JP2004076683A - Secondary air supply system for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily constitute a secondary air supply system for internal combustion engine at low cost. <P>SOLUTION: The intake port 17 of a negative pressure pump 16 is selectively connected to either one of the atmosphere and a negative pressure tank 21 through an intake-side selector valve 18, and the discharge port 25 of the negative pressure pump 16 is selectively connected to either one of an oil pan 27 and an air tank 30 through a discharge-side selector valve 26. A secondary air supplying nozzle 33 is mounted within an exhaust pipe 10a on the upstream side of a catalyst 12, and connected to the air tank 30 through a secondary air control valve 31 to supply the air stored in the air tank 30 to the catalyst 12. In general, the intake port 17 is connected to the negative pressure tank 21, and the discharge port 25 to the oil pan 27. When the air quantity in the air tank 30 is smaller than the allowable minimum quantity, the intake port 17 is connected to the atmosphere, and the discharge port 25 is connected to the air tank 30 to store the air discharged from the discharge port 25 in the air tank 30. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a secondary air supply device for an internal combustion engine.
[0002]
[Prior art]
There is known an internal combustion engine in which secondary air is supplied into an exhaust passage upstream of a catalyst in order to maintain an oxygen concentration in exhaust gas flowing into the catalyst within a target range (see Japanese Patent No. 2844555). ).
[0003]
[Problems to be solved by the invention]
However, it is generally necessary to newly provide an air pump to supply the secondary air into the exhaust passage, not limited to the above-described internal combustion engine. Therefore, there is a problem that not only the configuration becomes complicated but also the cost increases.
[0004]
Therefore, an object of the present invention is to provide a secondary air supply device for an internal combustion engine that can be simply and inexpensively configured.
[0005]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided an internal combustion engine including a negative pressure pump for generating a negative pressure in a negative pressure tank. The air discharged from the discharge port is secondarily supplied into the exhaust passage upstream of the catalyst.
[0006]
According to a second aspect, in the first aspect, the negative pressure pump comprises a negative pressure pump for supplying a negative pressure to the pressure chamber of the vacuum brake booster.
[0007]
According to a third aspect, in the first aspect, a suction side switching valve is connected to a suction port of the negative pressure pump, and the suction side switching valve connects the suction port of the negative pressure pump to the negative pressure tank and the atmosphere. Alternatively, it is selectively connected to either one of the positive pressure source.
[0008]
According to a fourth aspect, in the third aspect, in the third aspect, the suction-side switching valve connects the suction port of the negative pressure pump to the atmosphere or a positive pressure source when energized, and turns off when the energization is stopped. The suction port of the pressure pump is constituted by an electrically controlled switching valve connected to the negative pressure tank.
[0009]
According to a fifth aspect, in the first aspect, a suction air control valve is connected to a suction port of the negative pressure pump, and an amount of air sucked from the suction port of the negative pressure pump is controlled by the suction air control valve. By controlling, the amount of air discharged from the discharge port of the negative pressure pump is controlled.
[0010]
According to a sixth aspect of the present invention, in the first aspect of the present invention, only the exhaust gas upstream of the catalyst flows in the discharge air passage connecting the discharge port of the negative pressure pump and the exhaust passage upstream of the catalyst. A possible check valve is arranged.
[0011]
According to a seventh aspect of the present invention, in the first aspect, the air is supplied into the discharge air passage connecting the discharge port of the negative pressure pump and the exhaust passage upstream of the catalyst to the exhaust passage upstream of the catalyst. A secondary air control valve for controlling the amount of secondary air is provided.
[0012]
According to an eighth aspect of the present invention, in the seventh aspect of the present invention, the liquid is discharged from the discharge port of the negative pressure pump into the discharge air passage between the discharge port of the negative pressure pump and the secondary air control valve. An air tank for storing air is arranged.
[0013]
According to a ninth aspect, in the eighth aspect, an air pressure sensor for detecting an air pressure in the air tank is attached to the air tank.
[0014]
According to a tenth aspect, in the first aspect, lubricating oil of the negative pressure pump is contained in air discharged from a discharge port of the negative pressure pump. An oil separator for separating lubricating oil from air discharged from the discharge port of the negative pressure pump is disposed in a discharge air passage connecting the exhaust gas passage upstream of the catalyst and the exhaust passage.
