JPH01318730A - Detecting device for oxygen density by cylinder of exhaust gas - Google Patents

Abstract

PURPOSE:To detect an oxygen density by cylinder with high accuracy by performing the detection of an oxygen density by guiding one part of the exhaust gas fed from a pair of cylinders to one oxygen sensor with the switching of an exhaust gas guide plate and specifying the switching time conditions of the guide plate. CONSTITUTION:The manifold 11 for the exhaust of a four cylinder engine is composed of the branch pipes 11A-11D respectively connected to each cylinder 1A-1D, the yoked type manifolds 11E, 11F respectively shunting branch pipes 11A and 11D, and 11B and 11C and one exhaust pipe 11G to which both manifolds 11E, 11F are connected. In this case, oxygen sensors 14, 15 are provided at the center of each manifold 11E, 11F and exhaust gas guide plates 16, 17 are provided on each manifold 11E, 11F at the upper stream side than the respective oxygen sensor 14, 15. These guide plates 16, 17 are controlled by switching them at the time when the periodic number of the oxygen sensor output becomes more than the periodic number to be set according to the engine revolution number after the lapse of the specified time after the exhaust gas switching operation by the guide plates 16, 17.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an exhaust gas concentration detection device for, for example, an automobile multi-cylinder engine, and in particular, to a detection device for detecting exhaust gas concentration from two cylinders using one oxygen sensor. The present invention relates to a cylinder-by-cylinder oxygen concentration detection device for exhaust gas.

[Conventional technology]

Generally, in multi-cylinder engines for automobiles, injection valves are provided in each of the multiple branch pipes of the intake manifold, and an oxygen sensor is provided on the exhaust manifold side, and the oxygen concentration in the exhaust gas is detected by this oxygen sensor. The air-fuel ratio is controlled by feedback.

By the way, in the conventional technology, one oxygen sensor installed in the exhaust pipe of the exhaust manifold detects the oxygen concentration in the exhaust gas sequentially discharged from multiple cylinders, and the air-fuel ratio of the entire multiple cylinders is fed back at once. It is meant to be controlled.

[Problem to be solved by the invention]

However, with the conventional technology, for example, if the fuel injection amount of one of the injection valves in each cylinder is larger than the others, the oxygen sensor will absorb the entire amount of fuel by the exhaust gas from the cylinder corresponding to that injection valve. As a result, the exhaust gas outputs a signal indicating that it has a tendency to be rich in fuel, making it impossible to stably control the air-fuel ratio, causing the engine output to erroneously decrease, or causing various components in the exhaust gas to become unstable. There is a problem that an expensive catalyst is used excessively, and that it is not possible to cope with changes in the characteristics of each cylinder over time.

Therefore, in order to reliably feedback control the air-fuel ratio variations in each cylinder, an oxygen sensor is installed in each branch pipe connected to each cylinder of the exhaust manifold, and the oxygen concentration of the exhaust gas discharged from each cylinder is measured. It is possible to detect them individually. However, this increases the cost because the number of oxygen sensors corresponding to the number of cylinders in the engine is required, and the oxygen sensors are installed in branch pipes that are close to the cylinders and are subject to high temperatures. , there is an unresolved problem that it is easily affected by temperature.

The present invention was made in view of the above-mentioned shortcomings of the prior art, and it is possible to detect the oxygen concentration in the exhaust gas from a plurality of cylinders for each cylinder using a minimum number of oxygen sensors, thereby reducing the risk of injector valves and aging. The cylinder-specific oxygen concentration of exhaust gas enables highly accurate feedback control of the air-fuel ratio of each cylinder, which varies due to changes, and also allows the oxygen sensor to detect the oxygen concentration with high accuracy without being affected by exhaust temperature. A detection device is provided.

