JP4238540B2 - Secondary air supply device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a secondary air supply device for an internal combustion engine.
[0002]
[Prior art]
In order to maintain the oxygen concentration in the exhaust gas flowing into the catalyst within the target range, an internal combustion engine is known in which secondary air is supplied into the exhaust passage upstream of the catalyst (see Japanese Patent No. 2845055). ).
[0003]
[Problems to be solved by the invention]
However, not only the above-described internal combustion engine but generally, it is necessary to newly provide an air pump in order to supply secondary air into the exhaust passage. Therefore, there is a problem that the configuration is complicated and the cost is increased.
[0004]
Accordingly, an object of the present invention is to provide a secondary air supply device for an internal combustion engine that can be configured easily and inexpensively.
[0005]
[Means for Solving the Problems]
  In order to solve the above problems, according to a first aspect of the present invention, in an internal combustion engine having a negative pressure pump for forming a negative pressure in a negative pressure tank, the negative pressure pump is operated when the negative pressure pump is operated. Secondary air supply device for secondary supply of air discharged from the discharge port into the exhaust passage upstream of the catalystThe negative pressure pump lubricating oil is contained in the air discharged from the discharge port of the negative pressure pump, and the discharge port of the negative pressure pump and the exhaust passage upstream of the catalyst are connected to each other. An oil separator that separates lubricating oil from the air discharged from the discharge port of the negative pressure pump is disposed in the discharge air passage to be connected, and a discharge side switching valve is connected to the discharge port of the negative pressure pump to connect the discharge side A switching valve selectively connects the discharge port of the negative pressure pump to either the oil separator or the oil pan.is doing.
  According to a second invention, in the first invention, an air tank for storing air discharged from a discharge port of the negative pressure pump in the discharge air passage downstream of the oil separator, and the catalyst upstream A secondary air control valve for controlling the amount of secondary air supplied into the exhaust passage of the air tank, and an air pressure sensor for detecting the air pressure in the air tank is attached to the air tank, and the air When the air pressure in the tank is higher than the allowable lower limit value, the discharge side switching valve connects the discharge port of the negative pressure pump to the oil pan, and when the air pressure in the air tank is lower than the allowable lower limit value, the discharge side The discharge port of the negative pressure pump is connected to the oil separator by a switching valve.
  According to a third invention, in the second invention, a suction side switching valve is connected to the suction port of the negative pressure pump, and the suction side switching valve causes the suction port of the negative pressure pump to be connected to the negative pressure tank and the atmosphere. Alternatively, when the air pressure in the air tank is higher than the allowable lower limit value, the suction side switching valve causes the suction port of the negative pressure pump to be connected to the negative pressure source. The suction port of the negative pressure pump is connected to the atmosphere or the positive pressure source by the suction side switching valve when the air pressure in the air tank is lower than the allowable lower limit value.
[0006]
  Also,4According to a second aspect, in the first aspect, the negative pressure pump is composed of a negative pressure pump for supplying negative pressure into the pressure chamber of the vacuum brake booster.
[0008]
  Also,5According to the third invention, in the third invention, when the suction side switching valve is energized, the suction port of the negative pressure pump is connected to the atmosphere or a positive pressure source, and when the energization is stopped, It comprises an electrically controlled switching valve that connects the suction port to the negative pressure tank.
[0009]
  Also,6According to the second invention, in the first invention, a 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. Thus, the amount of air discharged from the discharge port of the negative pressure pump is controlled.
[0010]
  Also,7According to the second invention, in the first invention, in the discharge air passage that connects the discharge port of the negative pressure pump and the exhaust passage upstream of the catalyst to each other, the reverse flow that can only flow toward the exhaust passage upstream of the catalyst. A stop valve is provided.
[0015]
  Also,8According to the second invention, in the first invention, a plurality of catalysts are arranged in the exhaust passage, and the air discharged from the discharge port of the negative pressure pump is respectively supplied into the exhaust passage upstream of the catalyst. I have to.
[0016]
DETAILED DESCRIPTION OF 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 1 a is connected on the one hand to a common surge tank 3 via a corresponding intake branch pipe 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 disposed in the intake duct 4. Also, each cylinder 1a has a common exhaust manifold 9 and on the other hand.ExhaustThe exhaust turbine 11 is connected to the exhaust turbine 11 of the exhaust turbocharger 5 via the trachea 10, the outlet of the exhaust turbine 11 is connected to the casing 13 containing the catalyst 12 via the exhaust pipe 10a, and 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 very low. In other words, the throttle opening is held almost fully open over almost or almost all engine operating states.