[0015]
According to an eleventh aspect, in the first aspect, a plurality of catalysts are disposed in the exhaust passage, and the air discharged from the discharge port of the negative pressure pump is respectively placed in the exhaust passage upstream of the catalyst. I am trying to supply.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Referring to FIG. 1, a compression ignition type or spark ignition type engine body 1 includes, for example, four cylinders 1a. Each cylinder 1a is connected on the one hand to a common surge tank 3 via a corresponding intake branch 2 and the surge tank 3 is connected to a compressor 6 of an exhaust turbocharger 5 via an intake duct 4. A throttle valve 8 driven by a step motor 7 is arranged in the intake duct 4. Each cylinder 1a, on the other hand, is connected to the exhaust turbine 11 of the exhaust turbocharger 5 via a common exhaust manifold 9 and an exhaust pipe 10, and the outlet of the exhaust turbine 11 accommodates the catalyst 12 via the exhaust pipe 10a. The casing 13 is connected to the exhaust pipe 10b. Further, the exhaust manifold 9 and the surge tank 3 are connected to each other via an exhaust gas recirculation (hereinafter, referred to as EGR) passage 14, and an electrically controlled EGR control valve 15 is disposed in the EGR passage 14.
[0017]
FIG. 2 shows the throttle opening of the internal combustion engine of FIG. As can be seen from FIG. 2, the throttle opening is kept almost fully open except when the required load L is extremely low. In other words, the throttle opening is maintained almost fully over almost or almost all engine operating states.
[0018]
As described above, when the throttle opening is kept almost fully over most engine operating states, almost no negative pressure is generated in the intake passage downstream of the throttle valve 8. Therefore, the internal combustion engine shown in FIG. 1 is provided with, for example, an engine-driven vane-type negative pressure pump 16.
[0019]
In the embodiment according to the present invention, the negative pressure pump 16 is connected to the crankshaft of the engine body 1 via a cam drive shaft or, for example, a belt, and is thus constantly driven during operation of the engine. An electric control type suction side switching valve 18 is connected to a suction port 17 of the negative pressure pump 16, and the suction side switching valve 18 is connected to the atmosphere via an air filter 19 on one side and a check valve 20 on the other side. , Is connected to a negative pressure tank 21 for storing a negative pressure formed by the negative pressure pump 16. The check valve 20 can be circulated only from the negative pressure tank 21 to the suction side switching valve 18.
[0020]
Further, a pressure chamber of, for example, a vacuum brake booster 23 is connected to the negative pressure tank 21 via a check valve 22. The check valve 22 can flow only from the brake booster 23 to the negative pressure tank 21. When the brake pedal 24 is depressed, the pressure chamber of the brake booster 23 is opened to the atmosphere. When the brake pedal 24 is returned to the original position, the pressure chamber is shut off from the atmosphere and negative pressure is supplied from the negative pressure tank 21. That is, each time the brake pedal 24 is operated, the negative pressure in the negative pressure tank 21 is supplied to the brake booster 23. As described later, the negative pressure in the negative pressure tank 21 is also supplied to the EGR control valve 15 and the secondary air control valve 31.
[0021]
On the other hand, an electrically controlled discharge side switching valve 26 is connected to the discharge port 25 of the negative pressure pump 16, and the discharge side switching valve 26 is directly connected to an oil pan 27 on one side, and is connected to a cyclone type oil separator 28 on the other side. You. An oil outlet provided at the bottom of the oil separator 28 is connected to an oil pan 27, and an air outlet provided at the top of the oil separator 28 receives air discharged from the negative pressure pump 16 via a check valve 29. It is connected to an air tank 30 for storage. The check valve 29 can be circulated only from the oil separator 28 to the air tank 30.
[0022]
The lubricating oil of the engine body 1 is supplied to the negative pressure pump 16, and the lubricating oil is discharged from the discharge port 25 of the negative pressure pump 16 together with air. The oil separator 28 is for removing the lubricating oil contained in the air discharged from the negative pressure pump 16 as described above. The air from which the lubricating oil has been removed by the oil separator 28 passes through an air outlet formed at the top of the oil separator 28, and the lubricating oil passes through an oil outlet formed at the bottom of the oil separator 28. Is discharged to
[0023]
A secondary air supply nozzle 33 is connected to the air tank 30 via an electrically controlled secondary air control valve 31 and a check valve 32. The secondary air supply nozzle 33 is attached to the exhaust pipe 10a upstream of the catalyst 12. Has been. The check valve 32 can flow only from the secondary air control valve 31 to the secondary air supply nozzle 33. When the secondary air control valve 31 is opened, the pressurized air stored in the air tank 30 is injected from the secondary air supply nozzle 33 into the exhaust pipe 10a.
