provided in each exhaust pipe. Therefore, in such a case, it is necessary to supply secondary air separately to each catalyst.

  However, if a plurality of electric air pumps are installed, power consumption increases. For this reason, if these electric air pumps are driven at the same time, the voltage drop of the battery that supplies the power at the time of startup becomes extremely large, and there is a risk that sufficient operating current may not be supplied to the electronic control device that controls the vehicle. There's a problem.

In view of such circumstances, Patent Document 1 discloses an invention in which energization start timings of a plurality of electric air pumps are made different.
Moreover, in the said conventional apparatus, the electric air pump which supplies electricity first is determined based on the drive log | history of an electric air pump, and prevents the bias | inclination of deterioration of an electric air pump.
JP2007-270730 JP2007-24034

However, in the conventional apparatus, since the electric air pump that is driven first is set without considering the activation state of each catalyst, the exhaust gas characteristics may be temporarily deteriorated.

  The present invention has been made paying attention to this point, and an object of the present invention is to provide a secondary air supply device capable of appropriately activating the catalyst particularly when the internal combustion engine is started.

In order to solve the above problems, the present invention provides a secondary air supply control device for an internal combustion engine that controls the supply of air into a plurality of exhaust pipes in which a catalyst is arranged, and is provided upstream of the catalyst in each exhaust pipe. The secondary air supply control means for controlling a plurality of secondary air supply means for supplying air, and the second corresponding to the exhaust pipe having a low catalyst temperature when the detected difference in the catalyst temperature of each exhaust pipe is equal to or greater than a predetermined value Drive order control means for controlling the secondary air supply control means so that the secondary air supply means is driven before the secondary air supply means corresponding to the other exhaust pipes. A secondary air supply control device for an internal combustion engine is provided.
In the present invention, the integration means for integrating the operation time of the secondary air supply means corresponding to each exhaust pipe for each secondary air supply means, and the drive order control means include the detected catalyst temperature of each exhaust pipe. When the difference between the secondary air supply means is within a predetermined value, the secondary air supply control means is controlled so that the secondary air supply means with a short accumulated operation time is operated before the other secondary air supply means. The secondary air supply device for an internal combustion engine according to claim 1 is provided.

According to the secondary air supply device of the present invention, since the secondary air is supplied by operating the electric air pump from the side where the catalyst temperature is low, the catalyst can be appropriately warmed up from the side where the active state of the catalyst is bad and the emission is improved. Can be made.
Further, when the temperature difference between the catalysts is within a predetermined value, the electric air pumps are operated first from the one with the shortest drive integration time, so that it is possible to prevent the deterioration of the electric air pump.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an internal combustion engine equipped with the secondary air supply device of the present invention. In FIG. 1, reference numeral 1 denotes a main body of an internal combustion engine, and # 1 to # 4 denote a first cylinder, a second cylinder, a third cylinder, and a fourth cylinder, respectively. Each cylinder is provided with a corresponding fuel injection valve 21, 22, 23, 24. Each cylinder is connected to an intake pipe 4 via an intake branch pipe 3 corresponding to the cylinder. Further, a first exhaust branch pipe 5 is connected to the first cylinder and the fourth cylinder, and a second exhaust branch pipe 6 is connected to the second cylinder and the third cylinder. That is, when the first cylinder and the fourth cylinder are collectively referred to as a first cylinder group, and the second cylinder and the third cylinder are collectively referred to as a second cylinder group, the first cylinder group includes the first cylinder group. An exhaust branch pipe 5 is connected, and a second exhaust branch pipe 6 is connected to the second cylinder group. These exhaust branch pipes 5 and 6 merge on the downstream side and are connected to a common exhaust pipe 7.
The first exhaust branch pipe 5 is one exhaust branch pipe on the downstream side, but is branched into two on the upstream side, and the exhaust branch pipes branched into these two are the first cylinder and the first cylinder, respectively. It is connected to 4 cylinders. Similarly, the second exhaust branch pipe 6 is also one exhaust branch pipe on the downstream side, but is branched into two on the upstream side, and the two exhaust branch pipes branched into the second cylinder and the second branch branch pipe, respectively. Connected to the third cylinder.

