JP2025039359A - Diagnostic device for turbocharged V-engine - Google Patents

Abstract

To perform imbalance diagnosis which is adapted to a V-type engine with a supercharger.SOLUTION: An analysis device of a V-type engine with a supercharger is employed with a V-type engine with a supercharger having: a first wastegate valve for opening and closing a first bypass passage which bypasses a first turbine of a first supercharger arranged in a first exhaust passage of a first bank; a second wastegate valve for opening and closing a second bypass passage which bypasses a second turbine of a second supercharger arranged in a second exhaust passage of a second bank; a first air-fuel ratio sensor arranged at a downstream side of the first exhaust passage; and a second air-fuel ratio sensor arranged at a downstream side of the second exhaust passage. The analysis device performs imbalance diagnosis for analyzing a variation in air-fuel ratio between first cylinders by the first air-fuel ratio sensor, and in air-fuel ratio between second cylinders by the second air-fuel ratio sensor, and when both the first and second banks satisfy a prerequisite for the execution of the imbalance diagnosis, the analysis device performs the imbalance diagnosis by fixing openings of both the first and second wastegate valves to prescribed values.SELECTED DRAWING: Figure 2

Description

The present invention relates to a diagnostic device for a supercharged V-type engine.

An imbalance diagnosis is known that diagnoses the variation in the air-fuel ratio between cylinders of a turbocharged engine. The imbalance diagnosis is performed when certain prerequisites are met, with the opening of the wastegate valve fixed at a predetermined value (see Patent Document 1).

JP 2015-203378 A

In the case of a turbocharged V-type engine, the preconditions for performing an imbalance diagnosis can be met for each bank. For this reason, it is possible to perform an imbalance diagnosis for each bank. For example, if the preconditions are met for only one bank, it is possible to fix the opening of the wastegate valve on one bank and perform an imbalance diagnosis for only one bank without fixing the opening of the wastegate valve on the other bank. However, in this case, the boost pressure will be different between the two banks, which could increase engine rotation fluctuations.

Therefore, it is conceivable to perform an imbalance diagnosis on only one bank, with the wastegate valve opening on both banks fixed to a predetermined value. In this case, the wastegate valve opening on the other bank will be fixed, even though an imbalance diagnosis is not performed on the other bank. Even if the preconditions are met only for the other bank, an imbalance diagnosis is performed on the other bank, with the wastegate valve opening on the one bank fixed. As a result, the period during which the wastegate valve opening is fixed will be extended until the imbalance diagnosis is completed for both banks, which could cause various problems.

The present invention aims to provide a diagnostic device for a turbocharged V-engine that can perform imbalance diagnosis suitable for a turbocharged V-engine.

The above object is to provide an engine having a first bank having a plurality of first cylinders, a second bank having a plurality of second cylinders, a first wastegate valve for opening and closing a first bypass passage that bypasses a first turbine of a first turbocharger disposed in a first exhaust passage connected to the first bank, a second wastegate valve for opening and closing a second bypass passage that bypasses a second turbine of a second turbocharger disposed in a second exhaust passage connected to the second bank, a first air-fuel ratio sensor disposed downstream of the downstream end of the first bypass passage in the first exhaust passage, and a second air-fuel ratio sensor disposed downstream of the downstream end of the second bypass passage in the second exhaust passage. This can be achieved by a diagnostic device for a turbocharged V-engine that is applied to a turbocharged V-engine having a first air-fuel ratio sensor and performs an imbalance diagnosis in which the first air-fuel ratio sensor diagnoses the variation in the air-fuel ratio between the first cylinders and the second air-fuel ratio sensor diagnoses the variation in the air-fuel ratio between the second cylinders, and includes a determination unit that determines whether or not both the first and second banks satisfy the prerequisites for performing the imbalance diagnosis, and an execution unit that fixes the openings of both the first and second wastegate valves to a predetermined value and executes the imbalance diagnosis when a positive determination is made by the determination unit.

The present invention provides a diagnostic device for a turbocharged V-engine that can perform imbalance diagnosis suitable for a turbocharged V-engine.

FIG. 1 is a schematic configuration diagram of an engine. 4 is a flowchart illustrating an imbalance diagnosis control executed by the ECU. 6 is a timing chart illustrating imbalance diagnosis in this embodiment and a comparative example.

