Analysis device of v-type engine with supercharger

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

[Technical field]

[0001] The present invention relates to a diagnostic device for a supercharged V-type engine. [Background technology]

[0002] There is a known imbalance diagnosis for diagnosing the variation in the air-fuel ratio between cylinders of a turbocharged engine. The imbalance diagnosis is performed when a predetermined precondition is met, with the opening of the wastegate valve fixed at a predetermined value (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-203378 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the case of a turbocharged V-type engine, the preconditions for performing the imbalance diagnosis may be satisfied for each bank. For this reason, it is possible to perform the imbalance diagnosis for each bank. For example, if the preconditions are satisfied for only one bank, it is possible to fix the opening of the wastegate valve on one bank and perform the 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 may increase the fluctuation in engine speed.

[0005] Therefore, it is conceivable to perform an imbalance diagnosis for only one bank while the openings of the wastegate valves on both banks are fixed to a predetermined value. In this case, the opening of the wastegate valve on the other bank is fixed even though an imbalance diagnosis is not performed for the other bank. Even if the preconditions are met only for the other bank, an imbalance diagnosis for one bank is performed while the opening of the wastegate valve on the other bank is fixed. As a result, the period during which the opening of the wastegate valve is fixed becomes long until the imbalance diagnosis for both banks is completed, which may cause various problems.

[0006] SUMMARY OF THE PRESENT DISCLOSURE In view of the above, an object of the present invention is to provide a diagnostic device for a supercharged V-type engine that can perform an imbalance diagnosis suitable for a supercharged V-type engine. [Means for solving the problem]

[0007] The object of the present invention is to provide an engine having an engine that includes 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 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. The present invention 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 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, the diagnostic device for a turbocharged V-engine including: a determination unit that determines whether or not both of the first and second banks satisfy a prerequisite for performing the imbalance diagnosis; and 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. Effect of the Invention

[0008] According to the present invention, it is possible to provide a diagnostic device for a supercharged V-engine that can perform an imbalance diagnosis suitable for a supercharged V-engine. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic configuration diagram of an engine. [Diagram 2] 4 is a flowchart illustrating an imbalance diagnosis control executed by an ECU. [Diagram 3] 6 is a timing chart illustrating imbalance diagnosis in this embodiment and a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [Engine outline] 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 the 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 provided with a supercharger, which will be described later. That is, the engine 1 is a supercharged V-engine.

[0011] 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 this 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 together, but this is not limiting. 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.

[0012] The intake branch passage 4L has a branch portion that branches off from each other downstream and is connected to the intake ports of the cylinders #1, #3, and #5 of the bank 2L, respectively. 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 the cylinders #2, #4, and #6 of the bank 2R, respectively. 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 the cylinders #1, #3, and #5, respectively. Similarly, the intake branch passage 4R is provided with a port injection valve PR that injects fuel into the intake ports of the cylinders #2, #4, and #6, respectively. Note that an in-cylinder injection valve may be provided instead of the port injection valves PL and PR, or in addition to the port injection valves PL and PR.

[0013] Each of cylinders #1, #3, and #5 of bank 2L is provided with a spark plug IL that ignites a mixture of fuel and air. Similarly, each of cylinders #2, #4, and #6 of bank 2R is provided with a spark plug IR. Engine 1 also includes exhaust passages 5L and 5R connected to banks 2L and 2R, respectively.

[0014] The exhaust passage 5L has branched sections connected to the exhaust ports of cylinders #1, #3, and #5 on the upstream side. These branched sections join together on the downstream side. A turbine 6L, an air-fuel ratio sensor SL, and a catalyst 7L are provided downstream of the joining point, in this order from the upstream side.

[0015] The turbine 6L is provided in the turbocharger and rotates together with a compressor that supercharges the intake pressure. Although not shown, the compressor is disposed 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 portion, the turbine 6R, the air-fuel ratio sensor SR, and the catalyst 7R are provided in this order from the upstream side. The turbines 6L and 6R are examples of a first and second turbine. The air-fuel ratio sensors SL and SR are examples of a first and second air-fuel ratio sensor.

[0016] 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 provided in the exhaust passages 5L and 5R downstream of the downstream ends of the bypass passages 8L and 8R, respectively.

[0017] 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 an air flow meter 2S, a throttle valve 2V, port injection valves PL and PR, spark plugs IL and IR, air-fuel ratio sensors SL and SR, and wastegate valves 9L and 9R. The ECU 10 obtains 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.

[0018] [Immalance diagnosis] When a predetermined condition is satisfied, the ECU 10 executes 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 executes 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 executes an imbalance diagnosis for the bank 2R.

[0019] 2 is a flowchart illustrating the imbalance diagnosis control executed by the ECU 10. The ECU 10 determines whether or not the imbalance diagnosis has not been completed in the current trip (step S1). If the result in step S1 is No, that is, if the imbalance diagnosis has been completed in the current trip, this control ends. If the result in step S1 is Yes, the ECU 10 determines whether or not the prerequisites for the imbalance diagnosis have been met for both banks 2L and 2R (step S2).

