Secondary-air system and method for checking the operability of the secondary-air system

Abstract

A method for checking the operability of a secondary-air system of an internal combustion engine includes measuring a first pressure between a first secondary-air pump and a first master secondary-air valve as well as a second master secondary-air valve, measuring a second pressure between a second secondary-air pump and a first slave secondary-air valve and a second slave secondary-air valve, controlling the first master secondary-air valve and the first slave secondary-air valve together, and controlling the second master secondary-air valve and the second slave secondary-air valve together. A secondary-air system includes a first control and a second control, wherein a first master secondary-air valve and a first slave secondary-air valve are controllable together by the first control and wherein a second master secondary-air valve and a second slave secondary-air valve are controllable together by the second control.

Claims

1. A secondary-air system, comprising: a plurality of exhaust gas banks including a first master exhaust gas bank, a second master exhaust gas bank, a first slave exhaust gas bank, and a second slave exhaust gas bank; a plurality of secondary-air pumps including a first secondary-air pump and a second secondary-air pump; a plurality of secondary-air lines including a first secondary-air line, a second secondary-air line, a third secondary-air line, and a fourth secondary-air line, wherein, by using said secondary-air pumps, secondary air is guidable, via said secondary-air lines, to said exhaust gas banks; a plurality of secondary-air valves including a first master secondary-air valve, a second master secondary-air valve, a first slave secondary-air valve, and a second slave secondary-air valve, wherein in each case a respective one of said secondary-air valves is assigned to a respective one of said secondary-air lines; said first master exhaust gas bank being connected, via said first secondary-air line, to said first master secondary-air valve, said second master exhaust gas bank being connected, via said second secondary-air line, to said second master secondary-air valve, wherein, by using said first secondary-air pump, said first and said second master secondary-air valve and associated ones of said secondary-air lines can be supplied with secondary air; said first slave exhaust gas bank being connected, via said third secondary-air line, to said first slave secondary-air valve, said second slave exhaust gas bank being connected, via said fourth secondary-air line, to said second slave secondary-air valve, wherein, by using said second secondary-air pump, said first and said second slave secondary-air valve and associated ones of said secondary-air lines can be supplied with secondary air; and a plurality of controls including a first control and a second control, wherein, by using said first control, said first master secondary-air valve and said first slave secondary-air valve are controllable together and wherein, by using said second control, said second master secondary-air valve and said second slave secondary-air valve are controllable together.

2. The secondary-air system according to claim 1, including: a master engine control device and a slave engine control device; said first control being connected to said master engine control device, said second control being connected to said slave engine control device; and said first and said second control each having an electrically actuatable switching valve.

3. A method for checking an operability of a secondary-air system of an internal combustion engine, the method comprising: measuring a first pressure between a first secondary-air pump and a first master secondary-air valve as well as a second master secondary-air valve; measuring a second pressure between a second secondary-air pump and a first slave secondary-air valve and a second slave secondary-air valve; controlling the first master secondary-air valve and the first slave secondary-air valve together; controlling the second master secondary-air valve and the second slave secondary-air valve together: and providing the secondary-air system such that a first master exhaust gas bank is connected, via a first secondary-air line, to the first master secondary-air valve, a second master exhaust gas bank is connected, via a second secondary-air line, to the second master secondary-air valve, wherein, by using the first secondary-air pump, the first and the second master secondary-air valve and associated ones of the secondary-air lines can be supplied with secondary air, and such that a first slave exhaust gas bank is connected, via a third secondary-air line, to the first slave secondary-air valve, a second slave exhaust gas bank is connected, via a fourth secondary-air line, to the second slave secondary-air valve, wherein, by using the second secondary-air pump, the first and the second slave secondary-air valve and associated ones of the secondary-air lines can be supplied with secondary air, and providing the secondary-air system such that by using a first control, the first master secondary-air valve and the first slave secondary-air valve are controllable together, and such that by using a second control, the second master secondary-air valve and the second slave secondary-air valve are controllable together.