[General configuration of engine]
FIG. 1 is a schematic diagram of an engine 1. The engine 1 includes a pair of banks 2L and 2R arranged at an appropriate bank angle around a crankshaft. The bank 2L includes cylinders #1, #3, and #5. The bank 2R includes cylinders #2, #4, and #6. That is, the engine 1 is a V6 engine, but the number of cylinders is not limited to this. The engine 1 is a gasoline engine, but may be a diesel engine. The banks 2L and 2R correspond to the first and second banks, respectively. The cylinders #1, #3, and #5 correspond to the first cylinder. The cylinders #2, #4, and #6 correspond to the second cylinder. The engine 1 is also provided with a supercharger, as will be described later. That is, the engine 1 is a supercharged V-engine.

The engine 1 includes an intake passage 4M and intake branch passages 4L and 4R. The intake branch passages 4L and 4R branch off from the intake passage 4M downstream of the intake passage 4M and are connected to the banks 2L and 2R, respectively. The intake passage 4M is provided with an air cleaner 2, an air flow meter 2S, and a throttle valve 2V, in that order from the upstream side. The air cleaner 2 filters dust and the like from the intake air. The air flow meter 2S detects the amount of intake air. The throttle valve 2V adjusts the amount of intake air. Note that a single throttle valve 2V is provided in the intake passage 4M where the intake branch passages 4L and 4R join, but this is not limited to this. For example, an intake passage may be connected to each of the banks 2L and 2R individually, and a throttle valve and an air flow meter may be provided for each intake passage.

The intake branch passage 4L has a branch portion that branches off from each other downstream and is connected to the intake ports of cylinders #1, #3, and #5 of bank 2L. Similarly, the intake branch passage 4R has a branch portion that branches off from each other downstream and is connected to the intake ports of cylinders #2, #4, and #6 of bank 2R. Each of the branch portions of the intake branch passage 4L is provided with a port injection valve PL that injects fuel into the intake ports of cylinders #1, #3, and #5. Similarly, the intake branch passage 4R is provided with a port injection valve PR that injects fuel into the intake ports of cylinders #2, #4, and #6. Note that in place of the port injection valves PL and PR, or in addition to the port injection valves PL and PR, an in-cylinder injection valve may be provided.

Cylinders #1, #3, and #5 of bank 2L are each provided with a spark plug IL that ignites a mixture of fuel and air. Similarly, cylinders #2, #4, and #6 of bank 2R are each provided with a spark plug IR. Engine 1 also has exhaust passages 5L and 5R connected to banks 2L and 2R, respectively.

The exhaust passage 5L has branches connected to the exhaust ports of cylinders #1, #3, and #5 on the upstream side. These branches merge downstream. Downstream of the merger, a turbine 6L, an air-fuel ratio sensor SL, and a catalyst 7L are provided in this order from the upstream side.

The turbine 6L is provided in the turbocharger and rotates together with the compressor that supercharges the intake pressure. Although not shown, the compressor is arranged upstream of the air cleaner 2 in the intake passage 4M. The air-fuel ratio sensor SL detects the air-fuel ratio of the exhaust gas. The catalyst 7L purifies the exhaust gas. Similarly, the branching portion of the exhaust passage 5R joins on the downstream side, and downstream of the joining point, the turbine 6R, the air-fuel ratio sensor SR, and the catalyst 7R are provided in that order from the upstream side. The turbines 6L and 6R are examples of the first and second turbines. The air-fuel ratio sensors SL and SR are examples of the first and second air-fuel ratio sensors.

Bypass passages 8L and 8R are connected to the exhaust passages 5L and 5R, respectively. The bypass passages 8L and 8R bypass the turbines 6L and 6R, respectively. Wastegate valves 9L and 9R are provided in the bypass passages 8L and 8R, respectively. Air-fuel ratio sensors SL and SR are installed in the exhaust passages 5L and 5R downstream of the downstream ends of the bypass passages 8L and 8R, respectively.

The ECU (Electronic Control Unit) 10 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and the like. The ECU 10 is electrically connected to the air flow meter 2S, the throttle valve 2V, the port injection valves PL and PR, the spark plugs IL and IR, the air-fuel ratio sensors SL and SR, and the wastegate valves 9L and 9R. The ECU 10 obtains the detection values of the air flow meter 2S and the air-fuel ratio sensors SL and SR, and controls the throttle valve 2V, the port injection valves PL and PR, the spark plugs IL and IR, and the wastegate valves 9L and 9R based on the detection values, thereby controlling the entire engine 1. The ECU 10 also performs an imbalance diagnosis, which will be described below. The ECU 10 is an example of a diagnostic device for a supercharged V-type engine.