[0024]
The secondary air may be supplied at any time as long as the exhaust purification action of the catalyst 12 is not hindered. In the embodiment according to the present invention, the secondary air is supplied during the warm-up operation. That is, during the warm-up operation, the fuel injection amount is set so that the excess air ratio is lower than that after the completion of the warm-up. Therefore, a relatively large amount of unburned HC and CO is contained in the exhaust gas. I have. Therefore, if the secondary air is supplied at this time, the large amount of unburned HC and CO can be oxidized by the catalyst 12, and the temperature of the catalyst 12 can be quickly raised by the heat generation effect accompanying this oxidation reaction. It becomes possible to do.
[0025]
The electronic control unit 40 is composed of a digital computer, and is connected to each other by a bidirectional bus 41 such as 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. Is provided. A water temperature sensor 48 for detecting an engine cooling water temperature is attached to the engine body 1. The negative pressure tank 21 is provided with a negative pressure sensor 49a for detecting a negative pressure in the negative pressure tank 21, and the air tank 30 is provided with an air pressure sensor 49b for detecting the air pressure PA in the air tank 30. It is attached. Further, a load sensor 51 that generates an output voltage proportional to the amount of depression of the accelerator pedal 50 is connected to the accelerator pedal 50. Output signals from these sensors 48, 49a, 49b, 51 are input to the input port 45 via the corresponding AD converters 47, respectively. Here, the air pressure PA in the air tank 30 indicates the amount of air stored in the air tank 30, and the depression amount L of the accelerator pedal 50 indicates the required load. Further, the input port 45 is connected to a crank angle sensor 52 that generates an output pulse every time the crankshaft rotates, for example, by 30 °. On the other hand, the output port 46 is connected to the step motor 7, the EGR control valve 15, the suction-side switching valve 18, the discharge-side switching valve 26, and the secondary air control valve 31 via a corresponding drive circuit 53.
[0026]
In the embodiment according to the present invention, the suction-side switching valve 18 and the discharge-side switching valve 26 are each constituted by, for example, an electrically controlled switching valve 60 as shown in FIG. That is, as shown in FIG. 3, the switching valve 60 includes a casing 61, a solenoid coil 62 housed in the casing 61, and a valve made of a magnetic material supported in the casing 61 so as to be movable in the axial direction. And a body 63. In the casing 61, a first chamber 64a is formed on one side of the valve body 60, and a second chamber 64b is formed on the other side. The first chamber 64a and the second chamber 64b are formed on the peripheral surface of the valve body 63. Are communicated with each other by a communication path 65 formed in the first and second communication paths. Further, an inlet port 66 and a first outlet port 67a are connected to the first chamber 64a, and a second outlet port 67b is connected to the second chamber 64b. These first and second outlet ports 67a, 67b are located on a straight orbit of the valve body 63. In FIG. 3, reference numeral 68 denotes a compression spring for urging the valve body 63 toward the first outlet port 67a.
[0027]
When the solenoid coil 62 is energized, the valve 63 is displaced rightward in FIG. 3 against the spring force of the compression spring 68 by the magnetic attraction of the solenoid coil 62, opening the first outlet port 67a and opening the second outlet port 67a. The outlet port 67b is closed. As a result, the inlet port 66 is connected to the first outlet port 67a. On the other hand, when the energization of the solenoid coil 62 is stopped, the valve body 63 is displaced leftward in FIG. 3 by the spring force of the compression spring 68, closing the first outlet port 67a and closing the second outlet port 67b. Open. As a result, the inlet port 66 is connected to the second outlet port 67b. Thus, the inlet port 66 is connected to the first outlet port 67a or the second outlet port 67b.
[0028]
Therefore, in the case of the suction side switching valve 18, the suction port 17 of the negative pressure pump 16 is connected to the inlet port 66, the atmosphere is connected to the first outlet port 67a via the air filter 19, and the second outlet port 67b Is connected to a negative pressure tank 21 via a check valve 20. In the case of the discharge side switching valve 26, the discharge port 25 of the negative pressure pump 16 is connected to the inlet port 66, the oil pan 27 is directly connected to the first outlet port 67a, and the oil separator 27 is connected to the second outlet port 67b. 28 will be connected.
