JPH0734192Y2 - Cylinder oxygen concentration detector for exhaust gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a device for detecting exhaust gas concentration of, for example, a multi-cylinder engine for automobiles, and in particular, a single oxygen sensor separates exhaust gas from two cylinders into individual cylinders. The present invention relates to an exhaust gas-by-cylinder oxygen concentration detection device capable of detection.

[Conventional technology]

Generally, in a multi-cylinder engine for an automobile, etc., an injection valve is provided on each of a plurality of branch pipes of an intake manifold, an oxygen sensor is provided on the exhaust manifold side, and the oxygen sensor detects the oxygen concentration in the exhaust gas. The air-fuel ratio is feedback controlled.

By the way, in the prior art, the oxygen concentration in the exhaust gas sequentially discharged from a plurality of cylinders is detected by one oxygen sensor provided in the exhaust pipe of the exhaust manifold, and the air-fuel ratios of the plurality of cylinders are collectively fed back. It is designed to be controlled.

[Problems to be solved by the device]

However, according to the prior art, for example, when the fuel injection amount of one of the injection valves of each cylinder is large compared to the other, the oxygen sensor detects the entire exhaust gas from the cylinder corresponding to the injection valve. As a result, a signal indicating that the exhaust gas is rich in fuel (rich tendency) is output. As a result, the air-fuel ratio cannot be controlled stably, the engine output is erroneously reduced, or each component in the exhaust gas is unstable. Therefore, there is a problem that an expensive catalyst is excessively used, and further, there is a problem that it is not possible to cope with a secular change in characteristics of each cylinder.

Therefore, in order to reliably perform feedback control of the variation in the air-fuel ratio of each cylinder, an oxygen sensor is provided for each branch pipe connected to each cylinder of the exhaust manifold, and the oxygen concentration of the exhaust gas discharged from each cylinder is controlled. It is possible to detect them individually. However, in this case, the number of oxygen sensors corresponding to the total number of cylinders of the engine is required, which increases the cost, and the oxygen sensor is provided in the branch pipe that is in a high temperature state close to the cylinders. There is an unsolved problem of being easily affected.

The present invention has been made in view of the above-mentioned drawbacks of the prior art.It is possible to detect the oxygen concentration in the exhaust gas from a plurality of cylinders for each cylinder by using a minimum number of oxygen sensors, and thus, to detect the injection valve and secular change. (EN) An exhaust gas oxygen concentration-by-cylinder oxygen concentration detection device capable of realizing feedback control of an air-fuel ratio for each cylinder having variations at low cost and reducing the amount of catalyst used.

[Means for Solving the Problems]

Means of the present invention, which is configured to solve the above-mentioned problems, has a branch pipe connected to each cylinder of an engine, and two branch pipes are connected to one exhaust pipe as a pair. An exhaust manifold, one oxygen sensor provided for each connecting portion of each pair of branch pipes of the exhaust manifold, for detecting the oxygen concentration in the exhaust gas discharged from each branch pipe, and the vicinity of the oxygen sensor And an exhaust gas guide plate which is provided at a connecting portion of the exhaust manifold and which alternately guides the exhaust gas discharged from each of the branch pipes to the oxygen sensor side.

[Action]

The exhaust gas guide plate selectively guides the exhaust gas from the pair of cylinders to the oxygen sensor, so that the oxygen sensor is alternately exposed only to the exhaust gas from one of the cylinders. This oxygen sensor detects the oxygen concentration in the exhaust gas from the two cylinders for each cylinder.

〔Example〕

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In FIG. 1, reference numeral 1 denotes an engine body having, for example, four cylinders 1A, 1B, 1C, 1D. The engine body 1 reciprocates a piston by burning a mixture of air and fuel, and a crank (rotating shaft). 2), the engine main body 1 is provided with a water temperature sensor 3 for detecting the cooling water temperature and a crank angle sensor 4 for detecting the engine speed from the crank 2.

On the intake side of the engine body 1, an air cleaner 5 is provided at one end, an intake pipe 7 having an air flow meter 6 in the middle, a throttle body 8 having a throttle valve switch 8A, and an intake manifold 9 are connected. In each of the branch pipes, injection valves 10, 10, ... Are provided to inject and supply fuel to each cylinder 1A, 1B, 1C, 1D of the engine body 1 based on an injection pulse described later.

Reference numeral 11 denotes an exhaust manifold provided on the exhaust side of the engine body 1, and the exhaust manifold 11 includes branch pipes 11A, 11B, 11C and 11D connected to the cylinders 1A, 1B, 1C and 1D, respectively, and a first cylinder. A two-forked connecting pipe 11E that joins the branch pipe 11A of 1A and the branch pipe 11D of the fourth cylinder 1D with the connecting pipe 11B of the second cylinder 1B and the connecting pipe 11C of the third cylinder 1C. The exhaust pipe 11G includes a bifurcated other connecting pipe 11F and an exhaust pipe 11G in which the two connecting pipes 11E and 11F are connected to each other. The exhaust pipe 11G is provided with a muffler 12. Reference numeral 13 denotes a catalytic reaction device located upstream of the muffler 12 and provided in the middle of the exhaust pipe 11G. The catalytic reaction device 13 accommodates, for example, a three-way catalyst for cleaning exhaust gas.