[Immalance Diagnosis]
When a predetermined condition is satisfied, the ECU 10 performs an imbalance diagnosis for the banks 2L and 2R. In the imbalance diagnosis for the bank 2L, the ECU 10 acquires time series data of the air-fuel ratio for a predetermined number of combustion cycles based on the air-fuel ratio sensor SL. In the time series data of the air-fuel ratio detected by the air-fuel ratio sensor SL for one combustion cycle, the air-fuel ratios for the cylinders #1, #3, and #5 appear in order at time intervals of 120° of crank angle. A large amplitude of this time series data indicates a large variation in the air-fuel ratio between the cylinders #1, #3, and #5. Therefore, the ECU 10 performs an imbalance diagnosis based on the magnitude of the difference between the upper peak value and the lower peak value of the air-fuel ratio in the time series data. In a similar manner, the ECU 10 also performs an imbalance diagnosis for the bank 2R.

Figure 2 is a flowchart illustrating the imbalance diagnosis control executed by the ECU 10. The ECU 10 determines whether the imbalance diagnosis has not been completed in the current trip (step S1). If the answer is No in step S1, that is, if the imbalance diagnosis has been completed in the current trip, this control ends. If the answer is Yes in step S1, the ECU 10 determines whether the prerequisites for the imbalance diagnosis have been met for both banks 2L and 2R (step S2).

Prerequisites for the imbalance diagnosis include, for example, (1) the temperature of the engine 1 cooling water is equal to or higher than a predetermined value, (2) the atmospheric pressure is equal to or higher than a predetermined value, (3) the engine 1 revolution speed and load are within a predetermined range, (4) the main feedback control of the air-fuel ratio is being executed, (5) the rich control after fuel cut is not being executed, (6) the vapor concentration learning value per unit purge rate is equal to or higher than a predetermined value, and (7) the number of updates of the purge concentration learning value is equal to or higher than a predetermined value. The main feedback control in (4) is to control the fuel injection amount of each of the port injection valves PL and PR so that the detection values of the air-fuel ratio sensors SL and SR become the respective target values. The rich control after fuel cut in (5) is to control the target air-fuel ratio when returning from fuel cut to a rich air-fuel ratio smaller than stoichiometric for a predetermined time. The unit purge rate in (6) is the ratio of evaporated fuel gas to the intake air amount. The vapor concentration learning value (6) is a coefficient that reflects the concentration of the vapor component in the purge gas. The conditions (1) to (7) are merely examples of prerequisites for imbalance diagnosis, and are not limited to these.

The above conditions (1) to (3) can be satisfied in common for banks 2L and 2R. That is, if one of the conditions (1) to (3) is satisfied for either bank 2L or 2R, the other is also satisfied, and if one is not satisfied, the other is not satisfied. On the other hand, the above conditions (4) to (7) can be satisfied for each of banks 2L and 2R. That is, the conditions (4) to (7) can be satisfied for either bank 2L or 2R but not satisfied for the other. Therefore, for example, if one of banks 2L and 2R satisfies all of the conditions (1) to (7), and the other satisfies the conditions (1) to (3) but does not satisfy any of the conditions (4) to (7), the result of step S2 is No. If the result of step S2 is No, this control ends. Step S2 is an example of a process executed by the determination unit.

If both banks 2L and 2R satisfy all of the above conditions (1) to (7), the determination in step S2 is Yes. If the determination in step S2 is Yes, the ECU 10 requests that the openings of both wastegate valves 9L and 9R be fixed to predetermined values (step S3). Specifically, the ECU 10 requests that the openings of wastegate valves 9L and 9R be fully open or fully closed. The reason for fully opening or fully closing is to ensure that the exhaust gas hits the air-fuel ratio sensors SL and SR in a constant manner, thereby ensuring the accuracy of the imbalance diagnosis.

The ECU 10 determines whether or not to permit the request to fix the opening degree (step S4). If the answer is No in step S4, this control ends. If the answer is Yes in step S4, the ECU 10 fixes the opening degree of both wastegate valves 9L and 9R to fully open or fully closed in accordance with the request to fix the opening degree, and performs an imbalance diagnosis (step S5). Note that while the imbalance diagnosis is being performed, the ECU 10 switches the diagnosis in progress flag from OFF to ON.

The ECU 10 determines whether the number of combustion cycles during the execution of the imbalance diagnosis is equal to or greater than a predetermined value (step S6). If the answer is No in step S6, step S6 is executed again. If the answer is Yes in step S6, the ECU 10 completes the imbalance diagnosis (step S7). When the imbalance diagnosis is completed, the ECU 10 switches the diagnosis completion flag from OFF to ON.