Three-way catalysts 8 and 9 are arranged at the gathering portions of the exhaust branch pipes 5 and 6, respectively, and a catalyst 10 for purifying specific components in the exhaust gas is arranged in the exhaust pipe 7. The three-way catalysts 8 and 9 have a temperature equal to or higher than a certain temperature (so-called activation temperature) and the air-fuel ratio of the exhaust gas flowing into the three-way catalysts 8 and 9 is close to the theoretical air-fuel ratio. Removes harmful components (CO, HC, NOx) at a high purification rate.
Further, although not shown, catalyst temperature sensors are attached to the three-way catalysts 8 and 9.
In addition, air pipes 11 and 12 are attached to the gathering portions of the exhaust branch pipes 5 and 6 upstream of the three-way catalysts 8 and 9, respectively. The air pipes 11 and 12 include check valves 13 and 14, control valves 15 and 16, electric air pumps P 1 and P 2, and air filters 17 and 18, respectively, in the direction away from the collection portion of the exhaust branch pipes 5 and 6. Is arranged. Pressure sensors 19 and 20 for detecting the pressure of the air in the air pipes are attached to the air pipes 11 and 12 between the control valves 15 and 16 and the electric air pumps P1 and P2, respectively. The electric air pumps P1 and P2 are supplied with electric power from a common battery B 1, and the electric air pump operates with this electric power.

  The electric air pumps P1 and P2 take in air through the air filters 17 and 18 and discharge the air toward the collecting portion of the exhaust branch pipes 5 and 6, and their operations can be controlled independently. Is something. The control valves 15 and 16 are used for switching whether or not the air discharged from the electric air pumps P1 and P2 is supplied to the collection portion of the exhaust branch pipes 5 and 6. When the control valves 15 and 16 are opened, air is supplied from the electric air pumps P1 and P2 to the collecting portions of the exhaust branch pipes 5 and 6, and when the control valves 15 and 16 are closed, the electric air pumps P1 and P2 are supplied. Is cut off from the supply of air to the gathering portions of the exhaust branch pipes 5 and 6. The check valves 13 and 14 are for preventing fluid from flowing backward from the exhaust branch pipes 5 and 6 to the electric air pumps P1 and P2.

  As described above, the electric air pumps P1 and P2 whose operation can be independently controlled are provided for the three-way catalysts 8 and 9, respectively. It is possible to supply air at a flow rate suitable for.

  In FIG. 1, an electronic control unit (ECU) 100 includes an input port 102, an output port 103, a CPU (microprocessor) 104, a ROM (read only memory) 105, which are connected to each other by a bidirectional bus 101. In addition, a random access memory (RAM) 106 is included. Pressure sensors 19 and 20 are connected to the input port 102 of the ECU 100, and output signals from the pressure sensors 19 and 20 are input. Further, the output port 103 of the ECU 100 is connected to the control valves 15 and 16, the fuel injection valves 21 to 24, and the electric air pumps P1 and P2.

  By the way, in this embodiment, when each electric air pump P1, P2 should be operated, it is made to operate like the flow of FIG. That is, when the electric air pumps P1 and P2 are to be operated, first, in step S1, it is checked whether the temperature difference between the catalysts 8 and 9 is equal to or greater than a predetermined value. If it is within the value, the process proceeds to step S10.

  If it is determined in step S2 that the temperature of the catalyst 8 is lower, the electric air pump P1 is driven in step S3. If the electric air pump P1 is driven for a predetermined time in step S4, the electric air pump P2 is driven in step S5.

  If it is determined in step S2 that the temperature of the catalyst 8 is higher, the electric air pump P2 is driven in step S7, and if the electric air pump P2 is driven for a predetermined time in step S8, the electric air pump P1 is driven in step S9. To do.

  In step S10, the accumulated drive time of the electric air pumps P1 and P2 is checked. If the accumulated drive time of the electric air pump P1 is shorter, the electric air pump P1 is driven first in step S11, and the electric air pump P1 in step S12. If the drive has timed for a predetermined time, the electric air pump P2 is driven in step S13.

  If it is determined in step S10 that the integrated drive time of the electric air pump P2 is shorter, the process proceeds to step S14, where the electric air pump P2 is driven first, and in step S15, the drive of the electric air pump P2 is counted for a predetermined time. In step S16, the electric air pump P1 is driven.