14, 15 are two oxygen sensors that detect the oxygen concentration in the exhaust gas and output a signal corresponding to the oxygen concentration as an output voltage to a control unit 24, which will be described later. One oxygen sensor 14 is a branch pipe 11A, 11D. One connecting pipe 11E into which exhaust gas from the first cylinder 1A and the fourth cylinder 1D flows in via the
The oxygen sensor 15 is provided at the center of the branch pipes 11B and 11B.
It is provided in the center of another connecting pipe 11F into which the exhaust gas from the second cylinder 1B and the third cylinder 1C flows via C respectively.

Next, 16 is an exhaust gas guide plate located upstream of the oxygen sensor 14 and rotatably provided on the connecting pipe 11E. When the exhaust gas guide plate 16 rotates rightward in FIG. Exhaust gas discharged from the first cylinder 1A is guided to the oxygen sensor 14 side, and conversely, when it rotates leftward, the exhaust gas from the fourth cylinder 1D is selectively guided to the oxygen sensor 14 side. 17
Is another exhaust gas guide plate having the same function as the exhaust gas guide plate 16, and the exhaust gas guide plate 17 is another oxygen sensor 15
Is connected to the connecting pipe 11F so as to be rotatable on the upstream side of the second cylinder 1B by rotating in the right and left directions.
The exhaust gas from the first cylinder and the exhaust gas from the third cylinder 1C are selectively guided to the oxygen sensor 15 side.

Reference numeral 18 is an actuator for rotating the exhaust gas guide plates 16 and 17, and the actuator 18 includes a casing 18A and a diaphragm 18B defining the inside of the casing 18A into two chambers A and B as shown in FIG. An operating rod 18C having one end side slidably inserted in the casing 18A connected to the diaphragm 18B and the other end side rotatably connected to the exhaust gas guide plates 16 and 17, the casing 18A and the diaphragm 18B. And a return spring 18D stretched between the intake manifold 9 and the casing 18A, and an intake pipe 18E for sucking the air in the A chamber of the casing 18A by the negative pressure generated in the intake manifold 9. It consists of and. Then, in the middle of the intake pipe 18E of the actuator 18, a three-way switching valve 1 for switching the negative pressure and the atmospheric pressure in the chamber A of the casing 18A by a valve switching signal from the control unit 24.
9 are provided.

20 is a fuel tank, 21 is a medium oil fuel pump provided in the fuel tank 20, and the fuel pump 21 supplies the fuel in the fuel tank 20 to each injection valve 10 by pressure feed through a fuel pipe 22,
A part of this fuel is returned to the inside of the fuel tank 20 via the pressure regulator 23. Here, the pressure regulator 23 guides the pressure in the intake manifold 9 as a control pressure, and based on this control pressure, the fuel pipe
The fuel pressure inside 22 is controlled, and the fuel is injected from each injection valve 10 with this controlled fuel pressure.

Further, 24 is a control unit composed of, for example, a microcomputer, and the input side of the control unit 24 has a water temperature sensor 3, a crank angle sensor 4, an air flow meter 6, a throttle valve switch 8A, oxygen sensors 14 and 15, an engine switch, It is connected to a vehicle speed sensor, an inhibitor switch, etc. (none of which are shown), the output side is connected to each injection valve 10, the three-way switching valve 19, and a battery as a power source. Then, the control unit 24 calculates the basic injection amount from the engine speed by the crank angle sensor 4 and the intake air amount by the air flow meter 6, and the water temperature sensor 3, oxygen sensors 14, 1
The injection amount of each injection valve 10 is calculated from the detection signal from 5, etc., the air-fuel ratio feedback correction coefficient, the basic air-fuel ratio learning correction coefficient, and various other correction coefficients, and an injection pulse having a predetermined duty is output to the injection valve 10.

Further, the control unit 24 has a timer, and outputs a valve switching signal to the three-way switching valve 19 at intervals of, for example, 10 seconds to perform a switching operation between the atmosphere and the intake pipe 18E to perform a negative operation in the intake manifold 9. By the pressure, the A chamber of the actuator 18 is intermittently set to a negative pressure.

The present embodiment is configured as described above, and its operation will be described next.

When the engine body 1 is started by the start switch, the control unit 24 calculates the basic injection amount from the intake air amount and the engine speed, and further calculates the injection amount based on the detection signals from the water temperature sensor, the oxygen sensors 14 and 15, etc. Then, the injection pulse having a predetermined duty is output to the injection valve 10.