[Means to solve the problem]

The means of the present invention configured to solve the above-mentioned problems has a branch pipe connected to each cylinder of an engine, and two of the branch pipes are connected as a pair to one exhaust pipe. An exhaust manifold, an oxygen sensor provided at each connecting portion of each pair of branch pipes of the exhaust manifold, and detecting the oxygen concentration in the exhaust gas discharged from each branch pipe, and a vicinity of the oxygen sensor. an exhaust gas guide plate located at a connecting portion of the exhaust manifold and alternately guides exhaust gas discharged from each of the branch pipes toward the oxygen sensor; and an exhaust gas switch of the exhaust gas guide plate. elapsed time determining means for determining whether a predetermined time has elapsed after operation; and after the elapsed time determining means has determined that the predetermined time has elapsed, the number of cycles of the output of the oxygen sensor is preset according to the rotational speed of the engine. and a guide plate switching determining means for determining switching of the exhaust gas guide plate when the number of cycles exceeds a predetermined number of cycles.

[For production]

The exhaust gas guide plate directs the exhaust gas from the pair of cylinders to the oxygen sensor side when a predetermined time has elapsed and the output cycle number of the oxygen sensor reaches a predetermined number depending on the engine rotation speed. Guide each other alternately.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

In FIG. 1, l represents, for example, four cylinders IA.

An engine body having an IB, an IC, and a LD.The engine body 1 reciprocates a piston by burning a mixture of air and fuel, and derives rotational output from a crank (rotating shaft) 2. The main body I is provided with a water temperature sensor 3 that detects the coolant temperature, and a crank angle sensor 4 that detects the engine rotation speed and the like from the crank 2.

Connected to the intake side of the engine body 1 are an air cleaner 5 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. Each branch pipe of the engine body 1 is connected to each cylinder IA, IB, IC,
Injection valves 10, 10 that inject and supply fuel to the LD.・・・
・ is provided.

Reference numeral 11 denotes an exhaust manifold provided on the exhaust side of the engine body 1, and the exhaust manifold 11 is connected to each cylinder IA, IB.
, IC, and ID branch pipes 11A and II, respectively.
B, IIC, IID and the branch pipe 11A of the first cylinder IA
and a forked connecting pipe LIE that joins the branch pipe 11D of the fourth cylinder ID, and a connecting pipe 11B of the second cylinder IB.
and another fork-shaped connecting pipe 11F that joins the connecting pipe 11C of the third cylinder IC, and one exhaust pipe 11G that connects both the connecting pipes 11E and IIF. 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 houses, for example, a three-way catalyst for purifying exhaust gas.

'14.15 is two oxygen sensors that detect the oxygen concentration in 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, and one oxygen sensor 14 is connected to the branch pipe 11A.

11D respectively to the first cylinder IA and the fourth cylinder I.
The other oxygen sensor 15 is provided at the center of the - connecting pipe LIE into which the exhaust gas from D flows in, and the other oxygen sensor 15 is connected to the branch pipes 11B and II.
The connecting pipe 11F is provided at the center of another connecting pipe 11F into which exhaust gas from the second cylinder IB and the third cylinder IC flow in through the cylinder C, respectively.

Here, as shown in FIG. 3, each of the oxygen sensors 14 and 15 normally has a reference voltage level of about 450 to 500 mV, and outputs a detection signal of the oxygen concentration in the exhaust gas at a certain period that varies depending on the exhaust temperature. It is supposed to be done.

Next, 16 is an exhaust gas guide plate located upstream of the oxygen sensor 14 and rotatably provided on the connecting pipe 11E, and when the exhaust gas guide plate 16 is rotated to the right in FIG. The exhaust gas discharged from the first cylinder IA is guided to the oxygen sensor 14 side, and when the cylinder rotates counterclockwise, the exhaust gas from the fourth cylinder ID is alternatively guided to the oxygen sensor 14 side. Reference numeral 17 denotes another exhaust gas guide plate having the same function as the exhaust gas guide plate 16, and the exhaust gas guide plate 17 is located upstream of the other oxygen sensor 15 and connected to the connecting pipe 1.
It is rotatably provided on the 1F, and by rotating to the right or left, exhaust gas from the second cylinder IB and exhaust gas from the third cylinder IC are selectively guided to the oxygen sensor 15 side. It is supposed to be done.