  In step S6, the drive times of the electric air pump P1 and the electric air pump P2 are integrated and stored in the EEPROM 107, for example.

Thus, controlling the operation of the electric air pump has the following advantages. That is, when a catalyst is arranged in each exhaust pipe as in this embodiment, the temperature rise of each catalyst varies depending on the operating state, so if the catalyst is not warmed up properly, emissions will deteriorate. Connected. Moreover, since electric power is supplied to each electric air pump from one common battery B, when the operation of each electric air pump is started at the same time, the voltage of the battery B temporarily decreases rapidly.
However, if the operation start timing of each electric air pump is shifted depending on the temperature of each catalyst (the activated state of the catalyst) as in this embodiment, the catalyst can be appropriately prevented while avoiding such a sudden drop in battery voltage. Can be activated.

  As described above, in the present embodiment, when the electric air pumps P1 and P2 are to be operated, for example, when the internal combustion engine is started, the temperatures of the three-way catalysts 8 and 9 are predetermined (in particular, three This is when the original catalyst is lower than the so-called activation temperature at which its purification ability is exhibited. That is, when air is supplied from the electric air pump to the three-way catalyst during operation of the internal combustion engine (of course, when air is supplied to the three-way catalyst in this way, the corresponding control valves 15 and 16 are opened. The supplied air reacts with unburned hydrocarbons in the exhaust gas when it flows into the three-way catalyst, so that the temperature of the three-way catalyst rises. Therefore, when the temperature of the three-way catalyst is lower than the activation temperature, if air is supplied from the electric air pump to the three-way catalyst, the temperature of the three-way catalyst can be raised to the activation temperature.

  In the present embodiment, for example, when the previously driven electric air pump is P1, the predetermined time from when the first electric air pump P1 is activated to when the second electric air pump P2 is activated is, for example, It is determined based on the voltage of the battery B, the temperature of the cooling water for cooling the internal combustion engine, the outside air temperature, and the like. That is, after the first electric air pump P1 is operated, when the voltage of the battery B is lower than the normally scheduled value, the second electric air pump P2 is kept until the voltage of the battery B recovers to the normally scheduled value. You should wait for the start of operation. Therefore, when the voltage of the battery B is taken into account in determining the predetermined time, the predetermined time may be set longer as the voltage of the battery B is lower than a normally scheduled value.

  Further, as shown in FIG. 3, the present invention can also be applied to an internal combustion engine having a plurality of cylinder groups (two in the example of FIG. 3) consisting of a plurality of cylinders (three cylinders in the example of FIG. 3). It is. Next, the embodiment shown in FIG. 3 will be described. In FIG. 3, 1A and 1B respectively indicate the main body of the internal combustion engine, and # 1 to # 6 indicate the first cylinder, the second cylinder, the third cylinder, the fourth cylinder, the fifth cylinder, and the sixth cylinder, respectively. . Each cylinder is provided with a corresponding fuel injection valve 31, 32, 33, 34, 35, 36. An intake pipe 4 is connected to each of the first cylinder, the second cylinder, and the third cylinder via corresponding intake branch pipes 3A. Further, the intake pipe 4 is connected to the fourth cylinder, the fifth cylinder, and the sixth cylinder via the corresponding intake branch pipes 3B. Further, the first exhaust branch pipe 5 is connected to the first cylinder, the second cylinder, and the third cylinder, and the second cylinder is connected to the second cylinder, the fifth cylinder, and the sixth cylinder. An exhaust branch pipe 6 is connected. That is, when the first cylinder, the second cylinder, and the third cylinder are collectively referred to as a first cylinder group, and the fourth cylinder, the fifth cylinder, and the sixth cylinder are collectively referred to as a second cylinder group, A first exhaust branch pipe 5 is connected to the first cylinder group, and a second exhaust branch pipe 6 is connected to the second cylinder group. These exhaust branch pipes 5 and 6 merge on the downstream side and are connected to a common exhaust pipe 7.

  The exhaust branch pipes 5 and 6 are respectively provided with three-way catalysts 8 and 9, and the exhaust pipe 7 is provided with a catalyst 10 for purifying a specific component in the exhaust gas.