Figure 3 is a timing chart illustrating imbalance diagnosis in this embodiment and in a comparative example. Figure 3 shows whether the preconditions for each bank 2L and 2R are met, whether there is a request to fix the opening, the state of the diagnosis in progress flag, and the state of the diagnosis completion flag. This embodiment is shown with a solid line, and the comparative example is shown with a dotted line. Therefore, the overlapping parts between the lines of this embodiment and the comparative example are shown with a solid line.

First, a comparative example will be described. In the comparative example, when at least one of banks 2L and 2R satisfies the above-mentioned preconditions, an imbalance diagnosis is performed for that bank. When only bank 2L satisfies the preconditions (time t1-t2), the openings of both wastegate valves 9L and 9R are fixed, and an imbalance diagnosis is performed only for bank 2L. When both banks 2L and 2R satisfies the preconditions (time t3-t4), the openings of both wastegate valves 9L and 9R are fixed, and an imbalance diagnosis is performed for both banks 2L and 2R. The imbalance diagnosis for bank 2L is then completed (time t4). Next, when only bank 2R satisfies the preconditions (time t5-t6), the openings of both wastegate valves 9L and 9R are fixed again, and an imbalance diagnosis is performed only for bank 2R. The imbalance diagnosis for bank 2R is then completed (time t6).

In this way, the openings of both wastegate valves 9L and 9R are fixed until the imbalance diagnosis for both banks 2L and 2R is completed. This lengthens the period during which the openings of both wastegate valves 9L and 9R are fixed. For example, if the period during which both wastegate valves 9L and 9R are fixed fully open is extended, there is a risk that acceleration responsiveness will decrease and drivability will deteriorate. If the period during which both wastegate valves 9L and 9R are fixed fully closed is extended, there is a risk that fuel economy will deteriorate.

In this embodiment, when the preconditions are met only for bank 2L (time t1 to t2), the openings of the wastegate valves 9L and 9R are not fixed and imbalance diagnosis is not performed. Only when the preconditions are met for both banks 2L and 2R (times t3 to t4, t5 to t6), the openings of both wastegate valves 9L and 9R are fixed and imbalance diagnosis is performed for both banks 2L and 2R. Therefore, unlike the comparative example, it is possible to prevent the period during which the openings of both wastegate valves 9L and 9R are fixed from becoming long. This makes it possible to prevent a decrease in drivability or a deterioration in fuel economy. In this way, in this embodiment, an imbalance diagnosis suitable for a V-type engine 1 with a turbocharger can be performed.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as described in the claims.

1 Engine (V-type turbocharged engine)
2L bank (first bank)
2R Bank (2nd Bank)
#1, #3, #5 cylinders (1st cylinder)
#2, #4, #6 cylinders (2nd cylinder)
5L exhaust passage (first exhaust passage)
5R Exhaust passage (second exhaust passage)
6L turbine (first turbine)
6R Turbine (Second Turbine)
8L Bypass passage (first bypass passage)
8R Bypass passage (second bypass passage)
9L Wastegate valve (first wastegate valve)
9R Wastegate valve (second wastegate valve)
SL Air-fuel ratio sensor (first air-fuel ratio sensor)
SR Air-fuel ratio sensor (second air-fuel ratio sensor)
10 ECU (diagnostic device for turbocharged V-type engine)

Claims (1)

the first bank having a plurality of first cylinders, a second bank having a plurality of second cylinders, a first wastegate valve for opening and closing a first bypass passage that bypasses a first turbine of a first turbocharger disposed in a first exhaust passage connected to the first bank, a second wastegate valve for opening and closing a second bypass passage that bypasses a second turbine of a second turbocharger disposed in a second exhaust passage connected to the second bank, a first air-fuel ratio sensor disposed downstream of a downstream end of the first bypass passage in the first exhaust passage, and a second air-fuel ratio sensor disposed downstream of a downstream end of the second bypass passage in the second exhaust passage,
A diagnostic device for a supercharged V-type engine that performs an imbalance diagnosis to diagnose an air-fuel ratio variation between the first cylinders using the first air-fuel ratio sensor and to diagnose an air-fuel ratio variation between the second cylinders using the second air-fuel ratio sensor,
a determination unit that determines whether or not both of the first and second banks satisfy a prerequisite for executing the imbalance diagnosis;
an execution unit that, when a positive determination is made by the determination unit, fixes the opening degrees of both the first and second wastegate valves to predetermined values and executes the imbalance diagnosis.

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