[0018]
In this way, when the throttle opening is kept almost fully open over most engine operating states, almost no negative pressure is generated in the intake passage downstream of the throttle valve 8. Therefore, for example, an engine driven vane negative pressure pump 16 is provided in the internal combustion engine shown in FIG.
[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 a belt, for example, and is therefore always driven during engine operation. An electrically controlled suction side switching valve 18 is connected to the 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 the one hand, and via a check valve 20 on the other hand. The negative pressure tank 16 is connected to a negative pressure tank 21 for storing a negative pressure. The check valve 20 can only flow from the negative pressure tank 21 toward 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 only flow from the brake booster 23 toward the negative pressure tank 21. The pressure chamber of the brake booster 23 is released to the atmosphere when the brake pedal 24 is depressed, and is cut off from the atmosphere when the brake pedal 24 is returned to its original position, and negative pressure is supplied from the negative pressure tank 21. That is, every time the brake pedal 24 is operated, the negative pressure in the negative pressure tank 21 is supplied to the brake booster 23. As will be 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 the one hand and connected to a cyclone type oil separator 28 on the other hand. The The oil discharge port provided at the bottom of the oil separator 28 is connected to the oil pan 27, and the air discharge port provided at the top of the oil separator 28 passes air discharged from the negative pressure pump 16 through the check valve 29. It is connected to an air tank 30 for storing. The check valve 29 can only flow from the oil separator 28 toward the air tank 30.
[0022]
The negative pressure pump 16 is supplied with lubricating oil from the engine body 1, and this 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 in this way. The air from which the lubricating oil has been removed by the oil separator 28 passes through an air discharge port formed at the top of the oil separator 28, and the lubricating oil passes through an oil discharge port formed at the bottom of the oil separator 28, respectively. To be discharged.
[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, and this secondary air supply nozzle 33 is attached to the exhaust pipe 10 a upstream of the catalyst 12. It has been. The check valve 32 can only flow from the secondary air control valve 31 toward 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]
As long as the exhaust purification action of the catalyst 12 is not inhibited, the secondary air may be supplied at any time, but 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 after the warm-up is completed, and therefore, the exhaust gas contains a relatively large amount of unburned HC and CO. Yes. Therefore, if secondary air is supplied at this time, it becomes possible to oxidize this large amount of unburned HC and CO with the catalyst 12, and the temperature of the catalyst 12 is quickly raised by the exothermic action accompanying this oxidation reaction. It becomes possible to make it.
[0025]
The electronic control unit 40 is composed of 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 It comprises. A water temperature sensor 48 for detecting the engine cooling water temperature is attached to the engine body 1. A negative pressure sensor 49a for detecting the negative pressure in the negative pressure tank 21 is attached to the negative pressure tank 21, and an air pressure sensor 49b for detecting the air pressure PA in the air tank 30 is attached to 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. The output signals of these sensors 48, 49a, 49b, 51 are input to the input port 45 via corresponding AD converters 47, respectively. Here, the air pressure PA in the air tank 30 represents the amount of air stored in the air tank 30, and the depression amount L of the accelerator pedal 50 represents the required load. Further, the input port 45 is connected with a crank angle sensor 52 that generates an output pulse every time the crankshaft rotates, for example, 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 through corresponding drive circuits 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 composed of an electrically controlled switching valve 60 as shown in FIG. 3, for example. That is, as shown in FIG. 3, the switching valve 60 is a valve made of a magnetic material supported in a casing 61, a solenoid coil 62 accommodated in the casing 61, and movable in the axial direction in the casing 61. And a body 63. In the casing 61, a first chamber 64 a is formed on one side of the valve body 60, and a second chamber 64 b is formed on the other side. The first chamber 64 a and the second chamber 64 b are circumferential surfaces of the valve body 63. Communicating with each other by a communication passage 65 formed in the above. 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 67 a and 67 b are located on a linear track of the valve body 63. In FIG. 3, reference numeral 68 denotes a compression spring that urges the valve body 63 toward the first outlet port 67a.