4. The method according to claim 3, which comprises activating, in a first phase, both of the secondary-air pumps and opening the first master secondary-air valve, the second master secondary-air valve, the first slave secondary-air valve as well as the second slave secondary-air valve and checking whether the thereby measured first pressure is within a tolerance range and whether the measured second pressure is within a tolerance range.

5. The method according to claim 4, which comprises: opening, in a further phase, the first master secondary-air valve and the first slave secondary-air valve and closing the second master secondary-air valve and the second slave secondary-air valve; and closing, in a further phase, the first master secondary-air valve and the first slave secondary-air valve and opening the second master secondary-air valve and the second slave secondary-air valve and checking whether the thereby measured first pressure is within a tolerance range and whether the measured second pressure is within a tolerance range.

6. The method according to claim 5, which comprises carrying out the further phase only if the first pressure measured in the first phase or the second pressure measured in the first phase is outside the tolerance range.

7. The method according to claim 4, which comprises closing, in a second phase, the first master secondary-air valve, the second master secondary-air valve, the first slave secondary-air valve as well as the second slave secondary-air valve and activating both of the secondary-air pumps or keeping both of the secondary-air pumps activated and checking whether the thereby measured first pressure is within a tolerance range and whether the measured second pressure is within a tolerance range.

8. The method according to claim 5, which comprises closing, in a second phase, the first master secondary-air valve, the second master secondary-air valve, the first slave secondary-air valve as well as the second slave secondary-air valve and activating both of the secondary-air pumps or keeping both of the secondary-air pumps activated and checking whether the thereby measured first pressure is within a tolerance range and whether the measured second pressure is within a tolerance range.

9. The method according to claim 7, which comprises turning off, in a third phase, both of the secondary-air pumps and keeping the first master secondary-air valve, the second master secondary-air valve, the first slave secondary-air valve as well as the second slave secondary-air valve closed and checking whether the thereby measured first pressure is within a tolerance range and whether the measured second pressure is within a tolerance range.

10. The method according to claim 8, which comprises turning off, in a third phase, both of the secondary-air pumps and keeping the first master secondary-air valve, the second master secondary-air valve, the first slave secondary-air valve as well as the second slave secondary-air valve closed and checking whether the thereby measured first pressure is within a tolerance range and whether the measured second pressure is within a tolerance range.

11. The method according to claim 3, which comprises providing the secondary-air system such that the first control is connected to a master engine control device, the second control is connected to a slave engine control device and such that the first and the second control each include an electrically actuatable switching valve.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIG. 1 is a system diagram of a secondary-air system according to the invention; and

(2) FIG. 2 is a schematic graph of a measured pressure and switching states of the associated secondary-air pump and the secondary-air valves plotted against time t in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

(3) Referring now to the figures of the drawings in detail and first, particularly, to FIG. 1 thereof, there is shown a secondary-air system 1 of an internal combustion engine in a highly schematic manner. The internal combustion engine has four exhaust gas banks 2, 3, 4, 5. Each exhaust gas bank 2, 3, 4, 5 has at least one cylinder assigned thereto. Each exhaust gas bank 2, 3, 4, 5 can have in particular several cylinders, preferably four cylinders, assigned thereto. The internal combustion engine can in this case for example have a double V-type cylinder arrangement.

(4) The two exhaust gas banks 2, 3 can be referred to as master exhaust gas banks 2, 3 and the two exhaust gas banks 4, 5 can be referred to as slave exhaust gas banks 4, 5. The exhaust gas bank 2 forms in this case a first master exhaust gas bank 2 and the exhaust gas bank 3 forms a second master exhaust gas bank 3.

(5) Two secondary-air pumps 6, 7 are provided here. The first secondary-air pump 6 is assigned to the master exhaust gas banks 2, 3 and connected to them in a functionally effective manner via two secondary-air lines 8, 9. The second secondary-air pump 7 is assigned to the two slave exhaust gas banks 4, 5 and is connected to them in a respectively corresponding manner via two further secondary-air lines 10, 11. A secondary-air valve M1, M2, S1, and S2 is in each case disposed in the secondary-air lines 8, 9, 10, and 11. Four secondary-air valves M1, M2, S1, S2 are thus provided. The two secondary-air lines 8, 9 branch off from a junction point 12, wherein the two secondary-air valves M1 and M2 are disposed behind (i.e. downstream) of the junction point 12. The first secondary-air line 8 opens in this case into the first master exhaust gas bank 2 and the second secondary-air line 9 opens into the second master exhaust gas bank.