[0029]
On the other hand, the EGR control valve 15 and the secondary air control valve 31 are each composed of, for example, an electrically controlled negative pressure operated valve 70 as shown in FIG. That is, as shown in FIG. 4, the negative pressure operated valve 70 includes a casing 71, a diaphragm 73 that divides an inner space of the casing 71 into a pressure chamber 72a and a fluid chamber 72b, and a valve body 74 fixed to the diaphragm 73. And The pressure port 75 connected to the pressure chamber 72a is connected to, for example, an electrically controlled switching valve 76 including the switching valve 60 described above with reference to FIG. It is connected to the atmosphere via the check valve 78 on the other hand. On the other hand, an inlet port 79 and an outlet port 80 are connected to the fluid chamber 72b. In FIG. 4, reference numeral 81 denotes a compression spring for urging the valve element 74 in a direction to close the inlet port 79.
[0030]
When the switching valve 76 is energized, the pressure chamber 72a is connected to the negative pressure tank 21, and a negative pressure is introduced into the pressure chamber 72a. As a result, the valve element 74 is displaced upward in FIG. 4 against the spring force of the compression spring 81, and opens the inner end of the inlet port 79. Therefore, the inlet port 79 is connected to the outlet port 80 via the fluid chamber 72b. On the other hand, when the power supply to the switching valve 76 is stopped, the pressure chamber 72a is connected to the atmosphere, and the atmospheric pressure is introduced into the pressure chamber 72a. As a result, the valve element 74 is displaced downward in FIG. 4 by the spring force of the compression spring 81, and closes the inner end of the inlet port 79. Therefore, communication between the inlet port 79 and the outlet port 80 is interrupted.
[0031]
Therefore, in the case of the EGR control valve 15, the exhaust manifold 9 is connected to the inlet port 79, and the surge tank 3 is connected to the outlet port 80. In the case of the secondary air control valve 31, the air tank 30 is connected to the inlet port 79, and the secondary air supply nozzle 33 is connected to the outlet port 80 via the check valve 32.
[0032]
As is clear from the above description, the suction port 17 of the negative pressure pump 16 is eventually selectively connected to either the negative pressure tank 21 or the atmosphere via the suction side switching valve 18. . When the suction port 17 is connected to the negative pressure tank 21, a relatively small amount of air is sucked from the negative pressure tank 21, and as a result, the negative pressure in the negative pressure tank 21 is increased. On the other hand, when the suction port 17 is connected to the atmosphere, a relatively large amount of air is sucked into the negative pressure pump 16 and discharged from the negative pressure pump 16.
[0033]
On the other hand, the discharge port 25 of the negative pressure pump 16 is eventually selectively connected to one of the oil pan 27 and the air tank 30 via the discharge side switching valve 26. When the discharge port 25 is connected to the oil pan 27, the air discharged from the negative pressure pump 16 is discharged into the oil pan 27. On the other hand, when the discharge port 25 is connected to the air tank 30, the air discharged from the negative pressure pump 16 is stored in the air tank 30.
[0034]
Now, in the embodiment according to the present invention, normally, neither the suction side switching valve 18 nor the discharge side switching valve 26 is energized, and therefore the suction port 17 of the negative pressure pump 16 is connected to the negative pressure tank 21 and the discharge port 25 Is connected to the oil pan 27 bypassing the oil separator 28. By doing so, it is possible to maintain a large negative pressure in the negative pressure tank 21 while keeping the load of the negative pressure pump 16 small.
[0035]
However, when the secondary air is supplied from the secondary air supply nozzle 33, the air pressure PA in the air tank 30 gradually decreases, and then when the air pressure PA becomes lower than the pressure in the exhaust pipe 10a, the secondary air is no longer supplied. Can not supply.
[0036]
Therefore, in the embodiment according to the present invention, when the air pressure PA in the air tank 30 becomes lower than the permissible lower limit value PAL, the discharge side switching valve 26 is temporarily energized to connect the discharge port 25 of the negative pressure pump 16 to an oil separator. It is connected to the air tank 30 through 28. As a result, after the lubricating oil is removed from the air discharged from the negative pressure pump 16, the lubricating oil is supplied into the air tank 30.