Reference numeral 18 denotes an actuator that rotates the exhaust gas guide plates 16 and 17. As shown in FIG.
A diaphragm 18B defining the chambers A and B, one end slidably inserted into the casing 18A is connected to the diaphragm 18B, and the other end is connected to each exhaust gas guide plate 16.
17, a return spring 180 stretched between the casing 18A and the diaphragm 18B, and the intake manifold 9 and the casing 1.
8A, and an intake pipe 18E that sucks air in the A chamber of the casing 18A by the negative pressure generated in the intake manifold 9. and,
A three-way switching valve 19 is provided in the middle of the intake pipe 18E of the actuator 18, which switches the pressure inside the chamber A of the casing 18A between negative pressure and atmospheric pressure in response to a valve switching signal from the control unit 24.

20 is a fuel tank; 21 is an oil-immersed fuel pump provided in the fuel tank 20; the fuel pump 21 pressure-feeds the fuel in the fuel tank 20 to each injection valve 10 via a fuel pipe 22; A portion of this fuel is transferred to the pressure regulator 23
The fuel is returned to the fuel tank 20 through the fuel tank 20. Here, the pressure regulator 23 controls the fuel pressure in the fuel pipe 22 based on this control pressure by guiding the pressure in the intake manifold 9 as a control pressure, and uses this controlled fuel pressure to inject fuel from each injection valve 10. It is designed to spray.

Furthermore, 24 indicates a control unit constituted by a microcomputer etc., and the control unit 24 is constituted by including a processing circuit constituted by a CPU etc. and a storage circuit constituted by a RAM or ROM etc. It has a built-in counter and timer. and,
The input side of the control unit 24 is connected to a water temperature sensor 3, a crank angle sensor 4, an air flow meter 6, a throttle valve switch 8A, an oxygen sensor 14, 15, an engine switch, a vehicle speed sensor, an inhibitor switch, etc. (all not shown). , the output side is connected to each injection valve 10, three-way switching valve 19, and a battery as a power source. In addition, the program shown in FIG. 5 is stored in the memory circuit of the control unit 24, and the table 25 shown in FIG. 4 is also stored. Here, the table 25 contains a preset valve switching period n0 that indicates how many times the output period number n of the oxygen sensors 14 and 15 is repeated to switch the three-way switching valve 18 with respect to the engine speed N. The switching period number table 26 and the elapsed time t0 after the switching operation of the three-way switching valve 19, for example, to. A setting time table 27 in which 5 seconds is set is stored.

The control unit 24 calculates the basic injection amount from the engine speed detected by the crank angle sensor 4 and the intake air amount detected by the air flow meter 6, and also receives detection signals from the water temperature sensor 3, oxygen sensor 14, 15, etc., and the air-fuel ratio. The injection amount by each injection valve 10 is calculated from the feedback correction coefficient, the basic air-fuel ratio learning correction coefficient, and various other correction coefficients, and an injection pulse of a predetermined duty is output to the injection valve 10.

Further, the control unit 24 controls the three-way switching valve 1 based on the switching cycle number table 26 after a predetermined period of time has passed.
A valve switching signal is output to the actuator 18 to switch between the atmosphere and the intake pipe 18E, so that the negative pressure in the intake manifold 9 intermittently makes the chamber A of the actuator 18 negative pressure.

The embodiment is constructed as described above, and its operation will now be described.

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

The cylinders IA, IB, ... of the engine body L are the 1st and 3rd cylinders.
．． 4th. Explosion and exhaust are performed in the second order, and oxygen sensors 14 and 15 are connected to branch pipes IA and IB.

By detecting the oxygen concentration in the exhaust gas discharged through..., a signal corresponding to the oxygen concentration is outputted 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 oxygen sensor 14.15, increases or decreases the amount of fuel injected by each injector IO, and performs feedback control of the air-fuel ratio, so that the fuel becomes the intake air. On the other hand, it is designed to prevent the fuel from becoming too rich or too lean, and there is no difference from the conventional technology in terms of feedback control of the air-fuel ratio.

According to this embodiment, there are two cylinders IA.