[0020] The preconditions 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 the 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 the fuel cut in (5) is to control the target air-fuel ratio at the time of recovery from the fuel cut to a rich air-fuel ratio smaller than the stoichiometric ratio 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 in (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 the present invention is not limited to these.

[0021] The above conditions (1) to (3) may be satisfied in common for the banks 2L and 2R. That is, if one of the banks 2L and 2R satisfies the conditions (1) to (3), the other also satisfies the conditions, and if one does not satisfies the conditions, the other also does not satisfies the conditions. On the other hand, the above conditions (4) to (7) may be satisfied for each of the banks 2L and 2R. That is, the conditions (4) to (7) may be satisfied for one of the banks 2L and 2R but not satisfied for the other. Therefore, for example, if one of the 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 the determination in step S2 is No. If the result of the determination in step S2 is No, the present control ends. Step S2 is an example of a process executed by the determination unit.

[0022] 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 the wastegate valves 9L and 9R be fully open or fully closed. The reason for fully opening or fully closing the wastegate valves is to ensure the accuracy of the imbalance diagnosis by making the way the exhaust gas hits the air-fuel ratio sensors SL and SR constant.

[0023] 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 the wastegate valves 9L and 9R to fully open or fully closed in accordance with the request to fix the opening degree, and executes the imbalance diagnosis (step S5). Note that while the imbalance diagnosis is being executed, the ECU 10 switches the diagnosis in progress flag from OFF to ON.

[0024] 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 result of step S6 is No, step S6 is executed again. If the result of step S6 is Yes, 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.

[0025] Fig. 3 is a timing chart illustrating imbalance diagnosis in this embodiment and a comparative example. Fig. 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. The embodiment is shown with a solid line, and the comparative example is shown with a dotted line. Therefore, the overlapping portion between the line segment of this embodiment and the line segment of the comparative example is shown with a solid line.

[0026] First, a comparative example will be described. In the comparative example, when at least one of the banks 2L and 2R satisfies the above-mentioned preconditions, an imbalance diagnosis is performed for that bank. When only the bank 2L satisfies the preconditions (time t1 to t2), the openings of both the wastegate valves 9L and 9R are fixed, and an imbalance diagnosis is performed for only the bank 2L. When both the banks 2L and 2R satisfies the preconditions (time t3 to t4), the openings of both the wastegate valves 9L and 9R are fixed, and an imbalance diagnosis is performed for both the banks 2L and 2R. The imbalance diagnosis for the bank 2L is then completed (time t4). Next, when only the bank 2R satisfies the preconditions (time t5 to t6), the openings of both the wastegate valves 9L and 9R are fixed again, and an imbalance diagnosis is performed for only the bank 2R. The imbalance diagnosis for the bank 2R is then completed (time t6).

[0027] In this way, the openings of both the wastegate valves 9L and 9R are fixed until the imbalance diagnosis for both the banks 2L and 2R is completed. This lengthens the period during which the openings of both the wastegate valves 9L and 9R are fixed. For example, if the period during which both the wastegate valves 9L and 9R are fixed at fully open is long, there is a risk that acceleration responsiveness will decrease and drivability will deteriorate. If the period during which both the wastegate valves 9L and 9R are fixed at fully closed is long, there is a risk that fuel economy will deteriorate.

[0028] In this embodiment, when the preconditions are satisfied only for the bank 2L (time t1 to t2), the openings of the wastegate valves 9L and 9R are not fixed and the imbalance diagnosis is not performed. Only when the preconditions are satisfied for both the banks 2L and 2R (time t3 to t4, t5 to t6), the openings of both the wastegate valves 9L and 9R are fixed and the imbalance diagnosis is performed for both the banks 2L and 2R. Therefore, unlike the comparative example, it is possible to prevent the period during which the openings of both the wastegate valves 9L and 9R are fixed from becoming long. This makes it possible to prevent the deterioration of drivability or the deterioration of fuel economy. In this way, in this embodiment, it is possible to perform the imbalance diagnosis suitable for the V-type engine 1 with a turbocharger.

[0029] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0030] 1 Engine (V-type turbocharged engine) 2L Bank (1st Bank) 2R Bank (2nd Bank) #1, #3, #5 cylinders (1st cylinder) #2, #4, #6 cylinders (2nd cylinder) 5L exhaust passage (1st 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 (1st 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 engines)

Claims

[Claim 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 which bypasses a first turbine of a first turbocharger arranged in a first exhaust passage connected to the first bank, a second wastegate valve for opening and closing a second bypass passage which bypasses a second turbine of a second turbocharger arranged in a second exhaust passage connected to the second bank, a first air-fuel ratio sensor arranged downstream of a downstream end of the first bypass passage in the first exhaust passage, and a second air-fuel ratio sensor arranged 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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