(6) The two secondary-air lines 10 and 11 branch off accordingly from a junction point 13, wherein the third secondary-air line 10 opens into the first slave exhaust gas bank 4 and the fourth secondary-air line 11 opens into the second slave exhaust gas bank 5. A pressure sensor, which is not shown in the drawing, is provided between the first secondary-air pump 6 and the junction point 12, wherein the pressure sensor measures a first pressure 38 (see. FIG. 2) between the first secondary-air pump 6 and the two master secondary-air valves M1, M2. A second pressure sensor (not illustrated) is provided between the second secondary-air pump 7 and the second junction point 13, wherein this second pressure sensor measures a corresponding second pressure which arises between the second secondary-air pump 7 and the two slave secondary-air valves S1, S2.

(7) It is now particularly advantageous that the secondary-air valves M1, M2, S1, and S2 are controlled or, respectively, are controllable in a crosswise manner. The first master secondary-air valve M1 and the first slave secondary-air valve S1 are connected via a common line 14. The second master secondary-air valve M2 and the second slave secondary-air valve S2 are connected to a second control 17 via a second line 15. The controls 16, 17 are in particular embodied as electric switching valves. The electric switching valve of the control 16 is controlled by a master engine control device 18 and the electric switching valve of the control 17 is controlled by a slave engine control device 19.

(8) In the following, reference is made to FIG. 2, wherein now the method for checking the operability of the secondary-air system 1 is explained here. In the diagram 20, first of all the measured first pressure 38 of the corresponding pressure sensor is shown. In each case, a first pressure and a second pressure are measured, but only the first pressure 38 is shown here. A switching position 39 of the secondary-air pumps 6, 7 is shown here. Further, a switching position 23a of the first secondary-air valves, namely the first master secondary-air valve M1 and the first slave secondary-air valve S1, that are controlled together, is illustrated. Further, a switching position 23b of the second secondary-air valves, namely the second master secondary-air valve M2 and the second slave secondary-air valve S2, that are controlled together, is shown. The first pressure 38 and the switching position 39, 23a, 23b are in each case plotted versus the time t

(9) The above-mentioned disadvantages are now avoided in that the first pressure 38 between the first secondary-air pump 6 and the first master secondary-air valve M1 as well as the second master secondary-air valve M2 is measured, wherein the second pressure between the second secondary-air pump 7 and the first slave secondary-air valve S1 and a second slave secondary-air valve S2 is measured, wherein the first master secondary-air valve M1 and the first slave secondary-air valve S1 are controlled together and the second master secondary-air valve M2 and the second slave secondary-air valve S2 are controlled together. Through the use of this crosswise control, the switching position of the first master secondary-air valve M1 and of the first slave secondary-air valve S1 is the same. Further, the switching position of the second master secondary-air valve M2 and the second slave secondary-air valve S2 is the same.

(10) In a phase “0” that is to say in the initial state the first secondary-air pump 6 is inactive and all four secondary-air valves M1, S1, M2 and S2 are closed. Here, it is checked whether the first pressure 38 is within a tolerance range 24. In a subsequent first phase “1” the two secondary-air pumps 6, 7 are activated. Here, both of the first secondary-air valves M1 and S1 are opened and also the two second secondary-air valves M2 and S2 are opened. It is checked whether the first pressure 38 is within a tolerance range 25 which here corresponds to a higher pressure than the tolerance range 24 in the “phase 0.” If the measured pressure 38 is above the tolerance range 25, that is, in an error range 29 then there is a blockage of the secondary-air system 1. If the measured first pressure 38 is below the tolerance range 25, then the discharge capacity of the secondary-air pump 6 or, respectively, 7 is reduced or there is a leakage in the secondary-air system 1 or a blockage in front of the corresponding pressure sensor.