[0037]
Air is discharged from the discharge port 25 even when the suction port 17 of the negative pressure pump 16 is connected to the negative pressure tank 21. However, in this case, the amount of air discharged from the discharge port 25 is relatively small, and it takes a long time to replenish the air tank 30 with the target amount of air.
[0038]
Therefore, in the embodiment according to the present invention, when air is to be supplied into the air tank 30, the suction side switching valve 18 is temporarily energized to connect the suction port 17 of the negative pressure pump 16 to the atmosphere. As a result, the amount of air sucked into the negative pressure pump 16 through the suction port 17 can be significantly increased, and thus the amount of air discharged from the discharge port 25 can be significantly increased. In this case, the suction port 17 of the negative pressure pump 16 can be connected to a positive pressure source.
[0039]
In other words, normally, the suction port 17 of the negative pressure pump 16 is connected to the negative pressure tank 21, and the discharge port 25 of the negative pressure pump 16 is connected to the oil pan 27 bypassing the oil separator 28, and When the amount of stored air is less than the minimum allowable, the outlet 25 is temporarily connected to the air tank 30 and the inlet 17 is temporarily connected to the atmosphere or a positive pressure source. Will be.
[0040]
However, normally, the discharge port 25 is connected to the air tank 30, the suction port 17 is connected to the atmosphere or a positive pressure source, the suction port 17 is temporarily connected to the negative pressure tank 21, and the discharge port 25 is connected to the oil separator 28. Can be bypassed and temporarily connected to the oil pan 27.
[0041]
The negative pressure pump 16 is for generating a negative pressure in the pressure chamber or the negative pressure tank 21 originally. However, when the suction port 17 of the negative pressure pump 16 is connected to the atmosphere as described above, the negative pressure pump 16 is not for generating a negative pressure, but rather for pumping air. . This negative pressure pump 16 is generally provided in an internal combustion engine in which almost no negative pressure is generated in the intake passage as described with reference to FIG. This means that there is no need to provide a new pump to supply secondary air to the passage.
[0042]
As described above, while the suction port 17 of the negative pressure pump 16 is connected to the negative pressure tank 21, that is, while the negative pressure is formed, the air discharged from the negative pressure pump 16 at this time is stored in the air tank 30. You can also. Conventionally, the air discharged from the negative pressure pump 16 when the negative pressure is being formed has been discarded together with the lubricating oil in the oil pan 27, so that the idea of using this is as follows. Does not exist by.
[0043]
FIG. 5 shows a routine for executing the above-described secondary air supply control. This routine is executed by interruption every predetermined set time. Referring to FIG. 5, first, in step 100, it is determined whether or not the engine is currently warming up, based on, for example, the engine cooling water temperature. If the engine is currently warming up, the routine proceeds to step 101, where the secondary air control valve 31 is opened, so that secondary air is supplied into the exhaust pipe 20a upstream of the catalyst 12. Next, when the warm-up operation is completed, the process proceeds from step 100 to step 102, where the secondary air control valve 31 is closed, and the secondary air supply is stopped.
[0044]
FIG. 6 shows a routine for executing the above-described switching valve control. This routine is executed by interruption every predetermined set time. Referring to FIG. 6, first, in step 120, it is determined whether the air pressure PA in the air tank 30 is lower than the allowable lower limit value PAL. When PA ≧ PAL, the routine proceeds to step 121, where the suction side switching valve 18 is controlled to connect the suction port 17 of the negative pressure pump 16 to the negative pressure tank 21, and the discharge side switching valve 26 is controlled to control the negative pressure pump. The 16 discharge ports 25 are directly connected to the oil pan 27. As a result, a negative pressure is supplied into the negative pressure tank 21. On the other hand, if PA <PAL, then the routine proceeds to step 122, where the suction side switching valve 18 is controlled to connect the suction port 17 of the negative pressure pump 16 to the atmosphere for a certain time, and the discharge side switching valve 26 is controlled. Then, the discharge port 25 of the negative pressure pump 16 is connected to the oil separator 28 for a predetermined time. As a result, air is supplied into the air tank 30.
[0045]
By the way, as described above, when the suction port 17 of the negative pressure pump 16 is connected to the atmosphere by the suction side switching valve 18, the amount of air sucked from the suction port 17 increases remarkably. , The amount of air discharged from the discharge port 25 increases significantly. That is, the suction-side switching valve 18 has an operation of controlling the amount of air sucked from the suction port 17, that is, the amount of air discharged from the discharge port 25.