[0027]
When the solenoid coil 62 is energized, the valve element 63 is displaced to the right in FIG. 3 against the spring force of the compression spring 68 by the magnetic attraction force of the solenoid coil 62 to open the first outlet port 67a and the second. 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 to 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 to close the first outlet port 67a and to open the second outlet port 67b. Open. As a result, the inlet port 66 is connected to the second outlet port 67b. In this way, 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. Thus, the negative pressure tank 21 is connected via the 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 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 operating valve 70 as shown in FIG. That is, as shown in FIG. 4, the negative pressure operating valve 70 includes a casing 71, a diaphragm 73 that divides the internal space of the casing 71 into a pressure chamber 72 a and a fluid chamber 72 b, and a valve body 74 that is fixed to the diaphragm 73. It comprises. The pressure port 75 connected to the pressure chamber 72a is connected to, for example, an electrically controlled switching valve 76 constituted by the switching valve 60 described above with reference to FIG. And is connected to the negative pressure tank 21 via a check valve 78 on the other side. 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 that urges the valve body 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 negative pressure is introduced into the pressure chamber 72a. As a result, the valve body 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. Accordingly, the inlet port 79 is connected to the outlet port 80 via the fluid chamber 72b. On the other hand, when the energization to the switching valve 76 is stopped, the pressure chamber 72a is connected to the atmosphere, and atmospheric pressure is introduced into the pressure chamber 72a. As a result, the valve body 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, the communication between the inlet port 79 and the outlet port 80 is blocked.
[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 apparent 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 either the oil pan 27 or 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]
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. 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 bypassed through the oil separator 28 and connected to the oil pan 27. In this way, a large negative pressure can be maintained in the negative pressure tank 21 while maintaining a small load on the negative pressure pump 16.
[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. It cannot be supplied.
[0036]
Therefore, in the embodiment according to the present invention, when the air pressure PA in the air tank 30 becomes lower than the allowable 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 the oil separator. 28 is connected to the air tank 30. As a result, the lubricating oil is removed from the air discharged from the negative pressure pump 16 and then supplied into the air tank 30.
[0037]
Even when the suction port 17 of the negative pressure pump 16 is connected to the negative pressure tank 21, air is discharged from the discharge port 25. 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 air into the air tank 30 by a target amount.
[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 via the suction port 17 can be significantly increased, and therefore 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 into the air tank 30. When the amount of stored air is less than the minimum allowable amount, the discharge port 25 is temporarily connected to the air tank 30 and the suction port 17 is temporarily connected to the atmosphere or a positive pressure source. It 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 temporarily connected to the oil pan 27.
[0041]
The negative pressure pump 16 is originally for forming a negative pressure in the pressure chamber or the negative pressure tank 21. 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 forming a negative pressure, but rather for pumping air. . The negative pressure pump 16 is generally provided in an internal combustion engine in which a negative pressure is hardly formed in the intake passage as described with reference to FIG. 2. This means that it is not necessary to provide a new pump for supplying secondary air to the passage.
[0042]
As described above, the air discharged from the negative pressure pump 16 at this time is stored in the air tank 30 while the suction port 17 of the negative pressure pump 16 is connected to the negative pressure tank 21, that is, a negative pressure is formed. You can also. In this way, the air discharged from the negative pressure pump 16 when the negative pressure is formed has been conventionally discarded in the oil pan 27 together with the lubricating oil. Does not exist until.
[0043]
FIG. 5 shows a routine for executing the above-described secondary air supply control. This routine is executed by interruption every predetermined time. Referring to FIG. 5, first, at step 100, it is determined based on, for example, the engine coolant temperature whether or not the engine is currently warming up. When 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, the secondary air control valve 31 is closed, and the secondary air supply is stopped.
[0044]
FIG. 6 shows a routine for executing the switching valve control described above. This routine is executed by interruption every predetermined time. Referring to FIG. 6, first, in step 120, it is determined whether or not 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, negative pressure is supplied into the negative pressure tank 21. On the other hand, when PA <PAL, 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 predetermined time and the discharge side switching valve 26 is controlled. Thus, 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 is remarkably increased, and thereby the negative pressure pump 16. The amount of air discharged from the discharge port 25 is significantly increased. That is, the suction side switching valve 18 has an action of controlling the amount of air sucked from the suction port 17, and hence 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 can be performed. That is, the duty ratio that 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 decreased, the amount of air sucked from the suction port 17 is decreased.
[0047]
Similarly, in order to control the amount of air supplied from the negative pressure pump 16 to the air tank 30, the duty control of the discharge side switching valve 26 can be performed. Alternatively, the duty control of the secondary air control valve 31 can be performed 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 10 b downstream of the catalyst 12, and the exhaust pipe 10 c is connected to the casing 13 ′. The exhaust pipe 10b is equipped with an additional secondary air supply nozzle 33 'for supplying secondary air to the additional catalyst 12', and this additional secondary air supply nozzle 33 '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 temporarily opened.