(11) This further “phase 21 and 22” is carried out only when the first pressure 38 or the second pressure in the first phase “1” is outside the tolerance range 25. If the measured pressure 38 was above the tolerance range 25, then a further “phase 21 and 22” is carried out, otherwise the process continues with the second phase “2” and the “phase 21 and 22” is skipped. In the further “phase 21 and 22” the two secondary-air pumps 6, 7 continue to be activated. Both first secondary-air valves M1 and S1 are opened and both second secondary-air valves M2 and S2 are closed. The measured pressure 38 continues to rise and it is checked whether the measured pressure 38 is within a tolerance range 26. The tolerance range 26 is situated above the tolerance range 25. If the measured pressure is now above the tolerance range 26, then it can be concluded that the blockage relates to the first master exhaust gas bank 2 or the first slave exhaust gas bank 4 or the associated components of the secondary-air system 1, because the associated secondary-air valves M1, S1 are open. Whether it concerns in this case the first master exhaust gas bank 2 or the first slave exhaust gas bank 4 can be determined by comparing the first or second pressure (not illustrated). Now (see phase “22”), the two first secondary-air valves M1 and S1 are closed and the two second secondary-air valves M2 and S2 are opened. If the measured pressure 38 is now in a fault range 33 or, respectively, in a fault range 34, it can be concluded that the corresponding leakage or blockage is attributed to the second master exhaust gas bank 3 or the second slave exhaust gas bank 5 or the associated components of the secondary-air system 1.

(12) In the subsequent phase 2, the two secondary-air pumps 6, 7 continue to be activated, wherein now all secondary-air valves M1, S1, and M2 as well as S2 are closed. With this, the tightness of the overall secondary-air system 1 is checked. If the measured pressure 38 is within a tolerance range 27, then the tightness is in order, if the measured pressure 38 is below that, in a fault range 35, then the secondary-air system 1 has a leakage.

(13) In the subsequent third “phase 3” the two secondary-air pumps 6, 7 are turned off, wherein all four secondary-air valves M1, S1, M2, S2 are kept closed. If in this third “phase 3” the respective pressures 38 are above a tolerance range 28, then it can be concluded that either the associated pressure sensor is faulty or the corresponding secondary-air pump 6 or, respectively, 7 runs permanently. If the measured pressure 38 is below the tolerance range 28, in the fault range 37, it can be concluded that the pressure sensor is also faulty. The tolerance range 28 corresponds essentially to the tolerance range 24, because the phases “0” and “3” are equal in terms of the state of the secondary-air pumps 6, 7 or, respectively, the secondary-air valves M1, S1, M2, S2.

LIST OF REFERENCE CHARACTERS

(14) 1 Secondary-air system

(15) 2 First master exhaust gas bank

(16) 3 Second master exhaust gas bank

(17) 4 First slave exhaust gas bank

(18) 5 Second slave exhaust gas bank

(19) 6 First secondary-air pump

(20) 7 Second secondary-air pump

(21) 8 Secondary-air line

(22) 9 Secondary-air line

(23) 10 Secondary-air line

(24) 11 Secondary-air line

(25) 12 Junction point

(26) 13 Junction point

(27) 14 Line

(28) 15 Line

(29) 16 Control

(30) 17 Control

(31) 18 Master engine control device

(32) 19 Slave engine control device

(33) 20 Diagram

(34) 23a Switching position of the two first secondary-air valves

(35) 23b Switching position of the two second secondary-air valves

(36) 24 Tolerance range

(37) 25 Tolerance range

(38) 26 Tolerance range

(39) 27 Tolerance range

(40) 28 Tolerance range

(41) 29 Fault range

(42) 30 Fault range

(43) 31 Fault range

(44) 32 Fault range

(45) 33 Fault range

(46) 34 Fault range

(47) 35 Fault range

(48) 36 Fault range

(49) 37 Fault range

(50) 38 Pressure

(51) 39 Switching position of the two secondary-air pumps

(52) M1 First master secondary-air valve

(53) M2 Second master secondary-air valve

(54) S1 First slave secondary-air valve

(55) S2 Second slave secondary-air valve