[0046]
In order to more precisely control the amount of air sucked from the suction port 17, that is, the amount of air discharged from the discharge port 25, for example, duty control of the suction-side switching valve 18 may be performed. That is, the duty ratio, which is the ratio of the energization time to the cycle time, is controlled. In this case, when the duty ratio is increased, the amount of air sucked from the suction port 17 is increased, and when the duty ratio is reduced, the amount of air sucked from the suction port 17 is reduced.
[0047]
Similarly, duty control of the discharge side switching valve 26 can be performed to control the amount of air supplied from the negative pressure pump 16 to the air tank 30. Alternatively, duty control of the secondary air control valve 31 can be performed in order to control the amount of secondary air supplied to the catalyst 12.
[0048]
FIG. 7 shows another embodiment according to the present invention. In this alternative embodiment, a plurality of catalysts are arranged in series in the exhaust passage. Specifically, a casing 13 'containing an additional catalyst 12' is connected to the exhaust pipe 10b downstream of the catalyst 12, and an exhaust pipe 10c is connected to the casing 13 '. The exhaust pipe 10b is fitted with an additional secondary air supply nozzle 33 'for supplying secondary air to the additional catalyst 12', which is connected to an additional check valve 32 '. And an additional secondary air control valve 31 'connected to the air tank 30. When secondary air is to be supplied to the catalysts 12, 12 ', the corresponding secondary air control valves 31, 31' are respectively temporarily opened.
[0049]
In the example shown in FIG. 7, although the catalysts 12 and 12 'are arranged in series with each other, the present invention can be applied to a case where a plurality of catalysts are arranged in parallel with each other.
[0050]
In each of the embodiments according to the present invention described above, the air discharged from the discharge port 25 of the negative pressure pump 16 is stored in the air tank 30, and the air stored in the air tank 30 is stored in the catalyst 12 by the secondary air. They are supplied in the form of
[0051]
However, the air stored in the air tank 30 can be used for another purpose. For example, the pressurized air in the air tank 30 can be used as a positive pressure source of an electrically controlled positive pressure operating valve 170 as shown in FIG.
[0052]
As shown in FIG. 8, the positive pressure operating valve 170 includes a casing 171, a diaphragm 173 that divides the internal space of the casing 171 into a pressure chamber 172 a and a fluid chamber 172 b, and a valve body 174 fixed to the diaphragm 173. I do. An electrically controlled switching valve 176 composed of, for example, the switching valve 60 described above with reference to FIG. 3 is connected to the pressure port 175 connected to the pressure chamber 172a, and the switching valve 176 is connected to the air cleaner 177 on the one hand. To the atmosphere, and on the other hand to the air tank 30 via a check valve 178. On the other hand, an inlet port 179 and an outlet port 180 are connected to the fluid chamber 172b. In FIG. 8, reference numeral 181 denotes a compression spring that urges the valve element 174 in a direction of blocking communication between the outlet port 180 and the fluid chamber 172b.
[0053]
When the switching valve 176 is energized, the pressure chamber 172a is connected to the air tank 30, and a positive pressure is introduced into the pressure chamber 172a. As a result, the valve element 174 is displaced downward in FIG. 8 against the spring force of the compression spring 181, and communicates the outlet port 180 with the fluid chamber 172b. Accordingly, the inlet port 179 is connected to the outlet port 180 via the fluid chamber 172b. On the other hand, when the power supply to the switching valve 176 is stopped, the pressure chamber 172a is connected to the atmosphere, and the atmospheric pressure is introduced into the pressure chamber 172a. As a result, the valve element 174 is displaced upward in FIG. 8 by the spring force of the compression spring 181, and the communication between the outlet port 180 and the fluid chamber 172b is cut off. Accordingly, communication between the inlet port 179 and the outlet port 180 is cut off.
[0054]
The EGR control valve 15 or the secondary air control valve 31 may be constituted by such a positive pressure operated valve.
[0055]
Alternatively, the air in the air tank 30 may be supplied into an intake passage upstream of the compressor 6 of the exhaust turbocharger 5. By doing so, the compression work of the compressor 6 can be reduced.
[0056]
Furthermore, in the embodiments according to the invention described above, the vacuum pump 16 is connected to the internal combustion engine, for example via a belt, and is thus always driven. However, it is also possible to connect the negative pressure pump 16 to the internal combustion engine via an electromagnetic clutch, for example, and to drive the negative pressure pump 16 only when necessary. Alternatively, the negative pressure pump 16 can be constituted by, for example, an electric pump.