  Air pipes 11 and 12 are attached to the exhaust branch pipes 5 and 6 upstream of the three-way catalysts 8 and 9, respectively. In each of the air pipes 11 and 12, check valves 13 and 14, control valves 15 and 16, air pumps P1 and P2, and air filters 17 and 18 are arranged in the direction away from the exhaust branch pipes 5 and 6, respectively. Yes. Pressure sensors 19 and 20 are attached to the air pipes 11 and 12 between the control valves 15 and 16 and the air pumps P1 and P2, respectively. The air pumps P1 and P2 are supplied with electric power from one common battery B, and the air pump is operated with this electric power.

  Also in the embodiment shown in FIG. 3, the electronic control unit (ECU) 100 includes an input port 102, an output port 103, a CPU (microprocessor) 104, and a ROM (read) that are mutually connected by a bidirectional bus 101. Only memory) 105 and RAM (random access memory) 106. The pressure sensors 19 and 20 are connected to the input port 102 of the ECU 100, and output signals from the pressure sensors 19 and 20 are input. The output port 103 of the ECU 100 is connected to the control valves 15 and 16, the fuel injection valves 31 to 36, and the air pumps P1 and P2.

  Further, the internal combustion engine of the embodiment shown in FIG. 3 is a so-called V-type internal combustion engine. The V-type internal combustion engine shown in FIG. 3 has two banks 1A and 1B, and each bank 1A and 1B is provided with a cylinder group. Each cylinder group includes three cylinders (which correspond to the cylinders # 1 to # 3 and # 4 to # 6 in the embodiment shown in FIG. 3). In the V-type internal combustion engine, the banks 1A and 1B are arranged such that the central axis of the cylinder of one cylinder group and the central axis of the cylinder of the other cylinder group form a V shape.

  Thus, when the present invention is applied to a V-type internal combustion engine, an air pump is provided corresponding to each bank. Therefore, even if each air pump is a small air pump, the temperature is set to each three-way catalyst. A sufficient amount of air can be supplied to raise. Moreover, since the operation start timing of each air pump is shifted when both air pumps should be operated, a sudden drop in battery voltage can be avoided.

It is a figure which shows an example of the internal combustion engine provided with the air supply apparatus of this invention. It is a flowchart which shows the procedure of a secondary air supply control process. It is a figure which shows an example of the V-type internal combustion engine which can apply this invention.

Explanation of symbols

1, 1A, 1B: Internal combustion engine body 3: Intake branch pipe 4: Intake pipe 5, 6: Exhaust branch pipe 7: Exhaust pipe 8, 9: Three-way catalyst 10: Exhaust purification catalyst 11, 12: Air pipes 13, 14 : Check valve 15, 16: Control valve 17, 18: Air filter 19, 20: Pressure sensors 21-24, 31-36: Fuel injection valve 100: Electronic control unit (ECU)
101: Bidirectional bus 102: Input port 103: Output port 104: CPU
105: ROM
106: RAM
107: EEPROM
B: Battery P1, P2: Air pump

Claims (2)

A secondary air supply control device for an internal combustion engine that controls supply of air into a plurality of exhaust pipes in which a catalyst is disposed,
Secondary air supply control means for controlling a plurality of secondary air supply means for supplying air upstream of the catalyst in each exhaust pipe;
When the detected difference in the catalyst temperature of each exhaust pipe is equal to or greater than a predetermined value, the secondary air supply means corresponding to the exhaust pipe having a low catalyst temperature is driven before the secondary air supply means corresponding to the other exhaust pipes. A secondary air supply control device for an internal combustion engine, comprising: drive sequence control means for causing the secondary air supply control means to perform control. Integrating means for integrating the operation time of the secondary air supply means corresponding to each exhaust pipe for each secondary air supply means;
The drive sequence control means operates the secondary air supply means with a short accumulated operation time before the other secondary air supply means when the detected catalyst temperature difference between the exhaust pipes is within a predetermined value. 2. The secondary air supply device for an internal combustion engine according to claim 1, wherein the secondary air supply control unit controls the second air supply control unit to perform the control.

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