The cylinders 1A, 1B, ... Of the engine body 1 are exploding and exhausting in the order of first, third, second and fourth, and the oxygen sensors 14,15
Detects the oxygen concentration in the exhaust gas discharged through the branch pipes 1A, 1B, ..., And outputs a signal corresponding to the oxygen concentration to the control unit 24 as an output voltage. The control unit 24 rewrites the air-fuel ratio feedback correction coefficient based on the output voltage from each of the oxygen sensors 14 and 15, increases / decreases the fuel injection amount by each injection valve 10, and feedback-controls the air-fuel ratio, so that the fuel becomes intake air. On the other hand, prevent it from becoming too rich or lean.

Thus, according to this embodiment, one oxygen sensor 14 is provided in the connecting pipe 11E of the two branch pipes 11A and 11D connected to the two cylinders 1A and 1D, respectively, and the other two cylinders are provided. The other one oxygen sensor is installed in the connecting pipe 11F of the two branch pipes 11B and 11C which are respectively connected to 11B and 11C, and the connecting pipes 11E and 11F are located upstream of the oxygen sensors 14 and 15, respectively. Exhaust gas guide plates 16, 17 for selectively guiding the exhaust gas from the branch pipes 11A, 11D and 11B, 11C are provided. Then, the three-way switching valve 19 is switched by a valve switching signal at a predetermined interval from the control unit 24, for example, every 10 seconds, and the diaphragm 18B of the actuator 18 is operated by the negative pressure generated in the intake manifold 9 to operate. Each of the exhaust gas guide plates 16 and 17 is alternately changed in the left and right directions via the rod 18C.

As a result, the oxygen sensor 14 can be exposed alternately to the exhaust gas from the two cylinders 1A and 1D for a certain period of time, and the oxygen concentration of the exhaust gas from the two cylinders 1A and 1D can be different for each cylinder by one oxygen sensor 14. Can be detected. Further, the other oxygen sensors 15 can similarly detect the oxygen concentration of the exhaust gas from the two cylinders 1B and 1C for each cylinder.

Since the oxygen sensors 14 and 15 have a slow response in comparison with the cycle of the ignition timing of each cylinder, the timer in the control unit 24 does not synchronize with the ignition timing in the embodiment, and the oxygen sensor 14 and 15 are slowed, for example, every 10 seconds. The direction is switched in a cycle, and each oxygen sensor 14 and 15 is
The oxygen concentration in the exhaust gas from A, 1B, ... Is detected from the average flow rate for a certain period of time.

As described above, according to this embodiment, the concentration of each exhaust gas from the four cylinders 1A, 1B, ...
It can be detected individually at 4, 15 and the air-fuel ratio for each cylinder can be feedback-controlled as in the case of using four oxygen sensors. Therefore, since each component in the exhaust gas can be stabilized, the amount of catalyst used can be reduced, the cost can be reduced, and the air-fuel ratio can be controlled according to the secular change in the characteristics of each cylinder. The quality of exhaust gas can be improved.

In the embodiment, the four-cylinder engine is taken as an example, and the two oxygen sensors 14 and 15 are used to detect the oxygen concentration in the exhaust gas of all the cylinders 1A, 1B ,. In that case, three oxygen sensors may be used. In short, according to the present invention, the number of oxygen sensors is half the number of cylinders.

[Effect of device]

The present invention is as described above in detail, and an oxygen sensor is provided at a connecting portion of a pair of branch pipes connected to each cylinder, and exhaust gas from each cylinder is directed to the oxygen sensor side by an exhaust gas guide plate. Since the guide is provided as an alternative, it is possible to detect the oxygen concentration of the exhaust gas of all the cylinders for each cylinder by using the oxygen sensors that are half the number of cylinders. Therefore, it is possible to realize feedback control of the air-fuel ratio for each cylinder corresponding to the variation of the cylinder due to the characteristics of each injection valve or the characteristics of each cylinder that has changed over time, while reducing the number of oxygen sensors used and reducing the cost. As a result, the exhaust gas concentration can be maintained normal and the amount of catalyst used can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall configuration diagram of an exhaust gas cylinder-by-cylinder oxygen concentration detection device according to an embodiment of the present invention, and FIG. 2 is an enlarged sectional view of an actuator that constitutes the oxygen concentration detection device. is there. 1A, 1B, 1C, 1D …… Cylinder, 11 …… Exhaust manifold, 11A, 1
1B, 11C, 11D …… Branching pipe, 11E, 11F …… Connecting pipe, 14,15 ……
Oxygen sensor, 16, 17 ... Exhaust gas guide plate.

Claims (1)

[Scope of utility model registration request] 1. An exhaust manifold having a branch pipe connected to each cylinder of an engine, wherein two of the branch pipes are connected to one exhaust pipe, and a pair of each branch of the exhaust manifold. One oxygen sensor is provided for each connecting portion of the pipes, and an oxygen sensor for detecting the oxygen concentration in the exhaust gas discharged from each of the branch pipes and a connecting portion of the exhaust manifold located near the oxygen sensor are provided. And a cylinder-by-cylinder oxygen concentration detection device for exhaust gas, which comprises an exhaust gas guide plate that alternately guides the exhaust gas discharged from each of the branch pipes to the oxygen sensor side.