[0049]
In the example shown in FIG. 7, the catalysts 12 and 12 ′ are arranged in series with each other, but the present invention can also 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 so far, 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 as secondary air. It is made to supply 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 that is fixed to the diaphragm 173. To do. The pressure port 175 connected to the pressure chamber 172a is connected to, for example, an electrically controlled switching valve 176 composed of the switching valve 60 described above with reference to FIG. 3, and the switching valve 176 has an air cleaner 177 on the one hand. And is connected to the air tank 30 via a check valve 178 on the other hand. 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 body 174 in a direction to block 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 resists the spring force of the compression spring 181 and is displaced downward in FIG. 8 to connect the outlet port 180 to 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 energization to the switching valve 176 is stopped, the pressure chamber 172a is connected to the atmosphere, and atmospheric pressure is introduced into the pressure chamber 172a. As a result, the valve body 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 blocked. Accordingly, communication between the inlet port 179 and the outlet port 180 is blocked.
[0054]
The EGR control valve 15 or the secondary air control valve 31 can also be constituted by such a positive pressure operation valve.
[0055]
Alternatively, the air in the air tank 30 may be supplied into the intake passage upstream of the compressor 6 of the exhaust turbocharger 5. In this way, the compression work of the compressor 6 can be reduced.
[0056]
Further, in each of the embodiments according to the present invention described so far, the negative pressure pump 16 is connected to the internal combustion engine, for example, via a belt, and is therefore always driven. However, it is also possible to connect the negative pressure pump 16 to the internal combustion engine through an electromagnetic clutch, for example, so that the negative pressure pump 16 is driven only when necessary. Alternatively, the negative pressure pump 16 can be constituted by an electric pump, for example.
[0057]
【The invention's effect】
A secondary air supply device for an internal combustion engine can be configured easily and inexpensively.
[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 operating valve.
FIG. 5 is a flowchart for executing secondary air supply control;
FIG. 6 is a flowchart for executing switching valve control.
FIG. 7 shows another embodiment according to the present invention.
FIG. 8 is a diagram showing a configuration of an electrically controlled positive pressure operating valve.
[Explanation of symbols]
1 ... Engine body
10a ... exhaust pipe
12 ... Catalyst
16 ... Negative pressure pump
17 ... Negative pressure pump inlet
18 ... Suction side switching valve
20, 22, 29, 32 ... check valves
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 (8)

In an internal combustion engine equipped with a negative pressure pump for forming a negative pressure in a negative pressure tank, air discharged from the discharge port of the negative pressure pump when the negative pressure pump is operated enters the exhaust passage upstream of the catalyst. A secondary air supply device configured to supply secondaryly , wherein the negative pressure pump lubricating oil is contained in the air discharged from the discharge port of the negative pressure pump, and the negative pressure An oil separator that separates lubricating oil from air discharged from the discharge port of the negative pressure pump is disposed in a discharge air passage that connects the discharge port of the pump and the exhaust passage upstream of the catalyst, and the negative pressure pump A secondary of an internal combustion engine in which a discharge side switching valve is connected to the discharge port, and the discharge port of the negative pressure pump is selectively connected to either the oil separator or the oil pan by the discharge side switching valve Air supply device . An air tank for storing air discharged from the discharge port of the negative pressure pump in the discharge air passage downstream of the oil separator and the amount of secondary air supplied into the exhaust passage upstream of the catalyst are controlled. A secondary air control valve for controlling the air tank, and an air pressure sensor for detecting the air pressure in the air tank is attached to the air tank. When the air pressure in the air tank is higher than the allowable lower limit value, the discharge side The discharge port of the negative pressure pump is connected to the oil pan by a switching valve, and when the air pressure in the air tank is lower than the allowable lower limit value, the discharge port of the negative pressure pump is connected to the oil separator by the discharge side switching valve. The secondary air supply device for an internal combustion engine according to claim 1, wherein the secondary air supply device is connected. 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 either the negative pressure tank and the atmosphere or a positive pressure source. When the air pressure in the air tank is higher than the allowable lower limit value, the suction side switching valve connects the suction port of the negative pressure pump to the negative pressure tank, and the air pressure in the air tank is lower than the allowable lower limit value. 3. The secondary air supply device for an internal combustion engine according to claim 2, wherein when the pressure is lower, the suction port of the negative pressure pump is connected to the atmosphere or a positive pressure source by the suction side switching valve . 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 into a pressure chamber of a vacuum brake booster . Electrical 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 energization is stopped. The secondary air supply device for an internal combustion engine according to claim 3, wherein the secondary air supply device is constituted by a type switching valve . A 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, thereby being discharged from the discharge port of the negative pressure pump. 2. 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 capable of flowing only 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 device. 2. The internal combustion engine according to claim 1 , wherein a plurality of catalysts are arranged in the exhaust passage, and the air discharged from the discharge port of the negative pressure pump is supplied to the exhaust passage upstream of the catalysts. Secondary air supply device.

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