[0057]
【The invention's effect】
A secondary air supply device for an internal combustion engine can be simply and inexpensively configured.
[Brief description of the drawings]
FIG. 1 is an overall view of an internal combustion engine.
FIG. 2 is a diagram showing a throttle opening.
FIG. 3 is a diagram showing a configuration of an electrically controlled switching valve.
FIG. 4 is a diagram showing a configuration of an electrically controlled negative pressure operated valve.
FIG. 5 is a flowchart for executing secondary air supply control.
FIG. 6 is a flowchart for executing switching valve control.
FIG. 7 is a diagram showing another embodiment according to the present invention.
FIG. 8 is a diagram showing a configuration of an electrically controlled positive pressure operated valve.
[Explanation of symbols]
1. Engine body
10a ... exhaust pipe
12 ... catalyst
16 ... Negative pressure pump
17 ... Suction port of negative pressure pump
18 ... Suction side switching valve
20, 22, 29, 32 ... check valve
21 ... Negative pressure tank
23 ... Brake booster
25 ... Discharge port of negative pressure pump
26 ... Discharge side switching valve
27 ... oil pan
28 ... oil separator
30 ... Air tank
31 Secondary air control valve
33 ... Secondary air supply nozzle
49b ... Air pressure sensor

Claims (11)

In an internal combustion engine equipped with a negative pressure pump for forming a negative pressure in a negative pressure tank, air discharged from a discharge port of the negative pressure pump when the negative pressure pump is operated is discharged into an exhaust passage upstream of the catalyst. A secondary air supply device designed to supply secondary air. 2. The secondary air supply device for an internal combustion engine according to claim 1, wherein the negative pressure pump comprises a negative pressure pump for supplying a negative pressure to a pressure chamber of a vacuum brake booster. A suction side switching valve is connected to the suction port of the negative pressure pump, and the suction side switching valve selectively connects the suction port of the negative pressure pump to one of the negative pressure tank and the atmosphere or a positive pressure source. The secondary air supply device for an internal combustion engine according to claim 1, wherein: An electric control that connects the suction port of the negative pressure pump to the atmosphere or a positive pressure source when energized, and connects the suction port of the negative pressure pump to the negative pressure tank when the energization is stopped. 4. The secondary air supply device for an internal combustion engine according to claim 3, wherein the secondary air supply device comprises a switching valve. The suction air control valve is connected to the suction port of the negative pressure pump, and the amount of air sucked from the suction port of the negative pressure pump is controlled by the suction air control valve, so that the air is discharged from the discharge port of the negative pressure pump. The secondary air supply device for an internal combustion engine according to claim 1, wherein the amount of air is controlled. 2. The internal combustion engine according to claim 1, wherein a check valve that can only flow toward the exhaust passage upstream of the catalyst is disposed in a discharge air passage connecting the discharge port of the negative pressure pump and the exhaust passage upstream of the catalyst. Engine secondary air supply. A secondary air control valve for controlling the amount of secondary air supplied into the exhaust passage upstream of the catalyst in a discharge air passage connecting the discharge port of the negative pressure pump and the exhaust passage upstream of the catalyst. The secondary air supply device for an internal combustion engine according to claim 1, wherein: The air tank for storing air discharged from the discharge port of the negative pressure pump is disposed in the discharge air passage between the discharge port of the negative pressure pump and the secondary air control valve. Secondary air supply system for internal combustion engines. 9. The secondary air supply device for an internal combustion engine according to claim 8, wherein an air pressure sensor for detecting an air pressure in the air tank is attached to the air tank. Lubricating oil of the negative pressure pump is contained in air discharged from the discharge port of the negative pressure pump, and a discharge air passage connecting the discharge port of the negative pressure pump and the exhaust passage upstream of the catalyst to each other. 2. The secondary air supply device for an internal combustion engine according to claim 1, further comprising an oil separator for separating lubricating oil from air discharged from a discharge port of the negative pressure pump. 2. The internal combustion engine according to claim 1, wherein a plurality of catalysts are arranged in the exhaust passage, and air discharged from a discharge port of the negative pressure pump is supplied to the exhaust passage upstream of the catalyst. Next air supply device.

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