Two branch pipes 11A each connected to the ID.

One oxygen sensor 14 is provided in the connecting pipe 11H of 11D,
In addition, two branch pipes 11B and IIC connecting pipes 11F are connected to the other two cylinders 11B and 11C, respectively.
In addition to providing two oxygen sensors, each connecting pipe 11E, II
F is provided with exhaust gas guide plates 16, 17 located upstream of the oxygen sensors 14 and 15 to selectively guide exhaust gas from the branch pipes 11A, IID, IIB, and IIC. Then, the three-way switching valve 19 is switched in response to a valve switching signal from the control unit 24, and the diaphragm 18B of the actuator 18 is operated by the negative pressure generated in the intake manifold 9.
The direction of each of the exhaust gas guide plates 16 and 17 is alternately controlled to the left and to the right via the guide 8C.

Next, the switching control of each exhaust gas guide plate 16, 17 will be explained with reference to the flowchart shown in FIG.

First, when the engine 1 starts, the number of cycles n of the counter n and the elapsed time t of the timer t in the RAM constituting the control unit 24 are reset to zero (step 1). At this time, the three-way switching valve 19 is in a state in which the exhaust gas switching valves 16 and 17 are switched to one of the switching directions via the actuator 18. Next, in step 2, the predetermined time t0 is continuously read out from the set time table 27, and in the next step 3, the timer t starts counting the elapsed time t, and in step 4, the elapsed time t is set to the predetermined time t. It is determined whether or not the value has been reached, and if rNOJ, 1=1. Repeat the count in step 3 until .

On the other hand, if the determination in step 4 is YES, the engine speed N is read from the crank angle sensor 4 (step 5), and in step 6, the engine speed N is read from the switching period table 26 stored in the control unit 24. Read the valve switching cycle n0. Then, in step 7, the number of cycles n of the detection signal of each oxygen sensor 14, 15 is read, and in step 8, the number of cycles n is counted to determine whether the number of cycles n of the detection signal is greater than or equal to the valve switching frequency rIJIn 0. (Step 9). If rNOJ, return to step and n
Repeat counting until o=n is reached.

If rYES J is determined in step 9, the process moves to step 10, where a valve switching signal is output from the control unit 24 to the three-way switching valve 19. As a result, the pressure in chamber A of the actuator 18 is switched to negative pressure (atmospheric pressure), and the exhaust gas guide direction of each exhaust gas guide plate 16, 17 is switched via the actuation iron 18C.

The processing operation of the embodiment is as described above. In step 3), the time t after the valve switching reset in step 1 is counted, and whether or not the elapsed time t has passed with respect to the set time L0 read out in step 2. (Step 4)
This is a specific example of the elapsed time determining means of the present invention.

Also, when the output cycle number n of the oxygen sensor 14, 15 read in step 7 is counted (step 8), it is determined that the valve switching cycle n0, which is determined according to the engine speed N, has been reached (step 9). Operation to output a valve switching signal to (
Step 10) is a specific example of the guide plate switching determination means of the present invention.

As mentioned above, according to the embodiment, there are two cylinders IA.

Exhaust gas guide plate 16 that alternately guides exhaust gas from ID (or IB, IC) to one oxygen sensor 14 (15)
(17) is a switching operation when a predetermined time t0 has elapsed and the output cycle number n of the oxygen sensor 14 (15) reaches a valve switching cycle n0 that is preset according to the engine rotation speed N. Since it is configured so that each cylinder IA, ID (
The oxygen concentration in the exhaust gas of IB, IC) can be reliably detected for each cylinder.

In addition, the oxygen sensors 14 and 15 have a temperature-dependent characteristic in which the number of cycles of the detection signal per hour changes depending on whether the exhaust temperature is low or high. The number of cycles per hour of the detection signals of the oxygen sensors 14 and 15 changes between low rotation and high rotation, so the exhaust gas guide plates 16 and 17 are simply switched when the predetermined time L0 has elapsed. In this case, the oxygen concentration cannot be detected with high accuracy. However, according to the embodiment, the valve switching frequency corresponding to the engine speed N! tI]n
0 is set in advance, and the number of cycles n of the detection signal of the oxygen sensor 14 and 15 is the valve switching cycle n.

Since the configuration is configured such that when the temperature reaches the three-way switching valve 19, a valve switching signal is output to the three-way switching valve 19 to switch the exhaust gas guide plates 16, 17, so that each cylinder IA and
The oxygen concentration of IB, . . . can be detected with high accuracy.

Furthermore, according to the embodiment, the length of the predetermined time 1 counted when switching the exhaust gas guide plates 16 and 17 is as follows:
Since it can be set appropriately in consideration of the durability and responsiveness of the actuator 18, the durability of the actuator 18 can be improved.

Furthermore, the concentration of each exhaust gas from the four cylinders IA, IB, .
It is possible to perform feed pump control on the air-fuel ratio for each cylinder in the same way as when four oxygen sensors are used. Therefore, since each component in the exhaust gas can be stabilized, the amount of catalyst used can be reduced and costs can be reduced, and the air-fuel ratio can be controlled in response to changes in the characteristics of each cylinder over time. The properties of exhaust gas can be improved.

In this embodiment, a four-cylinder engine is used as an example, and two oxygen sensors 14 and 15 are used to control the gold cylinders IA and IB.

..., but for example, in a six-cylinder engine, three oxygen sensors may be used, and in short, according to the present invention, the number of oxygen sensors is half the number of cylinders. The number of items will be sufficient.

〔Effect of the invention〕

The present invention is as described in detail above (wherein, the exhaust gas guide plate that alternately guides the exhaust gas from a pair of cylinders toward one oxygen sensor side is configured so that when a predetermined period of time has elapsed, The oxygen sensor is configured to switch when the number of cycles reaches a preset number corresponding to the engine speed, so the oxygen sensor can detect the oxygen concentration of each cylinder with high accuracy without being affected by exhaust temperature, etc. In addition, it is possible to feedback control the air-fuel ratio of each cylinder in response to cylinder variations due to the characteristics of each injector or the characteristics of each cylinder that have changed over time.As a result, it is possible to maintain the exhaust gas concentration normally and use the catalyst. The amount can be reduced.

[Brief explanation of the drawing]

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, FIG. 2 is an enlarged sectional view of an actuator constituting the oxygen concentration detection device, and FIG. 3 is an oxygen sensor FIG. 4 is a diagram showing the output cycle of the detection signal, FIG. 4 is an explanatory diagram showing the structure of a table stored in the control unit, and FIG. 5 is a flowchart of control processing for detecting oxygen concentration for each cylinder. IA, IB, IC, ID...Cylinder, 1■...Exhaust manifold, IIA, IIB, IIC, IID...Branch pipe, IIE, IIF...Connecting pipe, 14.15...
Oxygen sensor, 16.17...Exhaust gas guide plate. Patent Applicant Japan Electronics Co., Ltd. Agent Patent Attorney Kazu Hirose Sorakai
Naoki NakamuraFigure 3Figure 4Figure 7-----L, --1

Claims (1)

[Claims] An exhaust manifold that has a branch pipe connected to each cylinder of the engine, and connects two of the branch pipes as a pair to one exhaust pipe, and each joint of each pair of branch pipes of the exhaust manifold. an oxygen sensor for detecting the oxygen concentration in the exhaust gas discharged from each of the branch pipes;
an exhaust gas guide plate that is located near the oxygen sensor and is provided at a connecting portion of the exhaust manifold, and that alternately guides exhaust gas discharged from each of the branch pipes toward the oxygen sensor; and the exhaust gas guide. elapsed time determining means for determining whether a predetermined time has elapsed after the exhaust gas switching operation of the plate; and after the elapsed time determining means determines that the predetermined time has elapsed, the number of cycles of the output of the oxygen sensor is determined by the number of revolutions of the engine; A cylinder-specific exhaust gas oxygen concentration detection device comprising a guide plate switching determining means for determining switching of the exhaust gas guide plate when the number of cycles exceeds a preset number of cycles according to the number of cycles.